Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade

B. Labit, T. Eich, G.F. Harrer, D. Gahle, S. Henderson

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Abstract

Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (n e,sep/n G ∼ 0.3), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened.

Original languageEnglish
Article number086020
Number of pages13
JournalNuclear Fusion
Volume59
Issue number8
Early online date16 May 2019
DOIs
Publication statusPublished - 26 Jun 2019

Keywords

  • ballooning modes
  • grassy ELMs
  • H-mode
  • plasma triangularity
  • separatrix density
  • type-II ELMs

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