Doctor of Philosophy, The Ohio State University, 2024, Electrical and Computer Engineering

We present an exposition on Koopman operator-based reduced-order modeling of high-dimensional electromagnetic (EM) systems exhibiting both linear and nonlinear dynamics. Since the emergence of the digital age, numerical methods have been pivotal in understanding physical phenomena through computer simulations. Computational electromagnetics (CEM) and computational plasma physics (CPP) are related yet distinct branches, each addressing complex linear and nonlinear electromagnetic phenomena. CEM primarily focuses on solving Maxwell's equations for intricate structures such as antennas, cavities, high-frequency circuits, waveguides, and scattering problems. In contrast, CPP aims to capturing the complex behavior of charged particles under electromagnetic fields. This work specifically focuses on the numerical simulation of electromagnetic cavities and particle-in-cell (PIC) kinetic plasma simulations. Studying electromagnetic field coupling inside metallic cavities is crucial for various applications, including electromagnetic interference (EMI), electromagnetic compatibility (EMC), shielded enclosures, cavity filters, and antennas. However, time-domain simulations can be computationally intensive and time-consuming, especially as the scale and complexity of the problem increase. Similarly, PIC simulations, which are extensively used for simulating kinetic plasmas in the design of high-power microwave devices, vacuum electronic devices, and in astrophysical studies, can be computationally demanding, especially when simulating thousands to millions of charged particles. Moreover, the nonlinear nature of the complex wave-particle interactions complicates the modeling task. Data-driven reduced-order models (ROMs), which have recently gained prominence due to advances in machine learning techniques and hardware capabilities, offer a practical approach for constructing "light" models from high-fidelity data. The Koopman operator-based data-driven ROM is a powerful met (open full item for complete abstract)

Committee: Mrinal Kumar (Advisor); Fernando Teixeira (Advisor); Ben McCorkle (Committee Member); Balasubramaniam Shanker (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Engineering; Physics; Plasma Physics

Doctor of Philosophy, The Ohio State University, 2024, Physics

In the seconds following their formation in core-collapse supernovae, `proto'-neutron stars (PNSs) drive neutrino-heated magneto-centrifugal winds. The neutrino-driven wind phase during the cooling of the PNS lasts $\sim 1-100$\,s. We construct unprecedentedly realistic models of the PNS cooling phase using two-dimensional axisymmetric magnetohydrodynamic simulations. We include the effects of neutrino heating and cooling, employ a general equation of state, consider strong magnetic fields along with a dynamic PNS magnetosphere, and include the effects of PNS rotation. We show that relatively slowly rotating magnetars (strongly magnetized PNSs) with initial spin periods $P_{\star0} \gtrsim 100$\,ms spin down rapidly during the cooling epoch. For polar magnetic field strengths $B_0\gtrsim10^{15}$\,G, we show that the spindown timescale is of the order seconds in early phases. We show that magnetars with mass $M$ born with $B_0$ greater than $\simeq1.3\times10^{15}\,{\rm\,G}\,(P_{\star0}/{400\,\rm\,ms})^{-1.4}(M/1.4\,{\rm M}_\odot)^{2.2}$ spin down to periods $> 1$\,s in just the first few seconds of evolution. We discuss the implications for observed magnetars, including the discrepancy between their characteristic ages and supernova remnant ages. On the other hand, we show that rapidly rotating magnetars with initial spin periods $P_{\star 0}\lesssim 4$\,ms and $B_0\gtrsim 10^{15}$\,G can release $10^{50}-5\times 10^{51}$\,ergs of energy during the first $\sim2$\,s of the cooling phase. Based on this result, it is plausible that sustained energy injection by magnetars through the relativistic wind phase can power gamma-ray bursts (GRBs). We also show that magnetars with moderate field strengths of $B_0\lesssim 5\times 10^{14}$\,G do not release a large fraction of their rotational kinetic energy during the cooling phase and hence, are not likely to power GRBs. We hypothesize that moderate field strength magnetars can be central engines of superluminous supern (open full item for complete abstract)

Committee: Todd Thompson (Advisor); James Beatty (Committee Member); Samir Mathur (Committee Member); Christopher Hirata (Committee Member) Subjects: Astronomy; Astrophysics; Nuclear Physics; Physics; Plasma Physics; Theoretical Physics

Doctor of Philosophy, The Ohio State University, 2024, Mechanical Engineering

Temporal and spatial distributions of the electric field in an atmospheric pressure, ns pulse, positive and negative polarity helium plasma jets are measured by ps Electric Field Induced Second Harmonic (EFISH) generation. The measurements have been done in a quasi-two-dimensional plasma jet impinging on liquid water, using a laser sheet and a focused laser beam positioned at different heights above the water surface. Absolute calibration of the electric field is obtained by measuring a known Laplacian electric field distribution for the same geometry and at the same flow conditions. The vertical component of the electric field is determined by isolating the second harmonic signal with the vertical polarization. The measured electric field is averaged over the span of the plasma jet, in the direction of the laser sheet or the focused laser beam. The spatial resolution of the laser sheet measurements is approximately 15 μm across the sheet, with the temporal resolution of 10 ns. The spatial resolution of the focused laser beam measurements is approximately 180 um across the beam, with the temporal resolution of 2.5 ns. The results show non-monotonous electric field distribution across the jet, with two maxima produced by the surface ionization waves propagating over water. Considerable electric field enhancement is detected near the surface. Residual charge accumulation on the water surface is detected only in the negative polarity pulse discharge. The results provide new insight into the charge species kinetics and transport in atmospheric pressure plasma jets, and produce data for detailed validation of high-fidelity kinetic models. Ionization wave development during ns pulse breakdown in nitrogen between two parallel plate, dielectric-covered electrodes is studied by ps Electric Field Induced Second Harmonic (EFISH) generation and kinetic modeling. The results indicate formation of two well-defined ionization waves in the discharge gap, which requires a relativ (open full item for complete abstract)

Committee: Igor Adamovich (Advisor); Jeffery Sutton (Committee Member); Bern Kohler (Committee Member); Joseph Heremans (Committee Member) Subjects: Aerospace Engineering; Chemistry; Mechanical Engineering; Optics; Plasma Physics

Doctor of Philosophy, University of Akron, 2023, Polymer Science

Plasma polymerization is a facile method of depositing robust films on a wide variety of substrates. While the nanoscale structure of films plasma polymerized in vacuum has been studied some, little is known of the nanoscale structure of the films deposited in the more complex atmospheric plasma polymerized (APP) films. To explore how deposition conditions affect APP film structures, APP films were deposited using hexamethyldisiloxane (HMDSO) precursor at varying power and in varying levels of relative humidity (RH). X-ray and neutron reflectivity measurements reveal that these APP-HMDSO films have a three-layer structure. A transition region of low mass density and carbon content forms next to the substrate as the deposition starts and etching by the plasma initially dominates deposition; a center region which still experiences some etching displays a uniform scattering length density (SLD) with respect to depth; a surface layer next to the air of mass density less than or equal to that of the center region forms whose SLD depends on how “filled in” the layer was when plasma generation was halted. Mass density was found to be sensitive to high humidity, which reduces the flux of monomer fragments to the substrate and allows them to pack more densely. Complementary analysis of depth-resolved X-ray photoelectron spectroscopy and water contact angle measurements show that composition and hydrophilicity are power-dependent. Films deposited at lower power lose more of their carbon to etching, making their composition more silica-like and making them more hydrophilic. Films deposited at higher power retain more of the carbon from the HMDSO monomer thanks to higher deposition rates; a film layer is buried by additional layers before all the residual carbon can be etched away. Neutron reflectivity measurements of the same APP-HMDSO films while exposing them to deuterated solvent vapor showed that vapor easily penetrated them without causing their thickness to increase, (open full item for complete abstract)

Committee: Mark Foster (Advisor); Mesfin Tsige (Committee Chair); Toshikazu Miyoshi (Committee Member); Ali Dhinojwala (Committee Member); Bi-min Newby (Committee Member) Subjects: Chemistry; Materials Science; Physics; Plasma Physics

Bachelor of Science (BS), Ohio University, 2023, Physics

The field of subatomic particles has existed for over a hundred years now. From the discovery of the electron that sparked the field, to the discovery of the Higgs Boson, physicists have always wanted to uncover the subatomic structure of the atoms, nuclei, and their constituents at smaller and smaller levels. By the 1930s, the proton, neutron, and electron had been discovered. These protons and neutrons are types of hadrons, and many different types of hadrons had been discovered by the 1960s. In 1964, Murray Gell-man and George Zweig independently proposed the quark model to explain the different hadrons. A quark is a particle that makes up a hadron, accounting for the many different types of hadrons that had been discovered; the other hadrons were composed of 2 or 3 of the 6 quarks. These include the up, down, top, bottom, charm, and strange quarks. The proton is made of 2 up quarks and 1 down quark, while the π0 particle is made of an up and an anti-up, or a down and an anti-down quark, for example. Advancements in technology allowed physicists to be able to accelerate particles and smash them together in particle accelerators and colliders. These new machines were how physicists were able to split open atoms, and the hadrons inside, to uncover these quarks. In the search for these different quarks, other particles were being discovered as well. This included the 6 leptons, the electron, the tau, and the muon, and their neutrino counterparts. The leptons are grouped separately from quarks because they participate only in electroweak interactions, while quarks also participate in strong interactions. Electroweak interactions describe the interactions caused by the electromagnetic force and the weak nuclear force. The strong interactions describe those caused by the strong nuclear force. These 3 forces, along with gravity, are the four fundamental forces of the universe, with the strong force being the strongest force and responsible for most of the energy in (open full item for complete abstract)

Committee: Justin Frantz (Advisor) Subjects: Nuclear Physics; Physics; Plasma Physics

Doctor of Philosophy, The Ohio State University, 2022, Physics

In this work we investigate the important phenomenon of relativistic transparency (RT) and the related effect of relativistic birefringence (RB) in the field of ultra-intense laser-plasma interactions. RT occurs when a highly intense laser (exceeding 1018 W/cm2) is incident on a classically opaque plasma. As the electrons are driven to relativistic speeds, there is an effective relativistic mass increase that can lead to a relativistically transparent plasma. Furthermore, the electrons are driven more in the polarization direction of the laser leading to a nonuniform dielectric tensor and a relativistically birefringent plasma. These two fundamental phenomena are present, to some degree, in all ultra-intense laser target interactions and can significantly influence applications of high power lasers. RT is a major contributor to the enhancement of laser-driven ion acceleration schemes and the utilization of plasmas as optical devices like mirrors, apertures, or polarizers. We present a computational study into RT and RB using a novel optical pump optical probe setup and the particle-in-cell (PIC) method. The framework is based on an experimental study at the Scarlet laser facility providing one of the few extant direct measurements of RT and the first experimental observation of RB. A high intensity 1021 W/cm2 pump was obliquely incident on an ultra-thin 20 nm 8CB liquid crystal (LC) target, exciting a relativistic plasma. A lower intensity 1018 W/cm2 probe was near normally incident with a varying polarization and delay time, relative to the pump, in order to diagnose the dynamics of RT and RB. In the simulations described here, the plasma target has its thickness and electron density proportionally scaled to simulate different pre-expanded targets with a constant areal density across all of them. Simulation diagnostics are utilized to assess the primary experimental diagnostics: the transmission and polarization state of each laser individually as a function (open full item for complete abstract)

Committee: Douglass Schumacher (Advisor); Enam Chowdhury (Committee Member); Christopher Orban (Committee Member); Richard Furnstahl (Committee Member) Subjects: Physics; Plasma Physics

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Physics

Compact stars (CSs) are the remnants of “dead” stars that were too small to form black holes; the category includes both white dwarfs (WDs) and neutron stars (NSs). To produce a full description of any magnetized compact star requires solving Einstein's equations in unison with Maxwell's equations. However, when putting these two sets of equations together, there is an additional degree of freedom that requires the inclusion of the equation of state (EOS) of the stellar matter in question. The most notable difference between CSs and other stars is that CSs consist of degenerate fermion matter. Fermionic matter exists in a degenerate state when the temperature is low compared to the Fermi energy. Such states arise due to the Pauli exclusion principle, which states that no two identical fermions (particles with half integer spin) in the same quantum system may inhabit the same quantum state. In the case of WDs, this degeneracy is caused solely by electrons; whereas, in NSs, the degeneracy is in several species of particles including neutrons and protons, but also more “exotic” baryons, such as Lambdas, Sigmas, and Cascades. In the grand canonical ensemble, the stellar EOS is typically expressed as the relation between the total energy density of a gas of particles and their pressure. It is calculated using thermodynamics with, in the NS case, an additional contribution from the strong nuclear force, which must be modeled. Due to computational difficulty, the EOS is often calculated in a simplified way, assuming that one aspect or another is not significant. As such, EOSs exist with temperature effects or with magnetic field effects, but not with both. For example, higher temperatures (without additional degrees of freedom) lead to higher pressures at the same energy density; the EOS is “stiffer.” Magnetic fields lead to a pressure anisotropy and Landau quantization, which gives rise to De Haas-Van Alphen oscillations in the EOS. This thesis breaks new ground by sim (open full item for complete abstract)

Committee: Veronica Dexheimer (Advisor); Michael Strickland (Committee Member); Gokarna Sharma (Committee Member); Lothar Reichel (Committee Member); Khandker Quader (Committee Member) Subjects: Astrophysics; Electromagnetism; High Temperature Physics; Particle Physics; Physics; Plasma Physics; Quantum Physics; Theoretical Physics

Master of Science, The Ohio State University, 2022, Mechanical Engineering

Time-resolved N2 vibrational temperature and translational-rotational temperature in quasi-two-dimensional atmospheric pressure plasma jets sustained by ns pulse and RF discharges in nitrogen / noble gas mixtures are measured by the broadband vibrational CARS. The results indicate a much stronger vibrational excitation in the RF plasma jet, due to the lower reduced electric field and higher discharge power. In a ns pulse discharge in N2/He, N2 vibrational temperature is significantly lower compared to that in N2/Ar, due to the more rapid V-T relaxation of nitrogen by helium atoms. In the RF plasma jets in N2/Ne and N2/Ar, the vibrational excitation increases considerably as the nitrogen fraction in the mixture is reduced. The experimental data in the RF plasma jet in N2/Ar jet are compared with the kinetic modeling predictions. The results indicate that nitrogen vibrational excitation in N2/Ar plasma jets with a small N2 fraction in the mixture (several percent) is controlled primarily by electron impact, anharmonic vibration-vibration (V-V) pumping, and vibration-translation (V-T) relaxation by N atoms. In comparison, V-V energy transfer from the vibrationally excited molecules in the first excited electronic state, N2(A3Σu+,v), which are generated primarily by the energy transfer from the metastable Ar atoms, has a minor effect on the vibrational populations of the ground electronic state, N2(X1Σg+,v). Although the discharge energy fraction going to electronic excitation is significant, the predicted quasi-steady-state N2(A3Σu+) number density, controlled by the energy pooling and quenching by N atoms, remains relatively low. Because of this, the net rate of N2(X1Σg+) vibrational excitation by the V-V energy transfer from N2(A3Σu+) is much lower compared to that by the direct electron impact. The results show that atmospheric pressure RF plasma jets can be used as sources of highly vibrationally excited N2 molecules and N ato (open full item for complete abstract)

Committee: Igor Adamovich (Advisor); Jeffrey Sutton (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering; Plasma Physics

Master of Science in Electrical Engineering (MSEE), Wright State University, 2021, Electrical Engineering

Building upon recent work to estimate electron and ion densities from paired interferograms, the current work develops a model for the 2D interference phase function. Unlike the previous work that only estimated a radial plasma profile from images of a singly exploded straight Cu wire, we estimate 2D properties from a colliding plasma generated from two simultaneously exploded wires. First, a 2D phase model is proposed for the interference patterns of the images taken at 1064 nm and 532 nm. Then, the model parameters are estimated using Fourier analysis. Secondly, the plasma region in each image is partitioned into subregions and analyzed using the Abel transform under the assumption of locally cylindrical conditions. The approach allows for analysis of the 2D plasma profile using semi-automated analysis of a time series of interferograms.

Committee: Michael A. Saville Ph.D., P.E. (Advisor); Josh Ash Ph.D. (Committee Member); Yan Zhuang Ph.D. (Committee Member) Subjects: Electrical Engineering; Plasma Physics

Doctor of Philosophy, University of Toledo, 2021, Engineering

Electrohydrodynamic (EHD) found a lot of attention in the scientific community because of its low energy and flexibility in addressing different challenges. The first chapter of this dissertation explains the history of using EHD to manipulate, separation and emulsion formation, and also talks about the theory and mechanism of gaseous discharge. The second chapter of this dissertation presents the results of experimental observations of the EHD flow induced in bulk dielectric liquid layers using corona discharge. The governing liquid properties for the deformations are discussed, indicating the vital role of surface tension and viscosity. Critical voltages at which rapid transformation of the liquid's deformation occurs are identified and discussed. The liquid layer thickness is shown to be a dominant parameter in the efficacy of such proposed pump designs. Chapter third discusses an experimental approach to study the effects of a contactless method on electrocoalescence of water in oil (W/O) emulsion. A positive corona discharge is utilized to create a nonuniform electric field for the coalescence of water droplets ranging from nano to macro sizes in oil mediums. Two approaches are employed in this chapter; qualitative analysis conducted by visually studying coalescence patterns in videos captured with a high-speed camera, and a quantitative analysis based on calculations obtained from dynamic light scattering (DLS) measurements. From the behavior of the water droplets under the electric field, it is observed that dipole-dipole interaction (DDI), migratory coalescence (electrophoresis (EP)), and dielectrophoresis (DEP) have major roles in promoting the coalescence events. Chapter fourth investigates the impacts of non-uniform and pulsed DC electric fields on the coalescence of water droplets inside an oil medium. The operating process parameters were experimentally calibrated and optimized to increase the effectiveness and energy consumption efficiency of the coa (open full item for complete abstract)

Committee: Hossein Sojoudi (Committee Chair); Abbas Semnani (Committee Member); Richard G. Molyet (Committee Co-Chair); Mohammed Niamat (Committee Member); Yakov Lapitsky (Committee Member) Subjects: Chemical Engineering; Electrical Engineering; Engineering; Fluid Dynamics; Petroleum Production; Physical Chemistry; Plasma Physics

Master of Science (MS), Wright State University, 2020, Physics

A one-dimensional kinetic particle-in-cell (PIC) MATLAB simulation was created to demonstrate the time-evolution of various plasma distributions. Building on previous plasma PIC programs written in FORTRAN and Python, this work recreates the computational and diagnostic tools of these packages in a more user- and educational-friendly development environment. Plasma quantities such as plasma frequency and species charge-mass ratios are arbitrarily defined. A one-dimensional spatial environment is defined by total length and number and size of spatial grid points. In the first time-step, charged particles are given initial positions and velocities on a spatial grid. After initialization, the program solves for the electrostatic Poisson equation at each time step to compute the force acting on each particle. Using the calculated force on each particle and the “leap-frog” method, the particle positions and velocities are updated and the motion is tracked in phase-space. Modifying parameters such as spatial perturbation, number of particles, and charge-mass ratio of each species, the time-evolution for various distributions are examined. The simulated distributions examined are categorized as the following: Cold Electron Stream, Electron Plasma Waves, Two-Stream Electron Instability, Landau Damping, and Beam-Plasma. The time evolution of the plasma distributions was studied by several methods. Tracking the electric field, charge density and particle velocities through each time step yields insight into the oscillations and wave propagation associated with each distribution. One key diagnostic missing from the original FORTRAN code was the electric field dispersion relation. The numerical dispersion relation allows for further insight into modelling plasma oscillations/waves in addition to the kinetic/field energies and electric field tracking present in the original code. Simulated results show agreement with other kinetic simulations as well as plasma theory.

Committee: Amit Sharma Ph.D. (Advisor); Ivan Medvedev Ph.D. (Committee Member); Sarah Tebbens Ph.D. (Committee Member) Subjects: Atmospheric Sciences; Atoms and Subatomic Particles; Physics; Plasma Physics

Doctor of Philosophy, The Ohio State University, 2020, Physics

Like many problems in physics, the interaction between high intensity laser pulses and solid materials depends critically on the relative timescales of the drive (the laser pulse with finite duration) and the material response. This is especially true for Laser-Induced Damage and Ablation (LIDA) of solids, where femtosecond (1 fs = 10e−15 s) laser pulses can achieve extremely high energy densities since there isn't enough time for energy to diffuse away during the laser pulse like there is for picosecond (10e−12 s) and nanoseond (10e−9 s) pulses,for example. The pulse duration dependence of fs-LIDA for Near-Infrared (NIR) pulses less than 100 fs is less well-understood, especially in the Few-Cycle Pulse (FCP) regime (<10fs) where energy is deposited faster than almost all of the processes associated with the material response. In this thesis, the pulse duration dependence of LIDA of transparent dielectric material systems down to the FCP regime is studied using a well-established time-and space-resolved imaging technique as well as high-resolution depth-profiling. LIDA of dielectric solids has large application spaces in precision micro-machining andsurface patterning, as well as improving the LIDA performance of dielectric thin-film opticsto increase the output of high power laser systems. Practical multilayer thin-film opticsintroduce more complexity to the LIDA process due to thin-film interference, so I startedwith a study of FCP-LIDA of the simplest thin-film system: a single layer. I found that dif-ferences in LIDA between two film thicknesses are exacerbated by Few-Cycle Pulses (FCPs)relative to 100 fs pulses. I wrote a Finite-Difference Time-Domain (FDTD) simulation thatmotivates a possible mechanism for this, suggesting FCPs result in a more spatially non-uniform excitation of the films. My results show that the models I used must be extendedto more completely describe my experimental observati (open full item for complete abstract)

Committee: Enam Chowdhury (Advisor); Gregory Lafyatis (Committee Member); Thomas Lemberger (Committee Member); Douglass Schumacher (Committee Member) Subjects: Condensed Matter Physics; Electromagnetism; Optics; Physics; Plasma Physics; Solid State Physics

Doctor of Philosophy, Case Western Reserve University, 2019, EECS - Electrical Engineering

Inkjet printing is rapidly emerging as a means to fabricate low cost electronic devices; however, widespread adoption is hindered because the technology is currently limited to a few metals and substrates due to the complexity of the inks and the relatively high processing temperatures associated with post-deposition sintering. In this dissertation, a new approach for inkjet printing based on off-the-shelf, particle-free inks formulated from inorganic metal salts and their subsequent low-temperature conversion to metallic structures by a non-equilibrium, inert gas plasma is described. This single, general method is demonstrated for a library of metals including gold (Au), silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), lead (Pb), bismuth (Bi), and tin (Sn). These metals were printed and plasma activated at substrate temperatures between 77°C and 138°C, depending on their reduction potential. This low activation temperature enables printing on substrate materials with low glass transition temperatures, such as polyethylene (PE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), and polycarbonate (PC) to name a few. The resistivities of the inkjet-printed and converted metals were measured to be between 2X and 10X of the respective bulk metals. Uniquely, the metal films were found to exhibit a very large surface area because of the plasma-initiated nucleation and growth process, making the printing technique attractive for sensor device applications. To demonstrate the utility of the printing technique developed in this dissertation, a number of sensors including a Bi-based trace Pb ion sensor, a Au-based amyloid-β sensor, a Au-based strain gauge, and a Ag-based thermistor were fabricated as representative chemical, biological, mechanical, and thermal sensors. Due to the large effective surface area and low resistivity of the printed metals, the inkjet-printed sensors exhibit enhanced sensitivity compared to analogues (open full item for complete abstract)

Committee: Christian Zorman (Committee Chair); R. Mohan Sankaran (Committee Co-Chair); Chung-Chiun Liu (Committee Member); Mandal Soumyajit (Committee Member) Subjects: Chemical Engineering; Electrical Engineering; Plasma Physics

Bachelor of Science (BS), Ohio University, 2019, Biological Sciences

The nucleolin protein is evolutionarily conserved and is expressed by cells internally (in the nucleolus, nucleus and cytoplasm), as well as externally (as a cell surface protein), and thus has many roles in the cell. Externally, it acts as a ligand on head and neck squamous cell carcinoma (HNSCC) cells for L-selectin. L-selectin is found on lymphocytes and helps cells adhere together, a process involved in cancer metastasis. According to the Surveillance, Epidemiology and End Results Program (SEER), the survival rate for oral cavity and pharynx cancer drops from around 83.7% to 38.5% as patients progress from stage 1 to stage 4. However, a relatively new technique, known as cold atmospheric plasma (CAP), may be a powerful tool to combat this devastating statistic of cancer. Plasmas are an ionized gas - essentially a gas that has been heated until the ions start to lose their electrons. Thermal plasma exists at very high temperatures (approaching 28,000K in lightning for example). These high temperatures make it impossible to use in any kind of clinical/translational aspect. This is why nonthermal or cold atmospheric plasma (CAP) is beneficial for biomedical and translational research. The reactions are not at equilibrium, resulting in hot electrons but cool ions and neutral particles. As a result, the plasma is at a temperature that will not thermally damage the application site (usually around 300K, 26.85°C), but when the electrons hit particles, energy is still transferred, and a multitude of reactions takes place. Among its many capabilities, CAP possesses the ability to open pores in the plasma membrane, creating the possibility of a novel transfection technique. However, there is very limited data on the actual radius of the pores that open up as a result of CAP treatment. The hypothesis of this study was that the radius of the pores formed in the plasma membrane by CAP treatment would be less than 6.5nm. It was first determined that both the head and neck (open full item for complete abstract)

Committee: Monica Burdick PhD (Advisor); David Burnette PhD (Other) Subjects: Biology; Biomedical Engineering; Biomedical Research; Cellular Biology; Chemical Engineering; Molecular Biology; Oncology; Plasma Physics

PHD, Kent State University, 2019, College of Arts and Sciences / Department of Physics

Relativistic heavy-ion collision experiments are currently the only controlled way to generate and study matter in the most extreme temperatures (T ~10e+12 K). At these temperatures matter undergoes a phase transition to an exotic phase of matter called the quark-gluon plasma (QGP). The QGP is an extremely hot and deconfined phase of matter where sub-nucleonic constituents (quarks and gluons) are asymptotically free. The QGP phase is important for different reasons. First of all, our universe existed in this phase up to approximately t ~10e-5 s after the Big Bang, before it cools down sufficiently to form any kind of quark bound states. In this regard, studying the QGP provides us with useful information about the dynamics and evolution of the early universe. Secondly, high-energy collisions serve as a microscope with a resolution on the order of 10e-15 m (several orders of magnitude more powerful than the best ever developed electron microscopes). With this fantastic probe, penetrating into the detailed structure of nucleons, and the discovery of new particles and fundamental phases are made possible. The dynamics of the QGP is based on quantum chromodynamics (which governs the interactions of quarks and gluons) and the associated force is "strong force". The strong collective behaviors observed experimentally inspired people to use dissipative fluid dynamics to model the dynamics of the medium. The QGP produced in heavy-ion collisions, experiences strong longitudinal expansion at early times which leads to a large momentum-space anisotropy in the local rest frame distribution function. The rapid longitudinal expansion casts doubt on the application of standard viscous hydrodynamics (vHydro) models, which lead to unphysical predictions such as negative pressure, negative one-particle distribution function, and so on. Anisotropic hydrodynamics (aHydro) takes into account the strong momentum-space anisotropy in the leading order distribution function in a consistent (open full item for complete abstract)

Committee: Michael Strickland (Advisor); Declan Keane (Committee Member); Khandker Quader (Committee Member); Xiaoyu Zheng (Committee Member); Peter Palffy-Muhoray (Committee Member) Subjects: Fluid Dynamics; Particle Physics; Physics; Plasma Physics; Theoretical Physics

Doctor of Philosophy, The Ohio State University, 2018, Electrical and Computer Engineering

Plasma is a significantly ionized gas composed of a large number of charged particles such as electrons and ions. A distinct feature of plasmas is the collective interaction among charged particles. In general, the optimal approach used for modeling a plasma system depends on its characteristic (temporal and spatial) scales. Among various kinds of plasmas, collisionless plasmas correspond to those where the collisional frequency is much smaller than the frequency of interests (e.g. plasma frequency) and the mean free path is much longer than the characteristic length scales (e.g. Debye length). Collisionless plasmas consisting of kinetic space charge particles interacting with electromagnetic fields are well-described by Maxwell-Vlasov equations. Electromagnetic particle-in-cell (EM-PIC) algorithms solve Maxwell-Vlasov systems on a computational mesh by employing coarse-grained superparticle. The concept of superparticle, which may represent millions of physical charged particles (coarse-graining of the phase space), facilitates the realization of computer simulations for underscaled kinetic plasma systems mimicking the physics of real kinetic plasma systems. In this dissertation, we present an EM-PIC algorithm on general (irregular) meshes based on discrete exterior calculus (DEC) and Whitney forms. DEC and Whitney forms are utilized for consistent discretization of Maxwell's equation on general irregular meshes. The proposed EM-PIC algorithm employs a mixed finite-element time-domain (FETD) field solver which yields a symplectic integrator satisfying energy conservation. Importantly, we employ Whitney-forms-based gather and scatter schemes to obtain exact charge conservation from first principles, which had been a long-standing challenge for PIC algorithms on irregular meshes. Several further contributions are made in this dissertation: (i) We develop a local and explicit EM-PIC on unstructured grids using sparse approximate inverse (SPAI) strategy and study mac (open full item for complete abstract)

Committee: Fernando Teixeira (Advisor); Kubilay Sertel (Committee Member); Robert Lee (Committee Member); Asuman Turkmen (Other) Subjects: Electrical Engineering; Electromagnetics; Plasma Physics

Doctor of Philosophy, The Ohio State University, 2018, Physics

This thesis studies the relativistic laser plasma interaction (a0 = eE0/meωc > 1) using joint experimental and computational approaches, the former using high power, short pulse laser systems and the latter via particle-in-cell (PIC) modeling and high performance computing. Different aspects are explored including determination of criteria for physically meaningful PIC simulations, development of the technology needed for such experiments including new systems for targetry and a new model for understanding dielectric plasma mirrors and, finally, a study of laser based ion acceleration in three different acceleration regimes. We have shown that, although in the laboratory frame an electron accelerated via direct laser acceleration undergoes a decreased oscillation frequency, the criterion on the time resolution required to model this process actually becomes more restrictive. This is due to the difficulty of resolving the stopping points in the electron trajectory giving rise to dephasing. It is shown that when using the Boris particle pusher, the time step must satisfy Δt << T/a0, where a0 is the dimensionless vector potential. An adaptive time step algorithm based on this criterion is demonstrated that achieves more than an order of magnitude improvement in preserving the constant of the motion γ - px/mec = 1 with only a 1/√a0 increase in the number of time steps required, as opposed to the 1/a0 scaling in the non-adaptive algorithm. High pulse contrast is crucial for performing many experiments on high intensity lasers in order to minimize modification of the target surface by pre-pulse. Dielectric plasma mirrors are commonly used to enhance the contrast of laser pulses and their subsequent ion production, but have not been modeled extensively. Presented here are novel 2D3V LSP particle-in-cell simulations of liquid crystal plasma mirror operation which include a dielectric model with a population of cold neutral atoms and incorporating multiphoton ioni (open full item for complete abstract)

Committee: Douglass Schumacher PhD (Advisor); Louis DiMauro PhD (Committee Member); Robert Perry PhD (Committee Member); Junko Shigemitsu PhD (Committee Member) Subjects: Physics; Plasma Physics

Doctor of Philosophy, The Ohio State University, 2018, Chemical Physics

Broadband ns coherent anti-Stokes Raman Spectroscopy (CARS) diagnostics is used to study vibrational energy transfer in the afterglow of a diffuse filament, ns pulse discharge in nitrogen, air, and their mixtures with carbon dioxide and hydrogen. The results indicate that nitrogen vibrational excitation in the discharge occurs by electron impact, with subsequent vibration-vibration (V-V) energy transfer within N2 vibrational manifold, vibration-translation (V-T) relaxation, and near-resonance V-V' energy transfer from N2 to CO2 asymmetric stretch vibrational mode. This considerably accelerates the net rate of energy thermalization and temperature rise in the afterglow and demonstrates that adding CO2 to nonequilibrium flows of nitrogen and air would result in a rapid temperature increase. Measurements of temperature, N2 vibrational temperature, and OH number density in nitrogen, air, and H2-air mixtures are used to study a possible effect of nitrogen vibrational excitation on low-temperature kinetics of HO2 and OH radicals, at high specific energy loading. CARS measurements demonstrate that the discharge generates strong vibrational nonequilibrium in air and H2-air mixtures. The kinetics of population and decay of N2 vibrational levels at these conditions are well understood. Laser Induced Fluorescence measurements of OH number density show that it peaks in the afterglow, at approximately the same time as N2 vibrational temperature. However, comparison of the experimental data with kinetic modeling predictions shows that OH number density at the present conditions is not affected by N2 vibrational excitation directly. Kinetic modeling predicts a transient OH number density overshoot at a higher discharge coupled energy, due to the temperature rise caused by N2 vibrational relaxation by O atoms, which may well be a dominant effect in discharges with high specific energy loading. CARS diagnostics has also been used to characterize a microwave discharge plasma in nitr (open full item for complete abstract)

Committee: Igor Adamovich (Advisor); Heather Allen (Committee Member); Shafaat Hannah (Committee Member); Schumacher Douglass (Committee Member) Subjects: Aerospace Engineering; Optics; Physical Chemistry; Physics; Plasma Physics

Master of Science (MS), Wright State University, 2018, Physics

The study of solar-terrestrial plasma is concerned with processes in magnetospheric, ionospheric, and cosmic-ray physics involving different particle species and even particles of different energy within a single species. Instabilities in space plasmas and the earth's atmosphere are driven by a multitude of free energy sources such as velocity shear, gravity, temperature anisotropy, electron, and, ion beams and currents. Microinstabilities such as Rayleigh-Taylor and Kelvin-Helmholtz instabilities are important for the understanding of plasma dynamics in presence of magnetic field and velocity shear. Modeling these turbulences is a computationally demanding processes; requiring large memory and suffer from excessively long runtimes. Previous works have successfully modeled the linear and nonlinear growth phases of Rayleigh-Taylor and Kelvin-Helmholtz type instabilities in ionospheric plasmas using finite difference methods. The approach here uses a two-fluid theoretical ion-electron model by solving two-fluid equations using iterative procedure keeping only second order terms. It includes the equation of motion for ions and electrons, the continuity equations for both species, and the assumption that the electric drift and gravitational drift are of the same order. The effort of this work is to focus on developing a new pseudo-spectral, highly-parallelizable numerical approach to achieve maximal computational speedup and efficiency. Domain decomposition along with Message Passing Interface (MPI) functionality was implemented for use of multiple processor distributed memory computing. The global perspective of using Fourier Transforms not only adds to the accuracy of the differentiation process but also limits memory calling when performing calculations. An original method for calculating the Laplacian for a periodic function was developed that obtained a maximum speedup of 2.98 when run on 16 processors, with a theoretical max of 3.63. Using this meth (open full item for complete abstract)

Committee: Amit Sharma Ph.D. (Advisor); Brent Foy Ph.D. (Committee Member); Ivan Medvedev Ph.D. (Committee Member) Subjects: Computer Science; Physics; Plasma Physics

Doctor of Philosophy, University of Toledo, 2017, Electrical Engineering

Electrically conductive hair-like structures, referred to as whiskers, can bridge the gap between densely spaced electronic components. This can cause current leakage and short circuits resulting in significant losses and, in some cases, catastrophic failures in the automotive, aerospace, electronics and other industries since 1946. Detecting a metal whiskers (MWs) is often a challenging task because of their random growth nature and very small size (diameters can be less than 1 µm, lengths vary from 1µm to several millimeters). Many decades ago the industry introduced whisker mitigating Pb in the solders used to fabricate electric and electronic parts. In recent years, this changed because the European Union (EU) passed a legislation in 2006, called “Restriction of the use of Certain Hazardous Substances (RoHS) in Electrical and Electronic Equipment”, which requires a reduction and elimination of the use of Pb in technology. Thus, the issue of undesirable and unpredictable whiskers growth has returned and there is a renewed interest in the mechanisms of formation of these structures. None of the whisker growth models proposed to date are capable of answering consistently and universally why whisker grow in the first place and why Pb addition suppresses their growth. Understanding MW nucleation and growth mechanism are of significant interest to this project, since this would potentially allow the development of new accelerated-failure testing methods of electronic components to replace existing testing methods which are generally found to be unreliable. In particular, this research is intended to study the effects of electric fields on the whisker growth, which according to the recently developed electrostatic theory[1] of whisker growth, are of crucial importance. This theory proposes that the imperfections on metal surfaces can form small patches of net positive or negative electric charge leading to the formation of the anomalous electric field (E), which go (open full item for complete abstract)

Committee: Daniel Georgiev Dr. (Committee Chair); Vijay Devabhaktuni Dr. (Committee Member); Victor Karpov Dr. (Committee Member); Devinder Kaur Dr. (Committee Member); Anthony Johnson Dr. (Committee Member) Subjects: Aerospace Materials; Chemical Engineering; Condensed Matter Physics; Electrical Engineering; Engineering; Experiments; Materials Science; Metallurgy; Nanoscience; Nanotechnology; Physics; Plasma Physics; Solid State Physics; Theoretical Physics