The SiPM photodetector of the ePIC dual-radiator RICH at the EIC: overview and beam test results

The dual-radiator RICH (dRICH) detector of the ePIC experiment at the upcoming Electron-Ion Collider (EIC) will use silicon photomultipliers (SiPMs) for single-photon detection of Cherenkov light. Several novel INFN driven modular prototype photodetections units (PDUs) have been constructed, each integrating 256 SiPMs, cooling infrastructure and front-end electronics. To achieve a large area coverage, eight PDUs were assembled totalling 2048 readout channels; the full system was then tested at the CERN-PS T10 beamline. The system operated reliably under realistic conditions, and particle identification performance was validated over momenta ranging from 2 to 11 GeV/c using different radiator configurations. Complementary to the testing of sensor on the beam test lines, R&D is also ongoing to ensure consistent performance under radiation exposure. In-situ annealing methods using forward-bias heating have been developed to recover radiation damage of SiPMs. These techniques proved effective, with a recovery of radiation-induced damage up to 97-98% as observed in reducing the dark current. The effects of these procedure on the photo-detection efficiency of the sensors was also tested. Through repeated annealing cycles at different temperatures, a yellowing of the SiPM window has been noticed in the 175° batch, the origin of this effect is still under investigation.