München 2019 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 18: Postersitzung
P 18.62: Poster
Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax
MHD activity and bootstrap current evolution during the first divertor campaign at the Wendelstein 7-X stellarator — •K Rahbarnia1, T Andreeva1, CD Beidler1, T Bluhm1, BB Carvalho2, J Geiger1, U Neuner1, J Schilling1, A v Stechow1, H Thomsen1, Y Turkin1, M Zanini1, M Zilker1, and W7X Team1 — 1Max Planck Institute for Plasma Physics, Wendelsteinstr. 1, 17491 Greifswald, Germany — 2Instituto de Plasmas e Fusao Nuclear Instituto Superior Tecnico, Lisbon, Portugal
During the past operational phase OP1.2b at Wendelstein 7-X (W7-X), wall conditioning via repeated boronization led to enhanced plasma performance. A plasma heating interlock signal, based on the measured diamagnetic energy (Wdia), supported safe W7-X operation. The pulse duration was significantly extended (up to 100s@2MW heating power) while keeping stable plasma conditions, which allows the study of bootstrap current evolution for several characteristic time scales. Previous results indicating current minimization in W7-X are further supported by a large number of dedicated experiments and comparisons to 1-D neoclassical transport simulations. Based on measurements from a total of 125 Mirnov probes, the underlying MHD activity during transient high plasma energy phases (Wdia∼ 1.2MJ) is investigated. Sudden energy crashes, induced by external current drive, as well as fast ion triggered plasma instabilities also provoke pronounced MHD activity. Preliminary mode number analysis results are discussed, complemented by Soft X-Ray, electron cyclotron emission and phase contrast imaging diagnostic measurements.