ADVANTAGES AND LIMITATIONS OF LSO SCINTILLATOR IN NUCLEAR-PHYSICS EXPERIMENTS

Light yield, light pulse shape due to gamma-rays and alpha-particles, energy and time resolutions for three different samples of the LSO scintillator were studied using an XP2020Q photomultiplier acid an S3590-03 photodiode. Light yields of 4200+/-200 phe/MeV and 18500+/-900 e-h pair/MeV;I were measured for the PM tube and the photodiode, respectively. The light pulse shape exhibits a pure exponential decay with a time constant of 47.2+/-1.3 ns for both gamma-rays and alpha-particles. Energy resolutions of 10% and 14.6% for the 662 keV gamma-rays from a Cs-137 source were obtained for the photomultiplier and the photodiode readout, respectively. A time resolution of 180 ns was observed for Co-60 y-rays at 1 MeV threshold and 400 ps for 100 keV threshold. The study confirmed a number of advantages of the LSO scintillator for nuclear physics experiments, however, for small size samples. For larger volumes the natural radioactivity of the LSO, about 300 counts/s/cm(3), may limit possible applications. The high number of e-h pair produced in the photodiodes makes LSO very attractive for small compact scintillation probes.