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Title: Microturbulence studies of pulsed poloidal current drive discharges in the reversed field pinch

Experimental discharges with pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed field pinch are investigated using a semi-analytic equilibrium model in the gyrokinetic turbulence code GENE. PPCD cases, with plasma currents of 500‚ÄČkA and 200‚ÄČkA, exhibit a density-gradient-driven trapped electron mode (TEM) and an ion temperature gradient mode, respectively. Relative to expectations of tokamak core plasmas, the critical gradients for the onset of these instabilities are found to be greater by roughly a factor of the aspect ratio. A significant upshift in the nonlinear TEM transport threshold, previously found for tokamaks, is confirmed in nonlinear reversed field pinch simulations and is roughly three times the threshold for linear instability. The simulated heat fluxes can be brought in agreement with measured diffusivities by introducing a small, resonant magnetic perturbation, thus modeling the residual fluctuations from tearing modes. These fluctuations significantly enhance transport.
Authors:
; ; ;  [1]
  1. University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
Publication Date:
OSTI Identifier:
22408000
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 1; 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; ASPECT RATIO; DISTURBANCES; ELECTRIC CURRENTS; FLUCTUATIONS; HEAT FLUX; ION TEMPERATURE; MAGNETIC RESONANCE; MST DEVICE; NONLINEAR PROBLEMS; PLASMA; REVERSE-FIELD PINCH; SIMULATION; TEARING INSTABILITY; TEMPERATURE GRADIENTS; TOKAMAK DEVICES; TRANSMISSION ELECTRON MICROSCOPY; TRAPPED ELECTRONS; TURBULENCE