Measurement of the Cu-65(n, Gamma) Cross Section Using the Detector for Advanced Neutron Capture Experiments at LANL

Improving our understanding of the origin of the elements in the observable universe as well as the nature of the environments responsible for their production has been of paramount importance to the nuclear physics community. More than half of the isotopes of these elements are created via neutron-capture processes, and thus accurate measurements of the salient underlying nuclear physics, such as neutron-capture cross sections, masses, and beta-decay half-lives are crucial. Of particular importance to the synthesis of isotopes in the mass range of A approximate to 60 to A approximate to 90, via the weak s process, are the neutron-capture cross sections of (CU)-C-63,-C-65, where large discrepancies between measurements exist. Recent measurements have addressed these discrepancies for Cu-63 [Weigand et al., Phys. Rev. C 95, 015808 (2017)]. but questions still remain for Cu-65. In this paper we report a new measurement of the Cu-65(n, gamma) cross section performed using the Detector for Advanced Neutron Capture Experiments located at the Los Alamos Neutron Science Center of Los Alamos National Laboratory. The Maxwellian-averaged cross section (MACS) for Cu-65(n, gamma) at kT = 30 keV deduced from this work is (37.0 +/- 0.3(stat)(.) +/- 3.3(sys)(.)) mb. The impact on weak s-process nucleosynthesis of new MACS values, calculated over the range of kT = 5 to 100 keV, for Cu-65, combined with the updated MACS for Cu-63 [Weigand et al., Phys. Rev. C 95, 015808 (2017)] and Ni-63 [Weigand et al., Phys. Rev. C 92, 045810 (2015)], were investigated. Results of this investigation show an increase of predicted nucleosynthesis yields of elements of Zn to Zr by as much as 20%.