Evaluation of projectile charge changing cross section and shielding effects for radiation safety in space

Abstract

We conducted experiments to measure the projectile total charge changing cross section for evaluation of radiation shielding materials for heavy ions in space. Composite materials of carbon fiber reinforced plastic and standard materials of polyethylene and aluminum were evaluated as potential shielding materials. These materials, stacked with CR-39 nuclear track detectors and the optical stimulated luminescence detectors, were exposed to ion beams of ¹H, ⁴He, ¹⁶O, ²⁸Si, and ⁵⁶Fe. The stopping power was estimated from the depth of the Bragg peak. The projectile total charge changing cross sections were derived from projectile reduction rates obtained with CR-39. The cross section per unit mass exhibited a reduction tendency with A^-1/3, where A represents the average atomic mass. Thus, hydrogen rich materials present effective radiation shielding in space. The composite materials demonstrated the intermediate stopping power and cross sections between polyethylene and aluminum. Monte Carlo calculations with the HTV module model made of the composite materials indicated approximately 1.7 times higher dose reduction rates by the galactic cosmic ray compared to the conventional aluminum alloy. Consequently, the composite materials have the potential to serve as alternative structural materials with relatively high radiation shielding effectiveness.