With the recent discovery of the giant magnetocaloric effect and the beginning of extensive research on the properties of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, a necessity has developed for a better understanding of the microstructure and crystal structure of this family of rare earth compounds with startling phenomenological properties. The aim of this research is to characterize the microstructure of the Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, with X {approx_equal} 2 and its phase change by using both transmission and electron microscopes. A brief history of past work on Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} is necessary to understand this research in its proper context.

Measurements of the b quark production cross section at the Tevatron and at Hera in the final decades of the 20th century have consistently yielded higher values than predicted by Next-to-Leading Order (NLO) QCD. This discrepancy has led to a large efforts by theorists to improve theoretical calculations of the cross sections and simulations of b quark production. As a result, the difference between theory and experiment has been much reduced. New measurements are needed to test the developments in the calculations and in event simulation. In this thesis, a measurement of angular correlations between b jets produced in the same event is presented. The angular separation between two b jets is directly sensitive to higher order contributions. In addition, the measurement does not depend strongly on fragmentation models or on the experimental luminosity and efficiency, which lead to a large uncertainty in measurements of the inclusive cross section. At the Tevatron, b{bar b} quark pairs are predominantly produced through the strong interaction. In leading order QCD, the b quarks are produced back to back in phase space. Next-to-leading order contributions involving a third particle in the final state allow production of b pairs that are very close together in …

In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, …

Capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) are widely used analytical separation techniques with many applications in chemical, biochemical, and biomedical sciences. Conventional analyte identification in these techniques is based on retention/migration times of standards; requiring a high degree of reproducibility, availability of reliable standards, and absence of coelution. From this, several new information-rich detection methods (also known as hyphenated techniques) are being explored that would be capable of providing unambiguous on-line identification of separating analytes in CE and HPLC. As further discussed, a number of such on-line detection methods have shown considerable success, including Raman, nuclear magnetic resonance (NMR), mass spectrometry (MS), and fluorescence line-narrowing spectroscopy (FLNS). In this thesis, the feasibility and potential of combining the highly sensitive and selective laser-based detection method of FLNS with analytical separation techniques are discussed and presented. A summary of previously demonstrated FLNS detection interfaced with chromatography and electrophoresis is given, and recent results from on-line FLNS detection in CE (CE-FLNS), and the new combination of HPLC-FLNS, are shown.

Homogeneous charge compression ignition (HCCI) engines are being considered as an alternative to diesel engines. The HCCI concept involves premixing fuel and air prior to induction into the cylinder (as is done in current spark-ignition engine) then igniting the fuel-air mixture through the compression process (as is done in current diesel engines). The combustion occurring in an HCCI engine is fundamentally different from a spark-ignition or Diesel engine in that the heat release occurs as a global autoignition process, as opposed to the turbulent flame propagation or mixing controlled combustion used in current engines. The advantage of this global autoignition is that the temperatures within the cylinder are uniformly low, yielding very low emissions of oxides of nitrogen (NO{sub x}, the chief precursors to photochemical smog). The inherent features of HCCI combustion allows for design of engines with efficiency comparable to, or potentially higher than, diesel engines. While HCCI engines have great potential, several technical barriers exist which currently prevent widespread commercialization of this technology. The most significant challenge is that the combustion timing cannot be controlled by typical in-cylinder means. Means of controlling combustion have been demonstrated, but a robust control methodology that is applicable to the entire range …

Dielectric reflectors that are periodic in one or two dimensions, also known as 1D and 2D photonic crystals, have been widely studied for many potential applications due to the presence of wavelength-tunable photonic bandgaps. However, the unique optical behavior of photonic crystals is based on theoretical models of perfect analogues. Little is known about the practical effects of dielectric imperfections on their technologically useful optical properties. In order to address this issue, a finite-difference time-domain (FDTD) code is employed to study the effect of three specific dielectric imperfections in 1D and 2D photonic crystals. The first imperfection investigated is dielectric interfacial roughness in quarter-wave tuned 1D photonic crystals at normal incidence. This study reveals that the reflectivity of some roughened photonic crystal configurations can change up to 50% at the center of the bandgap for RMS roughness values around 20% of the characteristic periodicity of the crystal. However, this reflectivity change can be mitigated by increasing the index contrast and/or the number of bilayers in the crystal. In order to explain these results, the homogenization approximation, which is usually applied to single rough surfaces, is applied to the quarter-wave stacks. The results of the homogenization approximation match the FDTD results …

In this dissertation, we present the results of a time-dependent angular analysis of B_s → J/ΨΦ decays performed with the use of initial-state flavor tagging. CP violation is observed in this mode through the interference of decay without net mixing and decay with net mixing, that is, B_s → J/ΨΦ and B_s → $\bar{B}$_s → J/ΨΦ . The time-dependent angular analysis is used to extract the decay widths of the heavy and light B_s eigenstates and the difference between these decay widths ΔΓ_s {triple_bond} Γ_s^L-Γ_s^H. Initial-state flavor tagging is used to determine the matter-antimatter content of the B_s mesons at production time. We combine flavor tagging with the angular analysis, which statistically determines the contributions of the CP-even and CP-odd components at decay time, to measure the CP-violating phase β_s. The phase β_s is expressed in terms of elements of the Cabibbo-Kobayashi-Maskawa matrix as β_s {triple_bond} arg (-V_tsV*_tb/V_csV*_cb), and is predicted by the Standard Model to be close to zero, β_s^SM = 0.02. In the measurement of ΔΓ_s, we use a dataset corresponding to 1.7 fb^-1 of luminosity, collected at the CDF experiment from proton-antiproton collisions at a center of mass energy √s = 1.96 TeV. In the measurement of …

Surface shape control techniques are applied to many diverse disciplines, such as adaptive optics, noise control, aircraft flutter control and satellites, with an objective to achieve a desirable shape for an elastic body by the application of distributed control forces. Achieving the desirable shape is influenced by many factors, such as, actuator locations, sensor locations, surface precision and controller performance. Building prototypes to complete design optimizations or controller development can be costly or impractical. This shortfall, puts significant value in developing accurate modeling and control simulation approaches. This thesis focuses on the field of adaptive optics, although these developments have the potential for application in many other fields. A static finite element model is developed and validated using a large aperture interferometer system. This model is then integrated into a control model using a linear least squares algorithm and Shack-Hartmann sensor. The model is successfully exercised showing functionality for various wavefront aberrations. Utilizing a verified model shows significant value in simulating static surface shape control problems with quantifiable uncertainties. A new dynamic model for a seven actuator deformable mirror is presented and its accuracy is proven through experiment. Bond graph techniques are used to generate the state space model of …

Over the last ten years, photonic band gap (PBG) theory and technology have become an important area of research because of the numerous possible applications ranging from high-efficiency laser diodes to optical circuitry. This research concentrates on reducing the length scale in the fabrication of layered photonic band gap structures and developing procedures to improve processing consistency. Various procedures and materials have been used in the fabrication of layered PBG structures. This research focused on an economical micro transfer molding approach to create the final PBG structure. A poly dimethylsiloxane (PDMS) rubber mold was created from a silicon substrate. It was filled with epoxy and built layer-by-layer to create a 3-D epoxy structure. This structure was infiltrated with nanoparticle titania or a titania sol-gel, then fired to remove the polymer mold, leaving a monolithic ceramic inverse of the epoxy structure. The final result was a lattice of titania rolds that resembles a face-centered tetragonal structure. The original intent of this research was to miniaturize this process to a bar size small enough to create a photonic band gap for wavelengths of visible electro-magnetic radiation. The factor limiting progress was the absence of a silicon master mold of small enough dimensions. …

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 …

The first proposal for plasma based accelerators was suggested by 1979 by Tajima and Dawson. Since then there has been a tremendous progress both theoretically and experimentally. The theoretical progress is particularly due to the growing interest in the subject and to the development of more accurate numerical codes for the plasma simulations (especially particle-in-cell codes). The experimental progress follows from the development of multi-terawatt laser systems based on the chirped-pulse amplification technique. These efforts have produced results in several experiments world-wide, with the detection of accelerated electrons of tens of MeV. The peculiarity of these advanced accelerators is their ability to sustain extremely large acceleration gradients. In the conventional radio frequency linear accelerators (RF linacs) the acceleration gradients are limited roughly to 100 MV/m; this is partially due to breakdown which occurs on the walls of the structure. The electrical breakdown is originated by the emission of the electrons from the walls of the cavity. The electrons cause an avalanche breakdown when they reach other metal parts of the RF linacs structure.

This thesis presents evidence for the B**{sup 0} and {Sigma}{sub b}{sup (*){+-}} hadrons in proton-antiproton collisions at a center of mass energy of 1.96 TeV, using data collected by the Collider Detector at Fermilab. In the search for B**{sup 0} {yields} B{sup {+-}} {pi}{sup {-+}}, two B{sup {+-}} decays modes are reconstructed: B{sup {+-}} {yields} J/{Upsilon}K{sup {+-}}, where J/{Upsilon} {yields} {mu}{sup +}{mu}{sup -}, and B{sup {+-}} {yields} {bar D}{sup 0}{pi}{sup {+-}}, where {bar D}{sup 0} {yields} K{sup {+-}} {pi}{sup {+-}}. Both modes are reconstructed using 370 {+-} 20 pb{sup -1} of data. Combining the B{sup {+-}} meson with a charged pion to reconstruct B**{sup 0} led to the observation and measurement of the masses of the two narrow B**{sup 0} states, B{sub 1}{sup 0} and B*{sub 2}{sup 0}, of m(B{sub 1}{sup 0}) = 5734 {+-} 3(stat.) {+-} 2(syst.) MeV/c{sup 2}; m(B*{sub 2}{sup 0}) = 5738 {+-} 5(stat.) {+-} 1(syst.) MeV/c{sup 2}. In the search for {Sigma}{sub b}{sup (*){+-}} {yields} {Lambda}{sub b}{sup 0}{pi}{sup {+-}}, the {Lambda}{sub b}{sup 0} is reconstructed in the decay mode {Lambda}{sub b}{sup 0} {yields} {Lambda}{sub c}{sup +}{pi}{sup -}, where {Lambda}{sub c}{sup +} {yields} pK{sup -} {pi}{sup +}, using 1070 {+-} 60 pb{sup -1} of data. Upon combining …

The focus of this thesis was first to characterize and improve the applicability of Fe(III) and Bi(V) doped PbO{sub 2} film electrodes for use in anodic O-transfer reactions of toxic and waste organic compounds, e.g. phenol, aniline, benzene, and naphthalene. Further, they investigated the use of alternative solution/electrode interfacial excitation techniques to enhance the performance of these electrodes for remediation and electrosynthetic applications. Finally, they have attempted to identify a less toxic metal oxide film that may hold promise for future studies in the electrocatalysis and photoelectrocatalysis of O-transfer reactions using metal oxide film electrodes.

The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performance both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol …

This dissertation reports on measurements of inclusive cross sections times branching fractions into electrons for W and Z bosons produced in p{anti p} collisions at {radical}s = 1.8 TeV. From an integrated luminosity of 84.5 pb{sup {minus}1} recorded in 1994--1995 by the D0 detector at the Fermilab Tevatron {Lambda} the cross sections are measured to be {sigma}p{anti p} {r_arrow} W + X {center_dot} B(W {r_arrow} e{nu}) = 2,310 {+-} 10 (stat) {+-} 50 (Syst) {+-} 100 (lum) pb and {sigma}(p{anti p} {r_arrow} Z + X) {center_dot} B(Z {r_arrow} ee) = 221 {+-} 3 (stat) {+-} 4 (Syst) {+-} 10 (lum) pb. The cross section ratio R is determined to be {sigma}(p{anti p} {r_arrow} W + X) {center_dot} B(W {r_arrow} e{nu})/{sigma}(p{bar p} {r_arrow} Z + X) {center_dot} B(Z {r_arrow} ee) = 10.43 {+-} 0.15 (stat) {+-} 0.20 (syst) {+-} 0.10 (NLO){Lambda} and R is used to determine B(W {r_arrow} e{nu}) = 0.1044 {+-} 0.0015 (stat) {+-} 0.0020 (syst) {+-} 0.0017 (theory) {+-} 0.0010 (NLO){Lambda} and {Lambda}{sub W} = 2.169 {+-} 0.031 (stat) {+-} 0.042 (syst) {+-} 0.041 (theory) {+-} 0.022 (NLO) GeV. The latter is used to set a 95% confidence level upper limit on the partial decay width of the …

A process for the deposition of yttria stabilized zirconia (YSZ) films, on porous substrates, has been developed. These films have possible applications as electrolyte membranes in fuel cells. The films were deposited from colloidal suspensions through the vacuum infiltration technique. Films were deposited on both fully sintered and partially sintered substrates. A critical cracking thickness for the films was identified and strategies are presented to overcome this barrier. Green film density was also examined, and a method for improving green density by changing suspension pH and surfactant was developed. A dependence of film density on film thickness was observed, and materials interactions are suggested as a possible cause. Non-shorted YSZ films were obtained on co-fired substrates, and a cathode supported solid oxide fuel cell was constructed and characterized.

The work presented here is the first measurement of the fraction of top quark pair production through gluon-gluon fusion. We use an integrated luminosity of 0.96 {+-} 0.06 fb{sup -1} of p{bar p} collisions at {radical}s of 1.96 TeV collected by the CDF II detector. We select t{bar t} candidates by identifying a high-p{sub T} lepton candidate, a large missing E{sub T} as evidence for a neutrino candidate and at least four high E{sub T} jets, one of which has to be identified as originating from a b quark. The challenge is to discriminate between the two production processes with the identical final state, gg {yields} t{bar t} and q{bar q} {yields} t{bar t}. We take advantage of the fact that compared to a quark, a gluon is more likely to radiate a low momentum gluon and therefore, one expects a larger number of charged particles with low p{sub T} in a process involving more gluons. Given the large uncertainties associated with the modeling of the low p{sub T} charged particle multiplicity, a data-driven technique was employed. Using calibration data samples, we show there exists a clear correlation between the observed average number of low p{sub T} charged particles and …

The Cryogenic Dark Matter Search (CDMS) experiment is designed to search for dark matter in the form of the Weakly Interacting Massive Particles (WIMPs). For this purpose, CDMS uses detectors based on crystals of Ge and Si, operated at the temperature of 20 mK, and providing a two-fold signature of an interaction: the ionization and the athermal phonon signals. The two signals, along with the passive and active shielding of the experimental setup, and with the underground experimental sites, allow very effective suppression and rejection of different types of backgrounds. This dissertation presents the commissioning and the results of the first WIMP-search run performed by the CDMS collaboration at the deep underground site at the Soudan mine in Minnesota. We develop different methods of suppressing the dominant background due to the electron-recoil events taking place at the detector surface and we apply these algorithms to the data set. These results place the world's most sensitive limits on the WIMP-nucleon spin-independent elastic-scattering cross-section. Finally, they examine the compatibility of the supersymmetric WIMP-models with the direct-detection experiments (such as CDMS) and discuss the implications of the new CDMS result on these models.

Alkali metal aluminohydrides have high potential as solid hydrogen storage materials. They have been known for their irreversible dehydrogenation process below 100 atm until Bogdanovic et al succeeded in the re-hydrogenation of NaAlH{sub 4} below 70 atm. They achieved 4 wt.% H{sub 2} reversible capacity by doping NaAlH{sub 4} with Ti and/or Fe organo-metallic compounds as catalysts. This suggests that other alkali and, possibly alkaline earth metal aluminohydrides can be used for reversible hydrogen storage when modified by proper dopants. In this research, Zr{sub 27}Ti{sub 9}Ni{sub 38}V{sub 5}Mn{sub 16}Cr{sub 5}, LaNi{sub 4.85}Sn{sub 0.15}, Al{sub 3}Ti, and PdCl{sub 2} were combined with LiAlH{sub 4} by ball-milling to study whether or not LiAlH{sub 4} is capable to both absorb and desorb hydrogen near ambient conditions. X-ray powder diffraction, differential thermal analysis, and scanning electron microscopy were employed for sample characterizations. All four compounds worked as catalysts in the dehydrogenation reactions of both LiAlH{sub 4} and Li{sub 3}AlH{sub 6} by inducing the decomposition at lower temperature. However, none of them was applicable as catalyst in the reverse hydrogenation reaction at low to moderate hydrogen pressure.

The goal of this thesis is to develop a new Channel Interface device for the MPICH Implementation of the MPI (Message Passing Interface) standard using MP{_}Lite. MP{_}Lite is a lightweight message-passing library that is not a full MPI implementation, but offers high performance MPICH (Message Passing Interface CHameleon) is a full implementation of the MPI standard that has the p4 library as the underlying communication device for TCP/IP networks. By integrating MP{_}Lite as a Channel Interface device in MPICH, a parallel programmer can utilize the full MPI implementation of MPICH as well as the high bandwidth offered by MP{_}Lite. There are several layers in the MPICH library where one can tie a new device. The Channel Interface is the lowest layer that requires very few functions to add a new device. By attaching MP{_}Lite to MPICH at the lowest level, the Channel Interface, almost all of the performance of the MP{_}Lite library can be delivered to the applications using MPICH. MP{_}Lite can be implemented either as a blocking or a non-blocking Channel Interface device. The performance was measured on two separate test clusters, the PC and the Alpha miniclusters, having Gigabit Ethernet connections. The PC cluster has two 1.8 GHz …

Summary and Conclusions - It was shown that segmentation and pulse-shape discrimination can improve the discovery sensitivity of a next-gen 0vBB-decay experiment by 90%. - However, when practical aspects are considered (such as instrumenting each segment with front-end electronics), the discovery sensitivity is decreased by 19%. - This has extremely important consequences to proposed next-gen experiments since the two active collaborations have strongly advocated the use of segmented detectors for all or part of the experiment. - New germanium detector technology, currently under development, has demonstrated excellent multi-site background rejection capabilities without the complexity of segmentation or complicated PSD algorithms. - The physically-segmented p-type germanium detector technology has proven to be a useful and practical tool in modern nuclear physics. The PSEG technology deserves further development as it has the potential for use in a variety of applications.

In a cellular array, a range of primary spacing is found to be stable under given growth conditions. Since a strong coupling of solute field exists between the neighboring cells, primary spacing variation should also influence other microstructure features such as cell shape and cell length. The existence of multiple solutions is examined in this study both theoretically as well as experimentally. A theoretical model is developed that identifies and relates four important microstructural lengths, which are found to be primary spacing, tip radius, cell width and cell length. This general microstructural relationship is shown to be valid for different cells in an array as well as for other cellular patterns obtained under different growth conditions. The unique feature of the model is that the microstructure correlation does not depend on composition or growth conditions since these variables scale microstructural lengths to satisfy the relationship obtained in this study. Detailed directional solidification experimental studies have been carried out in the succinonitrile-salol system to characterize and measure these four length scales. Besides the validation of the model, experimental results showed additional scaling laws to be present. In the regime where only a cellular structure is formed, the shape of the cell, …

We have used the Collider Detector at Fermilab (CDF-II) to set upper limits on the branching ratio of the flavor-changing neutral-current (FCNC) top quark decay t {yields} Zc using a technique employing ratios of W and Z production, measured in 1.52 fb{sup -1} of p{bar p} data. The analysis uses a comparison of two decay chains, p{bar p} {yields} t{bar t} {yields} WbWb {yields} {ell}{nu}bjjb and p{bar p} {yields} t{bar t} ZcWb {yields} {ell}{sup +}{ell}{sup -} cjjb, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the MC modeling of acceptance and efficiency for lepton identification over the multi-year dataset also using a ratio of W and Z production, in this case the observed ratio of inclusive production of W to Z-bosons, a technique that will be essential for precision comparisons with the standard model at the LHC. We introduce several methods of determining backgrounds to the W and Z samples. To improve the discrimination against SM backgrounds to top quark decays, we calculate the top mass for each event with two leptons and four jets assuming it is a t{bar t} event with one of the top quarks decaying to Zc. The upper limit on the Br(t …

Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95}, and to evaluate whether they could be used to produce dense, constrained Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} films at temperatures below 1000 C. To find the optimal sintering aid, Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800 C--a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aid's effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O1.95 indicated that …