It is well recongnized that there is an optimal separation between two parallel plates of hollow-cathode in order to establish a hollow cathode discharge (H. C. D). However, when inter-electrode separation is reduced well below the optimal separation, we have first observed that the merged negative glows of the hollow-cathode are pushed outward from the inter-electrode space and the maintaining voltage is increased.
Purposes of this research are to observe the existing separation of the discharge with respect to the operating pressure and to postulate a model to explain the sustaining mechanism of this discharge.
Expeiments are carried out in a Pyrex-glass discharge tube of 76mm (o. d.), which has a cathode consisted of two parallel discs of Al and a ring-shaped anode. Varying the operating pressure from 1 to 10 Torr of gas (Ar, Ne or N₂), we have observed the existing separation of this discharge as a function of the pressure. The second experiment, the radial distribution of the discharge current, has been carried out using the segmented disc-cathode. From the observation it is seen that the outmost segment draws all of the discharge current, which suggests that electrons emitted from outmost segment are accelerated toward the merged negative glow and finally to the anode. In order to sustain the discharge, there must be sufficient number of ionizations within the cathode fall region. Therefore, in order to fulfill the requirement the cathode fall is formed obliquely and electrons are accelerated obliquely so that electrons will travel longer path.

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An investigation is made for the lasing characteristics and discharge phenomena of a pulsed nanosecond discharge plasma in an 80 mm-bore copper vapor laser (CVL).
Lasing characteristics are obtained by varying one of the lasing conditions of the test pulse (single shot pulse) waveform, the interpulse duration and the gas temperature keeping the tube temperature and hence the copper vapor density constant. It is found that the laser output power increases proportionally to the voltage across the plasma in the CVL discharge tube and that the plasma voltage or the recovery of plasma resistance during the interpulse duration is more important for the increase of laser output power than the population density of the metastable lower laser level.

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In some applications of wave like laser or micro wave, it is necessary to reshape the beam intensity profile. For example, a rectangular and uniform intensity laser beam is very suitable for the laser photo chemistry. In this paper, we propose a beam-forming system which consists of deformable reflectors whose surfaces are specially deformed like deformable mirrors. We simulate the beam forming property using the Fresnel equation which is solved by Fourier transformation. A Gaussian beam is transformed to a rectangular uniform beam. The surface profile of the phase distortion compensation reflector is also calculated and it is simple enough to be compensated by a reflector with simple surface profile.

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Several characteristic features of large-area RF plasmas produced by an even surface wave travelling between two large-area dielectric plates are isclosed theoretically under a diffusion-controlled gas-discharge regime. In this theory, two first-order approximations with respect to an electron-neutral collision frequency for momentum transfer and the wave attenuation are employed to clarify the electrostatic surface wave. The characteristics disclosed are: (1) The produced plasma density is expressed with a simple specific function. (2) The axial gradient of the plasma density is much less than that in the case of standard cylinder tubes.(3) The propagation properties for the surface wave, such as RF power flow, wave attenuation and electric fields, are also clarified. Utilizability of the RF plasmas is discussed for industrial use such as material processing by plasmas.

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The authors have been developing extruded polymer insulated superconducting cables. Dielectric loss in the electrical insulation cannot be ignored in superconducting cables since conductor loss of the cables is considerably small. Studies so far made it clear that ethylene-propylene rubber (EPR) is suitable for an electrical insulating material of the extruded polymer insulated superconducting cable designed by authors owing to its excellent mechanical and relatively good electrical performances at cryogenic temperature. EPR widely used includes some kinds of additives, but their effect on tanδ of EPR at cryogenic temperature remains unknown.
In this paper, the effect of additives such as crosslinking agent and fillers on tanδ of EPR was examined at temperatures between 4.2K and 300K. Thickness dependence of tanδ was also measured by using EPR films of different thickness and an extruded EPR cable sample. The results show that additives increase tanδ of relatively thin films of EPR even in cryogenic temperature region, whereas they do not give intolerable dielectric loss in comparison with conductor loss and heat inflow of the superconducting cable. The remedy to tan δ increase due to the polymer contraction relative to shielding wires has been established.

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The MIM structures in the present investigation have the characteristics of the current source caused by diffusion of the carriers in LB heterofilms. The voltage generated in the MIM structures of LB heterofilms is analyzed by the diffusion. A relation between the voltage drop in the resistance in the outer circuit of the MIM and the value of the resistance is obtained by analysis based on diffusion of carriers. The relation mentioned above is satisfied with the experimental results.

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The newly developed flashover voltage test methods are proposed in this paper. These methods estimate the mean value of the distribution efficiently and stably by using breakdown and non-breakdown responses when the flashover voltages follow a normal distribution with known coefficient of variation. Electrical engineers have long been using the up-and-down method developed by Dixon & Mood to assess the flashover voltage distribution when both the mean and the standard deviation are unknown. However, the method is numerically unstable in obtaining the mean value when the sample size is extremely small, e. g. 5 to 10. The proposed methods, "the mean-shooting method" and "the modified up-and-down method", are extremely effective in a numerical stability sense comparing to the ordinary up-and-down method when the mean is unknown but the coefficient of variation is assumed to be known in advance. As for the estimating error of the mean value of the flashover voltage, the error obtained by the mean-shooting method is seen to be superior to that obtained by the ordinary up-and-down method; for instance, 15 shots in the mean-shooting method is equivalent to 20 shots in the iln-and-clown method

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Switching characteristics of two series-connected triggered vacuum gaps (TVGs) have been investigated experimentally. Each TVG was mechanically connected in series to be four connection modes. The withstand voltage of two series-connected TVGs was about 2 times greater than that of a single TVG. It was also observed that there was no effect of the connection modes against the withstand voltage of two series-connected TVGs when the impulse voltage polarity was positive or negative. The similar case was also shown in a single TVG.
The polarity effect to the switching time and the grounding were pronounced. When the lower TVG was grounded and both nonholed electrodes were positive, the switching time was short and nearly constant(1.4μs at 5 to 30kV). Conversely, when both nonholed electrodes were negative, the switching time was long. When the polarity of each nonholed electrode was different, the switching time was long. However the polarity effect to the switching time decreased.
When two series-connected TVGs was floating, it showed the shortest switching time and nearly constant(0.3μs at 5 to 25kV).

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The effect of mixed nitrogen on ozone synthesis in low pressure oxygen was investigated. The electrodeless discharge system was used in pressure range from 400 to 930Pa for glow discharge. As a result, the ozone yield efficiency had peak value at 50% nitrogen and oxygen mixture in low pressure. The parallel plate electrode system was used in higher pressure range (665-101kPa) for silent discharge. The yield efficiency of ozone decreased with increasing mixture rate of nitrogen and furthermore the yield efficiency had peak value in lower pressure than 6650Pa.
In order to clear the cause of above results, plasma parameters (electron temperature, electron density) in discharge space were measured. The ozone yield increased in proportion to the electron temperature and electron density. However, these electron temperature and electron density did not show remarkable dependence of nitrogen mixture rate. Furthermore, in order to investigate the influence of the luminosity of discharges on the effect of mixed nitrogen, the ozone yield efficiency was measured mixing oxygen and argon. It was clear that the peak characteristic of ozone yield efficiency was not depend on the luminosity of discharges.
As a result, in case of oxygen as a raw material, the ozone yield is small. On the other hand, in case of nitrogen mixture gas, many oxygen atoms are consumed by NO and NOx and the resolving reaction is controlled. In short, nitrogen controls the resolution of synthesized ozone.

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Mixing time of N₂ and SF₆ was measured. The local mixing ratio was determined by variation of the corona onset voltage on the needle-plane electrodes. Owing to the mass difference of two kinds of gases the mixing time was influenced by mixing methods. The mass difference makes flow of the gases in the mixing container and accelerates the diffusion. Then the wide range of diffusion (or turbulent diffusion) coefficients was obtained.

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A digitized phase sensitive detecting system(DPD)have been developed for precision measurement of voltage ratio. The system is composed of a personal computer, an analog-to-digital converter(ADC)and a software for mesurement and data treatment. Two sinusoidal voltages of a frequency applied to the DPD are converted into discrete data, and expressed as vectors by data treatment following to the principle of usual phase sensitive detector. Then an amplitude ratio and a phase difference of the two input voltages are calculated. Estimeted uncertainties of measured values by the DPD are less than 0.008[%]for amplitude ratio and 0.05 [mrad] for any phase difference at frequency of 50[Hz].The errors of the DPD caused by harmonic distortion of the applied voltages and asynchronus sampling by the ADC are also examined using a two-phase voltage source.

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In this paper, we report on dielectric breakdown characteristics of alumina-filled epoxy resin irradiated by γ-ray under a needle-plane electrode geometry. For that purpose, we studied relationship between breakdown voltage and filler parts, relationship between breakdown voltage and irradiation dose, and an influence of thickness of epoxy resin on breakdown voltage. In order to investigate these results, we made further experiments on Glass Transition Temperature change before and after γ-ray irradiation using a DSC method, and filler parts dependence of tan δ and ε We also investigated surface oxidization of epoxy resin from a wave analysis of spectra measured using FT-IR difference spectro-meter, We observed surfaces of epoxy resin before and after γ-ray irradianon using a Scanning Electron Microscope (SEM). The results are as follows: 1) In the case of 2mm thick, dielectric breakdown voltage of epoxy resin increases suddenly from 5 parts to 40 parts, and decreases slowly from 40 parts to 300 parts, under both positive and negative impulse voltage. 2) Dielectric breakdown voltage of epoxy resin with 2mm thick begins to decrease at 2MGy under positive impulse voltage, but it begins to decrease at 5MGy under negative impulse voltage.

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In order to measure the dielectric properties of film specimen for high field with minimized "edge effect", we developed new electrode system. This electrode system is so designed that the guard electrode is extended to cover main electrode by using a guard film.
In this paper, we examined relationship between guard film thickness and measurement accuracy in t9erms of both electric field analysis around main electrode edge and the experiment. It is clarified that the newly developed electrode system enables us to measure high field dielectric constant with high accuracy and that the measurement errors become one decade smaller.

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This paper describes the results of an investigation of the electric fieldinduced motion in mineral oil between metal electrodes after change of electrode polarity. We have observed time dependence of current and schlieren images of the motion for a range of charging period length extending from 5s to 3600s at ±10kV. Main results are as follows: (1) The motion occurs at the charging period length above 10s. A time delay exists between change of electrode polarity and the onset of motion. (2) The motion occurs in the vicinity of the interface of anode in the short range of charging period length from 10s to 80s and occurs in the vicinity of the interfaces of anode and cathode in the long range of charging period length above 80s. (3) The motion increases current and produces a peaked behaviour in the current waveform. (4) A increase time of current and a peak current time are inversely proportional to the quantity of charge carriers drifting between electrodes from the increase time of current to the time of peak current. (5) In the short range of charging period length, the experimental results are well explained by the established model.

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The extinction of the partial discharge (PD) pulse has been frequently observed in an epoxy specimen with a closed void during voltage endurance tests using a CIGRE Method- II electrode. The individual discharge pulse becomes so small that the discharges cannot be detected by conventional pulse detection methods. Such discharges are known as "swarming pulsive microdischarges" (SPMD). In this paper, the SPMD characteristics are investigated by varying the pressure and gap spacing used in the range of 10 to 760 torr and in the range of 0.025 to 0.25mm, respectively. As a result, the SPMD are found to occur at small gap spacing with high pressure or at large gap spacing with low pressure. Since the behaivior of gas discharge depends on gas density, the relation between p•d and SPMD seems to be meaningful, where p and d are the pressure and gap spacing, respectively. The SPMD occurs in the range of under 6 torr•mm. This region corresponds to the region of minimum sparking voltage of Paschen's law.

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The basic properties of silicon carbide thin films prepared by plasma-enhanced chemical vapor deposition using silicon tetrachloride were studied. It was found that the films prepared at the substrate temperature of higher than 700°C were polycrystalline, and the grain size of about 20nm was obtained for the films prepared at the substrate temperature of 800°C. The stoichiometric silicon carbide films showed n type conduction, while the carbon rich silicon carbide films showed p type conduction. Hall mobility and the carrier concentration were about 20cm²/V•sec and 2×10¹⁷cm^-3, respectively for the stoichiometric films prepared at the substrate temperature of 800°C. Thermoelectromotive force of silicon carbide films was measured and thermoelectric power, the sensitivity as sensor, was about 50μV/deg.

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High saturation magnetization films with soft magnetic properties are invest igated Fe, Fe-Ni and Fe-Si with thickness of 500-3000 A were deposited on GaAs single-crystal substrates. The substrates have their <111> axes oriented vertical to their plane. Tbe lattice parameters of the films are very close to the half of that of GaAs. This fitting makes the films grow with a single-crystal structure with (111) orientation. Since the effective crystalline anisotropy field in the (111) plane for bcc Fe is very weak, magnetic softness of those films are well enhanced when the X-ray diffraction data indicate good orientation of the (111) plane. Good orientation of the (111) plane is achieved when the substrate temperature is above 250°C. Hawever, atomic diffusion at the interface between the films and the substrates occurs during deposition This made it difficult to refine the deposition conditions for improving the quality of the crystals and heat treatments for adjusting the induced uniaxial anisotropy to improve the magnetic softness. Isotropic initial permeability which is expected theoretically for ideal single-crystal films were partly obtained for those films, indicating that production of films with isotropic permeability is possible if the induced uniaxial anisotropy is removed.

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