TOF Characterization of New MAPD-3NM-II SIPM

Silicon Photomultipliers (SiPMs) have become an integral part of time-of-flight positron emission tomography (TOF-PET) scanners in recent years. Their excellent photodetection efficiency and fast decay time are essential in state-of-the-art timing resolutions, which have enabled improvements in image quality for TOF-PET. However, most SiPMs share a common architecture: an array of single avalanche photodiodes. This design has a limitation: each pixel requires its own quenching resistor and conductive connections, creating inactive regions that reduce the effective detection area. In this paper we explored a new type of SiPMs called the Micropixel Avalanche Photodiodes (MAPD) for the purposes of TOF-PET. These devices utilize buried pixel technology, which minimizes detector dead zones and achieves an almost 100 % fill factor. We evaluated their noise characteristics, energy resolution, and coincidence timing resolution (CTR). Our findings indicate that although the MAPD-3NM-II devices exhibit higher dark count rates, notable optical cross-talk, and a narrower overvoltage range compared to the reference Hamamatsu S14160-3015PS SiPMs, they offer superior energy resolution—improving up to 17 % at 511 keV—while maintaining competitive timing performance at the same overvoltage. In particular, with 3.8×3.8×4 mm3LYSO crystals, the MAPD-3NM-II achieved a CTR of 336 ± 12 ps, a 5% improvement compared to Hamamatsu at the same overvoltage. Despite operating only up to 4.5 V, the MAPD-3NM-II demonstrates strong potential for TOF-PET applications, especially in scenarios prioritizing energy resolution. Further structural optimizations to reduce cross-talk and expand the operable voltage range could make this technology a competitive alternative to established SiPM architectures.