Quasi-coherent modes and electron-driven turbulence

TitleQuasi-coherent modes and electron-driven turbulence
Publication TypeJournal Article
Year of Publication2014
AuthorsH. Arnichand, R. Sabot, S. Hacquin, A. Kramer-Flecken, X. Garbet, J. Citrin, C. Bourdelle, G. Hornung, J. Bernardo, C. Bottereau, F. Clairet, G.L. Falchetto, J. Giacalone
JournalNuclear Fusion
Volume54
Issue12
Number12
Pagination123017
Abstract

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 ∼400 m s −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.

DOI10.1088/0029-5515/54/12/123017
Division

FP

Department

CPP-HT

PID

e609e9cd25503eb84da96d315a3025c4

Alternate TitleNucl. Fusion
LabelOA
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