Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Neutrino Transport (2)
- Neutron star (2)
- Physics (2)
- Spallation Neutron Source (2)
- Supernova (2)
-
- AEDC (1)
- Adaptive radiation therapy (1)
- Antiferromagnetism (1)
- Approximation (1)
- Asymptotic (1)
- Autoassociative kernel regression (1)
- Beam Diagnostics (1)
- Beam Instrumentation (1)
- Blender (1)
- Casimir energy (1)
- Charge Exchange Foils (1)
- Computational (1)
- Contamination (1)
- Core Collapse (1)
- Core-Collapse Supernova (1)
- Cryodeposit (1)
- Detection (1)
- Einstein Equations (1)
- Electron Gun (1)
- Emissivity Measurement (1)
- Equation of state (1)
- Euler (1)
- Explicit (1)
- Foil Test Stand (1)
- Genetic Algorithms (1)
Articles 1 - 17 of 17
Full-Text Articles in Physics
Fabrication, Measurements, And Modeling Of Semiconductor Radiation Detectors For Imaging And Detector Response Functions, Corey David Ahl
Fabrication, Measurements, And Modeling Of Semiconductor Radiation Detectors For Imaging And Detector Response Functions, Corey David Ahl
Doctoral Dissertations
In the first part of this dissertation, we cover the development of a diamond semiconductor alpha-tagging sensor for associated particle imaging to solve challenges with currently employed scintillators. The alpha-tagging sensor is a double-sided strip detector made from polycrystalline CVD diamond. The performance goals of the alpha-tagging sensor are 700-picosecond timing resolution and 0.5 mm spatial resolution. A literature review summarizes the methodology, goals, and challenges in associated particle imaging. The history and current state of alpha-tagging sensors, followed by the properties of diamond semiconductors are discussed to close the literature review. The materials and methods used to calibrate the …
Core-Collapse Supernova Simulations With Spectral Two-Moment Neutrino Transport, Ran Chu
Core-Collapse Supernova Simulations With Spectral Two-Moment Neutrino Transport, Ran Chu
Doctoral Dissertations
The primary focus of this dissertation is to develop a next-generation, state-of-the-art neutrino kinetics capability that will be used in the context of the next-generation, state-of-the-art core-collapse supernova (CCSN) simulation frameworks \thornado\ and \FLASH.\index{CCSN} \thornado\ is a \textbf{t}oolkit for \textbf{h}igh-\textbf{or}der \textbf{n}eutrino-r\textbf{ad}iation hydr\textbf{o}dynamics, which is a collection of modules that can be incorporated into a simulation code/framework, such as \FLASH, together with a nuclear equation of state (EOS)\index{EOS} library, such as the \WeakLib\ EOS tables. The first part of this work extends the \WeakLib\ code to compute neutrino interaction rates from~\cite{Bruenn_1985} and produce corresponding opacity tables.\index{Bruenn 1985} The processes of emission, …
Control And Calibration Strategies For Quantum Simulation, Paul M. Kairys
Control And Calibration Strategies For Quantum Simulation, Paul M. Kairys
Doctoral Dissertations
The modeling and prediction of quantum mechanical phenomena is key to the continued development of chemical, material, and information sciences. However, classical computers are fundamentally limited in their ability to model most quantum effects. An alternative route is through quantum simulation, where a programmable quantum device is used to emulate the phenomena of an otherwise distinct physical system. Unfortunately, there are a number of challenges preventing the widespread application of quantum simulation arising from the imperfect construction and operation of quantum simulators. Mitigating or eliminating deleterious effects is critical for using quantum simulation for scientific discovery. This dissertation develops strategies …
Meta-Heuristic Optimization Techniques For The Production Of Medical Isotopes Through Special Target Design, Cameron Ian Salyer
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 …
Neutron Star Structure From Electromagnetic And Gravitational Wave Observations, Mohammad Al-Mamun
Neutron Star Structure From Electromagnetic And Gravitational Wave Observations, Mohammad Al-Mamun
Doctoral Dissertations
Neutron star (NS) research primarily relied on spectral observations before the first gravitational wave (GW) detection from the binary neutron star merger was done by the LIGO-VIRGO collaboration. The GW170817 merger event provided mass and tidal deformability Λ˜ constraints for neutron stars. This project used these constraints and associated them with the constraints made by the NS X-ray observations to construct neutron star models. Selective X-ray sources were used in this work, which showed reliable uncertainties from their previous uses. The mass-radius constraints from the electromagnetic (EM) observations were constructed from seven quiescent low-mass X-ray binaries (QLMXBs), three photospheric radius …
An Explicit Asymptotic Approach Applied To Neutrino-Electron Scattering In The Neutrino Transport Problem, Aaron Michael Lackey-Stewart
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 …
Analysis Of Primary Stripper Foils At The Spallation Neutron Source By An Electron Beam Foil Test Stand, Eric Paul Barrowclough
Analysis Of Primary Stripper Foils At The Spallation Neutron Source By An Electron Beam Foil Test Stand, Eric Paul Barrowclough
Doctoral Dissertations
Diamond films are used at the Spallation Neutron Source (SNS) as the primary charge exchange foils (i.e., stripper foils) of the accelerated 1 GeV (Gigaelectron volts) hydride ions. The most common type of film used is a nanocrystalline diamond film, typically 17 mm x 45 mm (millimeter) with an aerial density of 350 μg/cm2 (microgram per square centimeter). The diamond film is deposited on a corrugated silicon substrate using plasma-assisted chemical vapor deposition. After the growth of the diamond film, 30 mm of the silicon substrate is etched away, leaving a freestanding diamond foil with a silicon handle that …
Phase Transitions And The Casimir Effect In Neutron Stars, William Patrick Moffitt
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 …
Optimization Of The Nedm Experiment, Patrick Rogers
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 …
Accuracy And Stability Of Integration Methods For Neutrino Transport In Core Collapse Supernovae, Kyle A. Gregory
Accuracy And Stability Of Integration Methods For Neutrino Transport In Core Collapse Supernovae, Kyle A. Gregory
Chancellor’s Honors Program Projects
No abstract provided.
Novel Physical Properties Of Non-Trivial Magnetic Materials: Cr1/3nbs2, Mnsi And Fe3gete2, Jieyu Yi
Novel Physical Properties Of Non-Trivial Magnetic Materials: Cr1/3nbs2, Mnsi And Fe3gete2, Jieyu Yi
Doctoral Dissertations
Helimagnets and quasi-two-dimensional layered materials have attracted much recent interest due to their rich physical properties and potential for spintronics applications. In this dissertation, the helimagnets Cr1/3NbS2 [chromium one-third niobium disulfide] and thin-film MnSi [manganese silicide] as well as the layered magnetic material Fe3GeTe2 [iron three germanium ditelluride] were extensively and carefully studied. Cr1/3NbS2 was previously reported to be helimagnet with a transition temperature of approximately 120 K. Cr1/3NbS2 has a layered structure with Cr3+ ions intercalating between NbS2 sheets, and is easily cleaved. Using in-situ …
Analysis, Prototyping, And Design Of An Ionization Profile Monitor For The Spallation Neutron Source Accumulator Ring, Dirk A. Bartkoski
Analysis, Prototyping, And Design Of An Ionization Profile Monitor For The Spallation Neutron Source Accumulator Ring, Dirk A. Bartkoski
Doctoral Dissertations
The Spallation Neutron Source (SNS) located in the Oak Ridge National Laboratory is comprised of a 1 GeV linear H- [H^-] accelerator followed by an accumulator ring that delivers high intensity 1 μs [microsecond] long pulses of 1.5x1014 [1.5x10^14] protons to a liquid mercury target for neutron production by spallation reaction. With its strict 0.01% total beam loss condition, planned power upgrade, and proposed second target station, SNS ring beam-profile diagnostics capable of monitoring evolving beam conditions during high-power conditions are crucial for efficient operation and improvement. By subjecting ionized electrons created during beam interactions with the residual …
Quantitative Techniques For Pet/Ct: A Clinical Assessment Of The Impact Of Psf And Tof, Joshua Donald Schaefferkoetter
Quantitative Techniques For Pet/Ct: A Clinical Assessment Of The Impact Of Psf And Tof, Joshua Donald Schaefferkoetter
Doctoral Dissertations
Tomographic reconstruction has been a challenge for many imaging applications, and it is particularly problematic for count-limited modalities such as Positron Emission Tomography (PET). Recent advances in PET, including the incorporation of time-of-flight (TOF) information and modeling the variation of the point response across the imaging field (PSF), have resulted in significant improvements in image quality. While the effects of these techniques have been characterized with simulations and mathematical modeling, there has been relatively little work investigating the potential impact of such methods in the clinical setting. The objective of this work is to quantify these techniques in the context …
Development Of A Novel Technique For Predicting Tumor Response In Adaptive Radiation Therapy, Rebecca Marie Seibert
Development Of A Novel Technique For Predicting Tumor Response In Adaptive Radiation Therapy, Rebecca Marie Seibert
Doctoral Dissertations
This dissertation concentrates on the introduction of Predictive Adaptive Radiation Therapy (PART) as a potential method to improve cancer treatment. PART is a novel technique that utilizes volumetric image-guided radiation therapy treatment (IGRT) data to actively predict the tumor response to therapy and estimate clinical outcomes during the course of treatment. To implement PART, a patient database containing IGRT image data for 40 lesions obtained from patients who were imaged and treated with helical tomotherapy was constructed. The data was then modeled using locally weighted regression. This model predicts future tumor volumes and masses and the associated confidence intervals based …
Atomistic Simulations Of The Fusion-Plasma Material Interface, Mostafa Jon Dadras
Atomistic Simulations Of The Fusion-Plasma Material Interface, Mostafa Jon Dadras
Doctoral Dissertations
A key issue for the successful performance of current and future fusion reactors is understanding chemical and physical processes at the Plasma Material Interface (PMI). The material surfaces may be bombarded by plasma particles in a range of impact energies (1 eV - a few keV) and kept at a range of temperatures (300 - 1000 K). The dominant processes at the PMI are reflection and retention of impacting particles and sputtering (chemical and physical). Sputtering leads to surface erosion and pollution of the plasma, both of which degrade reactor performance. Retention influences the recycling of the plasma, and in …
Water Ice Films In Cryogenic Vacuum Chambers, Jesse Michael Labello
Water Ice Films In Cryogenic Vacuum Chambers, Jesse Michael Labello
Doctoral Dissertations
The space simulation chambers at Arnold Engineering Development Complex (AEDC) allow for the testing and calibration of seeker sensors in cryogenic, high vacuum environments. During operation of these chambers, contaminant films can form on the components in the chamber and disrupt operation. Although these contaminant films can be composed of many molecular species, depending on the species outgassed by warm chamber components and any leaks or virtual leaks (pockets of gas trapped within a vacuum chamber) that may be present, water vapor is most common, and it will be the focus of this dissertation. In this dissertation, some properties of …
On The Behavior Of The Asymptotics Of Robertson-Walker Cosmologies As A Function Of The Cosmological Constant, Noah Thomas Schaefferkoetter
On The Behavior Of The Asymptotics Of Robertson-Walker Cosmologies As A Function Of The Cosmological Constant, Noah Thomas Schaefferkoetter
Masters Theses
An analysis of the Einstein Field Equations within a Robertson-Walker Cosmology. More specifically, what values of the cosmological constant will result in a Big Bang.