Evaluation of GAGG:Ce scintillators for future space applications

Cerium-doped Gd₃(Ga, Al)₅O₁₂ (GAGG:Ce) is a promising novel scintillator for gamma-ray detectors. While GAGG:Ce has already been implemented in various commercial products, its detailed characteristics and response to high-energy particles and gamma rays remain unknown. In particular, knowledge is lacking on the radiation tolerance of this scintillator against the gamma-ray and proton irradiation expected in future space satellite mission applications. In this study, we first investigate the light-yield energy dependence, energy resolution, decay time, radiation tolerance, and afterglow of GAGG:Ce scintillators under various temperature conditions. We find excellent linearity of ±3% between light yields and deposited energy over a wide range of 30-1836 keV; however, a light-yield deficit of more than 10% is observed below 30 keV of deposited gamma ray energy. We confirm that the temperature dependence of the light yield, energy resolution, and scintillation decay time is within 5-20% between -20 and 20C. We also evaluate the GAGG:Ce activation characteristics under proton irradiation and the light-yield degradation by accumulated dose using a ⁶⁰Co source. Moreover, we successfully identify various gamma-ray lines due to activation. Finally, we find a substantial afterglow for GAGG:Ce scintillators over a few hours; such an afterglow is only minimally observed in other scintillators such as CsI:Tl and Bi₄Ge₃O₁₂ (BGO). However, the afterglow can be substantially reduced through additional co-doping with divalent metal ions, such as Mg ions. These results suggest that GAGG:Ce is a promising scintillator with potential application in space satellite missions in the near future.