Characterization of a Sr co-doped LaBr[formula omitted]:(Ce) detector for [formula omitted]-ray spectroscopy

Abstract

In this paper we report about thorough characterization of Sr2+ co-doped LaBr3:Ce single crystal of dimensions 1.5′′×1.5′′. The properties studied include energy resolution, timing resolution, internal activity, intrinsic photo-peak efficiency and linearity over a range of 661.7 keV to 4.43 MeV using multiple γ-ray sources. While characteristics of regular Ce doped LaBr3 and its superiority over other inorganic crystals are now well established, the possibilities of improving them further by Sr2+ co-doping is a fledgling field of research. The primary aim of this work is to check whether addition of Sr by the manufacturer results in better performance than standard Lanthanum Bromide doped with Cerium. The results obtained were compared with measurements with standard LaBr3:Ce of similar size. The energy resolution of the co-doped crystal at 661.7 keV is same as that of a regular crystal of similar size and does not show any significant improvement. However, the timing resolution is found to be inferior to a similar LaBr3:Ce crystal. This is in conformity with reported measurement of spectral shape showing lengthening of decay time. Our result on energy resolution is at variance with previously published reports on very small volume co-doped crystals. Two very recent measurements with larger volume Sr co-doped crystals ( 1.5′′×1.5′′ and 3.0′′×3.0′′ ) have also shown improvement in energy resolutions. We conclude that more measurements are probably required to proclaim Sr2+ co-doped LaBr3 as significantly superior to LaBr3:Ce, irrespective of the shape, size and PMTs used. The observed improvement in energy resolution has to be consistent regardless the volume and use of PMTs or APDs and is required to be significantly better to compensate for the deterioration in timing.