Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies: Paper

Wendelstein 7-X Team, R C Wolf*, S Bozhenkov, A Dinklage, G Fuchert, Y O Kazakov, H P Laqua, S Marsen, N B Marushchenko, T Stange, M Zanini, I Abramovic, A Alonso, J Baldzuhn, M Beurskens, C D Beidler, H Braune, K J Brunner, N Chaudhary, H DammP Drewelow, G Gantenbein, Yu Gao, J Geiger, M Hirsch, U Höfel, M Jakubowski, J Jelonnek, T Jensen, W Kasparek, J Knauer, Søren Bang Korsholm, A Langenberg, C Lechte, F. Leipold, H Trimino Mora, U Neuner, S. K. Nielsen, D Moseev, H Oosterbeek, N Pablant, E Pasch, B Plaum, T Sunn Pedersen, A Puig Sitjes, K Rahbarnia, J. Rasmussen, M. Salewski, J Schilling, E Scott, M. Stejner, H Thomsen, M Thumm, Y Turkin, F Wilde

*Corresponding author for this work

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Abstract

For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising heating method even for the envisaged application in a fusion power plant. Wendelstein 7-X (W7-X) is equipped with a steady-state capable ECRH system, operating at 140 GHz, which corresponds to the 2nd cyclotron harmonic of the electrons at a magnetic field of 2.5 T. Ten gyrotrons are operational and already delivered 7 MW to W7-X plasmas. Combined with pellet injection, the highest triple product (0.68 × 1020 keV m−3 s), observed up to now in stellarators, was achieved (Sunn Pedersen et al 2018 Plasma Phys. Control. Fusion 61 014035). For the first time, W7-X plasmas were sustained by 2nd harmonic O-mode heating, approaching the collisionality regime for which W7-X was optimized. Power deposition scans did not show any indication of electron temperature profile resilience. In low-density, low-power plasmas a compensation of the bootstrap current with electron-cyclotron current drive (ECCD) was demonstrated. Sufficiently strong ECCD close to the plasma centre produced periodic internal plasma-crash events, which coincide with the appearance of low order rationals of the rotational transform.
Original languageEnglish
Article number014037
JournalPlasma Physics and Controlled Fusion
Volume61
Issue number1
Number of pages9
ISSN0741-3335
DOIs
Publication statusPublished - 2019
Event45th EPS Conference on Plasma Physics - Prague, Czech Republic
Duration: 2 Jul 20186 Jul 2018

Conference

Conference45th EPS Conference on Plasma Physics
Country/TerritoryCzech Republic
CityPrague
Period02/07/201806/07/2018

Keywords

  • Stellerator
  • Wendelstein 7-X
  • Electron-cyclotron-resonance heating and current drive

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