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Title: Development of electrostatic turbulence from drift-interchange instabilities in a toroidal plasma

Abstract

Electrostatic instabilities develop on TORPEX (TORoidal Plasma EXperiment) [A. Fasoli et al., Phys. of Plasmas, 13, 55902 (2006)] in the bad curvature region and propagate consistently with the drift wave dispersion relation. The wave number and frequency spectra are coherent at the location where the instabilities are generated, then broaden along the ExB convection. The phase coupling between spectral components at different frequencies, measured at different locations over the plasma cross section, indicates that the transition from a coherent to a turbulent spectrum is mainly due to three-wave interaction processes. Nonlinear interactions are measured between the linearly unstable mode and fluctuations with larger frequency, with transfer of energy away from the linearly unstable mode. The results are consistent with a nonlinearity induced by the convection of density fluctuations by the ExB fluctuating velocity.

Authors:
; ;  [1]
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  1. CRPP-EPFL, Association EURATOM-Confederation Suisse, Lausanne (Switzerland)
Publication Date:
OSTI Identifier:
20974981
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2731323; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CONVECTION; DISPERSION RELATIONS; DRIFT INSTABILITY; ELECTROMAGNETIC FIELDS; FLUCTUATIONS; FLUTE INSTABILITY; NONLINEAR PROBLEMS; PLASMA; PLASMA CONFINEMENT; PLASMA DENSITY; PLASMA DRIFT; TOKAMAK DEVICES; TURBULENCE; WAVE PROPAGATION

Citation Formats

Poli, F. M., Podesta, M., and Fasoli, A. Development of electrostatic turbulence from drift-interchange instabilities in a toroidal plasma. United States: N. p., 2007. Web. doi:10.1063/1.2731323.
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Poli, F. M., Podesta, M., & Fasoli, A. Development of electrostatic turbulence from drift-interchange instabilities in a toroidal plasma. United States. doi:10.1063/1.2731323.
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Poli, F. M., Podesta, M., and Fasoli, A. Tue . "Development of electrostatic turbulence from drift-interchange instabilities in a toroidal plasma". United States. doi:10.1063/1.2731323.
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@article{osti_20974981,
title = {Development of electrostatic turbulence from drift-interchange instabilities in a toroidal plasma},
author = {Poli, F. M. and Podesta, M. and Fasoli, A.},
abstractNote = {Electrostatic instabilities develop on TORPEX (TORoidal Plasma EXperiment) [A. Fasoli et al., Phys. of Plasmas, 13, 55902 (2006)] in the bad curvature region and propagate consistently with the drift wave dispersion relation. The wave number and frequency spectra are coherent at the location where the instabilities are generated, then broaden along the ExB convection. The phase coupling between spectral components at different frequencies, measured at different locations over the plasma cross section, indicates that the transition from a coherent to a turbulent spectrum is mainly due to three-wave interaction processes. Nonlinear interactions are measured between the linearly unstable mode and fluctuations with larger frequency, with transfer of energy away from the linearly unstable mode. The results are consistent with a nonlinearity induced by the convection of density fluctuations by the ExB fluctuating velocity.},
doi = {10.1063/1.2731323},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
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Journal Article:
DOI:  10.1063/1.2731323
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    Low frequency electrostatic instabilities are investigated on TORPEX [Fasoli, Labit, McGrath, Mueller, Podesta, and Poli, Bull. Am. Phys. Soc. 48, 119 (2003)], a toroidal device for basic plasma physics experiments with a toroidal magnetic field 100 mT and a small vertical magnetic field ({<=}4 mT). A two-dimensional (2D) profile of the frequency and amplitude of density and potential fluctuations is reconstructed using electrostatic probes with high space and time resolution. The measured phase velocity, corrected for the Doppler shift induced by the ExB drift, is consistent with the electron diamagnetic drift velocity. The local dispersion relation, measured along and acrossmore » the magnetic field, is in agreement with the predictions of a linear kinetic slab model for drift waves. Unstable modes are generated in regions of unfavorable curvature, where the pressure gradient is colinear with the magnetic field gradient. It is demonstrated that the curvature of the magnetic field lines is essential for driving the observed instabilities, which are therefore identified as drift-interchange modes.« less

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