Jena 2013 – scientific programme

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P: Fachverband Plasmaphysik

P 12: Plasmadiagnostik II

P 12.5: Talk

Thursday, February 28, 2013, 12:15–12:30, HS 2

Determination of electron density and temperature by an OES line-ratio technique in argon and argon-hydrogen discharges — •Sarah Siepa¹, Stephan Danko², Tsanko V. Tsankov¹, and Uwe Czarnetzki¹ — ¹Institute for Atomic and Plasma Physics, Ruhr-University Bochum, Germany — ²Dep. for Coating Technologies and Surface Engineering, Robert Bosch GmbH, Robert-Bosch-Platz 1, D-70839 Gerlingen-Schillerhöhe, Germany

Line-ratio techniques are widely used in Optical Emission Spectroscopy (OES) to determine plasma parameters such as electron density and temperature. The technique commonly uses the intensity of lines emitted from the 4p (2p in Paschen’s notation) levels of the argon atom. Due to differences in the excitation dynamics of the different 4p levels – excitation from the ground state vs excitation from a 4s state and radiation trapping – the ratio of the intensities is sensitive to the electron density and temperature. To extract these parameters from the measured line intensities, collisional-radiative models are usually developed.

This work presents results for pure argon CCP discharges in a wide pressure range as well as investigations of argon-hydrogen discharges, where the applicability of a line-ratio technique is limited due to strong quenching of the argon 4s levels. However, by using the results of pure argon, “absolutely” calibrated lines can be used to determine the parameters. Limitations of the used collisional-radiative model are discussed.