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P: Plasmaphysik

P 9: Dense Plasmas and Plasma Diagnostic (Poster Session)

P 9.23: Poster

Tuesday, April 3, 2001, 12:30–15:00, AT2

Electron Density Dependence of He-Line Ratios in Microwave Plasmas — •B. Heger^1,2, U. Fantz², and K. Behringer^1,2 — ¹Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, D-85748 Garching — ²Lehrstuhl für Experimentelle Plasmaphysik, Institut für Physik, Universität Augsburg, Universitätsstr. 1, D-86135 Augsburg

The helium line spectra of a microwave generated low density plasma (P_max=2400W, p=4−1000Pa, T_e=1−3.5eV, n_e=0.6−6· 10¹⁷ m⁻³) based on the principle of the duo plasmaline, was investigated by means of emission spectroscopy. A sensitive dependence of several line ratios on electron density is predicted for the parameter range of the discharge by using collisional-radiative models. Such dependencies were found experimentally by varying pressure, power input and gas mixture (pure helium and helium / hydrogen). The corresponding electron densities were obtained from Langmuir probe measurements. Experimental results will be compared with theoretical line ratios calculated on the basis of the ADAS code package. Apart from the influence of opacity and self quenching, the quenching of metastable states of the helium atom by admixture of molecular hydrogen to the plasma will be discussed.