Computation of electrostatic probe characteristics by quasilinearization.

Abstract

This paper describes the numerical solution of a mathematical model of a spherical electrostatic probe in a collision-dominated, partially ionized gas and the application of this solution to reduction of probe data gathered from a small hot-shot wind tunnel. In the simple plasma model considered, ionization and recombination are neglected, and current is assumed to flow between the probe and infinity. This mathematical model leads to a sixth-order nonlinear system of ordinary differential equations with two-point boundary conditions. An asymptotic quasineutral solution is used as an initial condition for a solution by quasilinearization. Distribution of charge carrier densities and potentials are presented for several values of dimensionless probe potential and radius, and one case is presented where the ion and electron temperature are not equal. Dimensionless current-voltage curves are presented for a range of dimensionless probe sizes for singly charged ions and equal electron and ion temperatures. A method is developed for analyzing experimental probe data using the numerical solution results.