Radiation hardness and annealing study of neutron-irradiated silicon photomultipliers

Silicon photomultipliers (SiPMs) are semiconductor photodetectors increasingly used in high-energy physics experiments. In the planned upgrade of the Large Hadron Collider beauty (LHCb) experiment, they are considered to be used to detect Cherenkov photons in the Ring Imaging Cherenkov (RICH) detectors. In this application, the biggest drawback of current SiPMs is their susceptibility to radiation damage, where the dark count rate (DCR), typically on the order of 105 Hz/mm2 at room temperature, significantly increases proportionally with the irradiation fluence, which hinders the single photon detection beyond fluence of 109 neq/cm2. In this work, 3 x 3 mm2 SiPMs from different producers and cell sizes, Hamamatsu (50 mu m, S13360-3050PE), Ketek (25 mu m, PM3325-WB and 50 mu m, PM3350-EB), AdvanSiD (40 mu m, NUV3S-P and RGB3S-P), SensL (35 mu m, MicroFJ-30035), a 3.7 x 3.7 mm2 SiPM from Broadcom (30 mu m, AFBR-S4N44C013), and a 1 x 1 mm2 SiPM from SensL (35 mu m, MicroRA-10035) were characterized. The SiPMs were irradiated at the Jo & zcaron;ef Stefan Institute TRIGA nuclear reactor with fluences from 109 neq/cm2 up to 1013 neq/cm2. The main objective was to determine the temperature at which irradiated SiPMs can still meet minimal performance requirements in future RICH detectors. The influence of the high-temperature annealing on SiPM performance post-irradiation was also investigated. For the SiPM characterization in all the cases, current-voltage (I-V curve) measurements, DCR measurements, and waveform analysis, including single photon time resolution (SPTR), were carried out at controlled temperature steps from room temperature down to the liquid nitrogen temperature. As a result, through a combination of annealing and cooling, 2 of the SiPMs withstood the highest irradiation fluence of 1013 neq/cm2 with an SPTR of about 200 ps.