Plasma and Beam Physics Commons^™

Simulations Of Atmospheric Pressure Streamer Discharges: Mechanisms Of Streamer Propagation And Related Physics, Dejan Nikic

Electrical and Computer Engineering ETDs

Gas discharge simulations are performed with particular focus on photoionization process in a positive streamer discharge. The effects of this process are investigated by isolating the change in photoionization mean free path (MFP) and keeping the additional processes constant. Furthermore, comparison are made between various effects of simulation parameters, such as initial conditions, geometry extent, simula- tion particle count etc. All of these simulations are performed using a modern Direct Simulation Monte Carlo Particle-in-Cell (DSMC-PIC) code developed by Sandia Na- tional Laboratories. Large scale simulations including 1 cm and 5 cm electrode gaps are performed under standard atmospheric condition air. …

Plasma-Enhanced Carbon Nanomaterial Synthesis: A Pathway To Reducing Greenhouse Gasses And Carbon-Based Waste., Zane Ronau

Electronic Theses and Dissertations

This research leveraged incorporation of capacitively coupled radio frequency plasma into chemical vapor deposition (CVD) for a reduction in the temperature requirements [a reduction of energy barrier] needed for the conversion of methane (CH₄), carbon dioxide (CO₂), and various carbon-based-waste to produce value-added carbon nanomaterials. An array of catalysts and catalyst supports were employed to optimize the synthesis of graphitic carbon under various gas environments, temperatures and pressures. The nanomaterials synthesized after fine tuning the growth parameters included graphene, carbon nanotubes (CNT), carbon microtubes and carbon nanocages with a variety of properties. Raman Spectroscopy was used …

Low Energy Ion Irradiation Effects In Electronic Devices And Materials, David C. Mccall

All Dissertations

The physics and engineering of ion-solid interactions are governed by the ion beam characteristics (flux, charge, energy) and target(s) in question. Here I present work on two projects related to the extraction of a high flux of low charge state Argon ions from a commercial plasma source and the irradiation of an engineered target, a transistor, with high charge state Argon ions.

An end-Hall ion source that produces a a high current plasma of ions and electrons in a rough vacuum environment is characterized. Using a Langmuir probe and multiple pressure measurements, the ion and electron content of the source …

Current Continuity In Auroral System Science, Jules Van Irsel

Dartmouth College Ph.D Dissertations

The Earth relies on the Sun's energy, but at times this energy can be overwhelming; the Sun expels plasma which, were it not for our humble magnetic field, would erode our atmosphere (Mars, c. 4 Ga). The protective interaction Earth has with the solar wind results in spectacular auroral displays---one such auroral form is discussed in this thesis: quiet discrete auroral arcs.

Such arcs have long been studied; they are abundant, have usable symmetries, and they can predict magnetic substorms that wreak havoc in our magnetosphere. The auroral emissions, albeit beautiful, are however only the visible end of a self-consistent …

A Modular Paradigm For The Directly Efficient Representation Of Kinetic Laser-Driven Plasmas, Roland D. Hesse

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

A natural inefficiency in conventional treatment of the plasma distribution arises from indiscriminate consideration of the contributions to field structure that are dynamically sourced from kinetic activity in disparate sectors of phase space. We introduce a range of techniques for model design to maximize representation efficiency without breaking key physical invariants indicative of physical reliability. An overview of varied adaptation to stable time-advance methods is given. Low-dimensional representation of a laser-driven plasma requires some creativity in differential structural modification, while direct efficiency is uncovered through the compression and rarefaction of a nonuniform momentum grid. These numerical models introduce embedded gains …

Plasma And Magnetic Coil Optimization, William Lee Austin, Lachlan Dean

Undergraduate Theses, Professional Papers, and Capstone Artifacts

Lachlan Dean Coil Optimization for a High-Beta Stellarator-Tokamak Hybrid Magnetic coil configurations are developed for a tokamak-stellarator hybrid that is stable to both pressure- and current-driven modes for high values of beta. Previous work on this configuration [A. S. Ware, et al., Phys. Rev. Lett, 89, 125003 (2002)] was carried out using a fixed-boundary equilibrium (i.e., with no set of external coils) and prior attempts to develop an initial coil set using the COILOPT code were not successful. In this work, the recently developed SIMSOPT code [M. Landreman, et. al., J. Open Source Software 6, 3525 (2021)] is used to …

Optical Investigation Of A Low-Pressure Plasma In A Superconducting Radio-Frequency Cavity, Zachary A. Caudell

Electrical & Computer Engineering Theses & Dissertations

The state-of-the-art cryomodules for particle accelerators use superconducting radio-frequency (SRF) cavities. It is known that accumulation of hydrocarbon impurities reduces the cavity surface work function, decreasing cryomodule performance metrics such as field emission, thermal stability, and accelerating gradients. An in-situ method of plasma processing has recently been developed to clean the cavities and restore cryomodule performance [1]. This study is to understand the properties of the low-pressure plasmas generated in a C100 SRF cavity and ultimately to improve the performance of plasma surface cleaning using optical emission spectroscopy. Using a 500 mm focal length Czerny-Turner monochromator coupled with a photomultiplier …

On The Nature Of Low-Frequency Power Spectra In Solar Wind Turbulence, Mason Alden Dorseth

Theses and Dissertations

An important challenge in the accurate estimation of power spectra of plasma fluctuations in the solar wind at very low frequencies is that it requires extremely long signals, which will necessarily contain a mixture of qualitatively different solar wind streams. This unavoidably affects the structure of the power spectra by conflating all these different properties into a single power spectrum. This work develops a conditional statistical analysis to accurately estimate the power spectrum at arbitrarily low frequencies for ``pure'' slow solar wind stream, based on estimated autocorrelation functions of signals excluding portions that do not satisfy the required conditions. The …

Non-Symmetry In The Shock Refraction At A Closed Interface As A Recovery Mechanism, Anna Markhotok

Physics Faculty Publications

The possibility of a shock wave recovery at a discrete closed interface with a heated gas has been investigated. A two-dimensional model applied to conditions of optical discharges featuring spherical, elliptical, and drop-like configurations demonstrated that non-symmetry in the shock refraction contributes to the specific mechanism of recovery other than simply its compensation. Even though the full restoration of the hypersonic flow state does not occur in a strict sense of it, clear reverse changes toward the initial shape of the shock front eventually take place, thus creating an appearance of a full recovery seen in experiments. From analysis of …

Thermocatalytic Plasma-Assisted Dry Reforming Of Methane Over Ni/Al2o3 Catalyst, Tyler Wong

Seton Hall University Dissertations and Theses (ETDs)

Plasma catalysis is an advantageous approach that combines the effects of plasma with the enhancements of a catalyst. By utilizing a nickel catalyst in the plasma discharge zone of a dielectric barrier discharge (DBD), it can give an enhancement to the electrical field, boost microdischarges, and increase conversion and selectivity rates of CH₄ and CO₂ in the dry reforming of methane (DRM) reaction.

Industrial application of nickel catalysts in DBD Plasma DRM process are limited by poor stability, which is caused by the sintering of active metal particles and coke deposition on the catalyst surface. In this work, …

On The Chronological Understanding Of The Homogeneous Dielectric Barrier Discharge, Xinpei Lu, Zhi Fang, Dong Dai, Tao Shao, Feng Liu, Cheng Zhang, Dawei Liu, Lanlan Nie, Chunqi Jiang

Bioelectrics Publications

Dielectric barrier discharges (DBD) are widely utilised non-equilibrium atmospheric pressure plasmas with a diverse range of applications, such as material processing, surface treatment, light sources, pollution control, and medicine. Over the course of several decades, extensive research has been dedicated to the generation of homogeneous DBD (H-DBD), focussing on understanding the transition from H-DBD to filamentary DBD and exploring strategies to create and sustain H-DBD. This paper first discusses the influence of various parameters on DBD, including gas flow, dielectric material, surface conductivity, and mesh electrode. Secondly, a chronological literature review is presented, highlighting the development of H-DBD and the …

Sars-Cov-2 Spike Conformation Determines Plasma Neutralizing Activity Elicited By A Wide Panel Of Human Vaccines, John E. Bowen, Young-Jun Park, Cameron Stewart, Jack T. Brown, William K. Sharkey, Alexandra C. Walls, Anshu Joshi, Kumail Ahmed, Asefa Shariq, Najeeha Talat Iqbal

Department of Paediatrics and Child Health

Numerous safe and effective coronavirus disease 2019 vaccines have been developed worldwide that use various delivery technologies and engineering strategies. We show here that vaccines containing prefusion-stabilizing S mutations elicit antibody responses in humans with enhanced recognition of S and the S1 subunit relative to postfusion S as compared with vaccines lacking these mutations or natural infection. Prefusion S and S1 antibody binding titers positively and equivalently correlated with neutralizing activity, and depletion of S1-directed antibodies completely abrogated plasma neutralizing activity. We show that neutralizing activity is almost entirely directed to the S1 subunit and that variant cross-neutralization is mediated …

Ultrashort Pulse Laser Filamentation Electrical And Optical Diagnostic Comparison, James E. Wymer

Optical Science and Engineering ETDs

Results presented here examine the effect of changing gas pressure on the radio frequency (RF) emissions of an ultrashort pulse laser filament plasma and how those emissions vary longitudinally in the laser focal region. We use a WR284 rectangular waveguide with a 1.5 cm hole that allows the beam through. A 3.2 GHz microwave signal is emitted in the waveguide, and signals are received through a waveguide-to-coax antenna connected to an HP8470B Schottky diode. By enabling and disabling the 3.2 GHz signal, we measure both the self-emitted RF from a USPL filament and subsequently the degree of attenuation a filament …

Electrothermal Plenum Thruster Simulations Varying Input Pressure And Voltage, Naomi Nicole Ingram

Open Access Theses & Dissertations

A radiofrequency electrothermal thruster is designed and simulated to create a low ionization energy plasma from a neutral propellant using a radio-frequency power. With an asymmetrical surface area ratio between the grounded and powered electrode, ion-neutral charge exchange collisions occurring within the propellant result in propellant heating. The Electrothermal Plenum Thruster conducts this propellant heating in an annular plenum chamber in attempt to maximize propellant heating. A software called CFD-ACE+ is utilized to demonstrate the effects of an enhanced sheath from the asymmetrical power coupling arrangement. Two sets of simulations are run to understand how input variables affect the plasma …

Whistler Waves: Modeling And Observations, Daniel Williams

Doctoral Dissertations and Master's Theses

The thesis presents the results of all the research from the published and in publication process research in the Journal of Geophysical Research [1]. This research focuses on whistler wave ducting events in the equatorial magnetosphere. High-density ducts are the main focus of whistler study in both studies as they are commonly observed by the Van Allen Probe satellites. A three-step procedure based on the analysis of the whistler wave dispersion relation and numerical simulations of the electron magnetohydrodynamics model. We use this model to identify the parallel and perpendicular wave numbers of the “most trapped” wave in an attempt …

Plasma-Laser Wakefield Acceleration, Jonathan Babu

Physics

Many texts detailing the derivations and science of Wakefield Acceleration are aimed at graduate and doctorate level scholars, and these may seem intimidating to new physics students. This paper is meant to be an introduction to the nature of plasmas, lasers, laser-plasma interactions, and Laser Wakefield Acceleration (LWFA), with sources given where extra detail may be required. I recognize that this paper is not meant to be an all-encompassing review on the nature of the topics, as these topics are complex and subject of entire textbooks. Instead, I aim to provide an introduction to these topics to a college-level scholar …

Plasma Aerodynamics: Experimental Quantification Of The Lift Force Generated On An Airfoil Using Plasma Actuation To Estimate Power Requirements In Small Uav Applications, Getachew Ashenafi

UNLV Theses, Dissertations, Professional Papers, and Capstones

This research addressed the amount of electric power required to induce specific changes in lift force using a NACA 2127 airfoil with a chord length of ~28 mm, connected to a micro load cell, in a wind tunnel of 103 square centimeter cross-section. A DBD plasma actuator supplied by a ZVS driven high voltage pulsed DC circuit, operating at a frequency of 17.4 kHz, was utilized for voltages of up to 5000 V. Two configurations of electrode gapping were compared to determine the efficient use of power. The configuration with a gap of ~1 mm between the upstream and downstream …

Investigation Of The Chemical Kinetics In An Atmospheric Cold Plasma Towards Co2 Conversion, Daniel Piatek

Seton Hall University Dissertations and Theses (ETDs)

Hydrogenation of carbon dioxide (CO2) to methanol (CH3OH) is a promising route for utilization of excess and residual CO2. The conversion of CO to methanol is a well-developed process but the ability to use CO2 as a feed gas still requires high pressures (30-300 atm) to attain conversion. In this work, the hydrogenation of CO2 is explored using H2O as well as H2 in an atmospheric pressure nonthermal (cold) plasma created with a dielectric barrier discharge (DBD) reactor. Different gas mixtures such as argon (Ar) and helium (He) are used to understand their interactions in the process of CO2 hydrogenation. …

Characterization Of A Novel Double Cooled Electrode Dbd Reactor For Ozone Generation, Gustavo Duarte

Seton Hall University Dissertations and Theses (ETDs)

The Dielectric Barrier Discharge (DBD) is used to generate atmospheric or higher-pressure non-thermal plasmas and has found various commercial applications such as in industrial large-scale ozone generation. Ozone (O₃ ) is a powerful chemical reactant that is used to kill bacteria, to deodorize and to perform water purification. The effectiveness of the DBD reactors depends on the electrode arrangements, gap lengths, dielectric materials, operating gases and feed gas quality to name a few. However, the production of O₃ is heat sensitive. In order to prevent O₃ destruction thermal cooling of the DBD is needed. The industry approach …

Characterization Of A Plasma Source Simulating Solar Wind Plasma In A Vacuum Chamber, Blake Anthony Folta

Masters Theses

"The United States has set an aggressive time line to not only return to the Moon, but also to establish a sustained human presence. In the Apollo missions dust was a significant factor, but the duration of those missions was short so dust and surface charging were problems, but they did not pose an immediate threat. For a long-term mission, these problems instead become incredibly detrimental. Because of this, research needs to be conducted to investigate these phenomena so that mitigation techniques can be developed and tested. To this end, this thesis serves to demonstrate the Gas and Plasma Dynamics …

The Population Densities Of Argon Metastable Levels, Nada Khogeer, Chelsy Gonzalez, Milka Nikolic

Physics and Astronomy

In this experiment, we used the optical emission spectroscopy (OES) method to obtain the main properties of low temperature Argon plasma. The experiment was sustained in powers and pressures that ranges from 30-100 W and 15-100 mTorr. We used numerical methods for the Argon kinetic model to calculate metastable levels and resonant states for the first excited states in low temperature Argon plasma. By finding the ratio of two spectral lines and finding another ratio from a different upper energy level that goes down to the same two lower energy levels, we can construct a system of two nonlinear equations. …

Evaluation Of X-Ray Spectroscopic Techniques For Determining Temperature And Density In Plasmas, Theodore Scott Lane

Graduate Theses, Dissertations, and Problem Reports (ETD)

Temperature and density measurements of plasmas are important for understanding various phenomena. For example, equations of state, most scaling arguments for Inertial Confinement Fusion and laboratory astrophysics all rely upon accurate knowledge of temperature and density. Spectroscopy is a non-invasive technique to measure these quantities. In this work we establish a new spectroscopic technique by using it to determine temperature. We also compare and contrast the capability of two codes, PrismSPECT and ATOMIC, to infer electron density from experimentally acquired spectra via Stark broadening.

We compare and contrast the capability of isoelectronic line ratios and inter-stage line ratios in an …

Pseudo Linear Hall Effect Thruster Characterization Through Potential, Magnetic, And Optical Measurements, Braeden A. Sheets

Theses and Dissertations

Electric propulsion systems are a more mass efficient method for providing a change in velocity, ΔV, to on-orbit spacecraft, than their chemical counterparts. In comparison, electric systems generally have a much higher specific impulse, Isp, than chemical systems. One option within the realm of electric propulsion is Hall Effect Thrusters, which have moderately high specific impulse values. From their advent in the 1960s, Hall Effect Thrusters have been used for orbit station keeping, attitude control, and orbit transfer. Although the discharge cavity is conventionally circular, pseudo-linear or racetrack shaped cavities have been developed. Even though Hall thrusters have decades of …

Nonlinear Waves, Instabilities And Singularities In Plasma And Hydrodynamics, Denis Albertovich Silantyev

Mathematics & Statistics ETDs

This work concentrates on Langmuir wave filamentation instability in the kinetic regime of plasma and computation of Stokes wave with high precision using conformal maps.

Nonlinear effects are present in almost every area of science as soon as one tries to go beyond the first order approximation. In particular, nonlinear waves emerge in such areas as hydrodynamics, nonlinear optics, plasma physics, quantum physics, etc. The results of this work are related to nonlinear waves in two areas, plasma physics and hydrodynamics, united by concepts of instability, singularity and advanced numerical methods used for their investigation.

The first part of this …

The Impact Of Base Stacking On The Conformations And Electrostatics Of Single-Stranded Dna, Alex Plumridge, Steve P. Meisburger, Kurt Andresen, Lois Pollack

Physics and Astronomy Faculty Publications

Single-stranded DNA (ssDNA) is notable for its interactions with ssDNA binding proteins (SSBs) during fundamentally important biological processes including DNA repair and replication. Previous work has begun to characterize the conformational and electrostatic properties of ssDNA in association with SSBs. However, the conformational distributions of free ssDNA have been difficult to determine. To capture the vast array of ssDNA conformations in solution, we pair small angle X-ray scattering with novel ensemble fitting methods, obtaining key parameters such as the size, shape and stacking character of strands with different sequences. Complementary ion counting measurements using inductively coupled plasma atomic emission spectroscopy …

Laser Shock Wave Assisted Patterning On Niti Shape Memory Alloy Surfaces, Dovletgeldi Seyitliyev, Peizhen Li, Khomidkhodza Kholikov, Byron Grant, Haluk E. Karaca, Ali O. Er

Mechanical Engineering Faculty Publications

An advanced direct imprinting method with low cost, quick, and less environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni₅₀Ti₅₀ shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generates pressure pulses up to 10 GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the NiTi surface. Scanning …

Power And Langmuir Probe Measurements Of H2 Rf Plasma, Alexander A. Stowell

Macalester Journal of Physics and Astronomy

Methane based gases are often used to produce thin films of biomaterials, such as diamond-like carbon, through Plasma Enhanced Chemical Vapor Deposition. The characterization of the H₂ plasma will give a deeper understanding of the physical processes occurring. Understanding these processes could lead to the optimization of the production of these thin films in the future. In this paper, we examine the H₂ plasma using a Langmuir probe to gain information on the electron temperature and density of the plasma discharge. We measured electron temperatures of 6eV. Our Langmuir probe data indicates the electron temperature remains constant as …

Dissociative Excitation Of H2 In An Rf Plasma, John Carlson

Macalester Journal of Physics and Astronomy

Plasma-enhanced chemical vapor deposition is a widely used method for depositing thin films. In order to optimize the properties of the films, it is important to understand the plasma processes that occur during film growth. In this research we use optical emission spectroscopy in order to measure the spectral emission lines of a plasma produced with hydrogen gas. In conjunction with other measurements and modeling, these measurements can provide insight to the electron energy distribution of the plasma.

Improving The Efficiency And Resolution Of Time Of Flight (Tof) Mass Spectrometer For Magnetospheric Applications., Zain Abbas

Honors Theses and Capstones

The Earth magnetosphere is the volume of space formed by the Earth magnetic field in response to the flow of plasma from the solar wind. Although the magnetopause shields us from the solar wind there are far more particles that penetrate with energy, and momentum to the Earths magnetosphere and interacts with the Earth’s magnetic field to create various plasmas and currents which shape and couple different regions of magnetosphere. The study of the dynamics of ions in and outside of the magnetosphere is done through mass spectrometer. Over the years, CODIF Ion TOF spectrometer have been used to understand …

Plasma Density Analysis Of Cubesat Wakes In The Earth’S Ionosphere, Robert M. Albarran Ii, Aroh Barjatya

Publications

Spinning or tumbling CubeSats with Langmuir probes deployed on booms will render spin-modulated plasma densities as the probes move in and out of the spacecraft wake. It is traditionally assumed that the lower-density measurements from the spin cycle are made in the spacecraft wake, and the higher-density measurements are outside the wake. Although this assumption is valid for larger spacecraft in the Earth’s ionosphere, this paper scrutinizes its validity for CubeSats in similar conditions. Spacecraft–plasma interactions (surface charging, plasma sheaths, and wakes) are less understood for CubeSats, and the small CubeSat dimensions must be considered with respect to characteristic length …