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

如果将高温超导体(HTS)的交流损耗降低到传统HTS技术的十分之一以下，那么高温超导的各种应用将变得更加可行，而不仅仅是直流应用。我们的研究目标是通过对高温超导电磁现象的深入了解，系统地开发降低高温超导应用中交流损耗的基本技术。为追求研究目标，我们确定了以下研究目标：a)开发高温超导导线、组合导线和绕组中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降低高温超导导线交流损耗的方法；c)研究和开发坚固耐用、低交流损耗绕组的结构设计方法；在本项目中，我们取得了以下重要成果：1)开发了一种电学测量总交流损耗的方法。通过与量热法的同步测量，验证了这种电学方法的有效性。2)我们提出了一种准扭转方法，将外部交流磁场引起的涂层导体的磁化损耗降低了一个数量级以上。3)我们证明了组合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中交流损耗的解析方法。5)计算了保护涂层导体线圈绕组免受失超破坏所需的铜量，给出了坚固耐用的线圈结构，基本完成了开发低交流损耗高温超导器件基础技术的研发目标。

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.