Better understanding of nu-p process with experimentally determined ⁵⁶Ni(n,p) reaction rate via direct measurements at LANSCE

For reaching out radioactive isotopes relevant for the nu-p process, a new capability of producing radioactive isotopes at Isotope Production Facility and performing direct measurements for (n,p) and (n,a) reactions has been commissioned at Los Alamos Neutron Science Center. We studied the ⁵⁶Ni(n,p) reaction, which has been identified as one of critical reactions for understanding heavy element productions in core-collapse supernovae. Using the hotLENZ (radioactive Low Energy NZ) instrument, the first directly measured cross sections of ^56,59Ni(n,p), ⁵⁶Co(n,p), and ⁵⁹Ni(n,a) reactions were obtained for deducing reaction rates. Updated ⁵⁶Ni(n,p) and ⁵⁶Co(n,p) reaction rates are compared with the current rates from REACLIB (Cyburt 2010), and used for hydrodynamics calculations with the parameters from Wanajo et al. (2011) and Nishimura et al. (2019) along with our parameters. The summary of this effort will be discussed in terms of potential further constrains on the nu-p process. The optimized solenoidal spectrometer development for radioisotope reaction studies at LANSCE will be presented.