Hiroshi Suzuki
(RIKEN Nishina Center)
The usefulness of the two-step scheme with a Sn beam was investigated [1], which was proposed for efficient production of medium-heavy very-neutron-rich radioactive isotopes (RI) [2] as an alternative method to the direct production by means of in-flight fission of a U beam (one-step scheme). The system of the two-step scheme consists of an isotope-separation online (ISOL) system and an in-flight fragment separator. Long-lived neutron-rich RIs (e.g., Sn) are produced by ISOL with a thick U target and a high-intensity proton beam in the first step, and more neutron-rich RI beams (e.g., Pd) are produced by a projectile fragmentation from the re-accelerated less-exotic RI beams in the second step.
We measured production cross sections of very neutron-rich RIs around a N = 82 region beyond Pd, up to which the cross sections had already been measured at GSI [3], with a 278-MeV/nucleon Sn beam produced by the BigRIPS separator [4] impinging on a 5.97-mm Be target. The yields obtained by the two-step and one-step schemes were estimated based on the measured cross sections, and we examined whether and to what extent the two-step scheme at future 1-MW beam facilities can reach further into the neutron-rich regions. This comparison suggests that the two-step scheme with the Sn beam provides yields 40-times higher than those with the one-step scheme for the very neutron-rich N = 82 region. Moreover, by using various RI beams over the nuclear chart from ISOL, certain regions of very neutron-rich RIs around N = 50, 60, 82, and 90 regions, including the supernova -process path, can be produced with greater yields than by the one-step approach.
References
[1] H. Suzuki et al., Phys. Rev. C 102, 064615 (2020).
[2] K. Helariutta et al., Eur. Phys. J. A 17, 181 (2003).
[3] D. Pérez-Loureiro et al., Phys. Lett. B 703, 552 (2011).
[4] T. Kubo, Nucl. Instr. and Meth. B 204, 97 (2003).
Hiroshi Suzuki
(RIKEN Nishina Center)
Daniel Bazin
(FRIB / MSU)
Naoki Fukuda
(RIKEN)
Prof.
Walter, F. Henning
(Argonne National Laboratory, Technische Universitaet Muenchen)
Nobuaki Imai
(CNS, the University of Tokyo)
Mr
Naohito Inabe
(RIKEN Nishina Center)
Dr
Keita Kawata
(CNS, University of Tokyo)
Dr
Noritaka Kitamura
(CNS, University of Tokyo)
Dr
Tetsuro Komatsubara
(RIKEN Nishina Center)
Zeren Korkulu
(IBS, CENS)
Dr
Toshiyuki Kubo
(RIKEN Nishina Center)
Dr
Kensuke Kusaka
(RIKEN Nishina Center)
Shin'ichiro Michimasa
(The University of Tokyo CNS)
Prof.
Jerry Nolen
(Argonne National Laboratory)
Mr
Makoto Ohtake
(RIKEN Nishina Center)
Dr
Hiromi Sato
(RIKEN Nishina Center)
Yohei Shimizu
(RIKEN)
Toshiyuki Sumikama
(RIKEN)
Hiroyuki Takeda
(RIKEN)
Oleg Tarasov
(FRIB / MSU)
Hideki Ueno
(RIKEN Nishina Center)
Dr
Yoshiyuki Yanagisawa
Koichi Yoshida
(RIKEN)
Deuk Soon AHN
(Center for Exotic Nuclear Studies, IBS)
