Volume 129, Number 3, February 2020
|Number of page(s)||7|
|Section||Physics of Gases, Plasmas and Electric Discharges|
|Published online||04 March 2020|
Local axisymmetry-breaking–induced transition of trapped-particle orbit and loss channels in quasi-axisymmetric stellarators
1 Institute of Fusion Science, School of Physical Science and Technology, Southwest Jiaotong University Chengdu 610031, China
2 National Institute for Fusion Science, National Institutes of Natural Sciences - Toki 509-5292, Japan
3 The Graduate University for Advanced Study, SOKENDAI - Toki 509-5292, Japan
4 College of Physics, Sichuan University - Chengdu 610065, China
5 Hefei Keye Electro Physical Equipment Manufacturing Co., Ltd. - Hefei 230000, China
Received: 17 December 2019
Accepted: 11 February 2020
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.
PACS: 52.55.Hc – Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices / 52.65.Cc – Particle orbit and trajectory
© EPLA, 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.