Scintillation properties of O 1×1 Inch3 LaBr3: 5%Ce3+ crystal

The scintillation properties of the first large O 1×1 inch³ LaBr₃:5%Ce³⁺ scintillator were studied under γ-ray excitation. This crystal is a LaBr₃:5%Ce³⁺ standard product from Saint Gobain company. The sample was cut and polished by the manufacturer from a larger size crystal boule. It was then assembled in a cylindric aluminum case with a front glass window. The results are compared with those recorded with a 0.4×0.3/,×0.5 inch³ unpacked crystal. The highest light yield of 21500±2200 photoelectrons per MeV (60500±6000 photons per MeV) of absorbed γ-ray energy was measured for the unpacked crystal-compared to 16800±1700 photoelectrons per MeV for the O1×1 inch³ sample. At room temperature the scintillation decays with a decay time of 16±1 ns. The 0.4×0.3×0.5 inch³ unpacked crystal-coupled to photomultiplier tube (Hamamatsu R1791) and measured at 662 keV-exhibited an energy resolution of 2.8%, better than the one of the O1×1 inch³ crystal (3.1%). Special attention was devoted to energy and temperature dependencies of scintillation properties: the results show a good proportionality for light output versus γ-ray energy. The light output deviates from the linear response of 5% between 20 keV and 2 MeV. Furthermore temperature dependency of gamma-ray excited decay time (80-700 K) does not indicate the presence of thermal quenching from the cerium 5d state. These characteristics suggest a broad range of applications for the LaBr₃:5%Ce³⁺ scintillator.