Monte Carlo simulations of energy losses by space protons in the CRaTER detector

The cosmic ray telescope for the effects of radiation (CRaTER) detector is carried on the lunar reconnaissance orbiter (LRO) spacecraft, which was launched in June 2009. In lunar orbit, CRaTER will be used to help characterize the lunar radiation environment and its biological impacts on humans. The aim of this work is to estimate the energy loss and the linear energy transfer (LET) in CRaTER from energetic protons, such as those found in solar energetic particle events and galactic cosmic ray environments. Simulations of CRaTER component responses to protons with energies between 100 MeV and 2 GeV are made using the recently-modified HETC-HEDS Monte Carlo radiation transport code and presented for each component in the detector stack. As a check on the validity of these results obtained from HETC-HEDS, energy loss and LET spectra for protons at incident energies of 300, 600 and 1000 MeV are obtained using the Monte Carlo code system for multiparticle and high energy applications (MCNPX) and compared with the HETC-HEDS predictions. Agreement between the predictions from these two codes for a variety of proton energies between 300 and 2000 MeV is found to be within approximately 10%.