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Title: Viscous relaxation of drift-Alfven waves in tokamaks and its application for triggering improved confinement regimes

Abstract

Viscous damping of the drift-Alfven modes in tokamaks and its application for triggering improved confinement regimes are considered. It is shown that these waves are effectively damped by the neoclassical viscosity with the upper limit for their frequency {omega} equal to the collision frequency of slow ions {nu}{sub i}/{epsilon}, where {epsilon} is the inverse aspect ratio. Quasistationary plasma poloidal and toroidal velocities and current drive produced by damping of these waves are estimated. Evaluations of the viscosity effects on the Alfven waves which were induced by the dynamic ergodic divertor in the Tokamak Experiment for Technology Oriented Research tokamak [K. H. Finken et al., Phys. Rev. Lett. 94, 015003 (2005)] are made.

Authors:
; ;  [1];  [2]
  1. Institute of Physics, University of Sao Paulo, Cidade Universitaria, 05508-900, Sao Paulo (Brazil)
  2. (Brazil)
Publication Date:
OSTI Identifier:
20960132
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 1; Other Information: DOI: 10.1063/1.2434792; (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; ALFVEN WAVES; ASPECT RATIO; COLLISIONS; CURRENTS; DAMPING; DIVERTORS; IONS; NEOCLASSICAL TRANSPORT THEORY; PLASMA; PLASMA CONFINEMENT; PLASMA DRIFT; RELAXATION; TOKAMAK DEVICES; VISCOSITY

Citation Formats

Tsypin, V. S., Elfimov, A. G., Galvao, R. M. O., and Institute of Physics, University of Sao Paulo, Cidade Universitaria, 05508-900, Sao Paulo, Brazil and Centro Brasileiro de Pesquisas em Fisica, Rua Xavier Sigaud 150, Rio de Janeiro, BR-22290180. Viscous relaxation of drift-Alfven waves in tokamaks and its application for triggering improved confinement regimes. United States: N. p., 2007. Web. doi:10.1063/1.2434792.
Tsypin, V. S., Elfimov, A. G., Galvao, R. M. O., & Institute of Physics, University of Sao Paulo, Cidade Universitaria, 05508-900, Sao Paulo, Brazil and Centro Brasileiro de Pesquisas em Fisica, Rua Xavier Sigaud 150, Rio de Janeiro, BR-22290180. Viscous relaxation of drift-Alfven waves in tokamaks and its application for triggering improved confinement regimes. United States. doi:10.1063/1.2434792.
Tsypin, V. S., Elfimov, A. G., Galvao, R. M. O., and Institute of Physics, University of Sao Paulo, Cidade Universitaria, 05508-900, Sao Paulo, Brazil and Centro Brasileiro de Pesquisas em Fisica, Rua Xavier Sigaud 150, Rio de Janeiro, BR-22290180. Mon . "Viscous relaxation of drift-Alfven waves in tokamaks and its application for triggering improved confinement regimes". United States. doi:10.1063/1.2434792.
@article{osti_20960132,
title = {Viscous relaxation of drift-Alfven waves in tokamaks and its application for triggering improved confinement regimes},
author = {Tsypin, V. S. and Elfimov, A. G. and Galvao, R. M. O. and Institute of Physics, University of Sao Paulo, Cidade Universitaria, 05508-900, Sao Paulo, Brazil and Centro Brasileiro de Pesquisas em Fisica, Rua Xavier Sigaud 150, Rio de Janeiro, BR-22290180},
abstractNote = {Viscous damping of the drift-Alfven modes in tokamaks and its application for triggering improved confinement regimes are considered. It is shown that these waves are effectively damped by the neoclassical viscosity with the upper limit for their frequency {omega} equal to the collision frequency of slow ions {nu}{sub i}/{epsilon}, where {epsilon} is the inverse aspect ratio. Quasistationary plasma poloidal and toroidal velocities and current drive produced by damping of these waves are estimated. Evaluations of the viscosity effects on the Alfven waves which were induced by the dynamic ergodic divertor in the Tokamak Experiment for Technology Oriented Research tokamak [K. H. Finken et al., Phys. Rev. Lett. 94, 015003 (2005)] are made.},
doi = {10.1063/1.2434792},
journal = {Physics of Plasmas},
number = 1,
volume = 14,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • The collisionless drift wave and drift-Alfven wave instabilities in a sheared magnetic field are considered using the complex transformation technique of Antonsen. It is shown that no unstable bounded eigensolutions for the finite-..beta.. radial eigenmode equations exist. We also present a more general technique based on the wave-flux conservation and find, furthermore, that the convective amplification of drift waves in the electrostatic limit can be anomalously large, which could lead to enhanced transport in tokamaks.
  • A new branch of solutions of the finite-beta drift-wave radial eigenmode equations has been found. The branch is heavily damped in the low-beta regime and identified with the shear Alfven wave. This branch and the usual electrostatic branch are damped in a collisionless plasma. Including trapped electron effects an introduces an instability which is potentially harmful to plasma confinement.
  • Orthogonal probes on a free-flying plasma diagnostics payload are used to study ELF electric disturbances in the auroral ionosphere that are due to the injection of powerful electron beams. Frequency spectrograms are presented for various pitch angles, pulsing characteristics, and other properties of the injected beams; the large scale DC ionospheric convection electric field is measured, together with auroral particle precipitation, visual auroral forms, and ionospheric parameters. In view of the experimental results obtained, it is postulated that the observed ELF waves are in the Alfven and drift modes, and are generated by the positive vehicle potential during beam injection.more » 15 references.« less
  • The method developed in Thoul, Similon, and Sudan [Phys. Plasmas [bold 1], 579 (1994)] is used to calculate the transport due to drift-Alfven-wave turbulence, in which electromagnetic effects such as the fluttering of the magnetic field lines are important. Explicit expressions are obtained for all coefficients of the anomalous transport matrix relating particle and heat fluxes to density and temperature gradients in the plasma. Although the magnetic terms leave the transport by trapped electrons unaffected, they are important for the transport by circulating electrons.