Design of the ASIC readout scheme for the JUNO-TAO experiment

Abstract

The Taishan Antineutrino Observatory (TAO) has been proposed to precisely measure the reactor antineutrino spectrum with an energy resolution better than 2% at 1 MeV. It can provide a reference spectrum to the Jiangmen Underground Neutrino Observatory (JUNO) to enhance its sensitivity to the neutrino mass ordering measurement. In addition, TAO can also provide a benchmark to verify the nuclear database and conduct new physics searches. The TAO detector is a 2.8-ton liquid scintillator detector equipped with a 10 m2 silicon photomultiplier (SiPM) array to collect the light with a coverage of 94%. The TAO detector will be operated at -50 °C to suppress the SiPM dark count rate. In this work, we report on the design of a readout system based on the KLauS6 chip to handle the outputs from the SiPMs, which exhibits advantages of high granularity (potentially good particle identification) and large dynamic range. A dedicated mockup system has been built and its performance carefully evaluated both at room and low temperatures, measuring gain, charge linearity, signal-to-noise ratio, and dead time. The testing results show that the performance of this system can meet the requirements of TAO. However, an abnormal increase in current at 1.8 V analog power of the KLauS6 chip has been observed when operating it at temperatures below -20 °C, resulting in a potential risk on the long-term reliability. Therefore, the KLauS-based readout design is considered as an alternative option for the future upgrading of the TAO's readout system. This study also provides a reference and guidance for other relevant applications.