Journal Article

Advanced electron cyclotron heating and current drive experiments on the stellarator Wendelstein 7-X

Braune, Harald, Beurskens, Marc, Brunner, Kai Jakob, Turkin, Yuriy, Hirsch, Matthias, Bozhenkov, Sergey, Langenberg, Andreas, Gantenbein, Gerd, Fuchert, Golo, Cappa, Alvaro, Rahbarnia, Kian, Wauters, Tom, Höfel, Udo, Brakel, Rudolf, Dinklage, Andreas, Erckmann, Volker, Bosch, Hans-Stephan, Hartmann, Dirk, Moseev, Dmitry, Marsen, Stefan, Mora, Humberto Trimino, Laqua, Heinrich Peter, Pasch, Ekkehard, Grulke, Olaf, Marushchenko, Nikolai, Pablant, Novomir, Tsujimura, Toru, Wolf, Robert, Stange, Torsten, Kasparek, Walter, Knauer, Jens, Gellert, Florian

2017

Overview

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.

• Publisher: EDP Sciences
• Subject: Cyclotron resonance / Cyclotron resonance devices / Electron cyclotron heating / Electron cyclotron resonance / Electron energy / Plasma