Effects of secondary particles on the total dose and the displacement damage in space proton environments

MCNPX, a powerful Monte Carlo charged particle transport code, is introduced in this paper for space-radiation effect applications. By using MCNPX version 2.1.5, the enhancement of the total dose and the displacement damage due to secondary particles generated by the protons in the typical space radiation environments was assessed, then the results were compared to those obtained by the continuous slowing down approximation (CSDA) method. The comparison showed that the effects of the secondary particles were up to +7% for the total dose and up to +25% for the displacement damage when compared to the respective CSDA results in heavy shielding applications where trapped and solar protons dominate. Also presented in this paper is a method to compute the neutron/proton displacement cross sections by using MCNPX. The cross sections obtained show an excellent agreement with previously published values.