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

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

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.

Our results indicated that the \(^{85}\) ${}^{85}$ Kr concentration in the HPN purified by HP activated carbon is 6.84 \(\upmu \) $\mathrm{\mu }$ Bq/m \(^{3}\) ${}^3$ , and the \(^{39}\) ${}^{39}$ Ar concentration is 3.6 \(\upmu \) $\mathrm{\mu }$ Bq/m \(^{3}\) ${}^3$ for overground HPN, while the \(^{85}\) ${}^{85}$ Kr concentration is 31.4 \(\upmu \) $\mathrm{\mu }$ Bq/m \(^{3}\) ${}^3$ for underground HPN. The \(^{85}\) ${}^{85}$ Kr concentration in the nitrogen purified by coconut shell activated carbon is 0.46 \(\upmu \) $\mathrm{\mu }$ Bq/m \(^{3}\) ${}^3$ .

After adsorption with activated carbon, the content of \(^{85}\) ${}^{85}$ Kr and \(^{39}\) ${}^{39}$ Ar in HPN is lower than the 50 \(\upmu \) $\mathrm{\mu }$ Bq/m \(^{3}\) ${}^3$ required by JUNO. This work validates that the \(^{85}\) ${}^{85}$ Kr and \(^{39}\) ${}^{39}$ Ar concentrations in HPN is fit the JUNO requirement.