RF waves and turbulence interaction

ASDEX Upgrade Seminar

  • Datum: 07.08.2019
  • Uhrzeit: 12:20 - 13:45
  • Vortragende(r): Ghassan Antar
  • Ort: Garching
  • Raum: Seminarraum L6, 2.Stock Süd
  • Gastgeber: IPP

Ghassan Antar, American University of Beirut: RF waves and turbulence interaction

Turbulence properties in the scrape off layer (SOL) in the presence of ion cyclotron frequency heating (ICRH) or Lower Hybrid (LH) waves are compared to instance where they are absent. It is shown both RF waves excite waves at frequencies about 1.7~MHz as a consequence of parametric decay instability. This is reflected in the power spectra of the ion saturation signals acquired at 200~MHz as well as in the cross-correlation between two toroidally distanced probes and in the bicoherence spectra. The velocity and the wavenumber of this perturbation are determined and they indicate that they may be ion sound waves. Furthermore, it is shown that they are nonlinearly coupled to the turbulent fluctuations leading to the strong modification of the power spectrum and could provide explanations about the decrease of the level of turbulence in the SOL during RF waves. This aspect is reflected in the enhanced three-wave coupling between these waves and turbulence studied by applying the bispectral analysis. Turbulence appears thus to be affected when RF waves are applied by the intermediate of ion sound waves. We deduce that RF waves may be used as an effective tool to control turbulence transport and to reduce ELMs induced transport.

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