Hannover 2010 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 3: Dusty Plasmas

P 3.1: Vortrag

Montag, 8. März 2010, 16:45–17:00, B 302

Dynamic light scattering on complex plasmas — •Andreas Aschinger and Jörg Winter — Lehrstuhl für Experimentalphysik II, Ruhr-Universität Bochum, D-44780 Bochum

The weakly coupled state (gaseouslike) of a complex plasma can hardly be analysed by common CCD camera observation techniques since the dust grains attain very high thermal energies and therefore the movement cannot be followed by the CCD device anymore.

To examine the weakly coupled state and phase transitions of a complex plasma dynamic light scattering is proposed. The basic idea is to measure fluctuations in the scattered intensity caused by the change of the particle density distribution and thereby get information about the dynamic processes taking place in the particle cloud. Two kinds of intensity fluctuations on different time scales are expected. First, the fluctuation of the number of dust particles in the scattering volume causes the intensity to fluctuate on a slow time scale. This fluctuations reveal informations about particle velocity distribution, free mean path length and particle oscillations in the dust cloud.

Second, the interference pattern of the scattered electric field changes due to the particle movement on a much faster time scale. This interference fluctuations can be measured by spectroscopic methods and give access to fundamental interactions like dust-neutral/ion collisions (Brownian motion), dust-dust collisions and charge fluctuations.