The Experts below are selected from a list of 2934 Experts worldwide ranked by ideXlab platform
Igor V Adamovich - One of the best experts on this subject based on the ideXlab platform.
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coherent anti stokes raman scattering and spontaneous raman scattering diagnostics of Nonequilibrium Plasmas and flows
Journal of Physics D, 2014Co-Authors: Walter R Lempert, Igor V AdamovichAbstract:The paper provides an overview of the use of coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman scattering for diagnostics of low-temperature Nonequilibrium Plasmas and Nonequilibrium high-enthalpy flows. A brief review of the theoretical background of CARS, four-wave mixing and Raman scattering, as well as a discussion of experimental techniques and data reduction, are included. The experimental results reviewed include measurements of vibrational level populations, rotational/translational temperature, electric fields in a quasi-steady-state and transient molecular Plasmas and afterglow, in Nonequilibrium expansion flows, and behind strong shock waves. Insight into the kinetics of vibrational energy transfer, energy thermalization mechanisms and dynamics of the pulse discharge development, provided by these experiments, is discussed. Availability of short pulse duration, high peak power lasers, as well as broadband dye lasers, makes possible the use of these diagnostics at relatively low pressures, potentially with a sub-nanosecond time resolution, as well as obtaining single laser shot, high signal-to-noise spectra at higher pressures. Possibilities for the development of single-shot 2D CARS imaging and spectroscopy, using picosecond and femtosecond lasers, as well as novel phase matching and detection techniques, are discussed.
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thomson scattering studies in he and he h2 nanosecond pulse Nonequilibrium Plasmas
52nd Aerospace Sciences Meeting, 2014Co-Authors: Andrew M Roettgen, Igor V Adamovich, Ivan Shkurenkov, Walter R LempertAbstract:Thomson scattering and kinetic modeling are used to study time evolution of electron density and electron temperature in a nanosecond pulse, diffuse filament electric discharge sustained between two spherical electrodes and operated at a low pulse repetition rate. The experiments have been done for three representative cases: (1) Helium, P=200 torr, discharge pulse energy 17 mJ/pulse; (2) Helium, P=100 torr, discharge pulse energy 0.6 mJ/pulse; and (3) 1% hydrogen in helium, P=100 torr, discharge pulse energy 0.8 mJ/pulse. In Case 1, peak electron number density and peak electron temperature are ne ≈ 3.5·10 15 cm -3 and Te ≈ 4 eV, respectively. The kinetic model predictions agree well with the temporal trends detected in the experiment (rapid initial rise of electron temperature and electron density during the discharge pulse and gradual decay in the afterglow), although peak electron temperature and electron density values during the pulse are somewhat overpredicted. Similar temporal trends, although at lower peak ne and Te, are observed at lower discharge pulse energies. The electron number density decay in a 1% H2 – He mixture is found to be much faster, by approximately a factor of 4, compared to helium at the same pressure and nearly the same discharge pulse energy. This is likely due to more rapid dissociative recombination of electrons in collisions with H2 + ions compared to dissociation recombination of electrons with He2 + ions. At these lower pulse energies, model predictions reproduce temporal trends fairly well, but overpredict peak electron density as well as the rate of electron cooling. D ow nl oa de d by I go r A da m ov ic h on F eb ru ar y 2, 2 01 4 | h ttp :// ar c. ai aa .o rg | D O I: 1 0. 25 14 /6 .2 01 413 58 52nd Aerospace Sciences Meeting 13-17 January 2014, National Harbor, Maryland AIAA 2014-1358 Copyright © 2014 by Andrew Roettgen. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. AIAA SciTech
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atomic oxygen measurements in o2 a1g injected Nonequilibrium Plasmas by two photon absorption laser induced fluorescence
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012Co-Authors: S Bowman, Igor V Adamovich, Walter R LempertAbstract:The paper presents new experimental and modeling results on the temporal evolution of atomic oxygen in nanosecond repetitively pulsed O2/Ar/H2 Plasmas, measured using the Two Photon Absorption Laser Induced Fluorescence (TALIF) technique. Experimental data, obtained by application of a burst of 10 – 450 nsec discharge pulses at a 40 kHz repetition rate, is found to be in satisfactory agreement with plasma chemical kinetic modeling predictions. Additional experimental measurements and modeling predictions focus on the effect of injected singlet delta oxygen, O2(aΔg), which is generated in a side RF discharge and transported to the nanosecond pulse discharge cell. No effect that can be unambiguously traced to SDO has been detected so far. One possible explanation is that it is difficult to experimentally isolate the effect of SDO from that of NO and/or NO2, which are also present in the gas mixture due to a requirement to titrate atomic oxygen also formed in the side RF discharge. SDO effect may well be reduced significantly due to rapid non-reactive quenching of O2(ag) quenching by HO2 and by H atoms generated in the nanosecond pulse discharge, although non-reactive quenching rates are known with some uncertainty. Kinetic modeling calculations, incorporating SDO quenching rates recommended in the literature predict no detectable effect of adding O2(aΔg) to the flow on number density of O atoms generated in the nanosecond pulse discharge, due to rapid collisional quenching of SDO. _______________________________________ 1 Graduate Research Assistant, Student Member AIAA 2 Professor, Associate Fellow AIAA 50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 09 12 January 2012, Nashville, Tennessee AIAA 2012-0242 Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. 2 American Institute of Aeronautics and Astronautics
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fundamental mechanisms predictive modeling and novel aerospace applications of plasma assisted combustion program overview
2009Co-Authors: Walter R Lempert, Igor V Adamovich, J Rich, Jeffrey A Sutton, Yiguang Ju, Richard B Miles, M M Shneider, Andrei Starikovskii, Alexander Fridman, R A YetterAbstract:Abstract : PRINCIPAL OBJECTIVE: "Develop experimentally validated kinetic mechanisms and modeling codes capable of predicting the impact of Nonequilibrium Plasmas on reactive processes, particularly on ignition,chemical energy release, and flameholding in combustors of flight vehicle engines." PRIMARY DELIVERABLES: * Extensive new experimental data sets of non-equilibrium plasma chemical energy conversion kinetics over a wide range of initial temperatures and pressures, in a variety of complementary new test facilities, specifically designed and fabricated for this program. * Detailed non-equilibrium plasma chemical energy conversion kinetic mechanisms, validated over a wide range of conditions, using data from multiple facilities. * Extensive experimental data sets on ignition delay, flameholding and laminar flame speed augmentation by Nonequilibrium discharges, including nsec pulsed, DC/RF, and microwave. * High fidelity multi-dimensional plasma combustion modeling codes, validated in a series of model flows, with emphasis on the high subsonic to supersonic flow regimes.
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Repetitively Pulsed Nonequilibrium Plasmas for Magnetohydrodynamic Flow Control and Plasma-Assisted Combustion
Journal of Propulsion and Power, 2008Co-Authors: Igor V Adamovich, Walter R Lempert, Munetake Nishihara, J. William Rich, Yurii UtkinAbstract:This paper demonstrates significant potential of the use of high-voltage, nanosecond pulse duration, high pulse repetition rate discharges for aerospace applications. The present results demonstrate key advantages of these discharges: 1) stability at high pressures, high flow Mach numbers, and high-energy loadings by the sustainer discharge, 2) high-energy fractions going to ionization and molecular dissociation, and 3) targeted energy addition capability provided by independent control of the reduced electric field of the direct current sustainer discharge. These unique capabilities make possible the generation of stable, volume-filling, low-temperature Plasmas and their use for high-speed flow control, nonthermal flow ignition, and gasdynamic lasers. In particular, the crossed pulsersustainerdischargewasusedformagnetohydrodynamic flowcontrolincoldM � 3 flows,providing firstevidenceof cold supersonic flow deceleration by Lorentz force. The pulsed discharge (without sustainer) was used to produce plasma chemical fuel oxidation, ignition, and flameholding in premixed hydrocarbon–air flows, in a wide range of equivalence ratios and flow velocities and at low plasma temperatures, 150–300 � C. Finally, the pulser-sustainer discharge was used to generate singlet oxygen in an electric discharge excited oxygen–iodine laser. Laser gain and output power are measured in the M � 3 supersonic cavity.
S. Rondón - One of the best experts on this subject based on the ideXlab platform.
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Reactions of O(^3P) with secondary C-H bonds of saturated hydrocarbons in Nonequilibrium Plasmas
Plasma Chemistry and Plasma Processing, 1995Co-Authors: P. Patiño, F. E. Hernández, S. RondónAbstract:The functionalization of three n-alkanes by means of a low-pressure oxygen plasma has been achieved. The plasma was generated by applying a low-Frequency high-voltage glow discharge through an oxygen flow. bit, activated species so produced have been allowed to interact with the surface of each one of the liquid compounds at a time. The hydrocarbon has been cooled down to a temperature low enough so that its vapor pressure is about 20–100 times lower than the O_2 pressure, this heing of the order of 0.1–0.4 torr. Under these conditions the main products of the reactions have been the alcohols, except for the primary ones, and the corresponding ketones. A remarkable result we have arrived at is that for the first time secondary carbon hydrogen bonds have shown to possess different reactivities with O (^3P). The latter has proved to he the most relevant active species of the plasma. A discussion is given to explain this novel result under two theoretical bases recently published: (i) a conformational analysis of the hydrocarbons according to molecular mechanics calculations, and (ii) an analysis of properties of the molecules based on calculations with charge distributions derived from 6–31G^* wave functions.
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reactions of o 3p with secondary c h bonds of saturated hydrocarbons in Nonequilibrium Plasmas
Plasma Chemistry and Plasma Processing, 1995Co-Authors: P. Patiño, F. E. Hernández, S. RondónAbstract:The functionalization of three n-alkanes by means of a low-pressure oxygen plasma has been achieved. The plasma was generated by applying a low-Frequency high-voltage glow discharge through an oxygen flow. bit, activated species so produced have been allowed to interact with the surface of each one of the liquid compounds at a time. The hydrocarbon has been cooled down to a temperature low enough so that its vapor pressure is about 20–100 times lower than the O2 pressure, this heing of the order of 0.1–0.4 torr. Under these conditions the main products of the reactions have been the alcohols, except for the primary ones, and the corresponding ketones. A remarkable result we have arrived at is that for the first time secondary carbon hydrogen bonds have shown to possess different reactivities withO(3P). The latter has proved to he the most relevant active species of the plasma. A discussion is given to explain this novel result under two theoretical bases recently published: (i) a conformational analysis of the hydrocarbons according to molecular mechanics calculations, and (ii) an analysis of properties of the molecules based on calculations with charge distributions derived from 6–31G* wave functions.
Jan Schäfer - One of the best experts on this subject based on the ideXlab platform.
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White paper on the future of plasma science and technology in plastics and textiles
Plasma Processes and Polymers, 2019Co-Authors: Uroš Cvelbar, James Walsh, Stephan Reuter, Thierry Belmonte, | Carles Corbella, Camelia Miron, Nataša Hojnik, Andrea Jurov, Harinarayanan Puliyalil, Jan SchäferAbstract:This white paper considers the future of plasma science and technology related to the manufacturing and modifications of plastics and textiles, summarizing existing efforts and the current state-of-art for major topics related to plasma processing techniques. It draws on the frontier of plasma technologies in order to see beyond and identify the grand challenges which we face in the following 5–10 years. To progress and move the frontier forward, the paper highlights the major enabling technologies and topics related to the design of surfaces, coatings and materials with Nonequilibrium Plasmas. The aim is to progress the field of plastics and textile production using advanced plasma processing as the key enabling technology which is environmentally friendly, cost-efficient, and offers high-speed processing.
Walter R Lempert - One of the best experts on this subject based on the ideXlab platform.
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coherent anti stokes raman scattering and spontaneous raman scattering diagnostics of Nonequilibrium Plasmas and flows
Journal of Physics D, 2014Co-Authors: Walter R Lempert, Igor V AdamovichAbstract:The paper provides an overview of the use of coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman scattering for diagnostics of low-temperature Nonequilibrium Plasmas and Nonequilibrium high-enthalpy flows. A brief review of the theoretical background of CARS, four-wave mixing and Raman scattering, as well as a discussion of experimental techniques and data reduction, are included. The experimental results reviewed include measurements of vibrational level populations, rotational/translational temperature, electric fields in a quasi-steady-state and transient molecular Plasmas and afterglow, in Nonequilibrium expansion flows, and behind strong shock waves. Insight into the kinetics of vibrational energy transfer, energy thermalization mechanisms and dynamics of the pulse discharge development, provided by these experiments, is discussed. Availability of short pulse duration, high peak power lasers, as well as broadband dye lasers, makes possible the use of these diagnostics at relatively low pressures, potentially with a sub-nanosecond time resolution, as well as obtaining single laser shot, high signal-to-noise spectra at higher pressures. Possibilities for the development of single-shot 2D CARS imaging and spectroscopy, using picosecond and femtosecond lasers, as well as novel phase matching and detection techniques, are discussed.
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thomson scattering studies in he and he h2 nanosecond pulse Nonequilibrium Plasmas
52nd Aerospace Sciences Meeting, 2014Co-Authors: Andrew M Roettgen, Igor V Adamovich, Ivan Shkurenkov, Walter R LempertAbstract:Thomson scattering and kinetic modeling are used to study time evolution of electron density and electron temperature in a nanosecond pulse, diffuse filament electric discharge sustained between two spherical electrodes and operated at a low pulse repetition rate. The experiments have been done for three representative cases: (1) Helium, P=200 torr, discharge pulse energy 17 mJ/pulse; (2) Helium, P=100 torr, discharge pulse energy 0.6 mJ/pulse; and (3) 1% hydrogen in helium, P=100 torr, discharge pulse energy 0.8 mJ/pulse. In Case 1, peak electron number density and peak electron temperature are ne ≈ 3.5·10 15 cm -3 and Te ≈ 4 eV, respectively. The kinetic model predictions agree well with the temporal trends detected in the experiment (rapid initial rise of electron temperature and electron density during the discharge pulse and gradual decay in the afterglow), although peak electron temperature and electron density values during the pulse are somewhat overpredicted. Similar temporal trends, although at lower peak ne and Te, are observed at lower discharge pulse energies. The electron number density decay in a 1% H2 – He mixture is found to be much faster, by approximately a factor of 4, compared to helium at the same pressure and nearly the same discharge pulse energy. This is likely due to more rapid dissociative recombination of electrons in collisions with H2 + ions compared to dissociation recombination of electrons with He2 + ions. At these lower pulse energies, model predictions reproduce temporal trends fairly well, but overpredict peak electron density as well as the rate of electron cooling. D ow nl oa de d by I go r A da m ov ic h on F eb ru ar y 2, 2 01 4 | h ttp :// ar c. ai aa .o rg | D O I: 1 0. 25 14 /6 .2 01 413 58 52nd Aerospace Sciences Meeting 13-17 January 2014, National Harbor, Maryland AIAA 2014-1358 Copyright © 2014 by Andrew Roettgen. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. AIAA SciTech
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atomic oxygen measurements in o2 a1g injected Nonequilibrium Plasmas by two photon absorption laser induced fluorescence
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012Co-Authors: S Bowman, Igor V Adamovich, Walter R LempertAbstract:The paper presents new experimental and modeling results on the temporal evolution of atomic oxygen in nanosecond repetitively pulsed O2/Ar/H2 Plasmas, measured using the Two Photon Absorption Laser Induced Fluorescence (TALIF) technique. Experimental data, obtained by application of a burst of 10 – 450 nsec discharge pulses at a 40 kHz repetition rate, is found to be in satisfactory agreement with plasma chemical kinetic modeling predictions. Additional experimental measurements and modeling predictions focus on the effect of injected singlet delta oxygen, O2(aΔg), which is generated in a side RF discharge and transported to the nanosecond pulse discharge cell. No effect that can be unambiguously traced to SDO has been detected so far. One possible explanation is that it is difficult to experimentally isolate the effect of SDO from that of NO and/or NO2, which are also present in the gas mixture due to a requirement to titrate atomic oxygen also formed in the side RF discharge. SDO effect may well be reduced significantly due to rapid non-reactive quenching of O2(ag) quenching by HO2 and by H atoms generated in the nanosecond pulse discharge, although non-reactive quenching rates are known with some uncertainty. Kinetic modeling calculations, incorporating SDO quenching rates recommended in the literature predict no detectable effect of adding O2(aΔg) to the flow on number density of O atoms generated in the nanosecond pulse discharge, due to rapid collisional quenching of SDO. _______________________________________ 1 Graduate Research Assistant, Student Member AIAA 2 Professor, Associate Fellow AIAA 50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 09 12 January 2012, Nashville, Tennessee AIAA 2012-0242 Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. 2 American Institute of Aeronautics and Astronautics
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fundamental mechanisms predictive modeling and novel aerospace applications of plasma assisted combustion program overview
2009Co-Authors: Walter R Lempert, Igor V Adamovich, J Rich, Jeffrey A Sutton, Yiguang Ju, Richard B Miles, M M Shneider, Andrei Starikovskii, Alexander Fridman, R A YetterAbstract:Abstract : PRINCIPAL OBJECTIVE: "Develop experimentally validated kinetic mechanisms and modeling codes capable of predicting the impact of Nonequilibrium Plasmas on reactive processes, particularly on ignition,chemical energy release, and flameholding in combustors of flight vehicle engines." PRIMARY DELIVERABLES: * Extensive new experimental data sets of non-equilibrium plasma chemical energy conversion kinetics over a wide range of initial temperatures and pressures, in a variety of complementary new test facilities, specifically designed and fabricated for this program. * Detailed non-equilibrium plasma chemical energy conversion kinetic mechanisms, validated over a wide range of conditions, using data from multiple facilities. * Extensive experimental data sets on ignition delay, flameholding and laminar flame speed augmentation by Nonequilibrium discharges, including nsec pulsed, DC/RF, and microwave. * High fidelity multi-dimensional plasma combustion modeling codes, validated in a series of model flows, with emphasis on the high subsonic to supersonic flow regimes.
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Repetitively Pulsed Nonequilibrium Plasmas for Magnetohydrodynamic Flow Control and Plasma-Assisted Combustion
Journal of Propulsion and Power, 2008Co-Authors: Igor V Adamovich, Walter R Lempert, Munetake Nishihara, J. William Rich, Yurii UtkinAbstract:This paper demonstrates significant potential of the use of high-voltage, nanosecond pulse duration, high pulse repetition rate discharges for aerospace applications. The present results demonstrate key advantages of these discharges: 1) stability at high pressures, high flow Mach numbers, and high-energy loadings by the sustainer discharge, 2) high-energy fractions going to ionization and molecular dissociation, and 3) targeted energy addition capability provided by independent control of the reduced electric field of the direct current sustainer discharge. These unique capabilities make possible the generation of stable, volume-filling, low-temperature Plasmas and their use for high-speed flow control, nonthermal flow ignition, and gasdynamic lasers. In particular, the crossed pulsersustainerdischargewasusedformagnetohydrodynamic flowcontrolincoldM � 3 flows,providing firstevidenceof cold supersonic flow deceleration by Lorentz force. The pulsed discharge (without sustainer) was used to produce plasma chemical fuel oxidation, ignition, and flameholding in premixed hydrocarbon–air flows, in a wide range of equivalence ratios and flow velocities and at low plasma temperatures, 150–300 � C. Finally, the pulser-sustainer discharge was used to generate singlet oxygen in an electric discharge excited oxygen–iodine laser. Laser gain and output power are measured in the M � 3 supersonic cavity.
D O Gericke - One of the best experts on this subject based on the ideXlab platform.
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analysis of thomson scattering from Nonequilibrium Plasmas
Physical Review Letters, 2011Co-Authors: D A Chapman, D O GerickeAbstract:We develop the theory for light scattering as a diagnostic method for Plasmas in Nonequilibrium states. We show how well-known Nonequilibrium features, like beam acoustic modes, arise in the spectra. The analysis of an experiment with strongly driven electrons demonstrates the abilities of the new approach; we find qualitatively different scattering spectra for different times and excellent agreement with the experimental data after time integration. Finally, an analysis of data from dense beryllium suggests that an energetic electron component exists in this experiment as well.