Biomagnetic measurement using SQUID is a noninvasive measurement and source location can be estimated from the spatial distribution of the biomagnetic field measured outside the body. A reliable and easily operative SQUID system is desired for the study of brain activity. In order to provide a high-reliable SQUID system, a process to fabricate DC-SQUID device, of which characteristics did not change after 30 times thermal cycling tests between 4.2K and room temperature, has been developed. A seven channel DC-SQUID system for biomagnetic measurement has been developed with the DC-SQUID devices. The pickup coil is 9mm in diameter and 30mm in baseline. The system noise was about 20fT/√Hz. The sensitivity of the system has not changed during a 8 months operation. The a rhythmic magnetic wave and the auditory evoked response were measured using this system in a magnetically shielded room.

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An arc burning through a polyethylene tube (PE arc) involves an axial gas flow due to ablation of the tube wall. This paper provides estimation of the mean gas flow velocities of core and sheath regions, ν_c and ν_s, in the PE arc, The "two-zone model" and some assumptions accompanied with the PE arc are applied to equilibrium equations of energy, momentum and mass. The ν_c and ν_s are derived as functions of electrical input energy, enthalpies and mass densities of core and sheath regions, ablation mass, and cross-sections of core region and tube. These variables are able to be obtained from experimental values on electrical field strength, radial temperature distribution and mass decrease of PE tube, and theoretical values on thermodynamic properties of PE vapor.
The values of ν_c and ν_s of the arc burning through a 10 mm-length PE tube are estimated for various currents (5, 10, 15 A) and tube inner diameters (2, 4mmφ). The result shows that ν_s agrees with the experimental one and ν_c is three to four times as high as ν_s.

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A high-speed wind tunnel, by use of a Ludwieg tube, has been successfully developed for a highly-repetitive discharge-pumped excimer laser, the characteristics of which have been evaluated. This apparatus allows the gas flow of velocity -200m/s and pressure -294kPa. As a result of the expansion cooling, the temperature of the gas is lowered to -254K from the incident room temperature. The excimer laser flow has been simulated by solving the unsteady two-dimensional Euler equations, and aerodynamic effects of the highly-repetitive pulse discharge are investigated. A large density perturbation appears in the main discharge region when the main discharge occurs and/or the gas heated by the upstream preionization discharge arrives at the main discharge region. The high-speed gas flow sweeps the main part of the density perturbation caused by the main discharge during the successive discharge pulses. The temperature dependence of the XeCl-lasing characteristics under the expansion cooling is also simulated. The simulation has indicated the enhancement of the laser output in the lower temperature.

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Because of the strong activity of atomic oxygen produced by partial discharges, it is very difficult for organic insulating materials to withstand it. Then in order to prevent the insulation deterioration due to partial discharges, it is a practical mean for long time to minimize the partial discharges in insulation or to use inorganic materials combined with organic materials. The authors discovered about 30 years ago that rubber shows excellent PD resistance in some condition, and this paper describes that every sulfur cured rubber shows excellent PD resistance, whereas pure rubber and peroxide cured rubber does not. Through the PD resistance test for thermo-plastic rubber with each element of sulfur curing agents, it has been clarified that the most important combination of elements is that of sulfur, ZnO and double bond of polymer. And in this case, it seems probable that some chemical bonds of sulfur with rubber are produced since there is no bloom of sulfur on cured samples.
An inorganic film is formed on the surface of samples after internal partial discharges, and it may perform partly as the protective film for deterioration due to discharges, but the main cause must exist in the action of the newly produced some sulfur bond, and it is the most important subject of future research to clarify this mechanism.

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In the field of high voltage engineering, it has been desired for long time to improve the internal PD resistance of epoxy resin without lowering other properties. Recently, the authors discovered that some sulfur compound as curing agents or simple additives improved the PD resistance of rubber markedly, and this time we have tried to apply this fact to the case of epoxy resin.
As was expected, some sulfur compounds containing-SS-bond suppress the deterioration of epoxy resin due to internal partial discharges, and the larger the molecular weight of organic group combining to the-SS-bond, the longer the effective life of additives. Moreover, in order to make full use of these additives, it is very improtant to restrict moisture in the insulation systems.
From this study, the authors have proposed the chemical formulation of suppressive effect of additives for deterioration of epoxy resin due to internal partial discharges.

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Katsuhide Tanaka, Associate, Tatsuo Takada, Member (Musashi Institute of Technology) Kerr electro-optic technique is an excellent method for the measurement of electric field distribution in dielectric liquids as it does not disturb the original electric field distribution. However this method is not suitable to an insulating liquid with a small Kerr constant such as an insulating transformer oil. For this reason, our group has developed a high sensitive measurement system of electric field strength by using the combined technique of an electric field modulation and an elliptically polarized incident light. This method has been applied to measure the uniform electric field distribution (only the electric field intensity) in a liquid.
A new measurement system has been recently developed to measure a non-uniform electric field distribution (electric field intensity and its direcion). This paper describes the measuement principle of two-dimensional electric field vector in dielectric liquids. Some results of electric field vector distribution in a composite solid-liquid electrical insulation are presented to demonstrate the effectiveness of the technique.
The main points are shows as follows:
(1) The theoretical equation for measuring the electric field vector is derived for the optical system which consists of a laser, a polarizer, a quarter-wave plate, a test cell (non-uniform electric field), a non-polarizing beam splitter, two analyzers and two photo-detectors.
(2) The effectiveness of the technique is confirmed by comparing the theoretical values with the experimental results. Furthermore the electric field vector distributions of the transformer oil in a compound insulation system of liquids and solids are measured.

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