The charge transport characteristics of polyimide under electron beam and dc voltage

Deposited charges in dielectric material under electron-beam radiation have an important influence on dc vacuum surface flashover. This paper investigates the charge transport characteristics of polyimide under electron-beam radiation and dc voltage. Based on the actual size of electrodes and polyimide, a physical model of electron-beam radiation is proposed. Considered the processes of charge deposition and transport and accumulation in polyimide radiated by low-energy electrons (electron energy: 5-30 keV, electron-beam density: 10^-10 ~10^-7A/m²), the distributions of space charge, potential and electric field can be obtained, and the total electric field at cathode triple junction under the combined action of electron radiation and dc voltage are analyzed. The calculation results indicate that when the electron-beam density is less relatively (<;10^-9 A/m²), the weakening effect of built-in electric field on applied electric field is unobvious. With the increase of electronbeam density, the built-in electric field is gradually increased, resulting in the decrease of total electric field at the cathode triple junction. The total electric field is 8×10⁵ V/m under the electron-beam density of 10^-7 A/m². It will reduce the initial electron emission at the cathode triple junction, and may enhance surface flashover voltage of dielectric material. Further experiment study will be carried out.