Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 52 (2019)

Cross-section measurement of neutron-rich isotopes produced from an
RI beam of 132 Sn using a two-step scheme
H. Suzuki,∗1 K. Yoshida,∗1 N. Fukuda,∗1 H. Takeda,∗1 Y. Shimizu,∗1 D. S. Ahn,∗1 T. Sumikama,∗1 N. Inabe,∗1T. Komatsubara,∗1 H. Sato,∗1 Z. Korkulu,∗1 K. Kusaka,∗1 Y. Yanagisawa,∗1 M. Ohtake,∗1 H. Ueno,∗1S. Michimasa,∗2 N. Kitamura,∗2 K. Kawata,∗2 N. Imai,∗2 O. B. Tarasov,∗3,∗1 D. P. Bazin,∗3,∗1 T. Kubo,∗4,∗1J. Nolen,∗5,∗1 and W. F. Henning∗5,∗6,∗1∗1
∗2
∗3∗4
∗5
∗6in this experiment at RIBF and the ones at GSI2) areshown with the cross-section formulae COFRA1.03) andEPAX3.1a.4) Both formulae reproduce the experimental
cross sections fairly well. Further detailed analyses arein progress.
4Atomic number (Z )1052Preliminary

350

1048

210

46
44

10
128

4240
2.55

127

PdPd

2.6

2.65

2.7

A/Q

2.75

2.8

2.85

1Fig. 1. The Z versus A/Q PID plot of 128 Pd setting in ZeroDegree. Partially-stripped contaminants are includedin the plot with the fully-stripped 127, 128 Pd.

102
SnAgCd101
InRhPd0Ru
1010-1
Tc
10-2
Nb Mo
10-3
10-4
GSI data
10-5 126
Pdsetting128
Pd setting
10-6 COFRA1.0
Preliminary
EPAX3.1a10-7
95 100 105 110 115 120 125 130 135 140

Production cross section [mb]The production cross sections of neutron-rich radioactive isotopes (RI), including 125–128 Pd produced from aless-exotic RI beam of 132 Sn, were measured using BigRIPS and ZeroDegree at the RIKEN RI Beam Factory(RIBF) in November 2017.
A two-step reaction scheme was proposed1) for the eﬃcient production of mid-heavy very-neutron-rich RIs. In
this scheme, a long-lived neutron-rich RI such as 132 Sn,
whose half-life is 40 s, is produced by an ISOL in the ﬁrst
step, and accelerated by post-accelerators. In the second
step, more exotic nuclei, such as 125–128 Pd, are produced
by a fragmentation reaction. With this scheme, one may
obtain greater yields of very neutron-rich RIs than thoseobtained by direct production through the in-ﬂight ﬁssion of a 238 U beam, which is currently a very popularmethod to produce them. To evaluate the yields of RIs
by the two-step scheme with a 132 Sn beam, we measured the production cross sections of neutron-rich Pd
isotopes beyond 125 Pd, up to which the cross sections
had already been measured at GSI together with theneighboring RIs.2)
In the experiment, the 132 Sn beam was produced
at BigRIPS by the in-ﬂight ﬁssion of a 40-pnA
345-MeV/nucleon 238 U86+ beam impinging on a 4mm-thick Be target. The 132 Sn-beam energy was278 MeV/nucleon, the intensity was 35 kHz, and thepurity was 50%. The neutron-rich Pd isotopes wereproduced by the fragmentation with a 6-mm-thick Be
target at the entrance of ZeroDegree. The particle identiﬁcation (PID) was performed by deducing the atomic
number Z, the mass-to-charge ratio A/Q, and the mass
number A of the RIs based on the TOF-Bρ-∆E-TKE
method in ZeroDegree. Two settings—the 126 Pd setting
and the 128 Pd setting—were applied for measuring thecross sections of 125, 126 Pd and 127, 128 Pd, respectively.
The Z vs A/Q PID plot of the 128 Pd setting is shownin Fig. 1. Many fully-stripped isotopes are observed withthe partially-stripped ones. 127, 128 Pd46+ are well identiﬁed in the plot. The events in the two blobs on theright side of 128 Pd46+ are the H-like ions of 126, 127 Pd45+ .
From the yields of RIs, their transmission in ZeroDegree,
and the beam dose of 132 Sn, the production cross sections were deduced. In Fig. 2, the cross sections obtained
RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo
National Superconducting Cyclotron Laboratory, Michigan
State UniversityFacility for Rare Isotope Beams, Michigan State University
Division of Physics, Argonne National Laboratory
Physik Department, Technische Universität München- 65 -Mass number (A)Fig. 2. The experimental cross sections of neutron-rich RIs
produced from 132 Sn beams at RIBF and GSI2) withcross-section formulae COFRA1.03) and EPAX3.1a.4)

References

1) K. Helariutta et al., Eur. Phys. J. A 17, 181 (2003).
2) D. Pérez-Loureiro et al., Phys. Lett. B 703, 552 (2011).
3) COFRA web page, http://www.usc.es/genp/cofra.
4) K. Sümmerer, Phys. Rev. C, 86, 014601 (2012).