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ECCD-induced sawtooth crashes at W7-X

W7-X Team; Zanini, M.; Laqua, H.P.; Thomsen, H.; Stange, T.; Brandt, C.; Braune, H.; Brunner, K.J.; Fuchert, G.; Hirsch, M.; Knauer, J.; Höfel, U.; Marsen, S.; Pasch, E.; Rahbarnia, K.; Schilling, J.; Turkin, Y.; Wolf, R.C.; Zocco, A.; Gantenbein, Gerd; Huber, Martina; ... mehr

Abstract (englisch):
The optimised superconducting stellarator W7-X generates its rotational transform by means of
external coils, therefore no toroidal current is necessary for plasma confinement. Electron
cyclotron current drive experiments were conducted for strikeline control and safe divertor
operation. During current drive experiments periodic and repetitive crashes of the central
electron temperature, similar to sawtooth crashes in tokamaks, were detected. Measurements
from soft x-ray tomography and electron cyclotron emission show that the crashes are preceded
by weak oscillating precursors and a displacement of the plasma core, consistent with a
(m, n)=(1, 1) mode. The displacement occurs within 100μs, followed by expulsion and
redistribution of the core into the external part of the plasma. Two types of crashes, with
different frequencies and amplitudes are detected in the experimental program. For these
non-stationary parameters a strong dependence on the toroidal current is found. A 1-D heuristic
model for current diffusion is proposed as a first step to explain the characteristic crash time.
Initial results show that the modelled current diffusion timescale is consistent with the initial
... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000125250
Veröffentlicht am 23.10.2020
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Hochleistungsimpuls- und Mikrowellentechnik (IHM)
Institut für Angewandte Materialien - Angewandte Werkstoffphysik (IAM-AWP)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 10.2020
Sprache Englisch
Identifikator ISSN: 0029-5515, 1741-4326
KITopen-ID: 1000125250
HGF-Programm 31.03.02 (POF III, LK 01)
Plasma Heizsysteme
Erschienen in Nuclear fusion
Band 60
Heft 10
Seiten Article no: 106021
Projektinformation EUROfusion (EU, H2020, 633053)
Vorab online veröffentlicht am 22.09.2020
Nachgewiesen in Web of Science
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