l=1 electrostatic instability induced by electron-neutral collisions in a nonneutral electron plasma interacting with background neutral gas
- Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)
This paper investigates theoretically the electrostatic stability properties of a nonneutral electron plasma interacting with background neutral gas through elastic collisions with constant collision frequency {nu}{sub {ital en}}. The model treats the electrons as a strongly magnetized fluid ({omega}{sub {ital pe}}{sup 2}/{omega}{sub {ital ce}}{sup 2}{lt}1) immersed in a uniform magnetic field {ital B}{sub 0}{bold {cflx e}}{sub {bold z}}, and assumes small-amplitude perturbations with azimuthal mode number l=1 and negligible axial variation ({partial_derivative}/{partial_derivative}{ital z}=0). The analysis also assumes weak electron collisions with {nu}{sub {ital en}}/{omega}{sub {ital ce}}={epsilon}{lt}1, and that the process of heat conduction is sufficiently fast that the electrons have relaxed through electron-electron collisions to a quasiequilibrium state with scalar pressure {ital P}({ital r},{theta},{ital t})={ital n}({ital r},{theta},{ital t}){ital T}, and isothermal temperature {ital T}. Assuming that perturbed quantities vary with time according to exp({minus}{ital i}{omega}{ital t}), the detailed stability analysis carried out to first order in {nu}{sub {ital en}}/{omega}{sub {ital ce}}{lt}1 shows that the real oscillation frequency and growth rate for the l=1 diocotron mode are given, respectively, by the simple expressions Re{omega}={omega}{sub 0} and Im{omega}=({nu}{sub {ital en}}/{omega}{sub {ital ce}}){omega}{sub 0}. Here, {omega}{sub 0}={ital Nec}/{ital r}{sup 2}{sub {ital wB}}{sub 0}, where {ital r}{sub {ital w}} is the perfectly conducting wall radius, and {ital N}={integral}{ital d}{sup 2}{ital x}{ital n} is the number of electrons per unit axial length. This analysis suggests that a measurement of the oscillation frequency and growth rate for the l=1 diocotron mode can be used to infer {nu}{sub {ital en}}, and thereby serve as a sensor for the background neutral pressure. {copyright} {ital 1996 American Institute of Physics.}
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 288815
- Journal Information:
- Physics of Plasmas, Vol. 3, Issue 9; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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