  An intense source of 37Ar was produced by the (n,alpha) reaction on 40Ca by
irradiating 330 kg of calcium oxide in the fast neutron breeder reactor at
Zarechny, Russia. The 37Ar was released from the solid target by dissolution in
acid, collected from this solution, purified, sealed into a small source, and
brought to the Baksan Neutrino Observatory where it was used to irradiate 13
tonnes of gallium metal in the Russian-American gallium solar neutrino
experiment SAGE. Ten exposures of the gallium to the source, whose initial
strength was 409 +/- 2 kCi, were carried out during the period April to
September 2004. The 71Ge produced by the reaction 71Ga(nu_e,e^-)71Ge was
extracted, purified, and counted. The measured production rate was 11.0 ^+1.0
_-0.9 (stat) +/- 0.6 (syst) atoms of 71Ge/d, which is 0.79 ^+0.09_-0.10 of the
theoretically calculated production rate. When all neutrino source experiments
with gallium are considered together, there is an indication the theoretical
cross section has been overestimated.
