Abstract: Yttrium-doped barium fluoride (BaF₂:Y) is a sub-nanosecond ultrafast scintillator characterized by effective suppression of its slow luminescence component and the ability to grow large, high-optical-quality single crystals, rendering it highly suitable for ultrafast radiation detection applications. Nevertheless, the underlying mechanisms of radiation damage and their dependence on yttrium doping remain poorly understood. We systematically irradiated a series of BaF₂:Y crystals with 0-20.0% Y (in atomic) doping level using γ-rays across a dose range of 10 krad to 10 Mrad. The results indicate that radiation-induced absorption and relative light output loss of crystals exhibit pronounced doping-concentration dependence. Within the 1.0%-7.5% (in atomic) range, both the emission-weighted radiation-induced absorption coefficient (EWRIAC) and relative light output loss of Y-doped crystal are lower than those of the undoped crystal, with optimal performance at 2.0% (in atomic): the EWRIAC values for the fast and slow components are 4.6 m^-1 and 4.0 m^-1, respectively, at 10 Mrad, corresponding to a relative light output loss of ~29%. In contrast, both EWRIAC and relative light output loss of Y-doped crystals exceed those of the undoped crystal at doping levels of 10.0%-20.0%. The emission peaks in the phosphorescence spectra exhibit distinct features: a broadband emission appears in all samples and shows a redshift with increasing Y doping level, while multiple distinct narrowband peaks are observed in Y-doped crystals with their intensity proportion increasing as the Y doping level rises. This study elucidates the influence of Y doping on the radiation damage characteristics of BaF₂:Y crystals, providing key experimental evidence for enhancing the radiation resistance of BaF₂:Y crystals and optimizing doping level design in practical applications.

Key words: barium fluoride, yttrium doping, ultrafast scintillator, radiation damage, radiation-induced absorption, radiation-induced phosphorescence