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Aachen PK 2003 – scientific programme

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P: Plasmaphysik

P 18: Plasma Wall Interaction

P 18.5: Talk

Friday, March 21, 2003, 11:50–12:10, FO1

Influence of wall materials at different temperatures on the vibrational population of molecular hydrogen — •S. Meir1,2, U. Fantz1, and K. Behringer1,21Lehrstuhl für Experimentelle Plasmaphysik, Institut für Physik, Universität Augsburg, D-86135 Augsburg — 2Max-Planck-Institut für Plasmaphysik, D-85748 Garching, EURATOM Association

The vibrational population in the ground state of molecular hydrogen is a key parameter in hydrogen discharges since it enhances the formation of negative hydrogen ions, the ionisation and dissociation rate coefficients. Furthermore the electron energy distribution function will be modified. Besides the volume processes the vibrational population can be affected by surface processes, either by direct reflection of molecular hydrogen or by recombining hydrogen atoms or ions at the target.
In order to measure the influence of different materials on the vibrational population, additional surfaces (carbon, tungsten, copper, aluminium; steel and quartz as reference) have been installed in the chamber of a planar inductively coupled plasma. The vibrational population was determined by emission spectroscopy of the Fulcher transition which is sensitive for the first four to five vibrational levels. The results for the different materials and the plasma without additional surface are compared. Since the chamber walls are cooled, the influence of the target temperature is investigated by cooling and heating the additional surface actively.

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