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.