Nonviscous motion of a slow particle in a dust crystal under microgravity conditions

Subsonic motion of a large particle moving through the bulk of a dust crystal formed by negatively charged small particles is investigated using the PK-3 Plus laboratory onboard the International Space Station. Tracing the particle trajectories shows that the large particle moves almost freely through the bulk of the plasma crystal, while dust particles move along characteristic $\alpha$-shaped pathways near the large particle. In the hydrodynamic approximation, we develop a theory of nonviscous dust particle motion about a large particle and calculate particle trajectories. Good agreement with experiment validates our approach.

Figure 1

The cross-sectional schematic of the plasma chamber.

Figure 2

(a) Snapshot of the microparticle cloud from a quadrant view camera (field of view is $35.7\text{mm}\times 26.0$ mm). On the left-hand side, a small track of initial movement of the probe particle (projectile) into the cloud is visible. The horizontal dashed line arrow shows schematically the path of projectile on the left-hand side (phase I); the vertical dashed line arrow shows the path of projectile from the void into the upper part of the microparticle cloud (phase II). (b) Snapshot of the microparticle cloud from a high-resolution view camera (field of view is $8.1\text{mm}\times 5.9$ mm). A small track on the right-hand side shows the projectile motion in phase II.

Figure 3

Recorded positions of dust particles and the projectile (negative images). Time interval between individual frames is (a) 0.1 s and (b) 0.02 s; (c) is a superposition of 12 frames with the time interval of 0.02 s. The projectile motion from void to chamber wall corresponds to frames from bottom to top.

Figure 4

Calculated trajectory of a dust particle moving about the projectile for $\nu \Delta t=2.5$. The solid line shows calculation using (8) and (9), and the dashed line shows numerical integration of Eqs. (6) for the same $d=0.163$. Dots mark the intervals $\nu t=1/4$.

Figure 5

Individual dust particles moving along the $\alpha$-shaped pathways. Traces are the superposition of frames obtained in the experiment (negative image, vertical trace marks the projectile trajectory), solid lines show calculation by formulas (8) and (9), and the dashed line indicates the trajectory portion “forced” by local crystallization.