Dust-Free Regions around Langmuir Probes in Complex Plasmas under Microgravity

Abstract

Dust-free regions around a Langmuir probe are studied in a complex plasma under microgravity. The dust particles settle in the presheath of the probe, where an equilibrium of the electric field force and the ion-drag force is established. The size and shape of the dust cloud are discussed with simple models. A more sophisticated presheath model is solved numerically to analyze the acting forces and the equilibrium position of the dust. The formation of distinct particle layers in the dust shell can be explained by the force gradients of the effective potential well.

Effects of charge depletion in dusty plasmas

“…It was shown in Ref. 33 that the size of this void shrinks when the probe potential approaches the ambient plasma potential. Therefore, we conclude that the operation of an emissive probe close to the plasma potential has only a small perturbing effect on the dust cloud.…”

Dynamics of dust-free cavities behind fast projectiles in a dusty plasma under microgravity conditions

“…Under microgravity conditions, the experimental sequence starts with injecting a large number of MF particles into the plasma, which form a spatially extended dust cloud with a central dust-free "void" region [21][22][23][24] in the volume between the electrodes. A vertical section through the cloud is shown in Fig.…”

Laser Manipulation of the Void Edge in Dusty Plasmas Under Microgravity

“…To perform a quantitative comparison of the experimental forces with the models of the ion drag, the plasma parameters have been obtained from Langmuir probe measurements [10]. At the void edge, the ion density is found to be newline n i = 1.0 × 10 14 m −3 and increases toward the plasma center with a gradient of ∆n i /∆x = 1.1 × 10 16 m −4 .…”

“…The plasma parameters such as the ion and electron density, the electron temperature, and the plasma potential are measured by a movable and retractable Langmuir probe (see [10]). The measured plasma parameters are exploited to determine the forces on the particles.…”