Hye Young Lee
Neutron-induced Reaction Studies on Stable and Unstable Nuclei at Los Alamos Neutron Science Center (LANSCE)
In nucleosynthesis network calculations, available experimental nuclear physics inputs are limited to the measure- ments on stable or accessible radioactive nuclei, remaining thousands of reactions to rely on the theoretically predicted reaction rates. Hauser-Feshbach (HF) formalism is widely used to predict these reaction rates, however difficulties like renormalizations of calculated neutron-capture cross sections to experimental observables like the averaged radiation width, < Gamma_gamma > =D0, or shape disagreements of neutron-induced charged particle reaction cross sections below 10 MeV among different HF codes have been addressed. At Los Alamos Neutron Science Center (LANSCE), neutrons are produced in the energy range of thermal to several hundreds MeV. Direct-measurements on neutron-induced reactions allow us to probe these nuclear input parameters used in HF formalism for enhancing the fidelity of these theoretical predictions through advanced nuclear reaction modeling. We have developed the LENZ (Low Energy NZ) instrument to investigate (n,p) and (n,alpha) cross sections in the focus of low detection thresholds and large solid angle coverage. I will present the on-going study on the precision measurement of the 16O(n,alpha) reaction cross section in the interest of nuclear application, since oxygen is abundant in air and as cooling water to require high-precision nuclear data. A new and exciting project is to measure the 56Ni(n,p) reaction cross section at LANSCE, which is directly to confirm the importance of nu-p process during neutrino-wind driven environment, for improving our understanding of heavy element production. 56Ni is a radioactive nucleus with a half life of 6 days, so we are developing to irradiate this isotope at the Isotope Production Facility at LANL and fabricate as a reaction target to be used with radiation resistant detection system at LANSCE. I will update the progress on this effort.