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 TF14: Plasma Modeling: Laser Produced Plasmas, Streamers and Striations |
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Chair: Sanjan Kerketta, University of Michigan Room: Virtual GEC platform |
Friday, October 8, 2021 8:00AM - 8:15AM |
TF14.00001: Laser-Produced Aluminum Plasmas Expanding in an Applied Field: Plasma Generation in Single Particle Aerosol Mass Spectrometers Amanda M Lietz, Jeffrey Musk, Matthew Hopkins, Benjamin Yee, Harry Moffat, Dora Wiemann, Taylor Settecerri, David Fergenson, Michael Omana Single particle aerosol mass spectrometers (SPAMS) are used to generate mass spectra of solid particles ranging in size from 10-7-10-5 m in diameter, which are critical in air pollution and climate science. In most SPAMS devices, one or more lasers are used to vaporize and ionize each particle. A high electric field ~105 V/m is also applied to the plasma to collect the positive and negative ions. In this presentation, we use computational modeling to investigate the effect of the applied electric field on the laser produced plasma as it expands into the surrounding vacuum. The model system of interest is a spherical aluminum particle which is ionized by a 248 nm laser with an 8 ns pulse. A zero-dimensional plasma chemistry model is used to investigate the dynamics. Immediately after the laser pulse, the high plasma density enables shielding of the applied field, and the influence of the field is relatively small. After expansion the decrease in plasma density results in the electrons being rapidly removed from the plasma by the applied electric field. The effect of the applied electric field on the total number of ions produced per particle is discussed in order improve future SPAMS devices. |
Friday, October 8, 2021 8:15AM - 8:30AM |
TF14.00002: Two-dimensional axisymmetric simulations of laser-produced chalcogen ion plumes using an effective plasma physics model Jacob H Paiste, Sumner B Harris, Joseph Edoki, Robert R Arslanbekov, Renato P Camata Simulations of laser plasmas are essential to improve laser synthesis of novel materials. They must account for the thermo-physical properties of specific species and include 3D effects. While embedding detailed mechanisms is desirable, simulations of practical utility need to be fast and predictive. In this work we balance these demands using an effective model that incorporates standard features of laser ablation plasmas: thermal evaporation, bremsstrahlung emission, photoionization, and free-free laser absorption by the plasma. An additional effective plasma absorption coefficient is introduced as a stand-in term for other mechanisms that are impractical to account for directly—due to computational cost or unavailability of physical parameters. The effective model is constrained by Langmuir probe experimental data. The simulations are set up in a 2D-axisymmetric geometry using a solver with an adaptive Cartesian mesh. We simulate plasmas of selenium (Se) and tellurium (Te), which are of current interest in synthesis of transition metal chalcogenide materials. Predictions of Se and Te plasmas for 4 J/cm2 laser fluence and 1.8 mm2 laser spot area show chalcogen plumes with spatial gradients of plasma density that are steeper than those for more commonly studied copper (Cu) plumes by up to three orders of magnitude. Their spatial ion distributions have central bulges, in contrast to the edge-only ionization of Cu. The range of plasma temperatures for Se and Te is higher than for Cu by more than 0.5 eV. |
Friday, October 8, 2021 8:30AM - 8:45AM |
TF14.00003: Vorticity Generation with Defocusing Effect for Dual-Pulse Laser Plasma in Air Sagar Pokharel, Albina Tropina, Mikhail Shneider We consider the dual pulse laser energy deposition, when plasma is already present in the focal area after the first pre-ionizing pulse. The subsequent laser pulse is partially reflected due to changes in the refractive index caused by the laser plasma formation, resulting in the deviation of the laser intensity profile from the Gaussian shape, defined as defocusing effect. We used a three-temperature plasma model coupled with Navier-Stokes equations and the beam propagation solver to quantify how the laser intensity changes with defocusing. The effect of defocusing on the vorticity generation and dual-pulse laser plasma dynamics in air is reported. |
Friday, October 8, 2021 8:45AM - 9:00AM |
TF14.00004: Computational study of the effects of solar and electric power on Solar-Enhanced Microwave Plasma CO2 decomposition rasool elahi, Juan Trelles The utilization of CO2 in the synthesis of fuels and chemicals using renewable energy can help limit CO2 emissions driving climate change. Plasmachemical CO2 decomposition processes can be highly efficient; however, solar thermochemical approaches, given their direct use of solar energy, can be more sustainable. Solar-Enhanced Microwave Plasma (SEMP) chemical conversion is an effective approach that combines the advantages of both methods. SEMP exploits the greater absorption of solar radiation by CO2 in thermal nonequilibrium (compared to CO2 in Local Thermodynamic Equilibrium) to enhance CO2 decomposition. A computational study of the effects of input solar power and input electric power on a SEMP reactor operating with Ar-CO2 (7:1) at atmospheric pressure is presented. The 2D model describes, via a completely-coupled solution approach, fluid flow, heat transfer, plasma dynamics, chemical kinetics, electromagnetic field evolution, and radiative transport in participating media. Simulation results reveal that CO2 conversion increases with increasing microwave and incident solar power, in good agreement with experimental results. Moreover, the results quantify the enhancement afforded by the incorporation of solar power and suggest strategies towards improved process performance. |
Friday, October 8, 2021 9:00AM - 9:15AM |
TF14.00005: Self-excited standing striations in moderate pressure dc nitrogen glow discharge Malik M Tahiyat, Jacob C Stephens, Vladimir I Kolobov, Tanvir I Farouk Despite the many experimental studies reported on plasma stratification, theoretical analyses and numerical modeling of this phenomenon have been mostly limited to rare gases. In this work, a one-dimensional fluid model with detailed electron and vibrational state kinetics is employed to simulate moderate-pressure (i.e. a few Torrs) dc discharge in nitrogen in a 15.5 cm long tube of radius 0.55 cm. The model includes ambipolar diffusion of ions and electrons to the wall. The model predicts self-excited standing striations in nitrogen for a range of discharge currents (~0.018 – 0.080 mA cm-2). The impact of electron induced reaction rates obtained from numerical solution of a local two-term and a multi-term Boltzmann equation on the predictions are assessed. Our analysis indicates that the striations result from the undulations in electron mean energy (temperature) caused by an interplay between ionization and vibrational excitation processes. The vibrationally excited molecules associated with the lower energy levels are found to significantly influence nitrogen plasma stratification and the striation properties. Parametric studies show that the striation length inreases linearly with increasing the tube radius but increases in a non-linear fashion with increasing discharge current. The predictions from the model agree favorably with our experimental measurements. |
Friday, October 8, 2021 9:15AM - 9:30AM |
TF14.00006: Numerical simulation of cathode directed streamer discharges in Air and CO2. Francis Boakye-Mensah, Hani Francisco, Ute Ebert, Nelly Bonifaci, Rachelle Hanna, Innocent Niyonzima Dielectric breakdown characterization in CO2 has become as important as that of SF6 gas in high voltage engineering. This is as a result of the urgent need for replacement of SF6 gas due to its high GWP. The first stage of breakdown in gases is the streamer discharge which occurs when a gas is suddenly exposed to a high voltage. Modeling streamer discharges numerically is needed to predict intrinsic characteristics of gases such as SF6 and CO2, which further allows for an accurate comparison of their dielectric performances. |
Friday, October 8, 2021 9:30AM - 9:45AM |
TF14.00007: Stable propagation of solitary positive streamer heads in air Hani Francisco, Jannis Teunissen, Behnaz Bagheri, Ute Ebert We studied positive streamers in STP air in a 4 cm gap and found a case wherein the streamer is not accelerating and expanding, but is propagating with a constant radius and velocity. We observed this for a simulated single streamer in a homogenous background field that is 17% of the breakdown field. This streamer got detached from the electrode from which it originated, so we dub it as a solitary streamer. The propagation behavior of the solitary streamer reminds us of the original definition of the streamer stability field, namely the homogenous electric field in which a streamer propagates in a stable manner. Our measurements agree well with empirical values for the stability field reported in earlier literature. The velocity and optical radius also agree well with earlier measurements of so-called minimal streamers. In electric fields above this limiting case of uniform translation, the streamers accelerated as they grew, and in electric fields below it, the streamers decelerated and some even stagnated. |
Friday, October 8, 2021 9:45AM - 10:00AM |
TF14.00008: Numerical Simulation for Analysis Electron and Heavy Particle Temperature Variation before Re-strike Occurrence in Parallel Electrode Zhenwei Ren, Yusuke Nemoto, Yuki Suzuki, Shinji Yamamoto, Gaku Asanuma, Toshiyuki Onchi, Toru Iwao For decreasing the interruption times of direct current circuit breaker, it is important to find out the trigger of re-strike phenomenon occurrence for improving the arc plasma velocity. In this research, the variation of electron and heavy particle temperature were analyzed by numerical simulation, which solves the energy conservation equations of electron and heavy particle respectively. It obtained that the temperature distribution of electron barely changed, while the peripheral of heavy particle temperature distribution extended forward. The reason of above differentce is the electron restricted by the strong electromagnetic field of arc plasma, and the arc plasma peripheral and forward location are dominated by heavy particles. As a result, the electrical conductivity of the re-strike point area is decided by the existed heavy particles on this area, which were transported by the synthesis flow derived from electrode jets. Therefore, it is elucidated that the occurrence of re-strike phenomenon is caused by the existence of heavy particles on re-strike point area which leads to the thermionic discharge. |
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