Neutron Interactions with 3He Revisited–II: Nonelastic Cross Sections in the Mega-Electron-Volt Range

Abstract

Reliable nonelastic cross-section measurements of fast neutrons with 3He are sparse. In the energy range up to 40 MeV, the data are dominated by unpublished nonelastic n-3He values derived from measurements made in 1982. As mentioned elsewhere, n-3He elastic cross-section data reported in the same report had not been corrected for the outgoing neutron attenuation even though the sample size was >7 mol. To check the database of existing nonelastic n-3He cross-section data, and in particular those from 1982, a detailed balance calculation of time-reversed charged-particle data was performed. Because there are few existing independent data, we provide an updated detailed balance analysis in the energy range up to 31 MeV for both 3He(n,p)3H and 3He(n,d)2H, supplying accurate absolute-angle-dependent differential cross sections. Subtracting the integrals of these and the elastic cross sections from the total provides a prediction for the sum of the 3He(n,2n)2p and 3He(n,n + p)2H cross sections. The relevant experimental data are compared with their time-reversed counterparts.