Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session HW1: Poster Session II (8:00-9:30AM) |
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Room: Ballroom Foyer |
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HW1.00001: PLASMA DATA EXCHANGE PROJECT |
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HW1.00002: A Web-based Delphi System for Evaluating Plasma Properties Jun-Hyoung Park, Mi-Young Song Plasma data bases are necessarily required to compute the plasma parameters, high reliable data bases are closely related with accuracy enhancement of simulations. Therefore, in this work, we developed a web-based Delphi system to obtain more accurate plasma properties such as electron-atom and electron-molecule collision cross sections. The Delphi method is a well-known structured communication technique which relies on a panel of experts. In principle, forecasts or decisions from a structured group of individuals are more accurate than those from unstructured groups. In our system, a number of plasma property experts can evaluate the plasma data using web sites that allow the process to be conducted in real-time. [Preview Abstract] |
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HW1.00003: Consistent set of electron cross sections for methane L.L. Alves, V. Guerra, C.D. Pintassilgo This contribution presents a complete consistent set of electron-impact cross sections for methane (CH$_{4})$, recently made available on the IST-LISBON database with the LXCat website [1]. The set is based on the cross sections originally compiled and adjusted in [2] and first used in [3]. The elementary processes taken into account are elastic momentum-transfer, vibrational excitation of the (1,3) and (2,4) modes, total dissociation into neutrals, and ionization producing CH$_{4}^{+}$ and CH$_{3}^{+}+$H. For the latter two processes we have adjusted the partial ionization cross section of Chatham \textit{et al.} [4] as to reproduce their measured total ionization. The new cross-section set is validated by comparing calculated and measured electron swarm parameters for $E/N=$ 0.1--400 Td. A discussion of similarities and differences with sets of CH$_{4}$ cross sections from other databases~is also presented.\\[4pt] [1] http://www.lxcat.laplace.univ-tlse.fr/\\[0pt] [2] C.D. Pintassilgo, Master Thesis, Instituto Superior T\'{e}cnico (Universidade T\'{e}cnica de Lisboa), 1996\\[0pt] [3] C.D. Pintassilgo \textit{et al.}, Plasma Sources Sci. Technol. \textbf{8}, 463 (1999)\\[0pt] [4] H. Chatham \textit{et al.}, J. Chem. Phys. \textbf{81}, 1770 (1984) [Preview Abstract] |
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HW1.00004: Updating the IST-LISBON electron cross sections for nitrogen L.L. Alves, L. Sombreireiro, P. Viegas, V. Guerra In this work we update the complete and consistent set of nitrogen (N$_{2})$ electron-impact cross-section with the IST-LISBON database, available on the LXCat website [1]. The update has extended, in energy scale up to 1keV, the cross sections for effective momentum-transfer, excitation to electronic states and ionization. The set further accounts for excitation to rotational and vibrational excited states. Calculations using BOLSIG$+$ [2] with the new cross sections give swarm parameters in very good agreement with available experimental data for the reduced mobility, the characteristic energy and the reduced ionization coefficient, for a very extended $E/N$ range up to 1000 Td. The influence of rotational excitations/de-excitations at low $E/N$ and different rotational temperatures is discussed. A critical evaluation of similarities and differences with sets of N$_{2}$ cross sections from other databases is carried out. Moreover, the procedure to de-convolute global cross sections into state-to-state vibrational level dependent cross sections is outlined and discussed.\\[4pt] [1] http://www.lxcat.laplace.univ-tlse.fr/ \\[0pt] [2] G.J.M. Hagelaar and L.C. Pitchford, Plasma Sources Sci. Technol. \textbf{14}, 722 (2005) [Preview Abstract] |
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HW1.00005: Pressing data needs for plasma-water interaction studies Bill Graham, Peter Bruggeman, Mark Kushner, Zoran Petrovic It is clear that there is a growing scientific and technological interest in the physics and chemistry of plasmas created in contact with or in the presence of water vapor. This requires knowledge of the cross sections or rate coefficients for a vast number of collision processes and there are some invaluable reviews of the available data [1], however much more data is needed. Our personal views on the most pressing needs will be presented but here are our top 5. (1) An electron impact cross section set for OH that is as extensive as that available for H$_{2}$O. ~(2) The rates for heavy particle reactions with vibrationally excited H$_{2}$O(v) and OH(v) (3) The cross sections/rate coefficients for reactions involved in positive and negative ion water clustering. (4) The temperature dependence of three body reactions. (5) The reactions at and yields from the plasma-liquid water surface interface, and their rates. In addition we need to be able to determine rates for collisions and reactions in liquid water.\\[4pt] [1] Y. Itikawa and N. Mason, J. Phys. Chem Ref Data. 34, 1 (2005) [Preview Abstract] |
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HW1.00006: Evaluation of theoretical cross sections for electron scattering from noble gases for plasma modeling Leanne Pitchford, O. Zatsarinny, K. Bartschat, D.V. Fursa, I. Bray, L.L. Alves, S. Biagi Can state-of-the-art theory now provide \textit{complete} sets of cross sections for electron scattering from noble gases suitable for use in Boltzmann calculations of swarm parameters and to the accuracy required for plasma modeling? The answer is a qualified ``yes'' for He, Ne, and Ar, but ``not yet'' for Kr and Xe. Purely theoretical cross section sets for electron scattering from these species are presently available on the LXCat website in the BRAY database for He (calculated using the convergent close-coupling technique, formulated in momentum space) and in the BSR database for the other rare gases (obtained with a convergent B-spline R-matrix with pseudo-states method, formulated in coordinated space). Although significant differences occasionally appear in some of the cross sections between experiment and theory, the calculated ionization rate coefficients as a function of reduced electric field strength, E/N, for He, Ne and Ar agree with experiment to within a few percent for the three lighter noble gases. [Preview Abstract] |
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HW1.00007: ATOMIC AND MOLECULAR PROCESSES |
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HW1.00008: Objects curvature at movement Ayman Kamel By simple experiment and notice its results, the objects curvature relativity to observer's measurements and that happened at movement the objects to others. By using Lorentz's transformations and modified it according to the experiment had done, the results prove that objects move in straight direction but in curve pathway. The results were proving that there are two sorts of curvature, the first is ``relative curvature'' and the second is ``self-curvature.'' According to two before hypothesis which the first is ``relative curvature'' and the second is ``self-curvature'' that depends on first assume, discovered new character has to all movement objects regardless of the observer's measurements. [Preview Abstract] |
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HW1.00009: Dynamic shielding effect on the polarization momentum transport collision in strongly coupled semiclassical plasmas Young-Dae Jung The influence of the quantum dynamic shielding on the polarization momentum transport collision is investigated in strongly coupled semiclassical plasmas. The electron-atom polarization momentum transport cross section is obtained by the Faxen-Holtzmark theory as a function of the collision energy, de Broglie wavelength, Debye length, thermal energy, and atomic quantum states. It is found that the dynamic shielding effect enhances the scattering phase shift as well as the polarization momentum transport cross section. The variation of quantum effect on the momentum transport collision due to the change of thermal energy and de Broglie wavelength is also discussed. [Preview Abstract] |
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HW1.00010: IAEA activities on atomic, molecular and plasma-material interaction data for fusion Bastiaan J. Braams, Hyun-Kyung Chung The IAEA Atomic and Molecular Data Unit (http://www-amdis.iaea.org/) aims to provide internationally evaluated and recommended data for atomic, molecular and plasma-material interaction (A+M+PMI) processes in fusion research. The Unit organizes technical meetings and coordinates an A+M Data Centre Network (DCN) and a Code Centre Network (CCN). In addition the Unit organizes Coordinated Research Projects (CRPs), for which the objectives are mixed between development of new data and evaluation and recommendation of existing data. In the area of A+M data we are placing new emphasis in our meeting schedule on data evaluation and especially on uncertainties in calculated cross section data and the propagation of uncertainties through structure data and fundamental cross sections to effective rate coefficients. Following a recent meeting of the CCN it is intended to use electron scattering on Be, Ne and N2 as exemplars for study of uncertainties and uncertainty propagation in calculated data; this will be discussed further at the presentation. Please see http://www-amdis.iaea.org/CRP/ for more on our active and planned CRPs, which are concerned with atomic processes in core and edge plasma and with plasma interaction with beryllium-based surfaces and with irradiated tungsten. [Preview Abstract] |
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HW1.00011: ELECTRON AND PHOTON COLLISIONS WITH ATOMS AND MOLECULES: EXCITATION |
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HW1.00012: Photon's Wavelength Stretching and Shrinking? Florentin Smarandache The photon is considered of having a dual form: wave and particle. (a) If the photon is a wave, it has been asserted that the photon's wavelength is stretched inside the intergalactic space, because of the expansion of the universe. But what happens with the photon's wavelength when the photon enters a galactic space (which is not expanding), and afterwards it exists the galactic space and enters an intergalactic space (which is expanding), and so on? But, when the wavelength increases the wave frequency decreases (redshift); therefore the wave's momentum and energy are diminished in the expansion of the universe. It seems to be an antithesis between the quantum mechanics (Copenhagen style) and the universe expansion. (b) If the photon is a particle, similarly because of the so-called expansion of the universe, does its pathlength increases inside the intergalactic space (which is expanding) and decreases inside the galactic space (which is not expanding)? Thus, what happens with its pathlength when the photon passes from an intergalactic space to a galactic space, then again to intergalactic space, and so on? [Preview Abstract] |
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HW1.00013: Electron Collision Radiative Parameters for $O^{2+}$ Swaraj Tayal The improved radiative and collision atomic parameters calculations for $O^{2+}$ 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 126 bound levels covering all possible terms of the ground $2s^22p^2$ and excited $2s2p^3$, $2p^4$, $2s^22p3s$, $2s^22p3p$, $2s^22p3d$, $2s2p^23s$, $2s^22p4s$, $2s^22p4p$, $2s2p^23p$, $2s2p^23d$, $2p^33s$, $2p^33p$, and $2p^33d$ configurations. The calculated excitation energies of the target levels are in excellent agreement with experiment and represent an improvement over the previous calculations. The present results of cross sections are compared with a variety of other close-coupling and distorted-wave calculations. The oscillator strengths and transition probabilities are in good agreement with other theories and available experimental data. The present cross sections are in good agreement with other theories for many transitions. [Preview Abstract] |
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HW1.00014: Nonperturbative electron-ion scattering theory incorporating the M{\o}ller interaction Christopher J. Bostock, Dmitry V. Fursa, Igor Bray Relativistic distorted wave studies by Fontes's etal~[\textit{Phys.~Rev.~A} {\textbf{47}}, 1009 (1993)] demonstrated that the Generalized Breit interaction (equivalently the M{\o}ller interaction) can affect electron-impact excitation cross sections of hydrogenlike ${\rm U}^{91+}$ by more that 50\% in comparison to calculations that employ the Coulomb interaction alone. We present the first calculations that investigate the effects of both the M{\o}ller interaction and close-coupling in the calculation of electron-impact excitation cross sections~[1]. Electron scattering from ${\rm U}^{91+}$ is used as a test case. The RCCC method is nonperturbative and we emphasise the restrictions and subsequent limitations associated with employing the M{\o}ller interaction in the RCCC method. \\[4pt] [1] C. J. Bostock, D. V. Fursa, and I. Bray, Phys. Rev. A 86, 042709 (2012). [Preview Abstract] |
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HW1.00015: Photoionization of Phosphorus cation induced by synchrotron radiation Antonio Ju\'arez, Alejandro Aguilar, Olmo Gonz\'alez, David Macaluso, Armando Antill\'on, Alejandro Morales, Dag Hanstorp, Aaron Covington, Kiattichart Chartkunchand, Guillermo Hinojosa, Sultana Nahar, Edgar Hern\'andez The photoionization of Phosphorus cation has been measured in the photon energy range of 18 eV to 50 eV with 40 meV resolution. A theoretical investigation is being conducted while more experimentation is being planned. The ALS is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. DOE Contract No. DE-AC02-05CH11231. AMC acknowledges financial support from the US DOE NNSA through Cooperative Agreement DE-FC52-06NA27616. DGAPA IN 113010, IN106813 and CONACYT CB-2011/167631. GH thanks technical support of ALS staff. [Preview Abstract] |
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HW1.00016: Photoionization of Cl II induced by synchrotron radiation Antonio Ju\'arez, Alejandro Aguilar, Olmo Gonz\'alez, David Macaluso, Armando Antill\'on, Alejandro Morales, Dag Hanstorp, Edgar Hern\'andez, Guillermo Hinojosa The photoionization of Chlorine ions is a fundamental process of interest in several plasma environments. For instance, in FC reactors, negative halogen ions beams are candidates for the injectors. In astrophysics Cl was detected in Io's ionosphere and is used as hydrogen abundance markers. The photoionization of Cl$^{+}$ was measured with a resolution of 20 meV in the photon energy range of 19.5 eV to 27.5 eV. The experiment was carried out in the 10.0.1 end station of the Advanced Light Source. Structures corresponding to Rydberg series are identified. Absolute cross sections were measured. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. DGAPA IN 113010, IN106813 and CONACYT CB-2011/167631. GH thanks technical support of ALS staff. [Preview Abstract] |
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HW1.00017: ELECTRON AND PHOTON COLLISIONS WITH ATOMS AND MOLECULES: IONIZATION |
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HW1.00018: Electron impact total cross sections for Furan, Tetrahedrofuran and 2, 5-Dimethylefuran (0.1 eV -- 5000 eV) Chetan Limbachiya, Minaxi Vinodkumar, Mohit Swadia Furan may serve as a prototype of a furanose-form building unit of biomolecules [1]. Electron interactions with tetrahydrofuran (THF), that links the phosphate groups in the DNA backbone, have been studied by both experimental and computational methods [2]. We have calculated various total cross sections for electron interactions with Furan, Tetrahedrofuran and an industrially relevant molecule 2, 5 -- Dimethylefuran. We have used R-matrix code [3] below 15 eV and Spherical Complex optical Potential (SCOP) and Complex Scattering Potential -- ionization contribution (CSP-ic) formalisms [4] beyond 15 eV.\\[4pt] [1] Szmytkowski et al. PHYSICAL REVIEW A \textbf{82}, 032701 (2010)\\[0pt] [2] Khakoo et al. PHYSICAL REVIEW A \textbf{85}, 052717 (2012)\\[0pt] [3] Bouchiha et al, J. Phys. B: At. Mol. Opt. Phys. \textbf{40}, 1259 (2007)\\[0pt] [4] Chetan Limbachiya et al, Phys. Rev. A, \textbf{83}, 042708(2011) [Preview Abstract] |
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HW1.00019: Deep minimum in the Coulomb-Born TDCS for inner-shell ionization of carbon by electron impact S.J. Ward, J.H. Macek Recently, a minimum in the TDCS of electron impact ionization of helium has been explained in terms of a vortex [1]. We have determined the kinematics to obtain a deep minimum due to a vortex in the TDCS for K shell ionization of carbon by electron impact using the Coulomb-Born (CB1) approximation [3]. The deep minimum occurs at an angle of the ejected electron of 239$^\circ$ for an incident energy of $1801.2 eV$, a scattering angle of $4^\circ$, and energy of the ejected electron of $5.5 eV$. At the angle of the minimum, both the real and imaginary parts of the T-matrix are zero. The integral of the velocity field around a closed path encircling the vortex position is $2 \pi$ [2]. Following the treatment of Ref.~[3], we decomposed both the Born (B1) and the CB1 T-matrix into their multipole components [4]. The $\ell=1$, $m=\pm 1$ CB1 multipole components are important in determining the shape of the CB1 angular distribution.\\[4pt] [1] J.H. Macek, J.B. Sternberg, S.Y. Ovchinnikov amd J.S. Briggs, Phys. Rev. Lett. {\bf 104}, 033201 (2010). [2] S.J. Ward and J.H. Macek, http://meetings.aps.org/link/BAPS.2011.DAMOP.Q1.63. [3] J. Botero and J.H. Macek, Phys. Rev. A {\bf 45}, 154 (1992). [4] S.J.Ward and J.H. Macek, Bull. Am. Phys. Soc. {58}, no. 6, p. 61 (2013). [Preview Abstract] |
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HW1.00020: Ionization cross sections and rate coefficients for CFCl$_{3}$ molecule by electron impact Satyendra Pal, Neeraj Kumar Chlorofluorocarbons (CFCs) or freons are important industrial material with wide-ranging applications as refrigerant, aerosol propellant and semiconductor etchant, etc. The large-scale industrial consumption is of particular environmental concern because of its potential for ozone destruction in the stratosphere. The present work reports the calculations for differential cross sections as a function of secondary/ ejected electron energy and the scattering angle in the ionization of CFCl$_{3}$ by electron collision leading to the production of various cations viz. CCl$_{3}^{+}$, CFCl$_{2}^{+}$, CCl$_{2}^{+}$, CFCl$^{+}$, CCl$^{+}$, Cl$^{+}$, CF$^{+}$, F$^{+}$, and C$^{+}$ through direct and dissociative ionization processes at a fixed incident electron energy of 200eV. A modified Jain-Khare semi-empirical formalism based on oscillator strength has been employed. To the best of our knowledge, no experimental and/or theoretical data is available for comparison of the present results for differential cross sections. The corresponding derived integral cross sections in terms of the partial ionization cross sections corresponding to these cations, in the energy range varying from ionization threshold to 1000 eV, revealed a reasonably good agreement with the experimental and theoretical data, wherever available. In addition to the differential and integral ionization cross sections, we have also calculated the ionization rate coefficients using the evaluated partial ionization cross sections and the Maxwell-Boltzmann distribution as a function of electron energy. [Preview Abstract] |
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HW1.00021: Electron Impact Ionization cross sections and rate coefficients for $\alpha $-tetra hydro furfuryl alcohol Neeraj Kumar, Satyendra Pal $\alpha -$tetrahydrofurfuryl alcohol (THFA; C$_{5}$H$_{10}$O$_{2})$ is an aromatic compound having the molecular structure similar to that of 2-deoxy-D-ribose (deoxyribose). This molecule has attracted enormous interest in the field of research because its electron charge cloud possesses a quite significant spatial extent (dipole polarizability, $\alpha = $ 70.18 au) and has a relatively strong permanent dipole moment ($\mu \sim$ 2D). In the present work, we have extended and generalized the modified Jain-Khare semi-empirical formalism for the evaluation of the total ionization cross sections corresponding to the formation of the cations in the electron impact ionization of molecules to the electron impact ionization of $\alpha $-tetrahydrofurfuryl alcohol (THFA; C$_{5}$H$_{10}$O$_{2})$, in the energy range varying from ionization threshold to 1000 eV. The evaluated cross sections revealed a reasonably good agreement with the experimental and theoretical data, wherever available. We have also calculated the ionization rate coefficients as a function of electron energy, using the evaluated total ionization cross sections and the Maxwell-Boltzmann distribution. [Preview Abstract] |
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HW1.00022: Electron Collisions with Argon at Low and Intermediate Energies Oleg Zatsarinny, Klaus Bartschat We have further developed the $B$-Spline $R$-matrix (BSR) method~[1] and the corresponding computer code~[2] to allow for a large number of pseudo-states in the close-coupling expansion. In the present work, we carried out semi-relativistic (Breit-Pauli) close-coupling calculations for elastic scattering, excitation, and ionization of argon from both the ground state and the metastable excited states. Coupling to the ionization continuum through the pseudo-states is important for low-energy elastic scattering (to represent polarizability effects), for excitation in the ``intermediate'' energy regime of about 1-3 times the ionization potential, and to allow for the calculation of ionization processes by transforming the results obtained for excitation of the positive-energy pseudo-states. The current results represent a significant extension of our earlier near-threshold work~[3] on the e-Ar collision system. Many of these data are now available in the LXCat database~[4].\\[4pt] [1]~O.~Zatsarinny and K.~Bartschat, J. Phys. B~{\bf 46} (2013) 112001.\\[0pt] [2]~O.~Zatsarinny, Comp. Phys. Commun.~{\bf 174} (2006) 273.\\[0pt] [3]~O.~Zatsarinny and K.~Bartschat, J.~Phys.~B~{\bf 37} (2004) 4693.\\[0pt] [4]~http://www.lxcat.laplace.univ-tlse.fr/database.php [Preview Abstract] |
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HW1.00023: ABSTRACT WITHDRAWN |
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HW1.00024: A new experimental technique for the measurement of absolute electron-impact partial ionization cross sections of radical species Darryl Jones, George da Silva, Michael Brunger We describe a new experimental methodology for measuring absolute partial ionization cross sections (PICS). The new technique employs pulsed and crossed electron and skimmed supersonic beams with an orthogonal pulsed-extraction time-of-flight mass spectrometer. Absolute scales for PICS of a species are determined through normalisation to a reference PICS. Here we determine the relative density of the target and the reference gases by normalisation of their centreline intensities in their expansions. Preliminary data demonstrating the validity of this technique will be presented. The potential of this new technique for performing new experimental measurements on transient radical species will be discussed. [Preview Abstract] |
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HW1.00025: Generalized Sturmian Functions approach for double photoionization of He Juan M. Randazzo, Gustavo Gasaneo, Lorenzo Ugo Ancarani, Flavio D. Colavecchia, Dario M. Mitnik Various techniques have been developed in the last decade allowing the ab initio treatment of three-body Coulomb problems. One of the most recent ones is the Generalized Sturmian Function (GSF) method that we have developed [1]. This spectral method allows one to correctly describe bound states of a large variety of systems, but more importantly to generate double continuum wave function for break-up processes possessing the correct asymptotic behavior. In the method, the scattering wave function is expanded in a properly symmetrized product of continuum-type, radial, generalized Sturmian basis functions. The proposal is then used to solve the driven equation for a given process. During the last years, we have studied several S-wave collision models which allowed us to understand the way in which the entangled, three--body, continuum wave is constructed. In this contribution, we consider the full three--body Schr\"{o}dinger equation for the double photoionization of He at intermediate incident energies. We will illustrate the success of the GSF method by comparing our theoretical cross sections (within different gauges) with those obtained with other approaches and with experimental data.\\[4pt] [1] G. Gasaneo et al, submitted to Adv. in Quantum Chem.; Mitnik et al, Comp. Phys. Comm. 182, 1145 (2011). [Preview Abstract] |
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HW1.00026: Angular distributions for electron-impact ionization of Na and Mg G.S.J. Armstrong, J. Colgan, K.L. Nixon, A.J. Murray, M.S. Pindzola We present angular distributions for electron-impact single ionization of sodium and magnesium at intermediate electron impact energies. In this work, the time-dependent close-coupling (TDCC) method is used to solve the two-electron time-dependent Schr\"{o}dinger equation in full dimensionality. The ionization process is treated as a two-active-electron process, where the two outgoing electrons move in the field of the frozen singly-charged ion. We compare calculated angular distributions with measurements taken over a range of intermediate electron impact energies, and in both coplanar symmetric and asymmetric geometries. Several new features are incorporated into the present TDCC approach, including a core orthogonalization at each time step to avoid unphysical de-excitation of the active electrons, an implicit time propagator, and a variable radial mesh. The latter is required to map out the inner atomic orbitals accurately, and the use of an implicit time propagator enables reasonably large time steps to be used. [Preview Abstract] |
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HW1.00027: BASIC PLASMA PHYSICS PHENOMENA IN LOW-TEMPERATURE PLASMAS |
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HW1.00028: Study of two-stream instability in low-pressure discharge Guiqiu Wang, Igor Kaganovich, Alexander Khrabrov, Hongyue Wang, Dmytro Sydorenko Electron emission from discharge chamber wall is important in low-pressure discharges, such as capacitively coupled plasma (CCP), divertor plasmas, direct current cathode discharges, direct current magnetrons, multipactors, electrostatic, Hall thruster and so on. It is well known that the electrons emitted from the wall are accelerated into plasma by the electric field in the sheath adjacent to the wall and form an electron beam. Such beams on the one hand play an important role in the maintenance of discharge and affect plasma and sheath characteristics, on the other hand, they may excite the two-stream instability in the plasma. As a result, the beam electrons are slowed down and the plasma electrons are heated. In this work, a one-dimensional Particle-in-Cell (PIC) simulation is carried out to study these effects in low-pressure discharge. The relationship between Electron velocity distribution function (EVDF) of plasma-beam system and the two-stream instability whether happens is discussed and the dispersion relation is studied in detail when the two-stream instability occurs. [Preview Abstract] |
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HW1.00029: Oscillatory modes of two particulates levitated in an RF plasma Amit Mukhopadhyay, John Goree, Bin Liu A dusty plasma contains micron-size particulates of solid matter. The particulates collect more electrons than ions from the plasma and charge to -4000 e. They are electrically levitated by a sheath electric field. We dropped 4.8 $\mu$m polymer microspheres into a capacitively coupled 13.56 MHz RF discharge with 13 mTorr Ar. By shaping the sheath above the horizontal electrode, we were able to confine just two particulates so that they were aligned vertically or horizontally. Using high-speed video microscopy as the diagnostic, we observed the random motion of the particulates, which we analyzed to determine their harmonic oscillations and correlations. Langevin simulations of the particulate motion, taking into account Debye shielding modified by the ion wakefield downstream of the particulates, are compared to experiments. Work supported by NASA and NSF. [Preview Abstract] |
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HW1.00030: Driving Azimuthal Modes in Magnetized Discharge with Segmented Anode Yuan Shi, Yevgeny Raitses, Ahmed Diallo Coherently rotating azimuthal modes in a magnetized discharge of the cylindrical Hall thruster were driven using segmented anode. Unlike naturally occurring spoke which rotates only in ExB direction with some specific frequency, coherently rotating modes can be driven in both ExB and -ExB directions, whose frequencies exactly follow driving frequencies. To drive these modes, square-wave voltage between 225 V and 275 V was applied onto four anode segments with successive 90$^{\circ}$ phase shift. The driving circuit was operated at frequencies ranged from 50 KHz to -50 KHz. Modes appeared to be less intense but more coherent in ``direct'' magnetic configuration compared to ``cusp''; and for each magnetic configuration, the degree of coherence showed strong dependence on driving frequency. Driving at frequencies deviate from the spoke frequency suppressed the naturally occurring azimuthal mode, while driving at spoke frequency enhanced the coherence of natural spoke. This resonant behavior was observed by a fast camera as well as current through anode segments. [Preview Abstract] |
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HW1.00031: Emission spectroscopy of anharmonic vibrational series for micro-hollow cathode discharge plasmas A. Lozano F., A.M. Ju\'arez The field of micro plasmas is currently very active, due to the useful properties and potential applications of micro-hollow cathode discharges.Our group is currently developing these discharge characterization techniques and, as a first obvious starting point, we are performing emission spectroscopy in normal discharges. The focus of this particular contribution is to present a study of vibrational eigenvalues of Morse potential for diatomic molecules. We performed the experimental measurements of these eigenvalues using a high resolution optical monochromator and a parallel plate nitrogen discharge in the glow regime. In particular we determined using this simple arrangement the ro-vibration transitions in N$_2$, between the electronic states $C^3\Pi_u-B^1\Pi_g$. Moreover, we evaluated theoretically the anharmonic eigenvalues of these transitions using Wigner function for a Morse potential. Based on experimental measurements and making use of the calculated Franck-Condon factors it is possible to extract energy potential parameters of these energy states directly from measured transitions. In particular we have calculated the internuclear separation between the excited states associated with the vibrational transitions observed. [Preview Abstract] |
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HW1.00032: Spectroscopic study of shock waves generated in a supersonic arcjet helium plasma Kazuki Kozue, Shinichi Namba, Takuma Endo, Ken Takiyama, Naoki Tamura Recently, we found that the shock cell appeared in an arcjet plasma expanding through a conical-shaped supersonic nozzle. In order to understand the characteristics of the shock wave, the visible/UV emission spectroscopy was carried out. The arcjet plasma was generated between an anode (copper) and a cathode (Ce/W) with a gap length of 2.5 mm and then expanded through the anode nozzle (throat diameter: 1.0 mm) into low pressure region (expansion section). The discharge current voltage and gas pressure were 40 A $\sim$30 V and $\sim$1000 mbar respectively. A visible spectrometer (focal length: 1.0 m, grating: 2400 grooves/mm) was used to measure the plasma emission The electron temperature was evaluated by Boltzmann plot of He I 2p$^{3}$\textit{Pn}d$^{3}D$ series ($n=$6, 7, 8 and 9), whereas the density was determined by Stark broadening (He I 438.8 nm). It was found that the density significantly increased at the shock region, which can be expected by the simple gas dynamic theory. However, no distinct change of the temperature was observed. [Preview Abstract] |
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HW1.00033: Optogalvanic spectroscopy: Towards a versatile plasma based tool for gas trace analysis Lina M. Hoyos-Campo, A.M. Juarez The real-time detection and quantification of molecular traces in atmospheric samples is currently a very active field in medical, homeland security and biological applications. The optogalvanic effect consists in the variation in the electrical properties of a plasma, induced by the interaction of resonant radiation with atoms or molecules present in it. This technique provides a very sensitive and selective spectroscopic tool for gas trace analysis. However, optogalvanic spectroscopy is not currently being exploited thoroughly, in our opinion, in these applications. In the present contribution we will discuss our current efforts towards developing a molecular trace detection facility focused on gas phase volatile compounds (VOC) detection using optogalvanic spectrometry. Our spectrometer consists of a hollow cathode discharge coupled to tunable lasers in the visible (400-800 nm) and mid-infrared, Quantum Cascade Laser (8000 to 10000 nm) spectral range. In particular we will present our preliminary results in the associative ionization induced in a helium (James Lawler, Phys. Rev. A. 22, 3, 1980), as well as an outlook of future work in this emerging area of medical and biological application of gas trace analysis based on optogalvanic spectrometry. [Preview Abstract] |
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HW1.00034: Particle-In-Cell simulation of a magnetized plasma column exhibiting a non-linear rotating structure Jean-Pierre Boeuf, Bhaskar Chaudhury, Stanimir Kolev A two-dimensional Particle-In-Cell Monte Carlo Collisions (PIC-MCC) model is used to study plasma transport across the magnetic field in a magnetized plasma column sustained by energetic electrons emitted from filaments and injected in the central part of the column. The conditions are similar to those of experimental magnetized plasmas studied for example in the MISTRAL device [1]. Experiments show that the boundary conditions at the end of the plasma column (presence of a limiter, applied voltages) play an essential role in the development of instabilities. Because of the 2D nature of the model, the column is supposed to be uniform in the direction parallel to the magnetic field (only flute instabilities can be described), but electron and ion losses at the ends of the plasma column are taken into account self-consistently in the model. Simulations performed under conditions close to those of the experiments of Ref. [1] (argon, pressure 10$^{\mathrm{-2}}$ Pa, magnetic field around 20 mT) predict the formation of a rotating electrostatic plasma structure with spiral arm whose properties are qualitatively and quantitatively close to those observed in the experiments. The model can in particular explain the unexpected distribution of ion velocity measured by Laser Induced Fluorescence in Ref. [1]. We discuss the nature of this instability and its relation with the modified Simon-Hoh instability. [1] C. Rebont, N. Claire, Th. Pierre, and F. Doveil, Phys. Rev. Lett. 106, 225006 (2011) [Preview Abstract] |
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HW1.00035: DC breakdown in ethanol vapor Zoran Petrovic, Jrelena Sivos, Nikola Skoro, Gordana Malovic, Dragana Maric DC breakdown is investigated in ethanol vapor at low pressure. Discharge is initiated in parallel-plate electrode system, with copper cathode and transparent conductive anode, 5.4 cm in diameter. The distance between electrodes is adjustable. We present Paschen curve for ethanol measured at electrode separation of 1.1 cm and at pd values between 0.1 Torr cm and 3 Torr cm. Paschen curve has a characteristic shape with a rapid increase of the voltage in the left part and somewhat slower growth in the right-hand branch. The minimum breakdown voltage of 450 V occurs at around pd = 0.35 Torr cm. After breakdown, the discharge operates stable up to pd = 0.7 Torr cm. At higher pd- s, the discharge falls into relaxation oscillations, where it was possible to estimate the breakdown voltages from oscillatory patterns. To investigate elementary processes in the breakdown, for every point of Paschen curve corresponding axial profiles of emission are recorded by ICCD camera. The profiles reveal strong emission peak near the cathode. This indicates that heavy-particle processes play important role in the discharge at all pd values covered by measurements. At the lowest pd values, in the left - hand branch of the Paschen curve, heavy particles (ions, fast atoms and molecules) are dominant. [Preview Abstract] |
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HW1.00036: PLASMA BOUNDARIES: SHEATHS, BOUNDARY LAYERS, OTHERS |
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HW1.00037: Characteristics of wall sheath and secondary electron emission under different electron temperature in Hall thruster Ping Duan, Haijuan Qin, Anning Cao, Xinwei Zhou, Long Chen, Hong Gao Characteristics of discharge channel wall plasma sheath in Hall thruster have great effects on its performance. In this paper, we establish a two-dimensional physical model in Hall thruster sheath area to investigate the influences of the different electron temperature, propellant and particle weight on sheath potential and secondary electron emission in Hall thruster, by the method of Particle In Cell (PIC) simulation. And the electric field at the particle position is obtained by solving the Poisson's equation. The numerical results show that when the electron temperature is low, the change of sheath potential drop is bigger than that with electrons at high temperature, the surface potential maintains a stable value and the stability of the sheath is good. When the electron temperature is high, the surface potential maintains persistent oscillation, and the stability of the sheath is reduced. Along with the increase of electron temperature, the coefficient of secondary electron emission in wall reduce after the first increasing. For three kinds of propellant (Ar, Kr, Xe), with the increase of ion mass, sheath potential and the secondary electron emission coefficient in turn reduce. [Preview Abstract] |
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HW1.00038: Ion velocity distribution function and electric field measurements in a dual-frequency rf sheath Nathaniel Moore, Walter Gekelman, Patrick Pribyl, Yiting Zhang, Mark Kushner Ion dynamics are investigated in a dual-frequency rf sheath above a 300 mm diameter biased silicon wafer in an industrial inductively coupled (440 kHz, 500 W) plasma etch tool. Ion velocity distribution (IVD) function measurements in the argon plasma are taken using laser induced fluorescence (LIF). Planar sheets of laser light enter the chamber both parallel and perpendicular to the surface of the wafer in order to measure both parallel and perpendicular IVDs at thousands of spatial positions. A fast (30 ns exposure) CCD camera measures the resulting fluorescence with a spatial resolution of 0.4 mm. The bias on the wafer is comprised of a 2 MHz low frequency bias and an adjustable 10-20 MHz high frequency bias. The bias voltages may be switched on and off (f$_{rep}$ up to 1 kHz, duty cycle 10-90\%). IVDs are measured with several different bias and timing combinations. For the 2 MHz bias, it was found that the IVD is uniform to within 5\% across the wafer. IVDs as a function of phase of the bias were also measured. The electric field in the sheath is measured volumetrically over the wafer at thousands of positions using an emissive probe. The experimental results are compared with a simulation specifically designed for this particular plasma tool. [Preview Abstract] |
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HW1.00039: On the Ar$^+$ and Xe$^+$ Velocities near the Presheath-Sheath Boundary in an Ar-Xe Discharge Jon T. Gudmundsson, Michael A. Lieberman We explore the velocities of positive ions near the presheath-sheath boundary in an Ar-Xe discharge by particle-in-cell/Monte Carlo collision simulation [1]. In the absence of ion-ion collisions, for a pure argon discharge the argon ion has almost the same velocity profile as it does in the mixture of argon and xenon. Similarly, for a xenon discharge the xenon ion has almost the same velocity profile as it does in the mixture of argon and xenon. Thus, each ion reaches its own Bohm speed at the presheath-sheath interface [1] which contradicts the experimental findings of Lee et al. [2] where the ion velocities approach the common ion sound speed for both ions in the Ar-Xe discharge. These results have been challenged due to the lack of ion-ion Coulomb collisions in our simulations [3]. We discuss the influence of adding ion-ion Coulomb interactions to the simulation as well as increased electron temperature. We estimate the ion-ion Coulomb collision cross section by a Coulomb momentum transfer cross section and assume isotropic angular distribution of the scattered ions.\\[4pt] [1] J. T. Gudmundsson and M. A. Lieberman, Phys. Rev. Lett. 107, 045002 (2011).\\[0pt] [2] D. Lee et al., Appl. Phys. Lett. 91, 041505 (2007)\\[0pt] [3] N. Hershkowitz et al., Phys. Rev. Lett. 108, 139501 (2012) [Preview Abstract] |
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HW1.00040: Kr ion Laser-Induced Fluorescence using a tunable diode laser near 729nm for Sheath experiments Greg Severn, Chris Yip, Noah Hershkowitz We have succeeded in obtaining a laser-induced fluorescence (LIF) signal from $Kr^+$, (83.8 amu) in a low temperature Kr plasma discharge, using a diode laser, for a wavelength near 729nm. An atomic energy level scheme that is accessible to diode lasers is $^{4}D_{7/2} \rightarrow$ $^{4}P_{5/2}^0 \rightarrow$ $^{4}P_{5/2}$. The metastable state, $^{4}D_{7/2}$, proved to be sufficiently populated in a low temperature DC plasma discharge ($T_e \sim 1 eV, n_i\sim 10^9 cm^{-3}$) to produce a high quality signal. We present results ofion velocity distribution functions (IVDFs) obtained by deconvolution. The principal complication in unfolding an IVDF from the measured LIF signal is the presence of the 4 main isotopic contributions, $^{86}Kr^+$,$^{84}Kr^+$, $^{82}Kr^+$, and $^{80}Kr^+$. Hargus et al. [1] have applied deconvolution techniques successfully to Kr II LIF signals from this transition for the case of Hall Thruster plasmas, in which ion temperatures are very large compared with the isotope shifts. Sheath formation experiments (multiple ion species plasmas) will operate in a much cooler regime for which the requirements for deconvolution techniques are more stringent.\\[4pt] [1] W.A. Hargus, Jr., et al., Rev.Sci.Instrum. {\bf 83}, 103111 (2012) [Preview Abstract] |
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HW1.00041: Identification of streaming instabilities in the presheath of plasmas with two ion species Scott Baalrud, Trevor Lafleur A recent theory proposes that ion-ion two-stream instabilities can arise in the presheath of plasmas with two ion species under certain conditions, and that these instabilities rapidly enhance the frictional coupling between the ion species.\footnote{Baalrud, Hegna and Callen, Phys.\ Rev.\ Lett.\ 103, 205002 (2009)} The threshold condition for instability onset along with the multi-species Bohm criterion allowed prediction of the speed of each ion species at the sheath edge. These predictions were later confirmed experimentally.\footnote{Yip, Hershkowitz and Severn, Phys.\ Rev.\ Lett.\ 104, 225003 (2010).} However, recent work has questioned the validity of this theory based on PIC simulations that did not observe instabilities under conditions similar to the experiment.\footnote{Gudmundsson and Lieberman, Phys.\ Rev.\ Lett.\ 107, 045002 (2011).} Using numerical solutions for the dispersion relation, we show that this discrepancy is due to a lower electron temperature in the simulations. This identifies an inaccuracy with an approximate instability criterion that predicted instability for the simulation parameters.\footnote{Baalrud, Hegna and Callen, Phys.\ Rev.\ Lett.} We thoroughly test this numerically. Additionally, for the first time we identify the ion-ion two-stream instabilities in the presheath using PIC simulations. [Preview Abstract] |
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HW1.00042: Magnetized Plasma Sheath Simulation with the Kinetic Finite Mass Method Christopher Young, David Larson, Mark Cappelli First results of a magnetized plasma sheath simulation using the Kinetic Finite Mass (KFM) Method are presented. The KFM Method, derived from the Finite Mass Method of [1], is a gridless Lagrangian simulation technique that partitions the system mass into packets that evolve over time. The packets have finite extent in 1D phase space, continuous Gaussian internal mass distributions, and a defining set of Gauss-Hermite quadrature points that move under the action of forces. Much like in a Particle-In-Cell (PIC) approach, the electric field is calculated by solving Poisson's equation over a temporary grid and the local Lorentz force is mapped back to the particle locations. A Gaussian Mixture Model is employed periodically to reset the Gaussian character of the packets after distortion by the system forces. Sheath results are compared with conventional PIC simulations. This work provides a demonstration of the powerful KFM method in preparation for simulating more complex plasma phenomena. \\[4pt] [1] C. Gauger et al. SIAM J. Numer. Anal. 26, 1744 (2005) [Preview Abstract] |
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HW1.00043: Neutral Resonant Ionization by Excited States in Optically Thick Plasmas John Vogel Ionization from surfaces of low work function explains many properties of both sputter sources of heavy anions and H$^{-}$ from RF plasma sources for heating magnetically confined plasmas. Surface ionization fails to fully account for intensities and operational peculiarities of either type of ion source, however. A blue plasma above cesium-sputtered material is well associated with intense stable anion beams used in accelerator mass spectrometry (AMS). A theory of neutral resonant ionization within this excited Cs plasma was developed [1] to explain a lack of isotopic fractionation seen in low energy AMS [2]. A similar theory of resonant ionization in hydrogen plasma is possible in which H(2s) atoms, sustained by the optical density of hydrogen for Lyman $\alpha $ radiation, have a path to gas phase production of H$^{-}$(1s$^{2})$ at high rates. The theory depends at present on data from multiple decades of unrelated experiments. Implications of the theory are used to suggest supportive or discrediting experiments.\\[4pt] [1] J.S. Vogel AIP Conf. Proc. 1515: 89 (2013).\\[0pt] [2] J.S. Vogel, et al. NIM B294: 340 (2013). [Preview Abstract] |
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HW1.00044: PLASMA DIAGNOSTIC TECHNIQUES |
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HW1.00045: Spectroscopic diagnostics of Ar atmospheric-pressure plasmas using optical emission spectroscopy and collisional-radiative modelin R. Gangwar, V. Dumont, L. Stafford Recently, we have studied the physics driving atmospheric-pressure, dielectric barrier discharges applied to the functionalization of wood substrates. In this context, a collisional-radiative (CR) model was developed to describe the evolution of the optical emission spectra and thus to analyze the evolution of the average electron energy in presence of wood outgassing. In this work, a similar approach is used to describe atmospheric-pressure Ar plasmas sustained by either the propagation of a 915 MHz electromagnetic surface wave or controlled by dielectric barrier. In both systems, the measured 2$p_{\mathrm{x}} \to 1s_{\mathrm{y}}$ line intensities in the 500-900 nm range were compared to those predicted by the model accounting for direct excitation, stepwise excitation, energy transfer processes, radiation trapping, and collisional quenching losses. In the microwave plasma, the average electron temperature was found to be slightly larger than that the excitation temperature determined from the Boltzmann plot using levels 3p, which are generally believe to be in thermal equilibrium with the electrons. [Preview Abstract] |
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HW1.00046: Influence of outgassing on plasma kinetics during wood treatment in dielectric barrier discharges at atmospheric pressure R. Gangwar, O. Levasseur, L. Stafford, N. Naude, N. Gherardi We have recently extended the range of applications of dielectric barrier discharges (DBD) at atmospheric pressure to the functionalization of wood surfaces with the objective of improving its durability following natural weathering. Having highly complex chemical composition and microstructure, it can release significant amount of impurities, which can play a crucial role on the plasma kinetics, and therefore on the process dynamics. The influence of wood outgassing on the physics driving DBD operated in nominally pure He was investigated using a combination of time-resolved optical emission spectroscopy (OES) and collisional-radiative (CR) modeling. For completely outgassed samples, the He I 588 nm-to-707 nm and 668 nm-to-728 nm line intensity ratios were relatively high early in the discharge cycle, decreased abruptly and then remained stable as the current increased and the discharge eventually extinguished. These results were correlated to a decrease of the electron temperature from about 1 eV early in the cycle to about 0.2 eV in the main discharge lifetime. As wood outgassing evolve, study revealed that the release of products (essentially air) from the wood substrate yields to an increase of the cycle-averaged electron temperature as well as to a significant quenching of He metastable atoms. Selected experiments in presence of trace amounts of N$_{2}$, O$_{2}$ and dry-air were also performed to better understand their respective roles. [Preview Abstract] |
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HW1.00047: Mass identification of the neutral products generated in the plasma treatment of polluted atmospheres David Seymour Plasmas produced using Dielectric Barrier Discharge (DBD) devices are very effective in the abatement of air pollution resulting from, for example, the emission of volatile organic compounds (VCOs) by a range of industrial and agricultural processes. The development and monitoring of effective DBD systems can be investigated by advanced mass spectrometric methods specifically configured for analysis at high and atmospheric pressures The present work involves the operation of a small DBD reactor which uses either a helium or nitrogen carrier gas to sustain the plasma to which may be added reactive gases, such as oxygen, as well as samples of pollutants such as chlorinated hydrocarbons, including trichloroethylene. The mass spectrometric analysis was performed using a specially configured system manufactured by Hiden Analytical Ltd. The DBD source may also be combined with a catalyst for plasma-enhanced catalysis. The neutral products of the reactions proceeding in the plasma at atmospheric pressure are sampled through the capillary sampling system which also reduces the pressure of the gas mixture delivered to the ionisation source of the quadrupole mass spectrometer. The ions produced are subsequently mass identified. We describe typical data and comment on the advantages of this technique. [Preview Abstract] |
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HW1.00048: Spatially Resolved Measurements of Emitting Species in Low Temperature Plasma Microjets Syed Hamid Razavi Barzoki, Soheila Mohades, Nazir Barekzi, Mounir Laroussi Non-thermal atmospheric pressure plasma microjets have recently been investigated for plasma processing including biomedical applications [1]. This is due to their ability of providing geometrically well-defined plasma plumes at room temperature and pressure, in air and not confined by electrodes. These microjets can be thought of as vehicles transporting reactive chemical species to a remote substrate. To study the chemical makeup of the plasma Optical Emission Spectroscopy (OES) is used. Since the plasma plume is in fact a series of plasma packets/bullets traveling at high velocities [2], the spatial distribution of the chemical species is a dynamic quantity that varies with the temporal location of the plasma bullet. This is due to substantial changes in size and content that the plasma bullet undergoes as it mixes with the surrounding air along its propagation path. In this paper we present OES measurements of various species generated by a low temperature plasma microjet. The spatial distributions of the emitting species along the axis of propagation of the plasma plume are measured and correlated with the physical position of the plasma bullet. \\[4pt] [1] M. Laroussi and T. Akan, \textit{Plasma Processes and Polymers} \textbf{4}, 777 (2007).\\[0pt] [2] X. Lu and M. Laroussi, \textit{J. Appl. Phys}. \textbf{100}, 063302 (2006). [Preview Abstract] |
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HW1.00049: Applications of DC-Self Bias in CCP Deposition Systems D.L. Keil, E. Augustyniak, Y. Sakiyama In many commercial CCP plasma process systems the DC-self bias is available as a reported process parameter. Since commercial systems typically limit the number of onboard diagnostics, there is great incentive to understand how DC-self bias can be expected to respond to various system perturbations. This work reviews and examines DC self bias changes in response to tool aging, chamber film accumulation and wafer processing. The diagnostic value of the DC self bias response to transient and various steady state current draw schemes are examined. Theoretical models and measured experimental results are compared and contrasted. [Preview Abstract] |
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HW1.00050: Structure of interfacial water molecules under externally-applied electric field studied by vibrational sum$-$frequency generation Takahiro Kondo, Tsuyohito Ito We report effects of electric field on the structure of water molecules in the CaF$_2$/water interfacial region by vibrational sum$-$frequency generation (VSFG) spectroscopy. VSFG gives molecular level information for several layers of molecules at the interface. At the CaF$_2$/water interface with low pH, the CaF$_2$ surface is known to be positively charged and form an electric double layer (EDL). Without externally applied electric field, the water molecules are aligned along the electric field inside the EDL (EF-EDL), with facing oxygen (oxygen-up) to CaF$_2$ surface. According to SFG peak at $\sim$3150 cm$^{-1}$ attributed to vibration of highly-ordered water molecules, the orientation of water molecules becomes higher as the external electric field is applied to the same direction of the EF-EDL. In contrast, with the applied field in opposite direction of the EF-EDL, the SFG intensity becomes weak and almost zero. When the applied field is further increased, the SFG intensity becomes stronger with the applied field increasing. This increase suggests that the water molecules can be realigned (oxygen$-$down to CaF$_2$ surface) by externally-applied electric field. Details on the experimental results and discussions will be presented at the meeting. [Preview Abstract] |
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HW1.00051: Electric Field Measurement in a Microwave Beam Milka Nikolic, Svetozar Popovic, Leposava Vuskovic, Gregory C. Herring We have developed a simple technique to infer electric field in a polarized microwave beam. The method is based on the measurement of breakdown at the surface of a conducting sphere facing the direction of the field. The concept is based on two approximate relations, the field on the sphere is threefold the ambient field [1], and the breakdown field increases linearly with pressure. The enhancement of the electric field at the sphere is strictly valid for the electrostatic field but is also applicable for the polarized microwave beam when the diameter of the sphere is smaller than the wavelength. It was readily utilized in a number of experiments [2]. The second relation is satisfied when the field frequency is negligible in comparison to the electron collision frequency. We demonstrate the technique by the measurement of axial distribution of the electric field in the beam emitted from a rectangular horn antenna at sub-atmospheric pressure. Measured field distribution is in accordance to the calculation. This technique can be used for free-space beam diagnostics and beam power reduction measurement in the presence of surface plasma at the aperture of the horn.\\[4pt] [1] J. D. Jackson, \textit{Classical electrodynamics, 3}$^{rd}$\textit{ Ed., J. Willey and Sons,} ISBN 0-471-30932-X.\\[0pt] [2] S. Popovi\'{c} \textit{et al, }Appl. Phys. Lett., \textbf{81} (2002) p. 1964. [Preview Abstract] |
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HW1.00052: Electric probe measurements of inductively coupled Ar/O$_{2}$/Ar-O$_{2}$ plasmas: comparison by the interpretation methods of the probe data Tae Hun Chung, Min Woo Seo Properties of low-pressure inductively coupled argon, oxygen, and Ar-O$_{2}$ mixture plasmas are investigated using an rf-compensated Langmuir probe measurement. In each gas discharge, the electron energy probability function (EEPF), the plasma density and the electron temperature were obtained by using the probe. The estimates of plasma density determined by using different methods to interpret the probe current-voltage curve are compared. The results show a good agreement between the plasma density values measured in ion saturation current at the floating potential and values measured using other classical methods. Especially, in low-pressure oxygen discharges, the plasma density determined from OML theory compares well with the densities obtained by other methods. At high rf powers, the measured EEPFs for argon, oxygen, and Ar-O$_{2}$ mixture plasmas were observed to be Maxwellian in the pressure range of 1 - 40 mTorr. The electron temperature was observed to decrease with increasing power and pressure and observed to remain not much changed with increasing Ar content in Ar-O$_{2\, }$plasmas. [Preview Abstract] |
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HW1.00053: Use of ``tuned'' particle in cell simulations for absolute atomic oxygen number density determination using actinometry Jim Conway, Samir Kechkar, Miles Turner, Stephen Daniels Actinometry is an optical diagnostic technique that can be used to quantitatively monitor atomic oxygen number density [O] in plasma. However, careless application of the technique can yield inaccurate information regarding atomic oxygen behavior in the plasma. One limitation on this technique is an accurate knowledge of the rate constants required, which is in turn hampered by an insufficiently precise knowledge of the plasma Electron Energy Distribution Function (EEDF). In this work Particle in Cell (PIC) simulations are used to generate theoretical EEDFs. To validate a simulation the electron density ne produced by the PIC code is compared to experimental ne values and PIC input parameters adjusted to optimize agreement between the PIC and experimental ne results thus ``tuning'' the simulation. The resulting EEDF is used to generate rate constants for the actinometry model which should improve the accuracy of the quantitative [O]. This approach was applied to an asymmetric capacitively coupled RF plasma source. The actinometry [O] results are then compared to [O] results obtained using Two-photon Absorption Laser Induced Fluorescence (TALIF) to validate this approach. [Preview Abstract] |
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HW1.00054: Time-Resolved Plasma Density and Magnetic Field Measurements in a Pulsed Plasma Deflagration Keith Loebner, Mark Cappelli Simultaneous time-resolved measurements of electron density and azimuthal magnetic field strength within a coaxial electromagnetic plasma accelerator operating in a pulsed deflagration mode are presented. Density measurements are performed via an optical interferometer of the Michelson type, while the Faraday rotation of the polarization plane of the same beam is measured in order to provide the magnetic field strength perpendicular to the direction of beam propagation. Experimental data is compared to magnetohydrodynamic simulation results and prior lower fidelity experimental results. Measurements were carried out over a wide range of operating conditions in order to validate the theoretical models describing the physics of the deflagration acceleration mechanism. [Preview Abstract] |
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HW1.00055: Estimation of homogeneous linewidth of the argon $\rm\bf 4s[3/2]^o_2-4p[3/2]_2$ transition by saturation spectroscopy S. Nishiyama, M. Goto, K. Sasaki We are developing a Stark spectroscopy system, on the basis of saturation spectroscopy, to measure electric field in argon-containing plasma. Saturation spectroscopy achieves a Doppler-free spectral resolution and a high frequency resolution of the saturation spectrum is required to realize sensitive Stark spectroscopy. In this work, we have investigated the linewidth of the saturation spectrum of the argon $\rm 4s[3/2]^o_2-4p[3/2]_2$ absorption line at various saturation parameters. The plasma source in the experimental apparatus was an inductively-coupled plasma source. The light source was a tunable cw diode laser, and the frequency of the laser was scanned over the Doppler width around the $\rm 4s[3/2]^o_2-4p[3/2]_2$ absorption line (763.51 nm). A small fraction of the laser beam was picked up for a weak probe beam, and the remaining intense beam was used for a pump beam. Homogeneous linewidth without the saturation broadening estimated from the linewidth of the saturation spectrum and the saturation parameter was approximately 10 MHz, while the natural linewidth of this line is 5.5 MHz. Collisional broadening and the instability of the laser frequency are possible reasons of this difference. [Preview Abstract] |
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HW1.00056: Real time monitoring of dielectric-film thickness on the surface of chamber wall for plasma processing Jin-Yong Kim, Chin-Wook Chung In this study, a dielectric film thickness monitoring system was developed. To measure the thickness of dielectric film on the probe, small sinusoidal voltage signals which have different frequencies are applied to an electrically floated planar type probe, then our system measure current signals and shifted V-I phase. A sheath circuit model is considered in order to measure the dielectric thickness in varying plasma status. In our experiments, accurate dielectric thickness was obtained regardless of RF power, gas pressure and argon-oxygen mixture ratio. This study may helpful to optimize periodic maintenance and increase productivity in semiconductor manufacturing process, such as chemical vapor deposition (CVD) and etching. [Preview Abstract] |
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HW1.00057: A study on measurement of the surface charge accumulation using anodic aluminum oxide template Seung-Ju Oh, Hyo-Chang Lee, Jun-Hyeon Moon, Chin-Wook Chung*, Soon-Ho Kwon, Jung-Joong Lee, Il-Gyo Koo, Soo-Jin Lee, Kyo-Seong Seong As the critical dimension of the nano-device shrinks, an undesired etch profile resulting from the local electric field by the surface charge accumulation is made on the plasma processing. To understand and monitor the surface charge accumulation, the measurement of the voltage difference between top electrode and bottom electrode on the anodic aluminum oxide (AAO) which has high aspect structure is performed in inductively coupled plasma. The voltage difference is changed with external discharge conditions, such as gas pressure, input power, and gas species, and the result is analyzed with the measured plasma parameters. [Preview Abstract] |
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HW1.00058: Cutoff Probe for Tokamak SOL Measurement Byung-Keun Na, Kwang-Ho You, Dae-Woong Kim, Shin-Jae You, Jung-Hyung Kim, Hong-Young Chang Since a cutoff probe was developed, there have been a lot of improvements in methodology and analysis for low temperature plasmas. However, in order to apply the cutoff probe to the Tokamak scrape-off layer (SOL), three important issues should be solved - speed, thermal protection, and short-distance (a few mm) wave propagation in magnetized plasmas. In this presentation, the improvement of cutoff probe for Tokamak is shown. The above problems can be solved using the following methods: (a) the cutoff probe can be used with short impulse of a few nano-seconds for speed improvement. (b) Ceramic covers were used for thermal protection. (c) In magnetized plasmas, the cutoff peak can be analyzed using circuit modeling and CST Microwave studio. To verify the proposed methods, the cutoff probe was applied to a Helicon plasma, and the results were compared to laser Thomson scattering results. Based on the result in the Helicon plasma, the cutoff probe will be applied to far-SOL region at the KSTAR 2013 campaign, and SOL region at the later campaign. [Preview Abstract] |
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HW1.00059: Non-invasive electrical method for measurement of electron temperature in an atmospheric pressure plasma jet source Young-Cheol Kim, Yu-Sin Kim, Hyo-Chang Lee, Jun-Hyeon Moon, Chin-Wook Chung* Electrical diagnostic method of electron temperature using non-perturbed floating harmonic technique is studied in an atmospheric pressure plasma jet source. When a sinusoidal voltage is applied to the quartz tube which surrounds plasma, the received current has harmonic component. From the relation of the harmonic currents with considerations of the collisional sheath and the applied voltage to the sheath, the electron temperature can be obtained. The measured electron temperature is in the range of 2 - 3 eV in helium discharge. [Preview Abstract] |
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HW1.00060: A new method for measuring pulsed plasma with high-time resolution based on floating harmonic method Yu-Sin Kim, Chin-Wook Chung A new method in high time resolution of up to 1?sec was proposed in this study to measure plasma density and electron temperature in pulsed plasma. The basic principle of the floating harmonic method is to use the current obtained by applying a sinusoidal voltage to the plasma [1]. The new method is to use boxcar mode method and phase-shifted sinusoidal voltage at regular intervals. When the trigger signal of pulse modulated power source is put in the sinusoidal voltage is applied to plasma. The phase of sinusoidal voltage shifts at regular interval until one cycle of sinusoidal current is obtained at the each time point of micro second. The method can measure plasma parameters in units of 1?sec and the measured results were compared to conventional single Langmuir probe method.\\[4pt] [1] M. H. Lee, S. H. Jang, and C. W. Chung, J. Appl. Phys. 101, 033305 (2007) [Preview Abstract] |
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HW1.00061: Effect of magnetic field on Langmuir probe measurements Jerome Bredin, Pascaline Grondein, Pascal Chabert, Valery Godyak, Ane Aanesland In the context of PEGASES thruster where an ion-ion plasma is formed across a localized magnetic field, a study to understand how magnetic field affects the Langmuir probe measurements has been made. Several theoretical works have predict that the plasma anisotropy created by a magnetic field will influence Langmuir probe measurement as a function of the orientation of the probe tip. The study has been made in an electropositive plasma of argon for a uniform magnetic field to avoid effects of magnetic field gradient. The electron energy distribution functions (EEDF) measured with various magnetic field show that the measurements with the probe tip along the magnetic field are depleted in the low energy range compared to the one perpendicular to the magnetic field. Comparison of the results obtained with different magnetic field and different probe orientations allows for evaluation the effect of magnetic field on accuracy of EEDF measurement in plasma with magnetic field. These results confirm the theory on Langmuir probes in magnetized plasma that predict a depletion of low electron energy for measurements along the magnetic field lines. [Preview Abstract] |
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HW1.00062: Characterization of a low pressure Microwave Induced Plasma Discharge Ahmed Hala, Erdogan Teke A low pressure (0.3-7 Torr) Argon gas Microwave Induced Plasma (MIP) discharge was characterized using Optical Emission Spectroscopy (OES). The electron temperature was measured using peak ratio of the Boltzman lines technique. Electron density was measured using the Stark line broadening technique. The electron temperature was found to decrease from 5000 K to around 3000 K for the pressure range of 0.3 to 7 Torr. This is due to the fact that most of the discharge power is directed to ionizing the gas rather than to heating the electrons. [Preview Abstract] |
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HW1.00063: Laser-Induced Fluorescence for Sheath Characterization in Low-Density Argon Plasmas Alexander C. Englesbe, Kapil U. Sawlani, John E. Foster Laser-induced fluorescence (LIF) spectroscopy has become a standard non-intrusive diagnostic technique for determining the energies and concentrations of ion and neutral species in plasmas. A limitation of this technique, however, is the small signal-to-noise ratio incurred when interrogating relatively low-density plasmas. This problem is exacerbated when examining regions such as the sheath at an electrode immersed in the plasma. If ion energetics within the sheath are of interest, then in principle thicker sheaths are desirable in that for a given laser spot size, the potential structure can be inferred with high resolution. We present a methodology for accomplishing LIF in the sheath of a low-temperature argon plasma with an electron density of the order $10^{7}-10^{8}$~cm$^{-3}$. This diagnostic is being developed for the purpose of studying the effect of secondary electron emission on sheath potential behavior in low-density plasmas. The plasma in this study is produced in a multipole ring-cusp ion source. A tunable diode laser excites the Ar II transition at 668.61 nm, which fluoresces at 442.72 nm. The LIF measurements of the ion density are corroborated with electrostatic probes at fixed locations, and the ion velocity distribution within the sheath is determined. [Preview Abstract] |
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HW1.00064: Measurement of resonance level densities in rare gas plasmas and modeling of their resulting VUV emissions J.B. Boffard, C.L. Culver, S. Wang, C.C. Lin, A.E. Wendt, S.B. Radovanov, H.M. Persing In the rare gases, the vacuum ultraviolet (VUV) emissions are dominated by the decays from the $1s_2$ and $1s_4$ (Paschen's notation) principal resonance levels. In isolation, atoms excited to these resonance levels have a short radiative lifetime ($<10$ns), but resonance blockade of the VUV transitions to the ground state significantly extend the effective lifetimes of these levels under typical plasma conditions with pressures greater than a mTorr. Despite this re-absorption, rare gas plasmas do produce copious VUV emissions that may play an important role in critical surface reactions under certain process conditions. We have measured the resonance level densities as a function of pressure in rare-gas discharges (Ne,Ar,Kr,Xe) in an inductively coupled plasma using both white-light absorption spectroscopy and optical emission spectroscopy by monitoring changes in the $2p_x \to 1s_y$ branching fractions [1]. The measured resonance level concentrations are subsequently used as inputs to a simple VUV transport model to determine the VUV flux to surfaces. These model VUV flux calculations are compared to measurements made with an absolutely calibrated VUV photodiode. \\[4pt] [1] Plasma Sources Sci. Technol. \textbf{18} (2009) 035017. [Preview Abstract] |
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HW1.00065: Stark-effect induced transformation in Rotational Spectra of the Nitrogen Molecule Yuri Shcherbakov, Leonid Nekhamkin We present results on spectroscopic studies of filamentary streamer discharge in short air gap in stage of primary streamer propagation. We have found that the mid-resolved nitrogen second positive system (SPS) spectra emitted from the primary streamer head changes essentially in form within some nanoseconds as compared to typical one. Namely, main peak near the band head formed by the P-branches of Pi3-to-Pi3 transition turns into a widened twin-peak hump; with inessential modification of smooth short-wave part of the SPS-band as whole. Preliminary analysis testifies that such a spectra transformation can be related to Stark-effect under the electric field around 100-300 kV/cm because of splitting of nitrogen rotational terms due to strong mutual perturbation of doubly degenerated Lambda-sublevels affected by the field-induced electric dipole moment. So, this effect might be applicable to determine/estimate electric field and its spatial gradient. Thorough corresponding theory needs to be developed. [Preview Abstract] |
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HW1.00066: Time-resolved measurements of plasma properties in a pulsed argon inductively coupled plasma A.E. Wendt, C.L. Culver, S. Wang, J.B. Boffard, C.C. Lin Pulsed plasmas present new degrees of freedom (frequency and duty factor) to tailor plasma properties as compared to continuous plasmas. Using optical emission spectroscopy (OES), we have performed time-resolved measurements of the gas temperature, electron temperature, electron density, and number densities of argon $3p^54s$ metastable and resonance level populations [1]. These measurements were made in a 5 mTorr, 500 W average power inductively-coupled argon plasma with a fixed 30\% duty factor for modulation periods of 10$\mu$s, 100$\mu$s, 1ms, and 6ms. Effective temporal resolution of the OES-derived values varied from 0.25$\mu$s for the shorter periods to 5$\mu$s for the longer periods. Results are compared with global model estimates [2] and time-resolved Langmuir probe measurements. For the shortest (10 $\mu$s) pulse period, the electron, metastable and resonance level densities vary little over the pulse period, but the electron temperature varies by a factor of two. The range of variations in all quantities grow with the length of the pulse period. Results obtained from different sets of emissions lines are used to study transient changes in the EEDF at the start of a pulse.\\[4pt] [1] JVSTA \textbf{31} (2013) 021303.\\[0pt] [2] Ashida et al. JVSTA \textbf{13} (1995) 2498. [Preview Abstract] |
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HW1.00067: Ion Velocimetry In Magnetized DC Sheaths Christopher Young, Andrea Lucca Fabris, Mark Cappelli Particle dynamics near the magnetic cusps in cusped field plasma thrusters are still not well understood; characterizing the ion velocity distribution functions in these regions can help thruster designs maximize electron trapping and minimize erosion of the channel wall. To that end, a robust argon ion velocity sensor is developed using a three-level laser-induced fluorescence (LIF) technique. The $3d^4F_{7/2} \rightarrow 4p^4D^0_{5/2}$ ArII transition at 668.61 nm is pumped with a 25 mW tunable external cavity diode laser, and fluorescence down to the $4s^4P_{3/2}$ state at 442.72 nm is collected with phase-sensitive detection. The Doppler shift in the acquired signal peak, compared to a stationary reference, gives the ion velocity component parallel to the exciting laser. We demonstrate this LIF scheme by obtaining the argon ion velocity profile through a magnetized DC sheath. The LIF measurement is used to validate a new optogalvanic velocimetry technique in which two lasers (chopped at different frequencies) intersect one another at $90^{\circ}$ in the measurement volume. Using a lock-in amplifier, changes observed in the DC discharge current at the sum and difference of the two chopping frequencies may be related back to the mean ion velocity at that point. [Preview Abstract] |
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HW1.00068: Measurement of Ion Energy Distribution in Magnetized ICP using Multi-channel Ion Energy Analyzer WooHyun Lee, Hyuk Kim, JiWon Kim, Hee Woon Cheong, Il Gyo Koo, Soojin Lee, Hyo-seong Seong, Ki-Woong Whang In plasma etch processes, the flux and energy of ions incident on the substrate are the important parameters that control the etch profile and the etch rate. In this regard, retarding field Ion Energy Analyzer(IEA) has been developed and applied to plasma etch. As the size of wafer and etch chamber increase, simultaneous measurement at multi points in radial and poloidal direction becomes important. For this purpose, Plasma lab in Seoul National University and SEMES jointly developed an IEA that can measure the ion energy distributions at five positions in 6-inch wafer at the same time. The IEA is composed of 4 mesh grids(floating, electron repelling, discriminator, secondary electron retarding) and one metal layer(Ion collector). We used a remote controllable voltage source and DAC to supply the stepwise wave form to discriminator voltage source. We used the developed IEA to measure the radial and polodial uniformity of energy distribution of ions incident on the substrate with the change of bias power, gas pressure and bias power frequency. [Preview Abstract] |
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HW1.00069: Spectroscopic determination of excited atomic states populations in CCP AR discharge Konstantin Kurchikov, Alexander Kovalev, Anna Vasilieva, Oleg Braginsky Capacitive Coupled Plasmas (CCP) is being used for plasma processing of different kinds of materials, including low-K films. One of main factors of Low-k damage is ultraviolet radiation of plasma. So control of density of high excited atomic levels is of big importance. For quantitative description of the plasma we have built multilevel Collisional Radiative Model with account of optical thickness effect. The model was tested by comparison of experimentally measured and calculated populations of four first excited levels 3p$^{5}$4s of Ar atom. Levels' populations have been determined experimentally by two methods: 1) measurements of lines intensity for plasmas with different effective sizes, 2) by comparison of intensities with two lines with the same upper level and differently absorbing lower levels. Dependences of levels' populations on plasma parameters have been analyzed. [Preview Abstract] |
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HW1.00070: CAPACITIVELY COUPLED PLASMAS |
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HW1.00071: Resonances and Electromagnetic Field Structure in CCP HF Discharge with Large Electrodes Sergey Dvinin Analytical expressions for CCP HF discharge impedance, taking into account excitation of surface waves [1], propagating along plasma--sheath--metal interface, and evanescent waves are presented. The waves are experimentally found in ICP plasma in vicinity of large RF electrode in [2]. The well-known plasma-sheath geometrical resonance corresponds to excitation of evanescent waves. Surface waves strongly decay at these conditions. When electrons density increases, skin depth falls. The role of evanescent waves in plasma decreases and the length and energy transferred by surface waves grow. At high plasma density discharge impedance is almost completely defined by surface waves. Influence of even and odd surface take into account. 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. It is found, that the role of even and odd waves is defined by geometry of discharge and properties of matching device. Analytical results are compared with numerical modeling. \\[4pt] [1] M.A. Lieberman, J.P. Booth, P. Chabert et al. Plasma Sources Sci. technol., 2002, 11, 283.\\[0pt] [2] W. Gekelman, M. Barnes, S. Vincena, P. Pribyl. Phys. Rev. Lett. 2009, 103, 045003. [Preview Abstract] |
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HW1.00072: The influence of the secondary electron induced asymmetry on the Electrical Asymmetry Effect in capacitively coupled plasmas Julian Schulze, Ihor Korolov, Aranka Derzsi, Zoltan Donko In geometrically symmetric capacitive radio-frequency plasmas driven by two consecutive harmonics a dc self-bias can be generated as a function of the phase shift between the driving frequencies via the Electrical Asymmetry Effect (EAE). Recently the Secondary Electron Asymmetry Effect (SEAE) was discovered (T. Lafleur, P. Chabert and J.P. Booth J. Phys. D: Appl. Phys. 46 135201 (2013)): unequal secondary electron emission coefficients at both electrodes were found to induce an asymmetry in single frequency capacitive plasmas. Here, we investigate the simultaneous presence of both effects by Particle in Cell simulations, i.e. a dual-frequency plasma driven by two consecutive harmonics with different electrode materials. We find, that the superposition of the EAE and the SEAE is non-linear, i.e. the asymmetries generated by each individual effect do not simply add up. The control ranges of the dc self-bias and the mean ion energy can be enlarged, if both effects are combined. [Preview Abstract] |
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HW1.00073: The effect of structured electrodes on heating and plasma uniformity in capacitive discharges Julian Schulze, Nico Schmidt, Edmund Schuengel, Uwe Czarnetzki The effect of structured (non-planar) electrode topologies, e.g. rectangular, rounded, and triangular trenches, on the electron heating dynamics and ion density profile in capacitive radio frequency plasmas is investigated experimentally and by an analytical model. 2D Phase Resolved Optical Emission Spectroscopy is utilized to study the dynamics of energetic electrons inside and outside these structures. In the presence of structured electrodes non-planar RF sheaths form, that affect the electron heating dynamics. We observe a local increase of energetic electrons above the structures caused by a combination of cross-firing of electron beams generated by sheath expansion heating and a temporal confinement of energetic electrons between the sheaths within the structure. The confinement within the trench is limited to the phase of sheath expansion. Also the ionization and, as a consequence the plasma density, are modified by these effects. This is characterized by radially resolved Langmuir probe measurements and described by a diffusion model. The control of the radial plasma density profile is demonstrated. Via customized electrode topologies high plasma uniformity at specific pressures and heights above the electrode is achieved. [Preview Abstract] |
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HW1.00074: Electron energy balance analysis of ccrf discharge plasmas in oxygen Igor Sheykin, Markus M. Becker, Detlef Loffhagen In capacitively coupled radio frequency (ccrf) oxygen plasmas at low pressure the mean electron energy is assumed to be a measure for etching, deposition and other surface processes. Hence, it is important to know its spatio-temporal distribution, dependence on applied voltage and discharge parameters. Here, an axially and phase resolved analysis of the mean electron energy has been performed by means of fluid modelling for discharge plasmas in a reactor with plane parallel electrodes. The model includes the coupled system of balance equations for heavy species, the electron component and the mean electron energy as well as Poisson's equation with the corresponding boundary conditions. The analysis has been done for pressures between $30$ and $50$\,Pa, applied voltage amplitudes from $100$ to $500$\,V and a frequency of $13.56$\,MHz. The impact of the different contributions to the electron energy balance is discussed. In particular, it was found that the ratio between energy gain due to Joule heating and energy flux in the plasma bulk depends strongly on the applied voltage and pressure of the gas. [Preview Abstract] |
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HW1.00075: Electron and ion dynamics in a multi-frequency low-pressure asymmetric capacitively coupled oxygen plasma Andrew Gibson, Arthur Greb, William Graham, Timo Gans Multi-frequency plasma sources are widely used in industrial processes. Most current implementations apply two significantly differing frequencies to avoid coupling between the frequency components and achieve separate control of electron and ion dynamics. However, at very high driving frequencies plasma non-uniformities may be produced as a result of electromagnetic effects involving the high-frequency component. Thus further investigation and understanding of the coupling between multiple lower frequencies, where electromagnetic effects are minimised is warranted. Presented here is a study of a capacitively coupled oxygen plasma using a voltage waveform comprised of multiple frequencies below the threshold required to induce significant electromagnetic effects in current generation plasma processing reactors. Plasma dynamics are simulated using a hybrid model of an asymmetric CCP. Simulations are performed in time over a 1D spatial domain across the discharge centre. The asymmetry in the model is comparable to our experimental setup (GEC reference cell). The effect of variations in the relative amplitude of each frequency component and also in the phase difference between the components on electron and ion dynamics within the excitation cycle is investigated and discussed. [Preview Abstract] |
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HW1.00076: Simulation model for analyzing voltage-current characteristics of the barrier type lamp filled with Hg-Ar gas Yoshio Watanabe, Tomohiro Yamaguchi, Ryosuke Imada The simulation model for DBD lamp filled with Hg-Ar gas is studied. The straight tube filled with Hg and Ar gases is employed as a lamp. Three kinds of applied voltage waveforms at high frequency are applied between the pair of stripe electrodes attached on the outside of the tube. One dimensional model is employed. Ionization frequency based on Townsend ionization coefficient is employed in this model. A try-and-error method is employed to estimate the value of each coefficient, and the calculated waveform is compared with the measured current waveform. The values by which the most similar current waveform to the measurement is obtained are selected as appropriate values. Using these coefficient values, the discharge current waveforms by the applying voltage with triangular waveform and trapezoidal waveforms are calculated and compared with the measured current waveforms. Good agreements between the calculation and the measurement in discharge current waveform are obtained for three types of applied voltage waveform. Then, the distributions of electric field, electron density and ion density in the discharge space are calculated. It is shown that the space charge layer is formed on the glass tube wall and ionization takes place mainly in the space charge layer. [Preview Abstract] |
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HW1.00077: The effect of dust on the electron heating in capacitively coupled H$_2$/SiH$_4$ single- and dual-frequency discharges Edmund Sch\"{u}ngel, Sebastian Mohr, Shinya Iwashita, Julian Schulze, Uwe Czarnetzki Hydrogen diluted silane discharges exhibit a high dust concentration under typical application conditions. Therefore, the role of dust in fundamental plasma processes needs to be understood. We study a capacitively coupled rf discharge in H$_2$/SiH$_4$ using Phase Resolved Emission Spectroscopy, two-dimensional laser light scattering on the dust particles as well as current and voltage measurements. The results show that the electron heating is strongly affected by the presence of dust particles. In particular, a mode transition occurs from the traditional $\alpha$-mode to a bulk drift field mode ($\Omega$-mode), if the amount of dust is increased. An analytical model of the electron dynamics in $\Omega$-mode has been developed. An asymmetric dust particle density profile, e.g. due to a gas temperature gradient, induces an asymmetry in the electron heating and, thereby, in the ion density profile of a single frequency parallel plate discharge. In electrically asymmetric discharges, the discharge asymmetry can usually be controlled via the phase angle between the applied harmonics. It is found that the Electrical Asymmetry Effect works in discharges operated in both $\alpha$- or $\Omega$-mode, as the width of the control interval is almost independent of the dust distribution. [Preview Abstract] |
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HW1.00078: Multi-Peaked Distributions of Escaping Electrons in RF-DC Discharge Alexander V. Khrabrov, Igor D. Kaganovich, Peter L.G. Ventzek, Lee Chen Hybrid RF-DC capacitively coupled discharges find important and growing technological applications. In RF-DC systems, secondary electrons emitted from electrodes undergo complicated motion defined by acceleration in, and bouncing between a steady and an oscillating sheath. For the emitted electrons that return to, and impinge upon the RF electrode, the arrival energy is a non-monotonic function of the driving phase at which they were emitted. This basic property leads to a velocity distribution with multiple peaks [1,2]. Such effect may explain the peaks in electron energy distributions measured in RF-DC system at the RF electrode [2,3]. In particular, the distribution of secondary electrons is sensitive to variations in the bouncing time, and may form several peaks if even a small high-frequency ripple is present in the RF sheath voltage [2], as may be the case due to the plasma-sheath resonance (PSR). We have found such features in test-particle simulations of the discharge, and analyzed the observed distributions.\\[4pt] [1] D. Israel \textit{et al.,} J. Appl. Phys. \textbf{99}, 093303 (2006).\\[0pt] [2] K.E. Orlov and A.S. Smirnov, Plasma Sources Sci. Technol. \textbf{10}, 541 (2001).\\[0pt] [3] L. Xu \textit{et al.,} Appl. Phys. Lett. \textbf{93,} 261502 (2008). [Preview Abstract] |
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HW1.00079: OTHER PLASMA SCIENCE TOPICS |
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HW1.00080: Reflection of Slow Electrons from Solid Surface Alexander Mustafaev, Matsak Ainov, Igor Kaganovich, Vladimir Demidov Given that progress of future plasma technologies depends on control of electron coefficient reflection $r_{0} $, the development of methods of measurement and control of $r_{0} $is of great importance. Published experimental data on $r_{0} $ for slow electrons are inconsistent and sometime give large values up to $r_{0} \approx 0,8$ and even higher. This talk presents a technique for $r_{0} $ measurements in low pressure plasmas in the presence of transverse magnetic field. It is found that for poly-crystal surface, effective reflection coefficient can really reach value of 0.8. It is demonstrated that it is connected to additional reflection from potential barrier near the surfaces. The contribution of electron reflection from the barrier and the surface has been divided and studied. The data have been confirmed at different mono-crystal surfaces. [Preview Abstract] |
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HW1.00081: A method for gas analysis in nonlocal plasma of a short argon microdischarge Anatoly Kudryavtsev, Margarita Stefanova, Petko Pramatarov Recently developed collisional electron spectroscopy (CES) method allows identification of gas impurities in a main gas in nonlocal plasma, where the different groups of electrons do not relax in energy by collisions in the volume and behave independently of each other. The fast electrons, released in processes of Penning ionization of the impurity particles by main gas metastable atoms, give narrow peaks in the EEDF near the energy of their appearance. Selective registration of groups of fast nonlocal electrons created in Penning ionization of the impurity atoms or molecules by metastable argon atoms is carried out. Argon is used as a main gas. The negative glow plasma of a short dc microdischarge at medium pressures is used as most suitable medium for nonlocal formation of the EEDF. Penning reactions with known gas impurities and sputtered cathode metal atoms are registered. The obtained maxima in the EEDF appear at the characteristic energies corresponding to the expected maxima for penning electrons of the known gas impurities used. This experiment contributes to the development of new microdischarge gas analyzer for gas impurities detection, whose dimensions can be dramatically reduced, compared to the exciting devices. [Preview Abstract] |
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HW1.00082: PLASMAS FOR NANOTECHNOLOGIES, FLEXIBLE ELECTRONICS AND OTHER EMERGING APPLICATIONS |
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HW1.00083: Microwave plasma produced carbon nanostructures Julio Henriques, Elena Tatarova, Claudia Luhrs, Jonathan Phillips, Ana Rego, Ana Ferraria, Miroslav Abrashev, Ana Dias, Carlos Ferreira A microwave, atmospheric argon plasma driven by surface waves has been used for synthesizing carbon nanostructures by passing vaporized ethanol through the plasma. The method is based on sending vaporized ethanol molecules through a microwave argon plasma environment, where decomposition of ethanol molecules takes place and carbon atoms are created. These carbon atoms agglomerate subsequently in the outlet gas stream to form nanostructures that are collected by nylon membrane filters. External, forced cooling/heating has been applied using a cryostatic system to fix the temperature in the nucleation zone of the plasma reactor. The synthesized carbon nanostructures were analyzed by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and micro-Raman spectroscopy. Graphene sheets and carbon nanoparticles have been selectively synthesized through the control of the outlet plasma stream temperature. [Preview Abstract] |
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HW1.00084: Microwave plasma based method for free standing graphene synthesis Elena Tatarova, Julio Henriques, Claudia Luhrs, Jonathan Phillips, Ana Rego, Ana Ferraria, Miroslav Abrashev, Ana Dias, Carlos Ferreira Microwave atmospheric pressure plasmas driven by surface waves were used to synthesize graphene sheets from vaporized ethanol molecules carried through argon plasma. In the plasma ethanol decomposes creating carbon atoms that form nanostructures in the outlet gas stream. The synthesized carbon nanostructures were analysed using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and micro-Raman spectroscopy. The existence of few layer graphene (from one to five sheets) has been confirmed by HRTEM images. Raman spectral studies were conducted to determine the ratio of the 2D to G peaks. Furthermore, the C 1s XPS region is dominated by the peak centred at 284.4 eV assigned to sp$^{2}$ carbon atoms bond to carbon. Forced external heating of the outlet gas stream results in an increase of the sp$^{2}$/sp$^{3}$ (\textgreater\ 4) and C/O (\textgreater\ 14) ratios. Analysis of the C 1s XPS energy loss spectra reveals plasmon energy losses attributed to $\pi $-$\pi $* collective excitation. [Preview Abstract] |
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HW1.00085: Plasma-water interactions at atmospheric pressure in a dc microplasma Jenish Patel, Lucie N\v{e}mcov\'a, Somak Mitra, William Graham, Paul Maguire, Vladimir \v{S}vr\v{c}ek, Davide Mariotti Plasma-liquid interactions generate a variety of chemical species that are very useful for the treatment of many materials and that makes plasma-induced liquid chemistry (PiLC) very attractive for industrial applications. The understanding of plasma-induced chemistry with water can open up a vast range of plasma-activated chemistry in liquid with enormous potential for the synthesis of chemical compounds, nanomaterials synthesis and functionalization. However, this basic understanding of the chemistry occurring at the plasma-liquid interface is still poor. In the present study, different properties of water are analysed when processed by plasma at atmospheric-pressure with different conditions. In particular, pH, temperature and conductivity of water are measured against current and time of plasma processing. We also observed the formation of molecular oxygen (O$_{2})$ and hydrogen peroxide (H$_{2}$O$_{2})$ for the same plasma conditions. The current of plasma processing was found to affect the water properties and the production of hydrogen peroxide in water. The relation between the number of electrons injected from plasma in water and the number of H$_{2}$O$_{2}$ molecules was established and based on these results a scenario of reactions channels activated by plasma-water interface is concluded. [Preview Abstract] |
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HW1.00086: Microplasma surface engineering of silicon nanocrystals for improved inorganic/polymer nanocomposites Somak Mitra, Vladimir Svrcek, Paul Maguire, Davide Mariotti Improved optoelectronic properties have been achieved by direct current (DC) microplasma-induced 3-dimesional (3D) surface engineering of silicon nanocrystals (SiNCs) in water with (Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) (PEDOT:PSS). Specifically, we have successfully shown that photoluminescence (PL) of SiNCs inside a water-based solution increases after microplasma processing. The experimental results show that optical properties of SiNCs do not deteriorate over time and remain stable in water with potential application impact for bio-related applications. We have also shown that fast oxidation process in water is prevented over longer period of time due to the microplasma processing in comparison to the unprocessed sample. Furthermore, the improved surface characteristics allow for the formation of water-soluble nanocomposites with improved opto-electronic properties; this can have direct implications for higher performance opto-electronic devices including solar cells. [Preview Abstract] |
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HW1.00087: Development and characterization of a neutral beam source for sub-10 nm etching Daniil Marinov, Ziad el Otell, Nicholas St. Braithwaite, Mark Bowden Neutral beam etching is a promising technology for damage-free sub-10 nm device fabrication. In this work a neutral beam is generated by surface neutralization of ions extracted from a pulsed ICP discharge in Ar/SF$_{6}$. Negative ions are extracted during the afterglow phase when an ion-ion plasma is formed. The evolution of ~the density of various charged species is measured with different techniques (Langmuir, hairpin and ion flux probes). High density plasma, with electron number density in the range 10$^{17}$ - 10$^{18}$ m$^{-3}$, is typically produced in the pulsed ICP. The electron heating in the active-glow phase is characterized using trace rare gas optical emission spectroscopy with Ar, Kr and Xe admixtures. The energy spectra and fluxes of the extracted ions are measured using a retarding field analyzer. The potential of pulse tailoring of the discharge for optimization of negative ion formation is investigated, while varying the extraction pulse waveform provides another degree of freedom to obtain desirable neutral beam characteristics. Finally, the etching performance of the neutral beam source is demonstrated on patterned and non-patterned silicon wafers. [Preview Abstract] |
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HW1.00088: SPECIAL ARRANGED SESSIONS |
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HW1.00089: Odd Length Contraction Florentin Smarandache Let's denote by $V_{E} \quad $the speed of the Earth and by$ V_{R}$ the speed of the rocket. Both travel in the same direction on parallel trajectories. We consider the Earth as a moving (at a constant speed $V_{E\, }- V_{R})$ spacecraft of almost spherical form, whose radius is $r$ and thus the diameter \textit{2r}, and the rocket as standing still. The non-proper length of Earth's diameter, as measured by the astronaut is: \[ L=2r\sqrt {1-\frac{\vert V_{E} -V_{R} \vert^{2}}{c^{2}}} <2r. \] Therefore Earth's diameter shrinks in the direction of motion, thus Earth becomes an ellipsoid - which is untrue. Planet Earth may increase or decrease its diameter (volume), but this would be for other natural reasons, not because of a\textellipsis flying rocket! Also, let's assume that the astronaut is laying down in the direction of motion. Therefore, he would also shrink, or he would die! [Preview Abstract] |
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HW1.00090: Ion distribution functions in magnetized rf Argon plasma presheaths M. Umair Siddiqui, Noah Hershkowitz A helicon plasma source was operated in a low power inductive mode to create a magnetized Argon plasma with densities of 10$^{11}$ -- 10$^{12}$ cm$^{-3}$ and electron temperatures from 3 -- 5 eV. A grounded plate oriented perpendicular to the axial magnetic field was placed 2.5 antenna lengths downstream from the near edge of the rf antenna. Using laser-induced fluorescence, the ion velocity distribution functions were investigated along the axis of the chamber in the bulk plasma and in the plate's presheath. Bimodal and non-Maxwellian distribution functions were observed in the presheath, though not in the bulk plasma. In certain situations ion populations traveling in opposite directions were observed. In this work the authors investigate these phenomena as a function of neutral pressure, rf power and axial magnetic field strength. [Preview Abstract] |
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