Study of the concentrations of Kr and Ar in high-purity nitrogen of JUNO

Purpose: In the JUNO, the LS serves as the medium for detecting neutrinos. When purifying the LS using HPN, it is essential to ensure low background levels of radioactive krypton and argon in the HPN Methods: Using the low-temperature physical adsorption properties of activated carbon to adsorb and separate radioactive gases such as radon, krypton, and argon from nitrogen in a liquid nitrogen environment. Results: Our results indicated that the <inline-formula id="IEq1"><alternatives><math><msup><mrow></mrow><mn>85</mn></msup></math><tex-math id="IEq1_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{85}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq1.gif"></inline-graphic></alternatives></inline-formula>Kr concentration in the HPN purified by HP activated carbon is 6.84 <inline-formula id="IEq2"><alternatives><math><mi mathvariant="normal">μ</mi></math><tex-math id="IEq2_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu $$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq2.gif"></inline-graphic></alternatives></inline-formula>Bq/m<inline-formula id="IEq3"><alternatives><math><msup><mrow></mrow><mn>3</mn></msup></math><tex-math id="IEq3_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{3}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq3.gif"></inline-graphic></alternatives></inline-formula>, and the <inline-formula id="IEq4"><alternatives><math><msup><mrow></mrow><mn>39</mn></msup></math><tex-math id="IEq4_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{39}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq4.gif"></inline-graphic></alternatives></inline-formula>Ar concentration is 3.6 <inline-formula id="IEq5"><alternatives><math><mi mathvariant="normal">μ</mi></math><tex-math id="IEq5_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu $$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq5.gif"></inline-graphic></alternatives></inline-formula>Bq/m<inline-formula id="IEq6"><alternatives><math><msup><mrow></mrow><mn>3</mn></msup></math><tex-math id="IEq6_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{3}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq6.gif"></inline-graphic></alternatives></inline-formula>for overground HPN, while the <inline-formula id="IEq7"><alternatives><math><msup><mrow></mrow><mn>85</mn></msup></math><tex-math id="IEq7_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{85}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq7.gif"></inline-graphic></alternatives></inline-formula>Kr concentration is 31.4 <inline-formula id="IEq8"><alternatives><math><mi mathvariant="normal">μ</mi></math><tex-math id="IEq8_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu $$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq8.gif"></inline-graphic></alternatives></inline-formula>Bq/m<inline-formula id="IEq9"><alternatives><math><msup><mrow></mrow><mn>3</mn></msup></math><tex-math id="IEq9_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{3}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq9.gif"></inline-graphic></alternatives></inline-formula>for underground HPN. The <inline-formula id="IEq10"><alternatives><math><msup><mrow></mrow><mn>85</mn></msup></math><tex-math id="IEq10_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{85}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq10.gif"></inline-graphic></alternatives></inline-formula>Kr concentration in the nitrogen purified by coconut shell activated carbon is 0.46 <inline-formula id="IEq11"><alternatives><math><mi mathvariant="normal">μ</mi></math><tex-math id="IEq11_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu $$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq11.gif"></inline-graphic></alternatives></inline-formula>Bq/m<inline-formula id="IEq12"><alternatives><math><msup><mrow></mrow><mn>3</mn></msup></math><tex-math id="IEq12_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{3}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq12.gif"></inline-graphic></alternatives></inline-formula>. Conclusions: After adsorption with activated carbon, the content of <inline-formula id="IEq13"><alternatives><math><msup><mrow></mrow><mn>85</mn></msup></math><tex-math id="IEq13_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{85}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq13.gif"></inline-graphic></alternatives></inline-formula>Kr and <inline-formula id="IEq14"><alternatives><math><msup><mrow></mrow><mn>39</mn></msup></math><tex-math id="IEq14_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{39}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq14.gif"></inline-graphic></alternatives></inline-formula>Ar in HPN is lower than the 50 <inline-formula id="IEq15"><alternatives><math><mi mathvariant="normal">μ</mi></math><tex-math id="IEq15_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu $$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq15.gif"></inline-graphic></alternatives></inline-formula>Bq/m<inline-formula id="IEq16"><alternatives><math><msup><mrow></mrow><mn>3</mn></msup></math><tex-math id="IEq16_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{3}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq16.gif"></inline-graphic></alternatives></inline-formula>required by JUNO. This work validates that the <inline-formula id="IEq17"><alternatives><math><msup><mrow></mrow><mn>85</mn></msup></math><tex-math id="IEq17_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{85}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq17.gif"></inline-graphic></alternatives></inline-formula>Kr and <inline-formula id="IEq18"><alternatives><math><msup><mrow></mrow><mn>39</mn></msup></math><tex-math id="IEq18_TeX">\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{39}$$\end{document}</tex-math><inline-graphic href="41605_2024_460_Article_IEq18.gif"></inline-graphic></alternatives></inline-formula>Ar concentrations in HPN is fit the JUNO requirement.