Electric Characteristics of Gamma-Ray Irradiated Shielding Window Glass

Abstract

Induced color of shielding window glass of various kinds by γ-ray irradiation is studied. With Co60−1 kc as radiation source, 23°±3°C as irradiation temperature, 105 R/h as exposure dose rate and 105−107 R as total exposure dose, the coloration increases gradually. Volume resistivity of glass and its change by gamma-ray irradiation are measured. 100 V dc is applied to a sheet of glass sandwiched between two electrodes to measure the change of its electric resistance with time. The quantity of induced space charge by radiation is calculated by time integration of the current which is obtained from reciprocal of the resistance. Resistance of high density glass is found to become minimum—hence the current becomes maximum—at the exposure dose of 106 R and increases as the dose increases, but resistance of medium density glass decreases gradually. Change of the resistance is exponential and the charge is always positive at any dose. This testifies that glass is electrized by radiation. On the other hand, linearity is established between the quantity of space charge and the dose in a range of 105 to 4×106 R. This suggests the possibility of the electrization to be utilized for dosimetry. The above not only demonstrates the physical properties of shielding window glass and the effect of radiation on it but seems to help to find the means of preventing the breakdown by radiation of glass.