SMuK 2023 – scientific programme

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P: Fachverband Plasmaphysik

P 11: Poster I

P 11.46: Poster

Wednesday, March 22, 2023, 14:00–15:30, HSZ EG

Investigation of Tearing Modes in ASDEX Upgrade — •Magdalena Bauer, Louis Giannone, Anja Gude, Felix Klossek, Marc Maraschek, Bernhard Sieglin, Wolfgang Suttrop, Hartmut Zohm, and The ASDEX Upgrade Team — Max Planck Institute for Plasma Physics, Garching

Tearing modes with toroidal mode number n=1 are precursors of and significantly involved in disruptions, especially when they are locked to the vessel. While rotating modes can be observed by many Mirnov coils measuring the time derivative of the poloidal magnetic perturbation field, locked modes require a radial field measurement. In addition to the saddle coils on the high field side, toroidally distributed radial field coils at two different poloidal positions on the low field side can be used to gain information on slowly rotating and locked modes. A 3D finite element model, simulating the field generated by a single helical perturbation current in all coils, has been improved by considering the detailed coil geometry and a better description of conducting in-vessel parts in which mirror currents affecting the local perturbation field are induced. Coupling of n=1 modes with different poloidal mode numbers is believed to play a large role in the disruption process. The projection of the measured complex amplitudes in all coils on the modelled perturbation amplitudes with single helicities allows to determine the contribution of different poloidal mode numbers for rotating modes. For locked modes, only the three poloidal positions of the radial field coils are available. The opportunities and limitations of the poloidal mode structure analysis are investigated.