Ar and Kr concentrations in nitrogen as a measure of the 39Ar and 85Kr activities in connection with the solar neutrino experiment

Among other radionuclides, 39Ar and 85Kr are potential background sources in the solar neutrino detector The expected low event rate requires that the nitrogen used in the experiment needs to have lower concentrations than 0.5 μBq/m3 for 39Ar and 0.2 μBq/m3 for 85Kr, corresponding to volume concentrations in N2 of 0.4×10−6 m3/m3 for Ar and 0.2×10−12 m3/m3 for Kr. Applying gas mass spectrometry and special care in the sampling technique we succeeded in finding the required purity. In addition, we studied the possibility to purify nitrogen from Kr by the adsorption method.