The stability criterion for the localized interchange mode is reexamined on the basis of the magnetohydrodynamics with double adiabatic laws. In plasma with double adiabaticity, the localized interchange mode is stabilized significantly due to coupling with the sound mode. This stabilization effect may explain the observed stability of LHD plasma beyond the predicted stability boundary.

抄録全体を表示

A mixed carbon and hydrogen beam was irradiated on to tungsten materials. In the case in which the carbon concentration and sample temperature were 0.95% and 653 K, respectively, large numbers and blisters of various sizes were formed. But in a low carbon concentration or high temperature case, no significant blisters were formed. It was found that carbon impurities in the beam play an important role in blister formation.

抄録全体を表示

Maximum-J (J is the second adiabatic invariant) capability, i.e., drift reversai capability, is examined in a quasi-poloidally symmetric steliarator as a possible mechanism for turbulent transport suppression. The radial variation of the uniform magnetic field component plays a crucial role for the drift reversal in a quasi-poloidally symmetric configuration.

抄録全体を表示

Fundamental processes of dust particles in low-temperature laboratory plasmas are summarized, particularly focusing on charging dynamics, in which the importance of electron energy distribution function is stressed. A delayed charging from local equilibrium charge may provide the energy to dust particles due to electrostatic field in the sheath, which may be the origin of spontaneously excited vertical oscillation.The dispersion relation for vertically polarized dust lattice wave is formulated, taking such a charging dynamics into account. Such dust waves excited externally as well as spontaneously are demonstrated experimentally. Recent observations show a great amount of dust near the divertor region in magnetic fusion devices. Role of dust in fusion devices are discussed in terms of tritium retention and safety. Some mechanisms for dust formation in fusion environment are suggested.

抄録全体を表示

Plasma wave propagation and particle wave motions in complex “dusty” plasmas are considered.The presence of dust affects plasma waves, in particular, by introducing a specific damping associated with the dust charging; on the other hand, plasma collective processes influence the arrangements and vibrations of colloidal “dust” particles in the dust clouds including Coulomb lattice structures.

抄録全体を表示

The three dimensional structure of the wake potential due to ion cyclotron waves in a dusty magnetized plasma with streaming ions is reviwed. We focused our attention to the situation when the test dust particulate is stationary, because it corresponds to the real laboratory experiment on plasma crystal. The role of the external magnetic field on the periodic attractive forces is clarified. Here, we consider the externally applied uniform magnetic field parallel to the sheath plane in Case A, and perpendicular to the sheath plane in Case B, separately. In Case A, the analysis includes the E × B drift effect in addition to the ions flow with a constant velocity u_i0 perpendicular to the magnetic field. In case B, the ions flow with a constant velocity u_i0 is parallel to the magnetic field.

抄録全体を表示

We review thermodynamical and dynamical properties of strongly coupled dusty plasmas, focusing on the recent development of molecular dynamics (MD) simulations. In the present paper, dusty plasmas are modeled by the Yukawa system, which is a collection of particles interacting through Yukawa (i.e., screened Coulomb) potentials. The phase diagram, wave dispersion relations and some transport coefficients of Yukawa systems are discussed.

抄録全体を表示

Formation and growth process of carbon fine particles in plasmas attract interests of researchers in the field not only of basic science but also of applied science. Since carbon has many bonding states, materials containing carbon could be formed in a variety of structures. Mechanism of the formation of the interstellar dusts and fine particles produced experimentally on earth is not well understood. This paper reports our experimental results on the formation of carbon fine particles in various laboratory conditions. Our results may suggest a mechanism of the formation of the interstellar dusts.

抄録全体を表示

Ionized gases contaminated with small particulates ranging in size from nanometers to micrometers (loosely referred to as dusty plasmas) appear in a wide variety of space environments. These include planetary and cometary magnetospheres, the heliosphere, supernova shells and a variety of interstellar regions. The interaction between the dust and the plasma leads to a variety of novel physical and dynamical processes. The systematic study of these processes, which was stimulated by the spacecraft observations of novel dust phenomena in Saturn's rings in the early eighties, is presently in an intensive phase, supported by theory, simulation, and dedicated laboratory experiments. The following is an overview of this area. While it is brief by necessity, it is hoped that it conveys to the reader both the scope and the vitality of field.

抄録全体を表示

Electron motions in laser fields are analyzed in cases when the laser field is non-relativistic and when it is relativistic. The typical eight-figure motion of an electron is obtained in weak laser field plane-polarized, while no such figure motion in circular-polarized case. Starting from the Lagrangian for an electron in a plane-polarized electromagnetic wave, constants of motions and the electron orbits are analytically obtained. It is demonstrated that the electron drifts with a constant velocity in the direction of wave propagation, and that the eight-figure motion is seen in the frame moving with the drift motion. In the case of the circular-polarize wave, the electron orbit is a spiral having the drift velocity same as does the plane-polarization.

抄録全体を表示

Validation studies of a neutrally balanced vertical plasma position, so-called ”neutral point”, have been carried out by computational simulations and experiments under trilateral Japan-US-EU collaborations. It was clarified that the neutral point, where VDEs (Vertical Displacement Events) are hardly occurred, does exit in the Alcator C-Mod and ASDEX-Upgrade tokamaks as well as the JT-60U, consistent with the simulations. Meanwhile, precise details of the VDE behavior exhibit their own characters according to the individual ofthe tokamaks such as an up-down asymmetry of plasma shape. Sensitivity of the neutral point to the plasma shape and current profile was also addressed in detail.

抄録全体を表示