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,∗1Y. 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. A80
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 tostudy 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

U345 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)

238

U345 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.
8Li, 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 Hesetting.

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)
74Ni, 75Ni, 76Ni
156
La
202Os(symbiotic)133
Sn(primary)

NP1712-RIBF141R1-01

T. Uesaka

ZeroDegree

8Li, 9Li, 10Be, 12Be, 12B

NP1912-RIBF135R1-01

K. Itahashi

BigRIPS

3HeNP1912-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

380

HH
3H
(BigRIPS tuning only)
203
Re
79
Ni
75
Zn
191
Bi124
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 ofa 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 wasconducted 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 theMRTOF-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 ourdatabase6) 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. B463, 158 (2020).

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