Study for s-process using neutron beam provided from ANNRI of J-PARC

¹ Japan Atomic Energy Agency, Tokai, Ibaraki, Japan
² Natonal Astronomical Observatory of Japan, Mitaka, Tokyo, Japan

Published online: 21 June 2016

Abstract

Most isotopes heavier than iron are synthesized by the slow neutron capture reaction process (s-process) in stars. Isomers in stable isotopes have sometimes an important role as a branching point in nucleosynthesis flow in the s-process. An isomer with a half-life of 14.1 y in ¹¹³Cd is a branching point from which a nucleosynthesis flow reaches to a rare isotope ¹¹⁵Sn. The astrophysical origin of ¹¹⁵Sn has remained still an open question. The s-process abundance of ¹¹⁵Sn depends on the ratio of the ¹¹²Cd(n, γ) ¹¹³Cd^m reaction cross section to the ¹¹²Cd(n, γ) ¹¹³Cd^gs reaction cross section. However, the isomer production ratio following the neutron capture reaction has not been measured in the energy region higher than the thermal energy. An intense neutron beam experimental system, ANNRI, in J-PARC has a high purity germanium (HPGe) detector system consisting of two cluster detectors. We have measured γ-rays decaying to the ground state and the isomer using the HPGe detectors in conjunction with a time-offlight method at ANNRI.