Influence of the ambipolar-to-free diffusion transition on dust particle charge in a complex plasma afterglow (original) (raw)

Influence of plasma diffusion losses on dust charge relaxation in discharge afterglow

2008

The influence of diffusive losses on residual dust charge in a complex plasma afterglow has been investigated. 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.

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.

Dust charge distribution in complex plasma afterglow

EPL (Europhysics Letters), 2008

Dust charge distributions have been measured for the first time in a complex plasma. Experiments were performed late in a discharge afterglow. Residual charges of few hundred particles have been determined. It was found that the mean residual charge is negative but the tail of the distribution extends into the positive charge region. The experiments were complemented by numerical simulations taking into account discreteness of the charging process and dependence of plasma parameters on the transition from ambipolar to free diffusion. It is shown that the existence of positively charged particles can be explained by the broadening of the dust charge distribution in the late complex plasma afterglow. PACS numbers: 52.27.Lw

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.

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 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.

Dust density influence on complex plasma decay

AIP Conference Proceedings, 2008

In this paper, the influence of dust particles on the plasma losses in a complex plasma afterglow is studied. It is shown that the dust particles can drastically shorten the plasma loss time by absorption-recombination onto their surfaces. The dust particle absorption frequency increases with the dust density but the dependence is not linear for high dust density. Finally, the possible use of dust absorption frequency measurements as a diagnostics for complex plasmas is mentioned and supported by comparison to existing experimental data.

Dust density effect on complex plasma decay

Physics Letters A, 2008

In this paper, the influence of dust particles on the plasma losses in a complex plasma afterglow is studied. It is shown that the dust particles can drastically shorten the plasma loss time by absorption-recombination onto their surfaces. The dust particle absorption frequency increases with the dust density but the dependence is not linear for high dust density. Finally, the possible use of dust absorption frequency measurements as a diagnostics for complex plasmas is mentioned and supported by comparison to existing experimental data.