Optimum shielding in Jovian radiation environment

At Jupiter, the most dominant particle constituent is the high-energy electrons with E>1 MeV (and can be as high as >100 MeV). Huge mass is required to shield these electrons to reduce the radiation doses to the acceptable level for spacecraft electronics. An adjoint Monte Carlo code, NOVICE, which was developed specifically for space radiation transport problems, was used as a primary tool to study an optimum shielding design for a Jupiter mission. Also, a traditional forward Monte Carlo code, MCNPX, was used to verify the NOVICE results. Here we studied two representative spacecraft-shielding materials: aluminum representing low/medium-Z material and tungsten representing high-Z material. A series of NOVICE and MCNPX runs were performed to compute the energy deposition in spherical shell geometry with a small silicon detector at the center of the sphere. Calculation results indicate that, for the radiation attenuation required for typical electronics used in a Jupiter mission, the low-Z material and the low/high-Z combination are a less-efficient shield per the same areal mass than the high-Z material in the Jovian radiation environment studied here. When massive shielding >10 g/cm2 is required to protect very radiation-sensitive electronics, then the low- /high-Z combination is a better shield per the same areal mass.