Performance of the Compact High Energy Camera SiPM Prototype Front-End Electronics proposed for the Cherenkov Telescope Array

The Compact High Energy Camera (CHEC) is a full-waveform capture camera, designed and proposed for the dual mirror, Schwarzschild–Couder, Small Sized Telescope of the Cherenkov Telescope Array. CHEC-S, the second prototype, is based upon silicon photomultiplier (SiPM) photodetectors optimised for single photon counting and nanosecond timing. The camera liquid-cooled focal plane plate comprises a total of 2048 SiPM pixels organised as 32 independent sensor and front-end electronics (FEE) modules providing event detection and signal digitisation of Cherenkov light flashes. Each module comprises an 8 × 8 tile of SiPM pixels, coupled to a 64-channel preamplifier-buffer followed by a FEE module based around the TARGET chipset, which combines triggering (T5TEA) and waveform capture (TARGET C) functionality. We describe a selection of end-to-end performance tests and results conducted at the University of Leicester in the UK. Testing was performed at single module level focusing on characterising the SiPM photodetectors, optimised preamplifier-buffer and updated CHEC-S FEE readout module. Presented results include single photoelectron response, gain-matching, signal range, electronic channel crosstalk, SiPM angular dependency and optical crosstalk.