Geant 4-based calculation of electric field in deep dielectric charging
基于Geant 4的介质深层充电电场计算

Based on Geant4 particle transfer simulation, the internal current density, dose rate and charge deposition profiles of Teflon are acquired, and then the electric field under high energy and low density e-beam radiation is calculated with radiation-induced conductivity model of charging dynamics, which includes the continuity equation, Poisson equation and deep trap equation. According to Geant4 package, the charging model of dielectric is simplified as a compound structure consisting of shielding aluminum and multiple-layer plates radiated by 1.0MeV energy and 0.1 pA/cm2 flux density surface source. With statistical method, the distributions of internal current density, dose rate and charge deposition are obtained and normalized with the above flux density. Substituting these results into RIC model, the distributions of electric field in Teflon are calculated under various grounding conditions. It shows that the charge density, electric field and potential for the back side grounding are higher than these for the front side grounding, which tends to induce internal discharging. The electric field calculated for the critical internal discharging conditions in space is also consistent with the threshold field of dielectric Teflon(1e7V/m).