INVESTIGATION OF GSO, LSO AND YSO SCINTILLATORS USING REVERSE AVALANCHE PHOTODIODES

The performance characteristics of GSO, LSO and YSO scintillators coup led to new ''reverse'' avalanche photodiodes (ReAPD) were investigated and compared to those of EGO. The energy and timing resolutions were measured as a function of photodiode bias and amplifier shaping time c onstant While the performance of EGO and GSO is critically dependent o n these operating parameters because the signal-to-noise ratio is degr aded by the dark and excess noise from the ReAPD, that of the high-lum inosity LSO and YSO scintillators is not The energy resolution in thes e crystals is demonstrated to be limited by the scintillator resolutio n. Further analysis indicates that excess variance in the number of ph otons generated in the crystal is mostly responsible for their disappo inting energy resolution. This feature appears to be related to the im portant non-linearity in scintillation response as a function of incid ent gamma-ray energy observed for these high-luminosity scintillators.