Formation of a thin carbonaceous layer has been found on cubic boron-nitride (cBN) {111} surface at the initial growth stage of epitaxial diamond thin film using dc plasma chemical vapor deposition (dc plasma CVD) method. During SEM (scanning electron microscopy) observation, the layer showed higher brightness as compared with cBN surfaces. After exposure to the air, no adsorvates has been found by AES (Auger electron spectroscopy) analysis.
From emission experiments performed in a high vacuum, the layer formed on {111} surface of a conductive cBN showed higher emission efficiency of electron as compared with the conductive cBN crystal itself, vacuum deposited Mo or amorphous carbon film on the cBN surface. The emission characteristics follows the field emission type as confirmed by linear relationships of the Fowler-Nordheim (F-N) plots. Calculated value of barrier height was approximately 2eV. It is found that a stable and low work function surface can be obtained on cBN single crystals utilizing the diamond CVD process.

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Recently, high reliability and safty have been required for electric power system. Many kinds of insulating materials and insulating structures have been developed. Semiconducting layer is widely used to improve the relaxation of electric field of power cable. However, the characteristics of the layer are still not cleared. The purpose of this research is to investigate effects of semiconducting layer on void discharge deterioration. In this paper, PMMA with an artificial needle void at a tip of semiconductive electrode (SE) was used as a sample. The tree initiation voltage was measured. The discharge magnitude distribution was measured by the partial discharge pulse measurement system. At the same time, the void condition and the tree development was observed by CCD camera. These measurements were carried out by using SEs of several kind of resistivity.
As a result, by measuring the discharge magnitude distribution, it became clear that SE inhibited the void discharge. It was confirmed that the electrode inhibited tree development, by image processing of tree. The highest tree initiation voltage and the lowest tree extension speed were got at the resistivity of 2kΩ•cm. The effects of SE on the void discharge deterioration were caused by the conductive matter sputtered from the electrode.

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When polymers are used for electrical insulation in space or at a nuclear power plant, radiation-induced space charges or surface charges may give rise to an unexpected surface discharge or breakdown. The charge generation and accumulation processes can be understood by examining the distribution of space charge inside the polymers irradiated by low-dose radioactive rays. Therefore, in this report, residual space charge distribution in gamma-irradiated polyethylene is examined. To measure the space charge distribution, the pulsed electroacoustic (PEA) method was employed. The PEA method is one of the advanced nondestructive techniques to measure the space charge distribution with high sensitivity and reproducibility. Samples of a commercially available low density polyethylene were irradiated by a⁶⁰Co source to a total dose of 1.2 to 12 kGy which is high enough to excite charges and low enough to avoid chemical damages such as oxidation. After gamma-irradiation, dc voltages of up to 15 kV were applied to the sample, and the time dependence and the applied voltage dependence of space charge distribution were measured using the PEA method. From these measurements, it became clear that a large amount of positive charges exist near the cathode in gamma-irradiated polyethylene, and these positive charges enhance the electric field at the interface between the cathode and the polyethylene. On the other hand, almost no space charge was observed in nonirradiated polyethylene. It is considered that the mobile carriers are electrons, and that such moved electrons and the remaining positive ions form the observed space charge distributions.

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Silent discharge is widely used for an industrial ozonizer and toxic gas treatments, hence they will become an electromagnetic noise source. In this paper, an experimental investigation from the point of view of electromagnetic compatibility (EMC) has been conducted to grasp noise characteristics of silent discharge type combustion flue gas cleaning systems. The silent discharge plasma reactor presently used is consists of ceramic made double coaxial cylinders. Discharge current and induced current waveforms are measured. The discharge current has multiple pulses with duration on the order of hundred microseconds at a specific phase of applied voltage, and the polarity effect in silent discharge that has already been reported by other investigators is observed. The peak value of discharge current increases suddenly with applied voltage at over 22kVpp and its order is 10A. Frequency components of discharge current at 40MHz is largest in frequency range of 1MHz to 100MHz. The maximum value of the discharge current time rise increases suddenly at 22kVpp. It is on the order of 10¹⁰ A/s. The induced current at the simulated DC control line 1.4m away from the reactor also increases suddenly at 22 kVpp. Both the discharge current and the induce current have large current component in common frequency. From the point of view of EMC, this type reactor should be operated below 22kVpp.

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Development of sodium immersed type Electro-Magnetic Pumps (EMP) is expected to improve reliability, safety, maintainability, and construction cost of FBR compared with the conventional mechanical pumps. In order to realize the EMP, establishment of a high-temperature-resistant electrical insulating system is indispensable.
We selected a mica-alumina combination for the insulating system at temperatures higher than 500°C. Using this insulating system, an ageing pre-test was performed. The ageing condition was to apply 1.5kV AC voltage in the nitrogen atmosphere at 550°C for 4000 hours. The dielectric properties before and after the ageing were measured to understand the tendency of temporal change in the ageing.
In this result, the dielectric performance after the ageing was improved compared with the initial performance. The curious phenomenon was clarified to be caused by a decrease of organic component in the insulation, which remained owing to incomplete burning. Also the possibility of the thermal runaway was considered to be higher as a dielectric breakdown mechanism.

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MIM elements of polyimide LB films were prepared about 7 years ago. In these elements, polyimide LB film of 7 monolayers (nonpolar, about 30A in thickness) are sandwiched by Al and Au evaporated electrodes. Characteristics of generated voltage are as follows;
(1) Generated voltage decreases with the decrease of atmosphere (He, N₂ or air) pressure.
(2) Value of generated voltage is changed by kinds of atmospheres.
(3) Generated veltage is incrased by the circulation of air atmosphere.
According to the above experimental facts, it is considered that decrease of the generated voltage mentioned above is due to not pressure but an interaction between LB films and gas molecules in atmosphere.

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