Radiation-Resistant Magnets for the Neutrino Beamline at J-PARC

The construction of the facility of the long baseline neutrino oscillation experiment using the J-PARC´s 50 GeV-0.75 MW proton beam [1] was completed at the end of 2008. The number of radiation-resistant magnets we have prepared for the neutrino beamline of J-PARC were 15 with Polyimide resin Insulation (PI) against up to 10⁸ Gy, and 4 magnets with completely Mineral Insulation Cable (MIC) for higher radiation dose up to 10¹¹ Gy, and 2 magnets with Epoxy resin Insulation. All magnets were equipped with remote handling system, i.e. automated magnet lifts, quick alignment guides, water connectors, electric power connectors and interlock-signal connectors. On April 23rd 2009, the first proton beam was successfully introduced to the neutrino beamline from the main accelerator of J-PARC and the long baseline oscillation experiment, T2K, started. Now the beamline is operated with 135 kW (30 GeV-4.5 ) primary proton beam. No serious problem happened on magnets until the great East Japan earthquake on March 11th.