SiPM photosensors for the ePIC dual-radiator RICH detector at the EIC

SiPMs are the baseline photodetector technology for the dual-radiator Ring-Imaging Cherenkov(dRICH) detector of the ePIC experiment at the future Electron-Ion Collider (EIC). SiPMs offersignificant advantages being cheap devices, highly efficient and insensitive to the high magneticfield (∼ 1 T) at the expected location of the sensors in the experiment. However, they are notradiation tolerant and one has to test whether the increase in dark count rate (DCR) can bemitigated to maintain single-photon performance with current SiPM technology in a moderatelyhostile radiation environment of < 10 11 1-MeV equivalent neutrons/cm 2 (n eq ). Several options areavailable to maintain the DCR to an acceptable rate (below ∼ 100 kHz/mm 2 ) by reducing the SiPMoperating temperature and by recovering the radiation damage with high-temperature annealingcycles. Moreover, by utilising high-precision TDC electronics the use of timing information caneffectively reduce background due to DCR. We present the current status of the R&D and theresults of studies performed on significant samples of commercial and prototype SiPM sensors.The devices have undergone proton irradiation in two campaigns aimed at studying the deviceperformance with increasing NIEL doses up to 10 11 1-MeV n eq , the device recovery with long high-temperature annealing cycles and the reproducibility of the performance in repeated irradiation-annealing cycles. In October 2022 the sensors were mounted inside the dRICH detector prototypeand successfully tested with particle beams at the CERN PS accelerator. The results are obtainedwith a complete chain of front-end and readout electronics based on the first 32-channel prototypesof the ALCOR chip, a new ASIC designed for SiPM readout.