Dc Glow Discharge Dusty Plasma Research Articles

Evolution of frequency clusters in the naturally occurring dust acoustic wave.

The spatiotemporal evolution of the naturally occurring dust acoustic wave mode is experimentally investigated in a weakly coupled dc glow discharge dusty plasma system over a range of neutral gas pressures through the application of a time-resolved Hilbert Transform. Frequency clusters are observed over a range of neutral gas pressures, though their spatial distribution varies with neutral gas pressure. It is also observed that the wave frequency is observed to drop by ∼ 10 Hz across these frequency clusters independent of the experimental parameters.

Secondary dust density waves excited by nonlinear dust acoustic waves

Secondary dust density waves were observed in conjunction with high amplitude (nd/nd0>2) dust acoustic waves (DAW) that were spontaneously excited in a dc glow discharge dusty plasma in the moderately coupled, Γ∼1, state. The high amplitude dust acoustic waves produced large dust particle oscillations, displacements, and trapping. Secondary dust density waves were excited in the wave troughs of the high amplitude DAWs. The waveforms, amplitudes, wavelengths, and wave speeds of the primary DAWs and the secondary waves were measured. A dust-dust streaming instability is discussed as a possible mechanism for the production of the secondary waves.

Thermal Properties of a Dusty Plasma in the Presence of Driven Dust Acoustic Waves

In this paper, the thermal properties of a weakly coupled dc glow discharge dusty plasma with driven dust acoustic waves are investigated. Here, the waves are driven using a current modulation at a fixed frequency with varying amplitudes. Stereoscopic particle image velocimetry is used to measure the velocity space distribution of the dusty plasma. It is shown that, with increasing amplitude of the modulation, there is a corresponding increase in the measured kinetic temperature. In addition, there is an evidence of non-Maxwellian features in the velocity distribution.

Laboratory Observations of Self-Excited Dust Acoustic Shocks

Repeated, self-excited dust acoustic shock waves (DASWs) have been observed in a dc glow discharge dusty plasma using high-speed video imaging. Two major observations are reported: (1) The self-steepening of a nonlinear dust acoustic wave (DAW) into a saw-tooth wave with sharp gradient in dust density, very similar to those found in numerical solutions of the fully nonlinear fluid equations for a nondispersive DAW [B. Eliasson and P. K. Shukla, Phys. Rev. E 69, 067401 (2004)], and (2) the collision and confluence of two DASWs.

Measurement of the kinetic dust temperature of a weakly coupled dusty plasma

Measurements of the kinetic velocity space distribution function of 3.11μm diam melamine and 1.51μm diam silica particles in an argon dc glow discharge dusty plasma are made through the use of stereoscopic particle image velocimetry. These distribution functions are then used to determine the kinetic temperature of the dust component. These measurements show that the kinetic temperature of the dust component is significantly larger than the other plasma components (electrons, ions, and background neutrals).

Initial measurement of the kinetic dust temperature of a weakly coupled dusty plasma

Measurements of the velocity space distribution function of 2.9μm diameter silica particles in an argon dc glow discharge dusty plasma are made through the use of stereoscopic particle image velocimetry (stereo-PIV). These distribution functions are then used to determine the kinetic temperature of the dust component. These measurements show that the kinetic temperature of the dust component is significantly larger than the other plasma components (electrons, ions, and background neutrals).

Excitation of Dust-Acoustic Waves in a DC Glow-Discharge Dusty Plasma by Means of Pulsed Gasdynamic Stimulation

A new method is suggested for the generation of density waves of the dust component in a dc glow-discharge dusty plasma by means of pulsed gasdynamic stimulation. This method is applied to structures consisting of spherical and disk-shaped dust particles. High-amplitude waves are obtained (compression factor of up to two). The wave profile in the case of spherical and disk-shaped particles remains unchanged. The interaction of self-excited waves and waves initiated by the effect of the gas flow pulse is observed. A mechanism of generation and propagation of density waves under gasdynamic stimulation is suggested.

Large-amplitude dust waves excited by the gas-dynamic impact in a dc glow discharge plasma.

A large-amplitude wave with two humps of dust density, separated by a dip was generated. To excite the wave in the dc glow discharge dusty plasma a gas-dynamic impact was used. The structure obtained had several interesting properties such as strong compression of dust in the humps, supersonic dust particles in the rarefaction zone, reconstruction of the initial dust configuration after the passing of the wave. The peculiarities of the phenomenon observed are discussed. The mechanism of generation and propagation for such kind of perturbation is proposed.

Periodic long-range transport in a large volume dc glow discharge dusty plasma

In an earlier paper, the authors reported on observations of a variety of particle transport phenomena observed in DUPLEX—the DUsty PLasma EXperiment at the Naval Research Laboratory [E. Thomas, Jr., W. E. Amatucci, C. Compton, and B. Christy, Phys. Plasmas 9, 3154 (2002)]. DUPLEX is a large, transparent polycarbonate cylinder that is 40 cm in radius and 80 cm in height. dc glow discharge argon plasmas are generated in DUPLEX. In this paper, the authors expand upon one particular feature of particle transport in DUPLEX, the long-range (i.e., greater than 15 cm), periodic (T∼2.5 min) transport of suspended alumina particles through the plasma. A detailed description of this particle motion through the plasma is presented. Finally, a qualitative model describing the phenomena that lead to this transport is also given.

Visualization of dust particle transport in DC glow discharge plasmas

The particle image velocimetry (PIV) technique is used to measure two-dimensional velocity profiles in DC glow discharge dusty plasma. By synchronizing the application of a known perturbation to the PIV measurement sequence, the characterization of perturbation-induced transport of the suspended dust particles can be reproducibly investigated. Images showing the temporal and spatial evolution of the velocity profile are presented.

Direct measurements of particle transport in dc glow discharge dusty plasmas

Many recent experiments in dc glow discharge plasmas have shown that clouds of dust particles can be suspended near the biased electrodes. Once formed, the dust clouds have well defined boundaries while particle motion within the clouds can be quite complex. Because the dust particles in the cloud can remain suspended in the plasma for tens of minutes, it implies that the particles have a low diffusive loss rate and follow closed trajectories within the cloud. In the experiments discussed in this paper, direct measurements of the dust particle velocities are made using particle image velocimetry (PIV) techniques. From the velocity measurements, a reconstruction of the three- dimensional transport of the dust particles is performed. A qualitative model is developed for the closed motion of the dust particles in a dc glow discharge dusty plasma.

Mechanism of dust-acoustic instability in a direct current glow discharge plasma

An observation of low frequency waves spontaneously excited in a dc glow discharge dusty plasma is reported. To analyze possible reasons for the instability observed, a linear dispersion relation which takes into account collisions with neutrals, dust grain charge variations, ion drift, and forces acting on dust particles is derived. Numerical analysis of the dispersion relation shows that the observed instability is the result of dust charge variations in the presence of external charge-dependent forces together with the ion drift effect.