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High-density nitrogen plasma was produced using a high-power pulsed power modulator to sputter titanium targets for the preparation of titanium nitride film. The high-power pulsed sputtering discharge unit consisted of two targets facing each other with the same electrical potential. The titanium target plates were used as target materials with dimensions of 60 mm length, 20 mm height, and 5 mm thickness. The gap length was set to be 10 mm. The magnetic field was created with a permanent magnet array behind the targets. The magnetic field strength at the gap between the target plates was 70 mT. The electrons were trapped by the magnetic and electric fields to enhance the ionization in the gap. The nitrogen and argon gases were injected into the chamber with 4 Pa gas pressure. The applied voltage to the target plates had an amplitude from −600 V to −1000 V with 600 μs in pulse width. The target current was approximately 10 A with the consumed power of 13 kW. The discharge sustaining voltage was almost constant and independent of the applied voltage, in the same manner as the conventional normal glow discharge. The ion density and electron temperature at the surface of the ionization region were obtained as 1.7 × 1019 m−3 and 3.4 eV, respectively, by the double probe measurements. The vertical distribution of ion density and electron temperature ranged from 1.1 × 1017 m−3 (at 6 cm from the target edge) to 1.7 × 1019 m−3 and from 2.4 eV (at 6 cm from the target edge) to 3.4 eV, respectively. From the emission spectra, the intensities of titanium atoms (Ti I), titanium ions (Ti II), and nitrogen ions (N2+) increased with increasing input power. However, the intensities ratio of Ti II to Ti I was not affected by the intensities from N2+. [ABSTRACT FROM AUTHOR]

The recent trend in thin film deposition is to prepare ceramic films capable of enduring violent environments, such as corrosive pollutant gases with high temperatures. Different kinds of plasma species existing in the same space are advantageous in order to facilitate a reactive deposition between the gaseous and metallic species. In this paper, we study a carbon shunting arc that triggers a gas discharge using a positively biased electrode. An electrode with a positive voltage of up to 500 V was set nearby the carbon shunting arc source. Nitrogen, methane, or argon was used as an ambient gas. The induced plasma was generated with a time delay from the moment of the generation of the shunting arc. The electrical and optical characteristics of the discharge were studied. The onset time of the induced plasma as a function of the ambient gas pressure has a Paschen-like V-shaped characteristic. The generated plasma includes both carbon and gaseous species. At the surface of the positively biased electrode, both spectrum emissions of carbon and gaseous species are observed, by which the plasma is confirmed to be mixed. This is based on the spectrum observation in addition to the change in the color of the plasma. A shunting arc is an easy method used in generating a hybrid plasma consisting of metallic (including carbon) and gaseous species. This method promises to efficiently prepare ceramic films by reactive deposition. This method is simple, and both plasma species, i.e., those of metal and gas particles, are easily mixed. The carbon shunting arc plasma plays both the roles of supplying the carbon species and triggering a gaseous plasma as an induced plasma. Index Terms--Arc discharge, emission spectrum, hybrid plasma, Paschen's law, shunting arc discharge.

A capacitor discharge joining technique used to fabricate an alumina-([Al.sub.2][O.sub.3]) tile-titanium-foil-[Al.sub.2][O.sub.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-[micro]F 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 [Al.sub.2][O.sub.3] 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-[micro]m-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. Index Terms--Alumina, ceramics joining, exploding, foil, pulse current, titanium.

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 [micro]F, 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 1 x [10.sup.8] and 2 x [l0.sup.7] [cm.sup.-3] for the delay times of 250 and 1000 [micro]s, respectively. The density at a 250-[micro]s delay time decreases from 1 x [10.sup.8] to 0.8 x 108 [cm.sup.-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. Index Terms--Carbon, ion current, ion extraction, magnetically driven, plasma-based ion implantation (PBII), shunting arc.

Ceramic dielectric material pellet shape effects on the performance of perfluoroethane ([C.sub.2][F.sub.6]) gas removal from simulated semiconductor process gas using packed-bed reactor' are experimentally investigated. The bench-scale cylindrical shaped (plasma part: 30-mm inner diameter and 20-mm length) plasma reactor consists of two metal mesh electrodes packed with spherical, cylindrical, or hollow cylindrical shaped ferro-electric pellets with various dielectric constants. The 60-Hz ac high voltage was applied to the mesh electrode. The 3000 ppm [C.sub.2][F.sub.6] gas diluted with nitrogen was used as simulated gas with flow rate of 30 mL/min. The [C.sub.2][F.sub.6] concentration was monitored using Fourier transform Infrared absorption spectroscopy measurements. The results show that the packed-bed plasma reactor with the hollow cylindrical-shaped pellets removed the [C.sub.2][F.sub.6] gas with energy efficiency of 3.7 g/kWh. This value was almost 1.5 times higher than the efficiency 2.5 g/kWh in case of the spherical pellets. The discharge characteristics in the reactor were also changed with the pellet shape. The discharge onset voltage decreases by changing the pellets shape from sphere to hollow cylinder. The quantity of charges accumulated with the microdischarge currents increases by changing the pellet shape from sphere to hollow cylinder in spite of fact that the energy consumed in the reactor decreases. Index Terms--[C.sub.2][F.sub.6], dielectric barrier discharge, ferro-electric, nonthermal plasma, packed bed, partial discharge, PFCs, semiconductor process flue gas.

In order to validate a non-thermal plasma model using nitrogen in a ferro-electric packed-bed reactor, the number density of the excited nitrogen molecules has been investigated by spectroscopic measurements. Experiments were conducted at applied voltages from 0 to 20 kV, 60 Hz and gas flow rates from 1 to 5 L/min in pure nitrogen gas. The results show that the number density for excited [N.sub.2] molecules increases with increasing applied voltage and dielectric constant and agrees qualitatively with the numerical modeling results at lower applied voltage. The vibrational temperature of the [C.sup.3][II.sub.u] (v') state of [N.sub.2] has been calculated from the light intensity emitted by the 2nd positive band. The vibrational temperature decreases with increasing gas flow rate and no significant effects of the applied voltage and dielectric constant were observed. Index Terms--Packed bed, non-thermal plasma, nitrogen, partial discharge, ferro-electric, perfluorocarbons, volatile organic compounds, dielectric barrier discharge.

Numerical modelling of ferro-electric packed bed non-thermal plasma reactor has been conducted to predict plasma parameters in a pure nitrogen environment. Simplified time averaged one-dimensional physical model based on Poisson's equation for electric field and transport equation for electrons was developed. The mean electron energy was obtained by a swarm relationship from calculated electric field profiles and plasma neutral conditions. For chemical model, [N.sup.+], [N.sub.2.sup.+],[N.sub.3.sup.+],[N.sub.4.sup.+], N*, [N.sub.2]* and electron were considered where N* and [N.sub.2]* are the total excited atoms and molecules, respectively. The results show that all the plasma parameters increase with increasing applied ac voltage and pellet dielectric constant. The numerical results also show that the dominant ion is [N.sub.4.sup.+] and the metastable molecule density is much higher than radical and the electron densities at atmospheric gas pressure. Index Terms--Packed bed, dielectric barrier discharge, non-thermal plasma, nitrogen, partial discharge, ferro-electric, PFCs.

An experimental study on nitrogen oxides (NOx) removal from a simulated diesel engine exhaust gas was carried out in geometry of various electrodes for dielectric barrier discharge reactor to improve the removal efficiency. The electrodes employed in the experiment were a plane, a trench, and a multipoint geometry. The right-pyramids, which were used as multipoint, had 45[degrees] tip angle and a height of 1-5 mm. The multipoint electrodes have 528-5000 pyramids in an area of 132 [cm.sup.2] (22 x 6 cm). The trench electrode has knife-edge rails with 5-mm height and 45[degrees] tip angle. The alumina dielectric barrier coated plane electrode was used as a high-voltage electrode, to which a sinusoidal high voltage was applied with frequency of several tens kilohertz. The [N.sub.2] : [O.sub.2] : 9 : 1 mixed gas containing 200-ppm NO was used as simulated gas with gas flow rate of 5 L/min. NO removals in case of the plane and the trench electrodes were lower than that in case of multipoint one. NO removal yield drastically decreases with increasing the number of pyramids on the electrode. NO removal efficiency was almost independent of the pyramid projection height under our experimental condition. Index Terms--Dielectric barrier discharge (DBD), multipoint, nonthermal plasma, NOx removal.

An experimental study on the removal of N[O.sub.x] in flue gas has been carried out using plasma chemical reactions in a dielectric barrier discharge. A multipoint-to-plane geometry is used for electrode to lower the operating voltage. The effect of the multipoint electrode configuration on the characteristics of a discharge and N[O.sub.x] removal has been investigated. Plasma is produced in a narrow gap by a dielectric barrier discharge at low applied voltage with sinusoidal waveform of 2-3 kV rms Specific energy to reduce NO is 63 eV. Electric energy consumed in the discharge increases linearly with area of multipoint electrode, and is approximately 1 [Mu]J/point at 2.7 kV. In regard to the multipoint electrode configuration, the consumed energy can be increased by making angle of the point small. However, the energy efficiency of NO removal becomes small if the point angle is small. It also decreases with reducing the number of points per unit area. In regard to treatment of exhaust gas from a diesel engine generator (20 kVA), NO can be almost completely depleted by the multipoint-to-plane barrier discharge for electrical load below 35% of the rated output. Index Terms - Barrier discharge, chemical reaction, flue gas treatment, low temperature plasma, N[O.sub.x], N[O.sub.x] reduction, silent discharge, streamer.

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We investigated the application of the dielectric barrier discharge process to the removal of NOx from exhaust gas of a 20-kVA diesel engine generator. A multipoint-to-plane geometry was used as an electrode for low-voltage operation. A pyrex glass plate with a 2-mm thickness was put on the plane electrode as the dielectric barrier. The reactor consists of six discharge cells, with each cell consisting of five stacked multipoint-to-plane electrodes where the exhaust gas flows with a high flow rate. The exhaust gas was successfully treated at a flow rate of 1.2 [m.sup.3]/min. In order to produce repetitive high-voltage pulse, we made two switching electronic devices, an insulated gate bipolar transistor (IGBT), and a pulse transformer. This pulse modulator supplied the voltage with peak value of 10 kV and repetition rate of 2.5 kp/s (pulses per second) to the reactor. The energy transfer efficiency of the pulse modulator is 65% at 300 W of the power consumed in the reactor. The NOx (NO + [NO.sub.2]) in the exhaust gas was reduced by 35 ppm with an electrical efficiency of 32 g/kWh. Index Terms--Barrier discharge, diesel engine, multipoint-to-plane, nonthermal plasma, NOx, pollutant control technology, pulse modulator.

Symmetric self-organized discharge filaments have been observed in the 140-[micro]m microgap dielectric-barrier discharge between two parallel glass plates. With increasing voltage, the number of filaments increases, and the distance between the filaments decreases. The gas flow velocity affects the arrangement of the filaments. The homogeneous structure appears around the upstream area at high flow velocity, and the homogeneous area spreads with increasing flow velocity. Index Terms--Atmospheric pressure, barrier discharge, gas flow, microplasma, self-organization.

This paper presents the images of a long gap discharge induced by a water jet. Spherical metal balls of 5-cm diameter were used as high-voltage, ground, and guiding electrodes. The distance between the high-voltage electrode and the ground one was 50 cm, and the distance between the high-voltage electrode and the guiding one was set to 75 cm. A tap water of 50 [OMEGA] x m resistivity was jetted from behind the guiding electrode toward the high-voltage electrode. A lightning impulse voltage of 1/40 [micro]s generated with an impulse generator was applied to the high-voltage electrode. The leader discharge developed from the tip of the water jet toward the high-voltage electrode. After the discharge bridged between the water jet and the high-voltage electrode, the discharge developed along the water jet. Index Terms--Leader development, long gap discharge, streamer discharge, surface discharge, triggered lightning, water jet.