Surface modification of PMMA (polymethylmethacrylate) was carried out by irradiation of low energy nitrogen ion and/or electron, which is expected to improve the surface hardness by introduction of a thin modified layer. Surface hardness was measured by using the nanoindentation test. To clarify the structure and the properties of the modified layer, composition and chemical bonds were analyzed using XPS (X-ray photoelectron spectroscopy) and FT-IR (Fourier transform infrared spectrometer).
From these results, it was confirmed that surface hardness increased and some chemical bonds including nitrogen was introduced. Thus, it was suggested that cross-linking structure including nitrogen atom contributed on the increase of surface hardness.

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We found that a generation of a uniform discharge in atmospheric-pressure air was possible at a frequency range from 32Hz to 1.1kHz using alumina as a barrier material of the DBD (Dielectric Barrier Discharge) device. We also found that there is a domain in voltages on the generation of the uniform discharge. The domain bocomes wider with the increase of the frequency. If the applied voltage is a bit higher than the upper limit voltage of stable generation of the uniform discharge, the uniform discharge changes to a non-uniform FD (Filamentary Discharge). In order to clarify the mechanism of the generation of the uniform discharge, we investigated how the barrier materials change the discharge mode by both the photographic observation and analysis of the electric circuit phenomena. We also carried out the experiments of a DBD device using a combination barrier of soda-glass and alumina. In this case, the uniform discharge and the FD appeared alternately in every half cycle. As the result, it was found that the uniform discharge was generated when the barrier of alumina was used and it becomes a cathode. From the analysis of the gap voltage and the current, it was also found that the uniform discharge is the APTD (Atmospheric Pressure Townsend Discharge) characterized by the electron avalanche. This paper describes the detail of experimental results and discussions.

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The pulsed arc discharges in liquid between a micro-gap composed of a tungsten wire and a copper rod were characterized for the application to electrical discharge micro-machining. We discussed the spark formation and optical emission spectral lines of micro-gap discharge in liquid. The discharge time lag depends on the breakdown process and discharge position on the surface of the plate electrode. Intense broadband continuum radiation was observed during the pulsed discharge before which clear spectral lines appeared. The excitation temperature of copper atom was obtained using the spectral lines.

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We have composed amorphous fluorocarbon (a-C:F) polymer films, which are low-k insulators, by plasma-enhanced chemical vapor deposition using C₈F₁₈ as the feedstock. In our previous attempts to form multi-layered a-C:F films under various combinations of plasma power density P and deposition time T, it was found that a-C:F films deposited at a high P (typically 2.0 W/cm³) in a short T (∼1 min) became wavy when they are deposited on other a-C:F films deposited at a low P (0.2 W/cm³). A heating experiment for the films showed that their thermal tolerance was dependent on P; films deposited at 0.2 W/cm³ started to melt at 250-270°C, while those deposited at 2.0 W/cm³ did at 350-370°C. It is considered that species of the precursors for the a-C:F film deposition are determined by P through the degree of C₈F₁₈ decomposition. The waving is induced by heating the lower layer during the deposition of the upper layer. The following conditions are necessary for the waving; the lower layer is deposited at a low P, the upper layer is deposited at a temperature at which the lower layer expands but does not melt, and the upper layer is not thickened excessively to keep its flexibility.

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We have studied the water treatment by pulsed power discharge in water droplets spray in air. Ethylene glycol was used for sample. The dependence of decomposition of ethylene glycol on initial concentration was investigated. It was found that intermediate product was generated by decomposing process of ethylene glycol. In the concentration of 50 mg/L, whole ethylene glycol was decomposed by water treatment for 4 hours. However whole intermediate product wasn't decomposed in 4 hours treatment. In the concentration of 25 mg/L, ethylene glycol and intermediate product were decomposed in treatment time at 4 hours.

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PTFE (Poly-tetra-fluoro-ethylene) has superior characteristic. But, it has low adhesion force. In order to improve adhesion force, we have studied on surface modification of PTFE by using discharge under high E/n (E:electric field, n:particle density) condition in nitrogen. From the results, it was deduced that ion energy around 40 eV is effective for polar groups introduction. In addition, treated surface unevenness did not increase compared with the untreated one. Then, we performed nitrogen ion irradiation by changing ion energy. From the results, it is shown that low ion energy is effective for polar groups introduction. It is also shown that high energy ion suppresses surface roughness.
Thus, we measured surface energy and composition of samples irradiated by high and low energy ions. When ion with 30 eV was irradiated for 5 minute and following it ion with 1060 eV was irradiated for 10 second, many polar groups were introduced and surface unevenness was kept at the untreatment level. From the results by XPS (X-ray Photoelectron Spectroscopy) analysis and FT-IR (Fourier transform Infrared Spectroscopy) analysis by using the ATR (Attenuated Total Reflection) method, it was confirmed that polar groups of oxygen component and cross-linked structure via nitrogen or carbon was introduced at the surface.

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Enlargement of capacity and functionality of the pulse power generator are hoped due to its use expansion to the industrial fields. We have developed the high repetitive static impulse generator using technologies of a successive trigger operation and resonant/parallel charging method and Thyristor switches. In this paper, we propose reliable and high functional trigger circuit system with a provision for miss-operation of trigger circuit due to the surge voltage, wide range operation voltage and high speed operation. And using five, seven, ten, and seventeen stage IG, we demonstrated its feasibility. In addition, replacing to IGBT with Thyristor, we improved its properties of rice time and voltage amplification ratio.

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We successfully generated two spherical tokamaks(ST) at two null points by using ex-vessel poloidal field(PF) coils only and succeeded in merging them. This scheme is called as a double null merging(DNM) scheme. First, two pairs of ex-vessel PF coils generate two null points where a poloidal field is zero at the upper and lower regions inside the vacuum vessel. Then a poloidal flux swing generates two STs at two null points, because a distance to a wall along the magnetic field is long at the null points. Finally, the coil currents push two STs toward the mid-plane and merge them into a single ST. Since a magnetic reconnection during merging transforms a magnetic energy into a thermal energy, this merged ST plasma is expected to have high beta. It must be noted that the DNM scheme generates a ST without a center solenoid coil. The DNM scheme was demonstrated on TS-3/4(JAPAN) and MAST(UKAEA). However, these devices have all PF coils inside the vacuum vessels, and initial plasmas were generated around PF coils, not null points. Since the internal coils are not feasible in a fusion reactor due to a high neutron flux, it is important to demonstrate the DNM scheme by using the ex-vessel PF coils.

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Recently polymer nanocomposite has been attracting much attention as an emerging insulating material. In this paper, we measured space charge distributions for two-layered dielectric films consisting of certain combination of low-density polyethylene (LDPE) and its nanocomposite with magnesia nano-fillers during the application of dc electric field of 25 kV/mm or 100 kV/mm. Both at room temperature and 50°C, space charge is formed at the interface of two different materials to maintain the continuity of current when the electric field is 25 kV/mm, while packet-like charge appears only in the LDPE when the electric field is 100 kV/mm. These phenomena are explained by assuming that the nano-fillers effectively suppress the increase in conductivity induced by the high electric field.

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The purpose of this paper is to present and compare disinfection effect of plasma by means of Atmospheric Pressure Glow plasma and streamer discharge. Geobacillus stearothermophilus was used as biological indicator for disinfection process. The effect of blades after irradiated in plasma was also studied by SEM analysis. It was found that the disinfection process was effective when the cylindrical configuration was applied. Carbon steel blade was also found to be deteriorated after immersed in plasma irradiation. Results indicate that disinfection can be achieved and at the same time deteriorations of the tools were observed.

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Simultaneous measurements for space charge and external current were carried out using a PEA measurement system with an electrometer on the back of a grounding electrode in order to clarify physical situation of a huge packet of positive space charges in LDPE films. A large number of positive charges from semi-conduction anode were accumulated at the interface between LDPE and Al-cathode under 1.5MV/cm of mean applied field and then they finally disappeared. Results of the simultaneous measurements showed that the external current kept a relatively high value during the charge accumulation and it further increased when the charges disappeared. Both the charge dynamics and the external current were restricted by addition of a low-molecular-weight paraffin wax, indicating that the carrier transport was influenced by micro structure of the polymer. Dynamics of residual charges after short-circuiting is also discussed.

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Poly-lactic acid (PLA), a biodegradable plastic, has excellent electrical insulation properties. Being a hard resin, however, PLA is difficult to apply to coated cable. In this study, we blended a plasticizer with PLA to soften it, and examined the effects of the plasticizer on the mechanical and electrical characteristics of PLA. The glass transition temperature (T_g) and the melting point (T_m) had a tendency to decrease with an increase in the amount of plasticizer. With an increase in the amount of plasticizer, the tensile strength had a tendency to decrease and the breaking elongation to increase. As described above, PLA became softer with an increase in the amount of plasticizer. At 25°C, dielectric breakdown strength (E_B) was about 5 MV/cm, irrespective of the presence of the plasticizer; the plasticizer showed almost no effect on E_B. At 80°C, however, E_B had a tendency to increase with an increase in the amount of plasticizer.

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The VHF broadband digital interferometer (DITF) observed two- (2D) and three-dimensional (3D) developments of summer positive cloud-to-ground (CG) lightning flashes with high time resolution. The characteristics of summer positive CG lightning flashes attract a great deal of interest. In the first stage, the in-cloud negative breakdown progresses about 15 km horizontally between 6 and 10 km high. In the next stage, the lightning location and protection system (LLS) detects the positive lightning stroke near the initiation point of the preceding negative breakdown. In the last stage, the negative breakdown runs through the channel of the first negative breakdown. For the positive return stroke to run through the first negative channel, the positive leader, which is not visualized by the DITF, progresses from the initiation point of the first negative channel and touches to the ground. The return stroke current propagates and penetrates in the opposite direction as visualized subsequent negative breakdown. This suggests the negative and positive breakdown progress together. To realize this situation, we conclude the necessity to apply the bi-directional leader progression concept. In a word, we observed bi-directional leaders in summer nature positive CG lightning flashes.

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This paper presents measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two-dimensional vector magnetic property measurement system, and a three-axial strain gauge. In order to know magnetostrictions in arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in thickness direction. In this paper, the three-dimensional magnetostriction in non-oriented and grain-oriented silicon steel sheets are compared.

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The effects of the addition of Y or both Y and Zr to Bi-Mn-Co-Sb-Si-Cr-Ni-added ZnO varistors (the same composition as one of commercial varistors) on the varistor voltage and the tolerance characteristics of electrical degradation were investigated. The tolerance characteristic of electrical degradation was deteriorated rapidly by addition of Y of more than approximately 1 mol%. The degree of deterioration for addition of both Zr and Y was smaller than that for addition of only Y. Moreover, the number of formed spinel (Zn_2.33Sb_0.67O₄)-type particles monotonically increased with increasing amount of Y. On the other hand, the number of formed willemite (Zn₂SiO₄)-type particles decreased by addition of Y of more than approximately 1 mol%. It was suggested that the deterioration of the tolerance characteristics of electrical degradation by the addition of Y is probably caused by an increase in the number of willemite-type particles. Moreover, it was suggested that the reduction in the average ZnO grain size due to the addition of Y was a major factor in the increased varistor voltage and the ZnO grain growth was inhibited by the formation of an unknown compound, of which main ingredients are Y, Zn, and Sb or Y, Zr, Zn, and Sb, after adding Y. The varistor voltage of a varistor with 2 mol% added Y increased by approximately 50% compared to a varistor with no Y added. A ZnO varistor with a varistor voltage of approximately 600 V/mm and excellent tolerance characteristics of electrical degradation was fabricated by adding approximately 1.25 mol% Y and approximately 0.45 mol% Zr to a Bi-Mn-Co-Sb-Si-Cr-Ni-added ZnO varistor.

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It is well known that magnetic properties of electrical steel sheet deteriorate due to stress in process of electrical apparatus. Therefore, it is important to clarify the relationship between the stress and the magnetic property of the electrical steel sheet. We develop new measurement system, which can evaluate the vector magnetic property under the biaxial stress. In this paper, the mechanism to apply the biaxial tensile stress is examined by measuring the principal stress. In addition, the vector magnetic property under the tensile stress of x and y direction is measured with the developed system.

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