Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session PR3: High Pressure Discharges and Liquids |
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Chair: L. Vuskovic, Old Dominion University Room: Addison Room |
Thursday, October 16, 2008 8:00AM - 8:15AM |
PR3.00001: Diagnostics of nonequilibrium atmospheric pressure plasma with ultra high electron density for surface cleaning processes Hirotoshi Inui, Yuto Matsudaira, Masaru Hori, Naofumi Yoshida, Hiroyuki Kano Surface cleaning process using a nonequilibrium atmospheric pressure plasma has advantage of high throughput, expandability to large-area and nonuse of vacuum system. In this study, the surface modification on a glass substrate by using a nonequilibrium atmospheric pressure plasma was investigated. To characterize the plasma, the gas temperature and electron density were measured using optical emission spectroscopy (OES), and the ground-state atomic oxygen radicals O($^{3}$P) were measured by vacuum ultraviolet absorption spectroscopy (VUVAS). Cleaning efficiency was estimated by the contact angle of water droplet on the glass surface after plasma treatment. The cleaning efficiency was increasing with the increasing mixing ratio O$_{2}$/(O$_{2}$+Ar) to 1{\%}, and then saturated. The cleaning mechanism will be discussed based on the relationship with O($^{3}$P) density and gas temperature. [Preview Abstract] |
Thursday, October 16, 2008 8:15AM - 8:30AM |
PR3.00002: Diagnostics of Microwave Bubble Plasma in Liquid Hirotaka Toyoda, Hiroyasu Sugiura, Ryota Saito, Tatsuo Ishijima Plasma production in the liquid phase has attracted much attention due to its potential applications such as biomedical or environmental processes. As a new technique, we have developed bubble plasma production in liquid with use of pulsed microwave from a slot antenna, and have succeeded in decomposing harmful chemicals such as trichloroethylene (TCE). In this work, optical emission and absorption spectroscopies were adopted to diagnose the microwave bubble plasma. OES result indicated strong OH emission from the plasma, suggesting production of reactive OH radical in the bubble plasma from water vapor. Furthermore, plasma density of the bubble plasma was investigated by time-resolved Stark broadening spectroscopy. To give insight into the reactive species in the liquid phase, plasma-treated water was investigated with UV/VIS optical absorption spectroscopy and a chemical reagent that is sensitive to hydrogen peroxide. From these measurements, existence of hydrogen peroxide in the liquid phase was confirmed. [Preview Abstract] |
Thursday, October 16, 2008 8:30AM - 8:45AM |
PR3.00003: Propagation of pulsed discharges in water Paul Ceccato, Olivier Guaitella, Antoine Rousseau The present discharge is a corona-like filamentary plasma at atmospheric pressure in water. Initiation and discharge propagation have been studied. Pulsed high voltage is applied in a point to plane electrode configuration for submicrosecond duration. In order to monitor the propagation of the discharge two ICCD camera are used with an adjustable delay. The discharge initiates at the positive electrode. A bright spot is formed at the point and can be interpreted as a gas bubble nucleation. Then several plasma filaments propagate radially and simultaneously from the electrode at a constant velocity of 3.5e6 cm/s. No streamer head can be seen even with gate as short as 1ns. After hundreds of nanoseconds branching occurs and the previous filaments become brighter as they supply more current. The propagation velocity does not depend on the applied voltage, the gap and the conductivity of the water. This propagation velocity remains constant during the propagation. The discharge stops when the applied voltage falls below a threshold voltage. The measured propagation velocity is one order of magnitude lower than gas phase streamers. [Preview Abstract] |
Thursday, October 16, 2008 8:45AM - 9:00AM |
PR3.00004: GEC Student Award for Excellence Finalist: Creation of Stable Plasma-Liquid Interfaced Reactive Field using Ionic Liquids Kazuhiko Baba, Toshiro Kaneko, Rikizo Hatakeyama The gas-liquid interfacial region which is the boundary between plasmas and liquids, activating physical and chemical reactions, has attracted much attention as novel reactive field in nano-bio material creation. Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we succeeded in creating the reactive gas (plasmas)-liquid (ionic liquids) interfacial field under a low gas pressure condition, where the plasma ion behavior can be controlled. The effects of plasma ion irradiation on the liquid medium are for the first time quantitatively revealed. In connection with the plasma ion irradiation, the potential structure and optical emission properties of the gas-liquid interfacial plasma are investigated by changing a polarity of the ionic liquid electrode in order to evaluate the ionic liquid-plasma interactions. These results would contribute to systematizing the field of gas-liquid interfacial plasma physics for its applications. [Preview Abstract] |
Thursday, October 16, 2008 9:00AM - 9:15AM |
PR3.00005: Properties of plasma-liquid system based on the discharge in gas channel with liquid wall at the ultrasonic cavitation Valeriy Chernyak, Sergey Olshewskii, Iryna Prysiazhnevych, Olena Solomenko The influence of the ultrasounic cavitation on the properties of the plasma-liquid system was studied. Discharge in the gas channel formed by airflow immersed into the liquid with microdefects was investigated. Different regimes of the discharge (with and without air) were explored. Optical emission spectroscopy was made of its plasma. Absorption spectra of distilled water after plasma treatment in such system were measured. It was found that presence of ultrasound in the plasma-liquid system during the discharge burning leads to the considerable enhancement of the intensity of main spectral components (hydroxyl band, copper and hydrogen lines). Revealed broadening of H$_{\alpha }$ line in the emission spectra of plasma of the investigated discharge can be connected with presence of cavitation effect in working liquid caused by applied ultrasound. It was shown that all liquids treated at the presence of ultrasound absorb more then those in case without ultrasound. Treated liquids are unstable in a time. [Preview Abstract] |
Thursday, October 16, 2008 9:15AM - 9:30AM |
PR3.00006: Diagnostics of plasma reaction fields in supercritical fluid by using micro-Raman spectroscopy Takaaki Tomai, Hirokazu Kikuchi, Koya Saito, Hiroharu Yui, Kazuo Terashima Supercritical fluid (SCF) is a promising medium, which has superior transport properties, such as liquid-like high density and gas-like high diffusivity. Recently, discharge plasma generated in SCF has attracted much attention as extremely high reaction field. In previous study, it was found that carbon nanostructured materials, such as carbon nanotubes, can be synthesized effectively from supercritical CO$_{2}$ near the critical point. In this study, to verify the existence of characteristic microstructures of SCF, we diagnose the molecular clustering and density fluctuation in barrier discharge plasma reaction fields by micro-Raman spectroscopy. It was found that the decrease in the density of CO$_{2}$ during plasma generation is less than 0.02 g/cm$^{3}$ (the critical density of CO$_{2}$: 0.467 g/cm$^{3})$, as compared with that in the case of the neat CO$_{2}$, for wide pressure ranges from gaseous to supercritical conditions. Moreover, it was experimentally verified that the density fluctuation observed near the critical point persists in the plasma reaction field. We will present the further detail with the results of other supercritical medium, CHF$_{3}$, in addition to CO$_{2}$, at 61$^{st}$ Gaseous Electronics Conference (GEC). [Preview Abstract] |
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