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

Nd and Tm-doped Lu-admixed BaY
₂
F
₈
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 Tm
³⁺
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
_0.8
Lu
_1.2
F
₈
single crystal reached nearly the same scintillation efficiency as the LaF
₃
: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.