The Project of Osaka Institute of Technology Electric-Rocket-Engine onboard Small Space Ship (PROITERES) was started at Osaka Institute of Technology in 2007. In PROITERES, a micro satellite with electrothermal pulsed plasma thrusters (PPTs) will be launched in 2010. The main mission is the first powered flight of micro satellite by electric thruster all over the world. This study aims at improvement in performance by changing configuration of PPTs. The total impulse of about 5 Ns was achieved with a teflon cylindrical discharge chamber 9.0 mm in length and 1.0 mm in diameter in 53,000-shot operation with 2.43 J/shot. Finally, the engineering model of PPT system was developed, and it is under operation as final test.

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Surface treatment of PEN (polyethylene naphthalate) film by pulsed atmospheric microplasma was experimentally investigated. Microplasma was generated with a pair of electrodes, covered with dielectric barrier, at relatively low discharge voltage of around 1 kV, and advantage of reducing the power and downsizing the entire plasma system. Electrodes were faced together with a spacer (thickness 100 um) in between. Streamers were generated between the electrodes, which generate various radicals and ions that could affect a target surface. We used Marx generator which generates negative pulsed for generating microplasma. Hydrophilization was confirmed measuring contact angle before and after the microplasma surface treatment with argon gas. Initial contact angle was about 73 degrees. As a result, the minimum contact angle was obtained at treatment time of 30 sec, discharge voltage of -1.3 kV, frequency of 24 kHz. Analysis by X-ray Photoelectron Spectroscopy (XPS) showed that decrease of C-H bond and increase of O=C bond and O-H bond.

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Radio-frequency plasma produced by capacitive discharge has been widely used for microelectronic industry because it has a simple structure in its device and its easy maintenance. However, it has disadvantage such as a low plasma-density with the magnitude of 10⁸-10⁹ cm^-3. In the paper, high-density radio-frequency capacitive-discharge plasma sources with various methods have been reviewed for thin-film preparation. These methods are the segmented electrode under high driving frequency, the high-secondary-electron-emission-electrode and the various hollow cathode electrodes. In this review, these solutions are assessed and discussed.

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This paper summarizes physical properties of pulsed streamer discharges caused by very fast polarity-reversals of an applied voltage and remarkable results of discharge treatments using the polarity-reversed voltage pulses in pollution control for exhausted gases and wasted water. The very fast polarity-reversal just after a dc voltage application is produced by direct-grounding of a charged coaxial cable because a traveling wave voltage reciprocates along the cable with a change in its polarity due to impedance mismatching between the grounding end and the coaxial cable. The inception voltage of streamer discharges in an air gap with a glass barrier subjected to the polarity-reversed pulse is much lower than that subjected to a mono-polar single pulse without the dc bias because charges accumulation on the glass surface under the dc field causes field enhancement in the air gap just after the polarity reversal. Due to the space charge effect in the discharge treatment with the polarity-reversed pulses, energy efficiency for removal of pollutants in gases, such as nitrogen oxides and volatile organic compounds produced in various manufacturing processes, can be high as compared with a classical barrier discharge treatment. Experimental results on decomposition of organic compounds in water and on inactivation of microorganisms in water are also reviewed.

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Development of intense pulsed heavy ion beam accelerator technology is described for the application of materials processing. Gas puff plasma gun and vacuum arc discharge plasma gun were developed as an active ion source for magnetically insulated pulsed ion diode. Source plasma of nitrogen and aluminum were successfully produced with the gas puff plasma gun and the vacuum arc plasma gun, respectively. The ion diode was successfully operated with gas puff plasma gun at diode voltage 190 kV, diode current 2.2 kA and nitrogen ion beam of ion current density 27 A/cm² was obtained. The ion composition was evaluated by a Thomson parabola spectrometer and the purity of the nitrogen ion beam was estimated to be 86%. The diode also operated with aluminum ion source of vacuum arc plasma gun. The ion diode was operated at 200 kV, 12 kA, and aluminum ion beam of current density 230 A/cm² was obtained. The beam consists of aluminum ions (Al^(1-3)+) of energy 60-400 keV, and protons (90-130 keV), and the purity was estimated to be 89 %.
The development of the bipolar pulse accelerator (BPA) was reported. A double coaxial type bipolar pulse generator was developed as the power supply of the BPA. The generator was tested with dummy load of 7.5 ohm, bipolar pulses of -138 kV, 72 ns (1^st pulse) and +130 kV, 70 ns (2^nd pulse) were succesively generated. By applying the bipolar pulse to the drift tube of the BPA, nitrogen ion beam of 2 A/cm² was observed in the cathode, which suggests the bipolar pulse acceleration.

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Operation tests of the smoke-tube boiler emission NOx treatment plant which consists of a plasma ozonizer using a pressure swing adsorption (PSA) oxygen generator and silent discharge for indirect NO oxidation and a Na₂SO₃ chemical scrubber are carried out for cogeneration boilers which uses a city gas and heavy oil as a fuel based on our proposed plasma-chemical hybrid NOx reduction principle. It is clear that amount of NO removed is almost same as the amount of corresponding O₃ concentration to oxidize NO regardless of fuels and flow rates of flue gas. After the relation between oxidation-reduction potential (ORP) and the NOx removal efficiency is obtained, continuous operation tests of this plant are performed. For gas firing boiler emission, the NO complete removal and the decrease in NOx from 32 ppm to 3 ppm are achieved for 300 min by keeping -30 mV of ORP. For the treatment of heavy oil boiler emission, the decrease in NOx from 90 ppm to less than 25 ppm is maintained for 250 min. It is demonstrated that the high NOx removal performance can be maintained for a long time by keeping the optimum value of ORP.

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The present paper reviews fundamentals of optical emission spectroscopy (OES) of plasmas and, in particular, its applications to processing plasmas. Collisional radiative model is described to understand the excitation kinetics and population distributions of excited states in order to examine the electron temperature and density. It is shown that corona equilibrium is often adopted as justifiable assumption of excitation kinetics for general processing plasmas. Two OES methods to understand molecular gas discharge plasmas are also reviewed. One of them is to determine vibrational or rotational temperatures of molecular gas discharge plasmas by OES measurement. The other is the actinometry measurement method to examine neutral radical density.

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We developed noble schemes to generate atmospheric-pressure microplasmas, in which the mass of initial materials such as gases or liquids is limited to a small amount. A miniature gas flow through a nozzle electrode was used to generate direct current glow or corona microdischarges with a metal or an electrolyte cathode. High-power microplasmas were operated by fast pulsed voltages. Pulsed microplasmas were created using a droplet or a filament of aqueous solution of ethanol.

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We proposed and examined a maskless plasma surface patterning technique to fabricate 3 mm pitches of front contact grooves on a single crystalline silicon solar cell, in which the surface discharge operated at atmospheric pressure etched the silicon nitride film of 150 nm thickness on a silicon layer. In addition, we investigated etching characteristics of flat surface silicon and the distribution of electric field in our proposed surface discharge etcher. The electrical field distribution of our proposed surface discharge etcher was concentrated at triple junction points, and its strength electrical field intensity was around 4.0 × 10⁶ V/m. Finally, we showed that the surface discharge could effectively etch the silicon nitride film in a 3 mm pitch.

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Chemical vapor depositions using nonthermal atmospheric pressure plasmas have attracted special attentions because they eliminate expensive and complicated vacuum systems and provide many more active chemical species. We report an advanced 2.45 GHz microwave-excited blowing plasma system which was fabricated using microstrip lines, instead of conventional waveguides. The plasma system provides a plasma source with a long lifetime, stability, robustness, and simplicity even at atmospheric pressure. The blowing plasma permits the carbon materials deposition in atmospheric ambient air.

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A microwave excited atmospheric pressure plasma source was set up and the surface modification of polyimide film and plasma cleaning experiment to an oil contaminated stainless steel plate was conducted, while considering the radical density in the plasma. Ar-O₂ or Ar-H₂O mixture gas was used as plasma gas. The high-speed treatment in about 1 second after plasma irradiation was observed in the polyimide film plasma treatment. In the plasma cleaning experiment, the sufficient removal of hydrocarbon oil contaminate was observed after 30 seconds treatment time. The results of these plasma treatments were discussed using the measured value of radical density and the numerically calculated axial distribution of various radicals.

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In this work, an atmospheric pressure plasma source was experimentally constructed by a coaxial arrangement with a discharge electrode and a dielectric tube of 6 mm in an inner diameter. The atmospheric pressure plasma was formed in a noble gas (He) stream exposed to dielectric barrier discharges on AC high-voltage applications. The axial plasma propagation was evaluated from the high-speed photograph and the inductive current. The plasma ignited by the barrier discharges was observed as a plasma bullet traveling from the discharge electrode to ambient air. The velocity of plasma bullet was hypersonic of 3×10³ ∼ 8×10³ m/s. The velocity varied according to time and traveling length. The optically identified characteristic of plasma propagation indicated the same tendency as time and space resolved profiles of the plasma bullet travelling which was observed utilizing a Rogowski coil as the current monitor. The plasma density was evaluated from the inductive current of plasma bullets along the gas stream axis, and the plasma density was in the order of 10¹⁶ m^-3.

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This paper reports plane-type microwave resonator (MWR) probe for electron density measurements in reactive processing plasmas. The sheath effects were investigated by electromagnetic field analysis with FDTD simulation, and the calculated characteristics were confirmed experimentally. The FDTD simulation revealed that the sheath formed around the probe leads to underestimation of electron density, in comparison to the real density given as an initial condition in the simulation, which is caused by a decrease in the effective dielectric constant. An increase in a slit width of the probe antenna suppressed the density underestimation. Actually, as the slit width increased, the electron density measured by the MWR probe approached that obtained by a reference surface wave probe. Therefore, it is useful to enlarge the slit width for improvement of accuracy of the density measurement with the MWR probe.

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In order to develop a high rate atmospheric film deposition process for functional films, as a basic study, deposition of titanium oxide film and zinc oxide film by solution precursor plasma spray (SPPS) was conducted in open air. Consequently, in the case of titanium oxide film deposition, anantase film and amorphous film as well as rutile film could be deposited by varying the deposition distance. In the case of anatase dominant film, photo-catalytic properties of the films could be confirmed by wettability test. In addition, the dye sensitized sollar cell (DSC) using the TiO₂ film deposited by this SPPS technique as photo voltaic device generates 49mV in OCV. On the other hand, in the case of zinc oxide film deposition, it was proved that well crystallized ZnO films with photo catalytic properties could be deposited. From these results, this process was found to have high potential for high rate functional film deposition process conducted in the air.

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Recent works for the decomposition of gaseous volatile organic compounds (VOCs) and environmental hazardous substances in water using discharge plasma are encapsulated. The kinds of reactors used for the decomposition of VOCs, the decomposition characteristics of VOCs by the reactors and the effects of the discharge type, applied voltage, etc. on VOCs decomposition are briefly described. Further, the detailed investigation of by-products from benzene, toluene and xylene and the estimation of decomposition path of acetone by discharge plasma treatment are introduced as works which contribute to the design of VOC-decomposition reactors and to assuring the safety of VOCs decomposition by the discharge plasma.
For the decomposition of environmental hazardous substances in water by discharge plasma, the treatment of aqueous phenol solution and organic dyes are focused. The effects of sparging gas, the conductivity of the solution, background-gas composition, etc. on phenol decomposition rate are described, and the mechanism that the species contributing phenol decomposition change with the background-gas composition is illustrated in detail. Recent works to clarify the by-products of phenol are also introduced. For the decomposition rate of organic dyes, the effects of pH of solution, background-gas composition, etc. on the decomposition rate and the species contributing the decomposition are shown. Further, the efficiency difference for organic-dye decomposition due to the kinds of discharge plasma reactor is introduced.

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The hardness and Young's modulus of the carbonaceous films formed by focused ion-beam-assisted chemical vapor deposition using Au or Si ions, before and after 800 °C annealing, were compared with those formed using Ga ions in the process. It is found that the hardness of the film formed using Au ions was harder than those formed using Si and Ga ions before annealing. After annealing, however, that formed using Si ions showed the largest value in hardness. From the X-ray photoelectron spectroscopy measurement, the implanted Si atoms were combined with carbon atoms chemically, indicating the hardening of the Si-containing carbonaceous films after annealing.

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Trace elemental analysis technologies using atmospheric plasma sources have been used in many fields such as environmental analysis, semiconductor industry and medicine. Since 1970's, argon inductively coupled thermal plasma (ICP) has been used as ionization or excitation source for atomic emission spectrometry or mass spectrometry because of the excellent power of detection and the ability to measure isotope ratios. However, it is difficult to determine high ionization potential elements such as halogens and rare gases by using argon plasma. In order to overcome argon ICP, many types of atmospheric plasma sources have been developed and investigated. Furthermore, some kinds of sample introduction systems have been developed and applied with the plasma sources. As a result, sub-pg/mL of detection limits for almost all elements are realized.

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Agricultural and food processing applications of pulsed power and plasma technologies are described in this paper. Repetitively operated compact pulsed power generators with a moderate peak power are developed for the agricultural and the food processing applications. These applications are mainly based on biological effects and can be categorized as germination control of plants such as Basidiomycota and arabidopsis; inactivation of bacteria in soil and liquid medium of hydroponics; extraction of juice from fruits and vegetables; decontamination of air and liquid, etc. Types of pulsed power that have biological effects are caused with gas discharges, water discharges, and electromagnetic fields. The discharges yield free radicals, UV radiation, intense electric field, and shock waves. Biologically based applications of pulsed power and plasma are performed by selecting the type that gives the target objects the adequate result from among these agents or byproducts. For instance, intense electric fields form pores on the cell membrane, which is called electroporation, or influence the nuclei. This paper mainly describes the application of the pulsed power for the germination control of Basidiomycota i.e. mushroom, inactivation of fungi in the soil and the liquid medium in hydroponics, and extraction of polyphenol from skins of grape.

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It is important to monitor the density of species in plasma or sputtering processes for controlling the process precisely because both composition and property of films are affected by the density of species such as radicals and ions. Absorption spectroscopy is a powerful method to monitor the density of species in the plasma. We have developed a multi-micro hollow cathode lamp (multi-MHCL) for monitoring densities of multi-metallic-atoms in the plasma or sputtering processes. The multi-MHCL is a compact light source in compared with the conventional light sources, and can emit multi-atomic lines simultaneously. The multi-MHCL was applied to an absorption spectroscopy for measuring densities of Zn and In atoms in a radio frequency magnetron sputtering process using IZO (Indium Zinc Oxide) target. The densities of Zn and In atoms were successfully measured in the range of 10⁹ to 10¹⁰cm^-3.

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Recently, extended MHD plasmas have been proposed, especially in both theoretical and computational fields of plasma physics. To test those experimentally, we propose a new project using two nonneutral plasmas: pure ion and electron plasmas. The experiment is performed on a linear machine in which a pair of positive and negative electrostatic potential wells is externally produced. In the positive potential well, an ⁷Li⁺ plasma is confined, while an electron plasma in the negative potential one. Then, those nonneutral plasmas are merged into an extended MHD plasma. The most remarkable advantage to employing nonneutral plasmas is that the ion skin depth, that is a typical scale length of the extended MHD plasmas, can be extended to the plasma radius. This actually alleviates experimental difficulties in diagnosing properties of the extended MHD plasmas. With precisely controlling densities of both pure ⁷Li⁺ ion and electron plasmas, the proposed method may explore an unrevealed research field of extended MHD plasmas.

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In order to analyze independently the various discharges of a point-to-plane air gap (steady glow, primary streamer, and secondary streamer discharges), the gas temperature in each of discharge region should be determined accurately by using the spectrum emitted from the second positive system bands of N₂. In this experiment, we investigate the laser triggered streamer discharge with a repetition frequency of 10 Hz from the dc positive glow corona. The results show that the temperatures of the glow, primary streamer and secondary streamer are in the range of 316∼356K, 335∼350K and 370∼390K, respectively, and are considerably lower than the value of the high-stable dc positive repetitive streamer corona published in the previous references.

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Perfluorooctanoic acid (PFOA) at a concentration of 500 mg/L in water was successfully degraded using pulsed plasmas generated inside oxygen or argon bubbles. 6 kV-200 ns pulsed voltages were applied to the water bubbles at repetition rates of 500∼2000 Hz and pulse plasmas were generated along the inner surface of gas bubbles. After 120 min operation, almost half of the fluorine atoms were detached from PFOA molecules. The decomposition energy efficiency for PFOA obtained with oxygen was 140 mg/kWh which value was quite large as comparing to the values obtained with other chemical methods.

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