Reflectivity and absorption coefficient of a borosilicate glass during 60Co-γ irradiation calculated from data measured by an integrating sphere

Abstract

Before and after 11 kGy 60Co-γ irradiation as well as after 150°C bleaching, reflectivity and absorption coefficient of a borosilicate glass were calculated from the intensity of transmitted light and the intensity of reflected light measured using an integrating sphere. The irradiation induced absorption in the studied wavelength range, while it only made the reflectivity change obviously in the range 4.5–5.6 eV (275–221 nm). The absorption coefficient spectrum and the reflectivity spectrum of the irradiated glass both recovered to a degree after 150°C bleaching. The relative error of irradiation-induced absorption coefficient calculated neglecting reflectivity change was studied, and the relative errors in the studied wavelength range theoretically increase when the thickness of glass sheet decreases, so if irradiation-induced absorption coefficients are studied using a thin glass sheet, reflectivity changes should be considered. The band gap of the glass was studied using Mott and Davis's theory, and it was found to reduce after irradiation, then after 150°C bleaching, it increased but still smaller than the one before irradiation.