skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Potential around a charged dust particle in a collisional sheath

Abstract

By employing a self-consistent kinetic approach, an analytical expression is derived for the potential of a test charge in a weakly ionized plasma with ion drift. The drift is assumed to be due to an external electric field, with the velocity being mobility-limited and much larger than the thermal velocity of neutrals. The derived expression is proven to be in excellent agreement with the measurements by Konopka et al. [Phys. Rev. Lett. 84, 891 (2000)] performed in the sheath region of a rf discharge.

Authors:
; ; ; ;  [1];  [2];  [3];  [2];  [3]
  1. Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching (Germany)
  2. (Russian Federation)
  3. (Germany)
Publication Date:
OSTI Identifier:
20974968
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2730498; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COLLISIONS; DUSTS; ELECTRIC FIELDS; HIGH-FREQUENCY DISCHARGES; ION DRIFT; MOBILITY; PLASMA; PLASMA SHEATH; POTENTIALS; VELOCITY

Citation Formats

Kompaneets, R., Konopka, U., Ivlev, A. V., Tsytovich, V., Morfill, G., Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching, General Physics Institute of the Russian Academy of Sciences, 117942 Moscow, and Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching. Potential around a charged dust particle in a collisional sheath. United States: N. p., 2007. Web. doi:10.1063/1.2730498.
Kompaneets, R., Konopka, U., Ivlev, A. V., Tsytovich, V., Morfill, G., Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching, General Physics Institute of the Russian Academy of Sciences, 117942 Moscow, & Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching. Potential around a charged dust particle in a collisional sheath. United States. doi:10.1063/1.2730498.
Kompaneets, R., Konopka, U., Ivlev, A. V., Tsytovich, V., Morfill, G., Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching, General Physics Institute of the Russian Academy of Sciences, 117942 Moscow, and Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching. Tue . "Potential around a charged dust particle in a collisional sheath". United States. doi:10.1063/1.2730498.
@article{osti_20974968,
title = {Potential around a charged dust particle in a collisional sheath},
author = {Kompaneets, R. and Konopka, U. and Ivlev, A. V. and Tsytovich, V. and Morfill, G. and Moscow Institute of Physics and Technology, 141700 Dolgoprudny and Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching and General Physics Institute of the Russian Academy of Sciences, 117942 Moscow and Max-Planck-Institut fuer Extraterrestrische Physik, 85748 Garching},
abstractNote = {By employing a self-consistent kinetic approach, an analytical expression is derived for the potential of a test charge in a weakly ionized plasma with ion drift. The drift is assumed to be due to an external electric field, with the velocity being mobility-limited and much larger than the thermal velocity of neutrals. The derived expression is proven to be in excellent agreement with the measurements by Konopka et al. [Phys. Rev. Lett. 84, 891 (2000)] performed in the sheath region of a rf discharge.},
doi = {10.1063/1.2730498},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The ion density and electric potential distribution are found within the linear kinetic approach using the dielectrical permittivity of a flowing collisional plasma around a charged particle. The parameters of the disturbed plasma flow near the dust particle are also calculated numerically through a self-consistent solution of the ion kinetic equation and the Poisson equation with the particle-in-cell Monte Carlo collision algorithm. Scaling laws are formulated from an analysis of the linear kinetic equation. Comparison of the ion and potential distributions for sub- and supersonic ion flows in the collisional and collisionless regimes lends support to these scaling laws formore » flowing plasmas.« less
  • The ion neutral collision can lead to interesting phenomena in dust charging, totally different from the expectations based on the traditional orbit motion limited theory. The potential around a dust grain is investigated for the collisional plasma considering the presence of ion neutral collisions. Fluid equations are solved for the one dimensional radial coordinate. It is observed that with the gradual increase in ion neutral collision, the potential structure around the dust grain changes its shape and is different from the usual Debye-H├╝ckel potential. The shift however starts from a certain value of ion neutral collision and the electron-ion densitymore » varies accordingly. The potential variation is interesting and reconfirms the fact that there exists a region of attraction for negative charges. The collision modeling is done for the full range of plasma, i.e., considering the bulk and the sheath jointly. The potential variation with collision is also shown explicitly and the variation is found to cope up with the earlier observations.« less
  • The screening length, the time-average electric field, and the particle charge as well as the local vertical gradients of these quantities are determined experimentally within a sheath of a capacitively coupled rf, 13.56 MHz, discharge at enhanced argon gas pressures of 30, 55, and 100 Pa. The parameters are derived directly from comparative measurements of levitation positions of the particles of different sizes and variations in the levitation heights caused by formation of new dust layers. The electrostatic effect of the horizontally extended dust layers on the sheath electric field is investigated.
  • Sheath formation is studied for collisional plasma in presence of dust. In common laboratory plasma, the dust acquires negative charges because of high thermal velocity of the electrons. The usual dust charging theory dealing with the issue is that of the Orbit Motion Limited theory. However, the theory does not find its application when the ion neutral collisions are significantly present. An alternate theory exists in literature for collisional dust charging. Collision is modeled by constant mean free path model. The sheath is considered jointly with the bulk of the plasma and a smooth transition of the plasma profiles frommore » the bulk to the sheath is obtained. The various plasma profiles such as the electrostatic force on the grain, the ion drag force along with the dust density, and velocity are shown to vary spatially with increasing ion neutral collision.« less
  • Models for the charging of dust particles in the bulk plasma and in the sheath region are discussed. A new model is proposed that describes collision-enhanced ion currents in the sheath. The collisions result in a substantial reduction of the negative charge of the dust. Experimental data for the dust charge in the sheath can be described by this model when a Bi-Maxwellian electron distribution is taken into account. Expressions for the dust charging rate for all considered models are presented and their influence on the rise of the kinetic dust temperature is discussed.