Bulletin of the American Physical Society
64th Annual Gaseous Electronics Conference
Volume 56, Number 15
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session QRP1: Poster Session II: Plasma Appl. II; Charged Particle Collisions II; Plasma Sources II; Plasma Data Exchange Project; Plasma Diag. Tech. II; Plasma Modeling/Simulations II; Basic Plasma Phenomena II |
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Room: Exhibit Hall AB |
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QRP1.00001: PLASMA APPLICATIONS II |
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QRP1.00002: ABSTRACT WITHDRAWN |
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QRP1.00003: Air Plasma Source for Biomedical Applications J. Henriques, E. Tatarova, F.M. Dias, C.M. Ferreira, B. Gordiets Plasma interactions with living matter are presently at the frontiers of plasma research and development. Plasmas contain numerous agents that influence biological activity. They provide essentially two types of biocidal species: reactive species, such as oxygen atoms that lead to lethality of micro-organisms through erosion, and UV radiation that can damage the DNA strands. In this work we investigate a surface wave (2.45 GHz) driven discharge plasma in air, with a small admixture of water vapor, as a source of ground state O($^{3}$P) oxygen atoms, NO molecules and UV radiation. A theoretical model describing both the wave driven discharge zone and its flowing afterglow is used to analyze the performance of this plasma source. The predicted plasma-generated NO(X) and O($^{3}$P) concentrations and NO($\gamma )$ radiation intensity along the source are presented and discussed as a function of the microwave power and water vapor percentage in the gas mixture. To validate the theoretical predictions, the relative concentrations of species have been determined by Mass Spectrometry, Fourier Transform Infrared Spectroscopy and Optical Spectroscopy. Acknowledgment: This work was funded by the Portuguese Foundation for Science and Technology, under research contract PTDC/FIS/108411/2008. [Preview Abstract] |
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QRP1.00004: Influence of Atmospheric Pressure Torch Plasma Irradiation on Plant Growth Yusuke Akiyoshi, Nobuya Hayashi, Satoshi Kitazaki, Kazunori Koga, Masaharu Shiratani Growth stimulation characteristics of plants seeds are investigated by an atmospheric discharge irradiation into plasma seeds. Atmospheric pressure plasma torch is consisted of alumina ceramics tube and the steel mesh electrodes wind inside and outside of the tube. When AC high voltage (8 kHz) is applied to the electrode gap, the barrier discharge plasma is produced inside the alumina ceramics tube. The barrier discharge plasma is blown outside with the gas flow in ceramics tube. Radish sprouts seeds locate at 1 cm from the torch edge. The growth stimulation was observed in the length of a stem and a root after the plasma irradiation. The stem length increases approximately 2.8 times at the cultivation time of 24 h. And the growth stimulation effect is found to be maintained for 40 h, after sowing seeds. The mechanism of the growth stimulation would be the redox reaction inside plant cells induced by oxygen radicals. [Preview Abstract] |
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QRP1.00005: Particle-in-Cell simulations of filamentary structures formation in DBD-tissue interaction Alexandre Likhanskii, Peter Messmer Recent studies demonstrated high potential of the dielectric barrier discharge (DBD) plasmas for medical applications, such as sterilization or tissue regeneration. Despite intensive experimental studies have been conducted, the mechanism of plasma-tissue interaction still remains unclear. One of the open questions for the plasma-medical applications is the mechanism of filamentary structures formation in plasma and their interaction with tissues. Since formation of filaments is a purely kinetic effect, this issue needs to be addressed using kinetic, Particle-In-Cell simulation approach. We will present results of such numerical study. We performed 2D simulations of multiple streamers generation in atmospheric air using Tech-X's 2D/3D hybrid simulation tool VORPAL. We will demonstrate the resolution of the filamentary structure and will report the plasma properties. We will also address the plasma-induced effects on the tissue. [Preview Abstract] |
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QRP1.00006: Modelling Positron Transport in Biological Media -- Towards a Positron Dosimetry Z. Petrovic, G. Garcia, R. White, M. Brunger, J. Sullivan, S. Buckman We have a combined program of measurement, analysis and modeling for positron interactions with biologically relevant molecules. The measurement involves direct determination of positron scattering cross sections including, most importantly, positronium formation, which are then combined into a set of cross sections and, together with energy loss spectra, serve as the input to a number of modeling approaches. These include both Monte Carlo and Boltzmann approaches and, ultimately, they aim to model interactions in liquid systems in order to best approximate tissue equivalents. Results for the archetypical system, water, will be presented as well as preliminary studies on other biologically relevant molecules. [Preview Abstract] |
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QRP1.00007: Removal of Chronic Intravascular Blood Clots using Liquid Plasma Jae-Chul Jung, Myeong Yeol Choi, Il Gyo Koo, Zengqi Yu, George J. Collins An electrical embolectomy device for removing chronic intravascular blood clots using liquid plasma under saline environment was demonstrated. We employed a proxy experimental blood clot model of deep vein thrombosis (DVT) and actual equine blood clot. Thermal damage to contiguous tissue and the collagen denaturing via the plasma irradiation were investigated by histological analysis using birefringence of the tissue and verified by FT-IR spectroscopic study, respectively, which showed the high removal rate up to 2 mm per minute at room temperature and small thermal damage less than 200 $\mu$m. [Preview Abstract] |
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QRP1.00008: Disinfection of Staphylococcus Aureus by pulsed non-thermal atmospheric plasma jet Shahriar Mirpour, Mahmood Ghoranneviss, Farhad Shahgoli The aim of this paper was to study the effect of low-temperature atmospheric plasma jet on non-pathogenic bacteria's colonies. In this regard, Germicidal effect of time and distance of ICP He and He/N2 plasma jet on Staphylococcus Aureus were reported. The gas discharges were generated by a 40 KHz high voltage power supply which led to the inductively coupled plasma. The results showed that He/N2 enhance the sterilization time in comparison of He plasma. To the best of our knowledge this is the first study which has compared the effect of sterilization of ICP Helium and Helium-Nitrogen plasma in listed conditions. Also, the distance dependence showed that the germicidal effect was not linear the distance of electrode and sample. The protein leakage test and SEM of bacteria morphology confirmed the sterilization effect of non-thermal atmospheric pressure plasma jet. [Preview Abstract] |
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QRP1.00009: State of Upright Metal-Coated Carbon Nanotwists Treated by Dielectric Barrier Discharge Yuki Sugioka, Yoshiyuki Suda, Hirofumi Takikawa, Hideto Tanoue, Hitoshi Ue, Kazuki Shimizu, Yoshito Umeda We have used carbon nanotwists (CNTws) as a base material of field emitter (FE), and CNTws were treated with dielectric barrier discharge (DBD) to make CNTws stand up on substrate [1]. In this study, we coated metal on the surface of FE [2] and then treated the FE with DBD. FE was prepared by screen-printing of the CNTw paste to Si or indium-tin-oxide (ITO) substrate. Cu or Pt film was coated on the FE surface by an ion coater, and Al film coated by vacuum evaporation. A thickness was 10 nm. The experimental conditions for the DBD treatment were as follows: discharge gas, N$_{2}$; gas flow rate, 2 L/min; discharge output power, 300 W; process time, 30 s; and gap distance, 0.75 mm. Lengths of upright CNTws ($L_{CNTw})$ between dots with Al, Cu, and Pt were 2.7 $\mu $m, 6.9 $\mu $m, and 8.1 $\mu $m, respectively. $L_{CNTw}$ on the dot with Al, Cu, and Pt coatings were 2.4 $\mu $m, 2.3 $\mu $m, and 1.7 $\mu $m, respectively. The FE characteristics of the CNTw coated with Cu film were as follows: the threshold electric field, 2.4 V/$\mu $m; the emission current density at 9 V/$\mu $m, 555.8 $\mu $A/cm$^{2}$. \\[0pt] [1] Y. Hosokawa, et al., \textit{J. Phys. D: Appl. Phys.}, \textbf{41}, 205418, 2008 \\[0pt] [2] Whikun Yi, et al., \textit{Adv. Mater.,} \textbf{14}, 1464, 2004 [Preview Abstract] |
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QRP1.00010: Nanoparticle network growth in arc generated fireballs of silicon powder Tsuyohito Ito, Mark Cappelli Recently we observed buoyant fireballs by arc igniting silicon that drift in air for several seconds and postulated that the low aggregate density was attributed to the formation of a network of nanoparticles that must completely surround the burning silicon core, trapping the heated vapor generated as a result of particle combustion [Ito et al, Phys Rev E 80, 067401 (2009)]. In this study, we describe the capturing of several of these fireballs in flight, and have confirmed this nanostructure by scanning electron microscopy. The nanoparticle network is found to have an unusually high porosity ( $>$ 99{\%}). It is also found that the overall nanoparticle network size is determined by the size of the molten silicon core, independent of the time of capture. In other words, the size and structure of the surrounding nanoparticle network seems to be limited by the vapor flux from the molten silicon core, which is determined by its surface area (size). Further details of both the experiments and analysis will be presented at the conference. [Preview Abstract] |
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QRP1.00011: A plasma-approach for catalyst-free carbon nanotubes growth on arbitrary mechanically-written Si features Shailesh Kumar, Igor Levchenko, Kostya (Ken) Ostrikov Synthesis of carbon nanotube arrays commonly involves complex multi-stage formation of the required patterns of catalyst nanoparticles. Integration of nanotubes into silicon-based nanodevice platforms ultimately requires completely catalyst-free growth. The presence of catalyst particles introdces the contact losses. Moreover, its catalytic activity is also challenging during the nucleation and growth process. A novel, uniquely plasma-enabled has been demonstrated for catalyst-free, and very fast growth of long vertically-aligned multiwalled carbon nanotubes arranged into dense high-quality arrays~strictly within arbitrary mechanically-written~patterns. This phenomenon is attributed to the unique features of the low-temperature plasma in direct contact with the hierarchically structured Si surface. This unique, yet simple and environmentally-benign plasma-enabled approach paves a pathway for integration of catalyst-free carbon nanostructures directly into a nanodevice platform for the future applications. [Preview Abstract] |
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QRP1.00012: Quantum chemical investigation for Chemical dry etching by flowing NF$_{3 }$into H$_{2}$ down flow plasma Toshio Hayashi, Kenji Ishikawa, Makoto Sekine, Masaru Hori, Akihiro Kono, Koukou Suu The molecular orbital calculations were carried out in order to clarify the reaction schemes of the chemical dry etching using H$_{2}$ down flow plasma and NF$_{3}$ flowing. It was found that not only HF formation but also F atom generation takes place. And this F atom generation mechanism is very important to realize the highly selective SiO$_{2}$ etching process. Probably F formation is suppressed under the three-body reaction regime and the higher gas flow rate of H$_{2}$ than that of NF$_{3}$. So, careful control of the pressure is a key factor. The examined reaction schemes do not only take place in the vapor phase but also in the condensed phase on the wafer surface. As a result, complex (NH$_{4})_{2}$SiF$_{6}$ is formed on the SiO$_{2}$ surface, and SiO$_{2}$ film is removed. This complex molecule is decomposed by elevating the wafer temperature to produce SiF$_{4}$ and the white powder based on NH$_{3}$-HF, which may be composed mainly by stratified n(NH$_{4}$F)$_{3}$ with C$_{3}$ symmetry axis. Increasing the wafer temperature moreover, up to 500 K, this white powder also decomposes to HF+NH$_{3}$. [Preview Abstract] |
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QRP1.00013: Etching rate and surface roughness of niobium samples and plasma properties of Ar/Cl$_{2}$ discharge in a SRF cavity. Janardan Upadhay, Svetozar Popovic, Leposava Vuskovic, Anne-Marie Valente, Larry Phillips Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. The crucial aspect of the technology development is dependence of the etching rate and surface roughness on the frequency of the power supply, pressure and power level during plasma processing. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. Plasma is generated in the asymmetric radiofrequency discharge between coaxial driven electrode and grounded cavity shell. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. We present the study of correlation between the measured local plasma properties and the etching rate/surface roughness. [Preview Abstract] |
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QRP1.00014: Suppression of film deposition in a plasma CVD system using gas flow Hirotaka Toyoda, Kazuki Keyamura, Tatsuo Ishijima In plasma-enhanced chemical vapor deposition, film deposition on undesirable surfaces sometimes becomes an issue. In this study, intentional suppression of film deposition in a plasma CVD system is examined with introduction of high-speed gas flow in the vicinity of the solid surface. In this study, microwave plasma is produced at total pressures of $\sim $10 Pa with C$_{6}$H$_{6}$ and rare gas (Ar or He). C$_{6}$H$_{6}$ is introduced through an independent gas inlet facing to the sample substrate. Ar gas is introduced along the substrate surface through a slit-structured gas inlet. Deposited film thickness is measured by a step profiler. Monotonic decrease in the deposition rate down to 10{\%} of initial (without Ar gas flow) value was observed at a Ar gas flow rate of 125 sccm iat a position of 1 cm away from the Ar gas inlet. By changing the rare gas species from Ar to He, effect of the gas flow on the C film suppression became less effective. This result suggests that momentum transfer between high speed rare gas flow and deposition precursors diffusing from the plasma is one of important factors. [Preview Abstract] |
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QRP1.00015: Application of Toroidal Magnetron Sputtering system: characteristics of ZnO:Al thin films Yonghyun Kim, Young-Woo Kim, Dae-Chul Kim, Jong-Sik Kim, Jung-Sik Kim To improve the disadvantages of the conventional magnetron sputter such as substrate heating by thermal radiation and damage of film surface by high energetic particles, etc., a newly designed Toroidal Magnetron Sputtering (TMS) system has been developed[1] and aluminum-doped zinc oxide (AZO) thin films were deposited on glass substrate at room temperature. The structural, electrical and optical properties of AZO films were investigated with DC power and oxygen gas ratio below 1 {\%} at a pressure of 1.7 mTorr. We obtained the AZO films with a resistivity of around 8.0x10$^{-4} \quad \Omega $ cm and an average transmittance of 90 {\%} in visible wavelength. Also the grain size of all AZO films kept about 30 nm, even though the different crystallinity. However, the mean free path of carriers was 1.5 to 2.5 nm and the carrier concentration was above 1x10$^{20}$ cm$^{-3}$ These results reveal that the mobility of AZO thin films does not depend on grain boundary scattering in our experiment. \\[4pt] [1] Thin Solid Films 518 (2010) 6650-6653 [Preview Abstract] |
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QRP1.00016: Oxygen transport through polyethylene terephthalate (PET) coated with plasma-polymerized acetylene at atmospheric pressure Erik Wemlinger, Patrick Pedrow, Manuel Garcia-P\'erez, Shyam Sablani Moser et al. have shown that oxygen transport through polyethyleneterephthalate (PET) is reduced by a factor of up to 120 when, at reduced pressure, hydrogenated amorphous carbon film with thickness less than 100 nm is applied to the PET substrate.\footnote{E.M. Moser, R. Urech, E. Hack, H. K\"{u}nzli, E. M\"{u}ller, \textit{Thin Solid Films}, \underline {317,} 1998, pp. 388-392.} Our work includes using atmospheric pressure cold plasma to grow a plasma-polymerized acetylene film on PET substrate and measuring reductions in oxygen transport. The reactor utilizes corona discharges and is operated at 60 Hz with a maximum voltage of 10 kV RMS. Corona streamers emanate from an array of needles with an average radius of curvature of 50 $\mu $m. The reactor utilizes a cylindrical reaction chamber with a vertical orientation such that argon carrier gas and acetylene precursor gas are introduced at the top then pass through the cold plasma activation zone and then through a grounded stainless steel mesh. Acetylene radicals are incident on the PET substrate and form plasma-polymerized acetylene film. [Preview Abstract] |
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QRP1.00017: Experimental and Computational Investigation of a Plasma Ion Accelerator with Multiple Magnetic Field Cusps Christopher Young, Mark Cappelli A cusped-field discharge produces efficient ionization by trapping electrons from an external cathode through magnetic mirroring between adjacent magnetic cusps. These discharges have applications in space propulsion, particularly at low power (under 200W). However, the underlying physics driving electron transport and ionization in these devices is still poorly understood. In the current study, the plasma potential of a 40--250 W cylindrical cusped-field discharge is characterized using a floating emissive probe. The potential exhibits a spatial structure that mimics visible light emission; elevated potential is observed in a surrounding conical region downstream of the discharge channel, concomitant with ion emission. The experimentally measured plasma potential is used in single-electron particle simulations to investigate transport processes associated with electron migration from the external cathode to the anode at the base of the discharge channel. [Preview Abstract] |
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QRP1.00018: CHARGED PARTICLE COLLISIONS II |
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QRP1.00019: Electronic density fluctuation associated to coherent plasmon excitations Juana Gervasoni, Silvina Segui, Nestor Arista In this work we analyze, in the frame of the coherent states, the fluctuation of the electronic collective modes associated with the wake potential generated by an external particle of charge Ze. This perturbation is described as coherent states of plasmons spatially localized in an average distance of the order of the velocity of the projectile divided by the plasmon frequency of the material. One of the most important features is that in all the cases, for different trajectories of the external particle, and for different structures of the material, the fluctuations are not negligible. In particular, we observe that due to the importance of the surface in nanostructured materials, the fluctuation of density is very sensitive to their geometry and composition, fact that must have taken into account for the nanodevices designs. [Preview Abstract] |
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QRP1.00020: Laser Electron-gamma-Nuclear Spectroscopy of Diatomic and Multiatomic Molecules Alexander Glushkov, Olga Khetselius, Andrey Svinarenko An important class of problems connected with modelling the cooperative laser-electron-gamma-nuclear phenomena in diatomic and multiatomic molecules is now of a great interest. It includes a calculation of the probabilities and energies of the mixed gamma-nuclear and optical quantum transitions in molecules, intensities of the complicated gamma-transitions due to the changing of the molecular excited states because of the gamma nuclear transition. We present a consistent, quantum approach to calculation of the probabilities of the different cooperative laser electron-gamma-nuclear processes in molecules (including the set of electron or vibration-rotational satellites of the gamma-nuclear spectrum). The calculation results for electron-gamma-nuclear transition probabilities in the diatomic (the nucleus 127I with E=203keV in molecule of HI) and vibration-nuclear transition probabilities for some three-atomic XY2, five-atomic XY4 molecules are given. In particular, we present the results of calculation for the vibration-nuclear transition probabilities in a case of the emission and absorption spectrum of nucleus 188Os (E=155 keV) in the molecule of OsO4 and nucleus 191Ir (E= 82 keV) in the molecule IrO4. [Preview Abstract] |
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QRP1.00021: Small Rare Gas Clusters in a Kinematically Complete (e,2e)-Experiment Alexander Dorn, Thomas Pflueger, Xueguang Ren, Arne Senftleben, Joachim Ullrich Single ionization of small Argon and Neon clusters at intermediate energies (i.e. 100 eV and 61 eV, respectively) have been performed. Triple differential cross-sections have been acquired over the complete solid angle of electron emission. 3D emission patterns for dimers and small clusters show significant differences compared to the ionization of the respective atomic target which most likely can be attributed to multiple scattering collisions. Coincidence measurements of two charged cluster fragments allow to obtain more detailed insight in multiple ionization reactions as well as energy and charge transfer processes between different atoms within the cluster. [Preview Abstract] |
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QRP1.00022: A kinematically complete experiment for positron impact ionization of helium at the positron beam facility NEPOMUC A. Dorn, M. Holzwarth, Th. Pflueger, A. Senftleben, X. Ren, J. Ullrich, L. Hargreaves, B. Lohmann, D. Slaughter, J. Sullivan, J. Lower, S. Buckman In the project presented ionizing collisions of positrons with simple atoms and molecules will be explored in unprecedented detail. By combining presently available high-intensity positron sources with an efficient multi-particle imaging spectrometer (reaction microscope) fully differential benchmark cross sections (FDCS) will become available to critically test theory and to advance our understanding of few-body quantum dynamics. Here the results of a pilot experiment on positron impact ionization of helium at the NEPOMUC positron beam facility are presented. Momentum distributions of the ionized electron and the scattered projectile along the incoming projectile beam axis are presented for E$_{0}$ = 80 eV and compared to respective electron impact results. For positron impact the electron momentum distribution is shifted significantly forward compared to the electron impact case indicating the reversed post-collision interaction in both cases. In future FDCS will be obtained also at the Australian Positron Beamline Facility. [Preview Abstract] |
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QRP1.00023: Energy Approach to Atoms, Ions and Nuclei in a Super Strong Laser Field Alexander Glushkov A consistent relativistic energy approach is applied to studying the interaction of the atoms and ions of plasma with an super intense electromagnetic (laser) field. Method bases on description of atom in a field by the k- photon emission and absorption lines. The lines are described by the QED moments of different orders, which can be calculated with the use of the Gell-Mann and Low S-matrix adiabatic formalism. In relativistic version the Gell-Mann and Low formulae expresses an imaginary part of the energy shift ImE through the QED scattering matrix, including interaction of atom with electromagnetic field and field of the photon vacuum. We present QED S-matrix energy formalism for calculation of the spectral lines shape in dense plasma. For any atomic level we calculate Im E as function of the laser pulse central frequency and further the moments of lines. Numerical modelling carried out for H, Cs, Ar, Yb, Tm atoms and H-, Li- and Ne-like ions. Especial interest attracts new relativistic treating of the drastic broadening effect of widths for the autoionization resonances in lanthanides. The direct interaction of super intense laser fields in the optical frequency domain with nuclei is studied and the AC Stark effect for nuclei is described within the operator perturbation theory and the relativistic mean-field model for the ground-state calculation of the nuclei 49Sc, 171Yb and compared with other available data. [Preview Abstract] |
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QRP1.00024: Evaluation of Electron Ionization Cross Sections for Carbon Fullerenes Satyendra Pal, Neeraj Kumar Recently, we have introduced a semi empirical formulation for the calculation of partial and total integral ionization cross sections for C$_{60 }$and C$_{70}$ in the energy range from ionization threshold to 1000 eV which yielded results which were in satisfactory agreement with available experimental and theoretical data. Subsequently, we extended and generalized the same revisited JK semi empirical formulation for the evaluation of partial integral ionization cross sections for C$_{2}$ dimmer and C$_{3}$ trimmer. The major input data required in the formulation is the oscillator strength which is taken from the statistical sum of individual carbon atoms. The results are found in satisfactory agreement with the only theoretical calculation based on the modified additive rule (MAR). In addition to the partial integral ionization cross sections, we have also evaluated the ionization rate coefficients using the calculated ionization cross sections and Maxwell-Boltzmann distribution for the electrons as a function of energy. [Preview Abstract] |
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QRP1.00025: Vibrational Excitation of Furan by Electron Impact Gabreila Serna, Rehab Al-Buraidi, Leigh R. Hargreaves, Murtadha A. Khakoo Normalized absolute experimental electron scattering differential cross-sections (DCS) (normalized to the elastic DCS of [1]) for the electron impact excitation of eight energy loss structures, mostly composite, for vibrational excitation of the ground state of furan will be presented. The incident electron energy range of the present study was 5-15eV. The analysis of these structures follows the detailed FTIR photoabsorption studies of [2]. The present DCS reveal that most of the vibrational structures do not display forward scattering typical of IR-active excitations. However, two of these features contain components that incorporate IR-active modes and these clearly display forward-scattering DCS at some incident electron energies, but not all.\\[4pt] [1] M. A. Khakoo et al., Phys. Rev. A, 81, 062716 (2010) \\[0pt] [2] A. Mellouki et al., Chem. Phys. 271, 239 (2001) [Preview Abstract] |
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QRP1.00026: Calculation of electron scattering from the ground state of ytterbium Dmitry Fursa, Christopher Bostock, Igor Bray We report on the application of the convergent close-coupling method (Phys. Rev. A {\bf 83}(2011)052710), in both relativistic and nonrelativistic formulations, to electron scattering from ytterbium. Angle-differential and integrated cross sections are presented for elastic scattering and excitation of the states $(6s6p){}^3 P^{\rm o}_{0,1,2}$, $(6s6p)^1P_1^{\rm o}$, $(6s7p)^1P_1^{\rm o}$ and $(6s5d)^1D_2^{\rm e}$ for a range of incident electron energies. We also present calculations of the total cross section, and angle-differential Stokes parameters for excitation of the $(6s6p){}^3 P^{\rm o}_{1}$ state from the ground state. A comparison is made with the relativistic distorted-wave method and experiments. Good agreement was found between the RCCC and CCC (with semirelativistic corrections) results indicating that relativistic effects do not dominate except for the $(6s6p)^3P_1^{\rm o}$ DCS at forward-scattering angles, which indicates that the fully relativistic RCCC formalism is more accurate in this case. Discrepancies between experiments in normalization of the $(6s6p)^1P_1^{\rm o}$ DCS have been analyzed and suggestions for cross section renormalization have been presented. [Preview Abstract] |
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QRP1.00027: Electron Impact Induced VUV Emission from Argon J.A. Young, C.P. Malone, P.V. Johnson Emission intensity and spectra are important tools for diagnosing plasma properties such as electron temperature and neutral density. In order to properly interpret emissions from low-density plasmas, accurate cross sections are needed, particularly low energy electron-impact cross sections. Of interest are the cross sections for Argon, a common species used in industrial and lighting applications. In this paper, we present recent measurements of electron-impact induced VUV emissions from Ar using a magnetically collimated monoenergetic beam of electrons and a 0.2m spectrometer. Specifically, we present emission excitation functions for both Ar I(1048{\AA}) and Ar I(1066{\AA}) emissions. Similarities and differences between current results and previously published emission results will be discussed. Also discussed will be the relation to recent electron energy loss results. [Preview Abstract] |
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QRP1.00028: Electron Impact Excitation Cross Sections for N-like ions Swaraj Tayal The improved atomic calculations for electron impact excitation cross sections of nitrogen like Mg VI and Si VIII ions have been performed using the B-spline Breit-Pauli R-matrix method. The flexible non-orthogonal sets of spectroscopic and correlation radial functions are employed for an accurate representation of the target states and scattering functions. The close-coupling expansion includes 76 bound levels of Mg VI and Si VIII ions covering all possible terms of the ground $2s^22p^3$ and excited $2s2p^4$, $2p^5$, $2s^22p^23s$, $2s^22p^23p$, and $2s^22p^23d$ configurations. The calculated excitation energies of the target levels are in excellent agreement with experiment and represent a significant improvement over the previous calculations. The present results of cross sections are compared with a variety of other close-coupling calculations. The oscillator strengths and transition probabilities for several transitions are noted to be in good agreement with other theories and available experimental data. The present cross sections are in good agreement with other theories and experiment for many transitions, but some differences in magnitude and shape for some other transitions are also noted. [Preview Abstract] |
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QRP1.00029: Rotationally elastic total cross sections for NH$_{3}$ on electron impact over a wide energy range Minaxi Vinodkumar, Chetan Limbachiya, Bobby Antony Electron molecule collisions are important over incident energy from very low (0.01 eV) to intermediate and high energies (10 keV). We present rotationally elastic total cross sections for electron scattering for NH$_{3}$ from 0.01 eV to 2 keV using two different theoretical formalisms. We use Quantemol-N formalism[1] for calculating total cross sections up to threshold of the target and the Spherical Optical Complex Potential (SCOP) method for calculating total cross sections beyond threshold up to 2 keV [2].\\[4pt] [1] J.Tennyson, D. B. Brown, J. M. Munro, I. Rozum, H. N. Varambhia, and N.Vinci, J. Phys.Conf. Series \textbf{86,} 012001 (2007).\\[0pt] [2] M. Vinodkumar, K. Korot, and H. Bhutadia, International Journal of Mass Spectrometry \textbf{294,} 54 (2010). [Preview Abstract] |
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QRP1.00030: Calculations of electron impact excitation in planetary atmospheres Michael Brunger, Laurence Campbell, Sudhaghar Jaya High-energy electrons from the Sun enter planetary atmospheres and interact with atoms and molecules to produce ions and lower-energy electrons. Photoionization by sunlight produces photoelectrons, which can similarly produce further ionization and lower-energy electrons. In both cases the lower-energy electrons produce excitation of atoms and molecules, leading to radiative emissions (aurora, dayglow and nightglow) which are measured and analyzed as a means of remote sensing of planetary atmospheres. The analysis often requires comparisons with computational models, in which the electron spectrum is multiplied by the electron impact excitation cross sections to predict excitation rates. A statistical-equilibrium calculation is then applied to determine the fraction of excitations that produce radiation (rather than the energy being lost in collisions). This radiation rate, multiplied by the density of the atoms or molecules, gives a prediction of the emitted radiation. We are making such computations, with particular emphasis on applying recently measured or improved electron impact cross sections. Several examples will be presented, including calculations of electron impact excitation of carbon monoxide in the atmospheres of Mars and Venus. [Preview Abstract] |
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QRP1.00031: Oscillations in the autoionization energy distribution of He2+ + H2 double capture collisions R.O. Barrachina, B.S. Frankland, J.-Y. Chesnel, F. Fremont The present study extends previous results in which the autoionization spectra in double capture He2+ + H2 collisions at low impact energies were observed to oscillate in angle. This effect was ascribed to a Young-type interference by the emitted electron acting on the two protons in a way analogous to a double-slit system. Now, a detailed analysis of the autoionizing 2s2 1S state by means of a Fast Fourier Transformation has revealed oscillations in the Auger energy distribution. The possible origin of this periodic structure is discussed, and shown to be essentially different from that previously observed in the angular distribution. [Preview Abstract] |
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QRP1.00032: Effect of projectile coherence on multiple differential cross sections for 75 keV proton impact on H$_{2}$ S. Sharma, K. Egodapitiya, D. Madison, M. Schulz, A. Hasan, A. Laforge, R. Moshammer Recent results in ion-atom collision experiments suggest that discrepancies between theory and experiment are at least partly due to the representation of incoming projectile by a delocalized wave (coherent treatment). Recently we reported an experiment designed to investigate this. There, DDCS were measured for two different positions of the collimating slit. In one case the width of the proton wave packet was larger than the inter-nuclear separation of a H$_{2}$ molecule (coherent case), while in the other it was much smaller than that (incoherent case). The two data sets were clearly different where in the coherent case a Young type interference structure was present and in the incoherent case it was not. Our next effort was to see the effects of projectile coherence on other processes such as single electron capture. Here we discuss the details of such an experiment and the observed results. [Preview Abstract] |
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QRP1.00033: PLASMA SOURCES II |
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QRP1.00034: Current-voltage-time characteristics of the reactive Ar/N$_2$ high power impulse magnetron sputtering discharge Jon Tomas Gudmundsson, Fridrik Magnus, Olafur B. Sveinsson, Sveinn Olafsson By pulsing a magnetron target to a high power density with unipolar voltage pulses, at a low frequency (a low duty cycle), very high electron densities are achieved. The high electron density results in a high ionization fraction of the sputtered vapor. This is referred to as high power impulse magnetron sputtering (HiPIMS). The discharge current and voltage waveforms have been measured in a reactive HiPIMS Ar/N$_2$ discharge with a Ti target for 400 $\mu$s long pulses. We observe that the current waveform in the reactive Ar/N$_2$ HiPIMS discharge is highly dependent on the pulse repetition frequency, unlike the non-reactive Ar discharge. The current is found to increase significantly as the frequency is lowered. This is attributed to an increase in the secondary electron emission yield for self-sputtering when the nitride forms on the target at low frequencies. In addition, self-sputtering runaway occurs at lower discharge voltages when nitrogen is added to the discharge. This illustrates the crucial role of self-sputtering in the behavior of the reactive HiPIMS discharge. The secondary electron emission yield is higher for a nitride target than a titanium target when self-sputtering is the dominant sputtering mechanism. This differentiates HiPIMS from dcMS where self-sputtering is not as important. [Preview Abstract] |
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QRP1.00035: A parametric study of DC-RF Penning-type plasma discharge Yevgeny Raitses, Pierre Baele, Vincent Donnelly A plasma cathode that utilizes electron extraction from a rf-plasma (2 MHz, 30-100 W) is shown to sustain a high current (1-5 A) operation of a low pressure (0.1-1 mtorr) dc discharge with applied magnetic field (0.01-1 kGauss) in the discharge voltage range of 20-100 V. Probe measurements of plasma potential, electron temperature and density revealed a strong effect of the magnetic field on plasma properties of this discharge. For example, at the discharge voltage of 50 V, the voltage potential drop in the magnetized part of the discharge increases from a few volts to about 20 V as the magnetic field increases from 35 to 160 Gauss. It is shown that the electron cross-field current in the Penning discharge is anomalously high and cannot be explained by classical collisional mechanism. [Preview Abstract] |
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QRP1.00036: Optimization and Characterization of a Helicon Ion Source on an Inertial Electrostatic Confinement Device for Helium-3 Fusion Gabriel Becerra, Gerald Kulcinski, John Santarius HELIOS is an inertial electrostatic confinement (IEC) fusion device designed for $^{3}$He-$^{3}$He fusion studies as part of the advanced fuels program at the University of Wisconsin [1]. HELIOS uses a helicon plasma as a source of ions, which are subsequently accelerated radially to fusion energies by the electrostatic field between the spherical chamber wall and a concentric cathode grid. The experimental setup, in which $^{3}$He-$^{3}$He fusion in an IEC system has previously been demonstrated, has since been upgraded to raise fusion rates to allow for diagnostic studies of IEC physics with helium-3 fuel, in order to benchmark the single-atomic-species formalism of a numerical code on spherically convergent ion flow [2]. The helicon ion source has been characterized through double probe measurements of plasma density and electron temperature for various rf antenna and magnetic field geometries and upgraded to deliver higher ion currents.\\[4pt] [1] G.R. Piefer et al., Fusion Sci. Technol. 47, 1255 (2005).\\[0pt] [2] G.A. Emmert and J.F. Santarius, Phys. Plasmas 17, 013502 (2010). [Preview Abstract] |
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QRP1.00037: Simulating Electron Cyclotron Resonance Heating in Kinetic and Dielectric Plasma Models with VORPAL Christine Roark, David Smithe, Peter Stoltz We present results of electron cyclotron resonance heating (ECRH) in a plasma sustained by microwaves using VORPAL. Specifically, we look at the electron temperature, sheath size, rate of plasma formation and power absorbed for simulations with an argon gas at 10s of mTorr pressure and 2.45 GHz. We look at the effects of including elastic, inelastic and ionizing Monte Carlo collisions on the formation of the kinetic plasma. We also discuss the use of higher-order particle algorithms for smoothing out the particle current and charge which can help reduce unphysical heating in PIC simulations of high pressure, low temperature plasmas and the effect this has on sheath size and electron temperature. We then compare these simulations to a method replacing the kinetic particles with an equivalent plasma dielectric model. [Preview Abstract] |
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QRP1.00038: Hybrid Fluid-Analytical Simulations of E to H Instability in Electronegative Discharges E. Kawamura, A.J. Lichtenberg, M.A. Lieberman, D.B. Graves The E to H instability in inductively driven electronegative plasmas has been previously observed experimentally [1] and explored theoretically [2]. A hybrid fluid-analytical code [3], which solves for both the inductive and capacitive coupling of the source coils to the plasma, is used to simulate a Cl$_2$ inductive reactor. Improvements were made to the code to allow simulations of highly electronegative gases. As the rf input current to the coils rises, the plasma transitions from a capacitive to an inductive mode. For a narrow range of input currents, the E to H transition is abrupt, exhibiting oscillations in electron, ion and neutral densities, electron temperature, power, etc.\\[4pt] [1] A.M. Marakhtanov, M. Tuszewski, M.A. Lieberman, A.J. Lichtenberg, J. Vac. Sci. Technol. A 21 (2003) 1849.\\[0pt] [2] P. Chabert, A.J. Lichtenberg, M.A. Lieberman, A.M. Marakhtanov, J. Appl. Phys. 94 (2003) 831.\\[0pt] [3] E. Kawamura, D.B. Graves, M.A. Lieberman, Plasma Sources Sci. Technol. 20 (2011) 035009. [Preview Abstract] |
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QRP1.00039: ABSTRACT WITHDRAWN |
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QRP1.00040: Measurement of power transfer efficiency and ion density in various radio-frequency inductively coupled plasma Jae-Won Lee, Hye-Ju Hwang, Ik-Jin Choi, Young-Kwang Lee, Chin-Wook Chung The power transfer efficiency and plasma density were measured in low pressure inductive coupled argon plasma at 20--100 mTorr, 20--80 W and 13.56--60 MHz. For this experiment, a variable-frequency matching box (matcher) was developed and a modified method to determine the power transfer efficiency was used. To match 13.5MHz, 40.68MHz and 60MHz rf power source, three vacuum variable capacitors and one fixed capacitor were built in matching box to the plasma characteristic impedance. We measured the feeding line current using Rogowski coil to obtain matcher resistance and plasma resistance, so the power transfer efficiency could be obtained. The calibration process, calculations of the exact current from the voltage, is not necessary to obtain power transfer efficiency. This is the advantage of using Rogowski coil. It is clearly observed that the power transfer efficiency decrease with increasing driving frequency and decreasing pressure, whereas the ion density shows the opposite tendency compared to power efficiency. [Preview Abstract] |
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QRP1.00041: ABSTRACT WITHDRAWN |
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QRP1.00042: A simple analysis of inductively coupled discharge using transformer circuit model Yound-Do Kim, Hyo-Chang Lee, Chin-Wook Chung Correlations between plasma parameters in an inductively coupled discharge were studied by an air-cored transformer model. By applying the transformer circuit model which is well-established by previous workers [1], for the maximum power transfer the optimal condition between external parameters (chamber dimension L, driving frequency $\omega )$ and internal parameters (skin depth $\delta $, electron-neutral collision frequency $\nu _{en})$ was obtained. From this work, it was found that a maximum power transfer condition correspond to $\delta \quad \approx $ L when $\nu _{en}$ / $\omega \quad <<$ 1, while $\delta $/ L $\approx $ (2$\omega $ / $\nu _{en})^{1/2}$ when $\nu _{en}$ / $\omega \quad >>$ 1. This result of circuit analysis is consistent to the state of H to E mode transition which is existing results based on calculation of Maxwell's equation [2]. Our experimental results, as well as other researchers' results are also compared and agreed well with the theoretical value. This study will offers another view point of analyzing characteristics of inductively coupled plasma, and the theoretical predictions will play a very useful role in the system design or improving process efficiency. \\[4pt] [1] Piejak R B, Godyak V A and Alexandrovich B M, \textit{Plasma Sources Sci. Technol.} \textbf{1} 179 (1992) \\[0pt] [2] Lee and Chung, \textit{Physics. Plasmas}, \textbf{13} 063510 (2006). [Preview Abstract] |
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QRP1.00043: Measurement of the electron energy distribution in magnetized solenoidal inductively coupled plasma Jin-Yong Kim, Hyo-Chang Lee, Young-Do Kim, Young-Cheol Kim, Chin-Wook Chung Study on the changes in the plasma parameters and electron energy distribution (EED) was performed in magnetized solenoidal inductively coupled plasma. Without DC magnetic field, the electron temperature was almost same in radial position and the EED in total electron energy scale was radially coincided, which indicate that the discharge property is governed by non-local electron kinetics. However, as the DC magnetic field was increased, dramatic changes in the plasma uniformity and electron temperature, and radially non-coincidence of the EED in total electron energy scale were measured. These changes show the transition from nonlocal to local electron kinetics and thus, with increasing the DC magnetic field, the electrons were cooled at the discharge center where the electron heating is absent. As a further work, we will also study Ar/O$_{2}$ gas mixing effect in the magnetized solenoidal inductively coupled plasma. [Preview Abstract] |
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QRP1.00044: Electrical characteristics and mode transition of power dissipation in an asymmetric capacitively coupled plasma Soo-Jin Lee, Hyo-Chang Lee, Chin-Wook Chung Electrical characteristics and plasma parameters were experimentally studied in an asymmetric capacitively coupled plasma with various argon gas pressures. At low discharge current region, the transferred power to the plasma was proportional to the current, while the transferred power increased proportionally to square of the current at high discharge current region. The transition of discharge resistance was also observed when the mode transition of power dissipation occurred. At low discharge current or low power, the plasma density linearly increased with the gas pressure, while at high discharge currents or high powers, the increase rate of the plasma density depended on the gas pressure. These changes in the electrical characteristics and the plasma parameters were mainly caused by the power dissipation mode transition in asymmetric capacitive discharge, which has extremely high self-bias voltage at the electrode. [Preview Abstract] |
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QRP1.00045: Experiment, simulation, and model investigations on capacitive oxygen rf discharges driven by two consecutive frequencies Edmund Schuengel, Quan-Zhi Zhang, Shinya Iwashita, Julian Schulze, Lu-Jing Hou, You-Nian Wang, Uwe Czarnetzki Using the combination of a fundamental frequency and its second harmonic (e.g. 13.56 MHz + 27.12 MHz), the symmetry of capacitive discharges is controlled by the phase between the two frequencies. Here, this concept is studied in an electronegative oxygen discharge by an experiment, a PIC/MCC simulation, and an analytical model. The results show that the generation of a dc self-bias is controlled via the phase. Meanwhile, the dissipated power and the total densities are kept constant. At low pressure, the self-excitation of plasma series resonance oscillations occurring due to the electrical asymmetry leads to resonance structures inside the plasma bulk. Funding: German Federal Ministry for the Environment (0325210B), Alexander von Humboldt Foundation, RUB Research Department Plasma, National Natural Science Foundation of China (Grant No. 10635010), and Research Fund for Doctoral Program of Higher Education of China (Grant No. 20090041110026). [Preview Abstract] |
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QRP1.00046: Secondary electrons in dual-frequency capacitive radio frequency discharges Julian Schulze, Edmund Schuengel, Uwe Czarnetzki, Zoltan Donko Two fundamentally different types of dual-frequency capacitive RF discharges can be used to realize separate control of the ion mean energy, $<$E$_{i}>$, and the ion flux, $\Gamma _{i}$, at the electrodes: (i) Classical discharges operated at substantially different frequencies, where the low and high frequency voltage amplitudes, $\phi _{lf }$and $\phi _{hf}$, are used to control $<$E$_{i}>$ and $\Gamma _{i}$, respectively. (ii) Electrically asymmetric (EA) discharges operated at a fundamental frequency and its second harmonic with adjustable phase shift, $\theta $, between the driving frequencies, which is used to control $<$E$_{i}>$. We study the effect of secondary electrons on the quality of this separate control in both discharge types in argon at different gas pressures by PIC/MCC simulations with focus on the effect of the control parameter for $<$E$_{i}>$ on $\Gamma _{i}$ for different secondary yields, $\gamma $. A dramatic effect of tuning $\phi _{lf}$ in classical discharges and a significantly less pronounced effect of tuning $\theta $ in EA discharges is observed. This is caused by a transition from $\alpha $- to $\gamma $-mode induced by changing $\phi _{lf}$ and not induced by changing $\theta $. [Preview Abstract] |
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QRP1.00047: 2-dimensional simulations of electrically asymmetric capacitively coupled RF-discharges Sebastian Mohr, Julian Schulze, Edmund Schuengel, Uwe Czarnetzki Capactively coupled RF-discharges are widely used for surface treatment like the deposition of thin films. For industrial applications, the independent control of the ion flux to and the mean energy of the electrons impinging on the surfaces is desired. Experiments and 1D3v-PIC/MCC-simulations have shown that this independent control is possible by applying a fundamental frequency and its second harmonic to the powered electrode. This way, even in geometrically symmetric discharges, as they are often used in industrial reactors, a discharge asymmetry can be induced electrically, hence the name Electrical Asymmetry Effect (EAE). We performed 2D-simulations of electrically asymmetric discharges using HPEM by the group of Mark Kushner [1], a simulation tool suitable for simulating industrial reactors. First results are presented and compared to previously obtained experimental and simulation data. The comparison shows that for the first time, we succeeded in simulating electrically asymmetric discharges with a 2-dimensional simulation. \\[4pt] [1] M. Kushner J. Phys. D: Appl. Phys. 42 (2009) 194013 [Preview Abstract] |
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QRP1.00048: Multiple frequency capacitive plasmas as a tool to optimize PVD processes Stefan Bienholz, Egmont Semmler, Peter Awakowicz Capacitively coupled plasmas are widely used in PVD processes over several years. Nowadays mainly DC-Magnetron sputter coaters are commonly used, which do not allow a separate control of ion flux and ion energy distribution at the target. A possibility to overcome this constriction consists of exciting the plasma at two different radio frequencies simultaneously. In this contribution we discuss the possibility of tuning electrical discharge quantities such as target voltage waveform and self bias voltage by using multiple excitation frequencies. The influence of the relative phase between one frequency and its second harmonic on these quantities is also investigated. The experiments show, that capacitively coupled multiple frequency discharges are a promising complement to existing PVD processes. The authors would like to acknowledge the funding provided by the ``Deutsche Forschungsgemeinschaft'' within the frame of the SFB-TR 87 and the ``Ruhr University Bochum Research School.'' [Preview Abstract] |
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QRP1.00049: Kinetic Effects in Low Pressure Capacitively Coupled Plasmas Alexandre Likhanskii, Christine Roark, Peter Stoltz We present results of particle-in-cell/Monte Carlo collision simulations of kinetic effects in low pressure capacitively coupled plasma discharge. In particular, we examine discharges of various gases (including Ar, Xe, and others) in the pressure range of 10s of mT and the frequency range of 10s of MHz. We track the formation of high energy electrons (e.g., at the ionization threshold or greater) as a marker for enhanced ionization, and look at the effects of elastic and inelastic collisions on the formation of these high energy electron bunches. We show results for 2D and 3D simulations where we include density gradient effects, and results for plasma chemistry effects on the bulk electron energy distribution function and the ion energy distribution function at a plasma surface interface. We discuss the role of the bunches on electron heating in the plasma bulk and on their presence on how electron heating is treated in fluid simulations of plasma sources. [Preview Abstract] |
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QRP1.00050: Calculation of 2D charged particles density distributions and current-voltage characteristics of RF CCP discharge by means of Galerkin method Sergey Dvinin, Won-Taek Park, Aleksey Kalinin, Andriy Kashaba, Nikolay Nikishin Effective using of low pressure CCP reactors demands uniformity and high density of plasma, and possibility to control reactor parameters. The simple way to optimize its characteristics is to use analytical model of the discharge, instead of (or in addition to) finite difference model. In the given work we offer the way to construct such model [1], based on Bubnov-Galerkin method. We have used eigenfunctions of the hydrodynamics equations (with ionization) and electromagnetic equations (accounting volume and surface waves), as functions to decompose exact solution. Space charge sheath is described by nonlinear phenomenological model. Specified approach allows to calculate discharge impedance and explains possibilities ambiguity of plasma characteristics, connected with electrodynamic resonances and chemical processes in plasma.\\[4pt] [1] S. Dvinin et al, Sov. Phys.: Fizika Plazmy, 9(5), 1058 (1983). [Preview Abstract] |
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QRP1.00051: Plasma formation in water vapour layers in high conductivity liquids C.P. Kelsey, L. Schaper, K.R. Stalder, W.G. Graham The vapour layer development stage of relatively low voltage plasmas in conducting solutions has already been well explored.\footnote{L. Schaper et al Plasma Sources Sci. Technol. \textbf{20}(2011) 034003} The nature of the discharges formed within the vapour layer however is still largely unexplored. Here we examine the nature of such discharges through a combination of fast imaging and spatially, temporally resolved spectroscopy and electrical characterisation. The experimental setup used is a pin-to-plate discharge configuration with a -350V, 200$\mu $s pulse applied at a repetition rate of 2Hz. A lens, followed by beam splitter allows beams to one Andor ICCD camera to capture images of the plasma emission with a second camera at the exit of a high resolution spectrometer. Through synchronization of the camera images at specified times after plasma ignition (as determined from current-voltage characteristics) they can be correlated with the spectra features. Initial measurements reveal two apparently different plasma formations. Stark broadening of the hydrogen Balmer beta line indicate electron densities of 3 to 5 $\times $10$^{20}$ m$^{-3}$ for plasmas produced early in the voltage pulse and an order of magnitude less for the later plasmas. [Preview Abstract] |
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QRP1.00052: Some chemical properties of plasmas created in liquid solutions Lucie Nemcova, Frantisek Krcma, Colin Kelsey, Bill Graham Underwater electrical discharges have become a major focus of study recently primarily due to their many practical applications. Such applications include degradation of hazardous organic compounds, killing of microorganisms, chemical synthesis and electrosurgery. A small multi-electrode system is used. The plasma is created using a small ($\sim $ 3.5 mm diameter) four electrode circular device with a coaxial earth and with each electrode driven with 100 kHz RF bipolar square wave voltage. Four different inorganic solutions were used: 0.15 mol KCl, NaCl, BaCl$_{2}$ and Na$_{2}$CO$_{3}$. These solutions were at room temperature at the start of experiment and were gradually brought to boiling. The chemical and physical plasma properties were studied. Optical emission spectroscopy has been used to demonstrate OH radical production which is important since this species is known to react readily with many pollutants. In all solutions except Na$_{2}$CO$_{3}$ hydrogen peroxide generation was also observed also. Hydrogen peroxide is one of the most important species which the plasma produces because it helps with water treatment. The pH values were examined also but remained stable during all measurements. [Preview Abstract] |
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QRP1.00053: Time-resolved OES measurement of microwave plasma produced inside controlled bubbles under water Tatsuo Ishijima, Haruka Suzuki, Hirotaka Toyoda Plasma generation inside bubbles under liquid has been given much attention because of its potential industrial applications such as water purification, sterilization, materials processing and so on. In our previous study, we have demonstrated that liquid temperature and operating pressure have great influences on the plasma production and decomposition of organic solutes in de-ionized water. However, physical and chemical processes occurring inside the bubbles are still unclear because the plasma is not produced under well-defined experimental conditions. In this work, we have developed a microwave bubble plasma system where reproducible microwave plasma is produced inside size-controlled bubbles. With the aid of this system, temporal variations of He I emission from discharge gas and H or OH emission from water vapor are measured by time-resolved photon-counting technique. After the plasma ignition, He I intensity rapidly increases within less than 100 ns. However, OH and H intensities increase $\sim $1 $\mu $s after the plasma ignition. This result suggests that the water vapor is produced by the plasma irradiation on the bubble surface. [Preview Abstract] |
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QRP1.00054: Atmospheric dc glow discharge using liquid anode for production of nano-particle Naoki Shirai, Satoshi Uchida, Fumiyoshi Tochikubo Non-thermal plasma in and with liquids has attracted considerable interest for its potential use in a wide range of applications. In particular, the use of a discharge with a liquid as an electrode for material processes has been reported. In this study, we focused on atmospheric glow discharge using liquid as anode, and the production of nano-particle by the atmospheric plasma reduction of aqueous cations. When atmospheric dc glow discharge with helium flow was generated, self-organized anode patterns were observed on the liquid. The pattern formation depends on the current, gap length and helium flow rate. With increasing discharge current or gap length, anode luminous spot changed to self-organized patterns. Anode pattern formation depends on the liquid conductivity. When AgNO$_{3}$ solution is used as liquid anode of the discharge, the liquid changed dark color near the plasma-liquid interface. We confirm the dark region including nano-particle which diameter is about 5-50 nm by TEM observation. The liquid anode discharge reduction of aqueous cations is specific and different from typical electrolysis. The diameter of nano-particle is changed by current, discharge time and addition of surface-active agent to liquid. [Preview Abstract] |
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QRP1.00055: Experimental and modeling investigation of DC Oxygen Discharge having Water Electrode Kei Ikeda, Mizuki Ando, Nozomi Takeuchi, Koichi Yasuoka Plasmas generated with water electrode have been developed for water purification. To investigate the plasma--water interactions in DC oxygen plasma, experimental and numerical modeling was conducted. The concentrations of hydrogen peroxide and acetic acid in the solution were compared with a discharge current between 1 to 7 mA. By adjusting the water vapor concentration within plasma, the reaction model coincided with the experimental results. Proposed 1D or 2D plasma models showed that the cross section for the current flow on the water electrode was a crucial factor and this modeling provided a practical procedure for considering vapor water evaporated from the water surface. [Preview Abstract] |
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QRP1.00056: Spatiotemporal discharge characteristics in saline plasma for the biomedical applications Jae-Chul Jung, Myeong Yeol Choi, Zengqi Yu, Il Gyo Koo, George J. Collins The spatiotemporal electron density profile of pulsed liquid plasma in salines is illustrated by the spectroscopic measurement using hydrogen beta line broadening, in which also the correlation between the bubble generation and the plasma ignition with elapse of time are closely examined. Overall, the density decreased with distance from the electrode, but it was shown to have different time and spatial distributions of fundamental atomic lines in saline solution. In this study, It shows a dependency of the power delivered to the saline determining the initial bubble generation and volume, then the following plasma parameters in saline (rotational temperature, density, V-I curve, etc.) [Preview Abstract] |
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QRP1.00057: Influence of charge accumulation on a dielectric capillary atmospheric pressure plasma jet Brian Sands, Shih Kang Huang, Jared Speltz, Matthew Niekamp, Biswa Ganguly Using a single ring electrode configuration and a positive unipolar pulsed voltage source, we examine the influence of the dielectric barrier on the distribution of ionization in a streamer-like dielectric capillary plasma jet utilizing a rare gas flow as a function of anode placement and pulse repetition frequency. At low frequencies, when the anode is recessed at least 5 mm along the capillary, two regions of enhanced ionization can be resolved near the anode and near the capillary tip that are associated with two distinct peaks in the discharge current and locally increased emission intensity in the residual streamer channel. With the anode placed $\sim$20 mm from the capillary tip, the two current peaks were $\sim$13 mA. Increasing the frequency between 6 and 10 kHz, the capillary tip enhancement expanded towards the anode and concentrated there at higher frequencies. The discharge current over this frequency range rose to 18 mA and was increasingly dominated by the earlier peak associated with ionization near the anode. This increased charging of the dielectric surface and reduced the potential available to the ionization front outside the capillary as indicated by a 25\% drop in velocity and reduced emission intensity. The surface charging effect is visualized at discharge inception using a Phantom high-frame-rate CCD camera. [Preview Abstract] |
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QRP1.00058: Identifying single electron avalanches in streamer discharges Gideon Wormeester, Sander Nijdam, Ute Ebert Although some properties of positive streamers in nitrogen-oxygen mixtures, such as velocity and diameter, are remarkably insensitive to the N 2 :O 2 -ratio of the background gas, the visible structure can be quite different. In particular, experiments in high purity nitrogen have demonstrated that streamers can exhibit a feather-like structure, with small hairs connecting to the main streamer channel. Such structures were not observed in mixtures with higher oxygen density, such as air. We hypothesize that these hairs are avalanches started by single electrons that move towards the positively charged streamer head. Using results from numerical simulations, the presence or absence of these hairs can be explained: In air, the electron density outside the streamer channel is high and avalanches overlap, while in high purity nitrogen, the electron density is sufficiently low that avalanches are distinct and visible individually. [Preview Abstract] |
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QRP1.00059: Effects of background- and photo-ionization on positive streamers Ute Ebert, Sander Nijdam, Gideon Wormeester, Eddie van Veldhuizen Positive streamers in air and other oxygen-nitrogen mixtures are generally believed to propagate against the electron drift direction due to photo-ionization. Photo-ionization is the ionization of O$_{2}${\-}molecules by UV radiation from excited N$_{2}$-molecules. The effect is non-local and therefore facilitates the propagation of the streamer head by creating free electrons ahead of it. The relative importance of photo-ionization depends on the ratio between oxygen and nitrogen. Another possible source of free electrons in front of the positive streamer is background ionization. This can be ionization left by previous discharges or by other processes such as cosmic rays or (natural) radio-activity. We study the effects of both photo- and background-ionization on propagation and morphology of positive streamers by changing gas composition and repetition frequency. One of the gas compositions that are used is pure nitrogen with the addition of a small amount of radio-active $^{85}$Kr to increase background ionization. We also check if streamers have a tendency to follow the paths of their predecessors in previous discharges. [Preview Abstract] |
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QRP1.00060: Design and characterization of a novel coaxial VHF plasma source for air plasma formation Brandon Byrns, Daniel Wooten, Steven Shannon A key challenge in the expansion of atmospheric plasma applicators into new markets is the effective surface area that these systems can efficiently treat. To this end, a large area atmospheric air glow discharge, with approximately 9.5cm$^{2}$ cross sectional area, is obtained using a simple coaxial structure. The room air plasma is driven by a 162MHz generator at powers ranging from 300W -- 1000W. The VHF drive appears to produce a steady state glow void of streamers or arcs typically found in atmospheric air systems. Electrical measurements coupled with a global plasma model and transmission line theory allow for the calculation of electron density. Densities calculated for 400W are approximately 10$^{11 }$cm$^{-3}$. Spectroscopy data shows dominant emissions consist of OH, N$_{2}$, and N$_{2}^{+}$, along with a continuum indicating neutral bremsstrahlung radiation; this is used for electron density calculations and model validation. In this presentation, source design, plasma characterization, and preliminary surface treatments of HDPE will be presented. [Preview Abstract] |
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QRP1.00061: Phase Contrast Imaging of Induced Airflow Topologies Produced by Dielectric Barrier Plasma Actuators Sirous Nourgostar, Noah Hershkowitz In this experiment, spatial and temporal evolution of both flow and plasma fields in parallel and asymmetric atmospheric pressure dielectric barrier discharge plasma are analyzed with the help of the phase contrast imaging method, and a gated intensified CCD. Buoyancy plumes rising from resistively heated tungsten wires along with the phase contrast technique were used to study the induced flow topology. The experiment was carried out using several electrode diameters/widths, applied high voltages and frequencies. Correlation between the electrode dimension, size of induced swirls above the exposed electrode and induced body force are also identified. Time-resolved phase contrast imaging of buoyant plumes passing through the discharge was used to measure the instantaneous velocity of various flow fields. [Preview Abstract] |
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QRP1.00062: The role of molecular air species in kHz driven atmospheric pressure plasma jets Qais Th. Algwari, Deborah O'Connell Non-thermal plasmas operated at ambient pressure and temperature are of particular technological interest. Mixing of ambient air with the plasma channel and its influence on the plasma sustainment and propagation mechanisms, and reactive species production is very important for controlling and delivering the plasma for applications. The excitation dynamics within the main plasma production region and the resulting plasma jets of a kHz atmospheric pressure dielectric barrier discharge (DBD) jet was investigated. The plasma is created within a quartz tube surrounded by two electrode rings and is operated in helium with nitrogen admixtures. The emission is measured phase, space and spectrally resolved. The plasma ignites as a streamer-type discharge and propagates in the gas channel into ambient air. The influence of varying nitrogen admixtures to the spatio-temporal dynamics of the guided streamer is presented. Interaction of the plasma jet channel with ambient air is investigated through interacting two gas flows; as the mixing of molecular air impurities changes along the channel, the plasma profile is observed to change accordingly influencing the plasma propagation and structure. [Preview Abstract] |
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QRP1.00063: PLASMA DATA EXCHANGE PROJECT |
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QRP1.00064: Coherent set of electron cross sections for argon L.L. Alves, C.M. Ferreira This paper presents a coherent set of electron impact cross sections for argon [1] (elastic momentum-transfer, inelastic for the excitation of 37 levels Ar(4s,4p,3d,5p,4d,6s) and ionization), which was recently uploaded onto the LXcat IST-Lisbon database [2]. The cross section set was validated by comparing calculated swarm parameters (electron mobility and characteristic energy) and rate coefficients (Townsend ionization coefficient and direct + cascade excitation coefficients to the 4s and 4p states) with available experimental data, for $E/N$ = 10$^{-4}$ -- 100 Td and $T_{g}$ = 300, 77 K. The validation procedure involves the solution to the homogeneous two-term electron Boltzmann equation, resorting to three different solvers: (i) IST-Lisbon's; (ii) BOLSIG+ (v1.2) with LXcat; (iii) BOLSIG+ (v1.23) [3]. The results obtained with these solvers are compared to evidence the importance of certain numerical features related with both the energy-grid (number of points, grid-type and maximum energy value) and the interpolation scheme adopted for the cross sections. In particular, the latter can cause a 6{\%} variation on the values of swarm parameters at intermediate E/Ns. [1] A. Yanguas-Gil, J. Cotrino and L.L. Alves, J. Phys. D 38, 1588 (2005). [2] http://www.lxcat.laplace.univ-tlse.fr/ [3] G.J.M. Hagelaar and L.C. Pitchford, Plasma Sources Sci. Technol. 14, 722 (2005). [Preview Abstract] |
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QRP1.00065: Electron scattering from krypton: High-resolution electron scattering experiments and B-spline R-matrix calculations Oleg Zatsarinny, Klaus Bartschat, Michael Allan In a joint experimental and theoretical effort, we carried out a detailed study of elastic scattering and electron impact excitation of the $\rm 4p^5 5s$ states in Kr. Independently normalized, absolute angle-differential cross sections over the entire angular range ($0^\circ - 180^\circ$) for a number of energies in the near-threshold region, as well as energy scans for selected angles, show very satisfactory agreement between the present experimental results and predictions from a fully relativistic Dirac \hbox{$B$-spline} \hbox{$R$-matrix} model~[1,2]. Consequently, we expect our angle-integrated elastic, momentum-transfer, and excitation cross sections to be very suitable for modeling applications. \\[4pt] [1] O.~Zatsarinny, K.~Bartschat, and M.~Allan, Phys. Rev.~A~{\bf 83} (2011) 032713\\[0pt] [2] M.~Allan, O.~Zatsarinny, and K.~Bartschat, J. Phys. B~{\bf 44} (2011) 065201 [Preview Abstract] |
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QRP1.00066: Compilation of cross sections for kinetic models of low pressure hydrogen discharges A.V. Phelps We report an initial compilation of cross sections that have been used to model\footnote{A. V. Phelps, {\it Phys. Rev. E} {\bf 79}, 066401 (2009).}$^,$\footnote{A. V. Phelps, {\it Plasma Sources Sci Technol.} {\bf 20}, 043001 (2011).} the collisional kinetics of low-pressure discharges in H$_2$. Processes that are considered include electron momentum transfer, excitation, and ionization collisions with H$_2$; momentum transfer, H$_\alpha$ excitation, ionization, and charged pair formation in collisions of H$^+$, H$_2^+$, H$_3^+$, H, H$_2$,and H$^-$ with H$_2$; collisions of electrons, H$^+$, H$_2^+$, H$_3^+$, H, H$_2$, and H$^-$ with graphite and Cu surfaces resulting in secondary electrons, particle reflection, and negative ion formation. For each major category, the compilation includes a section reviewing data sources. The recommendations are expressed as analytic formulas expected to be good to $\pm 10\%$. This compilation is expected to be refined from time to time. As part of the Plasma Data Exchange Project, the compilation will be made available at http://www.lxcat.laplace.univ-tlse.fr/ and/or http://www.icecat.laplace.univ-tlse.fr/. [Preview Abstract] |
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QRP1.00067: Implement of Data Collection and Evaluation System for Plasma Chemistry Jun-Hyoung Park, Mi-Young Song, Sung-Ha Hwang, Jung-Sik Yoon Since the characteristics of plasma depend strongly on the interactions between plasma particles, well-evaluated plasma chemistry data is needed to understand and produce various types of plasma. Therefore, many research groups have been researched for plasma chemistry with experimental or theoretical method. However, previously published data was not fully evaluated among them. In this work, therefore, we developed data collection and evaluation system for plasma chemistry, which supports well evaluated data by experties. [Preview Abstract] |
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QRP1.00068: Comparisons of sets of electron-neutral scattering cross sections and calculated swarm parameters in He and Ne S.F. Biagi, M.C. Bordage, G.J.M. Hagelaar, L.C. Pitchford, W.L. Morgan, A.V. Phelps, V. Puech In the context of the recently initiated GEC Plasma Data Exchange project, we compare measured swarm parameters with those calculated using sets of cross sections, compiled by different authors, in helium and neon. These data are on-line at www.lxcat.laplace.univ-tlse.fr. The cross section compilations for electron scattering from ground state helium or neon vary mainly in the level of detail provided for inelastic excitation, ranging from one effective excitation level to many individual levels. The swarm parameters were calculated using a 2-term Boltzmann solver and a Monte Carlo simulation. Calculated swarm parameters from the various compilations show good agreement among themselves in both gases, and generally good agreement is obtained between calculated and measured swarm parameters except for ionization coefficients at low E/N where measured ionization coefficients in both gases show strong influences of Penning ionization of impurities. We conclude that the cross section compilations and their use in a 2-term Boltzmann solver yield results sufficiently accurate for plasma modeling purposes. [Preview Abstract] |
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QRP1.00069: Comparisons of sets of electron-neutral scattering cross sections and calculated swarm parameters in Ar S.F. Biagi, L.L. Alves, C.M. Ferreira, M.C. Bordage, G.J.M. Hagelaar, L.C. Pitchford, W.L. Morgan, A.V. Phelps, O. Zatsarinny, K. Bartschat Extensive data are available in the literature for cross sections for electron-neutral scattering from argon and for swarm parameters in argon and argon-containing gas mixtures. Seven independently compiled sets of cross sections in argon are presently available on the LXCat website, including one set of data derived from theory. The recent theoretical elastic momentum transfer cross section is in excellent agreement with recent results from a swarm analysis. The purpose of this communication is to show intercomparisons of swarm parameters calculated using these different sets. For the most part and within the accuracy required for plasma modeling, calculated swarm parameters using the different cross section sets agree with experiement and among themselves. Swarm parameters calculated using classic 2-term Boltzmann solvers are in good agreement with those from Monte Carlo simulations except for the diffusion coefficients, where the 2-term approximation overestimates the values by about 30{\%} in the 5 to 100 Td range. The cross section sets and measured swarm parameters used in this work are available on-line at www.lxcat.laplace.univ-tlse.fr. [Preview Abstract] |
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QRP1.00070: Comparisons of sets of electron-neutral scattering cross sections and calculated swarm parameters in Kr and Xe M.C. Bordage, G.J.M. Hagelaar, L.C. Pitchford, S.F. Biagi, V. Puech Xenon is used in a number of application areas ranging from light sources to x-ray detectors for imaging in medicine, border security and high-energy particle physics. There is a correspondingly large body of data available for electron scattering cross sections and swarm parameters in Xe, whereas data for Kr are more limited. In this communication we show intercomparisons of the cross section sets in Xe and Kr presently available on the LXCat site. Swarm parameters calculated using these cross sections sets are compared with experimental data, also available on the LXCat site. As was found for Ar, diffusion coefficients calculated using these cross section data in a 2-term Boltzmann solver are higher than Monte Carlo results by about 30{\%} over a range of E/N from 1 to 100 Td. We find otherwise good agreement in Xe between 2-term and Monte Carlo results and between measured and calculated values of electron mobility, ionization rates and light emission (dimer) at atmospheric pressure. The available cross section data in Kr yield swarm parameters in agreement with the limited experimental data. The cross section compilations and measured swarm parameters used in this work are available on-line at www.lxcat.laplace.univ-tlse.fr. [Preview Abstract] |
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QRP1.00071: PLASMA DIAGNOSTICS TECHNIQUES II |
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QRP1.00072: Frequency probe measurements of electron density, plasma potential, and electron energy distribution in processing plasmas Dave Boris, Richard Fernsler, Scott Walton RF frequency probes are an attractive alternative to Langmuir probes due to their ability to measure electron density in reactive and depositing plasma chemistries. In addition, frequency probes provide the same variety of plasma parameters for which Langmuir probes are used (plasma density, electron temperature, plasma potential and electron energy distributions). This work presents frequency probes measurements of plasma density over a range of 10$^{9}$ to 10$^{12}$ cm$^{-3}$ in a variety of processing plasma chemistries (N$_{2}$, CH$_{4}$, NH$_{4}$, O$_{2}$ and SF$_{6})$. This work also features high resolution energy distribution function measurements using RF frequency probes which investigate the effects of molecular gases on electron energy distributions. [Preview Abstract] |
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QRP1.00073: Experimental investigation of argon metastable density and electron temperature in low-pressure plasma by line-ratio OES technique Young-Kwang Lee, Yu-Sin Kim, Jae-Won Lee, Hye-Ju Hwang, Chin-Wook Chung The measurement of metastable atom densities and electron temperatures are performed in inductively coupled plasma (ICP) source (13.56 MHz) combined with biased electrode (12.5 MHz), in pure argon or in mixtures of N2. The argon metastable densities and electron temperatures are derived under the different discharge conditions, i.e., E-H mode transition, rf power biasing and Ar-N2 mixtures. The observation of certain argon spectral lines (750.4, 751.5 and 811.5 nm) is made with optical emission spectroscopy (OES) at the pressure of 50 and 100 mTorr. In the same plasma conditions, rf-compensated Langmuir probe is used to measure the electron energy distribution functions (EEDFs) that provides the accurate rate coefficients to calculate the line-ratio OES method. It is found that the 1s5 metastable density was found to be the highest concentration at mode transition region but it decreases with increasing rf bias power or mixing ratio of N2. The measurements of electron temperature measured by line-ratio OES and probe confirmed that electron temperature was relatively uniform at mode transition but it increases with increasing rf bias power or mixing ratio of N2. [Preview Abstract] |
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QRP1.00074: Double probe using an ac bias signal for plasma parameters measurement Se-Jin Oh, Ik-Jin Choi, Jin-Yong Kim, Chin-Wook Chung In low temperature plasmas, the diagnostics of plasma characteristic parameters such as electron temperature and plasma ion flux are important to analyze the physical phenomena of plasmas or to control the condition of the processing plasmas. A double probe diagnostic using an ac bias signal between both probe tips was developed. The electron temperature and ion flux were derived by analyzing the first and third harmonic currents of the probe. The double probe was compared with the ion probe at various rf powers and pressures in an inductively coupled plasma. The electron temperature and ion flux measured from the double probe were in good agreement with those from the ion probe. This can be applied to an electrically isolated diagnostic system for processing plasmas. [Preview Abstract] |
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QRP1.00075: A study on floating harmonic method in non-Maxwellian plasmas Kyoung Yoo, Jin-Young Bang, Yu-Sin Kim, Chin-Wook Chung Electron energy distribution function (EEDF) is an important parameter to understand electron kinetics. Floating harmonic method provides the real-time measurement of plasma density and electron temperature at a floating potential with little perturbation to plasma. However, this method assumes a Maxwellian electron distribution and cannot measure the EEDF. In this study, we suggest a estimation method for the EEDF using the floating harmonic method without scanning an entire electron energy region. A theoretical study was also performed to calculate harmonic currents flowing through the probe in various EEDFs. According to theoretical results, the type of the EEDF was able to estimate by the ratio of the harmonic currents. Experiment results were in good agreement with the theoretical results in the various EEDFs. In conclusion, this method is expected to complement the conventional floating harmonic method in non-Maxwellian electron distributions. [Preview Abstract] |
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QRP1.00076: Measurement of the plasma density and electron temperature uniformities in inductively coupled plasmas using 2D real time measurement method Young-Cheol Kim, Yu-Sin Kim, Se-Jin Oh, Hyo-Chang Lee, Chin-Wook Chung Recently, two-dimensional (2D) wafer-type probe sensor for the measurement of spatial distribution of plasma parameters was developed based on the floating harmonic method by Chung and co-workers [1, 2]. In this study, the 2D plasma density profile and electron temperature were measured in inductively coupled plasma (ICP) with various external parameters such as RF power, gas pressure, gas mixing ratio. It was found that the plasma uniformity was significantly changed with external parameters, such as gas pressure, He gas mixing, and ICP power. These results are closely related to the electron kinetics, plasma diffusion neutral depletion and ionization process and give guide lines for plasma uniformity control method by changes in the external parameters. \\[4pt] [1] M. H. Lee, S. H. Jang, and C. W. Chung, J. Appl. Phys. 101, 033305 (2007).\\[0pt] [2] Y. C. Kim, S.H. Jang, G.H. Kim, and C. W. Chung, ``Real time two-dimensional spatial distribution measurement method of electron temperature and plasma density,'' 62nd Gaseous Electronic Conference, 2009 [Preview Abstract] |
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QRP1.00077: Catalytic probe measurements in a large scale CCP reactor Sasa Lazovic, Kosta Spasic, Nevena Puac, Gordana Malovic, Uros Cvelbar, Miran Mozetic, Zoran Lj. Petrovic A large scale cylindrical asymmetric CCP reactor is suitable for efficient treatment of materials like polymers, textile and plant seeds. Plasma is homogeneous and stable from transitions to streamers. For many biomedical and textile treatment effects, role of extremely reactive atomic oxygen species is very important. For instance, the formation of new oxygen-containing groups on the fiber surface is suggested to be due to the presence of extremely reactive atomic oxygen species in discharge during the air plasma processing and/or post-plasma chemical reactions when the activated fiber surface reacts with environmental species. Measurements were performed using nickel catalytic probe placed side-on to the powered electrode. Concentrations of neutral oxygen atoms were measured for a range of powers given by the RF generator, at several different distances from the powered electrode, in air at two different pressures. Oxygen atom concentrations coming to the surface of the samples can be controlled by adjusting the pressure, distance from the powered electrode and RF power. [Preview Abstract] |
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QRP1.00078: Time resolved ICCD images of an atmospheric pressure plasma jet Nevena Puac, Dejan Maletic, Sasa Lazovic, Gordana Malovic, Antonije Djordjevic, Zoran Lj. Petrovic Plasma bullet is a relatively new plasma source with a large field of potential applications, from biomedical to material processing and surface activation. Our plasma bullet was made of Pyrex glass tube with two electrodes. The width of the electrodes and distance between them was 15~mm. The buffer gas was helium with a flow of 4~slm. High voltage probe was used to obtain voltage waveforms while current waveforms were measured at the resistor. Working frequency was 80~kHz and the power transmitted to the plasma was less than 5~W. Time-resolved images obtained by fast ICCD camera show that the plasma is not continuous, but consisted of small packages of plasma traveling at high speeds. The velocity of these packages outside of the tube is much larger ($\sim $15~km/s) than the speed of the feed gas ($\sim $7~m/s). On the other hand, the velocities in the zone of the electrodes are smaller ($\sim $5~km/s) than the speed of the bullet, but still much higher than the speed of the flowing gas. [Preview Abstract] |
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QRP1.00079: Determination of Electron and Ion Energy Distribution Functions in a Plasma Ion Assisted Deposition (PIAD) Process J. Harhausen, R. Foest, A. Ohl High performance optical coatings are commonly produced by PIAD in order to achieve comparably high deposition rates. Here, the plasma source is a hot cathode direct current discharge with an auxiliary magnetic field (APS). Its design is such to generate a population of fast ions to be released into the deposition chamber. A detailed understanding of the plasma properties in the chamber is mandatory to increase the level of uniformity and reproducibility of the deposition process. In order to determine the electron and ion energy distribution functions (EEDF,IEDF) the concepts of the Langmuir probe, the retarding field energy analyzer and optical emission spectroscopy are employed. Fundamental findings are that the EEDF can be described in the framework of the non-local approximation and that the degree of ionization inside the APS is close to unity. The shape of the IEDF and its evolution along the beam path can be described consistently by considering charge exchange reactions with the background neutral gas and the profile of the plasma potential. [Preview Abstract] |
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QRP1.00080: Tomographic Reconstruction of Local Parameters of a Plasmoid in the Afterglow of a Supersonic Flow Microwave Discharge Ana Samolov, Milka Nikolic, Alexander Godunov, Svetozar Popovic, Leposava Vuskovic, Filip Cuckov The tomographic reconstruction of local plasma parameters has been used for characterization of a plasmoid in the afterglow region of an Ar supersonic microwave discharge. A cylindrical cavity was used to sustain a discharge in the pressure range of 100-600 Pa. The developed tomographic numerical method is based on the 2D Radon formula for a cylindrical cavity. The optical emission spectroscopy measurements are taken at different positions and under different directions to observe populations of excited and ionic species in the plasmoid region. ~An Automated Measurement System (AMS) has been built with the aim to increase the overall precision of the taken measurements as well as to streamline the measurement process. The AMS consists of the mirror and a microcontroller-based system, composed of two high-precision stepper motors and several sensors providing precise feedback control. The AMS has controlled the angle and distance of measuring system from the cylindrical cavity, within sub-degree angle precision and sub-millimeter distance precision. [Preview Abstract] |
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QRP1.00081: Electron Density Measurements in Nitrogen-Containing Pulse-Repetitive Microwave Discharge Milka Nikolic, Ana Samolov, Alexander Godunov, Svetozar Popovic, Leposava Vuskovic A simple, time and space-accurate technique for absolute measurements of the electron density in pulse-repetitive microwave discharges in air is proposed. It is a non-intrusive method based on analysis of molecular bands on Nitrogen Second Positive System C$^{3}\Pi _{u }\to $ B$^{3}\Pi _{g}$ (0-0) at 337.1 nm. The electron density is obtained from a numerical solution to the time-dependent equation for the population rate of N$_{2}$ C$^{3}\Pi _{u}$ (v=0) using the measured temporal waveforms of the absolute C$^{3}\Pi _{u }\to $ B$^{3}\Pi _{g}$ (0-0) band intensity, and the measured forward and reflected microwave power densities. The applicability of the method was tested in the surface plasma generated at the aperture of the horn antenna by a pulse repetitive microwave beam. The discharge was generated in air at 1.6 kPa with a X-band microwave generator using 3.5 $\mu $s microwave pulses at peak power of 210 kW. The electron density was time resolved on sub microsecond scale, within a single 3.5 $\mu $s pulse. We obtained (90 $\pm $ 0.6) $\times $10$^{13}$ cm$^{-3}$ for the peak value and (5.6$\pm $ 0.6) $\times $10$^{13}$ cm$^{-3}$ for the pulse average electron density in 1.6 kPa of air. [Preview Abstract] |
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QRP1.00082: Quantitative evaluation of the effect of multiphoton ionization in laser Thomson scattering diagnostics of low-temperature plasmas Akihiro Kono, Yukitaka Matsuda, Ken Okada, Mitsutoshi Aramaki Laser Thomson scattering technique allows one very high spatial-resolution measurements of electron density and temperature as required in diagnostics of microplasmas or measurement of regions very close to the wall. In such high-resolution measurements, laser energy density in the scattering volume must be very high for obtaining sufficient amount of scattering photons; therefore, electron production via multiphoton ionization by the laser beam may significantly affect Thomson scattering due to plasma electrons. In order to clarify the effect of multiphoton ionization in Thomson scattering diagnostics, we have been measuring absolute efficiency of multiphoton ionization caused by frequency-doubled Nd:YAG laser for various gases including rare gases, N$_{2}$, O$_{2}$, CF$_{4}$ and SF$_{6}$. It has been found that electrons produced via multiphoton ionization can reach a significant fraction of plasma electrons even at low pressures, depending on the gas species and laser focusing conditions. Details will be given in the presentation, including simulation results about how the escape of photoelectrons from the scattering volume affects the situation. [Preview Abstract] |
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QRP1.00083: DC Self Bias Trends in Dual Frequency PECVD Deposition Systems D.L. Keil, E. Augustyniak, C. Leeser, F. Galli Capacitively coupled plasma (CCP) etch systems commonly report the DC auto or self bias developed as a consequence of capacitively coupling RF to the plasma. Frequently, these systems employ wafer pedestals comprised of electrostatic chucks which must monitor the self bias as part of their normal operation. DC self bias is often found to correlate with various etch process behaviors or system states. It is less common, however, to find CCP deposition systems that report DC self bias. This work reports results of a study of DC self bias trends due to chamber pressure, chamber conditioning and aging, and changes in wafer pedestal hardware. In particular, chamber film accumulation is found to correlate to certain DC bias trends. The applicability of these results for process tracking and system monitoring is discussed. Additionally, the DC self bias response to deliberate perturbations to the RF system are examined. These perturbations include those not normally encountered during commercial deposition such as `bleeding' current to ground. [Preview Abstract] |
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QRP1.00084: PLASMA MODELING AND SIMULATION II |
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QRP1.00085: Simulations of positive streamers with highly accurate transport data Sasa Dujko, Gideon Wormeester, Ute Ebert Streamers are the first mode of electric breakdown of non-ionized matter exposed to strong electric fields. Growing streamer filaments can emerge in a wide variety of gases and pressures. Previous experiments and numerical simulations have shown that streamer properties such as velocity and diameter are remarkably insensitive to changes in gas composition. In our numerical simulations, we use a fluid model to compute the densities of charged particles, obeying drift-diffusion-reaction equations. Previously, we used a constant, empirical value for the diffusion and mobility coefficients in these simulations. Using a multi term theory for solving the Boltzmann equation, we now have highly accurate transport data, which we have used to simulate streamers in N$_{2}$:O$_{2}$ mixtures to compare with our previous results. It is found that the simulated streamers are more sensitive to the transport data than they are to the gas composition. [Preview Abstract] |
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QRP1.00086: Discharge dynamics in a helium capacitively coupled plasma with variable oxygen admixture Arthur Greb, Kari Niemi, Deborah O'Connell, Timo Gans The discharge dynamics in a helium capacitively coupled plasma with variable oxygen admixture are investigated by means of a one-dimensional numerical fluid model with semi-kinetic treatment of electrons and accompanying phase and space resolved measurements. The discharge is operated at 40 Pa with a sinusoidal driving voltage at a frequency of 13.56 MHz and is solved self-consistently in the model for each individual RF-cycle. Spatial profiles of dominant charged particles (O2+, O-, e) in the gas mixture exhibit a distribution change under variation of the oxygen admixture. Discharge excitation dynamics, in particular of the atomic oxygen line $\lambda $ = 844 nm (3P -3S) are investigated and compared to those observed from experiments. The simulations show and experiments confirm that additional oxygen in the helium discharge significantly changes the excitation mechanisms and promotes the excitation from secondary electrons. [Preview Abstract] |
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QRP1.00087: A spectral Poisson solver for kinetic plasma simulation Daniel Szeremley, Jens Obberath, 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) [1]. 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 this contribution we concentrate on the specialized Poisson solver for that tool. The plasma is represented by an ensemble of point charges. By expanding both the charge density and the potential into spherical harmonics, a largely analytical solution of the Poisson problem can be employed. For a practical implementation, the expansion must be appropriately truncated. With this spectral solver we are able to efficiently solve the Poisson equation in a kinetic plasma simulation without the need of introducing a spatial discretization.\\[4pt] [1] M. Lapke et al., Appl. Phys. Lett. {\bf 93}, 051502 (2008) [Preview Abstract] |
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QRP1.00088: Model of fusion kinetics for electrostatic inertial confinement discharges in D$_2$ A.V. Phelps A model\footnote{A. V. Phelps, {\it Plasma Sources Sci Technol.} {\bf 20}, 043001 (2011).} of the collisional kinetics of low-pressure glow discharges in H$_2$ is extended to predict the energy spectrum of the protons from the D-D fusion reaction in the deuterium-filled, inertial electrostatic confinement device of Boris et. al.\footnote{D. R. Boris, et. al. {\it J. Appl. Phys.} {\bf 107}, 123305 (2010).} Deuterium and hydrogen cross sections are assumed equal. D$^+$, D$_2^+$, or D$_3^+$ ions injected into a potential minimum created by cathode grid wires produce positive and negative ions, fast neutrals, and electrons. D nuclei undergo D-D fusion reactions with the background D$_2$ and produce protons with Doppler shifted peaks above and below the reaction energy of 3.02 MeV. The model shows the highest fusion flux, a good fit to the proton spectrum, and at good fit of the calculated$^1$ anion energy distribution to experiment\footnote{D. R. Boris, et. al. {\it Phys. Rev. E} {\bf 80}, 036408 (2009).} with D$_3^+$ injection using an effective discharge voltage of 27 kV for an applied voltage of 70 kV. The calculated proton flux is $\sim 10^{-10}$ of the injected ion flux. Predicted deuterium ion energy distributions are very different from that unfolded$^2$ from the proton spectrum. With D$_2^+$ injection, the proton flux is reduced by about an order of magnitude. [Preview Abstract] |
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QRP1.00089: Modeling and Simulation of the sheath in radio-frequency driven plasmas at atmospheric pressure Torben Hemke, Thomas Mussenbrock, Ralf Peter Brinkmann Microplasmas at atmospheric pressure recently gained increasing attention. Due to their extraordinary characteristics new fields of applications are explored. Various aspects of the discharge mechanisms have to be considered to model and simulate microplasmas. Since microplasmas are dominated by their spatial boundaries, this particularly holds for the sheaths. In this paper we focus on the sheath of radio-frequency driven microplasmas at atmospheric pressure. To account for the chemistry of characteristic applications we set up a multi-species model of the sheath. Based on a scale analysis in time and space we discuss resulting assumptions for the fluid equations for electrons and ions. We solve for these equations self-consistently coupled to Poisson's equation for the electrostatic potential. Finally, we present the density profiles of the electrons and ions depending on various discharge parameters. [Preview Abstract] |
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QRP1.00090: Kinetic simulation of radio-frequency driven plasmas in He/O$_2$ mixtures at atmospheric pressure Denis Eremin, Torben Hemke, Ralf Peter Brinkmann, Thomas Mussenbrock Over the past years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are radio-frequency plasma jets. This contribution investigates radio-frequency driven plasmas with an electrode gap of below 1 mm. The discharge is operated in a mixture of He and O$_2$ (0.5 percent) at atmospheric pressure. A typical simulation of this kind of discharges is based on the hydrodynamic approximation of the relevant species. Sometimes this approach is extended by a quasi-kinetic treatment of the fast electron component (hybrid codes). Still certain kinetic effects are neglected in both of these methods. In this work a 1d self-consistent Particle-in-Cell model of the discharge is developed, to investigate kinetic effects and to verify the validity of the corresponding fluid model. All the relevant species and reactions regarding the underlying chemistry are taken into account by means of a Monte Carlo Collision model. [Preview Abstract] |
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QRP1.00091: Chemical kinetics study of a nanosecond pulsed He-O2 plasma Jet Shengguo Xia, Chunqi Jiang Atmospheric-pressure, nanosecond pulsed plasma jets have shown promising applications in biomedical and dental fields. In order to better understand the mechanisms associated to the plasma processes, a zero-dimensional plasma chemistry model was used to study the chemical kinetics of an atmospheric-pressure, nanosecond pulsed He-O2 plasma jet. Density kinetics of the charged and neutral species in the plasma jet as a function of the input parameters including the oxygen concentration and the electric field are calculated. The roles played by different reactions in the kinetics schemes are assessed. In addition, both of He-O2 and He-O2-N2 plasma chemical kinetics reaction schemes are discussed to examine the effects of air entrainment on the characteristics of the plasma jet. [Preview Abstract] |
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QRP1.00092: Use of the shell model for plasma physics simulation Elisabetta Boella, Gianni Coppa, Antonio D'Angola, Frederico Fi\'uza, Luis O. Silva In problems of interest for plasma physics with a high degree of symmetry (spherical, cylindrical or planar), a particle-based computational technique can be adopted in which the electric field is calculated without using a spatial grid. As an example, referring to the spherical geometry, the electric field can be calculated assuming that each particle behaves like a ``shell'' and therefore $E(r)$ is proportional to the sum of the charges \textit{qi }of the shells with radii \textit{ri$<$r}. The technique has the double advantage of avoiding the use of a spatial grid and of allowing an infinite radial domain. It has been successfully used to study the expansion of spherical and cylindrical plasmas and to analyze the collision of two slabs of plasma with different densities and temperatures. [Preview Abstract] |
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QRP1.00093: Simulations of the Plasma Structure of a Radial Line Slotted Antenna Plasma Source Jun Yoshikawa The Radial Line Slot Antenna (RLSA) plasma source couples microwave power through a slot antenna structure and window to a plasma characterized by a generation zone adjacent to the window and a diffusion zone that contacts a substrate. The diffusion zone is characterized by a very low electron temperature. This property renders the source useful for soft etch applications and thin film processing for which low ion energy is desirable. Another property of the diffusion zone is that the plasma density falls from the axis to the walls. Static magnetic fields at the walls of other plasma sources have been shown to impede electron losses to walls lowering their loss rate and changing the plasma profile. [1] In this presentation, the impact of different magnetic field configurations on the diffusion zone plasma structure will be described. To do this, an ambipolar-electromagnetic field model previously used to describe RLSA plasmas is modified to account for the impact of magnetic fields on transport coefficients and plasma chemistry. Resonant and other effects of magnetic field are also discussed.\\[4pt] [1] J. Vac. Sci. Technol. B12 470 1994. [Preview Abstract] |
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QRP1.00094: Multi-dimensional modelling of atmospheric pressure discharges with complex chemistry M.M. Iqbal, M.M. Turner Atmospheric pressure discharges typically have complex chemistry. In particular, such discharges commonly operate in a mixture of helium and air. Understanding the chemical kinetics of such plasmas is important for the development of applications. There is presently little understanding of the relationship between the operating conditions of the discharge and the characteristics of the resulting plasma. This work discusses a three-dimensional simulation of a dielectric barrier discharge with helium-air chemistry. In particular, we examine the effect of the discharge gap and driving frequency on the spatial structure and chemical character of the plasma. Filamentation, for example, is inhibited at driving frequencies in excess of 70 KHz. We will also present comparisons with relevant experiments. [Preview Abstract] |
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QRP1.00095: Modeling of self-consistent artificial radiowave ionospheric turbulence pumping and damping Andrey Kochetov The numerical simulations of the action of self-consistent powerful radiowave absorption arising in the regions of artificial plasma turbulence excitation at formation, saturation and relaxation stages of the turbulence structures (Kochetov, A.V., Mironov, V.A., et. al., Physica D, Nonlinear phenomena, 2001, 152-153, 723) to refection index dynamics are carried out. The nonlinear Schr\"odinger equation in inhomogeneous plasma layer with incident electromagnetic wave pumping and backscattered radiation damping (Kochetov, et al, Adv. Space Res., 2002, 29, 1369 and 2006, 38, 2490) is extended with the imaginary part of plasma dielectric constant, which results the energy transformation from electromagnetic wave to plasma one at resonance interaction (D.V. Shapiro, V.I. Shevchenko, in Handbook of Plasma Physics 2, eds. A.A Galeev, R.N. Sudan. Elsevier, Amsterdam, 1984). The modeling reproduces the basic energy transformation peculiarities: hard excitation, non-linearity, hysteresis (A.V. Kochetov, E. Mj{\o}lhus, Proc. of IV Intern. Workshop ``SMP,'' Ed. A.G. Litvak, Vol.2, N. Novgorod, 2000, 491) and demonstrates that the calculated reflection and absorption index dynamics at the beginning of the saturation stage agrees qualitatively to the experimental results for ionosphere plasma modification study. (Thide B., E.N. Sergeev, S.M. Grach, et. al., Phys. Rev. Lett., 2005, 95, 255002). [Preview Abstract] |
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QRP1.00096: BASIC PLASMA PHYSICS PHENOMENA II |
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QRP1.00097: Spatiotemporal measurement of translational and vibrational temperatures after pulsed corona discharge using laser spectroscopy Ryo Ono, Yoshiyuki Teramoto, Yusuke Nakagawa, Atsushi Komuro, Tetsuji Oda Translational and vibrational temperatures are measured in pulsed corona discharge using spatiotemporally resolved laser-induced fluorescence (LIF) and coherent anti-Stokes Raman scattering (CARS). The discharge occurs in a 13-mm point-to-plane gap with pulsed voltage of approximately 30 kV. Immediately after the discharge pulse, the vibrational temperatures of N2(v) and O2(v), Tv, are much higher than the translational temperature, Tt. Then, after the discharge pulse, Tv decreases with time, and the energy released from the vibrational relaxation increases Tt. This vibration-to-translation (V-T) energy transfer is observed; Tv and Tt change by hundreds to a thousand K after the discharge pulse with time constants of 1 us to 1 ms. It is shown that the V-T rate is remarkably increased when the ambient air is humidified. It is caused by extremely rapid V-T process of H2O-H2O system. In addition, V-T acceleration of O2(v) by O atoms due to rapid V-T rate of O2(v)-O system is also measured. The spatial profile of Tv shows that Tv decreases with increasing distance from the tip of needle electrode. It indicates that Tv, and the resulting Tt, are higher in the secondary streamer channel than in the primary streamer channel. [Preview Abstract] |
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QRP1.00098: Mass analysis of trifluoro-iodo-methane in a Surface Barrier Discharge J.A. Rees, C.L. Greenwood, D.T. Lundie, D.L. Seymour Surface barrier discharges operated at atmospheric pressure are effective chemical reactors. Mass analysis of the reaction products is possible using suitable high pressure mass spectrometer systems. As an example of the behaviour of simple surface barrier reactor (SBDs), experiments on the decomposition of CF3I are described in which the output from the reactor is admitted via a capillary inlet system into a Hiden HPR20 mass spectrometer. The discharge was operated using helium as the carrier gas. The observed mass spectra are discussed in terms of the plasma dissociation and the subsequent ionisation of the dissociated products in the electron impact ionisation source of the mass spectrometer. When oxygen was added to the gas mixture in the SBD, CFxO species were generated in the plasma. Their influence on the observed mass spectra is shown. The results demonstrate aspects of the capabilities of SBDs for dissociating halocarbon gases at atmospheric pressure and the possibilities of direct mass spectrometric monitoring of such processes. [Preview Abstract] |
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QRP1.00099: Mechanisms of Ion-Molecule Reactions in Cyclohexane Charles Jiao, Steven Adams Cyclohexane is one of the important components in practical fuels and has been chosen as representative cycloalkanes in several proposed surrogate mixtures for jet fuels. We have recently studied the gas-phase ion-molecule reactions in cyclohexane, using Fourier-transform mass spectrometer (FTMS). By experiments with isotope reagents, the reaction mechanisms are studied. Hydride transfer is the most common reaction channel. For small reactant ions such as C$_{2}$H$_{3}^{+}$, it proceeds via direct hydride transfer mechanism, while for large reactant ions such as C$_{4}$H$_{7}^{+}$, it proceeds via complex formation. Other reaction mechanisms include charge transfer, H$_{2}^{-}$ transfer, H$_{3}^{-}$ transfer, CH$_{3}^{-}$ transfer, C$_{2}$H$_{4}^{-}$ transfer, and association. [Preview Abstract] |
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QRP1.00100: Ion Source for Study of the Interaction of High Ion Fluxes with Fusion Relevant Plasma Facing Materials Aleksander Bizyukov, Ivan Bizyukov, Kostyantyn Sereda, Oleksii Girka This work describes the theoretical and experimental study of properties of the Hall thruster with the ballistic and magnetic ion beam focusing (FALCON) [1]. Based on the ion trajectories numerical analysis, the improved shape of the cathode poles has been proposed, designed and manufactured. The current density profile has been obtained in the plane of the hydrogen beam crossover. It demonstrates the high power density localization. The set of experiments on the interaction of the intense hydrogen ions beam with the tungsten plates has been carried out. Significant weight-loss of the sample has been observed as a result of the bombardment. Corresponding erosion yield is 10-50 times higher than should be expected for sputtering mechanism. This indicates the anomalous surface erosion that could be caused by the blister formation. The experiment indicates the focusing efficiency of Hall thruster with implemented high current ion beam density and power density of a few MW/m2 in the plane of crossover. The obtained results can be used in the development of the ion sources for simulation of the plasma-wall interactions either for ion beam processing techniques. \\[0pt] [1] M. Gutkin, A. Bizyukov, V. Sleptsov, I. Bizyukov, K. Sereda. FALCON. U.S. Patent No US 7,622,721 B2, 2008/0191629 A1 [Preview Abstract] |
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QRP1.00101: Photoluminescence Observation of GaN Thin Films Treated by Inductively-Coupled Plasmas Keiji Nakamura, Noriyoshi Itoh, Yoshitaka Nakano, Hideo Sugai This paper reports observations of photoluminescence from plasma-treated GaN thin films. A 10 mTorr Ar ICP was used, and irradiation of 313 nm ultraviolet (UV) light from Hg-Xe light source induced the photoluminescence of the GaN film. In both in-situ and ex-situ observations, significant yellow luminescence was observed visually, and the ex-situ observed luminescence ranges in a wavelength of 500-800 nm corresponding to defect-states-related transition. The measurements also revealed that the luminescence also contains UV emission at a wavelength of $\sim $365 nm attributed to transition related to near band edges. In order to examine effects of the plasma on the luminescence, the ex-situ observation was made as a function of the plasma treatment time. As the treatment time increased, both the UV and the luminescence intensity decreased, and the decrease in the emission became significant when the 313 nm UV light was irradiated onto the plasma-exposed GaN surface. These results suggested that plasma-induced defect formation leads to the luminescence degradation, and that the photoluminescence observation will be useful for damage monitoring of the GaN surface. This work is partly supported by the 2nd stage Knowledge Cluster Initiative and Grant-in-Aid for Scientific Research (C) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. [Preview Abstract] |
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QRP1.00102: MHD Waves in a Flowing Partially Ionized Prominence Plasma with Oblique Magnetic Field Nagendra Kumar Prominences are dense and relatively cool partially ionized, magnetized plasma structures in solar corona. These structures display damped oscillations (MHD waves) and flows. We study the joint effects of ion-neutral collisions and flow on the behavior of MHD waves propagating in a partially ionized prominence plasma with oblique equilibrium magnetic field. We consider one-fluid MHD equations for partially ionized homogenous hydrogen prominence plasma permeated by inclined equilibrium magnetic field. Assuming small perturbations, dispersion relation for magenetoacoustic waves in an unbounded medium is derived and solved numerically. It is found that the presence of neutrals, equilibrium flow and oblique magnetic field in plasma modifies the dispersion characteristics and influences the damping of magnetoacoustic waves in prominence plasma. The coupling of oblique magnetic field and background flow along with ion-neutral collisions provides a more complete model for the damping of magnetosonic waves with the values of physical parameters observed in prominence oscillations. [Preview Abstract] |
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QRP1.00103: Study of evaporating droplet temperature in low pressure plasma Daisuke Ogawa, Matthew Goeckner, Lawrence Overzet A key parameter of misty plasmas is the temperature (Td) of the liquid droplets in the plasma. Td determines the rate at which droplets evaporate and is a consequence of the energy balance between plasma species which bring thermal energy and droplet evaporative cooling. We are using Rhodamine B (RhB) to estimate Td because the spectrum of this dye is known to be Td dependent. For example: RhB has been used to study the temperature of dust in plasmas and fuel droplets in combustion. A complication is that there are at least two major differences between dust particles and liquid droplets in plasmas: [1] droplets evaporate which changes their RhB concentration in time and [2] droplets are expected to be as much as 150 C cooler than dust grains. Both make calibration more difficult. In this poster, we will present our progress in using this technique to estimate the temperature of evaporating droplets in low pressure plasma. This will include our calibration procedures, the RhB spectral dependencies (concentration, and T) and measurements of both droplet evaporation kinetics as well as RhB spectra in vacuum and plasma. [Preview Abstract] |
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