Parallel shear flow instability in the tokamak edge

F. Schwander, G. Chiavassa, G. Ciraolo, Ph Ghendrih, L. Isoardi, A. Paredes, Y. Sarazin, E. Serre, P. Tamain

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The transition between the core and scrape-off layer of a tokamak corresponds to a marked momentum shear layer, owing to sheath acceleration on limiters which drives near-sonic flows along the plasma magnetic field in the scrape-off layer, and a parallel shear flow instability can possibly be triggered. The possibility of this instability driven by the velocity gradient is investigated numerically, using a minimum model of particle and parallel momentum transport in the edge of a tokamak, in a computational domain modelling a limiter plasma with background turbulence modelled as an effective diffusion. It is found that unstable regions can exist in the vicinity of a limiter, in agreement with experimental findings, when momentum radial transport - and therefore coupling between SOL and core flows - is sufficiently weak. Instability is reinforced by core rotation, and is found to be maximum downstream of the limiter (with respect to the core plasma flow).

Original languageEnglish
Pages (from-to)S601-S604
JournalJournal of Nuclear Materials
Volume415
Issue number1 SUPPL
DOIs
StatePublished - 1 Aug 2011
Externally publishedYes

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