Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

Particle-in-Cell Charged Particle Simulations, plus Monte Carlo Collisions with Neutral Atoms, PIC-MCC

Complex (dusty) plasmas: current status, open issues, perspectives

1 The Equations of Gas Dynamics 2 Magnetoplasma Dynamics 3 Waves in Magnetoplasmas 4 Magnetoplasma Stability 5 Transport in Magnetoplasmas 6 Extensions of Theory Bibliography Index

Physics of plasmas

Complex (dusty) plasmas are composed of a weakly ionized gas and charged microparticles and represent the plasma state of soft matter. Complex plasmas have several remarkable features: Dynamical time scales associated with microparticles are ``stretched'' to tens of milliseconds, yet the microparticles themselves can be easily visualized individually. Furthermore, since the background gas is dilute, the particle dynamics in strongly coupled complex plasmas is virtually undamped, which provides a direct analogy to regular liquids and solids in terms of the atomistic dynamics. Finally, complex plasmas can be easily manipulated in different ways---also at the level of individual particles. Altogether, this gives us a unique opportunity to go beyond the limits of continuous media and study---at the kinetic level---various generic processes occurring in liquids or solids, in regimes ranging from the onset of cooperative phenomena to large strongly coupled systems. In the first part of the review some of the basic and new physics are highlighted which complex plasmas enable us to study, and in the second (major) part strong coupling phenomena in an interdisciplinary context are examined. The connections with complex fluids are emphasized and a number of generic liquid and solid-state issues are addressed. In summary, application oriented research is discussed.

Complex plasmas: An interdisciplinary research field

Dusty plasmas are ubiquitous in low-temperature laboratory discharges as well as in the near-earth environment, planetary rings, and interstellar spaces. In this paper, updated knowledge of fundamentals of collective dust-plasma interactions and several novel phenomena are presented that have been observed in laboratories and in space dusty plasmas. Mechanisms that are responsible for the charging of dust grains are discussed, and the fact that the dust charge perturbation is a new dynamical variable in a dusty plasma. The underlying physics of different forces that act on a charged dust grain is reviewed. In dusty plasmas, there are new attractive forces (e.g., due to wakefield and ion focusing effects and dipole-dipole interactions between unevenly charged dust rods). Furthermore, in the presence of an ensemble of charged dust grains, there are collective dust-plasma interactions featuring new waves (e.g., the dust acoustic wave, the dust ion-acoustic wave, the dust lattice wave, etc.), new instabilities, and coherent nonlinear structures (dust acoustic and dust ion-acoustic shocks, dust voids, and dust vortices), which are also discussed. Theoretical models for numerous collective dust-plasma interactions are compared with existing observations from laboratories and space environments.

Colloquium : Fundamentals of dust-plasma interactions

A method has been developed to heat and control temperature in a two-dimensional monolayer dusty plasma. A monolayer of highly charged polymer microspheres was suspended in a plasma sheath. The microspheres interacted with a Yukawa potential and formed a triangular lattice. Laser manipulation was used to apply random kicks to the particles. Two focused laser beams were moved rapidly around drawing Lissajous figures in the monolayer. The kinetic temperature of the particles increased with the laser power applied, and above a threshold a melting transition was observed. Characteristics of a thermal equilibrium of the laser-heated dusty plasma in solid and liquid states are discussed.

/pdf/laser-method-of-heating-monolayer-dusty-plasmas-33wentifos.pdf

Laser method of heating monolayer dusty plasmas

Experiments on the excitation of vertical particle resonances by laser radiation pressure are presented. The vertical resonance is used for the measurement of the charge on particles forming plasma crystals. The laser excitation technique allows us to excite the vertical resonance of a single particle in the plasma trap, whereas in earlier experiments the entire plasma crystal was excited to vertical oscillations. From the close agreement of both resonance techniques the earlier values of the dust charge are reconfirmed.

Measuring the charge on single particles by laser-excited resonances in plasma crystals

Mach cones composed of shear waves were observed experimentally in a two-dimensional screened-Coulomb crystal. Highly charged microspheres suspended in a plasma and interacting with a repulsive Yukawa potential arranged themselves in a triangular lattice with hexagonal symmetry. Mach cones were excited by applying a force from the radiation pressure of a moving laser beam. They had a single-cone structure, which is explained by the almost dispersionless character of shear waves. The cone's opening angle obeyed the Mach-cone-angle relation. Results are compared to a molecular-dynamics simulation.

http://dusty.physics.uiowa.edu/%7Egoree/papers/Nosenko_2002_PRL_Shear_Mach_Cones.pdf

Observation of shear-wave Mach cones in a 2D dusty-plasma crystal.

Self-excited dust-density waves are experimentally studied in a dusty plasma under microgravity. Two types of waves are observed: a mode inside the dust volume propagating in the direction of the ion flow and a new mode propagating obliquely at the boundary between the dusty plasma and the space-charge sheath. A model for dust-density waves propagating at an arbitrary angle with respect to the ion-flow direction is presented, which explains the preference for oblique or parallel modes as a function of ion velocity.

Obliquely propagating dust-density plasma waves in the presence of an ion beam.

Experiments are carried out to investigate the rotation of dust clusters in a radio-frequency plasma sheath with a vertical magnetic field. Our observations are in disagreement with the standard model, in which it was assumed that the neutral gas is at rest and that a steady rotation is attained when the ion-drag force is balanced by neutral friction. Here, we re-examine this basic assumption by carefully designed experiments. Our results suggest that the neutral gas is set into rotation by E×B induced ion flow through ion-neutral collisions and that the dust particles are advected by this flow. A hydrodynamic model is proposed to describe the rotation of the neutral gas and it can explain our observations.

Alexander Piel

Papers

Laser method of heating monolayer dusty plasmas

Measuring the charge on single particles by laser-excited resonances in plasma crystals

Observation of shear-wave Mach cones in a 2D dusty-plasma crystal.

Obliquely propagating dust-density plasma waves in the presence of an ion beam.

Effect of neutral gas motion on the rotation of dust clusters in an axial magnetic field