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Title: Flux-driven simulations of turbulence collapse

Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E×B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when R{sub T} > 1 at t = t{sub R} (R{sub T}: normalized Reynolds power), while the conventional transition criterion (ω{sub E×B}>γ{sub lin} where ω{sub E×B} denotes mean flow shear) is satisfied only after t = t{sub C} ( >t{sub R}), when the mean flow shear grows due to positive feedback.
Authors:
; ; ;  [1] ;  [1] ;  [2] ;  [3]
  1. National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of)
  2. (United States)
  3. Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
Publication Date:
OSTI Identifier:
22408206
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 3; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; EDGE LOCALIZED MODES; ELECTRIC FIELDS; MAGNETIC FIELDS; NEOCLASSICAL TRANSPORT THEORY; NONLINEAR PROBLEMS; OSCILLATIONS; REYNOLDS NUMBER; SHEAR; SIMULATION; THREE-DIMENSIONAL CALCULATIONS; TOKAMAK DEVICES; TURBULENCE