Influence of a background plasma on the diocotron instability of a relativistic hollow electron beam
The influence of a background plasma on the diocotron instability of a relativistic hollow electron beam is investigated within the framework of a cold fluid model. The background plasma is taken to have a uniform density except at the mean radius of the electron beam where the density is assumed to be discontinuous. Of the charged species comprising the plasma, only the electrons influence the dynamics of the beam-plasma system; the effect of the ions is negligible because of their small plasma frequency. A dispersion relation for the eigenfrequencies of the system is derived and employed to examine instabilities. It is found that the fundamental (l = 1) mode, which is unconditionally stable for a hollow electron beam in a vacuum, is now unstable for certain parameter regimes. The appearance or growth of instabilities with increases in the plasma density discontinuity is observed, while increases in the relativistic factor ..gamma../sub b/ are seen to exert a stabilizing influence. It is also found that thin beams are generally more unstable than thick ones.
- Research Organization:
- Naval Surface Weapons Center, White Oak, Silver Spring, Maryland 20910
- OSTI ID:
- 6104765
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 52:12
- Country of Publication:
- United States
- Language:
- English
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