SMuK 2021 – scientific programme
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P: Fachverband Plasmaphysik
P 7: Helmholtz Graduate School III
P 7.1: Talk
Wednesday, September 1, 2021, 14:00–14:25, H4
Simplified nonlinear MHD models of external kink modes in stellarators — •Rohan Ramasamy1,2, Matthias Hoelzl1, Erika Strumberger1, Guillermo Suárez López1, Sophia Henneberg3, Karl Lackner1, and Sibylle Günter1 — 1Max Planck Institute for Plasma Physics, Garching, Germany — 2Max Planck Princeton Center for Plasma Physics, New Jersey, USA — 3Max Planck Institute for Plasma Physics, Greifswald, Germany
Non-linear magnetohydrodynamic (MHD) codes are an important tool in improving the understanding of disruptions in tokamaks. Recently, there has been renewed interest in advancing state-of-the-art MHD codes to model stellarators. Herein, two simplified models are explored, using the nonlinear code, JOREK, and the equilibrium code, VMEC.
VMEC is used to calculate the nonlinear saturated state of ideal external kink modes in simplified l=2 stellarators. These saturated states are then compared against a simpified axisymmetric approximation of the stellarator, implemented in JOREK. The axisymmetric approach includes the external rotational transform by means of a virtual current model.
This approach is then applied to an unstable quasi-axisymmetric configuration to assess the stabilising influence of increasing external rotational transform on the MHD activity. The results show that while the external modes are stabilised significantly, nonlinearly triggered internal modes degrade confinement further. A relatively large external rotational transform is necessary to avoid a significant loss of confinement.