Effect of gamma-ray irradiation on surface charge decaying characteristic of epoxy resin

Abstract

Epoxy resin used as insulating material in radioactive environment is subjected to a great risk of surface discharge that is originated from surface charge accumulation. For the safe use of the material, it is essential to gain a firm understanding of surface charge dynamics in response to high energetic irradiation. To investigate the effect of gamma-ray irradiation on surface charge decay of epoxy resin, by employing laminate epoxy resin with thickness of 1.5 mm as test sample, we experimentally investigated charge decay. Prior to the test, the sample was irradiated by 60Co gamma source with dosage rate of 10 kGy/h up to total dose of 100 kGy then to 1000 kGy. The sample surface was corona charged through a pair of needle-plane electrode. The charge distribution was measured by an electrostatic voltmeter, and thereby the decay behavior was obtained. The experimental results show that the decay process is bi-exponential. With the growth of the total dose of irradiation from 0 to 1000 kGy, surface charge decay is accelerated. The acceleration of negative charge decay is more remarkable than that of positive charge decay. It is proposed that the charge decay is mainly due to lateral charge spreading. Charge decay behavior is dependent upon the characteristics of surface trap that are varied by gamma-ray irradiation induced chemical reactions.