Bonn 2000 – wissenschaftliches Programm
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P: Plasmaphysik
P 16: Plasmadiagnostik (Poster)
P 16.41: Poster
Mittwoch, 5. April 2000, 10:30–13:00, Aula
Analysis of nonthermal effects in normal and abnormal hollow cathode discharge containing hydrogen — •N. Lang1, M. Kalatchev2, B.P. Lavrov2, L. Asare3, and J. Röpcke1 — 1Institut für Niedertemperatur-Plasmaphysik, Greifswald, Germany — 2Faculty of Physics, St. Petersburg State University, Russia — 3Institute of Atomphysics and Spectroscopy, University of Latvia, Riga, Latvia
For studying thermal equilibration processes we investigated a hollow cathode discharge by means of high resolution optical emission spectroscopy (Δλ = 0.005 nm). The discharge could be sustained in a pressure range from 15 Pa to 5 kPa of H2 and H2/He mixtures under flowing conditions with typical currents of 0.5 mA ≤ i ≤ 30 mA. To achieve an efficient cooling of the walls the lamp was inserted in a dewar filled with liquid nitrogen. For determination of the gas temperature Doppler broadened profiles of H2 lines (Fulcher-α diagonal Q-branch) were analysed. The pressure dependence of this temperature has been compared with rotational temperatures of the H2 ground state derived from populated d3Πu− rotational states. Under the studied discharge conditions a minimum of the gas temperature with increasing pressure could be observed. An analysis of the vibrational population of excited molecules showed a strong non-equilibrium distribution for lower pressures. Only for pressures higher than 1 kPa a relaxation to a Boltzmann distribution could be observed. For 3.5 kPa a vibrational temperature of ≈ 5500 K was found. The line profiles of atomic hydrogen showed anomalous Doppler broadening for pressures lower than 100 Pa corresponding to excited atoms having kinetic energies higher than thermal ones.