Timing and energy resolution of new near-UV SiPMs coupled to LaBr3:Ce for TOF-PET

The high light output and fast decay time of LaBr₃:Ce scintillation detectors leads to excellent timing performance. To realize the potential of timing resolution with LaBr₃:Ce we have investigated the performance with SiPMs which enable 1-to-1 coupling to individual crystals, and which have been optimized for the near-UV scintillation light emission of LaBr₃:Ce. Coincidence timing resolution of 100 ps was measured for a 4×4×5 mm³ LaBr₃:30%Ce crystal coupled to a 4×4 mm² NUV-SiPM with very little dependence on temperature in the range of -20° to 20°C. Optimal performance was achieved at an over-voltage of 4.5 V, at which high gain and PDE are achieved. Though saturation was evident at 511 keV, an energy resolution of 8% FWHM was measured after correcting for nonlinearity. We also measured 110 ps for a 4×4×5mm³ LaBr₃:5%Ce crystal and 245 ps for a 4×4×30 mm³ LaBr₃:5%Ce crystal. The poorer measurement for the 30-mm long crystal is due mainly to variations in the timing offset as a function of DOI. The excellent temperature stability, fast risetime, high gain and low noise of the NUV-SiPM make it a practical and highly appealing photodetector for the readout of a LaBr₃:Ce TOF PET detector.