Local axisymmetry-breaking–induced transition of trapped-particle orbit and loss channels in quasi-axisymmetric stellarators
Local axisymmetry-breaking–induced transition of trapped-particle orbit and loss channels in quasi-axisymmetric stellarators
复制标题
准轴对称仿星器中局部轴对称破缺引起的俘获粒子轨道和损失通道的转变
DOI：
10.1209/0295-5075/129/35001
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Y. Wan
中科院分区：
文献类型：
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作者：
Lang Yang;Haifeng Liu;A. Shimizu;Yuhong Xu;Xianqu Wang;Haifeng Liu;C. Tang;Yangbo Li;Jinmao Liu;Yang Luo;G. Xiong;C. Su;S. Kinoshita;M. Isobe;S. Okamura;Jie Huang;Xin Zhang;D. Yin;Y. Wan
本文研究了准轴对称构型中的俘获粒子轨道拓扑的转变，如中国第一个准轴对称仿星器（CFQS）。研究发现，QA组态中的轴对称破缺现象在某些特定的位置上具有重要意义，它很容易诱导阻塞粒子转变为定域粒子。本文提出了一种新的观点来解释俘获粒子轨道拓扑的跃迁机制，即，当非轴对称场的振幅沿半径方向沿着增加时，逐渐产生大的环形不均匀性区域，这使得捕获粒子轨迹的长度基本上变短，因此，可以将粒子限制到单个螺旋场周期。同时，在这样的位置的“伪轴对称”场的结果在耦合的最大径向漂移和最小极向漂移，这使得被捕获的粒子轨道拓扑结构的过渡相当大，并形成特定的损失通道，降低等离子体约束。这些结果可以揭示通过避免这种耦合相对于高能粒子约束的QA配置的优化。此外，这项工作也是有关的粒子通量沉积在偏转板上的不均匀性的产生。
The transition of trapped-particle orbit topologies has been investigated in quasi-axisymmetric (QA) configurations, such as the Chinese First Quasi-axisymmetric Stellarator (CFQS). It is found that the axisymmetry-breaking phenomenon in QA configurations is of great significance at some specific locations, which could easily induce blocked particles to transit into localized particles. A novel aspect is presented to interpret the transition mechanism of trapped-particle orbit topologies in this paper, i.e., as the amplitudes of non-axisymmetric field increase along the radius direction, the region of large toroidal inhomogeneity is gradually generated, which makes the length of the trapped-particle trajectory substantially short, and hence, may restrict particles to a single helical field period. Meanwhile, at such locations the “pseudo-axisymmetric” field results in coupling of the maximum radial drift and the minimum poloidal drift, which enables the transition of trapped-particle orbit topologies considerably and forms specific loss channels, degrading plasma confinement. These results may shed light on the optimization of QA configurations via avoidance of such coupling with respect to energetic particle confinement. Moreover, this work is also relevant to the generation of inhomogeneity of particle flux deposition on the devertor plates.