THE PENETRATION OF A DECELERATED CHARGED-PARTICLE BEAM INTO A PLASMA
STANFORD RESEARCH INST MENLO PARK CA
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Assuming a decelerated charged particle beam penetrating a uniform plasma, a relation for the growth rate of electrostatic instabilities is obtained. It is shown that the growth rate in a decelerated beam case is always higher than in a uniform one. An experimental method of determining the electron-plasma frequency of the plasma and the decelerating parameters beta and alphas also suggested. The stability of a non-relativistic beam of charged particles injected into a cold plasma is studied by means of the macroscopic equations which have been so useful in analyzing microwave tubes in the small signal approximation. In this approach, the simplifying assumptions are made that all quantities of interest vary only in the z direction and that they consist of a d.c. component and a much smaller a.c. component. In particular, I sub 0, the d.c. component of the beam current, is assumed to be uniform and infinite in extent in the z direction, while v sub 0, the d.c. component of the beam velocity, and rho sub 0, the d.c. component of the charge density, vary with z but in such a manner that I sub 0 rho sub 0v sub 0 is constant. To justify the neglect of the boundary effects of a beam of finite radius a, it is assumed that kperpendiculara is much greater than unity, where kperpendicular is the transverse propagation vector.
- Plasma Physics and Magnetohydrodynamics