Surface waves are studied in axially non-uniform cylindrical cold plasma with a linear density profile. The real frequency, damping rate, and eigenfunction for the transverse magnetic mode in pure surface waves are obtained for collisional plasmas, where the plasma resonance is taken into account. It is shown that the eigenfunction peaks at the position of the plasma resonance layer.

抄録全体を表示

A new RFP device with a very small aspect ratio (A = 2.1) is designed and constructed. The aspect ratio of A = 2.1 is much smaller than those of existing devices (A > 3). At this small A, no rational magnetic surface appears from the axis to ψ = 0.4 in the normalized flux surface coordinate, which may reduce the chaotic properties of the plasma in the core region. The proposed examination of bootstrap current generation could also be done. For this new device, a compact and high voltage center coil and an aluminum vacuum vessel (R/r_w = 0.53 m/0.25 m) are developed. The maximum plasma current is designed to attain 100 kA. The construction of the device has been completed successfully. In the initial series of discharges, a stable region with a very high Θ value up to ˜2.5 is newly found.

抄録全体を表示

The dependence of the lasing condition of fast capillary discharge plasmas on the initial plasma parameters has been experimentally investigated. The results show that there is an optimum initial condition for lasings. The experimental results also indicate that the variation of lasing power can be correlated with the electron density of the initial plasmas and that the initial condition is an important factor for obtaining larger laser energy using capillary discharges.

抄録全体を表示

Because of the three-dimensional magnetic configuration behaviors of trapped particles in a helical ripple are complicated and the confinement of energetic particles is one of the important issues in helical systems. This article presents recent advances in theoretical research on the energetic particle confinement of helical systems. The characteristics of energetic particle orbits and loss processes are briefly explained. The recent results of configuration studies of energetic particle confinement in quasi-symmetric systems, quasi-isodynamic systems, and heliotrons are reviewed. Finally, research topics in the energetic particle confinement of helical systems are discussed.

抄録全体を表示

Grid computing is a technology which allows uniform and transparent access to geographically dispersed computational resources, such as computers, databases, experimental and observational equipment etc. via high-speed, high-bandwidth networking. The commonly used analogy is that of electrical power grid, whereby the household electricity is made available from outlets on the wall, and little thought need to be given to where the electricity is generated and how it is transmitted. The usage of grid also includes distributed parallel computing, high throughput computing, data intensive computing (data grid) and collaborative computing. This paper reviews the historical background, software structure, current status and on-going grid projects, including applications of grid technology to nuclear fusion research.

抄録全体を表示

The structures of rotational and vibrational energy levels and the term symbols to classify different electronic states are described for diatomic molecules. Different classes of parity, (+/−), (e/f) and (s/a), associated with each rovibronic level are discussed. The transition probability, the Franck-Condon factors, the Hönl-London factors and the transition moments of electronic transitions and their selection rules are described.

抄録全体を表示

Applications of the hydrogen molecular spectroscopy in the visible region to fusion edge/divertor plasmas are reviewed. Molecular hydrogen in low temperature plasma, not only as a fuelling gas but also as recycling or buffer gas in gas-target divertor, plays important roles in determining the particle source and recombination phenomena. Moreover the molecular hydrogen modifies the spectral intensity and profile of the hydrogen Balmer series. Since their quantitative contributions depends much on the vibrational distribution in the ground electronic state, molecular spectroscopy for Fulcher band emissions combined with some proper excitation-emission models has been developed. Principle, spectroscopic system, method for the analysis and some results are shown. Other possibility of the Fulcher band spectroscopy is briefly mentioned.

抄録全体を表示

Fundamental plasma processes of negative ions in a low pressure region (a gas pressure P_g < 1.5 Pa) have been studied using the photodetachment technique and vacuum ultraviolet (VUV) spectroscopic measurements in the spectral range from 100 to 180 nm. Understanding the behavior of a plasma with negative ions, in particular, the correlation between H^- density and vibrationally excited H₂ density, is of great interest in the field of atomic-molecular physics and ion source developments. The volume and the surface effects of negative ions are discussed taking into account the e-V, the E-V, and the RD processes, and the measured VUV spectrum is compared with the synthetic one. The cascade transition to the B¹Σ⁺_u state by the electron excitation contributes to the production of the highly vibrationally excited levels of the X¹Σ⁺_g ground electronic state.

抄録全体を表示

Spectroscopic measurements of interstellar molecules are described. Since 1963 interstellar molecules have been discovered primarily by means of radio astronomical measurements, and some molecules have been detected in the infrared, optical, and ultraviolet regions. More than 120 species were detected including simple hydride, complex organic molecules, ring molecules, molecular ions, and radicals. Because of high frequency resolution fine- and hyperfine structure lines are easily observed by radio astronomical measurements, which are sometimes difficult to be resolved in ground-based laboratory measurements. Measured molecular spectra provide us with not only the precise motions of molecular clouds but excitation temperatures and molecular abundances as well. The Atacama Large Millimeter- and submillimeter Array (ALMA) is under construction in Chile through international collaboration of Japan, the US and the EU, and will soon unveil various mysteries of the universe.

抄録全体を表示

Optical diagnostics are between the most commonly used tools for the characterization of plasmas and for the better understanding of physical and chemical processes controlling their time and space dependencies. In this review paper the most popular spectroscopy techniques are described and examples of their applications to plasmas are indicated. An special emphasis is given to power saturation phenomena, encountered in laser based diagnostics. Numerical applications show that with commonly available lasers a great care must be taken to avoid saturation and to be really non-intrusive, as expected for a diagnostic tool.

抄録全体を表示

Laser spectroscopic study of particles produced by laser ablation can reveal fundamental processes of laser ablation plasmas. The investigation of molecular species that have internal degrees of freedom including rotation and vibration will provide much more detailed information regarding the process and energy dispersion of plasmas. In this article, molecular spectroscopic techniques applied to laser ablation plasma, in particular laser-induced fluorescence and optical emission spectroscopy, are reviewed. Rotational, vibrational, and transtational temperatures of diatomic molecules in laser ablation plasma are discussed.

抄録全体を表示

Anomalies in the Fulcher-band (d³Π_u-a³Σ⁺_g) spectra, which are widely used for the purpose of measuring ro-vibronic structure of the hydrogen molecule, are investigated using the hollow cathode glow discharge of 230V - 70 mA at 30 Pa. By making use of the recently developed analyzing scheme and experimentally determined lifetime of the state involved, the historical data in the Ginsburg and Dieke's publication are reanalyzed and compared with our present data. Populations of the vibronic state (v'≥4 in the Q branch can be corrected to a considerable extent by taking into account the lifetime of the states, while those of any v' the P and R branches cannot. However, the average values of the upper-Fulcher populations deduced from the P and R branches coincide with those from Q branch by taking into consideration the difference in the excitation from the ground electronic state.

抄録全体を表示