Physics Commons^™

Gamma-Ray Metallic Magnetic Calorimeters With Nbta Passive Persistent Switches And Electroformed Au Absorbers, Ruslan Hummatov

Physics & Astronomy ETDs

Metallic Magnetic Calorimeters (MMCs) are low temperature particle detectors which can be used for a wide range of applications including high-resolution γ -ray spectroscopy. High energy resolution in γ -ray spectroscopy is desired for Non Destructive Assay (NDA) of nuclear material and improved measurements of nuclear data. Our group has been developing γ -ray MMCs that should ultimately provide energy resolution more than an order of magnitude better than the benchmark detector technology, high purity germanium detectors (HPGe). Two components of these MMCs have been developed as a part of this dissertation: an on-chip passive superconducting persistent current switch and …

Proposed Method For Measuring The Let Of Radiotherapeutic Particle Beams, Stephen D. Bello

Physics & Astronomy ETDs

The Bragg peak geometry of the depth dose distributions for hadrons allows for precise and effective dose delivery to tumors while sparing neighboring healthy tissue. Further, compared against other forms of radiotherapeutic treatments, such as electron beam therapy (EBT) or photons (x and \(\gamma\)-rays), hadrons create denser ionization events along the particle track, which induces irreparable damage to DNA, and thus are more effective at inactivating cancerous cells. The measurement of radiation's ability to inactivate cellular reproduction is the relative biological effectiveness (RBE). A quality related to the RBE that is a measurable physical property is the linear energy transfer …

Nanowire-Based Light-Emitting Diodes: A New Path Towards High-Speed Visible Light Communication, Mohsen Nami

Physics & Astronomy ETDs

Nano-scale optoelectronic devices have gained significant attention in recent years. Among these devices are semiconductor nanowires, whose dimeters range from 100 to 200 nm. Semiconductor nanowires can be utilized in many different applications including light-emitting diodes and laser diodes. Higher surface to volume ratio makes nanowire-based structures potential candidates for the next generation of photodetectors, sensors, and solar cells. Core-shell light-emitting diodes based on selective-area growth of gallium nitride (GaN) nanowires provide a wide range of advantages. Among these advantages are access to non-polar m-plane sidewalls, higher active region area compared to conventional planar structures, and reduction of threading …

Miniclean Dark Matter Experiment, Juijen Wang

Physics & Astronomy ETDs

Particle Dark Matter is a hypothesis accounting for a number of observed astrophysical phenomena such as the anomalous galactic rotation curves. From these astronomical observation, about 23% of the universe appears to consist of dark matter. Among the possible candidates for dark matter, a plausible one is a Weakly Interacting Massive Particle (WIMP). A particle with the required properties is beyond the standard model of particle physics. The MiniCLEAN experiment is single-phase liquid-argon detector instrumented with 92 photomultiplier tubes placed inside the cryogenic liquid with 4-pi coverage of a 500 kg (150 kg) target (fiducial) mass. For this experiment, PMT …

Molecular Tracers Of Star Formation Feedback In Nearby Galaxies, Mark Gorski

Physics & Astronomy ETDs

The energy and momentum injected into the ISM from stars has a drastic effect on the star formation history of a galaxy. This is called feedback. It is responsible for the inefficient collapse of the ISM into stars. The ``Survey of Water and Ammonia in Nearby Galaxies" (SWAN) is a survey of molecular line tracers in four nearby galaxies. By using molecular tracers of feedback, we provide insights into the star forming ecosystem of the galaxies NGC 253, IC 342, NGC 6946, and NGC 2146. These galaxies were chosen to span an order of magnitude in star formation rate and …

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

Mathematics & Statistics ETDs

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

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

The first part of this …

Evaluation And Enhancement Of Clean Energy Systems: Analytical, Computational And Experimental Study Of Solar And Nuclear Cycles, Nima Fathi

Mechanical Engineering ETDs

Clean (and specifically renewable) energy is steadily improving its global share. However, finite availability of fossil fuels and the growing effects of climate change make it an urgent priority to convince the industry and governments to incentivize investment in the renewable energy field and to make it more attractive by decreasing the capital cost. Until recently, uncertainties in funding limited renewable energy development, especially in the US. That limitation has been one of the barriers to progress. Another limitation of many renewable energy systems is the variability in their output, which makes them unsuitable for baseline power production. Therefore, fossil …

Ion Size Effects On The Properties Of Charge Regulating Electric Double Layers, Divya Jyoti Prakash

Nanoscience and Microsystems ETDs

The behavior of charged interfaces formed in various systems like colloidal solution, fuel cells, battery, electro-deposition, catalysis is governed by the properties of electrical double layer(EDL). Civilized model with charge regulation boundary condition determined by thermodynamic equilibrium at the interface has been used to model electrical double layer and shows that size of the solvent plays a critical role in characterizing the properties of EDL using classical density functional theory.This thesis investigates the impact of ion size in electrolyte solutions on the electrical double layer formed at the interface using a similar model. It is found that ion size greatly …

Microdischarges Utilized In Portable Gas Sensing And Their Atmospheric Contaminants, Colin H. Sillerud

Chemical and Biological Engineering ETDs

Portable applications of microdischarges such as the chemical detection, remediation of gaseous wastes, or the destruction of volatile organic compounds will mandate operation in the presence of contaminant species. This work examines the temporal evolution of microdischarge optical and ultraviolet emissions during pulsed operation by experimental methods. By varying the pulse length of a microdischarge initiated in a 4-hole silicon microcavity array operating in a 655 Torr ambient primarily composed of Ne, we were able to measure the emission growth rates for different contaminant species native to the discharge environment as a function of pulse length. It was found that …

High Precision Refractive Index Measurement Techniques Applied To The Analysis Of Neutron Damage And Effects In Caf2 Crystals, Joseph P. Morris Ph.D.

Nuclear Engineering ETDs

Neutron irradiation damages material by atomic displacements. The majority of these damage regions are microscopic and difficult to study, though they can cause a change in density and thus a change in refractive index in transparent materials. This work utilized CaF₂ crystals to track refractive index change based on neutron radiation dose. High precision refractive index measurements were performed utilizing a nested-cavity mode-locked laser where the CaF₂ crystal acted as a Fabry-Pérot Etalon (FPE). By comparing the repetition rate of the cavity and the repetition rate of the FPE, refractive index change was determined. Following several irradiation experiments, …

Universal Disorder In Organic Semiconductors Due To Fluctuations In Space Charge, Tzucheng Wu

Physics & Astronomy ETDs

This thesis concerns the study of charge transport in organic semiconductors. These materials are widely used as thin-film photoconductors in copiers and laser printers, and for their electroluminescent properties in organic light-emitting diodes. Much contemporary research is directed towards improving the efficiency of organic photovoltaic devices, which is limited to a large extent by the spatial and energetic disorder that hinders the charge mobility. One contribution to energetic disorder arises from the strong Coulomb interactions between injected charges with one another, but to date this has been largely ignored. We present a mean-field model for the effect of mutual interactions …

Measurement-Based Quantum Computation And Symmetry-Protected Topological Order, Jacob E. Miller

Physics & Astronomy ETDs

While quantum computers can achieve dramatic speedups over the classical computers familiar to us, identifying the origin of this quantum advantage in physical systems remains a major goal of quantum information science. A useful tool here is measurement-based quantum computation (MQC), a computational framework utilizing the quantum entanglement found in many-body resource states. Not all resource states are useful for quantum computation however, so an important question is what properties of many-body entanglement characterize universal resource states, which can implement any quantum computation.

Many-body states are also studied in condensed matter physics, where the collective behavior of quantum many-body systems …

Search For New Physics Processes With Heavy Quark Signatures In The Atlas Experiment, Aaron Taylor

Physics & Astronomy ETDs

A program involving searches for new physics with heavy quark final states using data from the ATLAS experiment at the LHC is presented here. The signal and expected backgrounds for the decay , a rare decay whose branching ratio may be enhanced by the presence of certain Beyond the Standard Model processes, are studied, and the groundwork is laid for a future analysis. Possible mediators include horizontal gauge bosons, supersymmetry via sgoldstinos, and interactions with the hidden sector. To this end, a set of twelve triggers have been selected and studied, and their efficiency figures of merit have been calculated. …

Synchronous Generation And Coherent Control Of Extreme Wavelength Radiation And Ultrafast Spectroscopy, Aram Gragossian

Optical Science and Engineering ETDs

Recent progress in ultrafast laser science has made it possible to synthesize and control complex electromagnetic waveforms down to sub-femtosecond timescales. These tailored ultrashort laser pulses can generate coherent bursts of electromagnetic radiation in the extreme ultraviolet (XUV) and terahertz spectral regions with durations reaching the attosecond regime in the XUV region. This is accomplished by coherently controlling electronic motion in gas plasma targets. With these novel radiation sources, ultrafast time-resolved spectroscopy can be performed on a large variety of materials. Knowledge of the spectral phase of an ultrashort pulse is crucial for many applications. There are a variety of …