Accession Number : ADA194838

Title :   Vortex Formation and Particle Transport in a Cross-Field Plasma Sheath.

Descriptive Note : Memorandum rept.,

Corporate Author : CALIFORNIA UNIV BERKELEY COLL OF ENGINEERING

Personal Author(s) : Theilhaber, K

PDF Url : ADA194838

Report Date : 20 Mar 1988

Pagination or Media Count : 101

Abstract : The time-dependent behavior of a transversely magnetized, two-dimensional plasma wall sheath has been studied through particle simulations, with the aim of modelling plasma behavior in the vicinity of the limiters and walls of magnetized plasma devices. The simulations have shown that the cross field sheath between a wall and a plasma is a turbulent boundary layer, with strong potential fluctuations and anomalous particle transport. The driving mechanism for this turbulence is the Kelvin-Helmholtz instability, which arises from the sheared particle drifts created near the wall. Provided it is replenished by an internal flux of particles, the sheath maintains itself in a dynamic equilibrium, in which the linear edge instability, the nonlinear dynamics of the particles and the outward particle diffusion all balance each other. The sheath maintains large, long-lived vortices, with amplitudes which drift parallel to the wall at roughly half the ion thermal velocity. The sheath also maintains a large, spatially-averaged potential drop from the wall to the plasma in sharp distinction with the unmagnetized sheath, where the plasma potential is higher than at the wall. Accompanying the long-wavelength vortices is a spectrum of shorter-wavelength fluctuations, which induce an anomalous cross field transport.

Descriptors :   *CROSSED FIELD DEVICES, *PLASMA DEVICES, *PLASMA SHEATHS, *TURBULENT BOUNDARY LAYER, *VORTICES, ANOMALIES, DRIFT, DRIVES, DYNAMICS, EDGES, EQUILIBRIUM(GENERAL), FLUX(RATE), INTERNAL, IONS, LONG LIFE, LONG WAVELENGTHS, MAGNETIZATION, NONLINEAR SYSTEMS, PARTICLES, PLASMAS(PHYSICS), SIMULATION, STABILITY, THERMAL PROPERTIES, TIME DEPENDENCE, TRANSPORT, TURBULENCE, TWO DIMENSIONAL, VARIATIONS, VELOCITY, WALLS

Subject Categories : Plasma Physics and Magnetohydrodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE