Performance and stability of the prototype stereoscopic water Cherenkov detector array experiment

The Stereoscopic Water Cherenkov Detector Array (SWCDA) is a next-generation ground-based experiment designed for high-energy gamma-ray astronomy in the 100 GeV–100 TeV range. Utilizing a multi-layer detector structure, the SWCDA enables three-dimensional observation of both lateral distribution and longitudinal development of cosmic-ray air showers. Combined with a high-altitude observation site, this configuration achieves low energy thresholds and high sensitivity. The primary scientific objectives include observing extragalactic sources such as blazars, active galactic nuclei (AGNs and AGN flares), and gamma-ray bursts (GRBs), as well as transient phenomena in the 100 GeV – 100 TeV energy range. Each stereoscopic water Cherenkov detector consists of water containers, support structures, and photomultiplier tubes (PMTs), with key technologies involving optical isolation and multi-layer configuration. To validate the SWCDA concept and its basic performance, a prototype array covering 100 m2 (comprising 32 detector units) was deployed within the Tibet AS𝛾 experiment array in December 2024. Operating in conjunction with the existing Tibet AS𝛾 experiment, this prototype SWCDA leverages the established Tibet AS𝛾 observational results to verify and benchmark the SWCDA’s detection capabilities.