Experimental Determination of Dust-Particle Charge in a Discharge Plasma at Elevated Pressures

Abstract

The charge of dust particles is determined experimentally in a bulk dc discharge plasma in the pressure range 20-100 Pa. The charge is obtained by two independent methods: one based on an analysis of the particle motion in a stable particle flow and another on an analysis of the transition of the flow to an unstable regime. Molecular-dynamics simulations of the particle charging for conditions similar to those of the experiment are also performed. The results of both experimental methods and the simulations demonstrate good agreement. The charge obtained is several times smaller than predicted by the collisionless orbital motion theory, and thus the results serve as an experimental indication that ion-neutral collisions significantly affect particle charging.

Particle flows in a dc discharge in laboratory and microgravity conditions

“…spond to the present (previous [14,15]) experiments in laboratory. Solid squares are obtained from the analysis of parabolic flights experiments.…”

“…The agreement is convincing, indicating that the necessary ingredients have been properly incorporated into the model. [14,15]. Solid (red) circles correspond to the present laboratory experiment.…”

“…Being injected into the plasma, the particles become charged negatively and are transported through the positive column of the discharge by the combination of various forces. The dominant forces in the horizontal direction are the electrical, ion drag and neutral drag forces [14][15][16]. The particles are illuminated by a laser sheet and their motion is recorded by a video-camera, situated near the center of the tube.…”

“…In practice, Equation (14) along with the model equations for particle charge and ion drag force are solved to determine E ⊥ and the total electric field E. This fixes [14,15], solid curve is obtained using the model of the present paper.…”

Fluid approach to evaluate sound velocity in Yukawa systems and complex plasmas

“…The observations of DAWs and measurements of dust-acoustic (sound) velocities have been used to obtain useful information about dusty plasmas systems under various conditions [4][5][6][7][8][9][10][11][12][13][14][15] (we mainly concentrate on three-dimensional particle clouds here, which is also reflected in the reference list). In particular, experimentally measured DAW dispersion relations and sound velocities have been repeatedly used to estimate the electrical charge of particles in dusty plasmas under laboratory and microgravity conditions [16][17][18][19][20], employing various experimental techniques. For other aspects of DAWs and their significance for the field of dusty (complex) plasmas see, for instance, Refs.…”