Trap distribution of electron beam irradiated epoxy resin under repetitive pulse voltage

Epoxy resin has been widely used as dielectric material in irradiation environment, such as nuclear power plants, aerospace equipment and superconducting power apparatus. This paper investigated the effects of different electron beam irradiation doses on the trap distribution of epoxy resin under repetitive pulse voltage. Samples were irradiated at room temperature (20 °C) in air by high energy electron beam of 7.5 MeV with beam density ranging from 0.35 to 0.45 mA/cm
²
. The total irradiation dose was 0, 100, 500 and 700 kGy, respectively. The corona charging was performed under ± 6 kV pulse voltage with different pulse frequencies in atmospheric air with relative humidity of 20%. The surface potential was collected through an electrostatic voltmeter to obtain the trap distribution at room temperature, and the isothermal discharge current of the samples processed with different irradiation dose was measured to calculate the trap distribution in liquid nitrogen (LN
₂
). The experimental results indicate that both at room temperature and in LN
₂
, the trap level decreases first and then increases with the increase of irradiation dose. The trap level and the trap density have the positive correlation with pulse voltage frequency. At room temperature, the electron traps have higher energy level and deep trap density, but have lower shallow trap density than the positive charge traps.