Advanced electron cyclotron heating and current drive experiments on the stellarator Wendelstein 7-X
1 Max-Planck-Institute for Plasma Physics, Greifswald, Germany
2 Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain
3 Institute for Interfacial Process Engineering and Plasma Technology, University Stuttgart, Germany
4 Institute of Pulsed Power and Microwave Technology, Karlsruhe Institute of Technology (KIT), Germany
5 Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
6 National Institute for Fusion Science, Toki 509-5292, Japan
7 Laboratory for Plasma Physics, ERM/KMS, Brussels, Belgium
* Corresponding author: firstname.lastname@example.org
Published online: 23 October 2017
During the first operational phase (OP 1.1) of Wendelstein 7-X (W7-X) electron cyclotron resonance heating (ECRH) was the exclusive heating method and provided plasma start-up, wall conditioning, heating and current drive. Six gyrotrons were commissioned for OP1.1 and used in parallel for plasma operation with a power of up to 4.3 MW. During standard X2-heating the spatially localized power deposition with high power density allowed controlling the radial profiles of the electron temperature and the rotational transform. Even though W7-X was not fully equipped with first wall tiles and operated with a graphite limiter instead of a divertor, electron densities of n e > 3·1019 m-3 could be achieved at electron temperatures of several keV and ion temperatures above 2 keV. These plasma parameters allowed the first demonstration of a multipath O2-heating scenario, which is envisaged for safe operation near the X-cutoff-density of 1.2·1020 m-3 after full commissioning of the ECRH system in the next operation phase OP1.2.
© The authors, published by EDP Sciences, 2017
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