Fluid simulations of {nabla}T{sub e}-driven turbulence and transport in boundary plasmas
It is clear that the edge plasma plays a crucial role in global tokamak confinement. This paper is a report on simulations of a new drift wave type instability driven by the electron temperature gradient in tokamak scrapeoff-layers (SOL). A 2d fluid code has been developed in order to explore the anomalous transport in the boundary plasmas. The simulation consists of a set of fluid equations for the vorticity {nabla}{sub {perpendicular}}{sup 2}{phi}, the electron density n{sub c} and the temperature T{sub c} in a shearless plasma slab confined by a uniform, straight magnetic field B{sub z} with two divertor (or limiter) plates intercepting the magnetic field. The model has two regions separated by a magnetic separatrix: in the edge region inside the separatrix, the model is periodic along the magnetic field while in the SOL region outside the separatrix, the magnetic field is taken to be of finite length with model boundary conditions at diverter plates. The simulation results show that the observed linear instability agrees well with theory, and that a saturated state of turbulence is reached. In saturated turbulence, clear evidence of the expected long-wavelength mode penetration into the edge is seen, an inverse cascade of wave energy is observed. The simulation results also show that amplitudes of potential and the electron temperature fluctuations are somewhat above and the heat flux are somewhat below those of the simplest mixing-length estimates, and furthermore the large-scale radial structures of fluctuation quantities indicate that the cross-field transport is not diffusive. After saturation, the electron density and temperature profiles are flattened. A self-consistent simulation to determine the microturbulent SOL electron temperature profile has been done, the results of which reasonably agree with the experimental measurements.
- Research Organization:
- California Univ., Berkeley, CA (United States). Electronics Research Lab.
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Department of Defense, Washington, DC (United States)
- DOE Contract Number:
- FG03-90ER54079
- OSTI ID:
- 10186877
- Report Number(s):
- UCB/ERL-M-92/147; ON: DE94001304; BR: AT0520210/AT0540420; CNN: Contract N00014-85-K0809; TRN: 93:024086
- Resource Relation:
- Other Information: PBD: 15 Dec 1992
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
TOKAMAK DEVICES
DRIFT INSTABILITY
PLASMA SIMULATION
PLASMA SCRAPE-OFF LAYER
TEMPERATURE GRADIENTS
CHARGED-PARTICLE TRANSPORT
TURBULENCE
ELECTRON TEMPERATURE
MAGNETIC FIELDS
LIMITERS
DIVERTORS
NONLINEAR PROBLEMS
700340
700330
PLASMA WAVES, OSCILLATIONS, AND INSTABILITIES
PLASMA KINETICS, TRANSPORT, AND IMPURITIES