Effect of Gamma-Ray Irradiation on Surface Potential Decay Behavior of Polyethylene Terephthalate Film

Polyethylene terephthalate (PET) has been widely used as insulating material in electrical equipment such as aerospace and nuclear power plant, where it is possibly exposed to the gamma-ray. Therefore, it is of great significance to understand the influence of gamma-ray irradiation on the distribution of traps to ensure the safety of electrical equipment. In this work, PET films with thickness of $100~{\mathrm {\mu m}}$ were selected as samples. Then they were irradiated in air at room temperature by gamma-ray, the irradiation dose rate was $10 \sim 130$ Gy/min. The total irradiation dose was controlled at 0 kGy, 100 kGy, 500 kGy, 1000 kGy, respectively. Surface potential on the PET sample was established by dc corona charging with needle-to-plate electrode. Surface potential decay measurement was carried out with an electrostatic voltmeter, by which trap distribution of the sample could be extracted and the influence of total irradiation dose was estimated. The results showed that with the increase of the total irradiation dose, the deep trap center became deeper whereas the shallow trap center appeared to be shallower. The possible mechanism that was responsible for such behaviors was discussed on the basis of radiation induced variation in the chemical and physical structures.

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