Super-Kamiokande

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Super-Kamiokande (full name as Super-Kamioka Nucleon Decay Experiments, or abbreviated to Super-K for short) is a neutrino observatory which is underground of Mountain Kamioka mine (神岡鉱山) near the city of Hida, Gifu Prefecture, Japan. The observatory was designed to search for proton decay, study solar and atmospheric neutrinos, and keep watch for supernovas in the Milky Way Galaxy.

The Super-K is located 1,000 m (3,281 ft) underground in Kamioka Mining and Smelting Co.'s Mozumi Mine in Hida's Kamioka area. It consists of a cylindrical stainless steel tank that is 41.4 m (135.8 ft) tall and 39.3 m (128.9 ft) in diameter holding 50,000 tons of ultra-pure water. The tank volume is divided by a stainless steel superstructure into an inner detector (ID) region that is 33.8 m (110.9 ft) in diameter and 36.2 m (118.8 ft) in height and outer detector (OD) which consists of the remaining tank volume. Mounted on the superstructure are 11,146 photomultiplier tubes (PMT) 20 in (50.8 cm) in diameter that face the ID and 1885 8 in (20.3 cm) PMTs that face the OD. There is a Tyvek and blacksheet barrier attached to the superstructure that optically separates the ID and OD.

A neutrino interaction with the electrons or nuclei of water can produce a charged particle that moves faster than the speed of light in water. This creates a cone of light known as Cherenkov radiation, which is the optical equivalent to a sonic boom. The Cherenkov light is projected as a ring on the wall of the detector and recorded by the PMTs. Using the timing and charge information recorded by each PMT, the interaction vertex, ring direction and flavor of the incoming neutrino is determined. From the sharpness of the edge of the ring the type of particle can be inferred. The multiple scattering of electrons is large, so electromagnetic showers produce fuzzy rings. Highly relativistic muons, in contrast, travel almost straight through the detector and produce rings with sharp edges.

History

Construction of Kamioka Underground Observatory, the predecessor of the present Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo began in 1982 and was completed in April, 1983. The purpose of the observatory was to detect whether proton decay exists, one of the most fundamental questions of elementary particle physics.[1][2][3][4][5][6]

The detector, named KamiokaNDE for Kamioka Nucleon Decay Experiment, was a tank 16.0 m (52.5 ft) in height and 15.6 m (51.2 ft) in width, containing 3,048 metric tons (3,000 tons) of pure water and about 1,000 photomultiplier tubes (PMTs) attached to its inner surface. The detector was upgraded, starting in 1985, to allow it to observe solar neutrinos. As a result, the detector (KamiokaNDE-II) had become sensitive enough to detect neutrinos from SN 1987A, a supernova which was observed in the Large Magellanic Cloud in February 1987, and to observe solar neutrinos in 1988. The ability of the Kamiokande experiment to observe the direction of electrons produced in solar neutrino interactions allowed experimenters to directly demonstrate for the first time that the sun was a source of neutrinos.

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