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Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 04/05 Podcast
Particle manipulation in plasma device & Dynamics of binary complex plasma

Particle manipulation in plasma device & Dynamics of binary complex plasma

Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 04/05 vor 15 Jahren

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A complex plasma is a suspension of nano- to micron-sized dust
particles immersed in a plasma with ions, electrons and neutral gas
molecules. Dust particles acquire a few thousands of electron
charges by absorbing the surrounding electrons and ions, and
consequently interact with each other via a dynamically-screened
Coulomb potential. Dust particles in a complex plasma can be
controlled through a low frequency electrostatic distortion. We
studied the transport velocity of the particles as we modulate the
frequency and phase of the applied voltage by a segmented
electrode. We used molecular dynamics to simulate our experimental
observations, using plasma conditions from independent
particle-in-cell simulations. We found that the transport of dust
particles controlled by low-frequency modulation in our simulations
are in good agreement with our experimental findings. This work is
in the aim of, on one hand, providing a potential technique for
addressing the dust contamination issues in plasma processing
reactors and on the other hand, providing a setup for investigating
large two-dimensional complex plasma systems where boundary effects
can be avoided. We then proceeded to study the non-additivity
effect in a complex plasma containing two different sizes of dust
particles (binary complex plasma). For dust particles of type 1 and
2, the 1-2 (inter-species) interaction is always more repulsive
than the geometric mean of 1-1 and 2-2 interactions. This asymmetry
in the mutual interaction is called positive non-additivity. We
used Langevin dynamics simulations for the Yukawa interacting
particles characterized by positive non-additivity. We found that
the two types of particles can separate into fluid-fluid phases and
the growth of characteristic domain length follows a simple power
law with an exponent of about 1/3 until the coupling strength is
small enough, which is in a good agreement with the
Lifshitz-Slyozov growth law for the initial diffusive regime of
phase separation. We then used Langevin dynamics simulations to
probe the influence of non-additive interactions on lane formation.
We revealed a crossover from normal laning mode to a demixing
dominated laning mode. In addition, we found that the lane
formation is strongly influenced by the exact spatial
configurations at the very moment of contact between two different
complex plasmas. We also used hydrodynamics to model the evolution
of Mach cones in complex plasmas. The hydrodynamic model was able
to reproduce a compressional-wave Mach cone observed onboard the
International Space Station.