Performance of FBK low-afterpulse NUV silicon photomultipliers for PET application

The improvement of the coincidence resolving time (CRT) is one of the key factors for the next generation of positron emission tomography (PET) scanners. Silicon photomultipliers (SiPMs) are strong candidates to substitute photo multipliers tubes because of their compactness, ruggedness and insensitivity to magnetic fields. In order to achieve the best CRT, the SiPM should have high PDE which can be obtained increasing the bias voltage. We recently improved the NUV SiPM technology, with the addition of a new substrate type that provides significantly lower afterpulsing probability (Low-AP). This enables to extend the maximum bias voltage and thus obtain higher PDE. Additionally, we implemented a lower electric field version (Low-F) to reduce the field-enhanced thermal generation components of the dark count rate. In this work we present results of energy and timing resolution for PET application, using LYSO scintillator crystals, and coupled with 3x3 mm2 NUV SiPMs of three types: non-Low-AP, Low-AP and Low-AP + Low-F. All the devices reach very similar energy resolutions, around 9.5 %, and close to the intrinsic limit of the LYSO. Concerning the timing resolution, we found that the Low-AP substrate achieves an improvement of the CRT of 30 ps, confirmed with the Low-F. Using 4x4 mm2 Low-AP SiPMs coupled to 3xs3x5 mm3 and 3.8x3.8x22 mm3 LYSO crystals we obtained CRTs of 130 and 200 ps FWHM, respectively.