
Accession Number : AD0681160
Title : THE ROLE OF LANDAU DAMPING IN CROSSEDFIELD ELECTRON BEAMS AND INVISCID SHEAR FLOW.
Descriptive Note : Research rept.,
Corporate Author : AVCO EVERETT RESEARCH LAB EVERETT MASS
Personal Author(s) : Briggs,R. J. ; Daugherty,J. D. ; Levy,R. H.
Report Date : DEC 1968
Pagination or Media Count : 76
Abstract : Under certain circumstances the problem of the stability of low density crossedfield electron beams is precisely analogous to the problem of the stability of incompressible inviscid shear flows. The electron density, the drift velocity, and the potential correspond to the fluid vorticity, velocity, and the stream function respectively. The analogy is valid only for waves propagating in the direction of the unperturbed velocity. Neutrally stable normal modes of oscillation that are found when certain suitable stepfunction unperturbed electron density (vorticity) profiles are assumed seem to disappear when small gradients are present. In the context of a Laplace transform solution of the initial value problem, the vanishing normal modes can be found by analytic continuation of the solution onto another sheet of the cut complex omegaplane. The 'recovered' modes are found to be damped by a fluidwave resonant interaction which closely resembles the Landau damping of plasma oscillations in warm plasmas by particlewave resonance. An interesting feature of the neutral waves is that they have a negative energy and so are destabilized by the removal of energy from the system (for example, by slightly dissipative walls). The sign and magnitude of the Landau damping term is evaluated for a simple case and compared (for the electronic case) with the growth provoked by slightly lossy walls. (Author)
Descriptors : (*ELECTRON BEAMS, DAMPING), STABILITY, CROSSED FIELD DEVICES, ANALOG SYSTEMS, ELECTRON DENSITY, INTERACTIONS, MATHEMATICAL ANALYSIS
Subject Categories : Plasma Physics and Magnetohydrodynamics
Distribution Statement : APPROVED FOR PUBLIC RELEASE