Water Cherenkov detectors with fiber enhanced PMT for cosmic ray observation

TL;DR

This paper introduces a cost-effective Water Cherenkov detector design using a fiber-enhanced PMT, demonstrating significant improvements in light yield and good timing performance for cosmic ray observation.

Contribution

The work presents the first integration of a small PMT with wavelength-shifting fiber bundles in a WCD, enhancing light collection efficiency and performance.

Findings

Light yield increased by nearly 200% with fiber-PMT

Achieved 30 photoelectrons light yield and 2.3 ns time resolution

Demonstrated uniform performance under various trigger configurations

Abstract

Water Cherenkov detectors (WCDs) have been widely used in cosmic ray observations. This paper presents, for the first time, a cost-effective WCD design integrating a small photomultiplier tube (PMT) with wavelength-shifting fiber (WLS fiber) bundles. A WCD prototype was constructed in our laboratory, utilizing a fiber-PMT photosensor composed of a small PMT optically coupled with a WLS fiber bundle. This work details the structure of the fiber-PMT and the WCD. Measurements show the photosensor's time shift is 6.71 ns. Using cosmic ray muons, the WCD prototype demonstrated a light yield up to 30 photoelectrons with 2.3 ns time resolution under optimal conditions. Furthermore, tests under different trigger configurations indicate good performance uniformity. These findings validate the feasibility of the proposed design. A comparative analysis between a WCD using a standalone PMT and one equipped with the fiber-PMT shows that the fiber-PMT achieves nearly a 200\% improvement in light yield, albeit with a slight reduction in time performance.