A Voltage Controlled Oscillator for a Phase-Locked Loop Frequency Synthesizer in a Silicon-on-Sapphire Process (open access)

A Voltage Controlled Oscillator for a Phase-Locked Loop Frequency Synthesizer in a Silicon-on-Sapphire Process

Engineers from a government-owned engineering and manufacturing facility were contracted by government-owned research laboratory to design and build an S-band telemetry transmitter using Radio Frequency Integrated Circuit (RFIC) technology packaged in a Low-Temperature Co-fired Ceramic (LTCC) Multi-Chip Module. The integrated circuit technology chosen for the Phase-Locked Loop Frequency Synthesizer portion of the telemetry transmitter was a 0.25 um CMOS process that utilizes a sapphire substrate and is fabricated by Peregrine Semiconductor corporation. This thesis work details the design of the Voltage Controlled Oscillator (VCO) portion of the PLL frequency synthesizer and constitutes an fully integrated VCO core circuit and a high-isolation buffer amplifier. The high-isolation buffer amplifier was designed to provide 16 dB of gain for 2200-3495 MHz as well as 60 dB of isolation for the oscillator core to provide immunity to frequency pulling due to RF load mismatch. Actual measurements of the amplifier gain and isolation showed the gain was approximately 5 dB lower than the simulated gain when all bond-wire and test substrate parasitics were taken into account. The isolation measurements were shown to be 28 dB at the high end of the frequency band but the measurement was more than likely compromised due to the aforementioned …
Date: May 21, 2009
Creator: Garrison, Sean
System: The UNT Digital Library
Development of extreme ultraviolet and soft x-ray multilayer optics for scientific studies with femtosecond/attosecond sources (open access)

Development of extreme ultraviolet and soft x-ray multilayer optics for scientific studies with femtosecond/attosecond sources

The development of multilayer optics for extreme ultraviolet (EUV) radiation has led to advancements in many areas of science and technology, including materials studies, EUV lithography, water window microscopy, plasma imaging, and orbiting solar physics imaging. Recent developments in femtosecond and attosecond EUV pulse generation from sources such as high harmonic generation lasers, combined with the elemental and chemical specificity provided by EUV radiation, are opening new opportunities to study fundamental dynamic processes in materials. Critical to these efforts is the design and fabrication of multilayer optics to transport, focus, shape and image these ultra-fast pulses This thesis describes the design, fabrication, characterization, and application of multilayer optics for EUV femtosecond and attosecond scientific studies. Multilayer mirrors for bandwidth control, pulse shaping and compression, tri-material multilayers, and multilayers for polarization control are described. Characterization of multilayer optics, including measurement of material optical constants, reflectivity of multilayer mirrors, and metrology of reflected phases of the multilayer, which is critical to maintaining pulse size and shape, were performed. Two applications of these multilayer mirrors are detailed in the thesis. In the first application, broad bandwidth multilayers were used to characterize and measure sub-100 attosecond pulses from a high harmonic generation source and …
Date: May 21, 2009
Creator: Aquila, Andrew Lee
System: The UNT Digital Library
On Decays of B Mesons to a Strange Meson and an Eta or Eta' Meson at Babar (open access)

On Decays of B Mesons to a Strange Meson and an Eta or Eta' Meson at Babar

We describe studies of the decays of B mesons to final states {eta}K{sup *}(892), {eta}K{sup *}{sub 0}(S-wave), {eta}K{sup *}{sub 2}(1430), and {eta}'K based on data collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collier at the Stanford Linear Accelerator Center. We measure branching fractions and charge asymmetries for the decays B {yields} {eta}K{sup *}, where K{sup *} indicates a spin 0, 1, or 2 K{pi} system, making first observations of decays to final states {eta}K{sup *0}{sub 0}(S-wave), {eta}K{sup *+}{sub 0} (S-wave), and {eta}K{sup *0}{sub 2}(1430). We measure the time-dependent CP-violation parameters S and C for the decays B{sup 0} {yields} {eta}'K{sup 0}, observing CP violation in a charmless B decay with 5{sigma} significance considering both statistical and systematic uncertainties..
Date: April 21, 2009
Creator: Hirschauer, James Francis
System: The UNT Digital Library
Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment (open access)

Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment

This study reports the observation of the decays B{sup 0}{yields}D{sup (*)+}{sub S}{pi}{sup -} and B{sup 0}{yields}D{sup (*)-}K{sup +} in a sample of 230 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring, located at the Stanford Linear Accelerator Center. The branching fractions {beta}(B{sup 0} {yields} D{sup +}{sub S}{pi}{sup -}) = (1.3 {+-} 0.3 (stat) {+-} 0.2 (syst)) x 10{sup -5}, {beta}(B{sup 0} {yields} D{sup +}{sub S}K{sup +}) = (2.5 {+-} 0.4 (stat) {+-} 0.4 (syst)) x 10{sup -5}, {beta}(B{sup 0}{yields}D{sup (*)+}{sub S}{pi}{sup -}) = (2.8 {+-} 0.6 (stat) {+-} 0.5 (syst)) x 10{sup -5}, and {beta}(B{sup 0}{yields}D{sup (*)-}K{sup +}) = (2.0 {+-} 0.5 (stat) {+-} 0.4 (syst)) x 10{sup -5} are measured. The significance of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is a first observation of the decaysB{sup 0}{yields}D{sup (*)+}{sub S}{pi}{sup -} and B{sup 0}{yields}D{sup (*)-}K{sup +}. These results may potentially be useful in determining the CP asymmetry parameter sin(2{beta} + {gamma}) in the decays B{sup 0}{yields}D{sup (*)+}{sub S}{pi}{sup -}.
Date: August 21, 2007
Creator: Orimoto, Toyoko Jennifer
System: The UNT Digital Library
Reconstruction of B- to D*0 e- anti_nu_e Decays and Determination of |Vcb| (open access)

Reconstruction of B- to D*0 e- anti_nu_e Decays and Determination of |Vcb|

In this analysis the decay B- {yields} D*{sup 0}e{sup -}{bar {nu}}{sub e} is measured. The underlying data sampel consists of about 226 million B{bar B}-pairs accumulated on the {Upsilon}(4S) resonance by the BABAR detector at the asymmetric e{sup +}e{sup -} collider PEP-II. The reconstruction of the decay uses the channels D*{sup 0}{yields}D{sup 0}{pi}{sup 0}, D{sup 0} {yields} K{sup -}{pi}{sup +} and {pi}{sup 0} {yields} {gamma}{gamma}. The neutrino is not reconstructed. Since the rest frame of the B meson is unknown, the boost w of the D*{sup 0} meson in the B meson rest frame is estimated by {bar w}. The {bar w} spectrum of the data is described in terms of the partial decay width d{Gamma}/dw into an expectation of the measured {bar w} spectrum. d{Gamma}/dw depends on a form factor F(w) parameterizing the strong interaction in the decay process. To find the best descriptive d{Gamma}/dw a fit to the data determines the following two parameters of d{Gamma}/dw: (i) F(1)|V{sub cb}|, the product between F at zero D*{sup 0} recoil and the CKM matrix element |V{sub cb}|; (ii) {rho}{sup 2}{sub A1}, a parameter of the form factor F(w). The former parameter scales the height of d{Gamma}/dw and {rho}{sup 2}{sub A1} …
Date: August 21, 2007
Creator: Schubert, Jens
System: The UNT Digital Library
GaAs Blocked-Impurity-Band Detectors for Far-Infrared Astronomy (open access)

GaAs Blocked-Impurity-Band Detectors for Far-Infrared Astronomy

High-purity and doped GaAs films have been grown by Liquid-phase epitaxy (LPE) for development of a blocked impurity band (BIB) detector for far-infrared radiation. The film growth process developed has resulted in the capability to grow GaAs with a net active impurity concentration below 1 x 10{sup 13} cm{sup -3}, ideal for the blocking layer of the BIB detector. The growth of n-type LPE GaAs films with donor concentrations below the metal-insulator transition, as required for the absorbing layer of a BIB detector, has been achieved. The control of the donor concentration, however, was found to be insufficient for detector production. The growth by LPE of a high-purity film onto a commercially grown vapor-phase epitaxial (VPE) n-type GaAs doped absorbing layer resulted in a BIB device that showed a significant reduction in the low-temperature dark current compared to the absorbing layer only. Extended optical response was not detected, most likely due to the high compensation of the commercially grown GaAs absorbing layer, which restricts the depletion width of the device.
Date: December 21, 2004
Creator: Cardozo, Benjamin Lewin
System: The UNT Digital Library
Aspherical supernovae (open access)

Aspherical supernovae

Although we know that many supernovae are aspherical, the exact nature of their geometry is undetermined. Because all the supernovae we observe are too distant to be resolved, the ejecta structure can't be directly imaged, and asymmetry must be inferred from signatures in the spectral features and polarization of the supernova light. The empirical interpretation of this data, however, is rather limited--to learn more about the detailed supernova geometry, theoretical modeling must been undertaken. One expects the geometry to be closely tied to the explosion mechanism and the progenitor star system, both of which are still under debate. Studying the 3-dimensional structure of supernovae should therefore provide new break throughs in our understanding. The goal of this thesis is to advance new techniques for calculating radiative transfer in 3-dimensional expanding atmospheres, and use them to study the flux and polarization signatures of aspherical supernovae. We develop a 3-D Monte Carlo transfer code and use it to directly fit recent spectropolarimetric observations, as well as calculate the observable properties of detailed multi-dimensional hydrodynamical explosion simulations. While previous theoretical efforts have been restricted to ellipsoidal models, we study several more complicated configurations that are tied to specific physical scenarios. We explore clumpy …
Date: May 21, 2004
Creator: Kasen, Daniel Nathan
System: The UNT Digital Library
Development of Trivalent Ytterbium Doped Fluorapatites for Diode-Pumped Laser Applications (open access)

Development of Trivalent Ytterbium Doped Fluorapatites for Diode-Pumped Laser Applications

One of the major motivators of this work is the Mercury Project, which is a 1 kW scalable diode-pumped solid-state laser system under development at Lawrence Livermore National Laboratory (LLNL). Major goals include 100 J pulses, 10% wallplug efficiency, 10 Hz repetition rate, and a 5 times diffraction limited beam. To achieve these goals the Mercury laser incorporates ytterbium doped Sr{sub 5}(PO{sub 4}){sub 3}F (S-FAP) as the amplifier gain medium. The primary focus of this thesis is a full understanding of the properties of this material which are necessary for proper design and modeling of the system. Ytterbium doped fluorapatites, which were previously investigated at LLNL, were found to be ideal candidate materials for a high power amplifier systems providing high absorption and emission cross sections, long radiative lifetimes, and high efficiency. A family of barium substituted S-FAP crystals were grown in an effort to modify the pump and emission bandwidths for application to broadband diode pumping and short pulse generation. Crystals of Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F where x < 1 showed homogeneous lines offering 8.4 nm (1.8 times enhancement) of absorption bandwidth and 6.9 nm (1.4 times enhancement) of emission bandwidth. The gain saturation fluence of Yb:S-FAP …
Date: June 21, 2000
Creator: Bayramian, A. J.
System: The UNT Digital Library
Benchmarks and models for 1-D radiation transport in stochastic participating media (open access)

Benchmarks and models for 1-D radiation transport in stochastic participating media

Benchmark calculations for radiation transport coupled to a material temperature equation in a 1-D slab and 1-D spherical geometry binary random media are presented. The mixing statistics are taken to be homogeneous Markov statistics in the 1-D slab but only approximately Markov statistics in the 1-D sphere. The material chunk sizes are described by Poisson distribution functions. The material opacities are first taken to be constant and then allowed to vary as a strong function of material temperature. Benchmark values and variances for time evolution of the ensemble average of material temperature energy density and radiation transmission are computed via a Monte Carlo type method. These benchmarks are used as a basis for comparison with three other approximate methods of solution. One of these approximate methods is simple atomic mix. The second approximate model is an adaptation of what is commonly called the Levermore-Pomraning model and which is referred to here as the standard model. It is shown that recasting the temperature coupling as a type of effective scattering can be useful in formulating the third approximate model, an adaptation of a model due to Su and Pomraning which attempts to account for the effects of scattering in a stochastic …
Date: August 21, 2000
Creator: Miller, D. S.
System: The UNT Digital Library
Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects (open access)

Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects

Experimental and theoretical research conducted in two areas in the field of nuclear magnetic resonance (NMR) spectroscopy is presented: (1) studies of the coherent quantum-mechanical control of the angular momentum dynamics of quadrupolar (spin I > 1/2) nuclei and its application to the determination of molecular structure; and (2) applications of the long-range nuclear dipolar field to novel NMR detection methodologies.The dissertation is organized into six chapters. The first two chapters and associated appendices are intended to be pedagogical and include an introduction to the quantum mechanical theory of pulsed NMR spectroscopy and the time dependent theory of quantum mechanics. The third chapter describes investigations of the solid-state multiple-quantum magic angle spinning (MQMAS) NMR experiment applied to I = 5/2 quadrupolar nuclei. This work reports the use of rotary resonance-matched radiofrequency irradiation for sensitivity enhancement of the I = 5/2 MQMAS experiment. These experiments exhibited certain selective line narrowing effects which were investigated theoretically.The fourth chapter extends the discussion of multiple quantum spectroscopy of quadrupolar nuclei to a mostly theoretical study of the feasibility of enhancing the resolution of nitrogen-14 NMR of large biomolecules in solution via double-quantum spectroscopy. The fifth chapter continues to extend the principles of multiple quantum …
Date: December 21, 2004
Creator: Urban, Jeffry Todd
System: The UNT Digital Library
Towards Chip Scale Liquid Chromatography and High Throughput Immunosensing (open access)

Towards Chip Scale Liquid Chromatography and High Throughput Immunosensing

This work describes several research projects aimed towards developing new instruments and novel methods for high throughput chemical and biological analysis. Approaches are taken in two directions. The first direction takes advantage of well-established semiconductor fabrication techniques and applies them to miniaturize instruments that are workhorses in analytical laboratories. Specifically, the first part of this work focused on the development of micropumps and microvalves for controlled fluid delivery. The mechanism of these micropumps and microvalves relies on the electrochemically-induced surface tension change at a mercury/electrolyte interface. A miniaturized flow injection analysis device was integrated and flow injection analyses were demonstrated. In the second part of this work, microfluidic chips were also designed, fabricated, and tested. Separations of two fluorescent dyes were demonstrated in microfabricated channels, based on an open-tubular liquid chromatography (OT LC) or an electrochemically-modulated liquid chromatography (EMLC) format. A reduction in instrument size can potentially increase analysis speed, and allow exceedingly small amounts of sample to be analyzed under diverse separation conditions. The second direction explores the surface enhanced Raman spectroscopy (SERS) as a signal transduction method for immunoassay analysis. It takes advantage of the improved detection sensitivity as a result of surface enhancement on colloidal gold, the …
Date: September 21, 2000
Creator: Ni, J.
System: The UNT Digital Library
Sum-frequency spectroscopic studies: I. Surface melting of ice, II. Surface alignment of polymers (open access)

Sum-frequency spectroscopic studies: I. Surface melting of ice, II. Surface alignment of polymers

Surface vibrational spectroscopy via infrared-visible sum-frequency generation (SFG) has been established as a useful tool to study the structures of different kinds of surfaces and interfaces. This technique was used to study the (0001) face of hexagonal ice (Ih). SFG spectra in the O-H stretch frequency range were obtained at various sample temperatures. For the vapor(air)/ice interface, the degree of orientational order of the dangling OH bonds at the surface was measured as a function of temperature. Disordering sets in around 200 K and increases dramatically with temperature, which is strong evidence of surface melting of ice. For the other ice interfaces (silica/OTS/ice and silica/ice), a similar temperature dependence of the hydrogen bonded OH stretch peak was observed; the free OH stretch mode, however, appears to be different from that of the vapor (air)/ice interface due to interactions at the interfaces. The technique was also used to measure the orientational distributions of the polymer chains on a rubbed polyvinyl alcohol surface. Results show that the polymer chains at the surface appear to be well aligned by rubbing, and the adsorbed liquid crystal molecules are aligned, in turn, by the surface polymer chains. A strong correlation exists between the orientational distributions …
Date: December 21, 2000
Creator: Wei, Xing
System: The UNT Digital Library
Transition Metal Complexes of Cr, Mo, W and Mn Containing {eta}{sup 1}(S)-2,5-Dimethylthiophene, Benzothiophene and Dibenzothiophene Ligands (open access)

Transition Metal Complexes of Cr, Mo, W and Mn Containing {eta}{sup 1}(S)-2,5-Dimethylthiophene, Benzothiophene and Dibenzothiophene Ligands

The UV photolysis of hexanes solutions containing the complexes M(CO){sub 6} (M=Cr, Mo, W) or CpMn(CO){sub 3} (Cp={eta}{sup 5}-C{sub 5}H{sub 5}) and excess thiophene (T{sup *}) (T{sup *}=2,5-dimethylthiophene (2,5-Me{sub 2}T), benzothiophene (BT), and dibenzothiophene (DBT)) produces the {eta}{sup 1}(S)-T{sup *} complexes (CO){sub 5}M({eta}{sup 1}(S)-T{sup *}) 1-8 or Cp(CO){sub 2}Mn({eta}{sup 1}(S)-T{sup *})9-11, respectively. However, when T{sup *}=DBT, and M=Mo, a mixture of two products result which includes the {eta}{sup 1}(S)-DBT complex (CO){sub 5}Mo({eta}{sup 1}(S)-DBT) 4a and the unexpected {pi}-complex (CO){sub 3}Mo({eta}{sup 6}-DBT) 4b as detected by {sup 1}H NMR. The liability of the {eta}{sup 1}(S)-T{sup *} ligands is illustrated by the rapid displacement of DBT in the complex (CO){sub 5}W({eta}{sup 1}(S)-DBT) (1) by THF, and also in the complexes (CO){sub 5}Cr({eta}{sup 1}(S)-DBT) (5) and CpMn(CO){sub 2}({eta}{sup 1}(S)-DBT) (9) by CO (1 atm) at room temperature. Complexes 1-11 have been characterized spectroscopically ({sup 1}H NMR, IR) and when possible isolated as analytically pure solids (elemental analysis, EIMS). Single crystal, X-ray structural determinations are reported for (CO){sub 5}W({eta}{sup 1}(S)-DBT) and Cp(CO){sub 2}Mn({eta}{sup 1}(S)-DBT).
Date: September 21, 2000
Creator: Reynolds, M.
System: The UNT Digital Library
Analytical Chemistry at the Interface Between Materials Science and Biology (open access)

Analytical Chemistry at the Interface Between Materials Science and Biology

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Date: September 21, 2000
Creator: O'Brien, J. C.
System: The UNT Digital Library