High voltage RF systems are used to accelerate proton beams for nuclear physics experiments. The acceleration process shapes the proton beam into a train of narrow pulses with the same period as the RF. This bunched beam structure is used to separate and identify secondary particles that are produced when the proton beam is directed at a "target". An RF controller for a system that separates secondary particles was built. Control of high power RF cavities that operate near resonance is discussed. The emphasis is on developing a control model for resonant systems and building a control system based on hardware and software modules that can be easily configured for different RF systems. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This dissertation is focused on three lines of work. In the first part, we consider aspects of holography and gauge/gravity duality in lower and higher dimensions. In particular, we study the duality for exact solutions localized on the Randal-Sundrum 2-branes. We also test if some holographic principles in general relativity can be generalized to include higher derivative theories of gravity; namely Lovelock gravity. In the second part we consider the role of pseudo Nambu-Goldstone bosons (pNGBs) in inflationary cosmology. Specifically, we construct an inflationary model using string theory axions, and use these pNGBs to produce the observed coherent magnetic field in the Universe. The third part of the thesis is devoted to the study of the phenomenology of emergent phenomena. We investigated whether one could test if diffeomorphism invariance, the sacred symmetry of general relativity, is emergent. We also construct a new minimal vectorial Standard Model, and argue that the absence of mirror particles predicted by this model can give us a hint about the fundamental nature of space.

Experiment E143 at SLAC performed deep-inelastic scattering measurements with polarized electrons incident on polarized protons and deuterons. The data for the beam energy of 29 GeV cover the kinematical range of $x\sb{\rm Bj}>0.03$ and $1

We demonstrate how the heavy baryon method, previously applied to chiral perturbation theory calculations involving the interactions of nucleons and pions, can be generalized to include interactions with the first nucleon resonance--$\Delta$(1232). The formalism is developed in terms of a small scale $\delta$ expansion, which refers to soft momenta, the pion mass and the nucleon-delta mass splitting $\Delta$ = $M\sb{\Delta} - M\sb{N}$. First applications of this chiral theory are presented, in particular the calculation of mass and wavefunction renormalization, threshold neutral pion photoproduction, and forward Compton scattering.

In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function $g\sbsp{1}{n}(x,Q\sp2)$ of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized $\sp3$He target. The high beam energy allowed us to extend the kinematic coverage compared to the previous SLAC experiments to $0.014\leq x\leq0.7$ with an average $Q\sp2$ of 5 GeV$\sp2.$ We report the integral of the spin dependent structure function in the measured range to be $\int\sbsp{0.014}{0.7}dx\ g\sbsp{1}{n}(x,5\ {\rm GeV}\sp2)={-}0.036\pm0.004({\rm stat}.)\pm0.005({\rm syst}.).$ We observe relatively large values of $g\sbsp{1}{n}$ at low x that call into question the reliability of data extrapolation to $x\to0.$ Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. We perform a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions $g\sbsp{1}{p}$ and $g\sbsp{1}{n}$ paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, we evolve the data to $Q\sp2$ = 5 GeV$\sp2,$ determine the first moments of the polarized structure functions of the proton and neutron, and find agreement with the Bjorken sum rule.

Experiment E690 at Fermilab recorded 5.5 billion $p + p \to p + X$ events using an 800 GeV/c proton beam and a liquid hydrogen target, during the 1991 fixed target run. We use a 0.5 billion subset of this sample, to study the reaction $p + p \to p\sb{s}(\pi\sp+\pi\sp-)p\sb{f}$ for dipion invariant mass between threshold and 2.3 GeV/c$\sp2.$ We perform a partial wave analysis for dipion invariant mass between threshold and 1.5 GeV/c$\sp2.$ The assumption of S-wave dominance near threshold is sufficient to determine a single, continuous solution throughout the considered mass spectrum. Precision measurement of the production amplitude aids the mapping the low lying meson spectrum. Other possible studies using this data sample and analysis technique are: (1) the extension of the amplitude analysis above the 1.5 GeV/c$\sp2$ mass region using a the full event sample, and (2) the study of the produced amplitudes as a function of the relative angle between the two proton planes.

Results are presented on a study of resonant structure in the $\omega\pi\sp0$ and $\omega\eta$ final states produced in $\pi\sp-p$ interactions at 18 GeV/c where $\omega\to \pi\sp+\pi\sp-\pi\sp0,\ \pi\sp0\to 2\gamma,$ and $\eta\to 2\gamma.$ Final states such as $\omega\pi\sp0$ and $\omega\eta,$ which contain a vector meson are allowed in the extended flux-tube model for the decay of hybrid mesons. For the $\omega\eta$ final state, the data exhibit the well-known $b\sb1$(1235) and $\rho\sb3$(1690) resonances. A one-pion exchange mechanism is clearly seen for the $\rho\sb3$(1690). The result of a partial wave analysis for the $\omega\eta$ final state finds a new $1\sp{+-}$ meson state $h\sb1$(1540) with a mass $M = 1542\pm 13$ MeV and a width $\Gamma = 285\pm 30$ MeV, which shows phase motion relative to the $\omega$(1600). The decay mode of $\omega(1600)\to \omega\eta$ has not been previously reported.

The ⁵¹V(p,n)⁵¹Cr reaction was studied at four different proton beam energies namely 90, 120, 160, and 200 MeV. The experiment was performed in the angular range between 0 and 4°, using the beam swinger facility at National Accelerator Centre(NAC) at Faure, near Cape Town. The cross sections of the ground state, Isobaric Analog State, and the giant Gamow-Teller resonance were calculated at 0° for each beam energy. The ratio of the cross section of the giant Gamow-Teller resonance to the cross section of the Isobaric Analog State were studied at beam energies 90, 120, 160 and 200 Me V, and beam angles 0, 2 and 4 °. The Gamow-Teller strength was estimated for energies 120, 160 and 200 MeV. The fractions of Fermi and Gamow-Teller strength in the Isobaric Analog State were also estimated.

archives@tulane.edu / A block copolymer (BCP) consists of two or more covalently-bound chemically distinct homopolymer blocks. These macromolecules have emerging applications in energy storage, membrane separations, and nanolithography stemming from their propensity to self-assemble into regular nanoscale structures. For a pure BCP, this self-assembly is dictated entirely by the polymer’s degree of polymerization (N), chemistry (χ), composition (f), and chain architecture. Blending together different types of these polymers provides a simpler, synthesis-free method for tuning nanoscale morphology and feature size. This dissertation describes the use of dissipative particle dynamic (DPD) simulation to develop a fundamental understanding of phase behavior in BCP/homopolymer and cyclic-linear BCP blends. Block copolymer-homopolymer blends offer a simple method for tuning nanostructure sizes to meet application-specific demands. We systematically investigated morphology and feature size in ternary blends of symmetric linear copolymers and their constituent homopolymers (A-b-B/A/B), finding a close match between simulation results and known experimental behavior. Having established DPD simulation as a valid model, we used the simulation results to explore the relationship between polymer chain length, molecular packing, and the degree of lamellar swelling with homopolymer addition in ternary blends. A consensus of theoretical and simulation work suggests that cyclic BCPs form features up to 40% smaller than their linear analogues - while also exhibiting superior thin film stability and assembly dynamics – making them intriguing candidates for nanolithography. However, the complex syntheses required to produce these molecules mean that a need for pure cyclic BCPs would present a challenge to large-scale manufacturing. Thus, we aspired to understand the self-assembly of cyclic-linear copolymer blends. We first combined DPD simulation results and strong segregation theory to develop a scaling prediction for neat BCP feature size based on experimentally-tunable parameters (χ, N, f, and polymer architecture). The resulting Revised Scaling Law quantitatively predicts domain spacings over a wide range of BCP chain lengths, segregation strengths, and compositions and offers an explanation for the significant discrepancies between prior theoretical predictions and experimental results of cyclic BCP feature size. Next, we investigated the dimensions and interfacial roughness of nanofeatures formed by cyclic-linear BCP blends. For mixtures of symmetric cyclic and linear polymers of equivalent N, up to 10% synthetic impurity had minimal impact on cyclic BCP feature dimensions. On the other hand, we found that adding small amounts of cyclic BCP was an effective method for “fine-tuning” linear BCP feature sizes. We also analyzed our simulated blend domain spacings in the context of the revised scaling law, and found deviations between simulation and theory that arose from molecular-level packing motifs not included in theory. Finally, we investigated the impact of blending polymer architectures on the BCP order-disorder transition, finding that a mismatch in molecular size and architecture can strongly inhibit ordering. These insights into blend self-assembly will assist experimentalists in the rational design of BCP materials for advanced nanolithography applications. / 1 / Amy Dubetz Goodson

Bibliography: p. 221-225. / The deep inelastic scattering of leptons off a proton in the statistical model is considered. The interior of the nucleon is viewed as a thermalized assembly of up and down quarks and gluons. This enables the incorporation of features which are absent in the parton model. These include the presence of identical quarks and gluons in initial and final states and of quantum statistical correlations which have a role to play in the propagation of particles when considering Feynman diagrams containing internal lines in next-to-leading-order calculations. These features are incorporated through the use of Fermi-Dirac and Bose-Einstein distributions for quarks and gluons, respectively. Stimulated emission factors for final-state gluons and Pauli-blocking factors for final-state quarks are incorporated. The propagation of particles through a many-body medium is taken into account by using thermal Feynman rules for propagators and vertices. The statistical model could also be seen as an attempt to describe the interior of the nucleon at a more fundamental level than that attained through the use of arbitrary parton distributions containing many parameters in the parton model.