DC surface flashover characteristics of polyimide in vacuum under electron beam irradiation

In order to avoid the surface discharge of sensitive components on spacecraft, it is very important to understand the mechanism of surface flashover characteristics of the insulator materials, such as polyimide (PI). This paper studied the influence of electron beam irradiation on the negative polarity dc surface flashover characteristics of PI plate specimen in vacuum. Results showed that the flashover voltage under 0.5-40 keV electron beam irradiation is enhanced compared to none irradiation situation. The flashover voltage increased at first then decreased with the increase of the electron beam energy, reaching maximum at 20 keV. And under the constant electron beam energy irradiation, the voltage decreased with the increase of the beam density. The experiments suggest that the negative space charge of cathode triple junction (CTJ), radiation-induced conductivity (RIC) and radiation degradation are important reasons for the rise of flashover voltage under various radiation electron beam energy. Besides, the low energy primary electrons play critical roles in the reduction of surface flashover voltage under different beam density.