The ICRH System Planned for Wendelstein 7-X

The Max-Planck Institute for Plasma Physics is presently building the stellarator experiment Wendelstein 7-X (W7-X) at Greifswald, Germany. First plasma operation in planned after 2010. The plasma will be heated primarily using electron cyclotron resonance heating (ECRH) at a magnetic field of B=2.5 T, but also using ion cyclotron resonance heating (ICRH) and neutral beam injection heating (NBI). The latter heating methods are necessary to study high beta discharges and fast ion confinement. The ICRF system is planned to consist of two radially movable antennas powered by two generators with an output power of 2 MW each. The antenna plasma load will be matched in real time to the generator impedance using ferrite loaded transmission line elements. In addition, 3dB couplers will passively protect the generators from RF power reflections during rapid changes of the antenna plasma load that are too fast for the ferrite matching system