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Gamma radiation effects on some optical glasses

A study of the effects of Co60 gamma radiation on the transmission and index of refraction of several optical glass types is presented. The glasses have indices (nd) in the range of 1.486 to 1.581. They are multicomponent glasses from different families. UV-transmitting glasses having lower impurity levels are compared to the standard optical glasses. Transmission spectra in the range of 190 - 820 nm were recorded after exposure to various doses of radiation up to 725 krad. In all samples, the UV transmission edge shifted towards longer wavelengths and the visible transmission decreased. Differences in transmission spectra were observed depending on the glass composition and impurity levels. Fading curves of some glasses irradiated with different doses of gamma radiation were studied at room temperature and after heat treatment of 400 degree(s) C or 500 degree(s) C. At room temperature a slight recovery with time was observed. One fluorophosphate glass type recovered nearly completely after heating for a few hours. The effects of impurities on recovery is discussed.