D. Birus

The dedicated ICRH system for the stellarator Wendelstein 7-X

The current status of the mechanical and electromagnetic design for the ICRF antenna system for W7-X is presented. Two antenna plugins are discussed: one consisting of a pair of straps with pre-matching to cover the first frequency band 25-38 MHz and a second one consisting of two short strap triplets to cover a frequency band around 76 MHz. This paper focusses on the two strap antenna for the lower frequency band. Power coupling of the antenna to a reference plasma profile is studied with the help of the codes TOPICA and Microwave Studio, that deliver the scattering matrix needed for the optimization of the geometric parameters of the straps and antenna box. Radiation power spectra for different phasings of the two straps are obtained using the code ANTITER II and different heating scenarii are discussed. The potential for heating, fast particle generation and current drive is discussed. The problem of RF coupling through the plasma edge and of edge power deposition is summarized. The system contains a p...

IC Wall Conditioning antenna for W7-X with potential for Heating and Fast Particle Generation

The current planning of IC systems in W7‐X foresees in a first phase the construction of a single strap IC wall conditioning (ICWC) antenna, fed by one generator providing max 1MW at frequencies between 4 and 26 MHz. While this system is expected to be well suited for ICWC applications, we show that it could also be used for ICRF plasma heating and current drive (HC (ii) allowing flexible relative strap phasings for ICRF heating, fast particle generation and/or current drive; (iii) using the full ICRH power from the two generators available; (iv) with a compact design, such that it can be embedded in the wall panels, causing minimal perturbations for various magnetic configurations. The use of such an antenna would allow exploring experimentally various H&CD scenarios, and generate the necessary...

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.

ICRF heating for Wendelstein 7-X

Abstract The stellarator Wendelstein 7-X is being built in Greifswald, Germany, by the Max-Planck-Institut fur Plasmaphysik. Initially, the heating system will consist of 10 MW ECRH and 4 MW ICRF heating (both cw) and 5 MW NBI (for 15 s every 3 min). ECRH is the principal heating method at a magnetic field of B =2.5 T. At other magnetic fields or densities higher than the ECRH cutoff, ICRF heating will sustain the plasmas. 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, 3 dB 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.