Investigating CeBr3 for ultra-fast TOF-PET detector designs

Cerium Bromide (CeBr3) has high light output, a short decay time, and a very fast rise time — a combination of properties that should result in excellent timing resolution. Here we present results from several productions of Cerium Bromide (CeBr3) pixels investigated for use in the design of an ultra-fast TOF-PET detector. Compared to LSO/LYSO, CeBr3 also has the potential to be much less expensive when manufactured in large quantities because of the combination of less expensive raw materials and low melting point, even when considering the additional volume required for similar sensitivity. The CeBr3 productions were cut into pixels, all with a cross section of 4x4 mm2 and an assortment of lengths from 3mm to 30mm, and each pixel surface was fully polished. Measurements of rise time and decay time, energy resolution and timing resolution using a PMT readout and also a SiPM readout were performed. The effect of pixel length on the temporal properties of the scintillator emission and timing performance was studied. New productions of CeBr3 have an improved performance, particularly for longer pixels due to less self-absorption and self-trapping. Coincidence timing resolutions of 69ps to 126ps were measured over a range of pixel lengths from 5mm to 15mm using FBK NUV-HD SiPMs; with a PMT readout the coincidence timing resolutions varied from 96ps to 143ps over the same range of crystal lengths. Our goal is to use these measurements to determine how best to design a CeBr3-based detector, and these results also serve as a benchmark for evaluating of future advancements in CeBr3 production.