SAGE (Soviet–American Gallium Experiment)

SAGE (Soviet–American Gallium Experiment, or sometimes Russian-American Gallium Experiment) is a collaborative experiment devised by several prominent physicists to measure the solar neutrino flux.

SAGE was devised to measure the radio-chemical solar neutrino flux based on the inverse beta decay reaction, ⁷¹Ga${\displaystyle \left(\nu _{e},e^{-}\right)}$⁷¹Ge. The target for the reaction was 50-57 tonnes of liquid gallium metal stored deep underground at the Baksan Neutrino Observatory in the Caucasus mountains in Russia. About once a month, the neutrino induced Ge is extracted from the Ga. ⁷¹Ge is unstable with respect to electron capture (${\displaystyle t_{1/2}=11.43}$ days) and, therefore, the amount of extracted germanium can be determined from its activity as measured in small proportional counters.

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