Space charge accumulation in polymeric materials for spacecraft irradiated electron and proton

Charge accumulation characteristics in dielectric materials for a spacecraft were studied to elucidate spacecraft charging problems in a high-energy radiation environment. This study especially addressed spacecraft charging accidents caused by internal charge accumulation in dielectric materials irradiated by electron and proton beams. Internal charge measurements of those bulk materials were carried out using Pulsed Electro-Acoustic (PEA) and Pressure Wave Propagation (PWP) methods. For internal charge accumulation in the bulk irradiated by a proton beam, results showed a positive charge accumulation in the bulk samples after irradiation. However, a positive charge accumulation was not observed for quartz glass with an Al evaporated layer on the surface of the proton beam irradiation side. Therefore, in this paper, we compare the PEA's internal charge measurement results and energy band model for discussion of the charge formation mechanism in the bulk irradiated by a proton beam. Furthermore, we measure the space charge distribution in bulk materials (e.g., polyimide film, FEP, and cover glass) which are used for spacecraft irradiated by a proton beam during a satellite's orbit. We also measured the space charge distribution in identical samples under electron beam irradiation. The electron beam irradiation conditions resembled those encountered in a GEO synchronous earth orbit (GEO). We compare and discuss internal charge measurement results and charge accumulation results in the same bulk with mono energy electron beam irradiation.