Bulletin of the American Physical Society
69th Annual Gaseous Electronics Conference
Volume 61, Number 9
Monday–Friday, October 10–14, 2016; Bochum, Germany
Session NW3: Surface and Dielectric Barrier Discharges |
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Chair: Timo Gans, University of York Room: 2b |
Wednesday, October 12, 2016 3:00PM - 3:15PM |
NW3.00001: Surface discharges generated at metal-semiconductor-gas triple junctions. David Pai, David Babonneau, Sophie Camelio, Sven Stauss, Kazuo Terashima Discharges in air at atmospheric pressure as well as high-pressure CO$_{\mathrm{2}}$ up to 15 atm are generated on silicon surfaces using reactor geometries typical of surface dielectric barrier discharges (DBDs), in order to investigate plasma generation and properties at metal-semiconductor-gas triple junctions. Short (10 ns) or long (200 ns) high-voltage pulses are applied at pulse repetition frequencies of 1 -- 1000 Hz. Both p- and n-type silicon are investigated at different doping levels. Discharge generation can be achieved at applied voltages of about 1 kV or less, despite using silicon layers of 0.5 -- 1 mm thickness. The discharge current differs in character from that of other types of nanosecond discharges, such as glows, sparks, and DBDs. The experimental characterization of plasma and surface properties is also presented. [Preview Abstract] |
Wednesday, October 12, 2016 3:15PM - 3:30PM |
NW3.00002: Zero dimensional model of atmospheric SMD discharge and afterglow in humid air Ryan Smith, Efe Kemaneci, Bjoern Offerhaus, Katharina Stapelmann, Ralph Peter Brinkmann A novel mesh-like Surface Micro Discharge (SMD) device designed for surface wound treatment is simulated by multiple time-scaled zero-dimensional models. The chemical dynamics of the discharge are resolved in time at atmospheric pressure in humid conditions. Simulated are the particle densities of electrons, 26 ionic species, and 26 reactive neutral species including: O$_3$, NO, and HNO$_3$. The total of 53 described species are constrained by 624 reactions within the simulated plasma discharge volume. The neutral species are allowed to diffuse into a diffusive gas regime which is of primary interest. Two interdependent zero-dimensional models separated by nine orders of magnitude in temporal resolution are used to accomplish this; thereby reducing the computational load. Through variation of control parameters such as: ignition frequency, deposited power density, duty cycle, humidity level, and N$_2$ content, the ideal operation conditions for the SMD device can be predicted. The described model has been verified by matching simulation parameters and comparing results to that of previous works (Sakiyama, 2012, J. Phys. D: Appl. Phys. 45, pp. 425201). Current operating conditions of the experimental mesh-like SMD were matched and results are compared to the simulations. [Preview Abstract] |
Wednesday, October 12, 2016 3:30PM - 3:45PM |
NW3.00003: Study on the mode-transition of nanosecond-pulsed dielectric barrier discharge between uniform and filamentary by controlling pressures and pulse repetition frequencies Sizhe Yu, Xinpei Lu We investigate the temporally resolved evolution of the nanosecond pulsed dielectric barrier discharge (DBD) in a moderate 6mm gap under various pressures and pulse repetition frequencies (PRFs) by intensified charge-coupled device (ICCD) images, using synthetic air and its components oxygen and nitrogen. It is found that the pressures are very different when the DBD mode transits between uniform and filamentary in air, oxygen, and nitrogen. The PRFs can also obviously affect the mode-transition. The transition mechanism in the pulsed DBD is not Townsend-to-streamer, which is dominant in the traditional alternating-voltage DBDs. The pulsed DBD in a uniform mode develops in the form of plane ionization wave, due to overlap of primary avalanches, while the increase in pressure disturbs the overlap and DBD develops in streamer instead, corresponding to the filamentary mode. Increasing the initiatory electron density by pre-ionization methods may contribute to discharge uniformity at higher pressures. We also find that the dependence of uniformity upon PRF is non-monotonic. [Preview Abstract] |
Wednesday, October 12, 2016 3:45PM - 4:00PM |
NW3.00004: Influence of the gap size and dielectric constant of the packing on the plasma discharge in a packed bed dielectric barrier discharge reactor: a fluid modeling study Koen Van Laer, Annemie Bogaerts Packed bed dielectric barrier discharge (DBD) reactors have proven to be very useful sources of non-thermal plasma for a wide range of applications, of which the environmental applications have received most attention in recent years. Compared to an empty DBD reactor, a packing was introduced to either enhance the energy efficiency of the process, or, if the packing is catalytically active, steer the process towards a preferred end product. A wide range of geometries, bead sizes and bead materials have been tested experimentally in the past. However, since experimental diagnostics become more difficult with a packing present, a computational study is proposed to gain more insight. Using COMSOL's built in plasma module, a 2D axisymmetric fluid model is developed to study the influence of the gap size and the dielectric constant ($\varepsilon )$ of the packing. Helium is used as discharge gas, at atmospheric pressure and room temperature. By decreasing the gas gap, the electric field strength is enhanced, resulting in a higher number of current peaks per half cycle of applied rf potential. Increasing $\varepsilon $ also enhances the electric field strength. However, after a certain $\varepsilon $, its influence saturates. The electric field strength will no longer increase, leaving the discharge behavior unchanged. [Preview Abstract] |
Wednesday, October 12, 2016 4:00PM - 4:15PM |
NW3.00005: Properties Influencing Plasma Discharges in Packed Bed Reactors Juliusz Kruszelnicki, Kenneth W. Engeling, John E. Foster, Mark J. Kushner Atmospheric pressure dielectric barrier discharges (DBDs) sustained in packed bed reactors (PBRs) are being investigated for CO$_{\mathrm{2}}$ removal and conversion of waste gases into higher value compounds. We report on results of a computational investigation of PBR-DBD properties using the plasma hydrodynamics simulator \textit{nonPDPSIM} with a comparison to experiments. Dielectric beads (rods in 2D) were inserted between two coplanar electrodes, 1 cm apart filled by humid air. A step-pulse of -30 kV was applied to the top electrode. Material properties of the beads (dielectric constant, secondary emission coefficient) and gas properties (photoionization and photo-absorption cross-sections, temperature) were varied. We found that photoionization plays a critical role in the propagation of the discharge through the PBR, as it serves to seed charges in regions of high electric field. Increasing rates of photo-ionization enable increases in the discharge propagation velocity, ionization rates and production of radicals. A transition between DBD-like and arc-like discharges occurs as the radiation mean free path decreases. Increasing the dielectric constant of the beads increased electric fields in the gas, which translated to increased discharge propagation velocity and charge density until $\varepsilon $/$\varepsilon_{\mathrm{0}}\approx $100. Secondary electron emission coefficient and gas temperature have minimal impacts on the discharge propagation though the latter did affect the production of reactive species. [Preview Abstract] |
Wednesday, October 12, 2016 4:15PM - 4:30PM |
NW3.00006: Investigation of the Time Evolution and Species Production in a 2-Dimensional Packed Bed Reactor Kenneth Engeling, Juliusz Kruszelnicki, Mark Kushner, John Foster Plasma production in microporous media has potential to enable a number of technologies ranging from flameless combustion to environmental hazard mitigation addressing air borne pollutants. Packed bed reactors (PBRs) is one such technology that relies on plasma production in microporous media. The physics of plasma production and transport in such media however remains poorly understood. In order to better understand the plasma propagation and plasma driven chemical reaction within microporous media, absorption spectroscopy and time-resolved imaging diagnostics are being utilized. We report on plasma driven species formation and plasma discharge spatial structure and evolution characteristics found in the 2-dimensional representation of a PBR. [Preview Abstract] |
Wednesday, October 12, 2016 4:30PM - 4:45PM |
NW3.00007: 100{\%} N$_{\mathrm{2}}$ atmospheric-pressure microwave-line-plasma production with a modified waveguide structure Haruka Suzuki, Yuto Tamura, Hitoshi Itoh, Makoto Sekine, Masaru Hori, Hirotaka Toyoda Large-scale atmospheric pressure (AP) plasmas have been given much attention because of its high cost benefit and a variety of possibilities for industrial applications. Microwave discharge plasma using slot antenna is attractive due to its ability of high-density and stable plasma production, and we have developed a long-scale AP microwave plasma (AP microwave line plasma: AP-MLP) source using loop-structured waveguide and travelling wave and have reported spatially-uniform AP-MLP of 40 cm in length using Ar or He gas discharge. However, rare gas discharge is not always suitable for industrial applications because usage of large volume rare gas degrades the AP cost benefit. Furthermore, many industrial applications require chemically-reactive species and the AP-MLP using molecular gas will drastically increase the applications of the AP-MLP. In this study, we demonstrate 100{\%} N$_{\mathrm{2}}$ discharge of the AP-MLP with a modified waveguide structure. Cross-sectional structure of the waveguide is improved to enhance the microwave electric field in the slot. 100{\%} N$_{\mathrm{2}}$ plasma of 15 cm-long is successfully produced using CW microwave power of 2 kW. Low gas temperature of 1000 K is confirmed by optical emission spectroscopy, suggesting applications of the AP-MLP to low temperature processes. [Preview Abstract] |
Wednesday, October 12, 2016 4:45PM - 5:00PM |
NW3.00008: Simplified modeling of pulsed corona for dielectric design of high-voltage devices Sergey Pancheshnyi, Thomas Schefer Physics-based modeling of discharges in insulating gases (air, SF6, CO2, etc.) is required for quantitative prediction of withstand voltages of high-voltage devices. Breakdown of not very long gaps at elevated pressures occurs typically by streamer (or spark) mechanism. Glow or streamer corona can delay the inception of breakdown streamers. This is often attributed to the so-called corona stabilization effect that is lowering of electric field close to the stressed electrodes due to corona space charge. However, compared to corona-less streamer breakdown of short gaps at elevated pressures, breakdown voltages are typically lower if corona starts. Direct simulation of discharges are often computationally costly, especially for 3D cases, and simplified engineering approaches are developing. Such models are then used for prediction of the ``worst-case scenario'', which might lead to breakdown of gaseous insulation in real design. The engineering models used for simulation of corona inception and development for different voltage shapes (DC, AC, pulsed) will be discussed for several geometries, including rod-plane case and electrode-less inception near a dielectric surface. [Preview Abstract] |
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