Effect of electron irradiation on DC surface flashover of polyimide in vacuum

The vacuum surface flashover voltage of dielectric material irradiated by electron-beam is very low, which is the key scientific issue for developing high-voltage and high-power spacecraft technology. This paper proposes a novel research way of considering the combined impact of incident kinetic electrons flowing to dielectric surface and deposited electrons in dielectric surface layer on dc surface flashover performance in vacuum. The experiments on dc surface flashover of polyimide in vacuum after electron irradiation and during electron irradiation were investigated. The experimental results indicated flashover voltage showed a distinctly different variation tendency under the two cases. The dc surface flashover voltage of polyimide after electron irradiation became higher than that without electron irradiation, because of the effect of deposited electrons in dielectric surface layer. During electron irradiation, the dc surface flashover voltage exhibited a dramatic drop from 26.9 kV (energy: 5 keV) to 10.5 kV (energy: 30 keV). Furthermore, the surface flashover characteristics exerts different changes for incident electrons of different energies levels. It has been experimentally indicated that the energy and incident trajectory of incident kinetic electrons flowing to polyimide surface are altered by the combined action of the reverse electric field created by deposited electrons and the applied electric field. As a result, the surface flashover characteristics were changed. This work provides a new insight into the vacuum surface flashover of dielectric material under electron irradiation, and can be used as the research basis of surface flashover mitigation methods in space environment.