Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session GT61: Poster Session I (5:00-7:00 pm CDT) |
Hide Abstracts |
Room: GEC platform |
|
GT61.00001: Supersonic Hybrid Non-equilibrium Plasma Reactor for Co-Production of Hydrogen and Value-Added Solid Carbons from Methane Andrey Starikovskiy, Yiguang Ju The increasing concern of climate change requires immediate action to reduce CO2 emissions from directly burning fossil fuels. At the same time, the recent increase of renewable electricity and the need of large scale electricity storage provide a great opportunity to produce hydrogen and valuable carbon from natural gas by taking advantage of its abundant resource. The predominant commercial method for production of hydrogen and carbon from natural gas is the high temperature thermal cracking process. However, the thermal cracking method has low yield and produces less valuable carbon but large amounts of polluting emissions. The objective of this work is to develop and optimize an innovative supersonic hybrid non-equilibrium plasma reactor for efficient and tunable co-production of hydrogen and value-added solid carbons with negative CO2 footprint. The reactor for controlled methane reforming and H2/carbon synthesis is designed and assembled. Plasma modeling shows that a pulsed gliding arc can reach to 4000 K for transient chemical reforming. Supersonic nozzle provides rapid reaction quenching to enable non-equilibrium chemical synthesis to achieve higher yield and selectivity. |
|
GT61.00002: Variation in hysteresis phenomenon and electron density in Ar/He plasma Minseok Kim, Moo-Hyun Lee, Aixian Zhang, Chin-Wook Chung We observed changes in electron energy distribution and hysteresis phenomenon with varying Ar/He ratio in inductively coupled plasma. The results were obtained by measuring antenna current and electron energy probability function. Decrease of the hysteresis area is observed at 220 mTorr by increasing the helium, 'non-Ramsauer' gas, to the argon, 'Ramsauer' gas. Because the electron energy distribution changes from 'Druyvesteyn' to 'Maxwellian' in E-mode of the Ar/He plasma as the helium ratio increases. In helium plasma, there is no change in electron energy distribution which is 'Maxwellian' distribution. So as the helium ratio increases, it reduces the change in the electron energy distribution between mode transitions in ICP. Furthermore, in the case of pure helium plasma, we found that the electron density is higher than pure argon plasma in E-mode. Because the collisional energy loss of argon plasma in E-mode is larger than helium plasma, and the plasma absorption power is less than helium. |
|
GT61.00003: A study on the self-consistent step-wise global model: chamber geometry effect Jae Wang Ban, Hee Jung Yeom, Deuk-Chul Kwon, Jung Hyung Kim, Shin Jae You, Hyo-Chang Lee The global model based on the fluid approximation is a one of the efficient methods to understand the plasma parameters, such as electron temperature, excited densities, and plasma density, etc. In this study, we investigated the chamber geometry effect on the plasma parameters in argon inductively coupled plasmas using a self-consistent step-wise global model. External factors such as power, pressure, and chamber dimensions have been shown to significantly influence changes in plasma parameters and discharge characteristics. |
|
GT61.00004: Highly conductive carbon film deposition by DC and microwave power superposition Hansin Bae, Kensuke Sasai, Haruka Suzuki, Hirotaka Toyoda Highly conductive carbon film, a carbon film including high ratio of graphite-like structure (sp2 bond), is attractive material because of its superior properties such as its high electrical conductivity, anti-corrosion, low friction and so on. For the enhancement of the electrical conductivity of the film, higher ion flux as well as higher ion energy is required. In this study, high-density microwave plasma with high negative bias voltage source (<2 kV) was applied to deposit conductive carbon films. A vacuum vessel of 50 cm in length was equipped with a quartz plate (50×17 cm2) and was evacuated by a dry pump. Argon gas was introduced into the vessel through a mass flow controller and vaporized benzene (C6H6) was fed through another gas manifold at 3 cm away from the quartz plate toward a water-cooled substrate stage. In this study, the stage is negatively biased by a high impulse voltage generator (-2 kV, pulse frequency: 500 Hz, duty 10%). Film conductivity showed film sheet resistance drastically decreased at the bias voltage of ~ 1 kV, and was as low as 102W/sq. at 2 kV. Film conductivity was almost uniform at a length of ~20 cm along the waveguide direction. |
|
GT61.00005: A new atmospheric pressure plasma jet source with two plasma regions Eunseok Choe, Jung Hyung Kim, Dong-Wook Kim, Hyo-Chang Lee We studied effects of electrodes gap and tip shape on the discharge characteristics of a syringe-type atmospheric pressure plasma jet source (APPJS). The APPJS has a powered electrode and a floating electrode instead of a ground electrode. As the input power increases, a plasma column is first created in front of the tip of the powered electrode and is extended to the floating electrode which is capacitively coupled with powered electrode. As the plasma column reached to the floating electrode, the power transfers through the plasma and thus, the voltage of the floating electrode becomes similar to powered electrode voltage. Above a certain threshold voltage, the jet plasma is generated at the tip of the floating electrode and is emitted along the gas flow. Under the condition that the gap between the powered electrode and floating electrode is narrow, the threshold voltage for the ignition of the jet plasma is critically affected by the shape of the floating electrode tip. In the wide gap condition, on the other hand, the threshold voltage depends on the gap distance. |
|
GT61.00006: Two-dimensional effects of the asymmetric electrode on electron heating in dual-frequency capacitively coupled plasmas Ji Hyun Shin, Chang Ho Kim, Geon Woo Park Dual-frequency (DF) capacitively coupled plasmas (CCP) are commonly utilized in semiconductor etching and deposition processing because of their excellent spatial uniformity and easy control of ion energy. With a dual-frequency, the ion energy and the ion flux are separately controllable for the high-frequency (HF) and the low-frequency (LF) voltage waveforms, which are faster and slower than the ion transit time individually. Understanding the electron heating mechanism is essential to improve the performance of the process equipment. In this presentation, we report the asymmetry effect of the electrode structure on the spatial uniformity of the electron power deposition under DF driving conditions using a two-dimensional GPU-based particle-in-cell simulation [1, 2]. We found that the sheath width increases in the peripheral region of the asymmetric reactor when LF power increases so that electron heating inside the sheath also increases. It was also confirmed that the ion flux toward the wafer is uniform even for the asymmetric electrode when the upper electrode is longer than the lower electrode beneath the wafer. |
|
GT61.00007: Generation and control of electron beam via DC grid biased voltage in inductive coupled plasma Jiwon Jung, Moo-Young Lee, Chinwook Chung An electron beam generation using the grid system was investigated in an inductively coupled plasma (ICP). The electron beam was controlled and measured with varying pressure, ICP source power, and DC grid biased voltage. At low pressure (3 mTorr), an electron beam was generated even when a small voltage (10 V) was applied to the grid, but at high pressure (80 mTorr), an electron beam was generated when a higher voltage (30 V) was applied. At low pressure, the electron could be accelerated without collision between electrons and neutral species. However, when the applied DC voltage becomes too high, an electron beam is not generated, and the electron temperature decreases sharply. Because electrons gain high energy by the strong DC electric field, electrons lose their energy by ionizing neutral gases in the grid system. In addition, when the sheath length is shorter than the grid hole length, electrons that include both low and high energy electrons flow down through the grid freely. Therefore, generating an electron beam at the high electron density regime is difficult, such as increasing ICP source power because sheath length decreased. |
|
GT61.00008: The transition of electron energy distribution function according to Ar/O2 gas ratio in capacitively coupled plasmas Geonwoo Park In semiconductor manufacturing, oxygen plasmas are widely used in many processes such as photoresist ashing, polymer removal, oxidation, or deposition of thin-film oxides. These applications are adopted based on the advantages of oxygen plasmas in chemical diversity, such as several types of ions (e.g., O-, O+, and O2+) and chemically reactive species. Meanwhile, mixing Ar gas suitable for oxygen plasma can effectively generate ions and chemically reactive species under the same conditions. This work investigates the plasma characteristics by changing the mixture ratio of argon and oxygen using a two-dimensional particle-in-cell simulation parallelized with GPUs [1, 2]. The change in EEPF is observed according to the increase of the oxygen ratio. As the argon gas ratio decrease in an intermediate-pressure case (1 Torr), the electron energy probability function changes from the Druyvesteyn to the bi-Maxwellian distribution. |
|
GT61.00009: Instability-Induced Breakdown in Dual-Frequency Capacitively Coupled Plasmas Raymond Lau, Kentaro Hara, Jason Kenney, Shahid Rauf Capacitively coupled plasmas (CCPs) are commonly used in semiconductor fabrication as they allow precise control of ions and neutral radicals over large substrates. For high-aspect ratio etching and deposition, low-pressure operations are promising because more accelerated ions can be directed normal to the substrates. However, as the gas pressure decreases, the minimum threshold for plasma formation is reached (also known as breakdown). This phenomenon is well understood for dc discharges (as described by Paschen curves), but less understood for rf discharges. A 1D particle-in-cell, Monte Carlo collision coupled model is developed to investigate kinetic and non-Maxwellian behavior of a dual frequency, low temperature CCP at low pressures. A parametric study is performed varying the gas pressure from 2.6 Pa to 0.09 Pa at room temperature, below which the plasma is not formed. Preliminary plasma density and velocity distribution results suggest that at low pressures, bump-on-tail (or two-stream) instabilities are observed, which may play an important role in the dual-frequency rf breakdown. |
|
GT61.00010: Assessing effectivity and toxicity of misty plasma systems for disinfecting personal protective equipment Malik M Tahiyat, Nathan Ramanjulu, Yvonne Hui, Tanvir I Farouk, Traci L Testerman, Shamia Hoque Approximately 1.7 million health care associated infections occur each year in the U.S., killing 98,000 patients. COVID-19 has revealed further weaknesses in the preparedness of health care facilities, which lacked the ability to adequately disinfect existing personal protective equipment (PPE), exacerbating an already precarious situation. Chemical germicides, UV light etc. approaches have proven insufficient. Recently, application of dielectric barrier discharge (DBD) on biological substrates has been a topic of intense research. |
|
GT61.00011: A Fully Relativistic Approach to Photon Scattering and Photoionization for the Alkali Atoms Adam J Singor, Dmitry V Fursa, Igor Bray, Robert P McEachran Photoionization, Rayleigh and Raman scattering cross sections are of interest for modelling radiative transport, opacities and Raman spectroscopy. We have extended a method recently used to calculate Rayleigh and Raman scattering cross sections for hydrogen and the alkali atoms to a fully relativistic formalism. We model the alkali atoms as a single valence electron in a central local potential produced by frozen core electrons. Target bound states are obtained by diagonalizing the Dirac Hamiltonian in a basis of Dirac L-spinors that are commonly used in the relativistic convergent close-coupling method. Target continuum states are calculated using a finite-difference method, this allows a principal value integral to be taken over the continuum to deal with pole terms that arise in Rayleigh and Raman scattering for incident photon energies above the ionization threshold. This method has been used to calculate photoionization cross section from the ground and excited states of the alkali atoms: lithium, sodium, potassium, rubidium, and cesium. The influence of relativistic effects and core polarization on the depth and location of the Cooper--Seaton minimum in the photoionization cross section has been investigated and found to be important. Rayleigh and Raman scattering cross sections have also been calculated using this fully relativistic method, however we find that a semi-relativistic method is sufficient if core polarization is accounted for. |
|
GT61.00012: Effect of Laguerre-Gaussian beam propagation on TDLAS spectra observed using optical vortex Hiroki Minagawa, Hirokazu Kobayashi, Shinji Yoshimura, Kenichiro Terasaka, Mitsutoshi Aramaki The optical vortex (OV) is the center of the Laguerre-Gaussian (LG) mode, and its wavefront has a spiral shape. The particles in the OV feels the additional azimuthal doppler effect induced by the spiral wavefront. We are developing an optical vortex laser absorption spectroscopy (OVLAS) to detect the lateral particle flow using the azimuthal Doppler shift. Since the Doppler shift in the LG beam depends on the position in the beam cross-section, the fundamental LG beam is deformed inevitably by the non-uniform absorption. The deformed beam structure can be decomposed by the series of the LG modes. Since the Gouy phase shift depends on the order of the LG mode, the non-uniform beam structure represented by the superposition of different orders of the LG beams is varied with beam propagation. This unwanted change in beam structure deforms the Doppler spectrum obtained with OVLAS, so its effect must be clarified. We will discuss the detail of the propagation effect in the presentation. |
|
GT61.00013: Effect of laser plasma parameters on epitaxial growth of β-FeSe/SrTiO3 heterostructures Adam D. Smith, Kamron L Kopecky, Sumner B Harris, Mphande Phiri, Renato P Camata The combination of different materials in heterostructures often enables phenomena that are impossible to achieve in a single compound. A now-classic example is the interface-enhanced superconductivity of monolayer β-FeSe on (001)-oriented SrTiO3 (STO). Plasma-synthesized heterostructures based on this system are suitable for the creation of quantum materials configurations to study interface-enhanced processes, magnetic/superconducting proximity effects, and control of quantum properties via electrostatic gating. In this work, we show how tuning the laser-produced plasma of pulsed laser deposition can alter the structure and interface of β-FeSe/STO heterostructures. Langmuir probe diagnostics and thin film x-ray diffraction were utilized. Laser plasmas with electron density (ne) below ~5×1019 m-3 and electron temperatures (Te) of 0.1-0.2 eV lead to epitaxial c-axis oriented β-FeSe/STO with clear thickness fringes in dynamical x-ray diffraction (Pendellösung oscillations), indicating high crystal quality and sharp interface. On the other hand, plasmas with ne ~1020 m-3 and Te ≈ 0.5-0.6 eV result in β-FeSe with a mixture of two epitaxial orientations, less defined interface, and a greater degree of mosaicity or defects. We will describe how adjusting the laser plasma parameters may allow further control in plasma-mediated growth of β-FeSe/STO such as spatial modulation of nucleation sites, modification of island growth patterns, and activation of plasma-enhanced surface reactivity. |
|
GT61.00014: Filamentation in Capacitively Coupled Magnetized Plasmas Stephen Williams Recent experiments at the Magnetized Dusty Plasma Experiment (MDPX) at Auburn University have observed the formation of filamentary structures in capacitively-coupled, rf generated plasmas at high magnetic field (B ≥ 0.5 T) with distinct morphologies. For low neutral pressure (p ≤ 30 Pa), low RF power (PRF ≤ 5 W) conditions used in these studies, the plasma filaments, when viewed from the side, appear as bright vertical columns aligned parallel to the magnetic field. And, when viewed from the top, they form distinct structures that that can either be stable or mobile. In this work, the MDPX device is used to study the threshold conditions for filamentation formation under various pressure and applied magnetic field conditions. The experiments discussed here have identified and characterized the morphology of several distinct filamentary modes that are formed in low temperature argon plasmas. This presentation will focus on how those properties of the filaments compare with fundamental length scales in the plasmas (ion/electron gyroradii, collision mean free path, Debye length, etc.). |
|
GT61.00015: Plasma Streamer Propagation Across Free-flowing Bubbles in Water. Nicholas L Sponsel, Naveen Pillai, Igor A Bolotnov, Katharina Stapelmann Investigations into plasma dynamics confined by gaseous bubbles within a liquid medium has been of growing interest in the plasma-liquid community over the last decade. Computational investigations have demonstrated that ellipsoidal bubble shapes, along with topological deformations, result in enhanced or depleted local electric fields relative to spherical bubbles [1]. However, previous experimental methods tend to trap or hold bubbles in a manner that approximate a sphere. Our approach is to allow bubbles to flow freely, retaining their natural deformed ellipsoidal shape, and trigger a pulse generator as a function of bubble position. Plasma is generated in a bubble between a two-pin system by tripping a collimated triggering LED aligned within the path of the bubbles. Position and shape of bubbles are statistically assessed by gathering a large enough image-set of subsequent bubbles to define the boundaries of the system at time of trigger. Streamer propagation across the bubble is captured with a fast-gated iCCD camera and compared to the results of a 2D simulation previously carried out in our group using nonPDPSIM [2]. [1] N. Babaeva et al, Journal of Physics D: Applied Physics 50(36), 364001 (2017) [2] N. Pillai et al, Journal of Fluid Engineering (UNDER REVIEW). |
|
GT61.00016: Numerical simulation of an ionic-liquid meniscus generating a purely ionic electrospray Amin Taziny, Wai Hong Ronald Chan, Iain D Boyd Ionic liquid ion sources (ILISs) generate electrosprays by inducing emission of charged species from the menisci of moderately conductive ionic liquids (ILs) using a strong electric field. These electrospray sources have shown promise in micro-electric propulsion, especially when multiplexed as arrays of emitters. Though multiple emission modes have been observed, a pure ionic regime (PIR) yields the highest propulsive efficiency due to the large specific charge of the extracted species. This operational regime requires a high hydraulic impedance to balance the applied electric traction to sustain its low flow rate. To accurately model this system, the adoption of high-fidelity methods is imperative for interface capturing of ion transport in a rarefied external regime. Thus, a numerical study is presented to model the electrohydrodynamics of an IL meniscus attached to a porous reservoir held at a fixed electric potential. The upstream continuum model is used to investigate coupling conditions for a kinetic approach at and beyond the meniscus interface to simulate ion emission and far-field transport. |
|
GT61.00017: Modeling ion flux coefficient in high ion concentrated dusty plasmas using Langevin Dynamics simulations Vikram Suresh, Andrei Fendley, Ranganathan Gopalakrishnan The influence of dense and strongly coupled ions on the ion current to a particle is modeled in this work. LD is used to simulate the motion of N ions around a negatively charged grain in a periodic domain. The ion flux coefficient, β, is calculated using the grain-ion collision time distribution. In addition to the ion-ion electrostatic coupling strength Γ=e2/(4πε0kBTini-1/3), β is also influenced by the diffusive Knudsen number KnD=(mikBTi)1/2/fiap that characterizes the ion-neutral gas interactions (through the scalar friction factor fi), a concentration parameter χ=ap/ni-1/3 that compares the size of the grain ap to the mean inter-ion spacing ni-1/3, where ni is the ion number density and ΨE=-zpΓ/χ that denotes the strength of particle-ion interaction. The influence of KnD on the structure and self-organization of ions is demonstrated by analyzing the ion-ion pair correlation function and velocity distribution function. The model for β is presented as the ratio of the computed value to that obtained using a dilute charging model. The model will be validated against suitable experimental data from the literature. |
|
GT61.00018: Double layer formation and its possible effects on plasma transport across the transverse magnetic filter in the context of negative ion sources Miral Shah, Bhaskar Chaudhury, Mainak Bandyopadhyay, Arun Chakraborty, Pratik Ghosh In low temperature plasma based negative ion sources, plasma generated in the driver or source region extends in the expansion region and subsequently flows through the transverse magnetic filter field zone before encountering the plasma grid of the beam extracting system biased at a potential that is adjustable. Our 2D-3v PIC-MCC simulation of such a system, using the physical parameters of ROBIN ion source plasma during the volume mode operation when production of negative ions are very small and neglected in the simulation. reveal that the presence of inhomogeneous magnetic and electric fields leads to the asymmetry in the plasma parameters (plasma density, plasma temperature, plasma potential) [1]. By changing the biasing voltage of the plasma grid or magnetic field value, it is possible to alter the profiles of the plasma parameters near the filter magnetic field. The gradients in plasma parameters and associated different drifts and several collisional processes result in fluctuations or instabilities in the plasma. These instabilities are responsible for anomalous plasma transport across the transverse magnetic filter field. Different types of instabilities having different frequencies are due to density gradient, potential gradient and temperature gradient. In the simulation, instabilities are observed precisely at the location where an abrupt potential drop (double layer) occurs near the magnetic filter region under certain specific conditions. Further investigations show that the double-layer leads to ion acceleration also near the magnetic filter region in addition to ion trapping within the instability wavelengths. A systematic parametric study with different values of magnetic filter field and the bias voltage applied on the plasma grid is carried out and reported in the presentation. [1] Fusion Engineering and Design, Volume 151, February 2020, 111402. |
|
GT61.00019: Geometrical and energy scaling in a laser-generated multi-species low temperature plasma Kamron L Kopecky, Sumner B Harris, Chandler W Cotton, Renato P Camata The chemical diversity, variety of gas backgrounds, and shock wave characteristics of laser-generated plasmas provide many unexplored opportunities for processing of novel materials. Determining how experimental conditions impact the plasma parameters of these transient plasma flows is critical for harnessing their technical potential. In this study, we carry out Langmuir probe measurements of the multi-species plasma formed by nanosecond UV ablation of FeSe. This plasma is involved in the synthesis of β-FeSe/SrTiO3 heterointerfaces, that may enable electric-field controlled high-Tc superconducting devices. Measurements of electron temperature, electron density, Debye length, and Mach number of the plasma expansion as a function of laser fluence and spot area show two distinct plasma regimes in the 20-630 mJ pulse energy range. The dependence of the Mach number of the plasma front is particularly revealing. It increases with pulse energy up to 180 mJ, but exhibits a reversed, monotonically decreasing trend for greater energies. This reversal suggests a switch in energy apportionment between the directed and thermal motion components of the expansion. The uniform scaling of the plasma parameters with the number of available photons per absorber in the laser-plasma interaction volume, indicates that the regime transition is governed by laser-plasma interaction events. We will discuss how the interplay of laser absorption processes by the plasma influences this transition. |
|
GT61.00020: Influence of Pulse Modulation on Atmospheric Pressure RF Plasma Jet Shape Mahreen Khan, Veda Prakash Gajula, Satyananda Kar, Debaprasad Sahu, Ashish Ganguli In recent days, atmospheric pressure cold plasma jets are gaining attention due to their suitability for various biomedical and industrial applications. Usually, these plasma jets are formed in a regular conical shape and are generally influenced by the input parameters viz., excitation source characteristics, feed gas type, and flow rate, etc. In the present work, we demonstrate the excitation of a novel helical shape argon plasma jet using a pulse modulated 13.56 MHz RF power source at atmospheric pressure. This unconventional helical structure is observed for the first time and originates due to the pressure pulsation in the discharge region caused by on-off pulsing of the RF power at a 2 kHz modulation frequency. An appropriate selection of the modulation frequency, applied power, duty cycle, and gas flow rate provide control over the shape of the plasma jet i.e. from a conventional smooth conical shape to the unique helical one. This study will provide valuable insight into the fundamental physics of the origin of the helical shape of plasma which also has an impact in diverse fields which include lasers, communications, solar atmosphere, turbulent flows, biophysics, and other areas. The experimental scheme of helical plasma generation and its dependence on the input parameters will be presented. |
|
GT61.00021: Investigation of the power coupling efficiency in inductive discharges with radio-frequency substrate bias: dynamics of excitation and ionization patterns Katharina Noesges, Birk-Soeren Berger, Julian Schulze, Thomas Mussenbrock Inductive discharges with a radio-frequency substrate bias are widely used in the field of materials processing. This is in particular true for fabrication of microelectronic devices where high plasma densities in combination with energetic ion bombardment of the substrate are required. Recently, it has been experimentally shown by Berger et al. (Appl. Phys. Lett. 111, 201601, 2017) that for distinct phases between the inductive (13.56 MHz) and the capacitive (27.12 MHz) input power, energetic beam electrons generated by the expanding boundary sheaths are well confined, are accelerated efficiently, and propagate vertically through the skin layer at the instants of time of maximum azimuthal induced electric field within the fundamental RF (13.56 MHz) period. It has been shown that this in fact enhances the inductive stochastic electron heating, the power coupling efficiency, and finally the ion flux toward the substrate. We investigate this phenomenon (observed experimentally in argon and neon gas) computationally by using the Hybrid Plasma Equipment Model (HPEM) developed by Mark Kushner. Furthermore, first results in more complex and process-relevant plasmas are presented. |
|
GT61.00022: Nonlinear Ion Acoustic Shock Waves in an electron-positron-ion plasma with relativistic positron beam Sunidhi Singla, N.S. Saini Many satellite observes different kinds of charged particles in space and astrophysical environments that influence the characteristics of nonlinear structures in the framework of Maxwellian/non-Maxwellian velocity distribution. Owing to the occurrence of electron-positron–ion (EPI) in different space plasma environments, it is the frontline area of research for the last many years. The nonlinear aspects of ion-acoustic shock waves (IAShWs) dynamics in electron-ion or generally pair plasma has been extensively studied as a result of their vital importance in astrophysical sciences mainly ionospheric region. A dissipative system is the main reason for the formation of shock waves. The study of the nonlinear wave propagation in EPI plasmas is useful in understanding the dynamical behavior of astrophysical plasmas. In the ionospheric plasma system, there is always a possibility of its interaction with highly intense charged particles beam coming from outer space. It is seen that the nonlinear waves in the plasmas having positrons behave differently. Moreover, the behavior of IAShWs propagating in a relativistic EPI plasma model is strongly dependent on the ions and positrons temperatures, the mass ratio, and the relativistic effects. Higher-order corrections results in humped IAShWs and the kinematic viscosity, as well as the concentration of ion number density, play a pivotal role to understand the basic features of the produced IAShWs and the associated electric fields. Our findings may herald a model of EPI plasma to know the various effects of relativistic positron beam on plasma dynamics. |
|
GT61.00023: Effects on Langmuir probe characteristics owing to the finite impedance between the bulk plasma and the probe reference Montu P Bhuva, Shantanu Karkari, Sunil Kumar An experimental investigation on Langmuir probe measurements in a magnetized plasma column with two-temperature electron population in argon discharge is presented. Especially, the effect of finite impedance between the bulk plasma and the probe reference on the resulting I(U) traces has been emphasised with the help of an electrical analogy. It is a known fact that probe I(U) traces follow the usual exponential law if the measurements are performed with a reference electrode in good contact with plasma, which is usually a grounded discharge electrode. However, in the present case it is shown that when the grounded probe reference is not a part of the discharge circuit there exist a finite impedance between the probe reference and bulk plasma. This impedance effect is eventually reflected in the measured probe I(U) traces especially in terms of the lower values of electron saturation current as compared to the ideal scenario. An appropriate correction is thus required to account actual electron saturation current and thereby to extract subsequent plasma parameters. Therefore, a simple electrical analogy has been proposed to interpret appropriate correction factors to the probe I(U) traces resulting from such magneto-plasma devices, where reference to the probe is in partial or poor contact with the bulk plasma. |
|
GT61.00024: Dust acoustic solitons in polarized space dusty plasma manveet kaur, N.S. Saini The nonlinear structures in dusty plasmas in the framework of non-Maxwellian distribution have been potential area of study for the researchers. A number of investigations are witness of different physical aspects that incur their presence due to dust in various space/astrophysical environments. The presence of dust in electron-ion plasmas leads to the formation of variety of wave modes such as dust acoustic waves (DAWs) and dust ion acoustic waves (DIAWs). Due to deformation of Debye sheath around the dust particles, the polarization force comes into play and have great influence on the characteristics of nonlinear dust acoustic modes. We have derived the expression polarization force for generalized (r, q) distributed ions and studied the higher order corrections to dust acoustic (DA) solitons and energy of solitons under the influence of polarization force in a dusty plasma composed of negatively charged dust fluid, Maxwellian electrons and generalized (r, q) distributed ions. Our work is basically inspired from the difference in theoretical and experimental results and also due to role of generalized (r, q) distribution that provides a better way to explicate in various space and astrophysical regions. By imposing reductive perturbation method, the KdV and higher order KdV equations are derived and using renormalization method their solutions are derived. The contribution of higher order corrections and (r, q) distributed ions may play an important role on the energy carried by the DA solitons in the presence of polarization force. Further, the influence of various physical parameters of given plasma have also been explored. It is important to announce here that the outcomes of present investigation may shed light in understanding the nonlinear phenomena in planetary spokes and cometary tails. |
|
GT61.00025: In-situ detection of plasma emission using in-vacuum active optical sensor Osamu Sakai, Keiji Sakurai, Shigeyuki Miyagi Signal detection of plasma provides us information of internal underlying processes in plasma-enhanced active gas phase. Typical examples of plasma probing have been based on Langmuir-probe current-voltage analysis and optical emission spectroscopy, where passive metal tips in plasma chambers or optical sensors through vacuum windows contribute to data acquisition, respectively. To enhance signal-to-noise ratio and data accuracy, here we propose in-vacuum installation of a sensor device which includes a sensor head with photo-diode array, a one-chip data processor, and a wireless communication module. As shown in Ref. [1], we installed the sensor just 10-mm apart from plasma emissive region in Ar at 100 Pa, raw Red/Green/Blue signals being converted into digital data, and the data transfer via wireless communication between vacuum-air interface was successfully performed. Through the measurement procedure, the functions of the module electronic devices were invariant, all of which were popular and available without special demands. This result opens new possibilities for plasma diagnostics in which many sensors work simultaneously in a vacuum chamber. [1] O. Sakai, T. Kitagawa, K. Sakurai, G. Itami, S. Miyagi, K. Noborio and K. Taguchi, Sci. Rep. 11, 1364 (2021). |
|
GT61.00026: Analysis of Electrical Characteristics of Living Cells Exposed by Cold Atmospheric Plasma using the Equivalent Circuit Model Shota Yamauchi, Yuta Iwata, Ippei Yagi, Satoshi Uchida Multiple factors are involved in plasma medicine, but the balance of their influence and interaction have not been understood well. Therefore, the purpose of this study is to clarify the basic mechanisms of plasma medicine by focusing on the interaction with cells through the supply of electric field and charge, apart from the chemical reactions of reactive species that have been studied. Analysis of the electronic behavior of surface charging and membrane potential changes could reveal the mechanism of membrane transport. In this paper, the equivalent circuit is analyzed considering the situation where plasma is directly irradiated to a single cell. The resistance and capacitance were derived from references for the cell and from our previous data of fluid analysis for the plasma. The gas-phase gap is 2 mm and the applied voltage is 30 kV. The discharge generated is the atmospheric pressure Townsend-like discharge with an electron density of about 10-8 cm-3. In addition, the voltage and current applied to the membrane were deduced quantitatively. The maximum voltage of 5.8 mV was applied to the membrane. This is about half of the voltage applied to the entire cell. Under these conditions, the voltage had no significant influence on the membrane such as destructive damage. |
|
GT61.00027: Relationship between photon energy and current induced by photo-excited desolvation of hydrated electrons in atmospheric-pressure dc glow discharge Yoshinobu Inagaki, Koichi Sasaki Hydrated electrons are generated by plasma-liquid interaction. However, there have been limited reports on the detection of hydrated electrons in liquids interacting with plasmas. The difficulty is caused by the fact that hydrated electrons generated by the plasma irradiation are localized in a narrow region with a thickness of several nanometers below the plasma-liquid interface. To overcome the difficulty, we have developed a method to detect hydrated electrons in the interfacial region. Hydrated electrons in the interfacial region are converted to free electrons when they are irradiated with laser beam having a photon energy exceeding the desolvation energy. Free electrons produced by the desolvation are ejected into the gas phase. |
|
GT61.00028: Effects of Physiological Saline Solution Treated by Ar Dielectric Barrier Discharge on Proliferation of Jurkat Cell Eiji Oyama, Akhiro Shirai, Tadahiko Nakagawa, Masahiro Sogabe, Toshiya Okahisa, Kenji Teranishi Recently, applications of discharge plasma to medical fields have been actively studied by many research groups [1]. The authors have conducted fundamental study aiming to apply the discharge plasma to a therapy for autoimmune disease [2]. The present study investigated the effect of the physiological saline solution treated by argon dielectric barrier discharge (DBD) on Jurkat cells. The plasma-treated saline (PTS) solution was prepared by exposing physiological saline solution to the DBD generated by feeding 1-L/min argon for 15 minutes. Jurkat (RCB0806) cells were exposed to the PTS for 30 minutes and then incubated for 30 hours. The number of viable and non-viable cells were evaluated at the several time points of incubation using Trypan blue staining method. In the case of Jurkat cells unexposed to any solutions and plasma, the viable cell number was increased favorably during the 30-hours incubation while the non-viable cells were maintained almost constant in small numbers. These results also led to the favorable increase of the total cell number. In contrast, in the case of Jurkat cells exposed to the PTS, the number of viable and non-viable cells were respectively decreased and increased with incubation time, resulted in the slight decrease in the total cell number. From these results, it was found that the PTS inhibits the cellular proliferation of Jurkat cells and promotes the cell death. We are now conducting apoptosis detections by a flow cytometry to investigate further the cell death of Jurkat cells. |
|
GT61.00029: Electron transport and negative streamers in indium vapor Sasa Dujko, Jasmina Atić, Danko Bošnjaković, Ronald White, Peter Stokes, Laurence Campbell, Michael Brunger We investigate the transport of electrons and propagation of negative ionization fronts in indium vapor. Electron swarm transport coefficients are calculated using a numerical multi term solution of Boltzmann’s equation and a Monte Carlo simulation technique over a range of the reduced electric fields and the indium vapor temperatures. As many indium atoms are in the first (5s25p) 2P3/2 metastable state at vapor temperatures of a few thousands of Kelvin, the presence of thermal motion of the host gas atoms and superelastic collisions are carefully considered and implemented in our codes. We observed a significant sensitivity of the spatial relaxation of the electrons under non-hydrodynamic conditions in the steady-state Townsend experiment, with respect to the indium vapor temperature and the initial conditions used to release electrons from the cathode. In order to simulate the inception and propagation of negative ionization fronts in indium vapor, we here apply the classical fluid model, which is based on the drift-diffusion approximation, the local field approximation and Poisson's equation. This model is implemented numerically in 1D and 1.5D configurations without photoionization. Among many important points, we found tthat he transition from an avalanche into a negative ionization front occurs faster with increasing indium vapor temperature, due to enhanced ionization and more efficient production of electrons at higher vapor temperatures. |
|
GT61.00030: Comparative study of streamer inception in pulsed dielectric barrier discharges in Ar and N2-O2 mixture Aleksandar P. Jovanović, Hans Höft, Detlef Loffhagen, Markus M. M Becker Pulsed-driven single-filament dielectric barrier discharges (DBDs) in a symmetric configuration with hemispherical electrodes are investigated by time-dependent, spatially two-dimensional fluid modelling. The fluid model comprises balance equations for the particle number densities, the electron energy density, and the surface charges as well as Poisson's equation. The numerical analysis is carried out at atmospheric pressure for Ar and for N2 with an admixture of 0.1 vol. % of O2 to analyse different features during discharge inception and streamer propagation. The comparison of modelling results with measured currents and streamer velocities shows good agreement. The temporal evolution of the spatial profiles of the particle number densities and the electric field are used to study the Townsend prephase and the streamer breakdown of the DBDs. The discharges show a qualitatively similar behaviour during the streamer propagation, while the streamer inception differs significantly for the DBD in Ar and in the N2-O2 mixture. The current rise and streamer propagation are considerably slower in Ar, which is connected to the lower breakdown voltage in Ar compared to N2-O2. |
|
GT61.00031: Numerical Simulation of Arc Temperature Distribution Considering Crosswinds between Contact Wire and Contact Strip in Electric Railway Honoka Morishita, Yoshifumi Maeda, Zhenwei Ren, Yusuke Nemoto, Takamasa Hayasaka, Toru Iwao Electric railway is supplied from a contact wire through a contact strip. When the contact of wire and strip is poor, the arc generates, then the contact wire is sometimes damaged and disconnected. In this case, the train service suspended for over half a day because of the disconnection of contact wire. Thus, it is required to elucidate the disconnection condition of the contact wire in order to suppress the out of service. A few papers have researched that the arc figure is being measured when the running of the train is simulated by moving the contact wire in parallel, experimentally. The arc appearance is sometimes stagnation, moving, and restrike when the train runs. These phenomena depended on train and crosswind speed. In this time, the temperature distribution of arc and contact wire are important to suppress the contact wire disconnection. However, the arc generation is very fast phenomenon, and the measurement of contact wire temperature is very difficult. Therefore, the simulation method that regards the running the electric railways as crosswinds should be developed. In this research, the temperature distributions of the arc and the contact wire were calculated by the numerical simulation in the case of the small crosswind, the arc stagnation on the contact wire and the high crosswind. As a result, the arc was deflected by the crosswind, and the restrike phenomenon sometimes occurred. Therefore, it is considered that the contact wire is disconnected because of arc stagnation on it when the crosswind is low which means the train runs slowly. |
|
GT61.00032: Performance Characterization of an ECR Magnetic Nozzle Thruster Using Atmospheric Propellant Sophia Bergmann The performance of an electron cyclotron resonance (ECR) magnetic nozzle thruster operating on air is evaluated. This investigation is motivated by the possibility of using air-breathing plasma propulsion to perform drag compensation for spacecraft in very low earth orbit. ECR magnetic nozzles in principle are capable of operating on a wide variety of propellants. However, while there are experimental or analytical results for ECR magnetic nozzles operating on water vapor, argon, and xenon, little comparable information exists for such a thruster running on air. This work presents the results of a study characterizing the performance and efficiency of an ECR magnetic nozzle operating on air. Thrust and specific impulse are assessed using a pendulum thrust stand, and measurements performed with a diagnostic probe suite are used to estimate key contributions to the thruster efficiency, e.g. divergence and mass utilization. These results are interpreted in the context of a 0D power balance model. Potential strategies for improving performance are also discussed including the use of a two-frequency optimization scheme recently devised by Wachs [1]. |
|
GT61.00033: Ablation Gas Concentration Distribution with Opening Process of Electrodes Using Three-Dimensional Numerical Simulation Yuki Suzuki, Wataru Fuse, Yusuke Nemoto, Zhenwei Ren, Toru Iwao The role of circuit breakers is to disconnect the accident point from the power system. The reduction in the duration of instantaneous voltage drops after the accident is the important issue for circuit breakers. For this purpose, it is necessary to prevent the re-ignition after the current zero point. The current interruption using the ablation gas from the nozzle of circuit breakers has been studied in order to reduce the amount of SF6 gas consumption. The ablation gas mixing amount into the arc is important with opening process of electrodes in order to effectively utilize the interruption performance of ablation gas. Making the weak point that makes it difficult to maintain the arc will prevent the re-ignition even when the transient recovery voltage is applied. However, the physical phenomenon of ablation gas contamination during the opening process of electrodes has not been elucidated. In this paper, the ablation gas concentration distribution with the opening process of electrodes using the three-dimensional numerical simulation was calculated. As a result, the ablation gas was generated with the opening electrodes. In addition, the temperature transition caused by the contamination of ablation gas and the amount of ablation gas for each temperature range was obtained. |
|
GT61.00034: Convergent close-coupling calculations of the Fulcher-α linear polarization fraction in e-H2 collisions Liam H Scarlett, Una S Rehill, Mark C Zammit, Dmitry V Fursa, Klaus R Bartschat, Igor Bray Measurements of collisionally-induced fluorescence can reveal features of the collision dynamics not probed in standard scattering experiments, and hence provide some of the most sensitive tests of quantum-mechanical scattering theories. It is now commonplace to see outstanding agreement between measured and calculated Stokes parameters for scattering on atomic targets. However, in the case of molecular targets, both measurements and calculations of Stokes parameters are rare, and there have been no previous studies showing agreement between theory and experiment. |
|
GT61.00035: Measurements of single-filament pulsed positive streamer discharge and two-dimensional ozone density distribution in atmospheric-pressure nitrogen-oxygen mixture ― effects of oxygen concentration Akihiro Yoshino, Atsushi Komuro, Ryo Ono Streamer discharge is widely used in applications. Fundamental researches on streamer have been conducted using experiments and simulations, but the simulation is usually axisymmetric two-dimensional (2D), which cannot be compared with experimental results because of the branching and non-axisymmetric characteristics of streamer discharge. Recently, we have succeeded in generating a pin-to-plane single-filament pulsed positive streamer discharge that can be compared with 2D simulation. In the current work, the effect of oxygen concentration on the single-filament steamer in atmospheric-pressure N2/O2 mixture is investigated. The gap distance is 13 mm and the applied voltage pulse is 30 kV with 200 ns duration. The results show that, when the O2 concentration increases from 10% to 90%, the diameter and propagation velocity of streamer are almost constant irrespective of O2 concentrations, whereas the optical emission intensity decreases as O2 concentration increases. Next, 2D ozone density distribution produced in the streamer is measured using 2D photofragmentation laser-induced fluorescence. The results show that the total amount of O3 yield reaches the maximum when the O2 concentration is 40%. The measured results will be used for verifying our 2D simulation in future work. |
|
GT61.00036: Electron cross-field transport from sub plasma structures in an E×B Hall thruster discharge under the azimuthally modulated neutrals and magnetic field Junhwi Bak, Rei Kawashima, Giuseppe Romanelli, kimiya komurasaki The induced azimuthal electric field in a Hall thruster yields electron cross-field transport that is scaled by 1/B. In this study, we artificially induce a non-zero macroscopic equilibrium azimuthal electric field by modulating neutral particles and magnetic fields in the azimuth dimension. Both experimental and numerical efforts are made to understand the plasma structure formation over distinct regions of Hall thrusters, such as the ionization, acceleration, and plume region. With a fast Fourier transform analysis, sub-plasma structures are studied, and dominant components being responsible for the axial electron transport are identified. Lastly, spatial evolutions of affecting parameters on the transport by the azimuthal electric field are obtained, and regional characteristics are discussed. |
|
GT61.00037: A full fluid, drift-diffusion, magnetized model of Hall Effect Thruster, Impact of Magnetic Field Configuration, and Experimental Data Sajid Ahmed, Richard Branam, Robert Arslanbekov, Vladimir I Kolobov, Gabe G Xu Modeling of Hall Effect Thruster (HET) presents a challenge to the computational plasma physics, and there is a broad range of computational models, from the full PIC models to fluid description [1]. The fluid approaches have advantage of fast computational times and the ability to give quick design optimization guidelines, predict trends and uncover the underlying physical mechanism in a more transparent manner. In this work, we use a two-dimensional, axisymmetric model of HET based on a full fluid, magnetized approach. In this model the electron and ion species are described by the drift-diffusion (DD) approximation with tensor mobility and diffusion coefficients due to the presence of strong magnetic field coupled with the Poisson solver. The electron energy equation is solved in the same DD approximation which allows us to predict the spatial distribution of the electron temperature. The neutral species are solved for using a weakly compressible approach. The magnetic field profiles are computed using a range of available tools. The model predicts proper HET profiles and trends with such parameters as magnetic field strength and propellant gas type and density observed in the literature. The model is steady state but can be extended to pulsed operation. Our experimental capabilities include laser induced fluorescence (LIF). The LIF technique is extended to also track and measure neutral atoms and second ionization states of argon and xenon. |
|
GT61.00038: Probabalistic evaluation of closure models for the Hall thruster anomalous collision frequency Thomas A Marks, Benjamin Jorns The development of fully predictive simulations of crossed-field plasma discharges such as Hall effect thrusters is a longstanding goal of the low temperature propulsion community. However, in many cases, there are aspects of the underlying physics such as anomalous cross-field transport that are not sufficiently understood to produce fully predictive models. With this limitation in mind, we apply Bayesian inference to a new two-equation turbulence model for the anomalous transport in a Hall effect thruster. Using the output of validated simulations as surrogate data, we calibrate this model and obtain a posterior distribution of the model coefficients. We then sample from its coefficient distribution and run a high-fidelity multi-fluid Hall discharge simulation at each sampled set of model coefficients. We simulate the H9 magnetically shielded Hall thruster, which was not part of the training dataset. We repeat this at multiple operating conditions, obtaining probabalistic predictions of key thruster performance parameters, including thrust, discharge current, specific impulse and anode efficiency at each. These are then compared to data. |
|
GT61.00039: DC glow discharge modes and self-oscillations in argon Valeriy Lisovskiy, Stanislav Dudin, Serhii Rezunenko, Vladimir Yegorenkov The ignition and operation modes (Townsend, subnormal and transition to abnormal or normal modes) of a glow discharge in argon have been experimentally investigated. Oscillograms of voltage between electrodes and discharge current were obtained, as well as current-voltage characteristics of glow discharge in a wide range of argon pressure and for different values of ballast resistor and external capacitance. The dependences of the amplitude values of voltage, current and frequency of oscillations on the voltage at the output of the generator were also measured. It is proposed to distinguish 2 stages of oscillations. The first stage begins when the voltage at the electrodes reaches the upper stationary value, which causes a rapid increase in current. The voltage on the electrodes decreases until it reaches the lower stationary value, the discharge current at this point reaches a maximum. The subnormal mode has a negative differential resistance, which contributes to the occurrence of self-oscillations. At the beginning of the second stage, the voltage on the electrodes continues to decrease, reaches a minimum value and then increases due to the charging of the internal and external capacitors from the generator. |
|
GT61.00040: Verification of Various Probe Diagnostics for Pulse and Static Scenario of the PHASMA Device. Prabhakar Srivastav, Peiyun Shi, Earl Scime Langmuir probes single, double, and triple, are commonly used plasma diagnostics. Triple Langmuir probes (TLP) are used to measure electron temperature, density, and floating potential in the PHASMA (PHAse Space MApping) device during pulsed and steady-state operation. The TLP provides a straightforward approach for measuring temporal and spatially resolved plasma parameters. Here we describe a high-time resolution TLP developed for PHASMA. It consists of three closely spaced Langmuir probes. Two tips are connected in a double probe configuration and the third one samples the change in floating potential during the plasma pulse. The time-resolved measurement of electron temperature depends on the choice of the fixed bias used for the double probe pair. To obtain accurate electron temperature measurements, the fixed bias value is selected based on a comparison of TLP measurements with single and double Langmuir probe electron temperature measurements of the pulsed (plasma gun discharges) and steady-state (helicon source) PHASMA plasmas. We also present comparisons of electron temperature fluctuations measured with the TLP and a double probe. |
|
GT61.00041: Characterization and Modeling of DC & RF Breakdown in Microscale Gaps near Vacuum Christopher H Moore, Alexander Ruyack, Matthew Jordan, Gwendolyn Hummel, Sergio Herrera, Andrew Bingham, Adrian Schiess, Christopher Gibson, Christopher Nordquist Plasma breakdown in both radiofrequency (RF) driven and large-Knudsen number gaps requires lower voltage than the classical Paschen curve predicts. However, while these two regimes have been investigated independently in prior studies, we are unaware of any studies on RF-driven, large-Knudsen number gaps. The present work seeks to unify these two regimes and study the discharge behavior of large-Knudsen number gaps driven at GHz frequencies, thereby allowing very low voltage RF switches and limiters. We have fabricated gold-electrode devices with gaps as small as 100nm that can be operated in a vacuum chamber at DC to GHz frequencies and will report on the experimentally determined breakdown voltage vs. gap size at various pressures from atmospheric down to vacuum (from small-to-large Knudsen numbers) for both DC- and RF-driven devices. We also present simulations of device operation using the Particle-In-Cell Direct Simulation Monte Carlo (PIC-DSMC) electromagnetic plasma code EMPIRE, with a model that has ion-induced Secondary Electron Emission (SEE) and electron impact ionization, as well as Fowler Nordheim field emission and energy-dependent electron-induced SEE. |
|
GT61.00042: The phenomena at unstable plasma-liquid interface Lucia Potocnáková, Tomas Hoder The local plasma-induced changes of liquid properties at the interface of microplasma and dielectric viscous liquid droplet in a narrow gap can lead to radial viscous fingering. The dynamics of the initiated microflow were investigated experimentally employing synchronized optical and electrical time-resolved measurements. Temporal development was studied for the whole event lifespan, focusing on the primary instability, fingering process and final fragmentation of the droplet. The extensive parametric study showed that the oil viscosity and the applied voltage amplitude were among the most influential parameters affecting the interface evolution. Furthermore, the introduced methodology enabled spatially resolved quantification of the dissipated power density and of the unstable plasma-liquid interface velocity, proving a strong correlation between them. After a discrepancy of experimental results for the high voltages and theoretical prediction of a known model was noticed, a modification of the model based on the change of the liquid viscosity with increased heating at high applied voltage amplitudes was proposed. |
|
GT61.00043: Single-shot 2-D electron density measurement using laser-collision induced fluorescence data Brian Z Bentz, Kevin W Hoyt, Daniel J Scoglietti, Edward V Barnat The laser-collision induced fluorescence (LCIF) diagnostic allows determination of electron density in 2-D from the collision-dependent photon emission of the 33D to 23P transition in He (588 nm). Previous measurements in cathodic arcs with a single intensified camera required imaging many arc operations to remove the background plasma emission and recover the time dependent LCIF response at each camera pixel. This communication presents an improved approach using a fast-framing camera that enables single-shot acquisition of both the plasma emission before the laser pulse arrives and the subsequent LCIF temporal response. Electron density can then be determined in 2-D by solving an optimization problem where the differences between LCIF measurements and collisional-radiative model predictions are minimized. A single-shot LCIF diagnostic will enable study of the stochastic nature of cathodic arcs. |
|
GT61.00044: Plasma-Density Imaging using a Second-Harmonic, Dispersion Interferometer Frank J Wessel, Cameron T Chavez, Andrew Egly, Ivan Sepulveda, Matthew O'Meara Typical plasma density interferometers are robustly stabilized, two-arm, high-cost/high-maintenance installations. The Second-Harmonic Dispersion Interferometer (SHDI) is a significant departure, utilizing a common-path laser beam, frequency doubled before, and after, the plasma sample, allowing the dispersive-phase shift between beams to be measured in a simple system. |
|
GT61.00045: Simulations of Plasma Filamentation in Dielectric Barrier Discharges SHANTI THAGUNNA, Vladimir I Kolobov, Ananth N Bhoj, Sami Bayyuk, Jun-Chieh(Jerry) Wang Dielectric Barrier Discharges (DBDs) are widely used in various configurations to produce cold atmospheric pressure plasmas. Depending on operating conditions, they generate transient filamentary or homogeneous discharges. The DBD can be generated between two parallel electrodes covered by dielectrics interfacing with the plasma. Dynamics of pattern formation in such a DBD configuration have been observed in many experiments and simulations. In previous work, we have simulated plasma self-organization in Helium DBD [1]. It was shown that charge accumulation on dielectric surfaces is responsible for pattern formation. The present work aims to understand the underlying physics better and clarify the mechanisms of plasma filamentation in DBDs. For our studies, we use commercial CFD-ACE+ software to analyze the influence of the gas type, pressure and composition, dielectric type (resistivity, and secondary electron emission coefficient), and driving voltage (amplitude and frequency) on the pattern formation. The results of simulations are compared with available experimental data. We clarify the effects of plasma properties and surface processes on the self-organization phenomena at the plasma interface with solid dielectrics that could be valuable for more complex geometries and operating conditions used in practical applications. |
|
GT61.00046: On the determination of electric field in atmospheric pressure DBD Martina Mrkvičková, Lucia Potočňáková, Petr Bílek, Milan Simek, Zdeněk Navrátil, Pavel Dvořák, Igor V Adamovich, Tomas Hoder Precise knowledge of the electric field in discharges is the key for the quantification of the plasmochemical processes. In recent years, various methods of the electric field measurements were established or improved, adopting e. g. the simplest equivalent circuit model, the intensity ratio of emission lines, or electric field induced second harmonic generation (EFISH). Our goal is to test the robustness of these methods and their conformity on measurements of the atmospheric pressure Townsend discharge in pure nitrogen. The results of the time development of the electric field determined by all three methods will be compared and discussed. |
|
GT61.00047: Photoresist ashing in inductively coupled plasma with magnetic resonance wireless power transfer system Ju-Ho Kim, Young-Hun Hong, Chin-Wook Chung Photoresist ashing rate and uniformity is investigated in inductively coupled plasma with a magnetic resonance wireless power transfer system. An outer resonant antenna for the magnetic resonance wireless power transfer is installed at a distance of 5 cm from an inner powered antenna. When the resonance and the non-resonance are continuously changed through the switch connected to the outer resonant antenna, the profiles of plasma density and photoresist ashing rate are measured. The result is compared with the result when only powered antenna is installed and discussed along with the relevant physical mechanisms. |
|
GT61.00048: Repetitive pulse simulations of streamer discharges with detailed plasma chemistry and gas heating Hemaditya Malla, Jannis Teunissen, Andy Martinez, Ute Ebert We perform numerical simulations of streamer discharges under repetitively pulsed conditions. We use the drift-diffusion model with the Poisson's equation in a cylindrical symmetric geometry. Our model uses a detailed plasma chemistry data set consisting of 379 reactions, and 41 species. The reaction set consists of processes like ionization, attachment, detachment, ion-ion recombination, ion-electron recombination, etc. We also solve the Euler equations of gas dynamics to investigate the effect of the streamer discharges on the neural gas and vice versa. The Euler equations are coupled with the discharge model by a detailed energy transfer model which consists of a fast energy release term and a slow energy release term. In [1], it was observed that the voltage repetition frequency affects whether subsequent streamers follow the path of the old streamers, continue extending from the initial streamer tip or take a completely new path. We try to observe a similar phenomenon in our simulations and try to explain it using the detailed plasma chemistry. Furthermore, we try to study the time scales at which the neutral gas heating starts affecting the streamer dynamics. |
|
GT61.00049: Development of flat cutoff probe for real-time electron density measurement Hee Jung Yeom, Jung Hyung Kim, DaeHan Choi, Eun-Seok Choe, Min Young Yoon, Dae Jin Seong, Gwangho You, Shin Jae You, Hyo-Chang Lee As the semiconductor process, real-time in-situ plasma diagnostics have received attractive attention because they are expected to perform important functions such as increasing the process yield and abnormality detection. In this study, we developed a bar type flat cutoff probe (BCP) [1-3] embedded in the surface of the chamber wall and electrode to measure electron density during plasma processing. The BCP measures electron density near the plasma-sheath boundary, which is very closely adjacent to the chamber wall or wafer. Also, BCP can measure the electron density in real-time even though various types of wafers are placed on the BCP. In addition, we developed a circuit model of the BCP in which plasma and sheath are considered as coplanar capacitances. The result of the circuit model was verified through both the EM simulation and the experiment. |
|
GT61.00050: Measurements of axial and horizontal thrusts in a magnetically steered radiofrequency plasma thruster Ryoji Imai, Kazunori Takahashi Magnetic nozzle (MN) electrodeless plasma thrusters have been vigorously investigated as alternative options for high-power and long-lived electric propulsion devices because of the absence of the electrode exposed to plasmas, where physics studies relating to the thrust generation and improvement the thruster performances have been progressed. |
|
GT61.00051: Monitoring of Reactive Oxygen Species Generation with PVA-KI Probe by Argon Plasma Nguyen T Tran, Min Hu, Hiroto Matsuura Atmospheric pressure plasma jet (APPJ) inactivates bacteria and virus through in situ supply of reactive oxygen species (ROSs). These species are strong oxidative stress and/or trigger signaling pathways in biological cells. Polyvinyl Alcohol-Potassium Iodine (PVA-KI) were studied for testing radical productions with long silicone tube and expansion plasma jet. PVA-KI gel also investigated in radiotherapy such as radio chromic gel dosimeter. Visualization of ROSs concentration and distribution is an essential technique for accurate evaluation of absorption dose. |
|
GT61.00052: The role of reactive oxygen and nitrogen species on the conversion of volatile organic compounds in a twin surface dielectric barrier discharge Lars Schücke, Arisa Bodnar, Niklas Friedrichs, Alexander Böddecker, Niklas Peters, Andrew Gibson, Martin Muhler, Peter Awakowicz In consideration of the increasing consciousness for environmental protection, energy efficient processes for purification of exhaust gas streams, e.g. in industrial plants, are growing in demand. These gas streams can be contaminated with pollutants such as fine particles, volatile organic compounds (VOCs), and various microorganisms, depending on the industry and application. |
|
GT61.00053: Impact of Magnetic Focusing Effects on the Electron Beam Formation in the Solar Corona Bofeng Tang, Haihong Che, Gary P Zank, Vladimir I Kolobov Flare produced electron beams are widely believed to responsible for type III radio bursts. The height of the starting frequency of type III radio bursts is found commonly higher than the site of particle acceleration region of solar flares. The magnetic focusing effect, converting electron kinetic energy from perpendicular to parallel, alone is capable of accelerating the non-thermal electrons in the lower corona to reach and exceed the threshold of nonlinear electron two stream instability within an altitude of 0.5 solar radii as the electrons propagating away from the initial acceleration site along the magnetic field line. During the transport, the power-law energy spectral index of the non-thermal electrons maintains the original one produced in the acceleration region. For the first time, the effect of transferring electron kinetic energy from perpendicular to parallel caused by magnetic focusing has a maximum ratio is discussed. The efficiency of the acceleration of magnetic focusing effect subjected to relative drifting velocity, the magnetic field spectral index, and electron beam spectral index are shown. |
|
GT61.00054: A comprehenssive study on the discharge physics and atomic layer etching with radio frequency biased inductively coupled plasma in Ar/C4F6 mixture Min Young Yoon, Hee Jung Yeom, Jung Hyung Kim, Chegal Won, Yong Jai Cho, Deuk-Chul Kwon, Jong-Ryul Jeong, Hyo-Chang Lee In recent years, with the scaling-down of device and growing demand for damage-free etching techniques in the semiconductor industry, interest in the atomic layer etching (ALE) process has significantly increased. Even in the case of the high aspect ratio (HAR) trench etch process, the ALE is being used as the final etch step technique after the HAR etch for achieving the flattening of the bottom layer and the vertical side-wall. Among plasma sources, inductively coupled plasma (ICP) can be a candidate for ALE, but studies linking discharge physics and ALE processes have not been actively conducted. As an etching gas for ALE, C4F6 (hexafluoro-1,3-butadiene) with a low global warming potential is one of the challenging topic in ALE because it generates excessive polymer film. In this study, we investigated the discharge physics of ICPs with radio-frequency (RF) bias and Ar/C4F6 mixture to be considered in the ALE process1. For the modification step of ALE, the ICP characteristics were investigated in pure Ar and Ar/C4F6 mixture, and the RF biased ICP characteristics were investigated for the removal step of ALE. Based on the discharge characteristics, the ALE windows for silicon-based thin films such as a-Si, poly c-Si, SiO2, and Si3N4 were founded, and flat and vertical etch profile was obtained through the ALE even on patterned wafer. |
|
GT61.00055: Surface potential distribution and surface charge behavior in a plane-parallel DBD in atmospheric air China Natsume, Atsushi Komuro, Akira Ando Dielectric barrier discharges (DBDs) have been applied in a wide range of applications such as ozone generation and air flow control. In many cases of a DBD, microdischarges (MDs) often occur, which are filamentary discharges with extremely short current pulse widths (a few tens of ns), and numerous MDs are randomly distributed on the dielectrics due to the influence of residual surface charge. Thus, surface charge could be a key to control the performance of DBD applications. In this study, we measured the electrical potential on the dielectric in a DBD occurred in a parallel plate electrodes configuration in atmospheric air using the Pockels effect [1]. We applied a 5 kHz sinusoidal high voltage of several kV between parallel plate electrodes, where Bi4Ge3O12 (BGO) crystal is set between the electrodes with a gap length of less than 1 mm and generated multiple discharges. The Pockels effects were observed with a high-luminous LED and high-speed camera to obtain the spatiotemporal variations of the dielectric surface charge. The measurement of the surface potential showed that external voltage magnitude contributes to spatial memory effect of MD and diffusion of the surface charge. |
|
GT61.00056: Measurement and modeling of positron binding to chlorinated hydrocarbons. James R Danielson, Andrew R Swann, Gleb F Gribakin, Clifford M Surko Positron annihilation on molecules at low energies is dominated by vibrational Feshbach resonances. The downshift of the resonances relative to the known molecular vibrations provides a measure of the positron-molecule binding energy, $\epsilon_b$. Measured and calculated positron binding energies are presented for a range of hydrocarbons and their chlorine-substituted counterparts.\footnote{\small A. R. Swann, et al., arXiv:2104.05338 (2021).} The calculations are performed using a model correlation potential.\footnote{\small A. R. Swann and G. F. Gribakin, J. Chem. Phys. 149, 244305 (2018).}$^{,}$\footnote{\small A. R. Swann and G. F. Gribakin, Phys. Rev. Lett 123, 113402 (2019)} Generally good agreement is found between the model predictions and the experimental measurements. Both experiment and theory demonstrate the large effect that the chlorine atoms have on $\epsilon_b$ and the strong sensitivity of $\epsilon_b$ to the position of the Cl atoms. Overall trends with molecular polarizability, dipole moment, and geometry are discussed. Calculated wavefunctions and the electron-positron annihilation rates in the bound state will also be discussed. |
|
GT61.00057: Photodetachment of negative ions of N2O in a pulsed Townsend experiment Olmo González-Magaña, Jaime de Urquijo Swarm experiments in electronegative gases such as N2O have been extensively studied because of their importance in discharge formation and evolution in many low-temperature plasma processes. The presence of negative ions in a discharge can considerably influence its space charge distribution and temporal development due to electron detachment processes from unstable negative ions. In this context, the pulsed Townsend technique (PTT) has proven to be a successful and efficient tool to study several plasma processes, including those related to the formation of negative ions. However, due to relatively high pressures used, mass spectrometry is discarded, hence information about the species and the densities of negative ions formed in the avalanche can only be obtained from the PTT experiment from indirect means. To overcome this problem, an experimental technique based on the PTT has been developed for studying the photodetachment of negative ions in the realm of the electron avalanche. We report and discuss the photodetachment signals and properties derived therefrom at low E/N values. |
|
GT61.00058: Contribution of External Magnetic Field for Increasing Arc Voltage in Magnetic Driven Arc Jumpei Oya, Zhenwei Ren, Yusuke Nemoto, Yuki Suzuki, Toru Iwao The arc current reduces to zero when the arc voltage increases and equals to the source voltage during the interruption process of DCCB. Generally, an external magnetic field is applied to the arc for achieving better performance, because the electromagnetic force derived from it can increase the arc voltage increment. However, there are few reports about the physical properties change of arc plasma during its elongation with considering the application of external magnetic field. In this research, physical properties and movement of magnetic driven arc in a parallel electrode with different inter-electrode distance were analyzed. It found out that the anode spot was shifted from the edge to the electrode side by the strong cathode jet, which becomes stronger in a shorter inter-electrode distance. As a result, the arc voltage increased rapidly with applying external magnetic field in shorter inter-electrode distance and the interruption time decreased. |
|
GT61.00059: Development of Atmospheric Pressure Helium Collisional-Radiative Model by Including Atomic Collisions Keren Lin, Atsushi Nezu, Hiroshi Akatsuka A helium collisional-radiative (CR) model is expanded for use in the atmospheric pressure range. By including the atomic collision processes (atomic collision excitation and deexcitation, atomic collision ionization and atomic three-body recombination) in the low-pressure CR model, this new model is capable of diagnosing atmospheric-pressure helium plasma. The population density of all the excited states can be calculated by inputting the electron density, electron temperature, gas temperature, population density of ground state helium atoms, pressure, and geometrical parameters. Additionally, the electron temperature and density of atmospheric-pressure helium plasma can be estimated by inverting the previously described CR model and OES measurement. |
|
GT61.00060: Laser scattering diagnostic system in Korea Research Institute of Standards and Science Young-Gi Kim, Jung Hyung Kim, Hyo-Chang Lee The laser scattering system is installed in Korea Research Institute in Standards and Science (KRISS), which is well known diagnostics as the most accurate method for measuring electron temperature and electron density. Although it is challenging to measure the Thomson scattering signals in processing plasmas with low density and low temperature, each part of the system was carefully designed and aligned to maximize the collection efficiency as well as the spectral resolution. The frequency doubled Nd:YAG laser with the maximum energy of 1 J and the repetition rate of 10 Hz is adopted as a light source. The collecting optics transfers scattered photons into double-monochromators so that the highly resolved scattered spectrum would be recorded by intensified CCD. Both spectral and absolute calibration have been performed by measuring rotational Raman scattering spectra. The electron temperature and density are obtained from the spectral broadening and the intensity of the Thomson scattering spectrum, respectively. The system will be operated not only to study heating effects in various plasma sources, but also to compare the operating range and the accuracy of other diagnostics such as cut-off probes developed in KRISS. |
|
GT61.00061: Comparison of phase shifts and cross sections as a function of velocity for positron, electron and positronium elastic scattering from helium Cody M DeMars, Sandra J Ward Quintanilla, Peter Van Reeth, Josiah Claypool Previously, it has been shown that there is a remarkable degree of similarity between the total cross section for electron-helium and positronium-helium scattering as a function of velocity [1]. Using the Kohn and inverse Kohn variational methods we have computed S-, P-, D- and F-wave phase shifts for positron-helium scattering [2, 3]. Using the inverse Kohn phase shifts we have computed the partial-wave, elastic-differential, elastic-integrated and momentum-transfer cross sections for positron-helium scattering in the energy range where the only open channel is elastic scattering (ignoring positron annihilation) [3]. Also, using phase shifts from the literature for electron scattering and positronium scattering from helium [4-6], we have computed the corresponding cross sections. Recently, we have compared the phase shifts and cross sections as a function of velocity for the three projectiles (positron, electron and Ps) [3]. We plan to present at the GEC 2021 meeting this comparison. |
|
GT61.00062: Optical Emission Spectroscopy of N2/CH4 Plasmas for Plasma Catalytic Methane Coupling Ibukunoluwa Akintola, Deanna Poirier, Gerardo Rivera-Castro, Jinyu Yang, Jason C Hicks, David B Go Non-thermal plasmas (NTPs) can produce reactive chemical environments including electrons, ions, radicals, and vibrationally excited molecules. The integration of a catalyst with reactive NTPs can drive thermodynamically unfavorable chemical transformation at low temperatures and pressures. In particular, we are interested in the direct coupling of light hydrocarbons (e.g. methane) and nitrogen to produce value-added liquid chemicals (e.g. pyrrole and pyridine) in a plasma-assisted catalytic process. To design effective catalysts and plasma-catalytic systems requires comprehensive understanding of the plasma-phase chemistry alone, including thorough characterization of plasma-phase properties. While there have been many studies on nitrogen (N2) and methane (CH4) plasmas, there is limited understanding on how operating parameters (i.e. feed N2/CH4 gas ratio, plasma power) affect the plasma properties. In this work, we vary different plasma parameters and optically characterize the plasma using optical emission spectroscopy (OES) to determine relevant thermodynamic information such as the electron temperature and electron density to better understand their effects, if any, on product formation during methane coupling. |
|
GT61.00063: Electron impact excitation collision strengths and radiative parameters for Sc II spectral lines Swaraj S Tayal, Oleg Zatsarinny New large-scale calculations for electron impact excitation collision strengths and radiative parameters for Sc II spectral lines between the 145 fine-structure levels belonging to the 3p63d2, 3p63d4l (l=0-3), 3p63d5l (l=0-3), 3p63d6s, 3p64s2, 3p64s4l (l=0-3), 3p64s5l (l=0-1), and 3p64p2 configurations have been performed. Accurate description of the Sc II wave functions and adequate account of the various interactions between target levels are of crucial importance for the calculations of collision and radiative parameters and have been determined by a combination of the multiconfiguration Hartree-Fock and the B-spline box-based close-coupling methods together with the nonorthogonal orbitals technique [1]. The valence electron wave functions are described by multichannel expansions in a B-spline basis and are subjected to a boundary condition to become negligible at the boundary. This approach generates whole Rydberg series as well as considers the interaction between different series. The calculations of collision strengths have been performed using the close-coupling approximation based on the B-spline Breit-Pauli R-matrix method [2]. The relativistic effects in the scattering calculations have been incorporated in the Breit-Pauli Hamiltonian using the one-body Darwin, mass correction, and spin-orbit operators. The likely uncertainties in our results have been estimated by means of comparison with other calculations and experimental radiative parameters. 1 E-mail: stayal@cau.edu 2 E-mail: oleg.zatsarinny@drake.edu [1] Zatsarinny, O. and Froese Fisher, C. 2009 Comp. Phys. Comm. 180, 2041 [2] O. Zatsarinny 2006 Comp. Phys. Commun. 174 273 |
|
GT61.00064: Comparison of particle-in-cell and fluid simulations for the asymmetric structure effects in a capacitively coupled plasma Hwan Ho Kim, Chang Ho Kim, Ji Hyun Shin In low pressure plasmas where electrons are able to move freely without collisions, electron heating and electron energy consumptions by collisions have different spatio-temporal profiles and the non-local kinetic effect becomes important. In such a non-local regime in which electron energy relaxation length becomes similar to or larger than the length scale of a plasma device, fluid models are not able to describe non-local effects due to the intrinsic properties of fluid equations. In this research, the two-dimensional hybrid plasma equipment model (HPEM) and two-dimensional graphics processing unit (GPU) particle-in-cell (PIC) simulation were applied to capacitively coupled plasma equipment with two different structures. Non-local heating region was showed at low pressure asymmetric structure case in GPU PIC simulation. In case of longer electrodes, non-local heating effect increases and spatial electron temperature show big discrepancy with that of fluid simulation. As a result, we suggest the criterion for choosing a simulation method when investigating plasma properties. |
|
GT61.00065: An electrical diagnostic method for double probe applicable to processing plasma HyeonJung Lee Plasma parameters were measured by applying AC voltage to the double probe. The double probe has the advantage of measuring plasma parameters regardless of the condition of the wall of the processing chamber. When the area of the two probes is different, the plasma parameters were measured considering the area of the probe, and it agrees well with the results measured by the conventional method. Since the electron temperature and ion density are corrected using the phase difference between the applied voltage and the measured current, accurate measurement is possible even when a polymer is deposited on the probe tips. In various RF discharge conditions, the electron temperature and ion density of the proposed method and the conventional method were matched in the case of different areas and the case of deposition. Additionally, when measuring plasma parameters with an asymmetric double probe, the measurable density range is extended. |
|
GT61.00066: Fast and massive synthesis of silver nanoparticle by a liquid-flow plasma source using AgNO3 solution Haruka Suzuki, Kazuya Yamaguchi, Kensuke Sasai, Hirotaka Toyoda Plasma-liquid interaction has attracted much attention for various applications such as water purification, decomposition of liquid waste, biotechnology, agriculture, and material synthesis. However, there are many problems in applying the plasma treatment to industrial applications. First, many applications require treating large volumes of liquid, but the processing capacity of most plasma treatment systems is not adequate for the application. Furthermore, many liquids are difficult to ignite with plasma due to the electro conductivity of the liquids, the high electro negativity and the internal energy of the water molecules. |
|
GT61.00067: Are Electron Sheaths Common for Positive Electrodes at Pressures Above a Few Hundred mTorr? Brett Scheiner In low pressure discharges (P<100mTorr) the balance of global electron and ion current loss dictates that an electron-rich sheath can only occur at a positively biased electrode when the electrode area (AE) is small compared to the area of the other walls (AW) bounding the plasma. At these low pressures, it is well known that the area ratio must satisfy AE/AW<√2.3me/mi, a relation that has been verified by experiments and simulations[1]. In this work simulations show that electron sheaths can occur when AE/AW>√2.3me/mi if the neutral pressure exceeds roughly 300 mTorr. The increased neutral pressure facilitates larger density gradients in the plasma approaching the positive electrode, reducing the electron current collection at the electrode relative to the ion current collection at the walls. This feature lessens the area ratio requirement for global balance of current loss and makes the presence of electron sheaths at positive electrodes more likely at higher pressures. Further studies will be needed to determine the limits on the range of conditions under which electron sheaths occur at positive electrodes. |
|
GT61.00068: Spatio-temporal plasma development in a pulsed packed bed reactor: influence of voltage polarity and amplitude Zaka-ul-Islam Mujahid, Lars Schuecke, Thomas Mussenbrock, Julian Schulze Packed bed plasma reactors (PBPR) often use pulsed power supplies to improve energy efficiency. This work compares the spatial and temporal discharge structure in a PBPR with an electrode that is covered by a patterned dielectric that consists of multiple adjacent dielectric semispheres. The discharge is operated in Helium and powered by a unipolar symmetric voltage pulse. Experimentally, 2D time-resolved images, current, and voltage have been measured for both polarities as a function of applied voltage amplitude and pulse duration. The emission is first visible during the electron avalanche phase. This is followed by a cathode-directed positive streamer first in the volume and then along the dielectric surface. Once the surface streamer reaches the contact point between adjacent semispheres, a surface microdischarge is generated. Qualitatively all effects are reversed with the polarity of the pulse voltage. The streamer speed increases both in the volume and along the surface with the increase in voltage amplitude. Compared to sinusoidal operation in a similar geometry where multiple surface microdischarge pulses are observed [1], only a single pulse of surface microdischarge has been observed for the pulsed operation irrespective of the voltage amplitude and pulse duration. |
|
GT61.00069: Behavior of multiple Gaussian beam components in a single negative ion beam aimed at fusion plasma heating Yasuaki Haba, Kenichi Nagaoka, Mitsutoshi Aramaki, Katsuyoshi Tsumori, Katsunori Ikeda, Haruhisa Nakano, Masaki Osakabe Negative ion beams are utilized for advanced applications such as accelerators of particle physics and medical fields, and plasma experiments in nuclear fusion. It is because their neutralization efficiency is higher than that of positive ion beams. Well focused negative hydrogen and/or deuterium ion beams are required for neutral beam injection (NBI) systems for heating magnetically confined fusion plasmas and current drive. The study of a single negative ion beam clarified the detailed structure and divergence of the beam. Our research group with the National Institute for Fusion Science found that the single negative ion beam consists of multiple Gaussian beams, which have been measured with a pepper-pot type emittance meter. The peak positions of the components shift with the change in the acceleration voltage while keeping the extraction voltage constant. It implies that the shift of multiple Gaussian beam components can affect the resultant superimposed single negative ion beam's divergence. This presentation reports the spatial distributions of each component in a plane perpendicular to the beam direction, and their abundance ratio while changing the arc power. The abundance ratio could be used for the investigation of relative contributions of negative ions caused by the surface production at a plasma grid region. |
|
GT61.00070: Molecular Dynamics Simulations of Diffusion in Atmospheric Pressure Plasmas Marlena N Kot, Scott D Baalrud, Christopher H Moore Ion diffusion in the presence of other ions, electrons, and neutrals is important in regards to timescales for discharge evolution and for determining the fields which drive plasma chemistry. We apply molecular dynamics simulations to show that strong Coulomb coupling can influence diffusion coefficients at atmospheric pressure plasma conditions. This is done by computing the radial distribution functions and interdiffusion coefficients over a range of conditions relevant to atmospheric pressure plasmas. The simulations applied a model plasma utilizing the Lennard-Jones potential for neutral-neutral interactions, the charge induced dipole potential for charge-neutral interactions, and Coulomb potential for charge-charge interactions. Since existing kinetic theories are not valid at strong coupling conditions, the simulation results motivate that there is a need for generalized kinetic theories that accurately model charge particle transport in atmospheric pressure plasmas. |
|
GT61.00071: Singlet p-wave elastic electron-positronium scattering William J Mitchell, Sandra J Ward Quintanilla The photodetachment of Ps- has been observed [1]. |
|
GT61.00072: Implicit kinetic solvers with Adaptive Mesh in Phase Space for simulations of low-temperature plasmas Haoming Liang, Robert Arslanbekov, Vladimir I Kolobov The disparity of time scales calls for using implicit methods in plasma simulations [1]. This paper describes the development of implicit kinetic solvers for electrons with Adaptive Mesh in Phase Space (AMPS). We have previously developed AMPS solvers with splitting velocity and configuration scape (for 6D phase space [2]) and without splitting (for 2D and 3D phase space [3]) using explicit and multi-grid implicit solvers for diffusion. In this paper, we describe the implementation of an implicit AMPS solver with adaptive Cartesian mesh using spherical coordinates in velocity space and different coordinate systems in configuration space. Splitting velocity and configuration spaces facilitates coupling of the kinetic solver for electrons with Poisson solver for the electric field and fluid solvers for ions. We will illustrate the new solvers for spherical expansion of weakly collisional non-magnetized and magnetized (solar wind) plasma and for capacitively coupled collisional gas discharge plasma. The benefits of the implicit treatment of electrons for kinetic plasma simulations will be explained. |
|
GT61.00073: Methods and tools for data-driven science in applied plasma physics Nick Plathe, Robert Wagner, Kristian Wende, Henrike Brust, Detlef Loffhagen, Markus M. M Becker With the rapid emergence of data in applied plasma physics, such as plasma medicine and plasma agriculture, there is a need for the development of robust, reliable and reproducible analysis methods. Then, it is advisable that the analysis interacts with existing data stored in databases from different disciplines, with parameters set by the experimenter and with additional data containing information about mathematical models that can then be used for predictive methods in the future. Although plasma medicine has adapted methods from numerous fields, processing the data remains a challenge due to different, non-standardised data formats and differing needs throughout the various hypotheses. In the topical field of plasma agriculture, the need for elaborated data workflows has just been recognised and work is underway to standardise data collection and documentation and to integrate external databases into the research processes. We present an approach to data analysis based on uniformly annotated research data using electronic laboratory notebooks. It includes the KNIME Analytics Platform as well as the R programming language for automated data processing. This approach can also be applied in other application areas and similarly realised with alternative tools. |
|
GT61.00074: Electron density reduction in magnetized capacitively coupled plasmas induced by magnetic damping of the plasma series resonance Li Wang, Mate Vass, Zoltan Donko, Peter Hartmann, Aranka Derzsi, Yuan-Hong Song, Julian Schulze The effects of a homogeneous transversal magnetic field on the plasma density and electron dynamics in low pressure capacitively coupled plasmas (CCP) are studied by Particle-in-Cell/Monte Carlo collision (PIC/MCC) simulations. The plasma density increases monotonously as a function of the magnetic field at low frequencies due to the enhanced magnetic confinement of electrons. In contrast with this, a strong initial decrease is observed at higher frequencies (60 MHz) and low magnetic fields, which is caused by a magnetic damping of the self-excited Plasma Series Resonance (PSR) oscillations of the RF current and the attenuation of the corresponding Non-Linear Electron Resonance Heating (NERH). By further enhancing the magnetic field, the plasma density increases due to magnetically induced electric field reversals during sheath collapse and an enhanced interaction time of electrons with the expanding sheath edge. |
|
GT61.00075: Effect of the radial beam mode on expansion of laser-induced plasma plumes Michael Stokes, Omid A Ranjbar, Zhibin Lin, Alexey N Volkov Expansion of plasma plumes induced by a single and multiple short-pulse laser irradiation of a copper target into argon background gas is numerically studied using a two-dimensional hybrid computational model which includes a thermal model that describes the thermal state of the target and a kinetic model that describes non-equilibrium expansion of laser-induced plasma plume. The kinetic model is based on the Boltzmann kinetic equations for the gas mixture and is implemented in the form of a generalized direct simulation Monte Carlo method, which accounts for absorption of laser ablation as well as ionization and recombination processes. The radial beam mode is assumed to be either Gaussian TEM00 mode or TEM*01 mode with a donut-type intensity distribution. The results of simulations show that the plume structures induced by individual Gaussian and donut-type beams are qualitatively different. The simulations reveal a more complex plume structure created with the donut-type beam which contains multiple shock waves and high temperature regions near the axis of symmetry. It is shown that the radial beam mode also affects the degree of plasma shielding of the target from incident multi-pulse laser radiation. |
Not Participating |
GT61.00076: Electrical Breakdown in Gases with Electrode Gap at the Nanometer Scale Nelly Bonifaci, Sylvain Iseni, Hugo Lagarrigue, Olivier Lesaint, Christophe Poulain Electrical breakdown in gases is a critical aspect for applications relying on electrical insulation such as circuit breakers or contactors. The voltage breakdown (VK) can be estimated in a reasonable order using the Paschen’s law1. Theoretically based on ideal assumptions ‒e.g. perfectly uniform electric field, infinitely large electrode size, …‒ this analytical approach has shown remarkable capability to predict VK in an innumerable quantity of systems. Centered around the product pressure times inter-electrode distance (p·d), the Paschen’s law scales a large pressure range coupled with the gap distance which makes it very convenient to use. The robustness of the Paschen’s law to predict consistent values of VK clearly fails at gap distances shorter than a micrometer at atmospheric pressure. Many studies have brought experimental2, theoretical3 and simulation4 evidences of such limitations which seriously questions the insulation properties of gases at short distances. |
|
GT61.00077: Plasma Assisted Depolymerization of Polyethylene Terephthalate Roxanne Pinsky, John E Foster Currently, the world is facing a plastics crisis, with only ~10% being recycled. In this work, we investigate the use of nonthermal plasmas to assist in the chemical recycling of polyethylene terephthalate (PET) (a consumer plastic used in packaging), promoting depolymerization which can be upcycled into commodity plastics or other high value products. PET may be depolymerized into precursors terephthalic acid (TPA) and ethylene glycol (EG) in a liquid with heat, pressure, and/or chemicals (strong acids or bases) by hydrolysis. Nonthermal plasmas in contact with water can provide non-equilibrium conditions at the interface such as heat, UV, solvated electrons, a host of reactive oxygen and nitrogen species (ROS/RNS) and localized pH changes. These conditions are suitable to provide several pathways for polymer chain breaking, including hydrolysis, without the typical required heat and chemicals to alter the pH. This initial work aims to provide insight on the bulk conditions of the solution created during treatment, including plasma and gas temperature, ROS/RNS concentrations, and pH changes. Polymer analysis techniques, including mass spectrometry, FTIR, and Raman spectroscopy are used to understand reaction products as well as functional groups formed at the polymer surface. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700