Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session MWP1: Poster Session II (16:00-18:30) |
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Chair: I. Langmuir Room: Salon F-J |
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MWP1.00001: ELECTRON ATOM/MOLECULE COLLISIONS |
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MWP1.00002: The Coulomb Four-Body Problem: Electron Impact Double Ionization of Helium in the Threshold Regime XueGuang Ren, Alexander Dorn, Joachim Ullrich Double ionization of helium by electron impact represents one of the most fundamental four-body problems. While various experiments exist for fast collisions the threshold region where theories predict a strongly correlated and fully symmetric emission with 120$^{\circ}$ relative angles of the three electrons is unexplored concerning differential measurements. We present kinematical complete experiments for impact energies 27 eV and 5 eV above the threshold. At the lower energy clear signatures for the threshold region being reached and the symmetric electron emission are observed. [Preview Abstract] |
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MWP1.00003: Electron Impact K-shell Ionization Cross Sections M.A.R. Patoary, M. Alfaz Uddin, A.K.F. Haque, M. Shahjahan, A.K. Basak, M.R. Talukder, Bidhan Saha A new semi-empirical model comprising few important features of the DM [1] model and Bell [2] model is used to evaluate the electron impact K-shell ionization cross sections of 30 atomic targets ranging from H to U (Z=1-92). Details results will be presented at the conference [1] H. Deutsh, K. Becker, T. D. Mark, Int. J. Mass Spect. 177, 47 (1998). [2] K. L. Bell, H. B. Gilbody, J. G. Hughes, A. E. Kingston and F. J. J. Smith, Phys. Chem. Ref. Data 12, 891 (1983). [Preview Abstract] |
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MWP1.00004: Total and Total ionization Cross sections for Germanium hydrides GeH$_{x}$ (x=1-4) on electron impact from 0.1 eV to 5 keV Minaxi Vinodkumar, Chetan Limbachiya, Kirti Korot, K.N. Joshipura, Nigel Mason Germanium hydrides, in particular germane, GeH4, are widely used as feed gases in plasma deposition and doping processes in the semiconductor industries. In this paper we report electron impact total cross sections from 0.1 eV to 5 keV for GeH$_{x}$ (x=1-4). We employed R-matrix method using Quantemol N[1] till 15 eV and spherical complex optical potential formalism (SCOP) [2-3] beyond 15 eV. We also report total ionization cross sections using our Complex Scattering Potential -- ionization contribution (CSP-ic) [2,3] for these targets. \textbf{Ref.} [1] J.Tennyson, D.B. Brown, J.Munro I.Rozum, H.Varambhia, N.Vinci Journal of Physics: Conference Series \textbf{86 }(2007) 012001 [2] M. Vinodkumar, C. Limbachiya, K.N. Joshipura, K. Korot, Eur. J. Phys. D. (2008) DOI: 10.1140/epjd/e2008-00106-3 [3] M. Vinodkumar, C. Limbachiya, K.N.Joshipura, K. Korot, Nigel Mason Int. J. Mass Spectrom 273 (2008) 145. [Preview Abstract] |
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MWP1.00005: Low Energy Elastic Scattering from n-Propanol and n-Butanol M.A. Khakoo, J. Muse, H. Silva, M.C.A. Lopes, C. Winstead, V. McKoy, R.F. da Costa, E.M. de Oliveira, M.A.P. Lima, M.H.F. Bettega, L.G. Ferreira, M.T. do N. Varella Measured and calculated elastic electron scattering differential cross sections are reported at incident energies of 1, 2, 5, 10, 15, 20, 30, 50, and 100 eV. The measurements employed the relative flow method with He as the standard gas and an aperture collimating gas source. The calculated results are obtained from two different implementations of the Schwinger multichannel method: one that takes all electrons into account and is adapted for parallel computers and another that uses pseudopotentials and considers only the valence electrons. Both sets of calculations include polarization effects. Comparison between the measured and calculated cross sections is found to be quite satisfactory. [Preview Abstract] |
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MWP1.00006: Atomic Data of Electron Collisional and Radiative Processes and Modeling of non-LTE Krypton Plasmas Arati Dasgupta, Robert W. Clark, John L. Giuliani, Jack Davis We have developed a detailed multilevel atomic model for K-, L- and M-shell krypton, and investigated its impact on the radiation hydrodynamics on a krypton gas puff driven by the redesigned Sandia National Laboratory ZR accelerator. The atomic model employs an extensive atomic level structure to accurately model the dynamics and the spectroscopic details of the emitted radiation. The atomic data was obtained using the state-of-the-art Flexible Atomic Code, and all relevant collisional and radiative atomic processes such as electron-impact excitation, ionization, radiative and dielectronic recombination were included in generating the model. The enormous number of fine-structure levels were judiciously lumped to create a database that is detailed but manageable. We have analyzed the behavior in the krypton K- through M-shell ionization stages using temperature and density conditions that have been predicted in hydrodynamics calculations of implosions. [Preview Abstract] |
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MWP1.00007: Differential Cross sections for Electron-Impact Ionization of Atomic Helium and Molecular Hydrogen for both Coplanar and Perpendicular Plane Scattering Ola Al-Hagan, Don Madison, Xueguang Ren, Arne Senftleben, Alexander Dorn, Joachim Ullrich, Dmitry Fursa, Igor Bray The effect of electronic and nuclear charge distributions can be studied by comparing atomic and molecular ionizing collisions for homoelectronic and homonuclear atoms and molecules. Experimental and theoretical differential cross sections will be presented for electron-impact ionization of atomic helium and molecular hydrogen for both coplanar and perpendicular plane scattering. Since the effects of electronic charge distributions and nuclear charge distributions on the fully differential cross sections are most pronounced for low energy electrons, results will be presented for one electron having an energy of 4 eV and the other one having 12 eV in the final state. Electronic and nuclear effects will be analyzed individually. [Preview Abstract] |
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MWP1.00008: HEAVY PARTICLE COLLISIONS II |
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MWP1.00009: Electron--electron correlations assessed analyzing doubly differential angular distributions in double ionization of helium by proton impact Marcelo Ciappina, Michael Schulz, Tom Kirchner, Daniel Fischer, Robert Moshammer, Joachim Ullrich Double ionization (DI) of helium by ion impact presents a singular scenario to study electron-electron correlation in atomic physics. Recent experimental data have revealed signatures of this feature in the doubly differential cross sections in terms of the angles of the two emitted electrons [1]. We present an exhaustive theoretical and experimental study of these cross sections, by disentangling the contribution of the different mechanisms that contribute to DI [2]. To this end, first order and higher order distorted wave theories are implemented jointly with the Monte Carlo Event Generator method (MCEG) [3]. This latter tool allows us to incorporate efficiently all the experimental conditions in the theoretical models. [1] M. Schulz et al, J. Phys. B \textbf{38}, 1363-1370 (2005). [2] M. F. Ciappina et al, PRA (in preparation) (2008). [3] M. D\"{u}rr et al, Phys. Rev. A \textbf{75}, 062708 (2007). [Preview Abstract] |
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MWP1.00010: Theoretical Fully Differential Cross Sections for Heavy Particle Transfer-Excitation Collisions A.L. Harris, D.H. Madison, J.L. Peacher, M. Schulz Recent experimental measurements of four body collision processes present a stringent test of theory. To date, experimental results have been presented for ionization plus excitation, charge transfer plus excitation, and charge transfer plus ionization. Most of the experimental and theoretical effort so far has concentrated on ionization plus excitation. However, the transfer-excitation process provides a unique opportunity to study initial state electron correlation effects. In the transfer-excitation process for proton-helium scattering, an incident proton captures one electron from a helium atom, and the remaining electron is left in an excited bound state of the helium ion. We will present theoretical results using a full four-body approach, taking each particle into account. This allows for complete flexibility for treating each particle, which provides the opportunity to examine the effects of different types of interactions. Theoretical fully differential cross sections (FDCS) compared with experimental results will be presented. [Preview Abstract] |
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MWP1.00011: Theoretical Fully Differential Cross Sections for Transfer-Ionization A.L. Harris, D.H. Madison, J.L. Peacher Recent experimental measurements of four body collision processes present a stringent test of theory. To date, experimental results have been presented for ionization plus excitation, charge transfer plus excitation, and charge transfer plus ionization. Most of the experimental and theoretical effort so far has concentrated on ionization plus excitation. Theoretical fully differential cross sections (FDCS) will be compared with experimental results for the transfer-ionization process for proton-helium collisions. In the experiment, the incident proton captures one electron from a helium atom, and the remaining electron is ejected into the continuum as a free particle. The theoretical approach we use is a fully quantum-mechanical four-body approach, taking each particle into account. This approach has complete flexibility in the choice of wavefunctions, allowing for the role different interactions to be explored. [Preview Abstract] |
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MWP1.00012: PLASMA DIAGNOSTICS II |
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MWP1.00013: Separation of binary gas mixtures flowing through sampling orifices Rainer Johnsen, Barun Chatterjee Sampling of ions from a reaction vessel through a small orifice into a differentially pumped ion mass spectrometer is a standard plasma-diagnostic method. In this context one faces the question if and to what extent the composition of a gas mixture, e.g. a carrier gas with an admixture of a reagent, is altered by the outflow of gases through the orifice, which is often in the transition regime between molecular and viscous flow. Our experience has shown that gas separation must be taken into account in drift tube measurements of ion-molecule reaction. However, the effect is poorly understood, somewhat counter-intuitive, and no rigorous theoretical treatment is available. We report here a series of drift-tube measurements, in which we used ion-molecule reactions to determine actual reagent concentrations as a function of carrier gas flow. We show that a simple semi-empirical model, in which the coupling of gas flows is modeled using the Langevin equation, reproduces observations reasonably well. The formula can be expressed in terms of easily available parameters and thus may be useful to investigators who need to assess gas separation effects in their applications. [Preview Abstract] |
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MWP1.00014: ABSTRACT WITHDRAWN |
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MWP1.00015: Mass spectrometry of radicals created in plasma needle discharge Sasa Lazovic, Nevena Puac, Gordana Malovic, Antonije Djordjevic, Zoran Lj. Petrovic We present diagnostics of the properties of a plasma needle operating at atmospheric pressure. Our configuration has additional grounded copper ring placed near the tip of the needle. Generated plasma has a larger volume and lower ignition powers with the ring. This configuration is convenient both for treatment of samples and for mass spectroscopy. Our measurements were performed on a standard size plasma needle that we originally used for the treatment of plant cells. Similar work of Stoffels et al. has been done on the `robust' version of the plasma needle that generates an elongated jet of 4~mm length and consumes higher powers. After some efforts we were able to make plasma needle to operate for conditions similar to those used during the treatments of biological samples. Hiden HPR60 mass analyzer was used to obtain the mass spectra. Plasma mode transition was observed for higher values of power transmitted to plasma. Concentrations of N, O, NO, NO$_{2}$ and O$_{3}$ were measured. We have also measured spatial profiles of emission and voltage and current waveforms by derivative probes placed close to the tip of the needle. [Preview Abstract] |
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MWP1.00016: Electron-Beam Generated Air Plasma: Microwave I/Q Detection of Plasma Properties and Optical Measurements of Nitrogen and Ozone to Quantify Plasma Spatial Distribution Robert Vidmar, Chris Ramsayer, Kenneth Stalder Microwave and optical measurements are used to quantify the electron number density, the electron momentum transfer collision rate, nitrogen emissions, and ozone production. The plasma is produced by an electron beam source that generates 10-ms pulses of approximately 5 mA at 100 keV into a 400 liter test cell through a 12.7 $\mu $m aluminum transmission window. The target gas is laboratory air with measurements at pressures from 1 mTorr to 636 Torr. Details relating to the 10 GHz microwave In-phase and Quadrature detector are presented as well as representative measurements and the procedure to convert raw data to values of electron number density and electron momentum transfer collision rate. Detection of nitrogen emissions at 337.1 nm and ozone absorption at 254 nm are used to estimate the spatial volumetric ionization rate on the optical plane of observation and the spatial distribution across the optical plane. [Preview Abstract] |
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MWP1.00017: Generation and Diagnostics of Microwave Discharge Expanding Nitrogen Plasma Tomohiko Shibata, Kazuyuki Yoshida, Atsushi Nezu, Haruaki Matsuura, Hiroshi Akatsuka We examine a microwave discharge expanding nitrogen plasma on its vibrational and rotational temperatures (T$_{v}$, T$_{r})$ by using optical emission spectroscopy (OES), and on its electron density and temperature by using a double probe. In the present study, we generated microwave discharge plasma in a cylindrical quartz tube (26 mm i.d.) and the plasma flowed and expanded rapidly into a rarefied gas wind tunnel with its pressure 2.6$\times $10$^{-3}$ torr. The microwave output power was set at 300 W. The gas flow rate was set at 300 ml/min. In OES measurement, we measured the band spectra of 1stPS and 2ndPS. We compare the experimentally measured spectrum with the calculate one to determine T$_{v}$ and T$_{r}$ of the generated plasma. Electron temperature did not reduce monotonically, which is due to complicated energy relaxation process contributed by metastables or vibrational levels. Intensity of 2ndPS decreased more rapidly than that of 1stPS, which is considered to be mainly due to the lowering of T$_{e}$. We found different way of variation in T$_{v}$ of 1stPS and that of 2ndPS. [Preview Abstract] |
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MWP1.00018: Electric field measurements in high-pressure hydrogen environments with a few nanosecond time resolutions Kazunobu Kobayashi, Tsuyohito Ito, Uwe Czarnetzki, Satoshi Hamaguchi Coherent Raman scattering (CRS) measurement is a promising technique for measuring electric field in high-pressure environments. In this study, we demonstrate electric field measurements with a few nanosecond time resolutions in high-pressure hydrogen environments. The measurements are performed within the gap between two electrodes driven by pulsed nanosecond voltages. Two pulsed ns laser beams (532 nm and 683 nm) are employed for the measurements. In hydrogen molecules those two laser beams together with the electric field induce a coherent IR signal at a wavelength of 2.4 $\mu $m. Without discharge, the square root of the IR strength is proportional to the applied voltage, which is measured with a voltage probe and an oscilloscope at the powered electrode; suggesting that the measurements are successfully performed with a few ns time resolutions. Measurements with dielectric barrier discharges show reductions of the electric field probably due to charges near/on the dielectric barrier. [Preview Abstract] |
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MWP1.00019: The affects of micro-droplet injection on low pressure plasmas Daisuke Ogawa, Iqbal Saraf, M. Goeckner, L. Overzet Directly injecting liquid micro-droplets into low pressure plasmas opens a variety of possibilities including the ability to use new precursors for film deposition. Understanding how the injection of these droplets affects the plasma is important to an overall optimization. Toward that end, results of microwave interferometry and optical emission spectroscopy will be presented in conjunction with film microscopy and analysis. Our initial results show that the time dependent electron density as well as optical emission intensity in capacitively coupled plasmas can change substantially when injecting liquid micro-droplets. For example: There is a fast decrease in the electron density as the droplets enter the plasma (msec time-scale). This decrease in the electron density appears to be much faster than the pressure rise caused by the evaporation of the micro-droplets ($\sim $40 msec). In addition, there is a very slow rise back to the original state ($\sim $5 sec time scale) which is liquid dependent. Neither result is unexpected. Both will be discussed in the presentation. [Preview Abstract] |
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MWP1.00020: Visible emission from exploding wire in water Milan Simek, Vaclav Prukner, Jiri Schmidt, Karel Kolacek, Jaroslav Straus, Oleksandr Frolov Exploding wire in water generates non-ideal strongly coupled plasma, which can model some phenomena appearing in interior of stars, in inertial confinement fusion, in plasma physical-chemistry, in rocket engines, etc. This complicated 2-phase transitions process can be hardly modeled numerically because of missing material data at extremely high pressures. Therefore, the basic question relevant for radial energy transport estimates -- when between wire and water a water-vapor-layer is created (if any) -- has to be answered experimentally. For this purpose the waveforms of the driving current and the H-alpha line emission were measured simultaneously. First spectrometric results obtained by means of photon-counting technique will be discussed. Other spectroscopic data in visible range can yield valuable information about plasma periphery and about layer between plasma and surrounding liquid water. [Preview Abstract] |
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MWP1.00021: Direct Ion Energy Measurements at the RF Biased Electrode in Noble and Hydrocarbon Gas Discharges A. Baby, C.M.O. Mahony, P.D. Maguire We report direct measurements of ion energy distributions at the biased substrate electrode in a RF ICP discharge using a mass-energy analyser thus allowing exploration of greater bias voltage and frequency ranges. IEDs for pure Ar, He and He:Ar or Ar:C$_{2}$H$_{2}$ mixtures for pressures up to 90mTorr, mean bias voltages up to 150V and bias frequencies up to 27MHz, are compared with existing single and multi-species [1] IED models. With associated Langmuir probe, ion flux probe and sheath width measurements we observe that lighter ion IEDs deviate from the model and this also affects interpretation of the multiple-species IED model. At high biases we also note deviation from models, probably due to additional capacitively-coupled power input at the substrate electrode. We have mapped the IED spread and peak intensity variation across frequency and pressure ranges, respectively, in order to exploit IED tailoring for technological applications, particularly for the deposition of high integrity carbon based films. In Ar:C$_{2}$H$_{2}$ narrow spread IEDs were achieved, required for new diamond-like carbon deposition and growth modeling. Mean energies up to 100eV were obtained with 15{\%} - 20{\%} spread, depending on gas ratio, pulsed bias and frequency. [1] Sobolewski M A et. al. \textit{J. Appl. Phys.} \textbf{91}(2002) 6303. [Preview Abstract] |
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MWP1.00022: Comparison of measured metastable ion density with laser induced fluorescence, to electron number density determined with a Langmuir probe, in Ar plasmas as a function of pressure Young-chul Ghim(kim), Noah Hershkowitz The laser induced fluorescence (LIF) signal intensity measured with a diode laser in Ar plasmas is compared to Langmuir probe determined electron number density (n$_{e})$. Plasmas with n$_{e} \quad \sim $10$^{9}$ cm$^{-3}$ and T$_{e} \quad \sim $1 eV are generated for pressures varying from 0.05 - 5.00 mTorr in a dc multidipole hot filament discharge The Ar II excitation transition at 668.614 nm is adopted to create Ar ion metastable fluorescence, and the metastable Ar ion velocity distribution functions (ivdfs) in bulk plasmas are measured. The area under the ivdf curve increases as the pressure is raised, with a maximum signal area at 0.6 mTorr. Then the area decreases with further increases in pressure, whereas the electron number density increases monotonically. The LIF signal has not yet been found at neutral pressure greater than 5 mTorr. In addition, the profile of the area normalized to the electron number density shows that the ratio is fairly constant over the presheath regime and increases as the diagnosed volume gets closer to the sheath. [Preview Abstract] |
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MWP1.00023: Spatiotemporally Resolved E-H transition in an Inductively Coupled Plasma in Ar by using ICCD Camera Satoshi Morishita, Yuichiro Hayashi, Toshiaki Makabe Inductively coupled plasma (ICP) has been widely used as a high density plasma source in various applications. It is well-known that ICP has two operating modes, E and H modes, and the transition between both modes shows a strong hysteresis in electrical and optical characteristics. We have been investigating the characteristics of the ICP through a series of measurements. In our recent study, we exhibited 2D-plasma images from the net excitation rate of Ar(2p1) caused by high energy electrons with energy greater than 13.6 eV during the E-H transition in Ar at 300 mTorr in the ICP driven by a single-turn current coil on the sidewall of a quartz tube. The time-resolved 2D-space image is a result of the integrated signal along the axial direction perpendicular to the coil plane by ICCD camera. In the present work, we discuss the mode transition from the change of the active region in the 2D-t image of the net excitation rate of Ar(2p1) by sweeping the external coil current in Ar for 100, 300, and 500 mTorr. [Preview Abstract] |
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MWP1.00024: Estimation of Electron Temperature and Frequency Components in a Dual Frequency Capacitively-Coupled Plasma Processing Reactor Toru Ito, Yun Mo, Horigome Masahiro The measurement of electron temperature in RF plasma sources with Langmuir probes is difficult because of the influence of rf noise. We attempted to estimate the electron temperature in a capacitively-coupled plasma processing reactor with a Surface Wave Probe [1] which employs microwaves. We also estimated the frequency spectrum with the sensitive PAP [1, 2]. We measured the harmonics which appeared in the bulk plasma for various experimental conditions in the dual-frequency [60 MHz and 2MHz] capacitively-coupled plasma processing reactor. We estimated RF power spectra for several experimental conditions like RF power [500-2000W], gas pressure [3-20Pa], and gas species [Ar, CF$_4$]. The measurement results suggest the existence of energy transport among several frequency spectrum. \\[1ex] [1] K. Nakamura, M. Ohata, and H. Sugai: J. Vac. Sci. Technol. A \textbf{21}, 325 (2003). \\[0pt] [2] T. Shirakawa and H. Sugai : Jpn. J. Appl. Phys. \textbf{32}, 5129 (1993). [Preview Abstract] |
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MWP1.00025: Effect of wafers on measurement of gas temperature in RF plasma Vladimir Milosavljevic, David Kavanagh, Stephen Daniels Analyzing the optical emission spectrum of atomic fluorine and fluorine base molecules, a gas temperature is measured in an Oxford Instruments{\textregistered} RF plasma discharge. The experiments are conducted with silicon or photoresist wafers, as well without any wafer. The gas composition is pure SF$_{6}$ as well a mixture of SF$_{6}$ and O$_{2}$, the working pressure is 13 Pa and the flow for all gases is constant at 100 sccm. The RF power is changed from 75W to 300W. The dependence of gas temperature on the chemical structure of surface/wafer, RF power and gas composition ratio between SF$_{6}$ and O$_{2}$ is investigated. The gas temperatures were determined by recording molecular bands of SiF (436.82 nm) and CF$_{2}$ (248.7 nm), and the spectral line of F (703.75 nm). Since a rotational temperature has been used widely as a neutral gas temperature measurement in different types of plasmas, in this work we present a correlation between gas temperature determinate by molecular bands and atomic spectral lines. We have only direct control of SF$_{6}$ and O$_{2}$ gases, therefore the contribution of carbon and silicon in the plasma discharge is indirectly controlled only by the RF power. The results show that for some specific ratios of SiF$_{6}$ and O$_{2}$ the neutral gas temperature via molecule bands is difficult to determine. [Preview Abstract] |
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MWP1.00026: Experimental investigation of electron density in pulse plasma source by microwave resonance probe Albert R. Ellingboe, Vladimir Milosavljevic The time-dependent spatial electron density distribution in a constricted, pulsed plasma source is measured using a floating hairpin resonance probe and an extrapolation method is described for determining the peak in electron density from the experimental data. Using these techniques a detailed characterization of the spatio-temporal evolution of the electron density, outside the constricted region above the anode of the pulsed plasma source is presented. The electron density increases sharply during the creation phase and the rate of increase is found to decrease with distance from the axis of the constricted channel. By modeling the plasma creation characteristics versus position, the electron density along the axis of the constricted pulsed plasma sources can be determinated. [Preview Abstract] |
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MWP1.00027: Plasma diagnostic through the five prominent oxygen triplets Vladimir Milosavljevic, Emanuele Ragnoli, Stephen Daniels, Niall Macgearailt, Shane McLoone, John Ringwood Oxygen is one of most frequently used gas in plasma discharge. Therefore, determination of plasma parameters through analysis of oxygen emission would be a powerful tool. Fifteen most promenade oxygen spectral lines have been measured at different experimental plasma condition. Those oxygen lines belong to five oxygen triplets: 777, 844, 645, 725 and 615 nm. These fifteen O I spectral lines belong to the different transitions/multiplets and have the different upper energy level. The difference of upper energy levels among these oxygen spectral lines is greater than 2 eV. Also, the spectral lines from triplets 645 nm, 725 nm and 615 nm of O I have an upper energy level very close to dissociation of molecular oxygen (12.06 eV). Data is collected for a range of operator contribution in an Ar-O$_{2}$-Cl/HBr/C$_{2}$F$_{6}$ gas mixture discharge, by Jobin Yvon spectrometers. The emission strengths and profile shapes are found do be dependent on plasma tool settings (power, gas mixture and pressure). Correlation of plasma internal state will be presented. [Preview Abstract] |
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MWP1.00028: Measurement of Ar Excited Atoms Temperature in D.C planar Discharge by Diode laser technique Mona Mehranfar, Majid Eshghabadi, Kioumars Yasserian, Mahmood Ghoranneviss A diode laser has been used to measure the temperature of Ar atoms. A D.C discharge is employed to make the Ar excited atoms between two planar stainless steel electrodes in a Pyrex glass tub. The laser beam passes through the plasma. This laser is calibrated on 772.3nm corresponding to the high intensity wavelength of light which emitted by Ar atoms. The diode laser input power is modulated as saw tooth mode by a signal generator. The temperature of the Ar atoms is calculated by full-width-half-maximum (FWHM) of Doppler absorption curve. Details of results will be discussed in full paper. [Preview Abstract] |
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MWP1.00029: Langmuir probe RF plasma compensation using simulation method Aasim Yousif Azooz The problem of RF compensation in plasma Langmuir probe data is analyzed by simulation procedure. It is pointed out that this type of compensation can be accounted for through proper mathematical transformation applied to the RF contaminated Langmuir probe data to reproduced the actual probe I-V data which are not affected by the RF. Matlab based computer software is presented. The software automatically deduces the value of the probe voltage shift induced by the RF, apply the proper transformation to the I-V data and calculates the actual plasma parameters. These parameters include the plasma potential, plasma electron temperature, plasma electron density and the electron energy distribution function EEDF. [Preview Abstract] |
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MWP1.00030: PLASMA SURFACE INTERACTIONS |
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MWP1.00031: Simulation of surface roughness by 3D level set method Branislav Radjenovic, Marija Radmilovic-Radjenovic, Zoran Petrovic Reactive Ion Etching is a major process in the fabrication of semiconductors devices for transferring patterns from masks to semiconductors substrates. One of the limiting factors in applications of plasma etching in new generations of plasma technologies will be the control of plasma induced roughness or perhaps control of the surface roughness by plasma etching. In this paper we consider both large scale roughness, sidewall roughness and roughness in general by using a 3D level set method. Predictions of surface roughness are based on statistical variations of the properties of the material and ion flux. In addition, we study how stochastic properties of material on different scales and of the beam affect the resulting roughness. [Preview Abstract] |
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MWP1.00032: Simulation of Interaction Between RF Plasmas and Roughly Surface Ilgizar Sagbiev, Olga Pankratova, Victor Zheltoukhin An interaction between RF plasmas and roughly surface at pressure 13.3-133 Pa was investigated theoretically. A sheath near the specimen treated in RF plasmas consists of two zones. The first one is the Debay layer about 10 $\mu $m by thickness and the second one is oscillatory zone from 0.5 up to 2 mm by thickness. In the last electrons move synchronous to electric field change. The main role of oscillatory zone is acceleration of ions up to 100 eV. Ion stream is focused on surface asperities due to bending of electric intensity lines in the Debay layer. [Preview Abstract] |
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MWP1.00033: Start-up behavior of argon discharge near a flat dielectric Ana Sobota, Alexandre Lebouvier, Nicolaas J. Kramer, Winfred W. Stoffels, Eddie M. van Veldhuizen The topic of surface discharges on a dielectric is well known among electrical engineers, because streamer development on isolation material results in breakdown and short circuits. Discharge ignition in presence of a dielectric is interesting for the lighting industry as well, where the dielectric wall of a lamp plays a potentially important role in the lamp ignition. Fast measurements on the initial appearance and velocity of a discharge in presence of a dielectric were done in argon (100 mbar to 1 bar) using an ICCD camera. We found that the discharge velocity along dielectric surfaces has a tendency to increase as the discharge approaches the grounded electrode. The average discharge velocity decreases with increasing pressure, with increasing rise time of the high voltage ignition pulse and with increasing repetition rate of the high voltage pulses. Measured velocities are in range from 2$\times $10$^{5}$ to 2$\times $10$^{6}$ m/s. [Preview Abstract] |
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MWP1.00034: Analysis of dust particles produced due to interaction between graphite and deuterium helicon plasmas Shinya Iwashita, Kazunori Koga, Masaharu Shiratani Formation mechanisms of dust particles due to interaction between carbon walls and plasmas in fusion devices have attracted considerable attention, because they pose two potential problems: they can contain a large amount of tritium and their existence in fusion devices may lead to deterioration of plasma confinement. To obtain information on formation mechanisms of dust particles of nm in size in fusion devices, we have generated deuterium helicon discharge plasmas which simulate divertor plasmas in fusion devices and then we have collected and analyzed dust particles produced due to interaction between graphite and the plasmas. Dust particles are made of carbon and can be classified into three kinds: small dust particles below 1 $\mu $m in size, large flakes above 1 $\mu $m in size, and agglomerates which consist of primary particles of 10 nm. These three kinds suggest three formation mechanisms, that is, CVD growth, carbon films peeled from walls, and agglomeration [1]. There exist a large number of small dust particles below 1 $\mu $m in size. All of these features are quite close to those of dust particles collected during the main discharges of LHD. [1] Y. Watanabe, et al. J. Vac. Sci. Technol., A14, 540 (1996). [Preview Abstract] |
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MWP1.00035: Surface Control as a Function of Processing Conditions in an FC Plasma Environment Caleb Nelson, Sanket Sant, Lawrence Overzet, Matthew Goeckner Many factors are known to affect surface conditions in a plasma environment, including radical and ion fluxes, ion energy, surface temperatures, and surface materials. However, the complex nature of highly polymerizing plasmas often prohibits the isolation of individual control and variable processing conditions. A novel approach using a combination of the flexible modified GEC reference cell and a simplified surface model founded on the assumption that most surface processes occur at open bond sites yields sticking and etch coefficients of radicals and ions. The modified GEC reference cell allows the option of changing chamber dimension, wall material, and wall temperature. Such control is required to develop an understanding of plasma-wall and subsequent wall-to-wall interactions. Of particular importance is the variable electrode gap and the combination of various feed gas mixtures. This allows radical densities to be controlled almost independently of ions and etching radical densities. The isolation of these parameters permits the partial deconvolution of the film growth rate model and the quantification of sticking and etch yield coefficients. [Preview Abstract] |
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MWP1.00036: Polymer processing by electron beam generated plasmas in argon, oxygen, nitrogen environments and their mixtures Evgeniya Lock, Scott Walton, Richard Fernsler Polymers have unique physio-chemical properties that make them attractive for organic electronics applications. However, their inherent low surface energy can be problematic. Wet chemical processing, flames and plasma treatments have been successfully applied to alter the polymer surface properties but plasma treatments are often favored because they change only the surface without altering the bulk properties. Plasmas can also cause roughening or even surface damage. Electron beam generated plasmas have several unique features that distinguish them from the conventional discharges - intrinsically low electron temperature ($<$ 1 eV), resulting in smaller plasma potentials and in lower incident ion energies (1-5 eV). These energies are comparable with the bond strengths found in most polymers, so they are sufficient to invoke chemical surface modification with limited morphology changes. In this study, polymer modifications resulting from electron beam plasma generation in argon, oxygen and nitrogen environments and their mixtures are investigated. The polymers of interest include polystyrene, polymethylmetacrylate and ultra-high molecular weight polyethylene. The effects of the plasma process parameters including treatment time and duty factor, as well as mixture composition on surface energy, chemistry and morphology are presented. [Preview Abstract] |
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MWP1.00037: HIGH PRESSURE GLOW DISCHARGES |
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MWP1.00038: Experimental and theoretical investigations of singlet oxygen production by high-pressure microdischarges J. Santos Sousa, B. Eismann, S. Pancheshnyi, L.C. Pitchford, V. Puech The so-called Micro-Cathode Sustained Discharge (MCSD), which is a three-electrode configuration using a Micro-Hollow Cathode Discharge (MHCD) as a plasma cathode, can be operated as a non-self-sustained discharge with low values of the reduced electric field and of the gas temperature. As a result, these MCSDs can efficiently generate large amounts of singlet delta oxygen, O2(1D). The remarkable stability of the MCSD has allowed us to operate glow discharges, free from the glow-to-arc transition, in rare-gas/oxygen mixtures at pressures up to atmospheric (P=100--1000mbar). High concentrations of O2(1D), from 10$^{15}$ up to 10$^{16}$cm$^{-3}$, were measured in the MCSD afterglow for rare gas flow in the range 100-30000sccm, varying oxygen partial pressure (p(O2)=1--20mbar) and different discharge currents (I=1--12mA). The 0D plasma kinetics code ZDPlasKin [1] was used to calculate the generation of O2(1D) in the MCSD for different discharge and flow conditions and to estimate its density as a function of distance in the afterglow. Similar trends are observed in model and experiment, and detailed comparisons will be shown. [1] S.Pancheshnyi et al., these proceedings [Preview Abstract] |
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MWP1.00039: Characterization of a streamer-initiated atmospheric pressure plasma jet for spatially guided pulsed plasma generation Brian Sands, Biswa Ganguly We examine the characteristics of a streamer-initiated atmospheric pressure plasma jet (APPJ) terminated by a cathode ground plane in air. The plasma jet is generated using a 12 kV submicrosecond voltage pulse exciting a single positively biased electrode wrapped around a 3 mm diameter glass capillary with a 2 slm, 5{\%} Ar/He mixture, gas flow. This APPJ device is distinguished from flow-driven APPJs by its ability to generate excited species \textit{in situ} over its length. The presence of the cathode downstream provides ionization gain that is not characteristic of flow-driven APPJs in similar configurations but rather is characteristic of a single dielectric barrier microdischarge filament that is confined to the capillary axis. With a conducting cathode, this discharge filament can carry several Amps of current in a $\sim $30 ns pulse. In this experiment, we study this atmospheric pressure plasma source with cathode materials of varying resistivity including conducting metals, semiconducting silicon, and insulating dielectrics at distances up to 3 cm from the capillary tip. We monitored spatiotemporally resolved emission intensities from the Ar/He/air discharge to track the relative gain of electron impact excitation across the gap. This will be correlated with current and voltage measurements to estimate energy deposition in the gap. [Preview Abstract] |
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MWP1.00040: Repetitive nanosecond-pulsed discharge in high-pressure hydrogen environments Tsuyohito Ito, Kazunobu Kobayashi, Uwe Czarnetzki, Satoshi Hamaguchi High pressure discharges have attracted much attention recently, and employment of a repetitive nanosecond-pulsed power is one of the promising methods for generating non-thermal discharges in high pressure environments. Electric field is one of the most important parameters in discharge dynamics, which, we believe, should be understood to improve their applications. In this paper, we study the dynamics of a repetitive (10 kHz) nanosecond-pulsed discharges, generated in high pressure (near atmospheric pressure) hydrogen environments, with measurements of the time-dependent electric field distributions. The measurements are performed by coherent Raman scattering (CRS) analysis of hydrogen molecules, induced by two nanosecond laser beams and the electric field. The experimental results show temporal effects of charges in the space (and/or on the dielectric barrier, when we employ a dielectric barrier discharge). More details revealed by optical emission studies and particle simulations will be presented. [Preview Abstract] |
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MWP1.00041: Fluid modeling of a microwave micro-plasma at atmospheric pressure J. Gregorio, R. Alvarez, C. Boisse-Laporte, L.L. Alves In this paper we study a microwave (2.45 GHz) reactor that can produce high-density (10$^{14}$-10$^{15}$ cm$^{-3})$, low power ($\sim $10 W) plasmas in ambient air or in controlled environments at atmospheric pressure, within the end-gap of a microstrip line, by using a continuous wave excitation. The gap corresponds to a 50-200 $\mu $m slit, between two metal blades with 6-14 mm width. Here we present a numerical model describing the micro-plasma sustained with this device, in view of complementing its experimental characterization [1,2]. The simulation tool is a one-dimensional (between metal blades), stationary fluid-type code that solves the charged particle and the electron mean energy transport equations (for argon), together with Poisson's equation for the space-charge electrostatic field and Maxwell's equation for the electromagnetic excitation field. Results yield coupled powers of less than 10 W, for a slit with 100 $\mu $m and a maximum electron density of 10$^{14}$ cm$^{-3}$. [1] J.Gregorio, L.L.Alves, P.Leprince, O.Leroy, L.Teule-Gay and C.Boisse-Laporte, 2007 Bull. Am. Phys. Soc. 52, 22 [2] J.Gregorio, L.L.Alves, P.Leprince, O.Leroy and C.Boisse-Laporte, 2008 19$^{th}$ \textit{ESCAMPIG}, Granada, Spain [Preview Abstract] |
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MWP1.00042: Study of a microwave micro-plasma reactor at atmospheric pressure J. Greg\'orio, P. Leprince, O. Leroy, L.L. Alves, C. Boisse-Laporte In this paper we study a 2.45 GHz microwave micro-plasma source, working in air and in argon at atmospheric pressure. The discharge is sustained within a slit (50 $\mu $m -200 $\mu $m wide and 6mm width), delimited by two metallic blades placed at the end of a microstrip line [1]. The reactor has two impedance matching units that allow tuning the resonance frequency and the quality factor of the circuit. Optical emission spectroscopy diagnostics allow to deduce the plasma rotational temperature (T$_{rot})$. In air discharges, the N$_{2}$ transition C$^{3}\Pi_{u}$-B$^{3}\Pi_{u}$ yielded T$_{rot}$ between 900 and 1400 K, for 30-45 W input powers and 50-100 $\mu $m slits. In argon discharges, the OH transition A$^{2}\Sigma^{+}$-X$^{2}\Pi $ was used, and T$_{rot}$ was found between 500 and 600K, for 8-15W input powers and 50-150 $\mu $m slits. For these discharges, the argon electron excitation temperature was found between 0.3 and 0.6 eV. Measurements of the H$_{\beta}$ Stark broadening suggest an electron density of the order of 10$^{14}$ cm$^{-3}$. \newline [1] J. Gregorio, L.L. Alves, P. Leprince, O. Leroy and C.Boisse-Laporte, 2008 19$^{th}$ ESCAMPIG, Granada, Spain [Preview Abstract] |
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MWP1.00043: Modeling of high-frequency driven discharges at medium and high pressure Philipp Mertmann, Stefan Bienholz, Peter Awakowicz, Thomas Mussenbrock, Ralf Peter Brinkmann Since the end of the 1980s the interest in non-thermal plasmas at medium and high pressure is rapidly growing. Particularly diffuse homogeneous glow discharges are of great interest not only in the scientific context. Due to their enormous potential for technological applications these non-equilibrium discharges have drawn considerable attention. However, the number of contributions to systematical modeling and simulation of high-pressure glow discharges is small. To study the dynamics of such discharges we propose a model of a capacitive discharge for the medium-pressure and the high-pressure regime. The model consists of a set of simplified fluid equations for each charged species coupled self-consistently to Poisson's equation using the method of matched asymptotic expansion. First simulation results for the dynamics of the plasma sheath will be discussed. [Preview Abstract] |
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MWP1.00044: Numerical Simulations of an atmospheric pressure discharge using a two dimensional fluid model Muhammad M. Iqbal, Miles M. Turner We present numerical simulations of a parallel-plate dielectric barrier discharge using a two-dimensional fluid model with symmetric boundary conditions in pure helium and He-N$_2$ gases at atmospheric pressure. The periodic stationary pattern of electrons and molecular helium ions density is shown at different times during one breakdown pulse for the pure helium gas. The temporal behavior of the helium metastables and excimers species density is examined and their influences on the discharge characteristics are exhibited for an APD. The atmospheric pressure discharge modes (APGD and APTD) are affected with small N$_2$ impurities and the discharge mode structures are described under different operating conditions. The uniform and filamentary behavior of the discharge is controlled with the variable relative permittivity of the dielectric barrier material. The influence of nitrogen impurities plays a major role for the production of the filaments in the after glow phase of He-N$_2$ discharge and the filaments are clearly observed with the increased recombination coefficient of nitrogen ions. The creation and annihilation mechanism of filaments is described with the production and destruction of nitrogen ions at different applied voltages and driving frequencies for a complete cycle. The results of the fluid model are validated by comparison with the experimental atmospheric pressure discharge results in He-N$_2$ plasma discharge. [Preview Abstract] |
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MWP1.00045: RF Micro Atmospheric Pressure Plasma Jet: Numerical Simulation and Laser Diagnostics Kari Niemi, Jochen Waskoenig, Timo Gans Micro atmospheric pressure plasma jets ($\mu $-APPJs) can provide high concentrations of radicals at a low gas temperature, particularly for modification of sensitive surfaces, e.g. in biomedicine. The diagnostics of microplasmas is extremely challenging, therefore numerical simulations offer a further insight. The presented 1D-model is a numerical fluid-model across the discharge gap. Dual frequency excitation promises enhanced radical production. Numerical simulations are restricted due to the lack of available data for surface processes which are crucial in case of the extraordinary high surface to volume ratio. These data can be derived using measurable quantities as fixed input parameters of the model. The $\mu $-APPJ provides an excellent optical diagnostic access to the discharge volume. Absolute atomic radical densities can be measured by two-photon laser-induced fluorescence spectroscopy. Absolute measurements require knowledge of collision-induced de-excitation processes or time resolved measurement of the fluorescence decay, e.g. with a tuneable UV Fourier-limited Pico-second laser system. [Preview Abstract] |
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MWP1.00046: ArI and H$_{\beta }$ Line Broadening in Microplasma Jet and DC Microhollow Cathode Plasmas at Atmospheric Pressure Bogos Sismanoglu, Jorge Corr\^ea, Carlos Oliveira, Marcelo Gomes, Jayr Amorim Direct current microplasma jet and microhollow cathode discharges are studied in argon at atmospheric pressure. The microplasma jet consists of tungsten-carbide needle and a metallic plate. Various needle diameters (150 to 1000$\mu $m) were used. The needles are operated as the cathode or anode. Microhollow cathode is a sandwich of metal-dielectric-metal with a micro hole (200 to 1000$\mu $m diameter). Charged plasma particles induce broadening of lines due to Stark effect. The electric microfield also induces broadening of ArI 603.213nm and 565.070nm lines. These two lines are sensitive to Van der Waals and Stark broadening. The broadening of these two lines enables us to evaluate gas temperature, electron temperature and density. These parameters are dependent on discharge operating mode: abnormal (low and high current) and normal. Calculations take into account the characteristic of two-temperature plasma and the ion dynamic effect in lines broadening The results for microjets are well similar to those obtained also with Balmer H$_{\beta }$ and H$_{\alpha }$lines in Ar-2{\%}H$_{2}$ mixture gases: n$_{e}$ from 4.0x10$^{14}$ to 2.0x10$^{15}$cm$^{-3}$ and T$_{e} \quad \cong $ 0.6eV. As anode, the needle generates microjets with T$_{g}$ from 400 to 900K, at high current (from 20 to 130mA). [Preview Abstract] |
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MWP1.00047: Electrical and optical characteristics of a low-frequency atmospheric plasma discharge Christopher J. Oldham, Matthew R. King, C. Richard Guarnieri, Jerome J. Cuomo The electrical and optical characteristics of a capacitive discharge operated at atmospheric pressure were studied. The discharge was operated with and without dielectric barriers to investigate how the discharge behaved using a low frequency power source. Plasma formation was found at three main harmonics; 30 kHz, 80 kHz, and 150 kHz. In addition, other higher frequency components approaching the MHz regime were found to contribute to plasma generation. The presence of the dielectric barriers significantly effected discharge properties. With the electrodes covered by dielectric barriers, the alpha-gamma transition occurs with increasing power. Without dielectric barriers, the discharge was constricted and operated only in the abnormal mode of operation. Spatial results from the He I (706 nm) emission profile along with gas temperature measurements from the N2+ rotational band will be presented. [Preview Abstract] |
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MWP1.00048: Traces of Accumulated Charges on Dielectric Electrode in Self-Organization in Barrier Discharge Generated by Piezoelectric Transformer Haruo Itoh, Kenji Teranishi, Kazuto Kobayashi, Naoyuki Shimomura, Susumu Suzuki Discharge plasmas excited by nano-meter longitudinal vibration of piezoelectric transformers (PTs) has been investigated to construct compact plasma reactors for practical applications. In the experiments aimed to develop a PT-based excimer lamp, self-organization phenomenon in the DBD [1] was observed as regularly hexagonal patterns of microdischarges in He and Ar with a small amount of air impurities [2]. Time-resolved observation of the self-organized patterns is performed by ICCD camera to clarify the phenomenon. In the images, we found dark spots arrayed hexagonally in a weak emission on the PT surface whose arrangement well coincides with that of bright hexagonal filaments. The dark spots are considered as the traces of the accumulated charges on the dielectric electrode, which interrupt the hexagonally-filamentary discharges. [1] L. Stollenwerk et al., Phys. Rev. Lett., 98, 255001 (2007) [2] H. Itoh et al., IEEE Trans. Plasma Sci., 36, 1348 (2008). [Preview Abstract] |
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MWP1.00049: DIELECTRIC BARRIER DISCHARGES, DISPLAYS |
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MWP1.00050: Homogeneous DBD in N2: I. LIF, TALIF and electrical measurements Nicolas Gherardi, Et-Touhami Es-Sebbar, Christian Sarra-Bournet, Nicolas Naude, Francoise Massines In this paper we compare two different discharges that can be obtained in a DBD configuration, that is to say the filamentary discharge (usual regime in atmospheric DBD) with the Atmospheric Pressure Townsend Discharge (APTD), which is a homogeneous regime obtained in nitrogen atmosphere. The aim is to help in the understanding of the processes which control the transition from one regime to the other. To do so, the discharge is characterized through electrical measurements, coupled with optical diagnostics among which Laser Induced Fluorescence (LIF) for radical density measurements. The influence of the addition of small quantities of additives on the stability of the N2 APTD is followed: the absolute density of N, O and NO are reported in N2/O2 and N2/N2O mixtures. One interesting result is that while the electron density is much lower in the APTD than in the filamentary discharge, the Townsend discharge is really efficient for the creation of N atoms: densities as high as 3x10$^{14}$ cm$^{-3}$ has been measured. These measurements are used to validate numerical models presented in paper ``Homogeneous DBD in N2: II. Simulation in 0D and 1D approaches'' by S. Pancheshnyi et al. [Preview Abstract] |
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MWP1.00051: Cold Atmospheric-Pressure Plasmas Applied to Active Packaging of Fruits and Vegetables Patrick Pedrow, Sulmer Fernandez, Marvin Pitts Active packaging of fruits and vegetables uses films that absorb molecules from or contribute molecules to the produce. Applying uniform film to specific parts of a plant will enhance safe and economic adoption of expensive biofilms and biochemicals which would damage the plant or surrounding environment if misapplied. The pilot application will be to apply wax film to apples, replacing hot wax which is expensive and lowers the textural quality of the apple. The plasma zone will be obtained by increasing the voltage on an electrode structure until the electric field in the feed material (Argon + monomer) is sufficiently high to yield electron avalanches. The ``corona onset criterion'' is used to design the cold plasma reactor. The apple will be placed in a treatment chamber downstream from the activation zone. Key physical properties of the film will be measured. The deposition rate will be optimized in terms of economics and fruit surface quality for the purpose of determining if the technique is competitive in food processing plants. [Preview Abstract] |
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MWP1.00052: Efficiency of pulse-mode dielectric barrier discharge excimer lamp in constant duty cycle Haruaki Akashi, Akinori Oda, Yosuke Sakai Efficiency of pulse-mode dielectric barrier discharge (DBD) excimer lamp under constant duty cycle with increasing applied voltage has been simulated using two dimensional fluid model[1]. Xe gas with 300Torr pressure is assumed. And the simulated region considered in this model is 1cm(gap length)x3cm(radial length). Periodical boundary conditions are assumed for the radial direction boundaries. The both electrodes are covered with dielectrics and their thickness is 0.2cm. 5$\sim $8kV trapezoid shape voltage is applied with the same voltage rising ratio and 50{\%} duty ratio waveform with 200x10$^{3}$pps repetition rate. The discharge occurs at the rising edge and tailing edge of applied voltage. 172nm VUV intensity obtained from first discharge is higher than second one in lower applied voltage ($<$6kV) case. And in higher voltage case, the intensity from second discharge becomes higher. This is explained by shortening of interval time between the discharges. The short interval time makes higher initial electron density for second discharge. As a results, the input and 172nm VUV output power increases with increasing applied voltage, but the efficiency decreases. Because of inefficient surface discharge [1]H. Akashi et al, IEEE Trans. Plasma Science, Vol.33,No.2(2005,4)pp.308-309 [Preview Abstract] |
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MWP1.00053: The influence of impurities on the electrical behaviour of high pressure noble gas plasmas Tom Martens, Annemie Bogaerts, Wouter Brok, Jan van Dijk Since reactor designs are rarely completely the same, gases of different quality grades are being used and since in simulations the impurity levels are sometimes used to fit the simulated breakdown voltages to the experimental values, we focus our current research on the influence of different levels of gas impurity on the electrical characteristics of dielectric barrier discharges in atmospheric helium. For matters of simplicity and to be able to make comparison with results published in literature, we focus on nitrogen impurities and use a fluid model to describe the discharge. Our results show that when the nitrogen content rises, the amount of current pulses in each half period increases, a phenomenon that has been investigated experimentally by Radu et al. [IEEE Trans. Plasma Sci., Vol. 31(6), 1363-1378]. Interestingly, our results show that the power consumption shows a steep drop and becomes minimal at about 3800 ppm and quickly rises again for higher impurity levels. This drop coincides with the transition from 2 to 3 current pulses and appears to originate from the decrease of the peakwidth with rising nitrogen content. This drop is followed by a quick increase in power consumption due to an extra current pulse at 4000 ppm. [Preview Abstract] |
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MWP1.00054: Experimental study of a novel micro-wire dielectric barrier discharge Joris Creemers, Alec De Kuyper, Peter Bruggeman, Christophe Leys Many types of dielectric barrier discharge (DBD) configurations have been studied in the past as a way to produce non-thermal plasma at atmospheric pressure. Most are based on parallel plane or coaxial electrodes. The electrode configuration studied in this paper has a coaxial geometry, where the inner electrode is a novel glass-coated micro-wire coil. We investigate the effects of the very small diameter of the wire ($\sim$30 $\mu$m) on the characteristics of the discharge. The influence of the excitation frequency (50 Hz - 50 kHz) on the current waveform is analyzed. In view of applications, the ozone production efficiency is compared with standard DBDs. [Preview Abstract] |
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MWP1.00055: Self synchronization of surface discharges Katia Allegraud, Antoine Rousseau Surface dielectric barrier discharges (SDBD) are mainly investigated for airflow control. In this paper, they are used to study surface processes in dielectric barrier discharges. A previous study has shown the self triggered behavior of a SDBD: the plasma initiates through several simultaneous and adjacent filaments around the electrode [1]. This phenomenon has been investigated under the name of collective effects, where the light of a first filament can trigger the ignitions its neighbors [1, 2]. It allows initiating several tens of streamers during a current peak of $\sim $50 ns. In the present study, we propose to investigate the self synchronization of the discharge in a two electrodes system: the setup consists of two high voltage electrodes on the same glass plate. A third electrode, under the plate, is grounded. ICCD measurements show that the discharge appears simultaneously on both electrodes on a 50 ns time scale. Nanosecond resolved measurements of the streamers propagation reveal that the ignitions on one electrode can be delayed by few nanoseconds in respect to the other one. This means that the discharge from a first electrode can trigger the second one. Finally, iCCD measurements allow calculating the streamers propagation velocity, varying from 3.4x10$^{7}$ cm/s at the beginning of the propagation to 0.7x10$^{7}$cm/s at the end of the propagation [3]. [1] K. Allegraud, O. Guaitella, A. Rousseau, J. Phys. D.~: Appl. Phys. 40 7698--7706 (2007) [2] O. Guaitella, F. Thevenet, C. Guillard, A. Rousseau, J. Phys. D.: Appl. Phys. 39 2964--72 (2006) [3] K. Allegraud, A. Rousseau, submitted to IEEE Transactions on Dielectrics and Electrical Insulation [Preview Abstract] |
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MWP1.00056: Optical and electrical characteristics of N$_{2}$ micro-discharges produced in coplanar surface DBD geometry Milan Simek, Vaclav Prukner, Jiri Schmidt Basic optical and electrical characteristics of nitrogen micro-discharges generated in an AC surface DBD reactor with coplanar electrode arrangement were studied at atmospheric pressure by means of the ICCD microscopy and spectrometry complemented with the multi-channel photon-counting. Temporal evolutions of N$_{2}$-2.PG (second positive), N$_{2}$-HIR (Hermann infrared), NO-gamma and N$_{2}^{+}$-1.NG (first negative) bands induced by an individual H-shaped micro-discharge generated during positive/negative AC half-cycle were acquired and analyzed. Typical emission waveforms were inspected as function of both frequency and amplitude of the modulated AC driving high-voltage, in the case of a) a single micro-discharge produced during an AC half-cycle and b) multiple, equally spaced micro-discharges produced during an AC half-cycle. Observed waveforms and obtained characteristic time constants will be discussed in the frame of electron impact excitation/ionization, N$_{2}$(A)+N$_{2}$(A) energy pooling and N$_{2}$(A)+NO resonant energy transfer processes. [Preview Abstract] |
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MWP1.00057: COMPUTATIONAL METHODS FOR PLASMAS |
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MWP1.00058: A stabilized finite element method for gas discharge modelling Markus Becker, Detlef Loffhagen, Florian Sigeneger, Werner Schmidt Fluid models consisting of Poisson's equation for the electric potential, continuity equations for the relevant plasma species and the electron energy balance are widely used for the theoretical description and analysis of glow discharges. The discretization of the corresponding partial differential equations by means of standard finite difference and element methods leads to serious restrictions for the spatial mesh spacing $\Delta x$ resulting from the condition $|P_e|\leq 1$ for the local P\'{e}clet number $P_e$ whose fulfillment prevents spurious oscillations. To avoid this problem, a stabilized finite element method was developed by choosing upwind test functions instead of the same basis for the test and trial spaces. Using the example of a one-dimensional low-pressure glow discharge in argon with an electrode gap of 1~cm it is shown that this improved method yields stable and non-oscillatory results, even if the condition $|P_e|\leq 1$ is not fulfilled. As an advantage of the new technique it is demonstrated that the numerical results do not exhibit the excessive diffusive behavior as the often used stabilizing Scharfetter-Gummel scheme and upwind finite difference methods. [Preview Abstract] |
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MWP1.00059: Particle-in-Cell Simulations of an Overdense Plasma Sustained by Microwaves Ronald Bravenec, Christine Roark, Merritt Funk, Lee Chen, David Smithe, Peter Stoltz, Ed Kase Sustainment of plasmas by microwaves in an overdense state ($\omega <\omega _{pe})$, where the waves should be cut off, is not completely understood. Using the VORPAL particle-in-cell code,\footnote{C. Nieter and J. R. Cary, J. Comp. Phys., \textbf{196}, 448 (2004).} we study in 2-D the interaction of electromagnetic waves propagating through an insulating dielectric at arbitrary angle into an unmagnetized plasma. Of particular interest is the predicted resonance of the waves at the location in the sheath where $\omega =\omega _{pe}$.\footnote{Yu. M. Aliev, \textit{et al}., Plasma Sources Sci. Tech. \textbf{1}, 126 (1992).} This resonance can magnify the electric fields and accelerate electrons to high energies. The simulations include ionization using a Monte-Carlo type model with energy-dependant cross section, which allows us to study the buildup of plasma. We are also studying the effects of secondary emission from the dielectric surface, where copious secondary emission is seen to reduce or even momentarily reverse the sign of the sheath electric field. Our secondary emission model allows for energy and incident angle dependant yield, and produces a specific energy spectrum of outgoing particles. Simulations for various plasma densities and gas pressures will be presented. [Preview Abstract] |
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MWP1.00060: ZDPlasKin: a new tool for plasmachemical simulations Sergey Pancheshnyi, Benjamin Eismann, Gerjan Hagelaar, Leanne Pitchford We present ZDPlasKin (Zero-Dimentional Plasma Kinetics) freeware utility which was developed for a wide range of complex plasmachemical simulations in various gas mixtures. Our approach is based on a local approximation of the evolution of species densities obtained by solving the conservation equations. In a first step a pre-processor is used to translate a list of species, reactions and corresponding rate constants in a simple user-friendly text format into a FORTRAN 90 module. This automatically generated module contains the definition of the problem, an interface to the DVODE\_F90 ODE solver and a set of supplementary routines. It includes as well an automated link to BOLSIG+, a Boltzmann equation solver based on the two-term approximation, which provides the electron transport rates and the rates of electron-neutral collisions. In a second step, execution of the code yields the time evolution of the species densities and the reaction rates. A simple acquisition algorithm allows tracing of time-averaged species densities and corresponding source terms and reaction rates for sensitivity analyses. Examples will be presented to demonstrate the simple interface and efficiency of the utility. The utility will be soon available for downloading from the LAPLACE web site http://www.laplace.univ-tlse.fr. [Preview Abstract] |
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MWP1.00061: Electric dipole moments in conducting particle Coulomb crystals Ke Qiao, Lorin Matthews, Truell Hyde Coulomb crystals have been studied extensively, but in general assuming the constituent dust particles are comprised of some form of insulating material. Crystals formed from particles composed of conducting materials should exhibit differences in behavior due to the free electrons on the particle surface, which create a completely different surface charge distribution and electric dipole moments than those seen in insulating particles. A molecular dynamics (Box{\_}Tree) simulation is employed to investigate the structure and dynamics of conducting particle systems, including electric dipole effects. The results are compared to experimental data from ordered dusty plasmas systems comprised of gold-coated particles. [Preview Abstract] |
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MWP1.00062: LIGHTING PLASMAS: GLOWS, ARCS, FLAT PANELS, NOVEL SOURCES, OTHERS |
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MWP1.00063: Emission characteristics on light source array using micro hollow cathode plasma Takayuki Ohta, Naoki Takota, Yoshihiro Tachibana, Masafumi Ito, Yasuhiro Higashijima, Hiroyuki Kano, Shoji Den, Masaru Hori We have developed a light source array for an absorption spectroscopy using micro hollow cathode plasma. The light source is capable of emitting multi-lines of metallic atoms for measuring absolute densities of metallic atoms simultaneously in sputtering, MBE, CVD processes, and so on. In this study, the emission characteristics of the light source were investigated. Emission intensities of metallic atoms and the rotational temperatures of the N$_{2}$ second positive system were measured as functions of cathode length or cathode diameter. The emission intensity of Cu atom increased with a decrease in the cathode length from 20mm to 3mm. The applied voltage was 400 V, the pressure was 0.01 MPa, and the current was 40 mA. The current density which was applied to the Cu pipe cathode becomes larger in the shorter pipe length, so that the emission intensity became larger. The N$_{2}$ rotational temperature was used for evaluating the neutral gas temperature and was evaluated to be from 510 to 750 K. [Preview Abstract] |
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MWP1.00064: UV Discharge Lamp on Water Vapor Yurij Shpenik, Volodymyr Kelman, Yurij Zhmenyak, Andrij Heneral The development of non-coherent sources of UV radiation based on safe and nontoxic gaseous mixtures have good aspect for different applications. Present paper for the first time reports about experimental investigations of high voltage pulse-periodic discharge in water vapor. The observed time integrated emission spectra in the range 250-325 nm at the estimated water vapor pressure 0.1 mm Hg shown tree different parts: part I (250-275 nm) is attributed to B-A electronic transition of hydtoxyl OH molecule; part II (275-300 nm) and part III (300-325) -- to the A-X electronic transition of OH molecule. The most intensive were the bands, connecting with vibration transitions (1-0) 283 nm and (1-1) 309 nm. No other radiating species were detected. Time-dependent measurement clearly indicated that the emission pulse coincides with current pulse and the electron impact processes defines the properties of the discharge emission. The average output power of the lamp was estimated 1.5 W at 0.2 {\%} efficacy. The use of hard water D$_{2}$O instead of H$_{2}$O results the increasing of output power approximately to twice. [Preview Abstract] |
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MWP1.00065: The influence of double ionization on the arc attachment in high intensity discharge lamps$^*$ Frank Scharf, Andre Bergner, Juergen Mentel So far, only single ionization has been considered for the simulation of arc attachments in high intensity discharge lamps.$^{1,2}$ However, it was found (and supported by experiments$^{3}$) that the electrons reach temperatures where double ionization is not negligibly small anymore for certain conditions. To investigate the effect this has on the arc attachment, we qualitatively include double ionization in the calculation of the so-called transfer functions (namely the heat flux $q_p$ and current density $j$). These transfer functions are necessary to simulate the arc attachment numerically. In the new transfer functions, ion densities for ions with single and double charge are calculated from an analytical solution of the Saha equations. These densities are used to calculate a reduction of the ion energy caused by the additional energy drain the double ionization process represents. It is however assumed that the ion current is still driven by the singly charged ions. This simplification allows only qualitative results.\\[.5ex] $^1$ L. Darbringhausen {\it et al.} {\it J. Phys. D: Appl. Phys.} {\bf 38} (2005) 3128\\ $^2$ N. A. Almeida {\it et al.}, {\it J. Phys. D: Appl. Phys.} {\bf 37} (2004) 3107\\ $^3$ G. Kuhn and M. Kock, {\it Phys. Rev. E} {\bf 75} 1 (2007) 016406\\[.5ex] $^*$Supported by the DFG within Graduiertenkolleg 1051 [Preview Abstract] |
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MWP1.00066: Breakdown characteristics of high intensity discharge lamps filled with xenon Martin Wendt, Silke Peters, Manfred Kettlitz, Florian Sigeneger A comparison between measured and modelled breakdown voltages of HID lamps filled with xenon at pressures of $0.1$--$5$ bar is presented. Measurements of current and voltage characteristics and high speed photography were done on specially prepared lamps at voltage rise times of $1$ MV/s to $2\times 10^5$ MV/s. The model consists of the Poisson equation and continuity equations for electrons and ions using the drift-diffusion approximation for the particle fluxes. Transport parameters for the electrons as functions of E/N have been determined by solving the 0-D Boltzmann equation. Appropriate boundary conditions couple the plasma to the outer circuit. The model is solved on a 1-D, inhomogeneous grid using an adaptive time step. Following the cubic interpolated propagation scheme each time step is divided into advective and non-advective parts. The latter is solved by applying the Crank-Nicholson scheme. The model gives a cathode-directed ionization front which turns into a cathode sheath. The model breakdown voltages increase with filling pressure and voltage rise time and are in good agreement with experiments. [Preview Abstract] |
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MWP1.00067: Laser Induced Fluorescence on Molecular Discharges Hjalmar Mulders, Arij Rijke, Vincent Girault, Winfred Stoffels In the last half century, mercury has been used widely as the radiating species in many low pressure fluorescent lamps. Mercury primarily radiates at 254 nm and 185 nm. These photons excite a phosphor that fluoresces back to the ground state producing visible photons. This process reduces the efficiency because much of the energy of the UV photons has to be discarded. Using a species that emits light closer to or even in the visible range reduces these losses. Ideally the species (or a mixture of several species) should build up the whole visible spectrum, much like in HID lamps. InBr seems to be a good candidate for such a lamp, because it is an efficient radiator that emits most of its light around 370 nm; much closer to the visible part of the spectrum. In order to get insight in the energy transfer processes going on in these molecules we have conducted a laser induced fluorescence (LIF) experiment on InBr vapour and on a plasma. We have measured the decay times of different rovibrational levels of the InBr-molecule as well as the spectral distribution of the fluorescence from these levels. From the former we calculated the rotational temperature of the plasma and from the latter we calculated the Franck-Condon factors for the A-state as well as the vibrational temperature. [Preview Abstract] |
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MWP1.00068: Determination of Ba-emitter densities along electrodes in high pressure sodium lamps by optical absorption spectroscopy Michael Westermeier, Jens Reinelt, Peter Awakowicz, Juergen Mentel Nowadays, high pressure sodium lamps gain more importance in various fields of lighting e.g. for horticulture lighting. To achieve a long lifetime, a detailed understanding of the density of the barium emitter around the lamp electrodes and its interaction with them is needed. The lamp under investigation has a special research design. It is downscaled to a 140 W lamp and equipped with a sapphire discharge tube to allow optical observations. Ba is stored in a tungsten coil around the rod shaped tungsten electrodes and transported to the tip during operation. By measuring the absorption of the 553 nm Ba resonance line the spatially resolved Ba density around the electrodes during lamp operation is determined. As backlight a filtered UHP-lamp is installed. The measuring results show a decrease of Ba along the electrode axis representing a diffusion process. Further results will be shown for different lamp operating parameters (e.g. current, frequency) and combined with the measured electrode temperature profiles. [Preview Abstract] |
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MWP1.00069: Iodine pressure in high intensity discharge lamps Alexander Dunaevsky, Jun-Ming Tu The dynamics of the partial pressure of iodine influence the emission properties of metal halide lamps. In addition, various processes in the discharge affect the iodine pressure. Monitoring the partial pressure of iodine by high-resolution spectroscopy (HRS) can be a very powerful, non-destructive diagnostic tool for metal halide lamp development, if the mechanisms responsible for the pressure changes are understood. Thermodynamic modeling can help to interpret some effects observed experimentally. In this study, the iodine pressure in quartz sodium-scandium metal halide lamps with various chemical additive ratios is measured using the HRS technique. The correlations between partial pressures predicted by modeling and observed experimentally are analyzed. [Preview Abstract] |
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MWP1.00070: NEGATIVE IONS, SHEATHS AND DUSTY PLASMAS |
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MWP1.00071: Ion-ion plasmas by electron magnetic filtering: 2D fluid simulation and applications to space propulsion Albert Meige, Gerjan Hagelaar, Pascal Chabert A two-dimensional magnetized plasma fluid simulation is developed to investigate the electron magnetic filtering in an electronegative plasma. The model uses the first three moments of the Boltzmann equation, namely the continuity equation, the conservation of momentum and an energy equation for the electrons. An oxygen plasma in a grounded cylinder is simulated. The magnetic field is uniform and parallel to the system revolution axis. When the magnetic field strength is sufficient, electrons are confined in the center of the discharge, resulting in an ion-ion plasma (electron-free plasma) at the periphery of the discharge. Applications to space propulsion are presented. [Preview Abstract] |
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MWP1.00072: A study of negative ion production on surface in H$_{2}$ and D$_{2}$ plasma Gilles Cartry, Lo\"Ic Schiesko, Jounayd Bentounes, Marcel Carrere, Jean-Marc Layet We present a study of negative ion (NI) generation on surface in H$_{2}$ and D$_{2}$ plasmas. A mass spectrometer (EQP300) is placed in the diffusion chamber of a helicon plasma reactor and faces a one square centimetre sample (graphite, copper{\ldots}). The sample is negatively biased with respect to the plasma. Positive ions strike the sample in normal incidence and NI formed (H$^{-}$ and D$^{-})$ upon bombardment are repelled from the surface toward the plasma and collected by the mass spectrometer. Through the measurement of negative Ion Distribution Function (IDF) we investigate basic mechanisms governing NI production on surfaces in interaction with H$_{2}$ plasma. Particularly, we have shown that two electrons capture by incoming positive ions explains IDF tail but is not the main mechanism explaining NI production. On the contrary, we demonstrated sputtering of adsorbed hydrogen atom as NI accounts for most of negative ions created. We also demonstrated NI production on graphite surface is proportional to ion flux and has bell shape dependence with positive ion energy. [Preview Abstract] |
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MWP1.00073: The collisional capacitive RF sheath and the assumption of a sharp electron edge Ralf Peter Brinkmann The transition from quasi-neutrality to charge depletion is one of the characteristic features of the plasma boundary sheath. It is often described in terms of the so-called step model which assumes a transition point (electron step) where the electron density drops from a value equal to the ion density (in the bulk) to a value of zero (in the sheath). Inserted into Poisson's equation, the step model yields an expression for the field which is realistic deep in the sheath but fails to merge correctly into the ambipolar field of the bulk. This work studies the consequences of that approximation for the example of the collision-dominated, capacitive RF sheath by Lieberman [1]. First, the model is solved exactly, using a relaxation scheme. Then, the step approximation is applied which recovers Lieberman's semi-analytical solution. It is demonstrated that the step approximation induces a spurious divergence of the ion density at the sheath edge and prevents a matching of the sheath model to a bulk model. Integral sheath quantities, on the other hand, like the capacitance or the overall voltage drop, are faithfully reproduced. [1] M. A. Lieberman, IEEE Trans. Plasma Sci. 16, pp. 638-644 (1988). [Preview Abstract] |
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MWP1.00074: Study of an electron-attracting sheath: the effect of secondary electron emission Gilles Cartry, Lo\"Ic Schiesko, Marcel Carrere, Jean-Marc Layet A copper sample facing a mass spectrometer (EQP300) is biased positively beyond plasma potential in low pressure argon plasma. Some Ar$^{+}$ and Ar$^{2+}$ ions are created in the sheath by electrons extracted from plasma and are accelerated toward the mass spectrometer where they are detected according to their energy. Ion energy is related to the local sheath potential at which the ion has been created. Providing careful energy calibration of the mass spectrometer, Ion Distribution Function (IDF) allows probing in a non perturbative way electron attracting sheath potential. We observe a strong decrease of the ion signal some few volts before sample bias. We attribute this effect to the presence of secondary electrons shielding the sample potential. Potential profile and IDFs are computed using a model including secondary emission. Fit of Ar$^{+}$ and Ar$^{2+}$ IDFs provides an estimation of secondary emission yield and secondary electron temperature. [Preview Abstract] |
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MWP1.00075: Interaction of dust particles in a plasma with an external source of gas ionization Andrey Starostin, Anatoly Filippov, Alexander Pal, Anatoly Zagorodny The interaction of two dust particles in no equilibrium plasma at elevated pressures has been studied. An asymptotic theory of screening, which leads to a two-exponential dependence of the dust particle potential on distance with different shielding lengths, is used to determine the electrostatic energy of the system of charges associated with the two dust particles. The dependence of the electrostatic energy on interparticle distance has been found to have a minimum, as in equilibrium plasma. The interaction force between the dust particles has been determined. It turned out to be asymmetric - for different charges the forces acting on the first and second dust particles are not equal. The force equality takes place only for the sinks of plasma particles proportional to the dust particle charge. This is the result of an asymmetric charge separation near dust particles with different charges and indicates that the interaction force in no equilibrium plasma is no potential in the common case. The potential energy of the interaction between the dust particles has been determined for the case of equal forces. Attraction between likely charged particles with different (in magnitude) charges has been found to be possible only when they come very close to each other. Relations for modified coupling parameter of an interaction potential that consists of two exponential terms with different shielding lengths were derived. [Preview Abstract] |
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MWP1.00076: New insights into the anion formation mechanisms in dusty acetylene discharges Ming Mao, Jan Benedikt, Angelo Consoli, Annemie Bogaerts Dust (or nanoparticle) formation is a well-known phenomenon occurring in reactive gas plasmas, such as silane or acetylene. Under some conditions, the dust formation is considered to be harmful, whereas for other applications, it turns out to be beneficial. In this presentation, the initial mechanisms of nanoparticle formation and growth in radiofrequency (RF) acetylene (C2H2) plasmas are investigated by means of a comprehensive self-consistent one-dimensional (1D) fluid model. Based on the comparison of our calculation results with available experimental data for acetylene plasmas in the literature, some new mechanisms for negative ion formation and growth are proposed. Possible routes are considered for the formation of larger (linear and branched) hydrocarbons C$_{2n}$H$_{2}$ (n=3-5), which contribute to the generation of C$_{2n}$H$^{-}$anions (n=3-5) due to dissociative electron attachment. Moreover, beside the C$_{2n}$H$^{-}$ ions, also the vinylidene anion (H$_{2}$CC$^{-})$ and higher C$_{2n}$H$_{2}^{-}$ anions (n=2-4) are found to be important plasma species. This project was supported financially by the Fund for Scientific Research (FWO) Flanders (Project G. 0068.07), the Interuniversity Attraction Poles Programme of the Belgian State (Belgian Science Policy; Project P6/42) and the CALCUA computing facilities of the University of Antwerp. [Preview Abstract] |
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MWP1.00077: Peculiarity of Positron Annihilation on Atoms and Particles of Dust Space Plasma of Galactic Center Viktor I. Grafutin, Tat'yane L. Razinkova, Eugene P. Prokop'ev, A.I. Alikhanov Research of properties of positron states has great importance in a modern science and technology. Therefore last years intensive development of positronics of various substances and their states is observed. The special role is represented with researches in the field of space positronics. It is process positron annihilation in the dust space plasma on the basis of our calculations and data analysed. It is shown that formation of positronium atom in dust space plasma with the large concentration of the charged particles of a dust can occur as by means of processes of interaction of positrons to atoms $H$ and free electrons and processes of interaction of positrons with the charged particles of dust space plasma. In such space plasma the output of positronium atom about what speak experimental data of space laboratory Integral is possible practically 100 {\%}. Proceeding from sizes of diffusion coefficient the sizes of particles of a dust particles in space plasma exceeds size of the order 100 of nanometer. The size of particles is comparable to length of diffusion of positrons, i.e. $0,1\div 1$ microns. These received sizes of particles well coincide with data of optical observations. [Preview Abstract] |
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MWP1.00078: CAPACITIVELY COUPLED PLASMAS |
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MWP1.00079: Properties of capacitive He/SF$_6$/O$_2$ and He/CF$_4$/O$_2$ discharges at atmospheric pressure Takashi Kimura, Hiroki Tanahashi Electrical and optical measurements of atmospheric pressure capacitive radio frequency (13.56 MHz) He/SF$_6$/O$_2$ and He/CF$_4$/O$_2$ discharges are carried out at the mixture compositions of fluorine compound gas and oxygen of 0.5$\%$. Those discharges are produced between two planar electrodes of 40mm-$\phi$ at the gap length of 1.0 mm in the dissipated power range from 40W to 180W. The total flow rate of helium and reactive gases is kept at 7($\ell$/min), and the small amount of Ar (= 10 sccm) is also fed in order to estimate the atomic fluorine density by actinometry. From the measured waveforms of the applied voltage and the RF current, the atmospheric pressure He/CF$_4$/O$_2$ discharges are capacitive, whereas the He/SF$_6 $/O$_2$ discharges are greatly resistive at most of our experimental conditions. The atomic fluorine density in those discharges should be estimated by actinometry, where the intensities at 704 nm emitted from the excited atomic fluorine and 750nm emitted from the excited Ar are used. The atomic fluorine density increases markedly with increasing oxygen content, and then reaches each maximum when the ratio of the oxygen content to the sum of the oxygen and fluoride compound gas contents is around 0.2-0.5. The atomic fluorine density in those discharges is on the order of 10$^{14}$ cm$^{-3}$. This work was supported in part by Research Foundation for the Electrotechnology of Chubu. [Preview Abstract] |
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MWP1.00080: Plasma activation caused by local rf power supply F. Sigeneger, R. Basner, D. Loffhagen, H. Kersten The response of a capacitively coupled rf discharge in argon at 13.56\,MHz to a local supply of additional rf power at the passive electrode was investigated experimentally and theoretically. The study has been performed at the reactor PULVA-INP which posseses a segmented passive electrode. Its central pixel was driven by an additional rf voltage with the same frequency and phase as the main power supply. The large enhancement of the local power density becomes obvious from the intensive light emission in front of this pixel. Furthermore, the pronounced change of the potential was demonstrated by the sensitive response of microparticles in the sheath. An axisymmetric fluid model of the plasma has been implemented to study the observed phenomeon theoretically. The model comprises particle balance equations of electrons and ions, Poisson's equation and the electron energy balance equation. The results of the model calculations demonstrate the structural change of the potential and the local increase of the electron density and power density in front of the central pixel. The strongly increased excitation rate corresponds to the observed enlargement of the light emission. [Preview Abstract] |
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MWP1.00081: Diagnostics of ballistic electrons in a DC/RF hybrid capacitively coupled plasma reactor Lin Xu, Lee Chen, Alok Ranjan, Merritt Funk, Ron Bravenec, Demetre Economou, Vincent Donnelly, Radha Sundararajan The DC/RF hybrid is a capacitively coupled plasma etcher with RF voltage on the bottom electrode and negative DC bias on the upper electrode. This configuration can significantly alleviate the electron shading effect and preserve photoresist integrity during plasma etching. It is thought that a group of ballistic electrons is responsible for these results. These high-energy electrons start as secondaries emitted from the negatively-biased DC electrode and accelerate across the DC sheath. They acquire high enough energy in the sheath such that they can cross the bulk plasma without gas-phase collisions. The ballistic electrons either strike the RF electrode or are trapped in the plasma bulk depending on the RF phase. Two gridded energy analyzers mounted on the back of the RF electrode were used to determine the energy distribution of ballistic electrons. The dependence of the ballistic electron energy distribution on DC voltage, pressure and RF power will be presented and compared with simulation results. [Preview Abstract] |
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MWP1.00082: Secondary electrons in dual-frequency capacitive discharges Miles M. Turner Phase resolved optical emission spectroscopy has offered deep insight into the behaviour of electrons in plasma discharges, nowhere more so than in the case of dual-frequency discharges, where the presence of the two frequencies leads to complicated electron dynamics. An open question in the physics of these discharges is the importance of secondary electrons, emitted from electrodes by such processes as ion impact and photo-emission. Because the electrode surface state is poorly known, it is difficult to say anything a priori about the significance of these processes. In this paper we will present particle-in-cell simulations of dual-frequency discharges under conditions approximating those of the experiments, and we will attempt to draw conclusions concerning the importance of secondary electron effects, based both on the observed spatio-temporal pattern of optical emission, and on measurements of the plasma density carried out using hair-pin probes. The conclusion of this investigation is that secondary electron phenomena cannot be neglected under these conditions. [Preview Abstract] |
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MWP1.00083: Modelling and Simulation of multi-frequency capacitive discharges Stefan Bienholz, Philipp Mertmann, Peter Awakowicz, Thomas Mussenbrock, Ralf Peter Brinkmann In material processing applications the energy distribution function and the angular distribution function of energetic ions which are accelerated by the electric field in the plasma boundary sheath play a crucial role. The calculation of such distribution functions requires either large computational cost within the frame of numerical simulation of a plasma reactor as a whole or the electric field is assumed to be given by simple expressions. However, an appropriate discharge (or sheath) model is needed. In this contribution we propose a locally one-dimensional model of a capacitive discharge based on a ion fluid description self-consistently coupled to Poisson's equation. The model allows for self-consistent calculation of the electric field for (arbitrary) multi-frequent discharge excitation and thus for calculation of ion distribution functions by means of an efficient Monte-Carlo code. [Preview Abstract] |
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MWP1.00084: Skin effect in an asymmetrical, capacitive discharge Michael Klick, Torben Hemke, Thomas Mussenbrock, Ralf Peter Brinkmann The electrostatic approximation assumption reduces the set of Maxwell's equations to the much simpler Poisson equation and is often employed for modeling and simulation of radio frequency driven capacitive low pressure discharges. It is now widely acknowledged that the neglect of induction phenomena breaks down for large-area and high-density plasmas. But there is still a lack of analytical models which allow an easy handling and understanding of the skin effect in asymmetrical systems. We present an electrodynamic 2d model for a cylindrical, asymmetrical CCP. We use a simplified boundary condition for the RF current density to achieve a considerable simplification of the mathematical approach. Thus the sheath at the driven electrode can be included readily. Advantages and restrictions of the analytical solution are discussed in comparison to numerical simulation results. [Preview Abstract] |
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MWP1.00085: On the possibility of making a geometrically symmetric RF-CCP discharge electrically asymmetric Uwe Czarnetzki, Brian G. Heil, Ralf Peter Brinkmann, Thomas Mussenbrock A simple solution to the demand of controlling independently ion flux and ion energy in capacitive discharges is presented. When a temporally symmetric, multi-frequency voltage wave form containing one or more even harmonics is applied to a discharge, even a geometrically symmetric one, the two sheaths are necessarily asymmetric and a DC self bias develops. Optimally, this is achieved by simultaneously applying an RF voltage composed of the phase locked fundamental and its second harmonic. The resulting DC self bias and hence the ion energy is a nearly linear function of the phase angle between the two applied RF voltages. In geometrically symmetric discharges the roles of the two electrodes can be reversed by just using the phase. The phase angle control of the ion energy leaves the applied RF voltage and frequency and thereby the plasma density, electron temperature, and ion flux effectively unchanged. An analytical model and a hybrid fluid dynamic-Monte Carlo simulation analysis are presented. [Preview Abstract] |
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MWP1.00086: Electric Field Reversals in the sheath region of capacitively coupled RF discharges at different pressures Julian Schulze, Zoltan Donko, Brian Heil, Dirk Luggenhoelscher, Thomas Mussenbrock, Ralf Peter Brinkmann, Uwe Czarnetzki Electric field reversals in single and dual-frequency capacitively coupled RF discharges are investigated at different pressures. Phase resolved optical emission spectroscopy is used to measure the excitation of the neutral background gas caused by the field reversal during sheath collapse. The resulting spatio-temporal excitation profiles are compared to results of a fluid sheath model in the single frequency case and a Particle in Cell simulation in the dual-frequency case. The results show that field reversals occur in both cases, in different gases and at different pressures. An analytical model gives insight into the mechanisms causing the reversal of the electric field. In the dual-frequency case a comparison between PIC simulation and analytical model is performed. It shows that the field reversal is caused by a combination of electron inertia and collisions of electrons with the neutral background gas. The model also shows that at low pressures electron inertia is the cause of the observed field reversal. [Preview Abstract] |
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MWP1.00087: Multiband carbon monoxide laser (2.5 -- 4.0 and 5.0 -- 6.5 micron) pumped by capacitive slab RF discharge Andrey Ionin, Andrey Kozlov, Leonid Seleznev, Dmitry Sinitsyn Overtone lasing and fundamental band tuning was for the first time obtained in a carbon monoxide laser excited by repetitively pulsed capacitive slab RF discharge (81.36 MHz). RF discharge pulse repetition rate was 100--500 Hz. The active volume was 3x30x250 cubic mm. Laser electrodes were cooled down to 120 K. Gas mixture CO:air:He at gas pressure 15 Torr was used. The optical scheme ``frequency selective master oscillator - laser amplifier'' was applied for getting fundamental band tuning. Single line lasing with average power up to several tens of mW was observed on about 100 rotational-vibrational transitions of CO molecule within the spectral range 5.0--6.5 micron. Multiline overtone lasing was observed on about 80 spectral lines within the spectral range 2.5-4.0 micron, with maximum single line average output power 12 mW. The total output power of the slab overtone CO laser came up to 0.35 W, with laser efficiency 0.5 percent. The results of parametric studies of capacitive slab RF discharge in carbon monoxide mixtures, and overtone and fundamental band CO laser characteristics are discussed. [Preview Abstract] |
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MWP1.00088: PLASMA APPLICATIONS |
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MWP1.00089: Growth and characterization of CNT Forests using Bimetallic Nanoparticles as Catalyst Kyung-Hwan Lee, A. Sra, H. Jang, B. Choi, L. Overzet, G. Lee, D. Yang We study the growth of Multiwall carbon nanotubes (MWCNT) using bimetallic nanoparticles (NP) as catalyst rather than zerovalent metal ions such as Fe, Ni, Co. One advantage of using bimetallic NP is that both the size and shape and composition (atomic ordering) can be controlled. We will describe a simple method of producing bimetallic Fe-Pt, Fe-Co alloy nanoparticles and compare MWCNT growth using them to Fe catalyst growth. The synthesis of Fe, Fe-Pt, Fe-Co NP was carried out using a bottom-up polyol process. Subsequent growth of MWCNT forests was accomplished by PECVD using acetylene as precursor. TEM and SEM analysis of the sample cross-section grown at substrate temperature of 680 $^{\circ}$C indicates that the diameters of the CNTs are $\sim$ 10-20 nm while height of the forest varies from 30 $\mu$m for Fe to 5 $\mu$m for Fe-Pt and 80-100 $\mu$m for Fe-Co. The number of walls in the CNTs and the graphitization content could be manipulated by varying the temperature (increasing to 760 $^{\circ}$C) or by pre-treatment of the nanoparticles with oxygen plasma. [Preview Abstract] |
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MWP1.00090: Modeling of Electron Field Emission Properties of Carbon Nanotubes Marija Radmilovic-Radjenovic, Branislav Radjenovic The strength and flexibility of carbon nanotubes (CNTs) make them of potential use in controlling other nanoscale structures, which suggests they will have an important role in nanotechnology engineering. One of the most promising future applications is employing carbon nanotubes in electron field emission devices. Studies, however, have been mostly focused on using CNTs both as conductors and semiconductors. Nevertheless, the effect of the field emission in CNTs can be considered from the aspect of electrical breakdown. In this paper we are studying the case for CNTs as nanoelectrodes for electric discharges, operating at high E/N and with high field enhancement factors. It was shown that the electric field is dramatically enhanced near the cap of a nanotube with large variation of local field distribution. [Preview Abstract] |
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MWP1.00091: Audio frequency modulated RF discharge at atmospheric pressure Nicholas Braithwaite, Yvonne Sutton, David Sharp, Jon Moore An atmospheric pressure RF arc discharge, generated using a low voltage chopper and a Tesla coil resonant at about 300 kHz, forms a stable, silent, flame-like luminous region some 3 mm in diameter and 40 mm long, rooted to the electrodes by visible hot spots. It is known and we have confirmed that audio frequency modulation of the drive voltage makes the discharge act as an audio loudspeaker (tweeter) with its monopole radiation pattern constrained only by the electrodes. Time resolved `total' optical emission reveals an intensity variation that is synchronous with the audio frequency. Electrical characterisation of the high frequency discharge has been carried out. In the steady state, the high frequency arc burns without generating significant quantities of ozone, as determined by a commercial ozone detector. This is consistent with the high gas temperature within the arc, as measured by optical emission spectroscopy of molecular nitrogen. Phase-locked emission measurements illustrate the acoustic coupling. [Preview Abstract] |
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MWP1.00092: Reacting Flow Imaging Using Point to Plane Pulsed Air/Hydrocarbon Discharge David Wisman, Biswa Ganguly We report the use of a positive polarity point-to-plane pulsed corona discharge to obtain a time-resolved visualization of the reaction zone in a premixed propane-air flame. In the initial phases of the discharge the higher gas temperature along the flame reaction zone provides a higher E/n path that preferentially guides the streamer discharge to the cathode. Following the initial streamer phase, an increased plasma conductivity of the fully developed discharge, caused in part by lowering the attachment rate of electrons to O$_{2}$, allows the plasma conduction current to preferentially distribute along the high temperature flame reaction zone. The resulting N$_{2}$ C-B emission from the localized discharge provides a visualization of the flame front. The short ICCD gate time (100 ns) allows for capture of the N$_{2}$ C-B emission without the need for spectral filtering, and thus permitting imaging up to 1 kHz repetition rate. Imaging the plasma emission after the discharge has been fully developed allows for the monitoring of small scale instabilities in the reaction zone, which can be an important tool for understanding the combustion dynamics. We will also report the effect of flame equivalence ratio on the plasma emission intensity and its impact on the usefulness of high speed imaging. [Preview Abstract] |
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MWP1.00093: Characterization of Ar/H$_{2}$/Air Supersonic Flowing Microwave Discharges D.J. Drake, S. Popovic, L. Vuskovic We performed a detailed characterization of a microwave cavity discharge in the supersonic flow of Ar/H$_{2}$/Air mixtures. The supersonic flow was generated using a convergent-divergent nozzle upstream of the discharge region. Gases were premixed in the stagnation chamber at room temperature by adding up to 10{\%} hydrogen and up to 45{\%} air to pure argon. A cylindrical cavity was used to sustain a discharge in the mixtures in the pressure range of 100-600 Pa. Optical emission spectroscopy was used to observe the effects of hydrogen and air admixtures to plasma parameters and populations of excited species. [Preview Abstract] |
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MWP1.00094: Parametric Studies on Thrust Produced by Pulsed DBD Plasma Actuators Dmitry Opaits, Alexandre Likhanskii, Sohail Zaidi, Mikhail Shneider, Sergey Macheret, Richard Miles A number of works have demonstrated the utility of dielectric barrier discharge (DBD) plasma actuators for aerodynamic control. Recent experiments and computations showed that a novel voltage waveform consisting of high-voltage nanosecond repetitive pulses superimposed on a low-frequency sinusoidal voltage can produce significantly enhanced wall jets compared with those generated with conventional sinusoidal voltage. We proposed and used what is essentially a non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the low frequency (bias) voltage. The advantage of this non-self-sustained discharge is that the parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuator performance. This work will present results of parametric studies of the plasma produced thrust at different parameters of the voltage waveform, such as frequency and shape of the bias voltage and duration and repetition rate of the pulses. [Preview Abstract] |
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MWP1.00095: Improved Nonambipolar Electron Source operation with permanent magnets Jesse Gudmundson, Noah Hershkowitz The Nonambipolar Electron Source (NES), is a Radio Frequency (rf) plasma-based electron source that does not rely on electron emission at a cathode surface. All electrons are extracted at an electron sheath through a biased ring and all ions are lost radially to a biased Faraday shield. The electromagnetic B field in the original NES has been replaced by a NdFeB permanent magnet array. The magnet array consists of a ring of radially aligned magnets followed by a ring of axially aligned magnets producing a peak field of approximately 850 Gauss. Measurement of the magnetic field was in good agreement with field predicted by the FEMM code. Optimization of the single turn antenna and biased ring will be discussed. Operating with argon, at least 15 A of electron current was extracted using a flow rate of 15 sccm Ar at approximately 10 mTorr and 600 W of RF power at 13.56 MHz. For comparison, the original NES required 1200 W of power to achieve 15 A of extracted current. Compared to the previous coil design, the NdFeB magnets are lighter weight, require no power, and provide a greater peak magnetic field. [Preview Abstract] |
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MWP1.00096: Flow separation control by plasma actuator with nanosecond pulse discharge Andrei Starikovskii, Dmirty Roupassov, Andrei Nikipelov, Maryia Nudnova Boundary layer separation control by plasma actuator with high-voltage pulsed periodic nanosecond excitation is presented. Actuator-induced gas velocities show near-zero values for nanosecond pulses. The measurements performed have shown overheating of discharge region at fast ($\tau $ $\approx $ 1 $\mu $s) thermalization of the plasma imputed energy. The mean values of such heating for the plasma layer can reach 70, 200 and even 400 K for 7, 12 and 50 ns pulse duration, respectively. The emerging shock wave together with the secondary vortex flows disturbs the main flow. The resulting pulsed-periodic disturbance causes an efficient transversal momentum transfer into the boundary layer and further flow attachment to the airfoil surface. Thus for pulsed nanosecond periodic DBD the main mechanism of impact is the energy transfer and heating the near-surface gas layer. The following pulse-periodic vortex movement stimulates redistribution of the main flow momentum. The experiments have shown high efficiency of the given mechanism to control boundary layer separation, lift and drag force coefficients, and acoustic noise reduction in the Mach number range of 0.05 to 0.85. [Preview Abstract] |
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MWP1.00097: Streamer Discharges in Water and their Application Juergen F. Kolb, Shu Xiao, Noah Scully, Ravindra P. Joshi, Karl H. Schoenbach Electrical discharges in liquids have been widely investigated for transient high voltage insulation and switching applications. Despite extensive efforts, the mechanism of breakdown initiation and formation of streamers are not completely understood, in particular for the application of short, sub-microsecond pulses. Regardless, streamers in water generated under these conditions are an attractive means of water treatment for a variety of applications, such as remediation of chemical and biological pathogens in waste-water, purification of drinking water, the cleaning of algae from freshwater ponds. Radicals, ultraviolet light, high electric fields and shockwaves are all considered as possible mediators of the effects, and all of which are generated in the streamer propagation process. We will present experimental results on the initiation and propagation of streamers in water and discuss the mechanisms. Further selected applications will be presented. [Preview Abstract] |
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MWP1.00098: Decomposition of electrostatic-precipitated diesel particulate materials with nitric oxides using dielectric barrier discharge Yukihiko Yamagata, Yosuke Fujii, Katsunori Muraoka A newly developed decomposition technique for diesel particulate materials (DPM) and nitric oxides was demonstrated. This is based on the combination of dielectric barrier discharge (DBD) with condensation/localization technique. Using an electrostatic precipitation (EP) operated under a negative corona discharge, DPM were collected in a reactor that is able to generate DBD. More than 95{\%} of DPM emitted from a real diesel engine were continuously collected for 60 min at DC -5 kV. Subsequently, the EP-collected DPM were decomposed in a model gas including NO molecule by DBD operated at AC 60 Hz. In the presence of DPM, a large amount of NO was decomposed in comparison with that in the absence of DPM. It was shown that DPM and NO acting as the oxidant and reductant, respectively, were decomposed simultaneously and effectively by DBD. It is also suggested that water vapor in the exhaust gas improves the NOx decomposition rate. [Preview Abstract] |
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MWP1.00099: Pulsed-plasma destruction of phenol in an aqueous solution Kohki Satoh, Hideyuki Itabashi, Yasushi Miyazaki, Hidenori Itoh An aqueous solution of phenol is exposed to pulsed-discharge plasma, and the decomposition characteristics of phenol are investigated for the different composition of a background gas. It is likely that OH radicals, produced by the collision between water vapour and energetic electrons in the pulsed plasma creeping on a water surface, are responsible for the decomposition of phenol in the solution for all kind of background gases. It is probably that OH radicals, produced by N$_{2}$ molecules excited in metastable state (N$_{2}(A^{3}\Sigma _{u}^{+}))$, and O$_{3}$ assist the phenol decomposition in pure N$_{2}$ and in pure O$_{2}$, respectively. In N$_{2}$-O$_{2}$ mixture, the decomposition rates of phenol stay at lower values, since NO$_{x}$ reduces O$_{3}$ concentration and inhibits the O$_{3}$ production. In Ar-O$_{2}$ mixture, the decomposition rate of phenol increases with an increase of Ar mixture-ratio; therefore, Ar atoms excited in metastable states (Ar(4$^{3}$P$_{2})$, Ar(4$^{3}$P$_{0}))$ are responsible for the decomposition of phenol at higher mixture ratio of Ar. [Preview Abstract] |
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MWP1.00100: Interaction of DC Microhollow Cathode Discharge Plasma Micro Jet with Liquid Media WeiDong Zhu, Jose Lopez, Kurt Becker There have been different approaches in studying the interaction between plasma and liquid, such as sustained plasmas in contact with liquids and pulsed electric discharge in liquids. Recently, we have discovered that stable plasma can be sustained within a gas cavity maintained inside liquid media. A prototype device with key dimensions in sub-millimeter range were operated successfully in de-ionized water and turbo molecular pump oil with ambient air, pure nitrogen or pure oxygen used as the operating gas. Hydrogen Peroxide production in de-ionized water with ambient air as the working gas is estimated to be about 80 mg/L after 15 minutes plasma jet-water interaction while energy consumption is only about 8-10 W. With the radicals readily generated and directly introduced into the liquid media, it could lead to applications such as in-liquid bio-waste treatment, bio-rich liquid modification, in-situ monitoring/sensing, and filtration of by-products from VOC treatment by plasma. [Preview Abstract] |
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MWP1.00101: Properties of plasma-liquid system with transversal discharge Volodymyr Shapoval Description of different plasma-liquid systems and their comparative analysis are presented in this work. There are various types of self-sustained electrical discharges with electrodes submerged into liquid, and discharges with one ``liquid'' electrode as well as secondary discharges with ``liquid'' electrodes, which can be applied for water treatment. This dynamic plasma-liquid systems have well-developed plasma-liquid interface and large surface-to-volume ratio. Plasma-liquid system based on the discharge in the gas channel formed by the gas flow immersed into the liquid was studied in this work. Phenol solutions were used as working liquids. It was shown that investigated plasma-liquid system is very effective for the phenol destruction in water due to the formation of chemically active oxidants in sufficient amount. The efficiency of phenol destruction increases with increasing of the time of plasma-chemical processing in the reactor. It was shown that regime with negative polarity of ``liquid'' electrode is more effective for plasma-chemical processing than with positive polarity. [Preview Abstract] |
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MWP1.00102: Growth of carbon nanofibers in plasma-enhanced chemical vapor deposition Igor Denysenko, Kostya Ostrikov, Eugene Tam A theoretical model describing the plasma-assisted growth of carbon nanofibers with metal catalyst particles on top is proposed. Using the model, the plasma-related effects on the nanofiber growth parameters such us the surface diffusion growth rate, the effective carbon flux to the catalyst surface, the characteristic residence time and diffusion length of carbon on the catalyst surface, and the surface coverages, have been studied. It has been found how these parameters depend on the catalyst surface temperature and ion and etching gas fluxes to the catalyst surface. The optimum conditions under which a low-temperature plasma environment can benefit the carbon nanofiber growth are formulated. It has been also found how the plasma environment affects the temperature distribution over the length of the carbon nanofibers. Conditions when the temperature of the catalyst nanoparticles is higher than the temperature of the substrate holder are determined. The results here are in a good agreement with the available experimental data on the carbon nanofiber growth and can be used for optimizing synthesis of nanoassemblies in low-temperature plasma-assisted nanofabrication. [Preview Abstract] |
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MWP1.00103: Nanostructures under extreme non equilibrium plasma conditions of dense plasma focus device Mahesh Srivastava, Kostya Ostrikov In this poster, we will present the formation of nanostructures due to highly energetic, high fluence ions of different material produced due to high density, high temperature (1-2 KeV), extremely non-equilibrium pulsed plasma produced in a Dense Plasma Focus (DPF) device. Glow discharge and the magnetron sputtering discharge has weakly ionized, low temperature and low density plasma which produces ions in the discharge for the formation of nanostructures. In the present case we are using a 3.3 KJ Mather type DPF device which is powered by 30 microfarad 15 KV fast discharging energy storage capacitor. The material whose nanostructures is to be formed is fitted on the top of the anode in the form of a disc. The hot and dense argon plasma formed during discharge causes the ionization of the material. The material ions along with argon ions move upwards in a fountain like structures and the nanostructures are formed on different substrates which are mounted on the substrate holder and is inserted from the top of the plasma chamber. Kinetic Monte Carlo simulation is being used to explain the formation of such nanostructures. [Preview Abstract] |
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MWP1.00104: III-V Semiconductor Quantum Dots -- Plasma-related controls Amanda Rider, Kostya Ostrikov, Igor Levchenko, Eugene Tam Binary and ternary III-V semiconductor materials are of great interest for a range of applications. The ability to precisely tailor optoelectronic properties is required for widespread technological implementation of III-V quantum dots (QDs) -- this may be achieved through a deterministic level of control over QD size, composition and internal structure during the initial stages of growth. The aim of this paper is to achieve a stoichiometric QD composition at the earliest possible time and to elucidate the benefits of conducting QD growth in a plasma environment. To that end, binary and ternary III-V QD growth is simulated in both neutral- and ionized- gas environments. The impact of using plasma/ion-related effects (via ionizing a portion of the influx and the presence of an Ar background plasma) is taken into account by including substrate heating and a reduction in surface diffusion activation energy. Incorporating plasma-related tools at the beginning of growth affords many advantages -- in this work, however, we are predominantly interested in the smaller stoichiometrization times and thus more homogeneous QDs. [Preview Abstract] |
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MWP1.00105: Plasma grown surface bound single wall nanotubes Eugene Tam, Kostya Ostrikov Many researchers believe that Vertically Aligned Single Wall Carbon Nanotubes (VASWCNTs) are the answer to many foreseen issues with today's semiconducting industry involving miniaturization. However dense arrays of surface bound VASWCNTs can only ascertain a maximum length after which growth seems to halt, something of which is commonly attributed with catalyst poisoning. Nucleation of VASWCNTs also seems to require extremely high temperatures, unsuitable for direct growth of VASWCNTs onto nanoelectronic devices, however there has been some recent experimental evidence that sub 500\r{ }C growth of VASWCNTs is possible. In this poster, Monte-Carlo simulations have been used to elucidate the effects of plasmas on the substrate and lateral surfaces of the nanotubes, increasing mobility, adsorption and desorption. In addition to surface interactions, plasmas also allow for the control of precursor trajectories allowing adatoms to land closer to the base of the VASWCNT. We show that the precursor distribution along the lateral surface of the nanotubes is the primary cause for the VASWCNTs to slow down and, using appropriate plasma conditions, longer VASWCNTs and growth rates up to an order of magnitude higher than their neutral counter parts can be achieved in plasma environments. [Preview Abstract] |
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MWP1.00106: Plasma deposition of metal catalyst nanoparticles and carbon nanotubes: a KMC study Igor Levchenko, Kostya Ostrikov In this work, the formation of metal catalyst nanoparticles and growth of carbon nanotubes from a low-temperature plasma environment is studied by kinetic Monte Carlo numerical technique. The numerical simulations were used to model the main surface processes including the carbon diffusion on substrate and nanotube surfaces, metal catalyst saturation with carbon, and formation of the nanotubes on saturated catalyst. We demonstrate that control of the Ni and carbon influxes from plasma provides a very effective control of the surface processes, and eventually results in the formation of arrays of densely-packed metal catalyst nanodots and effective growth of single-wall nanotubes. The use of plasma of higher degree of ionization provides more uniform saturation of metal catalyst nanoparticles with carbon, and thus results in the formation of uniform array of the carbon nanotubes. We also demonstrate that the nano-structured electric fields near the substrate surface covered with growing nanotubes play a very important role in the growth, thus providing an additional effective tool for the growth control. [Preview Abstract] |
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MWP1.00107: Optimizing order in PECVD quantum dot arrays with applications in quantum information Michael Delanty, Kostya Ostrikov, Igor Levchenko, Stojan Rebic Quantum Dot Arrays (QDAs) are of increasing interest in nano-sized technologies due to their highly tunable optical and electronic properties. Spatially ordered, self organized QDAs are highly sought after in many applications such as lasers, solar cells and photo-detectors. However, current self organized fabrication approaches cannot produce high density spatially ordered QDAs, which has resulted in unwanted line broadening in the QDA spectra. Here we show that it is possible to create dense QDAs that are highly ordered using a plasma based technique. The local ordering parameters introduced take into account the highly confined wavefunctions of quantum dots and have wide application in characterizing experimental QDAs. The Plasma Enhanced Chemical Vapor Deposition (PECVD) model used is a multiscale, hybrid numerical simulation that improves upon previous work by including more realistic surface diffusion processes. The most ordered arrays are then used as the basis of a new type of optical quantum CNOT gate. The performance of this gate is assessed and its dependence on spatial order is demonstrated. This work represents a significant step forward in using PECVD for solid state quantum computing. [Preview Abstract] |
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MWP1.00108: Generation of dynamic metamaterial by using spoof surface plasmon on patterned silicon substrate assisted with microplasma array Dae-Sung Lee, Osamu Sakai, Kunihide Tachibana Recently, there has been a growing interest in metamaterials which are designed as composite materials and show extraordinary macroscopic properties. Dynamic metamaterials composed of an integrated assembly of microplasma with a 2D periodic structure, whose electron density is 10$^{13}$-10$^{16}$ cm$^{-3}$ and spatial distribution is macroscopically homogeneous and microscopically has a functional structure, have a potential to design the electromagnetic and optical properties of materials for a variety of applications. An array of microplasma cells was fabricated on a silicon substrate, which can not only be partially transparent in the terahertz spectral range but serve as a discharge electrode, and characteristics of a 2D dynamic metamaterial were investigated by terahertz wave time-domain spectroscopy. Such a periodic structure gives rise to an effective impedance or permittivity for surface modes which enables abnormal transmittance arising partly from spoof surface plasmons. In addition, since it is possible to control the generation of microplasmas by external parameters, permittivity of a metamaterial in bulk can be adjusted dynamically. [Preview Abstract] |
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MWP1.00109: Effect of ozone on sterilization of Penicillium digitatum using non-equilibrium atmospheric pressure plasma Takayuki Ohta, Sachiko Iseki, Masafumi Ito, Hiroyuki Kano, Yasuhiro Higashijima, Masaru Hori Methyl bromide has been sprayed to the crops for protecting from insects and virus, but has high ozone depletion potential. Thus, the development of substitute-technology has been strongly required. We have investigated a plasma sterilization for spores of Penicillium digitatum, which causes green mold disease of the crops, using non-equilibrium atmospheric pressure plasma. The sterilization was caused by UV light, ozone, O and OH radicals. In this study, ozone density was measured and the effect to sterilization was discussed. The plasma was generated at an alternative current of 6kV and Ar gas flow rate of 3L/min. In order to investigate the sterilization mechanism of ozone, the absolute density of ozone was measured using ultraviolet absorption spectroscopy and was from 2 to 8 ppm. The sterilization by this plasma was larger than that by the ozonizer (0$_{3}$:600ppm). It is confirmed that the effect of ozone to the sterilization of Penicillium digitatum would be small. [Preview Abstract] |
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MWP1.00110: An Atmospheric Pressure Cold Plasma Plume for Biomedical Applications XinPei Lu The roles of various plasma agents in the inactivation of bacteria have recently been investigated. However, up to now, the effect of the charge particles on the inactivation of bacteria is not well understood. In this paper, an atmospheric pressure plasma jet device, which generates a cold plasma plume carrying a peak current of 300 mA, is used to investigate the role of the charge particles in the inactivation process. It is found that the charge particles play a minor role in the inactivation process when He/N$_{2}$(3{\%}) is used as working gas. On the other hand, when He/O$_{2}$(3{\%}) is used, the charge particles is expected to play an important role in the inactivation of bacteria. Further analysis shows that the negative ions O$_{2}^{-}$ might be the charge particles that are playing the role. Besides, it is found that the active species including O, O$_{3}$, and metastable state O$_{2}^{\ast }$, can play a crucial role in the inactivation of the bacteria. But the excited He*, N$_{2}C^{3}\Pi_u $, and N$_{2}^{+}B^{2}\Sigma_u^+ $ have no significant direct effect on the inactivation of bacteria. It is also concluded that heat and UV play no or minor role in the inactivation process. [Preview Abstract] |
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MWP1.00111: Development of Bio-Compatible Films for Implantable Electronics G. Padron-Wells, Brandon Jarvis, Ashish K. Jindal, M.J. Goeckner Polyethylene glycols thin films have shown promise as nonfouling passivation layers for implantable devices. Plasma Enhanced Chemical Vapor Deposition (PECVD) is a popular tool for altering the surface chemistry of such devices, particularly in the realm of flexible electronics, where uniformity of film thickness and the chemical composition of the deposited film are of critical importance. In the present work an extensive FTIR gas phase analysis of Di(ethylene glycol) vinyl ether (DEGVE) pulsed plasma discharges was performed. It was found that nonfouling effectiveness, observed in previous studies by Wu,\footnote{Yuliang J. Wu, Richard B. Timmons, James S. Jen, Frank E. Molock. Colloids and Surfaces B: Biointerfaces 18 (2000) 235 -- 248} \textit{et al.}, of PECVD DEGVE films can be directly attributed to the chemical properties of the reacting plasma. This data allowed for the construction of a dissociative model of the DEGVE. [Preview Abstract] |
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