Tetsuo Kamimura

Generation of two-dimensional dust vortex flows in a direct current discharge plasma

The two-dimensional dust vortex flows are observed in a direct current discharge plasma near the edge of a metal plate which is situated in the dust-particle levitation region. Applying negative dc potential to the metal plate, dust particles are strongly accelerated toward the metal plate edge, and two symmetric dust vortex flows are generated on both sides of the metal plate. Numerical calculation including the effect of the ion drag force well demonstrates the dust vortex formation as in the experiment. A mechanism of the dust vortex generation could be explained by effect of an asymmetry of ion drag force near the metal plate.

Structure Controls of Fine-Particle Clouds in DC Discharge Plasmas

Publisher Summary As a series of the experiments on fine-particle clouds in plasmas, this chapter describes various kinds of experiments on structure controls of the fine-particle clouds in low-pressure dc discharge plasmas. The chapter presents a review of essential points of the results on vertical and radial profiles, phase transition, azimuthal votices and rotations, vertical spread of particle clouds, and vertical strings of periodic alignment of particles. The chapter also discusses active structure controls of the fine-particle clouds in plasmas, which are in liquid or in solid (Coulomb lattice) state, under several different dc situations.

Configurations of Coulomb clusters in plasma

The structures of Coulomb clusters formed by dust particles in a plasma are studied by numerical simulation. The present study reveals the presence of various types of self-organized structures of clusters confined in an electrostatic potential. The stable configurations depend on the number of dust particles in a cluster as well as on the form of the confining potential. One-dimensional strings, two-dimensional Coulomb lattices, and three-dimensional Coulomb crystals found in the simulation agree well with the observation in the laboratory dust plasma experiments. Elongated axisymmetric Coulomb clusters are found to be composed of a few fundamental configurations. The dynamical features of Coulomb clusters are also studied by the simulation.

Observation of Bow Structures in a Complex Plasma

A bow shock is observed in a two‐dimensional flow of charged micro particles in a complex plasma. A thin conducting wire is placed vertically against the flow to make a potential barrier as an obstacle against the flow. A void is formed around the potential barrier surrounding the wire. When the flow velocity exceeds the dust acoustic velocity, the density in front of the void increases and forms the bow shock.

Dynamics of Dust Particulates in Magnetic Field

Dynamic behavior of a cluster of charged dust particulates in a plasma in the presence of magnetic field is studied. Dust particulates confined in a harmonic potential are found to move in a circular motion, driven by the external magnetic field, with harmonic oscillations around the equilibrium orbit. The collisional effects of ions and neutral particles on dust particulates are examined.

Effect of magnetic field on the dynamics of Coulomb cluster

Summary form only given. A Coulomb cluster has been observed to levitate in the low temperature plasma device by the balance of the sheath electric and the gravitational forces acting on the cluster. Motivated by the observation of rotation of the cluster in the presence of magnetic field, we have studied the dynamics of the Coulomb cluster by a particle simulation as well by an analytical model. Our preliminary result was presented earlier. We study the effect of the magnetic field on the dynamics of the Coulomb cluster in detail. We consider a Hamiltonian.