Dust grain charging and levitation in a weakly collisional sheath

Abstract

An experiment is described in which monodisperse dust grains are levitated within a dc sheath above a conducting plate in argon plasma. For plate bias voltages that are not too negative ͑уϪ10 electron temperatures͒, the observed dust levitation heights are near to values calculated from a model combining equations for the sheath with those for grain charging. When the plate is more negatively biased, the theoretical levitation heights are higher than the observed heights as a consequence of the measured sheath thickness being smaller than values obtained from the models.

The effect of surface topography on the lunar photoelectron sheath and electrostatic dust transport

“…Over time, these models have become progressively more complex and realistic in their description of both the plasma environment around airless bodies and their treatment of dust grain motion; however, open questions still remain, including the role of both topography, such as craters or boulders, and varying solar zenith angle in modifying the near-surface plasma environment, the influence that complex electric fields near craters and boulders have on the electrostatic transport of dust grains, and the ability of craters to accumulate dust grains via electrostatic transport over long periods of time. Laboratory work has confirmed some aspects of the theory of electrostatic dust transport, including the ability to charge and levitate dust grains in a plasma sheath (Sickafoose et al, 2001(Sickafoose et al, , 2002Robertson et al, 2003;Flanagan and Goree, 2006;Wang et al, 2009), the presence of elevated electric fields near differentially charged surfaces (Wang et al, 2007), and the electrostatic transport of dust grains near an electron beam impact/shadow boundary (Wang et al, 2010(Wang et al, , 2011.…”

Experiments on dust transport in plasma to investigate the origin of the lunar horizon glow

“…[4] In our own previous experiments, dust particles in plasma were seen to lift from a surface and levitate in the sheath above it [Sickafoose et al, 2002]. The observed levitation heights were successfully modeled by a collisional sheath theory [Robertson et al, 2003]. Here we present experimental results on the transport of insulating dust on a conducting surface in plasma, including the temporal evolution of the distribution of the electric fields above a spreading pile of dust.…”

Lunar surface: Dust dynamics and regolith mechanics

“…There are two locations in the photoelectron layer or plasma sheath at which the electric force can balance the gravitational force. The lower of these potential levitation heights is roughly one Debye length above the surface, but particles at this height are unstable [ Nitter et al , 1998; Robertson et al , 2003]. Just below the lower equilibrium height, particles are accelerated down to the surface, while those above it will settle into the upper equilibrium height.…”