Plasma diagnostics of an analytical Grimm-type glow discharge in argon and in neon: Langmuir probe and optical emission spectrometry measurements

Comparative investigations were performed on a Grimm-type glow discharge source by Langmuir probe measurements and by optical emission spectrometry. The Langmuir probe measurements yielded electron temperatures and number densities of electrons, whereas the optical emission spectrometry measurements resulted in data for excitation and ionization temperatures of different species. The results confirm that there is no local thermal equilibrium in the discharge plasma. The operating-conditions of the glow discharge source and also the working gas and the cathode material were varied to investigate their influence on the plasma parameters. The outcome of the plasma diagnostics will be used to improve the modelling of relevant excitation and ionization processes by computer simulation. The major physical processes in the low pressure glow discharge plasma should be better understood if the analytical capability of this spectrochemical excitation and ionization source has to be further enhanced.