Dust charge distribution in complex plasma afterglow (original) (raw)
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Dust Charge in complex plasma afterglow
2006
In this talk, we report the first experiment in which the distribution of residual charges on dust grains after the decay of a dusty plasma was measured. The experiment was performed in the PKE-Nefedov reactor where the dust particles were physically grown in the plasma. A temperature gradient was introduced in the chamber to create an upward thermophoretic force to balance gravity. The residual charges were determined from an analysis of dust oscillations, which were excited by applying a sinusoidal bias to the bottom electrode. It was found the coexistence of positively and negatively charged dust as well as and non-charged dust for more than one minute after the discharge was switched off. The residual charges for 200 nm radius particles have been measured for two different pressures. The experimental data were compared with the predictions of a simple theoretical model that describes residual charge evolution in discharge afterglow.
Physics of Plasmas, 2008
The influence of diffusive losses on residual dust charge in a complex plasma afterglow has been investigated. The residual charge distribution was measured and exhibits a mean value Q dres ∼ (−3e − 5e) with a tail in the positive region. The experimental results have been compared with simulated charge distributions. The dust residual charges were simulated based on a model developed to describe complex plasma decay. The experimental and simulated data show that the transition from ambipolar to free diffusion in the decaying plasma plays a significant role in determining the residual dust particle charges. The presence of positively charged dust particles is explained by a broadening of the charge distribution function in the afterglow plasma.
Dependance of dust residual charge on plasma parameters
The dust residual charge distribution in the late afterglow of a dusty plasma has been measured for different operating pressures. It has been shown that the dust charge distribution can be approximated by gaussian function with mean value close to −3e, rms about 1e and a tail in the positive charge region. Numerical simulations of the evolution of the dust charge distribution showed that the shape of the charge distribution is very dependent on the transition from ambipolar to free diffusion during the plasma decay process.
Discharging of dust particles in the afterglow of plasma with large dust density
Physical Review E, 2013
The discharging of dust particles in the afterglow of plasma with large dust density is studied. We used measured electron and metastable dependencies to calculate the rate describing collection of electrons by dust particles by solving the electron balance equation. This rate is compared with the rate calculated using the orbital motion limited (OML) theory. It is found that the OML theory may not be applied for description of dust charging at large afterglow times, and the energetic electrons generated in metastable-metastable collisions significantly affect charging of dust particles. The time dependence for dust charge is calculated by two different approaches: first, the "standard" approach is used, which assumes that ion and electron fluxes to the dust particles are different in the afterglow. Second, the dust charge is calculated by assuming that desorption of electrons from dust particles is very fast. Both approaches gave similar results for dust charging. In addition, the effects of secondary emission due to ion-dust and metastable-dust collisions on dust discharging are investigated. The main source of dust charging in the late afterglow of plasma with large dust density are the energetic electrons generated in Ar m metastable-metastable collisions.
Residual dust charges in an afterglow plasma
An on-ground measurement of dust particle residual charges in the afterglow of a dusty plasma was performed in a rf discharge. An upward thermophoretic force was used to balance the gravitational force. It was found that positively-charged, negatively-charged and neutral dust particles coexisted for more than one minute after the discharge was switched off. The mean residual charge for 200 nm radius particles was measured. The dust particle mean charge is about −5e at pressure of 1.2 mbar and about −3e at pressure of 0.4 mbar.
Charging of dust particles in an illuminated open complex plasma system
2009
This paper presents an investigation of the charging of dust particles in a dusty plasma, irradiated by white light in near space at satellite altitudes. In deference to the recent emphasis on the character of openness in a dusty plasma, the investigation is based on the balance of the number density and energy of electrons, ions, and neutral particles as well as the energy balance of the dust particles and the charge neutrality condition. The accretion of electrons/ions and the emission of electrons by the dust particles, the ionization of neutral particles and the recombination of electrons and ions, and binary collisions between electrons, ions, and neutral atoms are the processes considered herein; the energy exchange associated with these processes has also been considered. The formulation is applicable to dusty plasmas in space and laboratory, where the photoemission of electrons is the dominant mechanism for electron generation. As an illustration a parametric study of the charging of the dust of Cs ͑cesium͒ coated bronze, LaB 6 , and CeO 2 , illuminated by solar radiation in a plasma environment, characteristic of day time ionosphere at an altitude of 150 km has been made. The theory is valid when the mean free path of electrons for accretion by the dust particles is less than the dimensions of the dust clouds.
Residual dust charges in discharge afterglow
Physical Review E, 2006
An on-ground measurement of dust particle residual charges in the afterglow of a dusty plasma was performed in a rf discharge. An upward thermophoretic force was used to balance the gravitational force. It was found that positively-charged, negatively-charged and neutral dust particles coexisted for more than one minute after the discharge was switched off. The mean residual charge for 200 nm radius particles was measured. The dust particle mean charge is about −5e at pressure of 1.2 mbar and about −3e at pressure of 0.4 mbar.
Charge properties of fine dispersed dust grains in space plasma
Introduction. Traditional approaches to the calculation of the equilibrium charge on a single dust grain use the condition that electron and ion currents toward the grain equal to each other [1,2]. To describe charge fluctuations on the grains we apply the discrete population balance (DPB) method used earlier for Fokker-Plank description of particle