Super-Kamiokande
Super-Kamiokande, or Super-K for short, is a neutrino observatory in
Japan. The observatory was designed to search for
proton decay, study
solar and atmospheric neutrinos, and keep watch for
supernovas in our
galaxy.
Super-K is located 1,000 m underground in Mozumi Mine of the Kamioka Mining and Smelting Co. in Hida city ,
Gifu,
Japan.
It consists of 50,000 tons of pure
water surrounded by about 11,200
photomultiplier tubes.
The cylindrical structure is 41.4 m tall and 39.3 m across.
Encyclopedia
Super-Kamiokande, or
Super-K for short, is a neutrino observatory in
Japan. The observatory was designed to search for
proton decay, study
solar and atmospheric neutrinos, and keep watch for
supernovas in our
galaxy.
Super-K is located 1,000 m underground in Mozumi Mine of the Kamioka Mining and Smelting Co. in Hida city ,
Gifu,
Japan.
It consists of 50,000 tons of pure
water surrounded by about 11,200
photomultiplier tubes.
The cylindrical structure is 41.4 m tall and 39.3 m across.
A neutrino interaction with the
electrons or nuclei of water can produce a 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 distinct pattern of this flash provides information on the direction and flavor of the incoming neutrino. The difference in time between the top of the cone reaching the detector wall and the bottom can be used to calculate the direction that the particle came from; the bigger the difference, the greater the angle from the horizontal of the particle's path. From the sharpness of the edge of the cone the type of particle can be inferred. The multiple scattering of electrons is large, so electromagnetic showers produce fuzzy cones. 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 proton decay, one of the most fundamental questions of elementary particle physics.
The detector, named
KamiokaNDE for Kamioka Nucleon Decay Experiment, was a tank which contained 3,000 tons of pure water and had about 1,000 photomultiplier tubes attached to the inner surface. The size of the tank was 16.0 m in height and 15.6 m in diameter. An upgrade of the detector was started in 1985 to allow the detector to observe solar neutrinos. As a result, the detector had become sensitive enough to detect neutrinos from
SN 1987A, a
supernova which was observed from in the
Large Magellanic Cloud in February 1987. Solar neutrinos were observed in 1988 adding to the advancements in neutrino astronomy and neutrino astrophysics. The ability of the Kamiokande experiment to observe the direction of electrons produced in solar neutrino interactions allowed the experimenters to directly demonstrate for the first time that the sun was a source of neutrinos.
Despite its success in neutrino observation, Kamiokande did not detect proton decay, its first aim. Also, even higher sensitivity was needed to observe neutrinos with high statistical confidence. This led to the construction of
Super-Kamiokande, with ten times more water volume and PMTs than Kamiokande. Super-Kamiokande started observation in 1996.
Super-Kamiokande Collaboration announced the first evidence of
neutrino oscillations in 1998, consistent with the theory that the neutrino has non-zero
mass. Until this, all observational evidences were consistent with neutrinos being massless, although theorists had speculated on the possibility of neutrinos having non-zero mass for many years.
On November 12, 2001, several thousand photomultiplier tubes in the Super-Kamiokande detector
imploded, apparently in a chain reaction as the
shock wave from the concussion of each imploding tube cracked its neighbours. The detector was partially restored by redistributing the photomultiplier tubes which did not implode, and by adding protective acrylic shells that are hoped would prevent another chain reaction from recurring .
In July 2005, preparation began to restore the detector to its original form by reinstalling about 6,000 PMTs. It was completed in June 2006.
See also
External links
