Development of an ASIC readout for nEXO’s large-scale SiPM testing*

The nEXO experiment will search for neutrinoless double-beta decay in xenon-136 and reach a half-life sensitivity of 1.35x10²⁸yr. nEXO’s photon detection surface will achieve an energy resolution <1% by using 4.6m² of silicon photomultipliers (SiPMs). Individual 6x6 mm² SiPMs from two different suppliers have been shown to meet the detector requirements, and large-scale testing of recently available 1x1 cm² SiPMs is being planned. SiPM tiles for the detector will be made of 96 SiPMs on a substrate, with custom Application Specific Integrated Circuits (ASICs) to readout and digitize signals. Front-end cryogenic ASICs have been successfully used for charge readout in ProtoDUNE and SBND; materials and expertise from these other experiments are being repurposed as a prototype readout system for nEXO. In this talk I will discuss the development of this prototype ASIC readout system including key components and necessary adaptations required for use with large-scale SiPM testing.