Hannover 2020 – scientific programme

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P: Fachverband Plasmaphysik

P 16: Poster Session 3

P 16.6: Poster

Wednesday, March 11, 2020, 16:30–18:30, Empore Lichthof

Electron Bernstein wave heating at harmonics of the electron cyclotron resonance frequency — •Alf Köhn-Seemann and Eberhard Holzhauer — IGVP, Universität Stuttgart, Germany

Electron Bernstein waves (EBWs) provide a method to transfer energy to a plasma whose density exceeds the corresponding cut-off density of an injected microwave. No high-density cut-off exists for EBWs and they are very well absorbed at harmonics of the electron cyclotron resonance frequency. In addition, they can also drive significant toroidal net currents with current drive efficiencies exceeding those normally achieved by standard electron cyclotron resonance heating. EBWs are, however, electrostatic waves and need thus be coupled to externally injected electromagnetic waves. We discuss the different coupling mechanisms and how their efficiency depends on the plasma parameters. We will use both, full-wave simulations and ray-tracing calculations to illustrate the effect of increasing harmonics number by decreasing magnetic field strength. It will be shown how going to higher harmonics will change the propagation paths and the coupling efficiencies. The results obtained from numerics will be compared with experimental results obtained from the TJ-K stellarator with its density gradient lengths comparable to the wavelength of the injected microwave.