Effects of Electron Beam Irradiation on the Trap Distribution of Epoxy under Repetitive Pulse Voltage

Abstract

Epoxy has been extensively applied as insulating material in irradiation environment and cryogenic engineering applications. Distorted electric field in the insulation system always causes the accumulation of surface charge which plays an important role in the acceleration of insulation failure. However, the characteristics of surface charge and trap distribution of irradiated epoxy in these areas are not clear. In this paper, effects of electron beam irradiation on the trap distribution of epoxy under repetitive pulse voltage were researched. Specimens were irradiated at 20 °C by high energy electron beam of 8.0 MeV with 0, 100, 500 and 700 kGy in irradiation dose respectively. The trap distribution at room temperature was analyzed based on surface potential decay (SPD), while the trap distribution in liquid nitrogen (LN2) was calculated based on the isothermal discharge current of various specimens. Obtained results show that the trap level decreases with the increase of irradiation dose until the dose exceeds 500kGy and the trap level is positively correlated with the frequency of pulse voltage, whether at room temperature or in LN2. What's more, the electron traps have higher energy level at room temperature than the positive charge traps.