Deduction of the absolute negative ion density by using planar and cylindrical electric probes simultaneously

Abstract

Analytic formulas are derived for the deduction of the absolute density of negative ions by using the measured electron temperatures and saturation currents of positive ions and negative charges from current-voltage curves taken by planar and cylindrical probes at two different pressures without assuming the sheath potential, sheath velocity, temperatures of positive and negative ions, and effective masses of positive ions. Ratios of ion and electron saturation currents and electron temperatures of two probes and sheath areas of a long thin cylindrical probe at two different pressures are incorporated into two equations with two unknowns for the negative ion density. The procedure to deduce the absolute negative ion density is given.