skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Effect of Heating on the Suppression of Tearing Modes in Tokamaks

Abstract

The suppression of (neoclassical) tearing modes is of great importance for the success of future fusion reactors like ITER. Electron cyclotron waves can suppress islands, both by driving noninductive current in the island region and by heating the island, causing a perturbation to the Ohmic plasma current. This Letter reports on experiments on the TEXTOR tokamak, investigating the effect of heating, which is usually neglected. The unique set of tools available on TEXTOR, notably the dynamic ergodic divertor to create islands with a fully known driving term, and the electron cyclotron emission imaging diagnostic to provide detailed 2D electron temperature information, enables a detailed study of the suppression process and a comparison with theory.

Authors:
; ; ; ; ;  [1]; ;  [2];  [3];  [4]
  1. FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, PO Box 1207, 3430 BE Nieuwegein (Netherlands)
  2. Department of Applied Science, University of California at Davis, Davis, California 95616 (United States)
  3. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
  4. Forschungszentrum Juelich GmbH, Institut fuer Plasmaphysik, Association EURATOM-FZJ, D-52425 Juelich (Germany)
Publication Date:
OSTI Identifier:
20861621
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevLett.98.035001; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CYCLOTRONS; ELECTRIC CURRENTS; ELECTRON EMISSION; ELECTRON TEMPERATURE; ITER TOKAMAK; NEOCLASSICAL TRANSPORT THEORY; PLASMA HEATING; TEARING INSTABILITY; TEXTOR TOKAMAK

Citation Formats

Classen, I. G. J., Westerhof, E., Donne, A. J. H., Jaspers, R. J. E., Pol, M. J. van de, Spakman, G. W., Domier, C. W., Luhmann, N. C. Jr., Park, H. K., and Jakubowski, M. W.. Effect of Heating on the Suppression of Tearing Modes in Tokamaks. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.035001.
Classen, I. G. J., Westerhof, E., Donne, A. J. H., Jaspers, R. J. E., Pol, M. J. van de, Spakman, G. W., Domier, C. W., Luhmann, N. C. Jr., Park, H. K., & Jakubowski, M. W.. Effect of Heating on the Suppression of Tearing Modes in Tokamaks. United States. doi:10.1103/PHYSREVLETT.98.035001.
Classen, I. G. J., Westerhof, E., Donne, A. J. H., Jaspers, R. J. E., Pol, M. J. van de, Spakman, G. W., Domier, C. W., Luhmann, N. C. Jr., Park, H. K., and Jakubowski, M. W.. Fri . "Effect of Heating on the Suppression of Tearing Modes in Tokamaks". United States. doi:10.1103/PHYSREVLETT.98.035001.
@article{osti_20861621,
title = {Effect of Heating on the Suppression of Tearing Modes in Tokamaks},
author = {Classen, I. G. J. and Westerhof, E. and Donne, A. J. H. and Jaspers, R. J. E. and Pol, M. J. van de and Spakman, G. W. and Domier, C. W. and Luhmann, N. C. Jr. and Park, H. K. and Jakubowski, M. W.},
abstractNote = {The suppression of (neoclassical) tearing modes is of great importance for the success of future fusion reactors like ITER. Electron cyclotron waves can suppress islands, both by driving noninductive current in the island region and by heating the island, causing a perturbation to the Ohmic plasma current. This Letter reports on experiments on the TEXTOR tokamak, investigating the effect of heating, which is usually neglected. The unique set of tools available on TEXTOR, notably the dynamic ergodic divertor to create islands with a fully known driving term, and the electron cyclotron emission imaging diagnostic to provide detailed 2D electron temperature information, enables a detailed study of the suppression process and a comparison with theory.},
doi = {10.1103/PHYSREVLETT.98.035001},
journal = {Physical Review Letters},
number = 3,
volume = 98,
place = {United States},
year = {Fri Jan 19 00:00:00 EST 2007},
month = {Fri Jan 19 00:00:00 EST 2007}
}
  • A study is made of the suppression of neoclassical tearing modes in tokamaks under anomalous transverse transport conditions when the magnetic well effect predominates over the bootstrap drive. It is stressed that the corresponding effect, which is called the compound suppression effect, depends strongly on the profiles of the electron and ion temperature perturbations. Account is taken of the fact that the temperature profile can be established as a result of the competition between anomalous transverse heat transport, on the one hand, and longitudinal collisional heat transport, longitudinal heat convection, longitudinal inertial transport, and transport due to the rotation ofmore » magnetic islands, on the other hand. The role of geodesic effects is discussed. The cases of competition just mentioned are described by the model sets of reduced transport equations, which are called, respectively, collisional, convective, inertial, and rotational plasmophysical models. The magnetic well is calculated with allowance for geodesic effects. It is shown that, for strong anomalous heat transport conditions, the contribution of the magnetic well to the generalized Rutherford equation for the island width W is independent of W not only in the collisional model (which has been investigated earlier) but also in the convective and inertial models and depends very weakly (logarithmically) on W in the rotational model. It is this weak dependence that gives rise to the compound effect, which is the subject of the present study. A criterion for the stabilization of neoclassical tearing modes by the compound effect at an arbitrary level of the transverse heat transport by electrons and ions is derived and is analyzed for two cases: when the electron heat transport and ion heat transport are both strong, and when the electron heat transport is strong and the ion heat transport is weak.« less
  • A dispersion relation is derived for resistive modes of arbitrary parity in a tokamak plasma. At low mode amplitude, tearing and twisting modes which have nonideal magnetohydrodynamical (MHD) behavior at only one rational surface at a time in the plasma are decoupled via sheared rotation and diamagnetic flows. At higher amplitude, more unstable compound'' modes develop which have nonideal behavior simultaneously at many surfaces. Such modes possess tearing parity layers at some of the nonideal surfaces, and twisting parity layers at others, but mixed parity layers are generally disallowed. At low mode number, compound'' modes are likely to have tearingmore » parity layers at all of the nonideal surfaces in a very low-[beta] plasma, but twisting parity layers become more probable as the plasma [beta] is increased. At high mode number, unstable twisting modes which exceed a critical amplitude drive conventional magnetic island chains on alternate rational surfaces, to form an interlocking structure in which the O points and X points of neighboring chains line up.« less
  • The stability of multihelical tearing modes in tokamaks with shaped cross sections is determined numerically. The method allows inclusion of a large number of singular surfaces resolved with high accuracy. Poloidal and radial couplings are discussed and the convergence is well understood. Modes of high poloidal m number are found to be unstable for typical equilibria. Completely stable current distributions have been constructed for D-shaped plasmas.
  • Recently an incorrect dispersion relation (Ref. 2 and 3) was used in a publication by Connor {ital et} {ital al}. (Ref. 1) for toroidally coupled tearing and twisting modes. The aim of this comment is to pointout how this incorrect assumption affects the derivation of the coupled modes. (AIP)
  • The authors contend that incorrect inferences are drawn by Ding Li regarding the sources of error and of the basis function method used in the calculations of toroidally coupled tearing modes. (AIP)