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:
- 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.
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.
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.
@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}
}
-
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 »
-
Resistive drift wave and interchange turbulence in a cylindrical plasma with magnetic and velocity shear
By solving numerically the two-field nonlinear model equations for the potential and density fluctuations in the presence of a density gradient, magnetic curvature with shear, and poloidal velocity shear, turbulent spectra and diffusion rates are studied. When the adiabatic parameter ({Omega}{sub {ital e}}/{nu}{sub {ital e}})({rho}{sub {ital s}}{sup 2}/{ital R}{sup 2})/({kappa}{rho}{sub {ital s}}) is small, a trend of a dual cascade, normal cascade of the density fluctuations, and an inverse cascade of the potential fluctuations, is seen in the wave number spectra, producing a large particle flux proportional to {nu}{sub {ital e}}{sup (1/3)}. Here {ital R} is the major radius, {rho}{submore » -
Vorticity scaling and intermittency in drift-interchange plasma turbulence
The effects of spatially varying magnetic field strength on the scaling properties of plasma turbulence, modelled by an extended form of Hasegawa-Wakatani model, are investigated. We study changes in the intermittency of the velocity, density, and vorticity fields, as functions of the magnetic field inhomogeneity C=-{partial_derivative} ln B/{partial_derivative}x. While the velocity fluctuations are always self-similar and their scaling is unaffected by the value of C, the intermittency levels in density and vorticity change with parameter C, reflecting morphological changes in the coherent structures due to the interchange mechanism. Given the centrality of vorticity in conditioning plasma transport, this result ismore » -
Transition from drift to interchange instabilities in an open magnetic field line configuration
The transition from a regime dominated by drift instabilities to a regime dominated by pure interchange instabilities is investigated and characterized in the simple magnetized toroidal device TORPEX [TORoidal Plasma EXperiment, A. Fasoli et al., Phys. of Plasmas 13, 055906 (2006)]. The magnetic field lines are helical, with a dominant toroidal component and a smaller vertical component. Instabilities with a drift character are observed in the favorable curvature region, on the high field side with respect to the maximum of the background density profile. For a limited range of values of the vertical field they coexist with interchange instabilities inmore » -
Toroidal Momentum Pinch Velocity due to the Coriolis Drift Effect on Small Scale Instabilities in a Toroidal Plasma
In this Letter, the influence of the ''Coriolis drift'' on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torquemore »