Dusty Plasma Liquid Research Articles

Microstructural Evolution and Irreversibility in the Viscoelastic Response of Mesoscopic Dusty-Plasma Liquids

We experimentally demonstrate the viscoelastic response and construct a microscopic dynamical picture using a quasi-2D dusty-plasma liquid confined in a mesoscopic gap and sheared periodically. The correlation between microdisplacement and structural evolution at the discrete kinetic level is explored. Through hopping, the structural rearrangement associated with shear enhanced stretching, kinking, breaking, and reconnection of local lattice lines generates irreversible plastic deformation. The strain energy accumulation in the twisted regions without topological rearrangement is the source for local rebound.

Explosion dynamics of dusty plasma liquids induced by laser ablation on suspended dust particles

Dusty plasma liquids can be formed by suspending negatively charged micrometer sized dust particles in a low pressure glow discharge. We investigate the dynamical behaviors of the expanding plume generated by the ablation on one of the suspended particles using a focused nanosecond pulsed laser, through monitoring the white light emission intensity and dust particle trajectories. In the initial 10μs, the diameter of the expanding plume scales as D∝P−0.37t0.31, where P is the background pressure. The surrounding dust particles start to be driven away radially after tens of microseconds. The diameter of the expanding cavity (plasma bubble) with dust depletion scales as D∝t0.33.

Dusty plasma liquid: structure and transfer phenomena

Results are given of the experimental investigation of three-particle correlation for liquid plasma-dust structures formed in the electrode layer of a capacitive rf discharge. The obtained three-particle correlation functions for experimental and numerical data are analysed and compared with the superposition approximation. The forming of clusters of macroparticles in plasma-dust systems being analysed is revealed. The experiments in heat transfer were performed in plasma of a capacitive radio-frequency (rf) discharge in argon (P ≈ 20 Pa) with particles 4 µm in mean diameter. The results are given of an experimental investigation of processes of heat transfer for fluid dust structures in rf-discharge. The analysis of steady-state, and unsteady-state heat transfer are used to obtain the thermal conductivity and diffusivity constants.

Dusty plasma liquids

Dusty plasma liquids are formed by suspending negatively charged micro-metre sized particles in a low pressure discharge background. They are good candidates for studying the generic spatio-temporal dynamical behaviours at the kinetic level through direct optical video-microscopy due to the sub-mm interparticle spacing and the slow time scale. In this paper, starting from the basic picture of the avalanche type stick–slip cooperative hopping process under the interplay of mutual coupling and stochastic thermal agitation, we briefly review our recent study on particle micro-motion and the associated structural rearrangement. The effects of mesoscopic confinement and external slow shear drive are also discussed.

Experimental study of laminar flow in dusty plasma liquid

It is for the first time shear viscosity of dusty plasma liquid defined by the screened Coulomb interaction of dust particles is estimated on the basis of experimental data. The results of the experimental studies of the laminar viscous dusty plasma flow are presented in the Letter.

Micro-excitations in Coulomb liquids

In a two-dimensional liquid melted from a triangular lattice, the accumulation of constructive perturbation from thermal noise and other external slow drive can cause stick–slip type particle hopping over the caging barrier formed by the surrounding particles, which in turn distort the order lattice structure and generate topological defects. Through the strong mutual coupling, these nonlinear threshold-type micro-excitations of fast particles and topological defects usually occur in the form of avalanche type clusters involving a small number of sites. The dusty plasma liquid formed by suspending negatively charged micrometre sized particles in a low pressure discharge background turns out to be a good candidate to study the above spatio-temporal dynamical behaviours at the kinetic level through direct optical video microscopy. In this paper, we review our recent studies on this issue and compare the generic behaviours with other nonlinear coupled complex system excited by noise and other slow drives.

Dynamics and structural properties of dusty plasma liquid in microgravity: experiments onboard the International Space Station

The results of numerical simulations of particles structure (ordering) and dynamics (diffusion constant) in a ‘liquid plasma’ state of strongly coupled dusty plasmas are considered. Static and dynamical properties of microparticle systems in the liquid state have been studied in experiments under microgravity conditions. The comparison of the experimental results with the results of numerical simulations of Debye systems was used to estimate the effective coupling parameter which governs particles structural and dynamical properties. This diagnostics tool allows one to estimate particle charge and plasma screening length which are very important characteristics of dusty plasmas.

2D Dusty Plasma Liquids in Mesoscopic Channels

We review our studies on the micro-motion at the kinetic level of quasi-2D thin dusty plasma liquids in mesoscopic gaps. The topological constraint from the straight boundary leads to the formation of several nearby layered structures with non-Gaussian bumpy transverse displacement (velocity) distributions due to the suppressed transverse hopping. The center region remains unaffected and exhibits isotropic motion and faster structural relaxation like bulk liquid. When the gap width W is reduced below 7 interlayers' width, transition to the layered structure with anisotropic motion and slow dynamics through the whole liquid occurs. Applying external shear for the liquid at width before the layering transition causes the formation of shear bands.

Microscopic observation of confinement-induced layering and slow dynamics of dusty-plasma liquids in narrow channels.

We report the microscopic observation of the confinement induced layering of quasi-2D dusty-plasma liquids in mesoscopic channels at a width W down to a few interparticle spacings. The two straight boundaries suppress nearby transverse hopping. It causes the formation of two to three layers with anisotropic diffusion nearby each boundary, and the randomly oriented bulklike liquid with isotropic diffusion in the center for a W>or=7 interlayer width. The pinching of the boundary layers from both sides leads to the transition to the layered structure with slow dynamics through the whole system as W decreases to five interlayer width. The packing and motion under an improper smaller W are also discussed.

Microdynamics of dusty plasma liquids in narrow channel: from disorder to order

We report direct observations on the microscopic dynamics of dusty plasma liquid confined in a narrow gap. We measure the horizontal and transverse displacement histograms as well as the transverse particle density distributions from particle trajectories. Under confinement, the liquid forms a layer structure. The dust particle motion at boundaries show anisotropy and three outermost layers is found due to the pinching effect of the boundaries. When the gap width is reduced to below 7d (d = inter-layer width), the dust particle motion in the central region shows a transition from isotropic motion to anisotropic discrete hopping motion, leading to a slower dynamics and layer structure through the whole liquid.

Microscopic visco-elastic motions of narrow two-dimensional dust Coulomb liquids under modulated shear stress

The microscopic visco-elastic motion of a quasi-2D dustyplasma liquid confined to a width of about 15 interparticle distances undersquare stress pulses shorter than thermal relaxation time from achopped laser beam is investigated experimentally. Thestress-enhanced excitations of hopping vortices are responsible for particles in thelaser driven zone reaching, after a higher initial velocity,a constant nonzero terminal forward velocity and partial plasticdeformation through the loss of the structure memory. Thedriven particles around domains with caged shear motion stillpartially keep the structural memory and demonstrate partialelastic backwards motion with exponential relaxation afterturning off the laser.

Observation of laser-pulse-induced traveling microbubbles in dusty plasma liquids.

We report a direct experimental observation of traveling microbubbles induced by intense laser pulses in strongly coupled dusty plasma liquids. The dense plasma ablated from a suspended dust particle generates a spherical plasma bubble with a low dust density, in the quiescent regime before a transition to self-organized longitudinal dust density waves. It travels downwards at a velocity about 6 cm/sec inside the dust liquid. Dust density fluctuations trailing the bubble are also observed. The bubble generated in the high pressure dissipative regime collapses right after formation.

Avalanche excitations of fast particles in quasi-2D cold dusty-plasma liquids.

We study the spatiotemporal cooperative microexcitations in quasi-2D cold dusty-plasma liquids from the view of the coupled subexcitable nonlinear dynamical system. Under the interplay of thermal noise and mutual coupling, cooperative fast-particle clusters are excited in the xyt space. The fast hopping plays a major role in the superdiffusion with non-Gaussian velocity distribution and causes the loss of bond-orientation memory. The size distribution of the excited clusters in the xyt space follows a similar avalanche-type power-law relation as in other subexcitable systems.

Laser enhanced transports in strongly coupled dusty plasmas

The stress induced microscopic responses of dust particles in strongly coupled dusty plasma liquids suspended in plasma traps are investigated experimentally. Narrow laser beams are used to generate stress on dust particles through optical pressure. Assisted by background thermal fluctuations, chaotic micro-vortices with decaying intensities from the laser beam are generated. The forward transport and transverse diffusion rate are enhanced and show nonlinear reponse to the external stress. Visco-elastic response is observed for an elongated liquid cluster driven by a periodically chopped laser beam. The shear wave is damped.

Nonlinear Motions in Dusty Plasma Crystals, Liquids, and Clusters

The dusty plasma with dust particles charged and suspended in the plasma background is a complex open dissipative nonlinear system. Dust Coulomb crystals, liquids and clusters with finite particle numbers can be formed under the strong coupling. The competition between the caged motion from the strong coupling and the thermally induced hopping generates rich microscopic nonlinear motions associated with vortex excitations leading to anomalous diffusion, which can be further enhanced by laser induced shears. The motion becomes anisotropic for particles near the system boundary. At the macroscopic level, the interplay between the dust particle motion, and the charge density and dark space width fluctuations through the ionization instability makes the system exhibit many self-organized spatio-temporal behaviors.