S. Pakhomov¹ , T. Kuzmina¹ , G. Shakhetov¹

¹Khlopin Radium Institute of the "Rosatom" State Corp.

Abstract:

One of the most conclusive evidences of a violation of CTBT is the presence in the subsoil air of elevated concentrations of 37Ar radionuclide, which is formed in large quantities in the interaction of neutrons with calcium in rocks. Traditionally, to measure the activity of 37Ar, proportional gas counters are used, which are filled with a counting gas prepared from samples of argon with the addition of methane. Further reduction of the detection limit of 37Ar is limited by the difficulty of a significant increase of argon sample volume placed in a proportional counter. Installation for the detection of argon-37 low activities based on the liquid scintillation principle is being developed at the Radium Khlopin Institute under contract with the CTBTO. The role of the scintillator in this installation is performed by the liquefied preparation of extracted from soil air argon itself. The use of liquefied argon samples allows one to multiply the volume of the measured samples without increasing the size of the measuring cell and shield elements, and allows significant reduction of detection limits of 37Ar. Installation is currently being tested and the results are given in this presentation.