Bulletin of the American Physical Society
64th Annual Gaseous Electronics Conference
Volume 56, Number 15
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session TF3: Plasma Jets and Thermal Plasmas |
Hide Abstracts |
Room: 255F |
Friday, November 18, 2011 9:30AM - 9:45AM |
TF3.00001: Operating Regimes of a Plasma Jet under Variable Pressures M. Arda Akman, Mounir Laroussi In this paper we investigate the effects of ambient pressure on a plasma jet. This is done by first generating a plasma jet using our tube reactor device which emits a plasma plume in ambient air when high voltage pulses are applied to its two electrodes and a gas such as helium is flown through it. In the experiments reported here the jet is introduced into a Pyrex chamber where the pressure and gas mixture can be controlled. Pressure in the chamber is regulated by controlling the gas flow and the evacuation rate. We discovered that there are four operating phases: First a stagnant phase where the jet length remains virtually constant. This is followed by a second phase where the jet inside the chamber rapidly increases in length (up to 30 cm) as the pressure decreases. Then an operational mode transition suddenly occurs where the plume length decreases dramatically. Further lowering the pressure in this third phase causes plasma to expand in all directions starting from the point where the plume enters the chamber. Below 2 Torr, the entire volume of the chamber gets filled with homogeneous plasma resulting in the fourth phase. These phases were observed by ICCD imaging, electrical characterization and optical emission spectra. [Preview Abstract] |
Friday, November 18, 2011 9:45AM - 10:00AM |
TF3.00002: Extraordinary properties of dielectric barrier discharge in argon gas flow triggered by molecular impurities Keiichiro Urabe, Keitaro Yamada, Yu Hiraoka, Osamu Sakai Atmospheric-pressure dielectric barrier discharge (DBD) in argon (Ar) gas flow with molecular impurities showed distinctive dependence on the impurity's fraction far from linear relationship. We found this phenomenon in experimental investigation of discharge-mode transition from filamentary to glow-like modes in a jet-type DBD using an Ar/organic mixed flow. Emission spectra measured in each discharge mode were different especially in C$_{2}$ and CH molecular emission intensities detected due to organic molecule's decomposition, and the measurement results suggest that reactions of excited species and/or chemical radicals in the jet-type DBD are led to nonlinear evolution in both time and space because of much shorter characteristics length for reactions and diffusion than the given reaction space in such a high pressure. Following the discharge-mode transition, fine structures of deposited material on a metal-plate electrode were changed drastically: polymer film, powder, web-like structure composed of gathered particles, etc. We discuss the discharge mechanisms from view points of this nonlinear characteristic and the potential applications of the Ar DBD with the impurities of organic or inorganic molecules. [Preview Abstract] |
Friday, November 18, 2011 10:00AM - 10:15AM |
TF3.00003: Time and wavelength resolved measurements of the VUV excimer emission generated in a windowless dielectric barrier discharge (DBD) in argon Rajesh Ganesan, Deborah Kane, Robert Carman Temporal analysis of the VUV emission from a windowless dielectric barrier discharge [1] in pure argon from 50-800 mbar were carried out to gain insight into the underlying kinetic processes relating to the first and second continuum emission bands of the Ar$_{2}$* excimer. Pulsed excitation using bi-polar voltage pulses with 2{\%} duty-cycle and 32kHz repetition frequency were employed to achieve a uniform discharge with well-controlled electrical breakdown characteristics. By comprehensively measuring the rising and decay time constants for $\sim $50 individual wavelengths within the first and second continuum of argon covering the range $\lambda $=107nm-140nm, the dominant collisional and radiative rates relating to Ar$_{2}$* excimer production and loss have been obtained. The variation of time constants as a function of wavelength and gas pressure has been determined. The VUV emission curves at the transition phase between the first and second continuum have been analyzed in detail. [1] R J Carman et al., J.Phys.D:Appl.Phys, 43, 025205 (2010). [Preview Abstract] |
Friday, November 18, 2011 10:15AM - 10:30AM |
TF3.00004: Effect of spatial distribution on emission diagnostics of He-H2 plasmas Shabnam Monfared, Lutz Huwel Electron densities have been measured in atmospheric pressure laser-induced helium and helium-hydrogen plasmas using optical emission techniques. Stark broadening (He at 5015, 4471, 4026 {\AA} and H at 4861 {\AA}) and peak splitting between allowed and forbidden components (He at 4471 {\AA}) were employed. Analysis of spatially averaged, temporally resolved data yields good agreement between all He based methods.\footnote{S. K. Monfared etal.Plasma Sources Sci. Technol. 20 (2011) 035001, and 20 (2011) 049503} However, large discrepancies were found between values extracted from the H$_{\beta}$ line and those form helium based methods - especially at times after breakdown shorter than about 7 $\mu$s (up to a factor of 100 at 1 $\mu$s in mixtures of 1 torr of hydrogen). Differences diminish with increasing hydrogen content and delay times. For partial pressure of hydrogen above about 50 torr, good agreement is found between all methods. The observed pattern is believed to be due to differences in the spatial distribution of helium and hydrogen. An equilibrium model confirms the possibility of such discrepancies. In addition, a detailed analysis of Abel-inverted data will be presented. [Preview Abstract] |
Friday, November 18, 2011 10:30AM - 10:45AM |
TF3.00005: Specific Localization of High-Voltage Discharge in Vicinity of Two Gases Sergey Leonov, Michail Shurupov, Michail Shneider, Anatoly Napartovich, Igor Kochetov A subject of paper is the appearance and dynamics of sub-microsecond long filamentary high-voltage discharge generated in atmosphere, and in non-homogeneous gaseous media. Typical discharge parameters are: maximal current 1-3kA, breakdown voltage $>$100kV, duration 30-100ns, gap distance 50-100mm. The effect of discharge specific localization within mixing layer of two gases is particularly discussed. The second discussed idea is the filamentary discharge movement within a region with concentration gradient of different components. For the short-pulse discharge the physical mechanism appears as the following. The first stage of the spark breakdown is the multiple streamers propagation from the high-voltage electrode toward the grounded one. In case of high-power electrical source those streamers occupy a huge volume of the gas, covering all possible paths for the further development. The next phase consists of the real selection of the discharge path among the multiple channels with non-zero conductivity. Experiments and calculations are presented for Air-CO$_{2}$ and Air-C$_{2}$H$_{4}$ pairs. The effects found are supposed to be applied for lightning prediction/protection, and for high-speed mixing acceleration. [Preview Abstract] |
Friday, November 18, 2011 10:45AM - 11:00AM |
TF3.00006: Combination of optical emission and broadband absorption spectroscopy for diagnostics of HID lamps Cornelia Ruhrmann, Andre Bergner, Thomas Hoebing, Juergen Mentel, Peter Awakowicz HID lamps are used in several fields of application e.g. in street or automotive lighting as well as in video projection systems. Most of these lamps contain mercury to generate a high pressure buffer gas filling and thereby an appropriate power input into the arc. Due to its toxicity, the replacement of mercury is of particular interest in recent research of HID lamps. Currently, the emission coefficient of a mercury double line is used to determine the plasma temperature and thereby particle densities inside an HID lamp. A combination of optical emission and broadband absorption spectroscopy allows evaluating the plasma temperature without the need of mercury emission lines. It offers in combination with emission spectroscopy the possibility to calculate the total density of atoms and ions of elements also inside a mercury-free HID lamp. In this paper the measuring method is applied to a mercury-containing special research HID lamp (YAG lamp), seeded with rare earth iodines. [Preview Abstract] |
Friday, November 18, 2011 11:00AM - 11:15AM |
TF3.00007: Electrostatic simulation of ignition aids for automotive HID lamps Egmont Semmler, Andre Bergner, Juergen Mentel, Peter Awakowicz High intensity discharge (HID) lamps are used in a broad field of application. A special field of interest is car headlights because of their high lumen output level. Due to the high background gas pressure of 1.5\,MPa in xenon, the technological requirements on the igniter are high. The ignition voltage of modern HID lamps for automotive application ranges from 15-20\,kV. This work deals with three dimensional electrostatic simulations of the electric field strength and potential distribution for typical ignition voltages. Using a commercial finite element (FEM) solver the influence of different ignition aids (e.g. electrical conductive foils on the backside of the burner, different antenna arrangements) is studied and optimized. The optimization regime focusses on improving the local electric field strength at the electrodes which results in a reduction of the ignition voltage. [Preview Abstract] |
Friday, November 18, 2011 11:15AM - 11:30AM |
TF3.00008: Investigation of circuit breaker arc properties in the vicinity of current-zero Patrick Stoller, Martin Seeger, Arthouros Iordanidis, Daniel Over, Bernardo Galletti In high voltage circuit breakers, the current is interrupted by drawing an arc between two contacts that is axially blown by a high pressure gas flow. The properties of this blown arc and its interaction with the flow immediately before a zero-crossing of the alternating current (current-zero) play an important role in determining if current interruption will be successful. A simple test device designed to represent the key features of a circuit breaker while allowing easy access for measurements was used to investigate a high current arc blown with synthetic air before current-zero. Transparent nozzles were used to permit optical investigations; the nozzles were equipped with pressure sensors to provide information about the flow conditions. The current immediately before the zero-crossing was measured with high resolution using a post-arc current measurement system. The electric field distribution in the arc was measured using a resistively coupled probe. Optical images and measurements of the arc voltage and current prior to zero-crossings of the current were compared to investigate the behavior of the arc immediately before successful and unsuccessful interruption attempts. [Preview Abstract] |
Friday, November 18, 2011 11:30AM - 11:45AM |
TF3.00009: Diffuse Guided Microwave High Pressure Plasmas for General Lighting Applications with High Color Rendering Index Ch. Kaiser, C.M. \"{O}g\"{u}n, R. Kling This contribution deals with the development of a novel plasma configuration for discharge lamps. A guided microwave mode (at 2.45 GHz) is used to drive a diffuse, electrode less InI discharge lamp in the pressure range up to 7 bar. Argon was used as start gas in the pressure range from 05 mbar up to 200 mbar. The discharge is designed to work in the undercritical electron density limit at the interface between plasma and fused silica. This work deals with a detailed analysis of the influences of the start gas pressure, the lamp geometry, the amount of InI and the absorbed microwave power on the spectral behavior of the lamp, the lamps luminous efficacy and the gained color rendering index. Within the use of this discharge configuration, bremsstrahlung broadened radiation in the visible range could be observed. A color rendering index of 95 was gained within a microwave power consumption of 120 W. Furthermore, diffuse high pressure plasma columns in the length of 4 cm within a radius between 2 mm and 6 mm where obtained. These columns showed a luminous efficacy of 40 lm/W in a not optimized laboratory sample. [Preview Abstract] |
Friday, November 18, 2011 11:45AM - 12:00PM |
TF3.00010: Ozone formation in pulsed SDBD in a wide pressure range Andrey Starikovskiy, Maryia Nudnova Ozone concentration in surface anode-directed DBD for wide pressure range (150 - 1300 torr) was experimentally measured. Voltage and pressure effect were investigated. Reduced electric field was measured for anode-directed and cathode-directed SDBD. E/n values in cathode-directed SDBD is higher than in cathode-directed on 50 percent at atmospheric pressure. E/n value increase leads to decrease the rate of oxygen dissociation and Ozone formation at lower pressures. Radiating region thickness of sliding discharge was measured. Typical thickness of radiating zone is 0.4-1.0 mm within pressure range 220- 740 torr. It was shown that high-voltage pulsed nanosecond discharge due to high E/n value produces less Ozone with compare to other discharges. Kinetic model was proposed to describe Ozone formation in the pulsed nanosecond SDBD. [Preview Abstract] |
Friday, November 18, 2011 12:00PM - 12:15PM |
TF3.00011: Air Breakdown Dynamics with a 1.5-MW, 110 GHz Gyrotron Jason Hummelt, Alan Cook, Michael Shapiro, Rick Temkin We examine breakdown created by a 1.5 MW, 110 GHz 3 $\mu $s length pulsed quasioptical beam in atmospheric pressure air. The plasma formed exhibits a filamentary array of streamers for an incident linearly polarized beam and disc like structures for a circularly polarized beam. A fast gating camera is used to study the time evolution of the plasma structures and propagation of the plasma back towards the gyrotron source. We measure the speed at which the plasma propagates toward the gyrotron to initially be greater than 100 km/s. The plasma streamer expansion for the case of the linearly polarized beam is found to be 5-10 km/s and shows good agreement with what is predicted with the simple ionization-diffusion equation. In addition, microwave measurements show the scattering of incident microwaves by the plasma through an angular distribution. A fast gating, high-resolution spectrometer and a broadband spectrometer are used to study breakdown plasma temperatures. Results are compared with previous microwave breakdown experiments. [Preview Abstract] |
Friday, November 18, 2011 12:15PM - 12:30PM |
TF3.00012: Magneto hydrodynamics simulations of pulsed high density plasmas in electromagnetic guns Hariswaran Sitaraman, Laxminarayan Raja Electromagnetic guns are a class of devices which uses the Lorentz force to accelerate bulk plasma/conducting solids to velocities $\sim $ km/s. This idea has been widely used in electromagnetic rail guns and in space propulsion systems. The electrically conducting region is typically a pulsed high density thermal plasma which interacts with the bounding solid surface resulting in ablation and materials chemical degradation. We perform a numerical modeling study of the plasma in an electromagnetic gun to understand the discharge physics and in particular study the plasma-surface interactions. The resistive Magneto hydrodynamics (MHD) equations which include the mass, momentum and energy equations for a conducting fluid along with the Maxwell's equations is used for this study. These equations constitute a stiff system with strong coupling between fluid dynamics and electromagnetics. The equations are solved on an unstructured mesh using a cell-centered finite volume formulation. Details of important species in the plasma and the particle and energy flux distribution at the solid boundaries are presented and the consequent plasma-surface interactions under varying operating conditions are discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700