Langmuir Probe Determination of Charged Particles in Ar and He Discharge Plasmas

Abstract

This paper presents results of cylindrical single Langmuir probe measurements of the electron and ion densities in argon and helium glow discharge plasmas. The gas pressure veries from 5 to 150 Pa. The electron density is determined from the electron probe current at the space potential. The positive ion density is determined from the probe ion saturated current according to Bohm pre-sheath model as well as according to collisional Zakrzewski and Kopiczynski model. At basic pressures of 80 Pa and higher, good agreement is obtained, for both gases, between the electron and ion densities with both models. For basic pressures less than 80 Pa down to 5 Pa, satisfactory agreement between the electron and ion densities is achieved with Zakrzewski and Kopiczynski model where the destruction of the orbital motion of ions in the sheath is still considered.