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

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 In the energy range up to 40 MeV, the data are dominated by unpublished nonelastic n-³He values derived from measurements made in 1982.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.