Light Yield Non-Proportionality and Energy Resolution of Praseodymium Doped LuAG Scintillator

Scintillation properties of praseodymium doped LuAG have been investigated. The crystal is a dense (6.7 ${\rm g}/{\rm cm}^{3}$) scintillator with a short decay time around 20 ns and wavelength emission spectrum peaked at 310 nm. The tested sample was 10 mm $\times \, $ 10 mm $\times \, $5 mm cuboid, polished on all surfaces. The dopant concentration amounts to 0.23 mol%. A light yield of ${16000}{\pm 1600}~ {\rm ph}/{\rm MeV}$ was measured using high sensitivity (13.7 $\mu {\rm A}/{\rm lmF}$) Photonis photomultiplier (PMT) XP5500B. High quantum efficiency of this PMT (35%) allowed us to register ${5600}{\pm 400} ~{\rm phe}/{\rm MeV}$ using 12 $\mu {\rm s}$ shaping time in the spectroscopy amplifier. The measured energy resolution was equal to ${5.0}{\pm 0.1}\%$. Response of LuAG:Pr to $\gamma $-rays was found to be proportional over wide energy range. Deviation from proportionality does not exceed 10% at 16.6 keV. This results in good intrinsic energy resolution of LuAG:Pr amounting to ${3.0}{\pm 0.3}\%$ , measured with 662 keV $\gamma $-rays from $^{137}{\rm Cs}$.