München 2019 – wissenschaftliches Programm
P 15.2: Hauptvortrag
Mittwoch, 20. März 2019, 11:30–12:00, HS 21
Reduction of microwave beam quality due to plasma density fluctuations — •Alf Köhn1, Pavel Aleynikov2, Lorenzo Guidi3, Eberhard Holzhauer1, Omar Maj3, Emanuele Poli3, Michael Brookman4, Antti Snicker3, Thomas Matthew5, Roddy Vann5, and Hannes Weber3 — 1IGVP, Universität Stuttgart, Germany — 2Max-Planck-Institut für Plasmaphysik, Greifswald, Germany — 3Max-Planck-Institut für Plasmaphysik, Garching, Germany — 4Institute for Fusion Studies, Austin, Texas — 5York Plasma Institute, York, U.K.
Microwaves are commonly used in plasma experiments for heating and diagnostic purposes. When passing through the plasma boundary, the microwaves have to traverse an area where significant density fluctuations are known to occur. The beam is disturbed, resulting in reduced heating efficiencies or ambiguous diagnostics results. This is in particular problematic for the stabilization of MHD modes, which requires a highly localized power deposition. Concern has been raised recently if ITER might suffer from this. Here we present full-wave simulations of the interaction of microwaves with a layer of fluctuating plasma density. A novel wave-kinetic equation solver using a statistical description of the turbulence is compared to the full-wave simulations. The broadening of a microwave beam is investigated as a function of the turbulence properties. The possibility of density variations leading to mode-scattering is discussed. Finally, experimental verification of microwave beam broadening caused by edge density fluctuations is presented and compared with simulations for the DIII-D tokamak.