Study on the performance of photomultiplier tube in liquid scintillator detector

The SWCDA (Stereoscopic Water Cherenkov Detector Array) represents a next-generation ground- based observatory, conceived as a significant evolution of traditional Extensive Air Shower (EAS) arrays. Its primary goal is to improve gamma-ray detection sensitivity by a factor of ten while pushing the energy threshold as low as 100 GeV. The system integrates two complementary components: an array of liquid scintillators (LS) and a stereoscopic array of water Cherenkov detectors. Within the LS subsystem, scintillation photons are channeled to photomultiplier tubes (PMTs), which transduce optical signals into measurable electrical pulses. Consequently, the PMT’s characteristics critically influence the detector’s overall efficiency and resolution. To assess candidate PMTs for this application, we constructed a dedicated test setup capable of characterizing key parameters: high-voltage response linearity, operational dynamic range, and Transit Time Spread (TTS). Five PMT types sourced from North Night Vision Science Technology Research and HAMAMATSU Photonics—were evaluated under identical conditions. Based on a balanced assessment of dynamic range and timing precision (TTS), the HAMAMATSU R4125- 6280 emerged as the optimal choice for integration into the LS array.