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P: Plasmaphysik
P 4: Diagnostics II
P 4.3: Vortrag
Dienstag, 3. April 2001, 17:00–17:15, 2032
Time-resolved gas temperature measurements on a pulsed helicon discharge in argon — •B. Clarenbach1, B. Lorenz1, M. Krämer1, and N. Sadeghi2 — 1Institut für Experimentalphysik II, Ruhr-Universität Bochum, 44780 Bochum — 2Laboratoire de Spectrométrie Physique, Université Joseph Fourier and CNRS,
The evolution of the temperature and density of the Ar*(3P0) metastable atoms in the high-density pulsed helicon discharge HE-S (ne ≤ 1020m−3,PHF=1.4 kW, f=25 MHz, Te≈ 4 eV, B=0.1 T, p=1 Pa argon, rp=2.8 cm, Lp=140 cm) was deduced from measurements of the absorption profile of the 772.42 nm argon line. From the Doppler width of these profiles we obtained temperatures up to 1000 K. As the metastable and ground state atoms are strongly coupled, the temperature of the Ar*(3P0) atoms reflects the gas temperature. From the time variation of the Ar*(3P0) density during the discharge pulse we found for the helicon regime that the neutral atoms was depleted by more than a factor of ten. In the afterglow, the Ar*(3P0) state is populated by electron-ion recombination mechanisms, and the temperature of the metastables is partially related to the temperature of the Ar+ ions. Gas temperature and the metastable density reveal a asymmetry typical for helicon discharges with helical antenna coupling.We also measured the time-dependent intensity of several optical thin argon lines which show the same temporal behaviour as the absorption measurements. With the aid of a collisional-radiative model we try to determine the electron energy distribution in the plasma pulse.
( Supported by the DFG, SFB 191, Teilprojekt A12)