Radiation Damage of GSAG:Ce Crystals with Codopants under Gamma-Ray Irradiation

Gadolinium scandium aluminum garnet scintillator crystals (GSAG:Ce) with Ca2+, Mg2+, and Li+ co-dopants are grown by the Bridgman method under reducing atmosphere. Crystals are irradiated with a Co-60 gamma-ray source to 10 kGy and 50 kGy doses for evaluation of the radiation hardness. A wide absorption band peaking at around 620 nm is observed in all as-grown uncodoped GSAG:Ce crystals. Air annealing at high temperatures and introduction of codopants result in elimination of this absorption band and improvement of transmittance in the visible range. The nature of the color center at approximate to 620 nm is discussed. GSAG:Ce crystals codoped with Li+ and Mg2+:Li+ combine both high transmission and least radiation damage.