Scintillation properties of O 1/spl times/1 Inch/sup 3/ LaBr/sub 3/: 5%Ce/sup 3+/ crystal

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Abstract
The scintillation properties of the first large O 1/spl times/1 inch/sup 3/ LaBr/sub 3/:5%Ce/sup 3+/ scintillator were studied under /spl gamma/-ray excitation. This crystal is a LaBr/sub 3/:5%Ce/sup 3+/ 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/spl times/0.3/spl bsol/,/spl times/0.5 inch/sup 3/ unpacked crystal. The highest light yield of 21500/spl plusmn/2200 photoelectrons per MeV (60500/spl plusmn/6000 photons per MeV) of absorbed /spl gamma/-ray energy was measured for the unpacked crystal-compared to 16800/spl plusmn/1700 photoelectrons per MeV for the O1/spl times/1 inch/sup 3/ sample. At room temperature the scintillation decays with a decay time of 16/spl plusmn/1 ns. The 0.4/spl times/0.3/spl times/0.5 inch/sup 3/ 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/spl times/1 inch/sup 3/ 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 /spl gamma/-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 LaBr/sub 3/:5%Ce/sup 3+/ scintillator.

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