Correlation of the tokamak H-mode density limit with ballooning stability at the separatrix

T. Eich, R. J. Goldston, A. Kallenbach, B. Sieglin, H. J. Sun

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

We show for JET and ASDEX Upgrade, based on Thomson-scattering measurements, a clear correlation of the density limit of the tokamak H-mode high-confinement regime with the approach to the ideal ballooning instability threshold at the periphery of the plasma. It is shown that the MHD ballooning parameter at the separatrix positionαsep ncreases about linearly with the separatrix density normalized to Greenwald density, ne,sep/nGW for a wide range of discharge parameters in both devices. The observed operational space is found to reach at maximum ne,sep/nGW ≈ 0.4-0.5 at values for αsep ≈22.5, in the range of theoretical predictions for ballooning instability. This work supports the hypothesis that the H-mode density limit may be set by ballooning stability at the separatrix.

Original languageEnglish (US)
Article number034001
JournalNuclear Fusion
Volume58
Issue number3
DOIs
StatePublished - Jan 15 2018

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Keywords

  • H-mode density limit
  • SOL decay lengths
  • ballooning instability
  • power width scaling

Fingerprint Dive into the research topics of 'Correlation of the tokamak H-mode density limit with ballooning stability at the separatrix'. Together they form a unique fingerprint.

  • Cite this