GEANT4 dose estimations of solar protons: Al and PMMA-Bi2O3 shielding for space exploration

Abstract

Adverse effects of long-term exposure to galactic cosmic radiation (GCR) pose a clear obstacle to future space exploration programs. In addition to GCR we have solar particle radiation. We simulated the latter using a scaled fluence profile of solar protons taken from a literature study that comprises about three solar cycles. The model is a three-layer stack that includes shielding material and muscular tissue. Our simulation strategy uses protons as precursor radiation of neutrons. Subsequently, the shield is adjusted for thickness, dictated by an average depth at which neutrons are created through various processes during the simulation. Neutrons are then energy-binned and a corresponding neutron flux is simulated. Particles generated during the second phase of the simulation, i.e. by neutrons, are then counted toward absorbed dose within the muscular tissue layer. Clearly, the dynamics of the process is not captured by the simulation, nevertheless an overview of neutron yield can be estimated and the absorbed dose. The objective is to provide some insight about the effect of the new composite shield, PMMA-Bi2O3, that has an intrinsic capability for gamma dose reduction, compared to a more traditional aluminum shield.