Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session QR1: Plasmas in Liquids |
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Chair: Toshiro Kaneko, Tohoku University Room: 162 |
Thursday, October 7, 2010 4:00PM - 4:15PM |
QR1.00001: Micro-Plasma Generation in Salt Containing Liquids Lucas Schaper, William G. Graham Here studies on the formation of a micro-plasma in a salt solution are presented. Single voltage pulses of negative polarity and amplitudes of up to 350V are applied to a coaxial electrode setup with a cylindrical centre electrode. Ohmic heating around the centre electrode leads to a phase transition of the liquid and forms a vapour layer, succeeded by plasma formation within the layer. Analysis is performed by using current-voltage waveforms and time dependant emission measurements. Shadowgraphy, in combination with ultra fast ICCD cameras, allows for exploration of vapour and plasma behaviour. Depending on the voltage amplitude single nanosecond discharges or continuous microsecond discharges are ignited. In both cases the emission spectra are very similar and dominated by sodium D-lines while no chlorine emission is observed. Recent experiments suggest that under discharge conditions the vapour liquid boundary as well as the electrode surface could be sources of sodium atoms. Space resolved spectroscopy reveals that discharges originate close to the electrode and, in the continuous case, propagate into the vapour volume in time. Results of our studies on the effect of plasma produced species on cells will also be presented. [Preview Abstract] |
Thursday, October 7, 2010 4:15PM - 4:30PM |
QR1.00002: Plasma Production in Liquids: Bubble and Electronic Mechanisms Natalia Yu. Babaeva, Mark J. Kushner Plasma production in or on liquids is of interest for water purification and plasma medicine. Modes of plasma formation in liquids include the bubble and electronic mechanisms. The first relies on the large E/N afforded by gas bubbles in the liquid to initiate plasmas which, through vaporization processes, eventually form gaseous conducting channels. This occurs in polar molecular liquids such as water. The second is similar to the breakdown of gases by electron impact ionization, and occurs in non-polar liquids having mobile charged particles such as liquid Ar (LAr). We have numerically investigated these processes using a 2-dimensional plasma hydrodynamics model in which liquids are treated the same as plasma with density dependent polarizations. Models for charge transport in high permittivity-polar liquids (e.g., electron solvation/hydration, proton hopping) and in low-permittivity non-polar liquids have been developed. We will discuss plasma propagation in water through chains of bubbles, bubble formation, the role of photo-ionization and charge injection from the liquid into bubbles. Breakdown in non-polar liquids (e.g., LAr) will be discussed from the perspective of gas streamer formation. Applications to wound healing will be shown. [Preview Abstract] |
Thursday, October 7, 2010 4:30PM - 4:45PM |
QR1.00003: Nonequilibrium liquid plasma - dynamics of generation and quenching Andrey Starikovskiy, Yong Yang, Young Cho, Alexander Fridman Typically plasmas in liquids are only considered to exist through the ionization of gases and typical production of plasmas in liquids has generated bubbles through heating or via cavitation and sustains the plasmas within those bubbles. Is it possible to produce liquid plasma without cracking and voids formation? We used a pulsed power system with 32 and 224 kV pulse amplitude, 12 and 0.4 ns pulse duration, 150 ps rise time. Discharge cell had point-to-plate geometry with a tip diameter of 100 $\mu $m. The measurements were performed with the help of 4Picos ICCD camera. It was found that discharge in liquid water forms in picosecond time scale. Emission intensity increase and plasma formation took 200-300 ps. Excited region size was $\sim $ 1 mm. After this initial stage emission rapidly decreased and plasma region becomes almost invisible in 500 ps. The absence of the emission during the rest of the pulse is explained by electrical field decrease on the boundary of conductive zone. Thus we have demonstrated possibility of formation of nonequilibrium plasma in liquid phase and investigated the dynamics of excitation and quenching of nonequilibrium plasma in liquids. [Preview Abstract] |
Thursday, October 7, 2010 4:45PM - 5:00PM |
QR1.00004: Influence of liquid temperature on the characteristics of atmospheric DC glow discharge using liquid electrode with miniature He flow Naoki Shirai, Kosuke Ichinose, Yusuke Hashizume, Satoshi Uchida, Fumiyosyi Tochikubo An atmospheric DC glow discharge using liquid (electrolyte: NaCl solution) electrodes and axial miniature helium flow was generated stably in ambient air. When the discharge current was increased further, yellow light emission which was originated from sodium atoms vaporized from the electrolyte surface was observed in the negative glow region. To examine the effect of temperature of liquid electrode, we controlled the electrolyte cathode temperature using injection type cooler or heater. The intensity of the sodium emission decreased with the refrigerated electrolyte cathode, while it increased with the heated electrolyte cathode. When we use pulse modulated DC voltage, the sodium emission appeared with a delay time from the start of the discharge, while the emission of nitrogen molecular lines appeared and reached their peaks immediately. The temperature of liquid cathode is important factor to control the plasma-liquid interaction from the discharges and to resolve the detailed mechanism of the electrolyte cathode discharges. [Preview Abstract] |
Thursday, October 7, 2010 5:00PM - 5:15PM |
QR1.00005: Dynamic Plasma--Liquid Systems and its applications Valeriy Chernyak, Sergej Olszewski, Iryna Prysiazhnevych, Vitaliy Yukhymenko, Dmitry Levko, Anatolij Shchedrin, Andriy Rybatsev, Vadym Naumov Results of investigations of plasma-liquid systems based on transversal discharges at atmospheric pressure such as transverse arc, secondary discharge supported by plasma of transverse arc, DC and Pulse discharges in a gas channel with liquid wall working in quiet and microporous bubbling liquids, discharge in a reverse vortex gas flow of tornado type with a ``liquid'' electrode applied for different ecological applications including reforming of liquid hydrocarbons (biofuels) for obtaining hydrogen-enriched synthesis gases, destruction of toxic hydrocarbons in aqueous solutions and synthesis of cacbon nanoparticles (metalofullerenes, nanotubes etc) from ethanol are presented and discussed in this work. [Preview Abstract] |
Thursday, October 7, 2010 5:15PM - 5:30PM |
QR1.00006: Influences of Liquid Temperature and Pressure on Microwave-Excited Bubble Plasma Production Tatsuo Ishijima, Kouji Kanetake, Haruka Suzuki, Hirotaka Toyoda So far, we have developed slot-antenna excited microwave discharge source as a novel technique for plasma production in liquids, and have pointed out the importance of bubbles in the vicinity of slot antenna for microwave plasma production [1]. In this study, we will report influences of liquid temperature and operating pressure on the plasma production in de-ionized water. Microwave was injected into a vacuum-tight vessel that is filled with de-ionized water with or without organic solutes at various water temperatures and ambient pressures. Decrease in the breakdown microwave power was observed when the water temperature was increased or the pressure was decreased, i.e., when the pressure inside the vessel is close to the saturated vapor pressure. These results suggest that reduction of microwave power that is required for the bubble production inside the water is important to suppress the breakdown microwave power. The power efficiency for the solute decomposition at various water temperatures and the pressures will be also discussed.\\[4pt] [1] T. Ishijima, H. Sugiura, R. Saito, H. Toyoda and H. Sugai, Plasma Sources Sci. Technol., \textbf{19}, 015010 (2010). [Preview Abstract] |
Thursday, October 7, 2010 5:30PM - 5:45PM |
QR1.00007: Selective reactions of reduction and oxidation by bubble supply via electrolysis and successive plasma generation in aqueous solution Osamu Sakai Plasmas in liquids were generated in bubbles of hydrogen and oxygen through electrolysis of aqueous solutions to create reaction fields which can be selected for reduction and oxidation. This chemically-active spaces work as decomposers of both CO$_{2}$ and organic compounds. CO$_{2}$ was transferred into CO and methane through hydrogen plasma generation, mainly due to reduction reaction by atomic hydrogen and also via dissociative attachment of electrons. We also observed phenol decomposition by generation of oxygen plasmas. These results confirm that synthesis of electrolysis and plasmas in liquids allows us to obtain on-demand chemical fields for oxidation and reduction. [Preview Abstract] |
Thursday, October 7, 2010 5:45PM - 6:00PM |
QR1.00008: Integrated-micro-solution plasma in porous dielectric electrodes and its application to water treatment Tatsuru Shirafuji, Keisuke Asano, Junko Hieda, Nagahiro Saito, Osamu Takai Organic contamination in water should be removed from the view point of environmental protection. Many plasma techniques have been applied for this issue. Atmospheric pressure plasma in water or on water surface is one of the candidates which can handle this issue. In our previous work, we have successfully obtained glow discharges in water (solution plasma). However, our solution plasma is ignited between two stylus electrodes, and actual treatment area is very small. In this work, we have obtained integrated microplasmas between a dielectric plate and a porous dielectric electrode which contain the water to be treated. The discharge area is 4 cm x 3 cm at this moment, but this can be scaled up. The applied voltage is 5 kV with pulsed waveform (frequency 15 kHz, pulse width 2 us). We have performed optical emission spectroscopy on this discharge, and confirmed that emission of OH radicals is available. We have applied this technique for decomposing organic materials in water. Methyleneblue has been used as the organic material in this work, and its decoloration rate has been investigated through the transmittance measurements on the solution. The methylene blue concentration has been reduced down to 50{\%} of the initial value for 26 minutes, which is comparable or faster than the rate reported by the other researchers. [Preview Abstract] |
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