Luminescence and Scintillation Properties of VUV Scintillation Crystals Based on Lu-Admixed BaY $_{2}$ F $_{8}$

Nd and Tm-doped Lu-admixed BaY₂F₈ crystals were grown by micro-pulling-down method. Lu was added to modify the host matrix to suppress the unwanted energy transfer from exciton levels to the Tm³⁺ 4f-levels. It was found that low Tm and Nd codoping does not bring much improvement of the scintillation performance and that 1%Nd-doped BaY_0.8Lu_1.2F₈ single crystal reached nearly the same scintillation efficiency as the LaF₃:Nd8% one, which is known as a suitable candidate for a VUV scintillator. It is clear there is a considerable room for an optimization of this material by changing the Lu/Y ratio and increasing the content of Nd. On the other hand, very high Tm concentrations (around 20%) suppress the excitonic emission (and also the 4f-4f emission) while increasing the 5d-4f one significantly.