Strongly coupled dusty plasmas: Finite and extended systems (original) (raw)

Dynamical states in two-dimensional charged dust particle clusters in plasma medium

Physical Review E

The formation of dynamical states for a collection of dust particles in two dimensions is shown using molecular dynamics simulations. The charged dust particles interact with each other with a Yukawa pair potential mimicking the screening due to plasma. An external radial confining force has also been applied to the dust particles to keep them radially confined. When the particle number is low (say, a few), they get arranged on the radial locations corresponding to multiple rings or shells. For specific numbers, such an arrangement of particles is stationary. However, for several cases, the cluster of dust particles relaxes to a state for which the dust particles on rings display intershell rotation. For a larger number of dust particles (a few hundred, for instance), an equilibrium state with a coherent rigid body displaying angular oscillation of the entire cluster is observed. A detailed characterization of the formation of these states in terms of particle number, coupling parameter, etc., is provided.

Phase transition of three-dimensional finite-sized charged dust clusters in a plasma environment

Physical Review E

The dynamics of a harmonically trapped three-dimensional Yukawa ball of charged dust particles immersed in plasma is investigated as function of external magnetic field and Coulomb coupling parameter using molecular dynamics simulation. It is shown that the harmonically trapped dust particles organize themselves into nested spherical shells. The particles start rotating in a coherent order as the magnetic field reaches a critical value corresponding to the coupling parameter of the system of dust particles. The magnetically controlled charged dust cluster of finite size undergoes a first-order phase transition from disordered to ordered phase. At sufficiently high coupling and strong magnetic field, the vibrational mode of this finite-sized charged dust cluster freezes, and the system retains only rotational motion.

Dynamical states in 2-D for charged dust particle clusters in plasma medium

arXiv: Plasma Physics, 2020

The formation of novel dynamical states for a collection of dust particles in two dimensions (2-D) has been shown with the help of Molecular Dynamics (MD) simulation. The charged dust particles interact with each other with Yukawa pair potential mimicking the screening due to plasma. Additionally, an external radial confining force has also been applied to the dust particles to keep them radially confined. When the particle number is low ( say a few), they get arranged on the radial location corresponding to multiple rings/shells. For specific numbers, such an arrangement of particles is stationary. However, for several cases, the cluster of dust particles relaxes to a state for which the dust particles on rings display inter-shell rotation. For a larger number of dust particles ( a few hundred for instance ) a novel equilibrium state with coherent rigid body displaying angular oscillation of the entire cluster is observed. A detailed characterization of the formation of these state...

Dynamic behaviors of dust particles in the plasma–sheath boundary

Physics of Plasmas, 2001

A variety of dynamic behaviors in dusty plasmas is expected under the experimental condition of weak friction with gas molecules. The device ''KAGEROU'' provides such an environment for dynamic collective phenomena. Self-excited dust oscillations in Coulomb crystals have been observed at low values of plasma density and gas pressure. An instability mechanism was identified to be delayed charging in an inhomogeneous equilibrium dust charge in the sheath. The theoretical growth rate was formulated in relation to the destabilization of a transverse dust lattice wave ͑T-DLW͒, which was found to be very sensitive to the presence of a small amount of hot electrons which produces a substantial positive equilibrium charge gradient ٌQ d-eq around the equilibrium position of dust particles in the plasma-sheath boundary. The first experimental observation of a correlated self-excited vertical oscillations in a one-dimensional dust chain indicates a destabilization of T-DLW. The experimental condition is very consistent with the parameter area which predicts numerically an instability of T-DLW.

Confinement of dust particles in a double layer

Physics of Plasmas, 1995

Negatively charged, micron-sized dust grains have been electrostatically confined in the high-potential region of an anode double layer formed in a single-ended Q-machine plasma. The levitated dust grains are large enough to be visually observed in the scattered light from the plasma source. The various forces on a dust grain in a plasma, i.e., gravitational, electric, ion drag, and neutral drag are estimated based on the measured plasma and dust parameters. The possibility of observing a Coulomb lattice in such a setup is discussed.

Confinement and structure of electrostatically coupled dust clouds in a direct current plasma–sheath

Physics of Plasmas, 1998

Mechanisms for the confinement and the internal structure of an electrostatically coupled dust cloud formed in a dc glow discharge have been investigated from a comparative viewpoint between experimental observations and a simple model. Two kinds of dust clouds with different internal structures are clearly observed, depending on the dispersion of the size distribution of dust particles. The dust cloud can be trapped only in the plasma–sheath boundary area, corresponding to the potential minimum region determined by gravitational and electrostatic forces in the cathode sheath. No dust particles were found deep inside of the sheath, which is consistent with the analysis because the dust particles may be charged positively due to an extreme reduction of the electron density. The internal structure of the electrostatically coupled dust cloud was found to be arranged so that the total potential energy, including the repulsive Coulomb interaction among negative dust particles, may become...

Numerical Description of Dust Particles in Plasma Sheath

Intr oduction The interface between plasma and its surrounding surfaces (walls, electrodes, substrates) is formed by a self-organizing structure, called the plasma-sheath. To gain additional insight, micro-sized particles can be used as electrostatic probes. Due to charge carrier fluxes these particles acquire a negative surface charge, allowing for trapping them within the plasma sheath. The particles attain an equilibrium position, where the sum of all acting forces vanishes. In our case, the system is dominated by gravitational force, electrostatic force and ion drag, while neutral drag, thermophoresis and photophoresis are of minor importance. The approach of suitable electrostatic particle probes has been successfully demonstrated in front of the powered electrode of a capacitively coupled rf discharge [1]. In the present work we focus on the behaviour of micro-particles of different sizes in front of a grounded or additional biased adaptive electrode, which is not the powered ...

Properties of two-dimensional dusty plasma clusters

Physics Letters A, 1999

Two-dimensional classical cluster of particles interacting through a screened Coulomb potential is studied. This system can be used as a model for "dusty particles" in high-frequency discharge plasma. For systems consisting of N = 2 − 40 particles and confined by a harmonic potential we find ground-state configurations, eigenfrequencies and eigenvectors for the normal modes as a function of the Debye screening length RD in plasma. Variations in RD cause changes in the ground-state structure of clusters, each structural rearrangement can be considered as a phase transition of first or second order (with respect to parameter RD). Monte Carlo and molecular dynamics are used to study in detail the melting of the clusters as the temperature is increased. By varying the density and the temperature of plasma, to which the particles are immersed, one can modulate thermodynamical properties of the system, transforming it in a controllable way to an ordered (crystal-like), orientationaly disordered or totally disordered (liquid-like) states. The possibility of dynamical coexistence phenomena in small clusters is discussed.

Formation of plasma dust structures at atmospheric pressure

Journal of Experimental and Theoretical Physics, 2006

The formation of strongly coupled stable dust structures in the plasma produced by an electron beam at atmospheric pressure was detected experimentally. Analytical expressions were derived for the ionization rate of a gas by an electron beam in an axially symmetric geometry by comparing experimental data with Monte Carlo calculations. Self-consistent one-dimensional simulations of the beam plasma were performed in the diffusion drift approximation of charged plasma particle transport with electron diffusion to determine the dust particle levitation conditions. Since almost all of the applied voltage drops on the cathode layer in the Thomson glow regime of a non-self-sustained gas discharge, a distribution of the electric field that grows toward the cathode is produced in it; this field together with the gravity produces a potential well in which the dust particles levitate to form a stable disk-shaped structure. The nonideality parameters of the dust component in the formation region of a highly ordered quasi-crystalline structure calculated using computational data for the dust particle charging problem were found to be higher than the critical value after exceeding which an ensemble of particles with a Yukawa interaction should pass to the crystalline state.

Dusty Plasmas: Elementary Processes, Examples and Possible Applications

This work presents an up-to-date account in dusty plasmas, a new field of current research's interest in applied physics and modern technology. These are complex systems containing nanometer or micrometer-sized particles suspended in plasma. Dust particles may be charged and the plasma and particles behave as plasma, following electromagnetic laws for particle up to about 10 nm or 100 nm if large charges are present. Dusty plasmas are interesting because presence of particles significantly alters the charged particle equilibrium leading to different phenomena. Electrostatic coupling between the grains can vary over a wide range so that the states of the dusty plasma can change from weakly coupled to crystalline. Such plasmas are of interest as a non-Hamiltonian system of interacting particles and as a means to study charging of dust particles in plasmas, electrostatic potential around a dust particle main forces acting on dust particles in plasmas, interaction between dust particles in plasmas, formation and growth of dust particles.