托卡马克超导磁体中心螺管模型线圈的失超研究

Compared with the water-cooled magnet, the superconducting magnet is of increasing interest in TOKAMAK reactor applications due to its low operating cost. In general, the superconducting magnet for TOKAMAK reactor has a large magnetic energy. Quench of the superconducting magnet is a likely event that can lead to a large hot spot temperature and a large helium pressure inside a jacket due to the electromagnetic and thermal disturbance. Therefore, an effective strategy for quench detection and quench protection system can be designed against degradation of the superconducting magnet during a quench..The quench propagation behavior of the Nb3Sn Cable-In-Conduit Conductor (CICC) and NbTi CICC are studied by using the numerical analysis and the experimental results. In this study, the quench behavior of the central solenoid (CS) model coil for Chinese Fusion Engineering Test Reactor (CFETR) superconducting magnet is studied experimentally. The relevant behavior of quench propagation of the superconducting magnet with different disturbance scenarios was analyzed. The objectives of this study are threefold, including the quench propagation behavior at different operating scenarios, the hot spot temperature of the cable and the thermal-dynamic behavior of the helium during a quench.The quench detection and quench protection for the CFETR CS coil can be optimized by analyzing the quench behavior of the CFETR CS model coil.

相对于常规水冷磁体，超导磁体应用于托卡马克装置上由于需要消耗较少的电能而备受青睐。通常情况下，托卡马克超导磁体储存的磁能较大。在电磁和热扰动下，超导磁体常常发生失超现象。超导磁体失超后导体的温度将很快上升，如果保护不及时，超导磁体很可能由于局部过热而导致其性能退化或损坏。.针对大型托卡马克超导磁体失超保护的重要性，本项目将利用数值模拟方法，结合中国聚变工程实验堆(CFETR)托卡马克超导磁体中心螺管模型线圈的失超实验，模拟该磁体所用的大型Nb3Sn和NbTi管内电缆导体在不同扰动机制下的失超传播行为，实验研究该超导磁体模型线圈在各种阈值电压和失超延迟判断时间下超导电缆的热点温度及导管内的氦压力等失超传播行为。通过研究该超导磁体模型线圈的失超行为能够为CFETR托卡马克超导磁体的失超检测及失超保护提供重要的理论和实验依据。

运行在高磁场下的低能耗、万安级大电流管内电缆导体是托卡马克装置实现高性能等离子体长脉冲稳态或准稳态运行的重要保障。基于管内电缆导体的超导磁体失超保护是未来聚变堆托卡马克需要解决的难题之一。管内电缆超导磁体失超后如何实现快速放电以降低导体热点温度而同时限制线圈端部电压，需要快速精确的失超检测系统、合理的失超电压阈值判断模型及有效的电路控制系统的有机结合。.三年来，课题组围绕着管内电缆导体超导磁体的失超传播机制及失超保护优化开展了深入的研究工作。通过构建超导磁体失超正常区传播模型探索失超电压的演化趋势揭示失超传播机制，为超导磁体的失超保护设计奠定基础。重要研究结果如下：1)利用线圈匝间及层间传热耦合，进一步发展了早期的失超传播模型,提高了结果的可靠性。2）采用正温度效应的移能电阻有效降低了超导磁体的失超热点温度及改善了超导磁体的失超端电压。3）失超保护电路的优化进一步降低超导磁体的端电压并且提高了失超保护的可靠性。此外，除本项目所列的研究内容之外，利用项目的成果开展了加速器超导磁体的优化设计、混合磁体电磁行为研究及混合磁体模型线圈的稳定性和失超研究，丰富了本项目的研究内容。项目成果的取得有助于提升聚变堆托卡马克超导磁体的失超保护设计水平及改善装置运行的可靠性。.在项目的资助下发表了SCI收录论文8篇，包括Nuclear Fusion 3篇(其中一篇封面文章)，Journal of superconductivity and novel magnetism 1篇，Journal of fusion energy 2篇，Springerplus 2篇。