High negative charge of a dust particle in a hot cathode discharge

Abstract

Dust particle levitation experiments in a plasma produced by a hot filament discharge, operating at low argon pressure, are presented. The basic characteristics of a dust grain trapped in a plate sheath edge in these experimental conditions are reported. Taking into account the sheath potential profiles measured with a differential emissive probe diagnostic, the forces applied to an isolated dust grain can be determined. Two different experimental methods yield approximately the same value for the dust charge. The observed high negative charge is mainly due to the contribution of the primary electrons emitted by the filaments as predicted by a simple model.

Lunar surface: Dust dynamics and regolith mechanics

“…Laboratory measurements of plasma sheaths show sheath potentials relative to the plasma potential described by an exponential, where Φ 0 is the potential bias of the surface, such as the lunar surface potential, and b is the inverse scale height [ Arnas et al , 1999, 2000, 2001; Sickafoose et al , 2002]. The electric field within the sheath therefore also falls off exponentially with distance from the surface.…”

Dust density effect on complex plasma decay

“…The presence of this new charged species leads to interesting phenomena that distinguish complex plasma from classic dust-free plasma [3][4][5]. In laboratory discharges, the dust particles can be either grown directly in the plasma chamber (by sputtering [6,7] or using reactive gases [8,9]) or injected inside the plasma [10,11]. Due to a higher mobility of the electrons the dust particles are negatively charged.…”

Experimental study of different carbon dust growth mechanisms

“…In this calculation, caution must be paid to take into account not only the electron and ion fluxes of the background plasma, but also the flux of primary electrons emitted by the tungsten filaments (for a detailed calculation, see Ref. [7]). One finds then an agglomerate charge of Q $ À2.3 · 10 À17 C (145 e À ), high enough to stop the agglomeration phase and to lead to a separated deposition because of mutual Coulomb repulsion.…”

“…Multiple cluster collisions can then lead to the formation of spherical particulates which may themselves undergo further collisions and form spherical agglomerates as observed in TEXTOR [6] and in our laboratory experiments. The agglomeration phase stops when the surface effective charge of the new aggregate-particulate specie stabilizes at a negative value [7].…”