V. N. Gavrin

Measurement of the solar neutrino capture rate with gallium metal

The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2 (+7.2-7.0) (+3.5-3.0) SNU, where the uncertainties are statistical and systematic, respectively. This represents only about half of the predicted Standard Solar Model rate of 129 SNU. All the experimental procedures, including extraction of germanium from gallium, counting of 71Ge, and data analysis are discussed in detail.

Results from SAGE (The Russian-American gallium solar neutrino experiment)

Abstract Fifteen measurements of the solar neutrino flux have been made in a radiochemical 71 Ga- 71 Ge experiment employing initially 30 t and later 57 t of liquid metallic gallium at the Baksan Neutrino Observatory between January 1990 and May 1992. This provides an integral measurement of the flux of solar neutrinos and in particular is sensitive to the dominant, low-energy p-p solar neutrinos. SAGE observed the capture rate to be 73 −16 +18 (stat.) −7 +5 (syst.) SNU. This represents only 56%−60% of the capture rate predicted by different Standard Solar Models.

Measurement of the response of a Ga solar neutrino experiment to neutrinos from an 37Ar source

An intense source of 37Ar was produced by the (n, α) reaction on 40Ca by irradiating calcium oxide in the fast neutron breeder reactor at Zarechny, Russia. The 37Ar was released from the solid target, sealed into a small source, and was used to irradiate 13 tonnes of gallium metal in the Russian-American gallium solar neutrino experiment SAGE. The initial source strength was 409 ± 2 kCi. The measured production rate of 71Ge on gallium metal was 11.0+1.0−0.9 (stat) ± 0.6 (syst.) atoms per day, which is 0.79+0.09−0.10 of the theoretically calculated production rate.

First results from the Soviet-American gallium experiment

Abstract The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is consistent with 0 SNU and is less than 72 SNU (68% CL) and less than 138 SNU (95% CL). This is to be compared with the flux of 132 SNU predicted by the Standard Solar Model.

Status of the Soviet‐American Gallium Experiment

A radiochemical [sup 71]Ga-[sup 71]Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of [sup 71]Ge atoms extracted from 30 tons of gallium in 1990 and from 57 tons of gallium in 1991 was measured in twelve runs during the period of January 1990 to December 1991. The combined 1990 and 1991 data sets give a value of 58 [plus] 17/ [minus] 24 (stat.) [plus minus] 14 (syst.) SNU. This is to be compared with 132 SNU predicted by the Standard Solar Model. 2 tabs, 1 fig, 14 refs.

Pilot installation of the gallium‐germanium solar neutrino telescope

The pilot gallium‐germanium installation with 7 t of Ga metal is described. Preliminary results of the yields of 71Ge and 69Ge from cosmic rays are given. The possibility of conducting a calibrating experiment using a metal target and a Cr neutrino source produced from enriched chromium is considered.

37Ar yield from irradiated calcium oxide under thermal treatment

We study the feasibility of using CaO as a target material for irradiation in fast-neutron reactors to produce an artificial high-intensity neutrino source on the basis of the37Ar isotope. The rate of37Ar emission from CaO samples under fast-neutron irradiation and vigorous heating was determined. The technique for measuring the yield is described in detail. An emission rate of <0.01% per hour is obtained for the best target type—pressed CaO—at a temperature of 900°C. It is shown that this rate does not meet the requirements for a high-intensity neutrino source.

Preliminary results from the Russian-American gallium experiment Cr-neutrino source measurement

The Russian-American Gallium Experiment has been collecting solar neutrino data since early 1990. The flux measurement of solar neutrinos is well below that expected from solar models. We discuss the initial results of a measurement of experimental efficiencies by exposing the gallium target to neutrinos from an artificial source. The capture rate of neutrinos from this source is very close to that which is expected. The result can be expressed as a ratio of the measured capture rate to the anticipated rate from the source activity. This ratio is 0.93 + 0.15, {minus}0.17 where the systematic and statistical errors have been combined. To first order the experimental efficiencies are in agreement with those determined during solar neutrino measurements and in previous auxiliary measurements. One must conclude that the discrepancy between the measured solar neutrino flux and that predicted by the solar models can not arise from an experimental artifact. 17 refs., 3 figs., 1 tab.

The Baksan Gallium Solar Neutrino Experiment

A radiochemical 71Ga-71Ge experiment to determine the integral flux of neutrinos from the sun has been constructed at the Baksan Neutrino Observatory in the USSR. Measurements have begun with 30 tonnes of gallium. The experiment is being expanded with the addition of another 30 tonnes. The motivation, experimental procedures, and present status of this experiment are presented.

A Radiochemical Installation for Handling Small Amounts of High-Purity Gases

A radiochemical installation capable of performing precision operations involving small amounts of gases, including high-purity radioactive gases, is described. The installation is used to produce, purify, and proportion the gaseous components of working mixtures for proportional counters. The basic parameters of the installation, as a whole, and of its systems are given. The potentialities of the installation are illustrated through a technique for the extraction and purification of 37Ar. This radioisotope is intended for use as a neutrino source for calibrating neutrino detectors.