<p>A total of 25,600 3-inch photomultiplier tubes (PMTs), along with their corresponding front-end electronics, have been installed at the Jiangmen Underground Neutrino Observatory. 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 <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\text {SF}_6$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>SF</mtext> <mn>6</mn> </msub> </math></EquationSource> </InlineEquation>-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 <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\text {SF}_6$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>SF</mtext> <mn>6</mn> </msub> </math></EquationSource> </InlineEquation> from the underwater boxes, a leak rate detection limit of <InlineEquation ID="IEq6"> <EquationSource Format="TEX">$2.3\times {10}^{-9}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>2.3</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mo>-</mo> <mn>9</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> Pa<InlineEquation ID="IEq7"> <EquationSource Format="TEX">$\,\text {m}^3$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mspace width="0.166667em" /> <msup> <mtext>m</mtext> <mn>3</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>/s in terms of <InlineEquation ID="IEq8"> <EquationSource Format="TEX">$\text {SF}_6$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>SF</mtext> <mn>6</mn> </msub> </math></EquationSource> </InlineEquation> was achieved, corresponding to <InlineEquation ID="IEq9"> <EquationSource Format="TEX">$1.6\times {10}^{-8}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1.6</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mo>-</mo> <mn>8</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> Pa<InlineEquation ID="IEq10"> <EquationSource Format="TEX">$\,\text {m}^3$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mspace width="0.166667em" /> <msup> <mtext>m</mtext> <mn>3</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>/s helium equivalent. This meets the sensitivity requirement of 1<InlineEquation ID="IEq11"> <EquationSource Format="TEX">$\times {10}^{-7}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mo>-</mo> <mn>7</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> Pa<InlineEquation ID="IEq12"> <EquationSource Format="TEX">$\,\text {m}^3$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mspace width="0.166667em" /> <msup> <mtext>m</mtext> <mn>3</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>/s. This system was critical in identifying and replacing a few cases of leaking underwater boxes before installation.</p>

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

期刊论文
发表日期：

2025年8月18日

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Ziliang Chu,
Diru Wu,
Miao He,
Jilei Xu,
Xiaoping Jing,
Jian Wang

摘要

A total of 25,600 3-inch photomultiplier tubes (PMTs), along with their corresponding front-end electronics, have been installed at the Jiangmen Underground Neutrino Observatory. 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 $\text {SF}_6$ ${SF}_{6}$ -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 $\text {SF}_6$ ${SF}_{6}$ from the underwater boxes, a leak rate detection limit of $2.3\times {10}^{-9}$ $2.3 \times 10^{- 9}$ Pa $\,\text {m}^3$ $m^{3}$ /s in terms of $\text {SF}_6$ ${SF}_{6}$ was achieved, corresponding to $1.6\times {10}^{-8}$ $1.6 \times 10^{- 8}$ Pa $\,\text {m}^3$ $m^{3}$ /s helium equivalent. This meets the sensitivity requirement of 1 $\times {10}^{-7}$ $\times 10^{- 7}$ Pa $\,\text {m}^3$ $m^{3}$ /s. This system was critical in identifying and replacing a few cases of leaking underwater boxes before installation.

A highly sensitive \(\text {SF}_6\)-based leak test system for JUNO 3-inch PMT underwater electronics boxes

摘要