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 AM2: Workshop on Weakly-ionized non-equilibrium air plasma at moderate and high pressures: generation and maintenance, modeling, diagnostics and applications |
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Chair: Mikhail Shneyder; Richard Miles, Princeton University Room: Ballroom II |
Monday, September 30, 2013 8:30AM - 8:35AM |
AM2.00001: WELCOME |
Monday, September 30, 2013 8:35AM - 9:05AM |
AM2.00002: Plasma-Based Mixing Actuation in Airflow, Quantitated by Probe Breakdown Fluorescence Sergey Leonov, Alexander Firsov, Michail Shurupov, Dmitry Yarantsev Effective mixing of fuel and oxidizer in air-breathing engine at compressible conditions is an essential problem of high-speed combustion due to short residence time of gas mixture in the combustor of limited length. The effect of the mixing actuation by plasma is observed because of the gasdynamic instability arisen after the long filamentary discharge of submicrosecond duration generated along the contact zone of two co-flown gases. The work is focused on detail consideration of the mechanism of gas instability, promoted by plasma, on effect of the discharge specific localization, and on diagnostics development for qualitative and quantitative estimation of the mixing efficiency. The dynamics of relative concentration of gas components is examined quantitatively by means of Probe Discharge Breakdown Fluorescence (PBF). In this method an optical emission spectra of weak filamentary high-voltage nanosecond probe discharge are collected from local zone of interest in airflow. The first measurements of the mixing efficiency in vicinity of wall-injected secondary gas are presented. It is shown that the method of PBF could deliver experimental data on state of the two-component medium with \textless 1mcs and \textless 5mm of time and spatial resolution, correspondingly. [Preview Abstract] |
Monday, September 30, 2013 9:05AM - 9:35AM |
AM2.00003: Towards fully hybrid simulations of atmospheric pressure plasmas Alexandre Likhanskii Recent experimental studies demonstrated high potential of using atmospheric pressure plasmas for a number of industrial application, such as plasma medicine, plasma processing, plasma aerodynamics and plasma transistors. Majority of the numerical efforts addressing this type of gas discharges were done using fluid plasma representation. However, fluid plasma models lack important plasma effects, such as non-Maxwellian EEDF in the cathode sheath of streamer head or formation of filamentary structures. These effects must be addressed using kinetic approach. The presentation will describe the developed hybrid (kinetic$+$fluid) model in Tech-X code VSim (formerly Vorpal) for simulation of wide range of discharges. The model incorporated majority of relevant physics processes, including photoionization for accurate description of filament development. The results of the simulation of atmospheric pressure discharges for relevant industrial problems using kinetic, fluid and hybrid approaches will be presented, and detailed comparison between the models will be provided. [Preview Abstract] |
Monday, September 30, 2013 9:35AM - 9:50AM |
AM2.00004: BREAK
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Monday, September 30, 2013 9:50AM - 10:20AM |
AM2.00005: Advanced laser diagnostics for gases and weakly ionized plasma Arthur Dogariu Recent advancements in laser-based gas and plasma diagnostics will be presented, ranging from resonant multiphoton ionization to femtosecond filamentation. Spectroscopy and remote trace gas detection down to parts-per-billion are demonstrated using a combination of resonant laser ionization through multiphoton excitation, and microwave scattering off the weakly ionized plasma. The Radar-REMPI (Resonantly Enhanced Multi-Photon Ionization) technique also allows for studying the dynamics of the weak plasma, and first direct measurements of the electron attachment rates in atmospheric air are demonstrated. The plasma dynamics not only reveals the electron loss mechanisms such as attachment and recombination, but can also be a good measure of the electron density. Laser based techniques such as Rayleigh scattering are used for gas temperature measurements, and in particular Filtered Rayleigh Scattering shows great promise in environments where background scattering is significant. Femtosecond Laser Electronic Excitation Tagging (FLEET) is a new non-invasive laser technique for flow velocity mapping, and it is based on imaging nitrogen emission in femtosecond filaments. FLEET has been recently proven to be adequate for measuring and mapping the gas temperature as well. [Preview Abstract] |
Monday, September 30, 2013 10:20AM - 10:50AM |
AM2.00006: Physical and biological mechanisms of nanosecond- and microsecond-pulsed FE-DBD plasma interaction with biological objects Danil Dobrynin Mechanisms of plasma interaction with living tissues and cells can be quite complex, owing to the complexity of both the plasma and the tissue. Thus, unification of all the mechanisms under one umbrella might not be possible. Here, analysis of interaction of floating electrode dielectric barrier discharge (FE-DBD) with living tissues and cells is presented and biological and physical mechanisms are discussed. In physical mechanisms, charged species are identified as the major contributors to the desired effect and a mechanism of this interaction is proposed. Biological mechanisms are also addressed and a hypothesis of plasma selectivity and its effects is offered. Spatially uniform nanosecond and sub-nanosecond short-pulsed dielectric barrier discharge plasmas are gaining popularity in biological and medical applications due to their increased uniformity, lower plasma temperature, lower surface power density, and higher concentration of the active species produced. In this presentation we will compare microsecond pulsed plasmas with nanosecond driven systems and their applications in biology and medicine with specific focus on wound healing and tissue regeneration. Transition from negative to positive streamer will be discussed with proposed hypothesis of uniformity mechanisms of positive streamer and the reduced dependence on morphology and surface chemistry of the second electrode (human body) being treated. Uniform plasma offers a more uniform delivery of active species to the tissue/surface being treated thus leading to better control over the biological results. [Preview Abstract] |
Monday, September 30, 2013 10:50AM - 11:20AM |
AM2.00007: Surface Wave Driven Air-Water Plasmas Elena Tatarova, Julio Henriques, Carlos Ferreira The performance of a surface wave driven air-water plasma source operating at atmospheric pressure and 2.45 GHz has been analyzed. A 1D model has been developed in order to describe in detail the creation and loss processes of active species of interest and to provide a complete characterization of the axial structure of the source, including the discharge and the afterglow zones. The main electron creation channel was found to be the associative ionization process N$+$O$\to $NO$^{+}+$e. The NO(X) relative density in the afterglow plasma jet ranges from 1.2{\%} to 1.6{\%} depending on power and water percentage according to the model predictions and the measurements. Other types of species such as NO$_{2}$ and nitrous acid HNO$_{2}$ have also been detected by mass and FT-IR spectroscopy. Furthermore, high densities of O$_{2}$(a$^{1}\Delta_{\mathrm{g}})$ singlet delta oxygen molecules and OH radicals (1{\%} and 5 {\%}, respectively) can be achieved in the discharge zone. In the late afterglow the O$_{2}$(a$^{1}\Delta_{\mathrm{g}})$ density is about 0.1 {\%} of the total density. The plasma source has a flexible operation and potential for channeling the energy in ways that maximize the density of active species of interest. [Preview Abstract] |
Monday, September 30, 2013 11:20AM - 11:50AM |
AM2.00008: RF discharge phenomena in miniaturized RF MEMS cavity-based filters Dimitrios Peroulis Reconfigurable filters are critical devices for the coming generation of high-frequency electronics. Several competing requirements including miniaturization, performance, frequency-agility and power handling need to be carefully considering in designing successful filters particularly for mobile-form-factor electronics. This talk will discuss the latest findings in state-of-the-art tunable cavity-based RF MEMS filters as relate to the aforementioned factors. Special attention will be paid on the role that RF gas discharge phenomena play in the performance and lifetime of these devices. [Preview Abstract] |
Monday, September 30, 2013 11:50AM - 12:50PM |
AM2.00009: LUNCH |
Monday, September 30, 2013 12:50PM - 1:20PM |
AM2.00010: High pressure noble gas plasmas in microcavities: a review of the discharge physics Sergey Macheret High pressure (from tens to hundreds of Torr) inert gas plasmas confined in microcavities are studied because of both applications and interesting physics. The presentation is a review of research literature on this topic, focusing on the dynamics of electric discharges in microcavities. [Preview Abstract] |
Monday, September 30, 2013 1:20PM - 1:50PM |
AM2.00011: SI Engine with repetitive NS spark plug Sergey Pancheshniy, Andrey Nikipelov, Eugeny Anokhin, Andrey Starikovskiy Now de-facto the only technology for fuel-air mixtures ignition in IC engines exists. It is a spark discharge of millisecond duration in a short discharge gap. The reason for such a small variety of methods of ignition initiation is very specific conditions of the engine operation.~First, it is very high-pressure of fuel-air mixture -- from 5-7 atmospheres in old-type engines and up to 40-50 atmospheres on the operating mode of HCCI. Second, it is a very wide range of variation of the oxidizer/fuel ratio in the mixture -- from almost stoichiometric (0.8-0.9) at full load to very lean ($\varphi =$ 0.3-0.5) mixtures at idle and/or economical cruising mode.~Third, the high velocity of the gas in the combustion chamber (up to 30-50 m/s) resulting in a rapid compression of swirling inlet flow. The paper presents the results of tests of distributed spark ignition system powered by repetitive pulse nanosecond discharge. Dynamic pressure measurements show the increased pressure and frequency stability for nanosecond excitation in comparison with the standard spark plug. Excitation by single nanosecond high-voltage pulse and short train of pulses was examined. In all regimes the nanosecond pulsed excitation demonstrate a better performance. [Preview Abstract] |
Monday, September 30, 2013 1:50PM - 2:20PM |
AM2.00012: Simulation of the ignition by a nanosecond spark discharge of a H$_2$-air mixture at atmospheric pressure Anne Bourdon, Fabien Tholin, Deanna Lacoste Since a few years, Nanosecond repetitively Pulsed Discharges (NRPD) have been extensively studied at atmospheric pressure as they efficiently produce many reactive chemical species at a low energy cost. Recent measurements have shown that in the ``spark'' regime of NRP discharges, an ultra-fast local heating of the gas could be obtained. This effect is of great interest for applications as flow control and plasma assisted combustion. In this work, we have carried out 2D simulations of the coupling of a nanosecond spark discharge in air at atmospheric pressure in a point-point geometry with the ambient air. In particular, we have simulated shock waves generated by a nanosecond spark discharge and we have compared our results with experiments. Then, we have studied the production of active species by a nanosecond spark discharge. Finally, we have simulated the flame ignition in a lean H$_2$-air mixture by a nanosecond spark discharge. Based on the results obtained at different gas temperatures, the relative importance for the combustion ignition of gas heating and production of active species by the nanosecond spark discharge is discussed. [Preview Abstract] |
Monday, September 30, 2013 2:20PM - 2:50PM |
AM2.00013: Characteristics of short dc glow microdischarges in atmospheric pressure air Anatoly Kudryavtsev The main reason that high pressure current-carrying plasmas tend to be unstable is various instability (primarily thermal) of the positive column (PC). So a promising approach is to use short (without PC) discharges that have growing voltage--current characteristic (VAC). These discharges are ignited near the minimum of the Paschen breakdown curve \textit{Lmin} and it usually have a gap \textit{pL \textless 10--20 cm Torr} when a distinct PC is absent. In this report the most stable microdischarges were burning with a flat cathode and rounded (or thin rod) anode, which located to a distance less than \textit{Lmin} when the microdischarge ``choose'' their length itself, so that to match the stable work near \textit{Lmin} by changing their binding on the anode. For simulations we used 2D hybrid model. Simulations predicted the main regions of the dc glow discharges including cathode and anode sheath and plasma of negative glow, Faraday dark space and transition region, in which the electric field is distributed no uniformly and plasma is nonlocal. Gas heating plays an important role in shaping the discharge profiles. [Preview Abstract] |
Monday, September 30, 2013 2:50PM - 3:20PM |
AM2.00014: High-Voltage Nanosecond Pulse Action on RF Discharge Leonid Vasilyak, Mikhail Pustylnik, Lujing Hou, Alexei Ivlev, Lenaic Couedel, Hubertus Thomas, Gregor Morfill, Vladimir Fortov After the discharge of atmospheric lightning from cloud to the ground the space electric charge appears. We investigated experimentally similar situation in a short discharge gap. A high-voltage (3-17 kV) 20 ns pulse was applied to the weakly-ionized RF discharge. The plasma evolution exhibits two regimes: a bright flash, occurring within 100 ns after the pulse, and a dark phase, lasting a few hundreds microseconds. Electron density increased during the flash remains high during the dark phase. 1D3V particle-in-cell simulation was made. The high-voltage nanosecond pulse is found to be capable of removing a significant fraction of plasma electrons out of the discharge gap. The flash is the result of the excitation of gas by the electron in the residual electric field of the bulk positive charge. High density plasma formed during the flash provides screening of the steady-state RF field, which leads to the electron cooling and, hence, a dark phase. [Preview Abstract] |
Monday, September 30, 2013 3:20PM - 3:35PM |
AM2.00015: BREAK |
Monday, September 30, 2013 3:35PM - 4:05PM |
AM2.00016: Nanosecond Glow and Spark Discharges in Ambient Air and in Water Vapor Christophe Laux, Diane Rusterholtz, Florent Sainct, Da Xu, Deanna Lacoste, Gabi Stancu, David Pai Nanosecond repetitively pulsed (NRP) discharges are one of the most energy efficient ways to produce active species in atmospheric pressure gases. In both air and water vapor, three discharge regimes can be obtained: 1) corona, with light emission just around the anode, 2) glow, corresponding to a diffuse nonequilibrium plasma, and 3) spark, characterized by higher temperatures and higher active species densities. The glow regime was initially obtained in air preheated at 2000 K. Based on a model defining the transition between glow and spark, we recently succeeded in obtaining a stable glow in ambient air at 300 K, using a judicious combination of electrode geometry, pulse duration, pulse frequency, and applied voltage. We will present these results and describe the characteristics of the discharge obtained in room air. The spark regime was also studied. NRP sparks induce ultrafast gas heating (about 1000 K in 20 ns) and high oxygen dissociation (up to 50{\%} dissociation of O$_{2})$. This phenomenon can be explained by a two-step process involving the excitation of molecular nitrogen followed by exothermic dissociative quenching of molecular oxygen. The characteristics of NRP discharges in water vapor will also be discussed. [Preview Abstract] |
Monday, September 30, 2013 4:05PM - 4:35PM |
AM2.00017: ROUND TABLE DISCUSSION |
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