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

PurposeIn 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
MethodsUsing 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.
ResultsOur results indicated that the ⁸⁵Kr concentration in the HPN purified by HP activated carbon is 6.84 μBq/m ³, and the ³⁹Ar concentration is 3.6 μBq/m ³for overground HPN, while the ⁸⁵Kr concentration is 31.4 μBq/m ³for underground HPN. The ⁸⁵Kr concentration in the nitrogen purified by coconut shell activated carbon is 0.46 μBq/m ³.
ConclusionsAfter adsorption with activated carbon, the content of ⁸⁵Kr and ³⁹Ar in HPN is lower than the 50 μBq/m ³required by JUNO. This work validates that the ⁸⁵Kr and ³⁹Ar concentrations in HPN is fit the JUNO requirement.