Abstract Details
Abstracts
Author: Linjin Zheng
Requested Type: Consider for Invited
Submitted: 2026-02-24 13:13:18
Co-authors: M. T. Kotschenreuther, F. L. Waelbroeck, and M. E. Austin
Contact Info:
The University of Texas at Austin
2515 Speedway
Austin, Texas 78712
USA
Abstract Text:
Resonant Magnetic Perturbations (RMPs) are applied externally in tokamaks like DIII-D, ASDEX Upgrade, and ITER, to control plasma instabilities by creating magnetic islands and stochastic regions at a specific rational q surface. We point out that in the presence of X points, the conventional surface-averaged q is not the best parameter to describe the field line pitch, which leads q become infinity everywhere poloidally at the plasma edge. It is more reasonable to use the dual q description that distinguishes the local q in the vicinity of the X point, where the local q tends to infinity, and that in the poloidal core region, where the local q is finite. This points to the possibility of applying toroidally axisymmetric RMPs in the X-point area for mitigating the edge localized modes. The theoretical framework was published in Phys. Plasmas 32, 012501 (2025). In this work, we demonstrate both analytically and numerically that a simple set of axisymmetric coils near the X point can indeed produce the magnetic islands and stochastic magnetic field. This is a much simpler RMP concept engineeringly. Our dual q description also helps to understand why the RMP suppression of edge localized modes is difficult to achieve in the double-null tokamak configurations, as compared with the single-null configuration. This research is supported by the Department of Energy Grant DE-FG02-04ER54742
Characterization: 2.0
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