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Jannis Teunissen - One of the best experts on this subject based on the ideXlab platform.

  • improvements for drift diffusion plasma fluid models with explicit time integration
    Plasma Sources Science and Technology, 2020
    Co-Authors: Jannis Teunissen
    Abstract:

    textabstractDrift-diffusion plasma fluid models are commonly used to simulate Electric Discharges. Such models can computationally be very efficient if they are combined with explicit time integration. This paper deals with two issues that often arise with such models. First, a high plasma conductivity can severely limit the time step. A fully explicit method to overcome this limitation is presented. This method is compared to the existing semi-implicit method, and it is shown to have several advantages. A second issue is specific to models with the local field approximation. Near strong density and Electric field gradients, electrons can diffuse parallel to the field, and unphysically generate ionization. Existing and new approaches to correct this behavior are compared. Details on the implementation of the models and the various approaches are provided.

Mark J Kushner - One of the best experts on this subject based on the ideXlab platform.

  • continuous wave laser oscillation on the 1315nm transition of atomic iodine pumped by o2 a1δ produced in an Electric discharge
    Applied Physics Letters, 2005
    Co-Authors: David L Carroll, J T Verdeyen, Darren M King, J K Laystrom, G F Benavides, J W Zimmerman, Brian S Woodard, K Kittell, Shane D Stafford, Mark J Kushner
    Abstract:

    Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ) which is produced using wet-solution chemistry. The difficulties in chemically producing O2(a1Δ) has motivated investigations into purely gas phase methods to produce O2(a1Δ) using low-pressure Electric Discharges. In this letter, we report on the demonstration of a continuous-wave laser on the 1315nm transition of atomic iodine where the O2(a1Δ) used to pump the iodine was produced by a radio-frequency-excited Electric discharge. The Electric discharge was sustained in a He∕O2 gas mixture upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(P1∕22) state. The laser output power was 220mW in a stable cavity composed of two 99.99% reflective mirrors.

  • avalanche process in an idealized lamp ii modelling of breakdown in ar xe Electric Discharges
    Journal of Physics D, 2004
    Co-Authors: Ananth Bhoj, Mark J Kushner
    Abstract:

    The breakdown phase of the startup of metal halide lamps is typically through a cold fill of a rare gas and the ambient vapour pressure of a dose of metals. The dynamics of the breakdown stage are of interest for improving the efficiency and lifetime of lamps. A computational investigation of the breakdown of Ar/Xe mixtures in an idealized lamp geometry was performed using global and two-dimensional (2-d) models to provide insight into the lamp ignition processes and to facilitate comparison with experiments. The experimental trends for breakdown for pressures of 10?90?Torr were qualitatively captured with the global model. Quantitative agreement required accounting for the temporal and spatial plasma dynamics included in the 2-d model. Small fractions of Xe in Ar were found to decrease the breakdown time as the ionization rates increased due to the lower ionization potential of xenon, while the electron energy distribution was not significantly affected. With higher Xe fractions the electron temperature in the ionization front decreased due to there being larger momentum transfer and inelastic losses to the Xe, and as a result the breakdown times increased. The compression of voltage ahead of the ionization front produced large Electric fields at the cathode that enabled significant contributions to ionization by secondary electrons.

  • measurement of positive gain on the 1315nm transition of atomic iodine pumped by o2 a1δ produced in an Electric discharge
    Applied Physics Letters, 2004
    Co-Authors: David L Carroll, J T Verdeyen, Darren M King, J K Laystrom, J W Zimmerman, Brian S Woodard, N Richardson, K Kittell, Mark J Kushner, Wayne C Solomon
    Abstract:

    Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ), which is produced using wet-solution chemistry. The system difficulties of chemically producing O2(a1Δ) has motivated investigations into gas phase methods to produce O2(a1Δ) using low-pressure Electric Discharges. In this letter we report on positive gain on the 1315nm transition of atomic iodine where the O2(a1Δ) was produced in a flowing Electric discharge. The Electric discharge was followed by a continuously flowing supersonic cavity that was necessary to lower the temperature of the flow and shift the equilibrium of atomic iodine more in favor of the I(P1∕22) state. A tunable diode laser system capable of scanning the entire line shape of the (3,4) hyperfine transition of iodine provided the measurements of gain.

David L Carroll - One of the best experts on this subject based on the ideXlab platform.

  • continuous wave laser oscillation on the 1315nm transition of atomic iodine pumped by o2 a1δ produced in an Electric discharge
    Applied Physics Letters, 2005
    Co-Authors: David L Carroll, J T Verdeyen, Darren M King, J K Laystrom, G F Benavides, J W Zimmerman, Brian S Woodard, K Kittell, Shane D Stafford, Mark J Kushner
    Abstract:

    Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ) which is produced using wet-solution chemistry. The difficulties in chemically producing O2(a1Δ) has motivated investigations into purely gas phase methods to produce O2(a1Δ) using low-pressure Electric Discharges. In this letter, we report on the demonstration of a continuous-wave laser on the 1315nm transition of atomic iodine where the O2(a1Δ) used to pump the iodine was produced by a radio-frequency-excited Electric discharge. The Electric discharge was sustained in a He∕O2 gas mixture upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(P1∕22) state. The laser output power was 220mW in a stable cavity composed of two 99.99% reflective mirrors.

  • measurement of positive gain on the 1315nm transition of atomic iodine pumped by o2 a1δ produced in an Electric discharge
    Applied Physics Letters, 2004
    Co-Authors: David L Carroll, J T Verdeyen, Darren M King, J K Laystrom, J W Zimmerman, Brian S Woodard, N Richardson, K Kittell, Mark J Kushner, Wayne C Solomon
    Abstract:

    Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ), which is produced using wet-solution chemistry. The system difficulties of chemically producing O2(a1Δ) has motivated investigations into gas phase methods to produce O2(a1Δ) using low-pressure Electric Discharges. In this letter we report on positive gain on the 1315nm transition of atomic iodine where the O2(a1Δ) was produced in a flowing Electric discharge. The Electric discharge was followed by a continuously flowing supersonic cavity that was necessary to lower the temperature of the flow and shift the equilibrium of atomic iodine more in favor of the I(P1∕22) state. A tunable diode laser system capable of scanning the entire line shape of the (3,4) hyperfine transition of iodine provided the measurements of gain.

Murielle Naïtali - One of the best experts on this subject based on the ideXlab platform.

  • Kinetics and Bacterial Inactivation Induced by Peroxynitrite in Electric Discharges in Air
    Plasma Chemistry and Plasma Processing, 2012
    Co-Authors: Murielle Naïtali, Georges Kamgang, Eugen Hnatiuc, Jean-marie Herry, Jean-louis Brisset
    Abstract:

    The mechanism of bacterial inactivation by Electric Discharges (non-thermal plasma) is examined on the basis of the action of the formed peroxynitrite and hydrogen peroxide on the external membrane of bacteria. A model accounts for the gas to liquid transfer of the active species which react with the bacterial wall at the liquid surface or /and in the bulk solution. Direct exposure to the glidarc discharge induces a pseudo zero order decay of the bacterial concentration, followed by a pseudo 1st order step for low concentrations. Post-discharge reactions develop after switching off the discharge according to a 1st order mechanism and show that active species drift in the solution. Additionally the bactericidal properties of pure water exposed to the discharge (i.e., “Plasma Activated Water”) was evidenced even 24 h after performing the plasma treatment.

  • Microbial inactivation using plasma-activated water obtained by gliding Electric Discharges
    Letters in Applied Microbiology, 2009
    Co-Authors: Georges Kamgang Youbi, Jean-louis Brisset, Jean-marie Herry, Marie Noelle Bellon-fontaine, Thierry Meylheuc, A. Doubla, Murielle Naïtali
    Abstract:

    Aim: To evaluate the microbial disinfection efficacy of a plasmachemical solu-tion obtained by the activation of water with gliding Electric Discharges.Methods and Results: Distilled water was activated for 5 min by a nonthermalquenched plasma of the glidarc type operating in humid air and at atmosphericpressure. The plasma-activated water (PAW) was then used to treat planktonicand adherent cells of Staphylococcus epidermidis, Leuconostoc mesenteroides (asmodels of Gram-positive bacteria), Hafnia alvei (a Gram-negative bacteria) andSaccharomyces cerevisiae (as a yeast model). The treatments were less efficienton adherent cells than on planktonic cells in the case of bacteria, but not ofS. cerevisiae. Inactivation was more effective for bacteria than for the yeast.Conclusions: Significant reductions in microbial populations were achieved inall cases, demonstrating the effectiveness of this new approach to treat conta-minated media.Significance and Impact of the Study: PAW is a promising solution withpotential application to the decontamination of equipment and surfaces.

  • Chemical reactivity of Discharges and temporal post-Discharges in plasma treatment of aqueous media: examples of gliding discharge treated solutions
    Industrial and engineering chemistry research, 2008
    Co-Authors: Jean-louis Brisset, Murielle Naïtali, Eugen Hnatiuc, Jean-marie Herry, Georges Kamgang Youbi, Avaly Doubla, David Moussa, Bogdan Hnatiuc, Marie Noelle Bellon-fontaine
    Abstract:

    Environmental applications of Electric Discharges are being considered increasingly more often: they imply the chemical properties of the activated species generated in and by the discharge. An overview of the resulting chemical effects is presented, based on rationalized classification, i.e., acid-base effects, oxidizing properties, complex forming reactions, and radical reactions. The gliding discharge is considered to be a specifically suitable plasma source for the treatment of liquids for pollutant abatement in the scope of sustainable environment, and this justifies an overview of the chemical properties. Special emphasis is devoted to temporal post-discharge reactions (TPDRs), which occur when the target is no longer exposed to the plasma source, and several typical examples are detailed. These recently evidenced TPDRs seem to present some general character. They are the key parameters to estimating the efficiency of a discharge treatment; they also have major technical and economical importance for the application of the plasma treatment to pollutant and/or micro-organism abatement at atmospheric pressure and quasi-ambient temperature.

  • Evidence of Temporal Postdischarge Decontamination of Bacteria by Gliding Electric Discharges: Application to Hafnia alvei
    Applied and Environmental Microbiology, 2007
    Co-Authors: Georges Kamgang Youbi, Jean-louis Brisset, Jean-marie Herry, Marie Noelle Bellon-fontaine, Avaly Doubla, Murielle Naïtali
    Abstract:

    This study aimed to characterize the bacterium-destroying properties of a gliding arc plasma device duringElectric Discharges and also under temporal postdischarge conditions (i.e., when the discharge was switchedoff). This phenomenon was reported for the first time in the literature in the case of the plasma destruction ofmicroorganisms. When cells of a model bacterium, Hafnia alvei, were exposed to Electric Discharges, followedor not followed by temporal postDischarges, the survival curves exhibited a shoulder and then log-linear decay.These destruction kinetics were modeled using GinaFiT, a freeware tool to assess microbial survival curves,and adjustment parameters were determined. The efficiency of postdischarge treatments was clearly affected bythe discharge time (t*); both the shoulder length and the inactivation rate kmax were linearly modified as afunction of t*. Nevertheless, all conditions tested (t* ranging from 2 to 5 min) made it possible to achieve anabatement of at least 7 decimal logarithm units. Postdischarge treatment was also efficient against bacteria notsubjected to direct discharge, and the disinfecting properties of “plasma-activated water” were dependent onthe treatment time for the solution. Water treated with plasma for 2 min achieved a 3.7-decimal-logarithm-unitreduction in 20 min after application to cells, and abatement greater than 7 decimal logarithm units resultedfrom the same contact time with water activated with plasma for 10 min. These disinfecting properties weremaintained during storage of activated water for 30 min. After that, they declined as the storage time increased.

Cristina Paradisi - One of the best experts on this subject based on the ideXlab platform.

  • dc corona Electric Discharges for air pollution control 2 ionic intermediates and mechanisms of hydrocarbon processing
    Plasma Processes and Polymers, 2008
    Co-Authors: Ester Marotta, Alessandro Callea, Massimo Rea, Xianwen Ren, Cristina Paradisi
    Abstract:

    A mechanistic study is reported on i-octane and hexane processing with +DC and -DC corona in air at room temperature and pressure. Current/voltage profiles are matched with the ion analysis data obtained by APCI mass spectrometry. With a -DC corona, the hydrocarbons do not modify the negative ion population with respect to uncontaminated air. In contrast, with a +DC corona many hydrocarbon-derived positive ions form. O( 3 P) and ˙OH were also investigated using chemical probes (ozone formation and CO oxidation, respectively). The results, combined with efficiency and product data, suggest that with -DC corona radical initiation steps occur, whereas with +DC corona ionic reactions prevail.

  • dc corona Electric Discharges for air pollution control part 1 efficiency and products of hydrocarbon processing
    Environmental Science & Technology, 2007
    Co-Authors: Ester Marotta, Alessandro Callea, Massimo Rea, Cristina Paradisi
    Abstract:

    A large (ca 0.7 L) wire-cylinder benchtop reactor was developed and tested for DC corona processing of VOC (volatile organic compound)-contaminated air at room temperature and pressure. The aim of our research is the identification and rationalization of the chemical reactions responsible for VOC removal. Model hydrocarbons, n-hexane and 2,2,4-trimethylpentane (i-octane), were used to characterize the process and compare the effects of DC corona polarity and of humidity on its energy efficiency and products. n-Hexane and i-octane behave very similarly. For both, the energy efficiency is significantly better with negative than with positive DC corona, especially in humid air. The effect of humidity is most interesting. Thus, while with -DC corona the process efficiency is significantly better in humid air, a slight inhibition is observed with +DC corona. Differences between +DC and -DC corona are also found in the amounts of volatile products formed, which include CO2, CO, and minor quantities of organic byproducts (aldehydes, ketones, alcohols, and lower hydrocarbons). A significant fraction of the carbon originally present as VOC is, however, unaccounted for by the analysis of gaseous and volatile organic products and must, therefore, end up as nonvolatile materials and aerosols.