Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session SR4: Plasmas in Liquids |
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Chair: Natalia Babaeva, University of Michigan Room: Salon DE |
Thursday, October 25, 2012 3:30PM - 3:45PM |
SR4.00001: Controlling Cold Plasma Jets Interacting with Liquids Stephan Reuter, Malte Hammer, Joern Winter, Kai Masur, Thomas von Woedtke, Klaus-Dieter Weltmann Plasmas interacting with liquids are of great interest for environmental, chemical, and biomedical applications. In this work we present optical diagnostics on atmospheric pressure plasma jets interacting with liquids. Combining the diagnostic results with numerical simulations yields an understanding of fundamental processes such as air species diffusion into the jet effluents. Especially for plasma treatment of physiological liquids in ambient air, atmospheric species play a key role. To achieve a desired reactive component output, the generation processes from these ambient air species are controlled. Plasma jets are characterized by laser induced fluorescence spectroscopy, by absorption and emission spectroscopy, and by flow simulations. With the gained knowledge we are able to tailor the reactive component composition and to influence plasma jet-liquid interaction. We show that reactive species generation within plasma treated liquid can be tuned and apply the findings to biological cells to investigate the effect of reactive oxygen and nitrogen species (RONS). The plasma treated liquids are investigated regarding their pH value, OH radicals, nitrate and nitrite, and H$_{2}$O$_{2}$ content. From the tailored plasma treatment a significant insight into the relevant processes in plasma acidification of liquids has been gained. [Preview Abstract] |
Thursday, October 25, 2012 3:45PM - 4:00PM |
SR4.00002: Time-resolved measurement of pressure evolution in underwater nanosecond discharge Ilya Marinov, Olivier Guaitella, Svetlana Starikovskaia, Antoine Rousseau Electrical discharges in water and other dielectric liquids have been extensively studied since almost fifty years, however reliable data on plasma parameters within the propagation phase is still missing. We report on shadowgraphic imaging and optical emission spectroscopy (OES) both with nanosecond time resolution of pulsed nanosecond discharge generated with point to wire electrode configuration. High voltage pulses of 10 kV and 30 ns duration (FWHM) are delivered by commercial pulse generator FPG 10 (FIG GmbH). Sub-millimeter discharge with filamentary structure develops at 50 km/s in axial direction of pin electrode. Using Hugoniot equations maximal discharge pressure at ignition can be obtained from shock wave front velocity. Analytical model of supersonic cavity expansion based on Kirkwood-Bethe approximation gives discharge pressure evolution from experimentally measured discharge channel expansion velocity profile. Thus, the pressure of 5 GPa is measured at the discharge ignition and drops drastically by the end of voltage pulse. Time-resolved OES spectrum shows a strong broadening of atomic Hydrogen (Balmer series) and oxygen (OI 777 nm) lines with almost continuum emission in the region 300-700 nm. Complex H$\alpha$ and OI 777 profiles are due to combined contribution of Van Der Waals and Stark broadening. Electronic density can be deduced from lorentzian fit of Stark broadening and gives for electronic density 10$^{24} - 10^{25}$ m$^{-3}$. [Preview Abstract] |
Thursday, October 25, 2012 4:00PM - 4:15PM |
SR4.00003: Simulations of Images and Optical Spectra of Plasmas Sustained in Bubbles in Water Wei Tian, Mark Kushner Plasmas in bubbles in water are being investigated for their ability to produce chemically reactive species for water purification and medical treatment. The gas in the bubbles is important to the production of these active species. In this paper, we report on a computational investigation of the dynamics of plasmas in bubbles in water. These simulations were performed using \textit{nonPDPSIM}, in which Poisson's equation, transport equations for charged and neutral species, and electron temperature are integrated in 2-dimensions on an unstructured mesh. Bubbles of specified composition and size ($\approx $3 mm diameter) in water at atmospheric pressure are placed at the tip of the powered electrode and water vapor is allowed to diffuse into the bubble from the vapor-water boundary. Voltage pulses (15-30 kV) produce plasma streamers in the bubble which typically hug the vapor-water boundary. Images, optical spectra and plasma properties will be discussed for bubbles of N$_{2}$, Ar and He, and compared to experiments [1]. The differences in plasma dynamics and appearance (e.g., volume discharge or surface hugging) depend in large part on the electron energy relaxation length, and the rate of diffusion of water vapor into the interior. Electron impact dissociative excitation of water vapor and excitation transfer processes from injected bubble gases to the water vapor are responsible for differences in the optical spectra and, by inference, differences in radical production. \\[4pt] [1] K. Tachibana, et al., Plasma Sources Sci. Technol. \textbf{20}, 034005 (2011). [Preview Abstract] |
Thursday, October 25, 2012 4:15PM - 4:30PM |
SR4.00004: An efficient method for producing standing sonoplasmas with the help of a metal mesh K. Sasaki, Y. Iwata, S. Tomioka, S. Nishiyama, N. Takada It is known that sonoplasmas are produced at the collapses of cavitation bubbles in liquids irradiated by ultrasonic waves. Sonoplasmas are probably produced in commercialized ultrasonic cleaners, but it is very difficult to detect optical emission from sonoplasmas in ultrasonic cleaners. In this work, we found an efficient, simple method for producing sonoplasmas. We prepared a rectangular container that was filled with water. An ultrasonic transducer was attached at the bottom of the container, and ultrasonic wave at a frequency of 34 kHz was propagated in water from the bottom toward the top. When we inserted a planar metal mesh into water from the top, we observed the efficient production of cavitation bubbles at a localized distance from the mesh. The production area of the cavitation bubbles was roughly standing. It was necessary to adjust the depth of water and the position of the mesh carefully to obtain the efficient production of standing cavitation bubbles. We adopted laser light scattering as a simple method for quantifying the production efficiency of cavitation bubbles, and optimized the depth of water and the position of the mesh. We succeeded in capturing the optical emission image of a sonoplasma using a charge-coupled device camera with an image intensifier. [Preview Abstract] |
Thursday, October 25, 2012 4:30PM - 4:45PM |
SR4.00005: Optical emission spectroscopy and shadowgraph imaging of pulsed laser plasmas generated in gaseous, liquid and supercritical CO$_{2}$ Toru Kato, Yoshihiko Takizawa, Sven Stauss, Motoyoshi Baba, Tohru Suemoto, Kazuo Terashima Pulsed laser ablation (PLA) in liquids has attracted a lot of attention due to its potential for the synthesis of a wide range of nanomaterials. Contrary to PLA in vacuum, in liquids the plasma plume is confined due to the high density of the medium. This restricts the diffusion of active species and leads to rapid quenching, which limits particle growth. Compared to liquids, supercritical fluids (SCFs) possess superior transport properties and PLA in SCFs has been used for realizing chemical synthesis of nanomaterials such as diamondoids. We have investigated the dynamics of PLA (laser: Nd-YAG, wavelength 532 nm; pulse width 7 ns; frequency 10 Hz; target: carbon, nickel) in gaseous (0.1-6 MPa), liquid and supercritical CO$_{2}$ ($T_{crit}$: 304.1 K, $P_{crit}$: 7.38 MPa). From shadowgraphs of PLA taken in gaseous, liquid and supercritical CO$_{2}$, images of PLA in SCF showed characteristics similar to that of PLA in liquid. Compared to PLA in the gaseous and liquid states, optical emission spectra in SCF revealed enhanced interactions between plasma and solvent species, especially near the critical point. Owing to the high density fluctuation near the critical point, PLA in SCF is expected to lead to a better control of the synthesis of diamondoids and other nanomaterials. [Preview Abstract] |
Thursday, October 25, 2012 4:45PM - 5:00PM |
SR4.00006: Experimental and Modeling Analysis of the Single Micro Bubble Generation by Micro Plasma in Water Peng Xiao, David Staack A single micro bubble (maximum diameter 50 to 600 $\mu$m) is shown to be formed by a single nanosecond duration micro plasma in liquid. The micro scale corona plasma discharges are created at the tip of a micro-electrode with high energy density. Discharge conditions are controllable with tip diameter 1um, applied voltage 5 kV to 10 kV, discharge duration 10 ns to 1 $\mu$s and discharge energy 1 mJ to 50 mJ per pulse. The energy input from the micro plasma to generate the micro bubble and to support its growth vary, which leads to variations in the rate of growth, maximum diameter, and the number of growth-collapse cycles of the micro bubble. These micro plasma based micro bubbles are visualized using a microscope based shadow graph system and two high speed cameras. The micro plasma discharge is captured with nano-second gating using an ICCD and the micro bubble generation and growth is recorded using million fps CCD video camera. The micro bubbles are found repeatedly generated. A Payleigh-Plesset model for growth and collapse of cavity bubble are compared to micro bubble videos and used to estimate the time dependent pressure, temperature and mass of the micro bubbles. [Preview Abstract] |
Thursday, October 25, 2012 5:00PM - 5:15PM |
SR4.00007: Microsparks Generated by Charged Particles in Dielectric Liquids Robert Geiger The electrodynamics of charged particles in dielectric liquids have been described by several authors [1,2]. As a charged particle approaches an electrode of opposite charge the local electric field eventually exceeds the dielectric strength of the liquid and a microspark is generated. These plasmas can be very small, about $<$ 5 $\mu $m, and may exhibit non-thermal behavior. Such non-thermal behavior can provide interesting and efficient chemical reactions [3]. An understanding of the plasma properties for this type of discharge can provide a simple means of generating non-thermal plasmas in dielectric liquids, such as oils or other hydrocarbons, which can be used to chemically process the liquids. Such a technology may lead to a highly efficient method of heavy oil upgrading which can be easily scaled. In order to understand the plasma properties optical emission spectroscopy is carried out for various hydrocarbons and voltage-current characteristics are used to determine the energy cost for this process. \\[4pt] [1] Melcher, James R. Continuum Electromechanics. Cambridge, MA: MIT Press, 1981.\\[0pt] [2] Jones, Thomas B. Electromechanics of Particles. Cambridge University Press 1995.\\[0pt] [3] Staack, D., Fridman, A., Gutsol, A., Gogotsi, Y. and Friedman, G. 2008, Angew. Chem., Int. Ed. 47, 8020. [Preview Abstract] |
Thursday, October 25, 2012 5:15PM - 5:30PM |
SR4.00008: Pulse discharge in the focus of the converging acoustic wave in the water Valeriy Chernyak, Sergij Sidoruk, Vitalij Yukhymenko, Evgen Martysh, Oleg Fedorovich Generation of the acoustic signals made by the two successive microsecond's discharges in the liquid system of cylindrical geometry was investigated. The ratio of the radius of stainless steel cylinder to its height is $\sim $ 13.5. Both discharges are realized between two electrodes placed on the cylinder axis. The ratio of the cylinder height to the distance between electrodes is $\sim $ 3. Controlled time delay between discharges was changed in the wide range: from the moment when the first divergent acoustic wave (generated by the first discharge in the water) reaches the metal wall of cylinder till the time after the axial collapse of the converging acoustic wave (reflected from the cylinder wall). The energy in storage capacitors was changing in the range of 1$\div $1000 joules. The air discharger and hydrogen thyratron were used as commutators for the first and the second discharges correspondingly. [Preview Abstract] |
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