Operation of a Radar Altimeter over the Greenland Ice Sheet

This thesis presents documentation for the Advanced Application Flight Experiment (AAFE) pulse compression radar altimeter and its role in the NASA Multisensor Airborne Altimetry Experiment over Greenland in 1993. The AAFE Altimeter is a Ku-band microwave radar which has demonstrated 14 centimeter range precision in operation over arctic ice. Recent repairs and improvements were required to make the Greenland missions possible. Transmitter, receiver and software modifications, as well as the integration of a GPS receiver are thoroughly documented. Procedures for installation, and operation of the radar are described. Finally, suggestions are made for further system improvements

Evidence of a compensated semimetal with electronic correlations at the CNP of twisted double bilayer graphene

Recently, magic-angle twisted bilayer graphene (MATBLG) has shown the emergence of various interaction-driven novel quantum phases at the commensurate fillings of the moir'e superlattice, while the charge neutrality point (CNP) remains mostly a vanilla insulator. Here, we show an emerging phase of nearly compensated semimetallicity at the CNP of twisted double bilayer graphene (TDBLG), a close cousin of MATBLG, with signatures of electronic correlation. Using electrical and thermal transport, we find almost two orders of magnitude enhancement of the thermopower in magnetic fields much smaller than the extreme quantum limit, accompanied by a large magnetoresistance($\sim 2500\%$) at CNP. This provides indisputable experimental evidence that TDBLG near CNP is a compensated semimetal. Moreover, at low temperatures, we observe an unusual sublinear temperature dependence of resistance. A recent theory predicts the formation of an excitonic metal near CNP, where small electron and hole pockets coexist. We understand the sublinear temperature dependence in terms of critical fluctuations in this theory

Development of the Multi-Level Seismic Receiver (MLSR)

The Advanced Geophysical Technology Department (6114) and the Telemetry Technology Development Department (2664) have, in conjunction with the Oil Recovery Technology Partnership, developed a Multi-Level Seismic Receiver (MLSR) for use in crosswell seismic surveys. The MLSR was designed and evaluated with the significant support of many industry partners in the oil exploration industry. The unit was designed to record and process superior quality seismic data operating in severe borehole environments, including high temperature (up to 200{degrees}C) and static pressure (10,000 psi). This development has utilized state-of-the-art technology in transducers, data acquisition, and real-time data communication and data processing. The mechanical design of the receiver has been carefully modeled and evaluated to insure excellent signal coupling into the receiver

Spins and orbits in semiconductor quantum dots

Spins in semiconductor quantum dots are among the most promising candidates for the realization of a scalable quantum bit (qubit), the basic building block of a quantum computer. With this motivation, spin and orbital properties of quantum dots in three different semiconductor systems are investigated in this thesis: depletion mode quantum dots in GaAs/AlGaAs heterostructures as well as in silicon-germanium core-shell nanowires (GeSi NW), and accumulation mode quantum dots formed in a fin field-effect transistor (FinFET). The chronological order of this thesis reflects two major shifts of focus of the semiconductor spin qubit research in recent years: a transition from lateral GaAs quantum dots towards scalable, silicon-based systems and a change from electrons towards holes as the host of the spin qubit because of better prospects for spin manipulation and spin coherence. In a lateral GaAs single electron quantum dot, a new in-plane magnetic-field-assisted spectroscopy is demonstrated, which allows one to deduce the three dimensional confinement potential landscape of the quantum dot orbitals, which gives insight into the alignment of the ellipsoidal quantum dot with respect to the crystal axes. With this full model of the confinement at hand, the dependence of the spin relaxation on the direction and strength of an in-plane magnetic field is investigated. To mitigate the spin relaxation anisotropy due to anisotropic in-plane confinement of the quantum dot, said confinement is symmetrized by tuning the gate voltages to obtain a circular quantum dot. Then, the experimentally observed spin relaxation anisotropy can be attributed to the interplay of Rashba and Dresselhaus spin-orbit interaction (SOI) present in GaAs. By using a theoretical model, the strength and the relative sign of the Rashba and Dresselhaus SOI was obtained for the first time in such a quantum dot. From the dependence of the spin relaxation on the magnetic field strength, hyperfine induced phonon mediated spin relaxation was demonstrated -- a process predicted more than 15 years ago. Here, the hyperfine interaction leads to a mixing of spin and orbital degrees of freedom and facilitates spin relaxation. Limited by this relaxation process, a spin relaxation time of 57 +/- 15 s was measured -- setting the current record for spin lifetime in a nanostructure. Inspired by the unprecedented knowledge of the confinement and the SOI in the quantum dots used, a new theory to quantify the various corrections to the g-factor was developed. Later, these theoretical predictions have been experimentally validated by measurements of the g-factor anisotropy using pulsed-gate spectroscopy. Due to short spin qubit coherence time in GaAs, which is limited by the nuclear spins, a better approach is to build a spin qubit in a semiconductor vacuum with little or no nuclear spins. Because holes have minimal overlap with the nuclei of the semiconductor due to the p-type symmetry of their wave function, this type of decoherence is strongly suppressed when changing the host of the spin qubit from electrons to holes. The longer coherence times in combination with the predicted emergence of a direct type of Rashba SOI (DRSOI) -- a particularly strong and electrically controllable SOI -- motivated the investigation of hole quantum dots in GeSi NW. In this system, anisotropic behavior of the leakage current through a double quantum dot in Pauli spin blockade was observed. This anisotropy is qualitatively explained by a phenomenological model, which involves an anisotropic g-factor and an effective spin-orbit field. While the dominant type of SOI could not be resolved conclusively, the obtained data is not inconsistent with the expectation of DRSOI. Because each wire has to be placed manually, this NW based system lacks scalability. Hole and electron quantum dots in an industry-compatible silicon FinFET structure, conversely, are promising candidates for scalable spin qubits and, therefore, hold the potential to be used in a spin-based quantum computer. Recently, DRSOI was predicted to also emerge in narrow silicon channels such as FinFETs. In this thesis, the formation of accumulation mode hole quantum dots in such a FinFET structure is reported -- an important first step towards the realization of a scalable, all-electrically controllable, DRSOI hole spin qubit

Experimental characterization of the Hitrap Cooler trap with highly charged ions.

The HITRAP (Highly charged Ions TRAP)facility is being set up and commissioned at GSI, Darmstadt. It will provide heavy, highly charged ions at low velocities to high-precision atomic physics experiments. Within this work the Cooler trap- the key element of the HITRAP facility was tested. The Cooler trap was assembled, aligned, and commissioned in trapping experiments with ions from off-line sources.The work performed within the scope of this thesis provided the baseline for further operation and maintenance of the Cooler trap

Analysis and design of a wide dynamic range pulse-frequency modulation CMOS image sensor

Complementary Metal-Oxide Semiconductor (CMOS) image sensor is the dominant electronic imaging device in many application fields, including the mobile or portable devices, teleconference cameras, surveillance and medical imaging sensors. Wide dynamic range (WDR) imaging is of interest particular, demonstrating a large-contrast imaging range of the sensor. As of today, different approaches have been presented to provide solutions for this purpose, but there exists various trade-offs among these designs, which limit the number of applications. A pulse-frequency modulation (PFM) pixel offers the possibility to outperform existing designs in WDR imaging applications, however issues such as uniformity and cost have to be carefully handled to make it practical for different purposes. In addition, a complete evaluation of the sensor performance has to be executed prior to fabrication in silicon technology. A thorough investigation of WDR image sensor based on the PFM pixel is performed in this thesis. Starting with the analysis, modeling, and measurements of a PFM pixel, the details of every particular circuit operation are presented. The causes of dynamic range (DR) limitations and signal nonlinearity are identified, and noise measurement is also performed, to guide future design strategies. We present the design of an innovative double-delta compensating (DDC) technique which increases the sensor uniformity as well as DR. This technique achieves performance optimization of the PFM pixel with a minimal cost an improved linearity, and is carefully simulated to demonstrate its feasibility. A quad-sampling technique is also presented with the cooperation of pixel and column circuits to generate a WDR image sensor with a reduced cost for the pixel. This method, which is verified through the field-programmable gate array (FPGA) implementation, saves considerable area in the pixel and employs the maximal DR that a PFM pixel provides. A complete WDR image sensor structure is proposed to evaluate the performance and feasibility of fabrication in silicon technology. The plans of future work and possible improvements are also presented

MONOLITHICALLY INTEGRATED, PRINTED SOLID-STATE RECHARGEABLE BATTERIES WITH AESTHETIC VERSATILITY

Department of Energy Engineering (Battery Science and Technology)With the advent of flexible/wearable electronics and Internet of Things (IoT) which are expected to drastically change our daily lives, printed electronics has drawn much attention as a low cost, efficient, and scalable platform technology. The printed electronics requires so-called “printed batteries” as a monolithically integrated power source that can be prepared by the same printing processes. The printing technology is a facile and reproducible process in which slurries or inks are deposited to make pre-defined patterns. The slurries/inks should be designed to fulfill requirements (such as rheology and particle dispersion) of the printing process. Development of printed batteries involves the design and fabrication of battery component slurries/inks. Most studies of the printed batteries have been devoted to the development of printed electrodes. However, in order to reach an ultimate goal of so-called “all-printed-batteries”, printed separator membranes and printed electrolytes should be also developed along with the printed electrodes. The objective of the research presented in this dissertation is to develop materials and printing-based strategies to fabricate a new class of monolithically integrated, printed solid-state rechargeable batteries with aesthetic versatility to address the aforementioned formidable challenges, with particular attention to comprehensive understanding of colloidal microstructure and rheological/electrochemical properties of printable battery component slurries/inks. Colloidal microstructure of the battery component slurries/inks is expected to play a viable role in realizing the monolithically integrated printed batteries, as it can significantly affect fluidic characteristics of the slurries/inks and also electrochemical properties. In particular, our interest is devoted to concentrated colloidal gels that exhibit thixotropic fluid behavior (i.e., they readily flow upon being subjected to external stress and quickly return to a quiescent state). Driven by such unique viscoelastic response, the slurries/inks show good dimensional stability and shape diversity on various objects. In addition to the viscoelasticity control of the slurries/inks, the interaction between colloidal conductive particles should be carefully tuned in order to secure facile ion and electron transport pathways. When the attractive interaction is dominant, the colloidal particles tend to be aggregated in disordered and dynamically arrested forms, yielding the highly reticulated three-dimensional networks. In an electrochemical system, these interconnected conductive particle networks act as electron conduction channels while the interstitial voids formed between the particle networks allows ion transport. In this dissertation, as a proof-of-concept, lithium-ion batteries (LIBs), electric double layer capacitors (EDLCs), and Zn-air batteries are chosen to explore the feasibility of this approach. The resultant solid-state printed batteries are fabricated through various printing processes such as stencil printing, inkjet printing, and pen-based writing. Notably, the printed batteries can be seamlessly integrated with objects or electronic devices, thus offering unprecedented opportunities in battery design and form factors that lie far beyond those achievable with conventional battery technologies.ope

Forecasting CO2 Sequestration with Enhanced Oil Recovery

The aim of carbon capture, utilization, and storage (CCUS) is to reduce the amount of CO2 released into the atmosphere and to mitigate its effects on climate change. Over the years, naturally occurring CO2 sources have been utilized in enhanced oil recovery (EOR) projects in the United States. This has presented an opportunity to supplement and gradually replace the high demand for natural CO2 sources with anthropogenic sources. There also exist incentives for operators to become involved in the storage of anthropogenic CO2 within partially depleted reservoirs, in addition to the incremental production oil revenues. These incentives include a wider availability of anthropogenic sources, the reduction of emissions to meet regulatory requirements, tax incentives in some jurisdictions, and favorable public relations. The United States Department of Energy has sponsored several Regional Carbon Sequestration Partnerships (RCSPs) through its Carbon Storage program which have conducted field demonstrations for both EOR and saline aquifer storage. Various research efforts have been made in the area of reservoir characterization, monitoring, verification and accounting, simulation, and risk assessment to ascertain long-term storage potential within the subject storage complex. This book is a collection of lessons learned through the RCSP program within the Southwest Region of the United States. The scope of the book includes site characterization, storage modeling, monitoring verification reporting (MRV), risk assessment and international case studies

One dimensional photonic crystal for label-free and fluorescence sensing application

The development of more sensitive and more reliable sensors aids medical applications in many fields as diseases detection or therapy progress. This thesis threats the development of an optical biosensor based on electromagnetic modes propagating at the interface between a finite one-dimensional photonic crystal (1DPC) and a homogeneous external medium, also named Bloch Surface Waves (BSW). BSW have emerged as an attractive approach for label-free sensing in plasmon-like sensor configurations. Besides label-free operation, the large field enhancement and the absence of quenching allow the use of BSW to excite fluorescent labels that are in proximity of the 1DPC surface. This approach was adapted to the case of angularly resolved resonance detection, thus giving rise to a combined label-free/labelled biosensor platform. BSW present many degrees of design freedomthat enable tuning of resonance properties. In order to obtain a figure of merit for an optimization, I investigated the measurement uncertainty depending on resonance width and depth with different numericalmodels. This has led to a limit of detection that can assist the choice of the best design to use. Two tumor biomarkers, such as vascular endothelial growth factor (VEGF) and Angiopoietin-2 (Ang2), have been considered to be detected with the BSW biosensing platform. For this purpose the specific antibodies for the two tumor biomarkers were immobilized on the 1DPC biochip surface. The conclusive experiments reported in this work demonstrated the successful detection of the VEGF biomarker in complex matrices, such as cell culture supernatants and human plasma samples. Moreover, the platformwas used to determinate Ang2 concentration in untreated human plasma samples using low volumes, 300 μL, and with short turnaround times, 30 minutes. This is the first BSW based biosensor assay for the determination of tumor biomarker in human plasma samples at clinically relevant concentrations