An electrode configuration with a series resistance 50kΩ that enables the unidirectional or bidirectional streamer to elongate along the fine insulated wire was constructed to study the elemental behaviours of impulse surface discharges free from interstreamer interactions.
A series of image converter camera streak photograph obserbations revealed the long gap high pressure discharge-like luminous streamers grew stepwise and intermittently with the global and tip speed on the order of 10⁶cm/s and presumably one order higher respectively. Being near for both polarities, the global speed was linear to the peak value of impressed impulse voltages above a certain threshold, nevertheless, positive streamers extend about twice their negative counterparts owing to the longer resting intervals of the formers.
The phenomena studied here concern with comparatively low voltage surges which may injure electronic instruments, computers etc.

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We have developed a large diameter plasma source by Whistler wave in the VHF band of frequency 144MHz. The experimental results have been obtained as follows: (1) The discharge mode could be explained by a Whistler mode. (2) The radial electoron density distribution could be flat (2%), whose diameter was equal to that of helical coilof 60cmφ. (3) The ion energy measured by a Faraday-cup decreased when the static magnetic field increased from resonant field. (4) The deposition of SiO₂ film was tried on a silicon wafer.

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Using a slowly rising DC voltage, the rapid current increase at a critical voltage and the breakdown voltage were measured in transformer oil with needle- or blade-plane geometries. The mechanism of the onset of positive breakdown was studied using experimental and computed results. The computation showed that the local field strength on the planar surface is increased very much by the space charge effect in accordance with the influence of liquid motion. This leads to the generation of new charges in front of the planar surface; the charges drift towards the sharp electrode tip. Consequently, it is suggested that partial discharge at the tip is initiated; a positive streamer then starts from the tip, and breakdown ensues. The generation of new charges is confirmed not only by the dust figure method but also by the signal pulse induced on the probe.

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We have already constructed a prototype of partial discharge (PD) measurement and degradation diagnosis system (PDM/ES-I) for insulating materials using a personal computer for insulating materials suffering PD. In this report, we applied PDM/ES-I to electrical tree degradation phenomena; we developed a system to detect when electrical tree is initiated and to assess the shape of the electrical tree by making use of the so-called Electrical Tree Detection System using Pattern Recognition, which is abbreviated as ETESPAR. We also developed a system to observe the treeing shape; The tree observation system (TOS) consisting of a microscope and an image processor can record temporal change of the shape of tree. Measurements of PD distribution patten were made. Using ETESPAR, we tried to determine the time of the tree initiation and to assess the developing tree shape for polyethylene sample with needle vs. plane electrode. The PD pattern measured at a given aging time was compared with five standard normalized PD patterns which had been registered in advance as five representative tree degradation stages. It has found ETESPAR allowed an exact determination of time when the tree was initiated. In addition, the result of the assessment by ETESPAR proved to agree well with the tree shape and degradation stage for the insulating material using pattern recognition of the PD pulse occurrence phase distribution.

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A high acceleration linear motor has been developed, which would be applied for semiconductor manufacturing equipments and precise machining systems. The linear motor has the more precise positioning and higher acceleration than conventinal. High energy Nd-Fe-B sintered magnet was used for magnetic circuit which had been simulated with FEM (TOSCA) to achieve 150 N of the maximum driving force. The control unit is comprised of a control circuit using a digital PID filter and an encorder. The tracing and positioning errors were able to be controlled within ±10μm and±2μm, respectively. The highest acceleration of 50m/s²(-5G) were obtained with the positioning error of ±2μm.

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Plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) method is developed for preparation of YBaCuO superconducting thin films. The discharge plasmas generated by using rf and microwaves are used to enhance decomposition of source materials of Y(dgm)₃, Ba(dpm)₂ and Cu(dpm)₂. The films are deposited under the conditions; total pressures of 0.6-5 Torr, O₂ contents of 0-30% and substrate temperatures of 500-650°C. Most of as-grown films prepared by the two techniques were porous and consisted of crystalline grains. After annealing at high temperatures, the films had c-axis orientations perpendicular to the substrate surface. The post-annealed films deposited by rf PE-MOCVD showed superconducting transition with zero-resistivity temperatures of 85-89K. The excitation temperatures estimated from the spectral line intensity ratios showed weak dependence on process conditions of the PE-MOCVD. However, numbers and intensities of plasma emission spectral lines depended on the oxygen partial pressures and the plasma production technique such as rf and microwave discharge. The results indicate that the as-grown YBaCuO films prepared by the microwave PE-MOCVD method have smooth surface and superconducting property with c-axis orientations.

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