Development of High Field Superconducting Magnet for High Energy Accelerator

为了追求能源前沿的粒子物理，高能加速器用超导磁体是非常重要的设备，它必须是高场、高质量的磁体。目前正在欧洲核子研究中心建造的大型强子对撞机（LHC）将使用6000多个超导磁体。在CERN与日本的LHC合作计划框架内，高能加速器研究组织KEK已经开发并制造了用于LHC相互作用区的16个超导插入四极磁体。在LHC首次运行之后，探索将继续扩大新粒子的发现潜力，并提高粒子特性测量的精度。这只能通过升级加速器来实现，并且需要更高场的超导磁体。作为开发的第一步，我们进行了两项调查：1）对批量生产磁体的各种特性进行了研究。2)在前期的研究中，我们获得了大量的大规模生产的四极棒在冷却、励磁试验和现场测量过程中的力学和电磁数据。这些数据将是非常有价值的和有用的未来高场磁体的发展。在后面的研究中，我们进行了基础研究，以获得1015 T区域内的较高Jc。虽然我们不能达到目标Jc（2000 A/mm^2，10 T，4.2 K），但发现Nb_3Al丝在低场（1015 T）下的特性与高场（> 20 T）略有不同，这是以前没有研究过的。通过本研究获得的数据将为高场超导线材的进一步发展提供有用的信息。

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.