Diffusive Motion in a 3-D Cluster in PK-4

Random motion of small solid particles is analyzed in a 3-D dusty plasma experiment under microgravity conditions. In this experiment, performed using the Plasmakristall-4 (PK-4) instrument on board the international space station, a cloud of microspheres was localized near a radio frequency coil that powered a neon plasma. We devised a method of correcting particle mean-square displacement (MSD) data to account for a small hydrodynamic flow. Using a time series of the MSD, we determined that random motion was nearly diffusive, with a diffusion coefficient of 0.0017 mm
²
/s. Another measure of displacements, the probability distribution function, fits a Kappa distribution with κ = 6.9$ , indicating that the random motion was nearly Gaussian.