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Title: Velocity shear, turbulent saturation, and steep plasma gradients in the scrape-off layer of inner-wall limited tokamaks

The narrow power decay-length (λ q), recently found in the scrape-off layer (SOL) of inner wall limited (IWL) discharges in tokamaks, is studied using 3D, flux-driven, global two fluid turbulence simulations. The formation of the steep plasma profiles is found to arise due to radially sheared E×B poloidal flows. A complex interaction between sheared flows and parallel plasma currents outflowing into the sheath regulates the turbulent saturation, determining the transport levels. We quantify the effects of sheared flows, obtaining theoretical estimates in agreement with our non-linear simulations. As a result, analytical calculations suggest that the IWL λ q is roughly equal to the turbulent correlation length.
Authors:
 [1] ;  [2]
  1. Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland); General Atomics, San Diego, CA (United States)
  2. Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland)
Publication Date:
Grant/Contract Number:
FC02-04ER54698
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 3; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Computational Simulation Centre of International Fusion Energy Research Centre (IFERC-CSC), Aomori (Japan)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; heat-flux width; plasma turbulence; scrape-off layer; sheared flows
OSTI Identifier:
1345664