Research of internal charging characteristics of Polyetherimide irradiated by energetic electrons

In the space irradiation environment, the energetic electrons can penetrate the shielding of the spacecraft and deposit in the dielectric, resulting in internal charging. The deposit charge is difficult to release due to the very low conductivity. When the electric field established by the deposit charge exceeds the threshold of the dielectric, the electrostatic discharges will occur. It is one of the important factors threatening the safe operation of spacecraft. Polyetherimide (PEI) is a high-performance thermoplastic, it maintains desirable electrical and mechanical properties up to 300°C and above. Due to the good processing behavior, it is considered to be used to manufacture the complex components of spacecraft. However, there is rare literature on the internal charging of polyetherimide. This is the primary purpose of this paper. In this paper, A threedimensional charge transport equation for internal charging in dielectric is established. Geant4 is used to calculate the charge deposition rate and energy deposition rate during the interaction of electrons and PEI. The electric field distribution in PEI under different initial energies, different beam densities and different grounding modes is calculated. Research shows that the maximum internal electric field of PEI irradiated by electrons depends on the beam current density, initial energy and the grounding types, which needs to be analyzed based on the operating environment.