Minoru Itagaki

Hysteresis motor using magnetically anisotropic Fe-Cr-Co magnet

For the rotor ring of the hysteresis motor, semihard Alnico magnets have been almost applied until now. However, the hysteresis motor using Alnico magnets has several disadvantages. In order to improve the disadvantages of conventional hysteresis motors, the Fe-Cr-Co magnet steel with magnetic anisotropy is applied for hysteresis rotor ring. Magnetic anisotropy is used to cause large reluctance torque and large hysteresis torque at synchronous pull out. It is made clear from experimental results that these hysteresis motors have large output, high efficiency, and high power factor, to add the reluctance torque to hysteresis torque effectively.

Effects of Electrode Geometry on Breakdown Voltage of a Single-Gap Pseudospark Discharge

The breakdown voltage of a single-gap pseudospark discharge device is measured for a wide range of nitrogen gas pressure, p, and various geometrical dimensions of the electrodes, i.e., anode-cathode gap distance, L, diameter of electrode hole, d, thickness of the electrode, t, and depth of the hollow cathode cavity, h. The breakdown voltage Vs is expressed as an empirical scaling relation, Vs=(197/p3.40L3.41){t(L/d)3.25/[t2(L/d)2+50]1/2}. The breakdown voltage characteristic can be qualitatively explained by the geometrical dependence of the penetrating electric field through electrode holes. The real discharge path length in the pseudospark discharge is estimated.

Influence of Metal Foil Width on Bonding Strength in Capacitor Discharge Ceramics Joining

A capacitor discharge joining technique used to fabricate an alumina-(Al2O3) tile-titanium-foil-Al2O 3-tile joint was investigated to clarify the influence of titanium foil width on bonding strength. A several-kiloampere pulse current was supplied from an 8.28-muF storage capacitor to the titanium foil while simultaneously applying a pressure of 8.3 MPa to the joint. The temperature of the foil rapidly increases owing to ohmic heating with a large current. As a result, the titanium foil melts and vaporizes in a short time. The Al2O3 tiles were successfully bonded when the charged voltage in the capacitor was almost the same value as the energy required for vaporization of the titanium foils. The bonding strength increases with the energy input to the foil. The attainable bonding also increases with increasing shear strength from 150 to 300 kg, which in turn increases with increasing foil width from 1 to 7.5 mm for a 50-mum-thick foil. The main reason of the shear-strength improvement was the increase of the joined area that was measured with image analysis of the joint surface

Bonding strength of alumina tiles joined using capacitor discharge technique

Abstract A capacitor discharge joining technique used to fabricate alumina–titanium interlayer–alumina joint was investigated to clarify the influence of an input energy and a compressing pressure on bonding strength. A high-current pulse was generated using 8.3-μF capacitor and an Ignitron closing switch. The alumina tiles were successfully bonded when the input energy is larger than the vaporization energy of a titanium foil used as an interlayer. The bonding strength increases with increasing the input energy into the foil. The bonding strength also increases from 600 to 1600 N with increasing compressing pressure of the alumina tiles from 1.1 to 8.3 MPa at 0.25-cm width of the titanium foil.

Production of Plasma Jet Based on High-Current Pseudo-Spark Discharge

A plasma jet based on a high-current pseudo-spark discharge has been developed. A pseudo-spark discharge (PSD) is a high-current glow-like discharge, which is formed on the left side of the minimum of the Paschen curve. Although the discharge current exceeds several tens of kiloamperes, the discharge retains the glow mode because of the hollow cathode effect. The PSD is formed with a large number of arc channels, which are usually narrow. Consequently, the PSD has a large cross section. In this study, the PSD anode has a hole with a larger diameter than that of the cathode in order to generate a plasma jet. The plasma is effectively accelerated by the electromagnetic force due to the modified shape of electrodes. The electron temperature and density of the plasma jet were measured by a double probe technique. At the discharge current of 10 kA, the temperature of the plasma jet reached approximately 1.9 eV and the density was of the order of 1014 cm-3 at the distance of 72 mm from the anode.

Ceramics joining using explosive metal foil

A capacitor discharge joining technique used to fabricate alumina (A12O3) tile - titanium foil - A12O3 tile joint was investigated with focusing to increase the bonding strength. Several kAs pulse current was supplied from 8.28 muF storage capacitor to the 50 mum thickness titanium foil which was sandwiched between the A12O3 tiles with various pressures. The temperature of the foil was rapidly increased owing to ohmic heating with the large current, and then the foil was liquefied and vaporized. The A12O3 tiles were successfully bonded when the input energy to the titanium foil was higher than the energy required for the foil vaporization. However, the foil explosion cracked the tiles when the input energy exceeds a critical value. Increasing the circuit inductance from 1.13 muH to 64.8 muH, the critical energy of tile cracking increases from 160 J to 507 J. The maximum bonding strength of 3200 N was obtained when the circuit inductance was 21.8 muH. An investigation of the interfacial structure of the joints using electron probe microanalysis revealed that distinct reaction areas existed in the interlayer.

GAMMA-RAY DETECTION AND SURFACE ANALYSIS ON A PALLADIUM ELECTRODE IN A DC GLOW-LIKE DISCHARGE EXPERIMENT

We performed glow-like discharge experiments using deuterated palladium cathode in deuterium atmosphere to investigate the possibility of inducing low-energy nuclear reaction. Anomalous gamma ray emissions in the 80 - 230keV region were sometimes observed. It was assumed that a nuclear reaction took place during the experiment, producing short-lived radioisotopes, and these radioisotopes emitted the gamma rays in their decay processes. Elements and their isotopic abundance on the palladium cathodes were investigated by time-of-flight secondary ion mass spectrometry to find evidence of a nuclear reaction.

Effects of Electrode Geometry and Gas Pressure on Breakdown Voltage of a Pseudospark Discharge

The breakdown voltage of a pseudospark discharge device is measured for a wide range of nitrogen gas pressure, p, and various geometrical dimensions of the electrodes, i.e., anode-cathode gap distance, L, diameter of hole, d, thickness of the electrode, t, and depth of hollow cathode cavity, h. The empirical scaling relation obtained is expressed as V s=3.06×102p-3.37L-1.16d-2.25. This relation shows that the breakdown voltage is a function of p3.37, as opposed to the p2L or pL dependence. The geometrical effect of the electrodes on the breakdown voltage characteristic can be explained by introducing the effective discharge length, which is defined as the width of the spatial profile of the calculated electric field.

Compact system for ceramics joining using explosive interlayer metal foil

A capacitor discharge joining technique used to fabricate alumina (Al/sub 2/O/sub 3/) tile-titanium foil-Al/sub 2/O/sub 3/ tile joint was investigated to optimize the energy injected into the foil. The large current was supplied to the foil sandwiched with Al/sub 2/O/sub 3/ tiles using storage capacitor which was charged up to several kVs. The Al/sub 2/O/sub 3/ tiles were successfully bonded when the charged voltage in the capacitor was same value with the energy required for vaporization of the titanium foils. The bonding strength increases with energy input to the foil. The bonding also increases from 600 to 1250 N shear strength with increasing compression stress on the Al/sub 2/O/sub 3/ tiles from 1.1 to 4.2 MPa at use of 5 mm width titanium foil as the interlayer. An investigation of the interfacial structure of the joints using electron probe micro-analysis revealed that distinct reaction areas existed in the interlayers.

Temperature and density measurement by using a double probe of pseudospark discharge plasma jet

Summary form only given, as follows. We have been doing research on the new type of plasma jet. Plasma jet is device that makes high temperature and high-density plasma flow at high speed In this research, we investigate the application of pseudospark discharge (PSD) to high power plasma jet in particular. PSD is low-pressure gas discharge. Electrodes have a hole on the center axis of parallel plane electrode and cathode has cylindrical hollow cavity behind the circular hole. Characteristics of PSD axe as follows. When discharge is formed by using this hollow cathode and on the condition in the low pressure region on the left hand side of the lowest point of a Paschens curve, discharge current becomes large because breakdown voltage is high. Moreover in this low-pressure region, since discharge dose not formed along the short discharge path but the long one, discharge path passes through the center hole from reverse side of electrodes. As a result, the points of the discharge to the cathode spread to the back surface in the hollow cathode. Due to the hollow cathode effect, discharge is kept on the glow mode at the high current discharge, resulting that damage on electrode will be small. To spout the high temperature and high-density plasma in PSD, geometric structure of electrode of PSD is modified. Due to the modification of the PSD electrodes, plasma is spouted from anode hole by the power of the Lorentz power.