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Ignition of the Beam-Plasma-Discharge and its Dependence on Electron Density

  • D. N. Walker
  • E. P. Szuszczewicz
  • C. S. Lin
Part of the NATO Advanced Study Institutes Series book series (NSSB, volume 79)

Abstract

A cold electron beam, propagating through a weakly ionized plasma will, under proper conditions, produce a modified beam-plasma state known as the Beam-Plasma-Discharge (BPD). As the subject of a continuing series of experiments in a large facility chamber it was previously determined that the BPD had an abrupt ignition threshold as the beam current (I) was increased at fixed beam energy. While a specific empirical relationship was established among the controlling parameters of beam current, energy and length as well as ambient pressure and magnetic field, a dependence of the BPD on plasma density of the form ω ∿ ω was suggested. We have since conducted a survey of various beam-plasma conditions covering beam currents from 8 to 85 ma, beam energies from 0.8 to 2.0 keV and magnetic fields at 0.9 and 1.5 gauss. This survey includes full determinations of radial profiles of electron density for each of the selected conditions extending from a low-density pre-BPD state to a strong BPD condition. At BPD threshold Ne was determined and ωp calculated with results that can be summarized by
$$ {\omega _p} = (5.8\begin{array}{*{20}{c}} + & {1.3} \\ - & {1.9} \\ \end{array} ){\omega _c} $$
as the density dependent threshold condition for BPD. The experimental results are shown to compare favorably with a developing theoretical model that considers BPD to be triggered by electron plasma wave excitation of a beam-plasma instability.

Keywords

Plasma Wave Radial Profile Electron Plasma Wave Relative Electron Density Sweep Current 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1982

Authors and Affiliations

  • D. N. Walker
    • 1
  • E. P. Szuszczewicz
    • 1
  • C. S. Lin
    • 2
  1. 1.Naval Research LaboratoryE.O. Hulburt Center for Space ResearchUSA
  2. 2.Bendix Field Engineering Corp.ColumbiaUSA

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