Abstract Details
Abstracts
Author: Carl R. Sovinec
Requested Type: Poster
Submitted: 2026-03-20 18:22:15
Co-authors: Sanket A. Patil, J. Vincent Cauilan
Contact Info:
University of Wisconsin-Madison
1500 Engineering Drive
Madison, Wisconsin 53706
USA
Abstract Text:
The magnetohydrodynamic stability of stellarators with respect to ballooning remains an open question regarding the influence of 3D shaping on linear stability and on whether linear instability leads to significant degradation of confinement. The Large Helical Device results of only non-disruptive MHD activity in discharges operating beyond the Mercier limit [1] suggest that linear ballooning instability could also be tolerated in other configurations. Recent nonlinear MHD simulations with the M3D-C1 code find benign saturation of Wendelstein 7-X standard configurations that are made linearly unstable to ideal-MHD ballooning [2,3]. Here, we apply the NIMSTELL code [4] to Mercier-optimized versions of the quasi-axisymmetric 2-field period design in Ref. [5], where the nonlinear interchange properties of the original design have already been investigated [6]. Linear NIMSTELL computations with minimal dissipation show ballooning instability using numerical methods that converge from the stable side. However, without artificial damping, it is not possible to numerically converge on a particular ideal ballooning mode, due to growth rate increasing with resolution. We consider the influence of different forms of physically motivated dissipation, such as viscosity and thermal conduction. Initial nonlinear results are also presented.
[1] K. Y. Watanabe, S. Sakakibara, Y. Narushima, et al., Nucl. Fusion 45, 1247 (2005).
[2] Y. Zhou, K. Aleynikova, C. Liu, and N. M. Ferraro, Phys. Rev. Lett. 133, 135102 (2024).
[3] Y. Zhou, K. Aleynikova, C. Liu, and N. M. Ferraro, Phys. Plasmas 33, 032505 (2026).
[4] C. R. Sovinec, S. A. Patil, J. V. Cauilan, UW-CPTC 25-1 (www.cptc.wisc.edu/reports).
[5] M. Landreman, S. Buller, and M. Drevlak, Phys. Plasmas 29, 082501 (2022).
[6] A. Wright and N. M. Ferraro, Phys. Plasmas 31, 082509 (2024).
Characterization: 1.0
Comments:
This should be placed with and before the poster, "Pressure-driven MHD instabilities in low-shear stellarator ...," where Sanket Patil is the first author.