Particle motion at the onset of polarity switching in the PK-4 microgravity experiment

The behavior micron-sized particles (dust) in a plasma system is of great interest and, because of the low charge to mass ratio of these particles, the dynamic time scales of the dust grains are long and easily accessible from an experimental perspective. However, the high mass leads to sedimentation effects in ground-based experiments. To reduce sedimentation effects, it is necessary to perform experiments in a free-fall ("microgravity") environment, such as in the ISS based experiment facility "Plasma-Kristall-4" ("PK-4"). In the PK-4 facility, particles are injected into a dc glow discharge plasma and flow along an axial electric field. Upon the application of a periodic oscillation of the electric field (polarity switching), a sudden change in the bulk motion of the dust and a change in the spatial ordering of the particles is observed. This poster will present the results of a study of the particle motion under the effects of polarity switching using Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) techniques under both ground-based and free-fall conditions.