Physics Commons^™

Thermal Conductivity And Mechanical Properties Of Interlayer-Bonded Graphene Bilayers, Afnan Mostafa

Masters Theses

Graphene, an allotrope of carbon, has demonstrated exceptional mechanical, thermal, electronic, and optical properties. Complementary to such innate properties, structural modification through chemical functionalization or defect engineering can significantly enhance the properties and functionality of graphene and its derivatives. Hence, understanding structure-property relationships in graphene-based metamaterials has garnered much attention in recent years. In this thesis, we present molecular dynamics studies aimed at elucidating structure-property relationships that govern the thermomechanical response of interlayer-bonded graphene bilayers.

First, we present a systematic and thorough analysis of thermal transport in interlayer-bonded twisted bilayer graphene (IB-TBG). We find that the introduction of interlayer C-C …

Design And Fabrication Of A Trapped Ion Quantum Computing Testbed, Christopher A. Caron

Masters Theses

Here we present the design, assembly and successful ion trapping of a room-temperature ion trap system with a custom designed and fabricated surface electrode ion trap, which allows for rapid prototyping of novel trap designs such that new chips can be installed and reach UHV in under 2 days. The system has demonstrated success at trapping and maintaining both single ions and cold crystals of ions. We achieve this by fabricating our own custom surface Paul traps in the UMass Amherst cleanroom facilities, which are then argon ion milled, diced, mounted and wire bonded to an interposer which is placed …

Investigation Of Defect Production And Displacement Energies In Wurtzite Aluminum Nitride, Sean Anderson

Masters Theses

"Aluminum Nitride is an active element of sensors that monitor the performance and well-being of the nuclear reactors due to its piezoelectric properties. Yet, the variations of its properties under irradiation are largely unexplored. We report the results of the molecular dynamics simulations of the structural changes in AlN under irradiation via the knock-on atom technique. By creating and evolving the irradiation cascades due to energetic particle interaction with the atom of the crystalline lattice we determine the rate of the defect production as a function of the deposited energy. Further, we determine a displacement energy, a key characteristic that …

Analysis Of Turbulent Flow Behavior In Helicopter Rotor Hub Wakes, Forrest Mobley

Masters Theses

The rotor hub is one of the most important features of all helicopters, as it provides the pilot a means for controlling the vehicle by changing the characteristics of the main and tail rotors. The hub also provides a structural foundation for the rotors and allows for the rotor blades to respond to aerodynamic forces while maintaining controllability and stability. Due to the inherent geometry and high rate of rotation, the rotor hub in its current form acts a large bluff body and is the primary source of parasite drag on the helicopter, despite its relatively small size. The rotor …

Transverse Energy Analysis In Small Collision Systems, Alexander L. Aukerman

Masters Theses

Heavy Ion Collisions performed in the LHC at Cern are capable of generating a new phase of nuclear matter known as the Quark Gluon Plasma. In addition to running heavy ion collisions, the detectors dedicated to studying the QGP perform collisions utilizing smaller collision systems for the sake of comparing key measurements associated with the creation of a QGP. The transverse energy of the particles generated from the collision is one such key measurement. For the sake of comparison an analysis is performed on the transverse energy measurements taken from proton-proton collisions.

Enigma - Ongoing Development Towards Novel Beta-Decay Spectroscopy Station At Isolde, Philipp Wagenknecht

Masters Theses

Beta decay and collinear laser spectroscopy are proven efficient tools to study nuclear structure far from stability. Two areas of significance are investigations into nuclear deformation and shape coexistence, as well as delayed neutron emissions used in nuclear energy applications. This contribution presents the ongoing development towards a novel beta-decay spectroscopy station for the VITO experiment at CERN’s radioactive ion beam facility ISOLDE. The setup will utilize both collinear laser spectroscopy and beta-decay spectroscopy to measure the energy and spin-parities of the ground and excited states of radioactive beams. Initial designs of the support structure, magnetic field, and detector array …

Meta-Heuristic Optimization Techniques For The Production Of Medical Isotopes Through Special Target Design, Cameron Ian Salyer

Masters Theses

Medical isotopes are used for a variety of different diagnostic and therapeutic purposes Ruth (2008). Due to recent newly discovered applications, their production has become rapidly more scarce than ever before Charlton (2019). Therefore, more efficient and less time consuming methods are of interest for not only the industry’s demand, but for the individuals who require radio-isotope procedures. Currently, the primary source of most medical isotopes used today are provided by reactor and cyclotron irradiation techniques, followed by supplemental radio-chemical separations Ruth (2008). Up until this point, target designs have been optimized by experience, back of the envelope calculations, and …

Particle Swarm Optimization For Critical Experiment Design, Cole Michael Kostelac

Masters Theses

“Critical experiments are used by nuclear data evaluators and criticality safety engineers to validate nuclear data and computational methods. Many of these experiments are designed to maximize the sensitivity to a certain nuclide-reaction pair in an energy range of interest. Traditionally, a parameter sweep is conducted over a set of experimental variables to find a configuration that is critical and maximally sensitive. As additional variables are added, the total number of configurations increases exponentially and quickly becomes prohibitively computationally expensive to calculate, especially using Monte Carlo methods.

This work presents the development of a particle swarm optimization algorithm to design …

Several Problems In Nonlinear Schrödinger Equations, Tim Van Hoose

Masters Theses

“We study several different problems related to nonlinear Schrödinger equations….

We prove several new results for the first equation: a modified scattering result for both an averaged version of the equation and the full equation, as well as a set of Strichartz estimates and a blowup result for the 3d cubic problem.

We also present an exposition of the classical work of Bourgain on invariant measures for the second equation in the mass-subcritical regime”--Abstract, page iv.

Numerical Investigations Of 2-D Magnetic Nozzles On Pulsed Plasma Plumes, Joshua Daniel Burch

Masters Theses

"This research presents studies of a novel type of magnetic nozzle that allows for three-dimensional (3-D) steering of a plasma plume. Numerical simulations were performed using Tech-X's USim® software to quantify the nozzle's capabilities. A2-D planar magnetic nozzle was applied to plumes of a nominal pulsed inductive plasma (PIP) source with discharge parameters similar to those of Missouri S&T's Missouri Plasmoid Experiment (MPX). Argon and xenon plumes were considered. Simulations were verified and validated through a mesh convergence study as well as comparison with available experimental data. Periodicity was achieved over the simulation run time and phase angle samples were …

Accelerating Dynamical Density Response Code On Summit And Its Application For Computing The Density Response Function Of Vanadium Sesquioxide, Wileam Y. Phan

Masters Theses

This thesis details the process of porting the Eguiluz group dynamical density response computational platform to the hybrid CPU+GPU environment at the Summit supercomputer at Oak Ridge National Laboratory (ORNL) Leadership Computing Center. The baseline CPU-only version is a Gordon Bell-winning platform within the formally-exact time-dependent density functional theory (TD-DFT) framework using the linearly augmented plane wave (LAPW) basis set. The code is accelerated using a combination of the OpenACC programming model and GPU libraries -- namely, the Matrix Algebra for GPU and Multicore Architectures (MAGMA) library -- as well as exploiting the sparsity pattern of the matrices involved in …

Modeling And Characterization Of Optical Metasurfaces, Mahsa Torfeh

Masters Theses

Metasurfaces are arrays of subwavelength meta-atoms that shape waves in a compact and planar form factor. During recent years, metasurfaces have gained a lot of attention due to their compact form factor, easy integration with other devices, multi functionality and straightforward fabrication using conventional CMOS techniques. To provide and evaluate an efficient metasurface, an optimized design, high resolution fabrication and accurate measurement is required. Analysis and design of metasurfaces require accurate methods for modeling their interactions with waves. Conventional modeling techniques assume that metasurfaces are locally periodic structures excited by plane waves, restricting their applicability to gradually varying metasurfaces that …

Calculation And Modeling Of The Neutron’S Magnetic Moment, Abhyuday Sharda

Masters Theses

This thesis presents the current state of neutron magnetic moment calcu- lations. It details the development of calculations through history. It also delves into an experiment measuring the neutron magnetic moment. It ex- plores other methods by which calculations can be improved to get a better/ more accurate number. The conclusion is that there are still a lot of areas unexplored in context of the calculation of neutron magnetic moment and areas relevant to be worked upon are detailed.

Machine Learning Applications For Waveform Analysis, Micah R. Cruz

Masters Theses

Since the later 20th century, the search for physics beyond the Standard Model (BSM) has been paramount to many nuclear and particle physicists. Neutron and nuclear beta decay experiments provide one avenue to search for evidence of BSM physics by contributing to the unitarity check of the Cabibbo-Kobayashi-Maskawa matrix. Many of these experiments detect neutron decay products as digitized waveforms. As computing power increases and novel algorithms are developed, it is compelling to investigate machine learning methods as an analytic tool for such waveform data. These methods can allow for very fast data exploration techniques, and if pseudodata is available …

A Simple Background Elimination Method For Miniaturized Fiber-Optic Raman Probe, Bohong Zhang

Masters Theses

"Raman scattering is called a photonic - molecular interaction based on the kinetic model of the analytic. Due to the uniqueness of the Raman scattering technique, it can provide a unique fingerprint signal for molecular recognition. However, a serious challenge often encountered in Raman measurement comes from the requirements of fast, real-time remote sensing, background fluorescence suppression, and micro-environmental detection.

A new Miniaturized Fiber-Optic Raman Probe (MFORP) for Raman spectroscopy, used especially for eliminating background fluorescence and enhancing sampling, is presented. Its main purpose is to provide an overview of excellent research on the detection of very small substances and …

A Compact Wavelength Meter Using A Multimode Fiber, Ogbole Collins Inalegwu

Masters Theses

“Wavelength meters are very important for precision measurements of both pulses and continuous-wave optical sources. Conventional wavelength meters employ gratings, prisms, interferometers, and other wavelength-sensitive materials in their design. Here, we report a simple and compact wavelength meter based on a section of multimode fiber and a camera. The concept is to correlate the multimodal interference pattern (i.e., speckle pattern) at the end-face of a multimode fiber with the wavelength of the input lightsource. Through a series of experiments, specklegrams from the end face of a multimode fiber as captured by a charge-coupled device (CCD) camera were recorded; the images …

An Explicit Asymptotic Approach Applied To Neutrino-Electron Scattering In The Neutrino Transport Problem, Aaron Michael Lackey - Stewart

Masters Theses

This thesis presents results of explicit asymptotic calculations applied to neutrino-electron collisions in the neutrino transport problem; a problem that is generally solved using implicit methods when simulating core collapsed supernovae. It is shown that the explicit asymptotic method provides stable solutions to these stiff systems of equations while also yielding comparative accuracy and time stepping to standard implicit treatments such as Backward Euler, Fixed Point Iteration, and Anderson Accelerated Fixed Point. Because implicit methods are found to be less efficient for large systems of stiff, coupled equations, these results could help cut costs in solving this problem while also …

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 …

Synthesis And Characterization Of Ion-Implanted Gold Nanoparticles, Nurlathifah Fnu

Masters Theses

Gold negative ions of 70 keV energy were implanted within the quartz substrates at room temperature at seven different fluences starting from 2 x 10¹⁶ particles/cm² to 8 x 10¹⁶ particles/cm² with the increment of 1 x 10¹⁶. Prior to the implantation, Stopping and Range of Ions in Matter (SRIM) calculations were carried to obtain the Bragg peak below the surface of quartz. Rutherford Backscattering Spectrometry (RBS) was carried out using 2.0 MeV He⁺⁺ ions to measure depth and implanted fluence of gold, and learn how they varied with fluence. Backscattered He particles …

Application And Evaluation Of Lighthouse Technology For Precision Motion Capture, Soumitra Sitole

Masters Theses

This thesis presents the development towards a system that can capture and quantify motion for applications in biomechanical and medical fields demanding precision motion tracking using the lighthouse technology. Commercially known as SteamVR tracking, the lighthouse technology is a motion tracking system developed for virtual reality applications that makes use of patterned infrared light sources to highlight trackers (objects embedded with photodiodes) to obtain their pose or spatial position and orientation. Current motion capture systems such as the camera-based motion capture are expensive and not readily available outside of research labs. This thesis provides a case for low-cost motion capture …

Streamwise Flow-Induced Oscillations Of Bluff Bodies - The Influence Of Symmetry Breaking, Tyler Gurian

Masters Theses

The influence of symmetry breaking on the flow induced oscillations of bluff bodies in the steamwise direction is studied. First, a series of experiments is conducted on a one-degree-of-freedom circular cylinder allowed to exhibit pure translational motion in the streamwise direction over a range of reduced velocities, 1.4 < U* < 4.4, corresponding to a Reynolds number range of 970 < Re < 3370. Two distinct regions of displacements were observed in reduced velocity ranges of 1.6 < U* < 2.5 and 2.75 < U* < 3.85. Measured force coefficients in the drag and lift direction were examined, along with the wake visualization, through the range of reduced velocities, to infer the resulting wake modes. A new Alternating Symmetric (AS) mode was found. This transition from symmetric to AS shedding occurred near the end of the first region of response. Similar tests were run with a square prism in the parameter space of 2.4 < U* < 5.8 and 757 < Re < 1900 over angles of incidence of 0° ≤ α ≤ 45°. A distinct region of lock-in is observed for α = 0°, 2.5°, 5°, 7.5° over 3.2 < U* < 5.4 for α = 0°, and decreasing with increasing α. The wake structures were found to be roughly symmetric for α = 0°, but transitioned towards asymmetry …

Modulated Photothermal Radiometry: Detector Sensitivity Study And Experimental Setup, Jessica Nicole Seals

Masters Theses

"This thesis outlines the development of a system used for determining the surface thermal diffusivity of both non-irradiated and irradiated materials. The motivation for this work is to establish a modulated photothermal radiometry (PTR) system on the campus of Missouri University of Science and Technology. One of the main efforts described in this thesis is the design and construction of the physical apparatus. Along the way, it was necessary to perform a detailed sensitivity analysis of the system to determine whether the expected signal emitted from the sample falls within the bounds of detectivity for the HgCdTe (MCT) detector used …

Universal Wavefront Transmission Through Disordered Media, Jayson Robert Summers

Masters Theses

”When electromagnetic waves propagate through random dielectric media, they scatter in a predictable, deterministic way. The process is also fully reversible. If one sends an exiting wave backward through the same material, it will converge back to its original form and location in the same amount of time it took to originally propagate through the material. Due to this predictability, a great deal of research has went into studying these scattering processes in multimode fibers, diffusers, biological tissues, and other media. Scientists have turned random scattering material into focusing lenses, image transmitters, and highly transmitting media by controlling the impinging …

Customized Multi-Group Cross Section Generation With Njoy For Discrete Ordinates Computed Tomography And Radiography Simulation, Steven Michael Wagstaff

Masters Theses

"The purpose of this work was to explore the creation of photoatomic multi-group cross section libraries to be used with a software package DOCTORS (Discrete Ordinates Computed TOmography and Radiography Simulator). This software solves the linear Boltzmann equation using the discrete ordinates method [1]. To create these libraries, NJOY2016 was used, creating both fine and broad energy multi-group cross section files. The cross section's accuracy was tested against an equivalent Monte Carlo simulation using MCNP6.

Two simulation geometries were used. The first, a cylindrical water phantom with a single source projection placed in front, simulating an X-ray radiography. The second …

Developing Computational Models For Pulsed-Inductive Plasma Formation, Zachary Aaron Gill

Masters Theses

"Pulsed-inductive discharges are a common method of producing a plasma. They provide a mechanism for quickly and efficiently generating a large volume of plasma for rapid use and are seen in applications including propulsion, fusion power, and high-power lasers. However, some common designs see a delayed response time due to the plasma forming when the magnitude of the magnetic field in the device is at a minimum. New designs are difficult to evaluate due to the amount of time needed to construct a new geometry and the high monetary cost of changing the power generation circuit. To more quickly evaluate …

Phase Transitions And The Casimir Effect In Neutron Stars, William Patrick Moffitt

Masters Theses

What lies at the core of a neutron star is still a highly debated topic, with both the composition and the physical interactions in question. In this thesis, we made assumptions regarding the composition to further study the interactions of matter during the transition phases. These phases, also known as nuclear pasta, come from the unique physical conditions which occur within neutron stars. We examine the feasibility of the Casimir effect manifesting during these phases, as well as the effects it would have on the total energy of the system. We find that the crust-core transition cannot support the proper …

Probing Pulse Structure At The Spallation Neutron Source Via Polarimetry Measurements, Connor Miller Gautam

Masters Theses

The Fundamental Neutron Physics Beamline (FNPB) at Spallation Neutron Source is used to probe fundamental forces via cold neutrons. The beamline's latest experiment is probing the hadronic weak interaction through the capture of polarized cold neutrons on ³He nuclei. While the strong nuclear force is dominant in this interaction, a weak signal can be observed in the parity violating momentum asymmetry in the reaction products. As the asymmetry measurement requires both neutron spin states, a means of controlling the neutron spin is required. In order to alternate the spins, a radio frequency spin rotator was installed for the experiment. …

Development Of Nuclear Underground Engineered Test Surrogates For Technical Nuclear Forensics Exploitation, Robert Boone Gilbreath

Masters Theses

A method for formulation and production of Nuclear UnderGround Engineered Test Surrogates (NUGETS) based on notional improvised nuclear device (IND) detonations in an underground environment analogous to the Nevada National Security Site (NNSS) is presented. Extensive statistical analyses of precursory geochemical and geophysical characteristics are combined with an augmented surrogate debris cooling technique and predictive IND contributions from the ORIGEN Fallout Analysis Tool. Precursory and resultant elemental compositions, cooling curve calculations, and visual comparison of NUGETS to genuine underground debris are reported. Application of NUGETS methodology to future studies in urban, underground post-detonation technical nuclear forensic (TNF) analysis is suggested.

Optimization Of The Nedm Experiment, Patrick Rogers

Masters Theses

The Neutron Electric Dipole Moment (NEDM) experiment is an upcoming experiment at ORNL to measure the size of an electric dipole moment inside of the neutron. This is being done to probe CP asymmetries that could give rise to a matter dominated universe. The experiment will utilize a nuclear reaction that outputs scintillation light in a manner that depends on the alignment of the spins of the reactant particles. This light will be detected and used to measure the NEDM. The amount of light collected for measurement will impact the accuracy of the results; the more photons collected the better …

Characterization Of Reactor Background Radiation At Hfir For The Prospect Experiment, Blaine Alexander Heffron

Masters Theses

This work describes an investigation of the background radiation present at the High Flux Isotope Reactor (HFIR) on behalf of the PROSPECT collaboration. The PROSPECT experiment is designed to make a precision measurement of the antineutrino spectrum at HFIR and search for sterile neutrinos. Temporal and spacial variation of neutron and gamma backgrounds at the experiment site for the PROSPECT detector are measured in order to determine if the reactor correlated radiation will contribute a significant background to the inverse beta decay signal. Knowledge of spacial background variation will also be used to inform the design of a local shield …