Breakthroughs in crystal growth and conductivity control of nitride semiconductors during last two decades have led to such developments as high-brightness blue, green and white light-emitting diodes and long-lived violet laser diode and so forth. The high electron saturation velocity in GaN is also suitable for application in high-speed/high power electronic devices. All of these nitride-based devices are the most environmentally-friendly ones available. They are tough and should enable a tremendous saving in energy. Further progress in the area of crystal growth and device engineering is necessary for the development of new frontier devices based on nitride semiconductors.

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In development of tungsten microcavity illuminants and tungsten cluster illuminants, the Complex Reractive Index of tungsten at the operating temperature of 2000-6000 K is necessary to evaluate their luminous efficacy and lifetime. Little is, however, known about the complex index of tungsten in such a high temperature region.
In this study, we have determined the complex index of tungsten using an ellipsometer at room temperature. In measurement, a He-Ne laser of 633 nm and a Nd: YAG laser of 532 nm were used as the light sources. The measured complex index of tungsten was 2.0 to 3.0 in real part and 2.5 to 3.0 in imaginary part at 633 nm. Also, the corresponding components at 532 nm were 1.8 to 2.8 and 2.4 to 2.8. Repeatable accuracy was estimated about 1 % in measuring the complex index repeatedly at the same point on individual tungsten plates. It was, however, found that the measured complex index was linearly proportional to the reflectivity. This dependence is attributed to surface conditions such as oxidation and roughness on a microscopic scale.

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We have investigated on a method of preparing a large-size anisotropic polypyrrole (PPy) film using a slab vessel consisting poly(tetrafluoroethylene), (PTFE) walls as well as its actuation abilities. The PPy film can be grown along one side of the PTFE walls and exhibits a morphological anisotropy of PPy packing density along the thickness direction. A piece of it bends in a regular direction (the surface in contact with the PTFE wall) and reverts during a redox cycle without the use of any additional processes such as lamination. The actuation properties of the anisotropic PPy actuator strongly depend on the size of the cation in the driving electrolyte and the bending behavior of this actuator at room temperature becomes slower for larger cations. As a result of investigating the temperature dependence of actuation properties, the arrival time of the actuator (the time required to the tip of the actuator to touch the electrolyte surface upon stepwise potential change) becomes shorter in all electrolyte solutions with different electrolytes. This result can be understood in terms of the thermally activated microscopic movement of the PPy main chains. Such a behavior based on electrochemical stimulus not only provides information related to ionic transfer and storage but also suggests that the anisotropic PPy film can be put to practical use an electrochemical actuator for artificial muscle which directly converts electrical energy into mechanical energy.

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In a recent trend that reduction of SF₆ used for electric power equipment is required to avoid global warming, dilution of SF₆ by other gases of less environmental load is considered as a practical solution. Gas mixtures such as SF₆/N₂ and SF₆/c-C₄F₈ have a desirable feature called synergy effect that the critical values of reduced electric field (E/N)_lim are higher than the partial-pressure-weighted values obtained from (E/N)_lim of their components. In order to obtain a guide to seek for new insulating gas mixtures with the synergy effect, we have investigated the synergy mechanism from a viewpoint of collaboration between electron energy loss by collisions and electron attachment. The following mechanisms have been indicated as primary factors of the synergy effect; (i) a large attachment cross section of SF6 lying in a low electron energy region plays the main role of the electron capture; (ii) in order to feed electrons into the low energy region of (i) efficiently, a steep rise of an inelastic collision cross section at its onset energy is required. We have evaluated these factors by a Boltzmann equation analysis, and have synthesized the synergy effect using model gases for demonstration.

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The authors have proposed the resin molded type of voltage-current sensor for the real time waveform observation in power distribution systems. The sensor have been designed and implemented based on the FEM, however, it was found that the current waveform will contain the remarkable high-frequency noise experimentally. The paper describes the effect of the outer noise on the current sensor waveform theoretically and experimentally.

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The fast multipole method (FMM) is an O(N) solver of a full linear system appearing in integral equation methods, for example, surface charge simulation method (SCM) and boundary element method (BEM). An effective preconditioning technique for the FMM, which employs a nested FMM having intentionally deteriorated precision, was proposed and applied to the FMM-SCM and FMM-BEM using the Bi-CGSTAB2. In this paper, this technique called minor iterative preconditioning is applied to the FMM-SCM using the GMRES in order to solve electrostatic field calculation problems. The comparison of CPU times and convergence properties with those by some variants confirms good acceleration performance of the utilized technique.

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The influence of soot particles on treatment of diesel exhaust using barrier discharge has been experimentally investigated. A diesel fuel and air diffusion flame burner system is used for simulation of diesel exhaust gas. It produces particulate, NOx and HC emissions similar to diesel exhaust. Barrier discharge plasma reactor consists of double coaxial cylinders. Different design electrode forms have been tested, with results indicating the importance of testing devices with soot. 1500 ppmC1 of C₃H₆ were added to burner gas to increase HC concentration. NO conversion efficiency increases with increasing specific energy density in both uniform field reactor and non-uniform field reactor. In the case of non-uniform field reactor, NO conversion efficiency is low, ; current waveform of discharge varies with soot, surface discharge occurs outside reactor due to soot fouling and barrier discharge decrease to resulting in relaxation of the electric field. In the case of uniform field reactor, NO conversion efficiency is high, and the conversion improves drastically with high HC concentration. Concentration of C₃H₆ decreases with increasing specific energy density. Soot deposits on the surface of reactor and the presence of soot in gas decrease the NO conversions. Therefore, it is suggested that soot in diesel exhaust gas influenced both the occurrence of discharge and the plasma reaction as for conversion of NO to NO₂.

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The current-sheet ejection phenomenon, which causes enhancement of the magnetic reconnection rate, was investigated in the TS-3 merging experiment at University of Tokyo. The current-sheet was ejected when two coaxial torus plasmas were compressed rapidly by the external force under high intensity toroidal field (about 500 [Gauss]). The magnetic reconnection rate γ increased sharply from 0.14 [1/μsec] to 0.33 [1/μsec] right after the ejection out of the X-point region, while the reconnction rate is low in an initial pile up phase. The current-sheet was separated and ejected from the diffusion region by the Lorentz force, j_t× B_z. We made new simple current sheet model on the basis of mass conservation law, and the theoretical curve of the inflow velocity increment u accorded with the experimental one generally.

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A dielectric barrier discharge in Ar and CH4 gas mixtures used for a-C:H film deposition was investigated. The number densities of Ar(1s₂: resonant level) and Ar(1s_3,5: metastable levels) atoms were measured using a high sensitive detection method based on plasma modulation and laser absorption spectroscopy. The CH(X²Π) radical number density was measured by an actinometry method. The excitation transfer process from the Ar(1s₅) atom to the CH(A²Δ) radical was detected by a laser collisionally induced fluorescence method. The a-C:H film properties (the content of sp³ and sp² hybridization and the content of the CH₃ and CH₂ hydrocarbon groups) were correlated with the number densities of the Ar(1s₅) atom and the CH(X²Π) radical. In the a-C:H film, maximum value of the sp³/sp² was obtained, when the CH(X²Π) number density in DBD plasma was minimum.

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Magnetic reconnection accompanying ion heating and acceleration has been investigated in observation of solar flare and laboratory experiments. In order to clarify this mechanism, particularly in laboratory experiments, we simulated neutral flow driven by ion flow using energy conserved LBM (Lattice Boltzmann Method) and, for verification of the results, measured neutral speed and temperature experimentally. A significant correlation between neutral flow and neutral heating was confirmed, which is in agreement with experimental results. In addition, this result shows that neutral out-flow speed at the midplane (z=0) reached 1.9km/s, whereas the ion speed reached 2.4km/s, which indicates that even if we measure hydrogen neutral Doppler shift and its broadening, so that we can interpret neutral speed as ion speed.

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The lifetime of metastable excited atoms for barrier discharges in a glass cell and plasma display panel (PDP) has been measured by an laser induced evanescent-mode fluorescence (LIEF) and compared with values measured in a bulk plasma. No significant differece between lifetimes of metastables in the vicinity of a wall and in a bulk plasma is found. An additional optical technique using pockels effect of an electro-optic crystal is introduced in order to observe a temporal and spatial behavior of a wall voltage due to charges accumulated on a dielectric surface.

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In this paper, the authors have been studying on magnetic and electric properties of ferromagnetic substance/semimetal, Fe/Bi, system multilayered thin films prepared by ion-beam sputtering method. The multilayered thin film was prepared with 99.6%Fe and 99.99%Bi. The experimental results are summarized as follow:From the result of XRD in small degrees region (2θ=2-4 deg.), Fe/Bi system thin films at number of Fe layers, N=3,4 and 5 have been formed structure of multilayers. Coercive force H_c increased with the rising at number of Fe layers. And maximum value was 4.522kA/m at number of Fe layers, N= 6. Then, coercive force decreased and its value was constant at more than 15 layers. Resistivity, ρ, of Fe/Bi system multilayered thin films was changed from conductivity to semiconductivity at temperatures range of T=380˜400K. Magneto-resistance (MR) ratio was decreased with increasing applied field H when current is parallel to an applied magnetic field (I//H ). MR ratio was maximum value of 0.154% at number of Fe layers, N=4, at room temperature.

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Lanthanum chromite (LaCrO₃) has excellent chemical stability at high temperature. LaCrO₃ doped with alkaline earth metals has high electric conductivity as a heater material having operating temperatures starting from room temperature. The purpose of this study is to fabricate heaters using thin films of LaCrO₃ doped with dopant (Ca,Sr), which is deposited on silicon and alumina substrates by RF magnetron sputtering and evaluate their characteristics. Thin films of Sr doped LaCrO₃ deposited on alumina substrate orient in the (220) or (004) direction contrary to Ca doped LaCrO₃. The resistance of thin films of LaCrO₃ decreases with increasing content of Ca or Sr. At the same Ca or Sr mixing ratio, the resistance of Ca doped thin LaCrO₃ films is smaller than that of Sr doped LaCrO₃. Degradation of heating characteristics due to the dc current drive may be mainly evaporation of component such as Cr2O3 from the junction of thin film and cathode electrode. On the other hand, with heating by ac current drive, the degree of the degradation is much smaller. Thin film heaters exhibit uniform heating characteristic. A maximum heating temperature over 1300°C is achieved.

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The effects of Si addition on the electrical degradation of the ZnO varistors were investigated by voltage-current (V-I ), capacitance-voltage (C-V ) methods, and Isothermal Capacitance Transient Spectroscopy (ICTS). The nonlinearity index α for the Bi-Mn-Si-added ZnO varistors didn’t show the remarkable change but that for the Bi-Co-Si-added ZnO varistors decreased by Si addition. Values of α after electrical degradation showed the local maximum at approximately 700molppm for Bi-Mn-added ZnO varistors and at approximately 500molppm for Bi-Co-added ZnO varistors. It is found that the electrical degradation can be hindered at these optimum Si contents. E_C-E_T showed the local maximum at the optimum Si content similar to α for the Bi-Mn-Al-added ZnO varistors but those for Bi-Co-Si-added ZnO varistors showed the local minimum at the optimum Si content contrary to α for Bi-Co-Al-added ZnO varistors. The density N_is of the interface trap levels obtained by C-V characteristics and ICTS for both kinds of ZnO varistor showed the local minimum at the optimum Si content similar to Al added Bi-Mn-added and Bi-Co-added ZnO varistors.

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This report deals with the experimental results of synchronized generation of creeping streamers. Two parallel spherical electrodes are placed on a insulator plate. A shading plate or a optical filter is located at the middle point of the electrodes. Lightning impulse voltage is applied to the electrodes. Applied voltage, current to the ground and surface dust figures on the insulator are recorded. This observation is repeated up to a hundred times and synchronization probabilities of two streamers started from several electrode are obtained. Without the shading plate or the optical filter between electrodes, two streamers are mostly synchronized. However, the shading plate is located, the probability decreases remarkably. The probability rapid increases again when the insulator is irradiated by ultraviolet light. In the case of the optical filters are used, the probabilities can be observed as a function of wavelength of discharge light. The probabilities are almost 100% with high-pass filter of 115 nm cutoff. This high probability is maintained until cutoff wavelength reaches 250 nm. After that, the probability sharply declines. The synchronization is induced by ultraviolet light from first streamers. Because the ultraviolet light irradiates the insulator and photoelectrons are generated as initial electrons, second streamers start from another electrode. Required energy for the synchronization is above 5eV that corresponding to wavelength of 250 nm. Not only UV region, but also the light of VUV region is effective for the synchronization.

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In this paper, protection resistance was measured as a parameter for the 3D shape of the dendrite, which was produced on the copper, printed wired board by the WDT method. The measurement was occurred using the 3D shape measurement system. We measured the 3D shape of a dendrite in a nonuniform electric field with a changing polarity. Moreover, the polar effect of ion-migration was examined by the 3D shape electric field analysis using ANSYS. Consequently, the height of the accumulation things at anode was higher than the negative pole side under round shaped cathode condition. Similarly, the quantity of the accumulation thing is also found larger at anode. On the other hand, the dispersal of the accumulation thing is observed between the anode and the negative pole under a round shaped anode conditions. And it turns out that there is also smaller accumulation thing at the tip part of a round shaped electrode. Moreover, for a same protection resistance, the amounts of generating of the accumulation objects per unit electric charge were larger for round shaped anode conditions comparing to the cathode. It is seen from 3d shape electric field analysis, that horizontal part of the electric field vector at anode is greater than the cathode. At the same time, the field intensity at anode is also larger than cathode. For a round shaped anode in 3D shape electric field analysis, the strongest electric field vector was found between a round shape electrode tip part and flat electrode. Although in the round shape cathode, the electric field vector had become the strongest between the flat electrode and the round shape electrode tip part. The electric field intensity of a nearby flat electrode was strong for a round shape electrode facing the field. Since the action states of the accumulation thing after a short circuit is different depending on the polarity of electrode for a nonuniform electric field conditions, it appears that it will not take much time to occur a failure

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The co-helicity merging operations of compact toroid(CT) and spherical tokamak(ST) have been performed with external toroidal field in the CT/ST merging device TS-4. The low-q(safety factor) CT mergings as the compact RFP merging and the spheromak merging show the flux conversion from toroidal to poloidal in the course of the reconstruction of the Taylor force free state. The relaxation to the Taylor state proceeds through the following three states; (1)axisymmetric merging with increasing toroidal flux, (2)increase in the poloidal flux Ψ and, (3)relaxation to the Taylor state. The high-q ST merging shows different relaxation process from those of the compact RFP and the spheromak mergings. Increases in Ψ were not clearly observed in the ST merging. The measured eigen values λ show that ST’s, especially high-q ST’s, approach a unique intrinsic equilibrium state that has a λ proportional to Ψ with a longer lifetime than that of CT’s. When external toroidal field is set in a certain range between the low-q operation and the high-q operation for ST’s, an abnormal phenomenon was found in the ST formation, namely, a drastic decrease in the plasma lifetime. This phenomenon is characterized by very week poloidal flux generations during the initial plasma production phase and the subsequent plasma separation phase when the plasma starts detaching from the flux-core.

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An ion Doppler spectrometer (IDS) using a compact 16 channel photomultiplier tube (PMT) has been developed and used to measure ion temperature and toroidal rotation speed on SSPX gun-spheromaks. Doppler broadening of OV spectral line shows higher ion temperature (-500 eV) as compared to the electron temperature, which indicates anomalous ion heating due to MHD relaxation. It has been also found that the plasma rotates with a speed of 60 km/s in the direction of E×B.

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