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

The effects of Co-60 gamma-irradiation on six Phi 2.54 x 2.54 cm(2) CsI(Tl) crystals, grown by the Kyropoulos technique, have been studied. The scinti llation light output and radiation-induced optical absorption spectra of th ese crystals have been measured over a wide range of gamma-ray doses. A hig h-Tl concentration always reduces radiation-tolerance and scintillation lig ht output. A group of six distinct absorption bands in the 350-600 nm regio n, referred to as the sextet band, and one infrared band peaked at 840 nm w ere observed in all samples following gamma-irradiation. Arguments are made that the 840 nm band and the sextet band induced by gamma-irradiation are the F-A and L bands, respectively. (C) 1999 Elsevier Science B.V. All right s reserved.