Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session MW1: Poster Session II |
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Room: Kyle Field HOC |
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MW1.00001: Scattering using Electron Vortex Beam Projectiles Allison Harris, Alexander Plumadore, Zoryana Smozhanyk In the last decade, a new type of electron wave packet has been experimentally realized that carries non-zero orbital angular momentum. Known as electron vortex beams (EVBs), these particles have many proposed applications, such as the control and rotation of nanoparticles and improved resolution in electron microscopy. Unfortunately, very little is known about how EVBs interact with individual atoms, and there are no experimental results yet for collisions between EVBs and atoms. There is also very little theoretical work on this topic, with only a handful of studies to date for EVB collisions with hydrogen atoms. If EVBs are to be used for any of the proposed applications, it is crucial to understand how electrons with non-zero angular momentum interact with atoms on a fundamental level. We present ionization cross sections for EVB projectiles colliding with simple atoms and explore their interactions with targets possessing non-zero angular momentum. [Preview Abstract] |
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MW1.00002: Electron capture and ionization in proton collisions with helium Alisher Kadyrov, Shukhrat Alladustov, Ilkhom Abdurakhmanov, Igor Bray, Klaus Bartschat We have developed a two-center convergent close-coupling approach to proton collisions with helium including electron capture [1]. The target is treated as a three-body system, where correlations between the electrons are taken into account. We use a frozen-core approximation, where one of the electrons remains in the He$^{\mathrm{+}}$ 1s orbital. The wave-packet approach is used to discretize the continuum of the target and the hydrogen atom formed after electron capture by the projectile. We present electron-capture and single- and double-ionization cross sections for protons incident on He in the ground state in the energy range from 15 keV to 1 MeV. In addition, the fully differential cross sections for electrons ejected with energy of 5.4 eV at 75 keV incident proton energy and the doubly differential cross sections for electrons ejected with energies up to 65 eV at intermediate projectile energies will also be presented. Results are convergent in terms of the number of the included pseudostates and are in fairly good agreement with the available experimental data. [1] Sh. U. Alladustov et al. Phys. Rev. A 99, 052706 (2019). [Preview Abstract] |
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MW1.00003: Target Dependence of Post-Collision Effects in Ionization by Proton Impact. Madhav Dhital, Aaron Silvus, Sujan Bastola, Esam Ali, Marcelo Ciappina, Don Madison, Michael Schulz We have measured singly charged recoil ions in coincidence with the momentum analyzed projectiles for ionization of Ne and Ar by 75 keV proton impact. From the data we extracted double differential cross sections (DDCS) for a broad range of fixed projectile energy losses as a function of the projectile scattering angle. Furthermore, the average scattering angle $\theta_{\mathrm{ave}}$ for a given energy loss were analyzed as a function of the ejected electron to projectile speed ratio v$_{\mathrm{e}}$/v$_{\mathrm{p}}$. Along with data obtained previously for H, H$_{\mathrm{2}}$, and He targets this made possible a systematic analysis of the dependence of post-collision effects on the target. For targets with a relatively small ionization potential $I$ pronounced minima in $\theta _{\mathrm{ave}}$ were found near v$_{\mathrm{e}}$/v$_{\mathrm{p}} \quad =$ 1, which were absent for targets with large $I$. This observation seems to suggest a decreasing importance of post-collision effects with increasing $I$. However, a possible alternative explanation is an increasing role of the repulsive nucleus-nucleus interaction with increasing $I$, which tends to lead to larger scattering angles. Furthermore, for v$_{\mathrm{e}}$/v$_{\mathrm{p}}$ \textless 1 $\theta_{\mathrm{ave}}$ decreases with increasing $I$, suggesting an increasing role of post-collision effects. [Preview Abstract] |
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MW1.00004: The effect of temperature on electron recombination with water and hydrocarbon ions in high-voltage nanosecond discharge afterglow Andrey Starikovskiy, Maksim Popov, Igor Kochetov, Nickolay Aleksandrov The results of the experimental and numerical study of high-voltage nanosecond discharge plasma decay in gaseous H2O:N2 and H2O:O2 mixtures and in ethane, propane and gas mixtures with them were presented for gas temperature from 300 to 630 K, electron temperature ranged from 300 to 25 000 K and pressures from 1 to 7 Torr. Time-resolved electron density during the plasma decay was measured with a microwave interferometer and effective recombination coefficients were obtained. Measured coefficients depend on gas and electron temperatures and on gas density. Numerical calculation of plasma decay was conducted using available data on recombination coefficients and calculated results were compared with measured ones. It was shown that plasma decay in room temperature gases is controlled by dissociative electron recombination with positive cluster ions. [Preview Abstract] |
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MW1.00005: Comparisons of electron transport and rate coefficients in CO2 and Ar/CO2 calculated from cross-section datasets available on LXCat L.C. Pitchford, L.L. Alves, V. Guerra, S.F. Biagi, I.V. Kochetov, A.P. Napartovich, W.L. Morgan, J. Stephens LXCat (www.lxcat.net) is an open-access, web-based platform for archiving and manipulating collections of data related to electron and ion scattering and transport in low-temperature plasmas (LTP's). LXCat is organized into individual databases containing data uploaded by individual contributors from the LTP community. This implies that data for any particular process can exist in multiple databases on LXCat, and if they differ, users of LXCat are confronted with the choice of which data to use. In this communication, we examine the "complete" sets of cross-sections for electron scattering in CO2 that are available in 6 different databases on LXCat, where ``complete'' implies that the major electron momentum and energy loss processes are well described in the dataset. When these sets of cross-sections are used as input to an electron Boltzmann equation solver, electron energy distribution functions and hence electron transport and rate coefficients can be calculated as functions of E/N, the ratio of the electric field to the neutral gas number density. These cross-section sets differ somewhat among themselves, yet each yields reasonable agreement with the measured transport and rate data that were available at the time each dataset was compiled, some dating back to the late 1970's. [Preview Abstract] |
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MW1.00006: Uncertainty in Computed Electron Transport Coefficients Rhys Doyle, Miles M. Turner Calculation of electron transport parameters from cross section data is central to most approaches to low-temperature plasma modelling. These calculations depend on knowledge of electron-neutral scattering cross sections, which are typically determined by experiments. Such experiments always deliver uncertain results, and this uncertainty necessarily influences any computed transport parameters. A global interest in uncertainty quantification requires that we understand the relationship between uncertainty in cross sections and uncertainty in transport parameters. In this work, we quantify the influence of this uncertainty on computed transport parameters. In general, the uncertainty in any particular transport parameter is a function of the uncertainty in every relevant cross section, but the nature of this relationship is non-obvious. We here employ a screening procedure (the Morris Method) to associate the uncertainty in several particular transport parameters (mobility, diffusion coefficient, certain rate constants) with the uncertainty in cross section data, for the particular cases of helium and nitrogen. [Preview Abstract] |
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MW1.00007: Classical theory of laser-assisted spontaneous bremsstrahlung Harindranath Ambalampitiya, Ilya Fabrikant Laser-assisted spontaneous bremsstrahlung is a process in which a photon with frequency $\Omega$ is created due to electron-atom or electron-ion scattering in the presence of an ac field with a lower frequency $\omega$. Previous studies of this process considered the electron-ion interaction perturbatively or focused on resonances which occur when the emitted photon's frequency is an integer multiple of the laser frequency. In the present paper, we investigate how the bremsstrahlung radiation is affected by the Coulomb focusing [1] when the attractive Coulomb potential focuses a part of the electron wave function during many electron-ion close encounters in the laser field. Using a purely classical approach, as justified in [2], we compute the radiation spectrum of a low-energy electron and report evidence for strong enhancement of the bremsstrahlung radiation due to the Coulomb focusing. $^1$ T. Brabec \textit{et al.}, Phys. Rev. A {\bf 54}, R2551 (1996). $^2$ M. V. Fedorov and M. Yu. Ivanov, Laser Physics {\bf 3}, 365 (1993) [Preview Abstract] |
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MW1.00008: Calculation of positron scattering on H$_2^+$ Dmitry Fursa, Nicolas Mori, Liam Scarlett, Ravshanbek Utamuratov, Igor Bray, Mark Zammit Studies of positron scattering on H$_2^+$ are important part of positron transport modelling through H$_2^+$ and H$_2$ gases and provide a testing ground for theoretical approaches to positron collisions with charged and more complex molecular systems. The convergent close-coupling (CCC) method has been applied to study positron scattering from the vibrational ground state of the molecular hydrogen ion and obtain cross-sections for total inelastic scattering, dissociative excitation, ionisation, proton production for incident energies from 10 to 500~eV. Mass stopping power and mean excitation energy have also been evaluated. The results have been compared with available previous calculations and with corresponding cross sections for positron and electron collisions with He$^+$, H$_2^+$, and H$_2$. In the absence of experimental data and scarcity of other theoretical work for this important collision system, the current calculations will provide a useful complete data set for positron transport studies. [Preview Abstract] |
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MW1.00009: Dust particle string formation in the PK-4 direct current neon discharge Peter Hartmann, Lorin S. Matthews, Evdokiya Kostadinova, Truell W. Hyde, Marlene Rosenberg Using multi-scale numerical modeling we provide a detailed and quantitative description of the dust chain structure formation in the PK-4 experiment operating onboard the International Space Station based on a realistic particle in cell simulation of the neon DC gas discharge, Monte Carlo type dust particle charging computations, and dust-dust interaction calculations. We show, (i) that ionization waves and fast transients appearing during the polarity switching in the gas discharge play an important role to create stable dust particle chains, (ii) how the streaming ions deform the inter-particle interaction potential, and (iii) the mode structure of dust density waves traveling along the dust particle chains. [Preview Abstract] |
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MW1.00010: Synthesis of core-shell nanoparticles with tin-droplet core using magnetron sputtering dusty plasma K. Sasaki, H. Koyama Core-shell nanoparticles with metal cores having low melting points can be applied to thermal management technologies, but a problem is the destruction of the shell film by the thermal tension when the core metal melts. A solution to this issue is to deposit the shell film onto the droplet of the core metal. In this work, we synthesized tin nanoparticles using high-pressure magnetron sputtering. The magnetron sputtering source was installed at the top of a vacuum chamber, and tin nanoparticles were transported to a capacitively coupled plasma (CCP) produced at the bottom. Tin nanoparticles were trapped above a ring CCP electrode by the sheath electric field, and they were heated by the heat flux from the plasma to realize their melting. Amorphous carbon films were deposited on tin droplets by introducing CH$_4$ into the CCP plasma. Another method to form shell films was the sputtering deposition of Cu using another magnetron source. Core-shell nanoparticles thus synthesized were collected by applying a positive bias voltage to a planar electrode. We confirmed the robustness of tin-carbon core-shell nanoparticles by heating them in a tunneling electron microscope. [Preview Abstract] |
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MW1.00011: The effect of electron attachment and detachment on electron energy probability function in an inductive oxygen discharge. Jiwon Jung, Mooyoung Lee, Chinwook Chung Electron energy probability functions (EEPFs) were measured with RF powers at various pressures in oxygen inductive discharge. In low pressures (\textless 50 mTorr), EEPFs are in a Maxwellian distribution and the low energy (1\textasciitilde 5 eV) electron temperature decreases with RF power. However, in high pressure of 100 mTorr, EEPFs are in a Druyvesteyn-like distribution and the low energy electron temperature increases with low powers (80\textasciitilde 100 W) and then it decreases. These change in the EEPF can be attributed to negative ion generation and electron detachment from the negative ions. An electronegativity ($\alpha )$ was measured with the two-probe method suggested by \textit{P.Chabert et. al}. It turns out that the changes in the EEPF are strongly correlated to those in the electronegativity and the change in electron generation and loss due to electron attachment and detachment leads to the electron temperature. [Preview Abstract] |
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MW1.00012: Emission model for determining EEDF in low-pressure oxygen plasmas Jessica Pachicano, John B. Boffard, Colie Keane, Nathaniel Ly, Colin Swee, Chun C. Lin, Amy Wendt Non-invasive diagnostics based on optical emission spectroscopy (OES) to determine the electron energy distribution function (EEDF) are an attractive tool for optimization and control of technological plasmas. Progress will be reported on an oxygen emission model for O and O$_2^+$ emitting states that accounts for both excitation and de-excitation, using the EEDF as an input. In addition to previously known excitation cross sections, the model also requires rates for the excitation of O$_2^+$ from the ion ground state as well as electron quenching of emitting states. Our past efforts have primarily used atomic O emission lines along with emission bands of the O$_2^+$ first negative system (FNS). Emissions from the O$_2^+$ second negative system (SNS) enhance the model, since they vary with plasma conditions differently than those of the FNS. Excitation and quenching parameters for FNS and SNS bands have been determined by fitting emission intensities as a function of electron density using data recorded at 2.5-30 mTorr and ICP powers of 100-2000 W. Preliminary results from application of the completed emission model to determine EEDFs, by finding the best match between emission model relative intensities and experimentally measured values, will also be presented. [Preview Abstract] |
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MW1.00013: A new diagnostic method for measurement of local plasma density Min Sup Hur, Salizhan Kylychbekov, Hyung Seon Song In this paper, we present a new method to measure the local plasma density at any desired position in a generally non-uniform plasma, without any mathematical inversion process of the integrated probe data. The idea is colliding two, slightly detuned electromagnetic pulses as a desired position inside the plasma. The frequencies of the pulses are assumed to be much higher than the plasma frequency, so that the pulses can propagate through the plasma without much absorption. At the collision point of the pulses, the beat wave train traps the background electrons and displace the electron bunch. After the pulse collision, the displaced electron bunch commence the plasma dipole oscillation, emitting radiation at the local plasma frequency. By measuring the radiation frequency, the plasma density at the position where the radiation originates can be determined. Since the dimension of the plasma dipole can be arbitrarily made small by adjusting the collision angle and spot size of the driving pulses, this method enables pin-point of the local plasma density. We summarize the substantial amount of two-dimensional particle-in-cell simulations demonstrating the frequency matching between the radiation and the local plasma frequency. [Preview Abstract] |
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MW1.00014: Development of a Sensitive Electric Field Probe in Ar plasmas using Optically Trapped Fine Particles Kentaro Tomita, Sakyo Okunaga, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani For advanced plasma processing, understandings of plasma-surface interactions are prerequisite. To obtain information about it, we have used optically-trapped fine particles in plasmas using a laser-tweezer technique. Ar plasmas were generated between a powered ring-electrode at the bottom of the reactor at 100 Pa by applying 13.36 MHz voltage. PMMA particles (10 µm in diameter) were injected into the plasmas. Some particles were suspended at plasma/sheath boundary by the balance among gravity, ion drag, and electrostatic forces. To trap the particle, a laser ($\lambda =$ 1064 nm) was irradiated from the bottom using an objective lens. Because the trapped particle was negatively charged, it can be a probe of electric fields. The trapped particle was moved to the horizontal direction. The particle was well controlled for a certain distance. However, there was a limit for the area where the stable control was possible. The movable area became large when the trapping force was increased. These results can be explained as follows: the electrostatic force to the trapped particle was changed when the particle was moved from the initial position. The trapping was failed when the increase of the electrostatic force overwhelms the trapping force. [Preview Abstract] |
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MW1.00015: A plasma diagnostic method by applying square voltages to a floating probe for deposition plasmas Moo-Young Lee, Chin-Wook Chung To measure electron temperatures and ion densities in an environment where a dielectric film can be deposited, the transient voltage of a capacitor connected in series to a floating probe is analyzed. When two square voltages with different amplitudes are applied to the probe tip, the current from plasma flows and charges the capacitor. To obtain plasma parameters, a circuit model is suggested. Electron temperatures and ion densities are obtained from the ratio of transient capacitor voltages. Because deposited film can be represented as a capacitor, the applied square voltage is divided into the dielectric film and the connected capacitor. From the ratio of divided voltages, the capacitance of dielectric film can be obtained. The measured electron temperatures and ion densities are compared with those from electron energy distribution functions. This method can be applied for processing plasma monitoring. [Preview Abstract] |
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MW1.00016: A method to measure the negative ion density distribution using Langmuir probes in low-pressure oxygen plasmas Aixian Zhang, Chin-Wook Chung A method, based on the floating harmonic method (FHM), of measuring the density distribution of negative ions is introduced, and the experiment is performed in an inductively coupled oxygen plasma. Electron temperatures and positive ion saturation currents are obtained through the FHM using a DC blocking capacitor. Whereas, the electron saturation currents are measured by applying a DC voltage without the blocking capacitor. Negative ion density profiles along the radial direction are obtained from the electron and positive ion currents. Furthermore, the changes in the distribution of negative ions with various pressures and applied powers are investigated, and they are compared with those from the two-probe theory by Chabert et. al.. This method can measure the negative ion density distributions qualitatively with ease. [Preview Abstract] |
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MW1.00017: Development of a Laser-Induced Fluorescence System to Measure the Electric Field Magnitude Induced by Energetic Electron Beams in a Gas Christopher Durot, Jenny Smith, John Foster A high energy electron beam in a gas induces an electric field by the time rate of change of the net current. This electric field can lead to an electrical breakdown of the gas and a return current that reduces the net current. Reliable measurement of the E-field magnitude is necessary to inform and validate models of the complicated dynamics of this interaction. In support of gas chemistry studies at the Naval Research Laboratory, the University of Michigan is developing a laser-induced fluorescence dip (LIF-dip) spectroscopy system. LIF-dip is a technique using two lasers to directly measure electric field magnitude. One laser populates the fluorescing state while the other depopulates it in a transition to Rydberg states. The electric field can be measured by analyzing the ``dip'' in the fluorescence signal as the second laser wavelength is scanned. The technique can sensitively detect electric field magnitude because Rydberg states are highly sensitive to the Stark effect. In this contribution, we describe the design and buildup of this laser spectroscopy system and present initial LIF measurements of argon metastables. [Preview Abstract] |
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MW1.00018: In situ Raman spectroscopy of silicon surfaces in contact with atmospheric-pressure pressure plasmas David Pai, Frederic Pailloux, David Babonneau We examine the use of in situ Raman spectroscopy for observing changes to surfaces in contact with atmospheric plasmas. As an example, we consider surface plasmas generated in air at atmospheric pressure on alumina thin film-silicon bilayer barriers. We use a nanosecond repetitively pulsed discharge to demonstrate Raman monitoring of the state of the surface, in particular the first order optical phonon of silicon, with a time resolution of 1 s. Depending on the duration of plasma operation, the Raman spectrum of silicon undergoes shifting to lower wavenumber and asymmetric broadening. These changes are consistent with the presence of nanostructured silicon. Ex situ electron micrographs confirm that such structuration occurs at several size scales, down to nanoparticles about 50 nm in diameter. Spectral lineshape analysis showed that these changes are consistent with phonon confinement, laser heating, and/or Fano interference between the scattering from phonons and electronic Raman scattering. We were also able to isolate a systematic change that occurs within the first few seconds of plasma exposure on a previously untreated surface. The Raman peak of Si undergoes a pure enhancement without any shifting or broadening, which is consistent with photon confinement. [Preview Abstract] |
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MW1.00019: A spectral-kinetic approach for the planar multipole resonance probe Michael Friedrichs, Junbo Gong, Ralf Peter Brinkmann, Jens Oberrath The planar multipole resonance probe (pMRP) is a diagnostic-tool based on the concept of active plasma resonance spectroscopy (APRS), which excites the plasma in the GHz range and records the response to detect resonances. Due to its planar design the pMRP is especially suited to monitor plasma processes without perturbing them. To determine plasma parameter from measured resonance, a model for the relation between plasma and resonance parameter is required. By means of the cold plasma model a relation between electron density and the resonance frequency can be derived. Another important plasma parameter is the electron temperature, which has to be determined by a different resonance parameter, namely the half-width of the resonance peak. However, a measured resonance peak in a low pressure plasma is broadened by kinetic effects, which requires a kinetic model to derive a correct relation between the half-width and the electron temperature. In this work a spectral kinetic approach - a particle simulation where the fields are calculated in the Fourier space - for the pMRP will be presented to analyze the influence of kinetic effects on the half-width. [Preview Abstract] |
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MW1.00020: A comprehensive collisional-radiative model for Xe$^+$ and Xe excited species Yan-Fei Wang, Xi-Ming Zhu, Yang Wang, Da-Ren Yu, Oleg Zatsarinny, Klaus Bartschat, Tsanko Tsankov, Uwe Czarnetzki Xenon is the most widely used propellant in Electric Propulsion (EP) systems. A collisional-radiative (CR) model for xenon excited species is needed for a better understanding of the kinetic mechanisms and to support optical emission spectroscopy in xenon plasmas. However, CR models concerning the kinetics of xenon ionic states are currently not available in the literature due to the lack of reliable cross section data. In this work, a CR model for atomic and ionic processes based on cross sections calculated by the Dirac B-Spline R-Matrix method is used to study the kinetic mechanisms of ionic 6s, 5d, and 6p states in electric propulsion discharges. [Preview Abstract] |
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MW1.00021: Quantifying Plasma transport in ROBIN negative ion source: PIC-MCC Simulations vs. Experiments Bhaskar Chaudhury, Miral Shah, Mainak Bandyopadhyay, Arun Chakraborty The RF based negative ion source ROBIN (Rf operated Beam source in India for Negative ion research) has been setup at IPR, India to investigate the different issues related to production, transport and extraction of negative hydrogen ions in negative ion sources for fusion applications. Quantifying plasma transport accurately in such sources is a challenging task, since the presence of non-uniform electric and magnetic (magnetic filter) field leads to different diffusion phenomena (classical, ambipolar, anomalous etc). The primary challenge is to understand the role of different diffusion and collisional processes in addition to the role of density gradients and drifts. We have used our in-house parallel 2D-3v PIC-MCC code [1] to quantify the role of different physical processes responsible for the plasma transport across magnetic filter under conditions similar to real ROBIN experimental setup [2]. The simulation results show similar behaviors as observed during the first phase of ROBIN experiments (without negative ions), and we have used exhaustive PIC simulations to quantify the contribution of different physical processes responsible for the plasma transport across magnetic filter. \begin{enumerate} \item Chaudhury B. et al., Hybrid Parallelization of PIC-MCC Algorithm for Simulation of Low Temperature Plasmas. Communications in Computer and Information Science, vol. 964, 2019. \item Bansal G., \textit{Negative ion beam extraction in ROBIN, Fusion Eng. Des. }\textbf{\textit{88,}}\textit{ 2013.} \end{enumerate} [Preview Abstract] |
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MW1.00022: Simulating long streamers in air with different reaction sets Andy Martinez, Jannis Teunissen, Ute Ebert Large scale streamer discharges in air are observed in a variety of environments: high voltage laboratory experiments, lightning discharges, sprites above thunderclouds, etc. However, most simulation studies have thus far only considered relatively short cm-scale streamers. For long streamers, additional chemical reactions have to be considered that affect the streamer's conductivity and thereby also its propagation. In this study we investigate which chemical reactions (positive and negative ion conversion, electron recombination, ion recombination, etc.) play an important role for metre-scale streamers in STP air and how big the influence of these reactions is on the streamer properties (velocity, radius, electric field at the tip). An axisymmetric streamer model with adaptive mesh refinement and parallelization is used to perform the simulations. [Preview Abstract] |
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MW1.00023: Kinetic Investigation of the Planar Multipole Resonance Probe Chunjie Wang, Michael Friedrichs, Junbo Gong, Jens Oberrath, Ralf Peter Brinkmann Active Plasma Resonance Spectroscopy (APRS) is a well-established plasma diagnostic method: A radio frequency signal is coupled into the plasma via a probe or antenna, excites it to oscillate, and the response is evaluated via a mathematical model. Many APRS probes are invasive and perturb the plasma by their physical presence. The planar Multipole Resonance Probe (pMRP) [1] solves this problem: It can be integrated into the chamber wall and minimizes the perturbations. Previous work has studied the pMRP in the frame of the cold plasma model (Drude model) [2], missing important effects like collision-less damping. In this work, a kinetic model is developed to investigate the behavior of the pMRP more closely. This model consists of the collision-less Vlasov equation, which is coupled with the Poisson equation under the electrostatic approximation. The spectral response of the probe-plasma system is found by calculating the complex admittance. This model covers kinetic effects and overcomes the limitations of the cold plasma model. [1] C. Schulz, T. Styrnoll, P. Awakowicz, I. Rolfes, IEEE Trans. Instrum. Meas. 64, 857 (2015). [2] M. Friedrichs and J. Oberrath, J. EPJ Techn. Instrum. 5, 7 (2018). [Preview Abstract] |
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MW1.00024: Multi-physics simulation of a capacitively coupled plasma reactor with a non-flat electrode Seung-Min Ryu, Dylan Pederson, Yunho Kim, Kenta Suzuki, Laxminarayan Raja, Namki Cho, Jinseok Lee, Chungho Cho, Jiho Uh, Sang-Jin Choi Plasma uniformity in a capacitively coupled reactor is normally controlled by changing tunable process parameters such as electrode power, gas flow rate, and process pressure etc. In this study, we report on the effects of electrode shape on plasma characteristics in dual frequency capacitive argon discharges using a multi-physics plasma fluid model. The geometry of the 2D axisymmetric model consists of a plasma sub-domain, an upper grounded electrode with gas inlet holes, a lower powered electrode that holds a wafer, and dielectric rings. The computational model is developed including a fluid plasma model, which solves the continuity equations for charged species and the electron energy balance equation, coupled with electromagnetic Maxwell's equations for the self-consistent description of the high frequency induced plasma. The simulation results yield the distribution of plasma characteristics such as the charged species density, electron energy distribution, electron temperature and sheath boundary etc. in the plasma space and are used to improve plasma uniformity on the wafer. [Preview Abstract] |
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MW1.00025: Fully Implicit Particle-in-Cell Simulations of the Electron Cyclotron Drift Instability Emanuele Cazzola, Kentaro Hara A fully implicit particle-in-cell (PIC) simulation is developed to model the electron cyclotron drift instability (ECDI) that occurs in low-temperature magnetized plasmas. In particular, theoretical studies have demonstrated that the ECDI shows its maximum growth rate for frequencies in the regime of cyclotron frequency and wavelengths in the regime of the electron gyroradius - respectively $\sim$ MHz and $\sim10^{-4}$ m for typical Hall thruster parameters. As explicit PIC simulations are constrained to simulating scales of the Debye length ($\sim 10^{-5}$ m) and the plasma frequency ($\sim$ GHz), the choice of a fully implicit PIC scheme allows us to gain at least one order of magnitude in each dimension. The possibility of simulating longer time scales and larger domain sizes will give an important boost to the investigation of those self-organizing structures seen within high turbulent flows. The implicit PIC simulations are developed to model Vlasov-Ampere and Vlasov-Poisson systems. The code is verified against published results on Landau damping and two-stream instabilities\footnote{Chen, G., Chacón L., Barnes D., J. Comput. Phys., 230 (2011), pp. 7018-7036}. The numerical results and performance of the implicit PIC method will be discussed. [Preview Abstract] |
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MW1.00026: A Data-Driven Approach to Model Calibration for Nonlinear Plasma Behavior Christine Greve, Kentaro Hara The physics of low-temperature magnetized plasmas is complex and still poorly understood despite the use of a variety of modeling methods (fluid, kinetic, hybrid, etc.). The dynamic nature of this phenomenon has yet to be modeled in a predictive manner using physics-based simulations, as most models attempt to validate against steady-state experimental results. In this work, a data-driven model approach that solves the inverse problem with a reference solution, such as a set of experimental data, is used to search for appropriate input parameter values for a set of governing equations. Specifically, the characterization of a data-driven approach to model calibration using time embeddings and the first Wasserstein distance is presented in this work. The convergence properties of the proposed approach are studied using numerical solutions, though experimental training data will be used in the future. The data-driven modeling framework is applied to model the discharge plasma of Hall effect thrusters, illustrating its potential use for further understanding the fundamental plasma physics. [Preview Abstract] |
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MW1.00027: Evaluation of electron collision cross sections using a Boltzmann equation solver. Deuk-Chul Kwon, Mi-Young Song, Hyo-Chang Lee The swarm analysis is widely used for evaluating or predicting the electron collision cross sections by comparing the calculated electron mobility using a Boltzmann equation solver and experimental results. In this work, electron collision cross sections were evaluated by comparing the electron energy probability functions (EEPFs) calculated using cross section data with the EEPFs measured with a Langmuir probe. In order to calculate the EEPFs, the Fokker-Planck equation is numerically solved for inductively coupled plasma sources. The electron collision data for nitrogen, oxygen, and argon plasma were evaluated, and the dependence of the EEPFs on the electron heating model was also investigated. [Preview Abstract] |
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MW1.00028: 2D axial-azimuthal Particle-In-Cell benchmark for low-temperature magnetized plasmas Thomas Charoy, Jean-Pierre Boeuf, Anne Bourdon, Pascal Chabert, Denis Eremin, Laurent Garrigues, Ken Hara, Tasman Powis, Andrei Smolyakov, Dmytro Sydorenko, Antoine Tavant, Willca Villafana In applications such as ion sources or plasma processing, the gas pressure is relatively low and plasma confinement by a magnetic field is required. We call these plasmas “partially magnetized plasmas” because electrons are strongly magnetized, while ions are not. The magnetic field can be responsible for a variety of instabilities that are difficult to describe quantitatively. A kinetic description is needed to understand these instabilities but prior to use a Particle-In-Cell (PIC) code extensively, it is important to be sure of its correctness. Unit tests can be used to verify specific modules and benchmarks can be defined in a more global approach, such as the 1D Helium benchmark of Turner et al, in which 5 independent PIC codes were giving similar results. However, we needed here a simulation case that was closer to the complex physics of an ExB discharge. A 2D axial-azimuthal simulation case was chosen and the results of 7 independent PIC codes have been compared extensively (mean parameters and instabilities characteristics). A particular focus has been made on the dependance on number of particles per cell, as it has been recently shown to influence numerical results. [Preview Abstract] |
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MW1.00029: Employing Reduced Chemistry Models on E-Beam/Gas Systems Matthew Hopkins, Christopher Moore, Benjamin Yee, Kate Bell, Andrew Fierro In this work we examine the impact of using reduced and/or modified sets of cross sections on the interaction of an electron beam and a low-pressure background gas. Because most collisional plasma systems lack extensive sets of cross sections to model electron-neutral and other particle interactions, one often cannot provide good estimates of errors or uncertainties in complex non-equilibrium plasma systems (e.g., electrons impacting molecular species in air). To begin to understand the impact of using necessarily reduced chemistry models in a complex system in the future, we analyze the effect of using reduced chemistry models in a simpler system where more extensive cross section data exists. To do this, we simulate the interaction of a 3-6 keV electron beam with a 100 mTorr background of neutral ground state argon in a 1 cm 1D gap. The Aleph simulation code is used, which combines PIC and DSMC methodologies. An RLC-type boundary condition is used to capture some of the coupled circuit behavior and inductive effects (full consistency requires an electromagnetic treatment). [Preview Abstract] |
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MW1.00030: The simulation of a three-dimensional fluid model for H2 inductively coupled plasma at low pressure Ying-Jie Wang, Fei Gao, You-Nian Wang A three-dimensional fluid model is developed to study the radio-frequency inductively coupled H2 discharge with an expansion region at low pressure for neutral beam injector. In simulation, the effective collision frequency are considered which include Ohmic heating and stochastic heating. It is found that with stochastic heating taken into account, the deposition power rises, so the electron density is much higher than that in the case without stochastic heating effect. Because stochastic heating effect is a main heating mechanism at pressures of 10 mTorr or less. Furthermore, the effects of absorption power and pressure on the electron density and temperature is demonstrated. The electron density and temperature rise with the absorption power increases. When the pressure increases, the electron density is also increase and the maximum of electron is from diffusion chamber to driver chamber. In addition, the plasma characteristics are also investigated with and without magnetic field. [Preview Abstract] |
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MW1.00031: Fluid simulations of discharge mode transition in inductively coupled Ar/O2 plasmas with an RF bias Jia-Wei Huang, Hong Li, Yu-Ru Zhang, Fei Gao, You-Nian Wang A two-dimensional fluid model is developed to investigate the influence of an RF bias power on planar coil inductively coupled Ar/O2 plasmas, in which the inductive discharge is mainly sustained by a power with a fixed frequency 13.56 MHz, while the capacitively-coupled bias power has a lower frequency. In the simulations, the bulk plasma is described by a fluid model, combined bi-directionally with a sheath model, and the stochastic heating caused by the RF sheath oscillation is considered by adding a heat flux at the bulk-sheath boundary. In addition, secondary electron emission at the bias electrode is also taken into account. Numerical results show that the discharge transits from the inductive mode (H mode) to the capacitive mode (E mode) by increasing RF bias power, and thus the electron density first decreases and then increases with bias power. [Preview Abstract] |
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MW1.00032: A hybrid simulation of radio frequency biased inductively coupled Cl2 discharges Lei Tong, Yu-Ru Zhang, Yuan-Hong Song, You-Nian Wang In a biased inductively coupled plasma (ICP) discharges, the sheath behavior has an important influence on the bulk plasma properties. Therefore, a hybrid model, which consist of a global model coupled bi-directionally with a fluid sheath model is employed to investigate the biased ICP discharges in electronegative Cl2 gases. The plasma parameters in the bulk region, such as the density of electron and various ions, as well as the electron temperature are calculated by the global model and they are input into the sheath model as boundary conditions. The sheath behavior is described by a sheath model, and the power absorption from the bias source and the sheath voltage drop are delivered to the global model. When the convergence is achieves, an ion Monte-Carlo collision model is executed. The influence of coil power, pressure and bias voltage waveform on the bulk, as well as on the ion energy and angular distributions for both Cl$+$ and Cl2$+$ ions on the bias electrode are investigated. [Preview Abstract] |
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MW1.00033: Three Dimensional Langmuir Probe Measurements of Fundamental Plasma Parameters in Pulsed ICP Operation Jia Han, Patrick Pribyl, Walter Gekelman Radio frequency plasma sources are widely used in low temperature industrial processing. Inductively coupled plasma (ICP) is an example, where plasma is generated by a stove-top coil mounted above the machine. Having reached a limit in process improvement available with steady state plasmas, the semiconductor industry has shown great interest in temporally modulated plasma operation. We performed 3D measurements of fundamental plasma parameters in a pulsed Argon plasma in a modified industrial etch tool. The ICP and bias RF can be independently pulsed at arbitrary repetition rates and duty cycles. This work reports Langmuir probe measurements of the dynamics of plasma parameters for pulsed operations. (A second poster at this meeting discusses magnetic and current measurements). The RF on the coil is switched on in less than 50 micro-seconds, however the plasma takes several milliseconds to reach steady state. After RF turn off, the plasma temperature decays much faster than the density. We also report profile dynamics of pulsed operation at a repetition rate $=$ 1 kHz, where the plasma does not have time to reach its nominal steady state. Results will be presented with and without interleaved sequenced bias voltage. [Preview Abstract] |
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MW1.00034: Three Dimensional Magnetic and Current Measurements in Pulsed ICP Operation Patrick Pribyl, Jia Han, Walter Gekelman Radio frequency plasma sources are widely used in low temperature industrial processing. Inductively coupled plasma (ICP) is an example, where plasma is generated by a stove-top coil mounted above the machine. Having reached a limit in process improvement available with steady state plasmas, the semiconductor industry has shown great interest in temporally modulated plasma operation. We performed 3D measurements of fundamental plasma parameters in a pulsed Argon plasma in a modified industrial etch tool. The ICP and bias RF can be independently pulsed at arbitrary repetition rates and duty cycles. This work reports magnetic probe measurements (B-dot) and the derived plasma current dynamics for pulsed operations. (A second poster at this meeting discusses Langmuir probe measurements). In general the current is concentrated near the top of the chamber, forming an induced image current from the antenna. As previously reported, the ohmic power is deposited close to the antenna, and not co-located with either the peak current or the density. We also report profile dynamics of pulsed operation at a repetition rate $=$ 1 kHz, where the plasma does not have time to reach its nominal steady state. [Preview Abstract] |
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MW1.00035: Effect of N$_{\mathrm{2}}$ on decomposition of CO$_{\mathrm{2}}$ using a hybrid plasma source Kwan-Yong Kim, Kyung-Hyun Kim, Ho-Jun Moon, Bum-Seok Kim, Chin-Wook Chung Conversion of carbon dioxide (CO$_{\mathrm{2}})$ into carbon monoxide (CO) and oxygen (O) is studied using a hybrid plasma source with N$_{\mathrm{2}}$/CO$_{\mathrm{2}}$ ratios. The hybrid plasma source consists of an antenna and an electrode, which are connected in parallel. An external variable capacitor (C$_{v})$ is installed in series with the antenna which can control current ratio between the antenna and the electrode. This plasma source can selectively control of inductive coupling and capacitive coupling. The Optical emission spectroscopy (OES) is used to measure the intensities of CO$_{\mathrm{2}}$, CO, and O. Electron temperatures, electron densities and energy probability functions (EEPFs) were measured using a single Langmuir probe. The decomposition energy efficiency and the decomposition efficiency of CO$_{\mathrm{2}}$ under various discharge conditions are obtained. Experiment shows that high energy electron population increases with N$_{\mathrm{2}}$ ratio, and CO from CO$_{\mathrm{2}}$ is increased. [Preview Abstract] |
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MW1.00036: Effect of capacitor termination to a planar antenna coil on electron density distribution in an inductively coupled plasma Taewoo Kim, Chinwook Chung The effects of capacitor termination to a planar antenna coil on electron density distributions and the electron energy distribution function (EEDF) are investigated in an argon inductive discharge. As changing the capacitance, the plasma parameters are significantly changed. When the reactance of the termination capacitor is half that of the planar coil, electrostatic coupling between the antenna coil and the plasma is suppressed. At low pressures, electron densities are maximized, while electron temperatures and plasma potentials are minimized. At high pressures, electron temperatures and plasma potentials are minimized, however, electron density is not maximized. Electron energy distribution functions (EEDFs) and electron density distributions are also measured. As pressure increases, non-local to local electron kinetics transition occurs. In local kinetics or high pressures, the experimental results show that the electron density distribution is changed by the position of the virtual ground of the antenna coil.. [Preview Abstract] |
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MW1.00037: On the E to H transition in a dual frequency inductively coupled plasma Young-Hun Hong, Ju-Ho Kim, Chin-Wook Chung E-H transition powers with various gas pressures are investigated in a dual frequency inductively coupled plasma. Driving frequencies of 2 MHz and 13.56 MHz are applied to antennas, respectively. At low pressures ($\nu $/$\omega $\textless 1), the E-H transition power decreases with the pressure, and at high pressures ($\nu $/$\omega $\textgreater 1), the transition power increases with the pressure. Therefore, the transition power has a minimum near $\nu $/$\omega $\textasciitilde 1. In experiments, the E-H transition power of 2 MHz is lower than that of 13.56 MHz at low pressures (\textless 10 mTorr). At high pressures (\textgreater 50 mTorr), the transition power of 13.56 MHz is lower than that of 2 MHz. However, at the dual frequency operation, the transition occurs between the transition power of 2 MHz and 13.56 MHz. These transition powers of the dual frequency are consistent with those from a power balance model including plasma absorbed power and plasma loss power. In the dual frequency ICP, the E-H transition is more independent of the pressure than a single frequency ICP. [Preview Abstract] |
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MW1.00038: Characterization of an inductively coupled plasma (ICP) source for ion implantation process- DaeChul Jung, ChinWook Chung Ion densities and electron temperatures are measured by using the floating harmonic method (FHM) in an argon inductively coupled plasma source for ion implantation process. Since the ion implantation processes operate at high vacuum, high voltages are required for ignition. However, ion energy losses increase, and ion densities decrease due to the high voltages. In this work, to reduce the ion energy loss, a capacitor connected in series to the termination of an antenna in the ICP. Ion densities and electron temperatures are quantitatively compared with and without the capacitor. When using the antenna with the capacitor, the transfer efficiency is lower than that of using the antenna without capacitor. however, the ion density is higher when using the antenna with the capacitor. [Preview Abstract] |
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MW1.00039: Spectroscopic diagnostics of microwave excited atmospheric pressure Ar plasma jet in open air Keigo Takeda, Mineo Hiramatsu, Kenji Ishikawa, Masaru Hori A microwave excited atmospheric pressure plasma jet (APPJ) with Ar gas was used to produce a plasma activated medium (PAM) for the cancer cell treatment in our group, as result, the antitumor effect of microwave excited PAM was stronger than the conventional PAM produced by an AC-excited Ar gas APPJ. For the APPJ treatment in atmosphere, the gas-phase reaction of APPJ with ambient air is an important issue for understanding the generation mechanism of reactive species. In this study, spectroscopic diagnostics of microwave excited Ar gas APPJ in open air was performed to understand the gas-phase reactions. Firstly, the gas temperature and the electron density of APPJ were estimated to be about 10$^{\mathrm{14}}$ cm$^{\mathrm{-3}}$ and 1000 K by fitting the emission spectra of Balmer-$\beta $ line of H atom and 2nd positive band of N$_{\mathrm{2}}$, respectively. And then the metastable Ar atom density generated by the APPJ in open air was measured by laser diode absorption spectroscopy. As result, the density decreased from 10$^{\mathrm{11}}$ to 10$^{\mathrm{10}}$ cm$^{\mathrm{-3}}$ with the increase in the Ar gas flow rate. It is considered that collisional quenching of metastable Ar atom with ambient air molecules increases with increasing the flow rate. [Preview Abstract] |
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MW1.00040: Impact of N$_2$O and O$_2$ admixtures on pulsed DBDs in N$_2$ at atmospheric pressure M. M. Becker, H. Hoft, M. Kettlitz, R. Brandenburg, D. Loffhagen The gas composition is a key parameter that determines basic properties of dielectric barrier discharges (DBDs). N$_2$ is a common working gas for DBD-based plasma processing and N$_2$O is frequently admixed as a precursor in plasma-enhanced chemical vapour deposition of thin oxide layers or for the control of layer stoichiometry in other layer deposition processes. Furthermore, O$_2$ impurities are known to have a strong impact on discharge characteristics and are difficult to avoid. The present contribution investigates systematically the impact of N$_2$O and O$_2$ admixtures on pulsed-driven, single-filament DBDs in N$_2$ at atmospheric pressure. Reaction kinetic modeling was used to analyze the change of plasma-chemical processes for different gas mixtures, and electrical measurements were performed. Similar non-monotonous changes of DBD properties caused by pre-ionization effects were observed both for increasing N$_2$O and O$_2$ content, although the underlying processes were found to be essentially different for N$_2$O and O$_2$ admixtures, respectively. A transition from electropositive to electronegative plasma conditions was found with increasing N$_2$O content, while the admixture of O$_2$ strongly affects the recombination of electrons with positive ions. [Preview Abstract] |
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MW1.00041: Temporal evolution of electron density in anomalously dense non-equilibrium plasma Taemin Yong, Mark Cappelli This study investigates generating dense non-equilibrium plasma states in high presure (up to 10 bar) gas with two methods. In the first method, initial discharge plasmas are generated using high voltage nanosecond pulses (10 kV, 20ns) in argon gas followed by electron heating using a relatively low energy picosecond laser (\textasciitilde 1 mJ, 532 nm). The electrode configuration consists of a pin-to-pin geometry with short gap (\textasciitilde 200 um). In the second approach, the initial plasma is replaced by YAG laser-induced discharges (\textasciitilde 100 mJ, 532 nm) in air. The temporal evolution of electron density is measured by optical emission spectroscopy using a streak camera with 10 picosecond-resolution. The electron density is inferred from the Stark broadening of H$_{\mathrm{\alpha }}$ line (656.2nm), Ar I line (696.5 nm), and O I line (777 nm). [Preview Abstract] |
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MW1.00042: Modeling of streamer interaction with dense and rarefied flat gaseous layers Andrey Starikovskiy, Nickolay Aleksandrov Streamer interaction with normal gaseous layers of various densities is numerically simulated in ambient air on the basis of a two-dimensional fluid model. It is shown that rarefied layers are greater obstacles to streamer propagation in comparison with dense layers. When intersecting a low-density layer, the streamer tends to initiate a radial ionization layer, which screens and weakens the electric field both on the axis in the layer and behind it. As a result, it is difficult to form a secondary streamer behind the layer. A streamer interacting with a high-density layer also can initiate a radial ionization wave, which develops in undisturbed air along the outer surface of the layer. The streamer can overcome a high-density layer at not-too-high values of the layer thickness. The effects of the layer thickness and the density difference on the streamer interaction with the layer are studied. [Preview Abstract] |
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MW1.00043: Charge accumulations evolution in dielectric barrier discharges with various dielectric surface conditions. Haruaki Akashi, Tomokazu Yoshinaga Atmospheric pressure oxygen dielectric barrier discharges have been simulated to investigate the effect of accumulated charges behavior. In the present model, we only considered desorption of accumulated electrons w/ and w/o adsorption energy from the dielectrics. At first, waveforms of accumulated charge at filament discharge center and off filament with no desorption were examined. In positive charge period, two waveforms are significantly different, but in negative charge period, they are very similar. Because at the center of streamer, there is intense ionization to increase the positive charges, but off the streamer, it is much less. While in negative charge period, electrons are easily to drift and diffuse, so spread out to cover the dielectric surface. As a result, dielectric surface becomes non uniform in positive but becomes uniform in negative. In the case of desorption with no adsorption energy, the charge accumulation in early stage becomes completely different, and positive charges off filament center become significantly small. And the decrease of negative charges becomes significant, but the other tendencies are similar to no desorption case. While in the case of desorption with adsorption energy, the waveforms has mixed tendencies of two cases mentioned above. [Preview Abstract] |
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MW1.00044: Influence of surface parameters on DBDs in argon at subatmospheric pressure M. Stankov, M.M. Becker, R. Bansemer, D. Loffhagen The properties of the isolating surface in dielectric barrier discharges (DBDs) strongly influence the DBD's characteristics. However, e.g.\ the secondary electron emission coefficient and permittivity of the dielectric are usually not very well known. This is particularly a problem if numerical modeling is applied to optimize specific devices. This contribution reports on a time-dependent, spatially one-dimensional fluid model of a DBD device operated in the pressure range from 100 to 1000\,mbar. For model verification and validation, argon is used as reference gas. The model comprises balance equations for the 1s and 2p levels of atomic argon, excimers, atomic and molecular ions and electrons. Furthermore, electron energy and surface charge balances as well as Poisson's equation are involved. Model calculations have been carried out for different values of the secondary electron emission coefficient and permittivity of the quartz dielectric. For validation of the model, current measurements have been performed and the experimental data are compared to the modeling results. It was found that specific discharge features observed in the experiment like, e.g., multipeak behavior, can only be reproduced by the model if correct surface properties are chosen. [Preview Abstract] |
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MW1.00045: Parametric study of TiN deposition with field-emitting surface dielectric barrier discharge Moriyuki Kanno, Tsuyohito Ito, Kazuo Terashima Field-emitting modes of discharges are useful tools to provide charges without significant reactivity and such mode in surface dielectric barrier discharge has been demonstrated in high-density fluids [1-3]. The ability of this discharge, which we named as field-emitting surface dielectric barrier discharge (FESDBD), to provide charges to materials has been also demonstrated recently [2]. In this study, we demonstrate electrophoretic deposition (EPD) of TiN films from TiN nanoparticles charged via FESDBD and its dependence on several processing parameters, such as voltage for FESDBD, the substrate bias, and deposition time. The deposition speed depends on the FESDBD voltage as well as the substrate bias. Furthermore, it has been found that deposition time dependence of the film thickness is well represented by Hamaker's mass balance law [4], indicating the deposition speed also depends on the particle density in the environment. Further details will be presented in the conference with benefits of FESDBD application for EPD. [1] D. Z. Pai \textit{et al.},\textit{ Plasma Sources Sci. Technol.}, \textbf{23} 25019 (2014). [2] T. Kawamura \textit{et al.},\textit{ J. Appl. Phys.}, \textbf{123} 043301 (2018). [3] M. Kanno \textit{et al.}, \textit{AIP Advances}, \textbf{9} 055111 (2019). [4] S. Put \textit{et al.}, \textit{Acta Mater.}, \textbf{51} 6303 (2003). [Preview Abstract] |
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MW1.00046: Behavior of Atomic Nitrogen in Medium Pressure Short-gapped Discharge Yusuke Nakagawa, Tatsuki Yoshii, Satoshi Uchida, Fumiyoshi Tochikubo Atmospheric plasma is worth applying to various fields due to its high chemical reactivity and low temperature. However, the lifetime of the radicals produced in the atmospheric plasma is short and the plasma region is local. Under the pressure of several tens kPa, which we call medium pressure, it is supposed that both plasma uniformity and long radical lifetime can be achieved. In order to elucidate the behavior of radicals in the medium pressure plasma, we measured the atomic nitrogen density produced in short-gapped pulsed dielectric barrier discharge by TALIF spectroscopy. The atomic nitrogen measurement is conducted in 30, 50, and 100 kPa N2 discharge with 0.5 mm discharge gap. Under each pressure, atomic nitrogen increases in the afterglow until 500 - 1000 micro seconds, and thereafter begins to decrease. The absolute density of atomic nitrogen is estimated using the decay rate of the recombination reaction under the assumption of the gas temperature as 400 K. The results indicate that the atomic nitrogen flux becomes larger as the pressure decreases, and the maximum flux of atomic nitrogen at 30 kPa is about triple of that at 100 kPa. The streamer radius at 30 kPa is double of that at 100 kPa, which means that medium pressure discharge improves the plasma uniformity. [Preview Abstract] |
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MW1.00047: The Pulsed Negative Corona in Nitrogen with Different Needle-Plane Electrodes Xing Zhang, Yulin Guo, Anbang Sun, Guanjun Zhang Corona discharge is widely used in many fields, such as material modification and pollution controlling. However, the understanding of pulse mode in electropositive gas is not deeper enough. In this work, the negative DC corona discharge in nitrogen with needle-plane electrodes is studied. Discharge phenomena under different needle radii (0.05-0.28mm) and interelectrode distances (5-15mm) are explored. The discharge modes of nitrogen corona include Townsend mode, pulsed mode and glow mode, which are similar to corona modes in air. With the increasing of needle radius and interelectrode distance, the quantity of electric charge transferring in single pulse increases. Because there will be more secondary electrons emission when needle radius increases. With interelectrode distance increasing the electrical field will be more non-uniform and higher around needle tip. So that the ionization will be stronger leading to larger current. [Preview Abstract] |
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MW1.00048: ABSTRACT WITHDRAWN |
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MW1.00049: High-pressure plasma source development through time-resolved diagnostics, PIC and global simulations Gunsu Yun, Minuk Lee, Woojin Nam, Seok Yong Jeong, Seungtaek Lee, Juho Lee, Jimo Lee, Jaemin Yoo, Jae Koo Lee High-pressure plasmas are an interesting state of matter where transport phenomena occur among multiple species (electrons, ions, neutrals, and cluster ions). Development of efficient high-pressure plasma source requires understanding of the energy transport process from external power source to electrons as well as internal transport processes among different species. In particular, confinement of electrons and energy transport from excited heavy species are critical for sustainment of the plasma state. Motivated by experimental findings of higher densities excited species in microwave driven plasmas, recent particle-in-cell (PIC) simulations on micro-sized (0.1--1 mm) high-pressure gas discharge between planar electrodes driven by microwave ($\sim 1$ GHz) showed that the electron confinement is substantially enhanced above a critical frequency. In addition, time-resolved measurements, PIC and global simulations showed that the generations of energetic electrons and reactive species are enhanced by pulsed microwave operation. A general rule of thumb design principles for the optimization of high pressure plasma sources has been deduced from the perspective of external power coupling and internal energy transport. [Preview Abstract] |
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MW1.00050: Frequency variation in micro atmospheric pressure plasma jets driven by tailored voltage waveforms Lena Bischoff, Gerrit Huebner, Ihor Korolov, Zoltan Donko, Yue Liu, Thomas Mussenbrock, Julian Schulze Radio frequency driven micro atmospheric pressure plasma jets ($\mu $-APPJs) are often used as efficient sources of reactive species at low temperatures for, e.g. biomedical applications and surface modifications. In the present work, we perform a systematic investigation of the electron heating dynamics and the generation of selected species in \textmu -APPJs driven by Voltage Waveform Tailoring (VWT) as a function of the fundamental frequency, the number of consecutive harmonics, the reactive gas admixtures (He/N$_{\mathrm{2}})$ and the peak-to-peak voltage amplitude based on experiments and kinetic particle-in-cell/Monte Carlo collision simulations. Our results demonstrate the potential of VWT to optimize and control the generation of selected reactive particle species. [Preview Abstract] |
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MW1.00051: Hysteresis and E-mode to H-mode Transition in a MEMS Device, Low-pressure, Microwave Driven Microplasma Patrick Hermanns, Stephan Westerdick, Simon Boeddeker, Peter Awakowicz Recent advances in miniaturization technology allow the shrinkage of measuring methods to small scale, sensor size (lab-on-a-chip device). Miniaturized mass spectrometers need an integrated ionization source. Requirements of miniaturized ionization sources are an elevated working pressure and excellent ion beam coupling. In this work, the authors present a MEMS fabricated plasma source integrated into a mass spectrometer. A conducting silicon antenna couples the microwave power into the plasma chamber. The electrons are extracted from the plasma volume by a 20 um x 300 um slit and an applied extraction voltage. Extracted electron currents are measured with a highly sensitive amperemeter. Electron densities and gas temperatures are measured by absolutely calibrated optical emission spectroscopy and small admixtures of nitrogen. A power variation leads to a hysteresis curve of the extractable electron currents and electron densities. It is proposed, that a mode transition from a capacitive E-mode to an inductive H-mode is performed with an increase of generator power. Changes in gas temperature during a mode transition supports the assumption of different energy coupling mechanisms. [Preview Abstract] |
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MW1.00052: Space-resolved oxygen radical measurement of atmospheric pressure microwave line plasma using vacuum ultraviolet absorption spectroscopy Hansin Bae, Hirotsugu Koma, Haruka Suzuki, Hirotaka Toyoda, Seigo Takashima Atmospheric pressure plasma is attractive due to its cost benefit and a variety of possibilities for industrial applications. Recently, we have developed atmospheric pressure microwave line plasma (APMLP) source of \textasciitilde 1 m in length, using a loop waveguide with a long slot and a microwave circulator that can control energy flow in one direction. In our previous work, we have confirmed spatial uniformity of electron density (\textasciitilde 10$^{\mathrm{20}}$ m$^{\mathrm{-3}})$, gas temperature, and light intensity of the APMLP[1]. However, in view of the industrial application, not only plasma parameters measurement but also radical density measurement is important. In this study, O radical density of the APMLP is measured by vacuum ultra violet absorption spectroscopy (VUVAS). In the case of \textasciitilde 0.1{\%} O$_{\mathrm{2}}$-admixed Ar, uniform O radical density of 1x10$^{\mathrm{13}}$ cm$^{\mathrm{-3}}$ in longitudinal length of 60 cm was observed. To give an insight into not only the radical density but also the radical flux, uniformity of the gas flow in the longitudinal direction was observed using a differential pressure gauge facing to the gas flow from the slot and uniform gas flow in the longitudinal direction was confirmed. [1] H. Toyoda et al.: 10$^{\mathrm{th}}$ Int. Workshop on Microwave Discharge (Zvenigorod, 2018). [Preview Abstract] |
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MW1.00053: Microscopic observation of an atmospheric-pressure microwave plasma produced in a meter-scale slot with sub-millimeter gap Hirotaka Toyoda, Hirotsugu Koma, Yoshiki Baba, Manh Hung Chu, Hansin Bae, Haruka Suzuki In recent years, techniques for applying non-thermal equilibrium atmospheric-pressure plasma to large surface treatment have been given much attention. Microwave atmospheric-pressure plasma sources are promising because they can produce high-density plasma easily. We developed a microwave plasma source to control the propagation direction of the electromagnetic waves in the waveguide in one direction to suppress standing wave and succeeded in producing atmospheric pressure plasma in the meter-scale slot with a slot gap of \textless 0.2mm. In this study, the detailed structure of the plasma inside the slot and its spatial distribution in the longitudinal direction is investigated by operating the microscope parallel to the slot. Strong emission in the vicinity of the slot edge is observed and this is presumably caused due to spatial variation of the gas density and the plasma density across the slot gap. The emission structure is observed in the longitudinal direction and very uniform emission structure is observed in the longitudinal length of 60 cm. In the presentation, very fast and uniform surface treatment will be also demonstrated. [Preview Abstract] |
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MW1.00054: Energy transport in atmospheric-pressure plasmas driven by pulsed microwave Woojin Nam, Seok-yong Jeong, Jae Koo Lee, Gunsu Yun Plasma state can persist after the removal of external driving power via the release of the energy stored in the plasma particles. The energy release contributes to the generation of excited species and subsequent radiative de-excitation, which is well known phenomena called afterglow in low-pressure plasmas. We have studied the energy transport in atmospheric-pressure argon plasma generated by microwave resonator with the focus on the temporal dynamics of the afterglow in pulse operation. Substantial afterglow in both continuum and atomic line emissions has been observed during the pulse-off time because the recombination rate of argon ions increases rapidly with the decrease of electron temperature. Compared to continuous wave (CW) operation, the time-averaged atomic line emission intensities are enhanced in the pulsed operation with high repetition rate ($>100$ kHz, 50\% duty). A global simulation incorporating the pulse power coupling shows that the impedance mismatch between the plasma and the resonator can be minimized in the pulse operation compared to CW operation. An optimization scheme for pulse operation has been deduced and can be utilized to maximize the power coupling efficiency and the generation of reactive species in plasma source devices of resonator type. [Preview Abstract] |
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MW1.00055: On the Similarities of High Pressure Microdischarges Yangyang Fu, Bocong Zheng, Janez Krek, Deqi Wen, Peng Zhang, John P. Verboncoeur Similarity and scaling laws are useful tools for understanding plasma characteristics when two or more discharge systems are compared. The similarity laws were previously validated and applied for low pressure discharges while they are disregarded due to the presence of three-body collisions at high pressures. In this study, similarity relations for high pressure microdischarges are investigated based on the voltage-current characteristics using a two-dimensional fluid model. Voltage-current characteristics of the microdischarge, including Townsend discharge, subnormal glow, normal glow, and abnormal glow discharges, are observed. The breakdowns of the microdischarge in the Townsend regime correspond to the right branch of the Paschen's curve and the breakdown scaling laws are found to be still valid even though the three-body conversions are considered. The similarity relations for the electron and ion densities in the high pressure microdischarges are also examined. [Preview Abstract] |
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MW1.00056: Analysis of Temperature Distribution Affected by Convection to Ring Electrode in Double-Flow Type Gas Circuit Breaker Yuji Komai, Yuki Suzuki, Jumpei Oya, Yoshifumi Maeda, Toru Iwao The arc temperature affected by the convection to ring electrode in double-flow type gas circuit breaker (GCB) was analyzed. The objective of this research to elucidate the contribution to arc extinction affected by the convection to ring electrode. GCB is an electric power equipment in order to interrupt the current quickly. The compressed gas in thermal chamber flows out in the two opposite directions to quench the arc plasma. The arc column is strongly curved and significantly lengthened by the convection of two opposite directions. Thus, it has been reported that the double-flow type GCB interrupts the current more easily than the single-flow type GCB. However, contribution of the convection to ring electrode for arc extinction in double-flow type GCB is not elucidated. In this paper, analysis of temperature distribution in double-flow type gas circuit breaker using 3-D electromagnetic thermal fluid simulation is investigated. As a result, the flow velocity to the ring electrode increased and the high temperature gas was transported with increasing the pressure of ring electrode area. Therefore, it was suggested that the flow field to electrode ring contributes the improvement of current interruption performance. [Preview Abstract] |
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MW1.00057: Numerical Analysis of Pulsed TIG Arc Welding under Consideration of Thermal and Chemical Non-Equilibrium Yusuke Nemoto, Yuji Komai, Zhenwei Ren, Yoshifumi Maeda, Toru Iwao TIG arc welding is widely used as a technology for joining metal materials. However, the current is limited in order to prevent wear of tungsten used for the cathode. Thus, the weld defects such as insufficient melting caused by insufficient heat input occurs. The pulsed TIG welding is used in order to prevent the weld defects. The pulsed TIG welding can obtain a deep penetration depth of the weld pool with changing the current into a pulse. However, the physical phenomena of pulsed TIG welding are not elucidated. Especially, it has not been reported the study about the thermal and chemical non-equilibrium. The thermal non-equilibrium becomes remarkable with changing the current rapidly. Moreover, the electron number density decreases with consideration of the reaction rate in comparison with the local thermal equilibrium. In this paper, the numerical analysis of pulsed TIG arc welding under consideration of thermal and chemical non-equilibrium using 3-D electromagnetic thermal fluid simulation is investigated. As a result, it was elucidated that the electron temperature was dominated by diffusion phenomenon. On the other hand, the heavy particle temperature was dominated by convection phenomenon. [Preview Abstract] |
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MW1.00058: Role of Neutral Gas Dynamics in Plasma Gun Devices Thomas Underwood, William Riedel, Mark Cappelli Neutral gas dynamics is described in plasma accelerators by considering the impact of the initial neutral gas distribution within the gun volume. A model based on the Rankine-Hugoniot formulation in combustion is presented and used to predict both characteristic operating regimes observed experimentally. Precise neutral gas triggering is used to change the gas distribution within the accelerator and modify the initial conditions governing the breakdown process. Both bulk energy transfer and time-of-flight measurements show that with increasing gas diffusion time, the directed energy in the flow decreases and the mode transitions from a deflagration to snowplow mode. Neutral gas simulations indicate that neutral gas governs the transition between these operating modes. This informs strategies to maintain high acceleration efficiency in pulsed plasma accelerators and eliminate shocking conditions caused by higher gas loadings. [Preview Abstract] |
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MW1.00059: Flow field characteristics of low-power arc-heated plasma jets Xian Meng, Jinwen Cao, Chunling Yang, Wenxia Pan, Chengkang Wu In an arc-heated plasma thruster, working gas is heated by a dc arc discharge to a temperature over 104 K, and subsequently, converted into a supersonic plasma jet through a convergent-divergent nozzle, issuing into the ambient atmosphere, where the pressure is a few pascals or even lower, producing a thrust force. It is desirable to know the structure of the flow field in such an arrangement. In this paper, with a self-designed low power DC arc-heated plasma thruster, the discharge processes and flow field of the plasma jet have been systematically studied based on experimental method. An observation system for plasma discharge and arc root attachment has been developed to detect the discharge condition in the thruster nozzle. The distributions of electron temperature and electron number density have been measured by using electrostatic probe method and emission spectroscopy method, and the axial distribution of the pressure within the nozzle has been measured by pressure sensor. Results show that the low-power arc-heated plasma thruster can be operated stably and repeatably; The plasma thruster tends to work in a small current and high voltage mode; The current density to the anode wall is only tens of mA/mm2, and there is almost no ablation on the anode surface. [Preview Abstract] |
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MW1.00060: Arc Deflection Length Affected by Frequency of Pulsed TIG Arc Welding with Lateral Gas Takuya Tashiro, Koki Matsumoto, Yoshifumi Maeda, Toru Iwao TIG arc welding is often used because this welding has high quality and strength. However, the heat transfer decreases with lateral gas and the heat transfer decrement causes welding defects. For this reason, it is necessary to prevent the arc deflection of the arc Thus, the transverse magnetic field is used The electromagnetic force affected by the external transverse magnetic field is applied to the arc in the opposite direction to the lateral gas. However, it is difficult to control the arc because of randomly changing the lateral gas direction and velocity. Thus, the pulsed arc is significant in order to prevent the arc deflection It has been reported that the increment of the current density at center of axis increased with increasing of pulsed frequency. The arc temperature was affected by the transient response because of not following increment of current. For this reason, the pressure gradient to axial direction is generated Therefore, it is considered that the arc stiffness increases with the increment of pulsed frequency. In this paper, the arc deflection length affected by the frequency of pulsed TIG arc welding with the lateral gas was elucidated. As a result, the arc deflection length decreased with increasing the pulsed frequency. [Preview Abstract] |
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MW1.00061: Simulation of electron interactions with liquid water and processes related to sub-nanosecond electrical breakdown Tomas Hoder, Petr Bilek, Milan Simek, Zdenek Bonaventura Sub-nanosecond electrical breakdown in dielectric liquids is of vital interest, e.g. for applications in high-voltage insulation and high-current switching. Liquid dielectrics in strong nonuniform electric fields are under influence of electrostrictive force that tends to move the fluid into the regions with higher electric field. If the voltage rise is fast enough, the liquid does not have enough time to be set into motion in order to reduce the internal stress. In this case the ponderomotive force induces significant stress in the bulk of the liquid which is manifested as a negative pressure. At certain threshold, the negative pressure causes cavitation ruptures of the fluid. Subsequently, free electrons can be produced by emission from the surface inside the cavity and accelerated to energies exceeding the energy for ionization of water and contribute to ultrafast electrical breakdown of water. In this work we investigate conditions under which appearing cavitation nanopores will expand and we will determine their size at the end of the fast voltage pulse, in order to get an estimation of energy that can an electron gain being accelerated in the void. [Preview Abstract] |
(Author Not Attending)
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MW1.00062: Fast optical and electrical measurements at a single microdischarge setup during plasma electrolytic oxidation (PEO) Anna Lena Schoene, Vera Bracht, Patrick Hermanns, Peter Awakowicz Plasma electrolytic oxidation (PEO) is a process for the passivation of lightweight metals like aluminum. During this process, short-living microdischarges occur stochastically distributed on the substrate surface. To understand the individual behaviour of these microdischarges, a single microdischarge setup with an aluminum wire anode of 1 mm diameter employed. The wire is surrounded by an isolating cladding to reduce the active metal surface to the front tip of the wire. As electrolyte, a solution of potassium hydroxide (KOH) in destilled water (1 g/l) is used. The small active surface area enables optical and electrical measurements of single microdischarges. Time-resolved shadowgraphy and fast optical measurements with a quad ICCD camera and an Echelle spectrometer are carried out for a better understanding of the development and evolution of single microdischarges. The different life time stages of the microdischarges can be observed by triggering on the microdischarge current and delaying the measurements within the microdischarge lifetime. The measurements are performed for different frequencies (100 Hz, 1 kHz, 10 kHz) as well as maximum current densities (2,5 A/cm2, 5 A/cm2). [Preview Abstract] |
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MW1.00063: Spectroscopic Study of an Atmospheric Pressure Plasma Glow through Electric Field Measurements Yao Kovach, Maria Garcia, John Foster A helium plasma discharge glow, which works under atmospheric pressure, has been developed for analysis of self-organization anode pattern formation on a liquid surface. In our previous study, plasma column characteristics such as gas temperature, electron density and species composition have been determined by means of optical emission spectroscopy (OES) techniques under the condition of self-organization pattern appearances. However, the mechanisms underlying self-organization of plasmas in this context is still poorly understood. In this recent effort, OES was continuously utilized to investigate the Stark Mixing as a means to infer the electric field. At different current interval controls, spatially resolved measurements of the electric field in atmospheric pressure DC glow were recorded from the cathode region to near liquid surface region. This work extends our understanding of self-organization and the physics of the discharge itself by not only interrogating the column to ascertain spatial plasma characteristics but also to understand the underlying mechanism associated with local electric field that might drive the self-organized plasma pattern formation on the liquid surface. [Preview Abstract] |
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MW1.00064: Dense plasma in supercritical argon fluid with long-lived clusters Seungtaek Lee, Juho Lee, Dong Eon Kim, Gunsu Yun Long-lived (over an hour) argon clusters are observed in supercritical argon fluid produced by continual compression into a high-pressure chamber (up to 300 bar). Laser scattering images show the Brownian motion of the clusters with the typical size of a few hundreds nanometers. In supercritical argon fluid with dense population of clusters ($\sim 1000 \mbox{ cm}^{-3}$), jet-like plasmas are produced by ns pulse laser (532 nm, 6 ns, 400 mJ, peak intensity $\sim 1$ TW/cm$^2$). The lifetime of the plasma jet is much longer than the laser pulse duration and becomes longer for higher number density of clusters. The electron temperature and density estimated from spectroscopic measurements are $\sim 1$ eV and $\sim 10^{21} \mbox{cm}^{-3}$, respectively. This suggests that the plasma jet has a high Coulomb coupling constant of the order of unity. [Preview Abstract] |
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MW1.00065: Radical activated solutions with bactericidal and plant-growth effects Masafumi Ito, Naoyuki Iwata, Vladislav Gamaleev, Hiroshi Hashizume, Jun-Seok Oh, Takayuki Ohta, Kenji Ishikawa, Masaru Hori In this study, we have investigated a bactericidal solution produced by radical exposure which can be effective in a neutral pH range, where many plants grow well. We firstly prepared phosphate buffer solution (PB) with the pH of 6.3 by dissolving Disodium Phosphate and Sodium Dihydrogenphosphate Dihydrate (Wako Chemical) into ultra-pure water obtained through Millipore Direct-Q 3UV system. Then, phenylalanine, tryptophan, tyrosine, which are known as the aromatic amino acids, and alanine as the control were dissolved into the PB solution with the concentrations of 80, 2, 50, and 80 $\mu $M respectively, using a magnetic stirrer and a rotor with the speed of 1500 rpm for 30 min. Subsequently, the amino-acid dissolved PB solutions were treated using an oxygen-radical source operated under a condition of a total gas rate of 5 slm and oxygen to Ar gas flow ratio of 0.6{\%} for several minutes. As a result, we have found that the bacteria can be killed through the oxygen-radical-treated solutions including organic compounds with benzene rings even in a neutral pH range with plant-growth promotion. [Preview Abstract] |
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MW1.00066: Atmospheric Plasma Inactivates Biofilm Produced by Hospital Bacteria. Muireann Fallon, Sarah Kennedy, Stephen Daniels, Hilary Humphreys BACKGROUND Hospital surfaces are a source of infection due to contamination by bacteria. A novel method of hospital surface decontamination is the use of cold atmospheric pressure plasma (CAPP) systems. CAPP has antimicrobial properties that can inactivate bacterial cells on these surfaces. As an effective hospital decontamination tool, CAPP must kill bacteria within biofilms. Biofilms confer a higher resistance to disinfectants than planktonic bacteria. Here we examine the effects of CAPP on bacterial biofilms. METHODS 48-hour biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) were grown on glass. Biofilms were treated with a CAPP system for 90 seconds. The plasma was produced from a single jet system with an ambient air source gas, powered by a 25 kHz power source. Air was filtered and supplied at approximately 10 slm. Biofilms were stained with BacLight Viability kit and imaged by confocal microscopy. Relative viability in images was calculated using imageJ. RESULTS CAPP treatment led to inactivation within the biofilm structure of all bacterial strains. The relative bacterial death after 90s CAPP treatment ranged from 51 to 82{\%} across images and the greatest killing effect was seen on E. coli biofilms. CONCLUSIONS CAPP treatment of bacterial biofilms resulted in a decrease of viable cells. This can be seen in both MRSA and E. coli biofilms. This suggests that CAPP may have a use in the decontamination of hospital surfaces to reduce infections. [Preview Abstract] |
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MW1.00067: Low temperature plasma for controlling iPS cell differentiation Mime Kobayashi, Kiichiro Tomoda, Michio Asahi, Shinya Kumagai Cold (non-thermal) atmospheric pressure plasma generates active species such as radicals, ions, and electrons. Plasma irradiation has been used for biological applications, including the selective killing of cells and enhancement of plant growth. Human induced pluripotent stem cells (hiPSCs) can differentiate into any types of cells while infinitely proliferate in vitro. Because of these distinct abilities, their application in regenerative medicine, drug discovery, and human developmental biology has been heavily investigated. Given plasma affects a broad range of biological events, it may also enhance differentiation or proliferation of hiPSCs. In this research, hiPSCs were treated with dielectric barrier discharge (DBD) air plasma (9 kV, 12.5 kHz) to gain insights into plasma applications. Different strength and duration of plasma have been tested. After optimizing irradiation conditions, the effects of the plasma on survival, proliferation, and differentiation of the irradiated cells will be examined. Refs. Kumagai et al. (2016) Jap. J. Appl. Phys. 55, 01AF01; Kobayashi et al. (2016) Appl. Phys. Express 9, 127001; Kime et al. (2016) Proc. Natl. Acad. Sci. USA 113, 12478 [Preview Abstract] |
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MW1.00068: ABSTRACT WITHDRAWN |
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MW1.00069: Influence of gas temperature and gas species on the characteristics of low-temperature plasma Shohei Moriya, Yuma Suenaga, Yusuke Iijima, Yuriko Matsumura, Atsuo Iwasawa, Akitoshi Okino Low temperature plasma is expected to be applied to medical and agriculture fields. We developed multi-gas temperature-controllable plasma jet which can stably generate plasma of various gas species, and control the plasma gas temperature stably from 0 to 120°C. The developed plasma source has enabled us to irradiate plasma of appropriate gas species to heat-sensitive objects such as plants and skin. Using this plasma source, we have conducted studies on sterilization in liquids and introduction of proteins into plants. Those results are dependent on not only the gas species but the plasma gas temperature. The main factors for those plasma processes are considered to be reactive species such as \textbullet OH, $^{\mathrm{1}}$O$_{\mathrm{2}}$ and \textbullet O$_{\mathrm{2}}^{\mathrm{-}}$ Therefore, in this study, the influence of the plasma gas species and the plasma gas temperature on the generation of reactive species were investigated. For instance, when the O$_{\mathrm{3}}$ concentration in the O$_{\mathrm{2}}$ plasma whose gas temperature controlled from 0 to 80°C were measured, the concentration varied with the gas temperature, and the concentration showed the highest value at 50°C. In the presentation, the gas temperature dependence of H$_{\mathrm{2}}$O$_{\mathrm{2}}$, O$_{\mathrm{3}}$, \textbullet OH and $^{\mathrm{1}}$O$_{\mathrm{2}}$ generated by the plasma using Air, Ar, O$_{\mathrm{2}}$, CO$_{\mathrm{2}}$ and N$_{\mathrm{2}}$ will be shown. [Preview Abstract] |
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MW1.00070: A novel approach for depyrogenation using a dielectric barrier discharge plasma system. Naman Bhatt, Duncan Trosan, Justin Brier-Jones, Cade Brinkley, Jann Smallwood, Wolff Kirsch, Katharina Stapelmann, Steven Shannon Endotoxins in pharmaceutical material have detrimental effects on patient well-being and can limit a material's viability for internal medicine applications. A low cost method to reduce endotoxin levels through plasma assisted depyrogenation is presented. Although plasma based depyrogenation has been demonstrated previously, the mechanisms that drive depyrogenation and development of a cost effective system for this process are in the preliminary stages. A methodology to better understand mechanisms and identify design rules for plasma assisted depyrogenation is presented. A dielectric barrier discharge is built to perform depyrogenation in a sealed environment. Experiments are performed with plasmas of different gases and nitrogen bearing gases are shown to be the most effective for endotoxin reduction. Material modification due to plasma exposure is measured using FTIR and Raman spectroscopy. Preliminary results are presented to show the reduction of endotoxin units as a function of plasma exposure time. Current efforts are to identify the fundamental mechanisms in the plasma that enables the endotoxin reduction and application of depyrogenation processes to complex material forms including micronized powders. [Preview Abstract] |
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MW1.00071: DBD Jet Delivery for Rapid CRISPR/Cas9 Editing in Plants Matthew Burnette, Min Huang, Stephon Warren, Michael Thomson, Endang Septiningsih, David Staack Gene editing in crop plants commonly employs clustered regularly interspaced short palindromic repeats (CRISPR) technology. After insertion of an RNA-guided Cas9 nuclease into plant cells, the CRISPR/Cas9 system precisely cleaves DNA and through endogenous molecular repair mechanisms induces gene insertions or deletions within the plant, allowing for precise gene validation studies. There currently is not an effective delivery mechanism for the CRISPR/Cas9 system that enables \textit{in vivo} plant transformation, as existing methods require a lengthy \textit{in vitro} tissue culture and regeneration process. This project tests a novel CRISPR/Cas9 delivery system, using a non-thermal atmospheric-pressure dielectric barrier discharge (DBD) jet to transfer CRISPR/Cas9 plasmids and ribonucleoproteins into rice tissues for rapid gene editing. This is based on a common microbiology technique called electroporation, wherein a high electric field near the cell induces pores to open in the cellular membrane. Here we test the ability to induce pores in the significantly thicker plant cell wall as well, which will enable \textit{in vivo} plant transformation. This technique shows promise to significantly shorten the transformation time for gene editing in plants. [Preview Abstract] |
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MW1.00072: Effect of direct irradiation of room-temperature helium plasma jet to fission yeast cells Shinji Yoshimura, Yoko Otsubo, Akira Yamashita, Kazunori Koga, Mitsutoshi Aramaki We have recently developed a room-temperature atmospheric-pressure plasma-jet device with feeding-gas cooling section which utilizes a Peltier device [1]. The device configuration was a single electrode one without a ground electrode, and the applied voltage and frequency were 5.4 kV peak-to-peak and 15 kHz, respectively. The flow rate of helium gas was 3 SLM. A wild-type fission yeast {\it S. pombe} was directly exposed to the plasma plume for one minute and incubated at 30 $^\circ$C for 24 hours. We observed that a few percent of the plasma-treated cells induced anomalous cell elongation, which is not seen in wild-type cells under normal conditions, and the elongated cells were not able to grow and produce colonies. It is suggested that the cell cycle control may be impaired by plasma exposure. In addition, a temperature-sensitive cell-division-cycle (cdc) mutant {\it cdc2-L7} was also directly exposed to the plasma plume. A preliminary result showed that the cell elongation, which is a typical phenotype of {\it cdc2} mutants, was observed even under the restrictive temperature (36 $^\circ$C). Comparison with oxidative stress induced by adding hydrogen peroxide will also be presented. \newline \newline [1] S. Yoshimura {\it et al.}, Jpn. J. Appl. Phys. {\bf 58}, SEEG03 (2019). [Preview Abstract] |
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MW1.00073: Hydroxyl radical densities in plasma treated liquid Brayden Myers, Pietro Ranieri, Katharina Stapelmann Hydroxyl radical concentrations in plasma treated liquid are measured using two different techniques: electron paramagnetic resonance (EPR) spectroscopy [1] and a terephthalic acid (TA) assay [2]. A COST Reference Microplasma Jet [3] is used with a variety of treatment durations, applied voltages, and helium based gas mixtures. As one of the most prominent radicals, $^{\mathrm{\bullet }}$OH is primarily produced through dissociative collisions with high energy electrons and metastables in the active plasma and jet effluent [4]. OH radicals are potent oxidizers and precursors to hydrogen peroxide and other reactive oxygen species important for biomedical applications. The source of $^{\mathrm{\bullet }}$OH in the plasma treated liquid is also identified using isotopic admixtures in the feed gas. [1] Y. Gorbanev et al., \textit{Phys. Chem. Chem. Phys.}, \textbf{4}, 2018 [2] S. Kanazawa et al., \textit{Int. J. Plasma Environ. Sci. Technol.}, \textbf{6}, 2012 [3] J. Golda et al., \textit{J. Phys. D: Appl. Phys.,} \textbf{49}, 2016 [4] J. Benedikt et al., \textit{Plasma Sources Sci. Technol.,}~\textbf{25,}~2016 [Preview Abstract] |
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MW1.00074: Plasma treatments for surface cleaning of orthopaedic implants Nishant Sirse, Cezar Gaman, Stephen Daniels, Miles Turner The cleaning process of manufacturing induced contamination from orthopaedic impants is an essential step to achieve surface biocompatibility and comply cleanliness requirement of implants for surgery. The current cleaning process involve removal of such residues by exposure to chemical detergents. An alternate approach to this process is to exploit low temperature plasmas. In this study, we investigated the removal of organic and inorganic process consumables using radio frequency atmospheric pressure multi-jet system. The plasma is operated in He/O$_{\mathrm{2}}$ gas mixture, with and without admixture of water vapour. The discharge chemistry is diagnosed and optimized using optical emission spectroscopy and laser induced fluorescence. The cleaning technique is applied on the polished medical grade and aluminum oxide grit blasted titanium metal samples, which is analogue to one used in traditional metal implants. The surface cleaning is further examined and validated by the X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared (FTIR) spectroscopy analysis. The results validate plasma cleaning as a viable alternative to wet-detergent cleaning. [Preview Abstract] |
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MW1.00075: Application of Plasma processing for conversion of salt infiltrated polymer films to metal oxide films. Jim Conway, Matthew Snelgrove, Ross Lundy, Pravind Kumar Yadav, Clara Zehe Oxygen plasma treatment is an alternative to Ultra-Violet-Ozone for conversion of metal-salt infiltrated polymer films to metal oxides films. Ion action at the surface can enhance the process chemistry and resulting film properties in plasma. A Design Of Experiment (DOE) was used to investigate the effects of process time, gas pressure and RF power on plasma processing of P2VP films infiltrated with AlNO$_{\mathrm{3}}$ or CuNO$_{\mathrm{3}}$. Optical Emission Spectroscopy and a Langmuir probe were used to monitor atomic oxygen (O) and ion plasma densities. The processed films were examined using XPS and Ellipsometry. RF and pressure were found to have a strong effect on O/ O$_{\mathrm{2}}^{\mathrm{+}}$ ratios in the plasma. XPS results indicated that polymer removal and salt conversion complete in minutes using plasma, while UV/O$_{\mathrm{3}}$ took several hours to achieve similar results. The XPS Silicon Oxide peaks were compared to unprocessed coupons to check for oxidation of the underlying silicon. [Preview Abstract] |
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MW1.00076: Effect of RF plasma on the growth of titanium carbide thin films using pulsed laser deposition. Heman Bhuyan, Miguel Escalona, Julian Schulze, Partha Saikia, Mario Favre, Felipe Veloso, Edmundo Wyndham, Julio Valenzuela The effect of radio frequency plasma on the growth of titanium carbide thin films by pulsed laser deposition technique will be presented. Studies have been carried out in a hybrid plasma configuration consisting of a Dual Radio Frequency Capacitively Coupled (2fCCP) system and a Pulsed Laser deposition (PLD) system. To investigate the plasma dynamics during the thin film deposition, time resolved optical emission spectroscopy and fast imaging are used. Different standard surface science diagnostic tools have been used to analyze the deposited thin films. The RF plasma assisted pulsed laser deposition (PA-PLD) have the advantage of preventing micro-particles reaching the substrate during thin film depositions. A comparative study of the thin films deposited by conventional PLD and PA-PLD, will be presented. Preliminary results shows that the PA-PLD technique improves the quality of the deposited films with respect to their stoichiometry, morphology and deposition rate. [Preview Abstract] |
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MW1.00077: Effects of Discharge Power on Deposition Cutoff of Carbon Nanoparticles Synthesized by High Pressure Ar$+$CH$_{\mathrm{4}}$ Multi-hollow Discharge Plasma CVD SungHwa Hwang, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani Structure-controlled carbon nanomaterials reveal unique properties compared to those in bulk [1]. Among many processes that produce nanocarbon, plasma is a practical alternative that allows a simple and continuous fabrication. So far, we have succeeded in the synthesis and deposition control of spherical carbon nanoparticles (CNPs) of which sizes are between 250 and 25nm using a multi-hollow discharge plasma chemical vapor deposition (MHDPCVD) method [2]. To decrease the size of CNPs, the gas residence times in the plasma discharge region is reduced by increasing Ar$+$CH$_{\mathrm{4}}$ gas flow rate from 10sccm to 200sccm at 2Torr. Above the high gas flow rate of 125sccm for the discharge power of 43W, no CNPs deposits on a substrate (Deposition cutoff). We employed the discharge power from 43 to 63W and confirmed that CNPs less than 15nm in size exist on a substrate over 125sccm. Therefore, the gas residence time and the discharge power are the key tuning knobs for their size and deposition control onto a substrate. [1] L. Xiao, et al., Nano Energy 19 (2016) 279. [2] M. Shiratani, et al., J. Phys. D44 (2011) 174038. [Preview Abstract] |
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MW1.00078: Nanostructured porous silicon-based materials for novel plasma energy systems Aleksandr Mustafaev, Rostislav Smerdov, Yulia Spivak The perspective application of functionalised nanostructured fullerene and porous silicon-based composite materials for promising alternative energy conversion systems is considered in this study. Fullerene and porous silicon (PS) are suggested for further implementation of PETE (photon-enhanced thermionic emission for solar concentrators) and thermionic energy converter (TEC) electrodes due to the remarkable properties displayed by these structures.\footnote{R.S. Smerdov, Yu.M. Spivak, et al., \textbf{J. Phys.: Conf. Ser.} 1038 012064} The investigation of PS-based materials functionalised with fractal-like silver clusters for PETE and TEC electrodes synthesis is reported. We utilised UV-Vis spectroscopy to characterise the surface structure of PS/Ag layers. Localised surface plasmon resonance (LSPR) phenomenon occurring within the array of Ag nanoparticles is observed. Two characteristic absorption bands located in the visible spectrum are detected; their nature is attributed to the LSPR effect taking place in the two distinct nanoparticle arrays forming during the synthesis process. It is possible to control the intensity of these bands with synthesis parameters of PS matrix.\footnote{R.S. Smerdov, A.S. Mustafaev, et al., \textbf{J. Phys.: Conf. Ser.} 1135 01203} [Preview Abstract] |
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MW1.00079: A 3D hexagonal-packed photonic crystal with a tunable plasma-filled defect. Benjamin Wang, Oliver Miller, Mark Cappelli In previous studies [1, 2], we demonstrated 1D (slabs) and 2D (square lattice cylinders) aluminum oxide photonic crystal defect tuning using plasma-filled vacancies. In this study, we characterize the electromagnetic response of a 3D hexagonal-packed photonic crystal comprised of 3 mm diameter silicon-nitride spheres (commercial bearings) with a vacancy defect that is occupied by a low pressure He-filled 3 mm diameter hollow aluminum oxide sphere ionized by an AC capacitively coupled discharge. The discharge plasma-filled defect serves to tune the defect state transmission generating an effective tunable microwave filter with relatively high quality factor. We will describe the fabrication of the photonic crystal and associated defect, and comparisons of measured transmission spectra to simulations using ANSYS HFSS and a presumed plasma density. [1] D. Pai, et al, The European Physical Journal D 73 (5), 97 (2019), [2] B. Wang and M.A. Cappelli, Applied Physics Letters 107 (17), 171107 (2015). [Preview Abstract] |
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MW1.00080: Plasma-assisted inkjet printing of poly(3,4-ethylenedioxythiophene) from 3,4-ethylenedioxythiophene stock solution Kaishu Nitta, Masanao Tsumaki, Tomoya Kawano, Kazuo Terashima, Tsuyohito Ito In recent decades, printing technologies, such as screen, gravure, and inkjet printing, have markedly progressed and have been applied to manufacture various printed devices [1]. Here, the simultaneous polymerization of 3,4-ethylenedioxythiophene (EDOT) monomer stock solution ink and printing of the resulting poly(3,4-ethylenedioxythiophene) (PEDOT) via plasma-assisted inkjet printing is demonstrated in an open air environment [2]. The plasma-induced polymerization of EDOT is confirmed by the spectroscopic measurements of the printed line. Furthermore, we also achieve plasma-induced polymerization of EDOT with poly(styrenesulfonate) (PSS) for the synthesis of an electrically conductive film from EDOT. The electrical conductivity of the fabricated films depend on the mixing ratio and plasma irradiation time. The details will be presented at the conference. [1] Y. S. Rim, \textit{et al.}, \textit{Adv. Mater.} \textbf{28} (2016) 4415 [2] K. Nitta, \textit{et al.}, \textit{J. Phys. D: Appl. Phys.} \textbf{52} (2019) 315202 [Preview Abstract] |
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MW1.00081: Progress in Particle-in-Cell Simulations of Plasma-Assisted Carbon Nanotubes Formation Sergey Averkin Nanomaterials such as carbon nanotubes (CNTs) have a wide range of applications ranging from water purification to new composite materials. The use of plasmas for nanomaterial generation has many advantages compared to conventional chemical vapor deposition, such as the presence of reactive species that allows lower operational temperature during production. While there is extensive experimental data on nanoparticle growth in plasmas, in many cases fundamental understanding of the underlying physical processes is lacking. Numerical simulations can shed light on the underlying physical mechanisms and enable better prediction of nanomaterial production. We present progress in the Particle-in-Cell (PIC) simulation of CNTs growth in a plasma environment. We use the commercial PIC code VSim, with extended surface chemistry, in order to simulate growth of a single CNT in the plasma environment. We use remeshing of the simulation domain to track changes in the CNT surface due to its growth; this allows us to capture changes in the particle fluxes. The augmented surface boundary conditions include surface diffusion, adsorption and desorption. VSim predictions of the CNT growth rates can be fed to existing plasma fluid codes such as USim for more accurate production modeling. [Preview Abstract] |
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MW1.00082: Plasma discharge drilling for deep subsurface access to Mars' polar layered deposits Xin Tang, Jacob Mallams, Kunpeng Wang, Christopher Campbell, Cameron Adkins, Tyler Barnes, David Staack, Gareth Meirion-Griffith, Fernando Mier-Hicks, Dan Goebel, Daniel Levine, William Reid, Kris Zacny Mars' polar layered deposits (PLD) contain the best historical record of the Amazonian time period. Compositional measurements of isotopes, volatiles, and dust trapped between PLD strata are essential to understanding Mars' climate evolution. Deep subsurface access at Mars' poles is challenging, however, due to the unique environmental conditions. Traditional mechanical drilling methods relying on in situ cutting fluids are likely infeasible; neither CO$_{\mathrm{2}}$ nor H$_{\mathrm{2}}$O are phase-stable under polar ambient conditions. Hot-tip melt-probes, an alternate to mechanical drills, are highly inefficient due to conductive losses. This work summarizes an investigation into the potential of plasma discharge drilling to enable efficient access to the polar subsurface. The approach enables rapid thermal shocking of the ice, producing fractures and reduced thermal conductivity. A glow discharge then penetrates the ice-CO$_{\mathrm{2}}$ mix, yielding the requisite melting/sublimation. The results of proof-of-concept tests performed under both Earth and Mars ambient conditions are discussed, along with the design of the experimental system and sample preparation. Experimental results are compared with those obtained from a simplified heat conduction model in COMSOL. [Preview Abstract] |
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MW1.00083: Investigation of Plasma Functionalization onto Multi-walled Carbon Nanotubes for the Enhancement of Mechanical Properties of Polyurethane Daisuke Ogawa, Hideo Uchida, Keiji Nakamura Functionalization is a crucial process to overcome a barrier of the application with carbon nanotubes (CNTs). A standard method to functionalize CNTs is to attach carboxyl groups (R-COOH) with nitric acid. In addition to the method, plasma processing can also functionalize CNTs. This presentation shows investigation on the functionalization with the plasma generated with a gas mixture of nitrogen and carbon dioxide to aim an enhancement of mechanical property of polyurethane. According to previous experimental results, the plasma-treated CNTs can enhance the wear-resistance of polyurethane by using them as a composite material. In order to identify the mechanism of the enhancement, an organic dye, acridine yellow G, is applied to the plasma-treated CNTs. The fluorescent measurement showed the indication of isocyanate groups on CNTs. Also, the measurement revealed that the fluorescence was from the location where there was no CNTs coagulation found with the observation of an optical microscope. This result recommended size selection with centrifugation onto plasma-processed CNTs. Then another fluorescent measurement showed that the plasma preferentially functionalizes smaller CNTs. [Preview Abstract] |
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MW1.00084: ABSTRACT WITHDRAWN |
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MW1.00085: Electrostatic enhancement of inlet particle separators for turbine engines Sanil John, Dennis Gifford, Jady Stevens Inlet particle separators only prevent 60-70% of fine dust particles (1-80 μm) from entering the core flow of the turbine engine. Therefore, operation of helicopters in dusty environments can cause significant damage to different sections of the turbine engines due to ingestion of fine dust particles. In this work, electrostatic enhancement of IPS performance was demonstrated for a vaneless IPS design for a standard test dust, without exceeding the limits on intake pressure loss, weight and power. The electrostatic enhancement was achieved by electrostatic enhancement was achieved by electrostatic charging of dust particles using corona discharge and their deflection into the scavenge flow path of the IPS. The dust ingestion tests were initially performed for sub-scale flow (0.6 lb/s) and then scaled-up to achieve full-scale flow (9.5 lb/s) at an engine manufacturer facility. A maximum improvement of 12% was achieved in dust separation efficiency by electrostatic enhancement. [Preview Abstract] |
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MW1.00086: Power absorption and radiation characteristics of electromagnetic waves penetrated from warm plasma layer coated metallic antenna surface. WENQIU LI Based on transcendental dispersion relations of azimuthally symmetric and asymmetric modes which penetrated from surface of a warm and collisional plasma layer covered cylindrical metallic surface, impacts of electron temperature and plasma density on sheath thickness, propagation constant, wave power absorption and wave field radiation enhancement intensity are investigated. Analytical results indicate that the sheath thickness has a significant effect on the propagation constant when the sheath thickness parameter $\delta $ ranges from 0.1 to 1; for the propagation constant, the electron temperature imposes an evident influence for the m$=$0 mode at $\omega_{pe} /\omega \in (0.001,10)$while for the m$=$1 mode the electron temperature effect can be ignored at $\omega_{pe} /\omega <10$; for the wave power absorption intensity, both of these two modes exhibit minimum value near the line $\omega_{pe} /\omega =1$; for the wave field radiation intensity, the m$=$0 mode appears a maximum value line which approximately start from the point ($\omega_{pe} /\omega =1.05$,$\nu /\omega =0.98)$ while the m$=$1 mode shows a maximum value line which approximately start from the point ($\omega_{pe} /\omega =1.05$,$\nu /\omega =1.32)$. [Preview Abstract] |
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MW1.00087: Production of Reactive Species in 2-D Packed Bed Reactors -- Impact of System Parameters Juliusz Kruszelnicki, Guy Parsey, Mark J. Kushner Control of chemical conversion using plasma-based Packed Bed Reactors (PBRs) is a complex function of system parameters, including gas flow rate, repetition rate and properties of the packing material. Impacts of these parameters were computationally investigated in a 2-dimensional PBR using the \textit{nonPDPSIM} modeling platform. The system consisted of seven, 700-$\mu $m dielectric rods ($\varepsilon_{\mathrm{r}} \quad =$ 9.0) inserted between two, coplanar electrodes with 10-ns DC pulses applied at frequencies between 100 Hz and 1 kHz. Humid air (N$_{\mathrm{2}}$/O$_{\mathrm{2}}$/H$_{\mathrm{2}}$O 78/21/1) was flowed through the system. Periodic boundary condition was applied to simulate the flow of gas through a longer PBR. We found that primary dissociation products (O, N, H, OH) formed at high rates near surfaces of the rods which then reacted with background gases, forming secondary species (O$_{\mathrm{3}}$, H$_{\mathrm{2}}$O$_{\mathrm{2}}$, HO$_{\mathrm{2}})$.. Increasing the permittivity of the rods led to higher plasma densities which favored production of reactive nitrogen species. Decreasing the separation between the rods led to similar effects while also producing gas-flow stagnation, which favored production of tertiary species (N$_{\mathrm{2}}$O$_{\mathrm{x}}$, HNO$_{\mathrm{4}})$. Decreased pulse frequency and increased gas flow were both found to mitigate this stagnation. [Preview Abstract] |
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MW1.00088: Measurement of supersonic plasma flow using Mach probe under grid bias Insun Park, Greg Severn, InJe Kang, Min-Keun Bae, MinJi Lee, Kyu-Sun Chung Supersonic flow plasma is one of the most important plasma flow for understanding of edge plasma and deduction of supernova. In experiment, Mach number [M$_{\mathrm{0}} \quad =$ v$_{\mathrm{d}}$ / (T$_{\mathrm{e}}$/m$_{\mathrm{i}})^{\mathrm{1/2}}$] was measured by a Mach probe, which composed of two electric probes is separated by an insulator and plasma chamber is the following the specification: length $=$ 64 cm, diameter $=$ 32 cm, plasma is filament DC discharge source and the following conditions: 5 × 10$^{\mathrm{8}}$ \textless n$_{\mathrm{e\thinspace }}$[cm$^{\mathrm{-3}}$] \textless 10$^{\mathrm{9}}$, 1 \textless T$_{\mathrm{e}}$[eV] \textless 4 using Langmuir planar probe, Bulk M$_{\mathrm{0}}$ \textasciitilde 0.06 at working pressure \textasciitilde 10$^{\mathrm{-4}}$ Torr and 5 × 10$^{\mathrm{-4}}$ Torr with Kr gas with bias $=$ 80 V and discharge current $=$ 1 A, negative grid bias $=$ -100 V for ions acceleration. As the experiment result, maximum M$_{\mathrm{0}}$ was about 2.3 near grid. [Preview Abstract] |
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MW1.00089: On the ignition of a pulsed CCRF discharge in argon: effect of different afterglow durations. XiangYu Wang, XiaoKun Wang, YongXin Liu, YouNian Wang It is well known that the light emission intensity generally exhibits a sharp peak at the ignition phase of a pulsed CCP, however, its physical process has not been precisely understood. In this work, the light emission intensity, electron density, amplitudes of applied rf voltage and current, etc. as a function of time during the igniting phase of a pulsed Ar CCRF discharge were studied by phase-resolved OES, time-resolved hairpin probe, and voltage/current probe. Particular attention is put on the effect of changing the afterglow duration on these time-dependent parameters. It is found that the electron power absorption mode during the igniting phase strongly depends on the duration of the afterglow, because the number of electrons remaining from the last afterglow play a key role in the re-ignition of the plasma. When the afterglow duration is long enough (e.g., Toff $\ge $ 200$\mu $s), there are very few seed electrons left, and the re-igniting of a pulsed plasma behaves like a plasma breakdown process. With time, plasma experiences multiple mode transitions, which are successively dominated by uniform electric field across the entire electrode spacing, drift electric field in the central region, and sheath electric field adjacent to electrode. [Preview Abstract] |
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MW1.00090: The Effects of Different Metal Electrodes on DBD plasmas and Resulting Gas Chemistry Shivam Patel, Alex Gemshiem, Matthew Goeckner, Lawrence Overzet Atmospheric dielectric barrier discharge (DBD) plasma is rapidly expanding as a research field because of its applications in medical, industrial, and processing technologies. To form a DBD plasma, a strong dielectric is used to separate two metal electrodes. This plasma dissociates the surrounding gas, producing reactive oxygen and nitrogen species (RONS). Two RONS of interest include ozone and nitric acid because of the potential to use them in myriad applications. The RONS concentrations in a particular environment can be time dependent. Here we make use of a GEC Reference Cell to create and maintain a well-controlled environment. The Cell is first evacuated, and then refilled to atmospheric pressure with precise mixtures of N2, O2 and H2O. Using Fourier transform infrared spectroscopy we are able to monitor the time evolution of several RONS created in the Cell. By using differing electrode materials, with all other parameters held constant, we are able to examine the effect of differing metal surfaces on RONS generation. For example gold electrodes enabled the production of 30{\%} more ozone and 3{\%} more nitric acid than copper electrodes at essentially the same operating conditions and time [Preview Abstract] |
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MW1.00091: 3D Kinetic Modeling and Quantification of Cathode Directed Streamer Evolution in an Azimuthally Swept Pin-to-Plane Wedge Geometry. Ashish Jindal, Chris Moore, Andrew Fierro, Matthew Hopkins Positive streamer evolution in 600 Torr air is modeled in pin-to-plane wedge geometries using a 3D kinetic particle-in-cell (PIC) code that simulates particle-particle collisions via the direct simulation Monte Carlo (DSMC) method. 3D wedges of 5, 15, 30, and 45 degrees are used to keep the problem space tractable. 6kV DC is applied to a 100 $\mu $m hemispherical anode seeded with a 1 eV-10$^{\mathrm{18\thinspace }}$m$^{\mathrm{-3}}$ spherical plasma of 100 $\mu $m radius at its tip, generating a 4 MV/m overvolted field across a 1.5 mm gap terminated by a planar grounded cathode. The air chemistry model includes Townsend breakdown (electron-neutral elastic, excitation, ionization, attachment, and detachment collisions and secondary electron emission) and streamer (photoionization and ion-neutral collisions) mechanisms via tracking excited state neutrals that can either quench via collisions or spontaneously emit a photon based on specific Einstein-A coefficients. Electrons are tracked with picosecond temporal resolution, spatially binned, and averaged over 6 randomly seeded simulations. Streamer dynamics are quantified for each wedge angle in terms of electron velocity and density. Results indicate solution convergence in terms of these parameters is achievable. [Preview Abstract] |
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