Dynamics of nonspherical, fractal-like water-ice particles in a plasma environment

Abstract

Plasmas containing small solid-state particles (also known as dust particles) are ubiquitous in nature and laboratories. Existing models typically assume that the dust particles are spherical but several observations and simulations indicate that a significant amount of dust particles are nonspherical. Because dust particles are not spherical they show different dynamics from spherical particles in a plasma environment namely, they align in the direction perpendicular to the force equilibrium line, rotate about their alignment axis due to the interaction between the dipole moment and the surrounding electric field, and show vortex motion while maintaining their alignment and rotation when they are exposed to a nonconservative drag force.

Observation of high phase velocity of dust acoustic waves with elongated dust grains in a cryogenic dusty plasma experiment

“…This might be related to the rotation of dust grains. We previously reported that the elongated dust grains rotate in a plasma with a rotation period between 20 and 50 Hz [31], however, we could not obtain statistically meaningful data in this study due to the fast motion of the dust grains. If we measure the rotational speed and add it to the translational speed, the discrepancy might be reduced.…”

“…It is noted that there is an upward thermophoretic force exerted on dust grains in our plasma because the top electrode is always cooler than the bottom electrode by 5-10 K because the cooling system of the upper electrode has a better cooling efficiency than that of the bottom electrode [31]. Thus, the gravitational force acting on the dust grains can be ignored and dust clouds are usually formed in both upper and lower regions of plasma.…”

Phase and Morphology of Water-ice Grains Formed in a Cryogenic Laboratory Plasma

“…The pumping speed is adjusted using an angle valve between the chamber and a turbopump. This causes a very small flow (<10 SCCM) in and out of the 3.8 liter chamber, such that the gas remains in the chamber long enough to come to a conductive thermal equilibrium profile (Chai 2018). While the gas nearest to the chamber walls remains near room temperature, the gas in the interelectrode gap maintains an average temperature closer to the cryogenic temperature of the electrodes.…”