The SiPM readout plane for the ePIC-dRICH detector at the EIC: Overview and beam test results

Abstract

The dual-radiator RICH detector of the ePIC experiment at the future Electron-Ion Collider will make use of SiPM sensors for the detection of Cherenkov light. The photodetector will cover $\approx$3 m² with 3 $\times$ 3 mm² pixels, for a total of more than 300k readout channels and will be the first application of SiPMs for single-photon detection in a HEP experiment. SiPMs are chosen for their low cost and high efficiency in magnetic fields ($\approx$1 T at the dRICH location). However, since they are not radiation hard, careful testing and attention are required to preserve single-photon counting capabilities and maintain dark count rates (DCR) under control over the years of running of the ePIC experiment. We present an overview of the ePIC-dRICH detector system and the current status of the R&D performed for the operation of the SiPM optical readout subsystem. Special attention will be paid to the recent results of the beam test of a prototype SiPM readout plane with a large area consisting of a total of up to 2048 3 $\times$ 3 mm² sensors. The prototype photodetector is modular and based on a new EIC-driven photodetection unit (PDU) developed by INFN, which integrates 256 SiPM pixel sensors, cooling and Time to Digital Converter (TDC) electronics in a volume of $\approx$5 × 5 $\times$ 14 cm³. Several PDU modules were built and successfully tested with particle beams at CERN-PS in October 2023 and May 2024. The data were collected with a complete chain of front-end and readout electronics based on the ALCOR chip, developed by INFN Torino.