New prototype scintillator detector for the Tibet AS$\gamma$ Experiment

TL;DR

A new prototype scintillator detector was developed to enhance the Tibet ASγ experiment's surface array, improving detection efficiency and resolution for cosmic-ray and gamma-ray observations.

Contribution

The paper introduces a novel scintillator detector design optimized for the Tibet ASγ array, including geometry, optical surface, and readout improvements.

Findings

Achieved positional non-uniformity within 10%

Time resolution of approximately 2.2 ns FWHM

Dynamic range from 1 to 500 minimum ionization particles

Abstract

The hybrid Tibet AS array was successfully constructed in 2014. It has 4500 m$^{2}$ underground water Cherenkov pools used as the muon detector (MD) and 789 scintillator detectors covering 36900 m$^{2}$ as the surface array. At 100 TeV, cosmic-ray background events can be rejected by approximately 99.99\%, according to the full Monte Carlo (MC) simulation for $\gamma$-ray observations. In order to use the muon detector efficiently, we propose to extend the surface array area to 72900 m$^{2}$ by adding 120 scintillator detectors around the current array to increase the effective detection area. A new prototype scintillator detector is developed via optimizing the detector geometry and its optical surface, by selecting the reflective material and adopting dynode readout. This detector can meet our physics requirements with a positional non-uniformity of the output charge within 10\% (with reference to the center of the scintillator), time resolution FWHM of $\sim$2.2 ns, and dynamic range from 1 to 500 minimum ionization particles.