On every list of outstanding astrophysical problems of the late twentieth century is the "solar neutrino problem," or the deficit of detected neutrinos compared to those expected from interior models of the Sun. Solar neutrinos are measured using perchloro- ethylne (cleaning fluid) in Homestake Mine in South Dakota. The chlorine atoms in this solution are converted to an argon-37 isotope by solar neutrinos and are then extracted to measure the rate of neutrino emission. The deficit in detected neutrinos was first discovered at Homestake over twenty years ago. It has led since to the construction of several other neutrino detection facilities in Russia, Japan, and Italy. This award will support the operations of the Homestake Experiment for an additional two years.
