Study of LaBr3 crystals coupled to photomultipliers and avalanche photodiodes

The performance of several BrilLanCetrade LaBr₃ crystals with the size of O6 times 6 mm² up to O38 times 38 mm² were studied coupled to the XP5212 and R6231MOD photomultipliers and in case of the small crystals, coupled also to large area avalanche photodiodes of Advanced Photonix, Inc. First, several photomultipliers of Photonis and Hamamatsu were compared in the work with LaBr₃ to select the best one, not affecting energy resolution, besides the photoelectron statistics. The light output and energy resolution for 662 keV gamma rays from ¹³⁷Cs source were measured for all crystals. Moreover, for some of them, the non-proportionality of the light yield and energy resolution versus gamma rays energy were measured and the intrinsic resolution of the crystals was calculated. For the smallest crystals of O6 times 6 mm² further comparative tests with LAAPD were carried out.