Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory ( SNO ) is a neutrino observatory, which was built in an old nickel mine near Sudbury, Ontario, Canada and commissioned in May 1999. The detector was switched off on 28 October 2006, obtained data since been analyzed. It was planned at the same time to use the existing infrastructure for further experiments, which now finds its continuation with the SNO experiment plus ( SNO , SNOplus ). Scintillator in SNO -plus experiment is particularly linear alkylbenzene ( LAB) be a raw material for surfactants. New start-up is likely to be 2014.

Director of the observatory since 1989 was Arthur Bruce McDonald.

The core of the SNO detector, the more than 2000 m is located below the earth's surface and 1,000 tons of heavy water ( D2O ) in a spherical tank containing acrylic glass. The tank is completely immersed for shielding and mechanical stabilization in a basin with normal water. Since the detector is so deep under the earth's surface, he is very well shielded against cosmic radiation. Due to the weak interaction of neutrinos with matter they reach almost unhindered the detector as a single particle. Electron neutrinos react with the neutrons of deuterium in the molecules of heavy water to a proton and an electron ( neutrino induced beta decay ). The passage of the electrons through the water creates Cherenkov radiation which is detected by approximately 9600 arranged around the tank photomultipliers.

Muon and Tauneutrinos can not trigger the aforementioned reaction, but can be detected by reactions of the elastic neutrino scattering on electrons or by disintegration of deuterium in proton and neutron in the detector. This is a distinction of electron neutrinos and the other allows neutrinos. Only in this way the solar neutrino problem ( too low for measuring rates of electron neutrinos ) was established experimentally explained by the theory of neutrino oscillation, because the missing electron neutrinos could be detected as a muon or Tauneutrinos. Recent measurements have shown that the total neutrino flux ( electron, muon and Tauneutrinos ) agrees very well with the expectation from the standard solar model. This neutrino oscillations have been proven beyond doubt.

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