Particles In Dusty Plasma Research Articles

Three-view stereoscopy in dusty plasmas under microgravity: A calibration and reconstruction approach

A three-camera stereoscopy setup is presented that allows to reconstruct the trajectories of particles in dusty plasmas under microgravity. The calibration procedure for the three-camera setup takes the special circumstances into account that occur in close-range imaging of small particles. Additionally, a reconstruction algorithm is presented that is based on the epipolar geometry and delivers the essential particle correspondences. Further improvements are achieved by analyzing the dynamic particle behavior. Two applications of our calibration and reconstruction procedure are presented: A two-dimensional dust structure in the laboratory with a large percentage of hidden particles, and particles inside the void of a dust cloud under microgravity.

Thermodynamic Properties of Dusty Plasma on the Basis of the Langevin Dynamics

AbstractRadial distribution functions of dusty plasma particles are calculated by the application of the Langevin dynamics to a system of particles interacting through the Yukawa potential. Proposed numerical model is first validated by the comparison of the numerical results with available experimental data. Both numerically determined and experimental radial distribution functions demonstrate a good coincidence, thus, enabling a calculation of the structural properties of dusty plasma for a wide range of parameters. On the basis of the performed calculations, dependencies of internal energy and excess pressure from the coupling and density parameters are presented (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structure formation in system of Brownian particle in dusty plasma

The stationary distribution function of grains in a dusty plasma is calculated with regard to electron and ion absorption by grains. It is shown that such distribution can be considerably different from the distribution function of ordinary Brownian particles in thermal equilibrium. The criterion of formation of non-equilibrium spatially ordered distributions of grains in dusty plasmas is discussed.

Solitary inertial Alfvén waves in dusty plasmas

Linear and nonlinear inertial Alfvén waves are studied in the presence of positively and negatively charged dust in electron-ion plasmas. The Sagdeev potential approach is employed to obtain solitary inertial Alfvén waves in such a multicomponent plasma. It is found that electron density dips are formed in the super Alfvénic region, which has behavior similar to the case of electron-ion plasmas. The amplitude of the electron density dip structure is decreased in the presence of positively charged dust particles, while it is increased due to negatively charged dust particles in dusty plasmas. The numerical results are shown for an illustrative purpose. The results can be applicable to explain some aspects of solar wind interactions with the comets and planets containing dusty plasma environments.

Particle positioning techniques for dusty plasma experiments

Video microscopy is a widely applied diagnostic to investigate the structure and the dynamics of particles in dusty plasmas. Reliable algorithms are required to accurately recover particle positions from the camera images. Here, four different particle positioning techniques have been tested on artificial and experimental data of dusty plasma situations. Two methods that rely on pixel-intensity thresholds were found to be strongly affected by pixel-locking errors and by noise. Two other methods-one applying spatial bandpass filters and the other fitting polynomials to the intensity pattern-yield subpixel resolution under various conditions. These two methods have been shown to be ideally suited to recover particle positions even from small-scale fluctuations that are used to derive the normal mode spectra of finite dust clusters.

Fluorescent microspheres as tracer particles in dusty plasmas

A technique has been developed to derive the dynamic properties of an ensemble of particles in dusty plasmas by using fluorescent tracer particles. The tracers form an integral part of the entire dust system. The dynamic properties of the dust system is reconstructed from the motion of the tracer. This technique allows long-duration experiments and is applied to a two-dimensional Coulomb cluster where the flow field, intershell rotation, and stagnation points of the flow have been identified.

Structure of spherical Yukawa clusters: A model for dust particles in dusty plasmas in an isotropic environment

The structure of spherical clusters composed of Yukawa particles is analyzed by molecular dynamics simulations and theoretical approaches as a model for dust particles in dusty plasmas in the isotropic environment. The latter condition is expected to be realized under microgravity or by active cancellation of the effect of gravity on the ground. It is found that, at low temperatures, Yukawa particles form spherical shells and, when scaled by the mean distance, the structure is almost independent of the strength of screening including the case of the Coulomb interaction. The positions and populations of shells and the conditions for the change of the number of shells are expressed by simple interpolation formulas. Shells have an approximately equal spacing close to that of triangular lattice planes in the bulk close-packed structures. It is shown that, when the cohesive energy in each shell is properly taken into account, the shell model reproduces the structure of spherical Yukawa clusters to a good accuracy.

Ordering of dust particles in dusty plasmas under microgravity

Structure formation of dust particles in dusty plasmas under microgravity has been simulated by the molecular dynamics method. It is shown that, at low temperatures, dust particles are organized into layered spherical shells. The number of shells is a function of the system size and the strength of screening by ambient plasma particles, while the dependency on the latter is much weaker. In the simulation, the condition of the charge neutrality satisfied by the system of dust particles and plasma particles is properly taken into account.

Laser heating of particles in dusty plasmas

Experiments on the heating and melting of two-dimensional finite dust crystals are performed using random laser excitation of the dust particles by a rapidly moving laser beam. The achievable dust temperatures scale with the square of the laser power. The heating process is described for different dust clusters under various plasma and cluster conditions. A single-particle model is developed to explain the observed behavior of the cluster under the random laser excitation. Good quantitative agreement is found when the radiation pressure is made responsible for the particle excitation by the laser. The dynamical properties of the system during heating are analyzed and the dominant modes are identified. From this, it is demonstrated that the heating process is of a nearly equilibrium nature in contrast to previous melting experiments. Finally, the melting of the dust cluster by laser heating is studied. From these experiments, a precise determination of the critical coupling parameter for the solid-fluid transition was possible. It is measured as Gamma = 270-480 for an N = 18 cluster.

Collective modes of quasi-two-dimensional Yukawa liquids.

Particles in dusty plasmas are often confined to a quasi-two-dimensional arrangement. In such layers--besides the formation of compressional and (in-plane) shear waves--an additional collective excitation may also show up, as small-amplitude oscillations of the particles perpendicular to the plane are also possible. We explore through molecular dynamics simulations the properties (fluctuation spectra, dispersion relation, Einstein frequency) of this out-of-plane transverse mode in the strongly coupled liquid phase of Yukawa systems.

Long-range attraction between particles in dusty plasma and partial surface tension of a dusty phase boundary

Effective potential of a charged dusty particle moving in homogeneous plasma has a negative part that provides attraction between similarly charged dusty particles. A depth of this potential well is great enough to ensure both stability of crystal structure of dusty plasma and sizable value of surface tension of a boundary surface of dusty region. The latter depends on the orientation of the surface relative to the ion flow, namely, it is maximal and positive for the surface normal to the flow and minimal and negative for the surface along the flow. For the most cases of dusty plasma in a gas discharge, a value of the first of them is more than sufficient to ensure stability of lenticular dusty phase void oriented across the counter-ion flow.

Analysis of pair correlation functions for macroscopic particles in dusty plasmas: Numerical simulation and experiment

Pair correlation is analyzed for systems of macroscopic particles with various isotropic interaction potentials. Under certain conditions, the behavior of the pair correlation function is determined by an effective order parameter and its decrease toward infinity follows an asymptotic power law. When the effective parameter is smaller than a certain critical value, the decay of pair correlation is much steeper. Experimental results concerning the form of the pair correlation function are presented for liquid-like dust structures localized in the near-electrode plasma sheath of a high-frequency capacitive discharge. An analysis of numerical and experimental results shows that melting dynamics in these systems are analogous to those characteristic of a topological phase transition.

Kinetic theory of dusty plasmas. V. The hydrodynamic equations

The collisional hydrodynamic equations for electrons, ions, and dust particles in dusty plasmas are derived from the kinetic equations [V. N. Tsytovich and U. de Angelis, Phys. Plasmas 6, 1093 (1999)] which consistently take into account the elastic and inelastic (charging) collisions of plasma particles with dust and the effects of dust charge fluctuations. These equations are valid in the parameter regime where the collisions of plasma particles with dust dominate with respect to the binary plasma collisions. New expressions for the fluid collision frequencies, transport coefficients, viscosity, and ion drag are found and compared with previous results.

Ground State Configurations of Two-dimensional Plasma Crystals under Long-range Attractive Particle Interaction Force

The configurational properties of two-dimensional clusters of charged dust particles in dusty plasma interacting with each other via a model potential with a short-range repulsion and a long-range attraction are investigated through the Monte Carlo simulation technique. The particles are confined by a harmonic potential. For the small number of particles, a hexagonal structure of the ground state changes into a shell configuration with increasing value of the attraction parameter α. For larger clusters, the increased attraction changes the defect locations and more particles energetically suit in the center of the cluster.

Effect of selective coagulation of the like charged particles in a dusty plasma trap

The phenomenon of selective coagulation of the like charged disperse particles in dusty plasma was theoretically predicted and experimentally revealed. The effect lies in sharp acceleration of coagulation processes after injection into a plasma trap particles which sizes appreciably exceed Debye length and the average size of the particles initially forming a dusty plasma cloud. The absorption process of the fine fraction by the larger particles takes place.

Fine particles in dusty plasmas

Dusty plasma is a four-component plasma system with fine particles suspended in a gaseous background with electrons, ions, and neutrals. The dust particles are usually negatively charged. The capability of forming fine particles in discharges opens a new window for various applications. The large mass and charges drastically alter the nature of the background plasma and generate many interesting collective behaviors. In this paper, we briefly review the recent researches on the fine particles in dusty plasmas, including the forces on the single particles, particle formation mechanisms, particle manipulation and removal, dust plasma crystals and liquids, and collective waves in dusty plasmas.

Positively charged particles in dusty plasmas.

The trapping of dust particles has been observed in a dc abnormal glow discharge dominated by electron attachment. A dust cloud of several tens of positively charged particles was found to form in the anode sheath region. An analysis of the experimental conditions revealed that these particles were positively charged due to emission process, in contrast to most other experiments on the levitation of dust particles in gas-discharge plasmas where negatively charged particles are found. An estimate of the particle charge, taking into account the processes of photoelectron and secondary electron emission from the particle surface, is in agreement with the experimental measured values.

Effect of Stochastic Grain Charge Fluctuation on the Kinetic Energy of the Particles in Dusty Plasma

Random charge fluctuations are always present in dusty plasmas due to the discrete nature of currents charging the dust particles. These fluctuations can be a reason of the heating of dust particle systems. In this paper we show by analytical evaluations and numerical simulation that charge fluctuations provide an effective source of energy and can heat the dust particles up to several eV, in conditions close to experimental ones.

Role of stochastic fluctuations in the charge on macroscopic particles in dusty plasmas

The currents which charge a macroscopic particle placed in a plasma consist of discrete charges; hence, the charge can undergo random fluctuations about its equilibrium value. These random fluctuations can be described by a simple model which, if the mechanisms for charging of macroscopic particles are known, makes it possible to determine the dependence of the temporal and amplitude characteristics of the fluctuations on the plasma parameters. This model can be used to study the effect of charge fluctuations on the dynamics of the macroscopic particles. The case of so-called plasma-dust crystals (i.e., highly ordered structures which develop because of strong interactions among macroscopic particles) in laboratory gaseous discharge plasmas is considered as an example. The molecular dynamics method shows that, under certain conditions, random fluctuations in the charge can effectively heat a system of macroscopic particles, thereby impeding the ordering process.