Determination of the levitation limits of dust particles within the sheath in complex plasma experiments

TL;DR

This study investigates the levitation limits of dust particles in a plasma sheath by analyzing particle trajectories and modeling electric forces, providing insights into sheath structure and particle behavior near the sheath edge.

Contribution

It introduces a method combining experimental particle trajectory analysis with fluid modeling to determine dust levitation limits and sheath edge location in plasma.

Findings

Lower levitation limit for dust particles identified.

Particles near the sheath edge are outside the linear electric field region.

Results compared with existing sheath models.

Abstract

Experiments are performed in which dust particles are levitated at varying heights above the powered electrode in a RF plasma discharge by changing the discharge power. The trajectories of particles dropped from the top of the discharge chamber are used to reconstruct the vertical electric force acting on the particles. The resulting data, together with the results from a selfconsistent fluid model, are used to determine the lower levitation limit for dust particles in the discharge and the approximate height above the lower electrode where quasineutrality is attained, locating the sheath edge. These results are then compared with current sheath models. It is also shown that particles levitated within a few electron Debye lengths of the sheath edge are located outside the linearly increasing portion of the electric field.