[en] Experimental study of nonstandard neutrino properties using high-intensity artificial neutrino sources requires the activity of the sources to be determined with high accuracy. In the BEST project, a calorimetric system for measurement of the activity of high-intensity (a few MCi) neutrino sources based on "5"1Cr with an accuracy of 0.5–1% is created. In the paper, the main factors affecting the accuracy of determining the neutrino source activity are discussed. The calorimetric system design and the calibration results using a thermal simulator of the source are presented

[en] The possibility of the BEST experiment on electron neutrino disappearance with intense artificial sources of electron neutrino ⁵¹Cr is considered. BEST has the great potential to search for transitions of active neutrinos to sterile states with Δ m ² ∼1 eV² and to set the limits on short baseline electron neutrino disappearance oscillation parameters. The possibility of the further constraints the oscillation parameters region with using ⁶⁵Zn source is discussed. (paper)

[en] The possibility of the BEST experiment on electron neutrino disappearance with intense artificial sources of electron neutrino ⁵¹Cr is considered. BEST has the great potential to search for transitions of active neutrinos to sterile states with Δm² ∼ 1 eV² and to set the limits on short baseline electron neutrino disappearance oscillation parameters. The possibility of the further constraints the oscillation parameters region with using ⁶⁵Zn source is discussed.

[en] 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)

[en] In April 2004, a neutrino source was produced by irradiating a 330-kg piece of pressed calcium oxide at the fast-neutron reactor BN-600 (Zarechny, Russia) for six months. The ³⁷Ar isotope was obtained via the (n, α) reaction on ⁴⁰Ca, and ³⁷Ar was extracted from an aqueous solution of nitric acid in which the solid target was dissolved. After that, ³⁷Ar was purified and sealed into a capsule. This source was used to measure the neutrino-capture rate in metalic gallium for neutrinos from ³⁷Ar decay, which have an energy close to that of the main line of solar ⁷Be neutrinos (863 keV). The target of the SAGE Gallium-Germanium Neutrino Telescope was irradiated by using this source at the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences). The source activity was measured by several methods during its production, in the course of irradiation, and after its completion. The weighted mean of the activity for six measurements was 409 ± 2 kCi at the beginning of irradiation of the gallium target (04:00 Moscow time, 30.04.2004). The scatter in the activity values obtained by different methods does not exceed 5%

[en] The Russian-American experiment SAGE began to measure the solar neutrino capture rate with a target of gallium metal in December 1989. Measurements have continued with only a few brief interruptions since that time. In this article we present the experimental improvements in SAGE since its last published data summary in December 2001. Assuming the solar neutrino production rate was constant during the period of data collection, combined analysis of 168 extractions through December 2007 gives a capture rate of solar neutrinos with energy more than 233 keV of 65.4_-3.0^+3.1 (stat) _-2.8^+2.6 (syst) SNU. The weighted average of the results of all three Ga solar neutrino experiments, SAGE, Gallex, and GNO, is now 66.1±3.1 SNU, where statistical and systematic uncertainties have been combined in quadrature. During the recent period of data collection a new test of SAGE was made with a reactor-produced ³⁷Ar neutrino source. The ratio of observed to calculated rates in this experiment, combined with the measured rates in the three prior ⁵¹Cr neutrino-source experiments with Ga, is 0.87±0.05. A probable explanation for this low result is that the cross section for neutrino capture by the two lowest-lying excited states in ⁷¹Ge has been overestimated. If we assume these cross sections are zero, then the standard solar model including neutrino oscillations predicts a total capture rate in Ga in the range of 63 SNU to 66 SNU with an uncertainty of about 4%, in good agreement with experiment. We derive the current value of the neutrino flux produced in the Sun by the proton-proton fusion reaction to be φ_pp^·=(6.0±0.8)x10¹⁰/(cm² s), which agrees well with the pp flux predicted by the standard solar model. Finally, we make several tests and show that the data are consistent with the assumption that the solar neutrino production rate is constant in time.