Development of Non Contraction High Current Superconducting Cable for Particle Accelerator

针对无力超导磁体系统新概念加速器“pipetron”的构建，进行了导体及相关设备的研制。由于加速器需要非常高的强度，因此本研究是与KEK的“超束”项目合作进行的。该导体由64根NbTi链和256根细丝编织而成。外层和内层用invar管加固。采用挤压法和挤压法在拉伸台上组装导体。结果表明，大电流不收缩电缆的制造是成功的。采用新研制的低温恒温器对电缆进行预试，测量电缆的热收缩。测量结果证实，与通常的超导体相比，其热收缩非常小。利用这种导体结构，作为合作项目在费米国家加速器实验室进行了模型磁体测试。系统冷却后，模型磁体达到设计电流75kA。然后，磁体加速，使其在最高电流下熄灭。淬火电流为104kA。与费米实验室模型一起测试的日本模型只有10cm长，但这次测试也验证了KEK磁体的不对称结构。这一结果将大大降低高能加速器超导磁体的建造和运行成本。现在提出了KEK质子同步加速器的转换等应用。未来磁体系统的实际构建将需要很长的冷却线，并且必须使用临界温度更高的超导体。本研究发明了一种新的Nb3Sn导体“DT （distributed Tin）”方法。DT导体在12T时的载流大于2kA/mm2，是普通超导体的两倍。总之，这项研究非常成功，不仅开发了构建未来高能加速器所需的导体，而且在未来创造了广泛的应用。少

The development of the conductor and the related equipments was performed aiming at the construction of "pipetron", a new concept of an accelerator with the force-free superconducting magnet system. Since accelerator needs to be very high intensity, this research was conducted with collaborative relations with the "superbunch" project at KEK. The conductor was made of a braid of 64 NbTi strands with 256 filaments. The outer layer and inner layer were reinforced by invar pipes. The assembly of the conductor was made by using both extrusion and intrusion method on a draw bench. As a result, the fabrication of the high current non-contraction cable was found successful. The pre-testing of the cable was made by a newly developed cryostat to measure the thermal contraction of the cable. The measured results confirmed the very small thermal contraction compared with the usual superconductors. Using this conductor structure, a model magnet testing was performed at Fermi National Accelerator L … More aboratory as a collaboration project. After the cool down of the system, the model magnet reached to 75kA of designed current. Then, the magnet was ramped up to make quench at the highest current. The quench current was 104kA. The Japanese model tested together with the Fermilab model was only 10cm in length but the asymmetric structure of KEK magnet was also verified in this test. This result will drastically bring down the construction and operation cost of superconducting magnet for high-energy accelerators. Applications such as the conversion of the KEK proton synchrotron are now proposed. The realistic construction of the future magnet system will require a very long cooling line and the use of superconductors with higher critical temperature will be necessary. A new method of Nb3Sn conductor called "DT (Distrbuted Tin)" was invented in this research. DT conductor carried more than 2kA/mm2, twice current of ordinary superconductor, at 12T. In summary this research was very successful not only to develop the conductor necessary for the construction of future high-energy accelerators but also to created a wide range of applications in the future. Less