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 language | English |
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Article number | 014037 |
Journal | Plasma Physics and Controlled Fusion |
Volume | 61 |
Issue number | 1 |
Number of pages | 9 |
ISSN | 0741-3335 |
DOIs | |
Publication status | Published - 2019 |
Event | 45th EPS Conference on Plasma Physics - Prague, Czech Republic Duration: 2 Jul 2018 → 6 Jul 2018 |
Conference
Conference | 45th EPS Conference on Plasma Physics |
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Country/Territory | Czech Republic |
City | Prague |
Period | 02/07/2018 → 06/07/2018 |
Keywords
- Stellerator
- Wendelstein 7-X
- Electron-cyclotron-resonance heating and current drive