Study on the dust vortex in a dusty plasma ratchet
Abstract
A dust vortex is a common phenomenon in the chip etching process and microgravity- and ground-based dusty plasma experiments. Therefore, it is of great significance to study the dust-vortex formation mechanism, which remains unclear due to difficulties in determining plasma parameters in the sheath where the charged dust particles reside. In this work, we observed the motion of a single dust vortex in a new experiment on dusty plasma ratchets and studied its motion patterns under various discharge conditions. By establishing a three-dimensional dusty plasma ratchet model, we numerically investigated the distribution characteristics of the plasma parameters in the saw channel and reproduced the observed experimental phenomenon in a Langevin simulation. The experimental and simulation results revealed asymmetry in the potential distribution within the saw channel wherein dust particles are suspended, resulting in a nonzero ion flow vorticity in the sawtooth. This nonequilibrium ion drag is the fundamental force driving the dust particles to generate the vortex motion.
