Studies of radiation tolerance and optical absorption bands of CsI(Tl) crystals

The effects of 60Co γ-irradiation on six PHI2.54x2.54 cm2 CsI(Tl) crystals, grown by the Kyropoulos technique, have been studied. The scintillation light output and radiation-induced optical absorption spectra of these crystals have been measured over a wide range of γ-ray doses. A high-Tl concentration always reduces radiation-tolerance and scintillation light output. A group of six distinct absorption bands in the 350-600 nm region, referred to as the sextet band, and one infrared band peaked at 840 nm were observed in all samples following γ-irradiation. Arguments are made that the 840 nm band and the sextet band induced by γ-irradiation are the FA and L bands, respectively. (author)