Suppression of afterglow in RbI:Tl scintillator by co-doping

RbI:Tl and RbI:Tl co-doped with Sb, Bi, Sm, and Yb were prepared using the vertical Bridgman-Stockbarger technique, and the effects by co-doping on photoluminescence (PL) and scintillation properties were researched. Only the sample co-doped with Bi showed reduction of PL quantum yield owing to self-absorption induced by Bi3+, and the others showed almost the same values. The afterglow levels at 20 ms after X-ray irradiation for 2 ms were reduced from 6000 ppm to 4300 and 4800 ppm in Sb- and Bi-co-doped samples, respectively. Sb and Yb co-doping increased the light yield (LY), and the highest LY of 7800 photons/MeV among the samples were obtained by co-doping Sb from results of the pulse height spectra under Cs-137 gamma-ray (662 keV) irradiation.