Radiation-induced Defects in Lead Silicate Glass

IN attempts to explain the process of coloration of glass by γ-radiation, it was suggested in a previous communication 1 that electrons are trapped in defects to form colour centres. Not only do these defects already exist in glass but they can also be created by exposure to radiation. If defects could not be so created, it would be expected that the concentration of colour centres, as measured by the optical density, would increase exponentially to a saturation value at a certain dose. In practice, it is found that the optical density increases exponentially with dose up to about 10 5.5 rads, but thereafter the increase is linear. This effect is shown in Fig. 1, which is divided into two sections having different scales for dose, the first section illustrating the exponential portion and the second the linear portion of the curve.