Progress in the 10-MW ECRH system for the Stellarator W7-X

During the last few years, electron-cyclotron resonance heating (ECRH) and electron-cyclotron current drive (ECCD) has proven to be one of the most attractive heating schemes for stellarators, as it provides net current free plasma start up and heating. Extensive measurements on stellarators at Garching provide a solid physical and technological basis for the ECRH system on the new stellarator facility W7-X, which is now under construction at the Max Planck Institute of Plasma Physics, Greifswald, Germany. The ECRH system will be built up from ten gyrotrons each with a power of 1 MW at a frequency of 140 GHz operating under almost stationary conditions (30 min.). The scientific goals of the superconducting stellarator and the demands for the ECRH system including the gyrotron development and the transmission lines are discussed.