A Caltech Library Service

A Nonlinear Study of Beam Plasma Amplification


Poeschel, Robert Leslie (1967) A Nonlinear Study of Beam Plasma Amplification. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2Z3J-2V17.


The interaction between an electron beam and the plasma oscillations it excites in traversing a plasma region effectively changes the magnitude and direction of the force between beam electrons. This effect has been studied theoretically and experimentally by computing and observing beam electron velocities and phases for a beam which is initially velocity modulated at frequency ω and allowed to drift through a plasma filled region of plasma frequency ωp. When ω > ωp the force between electrons is repulsive and effectively increases in magnitude as ω approaches ωp. When ω < ωp, the force between electrons becomes a force of attraction, to within a given inter-electron spacing, and the maximum effect is also at the resonance condition ω ~ ωp. This property could be used to improve the efficiency of electron bunching in a klystron type amplifier by filling the drift space with a plasma of appropriate density.

The beam behavior is studied theoretically by computing in an exact, nonlinear manner, the trajectories of a disc model electron beam which traverses a linear, dielectric model plasma. The parameters varied are the beam space charge conditions (beam current), the degree of initial velocity modulation, and the ratio of modulation frequency to plasma frequency (ω/ωp) Computations show that it is possible to bunch the beam electrons to within 85% of delta function bunching under some beam and plasma conditions. The electron beam behavior is studied experimentally by observing the beam electron velocity phase distribution with a crossed-field velocity analyzer, and observing the beam current waveform (density-phase distribution) using a wide-band sampling oscilloscope. Experimental results show essentially the same beam behavior as predicted by the computations with some differences which are attributed to variation in the plasma density along the beam path.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Electrical Engineering)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gould, Roy Walter
Thesis Committee:
  • Unknown, Unknown
Defense Date:8 November 1966
Funding AgencyGrant Number
Office of Naval Research (ONR)220(50)
Hughes Aircraft CompanyUNSPECIFIED
Record Number:CaltechETD:etd-10032002-160203
Persistent URL:
Related URLs:
URLURL TypeDescription ItemElectron Tube and Microwave Laboratory Technical Report 33
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3883
Deposited By: Imported from ETD-db
Deposited On:07 Oct 2002
Last Modified:19 Mar 2024 22:21

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page