Abstract Details
Abstracts
Author: Linjin Zheng
Requested Type: Consider for Invited
Submitted: 2024-04-05 22:37:54
Co-authors: M. T. Kotschenreuther, F. L. Waelbroeck
Contact Info:
University of Texas at Austin
2515 Speedway
Austin, Texas 78712
USA
Abstract Text:
Investigation of X-point equilibrium is important. On the plasma boundary, it is critical to clarify the edge transport and divertor physics; Inside the plasma, it helps to understand the physics mechanism for magnetic island formation, relating to tearing modes or RMP effects. We have developed the asymptotic equilibrium theory for X-point tip on the plasma boundary and inside the plasma torus using the conformal transformation. On the plasma boundary, It has often been thought that the X point is of letter “X” shape with the opposite angles being equal. However, the vacuum region is current-free and the plasma edge carries finite current. This makes that the opposite angles cannot be equal. We proved that [Phys. Plasmas, 30, 112508 (2023)] the X point can only exist in the vacuum region, instead of on the plasma-vacuum interface, unless each segment angle is 90 degrees. An acute angle of the plasma-filled segment leads to an obtuse opposite angle of vacuum segment and vice verse. Inside the plasma, we found that the ratio of the adjacent segment angles of X point depends on the ratio of the respective toroidal currents carried by each segment, noting that the transport inside the magnetic islands is different from the outside. This affects the initial formation condition of magnetic islands and their saturated level. Both the mathematical treatment and underlying physics will be detailed.
Comments:
Plasma equilibrium, stability, and transport