Small discharge not to accompany breakdown can occur under high electric field in vacuum, however the mechanism is not well clarified. We have found that the current of small discharge decreases with repeated voltage applications, and leads to electrode conditioning effect of raising withstand voltage. The inception of the current is delayed with the decrease of current, and the inception time and waveform change by gap length. On the other hand, under low vacuum condition, the current increases and reaches saturation with repeated voltage applications. From these discussions, we concluded that the generating process of small current depended on the adsorption and absorption gas of electrodes.

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Neutron Transmutation Doping (NTD), which is one of the semiconductor manufacturing methods, can produce impurity semiconductor with high quality. The neutron source currently used in the NTD is a nuclear reactor, which has some problems such as to become too old for use. Hence development of a new neutron source, which enables uniform irradiation, is desired. A new Inertial Electrostatic Confinement (IEC) device with a coaxial double cylindrical structure, which is especially designed to be capable of uniform neutron irradiation, was developed. As the feature of the device, it has triple electrode structure which consists of a cylindrical grid cathode between inner and outer anodes. Neutrons are centralized in the center of the device, and uniform neutron flux is obtained there. The device achieved a neutron production rate of 1.5×10⁶ n/s, and uniform neutron flux distribution was provided in the central hole of device. The largest size of the uniform neutron flux area was 35.2% (25 cm) of sample irradiation area in the axial direction, and 54.3% (10 cm) in the radial direction.

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Flashover discharge on the solar array is an issue of spacecraft charging, because the discharge potentially causes the catastrophic failure of a satellite. The discharge experiment on solar array has been carried out to investigate the propagation area of flash-over discharge. During the flash-over discharge, neutralization current flows on the solar array strings. The charge of neutralization current was calculated to investigate the relationship between the charge and the distance from the cathode spot. The experiment result in the maximum propagation area of flash-over plasma is 3m in simulated geostationary orbit.

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This paper deals with factors affecting the charging characteristics of insulators exposed to high voltages in vacuum. We examined the influence of voltage shape on charging. The charging was studied by using an electrostatic probe that measured electric field on the cathode. A ramped dc and an impulse voltage were tested in a low pressure and found that the electric field due to surface charging was larger for the impulse voltage than that for dc voltage. We also examined the influence of pressure that varied from 10^-5 Pa to 0.5 Pa and found that an insulator acquired more charge in a high pressure range than that acquired in a low pressure range. These results suggest that the charging may be assisted by electrons produced by ionization of gas molecules desorbed from the insulator surface.

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Particles diffused from vacuum arc can be used for thin film formation. Diffusion of particles from vacuum arc influences current breaking properties of a vacuum interrupter. For these application it is essential to clarify the behavior of particles diffused from vacuum arc at around current zero point. In this paper dependence of diffused charged particles current on the crest value of arc current before current interruption point was shown with Faraday cup in case of oxygen-free copper electrodes and CuCr (Cu:Cr=50:50) electrodes. Experimental results were as follows. Ions and electrons diffused from vacuum arc entered into the Faraday cup with pulsive and intermittent states, when vacuum arc of DC 100 A∼150 A was generated in case of oxygen-free copper electrodes. This phenomenon corresponds to the behavior of cathode spots. Electron current value was about 100 times as large as ion current value. The pulse width is about 1∼10μs. When the crest value of arc current were 2,000 A∼10,000 A in case of oxygen-free copper electrodes and CuCr (Cu:Cr=50:50) electrodes, the amount of charged particle current for CuCr before the current interruption point was larger than those for Cu. The ratios of the ion current to the electron current diffused from vacuum arc were calculated by the waveforms of electron and ion currents. The current ratios of 0∼0.02 were taken when the crest value of arc current 2,000 A∼10,000 A.

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This paper deals with the surface flashover characteristics of dielectric material in vacuum during electron beam irradiation in order to design adequately the conductive patterns on printed circuit boards used inside a spacecraft. The dielectric material, glass-fiber reinforced epoxy resin, and the electrodes printed on it were irradiated with electrons of the energy of 3-10 keV. DC high voltage was applied between the two electrodes during electron irradiation. The voltage was increased stepwise until the surface flashover occurred on the dielectric material.
We obtained the results that the surface flashover voltage increased with the insulation distance between the electrodes but electron irradiation made the flashover voltage lower. The flashover voltage characteristics were obtained as parameters of the electrode distance and the energy of the electron beam.

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The temperature characteristic of the eddy-current displacement sensor is important on the specification. There was an unsuitable and inconvenient point in the proposal of an analytical design approach though the technique with enough accuracy about the theoretical analysis was proposed. In this paper the sensor structure is modeled and it is analyzed on a condition near the real design. The influence given to the temperature characteristic of each element in designing EC displacement sensor became clear, and it proposed an analytical method that computational error becomes 5.3 %.

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Though general ozonizers based on silent discharge (barrier discharge) have been used to supply ozone at many industrial situations, there is still some problem, such as improvements of ozone yield.
In this work, ozone was generated by pulsed discharge in order to improve the characteristics of ozone generation. It is known that a pulse width gives strong effect to the improvement of energy efficiency in exhaust gas processing. In this paper, the effect of pulse duration on ozone generation by pulsed discharge in oxygen would be reported.

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In this paper, a novel magnetic domain model on grain-oriented electrical steel was established which is based on magnetostriction measurements for an interpretation of the magnetization behavior under rotational magnetization process. The novel model has brought about useful insights for understanding on reconstruction of magnetic domain and kinetics of magnetic domain wall.

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In this investigation, four kinds of epoxy/silica nanocomposites with different sizes of nano-fillers were experimentally investigated on treeing breakdown lifetime. The nanocomposite specimens used included 3 wt% nano-fillers of 12, 40, 90 and 300 nm in size, and were prepared with and without silane-coupling agents for evaluation. According to SEM observation, nano-fillers were considered to be well dispersed in all the specimens used. As a result, it was found that the nanocomposite specimens with 12 nm size fillers own much longer tree breakdown time than neat epoxy and other epoxy nanocomposite specimens under applied voltage of 10 to 30 kVrms. Difference in lifetime between neat epoxy and nanocomposites with 12 nm size fillers tends to be enlarged, as applied voltage is lowered. Furthermore, it was confirmed that the addition of coupling agents would help increase lifetime. The coupling in the interfaces is considered to suppress tree propagation in this process.

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