Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session KW81: Poster Session II (5:00-7:00 pm CDT) |
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Room: GEC platform |
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KW81.00001: Analysis of the Self-Sustaining Processes in a Hollow Cathode using Optical Emission Spectroscopy Kirk Boehm, Joshua Kirks, Richard Branam Hollow cathodes are used in just about every plasma process, endemic throughout our lives. The electron emission of the cathode reaches a self-sustaining mode, ion bombardment of the low work-function materials. This research proposes the theory that the self-sustaining mode is a complex result of a mix of ionization states (singly, doubly, ...), the thermodynamic state, the electron energy distribution, and electron production. Electron production in the plasma results from thermionic and secondary emitted electrons. Most computational models assume that only singly ionized particles are present (no plasma is composed of only singly ionized particles). The temperatures in the neutral gas and plasma are often assumed to be the same, but evidence suggest these temperatures are very different. Direct evidence from inside of the hollow cathode is needed to better describe the plasma physical phenomena (ion production, ion-surface impact, electron production at the surface) Producing accurate measurements of plasma composition, individual species’ temperatures, ionization states, and surface temperatures in a relatively confined space without influencing the plasma directly is the challenge. To produce this evidence, the focus is on developing and using optical emission (non-intrusive) measurement technics in combination with the branching fraction theory to quantify individual species properties. The final results will then be injected into plasma kinetic formulas and the collisional radiative model (CRM) to further explain the actual physical processes. The results of this research will allow reduced loss designs in the energy production processes, increase communications bandwidth, and reduce energy consumption in manufacturing plating processes. |
Not Participating |
KW81.00002: Dust Charge Measurement Techniques for Dusty Plasmas Under a Strong Magnetic Field Dylan Funk, Uwe Konopka, Edward E Thomas Dusty plasmas consist of components typically found in a plasma (electrons, ions and neutral particles) as well as micrometer sized dust particles. The structural and dynamic properties of a dusty plasma system are governed by the dust particle charging state. As such the knowledge of the exact charging state of the individual dust particles is very important. Theories such as OML and ABR theories have been used to determine dust charge value. Some recent experiments to determine particle charge indicate difference from theoretical models in the presence of a magnetic field. |
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KW81.00003: Measuring gold and platinum spectra using hollow cathodes for application in neutron star merger studies Brandon Martin, Steven Bromley, Mike Fogle, Stuart D Loch The recent detection of a binary neutron star merger using gravitation waves has opened up the possibility of using spectroscopy to determine the abundances of the very heavy elements believed to be generated via the r-process in such merger events. There is, however, a lack of high quality atomic data for the low charge state heavy elements that are of importance for such studies. Results are presented for gold and platinum line emission from neon-filled hollow cathode lamp spectra collected with a resolving power ~10,000 over a wavelength range from 200-1500nm. The spectra are compared to previous measurements on the Auburn Compact Toriodal Hybrid experiment and archived hollow cathode measurements. |
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KW81.00004: A Novel Route for Synthesis of High Entropy Transition Metal Borides via Microwave-Induced Plasma Bria Storr, Deepa Kodali, Kallol Chakrabarty, Paul A Baker, Vijaya Rangari, Shane A Catledge This research focuses on the benefits of microwave-induced plasma as a means to synthesize high entropy transition metal borides. This novel synthesis route allows rapid heating/cooling rates and investigation into potential heating mechanisms offered by combined electric/magnetic field components. These field components may act together to yield high entropy ceramics at lower temperatures and processing time compared to conventional convective heating routes. Our novel microwave plasma approach relies on boro/carbothermal reduction from metal oxide-containing precursor powders (with graphite and B4C as reducing agents). This precursor powder mixture allows efficient microwave energy absorption contributing to rapid and uniform sample heating. Potential interactions of the low-temperature microwave plasma with the precursor powder will be discussed in the context of dielectric and magnetic loss heating mechanisms. |
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KW81.00005: Microwave Plasma Chemical Vapor Deposition to Synthesize Multiphase Boron Nitride using External DC Bias. Kallol Chakrabarty, Paul A Baker, Vineeth M Vijayan, Shane A Catledge Boron nitride (BN) is a member of Group III-nitrides, and has aroused great interest among the scientific community during the past two decades for its outstanding properties including hardness, toughness, chemical inertness, thermally conductivity, and electrically insulation. Due to its low-cost and scalable production technology, chemical vapor deposition offers the most viable technology route for synthesizing BN. In this study, Microwave Plasma Chemical Vapor Deposition (MPCVD) was used to synthesize multiphase BN on silicon substrate. The produce BN coating has both sp2 and sp3 bonding. The applied negative DC bias was found to yield a higher content of sp3 bonded BN in both cubic and metastable wurtzite structural forms. Another metastable phase known as Explosion BN (E-BN) is also present in the coating which has a mixture of sp2 and sp3 bonding in the structure. To the best of our knowledge, we report the first synthesis of metastable phases of BN made by MPCVD. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) were used to characterize sp2 and sp3 bonded content in the BN coatings. Nano-indentation measurements reveal an average coating hardness of 25 GPa with some measurements as high as 31 GPa, consistent with a substantial fraction of sp3 bonding mixed with the hexagonal sp2 bonded BN phase. |
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KW81.00006: Development of probe diagnostics for EM wave measurements in the ALEXIS and MDPX devices Jared C Powell, Saikat Chakraborty Thakur, Edward E Thomas The Auburn Linear Experiment for Instability Studies (ALEXIS) and the Magnetized Dusty Plasma Experiment (MDPX) are both capable of generating magnetized plasmas that can support a variety of plasma instabilities and waves. In particular, both ALEXIS and MDPX have configurations in which strong density gradients can appear in the plasma. Specific diagnostic tools are required to fully investigate these phenomena. The goal of this project is to develop probe diagnostics for investigating electrostatic and electromagnetic waves in ALEXIS and MDPX. We will construct B-dot probes to measure the magnetic field fluctuations . These probes will be used in experiments that measure various types of EM plasma waves, such as Electromagnetic Ion Cyclotron (EMIC), and Alfven waves. Preliminary work will focus on developing a wave launching system to be used within ALEXIS, where we will attempt to measure the launched waves with our B-dot probes. Future work will involve transferring the probes to MDPX to be used in high-magnetic field experiments. |
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KW81.00007: Redistribution of Kinetic Energy in a Microgravity Complex (Dusty) Plasma Lori C Scott, Edward E Thomas, Saikat Chakraborty Thakur, Uwe Konopka, Jeremiah D Williams, Mikhail Pustylnik, Hubertus Thomas In the presence of gravity, the micron-sized charged dust particles in a complex plasma are compressed to thin layers, but under microgravity conditions, such as the Plasma Kristall-4 (PK-4) experiment on the International Space Station (ISS), the particles fill the plasma volume which allows the study of a 3D multi-particle system. When dust particles are injected into a dc glow discharge plasma they flow along an axial electric field until stopped by periodic oscillations of the electric field (polarity switching). This oscillation creates a change in the spatial ordering and thermal state of the particle system. |
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KW81.00008: Experimental Studies of Sheath Formation in Electronegative Plasma in a DC-discharge device (EPaX) at the University of San Diego (USD) Gregory Severn, Lena Belvin, Peixuan Li, Oliver Schmitz Despite the outstanding success of plasma processing applications using electronegative plasma over the last several decades, there remain open questions regarding the physics of sheath formation in such systems. While the model of Braithewaite and Allen (1988) is generally assumed to be the case, direct experimental benchmark experiments are still lacking. Further, a focused set of benchmarking experiments directly measuring potential profiles in the neighborhood of sheaths near conducting boundaries, for a variety of electronegativities, is also still lacking. A DC-discharge device at the University of San Diego (USD), a principally undergraduate institution, is nearing completion designed for discharges using corrosive gas feed stocks such as molecular iodine and oxygen. The plan is to commission the device in Argon, then Argon-Oxygen, and then Argon-Iodine discharges. The first discharges are now planned for Summer of 2021. Progress and results will be presented. |
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KW81.00009: Polarity Effects on Synthesis of Feroxyhite FeOOH Nanomaterials by DC Atmospheric Pressure Microplasma in Air Gregory Severn, Yucheng Lan, Tyrome Fowlkes, Kit Sze, Chiedozie B Ogueri, Alexander Nanor Our presentation deals with feroxyhite FeOOH nanomaterial production by an atmospheric pressure microplasma in the air under different polarities. A positive (negative) DC voltage was applied to a carbon rod facing an aqueous ferrous solution connected to a negative (positive) terminal of a high-voltage source via a carbon electrode. A four-time higher mass-production yielded under the positive polarity setup than under the negative polarity setup at 9.0 kV and 3.0 kV/mm. X-ray diffraction investigations showed that all products were the same phase with nanostructures. UV-vis spectra indicated that the negative polarities led to a fast synthesis of the nanomaterials in 5 min while the positive polarities produced the phase in 20 min, 4 times slower, under the same experimental conditions. The polarity effect was also confirmed at high voltages up to 25kV. Possible chemical reactions in solution are discussed in light of the different polarities of the discharge. Our results showed that the polarities can affect nanomaterial syntheses significantly in atmospheric pressure microplasma. |
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KW81.00010: Photo-discharging as a path to controlling dust charge in low-temperature plasmas Michael McKinlay, Saikat Thakur, Uwe Konopka, Edward E Thomas Charged microparticles (dust) in a plasma environment represent a potential tool for some experimenters and an unwanted contaminant for others. The lack of direct, independent control over the dust's equilibrium charge of the dust particles represents a significant obstacle to improving dust confinement or removal. Recent proof-of-concept tests on the Auburn Dusty Plasma Experiment (DPX) combining Lanthanum Boride (LaB6) particles with a high-intensity, near-UV source have demonstrated that photoelectric currents can significantly alter the equilibrium properties of the dust; and that by tailoring the light source to the material properties of the dust and the apparatus, this control can be accomplished with minimal perturbation to the background plasma. Probe measurements of the plasma and video analysis of the particle response to the application of UV are presented, and the potential of expanding photo-discharging to other materials and experimental regimes is discussed. |
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KW81.00011: Does the discrepancy between Langmuir Probe and emissive probe measurements of plasma potential in the presheath depend on ion flow? Gregory Severn, Adrian Woodley, Michael P Shahin, Peixuan Li, Oliver Schmitz It has recently been shown that that Langmuir probes (LPs) measure an unphysically positive plasma potential in the presheath of low temperature plasma, near conducting boundaries at which ion rich sheaths form. It has been argued heuristically that the difference between plasma potential profiles measured by LPs and emissive probes (EPs), in the presheath, is related to ion flow caused by sheath formation. A negatively biased plate (-100V) is immersed in a weakly collisional (λmfp» λD) low pressure (Pn ≤1 mTorr), low temperature (kTe ∼ 1 eV), single ion species plasma formed in a hot-filament DC discharge, where the feedstock gas is Ar or He or Xe or Kr. Here we present details of the LP and EP profile measurements in experiments designed to test whether the Bohm speed, vBohm= √(kTe/Mi), affects the difference between the potential profiles. |
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KW81.00012: Does the discrepancy between Langmuir Probe and emissive probe measurements of plasma potential depend on ion flow and sheath formation? How might LIF measurements help with model formation? Gregory Severn, Michael P Shahin, Adrian Woodley, Oliver Schmitz, Peixuan Li It has recently been shown that that Langmuir probes (LPs) measure an unphysically positive plasma potential in the presheath of low temperature plasma, near conducting boundaries at which ion rich sheaths form. It has been argued heuristically that the difference between plasma potential profiles measured by LPs and emissive probes (EPs), in the presheath, is related to ion flow caused by sheath formation. A negatively biased plate (-100V) is immersed in a weakly collisional (λmfp»λD), low pressure (Pn≤ 1 mTorr), low temperature (kTe ∼1 eV), single ion species plasma formed in a hot-filament DC discharge, where the feedstock gas is Ar or He or Xe or Kr. We are in the process of making needed upgrades to the laser-induced fluorescence (LIF) collection optics so that we can include LIF measurements with our results, which are designed to test whether the Bohm speed, vBohm = √(kTe/Mi), affects the difference between the potential profiles. |
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KW81.00013: Observation of hysteresis in low pressure neon inductively coupled plasmas Young-Hun Hong, Tae-Woo Kim, Moo-Young Lee, Min-Seok Kim, Yeong-Jae Jeong, Chin-Wook Chung A hysteresis is experimentally observed during the E mode to H mode transition in neon inductively coupled plasmas. The hysteresis phenomenon has generally been observed in high pressure Ramsauer gas discharges. However, in the neon plasmas, the hysteresis of an electron density and a coil current was observed at low gas pressure (5 mTorr). Furthermore, the hysteresis phenomenon was vanished with a slight increase in gas pressure (10 mTorr). To analyze the hysteresis phenomenon, electron energy distribution functions (EEDFs) were measured with increasing and decreasing RF power. Interestingly, the measured EEDF at low gas pressure has a Maxwellian distribution in the E mode discharge and evolves to a bi-Maxwellian distribution in the H mode discharge. This evolution of the EEDF causes the hysteresis phenomenon due to a strong nonlinearity of the collisional energy loss during the E to H and the H to E transition. |
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KW81.00014: Surface induced effects in the ion energy distribution of a symmetric capacitively coupled plasma Christian Schulze, Zoltan Donko, Jan Benedikt Secondary electron emission (SEE) coefficients are available from particle beam experiments but its determination in a plasma experiment is more difficult since ions, neutrals, metastables, electrons and photons can initiate SEE. Therefore, in-situ approaches typically determine an effective SEE coefficient based on the ratio of emitted electrons per incoming ion. To our knowledge, only two approaches are currently available: The γ-CAST method determines SEE coefficients from the ratio of α and γ electron excitation maximum in PROES measurements and a method that analyzes the plasmas I-V-characteristics. Here, we critically discuss the potentials and challenges of an alternative method that estimates the SEE coefficient from changes in the ion energy distribution function (IEDF) of a symmetric capacitively coupled plasma (CCP). |
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KW81.00015: Investigation of the effects of excited states in low-pressure inductively coupled argon plasmas using a self-consistent kinetic model Wei Yang, You-Nian Wang Low-pressure radio-frequency (RF) inductively coupled plasmas (ICPs) are extensively used for materials processing. In this work, we have developed a self-consistent kinetic model consisting of two-dimensional Maxwell equations, zero-dimensional electron Boltzmann equation, and global model. The kinetic model presented in this work is modified based on our previous model. The simulation results obtained by the improved model achieve a better agreement with the experiments. This work presents an investigation of the influence of excited states on normalized EEPF, plasma density, effective electron temperature as well as reaction dynamics in a low-pressure RF Ar ICP using the kinetic model. The excited states include 1s (metastable and resonant) and 2p states, due to these species presenting the highest number-density in low pressure discharges. The effect of higher excitation energy levels has been neglected. The developed kinetic model can be extended to more complex gas discharges, i.e., molecular gases, and to ultimately optimize the parameters of RF ICP sources used for industrial application. |
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KW81.00016: Multi-diagnostic experimental validation of 1d3v PIC/MCC simulations of low pressure capacitive RF plasmas operated in argon David A. A Schulenberg, Ihor Korolov, Florian Beckfeld, Zoltán Donkó, Aranka Derzsi, Julian Schulze We systematically compare results of one-dimensional particle-in-cell simulations to experimentally measured plasma parameters. Measurements of the gas temperature, electron density, spatio-temporal electron impact excitation dynamics, and ion flux-energy distribution at the grounded electrode are performed in a custom built geometrically symmetric reactor in argon gas at pressures ranging from 1 Pa to 100 Pa and at RF (13.56 MHz) voltage amplitudes between 150 V and 350 V. In the experiment, the gas temperature increases significantly beyond room temperature as a function of pressure. The computational results are sensitive to the gas temperature and to the choice of surface coefficients for electron reflection and secondary electron emission, which are both input parameters for the simulation. By adjusting these parameters, we achieve a good quantitative agreement between all measured and computationally obtained plasma parameters. This shows that PIC/MCC simulations can describe experiments correctly over a wide range of operating parameters, if appropriate values for the gas temperature and the surface coefficients are used. |
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KW81.00017: Neutral dissociation of methane by electron impact and a complete and consistent cross section set Dennis Bouwman, Andy Martinez, Bastiaan J Braams, Ute Ebert We present cross sections for the neutral dissociation of methane. With these cross sections the work of Song et al. [J. Phys. Chem. Ref. Data, 44, 023101, (2015)] can be extended which results in a complete and consistent set. Notably, the resulting cross section set does not require any swarm-fitting to reproduce swarm parameters. Therefore consistency can be considered an inherent trait of the set, since swarm calculations (with a Monte-Carlo code) are used exclusively for validation of the cross sections. Neutral dissociation of methane is essential to include (1) because it is a crucial electron energy sink in methane plasma, and (2) because it largely contributes to the production of hydrogen radicals. Finally, we compare the production rates of hydrogen species for a swarm-fitted data set with ours. The two consistent cross section sets predict different production rates, with differences of 45% (at 100 Td) and 125% (at 50 Td) for the production of H2 and a similar trend for production of H. With this comparison we underline that the swarm-fitting procedure can possibly deteriorate the accuracy with which chemical production rates are estimated. This is of particular importance for applications with an emphasis on plasma-chemical activation of the gas. |
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KW81.00018: Spintronics: Study of Zigzag Silicine Nanoribbons (ZSiNR) Soumita Mondal, Soubhik Mondal The main aim of this paper would be to summarise the results of the two main journals [1,2] and distinguish between the two main cases of Silicine (2D layered sheets of Graphene) and Manganese passivated Silicine. |
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KW81.00019: Improvement of power transfer efficiency using a parallel resonance in a 60 MHz capacitively coupled plasma Junho Lee, You He, Minseok Kim, Chinwook Chung A parallel resonance circuit is applied to improve the power transfer efficiency of 60 MHz capacitively coupled plasma. As the plasma resistance is inversely proportional to electron density, power transfer efficiency decreases with increasing input power. A parallel variable vacuum capacitor (VVC) is connected to the inductive load to improve power transfer efficiency. The inductive load is a series circuit consisted of a power line (usually denoted as an inductor), electrode, and plasma. As the capacitance of VVC approaches the parallel resonant point, the resistance of the parallel resonant circuit becomes much higher than without VVC, and the current flowing through the matching network decreases. Therefore, power transfer efficiency and electron density were increased. In addition, this effect is increased with increasing input power. At 100W, the power transfer efficiency and the electron density increase by 4.5% and 3.9%. However, at 200W, the power transfer efficiency and the electron density increase by 7.5% and 21%. |
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KW81.00020: MVDC circuit breaker hollow cathode plasma PIC modeling using EDIPIC-2D Svetlana Selezneva, Igor Kaganovich, Dmytro Sydorenko We will present recent results of MVDC circuit breaker hollow cathode plasma model Particle-in-Cell model using EDIPIC-2d code, that was previously used for Hall thruster modeling [1]. The code implements explicit leap-frog algorithm, Boris scheme for particle advance and Monte Carlo model of electron-neutral collisions. It accounts for self- consistent electrostatic field and externally defined non-uniform magnetic field. The later feature is useful to study the effect of various possible magnetic field configurations on hollow cathode plasma with the aim of its uniform spreading along the control grid. |
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KW81.00021: Measurement of individual ion density using floating harmonic method in Ar/He mixed inductively coupled plasma Moo-Hyun Lee, Min-Seok Kim, Chin-Wook Chung Argon and helium ion density were obtained in Ar/He mixed gas discharge. Experiments were performed at pressures of 10, 25, 50 mTorr in planar type inductively coupled plasma. The electron temperature, electron density, and ion saturation current were measured using the floating harmonic method and electron energy distribution function to obtain the ion density. Experimental results show that the relative density of argon ion ([nAr+]/[nAr+]+[nHe+]) increases with increasing the flow rate portion of argon ([Ar]/[Ar]+[He]). The results were reasonable considering the low ionization energy of argon and the penning ionization effect by He*. At 25 mTorr, when the flow rate portion of the argon is 90%, the relative ion density of the argon is maximized near the coil. On the other hand, when the flow rate portion of the helium is 90%, the relative ion density of the argon is maximized near the discharge center. The reason is that helium discharge has a relatively long energy relaxation length compared to argon, and as the portion of the helium increases, the electron relaxation length is extended. Also, because helium ions diffuse better than argon ions, the relative ion density of helium at the edge is high. |
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KW81.00022: The 2021 release of the Quantemol Database (QDB) Sebastian Mohr, Martin Hanicinec, Jonathan Tennyson Plasma processes are commonly used in a variety of industrial applications such as the manufacturing of semiconductors or the production of thin films. For a better understanding of the fundamental processes in plasmas as well as for the optimization of industrial applications, computational models are often used. These models require accurate and comprehensive data on the chemical reactions taking place in the plasma to accurately predict particle densities, fluxes, and energies which influence the desired plasma-surface interactions. The data are usually scattered across multiple publications and collecting the data for a specific gas mixture is a time-consuming process. To aid with the collection of data, several centralized databases have been developed. One is the Quantemol DateBase (QDB), which focuses on data for low temperature plasmas, but also contains data useful for fusion or combustion purposes. |
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KW81.00023: Real-time measurement of dielectric thickness on a millimeter scale using triple-frequency in inductively coupled plasma Jae-Hoon Choi The dielectric thickness is measured using a floating probe with triple-frequency in inductively coupled plasma (ICP). Previous studies show that they can only measure the thickness on a micrometer scale when using low frequencies (~30 kHz). In this study, we propose an electrical diagnostic method to measure the thickness of a thick dielectric using triple high frequency (600 kHz, 800 kHz, 1 MHz). Since the impedance of a dielectric is inversely proportional to applied frequency, the thickness of a thick dielectric could be measured using high frequencies. The capacitance and thickness of the dielectric were measured by applying small sinusoidal voltage signals (~2 V) with three different frequencies. The experiments are taken under argon gas, pressure range from 5 mTorr to 25 mTorr, and ICP power range from 100 W to 300 W condition. Several heights of dielectric (silicon dioxide cylinder) attached to the top of the probe tip. The results were in good agreement with the actual thickness range from 1 mm to 5 mm. |
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KW81.00024: Microwave manipulation for absorption, cloaking and scattering using plasma metamaterial composite with frequency dispersion Osamu Sakai, Chui Inami, Yota Noyori, Shigeyuki Miyagi High-power microwave is one of the promising candidates for wireless power transmission, although available tools for microwave manipulation are limited since typical specifications of integrated and discrete electronic microwave devices are for low-power operation (less than 100 mW). So far we have proposed plasma metamaterial composites (PMCs) to regulate microwaves, where a PMC, which is generated by electric power with tens of watts, is more compact in size [1] and more robust against high-power microwaves than conventional solid-state metamaterials. In this study, we demonstrate various functions of PMCs for microwave manipulations, like absorption, cloaking, and scattering. Since plasma and metamaterial are two independent elements as wave media, a PMC exhibits complicated frequency dispersion, leading to variety of microwave manipulation. For instance, results in this experimental study suggest that one of our PMCs works as an absorber around 2.6 GHz, as a cloaking device around 2.90 GHz, and as a scatterer around 3.1 GHz. This fact indicates that PMCs with metamaterial design and plasma density control can work as a high-power microwave manipulator. [1] A. Bambina, S. Yamaguchi, A. Iwai, S. Miyagi and O. Sakai, AIP Adv. 8, 015309 (2018) |
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KW81.00025: Optical vortex laser-induced fluorescence measurement using an l=10 Laguerre-Gaussian beam Shinji Yoshimura, Kenichiro Terasaka, Mitsutoshi Aramaki We have been studying the application of optical vortex beams to plasma measurement. Due to the additional Doppler effect in the azimuthal direction, the optical vortex laser-induced fluorescence (OVLIF) spectrum can be deformed by the motion of the particles in the direction vertically across the beam [1]. A proof-of-principle experiment for the perpendicular argon-ion flow detection was performed with the HYPER-I device at the National Institute for Fusion Science. A Laguerre-Gaussian (LG) beam with the topological charge l=10 was produced by converting a Hermite-Gaussian beam using a computer-generated hologram on a spatial light modulator. The LG beam was injected parallel to the surface of an electrode inserted in the plasma, and the OVLIF was detected by a photomultiplier tube. An increase in the standard deviation of the spectrum was observed as the negative applied voltage to the electrode was increased, which is qualitatively consistent with the prediction of our numerical study. |
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KW81.00026: Measurement of Arc Temperature during Automatic Welding Torch Control by Multi-point High-speed Spectroscopy Susumu Ichinose, Koki Matsumoto, Yu Shi, Yuki Suzuki, Zhenwei Ren, Yusuke Nemoto, Toru Iwao TIG arc welding is often used because this welding has high quality and strength. However, when the distance between electrodes is changed, the arc length and arc voltage are displaced, and the heat transfer rises or falls, causing welding defects. Therefore, it is necessary to adjust and control the distance between the electrodes automatically, because the number of special artisan is quite limited. In this research, the arc temperature displacement with respect to the displacement of the interelectrode distance was calculated by driving the welding torch vertically, automatically controlling the interelectrode distance, and measuring the arc temperature during the control. Specifically, the welding torch was controlled up and down by a microcomputer, and the arc voltage was measured. At the same time, the temperature was calculated from the spectra using the multi-point high-speed spectroscopy of the arc near the base metal and the gas vapor generated when the base metal melted down. As a result, it was possible to measure the arc temperature when welding defects occurred because of the displacement of the distance between electrodes. |
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KW81.00027: High-speed plasma diagnostics based on the floating harmonic method Beom-Jun Seo With the recent use of pulsed RF plasma in etch processes, a high-time resolution diagnostic method is required. To monitor the plasma in real-time , a high-speed plasma diagnostic method based on the floating harmonic method (FHM) is proposed. The conventional FHM is a diagnostic technique to obtain ion density and electron temperature by applying a sinusoidal voltage to a floating probe, and its frequency is usually kHz range. In this work, we increased frequency of the applied voltage to MHz range for high-speed plasma diagnostics. As the applied frequency to the probe is increased, harmonic currents increase abnormally. As we applied high frequency voltage to the probe, the additional currents flow through the ceramic sleeve of the probe. By subtracting the additional currents from the harmonic currents, the compensated results were in good agreement with measurements from the conventional floating harmonic method. The electron temperature and ion density of the pulsed plasma were also measured with high-time resolution. |
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KW81.00028: Contribution of Opening Speed of SF₆ Gas Circuit Breaker for High Temperature Area Decrement Using Three-Dimensional Electromagnetic Thermal Fluid Simulation Wataru Fuse, Yuki Suzuki, Yusuke Nemoto, Zhenwei Ren, Toru Iwao The arc extinguish chamber of SF₆ gas circuit breaker is expected to be smaller than the current one, while the thermal reignition can be prevented. It is important to obtain the rapid change of temperature distribution inside the extinguish chamber during the interruption process. However, it is difficult to obtain the rapid change of arc plasma with experiment, the numerical simulation is usually used to analyze the above process as well. Meanwhile, the temperature volume of arc increases along with the electrode opening process during the actual interruption process of circuit breaker. Therefore, it is necessary to consider the electrode opening process for analyzing the thermal reignition. The most difficult part of simulation for the electrode opening process is the treatment of interface between arc plasma and electrode, because the rapid change of physical properties with time variation. In this research, a calculation method of electrode opening process was proposed for high temperature area decrement. As a result, the high-temperature region decreased significantly when the electrode opening velocity was fast. |
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KW81.00029: Analysis of Ion Density at Sheath Region Affected by Moving Speed of Vacuum Arc Cathode Spot Using Three-Dimensional Electromagnetic Thermal Fluid Simulation Hiroto Suzuki, Masahiro Takagi, Zhenwei Ren, Yusuke Nemoto, Yuki Suzuki, Toru Iwao Vacuum arc discharge has been used in a wide range of fields such as circuit breakers, ion plating, and surface treatment. In vacuum arc discharges, the cathode spots move rapidly and irregularly, and it is necessary to obtain the factor which control the cathode spot movement for industrial applications. It is assumed that the movement of cathode spot is caused by the transport of ions, which leads to the field electron emission and the thermionic electron emission. The transport of ions from the original cathode spot forms the potential hump which depends on the ion density, and causes the increment of electric field density on the advance side of cathode spot. In this research, the velocity of cathode spot is set as parameter for elucidating the relation between ion density and current density at the sheath region, and aims to elucidate the critical ion density for causing the cathode spot movement. |
Not Participating |
KW81.00030: ZrxOy based layers investigated by the 3ω method Vitali Bedarev, Philipp A Maaß, Marina Prenzel, Marc Böke, Achim von Keudell Aim of the project is to develop a diagnostic technique to measure the thermal conductivity of thin ZrxOy layers which are deposited via PECVD and can be used for galvanic isolation. The 3ω method was selected as a surface-sensitive technique with high accuracy and short equilibration time. |
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KW81.00031: Analysis of Arc Behavior in Air Circuit Breaker with Applying Transverse Magnetic Field Shinichiro Kashiwagi, Zhenwei Ren, Yusuke Nemoto, Yuki Suzuki, Yoshifumi Maeda, Toru Iwao Recently, digital transformation is being promoted toward the establishment of next-generation power networks, and in order to this achieve, it is necessary to collect analysis data under a wide variety of conditions. Circuit breakers are also required to be developed for the overall optimal solution of the power system using monitoring and control technology, and it is expected that the efficiency of operations will be improved with the introduction of DX. The objective is to realize an air circuit breaker that suppresses switching surge voltage when shutting off, determines the opening speed according to the situation, and reduces the size and cost. Focusing on air circuit breakers, it is important to understand the basic characteristics of the arc generated between the electrode contacts in order to achieve miniaturization and high performance. However, few simulation analyzes of arc behavior in air circuit breaker with applying transverse magnetic field have been reported. In this research, the arc temperature distribution affected by the applying transverse magnetic field of the air circuit breaker was calculated using the 3-D electromagnetic thermal fluid simulation. |
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KW81.00032: Optics-Based First Measurement of Currents on a Load of X-Pinch System at Seoul National University Seongmin Choi, H.J. Woo, Seunggi Ham, Jonghyeon Ryu, Kyoung-Jae Chung, Y. S. Hwang, Y.-c. Ghim A X-pinch system is capable of generating high energy density plasmas with pulsed and large currents through a pair of crossed thin wires. Recently, we have developed a modular X-pinch device at Seoul National University [1]. With an aim of obtaining basic characteristics of the X-pinch system, we have developed and installed an optics-based current sensor utilizing the effect of Faraday rotation. We use a 100mW 1310nm cw laser and a photo-detector measuring light intensity passing through a single mode fiber acting as a sensor wound around the load and a polarizing fiber acting as an analyzer. We present configuration of our optics-based current measurement system and its first measurement together with a Rogowski coil measurement results for comparisons. |
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KW81.00033: Landau Damping of Dust Ion-Acoustic Waves in Semi-Bounded Dusty Plasmas Myoung-Jae Lee, Young-Dae Jung The dispersion property is investigated to determine the wave frequency and the corresponding Landau damping rate for the surface mode of dust ion-acoustic waves including the effect of ion temperature by using the general perturbation and the transverse truncation methods. It is demonstrated that the increase in ion temperature enhances the wave frequency. The effect of ion temperature is more prominent in the range of large wave numbers, and the wave frequency increases in proportion to a quarter power of the ion temperature in the realm of large wave number. The Landau damping of the dust ion-acoustic surface wave is found to be suppressed as the ion temperature increases. However, the effect of ion temperature becomes negligible as the wave number increases. The effects of dust charge and electron density on the Landau damping rate are also presented in this work. |
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KW81.00034: UV-vis and Infrared Spectroscopic Investigation of Feroxyhite Nanomaterial Synthesis by AC Atmospheric Microplasma Chiedozie B Ogueri, Alexander Nanor, Tyrome Fowlkes, Solomon Tadesse, Kit Sze, Souvik Pramanik, Gregory Severn, Yucheng Lan Feroxyhite nanomaterials were synthesized in aqueous solutions by AC atmospheric microplasma at room temperature. The synthesized nanomaterials were characterized by X-ray powder diffraction, Raman scattering, and electron microscopy. The chemical reaction during the plasma synthesis was in situ and ex situ investigated by UV-vis spectroscopy and infrared spectroscopy. The initiation phase of the nanomaterial was detected from UV-vis absorption and infrared bands of hydroxyl radical. The synthesis-time-dependent crystallographic quality was detected from the bandgap of the nanomaterials, which was calculated with the Tauc method from the UV-vis spectra. The effects of voltage and electric strength were investigated too. The mechanism of the plasma synthesis was discussed. |
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KW81.00035: The law of conservation of momentum proves Newton's law Han y Quan, Meng z qiang Suppose the initial state of two objects: M1V1, M2V2, the state after interaction is: M1V12, M2V22, the interaction of these two objects is only affected by the internal force of the interaction, so momentum is conserved, that is, M1V1+M2V2= M1V12+M2V22. V12=V1+a1t, V22=V2+a2t, M1V1+M2V2=M1(V1+a1t)+M2(V2+a2t), simplified to: M1a1t+M2a2t=0 because the interaction time must be equal. that is, M1a1+M2a2=0, according to Newton's second law F=am: F1+F2=0, that is, F1=-F2, The motion state of our fake M0 object is: M0V0, after a period of time, the speed of M0, V1=V0+at, according to Newton's second law F=am, a=F/m, the object is not subject to external force, that is, F=0, a must be zero, that is, a=0, V1=V0. In particular, when V0=0, the object is at rest. Prove Newton's first law |
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KW81.00036: Development of A Compact High-Density Blue-Core Helicon Plasma Device under Strong Magnetic Field of Ring Permanent Magnet Zhikang Lu, Guosheng Xu, Chi-Shung Yip, Dehong Chen, Xingquan Wu, Wei Zhang, Guanghai Hu, Chenyao Jin, Di Jiang Due to the high density and high ionization rate of helicon plasma, there is a keen interest in the application of helicon plasma, and efforts as been done to broaden their operatable parameter range, particularly with miniaturization of such devices [1,2]. Helicon plasmas are commonly generated in a cavity with a relatively large diameter or a relatively long plasma length[1], this comes from the consideration of the dispersion relation of the helicon waves and the basic consideration that the cavity length of the device is generally longer than at least one wavelength of helicon wave in order for helicon waves to be excited. But, in this paper, a bule-core helicon plasma device, seemingly more compact than allowed by the helicon dispersion relation, has been developed. The construction of this apparatus along with the experimental results are described. We have successfully produced high-density blue-core plasma using quartz tubes with small diameters of 26mm and length of 40cm, with the effective length of the plasma further limited by the magnetic fields of the permenant magnets. Blue-core transition is preliminarily found possible with a radio frequency power ~580 W and RF frequency 13.56 MHz, under the magnetic field strength ~2kG generated by a set of ring permanent magnet with a length of 20.8cm, in low pressure less than 1 Pa. |
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KW81.00037: On the Mechanism of Ionization Oscillations in Hall Thrusters Oleksandr Chapurin, Andrei I Smolyakov, G.J.M. Hagelaar, Yevgeny Raitses Low frequency ionization oscillations involving plasma and neutral density (breathing modes) are the most violent perturbations in Hall thrusters for electric propulsion. Because of its simplicity, the zero-dimensional (0-D) predator-prey model of two nonlinearly coupled ordinary differential equations for plasma and neutral density has been often used for the characterization of such oscillations and scaling estimates. We investigate the properties of its continuum analog, the one-dimensional (1-D) system of two nonlinearly coupled equations in partial derivatives (PDE) for plasma and neutral density. This is a more general model, of which the standard 0-D predator-prey model is a special limit case. We show that the 1-D model is stable and does not show any oscillations for the boundary conditions relevant to Hall thruster and the uniform ion velocity. We then propose a reduced 1-D model based on two coupled PDE for plasma and neutral densities that is unstable and exhibit oscillations if the ion velocity profile with the near the anode back-flow (toward the anode) region is used. Comparisons of the reduced model with the predictions of the full model that takes into account the self-consistent plasma response show that the main properties of the breathing mode are well captured. In particular, it is shown that the frequency of the breathing mode oscillations is weakly dependent on the final ion velocity but shows a strong correlation with the width of the ion back-flow region. |
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KW81.00038: Structures and anomalous transport in Penning discharge driven by the electron beam source Vedanth Sharma, Andrei I Smolyakov, Meghraj Sengupta, Mina Papahn Zadeh, Mikhail Tyushev, Yevgeny Raitses, Igor Kaganovich Dynamics of fluctuations, structures, and anomalous transport in cylindrical Penning discharge is studied with two-dimensional (azimuthal-radial) PIC simulations taking into account self-consistent ionization. The discharge is sustained by the axial electron beam producing the ionization of the background gas. We observe the development of azimuthal gradient-drift instabilities due to the radial density gradient and radial electric field. Structure formation, decay, and transitions between rotating small scale (large m) modes and box size structures are observed depending on the plasma and discharge parameters. Characteristics of rotating structure and resulting anomalous transport are investigated as functions of the magnetic field, background gas species, and pressure is investigated. |
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KW81.00039: Nonlinear regimes of the electron cyclotron drift instability in Vlasov simulations Arash Tavassoli, Andrei I Smolyakov, Raymond Spiteri, Magdi Shoucri We report on novel investigation of nonlinear features of the electron cyclotron drift instability (ECDI) with a continuum Vlasov simulations. This instability has been recently actively studied as a source of anomalous transport in Hall thrusters. It is shown that the instability occurs as a series of cyclotron resonances with the electron beam mode due to the $E\times B $ drift. Temporal and spatial spectra of nonlinear state are presented. In the nonlinear regime, fluctuations energy condensation occurs towards the low wavelength lowest mode resonance and below (inverse energy cascade) demonstrating several nonlinear mode transitions. Similar condensation picture is observed in the spectrum of the anomalous current. It is shown that the saturated state remains far from the criteria of the nonlinear transition to the ion sound regime. |
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KW81.00040: Nonlinear large scale current structures in simulations of Electron Drift Instability Andrei I Smolyakov, Dmytro Sydorenko Electron Drift Instability (EDI) driven by the electron current due to the external electric field perpendicular to the magnetic field has been actively studied as a robust source of fluctuations and transport in $E/times B$ plasma sources. The basic linear instability occurs on the short length scale determined by the cyclotron resonance conditions which may be modified by nonlinear broadening and other geometrical effects. Many simulations todate report the coherent structures in the mm range associated with such EDI modes and their modifications. Here, we report the excitation of nonlinear two-dimensional long wavelength structures in the anomalous electron current (current vorticies) that are observed in the simulations of an azimuthally wide system. These structures are moving with roughly the $E\times B$ velocity and occur at the edges of the azimuthal electron $E\times B$ beam presumably due to the shearing effects. The current vorticies provide large contribution to the net (averaged) anomalous electron current. |
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KW81.00041: Numerical investigation of gas-plasma phase inside a bubble immersed in a liquid Luis Vadovinos-Aguilar, Cecile Malardier-Jugroot, Manish Jugroot Atmospheric micro-discharges are promising applications for nanotechnology, water treatment, agriculture, medicine, or hydrogen generation, due to their ignition at atmospheric pressure, and possible interaction with the other states of matter. Moreover, the plasma behavior in presence of a liquid electrode introduces new physical properties - such as, the nucleation of micro- and nano-bubbles inside the liquid interface, which are of great interest. Hence, the plasma physics of liquids has been extensively studied due to different physical and chemical interactions between liquid bulk and plasma. The focus of the poster will be the plasma formation inside a μ-bubble immersed in the liquid bulk, as a medium, for the plasma-liquid interactions. A numerical multiphysics approach is being adopted to simulate the plasma processes in the dielectric liquid; in addition, an experimental study will characterize the interface region and gas/plasma properties. |
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KW81.00042: Influence of the RF voltage amplitude on a RF-LF discharge in α-γ mode Raphaël Robert, Gerjan Hagelaar, Nader Sadeghi, Luc Stafford, Françoise Massines The aim of this study is to understand the influence of the RF voltage amplitude on a RF (5MHz) - LF (50kHz) double frequency discharge in α-γ mode in an Ar-NH3 DBD at atmospheric pressure. This is achieved through argon (at 750 nm) and continuum (at 500 nm) emission intensity measurements performed by time and space resolved spectroscopy, combined with measurements of the population of Ar metastable atoms. It is found that a rise in the RF voltage leads to an increase in the continuum emission, while both Ar emission and Ar metastable population decrease. A 1D fluid model is used to reveal the origin of this behaviour. It turns out that, in relation with the RF voltage increase, the electron density increases, explaining the rise of continuum emission. This higher electron density induces a decrease in the gas voltage applied between the electrodes. The gas voltage drop then leads to a lower electric field in the cathodic sheath, causing a decrease of the reactions involving highly energetic electrons, i.e. the emission of Ar and the formation of metastable Ar atoms. |
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KW81.00043: Predicting the low-pressure branch of the Paschen curve for hydrogen Alexander V Khrabrov, Igor Kaganovich, David Smith, Svetlana Selezneva A physical and numerical model of Townsend discharge in molecular hydrogen has been developed for the gas switch project. The model allows to predict the low-pressure branch of the Paschen curve in 100 KV range. |
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KW81.00044: The problem of low temperature dielectronic recombination: A joint theoretical and experimental approach Isaac Garcia, Mike Fogle, Stuart D Loch The calculation of low temperature dielectronic recombination rate coefficients, of relevance for photo-ionized astrophysical plasmas, are known to have very large uncertainties. A summary of the discrepancies is given, showing that the uncertainties in resonance positions of low energy doubly excited states is the main factor contributing the uncertainty in the calculated rates. A summary is given of future experimental plans, to be performed on the CRYRING@ESR at the GSI facility in Germany, along with a theoretical approach using large-scale configuration interaction calculations, that aims to address this problem. In addition, a method is outlined to assess the uncertainty in calculated Auger matrix elements due to the use of Fermi's golden rule. |
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KW81.00045: Plasma polymerization in RF capacitive coupled discharge in acetylene Valeriy Lisovskiy, Stanislav Dudin, Sergiy Bogatyrenko, Alexey Minenkov, Pavlo Platonov We investigated nanoparticles formed in the plasma volume of RF discharge in acetylene. The experiments were carried out in discharge tube with vertically arranged electrodes. It was found that the polymer film deposited on vertical electrodes includes nanoparticles with diameter of about 10 nm, and there are no larger nanoparticles in the film. On the tube wall the polymer film is also deposited, as well as nanoparticles with diameter of the order of several hundred nm. These nanoparticles were held in the plasma volume by the ambipolar field and have fallen on the tube wall when the combined action of gravity and ion drag force were able to overcome the near-wall potential barrier. The emission spectra measured near the boundary of the near-electrode layer contain almost only lines of atomic and molecular hydrogen, as well as CH molecular band (431 nm) with a weak intensity. It is shown that short-wave radiation (in the blue part of the spectrum) is strongly absorbed by the grown polymer film, while the lines in the red and infrared parts of the spectrum are weakly absorbed. The effect of a "vacuum pump" is observed, the gas pressure after the ignition of the RF discharge rapidly decreases several times compared to the initial one. Acetylene molecules are effectively incorporated into the growing polymer film on the electrodes and into the growinging nanoparticles in the plasma volume, while a small amount of hydrogen is released. |
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KW81.00046: Study of the efficiency of molecular gases in an ECR-based plasma cathode for current extraction Tyler Topham, Anil Bansal, John E Foster, Michael McDonald Electron cyclotron resonance (ECR) sources are capable of high ionization efficiencies, which is why these sources have been investigated in the past for plasma cathode applications where the plasma generated is used to source electrons for a secondary application. Such devices have been featured on gridded ion thruster missions as a neutralizer. Much of the plasma cathode literature has focused on the use of inert gases. On the other hand, operation on molecular gases affords one with greater flexibility, reduced propellant management complexity, and higher fuel density. In this work we investigate the operation of an ECR plasma cathode on three molecular gases: dry air, N2 and CO2. Because of the myriad of energy loss pathways, discharge efficiency with such gases can be expected to be lower than operation with noble gases. Here we present discharge losses, measured as the ratio of total input power to extracted current as a function of discharge current and flow rate. Emission spectra was collected in the orifice to assess molecular speciation. Plasma conditions just outside the orifice were measured using a Langmuir probe. Energy partitioning between ECR discharge power, power losses due to inelastic molecular energy sinks, and plume production is also estimated. |
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KW81.00047: 3D computations in the discharge channel of the COST reference jet Sotiris Mouchtouris, George Kokkoris, Andreas Boudouvis A 3D plasma-fluid model is applied to the COST reference jet [1], for calculations in He/O2 mixtures. The model is based on the formalism and the assumptions of the 2D cross-field plasma model (CFPM) [2], allowing for fast calculations of species densities in the discharge channel of the jet, with a computational cost close to that of a 2D model. The results show that, due to proximity of the inter-electrode to inter-dielectric distance (ratio equal to 1), the phenomena taking place in the inter-dielectric direction (spatial variation of the species and wall losses on the dielectrics), and not considered in 1D and 2D models, cannot be ignored [3,4]. For low values of voltage and gas feed, the average difference of the species densities between the 2D and 3D model, is ~80%. |
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KW81.00048: Selective control of reactive nitrogen and reactive oxygen species in a DBD plasma source John E Foster, Mirko Gamba, Alex Szczuka, Roxanne Pinsky, Tyler Topham, Joseph R Groele Plasma activation of water has a host of applications ranging from fertilization of crops to the treatment of diseased tissue. Activated water is considered an indirect plasma treatment method with the active solution having a long shelf or half-life compared to the typical treatment times. For certain applications such as wound healing, higher reactive nitrogen species content is desirable. For other applications the such the washing of fruit or drinking water, it its desirable to control the nitrate concentration. We present here a plasma source that features variable flow chemistry that allows the ratio of nitrates/nitrites to reactive oxygen species concentration to be varied, thereby allowing for process optimization. This source was developed for the treatment of surfaces containing viral particles such as COV-19 or bacteria. Control of activated water quality is desirable if one is treating food surfaces and utensils for example or sensitive fabrics. RNS/ROS ratios versus input power and input flow conditions and input power are presented along with disinfection trial data. |
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KW81.00049: Theoretical Study of Three-Dimensional Coupling of Kinetic Instabilities Andrew C Denig, Prabhat Kumar, Sedina Tsikata, Kentaro Hara The mutual coupling of kinetic instabilities can affect electron transport across magnetic field lines in cross-field plasma discharges, such as the ones observed in Hall effect thrusters. The plasma instability and corresponding transport phenomena in such devices are multidimensional, hence requiring investigations of three-dimensional dispersion analysis. For instance, previous work using particle-in-cell (PIC) simulation by [Hara and Tsikata, Phys. Rev. E 102, 023202 (2020)] showed the enhancement of cross-field electron transport due to the multidimensional plasma waves initiated by the coupling of the electron cyclotron drift instability (ECDI) and the ion-ion two stream instability (IITSI) in a two-dimensional configuration, in the absence of dynamics parallel to the magnetic field. In this poster, the development of a 3D dispersion solver taking into account various instabilities, such as the ECDI, IITSI, and modified two-stream instability will be presented. We will discuss the growth rate of the linear instabilities accounting for the 3D plasma dynamics across and along the magnetic field lines. |
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KW81.00050: The Plasma Parameters of a Bimetallic Laser Plasma: Experiment and Simulation Mphande N Phiri, Braden L Spiller, Adam D. Smith, Jacob H Paiste, Robert R Arslanbekov, Renato P Camata Pulsed laser deposition (PLD) is a versatile technique for nonequilibrium growth of materials of complex stoichiometry. Kinetic manipulation of materials processing in PLD requires controlling the plasma parameters of its chemically complex and transient plasma flows. Here we compare trends in the plasma parameters measured for a laser plasma with predictions from a laser ablation/plasma fluid expansion simulation. Langmuir probes were used to measure the electron density, the electron temperature, and the Mach number of the plasma expansion. The fluid simulation accounts for singly and doubly charged ions, as well as electrons and neutrals, and is carried out in a multidimensional setting using a state-of-the-art, open-source adaptive Cartesian mesh framework. Experiment and simulation investigate a bimetallic plasma containing iron (Fe) and selenium (Se), obtained by ablating a solid pellet of FeSe with the 25 ns pulse of a KrF excimer laser (248 nm). For laser spot areas below 4.5 mm2, the peak values of the experimental electron density, electron temperature, and Mach number of the expansion all increase gradually when laser fluence is in the 0.5-4.0 J/cm2 range. The same trend is reproduced in the simulation. We will discuss how the measured time dependence of the plasma parameters can be used to constrain the simulation and test mechanisms of laser plasma formation that need to be invoked for accurate predictions of PLD plasmas containing multiple chemical species. |
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KW81.00051: Remote Plasma Generation of Radicals for Multistream Chemical Kinetic Studies Navheen Shanmugham Murugesan, Juan P Barberena Valencia, Laxminarayan L Raja Chemical kinetic mechanisms are instrumental for the successful modeling of a number of phenomena in aerospace engineering. The greatest uncertainties are observed in radical kinetics and experimental approaches for generation of radicals. Furthermore, studying their kinetics, remains difficult. As a result, we propose novel means for generation of different classes of radicals in different gas streams and the interaction among these radicals by impinging these streams onto each other. In this work, we computationally investigate a remote (downstream) plasma approach to generating radicals in specific single component gas streams and impinging these gas streams in an opposed flow configuration to study the radical interactions. We consider remote plasma generated either by microwave or inductive coil excitation and characterize the radical concentration downstream of the active plasma. |
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KW81.00052: Electron Energy Distribution Functions during the RF Breakdown Zoran L Petrovic, Marija Puač, Antonije Djordjević Non-equilibrium RF breakdown has been shown to occur with two modes (for fixed pressure and gap between electrodes) that are quite different in basic conditions and spatial profile of pertinent electron ensemble properties. We have presented the phenomenology of RF breakdown with detailed profiles and dependencies on relevant properties defined through scaling parameters. In that sense the process of RF breakdown itself is well understood up to the point when space charge begins to modify the field profiles and hence the rates of relevant processes. However, a different view of the underlying physics may be achieved by observing temporal (phase) dependencies of the electron energy distribution functions (EEDF), how and why they differ in the two modes of breakdown when double valued breakdown voltage exists. Having in mind the need to facilitate breakdown at atmospheric pressure in order to realize non-equilibrium discharges the EEDFs provide a tool for understanding the breakdown, especially if the distributions are presented as a function of energy and distance between the electrodes. We shall cover argon, that is best studied but also other relevant atmospheric gases. All calculations will be performed in our fully tested Monte Carlo code allowing connection both to the infinite space hydrodynamic transport coefficients and to non-local kinetic developments as a function of phase and frequency and to PIC simulations involving space charge effects. |
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KW81.00053: Fast simulation of gas heating effects during high power mmWave breakdown Pratik Ghosh, Bhaskar Chaudhury The high frequency high power microwave/millimeter (HPM) wave discharge continues to be an important research domain since decades due to its numerous applications in aerospace research, propulsion, high-speed combustion etc [1]. Several microwave discharges have been reported such as streamer, overcritical, subcritical and initiator based. The simulation of this highly nonlinear phenomena involves multiscale and multiphysics modeling. Most of the existing computational studies suggest the use of the plasma fluid model coupled with the Maxwell’s equations to study the EM-plasma interaction (hundreds of nanoseconds timescale). But the multi-scale nature of the problem as well as the stringent numerical requirements for capturing the sharp electric fields and plasma gradients present in the system makes it a computationally very expensive problem. Therefore, very few computational works have discussed the gas heating phenomenon involving longer timescales (>100 ns) for bigger problem sizes. We have proposed the application of a mesh refinement (MR) based selective gridding technique along with a MPI based parallelization which allows to accurately simulate the problem with significantly less simulation time [1]. The proposed algorithm has enabled to achieve an overall speedup of 30-80 times compared to a uniform fine mesh based finite difference algorithm. The fast MR based algorithm has enabled the investigation of large problem sizes involving plasma formation, subsequent energy exchange between EM wave and plasma, and afterwards between the gas and the plasma. In this work, we present the physics and the role of gas heating during HPM breakdown using 2D simulations. |
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KW81.00054: Computational study of the angular distribution of species in the expansion of laser-produced metallic plasmas Audrey Collins, Jacob H Paiste, Robert R Arslanbekov, Renato P Camata The forward peaking of nanosecond laser ablation plasma plumes is a hydrodynamic phenomenon that depends strongly on the photo-physics of the laser-plasma interaction. In pulsed laser deposition, heterogeneities in the angular distribution of plasma species may affect the properties of the resulting films. In this work, we use a laser ablation/fluid plasma expansion model to simulate the angular distribution of species in laser plasmas. We apply the model to plasmas produced by the ablation of metallic targets. The simulation is carried out in an adaptive Cartesian mesh framework over centimeter distances for proper evaluation of the angular distributions. The compressible solvers available in this framework were adapted to include the equations of state of the plasma, which link local Saha equilibrium with augmented ideal gas expressions that include the internal degrees of freedom of the atomic species. For the ablation of an FeSe target with 248-nm, 25-ns pulses over a spot area of 30 mm2, the model predicts an angular distribution for Fe+ ions with FWHM of ~30° at a fluence of 1.4 J/cm2, which decreases to ~12° for 2.6 J/cm2, in qualitative agreement with typical angular distributions observed in film growth. We will discuss differences in elemental vs. compound metallic plumes and subtle variations in predicted angular distributions of different chemical species in compound plumes, which are critical for reproducible film synthesis. |
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KW81.00055: Species-Weighted Automated Network Reduction via Principle Component Analysis Steven W Marcinko, Davide Curreli Expedient fluid simulations of large plasma volumes with complex chemistry are hampered by the large size to which reaction networks may scale. Manual simplification of reaction networks with methods such as lumping of excited states or truncation of less-important pathways are necessary to simulate larger plasma volumes, but correspondingly reduce simulation fidelity. In this work we show a method to reduce reaction networks automatically through a combination of principal component analysis and multivariate regression which simultaneously retains information about all species. We assess the species-specific reconstruction and prediction accuracy of the method for 0D simulations of both a He/O and U/O reaction network, including a comparison of scaling and weighting methods as well as the effects of species-specific network weighting, and show the extension towards multidimensional simulations. |
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KW81.00056: Efficacy study of Argon and helium cold plasma jet for organic dye degradation Veda Prakash Gajula, Deepchandra Joshi, Satyananda Kar, Shaikh Ziauddin Ahammad, T. R. Sreekrishnan The degradation of two organic dyes Rhodamine B and Methylene Blue is studied using the atmospheric pressure cold plasma jet. Under the same experimental reactor configuration only with a change in the feed gas from Argon to Helium, the treatment efficacy of both the plasmas is verified. A sinusoidal high voltage (1–6.5 kV), 25 kHz frequency is used to excite the argon and helium plasma jets. The aqueous dye sample of 1.5 ml is treated with the developed plasma jets. The effect of applied voltage, sample initial pH (3, 7 &10) and conductivity (1-20 mS/cm), treatment time (1-30 min), dye -concentration (1, 10 & 50 ppm), and sample-plasma distance on dye degradation are studied for both Rhodamine B, and Methylene Blue dye. For all sets of experiments, more efficacy is obtained using an Argon plasma jet compared to Helium. Further, the quantification of short-lived •OH radical using Coumarin-based chemical probe method and the long-lived H2O2 Potassium iodide (KI) based colorimetric method is performed. The individual effect of each of these two Oxygen species is also carried out, and it was found that the strong oxidant •OH radical has a major effect on dye degradation. The experimental configuration and outcomes for both the dyes treatment will be presented. |
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KW81.00057: Two-Dimensional Full-Fluid Moment Model for Low-Temperature Magnetized Plasmas Adnan Mansour, Kentaro Hara A two-dimensional full-fluid moment (2D FFM) model for plasma simulations is developed to study multidimensional effects in plasmas using the fluid description. The model simulates ions and electrons as fluids, accounting for inertial effects for both, and solves the Poisson equation to self-consistently evaluate the potential and electric field. The governing equations (conservation of mass, momentum and energy) are derived by taking the moments of the Boltzmann equation. A global Lax flux-vector splitting scheme with MUSCL reconstruction is used to solve the fluid equations, and kinetic fluxes are utilized for boundary conditions, connecting the fluid approach with kinetic theory. The model is an extension of a previously developed 1D FFM that was used to study inertial effects on electron transport in Hall-effect thrusters (HET). The model is tested in a 2D axial-azimuthal HET configuration and a 2D planar Penning type geometry, with the goal of investigating the instabilities inherent in cross-field plasma discharges. |
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KW81.00058: Thrust Increases in an Electron Cyclotron Resonance Thruster Using Custom Microwave Waveforms Benjamin Wachs, Benjamin Jorns Low power electric propulsion is an enabling technology for many small satellite missions. Several technologies are under development with many having reached orbit over the past 2 years. Magnetic nozzle thrusters offer several potential advantages for these applications including simple operation, long lifetime, and the ability to use reactive propellants. However, their performance to date has not matched that of traditional EP technologies, with in laboratory efficiencies less than 20% at power levels under 50 watts. The current state of the art magnetic nozzle thrusters use electron cyclotron resonance to ionize and heat the propellant. |
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KW81.00059: Single ionization of helium by high energy proton impact using the parabolic Sturmians representation Sergey A Zaytsev, D S Zaytseva, Alexander S Zaytsev, Konstantin A Kouzakov, Lorenzo Ugo Ancarani Ionization of helium by a proton constitutes a very challenging quantum mechanical four-body problem. For fast incident protons, one may reduce the difficulty by employing a frozen-core model for the target, and thus deal with a more tractable Coulomb three-body problem (e-, He+, p); the ionization problem is recast as an inhomogeneous Schroedinger equation. In this way, the ionization amplitude can be formally extracted from the asymptotic behavior of the function generated by the action of the three-body Green's function operator on the driven term of the inhomogeneous equation. In our approach we assume that for a high enough incident energy, we can approximate the Green operator by that corresponding to the Hamiltonian without the proton-electron interaction which is treated as a perturbation. Besides, we make use of a L2 parabolic Sturmians representation which allows us to calculate the amplitude analytically in terms of the expansion coefficients. We have made Fully Differential Cross Sections calculations at 1 MeV incident energy, and for several geometrical and kinematical configurations. Our results reasonably agree with the experiment [1] and recent WP-CCC cross sections [2]. |
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KW81.00060: Characterization of an atmospheric pressure misty plasma discharge Ayuob K Al wahaibi, Malik M Tahiyat, Sang H Won, Tanvir I Farouk Misty plasmas are typically defined as plasma containing small liquid droplets and therefore makes it a multiphase system. In an attempt to characterize an atmospheric pressure misty plasma discharge a flat plate dielectric barrier discharge (DBD) is designed that utilizes a stagnation flow field for the introduction of water droplet laden flow. The water droplets in the form of spray are introduced through an annulus from the bottom plate, which also acts as the grounded electrode. The interaction of the liquid spray and the DBD plasma discharge is characterized through measurements of the voltage-current characteristics, optical emission spectrum and discharge visualization. An AC driven power supply having a 22 KHz frequency was utilized to drive the DBD discharge and maintain a peak voltage and current of ~8 kV and ~100 mA respectively. Preliminary results show that the DBD discharge operates in the filamentary mode with visible emissions typical of an air discharge when no spray is introduced. With the introduction of the spray droplets the filament sizes decrease significantly but increases the emission intensity. The emissions in the range of ~550 – 750 nm are observed in the presence of water which are typical of water vapor emission lines. These emission lines suggest that the liquid phase water droplets undergo phase transition and interacts in the gas-phase plasma kinetics. Energy deposition measurement suggest that in presence of water droplets the net energy deposition is lower. |
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KW81.00061: Machine Learning Applications for Atomic and Molecular Collisions Allison L Harris The use of machine learning algorithms in the physical sciences has exploded in recent years, including many areas of physics such as high energy physics, quantum many body problems, quantum computing, molecular chemistry, and material science. However, despite their strong potential, these techniques have been slow to make their way into atomic collision physics. For fields such as plasma physics modeling, the success of the models relies, at least in part, on the accuracy and availability of electron scattering cross sections over a wide range of energies, target species, and collision processes. Unfortunately, the necessary data sets are often unavailable or incomplete due to the difficulty associated with detailed measurements and the challenges of widespread application of sophisticated theoretical models. Machine learning may be able to help fill the gap in available cross section data and could represent a major leap forward in the prediction of cross sections for complex atomic and molecular targets that are beyond the reach of existing theoretical models. Here, we review the current state of machine learning applications to problems in both atomic and molecular collision physics, as well as plasma modeling. We also present preliminary results for the calculation of collision cross sections using machine learning algorithms and address their potential to enhance and expand existing cross section data sets. |
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KW81.00062: Effect of CH4 dissociation products on the vibrational excitation of CO2 and CO in CO2-CH4 plasmas Edmond Baratte, Vasco Guerra, Olivier Guaitella The conversion of methane and carbon dioxide into value-added products (Dry Reformation of Methane) by plasma is a promising way to reach carbon-neutral and efficient energy storage. |
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KW81.00063: The Role of Instabilities in Electron Thermodynamics of a Magnetic Nozzle Shadrach T Hepner, Benjamin Jorns Magnetic nozzles heat a plasma and expand it through a magnetic field to convert thermal energy into thrust. They are theorized to exhibit high lifetimes and propellant ambivalence, thus being ideal candidates for long missions requiring in-situ resource utilization. However, the physics behind how these devices operate is still not fully understood. |
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KW81.00064: DOLI II upgrade and future investigation of the sheath structure in the presence of an ion beam Peixuan Li, Gregory Severn, Oliver Schmitz New features are being added to a triple plasma device at UW-Madison, DOLI-II (originally, Double Layer Investigator) that include a biasable, movable boundary plate, and collection optics for laser-induced fluorescence (LIF) in the central plasma chamber. The device consists of a central chamber and two outer chambers with biased grids placed in between. Plasma can be produced in each outer chamber by thermionic electrons which are emitted from the biased filament. Energetic ions are driven by the biased grids into the main chamber. The influence of the ion beam on the sheath structure in front of the boundary plate will be investigated. Plasma parameters are measured by the Langmuir probe, emissive probe, and LIF. The new features of DOLI will be presented here as well as some preliminary results. |
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KW81.00065: Electromagnetic (EM) and Electric Asymmetry (EA) Effects in Dual Frequency Collisional Nitrogen Capacitive Discharges Emi Kawamura, Michael A Lieberman, Pascal Chabert, Allan J Lichtenberg Intermediate pressure capacitive discharges containing nitrogen gas, are |
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KW81.00066: Dynamics of ns-SDBD Plasma Formation for Flow Control by Superfast Local Heating Andrey Starikovskiy, Nickolay Aleksandrov Paper presents results of numerical modeling of nanosecond surface dielectric barrier discharge (ns-SDBD) for flow control using a heat release in highly nonequilibrium pulsed plasma. The major attention is paid to the effects based on ultrafast (on nanosecond time scale at atmospheric pressure) local heating of the gas, since at present the main successes in high-speed flow control using gas discharges are associated with namely this thermal effect. Modeling the development of all structural elements of SDBD is a non-stationary three-dimensional problem in which all parameters of the discharge plasma change abruptly at small time and space scales. In this work, we tried to take into account all the most important processes, and obtained a reasonable agreement between the electric field measured in [8] at an air pressure of 345 Torr and a voltage at the high-voltage electrode of 20 kV, a dielectric layer 0.5 mm thick with dielectric permittivity coefficient \epsilon = 3.0. Comparison with the experiment demonstrates a good agreement, which shows the correct accounting for the main processes in the numerical model. |
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KW81.00067: Numerical Analysis of Ion Cloud Ejected from Thermal Plasma Contributing to Electron Emission in Vacuum Arc Masahiro Takagi, Yusuke Nemoto, Hiroto Suzuki, Zhenwei Ren, Yuki Suzuki, Toru Iwao Vacuum arc has been applied to valuable technology such as surface treatment of oxide layer and ion plating. Although it has been required to clarify the physics of cathode spots in vacuum arc for industrial applications, it has been unclear. The cathode spot in vacuum arc moves at high speed with evaporation from cathode metal caused by joule and ion heating. The evaporated metal is ionized, thermal plasma is generated above cathode. It is considered that the generated ions are transported from thermal plasma to outer region of cathode spot, ion cloud is generated and ejected from thermal plasma. The ion cloud produces high electric field induced between ion cloud and cathode, then field emission may occur, and the current path is changed. Based on this model, numerical analysis of ion cloud ejected from thermal plasma contributing to electron emission in vacuum arc is conducted in this research. As a result, ion cloud ejected from thermal plasma is calculated, high electric field contributing to movement of cathode spot was analyzed. |
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KW81.00068: Double-Tipped Impedance Probe Diagnostics for Dusty Plasmas Brandon D Doyle, Uwe Konopka Impedance probe diagnostics are a type of active resonance spectroscopy that utilize RF resonances at frequencies of the order of the electron plasma frequency, ωpe. Impedance probes used for steady-state plasmas, such as most low-temperature plasmas in laboratory environments, usually operate in a frequency-swept mode, probing the plasma’s frequency-dependent response to low-power RF signals. Such measurements may be desirable for use in dusty plasmas because the probes can be designed to be only mildly perturbing to dust particles, as compared to the large perturbative effects of Langmuir probe measurements, for example. A double-tipped impedance probe may be especially useful for use in dusty plasmas because it can be separately sensitive to plasma in areas near the probe tips and areas farther away in the chamber. |
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KW81.00069: Analysis of Temperature Distribution Affected External Magnetic Field in Short-Arc Lamps Using Three-Dimensional Electromagnetic Thermal Fluid Simulation Kazumasa Minamisawa, Zhenwei Ren, Yuki Suzuki, Yusuke Nemoto, Yoshifumi Maeda, Toru Iwao An arc lamp is a light source with high brightness and excellent color rendering emitted from an arc formed between electrodes, with high radiant power density and high energy plasma state. In industrial applications of arc discharge, it is required to increase the luminance. One possible method is to increase the current value of the arc discharge, the Joule heating, and the temperature dependent radiation. It was confirmed that the increase in radiation was different for the width of the high temperature region and the maximum temperature of the gas. However, when the input power increases, the energy efficiency decreases because the heat loss becomes larger. In addition, it has been confirmed in our laboratory by the arc converges when a high-frequency rotating magnetic field is applied. The objective of this research is increased the high temperature region by contracting the arc using an external magnetic field, thus improving the radiation per power of the arc lamp. In this research, the arc temperature distribution of a short-arc lamp, which is affected by external magnetic field, was calculated using the 3-D electromagnetic thermal fluid simulation. As a result, the radiation efficiency to electric power could increase with applying an external magnetic field. |
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KW81.00070: Performance at High Current Densities of a Magnetically-Shielded Hall Thruster Leanne Su, Benjamin Jorns Hall thrusters are a type of electric propulsion device with decades of heritage. With the advent of magnetic shielding, a technology that shapes the magnetic field lines in the thruster channel such that the erosion of channel walls by energetic ions is greatly reduced, Hall thruster lifetimes and mission spaces have been greatly expanded. One key remaining challenge is scaling to high powers in the 100-kW range, which is critical for the use of these thrusters for human exploration of the solar system. Historically, there have been issues associated with high-power, high-current density operation on unshielded thrusters. The need is then apparent for an investigation of performance of high current densities on a magnetically-shielded Hall thruster. |
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KW81.00071: Antimicrobial activity of cold plasma against E. coli and Listeria inoculated on raw meats, deli and produce Shijie Qin, Amit Morey Consumers trends indicate an increased demand for “all natural” and “no artificial” chemicals in foods while the food industry is working diligently to ensure food safety while complying with the stringent food safety standards. We investigated the application of cold plasma as an innovative technology conforming to the consumer demands while ensuring food safety. |
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KW81.00072: Effect of Cusp Magnetic Field on Ion Acoustic Wave Propagation Meenakshee Sharma, A. D. Patel, Narayanan Ramasubramanian, Y. C. Saxena, P.K. Chattopadhyay Surprises are galore when quiescent plasma is perturbed by small periodic voltages. For that, the achievable quiescence level in plasma is very important to start with. Multi-pole cusp configuration is found to be an ideal configuration in which the field is B~0 in the center as well as at the boundary magnetic field curvature is good for plasma confinement. The filamentary produced argon plasma confined in this configuration with six electromagnets is found to be very quiescent (<0.1%). |
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KW81.00073: Control of Spokes in Magnetron Discharges Mathews George, Wolfgang Breilmann, Julian Held, Volker Schulz-von der Gathen, Achim von Keudell Magnetron Sputtering is a Plasma Vapour Deposition (PVD) process widely used in industry and scientific communities. HiPIMS produces plasma pulses of very high density of the order of 1019 m−3 without overheating the target. The plasma shows localised zones of high brightness rotating in the E x B direction when observed with an ICCD camera with exposure times below 1μs. These local ionization zones, also called 'spokes' are assumed to play a role in the transport of particles and energy away from the target. This anomalous transport results in an enhanced deposition rate by counteracting the return effect. The primary objective of this project is to control spoke frequency in HiPIMS in-order to study its influence on the IEDF and metal ion flux from the target. DCMS was chosen for the development of spoke control as an initial test object since the spokes in DC regime are more uniform compared to HiPIMS. Amplified rectangular signals are applied to multiple probes to draw electron current from the plasma at the highest gradients in the E x B direction. The responses of the spoke frequency and intensity to the applied signal are measured with a flat probe. The metal ion flux from the target surface is measured time and energy resolved with a mass spectrometer. |
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KW81.00074: Treatment of Fungus Contaminated Water using Plasma generated remotely from the power source Houssem Eddine Bousba, Mouna Saoudi, Salah Sahli, Wail Seif Eddine Namous, Lyes Benterrouche A plasma jet generated remotely from its power source using a floating copper wire inside a plastic tube has been employed in cleansing and purification of water contaminated with fungus. Three samples of fungus known to be highly infectious to crops, plants and seeds (Fusarium culmorum, Fusarium pseudograminearum, Alternaria graminicola) have been studied. The plasma jet created in helium or in a mixture of helium and nitrous oxide (N2O) was completely immerged in the contaminated water. It appears that plasma ignited in the mixture is remarkably more efficient than that ignited in only helium. Adding N2O to helium leads to the creation in water of highly reactive species as reactive oxygen species (ROS) and reactive nitrogen species (RNS). These species react with the fungal spores and lead to their destruction and to stop their reproduction. After 5 minutes of plasma jet treatment using the mixture of gases, a total decontamination of treated water was achieved. |
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KW81.00075: Removing Noise from an RF Plasma Signal with the Hilbert-Huang Transform Dereth J Drake, James Henderson The Hilbert-Huang Transform uses the method of empirical mode decomposition in which a signal is decomposed into multiple signals called intrinsic mode functions (IMFs). A Hilbert Transform is then applied to these functions in order to obtain instantaneous frequency data. This results in a time dependent distribution of signal amplitudes, known as the Hilbert Spectrum. By applying this transform to a complex or noisy signal, the noise can be isolated and removed from the signal source. This allows for a much cleaner, easier to study signal. In this poster, we will show the theory behind this technique and demonstrate how it can be used to study the plasma pulse form an RF plasma system. |
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KW81.00076: Suppression of harmonics and improvement of plasma uniformity by a parallel resonance in a capacitively coupled plasma Yeong-Min Lim, You He, So-Young Park, Chin-Wook Chung A method for suppressing the non-linearity of plasma and improving the plasma uniformity in a capacitively coupled plasma (CCP) is developed. Plasma contains harmonics due to the non-linear characteristics of the sheath. These high frequency harmonic components have bad influence on the plasma uniformity because the electromagnetic effects such as standing wave effect become severe at the high frequency. To improve the plasma uniformity, the CCP using a parallel inductor which is connected to the powered electrode is developed. By generating the parallel resonance between the plasma and a parallel inductor, the ratio of the fundamental frequency component in the total plasma current was greatly increased and the ratio of the higher harmonic components was significantly decreased. Under the parallel resonance condition, the ratio of the second and third harmonic components was decreased by about half and one third, respectively, and the voltage and current of the plasma increased significantly. As a result, not only the plasma density but also the plasma uniformity is improved. |
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KW81.00077: Dust Clustering in Inductively Heated Plasma Jet Eva Kostadinova, Dmitriy M Orlov, Graeson Griffin, Jens Schmidt, Truell W Hyde Here we investigate the interaction between micron-sized dust particles and a low-temperature |
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