Modeling of secondary neutron production from space radiation interactions

A knockout-ablation-coalescence model capable of making quantitative predictions of neutron spectra produced in high-energy nucleon-nucleus and nucleus-nucleus collisions is presented. A Glauber model is used to describe neutrons produced in the knockout or abrasion stage of the reaction. In the ablation stage, a statistical evaporation model is used to calculate the neutron spectrum produced by the excited prefragment nucleus left over from the abrasion stage. The effects of coalescence in reducing free neutron emission by composite particle formation are included. Typical results for predicted neutron energy and double-differential spectra are presented and compared with recently reported measurements for a variety of projectile and target nuclei of interest in space radiation protection. Except for differences resulting from the neglect of isobar production and decay in the model, predictions are in fairly good agreement with the measured data.