Resistance to γ irradiation of LaBr3:Ce and LaCl3:Ce single crystals

LaBr3:Ce (Brillance 380) and LaCl3:Ce (Brillance 350) both exhibit a very good energy resolution and energy linearity response. They are also more sensitive to γ-rays than NaI(Tl) detectors, due to their higher density. m of this work is to determine the behaviour of those new single crystals in comparison with NaI(Tl) under severe γ-ray irradiation. Therefore we have irradiated three 25 by 25 mm cylinder crystals encapsulated in air-tight aluminium housing with 60Co beam. Crystals were tested as stand-alone material not to test the impact of radiation to our photomultiplier tube (PMT). Only encapsulated crystals (alone, without PMTs) were irradiated during several periods to achieve the final 3.4 kGy integrated dose. Intermediate measurements of 137Cs spectrum were done in order to evaluate the impact of the dose on the studied crystal performances. The radiation hardness of LaBr3:Ce and LaCl3:Ce was then compared to NaI(Tl). w in this paper that up to 3.4 kGy no permanent modification of the energy resolution nor colour change is observed for LaBr3:Ce and LaCl3:Ce crystals. The light output also seems quite stable. This is in stark contrast with the behaviour of NaI:Tl which exhibits continuously decreasing light output, colour change and worsening of energy resolution for doses above 5 Gy.