Bulletin of the American Physical Society
75th Annual Gaseous Electronics Conference
Volume 67, Number 9
Monday–Friday, October 3–7, 2022;
Sendai International Center, Sendai, Japan
The session times in this program are intended for Japan Standard Time zone in Tokyo, Japan (GMT+9)
Session HW6: Poster Session II (4:30-6:30pm, JST) |
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Room: Sendai International Center Sakura 1 |
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HW6.00001: Transport of electrons and propagation of negative streamers in CF3I-SF6 mixtures Sasa Dujko, Jasmina Atić, Danko Bošnjaković, Ilija Simonović, Zoran Petrović In this work, we present the electron swarm transport coefficients in CF3I-SF6 mixtures as a function of the reduced electric field E/N at room temperature. For E/N≥50 Td the calculations are performed using a multi term theory for solving the Boltzmann equation, while for E/N<50 Td, due to poor convergence of transport data, we apply a Monte Carlo simulation technique. We observed the reduction of the mean energy with increasing E/N for electrons in SF6, and the occurrence of negative differential conductivity in the bulk drift velocity of electrons in CF3I-SF6 mixtures. These kinetic phenomena are explained using the spatially-resolved swarm transport properties, distribution functions, and physical arguments. The calculated swarm transport coefficients are then used as input to the fluid equation-based models to investigate the transition from an electron avalanche to a negative streamer. We investigate how the properties of streamers, including electron density, electric field and streamer velocity, are affected by the introduction of CF3I to SF6. Special attention is given to the comparison between the results obtained in the classical fluid model and the corrected fluid model, which assumes the non-local description of electron attachment and electron-impact ionization. We found that the classic fluid model with bulk transport coefficients and the corrected fluid model agree very well. |
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HW6.00002: Water you waiting for? - A Complete and Consistent Set of Electron-H2O Collision Cross Sections for Plasma Modelling Maik Budde, Tiago C Dias, Luca Vialetto, Nuno R Pinhao, Vasco Guerra, Tiago Silva Although water is omnipresent in many plasma applications, often it is not taken into account in plasma |
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HW6.00003: Investigation of Negative Ion Mobility and Ion-Molecule Reactions in Atmospheric O2 with a Small Amount of H2O Based on Ion Mobility Measurement Yui Okuyama, Hirotake Sugawara A study of transport coefficients such as a mobility and a diffusion coefficient has been carried out in low pressure gases for collecting the fundamental data of discharge plasmas. Recently, the fundamental data are required for investigating atmospheric pressure plasmas. In this study, we carried out a Monte Carlo simulation using mobility of electrons, that of the ions obtained in the measurements, and rate coefficients of ion-molecule reactions. Then, we compared the experimental result with that of the simulation and estimated the ion mobility and rate coefficients of ion molecule reactions. The negative ion mobility was measured in O2 at pressures between 840 and 900 Torr with a little amount of H2O concentration between 15 and 17000 ppb. As the results, the mobility value 2.39 cm2/V∙s of O4ˉ is obtained in ultrahigh purity O2 of which the H2O concentration is between 15 to 100 ppb. Moreover, the mobility decreases with the H2O concentrations at which the ion species are considered to be O2ˉ∙(H2O)n (n = 1, 2, 3). Then we investigated the influence of each mobility of ions and rate coefficients of ion-molecule reactions on observed ion mobility in the measurement. |
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HW6.00004: Elastic scattering of electrons on ions Lukasz Klosowski, Mariusz Piwinski We observed some macroscopic effects of elastic electron scattering on a set of cold calcium ions. |
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HW6.00005: Ionic Heating of N2 and O2 Gas Discharges Brett Scheiner, Matthew M Hopkins, Mark C Zammit, Christopher H Moore, Eddy M Timmermans We explore the heating mechanisms of N2 and O2 neutral gas in discharges using 0D and 1D PIC-DSMC simulations for cases where either a constant or self-consistently determined electric field is applied. Previously, heating on nanosecond timescales has been attributed to quenching of excited states of neutral atoms (e.g. O(1D) + O2 -> O + O2) that converts energy in electronic states into kinetic energy of the neutral gas. While this is generally true for weakly ionized discharges on short timescales, another process that contributes at larger values of E/N and gas fractional ionization is direct heating by ions in elastic collisions with the background gas. These simulations demonstrate that in cases where the fractional ionization of the gas is large, the heating from ion-neutral collisions dominates over other mechanisms. Even for relatively weakly ionized discharges (~1% ionization), the energy input into the gas can be considerable on the time scale of 100s to 1000s of nanoseconds. |
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HW6.00006: On the Formation of the Inverse EDF and the Absolute Negative Conductivity of Electrons in a Gas-Discharge Plasma Anatoly Kudryavtsev, Chengxun o Yuan, Eugene Bogdanov A plasma with an inverse electron distribution function (EDF) can have an absolute negative conductivity (ANC) and amplify electromagnetic waves. Unfortunately, this important problem remains unresolved due to the significant simplification of the problem and the reduction of the Boltzmann equation to the homogeneous case. Finding the inverse EDF is reduced to searching for reactions that "eat away" the low-energy region on the EDF. However, such processes inevitably contribute to an increase in the electron transport frequency and prevent the formation of ANC. Since a real plasma is spatially inhomogeneous, one should solve the complete kinetic equation, which depends on energy and on spatial variables. In this case, an increase in the number of degrees of freedom of the system leads to the emergence of fundamentally new scenarios for the formation of the EDF. Thus, the divergence of the spatial flow can lead to an additional sink of electrons and thus provide the inversion of the EDF. The analysis shows that the EDF inversion conditions should be sought near the points of field reversal and/or a non-monotonic change in the plasma density [1, 2]. The simulation results showed that these conditions are fulfilled after the second field reversal point in the transition region from the Faraday dark space to the positive column of the glow discharge. |
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HW6.00007: Three-dimensional kinetic simulations of the collective processes in beam-plasma interaction Jian Chen, Haomin Sun, Andrew T Powis, Igor D Kaganovich Electron beam-plasmas have long been a topic of interest for the study of nonlinear wave-wave interactions and turbulence. Understanding these collective processes is important for the design of low-temperature, low-pressure discharge devices for industry. To date, simulations of electron beam-plasmas have mostly been performed with 2D codes. The limitations of these 2D simulations have, however, never been tested. Therefore, in this study, we make use of a GPU-accelerated code, LTP-PIC (Low Temperature Plasma Particle-In-Cell), to perform 3D fully kinetic simulations and investigate the collective effects of a mono-energetic electron beam propagating through a cold plasma. The classical theories describing the saturation of streaming instabilities and the Langmuir collapse are examined, for the first time, in three-dimensional simulations. By comparing the 2D and 3D simulation results, we study the influence of dimensionality on the Langmuir turbulence. The correlation between the anomalous electron transport and the Langmuir turbulence is also analyzed. |
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HW6.00008: Plasma Oscillations of Partially Magnetized E×B Discharge with Multiple Ion Species Jinyoung Choi, Y. S. Hwang, Kyung-jae Chung, June Young Kim* In various E×B sources, plasma oscillations in the ranges of tens of kHz occur due to relatively high ionization rates and different degrees of magnetization between electrons and ions. Plasma oscillation in E×B sources is directly related to device efficiency. In-depth studies on the correlation between ion mass and oscillation frequency in Hall thrusters and magnetron devices with a single inert gas discharge have been carried out. In the case of ion implantation E×B sources using molecular gas or mixed gas, several ion species exist and plasma oscillations are expected to be more complicated. However, plasma oscillations considering the existence of multiple ion species have not yet been observed experimentally nor theoretically. With Ar/Kr mixed gas discharges, we investigated the basic characteristics of plasma oscillation in the mixed gas discharge of E×B sources. The proportion of ion species is changed by adjusting the gas-mixture ratio, and the frequency and mode number of the plasma oscillations are analyzed through the Beall technique. Also, characteristics of the oscillations were investigated with varying magnetic fields. Finally, the frequency of plasma oscillations is predicted through the analytical model to compare with the experimentally obtained values. |
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HW6.00009: Threshold for Switching the Dynamic Pressure Dependence of Plasma Propagation Velocity Yambe Kiyoyuki, Iwao Ohyama The dependence of plasma propagation velocity on the force applied to the plasma bullet is investigated. The force applied to the plasma bullet is composed of the dynamic pressure with AC electric field and the collision with the neutral gas flow. Three cases are observed in the experimental results: directly proportional, inversely proportional, and non-proportional to the ponderomotive parameters at each dynamic pressure due to the helium gas flow. In the directly proportional case, the applied force is inversely proportional to the frequency of the applied voltage. When the blank period is shorter than the application time of the voltage, the next electromagnetic energy of the applied force is added to the residual plasma energy and the plasma propagation velocity is directly proportional to the frequency of the applied voltage. Consequently, in the inversely proportional case, the applied voltage is directly proportional to the frequency of the applied voltage. In the non-proportional case, the plasma propagation velocity depends on the dynamic pressure due to the helium gas flow. When the strength of the applied voltage is low, the plasma propagation velocity is proportional to the dynamic pressure due to the helium gas flow over a wide range of dynamic pressure. While, when the strength of the applied voltage is high, the plasma propagation velocity is non-proportional to the dynamic pressure due to the helium gas flow. Therefore, it is possible to investigate the threshold of the dynamic pressure at which the velocity dependence changes. |
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HW6.00010: low frequency shocks with higher order effects in multicomponent plasma Rajneet Kaur, Geetika Slathia, N.S. Saini The ubiquitary existence of dust in space plasma has been an extensive area of research and has attracted numerous researchers for study of different kinds of nonlinear structures. The presence of dust acoustic (DA) waves have been investigated in different space environments such as Jupiter, Titan, Earth’s magnetosphere, etc. The Jupiter magnetosphere has become one of the most fascinating environment to carry out research due to its various observations in dust ring system, auroras and radiation belts. Our work is basically inspired from the role of higher order effects of nonlinearity and dissipation and also due to importance of Cairns-Tsallis (CT) distribution that provides a better way to explicate in various space and astrophysical regions. In this investigation, the evolution of dust acoustic shock waves and dressed shock waves has been examined in the Jupiter magnetosphere. A five components plasma having positive dust grains, solar wind protons, CT distributed electrons, ions as well as solar wind electrons is considered. By imposing reductive perturbation method, the Burger and inhomogeneous Burger-type equations are derived and their solutions using tanh method their solutions are also derived. It is remarked that contribution of higher order corrections may play an important role on the characteristics of different kinds of DA shock waves. It is augmented that the findings of present investigation may be useful in laboratory, space/astrophysical environments and in Jupiter’s magnetosphere. |
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HW6.00011: Optimization of a negative oxygen ion beam Jia Han, Philippe Guittienne, Alan Howling, Ivo Furno, Florent Plane, Anders Meibom, Johanna Marin Carbonne Negative ion beams are of interest to a wide range of applications and many previous studies have investigated, e.g., the properties of negative hydrogen ion beams with beam diameters on the centimeter scale or larger. Less work has been done with other ion species and smaller beam sizes, in the millimeter range or smaller. However, such beam properties are required in Secondary Ion Mass Spectroscopy (SIMS). In this context, we are developing a negative oxygen ion source capable of long-term (days) steady state operation. The source utilizes inductively coupled plasmas using a novel antenna design. It can operate to produce positive or negative ion beams. A filter magnetic field was implemented at the beam exit for deviating electrons. Studies were done with the goal of optimizing the ion beam profile. Preliminary results show a linear relationship between beam current with RF power, and a non-linear relationship with filter magnetic field strength, chamber pressure, and voltage on the beam extraction grids. Changes in chamber size and wall temperature are also found to affect the beam quality, indicating the significance of surface effects in the creation/destruction of negative oxygen ions. Results will be presented in comparison with a traditional solenoid shape antenna. |
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HW6.00012: Study of propagation of nonlinear shock waves in a multicomponent beam plasma Geetika Slathia, N. S. Saini, Rajneet Kaur The various satellite observations have witnessed the existence of multicomponent plasmas in space and astrophysical environments where ions and two temperature electrons are present. The dynamics of electron acoustic waves (EAWs), which is a fundamental electrostatic wave mode has gained much attention over the last many years due to their confirmation by the satellite observations in the auroral and other regions of the magnetosphere. In this investigation, we have studied the evolution of electron acoustic shock waves in a four component unmagnetized collisionless plasma consisting of cold electrons fluid, inertialess hot electrons and stationary positive ions embedded with an electron beam. Using the reductive perturbation method, the Burgers equation is derived. Tanh-method is employed to derive its solution to study the electron acoustic shock wave structures. Further, by considering the contribution of higher order effects, the inhomogeneous Burgers-type equation is derived and its solution results in the formation of humped-type EA shocks. The combined effects of electron beam and other plasma parameters on the characteristics of different kinds of electron acoustic shock structures are analysed. The findings of this investigation may be useful to understand insight of physics of nonlinear phenomena for studying dynamics of electron acoustic shocks in space as well as astrophysical plasma environments especially in Earth’s magnetospheres. |
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HW6.00013: Collisional damping of surface ion-acoustic wave in semi-bounded plasmas Myoung-Jae Lee, Young-Dae Jung The dispersion property of surface ion-acoustic waves in a fully ionized and semi-bounded plasma is investigated by solving the dispersion integral formulated by employing the specular reflection boundary condition. Non-zero ion temperature and ion-ion collisions are considered in the dielectric permittivity. The calculated damping rate is composed of the collisionless Landau damping and the collisional dissipation. The distinction between them are addressed here. It is found that the collisionless damping is significant in the region where the wavelength is larger than the electron Debye length. The collisional dynamics, however, as well as the ion temperature, dominates the wave damping when the wavelength is smaller than the electron Debye length. |
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HW6.00014: Atomic oxygen interaction with surface materials in oxygen-containing plasmas Pedro Viegas, Jorge Silveira, José Afonso, Ana Sofia Morillo-Candas, Luca Vialetto, Vasco Guerra Heterogeneous surface kinetics plays a role in most plasma processes, where surfaces interact either with active discharges or their afterglow. It can affect both plasma and surface properties. In this work we employ deterministic and Kinetic Monte Carlo methods to simulate the surface kinetics of oxygen species in oxygen and carbon dioxide glow discharges interacting with silica-based materials. This description includes physisorption and chemisorption of oxygen atoms at the surface, together with their desorption, surface diffusion and recombination back into gaseous molecular oxygen. We further describe the formation of dangling bonds due to the arrival of fast particles to the surface. The simulation results are validated by comparisons with experimental measurements of atomic oxygen loss frequency. The change in the recombination regime experimentally observed at pressures around 1 Torr is well captured by the model. |
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HW6.00015: Langmuir probe PIC dynamic simulation of collisional plasma Jakub Palacký, Štěpán Roučka The low-temperature plasma physics has plenty of different applications from purely scientific ones like the study of chemical reactions in flowing afterglow to industrial applications like magnetron sputtering. All of them have in common that their success relies heavily on diagnostic of plasma properties. One of the most common and oldest methods is the probe diagnostic using the Langmuir probe. The theory for Langmuir probe measurement is very well described for collisionless plasma but with rising pressure the collisions with neutral background affects the probe results and the theoretical description is difficult. Also there are cases when it is required to perform the measurement in the shortest time possible due to time resolution of studied phenomenon or when there is a need to limit the probe exposure to plasma to prevent its damage by, for example, flow of high energy particles. Those dynamic properties of the probe are almost impossible to describe analytically and the experimental approach would provide only limited information. The particle simulation is well suited for this task since it provides very detailed information about the surroundings of the probe when its potential is changed. It provides the probe current same as the experiment would do, but it also gives the time evolution of potential near probe, sheath size and charge enclosed in sheath. Such information is crucial to obtain the time constant specific for plasma reaction to the probe potential change and determine the lowest time needed for the measurement to give reliable results. |
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HW6.00016: Advances in IEDF Measurements by Lock-in Detection Christian Lütke Stetzkamp, Tsanko V Tsankov, Jonas Thiel, Nikita D Lepikhin, Uwe Czarnetzki The distribution functions of the particles in a plasma provide the most complete description of its properties. Often the focus is on the distribution of the electrons, but the distribution of the ions can provide a wealth of information as well, such as the plasma and sheath potential, plasma density and electron temperature. The methods for experimentally obtaining the ion velocity distribution function (IVDF) have the added advantage of being essentially non-invasive. However, they usually lack the large dynamic range (several orders of magnitude) required for extracting this additional information. |
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HW6.00017: Optical emission spectroscopy of water vapor plasma in DC reactive magnetron sputtering of Zn Allen Vincent B Catapang, Jose Gabriel F Abalos, James Edward II A Hernandez, Magdaleno Jr R Vasquez, Motoi Wada The optical emission spectra of water vapor plasma in a DC reactive magnetron sputtering system and the factors affecting the ZnO film deposition is investigated. The line spectrum intensities of atoms and molecules such as Zn, O, H and OH are measured and correlated to the dissociation and local plasma parameters of the magnetron sputtering discharge. In an Ar-H2O plasma at increasing water vapor content, the ratio of the OI to ZnI and OI to Hα line was found to sharply increase as the H2O concentration exceeded 40 to 50%. The addition of hydrogen peroxide to the water vapor reservoir for increasing reactive gas dissociation and atomic oxygen or OH concentration is proposed. |
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HW6.00018: Production of metastable-state argon ions in an electron cyclotron resonance plasma investigated by laser-induced fluorescence spectroscopy Ryosuke Takahashi, Seiya Kito, Koji Eriguchi, Keiichiro Urabe A laser-induced fluorescence spectroscopy (LIF) is a measurement technique of particle density and movement without disturbance to target fluids. For the LIF of ions generated in low-pressure argon (Ar) plasmas, Ar ions in a metastable excited state (Ar+m) are generally target species, due to availability of excitation laser wavelengths. Therefore, careful consideration on production of Ar+m in tested plasma source is necessary for appropriate plasma characterization. In this paper, we measured behaviors of Ar+m in an electron cyclotron resonance (ECR) plasma source by the LIF method. Density and energy distribution of electrons are also investigated by a Langmuir probing method. The measured radial distribution of the plasma parameters indicated that the Ar+m relative density (LIF signal intensity) has different distribution from the average-energy electrons and the ground state Ar ion densities. The Ar+m relative density and the number of high-energy electrons over 15 eV showed similar pressure dependence and radial distribution. These LIF and probing results in ECR plasma suggests that presence of high-energy electrons is a key for the Ar+m production. |
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HW6.00019: Lamb dip spectrum in cavity ringdown spectroscopy at Balmer-α line of atomic hydrogen: toward sheath electric field measurement in plasmas Kimika Fushimi, Shusuke Nishiyama, Satoshi Tomioka, Koichi Sasaki We reported in a previous work (S. Nishiyama et al., J. Phys. D: Appl. Phys. 50 (2017) 234003) that the sheath electric field was determined by the Stark spectrum of the Balmer-α line of atomic hydrogen which was measured by saturation spectroscopy. The goal of the present work is to apply the Stark spectroscopy at the Balmer-α line to plasmas with weaker optical absorption. The strategy is saturated cavity ringdown spectroscopy (CRDS). A hydrogen plasma was generated inside an optical cavity. A single-mode cw diode laser beam was truncated using an acousto-optic modulator when the cavity length was resonant with the laser wavelength. The temporal decay of the laser intensity transmitted through the cavity was deviated from an exponential curve. A saturation parameter of ~ 100 was evaluated from the ringdown curve by fitting it with the theory of saturated CRDS. The maximum saturation parameter was observed at the center of the 2p2Po3/2 − 3d2D5/2 transition, indicating that saturated CRDS is applicable to the measurement of the Lamb-dip spectrum. |
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HW6.00020: Two-dimensional images of line integrated electron density for X-pinch plasmas using dark-field Schlieren and interferogram Seungmin Bong, H. J. Woo, Seunggi Ham, Jonghyeon Ryu, Kyoung-Jae Chung, Y. S. Hwang, Young-chul Ghim We present an interferogram analysis scheme for X-pinch plasmas which have current rising time of approximately 500 nsec. As X-pinch plasmas evolve in nano-second time scale, a short pulse width of ~150 psec laser beam (Nd:YAG, 532nm) is used as a light source of the imaging systems. Both the dark-field Schlieren with a ~600um-diameter solder ball and the Mach-Zehnder interferometer simultaneously image X-pinch plasmas with the pulsed laser beam. Since an interferogram analysis typically requires hand-tracing of dark fringes on the interferometer images, it is difficult to assess reliability of the hand-traced results unless they are compared with electron densities obtained by other independent diagnostic systems. As dark-field Schlieren image contains information about the gradient of line integrated electron density of X-pinch plasma, it can be qualitatively compared with the interferogram analysis results. The method of generating synthetic dark-field Schlieren images from the interferogram results is presented, and how it can support the interferogram analysis is discussed. Two-dimensional images of line integrated electron density for X-pinch plasmas using the proposed method are also presented. |
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HW6.00021: Development of asymmetric wireless double probe for two-dimensional measurement Taewung Hwang, Hyun-Dong Eo, Seong-Joon Park, Chin-Wook Chung A wafer-type wireless probe using asymmetric double probe is developed to measure two-dimensional plasma parameters (ion density, ni, and electron temperature, Te). The asymmetric wireless double probe system operates alone in the chamber. Thus, the two-dimensional plasma parameters can be measured and be monitored in real-time in floating or grounded wall chamber. As the pressures and gap lengths changes, the spatial profile of plasma parameters is changed from convex to saddle shape in inductively coupled plasma by the asymmetric wireless double probe. The measured plasma parameters are in good agreement with a wire two-dimensional floating probe method. |
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HW6.00022: Energy distribution function of substrate incident negative ions in DC magnetron sputtering of metal-doped ZnO target measured by magnetized retarding field energy analyzer Yoshinobu Matsuda, Shoma Uzunoe, Koki Watanabe In planar magnetron sputtering deposition using oxide targets, there is a problem of film composition and crystallinity degradation on the substrate surface opposite the target erosion region. This is believed to be due to the incident of high-energy particles emitted from the erosion zone of the oxide target onto the opposite substrate, but the details have not yet been clarified. Thus, it is extremely important to measure the energy distribution function (EDF) of the charged particles. |
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HW6.00023: Development of sensitive electric-field measurement method via electric-field-induced coherent anti-Stokes Raman scattering Takeru Koike, Hitoshi Muneoka, Kazuo Terashima, Tsuyohito Ito Electric fields in plasmas play key roles both in their physics and chemistry, and therefore electric field measurement is crucial for various applications to highly understand and control plasmas. |
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HW6.00024: Measurements of Spatial profiles of electron density and EEDF in a positive air-streamer discharge using laser Thomson scattering Toma Miyazawa, Kentaro Tomita, Atsushi Komuro, Ryo Ono Streamer discharges in atmospheric pressure air are used in various applications as an efficient reaction field for active species. In this discharge, the electron energy distribution function (EEDF), which determines the efficiency of active species production, is expected to clearly deviate from the Maxwell distribution. One experimental fact has been reported to support this prediction, but no detailed report exists yet. In order to obtain electron properties of streamer, we have attempted to measure the spatial and temporal variation of the EEDF using laser Thomson scattering (LTS) measurements. We use an air streamer discharge device that produces streamers with high spatial and temporal reproducibility using a special needle-electrode configuration. DC and pulsed power supplies were used as power sources, and a pulse voltage of 30 kV was applied to a 13 mm gap. The pressure in the reactor was set at 760 Torr and a synthetic gas of N2:O2=79:21 was supplied at 1000 sccm. The repetition rate of the discharge was set to a slow rate of 2 Hz to avoid changing the composition of the ambient gas. 532 nm wavelength, 10 ns pulse width, <0.1 pm spectral width, and 18 mj/pulse of a second harmonic Nd:YAG laser were used as the light source for the LTS measurements. The laser beam was focused onto the streamer using cylindrical lenses with focal lengths of 400 mm and 300 mm. In this case, measurements were taken at 1.5 mm, 4.5 mm, and 9 mm from the anode electrode tip. The laser was integrated 2000 times at the 1.5 mm position, 2500 times at 4.5 mm, and 3000 times at 9 mm. EEDF was greater than 100 Td at 1.5 mm and 4.5 mm, but less than 100 Td at 9 mm. Electron density decreased as increasing the length from the tip of the anode. |
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HW6.00025: Characterization of a low power 13.56 MHz RF atmospheric pressure plasma source for ion mobility spectroscopy Keith Nealson N Penado, Allen Vincent B Catapang, James Edward II A Hernandez, Motoi Wada The development of an atmospheric pressure plasma source using a low power (< 100 W) 13.56 MHz RF power source is explored in this study. The inductively coupled plasma (ICP) source utilizes a 24 mm long, 7 mm diameter inductor and a custom-built capacitor connected in series to the RF power source. The ICP electrode enclose a glass tube where a 2 mm grounded tungsten rod is positioned at the center to realize and stabilize the breakdown of the gas inside the tube. A flow rate of 1-5 L min-1 of Argon gas is utilized as the precursor gas. Observation of the ion species in the plasma and local plasma parameters are investigated using optical emission spectroscopy along the direction of the plume and perpendicularly using optical focusing methods. Double probe measurements of the plasma source are also investigated to observe the electrical characteristics of the plasma across the exit region of the plume. The results of the study are correlated to the ion transport from the plasma source to the exit region for ion mobility spectroscopy applications. |
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HW6.00026: Spectral investigations of discharges on complex structured cathodes Roman W Schrittwieser, florin Enescu, Claudia T Konrad-Soare, Dan G Dimitriu, Codrina Ionita Plasmas can form complex 3D structures hard to investigate in terms of space and time. Frequently the physical access is limited, and the dynamic behavior requires high temporal resolution of the diagnostic. Emission spectroscopy of low temperature plasmas, usually situated inside a steel vacuum chamber, has to be carried out through a glass or plexiglass window or by fiber optics inserted into the chamber by feed-throughs. Fiber optics have the advantage that the light can be collected near the plasma. Drawbacks are possible deposition on the fiber, perturbation of the discharge, and often intricate variations of the position. Readings from outside of the chamber are more straightforward. The so-called eyepiece projection creates an image of the plasma either on a 2D mobile screen with fixed fiber position or on a screen with grid holes where the optical fiber can be shifted. Here we present a setup for measuring electron density and temperature along an axis. The cathode system consisted of two concentric gridded cylinders. The temperature was determined from the average of the Boltzmann plot slope. Electron density profiles have been calculated using relative intensities of neutral atomic lines and singly charged ionic lines according to Saha-Eggert. |
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HW6.00027: Investigation on the harmonic currents in an asymmetric double Langmuir probe when AC voltage is applied Hyundong Eo, Chin-Wook Chung, NaYeon Kim, JaeHwi Kim, HyoJun Choi, Jeonghyun Lee Double Langmuir probes are mainly used when the plasma is electrically isolated. When an AC voltage (v0) is applied to the double probe, harmonic currents flow due to the nonlinearity of the current-voltage curve. In the case of a double probe with the same area, odd harmonic currents (Iω, I3ω, I5ω...) flow. Electron temperature can be measured from the ratio of harmonic currents. However, when v0/Te ~ 0.5, the ratio of I3ω to Iω is about 1/50, which is very small, so it is difficult to obtain accurate electron temperature measurement. In this study, an asymmetric double probe is used. Iω and I2ω are used to obtain the electron temperature and ion density. It is found that the magnitude of I2ω is given as a function of the area ratio of the two probes and the applied AC voltage. There is an area ratio at which I2ω is maximum at a given applied voltage. In the case of using a large driving voltage, we will present a way for measuring the accurate electron temperature and ion density. |
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HW6.00028: An Improved Calculation Scheme of Electron Flow in Propagator Method for Solving the Boltzmann Equation Tsukasa Kobayashi, Hirotake Sugawara, Kei Ikeda An improved technique to solve the Boltzmann equation by the propagator method (PM) has been investigated. In the previous PM, the time evolution of electron velocity distribution function (EVDF) due to the electron acceleration was calculated using the upwind scheme. This scheme needed very fine cells to obtain an acceptable calculation accuracy at low electric fields. In the improved PM, the upwind and the central differences are blended in a certain ratio to calculate the electron flow stably. The PM calculations for the EVDF in a gas mixture of Ar and Ar metastable species under RF electric fields have been carried out to verify the improved scheme. Unlike the previous PM, the present results are little affected by the cell resolution. At low electric fields below 1 Td, the improved calculation can provide satisfactorily accurate results even with cells an order of magnitude larger than the upwind case. Considering the acceptable error, the total calculation time of PM can be reduced because larger cells are allowed and the complexity of the blending scheme is compensated by the reduction of the number of cells. The robustness against coarse meshes makes the PM calculation much more efficient. This feature has been built into a new user-friendly program named BOSPROM® to enable the accurate and practical electron swarm analysis under RF electric fields. |
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HW6.00029: Best impedance matching seeking of capacitively coupled plasmas by numerical simulations Shimin Yu, Hao Wu, Zhijiang Wang, Wei Jiang, Ya Zhang Impedance matching can maximize the absorbed power transferred to the plasma load and minimize the reflected power, so it is critical and indispensable for capacitively coupled plasmas (CCPs). A self-consistent numerical method for coupling generalized external circuit and electrode driven plasma is proposed. The plasma is solved by a 1D PIC-MCC model, and the external circuit is solved by Kirchhoff's law. The circuit and plasma are coupled self-consistently. Based on the above method, we propose an impedance matching design method for single-frequency CCPs and tailored voltage waveform CCPs, which also has been studied by many scholars [1,2]. The selection method of matching network topology and the design process of matching parameters are studied in detail. The proposed method can be used to calculate the matching parameters in any condition consistently. The design method and iteration process of matching parameters are demonstrated by a simulation example of argon discharge. Through impedance matching design, the reflection coefficient of each frequency component can be reduced to a relatively low level, and the power absorption efficiency of the plasma load can reach the level of nearly 40%, which provides strong references for practical industrial design. The results show that impedance matching network plays an important role in discharge [3] and breakdown process [4]. |
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HW6.00030: Azimuthal structures and turbulent transport in Penning discharge Mikhail Tyushev, Mina Papahn Zadeh, Vedanth Sharma, Meghraj Sengupta, Yevgeny Raitses, Andrei Smolyakov Azimuthal structures in Penning discharge are investigated in the 2D3V model of Penning discharge with the axial magnetic field. The discharge is supported by ionization from the axial electron beam. We show that the large (m=1) spoke and small scale structures occur due to Simon-Hoh and lower hybrid instabilities driven by the electric field, density gradient, and collisions. It is shown that the steady-state discharge can be supported in two different regimes with different types of observed azimuthal structures. The transition between the regimes is controlled by the total energy input to the discharge. In the first regime, with the pronounced m=1 spoke activity, energy absorption dominates the power input due to the radial current and self-consistent electric field. In another regime, with prevalent small-scale m>1 spiral structures, the total energy input is dominated by the direct input of the kinetic energy from the axial electron beam. The latter regime with the lower values of the anomalous transport occurs when the injected axial current and total energy input are reduced. |
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HW6.00031: Numerical Simulation of a High-Repetition Nanosecond Pulsed Glow Nitrogen Discharge Plasma Masayuki Iida, Yusuke Kikuchi Nanosecond pulsed glow discharges under atmospheric and sub-atmospheric pressure have attracted attention in various fields because of their ability to generate high-density non-equilibrium plasma. This study reports numerical simulation results of a high-repetition nanosecond pulsed nitrogen glow discharges. In the simulation, a pair of parallel plate electrodes with a gap length of 30 mm was placed inside a cylindrical vessel. The upper electrode was grounded, and a repetitive pulsed negative voltage with a pulse width of 200 ns was applied to the bottom electrode at a frequency of 600 kHz. The gas pressure is 0.5 kPa. The dynamics of the discharge was described by a fluid (drift-diffusion) model consisting of the continuity equation for electron transport, the Maxwell-Stefan equation for the transport of ions and neutral species, and the Poisson’s equation for the space charge electric field. These equations were numerically solved by the finite element method. It was shown that the electron temperature and electron density of the afterglow plasma are about 0.5 eV and 0.5×1018 m-3, and the next pulsed voltage is applied before the afterglow decays, resulting in the quasi-steady generation of low-temperature and high-density plasma. |
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HW6.00032: Modeling of a (sub-)atmospheric pressure ns-pulsed plasma jet Jan Kuhfeld, Nikita D Lepikhin, Dirk Luggenhölscher, Uwe Czarnetzki, Zoltan Donko A ns-pulsed discharge between two plane-parallel electrodes at sub-atmospheric pressure (0.1 to 1 bar) is investigated by different numerical and analytical methods. The electrode separation is typically in the range of a millimeter and as model gas nitrogen is used. A spatially one dimensional (but including three dimensions in velocity space) particle-in-cell simulation with Monte-Carlo collisions (PIC/MCC) allows monitoring the fast increase of the plasma density during a discharge pulse by dynamic adjustment of the super-particle weights. Due to the relatively high pressure, recombination is seen to be important for the discharge development to a quasi-steady state. Using insights from the PIC/MCC simulation fluid models are developed, which are less computational demanding or can even be solved analytically. This allows the investigation of different discharge conditions (pressure, applied voltage, gap size). Various discharge regions are identified analogously to classical DC glow discharges and consequences for zero dimensional chemical models are discussed. |
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HW6.00033: Particle-In-Cell Simulation for Electron Velocity Dispersion in a Vacuum Tube for RF-DC Conversion Maho Matsukura, Kohei Shimamura, Shigeru Yokota To cause RF-DC conversion with a vacuum tube, an electromagnetic field is applied to the electron beam to induce cyclotron resonance, which accelerates the electrons and extracts energy from the electron beam at a potential depression collector. It has been found that the velocity dispersion of the electrons causes heat loss, which reduces the final energy conversion efficiency. Therefore, it is necessary to analyze the conditions that cause electron acceleration with less velocity dispersion while still producing resonance. In this paper, we used the particle-in-cell (PIC) method, which is the best for analyzing accurate particle behavior and for observing the velocity dispersion and electron acceleration under the interaction of electromagnetic fields. The initial energy of electrons entering the calculation region was assumed to be uniform and 1~2 keV. The conditions for efficient electron acceleration with low-velocity dispersion were investigated at frequencies from 2.45 GHz to the Ka-band, where the tube is expected to be operated. Preliminary results suggested that velocity dispersion was likely to increase under the same conditions as frequency increased. |
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HW6.00034: Computational fluid dynamics modelling of a post-discharge in low-temperature argon plasma jets Duarte Gonçalves, Stéphane Pasquiers, Joao Santos Sousa, Mário Lino da Silva, Luís L Alves Plasma jets provide an easily accessible form of producing plasma excited species. These unobtrusive sources are used in different applications [1], and through modeling we can help develop further applications. |
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HW6.00035: Surface Diffusion of Adatom on Tungsten Material Evaluated by Density Functional Theory Calculation Arimichi Takayama, Atsushi M Ito We are interested in tungsten nano structure (fuzz), which is formed due to helium irradiation with relatively low incident energy (less than about 100 eV), and have studied by use of numerical simulations. Its formation mechanism is not clear and is believed that multiple processes are involved. Motion of adatom which is trapped on a surface is regarded as one of these elementary processes. |
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HW6.00036: Evaluation of microwave propagation control by plasma-metamaterial composite using pattern comparison Yota Noyori, Chui Inami, Alexandre Bambina, Shigeyuki Miyagi, Osamu Sakai Up to now the level of cloaking, which is achieved by installation of metamaterial that is an artificial structure that control permittivity and permeability, is evaluated by observing electromagnetic waves going around a given object and suppression of scattering waves. Following those studies, we aim to visualize the levels of total wave manipulation schemes which includes not only cloaking but also absorption and scattering of waves. In this study, we used plasma that makes its composite with metamaterial more functional, and experimentally investigated this wave manipulation [1]. Changing electron density in the center by adjusting electric power of RF plasma at 27.12 MHz, we controlled spatial gradient of permittivity. And we introduced anisotropic permeability with directional metamaterial composed of split-ring resonators. We launched microwave at 2.89 GHz [1] and evaluated uniformity of detected signals in each case of Ar pressure by installing receiving antenna at each spatial point and scanning transmitting antenna. According to measurement results, the variation of the signals was reduced in comparison with the case in free space as the Ar pressure increased in the range from 50 to 200 Pa. The similar measurements are applicable to level estimation of absorption and scattering. [1] C. Inami et al., J. Appl. Phys 130, 043301 (2021). |
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HW6.00037: Numerical simulation of atmospheric-pressure helium DC glow discharge considering gas dynamics Takaki Goto, Fumiyoshi Tochikubo, Yusuke Nakagawa In DC glow discharge at atmospheric pressure, a local temperature rise occurs due to Joule heating. The change in temperature field also causes a local gas density change, which is an important factor because it affects the shape of the DC glow discharge. In this work, we developed a numerical model coupling the gas dynamics and the plasma in a nozzle-to-plane He glow discharge. The gas dynamics was obtained by solving the continuity equations for compressible fluids, and the plasma was calculated by coupling the continuity equations for charged species with Poisson's equation. The plasma and gas dynamics were numerically analyzed independently, and the coupling was achieved by repeating the calculations three times to reflect important parameters such as momentum, heat, gas density and temperature. The gas was a mixture of 99.9% He and 0.1% N2. DC +350 V was applied to the nozzle anode, and the grounded cathode was a metal plate with 300K. As a result, circulatory convection flow based on the heat and ion induced force was observed. It indicated the effect of heat convection. As the interaction analysis was repeated, the gas temperature near the cathode center increased from 300K to 462K. |
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HW6.00038: High density plasma activated by resonance properties of metamaterials and measurements of spatial distribution of plasma parameters Takuya Mizutomi, Youhei Sanami, Shigeyuki Miyagi, Osamu Sakai Microwave metamaterials in low-power levels are currently introduced into the industrial wireless communication devices, for instance, for antenna miniaturization activated by their resonance properties. When we increase the level of microwaves, metamaterials are expected to be applicable to plasma generation with high efficiency arising from their inherent resonances. In one previous study [1], microwave plasma generation was observed in a waveguide, where profiles of detected electron densities are nonuniform, depending on local shapes of a metamaterial unit. In this study, we aim at microwave plasma generation assisted by an inserted metamaterial for semiconductor plasma processing. The metamaterial consists of split ring resonators as a unit structure, and its two-dimensional array structure is regularly arranged in the disk configuration. The working frequency for plasma generation is 2.45 GHz, where the resonance frequency of the metamaterial ranges from 2.40 to 2.55 GHz. According to experimental results by a movable Langmuir probe with a three-dimensional scanner, generated plasma is homogeneous over the measurement space with electron density of 2-3 x 1017 m-3, which indicates that the plasma media is equivalent to the negative permittivity space. [1] A. Iwai et al., Plasma Sources Sci Technolo. 29, 035012 (2020). |
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HW6.00039: Electron drift velocity in acetylene and carbon dioxide determined from rf breakdown curves Valeriy Lisovskiy, Stanislav Dudin, Pavlo Platonov, Vladimir Yegorenkov In this work, we investigated the ignition of radio-frequency capacitive discharge in acetylene and in carbon dioxide. RF breakdown curves were measured in the range of distances between the flat electrodes from 4.5 mm to 30 mm in acetylene and from 5 mm to 40 mm in carbon dioxide at the frequency of 13.56 MHz. In the RF voltage range up to 2000 V, the diffusion-drift and Paschen’s branches are present in the breakdown curves. Diffusion-drift branches have a region of ambiguous dependence of the RF breakdown voltage on the gas pressure and, accordingly, the turning point. From the measured coordinates of the turning points on the diffusion-drift branches of the RF breakdown curves, the electron drift velocity was determined in the reduced electric field range 319 Td < E/N < 3409 Td (1 Townsend = 10−17 Vcm2) in acetylene and 272 Td < E/N < 6240 Td in carbon dioxide from turning points on the measured breakdown curves. The measured values of Pinhão et al. [PSST, 2020, 29, 045009] bulk drift velocity in C2H2, as well as their results of Monte Carlo simulation (“bulk” solution) are in good agreement with the data of other authors in the range E/N = 20 – 300 Td, but in a stronger reduced electric field they deviate towards the higher values of electron drift velocity. Our results for CO2 are approximately 1.15–1.2 times higher than the data of paper by H. Schlümbohm [Zeitschrift für Physik 182 (1965) 317]. |
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HW6.00040: Investigating the plasma dynamics of capacitive discharges driven by pulsed radio-frequency (RF) at low-pressure using particle-in-cell simulation Sarveshwar Sharma, Soham Banerjee, Peng Tian, Jason Kenney, Shahid Rauf, Dmytro Sydorenko, Alexander Khrabrov, Igor D Kaganovich, Andrew T Powis, Willca Villafana Capacitively coupled plasma (CCP) discharges have been widely used in semiconductor industry for etching processes over last few decades. Among the various innovative techniques applied in CCP discharges to get high quality uniform etching, pulsed radio-frequency (RF) CCP discharges is one of the well-known method which provide finer control over ion fluxes and ion energies. It is also observed that varying the properties of the driven pulsed power provides extra control over the electron energy distribution function (EEDF) and, subsequently, gives us the ability to tune the ion flux. In this work, we use a 1D/2D Electrostatic Direct Implicit Particle-In-Cell (EDIPIC) code to investigate the plasma dynamics of low pressure (of the order of mTorr) argon CCP discharges driven by a high-frequency RF (MHz) power source with a low frequency tailored voltage waveform (kHz). We have observed that by varying input parameters, such as the amplitude of voltage, frequency, duty cycle, and ramp results in non-linear plasma dynamics which significantly changes the plasma properties. We track and present the observed trends in electron and ion distribution functions, power absorptions, densities in different energy ranges etc. |
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HW6.00041: The influence of transverse magnetic field on the properties of a 13.56 MHz cylindrical CCRF device Swati Swati, Pawandeep Singh, Shantanu Karkari Magnetic field transverse to the sheath electric field is frequently used in capacitively coupled RF devices, in low-pressure, low-temperature regimes for a variety of applications. The magnetic field parallel to the electrode surface has been primarily investigated for parallel plate arrangement. This configuration results in an inhomogeneity in plasma density over the discharge plates due to inherent EXB drifts in the system, which results in non-uniform surface modification of the substrate. To address this issue, a cylindrical CCRF device with a pair of grounded annular rings having an axisymmetric magnetic field is proposed. Experiments conducted for a set of discharge pressure and applied RF power finds that the plasma density tends to increase with magnetic field strength while the electron temperature increases towards the edge. However, at a fixed applied RF power, the plasma density is found to fall beyond a critical value of magnetic field. This observation has been attributed due to strong confinement of ionizing electrons in the peripheral region, as the electron Larmor radius becomes comparable with the sheath width, with a corresponding fall in electron temperature in the central region. A qualitative discussion has been presented which explains the radial potential, plasma density and electron temperature variation in this system. |
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HW6.00042: Spatial distributions of hydrogen RF discharge plasma using a hollow cathode with double toroidal grooves combined with magnets Yasunori Ohtsu, Hokuto Hiwatashi, Julian Schulze A RF capacitively coupled plasma is an attractive plasma source, because it has a simple structure and maintenance can be done easily. However, such RF discharges provide only a low plasma density. In our previous work[1], a hydrogen RF plasma has been developed to solve this problem by using a hollow cathode with double hollow grooves and neodymium magnets consisting of a ring-shaped one at the center and 42 cylindrical ones fixed on an iron yoke disk. However, the surface loss of electrons and ions in the hollow grooves increased, because the magnetic flux lines crossed the groove bottom by using the iron yoke disk. In this work, spatial distributions of the ion flux have been measured at various hydrogen gas pressures from 1 to 20 Pa under conditions of improved magnet designs (reducing the cylindrically-shaped magnets without the iron yoke disk) to decrease the surface loss and the magnet cost. It is found that the hybrid discharge between a hollow cathode effect and magnetic confinement of electrons is attained for p ≥ 5 Pa, while for p ≤ 3 Pa, a conventional capacitive discharge is generated. The radial profile of the ion flux becomes uniform with increasing axial position for the hollow cathode discharge. |
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HW6.00043: Enhancement of photoresist ashing by controlling the impedance between bias electrode and ground in an inductively coupled plasma You He, Chin-Wook Chung A variable inductor (an inductor series connected with a variable vacuum capacitor) was connected between the bias electrode and the chamber ground of an inductively coupled plasma, this inductor is used for controlling the impedance between the bias electrode and the chamber ground. The electron temperature, the electron density, and the plasma potential are obtained from the measured electron energy distribution function. When the series resonance between the sheath capacitance and the variable inductor is achieved, the RF current flow through the bias electrode and the plasma potential dramatically increased, and the change in electron temperature and electron density is rare. The increase of plasma potential can be understood by the increase of the RF voltage across the sheath at the bias electrode. As the current flow through the bias electrode and the plasma potential increases, the etching rate of the photoresist on the wafer at the bias electrode is enhanced in the experiment. |
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HW6.00044: Modulation of IEADs by different bias waveforms in an ICP reactor: A fast hybrid simulation approach Ming-Liang Zhao, Jian-Kai Liu, Yu-Ru Zhang, You-Nian Wang In this work, a 2D fast hybrid model is developed to study the modulation of ion energy and angle distributions (IEADs) for a biased argon inductively coupled plasma. In the hybrid model, a numerical sheath module and an ion Monte Carlo module are coupled to a frequency domain electromagnetic module and a bulk fluid module to obtain the IEADs at different radial positions. In the bulk fluid module, the continuity equation and full momentum equation for ion and the energy conservation equation for electron are solved. The electron density is obtained by using the quasi-neutral condition, and the ambipolar electric field is obtained by using the no net current assumption. Since the inertial term is considered in the full momentum equation, the hybrid model is suitable for low pressure conditions. By using a single-frequency bias voltage source, the energy peak positions move to the high-energy region and the ion angle distribution moves to the small-angle region with the increasing bias voltage amplitude. Moreover, the width between two energy peaks is smaller at the edge of electrode than at the center. When a dual-frequency bias voltage source is used, the ion energy shows four peaks. The shape of IEADs can also be tuned by changing the phase between two frequencies. |
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HW6.00045: Plasma Density Enhancement of an Electron Cyclotron Resonance Plasma with Pulse-biased stage Ikumi Hamaguchi, Kensuke Sasai, Haruka Suzuki, Hirotaka Toyoda Large-area high-density plasma source is often used to enhance process productivity of large area substrates. Microwave plasma is one of candidates for this purpose. Furthermore, some application requires high-energy ion bombardment to improve film properties. In this study, an electron cyclotron resonance (ECR) plasma, one of high-density microwave plasma sources, in combination with the high voltage pulse power source was investigated. In the experiment, an aluminum chamber was evacuated by a dry pump below 0.1 Pa. Microwave power was introduced to the chamber through a vacuum-sealed quartz plate and quartz guide plates. An array of magnets was placed on the back of each quartz guide plate. Time-dependent plasma density during the pulse-bias application to the ECR plasma was measured by a Langmuir probe. Measured time constant of the density decay during the pulse-off fairly agreed with a simple model considering plasma volume and surface. Time constant of density rise during the pulse-on showed monotonic increase with increasing the pulse voltage. From these values, steady-state plasma densities during pulse-on and -off were evaluated. Plasma density enhancement was also evaluated as a function of secondary electron power injected from the stage. Density enhancement showed strong power dependence and saturation at higher secondary electron powers. |
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HW6.00046: Phase-resolved electron characteristics in a pulse-modulated RF plasma jet Sanghoo Park, Sung-Young Yoon Cold plasma jet has become one of the most attractive versatile plasmas, and active studies on plasma properties such as electron density (ne) and temperature (Te) have facilitated better development and implementation of plasma jets. In this contribution, we demonstrate the temporal evolution of ne and Te in a pulse-modulated radio-frequency (RF) argon plasma jet operating at atmospheric pressure. The plasma jet is driven by a 5-MHz sinusoidal rf power modulated by a 50 kHz square pulse with a 75% duty ratio. A 532 nm Nd:YAG laser is applied to the plasma, and laser Thomson scattering measurements are performed using a triple-grating spectrometer coupled to an intensified CCD camera. From this investigation, we find that ne and Te vary during the pulse repetition period of 20 µs in the ranges of (2–12) × 1018 m-3 and 0.3–6.0 eV, respectively. With respect to the 5 MHz period (200 ns), Te varies with the rf oscillating field, while ne remains constant. Special attention is given to three distinct electron characteristics depending on the pulse phase in the plasma jet—ionizing (on-pulse), stationary, and recombining (off-pulse) states. Our measurements will be valuable for related experimental and numerical plasma research and provide further insights into the effect of rf pulsing on the electron kinetics in atmospheric-pressure plasmas. |
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HW6.00047: Synthesis of ZnO Tetrapods by Atmospheric Pressure Microwave Plasma Jet and Their Enhanced Photocatalytic Performance Goo-Hwan Jeong, Seong-Gyu Heo, Jong-Min Seo Among various metal oxide semiconductors, ZnO has an excellent electrical, optical properties with n-type conductivity, and a sensitive bandgap of 3.4 eV in the UV region. It is highly likely to be applied as a photocatalytic material due to its high absorption rate along with physical and chemical stability to UV light. |
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HW6.00048: Quantification of molecular impurity ratio in high-pressure helium dielectric barrier discharge by laser absorption spectroscopy Keiichiro Urabe, Minami Toyoda, Yasunori Matsuoka, Koji Eriguchi In high-pressure low-temperature plasmas in rare gas flow, presence of impurities has critical influence on the discharge characteristics. Simulation studies have indicated that ppm-level variation of molecular impurities affects major positive-ion species and reactive neutral species. Therefore, in experimental studies on the high-pressure plasmas, it is indispensable to monitor the ratio of molecular impurities with a method not disturbing the discharge. In this study, we investigated molecular impurities in a helium (He) gas flow utilized in a dielectric barrier discharge (DBD). The DBD configuration is a tubular type that widely used in plasma jet studies. We estimated species of the molecular impurity from optical emission spectroscopy (OES) diagnostics. OH, H, and O emission suggested that a major molecular impurity in our setup was H2O vapor. A laser absorption spectroscopy (LAS) was performed to measure lifetimes of excited He atoms in a metastable state (Hem). In order to consider the influence of H2O dissociation by the DBD, we measured dependence of the Hem lifetime on the applied voltage frequency by the LAS method. From the frequency dependence, we calculated the H2O ratio in the He gas flow using a low-frequency-limit Hem lifetime. |
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HW6.00049: TALIF Measurements of Spatial Distribution of Atomic Oxygen in Sub-Atmospheric Pressure Oxygen Discharges Jion Oogaki, Yusuke Nakagawa, Fumiyoshi Tochikubo Atmospheric pressure plasma is expected to be applied in various fields with its abundant radical production. However, radicals produced in atmospheric pressure plasma have a short lifetime. Sub-atmospheric pressure plasma, in which the pressure is slightly reduced from atmospheric pressure, is considered as an effective tool of extending the lifetime of radicals while maintaining the radical production yield. In this study, the density of atomic oxygen was measured by TALIF produced in a sub-atmospheric pressure pure oxygen barrier discharge using pin-to-sphere electrodes and two power supplies with 300 ns or 35 ns voltage pulse width. The results show that the amount of atomic oxygen increased significantly near the cathode surface with dielectric in discharges using a long-pulse power supply. In contrast, the amount of atomic oxygen was almost independent of position in discharges using a short-pulse power supply. The lifetime of the atomic oxygen increased with decreasing pressure. One possible reason for the increased production of O atom near the dielectric in long-pulsed discharges is that the discharge area may have expanded due to surface discharges along the dielectric. |
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HW6.00050: Airflow impact on the collective behavior of microdischarges in DBD Azamat I Ashirbek, Yerbolat A Ussenov, Tlekkabul S Ramazanov, Maratbek Gabdullin, Merlan K Dosbolayev The study of microdischarge dynamics (MD) in dielectric barrier discharge (DBD) are gaining much attention due to high interest in the collective interaction of MD, memory effects and formation of self-organized patterns. In this work, the MD dynamics of atmospheric pressure air DBD were studied under the impact of forced external gas flow and natural convective flow. The discharge between rail electrodes in external airflow along the electrodes clarified the role of volume plasma and surface charges in the memory effect of MD[1]. The change in the gas flow regime from laminar to turbulent shows the complex dynamics of MD with trajectories downstream and upstream to the flow direction. The impact of convective flow due to the temperature gradient between discharge cell electrodes and ambient air was studied for parallel-plate electrode arrangement. It was shown that an increase in temperature during the discharge operation leads to an increase in MD number in the discharge gap. The convective gas flow velocity also increased at a higher thermal gradient, and MD channels follow the gas flow direction. The velocity of convective flow was estimated by the CFD simulation and compared with the mean velocity of MD channels obtained by the particle image velocimetry method. |
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HW6.00051: Measurement of spatio-temporal behavior of surface electrical potential in a dielectric creeping discharge using Pockels effect MAMI OGATA, Akira Ando A creeping discharge on dielectric surface has a great influence on the insulation design of power equipment and electronic devices, while it can be utilized in a wide variety of engineering applications, such as surface modification of materials, stall recovery of stable wings, and so on. As a streamer extends along the dielectric surface in a creeping discharge, charge-up phenomena on the surface are observed after the discharge, affecting the following breakdown on the surface. We have observed spatio-temporal behavior of electric potential on a dielectric surface using the Pockels effect, when a creepage discharge occurs at atmospheric pressure and a streamer propagates on the surface. |
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HW6.00052: Enhancing the Decomposition of Polluted Air Streams with Additional Metal Plates in a Multi-Electrode Twin Surface Dielectric Barrier Discharge System Arisa Bodnar, Alexander Böddecker, Lars Schücke, Peter Awakowicz, Andrew R. Gibson Reactive species created by surface dielectric barrier discharges (SDBD) can be used to decompose volatile organic compounds (VOCs, e.g. butoxyethanol and n-butane) in polluted air streams. This process can be operated close to room temperature, does not require air pumps or ramp-up time, and is scalable, which is highly relevant to industrial applications.In this work, strategies to increase VOCs conversion in a multi-electrode SDBD system are investigated. A system consisting of five electrodes with additional plates or meshes between them is used. Various plate materials, such as aluminium, titanium and manganese dioxide coated ceramics are chosen. The relative conversion is measured by flame ionization detectors. The potential influence of material properties as well as changes in the fluid flow within the reactor on the VOCs conversion are discussed. |
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HW6.00053: Calculation of SF6 Gas Contamination Rate Caused by Gas Flow Velocity with Changing Function of Gas Bluster Angle in Double-Flow Gas Circuit Breaker Wataru Fuse, Yuki Suzuki, Honoka Morishita, Masahiro Takagi, Yusuke Nemoto, Zhenwei Ren, Gustilo C Reggie, Toru Iwao The chamber size of SF6 gas circuit breaker is expected to get smaller than that of the current products. In addition, the re-ignition must prevent clearly. Thus, it is important to elucidate the transient phenomena of arc inside the extinguish chamber during the current interruption process. However, it is difficult to obtain the rapidly change of arc plasma with experiment, the numerical simulation is usually used to analyze the above process as well. 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 simulating the electrode opening process is the treatment of boundary between arc plasma and electrode because the rapidly change of physical properties with time variation. In this research, SF6 gas contamination rate caused by gas flow velocity with changing function of gas bluster angle in double-flow gas circuit breaker was calculated. As a result, the nozzle moves with the opening process of electrodes, and it elucidate that the gas bluster angle increases the SF6 gas contamination into the arc. |
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HW6.00054: Analysis of Radiation Distribution Effected by Interelectrode Distance in Arc Lamps Using 3D Electromagnetic Three-Dimensional Electromagnetic Thermal Fluid Simulation Kazumasa Minamisawa, Taisei Kudo, Hiroto Suzuki, Yuki Suzuki, Honoka Morishita, Masahiro Takagi, Zhenwei Ren, Yusuke Nemoto, Gustilo C Reggie, Toru Iwao Arc lamps generate light with high luminance and high color rendering properties using arc discharges between electrodes. Taking advantage of this feature, arc lamps are used as an industrial light source to restore crystallinity in the heat treatment process of the semiconductor material surface. In order to create thinner semiconductors in crystalline recovery, heat treatment with less thermal diffusion and shorter time is required. For this reason, arc lamps require a short time to calculate the radiation power for each wavelength and the temporal variation of the radiation power. However, control of lamp radiation makes it difficult to make measurements on the heat treatment of surfaces. Therefore, it is difficult to utilize these results in product design. Many researchers of radiation power from steady-state analysis have researched, but few reports of time-varying radiation power have been published. In this research, the radiation distribution affected by the interelectrode distance in arc lamp was analyzed using a three-dimensional electromagnetic thermal fluid simulation. As a result, the radiation power generated at a specific coordinate increases with increasing interelectrode distance, and radiation distribution was generated on the semiconductor material surface. |
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HW6.00055: Calculation of Object Heating Affected by Radiation Distribution of Arc as Function of Current in Arc Lamp Taisei Kudo, Kazumasa Minamisawa, Hiroto Suzuki, Yuki Suzuki, Yusuke Nemoto, Zhenwei Ren, Gustilo C Reggie, Toru Iwao Arc lamp is a light source with high radiation power and fast radiation start-up speed emitted from an arc formed between electrodes and are used for annealing in semiconductor manufacturing processes. In the annealing process, high intensity radiation is required for heating to high temperatures. One possible method is to increase the current of the arc discharge, which increases the temperature-dependent radiation energy with Joule heating. Although calculations of heating of objects from arc radiation have been performed, the optical thickness in the space between the emission source and the object has not been considered. To analyze the heating with synchrotron radiation during a current change, it is necessary to develop the calculation method that takes the optical thickness into account. In this research, object heating affected by radiation distribution of arc as function of current in arc lamp is calculated by three-dimensional electromagnetic thermal fluid simulation. |
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HW6.00056: High Temperature Gas Reflection as Function of Distance between Arc and Wall in Sealed Arc Extinguishing Chamber Akira Kono, Zhenwei Ren, Honoka Morishita, Masahiro Takagi, Yuki Suzuki, Yusuke Nemoto, Gustilo C Reggie, Toru Iwao The downsizing of direct current circuit breaker (DCCB) of electric vehicle is expected. However, it is not enough space to extend the arc in sealed arc extinguishing chamber of short distance to the wall. To extinguish the arc, extension of it is required with applying external magnetic field in DCCB. The arc and high temperature gas are moved to the wall. When high temperature gas reflects to the wall, it moves back to the opposite direction. A reflection of the high temperature gas from wall to inter-electrode area is caused. As a result, the electrical conductivity of inter-electrode area increment causes the arc re-strike. This phenomenon is difficult to be observed by experiment because physical phenomenon is complex. In this research, high temperature gas reflection as function of distance between arc and wall in sealed arc extinguishing chamber is analyzed using three dimensional electromagnetic thermal fluid simulation. |
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HW6.00057: High-viscous Ar plasma generation for plasma window application to electron beam welding in atmosphere Ohshi Yanagi, Kosuke Okuda, Yuta Sunada, Junya Kono, Daisuke Mori, Ayumu Saito, Makoto Takagi, Noriyasu Ohno, Naoki Tamura, Yuki Hayashi, Yukinori Hamaji, Suguru Masuzaki, HIroki Okuno, Kotaro Yamasaki, Shinichi Namba Plasma window has been paid attention as an innovative technique, by which a dense plasma can separate vacuum from atmosphere. The promising applications of the plasma window enable us to transmit charged particles and X-ray through plasma channel without significant beam scattering and attenuation, although a neutral gas flow is frozen effectively due to a high-gas viscosity. Thus, our application is to weld/cut the substances by an electron beam in air atmosphere. Note that the plasma windows make it possible to realize that the size of work piece for the welding is substantially mitigated, capable of applying this method to large structures that requires precise fabrications in air. |
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HW6.00058: Carrier avalanche multiplication quenching and pulse width control of nonlinear gallium arsenide photoconductivity switches Wei Shi, Cheng Ma, Lei Hou, Yue Wang, Hong Liu, Liqiang Tian, Lei Yang, Meilin Wu, Zhiyuan Chen, Haiqing Wang, Zhiquan Wang, Zhi Jin Non-linear Gallium arsenide photoconductivity semiconductor switch (GaAs PCSS) can generate high voltage and strong current electrical pulses with low light triggering at the order of micro joule. Due to the Lock-on effect of the GaAs PCSS, the output pulse width is usually on the order of hundreds nanoseconds or even tens of microseconds. This severely limits the application of nonlinear GaAs PCSS. This paper presents the output pulse width modulation of non-linear GaAs PCSS through the dual regulation of energy-storage capacitance and current-limiting resistance. When triggered by a pulse laser with a width of 10 ns and single pulse energy of 200 μJ, the switch can output the minimum pulse width of the 6.3 ns and the maximum pulse width of 196 ns. Since the energy provided by the energy-storage capacitance cannot maintain the Lock-on electric field, so a carrier quenching phenomenon occurs, and the output electrical pulse width is reduce. In the meantime, combined with the theoretical analysis of Photon-Activated Charge Domain (PACD), the electric field intensity of non-linear GaAs PCSS is less than the threshold electric field of PACD, and the switch will be turned off quickly, so that different pulse width can be output. |
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HW6.00059: The effect of radiation trapping on the ambient gas pressure in a stationary high-density He arcjet plasma Kosuke Okuda, Ohshi Yanagi, Yuta Sunada, Junya Kono, Daisuke Mori, Ayumu Saito, Makoto Takagi, Noriyasu Ohno, Naoki Tamura, Yuki Hayashi, Yukinori Hamaji, Suguru Masuzaki, HIroki Okuno, Kotaro Yamasaki, Shinichi Namba The purpose of this study is to investigate the effect of radiation trapping on the ambient He gas pressure by measuring He I resonance (11S-21P, 58.4 nm) and forbidden line (11S-23P, 59.1 nm) emissions in a stationary high-density He arcjet plasma. Here, by varying the gas pressure in the expansion chamber of arcjet, the resonance line intensity drastically changed due to a self-absorption, while the forbidden one did not suffer from it owing to less absorption coefficient. |
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HW6.00060: Time Transition of Temperature Distribution in Cross Section of Contact Wire Contacted with Disconnection Arc on Its Surface Asuka Kawasaki, Honoka Morishita, Masahiro Takagi, Yuki Suzuki, Zhenwei Ren, Yusuke Nemoto, Gustilo C Reggie, Takamasa Hayasaka, Toru Iwao The separation of the contact wire and the contact strip causes a disconnection arc, which rarely leads to disconnection of the contact wire, so its prevention is very important. To prevent the disconnection of contact wire, it is needed to elucidate the conditions for disconnection. Some researchers have simulated the appearance of the disconnection arc and the rising temperature of the contact wire. Few researchers have reported the time transition of temperature distribution in cross section of contact wire contacted with disconnection arc on its surface. This research using simulation shows how to rise the temperature of the contact wire which is higher than the softening temperature at connection point between the contact wire and disconnection arc. The initial temperature of the contact wire is calculated by Joule’s heating under consideration of current flow in contact wire for real situation. As a result, time transition of temperature distribution in cross section of contact wire contacted with disconnection arc on its surface is the area that is more than 700 K with time. Therefore, temperature rise of contact wire generated by Joule’s heating for current flow in contact wire plays an important role for disconnection of contact wire. |
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HW6.00061: Absolute intensity of luminol chemiluminescence induced in vicinty of water surface irradiated with atmospheric pressure helium dc glow discharge Shogo Uebayashi, toshiaki miyazaki, Yoshinobu Inagaki, Naoki Shirai, Koichi Sasaki We propose a method for estimating the absolute densities of short-lived species just below the plasma-liquid interface. The method is based on the measurement of the absolute emission coefficient (the number of photons emitted per unit volume and unit time) of the luminol chemiluminescence induced by the plasma-liquid interaction. We constructed a simplified rate equation model which simulates the reaction processes of luminol, and the experimental emission coefficient was compared with the solution of the rate equations. If we have the agreement between the experiment and the simulation, the densities of short-lived species in the simulation give us their estimations. The experiment was carried out using an atmospheric-pressure helium dc glow discharge produced between a needle anode and a liquid cathode with luminol. The experimental emission coefficient was 2×1025 m−3 s −1 assuming 10 µm for the thickness of the chemiluminescence region. The emission coefficient obtained by the simulation was 3 × 1025 m−3 s −1 , which was in close agreement with the experimental result. However, the simulation model has many uncertain assumptions, and the modification of the simulation model is a future issue. |
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HW6.00062: Numerical analysis of negative corona discharge from the tip of Taylor cone in electrospray Sohto Katsuno, Fumiyoshi Tochikubo, Yusuke Nakagawa The use of micro-droplets increases the contact area with plasma and enables efficient reactions. This study focuses on electrospray(ES) as a method to generate plasma and microdroplets simultaneously. We developed a numerical model of corona discharges and ES to elucidate the effect of negative corona discharges on Taylor cone formation and droplet emission. The ES and corona discharge are generated in nozzle-plate electrodes with 3 mm gap in atmospheric pressure air. From the nozzle, liquid is supplied. The ES simulation was performed by solving Navier-Stokes equation and current continuity equation. The discharge was calculated by continuity equations for charged species with Poisson’s equation. |
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HW6.00063: Analysis of polymerization and nanoparticle formation in silane plasma by unsupervised learning method and statistics in complex chemical network Osamu Sakai, Yota Noyori, Takuya Mizutomi, Satoru Kawaguchi, Tomoyuki Murakami Chemical reactions in low-temperature plasma are so functional for industrial processes, but are too complicated to understand what are going on in a specific process, and we frequently detect their outputs without their internal cause-effect relationships. Some previous studies [1] proposed visualization and centrality analysis based on complex network science to unveil such underlying processes. Following them, in this study, we investigate silane plasma chemistry, in which polymerization and nanoparticle formation are active, by two analytical methods. Using community detection, which is one of the unsupervised learning methods, we detect automatically one species group that contributes to this chemical processes. Furthermore, when we trace polymer molecules in the corresponding degree-distribution spectrum, we observe significant descents of degrees as the count of Si atoms involved in a molecule increases [2]. This fact indicates that, starting from a silane molecule which is the mother gas species, polymer growth makes heavier species less important, with possible removal of nanoparticles as process outputs without impacts on this chemical system. [1] T. Murakami and O. Sakai, Plasma Sources Sci. Technol. 29, 115018 (2020). [2] O. Sakai, S. Kawaguchi and T. Murakami, Jpn. J. Appl. Phys. 61 (2022) (in Press). |
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HW6.00064: Kinetics of O and H radicals in a nanosecond pulsed He+H2O pin-pin discharge Alexandra Brisset, Matthew S Bieniek, James L Walsh, Mohammad I Hasan, Erik Wagenaars A nanosecond pulsed discharge generated in a pin–pin 2.2 mm gap geometry in He + H2O was studied experimentally and by 1D fluid modelling. The density of O and H radicals were measured by ps-TALIF for varying concentrations of H2O. Good agreement was obtained on the absolute density and decay rate of O. The density of O peaked about 1 µs after the end of the current pulse, reaching 1x1016cm-3. It then remained about constant over 10 µs before decaying. Modelling suggested that O was predominantly produced by electron impact reactions: direct dissociation of O2 during the discharge (7 ns to 200 ns) and dissociative recombination of O2+ during the post-discharge. O2+ was produced primarily by charge exchange collisions of O2 with He2+ and H+ ions, and the 3-body recombination of O+ and O with He. The main loss mechanism of O was ionisation by electron impact from 10 ns to 190 ns, and 3-body recombination with O+ and He, between 190 ns and 1 μs. According to numerical simulations, the production of O was mostly unchanged for a range of pulse shapes with different ratios of maximum voltage to the voltage pulses width, between 0.1 to 4.0 kV/μs, with constant pulse energy. At higher ratios, the efficiency of O production increased by maintaining higher reduced electric fields. |
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HW6.00065: Shock-Waves Generated-Plasmas-Discharges Gaseous Electronics: Electrical-Discharges(EDS) Principles/Devices/Glow-Discharges Applied-Voltage DC/Low-Frequency AC Cataphoresis-Applications: Gas-Lasers/ Electron-Beams/... E Carl-Ludwig Siegel, Norman March, Paul Butcher, Ruben Braunstein, Peter Franken, Walter Munk, Mario Molina, Colin Maiden, Sidney Green, Victor Gregson Jr. Gas-(TEA/CO2)-lasers/electron-beams/shock-waves/shocks generated-plasmas-discharges [Gregson/Siegel [in:Lasers in Motion for Industrial Applications”,D.Belforte,Ed.,SPIE |
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HW6.00066: Update on Sandia National Laboratories Plasma Research Facility Shane M Sickafoose, Brian Z Bentz, Jonathan H Frank, Nils Hansen, Matthew M Hopkins, Christopher J Kliewer, Amanda M Lietz, Dirk van den Bekerom This presentation will provide an update on the activities and structure of Sandia’s Low-Temperature Plasma Research Facility (PRF), funded by DOE Office of Science, Office of Fusion Energy Sciences, General Plasma Science. The PRF is a resource available to anyone in the international Low-Temperature Plasma (LTP) community to access the advanced resources available at Sandia (not restricted to the US collaborators). Capabilities are accessed through an annual proposal process which opens immediately following the GEC conference. Available resources include both experimental and modeling capabilities that represent many person-years and millions of dollars of development through DOE and other investments (some for decades). Examples of real-time diagnostics include Laser-Induced Fluorescence (LIF), Laser-Collision-Induced Fluorescence (LCIF), Photofragmentation LIF (PF-LIF), and Molecular Beam Mass Spectrometry (MBMS). Advanced modeling capabilities are also available, including state-of-the-art PIC-DSMC modeling tools along with access to Sandia’s high-performance computing (HPC) capabilities (many 10K’s of cores). |
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HW6.00067: Surface Plasmon Resonance Excited by Super-aligned Multi-walled Carbon Nanotube Film Metasurfaces Yue Wang, Xiaoju Zhang, Zijian Cui, Xiang Zhang, Wei Shi Surface plasmon polaritons (SPPs) excited by the resonance interaction between the free electrons of the conductor and the electromagnetic field of the light play an important role in metamaterials. Here, we experimentally demonstrate the subwavelength, terahertz (THz) metasurfaces based on super-aligned multi-walled carbon nanotubes (MWCNT) film can support SPPs. The MWCNT film was prepared by drawing out from the super-aligned MWCNT arrays and then was transferred onto a silicon substrate. After that, periodic array structures were etched on the MWCNT films by a laser-machining technique to prepare MWCNT metasurfaces. The dielectric properties of the unetched MWCNT film were studied in detail in frequency range from 0.2 to 2.5 THz. The real part of the effective permittivity retrieved from the measured transmission spectra is negative, which is a critical condition to support propagating SPPs. The Drude-Lorentz model combined with Maxwell-Garnett effective medium theory was used to explain the measured results, which reveals an obvious metallic behavior of the MWCNT films. Obvious enhanced resonant peaks of transmission spectra of the MWCNT metasurfaces are observed experimentally, which are attributed to the surface plasmon polariton resonance. Furthermore, the surface plasmon resonance based on super-aligned MWCNT metasurfaces has been experimentally demonstrated to be applied for analytes sensing, showing the lowest detection mass of 10 ng and the sensitivities of 2.0 × 10−3/ppm. |
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HW6.00068: A study on the generation and control of electron beams and ultra-low electrons temperature plasma using two DC-biased grids. Minseok Kim, Chin-Wook Chung To generate ultra-low electron temperature (ULET) plasma (Te < 1 eV), two DC-biased grids are used. We can control the electron beam energy by adjusting the grid voltage. Since the gap between two grids is made shorter than the electron mean free path electrons can be fully accelerated from the grids. The electron beam energy in Ar & He ULET plasma in a two-grid system is investigated by measuring the electron energy distribution. It is observed that the electron beam energy is proportional to the grid voltage (-30 V ~ 0 V) at 3 mTorr. At high pressures (10 ~ 75 mTorr), ULET plasma (Te < 0.7 eV) is produced. The ULET plasma is formed faster in He than in Ar because the sheath length of He is longer and thus forms potential surface in the grid holes faster. And the electron density of the He ULET plasma is higher than that of Ar. This is because the number of high-energy electrons in the source region, which is the biggest factor determining the density of the beam, is greater in He ULET plasma than in Ar. So, the electron beam distribution and ULET plasma is clearly observed by measuring electron energy distribution with the Langmuir probe. It is expected that the electron beam generated by the grid voltage can selectively dissociate the neutral species into radicals, which is crucial for ALE and ALD.
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HW6.00069: Abstract Withdrawn
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HW6.00070: Etch Profile Analysis on Taper angle using Convolution Neural Network in Narrow Gap VHF+LF driven CCP Jihoon Park, Jaemin Song, Taejun Park, Sung Hyun Son, Hyunju Lee, Gon-Ho Kim In high aspect ratio etch process, it is challenge that maintaining profile shape and CD with "spec-in" condition. Varying equipment status and operation recipe by time also cause profile distortion e.g., tilt, bowing, tapering, twisting. Especially, in high stacked NAND process, etch profile is considered a critical parameter because small change of taper angle (<1º) causes dramatic degradation of cell characteristics and uniformity. ARDE (Aspect Ratio Dependent Etch) is representative technology for those challenges. As basis research for ARDE, correlation analysis between etch profile data (MI) with equipment status and plasma information are essential. Thus, precise measurement and parameterization of MI data are required. However, various operation condition, ambiguous etch profile and measurement error are obstacles decreasing accuracy of measurement. In this study, CNN based SEM image analysis was introduced to extract MI data with minimizing inaccuracy. Etching was performed using patterned wafer of Si3N4/SiO2 trench in narrow gap VHF+LF driven Fluorocarbon based CCP. Vertical SEM images were obtained along radial position in wafer. Extracted etch profile from SEM image using NN showed high similarity to actual etch profile with above 0.9 of SSIM and MS-SSIM value. Measured taper angles at center/edge region at LF bias power varying condition had precision below 1º angle with low error. These results show MI data from our method was precise enough to recognize variance of etch profile at high aspect ratio condition, and to be used as quantitative factor for etch profile evaluation. |
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HW6.00071: Properties of vanadium oxide film prepared using pulsed magnetron sputtering Yoshinobu Takagi, Takashi Kimura Vanadium dioxide is a well-known thermochromic material with a metal-to-insulator transition, which is associated with a reversible transformation between monoclinic structure and tetragonal structure at a critical temperature of about 341 K. The objective of this research was to investigate the relationship between microstructure of vanadium oxide synthesized using magnetron sputtering and the thermochromic characteristics. In this study, vanadium oxide thin films were prepared on glass substrates using reactive pulsed magnetron sputtering of Ar/O2 mixture gases at a total gas pressure of 0.8 Pa and an average power of 60 W in the partial pressure range of oxygen gas from 2% to 5%. The film thickness was about 100 nm. The film structure was analyzed using the Raman spectroscopy and X-ray diffraction (XRD) measurement. The film structure and the infrared transmittance at wavelength longer than 800 nm strongly depend on the partial pressure of oxygen gas as well as the peak target current. The peaks due to V2O5 or VO2 components were observed in the measured Raman spectra, showing the narrow process window for the synthesis of VO2-based films. |
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HW6.00072: Effect of Mixture Ratio of Ar Gas and C2H2 Gas on Gas-Injection Pulsed Plasma CVD Method for Ultra-High-Rate DLC Deposition Hikaru Ohhra, Naoto Nagata, Takahiro Bando, Hirofumi Takikawa, Toru Harigai, Shinsuke Kunitsugu, Hidenobu Gonda Diamond-like carbon (DLC) films have been used as a surface protective film. To use the DLC films in a wide range of applications, a faster DLC formation method than the conventional method is required. In this study, the effect of the mixture ratio of Ar gas and C2H2 gas on the DLC films prepared using a pulsed plasma CVD with the injection of the mixed gas is investigated. |
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HW6.00073: Investigation of atmospheric pressure nitrogen plasma assistance on mist CVD of zinc oxide thin films Hiroya Kobayashi, Keigo Takeda, Mineo Hiramatsu Zinc oxide (ZnO) is a widely applied material, but there are problems with equipment costs and film formation rates. In this study, we performed plasma assistance for mist CVD, which is known as an inexpensive and safe film formation method, and formed ZnO. |
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HW6.00074: Plasma Uniformity and Stability in Large Area Intermediate Pressure Capacitive Coupled Plasma (CCP) Reactors with N2/NH3 Chemistry Emi Kawamura, Michael A Lieberman 1D particle-in-cell (PIC) simulations of an intermediate pressure N2 capacitive discharge showed an alpha to gamma transition, characterized by a collapse of the sheath width when the rf sheath voltage amplitude exceeds a breakdown voltage of about 140 V. Smaller sheath widths enhance electromagnetic (EM) effects which may negatively affect plasma uniformity and stability. One solution is to use a dual frequency drive in which the lower fundamental frequency maintains the sheath width while the higher second harmonic frequency maintains the plasma density at lower overall voltages below the breakdown. Such configurations are known to lead to electric asymmetry (EA) effects, which are a function of the relative phase between the drives. Another solution is to add an electronegative gas such as NH3 to the N2 gas to increase the power threshold needed to transition to the gamma-mode, since sheath multiplication of the hot gamma electrons must now compete with their loss through attachment. We study the EA effects by conducting 1D PIC simulations of a dual frequency (13.56/27.12 MHz) symmetrically-driven 1.6 Torr N2/NH3 discharge at various relative phases between the drives. We then develop a dual frequency 2D EM fluid model for this discharge to study the EM effects. By combining the two solutions, we may be able to find the optimum operating conditions for enhancing stability and minimizing non-uniformity. |
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HW6.00075: Low-Temperature Formation of High-Mobility IGZO Thin Films Transistors Fabricated with Plasma-Assisted Reactive Processes Yuichi Setsuhara, Hibiki Komatsu, Susumu Toko, Kosuke Takenaka, Akinori Ebe Low-temperature formation of In-Ga-Zn-O thin films transistor fabricated with plasma-assisted reactive processes have been demonstrated. The plasma-assisted reactive sputtering deposition of amorphous In-Ga-Zn-Ox (a-IGZO) films for use as channel materials in TFTs has been studied, as a means of achieving low-temperature fabrication of IGZO TFTs. This advantage of fine control of reactivity during the deposition process is of great significance for film deposition of the transparent amorphous oxide semiconductor, a-InGaZnOx (a-IGZO), whose electrical properties are significantly sensitive to the reactivity during the film deposition. In the formation of IGZO TFTs, it is important to control the concentration of oxygen deficiencies at post-deposition process. Therefore, low-temperature post-deposition process using plasma as alternatives to thermal annealing have been developed to improve the electrical characteristics of the TFTs. It has been founded that the OH radical irradiation from plasma to a-IGZO thin films is more effective in improving the electrical properties of IGZO TFTs. The TFTs fabricated with IGZO thin films post-treated with plasma at a temperature as low as 300°C showed the best performance, with m values greater than 40 cm2 /Vs. |
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HW6.00076: An Optical Emission Spectroscopic Study of Deep Oscillation Magnetron Sputtering of Titanium Eisuke Yokoyama, Masaomi Sanekata, Nobuo Nishimiya, Masahide Tona, Hiroaki Yamamoto, Keizo Tsukamoto, Kiyokazu Fuke, Keijiro Ohshimo, Fuminori Misaizu Optical emission spectroscopy was investigated for sputtering plasma generated in deep oscillation magnetron sputtering (DOMS) of titanium in Ar gas in the present study. Temporal profiles of optical emissions of both gas particles and sputtered metal particles in DOMS plasma were observed at a distance in the range of 14 ? 74 mm downstream from the target surface. Almost the same temporal profiles of a given species were obtained for the emission lines which correspond to transitions to metastable and ground levels. On the other hand, the temporal profile was strongly dependent on the species, that is, the metal ion particles and the neutral particles. The peak intensity for the first discharge pulse at the distance of 14 mm was observed to be about 6 times higher for Ti+ than for neutral Ti. However, the Ti+ intensity for the first discharge pulse more rapidly decreases with increasing distance from the target compared with that of neutral Ti. In addition, the Ti+ intensity decreases almost at a distance of the edge of the magnetic trap from the target. Therefore, the present results suggest that the ions were confined in negative plasma potential formed by electron trapping in the strong magnetic field near the target. |
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HW6.00077: Pulsed microwave plasma coupled with MoO3-based heterogeneous catalysts for nitrogen fixation Babak Sadeghi, Omid Samadi Bahnamiri, Marie-Paule Delplancke, Rony Snyders Nitrogen fixation (NF) is a crucial industrial process to convert nitrogen into valuable compounds, such as NH3 or NOx. The renowned Haber–Bosch’s (H–B) process to synthesize NH3 relies on fossil fuel and releases CO2. Plasma-based processes are a green and efficient technology that could be an alternative. Taking advantage of a synergy between plasma and catalyst is a promising approach to improve the performances of the plasma-based processes. |
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HW6.00078: Study of ozone oxidation of dimethyl sulfide and surface analysis of iodine catalysts Yoshinori Mizuno, Ahmad Y Guji, Jaroslav Kristof, Eizo Murakami, Kazuo Shimizu This study, reports on ozone catalytic oxidation of dimethyl sulfide; a major odor material of waste water facilities. Xenon excimer lamp (XEL) was used for ozone generation, and iodine (I- and IO3-) were utilized as a catalyst. Activated carbon impregnated with iodine and sulfate, activated carbon impregnated with iodine and activated carbon without impregnation were tested as catalysts. Only activated carbon impregnated with iodine and sulfate had catalytic activity in the dynamic adsorption experiment. Breakthrough time of dimethyl sulfide was increased by 10 times by adding ozone in activated carbon impregnated with iodine and sulfate. Catalyst characterization by pH measurement and XPS analysis suggested that catalytic activity of iodine was influenced by the surface acidity. These results suggest that the XEL and activated carbon impregnated with iodine and sulfate are applicable in ozone catalytic oxidation in gas treatments. |
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HW6.00079: Auto-methanation using plasma catalysis at room temperature Shuya Xu, Chunyuan Zhan, Tomohiro Nozaki, Hyun-Ha Kim Recently, it has been reported that combined oxygen supply promotes the auto-methanation of CO2 at room temperature, which opens a new pathway for the conversion of CO2. In our previous studies, it was confirmed that plasma catalyst systems contribute to enhanced methanation, but there is no precedent whether auto-methanation can be achieved using plasma catalysis. In this study, we developed automatic methanation using plasma catalysis at room temperature and compared the CO2 conversion at different air pressures at the same GHSV. The results show that CO2 conversion can be 100% when the H2/CO2 ratio is greater than 5 times, and when the H2/CO2 ratio is 5 times, the CO2 conversion at low pressure reaches more than 90% compared to high pressure. Automated methanation is achieved at both pressures, with 91% CO2 conversion at 30 kPa at a lower temperature (310°C), while it takes 380°C at 80 kPa to achieve the same conversion. This study confirms that auto-methanation can be achieved at room temperature using a packed-bed DBD reactor with a plasma catalytic system, opening up a new way of using plasma to convert CO2 and providing the feasibility for further mechanistic analysis |
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HW6.00080: Dependence of structure of carbon nanowalls anode electrode on property of lithium-ion batteries Jumma Kagami, Mineo Hiramatu, Keigo Takeda Lithium-ion (Li+) batteries have become indispensable to modern society. Currently, the anode made of graphite-based material is used in most of the Li+ batteries. |
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HW6.00081: Polyaniline-Crystalline Rubrene nanosystem Synthesis by One-step Plasma Based Route: Application in Optoelectronics by Plasmonic Functionalization Deepshikha Gogoi Crystallization of organic small molecule Rubrene is a tedious job when conventional route such as vapour phase deposition is adopted for its synthesis. The amazingly high conductivity exhibited by crystalline Rubrene is the reason behind researchers looking for easy and sustainable alternate routes for its synthesis. In this report, a single step plasma based synthetic route of Rubrene is illustrated through which we have successfully synthesized Rubrene in crystalline form along with polyaniline thin film. In addition to the synthesis of plasma polymerized aniline (PPA)-crystalline Rubrene (CRB) thin film, we further incorporated magnetron sputtered gold nanoparticles (Au NPs) in it and integrated this PPA-CRB/Au structure in bilayer optoelectronic device architecture. The Au incorporated device exhibits enhanced photocurrent, responsivity and detectivity over the broadband wavelength range UV-visible-near infrared attributed to the increased absorption in the visible region due to Rubrene and the plasmon absorption of Au in the NIR region. Moreover, both the devices can operate in self-powered mode and show very fast response to the switching light signal of 1 Hz frequency. This study thus throws light on removing the hurdles of crystalline Rubrene synthesis and its application in optoelectronics. |
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HW6.00082: Inhibition of recurrence of mouse melanoma B16F10 tumors in mice using streamer discharge Ryuichiro Ito, Atsushi Komuro, Hideyuki Yanai, Ryo Ono Cancer recurrence is one of the major problems in cancer therapy. Recurrence occurs, for example, from the residue of microscopic cancer cells after surgical resection of tumors. In this study, we examined whether irradiation of streamer discharge to excisional scars of surgically resected tumors in mice can inhibit the recurrence. Mouse melanoma B16F10 tumors in the right leg of mice were surgically resected, and then the resection scars were irradiated with streamer discharge before suturing the scars. Thereafter, tumor recurrence was observed. Usually, when tumors are resected, a larger area than the visible tumor is resected to prevent recurrence. But in this experiment, only the visible tumor was removed to intentionally cause recurrence. The results showed that the discharge treatment reduced the tumor recurrence ratio by approximately half. The plasma treatment could be a promising method to inhibit tumor recurrence. |
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HW6.00083: Molecular introduction into barley seed growth point using plasma Ryosuke Ueshima, Yuki Hamada, Yoshihisa Ikeda, Yugo Kido, Takashi Yaeno, Masafumi Jinno If cells at the growth point are genome-edited, all cells after cell division will be genome-edited cells, and the target plant will acquire new traits. However, the technology to introduce genome editing tools directly and non-invasively into plant cells has not yet been established. In this study, we tried to introduce molecules into the growth point of barley seeds by plasma treatment. |
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HW6.00084: Inactivation of Breast Cancer Cells using Nitrogen-Oxygen-Radical-Activated Lactate Ringer's Solution Taiga Nishida, Naoyuki Iwata, Tomiyasu Murata, Hiromasa Tanaka, Masaru Hori, Masafumi Ito Plasma-activated lactate Ringer's solution (PAL) has been reported to be able to selectively inactivate various cancer cells against normal cells. However, plasma contains various factors and it has not been clarified which factors in plasma contribute the production of cytotoxicity effects in PAL. To investigate the individual contribution of these species, we employed an equipment that can irradiate only neutral species. Using this, we prepared nitrogen-oxygen-radical-activated lactate Ringer's solution (NORAL). In our previous study, NORAL has been reported to inactivated skin cancer cells. However, the inactivation effect on other cancer cells have not been fully investigated. Therefore, we have evaluated the effectiveness of NORAL on other cancer cells. The flow rates of Ar, N2 and O2 were set at 1.6, 0.12, and 0.48 slm, and the breast cancer cells and normal cells were treated with prepared NORAL. The cell viability of cancer cells was reduced to 19 and 42% using the 1- and 2-fold diluted NORAL whereas that of normal cells was reduced only to 48 and 75%, respectively. These results indicate that electrically neutral radicals are ones of key species for a production of cytotoxic effects in PAL. |
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HW6.00085: Plant disease suppression through the activation of plant immunity using N2O5 gas generated from air by atmospheric-pressure plasma device Daiki Tsukidate, Keisuke Takashima, Shota Sasaki, Shuhei Miyashita, Toshiro Kaneko, Hideki Takahashi, Sugihiro Ando We developed a plasma device which can produce high-concentration dinitrogen pentoxide (N2O5) gas from air, which is poorly understood in biological function. Here, we analyzed the effect of N2O5 gas on plant immunity using model plant Arabidopsis thaliana. First, A. thaliana was exposed to N2O5 gas and then inoculated with Botrytis cinerea, a fungal pathogen. After 2 days inoculation, significant reduction in lesion size of B. cinerea was observed in N2O5-gas-exposed plants compared to air-control, suggesting that disease resistance was enhanced by N2O5 gas. To examine changes in gene expression of defense-related genes, RNA-seq and qRT-PCR was performed using N2O5-gas-exposed plants. Gene Ontology analysis based on the RNA-seq results revealed that the signaling pathways for jasmonic acid (JA) and ethylene, phytohormones important for plant immunity, was activated by N2O5 gas exposure. In addition, qRT-PCR analysis showed that N2O5 gas exposure transiently activated gene expression involved in biosynthesis of antifungal substances. In JA signaling mutant, furthermore, B. cinerea resistance induced by N2O5 gas was compromised. Our results suggest that N2O5 gas generated from air plasma is available for development of environmentally friendly technology for plant disease control. |
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HW6.00086: Degradation of lignin model compounds using ambient-air glow discharge Ryuichi Ohashi, Naoyuki Iwata, Hiroyuki Kato, Motoyuki Shimizu, Masashi Kato, Masaru Hori, Masafumi Ito Lignin is a persistent polymer and needs to be degraded to obtain bioethanol from woody materials. In this study, we propose an environmentally friendly method of degrading lignin using plasma. We developed an ambient-air glow discharge(AAGD). The AAGD was developed as atmospheric pressure plasma sources allowed treatments of various targets by reactive species not employing vacuum systems. In this study, we attempted to cleave the structure of a lignin model compound, guaiacyglycerol-β-guaiacyl ether (GGE), using AAGD. The GGE solution was treated using the AAGD plasma for 0, 2.5, 5, 7.5, and 10 min. The decomposition degrees of GGE samples using the AAGD were estimated using a high-performance liquid chromatography (HPLC) connected with a photodiode array (PDA) detector. |
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HW6.00087: Investigation on Reaction of Plasma-generated Dinitrogen Pentoxide Gas with Amino Acids Yuto Oba, Shota Sasaki, Keisuke Takashima, Toshiro Kaneko Atmospheric-pressure plasma (APP) technology, enabling to convert air molecules into reactive species [e.g., reactive oxygen and nitrogen species (ROS and RNS)] with electricity, is of great interest and has been extensively investigated. Recently, we have developed a new air APP device/method that allows highly selective production of dinitrogen pentoxide (N2O5) exclusively from only air and electricity sources. In addition, we demonstrated the plasma-generated N2O5 gas elicited activation of plant immunity and plant disease resistance was enhanced in Arabidopsis thalianaexposed to the N2O5 gas. In this way, N2O5 is a promising chemical for a variety of applications, while the fundamental experiments using N2O5 are still scarce. In this study, we focused on the interaction of the plasma-generated N2O5 gas with several standard amino acids such as tyrosine and cysteine, and have investigated plasma-generated reactive species and amino-acid derivatives. In particular, composition of tyrosine derivatives generated by the treatment of the plasma-generated N2O5 gas strongly depended on reactive species other than N2O5 transferred into solution. In the presentation, we will introduce results using some kinds of amino acids derivatives and discuss the reaction mechanisms. |
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HW6.00088: Viscous reduction of carboxymethyl cellulose treated with ambient-air glow discharge using peristaltic pumps Kazuma Okamoto, Masahiro Maebayashi, Motoyuki Shimizu, Masashi Kato, Masaru Hori, Masafumi Ito Recently, the applications to biofuel processes have attracted much attention owing to the wide-spread concerning of fuel depletion. A highly promising way of production of low-cost biofuel is utilization of lignocellulosic materials. Lignocellulosic materials consist primarily of cellulose, hemicellulose, and lignin and are persistent. Therefore, chemical pretreatment methods such as acids and alkalis are necessary to improve the efficiency of enzymatic degradation. However, these methods have an environmental impact in the waste-liquid treatment. The radical irradiation of suspensions of carboxymethylcellulose (CMC) revealed that oxygen atoms are very effective to decrease CMC molecular weight for improving the efficiency of enzymatic degradation, but it was not suitable for practical use because it employs Ar and O2 gases. We have developed an atmospheric-pressure plasma device generating plasma using ambient air with peristaltic pumps to improve the reaction of radicals and CMC. From the results using the device, it was confirmed that the viscosity changes depending on the flow rate of the pump and found that molecular weight of CMC decreases more effectively than that of the oxygen radical irradiation. |
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HW6.00089: Calcium Based Systemic Activation of Plant Defense by Exposure to Plasma-generated N2O5 Hiroto Iwamoto, Shota Sasaki, Keisuke Takashima, Atsushi Higashitani, Masatsugu Toyota, Toshiro Kaneko Recently, we have developed a new air atmospheric pressure plasma (APP) system that allows selective production of dinitrogen pentoxide (N2O5). N2O5 is a promising chemical for a variety of applications, but it has not been used widely due to the difficulties of its production and storage. Our APP device/method enables in-situ production and supply of N2O5 with easy handling. Here, we explored the applicability of the APP-generated N2O5 in agriculture. O3 exposure has been reported to induce systemic acquired resistance in the phytohormone salicylic acid pathway, which generally causes growth retardation. On the other hand, we found that N2O5 exposure can induce plant defensin genes such as PDF1.2 that follow a jasmonic acid (JA) pathway without growth retardation in Arabidopsis thaliana. Cytosolic Ca2+ concentration was increased in a single leaf directly exposed to N2O5 and the Ca2+ signal propagated to non-exposed leaves within 1 min. The Ca2+ response is similar to a wound-induced response, which elicits a systemic defense response by JA. We also found that expression of JA-related genes was significantly induced in both exposed and non-exposed leaves. These results indicate that the APP-generated N2O5 exposure provokes a systemic defense response without growth retardation. |
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HW6.00090: Growth promotion of Arabidopsis thaliana using oxygen-radical-treated l-tryptophan solution Araki Shota, Tomomichi Ota, Hironaka Tsukagoshi, Naoyuki Iwata, Masaru Hori, Masafumi Ito Recently, plant-growth-promoting effects of oxygen-radical-treated amino-acid solutions are attracting interests. In this study, we evaluated the growth-promoting effect of oxygen-radical-treated l-tryptophan (l-Trp) solutions, reported to have strong bactericidal effects as well, on Arabidopsis thaliana (A. thaliana). An atmospheric-pressure radical source, which can selectively irradiate only electrically-neutral species in the plasma, was used to treat a 50 mM l-Trp solution. The radical source was driven with a gas mixture of Ar and O2, their flow rates were set at 4.96 and 0.03 slm, respectively. The treated solution was diluted to 1, 5, 10, 20, 50 μM, and then mixed with MS medium (supplemented with 1% sucrose and 1% agar). Seeds were germinated on control MS or with the diluted solution. Plants were grown vertically in a growth chamber at 22 °C under 16-h light/8-h dark conditions. We assessed whole root length when treated for 7days. On oxygen-radical-treated l-Trp medium, the root length was longer than that of MS medium. The maximum promoting effect was observed on the 5 µM oxygen-radial-treated l-Trp plate. These results suggest that oxygen-radical-treated l-Trp solutions with strong bactericidal effects have a potential to promote the growth of plants as well. |
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HW6.00091: Atmospheric pressure plasma generation at liquid interface for nitrogen fixation Ritsuki Fujita, Keisuke Takashima, Toshiro Kaneko In recent years, plasma nitrogen fixation has been proposed as a sustainable nitrogen fixation method, which composes nitrogen compounds exclusively from air and water. The energy cost for the plasma nitrogen fixation, reaction processes from nitrogen dissociation to storable nitrogen compounds such as nitrate, is an unresolved issue despite of its accessibility to renewable energy sources. This study focuses on exploring the nitrogen fixing reaction pathways at the plasma - liquid water interface, where radicals can directly reach and unknown reaction pathways, potentially beneficial to overcome the energy cost, might exist. This work specifically focuses on characterizing the air and nitrogen plasma generation at the liquid water interface with approximately 10 to 50 kHz AC high voltage, allowing significant specific energy input aiming for radical generation affecting near-surface reactions. Discharge plasma volume extension with multiple electrodes configuration is found effective for tuning the power density with 50 kHz burst AC discharge. These plasma control at the interface enables reaction studies at the plasma-liquid interface. Further discussion on the plasma-liquid interface will be presented, regarding the electric charge and the reactive species generation. |
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HW6.00092: Development of Gene Transfection Method Using Combined Plasma and Pulsed Electric Field in Liquid Ryosuke Honda, Shota Sasaki, Keisuke Takashima, Makoto Kanzaki, Takehiko Sato, Toshiro Kaneko There is a big demand of gene transfection technology in various fields including biological, agricultural, and medical field (e.g., cancer therapy, genetic modification, making the induced pluripotent stem (iPS) cells). In this study, experiments for development of a new method of gene transfection into living cells using discharge in liquid (plasma in liquid) have been conducted. As a new gene transfection method, a treatment using plasma in liquid combined with pulsed electric field was proposed. By the treatment with plasmid DNA (pDNA), we achieved a high transfection efficiency of more than 40% in an adherent cell line (MCF-7) and that of more than 20% in a floating cell line (Jurkat). In addition, cell viability at 24 hours after the treatment was over 60% in each cell line. These results indicated the proposed method was highly efficient and less invasive, and showed a potential to be further improved. In the presentation, recent results including improvement of gene transfection efficiency will be discussed. |
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HW6.00093: Nitrogen fertilization effects of Plasma Generated Dinitrogen Pentoxide Shouki Takeshi, Keisuke Takashima, Shota Sasaki, Atsushi Higashitani, Toshiro Kaneko Currently, nitrogen fertilizer, which is indispensable for crop production, is mainly synthesized by the Harbor-Bosch process consuming natural gas and a large amount of energy. Alternatives are awaited in terms of global sustainable development goals. Recently, selective synthesis of dinitrogen pentoxide, anhydride of nitric acid, has been established using air discharge plasmas exclusively from inexhaustible air. This plasma nitrogen fixation converting nitrogen in air into nitric acid precursor can play a role in fixing nitrogen even in farming field, while symbiotic rhizobia in legumes, directly converting nitrogen in air into ammonia, performs nitrogen fixation in nature. In this study, the growth of a model legume, Lotus japonicus, with the plasma nitrogen fixation (supply of dinitrogen pentoxide) was compared to the growth with rhizobia inoculation as a measure of the plasma nitrogen fixation efficacy. As a result, dinitrogen pentoxide became an indispensable nitrogen source for Lotus japonicus growth, when it was dissolved in water supply and directly blown onto plants as a gas. The balance between the damage caused by direct blowing to plants and the effects of nitrogen fertilization will also be presented in the poster. |
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HW6.00094: Spatiotemporal distribution measurements of ozone in the gas and liquid phases generated by non-equilibrium atmospheric pressure radical source Hiromi Alwi Yamamoto, Masaru Hori, Masafumi Ito The beneficial effects of plasma treatment are induced by active species of various lifetime. Especially, it is difficult to measure the temporal and special distributions of short-lived species including liquid phase as well as gas phase. To overcome the issue, we have constructed a novel measurement system that enables spatiotemporal absorption spectroscopy with high speed and spatial resolution. |
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HW6.00095: Measurement of Reactive Species Produced by Discharge in Medium for Highly Efficient Gene Transfer Kazuki Oikawa, Shota Sasaki, Ryosuke Honda, Toshiro Kaneko There is a big demand of highly-efficient and minimally-invasive gene transfer technology. Conventional gene transfer methods have some problems such as low efficiency, high cytotoxicity, and high side-effect. Our research group has developed a gene transfer method using plasma in medium, which could potentially overcome the problems. However, most of the mechanism of the gene transfer using the discharge in medium remains unclear. Specifically, reactive species generated by the discharge in medium can be responsible for transfer efficiency and cell viability, but have not been investigated well. In this study, we have tried to quantify reactive species (H2O2, •OH, HOCl/OCl−) generated by discharge in Opti-MEM, a well-known serum-reduced media for gene transfer. As number of discharges (N) increased, H2O2 and •OH were significantly detected and produced with the total discharge duration, while the concentration of HOCl/OCl− was not detected and was under the detection limit of 0.5 µM even at N = 10. This indicates that reactive oxygen species (ROS) can be predominantly generated compared to reactive chlorine species (RCS). In the presentation, chemical reactions induced after the discharge in Opti-MEM will be discussed. |
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HW6.00096: Numerical modeling on cell death induction by low-temperature plasma Hayata Kanda, Tomoyuki Murakami We propose a time-dependent 0D numerical modeling on apoptosis induction by low-temperature plasma, which involves activation of death-receptors, mitochondrial signaling cascade pathway including the disruption of mitochondrial membrane potential, initiator- and executor-caspases and regulators. The effects of plasma irradiation can be modelled as exogenous or endogenous influence. The biochemical system is kinetically solved through a time-dependent 0D numerical simulation involving about 100 agents and about 300 reactions. Our simulation suggests that mitochondrial membrane potential drops due to tBid-(Bax)2 generated by exogenous plasma effects, which in turn results in decreased ATP and released cytochrome c. We shows a time trace of concentration of activated caspase3 at the different H2O2 influx during the first 30 minutes. We suggest that the larger H2O2 dose causes the faster activation of caspase 3, which in turn results in the apoptosis. |
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HW6.00097: Numerical modeling on the dynamic behavior of immune cells Chihiro Takazawa, Tomoyuki Murakami Leukocytes (neutrophils and macrophages) are responsible for extremely effective immune functions in the human body. Each leukocyte has a dynamic behavior such as the ability to autonomously find bacteria (migration) and capture and sterilize them (phagocytosis), and they kill bacteria that invade the body in groups. The wound healing effect of low-temperature plasma is one that was recognized from a relatively early time. Plasma exposure to the affected area shortens the time required for healing. It has been suggested that this is mainly due to the bactericidal effect of ROS (Reactive Oxygen Species) generated by plasma exposure. While recently, it has also been suggested that plasma can affect the behavior of immune cells, the effect of plasma on the process of colonial leukocyte bactericidal action is still unknown. In addition, no attempt has yet been made to elucidate this event through mathematical modeling. Here, we develop a time-dependent two-dimensional mathematical model to simulate the most basic functions of immune cells, i.e. migration and phagocytosis. As a primary stage, this model describes the dynamic behavior of leukocyte bactericidal action, in which neutrophils and macrophages play important roles as innate immunity (cell-mediated immunity) agents. |
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HW6.00098: Characterization and Comparison of Atmospheric Pressure Plasma Sources for Medical and Biological Applications Sophia Gershman, Oliver Huang, Henry L Fetsch, Shurik Yatom, Yevgeny Raitses Plasma devices have been gaining acceptance in the medical field but haven’t yet reached an average consumer. Devices based on surface dielectric barrier discharges (DBD) in air at atmospheric pressure have the advantages of safety, portability, and ease of use and hence have the potential for broad applications and general consumer use. We characterize a single-barrier and a double-barrier DBD plasma source in terms of the production of active species, energy consumption, scalability, and disinfection efficiency. Similarly to other atmospheric pressure plasma sources operating in air, these devices produce higher relative concentrations of ozone at lower power and higher concentrations of reactive nitrogen species at higher operating power. Chemical output combined with plasma characterization provides information that can be used to compare various types of plasma devices. We discuss the feasibility and limitations of this and other approaches to comparing various plasma sources for medical and biological applications. |
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HW6.00099: Effect of the magnetic field topology on azimuthal spoke oscillations in Hall thruster Yevgeny Raitses, Andrei Smolyakov Low-frequency (typically <100 kHz) spoke oscillations are commonly observed in ExB devices including Hall thrusters, magnetron discharges etc. The spoke mode manifests itself as strong perturbations in plasma density that propagate in the ExB direction perpendicular to the crossed electric (E) and magnetic (B) fields, generating substantial components in electric field in this ExB direction [1]. In Hall thrusters, the spoke propagates in the azimuthal direction. The most prominent spoke oscillations are usually observed inside the thruster channel near the anode electrode [2]. In this work, we report the effect of the magnetic field topology in this thruster region on spoke oscillations, correlate this effect with measured plasma properties [3] and relate these experimental results to a collisionless Simon-Hoh instability [1]. |
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HW6.00100: High-enthalpy portable RF plasmatron for nonequilibrium flow analysis Andrey Starikovskiy Ground test facilities such as plasma torches are critical to understanding hypersonic flow and high enthalpy fields as they simulate hypersonic velocities and reentry conditions. In particular, they are used to reproduce the aerothermodynamic heating experienced by the aircraft during the entire flight, as well as to test and certify heat shields and thermal protection systems. The purpose of this program is to develop an apparatus for high-enthalpy low-pressure plasma generation using an induction-coupled discharge. The installation is designed to develop new methods for plasma diagnostics and testing of thermal insulating materials. The installation provide a continuous plasma flow with a mass flow rate of up to 0.1 grams per second with a specific enthalpy of up to 20 MJ/kg. The installation uses a standard high-frequency generator at frequency of 13.56 MHz and RF power 1.5 kW. |
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HW6.00101: Measurement of thrust induced by a water-fueled magnetron sputtering source Sota Shimizu, Kazunori Takahashi Development of a compact electric propulsion device is a key issue for orbital control of small satellites. In general, gaseous propellant introduced from a high-pressure gas storage tank is ionized and the ions are accelerated and exhausted from the system. To avoid the charge up of the satellite and the resultant spontaneous formation of the electric field pulling back the ions, a neutralizer has to be mounted as often used in gridded ion thrusters and Hall effect thrusters. Various approaches have been made for compact thrusters, such as liquid and solid propellants, a neutralizer-free radiofrequency thrusters, vacuum-arc thrusters, and so on. One of the authors has reported the thrust generation by a magnetron sputtering source, where the electrically neutral sputtered particles are responsible for the thrust generation. These results implies that the magnetron sputtering source does not require the neutralizer to obtain the thrust, while argon gas propellant has still been used to sustain the discharge. Here we report the operation of the magnetron sputtering source with a liquid water propellant and the induced thrust is assessed by using a target force stand. The results show the thrust-to-power ratio of about 3-4 mN/kW and the power level of the discharge is about 80 W. |
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HW6.00102: Numerical Simulations of the Plasma Dynamics in an ECR Thruster Experiment Subhasish Bag, Vikrant Saxena Electrodeless plasma thruster (EPT) is an advanced concept in the field of electric propulsion devices, in which instead of a solid nozzle, a magnetic nozzle (MN) helps to accelerate the plasma ions [1] using its convergent-divergent magnetic field. The principle mechanism of MN is to convert the internal thermal energy of electrons into the directed kinetic energy of the ions. In this way, the guided plasma expands and produces a significant amount of thrust. We are interested in studying the behavior of the expanding plasma coming out of a Compact ECR Plasma Source (CEPS) [2] developed by Plasma Physics Laboratory (PPL), IIT Delhi. The CEPS based on a permanent magnet produces high-density plasma and it is portable and flexible in use. We numerically investigate the plasma dynamics in the magnetic configurations [3] compatible with the CEPS. |
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HW6.00103: Plasma-CVD Enabling Seeded Growth of Nanocarbons from a Single Carbon-Nanoring Rikizo Hatakeyama, Hiroshi Ueno, Eunsang Kwon, Fuminori Misaizu Enormous interest for applications ranging from electronics to therapeutics has been given to nanoscale carbon members (nanocarbons) with different dimensions such as 0D fullerenes, 1D carbon nanotubes, 2D graphene, 3D nanodiamonds due to their unique physical and chemical properties [1]. Here, one of the future challenges is considered to establish dimensional-fusion science and technology of the nanoscale materials, where fundamental studies on their synthesis such as exploring alternative/new methods for precisely structure-controlled, selective, impurity-free, composite, and architectural growth are of inevitable importance to follow a path toward the goal. In this light, we have strived to synthesize 1D single-walled carbon nanotubes (SWNTs), 2D graphene and graphene oxides (GO), and 3D vertical graphene (VG) by alcohol plasma-enhanced chemical vapor deposition (PECVD) without using metal catalysts regarded as impurities, where a single hoop of carbon six-membered rings (carbon nanoring: CNR) [2] is adopted as the seeded-growth molecule. Depending on the PECVD-parameter (growth-substrate temperature: Tsub, intensity of plasma influx to substrate: mild or harsh) region, it is found for the first time that the precisely structure(chirality)-controlled SWNT, GO, VG, and single-layer graphene grow for Tsub=350 ℃ / mild plasma, 700 ℃ / mild, 700 ℃ / harsh, and 1000 ℃ / harsh, respectively. [1] R. Hatakeyama, Rev. Mod. Plasma Phys. 1, 7 (2017). [2] S. E. Lewis, Chem. Soc. Rev. 44, 2221 (2015). |
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HW6.00104: Effects of minor addition of N2/O2 impurities on silicon nanostructure formation behavior in hydrogen plasma process Toshimitsu Nomura, Naoki Tamura, Ken Sakamoto, Hiroaki Kakiuchi, Hiromasa Ohmi We have developed various Si processing techniques using a relatively high-pressure hydrogen plasma (> 3 kPa). In the course of developments, we found that hydrogen plasma treatment with minor air addition led to a micrometer-scale cone structure on the Si surface. Since this obtained surface showed very low reflectance (0.5%), this hydrogen plasma technique is expected to apply to high-performance photoelectric devices. In this study, we investigated the impacts of minor N2/O2 gas addition (flow rate concentration < 1%) into hydrogen plasma on the obtained Si surface morphology after the plasma process. As a result, we revealed that a small amount of N2 addition resulted in pillar Si nanostructure formation with rounded tips. On the other hand, O2 addition led to minor roughening Si surface. In addition, when the N2 and O2 were simultaneously supplied to the process atmosphere, the high-aspect-ratio Si nanocone could be obtained. The optical emission spectra of the plasma implied that minor O2 addition enhanced atomic hydrogen generation in the plasma. This result suggests that O2 addition promotes the formation of sharp-tipped nanocone structure through enhancement of chemical etching by atomic hydrogen. |
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HW6.00105: Investigation of optical property of tungsten-doped zinc oxide films deposited by sputtering Sho Kakuta, Takeru Okada, Katsuyoshi Washio Tungsten-doped zinc oxide (WZO) was deposited on quartz glass substrates by sputtering with tunable doping of tungsten for application as a phosphor material. The crystallinity and photoluminescence (PL) property of the films were characterized by X-ray diffraction (XRD) and PL measurement. The XRD patterns show that ZnWO4 and ZnO exist at low doping concentration, and the component of the WZO phase is changed to mixture of ZnWO4 and WO3 at high doping concentration. The WZO films show photoluminescence by ultraviolet light, resulting in a broad emission which is useful for white light emission. The highest internal quantum efficiency (QE) in our condition is 76% when 46 at.% of tungsten is doped and the QE are different between excitation side, which suggests the segregation of materials in the film thickness direction. The decreases of QE at low and high concentrations with a boundary of 46 at.% indicate absorption of excitation light by ZnO and WO3, that inhibits excitation of ZnWO4. These analyses suggest that QE is determined by segregation of biproduct in the films. Therefore, the suppression of formation of biproduct is considered essential to obtain strong luminescence from WZO. Our investigation provides importance of the doping control in WZO for white-LED applications. |
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HW6.00106: Elucidation of Ignition-Area Extension of Barrier Discharge under High Temperature and its Application to Precise Control of Nitridable Area Kaito Yakushiji, Saki Wakabayashi, Ryuta Ichiki, Kosuke Tachibana, Takashi Furuki, Seiji Kanazawa A planer DBD has recently been discovered to extend its ignition area gradually with increasing the ambient temperature. In this study, we investigated the physical mechanism of the DBD extension phenomenon under high temperature. Our numerical analysis of the reduced electric field showed that the increases in temperature (corresponding to the decrease in molecular density) and in applied voltage both increase the area of reduced electric field over 120 Td, which is the breakdown value. That is, the DBD extension phenomenon proved to result from extension of the reduced electric field. From this fact, we predicted that decreasing the applied voltage will suppress the DBD extension even under high temperature. Second, we conducted nitriding experiments to confirm if the nitridable area can be controlled following the controlled DBD ignition area. Here, N2-H2 mixture with H2 partial pressure of 10% is used. 20x20 mm2 steel samples were used as the ground electrode, the treatment temperature was 800 K, and the treatment time was 2 h. As a result, we succeeded in controlling the ignition area of DBD and the nitridable area even at 800 K by adjusting the applied voltage. The use of a point electrode with a diameter of 0.7 mm as the opposite electrode minimized the plasma ignition area and enabled submillimeter local nitriding without masking. |
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HW6.00107: Synthesis of nanographene-Si composite material using gas-liquid interface plasma Kazushi Masuda, Keigo Takeda, Mineo Hiramatsu Lithium-ion batteries use graphene as the anode material. To achieve the higher capacity, composite anode materials consisting of graphene and Si have been investigated. In this study, nanographene and Si particle composite materials were synthesized using a gas-liquid interface plasma synthesis process which can be performed under atmospheric pressure. |
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HW6.00108: Comparative Study on Formation of Boride Thin Films Deposited by Co-sputtering with Molybdenum Kazuki Nashimoto, Yoshiko Horiguchi, Akichika Kumatani, Takeru Okada Ammonia plays a crucial role in our society. Ammonia is used as a hydrogen carrier for energy conversion, combustion source without emitting carbon dioxides, and an important element for plant growth. The Harber-Bosch process, which consumes large amount of energy, still supports the demand for ammonia. In this situation, development of an alternative method for ammonia synthesis is required. In this study, we demonstrated deposition of metal contained borides by co-sputtering method and followed calcination to investigate crystal formation under relatively mild condition. The crystal structure of the deposited film is confirmed by x-ray diffraction, and underlayer of aluminum does not affect crystallization process of aluminum diborides films. In the case of molybdenum is co-sputtered, part of molybdenum is diffused into silicon substrate, resulting in formation of Mo-Si bonds. Suppression of diffusion process would be the key to the formation of highly crystalline borides. Surface morphology was observed by scanning electron microscope and layered-structure is found at the surface of the films. This structure is originated from 2D structure of borides. Additionally, we investigated electrocatalysis of molybdenum-aluminum boride thin film in a nitrogen-saturated electrolyte solution. Linear sweep voltammetry reveals that the film has an electrocatalysis of ammonia synthesis, confirming sufficient current density. |
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HW6.00109: Infrared absorption spectroscopy of astronomically relevant reddish substances produced by cryoplasma irradiation of ice surface Shota Ide, Phua Yu Yu, Noritaka Sakakibara, Hitoshi Muneoka, Tsuyohito Ito, Kazuo Terashima Plasmas are applied to simulate energetic processes in space, and production and analysis of red organic materials, that show similar features to red organic materials observed in the outer solar system, have been reported. These organics could lead to understanding the origin of life and the formation process of the solar system. Recently a phenomenon, in which ice surface turns reddish only in cryogenic temperatures below 150 K, was observed in an experiment using cryoplasma [1]. This temperature dependence of coloration had not been reported in previous studies. However, the material, which is responsible for the reddish coloration, still needs to be investigated, e.g. for understanding its structure. |
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HW6.00110: Plasma Carburizing and Nitrocarburizing for Composite Austenitic Stainless Steel with Tungsten Carbide Fabricated by LMD Shinichiro Adachi, Takuto Yamaguchi, Keigo Tanaka, Nobuhiro Ueda Plasma Carburizing and Nitrocarburizing for Composite Austenitic Stainless Steel with Tungsten Carbide Fabricated by LMD |
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HW6.00111: Relationship between vibrational temperature and CO2 methanation with plasma catalysis Susumu Toko, Taiki Hasegawa, Takamasa Okumura, Kunihiro Kamataki, Kosuke Takenaka, Kazunori Koga, Masaharu Shiratani, Yuichi Setsuhara CO2 methanation technology has been attracting attention in order to realize a sustainable society. It is desirable to proceed the process at lower temperatures from the viewpoint of catalyst stability and equilibrium state, since the reaction is exothermic reaction. Plasma catalysis is a promising method which can achieve lower process temperatures. Methanation with plasma catalysis can be proceeded at 100 °C lower than conventional thermal catalysis process, which need the high temprature over 250 °C. The main factor can be generation of vibrational excited species due to collisions between the molecules and electrons. In this study, the vibrational temperature, which is an indicator of the density of generated vibrational excited molecules, was determined by optical emission spectroscopy, and the relationship between the vibrational temperature and methanation was investigated. We can estimate the vibrational temperature from the emission spectrum of the plasma. To derive the vibrational temperature, we used pgopher, which is a simulation software for optical emission intensity. As a result, the vibrational temperature increased with decreasing pressure and increasing discharge power. In addition, the CH4 generation rate increases exponentially with vibrational temperature. |
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HW6.00112: Plasma application to the fabrication of solid photocatalysts Muneaki Yamamoto, Muneaki Yamamoto, Tetsuo Tanabe Silver nanoparticles (Ag NPs) were synthesized by a solution plasma method (SPM) in an aqueous solution of ammonia. Optical emission spectra of the plasma revealed that Ag NPs are fabricated with the sputtering of Ag rods as electrode by the produced energetic plasma particles such as H, OH and O radicals. In-situ optical absorption measurements of the solution during the discharge directly presented the concerted formation and aggregation processes of the Ag NPs, which controlled the size of Ag NPs. The synthesized Ag NPs were loaded on gallium oxide (Ga2O3) photocatalyst, and the photocatalytic activities of the obtained Ag loaded Ga2O3 (Ag/Ga2O3) samples were evaluated. Although the photocatalytic reaction proceeded over all the samples to produce CO, the CO production rates decreased with the reaction time. Measurements of DR UV-vis spectra and TEM images revealed that a part of the Ag NPs migrated and aggregated on the photocatalyst surface to become larger particles during the photocatalytic reaction, which would be related to the decrease of the photocatalytic activity. It was also found that the photoirradiation treatment on the prepared Ag/Ga2O3 sample before the use for the photocatalytic reaction improves the photocatalytic performance. |
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HW6.00113: Extraordinary field emission of diamond film developed by microwave plasma jet chemical vapor deposition Chun-Yu Lin, Jing-Shyang Yen, Kaviya Aranganadin, Chi-Wen Liu, Chii-Ruey Lin, Jwo-Shiun Sun, Hua-Yi Hsu, Ming-Chieh Lin The present work reports both numerical and experimental studies of reconditioning a microwave plasma jet chemical vapor deposition (MPJCVD) system for diamond film growth. A three-dimensional plasma fluid model is constructed for understanding and conditioning the MPJCVD system and optimizing its operating conditions. The methodology solves electromagnetic waves and plasma dynamics selfconsistently using an adaptive finite element method. The whole system has been modeled under varying parameters including the reactor geometry, microwave power, and working gas pressure. Using an operating condition identical to the optimized simulation results, the thin diamond film has been fabricated successfully. The SEM image reveals the presence of a diamond film uniformly distributed with particles at a size of ~1 mm. The field emission from the diamond film grown from this MPJCVD shows extraordinary properties, i.e., extremely low turn-on voltage and high current density. The turn-on electric field could be as low as ~4 V/mm. This work provides more physical insights of the system and improves the performance of design. It may find applications in surface hardening and bright field electron emission. |
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