Bremen 2017 – scientific programme
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P: Fachverband Plasmaphysik
P 15: Helmholtz Graduate School II
P 15.4: Poster
Tuesday, March 14, 2017, 16:30–18:30, HS Foyer
Experimental investigation of Ion Cyclotron waves interplay with magnetic perturbations and MHD phenomena. — •Guillermo Suarez Lopez1,2, Roman Ochoukov1, Matthias Willensdorfer1, Roberto Bilato1, Hartmut Zohm1,2, ICRF Team1, and ASDEX-U Team1 — 1Max Planck Institute for Plasma physics, Garching b. Munchen, Germany — 2Ludwig Maximillians University, Munich, Germany.
The excitation of compressional plasma waves at the ion cyclotron frequency is an effective technique for heating plasmas up to fusion temperatures. The main drawback of the technique comes from the necessity of placing embedded launchers (antennas) close to the plasma edge, due to the evanescent nature of these waves in low density plasmas, such as the ones present in the edge region of a tokamak device. The total distance along which the excited waves are evanescent up to the propagation layer, the R-cutoff, determines the amount of power lost in the decay and the coupling efficiency, that is, the fraction of non-reflected power coupled from the transmission line to the plasma. This distance can be indirectly modified in a non-axisymmetric fashion by the application of magnetic perturbation fields for other purposes, such as ELM mitigation, or plasma intrinsic phenomena such as MHD modes. Under these conditions, the antenna coupling efficiency can undergo significant variations. This study addresses experimentally the impact of non-axisymmetric plasma profiles on ion cyclotron heating coupling efficiency by means of antenna embedded reflectometry, ion-cyclotron probes, and plasma profile measuring diagnostics.