Effects of collision enhanced charging on dust crystal

TL;DR

This study uses numerical simulations to analyze how collision enhanced charging affects dust crystal structures in RF plasma, showing it reduces inter-particle spacing and aligns better with experimental data.

Contribution

It introduces a collision enhanced charging model into dust crystal simulations, improving accuracy over traditional models and providing detailed insights into dust crystal behavior.

Findings

Collision enhanced charging lowers dust grain charge and electric force.

Including CEC reduces inter-particle spacing in dust crystals.

CEC model aligns simulation results more closely with experimental data.

Abstract

Numerical simulations of monolayer dust crystals in an RF complex plasma were performed to examine the crystal structure and quantify the effects of including the collision enhanced ion current in the charging model. A GEC cell similar to a previous experimental work was modeled for a range of RF voltages, using a continuum description for the plasma and a particle description for dust grains. The time history of each dust grain was monitored. The dust charge was computed using both the OML and the collision enhanced charging (CEC) model applicable to the sheath region. The dust model accounted for the electric force, ion drag force, neutral drag force, gravity, and the ion wake. The CEC model produced a lower charge and lower electric force which agreed better with the experimental data. Then dust crystals composed of 40 to 100 grains were modeled and the levitation height and inter-particle spacing of the resulting crystals was examined. Including the collision enhanced current reduced the inter-particle spacing but only had a minor effect on the levitation height.