Development of Non Contraction High Current Superconducting Cable for Particle Accelerator

针对无力超导磁体系统加速器的新概念--“旋流管”的建造，开展了导体及相关设备的研制工作。由于加速器需要非常高的强度，这项研究是在KEK的“超束”计划的协作关系下进行的。导体是由256根NbTi股编成的。外层和内层均采用因瓦管加固。导线的装配是在拉伸台上采用挤压法和插入法两种方法制作的。结果，研制成功了大电流无收缩电缆。电缆的预测试是由新开发的低温恒温器进行的，以测量电缆的热收缩。测量结果证实，与通常的超导体相比，超导体的热收缩很小。利用这种导体结构，在费米国家加速器L…上进行了模型磁体测试作为一个协作项目，更多的是流产。系统冷却后，模型磁体达到了设计电流的75kA。然后，加大磁铁，使其在最高电流下熄灭。失超电流为104kA。与费米实验室模型一起测试的日本模型只有10厘米长，但KEK磁体的不对称结构也在这次测试中得到了验证。这一成果将极大地降低高能加速器用超导磁体的建设和运营成本。现在提出了一些应用，如KEK质子同步加速器的转换。未来磁体系统的实际建造将需要非常长的冷却线，使用临界温度更高的超导体将是必要的。本研究发明了一种新的制备Nb_3Sn导体的方法--DT(分布式锡)。在12T下，DT导体的载流量超过2kA/mm2，是普通超导体的两倍。总而言之，这项研究是非常成功的，不仅开发了建造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。较少

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