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Förslaget inkom 2008-05-30

Wave phenomena in complex plasmas under microgravity conditions

This M Sci thesis project is one of several that are offered in a cooperation between KTH and the Max Planck Institute in Garching, Germany, and is based on data from a plasma experiment on board the International Space Station, ISS. During the course of the project a visit to our collaborators at the Max Planck will be needed. Suitable background includes basic knowledge of plasma physics. Some programming skills and the ability to master the use of new software is desirable.

Charged dust particles embedded in a plasma, not only change the conventional plasma modes but also introduce new (low-frequency, 10-100 Hz) modes associated with the particle motion, alter dissipation rates, give rise to instabilities etc. Complex plasmas differ from other multi-species plasmas by the property that the dust charge fluctuates in response to plasma fluctuations and thus that the collection of plasma fluxes by the dust particles introduces new dissipation in the system. Depending on the magnitude of the inter-particle coupling, complex plasmas can be in weakly (gaseous-like) or strongly coupled (liquid-like) states. This allows us to investigate wave phenomena, in particular nonlinear waves, in different phase states at the kinetic level.

Waves structures observed in PKE-Nefedov experiment. The experiment is performed under microgravity conditions in an argon rf-discharge (12 Pa) with a mixture of 3.4 and 6.8 micron diameter particles. The waves were excited by applying a 22 Hz modulation voltage to the horizontal electrodes.

Pilot experiments with PKE-Nefedov have been performed to study these wave phenomena, and a good agreement between theoretical expectations/predictions and the experiments has been achieved. Later an extensive experimental campaign has been carried out in order to investigate these phenomena in-depth. Currently the data from this latter campaign are to be analysed. In the M Sci thesis offered here, detailed data analysis is to be performed with the goal to provide test for the original ideas.


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