Speaker
Description
PMTs have long dominated fast timing experiments for their excellent resolution and stability, but their high cost and limited availability have driven interest in SiPMs. SiPMs are being increasingly used, but when grouped into arrays to read large scintillators, their timing is sub-optimal.
This work describes the study of the coincidence time resolution (CTR) of several individual SiPM readily available in the market, from Broadcom, Onsemi and HPK, coupled to a small 3x3x5mm3 cubic LYSO. As timing reference for comparison we used a Hamamatsu PMT, model R9779, assembly H10570, MOD 3, featuring an 8-stage photomultiplier with a bialkali photocathode and a quartz window coupled to a cylindrical LaBr₃(Ce) crystal with 1” height and 1” diameter. The intrinsic individual contribution to the CTR of the detectors was evaluated using Na-22 (511keV) and Co-60 radioactive sources, after the signals were digitized using a DRS4 system for time-of-arrival analysis. Intrinsic time contribution to CTR below 100 ps FWHM was demonstrated for several 3 mm and 6mm individual SiPMs coupled to the LYSO cube. The best performers were chosen to develop larger arrays of SiPM (either with 6x6 mm2 SiPM pixels and 3x3 mm2 SiPM pixels), with variations of time-pickup schemes.
Comparison with newer PMTs models, aimed to replace the H10570 reference, will be presented as well.
Results scaled up of these arrays to build 1” and 2” segmented SiPM boards to couple to the larger LaBr₃(Ce) scintillators, will be presented.
We will continue this work in order to achieve a more complete
analysis.