Optimization of Single Photon Avalanche Diode array detectors with a custom simulator

Single Photon Avalanche Diodes (SPAD) are promising candidates for fast timing applications in high energy physics (HEP) and positron emission tomography (PET) for their excellent timing resolution and detection efficiency [1], [2]. However, as with many technologies, designing the best SPAD array involves many trade-offs. To facilitate the selection of optimal parameters for a specific application, as well as study the behavior of SPAD arrays, we developed a custom simulator. The size and number of individual SPAD cells affect the fill factor, which in turn changes the photon detection probability, the photon statistics and the dynamic range. However, the search for optimal pixel and array size has only been investigated with preexisting geometries; here we present a detailed parametric study. Fill factor is, as expected, a driving force for high coincidence time resolution (CTR), as is the choice of applied bias. The best combination of parameters with LYSO crystal leads to a CTR of 120 ps FWHM. The addition of prompt photons to the scintillation process could significantly improve CTR, reaching 34 ps FWHM with 500 prompt photons.