Berlin 2001 – scientific programme
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P: Plasmaphysik
P 11: Dusty Plasmas and Low Temperature Discharges (Poster Session)
P 11.4: Poster
Thursday, April 5, 2001, 12:30–15:00, AT2
Diagnostics at dusty plasmas — •Holger Kersten1, Gabi Thieme1, Marion Quaas2, Harm Wulff2, Rainer Hippler1, and Matthias Otte3 — 1Institute for Physics, University Greifswald, Domstrasse 10a, D-17487 Greifswald — 2Department of Chemistry, University Greifswald, Soldtmannstrasse, D-17487 Greifswald — 3MPI for Plasma Physics Greifswald, Wendelsteinstrasse, D-17489 Greifswald
The presence of powder particles affects the behaviour of the surrounding plasma as well as the sheath. In particular, the electrons are remarkably disturbed. Therefore, the experimental determination of the electron density is of great importance. It has been measured by Langmuir probes and by self-excited electron resonance spectroscopy (SEERS).
The injection of powder particles results in a short decrease of the electron density due to the charging of the particles. The decrease and relaxation time of the density depends on the amount of the powder. Knowing the powder concentration and the difference in the electron density it is possible to estimate the charge of the dust particles which is in the order of 5000 elementary charges.
Changes in the electron density have been also measured in a process plasma used for powder modification. Fluorescent particles have been coated by an alumina layer in a metal-organic discharge. Since the metal-organic monomers tend to form negative ions, the electron density shows only a weak variation with discharge power, whereas in an argon plasma a strong increase is observed.