What's Cosmic Ray?
About Each Group
Kamioka Observatory
Norikura Observatory
Akeno Observatory
Number of staff & Directors
The Institute for Cosmic Ray Research (ICRR) of University of Tokyo, was established in 1976 for the cosmic ray studies.

The predecessor was an experimental hut on Mt. Norikura, called Asahi hut, built in 1950 with the Asahi Bounty for Science. This experimental hut was developed into the Cosmic Ray Observatory of University of Tokyo in 1953.

Moreover, the Cosmic Ray Observatory had been developed. Two international research projects were merged into the work of Observatory in 1973. One project was the deep underground experiment at the Kolar Gold Mine in India, and the other was the high mountain experiment at Mt. Chacaltaya in Bolivia. The construction of MUTRON (electromagnet spectrometer) was also completed in 1975. The construction of the Akeno Observatory was started in the same year.

In 1976, Cosmic Ray Observatory was reorganized to the Institute for Cosmic Ray Research of University of Tokyo. Three cosmic ray divisions in Institute for Nuclear Study, University of Tokyo were incorporated into ICRR. The Various experiments were developed in this period, 1 km2 air shower detector at Akeno and the emulsion chamber at Mt. Fuji in 1979, the Japan-China collaboration on experiments using emulsion chambers in 1981 and the proton decay experiment at Kamioka in 1983. The facilities for the study of primary cosmic rays were also prepared.

In the latter half of 1980s' and the succeeding years, several significant experimental results were obtained. Kamioka Observatory reported the first detection of neutrinos from a supernova SN1987A in 1987, the deficit of the solar neutrinos (1988) and an anomalous flux of the atmospheric neutrinos (1994). The large increase of solar neutrons accompanied with a solar flare was observed at Norikura in 1989. Akeno Observatory constructed the 100km2 wide area air shower detector in 1990 and reported a most energetic air shower beyond the existent theory (1994). Cangaroo, the international collaboration in Australia, observed high energy gamma rays from an astronomical source for the first time in the southern hemisphere in 1992. The gravitational wave group newly joined to ICRR in the same year. The construction of detector for air shower gamma rays was started in Tibet in 1993. Super-Kamiokande was constructed in 1996. The Super-Kamiokande collaboration announced the existence of neutrino masses through neutrino oscillations based on two years atmospheric neutrino observation in 1998.

The long baseline neutrino oscillation experiment (K2K) started to investigate more details of neutrino oscillation in 1999. Neutrinos produced by the accelerator are injected from KEK (High Energy Accelerator Research Organization) to Super-Kamiokande in this experiment. Moreover, Research Center for Cosmic Neutrinos was established to study neutrinos based on data from various observations. The fund from the Japan Grant-in-aid for Scientific Research was approved to improve the high energy gamma ray observation in Australia.