ASIC Testing for Charge Readout and SiPM Array Testing in the nEXO Experiment

The nEXO experiment aims to detect neutrinoless double beta decay (0νββ) using a 5-tonne liquid xenon time projection chamber (LXe TPC) enriched to 90% in ¹³⁶Xe, with a projected half-life sensitivity greater than 10²⁸ years over a 10-year period. The observation of lepton number non-conserving 0νββ decay would suggest the existence of new physics and require neutrinos to be Majorana fermions. This talk will provide an overview of the nEXO experiment and highlight tests conducted at Stanford on prototype cryogenic application-specific integrated circuits (ASICs) designed for ionization charge readout in LXe. Additionally, progress on SiPM arrays utilizing external electronics will be discussed. Finally, we will describe the construction of a 64-kg LXe TPC, designed to accommodate four charge-readout modules, and its role in investigating cross-talk between the charge tiles as well as its impact on energy resolution. These prototypes are critical to the nEXO experiment, guiding key design decisions to optimize signal readout, reduce noise, and enhance the detector’s sensitivity to neutrinoless double beta decay.