Aspect ratio dependence of the ideal internal kink mode stability in a toroidal plasma with circular cross section
2004 (English)In: Physics of Plasmas, Vol. 11, no 5, 2119-2134 p.Article in journal (Refereed) Published
The theory by Bussac et al. [Phys. Rev. Lett. 35, 1638 (1975)] on the stability of the ideal, internal kink mode in a toroidal plasma with circular cross section is extended to finite values of the inverse aspect ratio ea. The aspect ratio dependence comes from the term following the Bussac term in a large aspect ratio expansion of the potential energy dW of the mode. Although formally of higher order in the inverse aspect ratio, this term is of the same order of magnitude as the Bussac term when the safety factor q is close to (but below) unity at the plasma center and ea is finite. The new term is always stabilizing, but affects dW only marginally when the poloidal beta value beta-p is small and/or ea is small. For values of ea relevant for most tokamaks and beta-p larger than 0.3-0.5, however, the new term strongly modifies dW and leads to a second stability regime of the ideal, internal kink mode, in agreement with earlier numerical calculations.
Place, publisher, year, edition, pages
2004. Vol. 11, no 5, 2119-2134 p.
IdentifiersURN: urn:nbn:se:uu:diva-70679OAI: oai:DiVA.org:uu-70679DiVA: diva2:98590