Vortex Formation and Particle Transport in a Cross-Field Plasma Sheath
Abstract
The time dependent behavior of a transversely magnetized, two- dimensional plasma wall sheath has been studied through particle simulations, which have shown that the cross field sheath develops into a turbulent boundary layer, with strong potential fluctuations and anomalous particle transport. The driving mechanism is the Kelvin Helmholtz instability, which arises from the sheared particle drifts created near the wall. The sheath acquires an equilibrium thickness l sub x approx. 5 rho sub i, and maintains large, long- lived vortices, with amplitudes del phi approx. -2T sub i/e, 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 vortices is a spectrum of shorter-wavelength fluctuations which induce an anomalous cross-field transport. A central simulation result is that for omega sub pi > or = 2 omega sub ci, the transport scales like Bohm diffusion, a result for which we have a qualitative analytic model.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 10, 1988
- Accession Number
- ADA199639
Entities
People
- Charles K. Birdsall
- K. Theilhaber
Organizations
- University of California, Berkeley