EAST装置超低密度等离子体中的逃逸电子行为研究

Runaway electron (RE) currents of several mega amperes are expected to be generated in ITER disruptions due to avalanche multiplication. An uncontrolled loss of these high-energy REs to the plasma facing components might cause serious damage. To understand the RE behavior during disruptions is one of the key issues for the future fusion reactor. Many diagnostic system cannot work well during disruptions due to high electron density and low electron temperature, limiting the valid achievement of plasma parameters for understanding RE generation and losses during disruptions. As an alternative proposal, a novel method is designed to research RE generation and losses on EAST in this project. An ultra-low electron density (<0.3*10^19 m-3) is programmed to operated in the EAST tokamak. With assistant of loop voltage feedback control system, the ratio of RE current to the whole plasma current increases to more than 50%, which is not much lower than the RE current fraction during disruptions. Based on the novel flat-top of high RE current fraction, the effects of the density increasing and external magnetic perturbation on RE losses will be carefully investigated on the EAST tokamak, respectively.

未来ITER破裂时，将会有高达70%的电流转化为逃逸电流。逃逸电流的反常损失会导致装置壁的熔化等损伤，影响装置寿命。因此，研究破裂期间逃逸电流行为对托卡马克装置安全运行至关重要。但是由于破裂期间密度极高、温度极低等客观条件，绝大多数等离子体诊断系统无法正常工作，限制了破裂期间逃逸电子行为的研究。本项目提出一种替代方案，在EAST装置运行超低密度等离子体，即电子密度运行在0.3*10^19 m-3以内，辅以环电压控制等方法，将逃逸电流份额提高到总电流的50%以上，在一定程度上模拟破裂期间逃逸电流的运行环境。在此高逃逸电流份额的平台基础上，通过补充充气提高电子密度，研究其对逃逸电流行为的影响；通过外加磁扰动，分析磁扰动和MHD宏观不稳定性与逃逸电流损失的关系。

未来ITER破裂时，将会有高达70%的电流转化为逃逸电流。逃逸电流的反常损失会导致装置壁的熔化等损伤，影响装置寿命。因此，研究破裂期间逃逸电流行为对托卡马克装置安全运行至关重要。但是由于破裂期间密度极高、温度极低等客观条件，绝大多数等离子体诊断系统无法正常工作，限制了破裂期间逃逸电子行为的研究。本项目在EAST装置上发展并完善了低密度等离子体运行平台，并将逃逸电流份额提高到总电流的50%以上，在一定程度上模拟破裂期间逃逸电流的运行环境。在此实验平台上，观察到高能量电子激发的阿尔芬本征模及其与GAM之间的相互作用；同时将低密度放电期间的逃逸电子行为与破裂过程中逃逸电子行为对比，为未来破裂期间逃逸电子抑制提供科学参考。