Layered structures in extended dust clouds under microgravity

Abstract

Three dimensional particle clouds in a plasma environment have been studied under microgravity conditions on parabolic flights. By using a stereoscopic 4-camera system, it was possible to reconstruct the three-dimensional particle motion in a selected volume. From this, a layered structure in the dust-cloud is revealed that is not observable with plain two-dimensional diagnostics. The spacing between the layers is found to be decisively larger than the interparticle distance inside the layer. This layered structure is observed in different situations, with and without waves. Further, it has been found that the position of the layers is stationary in the plasma even though the particles show an overall motion. The origin of the layer formation is discussed.

Configurational temperature in dusty plasmas

“…The three-dimensional dust cloud has been investigated on parabolic flights that allow to generate large, three-dimensional particle systems [35][36][37]. There, a symmetric parallel-plate discharge has been operated in push-pull mode.…”

“…1(b). The scattered light from the particles is then captured with a stereoscopic fourcamera system [36]. From that, the three-dimensional trajectories of particles in the illuminated volume are reconstructed; see Ref.…”

Three-Dimensional Reconstruction of Individual Particles in Dense Dust Clouds: Benchmarking Camera Orientations and Reconstruction Algorithms

“…To give an example of how the different algorithms performed with real data, they have also been applied to measurements from a dust cloud investigated under microgravity conditions [ 23 ]. The images were taken with a narrow-angled setup, and show a illuminated section of the larger dust cloud.…”

“…The last processing step (namely, particle tracking) is required in both situations, and denotes the process of linking particle positions in consecutive frames to generate trajectories. Different linking algorithms, such as nearest-neighbor or Wiener-filtering [21], are possible. Nearest neighbor tracking is only considerable when the motion from one frame to the next is much smaller than the interparticle distances, which can generally not be assumed.…”

“…For the application in the field of dusty plasmas, we adopted the so-called “shake-the-box”-algorithm, which is based on iterative particle reconstruction. Detailed information regarding this algorithm can be found in more specific publications [ 10 , 11 , 23 ]. Here, we will only give a very brief description of how the algorithm works.…”