RIKEN
Accelerator
Progress Report
Vol.

国立研究開発法人理化学研究所

仁科加速器科学研究センター

RIKEN Nishina Center for Accelerator-Based Science

55

RIKEN Accelerator Progress Report
Vol.

国立研究開発法人理化学研究所

55

仁科加速器科学研究センター

RIKEN Nishina Center for Accelerator-Based Science
Wako, Saitama, 351-0198 JAPANRIKEN Accelerator Progress Report 2021 Vol. 55
This is an unabridged version of the 55th volume of RIKEN Accelerator Progress Report(hereinafter referred to as APR), the official annual report of the Nishina Center for
Accelerator-Based Science.
A PDF version of APR can be downloaded from our website.
http://www.nishina.riken.jp/researcher/APR/index_e.html

Published by
RIKEN Nishina Center for Accelerator-Based Science
2-1 Hirosawa, Wako-shi, Saitama 351-0198 JAPANDirector of RIKEN Nishina Center for Acclerator-Based Science
Hiroyoshi Sakurai
Editorial Board
H.Haba (Editor-in-Chief), D. Suzuki, S. Naimi, A. Kohama, M. Kimura, E. Hiyama, T. Sumikama, R. Seidl,
T. Doi, T. Tada, T. Tamagawa, K. Takahashi, K. Ozeki, Y. Higurashi, K. Morimoto, M. Watanabe, H. Sato, T. Ikeda,
H.Yamazaki, I. Watanabe, H. Tsuneizumi, K. Tanaka, Y. Watanabe, H. Nagahama, M. Wada, K. Tateishi, H. Hasebe,
H.Ueno and I. Yoshida
Contact
progress@ml.riken.jp
All rights reserved. This report or any portion thereof may not be reproduced or used in any form, including photostatic
print or microfilm, without written permission from the Publisher.
Contents of the manuscripts are the authors' responsibility. The Editors are not liable for the content of the report.

RIKEN Nishina Center for Accelerator-Based Science, 1RYHPEHU 2022

PREFACE
The RIKEN Accelerator Progress Report is the annual
report of all the research activities conducted at the
RIKEN Nishina Center for Accelerator-Based Science(RNC). This volume covers the activities conductedduring the Japanese fiscal year 2021 (i.e., April 2021 toMarch 2022).
Masaaki Kimura launched a new laboratory,“Nuclear Many-body Theory Laboratory,” in October
2021 to further strengthen nuclear theory activities
cooperating with experimental programs at Radioactive
Isotope Beam Factory (RIBF). Yoshitaka Hatta has
been appointed as Group Leader of Theory Group in
RIKEN BNL Research Center (RBRC) as of May 2021.
Two years have passed since restrictions on social
activities were first imposed due to the coronavirus
crisis. However, we are yet to know what changes the pandemic will bring for us in future.
The COVID-19 vaccination drive began in 2021 along with implementation of other measures to prevent the spreadof the virus. Although we managed to overcome a huge rise in the coronavirus cases last summer, we had to face thespread of a new variant, Omicron, at the end of the year. The emergence of new variants of coronavirus counters theeffect of the vaccine. However, this cannot be prevented. Therefore, it is imperative to find ways to adapt to living
alongside the coronavirus.
Our society is progressively becoming polarized in the way people think: “virus” vs “vaccination,” “justice” vs“injustice,” “restriction” vs “ease,” “wealth” vs “poverty,” “authentic” vs “fake,” and “nation” vs “individual.” Because
science and technology always seek “authenticity,” according to me, the pandemic has not significantly changed how
science and technology is viewed. I believe that science and technology originate from curiosity and ideas of an“individual” and its end goal is welfare of humanity. Consequently, I anticipate that science and technology connecting“individual” with humanity will play a vital role despite the pandemic.
Many outstanding research results were obtained at RNC last year, some of which took less than a year since their
inception, while others were the fruition of research that took more than several decades. We will continue to strive tocontribute significantly to research, which we hope will yield results in future.
Eleven press releases were disseminated in FY2020. Selected strides made in 2020 have been compiled in the“Highlights of the Year” section in this volume, which show successful multi-disciplinary activities of RNC for science,technology, and innovation. It is noteworthy that these were achieved not only the in-house researchers and engineers in
RNC but also by collaborating users at RIBF, RBRC, and Rutherford Appleton Laboratory. “Measurement of neutronrich high-dense matter pressure,” published in Physical Review Letters is a result obtained with the SʌRIT TPC in the
SAMURAI magnet to give the information on equation-of-state in asymmetric nuclear matter. The heavy-ion beam
breeding successfully created a new type of Satsuma mandarin orange, which will have a huge impact on the orange
market in Japan. RNC has started delivering 211At for an investigator-initiated trial at Osaka University Hospital forrefractory thyroid cancer.
Colleagues of RNC were awarded: Tomoko Abe for the “IAEA Women in Plant Mutation Breeding Award,” andRyo Taniuchi for “Inoue Research Award for Young Scientist.” “Young Scientist Award of the Physical Society ofJapan” was given to Tokuro Fukui, Junki Tanaka and Takumi Yamaga. Masaomi Tanaka was awarded the “RIBF
Thesis Award.” “Student Presentation Award of the Physical Society of Japan” and “2021 Symposium on Nuclear Data
Poster Presentation Award” were given to Akira Hirayama and Kenta Sugihara, respectively. The “2021 RIKEN
Awards” included the “EIHO Award,” which was given to Kazuhide Tsuneizumi et al. “BAIHO Award” was given to
Tadaaki Isobe and Junki Tanaka, and “OHBU Award” to Momo Mukai and Minori Tajima.

Hiroyoshi Sakurai
Director
RIKEN Nishina Center for Accelerator-Based Science

CONTENTS

RIKEN Accel. Prog. Rep. 55 (2022)

C O N T E N T S
PagePREFACEGRAVUREFEATURE ARTICLE
RNC’s initiatives in the ImPACT program ······························································································S1

Ⅰ. HIGHLIGHTS OF THE YEAR
Investigation of a new production and separation technique for RI beams at BigRIPS, “In-separator two-step method”····
H. Suzuki et al.

S7Three quasiparticle isomers in odd-even 159, 161Pm: Calling for modified spin-orbit interaction for the neutron-rich region ··R. Yokoyama et al.

S8Pairing forces govern population of doubly magic 54Ca from direct reactions······················································
F. Browne et al.

S9Structure of 17B studied by the quasifree neutron knockout reaction ·································································Z. H. Yang et al.

S10

Probing the symmetry energy with the spectral pion ratio ············································································
J. Estee et al.

S11

Rapidity distributions of Z = 1 isotopes and the nuclear symmetry energy from Sn + Sn collisions with radioactive beams
at 270 MeV/nucleon ·················································································································· S12
M. Kaneko et al.
Estimation of radiative half-life of 229mTh by half-life measurement of other nuclear excited states in 229Th ···················
Y. Shigekawa et al.

S13

Toward ab initio charge symmetry breaking in nuclear energy density functionals ···············································
T. Naito et al.

S14

Total reaction cross sections in the island of inversion near N = 40··································································
W. Horiuchi et al.

S15

Asymmetry of antimatter in the proton···································································································
Y. Goto et al.

S16

Gluon EMC eﬀects in nuclear matter·····································································································
X.-G. Wang et al.

S17

Production of highly charged calcium-ion beam using high-temperature oven ····················································
T. Nagatomo et al.

S18First transport of unstable nuclei into SCRIT system ··················································································
Y. Abe et al.

S19

Performance study of wide dynamic range photon detection system using Ge detectors for muonic X-ray spectroscopy ···R. Mizuno et al.

S20

Development of inspection system for bus extender cable of RHIC-sPHENIX INTT detector ··································
H. Imai et al.

S21

Simple cubic self-assembly of PbS quantum dots by fine ligand control····························································
J. Liu, Y.-J. Pu et al.

S22

Co-precipitation behaviour of single atoms of rutherfordium in basic solutions ···················································
Y. Kasamatsu et al.

S23

Sodium ascorbate protects 211At-labeled antibodies from reactive oxygen species damage ······································
S. Manabe et al.

S25

Intratumoral administration of astatine-211-labeled gold nanoparticle for alpha therapy ·········································
H. Kato et al.

S26

Activation cross sections of proton-induced reactions on praseodymium up to 30 MeV ·········································
M. Aikawa et al.

S28

Activation cross section measurement of alpha-particle induced reactions on natural neodymium ·····························
M. Sakaguchi et al.

S29

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RIKEN Accel. Prog. Rep. 55 (2022)

Argon-ion-induced mutations in Arabidopsis EGY1 gene aﬀect chloroplast development in leaf guard cells ·················
A. Sanjaya et al.

S30

Ⅱ. RESEARCH ACTIVITIES I (Nuclear, Particle and Astro-Physics)
1. Nuclear Physics
RI beam production at BigRIPS in 2021 ·································································································
H. Takeda et al.

1

Status of the mass measurement of neutron-rich nuclei at A  50–60 using SLOWRI/ZD-MRTOF ····························

3

S. Iimura et al.
Highly precise mass measurements of neutron-rich nuclei at A = 82–92 at ZeroDegree-MRTOF(ZD-MRTOF) ·············
W. Xian, M. Rosenbusch et al.

4Mass measurements of neutron-rich nuclei around A = 112 with ZD-MRTOF-MS system ······································
D. Hou, A. Takamine et al.

5

Improved mass measurement of 257Db by decay-correlated mass spectroscopy ····················································
P. Schury et al.

6

Initial mass measurement of 258Db by decay-correlated mass spectroscopy ························································
P. Schury et al.

7

Status of the study of masses and half-lives of 252Cf fission fragments by the MRTOF-MS ······································
S. Kimura et al.

8First measurement of double Gamow-Teller giant resonance at RIBF ······························································
A. Sakaue

9Spectroscopy of pionic atoms in tin isotopes by (d, 3He) reactions ··································································S. Y. Matsumoto et al.

10Spectroscopy of three-neutron system via the 3H(t, 3He)3n reaction ·································································
K. Miki et al.

11

Re-measurement of the 4He(8He, 8Be) reaction ·························································································
S. Masuoka et al.

12

Mass measurements of neutron-rich Ni isotopes in Rare-RI Ring II ·································································A. Ozawa et al.

13

Mass measurements with the Rare-RI ring for the A = 130 r-process abundance peak II·········································S. Naimi et al.

14

Decay spectroscopy in exotic neutron-rich nuclei near the N = 50 shell closure ···················································
C. J. Griﬃn et al.

15

Half-lives and β-delayed neutron emission for the most exotic neutron-rich Se and Br isotopes ································
R. Caballero-Folch et al.

16

Identification of a new μs-isomer in the REP region ···················································································
A. Vitéz-Sveiczer, G. G. Kiss et al.

17

RIBF181: γ-ray spectroscopy in the vicinity of 78Ni ····················································································
R. Taniuchi et al.

18

Neutron intruder states and collectivity beyond N = 50 towards 78Ni ································································
L. Plagnol, F. Flavigny et al.

19

Charge state separation in the ZD spectrometer for the 132Sn region ·································································
T. Parry et al.

20

Observation of low-lying dipole states in the 11Li(p, n) reaction ·····································································
L. Stuhl et al.

21

Analysis of 48Cr(p, n) reaction in inverse kinematics···················································································
M. Sasano et al.

22

Measurement of proton elastic scattering from 132Sn at 300 MeV/nucleon in inverse kinematics ·······························
T. Harada et al.

23

Commissioning study of SCRIT facility with 138Ba nucleus ··········································································
K. Tsukada et al.

24

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RIKEN Accel. Prog. Rep. 55 (2022)

Yield measurements for 86Kr + 198Pt at KISS ····························································································Y. X. Watanabe et al.

25

In-gas-cell laser ionization spectroscopy of 200gPt using MRTOF-MS at KISS ·····················································
Y. Hirayama et al.

26

Isomer spectroscopy using multi-nucleon transfer reaction on 248Cm ································································
S. Go et al.

27

Proton entropy excess and possible signature of pairing reentrance in hot nuclei ·················································
B. Dey et al.

28

The ONOKORO project—Toward comprehensive understanding on clustering in heavy nuclei ·······························
T. Uesaka, J. Zenihiro et al.

29

2. Nuclear Physics (Theory)
Practical method for decomposing discretized breakup cross sections into components of each channel ······················
S. Watanabe et al.
Eﬀects of the Skyrme tensor force on 0+, 2+, and 3− states in 16O and 40Ca nuclei with second random phaseapproximation ·························································································································
M. J. Yang, C. L. Bai, and H. Sagawa

31

32

On the deformability of atoms·············································································································
T. Naito et al.

33

Comparative study of the dineutron in Borromean nuclei 11Li and 22C ······························································
M. Yamagami

34

Nuclear surface diﬀuseness of Ne and Mg isotopes in the island of inversion ·····················································
V. Choudhary et al.

35

Study of β-delayed one-neutron emission probabilities using a neural network model ···········································
D. Wu, C. L. Bai, H. Sagawa et al.

36

Reentrant of the pairing gap and α-correlation in 108Cd ················································································
K. Sugawara-Tanabe and K. Tanabe

37

α-correlation in 108Cd excitation energy spectrum of α removal from 112Sn ·························································
K. Sugawara-Tanabe et al.

38

Proof-of-principle calculations in the ab initio no-core Monte Carlo shell model ·················································
T. Abe et al.

39

Structure of few-alpha systems in cold neutron matter ················································································
H. Moriya, H. Tajima et al.

40

Second and fourth moments of the charge density and neutron-skin thickness of atomic nuclei ································
T. Naito et al.

41

Comment on “Breakdown of the tensor component in the Skyrme energy density functional” ·································
H. Sagawa, G. Colò, and L. Cao

42

3. Nuclear Data
Production of 93Zr sample in the 93Nb(n, p) reaction towards accurate determination of 93Zr half-life ··························
A. Takamine et al.

43

EXFOR compilation of data from RIBF in 2021 ·······················································································
T. Tada et al.

44

4. Hadron Physics
Simulation study of the charged current DIS cross-section measurement at the EIC ··············································
S. Shimizu

45

Resolution studies for the ECCE EIC detector proposal ···············································································
R. Seidl

46

Design of the zero degree calorimeter for the EIC ·····················································································
S. Shimizu et al.

47

Preparation for very-forward particle measurements in RHICf-II experiment ·····················································M. H. Kim

48

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RIKEN Accel. Prog. Rep. 55 (2022)

Measurement of J/ψ and ψ′ productions in p+d and p+p at SeaQuest·······························································
K. Nakano et al.
Transverse single spin asymmetries of forward neutrons in p + p, p + Al and p + Au collisions at √sNN = 200 GeV as afunction of transverse and longitudinal momenta ··········································································
R. Seidl

49

50

Analysis of transverse single spin asymmetry for the forward neutron at the RHICf experiment ·······························M. H. Kim

51

Status of the J-PARC E16 experiment in 2021 ··························································································
S. Yokkaichi

52

Analysis of Quark-Gluon plasma properties based on jets with ALICE experimental data ······································
T. Kumaoka

53

Performance evaluation for sPHENIX-INTT ladder with a beta source ·····························································
Y. Namimoto et al.

54

5. Hadron Physics (Theory)
6. Particle Physics
Search for an eﬀective change of variable in QCD simulations ······································································
P. Boyle et al.

55

Radiative corrections to Landau levels of a single electron revisited ································································
R. Yamazaki and M. Nio

56

Quarternion-spin-isospin model ···········································································································
Y. Akiba

57

7. Astrophysics and Astro-Glaciology
Broad-band spectral analysis of the gamma-ray binary system LS 5039 and its strong MeV gamma-ray emission ··········
H. Yoneda et al.

59

8. Accelerator
Distributed control by EPICS for the SRILAC beam energy position monitoring system using LabVIEW ···················
T. Watanabe et al.

61

Improvement of the transmission eﬃciency of RILAC ················································································
T. Nishi et al.

62

Development of FPGA-based machine protection system for RIBF ·································································
M. Komiyama et al.

63

Deployment of a beam interlock system driven by changes in magnet current (Curs-BIS) at the RI Beam Factory··········
K. Kumagai and A. Uchiyama

64

2021 Operational report for the Nishina RIBF water-cooling system ·······························································
T. Maie et al.

65

Development of a new indicator for the auto tuning system with high-intensity primary beams ································
T. Nishi et al.

66

Status of vacuum pumping systems in accelerator facilities ··········································································
Y. Watanabe et al.

67

9. Instrumentation
Development of auto-focusing and auto-centering system for the BigRIPS separator (II) ·······································
Y. Shimizu et al.

69

Development of new ionization chamber specialized in high-Z beam ·······························································
M. Yoshimoto et al.

70

Radiation transport calculation of BigRIPS separator··················································································
K. Yoshida

71

Present status of beam transport line from SRC to BigRIPS ··········································································
K. Kusaka et al.

72

Development of novel semiconductor detector towards high-rate heavy RI beam counting ·····································
T. Isobe et al.

73

A pilot experiment for collective flow in heavy-ion collisions········································································
S. Nishimura et al.

74

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RIKEN Accel. Prog. Rep. 55 (2022)

Silicon trackers for cluster knockout reactions in ONOKORO ·······································································
K. Higuchi, J. Tanaka et al.

75

Development of the GAGG(Ce) calorimeter for the cluster knockout reaction measurement ···································
R. Tsuji et al.

76

Development of a low-cost FPGA-Integrated TDC ····················································································
H. Baba77

Development of a high-bandwidth waveform processing system using RFSoC ···················································S. Takeshige et al.

78

Compensation for energy-spread growth in RUNBA ··················································································
M. Wakasugi et al.

79

Compensation for emittance growth in RUNBA························································································
M. Wakasugi et al.

80

Simulation study to compensate for growth in energy spread and emittance in RUNBA·········································
M. Wakasugi et al.

81

Improvements in the working environment for target handling at ERIS ····························································
T. Ohnishi et al.

82

Compact position-sensitive detector for in-ring diagnostics at the Rare-RI Ring ··················································S. Naimi and G. Hudson-Chang

83

Extraction test of photo ionized Bi in PALIS gas cell ··················································································
T. Sonoda et al.

84

Development of a timing detector for decay spectroscopy in conjunction with MRTOF-MS ····································
M. Mukai et al.

85

New developments and progress of the ZD-MRTOF system in 2021 ·······························································
M. Rosenbusch et al.

86

Fifth report on oﬄine tests for RF carpet transportation in RF ion guide gas cell at the SLOWRI facility·····················
A. Takamine et al.

87

Development of β-TOF detector for decay-correlated mass measurement of β-decaying nuclides ······························
T. Niwase et al.

88

Ion extraction from linear Paul trap via axially swinging field ·······································································
K. Imamura et al.

89

Oﬄine collinear laser spectroscopy of zirconium II····················································································
M. Tajima et al.

90

Fluorescence detection of the highly energetic radioactive Rb beams stopped in an optical cryostat at HIMAC ·············
K. Tsubura et al.

91

Development of dispersion matching optics in OEDO beamline ·····································································
S. Hanai et al.

92

Commissioning of the Si-CsI array TiNA for direct reactions at OEDO ····························································
B. Mauss et al.

93

First production of 6He beam at CRIB ···································································································
H. Yamaguchi et al.

94

Long polarization-maintaining fiber link (440 m) for magneto-optical trapping of francium atoms ····························
K. Nakamura et al.

95

RI nuclides produced in stacked Si and Al plates by 135-MeV/nucleon 12C beam·················································
T. Kambara and A. Yoshida

96

Construction status of the INTT silicon tracker for sPHENIX at RHIC ·····························································
I. Nakagawa et al.

97

Production of bus-extender for sPHENIX INTT detector ·············································································
T. Hachiya et al.

98

Detection eﬃciency of the RHIC-sPHENIX-INTT detector ··········································································
M. Morita et al.

99

Test beam experiment at ELPH in Tohoku University for sPHENIX INTT ························································
G. Nukazuka et al.

100

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RIKEN Accel. Prog. Rep. 55 (2022)

Computing and network environment at the RIKEN Nishina Center ································································
T. Ichihara et al.

102

CCJ operations in 2021 ·····················································································································
S. Yokkaichi et al.

103

Ⅲ. RESEARCH ACTIVITIES II (Material Science and Biology)
1. Atomic and Solid State Physics (Ion)
Crystal growth and β-NMR studies of the simplest copper oxide (CuO)····························································
H. Yamazaki et al.

105

Single-event damages on SiC junction barrier Schottky diodes ······································································
M. Iwata et al.

106

Analysis of diﬀraction patterns of laser spots in dual-microbeams generated by glass capillary optics for future
biological use··························································································································
K. Inayoshi et al.

107

2. Atomic and Solid State Physics (Muon)
μSR study on the low-temperature anomaly in triangular-lattice antiferromagnet CuOHCl ·····································
I. Yamauchi, X. G. Zheng, and I. Watanabe

109

Zero-field μSR measurements to investigate the magnetic ordering of Nd2Ru2O7 ·················································
U. Widyaiswari et al.

110

Spin dynamics of Nd2Pt2O7 at 0.3 K observed by longitudinal-field μSR measurements ·········································
U. Widyaiswari et al.

111

Novel quantum spin liquid state in Ba3ZnRu2O9 ························································································
Y. Yasui et al.
μ+SR Knight shift of the Mott insulator κ-(ET)4Hg2.78Cl8 ·············································································
D. P. Sari et al.

112
113

μSR study of the stabilization mechanism of antiferromagnetic state in molecular π-d system
λ-(BEDT-STF)2FexGa1−xCl4 ··········································································································
S. Fukuoka et al.

115

μSR study of Fe-substitution eﬀects on ferromagnetic fluctuations in nonsuperconducting heavily overdoped
Bi-2201 cuprates ······················································································································
T. Adachi et al.

116

Hole-doping eﬀect on the magnetic correlation in the undoped(Ce-free) superconductor T’-La1.8Eu0.2CuO4studied by μSR ························································································································
T. Kawamata et al.

117

3. Radiochemistry and Nuclear Chemistry
Isothermal gas chromatography study of Zr and Hf tetrachlorides using radiotracers of 88Zr and 175Hf—Towards
investigation of gas-phase chemistry of Rf— ····················································································
K. Shirai et al.

119

Online anion-exchange experiment of 89mZr in the Adogen 464/HNO3 system for the chemical research of Rf ···············
E. Watanabe et al.

120

Solvent extraction of Zr and Hf in trioctylamine/H2SO4 system ······································································
T. Yokokita and H. Haba

122

Determination of 236U in a Th target irradiated with Li ions by ICP mass spectrometry ··········································
A. Nagai et al.

123

Development of a photon measurement apparatus for observing the radiative decay of 229mTh produced from 229Pa ·········
Y. Shigekawa et al.

124

Surface ionization of protactinium toward implanting 229Pa into a CaF2 crystal ····················································
Y. Shigekawa and H. Haba

126

Development of RF carpet gas cell for extracting 229mTh ions·········································································
Y. Shigekawa et al.

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Preparation of an 225Ac source for 221Fr EDM measurement···········································································
M. Sato et al.

129

Accelerator production and chemical separation of theranostic radionuclide 141Ce ················································
K. Ooe et al.

130

Production of no-carrier-added Cr radiotracers in α-particle-induced reactions on Ti target ·····································
T. Yokokita and H. Haba

131

Production of 44Ti via the 45Sc(p, 2n)44Ti reaction for 44Ti/44gSc generator development ···········································
X. Yin et al.

133

HPLC elution behavior of heavy lanthanide metallofullerene: Ln@C82 (Tb, Dy, Ho, Er, Lu) on pyrenyl
stationary phase ·······················································································································
K. Akiyama et al.

134

Ionic liquid extraction of astatine for a nuclear medical utilization ··································································
Y. Nagai et al.

135

Synthesis of [211At]4-astato-L-phenylalanine by dihydroxyboryl-astatine substitution reaction in aqueous solution ·········
Y. Shirakami et al.

136

Neopentyl glycol as a scaﬀold to provide radiohalogenated theranostic pairs of high in vivo stability ·························
H. Suzuki et al.

137

Treatment for peritoneal dissemination of gastric cancer using 211At ································································
S. Nomura and H. Haba et al.

138

Analysis of complex formation between rhenium and various hydrophilic ligands using HPLC and preparationof 186Re-carrying liposomes ·········································································································I. O. Umeda et al.

139

Eﬀect of tumor size on the therapeutic eﬀect of 67Cu-labeled compounds targeting the somatostatin receptor ················
Y. Fujisawa et al.

141

Synthesis of 44mSc-DOTA-TATE for multiple-isotope PET imaging ·································································
T. Fukuchi et al.

142

Investigation of the usability of RIKEN 44mSc for radiolabeling on chelate-compounds ··········································S. Oshikiri et al.

143

Progress of double-photon coincidence imaging with 28Mg ···········································································
M. Uenomachi et al.

144

Source preparation technique of astatine-211 without electroplating for alpha spectroscopy ····································
S. Fujino et al.

145

Production cross sections of 225Ac and 225Ra in the 232Th(14N, xnyp) reactions at 56, 79, and 98 MeV/nucleon ················
X. Yin et al.

147

Production cross sections of 28Mg via the α-particle-induced reaction on aluminum ··············································
M. Aikawa et al.

148

Production cross sections of titanium radionuclides via proton-induced reactions on scandiumm ······························
M. Aikawa et al.

149

Production cross sections of 45Ti via deuteron-induced reaction on 45Sc ····························································
Ts. Zolbadral et al.

150

Production cross sections of 47Sc via proton-induced reactions on calcium ·························································
M. Aikawa et al.

151

Production cross sections of 47Sc via deuteron-induced reactions on natural calcium ·············································
M. Aikawa et al.

152

Activation cross sections of alpha-particle-induced reactions on natural calcium ·················································
M. Aikawa et al.

153

Activation cross sections of proton-induced reactions on manganese up to 30 MeV ··············································
H. Huang et al.

154

Activation cross sections of deuteron-induced reactions on natural chromium up to 24 MeV ···································
H. Huang et al.

155

Production cross-sections of 52mMn in alpha-particle-induced reactions in natural vanadium ····································
G. Damdinsuren et al.

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Measurement of production cross sections of medical isotope 110mIn in alpha-particle-induced reaction on naturalsilver up to 50 MeV ··················································································································
Ts. Zolbadral et al.

157

Cross sections of alpha-particle-induced reactions on natSb ···········································································S. Takács et al.

158

Activation cross sections of deuteron-induced reactions on praseodymium up to 24 MeV·······································
M. Aikawa

159

Production cross sections for α-particle-induced reactions on natLa ··································································
S. Ebata et al.

160

Production cross sections of 153Sm via alpha-particle-induced reactions on natural neodymium ································
M. Aikawa et al.

161

Production cross-sections of dysprosium-159 radioisotope obtained by α-particle-induced reactionsof natural gadolinium up to 50 MeV ·······························································································
D. Ichinkhorloo et al.

162

Production cross-sections of holmium-161 radioisotope from alpha-particle-induced reaction
on terbium-159 up to 29 MeV ······································································································
D. Ichinkhorloo et al.

163

4. Radiation Chemistry and Biology
Responsible gene analysis of phenotypic mutants revealed the linear energy transfer (LET)-dependent
mutation spectrum in rice············································································································
R. Morita et al.

165

Genetic characterization of large flower mutant ohbana1 induced by heavy-ion beam irradiationin Arabidopsis thaliana ··············································································································
V. Q. Nhat et al.

166

Ar17+ beam-induced mutants of the mycorrhizal mushroom Tricholoma matsutake defective in β-1,4 endoglucanase
activity better promote the Pinus densiflora seedling growth in vitro than the wild-type strain ···························
H. Murata et al.

167

Highly eﬃcient and comprehensive identification of ethyl methanesulfonate-induced mutations in Nicotiana tabacum L.
by whole-genome and whole-exome sequencing ················································································
H. Ichida et al.

168

40

Method of chromosome observation in the dioecious plant Silene latifolia ························································
T. Kobayashi et al.

169

Producing high brix content of the sweet potato Anno-Beni by mutation induced using ion-beam irradiation ················
T. Hashiguchi et al.

170

Isolation method of marine red alga Agardhiella subulate ············································································
K. Tsuneizumi et al.

171

Survival rate of yeast cells in diﬀerent storage media··················································································
Y. Nishimiya and H. Ichida

172

Eﬀect of irradiation ions and doses on the survival rate of yeast ·····································································
N. Lei et al.

173

Recruitment of Rad51 onto chromatin is suppressed by high dose heavy-ion irradiation in mammalian cells ················
M. Izumi and T. Abe

174

Ⅳ. OPERATION RECORDS
Program advisory committee meetings for nuclear physics and for materials and life experiments·····························
K. Yoneda et al.

175

Electric power consumption of RIKEN Nishina Center in 2021 ·····································································
M. Kidera et al.

176

Operation report on ring cyclotrons in the RIBF accelerator complex ······························································
T. Nakamura et al.

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RILAC operation ····························································································································
T. Ohki et al.

178

Operation report on the RIKEN AVF cyclotron for 2021 ··············································································
S. Fukuzawa et al.

179

Present status of liquid-helium supply and recovery system ··········································································
T. Dantsuka et al.

180

Impurity concentration in recovered helium gas of liquid-helium supply and recovery system ·································
M. Nakamura et al.

181

Operation of the BigRIPS cryogenic plant·······························································································
K. Kusaka et al.

182

Radiation safety management at RIBF ···································································································
K. Tanaka et al.

183

Operation of Pelletron tandem accelerator·······························································································
T. Ikeda et al.

185

Fee-based activities performed by the RI Application Research Group ·····························································
A. Nambu et al.

186

Ⅴ. EVENTS
International workshops on the extension project for the J-PARC hadron experimental facility (J-PARC HEF-ex WSs) ···F. Sakuma

187

SPIN2021 international spin symposium ································································································
Y. Goto and T. Uesaka

188

Small-x physics in the electron-ion collider era ·························································································
Y. Hatta et al.

189

RIKEN open day 2021 ·····················································································································
K. Tanaka et al.

190

Ⅵ. ORGANIZATION AND ACTIVITIES OF RIKEN NISHINA CENTER(Activities, Members, Publications & Presentations)
Organization
1. Organization Chart ················································································································

191

2. Finances ·····························································································································

192

3. Staﬃng ······························································································································

192

4. Research publication ··············································································································

193

5. Management ························································································································

194

6. International Collaboration (as of March 31, 2022) ··········································································

198

7. Awards ······························································································································

199

8. RIKEN Awards·····················································································································

200

9. Brief overview of the RI Beam Factory ························································································

201

Center Director ······························································································································

203

Laboratories
Nuclear Science and Transmutation Research Division
Radioactive Isotope Physics Laboratory ··························································································

205

Spin isospin Laboratory ·············································································································

212

Nuclear Spectroscopy Laborarory ··································································································

217

High Energy Astrophysics Laborarory ····························································································

222

Nuclear Many-body Theory Laboratory ··························································································

228

Superheavy Element Research Group ·····························································································

232

Superheavy Element Production Team······················································································

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Superheavy Element Device Development Team ·········································································

236

Astro-Glaciology Research Group ·································································································

238

Nuclear Transmutation Data Research Group ····················································································

241

Fast RI Data Team ·············································································································

242

Slow RI Data Team ············································································································

243

Muon Data Team ···············································································································

244

High-Intensity Accelerator R&D Group···························································································

247

High-Gradient Cavity R&D Team ···························································································

248

High-Power Target R&D Team ······························································································

249

Research Facility Development Division
Accelerator Group ····················································································································

251

Accelerator R&D Team ·······································································································

253

Ion Source Team ···············································································································

254

RILAC Team ···················································································································

255

Cyclotron Team ················································································································

257

Beam Dynamics & Diagnostics Team ······················································································

259

Cryogenic Technology Team ·································································································

261

Infrastructure Management Team ····························································································

262

Instrumentation Development Group ······························································································

263

SLOWRI Team ·················································································································

265

Rare RI-ring Team ·············································································································

268

SCRIT Team ····················································································································

270

Research Instruments Group ········································································································

273

BigRIPS Team ··················································································································

274

SAMURAI Team···············································································································

277

Computing and Network Team·······························································································

279

Detector Team ··················································································································

281

Accelerator Applications Research Division
Beam Mutagenesis Group ···········································································································

283

Ion Beam Breeding Team ·····································································································

284

Plant Genome Evolution Research Team ···················································································288

RI Application Research Group ····································································································

290

Nuclear Chemistry Research Team ··························································································

291

Industrial Application Research Team ······················································································

298

Subnuclear System Research Division
Quantum Hadron Physics Laboratory ·····························································································

299

Strangeness Nuclear Physics Laboratory ··························································································

304

Radiation Laboratory·················································································································

307

Meson Science Laboratory ··········································································································

312

RIKEN BNL Research Center ······································································································

317

Theory Group ···················································································································

319

Experimental Group ···········································································································

323

Computing Group ··············································································································

328

RIKEN Facility Oﬀce at RAL ······································································································

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RIKEN Accel. Prog. Rep. 55 (2022)

Safety Management Group ··········································································································

337

User Liaison Group ··················································································································

339

RIBF User Liaison Team······································································································

340

Outreach Team ·················································································································

341

Oﬃce of the Center Director ········································································································

342

Partner Institutions ··························································································································

345

Center for Nuclear Study, Graduate School of Science, The University of Tokyo ··········································

346

Wako Nuclear Science Center, IPNS (Institute of Particle and Nuclear Studies),
KEK (High Energy Accelerator Research Organization) ·································································

354

Ⅶ. APPENDICES
Symposia, Workshops & Seminars ·······································································································

357

Events ·········································································································································

364

Press Releases ·······························································································································

365

Preprints ·····································································································································

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FEATURE ARTICLE

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

RNC’s initiatives in the ImPACT program

nuclear reaction control methods,

The ImPACT Program
Since 2007, Radioactive Isotope Beam Factory(RIBF) 1) has been one of the world-leading heavy-ion accelerator facilities for low-energy nuclear physics. RIBF
has contributed to the expansion of the nuclear chart by
producing more than 150 new isotopes and has provided
a multitude of opportunities to discover new phenomena
originating from high isospin asymmetry. In parallel tosuch pure nuclear physics activities, a new and national
program of nuclear engineering was launched for social
beneﬁts. In the period of 2014–2018, the program entitled “Reduction and Resource Recycling of High-level
Radioactive Wastes through Nuclear Transmutation” 2)
was carried out as one of the ImPACT R&D programs
conducted by the Cabinet of Japan.
Since Hideki Yukawa left the Japan Atomic Energy
Commission in 1957, the nuclear physics and nuclear
engineering communities have been separated in Japan.
The incident of the Fukushima Dai-ichi Unit in 2011,
however, impelled Japanese nuclear physicists to seriously consider possible contributions to nuclear engineering. In 2014, a demonstration experiment was performed with RIBF. In this experiment, the inverse kinematics with energetic radioactive-isotope (RI) beams of137
Cs and 90 Sr was employed to study spallation reaction to ﬁnd an eﬃcient reaction pathway for reductionof the radioactivity.3) The experiment provided an opportunity to the physicists and engineers to work together. The potentials of RI beams at RIBF were also
demonstrated, and the fundamental reaction data obtained with RI beams were found highly useful for designing an accelerator-based transmutation system.
High-level radioactive waste has two main components: long-lived ﬁssion products (LLFPs) and minor
actinides (MAs). The transmutation of MAs has beenstudied in detail for the purpose of reprocessing spent nuclear fuel under the concept of using fast-breeder reactors
or accelerator-driven systems. The LLFP nuclides aresupposed to create risks in the geological disposal strategy because their half-lives are much longer than thoseof MAs. However, the transmutation of LLFPs has notbeen studied extensively. Considering the present situation of R&D activities in the ﬁeld of the radioactive
waste, the ImPACT program was jointly proposed by the
nuclear physicists and engineers, to focus on acceleratorbased transmutation of LLFPs.
The ImPACT program emphasized on the “resource
recycle” of radioactive waste. Thus, 107 Pd and 93 Zr werehighly prioritized as objectives. The program consisted
of ﬁve projects as follows:
Project-1: Development of separation and recovery
technologies,
Project-2: Production of nuclear reaction data and new

Project-3: Reaction theory modeling and simulation,
Project-4: Evaluation of the nuclear transmutation system and development of elemental technologies, andProject-5: Process design concept by nuclear engineers.
All the projects were managed coherently, and Project-2
and Project-4 were conducted by RIKEN Nishina Center.
An overview of the activities in Project-2 and -4 ispresented in this article.
Transmutation Reactions for Accelerator System
To design an accelerator system for the transmutation, the possible reactions for the transmutation wereintensively discussed at an early stage of the ImPACT
program.
First, we adopted nuclear reactions, not electromagnetic reactions. In the case of nuclear reactions induced
by “hadron” particles, which interact strongly with LLFP
nuclei, several reactions, such as spallation, knockout reactions, are applied with reaction cross sections of the order of 1 barn. Conversely, in the case of electromagnetic
reactions, the reaction candidate is only the photoabsorption process (γ, n), and its cross section is approximately 0.2 barns for LLFPs. To induce the (γ, n) reaction, secondary high-energy photons, of which energy ismore than 10 MeV, should be produced by high-energy
electron beams through the bremsstrahlung process in aconverter material or through the inverse Compton process with intense laser lights. However, the high-energy
photons are wasted to create the electron-positron pairs,
simply because the cross section of the pair creation is
10 barns, much higher than that of the photoabsorption. Thus, most of the electron-beam energy is wasted
in creating the electron-positron pairs, not in transmuting LLFP nuclides signiﬁcantly.
Next, several types of nuclear reactions were considered for transmutation and were categorized with respect
to transmutation throughput and reaction controllability. The candidate reactions are spallation reaction, neutron knockout reaction, such as (n, 2n), and muon capture reaction. The spallation reaction induced by highenergy proton- or deuteron-beams is very promising interms of throughput, but it is not excellent in terms ofcontrollability. When the spallation reaction is applied,the beams are irradiated directly to LLFP materials,
and the target thickness is determined from the stopping range of the beams. Higher energy beams lead tothicker targets, and hence, the throughput is increased
as a function of beam energy. However, according to theresults obtained in Project-2, higher beam energy produces more nuclides as spallation products, because a- S1 -

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FEATURE ARTICLE

RIKEN Accel. Prog. Rep. 55 (2022)

higher energy beam deposits higher energy in the target
nuclei, and the higher deposited energy in the nuclei isused to emit more protons and more neutrons from thenuclei. Thus, in the case of the spallation reaction, theoptimal beam-energy should be carefully considered interms of not only the throughput but also the costs necessary to treat radioactive nuclides produced in LLFP
materials after long-term irradiation.
The neutron knockout reaction is induced by highenergy neutrons with energy more than 8 MeV. In thecase of even-odd separated LLFP, especially for the Pd
nuclides, the neutron knockout reaction has very highreaction controllability. After the even-odd separation,
105
Pd and 107 Pd are left as nuclear waste (105 Pd is a stable nuclide, and 107 Pd is a long-lived one). The (n, 2n)reaction produces 104 Pd and 106 Pd which are both stable, and (n, 3n) reaction also could be applied to produce103
Pd and 105 Pd. The 103 Pd nuclide is not stable, but its
half-life is as short as approximately 17 days. The neutron energy range appropriate for (n, 2n) is 8–18 MeV,
and it gives the cross section of approximately 2 barns.
Higher energy neutron beams also induce (n, 3n). The
high energy neutron beams could be created by high energy deuteron beams via breakup reaction. The broad
energy range of neutrons is very useful because this leads
to the generation of high ﬂux neutron for transmutation.
The target thickness for the neutron knockout reaction
is determined from the mean-free path of the reaction,
which is of the order of 100 g/cm2 in Pd metal.
The other reaction candidate is the negative muon capture reaction. The negative muon capture process also
has high reaction controllability. A negative muon is aunique particle, which interacts electromagnetically andcan form a muonic atom where, like an electron, the negative muon is trapped by a nucleus. Then, the muon is
captured by a proton inside the nucleus by weak interaction, and the proton is converted to a neutron. The
capture probability per muon is almost 100% for Z >40 nuclides, when the negative muons are implanted tothe material with Z > 40. Because s muon is approximately 100 times heavier than an electron, the energy
transfer in the process is rather high, and a few neutrons
are emitted from the nucleus. Hence, the muon capture has reaction controllability for the proton number
and decrements the number by one. This feature of themuon capture is very useful for chemical separation. In
the case of Pd with atomic number of 46, the products
are only Rh with atomic number of 45. Although thenegative muon is very promising in terms of controllability, the production of a muon is rather energy consuming; the production of one muon needs 5 GeV. A negative
muon is created through decay of a negative pion, andthe pion is created by a high-energy nuclear reaction, forexample, proton induced nucleus collision, in which theproton energy should be higher than 300 MeV. The pion
production cross section highly depends on the energyof beams and isospin of beams. Accelerator facilities formuons, such as TRIUMF, PSI, RAL, and J-PARC, de-liver high-energy and intense proton beams with energyof more than 500 MeV, and the target thickness is limited
to avoid pion capture in the target. These facilities are
not optimized for negative muon productions. Instead ofproton beams, deuteron beams can produce four times
more negative muons than proton beams because of theisospin eﬀects.
Negative muons are also useful to produce 14 MeV
neutrons via muon catalyzed fusion of d + t. In the process, one muon can create approximately 100 14 MeV
neutrons. Thus, the energy cost for a 14 MeV neutron isapproximately 50 MeV. This value is smaller than thatin case of an accelerated deuteron beam inducing d + t
fusion, which is approximately 2 GeV.
Regarding the neutron capture process, it is noted thatneutron capture cross section for 107 Pd is higher than 1barn at a neutron energy below 100 keV and 10 barns at
10 eV to 1 keV. Thus, neutrons produced via spallation
reaction are also very useful for transmutation. In thecase of the even-odd separation scheme for the Pd nuclides, the neutron capture changes 105 Pd and 107 Pd to106
Pd and 108 Pd, respectively, which are both stable nuclides. Thus, a combination of the knockout reaction andneutron capture could lead to high throughput for transmutation. Considering all the above, we have decided todesign an accelerator system for deuteron beams. The
deuteron beams are utilized for a variety of applications:spallation reaction in direct irradiation as well as spallation neutron production, high energy neutron production
via the deuteron breakup reaction, and eﬃcient production of negative muons.
Nuclear Reaction Data with RIBF
Project-2 aimed to produce reaction data of the LLFPs
that could be evaluated and utilized as input for a simulation code as part of Project-3. As introduced in theprevious section, all the possible reactions for transmutation were discussed: proton-, deuteron-, and neutroninduced reactions and muon capture reactions.
In the case of direct irradiation of charged-particles
into an LLFP material, an energy-dependence study of
the reaction is quite important because of the stopping
power in the material. This argument is also applied
for the high-energy neutron-induced spallation reaction.
A challenge for the energy-dependence study is to build
a bridge over the Fermi energy; at a lower energy, thecollective natures of the reaction are dominant and at ahigher energy, the nucleon-based natures become dominant.
According to the experiences in the previous experiment of 137 Cs and 90 Sr,3) the reaction study for proton-,deuteron-, and neutron-induced reactions was conducted
in inverse kinematics at RIBF under a large domestic collaboration comprising the University of Tokyo, Tokyo Institute of Technology, Kyushu University, Miyazaki University, Niigata University, and RIKEN. Compared withthe traditional activation method via normal kinematics- S2 -

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FEATURE ARTICLE

RIKEN Accel. Prog. Rep. 55 (2022)!
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7,8695.?.D/@>287D;.),?287D:-DD D D.&@
(;D D D.$ @.@?;87,)9?@;.D7AD!;83)7D18;>.D6.?18-D .-9DD D.%@DFig. 1. Reaction study for long-lived ﬁssion products at RIBF in the ImPACT program. Major spectrometers such as, ZeroDegree, SAMURAI, and SHARAQ, were utilized.4)

with stable beams and RI targets, the inverse kinematics
technique gives clear particle identiﬁcation for reaction
products and easy control of RI beam energies for the
study of energy-dependence. In addition, we do not haveto prepare RI targets but stable-isotope targets, such as
protons and deuterons. All these advantages of inverse
kinematics result in reaction data of excellent quality at
RIBF.
As shown in Fig. 1, intense beams of LLFPs, such as
107
Pd and 93 Zr were produced at the in-ﬂight separator “BigRIPS” via ﬁssion reactions with a uranium beam
accelerated at Superconducting Ring Cyclotron (SRC),
and then were delivered to three spectrometers (ZeroDegree, SAMURAI, and SHARAQ), which were utilized
to identify and analyze the reaction products.5–9) ZeroDegree is suitable for inclusive measurements with relatively heavy fragments. SAMURAI has a wide acceptance in both momentum and scattering angle for reaction products. Hence, semi-exclusive measurements were
performed to detect reaction products as well as neutrons
in the projectile frame. At the SHARAQ spectrometer, CNS, the University of Tokyo and RIKEN worked
together to develop an eﬃcient deceleration scheme for
RI beams. A new device “OEDO” 10) was installed in
the SHARAQ beamline to control emittance growth bytransverse RF electric ﬁelds. An operation mode of
BigRIPS was developed to realize energy-decelerated
beams.11,12) The combination of OEDO and energydecelerated beams successfully led to a reaction study
at an energy of 20 MeV/nucleon.
Enhancement of element production by incomplete fusion reaction with weakly bound deuteron was observed
at 50 MeV/nucleon,9) as shown in Fig. 2, and the incident energy was much higher than the energy scale ofcomplete fusion reaction. The reaction mechanism could
be applied to produce a higher Z element by increasing
the atomic number by 2 via heavy loosely bound nuclei
such as 9 Be and 6 He. Another highlight is a deductionof neutron capture reaction via the Trojan horse methodwith a low energy RI beam at 20 MeV/nucleon.13) In
future, the new method can be widely applied not only
for nuclear engineering but also for nuclear astrophysics.
All these data stimulated theoretical works, and the
JAEA nuclear data group developed a new data library“JENDLE/ImPACT–2018” for proton- and neutroninduced reactions up to 200 MeV/nucleon.14) The newlibrary has been built in as a package of PHITS simulation code.15)
A test of 107 Pd transmutation with macroscopic quantities was conducted with normal kinematics by utilizing- S3 -

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FEATURE ARTICLE

RIKEN Accel. Prog. Rep. 55 (2022)

a low energy deuteron beam at the AVF cyclotron at
RIBF.16) Almost 100% enriched 107 Pd was prepared asa target and irradiated for several days. After the irradiation, the reaction products were identiﬁed from gammaray and ICP-MS measurements. The production yields
were found consistent with PHITS predictions.15)
Accelerator System
Project-4 proposes an accelerator-based transmutation system for LLFPs, and focuses on three objectives:(1) to design an accelerator system with a possible transmutation scenario, (2) to develop essential technologies
for a high-power accelerator system, and (3) to encourage ideas for new high-power and energy-saving accelerators. Four activities by the RIKEN Nishina Center are
selected and brieﬂy introduced.

Linear accelerator system ImPACT2017
Delivering high-energy and intense deuteron beams isessentially important for the nuclear transmutation as
described in the second section. The next question is theintensity of deuteron beams. In the existing facilities inoperation, the maximum intensity of proton beams is of
the order of 1 mA. As discussed in the ImPACT project,
the beam intensity necessary for the transmutation isat least 1 A, which is three orders of magnitude higher
than that of the present facilities. It should be noted that
1 A corresponds to approximately 1 mol/day. If all the
beams contribute to the transmutation, the throughput
would be approximately 100 g/day for the mass numberof 100, which corresponds to 36 kg/year.
To achieve a 1-A deuteron beam, we have made aconceptual design for a linear accelerator system called“ImPACT2017,” 17) as shown in Fig. 3. There are a few
key aspects of ImPACT2017. First, the system does notstart with a radio-frequency quadrupole (RFQ). Second,the RF cavity of the linear accelerator is made as a single
cell. The RFQ device is convenient and widely employedbecause a single RFQ device has three functions: beam
bunching, acceleration, and focusing. However, a small
beam aperture of RFQ (∼1 cm) limits the beam current
due to the space charge eﬀect. Thus, we must develop
other types of acceleration scheme, which is capable fora large size beam. To accelerate a high-intensity beam,
we must supply high RF power to the cavities. A standard conﬁguration has several cells in one cavity, and the
RF power is supplied to the cavity through RF couplers.
Each RF coupler has a limitation for transmitted power;
hence, many RF couplers should be attached to the cavity. In this case, a multi-cell conﬁguration may cause
problems in operation. Decrease the number of RF couplers is signiﬁcant for reasonable operation of the linear
accelerator, and we have decided to employ a single cell
conﬁguration for the cavity. Further details of the newidea are found in Ref. 17).

Fig. 2. Proton-induced and deuteron-induced cross sections
for the 103, 104, 105 Ag isotopes produced by 107 Pd as a function of total incident energy, taken from Ref. 9). Cross
sections on proton and deuteron are displayed by circles
and squares, respectively. Enhancement of the 103, 104 Ag
cross sections with deuterons is clearly observed at theincident energy of 100 MeV, i.e., 50 MeV/nucleon for
deuterons.

R&D of key technologies for high-power accelerator systemAs essential components for high power accelerator
systems, a superconducting RF cavity for low-velocity
charged-particles, material-free window-system for vacuum sealing, and liquid-target system for production
targets have been developed by the RIKEN acceleratorgroup.
R&D of a quarter-wave superconducting RF-cavity for
low-velocity charged-particles 18) is essential to achieve
low power consumption and space-saving. A prototypeof the cavity was designed, constructed, and tested. The
cavity was successfully cooled down to 4 K with liquid
He, and acceptably high values of Q (∼109 ) and acceleration electric ﬁeld (up to 9 MV/m) were achieved. Basedon the experiences in this R&D process, the linear accelerator RILAC has been recently upgraded by installinga similar type of superconducting RF-cavities.19)
A plasma-window with a diameter of up to 20 mm wasdeveloped as the material-free window system for vacuum sealing. The achieved pressure and the V -I characteristics as a function of diameter were investigated.

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RIKEN Accel. Prog. Rep. 55 (2022)

free society to avoid global warming. However, risk management in reactor operation has become a serious concern since the Fukushima incident, and the cost of nuclear energy has increased. Regardless of the promotionof or opposition to nuclear energy, the problem of highlevel radioactive waste needs to be solved because thewaste already exists. In Japan, approximately 18,000tons of spent fuel exists, and the location for the geographical disposal has not been decided. Mitigating therisk of the waste is an important issue because this negative legacy should be left to posterity. Pure nuclear
physics is now playing an important role in realizing aradioactive-waste free society.
Fig. 3. Schematic of the 1-A Linac, taken from the cover pageof Proc. Jpn. Acad. Ser. B 95(7).17)

Detailed information can be found in Ref. 20).
The new idea of a target accepting the high intensity
beam was proposed and published as patent.21)
Summary and Future Perspectives
The ImPACT program ran from 2014 to 2018 as theﬁrst step in the nuclear transmutation of LLFPs and successfully stimulated the interest of the nuclear chemists,
nuclear physicists, accelerator physicists, and nuclear engineers in Japan. The program created new data as well
as new ideas. In the second step, it is necessary to identify R&D items and proceed. For example, the transmutation scenario with high-energy neutrons still needs
nuclear reaction data with 99 Tc and other nuclides. In
addition, 1-A Linac would be highly desirable. R&D fora target to accept the very intense deuteron beam must
be conducted in the future. It should be noted that theseR&D can be linked to our future of pure nuclear physics,
where high intensity beams may become necessary. The
methodology of inverse kinematics can also be extended
to a reaction study for MAs.
In the program, as an alternative scenario, a transmutation with 14 MeV neutrons produced via muoncatalyzed fusion was also discussed; for which, an efﬁcient production of negative pions has been proposedwith an FFAG accelerator.22) To promote further themuon scenario, production cross sections of negative pions with a deuteron beam would be highly desirable. A
negative muon was also recognized as a charming particle that causes muon capture reaction and changes theatomic number of nuclei capturing the muon. Based on
the muon capture reaction, a new application of muons
was proposed to produce the isotope 99 Mo for medicaluse, where 99 Tc in the waste is utilized as the substancefor 99 Mo production via muon capture.23) Experimentsof muon capture were organized at the facility of RCNP
Osaka University, RAL muon facility, and J-PARC. The
results are being published.24,25)
The future role of nuclear reactors is being intensively
discussed in conjunction with the realization of a carbon-

Acknowledgment
The works introduced here were funded by the ImPACT Program of Council for Science, Technology, andInnovation (Cabinet Oﬃce, Government of Japan).
References
1) Y. Yano, Nucl. Instrum. Methods Phys. Res. B 261, 1009
(2007).
2) ImPACT: “Reduction and Resource Recycling of Highlevel Radioactive Waste through Nuclear Transmutation,” https://www.jst.go.jp/impact/hp_fjt/en/ .
3) H. Wang et al., Phys. Lett. B 754, 104 (2016).
4) H. Sakurai, Nucl. Phys. News 31, 26 (2021).
5) H. Wang et al., Prog. Theor. Exp. Phys. 2017, 021D01(2017).
6) S. Kawase et al., Prog. Theor. Exp. Phys. 2017, 093D03(2017).
7) K. Nakano et al., Phys. Rev. C 100, 044605 (2019).
8) S. Takeuchi et al., Prog. Theor. Exp. Phys. 2019, 013D02(2019).
9) H. Wang et al., Comm. Phys. 2, 78 (2019).
10) S. Michimasa et al., Nucl. Instrum. Methods Phys. Res.
B 463, 143 (2020).
11) J. Hwang et al., Prog. Theor. Exp. Phys. 2019, 043D02(2019).
12) T. Sumikama et al., Nucl. Instrum. Methods Phys. Res.
A 986, 164687 (2021).
13) N. Imai et al., in preparation.
14) S. Kunieda et al., J. Nucl. Sci. Technol. 56, 1073 (2019).
15) T. Sato et al., J. Nucl. Sci. Technol. 50, 913 (2013).
16) Y. Miyake et al., J. Nucl. Sci. Technol., published online(2022), https://doi.org/10.1080/00223131.2022.20
72012 .
17) H. Okuno et al., Proc. Jpn. Acad. Ser. B 95, 430 (2019).
18) K. Yamada et al., Proc. 28th Linear Accelerator Conference (LINAC2016), TUPLR061, p. 598 (2019).
19) N. Sakamoto et al., Proc. 19th Int. Conf. RF Superconductivity (SRF19), https://accelconf.web.cern.ch/
srf2019/doi/JACoW-SRF2019-WETEB1.html .
20) N. Ikoma et al., Rev. Sci. Instrum. 91, 053503 (2020).
21) H. Okuno et al., Patent Publication PCT/JP2020/003988.
22) Y. Mori et al., JPS Conf. Proc. 21, 011063 (2018).
23) T. Matsuzaki et al., 10th Int. Sym. on Technetium andRhenium—Science and Utilization (ISTR2018), October
3–6, 2018, Moscow, Russia.
24) T. Y. Saito et al., submitted to Phys. Rev. C.
25) M. Niikura et al., in preparation.

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I. HIGHLIGHTS OF THE YEAR<< Selection process of highlights >>Highlights are selected by a two-step process. In the first step, a referee who reviews a manuscript decides
whether she/he would recommend it as one of the highlights.
Members of the editorial board then make additional recommendations if they think an important contribution
has not been recommended by the referee.
The second step involves the editor-in-chief proposing a list of highlights based on the recommendation given
above to the editorial board. After discussing the scientific merits and uniqueness of the manuscripts fromviewpoints of experts/non-experts, the editorial board makes the final decision.

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Investigation of a new production and separation technique for RI
beams at BigRIPS, “In-separator two-step method”
H. Suzuki,∗1 N. Fukuda,∗1 H. Takeda,∗1 Y. Shimizu,∗1 M. Yoshimoto,∗1 K. Yoshida,∗1 Y. Yanagisawa,∗1 and
H. Sato∗1
A new production and separation method of neutronrich medium-heavy radioactive-isotope (RI) beams “inseparator two-step method” was proposed, and its usefulness was investigated. The beam intensities of such
RIs produced by this new method are expected to behigher than those produced by the standard method, inﬂight ﬁssion of a 238 U beam, when its intensity reaches
the goal value of 2000 particle nA in the RIBF upgrade
project and RI-beam total rates are limited at 1 kHz bydata acquisition (DAQ).
In the standard method, as shown in Fig. 1(a), an
objective RI beam (e.g., 128 Pd) is produced by in-ﬂight
ﬁssion at the F0 Be target. When the magnetic rigidity(Bρ) of the ﬁrst dipole is set at the momentum peak of128
Pd to maximize its yield, the total rate of the secondary beams becomes too high for DAQ or detectors
even with the current 238 U-beam intensity of 80 particle
nA. To reduce the total rate below 1 kHz, the Bρ setting
should be higher than the momentum peak. The 128 Pd
yield decreases with such adjustment; however, the total rates can be decreased more eﬃciently. When the
primary-beam intensity increases in the future, this Bρsetting shift should be larger. Thus, the 128 Pd yield will
increase only by a factor of 9, although the 238 U-beam
intensity will be 25 times larger than the current.
To produce the RI beams more eﬃciently within the
total-rate limit, the in-separator two-step method was
proposed, as shown in Fig. 1(b). The Be target is divided
into two at F0 and F2 for the ﬁrst and second reactions,
respectively. In the ﬁrst step, less-exotic RIs (e.g., 133 Sn
and neighboring RIs) relative to the objective RI are
produced and roughly separated. In the second step,
the objective RI is produced at the secondary target at
F2 and separated.

Through a simulation, the 128 Pd yield with the new
method is expected to be ∼3 times larger than that obtained using the standard method with a 2000-particlenA 238 U beam and 1-kHz total-rate limit.
A test experiment was performed at BigRIPS. The
yield of 128 Pd with the new method was measured with
2- and 3-mm Be targets located at F0 and F2, respectively, and 2- and 4-mm degraders at F1 and F5, respectively. The RI beams along the central trajectories
in the ﬁrst and second stages were 133 Sn and 128 Pd, respectively. The measured 128 P (total) rate was 0.19 Hz(1 kHz) per 2000 particle nA. For comparison, the 128 Pd
yield obtained using the standard method was simulatedwith the LISE++ code.1) A 5-mm F0 Be target, 5-mm F1
degrader, and 1-mm F5 degrader were used. Here, thesums of thicknesses of the targets and degraders were
the same in both the methods. The 128 Pd rate was estimated to be 0.074 Hz per 2000 particle nA. From theseresults, an improved setting with the new method was
obtained to produce 128 Pd, under the conditions of the
2000-particle nA 238 U beam and the 1-kHz total-rate
limit.
The region in the nuclear chart where the new method
is favorable will be searched using the LISE++ simulation. However, we have found that some problems should
be solved to perform reliable simulations. First, the momentum distribution and yields of ﬁssion products from238
U are not reproduced well. Second, the RI production
cross-sections from RI beams are not well known, except
for a 132 Sn-beam case.2) For further investigation, suchbasic data should be measured experimentally.
References
1) O. B. Tarasov, D. Bazin, LISE++ site, https://lise.
nscl.msu.edu/lise.html .
2) H. Suzuki et al., Phys. Rev. C 102, 064615 (2020).

Fig. 1. Schematics of RI-beam productions at BigRIPS. (a) Standard method. An objective RI beam is
produced from a 238 U beam in one step. (b) New method, “In-separator two-step method.” An objective RI
beam is produced via less-exotic RIs with two targets in two steps.
∗1

RIKEN Nishina Center- S7 -

1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Three quasiparticle isomers in odd-even 159, 161 Pm: Calling for
modiﬁed spin-orbit interaction for the neutron-rich region†
R. Yokoyama,∗1,∗2 E. Ideguchi,∗3,∗8 G. Simpson,∗4 Mn. Tanaka,∗3 Y. Sun,∗5 C. -J. Lv,∗5 Y. -X. Liu,∗6
L. -J. Wang,∗7 S. Nishimura,∗8 P. Doornenbal,∗8 G. Lorusso,∗8 P. -A. Söderström,∗8 Z. Y. Xu,∗11,∗2 J. Wu,∗10,∗8
T. Sumikama,∗8 N. Aoi,∗3,∗8 H. Baba,∗8 F. L. Bello-Garrote,∗12 G. Benzoni,∗13 F. Browne,∗14,∗8 R. Daido,∗15
Y. Fang,∗15 N. Fukuda,∗8 A. Gottardo,∗16,∗17 G. Gey,∗18,∗8 S. Go,∗1 S. Inabe,∗8 T. Isobe,∗8 D. Kameda,∗8
K. Kobayashi,∗19 M. Kobayashi,∗1 I. Kojouharov,∗20 T. Komatsubara,∗21,∗22 T. Kubo,∗8 N. Kurz,∗20 I. Kuzi,∗23
Z. Li,∗10 M. Matsushita,∗1 S. Michimasa,∗1 C. B. Moon,∗24 H. Nishibata,∗15 I. Nishizuka,∗9 A. Odahara,∗15
Z. Patel,∗8,∗25 S. Rice,∗8,∗25 E. Sahin,∗12 H. Sakurai,∗8,∗11 H. Schaﬀner,∗26,∗8 L. Sinclair,∗26,∗8 H. Suzuki,∗8
H. Takeda,∗8 J. Taprogge,∗27,∗28 Zs. Vajta,∗23 H. Watanabe,∗29,∗8 and A. Yagi∗15†

Condensed from the article in Phys. Rev. C 104, L021303(2021)∗1 Center for Nuclear Study, University of Tokyo∗2 Department of Physics and Astronomy, University of Tennessee, Knoxville∗3 Research Center for Nuclear Physics, Osaka University∗4 LPSC, Université Grenoble-Alpes, CNRS/IN2P3∗5 School of Physics and Astronomy, Shanghai Jiao Tong University∗6 School of Physics, Huzhou University∗7 School of Physical Science and Technology, Southwest University, Chongqing∗8 RIKEN Nishina Center∗9 Department of Physics, Tohoku University∗10 Department of Physics, Peking University∗11 Department of Physics, University of Tokyo∗12 Department of Physics, University of Oslo
∗13 INFN, Sezione di Milano∗14 School of Computing Engineering and Mathematics, University of Brighton∗15 Department of Physics, Osaka University∗16 Dipartimento di Fisica dell Universitá degli studi di Padova∗17 INFN, Laboratori Nazionali di Legnaro∗18 Institut Laue-Langevin, Grenoble∗19 Department of Physics, Rikkyo University∗20 GSI Helmholtzzentrum für Schwerionenforschung GmbH
∗21 Department of Physics, University of Tsukuba∗22 RISP, Institute for Basic Science, Daejeon∗23 Institute for Nuclear Research (ATOMKI)∗24 Department of Display Engineering, Hoseo University∗25 Department of Physics, University of Surrey∗26 Department of Physics, University of York∗27 Instituto de Estructura de la Materia, CSIC
∗28 Departamento de Fı́sica Teórica, Universidad Autónoma de
Madrid∗29 IRCNPC, Beihang University- S8 -(a) 159Pm(b) 161Pm
p5/2[532]
n7/2[633]
n1/2[521]

2500

Excitation energy (keV)

Excitation energy (keV)

Nuclear properties of neutron-rich rare-earth nuclei
at Z ≈ 60 could be the possible key to answer oneof the longstanding astrophysical questions: the formation of the A ≈ 160 (rare-earth) peak observed in theelemental abundance distribution. From the nuclearstructure perspective, the formation of a peak in elemental abundance originates in extra stability of local
nuclei. For example, in r-process, the neutron magic
number N = 82 and N = 126 are responsible for theprominent abundance peaks at A ≈ 130 and A ≈ 195,
respectively. Mumpower et al. identiﬁed that the nuclear properties of nuclei at N ≈ 100 are critical to
the rare-earth peak formation.1) In the case of the deformed rare-earth nuclei, a large shell gap between Nilsson single-particle orbitals stabilizes the nuclear shape

2000
1500
1000
500

(17/2+)exp.

PSM PSM
17/2+ 13/2+
p5/2[532]
n7/2[633]
n5/2[523]
6201/2-[521]
7/2+[633]

2500
2000
1500
1000
500

98

5/2-[523]
proton neutronp5/2[532]
n7/2[633]
n1/2[521](13/2+)
exp.

PSM
17/2+

p5/2[532]
PSM n7/2[633]13/2+
n5/2[523]
100

1/2-[521]
7/2+[633]

6205/2-[523]
proton neutron

Fig. 1. Excitation energies of the isomers in (a) 159 Pm and(b) 161 Pm compared with the PSM calculation with themodiﬁed Nilsson parameters.

at large deformation. Several theoretical works havepredicted the existence of the deformed shell gaps at
N ≈ 100.2) Recently, a 6− ν(5/2[523] ⊗ 7/2[633]) state
was discovered in 162 Gd98 ,3) indicating the large shell
gap at N = 98.
The spectroscopic study on neutron-rich rare-earth
nuclei was performed at RIBF using the in-ﬂight ﬁssion of 238 U86+ beam. The delayed γ rays were
measured using a Ge detector array, EURICA.4) Accordingly, we discovered new quasi-particle isomers in
159, 161
Pm98, 100 . The 3-qp isomers involve one quasiproton plus two quasi-neutrons near the Fermi surface
as shown in Fig. 1. A calculation employing the projected shell model (PSM)5) was performed to understand the isomers. The observation of the (17/2+) isomers cannot be explained by the PSM calculation withtraditional Nilsson parameters. We demonstrate thatto explain the observation, the strength of the spinorbit interaction needs to be changed according to theneutron number in exotic nuclei, as suggested by Liu etal.6) Furthermore, we also conﬁrmed that the reported
deformed shell gap at N = 983) is present both in eveneven and odd-mass nuclei.
References
1) M. R. Mumpower et al., Phys. Rev. C 86, 035803 (2012).
2) S. K. Ghorui et al., Phys. Rev. C 85, 064327 (2012).
3) D. J. Hartley et al., Phys. Rev. Lett. 120, 182502 (2018).
4) P. A. Söderström et al., Nucl. Instrum. Methods Phys.
Res. B 317, 649 (2013).
5) Y. Sun, Phys. Scr. 91, 043005 (2016).
6) Y. X. Liu et al., J. Phys. G 47, 055108 (2020).

1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Pairing forces govern population of doubly magic 54 Ca from direct
reactions†
F. Browne,∗1 S. Chen,∗2,∗1,∗3 P. Doornenbal,∗1 A. Obertelli,∗4,∗5,∗1 K. Ogata,∗6,∗7 Y. Utsuno,∗8,9∗ K. Yoshida,∗9and the SEASTAR2017 Collaboration
Despite the shell model calculations showing a signiﬁcant amplitude of excited neutron conﬁgurations in
the ground-state of 55 Sc, removing the π0f7/2 valence
proton populated predominantly the ground-state of54
Ca. This counter-intuitive result is attributed to theoﬀ-diagonal matrix elements of the pairing interaction
leading to a dominance of the ground-state spectroscopic factor.6) Owing to the ubiquity of the pairing
interaction, this argument should be generally applicable to direct knockout reactions from odd-even toeven-even nuclei.

In exotic nuclei, the proton-neutron attraction between orbits of the same angular momentum, but
diﬀerent intrinsic spin directions (j> =  + s andj< =  − s) can aﬀect the evolution of single-particle
energies.1) Tensor-driven shell evolution is responsible
for the emergence of two non-canonical nuclear magic
numbers, N = 34 in 54 Ca2) and N = 16 in 24 O.3) Inthese nuclei a lack of π0f7/2 and π0d5/2 occupation,
respectively, allows their neutron j< orbits to increase
through the absence of the tensor attraction.
Single-proton knockouts from the valence orbital of25
F (24 O plus one proton in π0d5/2 ) have shown a reduction of spectroscopic strength to the ground statecompared to expectation.4) The explanation of thiswas due to the mixing of the neutron conﬁgurations resulting from the tensor attraction between the π0d5/2
and ν0d3/2 orbitals. In 55 Sc (54 Ca plus one proton in
π0f7/2 ), a similar erosion of the N = 34 shell gap isobserved (e.g. Ref. 5)), therefore, a similar reductionof spectroscopic strength as in 25 F might be expected.
A primary beam of 70 Zn of intensity 240 particle nA
was accelerated to 345 MeV/nucleon and underwent
fragmentation on a 10-mm-thick 9 Be target. From thesecondary beam, 55 Sc isotopes were selected and transported to the MINOS LH2 target system where they
underwent knockout reactions at ∼200 MeV/nucleon.
Populated states of 54 Ca were measured through γ-ray
detection with the DALI2+ array, and invariant-mass
spectroscopy through detection of residual nuclei andtheir emitted neutrons in the SAMURAI set-up. Parallel momentum distributions were measured to determine the -value of the knocked out proton.
Level energies were calculated from the nuclear shellmodel employing the GXPF1Br interaction.2) Theoretical cross sections to states were calculated from DWIA
estimates multiplied by shell model spectroscopic factors, which quantify the overlap of the 55 Sc and 54 Ca
wavefunctions. A comparison between the observed
and predicted cross sections is shown in Fig. 1.
†
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9

Fig. 1. (Top panel) Observed cross sections to states following the 55 Sc(p, 2p) reaction. Above Sn the cross sections are shown at the energy centroids of ﬁtted values
and likely represent contributions from several states.
States with conclusive -value assignments are coloredaccordingly, otherwise are black. (Bottom panel) Theoretical predictions of state energies and their population
cross sections. Contributions to cross sections from proton removals from the diﬀerent orbitals are indicated.

References

Condensed from the article in Phys. Rev. Lett. 126, 252501(2021)RIKEN Nishina Center
Department of Physics, University of Hong Kong
State Key Laboratory for Nuclear Physics and Technology,
Peking University
Institut für Kernphysik, Universität Darmstadt
IRFU, CEA, Univerité Paris-Saclay
Research Center for Nuclear Physics, Osaka University
Department of Physics, Osaka City University
Center for Nuclear Study, University of Tokyo
Advanced Science Research Center, Japan Atomic Energy
Agency1) T. Otsuka et al., Rev. Mod. Phys. 92, 015002 (2020).
2) D. Steppenbeck et al., Nature (London) 502, 207(2013).
3) R. Kanungo et al., Phys. Rev. Lett. 102, 152501 (2009).
4) T. L. Tang et al., Phys. Rev. Lett. 124, 212502 (2020).
5) E. Leistenschneider et al., Phys. Rev. Lett. 126, 042501(2021).
6) S. Yoshida, Nucl. Phys. 33, 685 (1962).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Structure of 17 B studied by the quasifree neutron knockout reaction†
Z. H. Yang,∗1,∗2 Y. Kubota,∗2,∗3 A. Corsi,∗4,∗2 K. Yoshida,∗5 X. -X. Sun,∗6,∗7 J. G. Li,∗8 M. Kimura,∗9,∗10,∗1
N. Michel,∗11,∗12 K. Ogata,∗1,∗13 C. X. Yuan,∗14 Q. Yuan,∗8 G. Authelet,∗4 H. Baba,∗2 C. Caesar,∗15 D. Calvet,∗4
A. Delbart,∗4 M. Dozono,∗3 J. Feng,∗8 F. Flavigny,∗16 J. -M. Gheller,∗4 J. Gibelin,∗17 A. Giganon,∗4
A. Gillibert,∗4 K. Hasegawa,∗18 T. Isobe,∗2 Y. Kanaya,∗19 S. Kawakami,∗19 D. Kim,∗20 Y. Kiyokawa,∗2
M. Kobayashi,∗2 N. Kobayashi,∗21 T. Kobayashi,∗18,∗2 Y. Kondo,∗22,∗2 Z. Korkulu,∗20,∗23 S. Koyama,∗21,∗2
V. Lapoux,∗4 Y. Maeda,∗19 F. M. Marqués,∗17 T. Motobayashi,∗2 T. Miyazaki,∗21,∗2 T. Nakamura,∗22,∗2
N. Nakatsuka,∗24,∗2 Y. Nishio,∗25 A. Obertelli,∗4,∗2 A. Ohkura,∗25 N. A. Orr,∗17 S. Ota,∗3 H. Otsu,∗2 T. Ozaki,∗22
V. Panin,∗2 S. Paschalis,∗15 E. C. Pollacco,∗4 S. Reichert,∗26 J. -Y. Roussé,∗4 A. T. Saito,∗22,∗2 S. Sakaguchi,∗25,∗2
M. Sako,∗2 C. Santamaria,∗4 M. Sasano,∗2 H. Sato,∗2 M. Shikata,∗22,∗2 Y. Shimizu,∗2 Y. Shindo,∗25
L. Stuhl,∗20,∗2 T. Sumikama,∗18,∗2 Y. L. Sun,∗4 M. Tabata,∗25 Y. Togano,∗22,∗27,∗2 J. Tsubota,∗22 F. R. Xu,∗8
J. Yasuda,∗25 K. Yoneda,∗2 J. Zenihiro,∗2 S. -G. Zhou,∗6,∗7 W. Zuo,∗11,∗12 and T. Uesaka∗2,∗28
The halo structure of weakly bound nuclei has been
a topic of great interest in recent decades not only as anovel phenomenon in itself, but also provides an important terrestrial model system to study the correlations
and properties of dilute neutron-rich matter.1)
In the present work, we have studied the structureof the halo nucleus 17 B by using the quasi-free (p, pn)reaction. This study concerns a kinematically complete
measurement, combining the high-intensity beams provided by the RIBF and the state-of-the-art detector
instruments including the vertex-tracking liquid hydrogen target MINOS, in-beam γ-ray spectrometer DALI2,
and the SAMURAI spectrometer.2)
Shown in Fig. 1 is the relative-energy (Erel ) spec†

Condensed from the article in Phys. Rev. Lett. 126, 082501(2021)∗1 Research Center for Nuclear Physics, Osaka University∗2 RIKEN Nishina Center∗3 Center for Nuclear Study, University of Tokyo∗4 IRFU, CEA, Université Paris-Saclay∗5 Advanced Science Research Center, Japan Atomic Energy
Agency∗6 Institute of Theoretical Physics, Chinese Academy of Sciences∗7 School of Physical Sciences, University of Chinese Academyof Sciences∗8 School of Physics and SKLNPT, Peking University∗9 Department of Physics, Hokkaido University∗10 Nuclear Reaction Data Centre, Hokkaido University∗11 Institute of Modern Physics, Chinese Academy of Sciences∗12 School of Nuclear Science and Technology, University of Chinese Academy of Sciences∗13 Department of Physics, Osaka City University∗14 Sino-French Institute of Nuclear Engineering and Technology,
Sun Yat-Sen University∗15 Institut für Kernphysik, Technische Universität Darmstadt∗16 IPN Orsay, Université Paris Sud∗17 LPC Caen, Université de Caen Normandie∗18 Department of Physics, Tohoku University∗19 Department of Applied Physics, University of Miyazaki∗20 Center for Exotic Nuclear Studies, Institute for Basic Science∗21 Department of Physics, University of Tokyo∗22 Department of Physics, Tokyo Institute of Technology∗23 Institute for Nuclear Research, Hungarian Academy of Sciences∗24 Department of Physics, Kyoto University∗25 Department of Physics, Kyushu University∗26 Physik Department, Technische Universität München∗27 Department of Physics, Rikkyo University∗28 Cluster for Pioneering Research, RIKEN

Fig. 1. 16 B Erel spectrum ﬁtted with a sum of four resonances (inset is a zoom-in view of the 0–1 MeV region).

trum of 15 B+n. It is well ﬁtted using four 16 B resonances, after considering the experimental acceptanceand resolutions. For each state of 16 B, the transverse
momentum distribution and production cross section
were analyzed by the distorted-wave impulse approximation (DWIA) reaction model.3) And the corresponding 1s1/2 and 0d5/2 spectroscopic factors of the knockout neutron were thus determined, giving a surprisingly
small 1s1/2 component (∼9%) in 17 B.
Our ﬁnding of such a small 1s1/2 component and thepreviously reported halo features in 17 B (e.g., Ref. 4))
can be well explained by the deformed relativistic
Hartree-Bogoliubov theory in continuum (DRHBc),5)
revealing a deﬁnite but not dominant halo component in
17
B. Our result gives the smallest s- or p-orbital component among known nuclei exhibiting halo features andimplies that the dominant occupation of s or p orbitals
is not a prerequisite for the occurrence of halo. The
halo component, whether or not dominant, results in a
distinctive diﬀused surface and, thus, manifests itself inreactions sensitive to the surface properties.
References
1) I. Tanihata et al., Prog. Part. Nucl. Phys. 68, 215 (2013).
2) T. Kobayashi et al., Nucl. Instrum. Methods Phys. Res.
B 317, 294 (2013).
3) T. Wakasa et al., Prog. Part. Nucl. Phys. 96, 32 (2017).
4) A. Estradé et al., Phys. Rev. Lett. 113, 132501 (2014).
5) X. -X. Sun et al., Phys. Lett. B 785, 530 (2018).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Probing the symmetry energy with the spectral pion ratio†
J. Estee,∗1,∗2,∗3 W. G. Lynch,∗2,∗3 C. Y. Tsang,∗2,∗3 J. Barney,∗1,∗2,∗3 G. Jhang,∗1,∗2,∗3 M. B. Tsang,∗2,∗3
R. Wang,∗2 M. Kaneko,∗1,∗4 J. W. Lee,∗1,∗5 T. Isobe,∗1 M. Kurata-Nishimura,∗1 T. Murakami,∗1,∗4 H. Baba,∗1
G. Cerizza,∗1,∗2,∗3 N. Fukuda,∗1 B. Hong,∗5 T. Kobayashi,∗6 P. Lasko,∗7 J. L
 ukasik,∗7 A. B. McIntosh,∗8
∗1
∗7
∗1
∗1,∗2
∗2
H. Otsu, P. Pawlowski, H. Sakurai, C. Santamaria,
R. Shane, D. Suzuki,∗1 S. Tangwancharoen,∗2∗9∗8,∗10∗9
Z. G. Xiao, S. J. Yennello,
Y. Zhang, for the SπRIT Collaboration
and D. Cozma∗2,∗11
Many neutron star properties, such as the proton fraction, reﬂect the symmetry energy contributions to theequation of state that dominate when neutron and proton densities diﬀer strongly. To constrain these contributions at suprasaturation densities, we measure the spectra of charged pions produced by colliding rare isotopetin (Sn) beams of 270 MeV/nucleon with isotopically enriched Sn targets at RIBF.
Light charged particles, including π − and π + , were detected in the SπRIT time projection chamber,1,2) placed
inside the SAMURAI spectrometer.3) Charged particles were identiﬁed by their electronic stopping powers
dE/dx and magnetic rigidities.4) We focus on the mostcentral collisions with the highest charged particle multiplicities while retaining good statistical accuracy, corresponding to impact parameters of b < 3 fm.1)
Using ratios of the charged pion spectra measured
at high transverse momenta, we deduced the symmetry energy constraints of 42 < L < 117 and 32.5 <S0 < 38.1 MeV. We used the dcQMD semiclassicalquantum molecular dynamics model,5) which has provided reasonable predictions of the pion multiplicities
and ratios in the previous publication.6) By interpolating the results of dcQMD calculations (typical examples are shown in Fig. 1) with various values for
L and Δm∗np , i.e. the scaled diﬀerence between neutron and proton eﬀective masses, we ﬁt the single ratios
SR(π − /π + ) = [dM (π − )/dpT ]/[dM (π + )/dpT ] for boththe neutron rich 132 Sn+124 Sn system and the nearly
symmetric 108 Sn+112 Sn system at pT > 200 MeV/c,
where we could avoid complications arising from poorly
determined Δ baryon potentials. The results suggest
a representative symmetry pressure of Psym = 12 ±10 MeV/fm3 at ρ/ρ0 = 1.5. These L values are smaller
than the values L = 206 ± 37 and S0 = 38.3 ± 4.7 MeV
7)extracted from a new measurement of the neutron skin
thickness of 208 Pb,8) but close to the values 70 < L < 101†

Condensed from the article in Phys. Pev. Lett. 126, 162701(2021)∗1 RIKEN Nishina Center∗2 National Superconducting Cyclotron Laboratory, Michigan
State University∗3 Department of Physics, Michigan State University∗4 Department of Physics, Kyoto University∗5 Department of Physics, Korea University∗6 Department of Physics, Tohoku University∗7 Institute of Nuclear Physics PAN∗8 Cyclotron Institute, Texas A&M University∗9 Department of Physics, Tsinghua University∗10 Department of Chemistry, Texas A&M University∗11 Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering

Fig. 1. Single pion spectral ratios for 132 Sn + 124 Sn (top) and108
Sn + 112 Sn (bottom) reactions. The curves are dcQMD
predictions from diﬀerent L and Δm∗np values listed in thebottom panel. Taken from the published article.†and 33.5 < S0 < 36.4 MeV9) extracted from charge exchange reactions and elastic scattering.
References
1) J. Barney et al., Rev. Sci. Instrum. 92, 063302 (2021).
2) R. Shane et al., Nucl. Instrum. Methods Phys. Res. A
784, 513 (2015).
3) H. Otsu et al., Nucl. Instrum. Methods Phys. Res. B 376,
175 (2016).
4) J. Lee et al., Nucl. Instrum. Methods Phys. Res. A 965,
163840 (2020).
5) M. D. Cozma, M. B. Tsang, Eur. Phys. J. A 57, 309(2021).
6) G. Jhang et al., Phys. Lett. B 813, 136016 (2021).
7) B. T. Reed et al., Phys. Rev. Lett. 126, 172503 (2021).
8) D. Adhikari et al., Phys. Rev. Lett. 126, 172502 (2021).
9) P. Danielewicz et al., Nucl. Phys. A 958, 147 (2017).

- S11 -

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Rapidity distributions of Z = 1 isotopes and the nuclear symmetryenergy from Sn + Sn collisions with radioactive beams at
270 MeV/nucleon†
M. Kaneko,∗1,∗2 T. Murakami,∗1,∗2 T. Isobe,∗1 M. Kurata-Nishimura,∗1 A. Ono,∗3 N. Ikeno,∗4 J. Barney,∗5
G. Cerizza,∗5 J. Estee,∗5 G. Jhang,∗5 J. W. Lee,∗6 W. G. Lynch,∗5 C. Santamaria,∗5 C. Y. Tsang,∗5
M. B. Tsang,∗5 R. Wang,∗5 D. S. Ahn,∗1,∗7 L. Atar,∗8,∗9 T. Aumann,∗8,∗9 H. Baba,∗1 K. Boretzky,∗9
J. Brzychczyk,∗10 N. Chiga,∗1 N. Fukuda,∗1 I. Gašparić,∗11 B. Hong,∗6 A. Horvat,∗8,∗9 T. Ichihara,∗1 K. Ieki,∗12
N. Inabe,∗1 Y. J. Kim,∗13 T. Kobayashi,∗3,∗1 Y. Kondo,∗14,∗1 P. Lasko,∗15 H. S. Lee,∗13 Y. Leifels,∗9J. Łukasik,∗15 J. Manfredi,∗5 A. B. McIntosh,∗16 P. Morfouace,∗5 T. Nakamura,∗14,∗1 N. Nakatsuka,∗14,∗1
S. Nishimura,∗1 R. Olsen,∗16 H. Otsu,∗1 P. Pawłowski,∗15 K. Pelczar,∗17 D. Rossi,∗9 H. Sakurai,∗1 H. Sato,∗1
H. Scheit,∗8 R. Shane,∗5 Y. Shimizu,∗1 H. Simon,∗9 T. Sumikama,∗1 D. Suzuki,∗1 H. Suzuki,∗1 H. Takeda,∗1
S. Tangwancharoen,∗5 Y. Togano,12,∗14,∗1 H. Törnqvist,∗8,∗9 Z. Xiao,∗18 S. J. Yennello,∗16,∗19 J. Yurkon,∗5 andY. Zhang∗18 for the SπRIT Collaboration'5GS  GS  GS 6Q6Q

6Q6Q'5WS  WS  WS 6Q6Q

6Q6Q



'5GS

†

Condensed from the article in Phys. Lett. B 822, 136681(2021)∗1 RIKEN Nishina Center∗2 Department of Physics, Kyoto University∗3 Department of Physics, Tohoku University∗4 Department of Life and Environmental Agricultural Sciences, Tottori University∗5 NSCL and Department of Physics and Astronomy, Michigan
State University∗6 Department of Physics, Korea University∗7 Korea Basic Science Institute∗8 Institut für Kernphysik, Technische Unicersität Darmstadt∗9 GSI Helmholtzzentrum für Schwerionenforschung GmbH
∗10 Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University∗11 Division of Experimental Physics, Ruđer Bošković Institute∗12 Department of Physics, Rikkyo University∗13 Rare Isotope Science Project, Institute for Basic Science∗14 Department of Physics, Tokyo Institute of Technology∗15 Institute of Nuclear Physics, Polish Academy of Sciences∗16 Cyclotron Institute, Texas A&M University∗17 INFN-Laboratori Nazionali del Gran Sasso∗18 Department of Physics, Tsinghua University∗19 Department of Chemistry, Texas A&M University- S12 -

'5WS

Heavy-ion collisions at intermediate energies provide
a unique laboratory probe for the nuclear symmetryenergy at suprasaturation densities. A copious production of light cluster nuclei is one of the distinctive characteristics in this energy domain, and needs
to be understood for reliably extracting the symmetryenergy.1) This is because an explicit consideration ofcluster correlations in the collision dynamics may inﬂuence physical quantities sensitive to the stiﬀness ofthe symmetry energy, such as the neutron-proton dynamics and the consequent charged pion ratio.2) Thus,
we measured the rapidity distributions of hydrogen isotopes emitted from head-on collisions of 132 Sn + 124 Sn
and 108 Sn + 112 Sn systems at 270 MeV/nucleon with
the SπRIT time projection chamber3) installed inside
the SAMURAI magnet at RIBF.
The experimental results are compared with theantisymmetrized molecular dynamics (AMD) calculations, and the measured rapidity distributions canbe reasonably reproduced by the model after adjusting the in-medium two-nucleon cross section and the




([SGDWD$0'/ 0H9$0'/ 0H9


−






−





\  \ \FP 
11

Fig. 1. Double ratio for the cluster-to-proton relative yieldin the 132 Sn + 124 Sn system divided by that in the108
Sn + 112 Sn, and the AMD predictions for two casesof the symmetry energy. Left: the deuteron-to-proton
double ratio (DRd/p ). Right: the triton-to-proton double ratio (DRt/p ).

bound phase space for A = 2, 3 clusters. To investigate the dependence on the symmetry-energy stiﬀness,
two cases of the symmetry energy with slope parameters L = 46 MeV and L = 108 MeV were assumed in
calculations. Figure 1 presents the deuteron-to-proton
and triton-to-proton double spectral ratios (DRd/p andDRt/p ) together with the AMD predictions. A positive slope of the rapidity-dependent double ratios indicates a partial isospin mixing between the projectile
and target nuclei. As shown in the right panel of Fig. 1,
the experimental DRt/p supports the calculation with
L = 46 MeV, rather than L = 108 MeV. The adjustments applied in calculations do not signiﬁcantly inﬂuence DRt/p , and its symmetry-energy dependence.
To constrain the symmetry energy more accurately, amore comprehensive set of data including global observables, e.g., collective ﬂows, will be analyzed, anda comparison with diﬀerent models for deducing theoretical uncertainties is desired.
References
1) A. Ono et al., EPJ Web Conf. 117, 07003 (2016).
2) N. Ikeno et al., Phys. Rev. C 97, 066902(E) (2018).
3) J. Barney et al., Rev. Sci. Instrum. 92, 063302 (2021).

1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Estimation of radiative half-life of 229m Th by half-life measurement ofother nuclear excited states in 229 Th†
Y. Shigekawa,∗1 A. Yamaguchi,∗2,∗3 K. Suzuki,∗4 H. Haba,∗1 T. Hiraki,∗4 H. Kikunaga,∗5 T. Masuda,∗4
S. Nishimura,∗1 N. Sasao,∗4 A. Yoshimi,∗4 and K. Yoshimura∗4
The ﬁrst excited state in the 229 Th nucleus (229m Th)
has an excitation energy of ∼8 eV.1–4) This low-lying isomeric state allows the laser excitation and spectroscopyof the nucleus, potentially leading to an ultraprecise optical nuclear clock.5) This radiative half-life of 229m Th,
which determines the natural linewidth of the nuclear
transition between the ground state and 229m Th, is an
important parameter to estimate the performance of thenuclear clock. The radiative half-life has yet to be determined experimentally; however, it can be estimated fromthe reduced transition probabilities B(Xλ) of the interband transitions between the 5/2+ [633] and 3/2+ [631]rotational bands beginning with higher excited states
than 229m Th by applying the Alaga rule.6) The Alaga
rule states that the ratio of two B(Xλ) values for a pairof intra- or inter-band transitions equals the ratio of thesquares of Clebsch-Gordan coeﬃcients based on the assumption of the separable rotational motion of a nucleus.
In this study, we measured the half-lives of the excitedstates in the 5/2+ [633] and 3/2+ [631] bands to determine
the B(Xλ) values required to estimate the radiative halflive of 229m Th.
To determine the half-lives, we performed a coincidence measurement between γ rays and α particles emitted from a 233 U source, as described in Ref. 7). First, we
obtained the time trace of the 42.43-keV γ rays following the 4783.5-keV α particles (see Fig. 1 in this paper
and Fig. 2 in Ref. 7)). By ﬁtting a single exponential
decay function convoluted with a Gaussian function to
the time trace, the half-life of the 42.43-keV state wasdetermined to be 169(4) ps, which is consistent with thevalue of 172(6) ps reported previously.8) Next, we performed ﬁtting to the time trace of the 54.70-keV γ rays
following the 4729-keV α particles, yielding a half-life of103(12) ps. Moreover, by selecting the 97.14-keV γ rays,
we obtained a half-life of 88(9) ps. From the weighted average of these values, the half-life of the 97.14-keV state
was determined to be 93(7) ps. In the same manner, thehalf-life of the 71.82- and 163.25-keV states were determined for the ﬁrst time to be 120(40) and 220(30) ps by
ﬁtting to the time traces of the 71.82- and 66.12-keV γ
rays following the 4754-keV and 4664-keV α particles,
respectively.
We derived the B(Xλ) values using the obtained halflives, experimental γ branching ratios,1,9,10) mixing ra†
∗1
∗2
∗3
∗4
∗5

Condensed from the article in Phys. Rev. C 104, 024306 (2021)
RIKEN Nishina Center
Quantum Metrology Laboratory, RIKENPRESTO, Japan Science and Technology Agency
Research Institute for Interdisciplinary Science, Okayama University
Research Center for Electron-Photon Science, Tohoku University

Fig. 1. Energy levels of the 229 Th nucleus grouped into rotational bands, as well as the α and γ transitions used
for determining the half-lives of the excited states (units:keV).

tios,9,10) and internal conversion coeﬃcients.10,11) First,
for the intra-band transitions, we found that the B(M1)and B(E2) values of the transitions starting with the29.19-, 42.43-, 71.83-, and 97.14-keV states were consistent with the values estimated from the Alaga rule.
By contrast, for the transitions starting with the 163.25keV state, the B(M1) and B(E2) values deviated fromthe estimation based on the Alaga rule, as it often appears with increasing nuclear spins. Next, to investigate
the validity of the Alaga rule for the inter-band transitions, we calculated the B(M1; 229m Th→229g Th) values
from the B(M1) values of the 29.19→0, 71.83→42.43,
and 97.14→71.83 keV transitions based on the Alaga
rule. The values obtained from the 29.19→0 and
71.83→42.43 keV transitions agreed with each other(0.014(4) and 0.013(4) μN 2 , respectively). This indicatesthat the contribution of the Coriolis interactions is insigniﬁcant and the Alaga rule is applicable for the interband transitions between those low-spin states. The
weighted average of B(M1; 229m Th→229g Th) obtained
from these transitions was 0.014(3) μN 2 , from which
we estimated the radiative half-life of 229m Th to be
5.0(11) × 103 s.
References
1) B. R. Beck et al., Phys. Rev. Lett. 98, 142501 (2007).
2) B. Seiferle et al., Nature 573, 243 (2019).
3) A. Yamaguchi et al., Phys. Rev. Lett. 123, 222501 (2019).
4) T. Sikorsky et al., Phys. Rev. Lett. 125, 142503 (2020).
5) E. Peik, C. Tamm, Europhys. Lett. 61, 181 (2003).
6) G. Alaga et al., Dan. Mat. Fys. Medd. 29 (No.9), 1 (1955).
7) Y. Shigekawa et al., RIKEN Accel. Prog. Rep. 53, 51(2020).
8) H. Ton et al., Nucl. Phys. A 155, 245 (1970).
9) V. Barci et al., Phys. Rev. C 68, 034329 (2003).
10) T. Masuda et al., Nature 573, 238 (2019).
11) E. Browne, J. K. Tuli, Nucl. Data Sheets 109, 2657
(2008).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Toward ab initio charge symmetry breaking in nuclear energy density
functionals†
T. Naito,∗1,∗2 G. Colò,∗3,∗4 H. Z. Liang,∗1,∗2 X. Roca-Maza,∗3,∗4 and H. Sagawa∗5,∗2

†
∗1
∗2
∗3
∗4
∗5

Condensed from the article in Phys. Rev. C 105, L021304(2022)
Department of Physics, University of Tokyo
RIKEN Nishina Center
Dipartimento di Fisica, Università degli Studi di Milano
INFN, Sezione di Milano
Center for Mathematics and Physics, University of Aizu

−60.0
−62.5

ΔEtot (MeV)

The parameter sets of energy density functionals(EDFs) of the nuclear density functional theory (DFT)
are commonly determined phenomenologically to reproduce experimental masses and charge radii as well as
nuclear matter properties. To establish a link between
microscopic approaches and EDFs, an ab initio determination of the parameters of EDFs, as well as theirfunctional forms, is highly desired. To date, however,a direct correspondence between ab initio and DFT remains elusive. A sophisticated yet practical approachto pin down the EDF parameters is to combine the abinitio and phenomenological EDF calculations.
Even though the isospin symmetry breaking (ISB)
terms are small parts of the nuclear interaction, eﬀects
of the ISB terms on nuclear properties have received attention, while the ISB terms have often been neglected
in EDFs. The ISB interaction can be divided into twoparts: the charge symmetry breaking (CSB) and thecharge independence breaking (CIB) interactions.
Our aim in this study is to propose a comprehensive
methodology to determine the CSB terms in nuclear
EDFs adopting the ab initio results. We implement
the ISB terms in a Skyrme EDF to demonstrate ourmethodology. We will show that the mass diﬀerenceof mirror nuclei ΔEtot and the neutron-skin thickness
ΔRnp of doubly-magic nuclei calculated by ab initio
methods without and with the CSB terms, once they
are available, enable us to determine the CSB strength
in the EDF with an uncertainty of less than 6%, independently from other ISB forces such as CIB and
Coulomb forces.
The Skyrme-like CSB and CIB interactions read1)
τ1z + τ2z
s0 (1 + y0 Pσ ) δ (r1 − r2 ) ,vCSB (r1 , r2 ) =4(1a)
τ1z τ2z
u0 (1 + z0 Pσ ) δ (r1 − r2 ) , (1b)vCIB (r1 , r2 ) =2respectively, where τiz is the z-direction of the isospin
operator of nucleon i (i = 1, 2) and Pσ is the spinexchange operator. For simplicity, in the SAMi-ISB
EDF,2) y0 = z0 = −1 are chosen to select the spinsinglet channel. The CIB strength u0 = 25.8 MeV fm3
has been previously determined using the Brueckner
Hartree-Fock calculation of symmetric nuclear matter.2,3) The CSB strength s0 = −26.3 MeV fm3 has

48Ca-48Ni

−65.0
−67.5

SLy4
SLy5
SkM*
SAMi
SAMi-noISB
SAMi-CIB
SAMi-ISB

−70.0
−72.5
−75.0
−77.5
−80.0

0

10

20

30

−s0 (MeV fm3)

40

50

Fig. 1. Dependence of mass diﬀerence of mirror nuclei 48 Ca
Ca48
Ni48
and 48 Ni, ΔEtot = Etot
− Etot, on CSB strength s0 .

been determined to reproduce the isobaric analog energy of 208 Pb.2) In this study, as u0 has been alreadydetermined microscopically, we propose a way to determine s0 microscopically. Because the isobaric analog
energy is not available using ab initio methods at thismoment, we focus on alternative well-established observables: the nuclear radius and mass, which are moreeasily accessible than any ab initio method.
The dependence of the mass diﬀerence of mirror nuCa48
Ni48− Etot, on the CSB
clei 48 Ca and 48 Ni, ΔEtot = Etot
strength s0 is shown in Fig. 1. For comparison, results
calculated with the original SAMi-ISB and experimental data (AME2020) are also shown using crosses andhorizontal lines, respectively. Remarkably, one can notethat ΔEtot has a strong linear correlation to the CSB
strength s0 , and the correlation is universal among thefunctionals. Thus, the calculated results are ﬁtted to
ΔEtot = a − bs0 . As seen in the ﬁgure, s0 and ΔEtot
are highly correlated (r = 1.000), and the slope b isalmost universal among Skyrme EDFs. Note that theparameters a and b are determined with a 0.5% error.
Accordingly, among these functionals, the slope b deviates within 6% around the average value of b. Thus,
once the ab initio results for ΔEtot calculated withw/o CSB
andout and with the bare CSB interaction, ΔEtot
w/ CSB
ΔEtot, are obtained, using b, wecan determine s0
w/ CSB
w/o CSBas −s0 = ΔEtot− ΔEtot/b. As the uncertainty of b is 6%, the expected uncertainty of s0
is also 6%, assuming that the uncertainty associatedwith the ab initio calculations is negligible.
References
1) H. Sagawa et al., Phys. Lett. B 353, 7 (1995).
2) X. Roca-Maza et al., Phys. Rev. Lett. 120, 202501(2018).
3) H. Müther et al., Phys. Lett. B 445, 259 (1999).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Total reaction cross sections in the island of inversion near N = 40†
W. Horiuchi,∗1,∗2 T. Inakura,∗3 and S. Michimasa∗4

0.35
0.3

|β2|

0.25

Ti
Cr
Fe

0.2
0.15
0.1
0.05
0
0.2

β4

0.15
0.1
0.05
0
30

32

34

36

38

40

42

Neutron number
Fig. 1. Quadrupole (β2 ) and hexadecapole (β4 ) deformation
parameters of Ti, Cr, and Fe isotopes calculated with
SkM∗ (closed symbols with solid lines) and SLy4 (opensymbols with dashed lines).
†
∗1
∗2
∗3
∗4

Condensed from the article in Phys. Rev. C 105, 014316(2022)
Department of Physics, Hokkaido University
Department of Physics and NITEP, Osaka Metropolitan University
Laboratory for Zero-Carbon Energy, Tokyo Institute of Technology
Center for Nuclear Study, University of Tokyo

1950
Ti

1900
1850

σR (mb)A systematic analysis of the deformation phenomena of Ti, Cr, and Fe isotopes is performed to understand the nuclear structure in the “island of inversion”1)near the neutron number N = 40. As large nuclear
deformations are expected in this mass region, we describe various nuclear deformations using the SkyrmeHartree-Fock method in the three-dimensional coordinate space.2) A detailed analysis of the obtained nuclear
structure information not only the quadrupole deformation but also the hexadecapole deformation increases signiﬁcantly in the island of inversion. This is because of
the excess neutrons occupying elongated intruder orbits.
This characteristic is manifested as a change in the density distribution at the nuclear surface and can be observed as a signiﬁcant increase in the total reaction crosssection (σR ).
Figure 1 plots the quadrupole (β2 ) and hexadecapole(β4 ) deformation parameters of Ti, Cr, and Fe isotopes
as a function of the neutron number N . The results with

Cr
Fe

1800
1750
1700

240 AMeV

1650
1600
30

32

34

36

38

40

42

Neutron number
Fig. 2. Total reaction cross sections of Ti, Cr, and Fe isotopes
calculated with SkM∗ (closed symbols with solid lines)
and SLy4 (open symbols with dashed lines).

two Skyrme density functionals, SkM∗3) and SLy4,4)
are shown. SkM∗ predicts large quadrupole deformation for N > 34, which is consistent with empirical |β2 |values found in Ref. 5), while the SLy4 results showless deformed ground states for those isotopes. We
ﬁnd that the hexadecapole deformation also enhances
for N > 34 with SkM∗ owing to the occupation of the[nnz Λ]Ω = [330]1/2 Nillson orbit, where the hexadecapole moment becomes the largest for the most prolately elongated orbitals among the orbits belonging to
the same n, i.e., for n = nz and Λ = 0.
These diﬀerent deformations are well reﬂected in thedensity proﬁles near the nuclear surface and can be distinguished by total reaction or interaction cross section
measurements. Figure 2 displays the calculated σR on acarbon target at 240 MeV/nucleon of these nuclei. The
cross sections with SkM∗ are signiﬁcantly larger thanthose obtained with SLy4 for N = 36–40, where themagnitudes of the nuclear deformations are quite diﬀerent. The diﬀerence is at most approximately 2%, which
is signiﬁcant considering the precision of recent interaction cross section measurements was  1%.6) Such asystematic cross section measurement is desired to clarify the nuclear properties in the island of inversion nearN = 40.
References
1) E. K. Warburton et al., Phys. Rev. C 41, 1147 (1990).
2) T. Inakura et al., Nucl. Phys. A 768, 61 (2006).
3) J. Bartel et al., Nucl. Phys. A 386, 79 (1982).
4) E. Chanbanat et al., Nucl. Phys. A 627, 710 (1997).
5) B. Pritychenko et al., At. Data Nucl. Data Tables 107, 1(2016).
6) M. Tanaka et al., Phys. Rev. Lett. 124, 102501 (2020).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Asymmetry of antimatter in the proton†
Y. Goto,∗1 S. Miyasaka,∗2 K. Nagai,∗2 F. Sanftl,∗2 Y. Kudo,∗3 Y. Miyachi,∗3 K. Nakano,∗1,∗2 S. Nara,∗3
S. Sawada,∗4 and T. -A. Shibata∗1,∗2 for the SeaQuest Collaboration

†
∗1
∗2
∗3
∗4

Condensed from the article in Nature 590, 561 (2021)
RIKEN Nishina Center
Department of Physics, Tokyo Institute of Technology
Department of Physics, Yamagata University
Institute of Particle and Nuclear Studies, KEK- S16 -

2.5

2

SeaQuest/E906
Syst. uncert.
NuSea/E866
NA51

1.5
d/ u

The structure of the proton is a prototypical example of a strongly coupled and correlated systemwith quarks and gluons interacting according to quantum chromodynamics (QCD). An essential feature of
QCD is its ability to create matter-antimatter quark
pairs inside the proton that exist only for a very shorttime. Their ﬂeeting existence makes the antimatter
quarks within protons diﬃcult to study, but their existence is discernible in reactions in which a matterantimatter quark pair annihilates. In this picture ofquark-antiquark creation by the strong force, the probability distributions as a function of momentum forthe presence of up and down antimatter quarks shouldbe nearly identical, given that their masses are very
similar and small compared to the mass of the proton.1) Here, we provide evidence from muon-pair production measurements that these distributions are considerably diﬀerent, with down antimatter quarks moreabundant than up antimatter quarks over a wide rangeof momenta.
In the Drell-Yan process in hadron-hadron collisions,a quark and an antiquark annihilate into a virtual photon, which decays into a lepton-antilepton pair.2) The
ratio of the Drell-Yan cross-section on a deuterium target to that on a hydrogen target has a direct sensitivity¯¯ are the distributions
to d(x)/ū(x),where ū(x) and d(x)of up and down antiquarks in the proton, respectively,
as a function of the fractional momentum (x) of the¯ from the Drell-Yan process wasproton. The ratio d/ūﬁrst reported by NA51 at CERN.3) This result is consistent with the down antiquark dominance reported
in deep inelastic scattering by NMC at CERN.4) The
Fermilab NuSea experiment5) was able to measure thex dependence of the down antiquark dominance withan 800-GeV proton beam in the kinematic range of
0.015 < x < 0.35.
The Fermilab SeaQuest experiment was designed toinvestigate the ﬂavour asymmetry at higher x values
than NuSea with the newly constructed experimental apparatus. With a proton beam at an energy of
120 GeV, liquid hydrogen and deuterium targets, anda focusing magnet of 10 Tm after the target region, theexperiment was optimized for the study of target antiquarks in the intermediate region, with x around 0.3,
by detecting muon (μ+ μ− ) pairs from decays of thevirtual photons produced in the Drell-Yan process.
¯Figure 1 shows the ratios d(x)/ū(x)in the proton

1
Alberg and Miller
0.5
Basso, Bourrely, Pasechnik and Soffer
0
0

0.1

0.2

0.3

0.4

x

¯
Fig. 1. Ratios d(x)/ū(x).

(red ﬁlled circles) with their statistical (vertical bars)
and systematic (yellow boxes) uncertainties extracted
from the present data based on next-to-leading-order
calculations of the Drell-Yan cross-sections. Also
shown are the results obtained by the NuSea experiment (open black squares) with statistical and systematic uncertainties added in quadrature. The trends
between the two experiments at higher x are quite different. No explanation has been found yet for these
diﬀerences. The horizontal bars on the data points
indicate the width of the bins.
The present data are reasonably described by thepredictions of the statistical parton distributions of
Basso et al.6) (green band) and by the chiral eﬀective perturbation theory of Alberg & Miller7) (cyanband), which are also shown in Fig. 1. These two calculations emphasize rather diﬀerent non-perturbative¯
mechanisms that lead to the diﬀerences in d(x)andū(x). The present data show that d¯ is greater thanū for the entire x range measured in this experiment.
This provides important support for these and othernon-perturbative mechanisms of the QCD structure of
the proton that were disfavoured by the NuSea results.
References
1) D. A. Ross, C. T. Sachrajda, Nucl. Phys. B 149, 497(1979).
2) S. D. Drell, T. M. Yan, Phys. Rev. Lett. 25, 316 (1970);
erratum 25, 902 (1970).
3) A. Baldit et al., Phys. Lett. B 332, 244 (1994).
4) P. Amaudruz et al., Phys. Rev. Lett. 66, 2712 (1991);
M. Arneodo et al., Phys. Rev. D 50, R1 (1994).
5) R. S. Towell et al., Phys. Rev. D 64, 052002 (2001).
6) E. Basso et al., Nucl. Phys. A 948, 63 (2016).
7) M. Alberg, G. A. Miller, Phys. Rev. C 100, 035205(2019).

1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Gluon EMC eﬀects in nuclear matter†
X. -G. Wang,∗1 W. Bentz,∗2 I. C. Cloët,∗3 and A. W. Thomas∗1
The European Muon Collaboration (EMC) eﬀect,
which refers to the observation that spin-independent
structure functions of nuclei diﬀer from the naive sumof structure functions of their constituents, is still
one of the most challenging topics in modern nuclear
physics. Previous calculations1) have demonstrated
that the Nambu-Jona-Lasinio (NJL) model, when used
as an eﬀective quark theory of QCD to describe thequark substructure of hadrons, successfully reproduces
the unpolarized EMC data across the periodic table.
The key mechanism is the in-medium modiﬁcation of
the quark substructure of nucleons arising from scalarand vector mean ﬁelds acting on the quarks. The same
framework was used to predict a signiﬁcant medium
modiﬁcation of the polarized structure functions - thepolarized EMC eﬀect. An experiment at Jeﬀerson Lab
is planned to measure this eﬀect.2)
While the EMC eﬀects associated with the quark
content of nuclei have been investigated extensively,
there have been very few studies of the nuclear modiﬁcation of the gluon distribution or the “gluon EMC
eﬀect.” Exploring such changes is one of the primaryscientiﬁc goals of the planned Electron-Ion-Collider(EIC). In this work we focus on the gluon EMC effect within the framework of the NJL model and the
QCD evolution of parton distributions. By evolving
our medium modiﬁed quark distributions from the NJL
model scale (Q20 = 0.16 GeV2 ) to a scale of Q2 =5 GeV2 by using the QCD evolution code of Ref. 3)
in next-to-leading order (NLO) and next-to-next-toleading order (NNLO), we generate the medium modiﬁed gluon distributions.
The solid lines in Figs. 1 and 2 show our previous reA/F2N and thesults for the unpolarized EMC ratio F2NApolarized EMC ratio g1p /g1p in nuclear matter. HereF2N is the average of proton and neutron unpolarizedA
is the samestructure functions in vacuum while F2N
quantity in nuclear matter, and g1p is the polarizedA
structure function of the proton in vacuum while g1p
is the same quantity in nuclear matter. The dashedlines in Figs. 1 and 2 show the ratio gpA /gp for theunpolarized case and ΔgpA /Δgp for the polarized case.
Here gp (Δgp ) is the unpolarized (polarized) gluon distribution in the proton in vacuum while gpA (ΔgpA ) is
the same quantity in nuclear matter.
It is clear from the ﬁgures that our analysis predicts for the ﬁrst time a sizable gluon EMC eﬀect, bothfor the unpolarized and the polarized case. We ﬁnallymention two points: First, our evolved NJL model re†
∗1
∗2
∗3

Condensed from the article by J. Phys. G 49, 03TL01 (2022)
Department of Physics, University of Adelaide
Department of Physics, Tokai University
Physics Division, Argonne National Laboratory- S17 -

Fig. 1. Unpolarized EMC ratios in nuclear matter for the
structure functions (solid line) and the gluon distributions (dashed line) as functions of the Bjorken variable
x in NLO. The empirical data points are from Ref. 4).

Fig. 2. Polarized EMC ratios in nuclear matter for the
structure functions (solid line) and the gluon distributions (dashed line) as functions of x in NLO.

sults for all quark and gluon distributions agree very
well with the phenomenological results of the NNPDF
Collaboration.5) Therefore the assumption that at the
NJL model scale the gluons are frozen into the interactions between quarks is not unreasonable. Second, we
obtain almost the same results by using the Q2 evolution in NLO and NNLO. This reﬂects the fact thatαs /4π, which is the relevant parameter for Q2 evolution, is suﬃciently small to apply perturbative QCD
to models based on quark degrees of freedom.
References
1) I. C. Cloët et al., Phys. Lett. 642, 210 (2006).
2) The EMC Eﬀect in Spin Structure Functions, https://www.jlab.org/exp_prog/proposals/14/PR12-14-001.
pdf .
3) V. Bertone et al., Comput. Phys. Commun. 185, 1647
(2014).
4) I. Sick, D. Day, Phys. Lett. 274, 16 (1992).
5) R. D. Ball et al., J. High Energy Phys. 2015, 40 (2015);
E. R. Nocera et al., Nucl. Phys. B 887, 276 (2014).

1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production of highly charged calcium-ion beam using
high-temperature oven
T. Nagatomo,∗1 Y. Higurashi,∗1 J. Ohnishi,∗1 and T. Nakagawa∗1
The calcium-48-ion beam is one of the indispensable
beams for studying light nuclei with excess neutrons.
Before the upgrade of RILAC with superconducting(SC) acceleration cavities1) to provide calcium (Ca)beams for experiments at RIBF, a Ca11+ beam was
extracted from a normal-conducting electron-cyclotronresonance ion source (ECRIS) with a low-temperatureoven as an evaporator of Ca,2) accelerated by RILAC,
following which a Ca16+ beam was produced througha carbon-foil charge stripper. However, due to the upgrade of RILAC, the charge stripper is no longer available, because the materials sputtered from the stripper
into the beam pipe are adsorbed on the cryogenic surface of SC cavities, resulting in a serious reduction in
the acceleration voltage. Meanwhile, the ECRIS for
RILAC was also upgraded with the SC technology, andthe performance of the ion source has been improved
signiﬁcantly. Therefore, we conducted a test to directly
extract Ca16+ ions from the new SC-ECRIS.
It is also necessary to reduce the consumption of the
Ca sample as much as possible because of the recent
worldwide shortage of 48 Ca samples. Various ovens
to evaporate Ca2–4) were developed worldwide, but weselected a high-temperature oven (HTO)5) because it
was able to achieve a high enough temperature to directly decompose the CaO sample. We tested whether
a Ca16+ beam of suﬃcient intensity can be obtainedwith a small Ca consumption using the HTO as theevaporator.
The experiment was conducted using an SC-ECRIS
for RILAC (R28G-K).6,7) The magnetic mirror was set
to the same ﬁeld as that for the uranium-beam production, which is suitable for producing multiply charged
ion beams. An ion-extraction voltage of 9.99 kV wasapplied to ﬁt to the case of 48 Ca-ion acceleration. A
tablet-shaped CaO (natural Ca) sample, which was calcined at 1000◦ C for 2 h in the ambient atmosphere, wasplaced directly into a tungsten crucible of HTO, which
was surrounded by a molybdenum heat shield. In addition, by calcining with an HTO heating power below
200 W for 6 h in vacuum (∼ 10−4 Pa) in R28G-K, H2 O
and CO2 , which were contained in the CaO sample,
were completely eliminated.
High-intensity 40 Ca16+ -ion beams were successfully
extracted from R28G-K as a function of the total powerof microwaves at frequencies of 18 and 28 GHz to heat
the ECR plasma, as shown in Fig. 1. The ECR plasma
was stabilized by the O2 support gas. The heating
power of HTO (PHTO ) was changed from 300 W to
720 W, and the corresponding consumption rates (C.R.)∗1

RIKEN Nishina Center

Fig. 1. Obtained 40 Ca16+ -beam currents as a function of
the total power of the 18- and 28-GHz microwaves. The
red, black, and blue points show HTO heating powers of
600, 660, and 720 W, respectively.

are summarized in Table 1. The results clearly indicate that C.R. depends on the transmission eﬃciency
through the accelerators and the beam lines, and we expect to provide a Ca-ion beam of more than 0.5 particle
μA on the target with a Ca consumption of 0.5 mg/h.
Furthermore, we plan to study other support gases suchas N2 and diﬀerent crucible shapes to improve the ionization eﬃciency to reduce the Ca consumption further.
Table 1. Total consumption of the CaO sample ΔW as afunction of the HTO heating power PHTO and the operation time Δt. The consumption rate (C.R.) was estimated from the ratio of the atomic weights of Ca andO.
PHTO (W) Δt(hours) ΔW (CaO, mg) C.R.(Ca, mg/h)
300.
167.0
6.
0.03
600.
71.3
23.
0.23
660.
40.6
29.
0.51
720.
18.6
20.
0.78

References
1) N. Sakamoto et al., Proc. SRF2019, Dresden, Germany,(2019), pp. 750–757.
2) K. Ozeki et al., Rev. Sci. Instrum. 86, 016114 (2015).
3) D. Wutte et al., Rev. Sci. Instrum. 73, 521 (2002).
4) J. Y. Benitez et al., Rev. Sci. Instrum. 85, 02A961(2014).
5) J. Ohnishi et al., Proc. ECRIS2018, Catania, Italy,(2018), p. 180.
6) T. Nagatomo et al., Rev. Sci. Instrum. 91, 023318 (2020).
7) G. D. Alton et al., Rev. Sci. Instrum. 65, 775 (1994).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

First transport of unstable nuclei into SCRIT system
Y. Abe,∗1 T. Ohnishi,∗1 S. Ichikawa,∗1 A. Enokizono,∗1,∗2 R. Ogawara,∗1,∗3 K. Tsukada,∗1,∗3 H. Wauke,∗1,∗4
M. Watanabe,∗1 and M. Wakasugi∗1,∗3

6

Rate at 1W [atoms/s]

10

5

137

138

139

140

141

Mass number

Fig. 1. Isotope dependence of rate of Cs. Electron beam
power is approximately 1 W. Total amount of uranium
is 28 g.
∗2
∗3
∗4

400
300
200
100
0
-100
-1

-0.5

0

0.5

1

1.5

2

Time [ms]Fig. 2. Signal of 137 Cs beam at position monitor located at
entrance of SCRIT device.

References

4

10

3

∗1

500

The ERIS is almost ready for the world’s ﬁrst electron
scattering experiment with unstable nuclei, which will
be conducted in the future.

10

10

1 W under the ionization chamber and target condition.
After adjusting the electric currents of the ionizationchamber and target heater to 150 A and 900 A, respectively, the rate of the RIs increased by approximately one
order, and we transported the 137 Cs beam to the SCRIT
system by monitoring it using Faraday cups in the beamline. To produce 137 Cs ions, an electron beam was irradiated was at a power of approximately 15 W. The produced 137 Cs ions were stacked in the ERIS with a 50 ms
stacking time. The pre-pulsed 137 Cs ions were injected
into the FRAC and subsequently stacked and extracted
from the FRAC as a pulsed beam in a cycle of 1 s. The
pulsed 137 Cs beam was successfully transported from the
FRAC to the SCRIT system with approximately 100%transmission eﬃciency by carefully adjusting the optical parameters. Figure 2 shows the signal of the 137 Cs
beam at the position monitor located at entrance of the
SCRIT device. The number of 137 Cs ions transported to
the SCRIT system was 9.8 × 106 atoms/pulse. The yieldof 137 Cs may be improved by optimizing the optical parameters from the ERIS to the FRAC and the stacking
conditions of the FRAC. It can also be increased by optimizing the temperature of the ionization chamber andthe target heater.

Voltage [mV]The electron-beam-driven RI separator for the SCRIT(ERIS)1) at the SCRIT electron scattering facility2) is an
online isotope separator system. It is used to produce
low-energy RI beams via photoﬁssion of uranium. This
year, we transported a pulsed 137 Cs beam, which was
produced by a surface-ionization ion source and using
ion-stacking and pulse-extraction systems,3,4) into the
SCRIT system. We report the results obtained from theexperiments.
Details of the RI production method and the surfaceionization ion source of the ERIS are reported in Refs. 4)
and 5). In the measurements, self-made 43 uranium carbide disks6) were used as production targets. The total
amount of uranium was approximately 28 g. We measured the production rate of Cs isotopes using a particle
identiﬁcation (PID) system1) located at the exit of the
FRAC3) to estimate the rate of 137 Cs, because the lifeof 137 Cs is extremely long to measure γ-rays. In themeasurements, the electron beam power was adjusted toapproximately 1 W to reduce background events. The
target and the ionization chamber were heated to 1500–
2000◦ C by resistive heating. The electric currents applied to the ionization chamber and the target heater
were 120 A and 750 A, respectively. Ionized RIs wereextracted by the exit grid of the ionization chamber, accelerated to 10 keV, and transported to the PID system.
PID was performed by measuring speciﬁc γ-rays corresponding to the decay of the RIs using a Ge detector.
The measurement process is reported in Ref. 7). Figure 1 shows the isotope dependence of the rate of Cs
obtained from the experiments. The mass dependence issimilar to the trend reported from the ALTO8) , which is
expected to become ﬂat for masses lower than 139. From
this result, the rate of 137 Cs ion is estimated as approximately 1 × 105 atoms/s with an electron beam power of

RIKEN Nishina Center
Department of Physics, Rikkyo University
Institute for Chemical Research, Kyoto University
Research Center for Electron Photon Science, Tohoku University

1) T. Ohnishi et al., Nucl. Instrum. Methods Phys. Res. B
317, 357 (2013).
2) M. Wakasugi et al., Nucl. Instrum. Methods Phys. Res. B
317, 668 (2013).
3) M. Wakasugi et al., Rev. Sci. Instrum. 89, 095107 (2018).
4) T. Ohnishi et al., RIKEN Accel. Prog. Rep. 52, 142(2019).
5) T. Ohnishi et al., RIKEN Accel. Prog. Rep. 48, 229(2015).
6) T. Ohnishi et al., RIKEN Accel. Prog. Rep. 47, xiii (2014).
7) T. Ohnishi et al., RIKEN Accel. Prog. Rep. 53, 110(2020).
8) S. Essabaa et al., Nucl. Instrum. Methods Phys. Res. B
317, 218 (2013).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Performance study of wide dynamic range photon detection systemusing Ge detectors for muonic X-ray spectroscopy
R. Mizuno,∗1 T. Ikeda,∗2 S. Go,∗2 T. Y. Saito,∗1 H. Sakurai,∗1,∗2 M. Niikura,∗1 T. Matsuzaki,∗2 and
S. Michimasa∗3
GX5019 are an n-type 80% coaxial detector and a ptype 50% coaxial detector, respectively. The distancesfrom the target to the detectors were 5 cm (GMX80)
and 10 cm (GX5019), respectively. To suppress theCompton component, the main background of the Ge
detector’s spectrum, BGO detectors were used as aCompton suppressor. In this experiment, GX5019 wassurrounded by the BGO Compton suppressors to test
the performance of Compton suppression in such ahigh energy region. Signals from the detectors wereacquired by a waveform digitizer (Caen V1730B).
The spectrum of the γ-ray energy acquired with
GX5019 after Compton suppression is illustrated inFig. 2. Figure 2 shows 13 γ-ray peaks in 1.5–10.8 MeV
obtained more than 1000 counts for each peak for lessthan 3% statistical accuracy. Single escape peaks (SE)and double escape peaks (DE) were also observed in
the spectrum. Detailed analyses of the γ-ray spectrum
are carried out to estimate the Ge detectors’ photopeak eﬃciencies and energy resolutions. Accordingly,
we will discuss the performance of the photon detection system in a wide energy range below 10.8 MeV.
count (/1keV)

We are planning spectroscopy of the muonic atom ofheavy nuclei and muon-induced ﬁssion reaction. Theenergy of muonic X rays of heavy elements, such as
actinides, is above 6 MeV.1) Therefore, we develop awide dynamic range X-ray and γ-ray detection system to detect such high energy X-rays. Evaluationsof the detector’s eﬃciency and energy resolution are
required to understand the performance of the detector in a wide dynamic range. While standard γ-ray
sources can be used to evaluate detector performancein low energy regions below 1.8 MeV, there are nosources available for above a few MeV. Therefore, we
performed an experiment using the 992-keV resonancein the 27 Al(p, γ)28 Si reaction, primarily because the reaction emits several γ rays over a wide energy range
from 1.5 to 10.8 MeV, and their energies and relative
intensities are well known.2,3)
The experiment was performed at the RIKEN Pelletron facility. The proton beam at 1 MeV irradiateda 0.8-μm thick Al target. The energy loss of the beamin the target was estimated as 36 keV. The target
thickness and beam energy were suﬃcient to induce
a 992-keV resonance and not excite the nearest resonances at 937 and 1025 keV. The proton beam intensity was approximately 300 nA, and the measurement
time was 6.5 h. The experimental setup is shown in
Fig. 1. The photon detectors in the system consist of
high-purity Ge detectors with high energy resolution.
Two Ge detectors, GMX80 (Ortec) and GX5019 (Canberra), were used for γ-ray detection. GMX80 and

10

5

10

3

10

2



∗2
∗3

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
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$)(+

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2000

4000

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10000
Energy (keV)

Fig. 2. γ-ray energy spectrum measured by GX5019 suppressed by a compton suppressor. The γ rays from511 keV to 10.7 MeV can be observed. In the spectrum, SE (DE) means single (double) escape peaks corresponding γ-rays.



Fig. 1. Photograph of the experimental setup. Two Ge
detectors were set next to the target and at an angle of
90-degrees to the beam.
∗1

'',+
)#%#
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

0

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Department of Physics, University of Tokyo
RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo- S20 -

References
1) G. Fricke et al., At. Data Nucl. Data Tables 60, 177(1995).
2) A. Anttila et al., Nucl. Instrum. Methods Phys. Res.
147, 501 (1977).
3) P. M. Endt, Nucl. Phys. A 521, 1 (1990).

1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of inspection system for bus extender cable of
RHIC-sPHENIX INTT detector
H. Imai,∗1,∗6 Y. Akiba,∗1 D. Cacace,∗2 K. Cheng,∗3 H. En’yo,∗1 T. Hachiya,∗1,∗4 S. Hasegawa,∗1,∗5 M. Hata,∗4
T. Kondo,∗7 C. Kuo,∗3 H. -S. Li,∗8 R. -S. Lu,∗9 E. Mannel,∗2 C. Miraval,∗2 M. Morita,∗1,∗4 I. Nakagawa,∗1
Y. Nakamura,∗1,∗6 G. Nakano,∗1,∗6 Y. Namimoto,∗1,∗4 R. Nouicer,∗2 G. Nukazuka,∗1 R. Pisani,∗2 M. Shibata,∗1,∗4
C. Shih,∗3 M. Shimomura,∗4 M. Stojanovic,∗8 Y. Sugiyama,∗4 R. Takahama,∗1,∗4 W. -C. Tang,∗3 M. Watanabe,∗4
and X. Wei∗8
The sPHNEIX experiment is scheduled to begin
at Brookhaven National Laboratory (BNL) in 2023,
study quark-gluon plasma (QGP) by using a heavyion accelerator.1) We have developed a long, highsignal-line-density, ﬂexible substrate cable to transmit
data from one of the tracking detectors, INTermediate
Tracker (INTT), to a downstream data-processing circuit board. The cable is called Bus Extender (BEX),
which is 111 cm long and comprises 124 signal lines
separated by a space of 130 μm.
After ﬁve years of research and development, the cable is meets the speciﬁcations required by sPHENIX in
terms of both mechanical and electrical performances.
However, there is one remaining technical issue, namely,
a poor yield rate (30–50%) in mass production mainly
due to dust contamination during signal-line patterning. The contaminated dust causes abnormal patterns
in the signal lines, which tends to result in either shortor broken signal lines. The anomaly used to be manually inspected using a magnifying glass during the prototyping stage of the cable, which is not practical formass production because of the large area (a patternsheet accommodates four BEXs and the size is about
120 cm × 25 cm) to be inspected for 120 BEXs in total. The motivation of this study was to establish asemi-automated process for pattern inspection.
For this purpose, we developed an inspection ﬁxture,
which consists of a high-resolution microscope camera
on a moving aluminum frame, as shown in Fig. 1. The
aluminum base frame is set along the BEX signal line,
and the camera moves along the base frame, as shownwith the red arrow. A pattern image taken by the camera is then analyzed using a pattern-recognition software developed by us. The algorithm for anomaly detection from the image is as follows. First, the color
image is converted to black and white. Next, the number of pixels for each line and space in a direction perpendicular to the signal lines is counted for both black
and white zones and ﬁll number of pixel histograms,
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9

RIKEN Nishina Center
Physics Department, Brookhaven National Laboratory
Department of Physics, National Central University
Department of Mathematical and Physical Sciences, Nara
Women’s University
Japan Atomic Energy Agency
Department of Physics, Rikkyo University
Tokyo Metropolitan Industrial Technology Research InstituteDepartment of Physics and Astronomy, Purdue University
Department of Physics, National Taiwan University

Fig. 1. Inspection ﬁxture and camera for the signal-line pattern of BEX.

respectively, to evaluate the mean and standard deviations of the number of pixels as references. Finally, thealgorithm detects anomaly spots on the image, where
the pattern deviates by more than 5σ from the reference. The process described above is repeated to scanthrough the 111-cm-long signal lines. One of the abnormal patterns detected with this algorithm is indicatedusing the red circle in Fig. 2. This technique facilitatedinspections in mass production, which would have been
impossible otherwise.

Fig. 2. Example of anomaly spot and histogram of signalline pattern detected by the algorithm.

Reference
1) I. Nakagawa et al., in this report.

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Simple cubic self-assembly of PbS quantum dots by ﬁne ligand control†
J. Liu,∗1 K. Enomoto,∗1 K. Takeda,∗1 D. Inoue,∗1 and Y. -J. Pu∗1
Colloidal quantum dots (QDs) have attracted substantial attention due to their characteristic optoelectronic
properties based on the size conﬁnement eﬀect.1) They
are also known to self-assemble into highly ordered superlattices.2) The geometry of such self-assembled QDs
has been explored to better understand the ensemble
eﬀects on their optical and electrical properties.3) Accordingly, it is essential to prepare two-(2D) and threedimensional (3D) QD superlattices with diﬀerent geometry for their solid-state device applications.
Most colloidal quantum dots with a quasi -sphericalshape readily self-assemble into 3D face-centered cubic(fcc) or body-centered cubic (bcc) superlattices.4) In contrast, 3D simple cubic (sc) superlattices are diﬃcult toobtain from sphere-like QDs because of their relatively
low packing fraction of 0.52 and the low stability by entropy.5) Therefore, sc superlattices have been expected
to have diﬀerent optical and electronic properties fromother packing structures, and the quest has been on
to achieve 3D self-assembled sc superlattices. Here, we
achieve the selective control of the geometry of the quasi spherical PbS QDs in highly-ordered 2D and 3D superlattices: Disorder, sc, and fcc by selectively removing
the ligands from the QD surface through gel permeation
chromatography (GPC).
The uniform sphere-like PbS QDs with an average diameter of 7.3 nm were synthesized. The QD sample was
puriﬁed once by precipitation/redissolution process prior
to the GPC process (before-GPC). In the GPC process,the eluted QD solution was collected in 5 consecutive
portions (GPC-1 to GPC-5).
The thermogravimetric analysis (TGA) was carriedout to evaluate weight ratios of oleic acid (OA) ligands bound to QD surface (Fig. 1a) which gradually
increase from GPC-1 to GPC-5. To further determine
the ligand density, the atomic Pb/S ratios of GPC-2 andbefore-GPC were obtained from Rutherford backscattering (RBS) spectrometry in RIKEN Pelletron accelerator
facility (Fig. 1b).6) An average Pb/S ratio (1.27) combined with TGA results was used for estimating the ligand density. The TGA results (Fig. 1c) demonstrate thatthe ligand density of the PbS QDs gradually increases
from GPC-1 (0.6 nm−2 ) to GPC-5 (7.1 nm−2 ) and that
the GPC method can precisely and continuously control
the ligand density of the PbS QDs. We also estimatedthe ligand density by nuclear magnetic resonance spectroscopy. The obtained results are consistent with theligand density obtained from TGA (Fig. 1c).
Based on the diﬀerence in their ligand density, the 2D
self-assembly of these QDs was achieved by drop-casting
dilute solutions onto solid substrates. GPC-1–5 formed
2D superlattices with diﬀerent and unique geometries.
†∗1

Condensed from the article in Chem. Sci. 12, 10354 (2021)
RIKEN Center for Emergent Matter Science

a

b

c

d

e
100 nm

GPC-2

ϭϬʅŵ

100 nm

100 nm

GPC-5

ϭϬʅŵ

100 nmFig. 1. (a) TGA curves of before-GPC and GPC1-5; (b) RBS
spectra of GPC-2 and before-GPC; (c) Ligand density of
PbS QDs as a function of the GPC fraction; The scanning electron microscopy (SEM) images of the supercrystal surfaces for GPC-2 (d) and GPC-5 (e); inset: their
2D self-assembled TEM images and SEM images of 3D
supercrystals.

GPC-1 QDs showed a random assembly due to insuﬃcient ligands on the QD surface. However, GPC-2 QDs(inset of Fig. 1d) formed a square self-assembled geometry without the fusion between QDs. Also, the GPC-2
QDs in the square superlattice are highly oriented along
QD [100] facets. The GPC-3–5 QDs with suﬃcient ligands formed the hexagonal assemblies with non-oriented
facets (inset of Fig. 1e).
Furthermore, the long-range-ordered 3D self-assembled
supercrystals for GPC-2 and GPC-5 QDs were preparedby solvent evaporation. GPC-5 QDs can form triangularor hexagonal fcc supercrystals with a hexagonal arrangement on the crystal surface (Fig. 1e). It is noteworthy
that GPC-2 QDs self-assembled in cubic supercrystals
with sc packing on account of ﬁnely controlled ligand
removal by GPC, which is usually diﬃcult for quasispherical QDs.
In this report, we develop GPC as a method to control
the ligand density of the quasi -spherical PbS QDs andachieve the selective control of the geometry of QDs in
2D and 3D superlattices: Disorder, sc, and fcc. The precise control of QD self-assembled geometry is expected
to greatly improve the performance of next-generation
semiconductor devices and photocatalysis.
References
1) C. R. Kagan et al., Science 353, 885 (2016).
2) M. A. Boles et al., Chem. Rev. 116, 11220 (2016).
3) C. S. S. Sandeep et al., ACS Nano 8, 11499 (2014).
4) K. Bian et al., Chem. Mater. 30, 6788 (2018).
5) M. Boles, D. Talapin, J. Am. Chem. Soc. 137, 4494
(2015).
6) I. Moreels et al., ACS Nano 3, 3023 (2009).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Co-precipitation behaviour of single atoms of rutherfordium in basic
solutions†Y. Kasamatsu,∗1 K. Toyomura,∗1 H. Haba,∗2 T. Yokokita,∗1 Y. Shigekawa,∗1 A. Kino,∗1 Y. Yasuda,∗1
Y. Komori,∗1 J. Kanaya,∗2 M. Huang,∗2 M. Murakami,∗2 H. Kikunaga,∗3 E. Watanabe,∗1 T. Yoshimura,∗4
K. Morita,∗2 T. Mitsugashira,∗5 K. Takamiya,∗6 T. Ohtsuki,∗6 and A. Shinohara∗1
In heavy atoms, the relativistic eﬀects are strong,which would result in deviations of their chemical behaviours from those expected by simple extrapolationof the characteristics of the lighter homologues.1) It
is very challenging to perform chemical experimentson the heavy elements, because their nuclides are produced with extremely low production rates and tend to
decay rapidly; only one atom can be usually treated ata time. Thus, rapid transportation system of the nuclear reaction products and automated chemical separation apparatuses specialized for such elements areneeded. Chemical studies of heavy elements havemainly been conducted by two-phase partition methods. In particular, the formation of ﬂuoride, chloride,
nitrate, and sulﬁde complexes of Rf has been investigated in solution chemistry.1)
We focused on a precipitation approach to study
heavy element chemistry. In a previous study, a coprecipitation method with Sm, 10–20 μg, was developed, and the method was applied to various elements
using a multiple radiotracer source. The yields ofco-precipitate formed in solutions with several concentrations of ammonia (NH3 ) and sodium hydroxide(NaOH) were determined for elements from various
groups in the periodic table.2) From the consistent coprecipitation yields with their properties in hydroxide
precipitation and ammine complexation, it was concluded that the hydroxide and ammine complexationof heavy elements can be qualitatively investigated on
the basis of their co-precipitation behaviours with Sm.
Based on these ﬁndings, the purpose of the present
study is to investigate the co-precipitation behaviourof Rf with samarium hydroxide and get an insight into
the properties of its hydroxide and ammine complex
formation.
261
Rf was produced by the 248 Cm(18 O, 5n) reaction
using the AVF cyclotron at RIKEN RIBF. 169 Hf wassimultaneously produced to check the status of theonline ﬁltration apparatuses2) by monitoring Hf behaviour. After dissolution of the transported nuclear
reaction products in the dissolution apparatus, a basic
†
∗1
∗2
∗3
∗4
∗5
∗6

Condensed from the article in Nature Chem. 13, 226 (2021)
Graduate School of Science, Osaka University
RIKEN Nishina Center
Research Center for Electron Photon Science, Tohoku University
Radioisotope Research Center, Osaka University
Institute for Material Research, Tohoku University
Institute for Integrated Radiation and Nuclear Science, Kyoto University- S23 -

Fig. 1. The Y values of 261 Rf and 169 Hf (a) and those of88
Zr, 175 Hf, and 228 Th (b).

solution (aq. NH3 or NaOH) was added to produce thehydroxide precipitate. The co-precipitation yields, Y ,were determined from the radioactivity of precipitate
and total radioactivity.
The co-precipitation yields evaluated for 261 Rf and169
Hf are shown in Fig. 1(a). The yields of 88 Zr,
175
Hf, and 228 Th previously obtained2) are also shownin Fig. 1(b). The co-precipitation yields of 169 Hf determined in this study typically agreed with previously
obtained values for 175 Hf, suggesting that the online
experiment on 261 Rf was successful. In dilute OH−
solutions (aq. NH3 ), the Y values of all the elements
were high (76–100%), suggesting predominant precipitation. This indicates that the chemical properties of
Rf allow for the formation of a hydroxide precipitate;
namely, we extrapolate that Rf would form a hydroxide precipitate if in macro amounts. This behaviour
is typical of the hydroxides of group 4 elements, precipitation as M(OH)4 (M4+ = metal ion of group 4element). In addition, the yield of Rf in concentrated
NH3 solution was not markedly lower than the yields
in other concentrations, suggesting that Rf does notstrongly coordinate with NH3 molecules, similar to its
homologues. In concentrated OH− solutions (NaOH),
the Y values of Zr and Hf decreased with increasing1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

OH− concentration due to the formation of hydroxide complex ions such as [M(OH)5 ]− and [M(OH)6 ]2− ,whereas the yields of Rf and Th remained high. Indeed, the solubility products of [M(OH)5 ]− (log Ks5 =[M(OH)5 ]− /[OH]− ) for Zr, Hf, and Th are −3.6, −3.2,
and −5.8, respectively, and this sequence is consistent
with their Y values obtained with 6.0 M NaOH. We candeduce that log Ks5 of Rf would be lower than those ofZr and Hf. It suggests a weaker tendency of Rf towardhydroxide complexation than those of Zr and Hf.
References
1) M. Schädel, Phil. Trans. R. Soc. A 373, 20140191(2015).
2) Y. Kasamatsu, J. Nucl. Radiochem. Sci. 18, 24 (2018).

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RIKEN Accel. Prog. Rep. 55 (2022)

Sodium ascorbate protects 211 At-labeled antibodies from reactive
oxygen species damage†S. Manabe,∗1,∗2,∗3 H. Takashima,∗4 Y. Koga,∗4,∗5 K. Onuki,∗6 R. Tsumura,∗4 T. Anzai,∗4 N. Iwata,∗4
M. Yasunaga,∗4 Y. Wang,∗7 T. Yokokita,∗7 Y. Komori,∗7 D. Mori,∗7 H. Haba,∗7 H. Fujii,∗6 and Y. Matsumura∗4

∗4

∗5
∗6
∗7

25
20

SA (mg/mL)

Sn-IgG
IgG

∗3

37

6

∗2

Condensed from the article in ACS Omega 6, 14887 (2021)
Pharmaceutical Department, Hoshi University
Research Center for Pharmaceutical Development, Tohoku
University
Glycometabolic Biochemistry Laboratory, Cluster for Pioneering Research, RIKENDivision of Developmental Therapeutics, Exploratory Oncology Research and Clinical Trial Center, National Cancer Center
Department of Strategic Programs, Exploratory Oncology Research and Clinical Trial Center, National Cancer Center
Division of Functional Imaging, Exploratory Oncology Research and Clinical Trial Center, National Cancer Center
RIKEN Nishina Center

50

6ʹ10-2∗1100
75

610-4

†

(kDa)
150

0

Fig. 1. SDS-PAGE showing damaged 211 At-labeled trastuzumab
after 1 day.
SK-BR-3MCF-7
100

Cell viability (%)

100

Cell viability (%)

Radioimmunotherapy (RIT) is synonymous with nextgeneration antibody medication. α-particles are particularly suited to RIT on account of their potent linear
energy transfer (LET) and short path range. Among theseveral α-emitter nuclei, 211 At is preferable to the rest
owing to its short half-life (7.2 h) and inability to yield
cytotoxic daughter isotopes during decay. Successful delivery of α-particles to the tumor site is a key requisite
for eﬀective cancer treatment, which can be achieved byusing speciﬁc antibodies against tumor antigens.
We investigated 211 At-labeled antibodies for cancer
therapy.1) Brieﬂy, 211 At, generated by the RIKEN AVF
cyclotron, was conjugated to trastuzumab, a therapeutic antibody targeted against breast and stomach cancer. 211 At was immobilized onto trastuzumab carrying trimethylstannyl benzoate via an 211 At-Sn exchange
reaction, followed by puriﬁcation using size-exclusion
column chromatography. However, using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDSPAGE) analyses, we discovered that the 211 At-labeledtrastuzumab thus obtained was damaged. Further, ﬂow
cytometry revealed that the binding aﬃnity of 211 Atlabeled trastuzumab to human epidermal growth factor
receptor 2 (HER2) expressing SK-BR-3 cells was drastically compromised (Fig. 1).
We speculated that damage to the 211 At-conjugatedantibodies may have been caused by reactive oxygen
species (ROS), that were generated from water radiolysis by α-particles released from 211 At. Consequently,
we established an ROS detection system based on thechemiluminescence luminol assay. Aqueous 211 At solutions tested positive in the luminol assay, thereby indicating the presence of ROS. Further, the assay revealed
the quenching of ROS in the presence of 6×10−2 mg/mL
sodium ascorbate.
211
At-labeled trastuzumab in the presence of morethan 6 × 10−2 mg/mL sodium ascorbate was stableas seen using SDS-PAGE analyses, and its binding
aﬃnity was maintained. In addition, WST-8 assays
demonstrated more potent cytocidal eﬀects of 211 At-

80
60
40
20
0

80
60

1000

Radioactivity (Bq/well)

10000

At (SA -)211

At (6×10-4 mg/mL SA)

211

At (6×10-2 mg/mL SA)

211

At (6 mg/mL SA)

211

At-trastuzumab (SA -)211

At-trastuzumab (6×10-4 mg/mL SA)

40
20

211

0
100

211

100

1000

10000

At-trastuzumab (6×10-2 mg/mL SA)

211

At-trastuzumab (6 mg/mL SA)

Radioactivity (Bq/well)Fig. 2. Cytotoxic eﬀects of 211 At-labeled trastuzumab.

labeled trastuzumab in the presence of sodium ascorbate, against high HER2-expressing SK-BR-3 cells thanthose exerted by the immunoconjugate that was not under the protection (Fig. 2). These results conclusively
demonstrated that quenching of ROS is essential for efﬁcacious RIT. Moreover, the cytocidal eﬀects seemed to
be dependent on the level of HER2 on the cancer cells.
Compared with free 211 At, 211 At-labeled trastuzumab
more eﬃciently killed SK-BR-3 cells, whereas the cytotoxicity was mitigated against MCF-7 cells that express
lower levels of HER2 (Fig. 2).
While the reducing agent L-cysteine demonstrated
similar ROS-quenching activity as sodium ascorbate,others such as sodium hydrosulﬁte and maltose, had aweaker eﬀect.
We therefore conclude that 211 At-labeled antibodies
are damaged by ROS that are generated by the actionof 211 At on water. The presence of sodium ascorbate resulted in the quenching of ROS, which prevented 211 Atlabeled antibody damage, and maintained its function.
The present data warrant further studies for development of the above-described cancer therapy.
This manuscript has been condensed from the article
in ACS Omega. Figures are reproduced with permission
from American Chemical Society.
Reference
1) H. Takashima et al., Cancer Sci. 112, 1975 (2021).

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Intratumoral administration of astatine-211-labeled gold nanoparticle
for alpha therapy†
H. Kato,∗1 X. Huang,∗2 Y. Kadonaga,∗3 D. Katayama,∗1 K. Ooe,∗1 A. Shimoyama,∗2 K. Kabayama,∗2
A. Toyoshima,∗3 A. Shinohara,∗3 J. Hatazawa,∗4 and K. Fukase∗2,∗3
As a local radiation therapy for cancer and in addition to external irradiation with γ-rays or X-rays,
the eﬀectiveness of brachytherapy using a sealed Xray source for prostate cancer, breast cancer, uterine
cancer, head and neck cancer, and brain tumors iswell known. However, the invasiveness of the procedure, extra-lesion displacement of the sealed radiation
source, or adverse eﬀects caused by the leakage of Xrays from radionuclides with a long half-life into adjacent organs are problematic issues. α-ray-emitting nuclides have a high linear energy transfer (LET) and relative biological eﬀectiveness and are particularly toxic
to proliferating cells. Because of the short range of
α-ray emitters, normal tissues are minimally exposed
if the radiation sources are appropriately distributed.
211
At is a high-energy α-ray emitter with a relatively
short half-life and a high cytotoxicity for cancer cells.
Its dispersion can be imaged using clinical scanners,
and it can be produced in cyclotrons without the useof nuclear fuel material.

Fig. 2. The radioactivity distributions at 4, 19, and 42
hours after the administration of 211 At-AuNP-S-mPEG
are shown. Strong radioactivity was found at the transplanted tumor sites. No systemic accumulation of radioactivity was observed in any of the organs.

The objective of this study was to propose an eﬀective nanoseed brachytherapy with signiﬁcantly reduced
radiation exposure. In the present study, we investigated the systemic and intratumoral distributions andveriﬁed the antitumor eﬀect of 211 At-labeled AuNP administered intratumorally (Fig. 1).
AuNP with a diameter of 5, 13, 30, or 120 nm
that had been modiﬁed with poly (ethylene glycol)

Fig. 1. 211 At-labeled gold nanoparticles administered intratumorally. α-ray caused DNA double-strand breakand kill the malignant cells.
†
∗1
∗2
∗3
∗4

Condensed from the article in J. Nanobiotechnology 19, 223(2021)
Department of Nuclear Medicine and Tracer Kinetics, Osaka
University Graduate School of Medicine
Department of Chemistry, Graduate School of Science, Osaka University
Division of Science, Institute for Radiation Sciences, Osaka
University
Research Center for Nuclear Physics, Osaka University- S26 -

Fig. 3. Changes in the tumor volumes of the C6 glial cells
after intratumoral administration (1.4±0.4 MBq/tumor
for rats). The C6 gliomas treated with the 5 nm particles had the lowest growth rate, based on tumor size.

1

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

methyl ether (mPEG) thiol and labeled with 211 At(211 At-AuNP-S-mPEG) were intratumorally administered to C6 glioma subcutaneously transplanted intorodent models. A part of 211 At used in this work
was produced in the 209 Bi(α, 2n)211 At reaction using
the RIKEN AVF cyclotron. After intratumoral administration, 211 At-AuNP-S-mPEG became localized
in the tumor and did not spread to systemic organs
during a time period equivalent to 6 half-lives of 211 At(Fig. 2). Tumor growth was strongly suppressed by
211
At-AuNP-S-mPEG without any critical side eﬀects.
In the C6 glioma model, the strongest antitumor eﬀect
was observed in the group treated with 211 At-AuNPS-mPEG with the smallest diameter of 5 nm (Fig. 3).
The intratumoral single administration of a simple nanoparticle, 211 At-AuNP-S-mPEG, was shown tosuppress the growth of tumor tissue strongly in a particle size-dependent manner without radiation exposure
to other organs caused by systemic spread of the radionuclide.

2- S27 -

I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Activation cross sections of proton-induced reactions on
praseodymium up to 30 MeV†
M. Aikawa,∗1,∗2,∗3 Y. Hanada,∗2,∗3 H. Huang,∗2,∗3 and H. Haba∗3

†
∗1
∗2
∗3

Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 508, 29 (2021)
Faculty of Science, Hokkaido University
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center

2000
141Pr(p,2n)140Nd

Cross section (mb)

The medical radionuclide 140 Nd (T1/2 = 3.37 d) is expected to be used as a 140 Nd/140 Pr in-vivo generator for
positron emission tomography (PET).1) It can be produced via charged-particle-induced reactions. Amongthe possible production reactions, we focused on the
proton-induced reaction of 141 Pr. A survey revealed
three experimental studies of the reaction for 140 Nd production.2–4) However, the experimental cross sections in
the literature are largely scattered. Therefore, we performed an experiment to obtain the cross sections of the141
Pr(p, 2n)140 Nd reaction up to 30 MeV. The production cross sections of 141, 139m Nd and 139 Ce were also
determined.
We conducted an experiment using a 30-MeV proton
beam at the AVF cyclotron in RIKEN. We adopted thestacked-foil activation technique and high-resolution
gamma-ray spectrometry to determine the excitation
functions. The target consisted of pure metallic thinfoils of 141 Pr (99% purity), nat Ti (99.5% purity), and27
Al (>99% purity), which were purchased from Nilaco Corp., Japan. The nat Ti foil was used for thenatTi(p, x)48 V monitor reaction to assess beam parameters and target thicknesses. The 27 Al foil was interleaved to catch recoiled products. The side lengths andweight of each foil were measured to obtain the average thicknesses. The measured thicknesses of the two
141
Pr, nat Ti and 27 Al foils were 68.6 and 68.5 mg/cm2 ,9.1 mg/cm2 , and 2.2 mg/cm2 , respectively. The large
foils were cut into small pieces of 8 × 8 mm2 to ﬁt atarget holder. Eighteen sets of the Pr-Al-Ti-Ti-Al foils
were stacked in the target holder, which served as a
Faraday cup.
The stacked target was irradiated with a proton beamfor 15 min. The average intensity and primary energyof the beam were measured to be 201 nA and 30.2 MeV,
respectively. Energy degradation in the stacked target
was calculated using stopping powers obtained from the
SRIM code.5)
Gamma-ray spectrometry was performed using ahigh-purity germanium detector. Each 141 Pr foil wasmeasured together with the next 27 Al foil that caught
the recoiled products. The 141 Pr foils were measured
3–9 times to assess the decay curves of the products.
The cooling times were from 1.7 h to 31.9 d, and thedead time was maintained below 7.5%.
Cross sections of the nat Ti(p, x)48 V monitor reaction

Hogan (1971)
Zeisler (1999)
Hilgers (2005)
TENDL-2019
This work

1500

1000

500

0

5

10

15

20

25

30

Energy (MeV)

Fig. 1. Cross sections of the 141 Pr(p, 2n)140 Nd reaction withthe previous data2–4) and the TENDL-2019 values.7)

were derived for comparison with the IAEA recommended values.6) Based on the comparison, the thicknesses of the 141 Pr foils and the beam intensity werecorrected by +2% and −7% within the uncertainties.
The measured thicknesses of nat Ti and 27 Al were usedwithout any correction.
140
Nd has the ground state (T1/2 = 3.37 d) and themetastable state at 2.221 MeV (T1/2 = 0.60 ms). The
isomer fully decays to the ground state via the IT transition (IT: 100%). Because there are no measurable
gamma lines from 140 Nd, gamma rays with the decayof 140 Pr (T1/2 = 3.39 min) were instead measured under secular equilibrium with the decay of 140 Nd. Direct
production of 140 Pr during irradiation was negligible
because the cooling times were much longer than its
half-life. We measured the gamma line at 511 keV (Iγ= 102%) emitted from the irradiated foils, which were
sandwiched between copper plates to force positron annihilation. The result is compared with those of theprevious studies2–4) and the TENDL-2019 values7) inFig. 1. Our excitation function is largely diﬀerent fromthose of the previous studies. The TENDL-2019 values slightly overestimate our experimental data below
23 MeV.
References
1) S. K. Zeisler et al., Clin. Positron Imaging. 2, 324 (1999).
2) J. J. Hogan, J. Inorg. Nucl. Chem. 33, 3627 (1971).
3) S. K. Zeisler et al., J. Label. Compd. Radiopharm. 42,
Suppl. 1, S921 (1999).
4) K. Hilgers et al., Radiochim. Acta 93, 553 (2005).
5) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
6) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).
7) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Activation cross section measurement of alpha-particle induced
reactions on natural neodymium†
M. Sakaguchi,∗1,∗2 M. Aikawa,∗3,∗2 N. Ukon,∗4,∗2 Y. Komori,∗2 H. Haba,∗2 N. Otuka,∗5,∗2 and S. Takács∗6

†
∗1
∗2
∗3
∗4
∗5
∗6

Condensed from the article in Appl. Radiat. Isot. 176, 109826(2021)
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
Advanced Clinical Research Center, Fukushima Medical University
Nuclear Data Section, IAEA
Institute for Nuclear Research (ATOMKI)

400
natNd(,x)145Sm

350
Cross section (mb)Some samarium radionuclides can be used for nuclear medicine. 153 Sm (T1/2 = 46.3 h) is a beta andgamma emitter available to treat bone metastases.1)
145
Sm (T1/2 = 340 d) decays with the emission of lowenergy X rays, which is applicable in brachytherapy.2)
These samarium radionuclides can be generated simultaneously in alpha-particle-induced reactions on natural neodymium. Highly accurate cross sections of thereactions are indispensable for practical use. However,there is only one previous experimental study on thenat
Nd(α, x)153 Sm reaction up to 26.2 MeV.3) Further,
the literature survey did not reveal any experimental research on the nat Nd(α, x)145 Sm reaction. Therefore, wemeasure the cross sections of the alpha-particle-induced
reactions on natural neodymium up to 51 MeV.
The experiment was performed at the RIKEN AVF
cyclotron. The stacked-foil activation technique andhigh-resolution gamma-ray spectrometry were adopted
for the experiment. The target consisted of pure metal
foils of nat Nd (99.0% purity, Goodfellow Co., Ltd., UK)
and nat Ti (99.6% purity, Nilaco Corp., Japan). The
thicknesses of the nat Nd and nat Ti foils were 16.7 and2.35 mg/cm2 , respectively, which were deduced fromthe measurement of their weights and surface areas.
Twenty-one Nd and fourteen Ti foils were arranged inseven sets of Nd-Nd-Nd and Ti-Ti pairs. The second
and third Nd foils and the second Ti foil of each pair
were assumed to compensate the recoiled products. Thenat
Ti foils were inserted for the nat Ti(α, x)51 Cr monitor
reaction to assess the measured beam parameters andtarget thicknesses.
The stacked target was irradiated with an alphaparticle beam for 60 min. The measured beam energy
and intensity were 51.1 ± 0.2 MeV and 172 nA, respectively. Energy degradation through the stacked target
was calculated using the SRIM code.4) The gammaray spectra were acquired for the recoil-compensatedfoils by an HPGe detector without chemical separation.
Measurements were performed several times after cooling from 0.7 h to 4.0 d to follow the decay of the produced radionuclides with diﬀerent half-lives. The distances between the foils and the detector were adjusted

TENDL-2019
This work

300
250
200
150
100
50
0
5

10

15

20

25

30

35

40

45

50

alpha-particle energy (MeV)

Fig. 1. Excitation function of the nat Nd(α, x)145 Sm reaction
compared with the TENDL-2019 data.6) No experimental data published earlier was found in a survey.

to keep the dead time less than 5%.
The derived cross sections of the nat Ti(α, x)51 Cr
monitor reaction were compared with the IAEA recommended values.5) The observed shift on the energy scale
was corrected by changing the thickness of the Nd foils
by −1.5% within its 2% uncertainty to 16.4 mg/cm2 .
No additional adjustments were adopted for the data
analysis to determine the cross sections of the alphaparticle-induced reactions on natural neodymium.
145
Sm (T1/2 = 340 d) can be produced in (α, xn) reactions on the stable isotopes of 142, 143, 144, 145, 146 Nd
below 51 MeV. The gamma line at 61.2265 keV (Iγ= 12.15%) emitted with the decay of 145 Sm was measured after cooling for 1.4–4.0 days. The net countsof the gamma line were corrected by +8.4% becauseof the self-absorption eﬀect in the nat Nd foils. The
cross sections of the nat Nd(α, x)145 Sm reaction were
derived from the corrected net counts. The result isshown in Fig. 1 in comparison with theoretical values
from the TENDL-2019 library.6) The TENDL-2019 values are almost consistent with our experimental data.
Activation cross sections for other radionuclides 153 Sm,
151, 150, 149, 148m, 148g, 144, 143
Pm, and 149, 147 Nd were also
determined.
References
1) I. G. Finlay et al., Lancet Oncol. 6, 392 (2005).
2) R. G. Fairchild et al., Phys. Med. Biol. 32, 847 (1987).
3) S. Qaim et al., Radiochim. Acta 95, 313 (2007).
4) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
5) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).
6) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Argon-ion-induced mutations in Arabidopsis EGY1 gene aﬀect
chloroplast development in leaf guard cells†
A. Sanjaya,∗1 R. Muramatsu,∗1 S. Sato,∗1 M. Suzuki,∗1 S. Sasaki,∗1 H. Ishikawa,∗1 Y. Fujii,∗1 M. Asano,∗1
R. Itoh,∗2 K. Kanamaru,∗3 S. Ohbu,∗4 T. Abe,∗4 Y. Kazama,∗4,∗5 and M. Fujiwara∗1,∗4
Leaf tissues of higher plants such as Arabidopsis
thaliana contain chloroplasts in the mesophyll and epidermis. Until now, it has been indicated that there
exists a tissue- or cell-type-dependent control of chloroplast division in leaves. This raises a fundamental question about the control of chloroplast development in theleaf epidermis, or, more speciﬁcally, whether chloroplastbiogenesis-related factors in leaf mesophyll cells play anequivalent role in the leaf epidermis.
To address this issue, we examined the phenotypeof leaf epidermal chloroplasts using two argon ion
irradiation-derived, pale green mutants of A. thaliana,
Ar50-33-pg1 and Ar-28-pg1 (egy1-4 ).1–3) Both represent loss-of-function mutants of the Ethylene-dependent
Gravitropism-deﬁcient and Yellow-green 1 (EGY1 )gene, which encodes a thylakoid membrane-localized
protease for chloroplast development in the mesophyll.4) Moreover, the defects in the thylakoid structure
and pigmentation in the mutant mesophyll chloroplasts
are known to be pronounced during the later stages ofleaf (seedling) development.3,4)Fluorescence microscopy observations indicated severe chlorophyll deﬁciency in the chloroplasts of leaf
guard cells and guard mother cells of egy1 (Fig. 1).
This ﬁnding was in contrast to that observed in mesophyll cells, which retained a considerable amount ofchlorophyll. Labeling of plastids with stroma-targeted
ﬂuorescent proteins revealed that egy1 guard cells contained a normal number of plastids; however, their size
was moderately reduced compared to those of the wildtype guard cells (Fig. 1). Transmission electron microscopy further revealed that, in the egy1 chloroplasts,thylakoid development was impaired not only in mature
guard cells but also in the guard mother cell (Fig. 2).
Thus, the disorganization of the thylakoid structure andthe reduction in the chlorophyll contents showed a positive correlation.
Collectively, these observations demonstrate that
EGY1 is critical for chloroplast diﬀerentiation in guard
cells: egy1 guard cell chloroplasts apparently exhibit
permanent defects, starting from their development.
This prompts a revision to the current understanding ofchloroplast development, which has been based mainly
from on studies using mesophyll cells.
†
∗1
∗2
∗3
∗4
∗5

Condensed from the article in Plants 10, 1254 (2021)
Faculty of Science and Technology, Sophia University
Faculty of Science, University of the Ryukyus
Faculty of Agriculture, Kobe University
RIKEN Nishina Center
Faculty of Bioscience and Biotechnology, Fukui Prefectural
University

Fig. 1. Fluorescence microscopy images of chloroplasts during guard cell development in Ar50-33-pg1 expressing
a stroma-targeted GFP. Bright ﬁeld (DIC), chlorophyll
autoﬂuorescence (chl), and GFP images of leaf epidermis
from 18-day-old seedlings are shown. Bar = 10 μm.
Wild-type

Ar50-33-pg1

Fig. 2. Transmission electron microscopy analysis of chloroplasts in dividing guard mother cells of expanding leaves.
Primary leaves of 10-day-old wild-type and Ar50-33-pg1
plants were analyzed. Guard mother cells (A) and thechloroplasts therein (B). cp, chloroplast; n, nucleus; s,
starch; v, vacuole. Bar = 2 μm (A) and 0.5 μm (B).

References
1) Y. Kazama et al., RIKEN Accel. Prog. Rep. 43, 283(2010).
2) T. Hirano et al., Mutat. Res. 735, 19 (2012).
3) A. Sanjaya et al., Plants 10, 848 (2021).
4) G. Chen et al., Plant J. 41, 364 (2005).

- S30 -

1

II. RESEARCH ACTIVITIES I(Nuclear, Particle and Astro-Physics)

1. Nuclear Physics

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

RI beam production at BigRIPS in 2021
H. Takeda,∗1 N. Fukuda,∗1 H. Suzuki,∗1 Y. Shimizu,∗1 M. Yoshimoto,∗1 N. Inabe,∗1 K. Kusaka,∗1 M. Ohtake,∗1
Y. Yanagisawa,∗1 H. Sato,∗1 K. Yoshida,∗1 and T. Uesaka∗1
Radioactive isotope (RI) beam production at the BigRIPS fragment separator1) in 2021 is presented here.
Table 1 summarizes the experimental programs thatinvolved the use of the BigRIPS separator in this period and the RI beams produced for each experiment.
In the spring beamtime, the 238 U beam campaign
was conducted in the ﬁrst half, followed by the lightion beam campaign in the second half.
The 238 U beam campaign started in April. A
80
Zn beam was produced for a HiCARI experimentusing ZeroDegree spectrometer to study γ-ray spectroscopy in the vicinity of double-magic 78 Ni. During this experiment, mass measurements with a multireﬂection time-of-ﬂight mass spectrometer (MRTOFMS) located downstream of ZeroDegree spectrometer
were performed symbiotically. 74 Ni, 75 Ni, and 76 Ni
beams were produced for mass measurements using
the Rare RI Ring. Two BRIKEN experiments werethen conducted. A 156 La beam was produced to measure masses, half-lives, and β-delayed neutron emission probabilities. An 202 Os beam was produced to
study β-decay spectroscopy in the vicinity of the N =Table 1.

List of experimental programs with RI beams produced at the BigRIPS separator in 2021.

Primary beam (Period)

238

U
345 MeV/nucleon(Apr. 8 – May 5)

12C
250 MeV/nucleon(May 20 – May 29)2H
250 MeV/nucleon(May 31 – Jun. 9)
4He
200 MeV/nucleon(Jun. 12 – Jun. 21)

238U
345 MeV/nucleon(Nov. 20 – Dec. 3)∗1

126 closed shell. The symbiotic MRTOF-MS experiment was performed again during these BRIKEN experiments. At the end of the 238 U campaign, two machine studies were performed; an in-separator two-stepmethod to produce and separate neutron-rich midheavy RI beams with a 133 Sn beam2) and an automation tuning of the primary beamline using a machinelearning technique with a 238 U primary beam.
The light-ion beam campaign was started in May.
In the ﬁrst two experiments, search for the double
Gamow-Teller giant resonances (DGTGR) in ββ-decay
with a 12 C primary beam and high precision spectroscopy of pionic atoms with a 2 H primary beam, theBigRIPS F0-F5 section was used as a spectrometer inthe dispersion matched operation to analyze the momentum of ejected particles produced at the F0 target.
8
Li, 9 Li, 10 Be, 12 B, and 3 He beams produced withthe 12 C primary beam were used for the ion-opticaltuning and detector setup for these experiments. The
DGTGR experiment was performed with 12 B and 12 Be
settings. After switching to the 2 H primary beam, thepionic atom experiment was performed with the 3 He
setting.

Proposal No.
NP1912-RIBF181-02
PE21-01
NP1612-RIRING02-02
NP1612-RIBF148-07
NP1712-RIBF158-02
PE21-02
MS-EXP21-01
MS-EXP21-03

Spokesperson
R. Taniuchi
M. WadaA. Ozawa
G. Kiss
J. Wu
M. WadaH. Suzuki
T. NishiCourseZeroDegree
ZeroDegree
Rare RI Ring
ZeroDegree
ZeroDegree
ZeroDegree
ZeroDegree
BigRIPSRI beams
Zn(symbiotic)
74
Ni, 75Ni, 76Ni
156
La
202
Os
(symbiotic)
133
Sn(primary)

NP1712-RIBF141R1-01

T. Uesaka

ZeroDegree8

Li, 9Li, 10Be, 12Be, 12B

NP1912-RIBF135R1-01

K. Itahashi

BigRIPS

3

He

NP1912-RIBF135R1-02

K. Itahashi

BigRIPS

3

He

NP1712-SHARAQ11-01
MS-EXP21-06
MS-EXP21-07
DA21-04-02
NP2012-RIBF199-01
NP2012-RIBF202-01
INSPECTION21-03
NP1712-RIBF166-05
NP1712-RIRING01R1-02
NP2012-RIBF202-02

K. MikiS. Michimasa
K. Yoshida
H. Otsu
M. WadaM. Rosenbusch
K. Tanaka
T. Sonoda
S. Naimi
M. Rosenbusch

SHARAQ
SHARAQBigRIPS
ZeroDegree
ZeroDegree
ZeroDegree
BigRIPSPALIS
Rare RI Ring
ZeroDegree

3

80

H
H
3
H
(BigRIPS tuning only)
203
Re
79
Ni
75
Zn
191
Bi
124
Pd, 125Pd
79
Ni
3

RIKEN Nishina Center-1-1II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

After switching to a 4 He primary beam, a search
for three-neutron resonant states was performed witha 3 H beam. A machine study for the development of
a dispersion matched beam transport of the OEDO
beamline was conducted using another 3 H beam setting. At the end of the light-ion beam campaign, amachine study was conducted with the two 3 H beams
and the 4 He primary beam to investigate the vertical(Y) axis misalignment.3)
In the autumn beamtime, the 238 U campaign was
conducted again from November. During the BigRIPS
tuning, the performance of a newly developed ionization chamber specialized in high-Z beams installed at
F7 was examined with the 238 U primary beam.4) The
productions of an 237 Np beam and a reduced-energy
uranium beam were also tested. Two MRTOF-MS experiments were then performed in 203 Re and 79 Ni centered beam settings, respectively. A facility inspection was conducted using a 75 Zn beam. A PALIS
experiment was then performed with a 191 Bi beam,
and a Rare RI Ring experiment was conducted with124
Pd and 125 Pd beams. The auto-focusing and autocentering systems were tested5) in the BigRIPS tuning for the next MRTOF-MS experiment. During the
MRTOF-MS experiment with the 79 Ni beam, a serious
problem occurred on the refrigerator of the BigRIPS
separator making it inoperable. The remainder of thescheduled experiments were therefore canceled.
RI beam production at BigRIPS from the startof operation in March 2007 is summarized in our
database6) available at https://ribeam.riken.jp/ .
References
1) T. Kubo, Nucl. Instrum. Methods Phys. Res. B 204, 97(2003).
2) H. Suzuki et al., in this report.
3) K. Yoshida et al., in this report.
4) M. Yoshimoto et al., in this report.
5) Y. Shimizu et al., in this report.
6) Y. Shimizu et al., Nucl. Instrum. Methods Phys. Res. B
463, 158 (2020).

2-2-

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Status of the mass measurement of neutron-rich nuclei at A ∼ 50–60
using SLOWRI/ZD-MRTOF
S. Iimura,∗1,∗2,∗3 M. Rosenbusch,∗3 A. Takamine,∗1 D. Hou,∗4,∗3,∗5 M. Wada,∗3 S. Chen,∗3,∗6 J. Liu,∗4
W. Xian,∗3,∗6 S. Yan,∗7,∗3 P. Schury,∗3 S. Kimura,∗1 T. Niwase,∗8,∗1,∗3 Y. Ito,∗9 T. Sonoda,∗1 T. M. Kojima,∗1
Y. X. Watanabe,∗3 S. Naimi,∗1 S. Michimasa,∗10 S. Nishimura,∗1 A. Odahara,∗2 and H. Ishiyama∗1

56V+

56Ti+

13.000

56Mn

57Mn

58Mn

59Mn

60Mn

24

56Cr

57Cr

58Cr

59Cr

60Cr

23

55V

56V

57V

58V

59V

22

54Ti

55Ti

56Ti

57Ti

58Ti

21

53Sc

54Sc

55Sc

56Sc

57Sc

32

33

34

35

36

Fig. 2. Nuclei at approximately A = 50–60, for which themasses were measured using the ZD-MRTOF (circles
with colors: see text).

30 keV but larger than the uncertainties of AME2020.
These determined masses are well consistent with thevalues on AME2020 within their uncertainties. For 55 V,
indicated with a red circle, the uncertainty is approximately 90 keV owing to the low statistics. For nuclei enclosed with blue circles, the uncertainties are lessthan 30 keV and are smaller than the uncertainties of
AME2020. It is interesting to note that the values ofmasses of 58, 59 V and 58 Ti determined using the ZDMRTOF deviate from ones of AME2020 by 100 keV ormore. As a result, the uncertainties of the masses onseven nuclei can be improved signiﬁcantly.
These updated mass values enable us to discuss themagicites for N = 32 and 34 of Sc, Ti, and V isotopes,
using two neutron separation energies, empirical shellgaps, and other ﬁnite diﬀerence of binding energies. A
detailed discussion is in progress.

14N +
4

13.00625

Neutron number

Yield

56Cr+

Proton number

An RF carpet-type helium gas cell combined withan MRTOF mass spectrograph, the ZD-MRTOF, hasbeen installed downstream of the ZeroDegree spectrometer at the RIBF and is under operation as a collaboration between the RNC and KEK/WNSC. Mass measurement using the ZD-MRTOF can be performed parasitically during other experiments at BigRIPS. During experiments for gamma-ray spectroscopy (HiCARI
campaign), the ﬁrst online commissioning of the system
and mass measurements of neutron-rich nuclei were performed symbiotically using the ZD-MRTOF system.1,2)
The detailed experimental information including the experimental setup is available in other papers.3–6) Overall, masses of more than 70 isotopes have been measured
successfully. We have completed the analysis and determination of masses of the measured isotopes.
Figure 1 shows an example of a measured TOF spectrum for isobars with A = 56. The ZD-MRTOF yieldeda mass resolving power of approximately 500,000 during the online commissioning, resulting in high precisionmass determinations.
At approximately A = 50–60, the masses of 15 radioactive neutron-rich nuclei have been determined. Figure 2 shows the measured nuclei indicated with colored
circles on a nuclear chart.
For nuclei enclosed with green circles, the uncertainties of masses determined with the MRTOF are less than

13.012Time of flight (ms)Fig. 1. Example of measured TOF spectrum on isobars with
A = 56.
∗1

References

RIKEN Nishina Center
Department of Physics, Osaka University∗3 Wako Nuclear Science Center (WNSC), IPNS, KEK∗4 Institute of Modern Physics, Chinese Academy of Sciences∗5 School of Nuclear Science and Technology, Lanzhou University∗6 Department of Physics, University of Hong Kong
∗7 Institute of Mass Spectrometer and Atmospheric Environment, Jinan University∗8 Department of Physics, Kyushu University∗9 Advances Science Research Center, Japan Atomic Energy
Agency∗10 Center for Nuclear Study, University of Tokyo∗21) M. Rosenbush et al., RIKEN Accel. Prog. Rep. 54, S18(2021).
2) S. Iimura et al., RIKEN Accel. Prog. Rep. 54, 98 (2021).
3) M. Rosnebucsh et al., Nucl. Instrum. Methods Phys. Res.
B 463, 184 (2020).
4) W. Xian et al., RIKEN Accel. Prog. Rep. 54, 94 (2021).
5) D. Hou et al., RIKEN Accel. Prog. Rep. 54, 96 (2021).
6) S. Chen et al., RIKEN Accel. Prog. Rep. 54, 97 (2021).

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1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Highly precise mass measurements of neutron-rich nuclei at
A = 82–92 at ZeroDegree-MRTOF(ZD-MRTOF)
W. Xian,∗1,∗2 M. Rosenbusch,∗2 S. Chen,∗1,∗2 D. Hou,∗3,∗2 S. Iimura,∗5,∗4 H. Ishiyama,∗4 Y. Ito,∗6 S. Kimura,∗4
T. M. Kojima,∗4 J. Liu,∗3 J. Lee,∗1 H. Miyatake,∗2 S. Michimasa,∗10 S. Nishimura,∗4 T. Niwase,∗7,∗4,∗2 S. Naimi,∗4
P. Schury,∗2 T. Sonoda,∗4 A. Takamine,∗4 M. Wada,∗2 Y. X. Watanabe,∗2 H. Wollnik,∗8 and S. Yan∗9Counts / 3.6 [ns]

104

83

84

Se

Kr 1H+

13
84

+

+

Ge

C 1H 35Cl2+



C21H619F 35Cl+

32 +C4 H4 S

12

C 1H216O 19F 35Cl+

84

As+

10
1
15.87215.87415.87615.878

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be measured simultaneously. Stable molecules provided
isobaric references for extracting masses of ion of interest. On the other hand, the stable molecules also served
as benchmarks for the evaluation of the systematic uncertainties.
In total, the HiCARI campaign 2020 had ﬁve separate experiments, covering four diﬀerent regions. The
results introduced in this report were from the data acquired during NP1912-RIBF196 and NP1912-RIBF190.
Among other mass regions, abundant species of isotopes
have been observed in the mass range A = 82–92. In
total, 35 nuclides were measured in a neutron-rich region of Ga, Ge, As, Se, Br, Kr, and Rb in which 84 Ga,
86
Ge, 89 As, 91 Se, and 92 Br are the most exotic isotopes(see Fig. 2). Among those isotopes, mass uncertainties
of 86 Ge, 90 Se, and 91 Se, could be reduced signiﬁcantly toless than 5 keV. Moreover, for the ﬁrst time, the massesof 88, 89 As were unveiled. In addition to radioactive ions,at least one stable atomic or molecular ion was found foreach mass number, e.g., 82 Kr1 H+ , 83 Kr1 H+ , 12 C37 Cl+
2,
etc. The mass deviations of these ions from AME2020
enable an evaluation of system accuracy of the new ZDMRTOF system. The weighted mean deviation of themeasured masses from the precisely known values wasfound to be approximately only 2 keV, which proves avery high accuracy for future measurements.

C 35Cl 37Cl+
12

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

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Fig. 2. Meassured isotopes (A = 82–92) in on-line tests.

12

1

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Kr+

12

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84

103
102



A state-of-art multi-reﬂection time-of-ﬂight (TOF)
mass spectrograph (MRTOF-MS) coupling to a cryogenic helium ﬁlled gas catcher (gas cell) was developed
and prepared for on-line tests prior to the launch of the
HiCARI campaign 20201) for γ-ray spectroscopy. For
the ﬁrst time, the ZD-MRTOF system was operated
on-line running as parasitic experiment downstream of
the ZeroDegree (ZD) spectrometer. Produced by inﬂight ﬁssion of 238 U primary beam with 9 Be target, radioactive ions were selected, identiﬁed, and guided by
BigRIPS to the focal plane F8, where the exotic ionsreacted with a secondary target for in-beam γ-ray research. Reaction products were then analyzed using the
ZD spectrometer before they were ﬁnally entrapped by
the gas cell and measured by the MRTOF-MS.
Abundant stable molecules contribute to strong peaks
with long tails in a TOF spectrum, which causes diﬃculties identifying the much weaker peaks of the ionsof interest. Beneﬁting from the introduction of a new
mass ﬁlter method,2) we obtained low-contaminantbackground with high resolution isobaric TOF spectrums, as shown in Fig. 1. In this spectrum, in addition
to isobaric ions from the on-line beam, stable moleculesfrom background contaminations in the gas were also observed in the same measurement as several species can

15.880

TOF [ms]

Fig. 1. TOF spectrum at A = 84 with radioactive ions (red)and stable molecules (blue).
∗1

University of Hong Kong
Wako Nuclear Science Center (WNSC), IPNS, KEK∗3 Institute of Modern Physics, Chinese Academy of Sciences∗4 RIKEN Nishina Center∗5 Osaka University∗6 Advanced Science Research Center, Japan Atomic Energy
Agency∗7 Department of Physics, Kyushu University∗8 Department of Chemistry and Biochemistry, New Mexico
State University∗9 Jinan University∗10 University of Tokyo∗2

References
1) M. Rosenbusch et al., RIKEN Accel. Prog. Rep. 54, S18(2021).
2) S. X. Yan et al., RIKEN Accel. Prog. Rep. 54, S28 (2021).

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II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Mass measurements of neutron-rich nuclei around A = 112 with
ZD-MRTOF-MS system
D. Hou,∗1,∗2 A. Takamine,∗4 S. Iimura,∗4,∗5 S. Chen,∗2,∗6 Y. Hirayama,∗2 H. Ishiyama,∗4 Y. Ito,∗7 S. Kimura,∗4
T. M. Kojima,∗4 J. Liu,∗1 H. Miyatake,∗2 S. Michimasa,∗8 T. Niwase,∗4,∗2 S. Nishimura,∗4 S. Naimi,∗4
M. Rosenbusch,∗2 P. Schury,∗2 T. Sonoda,∗4 M. Wada,∗2 Y. X. Watanabe,∗2 H. Wollnik,∗9 W. Xian,∗2,∗6 andS. Yan∗2,∗9
The ZeroDegree-MRTOF (ZD-MRTOF) system combined with a gas catcher cell with radio-frequency ion
guide method has been developed at the downstream of
ZeroDegree spectrometer in RIKEN Nishina Center.1)
An online test for this system was performed with ﬁssion
reactions symbiotically with the in-beam γ-ray spectroscopy experiments2) at the end of 2020. The reaction products after the second target at the focal plane
F8 were selected and guided by the ZeroDegree spectrometer, then they were captured by the gas cell andtransported to the MRTOF for precise mass measurement. We measured more than 70 masses in total, andin this work, we concentrated on the masses in the rangeof neutron-rich isotopes A = 111–113.
In Fig. 1, an example of the TOF spectra obtained
from the experiments is shown. In the spectra, it canbe seen that the beam’s ions and their β-decay products
were observed. To ﬁt the peaks in the spectra, a Gaussian function coupled with two exponential tails3) was
employed during the data analysis process. The deﬁnition of the ﬁtting function is shown in Eq. (1),⎧c +ΔL )⎪
exp( ΔL (2t−2t)
t ≤ tL
⎪
2σ 2
⎪
⎪
⎨
2
c)
f (t) = A · exp( −(t−t)
tL < t < tR (1)
2σ 2
⎪
⎪
⎪
⎪
⎩
c +ΔR )
exp( ΔR (−2t+2t) t ≥ tR2σ 2Fig. 1. An example of TOF spectrum at A = 111 with radioactive ions and stable molecules. The red line indicates the ﬁt function deﬁned in Eq. (1).

In this work, we measured 15 masses of radioactive neutron-rich nuclei 111, 113 Ag, 111, 113 Rh, 111–113 Pd,
111–113Ru, and 111, 112 Mo (see in Fig. 2). Compared withthe mass values listed in AME2020, an excellent agreement between our results and previously reported values
has been observed. The mass measurement of 113 Ru was
improved, and the 112 Mo mass was measured for the ﬁrst
time. Based on our results, we investigated the double
neutron separation energy (S2n ) and empirical neutrons
shell gap (δ 2n ), and the results will be presented in a
future publication.

where A and tc are the amplitude and maximum positionof this function, σ is the width of the central Gaussianpart, tL (tL = tc − ΔL ) and tR (tR = tc + ΔR ) are thetransition points of the left and right side of the Gaussianfunction, where the Gaussian function smoothly changes
to an exponential function. The function value and its
ﬁrst derivative are continuous at the transition points.
Compared to Gaussian and exponential-Gaussian hybrid functions, the accuracy of ﬁtting results can besigniﬁcantly improved4) using the function described in
Eq. (1). We can calculate the ion mass accurately after
measuring the ions’ exact time-of-ﬂight.
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9

Fig. 2. Nuclei chart A ∼ 110, nuclei measured with ZDMRTOF are in red square, and the new mass is marked
with a star.

Institute of Modern Physics, Chinese Academy of Sciences
Wako Nuclear Science Center (WNSC), IPNS, KEK
RIKEN Nishina Center
Department of Physics, Osaka University
Department of Physics, University of Hongkong
Advanced Science Research Center, Japan Atomic Energy
AgencyCenter for Nuclear Study, University of Tokyo
Department of Chemistry and Biochemistry, New Mexico
State University
Institute of Mass Spectrometry and Atmospheric Environment, Jinan University

References
1) M. Rosenbusch et al., Nucl. Instrum. Methods Phys. Res.
B 463, 184 (2020).
2) M. Rosenbusch et al., RIKEN Accel. Prog. Rep. 54, S18(2021).
3) M. Rosenbusch et al., Phys. Rev. C 97, 064306 (2018).
4) P. Schury et al., Nucl. Instrum. Methods Phys. Res. B
335, 39 (2014).

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II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Improved mass measurement of 257 Db by decay-correlated mass
spectroscopy
P. Schury,∗1 T. Niwase,∗1,∗2,∗3 M. Wada,∗1 P. Brionnet,∗2 S. Chen,∗4 T. Hashimoto,∗5 H. Haba,∗2 Y. Hirayama,∗1
D. S. Hou,∗6,∗7,∗8 S. Iimura,∗9,∗2,∗1 H. Ishiyama,∗2 S. Ishizawa,∗10,∗2 Y. Ito,∗11,∗2,∗1 D. Kaji,∗2 S. Kimura,∗2
H. Koura,∗11 J. J. Liu,∗4,∗1 H. Miyatake,∗1 J. -Y. Moon,∗5 K. Morimoto,∗2 K. Morita,∗12,∗13 D. Nagae,∗13
M. Rosenbusch,∗1 A. Takamine,∗2 Y. X. Watanabe,∗1 H. Wollnik,∗14 W. Xian,∗4,∗1 and S. X. Yan∗15
We present an improved direct measurement of theatomic mass of the superheavy nuclide 257 Db. Atoms of257
Db (Z = 105) were produced online at the RIKEN
Nishina Center for Accelerator-Based Science using thefusion-evaporation reaction 208 Pb(51 V, 2n)257 Db. The
gas-ﬁlled recoil ion separator GARIS-II was used tosuppress both the unreacted primary beam and sometransfer products, prior to delivering the energetic beamof 257 Db ions to a helium gas-ﬁlled ion stopping cell
wherein they were thermalized. Thermalized 257 Db2+
ions were then transferred to a multi-reﬂection time-ofﬂight mass spectrograph (MRTOF) for mass analysis.
An alpha particle detector embedded in the ion timeof-ﬂight detector allowed disambiguation of the rare
257
Db2+ time-of-ﬂight detection events from backgroundby means of correlation with characteristic α-decays.
The extreme sensitivity of this technique,1) allowed aprecision atomic mass determination from 22 decaycorrelated events.
In our previous measurement of this nuclide,2) metallic Pb targets were utilized, limiting the permissible primary beam intensity to below 500 particle nA. In thismeasurement we tested PbS targets produced via sputtering. The targets were capable of withstanding 2 particle μA primary beam without degradation in their performance. This allowed for twice as many events in half
as much time as the previous measurement, while the
MRTOF’s mass resolving power was signiﬁcantly improved. Additionally, the implementation of a pulseddeﬂector,3) inside the MRTOF allowed selective rejection of transfer products such as 211 Po which had previously produced some spurious decay correlations.
Using the same correlation method as previously employed,2) a mass was determined for the detected ion ineach decay-correlated event. A histogram of the masses
is shown in Fig. 1. A Gaussian ﬁt to the histogram data,
shown in violet, indicates that a mass resolving powerof m/Δm = 800 000 was achieved; the ﬂight time wast ≈ 17 ms. The shape of the distribution indicates thateither only a single state was present or the isomeric
excitation energy is below 300 keV. The centroid of thehistogram indicates a mass excess of 100 408(75) keV/c 2
for the possible mixed ensemble of states. Regardless,however, the measured mass is not in agreement with
the Atomic Mass Evaluation.4)
Within the new set of data, only 8 decay-correlated
events were determined to have had observed α-decays
from 257 Db—the others having observed decays of 253 Lr
or 249 Md. A further followup eﬀort to gather moredata and better determine the state ordering via decaycorrelated mass analysis is planned for FY2022.
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∗1

Wako Nuclear Science Center (WNSC), IPNS, KEK
RIKEN Nishina Center∗3 Department of Physics, Kyushu University∗4 Department of Physics, University of Hong Kong
∗5 Institute for Basic Science∗6 Institute of Modern Physics, Chinese Academy of Sciences∗7 University of Chinese Academy of Sciences∗8 School of Nuclear Science and Technology, Lanzhou University∗9 Department of Physics, Osaka University∗10 Graduate School of Science and Engineering, Yamagata University∗11 Advanced Science Research Center, Japan Atomic Energy
Agency∗12 Department of Physics, Kyushu University∗13 Research Center for SuperHeavy Elements, Kyushu University∗14 New Mexico State University∗15 Institute of Mass Spectrometer and Atmospheric Environment, Jinan University
∗2

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Fig. 1. Histograms of evaluated atomic masses for ions detected with subsequent α-decays consistent with 257 Db,
253
Lr, or 249 Md. If present, isomeric state must have excitation below 300 keV. In the legend, “MRP” refers tomass resolving power.

References
1) T. Niwase et al., Nucl. Instrum. Methods Phys. Res. A,
953, 163198 (2020).
2) P. Schury et al., Phys. Rev. C 104, L021304 (2021).
3) M. Rosenbusch et al., submitted to Nucl. Instrum. Methods Phys. Res. A.
4) M. Wang et al., Chinese Phys. C 41, 030003 (2017).

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II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Initial mass measurement of 258 Db by decay-correlated mass
spectroscopy
P. Schury,∗1 T. Niwase,∗1,∗2,∗3 M. Wada,∗1 P. Brionnet,∗2 S. Chen,∗4 T. Hashimoto,∗5 H. Haba,∗2 Y. Hirayama,∗1
D. S. Hou,∗6,∗7,∗8 S. Iimura,∗9,∗2,∗1 H. Ishiyama,∗2 S. Ishizawa,∗10,∗2 Y. Ito,,∗11,∗2,∗1 D. Kaji,∗2 S. Kimura,∗2
H. Koura,∗11 J. J. Liu,∗4,∗1 H. Miyatake,∗1 J. -Y. Moon,∗5 K. Morimoto,∗2 K. Morita,∗12,∗13 D. Nagae,∗13
M. Rosenbusch,∗1 A. Takamine,∗2 Y. X. Watanabe,∗1 H. Wollnik,∗14 W. Xian,∗4,∗1 and S. X. Yan∗15
We present the ﬁrst direct measurement of the atomic
mass of the superheavy nuclide 258 Db. Atoms of 257 Db(Z = 105) were produced online at the RIKEN Nishina
Center for Accelerator-Based Science using the fusionevaporation reaction 208 Pb(51 V, 1n)258 Db. The gasﬁlled recoil ion separator GARIS-II was used to suppress
both the unreacted primary beam and some transfer
products, prior to delivering the energetic beam of 258 Dbions to a helium gas-ﬁlled ion stopping cell wherein they
were thermalized. Thermalized 258 Db2+ ions were thentransferred to a multi-reﬂection time-of-ﬂight mass spectrograph (MRTOF) for mass analysis. An alpha particle
detector embedded in the ion time-of-ﬂight detector allowed disambiguation of the rare 258 Db2+ time-of-ﬂight
detection events from background by means of correlation with characteristic α-decays. The extreme sensitivity of this technique1) allowed a precision atomic mass
determination from 22 decay-correlated events.
This measurement was made simultaneously with
257
Db while testing PbS targets produced via sputtering. The targets were capable of withstanding 2 particle
μA primary beam without degradation in their performance. The pulsed deﬂector2) inside the MRTOF wasoperated to allow passage of A/q = 128.5 and A/q = 129
while rejecting transfer products such as 211 Po that had
previously produced spurious decay correlations. The
observed rate of 258 Db relative to 257 Db is within expectations based on the excitation functions.3)
Using a similar correlation method as employed for257Db,4) extended to encompass spontaneous ﬁssion
events, a mass was determined for the detected ion ineach decay-correlated event. A histogram of the masses
is shown in Fig. 1. Based on the mass resolving power
seen for 257 Db2+ ,5) there appears to be an excess of      
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Fig. 1. Histograms of evaluated atomic masses for ions detected with subsequent α-decays consistent with 258 Db,
254
Lr, or 250 Md, 258 Rf, and spontaneous ﬁssion. The twopeak structure could indicate the isomeric excitation exceeds NUBASE estimates.6)

events in the low-mass tail. Applying two-peak ﬁttingwith ﬁxed resolution results in a good reproduction of
the observed distribution. Presuming this is not a statistical anomaly, it would indicate the isomeric excitation
to be 300 (150) keV, a signiﬁcant deviation from the
α-decay derived NUBASE value6) of 53 (14) keV.
A further followup eﬀort to gather more data in order
to better determine the isomeric excitation is planned
for FY2022. However, due to the small diﬀerences between α-particle energies emitted from the two states,
determination of the state ordering via precision decaycorrelated mass spectroscopy will require a considerably
improved detector station. Such a detector station ispresently in the initial design phase.

∗1

Wako Nuclear Science Center (WNSC), IPNS, KEK
RIKEN Nishina Center∗3 Department of Physics, Kyushu University∗4 Department of Physics, University of Hong Kong
∗5 Institute for Basic Science∗6 Institute of Modern Physics, Chinese Academy of Sciences∗7 University of Chinese Academy of Sciences∗8 School of Nuclear Science and Technology, Lanzhou University∗9 Department of Physics, Osaka University∗10 Graduate School of Science and Engineering, Yamagata University∗11 Advanced Science Research Center, Japan Atomic Energy
Agency∗12 Department of Physics, Kyushu University∗13 Research Center for SuperHeavy Elements, Kyushu University∗14 New Mexico State University∗15 Institute of Mass Spectrometer and Atmospheric Environment, Jinan University∗2

References
1) T. Niwase et al., Nucl. Instrum. Methods Phys. Res. A
953, 163198 (2020).
2) M. Rosenbusch et al., submitted to Nucl. Instrum. Methods Phys. Res. A.
3) J. M. Gates et al., Phys. Rev. C 78, 034604 (2008).
4) P. Schury et al., Phys. Rev. C 104, L021304 (2021).
5) P. Schury et al., in this report.
6) M. Wang et al., Chin. J. Phys. C, 45 030001 (2021).

-7-

1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Status of the study of masses and half-lives of 252 Cf ﬁssion fragments
by the MRTOF-MS
S. Kimura,∗1 M. Wada,∗2 H. Haba,∗1 S. Ishizawa,∗3 T. Niwase,∗2 M. Rosenbusch,∗2 and P. Schury∗2
for the SHE-Mass Collaboration

Intensity ratio, 92Br+ / 92Rb+

The nuclear data of neutron-rich nuclei, e.g., mass,
lifetime, and neutron-capture cross section, are important for understanding the rapid neutron-capture (r -)process, because a balance of net neutron-capture rateand β − -decay rate is crucial to determine its path.
Thus, accurate and high-precision nuclear data aboutboth neutron-rich isotopes’ mass and half-life are required.1)
The multi-reﬂection time-of-ﬂight mass spectrograph (MRTOF-MS) has been developed for not only
mass measurement but also isobar separation. Here,
we brieﬂy report the present status of the mass measurement of neutron-rich isotopes and, in addition,
the half-life measurement as an application of the
MRTOF-MS.
The mass measurement study of the neutron-rich
252
Cf-ﬁssion-fragments with the MRTOF-MS2) waspresented in the previous report.3) We had used the
350 kBq 252 Cf source and newly installed a more intense source (9.25 MBq). More than 200 isotopes
have been conﬁrmed in the time-of-ﬂight spectra andare shown in Fig. 1. In addition, many long-lived
isomers were also observed during the measurements.
The mass resolving power of the MRTOF-MS reaches
Rm > 5 × 105 ; thus, the measurements were achieved
with precision better than 10−7 in most of the cases.
We have developed a decay-scheme-independent

<4

10

<5

10

<6

30
10<7
50

60

70
80
Neutron number

90

100

110

Fig. 1. Location of the observed isotopes on the nuclear
chart. The observed isotopes are indicated with orangecolored squares. The black squares represent the stable
isotopes. The contour map shows the ﬁssion yield of
252
Cf.4)
∗1
∗2
∗3

250

450

half-life measurement method with the MRTOF-MS.
The experimental setup consists of a cryogenic gascell, the MRTOF-MS, and a suite of ion traps witha quadrupole ion guide (QPIG), a linear trap, and a
ﬂat trap used as an injector for the MRTOF-MS. Bychanging the operation cycle of the linear trap, theion storage time of the linear trap can be changed,
making it possible to measure the lifetimes of shortlived isotopes. We brieﬂy discuss here the lifetime
measurement of 92 Br as an example of this “storage
method.” Figure 2 shows the storage time dependenceof the yields of 92 Br+ ions normalized by the 92 Rb+
ion yields for canceling out the eﬃciency reduction due
to increasing of the storage time. A decreasing trendof 92 Br+ ion yields is clearly observed and the 92 Br+ ’s
half-life is measured to be 349(178) ms through a ﬁt
with the theoretical curve. This value is in agreementwith the value in the literature of 314(16) ms. In thisanalysis, we assumed that an inﬂuence of the decay
loss of the 92 Rb+ ion is negligibly small because its
half-life (4.48 s) is suﬃciently long compared to thestorage time.

40

40

1.5×10-3

Fig. 2. Intensity ratio of 92 Br+ /92 Rb+ as a function of storage time in the linear trap. A black line shows a ﬁt result. The measured half-life, 349(178) ms, is consistent
with the value in the literature of 314(16) ms.

Fission yield

Proton number

10-3Storage time in the linear trap ( ms )60

50

2.0×10t1/2 = 349(178) ( ms )

50

10<2

<3

-3

1.0×10-370

10

2.5×10

References
1) M. R. Mumpower et al., Prog. Part. Nucl. Phys. 86, 86(2016).
2) P. Schury et al., Nucl. Instrum. Methods Phys. Res. B
335, 39 (2014).
3) S. Kimura et al., RIKEN Accel. Prog. Rep. 53, 52(2019).
4) J. Katakura, JAEA-Data/Code 2011-025.

RIKEN Nishina Center
Wako Nuclear Science Center (WNSC), IPNS, KEK
Institute for Materials Research, Tohoku University-8-1II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

First measurement of double Gamow-Teller giant resonance at RIBF
A. Sakaue∗1 for the RIBF-141R1 Collaboration
momentum of the ejected particle was measured by using F0-F5 as a spectrometer, as established in pionic
atoms experiments.5) After passing through the tracking detectors of low-pressure multiwire drift chambers(MWDCs) at F5 focal plane, a particle was transferred
to F8 focal plane and stopped in a 9 Be stopper with athickness of 18.8 mm.
Delayed γ rays were detected by a DALI2 array at
F8. During the beam time, we measured the doublecharge exchange reaction for 40 hours for 48 Ca and 20
hours for 116 Cd, respectively. The left panel of Fig. 1
shows the energy spectrum of the photons measured
by DALI2 for the 48 Ca target. A peak at the energyof 511 keV is noticeable in the spectrum. The rightpanel of Fig. 1 shows the timing of the photon detection relative to the signal from a plastic scintillator at
F7. Here, the timing distribution of the events in theenergy region of 500 ± 100 keV is also shown. The
decay histogram is ﬁtted by an exponential curve anda constant background. The decay constant is 302.3 ±8.2 ns, which is close to the known value of the lifetime12of 12 Be(0+Be(0+2 ). This suggests that2 ) is successfully detected.
The analysis is ongoing. The excitation energy spectrum of 48 Ti will be obtained from the position measured by the MWDCs at F5. Currently, we are analyzing the MWDCs at F5.

The double Gamow-Teller (DGT) transition is a
nuclear process characterized by a (στ )2 operator inwhich both the spin and isospin change twice. Experimental information about the DGT transition is currently limited to data of double β decays, whose transition strength accounts for only a small proportion of
the entire transition strength of the DGT transition.
The remainder of the strength is expected to form a giant resonance in a high-excitation energy region. This
resonance, called the DGT giant resonance (DGTGR),
was proposed in 19891) and is still undiscovered experimentally. The aim of this research was to observe
the evidence of the DGTGR for the ﬁrst time, thereby
extending the study on two-phonon excitations to a
regime in which the spin-degrees of freedom contribute.
Although knowledge of the anharmonicity of the nuclear response in such a domain is scarce, observablesof the DGTGR, such as the centroid energy or thewidth, might provide its information.
Experimental information of the DGTGR is also potentially important for determining the nature of neutrinos. The transition strength and centroid energy of
the DGTGR are suggested to be strongly correlatedwith the nuclear matrix element of a neutrinoless double β decay.2) Theoretically predicted values of the nuclear matrix element have a large uncertainty depending on the chosen model.3) Experimental informationof the DGTGR will provide reference for the calculation of the nuclear matrix element.
In this study, the DGTGR was observed by missing mass spectroscopy using a double-charge exchange
reaction (12 C, 12 Be(0+2 )). We utilized an isomeric decay of 12 Be(0+),
forevent selection. 12 Be(0+22 ) has alifetime of 331 ± 12 ns and decays into the groundstate by emitting an electron-positron pair.4) Detecting back-to-back photons with an individual energy of
511 keV from the positron served to tag the events ofthe double spin-ﬂip mode.
In May 2021, we performed the ﬁrst measurement ofthe (12 C, 12 Be(0+2 )) reaction at the RI Beam Factory(RIBF). A 12 C primary beam with an intensity of 500
particle nA was accelerated to 250 MeV/nucleon andimpinged on a target at F0 focal plane of the BigRIPS
separator. We used 48 Ca or 116 Cd as the target, which
are important double β decaying nuclei. The thicknessof the target was 10 mg/cm2 for 48 Ca and 50 mg/cm2
for 116 Cd. The 48 Ca target was sandwiched between
4-micrometer-thick graphene sheets for preventing oxidation and nitridization when installing in the F0 vacuum chamber. Momentum spread of the primary beam
was suppressed by dispersion-matching optics. The
∗1

350

400
300

48Ca(12C, 12Be(0+2))

at 250 MeV/nucleon

200
100
0

0

counts [/10 ns]

counts [/10 keV]

500

300
250
200

48Ca(12C, 12Be(0+2))
at 250 MeV/nucleon

150
100
50

500

1000

1500

2000

Energy measured by DALI2 [keV]

0

0

500

1000

1500

Timing measured by DALI2 [ns]Fig. 1. (Left) Energy distribution of delayed γ rays measured by DALI2. (Right) Timing distribution of delayed
γ rays for events in energy region of 500 ± 100 keV. Red
curve is ﬁtting result.

References
1) N. Auerbach, L. Zamick, D. Zheng, Ann. Phys.
(Leipzig) 192, 77 (1989).
2) N. Shimizu et al., Phys. Rev. Lett. 120, 142502 (2018).
3) J. Engel, J. Menéndez, Rep. Prog. Phys. 80, 046301(2017).
4) S. Shimoura et al., Phys. Lett. B 654, 87 (2007).
5) T. Nishi et al., Nucl. Instrum. Methods Phys. Res. B
317, 290 (2013).

Center for Nuclear Study, University of Tokyo

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II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Spectroscopy of pionic atoms in tin isotopes by (d, 3 He) reactions∗1

Department of Physics, Kyoto University
RIKEN Nishina Center∗3 JINA and Department of Physics, University of Notre Dame
∗4 Department of Physics, Tokyo Institute of Technology∗5 GSI Helmholtzzentrum für Schwerionenforschung GmbH
∗6 Center for Nuclear Study, University of Tokyo∗7 Department of Physics, Toho University∗8 Japan Atomic Energy Agency∗9 Department of Physics, Saitama University∗10 Research Center for Nuclear Physics, Osaka University∗2- 10 -

      Fig. 1. Position distribution observed by p(d, 3 He)π 0 reactions. Blue, red and green lines represent data with CH2target at −3, 0, and +6 mm from beam center, respectively.







We performed systematic spectroscopy measurements of pionic tin isotopes by (d, 3 He) reactions. We
measured the masses of the reaction products, i.e., pionic atoms, by missing mass spectroscopy. The incident
deuteron beam energy was chosen as 500 MeV to enhance the formation cross-sections of the pionic atoms.
We installed A = 112, 115, 117, 119, 122, and 124 tin
isotopes at F0.
3
He emitted by an energy of ∼360 MeV wasmomentum-analyzed by using the BigRIPS. We installed two low-pressure multi-wire drift chambers1)(MWDCs) at F5, and measured 3 He tracks. The
MWDCs were operated with 30 kPa isobutane and had
suﬃcient eﬃciency. We installed plastic scintillators at
F5 and F7 for time-of-ﬂight measurements. Combining
the time-of-ﬂight information with the measured energy
loss at each scintillator, 3 He particles were identiﬁed.
One of the largest sources of resolution is the momentum spread of the primary beam, which was determinedas δp/p = 0.03% (σ). We constructed dispersion matching optics by analyzing the beam momentum at F0 tohave a dispersion of 44.6 mm/%. We developed a novel
method of tuning the optical condition, called “traceback method.”2) In this method, the particle tracks at
F3 and F5 are measured and the matrix elements in F0F3-F5 are evaluated. Finally the trajectories are traced
back to F0, and the phase distributions are deduced.
Figure 1 shows the position spectra of p(d, 3 He)π 0
reactions at F5 using a CH2 target. The spectra were
measured by placing the target at horizontal positions−3, 0, and +6 mm from the beam center. The beam
spot size was enlarged to approximately 15 mm (σ) for
the very large dispersion of 44.6 mm/% at the target.
Without the dispersion matching conditions, the displacement of 3.0 mm at the target position causes a
5.5-mm shift at the F5 focal plane and severe deterioration of the energy resolution. In the spectra, we observe similar position distributions for the three target
positions, which suggesting a nearly perfect realization



S. Y. Matsumoto,∗1 H. Asano,∗2 H. Baba,∗2 G. P. A. Berg,∗3 M. Dozono,∗1,∗2 H. Fujioka,∗2,∗4 N. Fukuda,∗2
N. Fukunishi,∗2 H. Geissel,∗5 S. Hanai,∗6 T. Harada,∗2,∗7 T. Hashimoto,∗8 S. Hayakawa,∗5 K. Higuchi,∗4
Y. Hijikata,∗1,∗2 K. Horikawa,∗4 N. Inabe,∗2 K. Itahashi,∗2 K. Kusaka,∗2 Y. Ma,∗2 R. Matsumura,∗9,∗2
S. Michimasa,∗6 N. Nakatsuka,∗4,∗2 T. Nishi,∗2 S. Ota,∗10 A. Sakaue,∗6 F. Sakuma,∗2 M. Sasano,∗2 R. Sekiya,∗1,∗2
Y. Shimizu,∗2 T. Sumikama,∗2 D. Suzuki,∗2 H. Suzuki,∗2 H. Takeda,∗2 Y. K. Tanaka,∗2 J. Tanaka,∗2 R. Tsuji,∗1,∗2
T. Uesaka,∗2 K. Yako,∗6 Y. Yanagisawa,∗2 H. Weick,∗5 K. Yoshida,∗2 M. Yoshimoto,∗2 and J. Zenihiro∗1,∗2 

     Fig. 2. Position spectrum measured using 124 Sn target.

of the dispersion matching conditions.
Figure 2 shows a typical position spectrum observedin the production setting. We employed an 124 Sn target
with a width of 6 mm and accumulated the data for
approximately 50 min. Pionic atoms in 1s and 2p states
are noticeable as peak structures.
We will continue the data analysis in terms of energy
calibration, resolution improvement, and other factors.
References
1) S. Y. Matsumoto et al., RIKEN Accel. Prog. Rep. 50,
205 (2017).
2) A. Sakaue et al., RIKEN Accel. Prog. Rep. 54, 86 (2021).

1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Spectroscopy of three-neutron system via the 3 H(t, 3 He)3n reaction
K. Miki,∗1,∗2 K. Kameya,∗1,∗2 N. Imai,∗3 S. Michimasa,∗3 S. Ota,∗3 M. Sasano,∗2 H. Takeda,∗2 T. Uesaka,∗2
Y. Hatano,∗4 M. Hara,∗4 H. Haba,∗2 T. Hayamizu,∗2 T. Chillery,∗3 M. Dozono,∗5,∗2 N. Fukuda,∗2 J. Gao,∗6
S. Hanai,∗3 S. Hayakawa,∗3 Y. Hijikata,∗5,∗2 K. Himi,∗7 J. Hwang,∗8 T. Kawabata,∗7,∗2 K. Kishimoto,∗9,∗2
S. Kitayama,∗1,∗2 K. Kusaka,∗2 J. Li,∗3 Y. Maeda,∗10,∗2 Y. Maruta,∗1,∗2 T. Matsui,∗1,∗2 H. Nishibata,∗9,∗2
M. Otake,∗2 H. Sakai,∗2 A. Sakaue,∗3 H. Sato,∗2 K. Sekiguchi,∗1,∗2 Y. Shimizu,∗2 S. Shimoura,∗3 L. Stuhl,∗8,∗2
T. Sumikama,∗2 H. Suzuki,∗2 R. Tsuji,∗5,∗2 S. Tsuji,∗7 H. Umetsu,∗1 R. Urayama,∗1,∗2 Y. Utsuki,∗1,∗2
T. Wakasa,∗9 K. Yako,∗3 Y. Yanagisawa,∗2 N. Yokota,∗9,∗2 C. Yonemura,∗9,∗2 K. Yoshida,∗2 and M. Yoshimoto∗2
MWDCs were also installed at focal planes
PPACs
for beam-tuning.
Plastics

Can we ﬁnd a nucleus that consists only of neutrons? This is a long-standing question in nuclear
physics. If any signature of multi-neutron bound orresonant states exists, it is a challenge to the current
description of nuclei. In particular, it has a significance on the understanding of high-isospin systems
such as neutron stars. In a recent study,1) a candidate of the tetra-neutron resonance was found in
the 4 He(8 He, 8 Be)4n spectrum. This peak located at
Ex = 0.83 ± 0.65 (stat) ± 1.25 (syst) MeV has notbeen understood yet with the theoretical calculations
based on ﬁrst principles. To investigate the simpler
and more fundamental case, we focused on the threeneutron (3n) system and performed a 3 H(t, 3 He)3n experiment at the incident energy of 170 MeV/nucleon.
The schematic layout of our experimental setup
is shown in Fig. 1. The primary 4 He beam of
200 MeV/nucleon impinged on the 9 Be target with athickness of 6 cm. Among the reaction fragments, thetriton beam of 170 MeV/nucleon was selected using the
BigRIPS separator with a purity higher than 99%. A
high intensity of 5×107 particles/sec was obtained owing to the cooperation of the accelerator and radiationsafety group at the RIBF. The beam was transported
to the SHARAQ target position in the achromatic ionoptics mode. The beam tuning was performed with
low-pressure MWDCs and PPACs installed at each focal plane of the beamline. The scattered 3 He particles
from the target were momentum-analyzed using theSHARAQ spectrometer and detected by the CRDCs
and plastic scintillators. A pair of liquid scintillation detectors were installed around the target, whichcounted the decay neutrons from the 3n system in coincidence with the focal plane detectors.
For the target, we have newly developed a tritiatedtitanium (Ti-3 H) target and used it for the ﬁrst time at
RIBF. The thickness of tritium is 3.5 mg/cm2 , which is

S2 CRDC
S0
Plastic
Secondary targets
Ti-3H, Ti, CH2, CD2, C, Blank

High Resolution
Beam Line

3

He2+

SHARAQ
Secondary beam on target
Particle : 3H+ 170 MeV/u
Intensity : 5 x 107 pps
Purity : >99%

He2+
200 MeV/u1000 pnA
4

BigRIPS

F0
Production
target9
Be (6 cm)

F2.5

Angular collimator
|'T_ < 15mrad

F1

Momentum slit
_'p/p| < 0.06%
3 +H
170 MeV/u

Fig. 1. Schematic layout of the experimental setup. The
detector layout is similar to the previous (t, 3 He) experiment.2)

almost two orders of magnitude larger than those used
in RI beam experiments in the past. This thick target
enables us to ﬁnd rare process such as the productionof 3n system in this study.
With this setup, the double diﬀerential cross section spectra for the 3 H(t, 3 He)3n reaction were obtained for the excitation energy of 0 ≤ Ex ≤ 20 MeV
and the scattering angle of 0 ≤ θ ≤ 4 degrees. The
1
H(t, 3 He)1n and 2 H(t, 3 He)2n spectra were also obtained in the same beamtime. This aids us to argue
the 1n, 2n, and 3n systems on an equal basis. Detailed
analyses are in progress.

∗1

Department of Physics, Tohoku University
RIKEN Nishina Center∗3 Center for Nuclear Study, University of Tokyo∗4 Hydrogen Isotope Research Center, University of Toyama∗5 Department of Physics, Kyoto University∗6 School of Physics, Peking University∗7 Department of Physics, Osaka University∗8 Center for Exotic Nuclear Studies, Institute for Basic Science∗9 Department of Physics, Kyushu University∗10 Faculty of Engineering, University of Miyazaki∗2

References
1) K. Kisamori et al., Phys. Rev. Lett. 116, 052501 (2016).
2) K. Miki et al., Phys. Rev. Lett. 108, 262503 (2012).

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RIKEN Accel. Prog. Rep. 55 (2022)- 12 -

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Mass measurements of neutron-rich Ni isotopes in Rare-RI Ring II
A. Ozawa,∗1,∗2 Y. Yamaguchi,∗2 N. Kaname,∗1 T. Moriguchi,∗1,∗2 A. Yano,∗1 Y. Abe,∗2 N. Fukuda,∗2
Y. Hijikata,∗2,∗3 S. Naimi,∗2 D. Shimizu,∗2 F. Suzaki,∗2,∗4 H. Suzuki,∗2 H. Takeda,∗2 T. Uesaka,∗2
M. Yoshimoto,∗2 M. Wakasugi,∗2 Y. Nagata,∗5 D. Nagae,∗5,∗2 M. Kanda,∗6,∗2 Y. Koizumi,∗6,∗2 S. Okubo,∗6
M. Otsu,∗6,∗2 H. Seki,∗6,∗2 N. Shinozaki,∗6,∗2 T. Suzuki,∗6 T. Yamaguchi,∗6,∗2 T. Chillery,∗7 M. Dozono,∗7
S. Hanai,∗7 N. Imai,∗7 J. Li,∗7 S. Ota,∗7,∗8 S. Michimasa,∗7 R. Yokoyama,∗7 H. F. Li,∗9 and S. Suzuki∗9
In spring 2021, we conducted an experiment at the
Rare-RI Ring (R3) to measure the masses of neutronrich Ni isotopes. Some of these nuclei were measured
before at R3,1) but the mass values of 74 Ni and 76 Ni
showed large systematic uncertainties. Since the topof the waveform in the previous kicker system is not
ﬂat, it causes a ﬂuctuation of approximately 10% in
the kick angle within an eﬀective duration of 100 ns.2)
Since the kick angle aﬀects the orbit inside R3, thisﬂuctuation was suspected to be a major source of systematic uncertainties. The kicker magnet system was
successfully upgraded in the fall of 2020.2) For injection, a 100 ns ﬂat top was realized, and the kick angle
ﬂuctuation is expected to be 1%. For ejection, a longﬂat top of approximately 400 ns was realized, enabling
the extraction of all stored events in a single step.
The experimental setup was essentially the same asthat in the previous experiments.1) A primary beamof 238 U accelerated in the Superconducting Ring cyclotron (SRC) to 345 MeV/nucleon impinged on a Be
target with a thickness of 8 mm. Secondary beams,
including 74 Ni isotopes, were produced via in-ﬂight ﬁssion. We adjusted the thickness of degraders locatedat F1 and F2 in BigRIPS such that the beam energies of 76 Zn became approximately 150 MeV/nucleon,
which was the proper energy for individual ion injection. Particle identiﬁcation was performed up to F3
in BigRIPS.1) The plastic scintillator at F3 provided
trigger signals for the kicker magnets to inject particles of interest into R3. To maintain the trigger rate of
the kicker magnets within 80 Hz, we applied TOF-ΔE
gates3) for the trigger signals. In this experiment, themomentum-dispersive focus was at F5 in BigRIPS. We
placed two parallel-plate avalanche counters (PPACs)
there to measure the beam momentum. At S0, theentrance of SHARAQ, we located a TOF counter,4)
which provided the start signal of the TOF in R3. We
also measured the TOFs of each particle between F3and S0, which is used for β calibration. The particles
injected into R3 were extracted after approximately
700 μs by using the same kicker magnets. After the
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9













 








 

Fig. 1. TOF in R3 (ns) versus momentum diﬀerence (%)
for extracted events in the experiment. Diﬀerent colors
show diﬀerent species. All species are extracted withina time window of 400 ns.

extraction, the particle impinged on a plastic scintillator, which provided a stop signal for the TOF in R3;
ﬁnally, it was stopped in a NaI scintillator.
In this experiment, we successfully extracted 5
species (78 Ge, 77 Ga, 76 Zn, 75 Cu, and 74 Ni). The
isochronous optics of R3 was tuned using 76 Zn suchthat the width of the TOF in R3 was the narrowest
for this nucleus. The observed momentum dependenceof TOF in R3 in this experiment is shown in Fig. 1.
All species were extracted within a time window of
400 ns. By careful tuning for trim coils, we achieved
better isochronicity than in the previous experiment.
To deduce the masses, the TOF in R3 should be corrected by the corresponding β or Bρ.
Data analysis is ongoing. At this moment, it is unclear whether the kicker upgrade aﬀects the systematic
uncertainties.
References
1) A. Ozawa et al., RIKEN Accel. Prog. Rep. 52, 5 (2019).
2) Y. Yamaguchi et al., RIKEN Accel. Prog. Rep. 54, 100(2021).
3) Y. Abe et al., RIKEN Accel. Prog. Rep. 52, 15 (2019).
4) S. Suzuki et al., Nucl. Instrum. Methods Phys. Res. A
965, 163807 (2020).

Institute of Physics, University of Tsukuba
RIKEN Nishina Center
Department of Physics, Kyoto University
Advanced Science Research Center, JAEA
Faculty of Sciences, Kyushu University
Department of Physics, Saitama University
Center for Nuclear Study, University of Tokyo
Research Center for Nuclear Physics, Osaka University
Institute of Modern Physics, Chinese Academy of Science- 13 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Mass measurements with the Rare-RI ring for the A = 130 r -process
abundance peak II
S. Naimi,∗1 Y. Yamaguchi,∗1 Y. Nagata,∗2 D. Nagae,∗2,∗1 Y. Abe,∗1 F. Suzaki,∗1,∗3 M. Wakasugi,∗1
N. Kaname,∗4 S. Suzuki,∗4 A. Yano,∗4 T. Moriguchi,∗4 A. Ozawa,∗4 M. Kanda,∗5 Y. Koizumi,∗5 K. Okubo,∗5
M. Otsu,∗5 K. Sasaki,∗5 H. Seki,∗5 N. Shinozaki,∗5 T. Suzuki,∗5 T. Yamaguchi,∗5 T. Chillery,∗6 S. Hanai,∗6
Y. Hijitaka,∗7,∗1 J. Li,∗6 R. Yokoyama,∗6 M. Dozono,∗6 S. Ota,∗6,∗8 S. Michimasa,∗6 H. Suzuki,∗1 N. Fukuda,∗1
Y. Shimizu,∗1 H. Takeda,∗1 M. Yoshimoto,∗1 H. F. Li,∗9 and T. Uesaka∗1
In the fall of 2021, we conducted an experiment at
the Rare-RI Ring (R3) aiming to measure masses ofneutron-rich silver (Ag) and palladium (Pd) isotopes.
The ﬁrst part of this experiment was conducted in thefall of 2018.1) Some of these nuclei were measured atthat time, however, the mass values of 125 Ag and 124 Pd
showed large systematic uncertainties that were suspected to be due to the narrow extraction timing of
the storage ring. Upgrade of the kicker magnets system was successfully conducted in the fall of 20202) andextraction timing window was extended from 100 ns to
400 ns, leading to extraction of all stored events at thesame time.
Particles of interest for this experiment were produced at RIBF by impinging a 60 particle nA Uranium beam on a 5-mm thick Be target. Particles wereidentiﬁed at BigRIPS by energy loss in an Ionization
Chamber (IC) placed at F3 and their Time-of-Flight(ToF) from F3 to F5. The ToF was measured by a
0.2 mm thick plastic scintillator at F3 and the PPAC’s
anode at F5. The particles were then transported to
the SHARAQ spectrometer and then injected into thering. After injection into the R3 and storage for about
1 ms, equivalent to almost 2000 turns, the particles
were extracted. To determine the mass, the total ToF
inside the ring is necessary. For this purpose, a timing detector3) was placed a the focal plane S0 of the
SHARAQ spectrometer for the start signal, while athin plastic detector was placed at the exit of the R3
for the stop signal.
Figure 1 shows the PID at F3 of all events produced
at BigRIPS and the extracted events from R3, which
are indicated by open black circles. These events wereselected by using the so-called TOF/dE gate methodthat is necessary for the individual injection method.4)
To estimate the extracted events for each isotone, a
PID gate of ±2σ for ToF from F3 to F5 as well as a ±2σgate for energy loss at F3 IC were performed. Unfor∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9

Energy Loss at F3 IC [ch]







Time-of-Flight F3 - F5 [ns]Fig. 1. Particle Identiﬁcation (PID) showing the energy
loss in the Ionizarion Chamber (IC) at F3 and ToF
from F3 to F5. Extracted particles from R3 are shownin black empty circles.

tunately, no events of 124 Pd were extracted, however,suﬃcient events of 125 Ag and reference particles wereextracted. Due to technical issues during the beamtransport from BigRIPS to R3 and circulation inside
the ring, the total eﬃciency was lower compared toprevious experiments.1,5)
In the near future, we will focus our eﬀorts on solving the technical issues encountered during the experiment. We then plan to continue mass measurements ofneutron-rich nuclei as well as neutron-deﬁcient nuclei.
References
1) H. F. Li et al., Phys. Rev. Lett. 128, 152701 (2022).
2) Y. Yamaguchi et al., RIKEN Accel. Prog. Rep. 54, 100(2021).
3) S. Suzuki et al., Nucl. Instrum. Methods Phys. Res. A
965, 163807 (2020).
4) Y. Abe et al., RIKEN Accel. Prog. Rep. 52, 15 (2019).
5) A. Ozawa et al., RIKEN Accel. Prog. Rep. 52, 5 (2019).

RIKEN Nishina Center
Faculty of Sciences, Kyushu University
Advanced Science Research Center, Japan Atomic Energy
AgencyInstitute of Physics, University of Tsukuba
Department of Physics, Saitama University
Center for Nuclear Study, University of Tokyo
Department of Physics, Kyoto University
Research Center for Nuclear Physics, Osaka University
Institute of Modern Physics, Chinese Academy of Sciences- 14 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Decay spectroscopy in exotic neutron-rich nuclei near the N = 50
shell closure

∗1
∗2
∗3
∗4
∗5
∗6

Physical Sciences Division, TRIUMF
School of Physics and Astronomy, University of Edinburgh
Depatment of Physics and Astronomy, University of Tennessee
Oak Ridge National Laboratory
Instituto de Fı́sica Corpuscular (IFIC)RIKEN Nishina Center- 15 -

10
2

500
400
300

0
0

39
5

100

46
1

26
7

200

50

100

150

200

250

300

350

400

450 500
Eγ [keV]

6

17

8

11

9

11

2

1000
900
800
700
600
500
400
300
200
100
0

50

100

150

500

550

600

650

200

1

9

44

250

300

350

400

450

500

750

800

850

900

950

1000

70

4

500

32

24

0

12

CountsFig. 1. Preliminary γ-spectrum for decays into 85 As, considering both β- and βxn-decay modes from parent nuclei.
Known peaks in 85 As are labelled in black and peaks
identiﬁed from the decay of 85 As into 85 Se are in red.

98

400
300

4

200
69

β-decay and β-delayed neutron emission play key
roles in determining the ﬁnal elemental abundancesof the rapid neutron-capture (r-) process. Current r process models rely heavily on theoretical data but,with new generations of radioactive ion beam facilities
coming online, swaths of neutron-rich nuclei will become available for experimental study. Delayed neutron
emission is expected to be the dominant decay mode forthese newly-accessible nuclei and has been shown to be
crucial in determining r -process abundances.1)
In 2016, the BRIKEN collaboration constructed andcommissioned the world’s most eﬃcient β-delayed neutron detector2,3) at RIBF to conduct a wide-ranging
and systematic study into the decay properties ofhundreds of the most exotic neutron-rich nuclei currently available. The BRIKEN detector consists of 140
3
He tubes within a HDPE moderator surrounding thehighly-segmented active stopper AIDA4) and two HPGeclover detectors in close geometry.
The NP1412-RIBF127R1 experiment implemented
the BRIKEN detector to measure β-delayed neutron
emission probabilities and half-lives, as well as conduct
decay spectroscopy studies, around the N = 50 shellclosure near the doubly-magic 78 Ni. This region has
been highlighted as sensitive to β-decay properties,5)
however, little to no spectroscopy data exist in this region.
The TRIUMF-based analysis focuses on γ-ray decay
spectroscopy of 85–90 Ge, 88–92 As, 91–95 Se and 94–97 Br
isotopes, with some high-statistics known cases atlighter masses studied for calibration. During theexperiment, approximately 7.5 · 104 85 Ge nuclei and5.75 · 106 86 Ge nuclei were implanted into AIDA. Figures 1 and 2 show preliminary decay spectra for thede-excitation of states within 85 As and 86 As, chosen as
two of the few isotopes in this region with any previous
spectroscopic data and also relatively high statistics.
With approximately two orders of magnitude fewer85
Ge implants compared to 86 Ge, a signiﬁcant fractionof the decays to 85 As are expected to come from the βndecay of 86 Ge, with its P1n value of 45%.6)
Many of the peaks identiﬁed in 85, 86 As by Mazzocchi
et al.7) are labelled in the spectra, as well as peaks identiﬁed from decays into the daughter nuclei 85, 86 Se.8,9)CountsC. J. Griﬃn,∗1 G. Carpenter,∗1,∗2 R. Caballero-Folch,∗1 I. Dillmann,∗1 R. K. Grzywacz,∗3 K. P. Rykaczewski,∗4
J. L. Tain,∗5 and S. Nishimura∗6 for the BRIKEN Collaboration

100
700

Eγ [keV]Fig. 2. Preliminary γ-spectrum for decays into 86 As, considering both β- and βxn-decay modes from parent nuclei.
Known peaks in 86 As are labelled in black and peaks
identiﬁed from the decay of 86 As into 86 Se are in red.

Analysis of the Ge, As, Se and Br isotopes of interest
is on-going and we expect to obtain the ﬁrst spectroscopic data for some of these isotopes.
References
1) M. R. Mumpower et al., Phys. Rev. C 85, 045801 (2012).
2) A. Tarifeño-Saldivia et al., J. Instrum. 12, P04006(2017).
3) A. Tolosa-Delgado et al., Nucl. Instrum. Methods Phys.
Res. A 925, 133 (2019).
4) C. J. Griﬃn et al., Proc. XIII Nuclei in the Cosmos, PoS(NIC XIII), 097 (2015).
5) T. Shafer et al., Phys. Rev. C 94, 055802 (2016).
6) K. Miernik et al., Phys. Rev. Lett. 111, 132502 (2013).
7) C. Mazzocchi et al., Phys. Rev. C 92, 054317 (2015).
8) Evaluated Nuclear Structure Data File (ENSDF).
9) J. V. Kratz et al., Nucl. Phys. A 250, 13 (1975).

1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Half-lives and β-delayed neutron emission for the most exotic
neutron-rich Se and Br isotopes
R. Caballero-Folch,∗1 I. Dillmann,∗1 S. Devinyak,∗1 C. J. Griﬃn,∗1 L. Sexton,∗1,∗2 J. Agramunt,∗3
R. K. Grzywacz,∗4 M. Pallas,∗5 K. P. Rykaczewski,∗6 J. L. Taı́n,∗3 A. Tarifeño-Saldivia,∗5 A. Tolosa-Delgado,∗3
S. Nishimura,∗7 and the BRIKEN Collaboration.
The BRIKEN collaboration performed measurements on several neutron-rich nuclei regions across thenuclear chart during the period 2017–2021. Focused on
the double magic 78 Ni region, the experiment RIBF127
aimed to determine experimental β-decay half-lives,
neutron emission probabilities, and γ spectroscopy of
isotopes beyond the N = 50 neutron shell, which are
all important parameters to provide reliable data formodels of the astrophysical rapid-neutron capture process. The most neutron-rich isotopes of elements fromFe (Z = 26) to Kr (Z = 36) were identiﬁed using the
BigRIPS spectrometer on an event-by-event basis with
the Bρ–ΔE–ToF method.1) At the end of the beamline, the detection setup consisted of the Advanced Impantation and Detector Array (AIDA)2) surrounded by
the BRIKEN detector.3) The AIDA consists of an array of six highly segmented layers of double-sided Si
detectors (DSSSD), enabling the detection of the implants of the ions and their β-decays. The BRIKEN
array is a high eﬃciency neutron detector based on 140
3
He counters embedded in a polyethylene matrix tomoderate the emitted neutrons, and two HPGe clover
γ detectors. It enabled the detection of the neutrons
and the γ-rays emitted after the β-decays.
The isotopic species of interest in this study are
91–94
Se and 94–96 Br. They have been implanted in
AIDA (see Table 1), and for most of them, the decay properties were determined for the ﬁrst time. The
data analysis is based on the time correlation of theimplants and β-decays registered in AIDA, and theneutrons and γ-rays detected with the BRIKEN detector. In addition to the time correlation, spatial correlations between implants and β-decays are studied
owing to the DSSSD’s segmentation. This allowed us
to adjust the best signal-to-noise rate in the correlations.4) Using the Bateman equations and corrections
due to the physical limitations of the detection systems,5,6) the half-life and the β-delayed neutron emission probability, P1n -value, were determined. Figure 1
shows the analysis of 91 Se, in which multiple simultaneous ﬁts of implant-β and implant-β-neutron correlation histograms were performed to determine its
∗1
∗2
∗3
∗4
∗5
∗6
∗7

Table 1. Number of implants of the isotopes of interest andavailable data in the literature.
Nucleus Number of ions Previous literature values
implanted
half-life (s) P1n value (%)
91

Se
Se
93
Se
94
Se
94
Br
95
Br
96
Br

59728
340337
16631
525
2627
2289
159

92

21(10)7)30(10)7)-0.27(5)0.070(20)-91

Se decay chain implant-β
correlations

91

Se β decays
Br β decays
Br β decays

91
90

102
91

CountsSe implant-βncorrelations

10

1− 1000

−500

0

500

1000
1500
Correltaion time (ms)

2000

2500

3000

Fig. 1. Implant-β (blue) and implant-β-neutron (red) correlation histograms for 91 Se. Fitted curves obtainedby simultaneously sharing common parameters, fromwhich the half-life and the P1n -value were determined.

properties. Preliminary results show slightly shorter
half-life and higher P1n -value compared with the literature for 91 Se. An upcoming publication will report
new half-lives and P1n values in the region, some ofthem for the ﬁrst time.
References
1) N. Fukuda et al., Nucl. Instrum. Methods Phys. Res. B
317, 323 (2013).
2) C. Griﬃn et al., POS (NIC-XIII), 097 (2014).
3) A. Tarifeño-Saldivia et al., J. Instrum. 12, (2017).
4) R. Caballero-Folch et al., Phys. Rev. C 95, 064322(2017).
5) A. Tolosa-Delgado et al., Nucl. Instrum. Methods Phys.
Res. A 925, 133 (2019).
6) J. Agramunt et al., Nucl. Instrum. Methods Phys. Res.
A 807, 69 (2016).
7) J. Liang et al., Nucl. Data Sheets 168, 1 (2020).

Physical Science Division, TRIUMF
Department of Physics, University of Surrey
Institut the Fı́sica Corpuscular de València
Department of Physics and Astronomy, University of Tennessee
Universitat Politècnica de Catalunya
Oak Ridge National Laboratory
RIKEN Nishina Center- 16 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Identiﬁcation of a new μs-isomer in the REP region
A. Vitéz-Sveiczer,∗1,∗2 G. G. Kiss,∗1 A. Tarifeño-Saldivia,∗3 M. Pallas,∗3 J. L. Tain,∗4 A. Estrade,∗5
S. Nishimura,∗6 J. Agramunt,∗4 A. Algora,∗4 N. T. Brewer,∗7 R. Caballero-Folch,∗8 F. Calvino,∗3 T. Davinson,∗9
I. Dillmann,∗8 N. Fukuda,∗6 R. K. Grzywacz,∗10 O. Hall,∗7 A. I. Morales,∗4 A. Navarro,∗3 N. Nepal,∗6
B. C. Rasco,∗7 K. P. Rykaczewski,∗7 N. T. Szegedi,∗1 A. Tolosa-Delgado,∗4 P. Vi,∗11 R. Yokoyama,∗10
K. Wang,∗5 M. Wolinska-Cichocka,∗12 and P. Woods∗9 for the BRIKEN collaboration
The solar r-process abundance distribution has two
characteristic maxima at A ≈ 130 and A ≈ 195, which
can be explained by neutron shell closures at N = 82
and N = 126, respectively. A smaller peak also exists between these two maxima at A ≈ 160, which is
known as the rare-earth peak (REP). The formationof the REP is sensitive to parameters that control theneutron density and neutron-to-seed ratio Ye in thelate stages of the r-process, such as the timescale forthe expansion of the material. However, these astrophysical conditions are entangled with nuclear physics
processes that provide additional neutrons, of which
β-delayed neutron emissions can be a main contributor.1) The mass region responsible for the formation of
the REP has previously been inferred.2)
During the NP1612-RIBF148 experiment’s heavier setting, exotic neutron-rich 159–166 Pm, 161–168 Sm,
165–170
Eu, and 167–172 Gd isotopes were produced(among others) at RIKEN Nishina Center by the fragmentation of a 238 U primary beam with an intensityof approximately 60 particle nA to produce isotopes as
close to the aforementioned region of nuclei as possible. The ﬁssion fragments were selected and identiﬁedusing the standard ΔE-Bρ-ToF method by BigRIPS.
The radioactive ions were implanted in the AIDA implantation detector3,4) after adjusting their kinetic energy with aluminum degraders placed at the F11 focal
point. The AIDA implantation detector was centeredin the BRIKEN neutron counter,5) which consistedof 140 3 He-ﬁlled proportional counters embedded ina large polyethylene moderator matrix. Moreover, two
CLARION-type clover detectors6) were inserted horizontally from the left and right sides into holes in thematrix that allowed facing the center of the stack of
double-sided silicon strip detectors (DSSSD).
Half-lives and P1n values were deduced from
implantation–β correlations and implantation–β–Fig. 1. Energy spectrum of isomer-delayed γ-rays from
164
Eu∗ . Inset: exponential function ﬁt to the isomeric
decay curve.

neutron correlations for the produced isotopes. These
results were used for variance-based sensitivity analysis
to reveal the inﬂuence of nuclear physics inputs on thecalculated abundance pattern for the case of REP.7)
Beta-delayed γ-spectroscopy was also performed using
the CLARION-type clover detectors. In most of thestudied nuclei, there was a signiﬁcant number of newly
identiﬁed γ-ray transitions. In order to build decayschemes, γ–γ coincidence analysis was performed aswell.
A μs-isomer candidate of 164 Eu was identiﬁed earlier
using implantation–γ correlations; however, no half-life
nor exact energy level was reported.8) We found thatthe 164 Sm → 164 Eu∗ β-decay populates a low-lying isomeric state located at Eexc. = 143.7(3) keV, which
de-excites through Eγ = 54 keV and Eγ = 89 keV
γ-transitions. The half-life of this isomeric state wasfound to be 6.9(9) μs. Figure 1 shows the measured
gamma spectra and the isomeric decay curve.
References∗1

Institute for Nuclear Research (ATOMKI)
Department of Physics, University of Debrecen∗3 Universitat Politècnica de Catalunya (UPC)∗4 Instituto de Fı́sica Corpuscular (IFIC)∗5 University College of Science and Engineering, Central
Michigan University (CMU)∗6 RIKEN Nishina Center∗7 Oak Ridge National Laboratory∗8 Physical Sciences Division, TRIUMF∗9 School of Physics and Astronomy, University of Edinburgh∗10 Department of Physics and Astronomy, University of Tennessee∗11 Faculty of Physics, VNU University of Science∗12 HIL, University of Warsaw

1) A. Arcones et al., Phys. Rev. C 83, 045809 (2011).
2) M. Mumpower et al., Phys. Rev. C 85, 045801 (2012).
3) C. J. Griﬃn et al., Proc. XIII Nuclei in the Cosmos,
PoS(NIC XIII), 097 (2015).
4) O. Hall et al., Phys. Lett. B 816, 136266 (2021).
5) A. Tolosa-Delgado et al., Nucl. Instrum. Methods
Phys. Res. A 925, 133 (2019).
6) C. J. Gross et al., Nucl. Instrum. Methods Phys. Res.
450, 12 (2000).
7) G. G. Kiss et al., in preparation.
8) Z. Patel et al., Phys. Rev. C 96, 034305 (2017).

∗2- 17 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

RIBF181: γ-ray spectroscopy in the vicinity of 78 Ni

The NP1912-RIBF181 experiment with the HiCARI
setup1) was conducted for 7 days in April 2021. Its objective is the spectroscopy of the nuclei in the vicinity of78
Ni, which is expected to be doubly magic (Z = 28,
N = 50).2,3) The experiment aimed to prove for the
possible shape coexistence phenomena associated withshell-quenching in both proton and neutron gaps at andbeyond this anchor-point nucleus, especially by the detailed spectroscopy of the proton single-particle statesin 79 Cu. 80 Zn and the one-proton removal channels were
centered in the BigRIPS and ZeroDegree (ZD) spectrometers, respectively.
The secondary beam was produced with a 4-mm beryllium target at the F0 focal plane by a 90-particle nA 238 U
primary beam at an energy of 345 MeV/nucleon. The
beam was puriﬁed using the Bρ-ΔE-Bρ method throughthe ﬁrst stage of BigRIPS with a wedge-shaped 8-mm
aluminium degrader installed at F1 and the second stage
with a 2-mm aluminium degrader at F5. To enhance theproduction yield of the 80 Zn beam, we selected the magnetic rigidity for a high total beam rate at F7 of about
5 × 104 counts per second (cps). This is much higher
than the upper limit (10 kcps) of the previous in-beam
γ-ray spectroscopy experiments at the ZD spectrometer.
A secondary target consisting of 6.8-mm-thick beryllium
was selected for an eﬃcient population yield of the γ rays
after the secondary reaction without eroding the advantage of the high-resolution spectrometer array.
The data acquisition (DAQ) system consisted of twoparts, the BigRIPS and HiCARI DAQs. The former processed all the data except the data from the HiCARI detector arrays, i.e., the data from the beamline detectors
and the timestamp values of the HiCARI DAQ with ashared dead-time mode within the subsystems. The latter recorded the waveforms of the HPGe detector signals
with a certain time window generated from the external
trigger pulse with practically no dead time. A live-time∗1

Department of Physics, University of YorkRIKEN Nishina Center∗3 IJCLab∗4 Research Center for Nuclear Physics, Osaka University∗5 Nuclear Science Division, Lawrence Berkeley National Laboratory∗6 Department of Physics, University of Hong Kong
∗7 Instituut voor Kern- en Stralingsfysica, KU Leuven∗8 Institut für Kernphysik, Universität zu Köln∗9 Department of Physics, Korea University∗10 Department of Physics, Tohoku University∗11 Department of Physics, University of Tokyo∗12 Department of Natural Sciences, Tokyo City University∗13 Department of Physics, University of Surrey∗14 IEM-CSIC∗2

Atomic number, Zdeg

R. Taniuchi,∗1,∗2 S. Franchoo,∗3,∗2 D. Suzuki,∗2 N. Aoi,∗4,∗2 H. Baba,∗2 F. Browne,∗2 C. M. Campbell,∗5
S. Chen,∗1,∗6 R. Crane,∗1,∗2 H. L. Crawford,∗5 H. de Witte,∗7,∗2 P. Doornenbal,∗2 C. Fransen,∗8 N. Fukuda,∗2
H. Hess,∗8,∗2 E. Ideguchi,∗4,∗2 S. Iwazaki,∗4,∗2 J. Kim,∗9 A. Kohda,∗4,∗2 T. Koike,∗10,∗2 T. Koiwai,∗11,∗2
B. Mauss,∗2 R. Mizuno,∗11,∗2 B. Moon,∗2 M. Niikura,∗11,∗2 D. Nishimura,∗12,∗2 T. Parry,∗13,∗2 M. Petri,∗1
P. Reiter,∗8 H. Sakurai,∗11,∗2 Y. Shimizu,∗2 H. Suzuki,∗2 H. Takahashi,∗12,∗2 H. Takeda,∗2 S. Thiel,∗8
K. Wimmer,∗14,∗2 Y. Yamamoto,∗4,∗2 and M. Yoshimoto∗2 for the RIBF 181 Collaboration
34
33
32
31
30
29
28
27
26
2.50

10๏

ແ๣Zn

10๎
10ํ
10

2.55

2.60

2.65

2.70

Mass-to-charge ratio, A/Q

2.75

2.80

1

Fig. 1. Preliminary particle identiﬁcation plot in BigRIPS
with the Zdeg method. 80 Zn is highlighted with a red
ellipse.

ratio of ≈87% with a trigger rate greater than 5 kHz wasachieved in the BigRIPS DAQ owing to a recently developed data acquisition system, MPV.5) To establish both
good timing and energy measurements with a high beam
rate in each plastic detector, a charge-to-time converter(QTC) module6) was utilized in addition to the standard
circuits.
The particle identiﬁcation for the secondary beams
was performed with the TOF-Bρ-ΔE technique. Insteadof using the standard MUSIC detector at F7, which suffered from a large number of pile-up hits, the Zdeg technique was conﬁrmed to be functional with a reasonable
resolution (Fig. 1). This method is to calculate the energy loss in the degrader at F5 from the diﬀerence in thereconstructed momenta between F3-F5 and F5-F7 andhas been applied before in other experiments in higher
Z regions around Z ≈ 50.4) The purity of the 80 Zn beam
is tentatively deduced as 4.8%. The same method wasapplied to the scattered particles with the ZD spectrometer. As a backup for the energy loss measurement, another 1-mm plastic scintillator was installed at F11 after
the standard one.
A set of high-statistics data is expected to provide not
only γ-ray energy spectra disentangling high density levels that were not resolved in the previous studies2,3) but
also systematic inclusive nucleon-removal reaction crosssections with a variety of isotopes in the vicinity of 78 Ni.
References
1) K. Wimmer et al., RIKEN Accel. Prog. Rep. 54, S27(2021).
2) R. Taniuchi et al., Nature 569, 53 (2019).
3) L. Olivier et al., Phys. Rev. Lett. 119, 192501 (2017).
4) Y. Shimizu et al., J. Phys. Soc. Jpn. 87, 014203 (2018);
N. Fukuda et al., J. Phys. Soc. Jpn. 87, 014202 (2018).
5) H. Baba et al., IEEE Trans. Nucl. Sci. 68, 1841 (2021).
6) T. Ishikawa et al., Nucl. Instrum. Methods Phys. Res. A
875, 193 (2017).

- 18 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Neutron intruder states and collectivity beyond N = 50 towards 78 Ni
L. Plagnol,∗1 F. Flavigny,∗1 for the RIBF196 and HiCARI collaborations

∗1

34

33
10

3

10

2

32

Z

Recent spectroscopy studies in the vicinity of 78 Ni1,2)
hint to the presence of low-lying deformed conﬁgurations. These intruder conﬁgurations are predicted tooriginate from the multiparticle-multihole excitations3)of nucleons above the N = 50 and Z = 28 shellgaps becoming competitive in energy owing to neutronproton correlations enhancing quadrupole collectivity.
The quantiﬁcation of collective eﬀects above N = 50 is
crucial since it directly impacts binding energies, dripline limits,4) and consequently r-process nucleosynthesis calculations. Because these states involve manyparticle excitations, their theoretical description is very
challenging: thus, identifying them experimentally is ofprime interest to constrain models.
We report here on the analysis status of the RIBF196
experiment to identify and characterize 2p-1h intruder
states above N = 50 in 83 Ge and 81 Zn for the ﬁrst timeusing a neutron knockout reaction from N = 52 isotopes. This selective reaction enables neutron removalfrom the g9/2 orbital populating preferentially 9/2+
states with a signiﬁcant intruder ν(g9/2 )−1 (s1/2 d5/2 )+2
conﬁguration. Simultaneously, low-lying states in 82 Zn
were populated using proton removal from 83 Ga, andtheir lifetimes will be extracted using line-shape analysis to better characterize the onset of deformation developing in Zn above N = 50.5)
To attain these scientiﬁc objectives, a secondary
cocktail beam containing 84 Ge, 83 Ga, and 82 Zn was produced and puriﬁed in the BigRIPS spectrometer to induce knockout reactions on a secondary 6-mm thick Be
target. De-excitation γ-rays of the reaction products
83
Ge, 82 Zn, and 81 Zn were detected using the HiCARI
germanium array6) surrounding the secondary reaction
target. Event-by-event particle identiﬁcation for beam
nuclei and reaction products was achieved in the BigRIPS and ZeroDegree spectrometers by reconstructing their atomic number (Z) and their mass-to-charge
ratio (A/Q) using the TOF-Bρ-ΔE method combinedwith a two-fold Bρ method.
We performed higher-order optical corrections of theA/Q values to compensate for remaining dependencies
on spectrometer variables such as as positions and angles at the focal planes. This additional correction isequivalent to a higher-order determination of opticaltransfer matrices and improves the identiﬁcation. It
was performed using a multi-dimensional ﬁtting procedure, considering cross-terms. An optically correctedparticle identiﬁcation diagram (PID) is shown in Fig. 1.
The A/Q resolution achieved through this opticalcorrection procedure is of 7.10−2 % calculated on theidentiﬁcation of 84 Ge in BigRIPS with an ameliorationof approximately 14% compared with the uncorrected

31

30

10

29
2.56

2.58

2.6

2.62

2.64

2.66

A/Q

2.68

2.7

2.72

2.74

1

Fig. 1. Particle identiﬁcation of the reaction products in the
ZeroDegree spectrometer. The black, red, and purple
ellipsoids indicate 83 Ge, 82 Zn, and 81 Zn, respectively:
see text for details.

A/Q resolution, and 9.10−2 % on 83 Ge in ZeroDegree
spectrometer with an amelioration of more than 50%.
In addition, we cleaned the PID by removing unwanted
events such as delta rays in PPAC detectors, pileup
events in plastic detectors and ionisation chambers, andchange in charge states. The most impacting selectionis the pileup events removal cutting away approximately
10% of events on the total PID.
The HiCARI detectors have been aligned in time, calibrated in energy (38 crystals and 376 segments) using
sources of 60 Co, 152 Eu, and 133 Ba, and the array eﬃciency was determined (2.9% at 1 MeV with a 0.5 mm
Pb shield). The non-linearities of the ADCs were quantiﬁed from the residuals of the energy calibrated spectra
and exhibit a saw-tooth pattern with variations up to 2–
3 keV.7) Their impact on Doppler corrected spectra will
be quantiﬁed using simulations. Finally, a preliminary
Doppler-corrected gamma spectrum has been produced
using photogrammetry positions of the clusters and aﬁxed velocity at the target, but we aim at improving
this result using event-by-event Doppler correction using the measured velocity distributions in the BigRIPS
and ZeroDegree spectrometers.
References
1) R. Taniuchi et al., Nature 569, 53 (2019).
2) X. F. Yang et al., Phys. Rev. Lett. 116, 219901 (2016).
3) K. Heyde, J. L. Wood, Rev. Mod. Phys. 83, 1467 (2011).
4) J. Erler et al., Nature 486, 509 (2012).
5) C. Shand et al., Phys. Lett. B 773, 492 (2017).
6) K. Wimmer et al., RIKEN Accel. Prog. Rep. 54, S27(2020).
7) K. Dolde et al., Nucl. Instrum. Methods Phys. Res. A
848, 127 (2017).

LPC Caen, CNRS/IN2P3- 19 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Charge state separation in the ZD spectrometer for the 132 Sn region
T. Parry,∗1 Zs. Podolyák,∗1 G. Bartram,∗1 Z. Q. Chen,∗1 M. Górska,∗2 M. Armstrong,∗2 A. Yaneva,∗2
K. Wimmer,∗3,∗4 P. Doornenbal,∗4 N. Aoi,∗5,∗4 H. Baba,∗4 F. Browne,∗4 C. Campbell,∗6 H. Crawford,∗6 H. De
Witte,∗7 C. Fransen,∗8 H. Hess,∗8 S. Iwazaki,∗5,∗4 J. Kim,∗4 A. Kohda,∗5,∗4 T. Koiwai,∗9,∗4 B. Mauss,∗4
B. Moon,∗4 P. Reiter,∗8 D. Suzuki,∗4 R. Taniuchi,∗10,∗4 S. Thiel,∗8 and Y. Yamamoto∗5,∗4
Isotopes produced in charge states become increasingly more common amongst higher mass beams. The
ability to separate and identify diﬀerent charges is important in preventing particle identiﬁcation contamination. In this report, we brieﬂy outline a commonly used method of charge state separation which
was utilised during the analysis of the RIBF-189 experiment conducted in November 2020 during the HiCARI campaign.1,2) The aim of the experiment was
to study excited states in N = 82 nuclei, focusing
on 129 Ag. A primary 345 MeV/nucleon beam of 238 U
was used and the ﬁssion fragments were identiﬁed in
BigRIPS, which was tuned for 130 Cd. After the secondary target, the reaction products were identiﬁed by
the ZeroDegree (ZD) spectrometer. Here the energyof the reaction products was relatively low at around
150 MeV/nucleon, which means that only about 80%of them were fully stripped. Charge state separation is based on magnetic rigidity measurements inthe two parts of the separator FP8-FP9 and FP9FP11. δ is calculated as δ = (Bρ − Bρ0 )/Bρ0 . Bρdenotes the measured magnetic rigidity for individual
particles. Bρ0 is the magnetic rigidity for the central
path. Figure 1 shows the charge state separation where

the structures correspond to diﬀerent changes of thecharge state (ΔQ) in the middle of the ZD spectrometer (FP9). Figure 2, showing Z vs A/Q identiﬁcation
plots, demonstrates the eﬀect of selecting ΔQ = 0 and
ΔQ = +1. Note ΔQ = 0 contains ions which are fully
stripped (labelled in black) and hydrogen like throughout the ZD spectrometer (red). Similarly ΔQ = +1 includes ions which change from fully stripped to H-like(black) and H-like to He-like (red). Using these identiﬁcation plots, one obtains γ-ray spectra associated to
the nucleus of interest free from the contributions ofother isotopes.
A/Q

2.55
51

2.6

2.65

2.7

50

132

49

Sn

132

δ8-9 (arb. unit)

Sn

131

In

48

130

Cd

Z

47
46
51

129

ΔQ=0

Ag

Δ Q=+1
132

ΔQ=+2

2.8

ΔQ=0

50

6

2.75

Sn

132

Sn

131

49

In

4
48

130

Cd

2
47

ΔQ=-2

0

46

−2

Fig. 2. ZD spectrometer particle identiﬁcation plots for
ΔQ = 0 (upper) and ΔQ = +1 (lower). N = 82 nuclei
are highlighted.

−4
−6
−10

ΔQ=+1

ΔQ=-1

−8

−4

−6

−2

0

2

4

6

8

δ9-11 (arb. unit)

References

Fig. 1. Charge state separation in ZD spectrometer.

1) T. Parry et al., RIKEN Accel. Prog. Rep. 54, 9 (2021).
2) K. Wimmer et al., RIKEN Accel. Prog. Rep. 54, S27(2021).

∗1

Department of Physics, University of Surrey
GSI Helmholtzzentrum für Schwerionenforschung GmbH
∗3 IEM-CSIC∗4 RIKEN Nishina Center∗5 Research Center for Nuclear Physics, Osaka University∗6 Nuclear Science Division, LBNL
∗7 Instituut voor Kern- en Stralingsfysica, KU Leuven∗8 Institut für Kernphysik, Universität zu Köln∗9 Department of Physics, University of Tokyo∗10 Department of Physics, University of York∗2

- 20 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Observation of low-lying dipole states in the 11 Li(p, n) reaction
L. Stuhl,∗1,∗2,∗3 M. Sasano,∗3 J. Gao,∗3,∗4 Y. Hirai,∗5 K. Yako,∗2 T. Wakasa,∗5 D. S. Ahn,∗3 H. Baba,∗3
A. I. Chilug,∗6,∗3 S. Franchoo,∗7 Y. Fujino,∗8 J. Gibelin,∗9 I. S. Hahn,∗1,∗10 Z. Halász,∗11 T. Harada,∗12
M. N. Harakeh,∗13,∗14 D. Inomoto,∗5 T. Isobe,∗3 H. Kasahara,∗5 D. Kim,∗1,∗15 G. G. Kiss,∗11 T. Kobayashi,∗16,∗3
Y. Kondo,∗17,∗3 Z. Korkulu,∗1,∗3 S. Koyama,∗18,∗3 Y. Kubota,∗3 A. Kurihara,∗17 H. N. Liu,∗19 M. Matsumoto,∗17
S. Michimasa,∗2 H. Miki,∗17,∗3 M. Miwa,∗20,∗3 T. Motobayashi,∗3 T. Nakamura,∗17,∗3 M. Nishimura,∗3 H. Otsu,∗3
V. Panin,∗3 S. Park,∗10 A. T. Saito,∗17,∗2 H. Sakai,∗3 H. Sato,∗3 T. Shimada,∗17 Y. Shimizu,∗3 S. Shimoura,∗2
A. Spiridon,∗6 I. C. Stefanescu,∗6 X. Sun,∗3,∗4 Y. L. Sun,∗19 H. Suzuki,∗3 E. Takada,∗21 Y. Togano,∗8,∗3
T. Tomai,∗17,∗3 L. Trache,∗6 D. Tudor,∗6,∗3 T. Uesaka,∗3 H. Yamada,∗17 M. Yasuda,∗17 K. Yoneda,∗3 K. Yoshida,∗3
J. Zenihiro,∗3 and N. Zhang∗22,∗2
The SAMURAI30 experimental program aims to systematically investigate the isovector response of light nuclei near the neutron drip line.1) No data are available
on spin-isospin collectivity for nuclei with large isospin
asymmetry factors, where (N − Z)/A > 0.25. GamowTeller (GT) and spin-dipole (SDR) transitions, including their giant resonances, were studied on 11 Li and14
Be using charge-exchange (p,n) reactions in inverse
kinematics combined with the missing-mass technique.2)
The setup of the PANDORA low-energy neutron timeof-ﬂight counter3) and SAMURAI magnetic spectrometer,4) as well as a thick liquid hydrogen target, enables
us to perform measurements with high luminosity. In
our previous experiments at RIKEN RIBF on 132 Sn, we
successfully demonstrated5) that we can obtain data on
unstable nuclei in the giant-resonance region with similar
statistics as data obtained on stable nuclei.
Preliminary results on GT giant resonance are alreadydetailed in a previous report.6) More than ﬁfteen diﬀerent decay channels were identiﬁed for the 11 Be reaction
product. A strong GT transition at 19 MeV, in agreement with previous beta-decay studies, was observed.
We showed experimental evidence for the GT peak shifting below the Isobar Analog State (IAS).
In 11 Be,10 Be, and 9 Be related decay channels, lowlying states were also identiﬁed in the excitation energy∗1Center for Exotic Nuclear Studies, Institute for Basic Science∗2 Center for Nuclear Study, University of Tokyo∗3 RIKEN Nishina Center∗4 School of Physics, Peking University∗5 Department of Physics, Kyushu University∗6 Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering∗7 Institut de Physique Nucléaire, Université Paris-Saclay∗8 Department of Physics, Rikkyo University∗9 Nuclear Physics Laboratory, LPC CAEN
∗10 Department of Physics, Ewha Womans University∗11 Institute for Nuclear Research (ATOMKI)∗12 Department of Physics, Toho University∗13 Department of Physics, University of Groningen∗14 GSI Helmholtzzentrum für Schwerionenforschung∗15 Department of Physics, Korea University∗16 Department of Physics, Tohoku University∗17 Department of Physics, Tokyo Institute of Technology∗18 Department of Physics, University of Tokyo∗19 Départment de Physique Nucléaire, CEA, Université ParisSaclay∗20 Department of Physics, Saitama University∗21 National Institute of Radiological Sciences (NIRS)∗22 Institute of Modern Physics, Chinese Academy of Sciences  

   

 

Fig. 1. Low-liying dipole states in excitation energy spectrum
in the 4◦ –6◦ (a) and 8◦ –10◦ (b) center-of-mass angularbins for beryllium-related decay channels.

range below 10 MeV. The angular-momentum distributions of these states show a peak at backward angles,
which is characteristic of dipole transitions. Similar lowlying SD states were predicted in previous theoretical
calculations on 11 Li by Suzuki7) in connection to theneutron-halo structure.
References
1) L. Stuhl et al., RIKEN Accel. Prog. Rep. 48, 54 (2015).
2) M. Sasano et al., Phys. Rev. Lett. 107, 202501 (2011).
3) L. Stuhl et al., Nucl. Instrum. Methods Phys. Res. A 866,
164 (2017).
4) T. Kobayashi et al., Nucl. Instrum. Methods Phys. Res.
B 317, 294 (2013).
5) J. Yasuda et al., Phys. Rev. Lett. 121, 132501 (2018).
6) L. Stuhl et al., RIKEN Accel. Prog. Rep. 53, 38 (2019).
7) T. Suzuki et al., Nucl. Phys. A 662, 282 (2000).

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II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Analysis of 48 Cr(p, n) reaction in inverse kinematics
M. Sasano,∗1 J. Gao,∗1,∗3 L. Stuhl,∗9,∗22 Y. Hirai,∗4 T. Wakasa,∗4 D. S. Ahn,∗1 J. K. Ahn,∗13 H. Baba,∗1
K. Chae,∗20 A. Chilug,∗5,∗1 K. Cook,∗15 Y. Fujino,∗7 N. Fukuda,∗1 B. Gao,∗19 S. Goto,∗4 I. S. Hahn,∗8,∗22
Y. Hamano,∗4 Z. Halász,∗9 T. Harada,∗10,∗1 S. Hong,∗20 S. Huang,∗1,∗3 N. Inabe,∗1 D. Inomoto,∗4 T. Isobe,∗1
H. Kasahara,∗4 D. Kim,∗8 T. Kobayashi,∗14,∗1 Y. Kondo,∗15,∗1 Z. Korkulu,∗1 A. Krasznahorkai,∗9 H. Miki,∗15
K. Miki,∗14,∗1 S. Mitsumoto,∗4 M. Miwa,∗18,∗1 T. Motobayashi,∗1 T. Nakamura,∗15,∗1 M. Nishimura,∗1
H. Oshiro,∗4 H. Otsu,∗1 V. Panin,∗1 S. Sakaguchi,∗4,∗1 D. Sakai,∗14 H. Sakai,∗1 S. Sakaki,∗4 H. Sato,∗1
T. Shimada,∗15 Y. Shimizu,∗1 B. Sun,∗21 X. Sun,∗1,∗3 H. Suzuki,∗1 J. Tanaka,∗1 Y. Togano,∗7,∗1 T. Tomai,∗15,∗1
T. Uesaka,∗1 Y. Utsuki,∗14 H. Wang,∗15 X. Xu,∗19 K. Yako,∗2 A. Yasuda,∗15 K. Yoneda,∗1 K. Yoshida,∗1
Y. Yoshitome,∗15 and J. Zenihiro∗1
In this report, we present the progress of data analysis of the SAMURAI11 experiments performed at the
RI Beam Factory of RIKEN Nishina Center in thespring of 2019. These experiments were conducted tomeasure the (p, n) reaction on N = Z unstable nuclei, 48 Cr and 64 Ge. Previously, in Refs. 1) and 2), we
reported the experimental setup and the particle identiﬁcation (PID) analysis of the reaction residues using
the SAMURAI spectrometer,3) respectively. Herein,
we present the analysis of the data recorded using theparticle analyzer neutron detector of real-time acquisition (PANDORA)4) system.
The PANDORA neutron detector setup consists of
37 plastic scintillators and was placed on the left
and right sides of a liquid hydrogen target.5) The
neutron-gamma pulse-shape discrimination method
was employed to separate low-energy neutrons fromthe gamma-ray background. The neutron kinetic energies were deduced employing the time-of-ﬂight method,whereas the neutron scattering angles of the (p, n) reaction in the laboratory frame were determined fromthe scintillator bar positions.
Figure 1 shows the kinetic curve for the48
Cr(p, n)48 Mn reaction. Here, the reaction residue
47
Cr was selected from the PID analysis. 47 Cr is pro-

Fig. 1. Two-dimensional plot of neutron kinetic energy vs.
neutron scattering angle in the laboratory frame. Solidand dashed curves represent the excitation energies andscattering angles in center-of-mass system of 48 Cr(p, n)reaction, respectively.

duced via the proton emission from the excited statesof 48 Mn populated by the (p, n) reaction. The proton
separation energy of 48 Mn is 2.05 MeV. We successfully identify a locus along the curve corresponding to
4 MeV excitation energy of 48 Mn, above the separationenergy. Figure 1 shows events due to the backgroundin a low kinetic-energy region below 500 keV. A further
analysis is ongoing to substract the background.
We are grateful to the RIKEN accelerator staﬀ and
the CNS, University of Tokyo, for their continuous efforts to accomplish this stable beam acceleration.

∗1

RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo∗3 School of Physics, Peking University∗4 Department of Physics, Kyushu University∗5 Horia Hulubei National Institute for R&D in Physics andNuclear Engineering∗7 Department of Physics, Rikkyo University∗8 Department of Physics, Ewha Womans University∗9 Institute for Nuclear Research, Hungarian Academy of Sciences∗10 Department of Physics, Toho University∗11 KVI - CART, University of Groningen∗12 GSI Helmholtzzentrum für Schwerionenforschung∗13 Department of Physics, Korea University∗14 Department of Physics, Tohoku University∗15 Department of Physics, Tokyo Institute of Technology∗16 Department of Physics, University of Tokyo∗18 Department of Physics, Saitama University∗19 Institute of Modern Physics, Chinese Academy of Sciences∗20 Department of Physics, Sungkyunkwan University∗21 School of Physics and Nuclear Engineering, Beihang University∗22 Center for Exotic Nuclear Studies, Institute for Basic Science∗2

References
1) M. Sasano et al., RIKEN Accel. Prog. Rep. 53, 40(2019).
2) J. Gao et al., RIKEN Accel. Prog. Rep. 54, 14 (2020).
3) T. Kobayashi et al., Nucl. Instrum. Methods Phys. Res.
B 317, 294 (2013).
4) L. Stuhl et al., Nucl. Instrum. Methods Phys. Res. A
866, 164 (2017).
5) M. Miwa et al., RIKEN Accel. Prog. Rep. 52, 149(2018).

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II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Measurement of proton elastic scattering from 132 Sn at
300 MeV/nucleon in inverse kinematics
T. Harada,∗1,∗2 J. Zenihiro,∗3,∗2 Y. Matsuda,∗4,∗2 S. Terashima,∗5,∗2 H. Sakaguchi,∗6 N. Aoi,∗6,∗2 H. Baba,∗2
M. Dozono,∗7 F. Endo,∗8,∗2 S. Enyo,∗3 Y. Fujikawa,∗3 S. Hanai,∗7 S. Hayakawa,∗7 Y. Hijikata,∗3,∗2
J. W. Hwang,∗7 N. Imai,∗7 K. Inaba,∗3 S. Ishida,∗4 T. Isobe,∗2 T. Kawabata,∗9,∗2 S. Kiyotake,∗10 A. Kohda,∗6,∗2
H. Kurosawa,∗4 R. Kojima,∗7 R. Maeda,∗4 Y. Maeda,∗10 S. Y. Matsumoto,∗3,∗2 R. Matsumura,∗1,∗2 B. Mauss,∗2
S. Michimasa,∗7 T. Murakami,∗3 D. Nishimura,∗11,∗2 T. Nishimura,∗10 K. Nosaka,∗4 S. Ota,∗7 K. Sakanashi,∗3
H. Shimizu,∗7,∗2 D. Suzuki,∗2 J. Tanaka,∗2 R. Tsunoda,∗7 T. Uesaka,∗2 and K. Yamamoto∗4
count/ 0.5 akaaka[degrees]aCounts / 0.5[degrees]

We report on the progress of data analysis of the
RIBF79 experiment performed at the RI Beam Factory of RIKEN Nishina Center in 2019. In this experiment, inverse kinematics proton elastic scattering
measurements were performed using a high-intensity
beam of 132 Sn at approximately 600 kcps. The double magic nucleus 132 Sn has a larger isospin asymmetry than 208 Pb. Therefore,132 Sn is expected to have alarger neutron skin thickness, which is deﬁned as thediﬀerence between the neutron and proton root-meansquare radii. Furthermore, 132 Sn is a ﬂagship nucleusof the equation of state of nuclear matter study. The
goal of this experiment is to extract the neutron density distribution of 132 Sn from the inverse kinematics
proton elastic scattering of 132 Sn.
In the previous reports,1,2) we discussed particle
identiﬁcation for beam particles and the experimental setup. Herein, we report on the analysis of therecoil proton spectrometer (RPS). RPS consists of a
1-mm-thick solid hydrogen target,3) two multi-wiredrift chambers, two plastic scintillators, and fourteen
NaI(Tl) calorimeters. The recoil angle and kinetic energy of recoil protons were measured using RPS. By
using missing mass spectroscopy, the excitation energy spectrum of 132 Sn was obtained. Figure 1 shows
the scattering angle distribution spectrum when elastic scattering is selected from the excitation energy
obtained. The pattern of increase and decrease corresponding to the interference is clearly visible. Above80◦ , the kinetic energy of the recoil protons was low
and could not be detected by NaI calorimeters. Figure 2 shows the excitation energy spectrum of the proton scattering from 132 Sn in the recoil angle 78◦ –79◦ .
Data analysis for determining the angular distributionof the cross sections and the density distribution of132
Sn is now in progress.

102

10

1
60

65

70

75

80

85

90

recoil angle [degrees]Fig. 1. Angular distribution spectrum for selected elastic
scattering events using NaI(TI) calorimeters.
Counts / 0.5[MeV]count / 0.5[MeV] aaa
キス

30

σ : ~670keV

25

20

15

10

5

0
<10

<5

0

5

10

15

20

Ex [MeV]Fig. 2. Excitation energy spectrum of 132 Sn at recoil angles
in the range of 78◦ –79◦ .

References
1) J. Zenihiro et al., RIKEN Accel. Prog. Rep. 53, 44(2019).
2) T. Harada et al., RIKEN Accel. Prog. Rep. 54, 18(2020).
3) Y. Matsuda et al., Nucl. Instrum. Methods Phys. Res.
A 643, 6 (2011).

∗1

Department of Physics, Toho University
RIKEN Nishina Center∗3 Department of Physics, Kyoto University∗4 Cyclotron and Radioisotope Center, Tohoku University∗5 School of Physics, Beihang University∗6 Research Center for Nuclear Physics, Osaka University∗7 Center for Nuclear Study, University of Tokyo∗8 Department of Physics, Tohoku University∗9 Department of Physics, Osaka University∗10 Department of Applied Physics, Miyazaki University∗11 Department of Natural Sciences, Tokyo City University∗2- 23 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Commissioning study of SCRIT facility with 138 Ba nucleus
K. Tsukada,∗1,∗2 Y. Abe,∗2 A. Enokizono,∗2 T. Goke,∗3 Y. Honda,∗2,∗3 Y. Ito,∗1 K. Kurita,∗4 Y. Maehara,∗1
T. Ohnishi,∗2 R. Ogawara,∗1,∗2 T. Suda,∗2,∗3 M. Watanabe,∗2 M. Wakasugi,∗1,∗2 and H. Wauke∗2,∗3
The Self-Conﬁning RI Ion Target (SCRIT) electron scattering facility was constructed to realize electron scattering experiments for short-lived unstable
nuclei.1) SCRIT uses a novel technique to achieve aluminosity of 1027 cm−2 s−1 , which is suﬃcient to perform elastic electron scattering experiments by trapping a small number of target ions, typically 108 particles/pulse, along the electron beam.
In 2021, we performed electron scattering from 138 Ba
for two electron beam energies, 150 and 300 MeV, asa commissioning experiment. 138 Ba is stable, and its
charge density distribution is known.2) This is the ﬁrst
time experiment with the gas target trapped in the
SCRIT since the present SCRIT device was installed
in 2020, and a drift chamber of the electron spectrometer was replaced with a new one in 2018. The present
SCRIT device has a larger cross-section and less material around the trapping region, and it provides muchbetter uniformity of the electric potential compared tothe previous device. The present drift chamber in frontof the spectrometer magnet provides both vertical andhorizontal information of the trajectories of scatteredelectrons, whereas the previous one provided only horizontal information.
The data for 150 MeV is analyzed in this report.
The beam current was 250 mA at the beginning of
the data acquisition and dropped to 150 mA at theend. The achieved luminosity was approximately 1 ×
1027 cm−2 s−1 on average.
Figure 1 shows the reconstructed vertex-point distribution along the beam line after the spectrometer acceptance correction. It is found that the target length
in the SCRIT device is about 300 mm and the distribution is almost ﬂat. Compared to the previous data,3)
the apparent bump structure caused by the distortionof the electric potential disappears, which makes thedata easier to analyze and interpret.
Figure 2 shows the yield distribution after the acceptance correction and background subtraction. The
solid line represents a calculation using a phase-shift
calculation code, DREPHA,4) with the charge-density
distribution of 138 Ba.2) The distribution of our data
is well reproduced by the calculation, except for theforemost point, which corresponds to the end of theacceptance.
In summary, the target ions are trapped in thepresent SCRIT device almost uniformly as expected,
∗1
∗2
∗3
∗4

Fig. 1. Reconstructed vertex-point distribution along thebeam line after acceptance correction.

Fig. 2. Yield distribution with varying eﬀective momentum
transfer after acceptance corrections. The solid line is aphase-shift calculation obtained using a charge-density
distribution of 138 Ba.2)

and the angular distribution is well reproduced by ourspectrometer. We are almost ready and will soon start
the world’s ﬁrst electron scattering experiment with an
unstable nuclear target.
References
1) M. Wakasugi et al., Nucl. Instrum. Methods Phys. Res.
317, 357 (2013).
2) H. de Vries et al., At. Data Nulc. Data Table 36, 495(1987).
3) K. Tsukada et al., Phys. Rev. Lett. 118, 262501 (2017).
4) B. Drepher, A phase-shift calculation code for elastic electron scattering (private communication with
J. Friedrich).

Institute for Chemical Research, Kyoto University
RIKEN Nishina Center
Research Center for Electron-Photon Science, Tohoku University
Department of Physics, Rikkyo University- 24 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Yield measurements for 86 Kr + 198 Pt at KISS
Y. X. Watanabe,∗1 Y. Hirayama,∗1 M. Mukai,∗2 T. Niwase,∗1 P. Schury,∗1 M. Rosenbusch,∗1 M. Wada,∗1
H. Miyatake,∗1 S. C. Jeong,∗1 S. Iimura,∗2,∗3 M. Oyaizu,∗1 and A. Taniguchi∗4

∗1
∗2
∗3
∗4

Wako Nuclear Science Center (WNSC), IPNS, KEK
RIKEN Nishina Center
Department of Physics, Osaka University
Institute for Integrated Radiation and Nuclear Science, Kyoto
University- 25 -

Extraction rate (pps)

100
90
80
70
60
50
40
30
20
10
0
0

Extraction Rate (pps)

We have been developing the KEK Isotope Separation System (KISS) for spectroscopic studies of neutronrich nuclei around N = 126. These neutron-rich nuclei
are considered to be eﬃciently produced by multinucleon transfer reactions with the target nucleus 198 Pt.
We have successfully extracted and performed nuclear
spectroscopy for neutron-rich nuclei, such as 199–201 Pt,
196–200
Ir, and 193–198 Os using the 136 Xe beam.1) The
yield development is essential for KISS to expand theresearch region toward N = 126. We attempted to use
the 238 U beam, with which the GRAZING calculations2)
predict more production yields. However, we observedthat the growth of the extraction yields slows down at
an intensity of approximately 30 particle nA in contrast
to 50 particle nA for the 136 Xe beam. Furthermore, theyields for various extracted isotopes were approximately
ten times smaller than those with the 136 Xe beam.3)
The reaction products are ﬁrst thermalized and neutralized in the argon gas ﬁlled in a gas cell at KISS.
They are transported via a laminar gas ﬂow and areirradiated using lasers to be element-selectively ionizedusing the laser resonance ionization technique immediately before they exit the gas-cell oriﬁce. These ions
are transported by several RF ion guides and are accelerated with a high voltage of 20 kV to be transmitted
to measurement areas. The reduction of the extraction
yields for the 238 U beam may be attributed to the reneutralization of the laser-ionized isotopes by free electrons generated via radiation from more dense plasma
in the gas induced by the elastic scattering of heavier
beams. We have performed yield measurements using
the 86 Kr beam to study the systematics of the extraction yields among diﬀerent types of beams for the originof the yield reduction with the 238 U beam.
The 86 Kr beam with an energy of 10.75 MeV/nucleon
from the RRC was decelerated using three 5-μm titanium foils and impinged on a 198 Pt target with a thickness of 12.5 mg/cm2 at an energy of 8.8 MeV/nucleon.
Radioactive nuclei 199, 200, 202 Pt, 196–198 Ir, and 195, 196 Os
were extracted. They were identiﬁed by measuring their
lifetimes at the β-decay station or their masses using the
MRTOF-MS. The top panel of Fig. 1 shows the beam
intensity dependence of the extraction rates of 199 Pt for
the 86 Kr, 136 Xe, and 238 U beams. The energies of the136
Xe and 238 U beams are 9.4 and 8.9 MeV/nucleon, respectively. The rates for the 136 Xe beam are scaled by
0.3. The growth of the rates for the 86 Kr beam slows
down at an intensity of approximately 80 particle nA,

136

Xe beam (× 0.3)

238

U beam86

20

40

60 80 100 120 140 160 180 200
Beam intensity (pnA)
136

2

10

Kr beamXe beam (50 pnA)86

Kr beam (80 pnA)

238

U beam (26 pnA)

238

U beam (36 pnA)

101

10−1 199 200 201 202
196
197
Pt
Pt Pt
Pt
Ir
Ir
Isotope

198

Ir

195

Os

196

Os

Fig. 1. (Top) Beam intensity dependence of the extraction
rates of 199 Pt for the 86 Kr (squares), 136 Xe (circles), and238
U (crosses) beams. The rates for 136 Xe (circles) are
scaled by 0.3. (Bottom) Extraction rates of various isotopes for the 86 Kr (squares), 136 Xe (circles), and 238 U(crosses and diamonds) beams.

which is 30 particle nA larger than that of the 136 Xe
beam. However, the extraction rates for the 86 Kr beam
are smaller than those for the 136 Xe beam. The bottom
panel shows a comparison of extraction rates for various radioactive isotopes for the 86 Kr (80 particle nA),
136
Xe (50 particle nA), and 238 U (26 and 36 particle nA)
beams. The extraction yields of 196, 197 Ir and 195, 196 Os
are comparable for the 86 Kr and 136 Xe beams. The extraction yields of 199, 200 Pt and 198 Ir for the 86 Kr beam
are smaller than those for the 136 Xe beam; however, thereduction is smaller than that for the 238 U beam for199
Pt. The comparison of the extraction rates for various isotopes does not indicate any signiﬁcant increasein the extraction eﬃciency using the lighter beam than136
Xe. Further investigation including the gas-cell design, in-gas-jet ionization, and helium gas cell will be
conducted to increase the extraction yields at KISS.
References
1) Y. Hirayama et al., Nucl. Instrum. Methods Phys. Res. B
463, 425 (2020).
2) A. Winther, Nucl. Phys. A 572, 191 (1994); Nucl. Phys.
A 594, 203 (1995).
3) Y. X. Watanabe et al., RIKEN Accel. Prog. Rep. 51, 71(2018).

1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

In-gas-cell laser ionization spectroscopy of 200g Pt
using MRTOF-MS at KISS
Y. Hirayama,∗1 M. Mukai,∗2 Y. X. Watanabe,∗1 P. Schury,∗1 J. Y. Moon,∗3 T. Hashimoto,∗3 S. Iimura,∗2
S. C. Jeong,∗1 M. Rosenbusch,∗1 M. Oyaizu,∗1 T. Niwase,∗1 M. Tajima,∗2 A. Taniguchi,∗4 M. Wada,∗1
and H. Miyatake∗1(b)Laser spectroscopy can be used to eﬀectively investigate the nuclear structure througth the measured isotope shifts (IS) Δν, changes in the mean-square charge
radii δr2 , and quadrupole deformation parameters|β22 |1/2 . In previous work1) related to 199g, 199m Pt
at the KEK Isotope Separation System (KISS),2) wereported the constant trend of |β22 |1/2 ∼ 0.14 (N ≥115) approaching N = 126 deduced from the measuredδr2  values using a droplet model. As a continuationof this work followed by 199g, 199m Pt laser ionization
spectroscopy toward N = 126 to investigate the trendof δr2  and |β22 |1/2 values and the nuclear structureof neutron-rich platinum nuclei, we performed the ﬁrst
laser ionization spectroscopy on 200 Pt (I π = 0+ andT1/2 = 12.6(3) h) using a multi-reﬂection time-of-ﬂight
mass spectrograph (MRTOF-MS) at KISS.
200g
Pt isotopes were produced via multi-nucleon
transfer reactions by impinging a stable 136 Xe beam
(50 particle nA) with an energy of approximately
10 MeV/nucleon on a 198 Pt target (12.5 mg/cm2 ,enriched 91% and approximately 3% for each
194, 195, 196
Pt). The singly charged isotopes, producedby the in-gas-cell laser ionization technique, with anenergy of 20 keV were extracted from the KISS gas
cell for hyperﬁne structure measurements. Using the
MRTOF-MS, the extracted ions were identiﬁed andthe number of the ions was determined. Futher details regarding the MRTOF-MS system can be foundin Ref. 3).
Figure 1 shows the measured TOF spectrum of
200g
Pt2+ using the MRTOF-MS at KISS. The 200g Pt2+
isotope can be clearly identiﬁed with the contaminantpeaks of 200g Au2+ and 200m Au2+ ions (“g” and “m”
indicate the ground and isomeric states, respectively),
which were transported to the MRTOF-MS as the survived ions. The masses of these nuclei have alreadybeen precisely reported. To acculately evaluate thelaser resonance spectrum of 200g Pt, we gated the relative time between 200 and 500 ns in Fig. 1 to deduce the number of ions detected by the MRTOFMS. The laser resonance spectrum, shown in Fig. 2,
was obtained by measuring the number of laser-ionized
200g
Pt as a function of the laser wavelength. One res∗1

∗2
∗3
∗4

Sum. of lines
200g

2+

200g 200g2+

200m200m2+

2+

Pt2+ Pt

200

Counts/3 ns

Au2+Au

20

Au Au

10

0

200

300

400

500

600

700

TOF - 6,225,770 [ns]Fig. 1. Measured TOF spectrum of 200g Pt2+ .
1
200g

Pt

Counts (cps)

0.8
0.6
0.4
0.2
0
−40 −30 −20 −10

0

10

20

30

40

Frequency - 1204992.36 [GHz]Fig. 2. Measured HFS spectrum of 200g Pt (I π = 0+ ). Horizontal uncertainty estimated from the accuracy of awavemeter.

onance peak was observed, which stemmed from theatomic transition of 200g Pt due to I π = 0+ . The ﬁtting
function was determined from the measured resonancespectrum of the stable nucleus of 198 Pt with the same
experimental conditions during beam time. From themeasured peak position, we can determine the isotope
shift value of 200g Pt to deduce the change in charge
radius and discuss nuclear deformation. Using theseresults, we plan to investigate the systematic trend of
IS values toward N = 126.

Wako Nuclear Science Center (WNSC), Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator
Research Organization (KEK)
RIKEN Nishina Center
Institute for Basic Science (IBS)
Institute for Integrated Radiation and Nuclear Science, Kyoto University (KURNS)

References
1) Y. Hirayama et al., Phys. Rev. C 96, 055805 (2017).
2) Y. Hirayama et al., Nucl. Instrum. Methods Phys. Res.
B 412, 11 (2017).
3) J. Y. Moon et al., RIKEN Accel. Prog. Rep. 53, 128(2019).

- 26 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Isomer spectroscopy using multi-nucleon transfer reaction on 248 Cm

∗1
∗2
∗3
∗4
∗5
∗6
∗7

10000

Counts / keV

8000
6000
4000

Gated by 0p transfer channels

265.7(249Cm)The Island of Stability, which is linked to the predicted doubly closed proton and neutron shells in superheavy nuclei, is still an unexplored region in nuclear physics. Owing to low expected cross sections
with current experimental techniques, the region has
not been accessible for detailed decay studies. Excitedstates in actinide nuclei can have an important rolein characterizing the stability of the island, as partof degenerate orbitals above predicted energy gaps at
Z = 114 and N = 184 can appear as excited states owing to the systematic development of quadrupole deformation. Pioneering studies1,2) identiﬁed a large component of high-j quasiparticle states originating fromthe νk17/2 orbital above the gap in 249 Cm. Thus, dataaround this region can provide benchmarks for theoretical calculations of the location and properties of
the Island of Stability.
One method to study the region of heavy actinides
is to produce them via the transfer reactions of heavy
ions onto radioactive actinide targets. The diﬃcultyof using actinide targets lies in their strong radioactivity. An experimental method, called the isomerscope method,3) is one of measurements to avoid thisproblem with the space-time separation. This method
was originally developed at JAEA to investigate isomeric states via deep inelastic collisions. The combination of γ-ray detectors and absorbers signiﬁcantly
enhanced the peak-to-background ratio of the delayed
γ-ray component. We applied this method to perform isomer spectroscopy of nuclei produced via multinucleon transfer reactions on actinide targets.
The experiment was performed at the JAEA tandem accelerator facility in May 2021. An actinide target of 248 Cm was prepared via electrodeposition onto a
1.8 μm aluminium backing. The target was irradiatedusing a 18 O beam with an energy of 96.5 MeV with anintensity of approximately 2.0 particle nA. The beamenergy was set to detect the light ejectiles identiﬁed
at backward angles. The produced nuclei were identiﬁed via speciﬁc transfer channels using an array of
ΔE-E telescopes. The selection of the beam energy

177.5
247
192.5 ( Cm)(249Cm)S. Go,∗1,∗2,∗3 R. Orlandi,∗4 T. Niwase,∗5,∗3 K. Sugiyama,∗1 T. Tomimatsu,∗1 T. Kai,∗1 K. Hirose,∗4
E. Ideguchi,∗6,∗3 Y. Ishibashi,∗1 Y. Ito,∗4 H. Makii,∗4 S. Matsunaga,∗1 K. Morita,∗1,∗3 D. Nagae,∗2,∗3
Y. Nagata,∗1 H. Nishibata,∗1,∗3 K. Nishio,∗4 T. T. Pham,∗6 S. Sakaguchi,∗1,∗3 T. K. Sato,∗4 T. Shizuma,∗7
F. Suzaki,∗4 K. Tsukada,∗4 K. Washiyama,∗2 and M. Asai∗4,∗2

2000

100

150

200

250

300

350

400

450

500

Energy (keV)

Fig. 1. Delayed γ-ray spectrum gated using 0p transfer
channels by the ΔE-E silicon telescope. The 177.5and 265.7-keV peaks resulted from the isomeric state of247
Cm with a half-life of 100.6 ns.4) The 192.5- and265.7-keV peaks resulted from the isomeric state of249
Cm with 19-ns half-life.2)

enabled us to place the telescope at the backward angles, which eﬀectively reduced the radiation damage on
the silicon detectors. An ejectile passing through oneof the four ΔE detectors (20 μm thick) was stopped in
the E detector (300 μm thick) to measure the residualenergy. Heavier nuclei were scattered in the forward
direction and stopped in a catcher foil. Four germanium and four LaBr3 detectors were placed close to
the foil to detect the delayed γ rays. A tungsten shield
was placed between the target and γ-ray detectors toabsorb the strong γ-radiation around the target.
Several known isomers belonging to nuclei in the region of 248 Cm were successfully observed in this study.
An example of the delayed γ-ray spectrum is shownin Fig. 1. The 178-keV peak correspond to the γ-ray
transition from the isomeric state of 247 Cm.4) The halflife value deduced by the preliminary analysis agreed
well with the literature value of 100.6 ns.4) The 192.5and 265.7-keV peaks corresponded to transitions froman isomeric state in 249 Cm.2) This short-lived 19-ns
isomer was successfully identiﬁed in this experimental
setup. Further analysis to identify new isomeric statesis in progress.

Department of Physics, Kyushu University
Research Center for Superheavy Elements, Kyushu University
RIKEN Nishina Center
Advanced Science Research Center, Japan Atomic Energy
AgencyWako Nuclear Science Center (WNSC), IPNS, KEK
Research Center for Nuclear Physics, Osaka University
Tokai Quantum Beam Science Center, National Institute forQuantum Science and Technology

References
1) I. Ahmad et al., Nucl. Phys. A 646, 175 (1999).
2) T. Ishii et al., Phys. Rev. C 78, 054309 (2008).
3) T. Ishii et al., Nucl. Instrum. Methods Phys. Res. A
395, 210 (1997).
4) I. Ahmad et al., Phys. Rev. C 68, 044306 (2003).

- 27 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Proton entropy excess and possible signature of pairing reentrance in
hot nuclei†
B. Dey,∗1 S. Bhattacharya,∗2 D. Pandit,∗3,∗4 N. D. Dang,∗5 N. N. Anh,∗6 L. T. Phuc,∗7,∗8 and N. Q. Hung∗7,∗8
We conducted a systematic study to understand theproton entropy excess ΔSp obtained for diﬀerent pairsof odd-even and odd-odd nuclei ranging from A = 90 to
238 (90 Y and 91 Zr, 196 Pt and 197 Au, 211 Po and 212 At,231
Th and 232 Pa, 237 U and 238 Np). The proton entropy
excess determined from the existing experimental nuclear level density (NLD) data was compared with themicroscopic calculation obtained within the exact pairing plus independent particle model (EP+IPM). The
latter has predicted an enhanced peak of ΔSp at an
excitation energy E ∗ 1 MeV in near spherical nuclei(90 Y and 91 Zr, 211 Po and 212 At), indicating a possible signature of pairing reentrance in hot nuclei. In
the cases under consideration, pairing reentrance occurs because of the weakening of the blocking eﬀectcaused by the odd nucleon in odd nuclei. As a result,the pairing gap of odd nuclei, which is ﬁnite at T = 0,
slightly increases at low T = 0, and decreases as T
increases further, as explained in Ref. 1).
We found that the experimental value of ΔSp as afunction of E ∗ exhibits a strong ﬂuctuation at E ∗ <1 MeV and reaches saturation at high E ∗ > 3–6 MeV.
The analysis using the microscopic EP+IPM calculations shows that the proton entropy excess is approximately 0.1–0.5 kB for spherical systems and approximately 1.0–1.2 kB for the deformed ones, which is ingood agreement with the experimental data, as shownin Figs. 1(a) and 1(b). These values of proton entropy excess are smaller than the neutron ones owing
to the eﬀect of the Coulomb interaction and proton
single-particle level density, which is less than the theneutron one. Moreover, the peak-like structure, which
is seen in the proton entropy excess obtained within
the EP+IPM at low energy E ∗ < 1 MeV, is explainedby the pairing reentrance phenomenon caused by the
weakening of the blocking eﬀect of an odd nucleon [SeeFigs. 1(c) and 1(d)].
This peak-like structure is found to be more pronounced in the spherical systems than in the deformed
ones because the pairing reentrance is stronger in
spherical nuclei than in deformed ones. However, thistheoretical peak-like structure is not well supported
†
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8

Fig. 1. [(a) and (b)] Proton entropy excesses ΔSp as functions of excitation energy E ∗ along with the results of
EP+IPM calculations for 211 Po–212 At and 90 Y–91 Zr.
[(c) and (d)] Exact proton Δp and neutron Δn pairing
gaps as functions of temperature T for diﬀerent nuclei.
Exp. data1 and Exp. data2 in (a) are obtained by using the associated NLD data from Refs. 2) and 3), respectively, whereas RIPL-data are calculated by using
the low-energy data taken from RIPL-34) averaged over
the angular-momentum distribution as in Ref. 2). Exp.
data in (b) are obtained by using the NLD data from
Refs. 5) and, 6).

by the experimental observation owing to the strong
ﬂuctuations in the measured data. Therefore, more
precise and direct experimental measurements in the
low-energy region (E ∗ < 1 MeV) are required in order
to conﬁrm our theoretical predictions.
References
1) N. Q. Hung et al., Phys. Rev. C 94, 024341 (2016).
2) B. Dey et al., Phys. Lett. B 789, 634 (2019).
3) P. Roy et al., Phys. Rev. C 94, 064607 (2016).
4) www-nds.iaea.org/RIPL-3/ .
5) M. Guttormsen et al., Phys. Rev. C 90, 044309 (2014).
6) M. Guttormsen et al., Phys. Rev. C 96, 024313 (2017).

Condensed from the article in Phys. Lett. B 819, 136445(2021)
Department of Physics, Bankura University
Department of Physics, Barasat Government College
Variable Energy Cyclotron Centre
Homi Bhabha National Institute
RIKEN Nishina Center
Dalat Nuclear Research Institute
Institute of Fundamental and Applied Sciences, Duy Tan
University
Faculty of Natural Sciences, Duy Tan University- 28 -1

II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

The ONOKORO project—Toward comprehensive understanding onclustering in heavy nuclei
T. Uesaka,∗1 J. Zenihiro,∗2,∗1 K. Ogata,∗3 J. Tanaka,∗1 R. Tsuji,∗2,∗1 Y. Hijikata,∗2,∗1 K. Higuchi,∗1,∗4
S. Takeshige,∗1,∗5 K. Yahiro,∗2 S. Kurosawa,∗6 K. Yoshida,∗7 Y. Chazono,∗3 M. Takano,∗8 S. Typel,∗9 and
H. Baba∗1 for the ONOKORO Collaboration
A new research project, “ONOKORO project,” hasstarted to investigate clustering in heavy nuclei using
cluster knockout reactions. Do nuclear systems, in general, have an inherent orientation that breaks uniformity? In this research, we try to answer this question
by studying formation mechanisms of deuteron, triton,
3
He, and α clusters in stable and unstable nuclei in awide mass range.
Since early days of nuclear physics, α cluster in nuclei have been discussed, ﬁrst to explain α decays ofheavy nuclei, while clustering is now mainly discussed
for light nuclei with masses lighter than 30. On theother hand, there are signiﬁcant progress in theories
of cluster formation in inﬁnite nuclear matter.1,2) Important predictions of the theories are that clusters develop signiﬁcantly in the low-density region below 1/10of the saturation density, and the cluster abundanceschange signiﬁcantly with the neutron-proton asymmetry. Typel predicted also such a phenomenon would
also occur in the low-density surface of heavy nuclei.3)
Our previous experiment for the 112–124 Sn(p, pα) reaction has conﬁrmed Typel’s prediction and has demonstrated the existence of α clusters in those nuclei.4)
The ONOKORO project will extend the scope toall the light clusters of d, t, 3 He, α in stable and unstable nuclei from calcium (Z = 20) to heavy nuclei
beyond lead (Z = 82). The (p, pX) cluster knockout
reactions, where X denotes d, t, 3 He or α, are used to
extract information of clusters in nuclei. Characteristic points of the ONOKORO project are:• d, t, 3 He, α clusters are studied on the same footing• Both stable and unstable nuclei are covered• Normal and inverse kinematics experiments are
combined
Simultaneous studies of d, t, 3 He, α are essentially
important because the diﬀerent clusters would manifest diﬀerent aspects of clustering depending on its
spin and isospin. As is discussed in Refs. 2) and 3),
dependence on neutron excess is essential in studies ofclustering in heavy ﬁnite nuclei and in nuclear matter,
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9

and thus the access to unstable nuclei is the core of the
project.
In order to cover both stable and unstable nuclei, we
will perform experiments at intermediate-energy accelerator facilities in Japan, the RIKEN RIBF, the QST
HIMAC, and the Osaka University RCNP cyclotron
facility. At RCNP, knockout reaction experiments under normal kinematics for stable nuclear targets are
conducted using proton beams and double-arm magnetic spectrometers, Grand Raiden and LAS, to obtainhigh energy-resolution data. State-by-state separationof the ﬁnal states enabled by the high resolution is aunique capability in experiments at RCNP. At RIBF
and HIMAC, inverse-kinematics experiments will be
carried out using unstable and stable heavy-ion beams,
respectively. The inverse kinematics experiment has
the advantage of covering a broad kinematic regionand simultaneous measurements for all clusters of d, t,
3
He, α.
In this project, we will construct a detector array,
TOGAXSI,5) designed speciﬁcally for inverse kinematics knockout reaction experiments. The array consistsof 100-μm pitch silicon strip detectors and GAGG:Cescintillators. GAGG:Ce scintillators have a good time
response of 1 ns rise time and <100 ns decay time.
Another good feature of GAGG:Ce is no hygroscopic
nature.
The cluster knockout reaction theory based on theimpulse approximation will be reﬁned to derive thecluster abundance from the experimental cross sections accurately. In particular, a theory that treats
the breakup eﬀect, which is essential in the knockout reaction of weakly-bound deuterons, will be developed using the continuum-discretized coupled-channel
method.6)
By comparing the cluster abundance obtained fromthe experimental data and the reaction theory with thenuclear structure and nuclear matter theories, we willverify the hypothesis of cluster formation in nuclear
matter and clarify the mechanism of cluster formation.
References

RIKEN Nishina Center
Department of Physics, Kyoto University
Research Center for Nuclear Physics, Osaka University
Department of Physics, Toho University
Department of Physics, Rikkyo University
Institute for Materials Research, Tohoku University
Advanced Science Research Center, Japan Atomic Energy
AgencyDepartment of Physics, Waseda University
Institut für Kernphysik, Technisch Universität Darmstadt

1) S. Typel et al., Phys. Rev. C 81, 015803 (2010).
2) Z. -W. Zhang, L. -W. Chen, Phys. Rev. C 95, 064330(2017).
3) S. Typel, Phys. Rev. C 89, 064321 (2014).
4) J. Tanaka et al., Science 371, 260 (2021).
5) T. Uesaka et al., RIBF Construction proposal NP2112SAMURAI72.
6) Y. Chazono et al., in this report.

- 29 -

12. Nuclear Physics (Theory)

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Practical method for decomposing discretized breakup cross sections
into components of each channel†
S. Watanabe,∗1,∗2 K. Ogata,∗3,∗4,∗5 and T. Matsumoto∗6

11

Be+T →10 Be(g.s.)+n+T

11

Be+T →

10∗

Be +n+T

The continuum-discretized coupled-channel method(CDCC)1) is one of the most powerful tools for describing breakup reactions. In the 1980s, three-body
CDCC was ﬁrst applied to d scattering by assuming then + p + T three-body model, where T denotes a target. Three-body CDCC has been successful in describing many kinds of three-body reactions. Nowadays,
three-body CDCC has been developed mainly in two
directions. One is four-body CDCC2) and the other isthree-body CDCC with core excitation.3) These methods address breakup reactions including multi-breakup
channels. For example, for 6 Li scattering in the fourbody model (n + p + α + T ), the four-body channel(6 Li + T → n + p + α + T ) and the three-body channel(6 Li + T → d + α + T ) coexist and couple each otherduring scattering. In CDCC, these breakup channels
are precisely considered on an equal footing. However,the corresponding breakup cross sections (BUXs) are
obtained as an admixture of these channels owing to
the discretization in the calculations. In this work,
we propose a practical method for decomposing discretized BUXs into components of each channel. Thismethod is referred to as the “probability separation (Pseparation).”
Before going to four-body scattering, we ﬁrst consider 11 Be + T scattering in the three-body model withcore excitation (10 Be + n + T ) because this scattering
provides an analogy regarding the mixture of diﬀerent
channels as

∗1
∗2
∗3
∗4
∗5
∗6









 














    Fig. 1. Decomposition of the breakup cross sections for the
scattering of 11 Be + p at 63.7 MeV/nucleon. The solidlines represent the exact BUXs (σ), whereas the solid
circles correspond to the approximate BUXs (σ̂).

with the exact ones quantitatively. In this report, weshow only the validity of the P separation.
Figure 1 shows the decomposition of the breakup
cross sections. The spin-parities J π = 1/2+ , 3/2+ ,5/2+ , 1/2− , and 3/2− are considered for 11 Be. First,
the discretized total BUX σ̂(tot) is compared with theexact BUX σ(tot). For the total breakup cross sections), σ̂(tot) = σ(tot) is satisﬁed, which suggests thatthe model space is suﬃciently large for calculating the
BUX. Next, the discretized BUX is decomposed into
the core-ground and the core-excited BUXs with the
P separation. The total [σ(tot)], core-ground [σ(0)],and core-excited [σ(2)] BUXs are shown from top tobottom. The approximate BUXs are in good agreement with the corresponding exact ones for each spinparity. Thus, the P separation is found to work for thediscretized BUX.
The P separation has an advantage that it is easily applied to four-body scattering for which the exact
breakup wave functions for the three-body projectile
are diﬃcult to obtain. The systematic analysis for thevalidation and the application to four-body CDCC arepresented in the original paper.†(core-ground channel),(core-excited channel),

where g.s. represents the ground state. This scattering
has an advantage in that it allows us to easily obtaineach channel’s exact breakup wave functions for the11
Be two-body projectile, unlike the 6 Li three-bodyprojectile. In the actual analysis,the BUXs are calculated using extended distorted-wave Born approximation (xDWBA)4) with the particle-rotor model. The
xDWBA enables us to calculate both the exact (continuous) and the approximate (discretized) T -matrix elements. Then, we can compare the approximate BUXs†

Condensed from the article in Phys. Rev. C 103, L031601(2021)
National Institute of Technology, Gifu College
RIKEN Nishina Center
Research Center for Nuclear Physics, Osaka University
Department of Physics, Graduate School of Science, Osaka
City University
Nambu Yoichiro Institute of Theoretical and Experimental
Physics (NITEP), Osaka Metropolitan University
Department of Physics, Kyushu University

References
1) M. Kamimura et al., Prog. Theor. Phys. Suppl. 89, 1(1986).
2) T. Matsumoto et al., Phys. Rev. C 70, 061601(R)(2004).
3) R. de Diego et al., Phys. Rev. C 89, 064609 (2014).
4) A. M. Moro, R. Crespo, Phys. Rev. C 85, 054613 (2012).

- 31 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Eﬀects of the Skyrme tensor force on 0+ , 2+ , and 3− states in 16 O
and 40 Ca nuclei with second random phase approximation†
M. J. Yang,∗1 C. L. Bai,∗1 H. Sagawa,∗2 and H. Q. Zhang∗3
2000

ph

+



(Xpν1 p2 h1 h2 a†p1 a†p2 ah2 ah1

X=

X1ν
,Y =
X2ν



B11
B21

Y1ν
.
Y2ν

A12 (A22 )−1 A21 +2S
 =B11 +
B11


2

†
∗1
∗2
∗3

6

B(E3)(e fm )2

SSRPAD

1000
500
10

20

30

40

50

AD
22 = δp1 p1 δp2 p2 δh1 h1 δh2 h2 (Ep1 + Ep2 − Eh1 − Eh2 ),(4)while we fully take into account the coupling between
the 2p-2h conﬁgurations in A22 in SRPA Eq. (2).
SSRPA calculations demonstrate a clear diﬀerence
between the eﬀects of two tensor interactions in
SGII+Te1 and SGII+Te3. The eﬀects of triplet-evenand triplet-odd tensor forces of SGII+Te3 on the 0+ ,2+ , and 3+ states cancel each other and no signiﬁcanteﬀect is observed. In contrast, in the case of SGII+Te1,
two tensor terms are added coherently, which improveremarkably the numerical results. Figure 1 presents an
example of IS 3− excitations in 16 O. These results indicate the importance of the triplet-odd and triplet-eventerms for realistic calculations of collective states.
We adopted two extreme cases in this study todemonstrate how the energies and the strengths areaﬀected by the tensor forces. Accordingly, we showedthat the tense eﬀects are observed even in the naturalparity states of SSRPA results, while they are negligible in RPA, except the case of 3− . Thus, by setting
appropriate tensor parameters, we will be able to improve further descriptions of the transition probabilities of low-lying collective states. This study remains
for the future work.

(2)

B12
,
B22

(3)



B12 (A22 )−1 B21 ,2

A12 (A22 )−1 B21 +(6.13,1300)
Exp

1500

where the diagonal approximation is adopted in A22
matrix,Indices 1 and 2 denote the shorthand notations for 1p1h and 2p-2h conﬁgurations, respectively. Matrices
A12 , B12 represent the coupling of 1p-1h and 2p-2h
conﬁgurations, and A22 , B22 denote the coupling between 2p-2h conﬁgurations. In SSRPA, A11 and B11
are modiﬁed as:AS11 =A11 +500

Fig. 1. Isoscalar octupole strength distributions in 16 O
calculated by RPA (upper panel) and SSRPA (lower
panel). Black dashed, red solid, and blue dasheddotted lines represent the results of SGII, SGII+Te1,
and SGII+Te3, respectively. Experimental data are denoted by (Ex , B(E3)) in units of MeV and e2 fm6 .

(1)

Xν
Xν
,
ν = h̄ων
Y
Yν

A12
,B =
A22

RPA

Ex(Mev)

where
A11
A21

IS3

-

1000

0

Suﬃxes p, p1 , p2 denote the particle states, while h, h1 ,h2 denote the hole states; X and Y denote forward andbackward amplitudes, respectively. The SRPA equation has the same matrix form as the RPA equation:

A=

SGII
SGII+Te1
SGII+Te3

O

0− Ypν1 p2 h1 h2 a†h1 a†h2 ap2 ap1 ).

B
−A∗

16

0
2000

p1 <p2h1 <h2

A
−B ∗

Exp

1500

2

6

B(E3)(e fm )The eﬀects of Skyrme tensor force on the naturalparity 0+ , 2+ , and 3− states of 16 O and 40 Ca werestudied via the subtract second random-phase approximation (SSRPA) by adopting Skyrme energy density
functionals (EDFs). To avoid the double counting
and divergence in SRPA, the subtracting procedure
was adopted in SSRPA calculations; consequently, SSRPA calculations can quickly converge with respect tothe the energy cut-oﬀ. In the calculations, two tensor parameterizations, SGII+Te1 and SGII+Te3, wereadopted, whose triplet-odd tensor terms have diﬀerent
signs, i.e., U = −350.0 MeVfm5 and +200.0 MeVfm5 ,respectively.
In the SRPA model,1,2) the particle-hole (p-h) excitation operator, Q†ν , can be written as,

ν †
ν †
(Xph
ap ah − Yphah ap )Q†ν =

B12 (A22 )−1 A21 .

2

Condensed from the article in Phys. Rev. C 103, 054308(2021)
College of Physics, Sichuan University
RIKEN Nishina Center
China Institute of Atomic Energy

References
1) D. Gambacurta et al., Phys. Rev. C 81, 054312 (2010).
2) C. Yannouleas, Phys. Rev. C 35, 1159 (1987).

- 32 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

On the deformability of atoms†
T. Naito,∗1,∗2 S. Endo,∗3,∗4 K. Hagino,∗5 and Y. Tanimura∗3,∗6

†
∗1
∗2
∗3
∗4
∗5
∗6

Condensed from the article in J. Phys. B 54, 165201 (2021)
Department of Physics, University of Tokyo
RIKEN Nishina Center
Department of Physics, Tohoku University
Frontier Research Institute for Interdisciplinary Science, Tohoku University
Department of Physics, Kyoto University
Graduate Program on Physics for the Universe, Tohoku University- 33 -

Noble gasHalf-closed shells-block
p-blockd-block

0.3
0.2
0.1

β

Atoms and atomic nuclei share common features as
quantum many-body systems of interacting fermions.
In atoms, the inter-particle interaction is the repulsive
Coulomb interaction, and there exists the spherical external Coulomb potential due to the nucleus. In contrast, in atomic nuclei, the inter-particle interaction isthe attractive nuclear force, with no external potential.
Despite the diﬀerences in the fundamental interactions,many similar properties have been observed in both systems, such as the shell structure and the associatedmagic numbers.
One of the most important properties of atomic nuclei
is collective nuclear deformation. It was discussed that
this collective deformation originates from the strong attractive interaction between protons and neutrons.1,2) A
natural question then arises: Can atoms be deformed
collectively as in atomic nuclei? Calculations of theatomic structure have been frequently conducted by assuming spherical symmetry, and the non-sphericity has
been addressed only in a few studies. Thus, it is widelybelieved that atoms are rather spherical, in stark contrast to deformed atomic nuclei. What is the physicalorigin of this diﬀerence? To what extent can electron
density distributions in atoms be deformed collectively?
To answer these questions, we calculate electron density distributions of atoms and their deformation parameters without assuming spherical symmetry. By estimating the change in the energy induced by the deformation,in nuclear systems, we ﬁnd that the spin-up and spindown particles tend to be deformed in the same manner
due to the attractive inter-particle nuclear interaction.
In contrast, in atomic systems, we ﬁnd that the spinup and spin-down particles prefer to be deformed in the
opposite manner, cancelling each other and resulting ina small deformation as a whole owing to the repulsive
inter-particle Coulomb interaction. Thus, the diﬀerence
between atoms and atomic nuclei in their deformability primarily originates from the diﬀerent natures of theinter-particle interactions.
Figure 1 shows the deformation parameters β foratoms from Li to Kr calculated using the unrestricted
Hartree-Fock method with the 6-31+G basis.3) All thenoble-gas atoms are spherical (β = 0). For the otheratoms, the electronic conﬁguration of their cores is thesame as that of the noble-gas atoms. Hence, as longas the core density is not deformed owing to non-trivial

0.0
−0.1
−0.2
−0.3

0

5

10

15

20

25

30

35

40

Z
Fig. 1. Deformation parameters β calculated using the unrestricted Hartree-Fock method with the 6-31+G basis.

many-body eﬀects, the deformation of the atom is expected to result only from the valence electrons. The
valence electrons of the s-block atoms only occupy an sorbital, and the many-body eﬀects between the valence
electrons and spherically symmetric core necessarily result in a spherical electron density distribution. This isalso true for the half-closed-shell atoms.
For the other open-shell atoms, the deformation parameters β are generally non-zero. The deformation parameters for the atoms with the same group exhibit similar tendencies, i.e., |β|  0.1–0.3 for the p-block atoms
and |β|  0.01 for the d-block atoms. This indicatesthat the nature of the few valence open-shell electrons
contributes signiﬁcantly to determining β of the wholeatom. This deformation originates from single-particle
valence orbitals and thus it is misleading to regard it
as collective deformation. For example, the deformationof the p-block atoms can be understood as the valence
p orbitals that primarily contribute to the deformation.
Indeed, |β|  0.1–0.3 of the p-block atoms are similarvalues in order of magnitude to that of a single p orbital, although |β|  0.3 might appear a large collective
deformation in nuclear physics sense. We conclude inthis paper that the p-block atoms can be regarded as analmost inert core plus valence p-electrons, while manybody eﬀects between the core and the valence electrons
are relevant in the d-block atoms. In the d-block atoms,
the core electrons tend to collectively cancel the deformation of the valence d orbitals.
References
1) P. Federman, S. Pittel, Phys. Rev. C 20, 820 (1979).
2) J. Dobaczewski et al., Phys. Rev. Lett. 60, 2254 (1988).
3) W. J. Hehre et al., J. Chem. Phys. 56, 2257 (1972).

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Comparative study of the dineutron in Borromean nuclei 11 Li and 22 C
M. Yamagami∗1
A recent knockout-reaction experiment for 11 Li measured the mean correlation angle between the momentaof two emitted neutrons,1) which is considered to reﬂect the mean opening angle θnn 0 between the momenta k1 and k2 of valence neutrons in the ground state.
In the current study, I discuss how θnn 0 reﬂects themomentum-space structure of the dineutron in the Borromean nuclei 11 Li and 22 C.
The three-body model calculation is performed using a ﬁnite-range n-n interaction,3) which reproduces
the ground-state properties of these nuclei. For example, the distance between the core and the center ofmass (cm) of the dineutron in 11 Li is 5.00 fm, whichis in agreement with the observed value of 5.01(32) fm.2)
θnn 0 for each core-n momentum kn is deﬁned byHere, f  =cos θnn 0 = cos θ12 Dkn /Dkn .
d3 k1 d3 k2 ρ2 (k1 , k2 )f (k1 , k2 ) is the mean value of afunction f (k1 , k2 ) for the two-neutron density distribution ρ2 (k1 , k2 ). θ12 is the opening angle between k1 andk2 . Dkn (k1 , k2 ) = δ(kn − |k1 |)δ(kn − |k2 |) picks up thecomponent of kn = |k1 | = |k2 | in ρ2 .
Here, k1 and k2 can be expressed as k{1} = ±krel +Fig. 2. (a) Mean opening angle θnn qc in 11 Li as a functionof kn . The dependence on the lower cutoﬀ qc is shown.
(b) The same as (a) but for 22 C. See the text for details.

2

qcm /2 with the relative and cm momenta krel and qcm ,respectively. As shown below, θnn 0 for a given kn contains the various qcm components of diﬀerent neutronpair structures. To illustrate this, Fig. 1(a) shows
the density distribution ρcm = δ(qcm − |k1 + k2 |) asa function of qcm . The root-mean-square core-n momentum k̄n is deﬁned for each qcm in a similar man-

Fig. 1. (a) Two-neutron density distribution ρcm as a function of qcm in 11 Li and 22 C. (b) Parametric curve of(k̄n , θ̄cm ). See the text for details.
∗1

Department of Computer Science and Engineering, Universityof Aizu

ner. Together with the associated opening angle θ̄cm =2 cos−1 (qcm /2k̄n ), the parametric curve of (k̄n , θ̄cm ) isshown in Fig. 1(b). For 11 Li, symbol A corresponds tothe peak position of ρcm . k̄n has a local maximum (minimum), as indicated by the symbol B (C). The corresponding cm momenta q (A) , q (B) , and q (C) are 0.20, 0.47,
and 0.65 fm−1 , respectively. θ̄cm > 90◦ at qcm < q (C) indicates the dineutron conﬁguration. The symbols a, b,
and c for 22 C have the same meaning as A, B, and C for
11
Li, respectively.
The mean opening angle θnn qc , which takes into account the component of qcm > qc in ρ2 , is also deﬁned.
Here, qc is a lower cutoﬀ. Figure 2 shows θnn qc in 11 Li
and 22 C. θnn 0 has a peak at kn ≈ 0.35 fm−1 . The peakof θnn 0 is cooperatively created by the peak componentof ρcm and the large θ̄cm in the region of qcm < q (C) (q (c) )in 11 Li (22 C). In 22 C, the enlargement of θnn 0 due tothe low-qcm component appears up to kn ≈ 0.9 fm−1 ,which corresponds to the local maximum value of k̄n .
This high local maximum value of k̄n is due to the dwave contribution. Such enlargement of θnn 0 is notobserved at high kn in 11 Li.
In conclusion, I discussed how the mean opening angle θnn 0 depends on the momentum-space structure of
the dineutron in 11 Li and 22 C. θnn 0 can be a promising probe for revealing the characteristic structure of the
dineutron in each Borromean nucleus.
References
1) Y. Kubota et al., Phys. Rev. Lett. 125, 252501 (2020).
2) T. Nakamura et al., Phys. Rev. Lett. 96, 252502 (2006).
3) M. Yamagami, RIKEN Accel. Prog. Rep. 54, 37 (2021).

- 34 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Nuclear surface diﬀuseness of Ne and Mg isotopes in the island of
inversion†

Diffuseness parameter (fm)V. Choudhary,∗1 W. Horiuchi,∗2,∗3 M. Kimura,∗2,∗4 and R. Chatterjee∗1
It had been suggested in the literature,1) that theisland of inversion close to N = 20 and 28 arises because of the ν(sd)−2 (f p)2 intruder conﬁgurations. It
was proposed that two neutrons from the sd-shell are
excited to the f p-shell become so low in energy thatthey manifest as the ground state of Z = 10–12 andN = 20–22 nuclei. This proposition was conﬁrmed bymass measurements and reactions involving neutronrich isotopes of Ne, Na and Mg, especially at RIBF.
This change in occupation of nucleons in diﬀerent energy levels not only results in large deformations but
also aﬀects the nuclear density proﬁle, particularly the
nuclear surface diﬀuseness. In this work, we attempt tosystematically investigate the connection between the
nuclear surface diﬀuseness and various spectroscopic
information of Ne and Mg isotopes (N = 19–28) ator near the island of inversion. We calculate the density and spectroscopic information of Ne and Mg isotopes using the antisymmetrized molecular dynamics(AMD) model.2,3) We then construct a two-parameter
Fermi density distribution (2 pF), with adjustable radius and diﬀuseness parameters. These parameters arethen estimated using two complementary methods one analyzing the static structure and the other dynamical, in which reaction observables involving these
nuclei are analyzed. In the ﬁrst method, the optimized
radius and diﬀuseness parameters of the 2 pF are estimated by minimizing the diﬀerence between densities obtained by AMD and 2 pF density distributions.
In the second, both the AMD and 2 pF densities aretaken as inputs to calculate the proton-nucleus elastic
scattering diﬀerential cross section using the Glaubermodel. We then demand that the ﬁrst peak position
and its magnitude are reproduced for both these densities as prescribed.4) We have veriﬁed that the parameters estimated using these complementary methods
agree within a margin of 1–3%.
The nuclear surface diﬀuseness, i.e., the diﬀusenessparameter of the 2 pF density of Ne and Mg isotopes
extracted from the matter density distribution of AMD
is plotted in Fig. 1. The diﬀuseness parameter has similar dependency on neutron number, illustrating thesimilarity in nuclear deformations for both Ne and Mg
isotopes.2,3) We observe that the neutron occupancy of
†
∗1
∗2
∗3
∗4

0.7
0.65
0.6
0.55

Mg
Ne

0.5
10 12 14 16 18 20 22 24 26 28

Neutron number
Fig. 1. Diﬀuseness parameters of Ne and Mg isotopes asa function of neutron number. The ﬁgure is adopted
from the original article.†

the weakly-bound 1p3/2 orbit has a signiﬁcant impact
on the global behavior of the diﬀuseness parameter.
The absence of intruder orbitals till N = 18 results innormal shell ﬁlling and hence diﬀuseness parameters
are very similar to the standard value of 0.54 fm. The
eﬀect of the intruder orbitals begins to be felt fromN = 19 onwards resulting in strong quadrupole deformation and mixing of p- and f -waves. 29 Ne and31
Mg (N = 19) have predominant 2p3h conﬁgurations
in which two particles are promoted from the sd- to
pf -shell. The increasing occupation probability of the
1p3/2 orbit not only results in a large diﬀuseness but
also the breakdown of the N = 20 and 28 magic numbers in this region. An exception, however, is notedfor 35–37 Mg where the ﬁlling up the holes in the deeply
bound sd-shell somewhat compensates the increase in
diﬀuseness due to ﬁlling up of the 1p3/2 orbit. Noticeably, for N = 22, 34 Mg has predominant 4p2h conﬁguration, whereas 32 Ne has an admixture of 4p2h and
2p0h conﬁgurations. This could be the reason why
34
Mg is more diﬀused than 32 Ne.
In conclusion our work shows that information about
the nucleus surface diﬀuseness in exotic neutron richnuclei can be extracted from the ﬁrst diﬀraction peakof nucleon-nucleus elastic scattering diﬀerential crosssection.

Condensed from the article in Phys. Rev. C. 104, 054313(2021)
Department of Physics, Indian Institute of Technology Roorkee
Department of Physics, Hokkaido University
Department of Physics and NITEP, Osaka Metropolitan
University
RIKEN Nishina Center

References
1) E. K. Warburton et al., Phys. Rev. C 41, 1147 (1990).
2) T. Sumi et al., Phys. Rev. C 85, 064613 (2012).
3) S. Watanabe et al., Phys. Rev. C 89, 044610 (2014).
4) S. Hatakeyama et al., Phys. Rev. C 97, 054607 (2018).

- 35 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Study of β-delayed one-neutron emission probabilities using a neuralnetwork model†
D. Wu,∗1 C. L. Bai,∗1 H. Sagawa,∗2 S. Nishimura,∗2 and H. Q. Zhang∗3
The β-delayed neutron emission is a key ingredient inastrophysical r-process nucleosynthesis, whose theoretical model predictions still contain large uncertainties.
In this work, we applied a novel feed-forward neuralnetwork (FNN) model to accurately calculate β-delayed
one-neutron emission probabilities.
We considered a three-layer FNN architecture consisting of input, hidden, and output layers with Nin ,Nh , and No neurons, respectively. The model wastrained with a set of input data of known physicalquantities, namely, one-neutron emission Q-value, Qvalue diﬀerence between the one- and two-neutron emissions, β-decay half-life, T1/2 , the distance from the least
neutron-rich nucleus with Qβ1n > 0 in each isotope,
N − ND , and the exponential form of the ratio of Qvalue, exp(−Qβ2n /Qβ1n ). The learning process was
performed to minimize the loss function via proper optimization methods. We used the root mean squared
prop (RMSProp) method to obtain the optimal network parameters.
First, we calculated the one-neutron emission probabilities, P1n , of the nuclei, which have only one-neutron
emission channels. The input data contain 127 nuclei and the size of the training set is 89. The follow3
T1/2 ,
ing inputs are given in the network: Qβ1n , ΔEw
G(Z, N ) = ΔEw ΔS2n , and N − ND , where ΔEw =Qβ1n − Qβ2n is actually Qβ1n in this special case, andΔS2n = S2n (Z + 1, N ) − S2n (Z + 1, N − 2). The input, hidden, and output layers contain 4, 40, and 1
neurons, respectively. The P1n diﬀerences between thepresent ML-FNN and experimental data of these nuclei are shown in Fig. 1, together with those obtainedby the FRDM12+(Q)RPA+HF1) and RHB+RQRPA
models.2) It can be observed that the results of thethree models are reasonable consistent with the experimental data. The diﬀerences between ML-FNN andexperimental data are distributed over −25% to 25%
and densely concentrated around 0, especially whenN > 40. The RMSD values of ML-FNN are 8.5% and9.0% for the training and for testing sets, respectively,
and 11.8% and 13.4% for the FRDM12+(Q)RPA+HF
and RHB+RQRPA models, respectively. A remarkable improvement of ML-FNN model can be seen in
the RMSD compared to the other two models.
The waiting-point nuclei are the key elements to determine the time scale of r-process and strongly af†
∗1
∗2
∗3

Condensed from the article in Phys. Rev. C 104, 054303(2021)
College of Physics, Sichuan University
RIKEN Nishina Center
China Institute of Atomic Energy- 36 -

Fig. 1. Diﬀerences of P1n between theoretical results
and experimental data for the nuclei, which have
only one-neutron emission channels.
The data of
FRDM12+(Q)RPA+HF and RHB+RQRPA are takenfrom Refs. 1) and 2), respectively.

Table 1. P1n of waiting-point nuclei at magic neutron
numbers N = 50 and 82. Three theoretical models,
FRDM12+(Q)RPA+HF,1) RHB+RQRPA,2) and MLFNN, are listed with experimental data with errors inthe brackets. The values are given in %.
Nuclides

FRDM12RHB

ML-FNNExp.

79
29 Cu5080
30 Zn5081
31 Ga50128
46 Pd82
129
47 Ag82130
48 Cd82

30.0
11.0
7.0
9.0
10.0
6.0

56.5
22.5
34.3
1.8
13.2
0.7

40.1
1.6
14.1
11.8
21.2
1.6

66(12)
1.36(12)12.5(8)10(7)17.9(14)3.0(2)

fect the ﬁnal abundance of elements in the solar system. The experimental and theoretical P1n values of
the waiting-point nuclei at the magic neutron numbers
N = 50 and 82 are listed in Table 1. It can be observed that the proposed ML-FNN model provides theP1n values of the waiting-point nuclei at N = 50 and
82 with the highest accuracy, both qualitatively andquantitatively.
References
1) P. Möller et al., At. Data Nucl. Data Tables 125, 1(2019).
2) T. Marketin et al., Phys. Rev. C 93, 025805 (2016).

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Reentrant of the pairing gap and α-correlation in 108 Cd
K. Sugawara-Tanabe∗1,∗2 and K. Tanabe∗3
20

Motivated by the experimental data of the reaction 112 Sn(p, pα)108 Cd,1) we solved the numberand angular-momentum-constrained Hartree–Fock–
Bogo liubov equation for 108 Cd by using the signatureinvariant representation. We started from the spherical
single-particle energies and included all the direct andexchange contributions from the residual monopoleand quadrupole pairing, and quadrupole–quadrupole
interactions among the same isospin shells and between
the proton (p) and neutron (n) shells. The canonical base represents the diagonalization of densities
in the generalized density matrix2) at the minimum
point of the total Hamiltonian determined under theconstraints self-consistently. We found, for the ﬁrst
time, the canonical base including the Coriolis coupling term, which provides details of the nuclear structure that depends not only on the particle number, butalso on the angular-momentum I.
In Fig. 1(A), we compare the theoretical backbending curve with the experimental one.3) The theoretical values (squares) reproduce the experimental ones
(circles) reasonably well. The backbending appears
from the 6+ state and the yrast level jumps to the new
band at the 10+ state. In Fig. 1(B), the average pairing gap Δ̄τ ± = i τ ± Δ̄îi /Nτ ± is calculated for eachshell, where Δ̄îi represents the level-dependent gap in
the canonical base, τ indicates p or n shell, and ± theparity of the shell. Nτ ± is the total level number belonging to the τ ± shell. The gradual decrease in Δ̄τ ±for τ = p or n is due to the Coriolis anti-pairing effect. The ﬁgure shows a sudden increase in the proton
gap between the 8+ and 10+ states, which indicatesthat the reentrant of the proton pairing gap appears
in high-spin states in 108 Cd. The single-particle energies in the canonical base, which includes self-energy,
chemical potential, and the cranking term, show thatthe 1g7/2, 1/2 level in the p+ shell comes down to the
Fermi surface suddenly from the 8+ state to the 10+
state. This triggers the reentrant of the proton gap.
The single-particle energy in the canonical base also indicates that the 1h11/2, 1/2 level in the n− shell causes
the backbending.
Owing to the reentrant ofthe proton pairing gap, the
α-correlation deﬁned by  i>0 Ci p Cî p Ci n Cî n  =
p ni>0 κîi κîi as a function of I has two peaks, one at the0+ state and the bump at the 10+ state (∼3.4 MeV),
where Ci τ denotes the spherical single-particle operator,  denotes the quasiparticle vacuum corresponding
∗1
∗2
∗3

A

108
 

I 

15

Cd





10






Theory 
Exp. 

5









0
0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

E MeV

Average pairing gap  MeV

2.0

B
1.5
1.0




n

108

n












 p  p

















0.5



0.0
0

Cd









5




10

15




20

I 
Fig. 1. (A): Comparison of the theoretical backbending
plot for 108 Cd with the experimental data.3) The abscissa represents the total energy diﬀerence ΔE =E(I) − E(I − 2) for I ≥ 2, and the ordinate the total
angular momentum I. Theoretical values are indicatedby squares, and experimental ones by circles. (B): Theaverage pairing gap Δ̄ in each shell as a function of angular momentum I. Solid and open symbols indicate
the results on “−” and “+” parity shells, respectively.
The squares indicate the values for the n shell, and thecircles for the p shell.

to I, and κτîi denotes the pairing matrix in the τ -shell.
References
1) J. Tanaka et al., Science 371, 260 (2021).
2) C. Bloch, A. Messiah, Nucl. Phys. 39, 95 (1962).
3) R. B. Firestone, V. S. Shirley, Table of Isotopes (John
Wiley and Sons INC, 1996).

RIKEN Nishina Center
Department of Information Design, Otsuma Women’s University
Department of Physics, Saitama University- 37 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

α-correlation in 108 Cd excitation energy spectrumof α removal from 112 Sn
K. Sugawara-Tanabe,∗1,∗2 K. Tanabe,∗3 J. Tanaka,∗1 and T. Uesaka∗1
20

We employed number- and angular-momentumconstrained Hartree-Fock-Bogoliubov (CHFB) equations for 108 Cd and 112 Sn using the same set of parameters. The parameters were quadrupole-quadrupole
force strength χp = χn = −0.04 and χpn = −0.13 inunit of MeV/b4 , monopole-pairing force gp = −0.24
and gn = −0.18 in unit of MeV, and quadrupolepairing force with 10% g in unit of MeV/b4 , where b isthe oscillator length. We excluded a tensor-type force
between proton-neutron pairs. Figure 1(A) shows acomparison of the theoretical and experimental backbending curves1) of 108 Cd (circles) and 112 Sn (triangles). The theoretical values (solid) match the experimental ones (open) reasonably well for both nuclei.
For 112 Sn, a vibrational level scheme with a constantenergy shift after the 2+ state is observed, whereas108
Cd shows a rotational one in which the proton pairing gap reoccures at the 10+ state. For 108 Cd, thedeformation parameter β2 is almost constant (∼ 0.15)
in the range of 0+ ∼ 16+ states, whereas γ ranges
from −2◦ to 5◦ depending on total angular momentum I (almost prolate shape). In contrast, for 112 Sn,
β2 remains zero, and γ is zero in the 0+ state (prolate shape) and approximately 60◦ in the 2+ ∼ 10+
states (oblate shape). For 112 Sn, the proton pairing
gap vanishes as a natural result of the magic number,and its neutron pairing gap of 1.61 MeV is 1.2 times
that of 108 Cd in the 0+ state. We consider that the
microscopic process creates an α-particle by the reaction, 112 Sn(p, pα)108 Cd2) is as follows. We assume
a physical picture that 112 Sn is composed of excited108
Cd and an α particle, and that the ﬁnal stage isthe energy spectrum of the observed 108 Cd. The overlap between the initial and ﬁnal states includes the αcorrelation,  i>0 (4/(2ji + 1))Ci∈p Cî∈p Ci∈n Cî∈n  =p ni>0 (4/(2ji + 1))κîi κîi . In the expression, the factor
comes from the Clebsch−Gordan coeﬃcient to form
iso-triplet pairs, Ci∈τ is the spherical single-particle
operator belonging to τ (proton or neutron), ket  isthe quasivacuum of the yrast state of I, and κτîi is thepairing matrix for the τ -shell in 108 Cd. In Fig. 1(B),the square of the α-correlation is shown as a functionof the excitation energy. Owing to the recurrence ofthe proton pairing gap, the square of the α-correlation
has two peaks as a function of I, one at the 0+ state
and another bump at the 10+ state (∼ 3.4 MeV). The
highly excited state corresponds to the high-spin states
∗1
∗2
∗3

108

I 

15

A

Cd 112 Sn

Theory
Exp.






 





10










5







 



 



0
0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

E MeVBΑcorrelation 2

0.15

0.10


0.05




0.00
0

1





2



3



4

5



6

Eexc MeV

Fig. 1. (A): Comparison of theoretical backbending plots of108
Cd (closed circles) and 112 Sn (closed triangles) withexperimental data (open symbols) from isotope table.1)
Abscissa is total energy diﬀerence ΔE = E(I)−E(I −2)
for I ≥ 2. Ordinate is for total angular momentum I.
(B): A square of α-correlation in 108 Cd as functions ofEexc = E(I) − E(0), where E(I) is the total energy of H  at I.

of Cd in the ﬁnal stage of the reaction. The ratio of
the ground state peak to the second peak at 3.4 MeV
is approximately 0.45, which coincides with the experimental value of 0.43 from Fig. 3A in Ref. 2). Summarizing we show that the CHFB calculation reproduces
the basic feature of the reaction as well as the high spinstates of 112 Sn and 108 Cd; however, the r-coordinate
and/or a ﬁnite range formalism are required particularly for the description of an α particle.
References
1) R. B. Firestone, V. S. Shirley, Table of Isotopes, 8th ed.
(John Wiley and Sons, INC, 1996).
2) J. Tanaka et al., Science 371, 260 (2021).

RIKEN Nishina Center
Department of Information Design, Otsuma Women’s University
Department of Physics, Saitama University- 38 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Proof-of-principle calculations in the ab initio no-core Monte Carloshell model†
T. Abe,∗1 P. Maris,∗2 T. Otsuka,∗3,∗1,∗4 N. Shimizu,∗5 Y. Utsuno,∗4,∗5 and J. P. Vary∗2
-4

†
∗1
∗2
∗3
∗4
∗5

Energy per nucleon (MeV)

Understanding of nuclear structure from ﬁrst principles is a major challenge in low-energy nuclear theory.
This challenge includes not only the conﬁrmation of existing experimental data but also the predictions where
the experimental information has not been available
yet. In addition, one hopes to extract a detailed understanding of a variety of complex nuclear phenomena,
described by successful nuclear models, from the underlying microscopic descriptions. Under these motivations, a number of ab initio investigations have been
actively done for more than a decade. This trend in
ab initio studies has been supported by the rapidly
growing computational power of supercomputers andcontinuing improvements of ab initio techniques fornuclear many-body calculations.
Here we report the proof-of-principle calculationsin the ab initio no-core Monte Carlo shell model(MCSM).1) This is the extension of the MCSM withan assumed inert core2–4) to the ab initio no-core shellmodel.3–5) Ground-state energies are obtained in thebasis spaces up to seven harmonic oscillator (HO) major shells (Nshell = 7) with several HO energies, h̄ω,
around the optimal h̄ω for the convergence of groundstate energies. These energy eigenvalues are extrapolated to obtain estimates of converged ground-stateenergies in each basis space using energy variances ofcomputed energy eigenvalues. We further extrapolatethese energy-variance-extrapolated energies obtainedin the ﬁnite basis spaces to inﬁnite basis-space results.
Figure 1 shows our results with two nonlocal N N
interactions6,7) in comparison with the experimental
data.8) In Fig. 1, the JISP166) and Daejeon167) results are shown by blue and red symbols, respectively,
with estimated error bars from our ﬁt to Nshell = 4–7
results at their respective optimal h̄ω values. From
Fig. 1, the JISP16 results yield overbinding at 12 C
and beyond. An improved picture emerges using Daejeon16 with some overbinding still evident when compared with experiments. There are encouraging trends
with the Daejeon16 results compared with the JISP16
results. However, this ﬁnding suggests the necessity offurther revisions of nonlocal N N interactions for theheavier-mass region beyond the p shell and/or the ex-

-6

4

He

8

JISP16
Daejeon16
AME2012

Be
12

C

16

O

20

Ne

-8

-10

-12
Fig. 1. Comparison of the no-core MCSM results for theenergy per nucleon with the JISP166) and Daejeon167)
N N interactions to experimental data.8) The MCSM
results are shown for the basis-space extrapolations using the Nshell = 4–7 energy-variance-extrapolated results with the respective optimal h̄ω values.

plicit inclusion of a 3N interaction. Note that the nocore MCSM results are in reasonable agreement withthe other ab initio results with the same interactions
where those are available.
The current study oﬀers a foundation for pathways
to investigate nuclear structure from ﬁrst principles,for instance, α-cluster structure and dineutron correlations of valence neutrons on the p-shell nuclei. Also
the sd-shell nuclei and beyond continue to provide richinsights into emergent nuclear phenomena. With improved nuclear interactions and increasingly precise abinitio tools for nuclear many-body calculations such as
the no-core MCSM, we expect an opportunity to probethese emergent phenomena and, at the same time, toprobe the limits of our knowledge of the strong andelectroweak interactions.
References
1) T. Abe et al., Phys. Rev. C 104, 054151 (2021).
2) T. Otsuka et al., Prog. Part. Nucl. Phys. 47, 319 (2001).
3) N. Shimizu et al., Prog. Theor. Exp. Phys. 2012,
01A205 (2012).
4) N. Shimizu et al., Phys. Scr. 92, 063001 (2017).
5) T. Abe et al., Phys. Rev. C 86, 054301 (2012).
6) A. M. Shirokov et al., Phys. Lett. B 644, 33 (2007).
7) A. M. Shirokov et al., Phys. Lett. B 761, 87 (2016).
8) G. Audi et al., Chin. Phys. C 36, 1603 (2012).

Condensed from the article in Phys. Rev. C 104, 054315(2021)RIKEN Nishina Center
Department of Physics and Astronomy, Iowa State University
Department of Physics, University of Tokyo
Advanced Science Research Center, Japan Atomic Energy
AgencyCenter for Nuclear Study, University of Tokyo- 39 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Structure of few-alpha systems in cold neutron matter†
H. Moriya,∗1 H. Tajima,∗2 W. Horiuchi,∗1,∗3 K. Iida,∗4 and E. Nakano∗4
The ﬁrst 0+ excited state of 12 C, the Hoyle state,1)
is important for generating 12 C elements in the triplealpha (4 He nucleus) reaction via the resonant groundstate of 8 Be, where alpha clusters are well developed.
An accurate description of such alpha-induced reactions in the astrophysical environment, such as corecollapse supernovae and neutron star mergers, is required.2) Recently, the quasiparticle properties of analpha particle in dilute cold neutron matter have been
discussed in terms of a Fermi polaron,3) where an alpha particle is treated as an impurity in majority neutron matter. In the polaron picture, the eﬀective massof the alpha particle depends on the density of neutron matter. We introduce medium-induced two- andthree-alpha interactions considering simple Feynman
diagrams wherein few-alpha particles exchange momenta.
This study investigates two- and three-alpha systems
in dilute neutron matter at zero temperature by precisely solving a few-alpha problem, including the quasiparticle properties of an alpha particle. We consider
the density of neutron matter up to 1/100th of thesaturation density, ρ0 ∼ 0.16 fm−3 , which corresponds
to the Fermi momentum, kF ∼ 0.360 fm−1 . We discuss the possible stability and structure changes in the
Hoyle state and ground state of 8 Be.
The eﬀective Hamiltonian for two- and three-alphasystems is given by:

 p2

(2)
(3)
i
H=
−T
+
+V
V
cm
αα,ij
eﬀ,ij +Vααα +Veﬀ ,
∗
2M
i
i>j

Fig. 1. Energies measured from two- and three-alphathreshold, E (right-hand scale) and rms pair distance(left-hand scale) of the Hoyle state, and ground state of8
Be as functions of the neutron medium Fermi momentum, kF . The dotted line indicates E = 0 MeV.

labeled C∗ , and the ground state of 8 Be as functionsof the Fermi momentum of background neutron matter. The energies of the Hoyle state and 8 Be decreased
for larger values of kF owing to the short-range attractive medium-induced two-alpha interaction. Eventually, 8 Be and the Hoyle state were bound in neutron
matter with kF ≥ 0.08 fm−1 and 0.16 fm−1 corresponding to ≈10−4 ρ0 and 10−3 ρ0 , respectively. Moreover, in terms of structural change, it can be observedthat the size of the Hoyle state and 8 Be decreased. The
rms pair distance monotonically decreased for larger
kF because the internal amplitude of wave functions
was strongly modiﬁed by the medium-induced interactions. Notably, the shrinkage is consistent with thestudy investigating the ﬁnite system, i.e., the α−α−ncluster system.7)
Thus, we point out the possible stability of fundamental light nuclear ingredients, the Hoyle state, and
8
Be. This could signiﬁcantly impact the modeling ofstellar collapse and neutron star mergers, as well as
relevant nucleosynthesis.

where M ∗ is the eﬀective mass of alpha particles, pi isthe momentum operator of the ith alpha particle, and
Tcm is the center-of-mass kinetic energy: moreover,Vαα and Vααα are the direct two- and three-alpha inter(2)(3)
actions, while Veﬀ and Veﬀ are the medium-induced
two- and three-alpha interactions, respectively. Notethat Vαα is deep and has forbidden states owing to
the Pauli principle. The physical constants and further calculation settings are given in Refs. 4) and 5).
The wave function of the few-alpha system can be expressed by superpositioning the correlated Gaussianbasis functions, whose parameters are obtained by thestochastic variational method.6)
Figure 1 shows the in-medium energies and rootmean-square (rms) pair distance of the Hoyle state,
†
∗1
∗2
∗3
∗4

References
1) F. Hoyle, Astrophys. J. Suppl. Ser. 1, 12 (1954).
2) M. Oertel et al., Rev. Mod. Phys. 89, 015007 (2017).
3) E. Nakano et al., Phys. Rev. C 102, 055802 (2020).
4) K. Fukatsu, K. Katō, Prog. Theor. Phys. 87, 151 (1992).
5) L. H. Phyu et al., Prog. Theor. Exp. Phys. 2020,
093D01 (2020).
6) K. Varga, Y. Suzuki, Phys. Rev. C 52, 2885 (1995).
7) M. Lyu et al., Phys. Rev. C 91, 014313 (2015).

Condensed from Phys. Rev. C 104, 065801 (2021)
Department of Physics, Hokkaido University
Department of Physics, Graduate School of Science, University of Tokyo
Department of Physics and NITEP, Osaka Metropolitan
University
Department of Mathematics and Physics, Kochi Univerisity- 40 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Second and fourth moments of the charge density and neutron-skinthickness of atomic nuclei†
T. Naito,∗1,∗2 G. Colò,∗3,∗4 H. Z. Liang,∗1,∗2 and X. Roca-Maza∗3,∗4
Recently, the fourth moment of the charge distribution has been highlighted as a possible proxy to access information of the neutron root-mean-square radius.1–3) This is because the neutron distributions ρn ofatomic nuclei do contribute to their charge density distributions ρch . In other words, precise measurementsof ρch may provide information on ρn as well as ρp .
For
 2 instance,Ref.
  the feasibility to extract 3) showedr n using r2 ch and r4 ch . This, however, relies
on a correlation for speciﬁc nuclei based on a speciﬁctype of models, and hence, it is questionable whether
that method can be applied, in general.
To answer this question, in this paper, we discuss
the feasibility of extracting r2 n from the second andfourth moments of ρch , avoiding as much as possible
the use of model-induced correlations. We also explore
a method to extract the neutron-skin thickness by employing the information of ρch of two neighboring eveneven isotopes to cancel a large part of the spin-orbit
contributions and reduce the uncertainty due to the
nucleon form factors and the pairing correlation.
We will show that the key issue is to extract r2 n from
 
 
 2
r ch and r4 ch to accurately determine r4 p .
The second and fourth moments of ρch readwhere Nτ = Z for the proton (τ = p) distribution
and Nτ = N for the neutron (τ = n) distribution, κτis the anomalous magnetic moment of the nucleon τ ,2and rMτ
is the second moment of magnetic distributionof the nucleon τ . The index a = (n, κ, m) is the setof quantum numbers of a single-particle orbital, theoccupation number of which is Naτ . It is also assumed
that the second moment of a single-particle orbital isapproximately equal to r2 τ , which is probably a good
approximation except in weakly
systems.
 boundWe then consider whether r2 n can be extracted  from experimental data of r2 ch and r4 ch by using
Eqs. (1a) and (1b). Our goal was to reduce model
assumptions to a minimum. To this end, we have discussed in detail two contributions
to the neutron mo
ment: rn SOτ and r4 p . As for the latter, we have 
seen that it can be related to r2 p in a quite robust
manner. Therefore, we deem that we have been abletothe mildest assumptions under which the 2determine
r n of a single isotope can be extracted.
Our main result has been the introduction of a novel
method to extract r2 n from ρch using the information of two neighboring even-even nuclei. The uncertainties due to the nucleon form factors and the approximation for rn SOτ are suppressed, whereas theuncertainties introduced by the pairing are negligible.
We advocate that this method, namely the consideration of two neighboring isotopes, is more reliable.
Despite our eﬀorts, we conclude that the main obstacle to an accurate determination  of the neutron radiusis the contribution from r4 p . Even if it is strongly 
correlated to r2 p , the resulting uncertainty cannot be
neglected. This uncertainty is strongly enhanced when
propagated from the fourth moment to the neutron
radius. Eventually, extracting theneutron radiusor
the neutron-skin thickness from r2 ch and r4 ch does
not seem to be feasible based on the present discussion. Despite these pessimistic conclusions, the equations derived in this paper may be useful for further
understanding and investigation and even more usefulif, in the future, a clever way to better determine theproton fourth moment can be envisaged.

 
 2
N 2
2
+ rEn
r ch = r2 p + rEp
Z
 2

N 2
+ r SOp +(1a)r SOn ,
Z
 
 2
 4
10
N 2  22
r n
rEp
r p + rEn
r ch = r4 p +
3
Z
 
N 4
N  4
4+ r4 SOp +
+ rEn
+ rEp
r SOn ,
Z
Z
(1b)
2
4
where rEτ
and rEτ
are the second and fourth momentsof the charge distribution of the nucleon τ , respectively.
The spin-orbit contributions rn SOτ read

 2
κτ
Naτ l · σ ,(2a)r SOτ  2
Mτ Nτ a∈occ

 4
r SOτ 2
κτ  2 
10r2 − rEτκτ
r τ + Mτ+2
Mτ N τ 532Mτ2
Naτ l · σ ,(2b)×References
1) H. Kurasawa, T. Suzuki,
Prog. Theor. Exp.
Phys. 2019, 113D01 (2019).
2) P. -G. Reinhard et al., Phys. Rev. C 101, 021301 (2020).
3) H. Kurasawa et al., Prog. Theor. Exp. Phys. 2021,
013D02 (2021).

a∈occ
†
∗1
∗2
∗3
∗4

Condensed from the article in Phys. Rev. C 104, 024316(2021)
Department of Physics, University of Tokyo
RIKEN Nishina Center
Dipartimento di Fisica, Università degli Studi di Milano
INFN, Sezione di Milano- 41 -

1

II-2. Nuclear Physics (Theory)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Comment on “Breakdown of the tensor component in the Skyrmeenergy density functional”†
H. Sagawa,∗1 G. Colò,∗2,∗3 and L. Cao∗4
In a recent paper published in Phys. Rev. C1) , hereafter referred to as Dong and Shang, the authors claimin the abstract that “the Skyrme original tensor interaction is invalid.” One should note that, although theoriginal idea by Skyrme dates back to the 1950s andthe Skyrme tensor force has been written out in Ref. 2),
there have been many studies on how to implement it
and ﬁt its parameters since then, even in recent years.
In 2014, some of us published a review paper on thetensor force within mean-ﬁeld and density functional
theory (DFT) approaches to the nuclear structure.3)
In that review, we quoted ≈30–40 papers where theSkyrme tensor is implemented and studied, authoredby diﬀerent colleagues. The conclusion of that review
paper is that evidences for a strong neutron-proton
tensor force exist, even in mean-ﬁeld and DFT studies. Therefore, if the tensor force proposed by Skyrme
were “invalid,” this would impact on a considerable
number of published works and conclusions drawn sofar. Accordingly, it would be appropriate to have astrong argument regarding this “invalidity.”
The argument against the Skyrme tensor force inRef. 1) was given as: “The Skyrme original tensor
force was introduced in an unreasonable way, because
the tensor-force operator S12 in momentum space butwith an r-dependent strength, i.e., fT (r)S12 (k), is applied as a starting point.” We note that S12 (k) can be
expressed as, S12 (k) = (σ1 · k)(σ2 · k) − k 2 σ13·σ2 . We
do not see any logic behind the sentence by Dong andShang. In physics, nothing forbids an interaction to beposition-dependent and momentum-dependent at thesame time. Bethe4) was one of the ﬁrst to advocatethat this ought to be the case if one wishes to introduce
an eﬀective potential for ﬁnite nuclei. Skyrme echoed
this at the beginning of his ﬁrst paper on this topic,
and it is useful at this stage to quote literally the sentence from Ref. 5): “in the case of a ﬁnite system theeﬀective potential must depend upon both momenta
and coordinate.”
Several authors have proposed Skyrme-type forces
with terms that have both momentum- and densitydependence. If the Skyrme tensor force is unreasonablebecause of the reason advocated by Dong and Shang,
the whole Skyrme force will be unreasonable. If this
†
∗1
∗2
∗3
∗4

were the case, this would discredit not only the results of a few hundred papers in which Skyrme tensor
terms are introduced but also some more ≈103 papers
in which Skyrme forces are used.
In the paper by Dong and Shang, it is also claimed
that the Skrme-type tensor interaction is introduced
in an unreasonable way since the Fourier transform ofsuch tensor interaction is diﬃcult or even impossible.
We disagree on this claim based on the procedure that
we discuss explicitly as follows. We show that if westart from a general central, spin-orbit or tensor interaction with a radial dependence such that the range isvery short, the Fourier transform produces the Skyrme
force in momentum space. Let us write the Fouriertransform of an interaction V (r) as
V (q) = eiq·r V (r)dr,(1)
where q = k − k is the momentum transfer (k andk are the initial and ﬁnal relative momenta, respectively). The tensor interaction in the coordinate spaceis expressed as
VT (r) = fT (r)S12 (r),where S12 (r) = (σ1 · r)(σ2 · r) − r2 σ13·σ2 =



(2)
8π
3 [(σ1 ·σ2 )(2) × r2 Y2 (r̂)](0) with the spherical harmonics Y2μ .
The Fourier transform can be evaluated asVT (q) ∝ r4 drfT (r)j2 (qr)[(σ1 ·σ2 )(2) ×Y2 (q̂)](0) . (3)using the multipole expansion of a plane wave. The
spherical Bessel function j2 (qr) is proportional to q 2 ,as j2 (qr) ∼ (qr)2 /5!! in the lowest order of expansion,and VT (q) becomes


4π 8π
(2)
2
(0)
r6 fT (r)dr.
VT (q)  −[(σ1 ·σ2 ) ×q Y2 (q̂)]15
3(4)
In this way, we obtain the tensor interaction in momentum space. This is a further, more detailed, andmathematically rigorous way to show that the arguments in the paper by Dong and Shang are invalid.
References

Condensed from the article in Phys. Rev. C 104, 039801(2021)RIKEN Nishina Center
Dipartimento di Fisica “Aldo Pontremoli,” Università degliStudi di Milano
INFN, Sezione di Milano
College of Nuclear Science and Technology, Beijing Normal
University

1) J. M. Dong, X. L. Shang, Phys. Rev. C 101, 014305(2020).
2) T. H. R. Skyrme, Nucl. Phys. 9, 615 (1959).
3) H. Sagawa, G. Colò, Prog. Part. Nucl. Phys. 76, 76(2014).
4) H. Bethe, Phys. Rev. 103, 1353 (1956).
5) T. H. R. Skyrme, Philos. Mag. 1, 1043 (1956).

- 42 -

1

3. Nuclear DataII-3. Nuclear Data

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production of 93 Zr sample in the 93 Nb(n, p) reaction towards accurate
determination of 93 Zr half-life
A. Takamine,∗1 H. Iimura,∗1,∗2 M. Tajima,∗1 H. Haba,∗1 N. Sato,∗1 S. Go,∗1 K. Imamura,∗1 A. Gladkov,∗1
H. Yamazaki,∗1 and H. Ueno∗1∗1∗2

RIKEN Nishina Center
Advanced Science Research Center, Japan Atomic Energy
Agency- 43 -

4

10

934 keV
1000
counts / ch

The half-live of a long-lived ﬁssion product (LLFP)
is not reliable, even though it is one of the important
basic data to evaluate the long-term radiological risk of
nuclear fuel waste. For example, although 93 Zr will be
the second signiﬁcant contributor to the ﬁssion product activity of nuclear wastes in 1000 years1) due to its
long half-life, the half-life of 93 Zr has been reported as
1.53 Myr,2) 1.13(11) Myr,3) and 1.64(6) Myr,1) and thediscrepancy between these values is as large as 30%.
Because it is impossible to measure the decay of radioactivity directly by observing it, the half-lives of
LLFPs have been deduced by the formula T1/2 =(ln 2)N/A where N is the number of the atoms and A
the radioactivity. In the measurements of A and N , impurities in samples cause unpredictable errors, such as
isobar impurities in a mass spectrometry. To reduce such
errors and to obtain reliable half-lives, we plan to establish a new method using the collinear laser spectroscopy
technique for the accurate determination of half-lives of
LLFPs, starting with 93 Zr. The 93 Zr samples in theprevious measurements were chemically separated froma spent nuclear fuel and a zircaloy cladding, but bothof them contain many nuclides which may lead to unexpected error. We instead prepared a 93 Zr sample using
the 93 Nb(n, p) 93 Zr reaction. Because other radioactive
nuclides produced simultaneously by fast neutron beams
on this target are almost limited to the Nb isotopes fromthe (n, xn) reaction, pure radioactivity of 93 Zr can beobtained by the chemical separation. The number of93
Zr will be determined from the resonance peak intensities in spectra measured by a collinear laser spectroscopyusing the 93 Zr sample added with a quantiﬁed neutral
Zr standard. This can avoid the errors from isobar impurities that could occur in a mass spectrometry.
We conducted a 1-day beam time test in October
2021. Neutrons with an energy of approximately 10 MeV
were produced in the 9 Be(d, n) reaction by irradiating a
30-MeV d beam from the AVF cyclotron onto a beryllium target of 1.85 g/cm2 . The 93 Zr isotopes were thenproduced in the 93 Nb target behind the 9 Be target by
the 93 Nb(n, p)93 Zr reaction. We prepared a 93 Nb target of 102.8 g/cm2 , which was composed of 120 layers of
1-mm thick and φ15 mm 93 Nb disks. During the beamtime, the d beam intensity was measured using a 9 Be
target holder as a Faraday cup. We evaluated that the9
Be target was irradiated with 5.8 × 1018 deutrons in
total. Based on the production cross section data fromJENDL-4.0, 92m Nb (T1/2 = 10.15 d) was expected to be

912 keV
100

10

1

0

500

1000

1500

2000

keV

Fig. 1. Example γ-ray spectrum for the neutron-irradiated93
Nb target.

the most abundant radioactive source in the target.
We started γ-ray measurements for the 93 Nb targets
5 days after the irradiation. The 120 93 Nb targets were
measured one by one using a Ge detector. Figure 1
shows the γ-ray spectrum from the most downstream93
Nb target, as an example, which presents intense peaksof 92m Nb at 934 keV and 912 keV. Using the γ-ray yieldsof 934 keV from 92m Nb, we evaluated the 92m Nb radioactivity of each target at the end of the beam time, taking
into account the measurement date, peak count rates,
half-life, γ-ray intensity, and detector eﬃciency. The
total radioactivity was found to be 27.39(9) MBq. A
further detailed analysis is in progress.
The target will be chemically separated to extract 93 Zr
after cooling down to reduce its radioactivity. Then, βparticles from the 93 Zr sample will be measured by liquid
scintillation counting to measure the 93 Zr radioactivity.
If we ﬁnd that the amount of 93 Zr is suﬃcient, we willproceed to the number measurement using our collinear
laser spectroscopy setup.4,5)
The production yields and their dependences on thetarget thickness obtained in this experiment for 92m Nb
and other nuclides can be used to check the validity ofthe evaluated fast neutron cross section data. We willcompare the present results with the predictions using,for example, PHITS6) with the JENDL data library.
References
1) P. Cassette et al., Appl. Radiat. Isot. 68, 122 (2010).
2) K. F. Flynn, private communication to NNDC (1972).
3) J. Yang et al., Radiochim. Acta 98, 59 (2010).
4) M. Tajima et al., RIKEN Accel. Prog. Rep. 53, 15 (2020).
5) M. Tajima et al., in this report.
6) T. Sato et al., J. Nucl. Sci. Technol. 55, 684 (2018).

1

II-3. Nuclear Data

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

EXFOR compilation of data from RIBF in 2021
T. Tada,∗1 M. Kimura,∗1,∗3,∗4 M. Aikawa,∗2,∗4 and N. Otuka∗4,∗5
Table 1. Entry numbers with references compiled fromRIBF data in 2021.

A nuclear database is the compilation of measured
reaction data and plays an essential role in providing
the best estimate for the safety and eﬀective use of nuclear reactions for various purposes. Thus, nuclear reaction databases support the most fundamental aspectof nuclear sciences and technologies, such as nuclear
physics, astrophysics, nuclear reactor development, environmental monitoring, dosimetry, radioisotope production, and radiotherapy.
One of the largest and globally used public nuclear
reaction databases is the EXchange FORmat (EXFOR) library for experimental nuclear reaction data.1)
The EXFOR library is a universal common repository for nuclear reactions. It was established in 1967.
The International Network of Nuclear Reaction Data
Centres (NRDC) maintains the EXFOR library under the supervision of the International Atomic Energy
Agency (IAEA).2) The EXFOR library covers a wide
range of nuclear reactions, such as neutron-, chargedparticle-, and photon-induced reactions.
The Hokkaido University Nuclear Reaction Data
Centre (JCPRG),3) founded in 1973, is responsible forthe compilation of the charged-particle- and photoninduced nuclear reaction experiments conducted inJapanese accelerator facilities.4) Our contributions to
the EXFOR database constitutes approximately 10%of the total amount of the data records. The database
covers papers published in peer-reviewed journals, anda unique EXFOR entry number is assigned to each paper. Each record includes the information of the bibliography, experimental setup, reaction code, measured
numerical data, and uncertainties for the reaction. For
the compilation of each record, we usually request thecorresponding authors to provide us the original data
for the numerical accuracy of the database.
Since 2010, JCPRG and RIKEN Nishina Center
have been cooperating for the compilation of data obtained by RIBF, which aims to enforce the availabilityof RIBF data. In 2021, we compiled 33 new articles
published by Japanese facilities. These include 16 articles from RIKEN, 4 registered articles, and 12 articles
still in the process of registration. The compiled data
are accessible by entry numbers, which are listed inTable 1.
We acknowledge that collaboration with RIKEN is
helpful for us to establish an eﬀective procedure forthe compilations. Most RIKEN data are very quickly
compiled after publication, and end-users can easily
∗1
∗2
∗3
∗4
∗5

New

Total

5)

E2670
E26768)
E268711)
E269714)
E270417)
E271520)

Entries
E26716)
E26829)E268912)
E269815)
E270518)

E26727)
E268510)
E269313)
E270316)
E271319)

16

access them. We also thank all authors of articles fromRIKEN, who provided us the numerical data. This
greatly helps increase the accuracy and quality of thedatabase.
References
1) N. Otuka et al., Nucl. Data Sheets 120, 272 (2014).
2) https://www-nds.iaea.org/ .
3) Hokkaido University Nuclear Reaction Data Centre,
https://www.jcprg.org/ .
4) M. Kimura, AAPPS Bulletin 28, 24 (2018).
5) K. J. Cook et al., Phys. Rev. Lett. 124, 212503 (2020).
6) T. L. Tang et al., Phys. Rev. Lett. 124, 212502 (2020).
7) S. Bagchi et al., Phys. Rev. Lett. 124, 222504 (2020).
8) H. Haba et al., Phys. Rev. C 102, 024625 (2020).
9) Z. Tsoodol et al., Appl. Radiat. Isot. 168, 109448(2021).
10) H. Suzuki et al., Phys. Rev. C 102, 064615 (2020).
11) L. Yang et al., Phys. Lett. B 813, 136045 (2021).
12) Z. H. Yang et al., Phys. Rev. Lett. 126, 082501 (2021).
13) M. Aikawa et al., Nucl. Instrum. Methods Phys. Res.
B 498, 23 (2021).
14) D. Ichinkhorloo et al., Nucl. Instrum. Methods Phys.
Res. B 499, 46 (2021).
15) M. M. Juhász et al., Phys. Lett. B 814, 136108 (2021).
16) M. Sakaguchi et al., Appl. Radiat. Isot. 176, 109826(2021).
17) M. M. Juhász et al., Phys. Rev. C 103, 064308 (2021).
18) D. Bazin et al., Phys. Rev. C 103, 064318 (2021).
19) F. Browne et al., Phys. Rev. Lett. 126, 252501 (2021).
20) M. Aikawa et al., Nucl. Instrum. Methods Phys. Res.
B 508, 29 (2021).

Graduate School of Science, Hokkaido University
Faculty of Science, Hokkaido University
Research Center for Nuclear Physics, Osaka University
RIKEN Nishina Center
Nuclear Data Section, International Atomic Energy Agency- 44 -

1

4. Hadron Physics

II-4. Hadron Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Simulation study of the charged current DIS cross-section
measurement at the EIC

∗1
∗2
a)

RIKEN Nishina Center
Japan Society for the Promotion of Science
Calorimeter clusters are used with zero-mass assumption. In
the future, tracking information could be included.

-

The precise understanding of the proton structure is
one of the keys to answering what matter is made of.
Precision is also an important factor as an input in the
LHC experiments1,2) that investigate new physics from
TeV-scale proton-proton collisions. While recent LHC
results have improved the precision, the electron-proton(ep) scattering data from HERA3) is still the most important input in the determination of the parton distribution in protons.
The primary process of interest at ep scattering is thedeep inelastic scattering (DIS). It is an electroweak process via the exchange of a virtual photon or weak boson
between the electron and a parton in the proton. The
kinematic variables used to describe DIS are the energy
scale Q2 , Bjorken x, and the inelasticity y. Charged current (CC) DIS proceeds via a W ± boson exchange andhence is a charge selective process. It has a sensitivity
to the distribution of quarks with the opposite charge ofthe incoming lepton.
The Electron Ion Collider (EIC) is the next collider
scheduled to be built at the Brookhaven National Laboratory in US. The EIC performs collisions of electronsand protons or nuclei. It has a few beam-energy settings and the highest centre-of-mass energy is 141 GeV.
The value is smaller than that of HERA; however, thehigh luminosity allows a measurement at the edge of thekinematic coverage of the EIC. The EIC is expected tohave ep DIS cross-section measurements at the region
with higher x values than the HERA data.
The ECCE detector4) is a multi-purpose detector proposed at the EIC. The full detector simulation is available, and the CC DIS analysis is performed using thesimulated samples. CC DIS events are generated as thesignal events and neutral current DIS and photoproduction events are generated as background events for ep
scattering at the highest beam-energy setting of 18 GeV
× 275 GeV.
In CC DIS, the incoming electron is scattered as aneutrino and cannot be detected. The kinematic variables are reconstructed only from the information of thehadronic ﬁnal state.a) Resolution of the reconstructedvariables are found to be typically at 15–25%, except
for the region corresponding to the calorimeter edges. A
large reconstruction bias is observed, possibly due to the
insuﬃcient calibration of the calorimeters.
The escaping neutrino creates an imbalance in transverse momentum (pT ) in the detected ﬁnal state. Eventswith pT imbalance are selected. Further criteria to ensure the quality of pT imbalance are deﬁned for the back-+p
σer,CCS. Shimizu∗1,∗2 for the ECCE inclusive reaction group

1

Q2 = 170 GeV 2

Q2 = 370 GeV 2

Q2 = 750 GeV 2

Q2 = 1500 GeV 2

Q2 = 3000 GeV 2

Q2 = 5000 GeV 2

0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0

1

Q2 = 8000 GeV2

10−1

1

x

0.6

ECCE
2nd simulation

0.4

CC e+p0.2

18 GeV x 275 GeV

0.8

L=37 fb

0
10−1

10−1

1

x

-1

1

x

Fig. 1. Reduced CC DIS cross section for e + p collisions
at 18 GeV × 275 GeV extracted from the ECCE 2nd
simulation samples. The total uncertainties are shownby vertical error bars. The statistical uncertainties are
smaller than the size of markers.

ground rejection. The measurement is restricted to theregion Q2 > 100 GeV2 and y < 0.9. The extraction of
the cross section is conducted in bins of (x, Q2 ). Owing to the large reconstruction bias, a coarse binning is
set to avoid unreasonably large event migration. The
uncertainties in the energy scale, energy resolution, andbackground estimation are propagated to the extracted
cross section. The values of ±2% and 5% are arbitrarily
assigned as the scale and resolution uncertainties, respectively.
Figure 1 shows the resulting cross section for 37 fb−1
of simulated collisions.
The measurement reaches(x, Q2 ) = (0.8, 8000 GeV2 ). The statistical uncertainty
is small and the maximum value is given as 4% at(x, Q2 ) = (0.8, 170 GeV2 ). The study covers a regionof higher x values than that of the HERA data,3) especially at the mild Q2 region.
The EIC explores a region of high x, oﬀering further
information on the proton structure. Once the detector
is adequately understood and properly calibrated, themeasurement would be substantially improved with ﬁner
binning and smaller uncertainties.
References
1) ATLAS collaboration, J. Instrum. 3, S08003 (2008).
2) CMS collaboration, J. Instrum. 3, S08004 (2008).
3) H1 and ZEUS collaborations, Eur. Phys. J. C 75, 580(2015).
4) https://www.ecce-eic.org/ .

- 45 -

1

II-4. Hadron Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Resolution studies for the ECCE EIC detector proposal
R. Seidl∗1
As the preparation for the electron-ion collider, EIC,
is progressing, detector proposals were submitted in
December 2021 to the EIC Project. One of these
proposals is the ECCE consortium1) that has based
its proposal around re-using the 1.5 T BaBar magnet
that is currently prepared for the sPHENIX experiment and also the outer sPHENIX hadronic calorimeter. Re-using these two components allows for moreresources to concentrate on the main detector components needed for a deeply inelastic scattering (DIS)
collider experiments, namely tracking, electromagnetic
calorimetry and particle identiﬁcation. Given the ongoing involvement of Japanese groups in PHENIX andsPHENIX, it is only natural to continue on the ECCE
proposal.
The main part of the proposal concentrated on thetechnical solutions to fulﬁll the scientiﬁc goals thatwere formulated in the EIC white paper,2) the National Academy of Science report and the Yellow Report.3) All of the key measurements were studied in fullgeant4 simulations of the ECCE detector. In DIS,
the main process is the incoming lepton scattering oﬀ
a quark from the incoming proton or nucleus. As such,the simplest way to reconstruct the hard interaction isby measuring the scattered lepton energy and scattering angle and reconstruct the momentum transfer Q2and the momentum fraction x that the quark carried
relative to the proton momentum. Figure 1 shows thefraction of events that get reconstructed in the same x
and Q2 bin as the true kinematics (bin retention fraction) for a ﬁne binning that was used in many impact
studies of the Yellow Report. As can bee seen, the DIS
kinematics can be reconstructed very well over a large
range of the phase space, but toward the bottom rightcorner (at low inelasticity y) the resolution suﬀers atvery small scattering angles. Here other reconstruction
methods that also make use of the hadronic ﬁnal state
are preferable.
Next, for many studies related to the spin and threedimensional structure of the nucleon, semi-inclusive
DIS measurements also make use of detecting at least aﬁnal-state hadron as well. One of the most important
quantities is the momentum fraction z this ﬁnal-state
hadron carries relative to the struck quark. At higherz the hadron is more likely to carry the struck quark
and therefore acts as ﬂavor analyzer. Other relevant
variables are the transverse momentum relative to thevirtual photon from the hard lepton-quark interaction
and the azimuthal angles of hadron and incoming proton spin orientation relative to the scattering plane.
In Fig. 2 the average resolution of z for pions in the∗1

Fig. 1. Bin retention fractions in DIS events of 18 GeV on
275 GeV e-p collisions in bins of x and Q2 when using
the scattered lepton to calculate the DIS kinematics.

Fig. 2. z resolutions for pions in DIS events of 18 GeV on
275 GeV e-p collisions in bins of x and Q2 when using
the scattered lepton to calculate the DIS kinematics.

same ﬁne x and Q2 binning can be seen. It also suﬀers
somewhat at lower z due to the scattered lepton reconstruction but otherwise is very well reconstructed.
The other semi-inclusive variables are even more robust. Using these resolution studies the same impact
studies as in the Yellow Report were revisited using arealistic detector simulation and show that the ECCE
proposal is capable to carry out these measurements
successfully.
References
1) https://www.ecce-eic.org/ .
2) A. Accardi et al., Eur. Phys. J. A 52, 268 (2016).
3) R. Abdul Khalek et al., arXiv:2103.05419.

RIKEN Nishina Center- 46 -

1

II-4. Hadron Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Design of the zero degree calorimeter for the EIC
S. Shimizu,∗1,∗2 Y. Goto,∗1 and Y. Yamazaki∗3 for the EIC Japan group and the EIC eRD27 collaboration
The Electron Ion Collider (EIC) is a future particle collider scheduled for construction in the US. By
colliding electrons and protons or nuclei, the EIC will
be a powerful tool to examine the structure inside of
protons and nuclei. A new electron beam facility isplanned to be built and will be operated together withthe existing ion beams at the Brookhaven National
Laboratory. The expected beam energies are 5–18 GeV
for electrons and 41–275 GeV for protons, providing
the highest centre-of-mass energy of 141 GeV. The EIC
will cover a large kinematic region, which allows for theinvestigation of the parton dynamics in protons andnuclei.
In some of the key EIC physics programs,1) it isessential to detect hadrons or photons from collisions
in the far-forward region of the ion-beam direction. A
suite of detectors will be placed there, in addition to
the central detector at the collision point. The Zero
Degree Calorimeter (ZDC) is one of the far-forward
detector systems and will detect photons and neutrons.
It will be placed ∼40 m downstream of the collision
point, with an aperture of ∼4.5 mrad.
The ﬁrst ZDC design is considered based on thephysics requirements for the ZDC. Examples of measurements that need the ZDC are as follows:1)

Fig. 1. ZDC design. Particles arrive from the left sideof the ﬁgure. The detector consists of a 7 cm crystal
layer (yellow) with a silicon pixel layer attached in front(magenta), 22 layers of tungsten/silicon planes (light
purple) with an additional silicon pixel layer in front,
12 layers of lead/silicon planes (gray), and 30 layersof lead/scintillator planes (green), corresponding to a
thickness of 8X0 , 22X0 , 2λI , and 5λI , respectively. The
total size is 60 cm × 60 cm × 162 cm. The segmentation
on each layer is as follows: 3 cm × 3 cm for the crystal,
1 cm×1 cm for standard silicon layers, 3 mm×3 mm forsilicon pixel layers, and 10 cm × 10 cm for scintillators.

The Crystal calorimeter is intended for the energy
measurement of low-energy photons.
The W/Si
calorimeter will measure the rest of the photon energy
and the shower development of photons and neutrons.
Silicon pixel layers are inserted for position measurement. Silicon layers are used in the Pb/Si calorimeterfor radiation hardness and for the neutron shower measurement. The last Pb/Sci calorimeters are intended
to measure the neutron energy.
The design is studied and optimized using theGeant44) simulation. The simulation has a few missing
pieces, e.g., no readout materials included for crystals
and scintillators. However, it allows the study of baseline performance of the detector complex. Figure 1
shows the optimized design. The performance is studied against single photons and single neutrons. It has
an energy resolution better than the requirement anda position resolution for photons better than 2 mm.
The design will be further optimized based on its
cost, radiation hardness, and the full simulation. The
optimization includes the choice of materials for the
crystal, such as PbWO4 (this study) and LYSO.

• Exclusive vector meson production in e + A collisions, which is sensitive to gluon saturation,2)• Spectator-neutron-tagged e+d deep inelastic scattering, which is sensitive to the nuclear eﬀect indeuterons,• Meson structure measurements,• Leading neutron measurements.
The required performance is as follows:• Tagging of O(100) MeV photons with >90% eﬃciency and an energy resolution of 20–30%,• Detection of 20–40 GeV photons with an energy
and a good position resoluresolution of √ 35%
E(GeV)

tion of O(1) mm,• Detection of neutrons with energy up to theion beam energy with an energy resolution of√ 50% + 5%, a position resolution of √3mrad ,E(GeV)

and a large lateral size of 60 cm × 60 cm.

E(GeV)

To fulﬁll these requirements, the ZDC is designed as
a complex of detectors, namely a Crystal calorimeter and three types of sampling calorimeters: ALICE
FoCal-E3) style Tungsten-Silicon (W/Si), Lead-Silicon(Pb/Si), and Lead-Scintillator (Pb/Sci) calorimeters.
∗1
∗2
∗3

References
1) R. A. Khalek et al., arXiv:2103.05419.
2) A. Accardi et al., Eur. Phys. J. A 52, 268 (2016).
3) ALICE collaboration, ALICE-PUBLIC-2019-005, (2019)https://cds.cern.ch/record/2696471 .
4) S. Agostinelli et al., Nucl. Instrum. Methods Phys. Res.
A 506, 250 (2003).

RIKEN Nishina Center
Japan Society for the Promotion of Science
Department of Physics, Kobe University- 47 -

1

II-4. Hadron Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Preparation for very-forward particle measurements in RHICf-II
experiment
M. H. Kim∗1 for the RHICf-II Collaboration
In June 2017, the RHIC-forward (RHICf) experiment1) measured the very-forward√ neutral particles inpolarized p + p collisions at s = 510 GeV by installing an electromagnetic calorimeter (RHICf detector) 18 m downstream of the STAR experiment. The
RHICf experiment has two experimental goals. The
ﬁrst one is the cross-section measurement to constrain
the hadronic interaction model, which is necessary to
study the origin of ultra high-energy cosmic-rays.2)
The other one is the transverse single spin asymmetry(AN )3) measurement to understand the spin-involved
production mechanism.
The ﬁrst result4) of the RHICf experiment showed
non-zero AN of the very forward π 0 , which shows apossibility of the diﬀractive contribution to the ANof π 0 . To study the underlying interaction of the ﬁrst
result in more detail and also measure various particles,
a follow-up experiment, RHICf-II, is being prepared.
Compared to the RHICf experiment,
the RHICf-II√
experiment will be performed at√ s = 200 GeV. The
AN of the very-forward π 0 at s = 200 GeV and
510 GeV will be compared for testing the xF scalingat the diﬀerent energies using the correlation with theSTAR detectors. The RHICf-II experiment will possibly include polarized proton-nucleus (p + A) collisions.
The ultra peripheral collision and the hadronic contributions to the very-forward neutron AN in polarized
p + A collisions5) can be studied in more detail withwider pT coverage. We will also measure the AN of thevery-forward π 0 in polarized p+A collisions for the ﬁrst
time to study the relation between the very-forward π 0
and neutron AN .
We are also planning to measure Λ and KS0 . Crosssection of KS0 is an important observable to study theatmospheric neutrino ﬂux background of the cosmic
neutrino detection. AN s of Λ and KS0 will enable toextend our understanding of the particle production
mechanism because the AN of Λ is a possible origin ofthat of the very-forward π 0 .
Because the acceptance of the RHICf detector was
not enough for Λ and KS0 measurements, a new larger
detector (RHICf-II detector) of 8 cm × 18 cm size isbeing developed. With the larger detector, we canmeasure Λ decay into n + 2γ and KS0 decay into 4γ.
Because their particle yields in the RHICf-II detector
are expected to be one order of magnitude lower thanthat of π 0 , a trigger logic to more eﬀectively measureΛ and KS0 is being studied.
We are developing the RHICf-II detector by transferring the technology of the ALICE FoCal-E detec∗1

Fig. 1. Longitudinal composition of ALICE FoCal-E detector.6)

tor.6) Figure 1 shows the longitudinal composition of
the ALICE FoCal-E. It is a sampling electromagnetic
calorimeter which is composed of tungsten and siliconlayers. Each layer is made up of high granularity layer(30 μm × 30 μm) for position measurement and low
granularity layer (1 cm × 1 cm) for energy measurement. To more eﬀectively measure neutron, the interaction length of the RHICf-II detector will be increased
compared to that of the RHICf detector.
We are proposing to perform the RHICf-II experiment at STAR in 2024. Currently, we’re discussing
the detailed plan with the STAR and ALICE FoCal
members. Two modules of the ALICE FoCal-E will be
used to cover the RHICf-II acceptance. A prototypeof the ﬁrst module is being developed now and its full
prototype will be prepared in 2022. The other prototype will be prepared in the next year while the ﬁrst
one is in the commissioning.
References
1) RHICf Collaboration, arXiv:1409.4860v1.
2) O. Adriani et al., J. High Energy Phys. 2018, 73 (2018).
3) M. H. Kim et al., in this report.
4) M. H. Kim et al., Phys. Rev. Lett. 124, 252501 (2020).
5) C. Aidala et al., Phys. Rev. Lett. 120, 022001 (2018).
6) ALICE Collaboration, CERN-LHCC-2020-009.

RIKEN Nishina Center- 48 -

1

II-4. Hadron Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Measurement of J/ψ and ψ  productions in p+d and p+p at
SeaQuest
K. Nakano,∗1,∗2 Y. Goto,∗2 Y. Miyachi,∗3 K. Nagai,∗4 S. Sawada,∗2,∗5 and T. -A. Shibata∗2,∗6
for the E906/SeaQuest Collaborationby the SeaQuest spectrometer.4) SeaQuest acquired
physics data from 2013 to 2017 to record 1.4 × 1018
beam protons on targets. The ﬁrst half of the recorded
data waw analyzed. The detection eﬃciency of J/ψ
was corrected by simulation. The beam intensity wasmeasured with a secondary-electron emission monitor(SEM) for normalizing the p+d and p+p cross sections.
We have reported the p+d/p+p ratio of the J/ψ
cross sections.5) It is sensitive to the relative sizes of
the q̄ and g distributions.
On the other hand, the absolute cross section of theJ/ψ production in p+p is sensitive to the absolute sizesof the q̄ and g distributions. Figure 2 shows the preliminary result measured by SeaQuest as a functionof xF . The solid line is the theory prediction basedon the NRQCD framework and the CT14nlo PDF. It
shows fair agreement with the measured result. The
dashed line is the theory prediction for the ψ  production. Further analysis of the SeaQuest data is underway to extract the ψ  absolute cross section.

The partonic structure of the proton is one of themost vital topics in hadron physics. The SeaQuest(E906) experiment at the Fermi National Accelerator Lab (FNAL) in USA is aimed at measuring the
ﬂavor asymmetry of light antiquarks in the proton,¯d(x)/ū(x),at large Bjorken x ( 0.3). It utilizes the120-GeV proton beam from the FNAL Main Injector
and targets of liquid hydrogen and liquid deuterium.
¯
The result of d(x)/ū(x)using the Drell-Yan process isbeing reported.1,2)
The data recorded by SeaQuest include J/ψ andψ  productions. The production cross sections of J/ψand ψ  are sensitive to distributions of both antiquarks
and gluons through the q q̄ annihilation (q q̄ → J/ψ orψ  ) and gluon fusion (gg → J/ψ or ψ  ), as shown in
Fig. 1. The q q̄ annihilation dominates in the region oflarge Feynman x (xF  0.4) where SeaQuest can measure. Therefore, the measurement of J/ψ is expected
to provide additional constraints on parton distribution functions (PDFs), particularly of antiquarks at
middle values of Bjorken x. Furthermore, the measurement of ψ  helps us disentangle the antiquark andgluon contributions because the ratio of the q q̄ andgg sub-processes in the ψ  production is diﬀerent fromthat in the J/ψ production, as evaluated by a calculation based on non-relativistic quantum chromodynamics (NRQCD).3)
Muon pairs from J/ψ and ψ  decays were detected

p+p at E=120GeVdσ/dxF (nb/nucleon)

beam

10

Preliminary
FY 2015 Data+/-10% beam luminosity uncertainty
1

J/ψ NRQCD CT14nlo
ψ’ NRQCD CT14nlo
J/ψ SeaQuest
−1

10

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

xF

Fig. 2. Absolute cross section of J/ψ and ψ  productions
vs. xF . The points are experimental J/ψ data obtainedby SeaQuest, with the statistical and systematic uncertainties drawn as vertical bars and shaded boxes, respectively. The two lines are theory predictions for the
J/ψ and ψ  production.3)
Fig. 1. Leading diagrams of J/ψ productions in proton+proton reaction.
∗1
∗2
∗3
∗4
∗5
∗6

References
1) Y. Goto et al., in this report.
2) J. Dove et al., Nature 590, 561 (2021).
3) C. Y. Hsieh et al., Chin. J. Phys. 73, 13 (2021).
4) C. A. Aidala et al., Nucl. Instrum. Methods Phys. Res.
A 930, 49 (2019).
5) K. Nakano et al., RIKEN Accel. Prog. Rep. 54, 60(2021).

Department of Physics, University of Virginia
RIKEN Nishina Center
Faculty of Science, Yamagata University
High Energy Nuclear Physics, Los Alamos National Laboratory
Institute of Particle and Nuclear Studies, KEK
College of Science and Technology, Nihon University- 49 -

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Transverse single spin asymmetries of forward neutrons in p + p,√
p + Al and p + Au collisions at sN N = 200 GeV as a function oftransverse and longitudinal momenta†
R. Seidl∗1 and the PHENIX Collaboration
In 2015 the PHENIX collaboration took data withtransversely polarized proton beams in proton-proton,
proton-Al and proton-Au collisions at center-of-massenergies of 200 GeV per nucleon. One of the mesurements that were performed with this dataset are very
forward neutron single-spin asymmetries that were detected with the zero-degree calorimeter in the direction of the polarized proton beam. It is located ca
18m downstream of the beam collision point. As reported, nonzero single spin asymmetries for protonproton collisions were already known,1) but the factthat sign and magnitude of such asymmetries were
diﬀerent in proton-nucleus collisions2) initially cameas a surprise. Since then it has been realized, thatapart from meson interchange,3) in p-A collisions increasingly also ulatraperipheral collisions (UPC) cancreate such asymmetries.4) In UPC, a nucleus emits
virtual photons that can collide with the proton andcreate ﬁnal states with forward neutrons, most notably
via the production of a Delta resonance.
Previously, these results were extracted integrated
over the transverse momentum pT of the neutron andthe longitudional momentum fraction xF relative tothe proton beam momentum and its direction. Using Bayesian unfolding as implemented in root thePHENIX experiment has now extracted also the explicit xF and pT dependence of these asymmetries forthe ﬁrst time. Additionally, the asymmetries were calculated in (anti) correlation with activity in other forward detectors (beam-beam counters, BBC) that are
predominantly sensitive to hard collisions and thus allow to enhance or reduce the contribution of the mostly
very soft UPC events.
It was found that the meson-based calculations
describe the proton-proton data very well, showing
roughly a linear transverse momentum dependencewith very little xF dependence. A comparison between
inclusive and hard-collision enahanced (BBC tagged)
asymmetries shows that some UPC contributions may
be present. In p+Al collisions the inclusive asymmetries are comparable with zero over most of the phasespace while the hard-collision enhanced sample is comparable to the p + p case. In contrast, the BBC-vetoedsample (softer processes such as UPC enhanced) shows
already positive asymmetries as shown in Fig. 1. The
asymmetries in this case are initially rising but do show
an indication of a decrease at higher transverse mo†∗1

Fig. 1. Neutron single spin asymmetries for p+Al collisions
either measured inclusively (blue), enhancing hard collisions (green, labelled BBC tagged) or enhancing UPC
events (red, labeled BBC veto) as a function of transverse momentum pT in bins of xF .

menta. Theoretical calculations4) that include both effects qualitatively describe the behavior but do not reproduce the details very well. However, the UPC based
calculations only take decays of resonances with onepion in addition to the neutron into account while unpolarized MCs show that other contributions are alsopresent. This likely explains the very sharp kinematic
dependence of the theory calculations as the phasespace for neutrons from Delta decays is very limited.
In p+Au collisions the contributions from UPC areeven larger as they increase quadratically with the
charge of the nucleus. Here, even some UPC events
seem to remain in the hard-collision enhanced data
sample where the asymmetries are nearly vanishing
while both inclusive and UPC enhanced asymmetries
are positive. They reach up to 40% and show a similar
behavior as in the UPC enhanced p+Al case.
These results will help further understand the mechanisms that create very forward neutron single spin
asymmetries.
References
1) Y. Fukao et al., Phys. Lett. B 650, 325 (2007).
2) C. Aidala et al., Phys. Rev. Lett. 120, 022001 (2018).
3) B. Z. Kopeliovich et al., Phys. Rev. D 84, 114012 (2011).
4) G. Mitsuka, Phys. Rev. C 95, 044908 (2017).

Condensed from the article in Phys. Rev. D 105, 032004(2022)RIKEN Nishina Center- 50 -

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RIKEN Accel. Prog. Rep. 55 (2022)

Analysis of transverse single spin asymmetry for the forward neutron
at the RHICf experiment
M. H. Kim∗1 for the RHICf Collaboration
In high energy p+p collision, a spin-involved production mechanism of the forward (pseudo-rapidity η > 6)
neutron can be studied by the transverse single spin
asymmetry (AN ), which is deﬁned by the left-rightcross section asymmetry with respect to the beam polarization. The forward neutron AN was measured by
the PHENIX experiment at the Relativistic Heavy Ion
Collider (RHIC) at three diﬀerent collision energies,
62.4, 200, and 500 GeV. Recently, the AN at 200 GeV
was unfolded as functions of longitudinal momentum
fraction (xF ) and transverse momentum (pT ).1)
The non-zero neutron AN is explained by an interference between the spin-ﬂip and non-ﬂip amplitudes
with non-zero phase shift. The model using the π anda1 meson exchanges between two protons for the spinﬂip and non-ﬂip showed a good agreement with the pT
dependence of the data.2)
In June 2017, the RHICf experiment3) measured theneutral particles in polarized p + p
AN of the forward√
collisions at s = 510 GeV. We installed an electromagnetic sampling calorimeter4) (RHICf detector) at
the zero-degree area which was 18 m away from the interaction point of the STAR experiment at RHIC. We
measured the neutrons of 0 < pT < 1 GeV/c which wasa wider pT coverage than those of previous measurements at PHENIX. The RHICf data can be comparedwith them and the validity of the π and a1 exchange
model in the higher pT range can be also tested. In thisarticle, we report the analysis status of the neutron AN
measurement.
First, the neutron candidate is separated from theelectromagnetic event using the diﬀerence between
their shower developments in the detector. A variable
called L2D which is deﬁned by the correlation between
the longitudinal depth of the detector where the accumulated energy deposit reaches 20% and 90% of thetotal was used for this separation.
RHICf detector has limited interaction length (1.6
λI ) for the neutron energy measurement. The xF and
pT distribution is obtained by the Bayesian unfolding5) method. Neutron Monte Carlo sample generated
by randomizing the energy and direction was used forthe input distribution. Figure 1 shows the pT projections of the input and unfolded distributions of neutrons. The input distribution was made based on the
QGSJET-II 04 model.6) One can see the unfolded distribution reproduces the input well. If the pT s ofeach bin are estimated based on the unfolded distribution, their diﬀerences to the original mean values are
smaller than 0.02 GeV/c.
∗1Counts

6

×10
0.3

Input
True
UnfoldUnfold

0.2

0.1

0
0

0.2

0.4

0.6

0.8

1

1.2

p (GeV/c)T

Fig. 1. Input and unfolded pT distribution of neutron.

After the unfolding, it is necessary to subtract thebackground AN because the electromagnetic contamination and the hadronic backgrounds like proton andcharged pion are still included in the unfolded distribution. Each background fraction was estimated basedon the Monte Carlo samples generated by QGSJET-II
04. The electromagnetic background AN was calculated by ﬁtting the L2D distributions of the neutron
candidates in the up and down polarizations using
the shape of the hadronic and electromagnetic samples studied from the QGSJET-II 04 model. Since
the backgrounds hadrons cannot be separated fromthe true neutron, their AN was assumed as a value
which was bigger than the one of the neutron candidates where they belonged to but smaller than 1 which
was the maximum AN a particle can have.
Currently, we are estimating the systematic uncertainties through the analysis procedures describedabove. It is expected that the analysis will be complete
and the result for the neutron AN covering the highest
pT range ever will be obtained soon.
References
1) U. A. Acharya et al., Phys. Rev. D, in press.
2) B. Z. Kopeliovich et al., Phys. Rev. D 84, 114012 (2011).
3) RHICf Collaboration, arXiv:1409.4860v1.
4) K. Kawade et al., J. Instrum. 9, P03016 (2014).
5) G. D’Agostini, Nucl. Instrum. Methods Phys. Res. A
362, 487 (1995).
6) S. Ostapchenko, Nucl. Phys. B, Proc. Suppl. 151, 143(2006).

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RIKEN Accel. Prog. Rep. 55 (2022)

Status of the J-PARC E16 experiment in 2021
S. Yokkaichi∗1 for the J-PARC E16 Collaboration
We proposed the experiment E161) to measure thevector meson decays in nuclei in order to investigate
the chiral symmetry restoration in dense nuclear matter.
The experiment started at the J-PARC Hadron Experimental Facility.
This experiment aims to systematically study thespectral modiﬁcation of vector mesons in nuclei, particularly the φ meson, using the e+ e− decay channel
with statistics that are two orders larger in magnitude
than those of the prior E3252) experiment performed at
KEK–PS. In other words, it aims to accumulate 1 × 105
to 2 × 105 events for each nuclear target (H, C, Cu, andPb) and deduce the dependence of the spectral modiﬁcation on the size of nucleus and meson momentum. The
number of modiﬁed mesons could be larger for larger
nucleus and lower meson momentum because the decay
probability inside the nucleus is enhanced for such cases.
Our proposed spectrometer consists of 26 modules.
As shown in Fig. 1, a module consists of Lead-glass
calorimeter (LG) and Hadron-blind detector (HBD) for
electron identiﬁcation, as well as three-layers of GEM
Trackers (GTR) and a single layer of silicon strip detector (SSD) as the tracking devices.
The ﬁrst commissioning run of E16 experiment, called
Run-0a, was successfully performed in June 4–20, 2020,
with the newly constructed ‘High-momentum beamline.’3) Owing to budget limitations, a limited numberof modules were installed in the commissioning run.
The second half, called Run-0b, was performed inFeb. 11–28, 2021, with the newly installed modules,
namely, 6(SSD)-8(GTR)-6(HBD)-6(LG) modules. Unfortunately, the beam time was aborted, after only
109.5 h of execution, because of a malfunction of MR
ESS.a) To compensate for the unexecuted beam time,
Run-0c was performed in May 29–June 9, 2021, for
134 h. In these two runs, 28 and 46 TB of raw data wererecorded. In our beam time, approximately 24 h wererequired to start-up the GEM-detectors under the beam
environment. The beam intensity was gradually increased during this period, and the ampliﬁcation voltage
of GEM was also increased carefully to avoid discharges.
Furthermore, another 24 h were required to conﬁrm thesatisfactory performance of electron ID counters. Thus,
for each divided beam time, we required at least 48 h
for the tuning of the GEM-detectors.
In Run0-c, we made the two-electron trigger to accumulate the physics data, and found the DAQ live time
was reduced to 15%, which contradicted with the measured DAQ dead-time length and trigger accept rate.
This was caused by the higher trigger-request rate, localized in time, over the Poisson distribution, owing to∗1
a)

RIKEN Nishina Center
J-PARC 30-GeV Main Ring Accelerator, Electro-static septum for the slow extraction.

Fig. 1. Plan view of the E16 spectrometer in the eightmodule conﬁguration for Run-1. The red lines show theparts that have been operated in Run-0b/c in 2021. The
SSD located in the innermost layer is not shown.

the beam micro structures of 5 ms and 5.2 μs cycles.
The latter was newly found in this beam line, while theformer was also observed in another beam line (K1.8)
with lesser strength. As a result of our analysis, origins
of both structures were estimated, and countermeasures
were prepared. Moreover, DAQ upgrade to reduce thedata transfer time is on-going, and the live time is 55%
in the simulation, assuming the present beam structure.
If the structures are reduced, the live time is recovered
to 75% or more.
After Run-0c, the HBD and GTR were uninstalled formaintenance, including exchange of the damaged GEMs.
The maintenance of the GTR is performed in J-PARC,
whereas the HBD maintenance should be performed at
the Main Bldg. in RIKEN Wako, using an N2 -ﬁlled glove
box located in a class-1000 clean room. In November
2021, two LG modules are newly installed in the spectrometer. Re-installation of the GTR (HBD) will becompleted in Aug. (Nov.) 2022.
The next beam time of J-PARC is planned to start in
Dec. 2022, or later. Before Run-1 (physics run), we planto perform a beam study to check whether the countermeasures can improve the DAQ performance, in cooperation with Beam line group and accelerator group at
J-PARC. Subsequently, Run-1 could be performed. This
plan has not been endorsed by PAC yet, thus a review
will be performed in 2022.
References
1) S. Yokkaichi et al., J-PARC proposal No. 16(http://j-parc.jp/researcher/Hadron/en/pac_0606/
pdf/p16-Yokkaichi_2.pdf); S. Ashikaga et al., JPS
Conf. Proc. 26, 024005 (2019).
2) R. Muto et al., Phys. Rev. Lett. 98, 042501 (2007).
3) S. Yokkaichi, RIKEN Accel. Prog. Rep. 54, 107 (2021).

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Analysis of Quark-Gluon plasma properties based on jets with ALICE
experimental data
T. Kumaoka,∗1,∗2 for the ALICE Collabolation
Quark-Gluon plasma (QGP) is deﬁned as a matter
phase at high temperatures and high densities. It is predicted using quantum chromodynamics. A few QGP evidences have been discovered through the LHC and RHIC
experiments. However, QGP features are not revealed,and various measurements are performed to clarify QGP
properties. Among these properties, the stopping power
and jet quenching mechanism can be clariﬁed by measuring the nuclear modiﬁcation factor (RAA ) in a wide
jet transverse momentum (pT ) range. RAA is the ratioof the jet yield in nuclear-nuclear collisions to that in
p-p collisions (Fig. 1). When RAA is less than 1, it implies that jets are suppressed by the QGP created owing
to nuclear collisions. Measured distributions can restrict
theoretical models and clarify the jet quenching mechanism.
In this study, we measure RAA in Pb-Pb collisions at√
sNN = 5.02 TeV by using the ALICE experimental dataof 2018. This data set possesses an integrated luminosity of 0.4 nb−1 , which is larger compared to the previous
study.1) The data are expected to include rare high-pT
jets than the previous measurements, extending the RAA
measurements to the higher pT region.a) Moreover, thelarge data statistics enables the study on RAA at various centralities (Fig. 2), which were limited owing to thelarge number of background particles along the low pT
direction in the case of the previous study. As peripheral
collisions provide a smaller background than central collisions, studies in the lower pT region become possible.
This study clariﬁes the correlation between the partonenergy suppression and centrality.
Data quality requirements were applied to the data,
and those marked as good demonstrate three times larger
statistics than the previous study.1) Jets were recon-

Fig. 1. RAA deﬁnition. The numerator and denominatordemonstrate the jet yields in heavy ion collisions and p-p.
∗1
∗2
a)

Department of Physics, University of Tsukuba
RIKEN Nishina CenterIn this measurement,
we will use the jet pT spectrum in p-p√
collisions at s = 5.02 TeV, which derived from the ALICE
experiment conducted in 2018, as the denominator of RAA .

Fig. 2. Collision centrality. The overlap of heavy ions is
known as centrality. In other words, centrality is deﬁned
as the percentile of the hadronic cross section corresponding to particle multiplicity, considering the count from themost central collisions.

structed using the anti-kT algorithm2) of the fast-jet
package3) without any modiﬁcation. The expected contribution to the jet pT based on background particles wasestimated for each jet on an event-by-event basis. By
subtracting the background, we obtained jet pT spectra
for various centralities. Figure 3 shows the normalized
jet pT spectrum for various centralities. Moreover, it
shows that jets are more suppressed in the central collisions compared with that in the peripheral collisions.

Fig. 3. Jet pT spectrum for each centrality. The horizontal
axis denotes jet pT and the vertical axis denotes jet yields
normalized by the pseudorapidity range and number of binary collisions. In the previous study, RAA was measured
in the area between the two dashed lines.

References
1) S. Acharya et al., Phys. Rev. C 101, 034911 (2020).
2) M. Cacciari et al., J. High Energy Phys. 4, 063 (2008).
3) M. Cacciari et al., Eur. Phys. J. C 72, 1896 (2012).

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RIKEN Accel. Prog. Rep. 55 (2022)

Performance evaluation for sPHENIX-INTT ladder with a beta
sourceY. Namimoto,∗1,∗4 Y. Akiba,∗1 D. Cacace,∗2 K. Cheng,∗3 H. En’yo,∗1 T. Hachiya,∗1,∗4 S. Hasegawa,∗1,∗5
M. Hata,∗4 H. Imai,∗1,∗6 T. Kondo,∗7 C. Kuo,∗3 H. -S. Li,∗8 R. -S. Lu,∗9 E. Mannel,∗2 C. Miraval,∗2
M. Morita,∗1,∗4 I. Nakagawa,∗1 Y. Nakamura,∗1,∗6 G. Nakano,∗1,∗6 R. Nouicer,∗2 G. Nukazuka,∗1 R. Pisani,∗2
M. Shibata,∗1,∗4 C. Shih,∗3 M. Shimomura,∗4 M. Stojanovic,∗8 Y. Sugiyama,∗4 R. Takahama,∗1,∗4
W. -C. Tang,∗3 M. Watanabe,∗4 and X. Wei∗8
The INTermadiate Tracker (INTT) is one of thethree tracking detectors for the sPHENIX experiment which will be started in 2023 at the Relativistic
Heavy Ion Collider in Brookhaven National Laboratory (BNL). It comprises 56 ladders, and each is composed of two silicon strip sensor modules. One module
is divided into 26 cells, and each cell contains 128 readout strips. One readout chip reads the signals fromone cell, 128 strips. The quality of all ladders need
to be evaluated to be ready for detector construction
scheduled for Spring 2022. Dead strips are one of thecritical parameters. We developed the test procedureusing a beta ray source 90 Sr to check for dead strips ina reasonable time scale.
All the strips need to be exposed by beta ray tolocate the dead strips. For that purpose, we developed
the source test ﬁxture shown in Fig. 1. In the ﬁxture,
an INTT ladder was placed with the sensor side down.
The source was placed on a movable stage in the ﬁxture
and moved from left to right during the measurement.
Its moving speed and movable range are adjustable.
Using the ﬁxture, we measured hit counts in each
strip, both with and without the source. The hit

counts without the source provide background hits.
In these measurements, the trigger was provided by
the sensor module and it is called “self-trigger mode.”
Figure 2 depicts the hit counts, the red (light blue) histogram corresponds to that with (without) the source.
In these measurements, one can distinguish the hit
by the source from the background even though thebackground is also visible since data was acquired by
the self-trigger with relatively low hit threshold. The
hit counts are statistically subtracted and shown as
the blue histogram in Fig. 2 to show the signal. If
the diﬀerence is consistent with zero, the strip can be
regarded as “dead strip.” Accordingly measured thedead strips for a ladder in September 2021 and foundno dead strips. The result is better than the requirement of less than 1% dead strips rate in a ladder.

Fig. 2. Number of hit distributions with and without threbeta ray source (red or light blue) and their diﬀerences(blue).

The measurements took eight hours for one sensor
module, therefore an INTT ladder needs 16 h two modules, approximately one day. It is planned that 80 and
40 ladders will be produced at BNL and National Taiwan University, respectively. Therefore, we can complete the quality evaluation within 80 days at most for
all ladders evaluation.
In summary, we developed a procedure to evaluate
the dead strips using a beta source. The ladder production is in progress and the evaluation with this procedure will commence soon.

Fig. 1. Source test ﬁxture.
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9

RIKEN Nishina Center
Physics Department, Brookhaven National Laboratory
Department of Physics, National Central University
Department of Mathematical and Physical Sciences, Nara
Women’s University
Japan Atomic Energy Agency
Department of Physics, Rikkyo University
Tokyo Metropolitan Industrial Technology Research InstituteDepartment of Physics and Astronomy, Purdue University
Department of Physics, National Taiwan University

Reference
1) I. Nakagawa et al., in this report.

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6. Particle Physics

II-6. Particle Physics

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Search for an eﬀective change of variable in QCD simulations
P. Boyle,∗1,∗2 T. Izubuchi,∗1,∗3 L. Jin,∗4,∗3 C. Jung,∗1 C. Lehner,∗5,∗1 N. Matsumoto,∗3 and A. Tomiya∗6
Lattice calculations of quantum chromodynamics(QCD) suﬀers from the critical slowing down as thecontinuum limit is approached. Furthermore, the topological sectors in the gauge ﬁeld space become apparent due to the separation by potential barriers in thislimit, and this fact makes it diﬃcult to explore theentire ﬁeld space in the simulation.
To circumvent these issues, Lüscher proposed1) using the trivializing map2) in lattice QCD. The idea is
to map the system of interest to a trivial system, where
the simulation can be performed eﬃciently. Precisely,
we evaluate the expectation value expressed in termsof the following path integral:
OS ≡

DU e−S(U ) O(U ),DU e−S(U )action:

≡
SF


=

j

This determination gives the best approximation of SF
in the sense that it minimizes the norm 2
 2|| ≡ (∂ A SF − ∂ A SF
)  SF .
||SF − SF

(1)

(6)

This is a calculable norm of the HMC force.
We use Eq. (5) to design the approximated map.
We deﬁne the inﬁnitesimal map Ft, , which evolves
the parameter t by  asaaFt, (V )x,μ ≡ e T Zt,x,μ (V ) Vx,μ .

(7)ais the kernel
Here Zx,μ(2)
ZtA ≡ −

where F∗ (V ) is the Jacobian matrix of the map F. In
other words, we construct a map F that makes theeﬀective action
SF (V ) ≡ S(F(V )) − ln det F∗ (V )(4)where the prime indicates quantities for the ﬁnite basis. The coeﬃcients βi can be determined with the
Schwinger-Dyson equation:5,6)βj ∂ A Wj ∂ A Wi SF = (∂ A )2 Wi SF .
(5)

DV det F∗ (V ) e−S(F (V )) O(F(V ))DV det F∗ (V ) e−S(F (V ))DV O(F(V )),βi Wi ,iwhere S(U ) is the lattice QCD action. The trivializingmap1) U = F(V ) is deﬁned such that
OS =



γi,t ∂ A Wi ,(8)iwhere the label A corresponds to (x, μ, a). Since γi canbe related to βi by



 B
γk,t ∂ A Wk ∂ A [−(∂ B )2 Wi + ∂ B SF
∂ Wi ] S

(3)

F

k

the target action Stg (V ) ≡ const: SF = Stg .
Lüscher explicitly constructed the trivializing map
as a ﬂow Ft for the pure Yang-Mills theory, which wasgiven in the form of an expansion with the ﬂow time t.
To the zeroth order in t, this map becomes the Wilson
ﬂow, the gradient ﬂow for the Wilson action. Combining the Hybrid Monte Carlo (HMC) with the Wilson
ﬂow1) seems promising, based on the observation of
positive eﬀects in the topological tunneling rate.4) The
subject of this study is to investigate the eﬀectivenessof the ﬁeld transformation in lattice QCD along thisline, extending the code to cover more general ﬂow
kernels for the trivializing maps.
To design an approximated map, we consider a different strategy from that of Lüscher’s. We ﬁrst prepare
a ﬁnite basis {Wi } and deﬁne the truncated eﬀective
∗1
∗2
∗3
∗4
∗5
∗6


= −(dβj,t/dt)∂ B Wj ∂ B Wi SF ,(9)

we can determine γi,t by specifying the functional form
of βi,t, or equivalently the target action Stg,t for all t.
In the case where the truncation error is negligible,
the above framework provides a way to construct thetrivializing map with a large freedom of choosing theintermediate trajectory in the space of actions.7) The
authors thank the US DOE for the resources, whichhave been necessary for the work.
References
1) M. Luscher, Commun. Math. Phys. 293, 899 (2010).
2) H. Nicolai, Phys. Lett. B 89, 341 (1980).
3) S. Duane et al., Phys. Lett. B 195, 216 (1987).
4) L. Jin, The 38th International Symposium on Lattice
Field Theory, ZOOM/GATHER@MIT, 2021.
5) A. Gonzalez-Arroyo, M. Okawa, Phys. Rev. D 35, 672(1987).
6) QCD-TARO Collaboration, P. de Forcrand et al., Nucl.
Phys. B 577, 263 (2000).
7) N. Matsumoto, BNL-HET & RBRC Joint Workshop“DWQ@25,” online, 2021.

Physics Department, Brookhaven National Laboratory
School of Physics and Astronomy, University of Edinburgh
RIKEN Nishina Center
Physics Department, University of Connecticut
Universität Regensburg, Fakultät für Physik
Department of Information Technology, International Professional University of Technology- 55 -

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II-6. Particle Physics

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RIKEN Accel. Prog. Rep. 55 (2022)

Quarternion-spin-isospin model
Y. Akiba ∗1
Table 1. Values of elementary action densities.

The standard model (SM) successully describes thenature, but it has at least 25 free parameters. Simple formulas with no free parameter for 24 SM parameters have been reported:1) 15 particle masses,
four Cabbibo-Kobayashi-Maskawa (CKM) quark mixing parameters, three neutrino mixing angles, the ﬁne
structure constant, and the strong coupling constant.
Moreover, the quarternion-spin-isospin (QST) modelthat predicts these formulas,2) and its implication to
gravity and cosmology3) have also been reported. This
article reports an update of the model.
In the QST model, the Planck time tpl = 5.3912 ×
10−44 s is the minimum time period in nature. tpl is afundamental constant in nature, similar to the speedof light in vacuum c and the Planck constant h̄. Consequently, the Planck length lpl = ctpl is the minimum
distance in nature; therefore, a spacetime point has aﬁnite minimum size.
Since a spacetime point has a ﬁnite minimum size,
the number of spacetime points in a ﬁnite spacetime
volume is also ﬁnite. Therefore, two integer indexes,
ns and nt , can be used for all of the spacetime points ina spacetime volume. Here ns and nt denote the index
number of space and time, respectively; Both ns andnt are natural numbers.
Let |ns , nt  denote the physical state at time nt on
spatial point ns . In the QST model, the change of|ns , nt  to |ns , nt + 1 is given by:|ns , nt + 1 = 1 + L̂(ns , nt )dVE |ns , nt , (1)(6π)2 0 iτ 3 (6π)2 0 i (6π)0 iτ 3 (6π0 i) (6π)0 0 iτ 3 0 i

L̂g3D
L̂g2D
L̂GG
L̂uG
L̂cG
L̂tG
L̂m
B
e
4a
μ
4a
τ
4a
ν1
ν2
ν3
ν3
U15
−12a
U17 3 × (−4)
D
−12a
u
4b
c
4b + 4 c
t
4c
d
−12a
s
−12b
b
4d
Z
H
W

−12a
−3
12a
−4a
12a
12a

3∗a
12
4
12
12

2b
2b
2
−2
2a
2b
1

−12b

12b∗
−4
12∗b

3∗b
3∗c

−12a

−3∗

6

3∗b
1
−6
−18∗

8a
24∗
8b
3∗d
27b 18a1
18c−27elementary action densities (EADs). An EAD corresponds to a term of Lagrangian density of the SM.
In the QST model, an EAD is given by:L̂p = ∂ˆp1 ∨ ∂ˆp2 ∨ · · · ∨ ∂ˆp48

where dVE is the minimum spacetime volume.
In the path integral formulation of the quantum ﬁeld
theory, the change of vaccuum state from ti to tf isgiven by:
|tf  = |ti  = Dφ exp i L[φ]dx3 dt |ti .

Here, ∂ˆpk (k = 1, · · · , 48) is one of the following 64
operators named normalized primordial action (NPA),and ∨ is the exterior product of the NPA space.
 I μ σ ν τ a τ a i I [c−a] τ a iτ 3

Ic
i
,
,
,
,
, − , − , −2, 2, i, 1 .
6π
3π 3π
3π
3π
2π π
The QST model contains 49 EADs which are summarized in Table 1. All 24 formulas of the parametersof the SM can be derived from the 49 EADs given in
the table. The model also predicts that the CP violation in the neutrino sector to be 100%. Thus, all 25
free parameters of the SM are derived from the QST
model. In additon, the model predicts that the product of the Hubble constant H0 and the Planck time tpl
is H0 tpl = 2 × (6π)−48 .
A paper describing the QST model is in preparation.

For a small spacetime volume, this equation becomes(2)|t + δt = 1 + iL[φ(x, t)]δx3 δt |t.
It can be observed that Eq. (1) corresponds to Eq. (2)and that L̂(ns , nt ) corresponds to the Lagrangian density L[φ(x, t)].
In the QST model, L̂(ns , nt ) is given by:L̂(ns , nt ) =δp (ns , nt )L̂p

References

Here, δp (ns , nt ) is a function of spacetime point thattakes only 0 or 1, and L̂p denotes operators named
∗1

18b
1
27a
1+4

0

3∗a
2a
24∗a
8a
24∗b
8b

1) Y. Akiba, RIKEN Accel. Prog. Rep. 54, 69 (2021).
2) Y. Akiba, RIKEN Accel. Prog. Rep. 54, 70 (2021).
3) Y. Akiba, RIKEN Accel. Prog. Rep. 54, 71 (2021).

RIKEN Nishina Center- 57 -

1

7. Astrophysics and Astro-GlaciologyII-7. Astrophysics and Astro-Glaciology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Broad-band spectral analysis of the gamma-ray binary system
LS 5039 and its strong MeV gamma-ray emission†
H. Yoneda,∗1 D. Khangulyan,∗2 K. Makishima,∗1,∗3,∗4 T. Enoto,∗5 K. Mine,∗3 T. Mizuno,∗6 and T. Takahashi∗4,∗3

†
∗1
∗2
∗3
∗4
∗5
∗6

Condensed from the article in Astrophys. J. 917, 90 (2021)
RIKEN Nishina Center
Department of Physics, Rikkyo University
Department of Physics, University of Tokyo
Kavli IPMU, University of Tokyo
Extreme Natural Phenomena RIKEN Hakubi Research Team
Hiroshima Astrophysical Science Center, Hiroshima University- 59 -

10−9— INFC (0.45 < φ < 0.9)
— SUPC (0.0 < φ < 0.45, 0.9 < φ < 1.0)

10−10ν Fν (erg cm-2 s-1)

With the development of GeV/TeV gamma-ray observation techniques, since the 2000 s it was established that several high-mass X-ray binary systems
emit strong non-thermal emissions. They are called
gamma-ray binary systems, and so far, approximately
ten sources have been identiﬁed.1) Their spectral energy distributions (SEDs) have a peak typically beyond
1 MeV. Such non-thermal emissions indicate that eﬃcient particle acceleration takes place in them, and they
are considered a new particle accelerator in the Universe. However, the nature of compact objects and theacceleration mechanism in these systems are not wellunderstood, and this has been a long-standing question.
LS 5039 is one of the brightest known gamma-ray
binary systems in our galaxy.2) Its companion star is
an O star with a mass of 23 M , but it is not known
whether its compact object is a black hole or a neutronstar. From X-ray and TeV gamma-ray observations, it
is suggested that this object accelerates TeV electrons
on the time scale of seconds, with an extremely higheﬃciency.3) Recently, by reanalysis of the COMPTEL
data, strong MeV gamma-ray emission has been foundfrom this source.4) These ﬁndings imply that it is essential to understand its broad-band spectrum from X-rays
to TeV gamma-rays. In this report, we present our results of the spectral analysis using the latest data.5)
By using 11 years of Fermi-LAT GeV gamma-ray
data and hard X-ray data of the NuSTAR observation, we updated the SED of LS 5039 with the highest
available statistics (see Fig. 1). The obtained SED and
its spectral modulation along the orbital phase suggestthat LS 5039 has at least four spectral components fromthe X-ray to TeV band: (1) an X-ray component up to
100 keV, (2) a spectral component that is dominant
above 100 keV up to a few tens of MeV, (3) a GeV
gamma-ray component that is almost independent of
the orbital motion, and (4) a TeV gamma-ray component. Existing theoretical models can interpret the ﬁrst
and fourth components, e.g., particle acceleration at thepulsar wind termination shock. However, we found thatthe second and third components are not explained well.
When the MeV emission is interpreted as synchrotron
emission, we can constrain the acceleration eﬃciency
parameter as η < 10. This result suggests that parti-

10−11

10−12

10−13 3
10

104

5

10

6

10

107

8

9

10
10
Energy (eV)

10

10

1011

1012

13

10

1014

Fig. 1. The SED of LS 5039 with the NuSTAR and 11 years
of Fermi LAT data. The red points represent the spectrain orbital phases around the inferior conjunction (INFC)
when the compact star is in front of the companion starfrom the observer’s perspective. The blue points denotethe spectra around the superior conjunction (SUPC)
when the compact star is behind the companion star.
See Ref. 5) for details.

cle acceleration operating in LS 5039 is diﬀerent fromthe diﬀusive shock acceleration (DSA) assumed in manymodels because DSA yields η > 10.
We have performed a broad-band spectrum analysisof the gamma-ray binary LS 5039 and summarized thefeatures of the emission components in each band. The
emission components from MeV to GeV remain uncertain, and further studies on this energy band are key tounderstanding this object’s nature. The MeV gammaray satellite COSI will be launched in 2025.6) Moreover, towards MeV/subGeV gamma-ray observation in
the 2030s, the GRAMS project with an unprecedentedly large eﬀective area has been proposed.7) We expect that these future observations will further deepen
our understanding of the mysterious gamma-ray binary
systems.
References
1) G. Dubus, Astron. Astrophys. Rev. 21, 64 (2013).
2) J. Casares et al., Mon. Not. R. Astron. Soc. 364, 899(2005).
3) T. Takahashi et al., Astrophys. J. 697, 592 (2009).
4) W. Collmar, S. Zhang, Astron. Astrophys. 565, A38(2014).
5) H. Yoneda et al., Astrophys. J. 90, 917 (2021).
6) J. Tomsick et al., Bull. Am. Astron. Soc. 51, 7 (2019).
7) T. Aramaki et al., Astrophys. J. 114, 107 (2020).

1

8. Accelerator

II-8. Accelerator

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Distributed control by EPICS for the SRILAC beam energy position
monitoring system using LabVIEW†
T. Watanabe,∗1 A. Kamoshida,∗1,∗2 A. Uchiyama,∗1 N. Fukunishi,∗1 R. Koyama,∗3 and K. Kaneko∗3
For stable operation of the newly constructed Superconducting RIKEN Heavy-ion Linac (SRILAC), nondestructive and highly sensitive measurement using thebeam energy and position monitor (BEPM) system isessential.1,2) A great advantage of this system is that it
can handle a time-chopped beam by synchronizing themeasurement system with the beam chopping signal.
Although the chopped beam intensity is of several electric nA, we can measure the beam position and energy
to accuracies of ±0.1 mm and precision in the order of
10−4 , respectively.
These measurements and controls are programmedwith LabVIEW. Further, by sharing these measured
values, such as beam positions and beam energies, witha large-scale EPICS control system, it is easy to obtainthe correlation of each relevant machine parametersin time series. A block diagram of the BEPMs anddata-acquisition system is shown in Fig. 1. All themodules, including digitizers, multiplexers and a embedded controller, are integrated into a PXI express
chassis. The signal process procedures are controlledusing the LabVIEW 2020 graphical programming language, and the module drivers are supported by the
National Instruments Corporation. The obtained data
are shared using CA Lab, which is a user-friendly,
lightweight, and high performance interface between

BEPM1
-1

BEPM (mm)1.0E-6'RZQVWUHDP

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7:47

Time

:LQGRZV
/DE9,(:
6RIW,2&&$ODE

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Fig. 2. Measured results showing the relationship between
the beam position at BEPM 1 and the vacuum between
cryomodules of CM1 and CM2.

(3,&6&KDQQHO$FFHVV

5

4.0E-8
7:20'%HDPLQWHUORFNV\VWHP
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the LabVIEW program language and the EPICS-based
control system. It allows easy reading and writing of
EPICS process variables (PVs). The PVs used by the
BEPM system include analog inputs, wave-forms, andanalog and binary outputs. The measurement results
are displayed on a local remote desktop. Furthermore,
once these data are saved to PVs, the Control System
Studio (CSS), which is an Eclipse-based tool to operate a large-scale control system, can display the results
anywhere in the control room.
Figure 2 shows one example of the measured results,
which presents the relationship between the beam position at BEPM 1 and the vacuum between the cryomodules of CM1 and CM2 when the 51 V13+ beam intensity
is increased to 2.5 particle μA. Based on this measurement, we established that the vacuum rapidly became
worse when the beam position shifted from −1 mm to−2 mm. Therefore, we changed the EPICS interlock
system to start the beam attenuator automatically toprevent vacuum deterioration.

We are currently working on measurement of thequadrupole moment to obtain the beam size, beam
intensity from the bunched signal, and TOF using a
lock-in amp technique.
References

Fig. 1. Block diagram of the BEPMs and DAQ.
†

∗1
∗2
∗3

1) T. Watanabe et al., Proc. the 18th Annual Meetingof Particle Accelerator Society of Japan, (Online, Aug.
2021), pp. 683–686.
2) T. Watanabe et al., Proc. 2020 Int. Beam Instrumentation Conf. (IBIC2020), (Santos Brazil, Online, Sept.
2020), pp. 295–302.

Condensed from the article in Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, (2021)
p. 683
RIKEN Nishina Center
National Instruments Japan Corporation
SHI Accelerator Service Ltd.

- 61 -

1

II-8. Accelerator

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Improvement of the transmission eﬃciency of RILAC
T. Nishi,∗1 T. Nagatomo,∗1 O. Kamigaito,∗1 N. Sakamoto,∗1 K. Yamada,∗1 and Y. Watanabe∗1
The performance of the RIKEN heavy-ion linac(RILAC) has been upgraded1) with a new superconducting electron cyclotron resonance ion source (SCECRIS)2) and a superconducting linac booster (SRILAC).3) Since July 2020, we have been successfully
providing a high-intensity V13+ beam with an energyof 6 MeV/nucleon to the GARIS-III4) experiment.
The RILAC facility leaves room for further improvement of the transmission eﬃciency to provide
higher-intensity beams. The beam from SC-ECRIS
is transported through the low-energy beam transport(LEBT) system, which is equipped with a slit tripletthat controls the beam emittance in RILAC. The beamis then bunched and accelerated by a radio frequency
quadrupole (RFQ) and injected to the RILAC cavities,
booster cavities, and SRILAC. The transmission fromthe entrance of the RFQ to the entrance of SRILAC
was inadequate at about 50%.
One of the causes of the low transmission eﬃciency was the mismatch of beam optics between the
RFQ and the ﬁrst acceleration cavity of RILAC. The
beam line consists of two quadrupole doublets (QDL15
and QDL16) and a re-buncher, as shown in Fig. 1.
The beam envelope should be narrowed inside the rebuncher because the duct radius in the re-buncher is
20 mm, which is smaller than the 32 mm duct radiusin the rest of the beam line. The problem was that
the QDL15 magnets were relatively far from an edgeof the vane of RFQ (515 mm) and close to the rebuncher. The beam spreading in the long drift space
after the RFQ should be suppressed in short drift spaceby a strong magnetic ﬁeld for it to pass through the
re-buncher. In contrast, the magnetic ﬁeld of QDL15a,
which is a horizontally focussing magnet, was limited
to suppress the enhancement of the beam size in thevertical direction. Consequently, the optics lost ﬂexibility and could not realize the emittance matching
and good transmission eﬃciency simultaneously.

Therefore, we rearranged the QDL15 quadrupole
magnets together with the other devices (a steerer, agate valve, and a proﬁle monitor) in September 2021.
The cooling pipes of the RFQ were also relocated to
avoid interference with the magnets. The improved
transmission eﬃciency and the current applied to themagnets are summarized in Table 1. These values were
measured when the beam was delivered to GARIS-III
after the transmission optimization by RILAC operators. The transmission eﬃciency was measured by
Faraday cups in the beam lines. L31, 014, 121, and
6A1 are the names of the locations where the Faraday cups are installed, representing the entrance to
the RFQ, the entrance of the ﬁrst cavity of RILAC,
the middle point of 1st and 2nd cavities, and downstream of the last cavity of RILAC, respectively. As
presented in Table 1, a larger current can be applied
to QDL15a as expected. The transmission eﬃciency isimproved by 5% upto 014 and 121 and by 10% upto
6A1. The simultaneous improvement in transmission
from L31 to 014 and L31 to 121 is expected to be theresult of increased ﬂexibility of the optics downstreamof the RFQ. For further increase in the transmission
eﬃciency, we plan to measure the phase ellipse withthe proﬁle monitors installed between the RFQ and
RILAC and to optimize the optics by realizing emittance matching to the acceptance of the ﬁrst cavity of
RILAC.
Table 1. Quadrupole magnet currents and transmission of
RILAC after optimization.
QDL15a (H)QDL15b (V)Current [A]
QDL16a (H)QDL16b (V)Transmission
014
eﬃciency from L31 [%]121
6A1

Jul. 2021 Dec. 2021
38.0
46.8
36.8
40.8
21.5
29.2
13.0
30.1
80–85
90
65
70
50–55
60–65

In conclusion, the beam transmission from the RFQ
was successfully improved. The upgrade of the aged
beam line upstream of RILAC is essential to improve
the transmission further.
References
1) RIKEN Accel. Prog. Rep. 54, S1 (2021).
2) T. Nagatomo et al., Rev. Sci. Instrum. 91, 023318(2020).
3) N. Sakamoto et al., Proc. SRF2019, (Dresden, Germany,2019), pp. 750–757.
4) H. Haba for RIKEN SHE Collaboration, Proc. EXON2018, (Petrozavodsk, Russia, 2020) pp. 192–199.

Fig. 1. Top view of the beam line from the RFQ to the 1stcavity of RILAC before the rearrangement.
∗1

RIKEN Nishina Center- 62 -

1

II-8. Accelerator

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of FPGA-based machine protection system for RIBF
M. Komiyama,∗1 M. Fujimaki,∗1 A. Uchiyama,∗1 and N. Fukunishi∗1

BIS Station 4

DI

DO

AI

PS

CPU

LINK

DO

AI

DI

LINK

PS

CPU

DO

AI

DI

LINK

2. Order to set FC

MELSECNET/H (SI Optical Cable, Double loop)
3. Output a signal toa beam stopper(Faraday cup)

DI

DO

ETHER

PS

CPU

BIS Station 1

LINK

AI

DI

DO

PS

CPU

FC status
information

BIS Station 5

EPICS-LAN

Set interlock pattern/ Monitor signals

N-DIM FC-***
3. Output a signal to a beam chopper

BIS-PC

Fig. 1. Hardware conﬁguration and process ﬂow in BIS.

Therefore, CompactRIO is expected to shorten the software development time. Another merit of using CompactRIO is its maintainability when the FPGA used is
updated, because LabVIEW is expected to absorb thediﬀerence between diﬀerent FPGA versions.
Based on the above considerations, CompactRIO has
greater merit for us. Therefore, we have been developing a prototype with a scale suﬃcient to conduct performance tests for the CompactRIO system, as shownin Fig. 2, since November 2021.
1. Input alarm signal

DO

FC status
information

BIS Chopper Unit

Monitor FC status

BIS Logic Unit (DI)

Chopper output
request information

Chopper set/reset signal from the console,users, devices, etc.

2. Order to set FC
2. Order to work a beam chopper

FPGA (on chassis)CPU- 63 -BIS Station 3

2. Order to work a beam chopper

LINK

RIKEN Nishina CenterPS∗1ex.) error of a magnet power supply
1. Input alarm signal
BIS Station 2

CPU

We have been investigating a new machine protection
system that will succeed the existing beam interlock
system (BIS)1) of RIBF since the latter half of 2020.
The hardware conﬁguration and the process ﬂow in the
BIS are shown in Fig. 1, where programmable logic controllers (PLCs) are used to process interlock signals.
The typical response time of BIS is 18 ms, which will be
insuﬃcient for higher-intensity beams expected in thenear future. Therefore, we plan to introduce a ﬁeldprogrammable gate array (FPGA) to process interlock
signals, aiming at reducing the response time for digital
input signals to less than 1 ms.
In the development of a BIS system using FPGAs(hereinafter, FPGA-BIS), the method of stopping abeam to protect the machine is basically the same asthat of the BIS and AVF-BIS.2) Each station that composes the FPGA-BIS will be installed at or near the
existing BIS station to maximally reuse the existing
signal wirings of the BIS. Therefore, the stations arewidely distributed in the facility as well as in the BIS.
Based on the experience of operating BIS and AVFBIS, we plan to use FPGAs and central processing
units (CPUs) properly according to the signal processing time required. Various interlock conditions are imposed on the existing BIS and FPGA-BIS for each input signal. In essence, the process from the input of analarm signal to the stopping of the beam through theevaluation of interlock conditions is performed on the
FPGA, and the condition setting for and monitoring ofeach signal are performed from a host server via theCPU. As in the case of the AVF-BIS, the EPICS will
be executed on the CPU.
In addition, since the BIS outputs a signal to thebeam choppers, the FPGA-BIS implements not only
the function of BIS, but also a function of controllingthe beam intensity by using a beam chopper. Consequently, it can be expected that the system for sending
signals to the beam choppers will be simpliﬁed relative
to the current situation.
To achieve the performance required in FPGA-BIS,
we compared two candidates: FA-M3 series PLC
with the addition of input/output (I/O) modules with
an FPGA (FPIO module, F3DF01-0N)3) and CompactRIO, a product by National Instruments.4) We concluded that both systems can meet the required performance as FPGA-BIS. Construction costs were also evaluated for both the systems with the same scale as theexisting BIS, and we found that the construction costusing CompactRIO is about half of that using the FAM3 PLCs. In a logic development of FPGA on the CompactRIO system, LabVIEW,5) which has many usefulfunctions and makes programming easier, can be used.

3. Output a signal
to a beam stopper (FC)EPICS-LAN
Set interlock pattern/ Monitor signals

N-DIM FC-***

3. Output a signal to a beam chopper

Fig. 2. Hardware constitution and process ﬂow of the
FPGA-BIS prototype using CompactRIO. FPGA ismounted on the chassis to which each module is installed.

References
1) M. Komiyama et al., RIKEN Accel. Prog. Rep. 39, 239(2006).
2) M. Komiyama et al., Proc. ICALEPCS2019, (2019),
p. 384.
3) Yokogawa Electric Corporation, “Catalog of F3DF010N,” unpublished.
4) CompactRIO, https://www.ni.com/ja-jp/shop/
compactrio.html .
5) LabVIEW, https://www.ni.com/ja-jp/shop/labview.
html .

1

II-8. Accelerator

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Deployment of a beam interlock system driven by changes in magnet
current (Curs-BIS) at the RI Beam Factory
K. Kumagai∗1 and A. Uchiyama∗1
The beam intensity has been gradually increasing at
the RI Beam Factory. To prevent accidents such as
melting of the vacuum chamber due to the beam orbit change, a system to detect the current change ofthe magnets due to unknown causes or noises during
the beam operation and to stop the beam is required.
The beam interlock system driven by changes in magnet current (Curs-BIS) was developed in 2019.1) The
developed system could detect the current values of 24
magnet power supplies per unit, and now it can detect
the current values of 48 power supplies. One unit of
the Curs-BIS is shown in Fig. 1. Various improvements
have been made to the sequence and web-based monitoring programs. The interlock signal is not erroneously
when the power supply is set from 0 A, and the inactivity time of the interlock signal was adjusted according
to the energizing characteristics of each power supply.
It is now possible to directly link the monitoring screen
to a table of power supply speciﬁcations and a graph of
ﬂuctuations in the current value of each power supply.
Three units of the system are currently installed in
IRC and SRC, four units in the beam transport line of
the RIBF, eight units in the RARF (the old facility)and fRC, three units in RILAC2 and AVF, three units
in RILAC. The sequence program is the same for allunits, and each unit can be operated independently bysimply changing the parameter ﬁle for magnet power
supply speciﬁcations, upper and lower limits of current
values, etc.
Accelerators have various types and ages of magnet
power supplies, and the current value of the magnet
power supply is detected in three main ways. Powersupplies with a very high current stability, such as cyclotron main power supplies, usually have a DCCT for
monitoring in addition to the DCCT for power supply control; therefore, the monitor output is used for
detection. For power supplies that do not have a highprecision DCCT for monitoring, an inexpensive external DCCT is installed to detect the current, although
the output accuracy is poor at ±1% of full scale. For
some power supplies, the signal from the feedback circuit is branched oﬀ and the signal through the isolation
ampliﬁer is detected. The Curs-BIS system is set toemit an interlock when the power supply current value
ﬂuctuates by more than ±1% of the rated current as
the initial value, but it can be changed. For the power
supply for steering magnets, the value is ±5% of the
rated value.
The system is also used for the early detection of supply current oscillation in scenarios in which the feedback∗1

Fig. 1. Picture of a unit of the beam interlock system driven
by changes in the magnet current (Curs-BIS).

control of the power supply is not operating properly.
A beam interlock system for detecting EIC and EDC
discharges was also build using the same method as theCurs-BIS. The EIC and EDC are electric-ﬁeld beam deﬂection channels used for beam injection and extractionof the cyclotron. The beam is deﬂected by applying ahigh voltage of approximately 100 kV to an electrodeplate placed in the beam orbit. Because a high electricﬁeld is applied between the plates of ten and several
millimeters, discharges often occur and the beam orbit
is changed. Therefore, the beam should be stopped assoon as the discharge occurs.
Discharges were detected using only the actual voltage change with an analog type circuit. Now, a system
similar to the Curs-BIS can stop the beam by detecting
the change in the actual voltage and current replenishment due to the discharge. The system was installedin the cyclotrons of the SRC and IRC in parallel usage with the analog circuit. Since the RRC and fRC
cyclotrons did not have a discharge detection system,
this system was newly installed. With the system, theallowable value can be changed on the monitor screen,
which was previously changed on site using the analog
circuit. The system can also stop the beam under a sudden change in the set voltage and maintain a log of thenumber of discharges per hour, which can be monitored
on the Web.
Most of the power supplies in the RIBF are now being monitored using Curs-BIS, but a few 10% of thepower supplies on the RARF remain to be set. We areplanning to increase the number of registered power
supplies.
Reference
1) K. Kumagai et al., RIKEN Accel. Prog. Rep. 52, 115(2019).

RIKEN Nishina Center- 64 -

1

II-8. Accelerator

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

2021 Operational report for the Nishina RIBF water-cooling system
T. Maie,∗1 K. Kusaka,∗1 E. Ikezawa,∗1 Y. Watanabe,∗1 M. Kidera,∗1 K. Kobayashi,∗2 J. Shibata,∗2
M. Oshima,∗3 and H. Shiraki∗3
Operation condition

OthersIn 2021, the cooling systems of Nishina and RIBF
were operated for a slightly longer period than theaccelerators. Excluding the time for an installationthat was performed continuously, RIBF’s cooling systems were operated for approximately three months.
Nishina’s cooling systems as for AVF standalone,
AVF+RRC, AVF+RRC+IRC, and RILAC2+RRC
were operated for approximately ﬁve months. No signiﬁcant troubles that might have caused the long-term
interruption of accelerator operation occurred, and thecooling systems were operated stably, with the exception of some minor problems.

The accelerator facility at the Nishina Center has
been operational in the Nishina Building for 35 years
and the RIBF facility has been operational for morethan 15 years. The same applies to the cooling equipment. With a limited budget, maintenance is performed every year, but the equipment is inevitably
aging. Moreover, cooling-water consumables used for
repairing pumps that have been used for more than
15 years are basically unobtainable or very diﬃcult
to obtain. Aging equipment is not only a cause of
failure, but also one of the causes of unstable accelerator beams. However, anti-aging costs The budget
for equipment maintenance is insuﬃcient to cover thecosts of anti-aging measures, and solving these problems will be a signiﬁcant challenge in the future.

Trouble report
In troubleshooting during FY2021, trouble symptoms were fortunately minor. Therefore, instead ofinterrupting the machine time for repairs, while providing emergency measures, repairs were carried out
during long-term accelerator outage periods such as
those for switching beams or summer maintenance.
Typical examples of troubles that occurred in
FY2021 are as follows: water leak from the coolingplumbing joint and deterioration of cooling-water purity due to the water leakage, bearing failure of thecooling water pump motor, inverter failure of the cooling water pump, and device outage caused by an instantaneous voltage drop due to a lightning strike (1–2
times a year).

Reference
1) T. Maie et al., RIKEN Accel. Prog. Rep. 54, 78 (2021).

Periodic maintenanceDuring the shutdown period of the accelerator, thefollowing activities were carried out as part of regular
maintenance.
(1) Cleaning of the cooling towers(2) Inspection and overhauling of the cooling-waterpumps(3) Replacement of some superannuated hoses,
joints, and valves used in the system(4) Cleaning of the strainers and ﬁlters used in thedeionized water production system(5) Extension of the sensing wires of the waterleakage alarm to ﬂoors of new areas(6) Flushing work of the cooling-water pipe that was
blocked by dirt
∗1
∗2
∗3

RIKEN Nishina Center
SHI Accelerator Service Ltd.
Nippon Air Conditioning Service Co., Ltd.

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of a new indicator for the auto tuning systemwith high-intensity primary beams
T. Nishi,∗1 N. Fukuda,∗1 N. Fukunishi,∗1 E. Iwai,∗2,∗3 H. Maesaka,∗2 Y. Shimizu,∗1 T. Sugimoto,∗2,∗3 H. Suzuki,∗1
H. Takeda,∗1 A. Uchiyama,∗1 Y. Yanagisawa,∗1 and M. Yoshimoto∗1

∗1
∗2
∗3

counts/0.5mm

6000
5000
4000
3000
2000
1000
0
−100

−80

−60

−40
−20
0
position at F1 [mm]2040(a) Positions with a 1-mm-thick Be target

counts/0.5mm

At the RIBF facility, more than 600 parameters, suchas quadrupole magnets, steerers, rebunchers, and radiofrequency (RF) voltages/phases, are manually adjusted.
After more than 10 years of operation, the local beamloss has been suppressed to a few percentage points.
However, in order to control the beam beyond 1 particle
μA, we need to optimize the parameters more precisely
according to the beam state at the time while keeping
the beam loss below 0.1%. Therefore, we decided to
conduct research to introduce automatic parameter optimization using machine learning.
In this project, we adopt an auto tuning program using sequential learning based on Gaussian process regression, which is developed and already integrated in
the regular operation at SACLA of SPring-8.1) We apply the program to RIBF via EPICS. As the ﬁrst step
to introduce the program to RIBF, we attempted to optimize the beam-line optics from the SRC to the ﬁrst
production target of BigRIPS, F0.
There are two approaches underway in this project:(A) the development of an auto tuning system for lowintensity beams using ﬂuorescent targets and (B) the
development of a new indicator for an auto tuning system with high-intensity beams using secondary beams.
For (A), we conducted a 12-h experiment in October
2020 using a faint U86+ beam of about 0.001 electric nA(enA) and succeeded in increasing the transmission efﬁciency by 2% and reducing the spot width by 13% at
F0 over the manually optimized optics.2)
For (B), we devised a method using diﬀerent charge
states as indicators for high-intensity primary beams.
A primary U86+ beam is injected to a 1-mm-thick Be
target at F0 to produce several charged-state particles.
The primary beam width and intensity on the target
are estimated from the trajectories and count rates ofcharge-converted particles at downstream focal planes
with parallel-plate avalanche counters (PPACs) and ascintillator at the F3 focal plane. Figure 1 shows the
distribution of diﬀerent charged states at the slit position F1. As shown, the production rate of particles
varies depending on each charge.3) One charge state is
selected by adjusting the Bρ of the beam line and theF1 slit condition. The measurements of the beam spot
size and intensity are realized for primary beams up to
10 enA by selecting charge states with lower production
rates as the primary beam intensity increases.
We conducted an experiment to test this indicator in
May 2021 with faint U86+ beams. The optimization pro-

4500
4000
3500
3000
2500
2000
1500
1000
500
0

−40

−20

0
20
40
position at F1 [mm]

60

80

100

(b) Positions with a 1-mm-thick Be and ﬂuorescent target
Fig. 1. Position distribution of U ions for diﬀerent charge
states at slit position F1.

gram developed in approach (A) was utilized with the
new indicator. The 1-mm-thick Be target was set behind
the ﬂuorescent viewer to compare the new indicator withthe spot image obtained by the ﬂuorescent target. We
conﬁrmed that the program optimized the 7 magnet currents simultaneously to increase value of the indicator.
However, it was revealed that the transmission eﬃciency
with optics “optimized” by our program was 10% worse
than that with the manually optimized optics by comparing the beam current with upstream and downstream
Faraday cups.
After investigation, we found that this was due to the
non-uniformity of the thickness of the ﬂuorescent target,
which increased the momentum spread and the beam
size at the slit position as shown in Fig. 1(b). The distribution width was not small enough compared with theslit width of 23 mm, and the counts of the downstream
scintillator strongly depended on the shape of the distribution at F1, rather than the primary beam intensity
at F0. In order to solve the problem, we aim to adopt
a 1-mm-thick Be solely to avoid enlarging the beam size
at slit position F1.
References
1) E. Iwai et al., Proc. PASJ2021, WEOB02 (2021).
2) T. Nishi et al., Proc. PASJ2021, TUOA03 (2021).
3) D. S. Ahn et al., RIKEN Accel. Prog. Rep. 52, 133 (2019).

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RIKEN SPring-8 Center
Japan Synchrotron Radiation Research Institute- 66 -

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Status of vacuum pumping systems in accelerator facilities
Y. Watanabe,∗1 M. Fujimaki,∗1 E. Ikezawa,∗1 O. Kamigaito,∗1 M. Kidera,∗1 T. Nishi,∗1 S. Watanabe,∗1
K. Yamada,∗1 M. Nishida,∗2 K. Oyamada,∗2 J. Shibata,∗2 K. Yadomi,∗2 and A. Yusa∗2
been in operation for 35–43 years.3) Therefore, in theﬁscal year 2021, one 5000 L/s TMP is scheduled to be
updated in the RILAC and another TMP is scheduled
to be replaced by a set of smaller TMPs (800 L/s and1100 L/s).
A large RP in the SRC-RES4 (Resonator 4) has malfunctioned owing to age-related deterioration, and a newspare large RP has been purchased, which has not been
installed. In addition, some oil leaks in the small RPs
were repaired by installing new O-rings and seals as
usual.
Malfunctions in the TPG have increased year by year.
The reason is unclear, but it is likely because of agerelated deteriorations. Three of the ﬁve malfunctioned
TPG controllers occurred when the power was restored
after an electrical power outage in August and October. This is one common pattern in malfunctions in vacuum pumping systems. Furthermore, all malfunctioned
gauges were replaced by spare units due to a contamination of the sensor head.
Regarding vacuum leaks at the RIBF, nearly all of
the vacuum leaks were caused by age-related deterioration and repaired by installing new O-rings or applying a repair material. For example, water leaks in thewater-cooling parts of the drift tubes in the RILAC cavities were repaired with a sealing agent, and multiple Orings were replaced with new parts. A water leak fromthe water-cooling pipe of a small compensation board in
the RILAC cavity #2 were also repaired with a sealing
agent. A vacuum leak in the coupling of a lower feedthrough trim coil (C8) in the AVF was repaired witha sealing agent because it was diﬃcult to replace theO-ring.

A vacuum pumping system in the RIBF accelerator facility comprises cryopump (CRP) systems, turbomolecular pump (TMP) systems, rough pumping systems (mechanical booster pump + rotary pump [RP]),
additional chamber pumping systems (TMP + RP), andsubpumping systems (TMP + RP) as subvacuum of aresonator.1,2) In addition, module-type vacuum gauges(total pressure gauge [TPG] controller combined with
two gauges) are used. In this paper, we report some
malfunctions of vacuum pumping system encounteredin 2021. Table 1 lists the malfunctions in the pumps,
compressors, and gauges from 2018 to 2021. The vacuum pumping systems were relatively stable to maintainand manage in 2021. A malfunction of TMPs (including power supply) and RPs were less in 2021 comparedto other years. Additionally, malfunctions of CRP and
TPG increased in 2021.
Six cryopump compressors of the SRC malfunctioned
around the G01 Faraday cup (SRC deﬂection beam line)in the uranium beam for the BigRIPS experiments during the months of April to May. The malfunctions of the
cryopump compressors were caused mainly in the SRC
room by a high environmental radiation dose. Therefore, we plan to relocate 13 compressors to a location
far (SRC-north area) from the region of high environmental radiation (SRC-south area) within a few years.
In addition, because the existing cryopump compressors (model; C30V, CRC-874) of the SRC and RRC
have been discontinued by the manufacturer and cannot repaired in the future, a new cryopump compressor(model; C30VRT, P-875CA) for the SRC and RRC has
been purchased as a spare unit in case of a malfunction.3)
Furthermore, because RRC cryopumps were manufactured in 1985 and the replacement of the cryopump to a
new model should be realized early, one unused cryopump system set of the IRC-valley cavity was relocatedto the RRC-valley cavity in 2020.3)
We must update large TMP systems (5000 L/s) in the
RILAC and RRC within a few years because they have

Table 1.

References
1) S. Yokouchi et al., RIKEN Accel. Prog. Rep. 41, 101(2008).
2) Y. Watanabe et al., RIKEN Accel. Prog. Rep. 50, 154(2016).
3) Y. Watanabe et al., RIKEN Accel. Prog. Rep. 54, 79(2020).

Number of malfunctions from 2018 to 2021.

Number of units

2018

2019

2020

> 80

4

6

7

TMP b)

> 138

3

8

4

RP c)

> 146

5

3

7

TPG d)

> 160

4

6

9

CRP a)2021
6 (Pump)8 (Compressor)
1 (Pump)4 (Power supply)
1 (Pump)5 (Controller)
7 (Gauge)a) Includes a compressor. b) Includes an attached power supply. c) Excludes an oil leak. d) Includes
a controller, Pirani, and cold cathode gauge.
∗1∗2

RIKEN Nishina Center
SHI Accelerator Service Ltd.

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of auto-focusing and auto-centering system for the
BigRIPS separator (II)∗1CountsWe are developing a fully-automatic system forradioactive-isotope (RI) beam production based on our
technological developments and experiences to reduce
the operation time. As the ﬁrst step, an auto-focusing
and auto-centering system1,2) to tune the superconducting triplet quadrupole (STQ) and dipole magnetsof the BigRIPS separator was developed. This is thesecond report on the auto-focusing and auto-centeringsystem.
In a previous development,2) auto-focusing or autocentering, including data taking, analysis, and magnet
adjustment, were performed for each focal plane. In
the present development, we aimed to fully automate
the focusing and centering at all the focal planes.
79
Ni-beam production using the auto-focusing andauto-centering system was conducted for the massmeasurement around the 78 Ni region (NP2012RIBF202-02). The 79 Ni yield was not high enough toperform centering and focusing quickly, and the 82 Ga
beam was used instead. To center the 79 Ni-beam positions on the beamline, the goal of the 82 Ga positions
were calculated as −2.7, −6.4, and −3.0 mm at F3,
F5, and F7, respectively.
The STQ and dipole magnets were changed simultaneously to perform auto-focusing and auto-centering
simultaneously at each focal plane. The focal plane forauto-tuning was automatically changed from upstream
to downstream, i.e., from F1 to F7. The positiondetector PPACs installed at F2 were used only for RIbeam tuning at F2. The F2-PPACs were moved automatically on and oﬀ the beamline before and after the
auto-tuning at F2. Figure 1 shows the positions andphase spaces at each focal plane after auto-focusing
and auto-centering. For the auto-centering, the dipole
magnet was tuned so that the center position of the distribution x0 at the focal plane obtained from the resultof Gaussian ﬁtting became the goal of the 82 Ga position. For auto-focusing, the STQ magnets were tuned
so that the ﬁrst-order coeﬃcient p1 obtained by ﬁtting
the phase space with the ﬁrst-order polynomial function was greater than 10, which corresponds to (x|a)
less than 0.1. After conﬁrming that auto-focusing andauto-centering were successful, the focal plane for thesetunings was changed to the next one. A sequence of
these procedures started by simply clicking an “AUTO
TUNING” button on the web browser, after selecting
the gate of the 82 Ga beam on an analysis program.
The results shown in Fig. 1 demonstrate the success offocusing and centering.

80

x 0 = −2.48

F3

θ (mrad)Y. Shimizu,∗1 N. Fukuda,∗1 H. Takeda,∗1 H. Suzuki,∗1 M. Yoshimoto,∗1 T. Sumikama,∗1 T. Baba,∗1 andK. Yoshida∗140

p 1 = +212.12

F3

20

60

0

40

− 20
20
− 40

40

−40

−20

0

20

−40

40

x (mm)

x 0 = −6.24

F5

θ (mrad)Counts

0

40

−20

0

20

40

x (mm)

p 1 = +13.70

F5

20

30

0

20

− 20
10
− 40

60

−40

−20

0

20

−40

40

x (mm)

x 0 = −3.18

F7

θ (mrad)Counts

0

40

−20

0

20

40

x (mm)

p 1 = +31.53

F7

20

40
0
− 20

20

− 40
0

−40

−20

0

20

40

x (mm)

−40

−20

0

20

40

x (mm)

Fig. 1. Positions (left column) and phase spaces (right column) at each focal plane (F3, F5, and F7) after the
auto-focusing and auto-centering. The pink curves andlines show the best-ﬁt functions of the Gaussian andﬁrst-order polynomial, respectively. The x0 and p1 values show the ﬁt results.

Thus, the development of a novel auto-focusing andauto-centering system was completed. An operation
test will be conducted by RI-beam physicists to conﬁrm that this system is applicable to the regular operation of RI-beam production.
References
1) T. Sumikama et al., RIKEN Accel. Prog. Rep. 54, 82(2021).
2) Y. Shimizu et al., RIKEN Accel. Prog. Rep. 54, 83(2021).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of new ionization chamber specialized in high-Z beam
M. Yoshimoto,∗1 N. Fukuda,∗1 R. Matsumura,∗1 D. Nishimura,∗2 H. Otsu,∗1 Y. Shimizu,∗1 T. Sumikama,∗1
H. Suzuki,∗1 H. Takahashi,∗2 H. Takeda,∗1 J. Tanaka,∗1 and K. Yoshida∗1∗1∗2

RIKEN Nishina Center
Department of Natural Sciences, Tokyo City University%HDPĺ

194

Ø70

Ø60
Ø80

Ø110

69

650

55

An ionization chamber (IC) is an essential detector
to identify particles in ﬂight in the BigRIPS separator
and ZeroDegree spectrometer.1) Generally, the atomic
number (Z) is deduced from the energy deposit (ΔE)
in the IC. However, so far, the Z resolution of particles
with Z > 80 emitted from the fragmentation of 238 U
primary beam on a production target is insuﬃcient forthe clear particle identiﬁcation. Here, we report on theconstruction and data acquisition of a new IC for high-Z
beam with an eﬀective diameter of 60 mm.
The deterioration in the Z resolution is caused by the
δ-rays2,3) and the ﬂuctuation of the ionic charge state.
The δ-rays bring about a long tail at the higher energy
side of the ΔE distribution. The Z resolution can be enhanced if the IC does not collect the electron-ion pairs
from the δ-rays. Accordingly, smaller electrodes were
employed for the new IC. The outer diameter of theelectrodes that form the electric ﬁelds was reduced from
280 mm for the conventional F7 IC to 80 mm for the new
IC. Consequently, the change reduces the eﬀective electrode diameter from 232 mm to 60 mm. The electrodesize eﬀects will be tested in the future.
The charge state ﬂuctuation of heavy ions in matter is a well-known phenomenon.4) The ΔE is proportional to the square of the charge state, instead of theZ of the particle. Therefore, the charge state ﬂuctuation by the ﬁlled gas and other materials in the IC
aﬀects the ΔE distribution and the Z resolution. Accordingly, the materials in front of the ﬁrst electrodeshould be reduced to measure the charge state incident
on the F7 chamber with the IC. Therefore, the thicknessof the upstream vacuum separation window was reduced
from 150 μm to 77 μm, and the length of the dead gas
from the vacuum separation window to the ﬁrst electrode was reduced from 89 mm to 16 mm. Furthermore,
we also adopted the methane gas with a smaller crosssection of the charge state changing, compared to theP10 (argon 90% + methane 10%) gas. The P10 andmethane pressures were 620 Torr. The distance between
the electrodes is 20 mm and the eﬀective gas thickness
is 480 mm, as shown in Fig. 1. Six signals each fromfour gas cells were digitized.
The response of the new IC to the gas species was measured at F7 using 238 U90+ beam with 320 MeV/nucleon.
The trigger rates at the F7 were approximately one kcps.
The geometrical averages for the six ADC values of theP10 and the methane gas are shown in Fig. 2.
To understand these distributions, the charge state
distributions in the IC were simulated with the
GLOBAL code.5) On the one hand, the charge statesat the ﬁrst→last electrode in the P10 is 76→37% for

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

104

16
600

Fig. 1. Cross sectional view of the new IC. The electrodefoil is aluminized (both sides) Mylar sheet with 2.5 μm
thickness.

Fig. 2. Energy distributions for 238 U90+ beam at 320
MeV/nucleon directed onto the new IC with the P10 gas(left) and the methane gas (right).

90+ and 19→45% for 91+. On the other hand, thosein methane are 79→68% for 90+ and 16→24% for 91+.
The average number of charge state changes from 90+
to 91+ is 0.9 times for P10 and 0.2 times for methane.
According to the simulation, the asymmetric energy distribution with the P10 was formed by the mixture of
charge 90+ and 91+. In contrast to the P10, the energy distribution with methane has two peaks. The ﬁrst
narrow peak was formed by charge 90+ and the second
peak was formed by 91+. Consequently, 0.9 times of thecharge state changes in the P10 appears to be small toaverage diﬀerent charge states and large for separating
ΔE of each charge state. If a gas with a large crosssection of the charge state changing is used, the distribution will be narrowed because the mixture of multiple
charge states is well averaged.
References
1) K. Kimura et al., Nucl. Instrum. Methods Phys. Res. A
538, 608 (2005).
2) Y. Sato et al., RIKEN Accel. Prog. Rep. 46, 159 (2013).
3) M. Pfützner et al., Nucl. Instrum. Methods Phys. Res. B
86, 213 (1994).
4) H. Weick et al., Phys. Rev. Lett. 85, 2725 (2000).
5) C. Scheidenberger et al., Nucl. Instrum. Methods Phys.
Res. B 142, 441 (1998).

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RIKEN Accel. Prog. Rep. 55 (2022)

Radiation transport calculation of BigRIPS separator
K. Yoshida∗1
Radiation transport calculations of the BigRIPS separator from the production target (F0) to the ﬁnal focus (F7) have been conducted to investigate the originof the neutron radiations in the BigRIPS room. During the BigRIPS operation, the power supplies andthe control panel of the superconducting quadrupole
magnets (STQs) in the BigRIPS room freeze occasionally owing to the neutron radiations. To prevent these
problems, radiation shielding is necessary. In designing an eﬃcient radiation shield, knowing the origin ofneutrons is important.
Thus far, radiation transport calculations of the BigRIPS separator have been conducted from F0 to theﬁrst focus (F1) region1–3) using the particle and heavyion transport code system (PHITS).4) In the present
study, we extended such a calculation to cover the entire BigRIPS region from F0 to F7. The previous geometry model was extended to include all magnets,
beam ducts, chambers, and slits of the BigRIPS separator. The building walls and radiation shielding
blocks in the BigRIPS room were also included in themodel. Calculations were performed with PHITS ver.
3.24 code installed in the HOKUSAI BW supercomputer at RIKEN. Hybrid-parallel computing, with 128
parallel processes of 10 threads, was used to conduct
the calculations. The calculations were performed under various conditions that replicated the experiments
performed at the Radioactive Isotope Beam Factory.
In a calculation, 100 million events were generated for
all incident beams except 238 U. The event number was
reduced to 30 million for the 238 U beam, because thecalculations needed a longer CPU time. A total CPU
time (CPU time summed over 1280 arithmetic cores)of 40–50 million seconds was used for one calculation.

Figure 1 shows the neutron dose distribution in the
BigRIPS room for the 238 U beam at 345 MeV/nucleon
impinging to a 5-millimeter-thick Be target. The BigRIPS separator was tuned for 79 Ni beam production.
In this setting, the 238 U beam was stopped at the
inner-side of the exit beam dump, which was locatedat the exit of the ﬁrst dipole magnet. High doses wereobserved at the target (F0) and the beam dump (BDin Fig. 1) regions where the 238 U beam decreased theirenergies. The neutron dose gradually decreased withthe distance from F2 in the F3-F7 region, whereas it
was slightly high around F5.
The calculated neutron doses were compared withexperimental measurements. Two neutron survey meter (TPS-451, manufactured by ALOKA Co., Ltd.)
were placed at the power supply and the control panelof the STQs and used for neutron measurements. The
observed doses were ∼1.8 μSv/h at the power supply and 0.8 μSv/h at the control panel with a 70particle nA (pnA) 238 U beam; normalized to a 100particle nA beam intensity, they were ∼2.5 μSv/hand ∼1.1 μSv/h, respectively. The calculated neutron
doses were ∼8 μSv/h and ∼2 μSv/h for a 100-particle
nA beam. Thus, the calculations reproduced the experimental observations by a factor 2–3. Based on thecalculations, the design of the shielding blocks is undergoing.
References
1) T. Ohnishi et al., RIKEN Accel. Prog. Rep. 44, 129(2011).
2) K. Tanaka et al., RIKEN Accel. Prog. Rep. 44, 132(2011).
3) K. Tanaka et al., Prog. Nucl. Sci. Technol. 4, 201 (2014).
4) T. Sato et al., J. Nucl. Sci. Technol. 55, 684 (2018).

Fig. 1. Neutron dose distribution in BigRIPS room for 238 U beam impinged on 5-mm-thick Be target. Red
circles represent positions of neutron survey meters that are used for neutron measurements.
∗1

RIKEN Nishina Center- 71 -

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II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Present status of beam transport line from SRC to BigRIPS
K. Kusaka,∗1 K. Yoshida,∗1 M. Ohtake,∗1 and Y. Yanagisawa∗1
A beam transport line delivering the primary beam
extracted from the SRC to the BigRIPS target has been
operated since 2007, and it is called the “T-course” beamline. The T-course beam line consists of 3 bending magnets and 17 quadrupoles.1) Two identical 50◦ bending
magnets DMT2 and DMT3 in the T-course are “2-Tesla”
room-temperature dipoles, with a maximum current of
650 A. They are designed as resistive-type magnets withsaddle-shaped correction coils in addition to main coils.
The correction coils are installed in the gap of the magnet, and were originally excited with the main coils inseries. Each main coil has 72 turns and consists of 6
double pancakes, in which a 13.5 × 13.5 mm hollow conductor is wound 6 times in each layer. In contrast, eachcorrection coil is a 12-turn double pancake in which a
14 × 10 mm rectangular hollow conductor is wound 6
times in each layer.1)
The layer isolation of the lower correction coil of the
DMT3 magnet was damaged in an October 2017 incident,2) and the upper correction coil was found to be
short-circuited in November 2019.3) Furthermore, thelower main coil of the DMT3 was damaged in a test
excitation performed in March 2020.4) When we energized only the main coils with a total current of 800 A
by adding an auxiliary power supply to the original one,
unstable behaviors were observed at the excitation voltages of the second and fourth pancakes of the lower maincoil.4) Although we considered that the upper main coil
was not critically damaged, we decided to replace themain coils with new ones.
We designed the new main coils for the DMT3 magnet
such that they are excited with the original DMT3 power
supply using neither correction coils nor additional auxiliary DC power supply in its circuit. We increased thenumber of turns of each main coil from 72 to 84. Furthermore, the shape of each main coil was designed to ﬁt in
the original DMT3 iron pole and yoke without any modiﬁcations. As shown in Fig. 1, the 12-layer new main coilin the upper-half has a pentagonal-shaped cross-section.
We choose the same 13.5 × 13.5 mm hollow conductor as
in the original DMT3 main coils. Each new coil consistsof three types of double pancake coils in which a hollow
conductor is wound 4, 6, and 8 times in each layer, respectively. Each new pentagonal-shaped coil is formedby combining one 4-turn, one 6-turn, and four 8-turnpancakes with epoxy resin. Because the lengths of cooling water channels are diﬀerent, we introduce valves andﬂow meters in each cooling channel at the cooling water header. The new coils were fabricated and tested by
HANMI TECHWIN in Korea under the supervision of
Toshiba and shipped to RIKEN in July 2021. The newcoils were successfully installed in the DMT3 magnet onsite, as shown in Fig. 2. Associated plumbing and wiring∗1

RIKEN Nishina Center

Fig. 1. Schematic of the upper-half cross section of DMT3
magnet with new main coil.

Fig. 2. Installation of new coil in DMT3 iron yokes.

Fig. 3. DMT3 magnet with new coils in T-course beam line.

works were ﬁnished in August 2021. After a series of test
excitations, the DMT3 magnet with the new main coils
was excited, and a 238 U beam was successfully transported from the SRC to the BigRIPS target in the beamtime from November to December 2021.
References
1) K. Kusaka et al., IEEE Trans. Appl. Supercond. 18, 318(2008), and references therein.
2) K. Kusaka et al., RIKEN Accel. Prog. Rep. 51, 173 (2018).
3) K. Kusaka et al., RIKEN Accel. Prog. Rep. 53, 104 (2019).
4) K. Kusaka et al., RIKEN Accel. Prog. Rep. 54, 104 (2020).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of novel semiconductor detector towards high-rate heavy
RI beam counting
T. Isobe,∗1 M. Togawa,∗2 M. Miyahara,∗2 J. Nishinaga,∗3 H. Okumura,∗4 M. Imura,∗5 and E. Takada∗6
The precise measurement of heavy ion track and energy loss is important for the identiﬁcation of projectile
fragments with a fragment separator such as BigRIPS at
RIBF. As the intensity of the primary beam increases,
a stronger radiation-resistant detector is required to realize a high-rate (≥1 MHz) RI beam experiment. A Si
detector has the characteristics of high-resolution energy
measurement, but it is weak in a high-radiation environment. In order to realize a radiation-resistant semiconductor detector, we have examined several types of novel
semiconductors that were developed for other purposes.
Table 1 lists the semiconductors we are testing. The
chalcopyrite compound Cu(In,Ga)Se2 (CIGS) is well investigated as it has potential for use as a semiconductorin thin-ﬁlm photovoltaic devices, such as solar cells.1)
CIGS can recover from radiation damage through the annealing of CIGS crystals. This characteristic is advantageous for a radiation detector since we often encountered
the damage to semiconductor detectors by high-rate ion
beams. GaN is one of the wide-bandgap semiconductorsthat are expected to be suitable for radiation detectors
with long-term stability due to a small intrinsic carrier
density and large threshold displacement energy.
We performed a detector test experiment at HIMAC
in Chiba, where a highly intense 400 MeV/nucleon Xebeam was irradiated on semiconductor samples: CIGS
and GaN. Figure 1 shows the sample of the CIGS detector, the thickness and eﬀective area of which are 2 μm
and 0.5 mm2 , respectively. This is thick enough to observe the signal with a 400 MeV/nucleon Xe ion, whichloses an energy of 3.5 MeV in the semiconductor. This

Fig. 1. CIGS samples (two pentagons shown at the center ofthe photograph) tested at HIMAC.

beam test was the ﬁrst time a heavy-ion signal was observed from those semiconductors.
In addition to checking the signal from CIGS and GaN,
we tested the hardness of each semiconductor against radiation damage by a Xe beam. Figure 2 shows the CIGS
pulse height as a function of the irradiated Xe beamyield. During the irradiation of a high-rate (106 pps) Xebeam on CIGS, the pulse height decreased down to 60%of the original pulse height. After annealing the CIGS
semiconductor (130◦ C, 5 h), we could observe the recovery of the pulse height to ∼85% of the original pulse
height.

Table 1. Speciﬁcations of modern semiconductor candidates
for radiation detection.
Normalized
Bandgap
Densitynumber of e-henergy3(g/cm )
pairs to Si
(eV)
Si
1.1
2.33
1
CIGS
1.2
5.7
2.93
SiC
3.2
3.21
0.64
GaN
3.4
6.15
1.07
Diamond
5.5
3.50
0.45
AlN
6.1
3.26
0.33
∗1
∗2
∗3
∗4
∗5
∗6

Fig. 2. CIGS negative pulse height as a function of irradiated
Xe beam yield. A 400 MeV/nucleon 106 pps Xe beam wasirradiated on a CIGS sample. After annealing the CIGS
sample, the recovery of the pulse height was observed asshown by the rightmost point.

RIKEN Nishina Center
Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK)
Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST)
Faculty of Pure and Applied Sciences, University of Tsukuba
Research Center for Functional Materials, National Institutefor Materials Science (NIMS)
Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology (QST)

We will continue to develop the next generation ofsemiconductor detectors by employing a novel type ofsemiconductor.
Reference
1) J. Nishinaga et al., Appl. Phys. Exp. 10, 092301 (2017).

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RIKEN Accel. Prog. Rep. 55 (2022)

A pilot experiment for collective ﬂow in heavy-ion collisions
S. Nishimura,∗1,∗2 T. Isobe,∗1 V. H. Phong,∗1 H. Tanabe,∗2 S. Yamamura,∗3 S. Esumi,∗2 Y. Hijikata,∗4
R. Mizuno,∗3 Y. Nakai,∗1 M. Niikura,∗1,∗3 and T. T. Yeung∗1,∗3
Asymmetric emissions of various particles in semicentral heavy-ion collisions are expected to be sensitive
probe for the equation of state (EOS) of high-density
nuclear matter.1) A pilot experiment was conductedby impinging 400 MeV/nucleon 132 Xe on a CsI target(500 mg/cm2 ) at beam intensities of 105 –106 particles/spill at the HIMAC SB2 beam line at NIRS. Our
primary goal is to conﬁrm asymmetric angular correlation of proton and neutrons at target rapidity withrespect to the reaction plane determined by charged
particles in forward rapidity.
A forward counter FC, 90 plastic scintillation detectors mounted in 3 rings centered along the beamaxis, was developed to determine the reaction planeof heavy-ion collisions on an event by event basis.
A cubic-shape plastic scintillator (25 × 25 × 25 cm3 )was coupled with a photomultiplier tube (Hamamatsu
R3478S; used for the CERN-NA44 experiment). Figure 1 shows the experimental setup, where left detectors correspond to the NiGIRI2) to measure theparticles at target rapidity region. The FC is installed at a distance of 43 cm, 46 cm, and 48 cm
downstream from a target for inner-, middle-, andouter-rings, respectively. The signals of NiGIRI, FC,and beam counters are recorded using fast digitizers(CAEN V1730B, V1740) together with the TDC module (CAEN V1190A), where newly developed RCDAQ

Fig. 2. Particle identiﬁcation in FC. A plastic scintillator
BC1 in the beam line is used for start timing of the
FC. Charged particles (p, d, t, and He) are selected forreaction plane determination.

was employed to recode the waveform of signals at trigger rate of up to 1 kHz with buﬀerling mode.3) A plastic scintillator BC1 is installed as a start counter in the
beam line.
Figure 2 shows a particle identiﬁcation spectrum obtained by the FC, where the horizontal and verticalaxes are the time-of-ﬂight and the energy loss ΔE,
respectively. The charged particles (p, d, t, He) in forward rapidity were identiﬁed from the background γrays. The collective ﬂow of protons and neutrons was
conﬁrmed successfully as a function of the transverse
momentum using the NiGIRI at target rapidity, where
the reaction plane was determined by the FC using a
sub-event sampling method.4)
In future, our experimental technique will be applied
using the higher energy Xe-beam and high intensity
radioactive beam at HIMAC and RIBF, respectively.
References
1) P. Danielewicz et al., Science 298, 1592 (2002).
2) H. Matsuzawa et al., RIKEN Accel. Prog. Rep. 48, 212(2015).
3) M. L. Purschke, 2012 18th IEEE-NPSS Real Time Conference (IEEE, 2012), DOI: 10.1109/RTC.2012.6418184.
4) H. Tanabe, Master thesis, Univ. of Tsukuba (2022).
5) S. Yamamura, Master thesis, Univ. of Tokyo (2022).

Fig. 1. Experimental setup for H447. Xe-beam is comingfrom left to right. CsI target is located at NiGIRI in
left. The FC is installed after the target.
∗1
∗2
∗3
∗4

RIKEN Nishina Center
Department of Physics, University of Tsukuba
Department of Physics, University of Tokyo
Department of Physics, Kyoto University- 74 -

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Silicon trackers for cluster knockout reactions in ONOKORO
K. Higuchi,∗1,∗2 J. Tanaka,∗1 T. Uesaka,∗1 R. Tusuji,∗3 J. Zenihiro,∗1,∗3 S. Kawase,∗4 S. Kurosawa,∗5
S. Takeshige,∗1,∗6 H. Baba,∗1 and Y. Hijikata∗1,∗3 for the ONOKORO Collaboration

Fig. 1. Silicon detectors mounted for the text experiment at
the HIMAC. A silicon wafer with vertical strips is placedin front of that with horizontal strips.
∗1
∗2
∗3
∗4
∗5
∗6

RIKEN Nishina Center
Department of Physics, Toho University
Department of Physics, Kyoto University
Department of Advanced Energy, Kyushu University
Institute for Materials Research, Tohoku University
Department of Physics, Rikkyo University- 75 -

count [ - ]In August 2021 at HIMAC, we evaluated the responses of the silicon detectors to proton and α beams.
Four silicon detectors, two each for measuring the positions in the X and Y directions with 100 μm strips,
were installed in the beamline. Figure 2 shows the energy loss spectra of the proton 100 MeV beam and theα particle 230 MeV/nucleon beam in one silicon layer,
respectively.
count [ - ]We developed silicon trackers for the cluster knockout
reactions toward the ONOKORO1,2) project at RIKEN,
Nishina Center. Particle tracking with a good position resolution is necessary to measure the angle of theemitted particles from the cluster knockout reactions.
The multi-channel signals from the silicon-strip detectors were pre-ampliﬁed and shaped (50 ns CR-RC circuit) using the ASIC integrated circuits APV25.3) Eachof these ASIC can treat 128 channels. The unit siliconwafers with 7.68 cm width (768 strips) require twelve
chips (see Fig. 1), which actually operate 1536 channels. The half (odd) channels were connected to thestrip electrodes of the silicon detector by wire bonding, and the other (even) half were used to measure
the sync common-mode noises and subtract them fromthe odd channels. Skipping channels with no signal reduces the number of readout channel. As it does not
generate a trigger signal by itself, the basic operation
involves synchronizing with external triggers. The output of the shaping circuit was held at the timing ofan external trigger and was converted into a serial signal using an analog multiplexer. The serial signal was
digitized using an ADC module (ADCM) and the data
was acquired by the DAQ based on the TRB3 (TDC
Readout Board V3) system.

600

400

400
200

200

0
0

200

400

(a)

600

Energy [ keV ]

0
0

200

400

(b)

600

Energy [ keV ]Fig. 2. Energy loss spectrum of (a) 100 MeV proton beam(b) 230 MeV/nucleon alpha-particle beam.

The distribution of small energy loss is known to bea Landau distribution. In (a) with proton beam, theﬁtting was performed using a Landau function convoluted by a Gaussian. It reproduced the pedestal widths(4.15 keV). In (b), the larger energy loss with the alphaparticle beam provides a rather symmetrical distribution. This result revealed that the responses of the silicon detectors, including the electric circuit, were undercontrol. Moreover, we also evaluated the detection eﬃciencies. The particles were guaranteed to pass throughthe detector by detecting them in the same events inthe front and back. In a low intensity (1 k cps) condition, 91.4% of the events had a single hit, and 8.10%
were double hits. In the double hits, 75.7% were adjacent strips. Events with more than triple hits were0.47%. Consequently, it was found that it is possible touniquely determine the hit position with 97.5% in eachsilicon layer. The high detection eﬃciency under smallenergy loss conditions encouraged us to develop the fullsilicon detector array in the future.
References
1) T. Uesaka et al., Grant-in-Aid for Specially Promoted
Research, Grant Number 21H04975.
2) T. Uesaka et al., RIBF Construction Proposal, “TOGAXSI: a new detector array for inverse-kinematics cluster and nucleon knock-out reaction experiments” (2021).
3) L. Jones, APV25-S1 User Guide V2.2 (2001).

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RIKEN Accel. Prog. Rep. 55 (2022)

Development of the GAGG(Ce) calorimeter for the cluster knockout
reaction measurement
R. Tsuji,∗1 J. Zenihiro,∗1 T. Uesaka,∗2 J. Tanaka,∗2 K. Higuchi,∗2,∗5 S. Kurosawa,∗3 H. Baba,∗2 S. Takeshige,∗4
and Y. Hijikata∗1,∗2
A new project named “ONOKORO” was recently
launched to investigate the cluster formation phenomena in nuclei and nuclear matter with cluster knockout reactions.1) In this project, we plan to performsystematic measurements for various stable and unstable nuclei at the following accelerator facilities: RIBF,
RIKEN, RCNP, Osaka University, and HIMAC at QST.
At RCNP, we will measure the knockout reactions fromﬁxed targets of stable nuclei with proton beams at 200–
400 MeV. The expeirmental technique is already established with double-arm high-resolution magnetic spectrometers. At RIBF and HIMAC, the knock-out reactions with inverse kinematics will be measured with stable and unstable heavy-ion beams on liquid or solid hydrogen targets. For this measurement, we have proposeda new detector telescope, named TOGAXSI,2) consisting of silicon strip detectors (SSD) and GAGG(Ce)calorimeters. In this paper, we report the results of theperformance test of the GAGG(Ce) calorimeters.
We chose the GAGG(Ce) scintillator to measure thekinetic energies of the recoil protons and knockout clusters (100–250 MeV/nucleon) because it has good scintillation properties compared to other standard scintillators such as NaI(Tl) and CsI(Tl). Figure 1 showsa photograph of the GAGG(Ce) crystal with a size of
40 × 40 × 120 mm3 . In the ONOKORO experiments,
high counting rates up to 100 kcps are expected; therefore, a good time response is required as well as a goodenergy resolution. To detect the scintillation photons,
we prepared several photo sensors of PMT (R7600U,
R11265U-20), APD (S8664-1010) and PD (S3584-08)
produced by Hamamatsu. The PMT has a fast time
response and a high gain, but low photo eﬃciency at∼500 nm compared to APD and PD. Because APD and

Fig. 1. The GAGG(Ce) crystal (40 × 40 × 120 mm3 ).
∗1
∗2
∗3
∗4
∗5

Fig. 2. Position dependence of the light outputs of the right(blue) and left (red) sensors located at X = ±60 mm.

PD have small gains, we newly designed a fast ampliﬁer
circuit with a high-speed operational ampliﬁer (Analog
Devices, AD8000).
To check the performance of the GAGG(Ce) calorimeter for high-energy charged particles, we performed
a test experiment using p and α beams at 75–
230 MeV/nucleon at HIMAC. We tested several detector conﬁgurations, but we brieﬂy report the results of
one setup: two photo sensors (PMT/APD/PD) were attached on both sides of the crystal, and p and α beams
at 75 and 100 MeV/nucleon were impinged on the longside. The energy resolutions are <1% and <0.6% for the
100 MeV/nucleon proton and α beams focused on thecenter of the crystal, respectively. We also used defocused beams to check the position dependence by tracking the beam trajectories with SSDs. Figure 2 shows
the correlation of the light outputs of the left and rightsensors versus the horizontal position of the beam (X).
On the far side from the sensor, attenuation eﬀects can
be clearly seen, but the signals are widely spread where
the beam is close to the sensor. This is because the solid
angle of the sensor drastically changes depending on thevertical (Y ) positions as well as X. We applied a correction of the X and Y position dependences, and ﬁnally, agood energy resolution of 0.3–0.6% for 100 MeV/nucleon
α beams was obtained in the wide range of the crystal.
The result is good enough to achieve a separation energy
resolution of ∼2 MeV in rms.
References

Department of Physics, Kyoto University
RIKEN Nishina Center
NICHe, Tohoku University
Department of Physics, Rikkyo University
Department of Physics, Toho University

1) T. Uesaka et al., Grant-in-Aid for Specially Promoted Research, Grant Number 21H04975.
2) T. Uesaka et al., RIBF Construction Proposal, NP2112SAMURAI72 (2021).

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RIKEN Accel. Prog. Rep. 55 (2022)

Development of a low-cost FPGA-Integrated TDC
H. Baba∗1
The time-to-digital converter (TDC) is an indispensable instrument to measure timing information in physics
experiments. In recent years, the TDC has been implemented in various methods using FPGAs and ASICs.1)
The tapped delay-line method is widely used to obtainan excellent timing resolution.2,3) However, this method
is disadvantageous in terms of cost because it consumes alarge number of logic gates. In contract, the multi-phaseclock method is suitable for many-channel systems witha moderate resolution.4)
In RIBF experiments, many-channel detectors are being developed to increase the rate tolerance of beam
detection. For example, SR-PPAC5) requires 152 TDC
channels per detector, which has the timing resolution of
250 ps (σ). We have began to develop a low-cost FPGAintegrated TDC based on the multi-phase clock method
for many-channel gaseous detectors such as PPACs anddrift chambers.
The prototype TDC board is shown in Fig. 1, and it
operates under the MPV system.6) We adopted Xilinx
XC7A35T-2FTG256I which is a cost-optimized FPGA,
to implement the TDC function. This board accepts
a low voltage diﬀerential signaling (LVDS) level only.
Thus, the production cost was signiﬁcantly suppressed.
The speciﬁcations of TDC are as follows: 64-ch hit input, 4-ch control I/O (1 ch for trigger), 125-ps LSB, 64us full scale range, multi-hit, leading and trailing edge
detection.
The TDC function consists of course timing (2-ns
steps) by using 500-MHz clock counter and ﬁne timing(125-ps LSB) using the dedicated circuit shown in Fig. 2.
Eight clocks with diﬀerent phases of 22.5 degrees each are
distributed to the entire FPGA through the clock linesthat has the almost equal length. Using an invert component, each clock can be shifted by 180 degrees. A totalof 16 multi-phase clocks are connected to the clock input

hit
010101

CE
D
Q

q0

CE
D
Q
◦

(180 )

0◦ clk0

q8

CE
D
Q

CE
D

q7

Q

q15

◦

(337.5 )157.5◦ clk7

Fig. 2. Circuit diagram for ﬁne timing.

ports of 16 ﬂip-ﬂops. To the D port (data), a signal that
toggles 0→1→0→1 is input in sync with each clock. The
inverted hit signals (hit) are connected to the CE ports(clock enable). If CE is “1,” output bits of q0–q15 arealways toggling. When a hit occurs, i.e. CE is “0,” thesetransitions are suspended. The bit pattern of q0–q15
determines the ﬁne timing. For example, if the patternis either “000000000000001111” or “111111111110000,”
the ﬁne timing is “4.”The multi-phase clocks are distributed to ﬂip-ﬂops
through the clock lines with a small skew. Because theadopted FPGA has only 12 clock lines, wiring from thehit to each CE input should be manually conﬁgured toensure that the propagation delay is as equal as possible. The variation of this delay determines the linearityof ﬁne timing that aﬀects the timing resolution. The differential non-linearity (DNL) and resolution for a typicalchannel was measured (Fig. 3). The timing resolution
was 78.9 ps in σ, which is suﬃcient for many-channel
gaseous detectors.
As shown in this report, we successfully conﬁrmed the
TDC functions. The implementation of the trigger processing is now in progress.

Fig. 3. Diﬀerential non-linearity and resolution.

References

Fig. 1. Photo of the FPGA integrated TDC board.
∗1

RIKEN Nishina Center

1) S. Tancock et al., IEEE Trans. Instrum. Meas. 68, 3406
(2019).
2) T. Yoshida, H. Baba, RIKEN Accel. Prog. Rep. 49, 200(2016).
3) T. N. Takahashi, RCNP Ann. Rep. 2017, (2017).
4) Y. Kataoka, Y. Hayato, 2018 IEEE NSS/MIC Conf. Proc.
2018, (2018)5) S. Hanai et al., CNS Ann. Rep. 2019, 317 (2021).
6) H. Baba et al., IEEE Trans. Nucl. Sci. 68, 1841 (2021).

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RIKEN Accel. Prog. Rep. 55 (2022)

Development of a high-bandwidth waveform processing system using
RFSoC
S. Takeshige,∗1,∗2 H. Baba,∗2 K. Kurita,∗1 Y. Togano,∗1 J. Zenihiro,∗3 and Y. Hijikata∗2,∗3
We are developing a real-time digital waveform processing unit using a GHz-band ﬂash-type analog-todigital converter (FADC) to establish a next-generation
data acquisition system at RIBF. Each particle needs tobe identiﬁed in experiments using radioactive ion (RI)
beams. Thus, detectors are installed along the beamline, and signals are acquired on an event-by-event basis. However, conventional CAMAC/VME ADC/TDC
modules become a measurement bottleneck because of
their slow processing rate with an increase in the amountof beams. For germanium detectors, real-time digital
waveform analysis is applied using 100-MHz FADCs instead of conventional ADC/TDC modules.1) However,the sampling rate of 100 MHz is insuﬃcient for signals with high-frequency components such as those fromplastic scintillators used as beam-line detectors. We
started to develop a new system named as CALDERA
using the Xilinx RFSoC ZCU111 evaluation kit2) thathas 8 channels of 4-GHz FADC since last year to apply
waveform processing to a beam-line detector.3)
First, we examined the performance of this device.
We measured the resolution of CALDERA, and we compared it with those of the conventional CAEN V792
QDC4) and V775 TDC.5) The energy resolution was
evaluated by measuring γ rays at 662 keV using a
LaBr3 (Ce) scintillator, and the timing resolution was
obtained from two NIM logic signals with a constanttime diﬀerence.
The results of the CALDERA measurements areshown in Fig. 1. The energy and timing resolutions of
CALDERA are 4.3% in FWHM and 15 ps in σ, respectively; those of QDC/TDC are 4.3% and σ = 27 ps,
respectively. CALDERA achieves the same or better
performance than that of the conventional QDC/TDC.
Next, this system was commissioned at the RIBF
experiment (NP1712-RIBF141R1).6) We acquired the
waveforms of the plastic scintillators installed at F5 andFig. 2. Particle identiﬁcation of 9 Li beam with CALDERA.

F7 in the 9 Li beam, and the charge and time information
were obtained through waveform analysis. The particle
identiﬁcation plot is shown in Fig. 2. CALDERA canbe used to acquire both charge and time information.
Further, we studied the algorithm to implement waveform processing in the FPGA. The timing information
is determined by the centroid of the waveform asG=Σxi yi.
Σyi(1)This equation can be written as a recurrence formula
qn = qn−1 + vn,
(2)
gn = gn−1 + qn
where vn , qn , and gn represent the value of the n-th
signal, denominator, and numerator, respectively.
The implementation of this waveform processing is
now in progress.
References

Fig. 1. Energy and timing resolutions with CALDERA. (a)137
Cs energy spectrum using LaBr3 (Ce) scintillator. (b)Time diﬀerence obtained from two NIM logic signals.
∗1
∗2
∗3

1) J. -P. Martin et al., IEEE Trans. Nucl. Sci. 55, 84 (2008).
2) Xilinx, Zynq UltraScale+ RFSoC ZCU111 Evaluation
Kit, https://japan.xilinx.com/products/boards-and-kits/
zcu111.html .
3) S. Takeshige et al., RIKEN Accel. Prog. Rep. 54, 103(2021).
4) CAEN, V792 - 32 Channel Multievent QDC, https://www.caen.it/products/v792/ .
5) CAEN, V775 - 32 Channel Multievent TDC, https://www.caen.it/products/v775/ .
6) A. Sakaue et al., in this report.

Rikkyo University
RIKEN Nishina Center
Kyoto University- 78 -

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Compensation for energy-spread growth in RUNBA
M. Wakasugi,∗1,∗2 Y. Abe,∗2 R. Ogawara,∗1,∗2 T. Ohnishi,∗2 H. Tongu,∗1 K. Tsukada,∗1 and Y. Yamaguchi∗2
A small heavy-ion storage ring, RUNBA,1) is underconstruction at E21. It will be used to develop a beam
recycling technique, which will be a novel tool for the nuclear reaction study of rare radioactive isotopes (RIs). A
few RIs, less than 10 in number, accumulate in RUNBA,
which is equipped with an internal target, and hit thetarget many times until a nuclear reaction occurs. Thisis the beam recycling technique, which is established bycompensating the energy loss U , energy straggling, andangular struggling given at a target. The energy loss
can be compensated for by a radio-frequency (RF) cavity. Specially designed devices are, however, required
to compensate for, turn by turn, the growth in energy
spread and emittance due to the straggling. We will install an energy dispersion corrector (EDC) in RUNBA tocompensate for energy-spread growth. Assuming a thinfoil internal target, we form a sinusoidal single-wave signal from the timing signal created when the beam passes
through the target. This correction signal is applied toan acceleration gap in EDC in synchronization with thebeam arrival. In this report, we analytically show therequired characteristics of EDC.
The invariant of the longitudinal particle motion in(δφ, δ) phase space is given as
2

Q(δφ, δ) =1 ηωrfqVrf ηωrf
δ2 +
2
2
β
Aβ 2 ET{cos(φs +δφ)−cos(φs )+δφ sin(φs )},(1)

where E is the energy of ions, δ = δE/E, φs a synchronous phase; A the mass number, q the charge, β thevelocity, T the revolution time, η the slipping factor, and
Vrf and ωrf are the amplitude and angular frequency ofRF, respectively. The RF phase is shifted by Δφt andΔφe due to the energy straggling Δt at the target andthe energy correction Δe given at EDC, respectively.
Assuming Δe is proportional to a time-of-ﬂight diﬀerence in the design value from the target to EDC, it isexpressed with a proportional coeﬃcient λe asΔe = Kte (λe ) δ + Δt + Kδ (λe )δt ,
(2)


2
+1 U
qλe
e ηte Tte
where Kte (λe ) = qλAβ
1 + γγ 2 −1
2E
E ; Kδ (λe ) = AE ;
ηte and Tte are the partial slipping factor and time ofﬁght between the target and EDC, respectively; and δtis the uncertainty in timing measurement. Since Δt andδt are stochastic variables, their probability density distributions are assumed to be Gaussian and denoted byψ(Δt ) and θ(δt ), with standard deviations of σt and στ ,respectively. The averaged time derivative of Q(δφ, δ)is calculated as dQ 

T = Q(δφ + Δφt + Δφe , δ + Δt + Δe )
dt
∗1
∗2

Fig. 1. (a) Time derivative of the invariant Q at λe = 40 V/ns
calculated using Eq. (3) and (b) Γ (λe ) calculated using
Eq. (4) for several cases of uncertainty στ .

− Q(δφ, δ) ψ(Δt )dΔt θ(δt )dδt .

(3)Since this is a function of the position in phase space(δφ, δ) and the coeﬃcient λe , we take its average withina separatrix as
 
dQ 
1
T dδφdδ.
(4)Γ (λe ) =S S dtΓ is a function of λe only. If Γ takes negative values,
the invariant Q(δφ, δ) decreases with time on average
and, consequently, the beam continues to circulate thering. Here we omit the explicit expression of Eqs. (3)and (4) because of the limited text space.
We assume in the following calculation that the beam
in RUNBA is a 10 MeV/nucleon 12 C6+ beam and thetarget is a thin 12 C foil with a thickness of 1018 /cm2 .
Figure 1(a) shows the time-derivative distribution in longitudinal phase space calculated using Eq. (3) at λe =40 V/ns. This has a quadric-like surface and is positivein the small δ region but negative in the large δ region.
The averaged time derivative calculated using Eq. (4) isshown in Fig. 1(b) for several cases of the uncertaintyστ . λe has two solutions for each case: one indicates theminimum required correction, and the other indicatesthe maximum limit to avoid the invariant growth due toovercorrection. Although the λe value can be chosen in
between the two solutions, the ﬂexibility is reduced as
uncertainty increases. Practically, the smallest possible
value is the most convenient because we can reduce thesignal power for EDC. The inset in Fig. 1(b) shows an
expanded view around the lower limit of λe . We foundthat this is insensitive to the uncertainty and the minimum required correction coeﬃcient is λe ∼40 V/ns.
Reference
1) M. Wakasugi et al., RIKEN Accel. Prog. Rep. 54, 87(2021).

Institute for Chemical Research, Kyoto University
RIKEN Nishina Center- 79 -

1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Compensation for emittance growth in RUNBA
M. Wakasugi,∗1,∗2 Y. Abe,∗2 R. Ogawara,∗1,∗2 T. Ohnishi,∗2 H. Tongu,∗1 K. Tsukada,∗1 and Y. Yamaguchi∗2
RUNBA (Recycled-Unstable-Nuclear Beam Accumulator) is a small heavy-ion storage ring equipped with aninternal target1) is under construction for developmentof a beam recycling technique, which is expected to serve
as a novel tool for nuclear reaction based studies of rareradioactive isotopes (RIs). Beam recycling is establishedby compensating for disturbances in beam motion at targets, which are an energy loss, an energy-spread growth
due to energy straggling and an emittance growth due toangular struggling. Since less than 10 RIs will be accumulated in RUNBA, timing and positioning signals canbe obtained when individual ions hit the target. The
signals are processed to appropriate wave forms and applied to specially designed devices, the energy dispersion corrector (EDC)2) and angular diﬀusion correctors(ADCh and ADCv). These devices correctly modulate
the beam motion in 6-dimensional phase space turn by
turn. In this report, we discuss the principle of ADC’sfor compensating the emittance growth, and show therequired characteristic for ADC’s.
The invariant of transverse particle motion in a storage ring is given by well-known Courant-Snyder invariant
W = γx2 + 2αxx + βx2 ,(1)where α, β, γ are twiss parameters at the target. The
angle x is irregularly modulated in one turn by Δxt due
to angular straggling at the target, a correction angleΔxh at ADC, and an adiabatic damping eﬀect Δxc at
the RF cavity. Assuming Δxh is proportional to theposition measured at the target, it is expressed asΔxh = κh (x + δx ),(2)

where κh is a proportional coeﬃcient and δx is an uncertainty in position measurement. When net change
in position in phase space including theses eﬀects is expressed as (Δx, Δx ), the time derivative of an invariantis
dW 1 
=W (x1 +Δx, x1 +Δx )−W (x0 , x0 ) ,(3)dt
Twhere T is the revolution time, and W (x1 , x1 ) =W (x0 , x0 ), as (x0 , x0 ) is transfered to (x1 , x1 ) in normal betatron motion in one turn. Since Δxt and δx are
stochastic variables and their probability density distributions are expressed as φ(Δxt ) and ψ(δx ), respectively,
the time derivative must be averaged as dW T =W (x1 + Δx, x1 + Δx )dt
(4)− W (x0 , x0 ) φ(Δxt )ψ(δx )dΔxt dδx .
∗1∗2

Institute for Chemical Research, Kyoto University
RIKEN Nishina Center- 80 -



Fig. 1. (a) Time derivative of the invariant dW
T at κh =dt
1 μrad/mm calculated by Eq. (4) and (b) Λ(κt ) calculated
by Eq. (5) for several cases of uncertainty δx .

Since this is a function of the position in transverse phasespace (x, x ) and the coeﬃcient κh , we consider the average of Eq. (4) in the transverse acceptance as1  dW 
T dxdx ,(5)Λ(κt ) =e e dtwhere e is the volume of acceptance, and Λ is a function of κh only. When Λ is negative with appropriate
κh setting, we can avoid growth in emittance, and consequently the beam continues to circulate in the ring.
We assume in the present calculation that the beam
in RUNBA is of 10 MeV/nucleon 12 C6+ , and the target is a thin 12 C foil of 1018 /cm2 thickness. ADCh(v)is placed for eﬀective correction at a position where thebetatron phase advance from the target is 1.25 (0.75).
Figure 1(a) shows the time-derivative distribution intransverse phase space calculated from Eq. (4) at κh =1 μrad/mm. This is a quadric-like surface and positivein a small region, but negative in large x region. The
averaged time derivative calculated by Eq. (5) is shownin Fig. 1(b) for several cases of uncertainty δx . There
are two zero-cross points for each case, and κh can be in
between these. The degree of freedom of κh decreases
as the uncertainty increases. A smaller value of κh isconvenient to reduce the load on ADCh(v). As seen in
inset of Fig. 1(b), the minimum required value of κh isapproximately independent of the uncertainty, and it isfound to be κh ∼ 3 μrad/mm. Since the largest beam
position in the acceptance is x ∼ 5 mm, the maximum
kick angle at ADCh(v) is ∼ 25 μrad. Assuming a stripline-type electrode with a gap of 0.1 m, length of 0.5 m,
and characteristic impedance of 50 Ω, the required transverse electric ﬁeld is ∼ 2 kV/m, and the supplied poweris ∼ 400 W.
References
1) M. Wakasugi et al., RIKEN Accel. Prog. Rep. 54, 87(2021).
2) M. Wakasugi et al., in this report.

1II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Simulation study to compensate for growth in energy spread andemittance in RUNBA
M. Wakasugi,∗1,∗2 Y. Abe,∗2 R. Ogawara,∗1,∗2 T. Ohnishi,∗2 H. Tongu,∗1 K. Tsukada,∗1 and Y. Yamaguchi∗2
A small heavy-ion storage ring called RUNBA,1)
equipped with an internal target, is under construction
at the E21 room. This project aims at the developmentof a beam recycling technique, which will be a novel toolfor nuclear reaction studies involving rare RI’s. A few
RIs, less than 10 in number, are accumulated in RUNBA,
which is equipped with an internal target, and they hit
the target many times until a nuclear reaction occurs.
For establishing this technique, we will install an energy
dispersion corrector (EDC) and angular diﬀusion correctors (ADCh and ADCv) to compensate for an energyspread growth and an emittance growth, respectively(see Fig. 1). Their required characteristics, which wereobtained analytically, are described in Refs. 2) and 3). In
this report, we show the results of a particle simulation
in RUNBA for supporting the analytical solutions.
When an ion passes through the target, its energy ismodulated by an energy straggling, Δt (= ΔEt /E), in
addition to an energy loss, U , and the angle (traveling
direction) is modulated by an angular straggling, Δxt .
The energy loss is recovered in a radio frequency (RF)cavity. The energy diﬀerence is correctly modulated byΔe at EDC, which is proportional to the diﬀerence inﬂight time from the design particle from the target and
EDC. It is expressed as qη T 
γ 2 + 1 U te te
δ + Δt1+ 2
Δe = λe
2
Aβ
γ −1E
qδt 
+
,
(1)
AE
where λe is a proportional coeﬃcient; A is the mass number; q is the charge numbers, E, γ, and β are the totalenergy (sum of mass and kinetic energy), Lorenz factor,
and velocity of the design particle, respectively; ηte is
the partial slipping factor between the target and EDC
deﬁned by the ring design; Tte is the ﬂight time of thedesign particle from the target to EDC; δ (= δE/E) is

Fig. 1. RUNBA structure (right) and the designed ADC and
EDC devices.
∗1∗2

Institute for Chemical Research, University
RIKEN Nishina Center

Fig. 2. Results of the present simulation. (a) Trends of thesurvival fraction and (b), (c) time evolution of the transverse invariant W and longitudinal invariant Q, respectively. The black and red curves show the simulation
results without and with appropriate correction at the
ADCs and EDC, respectively.

the energy diﬀerence from the design particle; and δt is
the expected uncertainty in the timing acquired at thetarget. Due to Δt and Δe , the RF phase is unusuallyshifted in one turn by Δφt and Δφe , respectively. On
the other hand, the angle of ion incidence is modulated
in one turn by an angular straggling, Δxt , at the target;
an angular correction, Δxh , at ADC; and an adiabatic
damping eﬀect, Δxc , at the RF cavity. Δxh is proportional to the position, x, measured at the target andexpressed asΔxh = κh (x + δx ),(2)

where δx is the uncertainty in the position measurement.
In this simulation, Δt , δt , Δxt , and δx are given as
random numbers with Gaussian statistical distributions.
Using the RUNBA lattice structure designed in Ref. 1)
and assuming that the beam is a 10 MeV/nucleon 12 C6+beam and the target is 12 C with a thickness of 1018 /cm2 ,we performed a particle tracking simulation taking all
the eﬀects described above into account. As shown in
Fig. 2(a), although the lifetime of the beam accumulation is less than 1 ms without corrections by the EDC
and ADCs, it can be extended to ∼1 s with the corrections. Appropriate corrections keep the invariants oftransverse motion, W ,3) and longitudinal motion, Q,2)
almost constant, as shown in Figs. 2(b) and 2(c). The
coeﬃcients λe and κh in this case are 240 V/ns and2.5 μrad/mm, respectively. They are consistent withthe solutions obtained analytically in Refs. 2) and 3).
On repeating this 1-s accumulation process for isotopes
with a production rate of 1 Hz, the collisional luminosity
reaches 1024 /(cm2 s).
References
1) M. Wakasugi et al., RIKEN Accel. Prog. Rep. 54, 87(2021).
2) M. Wakasugi et al., in this report.
3) M. Wakasugi et al., in this report.

- 81 -

1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Improvements in the working environment for target handling at ERIS
T. Ohnishi,∗1 Y. Abe,∗1 S. Ichikawa,∗1 and M. Wakasugi∗1,∗2
The electron-beam-driven radioactive isotope separator for SCRIT (ERIS)1) at the SCRIT electron scattering
facility2) is an online isotope-separator system used to
produce low-energy radioactive isotope (RI) beams using
the photoﬁssion of uranium. In this year, we transported
a 137 Cs beam to the SCRIT system installed inside theelectron storage ring3) and performed the RI trap. Under these circumstances, ERIS has become a full-scale
operation, around 4-month RI beam operation in a year.
Therefore, it is important to maintain the working environment of target handling. In this paper, we introduce
the working environment of the RI production target, as
one of the recent developments of ERIS.
Uranium carbide is used as a RI production target
using the ﬁssion reaction of uranium. It is more suitablefor RI production target than uranium oxide because its
vapor pressure and density are lower and higher thanthose of uranium oxide, respectively. Further, damages
to materials of the ion source can be reduced using asmall amount of oxygen.
The recent study shows that the porous structure with
the nano material is important for fast diﬀusion inside
the target and high-extraction eﬃciency of RI.4) However, this porous structure causes high susceptibility tooxidation. Figure 1 shows the oxidation reaction of uranium carbide in the air. The uranium carbide disks
shown in Fig. 1 are made with graphene. Oxidation
started 1 min after the removal from the vacuum container, and it ended after almost 10 min. The temperature of uranium carbide disks reaches around 800◦ C, as
shown in Fig. 1. After oxidation, these disks cannot holdtheir shape and turn into powder. The uranium oxide
powder is planned to be cemented solid after suﬃcientcooling.
A glove box was installed in the draft chamber at
the working area to handle uranium carbide targets
safely. Figure 2(a) shows the setup with the glove box.
Since this glove box has the capacity of vacuum gas replacement, the oxygen concentration becomes less than
0.001% vacuum gas replacement with nitrogen gas (lessFig. 2. (a) Photograph of the setup with the glove box inside the draft chamber. (b) Photograph of handling theuranium carbide disks inside the glove box.

than 2% per one replacement is performed three times).
In this situation, target handling can be performed without worrying about oxidation. One such example isshown in Fig. 2(b).
The present size of the glove box is smaller than thetarget chamber, and therefore, we need to work in the air
to install the target in the target chamber. A graphitetarget container with keyway, as shown in Fig. 3, is used
to reduce the installation time, and the target insertion
practice is performed beforehand. It took almost 5 sec toremove the graphite-target container with the uranium
target disks from the container ﬁlled with nitrogen gas,
insert it into the target holder inside the target chamber,and start the vacuum pump. This short time was suﬃcient, as evidenced by the small amount of gas released
during heating.
In the near future, the safety treatment of the production target will become an important issue because of
the high radiation (a few mSv/h), which is two orders ofmagnitude higher than the present value (∼10 μSv/h),and active operation. Therefore, we plan to introduce
a large glove box adapted to the target chamber andestablish a remote handling system.

Fig. 3. (a) Photograph of the graphite-target container withkeyway (left) and the target holder (right). (b) Photograph of keyway of the graphite-target container.

References
Fig. 1. Photograph of the oxidation reaction of uranium carbide disks in the graphite container. Diameter and thickness of a disk are 18 mm and 0.8 mm, respectively. The
amount of uranium in a disk is about 0.7 g.
∗1∗2

RIKEN Nishina Center
Institute for Chemical Research, Kyoto University

1) T. Ohnishi et al., Nucl. Instrum. Methods Phys. Res. B
317, 357 (2013).
2) M. Wakasugi et al., Nucl. Instrum. Methods Phys. Res. B
317, 668 (2013).
3) Y. Abe et al., in this report.
4) A. Gottberg, Nucl. Instrum. Methods Phys. Res. B 376,
8 (2016).

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II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Compact position-sensitive detector for in-ring diagnostics at the
Rare-RI Ring
S. Naimi,∗1 G. Hudson-Chang,∗1,∗2 D. Nagae,∗3 N. Kaname,∗4 A. Yano,∗4 T. Moriguchi,∗4 Y. Yamaguchi,∗1
S. Suzuki,∗4 A. Ozawa,∗4 Y. Abe,∗1,∗5 N. Sinozaki,∗6 and T. Yamaguchi∗6
We have developed a large area position-sensitive detector for the Rare-RI Ring.1,2) The position resolution
achieved was less than 2 mm. A higher resolusion closer
to that of the PPAC is needed for emittance matching
conﬁrmation at the injection of particles in the ring aswell as for particle tracking inside the ring. To improvefurther the resolution we designed a compact versionof the same detector. The horizontal size was kept thesame (an opening of 200 mm), however the vertical size
was reduced by 30%. We simulated the eﬀect on the
resolution of this size reduction for diﬀerent acceleration potential applied to the secondary electrons (SEs)emitted from the foil (see Refs. 1) and 2) for the detector’s principle). According to the simulation performed
with SIMION,3) the resolution of the detector should
improve by about 25% in both horizontal and verticaldirection, see Fig. 1. This is due to the reduction of
the time-of-ﬂight of SEs inside the detector. We built
and tested the compact detector as shown in Fig. 2.
The test experiment was conducted at HIMAC with a
200 MeV/nucleon 84 Kr beam. The experimental setup
is the same as previous experiment.1) A mask of 4 mm
thick copper with rectangular openings of 12 × 17 mm
separated with 3 mm in between was placed in front ofFig. 1. Simulation results of position resolution for diﬀerent
SEs acceleration voltages in the original detector (blue)and compact detector (orange). Mid, Top, Bot correspond to diﬀerent position in the detector, middle, top
and bottom, respectively.
∗1
∗2
∗3
∗4
∗5
∗6

RIKEN Nishina Center
Department of Physics, University of Surrey
Faculty of Sciences, Kyushu University
Department of Physics, University of Tsukuba
National Institute of Radiological Sciences (NIRS), National
Institutes for Quantum Science and Technology
Department of Physics, Saitama University- 83 -

     

Compact detector
6060

ID
ENTRIES
0.00
0.00
0.00

40

40

Original detector
6060

123
73490
0.00
0.00
0.00

0.00
0.735E+05
0.00

40

20

20

2020

00

00

-20
-20

-20-20-40-40-40-40

-60
-60
-60
-60

-40

-40

-20

0

20

40

60

-20
40 ID = 12360
020 Histogram
MCP XY(mm) tsM12L

MCP XY [mm]ID
ENTRIES
0.00
0.00
0.00

40

-60
-60
-60
-60

-40

-40

-20

0

127
71480
0.00
0.00
0.00

1.00
0.715E+05
0.00

20

-20
0
20
MCP XY(mm) tsM12L

40

40

60

60

Histogram ID = 127

MCP XY [mm]Fig. 2. (top) Picture of the compact and original size detectors with the size of the compact detector drawn inyellow on the original detector for reference. (bottom)
Beam image modiﬁed with a copper mask placed in frontof the detectors.

the detector. The beam image captured by both detectors under the same conditions is shown in the bottomof Fig. 2. As it can be seen, the resolution of the compact detector is improved and the rectangular openingsof the mask are more distinct compared to the original
detector. Detailed analysis of the resolution showed
an improvement of 24% in the horizontal direction and
20% in the vertical direction. The compact detector
was placed inside the Rare-RI Ring during the last experiment.4) The trajectory of the beam was conﬁrmed.
However, due to large noise further diagnostics was notpossible. The source of the noise, as well as possible
future improvements are under investigation. Further
improvements of the detector design are under consideration to limit the outgassing, which will improve thevacuum in the detector chamber and lead to less discharge.
References
1) R. Crane, S. Naimi, RIKEN Accel. Prog. Rep. 53, 117(2020).
2) G. Hudson-Chang et al., RIKEN Accel. Prog. Rep. 54,
101 (2021).
3) SIMION, https://simion.com/ .
4) S. Naimi et al., in this report.

1II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Extraction test of photo ionized Bi in PALIS gas cellT. Sonoda,∗1 V. Sonnenschein,∗2 H. Tomita,∗2 K. Hattori,∗2 D. Hou,∗3 S. Iimura,∗3 H. Ishiyama,∗1 I. Katayama,∗1
T. M. Kojima,∗1 S. Nishimura,∗1 M. Rosenbusch,∗3 A. Takamine,∗1 M. Wada,∗3 Y. X. Watanabe,∗3 and W. Xian∗3
for the BigRIPS Collaboration
We are developing a scheme for parasitic low-energy
radioactive isotope(RI) beam production (PALIS)1) inthe second focal chamber (F2) of the BigRIPS.
Our previous experiment,2) conﬁrmed the extractionof Bi isotopes after exiting the PALIS gas cell. As thenext stage, we are aiming for laser photo ionizationof Bi, which results in highly pure RI beam production. Figure 1 shows the present PALIS experimental
setup. Bi atoms are irradiated by two colors of laser
beam for multi-step resonance ionization. Photo ionized Bi species are emitted as a gas jet into diﬀerential
pumping area, where the ions are conﬁned by rf electricﬁelds and move along an axial direction to the rf-carpet.
The rf-carpet makes superimposed electric ﬁelds: one is
dc-guidance sloping to the small exit hole whereas, theother is rf-barrier that prevents the ions from hitting the
rf-carpet. For the fast evacuation, we utilized a large exit
aperture for the gas cell (3.0 mm) compared to that fora conventional gas cell. Owing to the small exit apertureof the rf-carpet (0.4 mm), eﬃcient diﬀerential pumping
can be realized, even though several small vacuum dry
pumps are arranged in the diﬀerential pumping area.
The extracted ions from the rf-carpet are detected byan ion counter in oﬀ-line experiments. In on-line beam
experiment, the ion counter is replaced by a silicon detector to observe the alpha rays created by the decay ofalpha-emitting Bi isotopes.
First, we examined the system performance by oﬀ-line
experiments. Stable Bi atoms were produced in the gas
cell via evaporation. The applied laser ionization schemeof Bi is shown in Fig. 2(1). For identiﬁcation of Bi ionization, the ﬁrst-step laser wavelength was scanned as afunction of the ion intensity shown in Fig. 2(2). We also
conﬁrmed reasonable performance of the rf-carpet byscanning its rf-voltage, and the plot is shown in Fig. 2(3).
In November 2021, a 12-h on-line beam experiment
was conducted for the extraction test of 191 Bi. The setting B ρ at the BigRIPS provided the speciﬁc isotope
region including 191 Bi in the order of 105 cps. We moni-Ion count(cps)
Ion count(cps)’bi.dat’

(1).

(2).

SextuPole Ion Guide

Gas cellQuadruPole Ion Guide(3).

RF-Carpet RF(Vpp)
1st-step laser wavelength(nm)Fig. 2. (1): Bi-ionization scheme and number of ions per
second versus (2): ﬁrst-step wavelength, (3): rf voltage
at the rf-carpet measured in oﬀ-line experiment.

tored the alpha rays after implantation of a catcher platein front of the silicon detector, during the beam wasstopped for avoiding background noise. Figure 3 shows
the accumulated signals at the silicon detector. We considered that a few signals caused by alpha rays were observed in the expected area, >180 (MCA-ch) area. As
the extraction eﬃciency was not achieved for expectedvalue, some improvements are in progress.
alpha spectrum (counts)

60-s Beam ON 60-s Beam OFF x 5

1000

Signal of-decay100

10Expected signal area by -decay

1

0.1

Laser

83Bi

0

100

200

300

400

500

600

MCA CHIon counting/
Alpha counting

Fig. 3. Observed signals at silicon detector in online experiment.
exit

differential pumping

rf-carpet(exit 0.4 mm)

photo ionized Bi

References

Bi atom

1) T. Sonoda et al., Prog. Theor. Exp. Phys. 113, D02(2019).
2) T. Sonoda et al., RIKEN Accel. Prog. Rep. 54, 91 (2020).

Fig. 1. Present experimental setup.
∗1
∗2
∗3

RIKEN Nishina Center
Faculty of Engineering, Nagoya University
Wako Nuclear Science Center, IPNS, KEK- 84 -

1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of a timing detector for decay spectroscopy inconjunction with MRTOF-MS
M. Mukai,∗1 Y. Hirayama,∗2 Y. X. Watanabe,∗2 P. Schury,∗2 S. C. Jeong,∗2 H. Miyatake,∗2 T. Niwase,∗2
M. Oyaizu,∗2 M. Rosenbusch,∗2 H. Ueno,∗1 and M. Wada∗2
The KEK Isotope Separation System (KISS)1) has
been used to perform the β-γ decay and laser spectroscopy of heavy neutron-rich nuclei of refractory elements. In most scenarios, we had isobar and isomer(or ground state) contaminants owing to the limited
mass resolution of a dipole magnet (A/ΔA ∼ 900).
The isobar contaminants are the survival ions extracted
from an argon gas cell, and isomer (or ground state)contaminants originate from the element-selective laser
ionization at the exit of the Ar gas cell. The isobar
and isomer contaminants often complicate2) analyzing
γ-ray energy spectra and decay half-lives. Therefore,
for the spectroscopy of a single nuclide identiﬁed precisely using a multi-reﬂection time-of-ﬂight mass spectrograph (MRTOF-MS), we will install a β-γ time-ofﬂight (TOF) detector that provides a stop signal of
the MRTOF-MS for a time-correlated measurement between the MRTOF-MS and β-γ detectors.
The current β-γ detector station consists of an aluminized Mylar tape transport system placed at the center of the detector station, a proportional gas counter,3)and germanium detectors. To perform the decay spectroscopy in conjunction with the MRTOF-MS, thedecay station must be installed downstream of the
MRTOF-MS, and the β-γ TOF detector must be installed at the front of the gas counter. The start timingof the TOF measurement is the timing of the ions injected into the MRTOF. The secondary electrons (SEs)emitted from the aluminized Mylar tape in the injection of mass-separated ions are detected by an annulartype MCP detector to supply the stop timing of the
MRTOF-MS. We call the MCP detector the β-γ TOF
detector. We report the simulation results of the SEs
detection using the β-γ TOF detector.
Figure 1 shows the cross-sectional view of the setup
for the detection of SEs. The setup consists of a solenoid
coil with a length of approximately 54 mm, an electrodefor the SEs transport to the MCP, and a metal platewith a thin pipe shielding the electric ﬁelds of the MCP
for the ion transport. The mass-separated ions from
the MRTOF-MS are accelerated up to 20 keV/q using
a pulse drift tube and impinged on the tape, as shownat the bottom of Fig. 1. The SEs emitted from thesurface of the tape (GND) are accelerated toward thesolenoid coil by a potential of +370 V and transported
upstream with a suﬃciently small orbital radius by amagnetic ﬁeld inside the solenoid coil and by the upstream electrode (+600 V). Subsequently, the SEs hit
the front surface of the MCP, and the TOF stop signal∗1∗2

RIKEN Nishina Center
Wako Nuclear Science Center (WNSC), IPNS, KEK- 85 -

Fig. 1. Simulated trajectory (black line) of SEs emitted
from the surface of an aluminized Mylar tape.

is obtained.
The SEs trajectories simulated using SIMION4) areindicated by black lines in Fig. 1. In the simulation,
SEs were generated at the tape position with the Gaussian distribution of 1 mm in standard deviation, andthe initial emission angle was assumed to be uniformin 2π. The initial kinetic energy was assumed to be anorder of 1 eV, which is the typical order of the energy
for SEs. The simulated transport eﬃciency of a single
electron from the tape position to the MCP surface was
77% and the time resolution was approximately 0.5 ns
in FWHM. We expect the number of SEs of ∼2.8 on
average, which was the measured value in a previous
study via a bombardment of W+ ions (15 keV) on an
Al2 O3 target.5) Therefore, we can expect a detection
eﬃciency of as high as 90%. The simulated time resolution of the electron transportation, ∼0.5 ns, is sufﬁciently small considering the typical TOF of approximately 15 ms and the contribution to the mass resolving
power is smaller than 3%.
The oﬄine study is ongoing. The setup will be installed early next ﬁscal year.
References
1) Y. Hirayama et al., Nucl. Instrum. Methods Phys. Res.
B 412, 11 (2017).
2) Y. Hirayama et al., Phys. Rev. C 98, 014321 (2018).
3) Y. Hirayama et al., Nucl. Instrum. Methods Phys. Res.
A 997, 165152 (2021).
4) SIMION 8.1, http://www.simion.com .
5) G. Staudenmaier et al., Int. J. Mass Spectrom. Ion Phys.
11, 103 (1976).

1

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

New developments and progress of the ZD-MRTOF system in 2021
M. Rosenbusch,∗1 M. Wada,∗1 A. Takamine,∗2 W. Xian,∗3 D. Hou,∗4 S. Chen,∗3 S. Iimura,∗2,∗5 P. Schury,∗1
T. Niwase,∗6,∗1,∗2 N. Fukuda,∗2 Y. Hirayama,∗1 H. Ishiyama,∗2 Y. Ito,∗7 S. Jeong,∗1 S. Kimura,∗2 T. Kojima,∗2
J. Liu,∗4 S. Michimasa,∗8 H. Miyatake,∗1 M. Mukai,∗2 S. Nishimura,∗2 Y. Shimizu,∗2 T. Sonoda,∗2 H. Suzuki,∗2
H. Takeda,∗2 Y. X. Watanabe,∗1 H. Wollnik,∗9 S. Yan,∗10 T. T. Yeung,∗11 and K. Yoshida∗2
After the successful online commissioning in 2020,1–3)
in the year 2021 the ZD-MRTOF system4) was subject to
new upgrades, further optimization, and new on-line experiments. One of the new major modiﬁcations is a novel
in-MRTOF deﬂector in the center region of the MRTOFMS (see Fig. 1, and also Ref. 5)) and references therein),which allows for the dedicated ejection of contaminantions at low electric ﬁelds of only about 40 V, so that themass accuracy for the wanted ions is not aﬀected in ameasurement. The principle is that the ion deﬂector isalways at 0 V if any ion of interest is crossing the deﬂection region, so that it can pass the region until a distanceis reached beyond the electrically well-shielded area. By
a newly developed timing system at the Wako Nuclear
Science Center, an electric pulse pattern is programmed
and applied to enable the selection of not only one preferred ion mass number, but several ion mass numbers
can be selected and survive the separation process at thesame time.
With the help of the new deﬂector system, molecular
contaminations coming from the He ﬁlled gas cell6) could
be eliminated in online experiments and clean spectra
have been observed.

Fig. 1. Photo of the new in-MRTOF deﬂector at the timeof assembly. At the center electrode (held by the whiteceramics) the pulsed electric ﬁeld is applied to deﬂect unwanted ions. Distances and sizes of the plated are chosen
for optimal shielding of the deﬂection region.
∗1

Wako Nuclear Science Center (WNSC), IPNS, KEK
RIKEN Nishina Center∗3 Department of Physics, University of Hong Kong
∗4 Institute of Modern Physics, Chinese Academy of Sciences∗5 Department of Physics, Osaka University∗6 Department of Physics, Kyushu University∗7 Advanced Science Research Center, Japan Atomic Energy
Agency∗8 Center for Nuclear Study, University of Tokyo∗9 Department of Chemistry and Biochemistry, New Mexico
State University∗10 Institute of Mass Spectrometer and Atmospheric Environment, Jinan University∗11 Department of Physics, University of Tokyo∗2

Fig. 2. New ion time-of-ﬂight spectra of the A = 74 isobars
Ga, Zn, Cu, and Ni in the left part, and A = 75 isobars
Zn, Cu, and Ni produced from on-line beam centered on
79
Ni and also from in-trap decay.

In November and December 2021 the ﬁrst part of thededicated experiments for the ZD-MRTOF system havebeen performed using SRC and BigRIPS+ZeroDegree(NP2012-RIBF 199/202), where due to a high-quality
beam from BigRIPS and the recent abilities of the ZDMRTOF system, new spectra on Ni isotopes could berecorded (see Fig. 2). The preliminary results are underanalysis and the experiment will continue after resolving
the recent incident at the accelerator facility.
In oﬀ-line studies, new eﬀorts for the mirror tuningof the MRTOF-MS have been spent by developing procedures for careful tuning. Together with an advanced
algorithm for software drift correction, resolving powers
of up to Rm = 106 have been reached enabling the identiﬁcation of low-lying nuclear isomers in many isotopes(down to about 40 keV excitation energy for A ≈ 40 and
190 keV for A ≈ 200). An initial accuracy test using stable molecules ionized in the gas cell at ten diﬀerent mass
numbers could be performed using data from the online
commissioning in 2020 and yielded an relative mean deviation of δm/m = 2.80(99) · 10−8 from the well known
values of the Atomic Mass Evaluation (AME) 2016.4) A
further important development, providing proof of theradioactivity for rare events, is a combined detector for
the ion’s time-of-ﬂight and their beta decay at the sametime called β-ToF detector.7)
References
1) S. Iimura et al., in this report.
2) W. Xian et al., in this report.
3) D. Hou et al., in this report.
4) M. Rosenbusch et al., arXiv:2110.11507, submitted toNucl. Instrum. Methods Phys. Res. A (2021).
5) P. Fischer et al., Rev. Sci. Instrum. 89, 105114 (2018).
6) A. Takamine et al., RIKEN Accel. Prog. Rep. 53, 108(2018).
7) T. Niwase et al., in this report.

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II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Fifth report on oﬄine tests for RF carpet transportation in RF ion
guide gas cell at the SLOWRI facility
A. Takamine,∗1 S. Iimura,∗1,∗2,∗3 D. Hou,∗3,∗4,∗5 M. Wada,∗3 M. Rosenbusch,∗3 W. Xian,∗3,∗6 P. Schury,∗3
Y. Ito,∗1,∗8 T. M. Kojima,∗1 T. Sonoda,∗1 Y. X. Watanabe,∗3 H. Ueno,∗1 and H. Ishiyama∗1

∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8

RIKEN Nishina Center
Department of Physics, Osaka University
Wako Nuclear Science Center (WNSC), IPNS, KEK
Institute of Modern Physics, Chinese Academy of Sciences
School of Nuclear Science and Technology, Lanzhou University
Department of Physics, University of Hong Kong
Institute of Mass Spectrometry and Atmospheric Environment, Jinan University
Advanced Science Research Center, Japan Atomic Energy
Agency30

36

Ar count rates @MRTOF

(a)

(b)

10 kHz
20 kHz
30 kHz
50 kHz70 kHz90 kHz

25
20
15
10
5
0

0

4
8
12
16
AF voltages applied on the 2nd RFC [Vpp]Kr count rates @MRTOF

140

86

We are developing an RF ion guide gas cell at the
SLOWRI facility. The present gas cell has a gutter structure1) where the ions travel over a long distance on the
2nd RFC after they are ﬁrst collected to the 1st RFC,
travel over a short distance on the 1st RFC, and arepulled to the 2nd RFC (see Fig. 1 in Ref. 2)). We adopted
the “ion surﬁng” method on the 2nd RFC by superimposing weak audio-frequency (AF) signals to form an ion
traveling potential wave.3) We have so far reported ofﬂine tests with ions from surface-ionization ion sourcesin an “ion current” mode where the electrodes of the RF
carpets and an ion beam guide were used as a Faradaycup.1,2,4,5) However the performance could be diﬀerent
from an online experiment because 1) ion currents contain many molecules and 2) ion currents of more than anorder of pA could cause a space charge or a charging-up
eﬀects.
We conducted oﬄine tests for 36 Ar+ and 86 Kr+ ionsproduced in the helium gas cell. We cannot evaluate
the absolute transport eﬃciency in these measurements
because the Ar and Kr contaminant rates in a heliumgas are unknown. However, we can solely measure thecount rates of 36 Ar+ or 86 Kr+ with the elimination of
isobar impurities owing to the high resolving power ofthe MRTOF-MS, and we can investigate the transport
performance in a similar condition as an online experiment.
We placed an 241 Am α-source behind the 6-μm-thick
Mylar gas cell window at the downstream side. The emitted alpha particles enter the gas cell through the windowand lose their energies in the helium gas to ionize the Ar
and Kr atoms that are contained. Figure 1 shows the
2nd RFC AF voltage dependence of the transport performance in 200 mbar, in a room-temperature equivalentvalue, of 70 K helium gas. The RF voltage applied to
the 2nd RFC was 103 Vpp at 11.8 MHz, and the pushDC ﬁeld onto the 2nd RFCs was 18 V/cm.
The present results for 36 Ar+ and 86 Kr+ clearly show
diﬀerent AF voltage dependence. This investigation has
been coducted in clear conditions for the ﬁrst time, i.e.,
only focused on a separated mass instead of an ion current of mixed molecules as shown in the previous re-

120
100
80
10 kHz
20 kHz
30 kHz
50 kHz70 kHz90 kHz

60
40
20
0

0

4
8
12
16
AF voltages applied on the 2nd RFC [Vpp]Fig. 1. Ion transportation count rates as a function of AF
voltages at diﬀerent AF frequencies for (a) 36 Ar+ and (b)86
Kr+ in oﬄine tests.

port.2) Contrary to the case when using a Cs ion source, aclearly diﬀerent trend for light masses and heavier masses
is now visible, showing a limited region of eﬀective AF
amplitudes for light masses of A ≈ 40. For the A ≈ 80
region, a stable transport is achieved for all tested amplitudes above 3 V. In both cases, the choice of the AF
frequency seems to play a minor role for the transport
eﬃciency, but has an impact on the transport time,3)
which becomes important for short-lived isotopes. We
plan to measure the transport time systematically in thegas cell for diﬀerent AF conditions, producing a pulsed
ion by placing a mechanical shutter in front of the αsource. We also plan to modify the 1st RFC conﬁguration to achieve a faster ion collection. The transport
time measurement results will be compared.
References
1) A. Takamine et al., RIKEN Accel. Prog. Rep. 52, 139(2019).
2) A. Takamine et al., RIKEN Accel. Prog. Rep. 54, 93(2021).
3) G. Bollen, Int. J. Mass Spectrom. 299, 131 (2011).
4) S. Iimura et al., RIKEN Accel. Prog. Rep. 53, 107 (2020).
5) A. Takamine et al., RIKEN Accel. Prog. Rep. 53, 108(2020).

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1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of β-TOF detector for decay-correlated massmeasurement of β-decaying nuclides
T. Niwase,∗1 W. Xian,∗2,∗1 M. Wada,∗1 M. Rosenbusch,∗1 S. D. Chen,∗2,∗1 A. Takamine,∗3 J. Liu,∗2,∗1
S. Iimura,∗4,∗3,∗1 D. S. Hou,∗5,∗6 S. X. Yan,∗7 H. Ishiyama,∗3 S. Nishimura,∗3 Y. Hirayama,∗1 S. Kimura,∗3
D. Kaji,∗3 H. Miyatake,∗1 K. Morimoto,∗3 P. Schury,∗1 Y. X. Watanabe,∗1 and H. Wollnik∗8                  

 

Fig. 1. TOF spectrum of 81 Ga2+ . The TOF singles spectra
are drawn in black, while β-decay correlated events areshaded in red.

 !
   

"!

A novel “α-TOF” detector,1) has been recently developed and installed on a multi-reﬂection time-of-ﬂight
mass spectrograph (MRTOF-MS). This detector canmeasure ion implantation to deduce the time-of-ﬂight(TOF), along with subsequent α-decay and spontaneousﬁssion (SF) events from the implanted ions. We recently
succeeded in the direct mass measurement of superheavy
nuclides, 257, 258 Db,2,3) wherein the count rate of 257 Db
was as low as two events per day.2) Furthermore, we haveinitiated a new ﬁeld of nuclear spectroscopy using decaycorrelated mass measurements.4) The potential of thistechnique was initially demonstrated using decay properties to discriminate between the two states of 207 Ra,
followed by mass analyses of each state; the two states
could not be independently resolved by the MRTOF.
While the α-TOF detector is limited to α-decay andSF nuclides, it would be valuable to expand its performance to encompass β-decays. Here, we report the development of a new “β-TOF” detector, an extension of
the α-TOF detector, that enables the decay-correlated
mass spectroscopy of α/β/SF decaying nuclides.
The β-TOF detector uses double-layered SSDs with athickness of 500 μm (Hamamatsu S-14605) to provide a
ΔE -ΔE telescope for β-decay. In the ﬁrst layer of theSSD, α-decay and SF are detected in the same manneras those in α-TOF. The basic characteristics—time resolution, α-particle energy resolution, implantation, andα-decay detection eﬃciency—of the β-TOF detector are
the same as those of α-TOF. Owing to the solid angle
coverage of the two SSDs, the telescope is geometricallylimited to a detection eﬃciency of 33% for β-rays.
Online commissioning for the β-TOF detector was
performed via MRTOF,5) located at the end of the ZeroDegree spectrometer beamline.6) The so-called ZDMRTOF was coupled to a cryogenic helium gas cell that
thermalized the relativistic beam delivered by BigRIPS.
In the ﬁrst online test of this new detector, we succeeded
in measuring the correlation between the TOF of theneutron-rich 81 Ga isotope and subsequent β-decay. Figure 1 shows the histogram of TOF singles and decaycorrelated TOF events. Accordingly, the detection ef-







#! Fig. 2. Measured decay time distribution of 81 Ga. The redsolid line and green dashed curve indicate the distribution
curve drawn with the experimental and literature (T1/2= 1.22 s) values, respectively.

ﬁciency for β-rays was found to be 27(7)%, which ingood agreement with the geometric estimation. The
half-life of 81 Ga was successfully extracted from the time
between individual implantations and subsequent decay
events. Figure 2 shows the decay time distribution withthe expected decay curve. The half-life of 81 Ga was determined to be 1.44(31) s, which is in agreement withthe value in literature, i.e., 1.217(5) s.7)
References

∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8

Wako Nuclear Science Center (WNSC), IPNS, KEK
Department of Physics, University of Hong Kong
RIKEN Nishina Center
Department of Physics, Osaka University
Institute of Modern Physics, Chinese Academy of Sciences
School of Nuclear Science and Technology, Lanzhou University
Institute of Mass Spectrometer and Atmospheric Environment, Jinan University
Department of Chemistry and Biochemistry, New Mexico
State University- 88 -

1) T. Niwase et al., Nucl. Instrum. Methods Phys. Res. A,
953, 163198 (2020).
2) P. Schury et al., Phys. Rev. C 104, L021304 (2021).
3) P. Schury et al., in this report.
4) T. Niwase et al., Phys. Rev. C 104, 044617 (2021).
5) M. Rosenbusch et al., arXiv:2110.11507.
6) T. Kubo et al., Prog. Theo. Exp. Phys. 2012, 03C003(2012).
7) C. M. Baglin, Nucl. Data Sheets 109, 2257 (2008).

1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Ion extraction from linear Paul trap via axially swinging ﬁeld
K. Imamura,∗1 A. Takamine,∗1 S. Go,∗1 M. Tajima,∗1 A. Gladkov,∗1 and H. Ueno∗1
Spin-polarized radioactive isotope (RI) beams havebeen used for the measurements of nuclear electromagnetic moments and spins to investigate nuclear structure. In many experiments, the polarization of nuclear
spin is generated via projectile fragmentation reaction.1)
The reaction mechanism has been well studied so far.
However, the achievable spin polarization is typically as
low as several percentage points. Laser optical pumping can realize spin polarization of more than a few tensof percentage points but the method is element-limited.
A highly eﬃcient and universal method for producing
spin-polarized RI beams is desired. For this purpose, weare developing a spin-polarized beam production apparatus using the atomic beam magnetic resonance (ABMR)
method. In this method, the spin polarization of neutral
atomic beams is generated by two-step spin selection using multi-pole magnets and one magnetic resonance.2)
The ABMR method itself has high spin selectivity. However, the eﬃcient production of a neutral RI atomic beamusing thermal energy is a signiﬁcant technical challenge.
We propose a new ion neutralization system based on amulti-segmented linear Paul trap.
In the proposed neutralization system, RI ions are simultaneously trapped with laser-cooled ions. The kinetic
energy of trapped RI ions will decrease due to mutual
Coulomb interaction between RI ions and laser cooledions. After the cooling of RI ions, RI ions are neutralizedusing a neutralization gas. In a general linear Paul trap,an RF electric ﬁeld is only used to conﬁne the radial
motion of trapped ions. However, neutralized ions arescattered around in the above situation because the axial component of the trapped ion motion is much smaller
than the radial component of the motion. In order to extract neutral RIs from a linear Paul trap eﬃciently, weapply an additional alternating electric ﬁeld in the axial
direction (swinging ﬁeld) to induce axial ion motion. We
constructed a ﬁve-segmented linear Paul trap to demonstrate ion extraction using an axially swinging ﬁeld. The
setup of the experiment is shown in Fig. 1(a). Rubidium
ions emitted from a surface ionization ion source wereguided to the trap operated at a frequency of 1.18 MHz
and 532 Vpp using a quadrupole mass separator. In order
to trap Rb ions, helium buﬀer gas of the pressured at a
1×10−4 Torr was ﬁlled in the trap chamber. The kinetic
energy of Rb ions decreased because of collision between
the ions and the He buﬀer gas, following which Rb ionswere conﬁned in the center electrode of the trap, denoted
as “C” in Fig. 1(a). After ion trapping, we superimposedsinusoidal voltages (frequency: 1 Hz, amplitude: 2 V) toeach trap electrode as the swinging ﬁeld. The phase
diﬀerence of the each sinusoidal voltage was 45◦ . The
time variation of the applied voltage of each trap electrode is schematically shown in Fig. 1(b). We turned oﬀ∗1

RIKEN Nishina Center

Fig. 1. (a) Schematic view of the experimental setup. The
time variation of the applied voltages of each electrodeduring ion swinging is schematically shown in (b).

Fig. 2. Number of detected ions at the CEM position
with/without an ion swinging ﬁeld.

all the voltages including that of the end electrode at agiven time after applying the swinging ﬁeld. The ions extracted toward the downstream direction were detectedusing channel electron multiplier (CEM) detector.
The number of ions detected using the CEM detector with/without the swinging ﬁeld is shown in Fig. 2.
The detected ion number shown in Fig. 2 is the averagevalue of 25 measurements. The error was calculated as
the standard deviation of the number of detected ions ineach measurement. As shown in Fig. 2, approximately
450 ions were detected at the CEM position when weapplied a swinging ﬁeld, while the signal rate decreased
almost to the background level in the case of no swinging ﬁeld. This result indicates that the trapped ionsobtain an axial momentum component suﬃcient to ejectin the axial direction using the swinging ﬁeld before ion
neutralization: that is ions neutralized using a gas aredelivered to the downstream spin-selection magnet as aneutral atomic beam. In a rough estimation, the extraction eﬃciency of the trapped ions reached approximately
10% so far. Further investigation and development are
in progress now.
References
1) K. Asahi et al., Phys. Lett. B 251, 488 (1990).
2) N. F. Ramsey, Molecular Beams (Oxford University Press,
New York, 1956).

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1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Oﬄine collinear laser spectroscopy of zirconium II
M. Tajima,∗1 A. Takamine,∗1 H. Iimura,∗2,∗1 M. Wada,∗3 H. A. Schuessler,∗4,∗1 Y. Matsuo,∗5,∗1 and H. Ueno∗1

∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
Nuclear Science and Engineering Center, JAEA
Wako Nuclear Science Center (WNSC), IPNS, KEK
Department of Physics and Astronomy, Texas A&M University
Department of Advanced Science, Hosei University

























The laser spectroscopy of atomic transitions is sensitive to nuclear structures in ground states. The measurement of isotope shifts and hyperﬁne splittings bycollinear laser spectroscopy (CLS) is a powerful tool forstudying radioactive isotopes (RIs) systematically alongisotope chains. Charge radii, quadrupole deformation,
electromagnetic moments, and spins have been extensively measured at ISOL-type facilities. We are preparing for the CLS of RIs at the gas-cell decelerator facility,
SLOWRI. Our main targets include refractory elements
near the N = Z line in the intermediate mass region,
where experimental data are not suﬃcient because of theexperimental diﬃculties at ISOL-type facilities. Barium
isotopes have been measured as a ﬁrst oﬄine demonstration of CLS.1) This report describes the next step
wherein an oﬄine measurement of zirconium ions was
performed.
Zirconium ions were produced from a disk-shaped
metal target by using pulsed-laser ablation. A Qswitched Nd:YAG laser (Coherent, Minilite II) was usedwith the time width of 5 ns at the repetition rate of 10 Hz
at the maximum. Ion beams were extracted at ∼10 keV
and mass separated so that a selected isotope could betransported to a photon detection region.1) We chosethe transition 4d2 (3 F )5p z4 G◦5/2 ↔ 4d2 (3 F )5s a4 F3/2 ,which is at 357 nm, and the strongest transition from theatomic ground state.2) A continuous-wave Ti:Sapphirelaser (M-square, SolsTis) pumped by a solid-state laser(Verdi, V10) was used to obtain the fundamental wavelength of 714 nm and a commercial second harmonics
generator with a LBO crystal (M-square, ECD-X) wasused. The fundamental wavelength was stabilized by awavelength meter within 10 MHz (FWHM); the power
was 0.5 mW at the detection region. The time-of-ﬂight(TOF) of the ions was measured by a channeltron (Photonis, Magnum 5901) at the downstream of the beamline. We found that the TOF of the resonant ions wereconcentrated within 50 μs. Therefore, a time gate forthe photon detection by a PMT was set to 50 μs for thetiming of the pulsed laser irradiation to suppress background counts.
Figure 1 shows the observed spectra with Voigt ﬁtting
curves. Since 90, 92, 94 Zr+ and 91 Zr+ were measured at
separate times and diﬀerent wavelengths were available
between them, the energy of ion beams was tuned to13.6 keV for 90, 92, 94 Zr+ and 10.6 keV for 91 Zr+ . The
background count rates were suppressed by a factor of1000 compared to that of the continuous measurement.
In the future, we plan to suppress backgrounds further





 

 
















 

 







 
 
!"#$%  
Fig. 1. Observed resonance spectra of Zr+ at 357 nm withthe time gate of 50 μs. Magenta lines represent the Voigt
ﬁtting curves.

with a shorter ion bunch by performing CLS with a multi
reﬂection TOF mass spectrometer3) where the bunch
length of 40 ns is possible. Although all 12 peaks were
not fully resolved for 91 Zr+ , hyperﬁne coeﬃcients forboth upper and lower levels were derived from ﬁve isolated peaks; these coeﬃcients were consistent with thosereported in previous measurements.4,5) In addition, thisexperiment is a benchmark for a new lifetime measurement of 93 Zr+ ,6) which is important to accurately evaluate the radioactivity of long lived ﬁssion products innuclear wastes.
References
1) M. Tajima et al., RIKEN Accel. Prog. Rep. 53, 15 (2020).
2) G. Ljung et al., Astron. Astrophys. 456, 1181 (2006).
3) P. Schury et al., Phys. Rev. C 104, L021304 (2021).
4) H. L. Thayer et al., J. Phys. G 29, 2247 (2003).
5) S. D. Rosner, R. A. Holt, J. Phys. B 49, 11501 (2016).
6) A. Takamine et al., in this report.

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II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Fluorescence detection of the highly energetic radioactive Rb beams
stopped in an optical cryostat at HIMAC
K. Tsubura,∗1,∗2 K. Imamura,∗2 A. Takamine,∗2 S. Akimoto,∗1,∗2 M. Ito,∗1,∗2 K. Kikuchi,∗1,∗2 R. Mitsuyasu,∗1,∗2
A. Gladkov,∗2 M. Tajima,∗2 S. Go,∗2 M. Mukai,∗2 M. Doi,∗1,∗2 M. Nishimura,∗1,∗2 T. Yamamoto,∗1,∗2
H. Endo,∗1,∗2 M. Hase,∗3 K. Kawata,∗4 H. Nishibata,∗2,∗5 Y. Ichikawa,∗2,∗5 H. Ueno,∗2 and Y. Matsuo∗1,∗2

∗1
∗2
∗3
∗4
∗5

Department of Advanced Sciences, Hosei University
RIKEN Nishina Center
National Institute of Materials Science (NIMS)
Center for Nuclear Study, University of Tokyo
Department of Physics, Kyushu University- 91 -

3.6
Fluorescence intensity[counts / 10 ms / spill]

We are developing a laser spectroscopy techniquecalled Optical RI-atom Observation in Condensed Helium as Ion- catcher (OROCHI) for the study of nuclear spins and moments. In the OROCHI experiment,
we catch highly energetic ion beams in superﬂuid helium (He II) in our cryostat to neutralize them and conduct in-situ laser spectroscopy. We irradiate neutralized
atoms with circularly polarized laser light to produce
spin polarization and measure atomic Zeeman and hyperﬁne splitting energies using laser-radio frequency andlaser-microwave double resonance method.
In a previous online experiment,1) our group observed
laser-rf double resonance spectra of 84–87 Rb ion beams
provided by the RIKEN RIPS at ∼60 MeV/nucleon. It
is known that the hyperﬁne structure constants of atoms
in superﬂuid helium are larger than those of free atoms
by 1%.2,3) Therefore, based on our interest in the hyperﬁne anomalies of atoms in superﬂuid helium, we plan
to measure the hyperﬁne splitting of the radioactive Rb,
Ag, Cs, and Au isotopes, to which this method has not
yet been applied.
In FY2019, we measured the beam yields of a higher
energy 84 Rb beam at the HIMAC SB2 beam line in orderto estimate the number of stopped atoms in the laserinduced ﬂuorescence (LIF) observation region (φ2 mm
× 5 mm).4)
Because the result of the FY2019 experiment showedthat the diameter of the beam stopping area was over
15 mm, we decided to expand the laser diameter and theobservation area to as large as possible (2 mm ×10 mm
× 5 mm). We here report the result of an experimentconducted in FY2021 using laser irradiation at HIMAC.
The 84 Rb beam produced in proton pickup reactions
by a 84 Kr beam with 350 MeV/nucleon on a Be target of 12 mm thickness was passed through a 2.1 mmthick Al degrader and a plastic in the pre-cryochamber,and stopped in He II at the center of the optical cryostat. In the pre-cryostat chamber, the number of beams
was counted using a trigger plastic scintillator and two
photomultiplier tubes. A laser beam ampliﬁed by a taper ampliﬁer (TA) was shaped to the above-mentioned
size and introduced to the cryostat. The laser lightwavelength was 780 nm with a bandwidth of 2.9 nm(FWHM), which corresponds to the Rb D1 excitationline in He II. The ﬂuorescence from the stopped atoms

Laser ON

3.2
2.8
0.8

Laser OFF

0.4
0

0

500

1000

1500 2000
Time [ms]

2500

3000

Fig. 1. Detected ﬂuorescence intensity for laser on (upper)
and oﬀ (lower).

was collected by a LIF detection system, passed throughthe optical ﬁber, the wavelength was selected by amonochromator with a resolution of 8 nm set to 794 nm,
and detected using a photomultiplier tube.
Figure 1 shows the detected photon intensity for when
the laser is turned on (upper) and oﬀ (lower). The incoming 84 Rb beam intensity was 3.7 × 104 particles per
spill with a beam purity of 50% (the beam repetition
cycle was 3.3 s). An evaluation revealed that 7% of the84
Rb was stopped in the observation region from the previous experimental results4) and a LISE++ calculation.
The irradiated laser power was 200 mW. The upper plot
clearly shows a long tail for the LIF based on remaining
84
Rb atoms compared with the beam-induced ﬂuorescence in the lower plot. This tail stems from Rb atom
diﬀusion caused by liquid helium ﬂow and it shows asimilar diﬀusion time of 1.77 s compared with the value(617 ms) that we measured in our previous experiment at
RIPS.5) The extended LIF decay time can be attributed
to the expansion of the observation region being larger
than that in the RIPS experiment.
We conﬁrmed LIF detection of 84 Rb and conclude that
OROCHI can be applied to the high energy beam from
HIMAC SB2. Currently, we are in the process of analyzing the data.
References
1) X. F. Yang et al., Phys. Rev. A 90, 052516 (2014).
2) Y. Takahashi et al., Z. Phys. B 98, 391 (1995).
3) T. Furukawa, Ph.D. thesis, Osaka University (2007).
4) K. Tsubura et al., RIKEN Accel. Prog. Rep. 53, 132(2020).
5) K. Imamura et al., Appl. Phys. Express 12, 016502(2019).

1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of dispersion matching optics in OEDO beamline
S. Hanai,∗1 S. Michimasa,∗1 T. Chillery,∗1 S. Ota,∗1 N. Imai,∗1 S. Shimoura,∗1 N. Fukuda,∗2 Y. Hijikata,∗3,∗2
K. Kameya,∗4,∗2 S. Kitayama,∗4,∗2 K. Kishimoto,∗5,∗2 K. Kusaka,∗2 J. Li,∗1 Y. Maeda,∗6,∗2 Y. Maruta,∗4,∗2
T. Matsui,∗4,∗2 K. Miki,∗4,∗2 D. Nagae,∗2 H. Nishibata,∗5,∗2 D. Nishimura,∗7,∗1,∗2 M. Sasano,∗2 Y. Shimizu,∗2
S. Sugawara,∗2 T. Sumikama,∗2 H. Suzuki,∗2 H. Takahashi,∗7 H. Takeda,∗2 T. Uesaka,∗2 R. Urayama,∗4,∗2
T. Wakasa,∗5 K. Yako,∗1 Y. Yamaguchi,∗2 Y. Yanagisawa,∗2 N. Yokota,∗5,∗2
C. Yonemura,∗5,∗2 and K. Yoshida∗2   The Optimized Energy Degrading Optics (OEDO)
beamline provides potential opportunities to perform
nuclear physics experiments with spatially and achromatically well-forcused low-energy RI beams1) or highmomentum resolution by selecting a suitable ion transportation method. High-quality low-energy RI beam
production has been achieved.2) Recently, several
beamline magnets in the OEDO beamline were rearranged aiming at the realizing a high momentum
resolution. To conduct nuclear spectroscopy with aresolution greater than the energy width of the incident beam, lateral and angular momentum dispersion
matching techniques are essential. Figure 1 shows adesigned dispersion matching ion optics from BigRIPS
F3 to SHARAQ S2 foci through the OEDO beamline.
The S0 intermediate focus, where a target will be inserted in a future experiment, has the largest momentum dispersion in the beamline of 14.7 m, and thismomentum dispersion vanishes at the ﬁnal focus, S2.
We report here a study showing dispersion matching
optics of the OEDO beamline.
We performed the study using an 82 MeV/nucleon
triton beam produced by the BigRIPS separator fromthe 200 MeV/nucleon 4 He primary beam. Position de-

∗2
∗3
∗4
∗5
∗6
∗7



   

   

Fig. 2. (a) Correlation between S0 and S2 horizontal positions. (b) Correlation between S0 horizontal position
and S2 horizontal angle. (a|δ) term is approximately
0.4 mrad/%.

tectors, a parallel-plate avalanche counter and a lowpressure multiwire drift chamber, were placed at thefoci from F3 to S2, to measure the transfer matrix elements at each focal plane. We veriﬁed the consistencyof the measured matrix elements by comparison withion optics calculation results.
By evaluating the matrix elements, the momentum
dispersion at S0 was deduced as 16.3 m, which corresponds to a dispersion of 0.025 mm/% and satisﬁes the lateral dispersion matching condition with the
SHARAQ spectrometer. Figure 2(a) shows that there
is no correlation between the horizontal position (momentum dispersion) at S0 and that at S2 and therefore, the condition of momentum dispersion matchingis fulﬁlled. Figure 2(b) shows the correlation between
the horizontal position (momentum dispersion) at S0
and the horizontal angle at S2, which suggests thatangular dispersion matching is eﬃciently satisﬁed. We
conclude that angular momentum dispersion matchingis also achieved at S2.
Consequently, we achieved dispersion matching ion
transportation through the OEDO beamline. Using
this ion-optical mode, we plan to conduct an approved
experimental program of direct mass measurements ofvery rare RI nuclei.

SHARAQ

Fig. 1. Trajectories of ion beam with dispersion matching
setting in BigRIPS-OEDO-SHARAQ beamline. Trajectories are calculated from ﬁrst-order matrix elements.
∗1





±
±

OEDO





±
±
±

BigRIPS

Center for Nuclear Study, University of Tokyo
RIKEN Nishina Center
Department of Physics, Kyoto University
Department of Physics, Tohoku University
Department of Physics, Kyushu University
Faculty of Engineering, University of Miyazaki
Department of Natural Sciences, Tokyo City University

References
1) S. Michimasa et al., Prog. Theor. Exp. Phys. 2019,
043D01 (2019).
2) S. Michimasa et al., CNS Ann. Rep. 2018, CNS-REP98, 35 (2020).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Commissioning of the Si-CsI array TiNA for direct reactions at
OEDO
B. Mauss,∗1 N. Ma,∗2 J. W. Hwang,∗2,∗3 D. Suzuki,∗1 N. Imai,∗2 T. Teranishi,∗4,∗1 S. Ota,∗2,∗5 A. Kohda,∗5,∗1
M. Dozono,∗2,∗6 S. Michimasa,∗2 T. Sumikama,∗1 C. Iwamoto,∗7 and N. Iwasa∗8,∗1
The energy-degrading beamline OEDO is operating
at RIBF to expand the scope of reaction studies forradioactive nuclei.1) TiNA is an array of Si and CsI
detectors for direct reaction studies at OEDO to address a wide range of objectives in nuclear structure
and astrophysics.2) The ﬁrst version of the detector
has been used in several transfer experiments.3,4)
The TiNA detector was upgraded in 2020 to increase
the solid angle and improve the resolution in angle
and energy.5) The upgraded TiNA consisted of two
types of detector assemblies. Four square telescopeswith a ﬁrst stage of double-sided strip silicon detectors (DSSD) and a second stage of CsI detectors werearranged in a barrel conﬁguration and placed just beyond the reaction target. The second detector assembly is a lampshade array consisting of six trapezoidal
telescopes with a ﬁrst stage of single-sided strip silicon detectors (SSSD) and a second stage of CsI detectors. The total angular coverage by the entire telescope
ranges from 10◦ to 80◦ in the laboratory frame.
For the data taking, two diﬀerent systems were uniﬁed. The DSSDs were connected to the General Electronics for TPCs (GET), an integrated system allowing the processing of a total of 1024 channels. The
test of the GET electronics has been reported in aprevious study.5) The signals from the rest of the detectors, including the CsI crystals and SSSDs, were fed
into standard analog ampliﬁers and digitized by VMEstandard ADC modules. Triggers from both systems
were merged in a trigger module. A common trigger issent to both DAQs and synchronizes the event number.
The detector was commissioned in-beam at the tandem accelerator facility of the Center for Accelerator
and Beam Applied Science, Kyushu University in January 2021. The aim of this commissioning was to measure the performances in terms of energy and angularresolutions, particle identiﬁcation for light ions, andDAQ capabilities.
A 14 MeV deuteron beam impinged on a 1 mg/cm2
thick 12 C target provided by the RCNP, Osaka University. At this beam energy, elastic scattering, inelastic scattering to excited states, and transfer (d, p) and
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8

counts/25keV

3.85 MeV, 5/2+

100
3.09 MeV, 1/2+-

g.s., 1/2

50

0

0
2
4
C excitation energy (MeV)

13

Fig. 1. Excitation energy spectrum for the 12 C(d, p)13 C
transfer reaction using a 14 MeV deuteron beam.

(d, α) reactions are allowed. The preliminary results
give an energy resolution of 125 keV FWHM for theelastic scattering events measured by the DSSDs. Figure 1 shows the excitation energy for the (d, p) transfer
reaction. The protons were selected by the E − ΔE
method using the CsI crystals and DSSDs. The excitation energy resolution is approximately 330 keV
FWHM for proton energies around 14 MeV. Analysis
is still ongoing to improve the resolution.
In conclusion, the full setup of the TiNA detector
was successfully commissioned at the tandem accelerator facility of the Kyushu University. The event correlation between the two independent data acquisition
systems was validated; however, some DAQ capabilities should be improved in the future. The analysis isongoing with encouraging preliminary results.
References
1) S. Michimasa et al., Prog. Theor. Exp. Phys. 2019,
043D01 (2019).
2) P. Schrock et al., CNS Ann. Rep. 2016, CNS-REP-96,
7 (2017).
3) K. Wimmer et al., CNS Ann. Rep. 2017, CNS-REP-97,
7 (2019).
4) N. Imai et al., CNS Ann. Rep. 2018, CNS-REP-98, 1(2020).
5) B. Mauss et al., RIKEN Accel. Prog. Rep. 54, 114(2021).

RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo
Center for Exotic Nuclear Studies, Institute for Basic Science
Department of Physics, Kyushu University
Research Center for Nuclear Physics, Osaka University
Department of Physics, Kyoto University
RIKEN Center for Advanced Photonics
Department of Physics, Tohoku University- 93 -

1

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

First production of 6 He beam at CRIB
H. Yamaguchi,∗1 M. Sferrazza,∗2 S. Hayakawa,∗1 N. R. Ma,∗1 H. Shimizu,∗1 K. Okawa,∗1 T. Furuno,∗3
S. Okamoto,∗4 N. Imai,∗1 T. Chillery,∗1 J. T. Li,∗1 S. Ota,∗1,∗3 N. Iwasa,∗5 and T. Kawabata∗3
Table 1. Summary of the secondary beam purity. Notethat the F2 data were taken with the PPAC trigger,
and F3 were with the SSD.

6
He is the second lightest unstable nuclide that
could be used as a radioactive-isotope (RI) beam. In
2021, we performed a production test of 6 He beam at
CRIB1–4) for the ﬁrst time, aiming to assess the feasibility of future experiments using this RI beam. The
beam production was performed as a Machine Study
beamtime in March, 2021. The primary beam was
7 3+
Li , accelerated with the AVF cyclotron up to anenergy of 8.3 MeV/nucleon. The maximum beam current at the entrance of CRIB during the beamtime was
3 particle μA (= 9 electric μA (eμA)). The RI beam
was produced with the 7 Li(d, 3 He)6 He reaction, which
was also used in other in-ﬂight facilities, such as RESOLUT of Florida State University.5) At RESOLUT, a
6
He beam was produced with an energy range of 18–
29 MeV (3–5 MeV/nucleon), an intensity of 104 pps,
and a purity of 40%. The target gas we used at CRIB
was D2 at 730 Torr, conﬁned in a cell, and cooled withthe cryogenic gas target system.3)
We tested the beam production at two magnetic rigidity conditions:
1) Bρ = 1.227 Tm(6 He2+ : 7.99 MeV/nucleon) with the original primary beam, and 2) Bρ = 1.032 Tm (6 He2+ :5.66 MeV/nucleon) by degrading the primary beamenergy to 6.5 MeV/nucleon with a 48-μm-thick Havar
foil. Particle identiﬁcation (PI) was performed by measuring the time-of-ﬂight and energy of the secondary
beam with the PPACs and silicon detectors at the F2and F3 focal planes. The identiﬁed particles are 6 He2+ ,3 1+
H , and a small number of 7 Li2+ .
After the optimization at F2 to maximize the 6 He
beam intensity, the beam was transported to F3 with atransmission eﬃciency of 28%. 7 Li2+ disappeared fromthe PI diagram, while 3 H1+ remained due to its chargeto-mass ratio identical to 6 He. Table 1 summarizes thepurities of secondary beam particles in each condition.
The purity of 3 H1+ appeared to be higher at F3 compared to F2, however, this is supposed to be from thelimited detection eﬃciency of the PPAC, which triggered the measurement at F2, against the light 3 H1+ion. The 6 He energy after one PPAC (thickness equivalent to 9.5 μm Mylar) was measured as (47.80 ± 0.44)
MeV or (7.943 ± 0.073) MeV/nucleon, where the energy loss in the PPAC (0.29 MeV) was in a good agreement with a calculated value (0.28 MeV).
We increased the primary beam current to conﬁrm
the highest intensity 6 He beam we can obtain. The
∗1
∗2
∗3
∗4
∗5

Ion

High Bρ (1.227 Tm)
F2
F3

Low Bρ (1.032 Tm)
F2
F3

He2+
H1+
7 2+
Li
4
He2+

85%
15%
0.2%
–

60%
17%

6

3

73%
27%
–
–

22%∗

61%
23%
5.9%
9.7%

* Summed purity of 7 Li2+ and 4 He2+ .

6

He rate increased almost proportional to the primarybeam current with a ratio of 370 kcps/μA. The detection eﬃciency of the PPAC was 70–80% or better,when the secondary beam rate was 300–400 kcps. The
intensity test was performed up to the primary beam
current of 2 electric μA (eμA), at which the PPAC efﬁciency dropped down to 42% for the secondary-beam
intensity of 630 kcps, even though we applied the possible maximum voltages on the PPAC electrodes.
The beam production test in the low-energy condition was performed basically in the same procedure as
the high-energy case. Due to the contamination ions of
7 3+
Li and 4 He2+ , we had a lower 6 He purity of about
60%, as shown in Table 1.
In conclusion, we succeeded in producing 6 He RI
beams at 7.99 MeV/nucleon and 5.66 MeV/nucleon
with an intensity of the order of 105 pps, superior to
the beam at RESOLUT,5) satisfying the requirementby the proposed 6 He+p experiment.6) The practicalbeam intensity is presently limited to about 2 ×105 pps
by the low detection eﬃciency of the PPAC for such alight-ion beam. To make the eﬃciency higher, we areplanning to use wire chambers (MWDC) in the main
experiment.
References
1) S. Kubono et al., Eur. Phys. J. A 13, 217 (2002).
2) Y. Yanagisawa et al., Nucl. Instrum. Methods Phys.
Res. A 539, 74 (2005).
3) H. Yamaguchi et al., Nucl. Instrum. Methods Phys.
Res. A 589, 150 (2008).
4) H. Yamaguchi et al., Nucl. Phys. News 30(2), 21(2020).
5) Web page of RESOLUT: https://fsunuc.physics.
fsu.edu/research/experimental_devices/#resolut .
6) M. Sferrazza, et al., proposal for RIBF NP-PAC-21,
NP2021-AVF70 (2020, unpublished).

Center for Nuclear Study, University of Tokyo
Department of Physics, Université Libre de Bruxelles
Department of Physics, Osaka University
Department of Physics, Kyoto University
Department of Physics, Tohoku University- 94 -

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Long polarization-maintaining ﬁber link (440 m) for magneto-opticaltrapping of francium atoms
K. Nakamura,∗1 S. Nagase,∗2 T. Nakashita,∗3 T. Hayamizu,∗4 T. Aoki,∗3 H. Nagahama,∗1 N. Ozawa,∗2
M. Sato,∗3,∗4 K. Yamane,∗3 M. Fukase,∗2 D. Uehara,∗2 A. Takamine,∗4 and Y. Sakemi∗1
We are currently developing an optical lattice francium (Fr) atom interferometer to determine the permanent electric dipole moment of an electron (eEDM). Fr
is the heaviest alkali atom with an eEDM enhancement
factor of approximately 799.1) The trapping of such Fr
atoms in the optical lattice leads to an ultra-sensitiveeEDM measurement system with a long interaction time
between the isolated atoms and electric ﬁeld. To load
the atoms into the optical lattice, they must be cooled
and trapped beforehand by techniques such as magnetooptical trapping (MOT). We developed a MOT systemand connected it to a 210 Fr production beamline, which
consists of a surface ionizer2) and neutralizer, installed in
the E7 vertical course. In addition, we linked the MOT
system to laser devices in the laser spectroscopy room
(referred to as L) on the ﬁrst basement ﬂoor of the RIBF
building with 440 m-long polarization-maintaining (PM)ﬁbers. In this paper, we report the performance of thePM ﬁber link.
The ﬁber link consists of a polyvinyl chloride (PVC)coated 400 m ﬂexible stainless steel tube cable (Nippon
Steel Welding & Engineering, Picoﬂec) from L to the E7
entrance and another 40 m tube cable from the E7 entrance to the MOT system (Fig. 1(a)). Seven PM ﬁbers
are housed in each cable; among these, four are Fujikura
PM63 (cutoﬀ wavelength is 520–620 nm, mode ﬁeld diameter is 4.5 ± 0.5 μm at 630 nm), two are PM85 (650–800 nm, 5.5 ± 0.5 μm at 850 nm), and one is PM98
(870–950 nm, 6.6 ± 0.5 μm at 980 nm). Both cables
are connected using ﬁber connectors inside the opticalrack installed at the E7 entrance. The typical transmission loss due to the connector was 0.25. The optical rack was also expected to serve as a hub base for
optical transmission to other laboratories. The lightsof the trapping lasers (wavelength of 718 nm for 210 Fr,
780 nm for 87 Rb, used for oﬄine test) and repumping
lasers (817 nm for 210 Fr, 795 nm for 87 Rb), which were
frequency-stabilized within the natural linewidth of relevant transitions (several MHz) using a wavelength meter (HighFinesse, WS8-2), were transmitted to the MOT
system via ﬁbers (PM63). In general, frequency instability due to a ﬁber is low (∼3 Hz for 6 km at 778 nm
in Ref. 3)), and thus, negligible for our optical transmission.
In the case of a high-power CW laser beam transmitted along a long ﬁber, there are concerns related to thelimit of transmitted power due to stimulated Brillouinscattering (SBS).4) To maximize the number of atoms
∗1
∗2
∗3
∗4

Center for Nuclear Study, University of Tokyo
Department of Physics, University of Tokyo
Graduate School of Arts and Sciences, University of Tokyo
RIKEN Nishina Center

Fig. 1. (a) Overhead view showing the path of a ﬁber link.
(b) Polarization crosstalk in the 400 m ﬁber and temperature measured at three sites. (c) Allan deviation of thecrosstalk.

to be captured, the trapping laser intensity (total of 6axes of 3D MOT) should be several times (8 times inRef. 5)) the saturation intensity of the cooling transition. The saturation intensity of 210 Fr (87 Rb) is ∼2.9(∼1.6) mW/cm2 . When using our trapping laser (SolsTiS, CW, linewidth <50 kHz), the SBS threshold output power for the 400 m ﬁber (PM63) was 30 mW at
718 nm. This value is suﬃcient for our three-axis 3D
MOT system (beam diameter of 1 cm) with opposing
mirrors.
The stability of polarization of the 400 m PM ﬁber
was investigated with a test laser (685 nm, 1 mW). The
polarization crosstalk calculated from the optical powerof the p- and s-polarized outputs split by the polarization beam splitter after launching from the 400 m PM
ﬁber and the temperature measured at three sites (L,E7, and N) are shown in Fig. 2(b). Site N is near theelevator on the second basement ﬂoor of the Nishina
Building (Fig. 1(a)). Figure 2(c) shows the Allan deviation calculated from the time series data of the polarization crosstalk. The PM ﬁbers housed in the PVC-coated
400 m tube were robust against large diel temperatureﬂuctuations along the ﬁber.
We achieved Rb MOT in July 2021 in an oﬄine test.
Online experiments are being conducted intermittently
to achieve Fr MOT, and we are getting closer to achieving it.
References
1) N. Shitara et al., J. High Energy Phys. 2021, 124 (2021).
2) N. Ozawa et al., RIKEN Accel. Prog. Rep. 54, 117 (2021).
3) B. deBeauvoir et al., Phys. Rev. Lett. 78, 440 (1997).
4) G. P. Agrawal, Nonlinear Fiber Optics, 5th Edition (Academic Press, Boston, 2013).
5) S. R. Muniz et al., Phys. Rev. A 65, 015402 (2001).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

RI nuclides produced in stacked Si and Al plates by 135-MeV/nucleon
12
C beamT. Kambara∗1 and A. Yoshida∗1
On the basis of a fee-based facility sharing program,private companies in Japan use heavy-ion beams to simulate single-event eﬀects (SEE) on space-use semiconductor devices by cosmic rays.1) The clients have utilized
ion beams of Ar, Kr, and Xe from the RIKEN Ring Cyclotron (RRC) at the E5A beam line. The primary ion
beam is spread with a scatterer foil and wobbler magnets
and extracted to atmosphere. Then, it passes throughtransmission-type detectors for dose measurements andan energy degrader for linear energy transfer (LET) adjustments. The setup and irradiation procedures were
described previously.2)
The samples irradiated by the primary beam are also
impinged on by various secondary particles produced by
nuclear processes in the upstream materials. To evaluate the eﬀects of the nuclear processes, we irradiate test
samples in the same beam condition as the clients’ irradiation and measure RI nuclides by radiochemical analyses. Similar studies have been reported for a Kr beam3)
and a Xe beam.4)
Since clients expressed interest in the utilizationof a C beam, we studied the characteristics of a
135 MeV/nucleon 12 C beam. During the beamtime, we
irradiated a stack of two Si plates (100-mm diameterand 0.5-mm thick) and two Al plates (3-mm thick) forradiochemical analyses. The irradiation setup is shownin Fig. 1. The primary beam passed through a 51.2-μmthick Kapton® window into the atmosphere and thenentered an ionization chamber (IC). From measurementwith the IC, the number of ions was estimated to beapproximately 1.08 × 1012 during 5 min of irradiation.
Then, the beam passed a 3-mm-thick plastic scintillator(not used) and an energy degrader of 18.42-mm-thick
Al. Its thickness was selected so that the primary ionsstopped in the second Si plate.
We measured the γ rays from each sample plate witha Ge detector from 13.4 min to 39.7 days after the irradiation for the Si plates and from 23.7 min to 6.49
days for the Al plates. Using the observed γ-ray spec-

Fig. 2. Production probabilities of RI nuclides in the sample
plates.

tra, we identiﬁed 10 radionuclides from 7 Be to 34m Cl.
We extrapolated the decay curve of the radioactivity ofeach nuclide to the end of the irradiation to obtain thenumber of the nuclei identiﬁed in the sample. Then, we
divided it by the number of primary ions to obtain the
production probability of the nuclide. The nuclides canbe produced by nuclear reactions either in the sample orin the upstream materials followed by transport to thesample.
The results are shown in Fig. 2, where the coloredbars indicate the probabilities in the sample plates. The
values of the probabilities in the Si plates are shown on
the left ordinate and those in the Al on the right so thatthe bar heights are scaled to the same number density ofthe sample atoms. Since the primary 12 C ions stopped
in the second Si plate, the nuclides in the Al plates were
either produced by secondary particles or transported
from the upstream. The γ rays of 28 Mg and 28 Al shownin Fig. 2(c) were measured only in the ﬁrst Si plate, andthose of 34m Cl in Fig. 2(b) were identiﬁed only in thesecond Si plate.
We are comparing the results with the simulationof nuclear processes using the Particle and Heavy Ion
Transport System (PHITS) code.5)
References

Fig. 1. Setup of the sample irradiation.
∗11) http://ribf.riken.jp/sisetu-kyoyo/ (Japanese).
2) A. Yoshida, T. Kambara, RIKEN Accel. Prog. Rep. 51,
185 (2018).
3) T. Kambara, A. Yoshida, Record of 2018 IEEE Radiation
Eﬀects Data Workshop (REDW), p. 94.
4) T. Kambara, A. Yoshida, RIKEN Accel. Prog. Rep. 52,
158 (2019).
5) https://phits.jaea.go.jp/index.html .

RIKEN Nishina Center- 96 -

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Construction status of the INTT silicon tracker for sPHENIX at RHIC
I. Nakagawa,∗1 Y. Akiba,∗1 D. Cacace,∗2 K. Cheng,∗3 H. Enyo,∗1 T. Hachiya,∗1,∗4 S. Hasegawa,∗1,∗5 M. Hata,∗4
H. Imai,∗1,∗6 T. Kondo,∗7 C. Kuo,∗3 H. -S. Li,∗8 R. -S. Lu,∗9 E. Mannel,∗2 C. Miraval,∗2 M. Morita,∗1,∗4
Y. Nakamura,∗1,∗6 G. Nakano,∗1,∗6 Y. Namimoto,∗1,∗4 R. Nouicer,∗2 G. Nukazuka,∗1 R. Pisani,∗2 M. Shibata,∗1,∗4
C. Shih,∗3 M. Shimomura,∗4 M. Stojanovic,∗8 Y. Sugiyama,∗4 R. Takahama,∗1,∗4 W. -C. Tang,∗3 K. Toho,∗10
K. Tsuruta,∗10 M. Watanabe,∗4 and X. Wei∗8
The sPHENX experiment1) at RHIC in Brookhaven
National Laboratory (BNL) will be launched in January,
2023. The sPHENIX detector complex has been alreadyin the construction phase in the experimental site at
RHIC. The refurbished Barbar magnet was mounted on
the outermost detector, i.e. hadron calorimeter in October, 2021 as shown in Fig. 1.
Japanese collaborators are in charge of development
and construction of the silicon strip detector, namely
INTermediate Tracker (INTT). Major components of
the INTT detector have been developed and fabricateddomestically, and the mass production of silicon ladder components (i.e. silicon sensors, high density interconnect (HDI) readout cables, and carbon ﬁber coolingplates) have been completed by the end of December,
2021. These components have been exported to the ladder assembly sites in BNL and Taiwan, and 70% of theladder assembly have been completed by January, 2022.
Shown in Fig. 2 is the mock-up of a quarter portion of
the INTT inner layer barrel assembled in BNL. The construction of the INTT barrel will be started in Spring,2022 and completed by early Summer, to be ready forthe installation to the experimental site in September.

Fig. 2. The mock-up of a quarter portion of the INTT inner
layer barrel assembled in BNL.

Fig. 3. The collaboration photo of the beam test at Tohoku
University.

Fig. 1. The Babar magnet assembly on the bottom portionof the outermost detector, i.e. hadron calorimeters.
∗1

RIKEN Nishina Center
Physics Department, Brookhaven National Laboratory∗3 Department of Physics, National Central University∗4 Department of Mathematical and Physical Sciences, Nara
Women’s University∗5 Japan Atomic Energy Agency∗6 Department of Physics, Rikkyo University∗7 Tokyo Metropolitan Industrial Technology Research Institute∗8 Department of Physics and Astronomy, Purdue University∗9 Department of Physics, National Taiwan University∗10 Laboratory for Nuclear Science, Tohoku University∗2- 97 -The readout cable chain of the INTT ladder consisted of the HDI, a bus extender,2) and a conversion
cable. While the bus extender is under mass production,
the conversion cable under development employing the
micro-coaxial cable technology. In December, 2021 we
executed 3rd beam test3) of the INTT ladder telescopesin Tohoku University.
References
1) Conceptual Design Report of sPHENIX (2018).
2) T. Hachiya et al., in this report and references therein.
3) G. Nukazuka et al., in this report and references therein.

1II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production of bus-extender for sPHENIX INTT detector
T. Hachiya,∗1,∗2 Y. Akiba,∗1 D. Cacace,∗3 K. Cheng,∗4 H. En’yo,∗1 S. Hasegawa,∗1,∗5 M. Hata,∗2 H. Imai,∗1,∗6
T. Kondo,∗7 C. Kuo,∗4 H.-S. Li,∗8 R.-S. Lu,∗9 E. Mannel,∗3 C. Miraval,∗3 M. Morita,∗1,∗2 I. Nakagawa,∗1
Y. Namimoto,∗1,∗2 Y. Nakamura,∗1,∗6 G. Nakano,∗1,∗6 R. Nouicer,∗3 G. Nukazuka,∗1 R. Pisani,∗3
M. Shibata,∗1,∗2 C. Shih,∗4 M. Shimomura,∗1 M. Stojanovic,∗8 Y. Sugiyama,∗2 R. Takahama,∗1,∗2 W.-C. Tang,∗3
M. Watanabe,∗2 and X. Wei∗8
sPHENIX is the second-generation heavy-ion collision experiment at the Relativistic Heavy-Ion Collider
aimed at studying the properties of strongly coupled
quark-gluon plasma. The intermediate tracker, INTT,
is a silicon strip detector in sPHENIX that is used
to perform precise tracking near the crossing pointof colliding nuclei.1) A special cable for INTT called
bus-extender is required to transmit large amounts ofdata from INTT to the readout electronics at highspeed. The bus-extender is more than 1 m long androuted with a curving path. We developed the busextender based on ﬂexible printed circuit (FPC) technology since no commercial cable is available.
The bus-extender is composed of four Cu layers including signal, power, and ground layers laminatedwith a liquid crystal polymer as a dielectric substrate.
The signal layer contains 62 pairs of low-voltage differential signals within a 5 cm width of the cable, andtheir lines and spaces are both 130 μm.
We built prototype bus-extenders with a length of
1.3 m, as shown in Fig. 1, and evaluated their electrical and mechanical performance. The signal loss
due to a long transmission line was 30%. The peelstrength among the laminated layers was greater than
15 N/cm. These results are summarised elsewhere.2)
From the results, the performance of the prototype is
suﬃcient to satisfy the requirements. We completed
the development and moved to the production stage.
The fabrication procedures are as follows: 1) the
pattern of signal lines is printed by photolithography
and etching, 2) all four layers are laminated by bonding
sheets with pressure, and 3) through holes are opened
and Cu-plated to connect the signal lines between the
inner and outer layers. During the fabrication, we
found that the yield rate was 30% because of shortand open circuits of signal lines. Figure 2 shows two
examples of short and open circuits found in the ﬁrst
fabrication procedure. This poor yield rate needs to be
improved for the mass production since the yield rate
directly impacts the production cost. We investigated
∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9

Fig. 1. Prototype bus-extender with a length of 1.3 m.

Fig. 2. Examples of short and open circuits after the photolithography (left) and etching (right).

why the short and open circuits were produced andfound that the major cause of the problem is the contamination of tiny dust particles, which can interrupt
light exposure and the ﬂow of the etching solution. To
solve the problem, we added two steps to the ﬁrst procedure. One is to remove dust particles as much as
possible using a silicon rubber roller. The other is tocheck the open/short lines after etching and to remove
the bad signal layer in the later lamination process if
found. With these new steps, the yield rate was improved to 75%. The visual inspection of signal lines
after etching is useful to improve the yield rate further. An inspection system to search the bad lines
semi-automatically is under development.3)
In summary, the development of the bus-extender
was completed, and new steps added to the fabrication procedure successfully improved the the yieldrate. The mass production of the bus-extender will
be started in January 2022 with the semi-automatedinspection system.
References

RIKEN Nishina Center
Nara Women’s University
Brookhaven National Laboratory
National Central University
Japan Atomic Energy Agency
Rikkyo University
Tokyo Metropolitan Industrial Technology Research InstitutePurdue University
National Taiwan University

1) I. Nakagawa et al., in this report.
2) T. Kondo et al., submitted to IEICE Electron. Expr.
3) H. Imai et al., in this report.

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Detection eﬃciency of the RHIC-sPHENIX-INTT detector
M. Morita,∗1,∗4 Y. Akiba,∗1 D. Cacace,∗2 K. Cheng,∗3 H. En’yo,∗1 T. Hachiya,∗1,∗4 S. Hasegawa,∗1,∗5 M. Hata,∗4
H. Imai,∗1,∗6 T. Kondo,∗7 C. Kuo,∗3 H. -S. Li,∗8 R. -S. Lu,∗9 E. Mannel,∗2 C. Miraval,∗2 I. Nakagawa,∗1
Y. Nakamura,∗1,∗6 G. Nakano,∗1,∗6 Y. Namimoto,∗1,∗4 R. Nouicer,∗2 G. Nukazuka,∗1 R. Pisani,∗2
M. Shibata,∗1,∗4 C. Shih,∗3 M. Shimomura,∗4 M. Stojanovic,∗8 Y. Sugiyama,∗4 R. Takahama,∗1,∗4
W. -C. Tang,∗3 K. Toho,∗10 K. Tsuruta,∗10 M. Watanabe,∗4 and X. Wei∗8
The intermediate tracker (INTT), consisting of 56
ladders of silicon strip detectors, is a tracking detectorof charged particles for the sPHENIX experiment1) at
the Relativistic Heavy Ion Collider. So far, by using
test pulses, radiation sources, cosmic rays, and proton
test beams at Fermilab, we have conﬁrmed that theperformance required of the INTT ladders is mostly
fulﬁlled. After the completion of the research and development of INTT, mass production and detector construction are now in progress.2)
A silicon detector is expected to have a detection
eﬃciency of almost 100%; however, we obtained an efﬁciency of 96.5 ± 0.5% from a previous test beam experiment.3) This low eﬃciency may have been causedby the missing beam clock information in the experimental data because one cannot conﬁrm whether each
hit in the detectors originated from one beam particle without the beam clock information. Thus, the
INTT data acquisition (DAQ) system was modiﬁed tosave the beam clock information and accept an external trigger.
In December 2021, at Research Center for Electron
Photon Science, Tohoku University, we performed a
new test beam experiment4) with the mass-produced
ladders and the new INTT DAQ system. Three ladders were collinearly placed along the beamline andsandwiched by trigger plastic scintillators. A positron
beam with an energy of 1 GeV impinged on these detectors.3)
The detection eﬃciency (Li ) of the i-th ladder Li
is calculated as
(Li ) =N (Li ∩ Lj ∩ Lk ),N (Lj ∩ Lk )Fig. 1. Fired strip-ID diﬀerence between two ladders. The
events in the 2σ region (enclosed by dashed lines) areused to evaluate the detection eﬃciency of each ladder.

ﬁciency. The strip ID of the hit clusters are determined by the weighted mean of the merged hits with
their analog-to-digital conversion (ADC) value. The
events in which the beam penetrates all ladders almost perpendicularly are used to evaluate the detection eﬃciency. The ﬁred strip-ID diﬀerence between
two ladders are utilized to select such events, as shownin Fig. 1. A smaller absolute value of the diﬀerence
between the ﬁred strip IDs corresponds to a smaller
position diﬀerence in the plane perpendicular to thebeam axis. The events inside the 2σ region in the ﬁred
strip-ID distribution (the region enclosed by dashedlines in Fig. 1) are treated as the coincidence condition
in Eq. (1). The mean of the ﬁred strip-ID diﬀerence isapproximately 4, implying that the position diﬀerence
between ladders is approximately 320 μm. The widthof the distribution is governed by the angular spreadof the beam. With the coincidence condition describedabove, the detection eﬃciencies of the three ladders are
determined to be 99.53 ± 0.02%, 99.39 ± 0.03%, and99.56 ± 0.02%, respectively. The high detection efﬁciency of the INTT detector is conﬁrmed, implyingthat the detector is ready for the day-one experimentof sPHENIX.

(1)(i, j, k = 0, 1, 2)(i = j = k)where N (x) is the number of hits under a condition x.
The events from noisy strips are excluded from theanalysis. Hit clusters are formed by merging adjacenthits in a ladder before the calculation of detection ef-

References
1) Conceptual Design Report of sPHENIX (2018).
2) I. Nakagawa et al., in this report.
3) A. Suzuki, Master thesis, Nara Women’s University(2019).
4) G. Nukazuka et al., in this report.

∗1

RIKEN Nishina Center∗2 Brookhaven National Laboratory∗3 Department of Physics, National Central University∗4 Department of Physics, Nara Women’s University∗5 Japan Atomic Energy Agency∗6 Department of Physics, Rikkyo University∗7 Tokyo Metropolitan Industrial Technology Research Institute∗8 Department of Physics, Purdue University∗9 Department of Physics, National Taiwan University∗10 Department of Physics, Tohoku University- 99 -

1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Test beam experiment at ELPH in Tohoku University
for sPHENIX INTT
G. Nukazuka,∗1 Y. Akiba,∗1 D. Cacace,∗2 H. En’yo,∗1 K. Cheng,∗3 T. Hachiya,∗1,∗4 S. Hasegawa,∗1,∗5
M. Hata,∗4 H. Imai,∗1,∗6 T. Kondo,∗7 C. Kuo,∗3 H. -S. Li,∗8 R. -S. Lu,∗9 E. Mannel,∗2 C. Miraval,∗2
M. Morita,∗1,∗4 I. Nakagawa,∗1 Y. Nakamura,∗1,6 G. Nakano,∗1,∗6 Y. Namimoto,∗1,∗4 R. Nouicer,∗2 R. Pisani,∗2
M. Shibata,∗1,∗4 M. Shimomura,∗4 C. Shih,∗3 M. Stojanovic,∗7 Y. Sugiyama,∗4 R. Takahama,∗1,∗4
W. -C. Tang,∗3 K. Toho,∗10 K. Tsuruta,∗10 M. Watanabe,∗4 and X. Wei∗8∗1

RIKEN Nishina Center
Physics Department, Brookhaven National Laboratory∗3 Department of Physics, National Central University∗4 Department of Mathematical and Physical Sciences, Nara
Women’s University∗5 Japan Atomic Energy Agency∗6 Department of Physics, Rikkyo University∗7 Tokyo Metropolitan Industrial Technology Research Institute∗8 Department of Physics and Astronomy, Purdue University∗9 Department of Physics, National Taiwan University∗10 Laboratory for Nuclear Science, Tohoku University∗2- 100 -PMT Trigger Sci.

INTT ladder-3

INTT ladder-2

INTT ladder-1

INTT ladder-0

PMT Trigger Sci.

Dark box

Additional
Lead Platee+ beam
1 GeV

PMTFingertipSci.

box containing four INTT ladders, which have 6656
strips in the active area of about 465.5×20.0 mm2 , wasset on the beamline, and two plastic scintillators wereplaced upstream and downstream as external triggers(Fig. 1). Depending on the trigger and veto conﬁgurations, the trigger rate was up to 100 Hz. Three ofthe ladders could take hit data successfully. A readoutcard acquires hit information from the ladders, and theDAQ stores hit coincidences with the external trigger
signal. A ﬁngertip scintillator was installed additionally to restrict the position of the hits in analysis.

NIM logic circuit
CAMAC DAQ

Readout Card

External
Trigger Input
INTT Signal Processes
External Trigger Processes

DAQ PC

Fig. 1. Schematic diagram of the setup.

Data acquisition for about 50 h, divided into 65 runs,
collected about 4 × 107 hits (Fig. 2). A hit map ofladder-1 with a typical setup (Fig. 3) shows the beam
proﬁle clearly. Data analysis is currently ongoing, andpreliminary results for the detection eﬃciency are discussed in this report.5)

Sum of thecllected hits

The sPHENIX1) collaboration will start data acquisition from 2023 to study quark-gluon plasma and cold
quantum chromodynamics at the Relativistic Heavy
Ion Collider (RHIC) in Brookhaven National Laboratory. The intermediate silicon tracker (INTT),2) one of
the tracking detectors in the sPHENIX detector complex, plays a crucial role in tracking and jet ﬂavor tagging with high precision and low background. Fifty-six
INTT ladders with about 370 thousand silicon strips
in total form a double-layer barrel to surround the interaction point. The position and timing resolutions of
the prototype showed satisfactory performance in theprevious experiment at Fermilab in 2019. Although a
detection eﬃciency of 100% is expected owing to its
high sensitivity to ionizing radiation, a detection efﬁciency about 96% was obtained in the experiment.3)
An internal clock of 9.4 MHz (beam clock, BCO) in thesystem drove the INTT while the signals synchronizedwith the beam collision drove at RHIC. The timing
mismatch of the BCO and the beam may explain the
insuﬃcient detection eﬃciency. The insuﬃcient detection eﬃciency in the experiment may be due to theunsynchronized operation of INTT with the test beam.
We performed a test beam experiment in December
2021 to test the hypothesis and perform the following:• Tests and performance evaluation of the massproduction ladders• Tests of the long readout extension cable of 1.2 m4)• Analog-digital converter distribution measurements with various beam injection angles with respect to the INTT ladders• Performance evaluation of the ladders in a multitrack condition similar to that in RHIC by installing a lead plate the upstream of the setup
We measured hits on INTT ladders with a positron
beam of 1 GeV at the Research Center for Electron
Photon Science (ELPH) in Tohoku University. A dark

5E+07
4E+07
3E+07
2E+07
1E+07
0E+00
20

30

40

50

60

70

80

90

Run
Fig. 2. Sum of the collected hits on the INTT ladders.

1II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

Fig. 3. Hit map of ladder-1.

References
1) A. Adare et al., sPHENIX proposal (2015).
2) I. Nakagawa et al., in this report.
3) A. Suzuki, Master thesis, Nara Women’s University(2020).
4) T. Hachiya et al., in this report.
5) M. Morita et al., in this report.

2- 101 -

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Computing and network environment at the RIKEN Nishina Center
T. Ichihara,∗1 Y. Watanabe,∗1 and H. Baba∗1
We operate the Linux cluster systems1) at the
RIKEN Nishina Center (RNC).
Figure 1 shows the current conﬁguration of theLinux servers at the RNC. Scientiﬁc Linux (SL) 7 andCentOS 8 have been installed in these systems.
CentOS 8 was released in September 2019, and it wasannounced that support will be planned until 2029.
However, in December 2020, there was a sudden announcement that support would end at the end of
2021. Therefore, we need to replace CentOS 8. In
the high-energy and nuclear physics community, it has
been proposed to migrate from CentOS 8 to CentOS
stream 8.2) Therefore, we have migrated CentOS 8 to
CentOS stream 8 in December 2021.
The host RIBF.RIKEN.JP is used as the mail server,
NFS server of the user home directory, and NIS masterserver.
The hosts RIBFSMTP1/2 are the mail gateways
used for tagging spam mails and isolating virusinfected mails. The latest version of Sophos EmailProtection-Advanced (PMX 6.4.9) was installed. The
support for Sophos PMX is scheduled to end in July
2023. Figure 2 shows the mail trends in 2021. Approximately 33% of the incoming mails were blocked by the
PMX ip-blocker.

Fig. 2. Mail trends: message categories in 2021.

A new TeX software, TEX Live 2021 was installed in
the RIBF00 and RIBF01 servers. The Japanese fontin TeX was changed from IPAex font to HaranoAjiFonts.3)
Temperature control in the computer server room
is important to prevent failure. The latest Cacti software4) was installed in the server RIBFSS, which monitors the temperature of the server rooms and someexperimental rooms.
An anonymous ftp server, FTP.RIKEN.JP, is managed and operated at the RNC. Major Linux distributions are mirrored daily for the convenience of theusers, and for facilitating high-speed access. Linux distributions Alma Linux, Rocky Linux, and SpringdaleLinux, which are binary compatible to the Red Hat
Enterprise Linux, were newly archived in the server in
2021.
We have been operating approximately 70 units ofwireless LAN access points in RNC for the convenienceof experiments and daily work. Two units of new wireless LAN access points (WAPM1266R) were installedin the experimental hole of the Linac Bldg. in 2021.5)
References
1) T. Ichihara et al., RIKEN Accel. Prog. Rep. 54, 120(2021).
2) https://linux.web.cern.ch/ .
3) https://github.com/trueroad/HaranoAjiFonts .
4) https://www.cacti.net/ .
5) https://ribf.riken.jp/comp/net/wireless.html .

Fig. 1. Conﬁguration of the RIBF Linux cluster.
∗1

RIKEN Nishina Center- 102 -

1

II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

CCJ operations in 2021
S. Yokkaichi,∗1 H. En’yo,∗1 T. Ichihara,∗1 W. Nakai,∗1 and Y. Watanabe∗1Overview
The RIKEN Computing Center in Japan (CCJ)1)
commenced operations in June 2000 as the largest oﬀsite computing center for the PHENIX2) experimentbeing conducted at RHIC. Since then, CCJ has been
providing numerous services as a regional computing
center in Asia. We have transferred several hundred
terabytes of raw data ﬁles and nDST a) ﬁles from theUSA.
Many analysis and simulation projects are being
conducted at CCJ, which are listed on the web page
http://ccjsun.riken.jp/ccj/proposals/. As of December 2021, CCJ has contributed to 46 published papers and 45 doctoral theses.
Computing hardware and software
The network conﬁguration and computing hardware(nodes) and software (OS, batch queuing systems,
database engine, etc.) are almost the same as describedin the previous APR3) and the number of servers are
summarized in the Table 1. One of disk servers, which
had a 13-TB built-in RAID, was replaced by one with
39 TB in November. The main server (users’ home directory, NIS, DNS, and NTP) and SAS RAID will be
replaced in March 2022. In 4Q 2021, Hewlett-Packerd
hardware was in short supply, owing to the “semiconductor crisis.” Thus, we gave up to purchase built-in
RAID as the previous server had. In addition, we operate two dedicated servers for the RHICf group4) andtwo servers for the J-PARC E16 group5) in order tomaintain their dedicated compilation and library environments along with some data.
Table 1. Number of servers and disk sizes.
main server
login serverinteractive server
calculation server 1
calculation server 2
work disk server(replaced in Nov.)
DB server
library(AFS) servertransfer server
docker test server

number disk (TB)
(type)
1
21 + 13
DL380eG82DL145G3/DL20G9
3-/DL320G6/DL160G9
16
10
DL180G6
8
20
DL180G6
2
26 / 13
DL180G9/DL180G6→39→DL385G10
1
1
DL145G3
1
9DL180G6
2
12 / 39 DL180G9/DL380G10
1
DL20G9a)Table 2. Number of malfunctioning HDDs in HP servers
during 2011–2021.
Type (TB) total 21 20 19 18 17 16 15 14 13 12 11
SATA (1.0) 192 10 9 8 16 18 8 14 11 16 20 9
SATA (2.0) 120
9 5 10 2 10 2 10 0 2 5 4
SATA (4.0)
26
2 0 0 0 - - - - - - SATA (6.0)
20
0 0 0 0 - - - - - - SAS (0.15)
38
5 3 6 3 1 5 3 2 0 1 1
SAS (0.3)
26
2 1 2 0 1 0 1 1 0 0 1

Joint operation with ACCC/HOKUSAI
CCJ and the RIKEN Integrated Cluster of Clusters(RICC) have been jointly operated since July 2009. In
April 2015, a new system named “HOKUSAI Greatwave”8) was launched by RIKEN Advanced Centerfor Computing and Communication (ACCC), and thejoint operation with CCJ continued, with the inclusionof a new hierarchical archive system in which approximately 1060 TB of CCJ data were stored as of December 2021. A breakdown of the data is presented inTable 3. Data transfer from J-PARC was performedin February and June during an experiment of over 18
and 12 days, and 28 and 46 TB of raw data were transferred to CCJ, respectively. The data were archived ina tape device in Hokusai.8)
Table 3. Tape usage in Hokusai as of December 2021.
user

total PHENIX KEK/ RHICf user-leveloﬃcial J-PARC
archivesize (TB) 1059
749
171
8
130

References

We operate 25 computing nodes, and 328 (= 8 × 17
nodes + 24 × 8 nodes ) jobs can be processed simultaneously by these computing nodes using a batch queu∗1

ing system, LSF 9.1.3.6) Table 2 lists the number ofmalfunctioning SATA or SAS disks in the HP servers,
namely, computing nodes and NFS/AFS servers. The
OS of nine calculation nodes and of one interactive
server were upgraded to SL7.9 from SL5.37) in October, and the remainder will be upgraded in March
2022.
Three 10-KVA UPSs are operated as power supplies
for these CCJ nodes and their batteries were replacedin March.

RIKEN Nishina Centerterm for a type of summary data ﬁles in PHENIX- 103 -

1) http://ccjsun.riken.jp/ccj/ .
2) http://www.phenix.bnl.gov/ .
3) S. Yokkaichi et al., RIKEN Accel. Prog. Rep. 54, 121(2021).
4) Y. Itow et al., arXiv:1409.4860 (Proposal).
5) S. Yokkaichi, in this report.
6) https://www.ibm.com/docs/en/spectrum-lsf/ .
7) http://www.scientificlinux.org/ .
8) https://i.riken.jp/en/supercom/ .

1

III. RESEARCH ACTIVITIES II(Material Science and Biology)

1. Atomic and Solid State Physics (Ion)III-1. Atomic & Solid State Physics (Ion)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Crystal growth and β-NMR studies of the simplest copper oxide(CuO)
H. Yamazaki,∗1 A. Gladkov,∗1 X. G. Zheng,∗2 A. Yamamoto,∗3 Y. Ichikawa,∗1 A. Takamine,∗1 H. Nishibata,∗4
K. Asahi,∗1 K. Kawata,∗1,∗5 K. Imamura,∗1 M. Tajima,∗1 K. Tsubura,∗1 and H. Ueno∗1
The signiﬁcance of oxide-based systems both in technology and basic science has been strongly emphasized.
Particularly, the strong electronic correlation caused by
Coulomb repulsion in the Cu-O framework is recognized
to play a key role in describing many unconventional
experimental observations. Even now, however, the origin of the high-Tc superconductivity in copper oxides
remains unclear. Meanwhile, another novel function ofcopper oxide was found about twenty years ago. The
simplest copper oxide, CuO (cupric oxide, tenorite),
which crystallizes in a monoclinic structure with thespace group C2/c, was found to show a cross-correlationeﬀect in one of its magnetically ordered states in the temperature range between 213 K and 230 K.1) In this socalled “multiferroic” phase, unconventional ferroelectricity emerges with the emergence of speciﬁc magnetic ordering.2) The theoretical proposal by Katsura-NagaosaBaratzky argues the microscopic polarization of electronsat oxygen sites in association with a noncollinear magnetic structure;3) however, no microscopic evidence ofthe polarization has been demonstrated so far.
CuO single crystals were grown in quartz tubes using the chemical vapor transport method (Fig. 1).4) Using 17 O-rich oxygen gas, single crystals of CuO with theoxygen sites substituted with 17 O nuclei (S = 5/2) werealso prepared for comparative 17 O-NMR experiments.
A large plate-like crystal was typically ∼10 mm in diameter. SEM images indicate that each crystal is composed of twinned single crystals, in which we can in manycases identify two diﬀerent rotated images of structural
domains with their c-axes nearly perpendicular to thesample plane. X-ray diﬀraction measurements were carried out to check the quality of the samples in detail.
Magnetic susceptibility measurements showed that themagnetic phase transition temperatures and sharpnessof the transitions were in good agreement with the literature data for high-quality CuO single crystals.
We performed β-NMR/NQR experiments using a 21 O
(S = 5/2) beam, where we used the nuclear reaction 22 Ne + 9 Be → 21 O + X for a 22 Ne energy of
70 MeV/nucleon with 250 particle nA. The β-rays emitted from the implanted 21 O nuclei were detected withplastic scintillator telescopes located above and below
the sample crystal. The resonance frequency can be derived from the peak or dip observed in the spectrum of
the up/down ratio of the β-ray count. We were allocatedthe following accelerator beamtime at the E6 (RIPS)
beam port in the RIBF facility: (1) 114 h [2–7 September, 2016] and (2) 111 h [10–14 March, 2020]. The former
was mainly used to evaluate the nuclear magnetic moment μ and the nuclear quadrupole moment Q inherent
to 21 O. Typical NQR spectra are shown in Fig. 2. The
following results were obtained: μ = 1.5118 ± 0.0012
and Q = 17.4 ± 2.4 emb. Based on this achievement,
during the latter beamtime, we attempted to obtain the
β-NMR spectra for the 21 O nuclei implanted in CuO
crystals at room temperature. This time, we could notobserve a clear NMR signal of 21 O in CuO, although
our experiments were performed for CuO in the paramagnetic phase (T > 230 K). It is considered that themagnetic low-dimensional correlations, which remain up
to ∼550 K,5) possibly aﬀected the polarization of the implanted 21 O, leading to a reduction of the polarization.
At the next beam time allocated in FY2022, we will also
have to check some technical issues such as the degree ofbeam collimation and the thickness of the CuO crystal.

Fig. 1. Conceptual diagram of the chemical vapor transport
method for the growth of CuO crystals.

Fig. 2. NQR spectra of 21 O in TiO2 reference crystals.

∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
Department of Physics, Saga University
Graduate School of Engineering and Science, Shibaura Institute of Technology
Department of Physics, Kyushu University
Center for Nuclear Study, University of Tokyo

References
1) X. G. Zheng et al., J. Phys. Soc. Jpn. 70, 1054 (2001).
2) T. Kimura et al., Nat. Mater. 7, 291 (2008).
3) H. Katsura et al., Phys. Rev. Lett. 98, 027203 (2007).
4) X. G. Zheng et al., J. Appl. Phys. 92, 2703 (2002).
5) T. Shimizu et al., J. Phys. Soc. Jpn. 72, 2165 (2003).

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III-1. Atomic & Solid State Physics (Ion)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Single-event damages on SiC junction barrier Schottky diodes
M. Iwata,∗1 M. Takahashi,∗1 and H. Shindou∗1
Silicon carbide (SiC) power devices are being applied
to various ﬁelds because of their excellent properties suchas high breakdown voltage and high frequency. Although
Si power devices have been used for space applications,
there is an urgent demand for SiC power devices for realizing future advanced missions. The mechanisms of
single-event eﬀects (SEEs) on SiC devices caused byheavy ions are yet to be well understood, and there is
no product that is suﬃciently resistant against space radiation. In this study, irradiation test results for SiC
diodes that use a junction barrier Schottky (JBS) structure, as shown in Fig. 1 are reported. This structure is
widely used in commercial products because of its lower
oﬀ-state leakage current.1)
In this study, the charge collection characteristics ofthe 1200 V commercial SiC JBS diodes were measured
by the EPICS system2) during irradiation. This systemenabled measurements of higher signal levels of ∼50 nC,
which is suﬃcient for detecting the sign of the singleevent burnout (SEB). Irradiation tests were performedby bombarding 136 Xe ions (544 MeV) perpendicularly
at the test device surface at room temperature in air
using RIKEN RILAC2 in combination with the RIKEN
Ring Cyclotron (RRC). The range of ions was calculated
as 30.0 μm in SiC by the SRIM code;3) this range is
suﬃcient to reach the active layer of the samples.
Figure 2 shows the collected charge spectra at diﬀerent reverse voltages, VR . The cross marks represent the
maximum collected charge for each spectrum. The total
counts of the spectra at VR = 240 V increased signiﬁcantly, especially at lower charges, and therefore, it did
not show the accurate number of the ion-induced charge.
This result indicates that a permanent leakage path was
created at this voltage. The maximum collected charge
did not reach the order of nanocoulombs, which is observed as the sign of the SEB in Si power metal-oxidesemiconductor ﬁeld-eﬀect transistors (MOSFETs). This

Fig. 2. Collected charge spectra taken by the EPICS system.

is attributed to the higher electron-hole pair creation energy of SiC compared to that of Si and the lack of acharge ampliﬁcation mechanism like the parasitic bipolartransistor in MOSFETs in the JBS diodes. If a leakage
path was created by local heating, a considerably large
current would ﬂow instantaneously in a tiny area. Transient current measurement is required to clarify the failure mechanism because charge collection measurements
cannot check the time distribution of the collection process.
The peaks of the spectra shifted to the higher charge
level, and the charge distribution was gradually divided
into two with an increase in VR . It is assumed that thesetwo peaks appear based on whether the heavy ions passthrough the Schottky interface or the p+ region because
only one peak is observed in our previous experiment of
the planar type SiC-SBD devices.4) The ratio of thesepeak levels indicate that the charge level of the ﬁrst
peak corresponds to the case wherein the incident ion
passes through the p+ region, while the second peaklevel corresponds to the one wherein the incident ion
passes through the Schottky region. Further, it is assumed that the charge generated by ions passing throughthe Schottky region is ampliﬁed further by impact ionization because the ﬂuctuation in the positions of thesecond peaks are larger than those of the ﬁrst peaks.
Therefore, it might be possible to increase the voltage at
which the leakage path is formed by adjusting the size,
pitch, and doping concentration of the p+ region suchthat the electric ﬁeld applied to the Schottky region isrelaxed.
References

Fig. 1. Cross-sectional structure of JBS diodes.
∗1

Research and Development Directorate, Japan Aerospace Exploration Agency

1) X. She et al., IEEE Trans. Ind. Electron. 64, 10 (2017).
2) S. Kuboyama et al., IEEE Trans. Nucl. Sci. 39, 6 (1992).
3) J. F. Ziegler et al., SRIM: the Stopping and Range of Ionsin Matter, http://www.srim.org/ .
4) S. Kuboyama et al., IEEE Trans. Nucl. Sci. 53, 6 (2006).

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1

III-1. Atomic & Solid State Physics (Ion)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Analysis of diﬀraction patterns of laser spots in dual-microbeams
generated by glass capillary optics for future biological use
K. Inayoshi,∗2,∗1 T. Ikeda,∗1,∗2 K. Ono,∗2,∗1 Y. Kozu,∗2 K. Sangu,∗2,∗1 Y. Hikima,∗2,∗1 and W. -G. Jin∗2
We have developed an ion microbeam irradiation system employing tapered glass capillary optics for biological use in the RIKEN Pelletron accelerator facility in the
Nishina R&D Building. Glass capillary optics is a simple
and reliable tool to generate ion/laser microbeams,1–3)
where both the ion and laser can be extracted from thecapillary outlet simultaneously. When an end window is
installed at the outlet, the microbeams can be applied totargets in the liquid/gas phase. At the microbeam irradiation port, cultivated living cells in a liquid medium orparts of small living insects in air are targets.4) The corresponding irradiation lengths are expected to be a few
micrometers or submillimeters for liquid and air, respectively. The ion species are H and He ions with energies
of a few MeV so that the range in water (approximately
100 and 30 μm for H and He ions, respectively) approximately corresponds to the sizes of the biological targets.
The maximum linear energy transfer (LET) is selected to
be 80 or 240 keV/μm for H or He ions, respectively, which
is suﬃciently high to cause serious damage to DNA. In
this ion irradiation, any mishits should be avoided because such a single ion hit may cause an undesirable effect on the living target. To realize precise ion targeting,a laser microbeam extracted from the same capillary isused as a laser sight of a μm-order scale. The laser microspot on the target consists of a center spot and higher
order rings of diﬀraction, which are diﬀerent from thoseof Fraunhofer diﬀraction. The higher order rings deteriorate the sharpness of the laser spot, which then reduces
the accuracy of the laser sight. In this study, to understand the mechanism of ring generation, the brightnessof each ring was measured according to the distance fromthe capillary outlet so that the results could be discussed
based on ray tracing simulations. For this purpose, thedistance range was selected to be in the order of 100 mm
because larger ring images can provide detailed information of light trajectories. The end window was not
introduced to obtain clear ring images.
Figure 1 shows the setup at Toho University. A visible
light laser with a wavelength λ = 488 nm from a source(Photochemical Research Associates Inc. LA15R) entered a glass capillary with an outlet diameter of 62 μm,
as shown in Figs. 2(a)–(c). The width of the input beam
was approximately 570 μm at the full width at half maximum (FWHM).2) Laser spots on a transparent screen
were recorded by a digital camera for a distance L ranging from 120 to 300 mm, where L was deﬁned as the
distance between the capillary outlet and the screen. An
ND ﬁlter was used to reduce the intensity of the input
beam so that rings of a lower brightness were clearly∗1∗2

RIKEN Nishina Center
Department of Physics, Toho University

Fig. 1. Experimental setup to obtain diﬀraction patterns oflaser spots. The distance L ranged from 120 to 300 mm.

Fig. 2. (a) Capillary inlet, (b) capillary outlet with a diameter of 62 μm, (c) the downstream view of the outlet, (d)a typical laser spot on the screen, and (e) relative densityof the brightness as a function of L.

recorded with an 8-bit dynamic range of the image ﬁles.
A typical laser spot image is shown in Fig. 2(d) alongwith the deﬁnition of the center spot (0th region) andhigher order rings (1st, 2nd, and 3rd rings). The total
brightness of each component (0–3) was obtained by integrating over the area, and the brightness density wascalculated by dividing by the area. To compare the Ldependence of each density, the density was normalized
by that at L = 120 mm, as shown in Fig. 2(e) with adashed line corresponding to L−2 . The density for the
3rd ring (#3) was found to follow the L−2 curve; thatis, #3 was emitted from a point-like source, which may
be owing to reﬂection at the inner surface around theoutlet. Although curve #0 was expected to be constantbecause it was the component without any reﬂection inside the capillary, the curve was found to depend on L.
The obtained behaviors of the curves will be comparedwith ray tracing simulation results.
References
1) T. Ikeda, Quantum Beam Sci. 4(2), 22 (2020).
2) W.-G. Jin et al., J. Phys. Soc. Jpn. 84, 114301 (2015).
3) S. Kawamura et al., J. Phys. Soc. Jpn. 89, 055002 (2020).
4) T. Ikeda et al., Nucl. Instrum. Methods Phys. Res. B 470,
42 (2020).

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12. Atomic and Solid State Physics (Muon)

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

μSR study on the low-temperature anomaly in triangular-lattice
antiferromagnet CuOHCl

Recently we found a new magnetodielectric
triangular-lattice compound CuOHCl. It showed geometric frustration and antiferromagnetic transition at
TN = 11 K. Then we observed an anomaly below ∼5 K,
with magnetic susceptibility and speciﬁc heat change,
as well as an increase in the dielectric constant.1)
Our μSR experiments on powder sample showed additional precession frequency for T < 5 K with an increase in its value. Considering the observed resultsof i) the small speciﬁc heat anomaly at 5 K; ii) theapparently stable antiferromagnetic spin arrangement
revealed by neutron diﬀraction experiments; iii) thecontinuity of the other muon precession frequencies,
and iv) the dielectric increase below 5 K, it is reasonable to assume a multiferroic transition occurring in
CuOHCl.1) However, the mechanism for this multiferroic-like state is unclear and further study is demanded. Since we succeeded in growing single crystals,
we proposed the use of single crystals for μSR experiments. Related experiments along three crystal-axis
directions were planned, but unfortunately due to limited beam time, only a part of them were performed.
As shown in Fig. 1, we observed an additional muon
spin precession frequency below T ∼ 5 K, which suggests that the low-temperature change is an intrinsic
property in CuOHCl and further detailed experiments
using the single crystals should be planned.
A new result has been obtained from the present
experiment. LF-μSR measurements as shown in Fig. 2
suggested a dynamical nature for the low-temperaturestate below ∼5 K.
In summary, we performed ZF-μSR and LF-μSR on
a newly found magnetodielectric compound CuOHCl
using high-quality single crystals.
The intrinsic
nature of the low-temperature phase below T <∼5 K has been veriﬁed. Further, persisting spin
ﬂuctuations have been found to exist in the lowtemperature phase. There are only few experimental realizations of triangular-lattice, in special, multiferroic systems in slightly nonstoichiometric oxides,
i.e., CuFeO2 (S = 5/2), CuCrO2 /AgCrO2 (S = 3/2)
and RbFe(MoO4 )2 (S = 5/2).2) The present systemprovides a precious structurally two-dimensional triangular lattice showing quantum spin-related properties
with perfect chemical stoichiometry.

∗1∗2

Precession frequency (MHz)I. Yamauchi,∗1 X. G. Zheng,∗1 and I. Watanabe∗2
frq1
frq2
frq3
frq4
frq5
frq6
frq7
frq8

8

6

4

2

0

0

2

4

6

8

10

12

T (K)
Fig. 1. Muon spin precession frequencies in single crystal
CuOHCl.

Fig. 2. μSR asymmetries in longitudinal external ﬁelds for
single crystal CuOHCl.

References
1) X. -G. Zheng et al., Phys. Rev. Mater. 2, 104401 (2008).
2) Y. Tokura, Rep. Prog. Phys. 77, 076501 (2014).

Department of Physics, Saga University
RIKEN Nishina Center- 109 -

1

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Zero-ﬁeld μSR measurements to investigate the magnetic ordering of
Nd2 Ru2 O7
U. Widyaiswari,∗1,∗2 H. Sakai,∗3 H. Hanasaki,∗3 D. P. Sari,∗4 B. Kurniawan,∗2 and I. Watanabe∗1,∗2
Pyrochlore oxides have a general formula A2 B2 O7 ,where A and B represent trivalent rare-earth andtetravalent transition metal ions, respectively. The pyrochlore oxides are constructed from the interpenetrating corner-sharing tetrahedral lattices of A and B sites.1)
The spins at vertices of the tetrahedral lattice are magnetically frustrated and can lead to various novel physical properties.1) The magnetic frustration, competition
between the exchange and dipolar interactions, and crystal electric ﬁeld eﬀect control the nature of the groundstate of pyrochlore oxide.2)
Pyrochlore ruthenate, A2 Ru2 O7 , has Ru 4d4 electrons
in the low-spin state with S = 1. In Nd2 Ru2 O7 , both Nd
and Ru are magnetic ions. The magnetic ground stateof Nd2 Ru2 O7 is an interesting research topic because we
can investigate the coupling between Nd and Ru spins
by comparing it with that of Nd2 Ir2 O7 known to have
Ir4+ ions with 5d electrons, and they show ferromagnetic coupling between Nd and Ir spins.3) Nd2 Ru2 O7
showed magnetic anomalies around 1.8 K, 21 K, and
146 K.4,5) At 1.8 K and 146 K, the magnetic transition
were attributed to the ordering of Nd and Ru spins, respectively.4) The origin of the anomaly at 21 K remains
debatable.4,5) Accordingly, we investigated the magnetic properties of Nd2 Ru2 O7 using various measurement techniques such as muon spin relaxation (μ+ SR)
measurement.
The polycrystalline Nd2 Ru2 O7 was prepared using
a solid-state reaction method.
μ+ SR experiments
were carried out on an HiFi spectrometer at the ISIS,
Rutherford Appleton Laboratory in the UK and on the
ARTEMIS spectrometer at Material and Life Science
Experiment Facility (MLF), J-PARC in Japan. We measured the μ+ SR time spectra in the zero-ﬁeld (ZF) condition at a temperature range of 2–150 K on HiFi, whereas
the time spectra below 5 K down to 0.3 K were obtainedby using Heliox cryostat on ARTEMIS.
The oscillations do not occur in the ZF-μ+ SR time
spectra of Nd2 Ru2 O7 , as shown in Fig. 1(a). However,the decreases in the initial asymmetry at t = 0 was observed by decreasing the temperature indicating the appearance of a magnetic ordered state. The time spectra
were analyzed using two exponential functions as
A(t) = A1 exp(−λ1 t) + A2 exp(−λ2 t)

∗2
∗3
∗4

rates.
The appearance of Ru ordering at 146 K is conﬁrmed
from a sharp peak observed in λ2 (T ), as shown in the inset of Fig. 1(b). λ1 decreases below 50 K with decreasing
temperature and shows a dip around 30 K; this anomaly
is not related to the anomaly at 21 K observed fromthe DC susceptibility measurement, which was expectedfrom the magnetic property of Nd3 RuO7 .6) Therefore,
the anomaly around 30 K in the temperature dependence of λ1 could be related to the short-range magnetic
interaction of Nd spins. The long-range ordering of Nd
spins was expected to appear around 2 K, as indicated bya peak in the temperature dependence of λ1 . Currently,
we cannot determine the magnetic interaction between
Nd and Ru spins. Further investigation using continuous muon beam is required to determine the internalﬁeld as a function of temperature that occurred in thissystem.

(1)

The ﬁrst and second components of Eq. (1) correspondto the slow and fast components of muon spin relaxation,
respectively, and λ represents the muon-spin relaxation∗1

Fig. 1. (a) ZF-μ+ SR time spectra of Nd2 Ru2 O7 . (b) Temperature dependence of λ1 ; the inset shows the temperature dependence of λ2 .

RIKEN Nishina Center
Department of Physics, Universitas Indonesia
Department of Physics, Graduate School of Science, Osaka
University
Innovative Global Program, Shibaura Institute of Technology

References
1) J. S. Gardner et al., Rev. Mod. Phys. 82, 53 (2010).
2) B. C. D. Hertog et al., Phys. Rev. Lett. 84, 3430 (2000).
3) R. Asih et al., J. Phys. Soc. Jpn. 86, 024705 (2017).
4) S. T. Ku et al., J. Phys. Condens. Matter 30, 155601(2018).
5) M. W. Gaultois et al., J. Phys. Condens. Matter 25,
186004 (2013).
6) U. Widyaiswari et al., Mater. Sci. Forum 1028, 3 (2021).

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1

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Spin dynamics of Nd2 Pt2 O7 at 0.3 K observed by longitudinal-ﬁeld
μSR measurements
U. Widyaiswari,∗1,∗2 Y. S. Chen,∗3 J. Kung,∗4 B. Kurniawan,∗2 L. J. Cheng,∗3 and I. Watanabe∗1,∗2
Pyrochlore oxides, A2 B2 O7 (A = trivalent rare-earth
ion and B = tetravalent transition metal ion), are constructed from the interpenetrating corner-sharing tetrahedra units of A and B sites.1) The spins at the verticesof the tetrahedra units are magnetically frustrated andlead to various novel physical properties, such as spinglass, spin-ice, and spin-liquid states.1) In Nd-based pyrochlores, Nd2 B2 O7 , an Ising-type magnetic interaction
occurs among the Nd spins with an easy local axis inthe 111 direction; therefore, the spins point either into or out from the center of the tetrahedra units.2–4)
In Nd2 B2 O7 with a nonmagnetic B ion, such as Zr,
Hf, and Sn, an Nd spin static ordered state is accompanied by spin ﬂuctuations.2–4) This phenomenon canbe explained by a spin fragmentation model based on
the spin-wave theory.5,6) Compared to Nd2 B2 O7 (B =Zr, Hf, Sn) pyrochlores that have either full or empty dorbitals, Nd2 Pt2 O7 has a nonmagnetic Pt4+ ion with a
5d6 orbital in a low-spin state, with a conﬁguration oft2g 6 eg 0 . The empty eg orbital can aﬀect the exchangeinteraction among the Nd spins and change the spin
dynamics of Nd2 Pt2 O7 .
Previous muon spin relaxation (μSR) measurements
on Nd2 Pt2 O7 conducted at the Paul Scherrer Instituteshowed that the initial asymmetry at t = 0 neither oscillated not decreased in the time spectra.7) It was inferred that the spin ﬂuctuations smeared out the signal
from the static ordered state, suggesting the occurrenceof spin fragmentation. We observed an ordered state indicated by a sharp peak at approximately 1.5 K in thetemperature dependence of the muon-spin relaxation
rate, λ.7) Persistent spin ﬂuctuations were expected tooccur from the observation of the remaining λ down to
0.3 K.7) Accordingly, we conducted measurements byusing a pulsed muon beam suitable for observing longtime relaxation and investigating the spin dynamics ofNd.
Polycrystalline Nd2 Ru2 O7 was prepared by mixing
the oxides precursors at 4 GPa and 1200◦ C, following the conditions obtained in a previous study,8) using a high-pressure apparatus at the Department ofEarth Sciences, National Cheng Kung University, Taiwan.9) μSR experiments were carried out on ARGUS
spectrometer at the ISIS, Rutherford Appleton Laboratory, UK. We measured the μSR time spectra in thelongitudinal-ﬁeld (LF) condition at 0.3 K.
The LF-μSR time spectra are shown in Fig. 1(a). At
∗1
∗2
∗3
∗4

RIKEN Nishina Center
Department of Physics, Universitas Indonesia
Department of Physics, National Cheng Kung University
Department of Earth Sciences, National Cheng Kung University- 111 -

Fig. 1. (a) LF-μSR time spectra of Nd2 Pt2 O7 at 0.3 K. (b)Field dependence of muon-spin relaxation rate at 0.3 K.

3850 G, the time spectrum shows a relaxation, indicating the persistent spin ﬂuctuation at 0.3 K. The baseline
shifting in the time spectra is attributed to the background signal when applying an external magnetic ﬁeld
because it also occurs in the paramagnetic state.
The time spectra were analyzed using two exponential functions:A(t) = AG exp(−(σt)2 /2) + AE exp(−λt)(1)

The ﬁrst and second components of Eq. (1) are
Gaussian-type and exponential-type components, respectively. This analysis function has been used to analyze the time spectra in the zero-ﬁeld condition, where
the Gaussian-type component occurs at early time spectra. For consistency, we kept the analysis functions
to treat the time spectra. The Gaussian-type component was related to the static ordered state of Nd spins,
whereas the exponential one corresponded to the spin
dynamics of Nd. Fig. 1(b) shows that no signiﬁcantchange in λ occurs by applying an external ﬁeld up
to 3850 G. This suggests that the muon spin is depolarized by a strong spin ﬂuctuation that occurs evenat 0.3 K. Accordingly, from the previous and current
μSR measurements, we suggest that the Nd spins are
fragmented into two parts: a static ordered state andﬂuctuating spins.
References
1) J. S. Gardner et al., Rev. Mod. Phys. 82, 53 (2010).
2) J. Xu et al., Phys. Rev. B 94, 064425 (2016).
3) V. K. Anand et al., Phys. Rev. B 95, 224420 (2017).
4) A. Bertin et al., Phys. Rev. B 92, 144423 (2015).
5) S. Petit et al., Nat. Phys. 12, 746 (2016).
6) O. Benton, Phys. Rev. B 94, 104430 (2016).
7) U. Widyaiswari et al., submitted.
8) H. R. Hoekstra, F. Gallagher, Inorg. Chem. 7, 2553
(1968).
9) F. B. Hua et al., Terr. Atmos. Ocean. Sci. 23, 647 (2012).

1

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Novel quantum spin liquid state in Ba3 ZnRu2 O9
Y. Yasui,∗1 D. P. Sari,∗2 I. Watanabe,∗3 and I. Terasaki∗4
We discovered a novel type of quantum spin liquidin Ba3 ZnRu2 O9 , which has a hexagonal lattice of Ru5+
dimers.1,2) In the temperature (T ) dependence of themagnetic susceptibility (χ) of Ba3 ZnRu2 O9 , no trace of
the Curie tail or glassy behavior has been detected down
to 50 mK. We studied the magnetic behavior of the Nbdoped system, Ba3 Zn(Ru1-y Nby )2 O9 , where Nb5+ (4d)0
is a non-magnetic ion that disturbs the formation of the
Ru5+ dimer. The χ-T curves of the Nb-doped system
also show no trace of the Curie tail at low temperatures, indicating that the local Ru5+ spin induced by
Nb-doping does not act like a free spin. The spin liquidstate of Ba3 ZnRu2 O9 has been found to be robust by
impurity doping.
To study magnetic dynamics at low temperatures, we
attempted to perform ZF-μSR and LF-μSR measurements on three samples of Ba3 Zn(Ru1-y Nby )2 O9 (y = 0,0.06, and 0.12), down to 0.3 K. First, we performed ZFμSR and LF-μSR measurements on Ba3 ZnRu2 O9 using
ARGUS. Figure 1 shows the ZF-μSR time spectra obtained at various temperatures for Ba3 ZnRu2 O9 . The
muon-precession behavior with small amplitude was observed below ∼35 K. The initial asymmetry began dropping below ∼100 K and the relaxation rate λ2 rapidly
increased at ∼100 K with decreasing T . In contrast, theinternal ﬁeld started developing from 80 K and saturated
below 3 K at 450 G. These results simply indicate theappearance of long-range magnetic ordering with a tiny
long-range ordered moment; however, a spin-liquid stateis expected in this sample, as suggested from other studies. Nevertheless, the results of LF-μSR measurementssuggest that the internal ﬁeld is 500 G with a 40% volume fraction. These results indicate that the spin is still
dynamic at 2 K and slows at 0.3 K. The spin system
coexists with an antiferromagnetic long-range state withtiny ordered moments and dynamical spin liquid state.
Next, we performed similar measurements on
Ba3 Zn(Ru1-y Nby )2 O9 with y = 0.06 and 0.12. However, owing to issues with the dilution refrigerator, we
performed ZF-μSR and LF-μSR measurements at temperatures above 2 K on the sample with y = 0.06 using ARGUS. Moreover, we performed ZF-μSR measurements above 10 K on the sample with y = 0.12 using
EMU. Although the temperature range was limited, we
observed similar decreasing behavior in the initial asymmetry at ∼100 K with decreasing T for y = 0.06 and0.12. However, the muon-spin precession behavior was
not observed in the measured temperature region for y =0.06 and 0.12, which may be due to the randomness eﬀect
by Nb-doping. Then, the overall scheme of the magnetic

(b)
(c)
(a)
(d)

Fig. 1. (a) ZF-μSR time spectra of Ba3 ZnRu2 O9 measured atvarious temperatures. Temperature dependence of (b) the
initial asymmetry Atotal, (c) relaxation rate λ2 , and (d)internal ﬁeld of Ba3 ZnRu2 O9 deduced from the analysis
of ZF-μSR time spectra.

behavior was found to be similar for all samples with y= 0, 0.06 and 0.12.
Using these results, we consider a novel scenario in
this system wherein a spin liquid state accommodates
long-range magnetic ordering with a tiny ordered moment. When Nb substitution is increasing, the coexistence of a spin-liquid state with long-range magnetic
ordering is suppressed by the random disconnection of
the frustrated magnetic path, and magnetic ordering becomes smeared. Thus, detailed ZF-μSR and LF-μSR
measurements are required, along with other measurements, for Ba3 ZnRu2 O9 (y = 0, 0.06, and 0.12).
Recently, Tanaka and Hotta reported a theoretical
study based on the intriguingly characteristics of the
Ba3 MRu2 O9 family.3) They adopted Heisenberg exchange interactions, J, J  , J  , and biquadratic interaction, B. Using a phase diagram with reasonable
J, J  , J  , and B parameters, they proposed the parameter regions of novel magnetic states such as thenonmagnetic singlet, Ferroquadrupolar nematic BoseEinstein condensation (FQ-p-BEC), AFM-solid, AFMBEC-coexistence, etc. states. It is signiﬁcantly interesting in the correspondence between the theoretically proposed novel magnetic states and the experimental resultsof present materials.
References

∗1
∗2
∗3
∗4

Department of Physics, Meiji University
College of Engineering, Shibaura Institute of Technology
Meson Science Laboratory, RIKEN
Department of Physics, Nagoya University

1) I. Terasaki et al., J. Phys. Soc. Jpn. 86, 033702 (2017).
2) T. D. Yamamoto et al., J. Phys. Condens. Matter 30,
355801 (2018).
3) K. Tanaka, C. Hotta, Phys. Rev. B 101, 094422 (2020).
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1

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

μ+ SR Knight shift of the Mott insulator κ-(ET)4 Hg2.78 Cl8D. P. Sari,∗1,∗2 Y. Cai,∗3,∗4 M. -V. deToro Sanchez,∗5,∗4 K. Kojima,∗3,∗4 I. Watanabe,∗2 Y. Ishii,∗1 and
H. Taniguchi∗6
The hole-doped organic superconductor κ(ET)4 Hg3-δ Br8 , (κ-HgBr), where δ = 11% and ET= bis (ethylenedithio) tetrathiafulvalene, has been the
key to bridge the knowledge gap between half-ﬁlled organics and doped cuprate systems, as the well-known
Mott-Hubbard model in the laboratory. Usually, organic superconductivity appears under pressure when
the ratio of Hubbard interaction and bandwidth, U/W,
is larger than 1. Nonetheless, the triangular lattice oforganics, unlike the square lattice in cuprates, provides
extensive geometrically control through nearest, t, andnext-nearest, t , transfer integrals between sites. In thecase of geometrically triangular frustration (t ∼ t ),the Mott insulating state cannot be magnetically ordered down to the miliKelvin (mK) order, becoming
a Mott quantum spin liquid.1) Speciﬁcally, both holedoped superconductors have a region corresponding toa strange metallic state at which resistivity exhibits alinear temperature dependence, ρ ∝ T , which is not a
Fermi-liquid (FL) behavior.1–3)
In 2015, an important model to study strange metal
was developed by Sachdev-Ye-Kitaev (SYK).4,5) It
consists of Majorana fermions with random all-toall interactions, leading to quantum information science and quantum many-body physics. Although therealization of the SYK-strange metal remains complex, Tsuji-Werner theoretically found an SYK-strange
metal region after an out-of-time-order correlation
treatment of a multi-band Hubbard model.6) In thestrange metal region, the electron behaves as a systemhaving a non-FL electronic scattering rate with ρ ∝ T .
In this region, the spin ﬂuctuates strongly while adjusting the competition between the localized spin in
the Mott insulating state and the itinerant one in the
FL state, and U/W should be close to unity, which
is known as a quantum critical point (QCP).6) Cha etal. further showed that when the itinerant spin-1/2
fermions interact via onsite U and random inﬁniteranged spin-spin interaction, the QCP appears withquantum spin liquid dynamics, identical to that of
SYK-local spin dynamics.7) On the other hand, thegrowth of antiferromagnetic spin ﬂuctuations (AFSFs)
towards low temperature without any long-range order can lead to the QCP at which a non-FL behavior
is observed, like in the heavy fermion system.1)
Our experiment8) showed that the time-reversal
∗1
∗2
∗3
∗4
∗5
∗6

College of Engineering, Shibaura Institute of Technology
RIKEN Nishina Center
SBQM Institute, University British Columbia
CMMS, TRIUMF
School of Physics and Astronomy, University of Edinburg
Department of Physics, Saitama University

symmetry is preserved in the superconducting stateof κ-HgBr down to 0.3 K, narrowing the similarity
down to that of cuprates despite the triangular lattice. To seek evidence of strong AFSFs towards theMott spin-liquid ground state, we also study the sister insulating compound, which has a diﬀerent doping
content yet slightly higher U/W than that of κ-HgBr,
κ-(ET)4 Hg3-δ Cl8 (κ-HgCl), with δ = 22%. It shows ametal-insulator transition at TMI = 20 K and ambientpressure.
The signature of strong AFSFs has been observed in
κ-HgBr, in which the temperature dependence of μ+
Knight shift, K(T ), is not proportional to that of susceptibility, χ(T ) in the low-temperature region below
50 K, unlike in other κ-type organic superconductors;
this signature is often found in heavy-fermion system.1)
One possible reason is that μ+ probes a hyperﬁne coupling constant diﬀerent from itinerant electrons in thehigh-T region and localized electrons. From the linear
part of the K -χ plot from 50 to 300 K, the hyperﬁne
coupling constant, Ahf , in κ-HgBr was reported to be
166 Oe/μB . If this deviation is a signature of such a
diﬀerent hyperﬁne coupling constant, we naively expect a larger Ahf in κ-HgCl.
We have followed the same experimental condition
to measure the μ+ Knight shift in κ-HgCl with thatof κ-HgBr.9) The measurement was performed using
DC muon beam on the NuTime spectrometer in M15
beamline, TRIUMF Canada, in a ﬁeld of 6 T. Figure 1
shows the measured μ+ SR time spectra after Fouriertransforming. From 300 down to 2 K, the central peakis gradually shifted to the positive side, and a prominent shift was detected below TMI . K(T ) follows Curie-

Fig. 1. Fourier transform of μ+ SR time spectra in the ﬁeldof 6 T in κ-(ET)4 Hg2.78 Cl8 measured at several temperatures, represented by colorful lines, from 276–2 K.

- 113 -

1

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

Weiss paramagnetic behavior well while χ(T ) has abroad peak at 70 K. From the linear region of the K -χplot above 100 K, our preliminary analysis obtained
Ahf = 230(20) Oe/μB . The value is about 40% larger
than that of κ-HgBr. Next, we are going to study thespin dynamics of κ-HgCl down to the mK order.
References
1) H. Oike et al., Nat. Commun. 8, 756 (2017).
2) B. Keimer et al., Nature 518, 179 (2015).
3) H. Taniguchi et al., J. Phys. Soc. Jpn. 76, 113709(2007).
4) S. Sachdev, J. Ye, Phys. Rev. Lett. 70, 3339 (1993).
5) A. Kitaev, J. Suh, J. High Energy Phys. 183 (2018).
6) N. Tsuji, P. Werner, Phys. Rev. B 99, 115132 (2019).
7) P. Cha et al., Proc. Natl. Acad. Sci. U.S.A. 31, 18341(2020).
8) D. P. Sari, RIKEN Accel. Prog. Rep. 54, S30 (2021).
9) K. Satoh et al., Physica B 404, 597 (2009).

2- 114 -

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

μSR study of the stabilization mechanism of antiferromagnetic state
in molecular π-d system λ-(BEDT-STF)2 Fex Ga1−x Cl4
S. Fukuoka,∗1 Y. Ito,∗1 A. Kawamoto,∗1 D. P. Sari,∗2 and I. Watanabe∗3
In some molecular conductors, the coexistence ofstrongly correlated π electrons and localized 3d spinsis realized by introducing magnetic molecules, such as−
FeCl−
4 and FeBr4 , as anion molecules. Such coexistentsystems are known as π-d systems. In π-d systems,
the magnetic interactions between strongly correlated
π electrons and localized 3d spins (π-d interaction) giverise to interesting magnetic and conducting properties.
λ-(BEDT-STF)2 FeCl4 , where BEDT-STF denotes
bis(ethylenedithio)dithiadiselenafulvalene, exhibits anantiferromagnetic ordering at 16 K.1,2) In the alloy
compound of λ-(BEDT-STF)2 Fe0.2 Ga0.8 Cl4 , an antiferromagnetic ordering is observed at 8 K. In contrast, λ-(BEDT-STF)2 GaCl4 shows no magnetic ordering down to 300 mK. These results indicate thatthe introduction of π-d interaction stabilizes the antiferromagnetic ground state. However, the stabilization
mechanism has not yet been demonstrated. This study
aims to clarify the stabilization mechanism of the antiferromagnetic ground state induced by π-d interaction.
In this study, we performed zero ﬁeld (ZF) μSR
measurements below 10 K and longitudinal ﬁeld (LF)
μSR measurements at base temperature and 10 K forλ-(BEDT-STF)2 Fe0.1 Ga0.9 Cl4 (Fe-0.1) and λ-(BEDTSTF)2 Fe0.05 Ga0.95 Cl4 (Fe-0.05), respectively.
Figure 1 shows the temperature dependence of the
ZF time spectra of Fe-0.1 and Fe-0.05. In this analysis,
we ﬁtted the time spectra by the following functions.
A(t) = A0 exp(−λ0 t) + GKT (t) + Abg ,(1)
A(t) = A1 exp(−λ1 t) + A2 cos(ωt + φ)exp(−λ2 t)(2)+ Abg ,
A(t) = A3 exp(−λ3 t) + A4 exp(−λ4 t) + Abg . (3)Here, Ai and λi denote the initial asymmetries andrelaxation rates, respectively. Abg is the backgroundcontribution derived from the muons stopped in thesample holder. G KT (t) is the Kubo-Toyabe function.
ω and φ are the precession frequency and phase ofmuon spin precession, respectively. The time spectra measured at high temperatures were ﬁtted using
Eq. (1), and those of Fe-0.1 and Fe-0.05 measured below 7 K were ﬁtted using Eqs. (2) and (3), respectively.
We conﬁrmed that the shape of the ZF time spectraof Fe-0.1 changes below 7 K, suggesting that an antiferromagnetic transition occurs around 7 K. In contrast,
no clear change was observed in the shape of the ZF
time spectra down to 1.5 K for Fe-0.05. As complemen∗1∗2∗3

Fig. 1. Temperature dependence of the ZF time spectra of(a) Fe-0.1 and (b) Fe-0.05.

tary experiments, we performed 13 C NMR measurements for λ-(BEDT-STF)2 Fe0.05 Ga0.95 Cl4 and conﬁrmed that no peak was observed in the temperaturedependence of the spin-lattice relaxation rate (1/T 1 )down to 4 K. These suggest that T N of Fe-0.05 is lower
than 4 K or does not exist and antiferromagnetic ordering is drastically stabilized in the small Fe content
region below x = 0.1. These results are consistent
with theoretical studies suggesting that the antiferromagnetic ground state is stabilized even for small
π-d interactions.3) However, our results indicate that
there exists a phase boundary between the no- andantiferromagnetic-ordered states in the low Fe content
region between x = 0 and 0.1, which is diﬀerent fromthe theoretical prediction. Detailed analysis regarding
the development of internal ﬁelds from the results of
μSR time spectra and comparison with the results oftheoretical studies are in progress.
References
1) S. Fukuoka et al., Phys. Rev. B 101, 184402 (2020).
2) S. Fukuoka et al., J. Phys. Soc. Jpn. 87, 093705 (2018).
3) H. Shimahara, K. Ito, J. Phys. Soc. Jpn. 83, 114702(2014).

Graduate School of Science, Hokkaido University
College of Engineering, Shibaura Institute of Technology
Meson Science Laboratory, RIKEN- 115 -

1

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

μSR study of Fe-substitution eﬀects on ferromagnetic ﬂuctuations in
nonsuperconducting heavily overdoped Bi-2201 cuprates
T. Adachi,∗1,∗2 Y. Komiyama,∗2 D. P. Sari,∗1,∗3 and I. Watanabe∗1

∗1
∗2
∗3

RIKEN Nishina Center
Department of Engineering and Applied Sciences, Sophia
University
College of Engineering, Shibaura Institute of Technology

Bi1.74Pb0.38Sr1.86Cu1-yFeyO6+G

22

Raw Asymmetry (%)

Hole-doped high-Tc cuprate superconductivity arises
by hole doping into a parent antiferromagnetic (AF)Mott insulator, suggesting that superconductivity is
mediated by AF spin ﬂuctuations in the underdoped
and optimally doped regimes. For the overdoped
regime, where superconductivity weakens and eventually disappears with hole doping, it has been theoretically suggested that a ferromagnetic (FM) phase exists
in the nonsuperconducting heavily overdoped regime
and competes with superconductivity.1) In fact, zeroﬁeld (ZF) μSR and transport measurements have revealed an FM order/FM ﬂuctuations in nonsuperconducting heavily overdoped La2−x Srx CuO4 2) and Bi2201.3) To understand the details of the FM ﬂuctuations, we previously performed ZF-μSR at RIKENRAL in 5% Fe-substituted Bi-2201 single crystals of
Bi1.74 Pb0.38 Sr1.88 Cu1−y Fey O6+δ . It was found that therelaxation rate of the muon spins was signiﬁcantly enhanced at low temperatures and a peak was observed
at approximately 6 K, which coincided with the onset
temperature of the hysteresis between the ZF-cooled
and ﬁeld-cooled magnetic susceptibility, TSG .4) These
results suggest the occurrence of an FM cluster spinglass state in which FM spin clusters are formed aroundFe and the random orientation of the spins between theclusters results in the formation of a spin-glass state.4)
However, the details have not yet been clariﬁed.
To further understand the Fe-substitution eﬀects on
FM ﬂuctuations, we performed ZF and longitudinalﬁeld μSR of 9.6% Fe-substituted single crystals of
Bi1.74 Pb0.38 Sr1.88 Cu1−y Fey O6+δ with y = 0.096 using
the HELIOX and VARIOX cryostats at the RIKENRAL.
Figure 1 shows ZF-μSR time spectra of the 9.6% Fesubstituted
singlecrystalsofBi1.74 Pb0.38 Sr1.86 Cu1−y Fey O6+δ with y = 0.096. At
high temperatures above 57 K, the spectra show
Gaussian-like relaxations due to nuclear dipole ﬁelds
randomly oriented at the muon site. Below 57 K, themuon spin relaxation becomes fast and an exponentiallike behavior is caused by the development of spin correlation. At 4.1 K, a muon spin precession in a short-time
region and slow relaxation in a long-time region are observed, suggesting the coexistence of a long-range magnetic order and slowly ﬂuctuating spins in a sample.
The spectra were analyzed using the following function:
A(t) = A0 exp(−λ0 t)GZ (Δ, t) +A1 exp(−λ1 t) cos(ωt + φ) + ABG . The ﬁrst, second,y = 0.096
Heavily
overdoped

20
18
T = 203 K
157 K
57 K
14 K
12 K
4.1 K

16
14
0

2

4

6

8

10

12

14

Time (Psec)
Fig. 1. ZF μSR time spectra of 9.6% Fe-substituted single crystals of Bi1.74 Pb0.38 Sr1.86 Cu1−y Fey O6+δ with y =0.096.

and third terms represent slowly ﬂuctuating component, muon spin precession component, and backgroundasymmetry, respectively. λ0 was found to exhibit a peakat approximately 12 K, which almost coincides with
TSG determined from magnetic susceptibility.4) The internal ﬁeld at the muon site, Bint , was estimated from ωas ∼92 G, which is comparable to Bint ∼100 G obtainedfor overdoped Bi-2201, in which an incommensurate AForder is formed.5) The magnetic volume fraction was estimated from the A0 at the base temperature as ∼33%,
suggesting the coexistence of long-range ordered andslowly ﬂuctuating regions.
The present results suggest that 9.6% Fe substitution forms a long-rage magnetic order, which is not observed in a 5% Fe-substituted sample. Accordingly, theFM ﬂuctuations are probably stabilized by the Fe substitution. Concurrently, considering the similar valuesof Bint of the heavily overdoped and overdoped5) samples, an incommensurate AF order might also occur inthe heavily overdoped Bi-2201. How the AF and FM
order/ﬂuctuations coexist in the heavily overdoped Bi2201 is to be clariﬁed in future.
References
1) A. Kopp et al., Proc. Natl. Acad. Sci. U.S.A. 104, 6123
(2007).
2) J. E. Sonier et al., Proc. Natl. Acad. Sci. U.S.A. 107,
17131 (2010).
3) K. Kurashima et al., Phys. Rev. Lett. 121, 057002(2018).
4) Y. Komiyama et al., J. Phys. Soc. Jpn. 90, 084701(2021).
5) H. Hiraka et al., Phys. Rev. B 81, 144501 (2010).

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1

III-2. Atomic & Solid State Physics (Muon)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Hole-doping eﬀect on the magnetic correlation in the undoped(Ce-free) superconductor T’-La1.8 Eu0.2 CuO4 studied by μSR
T. Kawamata,∗1,∗2 T. Sunohara,∗2 K. Shiosaka,∗2 T. Nagaoka,∗2 T. Adachi,∗1,∗3 M. Kato,∗2 I. Watanabe,∗1 andY. Koike∗1,∗2

∗1
∗2
∗3

RIKEN Nishina Center
Department of Applied Physics, Tohoku University
Department of Engineering and Applied Sciences, Sophia
University- 117 -

change to Lorentzian-type fast depolarization gradually with decreasing temperature for all x. The depolarization at low temperatures is the slowest for
x = 0.03 in all samples, indicating that the AF correlation becomes weak at x = 0.03. The AF transition temperature, TN , is estimated from the analysisof the μSR spectra and is plotted together with TNof the electron-doped and undoped superconductors
T’-La1.8 Eu0.2 CuO4−y Fy 6) in Fig. 1. It is found that
TN has a maximum for x = 0.01 and it decreases byboth hole and electron doping. These results are incompatible with a ﬁnite CT-gap model in which TN
increases with Sr substitution of the AF Mott insulator. Therefore, the present results suggest that theelectronic state of the undoped superconductor T’La1.8 Eu0.2 CuO4 is a strongly correlated metallic state
without a CT gap.4)
40
T’-La1.8-xEu0.2SrxCuO4

T’-La1.8-xEu0.2CuO4-yFy(Hole doped)(Electron doped)

30

T (K)

The electronic state of the high-Tc cuprate
lanthanide elements) with the
Ln2 CuO4 (Ln:
Nd2 CuO4 -type (so-called T’-type) structure has attracted great interest, because adequately oxygenreduced samples of T’-Ln2 CuO4 have been reported toshow superconductivity without electron-carrier doping.1,2) Regarding the electron-doped (Ce-doped) highTc superconductors T’-Ln2−x Cex CuO4 , it has been
believed since their discovery that superconductivity
appears at x > 0.14, while an antiferromagnetic (AF)long-range order is developed in oxygen-reduced samples with x < 0.14.3) Hence, the reason why superconductivity emerges without carrier doping in the undoped (Ce-free) superconductor T’-Ln2 CuO4 has yet
to be clariﬁed.
Two reasons have been suggested for the electronic state of the undoped superconductivity in T’Ln2 CuO4 . One is a strongly correlated metallic state
without a charge-transfer (CT) gap between the upper Hubbard band (UHB) of Cu3dx2 −y2 and the O2p
band.4) In this case, the half-ﬁlled Fermi surface witha good nesting condition is formed from UHB of
Cu3dx2 −y2 and the O2p band, indicating a strong AF
correlation. Therefore, the AF correlation is expected
to be weakened by electron- and hole-carrier doping,leading to a bad nesting condition. The other is astrongly correlated metallic state with a ﬁnite CT gap
and the UHB of Cu3dx2 −y2 having been doped withelectron carriers due to oxygen defects induced by reduction annealing.5) That is, superconductivity appears due to electron-carrier doping of the Mott insulator. In this case, the AF correlation is expected to arise
due to hole doping corresponding to a decrease in theelectron-carrier concentration. Accordingly, an investigation of changes in the AF correlation caused by hole
doping of the undoped superconductor T’-Ln2 CuO4
is expected to reveal why superconductivity emerges
without carrier doping.
We performed muon spin relaxation (μSR) experiments on the polycrystalline samples of T’La1.8−x Eu0.2 Srx CuO4 (x = 0.01, 0.02, 0.03), whereby
theundoped(Ce-free)superconductor
T’-La1.8 Eu0.2 CuO4 was doped with hole carriers.
It is found that the μSR spectra at high temperatures above 100 K show a Gaussian-type slow depolarization of the muon spins and that the μSR spectra

Tc

TN
20

10

0

0.15

0.10

0.05

x (Sr)

0

0.05

0.10

0.15

y (F)

Fig. 1. Doped-carrier concentration dependence of themagnetic transition temperature, TN , of T’-La1.8−x Eu0.2
Srx CuO4 and T’-La1.8 Eu0.2 CuO4−y Fy .6) Green solid
circles indicate the critical temperature, Tc , of T’La1.8−x Eu0.2 Srx CuO4 2) and T’-La1.8 Eu0.2 CuO4−y Fy .7)
Solid line is guide for the eyes. Arrows indicate thatsamples are not antiferromagnetic above ∼3.8 K.

References
1) O. Matsumoto et al., Physica C 469, 924 (2009).
2) T. Takamatsu et al., Phys. Procedia 58, 46 (2014).
3) Y. Tokura et al., Nature 337, 345 (1989).
4) T. Adachi et al., J. Phys. Soc. Jpn. 82, 063713 (2013).
5) M. Horio et al., Nat. Commun. 7, 10567 (2016).
6) T. Kawamata et al. (unpublished).
7) T. Sunohara et al., J. Phys. Soc. Jpn. 89, 014701 (2020).

1

3. Radiochemistry and Nuclear ChemistryIII-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Isothermal gas chromatography study of Zr and Hf tetrachlorides
using radiotracers of 88 Zr and 175 Hf —Towards investigation ofgas-phase chemistry of Rf—†
K. Shirai,∗1 S. Goto,∗1,∗2 K. Ooe,∗3 and H. Kudo∗4,∗2

†
∗1
∗2
∗3
∗4

Condensed from the article in J. Nucl. Radiochem. Sci. 21,
7 (2021)
Graduate School of Science and Technology, Niigata University
RIKEN Nishina Center
Graduate School of Medicine, Osaka University
Faculty of Science, Niigata University- 119 -










OQ WU7LVR PLQ.

The gas-phase chemical study of Rf, Z = 104, hasbeen carried out for its tetrachloride together with
ZrCl4 and HfCl4 , which are homologues of Rf in the periodic table.1) Zvára pointed out that the reported values of adsorption enthalpy (Δads H) were quite diﬀerent between experiments and attributed this to the differences in the modiﬁcation of the surface of the quartz
glass column by diﬀerent chlorinating reagents.2) To
overcome this problem, the present study aimed at obtaining reliable Δads H values of ZrCl4 and HfCl4 byusing isothermal gas chromatography.
The apparatus consisted of four components: (i) areaction part; (ii) a chloride collection part; (iii) an
isothermal part; and (iv) a measurement part. Parts(i)–(iii) were heated individually using an electric tube
furnace, and part (iv) was cooled with water to collect the chloride passed through the isothermal column. A straight quartz glass tube passed through thefour parts. The inner diameter of the isothermal partwas 4 mm, and its length was 30 cm.
The radioactive tracers of 88 Zr and 175 Hf were produced via 89 Y(d, 3n) and nat Lu(d, xn) reactions, respectively, by a 24 MeV deuteron beam supplied by
the RIKEN K70 AVF cyclotron. Zr and Hf tracers
were reacted with CCl4 at 600◦ C for 90 min, and theformed chloride was collected on carbon ﬁlter put upstream of the isothermal part. Then, the chloride was
evaporated at 400◦ C, and cumulative yields of the chloride were obtained with γ-ray measurement.
The surface-chlorinated quartz column was examined to study the eﬀect of the surface state of thecolumn on the behaviors of ZrCl4 and HfCl4 in theisothermal chromatography. The column was chlorinated with CCl4 at 600◦ C for 2 h. After the chlorination, the ZrCl4 and HfCl4 chromatography was carriedout. Chromatography experiments were performed atcolumn tempetatures of 135–160◦ C for the non-treatedcolumn and at 100–140◦ C for the chlorinated column.
In the column-migration model applied to isothermal chromatography,3) the average retention time (t̄r )is expressed as the following eqation: 
Δads H 1+kln t̄r Tiso = −R Tiso






E










²

²
7LVR ï .



 √ 
Fig. 1. Plot of ln t̄r Tiso versus 1/Tiso for ZrCl4 (a) and
HfCl4 (b). Triangles and circles indicate the type of thecolumn, non-treated and chlorinated, respectively. The
solid lines are the results of a least-square ﬁtting.

where k is a constat value including the√experimental
parameters. Therefore, a plot of ln t̄r Tiso against
1/Tiso is expected to yield a straight line and fromits slope, Δads H can be obtained independent of theambiguous experimental parameters. √Figure 1 plots the results of ln t̄r Tiso against
1/Tiso . From the slopes of the ﬁtted lines, the values of Δads H free from parameters were obtained forthe ﬁrst time and those of ZrCl4 and HfCl4 for the
non-treated column were −101.3 ± 4.0 kJ mol−1 and−98.1 ± 3.1 kJ mol−1 , respectively. For the chlorinatedcolumn, Δads H of ZrCl4 was −85.1 ± 4.5 kJ mol−1 andthat of HfCl4 was −84.2 ± 3.3 kJ mol−1 .
Comparing with the theoritical calculation by Pershina et al.,4) in both types of column, this is more
likely to include a physisorption of MCl4 . If this adsorption mechanism is adopted, RfCl4 is expected tohave an enthalpy close to that of the homologues.4)
References
1) A. Türler, V. Pershina, Chem. Rev. 113, 1237 (2013).
2) I. Zvára, The Inorganic Radiochemistry of Heavy Elements (Springer, Switzerland, 2008).
3) I. Zvára, Radiochim. Acta 38, 95 (1985).
4) V. Pershina et al., J. Chem. Phys. 141, 064315 (2014).

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Online anion-exchange experiment of 89m Zr in the Adogen
464/HNO3 system for the chemical research of Rf
E. Watanabe,∗1 T. Yokokita,∗2 Y. Kasamatsu,∗1 S. Hayami,∗1 K. Tonai,∗1 Y. Shigekawa,∗2 H. Haba,∗2 and
A. Shinohara∗1
Chemical elements with Z ≥ 104 are called superheavy elements (SHEs) and synthesized by heavyion-induced nuclear reactions using accelerators. The
chemical properties of SHEs are almost entirely unknown because of the very low cross sections of their
nuclides and short half-lives (T1/2 ≤ 1 min). Somechemical experiments on 104 Rf in an aqueous solution were reported; however, its chemical properties
are not suﬃciently understood owing to limited experimental methods. We previously developed an automated batch-type solid-liquid extraction apparatus(AMBER) and investigated the anion-exchange behavior of Rf in HCl and H2 SO4 to obtain the distribution
coeﬃcients (Kd ) of Rf under chemical equilibrium conditions.1,2)
In this study, we focus on the formation of the Rf nitrate complexes. The clear diﬀerence between the complexation of Th (pseudo homologue of Rf) and those ofZr and Hf (homologues) in HNO3 is known; Th forms
an anionic complex with large coordination numbersof 10 and/or 12, while Zr and Hf do not. We found ina previous study that anion-exchange reactions using
the Adogen 464 resin in HNO3 reach chemical equilibrium in 60 s. This suggests that this resin is suitablefor 261 Rf (T1/2 = 68 s) experiments. We also optimized
the experimental condition for 261 Rf with long-lived radiotracers, 88 Zr, 175 Hf, and 234 Th.3) To check the stability of AMBER in the accelerator-online situation,
we performed the online anion-exchange experimentsof 89m Zr in the Adogen 464/HNO3 system as a modelexperiment of 261 Rf.
89m
Zr (T1/2 = 4.16 min) was produced in the89
Y(d, 2n)89m Zr reaction. A d beam with 24-MeVenergy was extracted from the K70 AVF cyclotron
at RIKEN. The nuclear-reaction products were transported to the chemistry laboratory by using a He/KCl
gas-jet system and deposited on AMBER for 60 s.
Then, 89m Zr was dissolved in 270 μL of 8.1 M HNO3 .
The solution was loaded into a chemical reaction container containing 32 mg of the Adogen 464 resin. Aftershaking the container with a vortex mixer for 30–120 s,
only the liquid phase was pushed out of the container
by compressed air. Then, the solution samples werecollected in a 0.5 mL PP tube, and the 587.8-keV γ
rays of 89m Zr were counted with a Ge detector. The
residual 89m Zr adsorbed on the resin was stripped bywashing the resin four times with about 150 μL of
0.1 M HCl. Subsequently, the resin was conditioned∗1∗2

Graduate School of Science, Osaka University
RIKEN Nishina Center- 120 -

Fig. 1. Kd values of Zr and Th in the Adogen 464/HNO3
system.

with 8.1 M HNO3 twice. This procedures was repeated
30 times. The distribution coeﬃcient (Kd ) was determined by the equation
Kd = (ASTD − αAs )V /αAs w,
where As and ASTD are the radioactivities of 89m Zr in
the resin and the control solution, respectively; V isthe volume of the aqueous phase (mL); and w is themass of the dry resin (g). Note that α is a correction
factor that accounts for the adsorption of some 89m Zr
in the reaction container.
Figure 1 shows the Kd values of 89m Zr using
accelerator-online AMBER (“Online” in the ﬁgure) as
a function of shaking time, along with those of 88 Zr
and 234 Th previously obtained by AMBER in the ofﬂine condition and PP tube (“Oﬄine” and “Batch”
in the ﬁgure, respectively). The Kd of 89m Zr for all
shaking times are consistent with the values obtained
under equilibrium conditions (60 s) in the batch experiments. This result indicates that the distribution
coeﬃcient can be obtained under the conditions of online experiments for the short-lived 261 Rf.
In 30 consecutive anion-exchange experiments, theKd values of 89m Zr are obtained reproducibly. We havepreviously conﬁrmed good reproducibility for the Kdvalues of 234 Th by AMBER under the oﬄine condition.3) Therefore, a wide range of Kd values of anion
exchange in HNO3 can be obtained in consecutive experiments by AMBER. Irrespective of the behavior of
Rf in the system, we should be able to obtain reliable
Kd values for Rf.
In this study, the applicability of the anion-exchange
experiment to Rf in the Adogen 464/HNO3 system us-

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

ing AMBER was demonstrated by the success of themodel experiment with the short-lived nuclei 89m Zr. In
addition to the 261 Rf experiment, we plan to conduct
theoretical studies on Rf nitrate complexes using DFT
calculations.
References
1) T. Yokokita et al., Dalton Trans. 45, 18827 (2016).
2) T. Yokokita et al., RIKEN Accel. Prog. Rep. 54, 148(2021).
3) E. Watanabe et al., RIKEN Accel. Prog. Rep. 53, 166(2020).

2- 121 -

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Solvent extraction of Zr and Hf in trioctylamine/H2 SO4 system
T. Yokokita∗1 and H. Haba∗2
The chemical properties of superheavy elements(SHEs) with atomic number Z ≥ 104 are expected todeviate from the periodicity of their lighter homologues
in the periodic table. Thus, chemical studies on SHEs
are interesting. SHEs are produced at accelerators using heavy-ion-induced nuclear reactions. The production rates of SHEs are low, and their half-lives are short(T1/2 ≤ 1 min). Thus, the chemical studies of SHEs are
conducted on a single-atom basis, which makes it diﬃcult to perform chemical experiments with SHEs. Thusfar, the chemical properties of SHEs have been discussed
by comparing their behavior with those of homologous
elemenets.1)
We performed anion-exchange experiments of Rf andits homologous elements, Zr and Hf, to study its sulfate complexation.2) From the previous study, we obtained the distribution coeﬃcients of Rf, Zr and Hf in
0.060–0.46 M H2 SO4 .2) We need to identify the chemical species of the sulfate complexes of Zr and Hf under
the studied conditions to discuss the sulfate complexation of Rf based on the comparison of the anion-exchange
behavior of Rf and its homologous elements. In thiswork, we performed solvent extraction with an anion exchanger, trioctylamine (TOA), from H2 SO4 and ESI-MS
spectroscopy to deduce the anionic sulfate complexes ofZr and Hf under the experimental condition of Rf.
Radiotracers 88 Zr and 175 Hf were produced in89
Y(d, 3n)88 Zr and nat Lu(d, xn)175 Hf reactions, respectively, using the RIKEN AVF cyclotron. Then, thesetracers were puriﬁed by an anion-exchange method. The
solvent extractions of Zr and Hf were performed by employing the batch method with 1.6–20 mM trioctylaminein CH2 Cl2 from 0.11 M H2 SO4 . The distribution ratios(D) were obtained according to D = [M]org /[M]aq ; here,[M]org and [M]aq denote the metal concentration in theorganic and aqueous phases, respectively.
For ESI-MS spectroscopy, Zr and Hf samples in the organic phases were obtained in the solvent extraction of
9.4 mM Zr and 7.6 mM of Hf, respectively, from 0.15 M
H2 SO4 into 3.6 mM TOA-CH2 Cl2 solutions. Further,
we made blank samples, i.e., TOA-CH2 Cl2 solutions
without Zr and Hf. They were the organic phases obtained in the solvent extraction of 0.15 M H2 SO4 without the metal ions and 3.6 mM TOA-CH2 Cl2 solutions.
All samples were diluted with CH2 Cl2 before ESI-MS
measurement using LTQ Orbitrap XL mass spectrometer (Thermo Fisher Scientiﬁc).
The slopes of log D and log [TOA] of Zr and Hf wereobtained: the slope is related to the number of the protonated TOA cation (HTOA+ ) of the extracted species.
The slope values of both Zr and Hf were 1.9 ± 0.1, which
implies two HTOA+ cations are paired with the anionic∗1∗2Department of General Education, Salesian Polytechnic
RIKEN Nishina Center

Fig. 1. ESI-MS spectrum (negative mode) of the Zr sample.
The m/z values marked by the squares are the distinguishable peaks of the Zr sample.

sulfate complexes of Zr and Hf with a net charge −2 tobe extracted into the organic phase from the aqueous
phase.
In ESI-MS spectroscopy, the peaks of the ionized Zr
and Hf species in the organic phase were assigned bycomparing the mass spectra of Zr and Hf samples in
the organic phase with those of the blank samples. The
mass spectrum of the Zr samples is shown in Fig. 1. 7
distinguishable peaks were observed at m/z = 189.0,
238.0, 378.9, 396.8, 476.7, 830.0, and 1280.8, whichcorresponded to [Zr(SO4 )3 ]2− , [Zr(HSO4 )2 (SO4 )2 ]2− ,[Zr(OH)(HSO4 )2 (SO4 )]− ,[Zr[Zr(HSO4 )(SO4 )2 ]− ,−(HSO4 )3 (SO4 )] , (HTOA)[Zr(HSO4 )2 (SO4 )2 ]− , and(HTOA)2 [Zr(HSO4 )3 (SO4 )2 ]− , respectively. The extracted Zr species in organic phase contains the two
HTOA+ cations, and therefore, the Zr species before ionization are (HTOA)2 [Zr(SO4 )3 ], (HTOA)2 [Zr(HSO4 )2(SO4 )2 ],(HTOA)2 [Zr(OH)(HSO4 )(SO4 )2 ],and(HTOA)2 [Zr(OH)(HSO4 )3 (SO4 )].
For the Hf sample, 4 distinguishable peaks were observed at m/z = 234.0, 486.8, 919.6, and 1371.2, whichcorrespond to [Hf(SO4 )3 ]2− , [Hf(OH)(HSO4 )2 (SO4 )]− ,(HTOA)[Hf(HSO4 )2 (SO4 )2 ]− , and (HTOA)2 Hf(HSO4 )3(SO4 )2 ]− , respectively.
The extracted Hf species
in organic phase contains the two HTOA+ cations,and therefore, the Hf species before ionizationare (HTOA)2 [Hf(SO4 )3 ], (HTOA)2 [Hf(OH)(HSO4 )(HTOA)2 [Hf(OH)(HSO4 )3 (SO4 )],and(SO4 )2 ],(HTOA)2 [Hf(HSO4 )2 (SO4 )2 ].
These results indicate that the proposed Zr andHf species at 0.1 M H2 SO4 are [M(SO4 )3 ]2− ,[M(HSO4 )2 (SO4 )2 ]2− , [M(OH)(HSO4 )(SO4 )2 ]2− , and[M(OH)(HSO4 )3 (SO4 )]2− (M = Zr and Hf). However,
the main species of Zr and Hf in this studied condition
cannot be determined from the present study. A combination of other analytical methods must be performed
to identify the main chemical species.
References
1) A. Türler, V. Pershina, Chem. Rev. 113, 1273 (2013).
2) T. Yokokita et al., RIKEN Accel. Prog. Rep. 54, 148(2021).

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RIKEN Accel. Prog. Rep. 55 (2022)

Determination of 236 U in a Th target irradiated with Li ions by ICP
mass spectrometry
A. Nagai,∗1,∗2 K. Teranishi,∗1,∗2 R. Morita,∗1,∗2 H. Hosokawa,∗1,∗3 A. Yokoyama,∗1,∗3 A. Nakajima,∗1,∗4
A. Sakaguchi,∗1,∗5 Y. Shigekawa,∗1 A. Nambu,∗1 T. Yokokita,∗1 and H. Haba∗1
Neptunium-237 (T1/2 = 2.1×106 y) released from nuclear facilities is an important radioactive target nuclide
that contaminates the environment.1) The nuclide canbe analyzed by accelerator mass spectrometry; however,a spike material of neptunium for the measurement has
not been obtained, thus far. We previously proposed
the production of neptunium-236 (T1/2 = 1.5 × 105 y)
in a Th + Li reaction as a candidate for the material.2,3) However, the material prepared from the irradiated target may be contaminated with long-lived isobars of 236 Pu and 236 U, which are the decay products
from 236m Np, or a byproduct in the reaction. In addition, 235 U contained in Th as an impurity, may also absorb neutrons and produce 236 U. In this study, we aimed
to determine U isotopes contained originally in the Thtarget as well as those produced in the nuclear reaction by High Resolution ICP-MS (HR-ICP-MS). The
amount of 236 U produced in the reaction can be estimated by measuring a neutron ﬂux during irradiation
through the use of a monitoring foil of Au.
We irradiated a 232 Th target with 43 MeV 7 Li ions at
the RIKEN AVF cyclotron. Au metal foils (ca. 200 mgeach) and electrodeposited U samples (ca. 1 mg each)were placed at the end of the beam course to function
as a neutron monitor and a reference, respectively, as
illustrated in Fig. 1.
After irradiation, the neutron ﬂux was obtained from
activation of the Au foil measured by γ-ray spectroscopy using a Ge semiconductor detector. The Uelectrodeposited sample was dissolved in a concentrated

Fig. 1. Experimental setup of neutron monitor foils (Au)and U targets attached to the end of a target holder ofan irradiation beam course at RIKEN.
∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
Graduate School of Natural Science and Technology,
Kanazawa University
Institute and College of Science and Engineering, Kanazawa
University
Master’s Program in Chemistry, University of Tsukuba
Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba

Table 1. U isotopic ratios in U-electrodeposited samples by
ICP-MS.
IrradiatedU-1
235/238
236/238

U2

Ratio%
0.62~0.82
0.61~0.84(1–7)×0.82–4
0.5×0.82–4

UnirradiatedU-3
Ratio%
0.63~0.85
N.D

nitrate solution. Subsequently, the solution was diluted so that the U concentration was 0.1 or 1 ng/g,
as measured by HR-ICP-MS with a reference solution
of XSTC-13 supplied by SPEX Industries, Inc. for calibration.
From the measurements of photopeak intensities due
to 198 Au and 196 Au in the Au foils, the thermal neutron ﬂux and fast neutron ﬂux were 6.5 × 105 s−1 and1.6 × 107 s−1 , respectively. These values were calculated from induced radioactivities and the cross section
data4) of (n, γ) and (n, 2n) reactions. The isotope measurement results of the U-electrodeposited sample by
HR-ICP-MS are shown in Table 1, where the ratios denote the range of observation due to the large dispersionof the data depending on the sample. The abundance
ratios of 235 U to 238 U for all the samples are approximately 0.7%, corresponding to the natural abundanceof U. Some events due to 236 U were observed for the
samples attached to the target holder. However, theevents due to the unirradiated sample was less than thedetection limit. It was conﬁrmed that 236 U was produced in the U-electrodeposited samples. The amountof 236 U produced agrees with the amount estimatedfrom the thermal neutron ﬂux by the monitor withinsome uncertainty of the data. Based on the measured
concentration of U and the measured thermal ﬂux, thenumber of 236 U atoms produced in the target sample
was (0.9 − 2.0) × 102 , much less than the number of
236g
Np atoms estimated from the measured cross section,2) that is, approximately 1 mb. Thus, the amountof U was concluded to be negligible to contaminate a
Np tracer prepared from the irradiated target.
References
1) W. Rund, G. S. Goﬀ, in Radionuclide in the Environment, edited by D. A. Atwood (Wiley, 2013).
2) Y. Hayakawa et al., RIKEN Accel. Prog. Rep. 53, 179(2020).
3) A. Nakajima et al., RIKEN Accel. Prog. Rep. 54, 142(2021).
4) Japanese Evaluated Nuclear Data Library, JENDL-4.0,(2010), https://wwwndc.jaea.go.jp/jendl/Jendl_J.
html .

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Development of a photon measurement apparatus for observing theradiative decay of 229m Th produced from 229 Pa
Y. Shigekawa,∗1 Y. Wang,∗1 X. Yin,∗1 A. Nambu,∗1 T. Yokokita,∗1 and H. Haba∗1
The ﬁrst excited state in the 229 Th nucleus (229m Th)
has an excitation energy of ∼8.3 eV (150 nm),1) which
potentially enables an ultraprecise nuclear clock. We
have been aiming to observe the radiative decay (γrays) of 229m Th and to determine its radiative half-life,
which is an essential parameter to develop the nuclear
clock, by doping a CaF2 crystal with 229 Pa, which decays to 229m Th with negligibly small recoil energy.2)
In this study, we developed a photon measurement apparatus for observing the γ rays of 229m Th. We also
investigated the background photons originating fromthe decay of 229 Pa (T1/2 = 1.5 d) and other impurities such as 232 Pa (T1/2 = 1.31 d) and 230 Pa (T1/2 =17.4 d).
Figure 1 shows a schematic view of the developed
apparatus. Two photomultipliers are placed inside
a vacuum chamber: one is for measuring the γ raysof 229m Th in the vacuum ultraviolet (VUV) range(PMT1, Hamamatsu R10454), and the other is formeasuring scintillation photons produced from 229 Pa
and other isotopes in a CaF2 crystal (PMT2, Hamamatsu R7154). The events of PMT1 that coincidedwith those of PMT2 correspond to high-energy radiation that can produce scintillation photons, and thus,
such events can be excluded from the analysis of the
γ-ray events of 229m Th. Band-pass (BP) ﬁlters for photons of 151 ± 20 and 171 ± 20 nm (eSource Optics) areplaced between PMT1 and the CaF2 sample. The ﬁlters can be switched using a linear drive driven by astepper motor; the γ rays of 229m Th are expected to
be detected only for the 151-nm BP ﬁlter. PMT1 andPMT2 can be cooled to −25◦ C using a Peltier cooler,
reducing the dark count rate to 0.09 s−1 for PMT1 and0.25 s−1 for PMT2. Considering the half-life of 229m Th(103 –104 s), the 229 Pa-doped CaF2 can be rapidly introduced to the measurement position (∼10 min) as
follows without the leakage of the large vacuum chamber (Fig. 1). First, the sample ﬁxed on a linear drive isFig. 1. Schematic view of the developed apparatus (left)
and a photograph of the sample loading system (right).
∗1

RIKEN Nishina Center- 124 -

Fig. 2. Count rate of photons measured using PMT1 forthe 151-nm (circle) and 171-nm (square) BP ﬁlters with(closed) and without (open) anticoincidence using theevents measured by PMT2. The sum of the exponential
decay functions of 229 Pa and 230 Pa is ﬁtted to the countrate with anticoincidence for each ﬁlter (solid lines).

placed inside a small vacuum chamber, which is thenrapidly evacuated. Next, a gate valve is opened, andthe sample is moved to the large chamber for photon
measurement.
We investigated the background photons originating from 229 Pa and other isotopes, which may interfere with the observation of the γ rays of 229m Th. The
production and chemical separation of 229 Pa were performed similarly to those in a previous study.2) First,
two 232 Th metallic foils (total 138 mg/cm2 ) were irradiated with 1 μA of a 30-MeV proton beam for
10 h at the RIKEN AVF cyclotron. Next, the foils
were dissolved with concentrated HCl and fed onto ananion-exchange column (Muromac 1X8, 100–200 mesh,∼1.0 mL). After pouring concentrated HCl, 6 M HCl,and 8 M HNO3 to the column, Pa isotopes were eluted
with 9 M HCl/0.1 M HF. In this study, we performed
an additional anion-exchange process to reduce radioactive impurities such as 97 Zr as follows. First, Pa
isotopes were dissolved in 0.1 M HCl/0.1 M HF and fed
onto an anion-exchange column (Muromac 1X8, 100–
200 mesh, ∼0.5 mL). After pouring 0.1 M HCl/0.1 M
HF, Pa isotopes were eluted with 0.4 M HCl/0.1 M HF.
The ratio of radioactivity of 229 Pa isotopes to that ofother radioactive elements was ∼105 after the chemical separation. Thereafter, we dropped the 229 Pa solution on a CaF2 crystal, annealed it, and started a
photon measurement four days after the proton irradiation. Compared with the previous measurement,2)

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the amount of 229 Pa was dominant over other isotopes (229 Pa 48(3) kBq, 232 Pa 2.51(6) kBq, and 230 Pa
6.6(4) kBq); thus, we could evaluate the backgroundphotons produced by high-energy radiation from 229 Pa
more precisely.
As shown in Fig. 2, the count rate of photons detected by PMT1 for the 151-nm BP ﬁlter was ∼9 s−1
at the start of the measurement. Anticoincidence using PMT2 reduced the count rate to ∼1/3. For eachBP ﬁlter, the sum of the exponential decay functions of229
Pa and 230 Pa was well ﬁtted to the data, indicatingthat the photons originate from 229 Pa and 230 Pa. The
ratio of photons from 229 Pa to those from 230 Pa was∼1. In the presence of these background photons, if we
use a CaF2 sample doped with 100 kBq of 229 Pa, oursimulation indicated that we can observe the γ raysof 229m Th without the mass separation of 229 Pa anddetermine its half-life with a relative error of ∼25%;
the development of the apparatus for measuring the γrays of 229m Th is nearly complete.
References
1) B. Seiferle et al., Nature 573, 243 (2019).
2) Y. Shigekawa et al., RIKEN Accel. Prog. Rep. 54, 143(2021).

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RIKEN Accel. Prog. Rep. 55 (2022)

Surface ionization of protactinium toward implanting 229 Pa into a
CaF2 crystal
Y. Shigekawa∗1 and H. Haba∗1
The ﬁrst excited state in the 229 Th nucleus (229m Th)
has an excitation energy of ∼8.3 eV,1) which may allow
an ultraprecise nuclear clock. We aim to observe theγ rays of 229m Th and to determine its half-life, which
is an essential parameter to develop the nuclear clock,by doping a CaF2 crystal with 229 Pa, which decays to229m
Th with a negligibly small recoil energy.2) The doping with 229 Pa will be achieved by ionizing 229 Pa, implanting 229 Pa ions with high energy (>10 keV) into a
CaF2 crystal, and annealing the crystal. Ionizing 229 Pawith high eﬃciency and implanting ∼100 kBq of 229 Pa
are important to clearly observe the γ rays of 229m Th.
Surface ionization, which is the ionization of atoms on
the surface of a metal at a high temperature, is one of
the methods that can realize a high ionization eﬃciency(0.1–100%); however, the ionization eﬃciency for Pa is
as low as 0.001–0.01%3) because of the high stability of
Pa compounds such as Pa2 O5 . To overcome this difﬁculty, Pickett et al. developed a method to bring Pa
compounds into contact with colloidal graphite on thesurface of a Re ﬁlament, realizing an ionization eﬃciencyof 0.3–0.7%.4,5) Following this method, we performed experiments for ionizing 233 Pa (T1/2 = 26.975 d) in thisstudy toward the ionization of 229 Pa (T1/2 = 1.5 d).
233
Pa was separated from its mother nuclide 237 Np in
the following procedure. First, 9 M HCl solution containing 237 Np and 233 Pa was fed onto a TK400 resin’s
column (TrisKem). Next, 237 Np was eluted by pouring
9 M HCl, following which 233 Pa was eluted by pouring 1 M HCl. The eluate contacting 233 Pa was evaporated, dissolved with 0.1 M HCl/0.1 M HF, and fed onto
an anion-exchange column (Muromac 1X8). After pouring 0.1 M HCl/0.1 M HF, 233 Pa was eluted with 0.4 M
HCl/0.1 M HF. Finally, we prepared a stock solution of
233
Pa in 50 μL of 1 M HNO3 /0.4 M HF.
Figure 1 shows a schematic view of the setup for thesurface ionization and implantation of Pa, performed ina high vacuum (10−4 –10−5 Pa). A Re ﬁlament (0.0254×
0.762×10 mm) was ﬁxed by spot welding to two SUS316
wires (ϕ1.0 mm), which were connected to a vacuum
feedthrough to apply a current for heating the ﬁlament.
The temperature of the ﬁlament was measured using an
infrared thermometer. An Al electrode, where −15 kV
was applied, was placed 86.4 mm below the ﬁlament.
We ﬁxed a CaF2 crystal (ϕ12 mm, 0.5 mm thickness)or a Cu foil (ϕ12 mm, 0.05 mm thickness) to the Al
electrode. The Cu foil was used for optimizing the setup
and conditions of surface ionization. According to oursimulation, the collection eﬃciency of ions in the CaF2
crystal or the Cu foil is ∼100%; therefore, the collection
eﬃciency of Pa corresponds to the ionization eﬃciency.
∗1

RIKEN Nishina Center

Fig. 1. Schematic view of the setup for the surface ionizationand implantation of Pa.

The surface ionization and implantation of 233 Pa were
performed for the Cu foil (Run A) and the CaF2 crystal(Run B) as follows. First, the Re ﬁlament was heatedwith a current of ∼5.5 A for 10 min to remove impurities
on the ﬁlament. Next, 1 μL of water containing colloidal
graphite (EM Science 12650) was dropped on the ﬁlament and evaporated by applying a current of 0.7 A tothe ﬁlament. Then, 1 μL of the stock solution containing
19.1(2) kBq of 233 Pa was dropped on the Re ﬁlament andevaporated with a current of 0.7 A. After the ﬁlament
was placed in a vacuum chamber, the current applied
to the ﬁlament was gradually increased. At a ﬁlamentcurrent of 2.5 A, we applied a voltage of −15 kV to the
Al electrode (Fig. 1). The temperature of the ﬁlament
exceeded 1960◦ C with a current of ∼5.5 A and increased
to 2000◦ C in ∼20 min. The heating at ∼2000◦ C lasted
until the ﬁlament was broken (79 and 127 min for Runs
A and B, respectively).
The radioactivity of 233 Pa collected in the Cu foil (RunA) was measured to be 121(2) Bq. Considering the solid
angle between the ﬁlament and the foil, the radioactivity of 229 Pa atoms deposited on the foil was calculated
to be 15.8(2) Bq. Hence, the ionization eﬃciency was
0.55(1)%. The radioactivity of 233 Pa remaining on theﬁlament after heating was 4.3(1)% of that before heating, implying that highly stable 233 Pa compounds wereeﬃciently reduced and evaporated. For the case of theimplantation into the CaF2 crystal (Run B), the ionization eﬃciency was 0.53(1)%, which is close to the value
for the Cu foil, although CaF2 is a non-conducting material. We will be able to implant 100 kBq of 229 Pa, whichis expected to suﬃcient to clearly observe the γ rays of
229m
Th, by using a solution containing 19 MBq of 229 Pa.
References
1) B. Seiferle et al., Nature 573, 243 (2019).
2) Y. Shigekawa et al., RIKEN Accel. Prog. Rep. 54, 143(2021).
3) J. Fietzke et al., Nucl. Instrum. Methods Phys. Res. B
149, 353 (1999).
4) D. A. Pickett et al., Anal. Chem. 66, 1044 (1994).
5) C. -C. Shen et al., Anal. Chem. 75, 1075 (2003).

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Development of RF carpet gas cell for extracting 229m Th ionsY. Shigekawa,∗1 K. Tokoi,∗2 A. Yamaguchi,∗3,∗4 N. Sato,∗1 M. Wada,∗5 and H. Haba∗1
The ﬁrst excited state of a 229 Th nucleus (229m Th)
has an excitation energy of ∼8.3 eV.1,2) Because thisis close to the binding energy of the valence electrons,
decay modes of 229m Th [internal conversion (IC), electronic bridge (EB) transitions, and γ-ray emission]
may vary depending on the chemical environment.
However, EB transitions and γ-ray emission of 229m Th
have never been observed, because the IC process dominantly occurs in most chemical environments in whichelectron biding energies are below 8 eV. Examples
in which the IC process is inhibited are 229m Th ionstrapped in vacuum. The trapping of 229m Th2+ and229m
Th3+ , which have high ionization energies (18.3
and 28.65 eV, respectively), may lead to γ-ray emission. Moreover, because the electron transition energies in a Th+ ion are close to 8 eV, the trapping of
229m
Th+ may allow occurrence of an EB transition,
which is an unknown high-order decay mode along withthe transition of an occupied orbital electron to an unoccupied orbital and the emission of a photon. Observing such decay modes requires the extraction ofnumerous 229m Th ions to an ion trap. In this study,
we fabricated a radiofrequency (RF) carpet gas cell toeﬃciently extract 229m Th ions recoiling out of a 233 U
source. Moreover, we optimized and evaluated the device by extracting 220 Rn (T1/2 = 55.6 s) and 216 Po(T1/2 = 0.144 s) ions emitted from a 224 Ra source under the recoil energy of an α decay.
Figure 1 shows a photograph and schematic of thedeveloped gas cell. The ions emitted from a source
placed inside the gas cell are decelerated by He gas,
pushed toward an RF carpet by a positive (push) voltage, and transported to the central hole of the RF
carpet using the RF surﬁng technique.3) Subsequently,
the ions are guided to high vacuum by a quadrupole
ion guide (QPIG). The ions with a speciﬁc mass-tocharge ratio (m/z ) are separated by a quadrupole mass

separator (QMS) and guided to a channeltron detector. The vacuum chamber consists of conﬂat ﬂanges,
and it is baked to reach a base pressure of ∼1 × 10−7
Pa, to ensure that the amount of impurities emitted
from the gas cell is small. Thus, the neutralization
or molecularization of ions by impurities is minimized.
Because of the relatively small recoil energy of an α decay (∼100 keV), we shortened the length of the gas cellto 10 cm compared to that of the gas cell we developed
for the study of superheavy elements (26 cm).3)
We investigated the conditions under which the extraction eﬃciency is maximum, by extracting 216 Po+
ions emitted from a thin 224 Ra source3,4) (∼400 Bq)
placed inside the gas cell. The counts of 216 Po+ ions
measured by the channeltron detector reached maximum when the push voltage of the RF carpet was from
+5 V to +90 V, the oﬀset voltage of the RF carpet was+4 V (He 10 mbar) and +10 V (He 15 mbar), the RF
voltage of the RF carpet was 217 Vpp (15.43 MHz), theaudiofrequency voltage of the RF carpet was 2.6 Vpp(200 kHz), the DC voltage of the QPIG was +1 V, andthe RF voltage of the QPIG exceeded 106 Vpp.
We measured the mass spectrum of the ions emitted from the 224 Ra source under the above-mentioned
conditions. In Fig. 2, the peaks of 220 Rn+ , 216 Po+ ,212
Pb+ , 208 Pb+ , and 208 Tl+ are noticeable. Only when
He gas introduced in the gas cell is puriﬁed using puriﬁers (SAES PS3-MT3-R-1 and MC1-902F), the peaksof 216 Po2+ , 212 Pb2+ , 208 Pb2+ , and 208 Tl2+ are observed. Thus, when 229m Th2+ and 229m Th3+ ions areneeded, gas puriﬁcation should be conducted.
We measured the absolute maximum extraction efﬁciency of 220 Rn+ as the ratio of the number of extracted 220 Rn+ to that of 220 Rn+ emitted from the224
Ra source.3) The former was determined from thealpha-decay events of 220 Rn detected by the channeltron (the counts increased during extraction and decayed after stopping the extraction with a half-life of
55.6 s). The extraction eﬃciency was 16(2)% at He
10 mbar and 20(1)% at He 15 mbar with puriﬁed He

Fig. 1. Photograph (left) and schematic (right) of developed RF carpet gas cell.
∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
Graduate School of Science, Osaka University
Quantum Metrology Laboratory, RIKENPRESTO, Japan Science and Technology Agency
Wako Nuclear Science Center (WNSC), IPNS, KEK

Fig. 2. Mass spectra of ions extracted from 224 Ra source
without (left) and with (right) He gas puriﬁcation.

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gas. Hence, using a 233 U source with a diameter of
90 mm and a radioactivity of 100 kBq would enable
extracting 229m Th ions at a rate of ∼400 s−1 , which
is suﬃciently high to observe γ-ray emission and EB
transitions using photomultipliers.
References
1) B. Seiferle et al., Nature 573, 243 (2019).
2) A. Yamaguchi et al., Phys. Rev. Lett. 123, 222501(2019).
3) Y. Shigekawa et al., RIKEN Accel. Prog. Rep. 53, 168(2020).
4) Y. Shigekawa et al., Rev. Sci. Instrum. 87, 053508(2016).

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RIKEN Accel. Prog. Rep. 55 (2022)

Preparation of an 225 Ac source for 221 Fr EDM measurement
M. Sato,∗1,∗2 K. Yamane,∗2 H. Haba,∗1 A. Nambu,∗1 N. Ozawa,∗3 S. Nagase,∗3 T. Nakashita,∗2 M. Fukase,∗3
D. Uehara,∗3 T. Hayamizu,∗1 K. Nakamura,∗4 H. Nagahama,∗4 Y. Sakemi,∗4 and Y. Matsuda∗2
The origin of the matter-dominant universe is one of
the greatest mysteries in modern physics. It is considered that the violation of the charge conjugate andparity symmetry (CP violation) is needed to explain the
mystery.1) The existence of the electric dipole moment(EDM) of elementary particles could lead to the discovery of the source of CP violation and the prospectsof new physics beyond the standard model of particle
physics.
Francium (Fr), which is the heaviest alkali element,
has a large enhancement factor of about 103 for theelectron EDM.2) In addition, 221 Fr is sensitive to the
nuclear EDM. We aim to extract the nuclear EDM bycomparing it with the 210 Fr EDM, which is sensitive tothe electron EDM.
In this paper, we report the preparation of an 225 Ac
source to obtain the 221 Fr recoiling from it. 221 Fr, which
is produced from the alpha decay of 225 Ac with a halflife of 10 days, is convenient to conduct the EDM experiment without accelerator operation. We used anelectrodeposition method to ﬁx 225 Ac ﬁrmly on a plate.
To obtain suﬃcient statistics for EDM measurements,
we aimed to develop a source of 10 MBq or higher.
Figure 1 shows an overview of the cell used for theelectrodeposition experiment. A Pt plate (0.1 × 15 ×
15 mm3 ) on a water-cooled Ti block is used as a cathode, and a Pt rod (1-mm diameter) stuck into the solution is used as an anode applied with +1 kV. Siliconrubber with a hole of 5 mm diameter functions as anelectrode seal, and we can obtain an active target area
as we arranged.
Before preparing the Ac source, the best condition of
the electrodeposition was determined using Y, which is
chemically similar to Ac. The Y sample we prepared included 88 Y, which has a long half-life of 106.6 days andemits γ rays with energies of 898 and 1836 keV that can

Fig. 1. Overview of the cell for Ac electrodeposition.
∗1
∗2
∗3
∗4

RIKEN Nishina Center
Graduate School of Arts and Sciences, University of Tokyo
Department of Physics, University of Tokyo
Center for Nuclear Study, University of Tokyo

be detected using a germanium semiconductor detector.
By dividing the amount of Y electrodeposited on the Pt
plate by that used for electrodeposition, we could determine the electrodeposition yields. 88 Y was producedby irradiating a nat SrO target with a 24-MeV deuteronbeam for 4 h at the AVF cyclotron. The beam current was 3 μA. The target included 157.9 mg of nat SrO
and was pressed into a disc of 10-mm diameter at 1.6 t
for 5 min. After the irradiation, 88 Y was chemicallyisolated from the target by extraction chromatographyusing an Ln resin (particle size: 100–150 μm) ﬁlled ina column (internal diameter: ϕ5 mm, height: 50 mm).
This puriﬁed 88 Y was mixed with stable 89 Y and dissolved in 1 mL of 0.01 M HNO3 . 10 μL of the solution
was mixed with 2 mL 2-propanol for electrodeposition.
The number of Y atoms in the mixed solution was thesame as that of 1-MBq 225 Ac.
Figure 2 shows the time dependence of the electrodeposition yield. At an applied voltage of +1 kV and atroom temperature, the yields increased with time from∼15% at 10 min to ∼100% at 40 min. We could visuallyobserve the target layer on the Pt plate.
We purchased 225 Ac and attempted the electrodeposition with the optimized condition which achieved thehighest yield. As a result, a maximum yield of 77.9%
was achieved for the 225 Ac source of 20.4(6) MBq. A
suﬃcient dose was achieved, but the diﬀerence in yields
between Y and Ac may be due to subtle diﬀerences inchemical properties. The 225 Ac used in this research
was supplied by the U.S. Department of Energy Isotope Program managed by the Oﬃce of Isotope R&D
and Production.
The development of the experimental apparatus totrap 221 Fr from the 225 Ac source and measure the EDM
is now in progress.

Fig. 2. Time dependence of the electrodeposition yields of
Y at an applied voltage of +1 kV.

References
1) A. D. Sakharov, Sov. Phys. Usp. 34, 392 (1991).
2) N. Shitara et al., J. High Energy Phys. 2, 124 (2021).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Accelerator production and chemical separation of theranostic
radionuclide 141 Ce
K. Ooe,∗1,∗2 T. Watabe,∗1,∗2 Y. Shirakami,∗2 A. Nambu,∗3 H. Haba,∗3 and J. Hatazawa∗4

∗1
∗2
∗3
∗4

get, high radioactivities of short-lived 38 K (T1/2 =7.636 min) and 34m Cl (T1/2 = 31.99 min) were observed. These by-products are considered to be produced from nat Cl in the BaCl2 target and α beam.
Because of these by-products, the radiation dose fromthe irradiated BaCl2 target was quite high, and theγ-ray of 141 Ce was only observed after the decay ofthese by-products. On the other hand, in the γ-ray
spectrum of 141 Ce produced with BaO, no such interference nuclides were observed, and the γ-ray of 141 Ce
was observed soon after the end of irradiation. Therefore, BaO is considered to be a suitable target material
for the production of 141 Ce by the α beam.
The elution curves for nat Ba and 141 Ce from the Ln
resin are shown in Fig. 1 (BaO was used as the target
material). nat Ba was eluted before 141 Ce with 0.01 M
HCl. After the elution of nat Ba, 141 Ce was recoveredby elution with 1 M HCl. The recovery yield for 141 Ce
was greater than 99%. The contamination of nat Ba
into 141 Ce fraction was calculated as less than 3 μgin the ICP-MS measurement: the separation factor of141
Ce for nat Ba is greater than 104 .
In the next study, the radiopharmaceutical labelingof 141 Ce will be investigated.

0.01 M HCl

Eluted amount of

100
natBa or 141Ce (%)

Because all of the therapeutic radionuclides usedin clinical practice in Japan are imported from othercountries, domestic production using accelerators is desirable for the stable supply of therapeutic nuclides.
Cerium-141 (141 Ce, T1/2 = 32.5 d) is a candidate
radionuclide for theranostics (therapeutics + diagnosis) and can be produced in the 138 Ba(α, n)141 Ce reaction using accelerators. This nuclide emits β-particles(maximum β energy: 580.7 keV), which can be applied
to the therapy of tumors, as well as a γ-ray with an energy of 145.4 keV (branching ratio: 48.2%), which canbe used for imaging by single photon emission computed tomography (SPECT). In particular, 141 Ce is
expected to be useful for SPECT imaging because theenergy of the γ-ray of 141 Ce is similar to that of 99m Tc(140 keV), which is the most widely used SPECT nuclide in clinical application. However, 141 Ce has beenrarely applied to nuclear medicine. In this study, a
suitable target material of nat Ba for the accelerator
production of 141 Ce was investigated. A chemical separation method for 141 Ce from the irradiated nat Ba target was also investigated through column chromatography with a Ln resin (extraction chromatographic resinwith di(2-ethylhexyl) phosphoric acid).
For the determination of a suitable target materialof nat Ba, BaCl2 and BaO pellets (both approximately
100 mg) were irradiated with a 29-MeV alpha beam
(beam intensity: 1.3 particle μA, irradiation time:
10 min) using the RIKEN K70 AVF cyclotron. The
irradiated nat Ba targets were subjected to γ-ray spectrometry with a Ge semiconductor detector. In thechemical separation of 141 Ce from the nat Ba target,
the irradiated nat Ba target (approximately 100 mg)
was dissolved in 3 mL of 1 M HCl. After evaporation to dryness, the residue was dissolved in 3 mL of
0.01 M HCl solution and then fed into a Ln resin column (5-mm diameter × 50-mm height). nat Ba waseluted by 0.01 M HCl, following which 141 Ce was elutedby 1 M HCl solution by referring to the literature.1)
Each eluted sample (1 mL) was subjected to γ-ray
spectrometry with the Ge detector for the determination of 141 Ce radioactivity. After measurement with
the Ge detector, the concentration of nat Ba in each
eluted sample was measured by inductively coupledplasma mass spectrometry (ICP-MS).
In the production of 141 Ce from the BaCl2 tar-

1 M HCl

141Ce (Ȗ-ray spectrometry)80

natBa (ICP-MS)

60
40
20
0

0

2

4 6 8 10 12 14 16 18
Elution volume (mL)

Fig. 1. Elution curves of nat Ba and 141 Ce in chromatographic separation with Ln resin.

Reference
1) E. P. Horwitz, C. A. A. Bloomquist, J. Inorg. Nucl.
Chem. 37, 425 (1975).

Department of Nuclear Medicine and Tracer Kinetics, Graduate School of Medicine, Osaka University
Institute for Radiation Sciences, Osaka University
RIKEN Nishina Center
Research Center for Nuclear Physics, Osaka University- 130 -

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RIKEN Accel. Prog. Rep. 55 (2022)

Production of no-carrier-added Cr radiotracers in α-particle-induced
reactions on Ti target
T. Yokokita∗1 and H. Haba∗2
48

∗1
∗2

Department of General Education, Salesian Polytechnic
RIKEN Nishina Center

70

51

Crࠉࠉ

60 Charge 4.5 M HF

48

Vࠉࠉ

nat

Ti

c. HF

Elution (%)

50
40
30
20
10
0
0

5 10 15 20 25 30 35 40 45 50
Eluent volume (mL)Fig. 1. Elution curves of 51 Cr, 48 V, and nat Ti for the anionexchange chromatography.

fraction was evaporated to dryness, and the residue wasweighted.
The elution curves for the anion-exchange chromatography of 51 Cr, 48 V, and nat Ti are shown in Fig. 1. 95%
of 51 Cr were eluted with 15 mL of 4.5 M HF. The decontamination factor of the nat Ti for 51 Cr was 4.9 × 10−4 ,indicating that the anion-exchange separation was useful in the separation of the Cr radiotracers from the target material Ti. However, the decontamination factorof 48 V for 51 Cr was not satisﬁed (0.83). In regards tonat
Ti, 99% was eluted with 35 mL of c. HF. This highrecovery yield of nat Ti is promising for recycling of theenriched 46 Ti target material.
The elution curves in the cation-exchange chromatography of 51 Cr and 48 V are shown in Fig. 2. 94% of 51 Cr

Elution (%)

Cr is a promising radioisotope for a double photon
emission computed tomography.1) The proposed method
can achieve high spatial resolution and high signal-tonoise ratio.2) As 48 Cr, a pair of 112- and 308-keV photons can be used for coincidence imaging.1) We plan toproduce 48 Cr in the 46 Ti(α, 2n)48 Cr reaction. In nuclear
medicine, 48 Cr must be chemically separated from thetarget material and byproducts. In this study, we investigated a production method of no-carrier-added Cr
radiotracers from an α-particle-irradiated nat Ti (nat =natural isotopic abundance) target using 51 Cr (T1/2 =27.7 d) produced in the nat Ti(α, xn)51 Cr reaction. In
the future, 48 Cr can be produced using expensive enriched 46 TiO2 as the target material. Therefore, we also
investigated the recovery of the target material after the
production of the Cr radiotracers.
48, 51
Cr were produced in the nat Ti(α, xn)48, 51 Cr reactions using the RIKEN AVF cyclotron. A metallic nat Ti
plate of thickness 45 mg/cm2 was irradiated for 1.69 hwith a 28.9-MeV α beam of intensity 3.1 particle μA.
Upon irradiating the target, 48 V (T1/2 = 16.0 d) was
also produced in the nat Ti(α, x)48 V reaction and as theelectron-capture and β + -decay daughter of 48 Cr (T1/2 =21.6 h). It is desirable to remove the long-lived 48 V justbefore the imaging experiment with 48 Cr to increase thesignal-to-noise ratio.
The irradiated nat Ti plate (63.4 mg) was dissolved in a
mixture of 1 mL of concentrated HF (c. HF) and 0.3 mLof c. HNO3 by heating, and the solution was evaporated
to dryness. The residue was dissolved with 1 mL ofc. HF by heating, and the solution was evaporated todryness. The residue was dissolved in 6 mL of 4.5 M HF
by heating. Subsequently, the solution was fed into ananion-exchange column (Muromac 1X8, 100–200 mesh,
10 mm i.d. × 110 mm height). The resin was washedwith 9 mL (1 mL × 9) of 4.5 M HF and 35 mL (5 mL× 7) of c. HF. The 4.5 M HF fractions were combined,
and 3 mL of it was used for the ICP-MS measurement
to conﬁrm the contamination of nat Ti.
The remainder of the 4.5 M HF was evaporated todryness and further puriﬁed to remove 48 V using cationexchange chromatography. The residue was dissolved in
3 mL of 0.5 M HNO3 . The solution (1 mL × 3) was
fed into a cation-exchange column (Muromac 50WX8,
100–200 mesh, 5 mm i.d. × 50 mm height). The resin
was washed with 3 mL (1 mL × 3) of 0.5 M HNO3 and5 mL (1 mL × 5) of 6 M HNO3 .
Each eluent from the anion- and cation-exchange
columns were subjected to γ-ray spectrometry with a
Ge detector to obtain the elution curves of 51 Cr and48
V. To evaluate the elution curve of nat Ti, each c. HF

80
51
48
V
70 Charge Crࠉࠉ
6 M HNO 3
0.5 M HNO 3
60
50
40
30
20
10
0
0
3
6
9
Elution volume (mL)12
Fig. 2. Elution curves of 51 Cr and 48 V for the cationexchange chromatography.
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RIKEN Accel. Prog. Rep. 55 (2022)

was eluted with 6 mL of 0.5 M HNO3 . The decontamination factor of 48 V for 51 Cr was improved from 0.83 to
1.1 × 10−3 . The chemical yield of 51 Cr was 90% after
both the anion- and cation-exchange separations.
We propose a method for the production no-carrieradded Cr radiotracers from an α-particle-irradiated Ti
target. The 48 Cr produced using the proposed method
using enriched 46 TiO2 as the target material can be used
for double photon coincidence imaging experiments.
References
1) M. A. Choghadi et al., Radioisotopes 70, 271 (2021).
2) Y. Yoshihara et al., Nucl. Instrum. Methods Phys. Res.
A 873, 51 (2017).

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III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production of 44 Ti via the 45 Sc(p, 2n)44 Ti reaction for 44 Ti/44g Sc
generator development
X. Yin,∗1 T. Fukuchi,∗2 Y. Watanabe,∗2 and H. Haba∗1
Table 1. Activities of 44 Ti, 44m, 46 Sc at EOB.

44g

Sc is a promising radionuclide for PET imaging applications.
Its direct production via the44
Ca(p, n)44m, g Sc and 44 Ca(d, 2n)44m, g Sc reactions were
investigated by several groups.1–4) Owing to the shorthalf-life of 44g Sc (T1/2 = 3.9 h), daily irradiations close
to the site where it is used are required to maintaina constant supply of 44g Sc. An alternative approachto obtain 44g Sc is the production by the 44 Ti (T1/2 =59.1 y)/44g Sc generator.5) In this work, we investigatedthe production of 44 Ti via the 45 Sc(p, 2n)44 Ti reaction
to develop the 44 Ti/44g Sc generator.
A metallic 45 Sc (99.99%) disk target with a diameterand thickness of 10 mm and 0.90 g/cm2 , respectively,
was placed in an irradiation chamber with helium gas
and water cooling.6) The target was irradiated for 1.25 hwith a 0.25-μA proton beam from the RIKEN AVF cyclotron. The incoming and outgoing proton beam energies were 30 MeV and 15 MeV, respectively.
Large amounts of 44m Sc (T1/2 = 58.6 h) and 44g Sc
were also produced in the 45 Sc(p, x)44m, g Sc reactions.
The short-lived 44g Sc fully decays in several days. Thus,
the activities of 44m Sc and 44 Ti at the end of bombardment (EOB) were determined by ﬁtting the decay
curve of the 1157-keV gamma line of 44g Sc after radioactive equilibrium. The yields of 44 Ti and 44m Sc withthe beam energy range of 30–15 MeV were calculated
based on the cross-section data reported by L. Daraban.7) The calculated results agree well with the experimental results. In addition, 46 Sc (T1/2 = 83.8 d) was
co-produced via the secondary-neutron-induced reactionof 45 Sc(n, γ)46 Sc. The activity of 46 Sc was determinedby the 889-keV and 1121-keV gamma lines after 76 daysof cooling. The results from the two gamma lines agree
well with each other and are listed in Table 1.
44
Ti was separated from the target with ZR resin.
Firstly, the irradiated 45 Sc target (0.71 g) was dissolvedin 20 mL of 6 M HCl and heated to dryness. Subsequently, the residue was dissolved in 5 mL of 6 M HCl
and fed into a column ﬁlled with conditioned ZR resin(100–150 μm, 5 mm i.d. × 5 mm). Scandium passed
through the column while titanium was adsorbed on
the resin. Finally, 44 Ti was eluted with 6 mL of 3 M
HCl/0.325 M H2 O2 solution.8) The Ti/Sc separation factor was determined by the activity ratio of 44 Ti and 46 Sc
before and after separation. The recovery yield of 44 Ti
was 95%, and the Ti/Sc separation factor was >103 inthis scheme. The gamma-ray spectrum of 44 Ti after thechemical separation is shown in Fig. 1. Small amountsof long-lived 56 Co (T1/2 = 77.3 d) and 54 Mn (T1/2 =312.3 d) found in the irradiated target were successfully∗1∗2

Fig. 1. Gamma-ray spectrum of 44 Ti after separation.

removed by the chemical separation. Only gamma lines
from 44 Ti and its daughter, 44g Sc, were identiﬁed in the
gamma-ray spectrum. The radionnuclidic purity of 44 Ti
after chemical separation was evaluated to be >99%.
By assuming experimental conditions (incident beamenergy: 30 MeV; beam intensity: 10 μA; target thickness: 0.9 g/cm2 ; irradiation time: 10 d), 8 MBq of 44 Ti
can be produced at the EOB.
In the future, we will develop a prototype of the44
Ti/44g Sc generator with long-term stability, high yieldof 44g Sc, and no 44 Ti breakthrough.
References
1) C. Alliot et al., Nucl. Med. Biol. 42, 524 (2015).
2) G. W. Severin et al., Appl. Radiat. Isot. 70, 1526 (2012).
3) C. Müller et al., J. Nucl. Med. 54, 2168 (2013).
4) R. Hernandez et al., Mol. Pharm. 11, 2954 (2014).
5) D. Filosofov et al., Radiochim. Acta 98, 149 (2010).
6) S. Yano et al., RIKEN Accel. Prog. Rep. 50, 261 (2017).
7) L. Daraban et al., Nucl. Instrum. Methods Phys. Res. B
267, 755 (2009).
8) V. Radchenko et al., J. Chromatogr. A 1477, 39 (2016).

RIKEN Nishina Center
RIKEN Center for Biosystems Dynamics Research- 133 -

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III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

HPLC elution behavior of heavy lanthanide metallofullerene: Ln@C82(Tb, Dy, Ho, Er, Lu) on pyrenyl stationary phase
K. Akiyama,∗1,∗2 K. Amekura,∗1 H. Haba,∗2 and S. Kubuki∗1
Metallofullerene (MF) is a clathrate compound encapsulating metal atoms in a fullerene molecule. Lanthanide (Ln) EMF, Ln@C82 , have two or three chargetransferred electrons on the C82 cage from the encapsulated Ln atom, and their electronic states reﬂect the
number of charge transfer electrons.1) From the view
point of inorgnic chemistry, it is interesting to probe
the eﬀect of the electronic state for the series of the tenlanthanide elements (La, Ce, Pr, Nd, Gd, Tb, Dy, Ho,
Er, Lu) with the electronic states of (Ln3+ )@(C82 3− ) on
the electronic state of the Ln@C82 molecule from thediﬀerence in interaction with pylenyl stationary phase.
To this end, we have determined the retention time in
the pyrenyl stationary phase for ﬁve types of Ln@C82
from La to Gd by using radio chromatography withten Ln metal atoms activated by the thermal neutron
activation method. Moreover, the retention times inthe High Performance Liquid Chromatography (HPLC)
of Ln@C82 with heavy lanthanide elements have notbeen obtained, because the half-lives of the radionuclides produced by thermal neutron irradiation such as
165
Dy and 171 Er are very short. Moreover, the production of Ln2 @C82 and Ln2 C2 @C80 , whose production rate increase competitive products, inteferes withthe detection of Ln@C82 with increasing atomic number of Ln. In this paper, we report the HPLC retention time of Ln@C82 encapsulating heavy lanthanides
evaluated from HPLC data of already puriﬁed Ln@C82
and 139 Ce@C82 , where 139 Ce was produced using the
RIKEN AVF cyclotron as a comparative standard of
HPLC analysis.
Cerium-139 produced by 139 La(d, 2n)139 Ce reaction
using a nat La target irradiated with 5 μA of 24 MeV
deuterons for 5 h at the RIKEN AVF cyclotron was
puriﬁed from the target material of La by a solvent extraction method. The studied heavy Ln@C82 in thiswork were produced and separated by a previously reported method.2) The separated metallofullerene solutions were puriﬁed by HPLC with a Buckyprep-M
column (ﬂow rate: 3.2 mL min−1 , developing solvent:toluene) from other interfering metallofullerenes suchas Ln2 @C82 . These puriﬁed Ln@C82 with 139 Ce@C82
were injected into a buckyprep column, whose stationary phase is silicate modiﬁed with propylpylenylsilyl(ﬂow rate: 3.2 mL min−1 , developing solvent: toluene),monitored by UV absorption. Then, the elution components were fractionated every 20 seconds. The HPLC
retention times of 139 Ce@C82 and Ln@C82 were evaluated from the gamma-ray measurement of each sample∗1∗2

Department of Chemistry, Tokyo Metropolitan University
RIKEN Nishina Centerwith a Ge detector and HPLC chromatogram monitored by the UV absorption, respectively.
Here, we deﬁne the HPLC retention time of Ln@C82
obtained in this study and the void retention time corresponding to the void volume of column as tLn and t0 ,respectively, and the retention ratio of kLn of Ln@C82 isgiven by kLn = (tLn −t0 )/t0 . The separation coeﬃcient(α) can be expressed as the ratio of the retention ratio
for Ln@C82 (kLn ) to that for 139 Ce@C82 (kCe ). The
HPLC retention time tLn and the evaluated separationcoeﬃcient of the studied Ln@C82 are shown in Table 1.
Figure 1 shows the separation coeﬃcient for each heavy
lanthanide Ln@C82 as a function of the spin multiplicity of Ln, together with those for previously reported
α of light lanthanide Ln@C82 . Since a very good correlation can be seen between 2S + 1 and α of Ln@C82(Ln: La to Er), it is presumed that the small diﬀerencein the interaction between the pyrenyl stationary phaseand Ln@C82 is caused by the 4f electronic state of theencapsulated lanthanide atom. For Lu@C82 , the large
separation coeﬃcient cannot be explained. In the near
future, it is necessary to investigate the properties of
Lu@C82 in detail.
Table 1. HPLC retention time and separation coeﬃcient α
of studied Ln@C82 .
Tb
Dy
Ho
Er
Lu
kCe 10.17 10.16 10.11 9.196
9.303
kLn 10.38 10.20 10.19 9.307
9.453
α
1.021 1.004 1.008 1.012
1.016
Error of t and α is estimated to be less than 0.3%

Fig. 1. Relation between spin multiplicity of Ln and separation coeﬃcient α.

References
1) H. Shinohara, Rep. Prog. Phys. 63, 843 (2000).
2) K. Akiyama et al., RIKEN Accel. Prog. Rep. 53, 194(2019).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Ionic liquid extraction of astatine
for a nuclear medical utilization
Y. Nagai,∗1 K. Aoi,∗1 S. Maruyama,∗1 A. Yokoyama,∗2,∗3 K. Washiyama,∗4 I. Nishinaka,∗5 Y. Wang,∗3 X. Yin,∗3
A. Nambu,∗3 Y. Shigekawa,∗3 and H. Haba∗3
Astatine-211 is a nuclide with potential applicationsin α-ray internal therapy. Solvent extraction with an organic solvent has been used as a conventional method
for separating 211 At from the 209 Bi target irradiatedwith an α beam from an accelerator. Although organic
solvents are inexpensive and readily available, they arevolatile and ﬂammable, and therefore, they raise concerns about environmental pollution and handling of
dangerous substances.
In recent years, ionic liquids have attracted attention
as an alternative to organic solvents from the viewpointof green chemistry. Ionic liquids are in the liquid phaseat room temperature, have low volatility, and are ﬂameretardant: therefore, there is little environmental loador risk of accidents. Further, the amount of radioactive
waste can be reduced compared to that using organic
solvents because they can be used repeatedly. In addition, ionic liquids are considered promising solventsfor extracting 211 At given the reports on radiation resistance.1) However, few studies on the extraction of211
At with ionic liquids have been reported in the literature.2) Therefore, in this study, we investigated thesuitability of the HCl system, which has been reported
to show excellent performance for 211 At solvent extraction,2) depending on the type of ionic liquid.
The nuclide of 211 At was produced via the209
Bi(α, 2n) reaction at the RIKEN AVF cyclotron
and delivered to Kanazawa University. The irradiated Bi target was dissolved in 3 mL of 6 M HNO3
and mixed with an appropriate amount of H2 O toprepare a 1 M HNO3 solution, 7 mL of which wasused to extract the 211 At nuclide into 7 mL of dodecane solvent. After extracting 211 At to dodecanefrom HNO3 solution, it was further extracted to 0.1 M,
1 M, and 3 M HCl solutions. Then, 211 At was extracted into ﬁve kinds of ionic liquids: [C8 mim]+[PF6 ]− , [C8 mim]+ [BF4 ]− , and [C4,6,8 mim]+ [Tf2 N]− ,where [Cn mim]+ and [Tf2 N]− stand for alkylimidazolium ion and bis(triﬂuoromethanesulfonyl)imide ion,
respectively. Finally, it was back extracted into 0.1, 1,
and 3 M NaOH solutions. The radioactivity of 211 At
was measured with a liquid scintillation counter for the
HCl solution samples before and after extraction and
∗1
∗2
∗3
∗4
∗5

Graduate School of Natural Science and Technology,
Kanazawa University
Institute of Science and Engineering, Kanazawa University
RIKEN Nishina Center
Fukushima Global Medical Science Center, Fukushima Medical University
Quantum Beam Science Research Directorate, National Institutes for Quantum Science and Technology

Fig. 1. At extraction rates of ionic liquids from HCl solutions.

the NaOH solution samples after back extraction. The
extraction rate of 211 At from the HCl solution to theionic liquid and the back extraction rate from the ionicliquid to the NaOH solution were determined. Further,
the At chemical species in the HCl solution were inferred by the TLC analysis of dodecane before and after
extraction.
Figure 1 shows the extraction rates of 211 At fromthe HCl solutions for ﬁve ionic liquids of ion pairs
from three cations and three anions. When comparing cations, the larger the carbon chain, the higher isthe extraction rate. When comparing anions, the larger
the hydrophobicity, the smaller is the extraction rate.
The hydrophobicity of cations and anions in the ionicliquid aﬀects the ion exchange with At ions in the aqueous phase. In addition, the rates for [C8 mim] [Tf2 N]
have values exceeding 90% for both extraction and backextraction while [C8 mim] [PF6 ] and [C8 mim] [BF4 ] exhibit back extraction rates of less than 20%. Therefore,
one of the ion liquids studied is considered promisingfor 211 At solvent extraction in practical applications.
References
1) L. Yuan et al., J. Phys. Chem. B 113, 8948 (2009).
2) K. Kawasaki, Master thesis, Graduate School of Natural
Science and Technology, Kanazawa University (2020).

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RIKEN Accel. Prog. Rep. 55 (2022)

Synthesis of [211 At]4-astato-L-phenylalanine bydihydroxyboryl-astatine substitution reaction in aqueous solution†
Y. Shirakami,∗1 T. Watabe,∗2 H. Obata,∗3 K. Kaneda,∗1 K. Ooe,∗2 Y. Liu,∗2 T. Teramoto,∗1 A. Toyoshima,∗1
A. Shinohara,∗1 E. Shimosegawa,∗2 J. Hatazawa,∗1 and K. Fukase∗3
Radiopharmaceutical therapy, including targetedalpha-particle therapy (TAT), has recently emerged asa novel therapeutic modality for the treatment of tumor. We previously demonstrated the utility of [211 At]4astato-L-phenylalanine ([211 At]APA) for the treatmentof glioma in tumor-bearing mice by means of TAT.1)[211 At]APA speciﬁcally accumulates in tumor cells andare transported by the LAT1 transporters, which are
predominantly expressed on the surface of various tumor cells including the glioma cells. In a mouse model
xenografted with rat glioma cells, [211 At]APA signiﬁcantly decreased the tumor volume after a single injection of the agent (dose range: 0.1–1.0 MBq/mouse) in
the mouse.
Phenylalanine has been previously labeled with 211 At
using diﬀerent methods.2,3) However, most of the existing reactions for the synthesis of radiolabeled compounds either require the use of toxic and hazardous chemicals or are unable to yield a carrier-free ﬁnal product.
We have developed a new and improved method
for the preparation of [211 At]APA using 4-boronoL-phenylalanine (BPA) as the starting molecule.
[211 At]APA was synthesized by the electrophilic substitution of 211 At for a dihydroxyboryl (or borono)group on an aromatic ring of the corresponding precursor molecule BPA using N-bromosuccinimde (NBS;
NBS method) as an oxidant or KI (KI method) as
shown in Fig. 1. The radiochemical yield (RCY) andradiochemical purity (RCP) were better with the latter method. The reagents and compounds used forthe synthesis of [211 At]APA were commercially approved drugs and physiologically relevant for clinical use. The entire synthesis could be accomplishedin aqueous media; no organic solvents or toxic metals were required, suggesting that this method isrelevant for practical applications.
We also elucidated the diﬀerences between the chemical properties of iodine and astatine for the labeling reactions.
Based on our ﬁndings, the reaction scheme for the211
At labeling of arylboronic acids is depicted in Fig. 2.
In the NBS method, 211 At initially reacts with NBS toform the [211 At]astatosuccinimide intermediate (Fig. 2,
top). Then, [211 At]astatosuccinimide reacts with thearylboronic acid to produce [211 At]arylastatide. In the
KI method, 211 At reacts with KI to form the [211 At]AtI
and/or AtI−
Several
2 intermediate (Fig. 2, bottom).
†
∗1
∗2
∗3

Condensed from the article in Sci. Rep. 11, 12982 (2021)
Institute for Radiation Sciences, Osaka University
Department of Tracer Kinetics and Nuclear Medicine, Graduate school of Medicine, Osaka University
Department of Chemistry, Graduate School of Science, Osaka
University

O

O
OH
HO

B
OH

NH2

211At aq. soln.

KI or NBS, RT

OH
211

At

NH2

[211At]APA

BPA

Fig. 1. Radioastatination reaction of boronophenylalanine.

NBS[211At]N-Astatosuccinimde

211At Aq. soln.

KI[211At]AtI or
AtI2-

Arylboronicacid
Ascorbic acid
Arylboronicacid[211At]Arylastatide[211At]Arylastatide

Fig. 2. Mechanism of astatination of arylboronic acids.

studies have suggested that astatine can react with iodide and produce inter-halogen compounds such as AtI
4)
and AtI−
The AtI and/or AtI−
2.
2 intermediate reacts
with the arylboronic acid to give [211 At]arylastatide.
Compared to NBS, KI was found to be more eﬃcientfor the substitution of the dihydroxyboryl group by astatine in the aqueous media. KI can probably reduce
the hypervalent 211 At species present in the aqueous solution (∼10%), forming the reactive [211 At]AtI and/or
AtI−
2 intermediate that allows higher RCYs comparedto that obtained using the NBS method.
KI was originally intended to be used as the carrier
atom of 211 At since there are no natural stable isotopes
of astatine. Unexpectedly, the radiolabeling yield of[211 At]APA using KI was much higher than 95%, due
to the formation of [211 At]AtI and/or AtI−
2 as a reaction
intermediate in the aqueous solution.
It is well known that tyrosine can be labeled withradioactive iodine via an electrophilic substitution reaction in the presence of an oxidant, such as chloramine
T, Iodogen, N -chlorosuccinimde, NBS, or H2 O2 . Astatination of tyrosine, however, gave a low yield of [211 At]
astatotyrosine (<15%) with H2 O2 , and the product was
unstable under neutral and basic conditions. Additionally, the labeling yield was low. These results were suggestive of the diﬀerent chemical properties of astatine
and iodine.
In summary, we developed a novel method for the synthesis and puriﬁcation of [211 At]APA, which has potential clinical uses.
References
1) T. Watabe et al., Oncotarget 11, 1388 (2020).
2) G. J. Meyer et al., Appl. Radiat. Isot. 68, 1060 (2010).
3) N. Borrmann et al., Nuklearmedizin 52, 212 (2013).
4) G. W. Visser et al., Int. J. Appl. Radiat. Isot. 32, 905(1981).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Neopentyl glycol as a scaﬀold to provide radiohalogenated theranostic
pairs of high in vivo stability†
H. Suzuki,∗1 Y. Kaizuka,∗1 M. Tatsuta,∗2 H. Tanaka,∗2 N. Washiya,∗1 Y. Shirakami,∗3 K. Ooe,∗4 A. Toyoshima,∗3
T. Watabe,∗4 T. Teramoto,∗3 I. Sasaki,∗5 S. Watanabe,∗5 N. S. Ishioka,∗5 J. Hatazawa,∗6 T. Uehara,∗1 andY. Arano∗1
211

At is one of the most promising α-emitting radionuclides applicable to targeted α-therapy. Low-molecularweight targeting molecules are suitable for delivering211
At to target tissues because of its short half-life(7.2 h). Benzoate derivatives have been widely used
to prepare radioiodinated low-molecular-weight targeting molecules of high stability against in vivo deiodination.1) Although astatine shares some chemical properties similar to those of iodine, 211 At-labeled benzoate
derivatives are unstable against in vivo deastatination.2)
Therefore, a new scaﬀold applicable to a radiotheranostic system with 211 At and radioiodine needs to be developed.
We focus on a neopentyl glycol structure used for 2dihydroxymethyl-3-[18 F]ﬂuoropropyl-2-nitroimidazole([18 F]DiFA, Fig. 1) that shows high stability against invivo deﬂuorination.3) In this study, the neopentyl glycol structure was applied for heavier radiohalogens suchas radioiodine and 211 At; however, the dissociation energy of sp3 carbon-halogen bonds in alkyl halides is low
and decreases with an increase in the atomic number of
halogen.4) Three neopentyl iodide compounds with orwithout hydroxyl groups ([125 I]1a, [125 I]2, and [125 I]3,
Fig. 1) were synthesized to investigate the role played by
the hydroxyl groups before studying with 211 At-labeled
compounds.
All three neopentyl iodides remained stable against
the nucleophilic attack.
While [125 I]2 and [125 I]3were deiodinated by cytochrome P450 (CYP)-mediatedmetabolism, [125 I]1a remained stable against CYPmediated metabolism. The biodistribution study wascorrelated with the in vitro study of CYP-mediatedmetabolism; [125 I]1a showed the lowest accumulation in
the stomach and neck where free [125 I]I− accumulates.
The liberation of [125 I]I− was observed via the urine analyses of [125 I]2 and [125 I]3 but it was not observed for[125 I]1a, which indicates that the C-I bond of [125 I]1a
was stable against in vivo deiodination.
The structure of [125 I]1a was applied for 211 At to prepare [211 At]1b. 211 At used in this work was produced in
the 209 Bi(α, 2n)211 At reaction using the RIKEN AVF cyclotron. [211 At]1b showed high in vitro stability against
nucleophilic attack and the CYP-mediated metabolism.
†
∗1
∗2
∗3
∗4
∗5
∗6

Condensed from the article in J. Med. Chem. 64, 15846 (2021)
Graduate School of Pharmaceutical Sciences, Chiba University
Department of Chemical Science and Engineering, Tokyo Institute of Technology
Institute for Radiation Sciences, Osaka University
Graduate School of Medicine, Osaka University
Takasaki Advanced Radiation Research Institute, National Institutes for Quantum Science and Technology
Research Center for Nuclear Physics, Osaka University

Fig. 1. Chemical structures of neopentyl and benzoate
derivatives evaluated in this study.

Fig. 2. Biodistribution in selected organs after the injectionof [125 I]1a, [211 At]1b, [125 I]4a, and [211 At]4b.

When injected into normal mice, the radioactivity levelsin the stomach and the neck registered low levels. The
biodistribution proﬁles of [211 At]1b were similar to thoseof [125 I]1a (Fig. 2). However, the reference compound[211 At]4b (Fig. 1) exhibited pharmacokinetics diﬀerent
from [125 I]4a, with high radioactivity levels observed in
the stomach and the neck. Further, the urine analysis
showed that [211 At]At− was liberated from [211 At]4b but
not from [211 At]1b, which implies that the C-At bond of[211 At]1b was stable against in vivo deastatination.
In this study, a neopentyl structure with two hydroxyl
groups (neopentyl glycol) provided 125 I- and 211 Atlabeled compounds with high stability against nucleophilic attack and the CYP-mediated metabolism. Furthermore, both compounds registered similar biodistribution proﬁles and metabolic fate. These ﬁndings indicate that neopentyl glycol would constitute a useful
scaﬀold for developing a radiotheranostic system withradioiodine and astatine as radiolabels for further applications.
References
1) M. R. Zalutsky et al., Cancer. Res. 49, 5543 (1989).
2) G. Vaidyanathan, M. R. Zalutsky, Curr. Radiopharm. 1,
177 (2008).
3) N. Nakata et al., Nucl. Med. Biol. 70, 39 (2019).
4) H. H. Coenen et al., Radiochim. Acta 34, 47 (1983).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Treatment for peritoneal dissemination of gastric cancer using 211 At
S. Nomura,∗1 A. Sugiyama,∗2 H. Haba,∗3 Y. Wang,∗3 Y. Kumakura,∗4 N. Akimitsu,∗2 and Y. Wada∗
Peritoneal dissemination is one of the miserable patterns of recurrence of cancer. This recurrence patternis the most common in gastric cancer. There is no
way to cure it and there are only treatment methods todecelerate the cancer growing by chemotherapy or immunotherapy. External irradiation is also diﬃcult foravoiding intestinal irradiation. We developed murine
gastric cancer cell lines, YTN that can be transplanted
into C57BL/6, immunocompetent mouse.1) YTN16 candevelop peritoneal dissemination in C57BL/6 mice with
100% rate, when 1 × 107 cells are injected into theperitoneal cavity. We also have less aggressive subline
YTN2. Comparing mRNA expression between YTN16
and YTN2, using microarray, Fibroblast Growth Factor
Receptor 4 (FGFR4) was highly expressed in YTN16.
Since α-emitting 211 At is reported to be an eﬀective therapy for peritoneal dissemination,2) we sought to develop
the treatment for YTN16 peritoneal dissemination using
211
At-FGFR4 Ab.
YTN16 peritoneal dissemination mouse model was
made as we reported and 3 weeks later, 211 At was administered and the accumulation of 211 At into peritoneumwas measured using a gamma-counter after 4.5 hours, 16
hours, and 23 hours after administration. The 1 MBq
of free 211 At was administered through intra venous(0.2 mL), intra peritoneum (1.0 mL), and intra gastric(0.5 mL). The 211 At-FGFR4 Ab (1 MBq-16.4 μg Ab)
was administered through intra venous (0.2 mL) and intra peritoneum (1.0 mL). As shown in Fig. 1, 211 At conjugated with Ab accumulated in peritoneum 16 hours
and 23 hours after administration.
Next, to conﬁrm the treatment eﬀect of 211 At, we sacriﬁced the mice 5 weeks after transplantation of YTN16,
through 211 At treatment 10 days before sacrifying. The
severity of peritoneal dissemination could be diagnosed
macroscopically. As shown in Fig. 2, intraperitoneal

Fig. 2. Treatment eﬀect of 211 At for peritoneal dissemination.

administration of 211 At-FGFR4 Ab was most eﬀective
followed by intravenous administration of 211 At-FGFR4
Ab, and intraperitoneal administration of free 211 At.
Finally, the eﬀect for overall survival of mice was analyzed by Kaplan-Mayer curves. As shown in Fig. 3,
211
At-FGFR4 Ab signiﬁcantly prolonged the overall survival of mice with gastric cancer peritoneal dissemination.

Fig. 3. Kaplan-Mayer analysis for treated mice.

The 211 At-Ab treatment for peritoneal dissemination
was eﬀective for reducing the cancer and elongating overall survival. More improvement is needed for prolonging
the survival. Especially eﬀective methods for gathering211
At to cancer faster are needed.
Fig. 1. 211 At accumulation in peritoneum.
∗1
∗2
∗3
∗4

References

Department of Gastrointestinal Surgery, University of Tokyo
Isotope Science Center, University of Tokyo
RIKEN Nishina Center
Department of Radiology, Saitama Medical University

1) M. Yamamoto et al., Cancer Sci. 109, 1480 (2018).
2) H. K. Li et al., Cancer Sci. 108, 1648 (2017).

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III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Analysis of complex formation between rhenium and varioushydrophilic ligands using HPLC and preparation of 186 Re-carrying
liposomes
I. O. Umeda,∗1 Y. Hamane,∗1 M. Nagata,∗1 A. Tenzaki,∗1 H. Haba,∗2 A. Nambu,∗2 X. Yin,∗2 H. Fujii,∗3 and
T. Takahashi∗1
Theranostics is an emerging and expanding medical ﬁeld based on therapeutic interventions after
imaging to verify the presence of a biological target.
Radioisotope-based therapeutics, i.e., radiotheranostics, is perhaps the most clinically advanced application of theranostics, with many developments andemerging opportunities. A key aspect of radiotheranostics is that the selection of patients for radiotargeted treatments is based on imaging of the same target area. Therefore, imaging and therapeutic intervention are closely linked.1) Technetium-99m is themost widely used nuclide in diagnostic nuclear medical imaging, because the energy of the corresponding
gamma-ray emission (140 keV) is ideal for imaging using gamma cameras, and it can be generated on demand at medical facilities using 99 Mo/99m Tc generators. Rhenium, a group 7 homologous element of technetium, is assumed to have chemical properties similar
to those of Tc. 186 Re (half-life T1/2 = 3.72 days) emitsbeta rays of 1.07 MeV, appropriate for radionuclide
therapy. Thus, 186 Re and 99m Tc should be an ideal“theranostics pair.” To this end, 186 Re has been produced by neutron irradiation in nuclear reactors, which
is diﬃcult to realize in Japan. At the RIKEN RI beamfactory (RIBF), we succeeded in producing no-carrieradded, high-purity 186 Re using an accelerator-based
ion beam irradiation. We are aiming to develop new
radiotheranostics using 186 Re.
For radiotheranostics, a common platform for diagnostic and therapeutic nuclides is important. We havebeen investigating the application of liposomes, wellknown drug carriers, as a radiotheranostics platform.
Liposomes are promising tools for radiotheranostics,
because they can in principle encapsulate any radionuclides, and deliver them to the target lesion. In thisstudy, we conducted a basic investigation for eﬃcient
encapsulation of 186 Re into liposomes.
We encapsulated various radionuclides in liposomeswith high eﬃciency using the remote loading method,i.e., a ligand exchange reaction across the liposomal
membrane using lipophilic and hydrophilic ligands.2)
In this method, the complex formation between the
nuclide and ligand and their stability are importantfactors. There are few data on the complex formationof 186 Re. We ﬁrst developed an analytical method toevaluate their formation and stability using high per∗1∗2∗3Kavli IPMU, University of Tokyo
RIKEN Nishina Center
EPOC, National Cancer Center- 139 -

formance liquid chromatography (HPLC) and a stable
isotope of rhenium.
Rhenium-186 was produced in the 186 W(d, 2n)186 Re
reaction. A 24-MeV deuteron beam delivered fromthe AVF cyclotron was irradiated onto a 186 WO3pellet target (isotope enrichment of 186 W: 99.79%;
thickness: 580 mg/cm2 ). After irradiation, 186 Re
was puriﬁed by chemical separation.3) An aqueous solution of 186 Re-perrhenate in 0.01 M HCl(radioactivity concentration: 83.0 MBq/mL) was
supplied.
Ammonium perrhenate was used asa stable isotope of rhenium. DiethylenetriamineN, N, N  , N, N  -pentaacetic acid (DTPA), dimercaptosuccinic acid (DMSA), hydrazinonicotinamide(HYNIC), and ethylenedicysteine (EC) were examined as hydrophilic ligands. HPLC analysis was conducted using Shimazu Prominence LC-20 equippedwith aerosol-based detector NQAD and gamma-ray radiodetector. Liposomes comprised DSPC and cholesterol, or PEGylated, and preloaded hydrophilic ligands.
The formation of complexes between metal ions andligands is diﬃcult to analyze using conventional HPLC
systems, because these samples have no UV absorption, and are highly water-soluble. We realized thisusing unique columns, combination of cation exchange
column (CapcelPak CR) and unique ODS column(Capcell Core ADME), and a unique detector, NQAD.
Using this system, we were able to detect metal ions,
ligands, and the metal ion-ligand complexes as separate peaks. Figure 1 shows HPLC proﬁles of rhenium,
technetium, EC, and their complexes.
Using this system, the formation of complexes between rhenium and various hydrophilic ligands wasinvestigated. All the ligands used formed complexes
with 99m Tc. Under the conditions studied, DTPA and
HYNIC did not form complexes with rhenium. In caseof DMSA and EC, complex formation with rhenium
was observed. However, unlike 99m Tc, the complexes
were formed only under acidic conditions, high temperature, and required approximately ten times more
reducing agent than in the case of 99m Tc.
Next, we preloaded EC into liposomes and attempted to encapsulate 186 Re and 99m Tc into liposomes using the remote loading method. Incubation
at 40◦ C allowed only 99m Tc to be encapsulated, but
heating to 90◦ C allowed 186 Re to be encapsulated into
liposomes. Since 186 Re radioactivity was present in
the water-soluble fraction of liposomes, it was assumed

1

III-3. Radiochemistry & Nuclear Chemistry㻣㻡㻜㻌㻟㻚㻢㻡㻣㻌

㻡㻜㻜
㻡㻜

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Detector:㻌㻟㻚㻠㻤㻡

RIKEN Accel. Prog. Rep. 55 (2022)

㻜

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㻜

Ȗ-ray

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їRetention time (min)Fig. 1. HPLC separation of metal ions, ligands and metalligand complexes. Stable rhenium was used to determine the analytical conditions. NQAD was used for
detection. 99m Tc and 186 Re were then used to conﬁrm
the peaks.

that the 186 Re-EC complex was formed.
In this study, we have established a means to analyze complex formation between hydrophilic ligands
and rhenium, and evaluated optimal conditions for stable rhenium complex formation. Based on the results,
we have successfully prepared 186 Re-EC/99m Tc-ECencapsulated liposomes. These are expected to be useful radiopharmaceuticals for radiotheranostics. We arefurther investigating the quality control of the drugs
and their pharmacokinetics and tumor accumulation.
References
1) K. Herrmann et al., Lancet Oncol. 21, e146 (2020).
2) I. Ogihara-Umeda et al., J. Nucl. Med. 37, 326 (1996).
3) N. Shigeta et al., J. Radioanal. Nucl. Chem. 205, 85(1996).

2- 140 -

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Eﬀect of tumor size on the therapeutic eﬀect of 67 Cu-labeled
compounds targeting the somatostatin receptor
Y. Fujisawa,∗1 H. Haba,∗2 A. Nambu,∗2 Y. Shigekawa,∗2 Y. Wang,∗2 X. Yin,∗2 Y. Magata,∗3 and Y. Iida∗1
Nuclear medicine therapy, wherein a radiopharmaceutical is administered to patients for treatment, is aneﬀective medical treatment that targets cancer cells inthe body; it has garnered signiﬁcant attention in recent
years as an eﬀective treatment process that places lessburden on patients. Four nuclides are available in Japan,
namely, 131 I, 90 Y, and 177 Lu, which are β-particle emitting nuclides, and 223 Ra, which is an α-particle emitting
nuclide. 90 Y has a high energy β-particle of 2.28 MeV
and exhibits good therapeutic eﬀect; however, it has asigniﬁcant impact on the surrounding tissues and theinjected dose is limited by exposure to other organs.1)
Several other nuclides can be potentially used for nuclear
medicine therapy. For example, 67 Cu has a low energy
β-particle of 0.392 MeV; it can be administered in large
doses but its eﬀectiveness has not yet been suﬃciently
analyzed. Therefore, depending on the property of cancer tissue, eﬀective and eﬃcient treatment can be realized. It should be noted that the eﬀectiveness of nuclear
medicine therapy is aﬀected by the properties and size oftarget cancer tissue, radiation quality, and energy, suggesting that the most eﬃcient radiation energy may exist
for each target.2) In other words, although the range oftherapeutic eﬀect is limited owing to low energy, suﬃcient eﬀects can be obtained with low-energy β-particles
for small tumors, thus leading to eﬀective treatment.3)
We previously synthesized 67 Cu-ToDBTTATE targetingthe somatostatin receptor and demonstrated that thiscompound constricts tumor growth in model mice bearing AR42J rat pancreatic tumor cells.4) Further investigations regarding the characteristics of 67 Cu may contribute to eﬀective and eﬃcient treatment and/or customized medicine according to patient conditions.
In this study, we prepared model mice with tumors ofvarious sizes and attempted to investigate the diﬀerencesin the therapeutic eﬀect of 67 Cu-ToDBTTATE on thetumor size to clarify the relationship between tumor size
and the therapeutic eﬀects of 67 Cu-ToDBTTATE.
Tumor-bearing mice were prepared by implanting
AR42J tumor cells (5 × 106 cells), in 0.1 mL PBS, into
the ﬂanks of nude mice (BALB/c-nu/nu, male). Afterthe tumor grew to various sizes, 16.0–25.2 MBq of 67 CuToDBTTATE was injected into the mice from the tailvein. Saline or non-labeled ToDBTTATE-administeredmice were used as the control. All mice were weighed
and the tumor diameters were regularly measured using a caliper; the tumor volumes were determined us∗1
∗2
∗3

Faculty of Pharmaceutical Sciences, Suzuka University of
Medical Science
RIKEN Nishina Center
Department of Molecular Imaging, Hamamatsu University
School of Medicine

Fig. 1. Relationship between tumor size and the therapeutic eﬀect of 67 Cu-ToDBTTATE (◦: control, : 67 CuToDBTTATE). *: p < 0.05 (2-way ANOVA, sidack-test).

ing the following formula: (longer diameter) × (shorter
diameter)2 /2. This study was performed in accordancewith the recommendations by the Guide for the Careand Use of Laboratory Animals of Suzuka University of
Medical Science.
The mice were divided into four groups according to
the tumor size, i.e., less than 200, 200 to 400, 400 to
600, and 600 to 800 mm3 ; then, the 67 Cu-ToDBTTATEadministered mice were compared with the control ineach group. A tumor growth constricting eﬀect was observed in the 67 Cu-ToDBTTATE-administered mice inall groups compared with the control (Fig. 1). Sometumor growth was observed in the group with a tumor
size of less than 200 mm3 , which may be because thedays after cell implantation were short and the targeted
somatostatin receptor was not well expressed. No difference in the therapeutic eﬀect of 67 Cu-ToDBTTATEon the tumor size was observed in this study. In future
works, we plan to conduct comparative studies using
model mice with larger tumors.
References
1) G. A. Wiseman et al., Eur. J. Nucl. Med. 27, 766 (2000).
2) K. Fujimori et al., Kaku Igaku 31, 241 (1994).
3) E. B. van Dieren et al., Int. J. Radiat. Oncol. Biol. Phys.
36, 197 (1996).
4) Y. Fujisawa et al., RIKEN Accel. Prog. Rep. 53, 175(2019).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Synthesis of 44m Sc-DOTA-TATE for multiple-isotope PET imaging
T. Fukuchi,∗1 Y. Kanayama,∗1 A. Nambu,∗2 S. Usuda,∗2 Y. Shigekawa,∗2 Y. Wang,∗2 X. Yin,∗2 T. Yokokita,∗2
H. Haba,∗2 and Y. Watanabe∗1
Positron emission tomography (PET) is a useful tool
for radio-tracer imaging in a living organism. However, conventional PET can only be adapted for a single tracer because of the energy constancy of annihilation photons, which are utilized for PET imaging. To
overcome this disadvantage, we have developed a new
PET system that can be used for multiple-tracer simultaneous imaging. Our PET system, named multipleisotope PET (MI-PET), detects not only annihilation
photons but also prompt γ-rays, which are emitted successively after positrons. We have succeeded in proving the basic principle of MI-PET using a prototype
system.1)
The MI-PET system uses a positron-γ emitter,
which emits a de-excitation γ-ray after the positronemission in β + -decay, as a tracer, and identiﬁes thetracer by detecting the prompt γ-ray. For the MIPET tracer, a proper half-life, prompt γ-ray energy,
and emission ratio are required by the positron-γ emitter to ensure future clinical use. One promising candidates for this type of positron-γ emitter is 44 Sc (44m Sc),
which emits 1157 keV prompt γ-rays (99.9%) with ahalf-life of 3.97 h (44m Sc: 58.6 h). The imaging abilityof MI-PET for 44 Sc (44m Sc) has been already evaluated by several experiments using phantoms and animals.2,3) Therefore, as a next step, we have begun
to develop a useful drug, such as a cancer diagnosing
reagent labeled by 44 Sc (44m Sc). In our ﬁrst attempt,
we synthesized a 44m Sc labelled DOTA-TATE, which
is a compound containing tyrosine3-octreotate and asomatostatin receptor for numerous malignancies.
44m
Sc was produced via the reaction of 44 Ca(d,44m
Sc with a 24 MeV deuterium beam and was
2n)puriﬁed by chemical processes at the RIKEN AVF cyclotron. The produced 44m Sc was transported to the
RIKEN Kobe campus for the drug synthesis.
The labelling protocol was based on a method developed by Huclier-Markai et al.4) The protocol scheme
is shown in Fig. 1. DOTA-TATE (DOTA-[Tyr3]octreotide) was purchased from BACHEM (Switzerland). A total of 2.1 nmol of DOTA-TATE and7.7 MBq of 44m Sc were resolved into 55 μL of NaOH
(0.1 M) and 200 μL of ammonium acetate (pH 4.0,
0.25 M) and incubated at 95◦ C for 30 min with shaking. After incubation, 5.7 MBq of 44m Sc labeled
DOTA-TATE was washed out using an ion-exchange
column (Sep-Pak C18 1cc Vac cartridge) by 500 μL of
ethanol.
To evaluate the radio-labeling yield, TLC analyses∗1∗2

RIKEN Center for Biosystems Dynamics Research
RIKEN Nishina Center- 142 -

Fig. 1. Scheme for synthesis of 44m Sc labeled DOTATATE.

Fig. 2. TLC proﬁles of the free 44m Sc and 44m Sc-DOTATATE with developing solutions of citric acid (left),
NaCl/MeOH (center), and NaCl/MeOH/NH3 (right).
An imaging plate was used for analysis.

were performed by spotting onto TLC plates (silica gel
60 F254 ) with developing solutions of citric acid (pH4.0), NaCl/MeOH (3 : 1), and NaCl/MeOH/NH3 (3 :1 : 1). The TLC results obtained through an analysisof an imaging plate are shown in Fig. 2. These results
indicate that the labeling ratio for 44m Sc-DOTA-TATE
was above 90%.
References
1) T. Fukuchi et al., Med. Phys. 4, 2257 (2017).
2) T. Fukuchi et al., RIKEN Accel. Prog. Rep. 53, 21(2020).
3) T. Fukuchi et al., J. Instrum. 16, P01035 (2021).
4) S. Huclier-Markai et al., Nucl. Med. Bio. 41, e36 (2014).

1

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Investigation of the usability of RIKEN 44m Sc for radiolabeling onchelate-compounds
S. Oshikiri,∗1,∗2 S. Kubota,∗1,∗2 H. Kato,∗1,∗2 T. Yokokita,∗1 K. Suzuki,∗1,∗2 A. Hino,∗2 and H. Haba∗1
Scandium-44m (44m Sc) with a half-life of 58.61 h decays to scandium-44 (44 Sc) with a half-life of 3.97 h byemitting gamma rays. 44 Sc has been reported to bea promising radioisotope (RI) in positron emission tomography imaging, while 47 Sc, which emits a beta particle, is proposed as a promising therapeutic nuclide.1)
Furthermore, 44m Sc appears to be useful as an imaging RI2) and a surrogate nuclide for other Sc isotopes
in basic science research because of a relatively long
half-life. A study on the optimization of 44m Sc radiolabeling of macrocyclics-functionalized biomolecules has
been published.3)
We have been developing a production method of
44m
Sc via the nuclear reaction 44 Ca(d, 2n)44m Sc at the
RIKEN AVF cyclotron and distributing puriﬁed 44m Sc(RIKEN 44m Sc) to users.4) To conﬁrm the quality of
the RIKEN 44m Sc for research on radiolabeling, we
performed 44m Sc radiolabeling on chelate-compounds
in this study. To investigate the structural eﬀect ofchemical-compounds on 44m Sc radiolabeling, four commercially available compounds were selected: DOTASubstance P (DOTA-SP), DOTA-RGD2 , NOTA-RGD2
and NODAGA-RGD2 . The operations for 44m Sc radiolabeling are as described below.
Step 1: RIKEN 44m Sc (9.1 MBq) was dissolved in
0.05 M hydrochloric acid to prepare a 44m Sc
solution (79 MBq/mL). The radioactivity of
44m
Sc was determined using a germanium semiconductor detector.
Step 2: Each chelate-compound was dissolved in 0.75 M
sodium acetate buﬀer at pH3.0, 4.0, 5.0, and 6.0
to prepare 1.4 × 10−4 M sample solutions.
Step 3: 1.5 μL of the 44m Sc solution was added to 3 μLof each sample solution: the speciﬁc radioactivity of each sample solution was 0.29 MBq/nmol.
Step 4: The mixtures in Step 3 were heated at 97◦ C for
10 min and kept at 20◦ C for 5 min.
Step 5: Radiolabeling yields of 44m Sc-labeled compounds were determined using thin-layer chromatography (TLC) with a C18 reverse phase
TLC plate (NAGEL RP-18W/UV254), which
was eluted with a mixture of acetonitrile, 0.5 M
ammonium acetate, methanol, and tetrahydrofuran in a volume ratio of 4 : 3 : 2 : 1 using animage analyzer.
Consequently, the radiolabeling yields of each compound were over 90% at pH 5.0–6.0, although they were
diﬀerent from each other at lower pH values. In caseof compounds with the same aﬃnity moiety, DOTA∗1∗2

RIKEN Nishina Center
RI Research Department, FUJIFILM Toyama Chemical Co.,
Ltd.

Fig. 1. Relation between pH value of acetate buﬀer andradiolabeling yield (%) of 44m Sc-labeled compounds at
0.29 MBq/nmol (n = 1).

RGD2 was radiolabeled over 70% at pH 3.0 which
was higher than that of NODAGA-RGD2 and NOTARGD2 .
It has been reported that the suitable pH range for44m
Sc labeling with DOTA-based ligands is from 4 to
5.5.3) The result obtained in our study was consistent
with the result of the previous study. Moreover, regarding the diﬀerence in reactivity among chelators,
one report shows that DOTA is a better chelator thanNODAGA because NODAGA is more susceptible tocontamination metals than DOTA.5) Another reportshows that the thermodynamic stability of Sc-DOTA
is high compared to that of Sc-NOTA.6) These reports
are consistent with our radiolabeled result at pH 3.0.
Hence, these results support the possibility of further
radiolabeling studies using RIKEN 44m Sc.
We investigated the possibility of RIKEN 44m Sc forradiolabeling studies and compared our results withthose of previous reports of Sc radioisotopes. In addition, the pH responsiveness of the 44m Sc radiolabelingyield to compounds having diﬀerent chelating sites was
conﬁrmed. In future, we plan to optimize the radiolabeling condition of Sc isotopes, such as 44 Sc, which
is eluted from the 44 Ti/44 Sc generator, and conduct a
feasibility study for imaging tracer with 44m Sc.
References
1) C. Müller et al., J. Nucl. Med. 55, 1658 (2014).
2) T. Fukuchi et al., RIKEN Accel. Prog. Rep. 53, 21(2020).
3) S. Huclier-Markai et al., Nucl. Med. Biol. 41, e36 (2014).
4) H. Haba, Drug Deliv. Syst. 35, 114 (2020).
5) K. A. Domnanich et al., EJNMMI Radiopharm. Chem.
1, 8 (2016).
6) S. Huclier-Markai et al., Radiochim. Acta 99, 653 (2011).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Progress of double-photon coincidence imaging with 28 Mg
M. Uenomachi,∗1 F. Sensui,∗1,∗2 Z. Zhong,∗1,∗2 K. Shimazoe,∗1,∗2 H. Takahashi,∗1,∗2 Y. Shigekawa,∗1
A. Nambu,∗1 Y. Wang,∗1 X. Yin,∗1 and H. Haba∗1∗1∗2

RIKEN Nishina Center
School of Engineering, University of Tokyo- 144 -

(a)

28

(b)

Mg

1

30

0.9
20

0.8
0.7

10

y [mm]

In nuclear medicine, positron emission tomography(PET) and single photon emission computed tomography (SPECT) have been widely used for diagnosis.
However, the principles of these imaging technologies
constrain the type of radioisotopes that can be used.
Clinically available radioisotopes are positron emittersor single photon emitters with low energies (typicallyup to 400 keV). Recently, Compton imaging1) has beenstudied as a promising gamma-ray imaging technology
because it can oﬀer image capture for a wide range ofenergy (100 keV to a few MeV) without mechanicalcollimators. Therefore, this capability provides an opportunity for the exploitation of new radionuclides innuclear medicine.
In conventional Compton imaging, the source position can be estimated only on the surface of a conewith an opening angle θ, which is calculated from therecoil electron and scattered photon energies by following the equation of Compton scattering kinematics.
However, this results in low signal-to-background ratio(SBR) in the Compton image. For improvement in the
SBR, we have demonstrated the double-photon coincidence imaging technology.2–5) Some nuclides emitting
two or more successive gamma-rays with an intermediate state can be applied for the double-photon coincidence imaging (e.g. 60 Co,3) 43 K,4) and 111 In5) ). Thus,
one can specify the position at the intersection of two(or more) Compton cones by coincidence detection. In
this study, we focused on a radionuclide of 28 Mg. 28 Mg
is a promising radionuclide for bio-imaging owing to
its suitable half life of 21 hours. Moreover, because
it emits cascade photons with energies of 400.6 keV(Intensity: 35.9%), 941.7 keV (36.3%), and 30.6 keV(89%) via short duration, coincidence imaging can beapplied.
We produced 28 Mg via the 27 Al(α, 3p)28 Mg reaction
at the RIKEN AVF cyclotron. After chemical separation, 0.5 MBq in 37 μL HCl was dispensed in a 0.5 mL
micro tube. Figure 1(a) shows the experimental setup.
Eight Compton cameras surrounded the 28 Mg source.
The distance between the source and camera was approximately 42 mm. A Compton camera consists ofa scatterer and an absorber, which are 8 × 8 arraysof Gd3 (Al, Ga)5 O12 (Ce) (GAGG) scintillators (C&A
Co.) coupled to an 8 × 8 array of silicon photomultipliers (SiPM, Hamamatsu MPPC S13361-3050). The
GAGG crystal size is 2.5 mm × 2.5 mm, and the pitch
size is 3.2 mm × 3.2 mm. The thicknesses of the scatterer and absorber are 4 mm and 9 mm, respectively.

0.6
0
0.5

−10

0.4

−20

0.3
0.2

−30
−30

absorberscatterer

−20

−10

0

10

20

30

x [mm]

Fig. 1. (a) Photograph of the experimental setup.
Double-photon coincidence imaging of 28 Mg.

(b)

The 64 channel signals from the SiPM array are processed by the dynamic time over threshold method6)
and are then converted to digital signals of a time
width. The 128 channel digital signals from the scatterer and absorber are acquired using 125 ps samplingby a ﬁeld-programmable gate array-based data acquisition system. The data is recorded as list-mode data.
In analysis, coincidence events between the scatterer
and absorber were extracted as single-photon Compton
events. For double-photon coincidence imaging, coincidence events between two diﬀerent Compton camera
events were selected as double Compton events.
Figure 1(b) shows the preliminary double-photon coincidence imaging of 28 Mg. In image reconstruction,
double Compton events with energies of 400.6 keV
and 941.7 keV were used. Although we succeeded the
double-photon coincidence imaging, the detection efﬁciency is a disadvantage of this method. While theabsolute eﬃciency of the single-photon Compton imaging with our imaging system was 0.029% @ 400.6 keVgamma-ray, and 0.014% @ 941.7 keV gamma-ray, thatof the double-photon coincidence imaging was 8.2 ×
10−6 %. Unlike the annihilation gamma-rays emitted
at opposite directions, cascade gamma-rays are emitted without collinearity. We must improve the imaging
system geometry, such that it covers a wider range ofsolid angles to increase the detection eﬃciency.
References
1) R. W. Todd et al., Nature 251, 5471 (1974).
2) Y. Yoshihara et al., Nucl. Instrum. Methods Phys. Res.
A 837, (2017).
3) M. Uenomachi et al., Nucl. Instrum. Methods Phys.
Res. A 954, (2020) .
4) H. Takahashi et al., RIKEN Accel. Prog. Rep. 54,(2020).
5) T. Orita et al., IEEE Trans. Nucl. Sci. (in press).
6) K. Shimazoe et al., IEEE Trans. Nucl. Sci. 59, 6 (2012).

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Source preparation technique of astatine-211 without electroplating
for alpha spectroscopy
S. Fujino,∗1 K. Mori,∗1 S. Hamagami,∗1 T. Yamada,∗1,∗2 Y. Wang,∗3 X. Yin,∗3 and H. Haba∗3
211

At has attracted much interest because of its potential advantages in targeted alpha therapy. The
high-resolution alpha spectrometry is one of the mostimportant techniques in radiochemical analyses andprecise radioactivity measurements. The electroplating method is widely used as a conventional techniqueto prepare α sources. However, some diﬃculties areencountered in applying this method to 211 At owing
to its short half-life and high volatility. There diﬃculties were overcome by employing another practical
approach using a silver plate, which is one of the major
procedures of preparing solid radio-iodine sources,1) toprepare 211 At α sources. In addition, a coprecipitation
technique using AgNO3 was studied.
In this study, carrier-free 211 At produced via the209
Bi(α, 2n)211 At reaction at the RIKEN AVF cyclotron was used.2) Approximately 1 MBq of dried elemental 211 At was dissolved in 10 mL of ion-exchanged
water. Silver plates with a thickness of 0.1 mm wereused to ﬁx 211 At. In this study, approximately 10 μLof the 211 At solution was directly dropped onto silver
plates. As another approach, an 211 At source was also
prepared with ascorbic acid (AA) to avoid 211 At loss
due to volatilization.3) In this case, a 180 μL of 211 At
solution was mixed with 20 μL of AA solution witha concentration of 0.01 mg/mL, and the mixed solution was dropped onto silver plates. All sources weredried in the atmosphere at room temperature. To investigate the time dependence of the deposition yieldof 211 At, 211 At deposited on the plate was washed oﬀ
with ion-exchanged water in 15, 30, 45, 60, or 75 minfor the sources prepared without AA.
A 0.1 mg/g AgNO3 solution was used to prepare
the source using the coprecipitation technique. Here,
30 μL of the 211 At solution was directly dropped on
the plastic plate and 10 μL of the AgNO3 solution wasadded. These sources were dried in a desiccator withsilica gel. All the sources prepared were measured using a ZnS(Ag) scintillation detector with 2π geometry
and/or an ion-implanted Si detector (MIRRION PD
300-16-100 AM) with the deﬁned source-detector geometry in a vacuum.
Figure 1 shows the time dependence of the deposition yield of 211 At on the silver plates. The deposition
yield was determined as a ratio of the 211 At α countrate measured for each silver plate to that estimatedfrom the radioactivity concentration of the 211 At solu∗1∗2∗3

Graduate School of Science and Engineering, Kindai University
Atomic Energy Research Institute, Kindai University
RIKEN Nishina Center- 145 -

Fig. 1. Time dependence of the deposition yield.

tion and a weight of its drop on each plate. As shownin this ﬁgure, the deposition yield was saturated at approximately 75% in 30 min. For the sample dried withAA, the deposition yield reached 98% in this study.
However, the deposition yield of the sample coprecipitated with silver nitrate was 70%. The method withsilver nitrate is one of reliable methods for the standardization of the radio-iodine activity. These results
suggest that the methods applicable to the radio-iodine
cannot always be applied to the same halogen elemental astatine source without volatilization.
Alpha spectra were measured using the Si detector
for the sources prepared above. Two alpha-peaks of
211
At (Eα = 5.87 MeV) and 211 Po (Eα = 7.45 MeV)
were observed in each spectrum. As shown in Fig. 2,

Fig. 2. Measured α-spectra of 211 At (Eα = 5.87 MeV).

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

the FWHMs of the 5.87 MeV peak in the measured
spectra for the source prepared on a silver plate withand without AA were approximately 20 keV or less.
For the source prepared using the coprecipitation technique, signiﬁcant broadenings were observed, resulting
in a FWHM of 23.9 keV at 5.87 MeV.
Among three types of sources, the sources preparedon a silver plate with and without AA exhibited better
FWHM, and the source prepared on a silver plate withAA had the best deposition yield, while an additional
study using more samples is required. Therefore, themethod to prepare the source on a silver plate withAA can have potential advantage to be employed asa source preparation technique for radioactivity measurement using the solid angle α counting techniquewith a small correction for loss of radioactivity during
the drying process owing to its volatility.
Acknowledgement: The authors would like to thank to
Dr. Y. Komori and Dr. T. Yokokita.for their technicalassistance.
References
1) I. Cieszykowska et al., Nukleonika 50, 17 (2005).
2) Y. Wang et al., RIKEN Accel. Prog. Rep. 53, 192(2019).
3) A. Toyoshima et al., Radiat. Safe. Manage. 18, 13(2019).

2- 146 -

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections of 225 Ac and 225 Ra in the 232 Th(14 N, xnyp)
reactions at 56, 79, and 98 MeV/nucleon
X. Yin,∗1 A. Nambu,∗1 S. Oshikiri,∗1,∗2 K. Suzuki,∗1,∗2 A. Hino,∗2 and H. Haba∗1
225

Ac (T1/2 = 10.0 d) is one of the most promising alpha-particle-emitting radionuclides for targetedradionuclide therapy.1) Its precursor, 225 Ra (T1/2 =14.9 d), is useful to generate high-purity 225 Ac. Thus,
proton-induced reactions on 232 Th to form 225 Ac and225
Ra have been well investigated.2) Proton beams up to
210 MeV are available for 225 Ac production from RRC.
In 1991, Ambe et al.3) proposed the productionof radionuclides of a large number of elements (multitracer) by the spallation of metallic targets suchas nat Cu, nat Ag, and 197 Au irradiated with a 135MeV/nucleon 14 N (or 12 C, 16 O) beam from RRC. With
this 14 N beam, 225 Ac and 225 Ra can be producedin the 232 Th(14 N, xnyp)225 Ac, 225 Ra reactions.4) The
cross sections are essential to verify the feasibility of
the 232 Th(14 N, xnyp)225 Ac, 225 Ra reactions for practical productions of 225 Ac and 225 Ra with RRC. In
our previous paper,4) we reported the cross sections of
the 232 Th(14 N, xnyp)225 Ac, 225 Ra reactions at 116 and132 MeV/nucleon. In this work, the cross sections atlower energies of 56, 79, and 98 MeV/nucleon were measured to evaluate the production yields of 225 Ac and225
Ra more reliably.
The target consisted of three assemblies of three metallic 232 Th foils, each with a thickness of 69 mg/cm2 andsize of 12.5 × 12.5 mm2 . Two aluminum disks, eachwith a thickness of 370 mg/cm2 and diameter of 15 mm,
were interleaved between the thorium assemblies as beamenergy degraders. The target was placed in a multitracer production chamber.5) A 100.1-MeV/nucleon
14 7+
N beam was extracted from RRC. The target wasirradiated for 2 h with an 18-particle nA intensity. After irradiation, the middle 232 Th foils in every assembly
were subjected to γ-ray spectrometry to determine thecross sections of 225 Ac and 225 Ra. The beam energies on
the measured 232 Th targets were calculated to be 98, 79,
and 56 MeV/nucleon using the stopping power model inthe LISE++ program.6) The cross sections of 225 Ac and225
Ra were determined by ﬁtting the 440-keV γ-ray intensity of 213 Bi (T1/2 = 45.59 min) in their radioactive
decay chain.4)
The cross sections of 225 Ac and 225 Ra obtained in thiswork are shown in Fig. 1, together with those at 116 and132 MeV/nucleon in our previous work.4) The cross sections of 225 Ac are larger than those of 225 Ra by factorsof 4.2–5.3 at 56–132 MeV/nucleon, respectively. The experimental results are compared with those calculatedby the Particle and Heavy Ion Transport code System(PHITS).7) The PHITS code reproduces the cross sec∗1∗2

RIKEN Nishina Center
RI Research Department, FUJIFILM Toyama Chemical Co.,
Ltd.

Fig. 1. Experimental and calculated excitation functions forthe 232 Th(14 N, xnyp)225 Ac, 225 Ra reactions.

tions of 225 Ac above 98 MeV/nucleon, while it underestimates those at the lower energies. The cross sections
calculated for 225 Ra by the PHITS code are larger thanthe experimental ones. The calculated values increase
with the beam energy, while the experimental ones are
independent of the beam energy. In Fig. 2, production
yields of 225 Ac by 135-MeV/nucleon 14 N beams are compared with those by 210-MeV proton beams.2) The yields
of both reactions are comparable if we use a target withthe same thickness in the range of 0.5–5 g/cm2 .
By assuming experimental conditions (incident beamenergy: 132 MeV/nucleon; beam intensity: 1 particle
μA; target thickness: 4.5 g/cm2 ; irradiation time: 2 d),
165 MBq of 225 Ac can be produced at the end of bombardment via the 232 Th(14 N, xnyp)225 Ac reaction.

Fig. 2. Yields of 135-MeV/nucleon 14 N and 210-MeV proton
beams on 232 Th targets with diﬀerent thicknesses.

References
1) M. Ferrier et al., Radiochim. Acta 107, 1065 (2019).
2) J. Weidner et al., Appl. Radiat. Isot. 70, 2602 (2012).
3) S. Ambe et al., Anal. Sci. 7, 317 (1991).
4) X. Yin et al., RIKEN Accel. Prog. Rep. 54, 162 (2021).
5) H. Haba et al., Radiochim. Acta 93, 539 (2005).
6) O. B. Tarasov, D. Bazin, LISE++ site, https://lise.
nscl.msu.edu/lise.html .
7) Y. Iwamoto et al., J. Nucl. Sci. Technol. 54, 617 (2017).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections of 28 Mg via the α-particle-induced reaction
on aluminum
M. Aikawa,∗1,∗2 G. Damdinsuren,∗3,∗2 H. Huang,∗3,∗2 and H. Haba∗2

∗1
∗2
∗3

Faculty of Science, Hokkaido University
RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido University- 148 -

0.5
27Al(,3p)28Mg

0.4
Cross section (mb)The radionuclide 28 Mg has a half-life of T1/2 =20.915 h and decays with the emission of a β − particle and γ rays. These nuclear properties are appropriate for radiotracers in a wide range of applications.1) One of its promising production reactions
is the α-particle-induced reaction on aluminum. We
found ten experimental studies in the production crosssections of 28 Mg in a literature survey in the EXFOR
library.2) However, the cross sections of the previous
studies are largely scattered. Therefore, we conducted
an experiment to determine reliable cross sections of
the 27 Al(α, 3p)28 Mg reaction.
The experiment to measure the activation cross sections of the reaction was performed at the RIKEN AVF
cyclotron. The stacked-foil activation technique andhigh-resolution γ-ray spectrometry were used. Pure
metal foils of 27 Al (>99% purity) and nat Ti (99.6% purity) were purchased from Nilaco Corp., Japan. The
Ti foil was used for the nat Ti(α, x)51 Cr monitor reaction. The average thicknesses of the Al and Ti foils
were 13.7 and 2.23 mg/cm2 , respectively, which were
derived from the measured size and weight of each foil.
After the thickness measurement, the foils were cut
into small pieces of 10 × 10 mm2 to ﬁt a target holderthat served as a Faraday cup. The stacked target consisted of ten Al foils upstream and seven sets of Ti-TiTi-Al foils downstream of the beam line. The upstream
Al foils were used to derive activation cross sections of
the 27 Al(α, 3p)28 Mg reaction, the threshold energy ofwhich is 24.8 MeV. The following Ti-Ti-Ti-Al foils werestacked for the nat Ti(α, x)51 Cr monitor reaction in alower-energy region. The stacked target was irradiatedfor 30 min with an α-particle beam. The initial energy of the α-particle beam was determined using thetime-of-ﬂight method.3) The average beam intensity
was measured using the Faraday cup and found to be
216 nA. The energy degradation of the α-particle beamin the target foils was calculated using stopping powers
obtained from the SRIM code.4) The γ-ray spectrometry was performed using a high-purity germanium detector (ORTEC GEM30P4-70) and dedicated analysis software (SEIKO EG&G Gamma Studio). γ rays
emitted from each irradiated foil were measured without chemical separation three times (Ser. 1: 2.7–7.5 h,
Ser. 2: 8.0–32 h, Ser. 3: 1.9–3.6 d). The dead time
was kept below 1.4% throughout the measurements.
Nuclear data used for cross-section derivation were re-Nethaway (1958)
Martens (1970)
Nozaki (1975)
Probst (1976)
Rattan (1985)
Rattan (1986)
Karamyan (1992)
TENDL-2019
This work

0.3

0.2

0.1

0
25

30

35

40

45

50

Energy (MeV)

Fig. 1. Excitation function of the 27 Al(α, 3p)28 Mg reaction
in comparison with the previous studies found in the
EXFOR library2) and the TENDL-2019 values.6)

trieved from the online database, NuDat 3.0.5)
The γ line at 1342.2 keV (Iγ = 54%) emitted withthe decay of 28 Mg (T1/2 = 20.915 h) was measured
during the cooling time of 8.0–32 h (Ser. 2). The crosssections of the 27 Al(α, 3p)28 Mg reaction were determined using the measured spectra. Figure 1 compares
our preliminary result with the experimental data in
the EXFOR library2) and the TENDL-2019 values.6)
The cross section at the highest energy may be aﬀectedby the recoil eﬀect and slightly decreased. The previous data of Martens et al. 7) and Rattan et al. 8) areconsistent with our data, although their data deviate
from each other in the higher-energy region. The otherprevious data are systematically larger or smaller thanour data. The TENDL-2019 values are fairly smaller
than all the experimental data. We will ﬁnish analysesof the measured γ-ray spectra and determine the production cross sections of radioactive products in thereaction.
References
1) N. P. van der Meulen et al., Appl. Radiat. Isot. 115,
125 (2016) and references therein.
2) N. Otuka et al., Nucl. Data Sheets 120, 272 (2014).
3) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), (2014), p. 3566.
4) J. F. Ziegler et al., SRIM: the Stopping and Range ofIons in Matter (2008), http://www.srim.org/ .
5) National Nuclear Data Center, The NuDat 3.0
database, http://www.nndc.bnl.gov/nudat3/ .
6) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
7) U. Martens et al., Z. Phys. 233, 170 (1970).
8) S. S. Rattan et al., Radiochim. Acta 39, 61 (1986).

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections of titanium radionuclides via
proton-induced reactions on scandium
M. Aikawa,∗1,∗2,∗3 H. Huang,∗2,∗3 H. Haba,∗2 S. Takács,∗4 F. Ditrói,∗4 and Z. Szücs∗4
Titanium radionuclides can be used in nuclear
medicine. 45 Ti (T1/2 = 3.08 h, Iβ+ = 84.8%) and 44g Sc(T1/2 = 3.89 h, Iβ+ = 94.3%), which is the daughterof 44 Ti (T1/2 = 59.1 y), are positron emitters and suitable for positron emission tomography (PET).1) The
two titanium radionuclides 44 Ti and 45 Ti can be produced via charged-particle-induced reactions, such as αparticle-induced reactions on calcium and proton- anddeuteron-induced reactions on scandium in a no-carrieradded form. The former reaction on calcium requires
enriched 42 Ca targets. However, the composition of thisisotope in natural calcium is only 0.647%. For protonand deuteron-induced reactions, the monoisotopic element scandium 45 Sc can be used as a target material.
The proton- and deuteron-induced reactions on 45 Sc arethus promising for the production of both titanium radionuclides. We have previously studied the deuteroninduced reaction on 45 Sc.2) Subsequently, we focused on
the proton-induced reaction on 45 Sc. In a literature survey and in the EXFOR library,3) we found four and ten
experimental studies on the production cross sections of
44
Ti and 45 Ti isotopes, respectively. The cross sections
reported in these previous studies are largely scattered.
Therefore, additional and reliable cross sections of the
proton-induced reactions on 45 Sc are required.
We performed an experiment at the RIKEN AVF
cyclotron using well-established methods, namely, thestacked-foil activation technique and high-resolution γray spectrometry. Pure metal foils of 45 Sc (99.0%
purity, Goodfellow Co., Ltd., UK), nat Ti (99.6% purity, Nilaco Corp., Japan), and 27 Al (>99% purity, Nilaco Corp., Japan) were purchased and used for the
stacked target. The nat Ti and 27 Al foils were used
for the nat Ti(p, x)48 V monitor reaction and for catching recoiled products, respectively. The lateral size andweight of each foil were measured. The derived average thicknesses of the 45 Sc, nat Ti, and 27 Al foils were30.5, 2.25, and 13.7 mg/cm2 , respectively. The foils
were then cut into 10 × 10 mm pieces to ﬁt a target
holder that served as a Faraday cup. Twenty sets of
Sc-Al-Ti-Ti-Al foils were stacked in the target holder.
The stacked target was irradiated with a 30.1 ± 0.1MeV
proton beam for 60 min. The initial beam energy wasdetermined by the time-of-ﬂight method.4) The average beam intensity measured by the Faraday cup was
203 nA. The energy degradation of the beam in thestacked target was calculated using stopping powers de∗1
∗2
∗3
∗4

Faculty of Science, Hokkaido University
RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido University
Institute for Nuclear Research (ATOMKI)

Fig. 1. Excitation function of the 45 Sc(p, n)45 Ti reaction incomparison with the previous data found in the EXFOR
library3) and the TENDL-2019 values.7)

rived from the SRIM code.5) The γ-ray spectra fromeach irradiated foil were measured three times using ahigh-purity germanium detector (ORTEC GEM30P470). Nuclear decay data were obtained from the online
database NuDat 3.0.6)
The weak γ line at 719.6 keV (Iγ = 0.154%) emittedwith the decay of 45 Ti was measured. Due to its low
intensity, only four cross sections of the 45 Sc(p, n)45 Ti
reaction, with large statistical uncertainties, at aroundthe peak were determined. Our preliminary result incomparison with the earlier experimental data found in
the EXFOR library3) and the TENDL-2019 values7) isshown in Fig. 1. The peak position and amplitude ofour result are similar to the data obtained by McGeeet al. 8) The TENDL data are slightly smaller than ourdata at the peak.
Additional measurement after several months will be
performed for the long-lived radioisotope 44 Ti. Production cross sections of scandium radioisotopes in thereaction will be also determined.
This work was supported by Japan-Hungary Research Cooperative Program between JSPS and HUS,
Grant numbers JPJSBP120193808 and NKM-43/2019.
References
1) I. F. Chaple et al., J. Nucl. Med. 59, 1655 (2018).
2) Z. Tsoodol et al., Appl. Radiat. Isot. 168, 109448 (2021).
3) N. Otuka et al., Nucl. Data Sheets 120, 272 (2014).
4) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), (2014), p. 3566.
5) J. F. Ziegler et al., SRIM: the Stopping and Range ofIons in Matter (2008), http://www.srim.org/ .
6) National Nuclear Data Center, The NuDat 3.0, database,
http://www.nndc.bnl.gov/nudat3/ .
7) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
8) T. McGee et al., Nucl. Phys. A 150, 11 (1970).

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III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections of 45 Ti via deuteron-induced reaction on
45
Sc†
Ts. Zolbadral,∗1,∗2 M. Aikawa,∗2,∗3,∗4 D. Ichinkhorloo,∗1,∗2 Kh. Tegshjargal,∗5 N. Erdene,∗5 Y. Komori,∗3
H. Haba,∗3 S. Takács,∗6 F. Ditrói,∗6 and Z. Szücs∗6
45

†
∗1
∗2
∗3
∗4
∗5
∗6

Condensed from the article in Appl. Radiat. Isot. 168, 109448(2021)
Nuclear Research Center, National University of Mongolia
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
School of Engineering and Applied Sciences, National University of Mongolia
Institute for Nuclear Research (ATOMKI)

450
400

45Sc(d,2n)45Ti

Cross section (mb)

350
300
250
200
150

This work
Hermanne 2012TENDL-2019

100
50
0

0

5

10

15

20

25

Energy (MeV)

Fig. 1. Excitation function of the 45 Sc(d, 2n)45 Ti reaction.
2000
Physical Yield (MBq/μAh)

Ti (T1/2 = 184.8 min) is an appropriate positron
emitter isotope (Eβ + = 439 keV, Iβ + = 84.8%) for
positron emission tomography (PET). This radioisotope can be produced in the deuteron-induced reaction on a scandium-45 target at cyclotrons. However, the quality of experimental data on the cross sections of the 45 Sc(d, 2n)45 Ti reaction is not satisfactory.
Therefore, we aim to measure the cross sections of the45
Sc(d, 2n)45 Ti reaction and to investigate a route for45
Ti production.
The stacked-foil activation technique and γ-ray spectrometry were adopted to determine the cross sections.
The stacked target included metallic foils of 45 Sc (thicknesses of 25.8 and 250 μm with a purity of 99.0%),27
Al (18.5 μm, 99.6%), and nat Ti (20.2 μm, 99.6%).
The target was irradiated for 30 min with a 24-MeV
deuteron beam from the RIKEN AVF cyclotron. The
incident beam energy was measured using the time-ofﬂight method. The energy degradation in the stacked
target was calculated using the SRIM code.1) The beam
intensity was measured using a Faraday cup and doublechecked with the nat Ti(d, x)48 V monitor reaction.2) By
comparing the monitor reaction, the measured intensity(180 ± 9 nA) was corrected by decreasing it by 2% to176 ± 9 nA. The γ-ray spectra of the irradiated foils were
measured using a high-resolution and a high-purity germanium (HPGe) detector. The detector was calibratedusing a mixed γ-ray point source. In the measurements,
the dead time was kept below 7%.
Subsequently, the activation cross sections of 44, 45 Ti
and 44g, 44m, 46 Sc were determined. The measurementsof the 719.6-keV γ-ray (Iγ = 0.154%) from the 45 Ti
decay were used to derive the cross sections of the45
Sc(d, 2n)45 Ti reaction. Figure 1 shows our measured
excitation function of the 45 Sc(d, 2n)45 Ti reaction incomparison with previous experimental data3) and thetheoretical estimation retrieved from TENDL-2019.4)
The derived excitation function is consistent with thedata reported by Hermanne et al.;3) however, it is lessscattered. The peak position of the TENDL-2019 datais slightly shifted to a lower energy.
The physical yield of 45 Ti was deduced from the measured excitation function and is shown in Fig. 2. The

45Ti
1500

This work
Dmitriev+(1982)

1000

500

0
0

5

10

15

20

Energy (MeV)

Fig. 2. Physical yield of 45 Ti.

present yield curve of 45 Ti is slightly higher than the experimental data obtained by Dmitriev et al.5) at 22 MeV.
44
Ti is the only one co-produced radioactive isotope oftitanium in our experiment and can be formed by (d, 3n)reaction on 45 Sc above 15 MeV. Therefore, isotopicallypure 45 Ti production is possible in (d, 2n) reaction on
45
Sc in an energy range of 8–15 MeV.
This work is supported by JSPS KAKENHI Grant
Number 17K07004 and partly supported by the research program between the JSPS and HAS Contract No: JPJSBP120193808 and NKM-43/2019. Ts.Z
was granted a scholarship by the M-JEED project(Mongolian-Japan Engineering Education Development
Program, J11B16).
References
1) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res. B
268, 1818 (2010).
2) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).
3) A. Hermanne et al., Nucl. Instrum. Methods Phys. Res.
B 270, 106 (2012).
4) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
5) P. P. Dmitriev et al., INDC(CCP)-210, 1 (1983).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections of 47 Sc via proton-induced reactions on
calcium
M. Aikawa,∗1,∗2,∗3 Y. Hanada,∗2,∗3 H. Huang,∗2,∗3 H. Haba,∗3 S. Takács,∗4 F. Ditrói,∗4 and Z. Szücs∗4
Scandium radionuclides can be used for theranostics, a
combination of therapeutics and diagnosis.1) 43 Sc (T1/2= 3.89 h) and 44g Sc (T1/2 = 3.97 h) are positron emittersthat are used in positron emission tomography (PET).
47
Sc (T1/2 = 3.35 d) decays with beta particle emissions
that can be used for therapy. These radionuclides can beproduced via charged-particle-induced reactions on calcium. Only a few experimental studies of each reaction
were found with scattered cross sections in a literature
survey. Therefore, we performed experiments to measure reliable cross sections of proton-, deuteron-2) andalpha-particle-induced reactions on natural calcium.3)
The abundance of natural calcium is 40 Ca: 96.941%,
42
Ca: 0.647%, 43 Ca: 0.135%, 44 Ca: 2.086%, 46 Ca:
0.004%, and 48 Ca: 0.187%. In this report, we present
the preliminary results of the proton-induced reactions
on natural calcium for 47 Sc production. 47 Sc can bedirectly produced in the proton-induced reactions on
46,48
Ca. However, the contribution of the (p, γ) reaction on 46 Ca is expected to be negligibly small owing
to the extremely low abundance of 46 Ca and tiny crosssections of the (p, γ) reaction. Thus, the measured crosssections of the nat Ca(p, x)47 Sc reaction can be converted
to those on 48 Ca enriched targets and vice versa.
We performed an experiment using a 30-MeV proton
beam at the RIKEN AVF cyclotron. The stacked-foil activation technique and high-resolution gamma-ray spectrometry were employed.
Calcium targets were prepared from a calcium-ﬂuoride(CaF2 ) layer deposited on a high-purity 27 Al backing
foil (99.999% purity, Goodfellow Co. Ltd., UK). Additional foils of nat Ti (99.5% purity, Nilaco Corp., Japan)
and 27 Al (>99% purity, Nilaco Corp., Japan) were used
for the nat Ti(p, x)48 V monitor reaction and beam-energy
degradation, respectively. Based on size and weightmeasurements of each foil, average thicknesses of the
CaF2 layer, its 27 Al backing, the 27 Al degrader, and thenat
Ti monitor foils were derived as 0.148, 5.26, 27.3, and2.30 mg/cm2 , respectively. The foils were then cut intoa size of 8 × 8 mm to ﬁt a target holder served as a
Faraday cup. Each calcium target was composed of two
CaF2 layers sandwiched between the 27 Al backing foils
followed by a set of Ti-Ti-Al-Al foils. Eighteen calcium
targets were stacked together in the target holder.
The stacked target was irradiated for 60 min with a30.2 ± 0.1-MeV proton beam. The average beam intensity measured by the Faraday cup was 199 nA. Theenergy degradation of the beam in the stacked target
∗1
∗2
∗3
∗4

Faculty of Science, Hokkaido University
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Institute for Nuclear Research (ATOMKI)

Fig. 1. Excitation function of the nat Ca(p, x)47 Sc reaction incomparison with previously reported experimental datafor 48 Ca3) normalized to nat Ca and TENDL-2019 values.7)

was calculated using stopping powers derived from the
SRIM code.4) The irradiated foils without chemical separation were subjected to gamma-ray spectrometry using
a high-purity germanium detector. Nuclear data for determining the cross section were obtained from an online
database, NuDat 3.0.5)
We derived cross sections of the nat Ca(p, x)47 Sc reaction using a speciﬁc gamma line at 159.381 keV (Iγ =68.3%) emitted after the decay of 47 Sc. The co-produced47
Ca (T1/2 = 4.536 d) can also contribute to the production of 47 Sc. Our preliminary result on 47 Sc including
the partial contribution from the 47 Ca decay is shown in
Fig. 1 in comparison with previous experimental data6)
and TENDL-2019 values.7) The previously reported experimental data were normalized to those of nat Ca forthe comparison. Previous data are larger than our dataaround the peak. The TENDL-2019 values show a peak
amplitude that is consistent with our data, while thepeak position shifts to the lower energy region.
We continue to analyze the measured spectra in moredetails and to determine production cross sections ofother scandium radioisotopes as well.
This work was partly supported by the Japan-Hungary
Research Cooperative Program between JSPS and HAS,
Grant number JPJSBP120193808 and NKM-43/2019.
References
1) R. Mikolajczak et al., EJNMMI Radiopharm. Chem. 6,
19 (2021).
2) M. Aikawa et al., in this report.
3) M. Aikawa et al., in this report.
4) J. F. Ziegler et al., SRIM: the Stopping and Range of Ionsin Matter (2008), http://www.srim.org/ .
5) National Nuclear Data Center, The NuDat 3.0 database,
http://www.nndc.bnl.gov/nudat3/ .
6) T. S. Carzaniga et al., Appl. Radiat. Isot. 143, 18 (2019).
7) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections of 47 Sc via deuteron-induced reactions on
natural calcium
M. Aikawa,∗1,∗2,∗3 Y. Hanada,∗2,∗3 H. Huang,∗2,∗3 H. Haba,∗3 S. Takács,∗4 F. Ditrói,∗4 and Z. Szücs∗4
Production of scandium radionuclides is of interest forpractical use in nuclear medicine owing to the applicability of 43, 44g Sc in positron emission tomography (PET)and 47 Sc in therapy.1) We systematically study production cross sections of the radionuclides via chargedparticle-induced reactions on natural calcium. Preliminary results of the proton- and alpha-particle-induced
reactions have been reported in previous studies.2) In
this study, we focus on the deuteron-induced reactions
on natural calcium, in which the isotopic ratio is 40 Ca:
96.941%, 42 Ca: 0.647%, 43 Ca: 0.135%, 44 Ca: 2.086%,
46
Ca: 0.004%, and 48 Ca: 0.187%. In our survey, we
found only two experimental cross sections of the reaction below 25 MeV.3,4) In previous studies, however,cross sections for 47 Sc production were not presented.
Therefore, we conducted an experiment to measure theproduction cross sections of scandium radionuclides witha special focus on 47 Sc.
The experiment was performed at the RIKEN
AVF cyclotron. The stacked-foil activation techniqueand high-resolution gamma-ray spectrometry were employed.
The stacked target was prepared using nat Ca targets and nat Ti and 27 Al foils. Each nat Ca target
was composed of two calcium-ﬂuoride (CaF2 ) layers(0.148 mg/cm2 per layer) sandwiched between highpurity 27 Al backing foils (5.26 mg/cm2 , 99.999% purity,
Goodfellow Co. Ltd., UK). The nat Ti (2.30 mg/cm2 ,99.6% purity, Nilaco Corp., Japan) and 27 Al foils(13.7 mg/cm2 , >99% purity, Nilaco Corp., Japan)
were interleaved for monitoring the beam via thenatTi(d, x)48 V monitor reaction and energy degradationof a deuteron beam, respectively. The average thicknesses were determined from the measured sizes andweights of the original foils. Once the thicknesses were
determined, the original foils were cut into small piecesof 8 × 8 mm. Seventeen sets of a nat Ca target with TiTi-Al foils were stacked in a target holder served as a
Faraday cup.
The stacked target was irradiated for 60 min with a24.2 ± 0.1-MeV deuteron beam. The average beam intensity measured by the Faraday cup was 105 nA. Theenergy degradation of the beam in the stacked target
was calculated using stopping powers obtained from the
SRIM code.6) Gamma rays emitted from the irradiatedfoils were measured without chemical separation using
a high-purity germanium detector. Nuclear data required to determine activation cross sections were ob∗1
∗2
∗3
∗4

Faculty of Science, Hokkaido University
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Institute for Nuclear Research (ATOMKI)

Fig. 1. Measured excitation function of the nat Ca(d, x)47 Sc
reaction with a theoretical prediction of the TENDL-2019
values.7)

tained from the online database, NuDat 3.0.7)
We determined the production cross sections of 47 Sc(T1/2 = 3.35 d) via the deuteron-induced reactions on
nat
Ca. The cross sections were derived using the measured gamma line at 159.381 keV (Iγ = 68.3%) emitted with the decay of 47 Sc. The co-produced parent
47
Ca (T1/2 = 4.54 d) also contributed to the production of 47 Sc. Our preliminary result, including the partial contribution of 47 Ca, is shown in Fig. 1. Below thethreshold energy of the 48 Ca(d, 3n)47 Sc reaction (Eth =11.4 MeV), 47 Sc was dominantly formed from the reaction on 46 Ca. The result is compared with the crosssections of the 47 Sc direct production obtained from the
TENDL-2019 library.7) The TENDL-2019 values show
a slightly diﬀerent shape from that of our result. Previously published experimental studies on this subject
could not be found.
The measured spectra are analyzed in more detail,and the production cross sections of other scandium radioisotopes are determined. The results have potential
implications for application in nuclear medicine.
This work was partly supported by Japan-Hungary
Research Cooperative Program between JSPS and HAS,
Grant number JPJSBP120193808 and NKM-43/2019.
References
1) R. Mikolajczak et al., EJNMMI Radiopharm. Chem. 6,
19 (2021).
2) M. Aikawa et al., in this report.
3) T. J. de Waal et al., Radiochim. Acta 15, 123 (1971).
4) M. Alabyad et al., J. Radioanal. Nucl. Chem. 316, 119(2018).
5) J. F. Ziegler et al., SRIM: the Stopping and Range of Ionsin Matter (2008), http://www.srim.org/ .
6) National Nuclear Data Center, The NuDat 3.0 database,
http://www.nndc.bnl.gov/nudat3/ .
7) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Activation cross sections of alpha-particle-induced reactions on natural
calcium
M. Aikawa,∗1,∗2 Y. Hanada,∗3,∗2 D. Ichinkhorloo,∗4,∗2 H. Haba,∗2 S. Takács,∗5 F. Ditrói,∗5 and Z. Szűcs∗5

∗1
∗2
∗3
∗4
∗5

Faculty of Science, Hokkaido University
RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido University
Nuclear Research Center, National University of Mongolia
Institute for Nuclear Research (ATOMKI)

6
natCa(,x)47Sc

5
Cross section (mb)

We focused on the production of the therapeutic radionuclide 47 Sc (T1/2 = 3.3492 d) via alpha-particleinduced reactions on calcium. Owing to the relatively
small abundance of 46 Ca (0.004%) and 48 Ca (0.187%) in
natural calcium, the dominant route for 47 Sc productionis the reaction on 44 Ca (2.086%). Only one experimental study was found in a literature survey,1) and therefore, we performed an experiment to obtain the crosssections of the nat Ca(α, x)47 Sc reaction. The production cross sections of 46, 44m, 44g, 43 Sc and 47 Ca were also
determined.
The experiment was conducted with a 29-MeV alphaparticle beam at the RIKEN AVF cyclotron. Stackedfoil activation technique and high-resolution gamma-ray
spectrometry were used in the experiment. Calciumﬂuoride (CaF2 ) deposited on a high-purity 27 Al backing foil (99.999% purity, Goodfellow Co. Ltd., UK) wasused as the calcium target. In addition, two metallic
foils of nat Ti (99.5% purity) for the nat Ti(α, x)51 Cr monitor reaction and 27 Al (>99% purity) to catch recoiled
products were purchased from Nilaco Corp., Japan. The
measured average thicknesses of the 27 Al backing, 27 Al
catcher and nat Ti monitor foils were 2.57, 1.50 and2.30 mg/cm2 , respectively. The thickness of the CaF2
layer was 0.135 mg/cm2 , as derived from the measured
deposited area and net weight of CaF2 . Thickness uncertainties were estimated to be 5% for the CaF2 layerand 1% for the other foils. All foils were cut into a size of
10 × 10 mm2 to ﬁt a target holder. Each calcium target
consisted of two CaF2 layers sandwiched with the 27 Al
backing foils. Twelve calcium targets and seven sets of
the nat Ti monitor and 27 Al catcher foils were stacked
together in the target holder.
The stacked target was irradiated for 30 min with analpha-particle beam. The measured average beam intensity and energy were 175 nA and 29.0 ± 0.2 MeV,
respectively. The energy degradation in the stacked target was calculated using stopping powers obtained fromthe SRIM code.2)
The high-resolution gamma-ray spectrometry using ahigh-purity germanium detector was performed withoutchemical separation. The calcium targets were measured
ﬁve times with cooling times from 3.2 h to 77.0 d anddead times below 2.1%.
The derived cross sections of the nat Ti(α, x)51 Cr monitor reaction were compared with the IAEA recom-

Levkovski (1991) (44Ca)TENDL-2019
This work

4
3
2
1
0

0

5

10

15

20

25

30

Energy (MeV)

Fig. 1. Excitation function of the nat Ca(α, x)47 Sc reaction
in comparison with normalized data from the previous
study1) and TENDL-2019 values.4)

mended values.3) The comparison results indicated thatthe beam intensity and thicknesses of both 27 Al backing
and catcher foils were corrected within the uncertainties
by +5.6% and −1%, respectively. The measured thicknesses of the nat Ti monitor foil and the CaF2 layer wereadopted without any correction.
47
Sc can be produced directly from the 44 Ca(α, p)47 Sc
reaction and indirectly from the decay of the coproduced parents, 47 Ca and 47 K. The indirect contribution was negligible because the co-produced parents
can be formed only from the lower-abundant isotopes,
46
Ca and 48 Ca. The gamma line at 159.381 keV (Iγ =68.3%) from the 47 Sc decay was measured after coolingtimes of 1.2–2.8 d. The derived cross sections of thenatCa(α, x)47 Sc reaction are shown in Fig. 1 in comparison with the experimental data studied earlier3) andthe theoretical values provided in the TENDL-2019 library.4) The previous data of the 44 Ca(α, x)47 Sc reaction
are normalized to those using natural calcium targets.
The peak of the previous data shifts to the low-energy
region. The TENDL-2019 calculation largely overestimates the excitation function.
This work was supported by the Japan-Hungary Research Cooperative Program between JSPS and HUS,
Grant number JPJSBP120193808 and NKM-43/2019.
References
1) V. N. Levkovski, Cross Sections of Medium Mass Nuclide
Activation (A = 40–100 ) by medium energy protons andalpha particles (E = 10–50 MeV ) (Inter-Vesi, Moscow,
USSR, 1991).
2) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res. B
268, 1818 (2010).
3) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).
4) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Activation cross sections of proton-induced reactions on manganese up
to 30 MeV
H. Huang,∗1,∗2 M. Aikawa,∗1,∗2,∗3 and H. Haba∗2
51

∗1
∗2
∗3

Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University

120
Cross section (mb)Cr (T1/2 = 27.8 d) decays through electron capture.
It has been used to label the ethylenediaminetetraacetic
acid (51 Cr-EDTA), whose blood clearance counting responds to the glomerular ﬁltration rate.1) It has also
been used to label red blood cells as a tracer for measuring the of mass and volume of living systems.2)
This medical radionuclide is expected to be produced
via charged-particle-induced reactions on neighbor elements. In this research, we focused on the protoninduced reaction on manganese. Manganese has only
one stable isotope: 55 Mn. We found four former experimental data on the cross sections of the 55 Mn(p, x)51 Cr
reaction in the literature survey.3–6) However, they arescattered and not consistent with each other. Therefore, we performed an experiment to measure the crosssections of this reaction.
We conducted the experiment using a 30-MeV proton
beam at the AVF cyclotron at RIKEN. We adopted thewell-established stacked-foil activation technique, followed by high-resolution gamma-ray spectrometry to determine the excitation functions. The target consistedof manganin (Nilaco Corp., Japan), nat Ti (99.6% purity, Nilaco Corp., Japan) and 27 Al (>99% purity, Nilaco Corp., Japan) foils. Manganin is an alloy consistingof copper, manganese, and nickel. We analyzed the elemental ratio of the manganin foil using scanning electron
microscopy with energy dispersive spectroscopy (Hitachi
TM4000 Plus II). The measured mass ratios were 12.5%,
85.2% and 2.24% for Mn, Cu and Ni, respectively. Thenat
Ti foil was used for the nat Ti(p, x)48 V monitor reaction to assess beam parameters and target thicknesses.
The 27 Al foil was interleaved to collect recoiled products.
We measured the weight and size of these foils to obtain
their average thicknesses. The foils were then cut into
squares of 8 × 8 mm2 to ﬁt the size of a target holder,which also served as a Faraday cup. Seventeen sets of
Mn-Mn-Ti-Ti-Al foils were stacked as the target.
The stacked target was irradiated for 20 min. The
average intensity and primary energy of the beam were
measured to be 182 nA and 30.1 MeV, respectively. Energy degradation in the stacked target was calculated using the stopping powers obtained using the SRIM code.7)
The gamma-ray spectrometry was performed using ahigh-purity germanium detector (ORTEC GEM30P470) and analyzed using the analysis software (SEIKO
EG&G Gamma Studio). We assumed that the recoiled
nuclides from the ﬁrst foils compensate for the loss ofthe second foils. Only gamma spectra from second man-This work
TENDL-2019
F.Ditroi(2013)
M.Al-Abyad(2010)
R.Michel(1997)
V.N.Levkovski(1991)

100
80
60
40
20
0

0

5

10

15

20

25

30

Energy (MeV)
Fig. 1. Cross sections of the 55 Mn(p, x)51 Cr reaction withprevious data3–6) and TENDL-2019 values.8)

ganin and Ti foils were measured, The cooling times werefrom 18.4 to 52.8 h. The dead time was maintained below 3.6%. The cross sections of the nat Ti(p, x)48 V monitor reaction were derived and then compared with therecommended values of IAEA.8) According to the comparison, the thicknesses of all the foils were corrected by+1%. The other parameters were adopted without any
correction.
The gamma line emitted from the decay of 51 Cr withan energy of 320.08 keV (Iγ = 9.91%) was measured
to derive the cross sections of the 55 Mn(p, x)51 Cr reaction. We compared our data with previous experimental
studies3–6) and the theoretical values of TENDL-20199)
in Fig. 1. Our data had fewer total uncertainties thanformer studies because the partial uncertainties of target thickness and beam intensity were smaller. The peak
positions of previous experimental data were consistent
with ours, whereas the amplitudes of some data werelarger. The theoretical values of TENDL-2019 underestimated the experimental data.
References
1) S. J. Gray et al., J. Clin. Investig. 29, 1604 (1950).
2) A. A. Chaves et al., Clinics (Sao Paulo) 65, 607 (2010).
3) F. Ditroi et al., Nucl. Instrum. Methods Phys. Res. B.
308, 34 (2013).
4) M. Al-Abyad et al., Appl. Radiat. Isot. 68, 2393 (2010).
5) R. Michel et al., Nucl. Instrum. Methods Phys. Res. B
129, 153 (1997).
6) V. N. Levkovskii et al., Radiat. Eﬀ. 80, 223 (1984).
7) J. F. Ziegler et al., SRIM: the Stopping and Range of Ionsin Matter (2008), http://www.srim.org/ .
8) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).
9) A. J. Koning et al., Nucl. Data Sheets 113, 2841 (2012).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Activation cross sections of deuteron-induced reactions on natural
chromium up to 24 MeV
H. Huang,∗1,∗2 M. Aikawa,∗1,∗2,∗3 Y. Hanada,∗1,∗2 and H. Haba∗2
52g

∗1
∗2
∗3

Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University- 155 -

250
Cross section (mb)

Mn (T1/2 = 5.591 d) that decays by electron capture and positron emission can be used in positronemission tomography (PET).1) 51 Cr (T1/2 = 27.8 d)that decays by the same mode was used to label red
blood cells as a tracer in the measurement of the mass
and volume of living systems.2) These medical radionuclides can be produced via charged-particle-induced
reactions on neighbor elements. We focused on the
deuteron-induced reaction on natural chromium. Experimental literature data regarding the cross sectionsof the reaction are inconsistent,3–5) and therefore, we
performed the experiment to measure the production
cross sections of 52g Mn and 51 Cr. In addition, the crosssections of the by-products 48 V and 52m, 54 Mn were determined.
We adopted the well-established stacked-foil activation technique followed by high-resolution gamma-ray
spectrometry to determine excitation functions. The
target comprised nickel-chromium (NiCr) alloy (99.9%
purity, Goodfellow Co., Ltd., UK), nat Ti (99.6% purity, Nilaco Corp., Japan), and 27 Al (>99% purity,
Nilaco Corp., Japan) foils. The nat Ti foil was used
for the nat Ti(d, x)48 V monitor reaction to assess thebeam parameters. The 27 Al foil was interleaved to collect recoiled products. The average thickness of eachfoil was derived from their measured weight and size.
We analyzed the elemental ratio of the NiCr alloy foil
by a scanning electron microscope with an energy dispersive X-ray spectrometer (Hitachi TM4000 Plus II).
The measured mass ratios were Cr 21.5%, Ni 76.7%,
and Mn 1.7%, respectively. All foils were then cut into
squares of 8 × 8 mm2 to ﬁt the size of a target holderthat served as a Faraday cup. Thirteen sets of NiCrNiCr-Al-Ti-Ti-Al foils were stacked as the target.
The stacked target was irradiated for 15 min by a
24-MeV deuteron beam from the AVF cyclotron at
RIKEN. The average intensity and primary energyof the beam were measured to be 105 nA and 24.0
± 0.1 MeV. Energy degradation in the stacked target was calculated using stopping powers obtained by
the SRIM code.6) Gamma-ray spectrometry was performed using a high-purity germanium detector (ORTEC GEM30P4-70) and analyzed by the analysis software (SEIKO EG&G Gamma Studio). Only gamma
spectra from each second NiCr alloy and Ti foil were
measured assuming that recoiled nuclides from the second foils were compensated by those from the ﬁrst.

Hermanne(2011)
Simeckova(2018)
Bianchi(2020)
TENDL-2019
This work

200
150
100
50
0

0

5

10

15

20

25

Energy (MeV)
Fig. 1. Cross sections of the nat Cr(d, x)52g Mn reaction withprevious data3–5) and the TENDL-2019 values.8)

During 1 h–32 d cooling, NiCr alloy foils were measured 7 times to assess the radionuclides with diﬀerent
half-lives. The measurement distances were 3–50 cm.
The dead time was kept below 5.2%.
The cross sections of the nat Ti(d, x)48 V monitor reaction were derived and compared with the recommended values of IAEA.7) The comparison results indicated that, the beam intensity was corrected by −1.1%
within the uncertainty (5%). The other parameters
were adopted without any correction.
We derived the cross sections using the measurementof the 935.544-keV gamma line (Iγ = 94.5%) emittedwith the decay of 52g Mn. A short-lived metastable isomer 52m Mn (T1/2 = 21.1 min) decayed to the groundstate 52g Mn by isomeric transition with a branchingratio of 1.78%. Thus, we determined the cumulative
cross section of 52g Mn. We compare our data with theprevious studies3–5) and the TENDL-2019 values8) in
Fig. 1; our data are less scattered and in agreementwith the recently published data.4,5) The theoreticalvalues of TENDL-2019 obviously overestimate the experimental data.
References
1) I. F. Chaple et al., J. Nucl. Med. 59, 1655 (2018).
2) S. J. Gray et al., J. Clin. Investig. 29, 1604 (1950).
3) A. Hermanne et al., Nucl. Instrum. Methods Phys. Res.
B 269, 2563 (2011).
4) E. Šimečková et al., Phys. Rev. C 3, 034606 (2018).
5) F. Bianchi et al., Appl. Radiat. Isot. 166, 109329 (2020).
6) J. F. Ziegler et al., SRIM: the Stopping and Range ofIons in Matter (2008), http://www.srim.org/ .
7) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).
8) A. J. Koning et al., Nucl. Data Sheets 113, 2841 (2012).

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross-sections of 52m Mn in alpha-particle-induced reactionsin natural vanadium
G. Damdinsuren,∗1,∗2 M. Aikawa,∗1,∗2,∗3 Kh. Tegshjargal,∗4 N. Erdene,∗4 S. Ebata,∗5,∗2 and H. Haba∗2

∗1
∗2
∗3
∗4
∗5

Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
School of Engineering and Applied Sciences, National University of Mongolia
Graduate School of Science and Engineering, Saitama University

400

natV(,x)52Mn

350
300
Cross section [mb]The ground state of the 52m Mn radioisotope has a halflife of T1/2 = 5.6 days and decays via electron capture(70.6%) and positron emission processes (29.4%, Eβ+ = 242 keV). 52m Mn can be used in positron emission tomography (PET) imaging to study biological and physiological processes with a time scale similar to its decay.1) The routes for 52m Mn production include chargedparticle-induced reactions. Among the possible reactions, we focused on the α-particle-induced reaction on
natural vanadium targets. Eleven previous experimental studies were found in the EXFOR library.2) However,their data exhibited show large uncertainties and discrepancies. Therefore, we measured the excitation function of the nat V(α, x)52m Mn reaction. The experimental
result was compared with the literature data obtained
from the EXFOR database and TENDL-2019 data.3)
The stacked-foil activation technique and highresolution γ-ray spectrometry were used for cross-section
measurements. The experiment target consisted of puremetal foils of nat V (25-μm thick, 99% purity), nat Ti (5μm thick, 99.6% purity), and 27 Al (5-μm thick, 99.9%
purity) from Nilaco Corp., Japan. 27 Al foils were inserted to sandwich nat V foils to separate the recoiled reaction products from nat V and nat Ti foils. nat Ti foils
were used in the nat Ti(α, x)51 Cr monitor reaction to assess beam parameters and energy loss in the particles inthe stack.
The target thickness was derived using the measured size and weight of the foils. The derived thickness of nat V, nat Ti, and 27 Al foils was 20.4, 2.24, and1.22 mg/cm2 , respectively. These foils were then cut
into 8 × 8 mm pieces to ﬁt a target holder that served
as a Faraday cup. Eleven sets of V-Al-Ti-Ti-Al foils werestacked into the target holder.
The stacked target was irradiated with a 50.6 ±0.2 MeV alpha-particle beam for 30 min. The primaryenergy was measured by the time-of-ﬂight method.4) Energy degradation in the stacked target was calculated using the SRIM code.5) The average beam intensity measured by the Faraday cup was 194 nA.
The γ-ray spectra of each irradiated foil were measured
by a high-resolution HPGe detector (ORTEC GEM25185-P) and analyzed using dedicated software (SEIKO
EG&G Gamma Studio). Each nat V foil was measured
with the following 27 Al catcher foil for the recoiled products. The distance between the detector and foils was


250
200
150
100
50

This work
Bowman (1969)
Dmitriev (1969)
Michel (1982)
Rama (1987)
Levkovski (1991)
Singh (1993)
Sonzogni (1993)
Ismail (1993)
Singh (1995)
Chowdhury (1995)
Bindu (1998)
TENDL-2019













0
10

15

20

25

 
30

35

40

45

50

Energy [MeV]Fig. 1. Excitation function of the nat V(α, x)52m Mn reaction.

arranged to ensure a dead time of less than 3%.
The cross-sections of the nat Ti(α, x)51 Cr monitor reaction were derived to assess the beam parameters andtarget thickness. The γ line at 320.08 keV (Iγ = 9.91%)
from the decay of 51 Cr (T1/2 = 27.7025 d) in each
low-energy foil of Ti-Ti pairs were measured. The derived cross-sections were compared with the IAEA recommended values.6) Our result was consistent with therecommended values and no corrections were adopted fordata analysis.
Further, the cumulative cross-sections of the nat V(α,52mMn reaction were derived.
The shorter-lived
x)metastable state of the 52m Mn (T1/2 = 21.1 min) radionuclide decayed to the ground state 52m Mn (T1/2 =5.591 d) and 52 Cr (stable) soon after the end of thebombardment. The γ line at 935.544 keV (Iγ = 94.5%)
from the decay of 52m Mn was measured after cooling for
17 days. The cumulative cross-sections were obtained
from the net count of the γ line. Figure 1 shows thederived cross-sections in comparison to previous experimental studies and TENDL-2019 data.3) The present
cross-section data exhibited a smooth curve and they
were consistent with a part of previous experimental
data. The peak position and amplitude of TENDL-2019
data were diﬀerent from the experimental data.
G. Damdinsuren was granted a scholarship by the MJEED project (Mongolian-Japan Engineering Education
Development Program, J11B16).
References
1) F. Bianchi et al., Appl. Radiat. Isot. 166 (2020).
2) N. Otuka et al., Nucl. Data Sheets 120, 272 (2014).
3) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
4) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(2014), p. 3566.
5) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res. B
268, 1818 (2010).
6) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).

- 156 -

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Measurement of production cross sections of medical isotope 110m In
in alpha-particle-induced reaction on natural silver up to 50 MeV
Ts. Zolbadral,∗1,∗2,∗3 M. Aikawa,∗3,∗4,∗5 D. Ichinkhorloo,∗1,∗4 G. Damdinsuren,∗3,∗4 H. Huang,∗3,∗4 and
H. Haba∗4

∗1
∗2
∗3
∗4
∗5

400

natAg(,x)110mIn

350
Cross section (mb)

The metastable state of indium-110 (110m In) has
a half-life of 69.1 min and emits positrons (Eβ + =1011 keV, Iβ + = 61.3%). This radionuclide can beused to label proteins and peptides for application inpositron emission tomography (PET) imaging.1,2) Furthermore, 110m In emits a medium-energy and highintensity γ line that is useful for β + γ coincidence
PET.3)A suitable route for direct production of 110m In is the
α-particle-induced reaction on a silver target (107 Ag
51.839%, 109 Ag 48.161%). 110m In can be produced bythe (α, n) reaction (Ethr = 7.87 MeV) on 107 Ag andthe (α, 3n) reaction (Ethr = 24.92 MeV) on 109 Ag. Because most radioactive impurities can be eliminated,the 107 Ag(α, n)110m In reaction is a promising candidate for the production of 110m In;4) however an isotopically enriched 107 Ag target is required for the reaction.
The longer-lived ground state, 110g In (T1/2 = 4.92 h),is co-produced in the energy region in addition to
110m
In. To investigate the production route of 110m In,
reliable data on the cross sections of the α-induced reaction on a natural silver target are required.
Thus, the main aim of this study is to measure thecross sections of the nat Ag(α, x)110m In reaction and toinvestigate a route for 110m In production.
The cross sections were determined using thestacked-foil activation technique and γ-ray spectrometry.
Pure metallic foils of nat Ag (thickness of
10.1 mg/cm2 with a purity of 99.9%) and nat Ti (thickness of 2.2 mg/cm2 with a purity of 99.5%) werestacked to form the target.
The stacked target was irradiated for 30 min with a
50.2-MeV α-particle beam from the RIKEN AVF cyclotron. The energy of the incident beam was measured using the time-of-ﬂight method. The SRIM
code5) was used to calculate the energy degradationin the stacked target. The beam intensity was 213 nA
measured with a Faraday cup.
A high-resolution high-purity germanium (HPGe)
detector was used to measure the γ-ray spectra of
the irradiated foils. The detector was calibrated bya mixed γ-ray point source. In the measurements, thedead time was less than 10%.
The cross sections of the nat Ag(α, x)110m In reaction
were derived from the measurements of the 657.75-keV
Nuclear Research Center, National University of Mongolia
New Mongolia College of Technology
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University- 157 -

This work
Shahid 2017
Takacs 2010
TENDL-2019

300
250
200
150
100
50
0

0

10

20

30

40

50

Energy (MeV)

Fig. 1. Excitation function of the nat Ag(α, x)110m In reaction with previous experimental data6,7) and the
TENDL-2019 values.8)

γ line (Iγ = 97.74%) from the 110m In decay.
Figure 1 shows the preliminary results of the measured excitation function of the nat Ag(α, x)110m In reaction in comparison with recent experimental datareported by Shahid et al.,6) Takács et al.,7) and thetheoretical estimation from TENDL-2019.8)
Our measured excitation function of the nat Ag(α,110m
In reaction is consistent with those of the prex)
vious experimental data sets6,7) within uncertainties,
however, the peak position of our result shifts slightly
to lower energy.
The TENDL-2019 data show partial agreement withthe experimental data sets. The second peak in thehigher-energy region is much larger than the experimental data.
References
1) M. Lubberink et al., J. Nucl. Med. 43, 1391 (2002).
2) V. Tolmachev et al., Biochim. Biophys. Acta, Gen.
Subj. 1800, 487 (2010).
3) M. Sitarz et al., Appl. Radiat. Isot. 155, 108898 (2020).
4) F. Tárkányi et al., Nucl. Instrum. Methods Phys. Res.
B 351, 6 (2015).
5) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
6) M. Shahid et al., J. Radioanal. Nucl. Chem. 311, 1971(2017).
7) S. Takács et al., Nucl. Instrum. Methods Phys. Res. B
268, 2 (2010).
8) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Cross sections of alpha-particle-induced reactions on nat Sb†
S. Takács,∗1 F. Ditrói,∗1 Z. Szücs,∗1 K. Brezovcsik,∗1 H. Haba,∗2 Y. Komori,∗2 M. Aikawa,∗3,∗2 M. Saito,∗4,∗2
T. Murata,∗4,∗2 M. Sakaguchi,∗4,∗2 and N. Ukon∗5,∗2

†
∗1
∗2
∗3
∗4
∗1

Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 505, 24 (2021)
Institute for Nuclear Research (ATOMKI)
RIKEN Nishina Center
Faculty of Science, Hokkaido University
Graduate School of Biomedical Science and Engineering,
Hokkaido University
Advanced Clinical Research Center, Fukushima Medical University

natSb(D,x)123I

800

Cross section (mb)

Cross sections of alpha-particle-induced reactions
on natural antimony targets were investigated up to
51 MeV. Some produced iodine isotopes are frequently
used in nuclear medicine; therefore, their cross sections
can be interesting as alternative production routes. For
most of these reactions, the available experimental datain the literature are not suﬃciently consistent; therefore, additional experimental cross sections of these reactions are required. The experiment was performed at
the RIKEN AVF cyclotron. The stacked-foil activation
technique and high-resolution γ-ray spectrometry wereused. Thin Sb targets were prepared by vacuum evaporation onto Kapton (polyimide) (24.5 ± 0.25 μm, Goodfellow, Co., Ltd., UK). Kapton backings with a diameter of
13 mm were cut, numbered, and measured by weight before the evaporation process. Small grains of Sb (approximately 5 mg) were placed in a resistive heated tantalum
boat to evaporate it in vacuum and deposit a thin layerof Sb onto the Kapton backings with a 10 mm in diameter mask placed approximately 15 cm from the source ofevaporating Sb. This geometry provided relatively even
Sb layers on the Kapton backings. The thickness of theevaporated Sb layer was determined from the measured
weight and known surface of the evaporated spot. Eachsandwiched Sb target was composed of two Sb layers
enclosed between two Kapton backings with an average
thickness of ∼1 mg/cm2 . Pure nat Ti foils (99.9% Nilaco
Corp., Japan) with an average thickness of 5.3 ± 0.05 μm
were inserted into the stack to monitor the irradiation
parameters. To address the recoil eﬀect, an additional
Kapton catcher foil was used behind every Ti foil. The
irradiations lasted for 2 h with an alpha-particle beam of
50.42 ± 0.2 MeV and 50 nA. The incident beam energy
was measured using the time-of-ﬂight method.1) The
energy loss of the alpha particles was calculated using
the semi-empirical formula proposed by Andersen andZiegler.2) The average beam intensity measured using a
Faraday cup was cross checked with the nat Ti(α, x)51 Cr
monitor reaction.3) After applying a +5% correction of
the measured beam intensity, the re-measured cross sections for the nat Ti(α, x)51 Cr monitor reaction agreed perfectly with their recommended values3) indicating thata proper beam and target parameters were used. Three
series of γ-ray spectra were recorded for every irradiated foil by using a high-resolution HPGe detector-based

This work
TENDL-2019
Watson 1973
Homma 1976
Calboreanu 1982
Ismail 1990
Singh 1991
Bhardwaj 1994
Singh 1997
Hassan 2006
Tarkanyi 2009
Uddin 2011

600

400

200

0

0

10

20

30

40

50

Particle energy (MeV)

Fig. 1. Excitation function of the nat Sb(α, x)123 I reaction incomparison with previously reported experimental data
and results of the model calculation from the TENDL2019 database.5)

γ-spectrometer without chemical separation with average cooling times of 25, 75, and 180 h to follow the decay of the reaction products. Q-values and decay data
were obtained using the Q-value calculator4) and NuDat
2.7 database5) of National Nuclear Data Center, respectively.
Direct or cumulative cross sections for the formation of 121, 123, 124, 125, 126 I, 121m, g,123m, 125m Te, and118m, 120m, 122g
Sb were determined. The obtained experimental data were compared with the experimental data
available in the literature and the results of the TALYS
theoretical model calculation taken from the TENDL20196) data library.
A comparison with the theoretical estimation revealed
that the TALYS prediction provided an acceptable agreement with the experimental data except for the 125m Te
isotope, for which the prediction was far too conservative.
Cross section data were reported for the ﬁrst
time for the nat Sb(α, x)121m Te, nat Sb(α, x)123m Te,natnat
Sb(α, x)125m Te,
Sb(α, x)118m Sb,
and
nat
122g
Sb(α, x)
Sb reactions.
This work was conducted in the framework of a common research program between the JSPS and HAS (Contract No: JPJSBP120193808 and NKM-43/2019).
References
1) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), (2014), p. 3566.
2) H. H. Andersen, J. F. Ziegler, Helium Stopping Powers
and Ranges in all Elements (Pergamon, Oxford, 1997).
3) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).
4) NNDC, Q-calc, https://www.nndc.bnl.gov/qcalc/ .
5) NNDC, NuDat 2.7 database, http://www.nndc.bnl.gov/
nudat2/ .
6) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Activation cross sections of deuteron-induced reactions on
praseodymium up to 24 MeV†
M. Aikawa,∗1,∗2 T. Maehashi,∗3 D. Ichinkhorloo,∗1,∗2 S. Ebata,∗4,∗2 Y. Komori,∗2 and H. Haba∗2

†
∗1
∗2
∗3
∗4

Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 498, 23 (2021)
Faculty of Science, Hokkaido University
RIKEN Nishina Center
School of Science, Hokkaido University
Graduate School of Science and Engineering, Saitama University

1400

141Pr(d,3n)140Nd

1200
Cross section (mb)

The 140 Nd (T1/2 = 3.37 d) and 142 Pr (T1/2 = 19.12 h)radionuclides can be used for a 140 Nd/140 Pr in-vivo generator for positron emission tomography (PET)1) andfor the treatment for arteriovenous malformations,2) respectively. We focused on the deuteron-induced reaction on the monoisotopic element 141 Pr among possible
production reactions. In a literature survey, we foundonly two experimental studies on the 141 Pr(d, 3n)140 Nd
reaction, the experimental cross sections of which arescattered.3,4) Therefore, we conducted two experiments
to measure the cross sections of this reaction. The production cross sections of 141, 140 Nd, 142 Pr, and 141 Ce
were determined up to 24 MeV.
Two independent experiments were conducted using 24-MeV deuteron beams at the RIKEN AVF cyclotron. The stacked-foil activation technique and highresolution gamma-ray spectrometry were adopted forthe experiments. For the stacked targets, two 141 Pr(99% purity), two nat Ti (99.6% purity), and one 27 Al(>99% purity) metal foils were purchased from Nilaco Corp., Japan. The measured thicknesses of thefoils were 67.6 and 72.3 mg/cm2 (141 Pr), 2.34 and2.30 mg/cm2 (nat Ti), and 1.50 mg/cm2 (27 Al). The
ﬁrst (#1) and second stacked targets (#2) were composed of 141 Pr and nat Ti and 141 Pr, nat Ti, and 27 Al,
respectively. The nat Ti foils were interleaved for thenatTi(d, x)48 V monitor reaction to assess beam parameters and target thicknesses. The 27 Al foils were used
as catchers of the recoiled products and to address thevariation in energy degradation. Nine sets of Pr-Ti-Ti(#1) and Pr-Al-Ti-Ti-Al foils (#2), which were cut intoa size of 8 × 8 mm2 , were stacked into target folders
served as Faraday cups.
Both stacked targets were irradiated with deuteronbeams for 30 min. The average beam intensities measured by the Faraday cups were 107 (#1) and 110 nA(#2). The measured primary beam energies were 24.1(#1) and 24.3 MeV (#2). The energy degradation of
the beams in the stacked targets was calculated using
stopping powers obtained from the SRIM code.5)
Gamma rays emitted from the irradiated foils were
measured without chemical separation using a highpurity germanium detector. The 141 Pr foils with thefollowing 27 Al foils were measured several times with adead time below 5.2%.

Lange (1968)
Hermanne (2009)TENDL-2019
This work #1
This work #2

1000
800
600
400
200
0
10

15

20

25

30

Energy (MeV)

Fig. 1. Cross sections of the 141 Pr(d, 3n)140 Nd reaction withthe previous data3,4) and the TENDL-2019 values.7)

Cross sections of the nat Ti(d, x)48 V monitor reaction were derived to assess beam parameters and target thicknesses. A comparison with the IAEA recommended values6) indicated that the thicknesses of the141
Pr foils were corrected by +1% within the uncertainties (2%). The other target thicknesses and beam
parameters were adopted without any correction.
There are no gamma lines with the decay of 140 Nd(T1/2 = 3.37 d). Considering the secular equilibrium,
the gamma lines at 1596.1 keV (Iγ = 0.49%) and
511 keV (Iγ = 102%) emitted with the decay of 140 Pr(T1/2 = 3.39 min) were measured instead. The directly
produced 140 Pr decayed during the cooling times. The
cross sections of the 141 Pr(d, 3n)140 Nd reaction in theﬁrst experiment (#1) were deduced from the gammaline at 1596.1 keV, and those in the second experiment(#2) were determined from the gamma line at 511 keV.
A comparison of the results with previous studies3,4)
and TENDL-2019 values7) is shown in Fig. 1. Previous
experimental data are scattered, but almost consistent
with ours within the uncertainties. The TENDL-2019
values are slightly larger than our data.
References
1) K. P. Zhernosekov et al., Radiochim. Acta 95, 319(2007).
2) S. W. Lee et al., Phys. Med. Biol. 50, 151 (2005).
3) V. J. Lange et al., Radiochim. Acta 9, 66 (1968).
4) A. Hermanne et al., Nucl. Instrum. Methods Phys. Res.
B 383, 81 (2016).
5) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
6) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).
7) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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1

III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections for α-particle-induced reactions on nat La
S. Ebata,∗1,∗2 M. Aikawa,∗3,∗2 G. Damdinsuren,∗4,∗2 and H. Haba∗2

∗1
∗2
∗3
∗4

Department of Physics, Saitama University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
Graduate School of Biomedical Science and Engineering,
Hokkaido University

160

139

La(α,n)142Pr
TENDL

Cross section ( mb )The application of radionuclides was started several
decades ago. Given its widespread use, it is important
for the nuclear medicine ﬁeld to generate new medical isotopes using more safe and eﬀective methods. To
this end, radionuclides suitable for both therapy anddiagnosis have been investigated in recent years. The
radionuclide 142 Pr (T1/2 = 19.12 h) is one of the applicable candidates because of its β decay (Eβ −  = 810 keV,
96.3%) and low-intensity speciﬁc γ emission with Eγ =1575 keV (3.7%).1) Among the possible ways to generate 142 Pr, the proton-, deuteron-, and alpha-particle
induced reactions on cerium and lanthanum can beconsidered for on-site production at small light-ion accelerators used in hospitals. In the literature survey, only two experimental studies were found for thenatLa(α, x)142 Pr reaction,2,3) and they did not provide
consistent results (See Fig. 1.). Therefore, we focus on
the α-particle-induced reaction on natural lanthanum
and measure the production cross sections for the reaction using an activation method.
Two independent experiments were performed using
50-(#1) and 29-MeV (#2) α beams at the RIKEN AVF
cyclotron. The stacked-foil technique was adopted in
the activation method, and high-resolution germaniumdetector based γ-spectrometry was used to measure γ
rays from the generated radionuclides. The stacked targets comprised nat La (99% purity), 27 Al (> 99% purity), and nat Ti (99.6% purity) metal foils purchasedfrom Nilaco Corp., Japan. The natural abundances of138
La and 139 La are 0.09% and 99.91%, respectively.
The measured thicknesses of the foils were 15.4 mg/cm2(nat La), 2.25 mg/cm2 (nat Ti), and 1.22 mg/cm2 (27 Al).
The nat Ti foils were interleaved for the nat Ti(α, x)51 Cr
monitor reaction to assess beam parameters and target
thicknesses. The 27 Al foils were used as catchers forrecoiled products and for energy degradation. Eighteen
sets of La-Al-Ti-Ti (#1) and eight La-Al-Ti foils (#2),
which were cut into a size of 8 × 8 mm2 , were stacked
into target holders served as Faraday cups.
Both stacked targets were irradiated with α beams
for 30 min. The average beam intensities were 196 (#1)
and 210 nA (#2), which were measured on the Faradaycups. The measured primary beam energies were 50.6(#1) and 29.0 MeV (#2). The energy degradation of
the beams in the stacked targets was calculated using
stopping powers by the SRIM code.4)
The emitted γ rays from the irradiated foils were
measured using a high-purity germanium detector.

Furukawa 1966
Verdieck 1967

120

This work: 29 MeV
50 MeV
80

40

0

10

15

20

25

30

35

40

45

50

Energy ( MeV )Fig. 1. Cross sections of the 139 La(α, n)142 Pr reaction. The
previous studies2,3) and the TENDL-2019 values5) are
shown.

Each nat La foil with its following 27 Al catcher foil wasmeasured several times with a dead time less than 2.8%.
The nat Ti(α, x)51 Cr monitor reaction was used to assessbeam parameters and target thicknesses by comparing
the measured cross sections for the reaction with the
IAEA recommended values.5) Only the thickness of thenat
La foils was corrected by +1% within uncertainties
to ensure consistency with the recommended values.
The γ line at 1575 keV with the decay of 142 Pr
was analyzed to derive the cross sections of thenatLa(α, x)142 Pr reaction. The cross sections are practically the same as those of the 139 La(α, n)142 Pr reaction because the contribution of the capture reaction on
the less-abundant 138 La is negligible. The results with
50 and 29 MeV α beams are shown in Fig. 1 and arecompared to those reported in previous studies2,3) andthe TENDL-2019 values.6) Our independent data for 50
and 29 MeV agree well with each other. The present
cross sections are slightly larger than those reported
in the literature above 20 MeV, whereas the TENDL
values underestimate all experimental data. Moreover,the peak widths of the experimental data were broader
than those of the TENDL values.
References
1) M. Sadeghi et al., J. Radioanal. Nucl. Chem. 288, 937(2011).
2) M. Furukawa, Nucl. Phys. 77, 565 (1966).
3) E. V. Verdiegk, J. M. Miller, Phys. Rev. 153, 1253
(1967).
4) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
5) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).
6) A. J. Koning et al., Nucl. Data. Sheets 155, 1 (2019).

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III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross sections of 153 Sm via alpha-particle-induced reactions
on natural neodymium
M. Aikawa,∗1,∗2,∗3 M. Sakaguchi,∗2,∗3 N. Ukon,∗4,∗3 Y. Komori,∗3 H. Haba,∗3 N. Otsuka,∗5 and S. Takács∗6
Samarium radionuclides 153 Sm (T1/2 = 46.3 h)
and 145 Sm (T1/2 = 340 d) can be used to treatbone metastases1) and for brachytherapy,2) respectively. We investigated the production of the radionuclides via alpha-particle-induced reactions on natural
neodymium.3) However, the measured cross sections of
the nat Nd(α, x)153 Sm reaction exhibit signiﬁcant deviations from a previously published experimental study.4)
More speciﬁcally, the peak amplitude of the cross sections was diﬀerent from each other by a factor of morethan two. Therefore, we performed additional experiments to measure the activation cross sections of thereactions with an emphasis on the peak amplitude of
the nat Nd(α, x)153 Sm reaction.
Accordingly, two experiments (#1 and #2) were performed at the RIKEN AVF cyclotron using the stackedfoil activation technique and high-resolution gamma-ray
spectrometry. Two targets of the experiments were composed of pure metallic foils of nat Nd (99% purity, Goodfellow Co., Ltd., UK) and nat Ti (99.6% purity, Nilaco
Corp., Japan). The nat Ti foils were utilized for monitoring the beam via the nat Ti(α, x)51 Cr monitor reaction and for beam-energy degradation. The average foil
thicknesses, derived from the size and weight of the original nat Nd and nat Ti foils, were 16.7 and 2.25 mg/cm2 ,respectively. The original foils were cut into a size of
10 × 10 mm. The two stacked targets with diﬀerent conﬁgurations of six nat Nd and fourteen nat Ti target foils
were placed in target holders that served as Faraday
cups.
Both stacked targets were irradiated for 33 min with
28.9 ± 0.2-MeV alpha-particle beams. The energy
degradation of the beams in the stacked targets werecomputed using stopping powers obtained from the
SRIM code.5) The average beam intensities measured by
the Faraday cups were 103 nA (#1) and 104 nA (#2),
respectively. Gamma rays emitted from the irradiatedfoils were measured without chemical separation using
high-purity germanium detectors. To deduce activation
cross sections, nuclear data were retrieved from the online database, NuDat 3.0.6)
Cumulative cross sections of 153 Sm including contribution form decay of 153 Pm (T1/2 = 5.25 min) via thealpha-particle-induced reactions on natural neodymium
were determined. The cross sections were derived from
∗1
∗2
∗3
∗4
∗5
∗6

Faculty of Science, Hokkaido University
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Advanced Clinical Research Center, Fukushima Medical University
Nuclear Data Section, IAEA
Institute for Nuclear Research (ATOMKI)

Fig. 1. Cross sections of the nat Nd(α, x)153 Sm reaction withprevious experimental data3,4) and a theoretical prediction of the TENDL-2019 values.7)

measured net counts of the gamma line at 103.18 keV (Iγ= 29.25%), which was emitted from the decay of 153 Sm.
The attenuation of the low-energy gamma rays in thenat
Nd foil was calculated using the X-ray mass attenuation coeﬃcients7) and estimated to be 2.1%. The crosssections were determined using the corrected counts.
The preliminary results are depicted in Fig. 1 alongwith the experimental data published earlier3,4) and the
TENDL-2019 values.7) The present results conform witheach other and also with our previous study,3) however
the other literature data4) are inconsistent. Based on our
new results, the smaller cross sections would be more reliable. The TENDL-2019 values are even smaller thanthe experimental data.
In addition to the cross sections of the nat Nd(α,x)153 Sm reaction, those of the nat Nd(α, x)145 Sm reaction will also be determined. There are no experimental
data on the nat Nd(α, x)145 Sm reaction other than ourprevious study. The cross sections derived in this work
will increase the reliability of the cross sections.
References
1) I. G. Finlay et al., Lancet Oncol. 6, 392 (2005).
2) R. G. Fairchild et al., Phys. Med. Biol. 32, 847 (1987).
3) M. Sakaguchi et al., Appl. Radiat. Isot. 176, 109826(2021); M. Sakaguchi et al., in this report.
4) S. M. Qaim et al., Radiochim. Acta 95, 313 (2007).
5) J. F. Ziegler et al., SRIM: the Stopping and Range of Ionsin Matter (2008), http://www.srim.org/ .
6) National Nuclear Data Center, The NuDat 3.0 database,
http://www.nndc.bnl.gov/nudat3/ .
7) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
8) J. H. Hubble et al., X-Ray Mass Attenuation Coeﬃcients, NIST Standard Reference Database 126, https://dx.doi.org/10.18434/T4D01F .

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross-sections of dysprosium-159 radioisotope obtained by
α-particle-induced reactions of natural gadolinium up to 50 MeV†
D. Ichinkhorloo,∗1,∗2,∗3 M. Aikawa,∗1,∗4,∗3 Ts. Zolbadral,∗4,∗2,∗3 T. Murata,∗4,∗3 M. Sakaguchi,∗4,∗3 Y. Komori,∗3
T. Yokokita,∗3 and H. Haba∗3
Dysprosium and terbium radioisotopes are of interest for diagnosis and therapy in nuclear medicine.
Dysprosium-157 (T1/2 = 8.14 h), dysprosium-159 (T1/2= 144.4 d), and terbium-155 (T1/2 = 5.32 d) can be used
for bone scanning (skeletal imaging),1) determination ofbone mineral,2) and single-photon emission computerized tomography imaging,3) respectively.
Radionuclides can be produced in natural gadoliniumby charged-particle-induced reactions. In this study, theactivation cross-sections of α-particle-induced reactionsin natural gadolinium were investigated. Production
cross-sections of 155, 157, 159 Dy, 153, 155, 156g, 160, 161 Tb,
and 153 Gd were determined. The results were comparedwith TENDL-2019 data based on TALYS code calculation.4)
Experiments were conducted at the RIKEN AVF cyclotron, which in the stacked foil technique, the activation method and the high-resolution γ-ray spectrometry
to determine the activation cross-sections.
A stacked target was formed of 8 × 8 mm2 foils cut
from large Gd (25 μm, 50×50 mm2 , 99.9% purity, Nilaco
Corp., Japan) and Ti foils (5 μm, 50 × 100 mm2 , 99.6%
purity, Nilaco Corp., Japan). The isotopic composition of the natural Gd target was 152 Gd (0.2%), 154 Gd(2.2%), 155 Gd (14.8%), 156 Gd (20.5%), 157 Gd (15.6%),
158
Gd (24.8%), and 160 Gd (21.9%).
The sizes and weights of the large foils were measured
to derive the thicknesses of the Gd and Ti foils, whichwere found to be 25.4 and 2.29 mg/cm2 , respectively.
The Ti foils were used in the nat Ti(α, x)51 Cr monitor reaction to assess beam parameters and target thicknesses.
The cut foils were stacked into the target holder, which
was used as a Faraday cup.
An α-particle beam was accelerated to 51.1 MeV by
the RIKEN AVF cyclotron. The beam energy was obtained using the time-of-ﬂight method.5) The stacked
target was irradiated by the beam for 60 min with anaverage intensity of 257.6 nA. The beam intensity wasmeasured using the Faraday cup. Energy degradation in
the stacked target was calculated using the SRIM code.6)
The γ rays emitted from the irradiated foils were measured by a high-resolution high-purity germanium detector.
The γ-ray spectra were analyzed with the Gamma
†
∗1
∗2
∗3
∗4
∗5

Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 499, 46 (2021)
Faculty of Science, Hokkaido University
Nuclear Research Center, National University of Mongolia
RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido University
School of Science, Hokkaido University

Fig. 1. Excitation function of the nat Gd(α, x)159 Dy reaction
compared to TENDL-2019 data.4)

Studio (SEIKO EG&G) software.
The cross-sections of the nat Gd(α, x)159 Dy reaction
were determined using the γ-ray line at 58.0 keV (Iγ =2.27%) from the 159 Dy decay (T1/2 = 144.4 d). To reduce the γ-ray background from the short-lived radionuclides, the measurements were executed after coolingtimes of 25.4–28.8 d. The mass attenuation coeﬃcient
adopted for the γ-ray line at 58.0 keV was 12.8 cm2 /g.7)
The correction factor using Eq. (1) of Ref. 8) is 1.17. The
cross-sections of the 159 Dy production derived from thecorrected activities are presented with the TENDL-2019
data4) in Fig. 1. Our experimental data show peaks at
approximately 35 and above 50 MeV. The peak amplitudes and positions in the TENDL-2019 data agree with
our results. Reported experimental data were no foundin our literature survey.
155, 157
Dy,
Production
cross-sectionsof153, 155, 156g, 160, 161
153
Tb, andGd were also determined.
The results of this study are expected to contribute to
the research and development of nuclear medicine.
References
1) G. Subramanian et al., J. Nucl. Med. 12, 558 (1971).
2) D. V. Rao et al., Med. Phys. 4, 109 (1977).
3) C. Müller et al., J. Nucl. Med. 53, 1951 (2012).
4) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
5) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(2014), p. 3566.
6) J. F. Ziegler et al., SRIM: the Stopping and Range of Ionsin Matter, http://www.srim.org .
7) Photon Interaction Database, National Institute of Standards and Technology (2004), https://physics.nist.
gov/PhysRefData/XrayMassCoef/tab3.html .
8) Z. B. Alfassi et al., Appl. Radiat. Isot. 67, 240 (2009).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross-sections of holmium-161 radioisotope fromalpha-particle-induced reaction on terbium-159 up to 29 MeV
D. Ichinkhorloo,∗1,∗2,∗3 M. Aikawa,∗1,∗4,∗3 Ts. Zolbadral,∗4,∗2,∗3 Y. Hanada,∗4,∗3 G. Damdinsuren,∗4,∗3 and
H. Haba∗3
Terbium and holmium radioisotopes are of interest in medical applications.1,2) These radioisotopes
can be produced by charged-particle-induced reactions
on neighbor elements, such as gadolinium and terbium. Among such reactions, we focused on alphaparticle-induced reactions on the monoisotopic element
terbium-159 to produce the possible medical radioisotope, holmium-161. In a literature using the EXFOR library, only two relevant experimental studies
were found.3,4) Therefore, we performed an experiment
to measure the activation cross-sections of the reaction. In this work, the production cross-sections of160, 161
Tb and 160g, 160m, 161, 162m Ho were studied. The
results were compared with previous experimental data
and TENDL-2019 data based on calculations using the
TALYS code.5)
The experiment was performed the RIKEN AVF cyclotron. In the experiment, we used the stacked foil
technique, activation method, and high-resolution γ-ray
spectrometry to determine the activation cross-sections.
The stacked target consisted of 8 × 8 mm2 foils cut
from large 159 Tb (nominal thickness: 25 μm, size: 50
× 50 mm2 , 99.9% purity, Nilaco Corp., Japan), 27 Al(5 μm, 100 × 100 mm2 , 99.9% purity, Nilaco Corp.,
Japan), and nat Ti foils (5 μm, 50 × 100 mm2 , 99.6%
purity, Nilaco Corp., Japan).
The thickneses of Tb, Al and Ti foils were determined using the measured size and weight; they were
found to be 19.1, 1.50, and 2.29 mg/cm2 , respectively.
Ti foils were interleaved to check the beam parameters
using the nat Ti(α, x)51 Cr monitor reaction. The cut
foils were stacked in a target holder, which also served
as a Faraday cup.
The alpha-particle beam was accelerated to 29.1 MeV
by the RIKEN AVF cyclotron. The beam energy wasmeasured by the time-of-ﬂight method.6) The stacked
target was irradiated by the beam for 30 min with anaverage intensity of 201 nA. The beam intensity wasmeasured by the Faraday cup. Energy degradationin the stacked target was calculated using the SRIM
code.7)The γ-rays emitted from irradiated foils were measured by a high-resolution high-purity germanium(HPGe) detector. The detector eﬃciency was calibrated using a multiple γ-ray emitting point source.
The γ-ray spectra were analyzed by the software
∗1
∗2
∗3
∗4

Faculty of Science, Hokkaido University
Nuclear Research Center, National University of Mongolia
RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido University

Fig. 1. Excitation function of the 159 Tb(α, 2n)161 Ho reaction with previous experimental data3,4) and TENDL2019 values.5)

Gamma Studio software (SEIKO EG&G).
The cross-sections of the 159 Tb(α, 2n)161 Ho reaction were determined using measurements of the γline at 103.05 keV (Iγ = 3.9%) from 161 Ho decay(T1/2 = 2.48 h). To reduce γ-ray backgrounds fromshorter-lived radionuclides, measurements were executed after cooling for 3.7–8.5 h. The cross-sections of161
Ho production derived from the measured activities
are presented with previous experimental data3,4) andTENDL-2019 data5) in Fig. 1. Previous experimental
data demonstrated diﬀerent tendencies in comparison
to the present result. Our experimental data exhibited
peaks above 28 MeV. The peak position and amplitudeof TENDL-2019 data were also substantially diﬀerent.
In summary, we performed an experiment to measure
the excitation functions of alpha-particle-induced reactions on 159 Tb up to 29.1 MeV in the RIKEN AVF cyclotron. The production cross-sections of 160, 161 Tb and160g, 160m, 161, 162m
Ho were determined. Subsequently,
results were compared with previous experimental data
and TENDL data.
References
1) C. Müller et al., J. Nucl. Med. 53, 1951 (2012).
2) F. Tárkányi et al., J. Radioanal. Nucl. Chem. 298, 277(2013).
3) O. Bonesso et al., J. Radioanal. Nucl. Chem. Lett. 137,
29 (1989).
4) S. Mukherjee et al., Phys. Rev. C 55, 2556 (1997).
5) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
6) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC 2014), (2014), p 3566.
7) J. F. Ziegler et al., SRIM: the Stopping and Range ofIons in Matter, http://www.srim.org .

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4. Radiation Chemistry and Biology

III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Responsible gene analysis of phenotypic mutants revealed the linear
energy transfer (LET)-dependent mutation spectrum in rice†
R. Morita,∗1 H. Ichida,∗1 Y. Hayashi,∗1 K. Ishii,∗1 Y. Shirakawa,∗1 S. Usuda-Kogure,∗1 K. Ichinose,∗1
M. Hatashita,∗2 K. Takagi,∗2 K. Miura,∗3 M. Kusajima,∗3 H. Nakashita,∗3 T. Endo,∗4 Y. Tojo,∗5 Y. Okumoto,∗6
T. Sato,∗1,∗7 K. Toriyama,∗7 and T. Abe∗1
Linear energy transfer (LET), which refers to theamount of energy deposited per unit length of a particle’s path (keV/μm), is an important parameter forion beam mutagenesis. We previously demonstrated
that the C ion irradiation (30 keV/μm) of Arabidopsis results in single nucleotide variants (SNVs), small
indels (<100 bp), and translocations in the responsible genes for mutant phenotypes, with SNVs and small
indels representing more than 80% of the mutations.1)
Although the mutation frequencies induced by C ions(290 keV/μm) and Ar ions (290 keV/μm) are relatively
low, both irradiations frequently result in large deletions (100 bp) in the responsible genes for mutant
phenotypes.2) During an earlier whole-genome sequencing (WGS) analysis of Arabidopsis mutant lines conducted to compare the eﬀects of Ar and C ions, theAr ion (290 keV/μm) caused chromosomal rearrangements and large deletions more frequently than the Cions (30 keV/μm), whereas the C ions induced more
SNVs and small indels in the genomes.3) These results
indicated that the LETs of ion beams clearly aﬀected
DNA mutations in Arabidopsis. However, the eﬀects
of LETs of ion beams for mutation induction in plants
other than Arabidopsis are largely unknown.
In this study, we irradiated rice seeds (dry or imbibed seeds) with C, Ne, or Ar ions with various LETs.
The resulting mutant plants were isolated and the mutations in the responsible genes for the mutant phenotypes were examined using Sanger sequencing, wholeexome sequencing, or whole-genome sequencing to determine whether the mutation types diﬀered among the
LETs. We classiﬁed the mutations into the following four types: SNVs, small deletions (<100 bp), large
deletions (≥100 bp), and chromosomal rearrangements(CRs; inversions or translocations). We complied themutations according to the ion beam LETs and compared the tendencies of each irradiation. For the Cion (23, 30, 50, or 57 keV/μm) and Ne ion (63 or
70 keV/μm) irradiations, small deletions were the mostfrequent DNA mutations (Fig. 1). In contrast, the mostfrequent mutations induced by the Ar ion (290 keV/μm)
irradiation were large deletions. Thus, we compared the
proportions of the four types of mutations between the
†
∗1
∗2
∗3
∗4
∗5
∗6
∗7

Condensed from the article in Cytologia 86, 303 (2021)
RIKEN Nishina Center
The Wakasa Wan Energy Research Center
Fukui Prefectural University
Miyagi Prefectural Furukawa Agricultural Experiment Station
FUJICCO Co., Ltd.
Setsunan University
Tohoku University

Fig. 1. Mutations on responsible genes classiﬁed on the basisof the LET.

Ar ion and C ion irradiations, which revealed signiﬁcantdiﬀerences (p < 0.01; Fisher’s exact test). The diﬀerences were also signiﬁcant when we compared the proportions of the mutations between the Ar and Ne ion
irradiations (p < 0.01; Fisher’s exact test). However,the diﬀerences in the proportions of the mutations between the C and Ne ion irradiations were not signiﬁcant(p > 0.05; Fisher’s exact test). Our data indicated ion
beams with LETs of 23, 30, 50, 57, 63, and 70 keV/μm
tended to cause small deletions, whereas the Ar ion irradiation tended to induce large deletions. These observations were consistent with the results of our previous studies on Arabidopsis mutants irradiated with C
ions (23 or 30 keV/μm1) ) or Ar ions (290 keV/μm2,3) ).
Thus, C ions (23 or 30 keV/μm) tend to induce smalldeletions, whereas Ar ions (290 keV/μm) tend to induce
large deletions in the responsible genes for mutant phenotypes in rice and Arabidopsis. Therefore, we inferredthat in rice and Arabidopsis, C ion (23 or 30 keV/μm)
irradiations are suitable for eﬃciently inducing null mutants, whereas an Ar ion (290 keV/μm) irradiation issuitable for producing mutants with large deletions thatcan disrupt tandemly arrayed genes. Future investigations should clarify whether plant species other than riceand Arabidopsis exhibit similar tendencies regarding genetic mutations induced by ion beam irradiations. If
these tendencies are common among plant species, ion
beams with speciﬁc LETs may be used to induce particular mutation types, with important implications forresearch and plant breeding.
References
1) Y. Kazama et al., BMC Plant Biol. 11, 161 (2011).
2) T. Hirano et al., Mutat. Res. 735, 19 (2012).
3) Y. Kazama et al., Plant J. 92, 1020 (2017).

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RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Genetic characterization of large ﬂower mutant ohbana1 induced byheavy-ion beam irradiation in Arabidopsis thaliana †V. Q. Nhat,∗1 Y. Kazama,∗2,∗3 K. Ishii,3,∗4 S. Ohbu,∗3 H. Kunitake,∗1 T. Abe,∗3 and T. Hirano∗1,∗3
Flower size is an important trait that inﬂuences the
economic value of ornamental plants, and most cultivars have relatively larger ﬂoral organs than theircorresponding wild species. Thus, the genetic control of ﬂoral organ size is a principal target for ornamental plant breeding. The development of ﬂoral
organs is based on two distinct processes: cell proliferation and cell expansion, which increase the cellnumber and cell size, respectively. Positive and negative regulatory genes corresponding to each developmental process have been identiﬁed in Arabidopsis
thaliana. In this study, an Arabidopsis large ﬂower
mutant, ohbana1 (ohb1 ), was isolated from a mutant
library induced by heavy-ion beam irradiation.1–3) We
characterized the ﬂower phenotypes of ohb1 and revealed the gene responsible for the mutant phenotype
by the resequencing of the mutant genome to gain moreinsight on the regulatory network for ﬂoral organ size.
Flowers at stage 14, which had fully expanded petals
but had not been pollinated, were ﬁxed with a ﬁxative solution containing 86% ethanol and 14% acetic
acid. After ﬁxation, the ﬂowers were dissected using astereoscopic microscope, and abaxial epidermal cells inthe distal region of the petals were observed and photographed. The genomic DNA for whole-genome resequencing was isolated from the leaves of 40 M3 generation mutants. Library construction was performed according to the method reported by Hirano et al.4) The
obtained reads were input into the automated mutation analysis pipeline.5) The mutations in the mutant
induced by heavy-ion beam irradiation were selectedby removing pre-existent polymorphisms in the wild
type (WT) and false-positive mutations.
The sepal and petal sizes in the mutant were compared to those in the WT to evaluate the phenotypiccharacteristics of the ohb1 mutant; the ohb1 mutant
formed large petals and sepals. The petal area in theohb1 mutant was approximately 1.4 times larger thanthat in the WT (Fig. 1A). Furthermore, cell sizes in thepetal of the ohb1 mutant were also 1.4 times larger
than those of WT (Fig. 1B). We concluded that thelarge petal formation in ohb1 is mainly caused by cellsize increment because the increasing rates in whole
petals and its organizing cells are almost the same inohb1 petals.
†
∗1
∗2
∗3
∗4

Condensed from the article in Plants 10, 1881 (2021)
Faculty of Agriculture, University of Miyazaki
Faculty of Bioscience and Biotechnology, Fukui Prefectural
University
RIKEN Nishina Center
National Institutes for Quantum and Radiological Scienceand Technology- 166 -

Fig. 1. Flower phenotypes of the ohb1 mutant. Whole
ﬂower (A) and epidermal cells in the petal (B). Bars
= 1 mm (A) and 20 μm (B).

In the M3 generation, ﬁve homogenous mutationsin three loci, which had been predicted to aﬀect genefunction, were detected in the mutant genome. The results of the linkage analyses and complementation test
indicated that the mutated gene in AT4G04920 is responsible for the large ﬂower phenotype. The genein AT4G04920 encodes one mediator subunit, MEDIATOR (MED) 16, and it has been identiﬁed asa multifunctional regulator. MED16 restricted postmitotic cell expansion to control the ﬁnal ﬂower sizein Arabidopsis, and these results agree with a previous
study.6)
Interestingly, MED16 also contributed to seed-size
regulation. In double mutants crossed between ohb1
and the representative large ﬂower mutants, someof them formed larger and heavier seeds than eachparental single mutant. Therefore, size-regulation
pathways are believed to be partly diﬀerent between
ﬂoral organs and seeds. The ohb mutants derived fromheavy-ion irradiation are valuable genetic resources forinvestigating the size-regulation pathways, and they
can lead to further understanding of plant size control.
References
1) Y. Kazama et al., Plant Biotechnol. 25, 113 (2008).
2) Y. Kazama et al., BMC Plant Biol. 11, 161 (2011).
3) T. Hirano et al., Mutat. Res. 735, 19 (2012).
4) T. Hirano et al., Plant J. 82, 93 (2015).
5) K. Ishii et al., Genes Genet. Syst. 91, 229 (2016).
6) Z. Liu et al., Plant Cell 31, 1899 (2019).

1

III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Ar17+ beam-induced mutants of the mycorrhizal mushroom
Tricholoma matsutake defective in β-1,4 endoglucanase activity better
promote the Pinus densiﬂora seedling growth in vitro than thewild-type strain†
40

H. Murata,∗1 S. Nakano,∗1 T. Yamanaka,∗1 T. Shimokawa,∗1 T. Abe,∗2 H. Ichida,∗2 Y. Hayashi,∗2 and K. Tahara∗1
Unlike wood-decaying fungi, ectomycorrhizal fungi
have limited plant biomass degrading enzymes, which
are mostly hydrolytic enzymes.1) The model ectomycorrhizal fungus Laccaria bicolor requires its sole cellulolytic enzyme β-1,4 endoglucanase as an eﬀector forcell-wall remodeling during the ectomycorrhizal association with Populus tremula × P. alba.1) Unlike L. bicolor, Tricholoma matsutake, which is another ectomycorrhizal fungus that produces “matsutake” in association
with live pine trees, has many degrading enzymes suchas β-1,4 endoglucanase, β-glucosidase, α-gluculonidase,
xylanse and β-xylosidase.2) In the present study, we examined how T. matsutake mutants defective in β-1,4 endoglucanase activity behave in association with the natural symbiotic partner Pinus densiﬂora in vitro.
T. matsutake mutants Ar 5002 and Ar 5012
were generated by the argon-ion beam (40 Ar17+ ,160 MeV/nucleon) irradiation of T. matsutake NBRC
33136. Both mutants were defective in β-1,4 endoglucanase activity as per an agar plate assay that uses
potato dextrose agar containing 0.1% azurin-crosslinked(AZCL)-hydroxyethyl (HE)-cellulose (Fig. 1). T. matsutake has 11 potential cellulase genes, at least one ofwhich is predicted to encode β-1,4 endoglucanase; therest are classiﬁed in the same carbohydrate-active enzyme database (CAZy) family based on the JGI wholegenome information, which indicates a mutation could
have occurred in a regulatory region.
The wild-type strain NBRC 33136 signiﬁcantly promoted P. densiﬂora growth in vitro compared with theno inocula control (Fig. 2). Both T. matsutake mutants
Ar 5002 and Ar 5012 signiﬁcantly promoted P. densiﬂora growth compared to the growth achieved withthe wild-type. The former confers a signiﬁcantly higher
above-ground plant biomass, as well as total biomass,
than that with the wild-type strain, whereas the latter

Fig. 1. β-1,4 Endoglucanase (βEG) activities of T. matsutake.
†∗1∗2

Condensed from the article in Botany 99, 139 (2021)
Forest Research and Management Organization
RIKEN Nishina Center

Fig. 2. P. densiﬂora seedling growth after co-culturing with
T. matsutake strains for 140 d. Bars represent mean
±SEs. The same letters indicate treatments that should
be classiﬁed as same based on the results of Tukey-Kramer
tests.

Fig. 3. Cross-section micrographs of the root tissues ofP. densiﬂora seedlings associated with T. matsutake
strains. Abbreviations: co, cortical cell; ep, epidermal
cell; Hn, Hartig net; sh, mycelial sheath. Bars: 10 μM.

confers a signiﬁcantly higher above- and below-groundplant biomasses, as well as the total biomass, as shownin Fig. 2. No diﬀerences in the numbers of lateral roots
or mycorrhizal root tips were noted between the mutant
and the wild-type strains. No signiﬁcant diﬀerences inthe shoot/root (S/R) biomass ratios were noted between
the wild-type and mutant strains, as well. The Hartig
nets, a hallmark structure of ectomycorrhizal association, was observed among seedlings associated with thewild-type and mutant strains (Fig. 3).
The data suggest that T. matsutake without its own
β-1,4 endoglucanase activity exerts improved beneﬁcial
eﬀects on P. densiﬂora growth in vitro. However, further
clariﬁcation is required about whether the symbiotic relationship can be strengthened by such a mutated fungal
trait.
References
1) F. Zhang et al., New Phytol. 220, 1309 (2018).
2) T. Shimokawa et al., Mycoscience 58, 35 (2017).

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III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Highly eﬃcient and comprehensive identiﬁcation of ethyl
methanesulfonate-induced mutations in Nicotiana tabacum L. bywhole-genome and whole-exome sequencing†
H. Ichida,∗1 H. Udagawa,∗2 T. Takeuchi,∗2 T. Abe,∗1 and Y. Takakura∗2
Tobacco (Nicotiana tabacum L.) is one of the mostwidely cultivated non-food crops. It is a complex allotetraploid (2n = 4x = 48) species with a large genomeof 4.5 Gb, which possesses a high repetitive element
content.1) Tobacco carries a pair of duplicated genes(referred to as homeologs) from the S- and T-genomes,
and owing to this redundancy, loss-of-function mutations in any single homeolog are typically masked by
the correspondent, thereby limiting the use of forward
genetic phenotypic screens. Owing to its large genome
size, whole-genome sequencing is not readily applicable, as it requires a large amount of sequencing reads
and computational power and storage. Whole-exome
sequencing (WES) is an approach to primarily sequenceon genomic regions that encode proteins. Because theprotein-coding sequences only considers approximately
1.3% of the tobacco genome, this technique is particularly eﬀective in organisms with large genomes. In
the present study, we developed a set of whole-exon
capturing probes for tobacco and tested the set by analyzing 19 independent mutant lines produced by ethyl
methanesulfonate (EMS) mutagenesis.2,3) We also investigated the optimum conditions to detect mutations
in tobacco.
We employed 19 individual EMS-treated tobaccolines, designated NtEMS-01–19, and a technical replicate of NtEMS-19, called NtEMS-19-rep2, for the sequencing analyses. A commercial target enrichment
platform (SureSelect XT Custom kit, Agilent Technologies) was used to establish a whole-exon enrichment
method for tobacco. The custom-designed capturing kit
contained 517,835 oligonucleotide probes of 120 bases,
and it was expected to capture coding sequences with asize of 50.3 Mb spanning 41,038 genes that had at least
one coding sequence (CDS) deﬁned in the target genes.
After we produced the whole-exome capturing probes,
a new version of the K326 reference genome sequence,
Nitab-v4.5, which signiﬁcantly improves coverage andcontiguity, was published.4) Therefore, we translated
the target locations to the Nitab-v4.5 sequences andperformed all subsequent analysis based on the new reference genome sequence.
The number of read bases varied from 11.6 to 18.9 Gb
per sample, which corresponded to 165.3× to 270.8× of
the total CDS length and indicated that, as expected,
suﬃcient sequencing data were obtained. More than
98% of the reads were mapped to the reference se†∗1∗2

quences, resulting in an average read depth of 93.7×
in the CDS regions that commonly existed in the newand previous reference genome assemblies. An averageof 97.1% of the target CDS bases in the 19 NtEMS
lines were covered by at least 30 reads. Among all the
mapped read bases, approximately 75% were locatedon or were adjacent to the target regions, indicatingthat the whole-exome capturing was successfully accomplished here. In the variant calling, we used two
diﬀerent programs, GATK and BcfTools. Each program detected 60,884 and 50,260 mutations and resulted in a total of 61,146 non-redundant mutations.
Almost all (98.8%) of the detected mutations in the
19 NtEMS lines were single-nucleotide variations, while
95.6% of them were C/G to T/A transitions, which isconsistent with the known properties of EMS mutagenesis.The numbers of detected mutations varied from 1987
to 4966 in the 19 NtEMS lines. The average numbersof detected mutations in each line were 2715.7 (1987–3857) and 3511.3 (2415–4966) in 0.6% and 0.8% EMS
treatments, respectively. The mutation density waslargely proportional to the target CDS density in the
genome, indicating that the EMS-induced mutations
were suﬃciently random, at least practically, despitebase preferences resulting from the chemical nature of
EMS mutagenesis. A computational experiment using
down-sampled sequencing reads demonstrated that approximately 80% of the mutations located in the target
regions could be detected with 60× sequencing reads.
At 160× of the total CDS length equivalent, a total of 20,960 out of the 35,667 genes located within thetargets harbored at least one mutation in the CDS regions of the 19 NtEMS lines deﬁned by WES. This indicates that an average of 1103 genes could be expected
to have mutated within their CDS regions in the mutagenized NtEMS population that was partly analyzed in
the present study. Based on the probability formula,5)
one can expect at least one mutation from 95 lines (at95% conﬁdence level) in the NtEMS library, for all of
the 35,667 genes in the target regions.
References
1) N. Sierro et al., Nat. Commun. 5, 3833 (2014).
2) T. Tajima et al., Ann. Phytopathol. Soc. Jpn. 77, 258(2011).
3) Y. Takakura et al., Mol. Plant Pathol. 19, 2124 (2018).
4) K. D. Edwards et al., BMC Genom. 18, 448 (2017).
5) L. Clarke, J. Carbon, Cell 9, 91 (1976).

Condensed from the article in Front. Plant Sci. 12, 671598(2021)RIKEN Nishina Center
Leaf Tobacco Research Center, Japan Tobacco Inc.

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III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Method of chromosome observation in the dioecious plant
Silene latifolia †T. Kobayashi,∗1 M. Takahashi,∗2 R. Nishijima,∗1 R. Sugiyama,∗3 K. Ishii,∗4 T. Abe,∗4 S. Kawano,∗2,∗5 and
Y. Kazama∗1,∗4
Silene latifolia is a dioecious plants, which is considered to be evolved from monoecious plants to develop
heteromorphic sex chromosomes.1) The sizes of X andY chromosomes are approximately 400 Mb and 570 Mb,
respectively, such that they can be observed under a microscope. The architecture of these sex chromosomes
has been investigated by using cytological techniques,e.g. ﬂuorescence in situ hybridization analysis.2)
We previously irradiated heavy-ion beams to seeds
and pollens of S. latifolia and obtained hermaphroditic
and asexual mutants, which possessed deletions on the
Y chromosome.3) Subsequently, a Y-chromosome map
was constructed by conducting PCR-based deletion mapping. To further investigate the size of the deletions after
the heavy-ion irradiation and conﬁrm the accuracy of thedeletion map, observation of chromosomes in S. latifolia
is required. However, an eﬃcient method for the chromosome specimen preparation has not been fully developed
so far.
In many plants, root tip portions are typically used
for preparing chromosome specimens because they arehighly enriched in rapidly cycling cells with a steadystate of growth. Synchronization of cell cycle is typically achieved by using DNA synthesis inhibitors. In Silene latifolia, these methods were applied to prepare thechromosome specimens. However, the timing for chromosome preparation after initiating root tip growth was
not to be optimized. We hypothesized that the cell cycle was roughly synchronized during the ﬁrst few days
after rooting. Therefore, we investigated an appropriate
incubation period after germination, during which theroots possessed many metaphase chromosomes. Moreover, we investigated variations of telocentric chromosomes by changing the duration of the ice-cold treatment(8, 16, and 32 h).
Every six hours after the germination, root lengths ofthegerminating seeds were measured. The percentageof roots with a length of 2 mm that were amenable toenzyme treatment reached a maximum after 60 h of incubation starting (HAIS) at 23◦ C. The rough observationof metaphase cells in root tips from 48 to 60 HAIS by the
Feulgen method4) showed a high frequency of metaphasecells during 51 to 56 HAIS. Therefore, root tip samples
collected every hour from 51 to 56 HAIS were closely ex†
∗1
∗2
∗3
∗4
∗5

Condensed from the article in Cytologia 86, 323 (2021)
Department of Bioscience and Biotechnology, Fukui Prefectural University
Department of Integrated Biosciences, Graduate School of
Frontier Sciences, University of Tokyo
Botanical Garden, Faculty of Agriculture, Tokyo University ofAgriculture
RIKEN Nishina Center
Future Center Initiative, University of Tokyo

Fig. 1. Number of metaphase cells 51–56 hours after germination. Bars represent standard deviations.

Fig. 2. Photograph of metaphase chromosomes in a female
plant (Bar = 5 μm).

amined. The number of metaphase cells in the root tips
reached a peak at 54 HAIS (Fig. 1).
DNA synthesis inhibition for metaphase chromosome
preparation is typically achieved by using aphidicolin.
The aphidicolin treatment was initiated 24 h before 51–
56 HAIS and was terminated 9 h before 51–56 HAIS.
Consequently, a peak in the number of metaphase cells
was observed at 54 HAIS. The mean value of themetaphase cells at 54 HAIS with aphidicolin was fourteen times higher than that at 56 HAIS without aphidicolin (Wilcoxon rank sun test, p < 0.01). This result
indicates that DNA synthesis inhibition at the appropriate time helps increase the number of metaphase cells,
which facilitates an eﬀective chromosome observation.
With this sample, S. latifolia chromosomes were easily
observed using confocal microscopy (Fig. 2). These techniques can be applied to observe the chromosomes ofheavy-ion induced partial Y-deletion mutants.
References
1) S. Matsunaga, S. Kawano, Plant Biol. 3, 481 (2001).
2) Y. Kazama et al., Genome 49, 520 (2006).
3) Y. Kazama et al., Sci. Rep. 6, 18917 (2016).
4) R. Feulgen et al., Physiol. Chem. 135, 203 (1924).

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III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Producing high brix content of the sweet potato Anno-Beni bymutation induced using ion-beam irradiation
T. Hashiguchi,∗1 K. Yamane,∗1 J. Nagai,∗1 K. Fujikawa,∗1 K. Ishii,∗2 Y. Hayashi,∗2 and T. Abe∗2
Ion-beam irradiation eﬀectively induces plant mutations and is used for plant breeding.1) The sweet potato
cultivar Anno-Beni, which has a high sugar content,
is an important and exquisite product in the Tanegashima island area. There has been a high demandfor Anno-Beni with a high brix content that remains
stable. The dry-matter contents and brix contents inthe sweet potato are correlated.2) Therefore, by inducing mutations through ion-beam irradiation, lines withhigher dry-matter contents and higher brix contents
can be selected. In a previous report, we described 31lines selected from the population of the Anno-Beni
B1 line irradiated with a C-ion-beam.3) This report
describes the results of the continued selection.
In 2017, ﬁve lines with better growth and higher drymatter contents than those of the control were selectedfrom 31 lines.
In 2018, the ﬁve selected lines were cultured at theshoot apex to produce 20 lines. The 20 lines weregrown by vegetative propagation, and ﬁve individual
plants per line were cultivated in the ﬁeld. We selectedfour lines that grew better and had higher dry-matter
contents and higher brix contents (0.8–3.2 and 2.0–2.9,
respectively) than the control (Table 1).
In 2019, the four lines were grown by vegetative
propagation, and 30 individual plants per line were
cultivated in the ﬁeld. The four lines that grew better and had higher dry-matter contents and brix contents (2.4–4.1 and 1.1–2.4, respectively) than the control (Table 1).
The four lines had 22–35% lower yield contents
than the control. The shapes of the tuberous roots
were spindle to cylindrical for the control and No.36-2,
whereas it was long-spindle to cylindrical for No.19-1,
No.19-4, and No.20-2 (Fig. 1).

Table 1. Dry-matter and brix contents of four mutant linesof sweet potato.

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∗21) Control (upper), No.19-1(lower left end), No.19-4 (lower left
center), No.20-2 (lower right center), No.36-2 (lower right end).
2) Harvested on September 17, 2019 (planting period:132 days).

Table 2. Evaluation results of four mutant lines of sweet
potato.
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The four lines were examined for taste survey after
three days and after one month of storage (Table 2).
The sweetness of the four lines was higher than that of
the control after one month. The ﬂesh color of No.19-1,
No.20-2, and No.36-2 was lighter than that of the control after one month. The aroma of the four lines after
storage for one month were almost equal to that of thecontrol. The stickiness of No.19-1, No.19-4, and No.362 were equal to that of the control after storage for one
month. The sweetness, ﬂesh color, aroma, and stickiness tended to increase after storage for one month.
By selecting the dry matter rate from ion-beam irradiated postgrowth, we were able to select lines with highbrix contents and a sweet taste.
References  7KH WXEHURXV URRWV RI WKH IRXU OLQHV ZHUH VWHDPHG DQG GLOXWHG ZLWK∗1Fig. 1. Tuberous roots of the four lines and control.

Kagoshima Prefectural Institute for Agricultural Development (KIAD)
RIKEN Nishina Center- 170 -

1) T. Abe et al., Breed. Res. 16, 67 (2014).
2) M. Ouchida, K. Ueno, Rep. Kyushu Br. Crop Sci. Soc.
Jpn. 80, 22 (2014).
3) T. Hashiguchi et al., RIKEN Accel. Prog. Rep. 53, 207(2019).

1

III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Isolation method of marine red alga Agardhiella subulate
K. Tsuneizumi,∗1 M. Yamada,∗1 M. Mogamiya,∗2 Y. Sato,∗2 and T. Abe∗1
Agardhiella subulate, a red macroalga, is commonly
known as seaweed and it is consumed as aquatic food.
This sea vegetable is attracting increasing attention as an
emerging source of bioactive natural products.1) Breeding new cultivars with properties such as high yield,
high environmental adaptability, or high concentrationsof constituents with human health beneﬁts is desirable
to enhance its value. In this study, we attempted to establish mutagenesis in A. subulate using an argon (Ar)ion beam as mutagen to meet future demands. First, weobserved the growing point of the red algae.
The A. subulate were cultured with NORI SEED (Daiichi Seimo Co., Ltd.), a highly enriched culture solution.
A culture medium was prepared using 80 μL of NORISEED diluted with 300 mL of autoclaved sea water.
Microplantlets were cultivated for a month in a stirred
300 mL marine ﬂask with the culture medium. The ﬂask
was placed at 25◦ C under a 12 h photoperiod, with lightintensity of 50 μmol photons · m−2 s−1 and the culture
medium in the ﬂask was replaced every week. Each microplantlet was inoculated into a well of a 12-well platecontaining 2 mL of fresh culture medium.
For a morphometrical evaluation, we took photographs of growing tips of the algal thalli every day.
From the comparison of the branching patterns in each
image, the curved structure was observed in the same
position (Fig. 1c, arrow head), whereas a diﬀerence wasfound in the newly elongated tissue (Fig. 1c, white bar).
This result indicates that cell division and cell elongation
occurred in this region and there were growing points inthe tips of the algal thallus.
To develop an isolation method for the mutant line, weapplied a heavy-ion-beam irradiation system to A. subulate. The microplantlets were replaced into 15 mL conical tubes with fresh 2 mL of culture medium at each irra-

Fig. 1. Photographs of growing front edges of algal thalli.
(a) Control branching pattern of red alga. (b) Binarized
image of (a). (c) Merged data. The arrow head represents
the bended structure of thalli. The white bar represents
the diﬀerence in the length. (d) Binarized image of (e).
(e) One day after branching pattern of red alga. Scalebars represent 2.5 mm.
∗1∗2

RIKEN Nishina Center
Riken Food Co., Ltd.

Fig. 2. Mutant isolation method and isolated mutant alga.
(a) Diagram of the mutant isolation method. (b) A wholebody ﬁgure of the control alga. (c) A whole-body ﬁgureof the mutant alga.

diation condition. The tubes containing microplantlets
were placed in the automatic sample irradiation apparatus2) and each of them was irradiated with a heavy-ion
beam. Heavy-ion-beam irradiation was performed using
Ar (LET = 188 keV/μm) at 6 irradiation doses of 1, 2,
4, 8, 16, and 32 Gy generated via RIKEN RI Beam Factory.3) Four hours after irradiation, each microplantlet
was inoculated into a well of the 12-well plate containing
2 mL of fresh culture medium for each irradiation condition. The plates were placed at 25◦ C under a 12 h photoperiod with light intensity of 50 μmol photons · m−2 s−1
and the culture medium in the dishes was replaced every week. After monthly culture, the morphological mutants were selected with microscopic observation. The
most front edge of the algal thallus was cut oﬀ with
5 mm length and replaced into a well of a 6-well platecontaining 5 mL of fresh culture medium. Mutant lines
were established by repeating these processes four times(Fig. 2a). According to the comparison between control
and mutant lines, signiﬁcant diﬀerences were observedin shape and growth ratio (Figs. 2b and 2c). These phenotypes were stably observed at each isolation process.
These results suggest that the possibility of chimericalness in the apical meristem has been excluded. Thismethod will be useful in the future to screen valuablemutants with human beneﬁts.
References
1) M. Witvrouw et al., Antivir. Chem. Chemother. 5, 297(1994).
2) H. Ryuto et al., J. Biomed. Nanotechnol. 2, 88 (2006).
3) T. Abe et al., in Plant Mutation Breeding and Biotechnology, edited by Q. Y. Shu et al. (CABI, Oxfordshire, 2012),
p. 99.

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III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Survival rate of yeast cells in diﬀerent storage media
Y. Nishimiya∗1 and H. Ichida∗1
Yeast fermentation has played a vital role in foodproduction throughout the millennia of human history.
Notable examples of its applications include alcoholic
beverages, such as wine and beer, as well as breads
found globally.1) Besides its extensive industrial applications, yeast is an extensively used model organism
in studies on ageing,2) population genetics and othertopics.3) It is a highly common target organism in irradiation experiments and ensuing mutation breedingat the Beam Mutagenesis Group. It typically takes
3–5 days from the preparation of the target samples
for irradiation until they arrive at the partner institution for post-experiment examination. During thistime, including that for irradiation itself, yeast cells are
suspended in a liquid medium, for which phosphatebuﬀered saline (PBS) is commonly used. However, its
eﬀect on cell viability, including the possibility of using alternative media, has not been fully elucidated.
Therefore, we tested the survival of yeast cells in three
diﬀerent storage media over time, simulating the timeframe of common irradiation experiments.
A wild-type bakers’ yeast, Saccharomyces cerevisiae
BY4743, was chosen as the model. Three storage media including ultrapure water (Milli-Q water), PBS(8.1 mM disodium hydrogen phosphate, 1.47 mM
potassium dihydrogen phosphate, 2.68 mM potassium
chloride, 137 mM sodium chloride) and 10 mM magnesium sulfate (MgSO4 ) were tested.
First, a well-isolated colony was inoculated into atest tube ﬁlled with 5 mL YPD broth (10 g yeast extract, 20 g meat peptone and 20 g D-glucose, per litre).
A portion of this pre-culture was transferred to 20 mL
YPD in a 125-mL baﬄed ﬂask. The culture was incubated at 30◦ C, shaking at a rate of 225 rpm.
Second, S. cerevisiae cells were harvested by centrifugation of 12 mL of the above culture and washedthrice with one of the three tested storage media. The
cell concentration was adjusted to OD600 ≈ 1.0 (equivalent to ≈ 107 cells/mL) to replicate a typical irradiation target. After a given time at 4◦ C, 100 μL of thesolution was diluted with 10 mM MgSO4 and 30 μL of
the diluted solution was spread on ﬁve YPD plates.
Finally, after approximately two days of incubation
at 30◦ C, we recorded the number of colonies in eachplate. The survival rate was calculated based on themean colony count of three plates, eliminating the twoplates with maximum and minimum colony counts, respectively.
We repeated the above experiment thrice. The mostrepresentative result from the three trials is shown
here.
∗1

Fig. 1. Survival rate of BY4743 expressed relative to Day
0 control value set as 100%.

Figure 1 shows the survival rate of S. cerevisiae overten days, in which the dotted lines represent the exponential regression models applied to the data of thethree tested storage media.
For all of them, the coeﬃcients of determination, R2 ,between the days elapsed and the survival rate, aregreater than 0.7. Storage in PBS and water resulted
in similar trends wherein approximately 40% cells die
after only two days. In contrast, 10 mM MgSO4 allows
for a relatively higher rate at which approximately ahalf of the viable cells survives for six days.
The above results show that the viability of the yeast
cells signiﬁcantly diﬀers between the tested storage media. Despite the prominent use of PBS as a storage
medium, our results indicate that the survival rate of
the yeast cells therein is similar to that in water andhence, PBS is a non-ideal medium for long-term storage. In contrast, based on the higher survival rate,
10 mM MgSO4 is more recommendable for its use asa yeast storage medium.
References
1) S. Maicas, Microorganisms 8, 1142 (2020).
2) A. D. Lippuner, T. Julou, Y. Barral, FEMS Microbiol.
Rev. 38, 300 (2014).
3) C. Zeyl, Yeast 16, 773 (2000).

RIKEN Nishina Center- 172 -

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III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Eﬀect of irradiation ions and doses on the survival rate of yeast
N. Lei,∗1 T. Abe,∗1 and H. Ichida∗1
Yeast has been playing an important role in many human activities, such as winemaking, baking, and brewing
for a long period.1) The budding yeast, Saccharomyces
cerevisiae, has been considered as the most fundamental eukaryotic model organism. Its small genome size(around 12 Mb), fast growth character, and DNA repair system that is similar to that of plants and animals
make it a useful model for gene function and mutation
analyses.2,3)
Heavy ion beams cause mutations in the genome, suchas deletions, insertions, and base substitutions. Therefore, it has been used as a physical mutagen and to develop new cultivars in the last two decades. Carbon ionshave been used frequently because of the high mutation
rates and long penetration range, and heavier ions, suchas argon and iron, are more suitable for microbial mutagenesis, as they induce larger deletions and insertions,and are more stable than base substitutions.4)
In the present study, we investigated the dose-survival
relationship of a diploid baker’s yeast strain Hi1060(MATa/α his3 Δ1 leu2 Δ0 ura3 Δ0 ). It is geneticallyequivalent to BY4743 and is established by a cross between BY4741 and BY4742; It is more than three times
the size of single-colony isolations on a selective medium.
The strain and its parents are all derivatives of thewidely used and genome-sequenced laboratory strain
S288C. This strain is fully functional for DNA repair
by homologous recombination and non-homologous endjoining.
For heavy-ion beam irradiations, Hi1060 was grownin a liquid YPD medium, harvested by centrifugation at
3000 × g, and washed three times with 10 mM MgSO4 .
The cell concentration was adjusted to 1 OD600 unit per
mL, which is equivalent ∼107 cells per mL, with 10 mM
MgSO4 , and was kept at 4◦ C before and after irradiation. We irradiated 12 C6+ (135 MeV/nucleon, LET:
23 keV/μm; 0–1000 Gy), 40 Ar18+ (160 MeV/nucleon,
189 keV/μm; 0–800 Gy), and 56 Fe24+ (90 MeV/nucleon,
647 keV/μm; 0–800 Gy). After irradiation, the cells
were diluted to diﬀerent concentrations and spread on
YPD plates, and the survival rates were calculated asfollows:
Survival rate (%) = num. of the colonies in eachdose/non-irradiated control × 100
The determined survival rates and their ﬁtting resultsby exponential functions are shown in Fig. 1. The results showed that carbon-, argon- and iron-ion irradiations all decreased the survived cell ratio in a dosedependent manner. The survival curves were well represented by exponential functions with determination coeﬃcients (R2 ) of 0.9793, 0.7691, and 0.9509 in carbon,
argon, and iron ions, respectively. Ar showed unexpectedly higher and lower survival rates compared with the∗1

Fig. 1. Dose-survival responses of S. cerevisiae Hi1060(equivalent to BY4743) cells after irradiation by carbon,
argon, and iron ions with diﬀerent doses. The error bars
represent standard deviation in technical replicates.

other two ions. We are interested in further investigating
Ar irradiations soon.
The lethal eﬀects were more obvious in heavier argon
and iron ions than the lighter carbon ions. This is consistent with the previous observations that the relative
biological eﬀect of a radiation is higher in heavier ionsthan the lighter ones. This may reﬂect that heavier ions,which have higher LETs, induce more deleterious typesof mutations to the genome. The doses for 10% survival(D10 ) were 600 Gy for carbon- and 400 Gy for argonand iron-ions, respectively. These D10 values were in acomparable range to a previous yeast breeding project,
where 400 Gy irradiations with carbon and iron ionswere used to select high aromatic compound-producing
sake yeasts.5) Currently, we have been preparing to perform whole-genome sequencing of these irradiated yeast
cells. This will quantitatively describe the mutagenic
eﬀect of diﬀerent ions on yeast genomes. At the sametime, it would help to understand the relationship between irradiation conditions, survival rate, and the resulting genomic mutations in a base-pair resolution in agenome-wide manner.
References
1) R. K. Mortimer, Genome Res. 10, 403 (2000).
2) M. J. Harsch et al., FEMS Yeast Res. 10, 72 (2009).
3) H. Mewes et al., Nature 387, 7 (1997).
4) H. Ichida et al., Mutat. Res. 639, 101 (2008).
5) M. Yokobori et al., RIKEN Accel. Prog. Rep. 45, xxiii(2011).

RIKEN Nishina Center- 173 -

1

III-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Recruitment of Rad51 onto chromatin is suppressed by high doseheavy-ion irradiation in mammalian cells
M. Izumi∗1 and T. Abe∗1∗1

RIKEN Nishina Center$*\
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Among the DNA damages caused by an ionizing radiation, DNA double strand breaks (DSBs) are themost lethal because accumulation of misrepaired or unrepaired DSBs can lead to a loss of genetic informationand cell death. Mammalian cells have four pathways
to repair DSBs: canonical non-homologous end joining(NHEJ), homologous recombination (HR), alternative
NHEJ (alt-NHEJ), and single-strand annealing (SSA).
Recently, DNA repair pathways are considered as targets for cancer therapy, because their inhibitors increase
the eﬃcacy of radiotherapy. It is also important toknow whether error-prone pathways such as SSA and
alt-NHEJ are involved in DSB repair, to estimate therisk of secondary carcinogenesis in radiotherapy.
After exposure to low-linear energy transfer (LET)
radiation such as X-ray, NHEJ is the dominant repair
pathway throughout the cell cycle in mammalian cells,
whereas HR can only repair DSBs in the late S/G2
phase. Additionally, alt-NHEJ or SSA is eﬀective whenboth NHEJ and HR are impaired, and it contributes togenome rearrangements and oncogenic transformations.
Previous studies have suggested that the end-resection of
DSBs is stimulated after heavy-ion irradiation throughout the cell cycle,1,2) which can promote HR, SSA, or
alt-NHEJ. However, the repair mechanism after heavyion irradiation has not been fully understood.
Our previous study using mammalian cells and speciﬁc inhibitors against NHEJ or HR suggested that
NHEJ is the major repair pathway after 2 Gy heavyion irradiation.3) We also showed that HR is favored after heavy-ion irradiation in the G2-phase; however, theDSB repair by HR is less eﬃciently than that after X-ray
irradiation.4)
Recent studies revealed that the number of DSBs is anadditional key parameter of pathway selection because
several repair proteins limit HR at high doses in mammalian cells.5,6) In this study, we examined the amountof Rad51 on chromatin after irradiation, to investigate
the eﬀect of irradiation dose on the repair pathway selection. Rad51 is an essential core component of HR
and recruited around DSBs after irradiation. Exponentially growing HeLa cells were irradiated with argon ions
(LET = 300 keV/μm) of diﬀerent doses (0.5–15 Gy), andchromatin fractions were obtained and subjected to immunoblot analysis (Fig. 1(A)). The amount of Rad51 in
the chromatin fraction increased up to 5 Gy in a dosedependent manner (Fig. 1(B)). However, the amount of
Rad51 decreased following 15 Gy irradiation. We performed the same experiment using a carbon-ion beam
(LET = 80 keV/μm), which yielded similar results (datanot shown). These results suggest that HR is suppressed

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Fig. 1. Immunoblot analysis of chromatin-bound Rad51 after heavy-ion irradiation. (A) HeLa cells were irradiatedwith indicated doses of Ar ions, and 0.1% Triton-insoluble
fractions (chromatin franctions) were prepared at indicated time points and subjected to immunoblot analysis.
Phosphorylated histone H2AX (γH2AX) and lamin B1
were detected as an indicator of DSB and a loading control, respectively. (B) The relative intensity of Rad51
band was measured using luminoimage analyzer and normalized against the amount of lamin B1.

after high dose irradiation (∼15 Gy) of high-LET radiations (80–300 keV/μm). In contrast, the amountof chromatin-bound Rad51 increased up to 15 Gy anddecreased at 30 Gy after X-ray irradiation (data notshown).
We previously reported that trichostatin A (TSA), a
histone deacetylase inhibitor, enhanced radiosensitivity
at low doses, whereas TSA suppressed it at high dosesof heavy-ion irradiation by an unknown mechanism.7)
This ﬁnding also suggests that DNA damage response
induced by heavy-ion irradiation depends on the dose.
Currently, we are investigating the localization of several
repair proteins involved in NHEJ and SSA after irradiation of diﬀerent doses.
References
1) H. Yajima et al., DNA Repair 12, 936 (2013).
2) N. B. Averbeck et al., Cell Cycle 13, 2509 (2014).
3) M. Izumi, T. Abe, RIKEN Accel. Prog. Rep. 53, 24(2020).
4) M. Izumi, T. Abe, RIKEN Accel. Prog. Rep. 54, 33(2021).
5) F. Ochs et al., Nat. Str. Mol. Biol. 23, 714 (2016).
6) E. Mladenov et al., Nucl. Acid. Res. 48, 1905 (2020).
7) M. Izumi, T. Abe, RIKEN Accel. Prog. Rep. 48, 301(2015).

- 174 -

1

IV. OPERATION RECORDS

IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Program advisory committee meetings
for nuclear physics and for materials and life experiments
K. Yoneda,∗1 K. Ishida,∗1 H. Yamazaki,∗1 N. Imai,∗2 Y. X. Watanabe,∗3 K. Yako,∗2
Y. Hirayama,∗3 and H. Ueno∗1
The Program Advisory Committees (PAC) are in
charge of reviewing the scientiﬁc proposals submitted
for the use of the accelerator facility in the RIKEN
Nishina Center (RNC). Two PAC meetings were heldin ﬁscal year 2021; one for proposals in the ﬁeld of
nuclear physics (NP-PAC), and one for proposals in
the ﬁeld of materials and life sciences (ML-PAC).
NP-PACThe 22nd NP-PAC meeting was held from December 1 to December 3, 2021,1) with the attendance of 16
PAC members. As oversea travels were diﬃcult due to
COVID-19, the meeting was held online via Zoom. Before this NP-PAC meeting, seven PAC members were
replaced. The new members are: S. Grevy (CENBG),
M. Dasgupta (The Australian National University),
J. Dilling (Oak Ridge National Laboratory), M. Gorska(GSI), T. Kawabata (Osaka University), M. Matsuo(Niigata University), R. Zegers (Michigan State University). M. J. G. Borge from CSIC, Madrid, had
newly taken on the role of chairperson of the meeting.
31 proposals were reviewed, and 1 proposal and 13 proposals were approved as grade S and A, respectively.
The outcome of the NP-PAC meeting is summarizedin Table 1.
Table 1. Summary of the outcome of the 22nd NP-PAC
meeting. The proposals ranked as S and A are treatedas “approved” proposals.
22nd NP-PAC (December 1–3, 2021)
requested
approved
proposals (days)
proposals (days)
GARIS
3 (39)
1 (25)
CRIB (AVF)
2 (19)
0 (0)
RRC
1 (8)
1 (8)
KISS
1 (5)
1 (5)
BigRIPS/ZD
12 (97.5)
7 (55.5, inc. 11 of “S”)
SHARAQ/OEDO
1 (9.5)1 (2)Rare RI Ring
2 (36)0 (0)SAMURAI
10 (92)3 (22.5)
LOI
1 (-)
- (-)
Total
31 (306)
14 (93)Darmstadt/GSI), I. Moore (University of Jyvaskyla),
T. Saito (RIKEN), P. J. Woods (University of Edingurgh), A. Vitturi (University of Padova), X. Zhou
(Chinese Academy of Science), J. Dilling (Oak Ridge
National Laboratory), M. Dasgupta (The Australian
National University), M. Gorska (GSI), S. Grevy(CENBG), T. Kawabata (Osaka University), M. Matsuo (Niigata University), R. Zegers (Michigan State
University).
ML-PAC The 21st ML-PAC meeting was held via
email review, from December 9, 2021 to January 4,
2022.2) At that time there was no call for proposals
for RIKEN-RAL due to the planned long shutdown of
ISIS. Three proposals for the RIBF facility were reviewed, and two proposals were approved as grade A.
The outcome of this meeting is summarized in Table 2.
Table 2. Summary of the outcome of the 21st ML-PAC
meetings. The RIBF proposals ranked as A are treatedas “approved” proposals.
21st ML-PAC (December 2021–January 2022)
requested
approved
proposals (days)
proposals (days)
RAL
no callRIBF
3 (10)2 (7)The members of the 21st ML-PAC are as follows:
A. Hillier (ISIS, RAL, the chair), Y. Kobayashi (The
University of Electro-Communications), Y. Miyazawa(Yamagata University), T. Takayanagi (Saitama University), and Z. Qin (Chinese Academy of Sciences).

References
1) https://www.nishina.riken.jp/RIBF/NP-PAC/index.
html .
2) https://www.nishina.riken.jp/RIBF/ML-PAC/index.
html .

The members of 22nd NP-PAC are as follows:
M. J. G. Borge (CSIC, Madrid, the chair), N. Aoi(RCNP, Osaka University), R. Charity (Washington
University in St. Louis), G. Martinez-Pinedo (TU
∗1
∗2
∗3

RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo
Wako Nulcear Science Center, Institute of Particle and Nuclear Studies, KEK- 175 -

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IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Electric power consumption of RIKEN Nishina Center in 2021
M. Kidera,∗1 T. Maie,∗1 S. Watanabe,∗1 E. Ikezawa,∗1 and O. Kamigaito∗1
An electricity consumption of RIKEN Nishina Center (RNC) for each month in 2021 compared to 2019and 2020 is shown in Fig. 1. The reason for the large
increase in power consumption from April to June compared to last year is mainly due to a fact that no
RI Beam Factory (RIBF) experiments were conductedlast year due to the pandemic and failure of the RRC
cavities.

In 2021, a total annual power consumption of the
RNC was 63,746 MWh, an increase of 13% compared
to 2020. The increase in the total annual power consumption is mainly due to the RIBF experiment in
the previous period, as mentioned earlier. The total
power of the RNC reached a maximum of 17.5 MW
on November 18 when the RIBF experiment with auranium (238 U) beam was being tuned.

12000
2019

2020

Sep

Oct

2021

10000

>kWh@

8000

6000

4000

2000

0
Jan
Fig. 1.

∗1

Feb

Mar

Apr

May

Jun

Jul

Aug

Nov

Dec

Electricity consumption of RNC for each month in 2021 compared to 2019 and 2020.

RIKEN Nishina Center- 176 -

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IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Operation report on ring cyclotrons in the RIBF accelerator complex
T. Nakamura,∗1 K. Ozeki,∗2 T. Dantsuka,∗2 M. Fujimaki,∗2 T. Fujinawa,∗2 N. Fukunishi,∗2 S. Fukuzawa,∗1
M. Hamanaka,∗1 H. Hasebe,∗2 Y. Higurashi,∗2 E. Ikezawa,∗2 H. Imao,∗2 S. Ishikawa,∗1 O. Kamigaito,∗2
Y. Kanai,∗2 M. Kidera,∗2 K. Kobayashi,∗1 M. Komiyama,∗2 R. Koyama,∗1 K. Kumagai,∗2 T. Maie,∗2
T. Nagatomo,∗2 T. Nakagawa,∗2 M. Nakamura,∗2 M. Nishida,∗1 M. Nishimura,∗1 J. Ohnishi,∗2 H. Okuno,∗2
N. Sakamoto,∗2 J. Shibata,∗1 K. Suda,∗2 N. Tsukiori,∗1 A. Uchiyama,∗2 S. Watanabe,∗2 T. Watanabe,∗2
Y. Watanabe,∗2 K. Yadomi,∗1 K. Yamada,∗2 and H. Yamasawa∗2This paper presents an operation report on the ring
cyclotrons in the RIBF accelerator complex from January to December 2021. Table 1 presents a summaryof the beams accelerated by these cyclotrons. Availability can be deﬁned as the ratio of the actual beamservice time to the scheduled beam service time, which
is an index of stable operation of accelerators. Whencalculating each availability for the beam service times
completed earlier than scheduled, the scheduled times
were identiﬁed with the actual times. Further, multiple experiments performed with identical beams weretreated as one and presented in a row. The total actual
beam service time was 2198.3 h. The ratio of beam service time between the experiments conducted in the old(RARF) and new (RIBF) facilities was 32 : 68.
In the RARF, the actual beam service time was702.5 h, with an availability of 113.8%.
In the RIBF, ﬁve beam services were conducted; theactual beam service time was 1495.8 h with an availability of 98.3%. Accelerations in the light-ion mode
were conducted using the AVF as an injector for theﬁrst time in three years. Three types of beams of 2 H,
4He, and 12 C were supplied. A 4 He beam with an energy
of 200 MeV/nucleon was delivered for the ﬁrst time; the12
C beam was delivered for the ﬁrst time as well. Despite
the diﬃculties in transporting the ﬁrst beams (new ionsor energies), higher transport eﬃciencies were achieved
from the RRC to SRC in comparison to those of similar light ions or energies, and high-quality single-turn-

extracted beams could be supplied. In 4 He beam supply, we recorded the highest ever beam intensity of 1000
particle nA. In the ﬁnal phase of the experiment, theapparatus malfunctioned, which can be attributed to radiation. The availability of 2 H and 4 He was 100.7% and104.7%, respectively, because the beam services could bestarted ahead of schedule owing to smooth beam tuning.
The beam service of 12 C was interrupted for approximately 26 h owing to issues in the SRC helium refrigerator. However, it exhibited an availability of 102.3%
because the beam service began ahead of schedule andthe beam service time was extended by 8 h.
The beam services of 238 U 345 MeV/nucleon were conducted twice. In the ﬁrst U-beam service held in April
2021, discharges were frequently observed in SRC resonator 3 (SRC-RES3). An internal inspection was performed on SRC-RES3 and the burned-out RF contact
ﬁngers were replaced. In addition, the steering electromagnets installed at the exit of fRC (fRC-SH3, SV3)
tripped owing to thermal anomaly. In the aftermath, abeam changed its trajectory to hit a bellow upstreama gas stripper installed in the E1 hall, thus leading tovacuum leakage; the availability was 94.2%. In the second U-beam service held in November 2021, no serious
issues were observed in the accelerators. However, thebeam supply was suspended earlier than scheduled owing to issues in the compressor of the BigRIPS helium
refrigerator; the availability was 98.9%.
The total availability in the RARF and RIBF reacheda record high of 102.8%.

Table 1. Summary of accelerated beams in 2021.
Beam
particle
12

C

135

14

N
Ne
40
Ar
56
Fe

100
135
95
90

84

70

20

RARF

Kr

51

V
86
Kr

6
10.75

136

10.75

Xe

238

U
Ar
H
4
He
12
C
238
U (1st)
40
2

RIBF

238

∗1
∗2

Energy(MeV/nucleon)

U (2nd)

10.75
160
250
250
200
345

Acceleration mode

AVF-RRCRILAC2-RRC

AVF-RRC-IRC
AVF-RRC-SRC

RILAC2-RRC-fRC-IRC-SRC

Beam course
E5B (Biology)
E5A (Industry)E3B (RI Production)
E5B (Biology)
E5A (Industry)
E5B (Biology)
E5A (Industry)E3A (JAXA)
E6 (KEK/MRTOF)
E2B (KEK/KISS)
E2B (KEK/KISS)
E3A (JAXA)
E5A (Material)
E5B (Biology)
BigRIPSBigRIPS/SHARAQBigRIPS/ZDS

Beam intensity (particle nA)
Requested
Actual
2
541.7
2
183.3
200
320.0
2
120.0
1
82.4
2
9.2
2
10.5
2
8.1
2000
3576.9
500
555.6
100
140.0
1
100.0
2
214.3
2
30.3
200
220.0
> 500
1000.0500
500.0Beam service time (h)Scheduled
Actual
33.0
13.0
10.0
10.9
6.0
6.5
3.0
1.9
48.0
80.6
9.0
2.8
161.0
212.4
18.0
18.5
126.0
125.8
48.0
47.4
120.0
120.4
18.0
17.3
48.0
37.4
18.0
7.7
180.0
181.3
197.0
206.2
192.0
196.5

Availability (%)
100.0
109.2
108.3
100.0
167.8
100.0
131.9
103.0
99.8
98.8
100.3
100.0
100.0
100.0
100.7
104.7
102.3

BigRIPS/ZDS/Rare RI Ring

70

89.5

648.0

610.6

94.2

BigRIPS/ZDS/Rare RI Ring/PALIS

120

73.0
Total

304.5
2187.5301.2
2198.3

98.9
102.8

SHI Accelerator Service Ltd.
RIKEN Nishina Center- 177 -

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IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

RILAC operation
T. Ohki,∗1 M. Fujimaki,∗2 N. Fukunishi,∗2 H. Hasebe,∗2 Y. Higurashi,∗2 E. Ikezawa,∗2 H. Imao,∗2 O. Kamigaito,∗2
K. Kaneko,∗1 M. Kidera,∗2 M. Komiyama,∗2 R. Koyama,∗1 K. Kumagai,∗2 T. Maie,∗2 T. Nagatomo,∗2
T. Nakagawa,∗2 T. Nishi,∗2 J. Ohnishi,∗2 H. Okuno,∗2 K. Oyamada,∗1 K. Ozeki,∗2 N. Sakamoto,∗2 K. Suda,∗2
M. Tamura,∗1 A. Uchiyama,∗2 S. Watanabe,∗2 T. Watanabe,∗2 Y. Watanabe,∗2 K. Yamada,∗2 H. Yamauchi,∗1 andA. Yusa∗1
Originally, beam service was scheduled to start in January 2021. However, because of a failure owing to theaging of radio-frequency (RF) tanks of RILAC, repair of
the breakdown and preventive measures were performed
from January to March. In April, the external vacuum
windows and the vacuum ports were added to the RFtransmission line to energize the superconducting (SC)cavities, which were not used because of a vacuum leakage through the coupler ceramic windows. It operated
well and ten SC-cavities became available. A user beamservice started in May.
Some statistics regarding the RILAC operation fromJanuary 1 to December 31, 2021 are provided in Table 1.
Table 1. Statistics of RILAC operation from January 1 to
December 31, 2021.

Operation time of RILAC

3294.0 h

Mechanical problems

185.4 hStandalone RILAC

2141.5 h

Injection into RRC

0.0 h

Total beam service time of RILAC(8) Introduction of automatic operation system of thecooling fans of the cooling towers for the ion source
and the RFQ.
(9) Introduction of the automatic operation system of
the cooling fans of the cooling towers for SRILAC
and RILAC tanks with a function of alternating
operation control.
(10) Renewal of the GPIB control system of the magnet power supplies.
(11) Feasibility test of the gyrotron for newly constructed SC-ECRIS (R28G-K).
(12) Installation of the external vacuum windows andthe vacuum ports to the RF transmission lines of
the SC-cavities.
We encountered several machine troubles during thereporting beam service period, which are listed as follows.
(1) Signiﬁcant amount of coolant leakage from thedrift-tubes of the RILAC tanks.
(2) RF power shortage of the RF power source for RILAC tank #1 due to the aging of a power tetrode.
(3) RF power shortage of the 1st-stage RF ampliﬁer
for the RILAC tank #6.
(4) Abnormal RF ﬁeld error caused by the malfunctioning of the 1st-stage RF ampliﬁer.
(5) Leakage of the cooling water from the ﬁnal stage
ampliﬁer for RILAC tank #4.
(6) Burn out of the RF contacts for the shorting plateof the RFQ cavity due to a lack of cooling water.
(7) Leakage of the cooling water from the cooling pipeof the RFQ cavity.
(8) Leakage of the cooling water from the cooling pipe
adopted to the end drift-tube of the tank A1.
(9) Malfunction of the power source for the solenoid
coil (SoL11ab).
(10) Vacuum leakage from the bellows of the drive shaftof a mesh-beam-attenuator.
(11) Serious damage of the water pumps for the coolingsystem of the SRILAC RF ampliﬁers.

2141.5 h

We performed the following maintenance works during
the reporting period.
(1) Replacement of the leaky ﬂowmeters for the cooling channels of the drift-tube quadrupole magnets
in RILAC tanks and the quadrupole singlet magnets of the beam-transport-line.
(2) Rearrangement of the quadrupole magnets of theinjection transport line to the tank #1 to enhance
the transmission eﬃciency from the exit of the
RFQ to the exit of tank #1.
(3) Renewal of the control and driving system of thecoarse frequency tuners of RILAC tank #3 andtank #4.
(4) Removal of the ﬁne frequency tuner of RILAC
tank #2 because of the vacuum problem.
(5) Development of the beam interlock system (BIS)
against the failure of the magnet power supplies.
(6) Construction of the quick BIS which instantly
chops the beam when there is an error of the RF
control system.
(7) Improvement of the rough evacuation ducts of the
RILAC tanks by adding an automatic evacuation
system.
∗1∗2

All the troubles were successfully ﬁxed, and beam service was recovered instantly. The license of radiation
safety to use heavy-ion beams with an intensity of 10particle μA was updated after an inspection by the Secretariat of the Nuclear Regulation Authority.

SHI Accelerator Service Ltd.
RIKEN Nishina Center- 178 -

1

IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Operation report on the RIKEN AVF cyclotron for 2021
S. Fukuzawa,∗1 K. Suda,∗2 M. Fujimaki,∗2 N. Fukunishi,∗2 A. Goto,∗2 M. Hamanaka,∗1 H. Hasebe,∗2
Y. Higurashi,∗2 E. Ikezawa,∗2 H. Imao,∗2 S. Ishikawa,∗1 K. Kamakura,∗3 O. Kamigaito,∗2 M. Kase,∗2
M. Kidera,∗2 K. Kobayashi,∗1 M. Komiyama,∗2 Y. Kotaka,∗3 R. Koyama,∗1 K. Kumagai,∗2 T. Maie,∗2
T. Nagatomo,∗2 T. Nakagawa,∗2 T. Nakamura,∗1 M. Nishida,∗1 M. Nishimura,∗1 J. Ohnishi,∗2 H. Okuno,∗2
K. Ozeki,∗2 N. Sakamoto,∗2 J. Shibata,∗1 N. Tsukiori,∗1 A. Uchiyama,∗2 S. Watanabe,∗2 T. Watanabe,∗2
Y. Watanabe,∗2 K. Yadomi,∗1 and K. Yamada∗2
The annual report on the operation of the RIKEN
AVF cyclotron (hereafter denoted as AVF) for the period January–December 2021 is presented. The beams
accelerated using AVF in the period are listed in Table 1, where beam currents are the maximum values
measured by the Faraday cup FC-C01 at the exit of
AVF. The operation statistics are summarized in Table 2. The operation time for stand-alone operation
was increased to 2100 h from 1520 h, which was reduced because of the COVID-19 outbreak in 2020.
Moreover, the operation time for injection to RRC wasalso increased to 1816 h from 1182 h because the acceleration in the AVF-RRC-SRC mode was performed
for the ﬁrst time in three years from May to June, and2
H, 4 He, and 12 C beams were supplied to experimentsfor 28 days.
To supply high-quality beams required for the experiments and to reduce beam losses in two cyclotrons(RRC and SRC) downstream of AVF, AVF was tuned
to extract single turn beams so that components of different turns were minimized in the extracted beams.
The minimum mixing rate for 2 H beam was 2.3% ±1.3%.
In the stand-alone operation which supplied 7 Li3+
at 8.3 MeV/nucleon, the highest beam current of 5670
particle nA was achieved at FC-C01, which was increased by 2.4 times compared with that recorded ata slightly diﬀerent energy of 8.6 MeV/nucleon in an
acceleration test performed in 2011. The increase was
because of a high beam current of 70000 particle nA
extracted from the Hyper ECR ion source owing to a
modiﬁcation of an extraction electrode, as well as a
research for supporting gases.
A main trouble occurred at each compensator for
two Dees, which was used to tune a resonant frequency
by changing the capacitance. When compensator #2
was rotated, a vacuum was leaked through a driving
shaft, so that a vacuum degree of the main chamber
deteriorated from 10−5 Pa to 10−3 Pa. In the repair
process, the other leakage was found from compensator#1. The vacuum was recovered by replacing the Xrings.
As a recent improvement, we started monitoring
temperatures at the tips of septum electrodes for the
∗1
∗2
∗3

SHI Accelerator Service Ltd.
RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo- 179 -

Table 1. AVF beam list in 2021.
Particle
1+

H

Energy[MeV/nucleon]
19
30
4.93

2

H+

12
15
4.17

Acceleration
Mode
AVF
ˢRRCˢSRC
AVF
ˢRRCˢSRC

6.5
4

He2+

Li2+

7

Li

3+

12

C4+

14

N

16
18
20

8.3

40

84

5.54

O

6+

6.8

O6+

7

Ar11+

56

7

5+

Ne7+

AVF

6
4.93

Beam Current
at C01[particle nA]

E7V/RI production

10000

C03/RI production

10000

BigRIPS

7000

C03/RI production

19800

C03/RI production

13000

BigRIPS

1670

E7B/Student

6000

C03/RI production

7.25
12.5

7

Experimental
CourseˢRRCˢSRC

25000

E7B/RI Production
C03/RI production

3850

C03/RI production

8000

E7A/CRIB

5670

BigRIPS

1130

E5B/Biology
ˢRRC

880

E5A/Industry
E3B/Industry

AVF

450

E7A/CNS

4080

E7V/CNS

4580

7

ˢRRC

E5B/Biology

540

3.8

ˢRRCˢIRC

E5B/Biology

390

E5A/Industry

520

ˢRRC

E5B/Biology

110

E5A/Industry

230

5.2

Fe15+

5.01

Kr20+

3.97

Table 2. Comparison of AVF operation statistics with thatin the previous years.
AVF stand-alone operation
Tuning of AVF [h]Trouble of AVF [h]C01 MS [h]C03 Exp [h]E7V Exp [h]E7A Exp [h]E7B Exp [h]Sub total [h]AVF operation as injector of RRC
Tuning of AVF [h]Trouble of AVF [h]RRC-Exp (-IRC-Exp) [h]RRC-SRC-Exp [h]Sub total [h]Total [h]Year 2019
1314
0
0
873
36
790
153
3166
Year 2019
118
0
320
0
438
3604

2020
744
1
12
631
18
12
101
1519
2020
178
5
999
0
1182
2702

2021
1149
5
35
672
95
48
96
2100
2021
214
1
834
767
1816
3916

electrostatic deﬂector using a pair of thermocouples.
The monitor signals are fed into the beam interlock
system (AVF-BIS), so that beams are stopped automatically by a chopper and a Faraday cup, which arelocated before injection to AVF, if an increase of thetemperature caused by beam loss exceeds a certain
value. Currently, the preset value is 45◦ C.

1

IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Present status of liquid-helium supply and recovery system
T. Dantsuka,∗1 H. Okuno,∗1 M. Nakamura,∗1 S. Tsuruma,∗1 M. Takahashi,∗1 M. Kuroiwa,∗1 M. Ohshima,∗2
H. Shiraki,∗2 H. Hirai,∗2 K. Kimura,∗2 S. Okada,∗2 A. Mikami,∗2 M. Nagano,∗2 H. Shiba,∗2 and H. Hazama∗2
A liquid-helium supply and recovery system,1) which
can produce liquid helium at a liquefaction rate of
200 L/h from pure helium gas, has been under stable operation since the beginning of April 2001. However, because operation failures due to deterioration
over time have increased recently, the liqueﬁer was duplicated in 2017. The new liqueﬁer can produce liquid
helium at a liquefaction rate of 220 L/h from pure helium gas. Although the older helium liqueﬁer has been
failing since the summer of 2018, the new helium liqueﬁer provides a constant supply of liquid helium. The
older helium liqueﬁer was repaired in February 2020.
The volumes of liquid helium supplied each year
from 2001 to 2020 are illustrated in Fig. 1. From 2001
to 2013, there was a gradual increase in the supplied
volume, with two decrements in 2009 and 2011. In
2014, the supplied volume decreased owing to a system malfunction. However, in 2015, it returned to its
original value. In 2016, the supplied volume decreased,
whereas it increased slightly in 2017 and signiﬁcantly
in 2018. In 2019, approximately 140,000 L liquid helium was supplied despite the high price of helium gas.
In 2020, a supply volume decreases of approximately
15,000 L was caused by the inﬂuence of the new coronavirus.

200000180000160000LiquidHelium(L)140000120000However, the purity of helium gas recovered from thelaboratories has gradually deteriorated. At present,
the impurity concentration in the recovered gas isapproximately 1700 ppm, which aﬀects the liquefaction process and makes continuous operation diﬃcult.
Therefore, improving the purity of the recovered helium gas is necessary.
Furthermore, the volume of helium gas recoveredfrom each building in the Wako campus as well as thevolume transported to the liquid-helium supply and recovery system were measured. The recovery eﬃciency
was calculated as the ratio of the amount of recovered
helium gas to the amount of supplied liquid helium.
The recovery eﬃciency for the buildings on the south
side of the Wako campus, i.e., the Cooperation Centerbuilding of the Advanced Device Laboratory, Chemistry and Material Physics building, and Nanoscience
Joint Laboratory building, increased to approximately
96%.
Reference
1) K. Ikegami et al., RIKEN Accel. Prog. Rep. 34, 349(2001).

ExploratoryMaterialsTeam
AdvancedDeviceLaboratory
EmergentPhenomenaMeasurementResearchTeam
QuantumElectronDeviceResearchTeam
SurfaceandInterfaceScienceLaboratory
QuantumFunctionalSystemResearchGroup
CondensedMolecularMaterialsLaboratory
MesonScienceLaboratory
SurfaceChemistryLaboratory
RadioactiveIsotopePhysicsLaboratory
MagneticMaterialsLaboratory
LowͲTemperaturePhysicsLaboratory
Otherlaboratories

100000
80000
60000
40000
20000
0
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Fig. 1.
∗1∗2

FiscalYear
Volumes of liquid helium supplied to various laboratories for each ﬁscal year from 2001 to 2020.

RIKEN Nishina Center
Nippon Air Conditioning Service K.K- 180 -

1

IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Impurity concentration in recovered helium gas of liquid-helium
supply and recovery system
M. Nakamura,∗1 T. Dantsuka,∗1 H. Okuno,∗1 S. Turuma,∗1 M. Kuroiwa,∗1 M. Ohshima,∗2 H. Hirai,∗2
H. Shiraki,∗2 H. Shiba,∗2 K. Kimura,∗2 S. Okada,∗2 A. Mikami,∗2 H. Hazama,∗2 M. Nagano,∗2 and
M. Nakayama∗2
We use recovered helium gas for a liquid-helium supply system. However 1–2 ppm hydrogen gas, for example, was intermixed with the recovered helium gas, andwe had to stop the operation of our system for a few
month in 2004.1) To cope with such serious troubles, we
introduced gas chromatography equipment and havebeen analyzing the recovered helium gas. Then, we
could observe the concentration of impurity gas andthe condition of the recovered helium gas for eﬀective
operation. In this paper, we report the change in concentration of impurity gases in 2021.
The recovered helium was analyzed using SHIMADZ
2014 every day except Saturdays and holidays. The results from January 4 to December 28 in 2021 are shownin Fig. 1. The left axis shows the concentration of N2
and O2 , and the right axis shows that of H2 , CO2 , and
CO. The results for CO2 and CO are presented in a bar
chart because we could rarely observe these gases andthe results are diﬃcult to plot using polygonal lines.
The black, gray, and red lines show the N2 , O2 , and H2concentration, respectively. The blue and green bars
show the CO2 and CO concentration, respectively.
The concentration changes of N2 and O2 were almostin exact correspondence. The N2 and O2 concentrations changed from 1300 to 2000 ppm and from 900 to
1300 ppm, respectively. From April to September, theN2 and O2 concentrations reduced to approximately
1300 and 900 ppm, respectively. We presume that N2

and O2 from air intermixed into the helium gas when
helium was recovered. However, the ratio of N2 andO2 of our result is approximately 0.7 and not the sameas that of the air (0.25). The cause of this diﬀerence
cannot be explicated at present.
The ﬂuctuation of the H2 concentration was fairly
radical. Ordinarily, the H2 concentration settled
around 0.1 ppm. However, the concentration suddenly
increased to 0.3–0.7 ppm at several instances. The
correlation of H2 concentration change with that of N2
and O2 is not so clear. We presume that the H2 impurity intermixed into the recovered helium gas througha mechanism diﬀerent from that of N2 and O2 .
We cannot estimate the CO2 and CO impurity concentrations because these gases were observed only a
few times in this year.
In January, some parts included in the helium liqueﬁer were blocked, and we could not operate the heliumliqueﬁer. In the term of this trouble, we could observe
CO2 and CO several times, and H2 concentration increased to 0.7 ppm. The N2 and O2 concentrations
also increased. Hence, we can presume that this serious trouble was caused by impurity gases. However,the cause of this trouble could not be clariﬁed.
To keep the purity of liquid helium, we have to analyze the impurity gases in the recovered helium gas.
Reference
1) K. Ikegami et al., RIKEN Accel. Prog. Rep. 38, 286(2005).

Fig. 1.
∗1∗2

Impurity concentration in the recovered helium gas in 2021.

RIKEN Nishina Center
Nippon Air Conditioning Service Co., Ltd.

- 181 -

1

IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Operation of the BigRIPS cryogenic plant
K. Kusaka,∗1 M. Ohtake,∗1 K. Yoshida,∗1 M. Ohshima,∗2 A. Mikami,∗2 H. Hazama,∗2 H. Shiraki,∗2 H. Hirai,∗2
K. Kimura,∗2 M. Nagano,∗2 H. Shiba,∗2 and S. Okada∗2   















 











    

Fig. 1. Oil contamination at the entrance of the third coalescer vessel.
∗1∗2

RIKEN Nishina Center
Nippon Air Conditioning Services Co., Ltd.

  







  









 

  

Since the total operation time of the helium compressor unit has reached to 77,680 h in August 2021, the maincompressor was shipped to the manufacturer’s factory for
maintenance. The compressor unit was disassembled,
and its interior was cleaned. All the components werechecked carefully, and no signiﬁcant mechanical damage
was found.
In addition to maintaining the mechanical componentsof the compressor unit, we replaced the activated charcoal and molecular sieves in the adsorbent vessel in August 2021. We measured the operation interval of thedrain valves of the coalescer vessels in the compressor
unit, to evaluate the oil contamination level. We replaced coalescer ﬁlter elements ﬁve times since 2008. The
operation periods of replaced ﬁlter elements are from
Aug. 2008 to July 2010, Sept. 2010 to July 2012, Sept.
2012 to July 2014, Sept. 2014 to July 2016, and Sept.
2016 to June 2019. Figure 1 shows an estimate of the oil
contamination level at the entrance of the third coalescer
vessel as a function of the coalescer ﬁlter operation time.
The navy blue, green, and yellow diamonds represent
the estimates for the ﬁrst, the second, and the third elements, respectively. The fourth, the ﬁfth and the sixth
elements are shown with pink, red, and purple diamonds,
respectively. The oil contamination values measured using the oil check kit are also shown. The open triangles,
squares, and circles represent the results for the ﬁrst,
the second, and the third elements. The results for the
fourth and the ﬁfth elements are indicated by the open
diamonds and circles, respectively. The cross represents
the results of the sixth elements. Both estimations of theoil contamination level are consistent with each other,and the performance eﬃciency of the sixth ﬁlter element
is apparently better than that of the others.
At the end of October 2021, we started continuous



















    





Fig. 2. Vibration acceleration of the compressor unit.

operation of the BigRIPS cryogenic plant after summer
maintenance. This operation was terminated by an incident in the 2021 winter beam time. At 7:35 on December 3, the ﬁre alarm of the RI-Beam Factory (RIBF)
building rang, and the cryogenic plant operator foundsmoke emanating from the compressor unit of the BigRIPS cryogenic plant. After having made necessary
emergency contacts, the plant operator stopped the compressor unit safely at 7:50. Evaporated helium gas fromthe STQ cryostats was transferred to the RIKEN liquidhelium supply and recovery system using a temporary
recovery line. We inferred that the smoke was emitted
from the coupling side baring unit of the main motor of
the compressor unit, since burnt grease was found aroundthe coupling. A sudden increase in the operation currentof the motor unit from 30.6 A to 33.6 A, which was measured at 7:28, also indicates a breakdown of the main
motor.
We noticed an unusual noise produced by the main
motor of the compressor unit since November 2021. We
measured the vibrations of the compressor at the highpressure and low-pressure sides since 2015. Figure 2
shows the vibration acceleration in the vertical and horizontal directions as a function of the total operation
time. Continuous operation started with a total operation time of 77,683 h and the acceleration increased
rapidly. The ﬁnal measurement of the vibrations was
performed on Dec. 1. Two additional rapid increases inthe vibration acceleration at operation times of 59,000 h
and 71,000 h were caused by damage to the bearing unit
occurred in Dec. 20161) and in June 2019.2)
The main motor unit was dismounted from the compressor unit and shipped to the manufacturer’s factoryfor repairs in January 2022. The origin of the unusual
vibrations is under investigation.
References
1) K. Kusaka et al., RIKEN Accel. Prog. Rep. 50, 285 (2017).
2) K. Kusaka et al., RIKEN Accel. Prog. Rep. 53, 222 (2019).

- 182 -

1

Radiation safety management at RIBF
IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Radiation safety management at RIBF

Radiation safety management at RIBF

K. Tanaka,∗1 Y. Uwamino,∗1,∗2 H. Sakamoto,∗1 R. Hirunuma-Higurashi,∗1 H. Mukai,∗3 A. Akashio,∗1
T. Okayasu,∗1 R. Suzuki,∗4 M. Takekoshi,∗4 T. Sato,∗4 K. Igarashi,∗1 S. Iizuka,∗1 N. Usudate,∗1 Y. Shioda,∗1
and K. Sugihara∗1,∗5
dose of the γ-ray was lower than the limit. Therefore,
we inferred that the annual dose at the boundary wasless than 10 μSv/y, which is considerably lower thanthe legal limit.
The residual radioactivity at the deﬂectors of the cyclotrons was measured immediately before the maintenance work. The residual dose depends on factors
such as the beam intensity, accelerator operation time,and cooling time. The data were captured at the cyclotrons maintenance works, when the deﬂectors wereable to accessible. Therefore, the cooling times havenot been constant. The dose rates from 1986 are shownin Fig. 2. The dose rates for FRC, IRC, and SRC areshown for years after 2006, when the RIBF operation
started. For the AVF, the dose rate increased in 2006
because the radioisotope production started and thebeam intensity increased.
10

Dose rate (PSv/h)

The results of radiation monitoring at the RIBF,
performed at the border of the facility and theradiation-controlled area are reported. The residual
doses along the accelerator setups are also presented.
In 2021, a 238 U beam of about 345 MeV/nucleon wasprovided at an intensity of 70 particle nA in April,May, and November. Subsequently, light-ion beams
such as 12 C beam of about 200 MeV/nucleon of 500
particle nA, 2 H beam of about 250 MeV/nucleon, and4
He beam of about 200 MeV/nucleon were used in May
and June.
The dose rates at the boundary of the radiationcontrolled area were monitored. Neutron and γ-ray
monitors were used at three locations: roofs of theRRC, IRC, and BigRIPS. Figure 1 shows the annual
neutron dose at these positions. In 2021, even the highest annual dose of 18 μSv/y at the IRC roof was lower
than the legal limit of 5.2 mSv/y. The dose at the IRC
roof at 2021 is sensitive to IRC and SRC operation
time. In 2021, these were operated only four months.
Therefore, the annual dose of IRC roof was small.
The dose rates at the site boundary, where the legal
limit is 1 mSv/y, were monitored using neutron and γray monitors. The detection limit of the neutron monitor is 2 μSv/y. The annual dose in 2021 was 3.6 μSv ofneutrons after the background correction. The detection limit of the γ-ray monitor is 8 μSv/y. The annual䢢䣔䣔䣅䢢䣴䣱䣱䣨䢢䣋䣔䣅䢢䣴䣱䣱䣨䢢䣄䣫䣩䣔䣋䣒䣕䢢䣴䣱䣱䣨

2005

2010

2015

2020

PSv/y

year
Fig. 1. Radiation dose at the boundary of the radiationcontrolled area.

∗5

䢢䣃䣘䣈
䢢䣔䣔䣅
䢢䣋䣔䣅
䢢䣕䣔䣅
䢢䣈䣔䣅

2

1

1995

2000

2005

2010

2015

2020

Fig. 2. Dose rates of residual radioactivity at the deﬂectorsof ﬁve cyclotrons. Except for measurements, numbers
below 10 are preferably spelled out and those above
indicated numerically.

10

2000

∗4

3

Year

1

∗3

10

4

1990

100

∗2

10

10

1000

∗1

10

5

RIKEN Nishina Center
Japan Radioisotope Association
Japan Environment Research Corporation
Daiwa Atomic Engineering Corporation
Kyushu University- 183 -The residual radioactivity along the beam lines wasmeasured after almost every experiment. Figure 3
shows the locations of measurement points where highresidual doses were observed. Table 1 lists the dose
rates, beam conditions, and cooling time at the measurement points. The maximum dose was 13 mSv/h
at point 19, which is in the vicinity of the beam dumpof BigRIPS.
Although the radioactivity in the closed cooling system at BigRIPS have been reported annually, it isomitted because the radioactivity was not measured
in 2021.
The E-learning module, which can be accessed any-1IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

Table 1. Dose rates measured at beam lines in 2021.
Points 1–21 indicate the locations where measurements
were performed as shown in Fig. 3.
Dose rate

Date(μSv/h)(M/D)

EnergyIntensity

Decay(MeV/u)(pnA)period (h)

1

130

7/30

Li-7

6

1000

313

2

150

3

650

7/30

Li-7

6

1000

313

7/30

Li-7

6

1000

4

313

400

7/30

N-14

100

200

476

5

2400

7/20

α

74

1200

694

6

2200

7/20

α

74

1200

694

7

450

7/20

α

74

1200

694

8

100

7/20

α

200

1000

708

Point

Fig. 3. Layout of the beam lines at RIBF. The measurement locations listed in Table 1 are indicated.

time and from anywhere (even from outside RIKEN),
has been used for the re-training of radiation workers
at the RIBF. A total of 595 radiation workers completed the training in 2021. It is lower than that inrecent years because of COVID-19 restriction on immigration, etc.
As described above, radiation management to comply with lows and to maintain radiation level as low as
usual has been performed successfully.

2- 184 -

Particle

9

5100

7/20

α

200

1000

708

10

8000

7/20

α

200

1000

708

11

350

7/20

α

200

1000

708

12

130

7/20

α

200

1000

708

13

350

7/20

α

200

1000

708

14

380

7/20

α

200

1000

708

15

250

7/20

α

200

1000

708

16

240

12/14

U-238

345

72

269

17

1570

12/14

U-238

345

72

269

18

2300

12/14

U-238

345

72

269

19

13000

12/14

U-238

345

72

269

20

200

12/14

U-238

345

72

269

21

180

12/14

U-238

345

72

269

IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Operation of Pelletron tandem accelerator
T. Ikeda,∗1 K. Inayoshi,∗2,∗1 and H. Sato∗1
The Pelletron tandem accelerator (5SDH-2) managed
by the Detector Team of RNC provides ion beams accelerated by up to 1.7 MV. This accelerator is also registered as a joint-use equipment at the Wako campus formaterial analysis. As shown in the conﬁguration of theaccelerator and the beam lines (Fig. 1), two ion sources
are available. One is the RF charge-exchange ion source,called Alphatross, which is employed for experiments using He ion beams. The other is the Source of Negative
Ions by Cesium Sputtering (SNICS), which can generate
almost all other ions. Thus far, ion species of H, He, B,
C, O, and Au have been mainly accelerated in the rangeof 0.5–1.7 MV.
The maximum energies of diﬀerent accelerated ions arelisted in Table 1. Since 2019, the regulation of the maximum energy of carbon ions was changed from 7.2 MeV
to 11.9 MeV, where 12 C6+ is accelerated with the fullvoltage of 1.7 MV. However, owing to aged deterioration(more than 30 years), acceleration voltages of less than
1.4 MV have been used in recent years.
A unique feature of this facility is the ability to irradiate samples in liquid with a microbeam produced
by glass capillary optics at some beam lines.1) There
are four beam lines named BL-E/Wnn (nn denotes thebending angle of the east or west beam line). BL-E45
is dedicated to microbeam irradiation for samples in liquid.2) BL-E15 is used by user groups in the ﬁeld of material science to perform Rutherford backscattering (RBS)
spectrometry analysis.3) The RBS apparatus (Charles
Evans and Associates Model RBS-400) consists of a goniometer to rotate a sample and a particle detector at165◦ to the incident beam direction to measure the backscattered ion energies. Both are inside a vacuum chamber with a vacuum level of the order of 10−4 Pa. The
intensity of the input He2+ beam of 2.28 MeV is approximately 10 nA when the beam size is collimated to 5 mm
in diameter. On the west side, BL-W15 was previously
used for channeling experiments;4) however, since 2016,
it is employed as a multipurpose line for various equipment. Some examples are a proﬁle measurement system

Table 1. Approved conditions at RIKEN Pelletron.
,RQ

0D[LPXP(QHUJ\

,RQ

+

0H9%

0D[LPXP(QHUJ\0H9

+H

0H9&0H9

/L%H

0H9RWKHU

0H9X=±H[FOXGLQJGHXWHURQV0D[LPXPLQWHQVLW\LRQVV SP$

for an ion microbeam produced by glass capillary,5) microbeam irradiation tool to induce damage in DNA ofmammalian cells,6) cross-section measurement setup for
an international summer school, Nishina School, and detector calibration system based on proton-induced resonance reactions to produce γ rays of up to 10.8 MeV7)
BL-W30 was previously used for detector calibration;8)
however, since 2020, it is dedicated to a new microbeam
irradiation port equipped with an Olympus research microscope.
The total machine time (MT) from January 1 to December 31, 2021, was 27 days, which can be seen from
Table 2. The MT included a machine study on acceleration, whereas excluded the conditioning of the ion
sources. One team used both H and He ion beams in
one MT.
Table 2. Beam conditions employed in accelerator.
,RQ(QHUJ\>0H9@

%HDPFXUUHQW>SQ$@([SHULPHQW

2SHUDWLRQ
WLPH>GD\V@



+

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±,UUDGLDWLRQ 

±

5%6

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Points 1–5 below list the studies that used the beamlines, along with the number of days of MT. The Nishina
School experiment was not performed in 2021.
(1) Microbeam performance study with H ions using
glass capillaries at BL-W15 (10 days)(2) Microbeam (H/He ion) irradiation for single cells at
BL-W30 (4 days without samples)(3) RBS experiments (8 days)(4) Educational experiment of proton capture bycarbon/boron-nucleus for the Nishina School (0days)(5) Development of a charged-particle/γ-ray detector to
be used for RIBF experiments (5 days)
References

Fig. 1. Pelletron tandem accelerator and beam lines at
Nishina R&D Building.
∗1∗2

RIKEN Nishina Center
Department of Physics, Toho University

1) T. Ikeda, Quantum Beam Sci. 4, 22 (2020).
2) T. Kobayashi et al., Surf. Coat. Technol. 331, 206 (2017).
3) L. Jianjun et al., Chem. Sci. 12, 10354 (2021).
4) E. Yagi et al., J. Phys. Soc. Jpn. 85, 124601 (2016).
5) T. Ikeda et al., Nucl. Instrum. Methods Phys. Res. B 470,
42 (2020).
6) T. Ikeda et al., RIKEN Accel. Prog. Rep. 53, 215 (2020).
7) R. Mizuno et al., in this report.
8) F. P. Gustafsson et al., RIKEN Accel. Prog. Rep. 50, 209(2017).

- 185 -

1

IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Fee-based activities performed by the RI Application Research
Group

∗1

Zn-65
Cd-109
Y-88
Sr-85
Cu-67

20

10

0
2006

2010

2014

Year

150

Amount (MBq)This article summarizes the fee-based activities performed by the RI Application Research Group in 2021,
which include the distribution of radioisotopes (RIs)
and utilization of heavy-ion beams in the industry.
Since 2007, RIKEN has distributed RIs to users inJapan for a fee in collaboration with the Japan Radioisotope Association1) (JRIA). The nuclides include
65
Zn (T1/2 = 244 days), 109 Cd (T1/2 = 463 days), 88 Y
(T1/2 = 107 days), 85 Sr (T1/2 = 65 days), and 67 Cu(T1/2 = 61.8 hours) produced in the RIKEN AVF cyclotron by the Nuclear Chemistry Research Team of
the RI Application Research Group.
According to a material transfer agreement (MTA)
drawn between the JRIA and RIKEN, JRIA mediates
the transaction of RIs and distributes them to users.
65
Zn and 109 Cd are delivered approximately two weeks
after the acceptance of an order.
85
Sr, 88 Y, and 67 Cu, which have short half-lives, arenot stocked like 65 Zn and 109 Cd; instead, they are produced in a scheduled beamtime after an order is accepted. Therefore, they are delivered after two or moremonths.
Details regarding RIKEN RIs can be found on the
online ordering system, J-RAM,2) of JRIA.
In 2021, we delivered 4, 2, and 10 shipments of
65
Zn, 88 Y, and 85 Sr with a total activity of 31, 2, and36.4 MBq, respectively, and no shipment of 67 Cu and109
Cd. The ﬁnal recipients of RIs included 11 universities, two research institutes, one private company, andone medical research center.
Figure 1 shows the yearly trends in the number oforders and amount of distributed RIs.
Compared with 2020, the amount of distributed
65
Zn and 85 Sr increased, that of 109 Cd decreased, andthat of 88 Y remained the same. The amount of 85 Sr
distributed in 2021 was the highest since the beginningof its distribution. The number of orders for 65 Zn in
2021 was the highest in the last seven years; however,it was signiﬁcantly less than that in 2010.
The Industrial Application Research Team of the
RI Application Research Group promotes the utilization of heavy-ion beams in the industry. The RIKEN
Nishina Center allows the use of the AVF cyclotron,
RILAC, and RIKEN Ring Cyclotron (RRC) by private companies in Japan for a fee.3) Currently, themain users include semiconductor companies that irradiate space-use semiconductor devices with 40 Ar, 84 Kr,
or 136 Xe ions from the RRC to simulate single-event
eﬀects due to the heavy-ion components of cosmic radiation.

Number of Orders

A. Nambu,∗1 H. Haba,∗1 A. Yoshida,∗1 and T. Kambara∗1

2018

2022

Zn-65
Cd-109
Y-88
Sr-85
Cu-67

100
50
0
2006

2010

2014

Year

2018

2022

Fig. 1. Number of orders (upper) and amount (lower) of
RIs distributed yearly from 2007 to 2021. The distribution of 88 Y, 85 Sr, and 67 Cu started in 2010, 2015, and2018, respectively.

The proposals for beam utilization are reviewed bya program advisory committee dedicated to industrialuse (InPAC).
In January 2021, In-PAC reviewed and approved
three proposals via e-mail. In July, In-PAC held its
17th meeting, where it reviewed and approved sevenproposals, including two new proposals.
In 2021, four companies executed 13 fee-based beamtimes, nine of which used a 84 Kr beam with a total
beamtime of 161 h and four utilized an 40 Ar beamwith a total beamtime of 48 h. In response to user
demand, we are prepared to supply 12 C beam; furthdetails are provided elsewhere in this progress report.
References
1) http://www.jrias.or.jp/ (Japanese), http://www.
jrias.or.jp/e/ (English).
2) https://j-ram.org/ (Japanese).
3) http://ribf.riken.jp/sisetu-kyoyo/ (Japanese).

RIKEN Nishina Center- 186 -

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V. EVENTS

V. EVENTSRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

International workshops on the extension project for the J-PARC
hadron experimental facility (J-PARC HEF-ex WSs)
F. Sakuma∗1 for the J-PARC HEF-ex WS Local Organizing Committee
International Workshops on the Extension Project
for the J-PARC Hadron Experimental Facility (J-PARC
HEF-ex WSs) were held online on [ﬁrst] June 7–9, 2021,
and [second] February 16–18, 2022. The workshops wereorganized by Hadron Hall Users’ Association (HUA)
and supported by J-PARC Center, KEK Theory Center, RCNP, and RIKEN Nishina Center.
We have been extensively discussing a new plan for
the J-PARC Hadron Experimental Facility to extend
the existing experimental facility. The idea is to extend
the Hadron Hall to include another production target
downstream of the current production target and build
multiple new beamlines. Four new beamlines are being
planned to be constructed with the highest priority.
• A “high-intensity and high-energy-resolution beamline (HIHR)” and “high-purity and high-intensity lowmomentum charged K beamline (K1.1)” to solve theso-called hyperon puzzle through the super-precision
spectroscopy of Λ-hypernuclei and precise hyperonnucleon scattering measurement, respectively• A “high-intensity neutral KL beamline (KL2)” to explore new physics beyond the Standard Model by dramatically increasing the sensitivities of the kaon raredecay
• A “high-momentum particle-separated beamline(K10)” to resolve the conundrum of the strong interaction based on the investigation of Xi and Omega
baryons
We will develop new physics programs in particle and nuclear physics that cannot be implemented at the existing
facilities.
The J-PARC HEF-ex WSs were part of a series ofworkshops to discuss and detail the physics case at
the Hadron Experimental Facility. In the ﬁrst half of2021, several workshops were held focusing on the future physics case at the extended Hadron Experimental Facility; their outputs were summarized as the third
white paper.1) The extension project was reviewed by aninternational committee formed under J-PARC PAC in
August 2021 and was highly evaluated toward the early
realization of the facility extension. Detailed informationon the extension project can be found on HUA’s home
page.2)[First J-PARC HEF-ex WS on 7–9 June 2021]
The ﬁrst workshop was dedicated to discussions onimportant physics features at the extended J-PARC
Hadron Experimental Facility. This workshop included
plenary sessions by invited speakers, and the physics casefor the new beamlines was discussed.
 Project overview
 Strangeness nuclear physics at the HIHR and K1.1
∗1

Fig. 1. The Second J-PARC HEF-ex WS.

beamlines Flavor physics at the KL2 beamline
 Hadron physics at the K10 beamline
The workshop included 138 participants from 12 countries (42 participants from abroad). There were 12 plenary talks. The full program and presentation ﬁles areavailable online at the workshop website.3)[Second J-PARC HEF-ex WS on 16–18 February 2022]
In the second workshop, discussions were dedicated tothe physics case connecting the “present” and “future”
Hadron Experimental Facility of J-PARC. For that purpose, this workshop covered wide-ranging topics related
to experimental and theoretical activities conducted at
the Hadron Experimental Facility.
 S = −1 and −2 hypernuclei
 Meson in nuclei
 Baryon spectroscopy
 Kaon rare decays
 μ-e conversion
 Future facilities and instrumentation
The scientiﬁc program comprised plenary sessions by invited speakers and parallel sessions by invited and contributed speakers. The workshop included 250 participants from 15 countries (94 participants from abroad).
There were 19 plenary talks and 86 parallel talks (including 23 invited keynote talks). The full program andpresentation ﬁles are available online at the workshop
website.4) A group photo is shown in Fig. 1.
Following the success of the workshops, we are planning to conduct the third workshop in FY2022 to continuously discuss physics at the J-PARC Hadron Experimental Facility and its extension.
References
1) Taskforce on the extension of the Hadron Experimental
Facility, arXiv:2110.04462.
2) http://www.rcnp.osaka-u.ac.jp/~jparchua/en/index.
html .
3) https://indico2.riken.jp/event/3773/ .
4) https://kds.kek.jp/event/40010/ (An access key is required.).

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V. EVENTSRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

SPIN2021 international spin symposium
Y. Goto∗1 and T. Uesaka∗1 for the SPIN2021 Local Organizing Committee
The 24th International Symposium on Spin Physics(SPIN2021) was held at the Kunibiki Messe Convention Center in Matsue, Shimane Prefecture, Japan in
October 18–22, 2021. We aimed to cover a wide rangeof topics related to particle and nuclear spin physics
from low energy to high energy, including experimental, theoretical, computational and technological aspects and applications.
This symposium was originally scheduled to be heldin 2020 as SPIN 2020; however, it was postponed because of the COVID-19 pandemic. This symposium
series has been held jointly since 2000, combining theHigh Energy Spin Symposia and Nuclear Polarization
Conferences. The most recent symposia took place in
Dubna, Russia (2012); Beijing, China (2014); Urbana
Champaign, USA (2016); and Ferrara, Italy (2018).
The symposium was held in a hybrid style, i.e., inperson and online participation were possible. As aresult, in-person on-site participation was limited tothe symposium organizers, which was 20 people, while
online participation included about 160 presenters and
150 audience participants. The total number of participants was about 330, which is a larger number forthis symposium series.
The hybrid style was useful to invigorate our scientiﬁc discussions under the present situation of thepandemic. We had successfully tested the hybrid stylewith a domestic workshop on spin physics.1) In the hybrid style of the SPIN2021 symposium, the structure of
the plenary and parallel sessions was set up to be convenient for online participants residing outside Asia. In
the ﬁrst two days, the symposium started at 3 p.m. tofacilitate online participation from Europe, and in thelast two days, it started at 7 a.m. to facilitate online
participation from the United States.
The scientiﬁc program of SPIN 2021 included topics related to spin phenomena in particle and nuclear
physics and related ﬁelds. The following symposium
topics were covered:• Nucleon helicity structure• 3D structure of the nucleon:transversemomentum dependent distribution• 3D structure of the nucleon: general parton distribution• Fundamental symmetries and spin physics beyond
the Standard Model• Spin physics in nuclear reactions and nuclei• Low energy spin physics with lepton, proton andhadron probes• Future facilities and experiments• Acceleration, storage and polarimetry of polarized∗1

Fig. 1. Online participants of the SPIN2021 symposium.

beams• Polarized ion and lepton sources and targets• Applications of nuclear polarization techniques toother ﬁelds
The symposium format comprised discussions in plenary and parallel sessions. The plenary session beganwith a discussion on the recent major topic of muong-2 measurements, and two more special discussions
on spintronics and polarization measurements of thecosmic microwave background took place. In total, 29
plenary talks were given. Parallel sessions were held forthe aforementioned listed topics, with up to ﬁve sessions running in parallel. Few sessions were conducted
as joint sessions for multiple topics.
The symposium is hosted by RIKEN Nishina Centerand co-hosted by KEK, J-PARC, RCNP Osaka University, CNS University of Tokyo, and Yamagata University. Moreover, it is supported by RIKEN as a partof the RIKEN Symposium Series, and subsidy system
for international conferences in Matsue and Shimane
Prefecture.
A screenshot of online participants (not all the participants) is shown in Fig. 1. The full program and presentation slides presented in the sypmposim are available at the symposium website (https://indico2.
riken.jp/event/3082/), and the proceedings of the
SPIN2021 symposium will be pulished in the JPS Conference Proceedings.
Reference
1) Y. Goto, RIKEN Accel. Prog. Rep. 54, 197 (2021).

RIKEN Nishina Center- 188 -

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V. EVENTSRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Small-x physics in the electron-ion collider era
Y. Hatta,∗1,∗2 A. Morreale,∗3 F. Salazar,∗4 B. Schenke,∗2 and R. Venugopalan∗2
Understanding the high energy limit of hadronic andnuclear collisions is at the forefront of nuclear and particle physics. When boosted to ultrahigh energies, allhadrons and nuclei eventually transform into a universal form of matter called the Color Glass Condensate(CGC). The CGC is characterized by the high density(saturation) of small-x gluons which leads to distinct
experimental signatures. Tantalizing hints of the CGC
have been observed at HERA, RHIC and the LHC, but
the prospects for the discovery of the CGC are more
promising at future experiments such as the ElectronIon Collider (EIC) at Brookhaven National Laboratory
Indeed, according to the National Science Academy report published in 2019, one of the three major goals of
the EIC is to address the nature of the gluon saturation. (The other two are the mass and spin structureof the nucleons.)
With this in mind, the small-x community is gearing up to meet the challenges of the EIC era. Over the
past several years, there has been impressive progressin the next-to-leading order (NLO) calculations in the
CGC framework of various observables such as single
hadron production in proton-nucleus collisions, inclusive and exclusive dijet and trijet production in Deep
Inelastic Scattering (DIS), jet-plus-photon production
in DIS, etc. We expect that NLO calculations will be
the standard tool to confront future experimental dataat the EIC.
Another emerging trend of the community is the interplay between small-x physics and spin physics. The
RHIC result for the gluon helicity ΔG has underscoredthe necessity to understand the longitudinal spin structure of the proton at small-x. There have been theoretical indications that a signiﬁcant fraction of spinand orbital angular momentum is stored in the smallx region. As for the transversely polarized proton, asurprising new connection between the gluon Sivers
function at small-x and the QCD Odderon has been
pointed out and its implications at the EIC has been
discussed.
On 15–17, December 2021, we have held a 3-day
virtual workshop dedicated to small-x physics in orderto summarize the present status of the ﬁeld describedabove and to discuss future directions. A major focus of this workshop was to identify outstanding problems that could signiﬁcantly beneﬁt from collaborative eﬀorts amongst scientists working on formal, phenomenological, and computational aspects of small-x
physics. The topics covered include:
∗1
∗2
∗3
∗4

What are the best observables of gluon saturation
at the EIC?
• NLO calculations in the CGC• Interplay between spin and small-x• TMD, GPD and Wigner distributions at small-x• Initial conditions (momentum space, coordinate
space, nonperturbative input, . . . )• Hadronization (MC implementation, coupling toexisting event generators, . . . )• Outstanding open problems at small-x requiring
a topical theory collaboration
We have had 102 registered participants and 31 invited talks including 6 experimental talks in a very
interactive atmosphere. The most important outcomeof the workshop is that, after this workshop, the participants have decided to apply for a topical collaboration of the U.S. Department of Energy (DOE). One ofthe organizers, B. Schenke (BNL) is taking a lead in
this initiative and many other workshop participants
who have faculty positions in the U.S. are serving as
co-PIs. The workshop can be therefore regarded as agreat success.

RIKEN BNL Research Center
Physics Department, Brookhaven National Laboratory
Los Alamos National Laboratory
University of California, Los Angeles- 189 -

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V. EVENTSRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN open day 2021
K. Tanaka,∗1 M. Shishido,∗1 Y. Watanabe,∗1 N. Miyauchi,∗1 and A. Akashio∗1
RIKEN open day was held on April 17, 2021. Becauseof the COVID-19 pandemic, open day 2020 was canceled.
In 2021, the open day was held but limited to online only.
Figure 1 shows framework of contents. It was operated
by using Zoom video conference software.1) A breakout
room was assigned to a virtual laboratory which could relay an experimental room in RIKEN to the open day visitors. Nishina Center had two virtual laboratory rooms.
One oﬀers a virtual accelerator tour. The other provides
an introduction of RIBF research and collaborated with
the Center for Nuclear Study at the university of Tokyo(CNS) and the KEK Wako Nuclear Science Center.

the RIBF movie. Six time of tours were performed.
To present an introduction to RIBF research, experiments and researches about ZDS with HIKARI detector,
SAMURAI, SHARAQ by CNS, KISS by KEK, and nuclear chemistry were introduced. Six diﬀerent exhibition
tours were performed. Figure 3 shows a screen shot of
the introduction to the nuclear chemistry presentation.

Fig. 3. Screen shot of an introduction of research of virtuallaboratory.

Fig. 1. Contents for the RIKEN open day.

For the virtual accelerator tour, RIBF movie taken
along to the accelerator and downstream beamline wasshared to visitors. Figure 2 shows the movie shared for
the RIBF tour. SRC, BigRIPS, and SAMURAI were
contained in the movie. Researchers described about
RIBF accelerators and experimental instruments with

Fig. 2. Movie for the RIBF virtual tour.
∗1

RIKEN Nishina Center

Movies for RIKEN laboratories were also exhibited on
the RIKEN web page. Nishina Center released two, ﬁveminute movies. One was introduction to SRC and theother was about the discovery of the 113th element, Nihonium. These videos were shared for a month after the
open day.
RIKEN organized a special lecture and an experiencebased event. Dr. Tomoko Abe gave a special lecture,“Creating novel plants of your dreams using heavy-ion
beams.”She introduced studies about various biological eﬀects
of fast heavy-ions. Ion beams have been used to create
over 35 new varieties in RIKEN in the last two decades
and beneﬁcial mutants have been identiﬁed in various
species.
Nishina Center also presented at the experience-based
event. During a hands-on event for children, participants
made their own handmade spectrometers and used themduring the interactive online class to learn in a fun way
that light is composed of various colors, like a rainbow.
Spectroscope kits were distributed to registered participants in advance.
About 800 participants visited RIKEN open day. The
approximate numbers of visitors in the breakout rooms
for the virtual laboratory of Nishina Center were 200.
Twenty four staﬀ from Nishina Center participated in
the open day.
Reference1) https://zoom.us .

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VI. ORGANIZATION AND ACTIVITIESOF RIKEN NISHINA CENTER(Activities, Members, Publications & Presentations)VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

1. Organization㸧
1.1 Organization Chart as of March 31, 2022 㸦End of FY2021㸧

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

1.2 Topics in FY2021
Year

Date

Topics in Management

2021

Apr. 1

Newly appointed:
Team Leader of RILAC Team: Osamu KAMIGAITO

2021

May 1

Newly appointed:
Group Leader of Theory Gtoup: Yoshitaka HATTA

2021

Oct. 1

Newly appointed:
Director of Nuclear Many-body Theory Laboratory: Masaaki KIMURA

2. Finances
A transition of the RNC budget for the past four years is shown in following graph.
Million Yen

3,500
3,000
2,500
2,000
1,500

2,877

2,646

2,587

2,517

2019

2020

2021

1,000
500
0
2018

3. Staffing
At the start of FY 2021, there were 142 personnel affiliated with RNC and 418 researchers visiting RNC for research purpose. The following
graphs show a breakdown of personnel into six categories as of April 1, 2021, and a transition of the number of each category.

Permanent Researcher

68

Contract Researcher

30

Technical staff

1

Special Postdoctoral Researcher

2418

Junior Research Associate
3

External researcher

FY2021- 192 -

6
15
14

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

600
External researcher

500

Junior Research Associate
400
Special Postdoctoral
Researcher
Technical staff

300

Contract Researcher

200

Permanent Researcher

100
0
2018

2019

2020

2021

 
4. Research publication
The number of papers published annually from RNC is shown graphically using the data obtained from Clarivate Analytics’ Web of Science
Documents.
350

Source Documents

300
250
200
150
100
50
0
2018

2019

2020

2021

Publication Year

Citation analysis for the past four years
As of April 2022
Year
Indicators
Total number of papers

2018

2019

2020

2021

286

301

300

298

Percentage of papers in top 10%

20.63

9.63

12.67

14.1

Percentage of papers in top 1%

4.20

1.00

1.33

3.4

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

5. Management
Headed by the RNC Director Hiroyoshi SAKURAI, the RIKEN Nishina Center for Accelerator-Based Science (RNC) consists of:zzz

9 Laboratories
11 Groups with 27 Teams
2 overseas research centers with 3 Groups

as of the end of FY2021. There are also two 'Partner Institutes' which conduct research in the laboratories set up in RNC. RNC is managed
by its Director who takes into consideration the majority decision of the RNC Coordination Committee. The management of RNC is supportedby the following committees:zzzz

Program Advisory Committee
Safety Review Committee
RIBF Machine Time Committee
Public Relations Committee

There are also committees to support the President of RIKEN and/or the Director of RNC such as:z

Nishina Center Advisory Council with three subcommittees:
࣭RBRC Scientific Review Committee (SRC)࣭International Advisory Committee for the RIKEN-RAL Muon Facility
࣭RBRC Management Steering Committee (MSC)

Nishina Center for Accelerator-based Science
Executive Members (as of March 31, 2022)
Hiroyoshi SAKURAI
Director
Osamu KAMIGAITO
Deputy Director (Research Facility Development Division)
Tomoko ABE
Deputy Director (Accelerator Applications Research Division)
Masahiro IWASAKI
Deputy Director (Subnuclear System Research Division)
Yasushige YANO
Senior Advisor

RNC Coordination Committee
The following subjects relevant to the RNC management are deliberated under the chairmanship of the RNC Director:
z
z
z
z
z

Establishment of the new organization or reorganization in RNC
Personnel management of RNC researchers
Research themes and research budget
Approval of the Partner Institutes
Evaluation of the management of RNC and the response to the recommendations by external evaluation

The RNC Coordination Committee is held monthly.
Members (as of March 31, 2022)
Hiroyoshi SAKURAI
Osamu KAMIGAITO
Tomoko ABE
Masahiko IWASAKI
Yasushige YANOTomohiro UESAKA
Hideki UENO
Toru TAMAGAWA
Emiko HIYAMA
Masaaki KIMURA
Yuko MOTIZUKI
Kosuke MORITA
Hiroki OKUNO
Nobuhisa FUKUNISHI
Masanori WAKASUGIHiromitsu HABA

Director, RNC; Director, Radioactive Isotope Physics Laboratory and Nuclear Transmutation Data Research Group;
Team Leader, Muon Date Team
Deputy Director, RNC; Director, Accelerator Group and High-Intensity Accelerator R&D Group; Team Leader,
RILAC Team
Deputy Director, RNC; Director, Beam Mutagenesis Group; Team Leader, Ion Beam Breeding Team
Deputy Director, RNC; Director, Meson Science Laboratory and Quantum Hadron Physics Laboratory
Senior Advisor, RNC
Director, Spin Isospin Laboratory and Research Instruments Group
Director, Nuclear Spectroscopy Laboratory and User Liaison Group; Team Leader, Outreach Team
Director, High Energy Astrophysics Laboratory
Director, Strangeness Nuclear Physics Laboratory
Director, Nuclear Many-body Theory Laboratory
Director, Astro-Glaciology Research Group
Director, Superheavy Element Research Group
Deputy Group Director, Accelerator Group; Team Leader, Accelerator R&D Team, Cryogenic Technology Team, andHigh-Power Target R&D Team
Deputy Group Director, Accelerator Group; Team Leader, Beam Dynamics & Diagnostics Team
Director, Instrumentation Development Group; Team Leader, Rare RI-Ring Team and SCRIT Team
Director, RI Application Research Group; Team Leader, Nuclear Chemistry Research Team and Superheavy Element
Production Team- 194 -

VI. RNC ACTIVITIESKanenobu TANAKA
Hideaki OTSU
Naruhiko SAKAMOTO
Hiromi SATO
Toshiyuki SUMIKAMA
Takahide NAKAGAWA
Koji MORIMOTO
Atsushi YOSHIDA
Koichi YOSHIDA
Ken-ichiro YONEDA
Hironobu ISHIYAMA
Hidetada BABA
Hiroyuki Ichida
Masanori Kidera
Tsukasa TADA
Hideto EN'YO
Yoshitaka HATTA
Yasuyuki AKIBA
Taku IZUBUCHI
Toshiyuki HASHIMOTO

RIKEN Accel. Prog. Rep. 55 (2022)

Director, Safety Management GroupTeam Leader, SAMURAI Team and Fast RI Data Team
Team Leader, Cyclotron Team and High-Gradient Cavity R&D Team
Team Leader, Detector Team
Team Leader, Slow RI Data Team
Team Leader, Ion Source Team
Team Leader, Superheavy Element Device Development Team
Team Leader, Industrial Application Research Team
Team Leader, BigRIPS Team
Team Leader, RIBF User Liaison Team
Team Leader, SLOWRI Team
Team Leader, Computing and Network Team
Team Leader, Plant Genome Evolution Research Team
Team Leader, Infrastructure Management Team
Vice Chief Scientist, Quantum Hadron Physics Laboratory
Director, RIKEN BNL Research Center; Director, Radiation Laboratory
Group Leader, Theory Group, RIKEN BNL Research Center
Group Leader, Experimental Group, RIKEN BNL Research Center
Group Leader, Computing Group, RIKEN BNL Research Center
Director, Nishina Center and iTHEMS Promotion Office

Program Advisory Committee
The Program Advisory Committee reviews experimental proposals submitted by researchers and reports the approval/disapproval of the
proposals to the RNC Director. The Committee also reports to the RNC Director the available days of operation at RIBF or the Muon
Facility at RAL allocated to researchers. The Committee is divided into three categories according to the research field.
zzz

Nuclear Physics Experiments at RIBF (NP-PAC): academic research in nuclear physics
Materials and Life Science Researches at RNC (ML-PAC): academic research in materials science and life science
Industrial Program Advisory Committee (In-PAC): non-academic research

Program Advisory Committee for Nuclear Physics Experiments at RI Beam Factory (NP-PAC)
The 22nd NP-PAC was held on December 1í3, 2021 via Web meeting.
Members (as of March 31, 2022)
Maria J.G. BORGE (Chair)
Stéphane GREVY
Mahananda DASGUPTA
Jens DILLING
Magdalena GORSKA
Takahiro KAWABATA
Masayuki MATSUO
Remco ZEGERS
Nori AOI
Robert CHARITY
Gabriel MARTINEZ-PINEDO
Iain MOORE
Takehiko SAITOPhilip J. WOODS
Andrea VITTURI
Xiaohong ZHOU

Consejo Superior de Investigaciones Científicas
Centre d'Etudes Nucléaires de Bordeaux Gradignan
The Australian National University
Ork Ridge National Laboratory
GSI Darmstadt
Osaka University
Niigata University
Michigan State University
RCNP, Osaka University
Washington University in St. Louis
Technische Universität Darmstadt, GSI Helmholtzzentrum für Schwerionenforschung
University of Jyväskylä
RIKEN
University of Edinburgh
Universita' di Padova
Chinese Academy of Sciences

Program Advisory Committee for Materials and Life Science Researches at RIKEN Nishina Center (ML-PAC)
The ML-PAC of FY2021 was held between December 13, 2021 and January 20, 2022 via e-mail.
Members (as of March 31, 2022)
Adrian HILLIER (Chair)
Zhi QIN
Toshiyuki TAKAYANAGI
Yoshio KOBAYASHI
Yutaka MIYAZAWA

ISIS, RAL (UK)
Chinese Academy of Sciences (China)
Saitama University
The University of Electro-Communications
Yamagata University

Industrial Program Advisory Committee (In-PAC)
The 17th In-PAC was held on July 7, 2021 via Web meeting.
The 18th In-PAC was held between December 8 and 27, 2021 via e-mail.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Safety Review Committee
The Safety Review Committee is composed of two sub committees, the Safety Review Committee for Accelerator Experiments and the HotLab Safety Review Committee. These Committees review the safety regarding the usage of radiation generating equipment based on the
proposal submitted to the RNC Director from the spokesperson of the approved experiment.
Safety Review Committee for Accelerator Experiments
Members (as of March 31, 2022)
Hiromi SATO (Chair)
Kouji MORIMOTO
Takashi NAGATOMO
Hiromitsu HABA
Atsushi YOSHIDA
Koichi YOSHIDA
Naoki FUKUDA
Naruhiko SAKAMOTO
Daisuke SUZUKI
Masaki SASANO
Shunji NISHIMURATeam Leader, Detector Team
Team Leader, Superheavy Element Device Development Team
Senior Technical Scientist, Ion Source Team
Team Leader, Nuclear Chemistry Reaserach Team
Team Leader, Industrial Application Research Team
Team Leader, BigRIPS TeamTechnical Scientis, BigRIPS Team
Team Leader, Cyclotron Team
Research Scientist, Radioactive Isotope Physics Laboratory
Senior Research Scientist, Spin Isospin Laboratory
Senior Research Scientist, Radioactive Isotope Physics Laboratory

External members
Shinichiro MICHIMASA
Hidetoshi YAMAGUCHI
Yutaka WATANABE

Assistant Professor, Center for Nuclear Study, University of Tokyo
Lecturer, Center for Nuclear Study, University of Tokyo
Associate Professor, High Energy Accelerator Research Organization, KEK

Ex officio members
Kanenobu TANAKA
Hisao SAKAMOTO

Director, Safety Management Group
Technical Scientist, Safety Management Group

Hot-Lab Safety Review Committee
Members (as of March 31, 2022)
Tetsuya OHNISHI (Chair)
Kanenobu TANAKA
Hisao SAKAMOTO
Hiroki MUKAI
Rieko HIGURASHI
Hiromitsu HABA
Kazuya TAKAHASHI

Senior Research Scientist, SCRIT Team
Director, Safety Management Group
Technical Scientist, Safety Management Group
Technical Staff I, Safety Management Group
Technical Scientist, Safety Management GroupTeam Leader, Nuclear Chemistry Research TeamSpecial Temporary Research Scientist, Nuclear Chemistry Research TeamRIBF Machine Time Committee
Upon request of the RNC Director, the RIBF Machine Time Committee deliberates on the machine time schedule of RIBF and reports theresults to the Director.
Members (as of March 31, 2022)
Hideki UENO (Chair)
Osamu KAMIGAITO
Masanori WAKASUGITomohiro UESAKA
Nobuhisa FUKUNISHI
Hiroki OKUNO
Shunji NISHIMURA
Tomoko ABE
Hiromitsu HABA
Kanenobu TANAKA
Ken-ichiro YONEDA
Kouji MORIMOTO
Koichi YOSHIDA

Director, User Liaison Group and Nuclear Spectroscopy Laboratory
Director, High-Intensity Accelerator R&D Group and Accelerator Group
Director, Instrumentation Development Group
Director, Research Instruments Group and Spin Isospin Laboratory
Deputy Group Director, Accelerator Group
Deputy Group Director, Accelerator Group
Senior Research Scientist, Radioactive Isotope Physics Laboratory
Director, Beam Mutagenesis Group
Director, RI Application Research Group
Director, Safety Management GroupTeam Leader, RIBF User Liaison Team
Team Leader, Superheavy Element Device Development Team
Team Leader, BigRIPS Team

External members
Kentaro YAKO
Hidetoshi YAMAGUCHI
Yutaka WATANABE

Associate Professor, Center for Nuclear Study, University of Tokyo
Lecturer, Center for Nuclear Study, University of Tokyo
Associate Professor, High Energy Accelerator Research Organization, KEK- 196 -

VI. RNC ACTIVITIES

Observers
Hiroyoshi SAKURAI
Susumu SHIMOURA
Michiharu WADA
Hiroari MIYATAKE
Daisuke SUZUKI
Kosuke MORITA
Tohru MOTOBAYASHI
Hideyuki SAKAI
Yasuhiro SAKEMI
Hideaki OTSU
Atsushi YOSHIDA
Hironobu ISHIYAMA
Toshiyuki HASHIMOTO
Soh OSUKA

RIKEN Accel. Prog. Rep. 55 (2022)

Director, RNC; Director, Radioactive Isotope Physics Laboratory and Nuclear Transmutation Data Research Group;
Team Leader, Muon Data Team
Director, Center for Nuclear Study, University of Tokyo
Director, KEK Wako Nuclear Science Center
Professor, High Energy Accelerator Research Organization, KEK
Chair, The RIBF Users Executive Committee (RIBF-UEC), Research Scientist, Radioactive Isotope Physics
Laboratory
Director, Superheavy Element Research Group
Senior Advisor, RNC
Senior Advisor, RNC
Professor, Center for Nuclear Study, University of Tokyo
Team Leader, Fast RI Data Team and SAMURAI Team
Team Leader, Industrial Application Research Team
Team Leader, SLOWRI Team
Director, Nishina Center and iTHEMS Promotion Office
Manager, Nishina Center and iTHEMS Promotion OfficePublic Relations Committee
Upon request of the RNC Director, the Public Relations Committee deliberates and coordinates the following matters:zzzCreating public relations system for RNC
Prioritization of the public relations activities for RNC
Other general and important matters concerning the public relations of RNC

Members (as of March 31, 2022)
Toshiyuki HASHIMOTO (Chair) Director, Nishina Center and iTHEMS Promotion OfficeOsamu KAMIGAITO
Deputy Director, RNC; Director, Accelerator Group
Tomoko ABE
Deputy Director, RNC; Director, Beam Mutagenesis Group
Masahiko IWASAKI
Deputy Director, RNC; Director, Meson Science Laboratory
Tomohiro UESAKA
Director, Spin Isospin Laboratory and Research Instruments Group
Hideki UENO
Director, Nuclear Spectroscopy Laboratory and User Liaison Group
Yuko MOTIZUKI
Director, Astro-Glaciology Research Group
Narumasa MIYAUCHITechnical Staff I, Outreach Team
Yasushi WATANABE
Special Temporary Research Scientist, Outreach Team
Motohide YOKOTA
Coordinator, Office of the Center Director

RBRC Management Steering Committee (MSC)
RBRC MSC is set up according to the Memorandum of Understanding between RIKEN and BNL concerning the collaboration on the Spin
Physics Program at the Relativistic Heavy Ion Collider (RHIC). The 28th MSC was held on May 26, 2021.
Members (as of March 31, 2022)
Shigeo KOYASU
Hiroyoshi SAKURAI
Shoji NAGAMIYA
Robert TRIBBLE
Dmitori DENISOVHaiyan GAO

Executive Director, RIKEN
Director, RNC; Director, Radioactive Isotope Physics Laboratory and Nuclear Transmutation Data Research Group;
Team Leader, Muon Data Team
Senior Visiting Scientist, RNC
Deputy Director for Science and Technology, BNL
Deputy Associate Laboratory Director for High Energy Physics, BNL
Associate Laboratory Director for Nuclear and Particle Physics, BNL- 197 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

6. International Collaboration (as of March 31, 2022)

Country

Partner InstituteObjects

RNC contact person

Austria

Stefan Meyer Institute forSubatomic Physics

Framework

Masahiko IWASAKI, Director, Meson Science
Laboratory

China

China Nuclear Physics Society

Creation of the council for China -Japan
research collaboration on nuclear physics

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

Peking University

Nuclear Science

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

Institute of Modern Physics,
Chinese Academy of Science

Physics of heavy ions

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

School of Nuclear Science andTechnology, Lanzhou University

Framework

Masahiko IWASAKI, Director, Meson Science
Laboratory

School of Physics, Nanjing
University

Framework

Emiko HIYAMA, Director, Strangeness Nuclear
Physics Laboratory

Department of Physics, Faculty of
Science, The University of Hong
Kong

Experimental and educational researchcollaboration in experimental nuclear physics

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

School of physics, Nankai
University

Framework

Emiko HIYAMA, Director, Strangeness Nuclear
Physics Laboratory

School of Physical Sciences,
USTC

Framework

Masahiko IWASAKI, Director, Meson Science
Laboratory

Finland

University of Jyvaskyla

Basic nuclear physics and related
instrumentation

Hironobu ISHIYAMA, Team Leader, SLOWRITeamFranceNational Institute of Nuclear
Physics and Particle Physics(IN2P3)

Physics of heavy ions

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

Normandy University

Framework

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

Commissariat à l'énergie
atomique et aux énergies
alternatives (CEA, French
Alternative Energies and Atomic
Energy Commission)•Direction
des Sciences de la Matière (DSM)

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

The Institut National de Physique
Nucléaire et de Physique desParticules CNRS (CNRS/IN2P3)

Experiments with NEBULA-Plus array

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

GSI

Physics of heavy ions and accelerator

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

Department of Physics,
Technische Universität Darmstadt

Framework

Emiko HIYAMA, Director, Strangeness Nuclear
Physics Laboratory

Hungary

The Institute of Nuclear Researchof the Hungarian Academy of
Sciences (ATOMKI)

Nuclear physics, Atomic Physics

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

Indonesia

ITB, UNPAD, ITS, UGM, UI

Material science using muons at the RIKENRAL muon facility

Masahiko IWASAKI, Director, Meson Science
Laboratory

Hasanuddin University

Agricultural science and related fields
involving heavy-ion beam mutagenesis using
Indonesian crops

Tomoko ABE, Director, Beam Mutagenesis Group

National Agency for New
Technologies, Energy and theEnvironment (ENEA)

Framework

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

European Center for Theoretical
Studies in Nuclear Physics andRelated Areas (ECT*)

Theoretical physics

Masaaki KIMURA Director, Nuclear Many-body
Theory Laboratory

Germany

Italy- 198 -

VI. RNC ACTIVITIESCountry

Partner Institute

Italy

Istituto Nazionale
Nucleare (INFN)

Korea

RIKEN Accel. Prog. Rep. 55 (2022)

Objects

RNC contact person

Physics of heavy ions

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

College of Natural Science, Seoul
National University

Nishina School

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

College of Natural Science, Ewha
Women’s University

Framework

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

College of Natural Sciences,
INHA University

Framework

Emiko HIYAMA, Director, Strangeness Nuclear
Physics Laboratory

Malaysia

Universiti Sains Malaysia

Muon Science

Masahiko IWASAKI, Director, Meson Science
Laboratory

NorwayFaculty of Mathematics andNatural Science, University ofOslo䠄UiO MN䠅Framework

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

PolandThe Henryk Niewodniczanski
Institute of Nuclear
Physics, Polish Academy of
Sciences (IFPAN)

Framework

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

Romania“Horia Hulubei” National
Institute of Physics and Nuclear
Engineering Bucharest-Magurele,
Romania

Framework

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

University of Bucharest

Framework

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

Joint Institute for Nuclear
Research (JINR)

Framework

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

Russian Research Center“Kurchatov Institute”

Framework

Hiroyoshi SAKURAI, Director, Radioactive Isotope
Physics Laboratory

Switzerland

Paul Scherrer InstituteImprove the performance and reliability ofaccelerator systems

Osamu KAMIGAITO, Director, Accelerator Group

TaiwanTaiwan Instrumentation Detector
Consortium䠄TIDC)

Framework

Itaru Nakagawa, Senior Research Scientist,
Radiation Laboratory

USA

Brookhaven National Laboratory

Framework

Hideto EN’YO, Director, Radiation Laboratory

Columbia University

The development of QCDCQ

Hideto EN’YO, Director, Radiation Laboratory

Michigan State University

Comprehensive
The use of TPC (Time Projection Chamber)

Tomohiro UESAKA, Director, Spin Isospin
Laboratory

UK

UK Research Innovation

Framework

Masahiko IWASAKI, Director, Meson Science
Laboratory

VietnamVietnam Atomic Energy
Commission

Framework

EuropeThe European Organization for
Nuclear Research (CERN)

R&D and application of micro-pattern gas
detectors (MPGD) technology (RD51
Collaboration)

Hideto EN’YO, Director, Radiation Laboratory

The European Organization for
Nuclear Research (CERN)

Collaboration in the ALICE Experiment

Hideto EN’YO, Director, Radiation Laboratory

Russiadi

Fisica7. Awards

Awardee, Laboratory / Team
Masaomi TANAKA, Special Postdoctoral Researcher at
the Radioactive Isotope Physics Laboratory

Award
RIBF Users Group Thesis Awards
2021- 199 -

Organization

RIBF USER GROUP

DateAug. 6

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Tomoko ABE, Director of the Beam Mutagenesis Group

Outstanding Presentation Award

Carbon Recycling Fund Institute(CRF)

Sep. 7

Tomoko ABE, Director of the Beam Mutagenesis Group

Women in PlantMutation Breeding
Award

International Atomic Energy Agency(IAEA)

Sep. 20

Akira HIRAYAMA, Student Trainee at the Quantum
Hadron Physics Laboratory

The Student Presentation Award

The Physical Society of Japan (JPS)

Oct. 9Junki TANAKA, Postdoctoral Researcher at the Spin
Isospin Laboratory

The 16th Young Scientist Award of
the Physical Society of Japan for 2022
(the 28th KAKUDAN Best NewcomerAward)The Physical Society of Japan (JPS)

Oct. 21

Kenta SUGIHARA, Junior Research Associate at the
Safety Management Group

The Poster Presentation Award at the2021 Symposium on Nuclear Data

Nuclear Data Division Atomic Energy
Society of Japan

Nov. 18

Kanenobu TANAKA, Director of the Safety ManagementGroup

The Poster Presentation Award at the2021 Symposium on Nuclear Data

Nuclear Data Division Atomic Energy
Society of Japan

Nov. 18

Nobuhiro SHIGYO, Visiting Scientist at the Safety
Management Group

The Poster Presentation Award at the2021 Symposium on Nuclear Data

Nuclear Data Division Atomic Energy
Society of Japan

Nov. 18

Toshiya SANAMI, Visiting Scientist at the Safety
Management Group

The Poster Presentation Award at the2021 Symposium on Nuclear Data

Nuclear Data Division Atomic Energy
Society of Japan

Nov. 18

Ryo TANIUCHI, Visiting Scientist at the Radioactive
Isotope Physics Laboratory

The 38th Inoue Research Award forYoung Scientist (2022)

Inoue Foundation for Science

Dec. 13Tokuro FUKUI, Special Postdoctoral Researcher at theStrangeness Nuclear Physics Laboratory

The 16th Young Scientist Award of
the Physical Society of Japan for 2022
(the 23rd Best Paper Award in
Nuclear Theory)

The Physical Society of Japan (JPS)

Mar.15

Award

Laboratory

Date

8. RIKEN Awards

AwardeeMomo MUKAI

Ohbu Award 䠄ᱜ⯙㈹䠅
The 13th RIKEN Researcher Incentive
Awards 䠄◊✲ዡບ㈹䠅

Nuclear Spectroscopy Laboratory

Mar. 23

Minori TAJIMA

Ohbu Award 䠄ᱜ⯙㈹䠅
The 13th RIKEN Technician Incentive
Awards 䠄ᢏ⾡ዡບ㈹䠅

Nuclear Spectroscopy Laboratory

Mar. 23

Tsuneizumi KAZUHIDE, Mieko YAMADA, Katsunori
ICHINOSE, and Tomoko ABE

Eiho Award 䠄ᰤᓠ㈹䠅

Ion Beam Breeding Team

Mar. 23

Junki TANAKA

Baiho Award 䠄ᱵᓠ㈹䠅

Spin isospin Laboratory

Mar. 23

Tadaaki ISOBE

Baiho Award 䠄ᱵᓠ㈹䠅

Radioactive Isotope Physics
Laboratory

Mar. 23- 200 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

9. Brief overview of the RI Beam Factory
Intensity of Primary Beams

History of Beam Intensity Upgrade

Beamtime for experiments

SRC/BigRIPS-based experiments- 201 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Activities of The Center Director
Meeting Attendance as Ex Oﬃcio
International Meetings[NuPECC associate member]∗ September 17–18, 2021, online.
∗ January 14–15, 2022, online, Belgium, hybrid.
[IUPAP WG9]
∗ June 10–11, 2021 on-line.
Domestic Meetings[核物理委員会]
仁科センター報告，オンライン，2021 年 6 月 9 日.
仁科センター報告，オンライン，2021 年 9 月 15 日.
仁科センター報告，オンライン，2021 年 12 月 23 日.
仁科センター報告，オンライン，2022 年 3 月 16 日.

List of Publications & Presentations
Presentations[International Conferences/Workshops]
H. Sakurai (invited), “RIKEN Nishina Center,” IEEE Nuclear Science Symposium, Online, October 22, 2021.
H. Sakurai (invited), “Research activities in nuclear physics and engineering with RIBF,” 14th Vietnam Conference on Nuclear Scienceand Technology (VINANST-14), Hanoi, Vietnam, Hybrid, December 9–10, 2021.
H. Sakurai (invited), “RI Beam Factory,” RIKEN-Europe Symposium 2022 “Sustainable research infrastructure for a sustainable world,”
Online, Feburary 22, 2022.
H. Sakurai (invited), “Rare isotope science,” 15th Canada-Japan Joint committee on Science and Technology, Online, March 14–15, 2022.

[Domestic Conferences/Workshops]
櫻井博儀（招待講演）, 「理研 RIBF 高度化計画の最新情報」, 先端加速器科学技術推進協議会第 67 回技術部会, 2021 年 10 月 7 日.
櫻井博儀（招待講演）, 「元素を自在に変換する重イオンビームと関連技術」, 第 9 回理研イノベーションセミナー, 2022 年 1 月
21 日.
櫻井博儀（招待講演）, 「重イオン加速器を利用して世界人類の問題に挑む」, 第 35 回理化学研究所と産業界との交流会, 2022 年 3月 10 日.

- 203 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Radioactive Isotope Physics Laboratory
1. Abstract
This Laboratory works as one of core research groups conducting programs at the world-premiere heavy-ion accelerator facilityof RIKEN “RI Beam Factory (RIBF).” The Laboratory explores exotic nuclear structures and dynamics in exotic nuclei that havenever been investigated before, such as those with largely imbalanced proton and neutron numbers. Our aim is to develop new
experimental techniques utilizing fast radioactive isotope (RI) beams at RIBF, to discover new phenomena and properties in exotic
nuclei. The Laboratory is focusing three major subjects; shell evolution of very neutron-rich nuclei, the r-process path and equationof-state in asymmetric nuclear matter. The Laboratory has initiated international collaborations for in-beam gamma spectroscopy,
decay spectroscopy and heavy-ion induced reactions, and has formed a discussion forum for next generation gamma-ray detectors.

2. Major Research Subjects(1) Study of structure and dynamics of exotic nuclei through developments of new tools in terms of reaction- and technique-based
methodology(2) Research on EOS in asymmetric nuclear matter via heavy-ion induced reactions(3) Detector developments for spectroscopy and reaction studies

3. Summary of Research Activity(1) In-beam gamma spectroscopy
In the medium and heavy mass region explored at RIBF, collective natures of nuclei are one of important subjects, which are
obtained through production and observation of high excited and high spin states. To populate such states, heavy-ion induced reactions
such as fragmentation, ﬁssion are useful. So far, we have developed two-step fragmentation method as an eﬃcient method to identify
and populate excited states, and lifetime measurements to deduce transition strength.
Devices utilized for the in-beam gamma spectroscopy are ZeroDegree Spectrometer (ZDS) and a NaI array DALI2. Since the endof 2008, the ﬁrst spectroscopy on nuclei island-of-inversion region was performed, we have explored step-by-step new and unknown
regions in the nuclear chart. The second campaign in 2009 was organized to study background components originating from atomic
processes in a heavy target. Neutron-rich nuclei at N = 20 to 28 were studied in 2010. In 2011–2013, we conducted experiment
programs for Ca-54, Ni-78, neutron-rich nuclei at N = 82 and neutron-deﬁcient nuclei at Z = 50.
A multitude of data obtained with inelastic, nucleon knock-out, fragmentation channels have been analyzed and published. In
2011–2013, collective natures of Mg-36, 38 and Si-42 were both published in PRL. Excited states ﬁrstly observed in Ca-54 werereported in Nature to demonstrate a new nuclear magic number of 34. Fragmentation reaction has been found eﬃcient for nuclei
with A > 100 and low-lying excited state in Pd-126 has been successfully observed and reported in PRC. In 2019, results of the ﬁrst
spectrosocpy of 40 Mg was published in PRL, to demonstrate the exotic structure which is very diﬀerent from in other neutron-rich Mg
isotopes.
To further strengthen the in-beam gamma spectroscopy at RIBF, we have proposed a new setup of MINOS + DALI2 to search
for the 1st excited states in even-even neutron-rich nuclei with Z ∼ 20 to 40. The program was submitted to the PAC 2013 as a
new category of proposal, “proposal for scientiﬁc program” and was S-ranked. A dedicated collaboration “SEASTAR” has been
established as a subset of in-beam gamma collaboration “SUNFLOWER.” The three campaigns were organized in 2014, 2015 and2017 to study very neutron-rich isotopes, and were very productive to access very neutron-rich nuclei such as Ar-52, Ca-56, Ni-78,
Kr-100, Zr-110. In 2019, the result of the ﬁrst spectroscopy of Ni-78 was published in Nature.
A new project of high resolution gamma spectroscopy with fast beams “HiCARI” has been proposed at PAC 2018. MINIBALL
and several Ge tracking detectors from Japan, Europe, the USA and Korea are being combined to form an array of germanium
detectors. The new setup aims to accelerate researches of the nuclear structure by observing gamma-lines in even-odd nuclei andmeasuring lifetimes of excited states. The two workshops were organized in 2019, and the machine time of 43.5 days in total wasapproved at PAC 2019. A part of the HiCARI programs was successfully conducted in 2020 and 2021.
Concerning a next generation detector, a discussion forum has been established to write up a white paper on tracking germanium
detectors and high-eﬃcient crystal detectors such LaBr3 and GAGG.
(2) Decay spectroscopy
Beta- and isomer-spectroscopy is an eﬃcient method for studying nuclear structure, especially for non-yrast levels. We had
accumulated experimental techniques at the RIPS facility to investigate nuclear structure in light mass region via beta-gamma andbeta-p coincidence. Concerning the medium and heavy mass region available at RIBF, we have developed two position-sensitive
active-stoppers, strip-silicon detectors and a cylindrical active stopper called CAITEN, to achieve a low-background measurement by
taking correlation between heavy ion stop position and beta-ray emission position. A site of decay-spectroscopy at the new facility of
RIBF is the ﬁnal focal plane of ZDS, where high precision of TOF in particle identiﬁcation is obtained due to a long ﬂight path fromBigRIPS to ZDS.
At the end of 2009, the ﬁrst decay spectroscopy was organized with a minimum setup of four clover gamma detectors and silicon
strip detectors, to study neutron-rich nuclei with A ∼ 110. The ﬁrst campaign was found successful and eﬃcient to publish four
letter articles in 2011, two PRL’s and two PLB’s. One of the PRL papers is associated to the r-process path where half-lives for 18- 205 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

neutron-rich nuclei were determined for the ﬁrst time. The other PRL paper reported a ﬁnding of deformed magic number 64 in the
Zr isotopes.
The success of the ﬁrst decay-spectroscopy campaign stimulated to form a new large-scale collaboration “EURICA,” where a
twelve Euroball cluster array is coupled with the silicon-strip detectors to enhance gamma eﬃciency by a factor of 10. A construction
proposal of “EURICA” was approved in the PAC 2011, and the commissioning was successfully organized in spring 2012. Since
then, physics runs had been conducted for programs approved to survey nuclei of interest as many as possible, such as Ni-78, Pd-128,
Sn-100. The EURICA collaboration ﬁnished its physics programs in summer 2016. So far, 54 papers including 14 PRL’s and 13
PLB’s were published. One of the highlights is discovery of a seniority isomer in Pd-128, of which cascade gamma decay gives theenergy of ﬁrst excited state and robustness of N = 82 magic number, and the other is a half-life measurement for 110 neutron-richnuclei across the N = 82 shell gap, which shows implications for the mechanism and universality of the r-process path.
Beta-delayed neutron emission probability of medium and heavy neutron-rich nuclei is important to understand nuclear structure
and the r-process path. In 2013, a new collaboration “BRIKEN” has been established to form a He-3 detector array. A present
design of the array has neutron eﬃciency as high as 70% up to 3 MeV. The array was coupled with the AIDA silicon strip system. A
construction proposal was approved at the PAC 2013 and three physics proposals have been approved. The commissioning run was
conducted in autumn 2016. The major physics runs were conducted in 2017–2021.
A new project “IDATEN” has been launched in 2021 to measure lifetime of excited states with a large size LaBr3 array, which
is formed by combination of FATIMA and Khala arrays. The construction proposal was submitted to PAC, 2021, and proposals with
IDATEN will be evaluated at PAC, 2022.
The CAITEN detector was successfully tested with fragments produced with a Ca-48 beam in 2010.
(3) Equation-of-state via heavy-ion central collisions
Equation-of-state in asymmetric nuclear matter is one of major subjects in physics of exotic nuclei. Pi-plus and pi-minus yields
in central heavy ion collisions at the RIBF energy are considered as one of EOS sensitive observables at the RIBF energy. To observecharged pions, a TPC for the SAMURAI spectrometer is being constructed under an international collaboration “SπRIT,” Construction
proposal was submitted at the PAC 2012, and physics proposals were approved at the PAC 2012 and 2013. The physics runs weresuccessfully conducted in spring 2016. The ﬁrst three papers were published in 2020 and 2021. One of them has been ranked as theTOP 1% paper by WoS in 2021.
An international symposium “NuSYM” on nuclear symmetry energy was organized at RIKEN July 2010 to invite researchers
in three sub-ﬁelds, nuclear structure, nuclear reaction and nuclear astrophysics, and to discuss nuclear symmetry energy together.
Since then, the symposium series have been held every year and been useful to encourage theoretical works and to strengthen thecollaboration.
(4) Nucleon correlation and cluster in nuclei
Nucleon correlation and cluster in nuclei are matters of central focus in a “beyond mean-ﬁeld” picture. The relevant programswith in-beam gamma and missing-mass techniques are to depict nucleon condensations and correlations in nuclear media as a functionof density as well as temperature. Neutron-halo and -skin nuclei are objects to study dilute neutron matter at the surface. By changing
excitation energies in neutron-rich nuclei, clustering phenomena and role of neutrons are to be investigated.
In 2013, two programs were conducted at the SAMURAI spectrometer. One is related to proton-neutron correlation in the C-12
nucleus via p-n knockout reaction with a carbon target. The other is to search for a cluster state in C-16, which was populated via
inelastic alpha scattering. The data is being analyzed.
In 2018, a new project based on missing mass spectroscopy was launched to investigate an exotic cluster state in a very protonrich nucleus. The experiment was organized at GANIL with combination of RIKEN liquid hydrogen target CRYPTA and the MUST2
detector array in 2018.

Members
Director
Hiroyoshi SAKURAI
Research/Technical Scientists
Pieter Christiaan DOORNENBAL (Senior Research Scientist)
Tadaaki ISOBE (Senior Research Scientist)
Akihisa KOHAMA (Senior Research Scientist)

Yoichi NAKAI (Senior Research Scientist)
Shunji NISHIMURA (Senior Research Scientist)
Daisuke SUZUKI (Research Scientist)

Contract Researcher
Nobuya NISHIMURA
Special Postdoctoral ResearchersFrank BROWNE

Masaomi TANAKA- 206 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Postdoctoral Researchers
Phong VI

Zuxing YANG

Junior Research Associate
Takuma KOIWAI (Univ. of Tokyo)
International Program Associate
Jinn Ming YAP (Univ. of Hong Kong)
Special Temporary Research Scientist
Takashi ICHIHARA
Research Consultants
Masayasu ISHIHARA
Kenichi MATSUYANAGI

Hiroyuki MURAKAMI

Senior Visiting Scientists
Koichiro ASAHI (Tokyo Tech)
Shigeru KUBONO (Univ. of Tokyo)

Tetsuya MURAKAMI

Visiting Scientists
Nori AOI (Osaka Univ.)Frank BROWNE (CERN)
Hue BUI (Vietnam Academy of Sci. and Tech.)
Giordano CERIZZA (Michigan State Univ.)
Silvio CHERUBINI (Univ. of Catania)
Martha Liliana CORTES SUA (TU Darmstadt)
Mitsunori FUKUDA (Osaka Univ.)
Byungsik HONG (Korea Univ.)
Kei IIDA (Kochi Univ.)
Natsumi IKENO (Tottori Univ.)
Takuji IZUMIKAWA (Niigata Univ.)
Takashi KISHIDA (Aoyama Gakuin Univ.)
Gabor KISS (ATOMKI)
Khiem LE (Vietnam Academy of Sci. and Tech.)
Giuseppe LORUSSO (Nat’l Phys. Lab.)
Byul MOON (IBS)
Yoshiharu MORI (Kyoto Univ.)

Megumi NIIKURA (Univ. of Tokyo)
Evgueni NIKOLSKI (Kurchatov Inst.)
Daiki NISHIMURA (Tokyo City Univ.)
Takashi OHTSUBO (Niigata Univ.)
Akira ONO (Tohoku Univ.)
Naohiko OTSUKA (IAEA)
Kazuhiro OYAMATSU (Aichi Shukutoku Univ.)
Clementine Angelique Marie-Th SANTAMARIA (Berkeley
Lab)
Paer-Anders SOEDERSTROEM (IFIN-HH)
Ryo TANIUCHI (Univ. of York)Rensheng WANG (Soochow Univ.)
Hiroshi WATANABE (Beihang Univ.)
Kathrin WIMMER (GSI)
Jin WU (Argonne Nat’l Lab.)
Yasutaka YAMAMOTO (Osaka Univ.)

Visiting Technicians
Hilde DE WITTE (KU Leuven)

Herbert E. HESS (Univ. of Cologne)

Student Trainees
Takamichi AOKI (Univ. of Tokyo)
Linh BUI (Vietnam Atomic Energy Inst.)
Richard CRANE (Univ. of York)Miki FUKUTOME (Osaka Univ.)
Yumo INADA (Univ. of Tokyo))
Satoko IWAZAKI (Osaka Univ.)
Jiseok KIM (Korea Univ.)
Asahi KOHDA (Osaka Univ.)
Takuma KOIWAI (Univ. of Tokyo)
Kei KOKUBUN (Univ. of Tokyo)
Haruo KONDO (Univ. of Tokyo)
Jung Woo LEE (Korea Univ.)
Rurie MIZUNO (Univ. of Tokyo)

Nurhaﬁza MOHAMAD NOR (Osaka Univ.)
Norihide NOGUCHI (Niigata Univ.)
Thomas PARRY (Univ. of Surrey)
Takeshi SAITO (Univ. of Tokyo)
Sora SUGAWARA (Tokyo City Univ.)
Ryo TAGUCHI (Osaka Univ.)
Hiroyuki TAKAHASHI (Tokyo City Univ.)
Gen TAKAYAMA (Osaka Univ.)
Hidaka TANABE (Tsukuba Univ.)
Chun Yuen TSANG (Michigan State Univ.)
Chiaki UNE (Tokyo City Univ.)
Shu YAMAMURA (Univ. of Tokyo)
Tik Tsun YEUNG (Univ. of Tokyo)

Part-time Workers
Kiyomi ARAI (Research Part-time Worker I)
Mie DOI (Research Part-time Worker I)
Masanori KANEKO (Research Part-time Worker I)
Miki KANOU (Research Part-time Worker I)
Eiko MIZUMOTO (Research Part-time Worker I)

Noriko OKAYASU (Research Part-time Worker I)
Tsuneyo SUZUKI (Research Part-time Worker I)
Mayumi SAITO (Research Part-time Worker II)
Miyuki TAMABAYASHI (Research Part-time Worker II)- 207 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

List of Publications & Presentations
Publications[Original Papers]
R. -B. Gerst, A. Blazhev, K. Moschner, P. Doornenbal, A. Obertelli, K. Nomura, J. -P. Ebran, S. Hilaire, J. Libert, G. Authelet, H. Baba,
D. Calvet, F. Chateau, S. Chen, A. Corsi, A. Delbart, J. -M. Gheller, A. Giganon, A. Gillibert, V. Lapoux, T. Motobayashi, M. Niikura,
N. Paul, J. -Y. Rousse, H. Sakurai, C. Santamaria, D. Steppenbeck, R. Taniuchi, T. Uesaka, T. Ando, T. Arici, F. Browne, A. M. Bruce,
R. Caroll, L. X. Chung, M. L. Cortes, M. Dewald, B. Ding, F. Flavigny, S. Franchoo, M. Gorska, A. Gottardo, J. Jolie, A. Jungclaus,
J. Lee, M. Lettmann, B. D. Linh, J. Liu, Z. Liu, C. Lizarazo, S. Momiyama, S. Nagamine, N. Nakatsuka, C. R. Nita, C. Nobs, L. Olivier,R. Orlandi, Z. Patel, Zs. Podolyak, M. Rudigier, T. Saito, C. Shand, P. -A. Soderstrom, I. Stefan, V. Vaquero, V. Werner, K. Wimmer,
and Z. Xu, “γ-ray spectroscopy of low-lying yrast and non-yrast states in neutron-rich 94, 95, 96 Kr,” Phys. Rev. C 105, 024302 (2022).
S. Kim, J. Hwang, Y. Satou, N. A. Orr, T. Nakamura, Y. Kondo, J. Gibelin, N. L. Achouri, T. Aumann, H. Baba, F. Delaunay, P. Doornenbal, N. Fukuda, N. Inabe, T. Isobe, D. Kameda, D. Kanno, N. Kobayashi, T. Kobayashi, T. Kubo, S. Leblond, J. Lee, F. M. Marques,
R. Minakata, T. Motobayashi, D. Murai, T. Murakami, K. Muto, T. Nakashima, N. Nakatsuka, A. Navin, S. Nishi, S. Ogoshi, H. Otsu,
H. Sato, Y. Shimizu, H. Suzuki, K. Takahashi, H. Takeda, S. Takeuchi, R. Tanaka, Y. Togano, A. G. Tuﬀ, M. Vandebrouck, and
K. -I. Yoneda, “Spectroscopy of 17 C above the neutron separation energy,” Few-Body Syst. 63, 21 (2022).
T. Koiwai, K. Wimmer, P. Doornenbal, A. Obertelli, C. Barbieri, T. Duguet, J. D. Holt, T. Miyagi, P. Navratil, K. Ogata, N. Shimizu,
V. Soma, Y. Utsuno, K. Yoshida, N. L. Achouri, H. Baba, F. Browne, D. Calvet, F. Chateau, S. Chen, N. Chiga, A. Corsi, M. L. Cortes,
A. Delbart, J. -M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H. N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y. L. Sun, Y. Togano,
T. Uesaka, K. Yoneda, O. Aktas, T. Aumann, L. X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R. -B. Gerst, J. Gibelin, K. I. Hahn,
D. Kim, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B. D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S. Y. Park,D. Rossi, E. Sahin, P. -A. Soderstrom, D. Sohler, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu,
H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti, “A ﬁrst glimpse at the shell structure beyond 54 Ca: Spectroscopy of 55 K, 55 Ca,
and 57 Ca,” Phys. Lett. B 827, 136953 (2022).
B. Le Crom, M. Assie, Y. Blumenfeld, J. Guillot, H. Sagawa, T. Suzuki, M. Honma, N. L. Achouri, B. Bastin, R. Borcea, W. N. Catford,
E. Clement, L. Caceres, M. Caamano, A. Corsi, G. De France, F. Delaunay, N. De Sereville, B. Fernandez-Dominguez, M. Fisichella,
S. Franchoo, A. Georgiadou, J. Gibelin, A. Gillibert, F. Hammache, O. Kamalou, A. Knapton, V. Lapoux, S. Leblond, A. O. Macchiavelli, F. M. Marques, A. Matta, L. Menager, P. Morfouace, N. A. Orr, J. Pancin, X. Pereira-Lopez, L. Perrot, J. Piot, E. Pollacco, D. Ramos, T. Roger, F. Rotaru, A. M. Sanchez-Benitez, M. Senoville, O. Sorlin, M. Stanoiu, I. Stefan, C. Stodel, D. Suzuki,
J. -C. Thomas, and M. Vandebrouck, “Neutron-proton pairing in the N = Z radioactive fp-shell nuclei 56 Ni and 52 Fe probed by pairtransfer,” Phys. Lett. B 829, 137057 (2022).
W. P. Liu, Z. H. Li, J. J. He, X. D. Tang, G. Lian, J. Su, Y. P. Shen, Z. An, F. Q. Chao, J. J. Chang, L. H. Chen, H. Chen, X. J. Chen,
Y. H. Chen, Z. J. Chen, B. Q. Cui, X. C. Du, X. Fang, C. B. Fu, L. Gan, B. Guo, Z. Y. Han, X. Y. Guo, G. Z. He, J. R. He, A. Heger,
S. Q. Hou, H. X. Huang, N. Huang, B. L. Jia, L. Y. Jiang, S. Kubono, J. M. Li, M. C. Li, K. A. Li, E. T. Li, T. Li, Y. J. Li, M. Lugaro,
X. B. Luo, H. Y. Ma, S. B. Ma, D. M. Mei, W. Nan, W. K. Nan, N. C. Qi, Y. Z. Qian, J. C. Qin, J. Ren, C. S. Shang, L. T. Sun, W. L. Sun,
W. P. Tan, I. Tanihata, S. Wang, P. Wang, Y. B. Wang, Q. Wu, S. W. Xu, S. Q. Yan, L. T. Yang, Y. Yang, X. Q. Yu, Q. Yue, S. Zeng,
L. Zhang, H. Zhang, H. Y. Zhang, L. Y. Zhang, N. T. Zhang, P. Zhang, Q. W. Zhang, T. Zhang, X. P. Zhang, X. Z. Zhang, W. Zhao,
J. F. Zhou, and Y. Zho, “Progress of underground nuclear astrophysics experiment JUNA in China,” Few-Body Syst. 63, 43 (2022).
B. Moon, A. Gargano, H. Naidja, C. -B. Moon, A. Odahara, R. Lozeva, S. Nishimura, C. Yuan, F. Browne, P. Doornenbal, G. Lorusso,
Z. Patel, S. Rice, M. Si, L. Sinclair, P. -A. Soderstrom, T. Sumikama, H. Watanabe, J. Wu, Z. Y. Xu, A. Yagi, D. S. Ahn, H. Baba,
F. L. Bello Garrote, R. Daido, J. M. Daugas, F. Didierjean, Y. Fang, N. Fukuda, B. Hong, E. Ideguchi, N. Inabe, T. Ishigaki, T. Isobe,
H. S. Jung, D. Kameda, I. Kojouharov, T. Komatsubara, T. Kubo, Y. K. Kwon, C. S. Lee, P. Lee, S. Morimoto, D. Murai, M. Niikura,
H. Nishibata, I. Nishizuka, H. Sakurai, Y. Shimizu, H. Suzuki, H. Takeda, K. Tshoo, and R. Yokoyama, “First observation of theπ0h11/2 ⊗ ν0h9/2 partner orbital conﬁguration in the odd-odd 138 I nucleus,” Phys. Rev. C 105, 034334 (2022).
A. Vitez-Sveiczer, A. Algora, A. I. Morales, B. Rubio, G. G. Kiss, P. Sarriguren, P. Van Isacker, G. de Angelis, F. Recchia, S. Nishimura,
J. Agramunt, V. Guadilla, A. Montaner-Piza, S. E. A. Orrigo, A. Horvath, D. Napoli, S. Lenzi, A. Boso, V. H. Phong, J. Wu, P. -A. Soderstrom, T. Sumikama, H. Suzuki, H. Takeda, D. S. Ahn, H. Baba, P. Doornebal, N. Fukuda, N. Inabe, T. Isobe, T. Kubo, S. Kubono,
H. Sakurai, Y. Shimizu, C. Sidong, B. Blank, P. Ascher, M. Gerbaux, T. Goigoux, J. Giovinazzo, S. Grevy, T. Kurtukian Nieto, C. Magron, W. Gelletly, Zs. Dombradi, Y. Fujita, M. Tanaka, P. Aguilera, F. Molina, J. Eberth, F. Diel, D. Lubos, C. Borcea, E. Ganioglu,
D. Nishimura, H. Oikawa, Y. Takei, S. Yagi, W. Korten, G. de France, P. Davies, J. Liu, J. Lee, T. Lokotko, I. Kojouharov, N. Kurz,
H. Shaﬀner, and A. Petrovici, “The β-decay of 70 Kr into 70 Br: Restoration of the pseudo-SU(4) symmetry,” Phys. Lett. B 830, 137123(2022).
A. Yagi, A. Odahara, H. Nishibata, R. Lozeva, C. -B. Moon, S. Nishimura, K. Yoshida, N. Yoshinaga, C. Watanabe, K. Higashiyama,
T. Shimoda, R. Daido, Y. Fang, P. S. Lee, B. Moon, P. Doornenbal, G. Lorusso, P. -A. Soderstrom, T. Sumikama, H. Watanabe, T. Isobe,
H. Baba, H. Sakurai, F. Browne, Z. Patel, S. Rice, L. Sinclair, J. Wu, Z. Y. Xu, R. Yokoyama, T. Kubo, N. Inabe, H. Suzuki, N. Fukuda,
D. Kameda, H. Takeda, D. S. Ahn, Y. Shimizu, D. Murai, F. L. Bello Garrote, J. -M. Daugas, F. Didierjean, E. Ideguchi, S. Iimura,
T. Ishigaki, H. S. Jung, T. Komatsubara, Y. K. Kwon, C. S. Lee, S. Morimoto, M. Niikura, I. Nishizuka, and K. Tshoo, “Various nuclear
structures in 140 Xe studied by β decay of ground and isomeric states in 140 I,” Phys. Rev. C 105, 044325 (2022).
D. Bazin, N. Aoi, H. Baba, J. Chen, H. Crawford, P. Doornenbal, P. Fallon, K. Li, J. Lee, M. Matsushita, T. Motobayashi, H. Sakurai,
H. Scheit, D. Steppenbeck, R. Stroberg, S. Takeuchi, H. Wang, K. Yoneda, and C. X. Yuan, “Spectroscopy of 33 Mg with knockout
reactions,” Phys. Rev. C 103, 064318 (2021).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

F. Browne, S. Chen, P. Doornenbal, A. Obertelli, K. Ogata, Y. Utsuno, K. Yoshida, N. L. Achouri, H. Baba, D. Calvet, F. Chateau,
N. Chiga, A. Corsi, M. L. Cortes, A. Delbart, J. -M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota,
V. Lapoux, H. N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck,L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, K. Boretzky, C. Caesar, L. X. Chung,F. Flavigny, S. Franchoo, I. Gasparic, R. -B. Gerst, J. Gibelin, K. I. Hahn, M. Holl, J. Kahlbow, D. Kim, D. Korper, T. Koiwai,
Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B. D. Linh, T. Lokotko, M. MacCormick, K. Miki, K. Moschner, T. Nakamura, S. Y. Park,D. Rossi, E. Sahin, F. Schindler, H. Simon, P. -A. Soderstrom, D. Sohler, S. Takeuchi, H. Tornqvist, J. Tscheuschner, V. Vaquero,
V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti, “Pairing forces govern population of
doubly magic 54 Ca from direct reactions,” Phys. Rev. Lett 126, 252501 (2021).
S. Escrig, A. I. Morales, S. Nishimura, M. Niikura, A. Poves, Z. Y. Xu, G. Lorusso, F. Browne, P. Doornenbal, G. Gey, H. -S. Jung, Z. Li,
P. -A. Soderstrom, T. Sumikama, J. Taprogge, Zs. Vajta, H. Watanabe, J. Wu, A. Yagi, K. Yoshinaga, H. Baba, S. Franchoo, T. Isobe,
P. R. John, I. Kojouharov, S. Kubono, N. Kurz, I. Matea, K. Matsui, D. Mengoni, P. Morfouace, D. R. Napoli, F. Naqvi, H. Nishibata,A. Odahara, E. Sahin, H. Sakurai, H. Schaﬀner, I. G. Stefan, D. Suzuki, R. Taniuchi, V. Werner, and D. Sohler, “Persistence of theZ = 28 shell gap in A = 75 isobars: Identiﬁcation of a possible (1/2− )μs isomer in 75 Co and β decay to 75 Ni,” Phys. Rev. C 103, 064328(2021).
A. Fernandez, A. Jungclaus, P. Doornenbal, M. A. Bentley, S. M. Lenzi, D. Rudolph, F. Browne, M. L. Cortes, T. Koiwai, R. Taniuchi,
V. Vaquero, K. Wimmer, T. Arici, N. Imai, N. Kitamura, B. Longfellow, R. Lozeva, B. Mauss, D. R. Napoli, M. Niikura, X. PereiraLopez, S. Pigliapoco, A. Poves, F. Recchia, P. Ruotsalainen, H. Sakurai, S. Uthayakumaar, R. Wadsworth, and R. Yajzey, “Mirror
energy diﬀerences above the 0 f7/2 shell: First γ-ray spectroscopy of the T z = −2 nucleus 56 Zn,” Phys. Lett. B 823, 136784 (2021).
V. Girard Alcindor, I. Stefan, F. de Oliveira Santos, O. Sorlin, D. Ackermann, P. Adsley, J. C. Angelique, M. Assie, M. Assuncao,
D. Beaumel, E. Berthoumieux, R. Borcea, L. Caceres, I. Celikovic, M. Ciemala, V. Chudoba, G. D’Agata, F. de Grancey, G. Dumitru,
F. Flavigny, C. Fougeres, S. Franchoo, A. Georgiadou, N. Goyal, S. Grevy, J. Guillot, V. Guimaraes, F. Hammache, O. Kamalou,
J. Kiener, S. Koyama, L. Lalanne, V. Lapoux, I. Matea, A. Matta, A. Meyer, N. Michel, P. Morfouace, J. Mrazek, F. Negoita, M. Niikura,
D. Pantelica, L. Perrot, C. Petrone, J. Piot, C. Portail, T. Roger, F. Rotaru, A. M. Sanchez-Benitez, N. de Sereville, M. Stanoiu, C. Stodel,
K. Subotic, D. Suzuki, V. Tatischeﬀ, J. C. Thomas, P. Ujic, and D. Verney, “Probing nuclear forces beyond the nuclear drip line: thecases of 16 F and 15 F.” Eur. Phys. J. A 57, 93 (2021).
O. Hall, T. Davinson, A. Estrade, J. Liu, G. Lorusso, F. Montes, S. Nishimura, V. H. Phong, P. J. Woods, J. Agramunt, D. S. Ahn, A. Algora,
J. M. Allmond, H. Baba, S. Bae, N. T. Brewer, C. G. Bruno, R. Caballero-Folch, F. Calvino, P. J. Coleman-Smith, G. Cortes, I. Dillmann,
C. Domingo-Pardo, A. Fijalkowska, N. Fukuda, S. Go, C. J. Griﬃn, R. Grzywacz, J. Ha, L. J. Harkness-Brennan, T. Isobe, D. Kahl,
L. H. Khiem, G. G. Kiss, A. Korgul, S. Kubono, M. Labiche, I. Lazarus, J. Liang, Z. Liu, K. Matsui, K. Miernik, B. Moon, A. I. Morales,
P. Morrall, M. R. Mumpower, N. Nepal, R. D. Page, M. Piersa, V. F. E. Pucknell, B. C. Rasco, B. Rubio, K. P. Rykaczewski, H. Sakurai,
Y. Shimizu, D. W. Stracener, T. Sumikama, H. Suzuki, J. L. Tain, H. Takeda, A. Tarifeno-Saldivia, A. Tolosa-Delgado, M. WolinskaCichocka, and R. Yokoyama, “β-delayed neutron emission of r-process nuclei at the N = 82 shell closure,” Phys. Lett. B 816, 136266(2021).
J. Hu, H. Yamaguchi, Y. H. Lam, A. Heger, D. Kahl, A. M. Jacobs, Z. Johnston, S. W. Xu, N. T. Zhang, S. B. Ma, L. H. Ru, E. Q. Liu,
T. Liu, S. Hayakawa, L. Yang, H. Shimizu, C. B. Hamill, A. St J. Murphy, J. Su, X. Fang, K. Y. Chae, M. S. Kwag, S. M. Cha,
N. N. Duy, N. K. Uyen, D. H. Kim, R. G. Pizzone, M. La Cognata, S. Cherubini, S. Romano, A. Tumino, J. Liang, A. Psaltis,
M. Sferrazza, D. Kim, Y. Y. Li, and S. Kubono, “Advancement of photospheric radius expansion and clocked type-I X-ray burst models
with the new 22 Mg(α, p)25 Al reaction rate determined at the Gamow energy,” Phys. Rev. Lett. 127, 172701 (2021).
S. W. Huang, Z. H. Yang, F. M. Marques, N. L. Achouri, D. S. Ahn, T. Aumann, H. Baba, D. Beaumel, M. Bohmer, K. Boretzky,
M. Caamano, S. Chen, N. Chiga, M. L. Cortes, D. Cortina, P. Doornenbal, C. A. Douma, F. Dufter, J. Feng, B. Fernandez-Dominguez,
Z. Elekes, U. Forsberg, T. Fujino, N. Fukuda, I. Gasparic, Z. Ge, R. Gernhauser, J. M. Gheller, J. Gibelin, A. Gillibert, Z. Halasz,
T. Harada, M. N. Harakeh, A. Hirayama, N. Inabe, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki, D. Kim, S. Kim, S. Kiyotake,
T. Kobayashi, Y. Kondo, P. Koseoglou, Y. Kubota, I. Kuti, C. Lehr, C. Lenain, P. J. Li, Y. Liu, Y. Maeda, S. Masuoka, M. Matsumoto,
A. Matta, J. Mayer, H. Miki, M. Miwa, B. Monteagudo, I. Murray, T. Nakamura, A. Obertelli, N. A. Orr, H. Otsu, V. Panin, S. Park,
M. Parlog, S. Paschalis, M. Potlog, S. Reichert, A. Revel, D. Rossi, A. Saito, M. Sasano, H. Sato, H. Scheit, F. Schindler, T. Shimada,Y. Shimizu, S. Shimoura, H. Simon, I. Stefan, S. Storck, L. Stuhl, H. Suzuki, D. Symochko, H. Takeda, S. Takeuchi, J. Tanaka,
Y. Togano, T. Tomai, H. T. Tornqvist, E. Tronchin, J. Tscheuschner, T. Uesaka, V. Wagner, K. Wimmer, H. Yamada, B. Yang, L. Yang,
Y. Yasuda, K. Yoneda, L. Zanetti, and J. Zenihiro, “Experimental study of 4 n by directly detecting the decay neutrons,” Few-Body Syst.
62, 102 (2021).
S. Y. Jin, S. T. Wang, J. Lee, A. Corsi, K. Wimmer, F. Browne, S. Chen, M. L. Cortes, P. Doornenbal, T. Koiwai, C. X. Yuan, A. Algora,
D. Brugnara, J. Cederkall, J. Gerl, M. Gorska, G. Hafner, K. Kokubun, P. Koseoglou, S. Kubono, P. Li, P. Liang, J. Liu, Z. Liu,
T. Lokotko, J. Park, H. Sakurai, L. G. Sarmiento, Z. Y. Sun, R. Taniuchi, W. Xian, and I. Zanon, “Spectroscopy of 98 Cd by two-nucleon
removal from 100 In,” Phys. Rev. C 104, 024302 (2021).
M. M. Juhasz, Z. Elekes, D. Sohler, K. Sieja, K. Yoshida, K. Ogata, P. Doornenbal, A. Obertelli, H. Baba, F. Browne, D. Calvet, F. Chateau,
S. Chen, N. Chiga, A. Corsi, M. L. Cortes, A. Delbart, J. -M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi,
Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck,L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, N. L. Achouri, O. Aktas, T. Aumann, L. X. Chung, Zs. Dombradi,
F. Flavigny, S. Franchoo, I. Gasparic, R. -B. Gerst, J. Gibelin, K. I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr,
B. D. Linh, H. N. Liu, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S. Y. Park, D. Rossi, E. Sahin, P. -A. Soderstrom,
S. Takeuchi, H. Tornqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti,“First spectroscopic study of 63 V at the N = 40 island of inversion,” Phys. Rev. C 103, 064308 (2021).
M. Kaneko, T. Murakami, T. Isobe, M. Kurata-Nishimura, A. Ono, N. Ikeno, J. Barney, G. Cerizza, J. Estee, G. Jhang, J. W. Lee,W. G. Lynch, C. Santamaria, C. Y. Tsang, M. B. Tsang, R. Wang, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, J. Brzychczyk,- 209 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

N. Chiga, N. Fukuda, I. Gasparic, B. Hong, A. Horvat, T. Ichihara, K. Ieki, N. Inabe, Y. J. Kim, T. Kobayashi, Y. Kondo, P. Lasko,
H. S. Lee, Y. Leifels, J. Lukasik, J. Manfredi, A. B. McIntosh, P. Morfouace, T. Nakamura, N. Nakatsuka, S. Nishimura, R. Olsen,
H. Otsu, P. Pawlowski, K. Pelczar, D. Rossi, H. Sakurai, H. Sato, H. Scheit, R. Shane, Y. Shimizu, H. Simon, T. Sumikama, D. Suzuki,
H. Suzuki, H. Takeda, S. Tangwancharoen, Y. Togano, H. Tornqvist, Z. Xiao, S. J. Yennello, J. Yurkon, and Y. Zhang, “Rapidity
distributions of Z = 1 isotopes and the nuclear symmetry energy from Sn+Sn collisions with radioactive beams at 270 MeV/nucleon,”Phys. Lett. B 822, 136681 (2021).
A. Kubiela, H. Suzuki, O. B. Tarasov, M. Pfutzner, D. -S. Ahn, H. Baba, A. Bezbakh, A. A. Ciemny, W. Dominik, N. Fukuda, A. Giska,
R. Grzywacz, Y. Ichikawa, Z. Janas, L. Janiak, G. Kaminski, K. Kawata, T. Kubo, M. Madurga, C. Mazzocchi, H. Nishibata, M. Pomorski, Y. Shimizu, N. Sokolowska, D. Suzuki, P. Szymkiewicz, A. Swiercz, M. Tajima, A. Takamine, H. Takeda, Y. Takeuchi,
C. R. Thornsberry, H. Ueno, H. Yamazaki, R. Yokoyama, and K. Yoshida, “Production of the most neutron-deﬁcient Zn isotopes by
projectile fragmentation of 78 Kr,” Phys. Rev. C 104, 064610 (2021).
L. Lalanne, O. Sorlin, M. Assie, F. Hammache, N. de Sereville, S. Koyama, D. Suzuki, F. Flavigny, D. Beaumel, Y. Blumenfeld,
B. A. Brown, F. De Oliveira Santos, F. Delaunay, S. Franchoo, J. Gibelin, V. Girard Alcindor, J. Guillot, O. Kamalou, N. Kitamura, V. Lapoux, A. Lemasson, A. Matta, B. Mauss, P. Morfouace, M. Niikura, J. Pancin, A. Poves, T. Roger, T. Saito, C. Stodel, andJ. -C. Thomas, “Evaluation of the 35 K(p, γ)36 Ca reaction rate using the 37 Ca(p, d)36 Ca transfer reaction,” Phys. Rev. C 103, 055809(2021).
B. D. Linh, A. Corsi, A. Gillibert, A. Obertelli, P. Doornenbal, C. Barbieri, S. Chen, L. X. Chung, T. Duguet, M. Gomez-Ramos, J. D. Holt,
A. Moro, P. Navratil, K. Ogata, N. T. T. Phuc, N. Shimizu, V. Soma, Y. Utsuno, N. L. Achouri, H. Baba, F. Browne, D. Calvet,
F. Chateau, N. Chiga, M. L. Cortes, A. Delbart, J. -M. Gheller, A. Giganon, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux,
H. N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl,
Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, F. Flavigny, S. Franchoo, I. Gasparic, R. -B. Gerst,
J. Gibelin, K. I. Hahn, N. T. Khai, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, T. Lokotko, M. MacCormick,
K. Moschner, T. Nakamura, S. Y. Park, D. Rossi, E. Sahin, D. Sohler, P. -A. Soderstrom, S. Takeuchi, N. D. Ton, H. Tornqvist,
V. Vaquero, V. Wagner, H. Wang, V. Werner, X. Xu, Y. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti, “Investigation of theground-state spin inversion in the neutron-rich 47, 49 Cl isotopes,” Phys. Rev. C 104, 044331 (2021).
J. E. Riley, A. M. Laird, N. de Sereville, A. Parikh, S. P. Fox, F. Hammache, I. Stefan, P. Adsley, M. Assie, B. Bastin, F. Boulay, A. Coc,
S. Franchoo, R. Garg, S. A. Gillespie, V. Guimaraes, C. Hamadache, N. Hubbard, J. Kiener, A. Lefebvre-Schuhl, F. de Oliveira Santos,
A. Remadi, L. Perrot, D. Suzuki, G. Verde, V. Tatischeﬀ, and M. Williams, “Sub-threshold states in 19 Ne relevant to 18 F(p, α)15 O,”
Phys. Rev. C 103, 015807 (2021).
Y. Shigekawa, A. Yamaguchi, K. Suzuki, H. Haba, T. Hiraki, H. Kikunaga, T. Masuda, S. Nishimura, N. Sasao, A. Yoshimi, andK. Yoshimura, “Estimation of radiative half-life of 229m Th by half-life measurement of other nuclear excited states in 229 Th,” Phys.
Rev. C 104, 024306 (2021).
M. Tsumura, T. Kawabata, Y. Takahashi, S. Adachi, H. Akimune, S. Ashikaga, T. Baba, Y. Fujikawa, H. Fujimura, H. Fujioka, T. Furuno,
T. Hashimoto, T. Harada, M. Ichikawa, K. Inaba, Y. Ishii, N. Itagaki, M. Itoh, C. Iwamoto, N. Kobayashi, A. Koshikawa, S. Kubono,
Y. Maeda, Y. Matsuda, S. Matsumoto, K. Miki, T. Morimoto, M. Murata, T. Nanamura, I. Ou, S. Sakaguchi, A. Sakaue, M. Sferrazza,
K. N. Suzuki, T. Takeda, A. Tamii, K. Watanabe, Y. N. Watanabe, H. P. Yoshida, and J. Zenihiro, “First experimental determinationof the radiative-decay probability of the 3−1 state in 12 C for estimating the triple alpha reaction rate in high temperature environments,”
Phys. Lett. B 817, 136283 (2021).
H. Watanabe, C. X. Yuan, G. Lorusso, S. Nishimura, Z. Y. Xu, T. Sumikama, P. -A. Soderstrom, P. Doornenbal, F. Browne, G. Gey,
H. S. Jung, J. Taprogge, Zs. Vajta, H. K. Wang, J. Wu, A. Yagi, H. Baba, G. Benzoni, K. Y. Chae, F. C. L. Crespi, N. Fukuda,
R. Gernhauser, N. Inabe, T. Isobe, A. Jungclaus, D. Kameda, G. D. Kim, Y. K. Kim, I. Kojouharov, F. G. Kondev, T. Kubo, N. Kurz,
Y. K. Kwon, G. J. Lane, Z. Li, C. -B. Moon, A. Montaner-Piza, K. Moschner, F. Naqvi, M. Niikura, H. Nishibata, D. Nishimura,A. Odahara, R. Orlandi, Z. Patel, Zs. Podolyak, H. Sakurai, H. Schaﬀner, G. S. Simpson, K. Steiger, H. Suzuki, H. Takeda, A. Wendt,
and K. Yoshinaga, “Impact of shell evolution on Gamow-Teller β decay from a high-spin long-lived isomer in 127 Ag,” Phys. Lett. B
823, 136766 (2021).
K. Wimmer, F. Recchia, S. M. Lenzi, S. Riccetto, T. Davinson, A. Estrade, C. J. Griﬃn, S. Nishimura, V. Phong, P. -A. Soderstrom,
O. Aktas, M. Al-Aqeel, T. Ando, H. Baba, S. Bae, S. Choi, P. Doornenbal, J. Ha, L. Harkness-Brennan, T. Isobe, P. R. John, D. Kahl,
G. Kiss, I. Kojouharov, N. Kurz, M. Labiche, K. Matsui, S. Momiyama, D. R. Napoli, M. Niikura, C. Nita, Y. Saito, H. Sakurai,
H. Schaﬀner, P. Schrock, C. Stahl, T. Sumikama, V. Werner, W. Witt, and P. J. Woods, “Isomeric states in neutron-rich nuclei nearN = 40,” Phys. Rev. C 104, 014304 (2021).
D. Wu, C. L. Bai, H. Sagawa, S. Nishimura, and H. Q. Zhang, “β-delayed one-neutron emission probabilities within a neural networkmodel,” Phys. Rev. C 104, 054303 (2021).
R. Yokoyama, E. Ideguchi, G. S. Simpson, M. Tanaka, Y. Sun, C. -J. Lv, Y. -X. Liu, L. -J. Wang, S. Nishimura, P. Doornenbal, G. Lorusso,
P. -A. Soderstrom, T. Sumikama, J. Wu, Z. Y. Xu, N. Aoi, H. Baba, F. L. Bello Garrote, G. Benzoni, F. Browne, R. Daido, Y. Fang,
N. Fukuda, A. Gottardo, G. Gey, S. Go, S. Inabe, T. Isobe, D. Kameda, K. Kobayashi, M. Kobayashi, I. Kojouharov, T. Komatsubara,
T. Kubo, N. Kurz, I. Kuti, Z. Li, M. Matsushita, S. Michimasa, C. B. Moon, H. Nishibata, I. Nishizuka, A. Odahara, Z. Patel, S. Rice,E. Sahin, H. Sakurai, H. Schaﬀner, L. Sinclair, H. Suzuki, H. Takeda, J. Taprogge, Zs. Vajta, H. Watanabe, and A. Yagi, “Threequasiparticle isomers in odd-even 159, 161 Pm: Calling for modiﬁed spin-orbit interaction for the neutron-rich region,” Phys. Rev. C 104,
L021303 (2021).
S. Hayakawa, M. La Cognata, L. Lamia, H. Yamaguchi, D. Kahl, K. Abe, H. Shimizu, L. Yang, O. Beliuskina, S. M. Cha, K. Y. Chae,
S. Cherubini, P. Figuera, Z. Ge, M. Gulino, J. Hu, A. Inoue, N. Iwasa, A. Kim, D. Kim, G. Kiss, S. Kubono, M. La Commara, M. Lattuada, E. J. Lee, J. Y. Moon, S. Palmerini, C. Parascandolo, S. Y. Park, V. H. Phong, D. Pierroutsakou, R. G. Pizzone, G. G. Rapisarda,
S. Romano, C. Spitaleri, X. D. Tang, O. Trippella, A. Tumino, and N. T. Zhang, “Constraining the primordial lithium abundance: Newcross section measurement of the 7 Be + n reactions updates the total 7 Be destruction rate,” Astrophys. J. Lett. 915, L13 (2021).

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J. Estee, W. G. Lynch, C. Y. Tsang, J. Barney, G. Jhang, M. B. Tsang, R. Wang, M. Kaneko, J. W. Lee, T. Isobe, M. Kurata-Nishimura,T. Murakami, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, J. Brzychczyk, G. Cerizza, N. Chiga, N. Fukuda, I. Gasparic,
B. Hong, A. Horvat, K. Ieki, N. Inabe, Y. J. Kim, T. Kobayashi, Y. Kondo, P. Lasko, H. S. Lee, Y. Leifels, J. Lukasik, J. Manfredi,A. B. McIntosh, P. Morfouace, T. Nakamura, N. Nakatsuka, S. Nishimura, H. Otsu, P. Pawlowski, K. Pelczar, D. Rossi, H. Sakurai,
C. Santamaria, H. Sato, H. Scheit, R. Shane, Y. Shimizu, H. Simon, K. Snoch, A. Sochocka, T. Sumikama, H. Suzuki, D. Suzuki,
H. Takeda, S. Tangwancharoen, Y. Togano, H. Tornqvist, Z. Xiao, S. J. Yennello, Y. Zhang, and M. D. Cozma, “Probing the symmetryenergy with the spectral pion ratio,” Phys. Rev. Lett 126, 162701 (2021).
J. Barney, J. Estee, W. G. Lynch, T. Isobe, G. Jhang, M. Kurata-Nishimura, A. B. McIntosh, T. Murakami, R. Shane, S. Tangwancharoen,
M. B. Tsang, G. Cerizza, M. Kaneko, J. W. Lee, C. Y. Tsang, R. Wang, C. Anderson, H. Baba, Z. Chajecki,M. Famiano, R. HodgesShowalter, B. Hong, T. Kobayashi, P. Lasko, J. Lukasik, N. Nakatsuka, R. Olsen, H. Otsu, P. Pawlowski, K. Pelczar, H. Sakurai,
C. Santamaria, H. Setiawan, A. Taketani,J. R. Winkelbauer, Z. Xiao, S. J. Yennello, J. Yurkon, and Y. Zhang, “The SπRIT time
projection chamber,” Rev. Sci. Instrum. 92, 063302 (2021).
S. Koyama, D. Suzuki, M. Assie, N. Kitamura, L. Lalanne, M. Niikura, H. Otsu, T. Y. Saito, and O. Sorlin, “A liquid hydrogen target forradioactive beam experiments using the missing mass method,” Nucl. Instrum. Methods Phys. Res. A 1010, 165477 (2021).
H. Baba, T. Ichihara, T. Isobe, T. Ohnishi, K. Yoshida, Y. Watanabe, S. Ota, H. Shimizu, S. Shimoura, S. Takeuchi, D. Nishimura,
J. Zenihiro, A. O. Tokiyasu, and R. Yokoyama, “MPV-parallel readout architecture for the VME data acquisition system,” IEEE Trans.
Nucl. Sci. 68, 1841 (2021).
T. Okumura, T. Azuma, D. A. Bennett, P. Caradonna,I. H. Chiu, W. B Doriese, M. S. Durkin, J. W. Fowler, J. D. Gard, T. Hashimoto,R. Hayakawa, G. C. Hilton, Y. Ichinohe, P. Indelicato, T. Isobe, S. Kanda, M. Katsuragawa, N. Kawamura, Y. Kino, K. Mine, Y. Miyake,
K. M. Morgan, K. Ninomiya, H. Noda, G. C. O’Neil, S. Okada, K. Okutsu, T. Osawa, N. Paul, C. D. Reintsema, D. R. Schmidt,
K. Shimomura, P. Strasser, H. Suda, D. S. Swetz, T. Takahashi, S. Takeda, S. Takeshita, H. Tatsuno, Y. Ueno, J. N., Ullom, S. Watanabe,and S. Yamada, “Dynamical response of transition-edge sensor microcalorimeters to a pulsed charged-particle beam,” IEEE Trans.
Appl. Supercond. 31, 2101704 (2021).
M. Holl et al. (SAMURAI21 Collaboration), “Border of the island of inversion: Unbound states in 29 Ne,” Phys. Rev. C 105, 034301(2021).
H. Grawe, K. Straub, T. Faestermann, M. Górska, C. Hinke, R. Krücken, F. Nowacki, M. Böhmer, P. Boutachkov, H. Geissel,
R. Gernhäuser, A. Gottardo, J. Grebosz, N. Kurz, Z. Liu, L. Maier, S. Pietri, Zs. Podolyák, K. Steiger, H. Weick, H. J. Wollersheim, P. J. Woods, N. Al-Dahan, N. Alkhomashi, A. Ataç, A. Blazhev, N. Braun, T. Davinson, I. Dillmann, C. Domingo-Pardo,
P. Doornenbal, G. Farrelly, F. Farinon, G.de France, J. Gerl, N. Goel, T. Habermann, R. Hoischen, R. Janik, M. Karny, A. Kaskas,
I. Kojouharov, Th. Kröll, M. Lewitowicz, Yu.A. Litvinov, S. Myalski, F. Nebel, S. Nishimura, C. Nociforo, J. Nyberg, A. Parikh,
A. Procházka, P. H. Regan, C. Rigollet, H. Schaﬀner, C. Scheidenberger, S. Schwertel, P. -A. Söderström, S. Steer, A. Stolz, P. Strmeň,and the RISING Collaboration, “The (6+ ) isomer in 102 Sn revisited: Neutron and proton eﬀective charges close to the double shellclosure,” Phys. Lett. B 820, 136591 (2021).

[Review Article]
A. A. Aziz, N. S. Ahmad, S. Ahn, W. Aoki, M. Bhuyan, K. J. Chen, G. Guo, K. I. Hahn, T. Kajino, H. Abu Kassim, D. Kim, S. Kubono,
M. Kusakabe, A. Li, H. N. Li, Z. H. Li, W. P. Liu, Z. W. Liu, T. Motobayashi, K. C. Pan, T. -S. Park, J. R. Shi, X. D. Tang, W. Wang,
L. J. Wen, M. R. Wu H. L. Yan, and N. Yusof, “Progress in nuclear astrophysics of east and southeast Asia,” AAPPS Bulletin 31, 18(2021).

Presentations[Seminars]
R. Taniuchi, “Gamma-ray spectroscopy in the vicinity of double-magic 78 Ni,” NUSTAR Seminar, Online/GSI, Germany, June 2, 2021.
櫻井博儀, 「現代の錬金術による元素変換科学—元素合成, 魔法数から核変換まで—」, 日本物理学会第 5 回オンライン物理講話,
2021 年 10 月 23 日.

Award
谷内稜, 第 38 回 井上研究奨励賞（Inoue Research Award for Young Scientists）, 公益財団法人 井上科学振興財団, 2022 年 2 月 4 日.

Press Releases「高密度な中性子物質の硬さの測定に初めて成功—中性子星内の状態を実験室で再現—」, 2021 年 5 月 11 日.
「荷電対称性の破れを発見—クリプトン-70 とセレン-70 の形状は大きく異なっていた—」, 2021 年 5 月 19 日.

Outreach Activity
櫻井博儀, 2021 年度「はかる！」, 埼玉県立不動岡高等学校.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Spin isospin Laboratory
1. Abstract
The Spin Isospin Laboratory pursues research activities putting primary focus on interplay of spin and isospin in exotic nuclei.
Understanding nucleosyntheses in the universe, especially those in r- and rp-processes is another big goal of our laboratory.
Investigations on isospin dependences of nuclear equation of state, spin-isospin responses of exotic nuclei, occurrence of various
correlations at low-densities, evolution of spin-orbit coupling are main subjects along the line. We are leading a mass measurement
project with the Rare RI Ring project, too. Through the experimental studies, we will be able to elucidate a variety of nuclear
phenomena in terms of interplay of spin and isospin, which will in turn, lead us to better understanding of our universe.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)

Direct reaction studies of neutron-matter equation of state
Study of spin-isospin responses with RI-beams
r-process nucleosynthesis study with heavy-ion storage ring
Application of spin-polarization technique to RI-beam experiments and other ﬁelds
Development of special targets for RI-beam experiments

3. Summary of Research Activity(1) Direct reaction studies of neutron matter equation of state
Direct reactions induced by light-ions serve as powerful tools to investigate various aspects of nuclei. We are advancing experimental programs to explore equation of state of neutron matter, via light-ion induced reactions with RI-beams.
(1-1) Determination of a neutron skin thickness by proton elastic scattering
A neutron skin thickness is known to have strong relevance to asymmetry terms of nuclear equation of state, especially to aterm proportional to density. The ESPRI project aims at determining density distributions in exotic nuclei precisely by proton elastic
scattering at 200–300 MeV/nucleon. An experiment for 132 Sn that is a ﬂagship in this project has been successfully performed.
(1-2) Asymmetry terms in nuclear incompressibility
Nuclear incompressibility represents stiﬀness of nuclear matter. Incompressibility of symmetric nuclear matter is determined
to be 230 ± 20 MeV, but its isospin dependence still has a large uncertainty at present. A direct approach to the incompressibilityof asymmetric nuclear matter is an experimental determination of energies of isoscalar giant monopole resonances (GMR) in heavy
nuclei. We have developed, in close collaboration with Center for Nuclear Study (CNS) of University of Tokyo, an active gas target
for deuteron inelastic scattering experiments to determine GMR energies. The active gas target has been already tested with oxygen
and xenon beams at HIMAC and ﬁnally has been applied to a 132 Sn experiment at RIBF.
(1-3) Multi-neutron and α-cluster correlations at low densities
Occurrences of multi-neutron and α-cluster correlations are other interesting aspects of nuclear matter and deﬁne its low-density
behavior. The multi-neutron and α-cluster correlations can be investigated with the large-acceptance SAMURAI spectrometer. The
SAMURAI has been already applied to experiments to explore light neutron-rich nuclei close to the dripline. We plan to reinforce
experimental capabilities of the SAMURAI by introducing advanced devices such as MINOS (Saclay) and NeuLAND (GSI).
(1-4) Fission barrier heights in neutron-rich heavy nuclei
The symmetry energy has a strong inﬂuence on ﬁssion barrier heights in neutron-rich nuclei. Knowledge on the ﬁssion barrierheights, which is quite poor at present, is quite important for our proper understanding on termination of the r-process. We are planningto perform, in collaboration with the TU Munich group, (p, 2p)-delayed ﬁssion experiments at the SAMURAI to determine the ﬁssion
barrier heights in neutron-rich nuclei in Pb region.
(2) Study of spin-isospin responses with RI-beams
The study of spin-isospin responses in nuclei forms one of the important cores of nuclear physics. A variety of collective states,for example isovector giant dipole resonances, isobaric analogue states, Gamow-Teller resonances, have been extensively studied byuse of electromagnetic and hadronic reactions from stable targets.
The research opportunities can be largely enhanced with light of availabilities of radioactive isotope (RI) beams and of physics of
unstable nuclei. There are three possible directions to proceed. The ﬁrst direction is studies of spin-isospin responses of unstable nuclei
via inverse-kinematics charge exchange reactions. A neutron-detector array WINDS has been constructed, under a collaboration of
CNS, Tokyo and RIKEN, for inverse kinematics (p, n) experiments at the RI Beam Factory. We have already applied WINDS to the(p, n) experiments for 12 Be, 132 Sn and plan to extend this kind of study to other exotic nuclei.
The second direction is studies with RI-beam induced charge exchange reaction. RI-beam induced reactions have unique properties which are missing in stable-beam induced reactions and can be used to reach the yet-to-be-discovered states. We have constructed
the SHARAQ spectrometer and the high-resolution beam-line at the RI Beam Factory to pursue the capabilities of RI-beam induced
reactions as new probes to nuclei. One of the highlights is an observation of β+ type isovector spin monopole resonances (IVSMR) in
208
Pb and 90 Zr via the (t, 3 He) reaction at 300 MeV/nucleon.
The third direction is studies of neutron- and proton-rich nuclei via stable-beam induced charge exchange reactions, which is
conducted under collaboration with Research Center for Nuclear Physics (RCNP), Osaka University. We have performed the double- 212 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

charge exchange 12 C(18 O, 18 Ne)12 Be reaction at 80 MeV/nucleon to investigate structure of a neutron-rich 12 Be nucleus. Peaks corresponding to ground and excited levels in 12 Be have been clearly observed. Another double charge exchange reaction, (12 C, 12 Be(0+2 ))are being used to search for double Gamow-Teller resonances.
(3) r-process nucleosynthesis study with heavy-ion storage ring
Most of the r-process nuclei become within reach of experimental studies for the ﬁrst time at RI Beam Factory at RIKEN. The
Rare RI Ring at RIBF is the unique facility with which we can perform mass measurements of r-process nuclei. Construction of theRare RI Ring started in FY2012 in collaboration with Tsukuba and Saitama Universities. A major part of the ring has been completed
and the commissioning run is planned in FY2014.
We are planning to start precise mass measurements of r-process nuclei soon. A series of experiments will start with nuclei in the
A = 80 region and will be extended to heavier region.
(4) Application of spin-polarization technique to RI-beam experiments and other ﬁelds
A technique to produce nuclear polarization by means of electron polarization in photo-excited triplet states of aromatic molecules
can open new applications. The technique is called “Tripletd-DNP.” A distinguished feature of Triplet-DNP is that it works under alow magnetic ﬁeld of 0.1–0.7 T and temperature higher than 100 K, which exhibits a striking contrast to standard dynamic nuclear
polarization (DNP) techniques working in extreme conditions of several Tesla and sub-Kelvin.
We have constructed a polarized proton target system for use in RI-beam experiments. Recent experimental and theoretical studies
have revealed that spin degrees of freedom play a vital role in exotic nuclei. Tensor force eﬀects on the evolution of shell and possible
occurrence of p-n pairing in the proton-rich region are good examples of manifestations of spin degrees of freedom. Experimentswith the target system allow us to explore the spin eﬀects in exotic nuclei. It should be noted that we have recently achieved a proton
polarization of 40% at room temperature in a pentacene-d14 doped p-terphenyl crystal.
Another interesting application of Triplet-DNP is sensitivity enhancement in NMR spectroscopy of biomolecules. We started a
new project to apply the Triplet-DNP technique to study protein-protein interaction via two-dimensional NMR spectroscopy, in close
collaboration with biologists and chemists.
(5) Development of special targets for RI-beam experiments
For the research activities shown above, we are developing and hosting special targets for RI-beam experiments listed below:(a) Polarized proton target (described in (4))(b) Thin solid hydrogen target(c) MINOS (developed at Saclay and hosted by the Spin Isospin Laboratory)

Members
Director
Tomohiro UESAKA
Senior Research Scientists
Masaki SASANO
Ken-ichiro YONEDA

Juzo ZENIHIRO

Research Scientists
Sarah NAIMI

Kenichiro TATEISHI

Research & Development Scientist
Yohei SHIMIZU
Postdoctoral Researcher
Junki TANAKA
Junior Research Associates
Shutaro HANAITomoya HARADAInternational Program Associates
Siwei HUANG

Yutian LI

Research Consultants
Harutaka SAKAGUCHI (Osaka Univ.)
Yasuyuki SUZUKI

Kazuko TANABE- 213 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Senior Visiting Scientist
Hiroyuki SAGAWA (Univ. of Aizu)
Visiting Scientists
Satoshi ADACHI (Osaka Univ.)
Hidetoshi AKIMUNE (Konan Univ.)
Didier BEAUMEL (Inst. de Phys.Nucl.)
Konstanze BORETZKY (GSI)
Anna CORSI (CEA Saclay)
Masanori DOZONO (Kyoto Univ.)
Zoltan ELEKES (ATOMKI)
Zsolt FULOP (ATOMKI)
Tatsuya FURUNO (Osaka Univ.)
Igor GASPARIC (Rudjer Boskovic Inst.)
Valdir GUIMARAES (Inst.o de Fisica da Univ. de Sao Paulo)
Zoltan HALASZ (ATOMKI)
Kaori KAKI (Shizuoka Univ.)
Takahiro KAWABATA (Osaka Univ.)
Yuma KIKUCHI (NIT, Tokuyama College)
Yosuke KONDO (Tokyo Tech)
Zeren KORKULU (Inst. for Basic Sci. (IBS))
Attila KRASZNAHORKAY (ATOMKI)
Dorottya KUNNE SOHLER (ATOMKI)
Istvan KUTI (ATOMKI)
Valerie LAPOUX (Inst.ion CEA-Saclay)
Yury LITVINOV (GSI)
Hongna LIU (TU Darmstadt)
Yohei MATSUDA (Konan Univ.)

Kenjiro MIKI (Tohoku Univ.)
Tetsuaki MORIGUCHI (Tsukuba Univ.)
Sarah NAIMI (IJCLab (Laboratoire de physique des 2 inﬁnis Irene Joliot-Curie))
Takashi NAKAMURA (Tokyo Tech)
Noritsugu NAKATSUKA (Tokyo Tech)Alexandre OBERTELLI (TU Darmstadt)
Kazuyuki OGATA (Osaka Univ.)
Valerii PANIN (GSI)
Aldric REVEL (CEA Saclay)
Kimiko SEKIGUCHI (Tokyo Tech)
Laszlo STUHL (Inst. for Basic Sci. (IBS))
Baohua SUN (Beihang Univ.)
Yelei SUN (TU Darmstadt)
Shinji SUZUKI (Chinese Academy of Sci.)
Satoru TERASHIMA (Beihang Univ.)
Yasuhiro TOGANO (Rikkyo Univ.)
Takashi WAKUI (QST)
Atomu WATANABE (JSPS)
Takayuki YAMAGUCHI (Saitama Univ.)
Zaihong YANG (Osaka Univ.)
Juzo ZENIHIRO (Kyoto Univ.)
Yuhu ZHANG (IMP, CAS)

Visiting Technicians
Denis CALVET (CEA)
Alain DELBART (CEA/CE Saclay)
Clement HILAIRE (CEA Saclay)

Shoji SUZUKI (KEK)
Olivier TELLIER (CEA Saclay)

Student Trainees
Tomoki ADACHI (Kyushu Univ.)
Sota ANDO (Kyushu Univ.)
Paul ANDRE (CEA Saclay)
Naoki EBINA (Tokyo Tech)
Shiyo EN’YO (Kyoto Univ.)
Yuki FUJIKAWA (Kyoto Univ.)
Saiya FUJIWARA (Kyushu Univ.)
Jian GAO (Peking Univ.)
Shutaro HANAI (Univ. of Tokyo)
Sakumi HARAYAMA (Saitama Univ.)
Koshi HIGUCHI (Saitama Univ.)
Kouta HORIKAWA (Tokyo Tech)
Kento INABA (Kyoto Univ.)
Kakeru ISOBE (Tokyo Tech)
Koki KAMEYA (Tohoku Univ.)
Naoto KANAME (Tsukuba Univ.)
Masanori KANDA (Saitama Univ.)
Fumiya KAWAGUCHI (Tokyo Tech)
Yusuke KAWASHIMA (Kyushu Univ.)
Kanki KISHIMOTO (Kyushu Univ.)
Sho KITAYAMA (Tohoku Univ.)
Yukari KOIZUMI (Saitama Univ.)
Hyeji LEE (Tokyo Tech)
Hongfu LI (IMP, CAS)

Yoshiki MARUTA (Tohoku Univ.)
Takaya MATSUI (Tohoku Univ.)
Tomoki MATSUI (Tokyo Tech)
Riku MATSUMURA (Saitama Univ.)
Atsuyuki MORIYAMA (Tsukuba Univ.)
Shintaro OKAMOTO (Kyoto Univ.)
Kengo OKUBO (Saitama Univ.)
Misaki OTSU (Saitama Univ.)
Yuko SAITO (Tohoku Univ.)
Kosuke SAKANASHI (Osaka Univ.)
Kenta SASAKI (Saitama Univ.)
Hibiki SEKI (Saitama Univ.)
Yusuke SHINOHARA (Kyushu Univ.)
Naru SHINOZAKI (Saitama Univ.)
Kohei TAKAHASHI (Tokyo Tech)Ryotaro TSUJI (Kyoto Univ.)
Ren URAYAMA (Tohoku Univ.)
Kanta YAHIRO (Kyoto Univ.)
Kohei YAMAMOTO (Tohoku Univ.)
Wataru YAMASHITA (Kyushu Univ.)
Asahi YANO (Tsukuba Univ.)
Nozomi YOKOTA (Kyushu Univ.)
Chieko YONEMURA (Kyushu Univ.)
Ryohsuke YOSHIDA (Kyoto Univ.)- 214 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Assistants
Emiko ISOGAI

Yuri TSUBURAI

List of Publications & Presentations
Publications[Original Papers]
M. Holl, S. Lindberg, A. Heinz, Y. Kondo, T. Nakamura, J. A. Tostevin, H. Wang, T. Nilsson, N. L. Achouri, H. Al Falou, L. Atar,
T. Aumann, H. Baba, K. Boretzky, C. Caesar, D. Calvet, H. Chae, N. Chiga, A. Corsi, H. L. Crawford, F. Delaunay, A. Delbart,
Q. Deshayes, P. Dı́az Fernández, Z. Dombrádi, C. A. Douma, Z. Elekes, P. Fallon, I. Gašparic, J. -M. Gheller, J. Gibelin, A. Gillibert,
M. N. Harakeh, A. Hirayama, C. R. Hoﬀman, A. Horvat, Á. Horváth, J. W. Hwang, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki,
S. Kawase, S. Kim, K. Kisamori, T. Kobayashi, D. Körper, S. Koyama, I. Kuti, V. Lapoux, F. M. Marqués, S. Masuoka, J. Mayer,
K. Miki, T. Murakami, M. Najaﬁ, K. Nakano, N. Nakatsuka, A. Obertelli, F. de Oliveira Santos, N. A. Orr, H. Otsu, T. Ozaki, V. Panin,
S. Paschalis, A. Revel, D. Rossi, A. T. Saito, T. Y. Saito, M. Sasano, H. Sato, Y. Satou, H. Scheit, F. Schindler, P. Schrock, M. Shikata,Y. Shimizu, H. Simon, D. Sohler, O. Sorlin, L. Stuhl, S. Takeuchi, M. Tanaka, M. Thoennessen, H. Törnqvist, Y. Togano, T. Tomai,
J. Tscheuschner, J. Tsubota, T. Uesaka, Z. Yang, M. Yasuda, and K. Yoneda, “Border of the island of inversion: Unbound states in
29Ne,” Phys. Rev. C 105, 034301 (2022).
L. Olivier, R. Orlandi, Z. Patel, Zs. Podolyák, M. Rudigier, T. Saito, C. Shand, P. -A. Söderström, I. Stefan, V. Vaquero, V. Werner,
K. Wimmer, and Z. Xu, “γ-ray spectroscopy of low-lying yrast and non-yrast states in neutron-rich 94,95,96 Kr,” Phys. Rev. C 105,024302 (2022).
M. Janek, V. P. Ladygin, A. V. Averyanov, E. V. Chernykh, D. D. Enache, Y. V. Gurchin, A. Yu. Isupov, J. -T. Karachuk, A. N. Khrenov,
D. O. Krivenkov, P. K. Kurilkin, N. B. Ladygina, A. N. Livanov, O. Mezhenska, S. M. Piyadin, S. G. Reznikov, Y. T. Skhomenko,
A. A. Terekhin, A. V. Tishevsky, T. Uesaka, and I. S. Volkov, “Study of the dp elastic and dp breakup complementary processes using
polarized and unpolarized beam of nuclotron,” Few-Body Syst. 63, 3 (2022).
A. Watanabe, S. Nakai, Y. Wada, K. Sekiguchi, T. Akieda, D. Etoh, M. Inoue, Y. Inoue, K. Kawahara, H. Kon, K. Miki, T. Mukai,
D. Sakai, S. Shibuya, Y. Shiokawa, T. Taguchi, H. Umetsu, Y. Utsuki, M. Watanabe, S. Goto, K. Hatanaka, Y. Hirai, Y. Ikeda, T. Ino,
D. Inomoto, S. Ishikawa, M. Itoh, H. Kanda, H. Kasahara, Y. Maeda, S. Mitsumoto, K. Nonaka, H. J. Ong, H. Oshiro, Y. Otake,
H. Sakai, A. Taketani, D. T. Tran, T. Uesaka, T. Wakasa, Y. Wakabayashi, and T. Wakui, “Analyzing power measurement for p-3 Heelastic scattering at intermediate energies,” Few-Body Syst. 62, 112 (2021).
S. W. Huang, Z. H. Yang, F. M. Marqués, N. L. Achouri, D. S. Ahn, T. Aumann, H. Baba, D. Beaumel, M. Böhmer, K. Boretzky,
M. Caamaño, S. Chen, N. Chiga, M. L. Cortés, D. Cortina, P. Doornenbal, C. A. Douma, F. Dufter, J. Feng, B. Fernández-Domı́nguez,
Z. Elekes, U. Forsberg, T. Fujino, N. Fukuda, I. Gašparić, Z. Ge, R. Gernhäuser, J. M. Gheller, J. Gibelin, A. Gillibert, Z. Halász,
T. Harada, M. N. Harakeh, A. Hirayama, N. Inabe, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki, D. Kim, S. Kim, S. Kiyotake,
T. Kobayashi, Y. Kondo, P. Koseoglou, Y. Kubota, I. Kuti, C. Lehr, C. Lenain, P. J. Li, Y. Liu, Y. Maeda, S. Masuoka, M. Matsumoto,
A. Matta, J. Mayer, H. Miki, M. Miwa, B. Monteagudo, I. Murray, T. Nakamura, A. Obertelli, N. A. Orr, H. Otsu, V. Panin, S. Park,
M. Parlog, S. Paschalis, M. Potlog, S. Reichert, A. Revel, D. Rossi, A. Saito, M. Sasano, H. Sato, H. Scheit, F. Schindler, T. Shimada,Y. Shimizu, S. Shimoura, H. Simon, I. Stefan, S. Storck, L. Stuhl, H. Suzuki, D. Symochko, H. Takeda, S. Takeuchi, J. Tanaka,
Y. Togano, T. Tomai, H. T. Törnqvist, E. Tronchin, J. Tscheuschner, T. Uesaka, V. Wagner, K. Wimmer, H. Yamada, B. Yang, L. Yang,
Y. Yasuda, K. Yoneda, L. Zanetti, and J. Zenihiro, “Experimental study of 4 n by directly detecting the decay neutrons,” Few-Body Syst.
62, 102 (2021).
B. D. Linh, A. Corsi, A. Gillibert, A. Obertelli, P. Doornenbal, C. Barbieri, S. Chen, L. X. Chung, T. Duguet, M. Gómez-Ramos, J. D. Holt,
A. Moro, P. Navrátil, K. Ogata, N. T. T. Phuc, N. Shimizu, V. Somà, Y. Utsuno, N. L. Achouri, H. Baba, F. Browne, D. Calvet,
F. Château, N. Chiga, M. L. Cortés, A. Delbart, J. -M. Gheller, A. Giganon, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux,
H. N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl,
Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, F. Flavigny, S. Franchoo, I. Gašparić, R. -B. Gerst,
J. Gibelin, K. I. Hahn, N. T. Khai, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, T. Lokotko, M. MacCormick,
K. Moschner, T. Nakamura, S. Y. Park, D. Rossi, E. Sahin, D. Sohler, P. -A. Söderström, S. Takeuchi, N. D. Ton, H. Törnqvist,
V. Vaquero, V. Wagner, H. Wang, V. Werner, X. Xu, Y. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti, “Investigation of theground-state spin inversion in the neutron-rich 47,49 Cl isotopes,” Phys. Rev. C 104, 044331 (2021).
K. Inaba, Y. Sasamoto, T. Kawabata, M. Fujiwara, Y. Funaki, K. Hatanaka, K. Itoh, M. Itoh, K. Kawase, H. Matsubara, Y. Maeda, K. Suda,
S. Sakaguchi, Y. Shimizu, A. Tamii, Y. Tameshige, M. Uchida, T. Uesaka, T. Yamada, and H. P. Yoshida, “Search for α condensed
states in 13 C using α inelastic scattering,” Prog. Theor. Exp. Phys. 9, 093D01 (2021).
F. Browne, S. Chen, P. Doornenbal, A. Obertelli, K. Ogata, Y. Utsuno, K. Yoshida, N. L. Achouri, H. Baba, D. Calvet, F. Château,
N. Chiga, A. Corsi, M. L. Cortes, A. Delbart, J. -M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota,
V. Lapoux, H. N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck,L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, K. Boretzky, C. Caesar, L. X. Chung,F. Flavigny, S. Franchoo, I. Gasparic, R. -B. Gerst, J. Gibelin, K. I. Hahn, M. Holl, J. Kahlbow, D. Kim, D. Körper, T. Koiwai,
Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B. D. Linh, T. Lokotko, M. MacCormick, K. Miki, K. Moschner, T. Nakamura, S. Y. Park,D. Rossi, E. Sahin, F. Schindler, H. Simon, P. -A. Söderström, D. Sohler, S. Takeuchi, H. Törnqvist, J. Tscheuschner, V. Vaquero,
V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti, “Pairing forces govern population of
doubly magic 54 Ca from direct reactions,” Phys. Rev. Lett. 126, 252501 (2021).
M. M. Juhász, Z. Elekes, D. Sohler, K. Sieja, K. Yoshida, K. Ogata, P. Doornenbal, A. Obertelli, H. Baba, F. Browne, D. Calvet, F. Château,
S. Chen, N. Chiga, A. Corsi, M. L. Cortés, A. Delbart, J. -M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi,- 215 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck,L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, N. L Achouri, O. Aktas, T. Aumann, L. X. Chung, Zs. Dombrádi,
F. Flavigny, S. Franchoo, I. Gašparic, R. -B. Gerst, J. Gibelin, K. I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr,
B. D. Linh, H. N. Liu, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S. Y. Park, D. Rossi, E. Sahin, P. -A. Söderström,
S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti,“First spectroscopic study of 63 V at the N = 40 island of inversion,” Phys. Rev. C 103, 064308 (2021).
M. M. Juhász, Z. Elekesa, D. Sohlera, Y. Utsuno, K. Yoshida, T. Otsuka, K. Ogatagh, P. Doornenbal, A. Obertelli, H. Baba, F. Browne,
D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M. L. Cortés, A. Delbart, J. -M. Gheller, A. Giganon, A. Gillibert, C. Hilaire,
T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai,
M. Sasano, D. Steppenbeck, L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmers, K. Yoneda, N. L. Achouri, O. Aktas,T. Aumann,
L. X. Chung, Zs. Dombrádi, F. Flavigny, S. Franchoo, I. Gašparić, R. -B. Gerst, J. Gibelin, K. I. Hahn, D. Kim, T. Koiwai, Y. Kondo,
P. Koseoglou, J. Lee, C. Lehr, B. D. Linh, H. N. Liu, T. Lokotko. M. MacCormick, K. Moschner, T. Nakamura, S. Y. Park, D. Rossi,
E. Sahin, P. -A. Söderström, S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan,
Z. Yang, M. Yasuda, and L. Zanetti, “First spectroscopic study of 51 Ar by the (p, 2p) reaction,” Phys. Lett. B 814, 136108 (2021).
T. Aumann, C. Barbieri, D. Bazin, C. A. Bertulani, A. Bonaccorso, W. H. Dickhoﬀ, A. Gade, M. Gómez-Ramos, B. P. Kay, A. M. Moro,T. Nakamura, A. Obertelli, K. Ogata, S. Paschalis, and T. Uesaka, “Quenching of single-particle strength from direct reactions withstable and rare-isotope beams,” Prog. Part. Nucl. Phys. 118, 103847 (2021).
P. Ascher, L. Daudin, M. Flayol, M. Gerbaux, S. Grévya, M. Hukkanen, A. Husson, A. de Roubin, P. Alfaurt, B. Blank, K. Blaum,
B. Lachacinski, D. Lunney, E. Minaya Ramirezd, S. Naimi, S. Perard, and B. Thomas, “PIPERADE: A double Penning trap for mass
separation and mass spectrometry at DESIR/SPIRAL2,” Nucl. Instrum. Methods Phys. Res. A 1019, 165857 (2021).
J. Tanaka, Z. Yang, S. Typel, S. Adachi. S. Bai, P. van Beek, D. Beaumel, Y. Fujikawa, J. Han, S. Heil, S. Huang, A. Inoue, Y. Jiang,
M. Knösel, N. Kobayashi, Y. Kubota, W. Liu, J. Lou, Y. Maeda, Y. Matsuda, K. Miki, S. Nakamura, K. Ogata, V. Panin, H. Scheit,
F. Schindler, P. Schrock, D. Symochko, A. Tamii, T. Uesaka, V. Wagner, K. Yoshida, J. Zenihiro, and T. Aumann, “Formation of α
clusters in dilute neutron-rich matter,” Science 371, 260 (2021).
J. Zenihiro, T. Uesaka, H. Sagawa, and S. Yoshida, “Proton density polarization of the doubly magic 40 Ca core in 48 Ca and EoS parameters,” Prog. Theor. Exp. Phys. 4, 049301 (2021).

[Book]A. Obertelli and H. Sagawa, “Modern Nuclear Physics: From Fundamentals to Frontiers,” Springer Nature Singapore, 2022.

Presentations[International Conference/Workshop]
T. Uesaka, “Knock-out reaction studies of clustering in heavy nuclei—ONOKORO project—”, C2R2 Seminar, Online & IBS CENS,
Korea, July 8, 2021.

[Domestic Conference/Workshop]
佐川弘幸 (口頭発表), 「IV density and Isospin Symmetry Breaking (ISB) forces in N = Z nuclei」, 第 7 回クラスター階層領域研究会,
大阪大学核物理研究センター, 2021 年 12 月 27 日.

[Seminar]上坂友洋, 久保田祐樹, 「ノックアウト反応による大ニュートロンの空間構造抽出」, 物質階層を横断する会, オンライン, 2021 年 7
月 30 日.

Outreach Activity
上坂友洋, 「元素をつくる『巨大地下工場』〜工学が支える研究の現場に潜入!〜」, IEEE ウェビナーシリーズ第 24 回 Engineering
Spotlight, 2022 年 2 月 20 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Nuclear Spectroscopy Laborarory
1. Abstract
The research group has conducted nuclear-physics studies utilizing stopped/slowed-down radioactive-isotope (RI) beams mainly
at the RIBF facility. These studies are based on the technique of nuclear spectroscopy such as β-ray-detected NMR (β-NMR), γPAD (Perturbed Angular Distribution), laser, and Mössbauer among other methods that takes advantage of intrinsic nuclear properties
such as nuclear spins, electromagnetic moments, and decay modes. In particular, techniques and devices for the production of spincontrolled RI beams have been developed and combined to the spectroscopic studies, which enable high-sensitivity measurements ofspin precessions/resonances through a change in the angular distribution of radiations. Anomalous nuclear structures and properties of
far unstable nuclei are investigated from thus determined spin-related observables. The group also conducts nuclear-structure studies
based on large-scale numerical calculations such as ab initio calculations and large-scale shell-model calculations. The group also
aims to apply such techniques to interdisciplinary ﬁelds such as fundamental physics and materials science by exploiting nuclear
probes.

2. Major Research Subjects(1) Nuclear spectroscopy utilizing spin-oriented fast RI beams(2) Nuclear/Atomic laser spectroscopy & SLOWRI R&D(3) Application of RI probes to materials science

3. Summary of Research Activity(1) Nuclear spectroscopy utilizing spin-oriented fast RI beams
Measurements of static electromagnetic nuclear moments over a substantial region of the nuclear chart have been conducted forstructure studies on the nuclei far from the β-decay stability. Utilizing nuclear spin orientation phenomena of RIs created in the
projectile-fragmentation reaction, ground- and excited-state electromagnetic nuclear moments been determined by means of the βray-detected nuclear magnetic resonance (β-NMR) and the γ-ray time diﬀerential perturbed angular distribution (γ-TDPAD) methods.
In particular, a new method developed for controlling spin in a system of rare RIs, taking advantage of the mechanism of the two-step
projectile fragmentation reaction combined with the momentum-dispersion matching technique, has been developed and employedmaking fully use of world’s highest intensity rare RIBs delivered from BigRIPS for rare isotopes.
(2) Nuclear/Atomic laser spectroscopy & SLOWRI R&D
The group has been conducting system development for nuclear laser spectroscopy from the following two approaches in orderto realize experiments for rare isotopes at RIBF. One is collinear laser spectroscopy for a large variety of elements using sloweddown RI beams produced via a projectile-fragmentation reaction, which can be achieved only by the universal low-energy RI-beamdelivery system, SLOWRI, under installation in collaboration with the SLOWRI Team. This slowed-down RI-beam scheme enables
to perform high-precision laser spectroscopy even with fast-fragmentation-based RIBs without the elemental limitation problematicin the ISOL-based RIBs.
The other approach is a new method utilizing superﬂuid helium (He II) as a stopping medium of energetic RI beams, in which thecharacteristic atomic properties of ions surrounded by superﬂuid helium enables us to perform unique nuclear laser spectroscopy. RIions trapped in He II are known to exhibit a characteristic excitation spectrum signiﬁcantly blue-shifted compared with the emission
one. Consequently, the background derived from the excitation-laser stray light, which often causes serious problems in measurements,
can be drastically reduced.
(3) Application of RI probes to materials science
The application of RI and heavy ion beams as a probe for condensed matter studies is also conducted by the group. The microscopic material dynamics and properties have been investigated through the deduced internal local ﬁelds and the spin relaxation of
RI probes based on various spectroscopies utilizing RI probes such as β-NMR/NQR spectroscopy, Mössbauer spectroscopy, the γ-ray
time diﬀerential perturbed angular correlation (γ-TDPAC) spectroscopy. Furthermore, studies on the control of electrical conductivityof diamond by boron and nitrogen implantation are ongoing.
Provided that highly spin-polarized RI probes are produced independently of their element properties and doped into a substanceas an impurity, the constituent particle of the substance can be substituted by the same element RI probe without changing the material
structure. This scheme provides a new opportunity for materials-science researches, but a key technology, production of elementindependent highly spin-polarized RI beams, has not yet been achieved. In this subject, the group has conducted R&D studies torealize an ultra-slow & highly-spin-polarized RI beams, based on the technique of the atomic beam resonance.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Members
Director
Hideki UENO
Research/Technical Scientists
Hiroki YAMAZAKI (Senior Research Scientist)
Isao WATANABE (Senior Research Scientist)

Aiko TAKAMINE (Research Scientist)
Shintaro GO (Research Scientist)

Research & Development Scientist
Tetsu SONODA
Contract Researcher
Takashi ABE
Special Postdoctoral Researcher
Momo MUKAI
Postdoctoral Researchers
Minori TAJIMA

Kei IMAMURA (CPR)

Research Associate
Aleksey GLADKOV
Senior Visiting Scientists
Yukari MATSUO (Hosei Univ.)

Takaharu OTSUKA (Univ. of Tokyo)

Visiting Scientists
Hiroki NISHIBATA (Kyushu Univ.)
Tomoya SATO (Tokyo Tech)
Wataru SATO (Kanazawa Univ.)
Shinichiro TAKEDA (Univ. of Tokyo)
Andrew E. STUCHBERY (The Australian Nat’l Univ.)
Satoshi TSUTSUI (Japan Synchrotron Radiation Res. Inst.)
Shin WATANABE (JAXA)
Yasuhiro YAMADA (Tokyo Univ. Sci)
Deyan T. YORDANOV (CNRS-IN2P3)
Akihiro YOSHIMI (Okayama Univ.)

Dimiter L. BALABANSKI (IFIN-HH)
Jean-Michel DAUGAS (CNRS)
Georgi GEORGIEV (CNRS-IN2P3)
Yuichi ICHIKAWA (Kyushu Univ.)
Yoshio KOBAYASHI (Univ. of Electro-Commun.)
Kenya M. KUBO (Int’l Christian Univ.)
Kensaku MATSUTA (Osaka Univ.)
Jun MIYAZAKI (Tokyo Denki Univ.)
Takamasa MOMOSE (The Univ. of British Columbia)
Jin NAKAMURA (Univ. of Electro-Commun.)Student Trainees

Masaki NISHIMURA (Hosei Univ.)
Yurika OTANI (Osaka Univ.)
Takato SUGISAKI (Osaka Univ.)
Satoshi TANAKA (Hosei Univ.)
Kenta TSUBURA (Hosei Univ.)
Takumi YAMAMOTO (Hosei Univ.)
Mio YOSHIDA (Univ. of Electro-Commun.)

Sai AKIMOTO (Hosei Univ.)
Miru DOI (Hosei Univ.)
Hiroki ENDO (Hosei Univ.)
Manami ITO (Hosei Univ.)
Kai KIKUCHI (Hosei Univ.)
Yoko KIMURA (Osaka Univ.)
Rikuta MITSUYASU (Hosei Univ.)
Yusuke NAKASHIMA (Univ. of Electro-Commun.)Temporary Staﬃng
Emiko SUGISAKI
Assistants
Yuri TSUBURAI

Izumi YOSHIDA- 218 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

List of Publications & Presentations
Publications[Original Papers]
Y. Hirayama, P. Schury, M. Mukai, H. Choi, S. Imamura, X. Y. Watanabe, M. Wada, H. Watanabe, and H. Miyatake, “Three-dimensional
tracking multi-segmented proportional gas counter for β-decay spectroscopy of unstable nuclei,” Nucl. Instrum. Methods Phys. Res. A
997, 165152-1–10 (2021). DOI: 10.1016/j.nima.2021.165152 .
T. Aoki, R. Sreekantham, B. K. Sahoo, Bindiya Arora, A. Kastberg, T. Sato, H. Ikeda, N. Okamoto, Y. Torii, T. Hayamizu, K. Nakamura, S. Nagase, M. Ohtsuka, H. Nagahama, N. Ozawa, M. Sato, T. Nakashita, K. Yamane, K. S. Tanaka, K. Harada, H. Kawamura, T. Inoue, A. Uchiyama, A. Hatakeyama, A. Takamine, H. Ueno, Y. Ichikawa, Y. Matsuda, H. Haba, and Y. Sakemi, “Quantum
sensing of the electron electric dipole moment using ultracold entangled Fr atoms,” Quantum Sci. Technol. 6, 044008-1–17 (2021).
DOI: 10.1088/2058-9565/ac1b6a .
S. Kimura, Y. Ito, D. Kaji, P. Schury, M. Wada, H. Haba, T. Hashimoto, Y. Hirayama, M. MacCormick, H. Miyatake, J. Y. Moon,
K. Morimoto, M. Mukai, I. Murray, A. Ozawa, M. Rosenbusch, H. Schatz, A. Takamine, T. Tanaka, Y. X. Watanabe, and H. Wollnik,“High precision mass measurements of intermediate-mass neutron-deﬁcient nuclei via MRTOF-MS,” JPS Conf. Proc. 35, 011005-1–6(2021). DOI: 10.7566/JPSCP.35.011005 .
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa,
Y. Ito, D. Kaji, S. Kimura, H. Koura, J. J. Liu, H. Miyatake, J. -Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “First high-precision direct determination of the atomic mass of asuperheavy nuclide,” Phys. Rev. C 104, L021304-1–7 (2021). DOI: 10.1103/PhysRevC.104.L021304 .
T. Niwase, M. Wada, P. Schury, P. Brionnet, S. D. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama,
S. Ishizawa, Y. Ito, D. Kaji, S. Kimura, J. Liu, H. Miyatake, J. Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, T. Tanaka, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “α-decay-correlated mass measurement of 206, 207g, m Rausing an α-TOF detector equipped multireﬂection time-of-ﬂight mass spectrograph system,” Phys. Rev. C 103, 054312-1–8 (2021).
DOI: 10.1103/PhysRevC.104.044617 .
M. Ahmed, Y. X. Watanabe, Y. Hirayama, M. Mukai, J. H. Park, P. Schury, Y. Kakiguchi, A. Ozawa, M. Oyaizu, M. Wada, and H. Miyatake, “β-γ Spectroscopy of the 195 Os nucleus,” Phys. Rev. C 104, 044617-1–9 (2021). DOI: 10.1103/PhysRevC.103.054312 .
Y. X. Watanabe, P. M. Walker, Y. Hirayama, M. Mukai, H. Watanabe, G. J. Lane, M. Ahmed, M. Brunet, T. Hashimoto, S. Ishizawa,
S. Kimura, F. G. Kondev, Yu. A. Litvinov, H. Miyatake, J. Y. Moon, T. Niwase, M. Oyaizu, J. H. Park, Zs. Podolyák, M. Rosenbusch,
P. Schury, and M. Wada, “First direct observation of isomeric decay in neutron-rich odd-odd 186 Ta,” Phys. Rev. C 104, 024330-1–6.
DOI: 10.1103/PhysRevC.104.024330 .
A. Kubiela, H. Suzuki, O. B. Tarasov, M. Pfützner, D. -S. Ahn, H. Baba, A. Bezbakh, A. A. Ciemny, W. Dominik, N. Fukuda, A. Giska,
R. Grzywacz, Y. Ichikawa, Z. Janas, Ł. Janiak, G. Kamiński, K. Kawata, T. Kubo, M. Madurga, C. Mazzocchi, H. Nishibata, M. Pomorski, Y. Shimizu, N. Sokołowska, D. Suzuki, P. Szymkiewicz, A. Świercz, M. Tajima, A. Takamine, H. Takeda, Y. Takeuchi,
C. R. Thornsberry, H. Ueno, H. Yamazaki, R. Yokoyama, and K. Yoshida, “Production of the most neutron-deﬁcient Zn isotopes by
projectile fragmentation of 78 Kr,” Phys. Rev. C 104, 064610-1–7 (2021). DOI: 10.1103/PhysRevC.104.064610 .
B. Kolbinger, C. Amsler, S. Arguedas Cuendis, H. Breuker, A. Capon, G. Costantini, P. Dupré, M. Fleck, A. Gligorova, H. Higaki,
Y. Kanai, V. Kletzl, N. Kuroda, A. Lanz, M. Leali, V. Mäckel, C. Malbrunot, V. Mascagna, O. Massiczek, Y. Matsuda, D. J. Murtagh,
Y. Nagata, A. Nanda, L. Nowak, B. Radics, C. Sauerzopf, M. C. Simon, M. Tajima, H. A. Torii, U. Uggerhøj, S. Ulmer, L. Venturelli,
A. Weiser, M. Wiesinger, E. Widmann, T. Wolz, Y. Yamazaki, and J. Zmeskal, “Measurement of the principal quantum number
distribution in a beam of antihydrogen atoms,” Eur. Phys. J. D 75, 91-1–14 (2021). DOI: 10.1140/epjd/s10053-021-00101-y .
Y. Sato, Y. Yamada, Y. Kobayashi, K. M. Kubo, M. Mihara, W. Sato, J. Miyazaki, T. Nagatomo, T. Ando, N. Takahama, K. Some, M. Sato,S. Sato, and A. Kitagawa, “In-beam Mössbauer spectra of 57 Mn implanted into lithium aluminium hydride,” Appl. Radiat. Isot. 170,
109582-1–7 (2021). DOI: 10.1016/j.apradiso.2020.109582 .
Y. Kobayashi, M. Sato, Y. Yamada, K. M. Kubo, M. Mihara, W. Sato, J. Miyazaki, T. Nagatomo, A. Okazawa, S. Sato, and A. Kitagawa,“Chemical species of localized Fe atoms in solid hydrogen using in-beam Mössbauer spectroscopy,” Hyperﬁne Interact. 243, 13-1–8(2022). DOI: 10.1007/s10751-022-01793-3 .
S. Tsutsui, R. Higashinaka, R. Nakamura, K. Fujiwara, J. Nakamura, Y. Kobayashi, T. U. Ito, Y. Yoda, K. Kato, K. Nitta, N. Kawamura,
M. Mizumaki, T. D. Matsuda, and Y. Aoki, “Sm valence determination of Sm-based Intermetallics using 149 Sm Mössbauer and Sm
LIII-edge X-ray absorption spectroscopies,” Hyperﬁne Interact. 242, 32-1–10 (2021). DOI: 10.1007/s10751-021-01759-x .
O. Hall, T. Davinson, A. Estrade, J. Liu, G. Lorusso, F. Montes, S. Nishimura, V. H. Phong, P. J. Woods, J. Agramunt, D. S. Ahn, A. Algora,
J. M. Allmond, H. Baba, S. Bae, N. T. Brewer, C. G. Bruno, R. Caballero-Folch, F. Calviño, P. J. Coleman-Smith, G. Cortes, I. Dillmann,
C. Domingo-Pardo, A. Fijalkowska, N. Fukuda, S. Go, C. J. Griﬃn, R. Grzywacz, J. Ha, L. J. Harkness-Brennan, T. Isobe, D. Kahl,
L. H. Khiem, G. G. Kiss, A. Korgul, S. Kubono, M. Labiche, I. Lazarus, J. Liang, Z. Liu, K. Matsui, K. Miernik, B. Moon, A. I. Morales,
P. Morrall, M. R. Mumpower, N. Nepal, R. D. Page, M. Piersa, V. F. E. Pucknell, B. C. Rasco, B. Rubio, K. P. Rykaczewski, H. Sakurai,
Y. Shimizu, D. W. Stracener, T. Sumikama, H. Suzuki, J. L. Tain, H. Takeda, A. Tarifeño-Saldivia, A. Tolosa-Delgado, M. WolińskaCichocka, and R. Yokoyama, “β-delayed neutron emission of r-process nuclei at the N = 82 shell closure,” Phys. Lett. B 816, 1362661–7 (2021). DOI: 10.1016/j.physletb.2021.136266 .
T. Abe, P. Maris, T. Otsuka, N. Shimizu, Y. Utsuno, and J. P. Vary, “Ground-state properties of light 4n self-conjugate nuclei in ab initio nocore Monte Carlo shell model calculations with nonlocal NN interactions,” Phys. Rev. C 104, 054315-1–22 (2021). DOI: 10.1103/PhysRevC.104.054315 .
M. M. Juhász, Z. Elekes, D. Sohler, Y. Utsuno, K. Yoshida, T. Otsuka, K. Ogata, P. Doornenbal, A. Obertelli, H. Baba, F. Browne,
D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M. L. Cortés, A. Delbart, and L. Zanetti, “First spectroscopic study of 51 Ar by the- 219 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)(p, 2p) reaction,” Phys. Lett. B 814, 136108-1–8 (2021). DOI: 10.1016/j.physletb.2021.136108 .
T. Suzuki and T. Otsuka, “Structure of two-neutron halo in light exotic nuclei,” Few-Body Syst. 62, 32-1–5 (2021). DOI: 10.1007/s00601021-01612-5 .
N. Shimizu, Y. Tsunoda, Y. Utsuno, and T. Otsuka, “Variational approach with the superposition of the symmetry-restored quasiparticlevacua for nuclear shell-model calculations,” Phys. Rev. C 103, 014312-1–11 (2021). DOI: 10.1103/PhysRevC.103.014312 .
T. Otsuka, N. Shimizu, and Y. Tsunoda, “Moments and radii of exotic Na and Mg isotopes,” Phys. Rev. C 105, 014319-1–8 (2021).
DOI: 10.1103/PhysRevC.105.014319 .

[Review Article]
T. Otsuka, “Emerging concepts in nuclear structure based on the shell models,” Physics 4, 258–285 (2022). DOI: 10.3390/physics4010018 .

Presentations[International Conferences/Workshops]
H. A. Schuessler (oral), A. Takamine, M. Wada, H. Iimura, and J. Lassen, “Nuclei at extreme deformations and conﬁgurations: Touchinghorizon with on-line laser spectroscopy,” 29th Annual International Laser Physics Workshop (LPHYS’21), Online, July 19–23, 2021.
T. Abe (oral), “Ab initio description of nuclear structure in no-core Monte Carlo shell model,” XXXII IUPAP Conference on Computational Physics (CCP2021), Online, August 1–5, 2021.
M. Mukai (oral), “Isotope shift measurement of 182, 184 Hf and 185, 187, 188, 190 W,” SSRI-PNS Collaboration Meeting 2021, Online, September
2–3, 2021.
T. Otsuka (invited), “Spin contents of Na isotopes towards dripline,” 24th International Spin Symposium (SPIN2021), Online & Matsue,
Japan, Ocober, 18–22, 2021.

[Domestic Conferences/Workshops]
上野秀樹 (依頼講演), 「計画研究 B03 班 高偏極 RI ビームの生成と核・物質科学研究への応用」, 新学術領域研究「宇宙観測検出器と量子ビームの出会い. 新た応用の架け橋.」, 領域研究会 (第 3 回領域全体会議), オンライン, 2021 年 6 月 14–15 日.
今村慧 (依頼講演), 「RI 原子ビーム共鳴装置の開発」, 新学術領域研究「宇宙観測検出器と量子ビームの出会い. 新た応用の架け橋. 」, 領域研究会 (第 3 回領域全体会議), オンライン, 2021 年 6 月 14–15 日.
田島美典 (ポスター発表), 高峰愛子, 飯村秀紀, 「不安定原子核の同位体シフト測定に向けた開発」, 第 17 回原子・分子・光科学（AMO）討論会, オンライン, 2021 年 6 月 18–19 日.
山本匠 (ポスター発表), 「超流動ヘリウム中 107, 109 Ag 原子の超微細構造間隔測定へ向けた DPSS レーザーの導入」, 第 17 回原子・分子・光科学（AMO）討論会, オンライン, 2021 年 6 月 18–19 日.
土居三瑠 (ポスター発表), 「観測原子数補正システムを用いた 超流動ヘリウム中の Rb 原子の超微細構造間隔の測定」, 第 17 回原子・分子・光科学（AMO）討論会, オンライン, 2021 年 6 月 18–19 日.
伊藤愛美 (ポスター発表),「加速器実験に向けた二重共鳴法による外部磁場補正コイルの開発」, 第 17 回原子・分子・光科学（AMO）
討論会, オンライン, 2021 年 6 月 18–19 日.
郷慎太郎 (依頼講演), 「原子核物理学実験における偏光ガンマ線観測実験の将来」, 新学術領域研究「宇宙観測検出器と量子ビームの出会い. 新たな応用への架け橋. 」, 高精度硬 X 線・ガンマ線偏光計を用いた原子物理・原子核物理実験の検討小研究会, オンライン, 2021 年 8 月 19 日.
飯村俊, M. Rosenbusch, 高峰愛子, 和田道治, S. Chen, D. Hou, J. Liu, W. Xian, S. Yan, P. Schury, 木村創大, 庭瀬暁隆, 伊藤由太,
園田哲, 小島隆夫, 渡辺裕, 平山賀一, 宮武宇也, S. Naimi, 道正新一郎, 西村俊二, 小田原厚子, 石山博恒, 「新規開発された ZDMRTOF 装置を用いた中性子過剰 Sc, Ti, V 核の系統的質量測定」, 日本物理学会 2021 年 秋季大会, オンライン, 2021 年 9 月
14–17 日.
庭瀬暁隆, P. Schury, 和田道治, P. Brionnet, S. Chen, 橋本尚志, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 石澤倫, 伊藤由太,
加治大哉, 木村創大, 小浦寛之, 宮武宇也, J. Y. Moon, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 渡辺裕,
H. Wollnik, W. Xian, S. X. Yan, 「超重核 257 Db の直接質量測定」, 日本物理学会 2021 年 秋季大会, オンライン, 2021 年 9 月
14–17 日.
M. Rosenbusch, S. Chen, W. Xian, S. Yan, A. Takamine, D. Hou, S. Iimura, M. Wada, P. Schury, Y. Hirayama, H. Ishiyama, Y. Ito,
S. Kimura, T. M. Kojima, J. Liu, S. Michimasa, H. Miyatake, S. Naimi, S. Nishimura, T. Niwase, T. Sonoda, Y. X. Watanabe,
H. Wollnik, “New technologies for multi-reﬂection time-of-ﬂight mass spectrometry at BigRIPS,” 日本物理学会 2021 年 秋季大会, オンライン, 2021 年 9 月 14–17 日.
W. Xian, S. Chen, M. Rosenbusch, S. Yan, D. Hou, S. Iimura, A. Takamine, M. Wada, P. Schury, H. Ishiyama, Y. Hirayama, S. Kimura,T. Niwase, J. Liu, Y. Ito, T. M. Kojima, S. Naimi, S. Michimasa, H. Miyatake, S. Nishimura, T. Sonoda, Y. X. Watanabe, H. Wollnik,“New mass measurements of neutron-rich nuclei of Ge, As, and Se, and an accuracy study of the new ZD-MRTOF system,” 日本物理学会 2021 年 秋季大会, オンライン, 2021 年 9 月 14–17 日.
D. Hou, A. Takamine, S. Iimura, M. Rosenbusch, S. Chen, W. Xian, S. Yan, M. Wada, P. Schury, Y. Hirayama, H. Ishiyama, Y. Ito,
S. Kimura, J. Liu, S. Michimasa, H. Miyatake, S. Naimi, S. Nishimura, T. Niwase, Y. X. Watanabe, H. Wollnik, “Mass measurement in
the neutron-rich Mo region using the new ZD-MRTOF system,” 日本物理学会 2021 年 秋季大会, オンライン, 2021 年 9 月 14–17 日.
向井もも, 平山賀一, 渡辺裕, 渡邉寛, S. C. Jeong, 宮武宇也, M. Brunet, 石澤倫, F. G. Kondev, G. J. Lane, Yu. A. Litvinov, 庭瀬暁隆,
Zs. Podolyák, M. Rosenbusch, P. Schury, 和田道治, P. M. Walker, 「187 Ta のベータ崩壊核分光」, 日本物理学会 2021 年 秋季大会,
オンライン, 2021 年 9 月 14–17 日.
平山賀一, H. Choi, P. Schury, 渡辺裕, 向井もも, J. Y. Moon, T. Hashimoto, S. C. Jeong, M. Rosenbusch, 小柳津充広, 庭瀬暁隆,
谷口秋洋, 和田道治, 宮武宇也, 「KISS での核分光: MRTOF-MS を用いた不安定核のレーザー共鳴イオン化核分光」, 日本物- 220 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

理学会 2021 年 秋季大会, オンライン, 2021 年 9 月 14–17 日.
川田敬太, 大田晋輔, 堂園昌伯, 銭廣十三, 岩本ちひろ, 北村徳隆, 酒井英行, 増岡翔一朗, 道正新一郎, 横山輪, 矢向謙太郎, 原田知也,
西畑洸希, 角田理恵子, 今井伸明, N. Zhang, J. Hwang, 遠藤史隆, 「核破砕反応における核運動量移行」, 日本物理学会 2021 年 秋
季大会, オンライン, 2021 年 9 月 14–17 日.
大谷優里花, 三原基嗣, 松多健策, 福田光順, 若林諒, 沖本直哉, 福留美樹, 木村容子, 高山元, 泉川卓司, 野口法秀, 生越瑞揮, 佐藤弥紗,
高津和哉, 大坪隆, 西村太樹, 髙橋弘幸, 菅原奏来, A. Gladkov, 石山博恒, 北川敦志, 佐藤眞二, 百田佐多生, 奥村寛之, 森口哲朗,
小沢顕, 冨田啓介, 矢野朝陽, 「酸素イオン伝導体 YSZ 中における短寿命核 19 O のスピン格子緩和時間」, 日本物理学会 2021 年
秋季大会, オンライン, 2021 年 9 月 20–23 日.
郷慎太郎 (依頼講演), 「アルファ・ベータ・ガンマ線核分光測定から探る原子核構造研究」, 理研新領域開拓課題「物質階層原理研
究」&「ヘテロ界面研究」合同冬研究会, 埼玉県和光市 (理研) & オンライン, 2021 年 12 月 5–6 日.
阿部喬 (パネリスト), 「コロナ禍が研究生活にもたらしたもの」, 理研新領域開拓課題「物質階層原理研究」&「ヘテロ界面研究」
合同冬研究会, 埼玉県和光市 (理研) & オンライン, 2021 年 12 月 5–6 日.
阿部喬 (口頭発表), 「モンテカルロ殻模型による第一原理計算の進展」, 京大基研研究会「核力に基づいた原子核の構造と反応」, 京
都府京都市 (京大基研) & オンライン, 2021 年 12 月 7–10 日.
螺良健太 (口頭発表), 「核モーメント測定法開発のための 光学用クライオスタットにおける超流動ヘリウム中 Rb 原子の収量測, 日本量子医科学会第 1 回学術大会, オンライン, 2021 年 12 月 10–11 日.
定」大塚孝治 (招待講演), “Novel crossover between alpha clustering and quantum liquid in 12 C described by First Principles calculation,”
第 7 回クラスター階層領域研究会, オンライン & 宮城県仙台市 (東北大学電子光理学研究センター), 2021 年 12 月 27–28 日.
中下輝士, 松田恭幸, 酒見泰寛, 長濱弘季, 中村圭佑, 早水友洋, 青木貴稔, 永瀬慎太郎, 山根風樹, 小澤直也, 佐藤幹, 深瀬実来,
上原大祐, 高峰愛子, 「フランシウムの電気双極子能率探索に向けた冷却原子制御系の開発」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
永瀬慎太郎, 酒見泰寛, 長濱弘季, 中村圭佑, 早水友洋, 青木貴稔, 中下輝士, 山根風樹, 小澤直也, 佐藤幹, 深瀬実来, 上原大祐,
高峰愛子, 「原子の電気双極子能率探索に向けたレーザー冷却フランシウム源の開発」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
安藤蒼太, 市川雄一, 佐藤智哉, 篠原悠介, 西畑洸希, 岸本侃己, 山下渉, 横田望海, 郷慎太郎, 高峰愛子, 上野秀樹, 旭耕一郎,「EDM 測定に向けたガラスセル中 Xe 原子のスピン緩和機構の評価」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
庭瀬暁隆, P. Schury, 和田道治, P. Brionnet, S. Chen, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 伊藤由太, 加治大哉, 木村創大,
小浦寛之, 宮武宇也, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 渡辺裕, H. Wollnik, W. Xian, S. X. Yan, 「MRTOF+ α-TOF による 257, 258 Db の精密質量測定」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
今村慧, 高峰愛子, 郷慎太郎, 田島美典, Aleksey Gladkov, 上野秀樹, 「原子ビーム共鳴法による高スピン偏極 RI ビーム生成装置の開発」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
西畑洸希, Gladkov Aleksey, 上野秀樹, 市川雄一, 高峰愛子, 山崎展樹, 佐藤智哉, 田島美典, 今村彗, 川田敬太, 竹内由衣花, 螺良健一,
田中聡, 土居三瑠, 伊藤愛美, 秋元彩, 西村昌輝, 旭耕一郎, 三原基嗣, 足立智輝, 河本彩帆, 北川敦志, 佐藤眞二, 「スピン整列不安
定原子核を用いたベータ核磁気共鳴法の開発」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
高峰愛子, 「高偏極 RI 原子ビーム生成へ向けた低速 RI ビーム生成装置と中性化装置の開発」, 日本物理学会第 77 回年次大会 共催
シンポジウム, オンライン, 2022 年 3 月 15–19 日.
水野るり惠, 池田時浩, 郷慎太郎, 齋藤岳志, 櫻井博儀, 新倉潤, 松崎禎市郎, 道正新一郎, 「ミューオン原子 X 線分光のための Ge 検
出器を用いた広ダイナミックレンジ光子検出システムの性能評価」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月
15–19 日.

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Nuclear Science and Transmutation Research DivisionHigh Energy Astrophysics Laborarory
1. Abstract
In the immediate aftermath of the Big Bang, the beginning of our universe, only hydrogen and helium existed. However, nuclear
fusion in the interior of stars and the explosion of supernovae in the universe over 13.8 billion years led to the evolution of a world
brimming with the many diﬀerent elements we have today. By using scientiﬁc satellites or balloons to observe X-rays and gamma-rays
emitted from celestial objects, we are observing the synthesis of the elements at their actual source. Our goal is to comprehensively
elucidate the scenarios for the formation of the elements in the universe, together with our research on sub-atomic physics through theuse of an accelerator.

2. Major Research Subjects
(1)
(2)
(3)
(4)

History of nucleosynthesis in the universe
Physics in extreme conditions in the universe
Research and development of innovative radiation detectors
Apply radiation technology for human to live in space

3. Summary of Research Activity
High Energy Astrophysics Laboratory started in April 2010. The goal of our research is to reveal the mechanism of nucleosynthesis and the evolution of elements in the universe, and to observe/discover exotic physical phenomena in extremely strong magnetic
and/or gravitational ﬁelds. We have observed supernova remnants, strongly magnetized neutron stars, pulsars, black holes and galaxies
with X-ray astronomical satellites, balloons and ground-based telescopes.
(1) Nucleosynthesis in the universe(1-1) XRISM
X-Ray Imaging and Spectroscopy Mission (XRISM) is a new X-ray astrophysics observatory developed by a joint eﬀort between
Japan and US with participation of Europe. It is aimed at recovering the high-resolution X-ray spectroscopy of hot plasma in the
Universe initiated by the short-lived Hitomi satellite. The spacecraft, payload instruments, and science observation program arecurrently under development. In FY2021, the development and subsystem-level tests of the two payload instruments, Resolve and
Xtend, have been completed successfully. The two instruments are now on the spacecraft and ready for the spacecraft tests. The major
milestone was achieved also in the science observation program. The observation targets for the Performance Veriﬁcation (PV) phasehave been selected and released to public and a new program called the XRISM Guest Scientist has started to oﬀer researchers in theastrophysics community an opportunity to participate in scientiﬁc activities with the observations in the PV phase.
(1-2) MAXI
From April 2018, High Energy Astrophysics Laboratory hosts MAXI (Monitor of All-sky X-ray Image) onboard International
Space Station (ISS), which was attached on ISS in 2009. MAXI is a RIKEN-lead project collaborating with JAXA and other universities. In FY2021, MAXI discovered the 14th blackhole binary MAXI J1803-298, and two Be X-ray binary pulsars MAXI J0903-531
and MAXI J0709-159. The former was followed up by Swift and NICER, while the latter was by NuSTAR and NICER. We reported
28 ATELs (Astronomer’s Telegrams) on transient objects, and 8 GCNs (Gamma-ray Burst Coordinate Network) of gamma-ray bursts.
A new project OHMAN, which is automatic MAXI-NICER coordinate observations on ISS for quick follow-up of transient events
such as gamma-ray bursts and gravitational events, was begun in earnest since 2020 November. We cooperated to equip OHMAN
to ISS, and ﬁnally OHMAN has started on 2022 May 26. Immediate follow-up observations of X-ray transient objects detected by
MAXI are possible with a high-sensitivity X-ray telescope.
(2) Extremely strong magnetism and gravity(2-1) IXPE
We have contributed to the NASA’s world-ﬁrst X-ray polarimeter mission IXPE (Imaging X-ray Polarimeter Explorer). HighEnergy Astrophysics Laboratory is responsible for providing the gas electron multipliers (GEMs) to the IXPE mission: the GEM is a
key device of the X-ray polarimeter and produced based on our patent for space use. The IXPE satellite was successfully launched on
December 9, 2021 from Florida. After one month commissioning in orbit, IXPE started science observations of X-ray stellar objects
from January 11, 2022.
By using the IXPE satellite, we aim to proof the strong magnetism of Magnetars, which are one of the species of neutronstars which have ultra-strong magnetic ﬁeld B > 1011 T. In such ultra-strong magnetic ﬁeld, higher-order diagrams, O(eB/m2 ),O(eB/m2 )2 etc., never ignored in the QED perturbation theory. As the results, we observe newly-emerging phenomenon such as
vacuum polarization, vacuum birefringence, etc. If such exotic phenomena are detected, we sure that Magnetars have really ultrastrong magnetic ﬁeld. We have performed quick-analysis of a Magnetar, which is a neutron star with ultra-strong magnetic ﬁelds,
observed by IXPE in the very early stage of the scientiﬁc observations.
(2-2) Astrophysical data analysis
In parallel with the mission development/operations, we are studying gamma-ray binary systems, which are one of the mostimportant astrophysical targets in the MeV gamma-ray band. We analyzed the broad-band emission of gamma-ray binary LS 5039,- 222 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

a bright gamma-ray object in the MeV band, using NuSTAR and Fermi. The obtained spectrum with the highest available statistics
shows that the emission from MeV to sub-GeV bands is diﬃcult to explain with current theoretical models, suggesting particle
acceleration there is much more eﬃcient than well-known standard diﬀusive shock acceleration.
(3) Innovative breakthrough in astrophysics with a small satellite
We are developing technology and acquiring know-how to make space observation, which requires a lot of money, possible withsmall satellites at low cost. NASA and other space agencies around the world have realized the importance of this opportunities andhave started space observation activities using small satellites. NinjaSat is a micro-satellite mission (6U CubeSat; 30 × 20 × 10 cm3 )led by RIKEN in collaboration with universities. NinjaSat will be deployed from the ISS in 2022. Although several science missions
have recently been conducted using micro-satellites, NinjaSat is the world’s ﬁrst general purpose CubeSat mission to observe X-ray
sources. NinjaSat carries two Xe-ﬁlled gas detectors with 2-degree-wide collimators and performs spectroscopy between 2–50 keV
and timing obervation with a timing resolution of about 120 μs. Since the eﬀective area is not large (∼40 cm2 at 6 keV), the targetof the NinjaSat is a long-term monitoring of bright X-ray sources which are discovered by MAXI etc. In general, bright objects are
diﬃcult to observe and a continuous observations for long period is impossible with large satellite missions. The aim of NinjaSat is
to perform observations that are diﬃcult to perform on larger missions. For example, NinjaSat observes the time variability of binary
neutron stars and binary black holes in conjunction with the ground-based optical, radio and gravitational telescopes. We fabricatedand tested X-ray detectors for ﬂight in FY2021.
(4) Future X-ray and gamma-ray detectors
In collaboration with NASA Goddard Space Flight Center, we have developed and tested a hard X-ray polarimeter with a Time
Projection Chamber technique. This TPC polarimeter is one of candidates of the future satellite XPP (X-ray polarimeter Probe
mission) planned with an international consortium.
As an successor of the MAXI mission, we are also verifying the principle of a new concept, multiplexing lobster-eye (MuLE)
optics, to monitor the entire sky with a wide ﬁeld-of-view for detecting and immediate reporting transient objects such as a neutronstar merger. We published a paper on the conceptual design of MuLE, and proved the concept by a simple experiment.
To explore the MeV gamma-ray sky in the Universe, we are working on the technical development of the GRAMS (Gamma-Ray
and AntiMatter Survey) project, which aims at future MeV gamma-ray observations with a Compton telescope using a liquid argon
time projection chamber. We developed two types of event reconstruction algorithms for multiple Compton scattering events using
probabilistic and neural network methods. Based on them, we conﬁrmed that the advantage of the GRAMS project, which is anobservation with an eﬀective area larger than previous by 1-2 orders magnitudes, can be achievable with a current mission concept.

Members
Director
Toru TAMAGAWA
Research/Technical Scientist
Tatehiro MIHARA (Senior Research Scientist)
Special Postdoctoral Researcher
Hiroki YONEDA
Visiting Scientists
Aya BAMBA (Univ. of Tokyo)
Naohisa INADA (NIT, Nara College)
Satoru KATSUDA (Saitama Univ.)
Tomoki KIMURA (Tohoku Univ.)
Kazuki KOMIYA (Tokyo Metropolitan Industrial Tech. Res.
Inst.)
Toru MISAWA (Shinshu Univ.)
Ikuyuki MITSUISHI (Nagoya Univ.)
Yujin NAKAGAWA (JAMSTEC)
Student Trainees
Syoki HAYASHI (Tokyo Univ. Sci)
Naoyuki OTA (Tokyo Univ. Sci)
Tomoshi TAKEDA (Tokyo Univ. Sci)

Hirofumi NODA (Osaka Univ.)
Hirokazu ODAKA (Univ. of Tokyo)
Yuki OKURA (NAOJ/Nat’l Inst. of Natural Sci.)
Rohta TAKAHASHI (NIT, Tomakomai College)
Yoko TAKEUCHI (Tokyo Metropolitan Industrial Tech. Res.
Inst.)
Yukikatsu TERADA (Saitama Univ.)
Masaki WAKABAYASHI (Jakulin Commercial Company LC)
Shinya YAMADA (Rikkyo Univ.)
Keisuke UCHIYAMA (Tokyo Univ. Sci)
Yuto YOSHIDA (Tokyo Univ. Sci)

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

List of Publications & Presentations
Publications[Original Papers]
L. Baldini, M. Barbanera, R. Bellazzini, R. Bonino, F. Borotto, A. Brez, C. Caporale, C. Cardelli, S. Castellano, M. Ceccanti, S. Citraro,
N. D. Lalla, L. Latronico, L. Lucchesi, C. Magazzù, G. Magazzù, S. Maldera, A. Manfreda, M. Marengo, A. Marrocchesi, P. Mereu,
M. Minuti, F. Mosti, H. Nasimi, A. Nuti, C. Oppedisano, L. Orsini, M. Pesce-Rollins, M. Pinchera, A. Profeti, C. Sgrò, G. Spandre,
M. Tardiola, D. Zanetti, F. Amici, H. Andersson, P. Attinà, M. Bachetti, W. Baumgartner, D. Brienza, R. Carpentiero, M. Castronuovo,
L. Cavalli, E. Cavazzuti, M. Centrone, E. Costa, E. D’Alba, F. D’Amico, E. D. Monte, S. D. Cosimo, A. D. Marco, G. D. Persio,
I. Donnarumma, Y. Evangelista, S. Fabiani, R. Ferrazzoli, T. Kitaguchi, F. L. Monaca, C. Lefevre, P. Loﬀredo, P. Lorenzi, E. Mangraviti,
G. Matt, T. Meilahti, A. Morbidini, F. Muleri, T. Nakano, B. Negri, S. Nenonen, S. L. O’Dell, M. Perri, R. Piazzolla, S. Pieraccini,
M. Pilia, S. Puccetti, B. D. Ramsey, J. Rankin, A. Ratheesh, A. Rubini, F. Santoli, P. Sarra, E. Scalise, A. Sciortino, P. Soﬃtta,
T. Tamagawa, A. F. Tennant, A. Tobia, A. Trois, K. Uchiyama, M. Vimercati, M. C. Weisskopf, F. Xie, F. Zanetti, and Y. Zhou,“Design, construction, and test of the gas pixel detectors for the IXPE mission,” Astropart. Phys. 133, 102628 (2021).
P. Soﬃtta, L. Baldini, R. Bellazzini, E. Costa, L. Latronico, F. Muleri, E. D. Monte, S. Fabiani, M. Minuti, M. Pinchera, C. Sgro’,G. Spandre, A. Trois, F. Amici, H. Andersson, P. Attina’, M. Bachetti, M. Barbanera, F. Borotto, A. Brez, D. Brienza, C. Caporale,
C. Cardelli, R. Carpentiero, S. Castellano, M. Castronuovo, L. Cavalli, E. Cavazzuti, M. Ceccanti, M. Centrone, S. Ciprini, S. Citraro,
F. D’Amico, E. D’Alba, S. D. Cosimo, N. D. Lalla, A. D. Marco, G. D. Persio, I. Donnarumma, Y. Evangelista, R. Ferrazzoli, A. Hayato,
T. Kitaguchi, F. L. Monaca, C. Lefevre, P. Loﬀredo, P. Lorenzi, L. Lucchesi, C. Magazzu, S. Maldera, A. Manfreda, E. Mangraviti,
M. Marengo, G. Matt, P. Mereu, A. Morbidini, F. Mosti, T. Nakano, H. Nasimi, B. Negri, S. Nenonen, A. Nuti, L. Orsini, M. Perri,
M. Pesce-Rollins, R. Piazzolla, M. Pilia, A. Profeti, S. Puccetti, J. Rankin, A. Ratheesh, A. Rubini, F. Santoli, P. Sarra, E. Scalise,
A. Sciortino, T. Tamagawa, M. Tardiola, A. Tobia, M. Vimercati, and F. Xie, “The instrument of the imaging X-ray polarimetry
explorer,” Astron. J. 162, 208 (2021).
Q. Abarr, H. Awaki, M. G. Baring, R. Bose, G. D. Geronimo, P. Dowkontt, M. Errando, V. Guarino, K. Hattori, K. Hayashida, F. Imazato,
M. Ishida, N. K. Iyer, F. Kislat, M. Kiss, T. Kitaguchi, H. Krawczynski, L. Lisalda, H. Matake, Y. Maeda, H. Matsumoto, T. Mineta,
T. Miyazawa, T. Mizuno, T. Okajima, M. Pearce, B. F. Rauch, F. Ryde, C. Shreves, S. Spooner, T. -A. Stana, H. Takahashi, M. Takeo,
T. Tamagawa, K. Tamura, H. Tsunemi, N. Uchida, Y. Uchida, A. T. West, E. A. Wulf, and R. Yamamoto, “XL-calibur – A secondgeneration balloon-borne hard X-ray polarimetry mission,” Astropart. Phys. 126, 102529 (2021).
W. B. Iwakiri, M. Serino, T. Mihara, L. Gu, H. Yamaguchi, M. Shidatsu, and K. Makishima, “Discovery of a strong 6.6 keV emission
feature from EXO 1745-248 after the superburst in 2011 October,” Publ. Astron. Soc. Jpn. 73, 108 (2021).
M. Kimura, S. Yamada, N. Nakaniwa, Y. Makita, H. Negoro, M. Shidatsu, T. Kato, T. Enoto, K. Isogai, T. Mihara, H. Akazawa, K. C. Gendreau, F. -J. Hambsch, P. A. Dubovsky, I. Kudzej, K. Kasai, Tamás Tordai, E. Pavlenko, A. A. Sosnovskij, J. V. Babina, O. I. Antonyuk,
H. Itoh, and H. Maehara, “On the nature of the anomalous event in 2021 in the dwarf nova SS Cygni and its multi-wavelength transition,” Publ. Astron. Soc. Jpn. 73, 1262 (2021).
Y. Yao, S. R. Kulkarni, K. C. Gendreau, G. K. Jaisawal, T. Enoto, B. W. Grefenstette, H. L. Marshall, J. A. Garcı́a, R. M. Ludlam,
S. N. Pike, M. Ng, L. Zhang, D. Altamirano, A. Jaodand, S. B. Cenko, R. A. Remillard, J. F. Steiner, H. Negoro, M. Brightman, A. Lien,
M. T. Wolﬀ, P. S. Ray, K. Mukai, Z. Wadiasingh, Z. Arzoumanian, N. Kawai, T. Mihara, and T. E. Strohmayer, “A comprehensive X-ray
report on AT2019wey,” Astrophys. J. 920, 121 (2021).
M. Shidatsu, W. Iwakiri, H. Negoro, T. Mihara, Y. Ueda, N. Kawai, S. Nakahira, J. A. Kennea, P. A. Evans, K. C. Gendreau, T. Enoto,
and F. Tombesi, “The peculiar X-ray transient swift J0840.7-3516: An unusual low-mass X-ray binary or a tidal disruption event?,”
Astrophys. J. 910, 144 (2021).
R. Sasaki, Y. Tsuboi, W. Iwakiri, S. Nakahira, Y. Maeda, K. C. Gendreau, M. F. Corcoran, K. Hamaguchi, Z. Arzoumanian, C. Markwardt,
T. Enoto, T. Sato, H. Kawai, T. Mihara, M. Shidatsu, H. Negoro, and M. Serino, “The RS CVn-type Star GT mus shows most energetic
X-ray ﬂares throughout the 2010s,” Astrophys. J. 910, 25 (2021).
K. Makishima, T. Tamba, Y. Aizawa, H. Odaka, H. Yoneda, T. Enoto, and H. Suzuki, “Discovery of 40.5 ks hard X-ray pulse-phasemodulations from SGR 1900+14,” Astrophys. J. 923, 63 (2021).
T. Orita, G. Yabu, H. Yoneda, S. I. Takeda, P. Caradonna, T. Takahashi, S. Watanabe, Y. Uchida, F. Moriyama, H. Sugawara, M. Uenomachi, and K. Shimazoe, “Double-photon emission imaging with high-resolution Si/CdTe compton cameras,” IEEE Trans. Nucl. Sci.
68, 2279 (2021).
H. Yoneda, D. Khangulyan, T. Enoto, K. Makishima, K. Mine, T. Mizuno, and T. Takahashi, “Broadband high-energy emission of the
gamma-ray binary system LS 5039: Spectral and temporal features using NuSTAR and Fermi observations,” Astrophys. J. 917, 90(2021).
N. Tsuji, H. Yoneda, Y. Inoue, T. Aramaki, G. Karagiorgi, R. Mukherjee, and H. Odaka, “Cross-match between the Latest Swift-BAT and
Fermi-LAT catalogs,” Astrophys. J. 916, 28 (2021).
Y. Tsuzuki, S. Watanabe, S. Oishi, N. Nakamura, N. Numadate, H. Odaka, Y. Uchida, H. Yoneda, and T. Takahashi, “An application ofa Si/CdTe Compton camera for the polarization measurement of hard X rays from highly charged heavy ions,” Rev. Sci. Instrum. 92,
063101 (2021).
K. Makishima, T. Enoto, H. Yoneda, and H. Odaka, “A NuSTAR conﬁrmation of the 36 ks hard X-ray pulse-phase modulation in themagnetar 1E 1547.0-5408,” Mon. Notices Royal Astron. Soc. 502, 2266 (2021).
S. N. Pike, H. Negoro, J. A. Tomsick, M. Bachetti, McK. Brumback, R. M T. Connors, J. A. Garcı́a, B. Grefenstette, J. Hare, F. A. Harrison,
A. Jaodand, R. M. Ludlam, G. Mastroserio, T. Mihara, M. Shidatsu, M. Sugizaki, and R. Takagi, “MAXI and NuSTAR observations of
the faint X-ray transient MAXI J1848-015 in the GLIMPSE-C01 cluster,” Astrophys. J. 927, 190 (2022).

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M. Shidatsu, K. Kobayashi, H. Negoro, W. Iwakiri, S. Nakahira, Y. Ueda, T. Mihara, T. Enoto, K. Gendreau, Z. Arzoumanian, J. Pope,B. Trout, T. Okajima, and Y. Soong, “Discovery and long-term broadband X-ray monitoring of galactic black hole candidate MAXI
J1803-298,” Astrophys. J. 927, 151 (2022).
N. Numadate, S. Oishi, H. Odaka, M. Sakurai, T. Takahashi, Y. Tsuzuki, Y. Uchida, H. Watanabe, S. Watanabe, H. Yoneda, and N. Nakamura, “Polarization measurement of L-shell radiative recombination X rays from highly charged bismuth ions,” Phys. Rev. A 105,
023109 (2022).

[Proceeding]
B. D. Ramsey, P. Attina, L. Baldini, M. Barbanera, W. H. Baumgartner, R. Bellazzini, J. Bladt, S. D. Bongiorno, A. Brez, S. Castellano,
R. Carpentiero, M. Castronuovo, L. Cavalli, E. Cavazutti, F. D’Amico, S. Citraro, E. Costa, W. D. Deininger, E. D’Alba, E. Delmonte,
K. L. Dietz, N. D. Lalla, A. D. Marco, G. D. Persio, I. Donnarumma, S. Fabiani, R. Ferrazzoli, J. Footdale, M. Head, W. Kalinowski,
J. J. Kolodziejczak, L. Latronico, C. Lefevre, P. Lorenzi, L. Lucchesi, S. Maldera, A. Manfreda, E. Mangravati, H. L. Marshall, G. Matt,
M. Minuti, R. Mize, F. Muleri, H. Nasimi, B. Negri, A. Nuti, S. O’Dell, L. Orsini, D. Osborne, C. Pentz, M. Pilia, M. Perri, M. PesceRollins, C. Peterson, M. Pinchera, S. Puccetti, J. Rankin, A. Ratheesh, R. W. Romani, P. Sarra, F. Santoli, A. Sciortino, C. Schroeder,
C. Sgro, P. Soﬃtta, G. Spandre, A. Tennant, A. Tobia, N. E. Thomas, A. Trois, M. Vimercati, J. Wedmore, M. C. Weisskopf, F. Xie,
F. Zanetti, C. Alexander, D. Z. Allen, F. Amici, J. Andersen, A. Antonelli, S. Antoniak, M. Bachetti, R. M. Baggett, R. Bonino, C. Boree,
F. Borotto, S. Breeding, D. Brienza, H. K. Byggott, C. Caporale, C. Cardelli, M. Ceccanti, M. Centrone, D. Dolan, Y. Evangelista,
K. Ferrant, M. Ferrie, B. Forsyth, M. Foster, B. Garelick, S. Gunji, E. Gurnee, G. Hibbard, S. Johnson, E. Kelly, K. Kilaru, F. L. Monaca,
S. L. Roy, P. Lofredo, T. Maddox, G. Magazzu, M. Marengo, A. Marrocchesi, F. Massaro, D. Mauger, J. McCracken, M. McEachen,
P. Mereu, S. Mitchell, I. Mitsuishi, A. Morbidini, F. Mosti, T. Nguyen, M. Negro, I. Nitschke, M. Onizuka, C. Oppedisano, R. Pacheco,
A. Paggi, W. Painter, S. D. Pavelitz, R. Piazzolla, A. Profeti, J. Ranganathan, L. Reedy, N. Root, A. Rubini, S. Ruswick, J. Sanchez,
E. Scalise, T. Seek, K. Sosdian, C. O. Speegle, T. Tamagawa, M. Tardiola, R. Valerie, A. L. Walden, B. Weddendorf, and D. Welch,“The imaging X-ray polarimetry explorer (IXPE): Technical overview IV,” Proc. SPIE 11821, 118210M (2021).

Presentations[Domestic Conferences/Workshops]
玉川徹, 北口貴雄, 榎戸輝揚, 内山慶祐, 武田朋志, 三石郁之, 柏倉一斗, 田原譲, 郡司修一, 渡邉瑛里, 寺島政伸, 斎藤耀, 管佑真, 深沢
泰司, 水野恒史, 高橋弘充, 内田和海, S. Zhang, 岩切渉, 林田清, 朝倉一統, M. Weisskopf, B. Ramsey, S. O’Dell, P. Soﬃtta, L. Baldini,
ほか IXPE 衛星チーム, 「X 線偏光観測衛星 IXPE への参加現状 (7)」, 日本天文学会 2021 年秋季年会, オンライン, 2021 年 9 月.
三原建弘, 根来均, 岩切渉, 海老沢研, ほか MAXI チーム, 「OHMAN (MAXI-NICER ISS 上連携) の準備状況」, 日本天文学会 2021
年秋季年会, オンライン, 2021 年 9 月.
武田朋志, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 沼澤正樹, 三原建弘, 岩切渉, 内山慶祐, 吉田勇登, 大田尚享, 林昇輝, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「明るい X 線天体を狙う 6U キューブサット NinjaSat の進捗」, 日本天文学会 2021 年秋季年会, オンライン, 2021 年 9 月.
吉田勇登, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 沼澤正樹, 三原建弘, 岩切渉, 内山慶祐, 武田朋志, 大田尚享, 林昇輝, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「NinjaSat における信号波形による X 線と荷電粒子の弁別方法の開発」, 日
本天文学会 2021 年秋季年会, オンライン, 2021 年 9 月.
沼澤正樹, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 三原建弘, 岩切渉, 内山慶祐, 武田朋志, 大田尚享, 吉田勇登, 林昇輝, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「NinjaSat に搭載する観測機器のコンポーネント環境試験」, 日本天文学会
2021 年秋季年会, オンライン, 2021 年 9 月.
大田尚享, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 沼澤正樹, 三原建弘, 岩切渉, 内山慶祐, 武田朋志, 吉田勇登, 林昇輝, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「NinjaSat に搭載するアナログ信号処理基板の開発」, 日本天文学会 2021 年
秋季年会, オンライン, 2021 年 9 月.
内山慶祐, 玉川徹, 三原建弘, 榎戸輝揚, 沼澤正樹, 周圓輝, 江副祐一郎, 伊師大貴, 福島碧都, 内野友樹, 作田紗恵, 石川久美, 森下弘海,
関口るな, 辻雪音, 村川貴俊, 稲垣綾太, 上田陽功, 坂本貴紀, 「広視野を少数の撮像素子でカバーする多重化ロブスターアイ X 線
光学系」, 日本天文学会 2021 年秋季年会, オンライン, 2021 年 9 月.
Y. Ishisaki, R. L. Kelley, H. Akamatsu, H. Awaki, T. G. Bialas, G. V. Brown, M. P. Chiao, E. Costantini, J. -W. den Herder, M. J. Dipirro,
M. E. Eckart, Y. Ezoe, C. Ferrigno, R. Fujimoto, A. Furuzawa, S. M. Graham, M. Grim, T. Hayashi, A. Hoshino, Y. Ichinohe, R. Iizuka,
M. Ishida, K. Ishikawa, C. A. Kilbourne, S. Kitamoto, M. A. Leutenegger, Y. Maeda, D. McCammon, I. Mitsuishi, M. Mizumoto,
T. Okajima, S. Paltani, F. S. Porter, K. Sato, T. Sato, M. Sawada, H. Seta, P. J. Shirron, G. A. Sneiderman, Y. Soong, A. E. Szymkowiak,
Y. Takei, T. Tamagawa, M. Tsujimoto, Y. Uchida, C. P. de Vries, S. Yamada, N. Y. Yamasaki, S. Yasuda, and N. Yoshioka, 「X 線分光, 日本天文学会 2021 年秋季年会, オンライン, 2021 年 9 月.
撮像衛星 XRISM 搭載 Resolve の開発の現状 VII」
寺島政伸, 郡司修一, 渡邉瑛里, 管佑真, 斎藤耀, 玉川徹, 北口貴雄, 榎戸輝揚, 内山慶祐, 武田朋志, 三石郁之, 柏倉一斗, 田原譲, 深沢
泰司, 水野恒史, 高橋弘充, 内田和海, Z. Sixuan, 岩切渉, 林田清, 朝倉一統, M. Weisskopf, B. Ramsey, S. O’Dell, P. Soﬃtta, L. Baldini,
ほか IXPE 衛星チーム, 「IXPE におけるガンマ線バースト残光の観測クライテリア」, 日本物理学会 2021 年秋季大会, オンライ
ン, 2021 年 9 月.
高橋弘充, Q. Abarr, 青柳美緒, 朝倉一統, 粟木久光, M. G. Baring, R. Bose, D. Braun, Gianluigi de Geronimo, P. Dowkontt, J. Elliot,
榎戸輝揚, M. Errando, 深沢泰司, 古澤彰浩, T. Gadson, E. Gau, V. Guarino, 郡司修一, 袴田知宏, 萩原涼太, K. Hall, 花岡真帆,
K. Harmon, 服部憲吾, 林田清, L, S. Heatwole, A. Hossen, 井出峻太郎, 今村竜太, 今里郁弥, 今澤遼, 石橋和紀, 石田学, 石倉彩美,
石渡幸太, N. K. Iyer, F. Kislat, M. Kiss, 亀谷紀香, 鴨川航, 北口貴 G, D. Kotsifakis, H. Krawczynski, J. Lanzi, L. Lisalda, 前田
良知, 松下友亮, 眞武寛人, 松本浩典, 峯田大晴, 宮本明日香, 宮澤拓也, 水野恒史, 中庭望, 野田博文, 大出優一, 岡島崇, 岡崎
貴樹, I. Pastrani, M. Pearce, N, Z. Peterson, H. Poon, C. Purdy, B. Rauch, F. Ryde, 斎藤芳隆, 佐久間翔太郎, 佐藤淳矢, 澤上拳明,
C. Shreeves, G. Simburger, C. Snow, S. Spooner, Theodor-A. Stana, D. Stuchlik, 鈴木瞳, 武田朋志, 武尾舞, 玉川徹, 田村啓輔, 常深- 225 -

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博, 内田和海, 内田悠介, 内山慶祐, B. Vincent, A. West, E. Wulf, 山本龍哉, 楊冲, 米山友景, 吉田勇登, 善本真梨那, ほか XL-Calibur
チーム, 「硬 X 線偏光観測 XL-Calibur 気球実験の 2022 年フライトへ向けた準備状況」, 日本物理学会 2021 年秋季大会, オンラ
イン, 2021 年 9 月.
小高裕和, 高嶋聡, 南木宙斗, 馬場彩, 青山一天, 岩澤広大, 木村眞人, 櫻井真由, 田中雅士, 中曽根太地, 寄田浩平, 一戸悠人, 井上芳幸,
辻直美, 米田浩基, T. Aramaki, G. Karagiorgi, R. Mukherjee, ほか GRAMS コラボレーション「GRAMS 実験 5：全体報告」, 日本
物理学会 2021 年秋季大会, オンライン, 2021 年 9 月.
高嶋聡, 小高裕和, 南木宙斗, 馬場彩, 青山一天, 岩澤広大, 木村眞人, 櫻井真由, 田中雅士, 中曽根太地, 寄田浩平, 一戸悠人, 井上芳幸,
辻直美, 米田浩基, T. Aramaki, G. Karagiorgi, R. Mukherjee, ほか GRAMS コラボレーション, 「GRAMS 実験 6：マルチタスク深層学習によるイベント再構成手法の開発」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月.
青山一天, 岩澤広大, 木村眞人, 櫻井真由, 田中雅士, 中曽根太地, 寄田浩平, 小高裕和, 高嶋聡, 南木宙斗, 馬場彩, 一戸悠人, 井上芳幸,
辻直美, 米田浩基, T. Aramaki, G. Karagiorgi, R. Mukherjee, ほか GRAMS コラボレーション, 「GRAMS 実験 7：液体アルゴン
TPC における光子・電子信号のエネルギー分解能測定」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月.
櫻井真由, 青山一天, 岩澤広大, 木村眞人, 田中雅士, 中曽根太地, 寄田浩平, 小高裕和, 高嶋聡, 米田浩基, 一戸悠人, ほか GRAMS コ
ラボレーション, 「宇宙線反重陽子探索に向けた液体アルゴン検出器による宇宙線荷電粒子の識別」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月.
中曽根太地, 青山一天, 岩澤広大, 木村眞人, 櫻井真由, 田中雅士, 寄田浩平, 小高裕和, 高嶋聡, 米田浩基, 一戸悠人, ほか GRAMS コ
ラボレーション「宇宙反重陽子探索に向けた液体アルゴン検出器における原子核捕獲事象の検証」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月.
玉川徹, 北口貴雄, 榎戸輝揚, 内山慶祐, 武田朋志, 三石郁之, 柏倉一斗, 田原譲, 郡司修一, 渡邉瑛里, 寺島政伸, 斎藤耀, 管佑真, 深沢
泰司, 水野恒史, 高橋弘充, 内田和海, S. Zhang, 岩切渉, 林田清, 朝倉一統, M. Weisskopf, B. Ramsey, S. O’Dell, P. Soﬃtta, L. Baldini,
ほか IXPE 衛星チーム, 「X 線偏光観測衛星 IXPE」, 第 22 回宇宙科学シンポジウム, 相模原 (宇宙科学研究所), 2022 年 1 月.
玉川徹, 北口貴雄, 榎戸輝揚, 内山慶祐, 武田朋志, 三石郁之, 柏倉一斗, 田原譲, 郡司修一, 渡邉瑛里, 寺島政伸, 斎藤耀, 管佑真, 深沢
泰司, 水野恒史, 高橋弘充, 内田和海, Z. Sixuan, 岩切渉, 林田清, 朝倉一統, M. Weisskopf, B. Ramsey, S. O’Dell, P. Soﬃtta, L. Baldini,
ほか IXPE 衛星チーム, 「X 線偏光観測衛星 IXPE の現状 (1)」, 日本天文学会 2022 年春季年会, オンライン, 2022 年 3 月.
林昇輝, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 三原建弘, 岩切渉, 沼澤正樹, 武田朋志, 吉田勇登, 大田尚享, 内山慶祐, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「超小型 X 線衛星 NinjaSat に搭載するガス X 線検出器の開発 (3)」, 日本天文学会 2022 年春季年会, オンライン, 2022 年 3 月.
大田尚享, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 三原建弘, 岩切渉, 沼澤正樹, 武田朋志, 吉田勇登, 林昇輝, 内山慶祐, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「超小型 X 線衛星 NinjaSat に搭載するガス検出器用の電子回路基板の開発」,
日本天文学会 2022 年春季年会, オンライン, 2022 年 3 月.
加藤陽, 玉川徹, 榎戸輝揚, 北口貴雄, 三原建弘, 岩切渉, 沼澤正樹, 武田朋志, 吉田勇登, 大田尚享, 林昇輝, 内山慶祐, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「超小型 X 線衛星 NinjaSat に搭載する放射線帯モニターの開発」, 日本天文学会 2022 年春季年会, オンライン, 2022 年 3 月.
米田浩基, 辻直美, 小高裕和, 高嶋聡, 丹波翼, 南木宙斗, 馬場彩, 八幡和志, 青山一天, 岩澤広大, 櫻井真由, 田中雅士, 中曽根太地, 寄田
浩平, 一戸悠人, D. Khangulyan, 井上芳幸, 内田悠介, 須田祐介, 高橋弘允, 深沢泰司, 大野雅功, 広島渚, T. Aramaki, G. Karagiorgi,
R. Mukherjee, ほか GRAMS コラボレーション, 「GRAMS 計画 4:MeV ガンマ線観測・ダークマター探索気球実験」, 日本天文学会 2022 年春季年会, オンライン, 2022 年 3 月.
Y. Ishisaki, R. L. Kelley, H. Akamatsu, H. Awaki, T. G. Bialas, G. V. Brown, M. P. Chiao, E. Costantini, J. -W. den Herder, M. J. Dipirro,
M. E. Eckart, Y. Ezoe, C. Ferrigno, R. Fujimoto, A. Furuzawa, S. M. Graham, M. Grim, T. Hayashi, A. Hoshino, Y. Ichinohe, R. Iizuka,
M. Ishida, K. Ishikawa, C. A. Kilbourne, S. Kitamoto, M. A. Leutenegger, Y. Maeda, D. McCammon, I. Mitsuishi, M. Mizumoto,
T. Okajima, S. Paltani, F. S. Porter, K. Sato, T. Sato, M. Sawada, H. Seta, P. J. Shirron, G. A. Sneiderman, Y. Soong, A. E. Szymkowiak,
Y. Takei, T. Tamagawa, M. Tsujimoto, Y. Uchida, C. P. de Vries, S. Yamada, N. Y. Yamasaki, S. Yasuda, N. Yoshioka, 「X 線分光撮
像衛星 XRISM 搭載 Resolve の開発の現状 VIII」, 日本天文学会 2022 年春季年会, オンライン, 2022 年 3 月.
郡司修一, 渡邉瑛里, 寺島政伸, 管佑真, 斎藤耀, 玉川徹, 北口貴雄, 榎戸輝揚, 内山慶祐, 武田朋志, 三石郁之, 柏倉一斗, 田原譲, 深沢
泰司, 水野恒史, 高橋弘充, 内田和海, Z. Sixuan, 岩切渉, 林田清, 朝倉一統, M. Weisskopf, B. Ramsey, S. O’Dell, P. Soﬃtta, L. Baldini,
ほか IXPE 衛星チーム, 「IXPE 衛星によって開かれるイメージング X 線偏光観測」, 日本物理学会第 77 回年次大会, オンライ
ン, 2022 年 3 月.
渡邉瑛里, 郡司修一, 寺島政伸, 管佑真, 斎藤耀, 玉川徹, 北口貴雄, 榎戸輝揚, 内山慶祐, 武田朋志, 三石郁之, 柏倉一斗, 田原譲, 深沢
泰司, 水野恒史, 高橋弘充, 内田和海, Z. Sixuan, 岩切渉, 林田清, 朝倉一統, M. Weisskopf, B. Ramsey, S. O’Dell, P. Soﬃtta, L. Baldini,
ほか IXPE 衛星チーム, 「カニ星雲を用いた Chandra と IXPE のジョイント解析による偏光解析手法の開発」, 日本物理学会第 77
回年次大会, オンライン, 2022 年 3 月.
高橋弘充, Q. Abarr, 青柳美緒, 朝倉一統, 粟木久光, M. G. Baring, R. Bose, D. Braun, Gianluigi de Geronimo, P. Dowkontt, J. Elliot,
榎戸輝揚, M. Errando, 深沢泰司, 古澤彰浩, T. Gadson, E. Gau, V. Guarino, 郡司修一, 袴田知宏, 萩原涼太, K. Hall, 花岡真帆,
K. Harmon, 服部憲吾, 林田清, S. Heatwole, A. Hossen, 井出峻太郎, 今村竜太, 今里郁弥, 今澤遼, 石橋和紀, 石田学, 石倉彩美,
石渡幸太, N. K. Iyer, F. Kislat, M. Kiss, 亀谷紀香, 鴨川航, 北口貴雄, D. Kotsifakis, H. Krawczynski, J. Lanzi, L. Lisalda, 前田
良知, 松下友亮, 眞武寛人, 松本浩典, 峯田大晴, 宮本明日香, 宮澤拓也, 水野恒史, 中庭望, 野田博文, 大出優一, 岡島崇, 岡崎貴樹,
I. Pastrani, M. Pearce, Z. Peterson, H. Poon, C. Purdy, B. Rauch, F. Ryde, 斎藤芳隆, 佐久間翔太郎, 佐藤淳矢, 澤上拳明, C. Shreeves,
G. Simburger, C. Snow, S. Spooner, Theodor-A. Stana, D. Stuchlik, 鈴木瞳, 武田朋志, 武尾舞, 玉川徹, 田村啓輔, 常深博, 内田和海,
内田悠介, 内山慶祐, B. Vincent, A. West, E. Wulf, 山本龍哉, 楊冲, 米山友景, 吉田勇登, 善本真梨那, ほか XL-Calibur チーム, 「硬X 線偏光観測 XL-Calibur 気球実験の 2022 年フライトへ向けた準備状況」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3月.
武田朋志, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 三原建弘, 岩切渉, 沼澤正樹, 内山慶祐, 吉田勇登, 大田尚享, 林昇輝, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「超小型 X 線衛星 NinjaSat 搭載のガス X 線検出器の開発進捗」, 日本物理学- 226 -

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会第 77 回年次大会, オンライン, 2022 年 3 月.
吉田勇登, 玉川徹, 榎戸輝揚, 北口貴雄, 加藤陽, 三原建弘, 岩切渉, 沼澤正樹, 内山慶祐, 武田朋志, 大田尚享, 林昇輝, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「超小型 X 線衛星 NinjaSat における X 線と宇宙線の波形弁別方法の開発」,
日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月.
北口貴雄, 玉川徹, 榎戸輝揚, 加藤陽, 三原建弘, 岩切渉, 沼澤正樹, 内山慶祐, 武田朋志, 吉田勇登, 大田尚享, 林昇輝, 佐藤宏樹,
C. -P. Hu, 高橋弘充, 小高裕和, 丹波翼, 谷口絢太郎, 「超小型 X 線衛星 NinjaSat に搭載するデータ取得ボードの開発」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月.
後藤初音, 米徳大輔, 荻野直樹, 有元誠, 澤野達哉, 三原建弘, 「軟 X 線ビームラインによる Lobster Eye Optics の結像性能評価」,日
本物理学会第 77 回年次大会, オンライン, 2022 年 3 月.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Nuclear Many-Body Theory Laborarory
1. Abstract
The nuclear many-body theory laboratory aims to understand various aspects of nuclear structure and reactions due to the assemblyand disassembly of protons and neutrons in the nuclear many-body systems. For this purpose, we construct theoretical models andconduct numerical calculations to describe them. Our research topics include nuclear structure issues such as nuclear deformation,
shell structure, and clustering of unstable nuclei, and nuclear reactions in the Universe where elements originate. In addition to
fundamental research, we are also developing nuclear reaction database by combining the nuclear models and machine learning. The
database will be used for various scientiﬁc and technological applications such as nuclear reactors, medicine and industry.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Structure and reactions of unstable nuclei
Nuclear clustering and related nuclear reactions
Nuclear reactions in the universe
Research and development of the nuclear reaction database for applications

3. Summary of Research Activity(1) Structure and reactions of unstable nuclei
The study of the structure and reactions of unstable nuclei is an important subject of the Nishina Center, as well as one of the core
issues in modern nuclear physics. Our group approaches this problem by performing numerical calculations using theoretical models
such as antisymmetrized molecular dynamics and density functional theory.
In this ﬁscal year, we mainly discussed the nuclear deformation and shape coexistence phenomena induced by the disappearanceof the magic numbers in neutron-rich nuclei. One of the research highlights is the study of 44 S, in which we have found the onset ofthe large amplitude collective motion due to the disappearance of the magic number N = 28. We have shown that this nucleus does
not have deﬁnite shape but is always ﬂuctuating. We have also pointed out that the monopole transition strength is an experimental
probe to this shape ﬂuctuation. By using the obtained density distribution of unstable nuclei as an input to the Glauber model, we
also investigated how the disappearance of magic number and the shape of the nuclei aﬀect the reaction cross section and the angular
distribution of elastic scattering.
(2) Nuclear clustering and related nuclear reactions
The nuclear clustering, in which nucleons are conﬁned into into several subunits (clusters), is an eligible research subject forunderstanding the correlation of nucleons interacting with strong force. Since the clusters are linked to the nuclear reaction channels,
they also appear as the intermediate states of various nuclear reaction dynamics.
In this year, we have studied the 3α + n cluster structure in order to understand how the 3α cluster state (the 0+2 state of 12 C),
known as the Bose-Einstein condensate (BEC) of α clusters, is inﬂuenced by the addition of a neutron as impurity. Using the real-time
evolution method, we have identiﬁed the 3α + n cluster state as an excited state of 13 C, and have shown that its matter radius isconsiderably reduced than that of the 3α BEC due to the attraction of the additional neutron. In addition, by using the antisymmetrizedmolecular dynamics model, we have investigated how the α cluster formation probability in unstable Be and C isotopes changes asfunction of neutron skin thickness. We have demonstrated that the α cluster formation is hindered by the growth of the neutron skin,which is consistent with the experimental data reported for the Sn isotopes.
(3) Nuclear reactions in the universe
Fusion reactions that occur in stellar and explosive astronomical events are key to understanding the origin of the elements.
However, many reactions have extremely small cross sections, making direct experimental measurement diﬃcult, and estimating
reaction rates by theoretical calculation is critically important.
In this ﬁscal year, using the antisymmetrized molecular dynamics, we have obtained an estimate of the reaction rate of 12 C +12 C
fusion. It must be emphasized that this is a well-known key reaction which aﬀects the steller evolution and superburst of neutronstar, and that our result is the ﬁrst estimates from a full-microscopic nuclear model. We have shown that there are many resonances
within the Gamow window, and hence, the reaction rate at steller temperatures are not hindered but are enhanced in contradiction to
the estimation by a phenomenological model.
(4) Research and development of the nuclear reaction database for applications
Evaluated nuclear data are indispensable in the ﬁeld of nuclear science and technology, and the demand of nuclear data is altering
year by year with technical developments of nuclear science and technology. To catch up with the demands, an eﬀective method thatcan regularly generate evaluated nuclear data has been highly desired.
The machine learning technologies can be an answer to this demand, and we are training nuclear reaction models by adopting theBayesian optimization (BO) to eﬀectively produce the nuclear data. In this ﬁscal year, we have developed a prototype system which
combines the assembly of the nuclear reaction codes CCONE and BO with Gaussian regression. It is found that the optimization of
the reaction model parameter works well to reproduce the observed angular distributions of neutron and proton elastic scatterings at
various incident energies.

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Members
Director
Masaaki KIMURA
Visiting Scientists
Kenichi YOSHIDA (Kyoto Univ.)
Kazuyuki SEKIZAWA (TITECH)

Futoshi MINATO (JAEA)
Koichi SATO (Kochi Univ.)

AssistantIzumi YOSHIDA

List of Publications & Presentations
Publications[Original Papers]
V. Choudhary, W. Horiuchi, M. Kimura, and R. Chatterjee, “Enormous nuclear surface diﬀuseness of Ne and Mg isotopes in the island of
inversion,” Phys. Rev. C 104, 054313 (2021).
S. Shin, B. Zhou, and M. Kimura, “Shape of 13 C studied by the real-time evolution method,” Phys. Rev. C 103, 054313 (2021).
S. Shin, B. Zhou, and M. Kimura, “The isoscalar monopole strength of 13 C,” Few-Body Syst. 62, 93 (2021).
Q. Zhao, Y. Suzuki, J. He, B. Zhou, and M. Kimura, “α clustering and neutron-skin thickness of carbon isotopes,” Eur. Phys. J. A 57, 157(2021).
Y. Suzuki and M. Kimura, “Triaxial deformation and the disappearance of the N = 28 shell gap,” Phys. Rev. C 104, 024327 (2021).
Y. Taniguchi and M. Kimura, “12 C +12 C fusion S ∗ -factor from a full-microscopic nuclear model,” Phys. Lett. B 823, 136790 (2021).
M. Dan, R. Chatterjee, and M. Kimura, “A description of the structure and electromagnetic breakup of Be with microscopic inputs,” Eur.
Phys. J. A 57, 203 (2021).
P. Adsley, V. O. Nesterenko, M. Kimura, L. M. Donaldson, R. Neveling, J. W. Brümmer, D. G. Jenkins, N. Y. Kheswa, J. Kvasil,
K. C. W. Li, D. J. Marı́n-Lámbarri, Z. Mabika, P. Papka, L. Pellegri, V. Pesudo, B. Rebeiro, P. -G. Reinhard, F. D. Smit, and W. YahiaCherif, “Isoscalar monopole and dipole transitions in 24 Mg, 26 Mg, and 28 Si,” Phys. Rev. C 103, 044315 (2021).
Y. Taniguchi, K. Yoshida, Y. Chiba, Y. Kanada-En’yo, M. Kimura, and K. Ogata, “Unexpectedly enhanced alpha-particle preformation in48
Ti probed by the (p, pα) reaction,” Phys. Rev. C 103, L031305 (2021).
Z. H. Yang, Y. Kubota, A. Corsi, K. Yoshida, X. -X. Sun, J. G. i, M. Kimura, N. Michel, K. Ogata, C. X. Yuan, Q. Yuan, G. Authelet,
H. Baba, C. Caesar, D. Calvet, A. Delbart, M. Dozono, J. Feng, F. Flavigny, J. -M. Gheller, J. Gibelin, A. Giganon, A. Gillibert,
K. Hasegawa, T. Isobe, Y. Kanaya, S. Kawakami, D. Kim, Y. Kiyokawa, M. Kobayashi, N. Kobayashi, T. Kobayashi, Y. Kondo,
Z. Korkulu, S. Koyama, V. Lapoux, Y. Maeda, F. M. Marqués, T. Motobayashi, T. Miyazaki, T. Nakamura, N. Nakatsuka, Y. Nishio,
A. Obertelli, A. Ohkura, N. A. Orr, S. Ota, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, E. C. Pollacco, S. Reichert, J. -Y. Roussé,A. T. Saito, S. Sakaguchi, M. Sako, C. Santamaria, M. Sasano, H. Sato, M. Shikata, Y. Shimizu, Y. Shindo, L. Stuhl, T. Sumikama,
Y. L. Sun, M. Tabata, Y. Togano, J. Tsubota, F. R. Xu, J. Yasuda, K. Yoneda, J. Zenihiro, S. -G. Zhou, W. Zuo, and T. Uesaka, “Quasifree
neutron knockout reaction reveals a small s-orbital component in the Borromean nucleus 17 B,” Phys. Rev. Lett. 126, 082501 (2021).
M. Kimura, Y. Suzuki, T. Baba, and Y. Taniguchi, “Description of isospin mixing by a generator coordinate method,” Phys. Rev. C 105,
014311 (2021).
K. Yoshida, “Isovector giant monopole and quadrupole resonances in a Skyrme energy density functional approach with axial symmetry,”
Phys. Rev. C 104, 044309 (2021).
K. Uzawa, K. Hagino, and K. Yoshida, “Microscopic description of cluster decays based on the generator coordinate method,” Phys. Rev.
C 105, 034326 (2022).
K. Yoshida, “Super- and hyperdeformation in 60 Zn, 62 Zn, and 64 Ge at high spins,” Phys. Rev. C 105, 024318 (2022).
K. Hossain, K. Kobuszewski, M. M. Forbes, P. Magierski, K. Sekizawa, and G. Wlazłowski, “Rotating quantum turbulence in the unitary
fermi gas,” Phys. Rev. A 105, 013304 (2022).

[Review Article]
関澤一之, 「時間依存密度汎関数法で探る原子核ダイナミクス : 原子核反応から超流動現象, 中性子星まで」, 2021 年度原子核三者
若手夏の学校 原子核パート講義録, 原子核研究, Vol. 66, Suppl. 3, pp. 5–12 (2022).

Presentations[International Conferences/Workshops]
H. Masui (oral), W. Horiuchi, and M. Kimura, “Two-neutron halo structure and anti-halo eﬀect in 31 F,” Yamada Conference LXXII: The
8th Asia-Paciﬁc Conference on Few-Body Problems in Physics (APFB2020), Kanazawa bunka hall, Kanazawa, Japan, May 1–5, 2021.
S. Shin (oral), B. Zhou, and M. Kimura, “The shape of 13 C studied by the real-time evolution method,” Yamada Conference LXXII: The
8th Asia-Paciﬁc Conference on Few-Body Problems in Physics (APFB2020), Kanazawa bunka hall, Kanazawa, Japan, May 1–5, 2021.
H. Motoki (oral) and M. Kimura, “Research on the α condensate in 16 O using real time evolution method,” Yamada Conference LXXII:The 8th Asia-Paciﬁc Conference on Few-Body Problems in Physics (APFB2020), Kanazawa bunka hall, Kanazawa, Japan, May 1–5,
2021.

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M. Kimura (oral), “Shape of N = 28 isotonesand monopole transitions,” RIBF Users Meeting 2021, September 7–9, 2021.
H. Motoki (oral) and M. Kimura, “The structure of 0+ states in 16 O using real-time evolution method,” The 16th International Symposium
on Nuclei in the Cosmos (NIC-XVI), Online, September 21–25 2021.
V. Choudhary (oral), W. Horiuchi, M. Kimura, and R. Chatterjee, “Exploring the bubble structure in 22 O,” 65th DAE Symposium on
Nuclear Physics, Bhabha Atomic Research Centre, Mumbai, India, December 1–5, 2021.
T. Baba (oral), Y. Taniguchi, and M. Kimura, “9 Be + 9 Be correlation in the 4α linear chain of 18 O,” RCNP International Workshop on
Cluster Phenomena in Knockout and Astrophysical Reactions, Online, October 14–15, 2021.
K. Sekizawa (invited), “Entrainment eﬀects in neutron stars: Overview and progress,” JSPS/NRF/NSFC A3 Foresight Program, “Nuclear
physics in the 21st century,” Joint Annual Meeting, Online, Feburary 17–18, 2022.

[Domestic Conferences/Workshops]
木村真明, 「光核反応からのクラスター崩壊の理論研究と最高エネルギー宇宙線への応用」, 新学術領域「量子クラスターで読み解く物質の階層構造」ワークショップ, オンライン, 2021 年 6 月 14, 19 日.
渡辺証斗, 湊太志, 木村真明, 岩本信之, 「チャネル結合光学模型を用いた核子–原子核散乱に対するポテンシャルの最適化 (2)」, 日
本原子力学会 2021 年秋の大会, オンライン, 2021 年 9 月 8–10 日.
谷口億宇, 木村真明「天体において共鳴状態により誘発される 12 C +12 C 核融合反応」, 日本物理学会 2021 年秋季大会, オンライン,
2021 年 9 月 14–17 日.
本木英陽, 鈴木祥輝, 川合毅, 木村真明「中性子過剰核でのクラスター形成と中性子スキンの相関」, 日本物理学会 2021 年秋季大会,
オンライン, 2021 年 9 月 14–17 日.
木村真明, 鈴木祥輝, 馬場智之「生成座標法によるアイソバリックアナログ状態とアイソスピン混合の記述」, 日本物理学会 2021
年秋季大会, オンライン, 2021 年 9 月 14–17 日.
Vishal Choudhary, 堀内渉, 木村真明, Rajdeep Chatterjee, 「陽子弾性散乱でみる中性子過剰 Ne, Mg 同位体の核表面変化」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
鈴木祥輝, 木村真明, 堀内渉, 「中性子過剰 N = 28 核での変形共存現象の研究」, 日本物理学会 2021 年秋季大会, オンライン, 2021
年 9 月 14–17 日.
木戸英治, 稲倉恒法, 宇都野穣, 木村真明, 清水則孝, 民井淳, 長瀧重博, 「光核反応の超高エネルギー宇宙線伝播への影響 II」, 日本
物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
S. Shin, B. Zhou, and M. Kimura, “α cluster resonances studied by analytic continuation in the coupling constant,” 日本物理学会 2021
年秋季大会, オンライン, 2021 年 9 月 14–17 日.
S. Shin, B. Zhou, and M. Kimura, “α cluster resonances studied by analytic continuation in the coupling constant,” 「大規模シミュレー
ションと機械学習による原子核反応研究」, 北海道大学, 2021 年 11 月 17–19 日.
鈴木祥輝, 堀内渉, 木村真明, 「N = 28 核における変形共存現象」, 「大規模シミュレーションと機械学習による原子核反応研究」,
北海道大学, 2021 年 11 月 17–19 日.
本木英陽, 鈴木祥輝, 川合毅, 木村真明, 「軽い中性子過剰核におけるクラスター形成」, 「大規模シミュレーションと機械学習による原子核反応研究」, 北海道大学, 2021 年 11 月 17–19 日.
吉田賢市, “Anomalous quadrupole collectivity of neutron-rich Mg isotopes near the drip line,” 基研研究会「核力に基づいた原子核の構造と反応」, 京都大学/オンライン, 2021 年 12 月 7–10 日.
本木英陽, 木村真明, 「4α 微視的模型による 16 O の幾何学的構造の理解」, 第 7 回クラスター階層領域研究会, 東北大学電子光理学
研究センター, 2021 年 12 月 27–28 日.
木村真明, 「核データの取り組みについて」, 原子核物理学実験におけるデータ利活用による研究戦略会議, 理研神戸・融合連携イ
ノベーション推進棟, 2022 年 3 月 7 日.
湊太志, 「これまでの核データ研究活動と最新の取り組み」, 原子核物理学実験におけるデータ利活用による研究戦略会議, 理研神
戸・融合連携イノベーション推進棟, 2022 年 3 月 7 日.
馬場智之, 谷口億宇, 木村真明, 「9 Be + 9 Be 衝突による 4α 直鎖状態の生成可能性について」, 日本物理学会 第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
高津隆苑, 木村真明, 堀内渉, 「31 Ne の変形ハローと共鳴の研究」, 日本物理学会 第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
鈴木祥輝, 木村真明, 堀内渉, 「中性子数 28 近傍核における魔法数消失に伴う変形共存現象」, 日本物理学会 第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
谷口億宇, 木村真明「低エネルギー 12 C +13 C 核融合の微視的模型による評価」, 日本物理学会 第 77 回年次大会, オンライン, 2022
年 3 月 15–19 日.
吉田賢市, “Anomalous quadrupole collectivity of Mg isotopes near the neutron drip line,” 日本物理学会第 77 回年次大会, オンライン,
2022 年 3 月 15–19 日.
関澤一之, P. Magierski, A. Makowski, M. C. Barton, G. Wlazłowski, 「低エネルギー重イオン反応における新奇な超流動ダイナミク
ス」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
佐々木哲平, 関澤一之, 松尾正之, 「時間依存 Gross-Pitaevskii 方程式による量子渦のピン留め・ピン外れ機構の研究」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
佐藤弘一, 「日本物理学会第 77 回年次大会「2 次の集団演算子を入れた Adiabatic SCC 理論による集団経路の抽出」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
陳敬徳, 小野章, 木村真明, 石塚知香子, 千葉 敏, 「AMD による核分裂片のスピン, 相対軌道角運動量及びそれらの相関の研究」, 日
本原子力学会 2022 年春の年会, オンライン, 2022 年 3 月 16–18 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)[Seminars]
M. Kimura, Y. Suzuki, and W. Horiuchi, “Erosion of N = 28 shell gap: shape coexistence and monopole transitionsin the vicinity of 44 S,”
RIKEN RIBF Nuclear Physics Seminar, Online, January 8, 2022.
M. Kimura and Y. Taniguch, “Astrophysical S-factor for 12 C+12 C fusion reaction from a full-microscopic nuclear model,” CINA/COSNAP
Colloquium, October 19, 2022.

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Nuclear Science and Transmutation Research Division
Superheavy Element Research Group
1. Abstract
The heavy elements with atomic numbers exceeding 103 are called superheavy elements (SHEs). In Superheavy Element Research Group, Superheavy Element Production Team and Superheavy Element Devise Development Team work together to investigate
synthesis of SHEs, nuclear properties of SHE nuclei, and chemical properties of SHEs. We also develop and maintain SHE production
and separation devices, detectors, and chemistry apparatuses.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)
(6)
(7)

Search for new superheavy elements
Decay spectroscopy of the heaviest nuclei
Study of reaction mechanisms for production of the heaviest nuclei
Study of chemical properties of the heaviest elements
Development, maintenance, and operation of GARIS, GARIS-II, and GARIS-III
Development and maintenance of detector and DAQ system of GARIS, GARIS-II, and GARIS-III
Development and maintenance of target system of GARIS, GARIS-II, and GARIS-III

3. Summary of Research Activity
See the subsections of Superheavy Element Production Team and Superheavy Element Device Development Team.

Members
Director
Kosuke MORITA

List of Publications & Presentations
See the subsections of Superheavy Element Production Team and Superheavy Element Device Development Team.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Superheavy Element Research Group
Superheavy Element Production Team
1. Abstract

The elements with atomic number Z ≥ 104 are called as trans-actinide or superheavy elements (SHEs). Superheavy Element
Production Team synthesizes SHE nuclei including new elements and investigates synthesis mechanisms of SHE nuclei, nuclear
properties of SHE nuclei, and chemical properties of SHEs in collaboration with Superheavy Element Devise Development Team andNuclear Chemistry Research Team of RIKEN Nishina Center.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Search for new superheavy elements
Decay spectroscopy of the heaviest nuclei
Study of reaction mechanisms for production of the heaviest nuclei
Study of chemical properties of the heaviest elements

3. Summary of Research Activity(1) Search for new superheavy elements
In November 2016, the 7th period of the periodic table was completed with the oﬃcial approval of four new elements, nihonium(Nh, atomic number Z = 113), moscovium (Mc, Z = 115), tennessine (Ts, Z = 117), and oganesson (Og, Z = 118) by International
Union of Pure and Applied Chemistry. We have started to search for new elements to expand the chart of the nuclides toward to theisland of stability and the periodic table of the elements toward the 8th period. In January 2020, RIKEN heavy-ion Linear ACcelerator(RILAC) was upgraded as Superconducting RIKEN heavy-ion Linear ACcelerator (SRILAC). We developed the new gas-ﬁlled recoil
ion separator GARIS-III on the beam line of SRILAC. In June–July 2020, we conducted the commissioning of SRILAC and GARISIII using the 169 Tm + 40 Ar, 208 Pb + 40 Ar, and 208 Pb + 51 V reactions. Since October 2020, we have been conducting a synthesis
experiment of isotopes of new element 119 in the 248 Cm + 51 V reaction under the nSHE collaboration.
(2) Decay spectroscopy of the heaviest nuclei
In collaboration with KEK, we developed a multi-refection time-of-ﬁght mass spectrograph (MRTOF-MS) equipped with an
α-TOF detector on the focal plane of GARIS-II at RRC for decay-correlated mass measurements of low-yield and short-lived SHE
isotopes. In 2021, the ﬁrst high-precision direct determination of the atomic mass of a superheavy nuclide was successfully conducted
for 257 Db (Z = 105) produced in the 208 Pb(51 V, 2n)257 Db reaction. The atomic masses of 206, 207g, m Ra were also measured in the159
Tb(51 V, 4;3n)206, 207g, m Ra reactions.
(3) Study of reaction mechanisms for production of the heaviest nuclei
SHE nuclei have been produced by complete fusion reactions of two heavy nuclei. However, the reaction mechanism of thefusion process is still not well understood both theoretically and experimentally. We measured excitation functions for the quasielastic
scattering of the 248 Cm + 51 V reaction using GARIS III at SRILAC. The result was utilized to estimate the optimal incident beamenergy for production of isotopes of new element 119.
(4) Study of chemical properties of the heaviest elements
Chemical characterization of newly-discovered SHEs is an extremely interesting and challenging subject in modern nuclear andradiochemistry. In collaboration with Nuclear Chemistry Research Team of RIKEN Nishina Center, we are developing SHE production systems as well as rapid single-atom chemistry apparatuses for chemistry studies of SHEs. We installed a gas-jet transportsystem to the focal plane of GARIS at RILAC. This system is a promising approach for exploring new frontiers in SHE chemistry: thebackground radiations from unwanted products are strongly suppressed, the intense primary heavy-ion beam is absent in the gas-jet
chamber, and hence the high gas-jet extraction yield is attained. Furthermore, the beam-free conditions make it possible to investigate
new chemical systems. In 2021, we continued to develop an ultra-rapid gas-chromatograph apparatus, which consists of an RF carpet
gas cell and a cryo-gas-chromatograph column with a Si detector array, at the focal plane of GARIS for the gas chemistry of SHEs.
To realize aqueous chemistry studies of Sg (Z = 106) and Bh (Z = 107), we have been developing a continuous and rapid solvent extraction apparatus which consists of a continuous dissolution apparatus Membrane DeGasser (MDG), a Flow Solvent Extractor (FSE),
and a liquid scintillation detector for α/SF-spectrometry. In 2021, we also conducted model experiments for ion-exchange studies ofRf (Z = 104) in HNO3 and H2 SO4 using long-lived radiotracers of 88 Zr and 175 Hf.

Members
Team Leader
Hiromitsu HABA

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Research & Development Scientist
Daiya KAJI
Special Postdoctoral Researcher
Tomohiro HAYAMIZU
Visiting Scientists
Marc ASFARI (IPHC/Strasbourg Univ.)
Mahananda DASGUPTA (Australian Nat’l Univ.)
Olivier DORVAUX (Strasbourg Univ.)
Benoit Jean-Paul GALL (Strasbourg Univ.)
Zaiguo GAN (Chinese Academy of Sci.)
Shintaro GO (Kyushu Univ.)
David HINDE (The Australian Nat’l Univ.)
Minghui HUANG (IMP, CAS)

Hiroyuki KOURA (JAEA)
Daisuke NAGAE (Kyushu Univ.)
Satoshi SAKAGUCHI (Kyushu Univ.)
Mirei TAKEYAMA (Yamagata Univ.)
Taiki TANAKA (The Australian Nat’l Univ.)
Huabin YANG (IMP, CAS)
Zhiyuan ZHANG (IMP, CAS)

Student Trainees
Yuichi ISHIBASHI (Kyushu Univ.)
Tamito KAI (Kyushu Univ.)
Kieran KESSACI (IPHC/Strasbourg Univ.)
Raiden LEMON (The Australian Nat’l Univ.)
Milan LEONARD (The Australian Nat’l Univ.)
Sotaro MATSUNAGA (Kyushu Univ.)

Ikuto MURAKAMI (Kyushu Univ.)
Taiga MUTO (Kyushu Univ.)
Yuto NAGATA (Kyushu Univ.)
Koichi SUGIYAMA (Kyushu Univ.)
Taro TOMIMATSU (Kyushu Univ.)

List of Publications & Presentations
Publications[Original Papers]
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa,
Y. Ito, D. Kaji, S. Kimura, H. Koura, J. J. Liu, H. Miyatake, J. -Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “First high-precision direct determination of the atomic mass of asuperheavy nuclide,” Phys. Rev. C 104, L021304 (2021).
T. Niwase, M. Wada, P. Schury, P. Brionnet, S. D. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama,
S. Ishizawa, Y. Ito, D. Kaji, S. Kimura, J. Liu, H. Miyatake, J. Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, T. Tanaka, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “α-decay-correlated mass measurement of 206, 207g, m Rausing an α-TOF detector equipped multireﬂection time-of-ﬂight mass spectrographs system,” Phys. Rev. C 104, 044617 (2021).
T. Aoki, R. Sreekantham, B. K. Sahoo, B. Arora, A. Kastberg, T. Sato, H. Ikeda, N. Okamoto, Y. Torii, T. Hayamizu, K. Nakamura.,
S. Nagase, M. Ohtsuka, H. Nagahama, N. Ozawa, M. Sato, T. Nakashita, K. Yamane, K. S. Tanaka, K. Harada, H. Kawamura, T. Inoue,
A. Uchiyama, A. Hatakeyama, A. Takamine, H. Ueno, Y. Ichikawa, Y. Matsuda, H. Haba, and Y. Sakemi, “Quantum sensing of theelectron electric dipole moment using ultracold entangled Fr atoms,” Quantum Sci. Technol. 6, 044008 (2021).
A. Yakushev, L. Lens, C. E. Düllmann, M. Block, H. Brand, M. Dasgupta, T. Calverley, A. D. Nitto, M. Götz, S. Götz, H. Haba,
L. Harkness-Brennan, R-D. Herzberg, F. P. Heßberger, D. Hinde, A. Hübner, E. Jäger, D. Judson, J. Khuyagbaatar, B. Kindler, Y. Komori, J. Konki, J. V. Kratz, J. Krier, N. Kurz, M. Laatiaoui, B. Lommel, C. Lorenz, M. Maiti, A. K. Mistry, C. Mokry, Y. Nagame,P. Papadakis, A. Såmark-Roth, D. Rudolph, J. Runke, L. G. Sarmiento, T. K. Sato, M. Schädel, P. Scharrer, B. Schausten, J. Steiner,
P. Thörle-Pospiech, A. Toyoshima, N. Trautmann, J. Uusitalo, A. Ward, M. Wegrzecki, and V. Yakusheva, “First study on nihonium(Nh, element 113) chemistry at TASCA,” Front. Chem. 9, 753738 (2021).
E. Watanabe, Y. Kasamatsu, T. Yokokita, S. Hayami, K. Tonai, H. Ninomiya, N. Kondo, Y. Shigekawa, H. Haba, Y. Kitagawa,
M. Nakano, and A. Shinohara, “Anion-exchange experiment of Zr, Hf, and Th in HNO3 and quantum chemical study on the nitrate complexes toward chemical research on element 104, Rf,” Solvent Extr. Ion Exch. published online (December 31, 2021). DOI:
10.1080/07366299.2021.2020956 .
T. Hayamizu, H. Haba, K. Nakamura, T. Aoki, H. Nagahama, K. S. Tanaka, N. Ozawa, M. Ohtsuka, and Y. Sakemi, “Development of
ultracold francium atomic sources towards the permanent EDM search,” Few-Body Syst. 63, 11 (2022).
T. Yokokita, S. Yano, Y. Komori, and H. Haba, “Anion- and cation-exchange studies of Zr, Hf, and Th using ion-exchange resin and ﬁberin H2 SO4 media for chemical characterization of sulfate complex of Rf,” J. Radioanal. Nucl. Chem. 331, 1127 (2022).

[Book]
羽場宏光, 「新元素ニホニウムはいかにして創られたか」, 東京化学同人, 176 ページ, 2021 年 12 月 17 日.

Presentations[International Conferences/Workshops]
H. Haba (invited), “Production and applications of radioisotopes at RIKEN RI Beam Factory,” International Discussion Meeting on Futureof Accelerator Applications and Radiotracers Research (FAAARR2021), Online, July 26–27, 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

H. Haba (invited), “Production of radioisotopes for application studies at RIKEN RI Beam Factory,” Snowmass’21 Workshop on HighPower Cyclotrons/FFAs, Online, September 7–9, 2021.
H. Haba (invited), “Production and applications of radioisotopes at RIKEN RI Beam Factory—Search for new elements through diagnosis
and therapy of cancer—,” RIKEN-KFU (Kazan Federal University) 3rd Joint Symposium, Online, November 5–6, 2021.
T. Aoki (poster), R. Sreekantham, B. K. Sahoo, B. Arora, A. Kastberg, T. Sato, H. Ikeda, N. Okamoto, Y. Torii, T. Hayamizu, K. Nakamura,
S. Nagase, M. Ohtsuka, H. Nagahama, N. Ozawa, M. Sato, T. Nakashita, K. Yamane, K. S. Tanaka, K. Harada, H. Kawamura, T. Inoue,
A. Uchiyama, A. Hatakeyama, A. Takamine, H. Ueno, Y. Ichikawa, Y. Matsuda, H. Haba, and Y. Sakemi, “Quantum sensing of
the electron electric dipole moment using quantum entangled atoms,” International Symposium on Novel Materials and Quantum
Technologies (ISNTT2021), Online, December 16, 2021.

[Domestic Conferences/Workshops]
羽場宏光 (口頭発表), 「理研 RI ビームファクトリーにおける RI 製造供給」, 第 58 回アイソトープ・放射線研究発表会, オンライ
ン, 2021 年 7 月 7–9 日.
羽場宏光 (口頭発表), 「RIBF 施設紹介」, 新学術領域研究（研究領域提案型）『学術研究支援基盤形成』短寿命 RI 供給プラット
フォーム成果報告会 兼 RI 利用研究会, オンライン, 2021 年 7 月 19–20 日.
羽場宏光 (依頼講演), 「核化学ロードマップについて」, 第 59 回核化学夏の学校, オンライン, 2021 年 8 月 26–27 日.
庭瀬暁隆 (口頭発表), P. Schury, 和田道治, P. Brionnet, S. Chen, 橋本尚志, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 石澤倫,
伊藤由太, 加治大哉, 木村創大, 小浦寛之, 宮武宇也, J. Y. Moon, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 渡辺裕, H. Wollnik, W. Xian, S. X. Yan, 「超重核 257 Db の直接質量測定」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月
14–17 日.
庭瀬暁隆 (口頭発表), 和田道治, P. Schury, P. Brionnet, S. D. Chen, 橋本尚志, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 石澤
倫, 伊藤由太, 加治大哉, 木村創大, J. Liu, 宮武宇也, J. Y. Moon, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 田中
泰貴, 渡辺裕, H. Wollnik, W. Xian, S. X. Yan, 「MRTOF と α-TOF 検出器による, α 崩壊に相関した精密質量測定法の開拓」, 日本
放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
武藤大河 (口頭発表), P. Brionnet, 浅井雅人, 郷慎太郎, R. Grzywacz, 羽場宏光, 加治大哉, 木村創太, T. King, 森本幸司, K. Rykaczewski,
坂口聡志, 酒井英行, 森田浩介, 庭瀬暁隆, 田中聖臣, 「Si 検出器の波形解析による軽粒子識別」, 第 127 回日本物理学会九州支部
例会, オンライン, 2021 年 12 月 4 日.
木村創大 (口頭発表), 和田道治, 羽場宏光, 石澤倫, 森本幸司, 庭瀬暁隆, Marco Rosenbusch, Peter Schury for the SHE-Mass Collaboration, 「MRTOF-MS を用いた 252 Cf 自発核分裂片の網羅的精密質量測定」, 日本物理学会第 77 回年次大会 (2022 年), オンライ
ン, 2022 年 3 月 15–19 日.
庭瀬暁隆 (口頭発表), P. Schury, 和田道治, P. Brionnet, S. Chen, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 伊藤由太, 加治大哉,
木村創大, 小浦寛之, 宮武宇也, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 渡辺裕, H. Wollnik, W. Xian, S. X. Yan,
「MRTOF+α-TOF による 257, 258 Db の精密質量測定」, 日本物理学会第 77 回年次大会 (2022 年), オンライン, 2022 年 3 月 15–19 日.
横北卓也 (口頭発表), 羽場宏光, 「Zr 及び Hf のスルファト錯体推定に向けた TOA/H2 SO4 系の溶媒抽出」, 日本化学会第 102 春季
年会 (2022), オンライン, 2022 年 3 月 23–26 日.

Outreach Activities
羽場宏光 (依頼講演), 「ニホニウム発見への道のり」, 大宮北高校 SSH 特別講演会, 大宮市, 2021 年 10 月 4 日.
羽場宏光（依頼講演）, 「新元素でがん治療〜RIBF がつくるラジオアイソトープ〜」, 第 9 回理研イノベーションセミナー, オン
ライン, 2022 年 1 月 21 日.
羽場宏光（依頼講演）, 「ニホニウム発見への道のり」, 早稲田大学本庄高等学院課外講義, オンライン, 2022 年 3 月 12 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Superheavy Element Research Group
Superheavy Element Device Development Team
1. Abstract
A gas-ﬁlled recoil ion separator has been used as a main experimental device for the study of superheavy elements. This teamis in charge of maintaining, improving, developing, and operating the separators and related devices. In the RIBF facility, three gasﬁlled recoil ion separators are installed at RILAC and RRC facility. One is GARIS that is designed for a symmetric reaction such as
coldfusion reaction, and the other two are developed for an asymmetric reaction such as hot-fusion reaction, GARIS-II and GARIS-III.
New elements 278 113 were produced by 70 Zn + 209 Bi reaction using GARIS. Further the new element search is currently in progressby using GARIS-II and GARIS-III.

2. Major Research Subjects(1) Maintenance of GARIS, GARIS-II and development of new separator GARIS-III(2) Maintenance and development of detector and DAQ system for superheavy element research(3) Maintenance and development of target system for GARIS, GARIS-II and GARIS-III

3. Summary of Research Activity
The GARIS-II and III are newly developed which has an acceptance twice as large as existing GARIS, in order to realize higher
transmission. A new element search program aiming to element 119 was started using GARIS-II. And new separator GARIS-III wasdeveloped and installed into the RILAC experimental hall. After the some commissioning works of GARIS-III, new 119th element
search has been started. We will also oﬀer user-support if a researcher wishes to use the devices for his/her own research program.

Members
Team Leader
Kouji MORIMOTO
Senior Technical Scientists
Masaki FUJIMAKI

Daiya KAJI

Postdoctoral Researchers
Pierre BRIONNET

Sota KIMURA

Visiting Scientists
Shin-ichi GOTO (Niigata Univ.)
Eiji IDEGUCHI (Osaka Univ.)
Yuta ITO (JAEA)

Katsuhisa NISHIO (JAEA)
Toshitaka NIWASE (KEK)
Fuyuki TOKANAI (Yamagata Univ.)

Student Trainee
Kosaku KURAMOTO (Yamagata Univ.)

List of Publications & Presentations
Publications[Original Papers]
T. Niwase, M. Wada, P. Schury, P. Brionnet, S. D. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama,
S. Ishizawa, Y. Ito, D. Kaji, S. Kimura, J. Liu, H. Miyatake, J. Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, T. Tanaka, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “α-decay-correlated mass measurement of 206,207g,m Ra
using an α-TOF detector equipped multireﬂection time-of-ﬂight mass spectrograph system,” Phys. Rev. C 104, 044617 (2021).
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa,
Y. Ito, D. Kaji, S. Kimura, H. Koura, J. J. Liu, H. Miyatake, J. -Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “First high-precision direct determination of the atomic mass of asuperheavy nuclide,” Phys. Rev. C 104, L021304 (2021).

Presentations[International Conference/Workshop]
T. Niwase (invited), “Recent results of GARIS-II + MRTOF experiment,” TASCA21 workshop, Online, June 21, 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)[Domestic Conferences/Workshops]
庭瀬暁隆 (口頭発表), 「MRTOF+α-TOF による 257,258 Db の精密質量測定」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3
月 15–19 日.
庭瀬暁隆 (口頭発表), 「MRTOF と α-TOF 検出器による, α 崩壊に相関した精密質量測定法の開拓」, 日本放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
庭瀬暁隆 (口頭発表), 「超重核 257 Db の直接質量測定」, 日本物理学会 2021 年度秋季大会, オンライン, 2021 年 9 月 14 日–17 日.

[Seminars]
T. Niwase, “Direct mass measurement of superheavy nuclides via MRTOF mass spectrograph equipped with an α-TOF detector,” RIBF
Nuclear Physics Seminar, Online, February 22, 2022.
庭瀬暁隆, 「超重元素の質量測定」, 2021 年度核化学夏の学校, オンライン, 2021 年 8 月 26–27 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Astro-Glaciology Research Group
Summary of Research Activities
1. Abstract
Our Astro-Glaciology Research Group promotes both experimental and theoretical studies to open up the new interdisciplinary
research ﬁeld of astro-glaciology, which combines astrophysics, astrochemistry, glaciology, and climate science.
On the experimental side, we measure isotopic and ionic concentrations in ice cores drilled at Dome Fuji station, Antarctica,
in collaboration with the National Institute of Polar Research (NIPR, Tokyo). Here, the ice cores are time capsules which preserve
atmospheric information of the past. In particular, the ice cores obtained around the Dome Fuji site are very unique, because they
contain much more information on the stratosphere than any other ice cores obtained from elsewhere on Earth. This means that
we have signiﬁcant advantages in using Dome Fuji ice cores if we wish to study the Universe, since UV photons, gamma-rays, andhighenergy protons emitted by astronomical phenomena aﬀect the stratosphere. Our principal aim is thus to acquire and interpret
information preserved in ice cores regarding:• Signatures of past volcanic eruptions and solar cycles;• Relationships between climate change and volcanic activity, and climate change and solar activity as well;• Traces of past supernovae in our galaxy, in order to understand better the rate of galactic supernova explosions.
Moreover, we are promoting experimental projects on:• Development of an automated laser melting sampler for analyzing ice cores with high depth resolution;• Development of precise analytical techniques of high sensitivity for analyzing ice cores;• The evolution of molecules in space;• The application of analytical methods for measuring isotopes in ice cores to archaeological artifacts.
On the theoretical side, we are simulating numerically:• Chemical eﬀects of giant solar ﬂares and supernovae on the Earth’s atmosphere;• The explosive and the r-process nucleosynthesis in core-collapse supernovae.
Combining our experimental evidence and theoretical simulations, we are promoting the researches mentioned above. These all willcontribute to understanding relationships between the Universe and Earth. In particular, climate change is the most critical issue facing
the world in the 21st century. It is also emphasized that the frequency of supernova explosions in our galaxy has not yet been fully
understood, and it is the key to understand the r-process nucleosynthesis.

Members
Director
Yuko MOTIZUKI
Senior Research Scientist
Yoichi NAKAI
Special Temporary Research Scientist
Kazuya TAKAHASHITechnical Staﬀ
Yu Vin SAHOO
Senior Visiting Scientists
Yasushige YANO (Nishina Memorial Foundation)

Kunihiko KODERA (Meteorological Res. Inst.)

Visiting Scientists
Hideharu AKIYOSHI (Nat’l Inst. for Environmental Studies)
Hisashi HAYAKAWA (Nagoya Univ.)
Akira HORI (Kitami Inst. of Tech.)
Kazuho HORIUCHI (Hirosaki Univ.)

Yoshinori IIZUKA (Hokkaido Univ.)
Naoyuki KURITA (Nagoya Univ.)
Hideki MADOKORO (Mitsubushi Heavy Industries, Ltd.)
Hideaki MOTOYAMA (Nat’l Inst. of Polar Res.)

Visiting Technicians
Junya HIROSE (Fusion Tech. Co., Ltd.)

Yuma HASEBE (Denryoku Comp. Ctr., Ltd.)

Administrative Part-time Worker
Kanako FUJITA (Administrative Part-time Worker I)- 238 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

AssistantKeiko SUZUKI

List of Publications & Presentations
Publications[Original Papers]
K. Takahashi, Y. V. Sahoo, Y. Nakai, H. Motoyama, and Y. Motizuki, “Annually resolved proﬁles of δ34 S and sulfate in shallow ice core
DF01 (Dome Fuji, Antarctica) spanning the nineteenth century and their geochemical implications,” J. Geophys. Res. Atmos. 127,
2021JD036137 (2022).
Y. Miyake, N. Ikoma, K. Takahashi, Y. V. Sahoo, and H. Okuno, “Test of 107 Pd transmutation with macroscopic quantities,” J. Nucl. Sci.
Technol., published online (May 11, 2022). DOI: 10.1080/00223131.2022.2072012 .
K. Kanzawa, F. Miyake, K. Horiuchi, K. Sasa, K. Takano, M. Matsumura, T. Takahashi, Y. Motizuki, K. Takahashi, Y. Nakai, K. Ohtani,
Y. Tada, Y. Ochiai, H. Motoyama, H. Matsuzaki, A. Yamazaki, Y. Muramatsu, and T. Yamagata, “High-resolution 10 Be and 36 Cl datafrom the antarctic dome Fuji Ice core (100 years around 5480 BCE): An unusual grand solar minimum occurrenc?,” J. Geophys. Res.
Space Phys. 126, e2021JA029378 (2021).
S. Katsuda, H. Fujiwara, Y. Ishisaki, Y. Maeda, K. Mori, Y. Motizuki, K. Sato, M. S. Tashiro, and Y. Terada, “New measurement of
the vertical atmospheric density proﬁle from occultations of the crab nebula with X-ray astronomy satellites Suzaku and Hitomi,” J.
Geophys. Res. Space Phys. 126, e2020JA028886, (2021).
K. Kitajima, Y. Nakai, W. M. C. Sameera, M. Tsuge, A. Miyazaki, H. Hidaka, A. Kouchi, and N. Watanabe, “Delivery of electrons byproton-hole transfer in ice at 10 K: Role of surface OH radicals,” J. Phys. Chem. Lett. 12, 704 (2021).

[Books]
望月優子, 「シリース現代の天文学第 1 巻人類の住む宇宙第 2 版」(第 3 刷新規業績), pp. 147–149（「第 4 章太陽系 4.1.2 節太陽の現在」）
, 岡村定矩他編, 日本評論社, 2021 年 11 月, ISBN 978-4-535-60751-4.
望月優子, 佐藤勝彦, 「シリース現代の天文学第 1 巻人類の住む宇宙第 2 版」
（第 3 刷改訂）, pp. 99–144（「第 3 章元素の起源」）, 岡
村定矩他編, 日本評論社, 2021 年 11 月, ISBN 978-4-535-60751-4.

Presentations[International Conferences/Workshops]
Y. Motizuki (iPoster paper), Y. Nakai, K. Takahashi, J. Hirose, Y. V. Sahoo, Y. Yano, M. Yumoto, M. Maruyama, M. Sakasita, K. Kase,
S. Wada, and H. Motoyama, “A novel, ultra-high-resolution laser-melting sampler with resolution controllability for discrete analyses
of ion concentrations and stable water isotopic compositions in ice cores,” AGU Fall Meeting 2021, New Orleans & Online, December
13–17, 2021.
K. Kitajima (poster), Y. Nakai, W. M. C. Sameera, M. Tsuge, A. Miyazaki, H. Hidaka, A. Kouchi, and N. Watanabe, “A new electrochemical property of ice: negative charge transport triggered by reactions of surface OH radicals with electrons,” Workshop on Interstellar
Matter 2021, Sapporo, November 17–19, 2021.
Y. Nakai (poster), H. Hidaka, and N. Watanabe, “Methanol production via interactions of low-energy CH+3 ions with ASW surface:experimental investigation of ion-surface reaction,” Workshop on Interstellar Matter 2021, Sapporo, November 17–19, 2021.
Y. Motizuki, Y. Nakai, K. Takahashi, T. Imamura, and H. Motoyama, “A proxy for decadal solar cycles from AD 1600 to 1900 basedon nitrate concentrations in a Dome Fuji (Antarctica) ice core,” The 6th Workshop of the Astronomy & Astrophysics from Antarctica(SCAR AAA 2021), Virtual meeting, September 8–10, 2021.
K. Kitajima, Y. Nakai, M. Tsuge, A. Miyazaki, H. Hidaka, A. Kouchi, and N. Watanabe, “Veriﬁcation of proton-hole transfer in ice at
10 K via detection of surface OH radicals,” 36th Symposium on Chemical Kinetics and Dynamics, Online, Jun 2–4, 2021.
Y. Motizuki, Y. Nakai, K. Takahashi, J. Hirose, Y. V. Sahoo, Y. Yano, M. Yumoto, M. Maruyama, M. Sakasita, K. Kase, S. Wada, and
H. Motoyama, “A novel high-resolution laser-melting sampler for discrete analyses of ion concentrations and stable water isotopic
compositions in ﬁrn and ice cores,” virtual EGU General Assembly 2021 (vEGU21), April 19–30, 2021.
Y. Motizuki (invited), “Astro-glaciology sciences using antarctic ice cores—A key project of RNC for the origin of elements and climatechange,” Workshop3 on Climate Change and Geoscience, OIST-RIKEN Joint Symposium, Series 1: Green and blue planet—How canecological research shape our future?, Onna-Son, Okinawa, April 6–7, 2021. (With organizing and serving as a Discussion Leader ofWorkshop3)
Y. Motizuki (invited), “Some topics on gender issues related to nuclear astrophysics calendar - based on a keynote talk at the IAU
symposium on equality, equity, and inclusion in astronomy, celebrating the 100-year of IAU,” UKAKUREN Seminar, Online, March
7, 2022.

[Domestic Conferences/Workshops]
望月優子 (招待講演), 「地球アーカイブからさぐる, 宇宙と地球の歴史」, 朝日カルチャーセンター中之島教室 「宇宙と地球と元素」
シリーズ講座, オンライン, 2022 年 3 月 26 日.
勝田哲, 藤原均, 石﨑欣尚, 前田良知, 森浩二, 望月優子, 佐藤浩介, 田代信, 寺田幸功, 安井良輔, 「X 線天文衛星を用いた地球超高層
大気および太陽コロナの観測的研究」, 第 21 回高宇連研究会, 豊中, オンライン, 2022 年 3 月 9–11 日.
望月優子, 中井陽一, 高橋和也, 今村隆史, 本山秀明, 「南極ドームふじアイスコアを用いた 10 年スケール太陽周期の同時検出」,日
本天文学会 2022 年春季年会, オンライン, 2022 年 3 月 2–5 日.

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渡部直樹 (ポスター), 北島謙生, 中井陽一, 柘植雅士, 日高宏, 香内晃, 「極低温の氷と NH3 , H2 S 固体の界面における負電荷移動機
構」, 原子衝突学会第 46 回年会, オンライン, 2021 年 10 月 26–28 日.
勝田哲, 藤原均, 石﨑欣尚, 前田良知, 森浩二, 望月優子, 佐藤浩介, 田代信, 寺田幸功, 「Ｘ線天文衛星『すざく』と『ひとみ』が捉えたカニ星雲の地球大気遮蔽による大気密度鉛直プロファイルの測定」, 令和 3 年 (2021 年) 度・第 1 回 STE (太陽地球環境) 現象
報告会 (合同研究集会), 2021 年 9 月 28–30 日.
望月優子 (招待トーク), “A new-type, innovative automated ice-core sampler using laser melting method”, Online seminar “How to give
an impressive pitch presentation in global situation”, JST 世界で活躍できる研究者育成プログラム総合支援事業, オンライン, 2021
年 8 月 13 日.
望月優子 (招待講演), 「南極の氷からひもとく宇宙と地球の歴史」, 早稲田大学高等学院理工学特論, オンライン, 2021 年 4 月 20 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Nuclear Transmutation Data Research Group
1. Abstract
The nuclear waste problem is an inevitable subject in nuclear physics and nuclear engineering communities. Since the Chicago
Pile was established in 1942, nuclear energy has become one of major sources of energy. However, nowadays the nuclear waste
produced at nuclear power plants has caused social problems. Minor actinide components of the waste have been studied well as a fuelin fast breeder reactors or ADS. Long-lived ﬁssion products (LLFP) in waste, on the other hand, have not been studied extensively. A
deep geological disposal has been a policy of several governments, but it is diﬃcult to ﬁnd out location of the disposal station in termsof security, sociology and politics. To solve the social problem, a scientiﬁc eﬀort is necessary for nuclear physics community to ﬁnd
out eﬃcient methods for reduction of nuclear waste radioactivity. In the world-wide situation above, our Group aims to obtain reaction
data of LLFP at RIBF and other muon facilities for muon capture data. These data are necessary to design an accelerator-based system
for transmutation, and also may lead to a new discovery and invention for peaceful use of nuclear power and the welfare of humanity.

2. Major Research Subjects
The Group is formed by three research teams. The ﬁrst two Teams, “Fast RI Data Team” and “Slow RI Data Team,” are in
charge of proton- and deuteron-induced reaction data of LLFP in inverse kinematics at RIBF. The third Team “Muon Data Team” isto obtain muon capture data of LLFP at muon facilities. All of the teams are focusing to obtain high-quality data which are essentiallynecessary to establish reliable reaction models. Each team has its own subjects and promotes LLFP reaction programs based on theirlarge experiences, techniques and skills.

3. Summary of Research Activity
In 2014, all the teams polished up experimental strategies, formed collaboration and prepared experiments. Physics runs forspallation reaction were successfully organized at RIBF in 2015–2017. The muon program started at RCNP, Osaka University inspring 2016 and the data for Pd isotopes were successfully obtained in 2017–2019 via in-beam method with DC beams at RCNP, andvia activation method with pulsed beams at J-PARC and ISIS-RAL/RIKEN facilities.
The reaction data obtained with both fast and energy-degraded beams at RIBF encouraged the nuclear data group of JAEA, anda new database called “JENDLE/ImPACT-2018” has been released. The new database has been generated by a newly developed
reaction model “DEURACS” which treats deuteron-induced reactions. DEURACS reproduces very well cross section data, and muchbetter than other reaction models. A simulation code “PHITS” has been re-coordianted to use the database information.
In December 2018, the Team leader, Hideaki Otsu, was invited to join Technical Meeting of IAEA, entitled “Novel Multidisciplinary Applications with Unstable Ion Beams and Complementary Techniques.” Our activity has been demonstrated and recognizedinternationally. In November 2020, Hideaki Otsu organized a domestic conference entitled “RIKEN Sympoium on Nuclear Data
2020.”At the end of ﬁscal year 2021, the spallation reaction data with 99 Tc beam was obtained and a secondary beam test for 237 Np
production was conducted.

MemberDirector
Hiroyoshi SAKURAI

List of Publication & Presentation
Publication[Review Article]
H. Sakurai, “ImPACT under RIKEN Nishina Center,” Nucl. Phys. News 31, 26–29 (2021).

Presentation[International Conference/Workshop]
H. Sakurai (invited), “A challenge to solve the nuclear waste problem,” International Round Table on Applied Research and Innovations
at NICA, Dubna, Russia & Online, September 15–16, 2021.

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Nuclear Science and Transmutation Research Division
Nuclear Transmutation Data Research Group
Fast RI Data Team
1. Abstract
Fast RI team aims at obtaining and accumulating the cross section data for long lived ﬁssion products (LLFPs) in order to explore
the possibility of using accelerator for nuclear transmutation.
LLFPs as nuclear waste have been generated continuously in nuclear power plants for wealth for human lives, while people
noticed the way of disposal has not necessarily been established, especially after the Fukushima Daiichi power plant disaster. One of
the ways to reduce the amount of LLFP or to recover them as recycled resources is nuclear transmutation technique.
RIBF facility has a property to generate such LLFP as a secondary beam and the beam species are identiﬁed by event by event.
Utilizing the property, absolute values of the cross section of various reactions on LLFPs are measured and accumulated as a database.

2. Major Research Subjects(1) Measurement of reaction products by the interaction of LLFPs with proton, deuteron, and photon to explore candidate reactions for the transmutation of LLFPs(2) Evaluation of the cross section data for the neutron induced reactions from the obtained data

3. Summary of Research Activity
(1)
(2)
(3)
(4)

Acting as a collaboration hub on many groups which plan to take data using fast RI beams in RIBF facility
Concentrating on taking data for proton and deuteron induced spallation reactions with inverse kinematics
Accumulating the cross section data and evaluating them as evaluated nuclear data
Evaluating cross section of neutron induced reaction on LLFP by collaborating with the nuclear model calculation and evaluation group

Members
Team Leader
Hideaki OTSU (Concurrent: Team Leader, SAMURAI Team)
Visiting Scientist
Takashi TERANISHI (Kyushu Univ.)
Student Trainee
Koichi GOTO (Kyushu Univ.)

List of Publications & Presentations
Publication[Proceeding]
R. Matsumura, H. Otsu, and H. Wang et al., “Research for nuclear transmutation of high-radiotoxic nuclide 90 Sr via proton- and deuteroninduced reactions,” JAEA-Conf 2021-001, pp. 225–230 (2022).

Presentations[Domestic Conferences/Workshops]
松村理久, 大津秀暁, 王赫, 千賀信幸, 他 ImPACT-RIBF Collaboration, 「高放射性核種 90 Sr の陽子及び重陽子誘起反応による同位体
生成」, 日本物理学会 第 76 回年次大会, オンライン, 2021 年 3 月.
松村理久, 大津秀暁, 王赫, 炭竃聡之, 千賀信幸, 他, 「中性子入射断面積の評価に向けた安定核 95 Mo の陽子・重陽子入射反応による同位体生成断面積の測定」, 日本物理学会 第 77 回年次大会, オンライン, 2022 年 3 月.

Others[Master Theses]
松村理久, 修士論文, 「陽子・重陽子入射反応による 90 Sr, 95 Mo の同位体生成断面積の測定」, 埼玉大学, 2022 年 3 月.
西津美咲, 修士論文, 「79 Se に対する 200 MeV/u 陽子及び重陽子入射核破砕反応による同位体生成断面積測定」, 九州大学, 2022
年 3 月.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Nuclear Transmutation Data Research Group
Slow RI Data Team
1. Abstract
This team is in charge of the development of low-energy RI beams of long-lived ﬁssion fragments (LLFP) or minor actinides(MA) from the 238 U by means of degrading the energy of beams produced by the BigRIPS fragment separator.

2. Major Research Subjects
Studies of the slowing down and puriﬁcation of RI beams are the main subjects of the team. Developments of devices used forthe slowing down of RI beams are also an important subject.
(1) Study and development of the slowed-down methods for LLFP(2) Operation of the BigRIPS separator and supply the low energy LLFP beam to the experiment in which the cross sections of
LLFP are measured at the low energy(3) Development of MA (such as Np) beams for the nuclear data
(4) Development of the framework to seamlessly handle device, detector, DAQ, and analysis for the easy control of the complicate
slowed-down RI beam production and its development

3. Summary of Research Activity
A new OEDO beam line, designed for the slowed-down RI beams, was constructed under the collaboration with CNS, the University of Tokyo. Our group was responsible for the construction of the infrastructure such as the cooling water and the electricalequipment, and the movement and alignment of existing vacuum chambers, quadrupole magnets. The power supply for the Superconducting Triplet Quadrupoles (STQ) was made, which had a stability also under the low current condition.
Slowed-down 93 Zr beams with 20 or 50 MeV/nucleon were successfully developed at June 2016 for the ﬁrst time. The methods
to obtain the narrow energy, position, and angle distribution were developed. The methods of the energy adjustment and the particle
identiﬁcation at 50 MeV/nucleon were developed. The 93 Zr and 107 Pd beams with 50 MeV/nucleon were produced for the nucleartransmutation experiments using proton or deuteron targets in October 2016. The commissioning experiment of the OEDO beam line
was successfully performed at June 2017. The ﬁrst transmutation experiments using OEDO beam line were performed with 93 Zr,
107
Pd, and 79 Se around 20 MeV/nucleon.
With our developments, the slowed-down RI beams became ready for the transmutation experiments. On the other hand, theprocedure to make the slowed-down RI beams became highly specialized. In order to easily produce the slowed-down RI beam, theframework, called BYACO, is being developed to seamlessly handle the device, detector, DAQ, and analysis. The procedure of the
RI-beam energy control was implemented in the web application. The BYACO system was used also for an RI-beam automatic tuning
project by the BigRIPS team.
The extension of the RI-beam separation using the Bρ-ΔE-Bρ method by the charge state of RI beam was found to be essential toproduce the heavy RI beams. The simulation tool of this extended separation, called Q+ separation, was developed and implemented
into BYACO in 2021. With this tool, we succeeded to produce a 237 Np beam as a secondary beam by collaborating mainly with thefast RI data team and the BigRIPS team.

Members
Team Leader
Toshiyuki SUMIKAMA
Visiting Scientist
SungHan BAE (Inst. for Basic Sci.)
Student Trainees
Hiroya FUKUDA (Kyushu Univ.)
Masaya OISHI (Kyushu Univ.)

Misaki SAITSU (Kyushu Univ.)- 243 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
Nuclear Transmutation Data Research Group
Muon Data Team
1. Abstract
Dr. Yoshio Nishina observed muons in cosmic rays in 1937. The muon is an elementary particle similar to electron and classiﬁed
to lepton group. The muon has positive or negative electric charge, and the lifetime is 2.2 μsec. The negative muon (μ− ) is 207 times
heavier than the electron and behaves as a “heavy electron” in materials. The negative muon is captured by atomic orbits of nuclei
to form a muonic atom and cascades down to the 1s orbit to make muon nuclear capture. The muon is combined with a proton in
the nucleus to convert to a neutron and a neutrino. The muon nuclear capture reaction on a nucleus (ZA N) with the atomic number Z
A−x
N (x = 0, 1, 2, 3, 4) by emitting some neutrons in the reaction. The phenomenon isand mass number A generates the isotopes of Z−1
A−x
N reactions (x = 0, 1, 2, 3, 4) is one of importantcalled “muon nuclear transmutation.” The reaction branching ratio of ZA N(μ− , xnν)Z−1
factors toward various applications with nuclear transmutation technique. From a viewpoint of the nuclear physic, the muon nuclear
capture reaction is very unique and interesting. A high-energy compound nuclear state is suddenly generated in the nuclei associatedwith a weak conversion process of proton to neutron and neutrino. Many experimental results have been so far reported, however, thereaction mechanism itself is not well clariﬁed. The research team aims at obtaining the experimental data to investigate the reaction
mechanism of muon nuclear capture, and also at theoretical understanding on the nuclear capture reaction.

2. Major Research Subjects(1) Experimental clariﬁcation on the mechanism of nuclear muon capture reaction(2) Theoretical understanding on the nuclear muon capture reaction(3) Interdisciplinary applications with the nuclear transmutation technique

3. Summary of Research Activity
There are two experimental methods to study the muon nuclear capture reaction. The ﬁrst one is “muon in-beam spectroscopy
A−x
N nuclei are prompt events and are observed by the “muonmethod.” The neutron and γ-ray emissions from the excited states of Z−1
in-beam spectroscopy method” with a DC muon beam. The reaction branching ratio is directly determined by measuring the neutron
multiplicity in the reaction. The DC muon beam is available at the MuSIC (Muon Science Innovative Channel) muon facility in the
Research Center for Nuclear Physics (RCNP) at Osaka University. The second one is “muon activation method” with the pulsed
A−x
N make β+/− decays. The γ-rays associated with β+/− decays to the daughter nuclei aremuon beam. The produced unstable nuclei Z−1
observed in the experiment. The build-up curve of γ-ray yield at muon beam-on and the decay curve at beam-oﬀ are measured. Since
A−x
N nuclei are determined
the half-lives and decay branching ratios of β+/− -γ decays are known, the reaction branching ratios to the Z−1
by the γ-ray yield curves. The pulsed muon beam is available at the RIKEN-RAL Muon Facility in the UK and J-PARC muon facility.
Muon nuclear capture reactions are studied on ﬁve isotope-enriched palladium targets (104, 105, 106, 108, 110 Pd) and ﬁve isotopeenriched zirconium targets (90, 91, 92, 94, 96 Zr) employing two experimental methods. By obtaining the experimental data on the Pd and Zr
targets, the reaction mechanism is investigated experimentally, and the results are compared with appropriate theoretical calculations.
The 107 Pd is classiﬁed to a long-lived ﬁssion product (LLFP) and is contained in a spent nuclear fuel. The study of muon nuclear
capture on the Pd and Zr targets is aiming at exploring a possible reaction path to make the nuclear transmutation of the Pd and Zr
metal extracted from the spent nuclear fuel without an isotope separation process. This research was funded by the ImPACT Programof Council for Science, Technology and Innovation (Cabinet Oﬃce, Government of Japan).
(1) Experiments with “muon in-beam spectroscopy method”
Muon nuclear capture reactions were investigated on ﬁve palladium targets (104, 105, 106, 108, 110 Pd) by employing the DC muon
beam at MuSIC. The γ-ray and neutron in the muon nuclear capture reaction were measured with the time information relative toA−x
Rh reactions, wheremuon beam arrival. The measured neutron multiplicity gives the reaction branching ratio of 46A Pd(μ− , xnν)45
A = 104, 105, 106, 108, 110 and x = 0, 1, 2, 3, 4.
Employing a newly built neutron spectrometer, the neutron was measured to obtain the reaction branching ratios of muon capture
reactions on the Pd targets. We have constructed a neutron spectrometer named “Seamine”: Scintillator Enclosure Array for Muon
Induced Neutron Emission. The spectrometer consists of 21 liquid scintillation counters, 2 Ge γ-ray detectors, 7 BaF2 counters. The
Pd target, muon beam counters and muon degraders are placed at the center of spectrometer. The neutron counter is a BC-501A
liquid scintillation counter with 20 cm diameter and 5 cm depth and is connected to a 5” photo multiplication tube (H4144-01). The
total neuron detection eﬃciency is estimated 5%, where the distance is 4 cm from the target to neutron counters. The Ge γ-ray
detectors are placed at 10 cm form the target, and the typical detection eﬃciency is 0.5% for 200 keV γ-ray. The BaF2 counters arelocated beneath the target to detect fast γ-rays emitted from the compound nucleus formed in the reactions. Signals from the liquid
scintillation counters are processed in a CAEN V1730B waveform digitizer (16 channel, 14 bit, 500 M samplings/sec.). The neuron-γ
discrimination is performed on-line during the experiment, and the detailed data analysis is conducted oﬀ-line after the experiment.
The neutron energy spectrum is constructed in the digitizer. Signals from Ge detectors are also processed in the digitizer to obtain theenergy and time spectrum of γ-rays associated with the reaction. Signals from the BaF2 counters and muon beam counters are sent to
the digitizer to make the fast timing signals.
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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

is in progress to obtain the multiplicity, the energy and the TOF spectrum using start signals given by γ-rays detected in the BaF2
counters. The γ-ray data gives the energy spectrum of prompt γ-rays and muonic X-rays originated from the 104, 105, 106, 108, 110 Pdtargets.
(2) Experiments with “muon activation method” at the RIKEN-RAL Muon Facility
We conducted the experiments on the muon nuclear capture employing the muon activation method at the RIKEN-RAL Muon
Facility in the UK. The pulsed muon beam was irradiated on the 104, 105, 106, 108, 110 Pd targets. The γ-rays were detected by a Ge detector
located at the downstream of the Pd targets to maximize the detection eﬃciency. The build-up and decay curves of γ-ray intensities
were measured associated with β+/− decays of produced unstable nuclei to daughter nuclei. The γ-ray-yield curves give the absolute
A−x
Rh reactions. The
radiation activity produced by the reaction, and the reaction branching ratios are determined for 46A Pd(μ− , xnν)45
decay curves of γ-rays from the produced nuclei with long half-lives were measured under low γ-ray background at an experimental
apparatus built in a separated room. The detailed oﬀ-line data analysis is in progress.
(3) Experiments with “muon activation method” at J-PARC muon facility
The experiments employing the muon activation method were performed at J-PARC muon facility. The ﬁve isotope-enriched Pdtargets (104, 105, 106, 108, 110 Pd) were irradiated by the pulsed muon beam, and the build-up and decay curves of γ-ray intensities were
measured.
In addition to the Pd targets, the experiments on ﬁve isotope-enriched Zr target (90, 91, 92, 94, 96 Zr) were conducted to obtain theA−x
Y reactions, where A = 90, 91, 92, 94, 96. The obtained reaction branching ratios on thereaction branching ratios of 40A Zr(μ− , xnν)39
Pd and Zr targets are important to understand the reaction mechanism of muon nuclear capture. The 93 Zr is one of the LLFP and iscontained in a spent nuclear fuel. The experiment on the Zr targets is to explore a possibility to realize the nuclear transmutation of
the Zr metal extracted from the spent nuclear fuel.
−107−x
Rh reactions, the muon activation experiment was performed
In order to obtain the reaction branching ratio of 107
46 Pd(μ , xnν)45
107
employing a Pd target containing Pd of 15.3%. The γ-ray intensities associated with β+/− decays of produced unstable nuclei were
measured to obtain the build-up and decay curves. Once the branching ratios of the reactions on the 104, 105, 106, 108, 110 Pd targets are
obtained, these contributions are extracted from the branching-ratio data obtained for the Pd target with 107 Pd. The reaction branching−107−x
Rh reactions is ﬁnally determined. The detailed oﬀ-line data analysis is in progress.
ratio of 107
46 Pd(μ , xnν)45(4) Comparison with theory
The muon activation method gives the reaction branching ratios. The muon in-beam spectroscopy method gives the neutron
multiplicity and the neutron energy spectrum. These experimental results are important to understand the compound nuclear state andneutron emission mechanism. The reaction branching ratios obtained by the muon activation method are compared with the results ofneutron multiplicity measurements. The neutron energy spectrum is considered to be reﬂected by the energy distribution of compound
nuclear state and neutron emission mechanism. The experimental results are compared with the appropriate calculations employing theneutron emission mechanisms due to an evaporation, a cascade and a direct emission processes with assuming the energy distribution
at compound nuclear state.

Members
Team Leader
Hiroyoshi SAKURAI
Contract Researcher
Teiichiro MATSUZAKI
Part-time Worker
Takeshi SAITO (Research Part-time Worker I)

List of Publications & Presentations
Presentations[Domestic Conferences/Workshops]
水野るり惠, 他, 「ミューオン原子 X 線分光のためのコンプトンサプレッサー付き Ge 検出器開発」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
水野るり惠, 他, 「Ge 検出器を用いたミューオン原子 X 線分光のための光子検出システムの性能評価」, Muon 科学と加速器研究,大阪府豊中市 (大阪大学), 2022 年 1 月 6–8 日.
水野るり惠, 他, 「ミューオン原子 X 線分光のための Ge 検出器を用いた広ダイナミックレンジ光子検出システムの性能評価」,日
本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
齋藤岳志, 「原子核ミューオン捕獲に伴う放出中性子の測定」, RCNP 研究会「ミューオン原子核捕獲反応による原子核関連研究の, 大阪府茨木市（大阪大学核物理研究センター）, 2022 年 3 月 24–25 日.
可能性」
新倉潤, 他,「ミューオン原子 X 線測定のための検出器開発」, RCNP 研究会「ミューオン X 線 γ 線分光」, 大阪府茨木市（大阪大学
核物理研究センター）, 2022 年 3 月 24–25 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

齋藤岳志, 「ミューオン原子 X 線分光とその将来について」, ソフトエラー研究会, 山口県大島郡（ゲストハウス HOSHI-KAZE）,
2022 年 3 月 28 日.
水野るり惠, 他, 「Si ミューオン原子由来の生成原子核分岐比の絶対値測定実験」, ソフトエラー研究会, 山口県大島郡（ゲストハウス HOSHI-KAZE）, 2022 年 3 月 28 日.

Others[Master Thesis]
水野るり惠, 「ミューオン原子 X 線分光のためのコンプトンサプレッサー付きゲルマニウム検出器の開発」, 東京大学, 2022 年 3 月.

[PhD. Thesis]
T. Saito, “Study of muonic X-ray spectroscopy and nuclear muon capture reaction”, University of Tokyo, March 2022.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
High-Intensity Accelerator R&D Group
1. Abstract
The High-Intensity Accelerator R&D group, consisting of two teams, develops elemental technology of high-power acceleratorsand high-power targets, aiming at future applications to nuclear transmutations of long-lived ﬁssion product into short-lived nuclides.
The research subjects are superconducting rf cavities for low-velocity ions, design of high-power accelerators, high-power target
systems and related technologies.
Nuclear transmutation with high-intensity accelerators is expected to reduce the high-level radioactive wastes and to recycle
the precious resources such as rare-earth materials in future. This method is one of the important applications of the ion-accelerator
technologies that have been developed at RIKEN for a long time. Under the framework of ImPACT Fujita Program, we have conducted
R&D of elemental technology related to the high-power accelerators and high-power targets, from FY2014 to FY2018. We gained alot of experiences in these R&Ds. Among them, the development of a superconducting rf cavity has become the basis of the upgrade
program of the RILAC facility which started in 2016.

2. Major Research Subject
R&D of elemental technology of high-power accelerators and high-power targets.

3. Summary of Research Activity(1) A high-gradient rf cavity has been constructed and tested based on the superconducting rf technology.
(2) Several candidates for the high-power target have been proposed and their prototypes have been tested.
(3) A high-current deuteron RFQ has been designed.

Members
Director
Osamu KAMIGAITO(concurrent: Group Director, Accelerator Group)- 247 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
High-Intensity Accelerator R&D Group
High-Gradient Cavity R&D Team
1. Abstract
We develop new components for accelerators dedicated for low-beta-ions with very high intensity. Speciﬁcally, we are designingand constructing a cryomodule for superconducting linac eﬃcient for acceleration of low-beta-ions. In parallel, we try to optimize an
rf acceleration system by making computer simulations for acceleration of very high intensity beams.

2. Major Research Subjects(1) Development of high-gradient cavites for low beta ions
(2) Development of power saving cryomodules

3. Summary of Research Activity
Development of highly eﬃcient superconducting accelerator modules

Members
Team Leader
Naruhiko SAKAMOTO
Research/Technical Scientists
Yutaka WATANABE

Kazutaka OZEKI

Research & Development Scientist
Kenji SUDA

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Nuclear Science and Transmutation Research Division
High-Intensity Accelerator R&D Group
High-Power Target R&D Team
1. Abstract
The subjects of this team cover R&D studies with respect to target technology for the transmutation of the LLFPs.

2. Major Research Subjects(1) Liquid lithium target for production of neutron or muon
(2) Beam window without solid structure

3. Summary of Research Activity(1) Liquid lithium target for production of neutron or muon (H. Okuno)(2) Beam window with solid structure (H. Okuno)

Members
Team Leader
Hiroki OKUNO
Special Postdoctoral Researcher
Yasuto MIYAKE
Visiting Scientist
Katsuyoshi TSUMORI (Nat’l Inst. Fusion Science)- 249 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Accelerator Group
1. Abstract
The Accelerator Group, consisting of seven teams, pursues various upgrade programs on the world-leading heavy-ion accelerator
facility, RI Beam Factory (RIBF), to enhance the accelerator performance and operation eﬃciency. The programs include the R&D of
superconducting ECR ion source, charge stripping systems, beam diagnostic devices, radio-frequency systems, control systems, andbeam simulation studies. We are also maintaining the large infrastructure to realize eﬀective operation of the RIBF. Moreover, we are
actively promoting the applications of the facility to various research ﬁelds.
Our primary mission is to supply intense, stable heavy-ion beams for the users through eﬀective operation, maintenance, andupgrade of the RIBF accelerators and related infrastructure. The director members govern the development programs that are not dealt
with by a single team, such as intensity upgrade and eﬀective operation. We also discuss the future plans of RIBF along with otherlaboratories belonging to the RIBF research division.
Various improvements and developments have been carried out for the RIBF accelerators in order to upgrade the beam intensities
and stability. Owing to the eﬀorts, for example, we succeeded in accelerating the uranium beam of 117 particle nA through SRC in
October 2020. This surpassed the long-standing target of 100 particle nA, and also means that one of goals of the current mid-termplan of RNC has been achieved. Moreover, the beam availability for the RIBF experiments has increased to 98.3% in 2021, which is
the highest value since RIBF started operation.
At the RILAC facility, upgraded with a superconducting ECR ion source and superconducting booster linac, synthesis experimentsof new elements has been conducted since 2020. In the ﬁrst half of 2021, major repairs were made to the normal-conducting cavities.
The coupler part of the superconducting cavities, which had a vacuum leak problem, were modiﬁed during the summer shutdown. As
a result, a high intensity beam of 51 V is now being supplied stably. Moreover, construction of a new beam line for the R&D of mass
production method of 211 At has been almost completed, in cooperation with the Safety Management Group under the leadership of
the RI Application Research Group.
An upgrade plan of RIBF for further increasing uranium beam has been continuously discussed. Based on the basic design of the“charge-stripper ring (CSR),” which will be used to increase the overall stripping eﬃciency of the uranium beam, a pair of quadrupole
magnets was fabricated as a prototype. The measured magnetic ﬁeld was in good agreement with the simulations, including themagnetic ﬁeld leaking around the magnets. Design study of the extraction bending magnet was also performed.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Intensity upgrade of RIBF accelerators (Okuno)
Eﬀective and stable operation of RIBF accelerators (Fukunishi)
Stable operation of the upgraded RILAC facility
Promotion of the upgrade plan of RIBF

3. Summary of Research Activity(1) The beams were provided for the RIBF experiments at the intensities requested by the users.
(2) The beam availability for the RIBF experiments was 98.3% in 2021. This is the highest value since RIBF started operation.
(3) A high intensity beam of 51 V was supplied stably to the synthesis experiments of new elements at the upgraded RILAC
facility.
(4) An intensity-upgrade plan of the RIBF has been further investigated. Elemental R&D of the ﬁrst charge-stripper ring (CSR1)
is under progress.

Members
Director
Osamu KAMIGAITO
Deputy Directors
Hiroki OKUNO (for intensity upgrade)

Nobuhisa FUKUNISHI (for stable and eﬃcient operation)

Junior Research Associate
Kaori NAKAMURA
Research Consultants
Tadashi FUJINAWA

Masayuki KASE

Visiting Scientists
Eiji KAKO (KEK)
Hirotaka NAKAI (KEK)
Kensei UMEMORI (KEK)
Hiroshi SAKAI (KEK)

Taro KONOMI (KEK)
Masahiro OKAMURA (BNL)
Noboru SASAO (Okayama Univ.)
Yasutaka IMAI (Okayama Univ.)- 251 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Assistant
Karen SAKUMA
Administrative Part-time Worker II
Ryoko UMEZAKI

List of Publications & Presentations
Publication[Original Paper]
O. Kamigaito, “Scale invariance of electrodynamics in radio-frequency linear accelerators,” arXiv:2109.14273.

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Research Facility Development Division
Accelerator Group
Accelerator R&D Team
1. Abstract
We are developing the key hardware in upgrading the RIBF accelerator complex. Our primary focus and research is charge
stripper which plays an essential role in the RIBF accelerator complex. Charge strippers remove many electrons in ions and realizeeﬃcient acceleration of heavy ions by greatly enhancing charge state. The intensity of uranium beams is limited by the lifetime of the
carbon foil stripper conventionally installed in the acceleration chain. The improvement of stripper lifetimes is essential to increase
beam power towards the ﬁnal goal of RIBF in the future. We are developing the low-Z gas stripper. In general gas stripper is free fromthe lifetime related problems but gives low equilibrium charge state because of the lack of density eﬀect. Low-Z gas stripper, however,can give as high equilibrium charge state as that in carbon foil because of the suppression of the electron capture process. Another our
focus is the upgrade of the world’s ﬁrst superconducting ring cyclotron.

2. Major Research Subjects(1) Development of charge strippers for high power beams (highly oriented graphene ﬁlm, low-Z gas)
(2) Upgrade of the superconducting ring cyclotron(3) Maintenance and R&D of the electrostatic deﬂection/inﬂection channels for the beam extraction/injection

3. Summary of Research Activity(1) Development of charge strippers for high power beams (foil, low-Z gas)
(H. Hasebe, H. Imao, H. Okuno)
We are developing the charge strippers for high intensity heavy ion beams. We are focusing on the developments on highlyoriented carbon graphite ﬁlms and gas strippers including He gas stripper.
(2) Upgrade of the superconducting ring cyclotron(J. Ohnishi, H. Okuno)
We are focusing on the upgrade of the superconducting ring cyclotron.
(3) Maintenance and R&D of the electrostatic deﬂection/inﬂection channels for the beam extraction/injection(J. Ohnishi, H. Okuno)
We are developing high-performance electrostatic channels for high power beam injection and extraction.

Members
Team Leader
Hiroki OKUNO
Senior Research Scientist
Hiroshi IMAO
Technical Scientist
Hiroo HASEBE
Special Temporary Technical Scientist
Jun-ichi OHNISHI
Visiting Scientist
Noriyosu HAYASHIZAKI (Tokyo Tech)

List of Publications & Presentations
Publication[Original Paper]
H. Imao, “Charge stripper ring for RIKEN RI Beam Factory,” J. Instrum. 15, P12036 (2020).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Accelerator GroupIon Source Team
1. Abstract
Our aim is to operate and develop the ECR ion sources for the accelerator-complex system of the RI Beam Factory. We focus on
further upgrading the performance of the RI Beam Factory through the design and fabrication of a superconducting ECR ion sourcefor production of high-intensity heavy ions.

2. Major Research Subjects(1) Operation and development of the ECR ion sources(2) Development of a superconducting ECR heavy-ion source for production of high-intensity heavy ion beams

3. Summary of Research Activity(1) Operation and development of ECR ion sources(T. Nakagawa, M. Kidera, Y. Higurashi, T. Nagatomo, Y. Kanai, and H. Haba)
We routinely produce and supply various kinds of heavy ions such as zinc and calcium ions for the super-heavy element searchexperiment as well as uranium ions for RIBF experiments. We also perform R&D’s to meet the requirements for stable supply ofhigh-intensity heavy ion beams.
(2) Development of a superconducting ECR ion source for use in production of a high-intensity heavy ion beam
(T. Nakagawa, J. Ohnishi, M. Kidera, Y. Higurashi, and T. Nagatomo)
The RIBF is required to supply heavy ion beams with very high intensity so as to produce RI’s and for super-heavy element searchexperiment. We have designed and are fabricating an ECR ion source with high magnetic ﬁeld and high microwave- frequency, since
the existing ECR ion sources have their limits in beam intensity. The coils of this ion source are designed to be superconducting for the
production of high magnetic ﬁeld. We are also designing the low-energy beam transport line of the superconducting ECR ion source.

Members
Team Leader
Takahide NAKAGAWA
Senior Technical Scientists
Yoshihide HIGURASHI

Takashi NAGATOMO

Special Temporary Research Scientist
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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Accelerator GroupRILAC Team
1. Abstract
Our team is responsible for the operation, maintenance, and upgrade of the RIKEN heavy-ion linear accelerator (RILAC), a
unique variable-frequency linac that has been in operation since 1980. RILAC was upgraded in the 1990s as part of the RI Beam
Factory (RIBF) project, and made a signiﬁcant contribution to the synthesis and discovery of the element 113, nihonium. In 2019,a superconducting linac booster, SRILAC, was installed, and it will play a major role in the synthesis of heavier new elements,
development of the technologies for production of medical radioisotopes, and as a powerful injector to RIBF.

2. Major Research Subjects(1) Development of technology to operate RILAC with high intensity and high stability(2) Construction and maintenance of the RILAC beamlines(3) Eﬃcient operation, maintenance and management of the vacuum equipment in the RIBF accelerators

3. Summary of Research Activity
In 2021, we have made various improvements of the whole RILAC with the cooperation of other teams of the Accelerator Group,in order to provide high-intensity beams more stably to the new element synthesis experiments being conducted at GARIS III. For
example, leak of refrigerant in the normal conducting cavities was thoroughly investigated and repaired. In addition, vacuum leakat the couplers of the superconducting cavities, which had been a problem since its start, was repaired. With these eﬀorts, the beam
availability has been improved signiﬁcantly.
A beamline is being prepared at the RILAC facility for mass production of 211 At, which has potential medical applications.
Under the leadership of the RI Application Research Group and with the help of other teams of the Accelerator Group, the optical
calculations, electromagnet design, radiation shielding design, and overall beamline installation were undertaken and the beamline isalmost complete.
As in the past, we maintained the vacuum system of the whole accelerators at RIBF. While taking into consideration the aging of
the vacuum pumps, an eﬃcient maintenance plan was established and cost-conscious maintenance was executed.

Members
Team Leader
Osamu KAMIGAITO
Deputy Team Leader
Naruhiko SAKAMOTO
Research/Technical Scientists
Yutaka WATANABE (Senior Technical Scientist)

Takahiro NISHI (Research Scientist)

Research Consultant
Eiji IKEZAWA

List of Publications & Presentations[Proceedings]
T. Nishi, E. Iwai, A. Uchiyama, Y. Shimizu, T. Sugimoto, H. Suzuki, H. Takeda, N. Fukuda, N. Fukunishi, H. Fujii, H. Maesaka, andM. Yoshimoto, “Development of auto tuning system of ion optics for high intensity primary beam using machine learning,” Proceedingsof the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki Online, Japan, August 9–12, 2021, TUOA03, 71–74(2021). https://www.pasj.jp/web_publish/pasj2021/proceedings/PDF/TUOA/TUOA03.pdf .
T. Nakamura, K. Ozeki, S. Fukuzawa, M. Hamanaka, S. Ishikawa, K. Kobayashi, R. Koyama, M. Nishida, M. Nishimura, J. Shibata,N. Tsukiori, K. Yadomi, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, O. Kamigaito, Y. Kanai, M. Kidera, M. Komiyama, K. Kumagai, T. Maie, T. Nagatomo, T. Nakagawa, M. Nakamura, J. Ohnishi, H. Okuno,
N. Sakamoto, S. Kenji, A. Uchiyama, W. Shu, W. Tamaki, Y. Watanabe, K. Yamada, and H. Yamasawa, “Status report on the operation of RIKEN AVF cyclotron,” Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki
Online, Japan, August 9–12, 2021, TUP052, 575–579 (2021). https://www.pasj.jp/web_publish/pasj2021/proceedings/
PDF/TUP0/TUP052.pdf .
S. Fukuzawa, K. Suda, A. Goto, J. Ohnishi, M. Hamanaka, S. Ishikawa, K. Kobayashi, R. Koyama, T. Nakamura, M. Nishida,
M. Nishimura, J. Shibata, N. Tsukiori, K. Yadomi, M. Fujimaki, N. Fukunishi, H. Hasebe, Y. Higurashi, H. Imao, O. Kamigaito, M. Kase, M. Kidera, M. Komiyama, K. Kumagai, T. Maie, T. Nagatomo, T. Nakagawa, H. Okuno, K. Ozeki, N. Sakamoto,- 255 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

A. Uchiyama, S. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, K. Kamakura, and Y. Kotaka, “Status report on the operationof RIKEN AVF cyclotron,” Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki Online, Japan, August 9–12, 2021, WEP052, 760–764 (2021). https://www.pasj.jp/web_publish/pasj2021/proceedings/PDF/
WEP0/WEP052.pdf .
T. Ohki, H. Yamauchi, K. Oyamada M. Tamura, A. Yusa, K. Kaneko, N. Sakamoto, M. Fujimaki, E. Ikezawa, H. Imao, M. Kidera,
T. Nagatomo, T. Nishi, K. Ozeki, K. Suda, A. Uchiyama, T. Watanabe, Y. Watanabe, K. Yamada, and O. Kamigaito, “Present status of
RILAC,” Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki Online, Japan, August 9–12,
2021, THP059, 983–985 (2021). https://www.pasj.jp/web_publish/pasj2021/proceedings/PDF/THP0/THP059.pdf .

Presentations[International Conferences/Workshops]
T. Yanagisawa (invited), K. Yamada, T. Dantsuka, M. Fujimaki, E. Ikezawa, H. Imao, O. Kamigaito, M. Komiyama, K. Kumagai,
T. Nagatomo, T. Nishi, H. Okuno, K. Ozeki, N. Sakamoto, K. Suda, A. Uchiyama, T. Watanabe, Y. Watanabe, E. Kako, H. Nakai,
H. Sakai, K. Umemori, H. Hara, A. Miyamoto, and K. Sennyu, “Successful beam commissioning of heavy-ion superconducting linac
at RIKEN,” 2021 International Conference on RF Superconductivity (SRF2021), East Lansing, MI, USA, Online, June 28–July 2,
2021.
K. Yamada (invited), T. Nishi, M. Fujimaki, N. Fukunishi, H. Imao, O. Kamigaito, T. Nagatomo, N. Sakamoto, A. Uchiyama, T. Watanabe,
and Y. Watanabe, “Beam acceleration with the upgraded RIKEN heavy-ion linac,” 64th ICFA Advanced Beam Dynamics Workshop
on High-Intensity and High-Brightness Hadron Beams (HB2021), Batavia, IL, USA, Online, October 4–8, 2021.
A. Yusa (poster), A. Uchiyama, M. Fujimaki, N. Fukunishi, Y. Higurashi, E. Ikezawa, H. Imao, O. Kamigaito, M. Kidera, K. Kumagai, T. Nagatomo, T. Nishi, J. Ohnishi, K. Ozeki, N. Sakamoto, K. Suda, T. Watanabe, Y. Watanabe, K. Yamada, M. Komiyama,
A. Kamoshida, K. Kaneko, R. Koyama, T. Ohki, K. Oyamada, M. Tamura, and H. Yamauchi, “Control system of the SRILAC projectat RIBF,” 18th International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS 2021), China,
Shanghai, October 14–22, 2021.

[Domestic Conferences/Workshops]
西隆博 (招待講演), 「理化学研究所におけるガウシアンプロセスを用いた一次重イオンビームトランスポートの自動調整の開発」,
日本物理学会 第 77 回年次大会, オンライン, 2022 年 3 月 15 日–19 日.
吉本雅浩 (口頭発表), 西隆博, 岩井瑛人, 内山暁仁, 清水陽平, 杉本崇, 鈴木宏, 竹田浩之, 福田直樹, 藤井洋樹, 前坂比呂和, 「機械学習を用いた高強度一次ビームのイオン光学系の自動調整の開発」, 第 18 回日本加速器学会年会, オンライン, 2021 年 8 月 9–12 日.
上垣外修一 (ポスター発表), 大木智則, 小山田和幸, 山内啓資, 田村匡史, 遊佐陽, 金子健太, 坂本成彦, 藤巻正樹, 池沢英二, 今尾浩士,
木寺正憲, 長友傑, 大関和貴, 須田健嗣, 内山暁仁, 渡邉環, 渡邉裕, 山田一成, 「理研重イオンリニアックの現状報告」, 第 18 回日
本加速器学会年会, オンライン, 2021 年 8 月 9–12 日.
小高康照 (ポスター発表), 福澤聖児, 須田健嗣, 後藤彰, 大西純一, 濱仲誠, 石川盛, 小林清志, 小山亮, 仲村武志, 西田稔, 柴田順翔,
月居憲俊, 矢冨一慎, 藤巻正樹, 福西暢尚, 長谷部裕雄, 日暮祥英, 今尾浩士, 上垣外修一, 加瀬昌之, 木寺正憲, 込山美咲, 熊谷桂子,
眞家武士, 長友傑, 中川孝秀, 奥野広樹, 大関和貴, 坂本成彦, 内山暁仁, 渡部秀, 渡邉環, 渡邉裕, 山田一成, 鎌倉恵太, 「理研 AVF
サイクロトロン運転の現状報告」, 第 18 回日本加速器学会年会, オンライン, 2021 年 8 月 9–12 日.
山澤秀行 (ポスター発表), 仲村武志, 福澤聖児, 濱仲誠, 石川盛, 小林清志, 小山亮, 西田稔, 西村誠, 柴田順翔, 月居憲俊, 矢冨一慎,
大関和貴, 段塚知志, 藤巻正樹, 藤縄雅, 福西暢尚, 長谷部裕雄, 日暮祥英, 池沢英二, 今尾浩士, 上垣外修一, 金井保之, 加瀬昌之,
木寺正憲, 込山美咲, 熊谷桂子, 眞家武士, 長友傑, 中川孝秀, 中村仁音, 大西純一, 奥野広樹, 坂本成彦, 須田健嗣, 内山暁仁, 渡部
秀, 渡邉環, 渡邉裕, 山田一成, 「理研 RIBF におけるリングサイクロトロンの運転報告」, 第 18 回日本加速器学会年会, オンライ
ン, 2021 年 8 月 9–12 日.

Outreach Activity熊谷洸希, 渋谷遥斗, 森内厚佑, 水谷凜都, 登藤成琉, 丸田京華, 秋山翔希, 西隆博, 田中香津生, 遠藤金吾, 「秋田県における地上でのμ粒子検出頻度と天気ごとの地上気温、湿度、気圧との偏相関」, J. Sci. EGGS, 4, 2110004, 1–6 (2021). https://www3.e-kenkyu.
com/j-sci-eggs/uploads/manuscript/file/21/Vol.4-2110004_2021.pdf .

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Accelerator Group
Cyclotron Team
1. Abstract
Together with other teams of Nishina Center accelerator division, maintaining and improving the RIBF cyclotron complex. The
accelerator provides high intensity heavy ions. Our mission is to have stable operation of cyclotrons for high power beam operation.
Recently stabilization of the rf system is a key issue to provide 10 kW heavy ion beam.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)

RF technology for Cyclotrons
Operation of RIBF cyclotron complex
Maintenance and improvement of RIBF cyclotrons
Single turn operation for polarized deuteron beams
Development of superconducting linac

3. Summary of Research Activity• Development of the rf system for a reliable operation• Development of highly stabilized low level rf system• Development of superconducting linac• Development of the intermediate-energy polarized deuteron beams

Members
Team Leader
Naruhiko SAKAMOTO
Research/Technical Scientists
Kazutaka OZEKI (Senior Technical Scientist)

Kenji SUDA (Technical Scientist)

List of Publications & Presentations
Publications[Proceedings]
T. Nakamura, K. Ozeki, S. Fukuzawa, M. Hamanaka, S. Ishikawa, K. Kobayashi, R. Koyama, M. Nishida, M. Nishimura, J. Shibata,N. Tsukiori, K. Yadomi, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, O. Kamigaito, Y. Kanai, M. Kidera, M. Komiyama, K. Kumagai, T. Maie, T. Nagatomo, T. Nakagawa, M. Nakamura, J. Ohnishi, H. Okuno,
N. Sakamoto, S. Kenji, A. Uchiyama, W. Shu, W. Tamaki, Y. Watanabe, K. Yamada, and H. Yamasawa, “Status report on the operation of RIKEN AVF cyclotron,” Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki
Online, Japan, August 9–12, 2021, TUP052, 575–579 (2021). https://www.pasj.jp/web_publish/pasj2021/proceedings/
PDF/TUP0/TUP052.pdf .
S. Fukuzawa, K. Suda, A. Goto, J. Ohnishi, M. Hamanaka, S. Ishikawa, K. Kobayashi, R. Koyama, T. Nakamura, M. Nishida,
M. Nishimura, J. Shibata, N. Tsukiori, K. Yadomi, M. Fujimaki, N. Fukunishi, H. Hasebe, Y. Higurashi, H. Imao, O. Kamigaito, M. Kase, M. Kidera, M. Komiyama, K. Kumagai, T. Maie, T. Nagatomo, T. Nakagawa, H. Okuno, K. Ozeki, N. Sakamoto,
A. Uchiyama, S. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, K. Kamakura, and Y. Kotaka, “Status report on the operation of RIKEN AVF cyclotron,” Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki
Online, Japan, August 9–12, 2021, WEP052, 760–764 (2021). https://www.pasj.jp/web_publish/pasj2021/proceedings/
PDF/WEP0/WEP052.pdf .
T. Ohki, H. Yamauchi, K. Oyamada M. Tamura, A. Yusa, K. Kaneko, N. Sakamoto, M. Fujimaki, E. Ikezawa, H. Imao, M. Kidera,
T. Nagatomo, T. Nishi, K. Ozeki, K. Suda, A. Uchiyama, T. Watanabe, Y. Watanabe, K. Yamada, and O. Kamigaito, “Present status of
RILAC,” Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki Online, Japan, August 9–12,
2021, THP059, 983–985 (2021). https://www.pasj.jp/web_publish/pasj2021/proceedings/PDF/THP0/THP059.pdf .

Presentations[International Conference/Workshops]
K. Yamada (invited), T. Dantsuka, M. Fujimaki, E. Ikezawa, H. Imao, O. Kamigaito, M. Komiyama, K. Kumagai, T. Nagatomo, T. Nishi,
H. Okuno, K. Ozeki, N. Sakamoto, K. Suda, A. Uchiyama, T. Watanabe, Y. Watanabe, E. Kako, H. Nakai, H. Sakai, K. Umemori, H. Hara, A. Miyamoto, K. Sennyu, and T. Yanagisawa, “Successful beam commissioning of heavy-ion superconducting linac at
RIKEN,” 2021 International Conference on RF Superconductivity (SRF2021), East Lansing, MI, USA, Online, June 28–July 2, 2021.
K. Ozeki (poster), O. Kamigaito, N. Sakamoto, K. Suda, and K. Yamada, “FPC for RIKEN QWR,” 2021 International Conference on RF
Superconductivity (SRF2021), East Lansing, MI, USA, Online, June 28–July 2, 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

K. Suda (poster), O. Kamigaito, K. Ozeki, N. Sakamoto, K. Yamada, E. Kako, H. Nakai, H. Sakai, K. Umemori, H. Hara, A. Miyamoto,K. Sennyu, and T. Yanagisawa, “New frequency-tuning system and digital LLRF for stable and reliable operation of SRILAC,” 2021
International Conference on RF Superconductivity (SRF2021), East Lansing, MI, USA, Online, June 28–July 2, 2021.
N. Sakamoto (poster), H. Imao, O. Kamigaito, T. Nagatomo, T. Nishi, K. Ozeki, K. Suda, A. Uchiyama, and K. Yamada, “Operation
experience of the superconducting linac at RIKEN RIBF,” 2021 International Conference on RF Superconductivity (SRF2021), East
Lansing, MI, USA, Online, June 28–July 2, 2021.

[Domestic Conferences/Workshops]
仲村武志（ポスター発表）, 福澤聖児, 濱仲誠, 石川盛, 小林清志, 小山亮, 西田稔, 西村誠, 柴田順翔, 月居憲俊, 矢冨一慎, 大関和貴,
段塚知志, 藤巻正樹, 藤縄雅, 福西暢尚, 長谷部裕雄, 日暮祥英, 池沢英二, 今尾浩士, 上垣外修一, 金井保之, 木寺正憲, 込山美咲, 熊谷桂子, 真家武士, 長友傑, 中川孝秀, 中村仁音, 大西純一, 奥野広樹, 坂本成彦, 須田健嗣, 内山暁仁, 渡部秀, 渡邉環, 渡邉裕, 山田
一成, 山澤秀行, 「理研 RIBF におけるリングサイクロトロンの運転報告」, 第 18 回日本加速器学会年会, オンライン, 2021 年 8
月 9–12 日.
福澤聖児, 須田健嗣, 後藤彰, 大西純一, 濱仲誠, 石川盛, 小林清志, 小山亮, 仲村武志, 西田稔, 西村誠, 柴田順翔, 月居憲俊, 矢冨一慎,
藤巻正樹, 福西暢尚, 長谷部裕雄, 日暮祥英, 今尾浩士, 上垣外修一, 加瀬昌之, 木寺正憲, 込山美咲, 熊谷桂子, 真家武士, 長友傑,
中川孝秀, 奥野広樹, 大関和貴, 坂本成彦, 内山暁仁, 渡部秀, 渡邉環, 渡邉裕, 山田一成, 鎌倉恵太, 小高康照, 「理研 AVF サイクロ
トロン運転の現状報告」, 第 18 回日本加速器学会年会, オンライン, 2021 年 8 月 9–12 日.
大木智則, 小山田和幸, 山内啓資, 田村匡史, 遊佐陽, 金子健太, 坂本成彦, 藤巻正樹, 池沢英二, 今尾浩士, 木寺正憲, 長友傑, 大関和貴,
須田健嗣, 内山暁仁, 渡邉環, 渡邉裕, 山田一成, 上垣外修一, 「理研重イオンリニアックの現状報告」, 第 18 回日本加速器学会年会, オンライン, 2021 年 8 月 9–12 日.

Outreach Activity
坂本成彦, 私立武蔵越生高校講演会, 「加速器入門」, オンライン, 2021 年 12 月 13 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Accelerator GroupBeam Dynamics & Diagnostics Team
1. Abstract
Aiming at stable and eﬃcient operation of the RIBF cascaded cyclotron system, Beam Dynamics and Diagnostics Team developes
power supplies, beam instrumentation, computer control and beam dynamic studies. We have successfully increased the beam availability for user experiments to more than 98%. We have also established small-beam-loss operations. The latter strongly contributes
to recent high-power operations at RIBF.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)

More eﬃcient and stable operations of the RIBF cascaded cyclotron system
Maintenance and developments of the beam instrumentation
Developments of computer control system for more intelligent and eﬃcient operations
Maintenance and improvements of the magnet power supplies for more stable operations
Upgrade of the existing beam interlock system for high-power beams with few tens of kW

3. Summary of Research Activity(1) High-intensity heavy-ion beams such as 117-particle-nA (pnA) uranium, 173-pnA xenon, 486-pnA krypton, 788-pnA Zinc
and 740-pnA calcium beams have been obtained.
(2) The world-ﬁrst high-Tc SQUID beam current monitor has been developed.
(3) The bending power of the ﬁxed-frequency Ring Cyclotron has been upgraded to 700 MeV.
(4) The world-most-intense V beams are stably supplied to super-heavy-element-search experiments.
(5) The RIBF control system has been operated stably by replacing legacy hardware controllers carried over from our old facility
with new ones. Several useful operation tools are also developed.
(6) The dated power supplies exciting the main coils of RIKEN Ring Cyclotron has been upgraded to a new one having a betterlong-term stability than the old ones.
(7) Developments of automatic beam tuning methods based on recent machine-learning technology and adaptive control are in
progress.

Members
Team Leader
Nobuhisa FUKUNISHI
Senior Technical Scientists
Masaki FUJIMAKI
Keiko KUMAGAI
Akito UCHIYAMA

Tamaki WATANABE
Kazunari YAMADA

Expert Technician
Misaki KOMIYAMA
Postdoctoral Researcher
Takahiro NISHI
Research Associate
Hiroki FUJII
Visiting Scientists
Shin-ichiro HAYASHI (Hiroshima Int’l Univ.)
Atsushi KAMOSHIDA (Nat’l Instruments Japan Corporation)

Takuya MAEYAMA (Kitasato Univ.)

List of Publications & Presentations
Publication[Review Article]
K. Yamada, K. Ozeki, and K. Suda, “Helium cryogenic system for the RIKEN superconducting heavy-ion linear accelerator—System
overview and operation,” Teion Kogaku (J. Cryo. Super. Soc. Jpn.) 56, 201–208 (2021).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)[Proceedings]
A. Uchiyama, M. Komiyama, M. Kidera, and N. Fukunishi, “Data archive system for superconducting RIKEN linear accelerator at RIBF,”
12th International Particle Accelerator Conference (IPAC’21), Campinas, Brazil (virtual format), 2178–2181 (2021).
K. Yamada, T. Dantsuka, M. Fujimaki, E. Ikezawa, H. Imao, O. Kamigaito, M. Komiyama, K. Kumagai, T. Nagatomo, T. Nishi, H. Okuno,
K. Ozeki, N. Sakamoto, K. Suda, A. Uchiyama, T. Watanabe, Y. Watanabe, H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa, E. Kako,
H. Nakai, H. Sakai, and K. Umemori, “Successful beam commissioning of heavy-ion superconducting linac at RIKEN,” Proceedingsof 20th International Conference on RF Superconductivity (SRF2021), 167–174 (2021).
A. Uchiyama, M. Komiyama, M. Fujimaki, K. Kumagai, H. Yamaychi, and K. Kaneko, “Development of machine protection system for
SRILAC,” Proceedings of the 18th Particle Accelerator Society of Japan, TUP042, 532–535 (2021).
T. Watanabe, A. Kamoshida, A. Uchiyama, T. Nishi, R. Koyama, and K. Kaneko, “Distributed control by EPICS for the SRILAC beamenergy position monitoring system using LabVIEW,” Proceedings of the 18th Particle Accelerator Society of Japan, WEP026, 683–686(2021).
A. Uchiyama, M. Fujimaki, N. Fukunishi, Y. Higurashi, E. Ikezawa, H. Imao, O. Kamigaito, M. Kidera, M. Komiyama, K. Kumagai, T. Nagatomo, T. Nakagawa, T. Nishi, J. Ohnishi, K. Ozeki, N. Sakamoto, K. Suda, T. Watanabe, Y. Watanabe, K. Yamada,A. Kamoshida, K. Kaneko, R. Koyama, T. Ohki, K. Oyamada, M. Tamura, H. Yamauchi, and A. Yusa, “Control system of the SRILAC
project at RIBF,” 18th International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS2021),
Shanghai, China (virtual format), 147–152 (2021).
M. Komiyama, A. Uchiyama, M. Fujimaki, K. Kumagai, N. Fukunishi, T. Nakamura, and M. Hamanaka, “Performance veriﬁcationof new machine protection system prototype for RIKEN RI Beam Factory,” 18th International Conference on Accelerator and Large
Experimental Physics Control Systems (ICALEPCS2021), Shanghai, China (virtual format), 742–745 (2021).

Presentations[International Conferences/Workshops]
N. Fukunishi (poster), A. Uchiyama, M. Komiyama, and M. Kidera, “Data archive system for superconducting RIKEN linear accelerator
at RIBF,” 12th International Particle Accelerator Conference (IPAC’21), Campinas, Brazil (virtual format), May 24–28, 2021.
K. Yamada (invited), T. Dantsuka, M. Fujimaki, E. Ikezawa, H. Imao, O. Kamigaito, M. Komiyama, K. Kumagai, T. Nagatomo, T. Nishi,
H. Okuno, K. Ozeki, N. Sakamoto, K. Suda, A. Uchiyama, T. Watanabe, Y. Watanabe, H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa, E. Kako, H. Nakai, H. Sakai, and K. Umemori, “Successful beam commissioning of heavy-ion superconducting linac at RIKEN,”
20th International Conference on RF Superconductivity (SRF2021), MOOFAV01, East Lansing, USA, Online, June 28–July 2, 2021.
M. Hamanaka (poster), M. Komiyama, A. Uchiyama, M. Fujimaki, K. Kumagai, N. Fukunishi, and T. Nakamura, “Performance veriﬁcation of new machine protection system prototype for RIKEN RI Beam Factory,” 18th International Conference on Accelerator andLarge Experimental Physics Control Systems (ICALEPCS2021), Shanghai, China (virtual format), October 14–22, 2021.
A. Yusa (poster), A. Uchiyama, M. Fujimaki, N. Fukunishi, Y. Higurashi, E. Ikezawa, H. Imao, O. Kamigaito, M. Kidera, M. Komiyama,
K. Kumagai, T. Nagatomo, T. Nakagawa, T. Nishi, J. Ohnishi, K. Ozeki, N. Sakamoto, K. Suda, T. Watanabe, Y. Watanabe, K. Yamada,A. Kamoshida, K. Kaneko, R. Koyama, T. Ohki, K. Oyamada, M. Tamura, and H. Yamauchi, “Control system of the SRILAC project at
RIBF,” 18th International Conference on Accelerator and Large Experimental Physics Control Systems (ICALEPCS2021), Shanghai,
China (virtual format), October 14–22, 2021.
M. Hamanaka (poster), M. Komiyama, A. Uchiyama, M. Fujimaki, K. Kumagai, N. Fukunishi, and T. Nakamura, “Performance veriﬁcation of new machine protection system prototype for RIKEN RI Beam Factory,” 18th International Conference on Accelerator andLarge Experimental Physics Control Systems (ICALEPCS2021), Shanghai, China (virtual format), October 14–22, 2021.

[Domestic Conferences/Workshops]
金子健太 (ポスター発表), 内山暁仁, 込山美咲, 藤巻正樹, 熊谷桂子, 山内啓資, 「SRILAC 用マシンプロテクションシステムの構築」,
日本物理学会第 18 回年次大会, QST 高崎-オンライン, 2021 年 8 月 9–12 日.
金子健太 (ポスター発表), 渡邉環, 鴨志田敦史, 内山暁仁, 福西暢尚, 西隆博, 小山亮, 「LabVIEW を用いた SRILAC ビームエネ
ルギー・位置モニターシステムの EPICS による分散制御」, 第 18 回日本加速器学会年会, QST 高崎-オンライン, 2021 年 8 月
9–12 日.
仲村武志 (ポスター発表), 込山美咲, 他 37 名, 「理研 RIBF におけるリングサイクロトロンの運転報告」, 日本物理学会第 18 回年次大会, QST 高崎-オンライン, 2021 年 8 月 9–12 日.
福澤聖児 (ポスター発表), 込山美咲, 他 35 名, 「理研 AVF サイクロトロン運転の現状報告」, 日本物理学会第 18 回年次大会, QST
高崎-オンライン, 2021 年 8 月 9–12 日.
渡邉環 (招待講演), 「理研超伝導加速空洞用ビームエネルギー・位置モニター」, 第７回 IFMIF 研究会 〜ビーム診断・ビーム制御〜, 量子科学技術研究開発機構六ヶ所研（北郡六ヶ所村）, オンライン, 2022 年 3 月 7 日.

Patents
T. Watanabe and N. Fukunishi, “Charged particle beam current measurement apparatus（日本語: 荷電粒子ビームの電流測定装置）,”
2021, 6843903, JY Patent.
T. Watanabe and N. Fukunishi, “Charged particle beam current measurement apparatus,” 2021, 17836891.6, FR, DE Patent.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Accelerator Group
Cryogenic Technology Team
1. Abstract
We are operating the cryogenic system for the superconducting ring cyclotron in RIBF. We are operating the helium cryogenic
system in the south area of RIKEN Wako campus and delivering the liquid helium to users in RIKEN. We are trying to collecteﬃciently gas helium after usage of liquid helium.

2. Major Research Subjects(1) Operation of the cryogenic system for the superconducting ring cyclotron in RIBF
(2) Operation of the helium cryogenic plant in the south area of Wako campus and delivering the liquid helium to users in Wako
campus

3. Summary of Research Activity(1) Operation of the cryogenic system for the superconducting ring cyclotron in RIBF (H. Okuno, T. Dantsuka, M. Nakamura)(2) Operation of the helium cryogenic plant in the south area of Wako campus and delivering the liquid helium to users in Wako
campus(T. Dantsuka, S. Tsuruma, M. Kuroiwa, M. Takahashi, H. Okuno).

Members
Team Leader
Hiroki OKUNO
Senior Technical Scientist
Masato NAKAMURA
Technical Scientist
Tomoyuki DANTSUKA
Expert Technician
Takeshi MAIE
Research Part-time Worker
Mamoru TAKAHASHI (Research Part-time Worker I)
Administrative Part-time Workers
Shizuho TSURUMA (Administrative Part-time Worker I)

Mayumi KUROIWA (Administrative Part-time Worker II)- 261 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Accelerator Group
Infrastructure Management Team
1. Abstract
Our team is in charge of the design, operation, and maintenance of the large-scale infrastructure for the entire RI Beam Factory(RIBF), including cooling water, air conditioning, and electrical equipment, as well as the research and development of their advanced
management. In order to operate the RIBF eﬃciently, it is very important to ensure the sound operation of these infrastructures thatlead to the stable functioning of various devices. Another important mission is to coordinate the scheduling of major construction andrepair work related to the RIBF so that beamtime runs smoothly.
The recent issue is the aging of infrastructure equipment. In line with these measures, we are making modiﬁcations that contributeto the stability of accelerator equipment and energy saving. In addition, infrastructure equipment has many sensors for management,
and a huge amount of measurement data from these sensors is archived. We are planning to use this data to build a more advanced
management system.

2. Major Research Subjects(1) Operation, maintenance and monitoring of infrastructure of RI Beam Factory(2) Development of advanced management of infrastructure that contributes to accelerator and beam stability(3) Coordination of large construction work and modiﬁcation related to RI Beam Factory

Members
Team Leader
Masanori KIDERA
Technical Scientist
Takeshi MAIE
Special Temporary Technical Scientist
Shu WATANABE

List of Publications & Presentations
Publications[Proceedings]
仲村武志, 福澤聖児, 濱仲誠, 石川盛, 小林清志, 小山亮, 西田稔, 西村誠, 柴田順翔, 月居憲俊, 矢冨一慎, 大関和貴, 段塚知志, 藤巻正樹,
藤縄雅, 福西暢尚, 長谷部裕雄, 日暮祥英, 池沢英二, 今尾浩士, 上垣外修一, 金井保之, 木寺正憲, 込山美咲, 熊谷桂子, 真家武士,
長友傑, 中川孝秀, 中村仁音, 大西純一, 奥野広樹, 坂本成彦, 須田健嗣, 内山暁仁, 渡部秀, 渡邉環, 渡邉裕, 山田一成, 山澤秀行, 「理研 RIBF におけるリングサイクロトロンの運転報告」, “Status report on the operation of RIKEN RING Cyclotron,” Proceedings ofthe 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki Online, Japan, August 9–12, 2021, p. 575.
福澤聖児, 須田健嗣, 後藤彰, 大西純一, 濱仲誠, 石川盛, 小林清志, 小山亮, 仲村武志, 西田稔, 西村誠, 柴田順翔, 月居憲俊, 矢冨一慎,
藤巻正樹, 福西暢尚, 長谷部裕雄, 日暮祥英, 今尾浩士, 上垣外修一, 加瀬昌之, 木寺正憲, 込山美咲, 熊谷桂子, 真家武士, 長友傑,
中川孝秀, 奥野広樹, 大関和貴, 坂本成彦, 内山暁仁, 渡部秀, 渡邉環, 渡邉裕, 山田一成, 鎌倉, 恵太, 小高康照, 「理研 AVF サイ, “Status report on the operation of RIKEN AVF Cyclotron,” Proceedings of the 18th Annual Meeting of
クロトロン運転の現状報告」
Particle Accelerator Society of Japan, QST-Takasaki Online, Japan, August 9–12, 2021, p. 760.
大木智則, 小山田和幸, 山内啓資, 田村匡史, 遊佐陽, 金子健太, 坂本成彦, 藤巻正樹, 池沢英二, 今尾浩士, 木寺正憲, 長友傑, 大関和貴,
須田健嗣, 内山暁仁, 渡邉環, 渡邉裕, 山田一成, 上垣外修一, 「理研重イオンリニアックの現状報告」, “Present status of RILAC,”
Proceedings of the 18th Annual Meeting of Particle Accelerator Society of Japan, QST-Takasaki Online, Japan, August 9–12, 2021,
p. 983.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Instrumentation Development Group
1. Abstract
This group develops the core-experimental instruments at the RI Beam Factory. Four projects are currently going on. SLOWRI
is an experimental instrument to provide low and cold ion beam. The high energy RI beam is stopped by a gas catcher system andre-accelerated to several tens of keV to deliver a high-quality cold RI beam to the user. SCRIT is the world’s ﬁrst experimental facility
for electron scattering of unstable nuclei and was constructed oﬀ the main beamline of RIBF. The ﬁrst physic result was demonstrated
in 2017, and the electron scattering experiment for radioactive isotopes has been started in this year. An upgrade of the electron beam
power that drives RI beam production is currently underway. The Rare-RI Ring is an event-by-event-operated heavy ion storage ringfor precise mass measurement of extremely rare exotic nuclei. It is currently accepting applications for experimental proposals andhas already conducted PAC-approved experiments and published its ﬁrst physics results. Improvements are currently underway toachieve more precise mass measurements. The compact heavy-ion storage ring RUNBA is an R&D machine for the development ofbeam recycling techniques for nuclear reaction research on rare elements. This is currently under construction and some of the criticalcomponents of the ring are currently undergoing technical development. All instrumentations is designed to maximize the researchpotential of the world’s most intense RI beams, and dedicated RI Beam Factory equipment makes the experimental challenge possible.
The experimental technique and experience accumulated in this group provide opportunities for new experimental challenges and form
the basis for the future development of the RIBF.

2. Major Research Subjects
(1)
(2)
(3)
(4)

SCRIT Project
SLOWRI Project
Rear RI Ring Project
RUNBA project (Beam recycling development)

3. Summary of Research Activity
We are developing beam manipulation techniques to carry out the above projects. These are high-quality slow RI beam generation
technology (SCRIT, SLOWRI), beam cooling and stopping technology (SCRIT, SLOWRI) and beam accumulation technology in astorage ring (Rare RI Ring, RUNBA). The technical know-how accumulated in the project will play a major role in the next generationof RIBF. The current status and future plans for each project are described in the respective sections. We have successfully measured
electron elastic scattering from 132 Xe isotopes and obtained nuclear charge density distributions in SCRIT. Recently, we have started
electron scattering experiment for unstable nuclei. That will be the world’s ﬁrst electron-RI collision experiment. We are in the processof power upgrading of the electron beam from the RTM, which is the driving for RI production, and expanding the nuclei that can beaccessed. The Rare RI Ring is an event-by-event based mass measurement system, designed speciﬁcally for extremely low-producing
isotopes. We carried out PAC-approved experiments and successfully measured the masses of 74, 76 Ni, 122 Rh, 123, 124 Pd and 125 Ag
for the ﬁrst time. To improve mass resolution and eﬃciency, the ﬁrst-response kicker system and optical tuning system are being
improved. Test experiments are currently underway at SLOWRI to establish slow RI beam generation using two diﬀerent type of gas
cells. PALIS has been commissioned from 2015, and basic functions such as, the RI-beam stopping in Ar gas cell, the extraction
from the gas cell and laser ionization have beam evaluated. Movable mass spectrometer combining RF carpet gas cells (RPGC) andmultiple reﬂection time-of-ﬂight (MRTOF) are in operation at facilities such as Zero Degree and GARIS. The combination of RFGC
and MRTOF has been used successfully to measure the mass of 74, 75 Ni isotopes.
According to the future plans of Nishina center, a beam re-cycling technique is under development. Beam recycling technology
allows the circulation of RI beams to be maintained in a storage ring with a thin internal target until a nuclear reaction occurs. In
order to establish beam recirculation, the increase in energy width and emittance needs to be compensated for using a fast feedback
system. We have demonstrated the possibility of compensation in an analytical way and found the properties of EDC and ADC
devices necessary for compensation. To develop these new technologies, a compact heavy ion storage ring (RUNBA) connected to
ISOL (ERIS) is under construction at the SCRIT facility. Under a research cooperation agreement with ICR in Kyoto University,
technical development of the main components required for RUNBA i.e. the charge breeder, energy dispersion corrector, angular
diﬀusion corrector and internal target system are underway.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Members
Director
Masanori WAKASUGIContract Researcher
Ryo OGAWARA
Visiting Scientists
Akira OZAWA (Tsukuba Univ.)
Fumi SUZAKI (JAEA)

Kyo TSUKADA (Kyoto Univ.)

Student Trainee
Yoshiki MAEHARA (Kyoto Univ.)
Part-time Worker
Midori TAKEMON (Administrative Part-time Worker I)

List of Publications & Presentations
Publications and presentations for each project team are listed in subsections.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Instrumentation Development GroupSLOWRI Team
1. Abstract
SLOWRI is a universal low-energy RI-beam facility at RIBF that provides a wide variety of short-lived nuclei as high-purity andlow-emittance ion beams or stored ions in a trap, including a parasitic operation mode. The SLOWRI team develops and manages thefacility and performs high-precision spectroscopy experiments. The construction of the SLOWRI facility began in FY2013 and commissioning work is ongoing. From FY2019, SLOWRI has been started to be co-operated under RNC and WNSC/KEK collaboration.
High-energy radioactive ion beams from the projectile fragment separator BigRIPS are thermalized in a large He gas catcher cell
(RFGC) or in a small Ar gas catcher cell (PALIS cell). From these gas cells, the low-energy ion beams will be delivered via mass
separators and switchyards to various devices: such as an ion trap, a collinear fast beam apparatus, and a multi-reﬂection time of ﬂight
mass spectrograph. A multi-reﬂection time-of-ﬂight mass spectrograph (MRTOF) has been also developed.
Two mass measurement projects using MRTOF mass spectrographs have been started: one is for trans uranium elements at
the GARIS facility and the other is for r-process nuclides at SLOWRI facility. At GARIS-II, we installed second prototype RFCG
combined with MRTOF, which is a medium-sized cryogenic RF-carpet He gas cell. Using second prototype RFGC, more than 80
nuclear masses have been measured including ﬁrst mass measurements of Md and Es isotopes. In FY2021, masses on more than 100
radioactive isotopes from the ﬁssion source have been measured and the analysis is going on. At SLOWRI facility, third prototype
RFGC has been installed at F11, the downstream of ZeroDegree spectrometer, which is a 50-cm-long RF-carpet-type He gas cellcombined with MRTOF. In FY2020, we have successfully performed the on-line commissioning, symbiotically by using RIs provided
for HiCARI campaign. The extraction eﬃciency in total has been achieved at 1% in maximum and the masses on more than 70 nuclei
have been measured using RIs provided with BigRIPS. In FY2021, Mass measurement in the vicinity of double magic nucleus of 78 Ni
was successfully performed, which was approved at NP-PAC. As the result, masses of 74 Ni and 75 Ni have been measured for the ﬁrst
time. The analysis is going on.
Parallelly, the on-line commissioning for PALIS has been continuously performed at F2 of BigRIPS. In FY2021, the extraction of
α-emitter Ac Isotopes without a laser ionization has been conﬁrmed after the ion guide from PALIS gas cell. We will try to the laser
ionization in FY2022.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Construction of the stopped and low-energy RI-beam facility, SLOWRI
Development of a multi-reﬂection time-of-ﬂight mass spectrograph for precision mass measurements of short-lived nuclei
Development of collinear laser spectroscopy apparatus
Development of a parasitic slow RI-beam production method using resonance laser ionization

3. Summary of Research Activity(1) Construction of stopped and low-energy RI-beam facility (SLOWRI)SLOWRI consists of two gas catchers (RF carpet gas cell and PALIS gas cell), mass separators a 50-m-long beam transport line,
a beam cooler-buncher, an isobar separator, and a laser system. The RF carpet gas cell (RFGC) will be installed at the exit of the D5
dipole magnet of BigRIPS. The gas catcher contains a large cryogenic He gas cell with a large traveling wave rf-carpet. The PALIS
gas cell is installed in the vicinity of the second focal plane slit of BigRIPS. It will provide parasitic RI-beams from those ions lost in
the slits during other experiments. In this gas catcher, thermalized RI ions quickly become neutral and will be re-ionized by resonant
laser radiations. Oﬀ- and on-line commissioning is underway.
Based on test experiments with the prototype setups, the RF-carpet gas cell contains a three stage rf-carpet structure: a gutter rf
carpet (1st carpet) for the collection thermal ions in the cell into a small slit, a narrow (about 10 mm) traveling-wave rf-carpet (2ndcarpet) for collection of ions from the gutter carpet and for transporting the ions towards the exit, and a small rf carpet for extraction
from the gas cell. The oﬀ-line test has been completed in FY2019.
A 50-cm-long RFGC, which is a prototype for ﬁnal version RFGC with 1.5 m length, has been installed at F11 of ZeroDegreee
spectrometer of BigRIPS in FY2020, and the on-line commissioning has been successfully performed symbiotically using RIs provided with BigRIPS during HiCARI campaign. The extraction eﬃciency in total has been achieved at 1% in maximum. In FY2021,
ﬁrst experiment approved in NP-PAC has been performed, which has aimed the mass measurement in the vicinity of the double magic
nucleus of 78 Ni. As the result, masses of 74 Ni and 75 Ni have been measured with high precision less than 20 keV for the ﬁrst time.
(2) Development of a multi-reﬂection TOF mass spectrograph for short-lived nuclei
The atomic mass is one of the most important quantities of a nucleus and has been studied in various methods since the early daysof modern physics. From among many methods we have chosen a multi-reﬂection time-of-ﬂight (MRTOF) mass spectrometer. Slow
RI beams extracted from the RF ion-guide are bunched and injected into the spectrometer with a repetition rate of ∼100 Hz. A massresolving power of 170,000 has been obtained with a 2 ms ﬂight time for 40 K and 40 Ca isobaric doublet. This mass-resolving powershould allow us to determine ion masses with an accuracy of ≤ 10−7 . A new MRTOF has been assembled in FY2019 to be coupledwith the third prototype of RFGC and has been installed at F11 of BigRIPS in FY2020. Mass measurements using RIs provided withBigRIPS during HiCARI campaign have been symbiotically performed. As the result, atomic masses on more than 70 nuclei have

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been successfully measured. Among them, 11 isotope masses improve the present uncertainty signiﬁcantly and 3 isotope masses havebeen measured for the ﬁrst time. In FY2021, thanks to the ﬁne tuning and the improved data analysis, the mass resolving power has
reached up to ∼1 M in maximum for A/q ∼ 80/1+. Also, to eliminate contaminant ions, a TOF mass ﬁlter has been installed inside the
MRTOF, which has been working well.
(3) Development of collinear fast beam apparatus for nuclear charge radii measurements
The root-mean-square charge radii of unstable nuclei have been determined exclusively by isotope shift measurements of the
optical transitions of singly charged ions or neutral atoms by laser spectroscopy. Many isotopes of alkali, alkali-earth, and noble-gas
elements in addition to several other elements have been measured by collinear laser spectroscopy since these ions all have good
optical transitions and are available at conventional ISOL facilities. However, isotopes of other elements, especially refractory andshort-lived ones, have not been investigated so far.
In SLOWRI, isotopes of all atomic elements will be provided as well collimated, mono-energetic ion beams. This should expand
the range of nuclides available for laser spectroscopy. An oﬀ-line mass separator and a collinear fast beam apparatus with a largesolid-angle ﬂuorescence detector was built previously. A 617-nm transition of the metastable Ar+ ion at 20 keV was measured withboth collinear and anti-collinear geometry, which allowed determination of the absolute resonant frequency of the transition at restwith a relative accuracy better than 10−8 . A new setup is under preparation at the SLOWRI experiment area in collaboration with the
Nuclear Spectroscopy Laboratory.
(4) Development of parasitic slow RI-beam production scheme using resonance laser ionization
More than 99.9% of RI ions produced in projectile ﬁssion or fragmentation are simply dumped in the ﬁrst dipole magnet and theslits. A new scheme, named PALIS, meant to rescue such precious RI using a compact gas catcher cell and resonance laser ionization,
was proposed as a part of SLOWRI. The thermalized RI ions in a cell ﬁlled with Ar gas can be quickly neutralized and transported tothe exit of the cell by gas ﬂow. Irradiation of resonance lasers at the exit ionizes neutral RI atoms eﬃciently and selectively. PALIS
has been installed at F2 at the downstream of BigRIPS and oﬀ- and on-line commissioning is under progress.
At F2, due to high radiation from a beam dump, it is not easy to handle ions using electric ion guides. Therefore, a 70-cm-long gas
pipe from the Ar gas cell was newly installed to transport RIs to relatively low radiation area thanks for the Ar gas ﬂow. In FY2021,
we have conﬁrmed the transportation of ions of interest at the downstream of an ion guide behind the gas pipe using α-emitting Ac
isotopes provided with BigRIPS. Also, we have found a lot of contaminant ions from the gas cell, which are originated from impurities
in the gas. To reduce the inﬂuence of such contaminant, a quadrupole mass ﬁlter will be installed at the downstream of the ion guide.
In FY2022, an on-line test for resonant laser ionization is planned.

Members
Team Leader
Hironobu ISHIYAMA
Senior Research Scientist
Takao KOJIMA
Research Scientist
Aiko TAKAMINETechnical Scientist
Tetsu SONODA
Expert Technician
Takeshi MAIE
Junior Research Associate
Shun IIMURA
Visiting Scientists
Hideki IIMURA (JAEA)
Minoru TANIGAKI (Kyoto Univ.)

Hideki TOMITA (Nagoya Univ.)

Student Trainee
Shun IIMURA- 266 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

List of Publications & Presentations
Publications[Original Papers]
M. Tajima, A. Takamine, M. Wada, and H. Ueno, “Oﬄine ion source for laser spectroscopy of RI at the SLOWRI,” Nucl. Instrum.
Methods Phys. Res. B 486, 48–54 (2021).
T. Niwase, M. Wada, P. Schury, P. Brionnet, S. D. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama,
S. Ishizawa, Y. Ito, D. Kaji, S. Kimura, J. Liu, H. Miyatake, J. Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, T. Tanaka, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “α-decay-correlated mass measurement of 206, 207g, m Rausing an α-TOF detector equipped multireﬂection time-of-ﬂight mass spectrograph system,” Phys. Rev. C 104, 044617 (2021).
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa,
Y. Ito, D. Kaji, S. Kimura, H. Koura, J. J. Liu, H. Miyatake, J. -Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “First high-precision direct determination of the atomic mass of asuperheavy nuclide,” Phys. Rev. C 104, L021304 (2021).

[Proceeding]
S. Kimura, Y. Ito, D. Kaji, P. Schury, M. Wada, H. Haba, T. Hashimoto, Y. Hirayama, M. MacCormick, H. Miyatake, J. Y. Moon,
K. Morimoto, M. Mukai, I. Murray, A. Ozawa, M. Rosenbusch, H. Schatz, A. Takamine, T. Tanaka, Y. X. Watanabe, and H. Wollnik,“High precision mass measurements of intermediate-mass neutron-deﬁcient nuclei via MRTOF-MS,” JPS Conf. Proc. 35, 011005(2021).

Presentations[International Conferences/Workshops]
S. Iimura (poster), A. Takamine, M. Rosenbusch, M. Wada, S. Chen, D. Hou, J. Liu, W. Xian, S. Yan, P. Schury, S. Kimura, A. Niwase,Y. Ito, S. Sonoda, T. Kojima, Y. Watanabe, S. Naimi, S. Michimasa, S. Nishimura, A. Odahara, and H. Ishiyama, “Mass measurementof neutron rich nuclei of Sc, Ti, and V region using the new ZD-MRTOF system,” The 16th International Symposium on Nuclei in the
Cosmos (NIC-XVI), Online, China, September 21–25, 2021.
M. Rosenbusch (oral), S. Chen, W. Xian, S. Yan, A. Takamine, D. Hou, S. Iimura, M. Wada, P. Schury, Y. Hirayama, H. Ishiyama, Y. Ito,
S. Kimura, T. M. Kojima, J. Liu, S. Michimasa, H. Miyatake, S. Naimi, S. Nishimura, T. Niwase, T. Sonoda, Y. X. Watanabe, andH. Wollnik, “The new high-precision MR-TOF mass spectrograph at the ZeroDegree spectrometer of BigRIPS,” The 16th International
Symposium on Nuclei in the Cosmos (NIC-XVI), Online, China, September 21–25, 2021.
M. Rosenbusch (invited), “The new high-precision MR-TOF mass spectrograph at the ZeroDegree spectrometer of BigRIPS,” RIBF Users
Meeting 2021, Wako, Japan, Online, September 7–9, 2021.
H. Ishiyama (invited), “Present status of SLOWRI,” SSRI-PNS Collaboration Meeting 2021, Online, September 2–3, 2021.

[Domestic Conferences/Workshops]
富田英生 (口頭発表), V. Sonnenschein, 服部浩也, 山口穂乃花, 井坪暁, 寺林稜平, 島添健次, 園田哲, 石山博恒, K. Wendt, 「理研 RI
ビームファクトリー—低速 RI ビーム施設におけるレーザー共鳴イオン化イオン源の開発」, 日本原子力学会 2022 年春季大会,
オンライン, 2022 年 3 月 16–18 日.
飯村俊 (口頭発表), 高峰愛子, M. Rosenbusch, 和田道治, S. Chen, D. Hou, J. Liu, W. Xian, S. Yan, P. Schury, 木村創大, 庭瀬暁隆, 伊藤
由太, 園田哲, 小島隆夫, 渡辺裕, S. Naimi, 道正新一郎, 西村俊二, 小田原厚子, 石山博恒, “Mass measurement of neutron rich nucleiof Sc, Ti, and V region using the new ZD-MRTOF system,” 日本物理学会 2021 年度秋季大会, オンライン, 2021 年 9 月 14–17 日.
W. Xian (口頭発表), S. Chen, M. Rosenbusch, S. Yan, D. Hou, S. Iimura, A. Takamine, M. Wada, J. Liu, P. Schur, S. Kimura, T. Niwase,Y. Ito, T. Sonoda, T. M. Kojima, Y. X. Watanabe, S. Naimi, S. Michimasa, S. Nishimura, H. Ishiyama, and H. Wollnik, “New massmeasurements of neutron-rich nuclei of Ge, As, and Se, and an accuracy study of the new ZD-MRTOF system,” 日本物理学会 2021
年度秋季大会, オンライン, 2021 年 9 月 14–17 日.
D. Hou (口頭発表), A. Takamine, S. Iimura, M. Rosenbusch, S. Chen, W. Xian, S. Yan, M. Wada, P. Schury, Y. Hirayama, H. Ishiyama,
Y. Ito, S. Kimura, J. Liu, S. Michimasa, H. Miyatake, S. Naimi, S. Nishimura, T. Niwase, Y. X. Watanabe, and H. Wollnik, “Massmeasurement in the neutron-rich Mo region using the new ZD-MRTOF system,” 日本物理学会 2021 年度秋季大会, オンライン, 2021
年 9 月 14–17 日.
M. Rosenbusch (口頭発表), S. Chen, W. Xian, S. Yan, A. Takamine, D. Hou, S. Iimura, M. Wada, P. Schury, Y. Hirayama, H. Ishiyama,
Y. Ito, S. Kimura, T. M. Kojima, J. Liu, S. Michimasa, H. Miyatake, S. Naimi, S. Nishimura, T. Niwase, T. Sonoda, Y. X. Watanabe,and H. Wollnik, “New technologies for multi-reﬂection time-of-ﬂight mass spectrometry at BigRIPS,” 日本物理学会 2021 年度秋季大会, オンライン, 2021 年 9 月 14–17 日.
庭瀬暁隆 (口頭発表), P. Schury, 和田道治, P. Brionnet, S. Chen, 橋本尚志, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 石澤倫,
伊藤由太, 加治大哉, 木村創大, 小浦寛之, 宮武宇也, J. Y. Moon, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 渡辺裕,
H. Wollnik, W. Xian, and S. X. Yan,「超重核 257 Db の直接質量測定」, 日本物理学会 2021 年度秋季大会, オンライン, 2021 年 9 月
14–17 日.
服部浩也 (口頭発表), V. Sonnenschein, 山口穂乃花, 井坪暁, 寺林稜平, 島添健次, 園田哲, 石山博恒, K. Wendt, 富田英生, 「半導体レーザー直接励起 Ti:Sapphire レーザーを用いた高分解能共鳴イオン化分光法の開発」, 日本物理学会 2021 年度秋季大会, オンライン, 2021 年 9 月 14–17 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Instrumentation Development Group
Rare RI-ring Team
1. Abstract
The aim of Rare-RI Ring (R3) is to measure the masses of short-lived unstable nuclei far from the beta-stability line. In particular,a high-precision mass measurement for nuclei located around the r-process pass (rare-RI) is required in nucleosynthesis point ofview. Through the commissioning experiments by 2017, we conﬁrmed the high ability of R3 as a storage ring capable of handlingone event, and demonstrated that it is possible to perform the time-of-ﬂight Isochronous Mass Spectrometry (IMS) in shorter than
1 millisecond. In 2018, we performed mass measurement experiments for the ﬁrst time. In 2020, the kicker system was modiﬁed
to ﬂatten the magnetic ﬁeld distribution, and the performance study using unstable nuclei was successfully conducted. In this ﬁscal
year, we performed mass measurement experiments using the upgraded kicker system. The preliminary results of the experiment
dispelled concerns about the results of the previous experiment that the injection angle might greatly aﬀected the accuracy of the mass
determination. On the other hand, through the experiments of this ﬁscal year, a problem was found in the kicker power supply. We are
currently taking measures to the problem.

2. Major Research Subjects(1) Further improvement of experimental eﬃciency and mass measurement precision(2) Precision mass measurement for rarely produced isotopes related to r-process

3. Summary of Research Activity
In the commissioning experiments up to 2017, we conﬁrmed the unique performances of R3 and demonstrated the time-of-ﬂight
isochronous mass measurement method. The ring structure of R3 was designed with a similar concept of a separate-sector ring
cyclotron. It consists of six sectors and straight sections, and each sector consists of four rectangular bending magnets. Two magnets
at both ends of each sector are additionally equipped with ten trim coils to form a precise isochronous ﬁeld. We have realized informing the precise isochronous ﬁeld of less than 5 ppm with wide momentum range of Δp/p = ± 0.5%. Another performancerequired for R3 is to eﬃciently seize hold of an opportunity of the mass measurement for rare-RIs produced unpredictably. It was
realized by constructing the Isotope-Selectable Self-trigger Injection (ISSI) scheme which pre-identiﬁed rare-RI itself triggers theinjection kicker magnets. Key device was a fast response kicker system that has been successfully developed. Full activation of the
kicker magnetic ﬁeld can be completed within the ﬂight time of the rare-RI from an originating point (F3 focal point in BigRIPS) of
the trigger signal to the kicker position in R3.
Since R3 accumulates, in principle, only one event, we fabricated high-sensitive beam diagnostic devices in the ring. One of themis a cavity type of Schottky pick-up installed in a straight section of R3. The Schottky pick-up successfully monitored a single 78 Kr36+
ion circulation with the measurement time of less than 10 milliseconds in the ﬁrst commissioning experiment. We also conﬁrmedthat it is useful for ﬁne tuning of the isochronous ﬁeld. Another is a timing monitor called E-MCP, which detects secondary electrons
emitted from thin carbon foil placed on the circulation orbit. The thickness of the foil is 60 μg/cm2 . This timing monitor is working
well to observe ﬁrst several tens turns for injected event.
We performed mass measurement in the third commissioning experiment by using unstable nuclei which masses are well-known.
The masses of 79 As, 77 Ga, 76 Zn, and 75 Cu relative to 78 Ge were deduced with the accuracy of several ppm. In addition, we have
improved the extraction eﬃciency to 2% by considering the matching condition between the emittance of injection events and theacceptance of R3 in the fourth commissioning experiment. This extraction eﬃciency was suﬃcient to conduct the accepted two
proposals: mass measurements of Ni isotopes and Sn region.
In November 2018, we conducted the ﬁrst experiment using R3 to measure the masses for 74, 76 Ni in 4 days. After that, we alsomeasured the masses for 122 Rh, 123, 124 Pd, and 125 Ag in 4.5 days. These nuclei were successfully extracted from R3 with the eﬃciency
of 1–2%. However, unexpected deviation from the evaluated values of literature remained in the masses obtained by detailed analysis.
This was thought to be due to the following two reasons. One is that due to the kicker ﬁeld distribution is not ﬂattened, the injection
angle is diﬀerent between the reference and target nucleus, and therefore the relative value of TOF is incorrect. The other is that theabsolute value of beta or magnetic rigidity determined for each extracted event is incorrect.
In 2020, we modiﬁed the kicker system to ﬂatten the magnetic ﬁeld distribution as well as to dispel the concerns of the results ofﬁrst experiment. As a result of performance study using unstable nuclei, we succeeded in forming the kicker ﬁeld with 100 ns ﬂat-top
for injection and long ﬂat-top of 350 ns or more for extraction. The experimental eﬃciency had been improved by a factor of two or
more than previous condition because all nuclides can be extracted at once thanks to the long ﬂat-top.
Using this upgraded kicker system, we measured the mass for 74 Ni again in April 2021. Although the kicker ﬁeld distribution
was ﬂattened, the results of masses were the same as those of the ﬁrst experiment. In other words, concerns about the eﬀects ofdiﬀerences in injection angles have been dispelled. As a subsequent analysis, it was clariﬁed that the reason is the second concern
described above. The ﬁnal mass values will be determined soon. On the other hand, the ceramic capacitor of the kicker power supply
broken several times due to insulation breakdown. We are currently working on measures to prevent insulation breakdown of ceramic
capacitors, since this problem defects reliable mass measurement experiments.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Members
Team Leader
Masanori WAKASUGITechnical Scientist
Yoshitaka YAMAGUCHI
Expert Technician
Takeshi MAIE
Student Trainee
Yuto NAGATA (Kyushu Univ.)

List of Publications & Presentations
Publications[Review Article]
T. Yamaguchi, H. Koura, Yu. A. Litvinov, and M. Wang, “Masses of exotic nuclei,” Prog. Part. Nucl. Phys. 120, 103882-1–98 (2021).

[Proceedings]
A. Ozawa for Rare-RI Ring Collaboration, “Past and future for Rare-RI Ring,” JPS Conf. Proc. 35, 011011-1–5 (2021).
D. Nagae, S. Omika, Y. Abe, Y. Yamaguchi, F. Suzaki, K. Wakayama, N. Tadano, R. Igosawa, K. Inomata, H. Arakawa, K. Nishimuro,
T. Fujii, T. Mitsui, T. Yamaguchi, T. Suzuki, S. Suzuki, T. Moriguchi, M. Amano, D. Kamioka, A. Ozawa, S. Naimi, Z. Ge, Y. Yanagisawa, H. Baba, S. Michimasa, S. Ota, G. Lorusso, Yu. A. Litvinov, M. Wakasugi, T. Uesaka, and Y. Yano, “First demonstration of massmeasurements for exotic nuclei using Rare-RI Ring”, JPS Conf. Proc. 35, 011014-1–8 (2021).
S. Suzuki, A. Ozawa, T. Moriguchi, M. Amano, D. Kamioka, Y. Ichikawa, Y. Tajiri, K. Hiraishi, T. Matsumoto, D. Nagae, Y. Abe,S. Naimi, H. Li, T. Yamaguchi, S. Omika, Z. Ge, K. Wakayama, N. Tadano, H. Arakawa, K. Inomata, T. Kobayashi, A. Kitagawa, and
S. Sato, “Performance of a Time-Of-Flight detector and demonstration of a novel position-sensitive detector for mass measurementswith Rare-RI Ring”, JPS Conf. Proc. 35, 011017-1–6 (2021).
K. Inomata, T. Yamaguchi, Y. Abe, M. Amano, H. Arakawa, T. Fujii, D. Kamioka, A. Kitagawa, H. Li, T. Moriguchi, D. Nagae, S. Omika,
A. Ozawa, S. Sato, S. Suzuki, T. Suzuki, and K. Wakayama, “Basic study on delta ray detection for the determination of in-ring
revolution time”, JPS Conf. Proc. 35, 011020-1–4 (2021).
K. Inomata, T. Yamaguchi, H. Arakawa, A. Kitagawa, D. Nagae, K. Nishimuro, S. Omika, S. Sato, T. Suzuki, N. Tadano, andK. Wakayama, “Best test on a long scintillating ﬁber as a position sensor in a storage ring facility”, JPS Conf. Proc. 35, 0110211–5 (2021).
H. Arakawa, T. Yamaguchi, Y. Abe, M. Amano, K. Inomata, D. Kamioka, A. Kitagawa, H. Li, T. Moriguchi, D. Nagae, S. Omika,
A. Ozawa, S. Sato, S. Suzuki, T. Suzuki, and K. Wakayama, “Properties of a thin YAP(Ce) scintillation counter for heavy ions”, JPS
Conf. Proc. 35, 011022-1–5 (2021).
Z. Ge, S. Naimi, D. Nagae, Y. Abe, S. Omika, T. Uesaka, F. Suzaki, H. Li, Y. Yamaguchi, M. Wakasugi, K. Wakayama, T. Yamaguchi,
A. Ozawa, H. Arakawa, K. Inomata, T. Kobayashi, K. Nishimuro, S. Suzuki, T. Moriguchi, D. Kamioka, M. Mukai, M. Amano,
A. Kitagawa, S. Sato, G. Lorusso, and Y. Yano, “Development of mirror-type MCP detectors for mass measurements at the Rare-RI
Ring”, JPS Conf. Proc. 35, 011023-1–4 (2021).
K. Wakayama, T. Yamaguchi, Y. Abe, M. Amano, H. Arakawa, Z. Ge, K. Inomata, D. Kamioka, A. Kitagawa, T. Kobayashi, H. Li,
T. Moriguchi, D. Nagae, S. Omika, A. Ozawa, S. Sato, S. Suzuki, T. Suzuki, and N. Tadano, “A simple readout method for a positionsensitive detector using plastic scintillator bars”, JPS Conf. Proc. 35, 011024-1–5 (2021).
H. Li, Z. Ge, S. Naimi, D. Nagae, Y. Abe, T. Uesaka, F. Suzaki, M. Wakasugi, S. Omika, Y. Yamaguchi, T. Yamaguchi, K. Wakayama,
H. Arakawa, K. Inomata, A. Ozawa, S. Suzuki, and T. Moriguchi, “MCP with delay-line anode used for position sensitive detector atRare RI-Ring”, JPS Conf. Proc. 35, 011025-1–4 (2021).
S. Omika, T. Yamaguchi, Y. Abe, M. Amano, H. Arakawa, Z. Ge, K. Inomata, D. Kamioka, H. Li, H. Miura, T. Moriguchi, D. Nagae,
S. Naimi, K. Nishimuro, A. Ozawa, F. Suzaki, S. Suzuki, and T. Suzuki, “Development of experimental devices for precise massmeasurements at the Rare-RI Ring”, JPS Conf. Proc. 35, 011026-1–5 (2021).

Presentations[International Conference/Workshop]
T. Yamaguchi (invited), “Precision experiments of exotic nuclei at the storage rings,” Tsukuba Global Science Week 2021, Online,
Tsukuba, Japan, September 6–11, 2018.

[Domestic Conferences/Workshops]
森口哲明 (口頭発表), 「RI ビーム飛行時間検出器の開発. —理研稀少 RI リングのための検出器—」, 2020 年度 HIMAC 共同利用研
究成果発表会, オンライン, 2021 年 6 月 7–10 日.
山口貴之 (口頭発表), 「多価イオンビームによる２光子稀崩壊の観測」, 新学術領域研究「宇宙観測検出器と量子ビームの出会い.
新たな応用への架け橋」領域研究会, オンライン, 2021 年 6 月 14–15 日.
要直登 (ポスター発表), 「薄膜からの二次電子放出を利用した RI ビーム位置敏感型検出器の開発」, 第一回日本量子医学学会学術大会, オンライン, 2021 年 12 月 10–11 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Instrumentation Development GroupSCRIT Team
1. Abstract
The SCRIT Electron Scattering Facility has been constructed at RIKEN RIBF. This aims at investigation of internal nuclear structure for short-lived unstable nuclei by means of electron scattering. SCRIT (Self-Conﬁning RI Ion Target) is a novel method to form
internal targets in an electron storage ring. This is a unique method for making electron scattering experiments for unstable nuclei possible. Construction of the facility has been started in 2009. This facility consists of an electron accelerator (RTM), a SCRITequipped
electron storage ring (SR2), an electron-beam-driven RI separator (ERIS), and a window-frame spectrometer for electron scattering(WiSES) which consists of a large window-frame dipole magnet, drift chambers and trigger scintillators. Installation of all components in the facility was completed in 2015. After the comprehensive test and tuning, the luminosity was reached to 3 × 1027 /(cm2 s)
with the number of injected ions of 3 × 108 . In 2016, we successfully completed a measurement of diﬀraction of scattered electrons
from 132 Xe nuclei and determined the charge density distribution for the ﬁrst time. In 2021, we have been trying to obtain the worldﬁrst electron scattering data of unstable nuclei.

2. Major Research Subjects
Development of SCRIT electron scattering technique and measurement of the nuclear charge density distributions of unstable
nuclei.

3. Summary of Research Activity
SCRIT is a novel technique to form internal target in an electron storage ring. Positive ions are three dimensionally conﬁned in theelectron beam axis by transverse focusing force given by the circulating electron beam and applied electrostatic longitudinal mirror
potential. The created ion cloud composed of RI ions injected from outside works as a target for electron scattering. Constructionof the SCRIT electron scattering facility has been started in 2009. The electron accelerators RTM and the storage ring SR2 weresuccessfully commissioned in 2010. Typical accumulation current in SR2 is 250–300 mA at the energy range of 120–300 MeV that isrequired energy range in electron scattering experiment. The SCRIT device was inserted in the straight section of SR2 and connected
to an ISOL named ERIS (Electron-beam-driven RI separator for SCRIT) by 20-m long low energy ion transport line. A buncher
system based on RFQ linear trap named FRAC (Fringing-RF-ﬁeld-Activated dc-to-pulse converter) was inserted in the transport line
to convert the continuous beam from ERIS to pulsed beam, which is acceptable for SCRIT. The detector system WiSES consisting ofa high-resolution magnetic spectrometer, drift chambers and trigger scintillators, was constructed, and it has a solid angle of 100 msr,
energy resolution of 10−3 , and the scattering angle coverage of 25–55 degrees. A wide range of momentum transfer, 80–300 MeV/c,
is covered by changing the electron beam energy from 150 to 300 MeV.
We successfully measured a diﬀraction pattern in the angular distribution of scattered electron from 132 Xe isotope at the electron
beam energy of 150 MeV, 200 MeV, and 300 MeV, and derived the nuclear charge distribution by assuming two-parameters Fermi
model for the ﬁrst time. At this time, luminosity was reached to 3 × 1027 /(cm2 s) at maximum and the averaged value was 1.2 ×1027 /(cm2 s) with the number of injected target ions of 3 × 108 .
We are now under preparation for going to the experiments for unstable nuclei. There are some key issues for that. They are
increasing the intensity of the RI beams from ERIS, eﬃcient DC-to-pulse conversion at FRAC, improving the transmission eﬃciency
from FRAC to SCRIT, and eﬀective suppression of the background in measurement of scattered electrons. RI beam intensity will be
improved by upgrading the electron beam power from 10 W to 60 W, increasing the contained amount of U in the target ion source,and some modiﬁcations in mechanical structure in the ion source. For upgrading the electron beam power, the RF system of RTM
has been maintained intensively, and we will continue the development of RTM. For eﬃcient DC-to-pulse conversion, we establishedthe two-step bunching method, which is time compression at FRAC in combination with pre-bunching at the ion source using gridaction. Furthermore, we will improve the conversion eﬃciency and the transmission eﬃciency from FRAC to the SCRIT device bycooling the trapped ions using minuscule amounts of a buﬀer gas. These improvements on FRAC were already conﬁrmed in oﬀ-line
test. Since one of signiﬁcant contribution to the background for scattered electron is scattering from massive structural objects aroundthe trapping region originated from halo components of the electron beam, we remodeled the SCRIT electrodes. The vacuum pumpsystem at the SCRIT device has been upgraded to reduce the contribution of residual gases. Luminosity for radioactive Xe isotopes is
expected to be more than 1026 /(cm2 s) after these improvements. Then, we will be able to start experiments for unstable nuclei. Whenfurther upgrading in the RTM power planed to be 3 kW will be achieved, we can extend the measurements to more exotic nuclei.
In 2018, we developed several instruments. One is the introduction of the surface-ionization type ion source at ERIS in order
to increase kinds of radioactive beam and to produce high intensity beam. Another development is the upgrading of the drift chamber located in front of the magnetic spectrometer of WiSES to improve the momentum resolution and angular acceptance. Thesedevelopments help us to realize experiments for unstable nuclei.
In 2019, we installed a newly designed SCRIT electrodes. The main purpose of the replacement was to lower the background
during the measurement due to the electron scattering from the SCRIT electrodes itself but not from the ion targets for the experiment.
For that purpose, we employed thin metal wires to construct the electrodes rather than metal plates nor blocks. In addition, we
modiﬁed the inside structure of the SCRIT chamber to symmetrize the electric ground potential aﬀecting the potential curve inside theelectrodes.

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In 2020, we tested accelerators RTM and SR2 if they bear for long term experiment for 24 hours. Currently, we are adjusting theSR2 accelerator and ion source ERIS to be ready for the real electron scattering measurement of unstable nuclei.
In 2021, ERIS became ready to provide enough ions for the experiment of unstable nuclei. We have been trying to measureelectron scattering of unstable nuclei. Hopefully, we can publish those data very soon.

Members
Team Leader
Masanori WAKASUGI
Senior Research Scientist
Masamitsu WATANABE
Senior Technical Scientist
Tetsuya OHNISHI
Expert Technician
Takeshi MAIE
Contract Researcher
Yasushi ABE
Junior Research Associate
Hikari WAUKE
Research Consultants
Takashi EMOTO
Masahiro HARA

Toshitada HORI (Hiroshima Univ.)
Shinichi ICHIKAWA

Visiting Scientists
Akitomo ENOKIZONO (Rikkyo Univ.)
Yuki HONDA (Tohoku Univ.)

Toshimi SUDA (Tohoku Univ.)
Shuo WANG (Shandong Univ. (Weihai))Student Trainees
Taiga GOKE (Tohoku Univ.)
Yuma ISHIKURA (Tohoku Univ.)
Kazushi ISHIZAKI (Tohoku Univ.)

Clement V. LEGRIS (Tohoku Univ.)
Hikari WAUKE (Tohoku Univ.)

List of Publications & Presentations
Publications[Original Papers]
須田利美, 本多佑記, 瀧大祐, 郷家大雅, C. Legris, 石崎一志, 三浦禎雄, 武藤俊哉, 玉江忠明, 前田幸重, Z. Hang, 塚田暁, 「Proton
radius」, 原子核研究 66, 2–11 (2021).
須田利美, 本多佑記, 前田幸重, 塚田暁, 「陽子半径」, 高エネルギーニュース 40, 107–116 (2022).

[Proceeding]
T. Ohnishi, K. Adachi, A. Enokizono, T. Fujita, M. Hara, M. Hori, T. Hori, S. Ichikawa, K. Kurita, T. Suda, T. Tamae, K. Tsukada,
M. Togasaki, N. Uchida, M. Wakasugi, M. Watanabe, and K. Yamada, “The SCRIT electron scattering facility at RIKEN RI Beam
Factory,” JPS Conf. Proc. 35, 011027 (2021).

Presentations[International Conferences/Workshops]
T. Suda (oral), “Study of radii of proton and exotic nuclei by electron scattering,” 2021 Symposium on Nuclear Data, Online, November
18–19, 2021.
C. Legris (oral), “Commissioning results for the ULQ2 experiment towards the proton charge radius determination,” The Nineth International School for Strangeness Nuclear Physics, RCNP, Osaka University, Online, December 13–16, 2021.
T. Goke (oral), “New type scattering chamber optimized for proton radius measurement by low-energy electron scattering,” The Nineth
International School for Strangeness Nuclear Physics, RCNP, Osaka University, Online, December 13–16, 2021.

[Domestic Conferences/Workshops]
大西哲哉 (招待講演), 「The SCRIT e-RI scattering facility at RIKEN」, RCNP での次期計画検討会, 大阪府茨木市 (大阪大学核物理研究センター), 2021 年 9 月 27–29 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

H. Wauke (oral), “Study of internal structure of unstable nuclei by electron scattering,” The RIBF Users Meeting 2021, RIKEN, Japan,
Online, September 7–9, 2021.
T. Goke (poster), “Development of new vacuum scattering target chamber optimized for proton radius measurement by low-energy
electron scattering,” ELPH Symposium 2022, Sendai, March 11, 2022.
T. Goke (oral), “Future plans for proton radius measurement by low-energy electron scattering,” JPS 2021 Autumn Meeting, Kobe, Online,
September 14–17, 2021.
C. Legris (oral), “First test results for the ULQ2 experiment towards the proton charge radius determination,” JPS 2021 Autumn Meeting,
Kobe, Online, September 14–17, 2021.
H. Wauke (oral), “Isotope and isotone dependence of nuclear charge density distribution at SCRIT electron scattering facility,” 2022
Annual (77th) Meeting of The Physical Society of Japan, Okayama, Online, March 15–19, 2022.
T. Goke (oral), “Development of new vacuum scattering target chamber for proton radius measurement by low-energy electron scattering,”
2022 Annual (77th) Meeting of The Physical Society of Japan, Okayama, Online, March 15–19, 2022.
Y. Ishikura (oral), “Commissioning of the twin spectrometers for proton radius measurement by low-energy electron scattering,” 2022
Annual (77th) Meeting of The Physical Society of Japan, Okayama, Online, March 15–19, 2022.

[Seminar]
須田利美（招待講演）, 「陽子のサイズがおかしい？」, 千葉大学先進科学プログラム・オムニバスセミナー, 千葉県千葉市（千葉大学）, 2021 年 10 月 15 日.

Outreach Activities
須田利美 (インタービュー記事), 「陽子の半径の正確な値を突き止めよ—半世紀前の古い加速器だからこそできること」, 国立大学附置研・センター会議, http://shochou-kaigi.org/interview/interview_93/ .
須田利美（特別講義）, 「陽子などの物の大きさはどう測る？」, 埼玉県立熊谷高等学校, 埼玉県熊谷市 (埼玉県立熊谷高等学校), 2022
年 1 月 14 日.
須田利美 (集中講義), 「電子散乱による原子核研究」, 北海道札幌市 (北海道大学物理学科), 2021 年 12 月 13–15 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Research Instruments Group
1. Abstract
The Research Instruments Group is the driving force at RI Beam Factory (RIBF) for continuous enhancement of activities andcompetitiveness of experimental research. Consisting of four teams, we are in charge of the operation, maintenance, and improvementof the core research instruments at RIBF, such as the BigRIPS in-ﬂight RI separator, ZeroDegree spectrometer and SAMURAI spectrometer, and the related infrastructure and equipment. We are also in charge of the production and delivery of RI beams using the
BigRIPS separator. The group also conducts related experimental research as well as R&D studies on the research instruments.

2. Major Research Subjects
Design, construction, operation, maintenance, and improvement of the core research instruments at RIBF and related R&D studies.
Experimental studies on exotic nuclei.

3. Summary of Research Activity
The current research subjects are summarized as follows:(1) Production and delivery of RI beams and related research;(2) Design, construction, operation, maintenance, and improvement of the core research instruments at RIBF and their related
infrastructure and equipment;(3) R&D studies on the core research instruments and their related equipment at RIBF;(4) Experimental research on exotic nuclei using the core research instruments at RIBF.

Members
Director
Tomohiro UESAKA
Contract Researcher
Toshiyuki KUBO
Junior Research Associate
Rieko TSUNODA
Senior Visiting Scientist
Toshio KOBAYASHI (Tohoku Univ.)
Student Trainees
Fumitaka ENDO (Tohoku Univ.)
Kosuke ICHIMURA (Tohoku Univ.)

Rieko TSUNODA- 273 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Research Instruments GroupBigRIPS Team
1. Abstract
This team is in charge of design, construction, development and operation of BigRIPS in-ﬂight separator and its related research
instruments at RI beam factory (RIBF). They are employed not only for the production of RI beams but also the experimental studies
using RI beams.

2. Major Research Subjects
Design, construction, development and operation of BigRIPS in-ﬂight separator, RI-beam transport lines, and their related research
instruments.

3. Summary of Research Activity
This team is in charge of design, construction, development and operation of BigRIPS in-ﬂight separator, RI-beam transport lines,
and their related research instruments such as ZeroDegree spectrometer at RI beam factory (RIBF). They are employed not only forthe production of RI beams but also various kinds of experimental studies using RI beams. The research subjects may be summarized
as follows:(1) General studies on RI-beam production using in-ﬂight scheme;(2) Studies on ion-optics of in-ﬂight separators, including particle identiﬁcation of RI beams;(3) Simulation and optimization of RI-beam production;(4) Development of beam-line detectors and their data acquisition system;(5) Experimental studies on production reactions and unstable nuclei;(6) Experimental studies of the limits of nuclear binding;(7) Development of superconducting magnets and their helium cryogenic systems;(8) Development of a high-power production target system;(9) Development of a high-power beam dump system;(10) Development of a remote maintenance and remote handling systems;(11) Operation, maintenance and improvement of BigRIPS separator system, RI-beam transport lines, and their related research
instruments such as ZeroDegree spectrometer and so on;(12) Experimental research using RI beams.

Members
Team Leader
Koichi YOSHIDA
Senior Research Scientist
Yoshiyuki YANAGISAWA
Senior Technical Scientists
Naohito INABE
Kensuke KUSAKA

Masao OHTAKETechnical Scientists
Naoki FUKUDA
Yohei SHIMIZU

Hiroshi SUZUKI
Hiroyuki TAKEDA)

Postdoctoral Researcher
Masahiro YOSHIMOTO
Visiting Scientists
Deuk Soon AHN (Korea Basic Sci. Inst.)
Daniel P. BAZIN (Michigan State Univ.)
Hans GEISSEL (GSI)
Naohito IWASA (Tohoku Univ.)

Yutaka MIZOI (Univ. of Electro-Commun.)
Sadao MOMOTA (Kochi Univ. Tech.)David MORRISSEY (Michigan State Univ.)
Oleg TARASOV (Michigan State Univ.)

Student Trainees
Mika EGETA (Tohoku Univ.)
Taiga HAGINOUCHI (Tohoku Univ.)

Shunki ISHIKAWA (Tohoku Univ.)- 274 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

List of Publications & Presentations
Publications[Original Papers]
J. Estee, W. G. Lynch, C. Y. Tsang, J. Barney, G. Jhang, M. B. Tsang, R. Wang, M. Kaneko, J. W. Lee, T. Isobe, M. Kurata-Nishimura,T. Murakami, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, J. Brzychczyk, G. Cerizza, N. Chiga, N. Fukuda, I. Gasparic,
B. Hong, A. Horvat, K. Ieki, N. Inabe, Y. J. Kim, T. Kobayashi, Y. Kondo, P. Lasko, H. S. Lee, Y. Leifels, J. Łukasik, J. Manfredi, A. B. McIntoshl, P. Morfouace, T. Nakamural, N. Nakatsuka, S. Nishimura, H. Otsu, P. Pawłowski, K. Pelczar, D. Rossi,
H. Sakurai, C. Santamaria, H. Sato, H. Scheit, R. Shane, Y. Shimizu, H. Simon, A. Snoch, A. Sochocka, T. Sumikama, H. Suzuki,
D. Suzuki, H. Takeda, S. Tangwancharoen, H. Toernqvist, Y. Togano, Z. G. Xiao, S. J. Yennello, and Y. Zhang (SπRIT Collaboration)and M. D. Cozma, “Probing the symmetry energy with the spectral pion ratio,” Phys. Rev. Lett. 126, 162701 (2021).
G. Jhang, J. Estee, J. Barney, G. Cerizza, M. Kaneko, J. W. Lee, W. G. Lynch, T. Isobe, M. Kurata-Nishimura, T. Murakami, C. Y. Tsang,
M. B. Tsang, R. Wang, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, J. Brzychczyk, N. Chiga, N. Fukuda, I. Gasparici,
B. Hong, A. Horvat, K. Ieki, N. Inabe, Y. J. Kim, T. Kobayashi, Y. Kondo, P. Lasko, H. S. Lee, Y. Leifels, J. Łukasik, J. Manfredi,A. B. McIntosh, P. Morfouace, T. Nakamura, N. Nakatsuka, S. Nishimura, R. Olsen, H. Otsu, P. Pawłowski, K. Pelczar, D. Rossi,
H. Sakurai, C. Santamaria, H. Sato, H. Scheit, R. Shane, Y. Shimizu, H. Simon, A. Snoch, A. Sochocka, Z. Sosin, T. Sumikama,
H. Suzuki, D. Suzuki, H. Takeda, S. Tangwancharoen, H. Toernqvist, Y. Togano, Z. G. Xiao, S. J. Yennello, J. Yurkon, Y. Zhang, theSπRIT Collaboration, M. Colonna, D. Cozma, PawełDanielewicz, H. Elfner, N. Ikeno, C. M. Ko, J. Mohs, D. Oliinychenko, A. Ono,
J. Su, Y. J. Wang, H. Wolter, J. Xu, Y. -X. Zhang, and Z. Zhang, the TMEP Collaboration, “Symmetry energy investigation with pion
production from Sn+Sn systems,” Phys. Lett. B 813, 136016 (2021).
O. Hall, T. Davinson, A. Estrade, J. Liu, G. Lorusso, F. Montes, S. Nishimura, V. H. Phong, P. J. Woods, J. Agramunt, D. S. Ahn, A. Algora,
J. M. Allmond, H. Baba, S. Bae, N. T. Brewer, C. G. Bruno, R. Caballero-Folch, F. Calviño, P. J. Coleman-Smith, G. Cortes, I. Dillmann,
C. Domingo-Pardo, A. Fijalkowska, N. Fukuda, S. Go, C. J. Griﬃn, R. Grzywacz, J. Ha, L. J. Harkness-Brennan, T. Isobe, D. Kahl,
L. H. Khiem, G. G. Kiss, A. Korgul, S. Kubono, M. Labiche, I. Lazarus, J. Liang, Z. Liu, K. Matsui, K. Miernik, B. Moon, A. I. Morales,
P. Morrall, M. R. Mumpower, N. Nepal, R. D. Page, M. Piersa, V. F. E. Pucknell, B. C. Rasco, B. Rubio, K. P. Rykaczewski, H. Sakurai,
Y. Shimizu, D. W. Stracener, T. Sumikama, H. Suzuki, J. L. Tain, H. Takeda, A. Tarifeño-Saldivia, A. Tolosa-Delgado, M. WolińskaCichocka, and R. Yokoyama, “β-delayed neutron emission of r-process nuclei at the N = 82 shell closure,” Phys. Lett. B 816, 136266(2021).
M. Kaneko, T. Murakami, T. Isobe, M. Kurata-Nishimura, A. Ono, N. Ikeno, J. Barney, G. Cerizza, J. Estee, G. Jhang, J. W. Lee,W. G. Lynch, C. Santamaria, C. Y. Tsang, M. B. Tsang, R. Wang, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, J. Brzychczyk,
N. Chiga, N. Fukuda, I. Gašparić, B. Hong, A. Horvati, T. Ichihara, K. Ieki, N. Inabe, Y. J. Kim, T. Kobayashi, Y. Kondo, P. Lasko,
H. S. Lee, Y. Leifels, J. Łukasik, J. Manfredi, A. B. McIntosh, P. Morfouace, T. Nakamura, N. Nakatsuka, S. Nishimura, R. Olsen,
H. Otsu, P. Pawłowski, K. Pelczar, D. Rossi, H. Sakurai, H. Sato, H. Scheit, R. Shane, Y. Shimizu, H. Simon, T. Sumikama, D. Suzuki,
H. Suzuki, H. Takeda, S. Tangwancharoen, Y. Togano, H. Törnqvist, Z. Xiao, S. J. Yennellor, J. Yurkon, and Y. Zhang, SπRIT Collaboration, “Rapidity distributions of Z = 1 isotopes and the nuclear symmetry energy from Sn+Sn collisions with radioactive beams at
270 MeV/nucleon,” Phys. Lett. B 822, 136681 (2021).
H. Watanabe, C. X. Yuan, G. Lorusso, S. Nishimura, Z. Y. Xu, T. Sumikama, P. -A. Söderström, P. Doornenbal, F. Browne, G. Gey,
H. S. Jung, J. Taprogge, Zs. Vajta, H. K. Wang, J. Wu, A. Yagi, H. Baba, G. Benzoni, K. Y. Chae, F. C. L. Crespi, N. Fukuda,
R. Gernhäuser, N. Inabe, T. Isobe, A. Jungclaus, D. Kameda, G. D. Kim, Y. K. Kim, I. Kojouharov, F. G. Kondev, T. Kubo, N. Kurz,
Y. K. Kwon, G. J. Lane, Z. Li, C. -B. Moon, A. Montaner-Pizá, K. Moschner, F. Naqvi, M. Niikura, H. Nishibata, D. Nishimura,A. Odahara, R. Orlandi, Z. Patel, Zs. Podolyák, H. Sakurai, H. Schaﬀner, G. S. Simpson, K. Steiger, H. Suzuki, H. Takeda, A. Wendt,
and K. Yoshinaga, “Impact of shell evolution on Gamow-Teller β decay from a high-spin long-lived isomer in 127 Ag,” Phys. Lett. B
823, 136766 (2021).
S. E. A. Orrigo, B. Rubio, W. Gelletly, P. Aguilera, A. Algora, A. I. Morales, J. Agramunt, D. S. Ahn, P. Ascher, B. Blank, C. Borcea,
A. Boso, R. B. Cakirli, J. Chiba, G. de Angelis, G. de France, F. Diel, P. Doornenbal, Y. Fujita, N. Fukuda, E. Ganioğlu, M. Gerbaux,
J. Giovinazzo, S. Go, T. Goigoux, S. Grévy, V. Guadilla, N. Inabe, G. G. Kiss, T. Kubo, S. Kubono, T. Kurtukian-Nieto, D. Lubos,
C. Magron, F. Molina, A. Montaner-Pizá, D. Napoli, D. Nishimura, S. Nishimura, H. Oikawa, V. H. Phong, H. Sakurai, Y. Shimizu,
C. Sidong, P. -A. Söderström, T. Sumikama, H. Suzuki, H. Takeda, Y. Takei, M. Tanaka, J. Wu, and S. Yagi, “β decay of the very
neutron-deﬁcient 60 Ge and 62 Ge nuclei,” Phys. Rev. C 103, 014324 (2021).
T. Sumikama, N. Fukuda, N. Inabe, D. Kameda, T. Kubo, Y. Shimizu, H. Suzuki, H. Takeda, K. Yoshida, H. Baba, F. Browne, A. M. Bruce,
R. Carrol, N. Chiga, R. Daido, F. Didierjean, P. Doornenbal, Y. Fang, G. Gey, E. Ideguchi, T. Isobe, S. Lalkovski, Z. Li, G. Lorusso
R. Lozeva, H. Nishibata, S. Nishimura, I. Nishizuka, A. Odahara, Z. Pate, Zs. Podolyák, P. H. Regan, S. Rice, O. J. Roberts, H. Sakurai,
G. S. Simpson, L. Sinclair, P. -A. Söderström, M. Tanaka, J. Taprogge, H. Watanabe, V. Werner, O. Wieland, J. Wu, Z. Y. Xu, andA. Yagi, “Observation of new neutron-rich isotopes in the vicinity of 110 Zr,” Phys. Rev. C 130, 014614 (2021).
B. Moon, A. Jungclaus, H. Naı̈dja, A. Gargano, R. Lozeva, C. -B. Moon, A. Odahara, G. S. Simpson, S. Nishimura, F. Browne, P. Doornenbal, G. Gey, J. Keatings, G. Lorusso, Z. Patel, S. Rice, M. Si, L. Sinclair, P. -A. Söderström, T. Sumikama, J. Taprogge, H. Watanabe,
J. Wu, Z. Y. Xu, A. Yagi, D. S. Ahn, H. Baba, F. L. Bello Garrote, S. Bönig, R. Daido, J. M. Daugas, F. Didierjean, F. Drouet, Y. Fang,
N. Fukuda, R. Gernhäuser, B. Hong, E. Ideguchi, S. Ilieva, N. Inabe, T. Ishigaki, T. Isobe, H. S. Jung, D. Kameda, I. Kojouharov,
T. Komatsubara, T. Kröll, T. Kubo, N. Kurz, Y. K. Kwon, C. S. Lee, P. Lee, Z. Li, A. Montaner-Pizá, S. Morimoto, K. Moschner,
D. Mücher, D. Murai, M. Niikura, H. Nishibata, I. Nishizuka, R. Orlandi, H. Sakurai, H. Schaﬀner, Y. Shimizu, K. Steiger, H. Suzuki,
H. Takeda, K. Tshoo, Zs. Vajta, A. Wendt, R. Yokoyama, and K. Yoshinaga, “Nuclear structure of Te isotopes beyond neutron magic
number N = 82,” Phys. Rev. C 103, 034320 (2021).
R. Yokoyama, E. Ideguchi, G. S. Simpson, Mn. Tanaka, Y. Sun, C. -J. Lv, Y. -X. Liu, L. -J. Wang, S. Nishimura, P. Doornenbal, G. Lorusso,
P. -A. Söderström, T. Sumikama, J. Wu, Z. Y. Xu, N. Aoi, H. Baba, F. L. Bello Garrotel, G. Benzonil, F. Browne, R. Daido, Y. Fang,- 275 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

N. Fukuda, A. Gottardo, G. Gey, S. Go, S. Inabe, T. Isobe, D. Kameda, K. Kobayashi, M. Kobayashi, I. Kojouharov, T. Komatsubara,
T. Kubo, N. Kurz, I. Kuti, Z. Li, M. Matsushita, S. Michimasa, C. B. Moon, H. Nishibata, I. Nishizuka, A. Odahara, Z. Patel, S. Rice,E. Sahin, H. Sakurai, H. Schaﬀner, L. Sinclair, H. Suzuki, H. Takeda, J. Taprogge, Zs. Vajta, H. Watanabe, and A. Yagi, “Threequasiparticle isomers in odd-even 159, 161 Pm: Calling for modiﬁed spin-orbit interaction for the neutron-rich region,” Phys. Rev. C 104,
L021303 (2021).
A. Kubiela, H. Suzuki, O. B. Tarasov, M. Pfützner, D. -S. Ahn, H. Baba, A. Bezbakh, A. A. Ciemny, W. Dominik, N. Fukuda, A. Giska,
R. Grzywacz, Y. Ichikawa, Z. Janas, Ł. Janiak, G. Kamiński, K. Kawata, T. Kubo, M. Madurga, C. Mazzocchi, H. Nishibata, M. Pomorski, Y. Shimizu, N. Sokołowska, D. Suzuki, P. Szymkiewicz, A. Świercz, M. Tajima, A. Takamine, H. Takeda, Y. Takeuchi,
C. R. Thornsberry, H. Ueno, H. Yamazaki, R. Yokoyama, and K. Yoshida, “Production of the most neutron-deﬁcient Zn isotopes by
projectile fragmentation of 78 Kr,” Phys. Rev. C 104, 064610 (2021).
T. Sumikama, D. S. Ahn, N. Fukuda, Y. Shimizu, H. Suzuki, H. Takeda, H. Wang, K. Yoshida, J. Amano, N. Chiga, K. Chikaato,
A. Hirayama, N. Inabe, S. Kawase, S. Kubono, M. Matsushita, S. Michimasa, K. Nakano, H. Otsu, H. Sakurai, A. Saito, S. Shimoura,
J. Suwa, M. Takechi, S. Takeuchi, Y. Togano, T. Tomai, and Y. Watanabe, “Energy-control and novel particle-identiﬁcation methods
combined with range in a multi-sampling ionization chamber for experiments using slowed-down RI beams,” Nucl. Instrum. Methods
Phys. Res. A 986, 164687 (2021).

Presentations[Domestic Conferences/Workshops]
福田直樹, 「大強度不安定核ビームの生成〜理研超伝導 RI ビーム生成分離装置 BigRIPS の現在とこれから〜」, 日本物理学会 第76 回年次大会（2021 年）, オンライン, 2021 年 3 月 12–15 日.
吉留勇起, 近藤洋介, 中村隆司, N. L. Achouri, T. Aumann, 馬場秀忠, F. Delaunay, P. Doornenbal, 福田直樹, J. Gibelin, J. Hwang, 稲辺尚人, 磯部忠昭, 亀田大輔, 簡野大輝, S. Kim, 小林信之, 小林俊雄, 久保敏幸, S. Leblond, J. Lee, M. Marques, 本林透, 村井大地, 村上
哲也, 武藤琴美, 中嶋丈嘉, 中塚徳継, A. Navin, 西征爾郎, N. A. Orr, 大津秀暁, 佐藤広海, 佐藤義輝, 清水陽平, 鈴木宏, 高橋賢人,
竹田浩之, 栂野泰宏, A. G. Tuﬀ, M. Vandebrouck, 米田健一郎, 「25 O の不変質量核分光」, 日本物理学会 第 76 回年次大会, オンラ
イン, 2021 年 3 月 12 日.
N. M. Nor, A. Odahara, A. Yagi, R. Lozeva, C. B. Moon, S. Nishimura, H. Nishibata, P. Doornenbal, G. Lorusso, T. Sumikama, H. Watanabe, F. Brown, Z. Y. Xu, J. Wu, R. Yokoyama, T. Isobe, H. Baba, H. Sakurai, H. Suzuki, N. Inabe, D. Kameda, N. Fukuda, H. Takeda,
D. S. Ahn, Y. Shimizu, H. Sato, T. Kubo, S. Iimura, Y. Fang, R. Daido, T. Ishigaki, S. Morimoto, E. Ideguchi, T. Komatsubara, M. Niikura, I. Nishizuka and the EURICA Collaborators, “Nuclear structure study of neutron-rich Xe nuclei by beta decay of 141 I,” 日本物, オンライン, 2021 年 3 月 12–15 日.
理学会 第 76 回年次大会（2021 年）
道正新一郎, 小林幹, 清川裕, 大田晋輔, 横山輪, 西村太樹, D. S. Ahn, 馬場秀忠, G. P. A. Berg, 堂園昌伯, 福田直樹, 古野達也, 井手口栄治, 稲辺尚人, 川畑貴裕, 川瀬頌一郎, 木佐森慶一, 小林和馬, 久保敏幸, 久保田悠樹, C. S. Lee, 松下昌史, 宮裕之, 水上敦, 永倉弘康,
笈川浩之, 酒井英行, 清水陽平, C A. Stolz, 鈴木宏, 高木基伸, 竹田浩之, 武内聡, 時枝紘史, 上坂友洋, 矢向謙太郎, 山口勇貴, 栁澤, 日本物理学会 第 76 回年次大会（2021 年）, オンライン,
善行, 吉田光一, 下浦享, 「中性子過剰 62 Ti 核および近傍核の質量測定」
2021 年 3 月 12–15 日.
生越瑞揮, 本間彰, 武智麻耶, 大坪隆, 田中聖臣, 福田光順, 鈴木健, 西村太樹, 森口哲朗, 安得順, A. S. Aimaganbetov, 天野将道, 荒川裕樹, S. Bagchi, K. -H. Behr, N. Burtebayev, 親跡和弥, 杜航, 藤井朋也, 福田直樹, H. Geissel, 堀太地, 星野寿春, 伊五澤涼, 池田彩夏,
稲辺尚人, 猪股玖美, 板橋健太, 泉川卓司, 上岡大起, 神田直人, 加藤郁磨, I. Kenzhina, Z. Korkulu, Ye. Kuk, 日下健祐, 三原基嗣,
宮田恵理, 長江大輔, 中村翔健, M. Nassurlla, 西室国光, 西塚賢治, 大甕舜一朗, 大西康介, 大竹政雄, 王恵仁, 小沢顕, A. Prochazka,
櫻井博儀, C. Scheidenberger, 清水陽平, 杉原貴信, 炭竃聡之, 鈴木伸司, 鈴木宏, 竹田浩之, 田中悠太郎, 田中良樹, 和田太郎, 若山
清志, 八木翔一, 山口貴之, 柳原陸斗, 柳澤善行, 吉田光一, T. K. Zholdybayev, 「Ni 同位体の陽子標的荷電変化断面積」, 日本物理学会 第 76 回年次大会（2021 年）, オンライン, 2021 年 3 月 12–15 日.
髙橋弘幸, 西村太樹, 菅原奏来, 延與紫世, 福田直樹, 原田知也, 土方佑斗, 松村理久, 佐藤広海, 清水陽平, 鈴木宏, 竹田浩之, 田中純貴,
上坂友洋, 宇根千晶, 吉田光一, 銭廣十三, 「Th ビームの開発に向けたイオンチェンバーの性能評価」, 日本物理学会 第 76 回年次大会（2021 年）, オンライン, 2021 年 3 月 12–15 日.
阪上朱音, A. D. Soon, 板橋健太, 日下健祐, 清水陽平, 炭竃聡之, 鈴木宏, 竹田浩之, 上坂友洋, 西隆博, 馬場秀忠, 福田直樹, 福西暢尚,
稲辺尚人, 矢向謙太郎, 柳澤善行, 吉田光一, 松本翔汰, 関屋涼平, G. Hans, 田中良樹, 「BigRIPS における二重ガモフ・テラー巨, 日本物理学会 第 76 回年次大会（2021 年）, オンライン, 2021 年 3 月 12–15 日.
大共鳴探索実験のための光学系の開発」
土方佑斗, 銭廣十三, 上坂友洋, 延與紫世, 大田晋輔, 坂口治隆, 佐藤広海, 清水陽平, 菅原奏来, 鈴木宏, 髙橋弘幸, 武重祥子, 竹田浩之,
田中純貴, 辻崚太朗, 寺嶋知, 堂園昌伯, 西村俊二, 西村太樹, 馬場秀忠, 原田知也, 福田直樹, 松田洋平, 道正新一郎, 山村周, 吉田光一,「大強度かつ極めて重い不安定核ビームの粒子識別に向けた Xe ガスシンチレータの開発」, 日本物理学会 第 76 回年次大会（2021年）, オンライン, 2021 年 3 月 12–15 日.

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Research Facility Development Division
Research Instruments GroupSAMURAI Team
1. Abstract
In collaboration with research groups in and outside RIKEN, the team designs, develops and constructs the SAMURAI spectrometer and relevant equipment that are and will be used for reaction experiments using RI beams at RI Beam Factory. The SAMURAI
spectrometer consists of a large superconducting dipole magnet and a variety of detectors to measure charged particles and neutrons.
After the commissioning experiment in March 2012, the team prepared and conducted, in collaboration with researchers in individual experimental groups, the ﬁrst series of experiments with SAMURAI in May 2012. Then, several numbers of experiments were
well performed until now utilizing the property of SAMURAI. The team also provides a basis for research activities by, for example,
organizing collaboration workshops by researchers who are interested in studies or plan to perform experiments with the SAMURAI
spectrometer.

2. Summary of Research Activity
The current research subjects are summarized as follows:(1) Operation, maintenance and improvement of a large superconducting dipole magnet that is the main component of the SAMURAI spectrometer;(2) Design, development and construction of various detectors that are used for nuclear reaction experiments using the SAMURAI
spectrometer;(3) Preparation for planning experiments using SAMURAI spectrometer;(4) Maintenance and improvement of the SAMURAI beam lines;(5) Formation of a collaboration platform called SAMURAI collaborations;(6) Preparation for next generation spectrometer for nuclear reaction studies.

Members
Team Leader
Hideaki OTSU
Research & Development Scientist
Mizuki NISHIMURA

List of Publications & Presentations
Publications[Original Papers]
M. M. Juhasz et al., “First spectroscopic study of 63 V at the N = 40 island of inversion,” Phys. Rev. C 103, 064308 (2021).
B. D. Linh et al., “Investigation of the ground-state spin inversion in the neutron-rich 47, 49 Cl isotopes,” Phys. Rev. C 104, 044331 (2021).
F. Browne et al., “Pairing forces govern population of doubly magic 54 Ca from direct reactions,” Phys. Rev. Lett. 126, 252501 (2021).
J. Estee et al., “Probing the symmetry energy with the spectral pion ratio,” Phys. Rev. Lett. 126, 162701 (2021).
M. Kaneko et al., “Rapidity distributions of Z = 1 isotopes and the nuclear symmetry energy from Sn+Sn collisions with radioactive
beams at 270 MeV/nucleon,” Phys. Lett. B 822, 136681 (2021).
G. Jhang et al., “Symmetry energy investigation with pion production from Sn+Sn systems,” Phys. Lett. B 813, 136016 (2021).

[Proceeding]
S. W. Huang et al., “Experimental study of 4 n by directly detecting the decay neutrons,” Few-Body System 62, 102 (2021).

Presentations[International Conference/Workshop]
SAMURAI International Collaboration Workshop 2021, Online, August 30–September 1, 2021,
https://indico2.riken.jp/e/SAMURAIICW2021 .

[Domestic Conferences/Workshops]
磯部忠昭, 「重 RI ビーム衝突からの荷電パイ中間子測定による高密度核物質対称エネルギーの研究」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
倉田（西村）美月, 「重 RI ビームを用いた生成粒子の集団運動の観測と対称エネルギー依存性の研究」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
斗米貴人, 「直接反応による 31 Ne の非束縛励起状態のスペクトロスコピー」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年
9 月 14–17 日.

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中塚徳継, 「中性子過剰核の準弾性散乱実験で用いる反跳陽子検出器の開発」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年
9 月 14–17 日.
堀川晃太, 「中性子過剰核における短距離相関探索実験のための前方散乱粒子検出器の開発」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
海老名直樹, 「多中性子クラスター探索実験のための陽子飛跡検出シミュレーション」, 日本物理学会 2021 年秋季大会, オンライ
ン, 2021 年 9 月 14–17 日.
松井智輝, 「多中性子クラスター探索実験のための陽子全エネルギー検出器の開発 II」, 日本物理学会 2021 年秋季大会, オンライ
ン, 2021 年 9 月 14–17 日.
金子雅紀, 「RI ビームを用いた重イオン衝突における水素同位体生成と高密度核物質の対称エネルギー」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–18 日.
磯部忠昭, 「中性子過剰な原子核を用いた中性子星状態方程式の実験的研究」, 日本物理学会第 77 回年次大会, シンポジウム「宇宙観測, 加速器実験と理論の協奏で探る高密度核物質」, オンライン, 2022 年 3 月 15–18 日.

Master Thesis
西津美咲, 修士論文, 「79 Se に対する 200 MeV/u 陽子及び重陽子入射核破砕反応による同位体生成断面積測定」, 九州大学, 2022
年 3 月.

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Research Facility Development Division
Research Instruments Group
Computing and Network Team
1. Abstract
This team is in charge of development, management and operation of the computing and network environment, mail and information servers and data acquisition system and management of the information security of the RIKEN Nishina Center.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)

Development, management and operation of the general computing servers
Development, management and operation of the mail and information servers
Development, management and operation of the data acquisition system
Development, management and operation of the network environment
Management of the information security

3. Summary of Research Activity
This team is in charge of development, management and operation of the computing and network environment, mail and information servers and data acquisition system and management of the information security. The details are described elsewhere in thisprogress report.
(1) Development, management and operation of the general computing servers
We are operating Linux/Unix NIS/NFS cluster system for the data analysis of the experiments and general computing. This
cluster system consists of eight computing servers with 64 CPU cores and totally 200 TB RAID of highly-reliable Fibre-channelinterconnection. There are approximately 300 active user accounts on this cluster system (a total of about 800 accounts were registeredso far). We are adopting the latest version of the Scientiﬁc Linux (X86 64) as the primary operating system, which is widely used in
the accelerator research facilities, nuclear physics and high-energy physics communities in the world.
(2) Development, management and operation of the mail and information servers
We are operating RIBF.RIKEN.JP server as a mail/NFS/NIS server. This server is a core server of RIBF Linux cluster system.
Postﬁx has been used for mail transport software and dovecot has been used for imap and pop services. These software packages
enable secure and reliable mail delivery. Sophos Email Security and Control (PMX) installed on the mail front-end servers whichtags spam mails and isolates virus-infected mails. The probability to identify the spam is approximately 95–99%. We are operating
several information servers such as Web servers, Integrated Digital Conference (INDICO) server, Wiki servers, Groupware servers,
Wowza streaming servers. We have been operating approximately 70 units of wireless LAN access points in RNC. Almost the entire
radiation-controlled area of the East Area of RIKEN Wako campus is covered by wireless LAN for the convenience of experiments
and daily work.
(3) Development, management and operation of the data acquisition system
We have developed the standard data-acquisition system named as RIBFDAQ. This system can process up to 40 MB/s data. By
using crate-parallel readout from front-end systems such as CAMAC and VME, the dead time could be minimized. To synchronize theindependent DAQ systems, the time stamping system has been developed. The resolution and depth of the time stamp are 10 ns and48 bits, respectively. This time stamping system is very useful for beta decay experiments such as EURICA, BRIKEN and VANDLE
projects. One of the important tasks is the DAQ coupling, because detector systems with dedicated DAQ systems are transported to
RIBF from foreign facilities. In case of SAMURAI Silicon (NSCL/TUM/WUSTL), the readout system is integrated into RIBFDAQ.
The projects of MUST2 (GANIL), MINOS (CEA Saclay), NeuLAND (GSI) and TRB3 (TUM) cases, data from their DAQ systems
are transferred to RIBFDAQ and merged online. For SPIRIT (RIKEN/GANIL/CEA Saclay/NSCL), RIBFDAQ is controlled fromthe NARVAL-GET system that is a large-scale signal processing system for the time projection chamber. EURICA (GSI), BRIKEN(GSI/Univ. Liverpool/IFIC), VANDLE (UTK) and OTPC (U. Warsaw) projects, we adopt the time stamping system to apply individual
trigger for each detector system. In this case, data are merged in oﬄine. In addition, we are developing intelligent circuits based on
FPGA. General Trigger Operator (GTO) is an intelligent triggering NIM module. The trigger system in BigRIPS DAQ is managed
by 5 GTO modules. To improve the data readout speed of VME system, we have successfully developed the MPV system which isa parallel readout extension of the VME system. Data readout sequence is completely parallelized that helps to improve the DAQ
deadtime. Thanks to the MPV system, now the DAQ system in RIBF is 10 times faster than in 2007. Toward to the next generation
DAQ system, we have started to develop a real-time data processing unit based on Xilinx RFSoC that includes FPGA and 4 GHz FADC
for TOF measurements of plastic scintillators. For gaseous detectors like PPAC and drift chamber, the development of FPGA-based
dead-time free TDC is now in progress.
(4) Development, management and operation of the network environment
We have been managing the network environment collaborating with Information Systems Division in RIKEN. All the Ethernet
ports of the information wall sockets are capable of the Gigabit Ethernet connection (10/100/1000 bps). In addition, some 10 Gbps
networks port has been introduced to RIBF experimental area. Approximately 100 units of wireless LAN access points have been

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

installed to cover the almost entire area of Nishina Center.
(5) Management of the information security
It is essential to take proper information security measures for information assets. We are managing the information security of
Nishina Center collaborating with Information Systems Division in RIKEN.

Members
Team Leader
Hidetada BABA
Special Temporary Research Scientists
Takashi ICHIHARA

Yasushi WATANABE

Visiting Scientists
Kazuo IEKI (Rikkyo Univ.)

Shoichiro KAWASE (Kyushu Univ.)

Student Trainee
Shoko TAKESHIGE (Rikkyo Univ.)

List of Publications & Presentations
Publication[Original Paper]
H. Baba, T. Ichihara, T. Isobe, T. Ohnishi, K. Yoshida, Y. Watanabe, S. Ota, H. Shimizu, S. Shimoura, S. Takeuchi, D. Nishimura,
J. Zenihiro, A. O. Tokiyasu, and R. Yokoyama, “MPV—Parallel readout architecture for the VME data acquisition system,” IEEE
Trans. Nucl. Sci. 68, 1841 (2021).

Presentations[Domestic Conferences/Workshops]
馬場秀忠 (口頭発表), 「RIBFDAQ のアップグレード計画」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
武重祥子 (口頭発表), 馬場秀忠, 栗田和好, 栂野泰宏, 銭廣十三, 土方佑斗, 「RFSoC 波形処理システムの RI ビーム実験への実装」,
日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Facility Development Division
Research Instruments Group
Detector Team
1. Abstract
This team is in charge of maintenance and improvement of detectors which are used at BigRIPS separator and its succeeding
beam lines for beam diagnosis and particle identiﬁcation of RI beams. We are also engaged in R&D of new detectors that can be used
for higher-intensity RI beams. In addition, we are doing the R&D which uses the pelletron accelerator together with other groups.

2. Major Research Subjects
Development, fabrication, and operation of beam-line detectors which are used for the production and delivery of RI beams (beamdiagnosis and particle identiﬁcation). R&D which uses the pelletron accelerator.

3. Summary of Research Activity
The current research subjects are summarized as follows:(1) Maintenance and improvement of the beam-line detectors which are used at BigRIPS separator and its succeeding beam lines(2) Development of new beam-line detectors with radiation hardness and tolerance for higher counting rates(3) Management of the pelletron accelerator and R&D which uses the pelletron

Members
Team Leader
Hiromi SATO
Research/Technical Scientist
Tokihiro IKEDA (Senior Research Scientist)
Visiting Scientist
Takeshi KOIKE (Tohoku University)
Student Trainees
Yuka HIKIMA (Toho University)
Kotoko INAYOSHI (Toho University)

Keisuke ONO (Toho University)
Keito SANGU (Toho University)

List of Publications & Presentations
Publications[Original Papers]
J. Estee, W. G. Lynch, C. Y. Tsang, J. Barney, G. Jhang, M. B. Tsang, R. Wang, M. Kaneko, J. W. Lee, T. Isobe, M. Kurata-Nishimura,T. Murakami, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, J. Brzychczyk, G. Cerizza, N. Chiga, N. Fukuda, I. Gasparic,
B. Hong, A. Horvat, K. Ieki, N. Inabe, Y. J. Kim, T. Kobayashi, Y. Kondo, P. Lasko, H. S. Lee, Y. Leifels, J. Łukasik, J. Manfredi,A. B. McIntosh, P. Morfouace, T. Nakamura, N. Nakatsuka, S. Nishimura, H. Otsu, P. Pawłowski, K. Pelczar, D. Rossi, H. Sakurai,
C. Santamaria, H. Sato, H. Scheit, R. Shane, Y. Shimizu, H. Simon, A. Snoch, A. Sochocka, T. Sumikama, H. Suzuki, D. Suzuki,
H. Takeda, S. Tangwancharoen, H. Toernqvist, Y. Togano, Z. G. Xiao, S. J. Yennello, and Y. Zhang, “Probing the symmetry energy
with the spectral pion ratio,” Phys. Rev. Lett. 126, 162701 (2021).
M. Kaneko, T. Murakami, T. Isobe, M. Kurata-Nishimura, A. Ono, N. Ikeno, J. Barney, G. Cerizza, J. Estee, G. Jhang, J. W. Lee,W. G. Lynch, C. Santamaria, C. Y. Tsang, M. B. Tsang, R. Wang, D. S. Ahn, L. Atar, T. Aumann, H. Baba, K. Boretzky, J. Brzychczyk,
N. Chiga, N. Fukuda, I. Gas̆parić, B. Hong, A. Horvat, T. Ichihara, K. Ieki, N. Inabe, Y. J. Kim, T. Kobayashi, Y. Kondo, P. Lasko,
H. S. Lee, Y. Leifels, J. Łukasik, J. Manfredi, A. B. McIntosh, P. Morfouace, T. Nakamura, N. Nakatsuka, S. Nishimura, R. Olsen,
H. Otsu, P. Pawłowski, K. Pelczar, D. Rossi, H. Sakurai, H. Sato, H. Scheit, R. Shane, Y. Shimizu, H. Simon, T. Sumikama, D. Suzuki,
H. Suzuki, H. Takeda, S. Tangwancharoen, Y. Togano, H. Tornqvist, Z. Xiao, S. J. Yennello, J. Yurkon, and Y. Zhang, “Rapidity
distributions of Z = 1 isotopes and the nuclear symmetry energy from Sn+Sn collisions with radioactive beams at 270 MeV/nucleon,”Phys. Lett. B 822, 136681 (2021).
M. Holl S. Lindberg, A. Heinz, Y. Kondo, T. Nakamura, J. A. Tostevin, H. Wang, T. Nilsson, N. L. Achouri, H. Al Falou, L. Atar,
T. Aumann, H. Baba, K. Boretzky, C. Caesar, D. Calvet, H. Chae, N. Chiga, A. Corsi, H. L. Crawford, F. Delaunay, A. Delbart,
Q. Deshayes, P. Dı́az Fernández, Z. Dombrádi, C. A. Douma, Z. Elekes, P. Fallon, I. Gas̆parić, J. -M. Gheller, J. Gibelin, A. Gillibert,
M. N. Harakeh, A. Hirayama, C. R. Hoﬀman, A. Horvat, Á. Horváth, J. W. Hwang, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki,
S. Kawase, S. Kim, K. Kisamori, T. Kobayashi, D. Körper, S. Koyama, I. Kuti, V. Lapoux, F. M. Marqués, S. Masuoka, J. Mayer,
K. Miki, T. Murakami, M. Najaﬁ, K. Nakano, N. Nakatsuka, A. Obertelli, F. de Oliveira Santos, N. A. Orr, H. Otsu, T. Ozaki, V. Panin,
S. Paschalis, A. Revel, D. Rossi, A. T. Saito, T. Y. Saito, M. Sasano, H. Sato, Y. Satou, H. Scheit, F. Schindler, P. Schrock, M. Shikata,Y. Shimizu, H. Simon, D. Sohler, O. Sorlin, L. Stuhl, S. Takeuchi, M. Tanaka, M. Thoennessen, H. Törnqvist, Y. Togano, T. Tomai,
J. Tscheuschner, J. Tsubota, T. Uesaka, Z. Yang, M. Yasuda, and K. Yoneda, “Border of the island of inversion: Unbound states in
29Ne,” Phys. Rev. C 105, 034301 (2022).

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Presentations[Domestic Conferences/Workshops]
金衛国 (口頭発表), 小野敬祐, 池田時浩, 稲吉琴子, 神津雄哉, 三宮圭人, 引間宥花, 「ガラスキャピラリーによるレーザーマイクロ
ビームのスポット構造の解析: 高次リング成分の消失距離の測定」, 第 64 回放射線化学討論会, オンライン, 2021 年 9 月 6–8 日.
金衛国 (口頭発表), 稲吉琴子, 池田時浩, 小野敬祐, 神津雄哉, 三宮圭人, 引間宥花, 「ガラスキャピラリーによるレーザーマイクロ
ビームのスポット構造の解析: 各高次リング輝度の距離依存性」, 第 64 回放射線化学討論会, オンライン, 2021 年 9 月 6–8 日.
金衛国 (ポスター発表), 稲吉琴子, 池田時浩, 小野敬祐, 神津雄哉, 三宮圭人, 引間宥花, 「ガラスキャピラリーで生成されたレーザー
マイクロビームの各スポットリング輝度の距離依存性」, 第 41 回原子衝突若手の会 秋の学校, オンライン, 2021 年 11 月 27 日.
Y. Zhang (口頭発表), 金子雅紀, 村上哲也, 磯部忠昭, 倉田 (西村) 美月, 小野章, 池野なつ美, J. Barney, G. Cerizza, J. Estee, G. Jhang,
J. W. Lee, W. G. Lynch, C. Santamaria, C. Y. Tsang, M. B. Tsang, R. Wang, D. S. Ahn, L. Atar, T. Aumann, 馬場秀忠, K. Boretzky,
J. Brzychczyk, 千賀信幸, 福田直樹, I. Gas̆parić, B. Hong, A. Horvat, 市原卓, 家城和夫, 稲辺尚人, Y. J. Kim, 小林俊雄, 近藤洋介,
P. Lasko, H. S. Lee, Y. Leifels, J. Łukasik, J. Manfredi, A. B. McIntosh, P. Morfouace, 中村隆司, 中塚徳継, 西村俊二, R. Olsen, 大津
秀暁, P. Pawłowski, K. Pelczar, D. Rossi, 櫻井博儀, 佐藤広海, H. Scheit, R. Shane, 清水陽平, H. Simon, 炭竃聡之, 鈴木大介, 鈴木宏, 竹田浩之, S. Tangwancharoen, 栂野康宏, H. Tornqvist, Z. Xiao, S. J. Yennello, J. Yurkon, 「RI ビームを用いた重イオン衝突における水素同位体生成と高密度核物質の対称エネルギー」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
金衛国 (口頭発表), 稲吉琴子, 池田時浩, 小野敬祐, 神津雄哉, 三宮圭人, 引間宥花, 「レーザーマイクロビーム生成のためのガラス
キャピラリー内輸送特性の研究: スポット構造の距離依存性測定」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月
15–19 日.
道正新一郎 (口頭発表), 水野るり惠, 池田時浩, 郷慎太郎, 齋藤岳志, 櫻井博儀, 新倉潤, 松崎禎市郎, 「ミューオン原子 X 線分光のための Ge 検出器を用いた広ダイナミックレンジ光子検出システムの性能評価」, 日本物理学会第 77 回年次大会, オンライン, 2022
年 3 月 15–19 日.

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Accelerator Applications Research Division
Beam Mutagenesis Group
1. Abstract
This group promotes biological applications of ion beams from RI Beam Factory (RIBF). Ion Beam Breeding Team studies
various biological eﬀects of fast heavy ions and develops new technology to breed plants and microbes by heavy-ion irradiations.
Plant Genome Evolution Research Team choose baker’s yeast and the legume Lotus japonicus as model systems to characterize
genomic mutations using the population genomics approach with robust molecular biology and bioinformatics techniques.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Biological eﬀects of fast heavy ions
Molecular nature of DNA alterations induced by heavy-ion irradiation
Research and development of heavy-ion breeding
Genomics-based approach to revolutionize the mutagenesis in plants and microbes

3. Summary of Research Activity
Summary of research activities of the two teams are given in the sections of each team.

Members
Director
Tomoko ABE
Senior Visiting Scientist
Yutaka ARIMOTO
Visiting Scientist
Yoko AIDA (Univ. of Tokyo)- 283 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Accelerator Applications Research Division
Beam Mutagenesis GroupIon Beam Breeding Team
1. Abstract
Ion beam breeding team studies various biological eﬀects of fast heavy ions. It also develops new technique to breed plants andmicrobes by heavy-ion irradiations. Fast heavy ions can produce dense and localized ionizations in matters along their tracks, incontrast to photons (X rays and gamma rays) which produce randomly distributed isolated ionizations. These localized and dense
ionization can cause double-strand breaks of DNA which are not easily repaired and result in mutation more eﬀectively than singlestrand breaks. A unique feature of our experimental facility at the RIKEN Ring Cyclotron (RRC) is that we can irradiate living
tissues in atmosphere since the delivered heavy-ion beams have energies high enough to penetrate deep in matter. This team utilizes adedicated beam line (E5B) of the RRC to irradiate microbes, plants and animals with beams ranging from carbon to iron. Its researchsubjects cover study of ion-beam radiation mutagenesis, genome-wide analyses of mutation, and development of new plants andmicrobial varieties by heavy-ion irradiation. Thirty-nine new varieties have already been brought to the market.

2. Major Research Subjects(1) Study on the biological eﬀects by heavy-ion irradiation(2) Study on the molecular nature of DNA alterations induced by heavy-ion irradiation(3) Innovative applications of heavy-ion irradiation

3. Summary of Research Activity
We study biological eﬀects of fast heavy ions from the RRC using 135 MeV/nucleon C, N, Ne ions, 95 MeV/nucleon Ar ions,
90 MeV/nucleon Fe ions and from the IRC using 160 MeV/nucleon Ar ions. We also develop breeding technology of microbes andplants. Main subjects are:(1) Study on the biological eﬀects by heavy-ion irradiation
Heavy-ion beam deposits a concentrated amount of dose at just before stop with severely changing the linear energy transfer(LET). The peak of LET is achieved at the stopping point and known at the Bragg peak (BP). Adjusting the BP to target malignant
cells is well known to be eﬀective for cancer therapy. On the other hand, a uniform dose distribution is a key to the systematic study
for heavy-ion mutagenesis, thus to the improvement of the mutation eﬃciency. Plants and microbes therefore, are irradiated using ionswith stable LET. We investigated the eﬀect of LET ranging from 23 to 640 keV/μm, on mutation induction using dry seeds of the model
plants Arabidopsis thaliana and rice (Oryza sativa L.). The most eﬀective LET (LETmax) was 30 keV/μm in Arabidopsis. LETmax
irradiations showed the same mutation rate as that by chemical mutagens, which typically cause high mutation rate. The LETmax
was 23–39 keV/μm in buckwheat, 23–50 keV/m in rice and 50–70 keV/μm in wheat. By contrast, when LET was 290 keV/μm, themutation rate was low and the survival rate was greatly reduced in plants. In the case of microbe, ﬁlamentous fungus (Neurospora
crassa), the Ar ions at 290 keV/μm demonstrated higher mutagenic activity than the Fe-ions at 640 keV/μm. Thus, the LET is an
important factor to be considered in heavy-ion mutagenesis.
(2) Study on the molecular nature of DNA alterations induced by heavy-ion irradiation
A whole-genome analysis with high-throughput sequencing is a powerful tool used to characterize the nature of induced mutations.
We have been using whole genome sequencing to analyze DNA mutations in Arabidopsis and rice genomes. C ions with LETmax
mainly induced single nucleotide variants (SNVs) and small insertions and deletions (InDels), while the number of large deletions
and chromosomal rearrangements was low in Arabidopsis. However, 290 keV/μm Ar ions showed a diﬀerent mutation spectrum:
SNVs and number of small InDels was low, while the number of large deletions (100 bp) and chromosomal rearrangements washigh. Number of mutated gene induced by C-ion and Ar-ion irradiation is less than 10, relatively small, and often only 1 mutation isfound near the mapped location. Thus, irradiation with these ions can eﬃciently generate knockout mutants of a target gene and canbe applied to reverse genetics. Rice mutants of the causative gene induced by ion-beam irradiation were compared at 23–50 keV/μm
and 290 keV/μm with typical LETs. The most mutations irradiated with C ion at 23–50 keV/μm were small deletions (< 100 bp).
Irradiation with 290 keV/μm Ar-ion resulted in the highest number of large deletions and decreased small deletions. In rice, as in
Arabidopsis, the LETmax with high mutagenic eﬀects was dominated by SNVs and small deletion mutations, while large deletions
and chromosomal rearrangement mutations dominated LETs with high lethal eﬀects.
(3) Innovative application of heavy-ion irradiation
In 1999, we formed a consortium for ion-beam breeding consisting of 24 groups. In 2020, the consortium grew to 183 groups
from Japan and 20 from overseas. Previously, the ion-beam breeding procedures were carried out using mainly ﬂowers and ornamental
plants. We have recently put a new non-pungent and tearless onion, ‘Smile Ball,’ on the market along with ‘Kiku Meigetsu,’ anedible late ﬂowering chrysanthemum. In addition, a new project was launched to expand the cultivation area of this variety ofchrysanthemum in Yamagata prefecture. Beneﬁcial variants have been grown for various plant species, such as high yield sea weeds,
lipids hyperaccumulating unicellular alga, medicinal plant with high productivity of medicinal ingredient, peanuts without major
allergens, oranges with delayed coloring and one-month late harvest, and lettuce with a low browning property as a cut vegetable. As- 284 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

a result of a collaborative study with Shizuoka prefecture, we have created a new variety of ‘Haru Shizuka,’ which is late coloring.
The harvest time of the Satsuma mandarin has tended to come earlier due to global warming, ‘Haru Shizuka’ is harvested about amonth later than the original variety, but the fruits are sour when harvested. ‘Haru Shizuka’ is suitable for long-term storage and thefruits turn into good quality sweet oranges during storage till April. By broadening the target of heavy-ion breeding extending fromﬂowers to crops, the technology will contribute to solving the global problems of food shortage and environmental destruction.

Members
Team Leader
Tomoko ABE
Research/Technical Scientists
Tokihiro IKEDA (Senior Research Scientist)
Masako IZUMI (Senior Research Scientist)
Ryouhei MORITA (Technical Scientist)

Teruyo TSUKADA (Senior Research Scientist)
Kazuhide TSUNEIZUMI (Senior Research Scientist)

Technical Staﬀs
Yoriko HAYASHI
Yuki SHIRAKAWA

Sumie OHBU
Mieko YAMADASpecial Temporary Technical Scientists
Hiroshi ABE

Katsunori ICHINOSE

Research Consultant
Masahiro MII (Chiba Univ.)
Visiting Scientists
Ayumi DEGUCHI (Chiba Univ.)
Makoto FUJIWARA (Sophia Univ.)
Eitaro FUKATSU (Forestry and Forest Products Res. Inst.)
Tomonari HIRANO (Univ. of Miyazaki)
Akiko HOKURA (Tokyo Denki Univ.)
Kotaro ISHII (QST)
Yutaka MIYAZAWA (Yamagata Univ.)
Kazumitsu MIYOSHI (Chiba Univ.)

Koji MURAI (Fukui Prefectural Univ.)
Kyosuke NIWA (Tokyo Univ. of Marine Sci. and Tech.)Tadashi SATO (Tohoku Univ.)
Yoichi SATO (Riken Food Co., Ltd.)
Kenichi SUZUKI (Suntory Flowers Co., Ltd.)
Hinako TAKEHISA (Nat’l Agriculture and Food Res. Org.)
Masao WATANABE (Tohoku Univ.)

Visiting Technicians
Yukiko KANAZAWA (Nippon Beet Sugar Manufacturing Co.,
Ltd.)
Norihide KISHINO (Sanwa Norin Co. Ltd.)

Miho MOGAMIYA (Riken Food Co., Ltd.)
Daisuke SAITO (Riken Food Co., Ltd.)

Research Fellow
Hironari UCHIDA (Saitama Agricultural Tech. Res. Center)
Student Trainee
Yuzo MARUYAMA (Tokyo Denki Univ.)

List of Publications & Presentations
Publications[Original Papers]
R. Tabassum, T. Dosaka, H. Ichida, Y. Ding, T. Abe, and T. Katsube-Tanaka, “The conditional chalky grain mutant ‘ﬂo11-2’ of rice (Oryza
sativa L.) is sensitive to high temperature and useful for studies on chalkiness,” Plant Prod. Sci. 24, 230–243 (2020).
S. Muramatsu, K. Atsuji, K. Yamada, K. Ozawa, H. Suzuki, T. Takeuchi, Y. Hashimoto-Marukawa, Y. Kazama, T. Abe, K. Suzuki, andO. Iwata, “Isolation and characterization of a motility-defective mutant of Euglena gracilis,” PeerJ 8, e10002 (2020).
K. Tsuneizumi, M. Yamada, H. J. Kim, H. Ichida, K. Ichinose, Y. Sakakura, K. Suga, A. Hagiwara, M. Kawata, T. Katayama, N. Tezuka,
T. Kobayashi, M. Koiso, and T. Abe, “Application of heavy-ion-beam irradiation to breeding large rotifer,” Biosci. Biotechnol. Biochem.
85, 703–713 (2021).
H. Tojo, A. Nakamura, A. Ferjani, Y. Kazama, T. Abe, and H. Iida, “A method enabling comprehensive isolation of arabidopsis mutants
exhibiting unusual root mechanical behavior,” Front. Plant Sci. 12, 646404 (2021).
T. Kashiwabara, N. Kitajima, R. Onuma, N. Fukuda, S. Endo, Y. Terada, T. Abe, A. Hokura, and I. Nakai, “Synchrotron micro-X-ray
ﬂuorescence imaging of arsenic in frozen-hydrated sections of a root of Pteris vittate,” Metallomics 13, mfab009 (2021).

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A. Sanjaya, Y. Kazama, K. Ishii, R. Muramatsu, K. Kanamaru, S. Ohbu, T. Abe, and M. T. Fujiwara, “An argon-ion-induced pale green
mutant of arabidopsis exhibiting rapid disassembly of mesophyll chloroplast grana,” Plants 10, 848 (2021).
H. Udagawa, H. Ichida, T. Takeuchi, T. Abe, and Y. Takakura, “Highly eﬃcient and comprehensive identiﬁcation of ethyl
methanesulfonate-induced mutations in Nicotiana tabacum L. by whole-genome and whole-exome sequencing,” Front. Plant Sci. 12,671598 (2021).
Y. Sato, H. Nagae, G. N. Nishihara, and R. Terada, “The photosynthetic response of cultivated juvenile and mature Undaria pinnatiﬁda(Laminariales) sporophytes to light,” J. Appl. Phycol. 33, 3437–3448 (2021).
A. Sanjaya, R. Muramatsu, S. Sato, M. Suzuki, S. Sasaki, H. Ishikawa, Y. Fujii, M. Asano, R. D. Itoh, K. Kanamaru, S. Ohbu, T. Abe,Y. Kazama, and M. T. Fujiwara, “Arabidopsis EGY1 is critical for chloroplast development in leaf epidermal guard cells,” Plants 10,1254 (2021).
R. D. Itoh, K. P. Nakajima, S. Sasaki, H. Ishikawa, Y. Kazama, T. Abe, and M. T. Fujiwara, “TGD5 is required for normal morphogenesisof non-mesophyll plastids, but not mesophyll chloroplasts, in arabidopsis,” Plant J. 107, 237–255 (2021).
A. M. Okasa, R. Sjahril, M. Riadi, M. Mahendradatta, T. Sato, K. Toriyama, K. Ishii, Y. Hayashi, and T. Abe, “Evaluation of Toraja(Indonesia) local aromatic rice mutant developed using heavy-ion beam irradiation,” Biodiversitas 22, 3474–3481 (2021).
V. Q. Nhat, Y. Kazama, K. Ishii, S. Ohbu, H. Kunitake, T. Abe, and T. Hirano, “Double mutant analysis with the large ﬂower mutant,ohbana1, to explore the regulatory network controlling the ﬂower and seed sizes in Arabidopsis thaliana,” Plants 10, 1881 (2021).
Y. Sato, T. Hirano, H. Ichida, N. Fukunishi, T. Abe, and S. Kawano, Extending the cultivation period of Undaria pinnatiﬁda by using
regional strains with phenotypic diﬀerentiation along the Sanriku coast in northern Japan, Phycology 1, 129–142 (2021).
K. Ishii, S. Kawano, and T. Abe, “Creation of green innovation and functional gene analyses using heavy-ion beam breeding,” Cytologia(Tokyo) 84, 273–274 (2021).
T. Takesita, K. Takita, K. Ishii, Y. Kazama, T. Abe, and S. Kawano, “Robust mutants isolated through heavy-ion beam irradiation andendurance screening in the green Alga Haematococcus pluvialis,” Cytologia (Tokyo) 84, 283–289 (2021).
Y. Sato, T. Hirano, Y. Hayashi, N. Fukunishi, T. Abe, and S. Kawano, “Screening for high-growth mutants in sporophytes of Undaria
pinnatiﬁda using heavy-ion beam irradiation,” Cytologia (Tokyo), 84, 291–295 (2021).
K. Hashimoto, Y. Kazama, H. Ichida, T. Abe, and K. Murai, “Eincorn wheat (Triticum monococcum) mutant extra-early ﬂowering 4,
generated by heavy-ion beam irradiation, has a deletion of the LIGHT-REGULATED WD1 homolog,” Cytologia (Tokyo) 84, 297–302(2021).
R. Morita, H. Ichida, Y. Hayashi, K. Ishii, Y. Shirakawa, S. Usuda-Kogure, K. Ichinose, M. Hatashita, K. Takagi, K. Miura, M. Kusajima,
H. Nakashita, T. Endo, Y. Tojo, Y. Okumoto, T. Sato, K. Toriyama, and T. Abe, “Responsible gene analysis of phenotypic mutants
revealed the linear energy transfer (LET)-dependent mutation spectrum in rice,” Cytologia (Tokyo) 84, 303–309 (2021).
T. Hirano, Y. Matsuyama, A. Hanada, Y. Hayashi, T. Abe, and H. Kunitake, “DNA damage response of Cyrtanthus mackenii male gametes
following argon ion beam irradiation,” Cytologia (Tokyo) 84, 311–315 (2021).
A. Matsuta, T. Mayuzumi, H. Katano, M. Hatashita, K. Takagi, Y. Hayashi, T. Abe, K. Murai, and Y. Kazama, “The eﬀect of heavy-ion
beams with high linear energy transfer on mutant production in M1 generation of Torenia Fournieri,” Cytologia (Tokyo) 84, 317–322(2021).
T. Kobayashi, M. Takahashi, R. Nishijima, R. Sugiyama, K. Ishii, S. Kawano, and Y. Kazama, “Eﬀective chromosomal preparation
protocol for the dioecious plant Silene Latifolia,” Cytologia (Tokyo) 84, 323–328 (2021).
W. Aonuma, H. Kawamoto, Y. Kazama, K. Ishii, T. Abe, and S. Kawano, “Male/female trade-Oﬀ in hermaphroditic Y-chromosome
deletion mutants of the dioecious plant Silene Latifolia,” Cytologia (Tokyo) 84, 329–338 (2021).

[Review Articles]
常泉和秀, 阿部知子, 「重イオンビームで魚養殖餌料に適した大型ワムシを創る」, バイオサイエンスとインダストリー 79, 284–287(2021).
T. Abe, “Ion beam mutagenesis for crop improvement,” Plant Breeding & Genetics Newsletter 47, 17–19 (2021).
K. Murai and T. Abe, “Development of early-ﬂowering durum wheat suitable for the climate conditions of the Hokuriku region of Japanthrough conventional breeding aided by heavy ion beam mutagenesis,” Plant Breeding & Genetics Newsletter 47, 20–22 (2021).

[Book]
T. Abe, H. Ichida, Y. Hayashi, R. Morita, Y. Shirakawa, K. Ishii, T. Sato, H. Saito, and Y. Okumoto, “Ion beam mutagenesis—An
innovative and eﬀective method for plant breeding and gene discovery,” in S. Sivasankar, N. Ellis, L. Jankuloski, and I. Ngelbrecht(eds.), Mutation Breeding, Genetic Diversity and Crop Adaptation to Climate Change, The Joint FAO/IAEA Programme, CABI,
Oxfordshire UK, pp. 411–423 (2021).

Presentations[International Conferences/Workshops]
T. Abe (invited), “New varieties developed in various crops using ion-beam irradiation in Japan,” The Contribution of Innovative Nuclear
Technology to Sustainable Agriculture, VCDNP (Vienna Center for Disarmament and Non-proliferation), Online, April 1, 2021.
T. Abe (invited), “New mutagen-ion beam-development for ion-beam breeding technology over the last two decades in Japan,” Consultants
meeting on radiation-induced crop genetic diversity and functional genomics to accelerate variety development for tolerance to climate
extremes, Joint FAO/IAEA Center of Nuclear Techniques in Food and Agriculture, Online, August 2–6, 2021.
J. G. Pablo, M. Lindley, A. Isozaki, K. Hiramatsu, W. Peterson, K. Ishii, T. Abe, and K. Goda, “High-throughput Raman ﬂow cytometry- 286 -

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for directed evolution,” The Great Scientiﬁc Exchange 2021, Providence RI, USA, September 26–October 1, 2021.
H. Park, Y. Narasako, T. Abe, H. Kunitake, and T. Hirano, “Construction of mutant library by heavy-ion beam irradiation: toward eﬃcient
sweet potato breeding,” JKTC Extra Edition 2021 International Student Online Seminar, “The future of plant, environment, and human
with/after COVID-19,” Online, November 22, 2021.

[Domestic Conferences/Workshops]
T. Abe (口頭発表), K. Tsuneizumi, M. Yamada, H. J. Kim, H. Ichida, K. Ichinose, Y. Sakakura, K. Suga, A. Hagiwara, M. Kawata,
T. Katayama, N. Tezuka, T. Kobayashi, and M. Koiso, “Application of heavy-ion-beam irradiation to breeding large rotifer,” 第一回沖縄科学技術大学院大学—理研連携シンポジウム, 沖縄県国頭郡恩納村 (沖縄科学技術大学院大学), 2021 年 4 月 6–7 日.
T. Abe (口頭発表) and H. Ichida, “Heavy-ion beam mutagenesis and its molecular characteristics in plants,” ibid.
T. Abe (ポスター発表), R. Morita, H. Ichida, Y. Hayashi, Y. Shirakawa, and K. Ichinose, “Heavy ion mutagenesis in rice (Oryza sativaL.),” ibid.
常泉和秀 (口頭発表), 「重イオンビーム照射による有用系統の作出」, 理化学研究所—水産研究・教育機構連携ワークショップ, オ
ンライン, 2021 年 4 月 27 日.
阿部知子（招待講演）, 「イオンビーム育種技術による特産品の創成」, 先端技術セミナー兼福井イオンビーム育種研究会高エネル
ギービーム利活用に向けた展望〜イオンビームを用いた育種と社会実装に向けた研究〜, オンライン, 2021 年 9 月 15 日.
鳥山欽哉 (口頭発表), 武田信哉, 市田裕之, 阿部知子, 有村慎一, 風間智彦, 陳孫禄, 金岡義高, 貴島祐治, 「台中 65 号の細胞質を持つ
Oryza glaberrima の CMS 関連遺伝子の解析」, 日本育種学会第 140 回講演会, オンライン, 2021 年 9 月 23–25 日.
阿部知子 (口頭発表), 森田竜平, 市田裕之, 林依子, 石井公太郎, 白川侑希, 臼田祥子, 一瀬勝紀, 畑下昌範, 高城啓一, 三浦孝太郎, 草島美幸, 仲下英雄, 遠藤貴司, 奥本裕, 佐藤雅志, 鳥山欽哉, 「重イオンビームの LET がイネ変異体の原因遺伝子に与える影響」, 同上.
高倉由光 (口頭発表), 市田裕之, 宇田川久史, 竹内貴規, 阿部知子, 「Whole-exome sequencing を用いたタバコの EMS 変異体におけ, 同上.
る網羅的変異検出法の開発」
風間裕介 (ポスター発表), 黛隆宏, 松田彩花, 畑下昌範, 高城啓一, 阿部知子, 村井耕二, 「重イオンビームを用いたトレニア変異系
, 同上.
統の作出」
村井耕二 (ポスター発表), 橋本佳澄, 風間裕介, 阿部知子, 「CO-like 遺伝子の日周期発現パターンシフトが超極早生コムギ変異体
extra early-ﬂowering 4 (EXE4) における早生性」, 同上.
阿部知子 (ポスター発表), 田中朋之, 小林麻子, 「地球温暖化とお米の未来/福井のいろいろなお米」, ふるさと環境フェア 2021, 福
井県福井市 (福井県産業会館), 2021 年 11 月 23 日.
阿部知子 (口頭発表), 橋口太亮, 飯山光太郎, 長井純一, 藤川和博, 「サツマイモ『シロユタカ』と外観識別可能な『こなみずき』欠刻葉系統の作出」, 第 84 回（令和 3 年度）九州農業研究発表会, 作物部会, オンライン, 2021 年 12 月 7–8 日.
村井耕二 (ポスター発表), 橋本佳澄, 風間裕介, 阿部知子, 「WD リピートタンパク質遺伝子（WWDR1）を欠失した変異体 exe4 は
どうしてこんなに早生なのか？」, 第 16 回ムギ類研究会, オンライン, 2021 年 12 月 25 日.

Award
T. Abe, Women in plant mutation breeding award, Joint FAO/IAEA Center, September 20, 2021.

Press Release「赤ちゃんマグロの餌, ワムシの大型化に成功—重イオンビームで 『メガワムシ』が誕生—」, 理化学研究所, 水産研究・教育機構,
長崎大学, 2021 年 1 月 15 日.

Patents
久村麻子, 諸岡淳司, 阿部知子, 林依子, 平野智也, 石井公太郎, キク 「長崎 SYC1」, 品種登録出願番号 35321, 出願日 2021 年 3 月
26 日.
中村茂和, 中嶌輝子, 平井実季, 小林康志, 加々美裕, 澤野郁夫, 稲葉元良, 小野章子, 寺岡毅, 馬場明子, 荒木勇二, 青島加奈子, 吉川公規,
土田友香, 阿部知子, 福西暢尚, 龍頭啓充, ウンシュウミカン 「春しずか」, 品種登録出願番号 35533, 出願日 2021 年 6 月 28 日.

Outreach Activity
We established the “Asagao (morning glory) club” to deepen the understanding of our technology of mutation breeding. The club
distributes the morning glory seeds irradiated with C-ion on request, and collects and compiles the observation reports of their growth.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Accelerator Applications Research Division
Beam Mutagenesis Group
Plant Genome Evolution Research Team
1. Abstract
Established in May 2018 and succeed in October 2020, the plant genome evolution research team studies the eﬀect of heavyion induced mutations on plant and microbial phenotypes. Chromosome rearrangements including translocations, inversions, anddeletions are thought to play an important role in evolution and have a greater potential to achieve large phenotypic changes. However,this potential has not been fully investigated due to the lack of an eﬀective method to induce and analyze complexed mutations.
We employ the population genomics approach with robust molecular biology and bioinformatics techniques to characterize genomic
mutations in model and non-model plant and microbial species, and create the future of mutation breeding.

2. Major Research Subjects(1) Genomics-based approach to revolutionize the mutagenesis in model and non-model plants and microbes(2) De novo genome sequencing and assembly of cultivars and isolates, and its application to evolution and breeding studies

3. Summary of Research Activity(1) Genomics-based approach to revolutionize the mutagenesis in model and non-model plants and microbes
Recent advances in genome sequencing and bioinformatics technology enabled us to obtain a genome-wide view of the induced
mutations in unselected populations. We chose baker’s yeast and a legume Lotus japonicus as model systems, irradiated diﬀerent
doses of carbon-ion beams to these organisms, and determined the dose-survival correlation. We isolated a semi-dwarf L. japonicus
mutant, identiﬁed the responsible mutation by whole-genome sequencing, and started to characterize the phenotypic traits of thismutant. Phenotyping analysis indicated that the isolated semi-dwarf mutant shows signiﬁcantly shortened internode length while still
maintaining good seed production equivalent to the wild-type plants. The semi-dwarf L. japonicus mutant is suitable for high-density
cultivation in the laboratory environment and may serve as an eﬃcient model platform for legume-Rhizobium symbiosis.
(2) De novo genome sequencing and assembly of new cultivars and isolates, and its application to evolution and breedingstudies
We apply the latest de novo genome sequencing technology to elucidate genome sequences in diﬀerent cultivars and isolates andsuccessfully created some high-quality draft genome sequences. The determined and assembled draft genome sequences are subjected
to gene predictions and functional annotations, then shared in a searchable data visualization and analysis system accessible throughthe internet. With these fundamental genome information resources, we and our collaborators work together to achieve new ﬁndingsthat will achieve major advances in both science and practical applications. These resources as well as the overall experimental
techniques and the analysis pipeline are essential to further expand our genome-wide mutation and evolution approach to previously
uncharacterized non-model species.

Members
Team Leader
Hiroyuki ICHIDA
Postdoctoral Researcher
Ni LEI
Visiting Scientist
Yusuke KAZAMA (Fukui Prefectural Univ.)
Student Trainee
Alvin SANJAYA (Sophia Univ.)
Administrative Part-time Workers
Yusaku NISHIMIYA (Administrative Part-time Worker II)

Chiharu HINO (Administrative Part-time Worker II)

List of Publications & Presentations
Publications[Original Papers]
Y. Sato, T. Hirano, H. Ichida, N. Fukunishi, T. Abe, and S. Kawano, “Extending the cultivation period of Undaria pinnatiﬁda by using
regional strains with phenotypic diﬀerentiation along the Sanriku coast in northern Japan,” Phycology 1, 129–142 (2021).
K. Hashimoto, Y. Kazama, H. Ichida, T. Abe, and K. Murai, “Einkorn wheat (Triticum monococcum) mutant extra-early ﬂowering 4,
generated by heavy-ion beam irradiation, has a deletion of the LIGHT-REGULATED WD1 homolog,” Cytologia 86, 297–302 (2021).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

R. Morita, H. Ichida, Y. Hayashi, K. Ishii, Y. Shirakawa, S. Usuda-Kogure, K. Ichinose, M. Hatashita, K. Takagi, K. Miura, M. Kusajima,
H. Nakashita, T. Endo, Y. Tojo, Y. Okumoto, T. Sato, K. Toriyama, and T. Abe, “Responsible gene analysis of phenotypic mutants
revealed the linear energy transfer (LET)-dependent mutation spectrum in rice,” Cytologia 86, 303–309 (2021).
H. Udagawa, H. Ichida, T. Takeuchi, T. Abe, and Y. Takakura, “Highly eﬃcient and comprehensive identiﬁcation of ethyl
methanesulfonate-induced mutations in Nicotiana tabacum L. by whole-genome and whole-exome sequencing,” Front. Plant Sci. 12,671598 (2021).
H. Murata, S. Nakano, T. Yamanaka, T. Shimokawa, T. Abe, H. Ichida, Y. Hayashi, and K. Tahara, “Argon-ion beam induced mutantsof the ectomycorrhizal agaricomycete Tricholoma matsutake defective in β-1,4 endoglucanase activity promote the seedling growth ofPinus densiﬂora in vitro,” Botany 99, 139–149 (2021).
R. Tabassum, T. Dosaka, R. Morita, H. Ichida, Y. Ding, T. Abe, and T. Katsube-Tanaka, “The conditional chalky grain mutant ‘ﬂo11-2’
of rice (Oryza sativa L.) is sensitive to high temperature and useful for studies on chalkiness,” Plant Prod. Sci. 24, 230–243 (2021).
K. Tsuneizumi, M. Yamada, H. J. Kim, H. Ichida, K. Ichinose, Y. Sakakura, K. Suga, A. Hagiwara, M. Kawata, T. Katayama, N. Tezuka,
T. Kobayashi, M. Koiso, and T. Abe, “Application of heavy-ion-beam irradiation to breeding large rotifer,” Biosci. Biotechnol. Biochem.
85, 703–713 (2021).

Presentations[International Conference/Workshop]
T. Abe (invited), Y. Hayashi, R. Morita, Y. Shirakawa, and H. Ichida, “Ion-beam mutagenesis for creation of new varieties and discovery
of genes”, Bangabandhu International Conference on Sustainable Agriculture through Nuclear and Frontier Research, Online, January
2022.

[Domestic Conferences/Workshops]
H. Ichida (invited), “Heavy-ion beam mutagenesis and its molecular characteristics in plants”, RIKEN-OIST Joint Symposium, Series 1:
Green and Blue Planet How Can Ecological Research Shape Our Future?, Okinawa (OIST), April 2021.
森田竜平, 市田裕之, 林依子, 石井公太郎, 白川侑希, 臼田祥子, 一瀬勝紀, 畑下昌範, 高城啓一, 三浦孝太郎, 草島美幸, 仲下英雄, 遠藤, 日本育種学会
貴司, 奥本裕, 佐藤雅志, 鳥山欽哉, 阿部知子, 「重イオンビームの LET がイネ変異体の原因遺伝子に与える影響」
第 140 回講演会, オンライン, 2021 年 9 月 24 日.
市田裕之, 宇田川久史, 竹内貴規, 阿部知子, 高倉由光, 「Whole-exome sequencing を用いたタバコ EMS 変異体における網羅的変異検出法の開発」, 日本育種学会 第 140 回講演会, オンライン, 2021 年 9 月 25 日.
武田信哉, 市田裕之, 阿部知子, 有村慎一, 陳孫禄, 金岡義高, 貴島祐治, 鳥山欽哉, 「台中 65 号の細胞質を持つ Oryza glaberrima のCMS 関連遺伝子の解析」, 日本育種学会 第 140 回講演会, オンライン, 2021 年 9 月 25 日.
N. Lei, T. Abe, and H. Ichida, “Massive genome sequencing analysis of accelerated carbon-ion-induced mutations in Saccharomyces
cerevisiae”, RIKEN-OIST Joint Symposium, Series 2: Kinds of Minds—what is thinking?, Online, October 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Accelerator Applications Research Division
RI Application Research Group
1. Abstract
RI Application Research Group promotes industrial applications of radioisotopes (RIs) and ion beams at RIKEN RI Beam Factory(RIBF). Nuclear Chemistry Research Team develops production technologies of useful RIs for application studies in nuclear andradiochemistry. The team also develops technologies of mass spectrometry for trace-element and isotope analyses and apply themto the research ﬁelds such as cosmochemistry, environmental science, archaeology, and so on. Industrial Application Research Team
promotes industrial applications of the accelerator facility and its related technologies.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)

Research and development of RI production technologies at RIBF
RI application researchDistribution of RIs produced at RIBF
Development of radioactive targets and sources
Development of trace element analyses using accelerator techniques and their applications to geoscience and archaeologicalresearch ﬁelds
Development of chemical materials for ECR ion sources of the RIBF accelerators
Development of technologies on industrial utilization and novel industrial applications of RIBF
Support of industrial utilization of the heavy-ion beams at RIBF
Support of materials science experiments

3. Summary of Research Activity
See the subsections of Nuclear Chemistry Research Team and Industrial Application Research Team.

Members
Director
Hiromitsu HABA

List of Publications & Presentations
See the subsections of Nuclear Chemistry Research Team and Industrial Application Research Team.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Accelerator Applications Research Division
RI Application Research Group
Nuclear Chemistry Research Team
1. Abstract
The Nuclear Chemistry Research Team develops production technologies of unique radioisotopes (RIs) at RIKEN RI Beam Factory (RIBF) and applies them in the research ﬁelds of physics, chemistry, biology, engineering, medicine, pharmaceutical and environmental sciences. The puriﬁed RIs such as 65 Zn, 67 Cu, 85 Sr, 88 Y, and 109 Cd are delivered to universities and institutes through Japan
Radioisotope Association. We also develop new technologies of mass spectrometry for the trace-element analyses using accelerator
techniques and apply them to the research ﬁelds such as cosmochemistry, environmental science, archaeology, and so on. We perform
various isotopic analyses on the elements such as S, Pd, and Pb using ICP-MS, TIMS, and IRMS. We also develop radioactive targets
and sources, and chemical materials such as metallic 238 U, 238 UO2 , and 48 CaO for ECR ion sources of the heavy-ion accelerators at
RIBF.

2. Major Research Subjects(1) Research and development of RI production technologies at RIBF
(2) RI application research(3) Development of trace element analyses using accelerator techniques and their applications to geoscience and archaeologicalresearch ﬁelds(4) Development of radioactive targets and sources, and chemical materials for ECR ion sources of the heavy-ion accelerators at
RIBF

3. Summary of Research Activity(1) Research and development of RI production technologies at RIBF and RI application research
Due to its high sensitivity, the radioactive tracer technique has been successfully applied for investigations of the behavior ofelements in the ﬁelds of chemistry, biology, engineering, medicine, pharmaceutical and environmental sciences. We have been developing production technologies of useful radioisotopes (RIs) at RIBF and conducting their application studies in collaboration withmany researchers in various ﬁelds. With 30-MeV proton, 24-MeV deuteron, and 50-MeV alpha beams from the AVF cyclotron, we
presently produce about 100 RIs from 7 Be to 211 At. Among them, 65 Zn, 67 Cu, 85 Sr, 88 Y, and 109 Cd are delivered to Japan Radioisotope
Association for fee-based distribution to the general public in Japan. Our RIs are also distributed to researchers under the Supply
Platform of Short-lived Radioisotopes for Fundamental Research, supported by MEXT KAKENHI in FY2016-2027. On the other
hand, RIs of a large number of elements are simultaneously produced from metallic targets such as nat Ti, nat Ag, nat Hf, 197 Au, and 232 Th
irradiated with a 135 MeV/nucleon 14 N beam from the RIKEN Ring Cyclotron. These multitracers are also supplied to universities
and institutes as collaborative research.
In 2021, we developed production technologies of RIs such as 28 Mg, 44m Sc, 44 Ti, 67 Cu, 111 Ag, 141 Ce, 186 Re, 196 Au, 211 At, 212 Pb,
224
Ra, 225 Ac, and 229 Pa which were strongly demanded but lack supply sources in Japan. We also investigated the excitation functions
for the 27 Al(α, x), nat Ca(p, x), nat Ca(d, x), nat Ca(α, x), nat Cr(d, x), 45 Sc(p, x), 55 Mn(p, x), nat La(α, x), 159 Tb(α, x), and 141 Pr(p, x) reactions to eﬀectively and quantitatively produce useful RIs. We used radiotracers of 44 Ti, 211 At, 212 Pb, 224 Ra, and 229 Pa for application
studies in chemistry, 44m Sc, 67 Cu, 111 Ag, 141 Ce, 186 Re, 211 At, and 225 Ac in nuclear medicine, and 28 Mg, 44m Sc, 67 Cu, 186 Re, 196 Au, and211
At in engineering. We also produced 65 Zn, 67 Cu, 85 Sr, 88 Y, and 109 Cd for our scientiﬁc research on a regular schedule and supplied
the surpluses through Japan Radioisotope Association to the general public. In 2021, we accepted 2 orders of 65 Zn with a total activityof 15 MBq, 1 order of 67 Cu with 10 MBq, 8 orders of 85 Sr with 34.7 MBq, 2 orders of 88 Y with 2 MBq, and 1 order of 109 Cd with
5 MBq. We also distributed 28 Mg (2 MBq × 1), 67 Cu (100 MBq × 1), 88 Zr (1 MBq × 2), 95 Nb (1 MBq × 1), 111 Ag (1 MBq × 1), 141 Ce(0.24 MBq × 1, 0.5 MBq × 1), 175 Hf (1 MBq × 2), 179 Ta (0.5 MBq × 1), and 211 At (5 MBq × 3, 10 MBq × 1, 50 MBq × 6, 80 MBq
× 2, and 100 MBq × 3) under the Supply Platform of Short-lived Radioisotopes for Fundamental Research.
(2) Superheavy element chemistry
Chemical characterization of newly-discovered superheavy elements (SHEs, atomic number Z ≥ 104) is an extremely interesting and challenging subject in modern nuclear and radiochemistry. We are developing SHE production systems as well as rapid
single-atom chemistry apparatuses at RIBF. Using heavy-ion beams from RILAC and AVF, 261 Rf (Z = 104), 262 Db (Z = 105),265
Sg (Z = 106), and 266 Bh (Z = 107) are produced in the 248 Cm(18 O, 5n)261 Rf, 248 Cm(19 F, 5n)262 Db, 248 Cm(22 Ne, 5n)265 Sg, and248
Cm(23 Na, 5n)266 Bh reactions, respectively, and their chemical properties are investigated.
We installed a gas-jet transport system to the focal plane of the gas-ﬁlled recoil ion separator GARIS at SRILAC. This system isa promising approach for exploring new frontiers in SHE chemistry: the background radiations from unwanted products are strongly
suppressed, the intense primary heavy-ion beam is absent in the gas-jet chamber, and hence the high gas-jet extraction yield is attained.
Furthermore, the beam-free condition makes it possible to investigate new chemical systems. To realize aqueous chemistry studies of
Sg and Bh, we have been developing a continuous and rapid solvent extraction apparatus which consists of a continuous dissolution
apparatus Membrane DeGasser (MDG), a Flow Solvent Extractor (FSE), and a liquid scintillation detector for α/SF-spectrometry.
On the other hand, we produced radiotracers of 88 Zr, 95 Nb, 175 Hf, and 179 Ta at the AVF cyclotron and conducted model experiments
for aqueous chemistry studies on Rf and Db. We also developed a cryogenic RF-carpet gas cell, which will be placed on the focal- 291 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

plane of GARIS and connected to a gas-chromatograph apparatus, for the future gas-phase chemistry of the short-lived SHEs (half-life
T 1/2 < 1 s).
(3) Development of trace element analyses using accelerator techniques and their applications to geoscience and archaeologicalresearch ﬁelds
We have been developing the ECR Ion Source Mass Spectrometer (ECRIS-MS) for trace element analyses. We renovated thedetection system of ECRIS-MS and evaluated its sensitivity and mass resolution power. We equipped a laser-ablation system with an
ion source and a pre-concentration system to achieve high-resolution analyses for noble gases such as Kr and Xe.
Using the conventional ICP-MS, TIMS, IRMS, and so on, we studied Pb and S isotope ratios on cinnabar and asphalt samples
from ancient ruins in Japan to elucidate the distribution of goods in the archaic society and to reveal the establishment of the Yamato
dynasty in the period from Jomon to Tumulus. We established a sampling technique for pigment without any damages on the artifacts
or wall paintings, using a S-free adhesive tape. Then, we applied the technique to the analyses of vermilion used in three representative
tombs from Kofun period in Japan. We also applied the technique to the analyses of the red pigment from Roman ruins (Badalona,
Spain). Furthermore, we started to develop a method for the analyses of 3 isotopic abundance ratios (32 S, 33 S, and 34 S) of sulfur
as a new parameter for identiﬁcation of source mine. By analyzing these isotope ratios, it is possible to analyze the MIF (massindependent-fractionation) eﬀect. This is also expected to provide a new parameter for the analysis of environmental dynamics.
In FY2021, we operated ICP-MS as a shared-use instrument and analyzed a total of 179 samples from ﬁve laboratories.
(4) Development of chemical materials for ECR ion sources of the heavy-ion accelerators at RIBF
In 2021, we prepared 238 UO2 on a regular schedule for 238 U-ion accelerations with the 28-GHz ECR of RILAC II.

Members
Team Leader
Hiromitsu HABA
Research & Development Scientist
Hiroo HASEBE
Special Postdoctoral Researcher
Yudai SHIGEKAWA
Postdoctoral Researchers
Yang WANG

Xiaojie YIN

Technical Staﬀ
Akihiro NAMBU
Junior Research Associate
Motoki SATO
Special Temporary Research Scientist
Kazuya TAKAHASHI
Visiting Researcher
Mizuki UENOMACHI
Research Part-time Workers
Michiko KITAGAWA (Research Part-time Worker I)
Nozomi SATO (Research Part-time Worker I)

Sachiko USUDA (Research Part-time Worker I)
Minako OSANAI (Research Part-time Worker II)

Research Consultant
Hisaaki KUDO (Niigata Univ.)
Visiting Scientists
Msayuki AIKAWA (Hokkaido Univ.)
Kazuhiko AKIYAMA (Tokyo Metropolitan Univ.)
Takatoshi AOKI (Univ. of Tokyo)
Masato ASAI (JAEA)
Ferenc DITROI (ATOMKI)
Shuichiro EBATA (Saitama Univ.)
Osuke FUJIMOTO (Fujiﬁlm Toyama Chemical Co., Ltd.)
Yuichi FUNASE (Fujiﬁlm Toyama Chemical Co., Ltd.)
Takahiro HIRAKI (Okayama Univ.)

Hayato IKEDA (Tohoku Univ.)
Masamichi KAJITA (Fujiﬁlm Toyama Chemical Co., Ltd.)
Yoshitaka KASAMATSU (Osaka Univ.)
Hiroshi KATO (Fujiﬁlm Toyama Chemical Co., Ltd.)
Mayeen U. KHANDAKER (Sunway Univ.)
Hidetoshi KIKUNAGA (Tohoku Univ.)
Yoshikatsu KOGA (Nat’l Cancer Center)
Shoko KUBOTA (Fujiﬁlm Toyama Chemical Co., Ltd.)
Takumi KUBOTA (Kyoto Univ.)- 292 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Zoltan SZUCS (ATOMKI)
Sandor TAKACS (ATOMKI)
Hiroyuki TAKAHASHI (Univ. of Tokyo)
Miho TAKAHASHI (Tokyo Univ. of Marine Sci. and Tech.)
Miwako TAKAHASHI (QST)
Hiroki TAKASHIMA (Nat’l Cancer Center)
Atsushi TOYOSHIMA (Osaka Univ.)
Kazuaki TSUKADA (JAEA)
Naoyuki UKON (Fukushima Medical Univ.)
Ahmed R. USMAN (Umaru Musa Yar’adua Univ.)
Takahiro YAMADA (Kindai Univ.)
Chunli YANG (Inst. of Modern Phys./Chinese Academy ofSci.)
Akihiko YOKOYAMA (Kanazawa Univ.)
Zenko YOSHIDA (ATOX Co., Ltd.)
Koji YOSHIMURA (Okayama Univ.)

Takahiko MASUDA (Okayama Univ.)
Toshimitsu MOMOSE (Int’l Univ. of Health and Welfare)Eri NAKAMURA (Fujiﬁlm Toyama Chemical Co., Ltd.)
Kenichiro OGANE (Int’l Univ. of Health and Welfare)
Miki OHTSUKA (Waseda Univ.)
Kazuhiro OOE (Osaka Univ.)
Kai ORIHARA (Fujiﬁlm Toyama Chemical Co., Ltd.)
Shinobu OSHIKIRI (Fujiﬁlm Toyama Chemical Co., Ltd.)
Yasutaka SAITO (Fujiﬁlm Toyama Chemical Co., Ltd.)Aya SAKAGUCHI (Tsukuba Univ.)
Miho SATAKE (Fujiﬁlm Toyama Chemical Co., Ltd.)
Tetsuya SATO (JAEA)
Yuki SATO (Fujiﬁlm Toyama Chemical Co., Ltd.)
Kenji SHIMAZOE (Univ. of Tokyo)
Keisuke SUEKI (Tsukuba Univ.)
Kentaro SUZUKI (Fujiﬁlm Toyama Chemical Co., Ltd.)
Visiting Technicians

Daiki MORI (Japan Radioisotope Association)
Shingo NAKAMURA (Metal Tech. Co., Ltd.)
Hiroki SHIBAHARA (ATOX Co., Ltd.)
Yuki TAKEMURA (ATOX Co., Ltd.)
Yasutaka TAKEUCHI (ATOX Co., Ltd.)
Shusaku TAZAWA (ATOX Co., Ltd.)Sho TOMITA (ATOX Co., Ltd.)
Yuichirou WAKITANI (Japan Radioisotope Association)
Mami YUKI (ATOX Co., Ltd.)

Hideyuki ARAI (Metal Tech. Co., Ltd.)
Hiroshi ARATA (Metal Tech. Co., Ltd.)
Mai FUKUMORI (ATOX Co., Ltd.)
Hidehiro HASHIMOTO (Metal Tech. Co., Ltd.)
Yoshiyuki IIZUKA (ATOX Co., Ltd.)
Masataka IMAMURA (Japan Radioisotope Association)
Shota KIMURA (Japan Radioisotope Association)
Yukiyoshi KON (Osaka Univ.)
Takashi KURIHARA (Metal Tech. Co., Ltd.)
Takahiro MIKAMOTO (Japan Radioisotope Association)
Student Trainees

Kenichi MORI (Kindai Univ.)
Ayumu NAGAI (Kanazawa Univ.)
Akihisa NAKAJIMA (Tsukuba Univ.)
Ryohei NAKANISHI (Osaka Univ.)
Teruhito NAKASHITA (Univ. of Tokyo)
Koichi OKAI (Okayama Univ.)
Motoki SATO (Univ. of Tokyo)
Kei SAWAMURA (Osaka Univ.)
Fumiki SENSUI (Univ. of Tokyo)
Katsuyuki TOKOI (Osaka Univ.)
Eisuke WATANABE (Osaka Univ.)
Kazeki YAMANE (Univ. of Tokyo)
Zihan ZHANG (Rikkyo Univ.)
Zhihong ZHONG (Univ. of Tokyo)

Kjeld A.A.G. BEEKS (Vienna Univ. of Tech.)
Desheng CHEN (Univ. of Chinese Academy of Sci.)
Gantumur DAMDINSUREN (Hokkaido Univ.)
Shunsuke FUJINO (Kindai Univ.)
Saki GOTO (Hokkaido Univ.)
Ming GUAN (Okayama Univ.)
Sena HAMAGAMI (Kindai Univ.)
Yukina HANADA (Hokkaido Univ.)
Mariko HISAMATSU (Osaka Univ.)
Hiroyuki HOSOKAWA (Kanazawa Univ.)
Xuan HOU (Univ. of Tokyo)
He HUANG (Hokkaido Univ.)
Mizuho KATO (Tsukuba Univ.)
Cheonghun KIM (Univ. of Tokyo)
Hongchang LIN (Univ. of Tokyo)

List of Publications & Presentations
Publications[Original Papers]
M. Aikawa, T. Maehashi, D. Ichinkhorloo, S. Ebata, Y. Komori, and H. Haba, “Activation cross sections of deuteron-induced reactions on
praseodymium up to 24 MeV,” Nucl. Instrum. Methods Phys. Res. B 498, 23 (2021).
D. Ichinkhorloo, M. Aikawa, Z. Tsoodol, T. Murata, M. Sakaguchi, Y. Komori, T. Yokokita, and H. Haba, “Production cross sectionsof dysprosium, terbium and gadolinium radioisotopes from the alpha-induced reactions on natural gadolinium up to 50 MeV,” Nucl.
Instrum. Methods Phys. Res. B 499, 46 (2021).
S. Manabe, H. Takashima, K. Ohnuki, Y. Koga, R. Tsumura, N. Iwata, Y. Wang, T. Yokokita, Y. Komori, S. Usuda, D. Mori, H. Haba,
H. Fujii, M. Yasunaga, and Y. Matsumura, “Stabilization of an 211 At-labeled antibody with sodium ascorbate,” ACS Omega 6, 14887(2021).
M. Sakaguchi, M. Aikawa, N. Ukon, Y. Komori, H. Haba, N. Otuka, and S. Takács, “Activation cross section measurement of the alphaparticle induced reaction on natural neodymium,” Appl. Radiat. Isot. 176, 109826 (2021).

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Y. Shigekawa, A. Yamaguchi, K. Suzuki, H. Haba, T. Hiraki, H. Kikunaga, T. Masuda, S. Nishimura, N. Sasao, A. Yoshimi, andK. Yoshimura, “Estimation of radiative half-life of 229m Th by half-life measurement of other nuclear excited states in 229 Th,” Phys.
Rev. C 104, 024306 (2021).
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa,
Y. Ito, D. Kaji, S. Kimura, H. Koura, J. J. Liu, H. Miyatake, J. -Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “First high-precision direct determination of the atomic mass of asuperheavy nuclide,” Phys. Rev. C 104, L021304 (2021).
S. Takács, F. Ditrói, Z. Szűcs, K. Brezovcsik, H. Haba, Y. Komori, M. Aikawa, M. Saito, T. Murata, M. Sakaguchi, and N. Ukon, “Cross
section measurement of alpha-particle-induced reactions on nat Sb,” Nucl. Instrum. Methods Phys. Res. B 505, 24 (2021).
N. Kitamura, N. Imai, H. Haba, S. Michimasa, S. Shimoura, and Y. Yamaguchi, “Production of 178 Hfm2 and a simple chemical separation
method for Hf recovery,” J. Radioanal. Nucl. Chem. 330, 721 (2021).
T. Niwase, M. Wada, P. Schury, P. Brionnet, S. D. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama,
S. Ishizawa, Y. Ito, D. Kaji, S. Kimura, J. Liu, H. Miyatake, J. Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, T. Tanaka, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “α-decay-correlated mass measurement of 206, 207g, m Rausing an α-TOF detector equipped multireﬂection time-of-ﬂight mass spectrographs system,” Phys. Rev. C 104, 044617 (2021).
T. Aoki, R. Sreekantham, B. K. Sahoo, B. Arora, A. Kastberg, T. Sato, H. Ikeda, N. Okamoto, Y. Torii, T. Hayamizu, K. Nakamura,
S. Nagase, M. Ohtsuka, H. Nagahama, N. Ozawa, M. Sato, T. Nakashita, K. Yamane, K. S. Tanaka, K. Harada, H. Kawamura, T. Inoue,
A. Uchiyama, A. Hatakeyama, A. Takamine, H. Ueno, Y. Ichikawa, Y. Matsuda, H. Haba, and Y. Sakemi, “Quantum sensing of theelectron electric dipole moment using ultracold entangled Fr atoms,” Quantum Sci. Technol. 6, 044008 (2021).
M. Aikawa, Y. Hanada, H. Huang, and H. Haba, “Activation cross sections of proton-induced reactions on praseodymium up to 30 MeV,”
Nucl. Instrum. Methods Phys. Res. B 508, 29 (2021).
A. Yakushev, L. Lens, C. E. Düllmann, M. Block, H. Brand, M. Dasgupta, T. Calverley, A. D. Nitto, M. Götz, S. Götz, H. Haba,
L. Harkness-Brennan, R-D. Herzberg, F. P. Heßberger, D. Hinde, A. Hübner, E. Jäger, D. Judson, J. Khuyagbaatar, B. Kindler, Y. Komori, J. Konki, J. V. Kratz, J. Krier, N. Kurz, M. Laatiaoui, B. Lommel, C. Lorenz, M. Maiti, A. K. Mistry, C. Mokry, Y. Nagame,P. Papadakis, A. Såmark-Roth, D. Rudolph, J. Runke, L. G. Sarmiento, T. K. Sato, M. Schädel, P. Scharrer, B. Schausten, J. Steiner,
P. Thörle-Pospiech, A. Toyoshima, N. Trautmann, J. Uusitalo, A. Ward, M. Wegrzecki, and V. Yakusheva, “First study on nihonium(Nh, element 113) chemistry at TASCA,” Front. Chem. 9, 753738 (2021).
E. Watanabe, Y. Kasamatsu, T. Yokokita, S. Hayami, K. Tonai, H. Ninomiya, N. Kondo, Y. Shigekawa, H. Haba, Y. Kitagawa,
M. Nakano, and A. Shinohara, “Anion-exchange experiment of Zr, Hf, and Th in HNO3 and quantum chemical study on the nitrate complexes toward chemical research on element 104, Rf,” Solvent Extr. Ion Exch., published online (December 31, 2021). DOI:
10.1080/07366299.2021.2020956 .
T. Minami, A. Takeuchi, S. Imazu, M. Okuyama, Y. Higashikage, T. Mizuno, K. Okabayashi, and K. Takahashi, “Identiﬁcation of sourcemine using sulfur, mercury, and lead isotope analyses of vermilion used in three representative tombs from Kofun period in Japan,”
J. Archaeol. Sci. 37, 102970 (2021).
D. Kim, M. Uenomachi, K. Shimazoe, and H. Takahashi, “Evaluation of single scattering correction method in Compton imaging system,”Nucl. Instrum. Methods Phys. Res. A 1010, 165568 (2021).
羽場宏光, 「理研における At-211 の製造分離状況と将来計画」, 放射線科学フロンティア〜孟宗竹〜, 第 3 号, p. 9 (2021).
島添健次, 上ノ町水紀, 吉野将生, 「コンプトン PET ハイブリッドカメラによる PET/SPECT 診断・治療における多核種撮像技術の開発」, Med. Imag. Tech. 39, 206 (2021).
T. Hayamizu, H. Haba, K. Nakamura, T. Aoki, H. Nagahama, K. S. Tanaka, N. Ozawa, M. Ohtsuka, and Y. Sakemi, “Development of
ultracold francium atomic sources towards the permanent EDM search,” Few-Body Syst. 63, 11 (2022).
T. Yokokita, S. Yano, Y. Komori, and H. Haba, “Anion- and cation-exchange studies of Zr, Hf, and Th using ion-exchange resin and ﬁberin H2 SO4 media for chemical characterization of sulfate complex of Rf,” J. Radioanal. Nucl. Chem. 331, 1127 (2022).
M. Aikawa, Y. Hanada, D. Ichinkhorloo, H. Haba, S. Takács, F. Ditrói, and Z. Szűcs, “Production cross sections of 47 Sc via alpha-particleinduced reactions on natural calcium up to 29 MeV,” Nucl. Instrum. Methods Phys. Res. B 515, 1 (2022).
M. Uenomachi, K. Shimazoe, and H. Takahashi, “Double photon coincidence crosstalk reduction method for multi-nuclide Compton
imaging,” J. Instrum. 17, P04001 (2022).

[Review Article]
羽場宏光, 小林奈通子, 永津弘太郎, 西弘大, 籏野健太郎, 福田光宏, 間賀田泰寛, 山田崇裕, 鷲山幸信, 渡部浩司, 「2019 年度 RI 製
造・利用調査報告書」, Radioisotopes 70, 251 (2021).

[Books]
羽場宏光, 「新元素ニホニウムはいかにして創られたか」, 東京化学同人, 176 ページ, 2021 年 12 月 17 日.
南武志, 高橋和也, 「旧練兵場遺跡出土赤色顔料（朱）の硫黄同位体比分析」, 香川県立善通寺養護学校移転に伴う埋蔵文化財発掘調査報告書「旧練兵場遺跡 (第 26 次調査)」, 香川県教育委員会, pp. 391–403, 2022 年 3 月.

[Proceedings]
羽場宏光, 「モニタリングポスト 第 58 回アイソトープ・放射線研究発表会印象記 パネル討論 我が国の RI 製造供給の現状と将来」, Isotope News, 778, 12 月号, 58 (2021).
南武志, 高橋和也, 「みやき町大塚遺跡出土朱の産地推定」, みやき町文化財調査報告書第 28 集みやき町内遺跡 確認・試掘調査報
告書, 佐賀県みやき町教育委員会, pp. 391–413 (2021).
A. Mukai, S. Hara, K. Yamagishi, R. Terabayashi, K. Shimazoe, Y. Tamura, H. Woo, T. Kishimoto, H. Kogami, Z. Zhihong, M. Ueno-- 294 -

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machi, A. Naurrachman, H. Takahashi, H. Asama, F. Ishida, H. Ebi, E. Takada, J. Kawarabayashi, K. Tanave, K. Kamada, and
H. Tomita, “Optimization of detector movement algorithm using decision trees analysis for radiation source identiﬁcation based on
4π gamma imaging,” in 2022 IEEE/SICE International Symposium on System Integration (SII), IEEE, pp. 1026–1029 (2022).

Presentations[International Conferences/Workshops]
M. Uenomachi (poster), K. Shimazoe, and H. Takahashi, “Double photon coincidence crosstalk reduction method for multi-nuclide
Compton imaging,” 22nd International Workshop on Radiation Imaging Detectors (22nd iWoRiD), Online, June 27–July 1, 2021.
K. Tanaka (poster), K. Hirano, A. Yamaguchi, H. Muramatsu, T. Hayashi, N. Yuasa, K. Nakamura, M. Takimoto, H. Haba, K. Shirasaki,
H. Kikunaga, K. Maehata, N. Y. Yamasaki, and K. Mitsuda, “Challenge to improve the 229 Th isomer energy measurement with TES
calorimeters,” 19th International Workshop on Low Temperature Detectors (LTD19), Online, July 19–29, 2021.
A. Yamaguchi (oral), Y. Shigekawa, H. Haba, and M. Wada, “Development of an RF-carpet gas cell to obtain an ion beam of thorium-229,”
32nd International Conference on Photonic, Electronic and Atomic Collisions (ViCPEAC 2021), Online, July 20–23, 2021.
H. Haba (invited), “Production and applications of radioisotopes at RIKEN RI Beam Factory,” International Discussion Meeting on Futureof Accelerator Applications and Radiotracers Research (FAAARR2021), Online, July 26–27, 2021.
M. Sato (oral), “Search for permanent EDM by using Fr atoms,” CNS Summer School, Wako, Japan, August 16–20, 2021.
H. Haba (invited), “Production of radioisotopes for application studies at RIKEN RI Beam Factory,” Snowmass’21 Workshop on HighPower Cyclotrons/FFAs, Online, September 7–9, 2021.
M. Uenomachi (oral), K. Shimazoe, K. Kamada, T. Orita, M. Takahashi, and H. Takahashi, “Development of Compton-PET hybrid imaging system with CeBr3 -SiPM arrays,” The 12th International Conference on Position Sensitive Detectors (PSD12), Online, September
12–17, 2021.
H. Takashima (oral), Y. Koga, S. Manabe, K. Ohnuki, R. Tsumura, T. Anzai, Y. Wang, X. Yin, A. Nambu, N. Sato, S. Usuda, H. Haba,
H. Fujii, Y. Matsumura, and M. Yasunaga, “Antitumor eﬀect of astatine-211-labeled anti-tissue factor antibody stabilized with sodium
ascorbate,” The 80th Annual Meeting of the Japanese Cancer Association, Yokohama, Japan, September 30–October 2, 2021.
T. Fukuchi (oral), H. Kikunaga, H. Haba, S. Yamamoto, and Y. Watanabe, “Titanium-44 phantom production and PET imaging for photon
activation analysis,” 2021 IEEE Nuclear Science Symposium and Medical Imaging Conference, Online, October 16–23, 2021.
M. Uenomachi (oral/poster), K. Ogane, Z. Zhong, K. Shimazoe, K. Kamada, H. Takahashi, Y. Wang, and H. Haba, “Simultaneous PET,
SPECT and therapeutic nuclides imaging with Compton-PET hybrid camera,” 2021 Virtual IEEE Nuclear Science Symposium andMedical Imaging Conference (2021 IEEE NSS/MIC), Online, October 16–23, 2021.
M. Sato (oral), “Search for permanent EDM by using Fr atoms,” SPIN 2021, Online, October 18–21, 2021.
H. Haba (invited), “Production and applications of radioisotopes at RIKEN RI Beam Factory -Search for new elements through diagnosis
and therapy of cancer-,” RIKEN-KFU (Kazan Federal University) 3rd Joint Symposium, Online, November 5–6, 2021.
T. Aoki (poster), R. Sreekantham, B. K. Sahoo, B. Arora, A. Kastberg, T. Sato, H. Ikeda, N. Okamoto, Y. Torii, T. Hayamizu, K. Nakamura,
S. Nagase, M. Ohtsuka, H. Nagahama, N. Ozawa, M. Sato, T. Nakashita, K. Yamane, K. S. Tanaka, K. Harada, H. Kawamura, T. Inoue,
A. Uchiyama, A. Hatakeyama, A. Takamine, H. Ueno, Y. Ichikawa, Y. Matsuda, H. Haba, and Y. Sakemi, “Quantum sensing of
the electron electric dipole moment using quantum entangled atoms,” International Symposium on Novel maTerials and quantum
Technologies (ISNTT2021), Online, December 16, 2021.
A. Yamaguchi (oral), Y. Shigekawa, H. Haba, M. Wada, and H. Katori, “Development of an RF-carpet gas cell to obtain a low-energy
thorium ion beam,” Second Workshop of the Center for Time, Constants and Fundamental Symmetries, Online, March 23, 2022.

[Domestic Conferences/Workshops]
福地知則 (口頭発表/ポスター発表), 金山洋介, 蔵地理代, 中谷友香, 羽場宏光, 森大輝, 横北卓也, 小森有希子, 山本誠一, 渡辺恭良,「複数トレーサー PET を用いた異なるがん診断薬の直接比較」, 第 15 回日本分子イメージング学会総会・学術集会, 熊本市, 2021
年 5 月 26–27 日.
髙島大輝 (口頭発表), 眞鍋史乃, 大貫和信, 古賀宣勝, 津村遼, 安西高廣, Wang Yang, Ying Xiaojie, 南部明弘, 佐藤望, 臼田祥子, 羽
場宏光, 藤井博史, 松村保広, 安永正浩, 「アルファ線放出核種アスタチン-211 結合抗組織因子抗体の前臨床試験」, 第 37 回日本
DDS 学会学術集会, 千葉市, 2021 年 6 月 29–30 日.
羽場宏光 (口頭発表), 「理研 RI ビームファクトリーにおける RI 製造供給」, 第 58 回アイソトープ・放射線研究発表会, オンライ
ン, 2021 月 7 月 7–9 日.
南部明弘 (口頭発表), Y. Xiaojie, 羽場宏光, 押切忍, 加藤寛, 日野明弘, 「232 Th ＋ 14 N 反応による 225 Ac の製造」
, 第 58 回アイソトー
プ・放射線研究発表会, オンライン, 2021 月 7 月 7–9 日.
羽場宏光 (口頭発表), 「RIBF 施設紹介」, 新学術領域研究（研究領域提案型）『学術研究支援基盤形成』短寿命 RI 供給プラット
フォーム成果報告会 兼 RI 利用研究会, オンライン, 2021 年 7 月 19–20 日.
井上貴之 (口頭発表), 羽場宏光 (口頭発表), 「2019 年度 RI 製造・利用調査概要報告」, 新学術領域研究（研究領域提案型）『学術研
究支援基盤形成』短寿命 RI 供給プラットフォーム成果報告会 兼 RI 利用研究会, オンライン, 2021 年 7 月 19–20 日.
上ノ町水紀 (招待講演), 「二光子同時計測法を用いたマルチ RI トレーサーイメージング技術の開発」, 電気学会調査専門委員会「放射線技術を利用した微量分析およびイメージング技術」, オンライン, 2021 年 8 月 6 日.
羽場宏光 (口頭発表), 「核化学ロードマップについて」, 第 59 回核化学夏の学校, オンライン, 2021 月 8 月 26–27 日.
中島朗久 (口頭発表), 坂口綾, 早川優太, 羽場宏光, 塚田和明, K. Hain, J. Zheng, 瀬古典明, 保科宏行, 山崎信哉, 末木啓介, 横山明彦,「質量分析による環境中 237 Np 定量法確立に向けて」, 日本地球化学会第 68 回年会, 弘前市/オンライン, 2021 年 9 月 6–10 日.
合川正幸 (口頭発表), 前橋拓斗, ダグワドルジ イチンホルロー, 江幡修一郎, 小森有希子, 羽場宏光, 「141 Pr 標的への重陽子入射反- 295 -

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応による 140 Nd 生成反応断面積の測定」, 日本原子力学会 2021 年秋の大会, オンライン, 2021 年 9 月 8–10 日.
上ノ町水紀 (口頭発表), 島添健次, 織田忠, 鎌田圭, 高橋浩之, 「CeBr3 ピクエル検出器を用いた Compton-PET hybrid camera の開発」, 日本原子力学会 2021 年秋の大会, オンライン, 2021 年 9 月 8–10 日.
庭瀬暁隆 (口頭発表), P. Schury, 和田道治, P. Brionnet, S. Chen, 橋本尚志, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 石澤倫,
伊藤由太, 加治大哉, 木村創大, 小浦寛之, 宮武宇也, J. Y. Moon, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 渡辺裕, H. Wollnik, W. Xian, S. X. Yan, 「超重核 257 Db の直接質量測定」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月
14–17 日.
岡井晃一 (口頭発表), K. Beeks, 藤本弘之, M. Guan, 羽場宏光, 原秀明, 海野弘之, 笠松良崇, 北尾真司, 小早川大貴, 小無健司, 増田
孝彦, 宮本祐樹, 平木貴宏, 笹尾登, T. Schumm, 瀬戸誠, 重河優大, 玉作賢治, 植竹智, J. Wang, 渡部信, 渡部司, 山口敦史, 安田勇輝,
依田芳卓, 吉見彰洋, 吉村浩司, 吉村太彦, 「トリウム 229 アイソマー状態からの真空紫外光探索」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
庭瀬暁隆 (口頭発表), 和田道治, P. Schury, P. Brionnet, S. D. Chen, 橋本尚志, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 石澤倫, 伊藤由太, 加治大哉, 木村創大, J. Liu, 宮武宇也, J. Y. Moon, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 田中
泰貴, 渡辺裕, H. Wollnik, W. Xian, S. X. Yan, 「MRTOF と α-TOF 検出器による, α 崩壊に相関した精密質量測定法の開拓」, 日本
放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
床井健運 (ポスター発表), 豊嶋厚史, 大江一弘, 角永悠一郎, 寺本高啓, 中川創太, 吉村崇, 笠松良崇, 羽場宏光, 王洋, 篠原厚, 「At が形成するハロゲン結合の解離エネルギー測定に向けた AtI の生成条件と揮発性の分析」, 日本放射化学会第 65 回討論会 (2021),
オンライン, 2021 年 9 月 22–24 日.
永井歩夢 (ポスター発表), 寺西翔, 坂口綾, 中島朗久, 羽場宏光, 横北卓也, 南部明弘, 横山明彦, 「トリウム標的への Li イオン照射によって生じる 236 U の ICP-MS による定量」, 日本放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
永井雄太 (ポスター発表), 青井景都, 丸山俊平, 西中一朗, 鷲山幸信, 羽場宏光, 横山明彦, 「核医学用アスタチン抽出に利用できる
イオン液体の研究」, 日本放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
中川創太 (口頭発表), 豊嶋厚史, 角永悠一郎, 大江一弘, 寺本高啓, 床井健運, 神田晃充, 吉村崇, 永田光知郎, 笠松良崇, 羽場宏光,
王洋, 篠原厚, 「電解酸化反応を用いた分子標的薬への 211 At 標識化法の開発」, 日本放射化学会第 65 回討論会 (2021), オンライ
ン, 2021 年 9 月 22–24 日.
黄栩昊 (口頭発表), 加藤弘樹, 角永悠一郎, 下山敦史, 樺山一哉, 片山大輔, 大江一弘, 豊嶋厚史, 羽場宏光, 王洋, 篠原厚, 深瀬浩一,「新規アルファ線ブラキセラピー開発に向けた At-211 標識金ナノ粒子の合成と機能評価」, 日本放射化学会第 65 回討論会 (2021),
オンライン, 2021 年 9 月 22–24 日.
寺本高啓 (ポスター発表), 大江一弘, 王洋, 羽場宏光, 豊嶋厚史, 「アスタチン化合物の分光・可視化にむけた新規手法の提案」, 日
本放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
重河優大 (ポスター発表), 床井健運, 山口敦史, W. Yang, Y. Xiaojie, 南部明弘, 佐藤望, 和田道治, 羽場宏光, 「Th-229m の壊変特性の解明に向けた高周波イオン収集・質量分離装置の開発」, 日本放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月
22–24 日.
西村峻 (ポスター発表), 雨倉啓, 秋山和彦, 羽場宏光, 高宮幸一, 久冨木志郎, 「HPLC 分析によるランタノイド内包フラーレン（Ln3+ @C82 3− ）の電子状態に関する研究」, 日本放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
澤村慶 (ポスター発表), 笠松良崇, 重河優大, 篠原厚, 「低エネルギー励起核種 U-235m のハロゲン化物の半減期変化」, 日本放射化学会第 65 回討論会 (2021), オンライン, 2021 年 9 月 22–24 日.
梅田泉 (口頭発表), 永田みどり, 天﨑茜, 大貫和信, 柳下淳, 桂川美穂, 織田忠, 武田伸一郎, 羽場宏光, 藤井博史, 高橋忠幸,「Rhenium-186の錯体形成に関する諸検討」, 第 61 回日本核医学会学術総会, 名古屋市, 2021 年 11 月 4–6 日.
芝原裕規 (口頭発表), 竹村友紀, 福森麻衣, 殷小杰, 南部明弘, 結城真美, 田沢周作, 羽場宏光, 「TAT のための 228 Th/224 Ra/212 Pb ジェ
ネレータシステム開発（2）—高比放射能 212 Pb の製造—」, 第 61 回日本核医学会学術総会, 名古屋市, 2021 年 11 月 4–6 日.
武藤大河 (口頭発表), P. Brionnet, 浅井雅人, 郷慎太郎, R. Grzywacz, 羽場宏光, 加治大哉, 木村創太, T. King, 森本幸司, K. Rykaczewski,
坂口聡志, 酒井英行, 森田浩介, 庭瀬暁隆, 田中聖臣, 「Si 検出器の波形解析による軽粒子識別」, 第 127 回日本物理学会九州支部
例会, オンライン, 2021 年 12 月 4 日.
大島康宏 (ポスター発表), 鈴木博元, 花岡宏史, 佐々木一郎, 渡辺茂樹, 羽場宏光, 荒野泰, 対馬義人, 石岡典子, 「LAT1 を標的とした, QST 高崎サイエンスフェスタ 2021,
新規 α 線標的アイソトープ治療薬: 2-[211 At]astato-α-methyl-L-phenylalanine の非臨床評価」
高崎市/オンライン, 2021 年 12 月 7–8 日.
羽場宏光 (招待講演), 「短寿命 RI の製造・分離」, QiSS シンポジウム, 大阪市/オンライン, 2022 年 2 月 19 日.
山口敦史 (ポスター発表), 重河優大, 羽場宏光, 和田道治, 香取秀俊, 「原子核時計実現にむけたトリウムイオンのトラップ」, 第 9
回「光量子工学研究」—エクストリームフォトニクスが拓く未来の光科学—, オンライン, 2022 年 2 月 28 日–3 月 1 日.
羽場宏光 (口頭発表), 「ケミカルプローブ用ラジオアイソトープの製造開発」, Chemical Probe（生命現象探索分子）最終報告会（第4 回）, 和光市, 2022 年 3 月 1 日.
木村創大 (口頭発表), 和田道治, 羽場宏光, 石澤倫, 森本幸司, 庭瀬暁隆, M. Rosenbusch, Peter Schury for the SHE-Mass Collaboration,「MRTOF-MS を用いた 252 Cf 自発核分裂片の網羅的精密質量測定」, 日本物理学会第 77 回年次大会 (2022 年), オンライン, 2022
年 3 月 15–19 日.
平木貴宏 (口頭発表), Kjeld Beeks, 藤本弘之, 福永優太, 管明, 羽場宏光, 原秀明, 稲垣新, 小早川大貴, 笠松良崇, 北尾真司, 小無健司,
増田孝彦, 宮本祐樹, 岡井晃一, 笹尾登, T. Schumm, 瀬戸誠, 重河優大, 玉作賢治, 植竹智, 渡部司, 渡部信, 山口敦史, 安田勇輝, 依田
芳卓, 吉見彰洋, 吉村浩司, 吉村太彦, 「トリウム 229 アイソマー状態からの脱励起真空紫外光探索」, 日本物理学会第 77 回年次
大会 (2022 年), オンライン, 2022 年 3 月 15–19 日.
庭瀬暁隆 (口頭発表), P. Schury, 和田道治, P. Brionnet, S. Chen, 羽場宏光, 平山賀一, D. S. Hou, 飯村俊, 石山博恒, 伊藤由太, 加治大哉,
木村創大, 小浦寛之, 宮武宇也, 森本幸司, 森田浩介, 長江大輔, M. Rosenbusch, 高峰愛子, 渡辺裕, H. Wollnik, W. Xian, S. X. Yan,

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)「MRTOF+α-TOF による 257, 258 Db の精密質量測定」, 日本物理学会第 77 回年次大会 (2022 年), オンライン, 2022 年 3 月 15–19 日.
亀谷晃毅 (口頭発表), 三木謙二郎, 今井伸明, 上坂友洋, 大田晋輔, 笹野匡紀, 竹田浩之, 波多野雄治, 羽場宏光, 早水友洋, 原正憲, 道正
新一郎他, RIBF-SHARAQ11 Collaboration, 「3 H(t, 3 He)3 n 反応による三中性子系質量欠損測定の遂行」, 日本物理学会第 77 回年
次大会 (2022 年), オンライン, 2022 年 3 月 15–19 日.
高橋浩之 (口頭発表), 島添健次, 鎌田圭, 羽場宏光, 百瀬敏光, 「多光子ガンマ線時間・空間相関型イメージング法の研究 1(全体概要)」, 2022 年第 69 回応用物理学会春季学術講演会, 相模原市/オンライン, 2022 年 3 月 22–26 日.
島添健次 (口頭発表), 高橋浩之, 鎌田圭, 羽場宏光, 上ノ町水紀, 百瀬敏光, 大鐘健一朗, 「多光子ガンマ線時間・空間相関型イメー
ジング法の研究 2 (システム開発)」, 2022 年第 69 回応用物理学会春季学術講演会, 相模原市/オンライン, 2022 年 3 月 22–26 日.
横北卓也 (口頭発表), 羽場宏光, 「Zr 及び Hf のスルファト錯体推定に向けた TOA/H2 SO4 系の溶媒抽出」, 日本化学会第 102 春季
年会 (2022), オンライン, 2022 年 3 月 23–26 日.
中川創太 (口頭発表), 角永悠一郎, 大江一弘, 寺本高啓, 床井健運, 神田晃充, 笠松良崇, 永田光知郎, 羽場宏光, 王洋, 吉村崇, 豊嶋
厚史, 篠原厚, 「電解酸化反応を利用したアミノ酸へのアスタチン標識法の開発」, 日本化学会第 102 春季年会 (2022), オンライ
ン, 2022 年 3 月 23–26 日.
麻生彩佳 (口頭発表), 兼田加珠子, 下山敦史, 角永悠一郎, 白神宜史, 渡部直史, 豊嶋厚史, 羽場宏光, 王洋, 篠原厚, 深瀬浩一, 「新規アルファ線核医学治療薬剤開発を目指した 211 At-FAPI の合成と評価」, 日本化学会第 102 春季年会 (2022), オンライン, 2022 年
3 月 23–26 日.
床井健運 (口頭発表), 豊嶋厚史, 大江一弘, 角永悠一郎, 寺本高啓, 中川創太, 今田彩香, 吉村崇, 笠松良崇, 羽場宏光, 王洋, 篠原厚,
「アスタチンのハロゲン結合エネルギー測定に向けた条件検討」, 日本化学会第 102 春季年会 (2022), オンライン, 2022 年 3 月
23–26 日.
合川正幸 (口頭発表), 花田幸奈, ダグワドルジ イチンホルロー, 羽場宏光, タカッチ サンドール, ディトロイ フェレンチ, ズーチ ゾルタン, 「カルシウム標的へのアルファ粒子入射反応による Sc 生成反応断面積測定」, 日本原子力学会 2022 年春の年会, オンラ
イン, 2022 年 3 月 16–18 日.
上ノ町水紀 (口頭発表), 大鐘健一朗, Zhihong Zhong, 島添健次, 鎌田圭, 高橋浩之, Yang Wang, 羽場宏光, 「Compton-PET ハイブリッ
ドカメラを用いた診断治療核種同時撮像検証」, 日本原子力学会 2022 年春の年会, オンライン, 2022 年 3 月 16–18 日.

Award
上ノ町水紀, “Double photon emission coincidence imaging with GAGG-SiPM Compton camera,” 日本原子力学会放射線工学部会賞
奨励賞, 2021 年 9 月.

Press Release
難治性甲状腺がんに対する医師主導治験を開始—アスタチンを用いた新しい標的アルファ線治療—, 大阪大学, 理化学研究所, 2021
年 11 月 29 日. https://www.riken.jp/pr/news/2021/20211129_1 .

Patent安良田寛, 中村伸悟, 栗原嵩司, 羽場宏光, 「量子線照射のための標的保持装置, システム, 標的, および方法」, 特願 2021-190640.

Outreach Activities
羽場宏光 (依頼講演), 「ニホニウム発見への道のり」, 大宮北高校 SSH 特別講演会, 大宮市, 2021 年 10 月 4 日.
羽場宏光（依頼講演）, 「新元素でがん治療 〜RIBF がつくるラジオアイソトープ〜」, 第 9 回理研イノベーションセミナー, オン
ライン, 2022 年 1 月 21 日.
羽場宏光（依頼講演）, 「ニホニウム発見への道のり」, 早稲田大学本庄高等学院課外講義, オンライン, 2022 年 3 月 12 日.

Others
小川美香子, 渡部直史, 上原知也, 清野泰, 永津弘太郎, 藤井博史, 小川数馬, 羽場宏光, 「短飛程放射線を活用した核医学治療薬剤の現状と将来」, 第 2 回日本アイソトープ協会シンポジウムパネル討論, オンライン, 2021 年 11 月 29 日.
出光一哉, 大越実, 羽場宏光, 福谷哲, 坂井章浩, 「研究施設等廃棄物の埋設事業へ向けた取り組みについて」, 日本原子力学会 2022
年春の年会バックエンド部会企画セッション, オンライン, 2022 年 3 月 17 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Accelerator Applications Research Division
RI Application Research Group
Industrial Application Research Team
1. Abstract
Industrial application research team handles non-academic activities at RIBF corresponding mainly to industries.

2. Major Research Subjects
Support of industrial utilization of the RIBF accelerator beam.

3. Summary of Research Activity
RNC promote facility-sharing program “Promotion of applications of high-energy heavy ions and RI beams.” In this program,
RNC opens a part of the RIBF facility, which includes the AVF cyclotron, RILAC, RIKEN Ring Cyclotron and experimental instruments, to non-academic proposals from users including private companies. The proposals are reviewed by a program advisorycommittee, industrial PAC (IN-PAC). The proposals which have been approved by the IN-PAC are allocated with beam times and theusers pay RIKEN the beam time fee. The intellectual properties obtained by the use of RIBF belong to the users. In order to encourage
the use of RIBF by those who are not familiar with utilization of ion beams, the ﬁrst two beam times of each proposal can be assigned
to trial uses which are free of beam time fee.
In July 2021, the IN-PAC met and approved fee-based proposals from private companies; two proposals from new companies
and ﬁve proposals from continuously using companies. In January 2022, the IN-PAC held a mail review and approved two fee-based
proposals from continuous users. In 2020, four companies executed 23 fee-based beamtimes, twelve of which utilized a Kr beam witha total beam time of 221 h, nine utilized an Ar beam with a total beam time of 120 h and two of which utilized a Xe beam with a total
beam time of 20 h.

Members
Team Leader
Atsushi YOSHIDA
Research Consultant
Tadashi KAMBARA

List of Publications & Presentations
Other
Fee-based beamtimes for private companies: Kr beam 221 h, Ar beam 120 h, Xe beam 20 h.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Subnuclear System Research Division
Quantum Hadron Physics Laboratory
1. Abstract
Atomic nuclei are made of protons and neutrons bound by the exchange of pion and other mesons. Also, protons and neutrons
are made of quarks bound by the exchange of gluons. These strong interactions are governed by the non-Abelian gauge theory
called the quantum chromodynamics (QCD). On the basis of theoretical and numerical analyses of QCD, we study the interactions
between the nucleons, properties of the dense quark matter realized at the center of neutron stars, and properties of the hot quark-gluon
plasma realized in the early Universe. Strong correlations common in QCD and cold atoms are also studied theoretically to unravel
the universal features of the strongly interacting many-body systems. Developing perturbative and non-perturbative techniques inquantum ﬁeld theory and string theory are of great importance not only to solve gauge theories such as QED and QCD, but also to ﬁnd
the theories beyond the standard model of elementary particles. Various theoretical approaches along this line have been attempted.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)

Perturbative and non-perturbative methods in quantum ﬁeld theories
Quantum computing
Lattice gauge theory
QCD under extreme conditions
Nuclear and atomic many-body problems

3. Summary of Research Activity(1) Perturbative and non-perturbative methods in quantum ﬁeld theories(1-1) Theory of the anomalous magnetic moment of the electron
The anomalous magnetic moment of the electron ae measured in a Penning trap occupies a unique position among high precision
measurements of physical constants in the sense that it can be compared directly with the theoretical calculation based on the renormalized quantum electrodynamics (QED) to high orders of perturbation expansion in the ﬁne structure constant α, with an eﬀective
parameter α/π. Both numerical and analytic evaluations of ae up to (α/π)4 were ﬁrmly established. The coeﬃcient of (α/π)5 has
been obtained recently by an extensive numerical integration. The contributions of hadronic and weak interactions have also been
estimated. The sum of all these terms leads to ae (theory) = 1 159 652 181.606 (11)(12)(229) × 10−12 , where the ﬁrst two uncertainties
are from the tenth-order QED term and the hadronic term, respectively. The third and largest uncertainty comes from the current bestvalue of the ﬁne-structure constant derived from the cesium recoil measurement: α−1 (Cs) = 137.035 999 046 (27). The discrepancy
between ae (theory) and ae (experiment) is 2.4σ. Assuming that the standard model is valid so that ae (theory) = ae (experiment)
holds, we obtained α−1 (ae ) = 137.035 999 1496 (13)(14)(330), which is nearly as accurate as α−1 (Cs). The uncertainties are from thetenth-order QED term, hadronic term, and the best measurement of ae , in this order.
(1-2) Transport theory of chiral fermions under external gravity and ﬂuid ﬁeld
We formulated the kinetic theory of chiral matter in external gravitational ﬁelds, based on quantum ﬁeld theory. The resulting
kinetic theory reveals that the Riemann curvature induces non-dissipative transport phenomena of chiral fermions. In particular, wefound that the spin-gravity coupling results in the antiparallel ﬂow of the charge current and energy current of fermions, which is never
explained in the classical picture. These novel framework and phenomena takes place not only in cosmological systems involving
neutrinos but also in chiral matter aﬀected by background ﬂuid, such as quark-gluon plasma, graphene and Dirac/Weyl semimetals.
We demonstrated that a temperature gradient and ﬂuid vorticity induce a pressure correction and charge and energy ﬂow in Dirac/Weylsemimetals.
(1-3) Spin transport of massive fermion
We derived the spin kinetic theory under external electromagnetic and gravitational ﬁelds. We derived the global equilibrium
conditions from the kinetic equations and ﬁnd that the ﬁnite Riemann curvature or an external electromagnetic ﬁeld is necessary to
determine the spin-thermal vorticity coupling. Solving the equation of motion of axial vector part of the Wigner transformed fermion
propagator, we evaluated the Pauli-Lubanski vector, which expresses the spin polarization of massive fermions, at the local equilibriumand out of equilibrium. This formula is potentially important of the Λ polarization puzzle found in heavy-ion collisions, which cannot
be understood in the calculations based on global equilibrium assumption.
(1-4) Chiral vortical eﬀect in condensed matter systems
We revisited the chiral vortical eﬀect in condensed matter physics, by using the semiclassical wave-packet theory. In high-energy
physics, the chiral vortical current is conventionally deﬁned as the Noether current. Such a deﬁnition is however improper in thecontext of condensed matter systems since there potentially exists the contributions of the magnetization current. Indeed we showedthat the chiral vortical current is compensated by the magnetization current. Hence the chiral vortical eﬀect cannot be observed inpseudo-relativistic condensed matter systems, such as Dirac/Weyl semimetals. Instead, we demonstrated that the chiral vortical eﬀect
is an observable in several nonrelativistic matter, and suggested possible table-top experimental setups.
(1-5) Conformal ﬁeld theories and time-developments in higher dimensions
In quantum ﬁeld theories, symmetry plays an essential and exceptional role. Focusing on some proper symmetry and delving
into its meaning have been proven to be one of the most fruitful strategies. We try to extend the result obtained in two-dimensional
conformal ﬁeld theory using the formalism developed in a study of sine-square deformation of Euclidean conformal ﬁeld theory to- 299 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

higher dimensional conformal ﬁeld theory with both Euclidean and Lorentzian metric. Here the time developments of the system arechosen to honor the conformal symmetry of the system, yet they are classiﬁed into three distinct categories, each corresponds the cases
found in the study of two-dimensional conformal ﬁeld theory.
(2) Quantum computing(2-1) Hybrid quantum annealing via molecular dynamics
A novel quantum-classical hybrid scheme was proposed to eﬃciently solve large-scale combinatorial optimization problems. The
key concept is to introduce a Hamiltonian dynamics of the classical ﬂux variables associated with the quantum spins of the transverseﬁeld Ising model. Molecular dynamics of the classical ﬂuxes can be used as a powerful preconditioner to sort out the frozen andambivalent spins for quantum annealers. It was demonstrated that the performance and accuracy of our smooth hybridization are
better in comparison to the standard classical algorithms (the tabu search and the simulated annealing) by employing the MAX-CUTand Ising spin-glass problems.
(3) Lattice gauge theory(3-1) Dibaryon with highest charm number near unitarity from lattice QCD
A pair of triply charmed baryons, Ωccc Ωccc , is studied as an ideal dibaryon system by (2+1)-ﬂavor lattice QCD with nearly
physical light-quark masses and the relativistic heavy quark action with the physical charm quark mass. The spatial baryon-baryon
correlation is related to their scattering parameters on the basis of the HAL QCD method. The Ωccc Ωccc in the 1S0 channel taking into
account the Coulomb repulsion with the charge form factor of Ωccc leads to the scattering length aC0  −19 fm and the eﬀective range
CC
reﬀ
 0.45 fm. The ratio reﬀ/aC0  −0.024, whose magnitude is considerably smaller than that of the dineutron (−0.149), indicates that
Ωccc Ωccc is located in the unitary regime.
(3-2) Emergence of the ρ resonance from the HAL QCD potential in lattice QCD
We investigate the I = 1 ππ interaction using the HAL QCD method in lattice QCD. We employ the (2+1)-ﬂavor gauge conﬁgurations at mπ ≈ 411 MeV, in which the ρ meson appears as a resonance state. We ﬁnd that all-to-all propagators necessary in thiscalculation can be obtained with reasonable precision by a combination of three techniques, the one-end trick, the sequential propagator, and the covariant approximation averaging (CAA). The non-local I = 1 ππ potential is determined at the next-to-next-to-leading
order (N2LO) of the derivative expansion for the ﬁrst time, and the resonance parameters of the ρ meson are extracted. The obtained
ρ meson mass is found to be consistent with the value in the literature. This opens up new possibilities for the study of resonances inlattice QCD.
(3-3) Stress tensor around static quark-anti-quark from Yang-Mills gradient ﬂow
The spatial distribution of the stress tensor around the quark-anti-quark pair in SU(3) lattice gauge theory was studied. The
YangMills gradient ﬂow plays a crucial role to make the stress tensor well-deﬁned and derivable from the numerical simulations on
the lattice. The resultant stress tensor with a decomposition into local principal axes shows, for the ﬁrst time, the detailed structureof the ﬂux tube along the longitudinal and transverse directions in a gauge invariant manner. The linear conﬁning behavior of thepotential at long distances is derived directly from the integral of the local stress tensor.
(4) QCD under extreme conditions(4-1) Finite density QCD based on complex Langevin method
The complex Langevin method (CLM) is one of a promising approach to overcome the sign problem. The central idea of thisapproach is that the stochastic quantization does not require the probabilistic interpretation of the Boltzmann weight e−S even when theaction takes complex values. Although the equivalence between CLM and the familiar path integral quantization is quite nontrivial, it
is pointed out that the probability distribution of the drift term can judge the correctness of the CLM. This enable us to perform latticesimulation of QCD based on CLM in the ﬁnite density region in a self-contained manner. We discussed the applicability of the CLM
with four-ﬂavor staggered fermions on a 83 × 16 lattice with quark mass m = 0.01. In particular, we focus on the behavior of theeigenvalue distribution of the fermion mass matrix which is closely related to the appearance of the singular drift problem.
(4-2) Non-equilibrium quantum transport of chiral ﬂuids from kinetic theory
We introduced the quantum-ﬁeld-theory (QFT) derivation of chiral kinetic theory (CKT) from the Wigner-function approach,which manifests side jumps and non-scalar distribution functions associated with Lorentz covariance and incorporates both background ﬁelds and collisions. The formalism is utilized to investigate second-order responses of chiral ﬂuids near local equilibrium. Such nonequilibrium anomalous transport is dissipative and aﬀected by interactions. Contributions from both quantum corrections in anomalous hydrodynamic equations (EOM) of motion and those from the CKT and Wigner functions (WF) are considered in a relaxation-time approximation (RTA). Anomalous charged Hall currents engendered by background electric ﬁelds andtemperature/chemical-potential gradients are obtained. Furthermore, chiral magnetic/vortical eﬀects (CME/CVE) receive viscous corrections as non-equilibrium modiﬁcations stemming from the interplay between side jumps, magnetic-moment coupling, and chiralanomaly.
(4-3) Hadron-quark crossover in cold and hot neutron stars
We presented a much improved equation of state for neutron star matter, QHC19, with a smooth crossover from the hadronic
regime at lower densities to the quark regime at higher densities. We now use the Togashi et al. equation of state, a generalization of
the Akmal-Pandharipande-Ravenhall equation of state of uniform nuclear matter, in the entire hadronic regime; the Togashi equation ofstate consistently describes nonuniform as well as uniform matter, and matter at beta equilibrium without the need for an interpolation
between pure neutron and symmetric nuclear matter. We describe the quark matter regime at higher densities with the NambuJonaLasinio model, now identifying tight constraints on the phenomenological universal vector repulsion between quarks and the- 300 -

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pairing interaction between quarks arising from the requirements of thermodynamic stability and causal propagation of sound. The
resultant neutron star properties agree very well with the inferences of the LIGO/Virgo collaboration, from GW170817, of the pressure
versus baryon density, neutron star radii, and tidal deformabilities. The maximum neutron star mass allowed by QHC19 is 2.35 MS,
consistent with all neutron star mass determinations.
(4-4) Gluonic energy and momentum distribution at ﬁnite temperature
We studied the energy-momentum distribution of the gluons around a static quark at ﬁnite temperature on the basis of the eﬀective
ﬁeld theory (EFT) of thermal QCD. Spatial correlations between the Polyakov loop and the energy-momentum tensor were calculated
up to the next-to-leading order in EFT. The results were compared with the recent quenched lattice QCD calculation obtained byusing the gradient ﬂow formalism. The EFT results and the lattice QCD data agree quite well without any ﬁtting parameters at hightemperature above deconﬁnement. On the other hand, there is a substantial diﬀerence near the critical temperature especially in the
distribution of the energy density, which indicates some non-perturbative eﬀect.
(5) Nuclear and atomic many-body problems(5-1) Density functional theory for nuclear structure
The atomic nuclei are composed of protons and neutrons interacting via the nuclear and Coulomb interactions. The density
functional theory (DFT) is widely used to calculate the ground-state properties. Nevertheless, because of the lack of knowledge of
nuclear interaction in medium (eﬀective interaction), the eﬀective interaction is ﬁtted to experimental data, and it has been attained todevelop a high-accuracy one. As the ﬁrst step, the eﬀective interaction of the charge symmetry breaking term, a part of the nuclear
interaction, is proposed.
(5-2) Fundamental problems of density functional theory
The density functional theory (DFT) is one of the powerful methods to calculate ground-state properties of the quantum manybody problems, including atomic nuclei, atoms, molecules, and solids. The accuracy of the DFT depends on the energy density
functional (EDF), which contains information on the interaction. We develop a method to calculate EDF for electronic systems
purely microscopically using the functional renormalization group. In this method, energy density for so many various densities canbe calculated, and eventually, DFT calculation can be performed without ﬁtting energy density to some functional forms. We also
develop the relativistic DFT in which the ﬁnite-light-speed correction to the Coulomb interaction is also considered to calculate theground-state properties of super-heavy elements.

Members
Director
Masahiko IWASAKI
Vice Chief Scientist
Tsukasa TADA
Research/Technical Scientist
Takumi DOI (Senior Research Scientist)
Senior Scientist
Makiko NIO
Contract Researcher
Dang NGUYEN DINH
Special Postdoctoral Researchers
Matthias W.G. BERWEIN
Kazuya MAMEDA

Shoichiro TSUTSUI

Research Consultant
Takeo INAMI (Vietnam Academy of Sci. and Tech.)
Visiting Scientists
Shinya AOKI (Kyoto Univ.)
Tatsumi AOYAMA (KEK)
Gergely P. FEJOS (Eotvos Lorand Univ.)
Kenji FUKUSHIMA (Univ. of Tokyo)
Hideki HAMAGAKI (Nagasaki Inst. of Applied Sci.)
Koji HASHIMOTO (Osaka Univ.)
Masashi HAYAKAWA (Nagoya Univ.)
Tomoya HAYATA (Keio Univ.)
Takashi INOUE (Nihon Univ.)
Noriyoshi ISHII (Osaka Univ.)

Yuki KAMIYA (Helmholtz-Inst. fuer Strahlen- und Kernphysik Rheinische Friedrich-Wilhelms-Universitaet Bonn)
Phuc T. LE (Inst. of Fundamental and Applied Sci. Duy Tan
Univ.)
Haozhao LIANG (Univ. of Tokyo)
Takaya MIYAMOTO (NEC Corporation)
Kenji MORITA (QST)
Masaki MURATA (Japan Univ. of Economics)
Atsushi NAKAMURA (Osaka Univ.)
Takashi NAKATSUKASA (Tsukuba Univ.)- 301 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Hung NGUYEN (Duy Tan Univ.)
Yoji OHASHI (Keio Univ.)
RHINE KUMAR ARAYAKKANDI KEECH (Cochin Univ. ofSci. and Tech.)Student Trainees
Yutaro AKAHOSHI (Kyoto Univ.)
Asahi CHIKAOKA (Univ. of Tokyo)
Yixin GUO (Univ. of Tokyo)
Akira HIRAYAMA (Saitama Univ.)

Shoichi SASAKI (Tohoku Univ.)
Kenji SASAKI (Kyoto Univ.)
Hiroshi SUZUKI (Kyushu Univ.)
Motoi TACHIBANA (Saga Univ.)
Xun LIU (Univ. of Tokyo)
Yan LYU (Peking Univ.)
Kotaro MURAKAMI (Kyoto Univ.)
Tomoya NAITO (Univ. of Tokyo)

List of Publications & Presentations
Publications[Original Papers]
T. Naito, G. Colò, H. Liang, X. Roca-Maza, and H. Sagawa, “Toward ab initio charge symmetry breaking in nuclear energy density
functionals,” Phys. Rev. C 105, L021304 (2022).
Z. Wang, T. Naito, H. Liang, and W. H. Long, “Exploring eﬀects of tensor force and its strength via neutron drops,” Chin. Phys. C 45,
064103 (2021).
G. Accorto, T. Naito, H. Liang, T. Nikšić, and D. Vretenar, “Nuclear energy density functionals from empirical ground-state densities,”
Phys. Rev. C 103, 044304 (2021).
Y. Sekino, H. Tajima, and S. Uchino, “Optical spin transport in ultracold quantum gases,” arXiv:2103.02418.
K. Mameda, N. Yamamoto, and D. -L. Yang, “Photonic quantum kinetic theory in curved spacetime and the spin Hall eﬀect,” Phys. Rev.
D 105, 096019 (2022).
T. M. Doi, H. Tajima, and S. Tsutsui, “Complex Langevin study for polarons in an attractively interacting one-dimensional two-component
Fermi gas”, Phys. Rev. Res. 3, 033180 (2021).
Y. Akahoshi, S. Aoki, and T. Doi, “Emergence of the rho resonance from the HAL QCD potential in lattice QCD,” arXiv:2111.15138.
S. Tsutsui, M. Hongo, S. Sato, and T. Sagawa, “Quantum hydrodynamics from local thermal pure states,” arXiv:2106.12777.
H. Tajima, S. Tsutsui, T. M. Doi, and K. Iida, “Unitary p-wave Fermi gas in one dimension,” Phys. Rev. A 104, 023319 (2021).
T. Naito, “Eﬀects of ﬁnite-light-speed correction for the Coulomb interaction on nuclear binding energies and radii in spherical nuclei,”arXiv:2106.14270.
H. Tajima, S. Tsutsui, T. M. Doi, and K. Iida, “Three-body crossover from a Cooper triple to bound trimer statein three-component Fermi
gases near a triatomic resonance,” Phys. Rev. A 104, 053328 (2021).
T. Yokota and T. Naito, “Construction of energy density functional for arbitrary spin polarization using functional renormalization group,”
Phys. Rev. B 105, 035105 (2022).
H. Sotani, N. Nishimura, and T. Naito, “New constraints on the neutron-star mass and radius relation from terrestrial nuclear experiments,”
Prog. Theor. Exp. Phys. 2022, 041D01 (2022).
N. Itagaki, T. Naito, and Y. Hirata, “Persistence of cluster structure in the ground state of 11 B,” Phys. Rev. C 105, 024304 (2022).
H. Tajima, Y. Sekino, and S. Uchino, “Optical spin transport theory of spin-1/2 topological Fermi superﬂuids,” Phys. Rev. B 105, 064508(2022).
T. Yokota, Y. Asano, Y. Ito, H. Matsufuru, Y. Namekawa, J. Nishimura, A. Tsuchiya, and S. Tsutsui, “Perturbative predictions for color
superconductivity on the lattice,” arXiv:2111.14578.
S. Tsutsui, Y. Asano, Y. Ito, H. Matsufuru, Y. Namekawa, J. Nishimura, A. Tsuchiya, and T. Yokota, “Color superconductivity in a small
box: a complex,” arXiv:2111.15095.
H. Sagawa, S. Yoshida, T. Naito, T. Uesaka, J. Zenihiro, J. Tanaka, and T. Suzuki, “Isovector density and isospin impurity in 40 Ca,” Phys.
Lett. B 829, 137072 (2022).
K. Murakami, Y. Akahoshi, S. Aoki, and K. Sasaki for HAL QCD Collaboration, “Investigations of decuplet baryons from meson-baryon
interactions in the HAL QCD method,” arXiv:2111.15563.
Y. Namekawa, S. Tsutsui, Y. Ito, H. Matsufuru, J. Nishimura, S. Shimasaki, and A. Tsuchiya, “Flavor number dependence of QCD at
ﬁnite density by the complex Langevin method,” arXiv:2112.00150.
Y. Akahoshi, S. Aoki, and T. Doi, “Emergence of the rho resonance from the HAL QCD potential,” arXiv:2111.15138.
Y. Lyu, H. Tong, T. Sugiura, S. Aoki, T. Doi, T. Hatsuda, J. Meng, and T. Miyamoto, “Most charming dibaryon near unitarity,”
arXiv:2112.01682.
T. Doi, Y. Lyu, H. Tong, T. Sugiura, S. Aoki, T. Hatsuda, J. Meng, and T. Miyamoto, “Finite volume analysis on systematics of thederivative expansion in HAL QCD method,” arXiv:2112.04997.
Y. Lyu, H. Tong, T. Sugiura, S. Aoki, T. Doi, T. Hatsuda, J. Meng, and T. Miyamoto, “Optimized two-baryon operators in lattice QCD,”
Phys. Rev. D 105, 074512 (2022).
T. Naito, X. Roca-Maza, G. Colò, H. Liang, and H, Sagawa, “Isospin symmetry breaking in the charge radius diﬀerence of mirror nuclei,”arXiv:2202.05035.
N. Itagaki and T. Naito, “Consistent description for cluster dynamics and single-particle correlation,” Phys. Rev. C 103, 044303 (2021).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Z. Wang, T. Naito, and H. Liang, “Tensor-force eﬀects on shell-structure evolution in N = 82 isotones and Z = 50 isotopes in therelativistic Hartree-Fock theory,” Phys. Rev. C 103, 064326 (2021).
T. Naito, G. Colò, H. Liang, and X. Roca-Maza, “Second and fourth moments of the charge density and neutron-skin thickness of atomic
nuclei,” Phys. Rev. C 104, 024316 (2021).
T. Naito, S. Endo, K. Hagino, and Y. Tanimura, “On deformability of atoms—comparative study between atoms and atomic nuclei,”
J. Phys. B 54, 165201 (2021).

[Review Article]
内藤智也, 萩野浩一, 小林良彦, 「アイソスピンの符号の慣習をめぐって」, 日本物理学会誌 77, 99 (2022).

Presentations[Domestic Conferences/Workshops]
内藤智也 (招待講演), 「原子核構造で探る中性子星」〜中性子星の観測と理論〜研究活性化ワークショップ 2021, 埼玉県和光市(理化学研究所), 2021 年 8 月 10 日.
内藤智也 (招待講演), 「ミュオン波動関数計算コードの開発」, RCNP 研究会 「ミューオン X 線 γ 線分光—非破壊分析, 化学, 原子
核物理への新展開・ミューオン原子核捕獲反応による原子核関連研究の可能性」, 大阪府茨木市 (大阪大学 核物理研究センター),
2022 年 3 月 25 日.
T. Naito, “Isospin symmetry breaking in ground-state properties,” 85th DFT Meeting, 北海道札幌市 (北海道大学大学院理学研究院物理部門), 2022 年 1 月 25 日.
板垣直之, 内藤智也, 平田雄一, 「11 B のクラスター構造とその応用」, 日本物理学会 第 77 回年次大会, オンライン, 2022 年 3 月 15 日.

[Seminar]
内藤智也, 「Ab initio エネルギー密度汎関数に向けて」, 酒見グループセミナー (東京大学大学院理学系研究科附属原子核科学研究センター), オンライン, 2021 年 7 月 16 日.

Award
A. Hirayama, Student Presentation Award of the Physical Society of Japan, 2021 Autumn meeting.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Subnuclear System Research Division
Strangeness Nuclear Physics Laboratory
1. Abstract
We proposed accurate calculation method called ‘Gaussian Expansion Method using inﬁnitesimally shifted Gaussian lobe basis
function.’ When one proceeds to four-body systems, calculation of the Hamiltonian matrix elements becomes much laborious. In orderto make the four-body calculation tractable even for complicated interactions, the inﬁnitesimally-shifted Gaussian lobe basis function
has been proposed. The GEM with the technique of inﬁnitesimally-shifted Gaussians has been applied to various three-, four- andﬁve-body calculations in hypernuclei, the four-nucleon systems, and cold-atom systems. As results, we succeeded in extracting newunderstandings in various ﬁelds.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Structure of Hypernuclei and neutron-rich nuclei from the view point of few-body problem
Structure of exotic hadron system
Quantum atomic systems and ultra-cold atomic systems
Equation of state for neutron star

3. Summary of Research Activity

Motivaed by observation of Ξ hyperuclei, IBUKI, KINKA and IRRAWADDY events, to study Ξ N interaction, we study 14 N+Ξ
hyperncleus withing the framework of relativistic mean ﬁeld theory. We found that the s-wave interaction deduced from the HAL
LQCD results is rather weak to obtain the energy diﬀerence between IRRAWADDY and KINKA events. The p-wave interaction isadded and ﬁtted to reproduce the energy diﬀerence. The resulting interaction together with the s-wave one gives a reasonable energy
simultaneously for the IBUKI event as an excited Ξ p state.
(1) We investigate the role of interaction in the p-wave channel in a mixture of two kinds of fermions. We ﬁnd that three-bodybound states of 2+1 fermions which were known to exist only when the two kinds of fermions have very diﬀerent masses,
can in fact exist for any mass of the fermions when their interaction is taken into account in the p-wave channel.
(2) We predict a possible bound state of exotic titanium isotopes using the nuclear shell model based on the modern nuclear
force. In addition, we study nucleon-Ξ interaction in nucleon-Ξ scattering and deuteron-Ξ scattering. For the former, we ﬁndthat nucleon-Ξ interaction induces small coupling to deuteron continuum states, while, for the latter, the system shows small
contribution of the coupling between nucleon-Ξ and Λ-Λ channels.

Members
Director
Emiko HIYAMA
Senior Research Scientists
Takumi DOI

Pascal NAIDON

Contract Researchers
Etsuko ITOU

Daisuke INOTANISpecial Postdoctoral Researcher
Tokuro FUKUI
Research Consultants
Shoji SHINMURA

Wolfram WEISE (TU Munich)Senior Visiting Scientist
Makoto OKA (JAEA)
Visiting Scientists
Masayuki ASAKAWA (Osaka Univ.)
Kadir Utku CAN (The Univ. of Adelaide)
Jaume CARBONELL (Irène Joliot-Curie Lab.)
Akinobu DOTE (KEK)
Shimpei ENDO (Tohoku Univ.)
Tomokazu FUKUDA (Osaka Elec.-Com. Univ.)
Yasuro FUNAKI (Kanto Gakuin Univ.)
Takenori FURUMOTO (Yokohama Nat’l Univ.)
Philipp GUBLER (JAEA)
Satoru HIRENZAKI (Nara Women’s Univ.)

Atsushi HOSAKA (Osaka Univ.)
Jinniu HU (Nankai Univ.)
Tetsuo HYODO (Tokyo Metropolitan Univ.)
Yoichi IKEDA (Kyushu Univ.)
Masahiro ISAKA (Hosei Univ.)
Souichi ISHIKAWA (Hosei Univ.)
Daisuke JIDO (Tokyo Tech.)Hyun-Chul KIM (Inha Univ.)
Toshio MOTOBA (Osaka Elec.-Com. Univ.)
Takayuki MYO (Osaka Inst. of Tech.)- 304 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Hui TONG (Tianjin Normal Univ.)
Atsushi UMEYA (Nippon Inst. of Tech.)
Shin WATANABE (NIT, Gifu College)
Chengjun XIA (Zhejiang Univ.)
Masanobu YAHIRO (Kyushu Univ.)
Ulugbek YAKHSHIEV (Inha Univ.)
Taiichi YAMADA (Kanto Gakuin Univ.)
Yasuo YAMAMOTO (Tsuru Univ.)
Nodoka YAMANAKA (Nagoya Univ.)
Takuma YAMASHITA (Tohoku Univ.)
Ying ZHANG (Tianjin Univ.)
Xian-Rong ZHOU (East China Normal Univ.)

Sho NAGAO (Tohoku Univ.)
Satoshi NAKAMURA (Tohoku Univ.)
Kazuma NAKAZAWA (Gifu Univ.)
Hidekatsu NEMURA (Kyoto Univ.)
Jean-Marc RICHARD (Lyon Univ.)
Thomas RIJKEN (Univ. Of Nijmegen)Shoichi SASAKI (Tohoku Univ.)Hans-Josef SCHULZE (INFN)
Jirina STONE (Univ. of Tennessee)
Tingting SUN (Zhengzhou Univ.)
Hiroyuki TAJIMA (Univ. of Tokyo)
Hajime TOGASHI (Tohoku Univ.)
Masaaki TOKIEDA (INRIA)
Student Trainees
Naoto HASEGAWA (Tohoku Univ.)
Dongwook LEE (Kyushu Univ.)
Jie LIU (Nanjing Univ.)

Moemi MATSUMOTO (Tohoku Univ.)
Qi MENG (Nanjing Univ.)

Research Part-time Worker
Daisuke INOTANI (Research Part-time Worker I)
Administrative Part-time Worker
Yoko FUJITA (Administrative Part-time Worker I)

List of Publications & Presentations
Publications[Original Papers]
12
Y. Tanimura, H. Sagawa, T. Sun, and E. Hiyama, “Ξ hypernuclei (15Ξ C and and Ξ Be, and the ΞN two-body interaction,” Phys. Rev. C 105,
044324 (2022).
Y. Zhang, H. Sagawa, and E. Hiyama, “Prediction of exotic hyperon halos in neutron-rich Zr hypernuclei,” Prog. Theor. Exp. Phys. 2022,
023D01 (2022).
Q. Meng, M. Harada, E. Hiyama, A. Hosaka, and M. Oka, “Doubly heavy tetraquark resonant states,” Phys. Lett. B 824, 136800 (2022).
M. Honda, E. Itou, Y. Kikuchi, and Y. Tanizaki, “Negative string tension of higher-charge Schwinger model via digital quantum simulation,” PTEP 2022, 033B01 (2022).
M. Honda, E. Itou, Y. Kikuchi, L. Nagano, and T. Okuda, “Classically emulated digital quantum simulation for screening and conﬁnementin the Schwinger model with a topological term,” Phys. Rev. D 105, 014504 (2022).
T. Fukui, “Towards modeling cluster structure of 8 Be with chiral interaction,” J. Phys. G 49, 055102 (2022).
Y. Kamiya, K. Sasaki, T. Fukui, T. Hyodo, K. Morita, K. Ogata, A. Ohnishi, and T. Hatsuda, “Femtoscopic study of coupled-channel N-Ξand ΛΛ interactions”, Phys. Rev. C 105, 014915 (2022).
L. Coraggio, G. D. Gregorio, A. Gargano, N. Itaco, T. Fukui, Y. Z. Ma, and F. R. Xu, “Shell-model study of titanium isotopic chain withchiral two- and three-body forces,” Phys. Rev. C 104, 054304 (2021).
J. Singh, T. Matsumoto, T. Fukui, and K. Ogata, “Three-body description of 9 C: Role of low-lying resonances in breakup reactions,” Phys.
Rev. C 104, 034612 (2021).
K. Ogata, T. Fukui, Y. Kamiya, and A. Ohnishi, “Eﬀect of deuteron breakup on the deuteron-Ξ correlation function,” Phys. Rev. C 103,
065205 (2021).
M. Tokieda and S. Endo, “Equivalence of dissipative and dissipationless dynamics of interacting quantum systems with its application to
the unitary Fermi gas,” Front. Phys. 9, 730761 (2021).

[Proceedings]
E. Itou and Y. Nagai, “QCD viscosity by combining the gradient ﬂow and sparse modeling methods,” Proc. Sci. LATTICE2021, 214(2021).
K. Ishiguro, K. Iida, and E. Itou, “Flux tube proﬁles in two-color QCD at low temperature and high density,” Proc. Sci. LATTICE2021,
063 (2021).
T. Fukui, L. Coraggio, G. D. Gregorio, A. Gargano, N. Itaco, Y. Z. Ma, and F. R. Xu, “Realistic shell model with chiral interaction and its
application to drip-line predictions,” Few-Body Syst. 62, 64 (2021).
A. Ohnishi, Y. Kamiya, K. Sasaki, T. Fukui, T. Hatsuda, T. Hyodo, K. Morita, and K. Ogata, “Femtoscopic study of NΞ interaction andsearch for the H dibaryon state around the NΞ threshold,” Few-Body Syst. 62, 42 (2021).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Presentations[International Conferences/Workshops]
E. Hiyama (invited), “Recent progress of hypernuclear physics,” International Conference on Light Cone 2021—Physics of Hadron on
the Light Front, Online, November 29–December 4, 2021.
E. Hiyama (invited), “Few-body aspect of hypernuclear physics,” JPS Symposium on Intersection of Nuclear Physics in Japan and theUnited States, Online, September 17, 2021.
E. Hiyama (invited), “Four-body structure of tetra-neutron system,” Workshop on Neutron Unbound Systems Around the dripline, Online,
July 13–14, 2021.
P. Naidon (invited), “Eﬁmov physics and universality in few-body systems,” Lecture at the School on Critical Stability of Few-body
Quantum Systems, São Paulo, ICTP-SAIFR Brazil, Online, October 4–8, 2021.
E. Itou (oral), “Sparse modeling approach to obtaining the shear viscosity from smeared correlation functions,” The 38th International
Symposium on Lattice Field Theory (LATTICE 2021), Online, July 26–30, 2021.
E. Itou (invited), “Sparse modeling approach to obtaining the QCD shear viscosity from smeared correlation functions,” ECT* online
workshop “Tackling The Real-Time Challenge In Strongly Correlated Systems: Spectral Properties From Euclidean Path Integrals,”
Online, September 13–17, 2021.
E. Itou (invited), “Digital quantum simulation for screening and conﬁnement in gauge theory with a topological term,” RIKEN-Vancouver
Joint Workshop on Quantum Computing, August 24–25, 2021.
T. Fukui (oral), “Cluster-model calculations with chiral interaction,” Newcomers Seminar I, RIBF Nuclear Physics Seminar, Online, June
8, 2021.

[Domestic Conferences/Workshops]
肥山詠美子 (招待講演), 「ハイパー核の構造とハイペロンー核子間相互作用」, ELPH 研究会 C031 「多彩なビーム実験と多様な理論的手法で迫るハドロン間相互作用」, オンライン, 2021 年 11 月 4–5 日.
伊藤悦子 (招待講演), 「量子計算の場の理論への応用」, 金沢大学研究会「2022 計算物理学の発展」, オンライン, 2022 年 3 月 9 日.
伊藤悦子 (口頭発表), 「物理点におけるハドロン間力の計算に向けて—格子 QCD の配位生成」, 「富岳で加速する素粒子・原子核・
宇宙・惑星」シンポジウム, オンライン, 2022 年 1 月 17–18 日.
伊藤悦子 (口頭発表), 「2 カラー QCD の低温高密度相における状態方程式」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年
9 月 14–17 日.
伊藤悦子 (口頭発表), 「量子計算でみる負のストリングテンションの出現」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9
月 14–17 日.
福井徳朗 (口頭発表), L. Coraggio, G. D. Gregorio, A. Gargano, N. Itaco, Y. Z. Ma, F. R. Xu, 「現実的殻模型で探る Ca および Ti のドリップライン」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–17 日.
福井徳朗 (招待講演), 「『日本物理学会若手奨励賞受賞記念講演』3 体力の適正な取扱いに基づく第一原理殻模型計算の発展」, 日
本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–17 日.
福井徳朗 (口頭発表), 「カイラル相互作用に基づく現実的殻模型の進展」, 基研研究会「核力に基づいた原子核の構造と反応」, 京都市, 2021 年 12 月 7–10 日.
福井徳朗 (招待講演), “Frontiers of many-body calculations with chiral interaction,” ELPH 研究会 C031 「多彩なビーム実験と多様な, オンライン, 2021 年 11 月 4–5 日.
理論的手法で迫るハドロン間相互作用」
福井徳朗 (口頭発表), “Perspectives of many-body calculations with realistic nuclear force,” RCNP での次期計画検討会, オンライン,
2021 年 9 月 27–29 日.
猪谷太輔 (招待講演), 「量子計算を用いた (1+1) 次元 Schwinger 模型における実時間ダイナミクスの解析」, 国内モレキュール型研
究会「場の理論の量子計算 2022」, 京都市, 2022 年 2 月 24–25 日.

[Seminars]
P. Naidon, “Physics of ultra-cold atoms,” Lecture at Tohoku University GPPU seminars, Decembeer 8, 2021.
P. Naidon, “Prediction of a “mixed bubble,” quantum phase”, RIBF Nuclear Physics Seminar, Online, September 7, 2021.
E. Itou, “Digital quantum simulation for screening and conﬁnement in gauge theory with a topological term,” RCNP Nuclear Physics
Theory Seminar, July 16, 2021.
T. Fukui,「現実的殻模型の進展—カイラル 3 体力と諸現象—」, Seminar at CNS, University of Tokyo, Online, Japan, February 4, 2022.

AwardsE. Itou, “Editors’ Choice” of Progress of Theoretical and Experimental Physics 2022, Issue 3, March 2022.
福井徳朗, 第 16 回 (2022 年) 日本物理学会若手奨励賞 理論核物理領域 (第 23 回核理論新人論文賞).

Press Release
E. Itou, “Negative string tension of a higher-charge Schwinger model via digital quantum simulation,” RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program, March 9, 2022.
https://ithems.riken.jp/ja/news/
negative-string-tension-of-a-higher-charge-schwinger-model-via-digital-quantum-simulation .

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Subnuclear System Research Division
Radiation Laboratory
1. Abstract
When Yoshio Nishina passed away in 1951, the research activities in Nishina’s Laboratory in RIKEN were inherited by threelaboratories, and Radiation Laboratory is the one of them. The Radiation Laboratory, whose legacy has been kept for 64 years, leadby F. Yamazaki, T. Hamada, M. Ishihara and last 21 years by H. En’yo, is closed in March 2022. In the last 28 years, we haveproposed and built a polarized proton collider at RHIC, Relativistic Heavy Ion Collider at Brookhaven National Laboratory in theUSA, and discovered that gluons in the proton carry a sizable portion of the proton spin which is 1/2. We also identiﬁed W bosons
in the electron/positron decay channel and in the muon decay channel, with which we showed how much anti-quarks carry the proton
spin. We were successful at RHIC to create Quark Gluon Plasma, the state of Universe just after the Big Bang. Such creation was
conﬁrmed through the many interesting discoveries such as “Jet Quenching,” “Elliptic Particle Flows,” “Thermal Photon Radiation”
and so on. The RIKEN-CCJ, Linux-based Computer Cluster in Japan, was ﬁrstly built in Japan and is still operational in our laboratory
and lead many analyses towards those discoveries. We have discovered the ﬁrst hint of the restoration of Chiral Symmetry Breaking,the mechanism to create 99% of our weight, through the observation of phi meson mass-modiﬁcation in nuclear matter at the 12-GeV
Proton Synchrotron in KEK. This program is now acceded by the E16 experiment in J-PARC.
On the course of those experiments, we have conducted handful of technical developments, which include laser-induced novel
ion sources, helical snake magnets for RHIC and AGS, ﬁne-pitch silicon pixel detectors for PHENIX and sPHENIX experiments,
high-performance trigger electronics, gas-electron-multipliers for hadron-blind detectors and trackers. With some of those new developments, we are preparing and starting new experiments at J-PARC and Fermilab to study the nature of hadron and preparing for theelectron-ion collider (EIC) yet to be built at BNL in near future.
The legacy of our laboratory is taken over by RIKEN-BNL Research Center (RBRC) in BNL and by the new laboratory “RHIC
Physics Research Group” headed by Y. Akiba in RIKEN Nishina Center for Accelerator-Based Science.

2. Major Research Subjects(1) Spin physics with relativistic polarized-proton collisions at RHIC
(2) Study of nuclear matter at high temperature and/or at high density(3) Technical developments on radiation detectors and accelerators

3. Summary of Research Activity(1) Experimental study of spin structure of proton using RHIC polarized proton collider[See also RIKEN-BNL Research Center Experimental Group for the activities at BNL]
After the previously published central-rapidity neutral and charged pion double-spin asymmetries at the highest collision energies
at RHIC of 510 GeV now also the world’s ﬁrst direct photon results have been brought to publication. The direct photon probe
also restricts the initial, hard interaction to be predominantly between a quark and a gluon thus further increasing the sensitivity to
the gluon spin. It has therefore been considered the golden channel to access the gluon spin since the inception of the RHIC spin
program more than two decades ago. Because of the electromagnetic interaction involved in the direct photon process the statistics
are limited, compared to hadronic ﬁnal states. Therefore, it took the largest polarized data set to ﬁnally be able to extract these double
spin asymmetries. The results are found to be consistent with global ﬁts of the previous hadron and jet measurements from RHIC aswell as semi-inclusive DIS. All these results will be included in future global ﬁts of all the existing experimental data in the world andwill improve the sensitivity of quark and gluon spin contributions to the total spin of the nucleon.
While orbital angular momentum cannot be directly accessed at RHIC, several transverse spin phenomena have been observed
which relate to orbital angular momentum and the three-dimensional structure of the nucleon. These phenomena by themselves havebecome a major ﬁeld of research as the dynamics of the strong interaction can be studies with these functions. Various single spin
asymmetry measurements have been obtained for various rapidities. When moving to central rapidities, these left-right asymmetries
are known to be expectingly small for neutral pions. Since then, they have been conﬁrmed to be small also for eta mesons. A
substantially improved data set with signiﬁcantly reduced uncertainties has been recently published in PRD for both ﬁnal states. A
recently published measurement by PHENIX for charged pions at mid-rapidity shows also small asymmetries but at the same time alsoa hint of a charge separation. Such a charge separation could originate from a ﬂavor dependence and could also explain the smallnessof the neutral meson asymmetries where the eﬀects from up and down quark ﬂavors could cancel each other out.
For the ﬁrst time also direct photon single spin asymmetries have been extracted at RHIC. The direct photon asymmetries areagain important here as they are only sensitive to the transverse spin eﬀects in the initial state and not the fragmentation-related
eﬀects. Furthermore, it provides sensitivity to a gluon correlation function that is not accessible in other processes. The direct photon
results have been published in PRL.
In June of 2017, an electro-magnetic calorimeter, RHICf, was installed in the most forward area of the STAR experiment and took
polarized proton collision data for neutral particle production (neutron, photon, neutral pion). The cross-section measurement will give
us new inputs to develop high-energy particle-collision models which are essential to understand air-shower from ultra-high energy
cosmic rays. The ﬁrst photon cross section measurements at very forward rapidities have recently been submitted for publication.
At similar rapidities also neutron asymmetries have been observed in the past. While previously only their general magnitude wasobtained, using unfolding techniques it was possible to extract the ﬁrst asymmetries as a function of the neutron transverse moment- 307 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

for proton-proton collisions. The RHICf results have followed up these PHENIX results and, after conﬁrming the consistency at
small transverse momenta, extended the transverse momentum range signiﬁcantly. These results are currently being prepared for
publication. Similar PHENIX neutron asymmetries in proton-nucleus collisions have been analyzed as a function of both transverseand longitudinal momenta, as well as in (anti)correlation with hadronic detector activity elsewhere. These results have been publishedin PRD and clearly show the interplay between hadronic interactions that predominantly produce negative asymmetries and ultraperipheral collisions that produce positive asymmetries and gain in relevance with heavier nuclei.
Some of us are participating in the Fermilab SeaQuest experiment as a pilot measurement of muon pairs from Drell-Yan processusing a 120-GeV unpolarized proton at Fermilab. After ﬁnishing unpolarized measurements in 2017 to study the quark spin-orbit
eﬀect, a new measurement with a polarized proton target will start in 2022 to study the sea-quark orbit eﬀect of the polarized protonin the target. The ﬁrst result from the SeaQuest experiment on the asymmetry of the antimatter in the proton has been published in
Nature.
For many jet related measurements fragmentation functions are necessary to gain spin and or ﬂavor sensitivity. Those are currently
extracted by some of us using the KEK-Belle data. In addition to using the fragmentation results with RHIC measurements, they will
also provide the basis for most of the key measurements to be performed at the electron-ion collider. In 2021, a new fragmentation
analysis of predominantly vector mesons and D mesons decaying into two or three light hadrons has been prepared and is in theprocess of being ﬁnalized. All these measurements are essential to nearly all nucleon structure measurements at RHIC, semi-inclusive
DIS and the EIC.
As the Electron-Ion Collider is becoming a reality, many of us are participating in the various community eﬀorts to deﬁne thephysics goals of the EIC and how they inform on the choices of collisions energies, luminosities, and detector components. While theaccelerator eﬀorts are naturally led by the two main nuclear physics laboratories in the US, BNL and JLAB, a large EIC user group of
more than 1200 members from all around the world is working on making the EIC a reality. During 2021, the ﬁrst detector proposals
were prepared with the selection of the ﬁrst EIC detector by an external committee. The ﬁrst detector is part of the DOE based EIC
project. Given the participation in the sPHENIX experiment, we participated heavily in the ECCE proposal that also revolves aroundreusing the BABAR/sPHENIX magnet. We were leading the inclusive and semi-inclusive physics studies that showed the feasibilityof the main EIC goals with such a detector. Others participated strongly in the detector considerations for an ECCE zero-degreecalorimeter. At the end of 2021 the ECCE proposal was unanimously selected as the ﬁrst EIC detector and is currently being prepared
to form an actual collaboration.
(2) Experimental study of quark-gluon plasma using RHIC heavy ion collider[See also RIKEN-BNL Research Center Experimental Group for the activities at BNL]
We have completed several key measurements in the study of quark-gluon plasma at RHIC. As the top of them, we lead theanalysis of the ﬁrst thermal photon measurement in heavy ion collisions. The measurement indicates that the initial temperaturereached in the central Au + Au collision at 200 GeV is about 350 MeV, far above the expected transition temperature T c ∼ 170 MeV,
from hadronic phase to quark-gluon plasma. This work was rewarded by Nishina Memorial Prize given to Y. Akiba in 2011. We alsomeasured direct photons in d + Au and direct photon ﬂow strength ν2 and ν3 in Au + Au.
We led measurement of heavy quark (charm and bottom) using VTX, a 4-layer silicon vertex tracker which we jointly constructedwith US DOE. The detector was installed in PHENIX in 2011. PHENIX recorded approximately 10 times more data of Au+Au
collisions in the 2014 run than the 2011 run. PHENIX recorded high statistics p + p and p + A data in 2015, and the doubled the Au+ Au in 2016. PHENIX concluded its data taking in the 2016 run.
The results of the 2011 run were published in Physical Review C (Phys. Rev. C 93, 034904 (2016)). This is the ﬁrst publicationfrom VTX. The result showed that the electrons from bottom quark decay is suppressed for pT > 4 GeV/c, but the suppression factor issmaller than that of charm decay electrons for 3 < pT < 4 GeV/c. This is the ﬁrst observation of bottom electron suppression in heavy
ion collisions, and the ﬁrst result that shows the bottom and charm suppression is diﬀerent. A paper reporting the results of b → e
and c → e measurement in the 2015 p + p run has been published in Phys. Rev. D 99, 092003 (2019). The centrality dependence ofthe suppression b → e and c → e from the 2014 Au+Au data has been submitted for publication. The results show clear quark massdependence of energy loss in the QGP produced at RHIC. The 2016 run is the ﬁnal data taking run of PHENIX, and this run doubled
the dataset for heavy-ﬂavor measurement with VTX. The production of nDSTs of the 2016 VTX data is completed and they are readyfor physics analysis.
PHENIX published measurements of ﬂow strength in p + Au, d + Au, and 3 He+Au (Nature Physics 15, 214 (2019)). The results
provide strong evidence for formation of small droplet of quark gluon plasma in collisions of small systems at RHIC.
In Wako we are operating a cluster computer system (CCJ) specialized to analyze huge data sets taken with the PHENIX detector.
It consists of 25 nodes (17 old nodes and 8 new nodes) each of which has two CPUs and 10 sets of local disks for data repository(old node: quad-core CPU, 1 TB disk, new node: six-core CPU, 2 TB disk). There are 264 CPU cores and 380 TB disks in total.
This conﬁguration ensures the fastest disk I/O when each job is assigned to the node where the required data sets are stored. It is also
important that this scheme does not require an expensive RAID system and network. Through this development we have establisheda fast and cost-eﬀective solution in analyzing massive data.
The data of 1.1 PByte obtained by the PHENIX experiment is stored in a hierarchical storage system which is a part of HOKUSAI
BigWaterfall/SailingShip supercomputer systems operated by the Head Oﬃce for Information Systems and Cybersecurity. In addition,
we operate a dedicated server for the RHICf group and two servers for the J-PARC E16 group, to keep their dedicated compilationand library environments, and some data.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)(3) Study of properties of mesons and exotic hadrons with domestic accelerators
Preparation of the experiment E16 at J-PARC Hadron experimental facility is underway with several Grant-in-Aids. This experiment aims to perform a systematic study of the spectral modiﬁcation of low-mass vector mesons in nuclei to explore the physics ofchiral symmetry breaking and restoration in dense nuclear matter, namely, the mechanism proposed by Nambu to generate most of
hadron masses.
The Gas Electron Multiplier (GEM) technology is adopted for the two key detectors, GEM Tracker (GTR) and Hadron-blind
Cherenkov detector (HBD). To improve electron-identiﬁcation performance, lead-glass calorimeters (LG) are used in combination
with HBD. We are in the production phase. Read-out electronics and trigger logic modules are also installed and tested. We have beena member of the CERN-RD51 collaboration to acquire the read-out technology for GEM. The MoU for RD51 was extended for theperiod of 2019–2023.
Due to the budgetary limitation, we aim to install a part of the detectors at the beginning of the experiment, eight modules of aset of GTR, HBD and LG, out of 26 modules in the full installation. J-PARC PAC (Program Advisory Committee) gave us a stage-2
approval in July 2017 to perform commissioning runs (Run 0). Although there is a signiﬁcant delay from the originally planned dateof March 2016, the construction of the beam line by KEK was completed ﬁnally in early 2020 to perform this experiment.
After the successful commissioning runs held in JFY 2020, we performed the second commissioning run in June 2021. Twoelectron trigger to accumulate the data of vector meson decays were tested. The micro beam structures were newly found which
deteriorates DAQ and trigger performances. Countermeasures for the structures were already discussed in cooperation with theaccelerator group and Beam line group in J-PARC, and will be adopted in the coming beam time in the ﬁrst quarter of 2023. On theother hand, detector performances were almost satisﬁed. In our plan, physics run will be performed in 2023–24, after the beam study.
Approval of physics run will be discussed in PAC held in Summer 2022.
This activity is moved to Meson Science Laboratory after the closing of Radiation Laboratory.
(4) Detector development for PHENIX/sPHENIX experiment
The PHENIX experiment proposes substantial detector upgrades to go along the expected accelerator improvements, including
the future electron-ion collider “EIC.” The present PHENIX detector is repurposed to the sPHENIX (super PHENIX) detector whichreuses the Babar solenoid magnet at SLAC and is covered by the hadronic calorimeter which was not available in the previous RHIC
experiments. The sPHENIX was approved for the Project Decision-2/3 (corresponds to DOE’s Critical Decision-2/3) in May 2019.
We RIKEN group have been developing the one of the tracking devices of sPHENIX detector, so called intermediate tracker (INTT)
since 2015. The INTT provides the best timing resolution among the sPHENIX tracking system, in conjunction with a time projection
chamber and a MAPS based vertex detectors. The INTT silicon ladders have been demonstrated the satisfactory performance as
designed through the three beam tests in 2018, 2019, and 2021 in Fermilab Test Beam Facility (FTBF) and Research Center forElectron Photon Science, Tohoku University. The production of silicon-ladder assembly was completed by Spring 2022 in the Taiwan
Silicon Detector Facility (TSiDF) and in BNL. And the INTT barrel assembly has been started since June 2022 in BNL. The INTT
barrel is scheduled to be installed to the beam line at the sPHENIX site in January 2023 followed by the sPHENIX commissioning in
February 2023.
As the further investigation of the neutral pion production asymmetry discovered in the RHICf experiment, we started preparation
for the next phase of the experiment, namely RHICf-II. Since physics data taking at RHIC in 2024, which is required for RHICf-II,
will not be implemented, we are considering other possibilities to achieve its physics goal. The highlight of the upgraded experiment is
to adopt a larger acceptance with higher position resolution for the zero-degree calorimeter (ZDC). The detector technology developed
for the FoCAL upgrade project of the ALICE experiment at LHC well satisﬁes the RHICf-II performance requirement. We thus
resumed the associated membership of the ALICE collaboration, and the RHICf-II detectors are to be developed together with the
ALICE FoCAL collaboration. This new detector technology development is also a part of an essential R&D programs for a ZDC
detector for EIC.

Members
Director
Hideto EN’YO
Senior Research Scientists
Yuji GOTO
Itaru NAKAGAWA

Ralf SEIDL
Satoshi YOKKAICHI

Contract Researcher
Tomonori TAKAHASHI
Special Postdoctoral Researcher
Koki KANNO- 309 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Research Associate
Wataru NAKAI
Junior Research Associate
Tomoki MURAKAMI
Special Temporary Research Scientist
Yasushi WATANABE
Senior Visiting Scientist
Toshiaki SHIBATA (Nihon Univ.)
Visiting Scientists
Kazuya AOKI (KEK)
Wen-Chen CHANG (Inst. of Phys., Academia Sinica)
Tatsuya CHUJO (Tsukuba Univ.)
Shoichi HASEGAWA (JAEA)
Motoi INABA (Tsukuba Univ. of Tech.)Shunzo KUMANO (KEK)
Tsutomu MIBE (KEK)
Yuhei MORINO (KEK)

Ken-ichi NAKANO (Tokyo Tech)
Megumi NARUKI
Kyoichiro OZAWA (KEK)
Susumu SATO (JAEA)
Kenta SHIGAKI (Hiroshima Univ.)
Maya SHIMOMURA (Nara Women’s Univ.)
Kiyoshi TANIDA (JAEA)

Visiting Technician
Che-Sheng LIN (Academia Sinica)
Student Trainees
Daichi ARIMIZU (Kyoto Univ.)
Shunsuke KAJIKAWA (Tohoku Univ.)
Natsuki KURODA (Nara Women’s Univ.)
Shono KYAN (Tsukuba Univ.)
Miu MORITA (Nara Women’s Univ.)
Tomoki MURAKAMI (Univ. of Tokyo)

Satomi NAKASUGA (Kyoto Univ.)
Yumika NAMIMOTO (Nara Women’s Univ.)
Naoki OGATA (Kyoto Univ.)
Mika SHIBATA (Nara Women’s Univ.)
Runa TAKAHAMA (Nara Women’s Univ.)
Po-Hung WANG (Nat’l Central Univ.)

Interns
Hikaru IMAI (Rikkyo Univ.)
Miu MORITA (Nara Women’s Univ.)
Yusuke NAKAMURA (Rikkyo Univ.)
Genta NAKANO (Rikkyo Univ.)

Yumika NAMIMOTO (Nara Women’s Univ.)
Mika SHIBATA (Nara Women’s Univ.)
Runa TAKAHAMA (Nara Women’s Univ.)

AssistantKeiko SUZUKI

List of Publications & Presentations
Publications[Original Papers]
U. A. Acharya et al. (PHENIX Collaboration), “Improving constraints on gluon√ spin-momentum correlations in transversely polarized
protons via midrapidity open-heavy-ﬂavor electrons in p ↑ +p collisions at s = 200 GeV,” e-Print: 2204.12899 [hep-ex], April 27,(2022).
U. A. Acharya et al. (PHENIX Collaboration), “Measurements of second-harmonic Fourier coeﬃcients from azimuthal anisotropies in√
p+p, p+Au d+Au, and 3 He + Au collisions at sNN = 200 GeV,” e-Print: 2203.09894 [nucl-ex], March 18, (2022).
√
U. A. Acharya et al. (PHENIX Collaboration), “Study of φ-meson production in p+Al, p+Au, d+Au, and 3 He+Au collisions at sNN =200 GeV,” Contribution to 2022 Snowmass Summer Study, e-Print:2203.06087 [nucl-ex], March 11, (2022).
√
U. A. Acharya et al. (PHENIX Collaboration), “Measurement of direct-photon cross section and double-helicity asymmetry at s =510 GeV in p + p collisions,” e-Print: 2202.08158 [hep-ex], February 16, (2022).
U. A. Acharya et al. (PHENIX Collaboration),“Measurement of ψ (2S) nuclear modiﬁcation at backward and forward rapidity in p+p,√
p+Al, and p+Au collisions at s = 200 GeV,” e-Print: 2202.03863 [nucl-ex], February 8, (2022).
U. A. Acharya et al. (PHENIX√ Collaboration), “Transverse-single-spin asymmetries of charged pions at midrapidity in transversely
polarized p+p collisions at s = 200 GeV,” Phys. Rev. D 105, 032003 (2022).
U. A. Acharya et al. (PHENIX Collaboration), “Systematic study of nuclear eﬀects in p+Al, p+Au, d+Au, and 3 He+Au collisions at√
sNN = 200 GeV using π0 production,” Phys. Rev. C 105, 064902 (2022).
U. A. Acharya et al. (PHENIX Collaboration), “Transverse single spin asymmetries of forward neutrons in p+p, p+Al and p+Au colli√
sions at sNN = 200 GeV as a function of transverse and longitudinal momenta,” Phys. Rev. D 105, 032004 (2022).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)√
U. A. Acharya et al. (PHENIX Collaboration), “Kinematic dependence of azimuthal anisotropies in p+Au, d+Au, and 3 He+Au at sNN =200 GeV, Phys. Rev. C 105, 024901 (2022).
U. A. Acharya et al. (PHENIX Collaboration), “Probing gluon√ spin-momentum correlations in transversely polarized protons throughmidrapidity isolated direct photons in p ↑ +p collisions at s = 200 GeV,” Phys. Rev. Lett. 127, 162001 (2021).
U. A. Acharya √et al. (PHENIX Collaboration), “Transverse single-spin asymmetries of midrapidity π0 and η mesons in polarized p+p
collisions at s = 200 GeV,” Phys. Rev. D 103, 052009 (2021).
U. A. Acharya et al. (PHENIX √Collaboration), “Transverse momentum dependent forward neutron single spin asymmetries in transversely
polarized p+p collisions at s = 200 GeV,” Phys. Rev. D 103, 032007 (2021).
O. Adriani et al. (RHICf Collaboration), “Performance of RHICf detector during operation in 2017,” J. Instrum. 16, P10027 (2021).
T. N. Takahashi et al., “Data acquisition system in the ﬁrst commissioning run of the J-PARC E16 experiment,” IEEE Trans. Nucl. Sci.
68, 1907 (2021).

Presentations[International Conferences/Workshops]
Y. Goto (invited), “Prospective physics study at EIC,” 8th Asian Triangle Heavy-Ion Conference (ATHIC2021), Incheon, South Korea,
Online, Novermber 9, 2021.
T. N. Murakami (poster), “Construction and operation of gas electron multiplier tracker for the J-PARC E16 experiment in run0,” 2021
Virtual IEEE Nuclear Science Symposium, Online, October 16–23, 2021.
K. Kanno (invited), “Study of spectral change of vector mesons in nuclear medium at J-PARC,” 2nd International Workshop on the
Extension Project for the J-PARC Hadron Experimental Facility, Online, February 16–18, 2022.
S. Yokkaichi (invited), “J-PARC E16 has started—spectral change of vector mesons in nuclei—,” Reimei Workshop, “Hadrons in dense
matter at J-PARC”, Tokai, Japan, Hybrid, February 21–23, 2022.
S. Nakasuga (poster), “Commissioning of the electron identiﬁcation system for dilepton measurement in pA collisions at J-PARC,”
VCI2022 (The 16th Vienna Conference on Instrumentation), Online, February 21–25, 2022.

[Domestic Conferences/Workshops]
後藤雄二（招待講演）, 「RHIC Spin Physics」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 17 日.
√
後藤雄二（口頭発表）, 「PHENIX 実験での sNN = 200 GeV 偏極陽子＋原子核衝突による超前方中性子のシングルスピン非対称度の横運動量依存性」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 16 日.
高橋智則 (招待講演), 「有限密度媒質中でのクォーク相関の解明に向けたレプトン対精密測定」, 第 6 回クラスター階層領域研究会, オンライン, 2021 年 6 月 14 日, 6 月 19 日.
高橋智則 (招待講演), 「J-PARC E16 実験の計測システムの現状と課題」, 計測システム研究会 2021, 九州大学 (福岡市), ハイブリッ
ド, 2021 年 10 月 28–29 日.
村上智紀, 「J-PARC E16 実験 Run0 における GEM 飛跡検出器実機の性能評価」, 日本物理学会 第 77 回 年会, オンライン, 2022 年
3 月 15–19 日.
村上智紀, 「J-PARC 高運動量ビームラインを用いた原子核密度中における φ 中間子質量スペクトルの測定」, J-PARC ハドロン研究会, オンライン, 2022 年 3 月 22–24 日.

[Seminars]
H. En’yo, “Forty academic years with physics of high density nuclear matter (in Japanese),” Heavy Ion Pub, Nagoya University, Online,
November 12, 2021.
H. En’yo, “My 40 years seeking for the new phase of nuclear matter (in Japanese),” ELPH Seminar, Research Center for Electron Photon
Science (ELPH), Tohoku University, Sendai, Japan, Hybrid, December 23, 2021.

Press Release“Direct Photons Oﬀer Glimpse of Gluons’ Dynamic Motion—PHENIX data validate approach for future studies of proton spinand structure—,” October 12, 2011. https://www.bnl.gov/newsroom/news.php?a=119077,https://www.riken.jp/press/
2021/20211015_1/index.html .

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Subnuclear System Research Division
Meson Science Laboratory
1. Abstract
Particles like muons, pions, and kaons have ﬁnite lifetimes, so they do not exist in natural nuclei or matters. By implanting theseparticles into nuclei/matters, exotic phenomena in various objects can be studied from new point of view.
For example, kaon is the second lightest meson, which has strange quark as a constituent quark. It is expected that if one embeds
mesons into nuclei, the sizes of the nuclei become smaller, and one can form a high-density object beyond the normal nuclear density.
Study of this object could lead to better understanding of the origin of the mass of the matter and may reveal the quark degree of
freedom beyond the quark-conﬁnement. The other example is the weak interaction in nuclear matter. It can only be studied by the
weak decay of hypernuclei, which have Lambda particle in the nuclei.
Muon provides even wider scope of studies, covering condensed matter physics as well as nuclear and atomic physics, and weare trying to extend the application ﬁeld further into chemical and biological studies. For instance, stopping positively charged muonin a material, we obtain information on the magnetic properties or the local ﬁeld at the muon trapped site (μSR). Injecting negatively
charged muon to hydrogen gas, muonic hydrogen atom (μp) is formed. We use muonic atoms for proton magnetic radius measurement,muon catalyzed fusion and elemental analysis with muonic X-rays. We are also interested in precision measurement of muon property
itself, such as muon anomalous magnetic moment (g − 2).
In our research, we introduce diﬀerent kind of impurities into nuclei/matters, and study new states of matter, new phenomena, or
the object properties.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)

Study of meson property and interaction in nuclei
Origin of matter mass/quark degree of freedom in nuclei
Condensed matter and material studies with muon
Nuclear and particle physics studies via muonic hydrogen
Development of ultra cold muon beam, and its application from material science to particle physics

3. Summary of Research Activity(1) Hadron physics at J-PARC, RIKEN-RIBF, GSI and SPring-8
Kaon and pion will shed a new insight to the nuclear physics. The recent discovery of deeply bound pionic atom enables us toinvestigate the properties of mesons in nuclear matter. At RIKEN-RIBF, we are preparing precise experimental study of the pionicatom. Very lately, we succeeded to discover kaonic nuclear bound state, “K-pp,” at J-PARC. The yield dependence on momentumtransfer shows that observed system is unexpectedly small. We extended our study on Λ(1405) that could be K-p bound state. By theseexperiments, we are studying the KN − interaction, and clarify the nature of kaon in nuclei. At Spring-8 and at GSI, we are planning tostudy omega and η nuclei. By these experiments, we aim to be a world-leading scientiﬁc research group using these light meta-stableparticles.
(1-1) Deeply bound kaonic nuclei
J-PARC E15 experiment had been performed to explore the simplest kaonic nuclear bound state, “K − pp”. Because of the strong
attraction between KN − , the K − in nuclei may attract surrounding nucleons, resulting in forming a deeply bound and extremely dense
object. Measurement of the kaon properties at such a high-density medium will provide precious information on the origin of hadron
masses, if the standard scenario of the hadron-mass-generation mechanism, in which the hadron masses are depends on matter densityand energy, is correct. Namely, one may study the chiral symmetry breaking of the universe and its partial restoration in nuclear
medium.
The E15 experiment was completed to observe the “K − pp” bound state by the in-ﬂight 3 He(K − , n) reaction, which allows us
the formation via the invariant-mass spectroscopy by detecting decay particles from “K − pp”. For the experiment, we constructed a
dedicated spectrometer system at the secondary beam-line, K1.8BR, in the hadron hall of J-PARC.
With the Λpn ﬁnal states obtained in the ﬁrst stage experiment, we observed a kinematic anomaly in the Λp invariant mass near
the mass threshold of M(K − -pp) (total mass of kaon and two protons) at the lower momentum transfer q region. We conducteda successive experiment to examine the nature of the observed kinematical anomaly in the Λpn ﬁnal state, and we conﬁrmed theexistence of the bound state below the mass threshold of M(K − pp) at as deep as the binding energy of 40 MeV. The momentum
transfer q naturally prefers lower momentum for the bound state formation, but the observed event concentration extended having theform-factor parameter ∼400 MeV/c. Based on the PWIA calculation, the data indicated that the “K − pp” system could be as small as∼0.6 fm. It is astonishingly compact in contrast to the mean nucleon distance ∼1.8 fm.
This observed signal shows that a meson (qq− ) forms a quantum state where baryons (qqq) exist as nuclear medium, i.e., ahighly excited novel form of nucleus with a kaon, in which the mesonic degree-of-freedom still holds. This is totally new form of
nuclear system, which never been observed before.
(1-2) Precision X-ray measurement of kaonic atom
To study the KN − interaction at zero energy from the atomic state level shift and width of kaon, we have performed an X-ray
spectroscopy of atomic 3d → 2p transition of negatively charged K-mesons captured by helium atoms. However, our ﬁrst experimentis insuﬃcient in energy resolution to see the K − -nucleus potential. Aiming to provide a breakthrough from atomic level observation,- 312 -

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we introduce a novel X-ray detector, namely superconducting transition-edge-sensor (TES) microcalorimeter oﬀering unprecedented
high energy resolution, being more than one order of magnitude better than that achieved in the past experiments using conventional
semiconductor detectors. The experiment J-PARC E62 aims to determine 2p-level strong interaction shifts of kaonic 3 He and 4 He
atoms by measuring the atomic 3d → 2p transition X-rays using TES detector with 240 pixels having about 23 mm2 eﬀective area
and the average energy resolution of 7 eV (FWHM) at 6 keV. We carried out the experiment at J-PARC in June 2018 and successfully
observed distinct X-ray peaks from both atoms. The energies were determined to be 6224.5 +/− 0.4 (stat) +/− 0.2 (syst) eV and
6463.7 +/− 0.3 (stat) +/− 0.1 (syst) eV, and widths to be 2.5 +/− 1.0 (stat) +/− 0.4 (syst) eV and 1.0 +/− 0.6 (stat) +/− 0.3 (syst)
eV, for kaonic 3 He and 4 He, respectively. These values are nearly 10 times more precise than in previous measurements. The results
exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach and agree with calculations
based on optical-potential models.
Another important X-ray measurement of kaonic atom would be 2p → 1 stransition of kaonic deuteron (K − -d). We have measured
same transition of kaonic hydrogen (K − -p), but the width and shift from electro-magnetic (EM) value reﬂect only isospin average ofthe K bar N interaction. We can resolve isospin dependence of the strong interaction by the measurements both for K − -p and K − -d. The
experiment J-PARC E57 aims at pioneering measurement of the X-rays from K − -d atoms. Prior to full (stage-2) approval of the E57
proposal, we performed a pilot run with hydrogen target in March 2019.
(1-3) Deeply bound pionic atoms and η mesonic nuclei
We have been working on precision spectroscopy of pionic atoms systematically, which leads to understanding of the non-trivial
structure of the vacuum and the origin of hadron masses. The precision data set stringent constraints on the chiral condensate at
nuclear medium. We are presently preparing for the precision systematic measurements at RIBF. A pilot experiment performed in2010 showed a unprecedented results of pionic atom formation spectra with ﬁnite reaction angles. The measurement of pionic 121 Sn
performed in 2014 provided high-precision data and set constraints on the pion-nucleus strong interaction, which led to deductionof the chiral condensate at the normal nuclear density. In 2021, systematic high precision spectroscopy of pionic Sn atoms were
performed and the analysis is ongoing.
We are also working on spectroscopy of η mesonic nuclei in GSI/FAIR. Theoretically, peculiarly large mass of η is attributed
to UA(1) symmetry and chiral symmetry breaking. As a result, large binding energy is expected for η meson bound states in nuclei(η -mesonic nuclei). From the measurement, we can access information about gluon dynamics in the vacuum via the binding energy
and decay width of η -nuclear bound state. In 2022, we performed a new experiment using a large solid angle detector of WASA at
GSI to search for the η -nucleus bound state with an enhanced signal-to-noise ratio.
(1-4) 3Λ H lifetime puzzle and our approach
Three recent heavy ion experiments (HypHI, STAR, and ALICE) announced surprisingly short lifetime for 3Λ H hyper-nucleus’s
Mesonic Weak Decay (MWD), which seems to be inconsistent with the fact that the 3Λ H is a very loosely bound system. It is very
interesting to study this with a diﬀerent experimental approach. We proposed a direct measurement of 3Λ H MWD lifetime with ∼20%
resolution at J-PARC hadron facility by using K-meson beam at 1 GeV/c. As for the feasibility test, we also measure 4Λ H lifetime.
A Cylindrical Detector System (CDS) used in J-PARC E15/E31 experiment is employed to capture the delayed π− as a weak decay
40
product from 3,
Λ H a calorimeter is installed in the very forward region to tag fast π meson emission at ∼0 degree, which ensures that3, 4
H and quasi-free Λ andthe Λ hyperon production with small recoil momentum. By this selection, we can improve the ratio between Λ4
Σ background. A test beam for feasibility study with He target has been conditionally approved by J-PARC PAC. We will conduct
the experiment and to present the data in short.
(2) Muon science at RIKEN-RAL branch
The research area ranges over particle physics, condensed matter studies, chemistry and life science. Our core activities are
based on the RIKEN-RAL Muon Facility located at the Rutherford-Appleton Laboratory (UK), which provides intense pulsed-muonbeams. We have variety of important research activities such as particle/nuclear physics studies with muon’s spin and condensed
matter physics by muon spin rotation/relaxation/resonance (μSR).
(3) Condensed matter/materials studies with μSR
We share experimental equipment with those of RAL in order to make organization of RIKEN beam time schedules easier andto enhance the eﬃciency to carry out RIKEN’s experiments. We use shared cryostats and manpower supports available from RAL
as well we other experimental areas. Both two μSR spectrometers, ARGUS (Port-2) and CHRNUS (Port-4), are working well withmaintenance supports provide from RAL. Among our scientiﬁc activities on μSR studies from year 2017 to 2021, following studies
are most important subjects of material sciences at the RIKEN-RAL muon facility:(1) Multi magnetic transitions in the Ru-based pyrochlore systems, R2 Ru2 O7 ;(2) Magnetic properties of the nano-cluster gold in the border of macro- and micro- scale;(3) Novel magnetic and superconducting properties of nano-size La-based high-TC superconducting curates;(4) Determination of muon positions estimated from density functional theory (DFT) and dipole-ﬁeld calculations;(5) Chemical muonic states in DNA molecules.
(3-1) Nuclear and particle physics studies via ultra-cold muon beam and muonic atoms
If we can improve muon beam emittance, timing and energy dispersion (so-called “ultra-cold muon”), then the capability of μSR
studies will be drastically improved. The ultra-cold muon beam can stop in a thin foil, multi-layered materials and artiﬁcial lattices, so
one can apply the μSR techniques to surface and interface science. The development of ultra-cold muon beam is also very importantas the source of pencil-like small emittance muon beam for muon g − 2 measurement.

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Ultra-cold muon beam has been produced by laser ionization of muoniums in vacuum (bound system of μ+ and electron). We
developed a very promising materials for muonium production, laser ablated silica aerogel. We also developed a high power Lyman-αlaser in collaboration with laser group at RIKEN. In this laser development, we succeeded to synthesize novel laser crystals Nd:YGAG
and Nd:YSAG, which has an ideal wavelength property for laser ampliﬁcation to generate Lyman-α by four-wave mixing in Kr gas
cell. We are now building the actual muon source to be used for muon g − 2. Basic design has been completed and the manufacture isin progress.
We are planning a precise measurement of proton Zemach radius (with charge and magnetic distributions combined) using thelaser spectroscopy of hyperﬁne splitting energy in the muonic hydrogen atom. As a key parameter for designing the experiment, weneed to know the quench rate of the muonic proton polarization. We are analyzing data on muonic deuterium and muonic proton
polarization obtained in low pressure hydrogen gas.

Members
Director
Masahiko IWASAKI
Senior Research Scientists
Kenta ITAHASHI
Yue MA
Haruhiko OUTA

Fuminori SAKUMA
Isao WATANABE

Contract Researcher
Katsuhiko ISHIDA
Postdoctoral Researcher
Rie MURAYAMA
Junior Research Associates
Shun SEO

Muhamad UMAR

International Program Associates
Supparat CHAROENPHON
Muhammad CHE LAH
Li DENG

Anita PUTRI
Utami WIDYAISWARI

Research Consultant
Masayasu KAMIMURA
Senior Visiting Scientists
Hiroyuki NOUMI (Osaka Univ.)

Kazuhiro TANAKA (KEK)

Visiting Scientists
Tadashi ADACHI (Sophia Univ.)
Retno ASIH (Inst. Teknologi Sepuluh Nopember)
Fahmi ASTUTI (Inst. Teknologi Sepuluh Nopember)
Catalina Oana CURCEANU (INFN)
Zyun EZAWA (Tohoku Univ.)
Hiroyuki FUJIOKA (Tokyo Tech)
Masaki FUJITA (Tohoku Univ.)
Shuhei FUKUOKA (Hokkaido Univ.)
Takayuki GOTO (Sophia Univ.)
Maryam HASSANVAND (Isfahan Univ. of Tech.)
Wataru HIGEMOTO (JAEA)
Taichi HINOKIHARA (Univ. of Tokyo)
Ko-ichi HIRAKI (Fukushima Medical Univ.)
Satoru HIRENZAKI (Nara Women’s Univ.)
Koichi ICHIMURA (Hokkaido Univ.)
Yasuyuki ISHII (Shibaura Inst. of Tech.)
Ryosuke KADONO (KEK)
Takayuki KAWAMATA (Tohoku Univ.)
Seiko KAWAMURA (JAEA)
Hikomitsu KIKUCHI (Univ. of Fukui)
Takuya KOBAYASHI (Saitama Univ.)

Yoji KOIKE (Tohoku Univ.)
Kenji MATSUDA (Univ. of Toyama)
Hiroyasu MATSUURA (Univ. of Tokyo)
Mototsugu MIHARA (Osaka Univ.)
Takaaki MINAMIDATE (Tokyo Univ. Sci)
Yasuhiro MIYAKE (KEK)
Takehito NAKANO (Ibaraki Univ.)
Takahiro NAMIKI (Univ. of Toyama)
Katsuhiko NISHIMURA (Univ. of Toyama)
Agustinus NUGROHO (Inst. Teknologi Bandung)
Kazuki OHISHI (Comprehensive Res. Org. for Sci. and Soc.)
Yu OISHI (KEK)
Dita PUSPITA SARI (Shibaura Inst. of Tech.)
Muhammad RAMADHAN (Univ. Pertahanan Republik Indonesia)
Irwan RAMLI (Univ. Cokroaminoto Palopo)
RISDIANA (Padjadjaran Univ.)
Lusi SAFRIANI (Padjadjaran Univ.)
Naohito SAITO (KEK)
Shinichi SHAMOTO (Comprehensive Res. Org. for Sci. andSoc.)- 314 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Ichihiro YAMAUCHI (Saga Univ.)
Yukio YASUI (Meiji Univ.)
Masaru YOSOI (Osaka Univ.)
Wan Nurfadhilah ZAHARIM (UNIVERSITIMALAYSIA)
Xu-Guang ZHENG (Saga Univ.)
Johann ZMESKAL (Austrian Academy of Sci.)

Ichiro SHIRAKI (Univ. of Yamanashi)
Shukri SULAIMAN (Univ. Sains Malaysia)
Takao SUZUKI (Shibaura Inst. of Tech.)Takanori TANIGUCHI (Tohoku Univ.)
Andrea VACCHI (Udine Univ. (Italy))
Eberhard WIDMANN (Stefan Meyer Inst.)
Yasuhiro YAMAGUCHI (JAEA)

SAINS

Research Fellow
Harison ROZAK (Shibaura Inst. of Tech.)Student Trainees
Kanato HIGUCHI (Tokyo Tech)Harison ROZAK (Shibaura Inst. of Tech.)

Manaka YOSHIDA (Tokyo Univ. Sci)

Assistants
Kumiko TAKAHASHI

Mitsue YAMAMOTO

List of Publications & Presentations
Publications[Original Papers]
T. Hashimoto et al. (J-PARC E62 Collaboration), “Measurements of strong-interaction eﬀects in kaonic-helium isotopes at sub-eV precision with X-ray microcalorimeters,” Phys. Rev. Lett. 128, 112503 (2022).
F. Sakuma et al. (J-PARC E15/E80 Collaboration), “Recent results and future prospects of kaonic nuclei at J-PARC,” Few-Body Sys. 62,
103 (2021).
C. Pizzolottoa, A. Sbrizzia, A. Adamczak, D. Bakalov, G. Baldazzie, M. Baruzzoa, R. Benoccih, R. Bertoni, M. Bonesinih, H. Cabrera,
D. Cirrincione, M. Clemenza, L. Colace, M. Danailov, P. Danev, A. deBari, C. DeVecchi, M. DeVincenzik, E. Fasci, F. Fuschino,
K. S. Gadedjisso-Tossou, L .Gianfrani, K. I shida, C. Labanti, V. Maggi, R. Mazza, A. Menegolli, E. Mocchiutti, S. Monzani, L. Moretti,
G. Morgante, J. Niemela, A. Pullia, R. Ramponi, L. P. Rignanese, M. Rossella, M. Stoilov, L. Stoychev, J. J. Suárez-Vargas, L. Tortora,
E. Vallazza, and A. Vacchi, “Measurement of the muon transfer rate from muonic hydrogen to oxygen in the range 70–336 K,” Phys.
Lett. A 403, 127401 (2021).
T. Yamashita, K. Okutsu, Y. Kino, R. Nakashima, K. Miyashita, K. Yasuda, S. Okada, M. Sato, T. Oka, N. Kawamura, S. Kanda,
K. Shimomura, P. Strasser, S. Takeshita, M. Tampo, S. Doiuchi, Y. Nagatani, H. Natori, S. Nishimura, A. D. Pant, Y. Miyake, and
K. Ishida, “Time evolution calculation of muon catalysed fusion: Emission of recycling muons from a two-layer hydrogen ﬁlm,”
Fusion Eng. Des. 169, 112580 (2021).
A. D. Pant, K. Nagamine, E. Torikai, I. Shiraki, K. Shimomura, F. L. Pratt, H. Ariga-Miwa, K. Ishida, and J. S. Schultz, “Muonium
response to low oxygen levels in haemoglobin and other biological aqueous solutions and potential application towards monitoring
hypoxia,” Nucl. Instrum. Methods Phys. Res. A 1010, 165561 (2021).
M. D. Umar, K. Ishida, R. Murayama, D. P. Sari, U. Widyaiswari, M. Fronzi, I. Watanabe, and M. Iwasaki, “Muon-spin motion at thecrossover regime between Gaussian and lorentzian distribution of magnetic ﬁelds,” Prog. Theor. Exp. Phys. 2021, 083101 (2021).
K. Okutsu, T. Yamashita, Y. Kino, R. Nakashima, K. Miyashita, K. Yasuda, S. Okada, M. Sato, T. Oka, N. Kawamura, S. Kanda,
K. Shimomura, P. Strasser, S. Takeshita, M. Tampo, S. Doiuchi, Y. Nagatani, H. Natori, S. Nishimura, A. D. Pant, Y. Miyake, and
K. Ishida, “Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target,” Fusion Eng.
Des. 170, 112712 (2021).
A. Green, K. Ishida, B. V. Hampshire, K. Butcher, M. Pollard, and A. D. Hillier, “Understanding roman gold coinage inside out,” J.
Archaeol. Sci. 134, 105470 (2021).
J. Sugiyama, K. Ohishi, O. K. Forslund, M. Månsson, S. P. Cottrell, A. D. Hillier, and K. Ishida, “How Li diﬀusion in spinel
Li[Ni1/2 Mn3/2 ]O4 is seen with μ± SR,” Z. Phys. Chem. 236, 799 (2022).
W. N. Zaharim, S. N. A. Ahmad, S. Sulaiman, H. Rozak, D. F. H. Baseri, N. A. M. Rosli, S. S. Mohd-Tajudin, L. S. Ang, and I. Watanabe,“Density functional theory study of 12mer single-strand Guanine oligomer and associated muon hyperﬁne interaction,” ACS Omega 6,29641–29650 (2021).
A. Jamaludin, W. N. Zaharim, S. Sulaiman, H. Rozak, A. L. Sin, and I. Watanabe, “Density functional theory investigation of muon
hyperﬁne interaction in guanine-cytosine double-strand DNA,” J. Phys. Soc. Jpn. 91, 024301 (2022).
S. Yoon, W. Lee, S. Lee, J. Park, H. Lee, Y. S. Choi, S.-H. Do, W. -J. Choi, W. -T. Chen, F. Chou, D. I. Gorbunov, Y. Oshima,
A. Ali, Y. Singh, A. Berlie, I. Watanabe, and K. -Y. Choi1, “Quantum disordered state in the J1 -J2 square-lattice antiferromagnet
Sr2 Cu(Te0.95 W0.05 )O6 ,” Phys. Rev. Res. 5, 014441 (2021).
M. Miyajima, F. Astuti, T. Fukuda, M. Kodani, S. Iida, S. Asai, A. Matsuo, T. Masuda, K. Kindo, T. Hasegawa, Tatsuo C. Kobayashi,
T. Nakano, I. Watanabe, and T. Kambe, “Spin-gap formation due to spin-peierls instability in π-orbital-ordered NaO2 ,” Phy. Rev. B
104, L140402 (2021).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)[Review Articles]
M. Cataldo, M. Clemenza, K. Ishida, and A. D. Hillier, “A novel non-destructive technique for cultural heritage: Depth proﬁling andelemental analysis underneath the surface with negative muons,” Appl. Sci. 12, 4237 (2022).
A.D. Hillier, S. J. Blundell, I. McKenzie, I. Umegaki, L. Shu, J. A. Wright, T. Prokscha, F. B. K. Shimomura, A. Berlie, H. Alberto, andI. Watanabe, “Muon spin spectroscopy,” Nat. Rev. Meths. Primers 2, 4 (2022).
I. Watanabe, D. P. Sari, R. Ramadhan, B. Adiperdana, and S. Sulaiman, “Muon-site determination in materials by using computational
methods,” J. Comput. Chem. Jpn. 19, 115–123 (2020).

[Book]
A. D. Hillier, B. Hampshire, and K. Ishida, “Depth-dependent bulk elemental analysis using negative muons,” in “Handbook of Cultural
Heritage Analysis,” S. D’Amico and V. Venuti (Eds.), Springer, 2022, pp. 23–44.

Presentations[International Conferences/Workshops]
F. Sakuma (invited), “Light kaonic nuclei at J-PARC,” Strangeness Nuclear Physics Workshop 2021, Online, December 18–19, 2021.
F. Sakuma (invited), “Summary of the K-pp bound-state observation in E15 and future prospects,” International Conference on Exotic
Atoms and Related Topics (EXA 2021), Online, September 13–17, 2021.
M. Iwasaki (invited), “Experimental study toward spin-parity assignment of the ﬁrst Kaonic nuclear bound state, K-pp,” STRANU: Hot
Topics in STRANgeness NUclear and Atomic Physics, ECT*, Online, May 24–28, 2021.
T. Akaishi, “Experimental status toward the direct lifetime measurement of Hypertriton using the (K− , π0 ) reaction at J-PARC,” Particles
and Nuclei International Conference (PANIC), Online, September 5–10, 2021.
Y. Ma, “Towards solving the hypertriton lifetime puzzle with direct lifetime measurement: Update from J-PARC E73 experiment,” 19thInternational Conference on Hadron Spectroscopy and Structure in memoriam Simon Eidelman (HADRON 2021), Online, July 26–31,
2021.
K. Ishida, “Muon g-2 experiment at J-PARC,” 14th European Research Conference on Electromagnetic Interactions with Nucleons andNuclei (EINN2021), Online, November 2–6, 2021.

[Domestic Conferences/Workshops]
石田勝彦, 「ミュオン原子分子とスピン状態」, 新学術領域「宇宙観測検出器と量子ビームの出会い. 新たな応用への架け橋. 」, 第 1
回超低速負ミュオンビーム研究会, オンライン, 2021 年 12 月 20 日.
石田勝彦, 「RIKEN-RAL 施設」, 第 12 回「Muon 科学と加速器研究」, 第 6 回「文理融合シンポジウム 量子ビームで歴史を探る—
加速器が紡ぐ文理融合の地平—」, 「ミュオンで見る磁性・超伝導物質研究の最前線」, 合同研究会, 豊中市（大阪大学）, 2022 年
1 月 6–8 日.
石田勝彦, 「パルスミュオン施設でのミュオン科学研究」, 「ミューオン X 線 γ 線分光 非破壊分析, 化学, 原子核物理への新展開」,「ミューオン原子核捕獲反応による原子核関連研究の可能性」, 合同研究会, 豊中市（大阪大学 RNCP）&オンライン, 2022 年 3月 24 日.

Press Release
神田聡太郎, 下村浩一郎, 他「『理想の水素原子』で未知の物理現象を探索する, ミュオニウムのマイクロ波分光実験がスタート」,
高エネルギー加速器研究機構, J-PARC センター, 理化学研究所, 東京大学大学院理学系研究科, 東京大学大学院総合文化研究科,
2021 年 4 月 16 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Subnuclear System Research Division
RIKEN BNL Research Center
1. Abstract
The RIKEN BNL Research Center was established in April 1997 at Brookhaven National Laboratory with Professor T. D. Lee
of Columbia University as its initial Director. The Center is dedicated to the study of strong interactions, including spin physics,
lattice QCD and RHIC physics through the nurturing of a new generation of young physicists. Professor Lee was succeeded by BNL
Distinguished Scientist, the former BNL director, N. P. Samios, who served until 2013. The other former BNL director, S. H. Aronson
led the Center from 2013. Hideto En’yo succeeded the director position starting from JFY 2017. Support for RBRC was initially forﬁve years and has been renewed four times, and presently extends to March 2023. The ﬁve year extension from April 2023 is agreed
between BNL and RIKEN in order to cover the era of sPHENIX experiment which is the upgraded of the PHENIX experiment. Theoretical activities in the RBRC Theory and Computing Groups are closely and intimately related to those of the Nuclear Theory, HighEnergy Theory and Lattice Gauge Theory Groups at BNL. The RBRC Experimental Group jointly works with Radiation Laboratory
at Wako RIKEN, the RHIC Spin Group at BNL, the RHIC Spin Physics community, and the PHENIX/sPHENIX collaboration. Radiation Laboratory at Wako is closed in March 2022, and its functions are taken over by the new laboratory “RHIC Physics ResearchGroup” headed by Y. Akiba. BNL provides oﬃce space, management, computing and administrative support. The Deputy Directorof RBRC is D. Morrison (BNL). In May 2021 Y. Hatta (BNL) becomes Theory Group leader, succeeding D. Kharzeev. Y. Akiba(RIKEN) is Experimental Group leader and T. Izubuchi (BNL) is Computing Group leader.

2. Major Research Subjects
Major research subjects of the theory group are(1) Spin structure of proton;(2) Gluon saturation at small-x;(3) Physics of quark gluon plasma.
Major research subjects of the computing group are(1) Search for new law of physics through tests for Standard Model of particle and nuclear physics;(2) Dynamics of QCD and related theories;(3) Theoretical and algorithmic development for lattice ﬁeld theories, QCD machine design.
Major research subject of the experimental group are(1) Experimental Studies of the Spin Structure of the Nucleon;(2) Study of Quark-Gluon Plasma at RHIC;(3) sPHENIX detector construction.

3. Summary of Research Activity
Summary of Research Activities of the three groups of the Center are given in the sections of each group.

Members
Director
Hideto EN’YO
Deputy Director
David P. MORRISON
Administrative Staﬀ
Keiko IWANO (Administration Manager)
Pamela ESPOSITO (Administrative Assistant)

Maureen MCNEIL-SHEA (Administrative Assistant)

List of Publications & Presentations
Publications[Original Papers]
See the lists of each group.

Presentations[Seminars]
H. En’yo, “Forty academic years with physics of high density nuclear matter (in Japanese)”, Heavy Ion Pub, Nagoya University, Online,
November 12, 2021.
H. En’yo, “My 40 years seeking for the new phase of nuclear matter (in Japanese)”, ELPH Seminar, Research Center for Electron Photon
Science (ELPH), Tohoku University, Sendai, Japan, Hybrid, December 23, 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Press Release
Direct Photons Oﬀer Glimpse of Gluons’ Dynamic Motion—PHENIX data validate approach for future studies of proton spin andstructure—, October 12, 2011.
https://www.bnl.gov/newsroom/news.php?a=119077,
https://www.riken.jp/press/2021/20211015_1/index.html .

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Subnuclear System Research Division
RIKEN BNL Research Center
Theory Group
1. Abstract
The eﬀorts of the RBRC theory group are concentrated on the major topics of interest in High Energy Nuclear Physics, inparticular, the physics explored by the RHIC experiment at Brookhaven National Laboratory (BNL). This includes: understandingof the Quark-Gluon Plasma (QGP); the nature of dense quark matter; the initial state in high energy collisions, the Color Glass
Condensate and its evolution to QGP through a Glasma; QCD spin physics; physics relevant to the future Electron-Ion Collider at
BNL.

2. Major Research Subjects(1) Heavy Ion Collisions, QCD phase diagram(2) Perturbative Quantum Chromo-Dynamics (QCD)(3) Nucleon structure, mass and spin

3. Summary of Research Activity(1) Phase diagram of QCD
The major goal of RHIC heavy-ion program is to map out the QCD phase diagram at ﬁnite temperature and density. Together witha collaborator, V. Skokov has determined the precise location of the Yang-Lee edge singularity for the Ising universality class using
the functional renormalization group method and the epsilon expansion. This can be applied to the QCD phase diagram to determine
the location of the QCD critical point (which belongs to the Ising universality class) at ﬁnite chemical potential.
(2) QCD at small x
The initial condition of heavy-ion collisions at RHIC is governed by the Color Glass Condensate (CGC) which is the universal
form of matter in the high energy (small-x) limit of QCD. The RBRC scientists have made major contributions to this ﬁeld, and theeﬀorts continue to date. V. Skokov and collaborators showed that the Bose-Einstein correlation between two small-x gluons in thesaturated environment can be experimentally probed via three-jet production in Deep Inelastic scattering. He also continued a projectwith M. Li on the ﬁrst saturation corrections in pA collisions. Y. Mehtar-Tani and R. Boussarie further developed their proposal fora new semi-classical approach to gluon-mediated DIS processes. They derived a factorization formula that involves a novel gluontransverse momentum dependent (TMD) distribution function and showed that both the DGLAP and Regge limits are recovered.
(3) Jet quenching
Jets have become an important tool to uncover the transport properties of matter created in heavy-ion collisions and the nontrivial
parton structure in the nucleon. These are important goals of the sPHENIX and EIC experiments. Y. Mehtar-Tani and collaborators
showed that transverse momentum broadening of emergetic partons in QCD media can be formulated as a super-diﬀusive process due
to non-local quantum corrections. This yields anomalous system size dependence of momentum broadening. They also showed thatthe momentum broadening exhibits geometric scaling and heavy tails akin to Levy random walks.
(4) Resummation for jet angular distribution
Y. Hatta and collaborators continued to study the impact of soft gluon resummation on the azimuthal angular correlation of jets.
They calculated various types of angular correlation in lepton-jet production and inclusive dijet production in DIS, dijet production inpp collisions and lepton pair production in ultraperipheral collisions. They also studied the relative strengths of angular correlations
from soft gluon resummation and the linearly polarized gluon distribution. It is shown that the former can overshadow the signal fromthe latter.
(5) gT(x) contribution to single spin asymmetry
Y. Hatta and collaborators calculated the purely perturbative contribution to transverse single spin asymmetry which ﬁrst arises
in two-loop perturbation theory. It has been believed for more than 40 years that such a contribution is negligible. However, they
have demonstrated that at the future Electron-Ion Collider, it can be comparable to other sources of single spin asymmetry such as
three-parton correlation functions.
(6) Hydrodynamical simulation of heavy-ion collisions
C. Shen has developed a full 3+1-dimensiional dynamical framework based on Glauber geometry with string deceleration +hydrodynamics + hadronic transport model. This model provides good predictions for particle production in pp, pA and AA collisions
from GeV to TeV energy regions. It is an essential tool to quantify baryon stopping at the RHIC BES phas II and study the origin ofcollectivity in ultra-peripheral collisions at RHIC and LHC.
(7) Signature of the gluon orbital angular momentum
Y. Hatta and collaborators proposed a novel observable for the experimental detection of the gluon orbital angular momentum that
constitutes the proton spin sum rule. They proposed to study double spin asymmetry in diﬀractive dijet production in DIS. A concrete- 319 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

numerical prediction is given for the kinematics of the Electron-Ion Collider.

Members
Group Leaders
Hideto EN’YO

Yoshitaka HATTARBRC Researchers
Yacine MEHTAR-TANI
Chun SHEN

Vladimir SKOKOV

Visiting Scientists
Hiromichi NISHIMURA (Keio Univ.)

Yuya TANIZAKI (North Carolina State Univ.)

List of Publications & Presentations
Publications[Original Papers]
Y. Hatta, B. Xiao, F. Yuan, and J. Zhou, “Azimuthal angular asymmetry of soft gluon radiation in jet production,” Phys. Rev. D 104,
054037 (2021).
S. Benic, Y. Hatta, A. Kaushik, and H. Li, “gT (x) contribution to single spin asymmetries in SIDIS,” Phys. Rev. D 104, 094027 (2021).
S. Bhattacharya, R. Boussarie, and Y. Hatta, “Signature of the gluon orbital angular momentum,” Phys. Rev. Lett. 128, 182002 (2022).
S. Alzhrani, S. Ryu, and C. Shen, “Lambda spin polarization in event-by-event relativistic heavy-ion collisions,” arXiv:2203.15718.
D. Everett et al. [JETSCAPE Collaboration], “Role of bulk viscosity in deuteron production in ultrarelativistic nuclear collisions,”
arXiv:2203.08286.
W. Zhao, C. Shen, and B. Schenke, “Collectivity in ultra-peripheral Pb+Pb collisions at the large hadron collider,” arXiv:2203.06094.
C. Shen and B. Schenke, “Longitudinal dynamics and particle production in relativistic nuclear collisions,” arXiv:2203.04685.
A. De, C. Shen, and J. Kapusta, “Stochastic hydrodynamics meets hydro-kinetics,” arXiv:2203.02134.
H. Mantysaari, B. Schenke, C. Shen, and W. Zhao, “Bayesian inference of the ﬂuctuating proton shape,” arXiv:2202.01998.
K. J. Sun, R. Wang, C. M. Ko, Y. G. Ma, and C. Shen, “Relativistic kinetic approach to light nuclei production in high-energy nuclear
collisions,” arXiv:2106.12742.
D. Oliinychenko and C. Shen, “Resonance production in PbPb collisions at 5.02 TeV via hydrodynamics and hadronic afterburner,”arXiv:2105.07539.
G. Giacalone, B. Schenke, and C. Shen, “Constraining the nucleon size with relativistic nuclear collisions,” Phys. Rev. Lett. 128, 042301(2022).
X. An et al., “The BEST framework for the search for the QCD critical point and the chiral magnetic eﬀect,” Nucl. Phys. A 1017, 122343(2022).
√
V. Vovchenko, V. Koch, and C. Shen, “Proton number cumulants and correlation functions in Au-Au collisions at sNN = 7.7-200 GeV
from hydrodynamics,” Phys. Rev. C 105, 014904 (2022).
C. Gale, J. F. Paquet, B. Schenke, and C. Shen, “Multimessenger heavy-ion collision physics,” Phys. Rev. C 105, 014909 (2022).
S. Ryu, V. Jupic, and C. Shen, “Probing early-time longitudinal dynamics with the Lambda hyperon’s spin polarization in relativistic
heavy-ion collisions,” Phys. Rev. C 104, 054908 (2021).
S. Wu, C. Shen, and H. Song, “Dynamically exploring the QCD matter at ﬁnite temperatures and densities: A short review,” Chin. Phys.
Lett. 38, 081201 (2021).
G. Giacalone and C. Shen, “Manipulating strong electromagnetic ﬁelds with the average transverse momentum of relativistic nuclear
collisions,” Eur. Phys. J. A 57, 230 (2021).
C. Chiu and C. Shen, “Exploring theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions,” Phys. Rev.
C 103, 064901 (2021).
W. M. Serenone, J. G. P. Barbon, D. D. Chinellato, M. A. Lisa, C. Shen, J. Takahashi, and G. Torrieri, “Lambda polarization fromthermalized jet energy,” Phys. Lett. B 820, 136500 (2021).
S. Cao et al. [JETSCAPE], “Determining the jet transport coeﬃcient q̂ from inclusive hadron suppression measurements using Bayesianparameter estimation,” Phys. Rev. C 104, 024905 (2021).
M. A. Lisa, J. G. P. Barbon, D. D. Chinellato, W. M. Serenone, C. Shen, J. Takahashi, and G. Torrieri, “Vortex rings from high energy
central p+A collisions,” Phys. Rev. C 104, 011901 (2021).
P. Caucal and Y. Mehtar-Tani, “Universality aspects of quantum corrections to transverse momentum broadening in QCD media,”arXiv:2203.09407.
R. Boussarie and Y. Mehtar-Tani, “Gluon-mediated inclusive deep inelastic scattering from regge to bjorken kinematics,”
arXiv:2112.01412.
P. Caucal and Y. Mehtar-Tani, “Anomalous diﬀusion in QCD matter,” arXiv:2109.12041.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

J. Barata, Y. Mehtar-Tani, A. Soto-Ontoso, and K. Tywoniuk, “Medium-induced radiative kernel with the Improved opacity expansion,”
J. High Energy Phys. 09, 153 (2021).
Y. Mehtar-Tani, D. Pablos, and K. Tywoniuk, “Cone size dependence of jet suppression in heavy-ion collisions,” Phys. Rev. Lett. 127,
252301 (2021).
F. Rennecke and V. V. Skokov, “Universal location of Yang Lee edge singularity for a one-component ﬁeld theory in 1 ≤ d ≤ 4,”
arXiv:2203.16651.
H. Duan, A. Kovner, and V. V. Skokov, “Gluon quasiparticles and the CGC density matrix,” Phys. Rev. D 105, 056009 (2022).
M. Li and V. V. Skokov, “First saturation correction in high energy proton-nucleus collisions. Part III. Ensemble averaging,” J. HighEnergy Phys. 01, 160 (2022).
S. Mukherjee, F. Rennecke, and V. V. Skokov, “Analytical structure of the equation of state at ﬁnite density: Resummation versus
expansion in a low energy model,” Phys. Rev. D 105, 014026 (2022).
A. Kovner, M. Li, and V. V. Skokov, “Probing gluon bose correlations in deep inelastic scattering,” Phys. Rev. Lett. 128, 182003 (2022).
M. Li and V. V. Skokov, “First saturation correction in high energy proton-nucleus collisions. Part II. Single inclusive semi-hard gluon
production,” J. High Energy Phys. 06, 141 (2021).
M. Li and V. V. Skokov, “First saturation correction in high energy proton-nucleus collisions. Part I. Time evolution of classical Yang-Mills
ﬁelds beyond leading order,” J. High Energy Phys. 06, 140 (2021).
T. Altinoluk, N. Armesto, A. Kovner, M. Lublinsky, and V. V. Skokov, “Angular correlations in pA collisions from CGC: multiplicity andmean transverse momentum dependence of v2 ,” Eur. Phys. J. C 81, 583 (2021).
F. Oosterhof, J. de Vries, R. Timmermans, and U. van Kolck, “Nucleon decay in the deuteron,” Phys. Lett. B 820, 136525 (2021).

[Proceedings]
D. Oliinychenko and C. Shen, “Resonance production in Pb+Pb collisions at 5.02 TeV,” EPJ Web Conf. 259, 10008 (2022).
V. Vovchenko, V. Koch, and C. Shen, “Net-particle number ﬂuctuations in a hydrodynamic description of heavy-ion collisions,” EPJ Web
Conf. 259, 10011 (2022).
S. Ryu, S. McDonald, C. Shen, S. Jeon, and C. Gale, “Medium response from mini-jets and in-medium hadronization in relativistic heavy
ion collisions,” Proc. Sci. HardProbes2020, 160 (2021).
C. Shen, “Dynamic modeling for heavy-ion collisions,” EPJ Web Conf. 259, 02001 (2022).
Y. Mehtar-Tani, “A novel formulation of the unintegrated gluon distribution for DIS,” Contribution to: DIS2021, arXiv:2110.02105.
R. Boussarie and Y. Mehtar-Tani, “On gauge invariance of transverse momentum dependent distributions at small x,” Proc. Sci. HardProbes2020, 182 (2021).

Presentations[International Conferences/Workshops]
Y. Hatta (invited), “Quarkonium production near threshold,” CFNS Workshop on Open Questions in Photon-Induced Interactions, Stony
Brook, USA, April 26–28, 2021.
Y. Hatta (invited), “Odderon measurements at the EIC,” Saturation and Diﬀraction at the LHC and the EIC, ECT*, Italy, June 29–July 1,
2021.
Y. Hatta (invited), “Connection observables with diﬀerent terms contributing to the proton mass,” EICUG Summer Meeting, Remote
Workshop, August 2–7, 2021.
Y. Hatta (invited), “Parton orbital angular momentum,” QCD Structure of the Nucleon, University of Alcala, Spain, October 4–8, 2021.
Y. Hatta (invited), “Resummation of nonglobal logarithms,” Simons Center Workshop on Particle Jets in Quantum Field Theory, Stony
Brook, USA, March 21–25, 2022.
C. Shen (invited), “Computational challenges and opportunities in multi-messenger heavy-ion physics,” OSG All-Hands Meeting 2022,
March 14, 2022.
C. Shen (invited), “Challenges of hydrodynamic modeling at FAIR and NICA energies,” The 3rd Workshop on Physics Performance
Studies at FAIR and NICA, December 1, 2021.
C. Shen (invited), “Dynamical modeling of high energy nuclear collisions,” The 8th Asian Triangle Heavy-Ion Conference, November 6,
2021.
C. Shen (invited), “Local polarization from hydrodynamics,” The 6th International Conference on Chirality, Vorticity, and Magnetic Field
in Heavy-Ion Collisions, November 2, 2021.
C. Shen (invited), “Dynamical modeling for heavy-ion collisions,” Strangeness in Quark Matter 2021, May 18, 2021.
Y. Mehtar-Tani (invited), “Universality aspects of quantum corrections to transverse momentum broadening,” Simons Center Workshop
on Particle Jets in Quantum Field Theory, Stony Brook, USA, March 21–25, 2022.
Y. Mehtar-Tani (invited), “Jet quenching and quantum applications,” MITP for the Youngst@rs event on “The Quantumness of Hard
Probes,” Online, January 17–21, 2022.
V. Skokov (invited), “Entropies and multiplicity distribution in DIS,” RBRC Workshop: Small-x Physics in the EIC Era, Brookhaven
National Laboratory, December 15–18, 2021.
V. Skokov (invited), “Universality driven analytic structure of QCD crossover,” International Workshop, “FunQCD: from ﬁrst principles
to eﬀective theories,” Online, March 29–April1, 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)[Domestic Conference/Workshop]
Y. Hatta (invited), “Physics at EIC: Nucleon structure,” J. Polym. Sci. Symposium, Online, September 17, 2021.

[Seminars]
Y. Hatta, “Gravitational form factors of the proton,” Temple University, USA, November 15, 2021.
Y. Hatta, “Gravitational form factors of the proton,” Sun Yat-sen University, China, November 18, 2021.
Y. Hatta, “Two topics in QCD spin,” National Center for Nuclear Research, Poland, May 26, 2021.
Y. Hatta, “Azimuthal angular asymmetry of soft gluons in jet production,” University of Bergen, Norway, March 1, 2022.
C. Shen, “Longitudinal dynamics and particle production in relativistic nuclear collisions,” Wayne State PAN Seminar, February 4, 2022.
C. Shen, “Progress in dynamical modeling of heavy-ion collisions at high energy,” NBI Heavy-ion Seminar, September 16, 2021.
C. Shen, “Going with the ﬂow—Explore the nuclear phase diagram at the highest temperatures and densities,” The Ohio State University,
August 31, 2021.
C. Shen, “Probing early-time longitudinal dynamics with Lambda’s spin polarization,” Invited Nuclear Seminar, The BESTea Seminar,
July 30, 2021.
Y. Mehtar-Tani, “Anomalous diﬀusion in QCD matter,” Nuclear Theory Group Seminar, McGill University, Canada, Online, December
7, 2021.
Y. Mehtar-Tani, “Wave Turbulence and anomalous diﬀusion in QCD matter,” Physics Colloquium, Tata Institute of Fundamental Research,
India, Online, November 16, 2021.
Y. Mehtar-Tani, “Anomalous diﬀusion in QCD matter,” Heavy Ion Tea Seminar, LBNL, USA, Online, Septetmber 7, 2021.
Y. Mehtar-Tani, “Wave turbulence and anomalous diﬀusion of jets in the QGP,” ASU Theoretical Physics Colloquium, USA, Online, July
7, 2021.
Y. Mehtar-Tani, “The anatomy of jets in heavy ion collisions,” BNL Physics Colloquium, Online, June 22, 2021.
V. Skokov, “Analytic structure of QCD crossover,” Physics Department, Ben-Gurion University of the Negev, Israel, April 19, 2021.

Award
C. Shen, DOE early career award.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Subnuclear System Research Division
RIKEN BNL Research Center
Experimental Group
1. Abstract
RIKEN BNL Research Center (RBRC) Experimental Group studies the strong interactions (QCD) using RHIC accelerator at
Brookhaven National Laboratory, the world ﬁrst heavy ion collider and polarized p + p collider. We have three major activities: Spin
Physics at RHIC, Heavy ion physics at RHIC, and detector upgrades of PHENIX experiment at RHIC.
We study the spin structure of the proton using the polarized proton-proton collisions at RHIC. This program has been promoted
by RIKEN’s leadership. The ﬁrst focus of the research is to measure the gluon spin contribution to the proton spin. Results fromPHENIX π0 measurement and STAR jet measurement has shown that gluons in the proton carry about 30% of the proton spin. This isa major milestone of the RHIC spin program. The second goal of the spin program is to measure the polarization of anti-quarks in the
proton using W → e and W → μ decays. The results of W → e measurement was published in 2016. The ﬁnal results of W → μ was
published in 2018. The focus of the RHIC spin program is moved to study of transverse spin measurement.
The aim of Heavy ion physics at RHIC is to re-create Quark Gluon Plasma (QGP), the state of Universe just after the Big Bang.
Two important discoveries, jet quenching eﬀect and strong elliptic ﬂows, have established that new state of dense matter is indeed
produced in heavy ion collisions at RHIC. We are now studying the property of the QGP. We measured direct photons in Au + Au
collisions for 1 < pT < 3 GeV/c, where thermal radiation from hot QGP is expected to dominate. The comparison between the data
and theory calculations indicates that the initial temperature of 300 MeV to 600 MeV is achieved. These values are well above thetransition temperature to QGP, which is calculated to be approximately 160 MeV by lattice QCD calculations.
We had major roles in detector upgrades of PHENIX experiment, namely, the silicon vertex tracker (VTX) and muon trigger
upgrades. The VTX is the main device to measure heavy quark (charm and bottom) production and the muon trigger is essential
for W → μ measurement. The results from the ﬁrst run with VTX detector in 2011 was published. The results show that electrons
from bottom quark decay is strongly suppressed at high pT , but the suppression is weaker than that of charm decay electron for
3 < pT < 4 GeV/c. PHENIX recorded 10 times as much Au + Au collisions data in each of the 2014 run and 2016 run. A paper on the
suppression of electrons from charm and bottom decays in the 2014 run has been submitted for publication this year. The data shows
clear diﬀerent of the suppression of b → e and c → e.
PHENIX completed its data taking in 2016. We are now working on construction of intermediate-silicon tracker INTT forsPHENIX, a new experiment at RHIC that will be installed in the PHENIX IR and to start taking data in 2023. Production of allladders of INTT was complete, and the INTT detector is now being assembled at BNL. The INTT will be installed in sPHENIX in
early 2023.

2. Major Research Subjects(1) Experimental Studies of the Spin Structure of the Nucleon(2) Study of Quark-Gluon Plasma at RHIC
(3) sPHENIX INTT detector

3. Summary of Research Activity
We study the strong interactions (QCD) using the RHIC accelerator at Brookhaven National Laboratory, the world ﬁrst heavy ion
collider and polarized p + p collider. We have three major activities: Spin Physics at RHIC, Heavy ion physics at RHIC, and detector
upgrades of PHENIX experiment. Y. Akiba (Experimental Group Leader) is the Spokesperson of PHENIX experiment since 2016.
(1) Experimental study of spin structure of proton using RHIC polarized proton collider
How is the spin of proton formed with 3 quarks and gluons? This is a very fundamental question in Quantum Chromodynamics(QCD), the theory of the strong nuclear forces. The RHIC Spin Project has been established as an international collaboration between
RIKEN and Brookhaven National Laboratory (BNL) to solve this problem by colliding two polarized protons for the ﬁrst time inhistory. This project also has extended the physics capabilities of RHIC.
The ﬁrst goal of the Spin Physics program at RHIC is to determine the gluon contribution to proton spin. It is known that the spinof quark accounts for only 25% of proton spin. The remaining 75% should be carried either by the spin of gluons or the orbital angularmomentum of quarks and gluons. One of the main goals of the RHIC spin program has been to determine the gluon spin contribution.
Before the start of RHIC, there was little experimental constraint on the gluon polarization, ΔG.
PHENIX measures the double helicity asymmetry (ALL ) of π0 production to determine the gluon polarization. Our most recent
publication of π0 ALL measurement at 510 GeV shows non-zero value of ALL , indicating that gluons in the proton is polarized. Global
analysis shows that approximately 30% of proton spin is carried by gluon spin. PHENIX measured the parity-violating single spin
asymmetry AL of the W boson production in p + p in wide rapidity range. The results of the W boson measurements were publishedin 2016 and 2018, and these results give constraints on the anti-quark polarization in the proton. The focus of the spin physics is now
moved to the measurements of the single spin asymmetry AN .
√Figure 1 show the AN of isolated direct photons in polarized p + p collisions at s = 200 GeV at midrapidity. This is the ﬁrst
precise measurement of the AN of direct photons. The uncertainties of the results are a 50-fold improvement with respect to those of the
only prior measurement. Direct photons are clean probe of proton structure with no contribution from ﬁnal-state strong interactions.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Fig. 1. Single spin asymmetry AN of isolated direct photons in midrapidity in p + p collisions at
perturbative QCD. Published in Phys. Rev. Lett. 127, 162001 (2021).

√

s = 200 GeV compared with theoretical predictions ofFig. 2. Pt dependence of single spin asymmetry AN of very forward neutron in p + p, p + Al, and p + Au. Published in Phys. Rev. D 105, 032004 (2022).

These results constrain gluon spin-momentum correlations in transversely polarized protons. A paper of these results is published in
Physical Review Letters.
Figure 2 shows AN (pT ) of very forward neutron in p + p, p + Al and p + Au collisions. A model based on hadronic interaction(OPE) and electromagnetic interaction (UPC) qualitatively describe the data. A paper reporting these results is published in PhysicalReview D.
√
Figure 3 shows AN (pT ) of charged pions in p + p collisions at s = 200 GeV at midrapidity. A paper reporting these results ispublished in Physical Review D.
Members of our group also participate in RHICf experiment, a small experiment at RHIC to measure particle production andsingle spin asymmetry of particles produced at very forward direction. Figure 3 shows AN (xF ) of very forward π0 measured by RHICf
compared with other experiments, published in Physical Review Letters. This is the ﬁrst published results of RHICf experiment.
(2) Experimental study of Quark-Gluon Plasma using RHIC heavy-ion collider
The goal of high energy heavy ion physics at RHIC is study of QCD in extreme conditions i.e. at very high temperature and atvery high energy density. Experimental results from RHIC have established that dense partonic matter is formed in Au + Au collisions
at RHIC. The matter is very dense and opaque, and it has almost no viscosity and behaves like a perfect ﬂuid. These conclusions areprimarily based on the following two discoveries:• Strong suppression of high transverse momentum hadrons in central Au + Au collisions (jet quenching);• Strong elliptic ﬂow.
These results are summarized in PHENIX White paper, which has more than 3000 citations to date. The focus of the research inheavy ion physics at RHIC is now to investigate the properties of the matter. RBRC have played the leading roles in some of the mostimportant results from PHENIX in the study of the matter properties. These include (1) measurements of heavy quark production- 324 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Fig. 3. AN (pT ) of charged pions measured by PHENIX. Published in Phys. Rev. D 105, 032003 (2022).

from the single electrons from heavy ﬂavor decay (2) measurements of J/Ψ production (3) measurements of di-electron continuumand (4) measurements of direct photons.
Our most important result is the measurement of direct photons for 1 < pT < 5 GeV/c in p + p and Au + Au through their internalconversion to e + e− pairs. If the dense partonic matter formed at RHIC is thermalized, it should emit thermal photons. Observation ofthermal photon is direct evidence of early thermalization, and we can determine the initial temperature of the matter. It is predicted that
thermal photons from QGP phase is the dominant source of direct photons for 1 < pT < 3 GeV/c at the RHIC energy. We measured
the direct photon in this pT region from measurements of quasi-real virtual photons that decays into low-mass e + e− pairs. Strong
enhancement of direct photon yield in Au + Au over the scaled p + p data has been observed. Several hydrodynamical models canreproduce the central Au + A data within a factor of two. These models assume formation of a hot system with initial temperature of
T init = 300 MeV to 600 MeV. This is the ﬁrst measurement of initial temperature of quark gluon plasma formed at RHIC. Y. Akiba
received 2011 Nishina memorial Prize mainly based on this work.
PHENIX experiment recently measured the ﬂow in small collision systems (p + Au, d + Au, and 3 He + Au), and observed strong
ﬂow in all of these systems. Theoretical models that assume formation of small QGP droplets best describe the data. These results are
published in Nature Physics in 2019.
We constructed VTX detector of PHENIX. VTX is a 4-layer silicon tracker and it is the main device for measurement of charmand bottom quark production in PHENIX. VTX took data from the 2011 to 2016 when PHENIX completed data taking. PHENIX
recorded high statistics Au+Au data, approximately 20 billion events with VTX in each of the 2014 run and the 2016 run. Figure 4
shows the nuclear modiﬁcation factor RAA of electron from the charm and the bottom decays in Au+Au collisions relative to the p + p
collisions. The left panel shows the results of the most central 0–10% Au+Au collisions, and the right panel shows that of 40–60%
centrality. One can clearly see that the charm decay electrons (dashed curve) is more suppressed than the bottom decay electrons (solid
curve). This clearly indicates the quark mass dependence of the energy loss of quark in the QGP produced at RHIC. These results are
ﬁnal results of RAA measurement of charm and bottom decay electron from the 2014 data. A paper reporting these results is submitted
to Physical Review C.
(3) sPHENIX INTT detector
The group had major roles in several PHENIX detector upgrades, namely, the silicon vertex tracker (VTX) and muon trigger
upgrades. VTX is a high precision charged particle tracker made of 4 layers of silicon detectors. It is jointly funded by RIKEN andthe US DOE. The inner two layers are silicon pixel detectors and the outer two layers are silicon strip detectors. Y. Akiba is the project
manager. The VTX detector was completed in November 2010 and subsequently installed in PHENIX. The detector started taking
data in the 2011 run. With the new detector, we measure heavy quark (charm and bottom) production in p + p, A + A collisions
to study the properties of quark-gluon plasma. The ﬁnal result of the 2011 run was published. The result show that single electrons
from bottom quark decay is suppressed, but not as strong as that from charm decay in low pT region (3 < pT < 4 GeV/c). This is
the ﬁrst measurement of suppression of bottom decay electrons at RHIC and the ﬁrst observation that bottom suppression is smaller
than charm. We have recorded 10 times as much Au + Au collisions data in each of the 2014 run and 2016 run. The results ofbottom/charm ratios in p + p collisions at 200 GeV from the 2015 run was published (Phys. Rev. D 99 092003 (2019)). A paper
reporting measurements of the nuclear suppression factor RAA of charm and bottom in Au + Au collisions from the 2014 data has been
submitted for publication to Physical Review C.
PHENIX completed its data taking in 2016. We are now working on construction of intermediate silicon tracker INTT forsPHENIX, a new experiment at RHIC that will start taking data in 2023. INTT consists of 56 ladders of silicon detector, and production- 325 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Fig. 4. The nuclear modiﬁcation factor, RAA , of charm and bottom decay electrons by PHENIX. Submitted to PRC.

Fig. 5. Two INTT half barrels being assembled at BNL. In both of the half INTT, the B0L0 barrels are assembled.

of all ladders are complete. We are now assembling the INTT. Figure 5 shows two half INTT barrels being assembled in the silicon
lab in BNL. The INTT will be installed in sPHENIX in January 2023.

Members
Group Leader
Yasuyuki AKIBARBRC Researchers
Jan C. BERNAUER
Yuji GOTO
Takashi HACHIYA
Itaru NAKAGAWA

Genki NUKAZUKA
Ralf SEIDL
Atsushi TAKETANI
Satoshi YOKKAICHISpecial Postdoctoral Researcher
Minho KIM
Junior Research Associate
Takuya KUMAOKA
Special Temporary Research Scientists
Takashi ICHIHARA

Yasushi WATANABE- 326 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Senior Visiting Scientist
Rachid NOUICER (BNL)
Visiting Scientists
Stefan BATHE (City Univ. of New York)
Gaku MITSUKA (KEK)
Masahiro OKAMURA (BNL)

Takao SAKAGUCHI (BNL)
Takashi SAKO (Univ. of Tokyo)
Milan STOJANOVIC (Purdue Univ.)

Visiting Technician
Li-Hsin HSU (Nat’l Central Univ.)
Visiting Researcher
Shima SHIMIZU (JSPS)
Student Trainees
Kai-Yu CHENG (Nat’l Central Univ.)
Takuya KUMAOKA (Tsukuba Univ.)

Han-Sheng LI (Purdue Univ.)
Xiao RUI (Purdue Univ.)

List of Publications & Presentations
Publications[Original Papers]√
U. A. Acharya et al., “Systematic study of nuclear eﬀects in p+Al, p+Au, d+Au, and 3 He+Au collisions at sNN = 200 GeV using π0
production,” Phys. Rev. C 105, 064902 (2022).
U. √A. Acharya et al., “Transverse-single-spin asymmetries of charged pions at midrapidity in transversely polarized p + p collisions at
s = 200 GeV,” Phys. Rev. D 105, 032003 (2022).
√
U. A. Acharya et al., “Transverse-single-spin asymmetries of forward neutron in p+p, p+Al, p+Au collisions at sNN = 200 GeV,” Phys.
Rev. D 105, 032004 (2022).
√
U. A. Acharya et al., “Kinematic dependence of azimuthal anisotropies in p+Au, d+Au, and He+Au at sNN = 200 GeV,” Phys. Rev. C
105, 024901 (2022).
U. A. Acharya et al., “Probing √gluon spin-momentum correlations in transversely polarized protons through midrapidity isolated direct
photons in p+p collisions at s = 200 GeV,” Phys. Rev. Lett. 127, 162001 (2021).
√
U. A. Acharya et al., “Transverse sngle-spn asymmetries of midrapidty π0 and η mesons in polarized p + p collisions at s = 200 GeV”,
Phys. Rev. D 103, 052009 (2021).
U. A.√Acharya et al., “Transverse momentum dependent forward neutron ssingle spin asymmetries in transversely polarized p+ collisions
at s = 200 GeV”, Phys. Rev. D 103, 032007 (2021).

[Proceedings]
T. Todoroki, “Quark ﬂavor dependence of particle ﬂow in nucleus-nucleus collisions measured by PHENIX,” Nucl. Phys. A 1005, 121960(2021).
M. Connors, “Highlights from the PHENIX collaboration,” Nucl. Phys. A 1005, 121925 (2021).

Press Release「直接光子による陽子内グルーオンの運動の観測に成功—グルーオンの回転運動はあまり大きくなかった—」, 2021 年 10 月 15 日
理化学研究所. https://www.riken.jp/press/2021/20211015_1/ .

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Subnuclear System Research Division
RIKEN BNL Research Center
Computing Group
1. Abstract
The computing group founded in 2011 as a part of the RIKEN BNL Research Center established at Brookhaven National Laboratory in New York, USA, and dedicated to conduct researches and developments for large-scale physics computations important forparticle and nuclear physics. The group was forked from the RBRC Theory Group.
The main mission of the group is to provide important numerical information that is indispensable for theoretical interpretationof experimental data from the ﬁrst principle theories of particle and nuclear physics. Their primary area of research is lattice quantum
chromodynamics (QCD), which describes the sub-atomic structures of hadrons, which allow us the ab-initio investigation for stronglyinteracting quantum ﬁeld theories beyond perturbative analysis.
The RBRC group and its collaborators have emphasized the necessity and importance of precision calculations, which will precisely check the current understandings of nature, and will have a potential to ﬁnd a physics beyond the current standard model offundamental physics. We have therefore adopted techniques that aim to control and reduce any systematic errors. This approach has
yielded many reliable results.
The areas of the major activities are R&D for high performance computers, developments for computing algorithms, and researches of particle, nuclear, and lattice theories. Since the inception of RBRC, many breakthroughs and pioneering works has carriedout in computational forefronts. These are the use of the domain-wall fermions, which preserve chiral symmetry, a key symmetry forunderstanding nature of particle nuclear physics, the three generations of QCD devoted supercomputers, pioneering works for QCD
calculation for Cabibbo-Kobayashi-Maskawa theory, QCD + QED simulation for isospin breaking, novel algorithm for error reduction
in general lattice calculation. Now the chiral quark simulation is performed at the physical up, down quark mass, the precision formany basic quantities reached to accuracy of sub-percent, and the group is aiming for further important and challenging calculations,such as the full and complete calculation of CP violating K → ππ decay and ε /ε, or hadronic contributions to muon’s anomalous
magnetic moment g − 2. Another focus area is the nucleon’s shape, structures, and the motion of quarks and gluon inside nucleon
called parton distribution, which provide theoretical guidance to physics for sPHENIX and future Electron Ion Collider (EIC), Hyper
Kamiokande, DUNE, or the origin of the current matter rich universe (rather than anti-matter). Towards ﬁnite density QCD, they also
explore Quantum Computing to overcome the sign problem. The Machine Learning (ML) and Artiﬁcial Intelligence (AI) are the new
topics some of members are enthusiastically studying lately.

2. Major Research Subjects(1) Search for new law of physics through tests for Standard Model of particle and nuclear physics, especially in the frameworkof the Cabibbo-Kobayashi-Maskawa (CKM), hadronic contributions to the muon’s anomalous magnetic moment (g − 2) for
FNAL and J-PARC’s experiments, as well as B physics at Belle II and LHCb
(2) Nuclear Physics and dynamics of QCD or related theories, including study for the structures of nucleons related to physics
for Electron Ion Collider (EIC or eRHIC), Hyper Kamiokande, T2K, DUNE
(3) Theoretical and algorithmic development for lattice ﬁeld theories, QCD machine (co-)design and code optimization

3. Summary of Research Activity
In 2011, QCD with Chiral Quarks (QCDCQ), a third-generation lattice QCD computer that is a pre-commercial version of IBM’s
Blue Gene/Q, was installed as an in-house computing resource at the RBRC. The computer was developed by collaboration among
RBRC, Columbia University, the University of Edinburgh, and IBM. Two racks of QCDCQ having a peak computing power of 2 × 200
TFLOPS are in operation at the RBRC. In addition to the RBRC machine, one rack of QCDCQ is owned by BNL for wider use forscientiﬁc computing. In 2013, 1/2 rack of Blue Gene/Q is also installed by US-wide lattice QCD collaboration, USQCD. The group
has also used the IBM Blue Gene supercomputers located at Argonne National Laboratory and BNL (NY Blue), and Hokusai and
RICC, the super computers at RIKEN (Japan), Fermi National Accelerator Laboratory, the Jeﬀerson Lab, and others. From 2016, thegroup started to use the institutional cluster both GPU and Intel Knight Landing (KNL) clusters installed at BNL and University ofTokyo extensively.
Such computing power enables the group to perform precise calculations using up, down, and strange quark ﬂavors with proper
handling of the important symmetry, called chiral symmetry, that quarks have. The group and its collaborators carried out the ﬁrst
calculation for the direct breaking of CP (Charge Parity) symmetry in the hadronic K meson decay (K → ππ) amplitudes, ε /ε, which
provide a new information to CKM paradigm and its beyond. They also provide the hadronic contribution in muon’s anomalous magnetic moment (g − 2)μ . These calculation for ε /ε, hadronic light-by-light of (g − 2), are long waited calculation in theoretical physics
delivered for the ﬁrst time by the group. The K → ππ result in terms of ε /ε currently has a large error, and deviates from experimental
results by 2.1σ. To collect more information to decide whether this deviation is from the unknown new physics or not, the group continues to improve the calculation in various way to reduce their error. Hadronic light-by-light contribution to (g − 2)μ is improved bymore than two order of magnitudes compared to our previous results. As of 2019 summer, their calculation is among the most precise
determination for the g − 2 hadronic vacuum polarization (HVP), and only one calculation in the world for the hadronic light-by-light(HLbL) contribution at physical point. These (g − 2)μ calculations provide the ﬁrst principle theoretical prediction for on-going newexperiment at FNAL and also for the planned experiment at J-PARC. Other projects including ﬂavor physics in the framework of the- 328 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

48I-64I
24D
32D
48D
32Dﬁneaμ × 1010

25
20
15
10

−4
−6
−8
−10

5
0

0
−2

aμ × 1010

30

−12
0

0.05

0.1

0.15

0.2

−14

1/(mμ L)2

Connected diagrams

Fig. 1. Feynman diagrams for Lattice QCD computations of Muon’s anomalous magnetic moment (g − 2)μ to take into account for the eﬀects ofquark’s electric charges. Each diagram, in which the black dots connecting the quark propagators (solid curves) are the electric current emmitting or absorbing photons (wave curves), represents a part of the isospin
breaking eﬀects to hadronic vacuum polarization contribution to (g−2)μ(top plot).

0

0.05

0.1

0.15

0.2

1/(mμ L)2

Disconnected diagrams

Fig. 2. Current summary of the Hadronic Vacuum Polarization (HVP) contribution for Muon’s anomalous magnetic moment (g − 2)μ . Above theupper horizontal line shows various Lattice QCD determinations of HVP
while the red results from hadronic decay of electron positron scattering(R-ratio), the green bands is the experimental results of (g − 2)μ showing
a 3–4σ discrepancies.

CKM theory for kaons and B mesons that include the new calculation of b-baryon decay, Λb → p; the electromagnetic propertiesof hadrons; the proton’s and neutron’s form factors and structure function including electric dipole moments; proton decay; nucleon
form factors, which are related to the proton spin problem or neutrino-nucleon interaction; Neutron-antineutron oscillations; inclusive
hadronic decay of τ leptons; nonperturbative studies for beyond standard model such composite Higgs or dark matter models fromstrong strongly interacting gauge theories; a few-body nuclear physics and their electromagnetic properties; QCD thermodynamics
in ﬁnite temperature/density systems such as those produced in heavy-ion collisions at the Relativistic Heavy Ion Collider; Quantum
Information, Quantum Computing; and applications of Machine Learning (ML) in ﬁeld theories.
The RBRC group and its collaborators have emphasized the necessity and importance of precision calculations, which will provide
stringent checks for the current understandings of nature, and will have a potential to ﬁnd physics beyond the current standard modelof fundamental physics. We have therefore adopted techniques that aim to control and reduce any systematic errors. This approach
has yielded many reliable results, many of basic quantities are now computed within sub-percent accuracies.
The group also delivers several algorithmic breakthroughs, which speed up generic lattice gauge theory computation. These novel
technique divides the whole calculation into frequent approximated calculations, and infrequent expensive and accurate calculation
using lattice symmetries called All Mode Averaging (AMA), or a compression for memory needs by exploiting the local-coherenceof QCD dynamics. Together with another formalism, zMobius fermion, which approximate chiral lattice quark action eﬃciently, thetypical calculation is now improved by a couple of orders of magnitudes, and more than an order of magnitude less memory needs
compared to the traditional methods. RBRC group and its collaborators also provide very eﬃcient and generic code optimized to thestate-of-arts CPU or GPU, and also improve how to eﬃciently generate QCD ensemble.

Members
Group Leader
Taku IZUBUCHI
RBRC Researchers
Luchang JIN

Sergey SYRITSYNSpecial Postdoctoral Researchers
Nobuyuki MATSUMOTO

Akio TOMIYA

Visiting Scientists
Thomas BLUM (Univ. of Connecticut)

Hiroshi OKI (Nara Women’s Univ.)

List of Publications & Presentations
Publications[Original Papers]
M. Abramczyk, T. Blum, T. Izubuchi, C. Jung, M. Lin, A. Lytle, S. Ohta, and E. Shintani, “Nucleon mass and isovector couplings in
2+1-ﬂavor dynamical domain-wall lattice QCD near physical mass,” Phys. Rev. D 101, 034510 (2020).
T. Izubuchi, L. Jin, C. Kallidonis, N. Karthik, S. Mukherjee, P. Petreczky, C. Shugert, and S. Syritsyn, “Valence parton distributionfunction of pion from ﬁne lattice,” Phys. Rev. D 100, 034516 (2019).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

N. H. Christ, X. Feng, L. C. Jin, and C. T. Sachrajda, “Finite-volume eﬀects in long-distance processes with massless leptonic propagators,” Phys. Rev. D 103, 014507 (2021).
Y. Li, S. C. Xia, X. Feng, L. C. Jin, and C. Liu, “Field sparsening for the construction of the correlation functions in lattice QCD,” Phys.
Rev. D 103, 014514 (2021).
C. Y. Seng, X. Feng, M. Gorchtein, L. C. Jin, and U. G. Meißner, “New method for calculating electromagnetic eﬀects in semileptonic
beta-decays of mesons,” J. High Energy Phys. 10, 179 (2020).
X. Gao, L. Jin, C. Kallidonis, N. Karthik, S. Mukherjee, P. Petreczky, C. Shugert, S. Syritsyn, and Y. Zhao, “Valence parton distributionof the pion from lattice QCD: Approaching the continuum limit,” Phys. Rev. D 102, 094513 (2020).
HI +HI

X. Feng, L. C. Jin, Z. Y. Wang, and Z. Zhang, “Finite-volume formalism in the 2 −−−−−→ 2 transition: An application to the lattice QCD
calculation of double beta decays,” Phys. Rev. D 103, 034508 (2021).
R. Abdul Khalek et al., “Science requirements and detector concepts for the electron-ion collider: EIC yellow report,” arXiv:2103.05419.
X. Gao, N. Karthik, S. Mukherjee, P. Petreczky, S. Syritsyn, and Y. Zhao, “Pion form factor and charge radius from Lattice QCD at
physical point,” arXiv:2102.06047.
X. Gao, N. Karthik, S. Mukherjee, P. Petreczky, S. Syritsyn, and Y. Zhao, “Towards studying the structural diﬀerences between the pionand its radial excitation,” Phys. Rev. D 103, 094510 (2021).
G. Silvi, S. Paul, C. Alexandrou, S. Krieg, L. Leskovec et al., “P-wave nucleon-pion scattering amplitude in the Δ(1232) channel fromlattice QCD,” Phys. Rev. D 103, 094508 (2021).
M. Yu. Barabanov, M. A. Bedolla, W. K. Brooks, G. D Cates, C. Chen et al., “Diquark correlations in hadron physics: Origin, impact andevidence,” Prog. Part. Nucl. Phys. 116, 103835 (2021).
M. Engelhardt, J. R. Green, N. Hasan, S. Krieg, S. Meinel, J. Negele, A. Pochinsky, and S. Syritsyn, “From Ji to Jaﬀe-Manohar orbital
angular momentum in lattice QCD using a direct derivative method,” Phys. Rev. D 102, 074505 (2020).
G. Rendon, L. Leskovec, S. Meinel, J. Negele, S. Paul et al., “I = 1/2 S -wave and P-wave Kπ scattering and the κ and K ∗ resonancesfrom lattice QCD,” Phys. Rev. D 102, 114520 (2020).
Z. Fan, X. Gao, R. Li, H. -W. Lin, N. Karthik et al., “Isovector parton distribution functions of the proton on a superﬁne lattice,” Phys.
Rev. D 102, 074504 (2020).
H. T. Ding, S. T. Li, Swagato Mukherjee, A. Tomiya, X. D. Wang, and Y. Zhang, “Correlated Dirac eigenvalues and axial anomaly inchiral symmetric QCD,” Phys. Rev. Lett. 126, 082001 (2021).
M. Kawaguchi, S. Matsuzaki, and A. Tomiya, “Nonperturbative ﬂavor breaking in topological susceptibility at HotQCD criticality,” Phys.
Lett. B 813, 136044 (2021).
H. -T. Ding, C. Schmidt, A. Tomiya, and X. -D. Wang, “Chiral phase structure of three ﬂavor QCD in a background magneticﬁeld,” Phys.
Rev. D 102, 054505 (2020).
B. Chakraborty, M. Honda, T. Izubuchi, Y. Kikuchi, and A. Tomiya, “Digital quantum simulation of the Schwinger model with topologicalterm via adiabatic state preparation,” arXiv:2001.00485.

[Review Article]
T. Aoyama, N. Asmussen, M. Benayoun, J. Bijnens, T. Blum, M. Bruno, I. Caprini, C. M. Carloni Calame, M. Cè, G. Colangelo et al.,“The anomalous magnetic moment of the muon in the standard model,” Phys. Rept. 887, 1–166 (2020).

[Books]A. Tomiya, “An introduction to machine learning in physics,” (in Japanese), Kodansha, March 2021.
K. Hashimoto, A. Tanaka, and A. Tomiya, “Deep learning and physics,” Springer, February 2021.

[Proceedings]
T. Izubuchi, H. Ohki, and S. Syritsyn, “Computing nucleon electric dipole moment from lattice QCD,” Proc. Sci. LATTICE2019, 290(2020).
M. Bruno, T. Izubuchi, C. Lehner, and A. S. Meyer, “Exclusive channel study of the muon HVP,” Proc. Sci. LATTICE2019, 239 (2019).
M. Kawaguchi, S. Matsuzaki, and A. Tomiya, “Analysis on nonperturbative ﬂavor violation at chiral crossovercriticality in QCD,”
arXiv:2005.07003.
A. Tomiya and Y. Nagai, “Gauge covariant neural network for 4 dimensional non-abelian gaugetheory,” arXiv:2103.11965.
M. Kawaguchi, S. Matsuzaki, and A. Tomiya, “A new critical endpoint in thermomagnetic QCD,” arXiv:2102.05294.
Y. Nagai, A. Tanaka, and A. Tomiya, “Self-learning Monte-Carlo for non-abelian gauge theory withdynamical fermions,”
arXiv:2010.11900.
H. -T. Ding, S. -T. Li, A. Tomiya, X. -D. Wang, and Y. Zhang, “Chiral properties of (2+1)-ﬂavor QCD in strong magnetic ﬁelds atzerotemperature,” arXiv:2008.00493.
H. -T. Ding, S. -T. Li, S. Mukherjee, A. Tomiya, and X. -D. Wang, “Meson masses in external magnetic ﬁelds with HISQ fermions,”
arXiv:2001.05322.

Presentations[International Conferences/Workshops]
L. Jin (invited), “Lattice calculations in muon g − 2.,” The Hadron Mass and Structure Forum, Online, April 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

L. Jin (invited), “Muon g − 2: hadronic light-by-light contribution and lattice QCD,” The Muon g-2 Discussion Forum, Peking University,
Online, April 2021.
L. Jin (invited), “Pion electric polarizability,” the χ QCD Collaboration Meeting, Online, January 2021.
L. Jin (invited), “Lattice calculation of the hadronic light-by-light contribution to the muon magnetic moment,” The Hadron Physics
Online Forum, Online, August 2020.
S. Syritsyn (invited), “Nucleon form factors at high momentum transfer from lattice QCD,” Nuclear & Particle Theory Seminar, MIT/CTP,
March 9, 2020.
A. Tomiya (oral), “Self-learning Monte-Carlo for non-abelian gauge theory withdynamical fermions,” APS April Meeting, Virtual, April
20, 2020.
A. Tomiya (invited), “Self-learning Monte-Carlo for non-abelian gauge theory with dynamical fermions,” Workshop on Non-equilibrium
Systems and Machine Learning, Virtual, March 30, 2020.
A. Tomiya (oral), “Quantum computing for QCD phase diagram? Finite chemicalpotential and temperature?,” Kickoﬀ Meeting of C2QACenter, Virtual, BNL, October 30, 2020.
A. Tomiya (invited), “Machine learning and theoretical physics,” Progress of Particle Physics 2020, Virtual, Yukawa Institute for Theoretical Physics, Japan, Sepember 4, 2020.
A. Tomiya (oral), “Thermal ﬁeld theory with pure states,” Asia-Paciﬁc Symposium for Lattice Field Theory (APLAT 2020), Virtual, KEK,
August 6, 2020.
A. Tomiya (invited), “Applications of machine learning to computational physics,” A.I. for Nuclear Physics, JeﬀersonLaboratory, Virginia,
USA, March 3, 2020.

[Domestic Conferences/Workshops]
A. Tomiya (oral), “Gauge covariant neural network for 4 dimensional non-abelian gaugetheory,” Deep Learning and Physics, Virtual,
April 7, 2020.
A. Tomiya (oral), “Self-learning Monte-Carlo for QCD,” JPS, Virtual, March 13, 2020.
A. Tomiya (invited), “Machine learning for physics,” 5th Symposium on Statistical Machine Learning, Virtual, Nagoya University, December 5, 2020.
A. Tomiya (oral), “A lecture on usage of neural nets in physics,” DLAP 2020 Lecture, Virtual, Osaka University, November 26, 2020.

[Seminars]
L. Jin (invited), “Lattice calculations in muon g − 2.,” The Theory Seminar at the Department of Physics and Astronomy, University ofCalifornia, Davis, Online, May 2021.
L. Jin (invited), “Lattice calculations in muon g − 2.,” The Lunch Seminar at the Institute of Theoretical Physics, Chinese Academy of
Sciences, Online, April 2021.
L. Jin (invited), “First-principles calculation of electroweak box diagrams from lattice QCD,” The Physics Seminar in Hunan University,
Online, December 2020.
L. Jin (invited), “First-principles calculation of electroweak box diagrams from lattice QCD,” The Theory Seminar at the Institute ofModern Physics, Chinese Academy of Sciences, July 2020.
L. Jin (invited), “First-principles calculation of electroweak box diagrams from lattice QCD,” The BNL Nuclear Theory Seminar, Online,
May 2020.
L. Jin (invited), “Lattice calculation of the hadronic light-by-light contribution to the muon magnetic moment,” The QCD Seminar, Online,
May 2020.
S. Syritsyn (invited), “From quarks and gluons to nucleons and nuclei,” Seminar at IACS (Inst. Adv. Comp. Sci), Stony Brook, October
8, 2020.
A. Tomiya (oral), “Gauge covariant neural network for 4 dimensional non-abelian gaugetheory,” Virtual, MIT, April 29, 2020.
A. Tomiya (oral), “Applications of machine learning on theoretical physics,” Virtual, Ochanomizu University, Japan, May 19, 2020.
A. Tomiya (oral), “Gauge covariant neural network for 4 dimensional non-abelian gaugetheory,” Virtual, RIKEN Center for Computational
Science, Japan, April 28, 2020.
A. Tomiya (oral), “Applications of machine learning for theoretical physics,” Virtual, JPARC, Japan, March 18, 2020.
A. Tomiya (oral), “Self-learning Monte-Carlo for non-abelian gauge theory withdynamical fermions,” Virtual, Yukawa Institute for Theoretical Physics, Japan, December 7, 2020.
A. Tomiya (oral), “Applications of machine learning on theoretical physics,” Virtual, Shimane University, Japan, October 29, 2020.
A. Tomiya (oral), “Lattice gauge theory with quantum computers,” Virtual, RIKEN Center for Computational Science, Japan, June 3,2020.
A. Tomiya (oral), “Lattice gauge theory with quantum computers,” Virtual, Osaka University, Japan, May 12, 2020.

Award
A. Tomiya “Best presentation award,” SPDR program, RIKEN, 2021.

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Press Releases
Brookhaven National Laboratory, “Background on Brookhaven Lab’s Involvement in the Muon g-2 Experiment,” April 7, 2021. https://www.bnl.gov/newsroom/news.php?a=218814 .
CERN Courier, “An anomalous moment for the muon,” April 14, 2021. https://cerncourier.com/a/an-anomalous-moment-forthe-muon/ .
UConn Today, “UConn Physicists Focus on a Law-Breaking Particle,” May 20, 2021. https://today.uconn.edu/2021/05/
uconn-physicists-focus-on-a-law-breaking-particle/ .

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Subnuclear System Research Division
RIKEN Facility Oﬃce at RAL
1. Abstract
Our core activities are based on the RIKEN-RAL Muon Facility located at the ISIS Neutron & Muon Source at the Rutherford
Appleton Laboratory (UK), which provides intense pulsed-muon beams. The RIKEN-RAL Muon Facility is a signiﬁcant and longstanding collaboration between RIKEN and RAL in muon science—with 2020 being the 30th years of continuous agreements between
RIKEN and RAL. The Facility enables muon science throughout Japan and other ﬁeld—it continues to attract proposals from a wide
variety of Japanese universities and institutions (with over 80 groups having now used the facility), and including industrial users suchat Toyota, and has been instrumental in establishing scientiﬁc links with other Asian universities.
Muons have their own spins with 100% polarization, and can detect local magnetic ﬁelds and their ﬂuctuations at muon stoppingsites very precisely. The method to study the characteristics of materials by observing time dependent changes of muon spin polarization is called “Muon Spin Rotation, Relaxation and Resonance” (μSR method), and is applied to study electro-magnetic properties
of insulating, metallic, magnetic and superconducting systems. Muons reveal static and dynamic properties of the electronic state ofmaterials in the zero-ﬁeld condition, which is the ideal magnetic condition for research into magnetism. For example, we have carriedout μSR investigations on a wide range of materials including frustrated pyrochlore systems, which have variety of exotic groundstates of magnetic spins, so the magnetism study of this system using muon is quite unique.
The ultra-cold muon beam can be stopped in thin foil, multi-layered materials and artiﬁcial lattices, which enables us to apply theaSR techniques to surface and interface science. The development of an ultra-cold muon beam is also very important as a source of
pencil-like small emittance muon beam for muon g-2/EDM measurement. We have been developing muonium generators to create
more muonium atoms in vacuum even at room temperature to improve beam quality compared with the conventional hot-tungsten
muonium generator. We have demonstrated a strong increase in the muonium emission eﬃciency by fabricating ﬁne laser drill-holeson the surface of silica aerogel. We are also developing a high power Lyman-alpha laser in collaboration with the Advanced Photonics
group at RIKEN. The new laser will ionize muoniums 100 times more eﬃciently for slow muon beam generation.
Over the past 2–3 years, a signiﬁcant development activity in muon elemental analysis has taken place, proton radius experiments
have continued and been developed, and chip irradiation experiments have also continued.

2. Major Research Subjects
(1)
(2)
(3)
(4)

Materials science by muon-spin-relaxation method and muon site calculation
Development of elemental analysis using pulsed negative muons
Nuclear and particle physics studies via muonic atoms and ultra-cold muon beam
Other muon applications

3. Summary of Research Activity(1) Material science at the RIKEN-RAL muon facility
Muons have their own spins with 100% polarization, and can detect local magnetic ﬁelds and their ﬂuctuations at muon stoppingsites very precisely. The μSR method is applied to studies of newly fabricated materials. Muons enable us to conduct (1) material
studies under external zero-ﬁeld condition, (2) magnetism studies with samples without nuclear spins, and (3) measurements of muon
spin relaxation changes at wide temperature range with same detection sensitivity. The detection time range of local ﬁeld ﬂuctuations
by μSR is 10−6 to 10−11 second, which is an intermediate region between neutron scattering method (10−10 –10−12 second) and Nuclear
Magnetic Resonance (NMR) (longer than 10−6 second). At Port-2 and 4 of the RIKEN-RAL Muon Facility, we have been performing
μSR researches on strong correlated-electron systems, organic molecules, energy related materials and biological samples to study
electron structures, superconductivity, magnetism, molecular structures and crystal structures.
Among our scientiﬁc activities on μSR studies from year 2018 to 2021, following subjects of material sciences are most importantachievements at the RIKEN-RAL muon facility:(1) Quasi magnetic monopole state in the Ru-based pyrochlore systems, R2 Ru2 O7 ;(2) Novel magnetic and superconducting properties of nano-size La-based high-TC superconducting cuprates;(3) Determination of muon positions estimated from density functional theory (DFT) and dipole-ﬁeld calculations;(4) Chemical muonic states in DNA molecules.
Result-1) Quasi magnetic monopole state in pyrochlore systems gave us new interpretations to understand exotic phenomena,
like the quantum spin liquid and spin fragmentation states. Result-2) The same nano-size eﬀect was examined on the La-based
high-TC superconducting oxide changing the electronic state from insulating to superconducting. We conﬁrmed the reduction in themagnetic interaction and the disappearance of the superconducting state leading the increase in the ferromagnetic interaction within
the wide-range of the hole concentration. Result-3) Well known and deeply investigated La2 CuO4 has opened a new scheme of the
Cu spin. Taking into account quantum eﬀects to expand the Cu-spin orbital and muon positions, we have succeeded to explain newly
found muon sites and hyperﬁne ﬁelds at those sites. Result-4) Chemical states of the muon which attaches to DNA molecules were
investigated by the avoided level-crossing muon-spin resonance experiments. In conjunction with DFT calculations, we are trying toreveal the electron motion though the DNA molecule.
We have been continuing to develop muon-science activities in Asian countries. We enhanced international collaborations toorganize new μSR experimental groups and to develop muon-site calculation groups using computational method. We are creating- 333 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

new collaborations with new teams in diﬀerent countries and also continuing collaborations in μSR experiments on strongly correlated
systems with researchers from Taiwan, Indonesia, China, Thailand and Malaysia including graduate students. We are starting tocollaborate with the new Chinese muon group who are developing the Chinese Muon Facility and trying to develop more muon
activities in the Asian area.
(2) Development of elemental analysis using pulsed negative muons
There has been signiﬁcant development of elemental analysis using negative muons on Port 4 and Port 1 over the past coupleof years. Currently, elemental analysis commonly uses X-ray and electron beams, which accurately measure surfaces. However, asigniﬁcant advantage of muonic X-rays over those of electronic X-rays is their higher energy due to the mass of the muon. These highenergy muonic X-rays are emitted from the bulk of the samples without signiﬁcant photon self-absorption. The penetration depth ofthe muons can be varied by controlling the muon momentum, providing data from a thin slice of sample at a given depth. This can beover a centimeter in iron, silver and gold or over 4 cm in less dense materials such as carbon.
Some techniques for elemental analysis are destructive or require the material under investigation to undergo signiﬁcant treatment
and some of the techniques are only sensitive to the surface. Therefore, negative muons oﬀer a unique service in which they canmeasure inside, beyond the surface layer and completely non-destructively.
The areas of science that have used negative muons for elemental analysis have been very diverse. The largest area is the cultural
heritage community as the non-destructive ability is particularly important and will become more so. This community have investigated swords from diﬀerent eras, coins (Roman gold and silver, Islamic silver and from the Tudor Warship Mary Rose), miniatureboats from Sardinia, reliefs on Baptist church gate, Bronze Age tools and cannon balls. In addition, energy materials (Li composition
for hydrogen storage), bio-materials (search for iron to potentially help understand Alzheimer’s), engineering alloys (manufacturing
processes for new materials for jet engines), and functional materials (surface eﬀects in piezo electrics) have also been investigated.
The study was extended to see the diﬀerence by isotopes of silver and lead, which may give hint on the source of the material.
(3) Ultra-cold (low energy) muon beam generation and applications
Positive muon beam with thermal energy has been produced by laser ionization of muonium (bound system of μ+ and electron)
emitted from a hot tungsten surface with stopping surface muon beam at Port-3. The method generates a positive muon beam withacceleration energy from several 100 eV to several 10 keV, small beam size (a few mm) and good time resolution (less than 8 nsec). By
stopping the ultra-cold muon beam in thin foil, multi-layered materials and artiﬁcial lattices, we can precisely measure local magnetic
ﬁeld in the materials, and apply the μSR techniques to surface and interface science. In addition, the ultra-cold muon is very importantas the source of pencil-like small emittance muon beam for muon g − 2/EDM measurement. It is essential to increase the slow
muon beam production eﬃciency by 100 times for these applications. There are three key techniques in ultra-cold muon generation:
production of thermal muonium, high intensity Lyman-alpha laser and the ultra-cold muon beam line.
A high-power Lyman-alpha laser was developed in collaboration with the Advanced Photonics group at RIKEN. The new laser
system is used at J-PARC U-line and, upon completion, will ionize muoniums 100 times more eﬃciently for slow muon beam
generation. In this development, we succeeded to synthesize novel ceramic-based Nd:YGAG and Nd:YSAG crystals, which realized
a highly eﬃcient and stable laser system. We are working hard to improve the homogeneity of large size crystals in order to achieve
full design power.
We also succeeded in developing an eﬃcient muonium generator, laser ablated silica aerogel, which emits more muoniums into
vacuum even at room temperature. Study has been done at TRIUMF utilizing positron tracking method of muon decay position.
We demonstrated in 2013 at least 10 times increase of the muonium emission eﬃciency by fabricating ﬁne laser drill-holes on thesurface of silica aerogel. Further study was carried out in 2017 to ﬁnd the optimum fabrication that will maximize the muonium
emission. From the analysis, we found the emission has large positive correlation with the laser ablated area rather than with anyother parameters. We also conﬁrmed the muon polarization in vacuum. An alternative detection method for muonium emission using
muonium spin rotation, which will be sensitive even to muoniums near the surface, was tested at RIKEN-RAL in 2018 and was foundsuccessful. The study was further applied to the measurement of the temperature dependence.
In RIKEN-RAL Port 3, the ultra-cold muon beam line, which had been designed with hot tungsten, was completely rebuilt to use
advantage of the new room temperature silica aerogel target. The equipment was tested with surface muon beam and basic data suchas muon stopping in aerogel were taken. Based on the design, an ultimate cold muon source is under preparation for muon g − 2/EDM
at J-PARC.
(4) Other fundamental physics studies
We proposed the measurement of the proton radius by using the hyperﬁne splitting of the muonic hydrogen ground state. This
hyperﬁne splitting is sensitive to the Zemach radius, which is a convolution of charge and magnetic-dipole distributions inside proton.
We are planning to re-polarize the muonic hydrogen by a circularly polarized excitation laser (excites one of the F = 1 states andregenerates the muon spin polarization), and detect the recovery of the muon decay-asymmetry along the laser.
Preparation using muon beam is in progress. We measured the muon stopping distribution in low-density hydrogen-gas cell, whichgave us consistent results with beam simulation. Another key is the lifetime of the upper hyperﬁne state of the muonic hydrogen thatwill contribute the polarization. We successfully observed the clear muon spin precession of muonic deuterium atom in 2018 for theﬁrst time in the world. The measurement with muonic protium was carried out in 2019 and the data is being analyzed.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)(5) Facility operation and refurbishment
The research activity at RIKEN-RAL had severe restriction in FY2021 also since the COVID-19 pandemic continued. It was
impossible for users from outside RAL to carry out the experiment. Even though, we managed to carry out several μSR experimentswith mailed samples. Since July 2021, RIKEN-RAL muon facility is undergoing major refurbishment, ﬁrst time since its operation in
1994. The work covers many important components, such as the cooling water circuit, vacuum system, radiation shielding, magnet
power supplies and power cables, detectors and beamline control system.

Members
Director
Philip KING
Senior Research Scientist
Isao WATANABE
Contract Researcher
Katsuhiko ISHIDA

List of Publications & Presentations
Publications[Original Papers]
C. Pizzolottoa, A. Sbrizzia, A. Adamczak, D. Bakalov, G. Baldazzie, M. Baruzzoa, R. Benoccih, R. Bertoni, M. Bonesinih, H. Cabrera,
D. Cirrincione, M. Clemenza, L. Colace, M. Danailov, P. Danev, A. deBari, C. DeVecchi, M. DeVincenzik, E. Fasci, F. Fuschino,
K. S. Gadedjisso-Tossou, L .Gianfrani, K. I shida, C. Labanti, V. Maggi, R. Mazza, A. Menegolli, E. Mocchiutti, S. Monzani, L. Moretti,
G. Morgante, J. Niemela, A. Pullia, R. Ramponi, L. P. Rignanese, M. Rossella, M. Stoilov, L. Stoychev, J. J. Suárez-Vargas, L. Tortora,
E. Vallazza, and A. Vacchi, “Measurement of the muon transfer rate from muonic hydrogen to oxygen in the range 70–336 K,” Phys.
Lett. A 403, 127401 (2021).
T. Yamashita, K. Okutsu, Y. Kino, R. Nakashima, K. Miyashita, K. Yasuda, S. Okada, M. Sato, T. Oka, N. Kawamura, S. Kanda,
K. Shimomura, P. Strasser, S. Takeshita, M. Tampo, S. Doiuchi, Y. Nagatani, H. Natori, S. Nishimura, A. D. Pant, Y. Miyake, and
K. Ishida, “Time evolution calculation of muon catalysed fusion: Emission of recycling muons from a two-layer hydrogen ﬁlm,”
Fusion Eng. Des. 169, 112580 (2021).
A. D. Pant, K. Nagamine, E. Torikai, I. Shiraki, K. Shimomura, Francis L. Pratt, H. Ariga-Miwa, K. Ishida, and J. S. Schultz, “Muonium
response to low oxygen levels in haemoglobin and other biological aqueous solutions and potential application towards monitoring
hypoxia,” Nucl. Instrum. Methods Phys. Res. A 1010, 165561 (2021).
M. D. Umar, K. Ishida, R. Murayama, D. P. Sari, U. Widyaiswari, M. Fronzi, I. Watanabe, and M. Iwasaki, “Muon-spin motion at thecrossover regime between gaussian and lorentzian distribution of magnetic ﬁelds,” Prog. Theor. Exp. Phys. 2021, 083101 (2021).
K. Okutsu, T. Yamashita, Y. Kino, R. Nakashima, K. Miyashita, K. Yasuda, S. Okada, M. Sato, T. Oka, N. Kawamura, S. Kanda,
K. Shimomura, P. Strasser, S. Takeshita, M. Tampo, S. Doiuchi, Y. Nagatani, H. Natori, S. Nishimura, A. D. Pant, Y. Miyake, and
K. Ishida, “Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target,” Fusion Eng.
Des. 170, 112712 (2021).
A. Green, K. Ishida, Bethany V. Hampshire, K. Butcher, M. Pollard, and A. D. Hillier, “Understanding roman gold coinage inside out,” J.
Archaeol. Sci. 134, 105470 (2021).
J. Sugiyama, K. Ohishi, O. K. Forslund, M. Månsson, S. P. Cottrell, A. D. Hillier, and K. Ishida, “How Li diﬀusion in spinel
Li[Ni1/2 Mn3/2 ]O4 is seen with μ± SR,” Z. Phys. Chem. 236, 799 (2022).
W. N. Zaharim, S. N. A. Ahmad, S. Sulaiman, H. Rozak, D. F. H. Baseri, N. A. M. Rosli, S. S. Mohd-Tajudin, L. S. Ang, and I. Watanabe,“Density functional theory study of 12mer single-strand guanine oligomer and associated muon hyperﬁne interaction,” ACS Omega 6,29641–29650 (2021).
A. Jamaludin, W. N. Zaharim, S. Sulaiman, H. Rozak, A. L. Sin, and I. Watanabe, “Density functional theory investigation of muon
hyperﬁne interaction in guanine-cytosine double-strand DNA,” J. Phys. Soc. Jpn. 91, 024301 (2022).
S. Yoon, W. Lee, S. Lee, J. Park, H. Lee, Y. S. Choi, S. -H. Do, W. -J. Choi, W. -T. Chen, F. Chou, D. I. Gorbunov, Y. Oshima,
A. Ali, Y. Singh, A. Berlie, I. Watanabe, and K. -Y. Choi1, “Quantum disordered state in the J1 -J2 square-lattice antiferromagnet
Sr2 Cu(Te0.95 W0.05 )O6 ,” Phys. Rev. Res. 5, 014411 (2021).
M. Miyajima, F. Astuti, T. Fukuda, M. Kodani, S. Iida, S. Asai, A. Matsuo, T. Masuda, K. Kindo, T. Hasegawa, T. C. Kobayashi,
T. Nakano, I. Watanabe, and T. Kambe, “Spin-gap formation due to spin-Peierls instability in π-orbital-ordered NaO2 ,” Phys. Rev. B
104, L140402 (2021).

[Review Articles]
M. Cataldo, M. Clemenza, K. Ishida, and A. D. Hillier, “A novel non-destructive technique for cultural heritage: Depth proﬁling andelemental analysis underneath the surface with negative muons,” Appl. Sci. 12, 4237 (2022).
A. D. Hillier, S. J. Blundell, I. McKenzie, I. Umegaki, L. Shu, J. A. Wright, T. Prokscha, F. B. K. Shimomura, A. Berlie, H. Alberto, andI. Watanabe, “Muon spin spectroscopy,” Nat. Rev. Meth. Primers 2, 4 (2022).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

I. Watanabe, D. P. Sari, R. Ramadhan, B. Adiperdana, and S. Sulaiman, “Muon-site determination in materials by using computational
methods,” J. Comput. Chem. Jpn. 19, 115–123 (2020).

[Book]
A. D. Hillier, B. Hampshire, and K. Ishida, “Depth-dependent bulk elemental analysis using negative muons,” in “Handbook of Cultural
Heritage Analysis,” S. D’Amico and V. Venuti (Eds.), Springer, 2022, pp. 23–44.

Presentations[International Conference/Workshop]
K. Ishida, “Muon g-2 experiment at J-PARC,” 14th European Research Conference on Electromagnetic Interactions with Nucleons andNuclei (EINN2021), Online, November 2–6, 2021.

[Domestic Conferences/Workshops]
石田勝彦, 「ミュオン原子分子とスピン状態」, 新学術領域「宇宙観測検出器と量子ビームの出会い. 新たな応用への架け橋. 」, 第 1
回超低速負ミュオンビーム研究会, オンライン, 2021 年 12 月 20 日.
石田勝彦, 「RIKEN-RAL 施設」, 第 12 回「Muon 科学と加速器研究」, 第 6 回「文理融合シンポジウム 量子ビームで歴史を探る—
加速器が紡ぐ文理融合の地平—」, 「ミュオンで見る磁性・超伝導物質研究の最前線」合同研究会, 豊中市（大阪大学）, 2022 年
1 月 6–8 日.
石田勝彦, 「パルスミュオン施設でのミュオン科学研究」, 「ミューオン X 線 γ 線分光 非破壊分析, 化学, 原子核物理への新展開」,「ミューオン原子核捕獲反応による原子核関連研究の可能性」, 合同研究会, 豊中市（大阪大学 RNCP）&オンライン, 2022 年 3月 24 日.

Press Release
神田聡太郎, 下村浩一郎他, 「『理想の水素原子』で未知の物理現象を探索する, ミュオニウムのマイクロ波分光実験がスタート」,
高エネルギー加速器研究機構, J-PARC センター, 理化学研究所, 東京大学大学院理学系研究科, 東京大学大学院総合文化研究科,
2021 年 4 月 16 日. https://www.riken.jp/press/2021/20210416_1/index.html .

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Safety Management Group
1. Abstract
The RIKEN Nishina Center for Accelerator-Based Science possesses one of the largest accelerator facilities in the world, which
consists of two heavy-ion linear accelerators and ﬁve cyclotrons. This is the only site in Japan where uranium ions are accelerated.
The center also has electron accelerators of microtron and synchrotron storage ring. Our function is to keep the radiation level inand around the facility below the allowable limit and to keep the exposure of workers as low as reasonably achievable. We are also
involved in the safety management of the Radioisotope Center, where many types of experiments are performed with sealed andunsealed radioisotopes.

2. Major Research Subjects(1) Safety management at radiation facilities of Nishina Center for Accelerator-Based Science(2) Safety management at Radioisotope Center(3) Radiation shielding design and development of accelerator safety systems

3. Summary of Research Activity
Our most important task is to keep the personnel exposure as low as reasonably achievable, and to prevent an accident. Therefore,
we daily patrol the facility, measure the ambient dose rates, maintain the survey meters, shield doors and facilities of exhaust air
and wastewater, replenish the protective supplies, and manage the radioactive waste. Advice, supervision and assistance at major
accelerator maintenance works are also our task.
Minor improvements of the radiation safety systems were also done. The old exhaust equipment for the radiation-controlled areain the RIBF experimental building was replaced. A small and fully eﬀective shielding for the RI production beamline in the Linac
building was designed by using a Monte-Calo radiation transport calculation code.

Members
Director
Kanenobu TANAKA
Technical Scientists
Rieko HIGURASHI

Hisao SAKAMOTO

Expert Technician
Atsuko AKASHIO
Technical Staﬀ
Hiroki MUKAI
Junior Research Associate
Kenta SUGIHARA
Visiting Scientists
Masayuki HAGIWARA (KEK)Toshiya SANAMI (KEK)

Nobuhiro SHIGYO (Kyushu Univ.)
Hiroshi YASHIMA (Kyoto Univ.)

Administrative Part-time Workers
Kimie IGARASHI (Administrative Part-time Worker I)
Satomi IIZUKA (Administrative Part-time Worker I)
Tokie KUDO (Administrative Part-time Worker II)

Yukiko SHIODA (Administrative Part-time Worker II)
Naoko USUDATE (Administrative Part-time Worker II)

Temporary Staﬃng
Ryuji SUZUKI
Assistant
Tomomi OKAYASU

List of Publications & Presentations
Publication[Original Paper]
K. Sugihara, N. Shigyo, A. Akashio, and K. Tanaka, “Measurement of neutron energy spectra of 345 MeV/u 238 U incidence on a copper
target,” Nucl. Instrum. Methods Phys. Res. B 512, 102 (2022).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Presentations[International Conference/Workshop]
K. Sugihara (poster), N. Shigyo, E. Lee, T. Sanami, and K. Tanaka, “Study on JQMD and INCL models for α particle incident neutron
production,” 2021 Symposium on Nuclear Data (SN2021), Online, November 18–19, 2021.

[Domestic Conferences/Workshops]
田中鐘信 (招待講演), 「理研 RIBF における感染症対策と最近の安全管理状況」, 第 8 回加速器施設安全シンポジウム, オンライン,
2021 年 8 月 27 日.
杉原健太 (口頭発表), 池田裕二郎, 小林知洋, 池田翔太, 藤田訓裕, 大竹淑恵,「RANS-II の p-Li 中性子線源特性の実験的研究」, RANS
シンポジウム, 和光市 (理化学研究所), 2021 年 5 月 13 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

User Liaison Group
1. Abstract
The User Liaison Group is a group that provides user support, including various procedures required for accelerator use, in orderto promote collaborative-use of the RIBF facilities. The group will provide user support on matters necessary for RIBF experiments,from application to completion. The group will also provide technical support for the dissemination of information on the research
results of the RIBF.
The group consists of two teams. The RIBF User Liaison Team provides various supports to visiting RIBF users through the RIBF
Users Oﬃce. Managing RIBF beam time and organizing the Program Advisory Committee Meetings to review RIBF experimental
proposals are also important mission of the Team in order to enhance collaborative-use of the RIBF. The Outreach Team has createdvarious information materials, such as pamphlets, posters, and homepages, to introduce the research activities in the RNC. On the
homepage, we provide information on usage of the RIBF facility. The team also participate in science introduction events hosted bypublic institutions. In addition, the User Liaison Group also takes care of laboratory tours for RIBF visitors from public. The numbersof visitors usually amounts to 2,300 per year.

Members
Director
Hideki UENO
Assistants
Yu NAYA
Tomomi OKAYASU

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

User Liaison GroupRIBF User Liaison Team
1. Abstract
To enhance synergetic common use of the world-class accelerator facility, the Radioisotope Beam Factory (RIBF), it is necessary
to promote a broad range of applications and to maximize the facility’s importance. The facilitation and promotion of the RIBF are
important missions charged to the team. Important operational activities of the team include: i) the organization of international Program Advisory Committee (PAC) meetings to review experimental proposals submitted by RIBF users, ii) RIBF beam-time operation
management, and iii) promotion of facility use by hosting outside users through the RIBF Independent Users program, which is a
new-user registration program begun in FY2010 at the RIKEN Nishina Center (RNC) to enhance the synergetic common use of the
RIBF. The team opened the RIBF Users Oﬃce in the RIBF building in 2010, which is the main point of contact for Independent Usersand provides a wide range of services and information.

2. Major Research Subjects(1) Facilitation of the use of the RIBF
(2) Promotion of the RIBF to interested researchers

3. Summary of Research Activity(1) Facilitation of the use of the RIBF
The RIBF Users Oﬃce, formed by the team in 2010, is a point of contact for user registration through the RIBF Independent User
program. This activity includes:• registration of users as RIBF Independent Users,• registration of radiation workers at the RIKEN Wako Institute,• provision of an RIBF User Card (a regular entry permit) and an optically stimulated luminescence dosimeter for each RIBF
Independent User, and• provision of safety training for new registrants regarding working around radiation, accelerator use at the RIBF facility, andinformation security, which must be completed before they begin RIBF research. The RIBF Users Oﬃce is also a point ofcontact for users regarding RIBF beam-time-related paperwork, which includes:• contact for beam-time scheduling and safety review of experiments by the In-House Safety Committee, and• maintaining the above information in a beam-time record database.
In addition, the RIBF Users Oﬃce assists RIBF Independent Users with matters related to their visit, such as invitation procedures,visa applications, and the reservation of on-campus accommodation.
(2) Promotion of the RIBF to interested researchers• The team has organized an international PAC for RIBF experiments; it consists of leading scientists worldwide and reviews
proposals in the ﬁeld of nuclear physics (NP) purely on the basis of their scientiﬁc merit and feasibility. The team also assists
another PAC meeting for material and life sciences (ML) organized by the RNC Advanced Meson Laboratory. The NP PAC
meeting is organized once a year regularly, and the ML PAC meetings are organized once or twice a year.
• The team coordinates beam times for PAC-approved experiments and other development activities. It manages the operatingschedule of the RIBF accelerator complex according to the decisions arrived at by the RIBF Machine Time Committee.
• To promote research activities at RIBF, proposals for User Liaison and Industrial Cooperation Group symposia/mini-workshops
are solicited broadly both inside and outside of the RNC. The RIBF Users Oﬃce assists in the related paperwork.
• The team is the point of contact for the RIBF users’ association. It arranges meetings at RNC headquarters for the RIBF User
Executive Committee of the users’ association.
• The Team conducts publicity activities, such as arranging for RIBF tours, development and improvement of the RNC oﬃcial web
site, and delivery of RNC news via email and the web.

MemberTeam Leader
Ken-ichiro YONEDA- 340 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

User Liaison Group
Outreach Team
1. Abstract
The mission of the Outreach Team is to provide various “intangible” technical support for the dissemination of information on the
research in RNC. For instance, the team creates brochures introducing the RNC and the RIBF accelerator facility, posters of symposia
and the summer school hosted by RNC, the center homepage containing information such as details of RNC and the procedure for theuse of the RIBF facility, and images of equipment and facilities available for researchers inside and outside RIKEN, among the others.
Furthermore, the team also participates in science introduction events hosted by public institutions.

2. Major Work Contents
The major work contents of the Outreach Team is to promote the publicity of RNC, through the creation of various materials suchas brochures, websites, posters, and videos, among the others. The arrangement of tours of the RIBF facility and the exhibition andintroduction of the RIBF facility at science events are also conducted independently or in cooperation with RIKEN Public Relations
Oﬃce.

3. Summary of Work Activity
The speciﬁc work contents performed by the team are as follows:• [Website] The Team creates/manages the RNC oﬃcial website (http://www.nishina.riken.jp), which introduces the organization and its research activities. This website plays an important role in providing information to researchers who visit RNC
to conduct his/her own research.
• [Brochures] The Team has produced various brochures introducing the organization and the studies performed at RNC. The
brochures named “Your body is made of star scraps” explaining element synthesis in the universe and “Introduction of RIBF
Facility” in a cartoon style for children are among them.
• [Posters] Conference/Symposium posters connected with RNC were prepared on the request of organizers. For general purpose,a special poster featuring the nuclear chart has been prepared for distribution. In commemoration of the discovery of nihonium,
brochures and posters dedicated to the ceremony were made.
• [RIBF Cyclopedia] In April 2012, the permanent exhibition hall (RIBF Cyclopedia) located at the entrance hall of the RIBF
building was set up in cooperation with RIKEN Public Relations Oﬃce. Explanatory illustrations on nuclear science, research at
RIBF, RIBF history, a 3D nuclear chart built with LEGO blocks, and a 1/6-size GARIS model are displayed to help understanding
through visual means. The Team is also working on updating the exhibits.
• [RIBF facility tour] The Team arranges RIBF facility tour for over 2000 visitors per year. The tour is guided by a researcher.
• [Science event participation] In 2010, 2012, 2013, 2015, and 2016, the sub-team opened an exhibition booth of RNC to introduce
the latest research activities on the occasion of the “Science Agora” organized by Japan Science and Technology Agency (JST).
From time to time, the sub-team was invited to participate in scientiﬁc events by MEXT, Wako city, and Nissan global foundation.
One attraction targeting children is the hands-on work of assembling “Iron-beads” to create a nuclear chart or a shape of nihonium.
In addition to the above-noted work contents, the Team conducts a variety of works, such as taking pictures of meetings organized by
RNC, cooperation in the production of a 3D video to explain the accelerators and the research at RIBF, among the others.

Members
Team Leader
Hideki UENO
Deputy Team Leader
Yasushi WATANABE
Technical Staﬀ
Narumasa MIYAUCHI- 341 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Oﬃce of the Center Director
1. Abstract
This oﬃce is in place from JFY2018 to conduct works that the Center Director deems necessary for the operation of the research
center and the secretarial work related to the research center in general.

2. Major Work Contents• Nishina Center Monthly Meeting
The pupose of the meeting is to share information on activities within the Nishina Center with all of the members. The meetingcovers introduction of new comers, press-released achievements, announcement of events organized by or related to the Nishina
Center, safety issues, and others to be informed to all members. The meeting agenda is distributed to all of the members via
mailing-list.
• Conference Support
Assistant staﬀ members support coherently a large-size conference hosted by the Nishina Center.
• Orientation for new comers to the Nishina Center
The Orientation is organized once a year to the new comers to give instructions for emergency response, safety in research,
computer and network resources and security, and research misconduct prevention.

3. Summary of Work Activity• Nishina Center Monthly Meeting
Noriko Asakawa arranged the agenda and Hidetada Baba supported the on-line video system for the meeting.
– The 168th April 14, 2021
(1) Greetings from the RNC director to kick oﬀ new ﬁscal year
(2) Award
RIKEN Ohbu Award, RIKEN Baiho Award(3) Introduction of newcomers(4) Announcement of RIKEN Information Systems FY2021– The 169th May 12, 2021
(1) Introduction of newcomers:(2) Press release“Mixed bubbles in Bose-Bose mixtures” (P. Naidon)
Not oﬃcially announced yet (Isobe)(3) Report on RIKEN Open Day (Tanaka)(4) Report from the RNC Director– The 170th June 9, 2021
(1) Broadcast on Thai PBS program (Abe)(2) Moving of the Promotion Oﬃce to the new HQ bldg (Hashimoto)(3) Information on the Newcomers Seminar (Kohama)(4) Report from the RNC Director– The 171st July 14, 2021
(1) Machine learning and theoretical physics (A. Tomiya, SPDR, BNL)
(2) Report from the RNC Director
VIP visit to RIBF, COVID-19, Tokyo 2020 traﬃc regulations(3) Others– The 172nd September 8, 2021
(1) Article on “3 nucleon force” in Nikkei newspaper (Sekiguchi)(2) Diversity working group (Nio)(3) Report from the RNC Director– The 173rd October 13, 2021
(1) Introduction of newcomers
Masaaki Kimura (Director, Nuclear Many-body Theory Lab)
Phong Vi (PD Researcher, Radioactive Isotope Physics Lab)
Zuxing Yang (PD Researcher, Radioactive Isotope Physics Lab)
Kenichiro Tateishi (Research Scientist, Spin Isospin Lab)
(2) Awards
IAEA Women in Plant Mutation Breeding Award, Tomoko Abe (Director, Beam Mutagenesis Group)
RIBF Thesis Award, Masaomi Tanaka (SPD Researcher, Radioactive Isotope Physics Lab)(3) Report from the RNC director(4) Other- 342 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)– The 174th November 10, 2021
(1) Young Scientist Award of the Physical Society of Japan, 2022
Tokuro Fukui (SPDR, Strangeness Nuclear Physics Lab), Junki Tanaka (PD, Spin Isospin Lab), Takumi Yamaga(PD, Meson Science Lab),(2) Direct photons probe Gluon’s dynamic motion in the proton.
Yasuyuki Akiba (Group Leader, RBRC Beam Mutagenesis Group)(3) Introduction of a new textbook “Modern Nuclear Physics” (H. Sagawa)(4) Report from the RNC director(5) Other– The 175th December 8, 2021
(1) Introduction of a newcomer
Daisuke Inotani (Contract Researcher, Strangeness Nuclear Physics Laboratory)(2) Press release
Start of investigator-initiated clinical trial to treat refractory thyroid cancer - New targeted alpha particle therapy
using astatine - (Haba)(3) Report from the RNC director
Visit of the MEXT vice minister
COVID-19(4) Other– The 176th January 12, 2022
(1) New Year’s Greetings from the RNC Director(2) Introduction of a newcomer
Li, Yutian (IPA, Spin Isospin Laboratory), Yap, Jinn Ming (IPA, Radioactive Isotope Physics Laboratory)(3) Awards
Student Presentation Award of the Physical Society of Japan: A. Hirayama, Inoue Research Award for Young
Scientist: R. Taniuchi(4) Press Release“Breeding a new Satsuma mandarin variety suitable for long-term storage” (T. Abe)
(5) New book
“How was the new element nihonium created?” (H. Haba)(6) TV broadcast
Program on TV Saitama: “Shibusawa Kaitai Shinsho” (December 23, 2021) (Y. Watanabe)(7) Feature article
2022 February Issue of “Nikkei Science” (K. Sekiguchi)(8) Report from the RNC director(9) Other– The 177th February 9, 2022
(1) Award
2021 Symposium on Nuclear Data Poster Presentation Award(2) Special issue of “CYTOLOGIA” featuring heavy ion breeding (Abe)(3) Journal of the Particle of Accelerator Society of Japan: “Relocation and restoration of the third RIKEN cyclotron”(Okuno)(4) Fire drill (Tanaka)(5) Report from the RNC director(6) Other– The 178th March 9, 2022
(1) 2022 Calendar featuring “Women Scientists Who Made Nuclear Astrophysics” (Motizuki)(2) RIKEN Open Day on Apr. 23, recruiting explainers (Abe, Ikeda)(3) Report on the ﬁre drill on Feb. 25 (Tanaka)(4) Report from the RNC director(5) Greeting from the closing of the Radiation Laboratory (En’yo)• Conference Support
No large size conferences hosted by the Nishina Center were organized.
• Orientation for new comers to the Nishina Center
The Orientation was organized on May 20, 2021.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Members
Director
Hiroyoshi SAKURAI
Research Administrator
Narumasa MIYAUCHI
Assistants
Noriko ASAKAWA
Yu NAYA
Asako SAKIHAMA
Karen SAKUMA

Asako TAKAHASHI
Mitsue YAMAMOTO
Izumi YOSHIDA- 344 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Partner Institutions
The RIKEN Nishina Center for Accelerator-Based Science (RNC) has collaborated with universities and research institutes since2008 under the research partnership agreement. This collaboration framework permits an external institute to develop its own projects
at the RIKEN Wako Campus in equal partnership with the RNC. At present, two institutes—the Center for Nuclear Study (CNS), theUniversity of Tokyo and the Wako Nuclear Science Center (WNSC), Institute of Particle and Nuclear Studies (IPNS), High Energy
Accelerator Research Organization (KEK)—are conducting joint research under the research partnership agreement.
The CNS and RNC signed the research partnership agreement in 2008. Until then, the CNS had collaborated in joint programswith RIKEN under the “Research Collaboration Agreement on Heavy Ion Physics” (collaboration agreement) signed in 1998. The
partnership agreement redeﬁnes procedures related to the joint programs while keeping the spirit of the collaboration agreement. The
joint programs include experimental nuclear-physics activities using CRIB, SHARAQ, and GRAPE at the RI Beam Factory (RIBF),
accelerator development; and activities at RHIC PHENIX.
The KEK-WNSC and RNC signed a research partnership agreement on “Low-Energy Unstable Nuclear Beam Science” in 2011.
The joint experimental programs are based on the KEK Isotope Separation System (KISS). The KISS has been available for RIBF
users since 2015. The research collaboration agreement for the SLOWRI facility and the multi-reﬂection time-of-ﬂight (MRTOF)
mass spectrograph was then signed in 2019, based on which the SLOWRI Joint Operation Committee has been established for thecollaborative use and operation of the SLOWRI facility.
Experimental proposals that request the use of the above-noted devices of the CNS and KEK, together with other key devices at
the RIBF, are screened by the Program Advisory Committee for Nuclear Physics experiments at the RIBF (NP-PAC). The NP-PAC
meetings are co-hosted by the CNS and KEK.
Matters necessary for the smooth promotion of joint research based on the research partner agreement are determined at the Collaboration Liaison Council. More speciﬁc matters related to the execution of collaborative research are discussed at the Collaboration
Liaison Committee established under the Liaison Council. In order to enhance the eﬀectiveness of coordination and information sharing on joint research programs, the Joint Researchers Meeting was established in 2020 under the Collaboration Liaison Committee.
Several members of both institutes have also been invited to participate as external members in RNC committees related to theoperation of the RIBF, such as the Machine-Time Committee and the Safety Review Committee.
The activities of the CNS and KEK are reported in the succeeding pages.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Partner Institution
Center for Nuclear Study, Graduate School of Science
The University of Tokyo
1. Abstract
The Center for Nuclear Study (CNS) aims to elucidate the nature of nuclear system by producing the characteristic states where
the Isospin, Spin and Quark degrees of freedom play central roles. These researches in CNS lead to the understanding of the matterbased on common natures of many-body systems in various phases. We also aim at elucidating the explosion phenomena and theevolution of the universe by the direct measurements simulating nuclear reactions in the universe. In order to advance the nuclear
science with heavy-ion reactions, we develop AVF upgrade, CRIB and SHARAQ facilities in the large-scale accelerators laboratories
RIBF. The OEDO facility has been developed as an upgrade of the SHARAQ, where a RF deﬂector system has been introduced toobtain a good quality of low-energy beam. A new project for fundamental symmetry using heavy RIs has been starting to install new
experimental devices in the RIBF. We promote collaboration programs at RIBF as well as RHIC-PHENIX and ALICE-LHC with
scientists in the world, and host international meetings and conferences. We also provide educational opportunities to young scientists
in the heavy-ion science through the graduate course as a member of the department of physics in the University of Tokyo and throughhosting the international summer school.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)

Accelerator Physics
Nuclear Astrophysics
NUSPEQ/Low Energy Nuclear Reaction group
Quark physics
Nuclear Theory
OEDO/SHARAQ project
Exotic Nuclear Reaction
Active Target Development
Fundamental Physics

3. Summary of Research Activity(1) Accelerator physics
One of the major tasks of the accelerator group is the development of ion sources and the optimization of the beam transportsystem to CRIB, E7B, and C12 in the E7 experiment room. In 2021, the operating time of HyperECR ion source was 1773 hours.
The beam production methods for metallic ions such as Li, Mg, and Fe have matured. High brightness metallic ion beams to matchthe requirement for the experiments can now be achieved stably and sustainably. Together with undergoing studies on ECR plasma,further improvements in beam qualities are expected. For the development of the 4-dimensional emittance monitor for the extracted
beam from AVF cyclotron, the design of an optical system with a digital camera equipped with a tele lens was completed. Then, it isexpected that the monitor can be kept away from the beamline which was the radiation source caused by the ion beam.
(2) Nuclear astrophysics
The main activity of the nuclear astrophysics group is to study astrophysical reactions and special nuclear structure, such as
clusters, using the low-energy RI beam separator CRIB. In 2021, two major experimental projects at CRIB were completed andﬁnal publications were made; One was on the study of the 7 Be destruction process in the Big-bang nucleosynthesis, to solve thecosmological 7 Li abundance problem. The other is on the precise determination of the 22 Mg(α, p) astrophysical reaction, relevant in
X-ray bursts. In January 2022, we performed the ﬁrst physics experiment at CRIB after the pandemic, which was to simultaneously
study the 26 Si(α, α) scattering and the (α, p) reaction, relevant to the astrophysics.
(3) NUSPEQ/Low Energy Nuclear Reaction group
The NUSPEQ (NUclear SPectroscopy for Extreme Quantum system) and Low Energy Nuclear Reaction group study exotic structures in high-isospin and/or high-spin states in nuclei. The groups play a major role in the OEDO/SHARAQ project described below.
In 2021, analysis of a new measurement of the 4 He(8 He, 8 Be)4n reaction for better statistics and better accuracy has been proceeding.
A recoil particle detector for missing mass spectroscopy, named TiNA, at OEDO had been upgraded under the collaboration withRIKEN and RCNP. The original TiNA consisted of 6 sector telescopes and 12 CsI (Tl) crystals. Four TTT-type (1024 channels)
doubly-sided silicon detectors and twenty-two CsI(Tl) were added to make a TiNA2 array. The production cross sections of 178m2 Hf
were evaluated for the mass production in the future with a new and simple chemical separation method. The inelastic decays fromthe isobaric analog resonances of 97 Zr were studied for the single particle wave functions coupled to the second 0+ state in 96 Zr. The
nature of the diﬀerent shape of the second 0+ state from the ground state was revealed. The systematic studies of neutron-rich Zr
isotopes are planned. The CNS GRAPE (Gamma-Ray detector Array with Position and Energy sensitivity) is also a major apparatus
for high-resolution in-beam gamma-ray spectroscopy. The digital signal processing devices for the GRAPE are under development.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)(4) Quark physics
Main goal of the quark physics group is to understand the properties of hot and dense nuclear matter created by colliding heavy
nuclei at relativistic energies. The group has been involved in the ALICE experiment at Large Hadron Collider (LHC) at CERN.
The group has led the global commissioning of the ALICE upgrades in 2021. The group has involved in the data analyses, which
include the measurement of low-mass lepton pairs in Pb-Pb collisions, the measurement of long range two particle correlations in
p-Pb collisions, searches for thermal photons in high multiplicity pp and p-Pb collisions. The group has involved in the ALICE-TPC
upgrade using a Gas Electron Multiplier (GEM), where the group is very active in the development and benchmarking of the online
space-charge distortion corrections using machine learning techniques running on the Graphical Processing Unit (GPU).
(5) Nuclear theory
The nuclear theory group participates in a project, “Program for Promoting Researches on the Supercomputer Fugaku,” and has
been promoting computational nuclear physics utilizing the Fugaku supercomputer. In FY2021, we performed large-scale shell-model
calculations employing the Monte Carlo shell model and quasi-particle vacua shell model to investigate various exotic structures of
unstable nuclei. By using the no-core Monte Carlo shell model, we successfully describe the Hoyle state of 12 C from the ﬁrst principle
without assuming any cluster structure. In the medium-heavy mass region, we successfully described the shape phase transitionof Nd and Sm isotopes based on shell-model calculations and evaluated the nuclear matrix element of the neutrinoless double-beta
decay of 150 Nd. The nuclear Schiﬀ moment of 129 Xe was also investigated based on the shell model and we found an approximately
linear correlation between the Schiﬀ moment and the magnetic moment. In parallel, we promoted many research collaborations withexperimental groups for investigating the structure of various nuclei such as 40 Ca, 32 Mg, 47, 49 Cl, and 55 Cr.
(6) OEDO/SHARAQ project
The OEDO/SHARAQ group pursues experimental studies of RI beams by using the high-resolution beamline and the SHARAQ
spectrometer, and the OEDO for the decelerated RI beams. SHARAQ11 experiment with a tritium-doped titanium target, which has
been developed by Tohoku Univ., was successfully conducted. For SHARAQ13, a mass measurement by the TOF-Brho techniquefor very proton-rich nuclei, an active stopper detector has been developed. The optics study of OEDO is under way to improve thetransmission of the ion beams. For the high intensity RIBs, the delay-line PPACs have been replaced with the strip-readout PPACs.
The experimental study of 0− strength in nuclei using the parity-transfer charge exchange (16 O, 16 F) will be reported soon. As for The
OEDO beamline, the results of the ﬁrst and second experiments for LLFPs will be ﬁnalised and reported soon. The proﬁle of X rayfrom the RFD had been measured comprehensively, which ﬁnalised the design of the lead shield to enable us to conduct the in-beamgamma experiment at OEDO.
(7) Exotic nuclear reaction
The Exotic Nuclear Reaction group studies various exotic reactions induced by heavy-ion beams. We conducted a search of
double Gamow-Teller resonance by a double charge exchange reaction (12 C, 12 Be) at BigRIPS.
(8) Active target development
Three gaseous active target TPCs called CAT-S, CAT-M and GEM-MSTPC are developed and used for the missing mass spectroscopies. The CAT’s are employed for the study of equation of state of nuclear matter. The measurement of giant monopole resonancein 132 Sn at RIBF with CAT-S and the data analysis is ongoing. The CAT-M was employed for the systematic measurement of thedeuteron inelastic scattering of the Xe and Kr isotopes. Newly developed permanent dipole magnet system was installed to reducethe background due to the delta rays. The GEM-MSTPC is employed for the nuclear astrophysics study. The data analysis of (α, p)reaction on 18 Ne and 22 Mg and the β-decay of 16 Ne followed by α emission are ongoing.
(9) Fundamental physics
The development of an optical lattice interferometer to search for a permanent electric dipole moment (EDM) with Francium (Fr)atoms is now in progress at RIKEN. The lattice-like potential with a standing wave of laser light, the so-called optical lattice, canrealize a long interaction time of the trapped Fr atoms with external ﬁelds, which allows to measure the EDM with high precision.
The experimental apparatus to produce the cold Fr atoms trapped in the magneto-optical trap (MOT) is ready at present. We have
conﬁrmed that the newly developed surface ionizer can produce approximately 106 Fr+ /s as a secondary beam via nuclear fusion
reaction. We are now optimizing the experimental parameters to realize the high intensity cold Fr sources with 106 atoms to measure
the EDM.

Members
Director
Susumu SHIMOURA- 347 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Scientiﬁc Staﬀ
Susumu SHIMOURA (Professor)
Yasuhiro SAKEMI (Professor)
Kentaro YAKO (Associate Professor)
Nobuaki IMAI (Associate Professor)
Taku GUNJI (Associate Professor)

Noritaka SHIMIZU (Project Associate Professor)
Hidetoshi YAMAGUCHI (Lecturer)
Shin’ichiro MICHIMASA (Assistant Professor)
Shinsuke OTA (Assistant Professor)
Hiroki NAGAHAMA (Assistant Professor)

Guest Scientists
Yutaka UTSUNO (Guest Professor)
Daiki NISHIMURA (Guest Associate Professor)
Toshitaka KAJINO (Guest Post Doctoral Associate)

Ikuko HAMAMOTO (Guest Post Doctoral Associate)
Jongwon HWANG (Guest Post Doctoral Associate)

Academic Specialist
Reiko KOJIMATechnical Specialist
Yasuteru KOTAKA
Techinical Assistant
Masayoshi YAGYU
Project Research Associates
Masanori DOZONO
Seiya HAYAKAWA

Daiki SEKIHATARin YOKOYAMA

Post Doctoral Associates
Keisuke NAKAMURA
Keita KAMAKURA
Nanru MA

Yusuke TSUNODA
Kota YANASE
Thomas William CHILLERY

Assistant Teaching Staﬀ
Yuko SEKIGUCHI
Keita KAWATA

Akane SAKAUE
Shoichiro MASUOKA

Graduate Students
Hideki SHIMIZU
Rieko TSUNODA
Naoya OZAWA
Shutaro HANAI
Shintaro NAGASE
Ryotaro KOHARA

Jiatai LI
Daisuke UEHARA
Kodai OKAWA
Hitoshi BABA
Mirai FUKASE

Administration Staﬀ
Noriko SHIMANE
Ikuko YAMAMOTO

Yukino KISHI
Aki KOTAKA

List of Publications & Presentations
Publications[Original Papers]
S. Go, E. Ideguchi, R. Yokoyama, N. Aoi, F. Azaiez, K. Furutaka, Y. Hatsukawa, A. Kimura, K. Kisamori, M. Kobayashi, F. Kitatani, M. Koizumi, H. Harada, I. Matea, S. Michimasa, H. Miya, S. Nakamura, M. Niikura, H. Nishibata, N. Shimizu, S. Shimoura,
T. Shizuma, M. Sugawara, D. Suzuki, M. Takaki, Y. Toh, Y. Utsuno, D. Verney, and A. Yagi, “High-spin states in 35 S,” Phys. Rev. C
103, 034327 (2021).
H. Baba, T. Ichihara, T. Isobe, T. Ohnishi, K. Yoshida, Y. Watanabe, S. Ota, H. Shimizu, S. Shimoura, S. Takeuchi, D. Nishimura,
J. Zenihiro, A. O. Tokiyasu, and R. Yokoyama, “MPV-parallel readout architecture for the VME data acquisition system,” IEEE Trans.
Nucl. Sci. 68, 1841–1848 (2021).
R. Nakamoto, M. Ito, A. Saito, and S. Shimoura, “Extended Migdal-Watson formula to evaluate background strength in binary breakup
reactions,” Phys. Rev. C 104, 034602 (2021).
N. Kitamura, N. Imai, H. Haba, S. Michimasa, S. Shimoura, and Y. Yamaguchi, “Production of 178 Hfm2 and a simple chemical separation
method for Hf recovery,” J. Radioanal. Nucl. Chem. 330, 721–725 (2021).

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

S. W. Huang, Z. H. Yang, F. M. Marqués, N. L. Achouri, D. S. Ahn, T. Aumann, H. Baba, D. Beaumel, M. Böhmer, K. Boretzky,
M. Caamaño, S. Chen, N. Chiga, M. L. Cortés, D. Cortina, P. Doornenbal, CA. Douma, F. Dufter, J. Feng, B. Fernandez-dominguez,
Z. Elekes, U. Forsberg, T. Fujino, N. Fukuda, I. Gašparić, Z. Ge, R. Gernhäuser, J. M. Gheller, J. Gibelin, A. Gillibert, Z. Halász,
T. Harada, M. N. Harakeh, A. Hirayama, N. Inabe, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki, D. Kim, S. Kim, S. Kiyotake,
T. Kobayashi, Y. Kondo, P. Koseoglou, Y. Kubota, I. Kuti, C. Lehr, C. Lenain, P. J. Li, Y. Liu, Y. Maeda, S. Masuoka, M. Matsumoto,
A. Matta, J. Mayer, H. Miki, M. Miwa, B. Monteagudo, I. Murray, T. Nakamura, A. Obertelli, N. A. Orr, H. Otsu, V. Panin, S. Park,
M. Parlog, S. Paschalis, M. Potlog, S. Reichert, A. Revel, D. Rossi, A. Saito, M. Sasano, H. Sato, H. Scheit, F. Schindler, T. Shimada,Y. Shimizu, S. Shimoura, H. Simon, I. Stefan, S. Storck, L. Stuhl, H. Suzuki, D. Symochko, H. Takeda, S. Takeuchi, J. Tanaka,
Y. Togano, T. Tomai, H. T. Törnqvist, E. Tronchin, J. Tscheuschner, T. Uesaka, V. Wagner, K. Wimmer, H. Yamada, B. Yang, L. Yang,
Y. Yasuda, K. Yoneda, L. Zanetti, and J. Zenihiro, “Experimental study of 4 n by directly detecting the decay neutrons,” Few-Body
Systems 62, 102 (2021).
R. Nakamoto, M. Ito, A. Saito, and S. Shimoura, “Continuum strength of direct breakup induced by external isoscalar ﬁeld,” Few-Body
Systems 62, 107 (2021).
W. Horiuchi, T. Inakura, and S. Michimasa, “Large enhancement of total reaction cross sections at the edge of the island of inversion in
Ti, Cr, and Fe isotopes,” Phys. Rev. C 105, 014316 (2022).
R. Yokoyama, E. Ideguchi, G. S. Simpson, Mn. Tanaka, Y. Sun, C. -J. Lv, Y. -X. Liu, L. -J. Wang, S. Nishimura, P. Doornenbal, G. Lorusso,
P. A. Soderstrom, T. Sumikama, J. Wu, Z. Y. Xu, N. Aoi, H. Baba, F. L. B. Garrote, G. Benzoni, F. Browne, R. Daido, Y. Fang,
N. Fukuda, A. Gottardo, G. Gey, S. Go, S. Inabe, T. Isobe, D. Kameda, K. Kobayashi, M. Kobayashi, I. Kojouharov, T. Komatsubara,
T. Kubo, N. Kurz, I. Kuti, Z. Li, M. Matsushita, S. Michimasa, C. B. Moon, H. Nishibata, I. Nishizuka, A. Odahara, Z. Patel, S. Rice,E. Sahin, H. Sakurai, H. Schaﬀner, L. Sinclair, H. Suzuki, H. Takeda, J. Taprogge, Z. Vajta, H. Watanabe, and A. Yagi, “Threequasiparticle isomers in odd-even 159,161 Pm: Calling for modiﬁed spin-orbit interaction for the neutron-rich region,” Phys. Rev. C 104,
L021303 (2021).
R. D. Harding, A. N. Andreyev, A. E. Barzakh, J. G. Cubiss1, P. Van Duppen, M. Al Monthery, N. A. Althubiti, B. Andel, S. Antalic,
T. E. Cocolios, T. Day Goodacre, K. Dockx, G. J. Farooq-Smith, D. V. Fedorov, V. N. Fedosseev, D. A. Fink, L. P. Gaﬀney, L. Ghys,
J. D. Johnson, D. T. Joss, M. Huyse, N. Imai, K. M. Lynch, B. A. Marsh, Y. Martinez Palenzuel, P. L. Molkanov, G. G. O’Neill,
R. D. Page, R. E. Rossel, S. Rothe, M. D. Seliverstov, S. Sels, C. Van Beveren, and E. Verstraelen, “Laser-assisted nuclear decay
spectroscopy of 176, 177, 179 Au,” Phys. Rev. C 104, 024326 (2022).
N. Kitamura, K. Wimmer, T. Miyagi, A. Poves, N. Shimizu, J. A. Tostevin, V. M. Bader, C. Bancroft, D. Barofsky, T. Baugher, D. Bazin,
J. S. Berryman, V. Bildstein, A. Gade, N. Imai, T. Kröll, C. Langer, J. Lloyd, E. Lunderberg, F. Nowacki, G. Perdikakis, F. Recchia,
T. Redpath, S. Saenz, D. Smalley, S. R. Stroberg, Y. Utsuno, D. Weisshaar, and A. Westerberg, “In-beam γ-ray spectroscopy of 32 Mg
via direct reactions,” Phys. Rev. C 105, 034318 (2022).
A. Fernández, A. Jungclaus, P. Doornenbal, M. A. Bentley, S. M. Lenzi, D. Rudolph, F. Browne, M. L. Cortés, T. Koiwai, R. Taniuchi,
V. Vaquero, K. Wimmer, T. Arici, N. Imai, N. Kitamura, B. Longfellow, R. Lozeva, B. Mauss, D. R. Napoli, M. Niikura, X. PereiraLopez, S Pigliapoco, A. Poves, F. Recchia, P. Ruotsalainen, H. Sakurai, S. Uthayakumaar, R. Wadsworth, and R. Yajzey, “Mirror energy
diﬀerences above the 0f (7/2) shell: First gamma-ray spectroscopy of the T z = −2 nucleus 56 Zn,” Phys. Lett. 823, 136784 (2021).
S. Hayakawa, M. La Cognata, L. Lamia, H. Yamaguchi, D. Kahl, K. Abe, H. Shimizu, L. Yang, O. Beliuskina, S. M. Cha, K. Y. Chae,
S. Cherubini, P. Figuera, Z. Ge, M. Gulino, J. Hu, A. Inoue, N. Iwasa, A. Kim, D. Kim, G. Kiss, S. Kubono, M. La Commara, M. Lattuada, E. J. Lee, J. Y. Moon, S. Palmerini, C. Parascandolo, S. Y. Park, V. H. Phong, D. Pierroutsakou, R. G. Pizzone, G. G. Rapisarda,
S. Romano, C. Spitaleri, X. D. Tang, O. Trippella, A. Tumino, and N. T. Zhang, “Constraining the primordial lithium abundance: Newcross section measurement of the 7 Be+n reactions updates the total 7 Be destruction rate,” Astrophys. J. Lett. 915, L13 (2021).
S. Palmerini, M. La Cognata, F. Hammache, L. Acosta, R. Alba, V. Burjan, E. Chávez, S. Cherubini, A. Cvetinović, G. D’Agata,N. de Séréville, A. Di Pietro, P. Figuera, Z. Fülöp, K. Gaitán De Los Rios, G. L. Guardo, M. Gulino, S. Hayakawa, G. G. Kiss,
M. La Commara, L. Lamia, C. Maiolino, G. Manicó, C. Matei, M. Mazzocco, J. Mrazek, T. Parascandolo, T. Petruse, D. Pierroutsakou,
R. G. Pizzone, G. G. Rapisarda, S. Romano, D. Santonocito, M. L. Sergi, R. Spartà, A. Tumino, and H. Yamaguchi, “The 27 Al(p, α)24 Mg
reaction at astrophysical energies studied by means of the trojan horse method applied to the 2 H(27 Al, α 24 Mg)n reaction,” Eur. Phys. J.
Plus 136, 898 (2021).
J. Hu, H. Yamaguchi, Y. H. Lam, A. Heger, D. Kahl, A. M. Jacobs, Z. Johnston, S. W. Xu, N. T. Zhang, S. B. Ma, L. H. Ru, E. Q. Liu,
T. Liu, S. Hayakawa, L. Yang, H. Shimizu, C. B. Hamill, A. St J. Murphy, J. Su, X. Fang, K. Y. Chae, M. S. Kwag, S. M. Cha,
N. N. Duy, N. K. Uyen, D. H. Kim, R. G. Pizzone, M. La Cognata, S. Cherubini, S. Romano, A. Tumino, J. Liang, A. Psaltis,
M. Sferrazza, D. Kim, Y. Y. Li, and S. Kubono, “Advancement of photospheric radius expansion and clocked type-I X-ray burst models
with the new 22 Mg(α, p)25 Al reaction rate determined at the Gamow energy,” Phys. Rev. Lett. 127, 172701 (2021).
G. G. Kiss, M. La Cognata, R. Yarmukhamedov, K. I. Tursunmakhatov, I. Wiedenhöver, L. T. Baby, S. Cherubini, A. Cvetinović,G. D’Agata, P. Figuera, G. L. Guardo, M. Gulino, S. Hayakawa, I. Indelicato, L. Lamia, M. Lattuada, F. Mudò, S. Palmerini, R. G. Pizzone, G. G. Rapisarda, S. Romano, M. L. Sergi, R. Spartà, C. Spitaleri, O. Trippella, A. Tumino, M. Anastasiou, S. A. Kuvin, N. Rijal,
B. Schmidt, S. B. Igamov, S. B. Sakuta, Zs. Fülöp, Gs. Gyürky, T. Szücs, Z. Halász, E. Somorjai, Z. Hons, J. Mrázek, R. E. Tribble,
and A. M. Mukhamedzhanov, “Indirect determination of the astrophysical S factor for the 6 Li(p, γ)7 Be reaction using the asymptotic
normalization coeﬃcient method,” Phys. Rev. C 104, 015807 (2021).
U. A. Acharya √et al. [PHENIX], “Transverse-single-spin asymmetries of charged pions at midrapidity in transversely polarized p+p
collisions at s = 200 GeV,” Phys. Rev. D 105, 032003 (2022).
√
S. Acharya et al. [ALICE], “Production of light (anti)nuclei in pp collisions at s = 5.02 TeV,” Eur. Phys. J. C 82, 289 (2022).
S. Acharya et al. [ALICE],√ “Observation of a multiplicity dependence in the pT -diﬀerential charm baryon-to-meson ratios in proton–proton collisions at s = 13 TeV,” Phys. Lett. B 829, 137065 (2022).
S. Acharya et al. [ALICE], “Investigating charm production and fragmentation via azimuthal correlations of prompt D mesons with- 349 -

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charged particles in pp collisions at s = 13 TeV,” Eur. Phys. J. C 82, 335 (2022).
S. Acharya et al. [ALICE], “Measurement of prompt D+s -meson production and azimuthal anisotropy in Pb–Pb collisions at√
sNN =5.02 TeV,” Phys. Lett. B 827, 136986 (2022).
√
S. Acharya et al. [ALICE], “Prompt D0 , D+ , and D∗+ production in Pb–Pb collisions at sNN = 5.02 TeV,” J. High Energy Phys. 01, 174(2022).
U. A. Acharya et al. [PHENIX], “Transverse single spin asymmetries of forward neutrons in p + p, p+Al and p+Au collisions at√
sNN = 200 GeV as a function of transverse and longitudinal momenta,” Phys. Rev. D 105, 032004 (2022).
√
S. Acharya et al. [ALICE], “Measurement of inclusive charged-particle b-jet production in pp and p-Pb collisions at sNN = 5.02 TeV,”
J. High Energy Phys. 01, 178 (2022).
√
S. Acharya et al. [ALICE], “Production of light (anti)nuclei in pp collisions at s = 13 TeV,” J. High Energy Phys. 01, 106 (2022).
√
S. Acharya et al. [ALICE], “Prompt and non-prompt J/ψ production cross sections at midrapidity in proton-proton collisions at s = 5.02
and 13 TeV,” J. High Energy Phys. 03, 190 (2022).
√
S. Acharya et al. [ALICE], “Inclusive J/ψ production at midrapidity in pp collisions at s = 13 TeV,” Eur. Phys. J. C 81, 1121 (2021).
S. Acharya et al. [A Large Ion Collider Experiment and ALICE], “Measurement of the groomed jet radius and momentum splitting√
fraction in pp and Pb−Pb collisions at sNN = 5.02 TeV,” Phys. Rev. Lett. 128, 102001 (2022).
√
S. Acharya et al. [ALICE], “Measurements of the groomed and ungroomed jet angularities in pp collisions at s = 5.02 TeV,” J. HighEnergy Phys. 05, 061 (2022).
√
S. Acharya et al. [ALICE], “Polarization of Λ and Λ̄ hyperons along the beam direction in Pb-Pb collisions at sNN =5.02 TeV,” Phys.
Rev. Lett. 128, 172005 (2022).
√
S. Acharya et al. [ALICE], “KS 0 - and (anti-)Λ-hadron correlations in pp collisions at s = 13 TeV,” Eur. Phys. J. C 81, 945 (2021).
√
S. Acharya et al. [ALICE], “Anisotropic ﬂow of identiﬁed hadrons in Xe-Xe collisions at sNN = 5.44 TeV,” J. High Energy Phys. 10,
152 (2021).
√
U. A. Acharya et al. [PHENIX], “Kinematic dependence of azimuthal anisotropies in p+Au, d+Au, and 3 He+Au at sNN = 200 GeV,”
Phys. Rev. C 105, 024901 (2022).
S. Acharya et al. [ALICE], “Direct observation of the dead-cone eﬀect in quantum chromodynamics,” Nature 605, 440 (2022).
√(2455) production in proton–proton collisions at s = 13 TeV,”
S. Acharya et al. [ALICE], “Measurement of prompt D0 , Λ+c , and Σ0,++c
Phys. Rev. Lett. 128, 012001 (2022).
S. Acharya et al. [ALICE], “Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the
LHC,” Phys. Rev. D 105, L011103 (2022).
√
S. Acharya et al. [ALICE], “Measurement of the production cross section of prompt Ξ0c baryons at midrapidity in pp collisions at s =5.02 TeV,” J. High Energy Phys. 10, 159 (2021).
S. Acharya et al. [ALICE], “Experimental evidence for an attractive p-φ interaction,” Phys. Rev. Lett. 127, 172301 (2021).
S. Acharya et al. [ALICE], “Kaon–proton strong interaction at low relative momentum via femtoscopy in Pb–Pb collisions at the LHC,”
Phys. Lett. B 822, 136708 (2021).
√
S. Acharya et al. [ALICE], “Charged-particle multiplicity ﬂuctuations in Pb–Pb collisions at sNN = 2.76 TeV,” Eur. Phys. J. C 81, 1012
(2021).
S. Acharya et al. [ALICE], “Measurement of K∗ (892)± production in inelastic pp collisions at the LHC,” Phys. Lett. B 828, 137013(2022).
√
S. Acharya et al. [ALICE], “First measurements of N-subjettiness in central Pb-Pb collisions at sNN = 2.76 TeV,” J. High Energy Phys.
10, 003 (2021).
S. Acharya et al. [ALICE], “Measurement of the cross sections of Ξ0c and Ξ+c baryons and of the branching-fraction ratio BR(Ξ0c →Ξ− e+ νe )/BR(Ξ0c → Ξ− π+ ) in pp collisions at 13 TeV,” Phys. Rev. Lett. 127, 272001 (2021).
S. Acharya et al. [ALICE], “Investigating the role of strangeness in baryon–antibaryon annihilation at the LHC,” Phys. Lett. B 829,
137060 (2022).
√√
S. Acharya et al. [ALICE], “Production of Λ and K s0 in jets in p–Pb collisions at sNN =5.02 TeV and pp collisions at s=7 TeV,” Phys.
Lett. B 827, 136984 (2022).
S. Acharya et al. [ALICE], “Energy dependence of φ meson production at forward rapidity in pp collisions at the LHC,” Eur. Phys. J. C
81, 772 (2021).
S. Acharya et al. [ALICE], “Nuclear modiﬁcation factor of light neutral-meson spectra up to high transverse momentum in p–Pb collisions√
at sNN = 8.16 TeV,” Phys. Lett. B 827, 136943 (2022).
U. A. Acharya et al. [PHENIX], “Probing gluon√ spin-momentum correlations in transversely polarized protons through midrapidity
isolated direct photons in p↑ + p collisions at s=200 GeV,” Phys. Rev. Lett. 127, 162001 (2021).
√
S. Acharya et al. [ALICE], “Measurement of beauty and charm production in pp collisions at s = 5.02 TeV via non-prompt and prompt
D mesons,” J. High Energy Phys. 05, 220 (2021).
√
S. Acharya et al. [ALICE], “Measurements of mixed harmonic cumulants in Pb–Pb collisions at sNN = 5.02 TeV,” Phys. Lett. B 818,
136354 (2021).
S. Acharya et al. [ALICE], “First measurement of the |t|-dependence of coherent J/ψ photonuclear production,” Phys. Lett. B 817, 136280(2021).
√
S. Acharya et al. [ALICE], “Coherent J/ψ and ψ photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at sNN = 5.02 TeV,”
Eur. Phys. J. C 81, 712 (2021).

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S. Acharya
et al. [ALICE], “Long- and short-range correlations and their event-scale dependence in high-multiplicity pp collisions at√
s = 13 TeV,” J. High Energy Phys. 05, 290 (2021).
√
S. Acharya et al. [ALICE], “Production of pions, kaons, (anti-)protons and φ mesons in Xe–Xe collisions at sNN = 5.44 TeV,” Eur.
Phys. J. C 81, 584 (2021).
√
S. Acharya et al. [ALICE], “First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at sNN = 5.44 TeV,”
Phys. Lett. B 820, 136481 (2021).
√
S. Acharya et al. [ALICE], “Multiharmonic correlations of diﬀerent ﬂow amplitudes in Pb-Pb collisions at sNN = 2.76 TeV,” Phys. Rev.
Lett. 127, 092302 (2021).
K. S. Tanaka, K. Harada, T. Hayamizu, R. Kita, R. Kono, K. Maruta, H. Nagahama, N. Ozawa, Y. Sakemi, and R. Sugimori, “Theaccelerator experiment for junior and senior high school students to improve students’ involvement in fundamental physics,” Phys.
Edu. 57, 045013 (2022).
R. Mitra, V. S. Prasannaa, R. F. Garcia Ruiz, T. K. Sato, M. Abe, Y. Sakemi, B. P. Das, and B. K. Sahoo, “Towards CP violation studies
on superheavy molecules: Theoretical and experimental perspectives,” Phys. Rev. A 104, 062801 (2021).
T. Aoki, R. Sreekantham, B. K. Sahoo, Bindiya Arora, A. Kastberg, T. Sato, H. Ikeda, N. Okamoto, Y. Torii, T. Hayamizu, K. Nakamura,
S. Nagase, M. Ohtsuka, H. Nagahama, N. Ozawa, M. Sato, T. Nakashita, K. Yamane, K. S. Tanaka, K. Harada, H. Kawamura, T. Inoue,
A. Uchiyama, A. Hatakeyama, A. Takamine, H. Ueno, Y. Ichikawa, Y. Matsuda, H. Haba, and Y. Sakemi, “Quantum sensing of theelectron electric dipole moment using ultracold entangled Fr atoms,” Quantum Sci. Technol. 6, 044008 (2021).
K. S. Tanaka, U. Dammalapati, K. Harada, T. Hayamizu, M. Itoh, H. Kawamura, H. Nagahama, K. Nakamura, N. Ozawa, and Y. Sakemi,“Two-dimensional beam proﬁle monitor for the detection of alpha-emitting radioactive isotope beam,” Nucl. Instrum. Methods Phys.
Res. A 1017, 165803 (2021).
E. Ideguchi, T. Kibedi, J. Dowie, H. T. Hoang, Kumar Raju M., G. Lane, L. Bignell, T. K. Eriksen, A. J. Mitchell, A. Akber, B. Combes,
B. McCormik, T. Gray, A. Stuchbery, N. Shimizu, and Y. Utsuno, “Electric monopole transition from the superdeformed band in 40 Ca,”
Phys. Rev. Lett. 2022, 053D02 (2022).
S. Yoshida and N. Shimizu, “A new workﬂow of shell-model calculations with the emulator and preprocessing using eigenvector continuation,” Prog. Theor. Exp. Phys. 128, 252501 (2022).
T. Otsuka, T. Abe, T. Yoshida, Y. Tsunoda, N. Shimizu, N. Itagaki, Y. Utsuno, J. Vary, P. Maris, and H. Ueno, “α-Clustering in atomic
nuclei from ﬁrst principles with statistical learning and the hoyle state character,” Nat. Commun. 13, 2234 (2022).
N. Kitamura, K. Wimmer, T. Miyagi, A. Poves, N. Shimizu, J. A. Tostevin, V. M. Bader, C. Bancroft, D. Barofsky, T. Baugher, D. Bazin,
J. S. Berryman, V. Bildstein, A. Gade, N. Imai, T. Kröll, C. Langer, J. Lloyd, E. Lunderberg, F. Nowacki, G. Perdikakis, F. Recchia,
T. Redpath, S. Saenz, D. Smalley, S. R. Stroberg, Y. Utsuno, D. Weisshaar, and A. Westerberg, “In-beam γ-ray spectroscopy of 32 Mg
via direct reactions,” Phys. Rev. C 105, 034318 (2022).
T. Koiwai, K. Wimmer, P. Doornenbal, A. Obertellid, T. Miyagi, J. D. Holt, N. Shimizu, V. Soma, Y. Utsuno, K. Ogata, K. Yoshida,
N. Achouri, H. Baba, F. Browne, D. Calvet, F. Chateaue, S. Chen, N. Chiga, A. Corsi, M. L. Cortes, A. Delbart, J-M. Gheller,
A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H. N. Liue, T. Motobayashi, I. Murray, H. Otsu,
V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka,K. Yoneda,
O. Aktas, T. Aumann, L. X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R. -B. Gerst, J. Gibelin, K. I. Hahn, D. Kim, Y. Kondo,
P. Koseoglou, J. Lee, C. Lehr, B. D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S. Y. Park, D. Rossi, E. Sahina,
P. -A. Soderstrom, D. Sohlera, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wanga, V. Werner, X. Xu, H. Yamada, D. Yana,
Z. Yang, M. Yasuda, and L. Zanetti, “A ﬁrst glimpse at the shell structure beyond 54 Ca: spectroscopy of 55 K, 55 Ca and 57 Ca,” Phys.
Lett. B 827, 136953 (2022).
T. Otsuka, N. Shimizu, and Y. Tsunoda, “Moments and radii of exotic Na and Mg isotopes,” Phys. Rev. C 105, 014319 (2022).
B. D. Linh, A. Corsi, A. Gillibert, A. Obertelli, P. Doornenbal, C. Barbieri, S. Chen, L. X. Chung, T. Duguet, M. Gomez-Ramos, J. D. Holt,
A. Moro, P. Navratil, K. Ogata, N. T. T. Phuc, N. Shimizu, V. Soma, Y. Utsuno, N. Achouri, H. Baba, F. Browne, D. Calvet, F. Chateau,
N. Chiga, M. L. Cortes, A. Delbart, J. -M. Gheller, A. Giganon, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H. N. Liu,
T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y. L. Sun,
Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, F. Flavigny, S. Franchoo, I. Gasparic, R. B. Gerst, J. Gibelin,
K. I. Hahn, N. T. Khai, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, T. Lokotko, M. Maccormick, K. Moschner,
T. Nakamura, S. Y. Park, D. Rossi, E. Sahin, D. Sohler, P. -A. Soderstrom, S. Takeuchi, H. Tornqvist, V. Vaquero, V. Wagner, H. Wang,
V. Werner, X. Xu, N. D. Ton, Y. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti, “Investigation of the ground-state spin inversion
in the neutron-rich 47, 49 Cl isotopes,” Phys. Rev. C 104, 044331 (2021).
N. Kitamura, K. Wimmer, A. Poves, N. Shimizu, J. Tostevin, V. M. Bader, C. Bancroft, D. Barofsky, T. Baugher, D. Bazin, J. S. Berryman,
V. Bildstein, A. Gade, N. Imai, T. Kroll, C. Langer, J. Lloyd, E. Lunderberg, G. Perdikakis, F. Recchia, T. Redpath, S. Saenz, D. Smalley,
S. R. Stroberg, Y. Utsuno, D. Weisshaar, and A. Westerberg, “Coexisting normal and intruder conﬁgurations in 32 Mg,” Phys. Lett. B
822, 136682 (2021).
T. Abe, P. Maris, T. Otsuka, N. Shimizu, Y. Utsuno, and J. P. Vary, “Ground-state properties of light 4n self-conjugate nuclei in no-coreMonte Carlo shell model with nonlogcal NN interactions,” Phys. Rev. C 104, 054315 (2021).
R. Nakamoto, E. Ueda, M. Ito, and N. Shimizu, “Formulation of shell-cluster overlap integral with Gaussian expansion method,” Prog.
Theor. Exp. Phys. 2021, 113D01 (2021).
H. Kleis, M. Seidlitz, A. Blazhev, L. Kaya, P. Reiter, K. Arnswald, A. Dewald, M. Droste, C. Fransen, O. Möller, N. Shimizu, Y. Utsuno,
P. von Brentano, and K. O. Zell, “Lifetime measurements of excited states in 55 Cr,” Phys. Rev. C 104, 034310 (2021).
N. Shimizu, T. Mizusaki, K. Kaneko, and Y. Tsunoda, “Generator-coordinate methods with symmetry-restored Hartree-Fock-Bogoliubov
wave functions for large-scale shell-model calculations,” Phys. Rev. C 103, 064302 (2021).

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K. Kaneko, N. Shimizu, T. Mizusaki, and Y. Sun, “Triple enhancement of quasi-SU(3) quadrupole collectivity in strontium-zirconium
N ≈ Z isotopes,” Phys. Lett. B 817, 136286 (2021).

[Review Article]
Y. Utsuno, “Probing diﬀerent characteristics of shell evolution driven by central, spin-orbit, and tensor forces,” Physics 4, 185–201 (2022).

[Proceedings]
S. Michimasa, “Development of energy-degraded RI beam and expansion of nuclear reaction studies—Recent results obtained by the
OEDO-SHARAQ system,” Proceedings of the 2020 Symposium on Nuclear Data, November 26–27, 2020, RIKEN Nishina Center,
Wako, Japan, JAEA-Conf 2021-001, pp.59–64.
S. Gorbunov, E. Hellbar, G. M. Innocenti, M. Ivanov, M. Kabus, M. Kleiner, H. Riaz, D. Rohr, R. Sadikin, K. Schweda et al., “Deepneural network techniques in the calibration of space-charge distortion ﬂuctuations for the ALICE TPC,” EPJ Web Conf. 251, 03020(2021).
D. Sekihata for the ALICE Collaboration, “Low-mass dielectron measurements in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC,”
Proc. Sci. HardProbes2020, 047 (2021).
T. Hayamizu, H. Haba, K. Nakamura, T. Aoki, H. Nagahama, K. Tanaka, N. Ozawa, M. Ohtsuka, and Y. Sakemi, “Development of
ultracold francium atomic sources towards the permanent EDM search,” Few-Body Syst. 63, 11 (2022).
N. Shimizu, Y. Utsuno, and T. Togashi, “β-decay half-lives of neutron-rich N = 82, 81 isotones by shell-model calculations,” EPJ Web
Conf. 260, 11049 (2022).

Presentations[International Conferences/Workshops]
H. Yamaguchi (oral), “Nuclear astrophysics at the low-energy RI beam separator CRIB,” RIBF Users Meeting 2021, Web meeting hosted
by RIKEN, Wako, Saitama, Japan, September 7–9, 2021.
H. Yamaguchi (oral), “Experimental studies on astrophysical reactions at the low-energy RI beam separator CRIB,” The 16th International
Symposium on Nuclei in the Cosmos (NIC-XVI), Web symposium hosted by JUNA, China, September 21–25, 2021.
H. Yamaguchi (oral), “Cluster states and astrophysical (α, p) reactionss,” RCNP Workshop, “Cluster phenomena in knockout and astrophysical reactions,” Web workshop hosted by RCNP, Osaka University, October 14–15, 2021.
T. Gunji (invited) for the ALICE collaboration, “Future measurements from ALICE Run3 and Run4,” The 8th Asian Triangle Heavy-Ion
Conference (ATHIC2021), Inha Univ. Incheon, South Korea, Hybrid, November 5–9, 2021.
D. Sekihata for the ALICE Collaboration, “Low-mass dielectron measurement in ALICE at the LHC,” The 8th Asian Triangle Heavy-Ion
Conference, Inha Univ. Incheon, South Korea, Hybrid, November 5–9, 2021.
K. Nakamura (oral), “Development of a laser frequency stabilization and an optical transmission system for the francium electric dipole
moment search,” 29th Annual International Laser Physics Workshop (LPHYS’21), Online, Jul 23, 2021.
N. Ozawa (oral), “Current status of the electron EDM search using laser-cooled francium atoms,” 13th International Workshop on Fundamental Physics Using Atoms (FPUA2021), Online, August 4–5, 2021.
M. Sato (keynote talk), “Search for permanent EDM by using Fr atoms,” SPIN2021, Kunibiki Messe, Shimane, Japan, Hybrid, October
18–22, 2021.
Y. Utsuno (oral), “Present status of large-scale shell-model calculations for photonuclear reactions,” Second PANDORA Workshop,
September 10, 2021.
N. Shimizu (oral), “Microscopic description of the collective motions of medium-heavy nuclei based on shell-model calculations,” 13th
symposium on Discovery, Fusion, Creation of New Knowledge by Multidisciplinary Computational Sciences, Online, October 8, 2021.
Y. Tsunoda (oral), “Nuclear shapes and collective motions in the region of Sm,” 13th symposium on Discovery, Fusion, Creation of New
Knowledge by Multidisciplinary Computational Sciences, Online, October 8, 2021.
N. Shimizu (poster), “Gamow-Teller transition of neutron-rich N = 82, 81 nuclei by shell-model calculations,” 16th International Symposium on Nuclei in the Cosmos (NIC-XVI), Online, September 25, 2021.

[Domestic Conferences/Workshops]
S. Shimoura (invited): “High-resolution spectroscopy with SHARAQ and advice on HIHR,” the 2nd J-PARC HEF-ex workshop, Online,
February 16–18, 2022.
T. Chillery (oral): “Measurement of deuteron-induced pre-equilibrium reactions on 93 Zr at 30 MeV/u for the Treatment of Radioactive
Waste,” 2022 Annual (77th) Meeting of The Physical Society of Japan, Online, March 15–19, 2022.
R. Tsunoda (oral): “Observation of the isobaric analog resonances coupled to the excited state in Zr isotope,” 2022 Annual (77th) Meetingof The Physical Society of Japan, Online, March 15–19, 2022.
J. T. Li (oral): “New project to explore neutron-deﬁcient actinide nuclei,” 2022 Annual (77th) Meeting of The Physical Society of Japan,
Online, March 15–19, 2022.
S. Hanai (oral): “A fast-response tracking detector for high-intensity heavy ion beams,” Workshop for radiation detector and their uses,
KEK, January 24–26, 2022.
N. Imai (invited): “Nuclear Structure study with decelerated RI beams,” RCNP future workshop, October 27–29, 2021.
川田敬太 (口頭発表), 「核破砕反応における角運動量移行」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
早川勢也（口頭発表）：「7 Be+n ビッグバン元素合成反応の測定と原始 7 Li 生成量の検証」, 日本物理学会 秋季大会, オンライン,- 352 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

2021 年 9 月 14–17 日.
郡司卓 (招待講演), “Status of ALICE upgrade and commissioning for run3,” 第 7 回クラスター階層領域研究会, 東北大学, 2021 年 12月 27–28 日.
郡司卓 (招待講演), 「高密度クォーク物質探索の展望」, シンポジウム「宇宙観測, 加速器実験と理論の協奏で探る高密度核物質」,
日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
関畑大貴 (招待講演), 「光子・レプトン対・ハード測定」, 重イオン衝突の時空発展の理解に向けた理論・実験合同研究会, オンラ
イン, 2021 年 9 月 24 日.
√
D. Sekihata for the ALICE Collaboration, 「 sNN = 5.02 TeV 鉛+鉛原子核衝突における ALICE 実験の電子対測定」, 日本物理学会
2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
関畑大貴, 「ALICE 実験での電子対の結果と展望」, Heavy Ion Pub 研究会, オンライン, 2021 年 5 月 28 日.
関口裕子 for the ALICE Collaboration, 「LHC-ALICE 実験を用いた長距離２粒子相関のシステムサイズ依存性測定」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 15–19 日.
関口裕子 for the ALICE Collaboration, 「LHC-ALICE 実験を用いた小さな衝突系における 2 粒子相関測定」, 日本物理学会 2021 年
秋季大会, オンライン, 2021 年 9 月 14–17 日.
中村 圭佑（口頭発表）：「波長計による光周波数安定化、光ファイバー伝送システム」, 第 82 回応用物理学会秋季学術講演会, オンライン, 2021 年 9 月 11–13 日.
永瀬慎太郎（口頭発表）：「原子の電気双極子能率探索に向けたレーザー冷却フランシウム源の開発」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
中下輝士（口頭発表）：「フランシウムの電気双極子能率探索に向けた冷却原子制御系開発」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
山根風樹（口頭発表）：「永久電気双極子能率探索に向けたアクチニウム-225 電着基板を用いたフランシウム-221 原子線源の開発」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
鎌倉恵太 (ポスター発表), 「東京大学 CNS 14 GHz Hyper ECR イオン源の現状」, 第 18 回日本加速器学会年会, オンライン, 2021
年 8 月 9–12 日.
清水則孝（口頭発表）, 「CI 計算とその発展的手法による大規模原子核構造計算」, 2021 年度第２回 HPCIC 計算科学フォーラム,オンライン, 2022 年 3 月 28 日.
大塚孝治（口頭発表）, 清水則孝, 吉田聡太, 角田直文, 角田佑介, 「殻模型計算による中性子過剰 pf 殻核の構造」, 日本物理学会第76 回年次大会, オンライン, 2022 年 3 月 17 日.
清水則孝（口頭発表）, 「CI 計算とその発展的手法による大規模原子核構造計算」, 「富岳」成果創出加速プログラム シンポジウ
ム・研究交流会「富岳百景」2021 年度第２回 HPCIC 計算科学フォーラム, オンライン, 2022 年 3 月 14 日.
清水則孝（口頭発表）, 「大規模殻模型計算による中重核構造研究の進展」, 「富岳で加速する素粒子・原子核・宇宙・惑星」シン
ポジウム, オンライン, 2022 年 1 月 17 日.
富樫智章（口頭発表）, 清水則孝, 宇都野穣, 「殻模型計算による N = 82, 81 中性子過剰核のガモフテラー遷移」, 日本物理学会 2021
年秋の分科会, オンライン, 2021 年 9 月 14 日.
大塚孝治（口頭発表）, 角田佑介, 清水則孝, 「準粒子真空殻模型計算による中重核の構造の研究」, 日本物理学会 2021 年秋季大会,
オンライン, 2021 年 9 月 15 日.
大塚孝治（口頭発表）, 角田佑介, 清水則孝, 「準粒子真空殻模型計算による Sm 領域の構造の研究」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3 月 17 日.
吉永尚孝（口頭発表）, 柳瀬宏太, 清水則孝, 東山幸司, 「キセノン原子核のシッフモーメントと中性子 EDM 探索」, 日本物理学会第77 回年次大会, 2022 年 3 月 17 日.
清水則孝（口頭発表）, 宇都野穣, 角田佑介, 「大規模殻模型計算による M1 バンドの解析」, 日本物理学会 2021 年秋季大会, オンラ
イン, 2021 年 9 月 15 日.
宇都野穣（口頭発表）, 「非イラスト領域における原子核の秩序の探求」, RCNP での次期計画検討会, 2021 年 9 月 27 日.
宇都野穣（口頭発表）, “Cluster formation in nuclei from ﬁrst-principles Monte Carlo shell model,” 第 7 回クラスター階層領域研究会,
2021 年 12 月 27 日.

[Seminar]
T. Otsuka, “What determines the driplines of atomic nuclei?,” CNS+RIBF NP seminar, Online, November 5, 2021.

Press Releases
山口英斉, 早川勢也, Hu Jun, 「X 線バースト天体における不安定マグネシウム燃焼の解明」, 2021 年 10 月 20 日.
早川勢也, 山口英斉, 「ビッグバンで生成されるリチウム量の矛盾、解決へ一歩前進」, 2021 年 7 月 1 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Partner Institution
Wako Nuclear Science Center, IPNS (Institute of Particle and Nuclear Studies)
KEK (High Energy Accelerator Research Organization)
1. Abstract
The Wako Nuclear Science Center (WNSC) of KEK aims to promote low-energy nuclear physics and nuclear astrophysics research
as well as interdisciplinary studies using short-lived radioactive nuclei. WNSC operates the KEK Isotope Separation System (KISS),an electromagnetic isotope separator featuring elemental selectivity from resonance laser ionization in a gas catcher. The KISS
facility uniquely provides various neutron-rich isotopes of refractory elements via multinucleon transfer reactions to the users fromuniversities. Its provision of nuclei in the vicinity of the neutron magic number N = 126. Optical and β-γ spectroscopy have been
applied to these neutron-rich nuclear beams for nuclear structure and nuclear astrophysical studies. Several new developments—a
rotating target, a donut-shaped gas cell, and an in-jet laser ionization scheme—have been performed to improve the performance of the
KISS facility. The WNSC also leads comprehensive mass measurements of all-available nuclides at RIBF using multi-reﬂection timeof ﬂight mass spectrographs (MRTOF-MS). Three MRTOF setups were placed at the GARIS-II, the beam dump of the ZeroDegree
Spectrometer, and the KISS. The masses of more ore than 400 nuclides, including superheavy elements, were measured so far. KISSII is being considered a future project of WNSC. Combining KISS and MRTOF technologies, 10,000 times more performance thanconventional methods are expected. It aims to study the origin of uranium for the ﬁrst time.

2. Major Research Subjects
(1)
(2)
(3)
(4)
(5)
(6)

Production and manipulation of radioactive isotope beams for nuclear experiments
Explosive nucleosynthesis (r- and rp-process)Heavy ion reaction mechanism for producing heavy neutron-rich nuclei
Development of MRTOF mass spectrographs for short-lived nuclei
Comprehensive mass measurements of short-lived nuclei including superheavy elements
Development of KISS-II

3. Summary of Research Activity
The Wako Nuclear Science Center (WNSC) provides low-energy short-lived radioactive ion beams of neutron-rich refractory elements to researchers from universities using the KEK isotope separator system (KISS). In FY2021, ﬁve experiments with a total of 69
participants from 3 domestic institutes were executed. Due to the restrictions of COVID-19, the participation of foreign collaborators
was limited, and no experiment with foreign spokesperson was conducted. A highlight at the KISS facility was the discovery of a new
uranium isotope by means of mass spectrometry, described in a diﬀerent article of this report.
The team of WNSC leads comprehensive mass measurements of all available nuclides at RIKEN RIBF using multiple MRTOF
mass spectrographs. KEK announced a press release for the ﬁrst mass measurement of superheavy elements performed at the GARISMRTOF facility. It claims a new method for identifying new elements via a high precision mass measurement. Mass measurementof dubnium isotopes continued with a new sulﬁde target, allowing the use of much higher primary beam intensity. A newly installed
In-MRTOF mass ﬁlter eliminates molecular contaminants in a mass spectrum, making possible accurate mass determinations without
a need for decay correlation. Mass measurements at the BigRIPS-SLOWRI facility of RIBF continued for more exotic isotopes ofnickel. In total, more than 400 nuclides were measured in the campaigns led by WNSC.
The WNSC plans to extend the present KISS facility to investigate the nuclides in the neutron-rich region of uranium using themulti-nucleon transfer reactions of actinide targets to study the origin of uranium. The IPNS organized review committee meetings
for the design report of KISS-II and received high marks and helpful suggestions.

Members
Group Leader
Michiharu WADA
Researchers
Yutaka WATANABEPeter SCHURY
Sunchan JEONG

Yoshikazu HIRAYAMA
Hiroari MIYATAKE
Marco ROSENBUSCH

Technical Staﬀ
Yutaka KAKIGUCHI

Michihiro OYAIZU

Visiting Researchers
Hermann WOLLNIK (NMSU)
Sidong CHEN (HKU)
Wenduo XIAN (HKU)

Hiroshi WATANABE (Beihan University)
Dongsheng HOU (IMP)Toshitaka NIWASE (JPS PD)- 354 -

VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

Student Trainee
Shun IIMURA (PhD. Student, Osaka Univ.)
Assistant
Machiko IZAWA

List of Publications & Presentations
Publications[Original Papers]
M. Mukai, Y. Hirayama, Y. X. Watanabe, H. Watanabe, H. Koura, S. C. Jeong, H. Miyatake, M. Brunet, S. Ishizawa, F. G. Kondev,
G. J. Lane, Yu. A. Litvinov, T. Niwase, M. Oyaizu, Zs. Podolyák, M. Rosenbusch, P. Schury, M. Wada, and P. M. Walker, “Groundstate β-decay spectroscopy of 187 Ta,” Phys. Rev. C 105, 034331 (2022).
T. Niwase, M. Wada, P. Schury, P. Brionnet, S. D. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama,
S. Ishizawa, Y. Ito, D. Kaji, S. Kimura, J. Liu, H. Miyatake, J. Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, T. Tanaka, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “α-decay-correlated mass measurement of 206, 207g, m Rausing an α-TOF detector equipped multireﬂection time-of-ﬂight mass spectrograph system,” Phys. Rev. C 104, 044617 (2021).
P. Schury, T. Niwase, M. Wada, P. Brionnet, S. Chen, T. Hashimoto, H. Haba, Y. Hirayama, D. S. Hou, S. Iimura, H. Ishiyama, S. Ishizawa,
Y. Ito, D. Kaji, S. Kimura, H. Koura, J. J. Liu, H. Miyatake, J. Y. Moon, K. Morimoto, K. Morita, D. Nagae, M. Rosenbusch,
A. Takamine, Y. X. Watanabe, H. Wollnik, W. Xian, and S. X. Yan, “First high-precision direct determination of the atomic mass of asuperheavy nuclide,” Phys. Rev. C 104, L021304 (2021).
Y. X. Watanabe, P. M. Walker, Y. Hirayama, M. Mukai, H. Watanabe, G. J. Lane, M. Ahmed, M. Brunet, T. Hashimoto, S. Ishizawa,
S. Kimura, F. G. Kondev, Yu. A. Litvinov, H. Miyatake, J. Y. Moon, T. Niwase, M. Oyaizu, J. H. Park, Zs. Podolyák, M. Rosenbusch,
P. Schury, and M. Wada, “First direct observation of isomeric decay in neutron-rich odd-odd 186 Ta,” Phys. Rev. C 104, 024330 (2021).
M. Ahmed, Y. X. Watanabe, Y. Hirayama, M. Mukai, J. H. Park, P. Schury, Y. Kakiguchi, A. Ozawa, M. Oyaizu, M. Wada, and H. Miyatake, “β-γ Spectroscopy of the 195 Os nucleus,” Phys. Rev. C 103, 054312 (2021).
S. Kimura, D. Kaji, Y. Ito, H. Miyatake, K. Morimoto, P. Schury, and M. Wada, “Reduction of contaminants originating from primarybeam by improving the beam stoppers in GARIS-II,” Nucl. Instrum. Method Phys. Res. A 992, 164996 (2021).
Y. Hirayama, P. Schury, M. Mukai, H. Choi, S. Iimura, Y. X. Watanabe, M. Wada, H. Watanabe, and H. Miyatake, “Three-dimensional
tracking multi-segmented proportional gas counter for β-decay spectroscopy of unstable nuclei,” Nucl. Instrum. Methods Phys. Res. A
997, 165152 (2021).
M. Tajima, A. Takamine, M. Wada, and H. Ueno, “Oﬄine ion source for laser spectroscopy of RI at the SLOWRI,” Nucl. Instrum.
Methods Phys. Res. B 486, 48–54 (2021).
T. Day Goodacre, A. V. Afanasjev, A. E. Barzakh, B. A. Marsh, S. Sels, P. Ring, H. Nakada, A. N. Andreyev, P. Van Duppen, N. A. Althubiti, B. Andel, D. Atanasov, J. Billowes, K. Blaum, T. E. Cocolios, J. G. Cubiss, G. J. Farooq-Smith, D. V. Fedorov, V. N. Fedosseev,
K. T. Flanagan, L. P. Gaﬀney, L. Ghys, M. Huyse, S. Kreim, D. Lunney, K. M. Lynch, V. Manea, Y. Martinez Palenzuela, P. L. Molkanov, M. Rosenbusch, R. E. Rossel, S. Rothe, L. Schweikhard, M. D. Seliverstov, P. Spagnoletti, C. Van Beveren, M. Veinhard, E. Verstraelen, A. Welker, K. Wendt, F. Wienholtz, R. N. Wolf, A. Zadvornaya, and K. Zuber, “Laser spectroscopy of neutron-rich 207, 208 Hg
isotopes: Illuminating the kink and odd-even staggering in charge radii across the N = 126 shell closure,” Phys. Rev. Lett. 126, 032502(2021).

[Book]
和田道治, 「重元素の起源と短寿命核原子の質量」, in 「物理科学, この 1 年 2022」, パリティ編集委員会編, 丸善, 2022 年 01 月,
pp. 109–113.

[Proceeding]
H. Miyatake, “KISS project,” AIP Conf. Proc. 2319, 080006 (2021).

Presentations[International Conferences/Workshops]
M. Wada (invited), “KISS to KISS-II—exploring the origins of uranium,” JSPS/NRF/NSFC A3 Foresight Program, “Nuclear physics inthe 21st century” Joint Annual Meeting, Online, February 18, 2022.
M. Rosenbusch (oral), “The new high-precision MRTOF mass spectrograph at the ZeroDegree spectrometer of BigRIPS,” The 16th
International Symposium on Nuclei in the Cosmos 2021 (NIC-XVI), Chengdu, Online, September 21–25, 2021.
M. Rosenbusch (oral), “The new MRTOF mass spectrograph at the ZeroDegree spectrometer,” RIBF Users Meeting 2021, Online, September 7–9, 2021.
Y. Hirayama (oral), “Nuclear spectroscopy at KISS,” RIBF Users Meeting 2021, Online, September 7–9, 2021.

[Domestic Conferences/Workshops]
庭瀬暁隆 (口頭発表), 「MRTOF+α-TOF による 257, 258 Db の精密質量測定」, 日本物理学会第 77 回年次大会, オンライン, 2022 年 3
月 15–19 日.

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VI. RNC ACTIVITIESRIKEN Accel. Prog. Rep. 55 (2022)

平山賀一 (招待講演), 「KISS でのレーザー核分光」, 令和 3 年度専門研究会「短寿命 RI を用いた核分光と核物性研究 (VIII)」, オン
ライン, 2022 年 1 月 28 日.
庭瀬暁隆 (口頭発表), 「MRTOF と α-TOF 検出器による, α 崩壊に相関した精密質量測定法の開拓」, 日本放射化学会第 65 回討論会（2021）, オンライン, 2021 年 9 月 22–24 日.
庭瀬暁隆 (口頭発表), 「超重核 257 Db の直接質量測定」, 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
平山賀一 (口頭発表), 「KISS での核分光: MRTOF-MS を用いた不安定核のレーザー共鳴イオン化核分光」, 日本物理学会 2021 年
秋季大会, オンライン, 2021 年 9 月 14–17 日.
D. Hou (口頭発表), “Mass measurement in the neutron-rich Mo region using the new ZD-MRTOF system,” 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
W. Xian (口頭発表), “New mass measurements of neutron-rich nuclei of Ge, As, and Se, and an accuracy study of the new ZD-MRTOF
system,” 日本物理学会 2021 年秋季大会, オンライン, 2021 年 9 月 14–17 日.
飯村俊 (口頭発表), 「新規開発された ZD-MRTOF 装置を用いた中性子過剰 Sc, Ti, V 核の系統的質量測定」, 日本物理学会 2021 年
秋季大会, オンライン, 2021 年 9 月 14–17 日.
M. Rosenbusch (口頭発表), “New technologies for multi-reﬂection time-of-ﬂight mass spectrometry at BigRIPS,” 日本物理学会 2021
年秋季大会, オンライン, 2021 年 9 月 14–17 日.

[Seminars]
T. Niwase, “Direct mass measurement of superheavy nuclides via MRTOF mass spectrograph equipped with an α-TOF detector,” RIBF
Nuclear Physics Seminar, Online, February 12, 2022.
M. Wada, “KISS to KISS-II—An expedition to the origin of uranium—,” Nuclear Astrophysics Seminar, Online, November 19, 2021.
Y. Watanabe, “Production of neutron-rich nuclei around N = 126 and beyond using multinucleon transfer reactions at KISS project,”
Virtual SHE seminars, Online, October 12, 2021.

Award向井もも, 「196,197,198 Ir のガスセル内レーザー共鳴イオン化分光」, 2021 年度理化学研究所桜舞賞 (研究奨励賞), 2022 年 3 月.

Press Release
超重元素の初めての精密質量測定に成功〜新元素の新しい原子番号決定法の証明〜, KEK, RIKEN, Kyushu University, 2021 年 8 月
31 日, https://www.kek.jp/ja/press/202109010000/ .

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VII. APPENDICESVII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

List of Symposia & Workshops (April 2021ȷMarch 2022)
RNC
1International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility
online(J-PARC HEF-ex WS)
https://indico2.riken.jp/event/3773/

Jul. 7–9

2

RIBF Users Meeting 2021
https://indico2.riken.jp/event/3821/

onlineSep. 7–9

3ৈ崐崵嵓崖嵤崻嵤嵈ਹણ৷峕਱岻峉ன஦‫ع‬崌崒嵛崻嵤嵈峼৷岮峉୘ர峒঺ভৰಎ峕਱岻峉ଢ଼஢‫ع‬
http://www.werc.or.jp/newsdetail/img/R030806press2.pdf

onlineSep. 15

4

24th International SPIN Symposium
http://spin2021.riken.jp

Kunibiki Messe, Shimane

Oct. 18–22

5

BNL-HET & RBRC Joint Workshop "DWQ@25": The event marks the passage of twenty-five
onlineyears since the first numerical simulations with Domain Wall Quarks (DWQ)
https://indico.bnl.gov/event/13576/

Dec. 13–17

6

RBRC Workshop: Small-x Physics in the EIC Era
https://www.bnl.gov/smallxphysicsworkshop/

onlineDec. 15–17

7ਉ৕ற੟৶৾ৰୡ峕岴岻峵崯嵤崧ਹણ৷峕峲峵ଢ଼஢ਅറ‫ق‬ଢ଼஢ '; ৲௓ਤ崽崉嵛崱‫ك‬https://indico2.riken.jp/event/4016/

RIKEN Integrated
Innovation Building/online Mar. 7

KEK
1

SSRI-PNS Collaboration Meeting 2021
https://indico2.riken.jp/event/3807/overview

online- 357 -

Sep. 2–3

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

List of Seminars (April 2021ȷ0DUFK22)
Nuclear Physics Monthly Colloquium
Not held in 2021

RIBF Nuclear Physics Seminar
1

Emiko Hiyama(Tohoku U.)

Structure of light ¥Xi hypernuclei and Hyperon-Hyperon interaction (virtual)
https://indico2.riken.jp/event/3701/

2

Minho Kim
(Korea Univ./RIKEN)

Transverse single-spin asymmetry for very forward neutral particle production in high-energy
polarized p + p collisions (virtual)
May 11
https://indico2.riken.jp/event/3719/

3

Leung Tsz Tang
(Argonne National
Laboratory)

Study the role of the valence proton in 23,25F using the (p,2p) quasi-free knockout reaction(virtual)
https://indico2.riken.jp/event/3761/

Jul. 6

4

Pascal Naidon(RIKEN)

Prediction of a "mixed bubble" quantum phase (virtual)
https://indico2.riken.jp/event/3849/

Sep. 7

5

Tadaaki Isobe(RNC)

Measurement of spectral pion ratio in Sn+Sn collisions for the constraint of density
dependent nuclear symmetry energy (virtual)
https://indico2.riken.jp/event/3846/

Sep. 28

6

Rituparna Kanungo(Saint Mary’s U.)

Exploring nuclear shell structure in the neutron-rich landscape (virtual)
https://indico2.riken.jp/event/3867/

Oct. 5

7

Takaharu Otsuka(UT and RNC)

What determines the driplines of atomic nuclei? (Let's look back to basic concepts of nuclear
physics.) (Hybrid: Zoom + RIBF Hall)
https://indico2.riken.jp/event/3912/

Nov. 58

Masaaki Kimura(RNC)

Erosion of N = 28 shell gap, shape coexistence and monopole transitions in the vicinity of 44S(virtual)Jan. 18
https://indico2.riken.jp/event/3997/

9

Ralf Seidl(RNC)

Direct photon single spin asymmetries and gluon dynamics (virtual)
https://indico2.riken.jp/event/4019/

Feb. 810

Toshitaka Niwase(KEK)

Direct mass measurement of superheavy nuclides via MRTOF mass spectrograph equippedwith an Į-TOF detector (virtual)
https://indico2.riken.jp/event/4042/

Feb. 22

11

Takehiko Saito(RIKEN)

New directions in hypernuclear physics (virtual)
https://indico2.riken.jp/event/4079/

Mar. 29

Apr. 13

Seminar by Each Laboratory
High Energy Astrophysics Laboratory
1

Yuuki Wada
(RIKEN‫ك‬ৰୡಎ઼৫৅峘峃峃峫 (virtual)

Apr. 14

2

Shoda Munehiro(NAOJ)

Stellar wind from Sun-like stars: Implications for solar wind evolution (virtual)

May 193

Satoru Katsuda(Saitama U.)

Density profile of the earth’s upper atmosphere from its occultations of the Crab Nebula with
X-ray astronomy satellites) (virtual)Jun. 22

4

Tatsuki Washimi(NAOJ)

Gravitational wave detector KAGRA and background events induced by lightning (virtual)

Jul. 12

5

Toshiki SATO
(Rikkyo U.)தৗయਈ஥৖峑峘੪ಞ়ਛ: X ଍௴೾峕峲峵தৗయଋጱ৔峘ৈ崐嵛崰嵕崼嵤঱ಊ૴峘৅ৄ (virtual)Aug. 17- 358 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

6

Ting Wu(Gifu U.)

Strong lightning discharges associated with terrestrial gamma-ray flashes in winterthunderstorms (virtual)

Sep. 29

7

Shintaro Yoshiura(NAOJ)

ৗৎ৻峘଩ఢణਗ਼ణ௴೾-ഌຬગਗ਼௞岵峳พహৎ৻峘 21cm ଍ർਪ (virtual)Oct. 128

Yousuke Sato
(Hokkaido U.)

Development of a lightning model for the meteorological simulation (virtual)

Nov. 18

9

Yuko Ikkatai(Kanazawa U.)঩ম峕岴岻峵ఐ৾峢峘৘ড়૞ਸ (virtual)Dec. 20High Energy Astrophysics Lab. Seminar Ѝ http://astro.riken.jp/wordpress/?page_id=65

Subnuclear System Research Division1

Yoni Kahn(U. Illinois)

High-Energy Physics & RIKEN Theory Seminar
Discovering the new physics of g-2 with a muon collider (virtual)

Apr. 1

2

Cédric Lorcé(CPHT)

Nuclear Physics & RIKEN Theory Seminar
Revisiting the concept of relativistic charge distribution (virtual)

Apr. 2

3

Florentin Jaffredo(IJCLab Orsay)

High-Energy Physics & RIKEN Theory Seminar
Single Leptoquark Solutions to the B-physics anomalies (virtual)

Apr. 8

4

Brendan Reed
(Indiana U.)

RBRC Seminar
The neutron skin of Pb-208 and the structure of neutron stars (virtual)

Apr. 85Chirilli Giovanni(Regensburg)

Nuclear Physics & RIKEN Theory Seminar
High-energy OPE for polarized DIS (virtual)

Apr. 96

Dalibor Djukanovic(Mainz U.)

RBRC Seminar
Nucleon form factors from lattice QCD (virtual)

Apr. 15

7

Kallia Petraki(Sorbonne U.)

High-Energy Physics & RIKEN Theory Seminar
Dark matter goes nuclear: The role of bound states in thermal decoupling (virtual)

Apr. 158David Kaplan(Johns Hopkins U.)

High-Energy Physics & RIKEN Theory Seminar
Relaxing the cosmological constant and dark energy radiation (virtual)

Apr. 229Abhay Deshpande(Stony Brook U.)

RBRC Seminar
EIC: Science, status and prospects (virtual)

Apr. 22

10

Alexei Bazavov(Michigan State U.)

Nuclear Physics & RIKEN Theory Seminar
Efficient integration of gradient flow in lattice gauge theory and properties of low-storage
commutator-free Lie group methods (virtual)

Apr. 23

11

Xiaoling Cui (Chinese
Academy of Science)

SNP Seminar
Stability of quantum droplet against confinement and multi-component (virtual)

Apr. 28

12

Alexander Huss
(CERN)

High-Energy Physics & RIKEN Theory Seminar
Precision predictions for Higgs boson production (virtual)

Apr. 29

13

Julia Gehrlein and Peter
Boyle (BNL)

High-Energy Physics & RIKEN Theory Seminar
Muon magnetic moment: New physics or not (virtual)

May 6

14

Alexander Kovner(UConn)RBRC Seminar
High energy evolution and S-channel unitarity: An interesting problem that bothers no one(virtual)

May 6

15

Emilie Passemar(LANL)

RBRC Seminar
3UHFLVLRQWHVWVRIIXQGDPHQWDOSK\VLFVZLWKǅDQGǅĻPHVRQV (virtual)

May 1316

Matthias Neubert(U. Mainz)

High-Energy Physics & RIKEN Theory Seminar
Adventures in the ALPs — Effective Lagrangians, flavor observables and indirect searches foraxion-like particles (virtual)

May 1317

Koji Hashimoto(Kyoto U.)

RBRC Seminar
An attempt for deriving nuclear physics by holography (virtual)

May 14- 359 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

18

Li Sheng Geng
(Beihang U.)

SNP Seminar
Understanding of the LHCb pentaquark states as hadronic molecules, from masses, spinparities to production yields (virtual)

May 1419

Koji Hashimoto(Kyoto U.)

Nuclear Physics & RIKEN Theory Seminar
An attempt for deriving nuclear physics by holography (virtual)

May 1420

Soebur Razzaque(U. Johannesburg)

High-Energy Physics & RIKEN Theory Seminar
Non-unitary neutrino oscillations to reduce tension between the NOvA and T2K data
(virtual)

May 2021

Constantia Alexandrou(U. Cyprus)

RBRC Seminar
Parton distributions using lattice QCD (virtual)

May 2022

Jacopo Ghiglieri(SUBATECH)

Nuclear Physics & RIKEN Theory Seminar
Thermal gravitational wave production in the early universe (virtual)

May 21

23

Radja Boughezal(Argonne)

RBRC Seminar
Proton structure, new physics and more: The EIC potential for probing the unknown(virtual)

May 2724

Hiro Ejiri(RCNP Osaka U.)

SNP Seminar'HOWDLVREDU ƨ FRQWULEXWLRQWRQHXWULQRQXFOHDUUHVSRQVHIRUGRXEOHEHWDGHFD\ YLUWXDOMay 2825

Feng Yuan (Lawrence
Berkeley National Lab)

Nuclear Physics & RIKEN Theory Seminar
Single transverse-spin asymmetry and Sivers Function on lattice (virtual)

May 2826

Andreas Crivellin(CERN)

High-Energy Physics & RIKEN Theory Seminar
Discovering lepton flavour universality violating new physics (virtual)Jun. 3

27

Jamie Stafford(U. Houston)

RBRC SeminarFirst-principles-based equations of state for QCD at finite temperature and density (virtual)Jun. 328

Kenji Fukushima(U. Tokyo)

Nuclear Physics & RIKEN Theory Seminar
Toward understanding the high-baryon state of matter (virtual)Jun. 429

Naoyuki Itagaki(Kyoto U.)

SNP Seminar
Cluster structure comprised of shell model states (virtual)Jun. 430

Silas Beane(U. Washington)

Nuclear Physics & RIKEN Theory Seminar
Entanglement minimization in hadronic scattering (virtual)Jun. 1131

Kazuyuki SEKIZAWA(Tokyo Institute ofTechnology)

SNP Seminar
Dynamics of quantized vortices in superfluid fermionic systems: From cold atoms to neutronstars (virtual)Jun. 24

32

Jan Pawlowski(Heidelberg U.)

RBRC SeminarOn the phase structure of QCD (virtual)Jun. 25

33

Patrick Barry(Jefferson Lab)RBRC Seminar
Tagged deep inelastic scattering and its relation to pion parton distributions (virtual)

Jul. 1

34

Lucas PLATTER(U. Tennessee)

SNP Seminar
Few-body systems with a van der Waals interaction (virtual)

Jul. 235

Anna Stasto(Penn State U.)

RBRC Seminar
A new Wilson line-based action for gluodynamics (virtual)

Jul. 236

Yi Chen(CERN)

RBRC Seminar
Extraction of qhat in heavy-ion collisions with a Bayesian analysis (virtual)

Jul. 837

Son Dam Thanh(U. Chicago)

RBRC Seminar
Nonrelativistic conformal field theory and unnuclear physics

Jul. 938

Marlene Nahrgang(Subatech)

RBRC Seminar
Discovering the QCD critical point with dynamical fluctuations (virtual)

Jul. 15

39

Andrey Sadofyev (U.
Santiago de Compostela)

RBRC Seminar
Ab initio coupling of jets to collective flow in the opacity expansion approach (virtual)

Jul. 16

40

Veronica Dexheimer(Kent State U.)

RBRC Seminar
Equation of state from heavy-ion collisions to neutron stars (virtual)

Jul. 22- 360 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

41

Miguel Escobedo(Santiago de Compostela
U.)

RBRC Seminar
Phenomenological study of quarkonium suppression and the impact of the energy gap
between singlets and octets (virtual)

Jul. 23

42

Claudia Ratti(U. Houston)

RBRC Seminar
Equation of state from lattice QCD (virtual)

Jul. 29

43

Prasad Hegde (Indian
Institute of Science)

RBRC Seminar
A new way to resum the finite-density lattice QCD Taylor series (virtual)Aug. 19

44

Kazuhiro Watanabe(SUBATECH)RBRC Seminar
Hadronic quarkonium production at high pT in QCD factorization approach (virtual)Aug. 2045

Martin Hentschinski (BNL)

RBRC Seminar
TMD gluon distributions at NLO within high energy factorization (virtual)Aug. 26

46

Adrien Florio(Stony Brook U.)

RBRC Seminar
Gibbs entropy from entanglement in electric quenches (virtual)Aug. 27

47

Prithwish Tribedy(BNL)

RBRC Seminar
Blind analysis of isobar data for the CME search by the STAR collaboration (virtual)

Sep. 2

48

Xu-Guang Huang(Fudan U.)

RBRC Seminar
Phenomenology of spin polarization and vorticity (virtual)

Sep. 349

Ted Rogers(Old Dominion U.)

RBRC Seminar
Transverse momentum integrals and the properties of collinear PDFs (virtual)

Sep. 1050

Lex Kemper(North Carolina State U.)

RBRC Seminar
Examining topology and thermodynamics using quantum computers (virtual)

Sep. 16

51

Colin Morningstar(Carnegie Mellon U.)

RBRC Seminar
Multi-hadron physics in lattice QCD (virtual)

Sep. 1752

Dimitra Anastasia Pefkou(MIT)

RBRC Seminar
Gravitational form factors of hadrons from lattice QCD (virtual)

Sep. 2353

Chihiro Sasaki(Wroclaw)

RBRC Seminar
Chiral mixing in dense matter (virtual)

Sep. 24

54

Niklas Mueller(U. Maryland)

RBRC Seminar
Thermalization of gauge theories from their entanglement spectrum (virtual)

Sep. 30

55

Antonio Pineda(IFAE Barcelona)

RBRC Seminar
Theoretical description of the plaquette with exponential accuracy (virtual)Oct. 156

Muneto Nitta(Keio U.)SNP Seminar
3P2 superfluids and pulsar glitches from quantum vortex networks (virtual)Oct. 657

Yuuka Kanakubo(Sophia U.)

RBRC Seminar
Interplay between core and corona components in high-energy nuclear collisions (virtual)Oct. 7

58

Yukari Yamauchi(Maryland U.)

RBRC Seminar
Quantum algorithms for transport coefficients in gauge theories (virtual)Oct. 859

Yasuki Tachibana(Akita International U.)

RBRC Seminar
Description of medium response to jet propagation in quark-gluon plasma fluid (virtual)Oct. 14

60

Guang Juan Wang
(ASRC, JAEA)SNP Seminar
Novel coupled channel framework connecting quark model and lattice QCD: An investigation
on near-threshold Ds states (virtual)Oct. 1561

Peter Arnold(U. Virginia)

RBRC Seminar
Universality (beyond leading log) of soft radiative corrections to momentum broadening andenergy loss of high-energy partons in QCD matter (virtual)Oct. 15

62

Yasushi Nara
(Akita International U.)

RBRC Seminar
Transport theoretical approach for heavy-ion collision at high baryon densities (virtual)Oct. 2163

Jianhui Zhang(Beijing Normal U.)

RBRC Seminar
Recent updates on meson distribution amplitudes from lattice QCD (virtual)Oct. 22- 361 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

64

Daniel Boer
(U. Groningen)

RBRC Seminar
GTMD studies at small x (virtual)Oct. 2865

Dimitrios Bachtis(Swansea U.)

RBRC Seminar
Inverse renormalization group: Evading the critical slowing down effect (virtual)Oct. 29

66

Frédéric Chevy(LKB, ENS)

SNP Seminar
Impurity physics with cold atoms: Fermi polaron, Bose polaron and beyond (virtual)

Nov. 1067

Tuomas Lappi(U. Jyvaskyla)

RBRC Seminar
Loops in light cone perturbation theory (virtual)

Nov. 1268

Neha Shah(Indian Institute ofTechnology Patna)

SNP Seminar
Understanding hypernuclear interactions with heavy-ion collisions (virtual)

Nov. 17

69

Nobuyuki Matsumoto(Gakushuin U.)

RBRC Seminar
Worldvolume tempered Lefschetz thimble method as an algorithm towards solving the sign
problem (virtual)

Nov. 18

70

Pieter Taels(U. Antwerp)

RBRC Seminar
Quarkonium production at the EIC as a probe of gluon TMDs (virtual)

Nov. 19

71

Daisuke Inotani(RIKEN)

SNP Seminar
Strong-coupling effects of pairing fluctuations, and Anderson-Bogoliubov mode in neutron
superfluids in neutron stars (virtual)

Nov. 24

72

Andrey Tarasov(Ohio State U.)

RBRC Seminar
The role of the chiral anomaly in polarized deep inelastic scattering: Topological screening
and transitions from emergent axion-like dynamics. (virtual)Dec. 273

Jorge Noronha(U. Illinois)

RBRC Seminar
Hydrodynamic frames: The good, the bad, and the ugly (virtual)Dec. 374

Filip Bergabo(City U. of New York)RBRC Seminar
Coherent energy loss effects in dihadron azimuthal angular correlations in deep inelastic
scattering at small x (virtual)Dec. 975

Michal P. Heller(Max Planck Institute forGravitational Physics)

RBRC Seminar
The hydrodynamic gradient expansion diverges beyond Bjorken flow (virtual)Dec. 1076

Yuki Kamiya(Bonn U.)SNP Seminar
Femtoscopic study on the hadron-hadron interaction (virtual)Dec. 1777

Gabriel Santiago(Ohio State U.)

RBRC Seminar
Quark sivers function at small x: Spin-dependent odderon and the sub-eikonal evolution(virtual)Jan. 778

Lorenzo Contessi(IRFU)SNP Seminar
Universality in multi-fermion systems (virtual)Jan. 1279

Raju Venugopalan(BNL)

RBRC Seminar
Classicalization and unitarization of wee partons in QCD and gravity: The CGC-black holecorrespondence (virtual)Jan. 13

80

Jean-Paul Blaizot(IPhT U.)RBRC Seminar
Attractor and fixed points in Bjorken flows (virtual)Jan. 1481

Lájer Márton
(Eötvös Loránd U.)

RBRC Seminar
When cold, dense quarks are not a Fermi liquid (virtual)Jan. 2082

Ismail Zahed(Stony Brook U.)

RBRC SeminarOn the topological origin of hadronic mass and spin (virtual)Jan. 2183

Luigi Coraggio(U. Campania)

SNP Seminar
Microscopic approaches to the calculation of the nuclear matrix element for the neutrinolessdouble-beta decay (virtual)Jan. 24

84

Shohini Bhattacharya(BNL)

RBRC SeminarFirst global QCD analysis of the worm-gear TMD g1T (virtual)

Feb. 385

Giovanni Chirilli(Regensburg U.)

RBRC Seminar
Pseudo- and quasi-PDFs in the BFKL approximation (virtual)

Feb. 486

Chandrodoy
Chattopadhyay(North Carolina State U.)

RBRC Seminar
Far-from-equilibrium attractors in boost-invariant plasmas (virtual)

Feb. 10- 362 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

87

Simon Catterall(Syracuse U.)

RBRC Seminar
Symmetric mass generation and anomalies in particle and condensed matter physics(virtual)

Feb. 1188João Barata(U. Lisbon)

RBRC Seminar
Jet quenching in anisotropic media (virtual)

Feb. 1789

Michael Wagman(Fermilab)

RBRC Seminar
Few-nucleon systems in lattice QCD (virtual)

Feb. 18

90

Paul Caucal(BNL)

RBRC Seminar
Anomalous diffusion in QCD matter (virtual)

Feb. 24

91

Takumi Doi(RIKEN)RBRC Seminar
Hadron interactions from lattice QCD (virtual)

Feb. 25

92

Yasutaka Taniguchi(Kagawa College)

SNP Seminar
12
C+12C fusion astrophysical S-factor in a full-microscopic nuclear model (virtual)

Feb. 2593

Mendel Nguyen(NC State U.)

RBRC Seminar
Noninvertible symmetry and string tensions beyond N-ality (virtual)Mar. 394

Farid Sazalar(UCLA)

RBRC Seminar
Promoting gluon saturation to higher precision with dijets at the EIC (virtual)Mar. 495

Bing-Nan Lu(China Academy ofEngineering Physics)

SNP Seminar
Ab initio nuclear physics on the lattice (virtual)Mar. 496

Christian Schmidt(U. Bielefeld)

RBRC Seminar
Lee-Yang edge singularities in lattice QCD (virtual)Mar. 1097

Andrei Alexandru(The George Washington
U.)

RBRC Seminar
Three hadron scattering from lattice QCD (virtual)Mar. 1198

Yuya Tanizaki(YITP)

RBRC Seminar
Semiclassical description of confinement via center vortices and anomaly-preserving T2
compactifications (virtual)Mar. 17

99

Xabier Feal
(BNL)

RBRC Seminar
Infrared structure of QED as a many-body theory of worldlines (virtual)Mar. 18

100

Alexander Rothkopf(U. Stavanger)

RBRC Seminar
Static interquark potential from Euclidean and real-time lattices (virtual)Mar. 24

101

Ihsse Friederike(BNL)

RBRC Seminar
Towards resolving the QCD phase structure with discontinuous Galerkin methods (virtual)Mar. 31

SNP Seminar ĺ http://snp.riken.jp/seminar.html
RIKEN/BNL Lunch Time Talk ĺ https://www.bnl.gov/riken/events/- 363 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

Events (April 2021ȷMarch 2022)
RNC
Apr. 23

Wako Open Campus

May 26The 28th RBRC Management Steering Committee (MSC)

Jul. 7The 17th Industrial Program Advisory Committee (In-PAC)

Dec. 1–3

The 22nd Program Advisory Committee for Nuclear Physics Experiments at RI Beam Factory (NP-PAC)

Dec. 8–27

The 18th Industrial Program Advisory Committee (In-PAC)

Dec. 9–Jan. 4

The 21st Program Advisory Committee for Materials and Life Science Researches at RIKEN Nishina Center (ML-PAC)

CNS
Aug. 16–20

20th CNS International Summer School (CNSSS21)
https://indico2.cns.s.u-tokyo.ac.jp/event/145/- 364 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

Press Releases (April 2021ȷMarch 2022)
RNC
Apr. 16

New precise spectroscopy of the hyperfine structure in muonium with a highintensity pulsed muon beam

K. Ishida, M. Iwasaki, Meson Science
Laboratory

Apr. 26

Proton-3He elastic scattering at intermediate energies

H. Sakai, RNC

May. 11

Measurement of neutron rich high dense matter pressure—Reproducing the inside of neutron star matter in a laboratory—

T. Isobe, M. Nishimura, H. Sakurai, H. Otsu,
H. Baba, Radioactive Isotope Physics
Laboratory, SAMURAI Team, Computing and
Network TeamMay. 19

Discovery of a charge symmetry breaking—Large difference in the shape between Kr-70 and Se-70—

P. Doornenbal, H. Sakurai, Radioactive Isotope
Physics Laboratory

Aug. 30

Most charming dibaryon, "Charmed di-Omega"—Theoretical calculation using supercomputers predicts a new hexaquark state—

H. Tong, Y. Lyu, T. Doi, Quantum Hadron
Physics Laboratory

Sep. 1First high-precision direct determination of the atomic mass of a superheavy nuclide
evinces a new means to unambiguously determine atomic numbers

K. Morimoto, Superheavy Element Device
Development Team

Oct. 15

Measurement of gluon's motion inside the proton via "direct photon"—Data reveal that the dynamical motion of gluons is not very large—

Y. Akiba, Y. Goto, S. Ralf, I. Nakagawa,Experimental Group, RIKEN BNL ResearchCenter

Nov. 29୔੘ਙൖ૾Ꮳ岶峽峕ৌ峃峵ୢప਌଑੘ୡ峼৫઩

H. Haba, Nuclear Chemistry Research Team,RI Application Research Group崊崡崧崩嵛峼৷岮峉ৗ峁岮ఏ৓崊嵓崽崉଍੘௜Dec. 8Succeeded in creating a new breed of Satsuma mandarin orange

T. Abe, Ion Beam Breeding Team, Beam
Mutagenesis GroupFeb. 28

Negative string tension of higher-charge Schwinger model via digital quantum
simulation

E. Itou, Strangeness Nuclear Physics
Laboratory

Mar. 28

Measurements of strong-interaction effects in kaonic-helium isotopes at sub-eV
precision with X-ray microcalorimeters

F. Sakuma, Meson Science Laboratory

KEKத੎੪ಞ峘ੂ峫峐峘ಖഡସ୤೾৒峕ਛ඘
Aug. 31

P. Schury, M. Wadaৗ੪ಞ峘ৗ峁岮ਉ৕୞ಀৠ৒১峘઒৥https://www.kek.jp/ja/press/202109010000/- 365 -

VII. APPENDICESRIKEN Accel. Prog. Rep. 55 (2022)

List of Preprints (April 2021ȷMarch 2022)
RIKEN NC-NP
Not Applicable

RIKEN NC-AC
7

O. Kamigaito et al.

First Beam from SRILAC

RIKEN MP
Not Applicable

RIKEN QHP
494

Photonic quantum kinetic theory in curved spacetime and the spin Hall effect

K. Mameda et al.

495Complex Langevin study for polarons in an attractively interacting one-dimensional
two-component Fermi gas

T. M. Doi et al.

496

Emergence of the rho resonance from the HAL QCD potential in lattice QCD

Y. Akahoshi et al.

497

Quantum hydrodynamics from local thermal pure states

S. Tsutsui et al.

498

Unitary p-wave Fermi gas in one dimension

H. Tajima et al.

499

Effects of finite-light-speed correction for the Coulomb interaction on nuclear binding energies
and radii in spherical nuclei

T. Naito

500

Three-body crossover from a Cooper triple to bound trimer state in three-component Fermi gases
H. Tajima et al.
near a triatomic resonance

501

Construction of energy density functional for arbitrary spin polarization using functional
renormalization group

T. Yokota and T. Naito

502

New constraints on the neutron-star mass and radius relation from the terrestrial nuclear
experiments

H. Sotani et al.

503

Persistence of cluster structure in the ground state of 11B

N. Itagaki et al.

504

Optical spin transport theory of spin-1/2 topological Fermi superfluids

H. Tajima et al.

505

Perturbative predictions for color superconductivity on the latticeT. Yokota et al.

506

Color superconductivity in a small box: a complex

S. Tsutsui et al.

507

On the validity of the complex Langevin method near the deconfining phase transition in QCD at
S. Tsutsui et al.
finite density

508

Isovector density and isospin impurity in 40Ca

H. Sagawa et al.

509

Investigations of decuplet baryons from meson-baryon interactions in the HAL QCD method

K. Murakami et al.

510

Flavor number dependence of QCD at finite density by the complex Langevin method

Y. Namekawa et al.

511

Emergence of the rho resonance from the HAL QCD potential

Y. Akahoshi et al.

512

Most charming dibaryon near unitarity

Y. Lyu et al.

513

Finite volume analysis on systematics of the derivative expansion in HAL QCD method

T. Doi et al.

514

Optimized two-baryon operators in lattice QCD

Y. Lyu et al.

- 366 -

VII. APPENDICES

515

RIKEN Accel. Prog. Rep. 55 (2022)

Isospin symmetry breaking in the charge radius difference of mirror nuclei

T. Naito et al

CNS-REP100

CNS Annual Report 2020

H. Nagahama

Nishina Center Preprint server (not including Partner Institution) can be found at
http://nishina-preprints.riken.jp/- 367 -

理化学研究所
埼玉県 和光市 広沢
RIKEN 2022-039
ISSN 0289-842X