Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session DT3: Liquids I |
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Chair: Mikhail Shneider, Princeton University Room: Nassau Room |
Tuesday, October 1, 2013 10:00AM - 10:30AM |
DT3.00001: Microplasmas in liquids Invited Speaker: David Staack Plasma discharges from 1 ?m to 10 ?m in size can be generated in a variety of liquids by the use of nanosecond duration high voltage pulses of low energy. Through a variety of high temporal and spatial resolution diagnostic the plasma discharge formation, growth and properties are studied. Experiments reveal the plasma is confined inside of a small lower density region, or bubble, in the fluid. This bubble is generated commensurate with the plasma formation and the stability and rate of bubble growth is input energy and medium dependent. Emission spectroscopy indicates the microscale plasmas to be non-equilibrium but only when the lowest energy, and smallest, discharges are generated. The non-equilibrium and high surface to volume ratio of the microplasmas offers a unique set of liquid phase plasma chemistries. Various schema for generating both highly localized and volumetrically distributed non-equilibrium microplasmas in liquids are presented. When applied to the reforming of fuels and oils the advantages of the non-equilibrium discharge in liquid regime lead to more control over the product compositions. [Preview Abstract] |
Tuesday, October 1, 2013 10:30AM - 11:15AM |
DT3.00002: Tutorial on underwater electrical discharges: main features and applications Invited Speaker: Yakov Krasik Main features of underwater electrical discharge with short description of models (``bubble'', ``explosive emission'', ``ionization'' and ``thermal''), parameters of the discharge (threshold electric field versus polarity, time duration, frequency, pressure, interelectrode gap and area of electrodes, velocity of streamer propagation and density and temperature of the plasma, strong shock waves) and different electrical and optical diagnostics which were used in this research will be shortly reviewed. Such main applications of underwater electrical discharge as electro-hydraulic forming, destruction of rocks, low-inductance water spark gap switches, treatment of pollutants in water and extracorporeal shock wave lithotripsy will be discussed. Finally, results of application of underwater electrical explosion of single wires in nanosecond - microsecond timescales for research related to Equation of State of different materials at extreme conditions and underwater electrical explosion of wire arrays in cylindrical and spherical configurations for generation of converging strong shock waves using moderate high-power generators for research of compressed water at extreme conditions will be presented. [Preview Abstract] |
Tuesday, October 1, 2013 11:15AM - 11:30AM |
DT3.00003: Nanosecond Pulsed Discharges in Liquid Phase: Optical diagnostics of positive versus negative modes of initiation in water Yohan Seepersad, Alexander Fridman, Danil Dobrynin Recent work on nanosecond pulsed discharges in liquids has shown the possibility of producing plasma directly in the liquid phase without bubble formation or heating of the liquid. Paramount to understanding the physical processes leading to this phenomenon is a thorough understanding of the way these discharges behave under various conditions. This work explores the development of nanosecond pulsed discharges in water, for both positively and negatively applied pulses in a pin-to-plane configuration. Time resolved nanosecond ICCD imaging is used to trace the development of the discharge for applied voltages up to 24kV. From the results we are able to identify breakdown thresholds at which discharge is initiated for both modes. At voltages below the critical breakdown value, Schlieren and shadowgraphy techniques are used to investigate perturbations in the liquid layers near the electrode tip as a consequence of these fat rising pulses. [Preview Abstract] |
Tuesday, October 1, 2013 11:30AM - 11:45AM |
DT3.00004: Plasma Spark Discharge Generated Water Displacement Nathaniel Taylor, Danil Dobrynin, Alexander Fridman The physical displacement of water generated by plasma spark discharge has been investigated to determine the correlation between discharge parameters and displacement. Microsecond duration spark discharge pulses generate shockwaves and vapor which subsequently displaces the fluid over a period of milliseconds. Pulses ranging from 18 to 28 kV are generated inside of a sealed chamber and observed using a glass monometer. The displacement of the water has been measured using high-speed ICCD imagery and correlated to the plasma discharge energy and duration. [Preview Abstract] |
Tuesday, October 1, 2013 11:45AM - 12:00PM |
DT3.00005: Mechanism of efficient production of standing sonoplasmas with the help of a punching metal plate K. Sasaki, Y. Iwata, S. Tomioka, S. Nishiyama, N. Takada We have reported an efficient method for producing standing sonoplasmas. This method employs a punching metal plate which is inserted just below the water surface with the irradiation of ultrasonic wave. In this work, we carried out two experiments to investigate the mechanism of the efficient production of standing sonoplasmas. One was the measurement of the intensity distribution of the ultrasonic wave using an optical microphone. As a result, it was found that, at the optimum depth of water for producing sonoplasmas, the intensity of the ultrasonic wave was strong in the neighboring region to the water surface where the punching metal plate was inserted. In addition, we observed a local minimum in the distribution of the ultrasonic wave intensity. The location of the local minimum coincided with the standing point of cavitation bubbles or sonoplasmas. The other experiment was the shadowgraph imaging of cavitation bubbles. As a result, we found the efficient formation of seed bubbles in the adjacent region to the punching metal plate. The seed bubbles were transported to the local minimum of the ultrasonic wave intensity. We will discuss the mechanism of the efficient production of standing sonoplasmas on the basis of these experimental observations. [Preview Abstract] |
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