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Kamioka Observatory

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History and Outstanding Features


Kamioka Observatory, part of the Institute for Cosmic Ray Research, is located within mines in the Kamioka area of Hida City in Gifu Prefecture. Completed in 1983, it is constructed 1,000 meters underground, and contains the Kamiokande (KAMIOKA-Nucleon Decay Experiment) facility, built to search for and measure proton decay as predicted by the Grand Unified Theory. The Kamiokande comprised a tank containing 3,000 tons of ultra-pure water, and 1,000 photomultiplier tubes attached to the walls. On 23 February 1987, the Kamiokande succeeded in detecting neutrinos from a supernova (SN 1987A) which occurred in the Large Magellanic Cloud. This achievement led to Masatoshi Koshiba, Professor Emeritus at The University of Tokyo, being awarded the Nobel Prize in Physics in 2002.

The Super-Kamiokande (Super-KAMIOKA Nucleon Decay Experiment/Neutrino Detection Experiment) is a water Cherenkov detector, and is an upgrade of its predecessor, constructed to perform with higher sensitivity. Operation of the Super-Kamiokande began in 1996. The detector comprises a tank containing 50,000 tons of ultra-pure water, and around 13,000 photomultiplier tubes. The Super-Kamiokande is designed to examine and elucidate the properties of neutrinos, in addition to continuing the work of the Kamiokande experiment by searching for proton decay. Joint research is presently carried out with around 30 universities and research institutes from Japan, the US, Korea, China, Poland, and Spain.

In 1998, it was announced that the Super-Kamiokande had succeeded in discovering neutrino oscillation (where neutrinos change type as they fly through the air) through the observation of atmospheric neutrinos, and that it had established that neutrinos had non-zero mass. Moreover, in 2001, the discovery of solar neutrinos was announced.

Between 1999 and 2004, the accelerator at the High Energy Accelerator Research Organization (KEK) in Tsukuba City was used to artificially create neutrinos, which were then beamed to the Super-Kamiokande, located 250 kilometers away, for observation; this was the K2K experiment (Long Baseline Neutrino Oscillation Experiment from KEK to Kamioka), and confirmed the neutrino oscillation previously observed in atmospheric neutrinos through the use of the accelerator-generated neutrinos. The T2K experiment (Long Baseline Neutrino Oscillation Experiment from Tokai to Kamioka) was subsequently launched in 2009; it is hoped that this project, which uses a more powerful neutrino beam of heightened sensitivity will allow more precise observations of neutrino oscillation.

The Kamioka Observatory is also making preparations for the XMASS Dark Matter Search Experiment, which aims to detect cold dark matter using liquid Xenon. Full-scale experimentation is scheduled to begin in spring 2011. Elsewhere, the Observatory is conducting research to detect gravitational waves (ripples in spacetime) using the underground experimental facilities at Kamioka, as well as next-generation experiment-based projects to detect dark matter. The Kamioka Observatory is at the very forefront of cutting-edge research in space and elementary particle research.

Mar 9, 2011

About the author
Sachiko Toso is a reporter for Japanest NIPPON

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