Validation of a multi-layer Green’s function code for ion beam transport

To meet the challenge of future deep space programs, an accurate and efficient engineering code for analyzing the shielding requirements against high-energy galactic heavy ion radiation is needed. In consequence, a new version of the HZETRN code capable of simulating high charge and energy (HZE) ions with either laboratory or space boundary conditions is currently under development. This code, GRNTRN, is based on a Green’s function approach to the solution of the one-dimensional Boltzmann transport equation and like its predecessor is deterministic in nature. The computational model consists of the lowest order asymptotic approximation followed by a Neumann series expansion with non-perturbative corrections. The physical description includes energy loss with straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and down shift. Code validation in the laboratory environment is addressed by showing that GRNTRN accurately predicts energy loss spectra as measured by solid-state detectors in ion beam experiments with multi-layer targets. In order to verify and benchmark the code with space boundary conditions, measured particle fluxes are propagated through several thicknesses of shielding using both GRNTRN and the current version of HZETRN. The favorable agreement obtained indicates that GRNTRN accurately models the propagation of HZE ions in laboratory settings. It also compares very well with the extensively validated space environment HZETRN code and thus provides verification of the HZETRN propagator.