RICH position scans of the single-photon response of SiPM arrays, using multi-channel readout electronics with 25 ps precision

The identification of charged particles in LHCb relies on the detection of single Cherenkov photons, which requires photon sensors with excellent spatial resolution, timing precision, and low noise. The project focused on the performance evaluation of silicon photomultipliers (SiPMs) as potential replacements for the Multi-Anode Photomultiplier Tubes (MAPMTs), the current photodetectorss in the RICH system. As a preparatory step, detailed position scans of a MAPMTs were performed to validate the scanning setup and provide reference measurements. Subsequently, an 8×8 channel SiPM array was characterised through laser position scans, threshold scans, and timing measurements using a FastIC–PicoTDC readout chain. The studies assessed single-photon sensitivity, gain, dark count rates, occupancy, and uniformity across the array. The results demonstrate that SiPMs can achieve precise single-photon detection and picosecond-level timing, confirming their suitability as candidates for future upgrades of the LHCb RICH detectors.