The electron energy distribution function (EEDF) in the positive column of a glow discharge can be measured on basis of Druyvesteyn's probe theory. However, E. Berger and A. Heisen have reported that the measured values of EEDF by using the high frequency method were distorted by the plasma resistance between anode and probe. We improved the measuring circuit of the plasma impedance. From the frequency locus of the measured impedance between anode and probe, we estimated the stray capacitance which was contained in the measuring circuit, and determined the plasma impedance Zp of the positive column and the ion sheath impedance.
On the basis of this circuit, we made a correction of the impedance for measured value of EEDF by using the high-frequency amplitude method (AM method; carrier frequency=30kHz, signal frequency=720Hz). The corrected value of EEDF by using AM methods agreed approximately with EEDF by using the second harmonic methods (fundamental frequency=360Hz). The results show the adequacy of the estimated values for the plasma impedance Zp.

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In order to demonstrate the application feasibility of the reactor composed of a forced constricted type DC plasma jet generator and a feed ring to low pressure plasma processing, we have studied the production of ultrafine particles of refractory materials (Al₂O₃, ZrC, TiC) and the interaction between the plasma flow and the injected particles.
According to the experimental results, many ultrafine particles whose diameters are less than 0.1μm are prepared not only in atmospheric pressure but also in low pressure, although the number density of the prepared ultrafine particles, N, in low pressure is usually less than that in atmospheric pressure. It is also found that we can control the process of particle heating by changing the feed ring length, and that N in low pressure becomes equal to or greater than N in atmospheric pressure with increasing the feed ring length.

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In order to estimate the current distributions in the conductors and biological systems, we propose here a new method based on the Cauchy-Schwarz relation. A key idea of this method is to utilize a sampled pattern matching between the measured and assumed magnetic fields. As the practical two dimensional examples, our new method is applied to the shape identification problems of current carrying conductors and to the field source searching of human eye magnetic fields. Further, combination of two independent results leads to the quasi-three dimensional estimation of the current distributions of human hearts. These test examples reveal the validity of our approach and demonstrate its usefulness for medical diagnosis.

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Time-resolved Langmuir probe technique has been applied to the afterglow of pulsed discharge in low pressure Hg-Ar mixtures. The basic procedure consists in applying a ramp voltage, with a rise time of the order of a few minutes, to the probe and sampling with a 2-channel boxcar integrator the probe current and the probe voltage at specified times during the afterglow. The pmobe current _??_ voltage characteristics during the most portion of time of the afterglow exhibit normal curves for the positive ion saturation region, transition region and the electron saturation region, giving quite reasonable results of electron temperatures, plasma densities and space potentials respectively. From the logarithmic plotting of the plasma density against time we have obtained the ambipolar diffusion coefficient Dap=350cm2•s-1•Torr, in good agreement with calculated value Dap=360cm2•s-1•Torr, which is derived using Chanin's atomic mercury ion mobility in argon.
An unexpected result is that the probe characteristics just after the cut-off of the pulsed discharge (within 100μs after the ionizing field is removed).demonstrate the presence of high energy electrons. These are assigned to the acceleration by the field that possibly occurs between the plasma and the wall of the discharge tube

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On the basis of the electrooptic Kerr effect, a highly sensitive new measurement system of two-dimensional electric field distribution, the field intensity Edc and its direction WdC, in dielectric liquids is developed. The system can automatically measure the electric field intensity of 100V/cm at minimum and the algle of it's direction within 1.0 degrees in the transformer insulating oil. For obtaining the highly sensitive measurement of electric field insensity even when using short electrodes of below 10cm in length in the transformer oil, we use elliptically polarized incident light (phase difference is about 8 degrees) and a modulating electric field (the frequency is 10kHz) superimposing the static electric stress. Furthermore, for determining the angle of the electric field direction, a test cell containing the dielectric liquids is placed between two optical phase modulators of a Pockels device.
This optical system for measurement of two-dimensional electric field consists of a He-Ne Laser light source, polarizer, lst opical modulator, test cell, 2nd optical modulator, analyzer and photodetector. The light intensity passed through this optical system was analyzed by calculating Jones'matrix. This paper also discusses the detemination of the optimum fast axis and the phase difference of optical modulators. We demonstrate the two-dimensional lectrical field distribution in the test sample of tricresylephosphate liquid under dc and ac electric field applications.

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Flashover characteristics of nitrogen and nitrogen-oxygen mixture gases in a positive rod to plane electrode have been investigated over a temperature range of 20--160°C under the condition of constant gas density.
In nitrogen, the breakdown voltage of the gap with a sharp tip rod increases with reducing gas temperatures and its value at -160°C is 1.7 times of that at room temperature. When a tip radius of electrode increases or a few percent of oxygen is added in nitrogen, the increase in the breakdown voltage at low temperature tends to disappear. The temperature dependence of breakdown voltage is sensitively affected by the tip radius of the electrode and an amount of oxygen in nitrogen gas. These phenomena are discussed on the basis of the inception voltage of streamer corona which can subsequently induce the breakdown.

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In order to observe the progressing manner of the spark discharge along a long gap, a high speed streaking camera or an image converter camera has been used, but they are not available in the daytime and need a man-power to exchange a film. By the aid of recent opto-electronic techniques, the authors developed a novel measuring instrument, which does not need man-power and can be used even in the daytime.
This system converts light signals to electrical ones by 1, 600 pin-photo-diodes. Electrical signals are amplified and decomposed into 16-step signal strength. The fastest sampling time of memory is 0.1μsecond and the number of frames is 16, 000. A personal computer is used for controlling the whole system and can output the data in the various manners.
Using this system, the developing manner of leaders was observed for the impulse voltage test clearly and that of lightning discharges in winter seasons was observed in the coastal area of the Japan Sea.

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Electrical, mechanical, and thermal properties of epoxy resin materials for electrical insulation and their retention under the forced deterioration testings (FDT) with high temperature and high humidity were evaluated and the deterioration mechanisms in the materials were discussed.
Most of the electrical and mechanical properties of the materials decreased after the FDT. The decrease in the glass transition temperature of the materials, which reflects the changes of the chemical structure, showed poor correlation with the decreases in electrical and mechanical properties. The mercury porosimetry and the SLAM and SEM observations indicated the surface and internal crack growth in the materials during the FDT. The crack growth mainly depended on the humidity conditions in the FDT and the moisture content of the materials.
These results show the physical structure changes such as the crack growth in the materials deteriorate the electrical and mechanical properties of the materials.

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