The Russian-American Gallium solar neutrino Experiment (SAGE) is described. Beginning in September 1992, SAGE II data were taken with 55 tons of Ga and with significantly reduoed backgrounds. The solar neutrino flux measured by 31 extractions through October 1993 is presented. The result of 69 k 10 +5/-7 SNU is to be compared with a Standard Solar Model prediction of 132 SNU.

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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+3.5

The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted by solar models. To check the response of this experiment to low-energy neutrinos, a 517 kCi source of 51 Cr was produced by irradiating 512.7 g of 92.4%-enriched 50 Cr in a high-flux fast neutron reactor. This source, which mainly emits monoenergetic 747-keV neutrinos, was placed at the center of a 13.1 tonne target of liquid gallium and the cross section for the production of 71 Ge by the inverse beta decay reaction 71 Ga(νe, e − ) 71 Ge was measured to be [5.55 ± 0.60 (stat) ± 0.32 (syst)] × 10 −45 cm 2 . The ratio of this cross section to the theoretical cross section of Bahcall for this reaction is 0.95 ± 0.12 (expt) +0.035 −0.027 (theor) and to the cross section of Haxton is 0.87 ± 0.11 (expt) ± 0.09 (theor). This good agreement between prediction and observation implies that the overall experimental efficiency is correctly determined and provides considerable evidence for the reliability of the solar neutrino measurement. PACS number(s): 26.65.+t, 13.15.+g, 95.85.Ry