Influence of Yttrium Concentration on Scintillation Performance of Heavily Y-Doped Barium Fluoride Crystals

Barium fluoride (BaF2) crystal is a unique scintillator with a subnanosecond-fast scintillation component. Previous studies have demonstrated that slow scintillation components in the BaF2 crystal can be effectively suppressed through yttrium (Y) doping. In this study, a large, 10 at% heavily Y-doped BaF2 (BaF2:Y) crystal ingot with a length of up to 250 mm was grown in a vacuum using the vertical Bridgman method. Several series of small samples and a 200-mm-long large BaF2:Y crystal sample were cut from the large BaF2:Y crystal ingot. The actual doping concentration, distribution characteristic along the crystal growth direction, and the effective segregation coefficient ( ${K} _{\text {eff}}$ ) of yttrium in the BaF2 crystal with a 10 at% nominal yttrium doping were analyzed by using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The influence of yttrium concentration on optical transmittance, radioluminescence (RL), fast/slow component ratio (F/S) of light output (LO), light response uniformity (LRU), and so on was systematically investigated. Results reveal that the actual yttrium concentration increases along the growth direction with a ${K} _{\text {eff}}$ of 0.84. Compared to the undoped BaF2 crystal, 10 at% yttrium doping suppresses the intensity of the slow component by a factor of about 10, while the intensity of the fast component decreases to about 1/2 of that of the undoped crystal.