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Dependence of ideal-MHD kink and ballooning modes on plasma shape and profiles in tokamaks

Dependence of ideal-MHD kink and ballooning modes on plasma shape and profiles in tokamaks

Authors :
Alan M. M. Todd
J. Manickam
M. S. Chance
John M. Greene
M. Okabayashi
John L. Johnson
R.C. Grimm
Source :
Nuclear Fusion. 19:743-752
Publication Year :
1979
Publisher :
IOP Publishing, 1979.

Abstract

Extensive numerical studies of ideal-MHD instabilities have been carried out to gain insight into the parametric dependence of critical β's in tokamaks. The large number of interrelated equilibrium quantities involved in establishing a critical β has demanded a careful, systematic survey in order to isolate this dependence. The results of this survey establish the scaling with geometrical quantities including aspect ratio, elongation, and triangularity in the parameter regimes appropriate to both current and reactor-sized plasmas. A moderate dependence on the pressure profile and a strong variation with the current profile is found. The principal result is that, for aspect ratio R/a ≈ 3, critical β's are of the order of 2% for circular cross-sections and 5% for plasmas with elongation K ≈2; somewhat higher values could be achieved with more optimal shaping. Finally, sequences of equilibria have been analysed to compare critical β as a function of toroidal mode number n. It is concluded that the infinite-n analytic ballooning theory provides a sufficient condition for ideal-MHD internal-mode stability. Low-n free-boundary modes appear to set a lower limit.

Details

ISSN :
17414326 and 00295515
Volume :
19
Database :
OpenAIRE
Journal :
Nuclear Fusion
Accession number :
edsair.doi...........7b602d4ead086f01bbfb54ceaf1a0dbc
Full Text :
https://doi.org/10.1088/0029-5515/19/6/005