Speaker
Description
See full abstract here http://ocs.ciemat.es/EPS2019ABS/pdf/P5.3014.pdf
Dusty plasmas typically contain one species of monodisperse dust particles. Experiments under microgravity conditions allow to study the dynamics of individual particles in three dimensionally extended systems. Adding a second species of monodisperse particles of different size allows to study phase separation processes. Such binary systems exhibit phase separation even for small relative size disparities of about 3%. There, fluorescent particles have been used for one of the species. A video microscopy setup consisting of two cameras equipped with appropriate filters then allows to distinguish between the species despite of their small size disparity. A pair of example images is shown in fig. 1. The time between the injection of the mixed particles into the plasma and their complete separation is of the order of 10 s. As it is possible to track individual particles, the particle flux J can be obtained and the dynamics of the phase separation process can be studied. The diffusion coefficient D is calculated according to Fick's first law J=−D∇n, where n is the particle number density. The particle species separate with about 0.2 mm/s typically, whereas the particles also perform vortex-like flows on the order of 1 mm/s. Therefore, strategies have to be found to separate these two effects. Furthermore, the presented measurements were performed on parabolic flights and particle motion caused by residual gravity must be taken into account. In this contribution, different data analysis approaches are shown. This work was financially supported by DLR under grant no. 50WM1638.
Figure 1: Inverted snapshot of a cloud of particles with diameters of 6.84 and 7.12 microns, respectively, during the
phase separation process. Camera 1 observes all particles while camera 2 observes only the larger particles.
