Development of High Field Superconducting Magnet for High Energy Accelerator

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In order to pursue the particle physics in the energy frontier, superconducting magnets for the high-energy accelerator are very important equipment, and they must be high-field and high-quality magnets. The Large Hadron Collider (LHC), presently under construction at CERN, will employ more than 6000 superconducting magnets. In the framework of the LHC collaboration program between CERN and Japan, the High Energy Accelerator Research Organization, KEK, has been developed and fabricated the 16 superconducting insertion quadrupole magnets for the LHC interaction regions. After initial running of the LHC, the quest will continue to extend the discovery potential of new particles and to increase the precision of measurements of particle characteristics. This will be only achieved by upgrading the accelerator and it will require higher field superconducting magnets. As a first step of the development, we performed two investigations: 1) studies on the various characteristics of the mass production magnets. 2) development of the high field superconducting wires (rapid heating, quenching, and transforming processed Nb_3Al wires).In the former studies, we obtained a lot of mechanical and electromagnetic data of the mass production quadrupoles during the cool-down and excitation test, and the field measurement. These data will be very valuable and useful for the future high field magnet development. In the latter studies, we performed the basic research to obtain the higher Jc in the region of 1015 T. Although we could not reached the target Jc (2000 A/mm^2 at 10 T, 4.2 K), it was found that the characteristics of the Nb_3Al wires at the low field (1015 T), which has not been studied before, were slightly different from that of the high field (> 20 T). The data obtained through this study will give us useful information for the further development of the high field superconducting wires.