Doctor of Philosophy, The Ohio State University, 2021, Physics

Non-central collisions of relativistic atomic nuclei contain enormous angular momentum, $|\vec{J}|\sim\mathcal{O}(10^0-10^2\frac{\rm{TeV\cdot~fm}}{c}\approx10^3-10^5\hbar)$ in the collision energy range spanned by the capabilities of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab (BNL). The energy densities that exist in the collision interaction region are sufficient to deconfine constituent quarks from their bound nucleon states and thereby facilitate the short-lived ($\mathcal{O}(1\mathrm{fm}/c)$) formation of the so-called Quark-Gluon Plasma (QGP), to which some of the net $\vec{J}$ is transferred. The Solenoid Tracker At RHIC (STAR) is a set of detectors working in unison to reconstruct collision information, and is an indispensable tool used to study the QGP. I present here work surrounding $\vec{J}$, ranging from detector construction for STAR in order to accurately measure $\hat{J}$, experimental analysis of phenomena driven by $\vec{J}$ usig the STAR detector, and theoretical calculations involving the direction of $\vec{J}$ affected by event-by-event fluctuations. The ``Event-Plane Detector" (EPD), after years of prototyping and design, was largely constructed at Ohio State University in 2017-2018 and officially replaced its predecessor, the Beam Beam Counter (BBC), at STAR. While similar detectors have been constructed, including the BBC, unique challenges were faced in the construction of the EPD. Due to many factors, including careful construction, the EPD's performance was and remains phenomenal, providing experimentalists in the STAR collaboration with far-improved resolution on $\hat{J}$. The use of the EPD was essential for drastically reducing the statistical uncertainties on a number of analyses, including the spin alignment of $\Lambda$ hyperons with $\hat{J}$, $\PLambda$. In this thesis is detailed the process of extracting the $\vec{J}$-driven $\PLambda$ at the relatively low center-of-momentum nucleon-nucleon col (open full item for complete abstract)

Committee: Michael Lisa (Advisor); Ulrich Heinz (Committee Member); Thomas Humanic (Committee Member); Michael Poirier (Committee Member) Subjects: Nuclear Physics; Physics

Doctor of Philosophy, Case Western Reserve University, 2019, Physics

In this dissertation, we will describe work completed towards the Pierre Auger Observatory's AugerPrime Upgrade as well as auxiliary timing work, hardware design and finally a test of correlations of Starburst Galaxies with the arrival directions of Ultra High Energy Cosmic Rays (UHECRs). In the first three chapters, we review the history, observables and detection techniques of UHECR physics, both past and present. We then look at the future upgrade of Auger and give an in depth description of the firmware, software and hardware that make up the Upgraded Unified Board (UUB), which is to be at the heart of AugerPrime. A discussion of the scientific mechanisms and merits of event-by-event composition measurements is presented, and the necessity of a new board to support this is exposed. We then move into the precision timing implementation in AugerPrime, discussing GPS receiver selection and time-tagging system performance. We find that the timing resolution of the UUB is σ_det = 8.44 ± .15 ns, and confirm it using two methods. Subsequent to this, we discuss auxiliary timing projects which support Auger as well as the Cherenkov Telescope Array. Results are shown for an experiment to determine spatial correlations of GPS timing errors, and hardware for timing at CTA and in the Auger@TA cross calibration is described. In the final chapter of this work, we move on to examining the recent Starburst correlation result of the Auger Collaboration, and cross check this by invoking a magnetic field model and back-tracing the arrival directions of UHECRs seen by Auger. We test to see how likely it is that the observed UHECR sky is more correlated with the observed Starburst Galaxy (SBG) sky than an isotropically chosen set of random sources. The test shows a deviation from isotropy at the 1.6σ level. Finally, we describe future directions for SBG correlation tests.

Committee: Corbin Covault (Advisor); John Ruhl (Committee Member); Benjamin Monreal (Committee Member); David Kazdan (Committee Member) Subjects: Astrophysics; Electrical Engineering; Particle Physics; Physics

Master of Sciences, Case Western Reserve University, 2018, Physics

There are numerous applications of liquid crystals spanning many fields of technology. There are also many applications for detecting patterns of ionizing radiation such as X-rays. This project involves using well known properties of liquid crystals to design a detector to display two dimensional patterns of ionizing radiation. Polymerized liquid crystal films were fabricated with one surface being a transparent electrical conductor, and the other open to air. These films were designed so that an optical change in the layers occurs when charged particles are deposited on the surface. This allows for the creation of displays that show the spatial arrangement of deposited charges. It is well known that a gas with appropriate electrical fields can convert patterns of ionizing radiation into patterns of charge. We have explored different liquid crystal and polyimide combinations to create stable hybrid aligned and homeotropically aligned open cells. We have developed an electron source which generated the electrons needed to test the liquid crystal layers. Finally, we have done several tests to better understand the mechanism for inducing a transition in the layers, and to make the liquid crystal films more useful for charged particle detection.

Committee: Charles Rosenblatt (Advisor); Rolfe Petschek (Advisor); Benjamin Monreal (Advisor) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2015, Nuclear Engineering

The desire for room temperature, radiation hard, solid-state radiation detectors has driven research into many new semiconductor materials. One such material is the III-V compound semiconductor gallium nitride (GaN). With a bandgap of 3.39 eV, a large displacement energy, and high thermal stability, GaN is an excellent candidate for elevated temperature, high radiation field spectroscopy applications. However, two important parameters used to characterize other radiation detection materials are either missing or are unsubstantiated in the literature for GaN: the electron-hole pair creation energy (ε) and Fano factor. This work reports the first experimental determination for ε in GaN to be 8.33 ± 0.13 eV, with a theoretical Fano factor of 0.07 according to Klein's model. For this determination, vertical Ni/Au Schottky diode detectors were fabricated from hydride vapor phase epitaxy (HVPE) GaN, and α-spectra from a 241-Am source were collected. The measured value for ε in GaN was compared to experimentally measured values in other semiconductors and used to resolve a discrepancy between two models relating a material's bandgap and ε. It was found that two assumptions in the phenomological model of Klein: 1) a uniform energy distribution of e-h pairs after formation, and 2) an impact ionization threshold of 3/2 the material bandgap are likely overstated, and if reconsidered, agree well with the empirical model of Devanathan. Alpha particle measurements with the fabricated detectors were also used to estimate the hole diffusion length in GaN to be 280 nm. A time dependent lowering in the α-particle spectra centroid and degradation of energy resolution was also quantified and analyzed. Experiments detailing the application of GaN as a neutron detector were performed, with evidence of intrinsic neutron detection capabilities from neutron capture in nitrogen. A new technique to perform photolithographic patterning on wafers with a large number of macro defects was also de (open full item for complete abstract)

Committee: Lei Cao (Advisor); Thomas Blue (Committee Member); Tunc Aldemir (Committee Member) Subjects: Nuclear Engineering

Master of Science, The Ohio State University, 2014, Electrical and Computer Engineering

Vehicle classification data are used in many transportation applications, including: pavement design, environmental impact studies, traffic control, and traffic safety. Ohio has over 200 permanent count stations, supplemented by many more short-term count locations. Due to the high costs involved, the density of monitoring stations is still very low given the lane miles that are covered. This study leveraged the deployed detectors in the Columbus Metropolitan Freeway Management System (CMFMS) to collect and analyze classification data from critical freeways where the Ohio Department of Transportation has not been able to collect much classification data in the past due to site limitations. The CMFMS was deployed in an unconventional manner because it included an extensive fiber optic network, frontloading most of the communications costs, and rather than aggregating the data in the field, the detector stations sent all of the individual per-vehicle actuations (i.e., PVR data) to the traffic management center (TMC). The PVR data include the turn-on and turn-off time for every actuation at each detector at the given station. Our group has collected and archived all of the PVR data from the CMFMS for roughly a decade. The PVR data allows this study to reprocess the original actuations retroactively. As described in this thesis, the research undertook extensive diagnostics and cleaning to extract the vehicle classification data from detectors originally deployed for traffic operations. The work yielded length based vehicle classification data from roughly 40 bi-directional miles of urban freeways in Columbus, Ohio over a continuous monitoring period of up to 10 years. The facilities span I-70, I-71, I-270, I-670, and SR-315, including the heavily congested inner-belt. Prior to this study, these facilities previously had either gone completely without vehicle classification or were only subject to infrequent, short-term counts.

Committee: Benjamin Coifman (Advisor); Keith Redmill (Committee Member) Subjects: Electrical Engineering; Engineering; Transportation

Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering

Room temperature direct detectors operating in the so-called Terahertz (THz) region of the electromagnetic spectrum, and representing the most common detection technologies currently available, were characterized at 104, 280 GHz or 600 GHz within their intended range of operating frequencies. These detectors included commercial Schottky-diode rectifiers (Virginia Diodes and Spacek Labs), commercial pyroelectric detectors (Spectrum Detector), and a commercial Golay cell (QMCI). The characterization included antenna patterns, responsivity, electrical noise, noise equivalent temperature difference (NEΔT ), and noise equivalent power (NEP). Since all the characterization measurements were made the same way, quantitative comparisons can be made between the performances of the individual detectors and conclusions are drawn about their relative merits for particular applications. The noise characteristics of the amplifiers used in the experiments were also measured and taken into account in the characterization of the detectors.

Committee: Elliott Brown PhD (Advisor); Douglas T. Petkie PhD (Committee Member); Yan Zhuang PhD (Committee Member) Subjects: Electrical Engineering; Engineering; Physics

PHD, Kent State University, 2007, College of Arts and Sciences / Department of Physics

We investigated electron-induced two-nucleon emission from carbon with the goal of being sensitive to and studying short-range correlations using the 12C(e,e'pN) reaction in a triple-coincidence measurement. Two existing high-resolution spectrometers in Hall A at Jefferson Laboratory were used to detect coincident scattered electrons and struck nucleons. A large neutron detector designed and constructed specially for this experiment was used to detect the recoiling neutrons. We performed analysis of the 12C(e,e'pn) reaction, and made direct observation of short-range correlated n-p pairs. From our analysis we conclude that there are 17.9 ± 4.5 times more n-p short-range correlated pairs than p-p short-range correlated pairs.

Committee: John Watson (Committee Co-Chair); Douglas Higinbotham (Committee Co-Chair); Byron Anderson (Other); George Fai (Other); Christopher Woolverton (Other) Subjects: Physics, Nuclear

Master of Science (M.S.), University of Dayton, 2024, Electro-Optics

Light Detection And Ranging (LiDAR) technology continues to gain significance across various industries, including autonomous vehicles, surveying, mapping, and defense. The demand for precise 3D spatial data necessitates active sensing methods. Flash imaging and scanning LiDAR are two ways of achieving direct-detection LiDAR. Flash imaging LiDAR captures the entire scene instantaneously by emitting a single pulse and measuring the return. Scanning LiDAR, on the other hand, operates by directing a focused laser pulse in a controlled pattern, typically through mechanically steered mirrors, and measures the reflected signals at each point. Due to the losses in the optical system and light propagation in the atmosphere, the received light is at a much lower intensity than the emitted. This calls for the demand of sensitive detectors that are able to convert the returned light into a measurable electrical signal. Traditionally, low-light sensing has been achieved using linear mode or Geiger mode avalanche photodiodes (APDs). While linear mode APDs offer amplification akin to low-noise amplifiers, their gain values are often limited, and higher gain variants like those in HgCdTe are costly. Geiger mode APDs, despite their increased sensitivity, operate as switches with a notable dead time. In contrast, the discrete amplification photon detector (DAPD) offers a promising alternative by aiming to achieve single-photon detection without the drawbacks associated with APDs. This study gives comparison between flash and scanning LiDAR systems then focuses on the performance of the DAPD, evaluating the viability of the DAPD for LiDAR applications. As detector technology advances, it not only enhances LiDAR system performance but also broadens its applicability across diverse domains. This research contributes to advancing LiDAR technology, unlocking its potential for even broader adoption and innovation.

Committee: Paul McManamon (Advisor); Andrew Sarangan (Committee Member); David Rabb (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Optics; Physics

Honors Theses, Ohio Dominican University, 2024, Honors Theses

ɣ-hydroxybutyrate, or GHB is referred to as a “date-rape drug,” often used in the facilitation of Drug/Alcohol Facilitated Rape (DAFR) against females in clubs and bars, resulting in vomiting, hallucinations, loss of consciousness, and amnesia.1 Several studies have reported GHB detectors to aid in avoiding DAFR; however, a successful, cost-efficient detector has yet to be produced. We report a successful synthesis of GHB's precursor, ɣ-butyrolactone (GBL), from tetrahydrofuran (THF), supported by ¹H NMR. Our findings indicate significant progress was made towards a fluorescently activated α-cyanostilbene GHB detector via Knoevenagel condensation, supported by ¹H NMR and TLC (Rf = 0.43). Further studies should focus on the efficiency of this stilbene against GBL.

Committee: Christopher Martin (Advisor); Daniel Little (Advisor) Subjects: Chemistry; Organic Chemistry

Doctor of Philosophy (PhD), Ohio University, 2023, Chemistry and Biochemistry (Arts and Sciences)

In recent years, there took place a notable advancement observed in single-molecule fluorescence microscopy methods and its use in various biomolecular research. This technique allows for direct visualization of dynamics and its detailed complexities of various biological processes at the molecular level which is not possible in bulk measurement. Usually, in experiments related to single-molecule fluorescence measurements, the abundance of key molecules is intentionally minimized, which reduces the noise and improves the quality of imaging. However, such a strategy does not work when experiments involve weak interaction between biomolecules. In such a situation nonspecific interaction between molecules of interest and glass would lead to an unwanted fluorescence background signal, which compromises the imaging quality and reduces the measurement accuracy. In this work, glass surfaces have been functionalized in multiple steps. In the initial step, the glass coverslip surface is modified with (3-aminopropyl) triethoxysilane (APTES), and in the next step, the surface is functionalized using methoxy-terminated polyethylene glycol (mPEG) and biotin-terminated polyethylene glycol (bPEG) molecules. Each surface is characterized using dye-labeled protein molecules called neutravidin. for a variety of single-molecule fluorescence studies as PEG molecules are known to repel any nonspecific molecules binding on the functionalized surfaces. Then the surface is used for two-end immobilization of lambda DNA using biotin and neutravidin interaction. Once the surface is functionalized and characterized, lambda DNA is two ends immobilized on the surface using biotin and neutravidin interaction. Then we use that platform to study the intercalation and de-intercalation kinetics of various intercalating dyes such as single- intercalator (YO-PRO-1) and doubleintercalator (YOYO-1) at various experimental conditions of ionic strength and flow speed of the buffer (open full item for complete abstract)

Committee: Jixin Chen (Advisor) Subjects: Chemistry; Physical Chemistry

Doctor of Philosophy, University of Toledo, 2023, Physics

Cadmium Telluride (CdTe) has been long recognized as a semiconductor material well suitable for high-energy x-ray detection in spectroscopic, imaging, and radiation therapy applications. Its high-resolution makes CdTe an attractive material for radiation detectors in small field dosimetry. Interpretation of small-field measurements with pretty much any detector typically requires use of correction factors which depend on the detector construction and measurement conditions. A greatly preferable solution to account for perturbations compensation to achieve correction-less dosimetry is to design a water equivalent detector. In a recently proposed approach mass-density is utilized as the main factor of detector water-equivalence. We evaluated the approach for a range of geometric parameters utilizing CdTe and compared with traditional silicon (Si) diode sensitive media. Monte Carlo simulation was used to optimize dosimeter designs combining a semiconductor sensitive volume with an air-gap of various thickness, following a mass-density matching approach. It was discovered that, unlike Si, the relative response of a CdTe detector to water is energy dependent. The addition of air to the sensitive volume of a CdTe-based detector does not lead to an improved response to water. Moreover, we explored the relevant energy spectra, backscattered fluences, and their correlations with the critical detector metric of dose deposition. For this purpose, we modified electron spectra reaching and depositing energy in sensitive volume of CdTe detector using a multilayer structure of CdTe combined with metal back-reflectors of lead (Pb) and Copper (Cu). The total fluence of electrons scattered back in CdTe with a metal back reflector and CdTe alone were found to be increased by factors of 6 and 3.7 using Pb and Cu, respectively. This suggests that the detector signal can be adjusted in a multi-layered structure consisting of a sensitive volume and a metal back-reflector layer. A detailed (open full item for complete abstract)

Committee: David Pearson (Committee Chair); Nicholas Sperling (Committee Member); Suleiman Aldoohan (Committee Member); Richard Irving (Committee Member) Subjects: Physics; Radiation

Doctor of Philosophy, The Ohio State University, 2023, Electrical and Computer Engineering

High-energy physics (HEP) experiments such as the Large Hadron Collider (LHC) facilitate unveiling the mysteries inside the atom's nucleus and lead to a better understanding of the universe. They also enrich the capabilities of humanity by extending the limits of existing technologies and encourage the need for new technologies. An accurate measurement of the amplitude and time of arrival of high-energy particles or ionizing radiation is a recurrent requirement in HEP experiments and other applications such as the positron emission tomography (PET), Light Detection and Ranging (LiDAR), and X-ray imaging. Recent technology advancement requires improved amplitude and timing measurement precision. This research investigates the fundamental measurement limitations, targeting a complete system design, prototype fabrication, and experimental measurements. Furthermore, the fabricated electronics along with the radiation sensor is being integrated in one module to be used by the European organization for nuclear research (CERN) in the next LHC run. The system consists of a radiation hardened frontend readout integrated circuit (ROIC) and a backend scalable analog to digital converter (ADC). The ROIC contains a low noise preamplifier with second stage differential variable gain amplifier, followed by a Constant Fraction Discriminator (CFD). The CFD is used to provide a timing edge, while eliminating the influence of signal intensity on the measured timing (time walk). A new design methodology for the CFD is proposed to improve both time walk and jitter performance, incorporating an all-pass filter delay line to reduce the extra jitter, typically added by the CFD, and an optimum slew rate comparator to eliminate the time walk. The ROIC is designed in 65 nm CMOS technology. Three design, fabrication, and measurement iterations were completed to improve system reliability and to qualify the ROIC for deployment at CERN. A record low time walk of ±6 ps across a 30 dB signal d (open full item for complete abstract)

Committee: Waleed Khalil (Advisor); Tawfik Musah (Committee Member); Steven Bibyk (Committee Member) Subjects: Electrical Engineering

Master of Science, The Ohio State University, 2022, Electrical and Computer Engineering

Next-generation hybrid pixel detectors aim to achieve timing resolutions on the order of 100 ps. Of primary concern is the analog front-end, composed of preamplifier and discriminator, which introduce significant timing uncertainty to the sensor charge signal they transduce. This work presents an on-chip test circuit capable of characterizing the jitter of pixel detector analog front-ends constructed in 28 nm bulk CMOS. The test system injects an artificial sensor charge pulse at the input of the device-under-test and then measures the output timing variation with a time-to-digital converter. The measurement circuit can inject charge quantities up to 24,000 electrons, with a timing precision of 10.1 ps RMS, a maximum differential non-linearity of 0.25 LSB, and a dynamic range of 64 ns.

Committee: Wladimiro Villarroel (Advisor); Maurice Garcia-Sciveres (Committee Member); Ayman Fayed (Committee Member); Tawfiq Musah (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2021, Physics

The ΛCDM model of cosmology offers the most successful description of the large-scale Universe to date. Containing just two mysterious components, dark matter and dark energy, this model is able to tie together observations across 13.8 billion years of cosmic history and from megaparsec to gigaparsec scales into one cohesive picture. These observations have origin in the wealth of cosmological data produced by astronomical surveys over the last few decades. Observations taken by substantially more precise surveys expected over the next 10 years will permit researchers to test ΛCDM against alternative frameworks, better understand the growth of structure, better understand the expansion history of the Universe, and place the tightest constraints on cosmological parameters hitherto produced. To do this successfully, it is imperative that researchers be able to precisely model cosmological observables and their sources of systematic errors. In the first part of this dissertation, I present my work on modeling the clustering of biased tracers in redshift space to second order in perturbation theory using the Lyman-α forest as an example. I find that there are eight unique terms that arise at second order. I then determine the expected shift in the Lyman-α forest baryon acoustic oscillation (BAO) scale caused by one systematic -- namely, the streaming velocity effect -- when using this improved model. I find streaming velocity-induced shifts in the BAO scale of 0.081%–0.149% (transverse direction) and 0.053%–0.058% (radial direction), depending on the model for the biasing coefficients used. In the second part of this dissertation, I present work I led on charge diffusion and quantum yield measured in candidate flight detectors for the Nancy Grace Roman Space Telescope. I built new analytic expressions for charge covariance in H4RG-10 detectors incorporating interpixel nonlinearity (IPNL), classical nonlinearity (CNL), quantum yield, and charge diffusion based o (open full item for complete abstract)

Committee: Christopher Hirata (Advisor); John Beacom (Committee Member); Eric Braaten (Committee Member); Klaus Honscheid (Committee Member) Subjects: Astronomy; Astrophysics; Physics; Theoretical Physics

Doctor of Philosophy, The Ohio State University, 2021, Physics

Quantum information science is rapidly advancing and it is likely that society will experience a major shift in the way we handle information in the coming years. As critical advancements such as quantum computation and quantum cryptography progress, the full manifestation of a second quantum revolution is on the horizon. Photons will be an integral part of quantum information science, especially for communication purposes, so we will need to develop excellent single-photon detector technologies. In this thesis, I describe a promising single-photon detector candidate, superconducting nanowire single-photon detectors, and provide a new theoretical basis for understanding these detectors. Specifically, I explore the relationship between various detector parameters and the readout signal and show that its rising edge can be described using a characteristic time that is proportional to the square root of the length of the detector and is inversely proportional to the square root of the absorbed photon number n and bias current. Therefore, this work provides a theoretical basis for photon-number resolution in a conventional single-pixel superconducting nanowire single-photon detector. Based on these predictions, I describe a demonstration of photon-number resolution in superconducting nanowire single-photon detectors that correctly identifies more than 99.7% of n=1 events and more than 98% of n>1 events when distinguishing between n=1 versus n>1, as well as explore the effects of other parameters via experiment and by drawing from the literature. While seeking to understand the quality of the demonstrated photon-number resolution, I find that there is likely some spatial variation in the intrinsic detector parameters. I predict that this may result in some below critical temperature resistance in these detectors and verify this experimentally. The resistance ranges from around 50 Ohms at 0.9 K to multiple kOhms closer to the critical temperature. This is (open full item for complete abstract)

Committee: Daniel Gauthier (Advisor); Gregory Lafyatis (Committee Member); Ezekiel Johnston-Halperin (Committee Member); Richard Furnstahl (Committee Member) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2021, Nuclear Engineering

Semiconductor gamma ray detectors are highly demanded in numerical fields of applications, such as homeland security, industry, medical imaging and academic research. As the golden standard of gamma spectroscopy, the High Purity Germanium (HPGe) detector has an energy resolution of less than 0.5% Full-Width-Half-Maximum (FWHM) at 662 keV. However, HPGe detector needs liquid nitrogen cooling due to its small energy bandgap. As the only commercially available room temperature gamma ray detector, the Cadmium-Zinc-Telluride (CdZnTe) detector achieves an energy resolution of less than 1% FWHM at 662 keV. Nevertheless, the growth issues and the associated high cost of the CdZnTe detectors continue to drive the search for alternative radiation detection materials featuring low-cost growth methods. Recently, the lead (Pb) halide perovskites emerged as a promising candidate for hard radiation detection due to their favorable properties, such as high atomic number, large mobility-lifetime product, wide and tunable energy bandgap. In this research, we evaluated the performance of perovskite gamma ray and X-ray detectors, especially the inorganic CsPbBr3 single crystals made from low-cost solution grown method. The design principles of a gamma ray detector architecture were studied. The leakage current reduction performance of different detector structures, that is, Ohmic-Ohmic, Schottky-Ohmic, Schottky-Schottky, were compared theoretically. The role of Electron/Hole Transport Layers in a gamma ray detector was discussed. Processing sequences for CsPbBr3 detector fabrication were developed. Through well controlled surface processing, the leakage current as low as less than 5 nA at -200 V was consistently achieved, which is comparable to a CdZnTe detector. The investigation of perovskite detector architecture and development of detector processing sequences pave the way of effective design and fabrication of CsPbBr3 detector with consistent performance. The X-ray and alpha part (open full item for complete abstract)

Committee: Lei Cao (Advisor) Subjects: Nuclear Engineering

Doctor of Philosophy, Miami University, 2020, Geology and Environmental Earth Science

Recent studies have suggested that slow slip processes and high pore fluid pressures may have a role in promoting seismogenic events, particularly earthquake swarms. Swarms of seismicity have also been observed to be induced by the injection of fluid, either via hydraulic fracturing or wastewater disposal, such that this can provide a complimentary comparison. Here, we present three chapters that seek to detect and investigate the origin of earthquake swarms. In Chapter 1, we generate a catalog of earthquake swarms in Oaxaca, Mexico and find most events outline a steeply dipping fault in the overriding plate. Examination of GPS data reveals many of these swarms occur during slow slip events, although they occur during episodes of strike slip motion as opposed to thrust motion. This appears to be the first evidence for slow slip behavior on a sliver fault that helps to partition the oblique convergence. Conductivity studies indicate fluids released along the subduction interface may be channeled up this steep sliver fault, leaving the megathrust with drier conditions that could promote traditional fast slip behavior. In Chapter 2, we investigate the increase in seismicity in the Eagle Ford oil and gas field of south Texas and how hydraulic fracturing (HF) contributed. We compare times and locations of HF wells with a catalog of seismicity we enhanced through template matching (2014-2018). Several HF wells have seismicity nearby during operation, indicating seismicity from HF is more common in this area than previously thought. We find that HF strategy affects the probability of earthquakes. A MW 4.0 earthquake is the largest HF‐induced earthquake in the U.S. Thus, this study demonstrates that faults in this area are capable of producing felt and potentially damaging earthquakes due to ongoing HF. In Chapter 3, we seek to perform a deeper exploration of how HF has contributed to recent seismicity using template matching with newly deployed stations and a repeating sig (open full item for complete abstract)

Committee: Michael Brudzinski PhD (Advisor); Brian Currie PhD (Committee Member); Elizabeth Widom PhD (Committee Member); Jonathan Levy PhD (Committee Member); Aaron Velasco PhD (Committee Member) Subjects: Geology; Geophysics

Doctor of Philosophy, University of Akron, 2020, Electrical Engineering

In this dissertaton, methods of fabrication and testing micro- and nano-scaled thermoelectric microwave power detectors based on graphene are explored. Initial detectors show sensitivities of 0.87 mV/mW and each chapter herein describes the iterations and improvements made to the devices. In the end, detectors have shown sensitivities of up to 60.25 mV/mW when accounting for the reflection coefficient of the device, over a 690% increase in sensitivity. Commercially-available detectors that feature zero DC power consumption and operate over similar frequency ranges typically oer a power detection sensitivity of 500 mV/mW. However, state-of-the-art thermoelectric detectors based on CMOS and MEMS technologies over power detection sensitivities that are typically lower than 0.4 mV/mW. Unoptimized graphene based detectors have been shown to outperform CMOS and MEMS detectors. An outlook is provided on further optimizations that can be made to the devices.

Committee: Ryan Toonen PhD (Advisor); Kye-Shin Lee PhD (Committee Member); Igor Tsukerman PhD (Committee Member); Alper Buldum PhD (Committee Member); Ben Yu-Kuang Hu PhD (Committee Member) Subjects: Electrical Engineering

Master of Science, The Ohio State University, 2020, Electrical and Computer Engineering

Baud rate clock and data recovery circuits are critical to high speed serial links since these require only one sample per data period thereby requiring low speed samplers and comparators. This work models and discusses the backend of one particular Baud rate CDR – Mueller Muller, and analyses some of the building blocks of the CDR – Phase Detector, Phase Interpolator and the Quadrature Phase Generator. Firstly, a PAM-4 Quadrature Phase Detector operating at 80Gb/s is discussed. The challenges associated with designing a Mueller-Muller PD for an asymmetric channel are discussed and one way to resolve this issue is proposed. Then the underlying digital blocks that make up the Phase detector are expanded upon. Secondly, a 64-step digitally controlled Phase Interpolator running at 16GHz clock rate is analyzed and its design challenges with regards to achieving linearity and ensuring duty cycle fidelity are explored. Finally, a Quadrature Phase Generator with digital delay control is analyzed. It is modeled at 16GHz clock rate and the range/resolution problem and its impact on clock jitter is explored.

Committee: Tawfiq Musah (Advisor); Ayman Fayed (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2019, Electro-Optics

Infrared imaging is a powerful capability that has been technologically driven primarily by the defense industry over the past several decades. As a result, ultra-high-performance infrared imaging arrays with specialized functionality have been developed but at a relatively high cost. Meanwhile, economy of scale has driven the price of visible complementary metal oxide-semiconductor (CMOS) image sensors down drastically while simultaneously providing greater on-chip capability and performance. Silicon-based infrared sensors have the potential to leverage modern CMOS advancements and cost, but poor performance has inhibited the widespread adoption of this technology. In this work, I explored the potential for novel silicon based infrared sensors that exploit nanoscale structures to provide new methods of photodetection in silicon beyond the bulk bandgap response. Nanostructure fabrication developments and challenges were also investigated with the perspective of applying the underlying structure as a platform to detect infrared photons. Proposed solutions include improvement to existing detector technology (Schottky barrier photodiodes) as well as novel detector architectures (silicon quantum walls) that leverage the unique geometry of nanostructured silicon.

Committee: Andrew Sarangan Ph.D. (Advisor); Michael Eismann Ph.D. (Committee Member); Jay Mathews Ph.D. (Committee Member); David Forrai M.S. (Committee Member); Partha Banerjee Ph.D. (Committee Member) Subjects: Engineering; Optics; Physics; Quantum Physics