Quasi-coherent modes and electron-driven turbulence
Autor: | Xavier Garbet, C. Bottereau, Jonathan Citrin, Grégoire Hornung, G. Falchetto, F. Clairet, H. Arnichand, Clarisse Bourdelle, A. Krämer-Flecken, S. Hacquin, J. Bernardo, J. C. Giacalone, Roland Sabot |
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Rok vydání: | 2014 |
Předmět: |
Physics
Nuclear and High Energy Physics Tokamak Plasma Electron Tore Supra Condensed Matter Physics 01 natural sciences Instability Electron cyclotron resonance 010305 fluids & plasmas law.invention Nuclear magnetic resonance Physics::Plasma Physics law 0103 physical sciences Diamagnetism Atomic physics Phase velocity 010306 general physics |
Zdroj: | Nuclear Fusion, 54, 123017 Nuclear Fusion |
ISSN: | 1741-4326 0029-5515 1536-1055 0741-3335 |
Popis: | This letter reports on quasi-coherent (QC) modes observed in fluctuation spectra from Tore Supra and TEXTOR reflectometers. QC modes have characteristics in between coherent and broad-band fluctuations as they oscillate around a given frequency but have a wide spectrum. They are ballooned at the LFS midplane and appear usually on a frequency ranging from 30 to 120 kHz. In ohmic plasmas from both tokamaks, QC modes are detected only in linear ohmic confinement (LOC) regime and disappear in saturated ohmic confinement (SOC) regime. Linear simulations from Tore Supra predict that the LOC and SOC regimes are dominated by electron and ion modes respectively. Measurements of the perpendicular velocity of density fluctuations have been made from the top of TEXTOR by poloidal correlation reflectometry. They suggest that QC modes have a phase velocity similar to 400 ms(-1) higher in the electron diamagnetic direction than lower frequency fluctuations. Additionally, the onset of QC modes during electron cyclotron resonance heating has been observed in a Tore Supra region where turbulence is suspected to be driven by electron modes. These experimental results and instability calculations show a correlation between onsets of QC modes and predictions of trapped electron modes. |
Databáze: | OpenAIRE |
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