Hannover 2010 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 18: Poster: Diagnostics

P 18.17: Poster

Donnerstag, 11. März 2010, 16:00–18:00, Lichthof

Radiation trapping and the measurement of metastable density by optical emission spectroscopy — •Vladimir Sushkov, Hoang Tung Do, and Rainer Hippler — Institute of Physics, University of Greifswald, Felix-Hausdorff Strasse 6 17489 Greifswald

Radiation trapping of photons emitted from Ar and Ar/C₂H₂ radio frequency plasmas was studied both theoretically and experimentally. Intensities of lines emitted from level 2p₆ (Paschen notation) to levels 1s₄ (800.6 nm) and 1s₅ (763.5 nm) of argon were measured with optical emission spectroscopy (OES). The intensity ratio of these lines is proportional to their escape factor ratio which depends on the density of the lower states (1s₄* - resonant and 1s₅ - metastable). The escape factors were theoretically calculated in dependence on metastable and resonant densities, and utilized within the framework of effective lifetime concept. Metastable density was then calculated from the measured escape factor of photons emitted from the plasma. Metastable and resonant densities were also measured by means of tunable diode laser absorption spectroscopy (TDLAS). The results were compared which gives a very good agreement between the two measuring methods. OES is, therefore, an alternative way to measure metastable density.