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research article

Geometrical and Profile Effects on Toroidicity and Ellipticity Induced Alfven Eigenmodes

Villard, L.  
•
Fu, G. Y.
1992
Nuclear Fusion

The wave structures, eigenfrequencies and damping rates of toroidicity and ellipticity induced Alfven eigenmodes (TAEs, EAEs) of low toroidal mode numbers (n) are calculated for various axisymmetric ideal MHD equilibria with the global wave finite element code LION. The importance of the safety factor (q) and density (rho) profiles on the continuum damping rates is analysed. For realistic profiles, several continuum gaps exist in the plasma discharge. Frequency misalignment of these gaps yields continuum damping rates gamma/omega of the order of a few per cent. Finite poloidal beta lowers the TAE eigenfrequency. For beta values below the Troyon limit, the TAE enters the continuum and can thus be stabilized. Finite elongation allows the EAE to exist, but triangularity can have a stabilizing effect through coupling with the continuum. The localization of TAE and EAE eigenfunctions is found to increase with the shear and with n. Therefore, large shear, through enhanced Landau and collisional damping, is a stabilizing factor for TAEs and EAEs.

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Type
research article
DOI
10.1088/0029-5515/32/10/I01
Author(s)
Villard, L.  
Fu, G. Y.
Date Issued

1992

Publisher

IOP Publishing Ltd

Published in
Nuclear Fusion
Volume

32

Issue

10

Start page

1695

End page

1713

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
CRPP  
SPC  
Available on Infoscience
April 16, 2008
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/21184
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