Characterization of silicon photomultipliers in spaceborne high-energy astrophysics

Silicon photomultipliers (SiPMs) have emerged as key photodetectors in gamma-ray and cosmic-ray observatories due to their high photon detection efficiency, excellent timing resolution, and robustness. Their applications extend beyond astrophysics, finding use in medical imaging, LiDAR, and security systems. However, deploying SiPMs in space presents challenges, particularly in mitigating the effects of radiation exposure, which can degrade their performance through increased dark count rates (DCR), reduced photon detection efficiency (PDE), and shifts in breakdown voltage. This thesis focuses on the characterization of SiPMs for high-energy astrophysics, with an emphasis on their performance before and after irradiation. I evaluated under standard condition Near Ultraviolet High Density (NUV-HD) "lowCT" SiPM models produced by Fondazione Bruno Kessler (FBK) with sizes of 1 × 1 mm2 (with15 μm cell pitch) and 3 × 3 mm2 (with 40 μm cell pitch). Moreover, I studied NUV-HD "MT" SiPM models produced by FBK and Broadcom with sizes of 1 × 1 mm2 (with 15 μm, 25 μm and 40 μm cell pitch), and of 6 × 6 mm2 (with 40 μm cell pitch). I also evaluated the performance of the NUV-HD-lowCT technology after being subjected to the effects of Ionizing and Non- Ionizing Energy Loss (NIEL and IEL) damage. In particular I tested SPADs and SiPMs of 1x1 mm2 with cell pitch 15 and 40 μm after proton irradiation with fluence up to 1 × 10 11 p/cm2, and SiPMs of 3x3 mm2 with cell pitch of 15, 25 and 40 μm after X-ray irradiation between 69 and 100 kGy. My results are in agreement with the evaluation of the effects of NIEL and IEL damage on SiPMs reported in literature for space application and provide insights for the design of future solutions aimed at mitigating SiPMs and SPADs performance degradation.