Qingxian Zhang

The Large Ultra-High Energy Gamma-ray Source Stereoscopic Tracking Device (LACT) project will deploy 32 Cherenkov telescopes with a diameter of 6 meters in Haizishan, Daocheng County, Sichuan Province, to conduct precise structural measurements of more than ten ultra-high energy gamma-ray sources discovered by LHAASO.It is used to conduct precise structural measurements on more than ten ultra-high energy gamma-ray sources discovered by LHAASO.Among them, the photon detection efficiency (PDE) significantly affects the response sensitivity of the SiPM camera to weak Cherenkov light. This report conducted a comparative test of the PDE of SiPM samples from different manufacturers using multi-wavelength LED light sources.

This paper proposes an innovative detector to measure the radioactivity of water based on ZnS(Ag)-coated plastic scintillating fibers. The system includes an internal cavity for measuring the total α and total β activities in the test water sample and an external cavity for excluding muons from external background radiation and reducing gamma rays in the internal water sample through anti-coincidence measurement. Geant4 simulations modeled radiation interaction, scintillation light generation, and its propagation within the detector. Simulation results are used to determine the optimal thickness of the ZnS(Ag) coating, length of the plastic scintillating fibers in the inner cavity, and thickness of the aluminum cylinder between the inner and outer cavities. When the ZnS(Ag) layer thickness is 14 μm, fiber length is 400 mm, and 353 fibers are arranged in parallel, the minimum detection limit for α particles is 0.5 Bq/L within 1.65 hours of detection time, and within 4.82 hours, the detection limit for β particles reaches 1 Bq/L.