STUDIES OF BEAM-PLASMA INTERACTIONS IN A MAGNETIC FIELD.
JOHNS HOPKINS UNIV SILVER SPRING MD APPLIED PHYSICS LAB
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The interactions between a warm plasma and an electron beam, both immersed in a uniform magnetic field, were investigated theoretically and experimentally. The theoretical problem considered was that of growing waves in a cylindrical beam and plasma of equal radii propagating in a half-space z 0, and surrounded by a perfectly conducting cylinder having either radius a or infinity. Implicit dispersion equations yielding k komega are given which incorporate many of the important facets of a laboratory plasma, and solutions are obtained for certain cases. Experiments were performed with an electron beam and a plasma whose properties and geometrical configuration were as close to those of the theoretical model as practicable. The interaction that leads to the growing wave is shown to arise from the coupling of the electron-cyclotron wave in the plasma and the doppler-shifted electron-space-charge wave in the beam. Approximately 10 percent of the beam power was converted into oscillatory power by the time the wave growth had reached a nonlinear limit. Author
- Plasma Physics and Magnetohydrodynamics