Effect of Deposited Charge on Vacuum DC Surface Flashover Under Electron Beam Irradiation

Spacecraft operating environment is rather complex, including high vacuum and energetic electron radiation. Vacuum-insulation interface is usually the weakest link of the insulation system since surface flashover usually occurs at the interface. There are several theories for surface flashover, above which the secondary electron emission avalanche (SEEA) and the electron triggered polarization relaxation (ETPR) are the mainstream. Since researchers have usually assumed that there has been a preexisting positive charge on the insulation surface, when the insulation surface is negatively charged by electron beam irradiation, these theories cannot be directly applied. In this article, the particle tracking method is used to simulate the initial and secondary electron trajectories in the initial phase of surface flashover, and to explain the influence of negative surface charge on surface flashover. The results show that: on the one hand, the negative deposited charge weakens the electric field at the cathode triple junction (CTJ), inhibits the initial electron emission, and hinders the initiation of flashover; on the other hand, the negative deposited charge repels the secondary electrons away from the insulation surface and hinders the multiplication of the secondary electrons and the development of flashover.