等离子体破裂后期逃逸电流耗散与磁动能转换研究

The thermal and magnetic energies stored in large scale tokamak necessitate a highly reliable and efficient mitigation scheme for plasma major disruptions. The mitigation technique that is most advanced and has been chosen for ITER is the injection of high-Z impurities for the dissipation of magnetic, thermal and runaway electron energy. In recent years, substantial efforts have been undertaken in both experiments and modelling to improve the understanding of disruptions, the physics processes involved in mitigation and the optimization of the mitigation efficiency. There is now a much more mature qualitative, but also quantitative, understanding of the mitigation of electromagnetic and thermal loads. However with respect to runaway electrons, identifying a suitable mitigation scheme for ITER presents substantial challenges. Disruption mitigation has to ensure that: a) a high fraction of the thermal energy is radiated, b) the dissipation of magnetic energy is fast enough to prevent heat loads and halo currents, but not so fast as to generate excessively high eddy currents, and c) runaway electron generation is avoided or, if avoidance is not possible, that the magnetic and kinetic energy stored in the runaway beam is dissipated on a fast timescale. In this proposal, we are planning to investigate the dissipation of runaway current and the conversion of magnetic energy into runaway kinetic energy by high Z impurities injection during the runaway current plateau.

等离子体破裂缓解是目前磁约束聚变等离子体急需解决的关键科学技术问题之一。大型托卡马克装置运行期间具有极大的热能和磁能，这就要求其具有一套高效可靠的破裂缓解系统。近几年等离子体破裂机理和破裂缓解研究方面取得了不少进展，但是逃逸电子的抑制仍然是一个有待解决的关键问题。目前研究表明破裂前大量杂质注入无法避免下一代大型装置上逃逸电子的产生，最有效的措施为逃逸电流产生后将逃逸电流安全耗散。这就需要发展一套有效的逃逸电流耗散技术将存储在逃逸电流中的逃逸电子动能和磁能快速耗散从而实现装置的安全运行。本项目拟结合ITPA MHD组提出的WG-13研究任务，从实验和模拟方面开展大量杂质注入下逃逸电流耗散和磁能转换研究，为下一代装置的安全运行提供参考。

托卡马克等离子体破裂时会产生高能逃逸电子并形成逃逸电流。逃逸电流失控将导致高能量逃逸电子轰击、熔化托卡马克装置第一壁，造成装置损毁。逃逸电流是未来聚变堆面临的最大安全威胁，抑制与耗散逃逸电流是聚变堆研发的首要国际性难题。.在本课题项目中，在逃逸电子产生阶段使用大量气体注入系统向等离子体中注入惰性气体杂质，实现了对逃逸电流形成的有效抑制。研制了大流速、精准定向的拉瓦尔型杂质注入系统，克服了传统杂质注入流速小、定向性差，杂质难以穿透的世界难题，达到了28 MA/s的逃逸电流耗散速率，为世界最高。创新性地提出外加反向欧姆电场减少流入真空室的磁能的新方法，对总磁能的转移效率高达41.35%，并实现逃逸电流的软着陆。研究发现慢速电流焠灭会导致较高份额的磁能转化为逃逸电子动能，而快速电流焠灭仅有低份额的磁能转化为逃逸电子动能，这对逃逸电流耗散和软着陆具有重要指导意义。.依托本项目，共发表（含收录）科技论文21篇；培养硕士研究生12名，博士研究生4名。团队也受邀到ITER总部做特邀报告，推广经验，为ITER逃逸电流的抑制与耗散提供了全新的中国解决方案。