Enhanced Photon Traps for Hyper-Kamiokande

TL;DR

This paper introduces an innovative photon trap design for Hyper-Kamiokande that uses smaller, cost-effective PMTs combined with optical components to improve photon collection efficiency, potentially reducing costs.

Contribution

A novel photon trap design combining smaller PMTs with optical components, achieving comparable efficiency to larger PMTs at lower cost.

Findings

Photon traps with 12-inch PMTs match 20-inch PMT efficiency

Design reduces costs while maintaining collection efficiency

Timing resolution is somewhat reduced in the new design

Abstract

Hyper-Kamiokande, the next generation large water Cherenkov detector in Japan, is planning to use approximately 80,000 20-inch photomultiplier tubes (PMTs). They are one of the major cost factors of the experiment. We propose a novel enhanced photon trap design based on a smaller and more economical PMT in combination with wavelength shifters, dichroic mirrors, and broadband mirrors. GEANT4 is utilized to obtain photon collection efficiencies and timing resolution of the photon traps. We compare the performance of different trap configurations and sizes. Our simulations indicate an enhanced photon trap with a 12-inch PMT can match a 20-inch PMTs collection efficiency, however at a cost of reduced timing resolution. The photon trap might be suitable as detection module for the outer detector with large photo coverage area.