Assessment of MCNP6 and PHITS-predicted secondary neutron yields from experimentally emulated galactic cosmic ray interactions

Ratliff, H.; McGirl, N.*; Castellanos, L.*; Wang, H.-C.*; Srikrishna, A.*; Heilbronn, L.*

no journal, , 

Benchmark experiments conducted at the NASA Space Radiation Laboratory emulating cosmic ray interactions with spacecraft shielding materials measured the double-differential yields of neutrons and light ions produced from 15 different beams interacting with 8 different thick-target configurations over 500 hours of beam time. A large volume of simulations of the experiments were conducted using the PHITS and MCNP6 general purpose Monte Carlo particle transport codes; this work focuses on assessing the performance of the codes in their prediction of the measured neutron spectra. While the neutron spectra predicted by the codes were in general agreement with the experimental results, clear systematic deviations between the experimental and simulated results also emerged. In particular, the codes often overpredicted the high-energy peak at low angles associated with projectile fragmentation and significantly overpredicted the highest-energy portions of the yield spectra at higher detector angles (60 degrees and higher, relative to the beamline). This presentation seeks to explore the performance of PHITS and MCNP6 in these scenarios and specifically bring attention to where the codes underperform, highlighting where improvements to the physics models within the codes may need further development and/or tuning.