Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session PR1: Poster Session II (8:00-10:00AM) |
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Room: Salon CDE |
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PR1.00001: PLASMA SCIENCE II |
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PR1.00002: Simulation of the OH Emission Molecular Spectrum to Determine the Plasma Temperature and the Influence Noise to Signal Ratio on the Temperature Values Hossein Nassar, Ouloum Aoude The OH system (A$^2\Sigma^+$ - X$^2\Pi_{\rm{I}}$) molecular emission spectrum is frequently observed in plasma sources containing water. We have simulated the spectrum of (0,0) and (1,1) bands of this system from 3064 {\AA} for different rotational and vibrational temperatures. The influence of the noise to signal ratio has been studied, if the noise to signal ratio is about 10\% we found an error of 6\% at temperature 3000K and 10\% at 6000K. [Preview Abstract] |
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PR1.00003: Measuring effective electron temperatures with the argon 420.1-419.8 nm line ratio John B. Boffard, R.O. Jung, Chun C. Lin, L.E. Aneskavich, A.E. Wendt We explore the possibility of measuring the effective electron temperature in argon-containing plasmas using the line ratio of the 420.1 nm and 419.8 nm argon emission lines [1]. At high electron temperatures, the upper levels of both transitions are populated mainly by electron-impact excitation of ground state atoms and yield a line ratio near one. At lower electron temperatures, the upper level of the 420.1 nm line (the $J$=3 $3p_9$ level) is preferentially populated via excitation from the $J$=2 $1s_5$ metastable level [2], yielding line ratios as high as four. Variations in the energy dependence of the ground state cross sections [3] can also produce line ratios less than one when highly energetic electrons are abundant. We compare temperatures obtained with this single line pair ratio with measurements obtained from an analysis of 20+ $2p_x \to 1s_y$ emission lines in the 665-1150 nm wavelength range and with Langmuir probe measurements in a number of different plasmas (inductive, capacitive, helicon). \\[4pt] [1] J. Phys. D. \textbf{45}, (2012) 045201.\\[0pt] [2] Phys. Rev. A \textbf{75}, (2007) 052707.\\[0pt] [3] Phys. Rev. A \textbf{68}, (2003) 032719; At. Data Nucl. Data Tables \textbf{93}, (2007) 831. [Preview Abstract] |
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PR1.00004: Distribution and Dynamics of Argon Metastables in Supersonic Flowing Microwave Discharges and Post-Discharges Milka Nikolic, Ana Samolov, Charles I. Sukenik, Svetozar Popovic, Leposava Vuskovic Supersonic flowing microwave discharge in Argon exhibits a peculiar asymmetric post-discharge glow, which is detached from the discharge. We have studied the behavior of 4p Ar states using optical emission tomography and found their strong transversal motion possibly originating from rotational component of the flow [1]. In this work, we have employed Laser Induced Fluorescence (LIF) technique to obtain the excited state populations from the argon spectra in the post-discharge of the supersonic flowing microwave discharge. The experimental set-up consists of a pulsed tunable dye laser operating in the near infrared region and a cylindrical resonance cavity operating in TE111 mode at 2.45 GHz. The microwave discharge was obtained at the pressure of 2.4 Torr and the gas temperature in the post-discharge was gradually decreasing from $\sim $1100 to $\sim $ 800 K. We present the population distributions of 4p states and compare the results between the LIF and OES methods, and the population distributions of the 4s metastable states from LIF measurements. \\[4pt] [1] M. Nikolic, F. Cuckov, A. Samolov, A. Godunov, S. Popovic, and L. Vuskovic, ``Tomography as a Diagnostic Tool for Plasma Etching of SRF Cavities,'' Proc. IPAC, WEPPC104 (2012) (New Orleans, LA). [Preview Abstract] |
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PR1.00005: Development of a Thomson-type Mass and Energy Spectrometer for High-energy Plasma Beams with the Geant4 Monte Carlo Toolkit Gregory Rieker, Flavio Poehlmann, Mark Cappelli Thomson-type spectrometers characterize particle beams using parallel magnetic and electric fields to separate and detect ions of different mass, energy, and charge state. Traditionally, the output of these spectrometers is calibrated against particle beams of known species and energy, or less accurately, using particle trajectory calculations assuming uniform fields. We present the design and calibration of a Thomson spectrometer using the Geant4 Monte Carlo toolkit. By running Monte Carlo simulations using the precise spectrometer geometry, including the measured non-uniform magnetic field and two dimensional electric field simulations, it is possible to accurately predict and calibrate the output of the spectrometer without a known particle beam. We will describe the application of this spectrometer to the output of an electromagnetic plasma accelerator operating in a gas-puff mode, and quantify the error associated with calibrating the spectrometer assuming uniform fields. [Preview Abstract] |
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PR1.00006: Atmospheric Pressure Plasma Electron Density Measurments by Magnetohydrodynamic Generator (MHDG) Method Ali Gulec, Ferhat Bozduman, Erdogan Teke, Lutfi Oksuz In this work atmospheric pressure plasma discharge was immersed in a hollow box which is called as manetohydrodynamic generator (MHDG). This box consists of two conductors and two insulating edges. Permanent magnets were placed on the insulating edges for a magnetic field which is perpendicular to the discharge flow. Hall-effect voltage was observed between the opposite conductive edges of the MHDG. 1 kHz atmospheric pressure helium discharge density was calculated as 4.9x10$^{13}$ cm$^{-3}$ by using Hall-effect voltage and the discharge current. For different plasma conditions plasma density calculations will be given. [Preview Abstract] |
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PR1.00007: Non-intrusive measurements of ion fluxes and densities in pulsed RF plasmas containing nanoparticles I. Stefanovic, B. Sikimic, I. Denysenko, J. Winter Electrical probe measurements are widely spread for diagnostics of low-pressure plasmas. However, the probe measurements in plasmas for thin film deposition and nanoparticle formation are difficult. Thin film on the probe surface changes the probe characteristics and thus obscures the results. The probe tip disturbs locally the dust particle density and consequently the ion and electron flux to the probe. Braithwaite \textit{et al} developed the electrostatic probe method that proved as tolerant for thin film deposition, although the disturbance caused by the inserted probe should be taken into account. Following the ideas of Braithwaite \textit{et al} we developed the diagnostics for measuring the ion-current and ion density in pulsed RF plasmas with and without nanoparticles. The technique bases on measurement of electrode self-bias voltage thus avoiding plasma perturbation. The rate of voltage change can be attributed to the ion current to the electrode in the afterglow. Assuming the Bohm velocity of ions in the afterglow the ion density can be calculated. We compare and discuss the ion densities obtained like described with the independently measured electron densities for dust free and dusty argon plasma. N. St. Braithwaite \textit{et al} \textit{Plasma Sources Sci. Technol. }\textbf{5} (1996) 677 [Preview Abstract] |
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PR1.00008: Measurements of the energies of negative ions produced in processing plasmas David Seymour, Claire Greenwood, Sean Davies, Alan Rees The quality of the thin oxide films deposited on a variety of materials during exposure to plasmas containing oxygen depends strongly on the identity and energies of the negative oxygen ions arriving at the growing films. There have, however, been few experimental studies in which these ion energies have been measured and the available data is markedly less abundant than for the corresponding positive ions. We discuss reasons for the lack of data and suggest suitable techniques for obtaining energy distributions for mass identified ions for a variety of plasmas, including both steady-state and pulsed DC and RF plasmas. For asymmetric RF plasmas the distributions depend on the relative dimensions of the sheath regions in front of the discharge electrodes, whereas for DC magnetron systems a dominant parameter is the voltage applied to the magnetron cathode, particularly when this is pulsed. Sample data for O-, O2-,and O3- ions are shown for mixtures of oxygen and argon for a number of systems including a DC plasma system in which the ions were sampled through an orifice in the anode electrode, and a small magnetron device for which the ions arriving at a grounded substrate were observed. [Preview Abstract] |
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PR1.00009: On-axis Molecular Beam Mass Spectrometer measurements of a cold atmospheric pressure plasma jet Joern Winter, Mario Duennbier, Markus Wolfram, Ansgar Schmidt-Bleker, Klaus-Dieter Weltmann, Stephan Reuter The measured on-axis molecular species densities in the effluent of a cold plasma jet operated at atmospheric pressure were performed for different distances (3{\ldots}35 mm) with a molecular beam mass spectrometer (MBMS) (Hiden HPR 60). The investigated molecules are nitrogen (M = 28 u), oxygen (M = 32 u) and argon (M = 40 u). A stainless steel orifice with a diameter of 100$\mu $m in front of the first pump stage was used. After a calibration of the intensities of the mass spectrometer the absolute densities were calculated. These values are compared with a model of the gas flux and show excellent agreement. It is shown that because of the feed gas flow of the plasma jet the ambient air species (e.g. N$_{2}$ and O$_{2})$ are displaced in the case of small distances. For larger distances the diffusion of nitrogen and oxygen molecules into the effluent increases. Effects of composition distortion and pressure dependencies inside the MBMS were observed in the calibration curve and were taken into account. [Preview Abstract] |
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PR1.00010: Diagnostic of plasma jet by mid-IR absorption spectroscopy with quantum cascade laser Sylvain Iseni, Mario Duennbier, Joern Winter, Klaus-Dieter Weltmann, Stephan Reuter The interest in plasma jets operating at atmospheric pressure have considerably grown during the last decade. The non-equilibrium properties of the discharge enhances specific and interesting chemistry especially that of reactive nitric-oxide species (RNOS) such as O$_{3}$ or NO. It is already known that for instance O$_{3}$ has biological effects and have been used for sterilization of non-living objects. Thus, in order to investigate and control the biological reactive species produced by the jet, very accurate techniques are required. By using absorption spectroscopy in the mid-infrared range with quantum cascade laser, we were able to measure very accurate absolute production rates. The spectral range is restricted to the so-called fingerprint area (500-1500~cm$^{-1})$. Many approaches have been made to overcome the spectroscopic problems of the pressure broadening. One of those consists of simulating the spectrum online and then calculates the concentration by fitting the measurement with the simulation. We can assume an accuracy of 200~ppb with a lowest detection limit of 300~ppb. The diagnostic of O$_{3}$ is led on a MHz radiofrequency plasma jet operating with argon. The O$_{3}$ production is also compared regarding different admixtures such as O$_{2}$, N$_{2}$ or H$_{2}$O and surrounding atmosphere. [Preview Abstract] |
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PR1.00011: Transmission characteristics of the wave cut-off probe with parallel plates Hyun-Ju Kang, Yu-Sin Kim, Chin-Wook Chung A cut-off probe has been used to obtain an absolute electron density from a plasma frequency. A cut-off probe with parallel plates was constructed to investigate the transmission characteristics of electromagnetic waves and electrostatic waves at various gaps, pressures and powers. It is found that a clear cut-off peak at a plasma frequency and many other peaks due to plasma sheath series resonance, cavity resonance and transmission line are observed. By using circuit model of plasma and transmission line theory, the various peaks was analyzed and discussed. [Preview Abstract] |
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PR1.00012: Non-invasive, real-time measurements of plasma parameters with an industry standard spectrograph Shicong Wang, A.E. Wendt, John B. Boffard, Chun C. Lin, Svetlana Radovanov, Harold Persing Plasma process control applications require acquisition of diagnostic data at a rate faster than the characteristic timescale of perturbations to the plasma. Diagnostics based on optical emission spectroscopy (OES) of intense emission lines permit rapid non-invasive measurements with low-resolution ($\sim$1~nm), fiber-coupled spectrographs, included on many plasma process tools for semiconductor processing. Here we report on rapid analysis of Ar($3p^54p \to 3p^54s$) 650-800~nm emissions with such a system to obtain electron temperatures and metastable densities in argon and argon/mixed-gas (Ar/N$_2$, Ar/O$_2$, Ar/H$_2$) inductively coupled plasmas. The OES-derived values are compared to measurements made by electric probes, white-light absorption spectroscopy, and OES measurements made with a high-resolution 0.5~m spectrometer. In a pure Ar plasma, for example, we have measured the metastable densities to better than $\pm 15\%$~accuracy within 0.25~seconds. A number of subtraction procedures have been evaluated to extract the Ar emission intensities in the presence of overlapping molecular emissions. This is especially necessary for Ar/N$_2$ plasmas, which feature intense N$_2$ molecular emissions in the wavelength range of interest. [Preview Abstract] |
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PR1.00013: Collisionless spectral-kinetic Simulation of the Multipole Resonance Probe Wladislaw Dobrygin, Daniel Szeremley, Christian Schilling, Jens Oberrath, Denis Eremin, Thomas Mussenbrock, Ralf Peter Brinkmann Plasma resonance spectroscopy is a well established plasma diagnostic method realized in several designs. One of these designs is the multipole resonance probe (MRP). In its idealized - geometrically simplified - version it consists of two dielectrically shielded, hemispherical electrodes to which an RF signal is applied. A numerical tool is under development, which is capable of simulating the dynamics of the plasma surrounding the MRP in electrostatic approximation. In the simulation the potential is separeted in an inner and a vacuum potential. The inner potential is influenced by the charged partilces and is calculated by a specialized Poisson solver. The vacuum potential fulfills Laplace's equetion and consists of the applied voltage of the probe as boundary condition. Both potentials are expanded in spherical harmonics. For a practical particle pusher implementation, the expansion must be appropriately truncated. Compared to a PIC simulation a grid is unnecessary to calculate the force on the particles. This work purpose is a collisionless kinetic simulation, which can be used to investigate kinetic effects on the resonance behavior of the MRP.\\[4pt] [1] M. Lapke et al., Appl. Phys. Lett. 93, 2008, 051502. [Preview Abstract] |
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PR1.00014: Heavy Neutral Beam Probe Space Potential Measurements of the Helimak Experiment (Te $\sim$ 10 eV) Alvaro Garcia de Gorordo, Gary A. Hallock, Kenneth W. Gentle The Heavy Neutral Beam Probe (HNBP) for the Helimak low temperature plasma experiment has been developed at the University of Texas at Austin (UT-Austin). The HNBP is based on the highly successful Heavy Ion Beam Probe (HIBP), but is engineered to work in the low temperature plasma regime ($T_e < 40$ eV). The greatest difficutly to operation at low electron temperatures is that the measurement signal is enabled by electron-impact ionization events, which become increasingly rare when the temperature dips to $\sim 10$ eV. This problem is overcome by probing the plasma with a neutral alkali metal (Na) and by modulating the probing beaming with a square wave (chopping) and recovering the signal with phase sensitive detection. The Helimak experiment at UT-Austin approximates the infinite cylindrical slab with open field lines1. The geometry is like a torus, but with a rectangular cross-section and with vertical field coils, that combined with the toroidal field coils, give rise to a helical magnetic field inside the device. Because of the curved, sheared magnetic field, and its gradient, the Helimak simulates the scrape off layer (SOL) of a tokamak. [Preview Abstract] |
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PR1.00015: Spatial distributions measurement of negative ion density by using floating probe in the oxygen inductive coupled plasmas Hye-Ju Hwang, Yu-Sin Kim, Young-Choel Kim, Jun-Young Kim, Il-Seo Park, Chin-Wook Chung Spatial distributions of the negative ion density were measured in an oxygen inductive discharge from the measurement of the positive ion density and electron density by using a floating harmonic method [1]. When the probe was electrically floated by a direct current (DC) blocking capacitor, the positive ion density was measured, while the electron density was measured without the DC blocking capacitor. Thus, the spatial negative ion density distribution could be obtained from the measurement of the spatial difference between the positive ion density and the electron density. The spatial distributions of negative ion density from two single Langmuir probe consist of planar and cylindrical probe tip are compared with those by our method for the reliability. \\[4pt] [1] M. H. Lee, S. H. Jang, and C. W. Chung, J. Appl. Phys.101 033305 (2007). [Preview Abstract] |
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PR1.00016: Characterization of pulsed plasma jets by wave front distortion analysis Benjamin Wang, Flavio Poehlmann, Mark Cappelli Wave front distortion analysis is a non-perturbing plasma diagnostic technique used to measure the refraction of probing laser beams due to density gradients in the medium. A Shack- Hartmann wave-front sensor consisting of a micro-lenslet array coupled to a CCD sensor was used to characterize a pulsed co-axial discharge plasma jet experiment. A pulsed laser beam was passed through the plasma jet and the refraction angles of the beam as a result of the complex refractive index of the plasma were measured using a Shack-Hartmann wave front sensor. For axially- symmetric plasmas, an Abel inversion of the refraction angle data allows for the calculation of the line-integrated electron density gradient profile of the plasma jet. Wave front distortion measurements were also calculated from the refraction angle data. [Preview Abstract] |
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PR1.00017: Kinetics of Electrons in $Ar/BF_3$ Mixtures Zeljka Nikitovic, Vladimir Stojanovic, Svetlana Radovanov, Zoran Lj. Petrovic In this work we present electron transport coefficients in $Ar/BF_3$ mixtures for the conditions used in plasma assisted technologies for semiconductor production. Transport coefficients are used as the basis for a global model in $Ar/BF_3$ mixtures. We have used a two term numerical solution of the Boltzmann equation and also performed exact calculations using a Monte Carlo simulation. We have calculated electron transport coefficients for a binary mixture of 90\% Ar with 10\% of $BF_3$. Similar mixtures are often used in plasma assited ion implantation applications. In order to determine the role of radicals on kinetics, we have added 1\% of radical species F and $F_2$. The effect of radicals on electron kinetics is relatively small for abundances below 1\%. For higher abundances all transport coefficients, mean energies and rate coefficients are affected to a degree which could affect the operating conditions in plasmas. [Preview Abstract] |
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PR1.00018: 2D and 3D PIC-MCC simulations of a low temperature magnetized plasma on CPU and GPU Jonathan Claustre, Bhaskar Chaudhury, Gwenael Fubiani, Jean-Pierre Boeuf A Particle-In-Cell Monte Carlo Collisions model is used to described plasma transport in a low temperature magnetized plasma under conditions similar to those of the negative ion source for the neutral beam injector of ITER. A large diamagnetic electron current is present in the plasma because of the electron pressure gradient between the ICP driver of the source and the entrance of the magnetic filter, and is directed toward the chamber walls. The plasma potential adjusts to limit the diamagnetic electron current to the wall, leading to large electron current flow through the filter, and to a non uniform plasma density in the region between magnetic filter and extracting grids. On the basis of the PIC-MCC simulation results, we describe the plasma properties and electron current density distributions through the filter in 2D and 3D situations and use these models to better understand plasma transport across the filter in these conditions. We also present comparisons between computation times of two PIC-MCC simulation codes that have been developed for operations on standard CPU (Central Processing Units, code in Fortran) and on GPU (Graphics Processing Units, code in CUDA). The results show that the GPU simulation is about 25 times faster than the CPU one for a 2D domain with 512x512 grid points. The computation time ratio increases with the number of grid points. [Preview Abstract] |
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PR1.00019: Electronegative Plasma Equilibria with Spatially-Varying Ionization M.A. Lieberman, E. Kawamura, A.J. Lichtenberg Electronegative inductive discharges in higher pressure ranges typically exhibit localized ionization near the coil structure, with decay of the ionization into the central discharge. We use a two-dimensional fluid code [1] with chlorine feedstock to determine the spatial profiles of the plasma parameters in a cylindrical transformer-coupled plasma device excited by a planar coil. To compare with one-dimensional (1D) analytic modeling, the results are area-averaged. The ionization is found to decay roughly exponentially along the axial direction, allowing the ansatz of an exponentially decaying ionization to be used in a 1D computational model. The model captures the main features of the axial variations of the area-averaged fluid simulation, indicating that the main diffusion mechanisms act along the axial direction. A simple analytic global discharge model is developed, accounting for the asymmetric density and ionization profiles. The global model gives the scalings with power and pressure of volume-averaged densities, electron temperature, and ionization decay rate, also in reasonable agreement with the scalings obtained by averaging the simulation results. \\[4pt] [1] E.\ Kawamura, D.B.\ Graves, and M.A.\ Lieberman, Plasma Sources Sci.\ Technol.\ 20, 035009 (2012) [Preview Abstract] |
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PR1.00020: Space-Charge Limitations in Photon-Enhanced Thermionic Emission and Possible Solutions Tsuyohito Ito, Mark Cappelli Traditionally, thermionic energy conversion is most efficient at high temperatures ($>$ 1500 K). In a recent study [J.W. Schwede et al., Nature Materials 9, 762 (2010)], photon-enhanced thermionic emission (PETE) from semiconducting cathodes was shown to be a promising means of increasing the thermionically-driven cathode current density at relatively low cathode temperatures (500-1100K). However, at the high emitted current densities described in Ref. 1 (3 - 30 A/cm$^2$), one might expect that the electron transport will be space-charge limited. In this presentation, using a particle-in-cell (PIC) method, we simulate the PETE energy converter to clarify these space charge effects, and also to provide a possible solution to overcoming the limitation using an optically-produced non-equilibrium Cs plasma. [Preview Abstract] |
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PR1.00021: Hybrid modelling of a DC glow discharge with an analytical ionization source term of fast electrons Anatoly Kudryavtsev, Eugene Bogdanov, Ismail Rafatov In any type of existing fluid model (``simple'', ``extended'' and so on) the electron ensemble is considered as a whole and is characterized by the averaged parameters, namely, the averaged density, averaged energy (temperature), and averaged directional drift velocity. However, in reality the EDF in the near-cathode region is nonlocal, such that the different electron groups (especially the fast electrons emerged from the cathode layer) behave differently and separate from each others. Accordingly, they cannot be described by averaged parameters and kinetic analysis is needed. We developed and tested a simple hybrid model for a glow discharge, which incorporates nonlocal ionization by fast electrons into the fluid framework, and thereby overcomes the fundamental shortcomings of the fluid model. At the same time, proposed model is computationally much more efficient compared to the models involving Monte Carlo simulations. Calculations have been performed for an argon gas. Comparison with the experimental data as well as with the hybrid (particle) and fluid modelling results demonstated good applicability of the proposed model. [Preview Abstract] |
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PR1.00022: Kinetic modeling of electronically enhanced reaction pathways in Plasma Assisted Combustion Guy Parsey, Yaman G\"u\c{c}l\"u, John Verboncoeur, Andrew Christlieb The use of plasma energy to enhance and control the chemical reactions during combustion, a technology referred to as ``plasma assisted combustion'' (PAC), can result in a variety of beneficial effects: e.g. stable lean operation, pollution reduction, and wider range of p-T operating conditions. While experimental evidence abounds, theoretical understanding of PAC is at best incomplete, and numerical tools still lack in reliable predictive capabilities. In the context of a joint experimental-numerical effort at Michigan State University, we present here a modular Python framework dedicated to the dynamic optimization of non-equilibrium PAC systems. We first describe a novel kinetic global model, which aims at exploring scaling laws in parameter space, as well as the effect of a non-Maxwellian electron energy distribution function (EEDF). With such a model, we reproduce literature results and we critically review the effect of data uncertainty and limiting assumptions. Then, we explore means of measuring a non-Maxwellian EEDF through the use of a detailed collisional-radiative model, coupled to optical emission spectroscopy. Finally, we investigate the effect of different numerical integrators, as well as customized routines specifically designed to solve stiff sparse ODE systems. [Preview Abstract] |
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PR1.00023: Simulation of a capacitively coupled oxygen discharge using the oopd1 particle-in-cell Monte Carlo code J.T. Gudmundsson, M.A. Lieberman The oopd1 particle-in-cell Monte Carlo (PIC-MC) code is used to simulate a capacitively coupled discharge in oxygen. oopd1 is a one-dimensional object-oriented PIC-MC code in which the model system has one spatial dimension and three velocity components. It contains models for planar, cylindrical, and spherical geometries and replaces the XPDx1 series, which is not object-oriented. The revised oxygen model includes, in addition to electrons, the oxygen molecule in ground state,the oxygen atom in ground state, the negative ion O$^-$, and the positive ions O$^+$ and O$_2^+$. The cross sections for the collisions among the oxygen species have been significantly revised from earlier work using the XPDP1 code. Here we explore the electron energy distribution function (EEDF), the ion energy distribution function (IEDF) and the density profiles for various pressures and driving frequencies. In particular we investigate the IEDF for both O$^+$ and O$_2^+$ ions for various discharge conditions. We explore the role of fragmentation due to collisions of high energy O$_2^+$ ions with oxygen molecules its influence on the IEDF for O$^+$-ions. [Preview Abstract] |
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PR1.00024: Modeling of low temperature plasma for FOUP cleaning Diana Mihailova, Gerjan Hagelaar, Philippe Belenguer, Philippe Guillot, Laurent Therese, Bruno Caillier The contamination control in the processing stages in semiconductor industry is a major issue for the microelectronics yield and performance, as well as for the development of new technologies in the area. This mainly concern the wafer carrier boxes (FOUP), which typically provide environmental isolation, clean and secure wafer transport. However, molecule or wall contamination inside the carrier box, can strongly affects the production processes. The goal of this research is to find an efficient solution for decontamination of the FOUP by generating an uniform low temperature plasma inside the box. Various types of plasma are considered with the main task of cleaning using the plasma fluxes directed to the walls and in the same time not damaging the surfaces. In order to apply and test different types of plasma we make use of numerical modeling. The first studied type of plasma is a capacitive RF plasma generated inside a closed box. A time dependent 2 dimensional multi-fluid model is constructed in order to study the plasma behavior and plasma properties. The model is applied to a simplified 2D geometry with pure Ar gas. The influence of various parameters are studied and preliminary results are presented. [Preview Abstract] |
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PR1.00025: Particle based 3D modeling of streamer discharges Jannis Teunissen, Anbang Sun, Chao Li, Ute Ebert Streamers are rapidly growing plasma channels surrounded by a thin space-charge layer. They pave the way for sparks and lightning leaders, and they have many applications in plasma technology. There are fundamental open questions concerning streamers: Under what conditions do they emerge from electrodes? What determines properties like radius and velocity? When do they start to branch? To help answer these questions we have developed a 3D particle simulation with adaptive mesh refinement and dynamic particle control. This allows us to explore the full physics of streamer formation and initial propagation. We explain the modeling technique, present simulation results and discuss their implications. [Preview Abstract] |
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PR1.00026: 3D Spatially hybrid model for streamer discharge Anbang Sun, Jannis Teunissen, Ute Ebert Streamers are rapidly growing plasma filaments. They play an important role in the early stages of lightning, as well as in industrial application such as lighting, plasma assisted combustion and disinfection. In previous work, the first generation of 3D spatially hybrid codes was developed by Chao Li, to study the propagation of negative streamer without photoionization in a background field above the breakdown value. We now have set up the second generation codes to improve and optimize the original program, and to make it accessible. Adaptive Mesh Refinement and parallel computing technique are being adopted as well, to increase the accuracy, efficiency and parameter range of simulations. The codes are being used to study the streamers emergence from the inception cloud, streamers branching and feather formation in different N2:O2 ratios, and streamers interaction. [Preview Abstract] |
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PR1.00027: Secondary electron emission induced by fast argon neutrals and its effects on rf plasmas Aleksandar Bojarov, Marija Radmilovic-Radjenovic, Zoran Lj. Petrovic In this paper we have examined a dual-frequency rf discharge in argon that is strongly affected by the secondary emission of electrons from the electrodes. We have used implicit ``Particle In Cell'' code as a tool for investigation of different electrode surface conditions that define the secondary emission. For precise description of the secondary emission we use analytic formulas suggested by Phelps and Petrovic (Plasma Sources Sci. Technol 8, R21, 1999). Two surface conditions, atomically ``clean'' and ``dirty,'' describe the secondary emission as a function of the energy of impacting ion or atom on the electrode. In dual-frequency discharges one of the electrodes usually has some voltage bias, thus leading to greater production of fast neutrals on its side. Since on the biased electrode ion and neutral fluxes are greater than on the powered electrode, the secondary emission from biased electrode has a greater effect on the plasma. Results from our simulations show that secondary emitting fast neutrals can greatly affect the plasma, especially in discharges with intense production of neutrals in the sheath. We conclude that for precise description of rf discharges a realistic modeling of the secondary emission induced by ions and fast neutrals is necessary. [Preview Abstract] |
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PR1.00028: 2D Fluid/Analytical Simulation of MultiFrequency Capacitively Coupled Reactor E. Kawamura, M.A. Lieberman, D.B. Graves, A.J. Lichtenberg A fast 2D hybrid fluid-analytical multi-frequency capacitively-coupled plasma (CCP) argon reactor model was developed using the finite elements simulation tool COMSOL. The fluid-analytical code was also coupled to a particle-in-cell (PIC) code to obtain the ion energy and angular distribution (IED and IAD) at the wafer. A typical simulation takes less than an hour on a moderate 2.3 GHz, 8GB DRAM worksation. A bulk fluid plasma model is coupled with an analytical sheath model, where an actual vacuum sheath of variable thickness is modeled with a fixed-width sheath of variable dielectric constant. A gas flow model solves for the steady-state pressure, temperature and velocities of the neutrals. The analytical multi-frequency sheath model results were compared to PIC simulations, showing good agreement. By varying the reactor parameters such as input power for each frequency, pressure, discharge gap, wafer electrode radius, etc., we can observe the effect on the plasma density and uniformity as well as the IED and IAD. [Preview Abstract] |
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PR1.00029: Gyrokinetic Simulation for the Advanced Plasma Source Benjamin Schroeder, Ralf Peter Brinkmann This contribution presents a model based on gyrokinetic theory. The model can be applied to the ``Advanced Plasma Source'' by Leybold Optics and similar sources that are used for Plasma Ion Assisted Deposition (PIAD) of optical coatings. The source consists of an electron emitting lanthanum hexaboride cathode surrounded by a copper anode and a solenoid that generates an axissymmetric magnetic field of around 25mT. The pressure is typically 0.02 Pa. The electron mean free path exceeds the discharge dimension so that a kinetic model has to be applied. A kinetic equation is derived from Boltzmann's equation and describes the non-local behaviour along the magnetic field lines and diffusion across these. The numerical solution of the equation using different boundary conditions is presented. [Preview Abstract] |
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PR1.00030: Study of excitation and emission features in low pressure electronegative oxygen discharges with special regard to the actual electrode surface condition Arthur Greb, Kari Niemi, Deborah O'Connell, Timo Gans The presented study is based on a one-dimensional semi-kinetic fluid modelling approach, which accounts for a geometrical asymmetry of the radio frequency driven capacitively coupled oxygen plasma. The plasma is operated at a pressure of 40 Pa and with a sinusoidal driving voltage of 300 V amplitude. A simple plasma chemistry is accounted for including electrons, molecular oxygen positive ions (O$_2^+$), atomic oxygen negative ions (O$^-$) and metastable singlet delta oxygen (O$_2(^1\Delta)$). The actual electrode surface condition, which strongly affects the plasma-surface interaction processes, is varied in the model by means of changing the secondary electron emission yield from positive ions and the surface loss probability of metastable singlet delta oxygen. It is found that both factors significantly affect plasma parameters, such as the metastable concentration, electronegativity, spatial particle distribution as well as the excitation and ionization dynamics. Excitation pattern generated from simulations are then used to calculate the optical emission signal, which can directly be compared with phase resolved optical emission spectroscopy measurements. By correlating both simulations and experimental measurements plasma and electrode surface parameters can be predicted. [Preview Abstract] |
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PR1.00031: Particle simulation of a micro inductively coupled plasma source including an external circuit Yoshinori Takao, Masataka Sakamoto, Koji Eriguchi, Kouichi Ono A numerical study of micro inductively coupled plasma (ICP) sources has been conducted. We employ a two-dimensional axisymmetric particle-in-cell with Monte Carlo collisions (PIC-MCC) method, where a transformer model including the effect of capacitive coupling is incorporated. The plasma source is 5 mm in radius and 10 mm in length with a 5-turn helical coil around a cylindrical quartz chamber, where the Ar and Xe plasmas are excited. The simulation was performed for pressures in the range $1-500$ mTorr and rf frequencies in the range $1-500$ MHz at rf powers less than 10 W. The results indicated that capacitive coupling dominated over inductive coupling and the most of the rf power was deposited in the bulk area at high pressures while the power was absorbed in the sheath area at low pressures. On the other hand, the circuit model was also applied to a conventional large ICP source, and then the result showed that inductive coupling dominated over capacitive coupling. The micro ICP would be E-mode dominated plasmas under the present conditions. [Preview Abstract] |
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PR1.00032: Kinetics of Electrons in H$_{2}$O at High Values of Reduced Electric Field Zoran Petrovic, Jelena Sivos, Dragana Maric, Nikola Skoro, Vladimir Stojanovic In this work we present electron transport coefficients in H$_{2}$O for the conditions used in plasma assisted technologies. Monte Carlo technique, already used for similar discharges in nitrogen, argon and hydrogen is used to obtain transport parameters for a range of reduced electric field values (E/N=100-10 kTd). In this work we focus on anisotropic scattering of electron transport and its effects on spatially resolved emission. Agreement with experimental data for electron drift velocity and effective electron ionization for the conditions of moderate E/N allowed us to study production of heavy particles and subsequently spatial emission as a consequence of their transport. [Preview Abstract] |
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PR1.00033: Study of atmospheric pressure discharges with a novel hybrid code Denis Eremin, Torben Hemke, Ralf-Peter Brinkmann, Thomas Mussenbrock Numerical simulations bear special significance in helping to understand the phenomena taking place in the atmospheric discharges as the diagnostic capabilities are severely limited there due to small sizes of such discharges. In this work we study atmospheric pressure discharges with a fully self-consistent hybrid code, where the kinetically treated electron component is calculated on GPU using the PIC/MCC approach and ions are treated under the fluid approximation on CPU. The resulting code is fast, because the computationally intensive kinetic algorithm is parallelized on GPU, flexible, because it is straightforward to include complex chemistry processes for the ion component in the fluid model, and allows to capture all the essential physics due to quite general assumptions underlying the model. A comparison with fully fluid simulations is made. We demonstrate with our code that the kinetic description of electrons is important even for the atmospheric pressure discharges. [Preview Abstract] |
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PR1.00034: Optimization of an electron beam exciter via plasma fluid model simulation David Urrabazo, Stephan Thamban, Jimmy Hosch, Matthew Goeckner There are numerous computational models that can be used to study plasmas, each with advantages and disadvantages. Two of the most commonly used are the ambipolar model and the classical fluid model. The ambipolar model takes advantage of the ambipolar approximation, while the classical model includes the solving of the Poisson's equation. Both models were used to simulate the operation of the ICP electron source of the Electron Beam Exciter. Process conditions and geometrical variations were performed to optimize the electron density and electron to ion ratio in the beam extraction region. Results of this optimization along with deviations between the two models will be presented. [Preview Abstract] |
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PR1.00035: 3D CFDTD PIC/Fluid Hybrid Simulations on Plasma Processing of Materials M.C. Lin In this work, we propose to use a hybrid method to numerically model the plasma processing of materials including a magnetron sputtering, inductively coupled plasmas (ICPs), capacitively coupled plasmas (CCPs), and microwave plasma enhanced chemical vapor deposition (MPECVD) reactors for getting more physics insight in these plasma processes and better understanding. The neutral atoms in the weakly ionized plasma are represented by a fluid model and the plasma and externally applied fields are described by particle-in-cell (PIC) macro-particles evolving with a conformal finite-difference time-domain (CFDTD) method. Here, we will demonstrate the CFDTD PIC/fluid hybrid simulations of the plasma processing including a magnetron sputtering, an ICP, a CCP, and an MPECVD. All these simulation models are based on the experiments and are still under study and development in collaborating with the experimentalists in industry and academia. [Preview Abstract] |
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PR1.00036: Development of a New Industry Focused Plasma Simulation Tool Adam Williams, Sergio L\'opez-L\'opez, Derek Monahan, Will Brigg, Jonathan Tennyson Plasma processes are routinely used in a number of industrial settings. However, in the majority of these cases the techniques and procedures used to create the required plasma are determined by experimental trial and error. This advancement has been led in a large part by the technical ability of the engineers in charge of the processes. This mode of operation has largely worked thus far, however, with more complex plasma chemistries being developed and the continual drive for efficiency, simulations are rapidly becoming another instrument in the process engineer's toolset. This poses interesting requirements on any simulation software which is aimed toward industry, such as: ease of use/automation, robust chemistry libraries, simulation speed and reliability. It is the goal of this new project at UCL and Quantemol Ltd. to tackle these issues and more, by developing a simulation tool specifically targeted to industrial applications. This new software will allow the simulation of fully 3D geometries, implementing an automatically refined finite element method (FEM) to solve the appropriate fluid equations, coupled with kinetic simulation methods to improve model efficacy. [Preview Abstract] |
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PR1.00037: The effect of electrode diameter on the ignition of the dc discharge in nitrogen Valeriy Lisovskiy, Valeriy Malinovskiy, Veronika Koval, Vladimir Yegorenkov This report studied the effect of electrode diameter (55~mm, 25~mm, 12~mm, 5~mm, 2.4~mm and 0.8mm) on the ignition of the discharge in nitrogen and its modes of burning. The decrease in the electrode diameter was found at large gas pressure values to discharge ignition at lesser voltage values than for large size electrodes and at low gas pressure values to the shift of breakdown curves to higher breakdown voltage values. All breakdown curves we had registered intersected at the nitrogen gas pressure value of $p$~=~0.9~Torr close to the inflection point of the breakdown curves for large electrodes. To the left of the inflection point the distortion of the uniform distribution of the electric field between the electrodes of moderate diameter impedes the ionization multiplication within the discharge gap and the breakdown voltage grows, and to the left of the inflection point the conditions for gas breakdown became easier to meet due to the redistribution of the electric field. [Preview Abstract] |
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PR1.00038: Axial structure of dc glow discharge negative glow in nitrogen Valeriy Lisovskiy, Veronika Koval, Ekaterina Kravchenko, Vladimir Yegorenkov This paper reports the studies with a Langmuir probe technique of axial plasma parameters such as electron temperature, potential, electric field and plasma concentration of dc glow discharge negative glow in nitrogen at different gas pressure values. Electron temperature in the negative glow decreases from the cathode sheath boundary and it approaches the smallest value at the anode end of the negative glow. Along the negative glow the plasma potential lowers by about 5~V. Axial profile of plasma concentration possesses a maximum in the negative glow near the cathode sheath boundary similar to the case of low pressure. Along the negative glow the plasma concentration decreases by about 16 times and it approaches its minimum in the transition region to the Faraday dark space. Note that the plasma concentration decrease by 15-16 times was observed at all nitrogen pressure and discharge current values when the negative glow completely found its place within the inter-electrode gap. [Preview Abstract] |
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PR1.00039: Study of NO formation in a low pressure air-like plasmas at single pulse operation Sergej Gorchakov, Marko H\"ubner, J\"urgen R\"opcke, Detlef Loffhagen, Daniil Marinov, Olivier Guaitella, Antoine Rousseau The NO formation in low pressure N$_2$-O$_2$ plasmas has been studied for a single rectangular pulse using quantum cascade laser (QCL) absorption spectroscopy. To measure sensitive species concentrations with a time resolution in the microsecond range, a new spectroscopic technique based on QCL has been used. Absolute number densities of NO molecules have been obtained taking into account the influence of spectral distortions due to fast spectral scanning, i.e., rapid passage effect. The duration of the pumping pulse was about 5 ms for discharge currents between 50 and 150 mA. The theoretical analysis has been performed by means of a self-consistent model comprising the coupled solution of the time-dependent electron Boltzmann equation, a system of rate equations for various heavy particles and a current balance equation. Results for air-like plasmas are represented both for the active discharge phase and the afterglow. The modelling results show qualitative agreement with experimental data, while the density of NO molecules is underestimated compared to measurements. Possible reasons of this discrepancy are discussed. [Preview Abstract] |
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PR1.00040: Normal regime of dc discharge in N$_{2}$O Valeriy Lisovskiy, Ekaterina Artushenko, Vladimir Yegorenkov The present report is devoted to studying the normal regime of dc discharge in N$_{2}$O with the inter-electrode distance values $L$~=~0.5, 1 and 2~cm in a broad range of gas pressure. At large N$_{2}$O pressure the ratio of the normal current density to gas pressure squared was shown to remain constant and to equal $J_{n}$/$p^{2}$~=~0.44~$\pm $~0.03~mA/(cm$\cdot $Torr)$^{2}$ for any inter-electrode distance value (within the $L$ range we studied). On decreasing N$_{2}$O pressure the $J_{n}$/$p^{2}$ ratio grows and for narrow inter-electrode distance it may approach some or even some tens of mA/(cm$\cdot $Torr)$^{2}$. For $L$~=~2~cm the normal regime is observed only at the N$_{2}$O pressure values above the inflection point on the dc breakdown curve for this inter-electrode distance (\textit{pL}~$\ge $~0.6~Torr$\cdot $cm). But for narrow distance values $L$~=~0.5 and 1~cm the normal regime may exist in a much broader N$_{2}$O pressure range to the right as well as to the left of the dc breakdown curve minimum. Its existence region is limited from the low pressure side only by the appearance of the obstructed regime at the left-hand branch of the breakdown curve when a complete cathode sheath cannot fit the inter-electrode distance. [Preview Abstract] |
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PR1.00041: Characteristics of atmospheric pressure microwave plasma torch Ferhat Bozduman, Erdogan Teke, Ali Gulec, Lutfi Oksuz Atmospheric pressure microwave (2.45 GHz) plasma torch has been designed and built. The plasma optical and electrical characteristic have been investigated. The data has been compared with the kHz frequency rf torch. Electron temperature, density and gas temperatures are measured for different flow rates and for different gases. Optical emission spectrometer and ICCD camera are used to measure the argon and helium plasma characteristics and the results are compared for both designs. This Work has been supported by TUBITAK TEYDEB project no:9100036 [Preview Abstract] |
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PR1.00042: EEDF evolution in pulsed radio-frequency plasmas Ziad El Otell, Mark Bowden, Nicholas Braithwaite We investigate the evolution of the electron energy distribution function (EEDF) in pulsed radio-frequency plasmas using a simple form of trace rare gas optical emission spectroscopy. For steady-state discharges, methods exist to determine electron temperatures and EEDFs using emission measurements and collisional radiative models. However, these methods rely on the EEDF being stable and are difficult to use in the rapidly changing transients in a pulsed discharge. We assess a simpler technique in which we compare the time-dependence of emission from different plasma species in order to infer information about the evolution of the EEDF. The study was carried out in a capacitively coupled rf discharge generated in a Gaseous Electronic Conference (GEC) reference reactor. The gas mixture consisted of mainly argon with small amounts of xenon and krypton. Emission was measured on specific lines from argon, krypton and xenon, chosen due to their emission being predominantly due to direct excitation from the ground state. For the case of square pulse excitation, the EEDF in the early part of each pulse was dominated by beam-like electrons with high energy. This beam-like EEDF phase was absent when a pulse with a less steep rise time was used. [Preview Abstract] |
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PR1.00043: Kinetic simulation of the bounce resonance effect in capacitive discharges and beyond Sebastian Wilczek, Jan Trieschmann, Denis Eremin, Ralf Peter Brinkmann, Julian Schulze, Thomas Mussenbrock The electron heating in capacitive high frequency discharges at very low gas pressures is dominated by momentum transfer from the oscillating sheath. In this regime ohmic heating is not sufficient anymore to maintain the plasma. Under certain electric and geometric conditions highly energetic electrons are able to traverse the plasma bulk and interact with the opposite sheath. For proper frequencies and gap sizes the electrons gain energy, accelerate back and resonantly interact with first sheath. The circle may repeat itself. In this contribution the described bounce resonance effect is investigated by means of Particle-In-Cell simulations. It is found that the effect is connected with the excitation of electrostatic waves and the generation of harmonics in the discharge current. It is shown that it is also connected with a very efficient confinement of electrons. [Preview Abstract] |
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PR1.00044: Numerical investigation on fundamental properties in capacitively-coupled methane plasmas for deposition of diamond-like carbon films Akinori Oda, Hiroyuki Kousaka Capacitively-coupled methane (CH$_4$) plasmas for deposition of diamond-like carbon films have been simulated using a self-consistent one-dimensional fluid model, incorporating the mass balance equations for electrons, ions, radicals and non-radicals, the electron energy balance equation, coupled with the Poisson equation. Despite of low-pressure CH$_4$ gas condition, many positive-ion species, such as C$_2$H$_4^+$, CH$_4^+$, C$_2$H$_2^+$, CH$_5^+$ etc., have been found in the plasmas. The non-radical neutrals, such as C$_2$H$_4$, C$_3$H$_8$, C$_2$H$_2$ and C$_2$H$_6$, have also found with higher densities comparable to the source gas density. This result indicates that this complexity of background gas in CH$_4$ plasmas is strongly affected to the electron energy distribution function, which is important for the determination of plasmas properties. [Preview Abstract] |
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PR1.00045: Kinetic simulations of magnetized capacitively coupled discharges Jan Trieschmann, Mohammed Shihab, Denis Eremin, Ralf Peter Brinkmann, Julian Schulze, Thomas Mussenbrock Capacitive high frequency discharges are of crucial importance in the context of plasma etching, deposition and surface modification. As these single or multiple frequency discharges are oftentimes operated at low pressures of less than a few pascal, a high plasma density is commonly achieved with the use of external magnetic fields. In this work kinetic simulations are used to investigate the effect of inhomogeneous external magnetic fields on the discharge dynamics in a strongly nonlocal pressure regime. We found that capacitively coupled discharges can be largely asymmetrized by applying strong magnetic fields in front of a given target electrode. This not only has an effect on the plasma density, but also on the ion energy distribution functions (IEDF) at the electrodes and on the acceleration of fast electrons in the plasma sheath regions. In consequence in the discharge currents a generation of higher harmonics of the driving frequency can be observed. We investigate these scenarios in terms of 1D-3V Particle in Cell simulations. [Preview Abstract] |
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PR1.00046: Hydrodynamic modelling of ccrf discharge plasmas in oxygen Markus M. Becker, Igor Sheykin, Detlef Loffhagen, Christian K\"ullig, Kristian Dittmann, J\"urgen Meichsner Capacitively coupled radio frequency (ccrf) oxygen plasmas are widely used for surface treatment applications. In the present contribution hydrodynamic modelling has been performed for discharge plasmas in a reactor with plane parallel electrodes to analyze the impact of negative ions and metastable molecules. Assuming radial symmetry of the plasma a time-dependent, spatially one-dimensional model has been used. The coupled system of Poisson's equation, of balance equations for the densities of 17 heavy particle species and the electrons as well as of the electron energy density has been solved taking into account about 180 collision processes in the reaction kinetics. Main features of the model are given and results for discharges at pressures from 30 to 100~Pa, applied voltages between 0.2 and 1~kV at a frequency of 13.56~MHz are reported. In particular, the electronegativity characteristics and the influence of the secondary electron emission coefficient are discussed. The comparison of modelling results with experimental data of electronegativity and excitation rate of atomic oxygen shows fair agreement. [Preview Abstract] |
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PR1.00047: The role of nonlocal electron energy transport in the formation of spatial distributions of the two-chamber plasma density of ICP discharge at change of gas pressure Anatoly Kudryavtsev, Konstantin Serditov 2D simulations of the two-chamber ICP source where power is supplied in the small discharge chamber and extends by electron thermal conductivity mechanism to the big diffusion chamber is performed. Depending on pressure two main scenarios of plasma density and its spatial distribution behavior were identified. The first case of higher pressure is characterized by localization of plasma in small driver chamber where power is deposed and corresponds to small thermal conductivity length compared with diffusion length. The second case of lower pressure represents diffusion chamber as a main source of plasma with maximum of electron density with greater thermal conductivity length compared with diffusion length. The differences in spatial distribution are caused by local or non-local behavior of energy transport in discharge volume due to the different characteristic scale of heat transfer with electronic conductivity. As a result changing of geometrics and gas pressure gives the possibility to set ratio between diffusion and thermal conductivity characteristic lengths. Thus, one can control heat input and, in turn, obtain several types of plasma profiles. [Preview Abstract] |
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PR1.00048: Control of plasma density profile via wireless power transfer in an inductively coupled discharge Hee-Jin Lee, Jin-Young Bang, Hyo-Chang Lee, Young-Cheol Kim, Chin-Wook Chung Wireless power transfer via a strongly coupled magnetic resonance was applied to the field of plasma. Two antennas (an inner antenna coil was connected to the RF power and an outer antenna was a resonant antenna with a variable capacitor) were placed on the top of a chamber. The resonant antenna is electrically separated from the inner antenna coil. As the self-resonance frequency of the resonant antenna was adjusted, the power transfer ratio of the inner antenna to the outer antenna was changed and a dramatic evolution of the plasma density profile was measured. The density profiles were changed from a concave shape to a convex shape by varying the self-resonance frequency of the outer antenna. This result shows that the plasma density spatial distribution can be successfully controlled via wireless power transfer. [Preview Abstract] |
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PR1.00049: Permanent-magnet helicon discharges at 13 and 27 MHz Francis F. Chen A small argon helicon discharge 5 cm in diameter and 5 cm long with a permanent-magnet B-field was studied at 13.56 and 27.12 MHz. RF power varied from 200 to 1000W, and pressures from 0.7 to 60 mTorr. The plasma was injected into a large chamber, and the radial density $n$ and temperature $T_{e}$ profiles were measured at three distances below the source. The results show the inadequacy of existing theories which assume uniform B-fields and long cylinders. The HELIC code\footnote{ D. Arnush, Phys. Plasmas \textbf{7}, 3042 (2000).} used for design showed that 27 MHz should give better antenna coupling than 13 MHz, and that the plasma density should increase linearly with power. When the plasma is immediately ejected from the source, however, the density in the source remains relatively low, and the B-field has to be lowered to match it. With optimized B-field, the plasma conditions are quite different from those in ideal theory. The higher densities at 13 MHz are probably due to the fact that the 13-MHz antenna has three turns instead of one, as required to get an inductance that the matching circuit can handle. At 1000W, $n \approx $ 0.8 $\times $ 10$^{12}$ cm$^{-3}$ was achieved 16.9 cm below the source. At 6.8 cm below the source, the Trivelpiece-Gould density peak can be seen at the edge. [Preview Abstract] |
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PR1.00050: Warm Magnetized Primary and Secondary Electron Vlasov Equilibria Robert Terry A Vlasov equilibrium is developed for steady state emission into a magnetized gap in coaxial geometry. The outer cathode boundary conditions are those of a perfect conductor that emits a Maxwellian electron flux radially, azimuthally, and axially. The interior anode boundary conditions are those of a perfect conductor with a fixed secondary emission coefficient ($0 < \gamma \leq 1$). The anode carries a fixed current and the radial gap is set to a fixed voltage. The angular momentum of emitted secondary electrons around the anode is found to materially change the orbit turning points. When energy conserving solutions are examined it is found that the secondaries axial velocities must remain bounded above by a well defined function of radius, magnetic field, and voltage. A fully nonlinear and self consistent Vlasov-Poisson problem is formulated and solved for the space charge distribution implied by the Vlasov equilibrium. The conditions for magnetic insulation of the secondary electron population are then established. [Preview Abstract] |
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PR1.00051: ABSTRACT WITHDRAWN |
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PR1.00052: Variation of spatial distribution of excited species in He/Ar/O$_{2}$ admixtures in an atmospheric pressure plasma jet Sarah Taylor, Robert Leiweke, Biswa Ganguly Variation of cathode directed streamer initiated pulsed glow current and spatial distribution of excited species outside the 4 mm capillary of a He/Ar/O$_{2}$ plasma jet have been measured using a partially optically transmitting conducting cathode. For 18 mm inter-electrode gap, 15 ns rise time unipolar 12.5 kV pulsed applied voltage with 6 kHz repetition rate, the pulsed glow current peaked at 150 mA with 1{\%} Ar added to He flow, compared to 100 mA in pure He, into ambient air at 1.6 SLM. Spatiotemporally and spectrally resolved head-on emission images from He 3$^{3}$D$\to $2$^{3}$P, Ar 2p$_{1}\to $1s$_{2}$, O $^{5}$P$\to ^{5}$S, and N$_{2}^{+}$ B$^{2}\Sigma \to $X$^{2}\Sigma $ transitions were acquired along the discharge propagation axis using a 5 ns gate ICCD camera. A fiber-couple PMT lens viewing normal to the propagation axis collected the same species emission, at 4 and 8 mm from the capillary tip, in order to correlate temporal emission profiles from streamer to glow transition. For each admixture, the ICCD radial emission profile for each excited species peaks on axis with a mean FWHM of $\sim $1.5 mm, whereas for pure He the intensity distribution of all excited species is annular. Concurrent with the increased discharge conductivity with 1{\%} Ar admixture, the 777 nm O atom emission intensity increased in both streamer and glow phases. [Preview Abstract] |
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PR1.00053: Self-organization, generation, annihilation, and dynamics of filaments in dielectric barrier discharges J.P. Boeuf, B. Bernecker, T. Callegari, S. Blanco, R. Fournier The localized objects forming the patterns in Dielectric Barrier Discharges (DBDs) are luminous plasma filaments that exhibit particle-like behaviour, i.e. generation, annihilation, dynamics, scattering, and collective effects leading to self-organized structures (hexagons, stripes, concentric rings, spirals). We use simple experiments and models to study the basic mechanisms behind pattern formation and dynamics in DBDs. Experiments and models show that the formation of filaments can be described in term of activation and inhibition mechanisms, and that the physical quantities playing the role of activators and inhibitors can be clearly identified. We analyze in details the formation of a self-organized pattern after a few cycles of the applied voltage and show how the pattern can evolve on a longer time scale. We also show that the model can reproduce well some aspects of the filament dynamics that are observed in fast imaging experiments, such as division and merging of filaments. The motion of a filament along the dielectric layer can be observed under some conditions and we show that this apparent motion can be the result of an interaction between two filaments, a visible one operating in a glow regime, and a less visible or invisible one operating in a low current, Townsend regime. We discuss how the association of activation-inhibition mechanisms with the important property of bistability of non equilibrium discharges can lead to a large variety of patterns that are very similar to patterns observed in other physical, chemical, or biological systems. [Preview Abstract] |
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PR1.00054: Characterization of three kinds of dielectric barrier discharge reactor for surface treatment of polymers Min Hur, Woo Seok Kang, Young Hoon Song Low surface energy of polymers is the chief obstacle to prevention of their wider application. It is well known that the exposure of polymers to the plasma leads to the improvement of their printability, dyeability, and adhesion on the one hand by etching their surface on the other hand by grafting functional groups on their surface. In this work, three kinds of dielectric barrier discharge (DBD) reactor are proposed for surface treatment of polymer substrates. The discharge characteristics are investigated by using the voltage-current waveforms and optical emission spectroscopy. The plasma-modified polymer surfaces are characterized with contact angle measurement, scanning electron microscope, and x-ray photoelectron spectroscopy. Finally, the applicability of three kinds of DBD reactors to the polymer surface treatment is discussed based on the experimental results. [Preview Abstract] |
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PR1.00055: Characteristics of low frequency air glow dielectric barrier discharges at atmospheric pressure Nakyung Hwang, Seong-kyun Im, Moon Soo Bak, Mark A. Cappelli In this paper we present recent studies of dielectric barriers discharges in air. The discharges are generated using an AC power supply operating at a relatively low frequency of 60 Hz between two sheets of porous dielectric material of varying thickness measuring 20 mm $\times$ 20 mm in area. Measurements are made of the optical emission and voltage--current waveforms from which we extract discharge properties including electron density, under different input voltage, electrode separation, and dielectric thickness. Stable and continuous air glow discharges were obtained at atmospheric pressure in the range of 2--5 kV and current densities of a few mA for 0.5--2.5 mm discharge gaps. Regions of stable glow discharges are mapped out and a plausible mechanism is described for the transition from glow to streamer mode. The experimental results are compared to one-dimensional numerical simulations that are carried out for a discharge pressure range of 100--760 Torr. [Preview Abstract] |
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PR1.00056: Electric arc discharge in the transverse gas flow at atmospheric pressure Valeriy Chernyak, Iryna Prysiazhnevych, Evgen Martysh, Tamara Lisitchenko Physical features of the transverse arc discharge (TA) and its atmospheric pressure plasma were investigated for the wide range of gas flow rates (0 $\div$ 3/4 of the sound speed) and for the different gas content (atomic - Ar, molecular - air) and different character of gas flows (from laminar to turbulent). Component composition of the plasmaforming gas; electronic excitation temperatures T$_{e}^{\ast }$ of atoms, vibration T$_{v}^{\ast}$ and rotation T$_{r}^{\ast}$ temperatures of molecules in the generated plasma were determined by optical emission spectroscopy. The electron distribution function and its average energy were calculated by using Bolsigplus code. The difference between T$_{e}^{\ast}$ of electrode material atoms (cooper) and atoms of blowing gas (oxygen, hydrogen, argon) was found. It can be explained by the additional mechanism of the population of electronic states of cooper atoms due to the ion-ion recombination. It was shown that when the gas flow rate achieves values larger than the drift velocity of ions in an electric field of the discharge further increasing of the voltage drop on the discharge starts with the gas flow rate growth, which is accompanied by appearance of numerous filament structures oriented along the gas flow. [Preview Abstract] |
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PR1.00057: Modeling of the DBD in Xe-Cl$_{2}$ mixtures: effect of chlorine concentration and pressure Svetlana Avtaeva, Belkacem Saghi, Bouabdellah Rahmani Characteristics of the DBD in Xe-Cl$_{2}$ mixtures were simulated using the 1D fluid model at gas pressure 150-300 Tor and chlorine concentration in the mixtures 0.1- 5{\%}. The discharge gap is fixed at 4 mm. Two dielectric layers have an identical thickness 2 mm and relative permittivity 4. The source voltage $U_{S}=U_{0}$\textit{sin$\omega $t} with $f$=100 kHz and $U_{0}$=4.25 or 5 kV is applied to the electrodes. Simulations show at all chlorine concentrations in the Xe-Cl$_{2}$ mixtures the most abundant negative species in the discharge are Cl$^{-}$ ions, the most abundant positive ions are Xe$_{2}^{+}$. At the current pulse densities of electrons and Xe$^{+}$ ions near the dielectric barrier sharply increases. The potential drop across the discharge gap increases and the magnitude of the current pulse falls with chlorine content in the mixture. Power deposited into heating of positive and negative ions grows with chlorine concentration; power deposited into electrons mainly decreases with chlorine concentration. Growth of the chlorine content in Xe-Cl$_{2}$ mixtures results in increase of electron energy expenses on Cl$_{2}$ dissociation, Xe and Cl$_{2}$ ionization, and Cl$_{2}^{\ast }$ and Xe$^{\ast \ast }$ excitation. At chlorine concentration higher than 0.1{\%} emission of the XeCl$^{\ast}$ 308 nm band predominates in radiation flux. The DBD radiative efficiency decreases with pressure and has maximum at small chlorine concentration. [Preview Abstract] |
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PR1.00058: Fully kinetic particle simulations of high pressure streamer propagation David Rose, Dale Welch, Carsten Thoma, Robert Clark Streamer and leader formation in high pressure devices is a dynamic process involving a hierarchy of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. We have performed 2D and 3D fully EM implicit particle-in-cell simulation model of gas breakdown leading to streamer formation under DC and RF fields. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm [D. R. Welch, \textit{et al}., J. Comp. Phys. \textbf{227}, 143 (2007)] that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge. These models are being applied to the analysis of high-pressure gas switches [D. V. Rose, \textit{et al}., Phys. Plasmas \textbf{18}, 093501 (2011)] and gas-filled RF accelerator cavities [D. V. Rose, \textit{et al}. Proc. IPAC12, to appear]. [Preview Abstract] |
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PR1.00059: Experimental study of pulsed corona discharge in air at high pressures Yunghsu Lin, Dan Singleton, Jason Sanders, Andras Kuthi, Martin A. Gundersen Understanding of the dynamics of nanosecond scale pulse discharges in air at multiatmospheric pressure is essential for the development of transient plasma enhanced combustion in internal combustion engines. Here we report the result of our experimental investigation of cathode-directed streamer discharges in synthetic air at pressures ranging from 1 to 20 bar. Two pulse generators with maximum pulse amplitudes of 50 kV and 65 kV, pulse width of approximately 12 ns and 85 ns and pulse rise times of 5 ns and 50 ns are used to generate streamers. The electrodes are coaxial with various radial gaps up to 11.75 mm. The discharge chamber is evacuated and backfilled with synthetic dry air at room temperature. Optical data is obtained from PI-MAX 3 ICCD camera with 3 ns gate width. The streamer propagation velocity variation with applied voltage, different pressures and reduced electric field, E/P, will be shown. Preliminary results indicate that the (pd) similarity law is violated at high pressures in agreement with other recent experiments [1].\\[4pt] [1] ``Nanosecond Scale Discharge Dynamics in High Pressure Air,'' Pierre Tardiveau, Nicolas Moreau, Fran\c{c}ois Jorand, Christian Postel, St\'ephane Pasquiers, and Pierre Vervisch, IEEE Trans. on Plasma Sci., Vol. 36, No. 4, 2008. [Preview Abstract] |
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PR1.00060: Estimates of the Electric Field in Fast Ionization Waves Benjamin Yee, Brandon Weatherford, Edward Barnat, John Foster The non-equilibrium nature of fast ionization waves (FIWs) makes an assessment of energy transport difficult. Their high fields and short-lived nature complicate even the most simple diagnostics and tends to preclude the application of any physical probe. On the other hand, optical probes generally require the excitation, equilibration, and decay of atomic or molecular states, each of which takes a finite amount of time. In the case of an FIW, measurement of optical transitions will necessarily take place in the afterglow of the plasma. Fortunately, the electron and excited state densities produced by the wavefront are essentially fixed for a few hundred nanoseconds after the pulse. We propose a technique which uses measurements of the absolute metastable and electron densities to determine an effective electric field in the wavefront. The approach is evaluated for self-consistency and is in compared with other estimates of the electric field in similar discharges. [Preview Abstract] |
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PR1.00061: Influence of electrode positions and gas flow on the onset and propagation of an atmospheric pressure plasma jet Claire Douat, Gerard Bauville, Michel Fleury, Vincent Puech Plasma jets produced in noble gases by pulsed discharges and propagating in surrounding air have recently attracted a lot of attention due to their physical properties enabling the development of new applications, such as plasma medicine. Our device consisted of a quartz tube with inner and outer diameters equal to 2mm and 4mm, respectively. Helium was flowing through the inner electrode connected to a pulsed high voltage, while a grounded copper electrode was wrapped around the tube. Helium flow was in the range from 1 to 6 slm. The plasma jet propagated inside grounded metallic tubes of different diameters, allowed to study the influence of the location of the external potential on the propagation of the plasma. It will be shown that the discharge breakdown voltage, the onset of a plasma jet, its length of propagation and the velocity of the ionization front are sensitive function of the electrode arrangement, of the location of the reference potential and of the gas flow. All these parameters interplayed in a complex manner. It will be shown how minor changes in the overall configuration can induce dramatic effects on the properties of the plasma jet. [Preview Abstract] |
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PR1.00062: Experimental studies and modeling of microwave plasmas in argon M. Andrasch, M. Baeva, J. Ehlbeck, D. Loffhagen, K.-D. Weltmann A microwave (MW) induced plasma in argon at pressures from 5 to 100 hPa has been studied by experiments and modeling. The plasma source is placed inside a vacuum vessel and is operated with a TEM supply at a field frequency of 2.45~GHz provided by a 2~kW magnetron. To provoke the discharge, a resonant structure has been used which is integrated at the end of the inner conductor. The gas flow rate is 30 to 1000~sccm and the absorbed power derived from the incoming and reflected power is between 20 and 125~W. The temporally resolved electron density in the plasma afterglow has been determined by a heterodyne MW interferometer working at 45.5~GHz. In addition, a two-dimensional fluid model describing in a self-consistent manner the gas flow and heat transfer, the energy in-coupling, and the reaction kinetics has been utilized to obtain the gas and electron temperature, the electron, ion, and excited state densities, and the power deposited into the plasma for given gas flow rate and temperature at the inlet and input power of the incoming TEM microwave. A maximum electron density above 1$\times 10^{20}$~m$^{-3}$ and gas temperature above 600~K have been determined in front of the resonant structure. Modeling and experimental results demonstrate good agreement. [Preview Abstract] |
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PR1.00063: Generation of Energetic Species by RF Microplasma Arrays W.T. Rawlins, S. Lee, D.B. Fenner, S.J. Davis, A.R. Hoskinson, J. Hopwood We present preliminary results from the first implementation of a prototype single-board RF micro-discharge, linear array device in a discharge-flow reactor for quantitative determinations of ozone and singlet-oxygen production from microplasmas in O$_{2}$ and air at 1 atm. The ultimate objective is to develop compact, portable low-power micro-discharge based systems to generate energetic species for atmospheric-pressure applications including decontamination and disinfection. The technology uses application of low DC voltages and low applied powers ($\sim $25 W) at $\sim $1 GHz frequencies, across small gaps in arrays of resonators to ignite and sustain highly energetic microplasmas at elevated pressures. A set of 15-resonator micro-discharge assemblies was designed, fabricated, and tested in static and flowing environments for O$_{2}$, air, and Ar flows at pressures of 20 Torr to 1 atm. O$_{3}$ production was measured by UV absorption spectrometry, and O$_{2}$(a$^{1}$delta-$_{g})$ (``singlet-oxygen'') concentrations were determined by absolute near-infrared emission spectroscopy. Near-infrared emission spectra from an argon plasma were also recorded, and showed extensive excitation of the Ar(I) 3p$^{5}$4p -- 3p$^{5}$4s emission system near 12 eV. [Preview Abstract] |
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PR1.00064: Radial profile of micro-discharge temperature measured by ultraviolet laser Rayleigh scattering Steven Adams, James Caplinger Air micro-discharge temperature profiles have been derived from measurements of elastic Rayleigh scatter of an ultraviolet laser pulse. Rayleigh scatter images have been recorded to measure spatially resolved translational temperatures along the radial dimension of the dc micro-discharge at various currents. The scatter image intensity along the laser beam axis is proportional to the background gas target density and thus, according to the ideal gas law, is inversely proportional to gas translational temperature. By measuring the scatter image with and without a discharge, the temperature was determined in one-dimension along the laser beam passing radially through the discharge. This laser scatter technique was compared to the technique of measuring rotational and vibrational temperatures by passive optical emission spectroscopy (OES) of the N$_{2}$ second positive system. Results were generally consistent with the common assumption that T$_{vibrational}>>$T$_{rotational}$=T$_{translational}$. Slight differences between T$_{rotational}$ and T$_{translational}$ measured by laser scatter and OES techniques respectively are discussed. [Preview Abstract] |
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PR1.00065: Surface-wave capillary plasmas in helium: modeling and experiment M. Santos, L.L. Alves, C. Noel, T. Belmonte In this paper we use both simulations and experiments to study helium discharges (99.999{\%} purity) sustained by surface-waves (2.45 GHz frequency), in capillary tubes (3 mm radius) at atmospheric pressure. Simulations use a self-consistent homogeneous and stationary collisional-radiative model that solves the rate balance equations for the different species present in the plasma (electrons, the He$^{+}$ and He$_{2}^{+}$ ions, the He(n$<$7) excited states and the He$_{2}$* excimers) and the gas thermal balance equation, coupled to the two-term electron Boltzmann equation (including direct and stepwise collisions as well as electron-electron collisions). Experiments use optical emission spectroscopy diagnostics to measure the electron density (H$_{\beta }$ Stark broadening), the gas temperature (ro-vibrational transitions of OH, present at trace concentrations), and the populations of different excited states. Model predictions at 1.7x10$^{13}$ cm$^{-3}$ electron density (within the range estimated experimentally) are in good agreement with measurements (deviations $<$ 10{\%}) of (i) the excitation spectrum and the excitation temperatures (2795 $\pm $ 115 K, obtained from the Boltzmann-plot of the excited state populations, with energies lying between 22.7 and 24.2 eV), (ii) the power coupled to the plasma ($\sim $ 180 $\pm $ 10 W), and (iii) the gas temperature ($\sim $ 1700 $\pm $ 100 K). We discuss the extreme dependence of model results (particularly the gas temperature) on the power coupled to the plasma. [Preview Abstract] |
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PR1.00066: ABSTRACT WITHDRAWN |
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PR1.00067: Kinetic simulations of artificial plasma material structures Jan Trieschmann, Thomas Mussenbrock Artificially structured materials with underlying spatial periodicity (photonic crystals) are known for their unique electromagnetic properties. These materials allow to restrict propagation of electromagnetic waves within certain frequency ranges, in particular in the microwave regime. Electromagnetic bandgaps as well as complex waveguide structures can be achieved. In this contribution we study the influence of microplasmas on the electromagnetic behavior of these metamaterials. We show that the electromagnetic wave propagation can be completely suppressed by activating the microplasmas. In order to understand the interaction in detail, we investigate the electromagnetic response of a bulk plasma as well as a one-dimensional array of plasmaslabs by means of self-consistent kinetic simulations. Hereby we find that fully plasma based photonic crystals indeed can be achieved, enabling for the unique switchable manipulation of electromagnetic waves in the microwave regime. [Preview Abstract] |
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PR1.00068: Ionization coefficient measurements in DC microplasmas Ilija Stefanovic, Thomas Kuschel, Joerg Winter, Dragana Maric, Zoran Lj. Petrovic While steady state Townsend discharges may provide data for ionization coefficients those are often not as accurate as those produced in dedicated pulsed current growth experiments. In this paper we show that one may be able to measure ionization coefficients in DC microdischarges that are of excellent quality. Measurements were made for argon and argon/nitrogen mixtures with different gas flow rates. The technique based measuring the spatial profile of emission a Townsend discharge. In spite of having the drift length of only 1 mm, excellent agreement has been found between our new measurements and the data for low-pressure, larger dimension (2-4cm) discharges in argon (Jelenak \textit{et} \textit{al}) for the $E/N$ in the range from 300 Td to 4000 Td, where $E/N$ is normalized electrical field strength. Below 300 Td our measured values are larger then those by Jelenak \textit{et} \textit{al}. This discrepancy with previous measurements will be discussed. The influence of the gas flow-rate and nitrogen concentration on the radial discharge profile in the Townsend mode will also be presented and discussed. Jelenak \textit{et al} 1993 \textit{Phys. Rev.} E \textbf{47} 3566 [Preview Abstract] |
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PR1.00069: Investigating voltage recovery after breakdown supercritical nitrogen Aram Markosyan, Jin Zhang, Bert van Heesch, Ute Ebert We simulate the thermal shock and induced pressure waves caused by electrical breakdown of supercritical nitrogen. The goal is to investigate the temperature evolution after breakdown, thus predicting the recovery rate of a plasma switch based on supercritical liquids. The system of fluid equations is used to obtain the spatial and temporal evolution of liquid density, pressure, velocity and energy. We compare simulation and experimental results. [Preview Abstract] |
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PR1.00070: Influence of gas composition on characteristics of self-organized pattern formation observed in atmospheric DC glow discharge using liquid anode Naoki Shirai, Satoshi Uchida, Fumiyoshi Tochikubo Non-thermal plasma in and with liquids has attracted considerable interest for its potential use in a wide range of applications. In particular, the use of a discharge with a liquid as an electrode for analytical techniques and material processes has been reported. Previously, we investigate fundamental characteristics of atmospheric dc glow discharge using liquid electrode with miniature helium flow. Especially, when liquid anode discharge is generated, self-organized luminous patterns are observed on the liquid surface at a creation condition. Although the mechanisms of this pattern formation have not understood completely, we assume that the patterns are dependence on negative ion in the discharge from previous results. In this study, we feed oxygen gas flow to atmospheric dc discharge using liquid anode in order to investigate the influence of negative ion on the condition of self-organized pattern formation. When oxygen gas flow is fed to the discharge space, anode luminous patterns are changed from ring patterns to several dots patterns. Therefore the pattern formation may depend on the negative ion in the discharge. It presumes that a certain reaction such as generation and quenching of electron has occurred on the anode surface. [Preview Abstract] |
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PR1.00071: Atmospheric negative corona discharge using a Taylor cone as liquid electrode Ryuto Sekine, Naoki Shirai, Satoshi Uchida, Fumiyoshi Tochikubo We examined characteristics of atmospheric negative corona discharge using liquid needle cathode. As a liquid needle cathode, we adopted Taylor cone with conical shape. A nozzle with inner diameter of 10 mm is filled with liquid, and a plate electrode is placed at 10 mm above the nozzle. By applying a dc voltage between electrodes, Taylor cone is formed. To change the liquid property, we added sodium dodecyl sulfate to reduce the surface tension, sodium sulfate to increase the conductivity, and polyvinyl alcohol to increase the viscosity, in distilled water. The liquid, with high surface tension such as pure water could not form a Taylor cone. When we reduced surface tension, a Taylor cone was formed and the stable corona discharge was observed at the tip of the cone. When we increased viscosity, a liquid filament protruded from the solution surface was formed and corona discharge was observed along the filament at position 0.7-1.0 mm above from the tip of the cone. Increasing the conductivity resulted in the higher light intensity of corona and the lower corona onset voltage. When we use the metal needle electrode, the corona discharge depends on the voltage and the gap length. Using Taylor cone, different types of discharges were observed by changing the property of the liquid. [Preview Abstract] |
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PR1.00072: Plasma-Generated Reactive Species in physiological Solutions Malte U. Hammer, Helena Tresp, Ansgar Schmidt-Bleker, J\"orn Winter, Klaus-Dieter Weltmann, Stephan Reuter Plasma-generated reactive species, like ROS and RNS, in liquids are essential for plasma medicine caused by their role in mammalian systems. Especially free radicals and nitric monoxide are important. Here the focus is set on plasma-generated reactive species in physiological solutions such as cell culture medium, sodium chloride solution, and phosphate buffered saline. The detection of free radicals was performed via electron paramagnetic resonance (EPR) spectroscopy. Additionally electro chemical detection for pH value and concentration of H$_{2}$O$_{2}$ was realized in parallel to each experiment. Because nitric oxide is rapidly oxidized to nitrate and/or nitrite by oxygen, the measurement of nitrate and nitrite concentration as the end products of NO hold as an index for the integrated nitric oxide production. Nitrite and nitrate play a key role in plasma-treated liquids. For this work a colorimetric assay was used for nitrate and nitrite concentrations measurements. The control of species, which can diffuse into the effluent of an atmospheric pressure plasma jet, is necessary. A gas curtain was build and its effect on reactive species production in liquids was investigated. The gas curtain was used with varying ratios of nitrogen and oxygen as shielding gas. [Preview Abstract] |
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PR1.00073: Optical Emission Studies of Micro-Plasma Balls Formed from Laser Induced Breakdown in Water L. Huwel, O. Finard, R. Haydar, E.B. Jones, T.J. Morgan, W. Graham We present experimental results on the optical emission resulting from nanosecond pulse laser induced breakdown in distilled water. A Q-switched 1064 nm wavelength Nd:YAG laser is focused into a water cell and light is observed at 90 degrees to the laser beam propagation axis using two synchronized intensified-CCD cameras and a spectrometer. Both temporal and spatial emission dependence have been recorded. Signal is observed up to 500 ns after ignition. The spatial extent of the emission is about 3.5 mm and the center-of-emission intensity propagates away from the laser with delay time. The emission data reveal a disconnected string of micro-plasma balls along the laser propagation axis of size tens of microns resulting from a single laser shot, and correlated in time and space. Detailed analysis of the structure and time evolution of the data will be presented at the conference including spectroscopic results. [Preview Abstract] |
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PR1.00074: Plasma formation inside deformed gas bubbles submerged in water Bradley Sommers, John Foster Plasma formation in liquids produces highly reactive products that may be desirable for a variety of applications, including water purification and waste processing. The direct ignition of plasma in these environments, however, is limited by the large breakdown strength of liquids, which imposes severe voltage and energy requirements on the design of practical devices. One way to address this issue is by first igniting plasma in gas bubbles injected into the water. These bubbles provide an environment with higher reduced electric field (E/N) that is more suitable for plasma formation. If the same bubbles can be excited into strong distortions of their shape and volume, then it is possible to further alter E/N, both by field enhancement at the bubble's highly distorted dielectric interface (via E) and by fluctuations in its internal gas pressure (via N). This principle is investigated by trapping a single bubble at the node of a 26.4 kHz underwater acoustic field and driving it into violent oscillations using an A.C electric field. A third high voltage needle is placed nearby and used to ignite plasma in the bubble at various points during its oscillation. The bubble response is captured using a high speed camera capable of up to 30,000 frames per second. [Preview Abstract] |
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PR1.00075: Time Resolved Spectroscopy: Dynamic Study of a Dielectric Barrier Discharge Plasma Sarah Gucker, Maria Garc\'Ia, Benjamin Yee, John Foster Atmospheric pressure plasmas have prompted strong interest due to their potential application to a wide range of fields and technologies (such as materials processing and medical applications). When these atmospheric discharges are created within a gas bubble and liquid water medium, vast quantities of short-lived, highly oxidative particles are produced. These plasmas have been shown to possess the capacity to decompose aromatic compounds and other contaminants, thereby leading to the sterilization of the water. Here, the results from a dielectric barrier discharge plasma jet in liquid water operating on a variety of gases are presented. These plasmas display several distinct physical characteristic over a power cycle; therefore, the chemical dynamics taking place in the liquid is also expected to have a similar time dependence. Non-evasive, dynamic methods are necessary to probe these dynamic systems. Presented here are time-resolved optical emission spectroscopy measurements aimed at quantifying the fundamental characteristics of the plasma such as temperature and density- and how they evolve throughout the discharge cycle. [Preview Abstract] |
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PR1.00076: Ambipolar diffusion in strongly electronegative plasma Valeriy Lisovskiy, Vladimir Yegorenkov This paper presents the treatment of the analytical model of ambipolar diffusion in quasi-neutral electronegative plasma consisting of electrons, a single species of negative ions and a single species of positive ions, which was proposed by Thompson J.B. [Proc. Phys. Soc., 73 (1959) 818]. We demonstrate that in plasma with the concentration of negative ions more than 10 times exceeding that of electrons one has to take into account the mobility of negative and positive ions. We established that in strongly electronegative plasma when both conditions $\alpha $~$>>$~1 ($\alpha $~=~$n_{-}$/$n_{e})$ and $\mu _{e}$~$<<$~$\alpha \cdot \mu _{-}$ hold, the ambipolar diffusion coefficients for positive and negative ions as well as electrons are close to the coefficients of their free diffusion. Consequently in strongly electronegative plasma the diffusion ceases to be ambipolar (even for large plasma concentration) and becomes to be free, i.e. charged particles of different species and sign cease to affect the diffusion motion of each other. [Preview Abstract] |
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PR1.00077: Study of dust particle charge screening within the nonlocal charging theory Natalia Demkina, Ivan Derbenev, Anatoly Filippov In papers [1,2] it was shown that in a non-equilibrium plasma with one type of positive ions the dust particle potential was described by two exponentials, and for the case of three types of ions the potential was described by the superposition of three exponentials with three different screening constants [3]. In the present paper the EEDF non-locality influence on a dust particle potential distribution is considered in a two-component plasma of noble gases and nitrogen on the basis of a nonlocal charging model which consists of the electron and ion balance equations, the Poisson equation and the electron energy balance equation, obtained from the non-local momentum method [4]. It was found that the potential distribution in the vicinity of a dust particle is described by the sum of three exponentials. The screening constants and the pre-exponential coefficients are defined by the plasma parameters and the electron and ion sinks.\\[4pt] [1] A.V. Filippov et al., JETP Letters 81 (2005) 146.\\[0pt] [2] A.V. Filippov et al., JETP 104 (2007) 147.\\[0pt] [3] I.N. Derbenev and A.V. Filippov, Plasma Phys. Rep. 36 (2010) 105.\\[0pt] [4] A.V. Filippov et al, Plasma Phys. Rep. 29 (2003) 190. [Preview Abstract] |
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PR1.00078: Anomalous electron density behaviour in dusty plasma afterglow Irina Schweigert, Andrey Alexandrov The anomalous increasing of electron density in RF discharge plasma with strong dust contamination after discharge switching-off was observed in experiment (J. Berndt et al, Plasma Sources Sci. Technol., 2006, {\bf 15}, 18). A possible mechanism of this is the discharging of negatively charged dust particles in afterglow plasma. The existing theoretical models of dust discharging due to ion flux show that it is not efficient to provide the observed electron density growth. In this work, it is assumed that the more fast mechanism of dust discharging is electrons desorption from dust surface. The afterglow of heavy dusted plasma in argon was simulated by PIC-MCC method, including electrons desorption from dust and metastable argon atoms kinetics. The analysis of the electron energy distribution function shows, that the fast electrons rapidly depart from the plasma volume, thus leading to dust surface potential magnitude and hence the dust charge drop. As a result, the electrons are released from dust particles, providing the anomalous electron density increasing. The metastable pooling ionization enlarges the electron density and temperature, but cannot provide the anomalous peak of electron density. [Preview Abstract] |
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PR1.00079: Electrical asymmetry effect for controlling the transport of micrometer-sized particles in capacitively coupled plasmas Shinya Iwashita, Edmund Schuengel, Julian Schulze, Giichiro Uchida, Kazunori Koga, Peter Hartmann, Masaharu Shiratani, Zoltan Donko, Uwe Czarnetzki We have developed a novel method to control the dust particle transport in capacitively coupled plasmas via the electrical asymmetry effect (EAE) [1]. At low pressures the EAE allows controlling the spatial potential profile and the ion density distribution by adjusting the phase angle between a fundamental frequency and its second harmonic, resulting in control of forces exerted on dust particles such as electrostatic and ion drag forces. We report the experimental results of this method using SiO$_{2}$ particles of 1.5 $\mu $m in size, which are inserted into an argon discharge. Initially dust particles tend to be confined at the sheath edge near the bottom electrode, and the change of their equilibrium position with plasma due to the adiabatic phase shift can be well understood by the electric field profile obtained from a simple analytical model. By applying the abrupt change of phase angle from 90\r{ } to 0\r{ } dust particles are transported between both sheaths through the plasma bulk [1]. Based on the model of this transport [1] the potential profile can be obtained by experimental results.\\[4pt] [1] Iwashita S et al., Plasma Sources Sci. Technol. \textbf{21} (2012) 032001. [Preview Abstract] |
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PR1.00080: The technique to measure the internal temperature of particulates/droplets: Two-color laser induced fluorescence Daisuke Ogawa, Lawrence Overzet, Matthew Goeckner In a multi-phase plasma (such as dusty plasma and plasma spray etc.), it is important to know the internal temperature of particulates. This is because the temperature affects chemical properties of the particulates. For example, it affects the chemical reaction rate, the material state, the vapor flux etc. Among some techniques to measure the temperature, we selected the technique called two-color laser induced fluorescence (2cLIF) in order to find the droplet temperature in argon plasma. In fact, the use of two wavelengths for the particulate pyrometery is known. This technique uses the ratio of two fluorescent intensities which emit from dye (rhodamine b) in the droplets. The ratio cancels out some unknown parameters (optical constants, incident intensity etc.) and depends on the particulate temperature. Our preliminary measurements showed that the ratio of the intensity at 580 to 605 nm monotonically decreased as the liquid temperature increased. Currently, we found the temperature decreased approximately 40 to 70 degrees C at low pressure (100 mTorr, no plasma) compared to droplets injected to atmospheric pressure. In our poster, the theory behind the technique and the actual measurements with the technique will be shown. [Preview Abstract] |
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PR1.00081: Hole current confinement effects in elliptic tokamak plasmas with triangularity Pablo Martin, Enrique Castro, Julio Puerta The effect of hole currents in tokamak plasma confinement is analyzed here. Banana width and inward pinch due to toroidal electric field are considered for tokamak plasmas with the same ellipticity and triangularity but with or without hole currents. The banana width increases with the banana amplitude for plasmas with no-hole current, however, with hole current the maximum width happens for intermediate amplitudes. The plasma ellipticity and triangularity influences also the results, which will be shown analytic and graphically. All our calculations show that in the limit of large aspect ratio with circular plasmas shape the well known Ware Pinch is recovered. Positive triangularity will be only considered in this work. The analyses were carried out using the profiles of the toroidal density current in JT-60U and JET. [Preview Abstract] |
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PR1.00082: Secondary Electron Yield from Plasma-Treated Niobium Milos Basovic, Rajintha Tiskumara, Ana Samolov, Filip Cuckov, Svetozar Popovic, Leposava Vuskovic Future room-size linear accelerators, incorporated in compact light sources and medical therapeutic systems, will use Superconducting Radio Frequency (SRF) cavities to achieve the required beam energy over limited distances. The inhibiting phenomena in these designs are among others resonant multipactor discharges. Present study is intended to help complex cavity surface modification leading to mitigation of multipactors. Behavior of the multipactor discharges depends on the microwave field configuration and on the Secondary Electron Yield (SEY) from the cavity surface. Contaminated surfaces show substantial increase of SEY. Our aim is to reduce SEY using \textit{in-situ} surface treatment with microwave discharge. We have developed an experimental set up to study the effect of plasma surface treatment on SEY. The system is designed to measure energy distribution of SEY on coin like samples under different incident angles. Clean, contaminated, and plasma-treated samples are placed in a carousel target manifold. Samples and the manifold are manipulated by robotic arm providing multiple degrees of freedom of a whole target system. Here we are reporting our progress and preliminary results from testing the Nb surface samples. [Preview Abstract] |
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PR1.00083: Rotating arc plasma characteristics in the presence of methane flame Nakyung Hwang, Dae Hoon Lee, Kwan Tae Kim, Young-Hoon Song Plasmas can ignite and stabilize flames under extreme conditions and have already been applied in practical combustors, but further studies are needed to elucidate the complex flame--plasma interactions. Here, we present the results of an experimental study on the interactions between a methane flame on a rotating arc plasma, with particular focus on the influence of flame conditions on plasma generation. A gas chromatograph, chemiluminescent NO$_{x}$ analyzer, optical emission spectrograph, and intensified charge-coupled device were used to monitor product gases (CO$_{2}$, H$_{2}$, CO, C$_{2}$, C$_{3}$, and NO$_{x})$ with and without the plasma and also plasma characteristics (arc length, angular speed, and peak voltage) under different flame equivalence ratios $\Phi$. The results confirmed that the rotating arc indeed stabilized the flame and extended both flammability limits. In addition, the rotating arc was pushed upward and out of the reactor for rich and lean mixtures. The highest NO$_{x}$ concentration was obtained at the lower flammability limit in the presence of the plasma, but at $\Phi$ = 1.0 without the plasma. [Preview Abstract] |
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PR1.00084: Current Distribution Characterization and Circuit Analysis of a High Energy Pulsed Plasma Deflagration Keith Loebner, Flavio Poehlmann, Mark Cappelli Measurements and analysis of the transient current density within a coaxial electromagnetic plasma accelerator operating in a pulsed deflagration mode are presented. Current measurements are performed using an axial array of dual-Rogowksi coils in a balanced circuit configuration. An equivalent circuit model of the accelerator is formulated and compared with experimental data. Current distribution measurements were carried out over a wide range of operating conditions and compared with the equivalent circuit model in order to determine the governing physics of the discharge and verify the existence of a deflagration at all tested conditions. [Preview Abstract] |
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PR1.00085: Effect of Li in the ITER neutralizer Franck Dur\'e, Tiberiu Minea, Gilles Maynard, Agustin Lifschitz Recently, a new design for the neutralizer stage of the ITER neutral beam injector has been proposed. Using Li instead of D2 gas. The gas load could be reduced by the use of a metal vapor easily frozen by surfaces and cryogenic pumping limitations would be exceeded allowing the accumulation of a thicker layer. This characteristic depends on the vaporization temperature of the lithium at low pressure ($\sim $0.1Pa). Calculations showed the efficiency of the beam neutralization and the beam focusing. PIC simulations with the code OBI-2 (Orsay Beam Injector--2D) have shown the formation of a plasma between the neutralizer plates. It was also found that the positive ions of the plasma screen efficiently the beam space charge so that the beam divergence is reduced. The injection of Li has been investigated and compared to D2 one. Parametric study of the Li based neutralizer has been performed since the length and/or density of Li injected can be modified. The Li density profile has been estimated through Monte-Carlo 3D code developed in the LPGP. The resulted profile has been implemented as an input of the PIC-MCC code and results are presented. [Preview Abstract] |
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PR1.00086: PLASMA DATA EXCHANGE PROJECT |
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PR1.00087: Comparisons of sets of electron-neutral scattering cross sections and calculated swarm parameters in N2 and H2 Leanne Pitchford, G.J.M. Hagelaar, S. Pancheshnyi, M.C. Bordage, L.L. Alves, C.M. Ferreira, S.F. Biagi, Y. Itikawa, A.V. Phelps The GEC Plasma Data Exchange Project is an informal effort on the part of the low temperature plasma community to organize the collection, evaluation, and distribution of data both for modeling and for interpretation of experiments. In the context of this project, we present a description of the four sets of independently-compiled, electron-neutral scattering cross sections for N2 and for H2 presently available on the open-access LXCat site (www.lxcat.net). These sets are complete in that the main momentum and energy loss processes are taken into account, if we can neglect internal excitation in the gas. Three of these sets were derived using the requirement that they be consistent with available experimental swarm data, and the fourth set consists of recommended values from beam experiments and theory. To assess the validity of each of these cross section sets for use in modeling low temperature plasmas, we calculated electron transport and rate coefficients using these cross sections as input and compared with measured values also available on the LXCat site. We will discuss the influence of rotational temperatures between 77 and 300 K, and we again confirm that a two-term Boltzmann solver yields results in very good agreement with Monte Carlo simulations. [Preview Abstract] |
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PR1.00088: Comparisons of sets of electron-neutral scattering cross sections and calculated swarm parameters in O2 Leanne Pitchford, M.C. Bordage, G.J.M. Hagelaar, S. Pancheshnyi, S.F. Biagi, Y. Itikawa, I. Kochetov, A. Napartovich, A.V. Phelps The purpose of this communication is to describe the four independently-compiled sets of electron-O2 scattering cross section sets that are presently available on the LXCat site (www.lxcat.net). Three of these cross section sets were assembled and adjusted for good agreement with swarm parameters, and the fourth set consists of recommended data resulting from an evaluation of beam experiments and available theoretical. The cross sections sets are intended to be ``complete'' in the sense that the major electron energy, momentum, and number changing processes are taken into account, but it should be noted that the electronically excited levels included in the compilations differ from one cross section data set to another. We use these different data sets as input to a Boltzmann equation solver and calculate the electron transport and rate coefficients. Comparisons of calculated transport and rate coefficients with experimental data will be presented for each cross section set. We note that the consistency of the experimental data in O2 is not as good as the data for H2 and N2 (see previous poster). Some cross section data for electron scattering from Reactive Oxygen Species (ROS) are also available on LXCat. [Preview Abstract] |
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PR1.00089: Interpretation of calculated transverse and longitudinal diffusion for electrons in gases A.V. Phelps, G.J.M. Hagelaar Ratios of transverse $D_T$ and longitudinal $D_L$ diffusion coefficients to mobility $\mu$ and mean energies for electrons in gases are calculated for a wide range of $E/N$ for He, Ar, Xe, H$_2$, N$_2$, and CO. These transport coefficients are determined from spatial-gradient expansion, two-term spherical harmonic theory\footnote{J. H. Parker and J. J. Lowke, Phys. Rev. {\bf 181}, 290 (1969).}$^,$\footnote{G. J. M. Hagelaar (unpublished codes, 2012).} and from Monte Carlo simulations.\footnote{Ibid.}$^,$\footnote{S. F. Biagi, Nucl. Instr. and Meth. A {\bf 421}, 234 (1999).} As predicted by simplified theory\footnote{Parker, Lowke, Op. cit.} applied to the heavier rare gases, e.g., Ar and Xe, the ratio $D_T$/$D_L$ reaches 7 to 10 at mean electron energies for which the momentum transfer cross sections are rapidly rising functions of energy. Comparisons are made of simplified\footnote{Ibid.} and detailed predictions of $D_L$/$D_T$ values for N$_2$ and CO at low electron energies where the effects of scattering by the quadrupole potential of N$_2$ versus the dipole/quadrupole potential of CO are expected to be observed. [Preview Abstract] |
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PR1.00090: Quantemol-N calculation of electron molecule cross sections and related parameters Will Brigg, Adam Williams, Derek Monahan, Jonathan Tennyson Quantemol-N was originally developed as a wrapper for the UK Molecular R-Matrix codes, significantly accelarating data production rates for electron molecule collision calculations. Since its conception Quantemol-N has continuously been developed in the direction of the plasma industry, with many features being added to produce extended cross sections sets and related parameters. Recent additions include the calculation of differential cross sections, which provide momentum transfer and rotational excitation cross sections. These are used in turn to provide transport coefficients for verification of swarm calculations. Electron collisions with water have been used as a test bed. The code has also been generalised to calculate cross sections for aligned molecules, for example ones trapped on surfaces. [Preview Abstract] |
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PR1.00091: WORKSHOP POSTERS |
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PR1.00092: Noninertial Multirelativity Florentin Smarandache We firstly propose an extension of Einstein's thought experiment with atomic clocks of the Special Theory of Relativity: considering non-constant accelerations and arbitrary $3D$-curves for both a particle's speed and trajectory inside the rocket and respectively the rocket's speed and trajectory. And secondly we propose as research multiple reference frames $F_{1}, F_{2}$\textit{, {\ldots}, F}$_{n}$ moving on respectively arbitrary $3D$-curves $C_{1}, C_{2}$\textit{, {\ldots}, C}$_{n }$with respectively arbitrary non-constant accelerations $a_{1}, a_{2}$\textit{, {\ldots}, a}$_{n}$ and respectively initial velocities $v_{1}, v_{2}$\textit{, {\ldots}, v}$_{n}$. The reference frame $F_{i }$is moving with a nonconstant acceleration $a_{i }$and initial velocity v$_{i}$ on a $3D-$curve $C_{i}$ with respect to another reference frame $F_{i+1}$ (where \textit{1 $\le $ i $\le $ n-1}). [Preview Abstract] |
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PR1.00093: The effect of plasma jet on morphology of the apoptosis cancer cell Shahriar Mirpour, Maryam Nikkhah, Somaye Pirouzmand, Hamid Reza Ghomi In recent years, many studies have been carried out to understand the effect of non-thermal plasma on cancer cells. The previous studies showed that non-thermal plasma has apoptosis effect on cancer cells. Also they discovered that after plasma treatment three distinct regions (Death cells, Void zone and live cells) were observed in wells treated [1]. The aim of this paper is to study the effect of plasma jet on these three regions. For this purpose a variable voltage power supply with 20 kHz frequency are used experimentally. The results showed the detached cells rate were increased by increasing the voltage. \\[4pt] [1] A. Shashurin, M. Keidar, S. Bronnikov, R. A. Jurjus, and M. A. Stepp, Appl. Phys. Lett. 93, 181501 (2008), DOI:10.1063/1.3020223 [Preview Abstract] |
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PR1.00094: Verification of particle-in-cell simulations with Monte Carlo collisions M.M. Turner Verification is the process of accumulating evidence that a computer simulation code is correct. For computer simulations in the physical sciences, this is usually understood to mean demonstrating that the results of a simulation correctly correspond to a solution of the underlying physical model. A particularly powerful way to accomplish this is by comparison with an exact solution or solutions of the physical model. When no single solution that exercises every part of the simulation programme exists, one can seek to develop a suite of solutions that in combination exercise all parts of the code. When a code correctly reproduces such a suite of solutions, one can feel a high degree of confidence that no errors are present. This paper discusses the verification of a particle-in-cell simulation with Monte Carlo collisions using this approach. [Preview Abstract] |
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