×
Department Library
James Adams (Capstone, August 2020, Advisor: Steve Turley )

Abstract

Our team is focused on testing mirrors and other phenomena in the Extreme Ultraviolet (XUV). For this, we need a way to select wavelengths used for testing. A grazing incidence monochromator is one way to achieve this goal, and so one is installed in our system. The focus of this project was to automate the positioning of the monochromator and thus automate wavelength selection. Over the course of this project, a system was designed to attach a motor to the micrometer knob controlling the position of the monochromator. Once designed, the system was constructed and installed in the overall system. The system was then calibrated to correlate motor position to wavelength selected. The motor accurately positions the micrometer knob to within 0.001mm, which translates to within 0.008nm of the desired wavelength, and the support system meets all design goals.

Paul W. Bailey (Senior Thesis, April 2020, Advisor: Jean-Francois Van Huele )

Abstract

I propose to incorporate two GaAs/InAs quantum dots in a larger circuit comprised of linear optical elements to create a spin-spin-photon polarization three-qubit Deutsch gate. Since the Deutsch gate is a universal quantum logic gate, any quantum computing task can be completed using a combination of Deutsch gates. I argue the significance of the spin-spin-photon Deutsch gate protocol, given that no Deutsch gate has been experimentally realized and the only other published Deutsch gate proposal does not use a flying qubit. The use of a flying photonic qubit facilitates quantum communication applications. In addition, I show that the versatility of my protocol can lead to two different constructions of the Toffoli gate either by fixing a parameter of the Deutsch gate or by taking a sub-circuit of the Deutsch gate. Within my Deutsch gate circuit is a smaller Toffoli gate circuit. I calculate the fidelity of the Toffoli gate circuit for different material parameters of the GaAs/InAs quantum dots. I display a schematic of the Deutsch gate circuit with removable mirrors that allow the circuit to switch into a Toffoli gate. Finally, I discuss how appropriate Toffoli gates can be adapted into Deutsch gates using a sub-circuit of the original Deutsch gate circuit.

Tyler Bennett (Senior Thesis, April 2020, Advisor: Scott Bergeson )

Abstract

Ion collisions in a strongly coupled ultracold neutral plasma are useful for simulating collisions and properties found in high energy dense plasmas. Ultracold plasmas can be created from atoms that are cooled and trapped in a magneto-optical trap. After ionization, the resulting ions can be trapped using a linear quadrupole ion trap, making it possible to measure ion collisions for times scales greater than 10 μs. We report on designing and constructing a 5 MHz helical resonator for use in our dual species magneto optical ion trap. We obtained a quality factor of 153 with a coupling efficiency of 75%. We measured the density of trapped Ca atoms using florescence measurements.

Alexandra Christensen (Senior Thesis, April 2020, Advisor: John Colton )

Abstract

Brachytherapy is the use of ionizing radiation at short distances to treat disease, delivering the appropriate dose via an implant through which radionuclides can travel in or on the body. The geometry of implant placement is critical to achieving brachytherapy plans that do not overdose the target region. Implants are typically designed based on the radiation oncologist’s experience, and although some groups have created parameters for quantitative implant comparison, most lack simplicity and objectivity. This project describes an investigation of alternative indices that can be used for brachytherapy implant evaluation. The surface area to volume ratio of isodose surfaces and the number of non-contiguous isodose surfaces were calculated as functions of dose contour value. Several simple geometric target volumes were created to test the ability of these new metrics to differentiate between implant configurations. The surface area to volume ratio demonstrated the highest discernment power. A higher surface area to volume ratio correlates with the configuration expected to represent a more optimal implant. This is particularly useful when comparing implants with similar target coverage and can be used to evaluate implants with geometries for which experience is limited. This approach is sensitive to differences in implant geometry and has the simplicity of being a single number that can be used for comparison or as a parameter in optimization.

John Christensen (Senior Thesis, April 2020, Advisor: Gus Hart )

Abstract

Materials discovery is bottle necked by limited computational resources. One common method of computing a materials properties, Density Functional Theory (DFT), requires that the electronic band structure of a materials to be integrated. The electronic band structure of metals is very difficult to perform because of the discontinuities introduced by the Fermi level. Currently the most commonly used integration technique is a simple Riemann sum. Using this method requires very dense sampling because the integral converges slowly. Significant effort has gone into finding integration techniques that converge more quickly. New integration techniques that rely on non-uniform sampling have been proposed, but are not able to take full advantage of conventional symmetry reduction techniques. To ensure optimal symmetry reduction, calculations should be performed in the symmetrically irreducible Brillouin zone (IBZ). We present an algorithm for finding the IBZ for an arbitrary lattice.

Ian Clark (Senior Thesis, April 2020, Advisor: Denise Stephens )

Abstract

In this paper, we present observations of ZZ Psc secured with the 0.4-meter OPO and 0.9-meter WMO telescopes at BYU and augmented with data from the AAVSO to search for previously unknown periods for ZZ Psc and verify those that have already been determined. We found what could possibly be a previously undiscovered period at 901 seconds. We found that many pulsation modes change in amplitude over the timescales of about a year. To find stabilities in these periods, we used O-C techniques. We found that nearly all these periods remained constant in observations with Johnson B, V, and clear filters.

Carter Day (Senior Thesis, June 2020, Advisor: Richard Sandberg )

Abstract

Here I present a study on the effect of "large" three-dimensional objects in Interference Pattern Structured Illumination Imaging (IPSII). Due to the nature of the IPSII method, objects with a lot of depth in the imaging field create "shadows" or areas where the structured illumination fails This is because IPSII's structured illumination may be projected at a given angle θ from the object normal. These shadows are characterized by the absence of interference, not always the absence of light, and cause blurring around edges in the resulting image. The more depth an object has, the more fringe effects appear in the resulting image. This thesis reviews simulations that capture this reduced interference and therefore breakdown of IPSII due to shadowing. Also, initial experimental results are presented in an effort to demonstrate this effect. Finally, a discussion of what next steps should be taken is presented.

Nicolas Ducharme (Senior Thesis, April 2020, Advisor: Benjamin Frandsen )

Abstract

Dilute magnetic semiconductors (DMSs) are of interest to physicists and materials scientists due to their potential applications in spintronics and quantum computing. The research I will present is not directly aimed at spintronic or quantum computing applications. Rather, it is aimed at understanding the detailed atomic and magnetic structure of DMSs, which will enable a more fundamental understanding of their properties and facilitate future applications. Two DMSs, Li(Zn,Mn)As and (Ba,K)(Zn,Mn)2As2 were investigated experimentally, with the data analyzed via pair distribution function (PDF) analysis of x-ray and neutron scattering data. Li(Zn,Mn)As was found to lack local structural deviations and possesses only weak magnetic order, while (Ba,K)(Zn,Mn)2As2 was found to have significant local structural deviations and possess more robust magnetic order. These findings suggest that useful magnetic correlations may be connected to local structural deviations. Keywords: dilute magnetic semiconductor; local structure; magnetic correlations; short-range magnetic order; spintronics

John-Michael Eberhard (Senior Thesis, April 2020, Advisor: Denise Stephens )

Abstract

Brown dwarf binary systems provide key insights into the formation and evolution of brown dwarfs. To discover more binary systems, brown dwarf atmospheric models were fitted to the observed spectra of several brown dwarf systems. Spectral data for the systems was retrieved from the SpeX Spectral Library, the InfraRed Telescope Facility Library and the InfraRed Spectral Archive. The collected models predicted the spectrum a singular brown dwarf would have based on its temperature, surface gravity, cloud density, and amount of convection in the atmosphere. Binary models were created from the singular models and all of the models were compared to the observed spectra. Using a chi-squared analysis, the goodness of fit was calculated for each model. The best binary and singular fits were compared, and statistical analysis was performed to determine at what level of confidence each system could be claimed as binary. Twenty-six systems were studied and seven were found to be binary at a 99% confidence level: 2MASS 05591914-1404488, SDSS J042348.57-041403.5, 2MASSW J0320284-044636, 2MASS 14313097+1436539, DENIS-P J225210.73-173013.4, 2MASS 20282035+0052265, and SDSS J141624.08+134826.7. The method proved to be effective and can be used to more efficiently discover brown dwarf systems.

James Erikson (Senior Thesis, April 2020, Advisor: David Allred, John Colton )

Abstract

Temperature is an important parameter in many processes being studied with microfluidic devices. As such, improved temperature sensing methods compatible with the size and sensitivity required for microfluidics need to be found. This work investigates the photoluminescence lifetime of Rhodamine B and CdTe quantum dots for potential use in microfluidic devices. Lifetime values were sampled over a range of known temperatures through time-correlated single photon counting. Spectral measurements were also taken at each temperature. In Rhodamine B, lifetime was obtained through numerical deconvolution, however, results obtained in this way were unreliable due to variability within the sample itself over time. Similar methods proved similarly unreliable for CdTe quantum dots, which also show variability over time, though to a lesser extent. Through the application of machine learning algorithms, temperatures in CdTe quantum dots can be accurately determined with uncertainties ranging from 7.7 K at cryogenic temperatures to 0.1 K near room temperature. This success shows that temperature dependent photoluminescence is a valid option for future applications in microfluidic devices.

Jacob Fields (Senior Thesis, July 2020, Advisor: David Neilsen )

Abstract

Gamma-ray bursts (GRBs) are the most luminous electromagnetic phenomena in the universe, but much remains unknown about them. Many models invoked to explain their highly variable light curves are based on complicated dynamics and interactions involving the GRB progenitor but assume simple circumstellar environments. Many long GRBs, however, show late time optical and x-ray flares that may be an indication of a much richer environment. Relativistic hydrodynamics simulations are used to study a family of initial data with a relativistic blast wave encountering a dense circumstellar shell of matter, similar to what an aging star expelling the outer layers of its atmosphere might generate. The possibility that some of this late time curve variability results from these interactions is tested. A characterization of the profiles of the resulting reverse shocks and a preliminary analysis of the subsequent radiation are presented. The results suggests a noticeable increase in the synchrotron spectrum immediately following the interaction and possible infrared and optical emissions due to black-body shortly afterward.

Nate Foulk (Senior Thesis, August 2020, Advisor: Gus Hart )

Abstract

One important part of density-functional theory (DFT) calculations is the numerical integral of the electronic band structure. Unfortunately, this critical step of DFT simulation is the most computationally expensive, because each $k$-point (sampling point) requires solving a large eigenproblem. For metals, almost all of the error in the band energy integral comes from misrepresenting the Fermi surface, so the most important part of any integration technique is approximating the Fermi surface correctly. Current DFT codes approximate the bands by sampling the bands with a uniform mesh, and using each sampling point to perform a zeroth-order interpolation, approximating the area around each sampling point as a constant function. The integration of the approximated bands is therefore reduced to simple Riemann sums. This zeroth-order interpolation represents the bands very poorly, making an accurate approximation of the Fermi surface impossible. I present an integration scheme consisting of the quadratic interpolation of the electronic bands using Bezier triangles. The Fermi energy can then be continuously varied in order to best represent the Fermi surface, and thereby achieve the same accuracy with fewer $k$-points. I also explore further improvement by using an adaptive mesh refinement technique in those integration regions which contain the Fermi surface. Preliminary results suggest that 1 meV accuracy can be achieved using \textasciitilde$10\times$ fewer $k$-points.

Benjamin Lane Francis (PhD Dissertation, June 2020, Advisor: Mark Transtrum )

Abstract

In this dissertation, I consider the problem of model reduction in both oscillatory and networked systems. Previously, the Manifold Boundary Approximation Method (MBAM) has been demonstrated as a data-driven tool for reducing the parametric complexity of so-called sloppy models. To be effective, MBAM requires the model manifold to have low curvature. I show that oscillatory models are characterized by model manifolds with high curvature in one or more directions. I propose methods for transforming the model manifolds of these models into ones with low curvature and demonstrate on a couple of test systems. I demonstrate MBAM as a tool for data-driven network reduction on a small model from power systems. I derive multiple effective networks for the model, each tailored to a specific choice of system observations. I find several important types of parameter reductions, including network reductions, which can be used in large power systems models. Finally, I consider the problem of piecemeal reduction of large systems. When a large system is split into pieces that are to be reduced separately using MBAM, there is no guarantee that the reduced pieces will be compatible for reassembly. I propose a strategy for reducing a system piecemeal while guaranteeing that the reduced pieces will be compatible. I demonstrate the reduction strategy on a small resistor network.

Caleb Gaunt (Senior Thesis, April 2020, Advisor: Joseph Moody )

Abstract

ROVOR is Brigham Young University’s remote observatory in Delta, UT that currently runs on TheSkyX software and other scripts. The current system, though, can be complicated and can only be accessed by one student or faculty member at a time. To solve these problems, a new observatory control system is being developed. The new system, Remote Observe, uses a web-based approach to provide easier access and greater extensibility to the system. Remote Observe has a user interface built using React and is hosted by Google Firebase with a database that tracks commands given to the system. Bret Little has programmed these parts to accept modules designed to interface with different pieces of equipment that utilize ASCOM Alpaca drivers, which present the equipment as an HTTP API. In order to complete a proof of concept, I have programmed a controller for a weather monitor and our custom Lifferth dome using Node.js. I researched the tools and libraries needed to accomplish the development of these controllers. After that, I engaged in a test-first development approach by writing code for automated unit tests that would verify the functionality of the controllers. I then developed the code for controllers until they functioned properly. To validate the system as it is, I found an ASCOM-made Alpaca equipment simulator and connected it the controllers, which I registered with the rest of the existing system. After finding a few bugs and writing a few more tests, I modified the code to where the system integrated with the simulator as expected. In the future, the system will be further developed by obtaining Alpaca-compatible equipment to connect the system to, developing the front-end, rewriting the script that controls the Lifferth dome in Node.js, and configuring the whole thing to run on Raspberry Pis onsite in Delta.

Parker Hamilton (Senior Thesis, April 2020, Advisor: Gus Hart )

Abstract

Superalloys are a vital material in our technological infrastructure because of their high operating temperatures. Ni-based superalloys are used often in turbines for engines and energy production because they exhibit an FCC $\gamma$ phase with a $\gamma^{\,\prime}$ phase precipitate that reinforces the lattice structure and maintains a high mechanical strength at elevated operating temperatures. Co-based superalloys do not exhibit this same phase, but they are highly corrosion resistant and generally have a longer operating lifespan than Ni-based superalloys as a result. Experimental work has shown ternary Co-based superalloys with a metastable $\gamma$-$\gamma^{\,\prime}$ phase, but it separated into other phases during a heating process. Density functional theory (DFT) allows for the energy of an atomic configuration to be calculated from first principles, but DFT calculations are inherently performed at 0 K. We use a method called nested sampling, along with a machine learned interatomic potential, to derive a high temperature phase behaviour of a ternary Co-Al-W alloy. The nested sampling method overcomes the sampling problem of being stuck at local minima. The machine learned interatomic potential, a moment tensor potential, is trained on DFT calculations, leveraging the accuracy of first principle calculations. The nested sampling method uses this interatomic potential to sample the energy of configurations in the Co-Al-W system to approximate the thermodynamic partition function. Heat capacity can be derived from the partition function and can then be used to find phase transition temperatures. These transition temperatures, across many compositions, can then be used to build a full phase diagram.

Dallin Haslam (Capstone, August 2020, Advisor: Timothy Leishman )

Abstract

Guitar amplifiers are specialized loudspeakers with complex configurations. Considerations of where a microphone is placed relative to an amplifier and where amplifiers are placed in a live venue or recording studio are affected by directivity of each individual amplifier. This paper presents measured transverse-plane polar, and interpolated spherical directivities of four guitar amplifiers in an anechoic space. Using this data one may observe how differences in amplifier configurations affect their directivity characteristics.

Derek Hensley (Senior Thesis, April 2020, Advisor: Gus Hart )

Abstract

Grain Boundaries (GBs), the interfaces between individual crystals in metals, influence many of the physical properties observed in metals such as corrosion, electrical conductivity, and strength. I look to map the metastable states, states that are stable but not at the lowest energy, of specific GB subsets where the macroscopic parameters are kept constant. By using machine learning, I am able to cluster these GB subsets to possibly find the unique metastable states. Applying this technique to 1797 Σ5-(012) symmetric twist GBs, I found the optimal number of clusters was based on the representation of the GB that was used. While these clusters cannot be proven to correspond to the metastable states, analyzing the clusters based on Principal Component Analysis and energy gives confidence that they do. With knowledge of these metastable states, material design and GB engineering, the deliberate manipulation of GBs to improve properties, can be improved.

Daniel Hodge (Senior Thesis, May 2020, Advisor: Michael Ware )

Abstract

According to the Lorentz force, when high-intensity light is incident on a free electron, the electric and magnetic field of the laser influences the electron’s trajectory and what radiation it produces. As laser intensity increases, electrons reach relativistic speeds as they oscillate in the laser field. Particularly, in our lab we used a high-intensity pulsed laser with the intensity 10^18 W/cm^2 to allow us to study Thomson scattering in this relativistic regime. When a free electron is moving at this speed, it radiates light at harmonics of the incident laser wavelength. Specifically and most importantly, with the added dimension of polarization, we measured the fundamental, second, and third harmonic emissions from electrons in a high-intensity laser focus. Consequently, we obtained graphs depicting each harmonic’s own unique angular distribution of light. Furthermore, I investigate how varying the laser intensity alters the angular distribution of light emitted by radiating electrons for the azimuthal and longitudinal polarizations. Also, I compare the ratio of light distribution between the azimuthal and longitudinal polarizations as intensity increases. Ultimately, we gathered this information to analyze the electron dynamics in the high-intensity laser focus and to understand the details of the vector-field distributions in this focus.

Jake Hughes (Capstone, August 2020, Advisor: Benjamin Frandsen )

Abstract

The properties of materials are strongly dependent on the crystal structure of the material. The atomic pair distribution function (PDF) method is a powerful method for investigating the structure of materials on length scales of several unit cells. Determining the positions of atoms within the unit cell is crucial to gaining an understanding of the overall structure of the material, but traditional methods of refining a model against experimental PDF data to determine atomic positions can be time intensive and possibly unreliable. We have taken a new approach to traditional PDF modeling using symmetry mode analysis enabled by the ISODISTORT program. Instead of using conventional Cartesian coordinates as fitting parameters, we fit symmetry mode amplitudes to try to reproduce simulated data and determine which distortion modes are active in each structure. This approach may lead to more effective modeling of experimental data and more accurate determinations of crystal structure.

Zachary Jones (Capstone, July 2020, Advisor: Kent Gee )

Abstract

In community noise measurements, two standard setups require elevated or ground-based microphones. This study compares elevated and ground-based microphone measurements, particularly for low-frequency wind-induced microphone self-noise. To understand wind-related microphone noise, simultaneous sound level and wind speed measurements were employed using both elevated and ground-based approaches. The elevated setup utilized a commercial outdoor windscreen, whereas the ground setup included an acoustically reflective plate and was surrounded by a larger windscreen. Measurements were taken at several locations of varying geography in Juab County, UT; Utah County, UT; and Tooele County, UT. The results show the ground plate setup is preferable for outdoor noise measurements for two reasons. First, the wind speed is lower near the ground. Second, the larger windscreen yields superior wind noise rejection. These observations are quantified to expand the noise database for a predictive machine-learning soundscape model.

Charles Lewis (Senior Thesis, June 2020, Advisor: John Colton )

Abstract

Various biological processes require accurate temperature sensing through microfluidic devices,so improved temperature sensors methods are needed. Previously, machine learning techniques have been used for predicting temperatures through thermal images. To develop a new, accurate temperature sensor model, photoluminescence (PL) spectra and time-resolved photoluminescence (TRPL) spectra of CdTe quantum dots were measured as functions of temperature for use in training an artificial neural network (ANN). A low-temperature regime from 10-300 K and a high-temperature regime from 298-319 K were measured with additional data provided through interpolation. The optimized neural network is able to determine temperatures with a mean average error of 7.7 K and 0.1 K for the low and high-temperature regimes respectively. The mean absolute error of the low-temperature regime improves to 0.4 K when restricting to temperatures between 100-300 K.

Jessica Martin (Capstone, August 2020, Advisor: Nathan Powers )

Abstract

Following current physics education recommendations, the undergraduate physics labs at Brigham Young University are undergoing a shift in focus from conceptually-based to experimentally-based practices, which requires lab assistants to undergo a similar shift in attitude in order to perform at the higher level now asked of them. To assist with this change, we present a method involving new training techniques and attitude assessments based upon the three fundamental factors of attitudes—affect, behavior, and cognition—that identify attitude strength and weakness and pinpoint the underlying causes in a group of lab assistants. With the improved understanding of attitude causes from the data, faculty can target current training practices in real time to help solidify weak attitudes, as well as track attitude development over time. In our case study, we use the proposed method to successfully identify areas of attitude weakness and strength, their causes, and propose improvements for future targeted training meetings within a group of 20 lab assistants. We also propose a more comprehensive longitudinal future study to track attitude shifts over time.

Alden Roy Pack (PhD Dissertation, April 2020, Advisor: Mark Transtrum )

Abstract

We computationally explore the dynamics of superconductivity near the superheating field in two ways. First, we use a finite element method to solve the time-dependent Ginzburg-Landau equations of superconductivity. We present a novel way to evaluate the superheating field Hsh and the critical mode that leads to vortex nucleation using saddle-node bifurcation theory. We simulate how surface roughness, grain boundaries, and islands of deficient Sn change those results in 2 and 3 spatial dimensions. We study how AC magnetic fields and heat waves impact vortex movement. Second, we use automatic differentiation to abstract away the details of deriving the equations of motion and stability for Ginzburg-Landau and Eilenberger theory. We present calculations of Hsh and the critical wavenumber using linear stability analysis.

Dallen Petersen (Senior Thesis, April 2020, Advisor: Richard Sandberg )

Abstract

A simple, low-cost, high-precision, motorized mirror controller is presented that was developed for use in a lensless imaging experiment. The goal was to achieve angular precision of better than 20 arc seconds while costing less than comparable commercial options. This is done using a standard kinematic mirror mount, high-pitch screws and stepper motors held together by 3D printed parts. The mount can be controlled by a python script on a Raspberry Pi or any other microcontroller connected to the motors. The mount can be quickly assembled for less than \\$350 and achieves a large angular range (10 degrees). The accuracy is tested using a laser reflected off of a mirror controlled by the mount and projected onto the CCD of a webcam. The tested accuracy was 7.67 arc seconds with a standard deviation of 4.71 arc seconds.

Brittni Tasha Pratt (Masters Thesis, August 2020, Advisor: Michael Ware )

Abstract

Thomson scattering from free electrons in a high-intensity laser focus has been widely studied analytically, but not many measurements of this scattering have been made. We measure polarization-resolved nonlinear Thomson scattering from electrons in a high-intensity laser focus using a parabolic mirror. The weak scattering signal is distinguished from background noise using single-photon detectors and nanosecond time-resolution to distinguish a prompt scattering signal from noise photons. The azimuthal and longitudinal components of the fundamental, second, and third harmonics were measured. Our measurements reasonably match theoretical results, but also show some asymmetry in the emission patterns.

Timothy Puente (Capstone, April 2020, Advisor: Brian Anderson )

Abstract

During production, Burr OAK Inc. ran into several problems with their die presses. The problem that they had is their current design of their cut-off. They identified the problems with the design and asked us to redesign the drive system of the cut-off mechanism. Alternative power sources were considered, the amount of force that is required to cut through aluminum and steel sheets was calculated, and the configurations of the actuators were compared. An alternative cut-off design was developed through product development, analyzed using computational analysis of the pressure and CFM, and then tested with aluminum and steel sheets, and then adjusted based on the results of the tests. The results of the tests and the readjustments resulted in the design of pneumatically powered cut-off that is able to cut through aluminum and steel sheets, which are the most common materials that Burr OAK Inc. uses.

Spencer Roberts (Senior Thesis, August 2020, Advisor: Robert Davis )

Abstract

Neural probes allow researchers and medical professionals to read neural activity and send signals directly to the brain. However, mechanical stiffness mismatch between neural probes and brain tissue leads to chronic irritation and trauma, which eventually causes loss of signal. Viable long-term commercial implants will require flexible probes that match the brain’s stiffness. We have designed a carbon nanotube (CNT) based neural probe array that has high spatial resolution and high-aspect ratio flexible probes that have tunable stiffness via carbon infiltration. In this work, we characterize the Young’s modulus of our CNT probes at various infiltration levels using a dual deflection wire test. Results indicate that the minimum modulus of the probes is about 678 MPa, which is comparable to contemporary flexible polymer probes, indicating probable long-term biocompatibility without sacrificing spatial resolution or aspect ratio.

Mahonri Romero Carranza (Senior Thesis, August 2020, Advisor: Michael Ware )

Abstract

We investigate nonlinear Thomson scattering from electrons driven relativistically in an intense laser focus. At low intensities, the magnetic field is negligible and does influence the electron fractior. At high-intensity ( 1:51018 W/cm2), the magnetic field contributes markedly to the Lorentz force, resulting in characteristic relativistic movement. Strongly driven electrons emit harmonic light in all directions from the focus. We investigate nonlinear Thomson scattering using a focused 800 nm Ti:sapphire laser with 40 fs pulses that fire at 10 Hz. For the first time, Thomson scattering is recorded via single-photon counting using an avalanche photodiode and photomultiplier tube, We also make the first polarized-resolved observations of harmonics emitted out the side of the laser focus. The minimal useful focal spot size is computed theoretically through mathematical models. Furthermore, data taken by our research group in collaboration with a group at the University of Nebraska-Lincoln is compared to theoretical modeling.

Paige Simpson (Senior Thesis, June 2020, Advisor: Brian Anderson )

Abstract

Time reversal may be used as an energy-focusing technique. It is applied in many different ways including, for example, nondestructive evaluation (NDE) of cracks in structures, reconstructing a source event, and providing an optimal carrier signal for communication. In NDE applications, it is often of interest to study small samples or samples that do not lend themselves to the bonding of transducers to their surfaces. A reverberant cavity, called a chaotic cavity, attached to the sample of interest provides space for the attachment of transducers as well as a more reverberant environment, which is critical to the quality of time reversal focusing. Transducers are attached to the chaotic cavity which is attached to the sample under test. The goal of this research is to explore the dependence of the quality of the time reversal focusing on the size of the chaotic cavity used. An optimal chaotic cavity will produce the largest focusing amplitude, best spatial resolution, and most linear focusing of the time reversed signal. This thesis shows experimentally that as the size of an aluminum rectangular chaotic cavity increases, the peak amplitude of the time-reversed focus tends to increase as well.

Nathan Stone (Senior Thesis, April 2020, Advisor: Jean-Francois Van Huele )

Abstract

Secure information transfer lies at the basis of today’s information age. The computation complexity of factoring a number into its prime components is the method used for information encryption. Shor’s algorithm, when implemented on a quantum computer, can factor a number with an operational complexity of approximatly O(n^3) where n is the number of qubits needed to represent the number to be factored N. Using the structure of Shor’s algorithm, I construct an algorithm that takes advantage of weak value amplification and postselection (WVAP) to construct a new "Super Prime Factorization Algorithm" which factors a number in linear computational complexity O(n) while still using the same number of qubits required in Shor’s algorithm. The results of this paper show that if a successful post selection with high probability can be obtained, then this Super Prime Factorization Algorithm, along with WVAP computation, will be instrumental for the future of quantum information and computation.

Yance Sun (Senior Thesis, August 2020, Advisor: Justin Peatross )

Abstract

We measure nonlinear Thomson Scattering generated by an intense laser pulse. At BYU, we investigate second and third harmonic light scattered out the side of the laser focus. Electrons are provided by low-density helium, neon, or argon. Multiple electrons are ionized from atoms in the focus during the early part of the laser pulse. We investigate theoretically the trajectories of electrons born from the same atom at various locations within the focus. If the electrons emerging from the same atom remain bunched together, one would expect an enhancement in the emission proportional to the square of the number of electrons that ionize. In contrast, we find that the trajectories for the different electrons quickly diverge, making emission nearly incoherent.Simulations agree with our experimental measurements, which indicate that emission is roughly proportional to the number of electrons rather than to the square of the number.

Ellyse Taylor (Senior Thesis, August 2020, Advisor: Justin Peatross )

Abstract

Atomic vapor and micron-scale channels are an important component in many types of compact metrology tools. By understanding the transport velocity of vapors through narrow channels, micron-scale structures can be optimized for creating ideal atomic beams. Atomic beams are useful for allowing precise control over the internal state of an atom as is used in optical frequency standards and precision spectroscopy. This thesis explores the flow rate of atomic vapors through different structured thin channels. It outlines the design and experimental purpose of various thin-channel shapes as well as the process of etching the structures into silicon. This setup successfully measures the rate at which rubidium vapor is transported through the various channels. It will work as a guide for creating a mathematical model describing the parameters that govern the transport of vapors through micron-scale channels. The goal of this research is to provide a simple platform for designing the structures involved in creating atomic beams for use in precision metrology.

Joel Temple (Capstone, August 2020, Advisor: Jean-Francois Van Huele )

Abstract

The physics curriculum trains students in problem-solving, teamwork, and particularly in higher-level coursework, systems-thinking. Within the program, the scope of such problems is focused on physical systems. As evidenced by my experiences outside of the physics program, such a skillset proves useful in application to non-physical systems, specifically within the realm of social issues.

David Franklin Van Komen (Masters Thesis, August 2020, Advisor: Traci Neilsen )

Abstract

[Abstract]

Aaron Burton Vaughn (Masters Thesis, August 2020, Advisor: Kent Gee )

Abstract

[Abstract]

Carla Wallace (Senior Thesis, August 2020, Advisor: Brian Anderson )

Abstract

Time reversal (TR) focusing of airborne ultrasound in a room is demonstrated. Various methods are employed to increase the amplitude of the focus. These methods include creating a small wooden box (or chamber) to act as a miniature reverberation chamber, using multiple sources, and using the clipping processing method. The use of a beam blocker to make the sources more omnidirectional is examined, and it is found that for most source/microphone orientations, the use of a beam blocker increases the amplitude of the focus. A high-amplitude focus of 134 dB peak re 20 µPa SPL is generated using TR. The waveform and spectrum of the focus are examined to determine if it the focus is loud enough to generate nonlinear effects in the air. Using 4 sources centered at 36.1 kHz and another 4 sources centered at 39.5 kHz, nonlinear difference frequency content near 3.4 kHz is observed in the focus signal. If the nonlinearities are generated in the air, the TR setup could perhaps be used to create a virtual sound source (spherically symmetric parametric array) within a room, from which audible sound may propagate.

Tyler Richard Westover (Masters Thesis, April 2020, Advisor: Robert Davis )

Abstract

DNA origami templates have been studied due the versatility of shapes that can be designed and their compatibility with various materials. This has potential for future electronic applications. This work presents studies performed on the electrical properties of DNA origami templated gold nanowires. Using a DNA origami tile, gold nanowires are site specifically attached in a “C” shape, and with the use of electron beam induced deposition of metal, electrically characterized. These wires are electrically conductive with resistivities as low as 4.24 x 10-5 Ω-m. During moderate temperature processing nanowires formed on DNA origami templates are shown to be affected by the high surface mobility of metal atoms. Annealing studies of DNA origami gold nanowires are conducted, evaluating the effects of atom surface mobility at various temperatures. It is shown that the nanowires separate into individual islands at temperatures as low as 180° C. This work shows that with the use of a polymer template the temperature at which island formation occurs can be raised to 210° C. This could allow for post processing techniques that would otherwise not be possible.

Benjamin Whetten (Senior Thesis, April 2020, Advisor: Richard Sandberg )

Abstract

A lensless imaging method known as Interference Pattern Structured Illumination Imaging (IPSII) is discussed. Because it does not require a lens, IPSII has a higher theoretical resolution limit than traditional optical microscopes. However, the quality of IPSII images is currently limited by mechanical noise in its mirror movements. This thesis characterizes the resulting distortions caused by uncertainty in IPSII mirror movements. To do so, a model is presented that simulates the propagation of mechanical noise in the experimental IPSII setup to the resulting image data. It is shown that this noise causes errors in both the phase and amplitude of the Fourier transform of the image. Finally, a method to partially correct the resulting image distortions using phase retrieval algorithms in presented.