Seizo Furuya

Simulation of nonlinear coaxial line using ferrite beads

A ferrite sharpener is a nonlinear coaxial line using ferrite beads which produces high-voltage, high-dV/dt pulses. We examined the characteristics of ferrite sharpeners experimentally when the following parameters were changed independently: (1) magnetic field bias, (2) amplitude of input voltage pulse, (3) rise time of input voltage pulse and (4) sharpener length. Then we made a simulation of the ferrite sharpener and compared the predictions with the experimental results in detail to analyze the characteristics of the sharpener. The predictions of the simulation are found to be in good agreement with the experimental results, thus it is confirmed that the simulation is a powerful tool for designing the sharpener.

Characteristics of Multichannel Arc Gap

The characteristics of multichannel arc gap are investigated experimentally. The gap comprises 12 or 24 steel needle electrodes and a brass rod electrode. We examined the characteristics of the number of arc channels when the parameters below were changed: (a) rising rate of voltage pulse applied to the gap (b) length of feeders which transmit voltage pulse from the ferrite sharpener to each needle electrode (c) gap length (d) kind and pressure of inter-gap gas (e) with and without ultraviolet irradiation.

Rail Gap Switch Using Porous Metal as Electrode

For multichannel gap switches, the shorter the formative and statistical time lags of each gap, the larger the number of arc channels. As we examined the breakdown characteristics of a sphere/plane gap using a mirror-finished brass plate and a porous metal as plane electrodes, we confirmed that formative and statistical time lags decrease when porous metals are used as a discharge electrode, so we expect that the number of arc channels increases when porous metal is used as one of the electrodes of a rail gap. We compared experimental results to confirm this. As a result, in the case of a gap length of 1 mm, the number of arc channels increases when porous metal is used as an electrode.

The Fundamental Properties of Disk-Shaped MHD Accelerator

Although the Disk-shaped MHD Accelerator has seldom been studying at anywhere, it has many predictable merits. The purpose of this paper is to verify and analyze the performances of the Disk-shaped MHD Accelerator and to confirm its advantages. From the present results, shorter MHD channel, in particular, the gas velocity of channel length of 4.5 cm showed the highest performance and the thermal loss also decreased to about 9.36 %. Despite MHD compression appeared, we have found that these performances could be improved by increasing the channel height. Nomenclature u = Gas velocity, m/s E = Electric field, V/m j = Current density, A/m 2 σ = Electrical conductivity, S/m β = Hall Parameter ρ = Fluid density, kg/m 3

Application to Marine Paint Adhesion Improvement by Atmospheric Pressure Discharge Plasma

The paint at the bottom of the ships has long period history by using many traditional methods and various artifices. For instant, artifices of the tar, mercury, and copper were used. Afterwards, the development of ships bottom antifouling paint was also actively carried out by the composition of various chemical substances. The possibility of the adhesive strength improvement was studied by the application of atmospheric pressure discharge plasma. It’s expected that the adhesion properties don’t sufficient to fulfill its function because of the interrupting of substances existed at the position between the coating and the coated surface. From this point of view, it is questioned whether or not this could be able to fulfill the function by using the application of atmospheric pressure discharge plasma. In the present study, the following conclusions were drawn: 1) It was able to confirm the effect of the plasma treatment. 2) It is necessary to carry out the more detailed examination.

Breakdown Characteristics of Porous Metals

We have investigated the breakdown characteristics of porous metals as discharge electrodes, for applications to multichannel arc gaps. We examined a single-needle/plane gap as a nonuniform electric field gap and a sphere/plane gap as a uniform one using a mirror-finished brass plate and a porous metal as plane electrodes. First, we examined the breakdown characteristics of the single-needle/plane gap. The characteristics we investigated are the DC flashover voltage of the gap, and the formative and statistical time lags of flashover when a flat-top nanosecond pulse was applied to the gap. We predicted that the formative and statistical time lags decrease when porous metals are used as a discharge electrode instead of a mirror-finished electrode. However, contrary to our prediction, a significant difference was not observed in the needle/plane experiments. Then we examined a sphere/plane gap. In this case, a significant difference was observed. Therefore, we confirm that the porous metal is a suitable electrode material for the rail gap.

Surge Impedance of Nonlinear Coaxial Line Using Ferrite Beads

A ferrite sharpener is a nonlinear coaxial line using ferrite beads, which produces high-voltage, high-dV/dt pulses. Although the surge impedance of sharpener in the region where the ferrite is generally considered to be saturated is very important in practical applications, surge impedance and relative permeability in the region have not been clarified so far. Therefore, using three evaluation methods, we attempted to clarify the surge impedance and relative permeability of the ferrite sharpener in the region where the ferrite is generally considered to be saturated when the following parameters are changed: (1) magnetic field bias and (2) terminating resistance. We confirmed that different values of surge impedance and relative permeability were obtained in the experiments using the three evaluation methods. Also, we found that the simulation could reproduce a tendency similar to the experimental results.

Comparative Study Inflow and Outflow of Disk MHD Accelerators

Although Disk MHD Accelerator has seldom been studying at anywhere, it has many predictable merits and it is able to flow to Inflow and Outflow direction. The purpose of this paper is to compare with the performances of Inflow and Outflow Disk MHD Accelerators and to confirm their advantages. From the present results, Inflow of 1MW case, thermal loss was slightly more than that of Outflow case. However it was shown that input current was able to reduce 15% in order to acquire same performances. And achieved the gas velocities at the exit was about 3200m/s for both cases of Inflow and Outflow. Nomenclature u = gas velocity, m/s E = electric field, V/m j = current density, A/m 2 σ = electrical conductivity, S/m β = Hall parameter ρ = gas density, kg/m 3