J- PARC (Japan Proton Accelerator Research Complex) is located on the Pacific coast, a Japanese research complex at Tōkai in Ibaraki Prefecture, about 120 km north of Tokyo. Two proton synchrotron with maximum particle energies of 3 and 50 GeV are operated here in the framework of a cooperation between the Japan Atomic Energy Agency JAEA and the Research Centre for High Energy Physics KEK. They are used for production of secondary beams such as muons and neutron beams for the material and biological sciences as well as neutrino and kaon beams for particle and nuclear physics.
The J- PARC is the successor of operating in Tsukuba from 1976 to 2005 at the KEK 12 - GeV proton synchrotron ( KEK -PS). Construction of the complex was in 2001. Synchrotron With the smaller the targeted proton energy of 3 GeV was reached in 2008 and the end of the same year were the first muons and neutron beams are made available to the experiments with the spallation target. The end of 2008 was achieved with the main ring proton energy of 30 GeV and in the first half of the following year was the beamline for hadron experimental hall and placed in service for the T2K experiment in operation.
The Tōkai -to- Kamioka experiment ( T2K ) is the successor of the K2K experiment ( KEK -to- Kamioka ) in the west to the end of 2005 with the help of the KEK - PS neutrinos of Tsukuba for the Super - Kamiokande detector in the 250 km located Kamioka (now Hida ) have been sent. The first neutrino event of the beam from J- PARC from the Tōkai 295 km away, was registered in February 2010 by the detector. The aim of the experiments is to study the neutrino oscillation for the determination of the neutrino mass.
Since the J- PARC only 200 km from the epicenter was the Tōhoku earthquake in 2011, it came on 11 March 2011 in severe damage to infrastructure, to the accelerators and experiments. The tsunami reached here but only a height of 3 meters and 8 meters designed for flood protection measures prevented the flooding of the area. By the end of December, the damage could be repaired and the operation can be resumed.
On May 23, 2013, came in the hadron experimental hall to an intermediate case in which it came to the release of radioactive material and 34 people a radiation dose of up to 1.7 mSv were exposed (the maximum allowed annual effective dose for occupationally exposed persons in Germany is 20 mSv ). The failure was in an unusually rapid extraction of protons from the ring main 50 GeV (within 5 milliseconds, instead of the typical 2 s), leading to the destruction of a target, and thus to the release of radioactivity. All accelerators and experiments were then initially turned off or adjusted and started to investigate.
Construction and operation
The J- PARC has three particle successively accelerate protons up to 50 GeV. A multi-stage linear accelerator ( LINAC ) brings to 181 MeV and is in a further stage of development reach 400 MeV for injection into the first synchrotron, as well as for planned separate experiments for transmutation of radioactive waste energy of 600 MeV. The first synchrotron has a circumference of 348 m and accelerates the protons of the LINAC, 3 GeV. Due to the relatively high frequency of the orbiting proton packets of 25 Hz, it is referred to as a rapid cycle synchrotron (RCS). About 96 % of the protons of the RCS are passed through a beam line in the experimental hall of material and life sciences, where muons and neutron beams are produced as secondary beams with them. The hall is located within the 50 - GeV main ring ( Main Square), in the remaining four per cent of the 3- GeV protons are introduced approximately every 3 s. This synchrotron has a circumference of 1568 meters and accelerates the protons of the RCS on currently (2013 ) 30 GeV; a further increase to 50 GeV is planned. The main ring feeds the beam lines to the hadron experimental hall and the T2K experiment.
Specificity of the J- PARC is the desired high beam power proton synchrotron of up to one megawatt, which particularly powerful secondary beams can be produced. These current intensities of radiation of more than 300 uA at RCS or about 10-20 uA at the main ring are required; to 2011 stable beam powers were obtained from 100-200 kW. The J- PARC is one next to the Spallation Neutron Source (SNS ) at Oak Ridge National Laboratory in the U.S. and the UK ISIS Rutherford Appleton Laboratory to the world's most powerful plants for the production of muons and neutron rays.