Seiji Mukaigawa

Production of atmospheric-pressure glow discharge in nitrogen using needle-array electrode

An atmospheric pressure glow discharge was generated using a needle-array electrode in nitrogen, and the voltage–current characteristics of the glow discharge were obtained in a range from 1 mA to 60 A. A pulsed high voltage with short rise time under 10 ns was employed to generate streamer discharges simultaneously at all needle tips. The large number of streamer discharges prevented the glow-to-arc transition caused by inhomogeneous thermalization. Semiconductor opening switch diodes were employed as an opening switch to shorten the rise time. The glow voltage was almost constant until the discharge current became 0.3 A, whereas the voltage increased with the current higher than 0.3 A. Electron density and temperature in a positive column of the glow discharge at 60 A were obtained to 1.4×1012cm−3 and 1.3 eV from calculation based on nitrogen swarm data.An atmospheric pressure glow discharge was generated using a needle-array electrode in nitrogen, and the voltage–current characteristics of the glow discharge were obtained in a range from 1 mA to 60 A. A pulsed high voltage with short rise time under 10 ns was employed to generate streamer discharges simultaneously at all needle tips. The large number of streamer discharges prevented the glow-to-arc transition caused by inhomogeneous thermalization. Semiconductor opening switch diodes were employed as an opening switch to shorten the rise time. The glow voltage was almost constant until the discharge current became 0.3 A, whereas the voltage increased with the current higher than 0.3 A. Electron density and temperature in a positive column of the glow discharge at 60 A were obtained to 1.4×1012cm−3 and 1.3 eV from calculation based on nitrogen swarm data.

Purification of High-Conductivity Water Using Gas–Liquid Phase Discharge Reactor

Water purification by streamer discharge using pulsed-power generator under a high-conductivity water containing pollutants has been investigated. A gas-liquid separated reactor was developed to treat highly conductive solution. A wire electrode was placed in the gas phase and a plane electrode was immersed in the water. A pulsed high voltage generated by six stacked Blumlein lines was applied to the wire electrode to generate streamer discharge in the gas phase, which propagated into the air bubble injected into the water. Indigo carmine solution was employed as a specimen. Natrium chloride was used to adjust the solution conductivity in the range from 10 to 30 000 S/cm. A solution with 30 000- S/cm conductivity was successfully decolorized with energy efficiency of 75 mg/Wh. Some species of gas such as air, oxygen, nitrogen, and argon were injected to clarify dominant reactions of the decolorization. The result showed that the ozone produced by gas-phase discharges mainly contributed to the decolorization of the solution. The decolorization rate depended on the chloride ion supplied from the natrium chloride by scavenging of hydroxyl radical and on the copper ion eluted from the plane electrode by redox reactions such as Fenton reactions.

Ion extraction from carbon shunting arc plasma

The ion current characteristics of the shunting arc discharge are described in this letter. A carbon rod with 2 mm diameter and 40 mm length was employed for arc generation. The combination of the shunting arc and the negative pulse voltage applied to target is promising for plasma-based ion implantation and deposition for metallic or semimetallic three-dimensional materials. The delay time, which is defined as the time between the start of the arc current and applying the pulse voltage, was varied. The ions are extracted from the shunting arc plasma by applying a pulsed bias voltage to a target set nearby the arc source. The arc current lasts 40 μs, of which peak is 1.7 kA. The extracted target current has a sharp peak at the initial stage, followed by a stationary state. The stationary current decreases with increasing the delay time and increases with increasing the bias voltage. Under the assumption of a collisionless ion sheath, the plasma density was estimated. At the boundary between the ion sheath...

Energy Efficiency of Corona Discharge Reactor Driven by Inductive Energy Storage System Pulsed Power Generator

Characteristics of a pulse corona reactor driven by an inductive energy storage (IES) pulsed power generator are described in this paper with focusing on the influence of streamer-to-glow transition on NO removal efficiency. A pulsed high voltage with a short rise time of under 30 ns is employed to generate streamer discharges homogeneously in whole the discharge region. Fast recovery diodes are used as semiconductor opening switch (SOS) to shorten the rise time. The various resistors are employed as dummy load to clarify a suitable circuit parameter such as the capacitance of a primary energy storage capacitor and/or the inductance of a secondary energy storage inductor. The energy transfer efficiency of the pulsed power generator has a maximum value of 50% at 714 Omega dummy load resistance. A co-axial cylinder type discharge chamber was used as the corona discharge plasma reactor driven by the IES pulsed power generator. The pulsed power generator supplies 30 kV pulse with 300 pps repetition rate. The co-axial cylinder plasma reactor consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm length. NO removal from the simulated diesel engine exhaust gas (N2:O2=9:1, Initial NO concentration=200 ppm) increased with input energy into the reactor. The energy efficiency for NO removal was obtained to be 25 g/kWh at 30 % removal in gas flow rate of 2 L/min. However, the energy efficiency decreased to 5 g/kWh with increasing capacitance of the primary capacitor from several hundreds pF to several nF. This decrease was caused by a streamer-to-glow transition. The efficiency was affected by oxygen concentration in the gas mixture.

Measurement of Copper Drift in Methylsilsesquiazane-Methylsilsesquioxane Dielectric Films

Measurement of Cu drifts in methylsilsesquiazane-methylsilsesquioxane dielectric films in the presence of an electric field was conducted using bias-temperature stress (BTS) and capacitor-voltage (CV) analysis as well as time dependent dielectric breakdown (TDDB) stress. The amount of Cu ions in the dielectric films can be estimated making use of the flatband voltage shift ΔVFB from the BTS. Comparing the flatband voltage measured by CV analysis with the leakage current integrated over time, it is found that the main content of the leakage current during BTS is ionic current that can be attributed to the drift of Cu and mobile ions. The Cu ions cause the leakage current during TDDB stress to increase. The drift rate of Cu in methylsilsesquioxane is lower than the reported values in polyarylene ether (PAE) and fluorinated polyimide (FPI), and larger than that in plasma enhanced chemical vapor deposition (PECVD)-SiON.

Characteristics of shunting arc discharge for carbon ion source

Abstract The criteria of initial resistance of carbon rod for shunting arc ignition are described in this article. The five different resistances were used. The rods are 40 mm in length and 2 mm in diameter. The carbon rod was set in the vacuum and was initially heated up with a pulsed current supplied by a charged capacitor with a capacitance of 20 μF, followed by a self-ignition. The heating energy is almost independent of the charging voltage of the capacitor. The heating energy increases with decreasing the rod resistance, whereas the energy deposited in the plasma and the utilizing efficiency of the charged energy in the capacitor decreases.

Production of Pulse Glow Discharge in Atmospheric Pressure Nitrogen Using Needle-Array Electrode

An atmospheric pressure glow discharge was generated using a needle-array electrode in nitrogen. A pulsed high voltage with short rise time under 10 ns was employed to generate streamer discharges simultaneously at all needle tips. The large number of streamer discharges prevented glow-to-arc transition caused by inhomogeneous thermalization. Semiconductor opening switch (SOS) diodes were employed as an opening switch to shorten the rise time. The glow current was drastically decreased by eliminating the SOS diode, in which case the charging voltage was directly applied to the electrode. Spatial- and time-averaged electron densities in a positive column were estimated from calculations based on nitrogen swarm data. The density was estimated to be 1.8×1011 cm-3, which was much larger than 9.7×109 cm-3 in the case without the SOS diode.

Duty Factor Effect on Ozone Production Using Dielectric Barrier Discharge Reactor Driven by IGBT Pulse Modulator

Abstract An ozone production using pulse voltage driven dielectric barrier discharge (DBD) reactor was investigated experimentally to clarify an influence of a duty factor of applied pulse voltage on ozone yield. A square of 10 kV applied voltage was generated using a pulse modulator. Insulated gate bipolar transistor (IGBT) switches were employed to generate the square pulse with 1 kHz in pulse repetition rate. Duty factor of the pulse voltage was controlled in range from 10 to 80% by timing of a gate signal to the IGBT switches. The output voltages of the power supply were applied to a multipoint electrode type DBD reactor in order to operate at low applied voltage. The ozone yield was obtained to be around 100 g/kWh at several thousands ppm ozone production in pure oxygen circumstance at 5 L/min. gas flow. The ozone yield decreased with increasing ozone concentration and was almost independent of the duty factor of square applied voltage under the present experimental condition. Power loss consumed in the pulse modulator was successfully reduced by decreasing duty factor of the output voltage without decrease of the ozone production.

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

Ion Extraction From Magnetically Driven Carbon Shunting Arc Plasma

Shunting arc discharge is a pulsed plasma source of metals and semimetal materials and is ignited without any trigger sources at a wide range of gas pressures, from vacuum to atmospheric pressure under identical discharge conditions. In this paper, an ion extraction from magnetically driven carbon shunting arc discharge and a criterion of the arc ignition are described. A carbon rod with a diameter of 2 mm and a length of 40 mm was employed for arc ignition. The carbon rod was set in the vacuum and was initially heated up with a pulsed current supplied by a charged capacitor with a capacitance of 20 muF, followed by self-ignition. The heating energy is almost independent of the charging voltage of the capacitor and changes with the rod position on the rail. The ions are extracted from the arc plasma by applying a negative pulse voltage to a target. The target current has a sharp peak at the initial stage, followed by a stationary state. The stationary current decreases with increasing the distance to the target from a muzzle of the shunting arc plasma gun. Under the assumption of a collisionless ion sheath, the ion density at a 20-mm target-muzzle distance is estimated as 1times10 8 and 2times107 cm-3 for the delay times of 250 and 1000 mus, respectively. The density at a 250-mus delay time decreases from 1times108 to 0.8times108 cm-3 by increasing the distance from 20 to 140 mm. The ion density increases as the charging voltage of the capacitor for arc generation is increased