Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session DTP: Poster Session II (14:00-15:30) |
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Room: 8 and 251 |
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DTP.00001: GLOWS |
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DTP.00002: Effect of added molecular gases (H$_{2}$, O$_{2}$, N$_{2}$) in an analytical glow discharge on the ion signal intensities obtained using a high resolution mass spectrometer Viktoria Weinstein, Edward B.M. Steers, Tamara Gusarova, Karol Putyera Glow discharge plasma sources in combination with either mass spectrometry or optical emission spectroscopy are routinely used for spectrochemical analysis of solid samples. Analytical results can be significantly affected by traces of molecular gases as H$_{2}$, O$_{2}$, N$_{2}$ which may be present in the plasma gas (argon), often arising from sample constituents. With the main purpose of understanding better the processes occurring in the plasma, small fractions (0-2{\%}) of H$_{2}$, O$_{2}$ and N$_{2}$ were introduced into the discharge gas and the changes in ion signal intensities for sputtered analyte, plasma gas and trace gases were examined for various samples. The sputter rates are also affected by alternative gases; they may be reduced due to reduced Ar ion and atom population or due to poisoning effects of the added gas on the surface. Therefore the changes in the sputter rates give additional information which helps to interpret the data. Time resolved analysis with a pulsed dc mode will be used to find out in which sequence ions are built in the discharge process. [Preview Abstract] |
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DTP.00003: Obstructed DC glow discharge in nitrogen Valeriy Lisovskiy, Ekaterina Kravchenko, Ekaterina Skubenko, Nadiia Kharchenko, Vladimir Yegorenkov We studied in experiment the obstructed and abnormal modes of dc glow discharge in nitrogen as well as the transition between them. The measurements were made in a tube of 55 mm in radius with the inter-electrode gap of 10 mm. It is shown that the obstructed discharge may exist only in the gas pressure range p $<$ 0.2 Torr under conditions corresponding to the left-hand branch of Paschen curve (the breakdown curve minimum was at pressure of p = 0.55 Torr). The dc glow discharge in the nitrogen pressure range p $<$ 0.2 Torr was shown to possess an S-shaped current-voltage characteristics (obstructed and abnormal burning modes possess growing CVCs but the transition between them was accompanied by the negative CVC). The transition from the obstructed mode to the abnormal is shown to be accompanied by LF relaxation oscillations of the discharge current in a kilohertz range. These oscillations are probably due to the negative glow forming and decaying near the anode. They are observed in a limited nitrogen pressure and current ranges. [Preview Abstract] |
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DTP.00004: Study on Microwave Plasma Source with TM-wave Cavity, of which Bottom Plate Replaced with High-Density Plasma Sumio Kogoshi, Noboru Katayama, Shinji Nakatui It is well known that a microwave plasma source with a resonant cavity for TM modes may efficiently sustain high density plasma. The aim of this paper is to present the formula to calculate the length of a resonant cavity, of which the end plate is replaced with high density plasma. The resonant cavity consists of air gap and a dielectric window because a plasma chamber must be sealed with the latter one. The formula derived analytically, which considers the reflection of microwave from the surface of the dielectric window, can predict a resonant cavity length for TM modes, at which a local density peak would appear. The prediction of local density peaks from the formula agrees with experimental results. Finite-difference time-domain (FDTD) simulations for electromagnetic fields inside the cavity support that a resonant cavity is formed when the local density peak appears. This formula will be useful to design a microwave plasma source with a resonant cavity for TM modes. [Preview Abstract] |
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DTP.00005: Theoretical analysis of direct current glow discharge plasma in a coaxial structure Alireza Niknam, Saber Abdi, Ahmadreza Rastkar The direct current (dc) glow discharge plasma in a gas medium is widely used in the material processing industry and thin film deposition. Therefore, the modeling of the dc discharge at low pressure Argon plasma in a coaxial structure is presented. This structure consists of three media: plasma, dielectric and air. This system surrounded by a long cylindrical loss-free metal with a metallic rod in its center. Also, the model is based on the diffusion theory of gas discharge. Therefore, the radial electron density profile in the plasma region is obtained using the diffusion equation. Then, solving the Poisson's equation and considering the appropriate boundary conditions, we investigate the radial distributions of the dc electric field and potential in this coaxial configuration. [Preview Abstract] |
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DTP.00006: A Travelling Wave Sustained Hydrogen Discharge Elena Tatarova, Edgar Felizardo, Francisco Dias, Carlos Ferreira, Boris Gordiets An investigation of the spatial structure of a long H$_{2}$ plasma column sustained by a propagating surface wave (SW) is presented. The discharge is created using a surfatron-based setup powered by a 500 MHz generator, whose output was varied from 65 to 100 W, and takes place inside a Pyrex tube. Plasma-emitted radiation is collected perpendicularly to the discharge tube by an optical system comprising an imaging optical fiber coupled to a SPEX 1250M spectrometer equipped with a nitrogen cooled CCD camera. Phase and amplitude measurements using a vector voltmeter were carried out in order to obtain the SW dispersion characteristics. The gas temperature ranges from about 700K, at the beginning of the column, to about 350 at its end. Selective heating of H atoms has been detected. The Doppler temperatures corresponding to the H$_{\gamma}$ line broadening are much higher than the gas temperature. The experimental results are analyzed in the framework of a self-consistent kinetic model, which accounts for the main plasma balances governing the discharge production, including bulk and surface processes. The experimental gas and H atom temperatures and atomic line intensities confirm the main trends of the model predictions. The crucial role of the wall conditions on the discharge physics is analyzed. [Preview Abstract] |
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DTP.00007: Electron current evolution of a two-surface multipactor discharge Timothy Graves, Rostislav Spektor, Daniel Larson Multipactor discharge can occur as electrons impact surfaces in resonance with RF or microwave fields. This pure electron discharge is sustained by secondary electron emission from the electrode materials. The growth in the electron number density requires sufficient secondary electron emission to overcome particle losses, mandating a secondary electron yield (SEY) greater than unity for successful multipactor development. The rate at which the multipactor develops is determined primarily by the magnitude of the SEY at the primary electron impact energies, which is also coupled to the multipactor resonant conditions. In this work, we experimentally measure the multipactor rise time of the discharge at frequency ranges between 0.5 and 2 GHz in both parallel plate and coaxial geometries. Using high gain current amplifiers, the temporal evolution of the discharge current is measured at different frequencies, geometries, and power levels and compared to the discharge saturation time. Such current measurements provide experimental insight toward the various ``Crossing Rules'' used to determine multipactor margin in multicarrier RF systems. Employing multiple fast electron current probes, an electron time-of-flight diagnostic for multipactor location determination is demonstrated in a rigid coaxial transmission line. [Preview Abstract] |
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DTP.00008: Spectroscopic studies of long-lived excited species in flowing nitrogen afterglows at intermediate pressures Robert Carman, Scott Allan, Peter Ha, Conor Martin, Satya Barik, Cormac Corr, Rod Boswell Plasma kinetics issues associated with the production and quenching of long-lived N$_{2}$*(A) and N*($^{2}$D, $^{2}$P) metastable species present in the flowing afterglows of pure nitrogen plasmas are currently of topical interest. These plasmas are used in emerging applications such as remote plasma chemical vapour deposition (RPCVD) to grow group III nitride thin films. We have generated flowing N$_{2}$ afterglows at intermediate pressures (1-50 torr) experimentally using both microwave (2.45GHz) and RF (13.56MHz) excitation methods. The afterglows have been studied using optical emission spectroscopy (ACTON VM502 monochromator/photomultiplier operating in photon counting mode) with particular emphasis on the ultraviolet range 220-340nm to detect the very weak Vegard-Kaplan band system corresponding to the slow decay of the N$_{2}$*(A) metastables. Preliminary results reveal the presence of NO($\gamma )$ band system (210-280nm) in the late afterglow, highlighting the sensitivity of the N$_{2}$*(A) population to strong quenching by background O$_{2}$/H$_{2}$O trace impurities. [Preview Abstract] |
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DTP.00009: Virtual Cathode lifetimes and floating potential measurements in a Polywell{\texttrademark} fusion device Matthew Carr, Joe Khachan The Polywell {\texttrademark} is a spherically convergent ion focus concept first developed by R Bussard in the 1980s as a possible device for controlled thermonuclear fusion. The device aims to magnetically confine electrons with a quasi-spherical-cusp magnetic field, forming a deep potential well in the centre of the device, which can attract and maintain a high density of local energetic ions passing through the potential well. Careful design of the magnetic field and coil formers might help to substantially reduce the former/grid collision losses that plague other IEC devices. Floating potential measurements in the core of a Polywell have shown that a virtual cathode is established, with floating potentials of up to -250V obtained for milliseconds. The lifetime of the virtual cathode was determined only by the shape and duration of the magnetic coil current. This implies that currents of increasing duration will increase the lifetime of the virtual cathode. Further measurements reveal that virtual cathode formation could only be established within a narrow magnitude range of coil currents. We find that the floating potential increases with decreasing gas pressure. [Preview Abstract] |
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DTP.00010: ABSTRACT WITHDRAWN |
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DTP.00011: Study on expansion of electron sheath and breakdown in it Yeong-Shin Park, Da-Hye Choi, Kyoung-Jae Chung, Yong-Seok Hwang Electron sheath forms in front of a small electrode biased positively with respect to the potential of surrounding plasma. Based on the collisionless Child-Langmuir model for ion sheath in low pressure plasma, electron sheath model has been suggested. Equation of electron sheath thickness derived from the model describes that the thickness is determined by plasma density, electron temperature and sheath voltage as the ion sheath is. However, electron sheath is about 1.6 times thicker than ion sheath at same conditions. The calculated sheath thicknesses are verified by probe diagnostics as well as particle simulation. Monitoring the variation of ion saturation current of Langmuir probe with tiny tip with respect to sheath voltage, locations of sheath edge are measured at different plasma densities and electron temperatures. Using the 1D particle-in cell code, thickness of electron sheath are investigated, as well. Outbreak voltages of the breakdown in the electron sheath are gauged at various pressures and powers. Regarding the plasma as a cathode, biased electrode as an anode and electron sheath thickness as a discharge gap respectively, one-dimensional breakdown model is suggested. Applying Townsend's criteria of DC discharge to this breakdown model, a nonlinear equation for breakdown voltages is derived. Comparison of model-based numerical calculations to experimental results shows a good agreement between them. [Preview Abstract] |
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DTP.00012: Electrical characteristics of an atmospheric pressure plasma jet with helium flow Gordana Malovic, Dejan Maletic, Nevena Puac, Sasa Lazovic, Antonije Djordjevic, Zoran Petrovic In the last few years atmospheric nonthermal plasma jet increasingly attracts interest because of its potential in biomedical applications. We have constructed a plasma jet that operates in the range of 5-10 kV and 25-150 kHz. It is made of Pyrex glass tube (I.D. 4 mm; O.D. 6 mm) with two cylindrical electrodes made of copper foil (13 mm wide). The buffer gas was helium with a flow of 2-7 slm. High voltage probe was used to obtain voltage waveforms while current waveforms were measured at the resistor (100 kOhm) placed in the grounded branch of the electrical circuit. Measurements are performed for increasing and decreasing applied voltage in order to observe hysteresis. RMS voltage/current values and mean power values are calculated. Our results show that plasma is a nonlinear load in the electrical circuit and that there is a significant hysteresis. It was possible to control the mean power in all cases to be below 10 W which is required for biomedical applications. The electrical measurements are coupled to ICCD measurements of the plasma profile and motion. [Preview Abstract] |
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DTP.00013: Modeling of heavy particle collisions in high E/N discharges in helium Zoran Petrovic, Zeljka Nikitovic, Svetlana Radovanov, Vladimir Stojanovic We have compiled a set of collision cross sections for electrons, ions and fast neutrals in helium. The sat has been used as the basis for modeling of heavy particle excitation and other effects that occur at very high E/N. As a first step modeling was performed for Townsend discharges in uniform electric field. We calculate spatial profiles of emission with imprints of both electron and heavy particle excitation and compare them to the experiment. Non-hydrodynamic transport close to electrodes at low pressures is illustrated and effects of reflection of particles, secondary particle emission and surface excitation are included in the model. We also present the spatial profile of fluxes of all particles and we calculate line profiles that show Doppler broadening that may be detected in gas discharges. We also analyze kinetics of electrons, ions and fast neutrals in helium discharges with inhomogeneous electric field. [Preview Abstract] |
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DTP.00014: New Method for Homogeneous Plasma Production at Gas Pressure 0.005 -- 5 Pa Used for Substrate Etching, Nitriding, Ion Implantation and Coating Deposition Alexander Metel, Sergei Grigoriev, Yuriy Melnik, Vladimir Prudnikov DC glow discharge with electrostatic confinement of electrons is used for homogeneous plasma production inside working vacuum chamber of technological system ``Bulat-6'' at argon or nitrogen pressure $p$ ranging from 0.005 Pa to 5 Pa. Plasma nonuniformity at $p \quad <$ 0.05 Pa does not exceed $\sim $ 10{\%} and rises to $\sim $ 20{\%} at $p$ = 0.5 -- 5 Pa. The argon plasma enables conductive substrates etching and targets sputtering with energetic ions as well as heating and melting metals and dielectrics with energetic electrons. The nitrogen plasma enables cost-effective ion implantation and nitriding of conductive substrates, which are negatively biased using a simple DC high-voltage power supply. [Preview Abstract] |
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DTP.00015: Characterization of high-power atmospheric pressure transient micro-glow discharge using double-pulsed high-voltages Shinji Ibuka, Jun Kikuchi, Naoaki Yoshida, Koichi Igarashi, Shozo Ishii A high-power transient micro-glow discharge is a promising candidate for atmospheric pressure plasma processes. Although the utilization of a highly repetitive pulsed high-voltage is effective to generate the spatially uniform transient micro-glow discharge without a glow-to-arc transition, its stabilization mechanism has not been fully understood yet. In this study, the transient micro-glow discharges powered by double-pulsed voltages were investigated for various pulse-intervals and helium flow rates. The electrical and the optical emission spectroscopic characterizations illustrated the important roll of the metastable species with long excitation lifetime for stability enhancement. The helium flow rate had also remarkable effect on the plasma parameters. According to the Stark broadening of the hydrogen Balmer lines, the electron density reached over $10^{15}$cm$^{-3}$ during the high-voltage applied period and maintained above $10^{14}$cm$^{-3}$ for several microseconds. The results show the feasibility of the atmospheric pressure reactive plasma generation having high electron density using MHz order repetitive pulsed voltages. [Preview Abstract] |
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DTP.00016: Qualitative theory of multi-hollow microwave plasma source Ivan Ganachev, Iji Liang, Hideo Sugai The performance, in particular uniformity, of planar surface- wave plasma sources can be enhanced by modifying the dielectric- plasma interface to include an array of hollows cut into the dielectric (``multi-hollow plasma source''). Recently\footnote {Sugai et al.:\it{\ Proc.\ 7th Int.\ Workshop Microwave Discharges:\ Fundamentals and Applications, Hamamatsu 2009}, p.\ 85} we found that with increasing overall power the number of ignited hollows increases, but the power absorbed by each one of them remains almost constant for fixed gas type and pressure (about 7 Watt per hollow in Ar at 1.3 Pa and 2.45 GHz). In the present contribution we propose an explanation to this behavior: We show that small plasma-filled hollows have a discrete spectrum of resonance densities. In the particular case of small hemispherical hollows, the electron density of the $n$-th mode is $n_e(n)=n_c[1+ \epsilon_d(2n+1)/2n]$, $n=1,2,\dots$, where $n_c$ is the cut-off density and $\epsilon_d$ is the dielectric constant of the plate carrying the hollows. This spectrum is rather narrow (from 5 to 7 times $n_c$ for the aforementioned example). Once the highest resonance density is reached in all currently ignited hollows, any additional power spills over and eventually ignites one of the remaining hollows. With sufficient power, the discharge expands uniformly to all hollows. [Preview Abstract] |
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DTP.00017: Numerical analyzing of unstable modes propagating along the magnetic field on magnetized microwave produced plasmas Mohammad Ghorbanalilu The stability of plasma produced under the interaction of high frequency Microwave (MW) field with a dilute neutral gas is investigated in the present of axially external magnetic field. The electromagnetic waves propagating along the external magnetic field are considered for short and long wavelength limits. It is shown that the unstable Weibel mode grew under the competition between MW and external magnetic fields. However, increasing the MW field amplitude increased Weibel instability growth rate, instability disappeared by sufficiently strong magnetic field. We found that in contrast to the non-magnetized case that Weibel mode was non-oscillate, this mode oscillated very slowly on time on the magnetized Microwave Produced Plasma (MWPP). In addition, the numerical calculation indicated that the new type of unstable mode is generated during plasma production. This type of instability oscillated and grew very fast on time, compared to the Weibel instability. [Preview Abstract] |
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DTP.00018: MAGNETICALLY ENHANCED PLASMAS: ECR, HELICON, MAGNATRON, OTHERS |
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DTP.00019: Production and Application of Magnetized Plasmas Generated by Rotating Magnetic Fields John Slough The use of rotating magnetic fields (RMF), where $\omega $ lies between the ion and electron gyro frequency in the RMF field, readily generates both a high density plasma (n $\sim $ 10$^{19}$ -- 10$^{20}$ m$^{-3})$, and large plasma currents (10-50 kA). These large currents in turn produce a significant confining magnetic field. Previously RMF current drive has been studied using dielectric vacuum chambers with the RMF coils located outside the chamber. Methods for studying RMF current drive in conducting metal vacuum chambers have been developed by moving the RMF coils inside the vacuum chamber. The experiments to be described employed three distinct RMF coil geometries with each demonstrating a potential application. The first coil set was successfully deployed in a plasma thruster configuration. The second coil set demonstrated the ability to couple energy to plasma tied to a static dipole magnet suspended inside the RMF coils in a manner suitable for plasma processing applications. The third coil set demonstrated that RMF current drive can be achieved outside the RMF coils with the coils fully immersed in the center of the RMF driven plasma. This coil geometry is relevant to the Plasma Magnet propulsion concept, where RMF currents would be driven at large distances from a central spacecraft creating a mini-magnetosphere. For all three RMF coil sets, plasma diagnostics reveal the formation of a stable, high $\beta$ plasma. [Preview Abstract] |
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DTP.00020: A novel equilibrium theory of helicon discharges Davide Curreli, Francis F. Chen The equilibrium of helicon discharges was investigated using a non-standard diffusion theory in which the Simon short-circuit effect was taken into account. The problem was reduced to a system of ordinary differential equations yielding universal radial profiles of plasma density and potential, and of neutral density. In particular, it is shown that the plasma density is always peaked on axis even if the ionization is concentrated at the edge by the Trivelpiece-Gould mode. The results agree with experimental data. [Preview Abstract] |
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DTP.00021: Two-dimensional self-consistent model of an end-Hall (gridless) ion source Noureddine Oudini, Gerjan Hagelaar, Laurent Garrigues, Jean-Pierre Boeuf In an end-Hall source an ion beam is extracted from a magnetized plasma and accelerated by the plasma electric field without grids. The principles of end-Hall sources is similar to that of Hall effect thrusters (or closed-drift thrusters) but their design is optimized for processing applications (ion-beam assisted deposition or substrate cleaning) rather than propulsion. The beam divergence is larger in end-Hall ion sources and these sources can operate at low ion energy. Although end-Hall sources are commonly used in the surface processing industry, no detailed modeling of these sources is available and their operation is quite empirical. We present a self-consistent, two-dimensional quasi-neutral model of an end-Hall ion source. The model is used to improve the understanding of the basic physics of these plasma sources and to quantify the parameters controlling the properties of the extracted ion beam. Plasma properties and ion beam characteristics as a function of gas flow rate, discharge current, and magnetic field configuration, are discussed. [Preview Abstract] |
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DTP.00022: Improvement of the fluid electron description in a hybrid model of a Hall effect thruster by means of the ion velocity profile measurements Laurent Garrigues, St\'ephane Mazouffre, Guillaume Bourgeois Hall effect thrusters are now used on board geostationary satellites. A xenon flow is released at the inlet of a cylindrical channel through the anode plane. A radial magnetic field is generated at the end of the channel to impede the axial electron current arising from an external cathode. A discharge voltage is applied between the electrodes. Such a ExB configuration leads to a high ionization of the neutral propellant flow and a the classical theory to describe the electron transport across the magnetic field barrier falls down. A two-dimensional model of the thruster has been developed, where a kinetic description is used for the ions and the electrons are treated as a fluid. The goal of this work is to show that measurements of the axial ion velocity profile leads to a better description of the electron transport diffusion coefficient used in the fluid approach. [Preview Abstract] |
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DTP.00023: Controlling Plasma Properties in Collisionless Magnetized Plasma with Active Boundaries Yevgeny Raitses, Igor D. Kaganovich, Vladimir I. Demidov, Valery Godyak, Noah Hershkowitz The plasma-surface interaction in the presence of strong electron emission has been studied theoretically and experimentally. The electron flux from the plasma to the wall is determined by the electron velocity distribution function (EVDF) and by the sheath potential, which are consistent with the wall properties. In a typical low-pressure gas discharge, the EVDF can significantly deviate from Maxwellian that may substantially alter the sensitivity of the collisionless plasma to the electron emission from the wall [1,2]. We will review recent results which demonstrated these effects in collisionless magnetized plasmas with active boundaries including electron emitting and biased walls and plasma boundaries [3].\\[4pt] [1] Y. Raitses, et al, IEEE TPS \textbf{34}, 815 (2006).\\[0pt] [2] D. Sydorenko, et al, PRL \textbf{103}, 145004 (2009).\\[0pt] [3] B. Longmier, et al, Rev. Sci. Instrum., \textbf{77}, 113504 (2006). [Preview Abstract] |
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DTP.00024: Two-dimensional Particle-in-cell model of a Hall effect thruster Philippe Coche, Laurent Garrigues Hall effect thruster is a type of space propulsion engine in which the thrust arises from the acceleration of ions by an electric field. One of its particularity is the use of a magnetic field whose purpose is to increase the ionization rate and create a high electric field zone where the ions are accelerated. The incoming electrons from the cathode drift through the magnetic barrier where ionization is greatly enhanced, toward the anode where the neutral propellant gas is injected. We present a two-dimensional particle-in-cell model of a Hall effect thruster, where a particle rezoning method is applied to decrease the computational time. In the region of low neutral density and high magnetic field magnitude, the classical theory predicts a cross-magnetic field mobility by two orders of magnitude lower than the measured one. The model is used to improve the understanding of the physics responsible of the so-called anomalous mobility through plasma turbulence. [Preview Abstract] |
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DTP.00025: Resonance Hair Pin Probe and Laser Photo Detachment Technique for Measuring Time Resolve Negative Ion Density in Pulsed DC Magnetron Discharge N. Sirse, S.K. Karkari, R. Dodd, S.-D. You, J.W. Bradley The Resonance hairpin probe technique in conjunction with laser photo detachment has been applied in a pulse dc magnetron discharge to measure time-resolved negative ion density. The magnetron was operated at 10 kHz with a 50{\%} duty cycle in argon-oxygen plasma. At a position close to the magnetic null 75mm from the cathode, the ratio of negative ion density to electron density was found to be higher ($\alpha \approx $1.3) during the pulse off-phase than during the on-phase ($\alpha \approx $0.3) due to a significant fall in the electron impact dissociation frequency of negative ions in the cooling off-phase. In the magnetized region of the discharge, where B $\approx $ 100 G, the decay in the photo-detachment density after the laser shot is longer as compared to measurements made in the field-free region (magnetic null) along the centre line. This phenomenon will be discussed in terms of cross-field transport and particle balance in Hall-type magnetized plasmas. [Preview Abstract] |
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DTP.00026: Experimental Investigation of Expandable Multiple Helicon Ignition with Permanent Magnets Sanghyuk An, Hongyoung Chang Helicon source is a promising source due to its higher density than other plasma sources. However, it not been widely used owing to its complex setup Although some helicon sources have been conducted to the industrial processing, they are not suitable for the process yet. However, since Chen developed a new concept of helicon source using permanent magnets, a possibility for a large-area processing is opened because of its simple setup and expandability. We have investigated the newly developed helicon source using annular permanent magnets with regard to the expandability. The higher resistance of helicon plasma than other sources makes several tubes ignite in same amount for the parallel ignition. The calculated resistance is compared with the measured one with VI-probe. We also compared the helicon plasma with ICP with respect to the resistance and the phase which affects the power coupling efficiency mostly. Helicon source gives higher resistance and lower phase than ICP A 4-tube multiple helicon source was built for a large area processing. The four tubes are in line and each source is 150 mm apart. Every tube is not turned on at low power; however, all tubes are ignited in the same amount as the input power increased. It means that the input power is distributed equally due to high resistance after the plasma is transferred from inductive to helicon mode. The uniformity is achieved by a Langmuir probe [Preview Abstract] |
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DTP.00027: Concept of Dynamic Control of Magnetic Field for High-Throughput and Wide-Area Etching by Neutral Loop Discharge Plasma Hirotake Sugawara Neutral loop discharge (NLD) plasma is a magnetically enhanced high-density low-pressure inductively coupled plasma for dry etching. It is generated along a magnetically neutral loop (NL) at which the magnetic fields induced by three coaxial coils surrounding the plasma chamber cancel each other.\footnote{T. Uchida and S. Hamaguchi: {\it J. Phys. D: Appl. Phys.} {\bf 41} (2008) 083001.} A Monte Carlo analysis of electron transport in an NLD plasma revealed that electrons obtain energy near the NL and diffuse towards the wafer along a separatrix of the quadrupole magnetic field.\footnote{H. Sugawara, T. Osaga, H. Tsuboi, K. Kuwahara and S. Ogata: {\it Japan. J. Appl. Phys.} (accepted for publication).} This result indicates that etchant species are produced around the separatrix and that the etching rate is high around the position at which the separatrix crosses the wafer. To obtain flat etching rate profile over the wafer and high etching throughput by the NLD plasma, concept of a round arrangement of wafers and a control technique to let the separatrix sweep over the wafers is proposed. [Preview Abstract] |
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DTP.00028: The Optimization of Magnetron System Operating Characteristics by Varying Additional Transverse Anode Magnetic Field A. Bizyukov, O. Girka, K. Sereda, V. Sleptsov, A. Chunadra In current paper the control of planar magnetron sputtering system operating modes by additional anode magnetic field was investigated. The additional anode magnetic field was created by the permanent magnets and magnetic circuits system out of conventional magnetron-sputtering system. The influence of magnetic field configuration alteration on discharge characteristics was investigated both theoretically and experimentally. It was shown that additional anode magnetic field substantially affects to planar magnetron-sputtering system balancing and allows adjusting the electron fluxes intensity to the operating surface. It was experimentally shown that the magnetic field intensity increasing stabilizes the low-current discharge. The magnetic field intensity increasing prevents the discharge extinction by the ignition of semi-self-maintained magnetron-type discharge in magnetic arc upon the sputtering target. The transverse anode magnetic field provides the electrons drift in the same direction as in cathode arc magnetic field. The additional anode magnetic field creation by the outer magnets and magnetic circuits application allows providing any required magnetron sputtering system operating conditions without additional power supplies and basic construction conventional equipment engineering change. [Preview Abstract] |
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DTP.00029: Simulating ECRH with VORPAL, a Particle-in-Cell Code, using Higher-Order Particles Christine Roark, Paul Mullowney, Kevin Paul, David Smithe, Peter Stoltz We present results of using higher-order particles to suppress artificial heating for modeling electron cyclotron resonant heating in a plasma sustained by microwaves. We compare these results to those using standard first-order particles and to a plasma dielectric model. Specifically, we compare the electron temperature, sheath size, and rate of plasma formation for simulations with an argon gas of 0.05 Torr pressure at 2.45 GHz. We also compare the effect of magnetic profiles on the plasma density and the effects of elastic, inelastic and ionizing collisions. Researchers often would like to apply Particle-in-Cell (PIC) methods to model cold, high pressure plasmas in order to discern any kinetic, nonlinear or space charge effects. However, the PIC method typically does not perform well at low temperatures and high densities due to limitations on time and space scales for numerical and practical reasons. One of these limitations is the requirement to resolve the Debye length. Failure to resolve the Debye length in a PIC simulation typically results in artificial heating of the plasma known as grid heating. For applications such as plasma processing, the rate of plasma production is a sensitive function of the electron temperature, so grid heating can make simulation results entirely unreliable. To eliminate this unphysical heating and allow cold, dense plasmas to be simulated using PIC, we use higher-order particle algorithms that smooth out the particle current and charge. [Preview Abstract] |
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DTP.00030: Evolution of electron energy distribution and its diagnostics on high density electron cyclotron resonance hydrogen plasma Lekha Nath Mishra, Ashild Fredriksen The high density hydrogen plasma of the Menja device is produced by means of a 2.45 GHz electron cyclotron resonance source at 500 W microwave power. Experiments are performed within the pressure range 10$^{-5}$ -- 10$^{-4}$ mbar with a gas flow rate 1.5 -- 10 sccm. The key parameters of the plasma are studied with the electric probe measurement technique. Thus generated plasma is characterized in terms of ion saturation current, floating potential, plasma potential, electron temperature and plasma density. However, to obtain information on electron energies and their interaction with plasma, it is also necessary to characterize the electron energy distributions (EEDs). To derive the EEDs, the 2$^{nd}$ derivative of the current characteristics of a swept probe must be obtained. For this purpose, an analogue differentiation circuit was built and tested. We report here the evolution of electron energy distributions and its diagnostics in Menja by this method. [Preview Abstract] |
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DTP.00031: PLASMA DEPOSITION II |
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DTP.00032: Novel method to produce catalysts for oxygen reduction reaction by dual plasma process Christian Walter, Volker Br\"user, Antje Quade, Klaus-Dieter Weltmann Polymer electrolyte membrane fuel cells (PEMFCs) have been recognised as a potential future power source for zero emission vehicles. Today, Pt is the only efficient catalyst for the oxygen reduction reaction (ORR) in PEMFCs. But for reasons of availability and cost efficiency there is a great desire to replace Pt with inexpensive and abundant catalysts (Non-noble-metal catalysts (NNMCs)). Metal (Co/Fe)/N/C composites have emerged as the most promising alternatives within the NNMcs. Those composites are presently mostly produced by pyrolisation, either of Co- and Fe-N$_4$-macrocycles or of separately introduced metal and nitrogen precursors. It has already been shown that a dual PECVD/PVD process can also be used to produce metal-polymer composites with different properties [1]. Here we use such a process with pyrrole as nitrogen precursor and cobalt as metal to obtain novel catalytically active compounds. Since it is also known that some Co-N$_4$-macrocycles can be further improved by using a plasma process instead of pyrolysis, it is promising to produce NNMCs with only a plasma process. FT-IR, XPS, XRD, BET and electrochemical measurements of so-produced samples are presented and discussed.\\[4pt] [1] C. Walter et al.; { \it Plasma Process. Polym.}; {\bf2009}, 6, 803-812 [Preview Abstract] |
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DTP.00033: Characteristics of Near-Infrared n-Type Nanocrystalline FeSi$_{2}$/i-Si/p-Type Si Heterojunctions prepared by Facing-Targets Direct Current Sputtering Nathaporn Promros, Kenji Kawai, Mahmoud Shaban, Tsuyoshi Yoshitake Nanocrystalline (NC) iron disilicide (FeSi$_{2})$, which comprises crystals with diameters ranging of 3-5 nm, is a new semiconducting material. NC FeSi$_{2}$ possesses the similar semiconducting properties to $\beta $-FeSi$_{2}$. In our previous research, we have successfully deposited NC FeSi$_{2}$ films by facing-targets direct current sputtering using sintered FeSi$_{2}$ targets with a chemical composition between Fe and Si of 1:2. In this study, near-infrared n-type nanocrystalline FeSi$_{2}$/i-Si/p-type Si heterojunction photodiodes were prepared by the same sputtering method. The current-voltage characteristics were measured in the temperature range of 60 - 300 K. With a decrease in the temperature, the dark current was markedly reduced and at 60 K a rectifying current ratio in the dark became more than three orders of magnitude at between applied voltages of $\pm$1 V. The ratio of the photocurrent to the dark current was also dramatically enhanced to be more than three orders of magnitude, and the device detectivity was estimated to be 3.0 $\times$ 10$^{11}$ cm Hz$^{1/2}$/W for 1.31-$\mu $m light at 60 K. [Preview Abstract] |
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DTP.00034: Water-Repellent Thin Film Deposition using a Gas-Liquid Mixed Phase Plasma Jet Yoshihito Takahashi, Junko Hieda, Tatsuru Shirafuji, Nagahiro Saito, Osamu Takai Water-repellent surface modification has attracted much attention because of their application in a variety of engineering fields. Wet processing methods are already known to be applicable to obtain the water-repellent surface. On the other hand, dry processing, particularly plasma processing, also provides a good solution to deposit the water-repellent thin films on various substrates without changing their bulk properties. Atmospheric-pressure plasma-jets operated with a low frequency of several kHz have advantages on three-dimensional low-temperature surface treatments without vacuum systems. Using this feature, we have investigated a possibility of preparing a water-repellent surface by using the plasma-jets with a liquid SiOC source material of hexamethyldisiloxane, which is non-toxic and has sufficient vapor pressure at room temperature. Resultant thin films were analyzed by using contact angle measurements, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. [Preview Abstract] |
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DTP.00035: Differences in nano structure on PET films formed with low-pressure and atmospheric pressure plasmas Takashi Kuriki, Masanori Kawaguchi, Tatsuru Shirafuji, Sung-Pyo Cho, Nagahiro Saito, Osamu Takai At present, dielectric barrier discharge methods is commonly used for treatment of polymer films. Many works are reported on cleaning and adhesion improvement of them, and recently, roll-to-roll atmospheric pressure treatment is also available However, there are few reports on the detailed discussion on the nano-structure formation on the polymer surface. We have investigated differences between PET surface treatments with low-pressure and atmospheric-pressure plasmas. In the case of low-pressure oxygen-plasma treatment, we can obtain fine nano-structured roughness on the PET after the treatment. This brings about super hydrophilic feature on the surface, and super hydrophobic feature is available after forming hydrophobic self-assembled monolayer on it. In the case of atmospheric-pressure plasma treatment, we cannot obtain the fine roughness but broader roughness. This is considered to be due to a kind of ``loading effect.'' A possible method for preventing the loading effect is proposed. [Preview Abstract] |
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DTP.00036: Inductively Coupled Plasma Assisted Sputter-Deposition of Al-doped ZnO Thin Films Yoshinobu Matsuda, Ryota Shindo, Akinori Hirashima, Masanori Shinohara Tin-doped Indium oxide (ITO) has been mainly used as transparent conducting oxide films so far due to its high transmittance in the visible region, high chemical stability and low resistivity. For the last ten years, however, aluminum-doped zinc oxide (AZO) received attention as one of the alternatives to the ITO. In this work, deposition process of AZO thin films by ICP assisted sputtering was investigated in particular from the view point of influence of ICP RF power. The results obtained in this study can be summarized as follows. All the thin film characteristics (deposition rate, transmittance, resistivity, crystallinity) improve with increasing ICP RF power. Both the relative ratio of Al to Zn atom density in gas phase and the elemental ratio of Al in the deposited film increase with increasing ICP RF power. In addition, crystallinity of AZO film is promoted with increasing ICP RF power. We obtained good quality AZO film with resistivity of 2x10$^{-3}$ ohm cm, transmission of more than 85{\%} at deposition rate of 0.28nm/s at the working pressure of 30mTorr (Ar) with the target power of 40W and with ICP RF power of 300W. [Preview Abstract] |
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DTP.00037: Synthesis of microcrystalline SiC film at low temperature ($\le$ 600$^{\circ}$C) by hydrogen plasma chemical transport at sub atmospheric pressure Hiromasa Ohmi, Tetsuya Mori, Takahiro Hori, Hiroaki Kakiuchi, Kiyoshi Yasutake This paper demonstrates that the $\mu $c-SiC film for solar cell application could be prepared by plasma enhanced chemical transport technique at sub-atmospheric pressure. The SiC film was synthesized by using graphite and Si solid sources. The hydrogen plasma was generated in the gap ($\sim $1mm) between the solid source and substrate at 200 Torr. The influence of the substrate temperature (T$_{sub})$ on the film properties was investigated. Based on the structural analysis, it became clear that the $\mu $c-3C-SiC film could be prepared at low T$_{sub}$ (100 - 600$^{\circ}$C). The electric conductivity of the SiC film increased with increasing T$_{sub}$ and reached to 1.68S/cm for the SiC film prepared at 600$^{\circ}$C. The n-type 3C-SiC film was prepared on the p-type Si to fabricate a pn diode. The current --voltage characteristic of the pn diode showed good rectifying characteristics. Furthermore, photovoltaic characteristic of the prepared diode was checked up. [Preview Abstract] |
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DTP.00038: Fabrication of transparent protective DLC films on polymer materials Sangmin Baek, Tatsuru Shirafuji, Nagahiro Saito, Osamu Takai, SeongHwan Lee, Heon Lee In this work, a-C:H and Si doped a-C:H films were prepared by a pulse biased inductively coupled plasma chemical vapor deposition system using a C$_{2}$H$_{2}$ gas and a C$_{2}$H$_{2}$+Si(CH$_{3})_{4}$ gas mixture, respectively. The effects of Si incorporation on the optical and mechanical properties of the films were investigated. The optical band gap of the films was improved by Si incorporation in them. Structural characterization through Raman analyses showed that the addition Si in the films leads to the increase of sp$^{3}$ fraction. The hardness of the Si-doped films slightly decreased in comparison to that of non-doped films (from 12.09 to 11.77 GPa). The critical load related to adhesion strength increased from 13.33 to 15.88 mN. The reduction of residual stress with Si-doping is considered to result in the decrease of the hardness and the increase of adhesion strength. [Preview Abstract] |
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DTP.00039: Plasma polymerized PEDOT thin films by double discharge technique Hilal Goktas, Taylan Gunes, Betul Atalay, Dogan Mansuroglu, Ismet Kaya Poly(3,4-ethylenedioxythiophene) (PEDOT) has emerged as the dominant class of polymers for optoelectronic applications due to their chemical and environmental stability, easy processability, high luminescence efficiency and excellent electronic-semiconducting properties. The way of producing organic thin film has a strong influence on the morphology and molecular structures. The synthesis of PEDOT thin films by superposing simultaneously a continuous and pulsed discharge and the characterizations of these samples are presented. The PEDOT thin films are synthesized for the first time by such technique. The substrates were ITO (indium tin oxide) and quartz glass plates and placed at different locations at the reactor to evaluate the influence of the position on the molecular structure of the obtained thin films. The FTIR and UV-visible results reveal that due to the fragmentation of the monomer during the film formation at plasma processes, the molecular structures of the synthesized thin films are different from that of the one produced by conventional techniques. Upon the iodine doping, the optical energy band gab (E$_{g})$ drops down from 2.9 eV to 2.2 eV. [Preview Abstract] |
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DTP.00040: Influences of Repetition Rate of Laser Pulses on Growth of AlN Thin Films on Sapphire(0001) by Reactive Pulsed Laser Deposition Tomohiro Yoshida, Kazushi Sumitani, Ryota Ohtani, Satoshi Mohri, Tsuyoshi Yoshitake Hexagonal AlN ($\alpha $-AlN) is a promising material for applications. On the other hand, few studies have been reported on metastable cubic AlN ($\beta $-AlN). $\beta $-AlN is expected to possess higher ballistic electron velocities, thermal conductivity, and acoustic velocity than $\alpha $-AlN due to its higher crystallographic symmetry. Pulsed laser deposition (PLD) is a quite simple and effective method for fabrication of compound films. Especially, a non-equilibrium condition in a PLD process is beneficial on the growth of metastable phases. In this study, AlN thin films were deposited in a nitrogen atmosphere by PLD using a sintered AlN target. The film preparations were made at different repetition rates of laser pulses from 10 to 50 Hz, and the influences of the repetition rate on the crystalline structure and morphology were investigated. Employment of high frequency laser pulses enhanced the crystalline growth and in addition it afforded the crystal growth at higher nitrogen pressures. Crystalline growth of $\alpha $-AlN was strongly influenced by the repetition rate. Metastable $\beta $-AlN was grown at high repetition rates and high nitrogen pressures. [Preview Abstract] |
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DTP.00041: Preparation of AZO thin films by pulsed laser deposition for all-solid-state ECDs Tamiko Ohshima, Yuuki Murakami, Hiroharu Kawasaki, Yoshiaki Suda, Yoshihito Yagyu We prepared Al-doped zinc oxide (AZO) thin films by pulsed laser deposition (PLD) at various oxygen gas pressures, while maintaining the substrate temperature at room temperature. We investigated the optical, structural, and electrical properties of the films as a function of the oxygen gas pressures. High quality AZO thin films with low electrical resistivity of 7 $\times$ 10$^{-4} \quad \Omega \cdot $cm and high optical transmittance of over 80{\%} in the visible region are deposited on a glass substrate at room temperature under oxygen gas pressure of 1 Pa. [Preview Abstract] |
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DTP.00042: Formation of n-Type $\beta $-FeSi$_{2}$/p-Type Si Heterojunctions by Facing-Targets Direct-Current Sputtering Shota Izumi, Nathaporn Promros, Mahmoud Shaban, Keita Nomoto, Tsuyoshi Yoshitake Semiconducting iron disilicide ($\beta $-FeSi$_{2})$ possessing a direct band gap of 0.85 eV and a large absorption coefficient of 10$^{5}$ cm$^{-1}$ at 1.5 eV is a new promising material for infrared photodiodes. In order to fabricate the heterojunction with Si, the diffusion of Fe atoms from the $\beta $-FeSi$_{2}$ layer into the Si substrate should be suppressed because the Fe atoms form trap centers in the Si. Epitaxial as-growth of $\beta $-FeSi$_{2}$ films at a low substrate-temperature is preferable. In this study, $\beta $-FeSi$_{2}$ thin films were epitaxially grown on Si(111) substrates at a substrate-temperature of 600 \r{ }C by facing-targets direct-current sputtering (FTDCS) without post-annealing at high temperatures. The $\beta $-FeSi$_{2}$ thin film exhibited a smooth surface with few pinholes and a sharp interface with the Si substrate. It was confirmed that the $\beta $-FeSi$_{2}$ film is epitaxially grown on Si(111) by the XRD measurements. The n-type $\beta $-FeSi$_{2}$/p-type Si heterojunction showed a typical rectifying action with a rectification ratio of more than two orders of magnitude at bias voltages between $\pm$ 1 V at room temperature. [Preview Abstract] |
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DTP.00043: Fabrication of a-ZnON films by Ar/N$_{2}$ sputtering for solid-phase crystallization of ZnO Naho Itagaki, Kazunari Kuwahara, Kenta Nakahara, Daisuke Yamashita, Kunihiro Kamataki, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani We propose a novel method for fabricating high crystallinity ZnO films via solid-phase crystallization (SPC) from amorphous phase films. As the amorphous phase films, we employ amorphous ZnON (a-ZnON) prepared by sputtering ZnO target in Ar/N$_{2}$, because we have difficulty in synthesizing amorphous ZnO films especially by sputtering. Optical emission spectroscopy suggests that the density of high energy electrons in the plasma, which dissociate N$_{2}$, increases with decreasing the total gas pressure. Therefore, incorporation of N in films disorders ZnO crystal structure and yields a-ZnON films at low gas pressure. SPC is realized by annealing such a-ZnON in oxidization atmosphere, since the dissociation energy of Zn-O is higher than that of Zn-N. The resultant ZnO films are highly orientated to (001) even on quartz glass substrates and have higher crystallinity than the films prepared by the conventional sputtering method. [Preview Abstract] |
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DTP.00044: Crystallographic Study of Cubic Phase AlN Thin Films Heteroepitaxially Grown on Sapphire (0001) Substrates by Pulsed Laser Deposition Kazushi Sumitani, Ryota Ohtani, Tomohiro Yoshida, Satoshi Mohri, Tsuyoshi Yoshitake Cubic phase AlN films were successfully grown on sapphire (0001) substrates by pulsed laser deposition. The crystallographic nature of the films was evaluated by X-ray diffraction using synchrotron radiation at the SAGA Light Source. It was found from the measurements that c-AlN with a lattice constant of 7.90 $\pm$ 0.06 {\AA} was heteroepitaxially grown on the substrate with a relationship of AlN(111)[1-21]/Al$_{2}$O$_{3}$(0001)[11-20]. Due to the deposition of high-energy ions and non-equilibrium condition in the PLD growth, heteroepitaxial growth of c-AlN is realized. [Preview Abstract] |
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DTP.00045: Effects of Ambient Nitrogen on Growth of Cubic AlN Films on Sapphire (0001) Substrates by Pulsed Laser Deposition Kazushi Sumitani, Ryota Ohtani, Eisuke Magome, Tomohiro Yoshida, Satoshi Mohri, Tsuyoshi Yoshitake Cubic AlN films were prepared in nitrogen atmospheres by pulsed laser deposition. Their crystalline structures were precisely investigated using synchrotron X-ray diffraction techniques, and the effects of the nitrogen atmosphere on the growth were studied. At a pressure of 80 Torr, a series of diffraction peaks originating only in cubic AlN with a lattice constant of 7.913 {\AA} was observed in $\theta $-2$\theta$ measurements. On the other hand, at 30 Torr diffraction peaks from another cubic structure with a lattice constant of 4.045 {\AA} were observed. This indicates that the supply of a large amount of activated nitrogen ions on the surface is an important factor for the fabrication of c-AlN crystallites. [Preview Abstract] |
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DTP.00046: Preparation of n-Type $\beta $-FeSi$_{2}$/p-Type Si Heterojunctions for Near-Infrared Photodetectors by Pulsed Laser Deposition Nathaporn Promros, Chen Li, Wataru Yokoyama, Tsuyoshi Yoshitake Semiconducting $\beta $-FeSi$_{2}$ has attracted much attention owing to its attractive properties. $\beta $-FeSi$_{2}$ thin films have been fabricated by various methods. On the other hand, there have been few researches employing pulsed laser deposition (PLD), although it appears to be suitable for growing $\beta $-FeSi$_{2}$ films due to the following features: i) in order to suppress the diffusion of Fe atoms into Si substrates, deposition at a low substrate-temperature is preferable. PLD makes possible low temperature growth due to highly energetic species; ii) the chemical composition between the target and film is hardly changed in PLD. By using a sintered FeSi$_{2}$ target, $\beta $-FeSi$_{2}$ films expected to be as-grown on Si. In this study, $\beta $-FeSi$_{2}$ films were grown on Si(111) substrates at a substrate-temperature of 600 \r{ }C by PLD without post-annealing. The epitaxial relationships between the $\beta $-FeSi$_{2}$ film and Si(111) substrate were examined by X-ray diffraction (XRD). Several types of crystalline orientations co-existed in the film. The $\beta $-FeSi$_{2}$ film exhibited n-type conduction without doping, which might be due to Co and Ni impurities in the target that act as a donor in $\beta $-FeSi$_{2}$. Dark $I-V$ characteristics of the heterojunction showed a rectifying behavior. The photocurrent for irradiation with a 1.31-$\mu $m laser was low. [Preview Abstract] |
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DTP.00047: Influences of Boron-Doping on Growth of Ultrananocrystalline Diamond$\cdot $Hydrogenated Amorphous Carbon Composite Films by Pulsed Laser Deposition Tsuyoshi Yoshitake, Shinya Ohmagari, Kenji Hanada, Akira Nagano, Ryota Ohtani, Kazushi Sumitani It has been reported that boron-doping improves the structural perfections of diamond crystals grown by chemical vapor deposition. In addition, whereas the crystal size is slightly decreased by increasing the amount of doped boron, the nucleation density is enhanced. Ultrananocrystalline diamond.$\cdot $hydrogenated amorphous carbon composite (UNCD.$\cdot $a-C:H) films possess a distinctive structure wherein UNCD crystallites with diameters less than 10 nm are embedded in an a-C:H matrix. Since UNCD crystallites can be regarded as nuclei, the growth must strongly be influenced by boron-doping and preparation method. In this study, we investigated influences of boron-doping on the growth of UNCD crystallites prepared by pulsed laser deposition. The crystallite size increased from 5 to 20 nm with a increase in the boron content up to 13 at.{\%}. This evidently indicates that the boron-doping enhances the UNCD crystallite growth. The near-edge x-ray absorption fine structure measurement revealed the preferentially incorporation of boron atoms into grain boundaries. We consider that boron atoms facilitate the UNCD crystallite growth after the nucleation. [Preview Abstract] |
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DTP.00048: The influence of substrate biasing on the crystallinity of Al$_2$O$_3$ films Marina Prenzel, Tim Baloniak, Achim von Keudell Substrate biasing is an established technique to control and adjust material properties during thin film deposition from a plasma. Film properties of Al$_2$O$_3$ like adhesion, wear resistance, or film hardness are related to the degree of crystallinity. The external bias voltage manipulates the energy distribution function of the ions impinging on the substrate (IEDF). In our contribution, we report the influence of sinus RF biasing at \mbox{1 MHz} on the crystallinity of aluminium oxide films. The films are prepared in a magnetically enhanced, capacitively coupled argon/oxygen discharge, which is excited by \mbox{13.56 MHz} and \mbox{71 MHz} frequencies and used for reactive sputtering of an aluminium target. The target is mounted on the powered electrode and the silicon substrate is placed on an additionally biased electrode maintained at a temperature of \mbox{600$^\circ$ C}. A feedback loop is used to control the partial pressure of O$_2$ in the plasma. The IEDF is measured with a retarding field analyser. The results show that the energy distribution with which the ions hit the surface is important for the control of crystallinity. The diffraction pattern of films biased by a rectangular signal indicates a defined crystal orientation. Additionally, stoichiometry is identified by XPS measurements. The results of the study will be used in the future to get a deeper insight into the nucleation of the film. [Preview Abstract] |
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DTP.00049: Evaluation of aluminum nitride films deposited by using magnetron sputtering technique under controlled gas flow Yusuke Ohtsuka Non-destructive inspection technique using ultrasonic wave, generated by an electromagnetic acoustic transducer (EMAT), is introduced for the in-service inspection of fast breeder reactors. However the ultrasonic signal shows a low signal to noise ratio, so that a new structure of EMAT with multi-layers of thin films has been proposed. The author has already studied the deposition multi-layers of aluminum nitride (AlN) as an insulator and copper (Cu) as a conductor, but the bad adhesion on the substrate and the micro-cracks on the film were observed due to large residual stresses. This is a problem to be solved for the current driven EMAT. The present study aims to improve the characteristic of AlN films by controlling the mixing ratio of charged gases. AlN films deposited by controlling a nitrogen gas flow in step during deposition have been investigated using magnetron sputtering. The X-ray diffraction (XRD) spectrum of the deposited AlN films shows two distinct peaks at 2$\theta $ = 33 and 36 degrees, corresponding to orientation of (100) and (002) of AlN films, respectively. The (002) preferred orientation at 2 sccm increment of N2 gas flow is obtained, while it gradually proceeds toward (100) when the N2 gas flow in steps is more slowly increased. In the case of 0.5 sccm increment, a strong (100) preferred orientation with a weak (002) peak is found. However the two weak XRD peaks resulting from aluminum also are found. [Preview Abstract] |
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DTP.00050: Silicon oxide permeation barrier coating of PET bottles and foils using a biased microwave plasma Simon Steves, Michael Deilmann, Nikita Bibinov, Peter Awakowicz There is a growing demand for bottles made of polyethylene terephthalate (PET) on the global market. However, PET offers poor barrier properties against gas permeation and the shelf live of packaged food is reduced. A permeation barrier coating of PET bottles and foils is developed by means of a microwave driven low pressure plasma reactor based on a modified Plasmaline antenna. Barrier performance is enhanced by depositing a transparent plasma polymerized silicon oxide ($\rm{SiO_{x}}$) coating on the inner surface of the PET bottle. To improve $\rm{SiO_{x}}$-barrier coatings the ion energy is modified using a substrate bias. The influence of ion energy on the characteristics of plasma and coating is investigated. Ion energy distribution (IDF) is determined using a plasma monitor and a retarding field analyzer. The composition of the coatings is analyzed by means of Fourier transform infrared (FTIR) spectroscopy regarding carbon and hydrogen content. A strong relation between barrier properties and film composition is found: good oxygen and carbon dioxide barriers are observed as carbon and hydrogen content in the coating is reduced. [Preview Abstract] |
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DTP.00051: Behaviour of Hybrid PVD-PECVD Process in Comparison with Conventional Reactive Magnetron Sputtering Tereza Schmidtova, Petr Vasina Hybrid PVD-PECVD sputtering process was studied in comparison with conventional reactive magnetron sputtering. Ti target was sputtered in nitrogen and oxygen atmosphere for conventional reactive sputtering and in acetylene and methane for hybrid process. The hybrid PVD-PECVD combines aspects of both processes: conventional sputtering of metal target but source of carbon is hydrocarbon vapour. In conventional reactive sputtering, oxygen/nitrogen is consumed on all surfaces of deposition chamber and forms oxides/nitrides of sputtered metal. Due to difference between sputtering yields of pure metal and metal oxide/nitride process suffers with hysteresis. For hybrid process, hydrocarbon vapour in plasma decompose into fragments that are capable of attaching to surfaces without presence of metal atom and amorphous hydrogenated carbon layers can be formed. We report differences in behaviour of these processes, discuss necessary time for hybrid process to achieve steady state conditions and suggest modification of model for reactive magnetron sputtering to predict behaviour of hybrid process. [Preview Abstract] |
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DTP.00052: PLASMAS FOR NANOTECHNOLOGIES |
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DTP.00053: Pt Germanidation of a-Ge:H Enhanced by Remote Hydrogen Plasma Exposure Katsunori Makihara, Yusuke Miyazaki, Tomohiro Fujioka, Tatsuya Matsumoto, Mitsuhisa Ikeda, Seiichi Miyazaki We have studied germanidation of hydrogenated amorphous Ge films (a-Ge:H) by exposing to remote plasma of pure hydrogen (RP-H$_{2})$ without external heating after Pt film deposition. Raman scattering signals attributable to Pt-Ge phase were observable within the first 1 min of RP-H$_{2}$ exposure. In exposing for 20 min, full-germanidation of $\sim $80nm-thick a-Ge:H was achieved and its resultant sheet resistance as low as $\sim $4.5$\Omega $/sq. was obtained. X-ray diffraction patterns confirm the formation of Pt$_{2}$Ge in the initial stages of the reaction between Pt and a-Ge:H and subsequent phase transition to PtGes. The driving force of such germanidation reaction is attributed to heat transfer caused by efficient recombination of atomic hydrogen on the Pt surface. [Preview Abstract] |
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DTP.00054: Pulsed Nd:YAG Laser heating of Multi-walled carbon nanotubes film Ryosuke Kozai, Toshiyuki Nakamiya, Yoichiro Iwasaki, Yoshito Sonoda, Fumiaki Mitsugi, Keisuke Semba, Tomoaki Ikegami, Shin-ichi Aoqui, Ikuya Muramoto Multi-walled carbon nanotubes (MWCNTs) film surface is flashed with the second harmonic ($\lambda $=532 nm) of a single pulse of Nd:YAG laser. The dynamics of pulsed nanosecond laser heating process is simulated by the solution of the one-dimensional heat flow equation. When MWCNTs film is irradiated with a pulsed Nd:YAG laser of 23.7 mJ/cm$^{2}$, the calculated value of maximum surface temperature becomes 304$^{\circ}$C. The surface temperature increases from 595$^{\circ}$C to 2968$^{\circ}$C with the increase of laser power from 59.4 mJ/cm$^{2}$ to 469 mJ/cm$^{2}$. MWCNTs film is examined by the intensity of the two characteristic Raman shifts I$_{D}$ (defect-induced mode: D-band) and I$_{G}$ (graphite-induced mode: G-band) to clarify the effect of pulsed Nd:YAG laser heating. Moreover, we propose an automatic measurement algorithm of the diameters of MWCNTs using Scanning Electron Microscopy (SEM) images. This method is useful to discriminate the diameter of as-grown CNTs and after annealing with a pulsed Nd:YAG laser. [Preview Abstract] |
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DTP.00055: Microwave plasma synthesis of magnetic nanoparticles Vit Kudrle, Ondrej Jasek, Petr Synek, Bohumil David, Nadezda Pizurova We focused on synthesis of specific iron compounds in nanoparticle form produced in microwave plasma. Due to a small size of the nanoparticles causes unique properties of the material, including magnetic properties. We used two types of microwave discharges -- atmospheric plasma torch and low pressure surface wave plasma. Using XRD (X-ray diffraction), HR-TEM (high resolution transmission electron microscope), Raman spectroscopy and Mossbauer spectroscopy we identified the elemental and phase composition of the nanoparticles. The magnetic properties of the prepared nanoparticles were measured, too. During the plasma synthesis process we carried out a plasma diagnostics using optical emission spectroscopy. Finally, we correlated the external and internal parameters of the plasma synthesis process with the properties and composition of the nanoparticulate product. [Preview Abstract] |
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DTP.00056: Fabrication of Diamond-Like Carbon Nano-whiskers Tooru Harigai, Akimitsu Hatta Diamond-like carbon (DLC) whiskers were fabricated by etching of DLC films using radio frequency (RF) O$_{2}$ plasma. The DLC films were grown on silicon substrates using RF plasma chemical vapor deposition (CVD) method. Fine metal particles were deposited on the DLC film using a DC magnetron sputtering method before etching. DLC whiskers were found on the DLC film surface using an FE-SEM. Fabricated DLC whiskers were 20 nm in diameter and 500 nm long. It was found that the DLC whiskers bent and stuck together during FE-SEM observation. The structural change during observation can be explained as follows; because of secondary-electron emission from DLC whisker irradiated by the electron beam, a DLC whisker is positively charged up and the surrounding whiskers are negatively charged up. The positively charged whisker and the negatively charged whiskers will stick each other during the slow scanning. [1] C.Y. Li et al., Diamond Relat. Mater. 14 (2005) 1780. [2] Properties of Amorphous Carbon, ed. by S.R.P. Silva, INSPEC, IEE, London, UK (2003) 168-175. [Preview Abstract] |
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DTP.00057: Application of helium plasma irradiated tungsten material as a new photocatalyst Tomoko Yoshida, Reo Etoh, Hisao Yoshida, Shin Kajita, Noriyasu Ohno Recent works have shown that helium ions at the incident energy below the threshold value of physical sputtering produce nanostructures on the surface of bulk W. In the present work, we tried to use the nanostructured tungsten as a new type photocatalyst. After the helium plasma irradiation with the fluence of 2$\times $10$^{21}$/cm$^{2}$, a huge number of nanostructured rods with the average thickness of ca. 150-200 nm were observed by the SEM measurement. XPS and diffuse reflectance UV-vis analyses showed that the surface of the sample was oxidized from W(0) to WO$_{3}$ during the retention of the sample in air. Such nanostructured tungsten oxide was fundamentally maintained after the heat-treatment at 573 K for 30 min in air, although the average thickness of the nanostructured rods grew to ca. 200-300 nm. These nanostructured tungsten oxides exhibited photocatalytic activity under visible light irradiation. The photocatalytic decomposition of methylene blue proceeded over these samples whereas it was negligible over the commercial WO$_{3}$ powder sample. It has been suggested that the photocatalytic activity depends not only on the surface area but also on the size and/or chemical state of nanostructured tungsten oxide. [Preview Abstract] |
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DTP.00058: On the kinetic description of Martian Entry Plasma Dereth Drake, Milka Nikolic, Svetozar Popovic, Leposava Vu\v{s}kovic We are presenting results, which proved the basis for the study of processes that are of interest for utilizing Martian Atmospheric Entry Plasma (MAEP), such as oxygen production, effects of water presence, magnetohydrodynamic control of the plasma flow, and energy conversion. In our continuous effort to explore systems that utilize energy dissipated in MAEP [1, 2], we have assessed the newly consolidated data on the Martian atmospheric conditions, which demand corrections in the kinetic model of the MAEP. Conditions in Mars ionosphere provide seeding electrons that contribute to the formation of the ionizing wave in MAEP. Distribution of electron density and the temperature in the ionizing wave define the reduced electric field, which varies by several orders of magnitude during the entry trajectory. To the less extent, the reduced electric field also varies across the ionizing wave. We combined the MAEP flow models with the charge particle kinetics to determine the reduced electric field distribution, examine the conditions for formations of lateral instabilities, and determine local MAEP gas composition. [Preview Abstract] |
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DTP.00059: Structural Analysis of ZnO Nano-phosphors Fabricated by Pulsed Laser Ablation under the Glow Discharge Condition Qiang Ma, Teguh Endah Saraswati, Akihisa Ogino, Masaaki Nagatsu Zinc oxide (ZnO) has many potential applications in photoelectric devices, since it has a wide band gap of 3.37 eV and a large exciton binding energy of 60 meV at room temperature. Especially ZnO nanostructures exhibiting unique physical, chemical and optical properties show great promise for nanoscale photoelectric devices. However, if the particle size is reduced, the specific surface area increases and the density of atoms with unsaturated bonds (i.e., surface defects) increases in the surface layer, which can act as trapping centers and quench the excitonic luminescence of ZnO. Hence, understanding the role of defects and controlling their spatial distribution inside nano-structured ZnO are extremely important for the luminescence efficiency of nano-sized phosphors in many applications. In this letter, ZnO nanophosphors were produced by a Pulsed laser ablation. A direct current glow discharge was used to introduce the oxygen radical atoms/ions into the growth process of nanophosphors. The results of Cathodluminescence (CL) spectra show that the ultraviolet (UV) peak intensities of ZnO nanophosphors with a fine crystalline structure were enhanced. These results imply that the growth of the oxygen-related defects is confined under the plasma circumstance. [Preview Abstract] |
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DTP.00060: Synthesis of nanopowders of elements and compounds in thermal plasma Andrey Samokhin, Nikolay Alexeev, Sergey Kornev, Michael Sinayskiy, Alexey Astashov Nanosized powders with particle size less than 100 nm are the base for production of various nanostructured materials with improved operating characteristics. Synthesis in thermal plasma of electric discharges is the advantageous process for producing nanopowders of elements and compounds. Production of inorganic nanosized powders in thermal plasma jet generated in DC arc plasma torch is considered. Reactor with intensively water-cooled walls is used for nanoparticles production by chemical condensation from gas during plasma jet propagation and cooling in the reactor volume. CFD simulation of the reactor with confined plasma jet is carried out and temperature and line of gas flow distributions are calculated as a function of thermal plasma initial conditions. The results of experimental investigations of synthesis of nanopowders (metals, oxides, carbides) in thermal plasma as well as the development of methods to control dispersed, phase and chemical composition of nanopowders during plasma process are developed and discussed. Plasma system for various inorganic nanopowders production by redox, decomposition and recondensation processes is designed and supplied to customers. [Preview Abstract] |
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DTP.00061: Nanoparticle film deposition via mist-included plasma source Kosuke Takenaka, Yusuke Okumura, Ken Cho, Yuichi Setsuhara Oxide-ceramics nanoparticles are expected as functional materials in wide range of applications including power devices and environmental protection system. For fabrication of nanoparticle films, it is significant to establish modification techniques of nanoparticles in terms of phase structures and/or chemical states of surfaces. However, modification of these nanoparticles via conventional annealing processes involves problems associated with agglomeration nature of nano-particles: grain growth due to sintering and/or formation of complex oxide compounds. In order to overcome these constraints, mist-included high-density RF plasma source has been developed for gas-phase modification and direct deposition of nanoparticles. For the modification and deposition of nanoparticles, the inductively coupled RF discharge was generated with injection of mists. In this presentation, performance of plasma source will be reported together with properties of nanoparticles films deposited after passing through the plasmas. [Preview Abstract] |
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DTP.00062: Formation of Nanosize-Needle and Nanosize-Cauliflower on Carbon Surface with Cold Plasma and its Applications Masaaki Katoh, Takashi Kano, Atsushi Suzuki, Michiya Ota, Takeo Ohte, Eiichi Yasuda By oxygen plasma treatment of glass-like carbon, nano-sized needle-shaped structure (carbon nano needles) was formed on GC surface placed at power-electrode connected to high-frequency power source through matching circuit. On the other hand, nano-sized cauliflower-shaped structure was formed on GC surface connected to earth-electrode. This difference of formation between power-electrode and earth-electrode is whether or not self-bias voltage is generated by. In case of self-bias voltage generation, oxygen ions play an important role in formation the carbon nano needles. On the contrary, no self-bias voltage generation, radicals play an important role in formation the carbon nano cauliflowers. From the experimental results, length of needles shortens from 3.6 to 2.5 [$\mu$m] and diameter of them get thin from 120 to 43 [nm] when treatment pressure was increasing from 9.31 to 66.5 [Pa]. Length of needles lengthen from 0.30 to 3.5 [$\mu$m] and diameter of them get thin from 120 to 70 [nm] when treatment power increasing from 30 to 200 [W]. Field-emission (FE) measurements showed that the carbon nano needles were excellent electron field emitters which indicate that the carbon nano needles are employed as field emitters. [Preview Abstract] |
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DTP.00063: Multi-colored luminescence from luminescent nanocrystalline silicon particles terminated by nitrogen Tomonori Fujino, Keisuke Sato, Kenji Hirakuri, Yasuhiro Fukui The visible luminescence from the hydrogen-terminated nanocrystalline silicon (nc-Si) particles rapidly degrades by just after immersion in pure water. This was closely related to the formation of the defects due to the hydrogen-desorption from the particle surface. In solving the problem on the short time, it is necessary to fabricate a stable bonding in surrounding surface by other elements. In this paper, the photoluminescence (PL) property of the nitrogen-terminated nc-Si particles with multi-colored luminescence in pure water has been investigated. The surface composition and the luminescence property of samples were estimated by using a FT-IR spectroscopy and PL measurements. On the PL property of the samples, the nitrogen-terminated nc-Si particles brought the multi-colored luminescence and stability in the long term in comparison with the hydrogen-terminated nc-Si particles. By these results, the nitrogen- terminated nc-Si particles are expected to use in the industrial applications. [Preview Abstract] |
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DTP.00064: One dimensional micro-patterning on flexible substrate by low frequency atmospheric pressure micro jet plasma Heesoo Jung, Dan Bee Kim, Bomi Gweon, Jong-Joo Rha, Wonho Choe Micro-patterning is an attractive technology for satisfying current electronic market needs, especially for fabricating the smaller and slimmer devices. Upon considering that the traditional etching process is performed at the complex high vacuum system, high speed micro patterning based on the micro plasma generated in the ambient air is an innovative and economically beneficial method for electronics industry. In this study, the plasma source of 500 $\mu $m hole was developed to perform the feasibility study of micro-patterning. The analyses using the measured discharge current and voltage characteristic curves, optical emission spectroscopy, and intensified charge coupled device image were performed to characterize the plasma. One-dimensional micro-patterning was carried out on the super water repellent treated substrate (polyimide film or PI) surface using the micro plasma jet mounted on a XYZ stage. After the plasma treatment, the silver ink was applied to the hydrophilic line on PI film formed by the plasma. The line width was measured to be as small as 200 $\mu $m. It varied from 200 $\mu $m to 4000 $\mu $m by the applied voltage and gas flow rate. Further reduction of the line width is on-going. [Preview Abstract] |
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DTP.00065: Morphological control of carbon nanowalls by reactive ion etching Masaru Hori, Hiroki Kondo, Shingo Kondo, Yudai Miyawaki, Hajime Sasaki, Mineo Hiramatsu Carbon nanowalls (CNWs), two-dimensionally-standing graphene sheets, were one of carbon nanomaterials expected to realize novel functional devices, such as electron emission devices, electrode of fuel cell, gas filter, and so forth. In order to apply CNWs to those devices, modification techniques of their shapes and morphologies are required. In this study, we have demonstrated the reactive ion etching (RIE) of CNWs. By the RIE employing H2/N2 gases, the CNWs were anisotropically-etched at a relatively high rate of an approximately 250 nm/min. On the other hand, the 10 nm-thick interface layers between CNWs and Si substrates still remained and were not completely etched. The RIE employing Ar/H2 gases enabled us to remove completely the interface layer. The Ar/H2 RIE was also carried out on the bottom surface of CNWs after they were exfoliated from the Si substrates. As a result, the free-standing CNW film of 550 nm in thickness without an interface layer for membrane filters was successfully formed. [Preview Abstract] |
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DTP.00066: Low-Hydrogen-Content SiN$_{x}$ Films Prepared Under Low-Temperature Conditions and Its Application to Encapsulation Layers for Top-Emission Organic Light-Emitting Devices Kazufumi Azuma, Satoko Ueno, Masayasu Suzuki, Yoshiyuki Konishi, Shinichiro Ishida We have succeeded in obtaining transparent SiN$_{x}$ films under 110$^{\circ}$C with the water vapor transmission rate (WVTR) of less than 1x10$^{-5}$ g/m$^{2}$/d. To use the top-emission OLED encapsulation films, high transparency and low WVTR ($<$10$^{-5}$ g/m$^{2}$/d) are required in a low-temperature process. However, low-temperature-prepared SiN$_{x}$ film contains more than 30at{\%} hydrogen, which causes low density of the film. Furthermore, high-hydrogen-content film may have many hydrophilic function groups such as N-H, Si-H and O-H, which deteriorates the encapsulation property. We have developed a microwave-excited Surface-Wave-Plasma Chemical Vapor Deposition (SWP-CVD) system using SiH$_{4}$/NH$_{3}$/Ar. The hydrogen content of the SiN$_{x}$ films could be controlled from 16 to 40 at{\%} by changing the distance between the plasma and the substrate during the low-temperature deposition. It was clarified that the hydrogen content in the SiN$_{x}$ film clearly corresponded to the WVTR result. The WVTR value became smaller with decreasing hydrogen content. We also evaluate the SiH$_{4}$+N$_{2}$ series for the synthesis of low-hydrogen-content SiN$_{x}$ films. Details will be discussed at the meeting. [Preview Abstract] |
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DTP.00067: Surface Modification by Water Vapor Plasma for Damage-free Roughness Smoothing of 4H-SiC Kazuya Yamamura, Tatsuya Takiguchi, Masaki Ueda, Azusa N. Hattori, Nobuyuki Zettsu We have proposed a novel machining method combined with the irradiation of atmospheric pressure water vapor plasma for the finishing of hard materials, such as SiC, tungsten carbide (WC) and alloy tool steel. The irradiation of helium-based water vapor plasma modified the surface of 4H-SiC (0001), and a ball-on-disc test using an alumina ceramic ball revealed that the wear rate of SiC, the surface of which was modified by the irradiation of water vapor plasma, is 20-fold higher than that of the surface without plasma irradiation. The XPS measurement reveals that the surface irradiated water vapor plasma is oxidized, and nanoindentation test result indicates that hardness of that surface decreases in one order of magnitude. Plasma-assisted polishing using CeO$_{2}$ abrasives enabled us to smooth the surface roughness of 4H-SiC without introducing crystallographical subsurface damage, and a scratch-free surface with a roughness of less than 0.15 nm rms was obtained. [Preview Abstract] |
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DTP.00068: Fabrication of a single layer of polystyrene nanoparticle array, and their use as templates for NIR-light responsible metallodielectric plasmonic nanoshells Shuhei Uchida, Kazuya Yamamura, Nobuyuki Zettsu We have proposed a facile methodology to fabricate two-dimensionally periodic non-close packed (ncp) arrays of spherical polystyrene nanoparticles with controllable their structural parameters through stepwise integration including the preparation of a single layer of hexagonally close-packed (hcp) spherical PS nanoparticles and atmospheric pressure He plasma-induced isotropic etching. The plasma process converted the hcp arrangement into ncp arrangements with remaining unchanged their original spherical shape and periodicity. The structural parameters of the 2D colloidal crystal could be precisely controlled with nanometric accuracy by the plasma treatment time. We also demonstrated that the isolated PS nanoparticles array can be utilized as a template for making a near infra-red light responsible metallodielectric plasmonic nanoshells array. It was revealed that the strong sharp extinction peak at the NIR region should be assigned to localized surface plasmon resonance in the nanoshells. [Preview Abstract] |
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DTP.00069: Catalyst-free electroless Cu plating of fluoropolymer surface through an atmospheric pressure plasma assisted self-assembly Nobuyuki Zettsu, Hiroki Akiyama, Kazuya Yamamura In this work, we address the issue of surface copperization of fluoropolymers by electroless plating for the fabrication of printed circuit boards. Herein, we have demonstrated catalyst-free electroless deposition of an adhesion Cu layer on a P4VP-g-PTFE surface through an atmospheric pressure plasma assisted self-assembly. The polymer surface densely and homogeneously seeded with the self-assembled Cu nanoparticles enable to initiate autocatalytic electroless deposition of Cu layer without need for any prior sensitizingconventionally used SnCl$_{2}$ and Pd species. A high adhesion Cu layer can be obtained without requiring an anchoring effect. The adhesion strength was substantially improved to more than 100 times magnitudes in comparison to the bare PTFE surface. [Preview Abstract] |
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DTP.00070: Immobilization of Biomolecules onto Graphene Layer-Encapsulated Magnetic Nanoparticles Functionalized by Inductively Coupled Plasma Teguh Endah Saraswati, Akihisa Ogino, Masaaki Nagatsu Magnetic nanoparticles have many great interests in potential to bio-application such as drug delivery system, hyperthermia treatments, magnetic resonance imaging contrast enhancement, etc. Carbon coating of the magnetic nanoparticles can leave the toxicity out without detracting their magnetic properties and stabilize the nanoparticles so that compatible to be used in bioapplications. Among various functional groups, the introduction of amino groups to the particles surface achieves enhanced wettability and improves its adhesion. However, this modification has not been deeply studied on carbon encapsulated magnetic nanoparticles. In fact very few information can be found on the topic of graphene layer-encapsulated iron nanoparticles related to the plasma surface treatment in order to introduce nitrogen-containing group functionalities, such as amino group. In this study, we mainly functionalize the graphene layer-encapsulated magnetic nanoparticles using Ar and ammonia plasma performed by an inductively-coupled RF plasma. After plasma treatment, the biomolecules are immobilized to the particles to test the role of the nitrogen-containing group as a linker to the biomolecules. The XRD, XPS, HR-TEM and EDS elemental mapping were used to characterize and analyze the results. [Preview Abstract] |
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DTP.00071: Numerical study of the plasma chemistry for an inductively coupled plasma used for the synthesis of carbon nanotubes Ming Mao, Annemie Bogaerts Carbon nanotubes (CNTs) are gaining increasing interest, due to their unique physical, chemical and electronic properties, giving rise to a variety of (potential) applications. Plasma enhanced chemical vapour deposition (PECVD) has become a very promising technology for the direct synthesis of vertically aligned CNTs. In this presentation, a hybrid model, called the hybrid plasma equipment model (HPEM), is used to describe the plasma chemistry in an inductively coupled plasma, operating in a gas mixture of CH$_{4}$ with either H$_{2}$ or NH$_{3}$, as typically used for carbon nanotube (CNT) growth. Two-dimensional profiles of power density, electron temperature and density, gas temperature, and densities of some plasma species are plotted and analyzed. Besides, the fluxes of the various plasma species towards the substrate (where the CNTs can be grown), as well as the decomposition rates of the feedstock gases (CH$_{4}$, NH$_{3}$ and H$_{2})$, are calculated as a function of the CH$_{4}$ fraction in both gas mixtures. Finally, the influence of O$_{2}$ addition to CH$_{4}$/H$_{2}$ mixture on the plasma chemistry will be discussed and analyzed. [Preview Abstract] |
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DTP.00072: Time-Programmed Plasma CVD for Detailed Structure Control of Single-Walled Carbon Nanotubes Toshiaki Kato, Rikizo Hatakeyama Detailed structure control of single-walled carbon nanotubes such as tube diameter, chirality, and length is indispensable for a variety of application fields. We have established a novel method for controlling the diameter, chirality, and length distributions at the same time based on time-programmed plasma CVD. Precise time evolution growth [1] reveals that there is a clear dependence of tube diameter on the incubation time, which is narrowed by strictly controlling their growth time at the initial stage. In addition, the length distribution is also fairly narrow and almost all of SWNTs are very short ($\sim $100 nm) in the case of such narrow diameter-distributed SWNTs. Furthermore, photoluminescence study [2] reveals that the chirality distribution at the initial growth stage is also fairly narrow and only a few chirality species are included in this sample. \\[4pt] [1] T. Kato and R. Hatakeyama: Appl. Phys. Lett. 92 (2008) 031502. \\[0pt] [2] T. Kato and R. Hatakeyama: J. Am. Chem. Soc. 130 (2008) 8101. [Preview Abstract] |
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DTP.00073: Large Area DC Plasma Filter for Antenna Shen Shou Max Chung Antenna often represents the largest radar cross section (RCS) source in many vehicles, and it is challenging to reduce the RCS without affecting the functionality of the antenna. Plasma as an electromagnetic wave absorber provides an interesting option for this application. We design a DC plasma screen with wire electrodes, and calculate the radar signal absorption capability in various frequencies. The results is a combined effect of the wire electrode array that is used to generate the plasma and the plasma dispersion relation. [Preview Abstract] |
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DTP.00074: PLASMA PROPULSION |
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DTP.00075: Small-sized plasma jet by a high current pseudo-spark discharge and its electrode durability M. Watanabe, Y. Suzuki, M. Miyahara, T. Kamada In this research, a small size of the plasma jet by a modified pseudo-spark discharge (PSD) has been developed. In the previous researches, the damage of the electrode with the PSD discharge was regarded as small because the discharge can keep the glow mode even if the discharge current exceeds the several kilo amperes high. This PSD is applied to the plasma source of the high current plasma jet. An electromagnetic force accelerates the plasma, similar to the MPD Thruster. In our experiment, the plasma jet has been experimentally conformed by an electric double probe and the temperature and density of the plasma jet were estimated by this measurement. The temperature was 3-5eV and the density was in the order of 10$^{19}$ m$^{-3}$ at the maximum discharge current of 2kA. The temperature will depend on the intensity of the discharge current and the density will depend on the volume inside the cathode cavity. The durability of the electrodes has been tested at the present time. The concentration of the electrode erosion has been observed around the cathode hole after series of the several hundred PSD discharges. In this experiment, the cathode damage by heat flux was a serious and the damage of the anode and inside the hollow cathode does not observe. [Preview Abstract] |
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DTP.00076: Discharge activated supersonic pulsed gas jets Nikolay Korobeishchikov, Alexandr Zarvin, Valeriy Kalyada The influence of a transversal electric arc on pulsed supersonic gas jets has been experimental investigated. It has been detected that by transversal discharge the blocking of supersonic gas jets is observed. The blocking time does not depend on gas; it is determined by discharge sustention. After quenching the discharge the delay gas impulse of neutral gas particles is generated. The intensity of the delayed impulse can exceed it's without discharge. The flux of the fast ions, which reaches the detector before the main gas impulse, appears also. [Preview Abstract] |
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DTP.00077: Control of the plasma potential in strong electronegative plasmas and ion-ion plasmas Lara Popelier, Ane Aanesland, Pascal Chabert Extraction and acceleration of both positive and negative ions perpendicularly to a magnetic field from a strong electronegative plasma and from an ion-ion plasma is investigated in the PEGASES thruster, working with oxygen and SF6. The plasma is generated in a cylindrical quartz tube terminated by metallic endplates, where electrons are confined by a static magnetic field along the axis of the cylinder. The electron mobility along the field is high and the plasma potential can therefore be controlled by the bias applied to the endplates. Langmuir probe and RFEA measurements are done in the perpendicular direction, in which an ion-ion plasma may form as a result of electron confinement. The measured ion energy distributions show a single peak consistent with a linear increase of the plasma potential with the variation of the applied positive voltage on the end plates. When the endplates are biased negatively, the plasma potential always remains at or above 15 V. However a beam of negative ions is observed under certain conditions when the endplates are biased negatively. [Preview Abstract] |
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DTP.00078: Transverse component of Xe$^{+}$ ions velocity in the crossed field discharge of a Hall Effect Thruster Guillaume Bourgeois, Stephane Mazouffre, Nader Sadeghi Electric propulsion is a well-established technology for satellite orbit correction and interplanetary exploration missions. A Hall Effect Thruster, used e.g. on the SMART-1 probe for a Moon mission, is a low pressure xenon dc discharge in crossed electric and magnetic fields. The anode is located at the back of an annular ceramic chamber while the cathode is placed outside. The radial magnetic field is maximum at the chamber exit, where it confines the electrons. Thrust is produced by the acceleration along the channel axis of Xe$^{+}$ ions formed inside the channel. The aim of this work was to measure by the Doppler-shifted LIF technique [1] the azimuthal ion velocity that originates in the Lorentz force. Surprisingly, the measured velocity amplitude reaches several times the calculated one ($\sim$ 100 m/s). Besides, its direction does not always depend on the B field polarity. Velocity properties can be explained accounting for the drift of ions toward the external cathode. \\[4pt] [1] D. Gawron \textit{et al}, PSST \textbf{17} (2008), 025001 [Preview Abstract] |
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DTP.00079: Experimental investigation of optical discharges with an ablative wall in channels E. Yu. Loktionov, Yu. Yu. Protasov Active medium flow in laser plasma thrusters is supposed to be radially confined, but most of plasma plume dynamics research is conducted using free surface targets. Some papers present results of integral momentum experimental evaluation for condensed matter ablating targets mounted in nozzles, but dynamics and plume morphology features of confined flows are not described. We present the results of shadowgraphic, schlieren and interferometric observation of polymers ((C$_{2}$F$_{4})_{n}$, (CH$_{2}$O)$_{n})$ laser ablation ($\lambda \sim $532, 1064 nm, $\tau _{0.5}\sim $12 ns) radially confined (10x10 mm) plumes dynamics and macrostructure experimental investigation both at ambient and vacuum conditions. Results are compared to free surface case for the same targets and experimental conditions in terms of shockwave velocity, pressure and temperature, target material vapors velocity and density. [Preview Abstract] |
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DTP.00080: Plasma detachment from a magnetic nozzle Paul-Quentin Elias, Renaud Gueroult Electrodless and gridless plasma thruster are currently considered for micro propulsion applications. These thrusters, such as the Helicon thruster, are appealing because they do not require a neutralizer, and are insensitive to grid erosion. However, they use for plasma confinement and acceleration magnetic nozzles. An important issue is then to understand the detachment of the plasma from this nozzle, which affects the beam divergence and thus the thruster Isp. In this study, we consider this problem, using ray-tracing model and 2 dimensional Particle in Cell modelling. The goal is to determine the relevant parameters which control the plasma expansion and detachment, and how they can affect the beam divergence. [Preview Abstract] |
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DTP.00081: Development of Upper Atmosphere Simulator for Air Breathing Ion Engine Yasuyoshi Hisamoto, Kazutaka Nishiyama There is an increasing need for super low Earth orbiting satellites to observe the terrestrial environment from an altitude of 150km to 250km. These satellites have to cancel the air drag to stay in such an orbit for several years. A completely new concept, the Air Breathing Ion Engine (ABIE), has been proposed for spacecraft drag compensation. The ABIE takes in and uses the low-density atmosphere surrounding the satellite as a propellant. A laboratory environment which imitates the orbital conditions on such a super low earth orbit is essential to study ABIE on ground. This project attempts to synthesize the environment in super low Earth orbit using a 6cm ECR plasma source. An atomic oxygen beam with 5eV was realized by reflecting plasma off a metallic surface. The atomic oxygen flux is measured by polyimide covering a QCM using polyimide erosion. There is a radial distribution of the atomic oxygen flux, and we think that reflecting plasma occurs at a cusp on one of the magnets providing the ECR magnetic field. We achieved a flux of 5E14 atom/cm2/sec, which corresponds to the orbital conditions at an altitude of 250km. The next step is retrofitting the laboratory equipment to use as an intake feed for the air breathing ion engine. [Preview Abstract] |
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DTP.00082: Plasma assisted combustion of paraffin Valeriy Chernyak, Oleg Nedybaliuk, Sergij Olszewski, Leonid Bulavin, Yurij Zabashta, Olena Aktan, Vasyl Lendel, Svetlana Orlovska, Olexandr Svechnikov, Farida Karimova, Maxim Shkoropado Gasoline, diesel, and turbine engines could soon burn cleaner or be more fuel efficient through the application of Plasma Assisted Combustion. The using of plasma for rocket engineering can to help resolve a series of additional problems. It is the fuel regression rate or steerability of rocket engine wholly. The general advantages of paraffin as a green rocket fuel are high caloricity, ecological compatibility, safety of keeping and high chemical inertness to external factors, etc. The results of assembly investigations of combustion, plasma assisted combustion and paraffin fusion kinetics are represented in this work. [Preview Abstract] |
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DTP.00083: Supersonic Flow Control by a Nanosecond Pulse Surface Dielectric Barrier Discharge Igor Adamovich, Munetake Nishihara, Keisuke Takashima, J. William Rich Results of experiments demonstrating Mach 5 bow shock control by a nanosecond pulse surface dielectric barrier discharge are presented. The experiments are conducted in a blowdown Mach 5 wind tunnel. A steady-state bow shock is generated ahead of the cylinder model. A surface DBD discharge powered by repetitive nanosecond pulses (peak voltage 30 kV, pulse duration 5 nsec, pulse repetition rate up to 100 kHz) is sustained on the model. Phase-locked schlieren images show that several microseconds after the nanosecond discharge pulse, an additional shock wave is generated upstream of the baseline shock. At longer delay times, the shock wave generated by the discharge pulse moves to the periphery of the baseline bow shock, until the two shocks merge. This suggests that the use of a higher pulse repetition rate, of the order of 100 kHz, would result in a quasi-steady state change of the bow shock shape, rather than a periodic change observed at the present conditions. The fundamental difference of the present approach from supersonic flow control using high-power lasers, plasma torches, and arc discharges is that the flow field is modified due to rapid localized energy coupling (on the time scale of 10 nsec) in a low average power plasma actuator placed on the surface of a model in the supersonic flow. [Preview Abstract] |
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DTP.00084: Microwave frequency tuning of an ECR ion thruster Kazutaka Nishiyama Microwave power reflection of a 20-cm xenon ECR ion thruster for spacecraft propulsion should be decreased because the incident microwave power of 100W is nearly the maximum power for light-weight coaxial cables and high reflectance may damage the microwave components and degrades thrust efficiency. Impedance matching characteristics of the thruster has been experimentally investigated by adjusting the microwave frequency by one percent without using any mechanical tuners which is not suitable for space applications. The ion thruster should work at xenon flow rates between 4 and 13 sccm (standard cubic centimeters per minute). In that operating range, the best frequency was 4.266 GHz with only 1{\%} of reflectance at the maximum flow rate. Frequency offset by only 0.6{\%} reduced the thrust by 30{\%} due to a very high microwave reflectance of 43{\%}. When the flow rate was decreased to the minimum level, the frequency little affected the thrust performance and the reflectance and reflectance of 30{\%} at that condition was acceptable. [Preview Abstract] |
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DTP.00085: Detachment mechanisms in a magnetic nozzle Mario Merino, Eduardo Ahedo A 2D model of the supersonic plasma expansion in a divergent magnetic nozzle generated by an external coil is considered. The plasma is assumed collisionless, low-beta, and constituted of fully-magnetized electrons and cold, partially-magnetized ions. Thus, electrons are attached to the magnetic streamtubes by the gyro-force, whereas ions are attached electrostatically to electrons, i.e. by quasineutrality. The gain in plasma kinetic energy is driven mainly by electrothermal acceleration. Hall current runs opposite to the coil current, as it is mandatory to provide confinement and thrust. For a non-rotating jet, a modest (ion) swirl current develops, cancelling partially the Hall current. Three feasible detachment mechanisms have been proposed in the literature, based (1) in the plasma induced field, (2) electron inertia, and (3) collisions. The relevance of each one depends on the plasma collisionality and beta, and the upstream conditions, but they all rely on the plasma azimuthal (i.e. Hall plus swirl) current. A critical assessment of detachment theories for a propulsion device will be carried out. Inertial and resistive detachment mechanisms are found to be divergent (i.e. the radial detachment of electron streamtubes is outwards), in contrast to the prevailing theory. Magnetically-induced detachment depends on the direction of the Hall current. Established theory, which postulates a stretching of the magnetic field, does not hold for thrusting plasmas. [Preview Abstract] |
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DTP.00086: Three-Dimensional Simulations of Surface Air Plasma Discharge Phenomena Shankar Mahadevan, Laxminarayan Raja Computational simulations of air plasma discharges are presented. The glow discharge model is based on a self-consistent continuum description of the plasma. A finite-rate air chemistry model with 11 species is used to model air plasma at pressures $\sim $1-20 Torr typical of plasma actuator operating conditions for high-speed flow control applications. Practical limitations on the grid size and number of species in the chemistry model motivate the need for the development of parallel plasma models. The parallelized model is used to study physical structure and chemical composition of a surface direct-current glow discharge with circular pin electrodes. The three-dimensional structure of the discharge is captured by the model. For a discharge current of 25 mA, the peak plasma density is found above the cathode covering the entire cathode surface with a spot attachment at the anode. The plasma is electronegative with the O$^{-}$ ion density about three times higher than the electron density. In general, qualitative agreement is found between the three-dimensional and corresponding two-dimensional simulations for the same operating parameters. The peak gas temperature from the computations is found to be about 1000 K in the three-dimensional case and 1180 K in the two-dimensional simulation. [Preview Abstract] |
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DTP.00087: Alternative propellant for spatial propulsion Lahib Balika, Titaina Gibert, St\'ephane Pellerin The xenon is the most often propellant used for plasma spatial propulsion due to its low ionization potential and its high atomic mass. Nevertheless for long time missions; the thrusters need to carry an initial heavy total mass of propellant. A solution to reduce the weight of the propellant is to increase the autonomy of the thruster. If the propellant can be extracted from the environnemental atmosphere, the life time of the thruster is improved. We present a Hall thruster initially optimized for operating with xenon. This thruster has been tested in the GREMI facility with nitrogen as propellant. The ionization potential, the mass and the diatomic molecular aspect change the behavior of the plasma plume. Our investigation is based on the measurement of discharge current, tension and comparison with the operation with xenon. [Preview Abstract] |
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DTP.00088: Plasmadynamic, electrogasdynamic and magnetohydrodynamic control of the body supersonic streamline Tatiana Lapushkina, Alexander Erofeev, Sergey Ponyaev This work is concerned with possibility to control the shock-wave configuration by non-mechanical methods. The three types of action on structure of supersonic flow around semicylindrical body were considered: a plasmadynamic method coming from features of supersonic flows of highly nonequlibrium plasmas, electrogasdynamic (EGD) realized due to heating of a gas in gas discharges of high intensity, and magnetohydrodynamic (MHD) by action of Lorentz force appeared at organized in gas discharge electric current at transversal magnetic field. In the plasmadynamic control method a discharge creates a strongly nonequilibrium plasma in the flow before the body. In the EGD and MHD methods, a discharge was organized in the near surface area of the nose part of the body. Change of bow shock-wave position is investigated at: a) change of nonequliubrium degree $T_{e}/T_{h}$ of incoming flow; b) increase of heating parameter$N=\frac{jE\Delta t}{\rho u^2}$; c) increase of Steward parameter$St=\frac{jBL}{\rho u^2}$. Where $j $is current density, {\AA} is electric field intensity, \textit{$\Delta $t} is interaction time, {\AA} is magnetic field induction, $L$ is width of interaction zone,\textit{ $\rho $} and $u$ are density and velocity of incoming flow. Experiments were conducted at the setup based on a shock tube. Xenon and air were used as a working gas. [Preview Abstract] |
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DTP.00089: GREEN PLASMA TECHNOLOGY |
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DTP.00090: Decomposition of CO$_{2}$ by large flow atmospheric microwave plasma (LAMP) Shankar Parajulee, Ikezawa Shunjiro, Anil Pandey, Masahiro Hayakawa We have studied here the rate of decomposition of carbon dioxide using large flow atmospheric microwave plasma (LAMP) of 600W, frequency 2.45 GHz with a wave guide converter from TE10 to co axial mode to excite the plasma as atmospheric surface wave plasma. When air and carbon dioxide was supplied, accompanied with the KH instability in the plasma, the CO intensity band was found to increase with the increasing CO$_{2}$ flow rate. But, when H$_{2}$ was mixed with it, CO intensity band was found to decrease and increase. Presence of H$_{2}$ would have caused to decompose CO$_{2}$ to C and CO which shows a characteristic point. Decomposed carbon was collected in paper filter (Elleair tissue 78$\sim $508$\mu )$. For the CO$_{2}$ flow rate of 10 L/M at 30 sec, 16 mg decomposed carbon was collected while the total carbon was 2.68 g. Thus, it is expected that decomposition rate of CO$_{2}$ can be increased by increasing microwave power. [Preview Abstract] |
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DTP.00091: Pt based thin films deposited by magnetron sputtering for PEMFC and DMFC fuel cells Marjorie Cavarroc, Aboubakr Ennajdaoui, Matthieu Vogt Recent research effort in low temperature fuel cell field, namely PEMFC and DMFC are devoted to electrode manufacturing using plasma processes. Several reasons justify this choice. Unlike liquid way methods, plasma deposition has the advantage to get ride of solvents, which ask the question of treatment and recyclability. This method allows depositing various materials, which can be components of the electrode. In this frame, MID develops several research activities on pre-industrial plasma equipments. Advantages of plasma sputtering to deposit Pt for PEMFC electrodes have already been demonstrated: very good results (i.e. 20 kW/g$_{Pt})$ have been obtained. The study we present here concerns magnetron sputtering of various electrode components realised thanks to a multi-target configuration in the P3 prototype. Depositions are performed onto two commercial supports: Nafion$^{\mbox{{\textregistered}}}$ 212 membrane, and uncatalyzed gas diffusion layer E-Tek$^{\mbox{{\textregistered}}}$. Layer morphology is determined thanks to SEM observation, growth rate are estimated using profilometry measurement. Finally, membrane electrode assembly (MEA) performances are measured on a fuel cell tester (H$_{2}$/O$_{2})$ in the MID laboratory. Those performances, compared from one support to the other, are discussed on the analyses base. [Preview Abstract] |
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DTP.00092: Plasma-assisted dry reforming of methane in atmospheric AC gliding arc discharge Xin Tu, Helen J. Gallon, J. Christopher Whitehead Plasma-catalytic dry reforming of CH$_{4}$ with CO$_{2}$ has been carried out in an atmospheric pressure gliding arc reactor. Two semi-ellipsoidal Al plates coated with different materials (Ni, Zn and Cu) are used as electrodes. The plasma arc dynamic has been investigated by means of electrical diagnostics and high speed photography. Different arc breakdown regimes are reported, and the restrike mode is identified as the typical fluctuation characteristic of the gliding arc in CH$_{4}$/CO$_{2}$ mixture. In addition, global thermodynamic equilibrium calculation for dry reforming of CH$_{4}$ has been carried out. The effects of both plasma (reactor geometry, coating material and arc power) and process parameters (feed flow rate and CH$_{4}$/CO$_{2 }$molar ratio) on the conversion, product selectivity and energy efficiency of the process have been investigated to get optimal operating parameters for the reaction. The possible reaction mechanisms involved in the plasma dry reforming chemistry are also suggested. [Preview Abstract] |
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DTP.00093: Novel Cu and Co oxide based catalysts for PEMFC obtained by plasma-enhanced metal-organic chemical vapor deposition PEMOCVD Piotr Kazimierski, Lukasz Jozwiak, Ryszard Kapica, Adam Socha The study concerns none noble metal catalytic films for Proton Exchange Membrane Fuel Cell (PEMFC), based on cobalt and cooper oxides, including mixed oxide known as spinel type Cu$_{x}$Co$_{3}$-xO$_{4}$ (x = 0, 0.3, and 1.0). Thin catalytic layers were obtained from cyclopentadienyldicarbonyl-cobalt(I) and cooper (II) acetylacetonate by plasma method called plasma enhanced metal-organic chemical vapor deposition (\textbf{PEMOCVD)}. Organic precursors were introduced to the reactor with carrier gases like argon, oxygen or mixture of both. Then deposited layers were analyzed by means of Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and electrochemical methods such as single cell test and cyclic voltammetry CV. In all types of investigated materials catalytic activity was observed. Single cell test showed that the best results were attained for the layers deposited in pure argon plasma. To learn more about the phenomenon, a number of CV tests were performed. [Preview Abstract] |
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DTP.00094: Decomposition Mechanism of Organic Compounds in Water Plasma under Atmospheric Pressure Narengerile, Takayuki Watanabe Decomposition of aqueous acetone or glycerin was performed by water plasmas generated by DC discharge at atmospheric pressure. Both of acetone and glycerin were thermally decomposed by the water plasma, and then H2, CO, CO2, and CH4 were generated as the major products in the effluent gas. For the acetone decomposition, the decomposition rate was reached as high as 99.7{\%}, and 80{\%} of the fed carbon in acetone was transformed into solid carbon at 5mol{\%} of the injected solution. In contrast, the solid carbon formation from glycerin at 5mol{\%} of the injected solution was negligible. This results indicated that the different decomposition mechanism between acetone and glycerin in the water plasma. The decomposition mechanisms were investigated from the comparative study on the acetone and glycerin decomposition on the basis of the experimental results and kinetics consideration. The incomplete oxidation of acetone in the water plasma leads to the C2H2 formation as the by-product and the large amount of solid carbon formation, while glycerin was completely decomposed even at high concentration. The complete decomposition of glycerin indicated that OH radical enhanced the oxidation of organic intermediate products. [Preview Abstract] |
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DTP.00095: Plasma reforming of ethanol in plasma-liquid system with discharge in gas channel with liquid wall Valeriy Chernyak, Vutaliy Yukhymenko, Sergij Olszewski, Sergij Sidoruk, Dmitrij Levko, Anatolij Shchedrin, Vadim Naumov, Valentina Demchina This paper presents the results of experimental and theoretical investigations of the process of nonthermal plasma-assisted reforming of aqueous ethanol solutions in the dynamic plasma liquid systems using the DC electric discharges in a gas channel with liquid wall and the additional excitation of ultrasonic field in liquid. The experiments show possibilities and efficiency of low-temperature plasma-chemical conversion of liquid ethanol into hydrogen-rich synthesis gas in different regimes. The numerical modeling clarifies the nature and explains the kinetic mechanisms of nonequilibrium plasma-chemical transformations in the plasma-liquid systems in different modes. [Preview Abstract] |
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DTP.00096: Reforming of ethanol in plasma of discharge with gas flow of ``tornado'' type and "liquid" electrode Valeriy Chernyak, Oleg Nedybaliuk, Sergij Olszewski This paper presents the results of experimental and theoretical investigations of the process of non-thermal plasma-assisted reforming of aqueous ethanol solutions in the dynamic plasma liquid system using the DC discharge in a reverse vortex gas flow of tornado type with a ``liquid'' electrode (TORNADO-LE). Mass-spectrometry of synthesis gas for the ethanol reforming in the TORNADO-LE was measured. Coefficient of energy transformation for the ethanol reforming in the TORNADO-LE was obtained. Also output gas composition was measured by gas-chromatography (H$_{2}$ - 28{\%}, CO - 17,5{\%}, N$_{2}$ - 55{\%}, CO$_{2}$ - 4,5{\%}). [Preview Abstract] |
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DTP.00097: Plasma-stimulated destruction of phenol in water solutions Valeriy Chernyak, Sergij Olszewski, Vitaliy Yukhymenko, Sergij Sidoruk, Olena Solomenko The process of phenol destruction in water solutions, which occurs under the influence of plasma, was investigated to different plasma-liquid systems. The basic factor for the proper comparison of the efficiency of all presented plasma-stimulated phenol destruction systems was used. The value of this factor was obtained from spectrophotometric measurements data for initial and treatment phenol solutions. There's a two mechanisms of the plasmolytic destruction of organic molecules in the water solutions. One of this is based on direct chemical reactions, other -- based on cascade chemical reactions. The mechanism of the plasmolytic organic molecules' destruction, based on direct reactions, uses the energy, spent on plasma support, and it's in order of magnitude more effective then the mechanism based on cascade reactions. The most effective system for phenol plasmolytic destruction in water solutions is plasma-liquid system, based on the impulse discharge in the gas channel with liquid wall. [Preview Abstract] |
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DTP.00098: Ethanol reforming in pulse plasma-liquid system with postdischarge pyrolitic chamber Valeriy Chernyak, Sergij Sidoruk, Sergij Olszewski This paper presents the results of experimental investigations of the process of nonthermal plasma-assisted reforming of aqueous ethanol solutions in the dynamic plasma liquid systems using the Pulse electric discharges in a gas channel with liquid wall. Also plasma assisted high temperature partial oxidation pyrolisis of ethanol was investigated. The energy efficiency vs. pyrolisis chamber temperature and vs. ethanol-to-oxygen molar ratio were obtained. The best regimes for highest energy efficiency were obtained. The outflow syngas components was investigated. [Preview Abstract] |
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DTP.00099: Nonequilibrium Plasma Assisted Dissociation of Hydrogen Sulfide Kirill Gutsol, Tomas Nunnally, Alexander Rabinovich, Andrey Starikovskiy, Alexander Fridman, Alexander Gutsol, Abdenour Kemoun H$_{2}$S is a byproduct of oil refinement and comprises a significant portion of natural gas deposits. Therefore, efficient H$_{2}$S treatment and utilization are crucial to the oil and gas industry. The dissociation energy of H$_{2}$S into hydrogen and sulfur is only 0.2 eV/molecule, which can make a H$_{2}$S a much less energy consuming source of hydrogen than water (2.5 eV/molecule). Such prospects are particularly important for oil industry, which consumes large amounts of hydrogen in oil hydro-desulfurization for production of low sulfur fuels and could benefit from a low cost method of H$_{2}$S dissociation. The experiments in corona, DBD, spark, and low-current arc discharges showed that: H$_{2}$S dissociation in plasma is not a chain reaction, so that H and HS radicals created by the plasma do not cause chain reactions at low temperatures. The low temperature discharges with high reduced electric field and low current produce results characterized by the common specific energy requirement (SER) higher than 10 eV/molecule, which corresponds to direct dissociation by electronic impact. The results obtained in arc filament discharge at low reduced electric field have SER $\sim $2.5 eV/molecule, and is close to thermodynamic equilibrium. [Preview Abstract] |
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DTP.00100: UV and high-voltage pulsed discharge induced degradation of organic molecules in water Olga Tchaikovskaya, Stanislav Chaikovsky, Irina Sokolova, Georgy Mayer, Valery Svetlitchnyi, Ivan Lapin, Anatoly Maltsev Wastewater treatment generally consists of a primary, secondary, and sometimes an advanced treatment stage, with different biological, physical, and chemical processes for each stage of treatment. High voltage pulse forms two kinds of physical processes in water, as pulsed electric field in parallel electrode configuration, and plasma generation by pulsed discharge in water phase with a concentrated electric field. In this study, we use bioluminescence of \textit{Photobacterium phosphoreum} to definite the toxicity of organic molecule solutions under electrical barrier discharge and UV-irradiation. It was shown that the primary OH radicals generated within streamer filaments react very quickly and locally with each other to form mainly H$_{2}$O$_{2}$, which cannot oxidize directly nitrophenols. The organic molecules degradation was improved by using higher voltages, a vigorous stirring of the water solution and an optimal concentration of humic acids. [Preview Abstract] |
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DTP.00101: Experimental and Computational Study of Carbon Dioxide Dissociation in an Atmospheric Pressure Microwave Discharge Laura Spencer, Alec Gallimore Rising concerns of atmospheric carbon dioxide (CO2) concentrations has increased scientific effort to mitigate the effects of global warming. This project proposes using a plasma source to reduce CO2 emissions by breaking down the molecule to CO and O2 via electron impact inelastic collisions. An atmospheric pressure plasma source excited by microwaves is experimentally investigated to demonstrate the dissociation capabilities of the device. Diagnostics are taken using a residual gas analyzer to monitor the gas species present in the plasma discharge, demonstrating that CO and O2 are the main products of dissociation. The experimental results are compared to a global, zero-dimensional kinetic model called GlobalKin, which assumes a homogeneous plasma where the concentration of species is spatially independent. [Preview Abstract] |
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DTP.00102: Gas phase optical emission spectroscopy during remote plasma chemical vapour deposition of GaN and relation to growth dynamics Cormac Corr, Robert Carman, Rod Boswell, Conor Martin, Marie Wintrebert-Fouquet, Satya Barik The remote plasma chemical vapour deposition (RPCVD) process being developed by the Australian company BluGlass offers several potential advantages over existing deposition techniques used to produce LED's. These include lower substrate temperature and a clean nitrogen gas as the N-atom source. In this work a nitrogen plasma discharge is created upstream of the growth region to provide the nitrogen precursors. Excited species from the plasma flow downstream interacting with gallium precursors in the deposition chamber. Optical emission spectroscopy is employed to correlate plasma species in the source and afterglow region with GaN film growth properties. In particular, the presence of hydrogen in the plasma gas stream significantly influences the excited plasma species, GaN layer growth dynamics and surface morphology of the films. [Preview Abstract] |
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DTP.00103: Efficient non-thermal plasma processing by 5 ns pulsed discharge Takao Matsumoto, Takao Namihira, Hidenori Akiyama Non-thermal plasma has been widely used for various applications, such as ozone generation, exhaust gas treatment, dioxin decomposition, volatile organic compounds removal and laser excitation. In our laboratory, the pulsed discharge plasmas have been used to treat exhaust gases. Since pulse duration of an applied voltage has a strong influence on an energy efficiency of a pollutant removal, the development of short pulse generator is of paramount importance for the practical applications. Recently, it is demonstrated by our research group that the non-thermal plasma produced using the 5 ns pulsed discharge has extremely higher energy efficiency to produce of ozone and abate nitric oxide. Typically, the yields of ozone generation are 550 g-O$_{3}$/kWh in oxygen and 250 g-O$_{3}$/kWh in dry air, and the energy efficiency of NO removal from the simulated exhaust gas having 200 ppm of NO in nitrogen is 24 g-NO/kWh. The efficiencies are the highest value in the literatures. In the presentation, the 5 ns pulsed discharge processing would be introduced. [Preview Abstract] |
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DTP.00104: BASIC PLASMA PHYSICS |
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DTP.00105: Measurement of Spatiotemporal Gas Temperature during Pulsed Discharge Sho Okada, Douyan Wang, Takao Namihira, Sunao Katsuki, Hidenori Akiyama Pulsed power technology has been used in many applications such as control of NOx and SOx from exhaust gases, treatment of dioxins, generation of ozone, and laser excitation. In this situation, the temperature during pulsed discharge is important parameter. Therefore, in this work, the temperature of medium gas in discharge reactor was measured during pulsed discharge process. As the experimental method, the rotational temperature during the pulsed discharge in atmospheric gas gap was measured by analysis of optical emissions. In this paper, the spatial and the temporal dependences of the rotational temperature during pulsed discharge would be reported. [Preview Abstract] |
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DTP.00106: Synergistic effect of dual power on plasma density by shift of power absorption region in inductively coupled plasma Jin Young Bang, Jin Yong Kim, Chin Wook Chung Spatial distributions of plasma densities and plasma potentials were measured in a side type ferrite inductively coupled plasma (ICP) driven by 400 kHz as an auxiliary power of 13.56 MHz was increased through a single-loop antenna located on the top of the chamber. In the absence of the auxiliary power, the center density was lower than the edge density because most of the ionization was occurred at the side of the chamber. As the additional electric field was induced around the center by the auxiliary power though the single-loop antenna, the center density also increased due to the ionization around the center, however, the edge density rather decreased even though the main power was fixed. This result can be explained by the spatial variation of the plasma potential. The increase in the plasma potential at the center compared with the edge potential leads to the change of the location, where the electron energy supplied from the main power at the edge dissipates through the inelastic collision, from the edge to the center. As a result, the spatial variation of the plasma potential results in the diffusion of the dissipated power supplied at the edge. [Preview Abstract] |
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DTP.00107: On the Boltzmann relation in a cold magnetized plasma Lorenzo Nasi, Jean-Luc Raimbault A systematic and exact comparison between the forces acting on magnetized electrons is considered within a fluid model. We show that the Boltzmann relation is fulfilled in the drift-diffusion approximation when $(h_i/h_e)(1 + h_e^2)/(1 + h_i^2) \ll 1$ where $h_e$ (or $h_i$) is the ratio of the electron (or ion) cyclotron to the collision frequency. When the non-linear inertia terms are taken into account, the previous criterion is too rough and must be modified. In particular it is proved that the Boltzmann relation is not uniformly valid in the discharge. The case of bounded plasmas where the electron temperature must be determined self-consistently is discussed in detail. [Preview Abstract] |
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DTP.00108: Energetic Charged Particle Collisions in Electronegative Plasmas Svetlana Radovanov, Ludovic Godet, Timothy Miller, Nicholas Chamberlain, George Papasouliotis Plasmas used for ion implantation often contain large amounts of energetic electrons and negative ions. The existence of negative ions affects the transport and spatial distribution of charged particles and the spatial structure of the sheath. This is particularly important in pulsed DC plasmas. Understanding of the basic properties of such electronegative plasmas is important for advanced materials processing. In this paper, we study how secondary electrons affect plasma parameters in BF$_{3}$, and BF$_{3}$ mixtures with Ar and He. Electron densities as well as positive and negative ion densities extracted from a radio-frequency inductively coupled discharge are measured during the on and off period of a pulsed DC bias with repetition frequencies between 0.1 and 10 kHz, and voltages of 0.5-10kV at pressures of $\sim $1-100 mTorr. The negative ion to electron density ratio is discussed and evaluated. We also study transitions from the electropositive to the electronegative regime. The effect of conductive and insulating surfaces on plasma conditions is studied as a function of bias voltage. [Preview Abstract] |
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DTP.00109: Effect of electron beam on Propagation of Dust Ion Acoustic waves Amir Mohammad Ahadi, Samad Sobhanian In this work, we have studied analytically, the effect of electron beam on propagation of Dust-Ion acoustic waves (DIAWs) in an unmagnetized and collisionless dusty plasma. We have supposed that the plasma contains of thermal ions, thermal electrons, warm dust particles (that is described as a fluid) and electron beam. We have obtained the dispersion relation for new situation. The obtained results show that the beam reduces the phase (and group) velocity of DIAWs. Electron number density of beam and cathode potential are two main factors to decrease the speed of these waves. [Preview Abstract] |
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DTP.00110: Modeling of Hydrogen Negative Ions in Sheet Plasma Hiroyasu Komukai, Akira Tonegawa, Takashi Torada, Tomochiko Ono, Kazutaka Kawamura Hydrogen negative ions (H$^{-})$ are formed by the dissociative attachment of low-energy electrons (T$_{e}\sim $1 eV) to highly vibrationally excited molecules H$_{2}$*($v$''$>$5), which are attributed to the electron-impact excitation of molecules by high- energy electrons (T$_{e}>$15 eV) in the plasma. In order to produce negative ions in plasmas, we have designed a system of a magnetized sheet plasma crossed with a vertical gas flow. The magnetized sheet plasma is suitable for the production of negative ions, because the electron temperature in the central region of the plasma is as high as 10 -15 eV, whereas in the periphery of the plasma, a low temperature of 1 eV is obtained. We have carried out the modeling of hydrogen negative ions taking into account of vibrationally excited hydrogen molecules in hydrogen plasma. H$^{-}$ ions are localized in the periphery region where there are low energy electron from the edge of the sheet plasma. A zero-dimensional model based on available rate coefficients was found to predict the observed dominant ion densities. [Preview Abstract] |
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DTP.00111: Ill-posed problems in low temperature plasmas Raoul Franklin Godyak and Sternberg pointed out that treating the plasma-sheath problem for an active plasma by integrating inwards from a plane wall towards a semi-infinite plasma was ill-posed in the sense that the wall flux was finite while the generation was infinite. Here we further examine this type of situation in other geometries and with a magnetic field. Some workers have sort to deal with the problem by supposing that in the body of the plasma generation is balanced by recombination, but at low pressures this is not physically realistic since three-body recombination is negligible, and electron-ion recombination rates are orders of magnitude smaller than typical generation rates. Our general conclusion is that active plasmas are necessarily finite -- that is they ``know'' they are bounded. This leads to the plasma balance, or global equation involving the generalized Bohm speed. [Preview Abstract] |
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DTP.00112: Diffusion-ionization plasma propagation and pattern formation during microwave breakdown Guo-Qiang Zhu, Bhaskar Chaudhury, Jean-Pierre Boeuf A 1D model of the expansion of a collisional plasma under the combined effect of diffusion and ionization is presented. It is shown that a simple quasi-neutral model of the plasma using an effective diffusion coefficient can accurately describe the plasma front propagation. The effective diffusion coefficient describes the transition from free electron diffusion in the plasma front to ambipolar diffusion in the bulk. Comparisons with ``exact'' solutions from a drift-diffusion Poisson model show excellent agreement in the simple case of a constant ionisation frequency, but also when the plasma front propagation is due to microwave breakdown. In the latter case the plasma model is solved together with Maxwell's equations and the ionisation frequency in the front is modulated in time due to the formation of standing waves in the plasma front region, leading to the formation of plasma patterns. [Preview Abstract] |
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DTP.00113: Study of the nonresonant Buneman instability throughout the negative diffusion equation Mohammad Mohsen Hatami, Babak Shokri, Ali Reza Niknam Using hydrodynamics equations for a weakly ionized quasineutral plasma, the dynamic behavior of the plasma density is investigated when the plasma is under the development of the low-frequency nonresonant Buneman instability. It is assumed that a constant electric field acts on the plasma and the collision between the charged particles and the neutrals is taken into account. In this case, it is shown that the plasma density satisfies a nonlinear diffusion-like equation with negative diffusion coefficient. Using Adomian decomposition method to solve this equation, it is shown that the small perturbations of the plasma density are amplified and the density profile is steepened due to development of the Buneman instability. [Preview Abstract] |
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DTP.00114: Influence of Dissipation on Weak Beam-Plasma Interaction Eduard Rostomyan Present investigation substantiates a new type of dissipative beam instability that develops in conditions weak beam-plasma coupling i.e. when the beam and the plasma fields are overlaped slightly. Waveguide with plasma and beam layers is considered. Consideration is carried out in general form, without specifying the shape of the waveguide's cross-section. The approach actually corresponds to perturbation theory and is based on smallness of beam-plasma coupling. Depends on combinations of parameters the system may be stable or (in absence of dissipation) instability may be due to excitation of negative energy beam wave. Dissipation leads to a new type of dissipative beam instability with growth rate that depends on dissipation inverse proportionally. The growth rate is calculated for an arbitrary level of dissipation i.e. for arbitrary value of the ratio of dissipation to the growth rate of no dissipative instability. [Preview Abstract] |
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DTP.00115: Development of a compact, versatile electron beam source Scott Walton, David Boris, Christopher Compton, Christopher Cothran, Richard Fernsler, William Amatucci, Robert Meger The operating characteristics of a high-energy electron beam source are described. Electrons are extracted from a hollow cathode plasma and then accelerated by anode located downstream from the cathode. The anode to cathode surface area ratio is less than the root of the electron to ion mass ratio such that an electron sheath forms at the anode; a bias on this anode then accelerates the electron flux into a beam. Varying the hollow cathode current allows direct control of the beam current, while the bias on the accelerating anode determines the beam energy. A magnetic field can be used to assist in the beam collimation. Beams up to 5kV and 100mA have been produced with this device. Critical component designs for stable operation in both CW and pulsed operation are discussed. [Preview Abstract] |
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DTP.00116: Dynamics of ion beam current compensation by RF pulsed electron flow emitted from the single-grid ICP source Dmytro Rafalskyi, Stanislav Dudin The investigation results of the time-dependent current and potential of the target under bombardment by combined ion-electron flow extracted from the single-grid ICP source with RF grid biasing are presented. Experimental measurements of the floating target potential show that the target potential oscillation amplitude is about 4{\%} of the RF grid biasing amplitude. It is shown that the floating target potential and the target current oscillate with doubled frequency of the RF bias that is caused by electron transient effects in the ion-beam plasma in the beam transport space. The obtained results allow optimizing the regime of ion-beam processing of thin nano-scale dielectric films in the context of their electrical breakdown prevention. The etching test results are also presented. [Preview Abstract] |
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DTP.00117: Plasma transport across magnetic field lines in the linear machine Mistral Alexandre Escarguel, Cyril Rebond, Nicolas Claire, Tony Lefevre, Fabrice Doveil Plasma transport across magnetic field lines has been experimentally studied in the linear machine Mistral. This addresses the physics of plasmas encountered in controlled magnetic fusion machines in the shadow of limiteurs. It is still not completely predictable in new configurations and needs to be studied in laboratory plasmas, where parameters can be easily controlled. The Mistral device is dedicated to study plasma instabilities in the presence of a magnetic field, essentially by optical diagnostics [1]. In this work, we present the study of plasmas instabilities regularly rotating around a central plasma. The radial evolution of the ionic velocity distribution function has been measured by Laser induced Fluorescence (LIF) inside the instability. Considering the momentum equations for ions and electrons [2, 3], a physical model has been developed to interpret the experimental data. The solutions are in good agreement with the experience and the physics is discussed. \textbf{Reference} [1] A. Escarguel, ``Optical diagnostics of a low frequency instability rotating around a magnetized plasma column'', Eur. Phys. J. D, 56, 209-214 (2010). [2] J. E. Allen, Contrib. Plasma Phys., 400 (2008). [3] B. M. Annaratone, A. Escarguel, T. Lefevre, C. Rebont, N. Claire and F. Doveil, in preparation. [Preview Abstract] |
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DTP.00118: NON-EQUILIBRIUM KINETICS |
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DTP.00119: Influence of the oxygen feed position on the compositions and isotopic contents of reaction products in N$_{2}$ glow discharge Shinsuke Mori, Masashi Ichikawa, Thi Anh Nga Nguyen, Masaaki Suzuki We have performed the nitrogen isotope separation by the plasma chemical reactions in N$_{2}$-O$_{2}$ glow discharge system and investigated the influence of the oxygen feed position on the compositions and isotopic contents of reaction products in N$_{2}$ glow discharge. This isotope separation method is due to the vibration-to-vibration energy exchange among the vibrational states of N$_{2}$ molecules. When the oxygen is fed into the N$_{2}$ glow discharge from the upstream of the discharge area, the nitrogen-15 enrichment is observed and the maximum nitrogen-15 separation factor of 1.6 is obtained in the NOx products while the ozone is the main component in the reaction products. On the other hand, when the oxygen is fed into the N$_{2}$ glow discharge from the downstream of the discharge area, the formation of ozone is negligible and NOx is the main component in the reaction products. However, when the oxygen is fed into the downstream of the discharge area, the nitrogen-15 isotope separation factor in NOx products is much smaller than that for the premixing case. [Preview Abstract] |
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DTP.00120: Kinetic processes in complex thermally non-equilibrium plasma produced by shock wave Alexander Starik, Ilya Arsentiev, Alexander Savel'ev, Nataliya Titova A comprehensive analysis of charged and neutral species formation in N2-O2-Ar and CO2-N2 systems containing nanoparticles behind strong shock wave is conducted on the basis of extended thermally nonequilibrium model with careful allowance for reactions with both vibrationally and electronically excited molecules, vibration-electron-chemistry coupling and charging of nanoparticles. The novel model is developed to describe with high accuracy the vibration-chemistry interconnection. The model is validated against various experimental data. Two principally distinctive modes of particle charging were revealed. [Preview Abstract] |
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DTP.00121: N2(B,v'=0-12) populations in Ar-N2 and N2 flowing afterglows of microwave and Corona discharges Andre Ricard, Freddy Gaboriau, Anne-Marie Pointu Production of N2(B,v') states is analysed from the N2 1st pos. System intensity in Ar-N2 and N2 afterglows of microwave and Corona discharges. A strong emission at 1040 nm from the N2(B,0- A,0) band is obtained in Corona N2 afterglow. Such emission is largely stronger than in microwave afterglows at low N2 pressure and at atmospheric Ar-xN2 gas pressure with x=1.5-23\%. [Preview Abstract] |
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DTP.00122: Kinetic of propane in homogeneous high pressure low temperature plasmas of atmospheric gases S. Pasquiers, N. Moreau, N. Blin-Simiand, L. Magne, P. Jeanney, F. Jorand The kinetic of propane in non-thermal plasmas of N$_{2}$/O$_{2}$ mixtures is currently under study owing to applications such as cleaning of polluted air streams or plasma assisted ignition and combustion. We have recently suggested that, for C$_{3}$H$_{8}$ diluted in N$_{2}$, quenching collisions of the nitrogen metastable states on the hydrocarbon leads to produce H$_{2}$ and propene (N. Moreau et al., to appear in J. Phys. D : Appl. Phys.). The present work deals with the effect of oxygen addition on propane consumption in a photo-triggered discharge (homogeneous plasma) working at 460 mbars. By-products are identified and their concentrations are quantified (chromatography) as functions of the O$_{2}$ concentration (up to 20{\%}), at 0.5{\%} propane concentration. H$_{2}$ concentration decreases when the oxygen concentration increases, but do not drop to zero in the air-like mixture. This effect is explained using a self-consistent 0D discharge and kinetic model. The removal of C$_{3}$H$_{8}$ and the production of H$_{2}$ follow from a balance between quenching processes and oxidation kinetic of the hydrocarbon. The model predictions are also compared to the measure of the absolute OH-radical density as function of time in the discharge afterglow (UV-absorption). [Preview Abstract] |
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DTP.00123: Anomalous Doppler Broadening of Hydrogen Lines Caused by Exotermic Reactions Jayr Amorim, Jorge Loureiro Large controversy is nowadays associated with possible explanations of the anomalous Doppler broadening of hydrogen Balmer lines observed in low-pressure plasma discharges. The interest was triggered by the observation of extraordinary wide wings on the spectrum of atomic hydrogen emitted lines. For full clearness of this point we present in this work a theoretical study in which the three-dimensional and one-dimensional velocity distributions of product species created by an exothermic reaction H$^{+}_{2}$ + H$_{2}$ --$>$ H$^{+}_{3}$ + H, with internal energy defect $\Delta $E, are determined using energy conservation requirement. It is shown that deviations relatively to Maxwell-Boltzmann distribution are significant as $\Delta $E increases and hence the profiles of H(n$\ge $3) emitting atoms created in the sequence of this reaction are not Gaussian. The determination of the species temperature from the full-width at half- maximum of hydrogen Balmer lines, as well as the fit of these lines by multimodel Gaussian functions are questioned. [Preview Abstract] |
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DTP.00124: Electron Velocity Distribution Function in Beam Plasmas Alexander Mustafaev, Vladimir Demidov The characteristic features of the relaxation of the energy and momentum distribution functions of the electrons in plasma produced by a low-voltage beam discharge in helium are investigated. It is shown that the energy of an intense electron beam may relax due to the wave excitation. The critical currents corresponding to a jumplike transition from one relaxation mechanism to another are measured. An intense electron beam is found to become more isotropic in the course of its interaction with Langmuir waves in collisionless plasma. The cross section for quasi-elastic collisions between the electrons and Langmuir plasmons is estimated. The wave nature of the beam-plasma mechanism for the relaxation of the anisotropic electron energy distribution function is demonstrated. The experimental threshold criterion for the energy relaxation of an intense monoenergetic beam is obtained. The threshold criterion for the relaxation of the anisotropic electron energy distribution function is universal in character regardless of the cause of anisotropy. The authors are grateful to Prof. V. S. Litvinenko for permanent support. [Preview Abstract] |
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DTP.00125: Vacuum UV emission spectroscopy of discharge excited by a RF helical coupling device in N$_{2}$-Ar mixtures Pavel Veis, Corinne Foissac, Adriana Annusova, Jaroslav Kristof, V. Martisovits, Philippe Supiot Optical emission spectroscopy in Vacuum Ultra-Violet spectral range is applied to study densities, vibrational and rotational temperatures of N$_{2}$(a$^{1}\Pi _{g})$ specie in a N$_{2}$-Ar (0-95{\%} Ar) plasma induced by a helical cavity excited at 27MHz and 400Pa. The N($^{2}$P) atoms are also analyzed versus the Ar percentage. The strong dependence of the temperatures and density species toward the Ar amount in the gas mixture is consistent with kinetics where the argon metastables play an important role. [Preview Abstract] |
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DTP.00126: Mechanism of fast gas heating in a non-equilibrium weakly ionized air discharge plasma at high electric fields Nickolay Aleksandrov, Svetlana Kindysheva, Marya Nudnova, Andrey Starikovskiy Observations of a shock wave propagating through a decaying plasma in the afterglow of an impulse high-voltage nanosecond discharge and of a surface dielectric barrier discharge in the nanosecond range are analyzed to determine the electron power transferred rapidly into heat in air plasmas at high electric fields. It is shown that around a half of the discharge power can go to heat for a short ($<$ 1 $\mu $s) period of time when reduced electric fields are about 10$^{3}$ Td. A kinetic model is developed to describe the processes contributing to the fast transfer of electron energy into thermal energy under the conditions considered. Calculations based on the model developed agree qualitatively with the analysis of the observations in the high-voltage nanosecond discharges. [Preview Abstract] |
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DTP.00127: GAS PHASE PLASMA CHEMISTRY |
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DTP.00128: Role of nitrogen metastable states in the removal of formaldehyde by non-thermal high pressure N$_{2}$ and N$_{2}$/O$_{2}$ mixture plasmas N. Blin-Simiand, F. Jorand, L. Magne, S. Pasquiers Formaldehyde is one of the most toxic VOC coming from human activities. Few works have been performed in order to understand mechanisms involved in the removal of this molecule in air using non-thermal plasmas generated by pulsed discharges, most often dielectric barrier (DBD) or corona ones. Even in the N$_{2}$/CH$_{2}$O mixture, a comprehensive kinetic interpretation of measurements remains not so easy because it requires a self-consistent modelling of both the streamer physics and the strongly reactive plasma chemistry. This difficulty can be overcome in case of a spatially homogeneous plasma. So our study deals with the removal of CH$_{2}$O (max. 900 ppm) in N$_{2}$/CH$_{2}$O mixtures using : i/ a DBD energised by a pulsed high voltage power supply, at 1 bar, and ii/ a photo-triggered discharge at 400 mbars. The removal efficiency is the highest for the homogeneous plasma. Effect of the addition of a small amount of O$_{2}$ is examined in case of the photo-triggered reactor, in order to get more consistent information on the role of the nitrogen metastable states in the decomposition of the pollutant molecule. It is shown that quenchings of N$_{2}$ states by CH$_{2}$O play an important role, which is progressively counterbalanced by the oxidation kinetic when O$_{2}$ is added to the mixture. [Preview Abstract] |
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DTP.00129: Nitrous oxide production-loss balance in non-thermal high pressure N$_{2}$/O$_{2}$ plasmas and correlation with acetaldehyde removal W. Faider, S. Pasquiers, P. Jeanney, L. Magne, N. Blin-Simiand, F. Jorand Various nitrogen oxides and ozone molecules are produced in high pressure non-equilibrium plasmas in N$_{2}$/O$_{2}$ mixtures. Amongst these compounds, the production-loss balance of N$_{2}$O involves excited states of atomic and molecular oxygen and nitrogen, in particular metastables which play important role in the conversion of hydrocarbons and VOCs. The measure of the N$_{2}$O density should help in the understanding of the excited states kinetics if measurements can be compared to predictions of a self-consistent modelling of the discharge and plasma reactivity. This is the case for the photo-triggered discharge which allows to create a transient homogeneous plasma. The present work deals with the N2O kinetic processes studied with the help of model predictions compared to the measure of the molecule density by laser absorption spectroscopy in the infrared (QCL). Main parameters are the O$_{2}$ percentage in the mixture (at 460 mbars) and the specific deposited energy. Results are discussed with respect to the existing literature on the N$_{2}$O kinetic. The effect of addition of a small amount of acetaldehyde (less than 0.5 {\%}) to the N$_{2}$/O$_{2}$ mixture is examined in order to get information about the role of N$_{2}$ and O metastable states in the removal of the pollutant molecule. [Preview Abstract] |
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DTP.00130: Kinetics of $A^3\Sigma_u^+$ state of molecular nitrogen in inductively-coupled nitrogen plasmas Yoshimine Horikawa, Kazuaki Kurihara, Koichi Sasaki This paper discusses the loss kinetics of the metastable $A^3\Sigma_u^+$ state of molecular nitrogen in inductively- coupled nitrogen plasmas. The loss frequency of the $A^3\Sigma_u^+$ state was evaluated from its density and the production rate. The density of the $A^3\Sigma_u^+$ state was measured by diode laser cavity ringdown absorption spectroscopy. The production frequency was estimated by evaluating the rate coefficients for electron impact excitation to the $A^3\Sigma_u^+$, $B^3\Pi_g$, and $C^3\Pi_u$ states. In the evaluations of the rate coefficients, we took into account the variation of the electron temperature, which was estimated on the basis of optical emission intensities. The variation of the loss frequency, which was evaluated from the balance between the production and loss frequencies, suggested the quenching loss of the $A^3\Sigma_u^+$ state in the gas phase. However, the loss frequency of the $A^3\Sigma_u^+$ state according to the rate coefficients of quenching processes known to date (${\rm N}_2(A^3\Sigma_u^+) + {\rm N}(^4S) \rightarrow {\rm N}_2 (X^1\Sigma_g^+) + {\rm N}(^2P)$, ${\rm N}_2(A^3\Sigma_u^+) + {\rm N}_2(A^3\Sigma_u^+) \rightarrow {\rm N}_2(B^3\Pi_g) + {\rm N}_2(X^1\Sigma_g^+)$, and ${\rm N}_2(A^3\Sigma_u^+) + {\rm N}_2 (A^3\Sigma_u^+) \rightarrow {\rm N}_2(C^3\Pi_u) + {\rm N}_2(X^1 \Sigma_g^+)$) are smaller than the diffusion loss frequency. Further investigations are necessary to identify the dominant loss process of ${\rm N}_2(A^3\Sigma_u^+)$ in nitrogen plasmas. [Preview Abstract] |
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DTP.00131: Reduction of Reaction Mechanisms in Oxygen Plasma Vera Hrachova, Rudolf Hrach For the study of processes in chemically active plasmas a macroscopic kinetic approach is very useful. This technique is based on the system of chemical reactions between plasma species. If the number of species in the model is moderate, there exist various numerical techniques to solve the resulting set of differential equations. However, when the kinetic scheme of the model is complicated, the set of input chemical reactions must be reduced first in order to be able to solve the model. In the contribution one of these techniques is analysed. The method is based on the monitoring of the speed of every reaction during the kinetic calculation. The main goal is to preserve only the reactions influencing profoundly the resulting concentrations of main products. Developed reduction technique was applied to the analysis of active discharge in both oxygen and oxygen-argon mixtures. The input experimental data were obtained from the measurements in oxygen containing gas mixtures performed in our laboratory. In the final part of the contribution, the role of most important chemical reactions in the dependence on various plasma parameters is discussed. [Preview Abstract] |
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DTP.00132: Synthesis of liquid hydrocarbons from CH4 / CO2 in a atmospheric pressure Dielectric Barrier Discharge Giorgina Scarduelli, Graziano Guella, Daniela Ascenzi, Paolo Tosi The conversion of natural gas into more useful compounds, represents one of the present-day most attractive goals. Particularly relevant is the dry reforming process that realizes the simultaneous conversion of methane and carbon dioxide into syngas. Since CH4 and CO2 are both greenhouse gases, this process is of great environmental interest because it couples the advantages of an efficient transformation of natural gas into useful chemicals with the potential positive effects on global warming related to CO2 recycling. In a dielectric barrier discharge of CH4/CO2 at atmospheric pressure, in addition to syngas we have observed the formation of liquid chemicals. This is quite fascinating since the production of liquid fuels by CH4 and CO2 is a very attractive way to store and transport energy. The nature of the liquid has been investigated by using gas-chromatography, infrared spectroscopy and nuclear magnetic resonance spectroscopy. The non volatile component of the liquid products consists of a broad distribution of hydrocarbons, highly branched mainly by methyl groups. In addition we have observed the production of a minor amount (5{\%}) of oxygenated compounds (tertiary alcohols, ketones, esters and carboxylic acids). [Preview Abstract] |
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DTP.00133: Kinetic Model for Water Vapour Plasma of the UV Discharge Lamp Svetlana Avtaeva, Andriy General The discharge lamp on water vapour (WV) is an effective source of the OH$^{\ast}$ hydroxyl emission in the VUV and UV spectral range. The lamp represents a gas discharge tube from fused silica with inner diameter of 12 mm and gap length between electrodes disposed on the exterior tube surface of 20 cm. Pressure of WV was 150Pa. Pulse voltage 2-4 kV with frequency 2 - 10 kHz was applied to electrodes. In the emission spectrum intensive molecular bands of the OH$^{\ast}$ hydroxyl and atomic hydrogen lines are observed. The kinetic model based on solution of the kinetic equations for plasma species and an equation of the electron energy balance was used to calculate time dependencies of densities of WV plasma species. The calculations have shown that $E/N \quad \sim$ 190-200 Td is critical for WV plasma, with increase in $E/N$ there is a transition from electronegative to electropositive plasma. Electronegative plasma can be maintained only at presence of the preliminary ionization. Basic positive ions in WV plasma are H$_{3}$O$^{+}$ ions, basic negatively ions are OH$^{-}$ ions. Kinetic curves of the primary and secondary products of the plasma-chemical reactions differ, the secondary products, H$_{3}$O$^{+}$ excepted, occur later in a time and their densities are below in comparison with densities of the primary products. [Preview Abstract] |
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DTP.00134: Modelling and diagnostics of microwave H2/CH4/B2H6 plasma for boron-doped diamond deposition Nadira Derkaoui, Catherine Rond, Fabien Benedic, Alix Gicquel High power electronic industry needs high quality boron doped p-type semiconducting diamond that can be grown by microwave plasma operating in H2-B2H6-CH4 mixtures. The understanding of the processes involved in the plasma phase needs to develop a research based on plasma modelling as well as spectroscopic analysis, the goal in particular being identifying the boron containing species responsible for boron diamond doping. A thermochemical modelling for describing H2/CH4/B2H6 mixture discharges include a rather detailed chemical kinetics model for carbon and hydrogen containing species, and a simpler B-species model involving only BHx species (x=0-3). Calculations draw up spatial profiles of gas and electron temperatures, as well of different species densities. Furthermore, spatially resolved spectroscopic measurements are compared to calculations, allowing us to draw some conclusions on the key processes for production and loss of B containing species in gas phase a well as on the surface. [Preview Abstract] |
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DTP.00135: Dissociation channels of c-C$_{4}$F$_{8}$ to CF$_{2}$ radical in reactive plasma Toshio Hayashi, K. Ishikawa, M. Sekine, M. Hori, A. Kono, K. Suu c-C$_{4}$F$_{8}$ has been widely used in the area of dielectric etching in microelectronics fabrication processes. This trend brought about many experimental studies, in which CF$_{2}$ radical was a main component in c-C$_{4}$F$_{8}$ plasmas. This is the basis of the model of c-C$_{4}$F$_{8}$ dissociation to CF$_{2}$ through C$_{2}$F$_{4}$. Font et al. [1] considered comparatively the dissociation cross sections ($\sigma )$ of c-C$_{4}$F$_{8}$ obtained by many researchers and finally adopted the$\sigma $and rate coefficient estimated by Radtke et al. [2]. However, the main dissociation channels are yet unclear. Theoretical studies were reported for C$_{2}$F$_{4}$ excited states and electron interactions by Winstead and Mckoy [3], and Yoshida et al. [4]. The energy of the dissociation channel to CF$_{2}$ showed good agreement with the electron attachment value obtained by Goyette et al. [5]. However, they did not mention the excitation dissociation of neutral C$_{2}$F$_{4}$. Therefore, studies for dissociation reactions of c-C$_{4}$F$_{8}$ and C$_{2}$F$_{4}$ are limited and yet ambiguous. We calculated the dissociation channels of c-C$_{4}$F$_{8}$ and C$_{2}$F$_{4}$ using \textit{Gaussian 03} program, in order to clarify the main dissociation channels. [1] G. I. Font et al., J. Appl. Phys., 91 (2002) 3530. [2] M. T. Radtke et al., J. Vac. Sci. Technol., A21 (2003) 1038. [3] C. Winstead and V. Mckoy, J. Chem. Phys., 116 (2002) 1380. [4] K. Yoshida et al., J. Appl. Phys., 91 (2002) 2637. [5] A. N. Goyette et al., J. Chem. Phys., 114 (2001) 9832. [Preview Abstract] |
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DTP.00136: Gaseous Chemistry induced by a CCP RF discharge in a N2 CH4 mixture Nathalie Carrasco, Thomas Gautier, Arnaud Buch, Ella Sciamma-O'Brien, Cyril Szopa, Guy Cernogora The gaseous chemistry occurring in Titan's atmosphere is simulated with a CCP RF discharge in N2 - CH4 mixture. This experiment produces solid particles, which are assumed to be similar to Titan's aerosols. Here are presented results on the conversion of N2 and CH4 in more complex molecules. In situ Mass Spectrometry measurements show for example the production of hydrogen cyanide (HCN) and acetonitrile (CH3CN) in the gas phase. Gases produced in the plasma are also condensed in a trap cooled by liquid nitrogen downstream the plasma. It is shown that the amount of trapped gas increases with the percentage of CH4 injected in the plasma. Gas trapped are analysed by Gas Chromatography coupled to Mass Spectrometry. This analysis reveals hydrocarbons and a large amount of nitrile species (both way are detected until C5) in the gas phase. [Preview Abstract] |
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DTP.00137: Kinetics of pulsed DC discharge in N$_{2}$/O$_{2}$/N$_{x}$O$_{y}$ mixtures studied by quantum cascade laser absorption spectroscopy Daniil Marinov, Olivier Guaitella, Antoine Rousseau, Marko Huebner, Jurgen Roepcke In this work we study the kinetics of NO, NO$_{2}$ and N$_{2}$O in a pulsed low pressure ($\sim $1.3 mbar) DC discharge in N$_{2}$ and N$_{2}$/O$_{2}$ using \textit{in-situ} QCLAS absorption. Gas mixture of 1{\%} NO, NO$_{2}$ or N$_{2}$O in pure N$_{2}$ or air is exposed to a single plasma pulse (1-10ms, 25-150 mA). In pure N$_{2}$ plasma, NO and NO$_{2}$ are destroyed completely within few ms after the beginning of the pulse. In air plasma NO$_{2}$ is transformed into NO while NO concentration reaches a steady state. N$_{2}$O destruction in both cases is 10 times slower while N$_{2}$O in the discharge undergoes strong vibrational excitation. Vibrational relaxation of N$_{2}$O in the post-discharge occurs within several 10s of ms, indicating the presence V-V$^{\mbox{'}}$ transfer from N$_{2}$(v). In this way one can use N$_{2}$O as an indicator of the excitation of IR inactive N$_{2}$ and follow the relaxation of vibrational temperature of N$_{2}$. Laser absorption measurements are strongly influenced by the effect of gas heating, so measurements of T$_{g}$ using N$_{2}$ (2$^{+})$ emission are underway. [Preview Abstract] |
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DTP.00138: A State-to-State Model for High-Temperature N$_{2}$-CH$_{4}$ Plasmas Dzmitry Tsyhanou, M\'ario Lino da Silva, Vasco Guerra, Jorge Loureiro Since the landing of the space probe Huygens on the surface of Titan in 2005, a renewed interest exists for studies of N$_{2}$-CH$_{4}$ Plasmas. The atmosphere of Titan is composed from 98{\%} N$_{2}$-2{\%} CH$_{4}$ and therefore, chemical kinetics involving the N$_{2}$ molecule is predominant. In particular, the reaction CN+N $<->$ N$_{2}$+C is known to significantly affect the radiation of the CN Violet system, which is often considered as an important system for diagnostics of these plasmas. This reaction depends strongly from the concentration of atomic N, which in turn is correlated to the dissociation dynamics of N$_{2}$. In this work we show that the application of an improved multiquantum FHO model for dissociation, as opposed to the traditional first-order SSH approach, improves the predicted concentrations of the radiative states of CN. [Preview Abstract] |
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DTP.00139: SHEATHS |
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DTP.00140: Temporal Sheath Profiling Michael Barnes, Walter Gekelman, Patrick Pribyl, Brett Jacobs A Monte Carlo model of an rf plasma sheath was modified to allow sampling in rf phase as a function of height above the surface to which it derives from. The trajectories of argon ions were simulated in the presence of a temporal and spatially varying electric field including elastic and charge exchange collisions using the self scattering (or null collision) technique. The unique observation in this work lies in the transition regime between resistive and capacitive rf sheaths that occurs near the ion plasma frequency. During this transition, the average ion impact energy on the electrode surface significantly exceeds the dc sheath potential. This is also a scalable property as it can be shown to be a function of the sheath scaling parameter, the ratio of the ion transit time to the rf period. Temporal sheath profiling will illustrate the ion energy distribution functions at four phases as a function of sheath distance above the electrode surface. Several frequencies in the resistive, capacitive and transition regimes will be presented to enhance the mechanistic understanding whereby the average ion energy is able to considerably exceed the dc sheath potential. Experimental results from LIF measurements will validate the results of the numerical model. [Preview Abstract] |
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DTP.00141: On the study of ion mass in the collisionless magnetized plasma sheath Hossein Goudarzi, Alireza Niknam, Hamid Ghomi The ion dynamics that enter the collisionless plasma sheath have been investigated in the presence of an external magnetic field. In various masses of the ions and various directions of the magnetic field, the electron and ion density distribution, ion flow velocity have been calculated numerically by using a fluid model. In this work, the ion mass dependence of the characteristics of collisionless plasma sheath is examined. Moreover, the structure of plasma sheath in an oblique magnetic field is studied. It will be shown that, the lighter ions have more gyration then heavier ones. [Preview Abstract] |
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DTP.00142: Ion Temperature Effects on the Sheath Structure in the Magnetized Electronegative Plasma Mansour Khoramabadi, Hamid Ghomi The electronegative gases with high absorption ability of the electrons cause to create the so called electronegative plasmas. These plasmas have many applications in plasma processing. In order to control the processes, one has to know the plasma and plasma sheath structure. In material surface processing by magnetron, the presence of an oblique magnetic field modifies the plasma sheath structure. Some authors have investigated the magnetic field effect on the sheath structure of the electronegative plasma. Here we will evaluate the normal to wall component of magnetic field and the negative and positive ion temperature effects on the sheath parameters such as sheath width, particle densities, particle fluxes on the wall, space charge distribution, and wall floating potential in the magnetic electronegative plasmas. [Preview Abstract] |
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DTP.00143: Laser-induced fluorescence measurements deformation of neutrals distribution function in the vicinity of a surface Nicolas Claire, St\'ephane Mazouffre, Cyril Rebont, Fabrice Doveil Sheath region is of great interest for all plasma reactors and applications. Because this region is restricted to a few Debye lengths, it is impossible to make measurements with classical intrusive diagnostics like Langmuir probes. Laser Induced Fluorescence is a good way to access to the Argon neutral velocity distribution function in the vicinity of a conductive surface. We have made such measurements in a multipolar plasma device. Nevertheless, some artifacts can be present and must be taken into account. For example, the laser power absorption plays a significant role for high neutrals density. The non-elastic collision coefficient of neutrals with the surface is calculted with respect to the distance to the surface with a spatial definition of $0.1$mm. A neutral fluid acceleration with the distance to the surface is also observed which still remains to be explained. [Preview Abstract] |
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DTP.00144: Kinetic approach to the nonlinearity of RF modulated sheath M. Shihab, D. Ziegler, T. Mussenbrock, R.P. Brinkmann Plasma processing technology, especially plasma etching and plasma deposition, is very important to several large manufacturing industries. In this contribution, a kinetically self consistent approach is developed to describe the sheath and the presheath regions of RF driven low pressure gas discharges. The model allows for the calculation of ion trajectories within the sheath assuming one space coordinate and three velocity coordinates. The ions start deep in the bulk with a kinetic energy of several meV corresponding to the assumed gas temperature and with a phase uniformly distributed between $0$ and $2\pi$. The trajectories are calculated on a grid which is two dimensional in time and space. The set of all ion trajectories gives a representation of the response of the ions to the electric field. It can be shown that the ions respond to the time averaged electric field if the relation $\omega_{\rm RF}\gg\omega_{\rm pi}$ holds. In case of $\omega_{\rm RF}\leq\omega_{\rm pi}$ the ions start to be modulated by the instantaneous RF electric field. The effect on the ion energy distribution function will be discussed. [Preview Abstract] |
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DTP.00145: Control of ion bombardment energies in low-temperature plasmas Tim Baloniak, R\"{u}diger Reuter, Achim von Keudell Ion bombardment of the substrate is a significant parameter in plasma processing such as dry etching or thin film deposition. The energies of the ions are manipulated by external bias voltages which are applied to the substrate holder. It is desirable to posses a technique to tailor ion energy distributions to the needs of different applications. In this contribution, we report about the control of ion bombardment energies in low-temperature plasmas by means of arbitrary radio-frequency bias voltage waveforms. The substrate voltage is monitored and controlled in the frequency domain using fast Fourier transformation. Ion energy measurements are performed by a miniaturized floating retarding field analyzer. A full modulation of the ion energy distribution function is only obtained if sufficiently high sheath voltages are applied. If the applied sheath voltages become too low, the distribution functions are only partly determined by the bias waveforms and the system response becomes nonlinear. This nonlinear behavior is visible both in the electrode voltage and in the ion energy distributions. It is shown that a combined DC and RF biasing is required to gain full control over the ion bombardment of the substrate. [Preview Abstract] |
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DTP.00146: Collisional sheaths and resulting ion energy distributions at rf biased electrodes X. Victor Qin, A.E. Wendt In plasma processing of materials, ions are accelerated toward the substrate by a sheath electric field generated by an rf bias voltage applied to the substrate electrode. By tailoring the shape of the periodic voltage waveform, ion energy distributions (IEDs) dominated by a single peak at a specified energy can be created at low pressures. We use the capability to manipulate the substrate voltage waveform as a tool to systematically examine the effects of collisions within the sheath on the IED at a biased substrate. Single peaked IEDs were recorded with a retarding field energy analyzer (RFEA) for a range of argon pressures (10-80 mTorr), power input for plasma generation (300-900 W) and sheath voltages (20-300V). We characterize the collisionality of the resulting IEDs by the fraction of the ion flux in the narrow IED peak. This fraction is found to be a monotonically decreasing function of a collisionality parameter, defined as the ratio of sheath thickness to ion mean free path, over this range of parameters. Results will be compared with predictions based on a Fick's Law analysis, and implications for arbitrary shapes of bias voltage waveforms as well as processing applications will be discussed. [Preview Abstract] |
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DTP.00147: MODELING AND SIMULATION II |
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DTP.00148: A global model of a micro atmospheric pressure plasma jet Alexander Wollny, Torben Hemke, Dennis Ziegler, Ralf Peter Brinkmann, Thomas Mussenbrock Micro atmospheric pressure gas discharges offer new applications in biomedical treatment and material processing $[1]$. A global model is presented, which describes the bulk chemistry with wall looses and an electron temperature as a function of time. The chemical model is self-consistently coupled to an electrical model. The latter considers a capacitively coupled rf-discharge by means of a non-linear lumped circuit model which accounts for non-linear electron resonance heating $[2]$. In this contribution a geometry, based on the micro atmospheric pressure plasma jet is considered. This device is investigated by {{V. Schulz-von der Gathen}} and co-workers at Ruhr-University Bochum. Various parameter studies are performed and results are shown for Helium as a working gas.\\[0.5em] $[1]$ F. Iza, et al., Plasma Process. Polym., \textbf{5}, 322 (2008)\\ $[2]$ D. Ziegler, et al., Physics of Plasmas, \textbf{16}, 023503 (2009) [Preview Abstract] |
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DTP.00149: Dependence of ozone generation on the surface condition of dielectrics Go Takahashi Since 1990s, it has been reported that ozone concentration becomes almost zero while ozone is generating using dielectric barrier discharge, So call ozone-zero phenomena. But this phenomena has not been cleared yet. In this paper, for the first step to explain ozone-zero phenomena, the modeling of AC atmospheric pressure dielectric barrier discharges in oxygen has been done. Simulated region is 0.2cm (X:gap length) x 0.6cm (Y:lateral direction), and electrodes are covered with 0.05cm dielectric barriers. And the electrode at x=0.0cm is grounded and applied voltage Va is applied to the other electrode ( f=200kHz, 7.5kV). Oxygen gas is considered and its pressure is 760Torr. The continuity equations for electrons, O+, O2+, O- , O2- and , O3- ions, electron energy equation and 60 rate equations are solved with Poisson's equation. In this simulation, a few streamer discharges are observed. In the present simulation, the ozone is mainly generated in the vicinity of dielectrics. So the surface condition of dielectrics should be one of the important parameters. Secondary electron emission coefficient dependence has been also examined. Higher secondary electron emission coefficient condition, gas temperature and atomic oxygen density are obtained higher, and the ozone is obtained not only from streamers but off the streamer too. [Preview Abstract] |
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DTP.00150: Simulation of Nanosecond Repetitively Pulsed Discharges in Air for Plasma Assisted Combustion Fabien Tholin, Zdenek Bonaventura, Jaroslav Jansky, Anne Bourdon Recently, the potential of nanosecond repetitively pulsed discharges for plasma assisted combustion has been demonstrated experimentally. However, synergy effects of successive pulses are not clearly understood so far. In this work, 1D and 2D simulations of point to point discharges have been conducted in air at atmospheric pressure to study these synergy effects. In particular, we have studied the influence of electrode geometry, pulse frequency and applied voltage on the successive discharges. In 1D simulations, the discharge is assumed to be homogeneous on the discharge axis and then 1D radial simulations are used to simulate a significant number of pulses to study the conditions to obtain a discharge in steady-state. 2D calculations present some challenging numerical problems, due to the very different temporal and spatial scales involved in the discharge and post-discharge phases. Then, we have carried out 2D simulations of two pulses at high frequency. A simple chemistry model is taken into account in the simulations to compute the optical emissions of the discharge and the production of excited species and atoms as atomic oxygen, a key species for plasma assisted combustion. [Preview Abstract] |
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DTP.00151: Modeling the sheath in a radio frequency driven micro-plasmajet at atmospheric pressure Torben Hemke, Ralf Peter Brinkmann, Thomas Mussenbrock Among the number of different microplasma sources developed over the last years there is the atmospheric pressure plasma jet, the so called APPJ. The types of APPJs differ in geometries, the driving frequency and the chemistry. The $\mu$-APPJ invented by Schulz-von der Gathen and co-workers can be regarded as a downscaled symmetric CCP, driven at 13.56 MHz. Although microplasmas at atmospheric pressure became the focal point of both, experimental and theoretical investigation recently there is still a lack of understanding the physics of the discharges. In this paper we concentrate on the RF modulated sheath of the $\mu$-APPJ. Based on a scale analysis in time and space we discuss resulting assumptions concerning the fluid equations for electrons and ions. We develop an approximation of the electric field in the sheath and solve the equation of motion for the ions. We make use of plasma parameters -- as the plasma density and the electron temperature -- derived by fluid simulations as operating parameters of the sheath. Finally, we present the density profiles of the electrons and ions depending on these discharge parameters. [Preview Abstract] |
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DTP.00152: Determination of Reduced Electric Field in Streamer Discharges in Air at Atmospheric Pressure from Space and Time Integrated Optical Emissions of Excited Nitrogen Molecules and Their Ions Anne Bourdon, Zdenek Bonaventura, Sebastien Celestin, Victor Pasko The ratio of excitation frequencies of $N_2$C and $N_2^{+}$B is a sensitive function of electric field and is used in experiments for determination of total electric field in the discharge. Usually a quasi-steady-state approximation that assumes the balance between the rate of population of excited levels and emission and quenching is used to interpret space and time integrated experimental data. However, for streamer discharges in air at atmospheric pressure the quasi-steady-state conditions are not fulfilled. This brings some uncertainty in the interpretation of electric field measurements. It is generally believed that estimated values of the electric field are close to the maximum electric field in the streamer heads due to the high emission intensity of streamer heads. In this contribution we present a numerical simulation of optical emissions of a streamer discharge in air at atmospheric pressure and we calculate a correction factor to derive easily the real electric field from the field derived assuming quasi-steady-state of integrated optical emissions usually obtained in experiments. [Preview Abstract] |
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DTP.00153: Modeling of Argon Plasma Afterglow With Large Dust Density Ilija Stefanovic, Igor Denysenko, Brankica Sikimic, J\"org Winter, Nikolay Azarenkov A spatially-averaged model for argon plasma afterglow with nano-sized particles is presented. The model consists of balance equations for electrons, ions and argon metastable and resonance state atoms, equation for the dust particle charge and power balance equation. The dust charge density is assumed larger than the electron density. The calculated densities in the afterglow are in a good qualitative agreement with those measured in the experiment [1]. The metastable density in the dusty plasma is essentially larger than the density in the dust-free plasma. The metastable density in dusty plasma increases due to enhancement of the electron temperature comparing with the dust-free plasma. In the dust-free as well as dusty plasma afterglows, the argon metastable atoms are lost from the discharge mainly due to their diffusion to the electrodes. In the dusty case, the diffusion loss dominates over the loss in metastable-dust collisions [1]. The electron temperature decreases faster in the dusty plasma afterglow than that in the dust-free plasma. [1] I. Stefanovic, N. Sadeghi, and J. Winter, \textit{J. Phys. D: Appl. Phys.} \textbf{43,} 152003 (2010). [Preview Abstract] |
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DTP.00154: Modeling of electron transport parameters in methane and air mixture gas Haruaki Akashi, Koichi Sasaki Recently, plasma-assisted combustion [1] has been focused on due to achieving more efficient way of fossil fuels combustion, reducing pollutants and so on. Shinohara et al [2] has reported that the flame length of methane and air premixed burner shortened by irradiating microwave power without increase of gas temperature. So it is suggested that this phenomena may result by the electron heating of non-equilibrium plasma. To clarify this phenomena, electron behavior under microwave power should be examined. For the first step, electron Monte Carlo simulation in methane and air mixture gas has been done. The electrons swarm parameters are sampled and electron energy distribution function(eedf) is also determined. The transport parameters under microwave power in atmospheric pressure have been reached to equilibrium condition very fast. It is obvious that the electrons are accelerated by the high frequency electric field, and most of the electrons stay in low energy region. But there are a few high energy electrons($>$15eV). These electrons might be the key for the plasma-assisted combustion.\\[4pt] [1] V.Bychkov et al. IEEE Trans. Plasma Sci.,37,12 2280-2285(2009)\\[0pt] [2] K. Shinohara et al, J. Phys. D:Appl. Phys., 42, 182008 (1-7) (2009) [Preview Abstract] |
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DTP.00155: Kinetic theory approach of the wave instabilities of collisionless plasma Sanaz E. Namini, Hadi Zakeri Khatir, Mahmood Ghorannevis, Mojtaba (Farzin) Aghamir In this paper the wave properties and instability in magnetized and collisionless plasma by taking self-electric and self-magnetic fields are considered. The equilibrium particle distribution is assumed to be Maxwellian for nondegenerate plasma. The dielectric tensor for the collisionless plasma is obtained on the basis of Vlasov equation. The result of this study is compared with the finding of the previous investigation in which wave properties and instability in magnetized and collisionless plasma in the fluid approximation. Also we have investigated the effect of self-magnetic field in wave properties in magnetized and collisionless plasma. [Preview Abstract] |
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DTP.00156: New Methodology for Modeling Quantum Well Infrared Photodetectors Mohamed El Tokhy, Imbaby Mahmoud, Hussien Konber The paper presents a method for modeling quantum well infrared photodetectors (QWIPs). Their block diagram models are devised. VisSim environment is used to achieve this purpose. Block diagram simulation results are validated against published work and full agreements are obtained. Using of graphical user interface allows a quick experimentation with alternative values of performance parameters such as number of quantum well, temperature, and spacing between the wells of QWIPs. Moreover, implicit solutions of dynamic equations governing QWIPs provide exact handling of the device performance. Several performance parameters are tuned to enhance the performance of these detectors through the presented methodology. [Preview Abstract] |
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DTP.00157: Numerical investigation of fs pulsed laser interaction with an underdense plasma Fatemeh Jokar, Esmaeil Eslami In this paper the wakefield generation due to propagation of a Gaussian laser pulse at high intently through a plasma has been analyzed. A differential equation governing the wakefield potential is derived analytically and is solved numerically for the different laser-plasma conditions. On the basis of our numerical studies we observed that the effects of the laser intensity and pulse duration are to increase the strength of the wakefield. This means the higher intensity pulses will excite the larger density perturbation in the plasma. However, the amplitude of wakefield get decrease at larger beam waist and higher laser frequency. [Preview Abstract] |
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DTP.00158: Using a non-diffusive hybrid scheme for simulation of filamentary discharges Sergey Pancheshnyi, Ilia Popov, Andrey Starikovskiy A pulsed discharge in gas propagates typically in form of moving through the gas avalanches or streamers. Direct fluid modeling of these phenomena demonstrated a good success during last decades mainly due to relative simplicity of realization and rather low computational requirements. The principal limit of fluid approach validity consists in the assumption of continuity of media, i.e. in a continuous distribution of species involved in modeling. This assumption is usually valid inside the avalanche head or inside the streamer channel due to relatively high density of species while it often fails in regions at a distance from the front where the density of species (electrons, mainly) can be below than that is required for fluid approximation. In the present work, a hybrid model based on conventional fluid model coupled to a simplified Random Choice Method is proposed. This approach allows multi-dimensional simulation of avalanches and streamers treating individual particle in non-fluid regions that is of interest for investigation of streamer inception and branching phenomena. In this work, a comparison of the conventional fluid and the developed hybrid approaches is presented for avalanche to streamer transition in plain-plain geometry and for positive streamer development in rod-plain geometry. [Preview Abstract] |
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DTP.00159: Feather-like structures in positive streamers Gideon Wormeester, Sander Nijdam, Ute Ebert In experiments positive streamers can have a feather-like structure, with small hairs connected to the main streamer channel. These feathers were observed in pure nitrogen (with impurities of 1ppm oxygen or less) but not in air. Based on results of numerical simulations, we provide a theoretical explanation for the emergence of these hairs as well as why the hairs are visible in nitrogen, but not in air. [Preview Abstract] |
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DTP.00160: Stability of current transfer to cathodes of DC glow discharges M.J. Faria, P.G.C. Almeida, M.S. Benilov, V.V. Mikhailenko Multiple solutions in the theory of DC glow discharges have been computed recently and are presumably associated with modes with different spot patterns observed in DC glow microdischarges. In this work, stability of the axially symmetric steady-state modes against axially symmetric and 3D perturbations is analyzed numerically. Stability of the 1D mode at very low currents against 1D perturbations is investigated analytically. Simulations are based on the simplest self-consistent model, which accounts for a single ion species and employs the drift--diffusion approximation. The non-stationary term in the electron conservation equation affects the calculated spectrum very weakly; an indication that the perturbations develop on a time scale governed by drift of ions. Results on stability are given for the fundamental mode (the one that exists at all current range) and for ten further 2D modes. [Preview Abstract] |
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DTP.00161: A Functional Analytic Description of the Multipole Resonance Probe Jens Oberrath, Martin Lapke, Thomas Mussenbrock, Ralf Peter Brinkmann The plasma resonance spectroscopy is a well established plasma diagnostic method and realized in several designs. Based on Hilbert-space methods it is possible to derive a general mathematical solution for arbitrary diagnostic designs. An analysis shows the main feature of this family of methods, it is the ability of the system to resonate. An interpretation in terms of a lumped element circuit reveals the main weakness of certain realizations. A complicated resonance structure that impedes a clear and simple analysis of the measured spectrum is observed. The multipole resonance probe (MRP) is presented as an idea to overcome this problem in terms of a high geometrical and electrical symmetry [1]. To determine its resonance structure an analytic expression for the probe response is needed. We derive a solution to this special diagnostic design based on the functional analytic description. \\[4pt] [1] M. Lapke et al., Appl. Phys. Lett. {\bf 93}, 051502 (2008) [Preview Abstract] |
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DTP.00162: Highlighting of the discharge instabilities in high-pressure plasmas for excimer lasers Zahir Harrache, Driss Amir-Aid, Ahmed Belasri, Maria Dolores Calzada The XeCl laser has a number of important applications related to its high power and the fact that it produces UV radiation ($\lambda$=308 nm). Despite this remarkable properties, XeCl laser suffers from some limitations; when sustained by high-pressure discharges, it is subject to instabilities. Instabilities are more likely to occur at high pressure because (i)- streamers can appear near each electrode and lead to arcing during the formation of the plasma [1], (ii) once the plasma is formed, chemical kinetic instabilities can lead to plasma filamentation due to volume instability known as halogen depletion instability [2]. The experimental investigation of XeCl laser has proved that the instabilities occur before the end of laser emission. In this work, we discuss the streamer and the halogen depletion instabilities in high-pressure discharges. The obtained results show clearly that the plasma uniformity and the power deposition in the medium are strongly sensitive to volume instabilities. \\[4pt] [1] A. Belasri et al., Phys. Plasmas 10, 4874 (2003).\\[0pt] [2] Z. Harrache et al., Europhys. Lett. 66, No. 1, 76 (2004). [Preview Abstract] |
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DTP.00163: A New Simulation Approach to Control Plasma Uniformities Akihiro Tsuji, Yasuyoshi Yasaka Plasma simulations have never been used for a device control in the field although they have been useful to understand physical phenomena in global and local regions. It is because the existing plasma simulations cannot calculate input parameters such as the distributions of power and gas from output parameters such as the distribution of the electron density $n_{e}$. To build a new control method with a simulation system, the framework of the existing simulation should be reconstructed as the inverse problem. A new simulation system is being developed as the first step. It consists of a power feeding part, a fluid simulation part and a transfer function part. The main points of the simulation system are to introduce the power coupling coefficient $a_{p}$ which gives information of the device setting and to add some functions to inversely calculate the $a_{p}$ from the distribution of the plasma parameters. In the verification of the two-dimensional model, it is shown that the root-mean-square error between the distribution of $n_{e}$ calculated by the simulation and the target distribution is 1.8 {\%}. The some input parameters can be inversely calculated from the output parameter by using the same procedure. Therefore, this approach can be one of the solutions to control plasma uniformities. [Preview Abstract] |
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DTP.00164: Model for the investigation of chemical non-equilibrium in a silicon purification process by thermal plasma with validation by spectroscopic measurements Mickael Majchrzak, Jochen Altenberend, Yves Delannoy, Guy Chichignoud We have developed a two-dimensional Fluent based model at chemcial non-equilibrium of an Ar-O$_{2}$-H$_{2}$ plasma. For this model we have calculated the transport properties of the species using the Chapman-Enskog method. Eleven different species were introduced together with 12 reversible chemical reactions. The aim of this work is to give the concentration of the different species which will be present and will react with impurities at the interface between the plasma and the silicon bath. We have developed simultaneously a method for the spatially resolved measurement of the temperature and the concentration of atomic oxygen and atomic hydrogen. The method is based on atomic emission spectroscopy with the assumption of local thermal equilibrium which is validated by the results. At the high temperature gradient between the plasma and the silicon quantitative measurements are not possible. We have also developed a qualitative method for the velocity measurement using the cross correlation between different pixels of a high speed video. [Preview Abstract] |
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DTP.00165: Numerical modeling of distribution of conducting and nonconducting matter in the discharge channel upon electrical wire explosion Svetlana Tkachenko, Dmitri Beznosov, Alexey Boldarev, Vladimir Gasilov, Olga Olhovskaya Distribution of matter in the discharge channel formed upon a nanosecond electrical explosion of micron wire was studied. The simulations of electrical wire explosion were performed by means of Lagrangian--Eulerian MHD code based on Braginskii two--temperature model. The radiation energy transport was simulated in multigroup spectral approximation with the use of diffusion model. Heat-- and electro-- conductivity anisotropy in magnetic field is taken into account. The code allows utilization of data tables for thermal and optical matter properties. We have investigated the influence of initial data (in particularly ``cold start'' simulation) and the radiation energy transfer upon the evolution of matter parameters and current density distribution in the discharge channel. Several variants with differing amounts of spectral groups were evaluated. The numerical results are compared with experimental data. [Preview Abstract] |
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DTP.00166: DIAGNOSTICS |
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DTP.00167: Development of a Collective Thomson Scattering System for Diagnostics of Laser Produced EUV Plasmas Kentaro Tomita, Kota Ohara, Kazuki Nakayama, Kiichiro Uchino After the 32 nm half-pitch technology node, extreme ultraviolet (EUV) lights are going to be used for semiconductor lithography. In order to diagnose laser produced plasmas for EUV light sources, a collective laser Thomson scattering system has been developed. Clear ion term spectra were observed from laser produced carbon plasmas and spatiotemporal evolutions of electron density, electron temperature and averaged ionic charge in these plasmas were successfully measured. [Preview Abstract] |
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DTP.00168: Diode laser atomic absorption and laser Induced fluorescence of Argon in a TCP plasma used for thin film sputter deposition Titaina Gibert, Christine Charles, Amael Caillard, Pascal Brault, Martin Cormier A mobile laser platform is tested on a Transformer Coupled Plasma (TCP) radiofrequency (13.56 MHz) plasma of Argon used to sputter deposit metallic clusters or thin films on hydrogen fuel cell electrodes. The aim is to measure atomic absorption and laser induced fluorescence for the investigation of plasma parameters such as density and temperature. A tunable Toptika Laser diode is tuned on the 1s$^{2}$ to 2p$^{2}$ resonance line of atomic argon at the vacuum wavelength of 826,680nm. The laser beam power is measured after crossing about 20 cm of plasma giving the wavelength dependent absorption profile. The absorption is averaged on the whole path of the encountered plasma. The evolution of the absorption profiles with pressure and radiofrequency power is presented. A preliminary investigation of the fluorescence emission signal at right angle at the same wavelength is carried out. Future work on the investigation of less conventional lines (e.g. Platinum, Palladium) using this mobile platform will be discussed. [Preview Abstract] |
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DTP.00169: Application of a Fizeau Interferometer to Fast High Resolution Measurements of the Spectral Line Shapes of Plasma Species Ian Falconer, Ondrej Nov\'ak, Roberto Sangin\'es, David McKenzie, Marcela Bilek An interferometer has been developed for fast, time resolved, high resolution measurements of the shape of spectral lines emitted by ionized and neutral atoms in pulsed plasmas. This system provides a valuable diagnostic tool for measuring the pressure broadening and especially the Doppler broadening -- and shift -- for emission lines from plasma species. As the primary dispersing element is an interferometer, this instrument has a higher resolution combined with a higher optical throughput than a grating spectrometer of comparable physical dimensions. This instrument is a combination of a Fizeau interferometer, an intensified CCD camera and a grating spectrometer, and has been used to obtain time-resolved spectral line shapes for species emitted from the cathode spots of a high-current cathodic arcs. We will discuss the factors affecting the spectral resolution and optical throughput of this instrument, give examples of spectral line shapes recorded by it, and discuss its calibration to determine the shift of the centre of the line profile. [Preview Abstract] |
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DTP.00170: Real-Time Endpoint Detection for SiO$_{2}$ Film Plasma Etching Using Impedance Analysis with Modified Principal Component Analysis Haegyu Jang, Daekyoung Kim, Kyounghoon Han, Heeyeop Chae Plasma etching is used in various semiconductor processing steps. Commonly, optical emission spectroscopy is widely used for real-time endpoint detection for plasma etching, In this research, the object is to investigate the suitability of using impedance analysis for real-time endpoint detection. The endpoint were determined by impedance measurement and an equivalent circuit model. Especially, third harmonic changed sharply at the endpoint when SiO$_{2}$ film on Si wafer is etched by CF$_{4}$ plasma on capacitive coupled plasma. And modified principal component analysis (PCA) is applied to them for increasing sensitivity. For verifying this method, detected endpoint from impedance analysis is compared with optical emission spectroscopy and ion current probe, From impedance data, we tried to analyze physical properties of plasma, and real-time endpoint detection can be achieved. This method can be applied to the other fault detections. [Preview Abstract] |
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DTP.00171: Characterization of Nanosecond Repetitively Pulsed Discharges by Infra-Red Laser Absorption Spectroscopy Julien Jarrige, Diane L. Rusterholtz, Gabi D. Stancu, Deanna A. Lacoste, Christophe O. Laux Nanosecond repetitively pulsed discharges (NRPD) have received great attention for their potential in new industrial applications such as plasma-assisted combustion. It has been shown that NRPD can stabilize and improve the efficiency of turbulent lean flames. In this work, we present time-resolved in-situ laser absorption spectroscopy (LAS) measurements in a pin-to-pin reactor containing methane-air mixtures. NRPD (with a frequency in the range 1-30 kHz) are operated in the spark regime. A Quantum Cascade Laser and a tunable Differential Frequency Generator system are used to perform infra-red absorption with a time resolution of a few tens of nanoseconds. The production of nitrogen oxides and the decomposition of methane are monitored during a single pulse. The gas temperature increase is determined by comparing experimental absorption spectra with HITRAN simulations. [Preview Abstract] |
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DTP.00172: In-Situ Monitoring of Film Thickness and Chamber Condition of Dielectric PECVD Process with Impedance Analysis Daekyoung Kim, Haegyu Jang, Heeyeop Chae In semiconductor production, PECVD with good reproducibility for a wide variety of film thickness is required. As devise size is smaller, an accurate control of film thickness real time control of film thickness is needed. Generally, film thickness is controlled by time. But time control method doesn't know real time thickness of film. Therefore, we investigated real time monitoring of film thickness by using impedance monitoring. The effects investigated in this work include dielectric constants of films, thickness of films in chamber wall, plasma densities, and ion energies on impedance by equivalent circuit models. In the model plasma was modeled with resistors and capacitors. The dielectric film and chamber wall were deposited by PECVD with tetraethylorthosilicate (TEOS-Si (OC2H5)4) and O2 at 1.5torr and 473K. As parameter of chamber wall put in electric circuit, film thickness was separated from impedance of chamber. [Preview Abstract] |
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DTP.00173: Plasma parameter measurements of Ar+H2+C7H8 plasmas in H-assisted plasma CVD reactor Takuya Nomura, Tatsuya Urakawa, Yuki Korenaga, Daisuke Yamashita, Hidefumi Matsuzaki, Kazunori Koga, Masaharu Shiratani, Yuichi Setsuhara, Makoto Sekine, Masaru Hori In recent years, hard carbon films attract much attention due to their superior film properties [1]. Deposition profile of the films on trench substrates is one of the concerns to realize coatings on such substrates. We have succeeded in controlling deposition profile of Cu on trench substrates, and have realized anisotropic deposition profiles using a H-assisted plasma CVD method [2-4]. This method provided independent control of dissociation of deposition material and generation of H atoms [2-4]. We are applying the method to control deposition profile of plasma CVD carbon films. In this presentation, we report Ha emission intensity and electron density in the CVD plasmas to identify conditions of a high H flux on film surfaces, because H atoms modify deposition profile.\\[4pt] [1] J. Robertson, Materials Sci. and Engineering R, 37 129-281 (2004).\\[0pt] [2] K. Takenaka, et al., J. Vac. Sci. Technol. A, 22 (2004) 1903.\\[0pt] [3] K. Takenaka, et al., Pure and Appl. Chem., 77 (2005) 391.\\[0pt] [4] J. Umetsu, et al., Surf. Coat. Technol., 202, 5659 (208). [Preview Abstract] |
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DTP.00174: Measurement of multiphoton ionization efficiency for reliable laser Thomson scattering diagnostics Yukitaka Matsuda, Mitsutoshi Aramaki, Akihiro Kono In laser Thomson scattering diagnostics for low temperature plasmas, the laser energy density in the focal region is very high. The gases in plasma may be ionized via multiphoton ionization process and we should be careful about the process. To clarify the effect of multiphoton ionization quantitatively in Thomson scattering diagnostics, we are carrying out systematic measurements of multiphoton ionization efficiency for various gases. A frequency-doubled Nd:YAG laser beam (532nm, 150$\sim $240 mJ) was focused with a spherical lens (f=400 mm) into the space between dc-biased parallel plates and the current induced via multiphoton ionization of ground-state Xe, Kr, Ar, N$_{2}$ and O$_{2}$ atoms was recorded. The laser-beam profile in the focal region was also measured using a knife edge to obtain the absolute ionization efficiency. The results indicates that multiphoton ionization efficiency for Xe and O$_{2}$ is relatively large and may affect Thomson scattering diagnostics for low-pressure conditions; for Xe, the electron density produced via multiphoton ionization could reach 10$^{12}$cm$^{-3}$ at a few mTorr gas pressure. [Preview Abstract] |
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DTP.00175: On the Perturbation of Plasma by Emissive Probes Codrina Ionita, Milan Cercek, Boris Fonda, Tomaz Gyergyek, Gregor Filipic, Jernej Kovacic, Roman Schrittwieser Often it is claimed that the floating potential of emissive probes remains below the plasma potential and that they strongly perturb the plasma. Obviously, for negative bias with respect to the plasma potential the full emission current flows to the plasma which can lead to strong perturbations. In a magnetized plasma we even saw additional ionization when the probe was biased below the ionization potential of the background gas. However, under ideal conditions the floating potential of a probe with well-adjusted emission was found to be almost equal to the plasma potential. Moreover, in this case no perturbation of the plasma by the emissive probe is seen. This was tested by a small cylindrical cold probe on the same magnetic field line as the emissive probe further upstream. [Preview Abstract] |
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DTP.00176: Electron density measurements in technological plasmas using the Multipole Resonance Probe T. Styrnoll, M. Lapke, C. Schulz, R. Storch, J. Oberath, T. Musch, I. Rolfes, P. Awakowicz, T. Mussenbrock, R.P. Brinkmann This paper deals with the realization of the `Multipole Resonance Probe (MRP)' [1], and shows its applicability for the measurement of the electron density in technological plasmas. The probe consists of two metallic hemispheres, mounted on a thin holder that serves as balancing unit for the unbalanced signal from the network analyzer. The absorption spectrum is measured by a network analyzer in the range of approximately 100 MHz to 10 GHz. It shows characteristic resonances from which plasma parameters like the electron density can be derived. Due to the spherical symmetry of the probe we are able to obtain algebraic expressions for the resonance frequencies and thus evaluation schemes for the electron density. We study the power and pressure influence of the frequency behavior and show comparisons of Langmuir probe data with the results of the MRP. It shows an excellent agreement and confirms the applicability of the MRP in the challenging environment of technological plasmas. Supported by BMBF (Pluto: Plasma and optical technologies).\\[4pt] [1] M. Lapke et al., Appl. Phys. Lett. {\bf 93}, 051502 (2008) [Preview Abstract] |
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DTP.00177: Diagnostics of Pulsed Powered Microplasma Discharge in N$_{2}$ by Emission Spectroscopy Marius Blajan, Kazuo Shimizu The aim of this paper is to analyze the emission spectrum of the microplasma, which is atmospheric pressure nonthermal plasma, generated by a pulse power supply in nitrogen gas. Microplasma discharge in N$_{2,}$ generated at relatively low discharge voltages around 1 kV, was investigated with an ICCD camera, a spectrometer and a photomultiplier tube. A Marx Generator with MOSFET switches was developed and used as a pulse power supply. It has a negative output up to -- 2 kV, rise time 100 ns, pulse width 1 us. Discharge current was confirmed at rising point of discharge voltage. About -2.5 A was obtained at -1.5 kV for negative pulse. Emission spectrum showed N$_{2}$ Second Positive System band (N$_{2}$ SPS), N$_{2}^{+ }$First Negative System Band (N$_{2}^{+}$ FNS) and N$_{2}$ First Positive System band (N$_{2}$ FPS). Lifetime emission signal of N$_{2}$ SPS peak of 337.1 was about 60 ns. Temperature calculation showed that microplasma is non equilibrium plasma due to the inequality Te$>$Tvib$>$Trot. [Preview Abstract] |
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DTP.00178: Investigations on metastable helium atoms in a capacitively coupled plasma in a mixture of He, Ar and CF4 Wen-Cong Chen, Dirk Luggenh\"olscher, Jiang Li, Feng Xie, Fei-Xiang Liu, Xi-Ming Zhu, Yi-Kang Pu Spatially resolved density and temperature of helium metastable state 2$^{3}$S$_{1}$ in a parallel plate capacitively coupled plasma in He/Ar/CF4 are measured by laser absorption spectroscopy using a 1083nm distributed feed-back semiconductor laser. Because of lower electron density and possible quenching processes in the sheath, the profile of metastables density shows that the density has a more pronounced fall-off in the sheath than in the bulk plasma. It is also found that the metastables temperature near the powered electrode is higher than that near the grounded one. Other diagnostics are also used to determine related plasma parameters. The electron density is obtained by an emission line-ratio method, and the gas temperature is estimated from rotational spectra of nitrogen molecules. Ion energy distributions, ion fluxes and radical densities are measured by an energy-resolved mass spectrometer. The behavior of metastables helium atoms and the possible kinetic processes will be discussed in this work. [Preview Abstract] |
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DTP.00179: Interferometry phase and amplitude shift fields deep processing for femtosecond laser ablation plasma plume characterization K. Yu. Kuvaev, R.R. Khaziev, E. Yu. Loktionov, Yu. Yu. Protasov Interferometry is a powerful tool for plasma parameters characterization, but its both hardware realization and obtained data processing are rather complicated. For femtosecond laser ablation plasma investigation it is practically the only suitable quantitative method due to its high sensitivity, spatial and temporal resolution. Plasma induced phase shift fields are usually transformed to electron number density fields using Abel transformation for axis symmetry flows. We present the results of laser ($\lambda \sim $266, 400, 800 nm, $\tau _{0.5}\sim $45-70 fs) plasma induced phase and amplitude shift spatio-temporal fields to evaluate such plasma parameters as refraction and extinction coefficients, electron (n$_{e} \quad \sim $ 10$^{16}$-10$^{19}$ cm$^{-3})$ and lattice (n$_{l}\sim $10$^{16}$-10$^{19}$ cm$^{-3})$ number densities, temperature (T$\sim $0,05--5 eV), pressure (p$\sim $10$^{3}$--10$^{7}$ Pa), velocity (v$\sim $0,1--25 km/s), momentum (I$_{m}\sim $10$^{-10}$--10$^{-8}$ N$\cdot $s) and momentum coupling coefficient (C$_{m}\sim $10$^{-5}$--10$^{-3}$ N$\cdot $s). [Preview Abstract] |
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DTP.00180: Measurement of the electron energy distribution function and E-H mode transition in inductively coupled plasma with various gases Jung-Kyu Lee, Hyo-Chang Lee, Chin-Wook Chung A study of the E-H mode transition was performed in Ar, O2, N2, and mixture gas inductively coupled plasma (ICP) from the measurement of the electron energy distribution function (EEDF). Change of the EEDF and characteristic of the discharge on the E-H mode transition were discussed. At each E mode, the measured EEDFs had different shapes depending on the gas type and pressure, while the EEDFs evolved into Maxwellian distribution with the E-H transition due to electron-electron collisions. This study was also focused on the transition ICP power from E mode to H mode. As the ICP power increased in Ar discharge, the transition ICP power had minimum value at a particular pressure, while the transition ICP power was gradually increased with gas pressures in molecule gas discharge. The transition ICP power with gas mixing ratios was also studied in Ar/O2/N2 mixture gas discharge. [Preview Abstract] |
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DTP.00181: Electrical characterisation of an industrial capacitively coupled plasma processing chamber for actinometry studies in Ar/O$_{2}$/SF$_{6}$ gas mixtures with global model comparisons Chanel Hayden, Evgueni Gudimenko, Stephen Daniels, David Gahan Actinometry is an optical emission technique for estimating concentrations of radical particle densities in plasmas. This technique is based on normalised emission intensity of a radical to that of an inert gas giving a ratio of concentrations. To determine radical concentrations, electrical characteristics such as electron density, n$_{e}$, electron temperature, T$_{e}$ and electron energy distribution function (EEDF) must be known. A number of electrical diagnostics are used to measure these parameters which are subsequently used in calculation of radical particle densities of a given reactive gas. An investigation of the pressure and power effect on the electron and ion energy distribution functions (IEDF) was carried out for a number of discharge gases including Ar, O$_{2}$ and SF$_{6}$ in a capacitively coupled plasma reactor. A hairpin probe is used to measure the electron density in the centre of the discharge and a Langmuir probe determines the EEDF. In addition, the EEDF and IEDF at the surface of the electrode are investigated using a retarding field energy analyser (RFEA) for comparison. The data is compared with a global model of the discharge and the results presented. [Preview Abstract] |
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DTP.00182: ABSTRACT WITHDRAWN |
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DTP.00183: Development of an embedded two-dimensional probe for diagnostic of the spatial uniformity in plasmas Jinyong Kim, Ik-Jin Choi, Chin-Wook Chung The spatial measurement of plasma parameters on the wafer is important in the processing plasmas. We developed the wafer-type probe arrays to measure the electron temperature, the plasma density, and the ion flux to the wafer two-dimensionally. The double Langmuir probe with harmonic method was used for this apparatus. The plasma parameters are determined by comparing amplitudes of the 1st and 3rd harmonic currents. Because all measurement circuits and calculation module are embedded, it can be equipped inside the plasma chambers without external controllers. The experimental results were in good agreement with those measured by conventional two-dimensional probes under various processing conditions. This method will be able to contribute to plasma uniformity monitoring in real-time, by measuring the spatial distribution of the plasma parameters in the plasma process. [Preview Abstract] |
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DTP.00184: On the possibility of measuring the optical spectrum of light sources by means of a rotating mirror Luis Bilbao, Luis Bernal We report the operation of an apparatus for measuring optical Doppler shift based on a rotating mirror, and its preliminary application to the measurement of the spectrum of some light sources. Optical Doppler shift experiments are not a simple task since light source cannot usually be moved in a sufficiently smooth and uniform manner to keep the level of noise well below of that of the signal. Using a rotating mirror it is possible to overcome many of the noise generating effects. The beam from a light source passes a beam splitter that separates the beam, part is reflected from the advancing side of a rotating mirror; part is reflected from the receding part of a rotating mirror. After reflection the beams are recombined using a beam splitter and measured by a fast photodiode. Beat between the two beams produces fluctuations in the light intensity at the photodetector [1]. Since the spectrum of the measured interference signal is proportional to the spectrum of the original source, then it is possible to use this experiment as an online scanner of the light spectrum of the source. We describe the preliminary results, and discuss the detection limits and the possibility of using the apparatus for plasma diagnostic. \\[4pt] [1] L. Bernal and L. Bilbao, Am. J. Phys. 75, 216-219 (2007). [Preview Abstract] |
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DTP.00185: Interpreting Broadband Infrared Spectra with Variable Gas Temperatures in Fluorocarbon Plasmas Caleb Nelson, Lawrence Overzet, Matthew Goeckner Fourier transform infrared spectroscopy (FTIR) is a useful diagnostic in processing plasmas because of its ability to provide density measurements for a wide array of species and reveal unanticipated chemistries. However, \textit{in situ }species identification and density measurements in plasma environments are complicated by incomplete reference spectra databases, overlapping band structures, spatial and temporal temperature changes, resolution limitations, and the possibility of nonlinear absorption in large density and pathlength combinations. Here, we address these problems for stable radicals found in fluorocarbon discharges. Integrated absorption cross-sections are presented for all fundamental bands in the 650 cm$^{-1}$ to 2000 cm$^{-1}$ region for C$_{3}$F$_{6}$, C$_{4}$F$_{8}$, C$_{3}$F$_{8}$, C$_{2}$F$_{6}$, C$_{2}$F$_{4}$, and CF$_{4}$. In addition, the binary and ternary combination bands up to 4000 cm$^{-1}$ are presented for each species. The results show that with the exception of CF$_{4}$ the integrated absorption cross-sections do not change significantly as gas temperature increases. The internal temperature of the absorbing species can be estimated from the rotational band maximum in most cases. Subtracting temperature-adjusted reference spectra, allows accurate density measurements of low density species and the separation of overlapping spectra such as CF$_{2}$ and C$_{2}$F$_{6}$. [Preview Abstract] |
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DTP.00186: Gas Temperature Measurement in Atmospheric Nitrogen Discharge by Laser REMPI-LIF Technique Steven Adams, James Williamson A remote laser-based technique for measuring the neutral molecule gas temperature in an atmospheric discharge containing nitrogen is presented. It has been demonstrated that the rotational temperature of molecular nitrogen at atmospheric pressure can be determined by direct optical probing of the N$_{2 }$(X,v=0) ground state with subsequent analysis of the rotational state distribution. A tunable probe laser was used to excite resonant enhanced multi-photon ionization transitions from various N$_{2}$(X,v=0,J'') rotational states to N$_{2}$(b,v=6,J') states. At atmospheric pressure, the laser photo-ionization has been found to induce nitrogen fluorescence bands. Analysis of the relative N$_{2}^{+}$(B-X) fluorescence as a function of laser wavelength produced a calculated N$_{2}$(X,v=0, J) rotation state distribution and the assignment of a rotational temperature. Results of the technique are compared in its application to a heated nitrogen gas flow in thermal equilibrium and a nitrogen gas discharge, both at atmospheric pressure. [Preview Abstract] |
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DTP.00187: Trace-rare-gas optical emission spectroscopy of argon dc glow discharges Jason Afonso-Ferreira, Luc Stafford Trace-rare-gas-optical-emission-spectroscopy (TRG-OES) was used to determine the electron temperature, T$_{e}$, in a direct-current argon glow discharge with aluminum electrodes. The TRG-OES method is based on a comparison of atomic emission intensities from trace amounts of Ne, Ar, Kr, and Xe added to the plasma, with intensities calculated from a model. In the positive column region, T$_{e}$ was 0.8 $\pm $ 0.1 eV and was fairly independent of pressure (160 -- 500 mTorr) and current (4 - 70 mA). In the negative glow region, the electron temperatures were slightly higher and increased with current, going from 0.9 eV at 4 mA to 1.6 eV at 67 mA for a 200 mTorr Ar plasma. Over the whole range of experimental conditions investigated, the metastable-to-neutral number density ratios were relatively low ($<$10$^{-6})$ such that rare gas emission lines were excited mostly from the ground state. Therefore, the values of Te determined by TRG-OES were characteristic of the high-energy portion of the electron energy distribution function (EEDF). Overall, the measured values of Te were much lower than those expected from a zero-dimensional global model assuming a Maxwellian EEDF (e.g. 1.9 eV at 200 mTorr). The values were, however, consistent with those predicted by Boltzmann simulations (Boltzig) in the 10-16 eV portion of the EEDF. [Preview Abstract] |
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DTP.00188: Experimental results of two dimensional spatial distribution of plasma parameters in CVD processing plasma Young-Cheol Kim, Yu-Sin Kim, Chin-Wook Chung Two dimensional spatial distribution of plasma parameters was recently developed by using floating harmonic methods1,2. In this study, this method was applied for real plasma processing CVD reactor with H2/SiH4 gas mixture. The measured plasma uniformity was not changed a lot with RF powers and gas mixing ratios, while the plasma uniformity was dramatically changed from convex to concave profile with gas pressures. This remarkable change in the plasma uniformity could be explained by decrease of plasma diffusivity in higher gas pressure. It is expected that this method can be novel one of the diagnostic tools for both spatial profile measurement of the plasma parameters and improvement of the plasma uniformity. [Preview Abstract] |
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DTP.00189: \textit{In situ} feedback control of ion flux by using a floating harmonic method in processing plasmas Yu-Sin Kim, Se-Jin Oh, Sung-Ho Jang, Chin-Wook Chung In plasma processing such as etch and deposition, ion fluxes relate closely to processing results. A real time feedback control of ion fluxes can improve processing performance. In this study, the ion fluxes were measured by using floating harmonic method in real time. The measured ion fluxes were transmitted to an actuator to control processing input parameters. The feedback control technique was used PID (Proportional, Integral, and Derivative). The experimental results showed this control system allowed the ion fluxes to keep the desired values below 0.1 {\%} of the state error. [Preview Abstract] |
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DTP.00190: Analysis of current harmonics and application on the floating harmonics method with multiple voltage waveforms in a plasma Young-Do Kim, Yu-Sin Kim, Hyo-Chang Lee, Chin-Wook Chung In this paper, it was shown that measured probe currents have specific harmonics depending on the types of the input voltage waveforms due to nonlinearity of the sheath in plasma. In this experiment the voltage waveforms of sinusoidal, saw-tooth, square, and triangular types were applied, and the currents were analyzed using the Fourier transform of various periodic functions. The results were discussed including circuit model analysis. It was revealed that the harmonics of the probe current waveforms and the stray currents had different characteristics against each applied voltage waveform. It was also found that the floating harmonic method by using the triangular waveform has a valuable potential to measure plasma parameters such as plasma density and electron temperature. The plasma parameters obtained from our method were good agreements with the results from single Langmuir probe and sinusoidal floating harmonic methods. [Preview Abstract] |
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DTP.00191: Analyses of electron and negative atomic oxygen ion density by means of 160 GHz microwave interferometry and laser photodetachment in oxygen cc-rf plasma Christian K\"ullig, Kristian Dittmann, J\"urgen Meichsner Microwave interferometry at 160.28 GHz with Gaussian beam propagation and laser photodetachment were simultaneously applied for analysis of negative atomic oxygen ions in the bulk plasma of an asymmetric capacitively coupled 13.56 MHz discharge. The line integrated negative oxygen ion density amounts between 2*10$^{14}$ m$^{-2}$ and 10$^{15}$ m$^{-2}$ depending on total oxygen pressure and rf power. Furthermore, the decay of the detachment signal reveals two modes of rf oxygen plasma characterized by different electronegativity $\alpha $=n$_{-}$/n$_{e}$. In the case of $\alpha >$2 the decay time constant amount to few $\mu $s, only, whereas in oxygen plasmas with low electronegativity, $\alpha <$1, the relaxation of electron density needs much longer with typical decay time constants up to about 100 $\mu $s. The transition between the two modes shows a step-like characteristic and was observed at a specific rf power depending on the oxygen pressure. For high electronegativity the electron density relaxation can be described by a simple 0D-attachment-detachment model taking into consideration a constant density for positive ions and neutral oxygen species. This model indicates that the metastable O$_{2}$(a$^{1}\Delta _{g})$ plays an important role, both in formation and loss of negative atomic oxygen ions. [Preview Abstract] |
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DTP.00192: HIGH PRESSURE PLASMA II |
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DTP.00193: Shadowgraph Visualizations of Pulsed Discharge Phenomena in Pressurized Carbon Dioxide up to Supercritical Conditions Tsuyoshi Kiyan, Takeshi Ihara, Sunao Katsuki, Takashi Sakugawa, Masanori Hara, Hidenori Akiyama In this study, pulsed discharge phenomena under high-pressure carbon dioxide including supercritical phase were visualized by means of shadowgraph method. A series of experiments is conducted by varying pressure from 0.1 to 15 MPa at the desired temperatures of 313, 308 and 298 K. The sequence of pulsed discharge plasma is observed by ICCD camera with Ar laser system. The observations show as follows: pre-breakdown phenomena with streamer; breakdown process and shock wave; collapse process and the observation of Rayleigh-Taylor instability. [Preview Abstract] |
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DTP.00194: Understanding halo and sprite discharges above thunderclouds Ute Ebert, Alejandro Luque Halos, sprites and other transient luminous discharges can emerge high above thunderclouds. They are generated by the electromagnetic fields of lightning strokes where air density decreases with altitude, while free electron density increases. We present simulations of diffuse halo and subsequent structured sprite discharge, taking all these features into account from the 90 km earth-ionosphere distance down to the inner scales of sprite streamers on the scale of meters. The simulations quantitatively match the observations and can actually be developed into a probe for electron density at hardly accessible altitudes in the atmosphere. \\ {[1]} {\it Emergence of sprite streamers from screening-ionization waves in the lower ionosphere}, A. Luque, U. Ebert, Nature Geoscience {\bf 2}, 757-760 (2009). \\ {[2]} {\it Sprites in varying air density: charge conservation, glowing negative trails and changing velocity}, A. Luque, U. Ebert, Geophys. Res. Lett. {\bf 37}, L06806 (2010). \\ {[3]} {\it Review of recent results on streamer discharges and their relevance for sprites and lightning}, U. Ebert {\it et al.}, J. Geophys. Res., in press. [Preview Abstract] |
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DTP.00195: Novel Electrode Configuration for Ionic Wind Generation in Air at Atmospheric Pressure Dorian Colas, Antoine Ferret, Ignazio Sciacca, David Z. Pai, Deanna A. Lacoste, Christophe O. Laux A novel electrode configuration is presented to generate ionic wind with a DC corona discharge in air at atmospheric pressure. The objective of the work is to maximize the power supplied to the flow to increase acceleration while avoiding breakdown. Thus, the proposed experimental setup addresses the problem of de-coupling the mechanism of ion generation from that of ion acceleration. Using a wire-plate configuration as a reference, we have focused on improving the topography of the electric field to 1) create separate ionization and acceleration zones in space, and 2) guide the trajectory of charged particles as parallel to the median axis as possible. In the new wire-cylinder-plate setup, a DC corona discharge is generated in the space between a wire and two cylinders. The ions produced by the corona then drift past the cylinders and into a channel between two plates, where they undergo acceleration. Experimentally, the optimized reference setup and the new configuration provide flow velocities up to 8 and 10 m/s, respectively, as well as a thrust by unit up to 0.24 and 0.35 N/m. In comparison with a DBD configuration, the experimental results show that the generated thrust is an order of magnitude higher. [Preview Abstract] |
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DTP.00196: Flow Separation Control on Airfoil With Pulsed Nanosecond Discharge Actuator Ilya Popov, Giuseppe Correale, Aleksandr Rakitin, Andrey Starikovskii, Leo Veldhuis, Steven Hulshoff An experimental study of flow separation control with a nanosecond pulse plasma actuator was performed in two windtunnels of TU Delft. The first series of experiments was carried out with a NACA-0015 airfoil with a chord of 20~cm. A linear actuator of different geometries was attached to the airfoil at different positions. The discharge used had a pulse width of 20~ns and a rising time of 2~ns, and with voltage up to 12~kV. Varied parameters included discharge frequency, actuator geometry (insulator thickness, gap width, and the number of electrodes) and the position on the wing. Separation elimination was shown at velocities up to 40~m/s with a lift increase up to 20\% and an increase of the separation angle of attack of several degrees. The second series of experiments was carried out with a laminar airfoil NLF--MOD22A with a chord of 60~cm. Separation elimination and L/D improvement was shown at velocities up to 80~m/s. The experiments are supported by numerical simulation of the interaction of the shock wave produced by the discharge with the boundary layer. [Preview Abstract] |
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DTP.00197: The study of the parameters of a streamer corona at high frequency pulses in the gas flow Alexander Ponizovskiy, Serge Gosteev, Vlad Melnikov, Serge Filippov, Vladimir Maevskiy The streamer corona at high frequency pulses (100-1000 Hz) arises in conditions when inside of interaction space a high concentrations of ozone, nitrogen oxides, excited and ionized molecules of oxygen and nitrogen are produced. The influence of the gas flow rate (V) on the parameters of a streamer corona and the single streamers has been studied. Streamer corona was generated inside of coaxial reactor camera. The measurements of single streamer's parameters were conducted by wire probe located on the grounded wall of RC. It was found that both the integral streamer current (Ist) and input in gas power (W) at constant U and f falls when V of air is reduced. The dependence of ozone yield (G(V)) from energy consumption on its production (Wsp(V)) have an extreme character, moreover, the G maximum and Wsp minimum corresponds to V values when a laminar flow transforms into turbulent one. Our probe may catch the single streamer after it crossing the space (d=3cm). It gives us the possibility to describe three scenario of the streamer development: No discharge, Streamer discharge on the front or trailing edge of pulses. [Preview Abstract] |
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DTP.00198: Flow Control around Cylinder by HF DBD Discharge Ivan Moralev, Valentin Bityurin, Anatoly Klimov, Pavel Kazansky, Denis Chertov Control of airflow around a cylindrical model by pulse-repetitive HF discharge (F$_{HF}\sim $ 350kHz) is studied at airflow velocity up to 120m/s and Reynolds number Re = 2x10$^{4}\div $2x10$^{5}$. It is obtained that HF pumping higher that the critical one changes airflow around cylindrical model and decreases wake's diameter. Pressure distribution in a model's wake and on the model surface are obtained at different HF discharge power, different duty cycle and different pulse repetitive frequency. Shadow pictures of airflow around a cylinder are obtained. Creation of a secondary large-scaled vortex in the cylinder's wake is recorded in these pictures . Mean discharge power input doesn't exceed 10W/cm, peak HF power doesn't exceed 1 kW. Main parameters of a surface HF discharge are measured. The possible physical mechanism of the surface discharge interaction with airflow in a separation region is discussed in this work. [Preview Abstract] |
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DTP.00199: The effect of the normal current density and plasma spatial structuring in the DBD in argon Ivan Shkurenkov, Yuri Mankelevich, Tatyana Rakhimova The DBDs is one of the most popular systems for producing low-temperature non-equilibrium plasma. Due to the DBD wide technical application, its spatial structure is of great interest. The high pressure DBD in argon was simulated using the developed 2D model. The DBD of kilohertz range non-uniformity observed during the calculations-- the system of concentric plasma rings formation. The simulated structuring process obtained in our model is consistent with the experimental observations. The effect of the normal current density was obtained numerically in our simulation. Both the effect of normal current density and the filaments formation are caused by the nonstationarity at the current channel boundary. The increase in the discharge current occurs due to increase in the number of rings and as a result in the discharge area. The electron concentration and current density in each ring with the applied voltage increase or drop tend to be the same. The DBDs with different dielectrics are studied. The calculations showed that the filamentation process depend on the dielectric layers properties. It was shown that the radial electric field is smoother in the DBD with thinner dielectric layers. It results in more uniform (over the radius) discharge. [Preview Abstract] |
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DTP.00200: Time-resolved Spectral Investigations of Pulsed Atmospheric Dielectric Surface Flashover Discharges Klaus Frank, George Laity, Andreas Neuber, Garrett Rogers, Lynn Hatfield, James Dickens, Magne Kristiansen, Andrew Fierro In an attempt to identify the mechanisms leading to pulsed dielectric surface flashover in atmospheric conditions, a surface flashover event occurring on a magnesium fluoride (MgF$_{2})$ window was studied. The electrode configuration and the applied pulsed voltage level were chosen such that the generated electric field was symmetric with respect to the centerline between the electrodes. Sharpened stainless steel electrodes (estimated tip radius of 200$\mu $m) are attached to springs which press down onto the MgF$_{2}$ surface a distance of 8 mm apart. Diagnostics include time resolved emission spectroscopy in the VUV range and gated ICCD optical imaging of streamer progression during the first 30 nanoseconds of breakdown (with 3 nanosecond resolution) in the visible wavelength range. One important parameter on which the streamer formation and the subsequent breakdown strongly depends is the gas type and/or the gas composition. That is why the streamer formation was recorded for gated intervals from 3 to 50 ns in lab air, standard nitrogen, oxygen and SF$_{6}$. The results are compared to those ones in purified air, oxygen and nitrogen. [Preview Abstract] |
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DTP.00201: Spatio-temporal post-discharge analysis of nanosecond scale discharges in atmospheric pressure air Amath Lo, Gillaume Cleon, Armelle Cessou, Pierre Vervisch Nanosecond discharges are envisaged to improve the processes of ignition or assisted combustion. The characterization of energy transfers within the post-discharge is essential for understanding the mechanisms of radical formation and determining the mechanism of temperature increase. The pulse discharge occurs in air between a point-to-plane gap of 6.5mm length. A pulse high voltage of 25kV and 25ns is applied at the repetitive rate of 10Hz. In the range of 150ns to 10ms and at different locations in the gap, radial profiles of N$_{2}$(X) vibrational and rotational temperatures have been measured by Spontaneous Raman Scattering. An excitation of high vibrational levels (up to v=16) is observed at 150ns allowing us to observe clearly a strong vibrational non-equilibrium with two vibrational temperatures. The results show that the vibrational temperatures are higher in the first stage of post-discharge and gradually decrease. The rotational temperature increases and reaches a maximum (1900K) at 50$\mu $s. The rapid gas heating obtained just after the pulse discharge leads to a propagation of a pressure wave from the axis to the sides. These results will be useful to well-understand physical processes involved in ignition. [Preview Abstract] |
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DTP.00202: Characterization of the Different Regimes of Nanosecond Repetitively Pulsed (NRP) Discharges in Air at Atmospheric Pressure and Ambient Temperature Diane Rusterholtz, Julien Jarrige, David Pai, Deanna Lacoste, Christophe Laux Nanosecond Repetitively Pulsed discharges of the corona, glow and spark types have been obtained in atmospheric pressure air at ambient temperature. Pai \textit{et al} had predicted that the glow NRP discharges could be obtained at 300 K if the radius of the electrodes were reduced or the duration of the pulsed were increased. We built a reactor in a pin-pin configuration and used a 2-50 ns pulse duration generator and obtained glow discharges at 300 K. Experiments have been performed to determine the parameter space (interelectrode gap distance, pulse repetition frequency, applied voltage, pulse duration, radius of curvature of the electrodes) of the glow regime at 300 K. Investigations of the electrical characteristics and radiative properties of the different discharge regimes are carried out using voltage - current measurements, fast ICCD imaging and time resolved Optical Emission Spectroscopy. [Preview Abstract] |
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DTP.00203: Non-intrusive Diagnostics of Dielectric Barrier Discharge Plasma Actuator Joshua Stults, Richard Huffman Dielectric Barrier Discharge (DBD) plasma actuators are an emerging possibility for active flow-control in low-speed, atmospheric pressure aerodynamics. They rely on imparting small amounts of momentum into the boundary layer, which can delay separation and increase lift at critical conditions such as stall in an airfoil or off-design conditions in a turbine. This work incorporates a numerical wave-propagation model into an optimization framework to integrate multiple interferometry measurements into a reconstruction of the spatial variation of electron density in the DBD plasma. [Preview Abstract] |
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DTP.00204: Application of high-voltage pulsed-driving discharge to ignition and detonation initiation K. Korytchenko, V. Bolyukh, O. Stahovskiy The new system producing a driving pulsed arc is offered in this report. It permits to create an efficient thermal source, the volume of which exceeds 5~mm$^{3}$ with the energy deposition about 1 J. High efficiency of the designed system is achieved due to the change of the voltage applied across the discharge gap during the pulsed arc development. It is shown that the forced change in the field strength inside the pulsed arc by an external electric circuit involves: 1) a rise in a resistance of the discharge channel by diminishing the plasma conductivity; 2) an increase in a rate of gas heating by the discharge current due to the growth in electron-ion collision rate; 3) an approach of the ionization degree of the plasma to the thermally equilibrium one through limitation of the electron temperature. Therefore the drive of the field strength into a pulsed arc allows not only fulfilling the growth condition of the energy fraction deposited into the discharge gap but it advances the efficiency of the electric energy transformation into thermal one of the gas-discharge environment. The calculation of optimal strength of the field is done on the basis of a balance equation of electrons energy, a state equation, an equation of Sakha and taking into account the process of dissociation. The two-temperature model of highly-ionized plasma is used where the electrons temperature is differ from ions one. The calculation results concerned the discharge into oxygen environment show that the field strength necessary to reduce when the channel temperature increases. [Preview Abstract] |
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DTP.00205: Non Equilibrium Gliding Arc Plasma Reforming of Pyrolysis Gas Fuel Fela Odeyemi, Alexander Rabinovich, Alexander Fridman This paper emphasizes plasma assisted conversion of Pyrolysis gas (Pyrogas) fuel. Pyrogas is a product of Biomass, Municipal Wastes or Coal gasification process that contains H2, CO as well as unreacted light hydrocarbons (especially CH4, C2H2 and C2H4) and heavy hydrocarbons such as tar. These undesired hydrocarbons diminish Pyrogas fuel value thereby making significant removal of the unwanted hydrocarbons necessary. Various conditions and reforming reactions were considered for the conversion of Pyrogas into Synthesis gas -- a combination of H2 and CO. Non thermal plasma is an effective homogenous process for fuel reforming without using catalysts. The effectiveness of the Gliding arc plasma is demonstrated in the fuel reforming reaction processes with the aid of a specially designed low current device called GlidArc Plasmatron. Gliding arc discharge is a non equilibrium plasma discharge with multiple advantages over other reforming techniques which will be further discussed in the paper. Thermodynamic simulation results were compared with experimental results with emphasis on yield, efficiency, enthalpy at different H2O/C ratios and reaction temperatures. [Preview Abstract] |
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DTP.00206: Experimental and simulation study of the OH radical generation in atmospheric pressure microwave plasma Margarita Baeva, Kristian Rackow, J\"{o}rg Ehlbeck Hydroxil radicals play an important role in non-equilibrium plasmas for decomposition of gaseous pollutants, initiation of surface reactions, synthesis of methanol from methane, etc. Experimental and simulation studies of a coaxial microwave plasma source operating at $2.45$ GHz in atmospheric pressure $H_{2}O$/$N_{2}$/$O_{2}$ gas are carried out. Optical emission spectroscopy is applied to observe the OH (A-X, 309 nm) emission intensity. The variation of the $O_{2}$ concentration allowed to look at the transition from the $N_{2}$ dominated emission spectrum to NO emission spectrum. The rotational temperature is obtained from simulated spectra of the $N_{2}^{+}$ first negative system and NO transitions at 248 nm and 272 nm. The experiment is completed with a global kinetic model delivering the electron density and temperature, the electric field amplitude, and the species densities for absorbed microwave power from 500 W up to 1000 W and gas temperatures between 3000 K and 5000 K. A 2D model of the plasma source based on Maxwell's equations is applied to obtain the distribution of the electric field and the absorbed power density. [Preview Abstract] |
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DTP.00207: Periodic pulse discharge self-focusing and streamer-to-spark transition in under-critical electric field Andrey Starikovskiy, Aleksandr Rakitin, Sergey Pancheshnyi Repetitive pulsed nanosecond discharge was investigated for point-to-plate geometry. The sequence of electrical pulses has been investigated one-by-one. The measurements were performed with the help of 4Picos ICCD camera with camera gate 1 ns. The discharge starts at the high voltage electrode, and after about 4 ns, the streamer channel bridges the discharge gap. The return stroke leads to redistribution of the potential along the gap. The reduced electric field in the plasma channel becomes lower than the breakdown field (about 120 Td for room-temperature air), and slow plasma recombination begins. Plasma recombination does not affect the discharge current and gas excitation during the pulse ($\sim $ 10 ns). At this time, the plasma channel becomes invisible. Next pulses lead to streamer propagation through the pre-excited media. Streamer channel diameter decrease (self-focusing) was observed for pulses 2-4. Gas heating leads to the density decrease and increase of reduced electric field. Transition to spark was observed in next pulses. Discharge energy increases from 2 to 25 mJ/pulse for pulses 1 to 10. [Preview Abstract] |
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DTP.00208: Shedding light on arc cathode spots Ian Falconer, Roberto Sangines, Ondrej Novak, Adam Israel, David McKenzie, Marcela Bilek We have used a high-speed camera to analyze the motion of the multiple co-existent cathode spots in the University of Sydney's high-current pulsed arc, which move in a direction opposite to that expected from Lorentz force equation, and developed a model to explain our observations. Time resolved optical emission spectroscopy has also been employed to link the emission intensity of the species in the arc plasma with the cathode spot dynamics and to infer trends in the evolution of the charge state distribution.~~ The shape of the spectral line of the excited species that are ejected from the spots is of relevance to understanding the physics of the spots. As these ions are created towards the edge of the spot and lose their excitation as photons at the boundary of the spot the line shape and shift will give the velocity of the ions near the boundary of the spot. A combination of a Fizeau interferometer, an intensified CCD camera and a grating spectrometer have been used to obtain time-resolved spectral line shapes for the pulsed arc. The results of these measurements will be discussed. [Preview Abstract] |
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DTP.00209: Non-equilibrium simulation of the spatial and temporal behaviour of a magnetically rotating arc in argon Margarita Baeva, Dirk Uhrlandt, Detlef Loffhagen A three-dimensional magnetohydrodynamic model of a DC plasma torch with a rod-type cathode at atmospheric pressure in argon has been developed. The model takes into account a non-equilibrium description of the plasma in the whole computational region. Since the electron temperature remains significantly higher than the heavy particle temperature near the electrodes, the electric conductivity is high enough to ensure current conservation in front of the electrodes. The arc attachment at the anode results from the interplay between the gas dynamic drag force and the Lorentz force. In the presence of an external axial magnetic field, the hot plasma region constrains in the axial and expands in the radial direction. The arc is driven in rotation by the external magnetic field. At moderate magnetic field strength the magnetically driven plasma rotation is resolved and deviations from the axial symmetry have been observed. Results for different plasma and flow parameters are presented and discussed. [Preview Abstract] |
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DTP.00210: Density and translational temperature of Pb atom in the multi-Micro Hollow Cathode Lamp measured by diode laser absorption spectroscopy Mari Inoue, Takayuki Ohta, Naoki Takota, Masafumi Ito, Hiroyuki Kano, Koji Yamakawa, Masaru Hori In various processes, especially in sputtering process using metal composite target, it is important to measure multi metallic atoms simultaneously for understanding and controlling the behavior of metallic atoms in gas phase. We have investigated the multi-Micro Hollow Cathode Lamp (multi-MHCL) based on the micro hollow cathode discharge for a light source of absorption spectroscopy to monitor the densities of multi metallic atoms simultaneously and quantitatively. In this study, we have measured the density and translational temperature of Pb atom in the multi-MHCL with diode laser absorption spectroscopy. The multi-MHCL was operated under 40 mA and 390 V. Diode laser was scanned around the absorption wavelength of 405.78 nm. The Pb atom density in the multi-MHCL was measured to be 10$^{11}$ cm$^{-3}$ at He pressure range of 0.005-0.0075 MPa. The translational temperature was estimated to be from 950 to 1010 K from FWHM of the absorption profile. The density and translational temperature of Pb atom were increased with decreasing the pressure. [Preview Abstract] |
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DTP.00211: Propagation dynamics of a room-temperature pulsed argon plasma plume through a simple dispersion-grating diagnostic method Qing Xiong, Anton Nikiforov, Xinpei Lu, Christophe Leys In this paper, a novel grating-ICCD camera dispersion diagnostic method was designed to investigate the propagation behaviors of an open-air pulsed argon plasma plume. Based on the dispersion feature of gratings, the irradiative plasma plume was dispersed into several emission-volumes corresponding to different wavelengths. And a series of high-speed dispersed emission-image sequences were captured by the ICCD camera. From these sub-microsecond emission-images at different wavelengths, the temporal and spatial propagation behaviors of excited species in the plasma plume was observed clearly. [Preview Abstract] |
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DTP.00212: Destruction of volatile organic compounds under atmospheric conditions by usage of a multi stage packed bed reactor J. Roepcke, M. Huebner, O. Guaitella, A. Rousseau This contribution reports a new method used for the destruction of harmful volatile organic compounds, VOC, introduced by Whitehead, Harling and co-workers [1]. They used several packed bed reactors and reported that a serial arrangement of them leads to a nonlinear increasing of the destruction rate. This synergistic effect was investigated. Therefore, up to three model stages were combined, where one stage is made of one layer of glass beads held between two stainless steel electrodes. For a variable number of active stages the initial concentration of the test VOC ethylene was held constant. Contrary to what has been reported, the synergistic effect could not be confirmed. All gas compositions were identified and quantified using FTIR spectroscopy. Results are presented about the influence of variable amount of water, gas flow, inter stage distance and stability of the bed material. \\[4pt] [1] DOI: 10.1021/es703213p [Preview Abstract] |
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DTP.00213: The influence of confining walls on 2D electron dynamics in radio frequency driven atmospheric pressure plasmas Colm O'Neill, Jochen Waskoenig, Timo Gans Radio-frequency driven atmospheric pressure plasmas (RF-APPs) can provide high concentrations of various radicals at a low gas temperature particularly for modification of sensitive surfaces, such as in biomedicine or for surface coatings. Ionization, excitation and dissociation are governed by the detailed electron dynamics within the plasma. Here, we present 2D numerical simulations of an RF-APP with an electrode spacing of 1 mm, confined by quartz surfaces forming a 1x1 mm$^{2}$ cross section. The used fluid model, with semi-kinetic treatment of electrons, has been benchmarked by phase resolved optical emission spectroscopy measurements. Surface charges at the quartz surfaces lead to electric fields parallel to the electrodes. Since the charge carrier density decreases towards the confining walls, even relatively weak electric fields can lead to sufficient power coupling per electron. Hence an increased electron impact excitation and ionization close to the quartz surfaces is observed. This results in off centered maxima of the electron density shifted towards the confining quartz walls. [Preview Abstract] |
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DTP.00214: The application of electro-acoustic metrology to atmospheric pressure plasma ablation of gelatine Victor Law, Niall Durham Atmospheric pressure plasma jets are finding increasing used in hard surface engineering applications and the treatment of selected biological soft-tissues: For example, wound healing, removal of skin blemishes and the ablation and sterilization of irreversibly hydrolyzed collagen (gelatine) scaffold material. This paper reports upon a helium atmospheric pressure plasma ablation process of gelatine (beef) and the real-time electro-acoustic plasma metrology of the process. It is shown that the acoustic signal emerging from the plasma interaction with soft tissue material can be used to monitor the process, along with electrical feedback from the plasma power supply. The plasma process is compared to the treatment of a sold glass surface to reveal the acoustic signal from the gelatine soft tissue. [Preview Abstract] |
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DTP.00215: MICRODISCHARGES |
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DTP.00216: Space resolved density measurements of argon and helium metastable atoms in radio-frequency generated He-Ar micro-plasmas Benedikt Niermann, Marc B\"oke, Nader Sadeghi, J\"org Winter Space resolved concentrations of helium He* ($^3\mbox{S}_1$) and argon Ar* ($^3\mbox{P}_2$) metastable atoms in an atmospheric pressure radio frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. Even small absorptions down to $10^{-4}$ could be measured using lock-in technique. The absolute density of metastable atoms densities at different rf-power, flow rate and gas mixture was deduced from measured absorption rates. Metastable concentrations range from 10$^{9}$ to 10$^{11}$ cm$^{-3}$. Analysis of spectral profiles provided the pressure broadening coefficients of both metastable atoms by helium. The spatial distribution of metastable atoms in the plasma volume was obtained for various discharge conditions. Density profiles between the electrodes reveal the sheath structure and reflect the plasma excitation distributions in the discharge volume. It reveals the dominance of the $\alpha$-mode discharge. [Preview Abstract] |
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DTP.00217: Driving frequency effects on atmospheric-pressure RF helium microplasmas: plasma density, electron energy and plasma impedance Kirsty McKay, Felipe Iza, Michael G. Kong The effects of the driving RF frequency on the properties of low temperature atmospheric pressure helium microplasmas are discussed in light of simulation results of a 500 micron discharge driven at constant input power with a 10MHz-2.45GHz voltage source. The electron density is found to be a non-monotonic function of the driving frequency and agrees with experimental observations made in different frequency bands with different devices. The physics underpinning this non-monotonic behaviour are investigated and the increasing penetration of the electric field as frequency increases is identified as a key factor. Additionally, the relation between the plasma impedance and the mean plasma density is investigated, and the validity and accuracy of equations commonly used to infer the plasma density from experimental impedance measurements discussed. While this method can provide quantitative estimations, the accuracy suffers when the discharge operates in the gamma mode and in low-density high-frequency discharges where the displacement current across the bulk plasma cannot be neglected. [Preview Abstract] |
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DTP.00218: Analysis of striations in dielectric barrier microdischarges at atmospheric pressure Markus M. Becker, Ronny Brandenburg, Tom\'a\v s Hoder, Detlef Loffhagen, Christian Wilke When studying microdischarges in asymmetric barrier discharges in argon, where one electrode only is covered by a dielectric, striated structures similar to the known relaxation structures in low-pressure glow discharges have been observed. In order to assist the experimental investigations of the striated structures and to understand the inherent processes, model calculations of the spatiotemporal evolution of a microdischarge have been performed. The hydrodynamic description comprises the particle balance equations of electrons, 11 excited argon states, Ar$^+$ and Ar$_2^+$ ions and the electron energy balance equation involving the fluxes in drift-diffusion approximation as well as Poisson's equation. The coupled system is numerically solved taking into account the effect of surface-charge accumulation at the dielectric electrode. First results of the numerical computations are presented and compared with experimental data. Depending on the applied voltage microdischarges with and without striated structures are found by experiments and model calculations. Pronounced current peaks occur in normal microdischarges (without striations), while several moderate current pulses correlate with the appearance of striated microdischarges. [Preview Abstract] |
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DTP.00219: Microwave micro-plasma sources based on microstrip-like transmission lines J. Greg\'orio, O. Leroy, P. Leprince, C. Boisse-Laporte, L.L. Alves We study three sources based on a planar transmission line configuration, corresponding to linear resonators, which use a 2.45 GHz (1-50 W) continuous excitation to produce stable micro-plasmas at atmospheric pressure in air, Ar and He. In all sources, micro-plasmas are produced within the 50-200 $\mu $m gap created between two metal electrodes placed at the open-end of a microstrip-like transmission line. The sources design and optimization uses the numerical tool CST Microwave Studio{\textregistered} and an analytical model of the transmission line, in a complementary approach that also measures the return loss. Plasma diagnostics, based on optical emission spectroscopy measurements, enable to obtain (i) the rotational temperature ($T_{rot})$ and the vibrational temperature ($T_{vib})$, using the N$_{2}$ (in air) and the OH (in Ar and He) rovibrational spectra; (ii) the excitation temperature ($T_{exc})$ and the electron density ($n_{e})$ in Ar, using atomic line transitions and the Stark broadening of H$_{\beta }$, respectively. Typically, we obtain $T_{rot}\sim $1000 K in air, $\sim $600 K in Ar and $\sim $400 K in He; $T_{vib}\sim $5000 K in air; $T_{exc}\sim $6000 K in Ar and $\sim $4000 K in He; and $n_{e}\sim $10$^{14}$ cm$^{-3}$ in Ar. [Preview Abstract] |
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DTP.00220: Sheath and electron density dynamics in a micro hollow cathode discharge in argon Claudia Lazzaroni, Pascal Chabert, Antoine Rousseau, Nader Sadeghi A microplasma is generated in the 400 $\mu $m diameter microhole of a molybdenum-alumina-molybdenum sandwich (MHCD type) at medium pressure (30-200 Torr) in pure argon. Imaging and emission spectroscopy are used to study the sheath and electron density dynamics. Experiments are performed during the normal regime and the self-pulsing regime. The evolution of the microdischarge structure is studied by recording the emission intensity of the Ar (5p[3/2]$_{1}$-4s[3/2]$_{1})$ line at 427.217 nm, and Ar$^{+}$ (4p'$^{2}$P$_{3/2}$-4s'$^{2}$D$_{5/2})$ line at 427.752 nm. The maximum of the Ar$^{+}$ line is located in the vicinity of the sheath-plasma edge. In both regimes, the experimental observations are consistent with the position of the sheath edge calculated with an ionizing sheath model. The electron density is deduced from the Stark broadening of the H$_{\beta}$-line. In the self-pulsing regime, the electron density can reach a maximum value of 4$\times $10$^{15}$ cm$^{-3}$ at 150 Torr, a few tens of nanoseconds later than the discharge current maximum. The electron density then decays with a characteristic decay time of about 2 $\mu $s, while the discharge current vanishes twice faster. The electron density in the steady-state regime is two orders of magnitude lower, at about 6-8$\times $10$^{13}$ cm$^{-3}$. [Preview Abstract] |
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DTP.00221: ABSTRACT WITHDRAWN |
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DTP.00222: Removal of carbon based deposits using microplasma jets Soren Boyn, Richard Clergereaux, Freddy Gaboriau, Leanne Pitchford, Claire Douat, Vincent Puech ITER is currently planning to use some carbon target tiles in the divertor. Modeling and experiments suggest that carbon-based deposits will accumulate, trapping tritium, and it will be necessary to remove such accumulations periodically. In this context, we are studying plasma-induced erosion of hydrogenated amorphous carbon (a-C:H) thin films. The plasma source (a few watts) is a microplasma jet generated application of fast-rising, high voltage pulses (up to 5 kV) at 10s of kHz. Pure He or He/O2 mixtures flow through the tube into open air and the film is exposed to the plasma jet which extends several cm past the end of the tube. Ellipsometric measurements show that the film on Si substrate is totally removed over a width comparable to the jet diameter after 3~minutes. The erosion profile is conic and about 10 mm wide. In contrast, with a stainless steel substrate, the eroded surface is flat over a 6-7~mm diameter area. Possible reasons for the influence of the substrate will be discussed and a temporal study of the interaction between the plasma bullet and the a-C:H film deposited on different substrates will be presented. [Preview Abstract] |
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DTP.00223: Microhollow cathode discharges - ignition and instabilities in diamond arrays Sebastien Mitea, Daniel Barthaud, Jan Kowal, Nicholas Braithwaite, Mark Bowden Microhollow cathode discharges have been developed and studied over the last ten years, with various diagnostic techniques being used to study devices fabricated with a range of sizes and in a range of different materials. The aim of our project is to investigate ignition processes and the instabilities that arise when devices are fabricated using diamond instead of silicon as the substrate material. Preliminary results of the study are reported, focusing on the dependence of ignition processes with device dimension. Measurements of current- voltage characteristics, integrated plasma emission and visible spectra will be presented. [Preview Abstract] |
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DTP.00224: Nanosecond pulsed atmospheric pressure argon microplasmas James Walsh, Felipe Iza, Michael Kong This study details the generation and characterisation of a 3 nanosecond pulsed atmospheric pressure Argon discharge, and provides a comparison with a comparable DC discharge. There is a growing interest in short pulsed excitation of microplasmas as a gateway to access highly non-equilibrium discharge chemistry that is inaccessible using other excitation mechanisms. By combining time-resolved electrical and optical diagnostics the repetitive 3 nanosecond pulses considered in this study are shown to produce highly transient discharges with electron densities in excess of 10$^{17}$cm$^{-3}$. During the afterglow period electrons rapidly cool below the excitation threshold suggesting emission from excited Argon neutrals should also diminish rapidly. However, Argon emissions are observed for several microseconds after each applied pulse, far in excess of their radiative lifetimes. Potential repopulation mechanisms are considered and it is concluded that electron-ion recombination is the most likely recombination process. [Preview Abstract] |
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DTP.00225: Experimental and theoretical studies of the DC breakdown voltage in argon at micrometer separations Matej Klas, Stefan Matejcik, Marija Radmilovic-Radjenovic, Branislav Radjenovic The microdischarge is not only interesting due to its potential applications, but also as an ideal system to test the scaling laws in the electric discharges. One of the most common scaling laws is the ``Paschen law'' that describes the dependence of the DC breakdown voltage $U$ on the \textit{pd} product. The validity of the Paschen Law was confirmed for variety of DC discharge conditions (pressures, distances, electrode materials). At micrometer separations, however, the \textit{pd} scaling could be affected by phenomena like field emission, phase transitions in the gas at high pressures, tunnelling effects and a few more. The DC breakdown voltage in argon has been measured in discharge system consisting of two parallel planar Cu electrodes at separations from 20 to 500 $\mu $m, while the pressure was varied between 6 mbar up to 920 mbar. The analysis of the experimental data has been carried out in terms of semi empirical Paschen law and the dependence of secondary electron yield $\gamma $ on the reduced electric field has been estimated based on the experimental data. [Preview Abstract] |
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DTP.00226: Investigations on a thin cathode discharge in argon at atmospheric pressure Sebastian Mohr, Beilei Du, Dirk Luggenhoelscher, Uwe Czarnetzki The thin cathode discharge (TCD) consists of two electrodes separated by a dielectric layer which is about 100 $\mu$m thin. The cathode is of the same dimension as the dielectric layer, while the shape of the anode can be chosen arbitrarily. The discharge burns in a hole with a diameter of 200 $\mu$m drilled through this setup. Due to the small dimension, the TCD can be operated at pressures up to atmospheric pressure. When operated at such high pressures, the TCD shows a self-pulsing behavior which is caused by the repeated ignition of a short-living spark discharge. In this self-pulsing mode, electron densities of several $10^{16}~cm^{-3}$ can be reached and maintained over several 100 ns. However, due to the high collision frequencies at these high pressures, the lifetime of the afterglow should be much shorter. To find an explanation for this long lifetime, a kinetic model of the afterglow was developed. It showed that the prolonged afterglow is caused by the high density of metastables which produce and heat electrons by various processes like Penning-ionization and superelastic collisions. [Preview Abstract] |
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DTP.00227: Production and diagnostics of atmospheric-pressure microplasma jet excited by microwave Tomohiro Shirasaki, Mitsutoshi Aramaki, Akihiro Kono An atmospheric-pressure microplasma jet can be produced by placing a microwave-driven (2.45GHz) needle-like electrode in Ar flow. To find possible applications, characterization of this kind of plasma jet is being carried out. In pure Ar flow with varying flow speed and microwave power, the maximum plasma length was approximately the quarter wavelength of the microwave, which suggests that the plasma column is maintained by the microwave current flowing through the column. The electron density and temperature were measured using a laser Thomson scattering technique. A frequency-doubled Nd:YAG laser was focused into the plasma column (having a diameter of $\sim $ 1mm) and the scattered light was detected using a triple-grating spectrograph and an ICCD camera. The resulting electron density was of the order of 10$^{14}$cm$^{-3}$ and the electron temperature was 1.1eV. The gas temperature estimated from impurity N$_{2}$ optical emission (Second Positive band) was 1600K. The effect of the addition of N$_{2}$ or O$_{2}$ gas to the Ar flow was studied. Even at a small mixing ratio ($<$1{\%}), the plasma length was substantially shortened and the optical emission spectra suggest a large decrease in the electron density; the effect was more prominent for N$_{2}$ than for O$_{2}$. [Preview Abstract] |
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DTP.00228: 11-GHz Microwave-Excited Microplasma Source for Electrothermal Thruster Takeshi Takahashi, Yoshinori Takao, Koji Eriguchi, Kouichi Ono The trend of space systems has recently been focused on miniaturization and simplification of the structure, to reduce the mission costs and increase the launch rates. Such concept has supported a new approach to develop micropropulsion systems, particularly for high-accuracy station-keeping and attitude control. We report on a microplasma thruster using 11-GHz microwave-excited microplasma sources, instead of 4-GHz microwaves in our previous work. Higher frequency microwaves have a shorter wavelength, and then are expected to enable more compact design suitable for miniaturizing. The thruster consists of a microplasma source and a micronozzle for exhausting the plasma. The plasma source is composed of a quartz chamber, 1.0 mm in radius and 4.5--10 mm long, and a metal around the chamber. Microwaves propagate through a coaxial cable connected to the end of the plasma chamber, and then penetrate into the chamber, where the propellant is ionized and heated up. The thermal energy is converted into directional kinetic energy through the micronozzle to obtain the thrust. We carried out numerical simulations of the microplasma production and micronozzle flow, and the numerical and experimental results indicated a significant improvement in thrust performance. [Preview Abstract] |
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DTP.00229: Characteristics of cryoplasma below boiling temperature of N$_2$ Hitoshi Muneoka, Jai Hyuk Choi, Kazuo Terashima Cryogenic plasmas, whose gas temperatures are below room temperature, possess interesting characteristics. The temperature dependences of fundamental characteristics of cryoplasma were studied in detail. We used two types of parallel plate electrodes and the ambient He gas temperature was set to values less than boiling temperature of N$_2$. The breakdown voltage and excited species changed drastically at a temperature of {40 K}. Two discharge modes (Townsend and glow mode) were observed by current-voltage measurements and the power consumption in the Townsend mode was confirmed to be lower than {30~mW}. [Preview Abstract] |
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DTP.00230: Optical measurements of reactive oxygen species in atmospheric pressure plasma jets J.S. Sousa, V. Puech, Q. Algwari, L.J. Cox, K. Niemi, T. Gans, D. O'Connell Atmospheric pressure plasma jets (APPJs) have great technological potential, notably in biomedicine. For a better understanding of the fundamentals of these stable non-equilibrium plasmas, two different APPJs have been experimentally studied. The first, formed inside a cylindrical glass tube ({\o}=4mm) between two external ring electrodes driven at a 20kHz excitation frequency, produces relatively long pulsed plasma jets (few cm). The second is a homogeneous glow discharge sustained between two parallel plates (electrode spacing: 1mm) at radio-frequency (rf) excitation of 13.56MHz Both APPJs are operated in He/O$_{2}$ mixtures (O$_{2 }<$1.5{\%}), and the effluent is emitted into ambient air. Various energy carrying species suitable for biomedical applications are produced. Optical diagnostics of the discharge volumes and the effluent regions have been performed, allowing the measurement of O$_{3}$ (UV OAS) and O$_{2}$(a) (IR OES) densities. High concentrations of O$_{2}$(a), up to 6 10$^{15}$cm$^{-3}$, have been obtained at 5-10cm downstream. Our results show that the rf APPJ generates one order of magnitude more O$_{2}$(a) molecules. The effect of different parameters, such as gas flows and mixtures, and power coupled to the plasmas, are discussed in the study. [Preview Abstract] |
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DTP.00231: Formation of reactive oxygen species and negative ions in radio-frequency driven He/O$_{2}$ atmospheric pressure plasmas Jochen Waskoenig, Timo Gans Revealing and tailoring the formation mechanisms of reactive oxygen species (ROS) in cold helium-oxygen atmospheric pressure plasmas is crucial for controlled technological exploitations, in particular for sensitive treatments in bio-medicine. One- and two-dimensional numerical simulations are used to investigate the dynamic plasma chemistry in radio-frequency driven plasmas. The presented fluid model, with semi-kinetic treatment of electrons, is benchmarked against high-speed imaging of the electron dynamics and active optical measurements of ROS. The code describes 17 plasma species with 142 reactions among them. The obtained simulation results agree very well with the experimental measurements and provide deep insight into details of production and destruction mechanisms. The formation of ROS and negative ions can be described fairly accurately by only a few important plasma chemical reactions. This allows a relatively simple analytical description based on coupled balance equations. The total density of negative ions is predominantly governed by the effective mean electron energy and relatively independent of the plasma density. Consequently, the electro-negativity of the plasma is comparatively high at low input powers and decreases towards higher powers. [Preview Abstract] |
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DTP.00232: Tailoring electron dynamics through frequency coupling in dual radio-frequency driven atmospheric pressure plasmas Colm O'Neill, Jochen Waskoenig, Timo Gans Dual frequency operation of radio-frequency driven atmospheric pressure plasmas offers enhanced control over power coupling and ionization mechanisms [1]. Non-linear frequency coupling in the plasma boundary sheath governs the dynamics of plasma ionization and associated mode transitions. Variations of the frequencies, voltages, and relative phase allow us to manipulate the temporal and spatial structures of plasma ionization. This can be exploited for enhanced plasma production improving plasma efficiency and/or controlled variations of the electron energy distribution function for possible tailoring of the plasma chemistry. \\[4pt] [1] J. Waskoenig and T. Gans, Appl. Phys. Lett. \textbf{96}, 181501 (2010) [Preview Abstract] |
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DTP.00233: Characteristics of DC discharges of high pressure micro gas jet in vacuum Yusuke Mizobuchi, Akimitsu Hatta We have been proposing material processing using microplasma in SEM with \textit{in-situ} observation. It is necessary to produce a small-size and locally confined plasma on the surface of specimen in the vacuum environment. The microplasma processing in SEM is expected to be used for fabrication of MEMS (Micro Electro Mechanical Systems) devices and for local restoration of microelectronics devices such as large scaled integrated circuits (LSIs). It has been confirmed that a micro orifice is suitable to introduce local high pressure micro gas jet into vacuum. Characteristics of DC gas discharges with the micro gas jet were investigated by applying negative or positive DC voltage to the orifice and supplying almost atmospheric pressure of Ar gas to the orifice. A stable DC discharge was observed when the orifice was positively biased. The observed plasma size was the minimum when anode jet was operated at 50 kPa Ar pressure and 1.2mm-gap between the orifice and a counter electrode. [Preview Abstract] |
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DTP.00234: Simulation of Breakdown in Gas Volumes Inside Dielectrics Igor Pashinin, Sergey Pancheshnyi, Severine Le Roy, Leanne C. Pitchford The objective of the present work is to develop a self-consistent model of DC and AC discharges in small voids in insulating materials encompassing an improved description of processes linked to the dielectric itself. To this end, a 1D fluid model based on transport equations for charge carriers coupled to Poisson's equation for electric fields was constructed for dielectrics containing air-filled voids of various sizes. Electron emission from the dielectric surface at the dielectric-gas interface is either continuous or discrete and is supposed to depend on the electric field at the surface. For DC voltages we find that current pulses exist for a range of conditions. These are due to the rapid accumulation of positive charges at the interface in partial discharge events and their eventual neutralization by electrons injected from the cathode and moving in the bulk dielectric. In AC, the transport of charges inside the dielectric has little influence on the discharge dynamics in gas, and the emission properties at the interface determine the shape and repetition rate of the current pulses. [Preview Abstract] |
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