Performance of the Mass Testing Setup for Arrays of Silicon Photomultipliers in the TAO Experiment

Modern neutrino physics detectors often employ thousands, and sometimes even hundreds of thousands, of Silicon Photomultipliers (SiPMs). The TAO experiment [1] is a notable example that utilizes a spherical scintillator barrel with a diameter of 1.8 meters, housing approximately 130,000 SiPMs organized into 4,100 tiles. Each tile with size of 5 x 5 cm 2 consists of a 32-SiPM array functioning as a single detector unit. To achieve an unparalleled energy resolution of 2% at 1 MeV within this volume, the SiPMs must possess cutting -edge parameters, including a photon detection efficiency (PDE) exceeding 50%, cross -talk of approximately 10%, and an extremely low dark count rate (DCR) below 50 Hz/mm 2 . Maintaining the setup at a negative temperature of - 50 degrees C is necessary to achieve the desired DCR. This article presents the setup and methods employed to individually characterize the mass of SiPMs across all 4,100 tiles at the specified negative temperature.