Chemically, its properties are very similar to water, but it has different nuclear properties that make it undergo different reactions with neutrinos. Heavy water is identical to normal water, except that it contains deuterium, an isotope of hydrogen. (SNO Collaboration 1987) The location was very favorable for the experiment, but another uniquely Canadian element was essential to the technical success of the SNO experiment. The seismic stability and radioactive suitability of the mine were also considered and found to be adequate for the detector. The Creighton mine was to be in operation for several decades, and the planned site for the detector was separated enough from mining operations to ensure minimal disruption of the experiment. The detector would also, during its construction and operation, require a significant infrastructure to be active for an extended period of time. The nature of the experiment required that it be adequately shielded from cosmic radiation, which would cause errant results, and the two-kilometer depth of the site was deemed sufficient for this. The site was selected for several reasons. The observatory itself is located more than two thousand meters underground, in a branch of the Creighton mine of INCO Ltd. Several other neutrino detector experiments are in operation around the world, such as GALLEX in Italy, Super Kamiokande in Japan, and AMANDA in Antarctica, but SNO is the only one of these to use heavy water, and the only one currently able to differentiate neutrino flavors. (SNO Collaboration 1987) Because the transformation of neutrinos into other flavors would imply that at least one flavor had mass, such a finding would be proof for neutrino mass and have major implications for particle physics as well. The use of heavy water would make SNO able to differentiate between neutrino flavors, and thus resolve the solar neutrino problem. To this end, SNO was conceived as a heavy water detector. SNO was created to test the hypothesis that the neutrinos being emitted from the sun were being transformed into other types, or “ flavors” of neutrinos, that were previously undetectable. Various explanations were attempted, but the problem proved persistent, eventually becoming known as the “ Solar Neutrino Problem”. (Bahcall 2002, also Neutrino Wiki) However, the results then found, and later confirmed by following experiments, showed a discrepancy between the number of neutrinos expected from the theory, and the number actually measured. It was believed that the fusion reactions that powered the sun should produce neutrinos, and this was confirmed by Ray Davis in 1968 using an underground detector full of carbon tetrachloride, or dry cleaning fluid. Their existence was first postulated by Wolfgang Pauli in 1931, but because of their weakly interacting nature, were not discovered until 1956 (Neutrino Wiki). Neutrinos are a class of sub-atomic particles produced in various nuclear reactions. The observatory was to be a research venue for both astrophysics and particle physics, by measuring neutrino radiation from the sun to study solar processes, as well as observing properties of neutrinos. The proposal for the Sudbury Neutrino Observatory was submitted to the Canadian government at the end of 1987. Lord Brawl says: "This facility features prominently in Robert Sawyer's Hugo-winner Hominids and sequels." Thanks! The observatory did indeed detect mu and tau neutrinos, indicating that neutrinos do have mass, do oscillate, and effectively resolving the Solar Neutrino Problem. Queen's University is heavily involved in the project.Ī more recent note: the results are in. SNO is situated 6800 feet under ground, in the second-to-bottom drift (jokingly referred to as the SNO drift) of INCO's Creighton Mine, near Sudbury, Ontario, Canada. Preliminary data from SNO seems to support the theory, but no official papers have been published as of October 19, 2000. Neutrino oscillations, if they exist, could resolve the Solar Neutrino Problem. This is important, as it allows the theory of neutrino oscillations to be tested. The Sudbury Neutrino Observatory, or SNO for short, differs from other neutrino observatories in that it uses heavy water as its detection material, allowing mu and tau type neutrinos to be detected, while most others, such as Super Kamiokande, can only detect the electron neutrino.
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