Energy resolution of LaBr_3:Ce in a phoswich configuration with CsI:Na and NaI:Tl scintillator crystals

摘要

We studied the performances of the LaBr_3:Ce scintillator when optically coupled to Nal:Tl and Csl:Na in a Phoswich detector for the R&D phase of the gamma ray calorimeter PARIS (Photon Array for the studies with Radioactive Ion and Stable beams). This detector has the purpose to measure γ-energies in a wide range (100 keV-40 MeV), and it will be used principally as a part of the SPIRAL2 instrumentation at GANILIn this communication we report on the study of the light yield and energy resolution for gamma detection realized by coupling the phoswiches with various photomultiplier tubes, providing different characteristics. We were interested in investigating the possible degradation of the scintillation light produced by the LaBr_3:Ce due to the presence of Nal:Tl/Csl:Na crystals, before being detected on the photocathode. For this purpose we realized all the measurements employing a standard ADC and QDC read-out system leading the possibility to perform a gate-based event selection.In this study we measured an energy resolution of 4.6% with an uncollimated ~(137)Cs source for a 50.8 × 50.8 × 50.8 mm~3 LaBr_3:Ce coupled to a 50.8 × 50.8 × 152.4 mm~3 Nal:Tl. This value is 30% bigger than the energy resolution measured for a 50.8 × 50.8 × 101.6 mm~3 stand-alone LaBr_3:Ce but still in the specifications for the PARIS collaboration physics list.