This report deals with the mechanism of space charge accumulation in cross-linked polyethylene (XLPE) under DC electric field. Space charge was measured by the pulsed-electroacoustic method with applying DC stress of 20kV/mm. A large amount of hetero space charge accumulated in fresh XLPE sample. Factors to influence the space charge accumulation were analyzed in regard to cross-linking by-product and antioxidant. No space charge was seen when the fresh sample was degassed to remove cross-linking by-products. Introducing acetophenone, one of the cross-linking by-products, in the degassed sample brings no space charge, suggesting that acetophenone itself could not be the direct factor of space charge formation. However, heating this sample up to 150°C brings hetero space charge as were seen in the fresh sample. It is concluded that the hetero space charge may be formed when impurities such as antioxidant dissociate thermally with the help of acetophenone and that the dissociate species are attracted towards both electrodes under DC field to form the hetero space charge.

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We investigated the factors affecting space charge behavior of the insulating materials by using pulsed electroacoustic method (PEA). The influences of two important factors, moisture and temperature, were studied with sheet samples made from various polyethylene such as low density polyethylene (LDPE), crosslinked LDPE (XLPE) and high density PE (HDPE). The results shows that moisture in LDPE makes a change in the space charge distribution. Hetero charges were observed in XLPE when curing by-products were co-existed with moisture. It implies that curing by-products may be ionized by the moisture since water works as a solvent to such polar organic impurities as acetophenone. At high temperature, LDPE shows a homo-chage characteristics which is the same as at the room temperature. The quantity of the homo-charge decreased with temperature increase. Therefore, injected homo charges under the higher temperature condition migrated to the inner part of the specimen and neutralized more rapidly. Temperature increase made the decrease in homo-charges also in HDPE. The mechanisms responsible for the influences of moisture and temperature on the charge accumulation and migration were discussed from the view points of ionization and ionic conduction.

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Ferrite loaded radio-frequency (rf) cavity with resonant frequency of several MHz is commonly used for proton synchrotrons. The high-intensity proton synchrotron like the JHP (Japan Hadron Project) requires high accelerating voltage at the maximum repetition rate of 50Hz. In order to select or develop ferrites which meet these requirements, a high power ferrite test bench was fabricated.
This paper presents the theoretical relations between ferrite properties and characteristics of rf cavity. Next, description is made for the fabricated test bench which consists of a test cavity, a measuring system, a bias power supply and an rf power supply. Three ferrites with large diameter over 500mm were successfully tested by 1kW rf input power and data equivalent in actual operation of rf cavity were acquired. As a result, usefulness of the test bench was verified.

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Thin films of magnesia stabilized zirconia (MSZ) for solid oxide fuel cell (SOFC) were prepared on Si (100) substrate by plasma-enhanced chemical vapor deposition (PECVD) using zirconium alkoxide, Zr(0-nBu)₄, and magnesium acetyl-acetonate, Mg(C₅H₇O₂)₂. It is seen from Plasma spectroscopic measurement that the oxygen radical produced in a reduced pressure of 0.2 mTorr can be sufficiently facillitated the elimination and adsorption reactions of organometallic compounds. MSZ fi1m was obtained at deposition pressure of 0.5 mTorr and substrate temperature of 400°C by PECVD of Zr(O-nBu)₄ and Mg (C₅H₇O₂)₂, which were transported with nitrogen carrier gas. Furthermore, this film was grown in a columnar structure with deposition rate of about 12nm/min. It is also found that when MSZ film was annealed at temperature ranges from 600°C to 1000°C, it has Partially stabilized zirconia (PSZ) structure without Phase transition to a monoclinic Phase.

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The accuracy of a stylus probe method in measuring localized magnetic properties of grain-oriented silicon steel sheet was investigated and its application was studied. The measuring error for the localized flux density was determined to be less than 1.7% for the load onto the stylus tip lighter than 300g when the yoke structure was symmetrical with respect to the sheet plane. The average of localized iron losses measured with the combination of a stylus probe and a Hall probe was in linear relation with the loss in the whole sheet. This method revealed that the localized magnetic properties vary markedly portion to portion in a sheet and that the localized iron loss depends on the localized flux density, domain wall spacing and yaw angle of grain orientation.

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Interfaces between two different kinds of materials are usually found in underground high voltage equipment. In composite insulating system, interface usually has been considered as a weak point of electrical insulation. On the other hand, it is widely accepted that electrical deterioration in bulk-manufactured insulation materials usually occurs through treeing. Therefore, it is important to research on interface effects on treeing breakdown characteristics in composite materials. Recently, prefabricated-type joint (PJ) has been developed and used on high voltage cables. In the insulation system of the PJ, there are two interfaces exist. One exists between XLPE/EPR and another between EPR/EX. The interface between EPR/EX is an inclined plane. For clarifying effects of the inclined interface and its inclination angle effect on treeing breakdown characteristics, we have done some experimental investigation by making an interface between XLPE and EX. Results are described in this paper. It is found that interface conditions and their inclination angle have great effects on time of treeing breakdown. With the decreasing of the inclination angle, the time of treeing breakdown is reduced. Effect of silicone oil applied on the interface is different at different inclination angle.

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The discharge using pulse power with a short pulse width can produce a lot of electrons with high energy. This method has a possibility to remove poisonous gases with low energy consumption. In this paper, the inductive energy storage pulsed power generator, which can generate narrow and high voltage pulses (FWHM less than 100ns, output voltage of about 100kV), is used to remove NO_x gas. It is found from spectrum measurement that this generator can produce high energy electrons, more than 10eV, in the discharge region at atmospherics pressure. The mixed gases of NO and N₂ are used as a trial gas. The NO removal ratio of about 95% is achieved without producing NO₂. These chemical phenomena are approximately explained by solving rate equations.

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Railguns are facilities to accelerate projectiles up to several km/s by the electromagnetic force due to a driving current. A variety of current waveforms are used for railguns developed in the world This paper describes the dependence of a railgun operation on a rising rate of the driving current. The use of the exploding wire as an opening switch enables to change the rise time of the driving current. A secondary arc is likely to appear and the erosion on a rail surface is more severe when the current with a short rise time is used. According to the non-dimensional railgun plasma simulation, the current with a short rise time heats up the plasma so fast that plenty of particles ablated from the bore surface, which seem to be the cause of the secondary arc, increase rapidly in the early phase of acceleration.

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The propagation characteristics of the creepage discharge in parallel plane electrode gap with protruding point in transformer oil are observed and investigated in detail under an impulse voltage application, by using a high-speed Schlieren optical technique and a current measurement system by LED.
The streamer-like density changes appeared from the protruding point tip of one high voltage plane electrode and propagated to other earthed plane electrode.
In the present paper, the effect of an arrangement of a barrier insulator and an electric field direction on the propagation of the creepage discharge is discussed.

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The paper describes a charge simulation method named β-method which simulates the field with fictitious charges only near the boundary surrounding the dielectric with higher dielectrlc constant. The comparative calculation has shown that the β-method keeps good accuracy even in the condition the conventional technique (α-method) fails to give reasonable results. The β-method is more advantageous when the ratio of dielectric constant exceeds about 4. The paper also compares two methods in a mixed (capacitive-resistive) field where the conductivity may change by many orders.

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This paper describes a simulation method and its results concerning the discharge on the surface of an insulating plate in SF₆. The method is to apply the streamer inception criterion on the electric field distribution formed by the surface charge. The calculation considering the voltage gradient in a leader discharge has given accumulated surface charge density and extension length on the leader, which both agree reasonably well with the measured values. The simulation method promises to be a useful, quantitative technique for analyzing surface discharge characteristics.

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