On every list of outstanding astrophysical problems in the late twentieth century is the "solar neutrino problem." This problem refers to the measured low rate of neutrino production in the Sun compared to rates expected from theoretical interior models of the Sun. Since the rate of neutrinos generated is proportional to the thermonuclear energy rate in the Sun, there is a keen interest to confirm our basic understanding of what makes the Sun shine. The discrepancy between the observed and predicted rate calls this understanding into question, hence the term "solar neutrino problem." The Principal Investigator (PI) proposes a three-year continuation of his work in the Soviet-American Gallium Experiment (SAGE) located in the Bakyan Neutrino Laboratory in the Soviet Union. This experiment will provide the most sensitive test yet of solar interior and neutrino theories because it is sensitive to low and moderate energy neutrinos, whereas existing experiments (at Homestake, South Dakota and Kamiokande in Japan) are sensitive to the relatively few high energy neutrinos produced by side-nuclear reactions. The SAGE experiment became operational in early 1990 and has already produced exciting results, an extreme dearth of neutrinos relative to the theoretical predictions. If future monitoring of the Sun with more sensitive equipment confirms these early results, then either our understanding of the Sun's interior structure or the fundamental nature of neutrinos must be changed. The PI has played a vital role in constructing the proportional counter detectors for the SAGE experiment. The PI proposes to continue this role both because the old detectors deteriorate with time and also because more detectors will provide a more sensitive test of the neutrino discrepancy. In addition, these detectors provide a means of discriminating between bonafide solar neutrinos and neutrinos produced by alternate processes on the Earth. Thus, the PI's efforts will help to define the extent of the neutrino discrepancy, leading to its earlier resolution.
