Left unprotected, both transmissive and reflective final optics in a laser-driven inertial fusion power plant would quickly fail from melting, pulsed thermal stress, or degradation of optical properties as a result of ion implantation. One potential option for mitigating this threat is to magnetically deflect the ions such that they are directed to a robust energy dump. In this paper we detail integrated studies that have been carried out to assess the viability of this approach for protecting final optics.

The authors present a measurement of B({pi}{sup 0} {yields} e{sup +}e{sup -}{gamma})/B({pi}{sup 0} {yields} {gamma}{gamma}) using data taken in 1999 by the E832 KTeV experiment at Fermilab. The {pi}{sup 0}s were produced by K{sub L} decays in flight that are fully reconstructed. They find 63,693 K{sub L} {yields} 3{pi}{sup 0} {yields} {gamma}{gamma} {gamma}{gamma} e{sup +}e{sup -}{gamma} decays in KTeV data (an increase of a factor of {approx} 20 in event statistics over previous experiments), and normalize to K{sub L} {yields} 3{pi}{sup 0} {yields} 6{gamma}, to extract B({pi}{sup 0} {yields} e{sup +}e{sup -}{gamma}, m{sub e{sup +}e{sup -}} > 15 MeV/c{sup 2})/B({pi}{sup 0} {yields} {gamma}{gamma}) = (3.920 {+-} 0.016 {+-} 0.036) x 10{sup -3}, where the first error is statistical and the second is systematic. Using the Mikaelian and Smith prediction for the e{sup +}e{sup -} mass spectrum as implemented in the KTeV Monte Carlo to correct to the full e{sup +}e{sup -} mass range yields B({pi}{sup 0} {yields} e{sup +}e{sup -}{gamma})/B({pi}{sup 0} {yields} {gamma}{gamma}) = (1.1559 {+-} 0.0046 {+-} 0.0107)%. This result is consistent with previous measurements and with theoretical predictions, and the uncertainty is a factor of three smaller than any previous measurement.

This dissertation consists of two closely related parts: theory development and coding of correlation effects in a model potential for solvation, and study of solvent effects on chemical reactions and processes. The effective fragment potential (EFP) method has been re-parameterized, using density functional theory (DFT), more specifically, the B3LYP functional. The DFT based EFP method includes short-range correlation effects; hence it is a first step in incorporating the treatment of correlation in the EFP solvation model. In addition, the gradient of the charge penetration term in the EFP model was derived and coded. The new method has been implemented in the electronic structure code GAMESS and is in use. Formulas for the dynamic dipole polarizability, C{sub 6} dispersion coefficient and dispersion energy were derived and coded as a part of a treatment of the dispersion interactions in the general solvation model, EFP2. Preliminary results are in good agreement with experimental and other theoretical data. The DFT based EFP (EFP1/DFT) method was used in the study of microsolvation effects on the S{sub N}2 substitution reaction, between chloride and methyl bromide. Changes in the central barrier, for several lowest lying isomers of the systems with one, two, three and four waters, were …

Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation(ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis. In this work, ECAR was shown to effectively reduce 550 - 580 mu g=L arsenic (including both As[III]and As[V]in a 1:1 ratio) to below the WHO recommended maximum limit of 10 mu g=L in synthetic Bangladesh groundwater containing relevant concentrations of competitive ions such as phosphate, silicate, and bicarbonate. Arsenic removal capacity was found to be approximately constant within certain ranges of current density, but was found to change substantially between ranges. In order of decreasing arsenic removal capacity, the pattern was: 0.02 mA=cm2> 0.07 mA=cm2> 0.30 - 1.1 mA=cm2> 5.0 - 100 mA=cm2. Current processing time was found to effect arsenic removal capacity independent of either charge density or current density. Electrode polarization studies showed no passivation of the electrode in the tested range (up to current density 10 mA=cm2) and ruled out oxygen …

A measurement of the top quark mass in p{bar p} collisions at {radical}s = 1.96 TeV is presented. The analysis uses a template method, in which the overconstrained kinematics of the Lepton+Jets channel of the t{bar t} system are used to measure a single quantity, the reconstructed top quark mass, that is strongly correlated with the true top quark mass. in addition, the dijet mass of the hadronically decaying W boson is used to constrain in situ the uncertain jet energy scale in the CDF detector. Two-dimensional probability density functions are derived using a kernel density estimate-based machinery. Using 1.9 fb{sup -1} of data, the top quark mass is measured to be 171.8{sub -1.9}{sup +1.9}(stat.) {+-} 1.0(syst.)GeV/c{sup 2}.

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This work is a theoretical investigation on the physical properties of semiconductor-based two-dimensional photonic crystals, in particular for what concerns systems embedded in planar dielectric waveguides (GaAs/AlGaAs, GaInAsP/InP heterostructures, and self-standing membranes) or based on macro-porous silicon. The photonic-band structure of photonic crystals and photonic-crystal slabs is numerically computed and the associated light-line problem is discussed, which points to the issue of intrinsic out-of-lane diffraction losses for the photonic bands lying above the light line. The photonic states are then classified by the group theory formalism: each mode is related to an irreducible representation of the corresponding small point group. The optical properties are investigated by means of the scattering matrix method, which numerically implements a variable-angle-reflectance experiment; comparison with experiments is also provided. The analysis of surface reflectance proves the existence of selection rules for coupling an external wave to a certain photonic mode. Such rules can be directly derived from symmetry considerations. Lastly, the control of wave propagation in weak-index contrast photonic-crystal slabs is tackled in view of designing building blocks for photonic integrated circuits. The proposed designs are found to comply with the major requirements of low-loss propagation, high and single-mode transmission. These notions are then collected …

The FOCUS experiment is designed to investigate charm particle decays. These charm particles are produced by the interaction of a photon beam with an average energy of 175 GeV on a BeO target and travel an average of few millimeters before decaying in the spectrometer. By reconstructing the daughters from the decay, we can infer properties of the charm particles. Semileptonic decays have been used to measure many CKM matrix elements. These decays are interesting due to the simplicity of their theoretical description but they are experimentally challenging due to the fact that a neutrino is not detected. Analysis of semileptonic decays in the charm sector are of great interest because they provide an excellent environment to test and to calibrate theoretical calculation that can be implemented in the determination of poorly known matrix elements such as V{sub ub}. In this thesis we report an analysis of the decays D{sup 0} {yields} {pi}{sup -}{mu}{sup +}{nu} and D{sup 0} {yields} K{sup -} {mu}{sup +}{nu}. We measure the relative branching ratio as well as the ratio of the form factors f{sub +}{sup {pi}}(0)/f{sub +}{sup K}(0). Using a weighting technique, we further report a parametric analysis of the q{sup 2} dependence for both …

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We calculate the exclusion region in the parameter space of {nu}{sub {mu}} {yields} {nu}{sub e} oscillations of the LSND type using a combined fit to the reconstructed energy distributions of neutrino candidate samples from the MiniBooNE data obtained with two different particle identification methods. The two {nu}{sub e} candidate samples are included together with a high statistics sample of {nu}{sub {mu}} events in the definition of a {chi}{sup 2} statistic which includes the correlations between the energy intervals of all three samples and handles the event overlap between the {nu}{sub e} samples. The {nu}{sub {mu}} sample is introduced to constrain the effect of systematic uncertainties. This analysis increases the exclusion limit in the region {Delta}m{sup 2} {approx}< 1eV{sup 2} when compared with the result previously published by the collaboration, which used a different technique.

This dissertation reports on a study of search for an orbitally excited state of charmed baryons {Sigma}{sub c}{sup 0}(2800) and {Sigma}{sub c}{sup ++}(2800). They measure the widths, momentum spectrum and production cross-section for these states decaying into a {Lambda}{sub c}{sup +} and a charged {pi}. The analysis uses 230 fb{sup -1} of data collected at BABAR detector operating at PEP-II collider at Stanford Linear Accelerator Center. The data is collected in the region of {Upsilon}(4S) an {approx} 40 MeV below the resonance. {Lambda}{sub c}{sup +} baryon is reconstructed in the decay mode pK{sup -}{pi}{sup +}. The {Sigma}{sub c}(2800) baryon production at continuum is observed to be quite significant for x{sub p} > 0.7, where x{sub p} = p/{radical}E{sup 2}+M{sup 2} is the scaled momentum and varies from 0.0 to 1.0. The momentum spectrum is measured by considering the corrected yield for momentum bins above x{sub p} > 0.5 and can be parameterized very well by a Peterson function, given by: dN/dx{sub p} {proportional_to} 1/x{sub p}(1 - 1/x{sub p} - {epsilon}/1-x{sub p}){sup 2}. The values for the peterson parameter {epsilon}, are found to be 0.050 {+-} 0.010 for {Sigma}{sub c}{sup 0}(2800) and 0.057 {+-} 0.012 for {Sigma}{sub c}{sup ++}(2800). They use …

The family of R{sub 5}Si{sub x}Ge{sub 4-x} alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R{sub 5}Si{sub x}Ge{sub 4-x} systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R{sub 5}Si{sub x}Ge{sub 4-x} systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb{sub 5}Si{sub x}Ge{sub 4-x} and Sm{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys with 0 {le} x {le} 4 have been examined by using single crystal and powder x-ray …

This dissertation describes a measurement of the rate of associated production of the W boson with the charm jet in the proton and anti-proton collisions at the center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. The measurement has direct sensitivity to the strange quark content inside the proton. A direct measurement of the momentum distribution of the strange quark inside the proton is essential for a reliable calculation of new physics signal as well as the background processes at the collider experiments. The identification of events containing a W boson and a charm jet is based on the leptonic decays of the W boson together with a tagging technique for the charm jet identification based on the semileptonic decay of the charm quark into the muon. The charm jet recoiling against the W boson must have a minimum transverse momentum of 20 GeV and an absolute value of pseudorapidity less than 2.5. This measurement utilizes the data collected by the D0 detector at the Fermilab Collider. The measured rate of the charm jet production in association with the W boson in the inclusive jet production with the W boson is 0.074 {+-} 0.023, which is in agreement with …

This thesis is concerned with both the application and the extension of quantum chemical methods. Each chapter of the thesis represents a paper that has been published in or will be submitted to a scientific journal. The first three chapters of this thesis describe contributions made to chemistry through the use of quantum chemical methods, while the final two chapters illustrate the development of new methods. Chapter 2 and Chapter 3 characterize a study of the electronic structure and magnetic properties of homodinuclear titanium(III) complexes, in order to determine trends related to their potential use as molecular magnets. Chapter 2 focuses on hydride and halide bridging and terminal ligands, while Chapter 3 explores bridging ligands from other groups in the periodic table. Chapter 4 portrays a study of the solvation of glycine. Microsolvation and continuum solvation approaches are investigated in order to study the structures of small glycine-water clusters and determine the energy difference between the zwitterionic and nonionized forms of glycine, the simplest amino acid. Chapters 5 and 6 describe the implementation of analytic gradients, which are required for efficient molecular geometry optimizations, for two open-shell second-order perturbation theory methods. Chapter 5 discusses gradients for unrestricted Moeller-Plesset perturbation theory, …

This thesis consists of two parts: In the first part we describe the Photomultiplier Tube (PMT) selection and testing processes for the Hadronic Forward (HF) calorimeter of the CMS, a Large Hadron Collier (LHC) experiment at CERN. We report the evaluation process of the candidate PMTs from three different manufacturers, the complete tests performed on the 2300 Hamamatsu PMTs which will be used in the HF calorimeter, and the details of the PMT Test Station that is in University of Iowa CMS Laboratories. In the second part we report the {Xi}{sub c}{sup +} lifetime measurement from SELEX, the charm hadro-production experiment at Fermilab. Based upon 301 {+-} 31 events from three di.erent decay channels, by using the binned maximum likelihood technique, we observe the lifetime of {Xi}{sub c}{sup +} as 427 {+-} 31 {+-} 13 fs.

The CDF experiment has searched for production of a third generation vector leptoquark (VLQ3) in the di-tau plus di-jet channel using 322 pb{sup -1} of Run II data. We review the production and decay theory and describe the VLQ3 model we have used as a benchmark. We study the analysis, including the data sample, triggers, particle identification, and event selection. We also discuss background estimates and systematic uncertainties. We have found no evidence for VLQ3 production and have set a 95% C.L. upper limit on the pair production cross section {sigma} to 344 fb, and exclude VLQ3 in the mass range m{sub VLQ3} > 317 GeV/c{sup 2}, assuming Yang-Mills couplings and Br(LQ3 {yields} b{tau}) = 1. If theoretical uncertainties on the cross section are taken into account, the results are {sigma} < 353 fb and m{sub VLQ3} > 303 GeV/c{sup 2}. For a VLQ3 with Minimal couplings, the upper limit on the cross section is {sigma} < 493 fb ({sigma} < 554 fb) and the lower limit on the mass is m{sub VLQ3} > 251 GeV/c{sup 2} (m{sub VLQ3} > 235 GeV/c{sup 2}) for the nominal (1{sigma} varied) theoretical expectation.

We are becoming dependent on energy more today than we were a century ago, and with increasing world population and booming economies, sooner or later our energy sources will be exhausted. Moreover, our economy and welfare strongly depends on foreign oil and in the shadow of political uncertainties, there is an urgent need for a reliable, safe, and cheap energy source. Thermonuclear fusion, if achieved, is that source of energy which not only will satisfy our demand for today but also for centuries to come. Today, there are two major approaches to achieve fusion: magnetic confinement fusion (MFE) and inertial confinement fusion (ICF). This dissertation explores the inertial confinement fusion using the fast ignition concept. Unlike the conventional approach where the same laser is used for compression and ignition, in fast ignition separate laser beams are used. This dissertation addresses three very important topics to fast ignition inertial confinement fusion. These are laser-to-electron coupling efficiency, laser-generated electron beam transport, and the associated isochoric heating. First, an integrated fast ignition experiment is carried out with 0.9 kJ of energy in the compression beam and 70 J in the ignition beam. Measurements of absolute K{sub {alpha}} yield from the imploded core revealed …

The computational part of the thesis is the investigation of titanium chloride (II) as a potential catalyst for the bis-silylation reaction of ethylene with hexaclorodisilane at different levels of theory. Bis-silylation is an important reaction for producing bis(silyl) compounds and new C-Si bonds, which can serve as monomers for silicon containing polymers and silicon carbides. Ab initio calculations on the steps involved in a proposed mechanism are presented. This choice of reactants allows them to study this reaction at reliable levels of theory without compromising accuracy. The calculations indicate that this is a highly exothermic barrierless reaction. The TiCl{sub 2} catalyst removes a 50 kcal/mol activation energy barrier required for the reaction without the catalyst. The first step is interaction of TiCl{sub 2} with ethylene to form an intermediate that is 60 kcal/mol below the energy of the reactants. This is the driving force for the entire reaction. Dynamic correlation plays a significant role because RHF calculations indicate that the net barrier for the catalyzed reaction is 50 kcal/mol. They conclude that divalent Ti has the potential to become an important industrial catalyst for silylation reactions. In the programming part of the thesis, parallelization of different quantum chemistry methods is …

The discovery that ultra-intense laser pulses (I > 10{sup 18} W/cm{sup 2}) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 10{sup 18} W/cm{sup 2}), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U{sub p} = ([1 + I{lambda}{sup 2}/1.3 x 10{sup 18}]{sup 1/2} - 1) m{sub o}c{sup 2}, where I{lambda}{sup 2} is the irradiance in W {micro}m{sup 2}/cm{sup 2} and m{sub o}c{sup 2} is the electron rest mass. At laser irradiance of I{lambda}{sup 2} {approx} 10{sup 20} W {micro}m{sup 2}/cm{sup 2}, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate …

The discovery that ultra-intense laser pulses (I > 10{sup 18} W/cm{sup 2}) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 10{sup 18} W/cm{sup 2}), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U{sub p} = ([1 + I{lambda}{sup 2}/1.3 x 10{sup 18}]{sup 1/2} - 1) m{sub o}c{sup 2}, where I{lambda}{sup 2} is the irradiance in W{micro}m{sup 2}/cm{sup 2} and m{sub o}c{sup 2} is the electron rest mass.At laser irradiance of I{lambda}{sup 2} {approx} 10{sup 20} W{micro}m{sup 2}/cm{sup 2}, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the …

Fatigue and wear in micron-scale polysilicon structural films can severely impact the reliability of microelectromechanical systems (MEMS). Despite studies on fatigue and wear behavior of these films, there is still an on-going debate regarding the precise physical mechanisms for these two important failure modes. Although macro-scale silicon does not fatigue, this phenomenon is observed in micron-scale silicon. It is shown that for polysilicon devices fabricated in the MUMPs foundry and SUMMiT process stress-lifetime data exhibits similar trends in ambient air, shorter lifetimes in higher relative humidity environments and no fatigue failure at all in high vacuum. Transmission electron microscopy of the surface oxides of the samples show an approximate four-fold thickening of the oxide at stress concentrations after fatigue failure, but no thickening after fracture in air or after fatigue cycling in vacuo. It is found that such oxide thickening and fatigue failure (in air) occurs in devices with initial oxide thicknesses of {approx}4-20 nm. Such results are interpreted and explained by a reaction layer fatigue mechanism; specifically, moisture-assisted subcritical cracking within a cyclic stress-assisted thickened oxide layer occurs until the crack reaches a critical size to cause catastrophic failure. Polysilicon specimens from the SUMMiT process are used to study …

Electromagnetic, thermal and structural analyses of radio-frequency (RF) cavities were performed as part of a developmental RF cavity program for muon cooling. RF cavities are necessary to provide longitudinal focusing of the muons and to compensate for their energy loss. Closing the cavity ends by electrically conducting windows reduces the power requirement and increases the on-axis electric field for a given maximum surface electric field. Many factors must be considered in the design of RF cavity windows. RF heating can cause the windows to deform in the axial direction of the cavity. The resulting thermal stresses in the window must be maintained below the yield stress of the window material. The out-of-plane deflection must be small enough so that the consequent frequency shift is tolerable. For example, for an 805 MHz cavity, the out-of-plane deflection must be kept below 25 microns to prevent the frequency of the cavity from shifting more than 10 kHz. In addition, the window design should yield smooth electric and magnetic fields, terminate field leakage beyond the window, and minimize beam scattering. In the present thesis, gridded-tube window designs were considered because of their high structural integrity. As a starting point in the analysis, a cylindrical …

Jefferson Lab kaon experiments E91016/E93018 produced data on both strangeness and vector meson electroproduction. The latter part of the experiments was focused on the electroproduction of the omega meson for momentum transfer Q 2 near 0.5 (GeV/c) 2. This reaction was selected from the inelastic ep channel, H-1 (e, e' p)X, by performing involved signal background separation. Tagging the omega meson production only on electron and proton not only introduced appreciable statistical error but also a sizeable systematic uncertainty due to the background removal. Nevertheless, the analysis yielded angular distributions of the differential cross section in the threshold regime extracted with an unprecedented granularity and relatively small errors.

CDF (Collider Detector at Fermilab) is a particle detector located at Fermi National Laboratories, near Chicago. it allows to study decay products of p{bar p} collisions at center-of-mass energy of 1.96 TeV. During its first period of data taking (RunI), CDF observed for the first time the top quark (1995). The current period of data taking (RunII) is devoted to precise measurements of top properties and to search for new physics. This thesis work is about the top decay channel named {tau} + jets. A t{bar t} pair decays in two W bosons and two b quarks. In a {tau} + jets event, one out of the two W decays into two jets of hadrons, while the other produces a {tau} lepton and a neutrino; the {tau} decays semileptonically in one or more charged and neutral pions while b quarks hadronize producing two jets of particles. Thus the final state of a {tau} + jets event has this specific signature: five jets, one {tau}-like, i.e. narrow and with low track multiplicity, two from b quarks, two from a W boson and a large amount of missing energy from two {tau} neutrinos. They search for this signal in 311 pb{sup -1} …