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Title: Finite ion temperature effects on scrape-off layer turbulence

Ion temperature has been measured to be of the same order, or higher, than the electron temperature in the scrape-off layer (SOL) of tokamak machines, questioning its importance in determining the SOL turbulent dynamics. Here, we present a detailed analysis of finite ion temperature effects on the linear SOL instabilities, such as the resistive and inertial branches of drift waves and ballooning modes, and a discussion of the properties of the ion temperature gradient (ITG) instability in the SOL, identifying the η{sub i}=L{sub n}/L{sub T{sub i}} threshold necessary to drive the mode unstable. The non-linear analysis of the SOL turbulent regimes by means of the gradient removal theory is performed, revealing that the ITG plays a negligible role in limited SOL discharges, since the ion temperature gradient is generally below the threshold for driving the mode unstable. It follows that the resistive ballooning mode is the prevailing turbulence regime for typical limited SOL parameters. The theoretical estimates are confirmed by non-linear flux-driven simulations of SOL plasma dynamics.
Authors:
; ; ; ;  [1]
  1. École Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland)
Publication Date:
OSTI Identifier:
22407994
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 1; Other Information: (c) 2015 EURATOM; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BALLOONING INSTABILITY; ELECTRON TEMPERATURE; ION TEMPERATURE; NONLINEAR PROBLEMS; PLASMA SCRAPE-OFF LAYER; PLASMA SIMULATION; TEMPERATURE GRADIENTS; TOKAMAK DEVICES; TURBULENCE; WAVE PROPAGATION