Systemization of elementary technology for high temperature superconductor AC applications based on electro-magnetics of fine structures of conductors

如果能够开发出将高温超导体（HTS）的交流损耗降低到传统高温超导技术的十分之一以下的技术，那么高温超导体（HTS）的各种应用将变得可行，而不仅仅是直流应用。我们的研究目标是通过深入了解高温超导的电磁现象，系统地开发降低高温超导应用中交流损耗的基础技术。为了追求研究目标，我们设定了以下研究目标；a)开发高温超导导线、组装导线和绕组交流损耗的测量方法；b)研究和开发在高温超导设备的电磁和机械环境中大幅度降低高温超导导线交流损耗的方法；c)研究和开发坚固和低交流损耗绕组结构的设计方法；在这个项目期间，我们取得了以下重要成果：我们开发了一种电测量总交流损耗的方法。用量热法同时测量，证明了电法的有效性。2)我们开发了一种准扭转方法，将外部交流磁场引起的涂层导体的磁化损失降低了一个数量级以上。3)我们发现，组装导体中相邻导体产生的磁场大大降低了损耗。4)提出了利用导线损耗数据计算线圈交流损耗的解析方法。在此分析方法的基础上，给出了使交流损耗最小的最优线圈结构。5)我们计算了保护涂层导体线圈绕组免受淬火损坏所需的铜量，并给出了坚固线圈的配置。通过这些成果，我们基本完成了开发实现低交流损耗高温超导器件的基本技术的研发目标。

If technologies are developed to reduce AC losses in high temperature superconductor (HTS) to less than one tenth of those of the conventional HTS technology, more various applications of HTS become feasible than just DC applications. Our research object is to systematically develop elementary technologies to reduce the AC losses in HTS applications by deep understanding of electromagnetic phenomena of HTS. To pursue the research object we set the following research targets;a)To developed measurement methods of AC losses in HTS wires, assembled conductors and windings;b)To research and develop methods to greatly reduce the AC losses in HTS wires in electromagnetic and mechanical environment of HTS apparatuses;c)To research and develop design methods of structures of robust and low AC loss windings;We obtained the following important achievements in the term of this project.1)We develop a method to electrically measure the total AC losses. The validity of this electric method was proven by the simultaneous measurements with a calorimetric method.2)We developed a quasi-twisting method to reduce magnetization losses in coated conductors due to external AC magnetic fields by more than one order of magnitude.3)We showed that the losses were greatly reduced by the magnetic field produced by the neighboring conductors in the assembled conductors.4)Analytic method to calculate the AC losses in the coil using the loss data of wires was developed. Based on this analytic method, optimal configuration of a coil was shown to minimize the AC losses.5)We calculated necessary amount of copper to protect a coil wound of coated conductors from damages caused by a quench and showed a configuration of robust coils.With those achievements, we almost fulfill the R＆D objects to develop elementary technologies to realize low AC loss HTS apparatuses.