Physical Sciences and Mathematics Commons^™

Nuclear Transparency From Quasi-Elastic $^{12}C(E,E'P)$ Scattering Reaction Up To $Q^2=14.2 ~(Gev/C)^{2}$ In Hall C At Jefferson Lab, Deepak Kumar Bhetuwal

Theses and Dissertations

Color Transparency $(CT)$ is a unique prediction of Quantum Chromodynamics $(QCD)$ where the final (and/or initial) state interactions of hadrons with the nuclear medium are suppressed for exclusive processes at high momentum transfers. While this phenomenon has been observed for mesons, there has never been a conclusive observation for baryons. A clear signal of $CT$ for baryons would be the first evidence of baryons fluctuating to a small size in the nucleus, and the onset would show the transition from nucleon-meson picture to quark-gluon degrees of freedom. The experiment $E1206107$, searching for the onset of $CT$ in protons was completed …

Design, Assembly, And Testing Of A Small 3d-Printed Thick-Gem, Jerry Lamar Collins Ii

Theses and Dissertations

Thick GEMs are a type of gas electron multiplier, a micropattern gaseous detector, with many applications in research. The subject of this study is whether or not a small 3D printed thick GEM board can be used to form a well-functioning detector. A Thick GEM having three separate board sectors, each having different sized clearance rim annuli around their holes, was designed, printed, and assembled. Several studies to quantify its behavior over both short and long time intervals were conducted, and the results calculated. The THGEM sector with 0.1 mm annulus rims was able to achieve primarily 102 gain, whereas …

Conceptual Insight Into The Application Of Innovative Educational Methods In Astronomy, Wahltyn A. Rattray

Theses and Dissertations

University students taking introductory astronomy courses were studied with a control group enrolled in a class with standard curriculum and an experimental group enrolled in a class with a curriculum using innovative instructional methods. Using multiple assessments, I analyzed the students’ astronomy knowledge and overall class experience to determine which curriculum was more instructionally effective. The innovative methods were developed with the ADDIE method and were based on the Karplus learning cycle which provided the framework for the astronomy curriculum. The end goal of the innovative curriculum is to produce graduates with better conceptual understanding of astronomy than with the …

Dynamical Casimir Effect In A Superconducting Circuit Periodic Lattice, Andres Cuellar Vega

Theses and Dissertations

The dynamical Casimir effect (DCE) is the generation of real photons out of the quantum vacuum due to a rapid modulation of boundary conditions for the electromagnetic field, such as a mirror oscillating at speeds comparable to the speed of light. Previous work demonstrated experimentally that DCE radiation can be generated in electrical circuits based on superconducting microfabricated waveguides, where a rapid modulation of boundary conditions corresponding to semi-transparent mirrors is realized by tuning the applied magnetic flux through superconducting quantum-interference devices (SQUIDs) that are embedded in the waveguide circuits. We propose a novel SQUID periodic lattice architecture, in which …

Contributions To The Heat Capacity Of Neutron Stars, Pedro Paulo Barboza Sanson

Theses and Dissertations

In this thesis, we review the contribution to the heat capacity of different matter phases that can appear inside a Neutron Star's core, paying special attention to the magnetic dual chiral density wave (MDCDW) phase, which is characterized by an inhomogeneous chiral condensate in the presence of a magnetic field and that is expected to be favored at intermediate densities and low temperatures. Furthermore, we compare our results with the observational lower limit of the core heat capacity established from observations of transiently accreting neutron stars which give us crucial information whether certain phases are feasible to appear in the …

Effects Of Collaborative Group Activities On Students’ Interest, Course Participation, And Performance In An Online Physics Course, Airik R. Sanchez

Theses and Dissertations

The purpose of this study was to investigate the impact of the use of collaborative work activities in online physics courses as perceived by students. Nearly identical surveys were administered at the beginning and end of two semesters to ascertain student perception on the impact of the utilization on their level of interest, participation, performance as well as teamwork skills. The results show that the majority of the population tested strongly agree that collaborative work had significant effect on all core areas tested, and they support the notion that it should be further utilized in both lecture and lab portions …

Development Of A Magnetic Confinement Attachment For Enhanced Signal In Handheld Laser Induced Breakdown Spectroscopy Soil Analysis, Alfred C. Anderson

Theses and Dissertations

Field techniques for characterizing low levels of heavy elements of less than 100 parts per million in soils tend to be unreliable because of the relatively weak signal of these elements and the large, variable background inherent to analyzing soils with minimal sample preparation. To enhance the detection and analysis capability of a handheld laser-induced breakdown spectroscopy (LIBS) instrument, this work investigates the effects of a unique magnetic confinement apparatus on signal intensities, focusing on five iron lines as well as those from actinides in 11 soil samples. The proposed magnetic confinement apparatus achieved over 0.8 T but did not …

Characterization Of Infrared Metasurface Optics With An Optical Scatterometer, Matthew R. Miller

Theses and Dissertations

An optical scatterometer is used to characterize the infrared scatter of a dielectric metasurface cylindrical lens and two variants of that design. The design uses dielectric nanopillars to create the parabolic phase delay required for lensing; the variants change the length of the nanopillars from the design length of 4 microns to 0.9 and 5.2 microns. Scatter measurements were made at the design wavelength of 4 microns, and at 3.39 and 5 microns. These measurements showed wide-angle scatter greater than that measured for a conventional refractive optic, and that these metasurfaces perform their optical function best at the design wavelength …

Shedding Light On The Coupling Dynamics In Hybrid Nanostructures, Saba Arash

Theses and Dissertations

Here we present all-optical investigations of two hybrid nanostructures. In the first hybrid system, we study Janus-type nanofibers consisting of two hemi-cylinders of ferroelectric barium titanate and ferrimagnetic cobalt ferrite. Using the magnetic field-dependent polarization-resolved second harmonic generation technique, we observe a strong magnetoelectric coupling between the two ferroic constituents at room temperature. Corroborating these results by X-ray diffraction, we can also extract repeatable memory-dependent behaviors in these biphasic nanofibers. In the second hybrid system, we study the interaction between the semiconductor indium/gallium arsenide quantum dots and surface plasmon supporting silver structures in the weak coupling regime. When quantum dots …

Improved Out-Of-Plane Brdf Measurement And Modeling, Todd V. Small

Theses and Dissertations

The bi-directional reflectance distribution function (BRDF) describes the directional (spatial) nature of light’s reflectance from a material surface. When incident light of a particular wavelength strikes a material surface from a particular direction, portions of that incident light will be reflected into various directions in various amounts, depending on the material’s surface characteristics. Historically, the vast majority of BRDF measurement and modeling research has focused on reflection within the plane-of incidence (in-plane) and dealt primarily with simplified isotropic BRDFs. Remote sensing applications, such as satellite light curve analysis, typically rely on closed-form microfacet models for efficiency. There are many factors, …

Improvements To Emissive Plume And Shock Wave Diagnostics And Interpretation During Pulsed Laser Ablation Of Graphite, Timothy I. Calver

Theses and Dissertations

This dissertation covers nanosecond pulsed laser ablation of graphite for 4-5.7 J/cm² fluences with 248 nm and 532 nm lasers in 1-180 Torr helium, argon, nitrogen, air, and mixed gas. Three experiments were performed to improve the interpretation of common diagnostics used to characterize pulsed laser ablation, find simple but universal scaling relationships for comparing dynamics across different materials and ablation conditions, and provide a systematic analysis of graphite emissive plume and shock wave dynamics. A scaling of the Sedov-Taylor energy ratio was developed and validated for a range of studies despite differences in wavelength, pulse duration, fluence, and …

Neutron Energy Tuning Assemblies For Nuclear Weapon Environment Applications At The National Ignition Facility, Nicholas J. Quartemont

Theses and Dissertations

An energy tuning assembly was developed to spectrally shape the National Ignition Facility deuterium-tritium fusion neutron source to a notional thermonuclear and prompt fission neutron spectrum to fulfill neutron source capability gaps. The experimental neutron environment was characterized with activation dosimetry, neutronics and covariance models, and unfolded to determine the as-fielded neutron spectrum. The first energy tuning assembly was demonstrated to create synthetic spectrally accurate post-detonation fission products, enhancing U.S. technical nuclear forensics capabilities. ATHENA, a second-generation energy tuning assembly, was also optimized to meet similar objectives, but the new platform neutron fluence efficiency was increased by a factor of …

Analysis Of Space To Ground Ladar Performance With Non-Traditional Optics, Prayant P.S. Hanjra

Theses and Dissertations

Two major obstacles to space-based LADAR systems are low power returns from targets and limitations on size and weight for transporting large optics into orbit. Signals incur significant losses during roundtrip propagation through the atmosphere and from diffuse scattering off of targets. Models, such as the Laser Environmental Effects Definition and Reference (LEEDR) simulator and High Energy Laser End to End Operational Simulation (HELEEOS) can predict these losses due to the atmosphere and optical components for a variety of atmospheric and environmental conditions across the globe. A transmissometer is used to validate these models. These losses are used to determine …

Transport, Photoluminescence & Photoconduction Characteristics Of Free Standing Two-Dimensional Γ-Alumina & Titanium Superlattice Doped Two-Dimensional Γ-Alumina Grown By Graphene-Assisted Atomic Layer Deposition, Elaheh Kheirandish

Theses and Dissertations

This study presents a facile high-yield bottom-up fabrication, morphology, crystallographic and optoelectronic characterization of free-standing quasi-2D γ-alumina, a non van der Waals 2D material. The synthesis comprises a multi-cycle atomic layer deposition (ALD) of amorphous alumina on a porous interconnected graphene foam as a growth scaffold and removed next by annealing and sintering the alumina/graphene/alumina sandwich at ~ 800 °C in air . The crystallographic and structural characteristics of the formed non-van der Waals quasi 2D γ-alumina were studied by X-ray diffraction (XRD), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). This analysis revealed the synthesized 2D …

Gravitational Wave Timing Residual Models For Pulsar Timing Experiments, Casey Mcgrath

Theses and Dissertations

The ability to detect gravitational waves now gives scientists and astronomers a new way in which they can study the universe. So far, the scientific collaboration LIGO has been successful in detecting binary black hole and binary neutron star mergers. These types of sources produce gravitational waves with frequencies of the order hertz to millihertz. But there do exist other theoretical sources which would produce gravitational waves in different parts of the frequency spectrum. Of these are the theoretical mergers of supermassive black hole binaries (SMBHBs), which could occur upon the merging of two galaxies with supermassive black holes at …

Developing Effective Theories: A Case Study In Monolayer Iron Selenide, Joseph O'Halloran

Theses and Dissertations

In this work, we outline the development of a series of models which have allowed us to investigate the low-temperature phases of monolayer FeSe. These models are built using group theoretic arguments to ensure the constraints provided by the crystal symmetry are satisfied. We investigate the interplay between stripe antiferromagnetism and spin-vortex crystal order in the framework of the Landau theory of phase transitions. By considering inversion symmetry breaking terms in the Landau free-energy, we show that the spin-vortex crystal is preferred when the non-symmorphic parent symmetry group $P4/nmm$ is reduced to a symmorphic subgroup.

We also consider symmetry constraints …

The Exact Factorization Equations For One- And Two-Level Systems, Bart Rosenzweig

Theses and Dissertations

Exact Factorization is a framework for studying quantum many-body problems. This decomposes the wavefunctions of such systems into conditional and marginal components. We derive corresponding evolution equations for molecular systems whose conditional electronic subsystems are described by one or two Born-Oppenheimer levels and develop a program for their mathematical study.

Characterization And Modeling Of Upward Lightning At The Gaisberg Tower, Naomi Watanabe

Theses and Dissertations

The majority of cloud-to-ground lightning is downward. Upward lightning rarely occurs; less than 1% of cloud-to-ground lightning is upward. Upward lightning differs from its downward counterpart in how it is initiated. Upward lightning is initiated by an upward moving leader from a tall (> 100 m) object on ground that reaches into the charge regions of an overhead thundercloud resulting in a relatively-long-duration (tens to hundreds of milliseconds), low-level (tens to hundreds of amperes) current called the initial continuous current. It is of significant importance to understand in detail the processes associated with upward lightning as it affects ground-based infrastructure …

Π+Π- Electroproduction Off Protons In Deuterium: Measurements Of Quasi-Free Cross Sections And Kinematic Probing Of Final State Interactions, Iuliia Skorodumina

Theses and Dissertations

In this study, the process of π⁺π^- electroproduction off protons bound in deuterium nuclei is explored. The exploration is performed through the analysis of experimental data on electron scattering off the deuteron target, collected in Hall B at Jefferson Lab with the CLAS detector. As a main result, the set of integrated and single-differential cross sections of the reaction $\gamma_{v}p(n) \rightarrow p' (n')\pi^{+}\pi^{-}$ is obtained. The cross sections are extracted in the quasi-free regime, which implies that only events not affected by final state interactions are subject to selection. The measurements are performed in the kinematic region …

Large-NC Constraints For One- And Two-Nucleon Currents In Effective Field Theory, Thomas Richardson

Theses and Dissertations

There is a long-standing goal of understanding nuclear physics in terms of quarks and gluons, the constituent particles of nucleons. However, the underlying theory is strongly coupled at the scales relevant for nuclear physics; therefore, this goal can only be achieved through nonperturbative calculations. Additionally, nuclear targets are employed in a variety of experiments ranging from electroweak processes to Beyond the Standard Model physics. Thus, it is important to have a strong theoretical foundation for nuclear physics in the presence of external fields in order to interpret experimental results. Effective field theory (EFT) for nuclear physics constitutes a systematic and …

Two Aspects Of Magnetic Nanoparticle Self-Assembly On Thin-Film Multilayers: Custom Media Properties And Accurate Determination Of Nanoparticle Anisotropy Constant, Sara L. Fitzgerald

Theses and Dissertations

ZFC/FC moment versus temperature measurements are a common technique to determine magnetic properties of nanoparticles. In this work, I varied both applied field strength and nanoparticle concentration to study resulting changes in blocking temperature, T_B, and anisotropy constant, K. T_B and K values were obtained using both existing and new analytic methods. Accurate determination of these parameters helps researchers optimize the use of magnetic nanoparticles for a variety of applications, including magnetic heating, drug delivery, and magnetic field-directed self-assembly. For magnetic self-assembly particularly, not only nanoparticle properties, but also the magnetic properties of the substrate alter …

On-Chip Nanoscale Plasmonic Optical Modulators, Abdalrahman Mohamed Nader Abdelhamid

Theses and Dissertations

In this thesis work, techniques for downsizing Optical modulators to nanoscale for the purpose of utilization in on chip communication and sensing applications are explored. Nanoscale optical interconnects can solve the electronics speed limiting transmission lines, in addition to decrease the electronic chips heat dissipation. A major obstacle in the path of achieving this goal is to build optical modulators, which transforms data from the electrical form to the optical form, in a size comparable to the size of the electronics components, while also having low insertion loss, high extinction ratio and bandwidth. Also, lap-on-chip applications used for fast diagnostics, …

Engineered Nanostructured Nitrogen-Doped Carbon Network (Ndc) Electrodes With Unprecedented Cycling Stability For Water Capacitive Deionization In Harsh Conditions, Soha Essam Anwar

Theses and Dissertations

Capacitive deionization (CDI) is a feasible low-cost desalination technique for low-to-medium (brackish) salinity water. However, cycling stability and regeneration of the CDI electrodes are the bottlenecks hindering the practical application of the technology on large scale. Oxidation of the electrodes during the sequential adsorption-desorption processes is one of the most challenging problems hindering their long-term cycling performance. Herein, we demonstrated the ability to design and fabricate exceptionally stable CDI electrodes via a one-pot pyrolysis protocol. The optimized pyrolysis of nitrogen-carbon precursors at different temperatures enabled the fabrication of carbon materials with a controlled amount nitrogen dopant (NDCs) with exceptional cycling …

One Dimensional Study Of Magnetoplasmadynamic Thrusters For A Potential New Class Of Heavy Ion Drivers For Plasma Jet Driven Magnetoinertial Fusion, Patrick M. Brown

Theses and Dissertations

Plasma Jet Driven Magnetoinertial Fusion (PJMIF) requires high velocity heavy ion drivers in order to compress a magnetized target to fusion conditions. Previous work with heavy ion drivers has revealed sub-par accelerations due to plasma instabilities; thus, it is necessary to investigate new methods of heavy ion plasma acceleration. One such method is Magnetoplasmadynamic (MPD) thrusters. Past studies of these thrusters have been conducted at an initial temperature at or below the energy of full ionization. Here MPD thrusters are investigated using a Godunov type MHD solver with a Harten-Lax van Leer-D (HLLD) flux solving scheme assuming the plasma is …

Correlated Positron-Electron Orbital (Cpeo): A Novel Method That Models Positron-Electron Correlation In Virtual Ps At The Mean-Field Level, Kevin E. Blaine

Theses and Dissertations

The Correlated Positronic-Electronic Orbital (CPEO) method was developed and implemented to capture correlation effects at between the positron and electron in the modeling of systems that involve a bound positron. Methods that effectively model these systems require many hundred basis functions and use a mean field approach as the beginning step. CPEO builds an orbital for virtual Positronium (Ps) that contains a positron in a bound state along with an accompanying electron to the larger system. Assigning the virtual Ps orbital allows for the two particle variational optimization in conjunction with the other particles that compose the whole system. This …

Neutron Pulse-Time Extension Through Conversion To Positronium, Shawn T. Mctaggart

Theses and Dissertations

Laser-Plasma interactions have strong potential as future neutron sources. Measuring the neutron rate is difficult due to several issues: the very short duration of the laser pulse and subsequent fusion events (on the order of a few picoseconds), the corresponding short duration of the neutron pulse, and the simultaneous emission of other ionizing particles such as protons and electrons. A system was designed to measure neutron emission by imposing a delay from the emission of other radiation by conversion of the neutrons into ortho-positronium (o-Ps), the triplet state of positronium. This lifetime extension enables more sensitive and selective detection of …

Extracting Information From Compact Binary Coalescences With Gravitational Waves, Xiaoshu Liu

Theses and Dissertations

Gravitational waves (GWs) radiated by compact binary coalescences (CBCs) carry useful information about their sources. These source properties obtained via the parameter estimation technique can help us to answer a wide range of physics problems. In this dissertation, I will present three major research projects. Firstly, binary neutron stars (BNSs) detected by Advanced LIGO and Advanced Virgo are ideal to study the equation of state (EoS). The EoS enters GW waveforms through tidal deformability, which can be measured by Advanced LIGO and Advanced Virgo. By performing Bayesian model selection, we can test plausible models from a large set of proposed …

Investigation Of G Protein-Coupled Receptor Quaternary Structure Through Fluorescence Micro-Spectroscopy And Theoretical Modeling: Interdependence Between Receptor-Receptor And Receptor-Ligand Interactions, Joel David Paprocki

Theses and Dissertations

Proteins are of high interest in biophysics research due to the important roles they play within cells, such as sensing of chemical (ions and small molecules) and physical (e.g., light) stimuli, providing structure, transporting ions/molecules, signaling, and intercellular communication. The studies described in this dissertation focus on a particular type of membrane proteins known as G protein-coupled receptors (GPCR), which play a key role in cellular response to external stimuli. We used the sterile 2 α-factor mating pheromone receptor (Ste2), a prototypical class D GPCR present within Saccharomyces cerevisiae (baker’s yeast). Ste2 is responsible for initiating the second messenger signal …

Measurement Of The Top Quark Mass Using Leptonic Observables In Tt Events Produced In Pp Collisions At Sqrt S = 13 Tev With The Cms Experiment At The Lhc, Mark Douglas Saunders

Theses and Dissertations

A novel method is presented for the measurement of the top-quark mass using only leptonic observables in tt events produced in pp collisions at SQRT(s)= 13 TeV.Data, corresponding to an integrated luminosity of 35.9 fb−1, were collected with the CMS detector during LHC Run II in 2016. The measurement uses the top-quark mass dependence of multiple kinematic distributions comprised from the dilepton eμ final state of tt events. The top-quark mass dependence of each kinematic distribution is calibrated using events generated with a NLO Monte Carlo simulation, and for the first time, with a second simulation that includes the exact …

Numerical Modeling For Patch Antennas, Luis Mario Bres Castro

Theses and Dissertations

This thesis will focus on creating a number of designs that will be tested in a simulation environment using an electromagnetic solver software called Computer Simulation Technology(CST) as well as we are going to develop our own model to be able to simulate more complex design due to the limitations of CST licensing. The simulations will help us optimize the parameters of gain-frequency allocation for future projects of antenna building. After doing a parametric study of a patch antenna we will develop a model for the return signal of a signal patch antenna, we will present four potential models. The …