|Gigantic Observation Device Opens the Door
to the Mysteries of Space
Kamioka Town in northern Gifu Prefecture was once a mining town that produced more zinc than any other place in Japan. At 1,000 meters (3,281 feet) underground in this abandoned mine lies "Super-Kamiokande," a facility for cosmic particle research that was built by a U.S.-Japan joint research team including members of the Institute for Cosmic Ray Research of the University of Tokyo. The device consists of a huge cylindrical water tank, 41.4 meters (136 feet) tall and 39.3 meters (129 feet) in diameter, and photomultiplier tubes lined up on the entire surface of its inside wall. The cylinder is filled with 50,000 tons of purified water. The facility is designed to detect neutrinos which come flying in from outer space.
A neutrino is an elementary particle that experts think exist in great quantities in space. Because neutrinos barely interact with other substances and even pass through the earth, it is very difficult to detect neutrinos, and so little is known about the nature of neutrinos. The Super-Kamiokande can detect a subtle beam generated when a neutrino collides with a particle of water. By using the device, the project aims to reveal information about neutrino and then to deduce the history and evolution of the universe.
The Super-Kamiokande was built so deep into the ground in order to shield the device from cosmic rays and other particles which can adversely affect observation. Construction started in 1991 and the observation facility went into operation in April 1996.
Photos: The inside of Super Kamiokande (Institute of Cosmic Ray Research, University of Tokyo).
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