Masayoshi Nagata

Application of Finite Element Method to Analysis of Induced Current Densities Inside Human Model Exposed to 60-Hz Electric Field

The finite eleiment method(FEM) has been applied bt the analysis of the indiced current densities inside axisyrmtrical h. buman medels. It is assumed in the calculations that those models are made of a biological organism whose corndctivity and permittivity are on the sare order as those of humah body tissues. In the experiments, they are made of wood and insulating material covered with aluminium foil.The finite eleiment method(FEM) has been applied bt the analysis of the indiced current densities inside axisyrmtrical h. buman medels. It is assumed in the calculations that those models are made of a biological organism whose corndctivity and permittivity are on the sare order as those of humah body tissues. In the experiments, they are made of wood and insulating material covered with aluminium foil.

Mechanism of unstable behavior of parallel fuses as an opening switch

Fuses, when used as an opening switch, are often connected in parallel to handle large energies. Here, an experiment using two fuses is carried out to understand the behavior of parallel fuses clearly. The waveforms of current flowing through each fuse are different. Unstable behaviors, in which the difference of the currents flowing into the two fuses increases, are observed, and the condition and probability of appearance of the unstable behavior are discussed. The cause of the unstable behavior is that the rate of change of fuse-resistivity with input energy is different depending on the state of the wire. Any differences in initial dimensions of the parallel fuses or any kind of disturbance during the fuse action could immediately trigger off the unstable behavior. >

Unstable Behavior in Exploding Wire Array

Although considerable investigations have been reported on z-pinches to achieve nuclear fusion, little attention has been given from the point of view of how a wire array consisting of many parallel wires explodes. In this paper, the unstable behavior of a wire array is investigated. The instability occurs by the deviation from the homogeneous current flow through many wires. The expressions discriminating between the stability and the instability are derived. Using the resistivity variation of the wire, the unstable behavior during the explosion of the wires is predicted and the strength of the tendency to an unstable behavior is evaluated. The unstable region on a map of resistivities is independent of the wire number while the strength of the tendency to the unstable behavior depends on the wire number.

Effects of wire shape on unstable behavior of parallel fuses [in IES pulsed power generators]

The cause of unstable behavior of a parallel fuse used as an opening switch is experimentally investigated by changing the shape of one of the parallel fuses. When instability exists in the behavior of parallel fuses, flaws on the surface of a wire are a critical factor which triggers the unstable behavior.

High voltage generation from inductive pulsed power generator using a Marx circuit and an exploding wire

High voltage output up to 800 kV with voltage risetimes of 15 to 40 ns is successfully generated by a compact pulsed power generator (60×120×150 cm3) with an inductive energy storage system. This pulsed power generator consists of a Marx circuit, an inductor, and a thin and long exploding copper wire. The circuit parameters including an exploding wire are optimized for a high voltage generation, avoiding a re-strike of the wire. It is shown that the ratio of the energy in a storage inductor at the beginning of wire vaporization on the energy consumed during wire vaporization is essential in the production of a high voltage.

Numerical analysis of multichannel gap switch in pulsed power generators

It is difficult to ascertain the detail behavior of multichannel gap switches from experimental studies only. The behavior of multichannel gap switches is investigated by a numerical analysis. The waveforms of the output voltage are numerically obtained and the statistical characteristics of a pulsed power switch are evaluated. The numerical analysis is useful for designing the switches and to investigate the breakdown phenomena.

Compact pulsed power generator using a Marx circuit and an optimized exploding wire

The pulsed power generator with an inductive energy storage system is investigated as a driver for a high power microwave source. The length and diameter of an exploding wire as an opening switch are optimized by numerical analysis taking into account the stored energy in an inductor at the beginning of wire vaporization and energy consumed for wire vaporization. Following the results of numerical analysis, a Marx circuit and a thin and long exploding wire are adopted for the developed inductive pulsed power generator. The output voltage up to 800 kV and the voltage risetime of 15 ns were obtained.

Generation of ozone by ns-width pulsed power

The demand of ozone will be increasing for wholesome and environment-conscious sterilizations. The generation of ozone using the pulsed power discharge will apply electron accelerations around the head of streamer discharge principally. The breakdown in reactor often limits the efficient generation. Therefore, the pulse shape should be controlled for dimension of the reactor. It is clear that a pulse shortening is one of effective approaches. Pulsed power voltage with ns-width applies for ozone generation. The effects, on concentration and efficiency of generation, of pulse shape, repetition rate of pulse, flow rate of oxygen gas, and dimension and configuration of reactor, are discussed. The dimension and configuration of the reactor are optimized for the pulse width.

Unstable behavior in wire array discharges and effect of wire shape

Z pinches using wire arrays have been investigated to achieve nuclear fusion. Suppression of instabilities in Z-pinch plasma is one of extremely important tasks. The explosions of the wires in an array do not simultaneously proceed and the currents through wires do not balance, and then an unstable behavior of current glows in wire explosion. As a result, nonuniform distribution of wire currents will cause azimuthal Rayleigh-Taylor instability of Z-pinch plasmas. The inhomogeneous deviation of wire array current is induced by inconstant increase in resistance of wire material, e.g., rapid increase in the evaporation. Here, the effect of the wire shape, e.g., scratches on the wires and/or dimensional process error of wires, on the unstable behavior of discharging current is numerically analyzed. The non-uniformity of wire shape causes the local asynchronous heating and will trigger the unstable behavior. The inductance of wire and the fast rise of generator current can restrain the inhomogeneous deviation of wire array current.

Compact pulsed power generator using a Marx circuit and a exploding wire

Summary form only given. A compact pulsed power generator with an inductive energy storage system is investigated. The energy transfer ratio into the load is considered by generic calculations, which confirmed the need of a high fuse opening resistance. Long and thin wires are suitable to generate the high voltage as a fuse opening switch. The generator circuit parameters are optimized by numerical analysis, taking into account the stored energy in the inductor at the beginning of wire vaporization and energy consumed during wire vaporization. The generator is designed for high voltage applications. Although the output current is low because of the low initial charging energy, the voltage multiplication factor is, accordingly, high. The inductive pulsed power generator consists of a Marx circuit, an inductor, and a thin and long exploding copper wire. An output voltage up to 800 kV and voltage risetimes of 15 to 40 ns are experimentally obtained.