A Consideration on the Accumulation of Electric Charge in Glass by γ-Ray Irradiation

Abstract

The authors reported the thermally stimulated current (TSC) and thermo luminescence (TL) of γ-irradiated radiation shielding glass in I. C. G., 1966. The present paper is concerned with the details of the report. From the data, it has been clarified that the thermal functions of negative and positive charges which are produced in the surface region by γ-irradiation are as follows.(1) When the glass surface is irradiated by X- or γ-ray from one direction, the surface is positively charged because electrons produced by photon-electric or Compton effect have a momentum to the inner part of glass.(2) Therefore, it is considered that thin electric double layer is produced in the surface layer of which field strength depends on the γ-ray dose, initial photon energy and on the electrical property of the glass.(3) By heating the irradiated glass, the trapped electrons released in the vicinity of the electric double layer drift forward to the positively charged surface, because TSC is observed at lower temperature than temperature of positive ion conductivity. According to the content of luminescent impurity atoms, TL is also observed. The mechanism of electric breakdown of shielding glass is clarified when it is exposed by γ-ray for a long time. The above considerations, showed that thermal annealing is an important process to prevent the accumulation of electric charges in the glass.