Erlangen 2018 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 11: Helmholtz Graduate School - Poster
P 11.31: Poster
Dienstag, 6. März 2018, 16:15–18:15, Redoutensaal
Experimental Characterisation of Parametric Decay Instabilities at ASDEX Upgrade — •Søren Kjer Hansen1,2, Stefan Kragh Nielsen2, Jörg Stober1, Jesper Rasmussen2, Morten Stejner2, and The ASDEX Upgrade Team1 — 1Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München, Germany — 2Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
When high power wave beams are injected into a plasma, e.g. for heating, current drive or diagnostic purposes, the wave amplitude may become so large that the linear approximation breaks down and a parametric decay instability (PDI) is excited. The present work concerns PDIs occurring for gyrotron radiation near the upper hybrid resonance at the ASDEX Upgrade tokamak, and is motivated by observations of strong anomalous (PDI generated) scattering made using the collective Thomson scattering (CTS) diagnostic. We measure the frequency power spectrum generated by the PDI with the high resolution fast receiver CTS system installed at ASDEX Upgrade and characterise its dependence on the injected gyrotron power by means of fast analog modulation of said power. The experimental observations are in reasonable agreement with previously published theoretical results. Apart from characterising anomalous scattering during CTS experiments, the present results may also have relevance for O-X-B heating experiments, planned for Wendelstein 7-X, and 1st harmonic electron cyclotron resonance heating, planned for ITER.