Aachen PK 2003 – wissenschaftliches Programm
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P: Plasmaphysik
P 4: Poster I
P 4.10: Poster
Montag, 17. März 2003, 17:45–19:15, Foyer
Time-dependent gas density and temperature measurements in pulsed helicon discharges in argon — •B. Clarenbach1, M. Krämer1, B. Lorenz1, S. Lützenkirchen1, and N. Sadeghi2 — 1Experimentalphysik II, Ruhr-Universität Bochum, — 2Laboratoire de Spectrométrie Physique, Université Joseph Fourier, Grenoble I & CNRS, B.P. 87 38402 Saint Martin d’Hères cedex, France
Time-dependent absorption spectroscopy measurements on Ar*(3p0) metastable atoms in the pulsed helicon discharges HE-S and HE-L are presented. A single-mode tuneable diode laser is used for recording the absorption profiles of the 772.42 nm argon line. The density and temperature (Tm≤ 1000 K) of the metastable is obtained, respectively, from their integral and Doppler width. Due to strong coupling of the metastables and the ground state atoms (Tg ≅ Tm), we could also deduce the density of the ground state argon atoms and found that they can be depleted by 90 % while the ionisation degree grows up to 65 %. In addition, we analysed the plasma-induced emission of the Ar (750 nm) and Ar+ (461 nm) lines as well as the e− density to understand the plasma evolution and the transition from the ICP to the helicon regime. In the afterglow, the excited states of argon are fed by e−-Ar+ ion recombination. The very high temperature of Ar*(3p0) atoms measured is partially related to the temperature of the Ar+ ions. Production of Ar+ in its excited states is also observed during several hundred µs in the afterglow. It is related to the e−-Ar++ ion recombination thus indicating a significant amount of doubly charged argon ions in helicon plasmas.
Supported by the DFG (KR 1058 & SFB 1944, Teilprojekt A7)