Speaker
Description
Yttrium-doped barium fluoride (BaF2:Y) is attractive for high-rate radiation detection because Y doping suppresses the slow self-trapped-exciton emission while retaining the ultrafast core-valence luminescence of BaF2. Its practical use, however, requires both scalable crystal growth and control of position-dependent light collection. We address these requirements through two complementary studies using separate large-diameter BaF2:Y ingots. In the first study, measured thermophysical properties and thermal-stress analysis were used to define allowable growth and cooling conditions for BaF2 with Y doping concentration up to 15 at.%. An axial temperature gradient of 9 °C∙cm-1 and a temperature-dependent segmented cooling schedule enabled the crack-free growth of a 4-inch-diameter, 8-cm-long crystal. The crystal maintained high visible-range transmittance over most of the measured region, although the tail-end optical quality requires further improvement. In the second study, transverse light-response uniformity was investigated using 10 × 10 × 55 mm3 bars cut from an ingot with a nominal Y concentration of 10 at.%. LA-ICP-MS showed no measurable macroscopic radial Y gradient within the selected region, yet dual-ended measurements revealed a clear position dependence in the collected response. Quotient analysis showed limited light-yield-related asymmetry and substantially larger transport-related asymmetry. Measurements under different wrapping conditions established sensitivity to the optical boundary. Under the fixed inputs used in optical-only Geant4 simulations, surface and interface losses exceeded bulk absorption. Together, these results connect thermal-field control, composition assessment and optical-boundary engineering in the development of large BaF2:Y scintillators with controlled detector response. Future work will validate the spatial and temporal response of longer crystals using controlled optical packaging and detector-representative readout conditions.
