Design of the PMT underwater cascade implosion protection system for JUNO

TL;DR

This paper presents the design, material selection, and validation of a protection system for underwater 20-inch PMTs to prevent cascade implosions in neutrino experiments, ensuring long-term operational safety.

Contribution

It introduces a novel protection structure for PMTs, including design, manufacturing, and validation processes, to mitigate cascade implosion risks in underwater neutrino detectors.

Findings

Protection system effectively prevents cascade implosions.

Simulation and underwater tests validate the design.

Material and manufacturing processes are optimized for durability.

Abstract

Photomultiplier tubes (PMTs) are widely used underwater in large-scale neutrino experiments. As a hollow glass spherelike structure, implosion is unavoidable during long-term operation under large water pressure. There is a possibility of cascade implosion to neighbor PMTs due to shockwave. Jiangmen Underground Neutrino Observatory designed a protection structure for each 20-inch PMT, consisting of a top cover, a bottom cover, and their connection. This paper introduces the requirement and design of the PMT protection system, including the material selection, investigation of manufacture technology, and prototyping. Optimization and validation by simulation and underwater experiments are also presented.