Berlin 2005 – scientific programme

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P: Plasmaphysik

P 21: Poster: Plasma-Wand Wechselwirkung 2, Theorie 2, Dichte Plasmen 1, Schwerionen- und lasererzeugte Plasmen 2

P 21.2: Poster

Monday, March 7, 2005, 16:30–18:30, Poster HU

Experimental Investigation on the Plasma-Wall Transition — •Tilmann Lunt¹, Naomichi Ezumi², Gerd Fussmann¹, and Werner Bohmeyer¹ — ¹Institut für Physik der Humboldt-Universität zu Berlin, Berlin, Germany — ²Nagano National College of Technology, Nagano 381-8550, Japan

The streaming of an argon plasma towards an absorbing target plate was studied experimentally by means of Laser Induced Fluorescence. This non-pertubative diagnostic allows the measurement of the ion velocity distribution, and thus the streaming velocity and the ion temperature in particular. In contrast to expectations based on B2-Eirene code simulations[1] which model the streaming of a hydrogen plasma through a magnetic nozzle field, it is found that the flow is generally sub-sonic in the region behind the last magnetic coil and the neutralizing target. Half-sided Maxwellian ion-distribution functions as predicted by Emmert[2] with Mach numbers around M∼ 0.5 are typical for standard recycling conditions within a distance of the mean free path length from the target. Larger flow velocities with highly non-Maxwellian distributions, possibly exceeding M = 1, are, however, observed under maximum gas pumping conditions. The delicate influence of the neutrals on the flow behaviour is also corroborated by numerical simulations.

[1] H. Kastelewicz and G. Fussmann, Contrib. Plasma Phys. 44, N0.4, 352-360 (2004)

[2] G. A. Emmert, R. M. Wieland, A.T. Mense et al., Phys. Fluids 23, 803-812 (1980)