Radiation damage of CsI(Tl) scintillators: blocking of energy transfer process of Vk centers to Tl+ activators

This paper reports the emission spectra, light output, transmission and decay curves of CsI(Tl) crystals irradiated with gamma rays at different doses, ranging from 1×105 to 5×105 Gy. The crystals were coated with black or white tapes. Significant decreases in the emission spectra and light output values were observed for the crystals coated with white tape as the radiation dose increased. The decrease in the degree of the rising part of the decay curve in the irradiated crystals is attributed to the blocking of the energy transfer processes of Vk lattice disorders, which were produced in irradiated crystals. The scintillation mechanism is affected in the crystal irradiated at 5×105 Gy. However for crystals irradiated below 105 Gy the mechanism process is not altered, and the decrease in the light output is due to internal transmission loss. It was also observed that the damage for irradiation is not permanent and it obeys a bi-exponential function.