Measurement of the activity of an artificial neutrino source based on 37Ar

The activity of an artificial neutrino source based on 37Ar was measured by a specially developed method of directly counting 37Ar decays in a proportional counter. This source was used to irradiate the target of the SAGE radiochemical gallium-germanium neutrino telescope at the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences, Moscow), whereupon the measurements were performed at the Institute of Reactor Materials (Zarechny, Sverdlovsk oblast, Russia). The method used to prepare gaseous samples for measurements in proportional counters and the counting procedure are described. The measured activity of the 37Ar neutrino source is 405.1 ± 3.7 kCi (corrected for decays that occurred within the period between the instant of activity measurement and the commencement of the irradiation of Ga target at 04:00 Moscow time, 30.04.2004)