Speaker
Description
In gamma-ray astronomy, Water Cherenkov Detectors (WCDs) have been proven by large-scale projects like HAWC and LHAASO to be a highly effective technology for constructing large-area air shower observation arrays. For such arrays, the timing performance of individual detector units is of critical importance to the angular resolution. This study presents the prototype testing of a surface WCD based on the lake concept, designed for future ultra-high-energy cosmic ray (UHECR) and gamma-ray observatories.
The surface detector comprises a film-based bladder filled with purified water, which serves as the Cherenkov medium. This containment film is engineered to provide high mechanical strength and excellent light-tightness. Furthermore, it exhibits a low reflectivity of less than 6% for photons in the 350–750 nm wavelength range. As a result, the 8-inch photomultiplier tube (PMT)—mounted at the base of the detector and facing upwards—predominantly collects direct Cherenkov photons rather than delayed photons reflected along different optical paths. This minimization of scattered light significantly enhances the timing capabilities of the unit. Signal acquisition is performed using a CAEN V1743 digitizer for high-precision waveform analysis.
To systematically characterize the prototype, essential performance metrics such as light yield and time resolution were evaluated. Tests utilizing both vertical and inclined muon incidences across multiple positions revealed an inverse correlation between the measured charge and horizontal distance. This behavior closely mirrors the Geant4 simulations. As a key outcome, the detector unit achieved a remarkable time resolution of better than 2 ns, which provides immense potential for achieving high angular resolution of future surface WCD arrays.
