Nobel Neutrino Experiment

9 October 2002

Raymond Davis Jr, pioneer of experiments to detect solar neutrinos, has been rewarded with a share of the 2002 Nobel prize for Physics. Davis's experiment, situated in the Homestake gold mine in South Dakota was the first to detect neutrinos from the Sun, in the early 1970s. His detector consisted of a tank of 615 tonnes of perchloroethylene - a dry-cleaning fluid. On very rare occasions - about twice every three days - a neutrino would interact with a nucleus of chlorine in the liquid and produce a nucleus of radioactive argon.  Davis developed techniques to extract the few atoms of argon created each month and to count them through monitoring their radioactivity. He found fewer neutrinos than expected - the famous "solar neutrino problem" - which only recently appears to have been solved. Not until 1988 were Davis's findings confirmed in another experiment, called Kamiokande, in Japan. Masatoshi Koshiba, who was head of the Kamiokande experiment, shares the Nobel prize with Davis, together with Riccardo Giacconi who pioneered X-ray astronomy.

Credit: Brookhaven National Laboratory