Investigation on the radiation induced conductivity of space-applied polyimide under cyclic electron irradiation

Radiation induced conductivity (RIC) is an important property of dielectric materials to evaluate the charge/discharge effect in orbit-service spacecraft. RIC of space-applied polyimide film was in situ measured and studied under continuous and cyclic electron irradiation in this paper. The results indicate that, for cyclic electron irradiation, there is a similar increasing-mode of RIC to those for continuous irradiation with the electron irradiation time. However, under the cyclic electron irradiation, the RIC of polyimide shows an obvious irradiation-history characteristic, namely preliminary irradiation dose effect (PIDE). In this case, the steady RIC value presents an "overshoot" behavior in the first few irradiation cycles and then decrease to a stable one as that under continuous irradiation. Prolonging the initial irradiation duration may avoid occurrence of overshoot phenomenon. The behaviors of irradiation-induced free radicals in polyimide could be applied to explain the RIC evolution processes.