Sawtooth stability in neutral beam heated plasmas in TEXTOR

TitleSawtooth stability in neutral beam heated plasmas in TEXTOR
Publication TypeJournal Article
Year of Publication2008
AuthorsI.T. Chapman, S.D Pinches, H.R Koslowski, Y. Liang, A. Kramer-Flecken, M. De Bock
JournalNuclear Fusion
Volume48
Number3
Pagination9
Date PublishedMar
Type of ArticleArticle
ISBN Number0029-5515
Accession NumberISI:000255111500007
KeywordsCONFINEMENT, CYCLOTRON CURRENT DRIVE, DISCHARGES, INTERNAL KINK MODE, PERIOD, PROFILE, ROTATION, STABILIZATION, TOKAMAK, TOROIDAL PLASMA
Abstract

The experimental sawtooth behaviour in neutral beam injection (NBI) heated plasmas in TEXTOR is described. It is found that the sawtooth period is minimized with a low NBI power oriented in the same direction as the plasma current. As the beam power is increased in the opposite direction to the plasma current, the sawtooth period increases to a maximum before it begins to shorten once more. Results from both magnetohydrodynamic stability modelling including toroidal flows and modelling of the kinetic effects of the fast ions resulting from NBI heating are also presented. This model combining the gyroscopic and kinetic effects upon the stability of the n = 1 internal kink mode-thought to be associated with sawtooth oscillations-qualitatively recovers the sawtooth behaviour exhibited in the experiment. It is proposed that the sawtooth period is minimized in the co-NBI direction at the point at which the stabilization of the kink mode due to rotation is weakest. This occurs when the plasma rotation induced by the NBI balances the intrinsic rotation of the plasma. The sawtooth behaviour in the counter-NBI regime is attributed to a subtle balance of the competing stabilization from the toroidal rotation and destabilization from the presence of energetic ions.

URL<Go to ISI>://000255111500007
Division

Fusion Physics

PID

20adf137bfda929380908e46279581f7

Alternate TitleNucl. Fusion

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