A highly sensitive SF$_6$-based leak test system for JUNO 3-inch PMT underwater electronics boxes

Fuente: arXiv
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Autores principales: Chu, Ziliang, Wu, Diru, He, Miao, Xu, Jilei, Jing, Xiaoping, Wang, Jian
Formato: Preprint
Publicado: 2025
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author Chu, Ziliang
Wu, Diru
He, Miao
Xu, Jilei
Jing, Xiaoping
Wang, Jian
author_facet Chu, Ziliang
Wu, Diru
He, Miao
Xu, Jilei
Jing, Xiaoping
Wang, Jian
contents A total of 25600 3-inch photomultiplier tubes (PMTs), along with their corresponding frontend electronics, have been installed at the Jiangmen Underground Neutrino Observatory (JUNO). These electronics are housed in 200 stainless steel boxes that operate underwater. To verify the sealing integrity of the underwater boxes following integration, we developed an SF$_6$-based leak test system, opting against the typical helium-based system due to helium's ability to penetrate the PMT glass. After a few hours of accumulating leaking SF$_6$ from the underwater boxes, a leak rate detection limit of $2.3\times{10}^{-9}$~Pa$\cdot$m$^3$/s in terms of SF$_6$ was achieved, corresponding to $1.65\times{10}^{-8}$~Pa$\cdot$ m$^3$/s helium equivalent. This meets the sensitivity requirement of 1$\times$10$^{-7}$~Pa$\cdot$m$^3$/s. This system was critical in identifying and replacing a few cases of leaking underwater boxes before installation.
format Preprint
id arxiv_https___arxiv_org_abs_2505_24142
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A highly sensitive SF$_6$-based leak test system for JUNO 3-inch PMT underwater electronics boxes
Chu, Ziliang
Wu, Diru
He, Miao
Xu, Jilei
Jing, Xiaoping
Wang, Jian
Instrumentation and Detectors
High Energy Physics - Experiment
A total of 25600 3-inch photomultiplier tubes (PMTs), along with their corresponding frontend electronics, have been installed at the Jiangmen Underground Neutrino Observatory (JUNO). These electronics are housed in 200 stainless steel boxes that operate underwater. To verify the sealing integrity of the underwater boxes following integration, we developed an SF$_6$-based leak test system, opting against the typical helium-based system due to helium's ability to penetrate the PMT glass. After a few hours of accumulating leaking SF$_6$ from the underwater boxes, a leak rate detection limit of $2.3\times{10}^{-9}$~Pa$\cdot$m$^3$/s in terms of SF$_6$ was achieved, corresponding to $1.65\times{10}^{-8}$~Pa$\cdot$ m$^3$/s helium equivalent. This meets the sensitivity requirement of 1$\times$10$^{-7}$~Pa$\cdot$m$^3$/s. This system was critical in identifying and replacing a few cases of leaking underwater boxes before installation.
title A highly sensitive SF$_6$-based leak test system for JUNO 3-inch PMT underwater electronics boxes
topic Instrumentation and Detectors
High Energy Physics - Experiment
url https://arxiv.org/abs/2505.24142