The interaction between plasma rotation, stochastic fields and tearing mode excitation by external perturbation fields

TitleThe interaction between plasma rotation, stochastic fields and tearing mode excitation by external perturbation fields
Publication TypeJournal Article
Year of Publication2008
AuthorsM.FM de Bock, I.G.J. Classen, C. Busch, R.JE Jaspers, H.R Koslowski, B. Unterberg
JournalNuclear Fusion
Volume48
Number1
Pagination16
Date PublishedJan
Type of ArticleArticle
ISBN Number0029-5515
Accession NumberISI:000253482200008
KeywordsDIII-D, DYNAMIC ERGODIC DIVERTOR, ERROR-FIELD, FLUID ROTATION, PENETRATION, RESONANT MAGNETIC PERTURBATIONS, STABILIZATION, TEXTOR, THRESHOLD, TOKAMAK PLASMA
Abstract

For fusion reactors, based on the principle of magnetic confinement, it is important to avoid so-called magnetic islands or tearing modes. They reduce confinement and can be the cause of major disruptions. One class of magnetic islands is that of the perturbation field driven modes. This perturbation field can, for example, be the intrinsic error field. Theoretical work predicts a strong relationship between plasma rotation and the excitation of perturbation field modes. Experimentally, the theory on mode excitation and plasma rotation has been confirmed on several tokamaks. In those experiments, however, the control over the plasma rotation velocity and direction, and over the externally applied perturbation field was limited. In this paper experiments are presented that were carried out at the TEXTOR tokamak. Two tangential neutral beam injectors and a set of helical perturbation coils, called the dynamic ergodic divertor (DED), provide control over both the plasma rotation and the external perturbation field in TEXTOR. This made it possible to set up a series of experiments to test the theory on mode excitation and plasma rotation in detail. The perturbation field induced by the DED not only excites magnetic islands, it also sets up a layer near the plasma boundary where the magnetic field is stochastic. It will be shown that this stochastic field alters both the rotational response of the plasma on the perturbation field and the threshold for mode excitation. It therefore has to be included in an extended theory on mode excitation.

URL<Go to ISI>://000253482200008
Division

Fusion Physics

PID

bdb87dd2b24f796537ab406121542201

Alternate TitleNucl. Fusion

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