Mobility of Nonequilibrium Conduction Electrons in Air
Final rept. Oct 1988-Sep 1989
HARRY DIAMOND LABS ADELPHI MD
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An integro-differential equation is derived describing the time evolution of the electron energy distribution function in a gas in a transient electric field. A finite-difference approximation and a time-stepping algorithm using matrix-vector techniques are devised to solve the integro-differential equation. An extensive published cross section set is added to the time-stepping algorithm, enabling one to calculate realistic energy distribution functions in air. Also described is a projection method that allows computation of electron swarm properties such as collision volume inversely related to mobility using measured data for equilibrium distributions. This projection method is shown to have desirable variational properties in calculating the swarm properties. Compare orthogonal and nonnegative projection methods with conventional techniques for their ability to reduce error in estimates of collision volume arising from cross-section-induced error in the energy distribution function. A single-vector projection with cleanup of approximation error performs best, leading to significant reduction of collision volume error when the distribution function maximum occurs at not more than about 0.1 eV. Other projections perform poorly compared to conventional methods of calculating swarm collision volume, because of inherent dependence of the projection basis of equilibrium distributions and resulting ill-conditioning of the projection matrix. Keywords Plasma, Conductivity, Transients, Variational principle, Electron.
- Plasma Physics and Magnetohydrodynamics