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Progress in the 10-MW 140-GHz ECH system for the stellarator W7-X

Authors :
Thumm, Manfred
Brand, Peter
Braune, Harald
Dammertz, Gunter
Erckmann, Volker
Gantenbein, Gerd
Illy, Stefan
Kasparek, Walter
Laqua, Heinrich Peter
Lechte, Carsten
Leonhardt, Wolfgang
Michel, Georg
Neffe, Gunter
Piosczyk, Bernhard
Schmid, Martin
Weissgerber, Michael
Source :
IEEE Transactions on Plasma Science. April, 2008, Vol. 36 Issue 2, p341, 15 p.
Publication Year :
2008

Abstract

During the last years, electron cyclotron heating (ECH) was proven to be one of the most attractive heating schemes for stellarators because it provides net-current-free plasma startup and heating. Both the stellarator Wendelstein 7-X (W7-X), which is under construction at the Max-Planck-Institut fur Plasmaphysik, Greifswald, Germany, and the International Thermonuclear Experimental Reactor (ITER) tokamak, which will be built in Cadarache, France, will be equipped with a strong ECH and current-drive system. Both systems are comparable in frequency and have continuous-wave capability (140 GHz, 10 MW for W7-X and 170 GHz, 24 MW for ITER). The commissioning of the ECH plant for W7-X is well underway; the status of the project and the first integrated full-power test results from two modules are reported and may provide valuable input for the ITER plant. The ten gyrotrons at W7-X will be arranged in two subgroups symmetrically to a central beam duct in the ECH hall. The RF wave of each subgroup will be combined and transmitted by a purely optical multibeam-waveguide (MBWG) transmission line from the gyrotrons to the torus. The combination of five 1 MW gyrotron beams to one beam line with a power of 5 MW reduces the complexity of the system considerably. The single- and MBWG mirrors and the polarizers have been manufactured. Cold tests of a full-size uncooled prototype line delivered an efficiency exceeding 90%. The microwave power will be launched to the plasma through ten chemical-vapor-deposited-diamond barrier windows and in-vessel quasi-optical plug-in launchers, allowing each 1-MW RF beam to be steered independently. The polarization, as well as the poloidal and toroidal launch angles, will be adjusted individually to provide optimum conditions for different heating and current-drive scenarios. Index Terms--Electron cyclotron heating (ECH), high-power continuous-wave (CW) gyrotron, quasi-optical transmission, stellarator.

Details

Language :
English
ISSN :
00933813
Volume :
36
Issue :
2
Database :
Gale General OneFile
Journal :
IEEE Transactions on Plasma Science
Publication Type :
Academic Journal
Accession number :
edsgcl.178219217