Ion acoustic wave velocity measurement of the concentration of two ion species in a multi-dipole plasma

Abstract

The concentration of two species in a multi-dipole plasma was determined by measuring the ion acoustic wave group velocity and the electron temperature. The wave was launched from a grid immersed in the plasma and was detected by a Langmuir probe. Electron temperature was found separately from an I–V characteristic trace. The measurements were performed in helium/xenon and argon/xenon plasmas. Typical parameters of the plasma were Te∼0.5–3 eV, density 1010 cm−3, plasma potential of 3–5 V, and pressure range from 1 to 20 mTorr. The accuracy of the measurement was from 2% to 4% depending on the mass difference between the two species and how accurately the group velocity and electron temperature are measured.