II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

RI beam production at BigRIPS in 2020
H. Takeda,∗1 N. Fukuda,∗1 H. Suzuki,∗1 Y. Shimizu,∗1 N. Inabe,∗1 K. Kusaka,∗1 M. Ohtake,∗1 Y. Yanagisawa,∗1H. Sato,∗1 K. Yoshida,∗1 and T. Uesaka∗1
The radioactive isotope (RI) beam production at theBigRIPS fragment separator1) in 2020 is presented here.
Table 1 summarizes the experimental programs that involved the use of the BigRIPS separator in this period
and the RI beams produced for each experiment. All theexperiments originally scheduled for the spring beamtime were postponed owing to the COVID-19 pandemic.
In the autumn beamtime, 238 U and 70 Zn primary beams
were provided.
The 238 U beam campaign started in October. During
a tuning phase of BigRIPS at startup, an auto-focusing
and auto-centering system was tested with a 82 Ge beam
for the ﬁrst time at RIBF.2) After the BigRIPS tuning phase followed by the commissioning of HiCARI,a PALIS experiment was performed with an RI beamaround 191 Bi to evaluate the extraction eﬃciency usingalpha emitters in the 191 Bi region.
Five HiCARI experiments were subsequently performed with the ZeroDegree spectrometer. A cocktail
beam of 84 Ge/83 Ga/82 Zn was produced to study neutron
intruder states and collectivity. 86 Se/84 Ge, 88 Se/86 Ge,
and 90 Se beams were produced to explore quadrupole
and octupole collectivity. A cocktail 111 Nb/112 Mo/113 Tc
beam was produced to perform high-resolution spectroscopy and lifetime measurements. A 130 Cd beam
was produced to study single-particle states in 129 Ag.
A 136 Te beam was produced to characterize a strongly
Coulomb-excited state above 4 MeV in 136 Te. During these HiCARI experiments, mass measurementswith a multi-reﬂection time-of-ﬂight mass spectrometer (MRTOF-MS) located downstream of the ZeroDegree spectrometer were performed symbiotically. Subsequently, a machine study for the Rare RI Ring wasperformed with a 75 Ga beam.
At the end of the 238 U beam campaign, a machine
study for a high-purity Th-beam development including performance evaluations of beamline detectors for ahigh-Z, high-rate RI beam was performed using a 220 Thbeam.3)
After switching to the 70 Zn primary beam, two HiCARI experiments were conducted with the ZeroDegree
spectrometer. 56 Ti and 58 Ti beams were produced tostudy the evolution of collectivity in Ti isotopes. 36 Ca,38
Ca, 48 Ca, and 54 Ca beams were produced to investigate systematically the reduction factor for the deduced
spectroscopic factors. A symbiotic MRTOF experiment
was performed again.
A new isotope search experiment was conductedaround the 45 Si region at the end of the 70 Zn beam campaign.4)
The RI beam production at BigRIPS from the startof operation in March 2007 is summarized in ourdatabase.5) At ﬁrst, you will be redirected to the welcome page. Follow the links “Database of RI Beams Produced at BigRIPS” → “List of Experiments” → “Summary” to reach the summary page; you can reach thepage in subsequent attempts.
References

1) T. Kubo, Nucl. Instrum. Methods Phys. Res. B 204, 97(2003).
2) Y. Shimizu et al., in this report.
3) N. Fukuda et al., in this report.
4) H. Suzuki et al., in this report.
5) Y. Shimizu et al., Nucl. Instrum. Methods Phys. Res. B,463, 158 (2020). Available at https://ribeam.riken.jp/ .

Table 1. List of experimental programs together with RI beams produced at the BigRIPS separator in 2020.
Primary beam (Period)

Exp. Prog. No.

Spokesperson

CourseRI beams

U
345 MeV/nucleon(Oct. 25–Nov. 24)

NP1712-RIBF166-03
NP1912-RIBF196-01
NP1912-RIBF190-01
NP1912-RIBF187-01
NP1912-RIBF189-02
NP1912-RIBF193-01
PE19-02 / PE20-01
MS-EXP20-04
MS-EXP20-02

T. Sonoda
F. Flavigny
F. Browne
W. Korten
Z. Podolyak
A. Jungclaus
M. WadaY. Yamaguchi
N. Fukuda

PALIS
ZeroDegree
ZeroDegree
ZeroDegree
ZeroDegree
ZeroDegree
ZeroDegree
Rare RI Ring
ZeroDegreeBi
Ge/83 Ga/82 Zn
86
Se/84 Ge, 88 Se/86 Ge, 90 Se
111
Nb/112 Mo/113 Tc
130
Cd136
Te(symbiotic)
75
Ga
220Th

Zn
345 MeV/nucleon(Dec. 2–Dec. 13)

NP1912-RIBF142R1-01
NP1912-RIBF170R1-01
PE20-02
DA20-03

T. Koiwai
H. Crawford
M. WadaH. Suzuki

ZeroDegree
ZeroDegree
ZeroDegree
BigRIPSTi, 58 Ti
Ca, 38 Ca, 48 Ca, 54 Ca(symbiotic)
45Si

23870∗1

191
84

56

36

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