The determination of plasma electron density from refraction measurements

Abstract
A mathematical analysis is developed which allows the axial electron density of an axisymmetric plasma to be determined without inverting an integral equation. The required input includes the angle of refraction of a laser beam as a function of incident beam lateral displacement. Data at several wavelengths are required to eliminate contributions to the refractivity due to atoms and ions. Either long laser wavelengths or large electron densities are necessary to cause measurable refraction angles. Experimental data have been collected at several wavelengths for a stable argon arc discharge at atmospheric pressure. The analysis of these data yield electron densities which are in good agreement with thermodynamic calculations.