Effects of Bi3+ codoping on the optical and scintillation properties of CsI:Tl single crystals

CsI:Tl single crystals with different Bi3+ concentrations from zero to 0.05 mol% were grown by the vertical Bridgman technique. The effects of Bi3+ codoping on the scintillation properties of CsI:Tl single crystals were investigated, including afterglow level, relative light yield, energy resolution, scintillation decay time and radioluminescence spectra. Afterglow suppression by Bi3+ codoping was confirmed, but it resulted in a considerable decrease of light yield and energy resolution. The deterioration of light yield was ascribed to the self-absorption effect induced by Bi3+ ions. The physical mechanism and role of Bi3+ ions in afterglow suppression were proposed.