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Quasi-coherent modes and electron-driven turbulence

(2014) NUCLEAR FUSION. 54(12).
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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 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.
Keywords
DISCHARGES, turbulence, CONFINEMENT, REFLECTOMETRY, TRANSPORT, TORE-SUPRA, micro-instabilities, reflectometry, ohmic confinement, PLASMAS

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Citation

Please use this url to cite or link to this publication:

Chicago
Arnichand, Hugo, R Sabot, S Hacquin, A Kramer-Flecken, X Garbet, J Citrin, C Bourdelle, et al. 2014. “Quasi-coherent Modes and Electron-driven Turbulence.” Nuclear Fusion 54 (12).
APA
Arnichand, H., Sabot, R., Hacquin, S., Kramer-Flecken, A., Garbet, X., Citrin, J., Bourdelle, C., et al. (2014). Quasi-coherent modes and electron-driven turbulence. NUCLEAR FUSION, 54(12).
Vancouver
1.
Arnichand H, Sabot R, Hacquin S, Kramer-Flecken A, Garbet X, Citrin J, et al. Quasi-coherent modes and electron-driven turbulence. NUCLEAR FUSION. IOP PUBLISHING LTD; 2014;54(12).
MLA
Arnichand, Hugo, R Sabot, S Hacquin, et al. “Quasi-coherent Modes and Electron-driven Turbulence.” NUCLEAR FUSION 54.12 (2014): n. pag. Print.
@article{5797961,
  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 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.},
  articleno    = {123017},
  author       = {Arnichand, Hugo and Sabot, R and Hacquin, S and Kramer-Flecken, A and Garbet, X and Citrin, J and Bourdelle, C and Hornung, Grégoire and Bernardo, J and Bottereau, C and Clairet, F and Falchetto, G and Giacalone, JC},
  issn         = {0029-5515},
  journal      = {NUCLEAR FUSION},
  keywords     = {DISCHARGES,turbulence,CONFINEMENT,REFLECTOMETRY,TRANSPORT,TORE-SUPRA,micro-instabilities,reflectometry,ohmic confinement,PLASMAS},
  language     = {eng},
  number       = {12},
  pages        = {7},
  publisher    = {IOP PUBLISHING LTD},
  title        = {Quasi-coherent modes and electron-driven turbulence},
  url          = {http://dx.doi.org/10.1088/0029-5515/54/12/123017},
  volume       = {54},
  year         = {2014},
}

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