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Ballooning stability analysis of JET H-mode discharges

Research output: Chapter in Book/Report/Conference proceedingConference contribution

  • D.P. O'Brien
  • R. Galvao
  • M. Keilhacker
  • E. Lazzaro
  • M.L. Watkins
  • C.M. Bishop

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Original languageEnglish
Title of host publication Proceedings 16th European Conference on Controlled Fusion and Plasma Physics
Pages229-232
Number of pages4
Volume1
Publication statusPublished - 1989

Abstract

Previous studies of the stability of a large aspect ratio model equilibrium to ideal MHD ballooning modes have shown that across the bulk of the plasma there exist two marginally stable values of the pressure gradient parameter α. These define an unstable zone which separates the first (small α) stable region from the second (large α) stable region. Close to the separatrix, however, the first and second regions can coalesce when the surface averaged current density, Λ, exceeds a critical value. The plasma in this region is then stable to ballooning modes at all values of the pressure gradient. In this paper we extend these results to JET H-mode equilibria using a finite aspect ratio ballooning formalism, and assess the relevance of ideal ballooning stability in these discharges. In particular we analyse shot 15894 at time 56 sec. which is 1.3 s into the H-phase.

ID: 24616398