Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session GT3: Discharges in Liquids IFocus
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Chair: Juergen Kolb, Leibniz Institute for Plasma Science and Technology Room: 2b |
Tuesday, October 11, 2016 4:00PM - 4:30PM |
GT3.00001: Plasma-water systems studied with optical diagnostics including sum-frequency generation spectroscopy Invited Speaker: Tsuyohito Ito Recently, various applications of plasma-water systems have been reported, such as materials synthesis, agricultural applications, and medical treatments. As one of basic studies of such systems, we are investigating water surface structure influenced by a plasma via vibrational sum-frequency generation spectroscopy. Vibrational sum-frequency generation spectroscopy is known to be an interfacially active diagnostic technique, as such process occurs in noncentrosymmetric medium. Visible and wavenumber-tunable infrared beams are simultaneously irradiated to the interface. The interfacial water has ice-like (\textasciitilde 3200 cm--1), liquid-like (\textasciitilde 3400 cm--1), and free OH (3700 cm--1) structures (assignment of the ice-like structure still remains contentious), and the intensity of the signal becomes stronger when the tunable infrared beam resonates with a vibration of the structures. The results indicate that with generating air dielectric barrier discharges for supplying reactive species to the water surface, all investigated signals originating from the above-mentioned three structures decrease. Furthermore, the signal strengths are recovered after terminating the plasma generation. We currently believe that the surface density of the reactive species should be high when they are found at the water surface. Details on the experimental results of the sum-frequency generation spectroscopy, as well as other spectroscopic results of plasma-water systems, will be presented at the conference. [Preview Abstract] |
Tuesday, October 11, 2016 4:30PM - 4:45PM |
GT3.00002: Simulation of Discharge Production in a Water Vapour Layer on an Electrode. Mohammad Karim, Benjamin Evans, Leonidas Asimakoulas, Kenneth Stalder, Thomas Field, Bill Graham, Tomoyuki Murakami Electrical discharges in water are receiving increasing attention because of chemical, environmental and biomedical applications.The work to be presented focuses on plasmas created directly in high conductivity water, saline solution. Here the plasma is produced at low voltage (\textasciitilde 200V) and is clearly associated with an initial vapour layer on the electrode surface that isolates the electrode from the liquid. In a previous paper (1) a finite element multi-physics program, incorporating all relevant electrical and thermal properties of the solution was shown to reproduce the experimentally observed pre-plasma vapour layer behaviour. The results of a simulation of the plasma production in vapour layers of the same size and shape as predicted in (1) will be presented, At present inert gas fills the ``vapour layer''. However this produces spatial distributions of the electron parameters that are consistent with the electric fields predicted in the original simulations. The water plasma simulation recently developed by Murakami is currently being included. It is anticipated that results of the coupled codes, showing the temporal and 2-D spatial development of the vapour and plasma, will be presented. (1) L. Schaper, W.G. Graham and K.R. Stalder, \textit{Plasma Sources Sci. Technol.} \textbf{20} (2011) 034003. [Preview Abstract] |
Tuesday, October 11, 2016 4:45PM - 5:00PM |
GT3.00003: Nanosecond time resolved spectral characteristics of a pulsed discharge in water Emile Carbone, Bang-Dou Huang, Yi-Kang Pu, Uwe Czarnetzki The dynamics of short pulsed plasmas generated directly inside liquids are still not well understood. Such discharges are highly collisional making them difficult to investigate experimentally. In this contribution, we present the experimental characterization of a stable nanosecond pulsed discharge in water with a pin to plate configuration. The peak applied voltage is 25 kV with a pulse duration of about 15 ns and 25 Hz repetition frequency. Although the discharge is intrinsically stable (breakdown jitter less than 5 ns), an optical delay line was constructed to couple the light into a spectrometer (1200 g/mm, 30 cm focal length). The plasma light is then spectrally resolved with (sub)-nanosecond temporal resolution using a streak camera. This allows us to measure without jitter the spectral characteristics of the discharge with nanosecond temporal resolution. The plasma emission is studied and no atomic lines or molecular bands are observed. Instead, a large continuum emission spectrum over the complete visible range is measured both during the discharge and afterglow periods. The possible origins of this continuum are discussed. [Preview Abstract] |
Tuesday, October 11, 2016 5:00PM - 5:15PM |
GT3.00004: Spectral analysis of optical emission of microplasma in sea water. Vladislav Gamaleev, Hayato Morita, Jun-Seok Oh, Hiroshi Furuta, Akimitsu Hatta This work presents an analysis of optical emission spectra from microplasma in three types of liquid, namely artificial sea water composed of 10 typical agents (10ASW), reference solutions each containing a single agent (NaCl, MgCl$_{\mathrm{2}}+$H$_{\mathrm{2}}$O, Na$_{\mathrm{2}}$SO$_{\mathrm{4}}$, CaCl$_{\mathrm{2}}$, KCl, NaHCO$_{\mathrm{3}}$, KBr, NaHCO$_{\mathrm{3}}$, H$_{\mathrm{3}}$BO$_{\mathrm{3}}$, SrCl$_{\mathrm{2}}+$H$_{\mathrm{2}}$O, NaF) and naturally sampled deep sea water (DSW). Microplasma was operated using a needle(Pd)-to-plate(Pt) electrode system sunk into each liquid in a quartz cuvette. The radius of the tip of the needle was 50$\mu $m and the gap between the electrodes was set at 20$\mu $m. An inpulse generator circuit, consisting of a MOSFET switch, a capacitor, an inductor and the resistance of the liquid between the electrodes, was used as a pulse current source for operation of discharges. In the spectra, the emission peaks for the main components of sea water and contaminants from the electrodes were detected. Spectra for reference solutions were examined to enable the identification of unassigned peaks in the spectra for sea water. Analysis of the Stark broadening of H$\alpha $ peak was carried out to estimate the electron density of the plasma under various conditions. The characteristics of microplasma discharge in sea water and the analysis of the optical emission spectra will be presented. [Preview Abstract] |
Tuesday, October 11, 2016 5:15PM - 5:30PM |
GT3.00005: Numerical investigation of the interaction of positive streamers with bubbles floating on a liquid surface Natalia Yu. Babaeva, George V. Naidis, Mark J. Kushner Streamer discharges in air intersecting with liquids are being investigated to produce reactivity in the liquid. In this talk, we discuss results from a 2-d computational investigation of streamers in air intersecting an isolated liquid, air filled bubble floating on a liquid surface. The 15 mm diameter bubble is conducting water ($\varepsilon $/$\varepsilon _{\mathrm{0}}=$80, $\sigma =$7.5 x 10$^{\mathrm{-4}} \quad \Omega ^{\mathrm{-1}}$ cm$^{\mathrm{-1}})$ or transformer oil ($\varepsilon $/$\varepsilon_{\mathrm{0}}=$2.2, $\sigma =$1.5 x 10$^{\mathrm{-13}}$ $\Omega^{\mathrm{-1}}$ cm$^{\mathrm{-1}})$ [1]. A needle electrode is positioned d$=$0--10 mm from the bubble center. With a water bubble (d$=$0) the streamer slides along the external surface but does not penetrate the bubble due to electric field screening by the conducting shell. If the electrode is shifted (d$=$3-10 mm) the streamer deviates from the vertical and adheres to the bubble. If the electrode is inserted inside the bubble, the streamer path depends on how deep the electrode penetrates. For shallow penetration, the streamer propagates along the inner surface of the bubble. For deep penetration the streamer takes the shortest path down through the gas. Due to the low conductivity of the oil bubble shell the electric field penetrates into the interior of the bubble. The streamer can then be re-initiated inside the bubble. Charge accumulation on both sides of the bubble shell and perforation of the shell will be also discussed. [1] Yu Akishev et al, \textit{Plasma Sources Sci. Technol.} \textbf{24, }065021 (2015). [Preview Abstract] |
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