How to make large, void free dust clusters in dusty plasma under microgravity

TL;DR

This study uses a self-consistent fluid model to analyze how to create large, void-free dust clusters in microgravity dusty plasma experiments by controlling the driving potential, highlighting the role of self-organization.

Contribution

The paper introduces a comprehensive fluid model that predicts void closure in microgravity dusty plasma, emphasizing self-organization effects and providing insights for experimental control.

Findings

Void closure achieved by lowering driving potential.

Self-organization influences void formation and closure.

Good agreement with experiments when charge-exchange collisions are neglected.

Abstract

Collections of micrometer sized solid particles immersed in plamsa are used to mimic many systems from solid state and fluid physics, due to their strong electrostatic interaction, their large inertia, and the fact that they are large enough to be visualized with ordinary optics. On Earth, gravity restricts the so called dusty plasma systems to thin, two-dimensional layers, unless special experimental geometries are used, involving heated or cooled electrons, and/or the use of dielectric materials.In micro-gravity experiments, the formation of a dust-free void breaks the isotropy of three-dimensional dusty plasma systems. In order to do real three-dimensional experiments, this void has somehow to be closed. In this paper, we use a fully self-consistent fluid model to study the closure of a void in a micro-gravity experiment, by lowering the driving potential. The analysis goes beyond the simple description of the virtual void, which describes the formation of a void without taking the dust into account. We show that self-organization plays an important role in void formation and void closure, which also allows a reversed scheme, where a discharge is run at low driving potentials and small batches of dust are added. No hysteresis is found this way. Finally, we compare our results to recent experiments and find good agreement,but only when we do not take charge-exchange collisions into account.