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THE CONTINUUM THEORY OF SPHERICAL ELECTROSTATIC PROBES. Report 605

Technical Report ·
OSTI ID:4772153
;
A continuum theory for negatively charged spherical electrostatic probes in a slightly ionized plasma is developed. The density of the plasma is taken to be sufficiently high such that both ions and electrons suffer numerous collisions before being collected by the probe. The probe surface is assumed to be absorbing. The ion and electron temperatures may have different values but are uniform in space. By confining attention to highly negative probe potentials, the Boltzmann distribution for electron number density is shown to be the correct approximation. Under the assumption that the probe radius, r/sub p/, is large compared with the electronic Debye distance, h/sub e/, and that the probe potential is sufficiently negative, the structures of the potential, electron, and ion density distributions are discussed in some detail. It is found that under such circumstances the boundary condition for ion density at the probe is unimportant. Analytical behavior of the solutions are given and a simple closed- form ion-current-voltage characteristic is obtained. Numerical computation is cai ried out to supplement the analysis and to cover a wider range of probe sizes. Two kinds of current-voltage characteristics are constructed. One of them is specially appropriate for the determination of the ionization density. Finally, the disturbance in the plasma is found to be confined mainly to a layer adjacent to the probe. It is shown that the thickness of this layer is not of order of Debye length whenever P/sub p/ >> h/sub e/. (auth)
Research Organization:
Princeton Univ., N.J.
NSA Number:
NSA-16-032474
OSTI ID:
4772153
Report Number(s):
AFOSR-3067
Country of Publication:
United States
Language:
English

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Related Subjects

ABSORPTION
BOUNDARY CONDITIONS
CURRENTS
DEBYE LENGTH
DENSITY
DIAGRAMS
DISTRIBUTION
DISTURBANCES
ELECTRIC CHARGES
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ELECTRONS
ELECTROSTATICS
INTERACTIONS
IONIZATION
IONS
LAYERS
MAXWELL DISTRIBUTION
NUMERICALS
PHYSICS
PLASMA
PROBES
SPHERES
SURFACES
THICKNESS