Digital Commons Network^™

Application Of Adaptive Optics To The Spectroscopic Investigation Of Small-Scale Solar Structures, Klaus Hartkorn

Dissertations

We study bright points, umbral dots and the G-band using a two-dimensional spectrometer and an Adaptive Optics system, which allows us to record high-resolution dopplergrams and residual intensity images. We find evidence that bright points are smaller than 120 km in diameter. Bright points are situated exclusively in regions of enhanced G-band brightness and do not show a change in their shape or a displacement in their position of more than 120 km horizontally over a height range from 0 km to 320 km above photospheric level T = 1. We do not find velocity differences of more than 100 …

The Babar Mini, Duncan Brown

Physics - All Scholarship

BaBar has recently deployed a new event data format referred to as the Mini. The Mini uses efficient packing and aggressive noise suppression to represent the average reconstructed BaBar event in under 7 KBytes. The Mini packs detector information into simple transient data objects, which are then aggregated into roughly 10 composite persistent objects per event. The Mini currently uses Objectivity persistence, and it is being ported to use Root persistence. The Mini contains enough information to support detailed detector studies, while remaining small and fast enough to be used directly in physics analysis. Mini output is customizable, allowing users …

Study Of Scalar Mesons And Related Radiative Decays, Joseph Schechter, Deirdre Black, Masayasu Harada

Physics - All Scholarship

After a brief review of the puzzling light scalar meson sector of QCD, a brief summary will be given of a paper concerning radiative decays involving the light scalars. There, a simple vector meson dominance model is constructed in an initial attempt to relate a large number of the radiative decays involving a putative scalar nonet to each other. As an application it is illustrated why a_0(980)-f_0(980) mixing is not expected to greatly alter the f_0/a_0 production ratio for radiative \phi decays.

Unlv Transmutation Research Program Proposal Year Iii: Design And Evaluation Of Processes For Fuel Fabrication, Georg F. Mauer

Fuels Campaign (TRP)

The objective of this project is the design and evaluation of manufacturing processes for transmuter fuel fabrication. The large-scale deployment of remote fabrication and refabrication processes will be required for all transmutation scenarios. Current program emphasis is on a five-year effort to determine the feasibility of transmutation as a technology to limit the need for repository storage of spent commercial fuel. The evaluation of the fabrication processes will create a decision support data base to document design, operations, and costs. Fabrication processes required for different fuel types differ in terms of equipment types, throughput, and cost. Differential cost Implications of …

Structure And Magnetic Properties Of Sputtered Hard/Soft Multilayer Magnets, W. Liu, Z.D. Zhang, J. Ping Liu, B.Z. Cui, X.K. Sun, J. Zhou, David J. Sellmyer

David Sellmyer Publications

The films with HM = (Pr,Dy)(Fe,Co,Nb,B) _5.5 and SM=Fe, FeCo were prepared by sputtering and subsequent heat treatment. The coercivity of Ti-buffered (Pr,Dy)(Fe,Co,Nb,B) _5.5 single-layer film with 320 nm thickness is as large as 18.8 kOe at room temperature. X-ray diffraction results reveal that the Pr₂Fe₁₄B-type phase is randomly oriented in almost all the multilayer films. For the multilayers of Ti(30 nm)/[HM(16 nm)Fe(x nm)]×20/Ti(30 nm)/Si(substrate), the remanence increases and the coercivity decreases with the addition of Fe content, in comparison with the results of the single-layer film and the maximum energy product of 14.8 MGOe is …

Exchange Through Nonmagnetic Insulating Matrix, Ralph Skomski, Arti Kashyap, Y. Quiang, David J. Sellmyer

David Sellmyer Publications

Exchange interactions between hard-magnetic particles in a nonmagnetic matrix are investigated by model calculations. A Landau–Ginzburg approach is developed to describe the net exchange interactions between spheres of arbitrary diameters. Introducing cylindrical coordinates and integrating over the surfaces of the adjacent spheres yields an exchange coupling which decreases with a decay length depending on interatomic exchange, intra-atomic exchange, and temperature. Typically, the decay length does not exceed a few interatomic distances. The decay is exponential but also contains a prefactor depending on the surface curvature of the grains. It increases with decreasing curvature, but this dependence is only a small …

Development Of Dose Coefficients For Radionuclides Produced In Spallation Neutron Sources, Phillip W. Patton

Transmutation Sciences Physics (TRP)

A research consortium comprised of representatives from several universities and national laboratories has been established as part of this on-going project to generate internal and external dose conversion coefficients for radionuclides produced in spallation neutron sources. Information obtained from this multi-year study will be used to support the siting and licensing of future accelerator-driven nuclear initiatives within the U.S. Department of Energy complex, including the Spallation Neutron Source (SNS) and the Advanced Fuel Cycle Initiative (AFCI) Projects. Determination of these coefficients will also fill data gaps for several hundred radionuclides that exist in Federal Guide Report No. 11 and in …

Finite-Temperature Spin Polarization In Half-Metallic Ferromagnets, Peter A. Dowben, Ralph Skomski

Peter Dowben Publications

The temperature dependence of the spin polarization of half-metallic ferromagnets is investigated. A unitary spinor transformation shows that the corresponding spin mixing goes beyond finite-temperature smearing of the Fermi level, leading to a nonzero density of states in the gap of the insulating spin channel. As a consequence, the resistance ratio of the two spin channels changes from infinity to some finite value and, in a strict sense, half-metallic ferromagnetism is limited to zero temperature. Bloch-type spin waves and crystal imperfections contribute to the density of states in the gap but only partly explain the pronounced changes at about 0.2 …

Cation Intermixing And Ordering Phenomenon In M-O Layer Of Msr2ycu2oz(M-1212) Compounds With M=Fe, Co, Al, And Ga: A Neutron Powder Diffraction Study, V. P.S. Awana, E. Takayama-Muromachi, S. K. Malik, William B. Yelon, M. Karppinen, H. Yamauchi, V. V. Krishnamurthy

Physics Faculty Research & Creative Works

M-1212 compounds with the composition MSr₂YCu2Oz (with M = Fe, Co, Al and Ga) were studied. the phenomena of M-cation intermixing with Cu, and the ordering in the M-O layer of the M-1212 compounds when compared with the parent CuBa₂YCu₂O_7-δ compound were investigated. Magnetization measurements and neutron powder diffraction results were presented.

Spin Structure At Nanojunctions And Constrictions, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

A micromagnetic Green-function approach is used to investigate the effect of nanojunctions, constraints, and other obstacles on spin-dependent conduction. Depending on geometry, the determination of the spin structure involves several types of Bessel functions. A common feature of the Green functions is the involvement of the domain-wall width of the main phase, which can be interpreted as the decay length of the magnetization perturbation away from the junction. This length is typically on the order of 10 nm and independent of the strength of the perturbation. Only the magnitude of the magnetization perturbation depends on the strength of the inhomogenity. …

Spin-Wave Modes In Magnetic Nanowires, Ralph Skomski, M. Chipara, David J. Sellmyer

David Sellmyer Publications

Spin-wave modes in magnetic transition-metal nanowires having diameters of about 10 nm and lengths on the order of 1 µm are investigated by model calculations. There are quasicontinuous modes with k vectors parallel to the wires axis and discrete modes with k vectors perpendicular to the wire axis. Due to the small cross section of the wires, the perpendicular modes can be ignored in many cases and the low-temperature behavior of the wires is quasi one-dimensional. Using an analytic approach and exploiting the analogy between micromagnetism and quantum mechanics it is shown that all spin-wave modes with k vectors parallel …

Linearized Stability Analysis Of Accelerated Planar And Spherical Fluid Interfaces With Slow Compression, John D. Ramshaw, Peter A. Amendt

Physics Faculty Publications and Presentations

We present linearized stability analyses of the effect of slow anisotropic compression or expansion on the growth of perturbations at accelerated fluid interfaces in both planar and spherical geometries. The interface separates two fluids with different densities, compressibilities, and compression rates. We show that a perturbation of large mode number on a spherical interface grows at precisely the same rate as a similar perturbation on a planar interface subjected to the same normal and transverse compression rates.

Comparing The Higgs Sector Of Electroweak Theory With The Scalar Sector Of Low Energy Qcd, Joseph Schechter, Abdou Abdel-Rehim, Deirdre Black, Amir H. Fariborz, Salah Nasri

Physics - All Scholarship

We first review how the simple K-matrix unitarized linear SU(2) sigma model can explain the experimental data in the scalar pi pi scattering channel of QCD up to about 800 MeV. Since it is just a scaled version of the minimal electroweak Higgs sector, which is often treated with the same unitarization method, we interpret the result as support for this approach in the electroweak model with scaled values of tree level Higgs mass up to at least about 2 TeV. We further note that the relevant QCD effective Lagrangian which fits the data to still higher energies using the …

Light Scattering Investigation Above The Nematic-Smectic-A Phase Transition In Binary Mixtures Of Calamitic And Bent-Core Mesogens, Mohammad Reza Dodge, Rolfe G. Petschek, Charles Rosenblatt

Faculty Scholarship

An investigation on light scattering above the nematic - smectic-A phase transition in binary mixtures of bent-core mesogens and calamitic was performed. With dopant concentration X, the regular part of the bend elastic constant decreased strongly. It was found that the divergent part of the bend elastic constant decreased rapidly with X, when close to the nematic - smectic-A phase transition temperature.

Scaling Violations And Determination Of ΑS From Jet Production In Γp Interactions At Hera, S. Chekanov, D. Krakauer, J. H. Loizides, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch

Faculty Publications

Differential cross sections for jet photoproduction in the reaction ep → e jet X have been measured with the ZEUS detector at HERA using 82.2 pb-1 of integrated luminosity. Inclusive jet cross sections are presented as a function of the jet transverse energy, ETjet, for jets with ETjet > 17 GeV and pseudorapidity -1 <ηjet >

Millimeter-Wave Spectroscopy Of Cold Rb Rydberg Atoms In A Magneto-Optical Trap: Quantum Defects Of The Ns, Np, And Nd Series, Wenhui Li, I. Mourachko, Michael Noel, T. F. Gallagher

Physics Faculty Research and Scholarship

By using a magneto-optical trap we have measured the Rb ns-(n+1)s and nd(j)-(n+1)d(j) two-photon millimeter-wave transitions for 32less than or equal tonless than or equal to37, observing 100-kHz-wide resonances, in spite of the trap's 10 G/cm magnetic-field gradient, in which one might expect to observe resonances 5 MHz wide. This resolution is possible because of the similarity of the g(j) factors in the initial and final states. Under the same conditions, the single-photon ns-np resonances are similar to5 MHz wide. To make useful measurements of these intervals, we turned off the trap field and used the 300-K atoms of the …

Spheromak Merging And Field Reversed Configuration Formation At The Swarthmore Spheromak Experiment, C. D. Cothran, Abram Lockhart Falk , '03, Matthew J. Landreman , '03, Michael R. Brown, M. J. Schaffer

Physics & Astronomy Faculty Works

The initial results of coaxial co- and counter-helicity spheromak merging studies at the Swarthmore Spheromak Experiment (SSX) [M. R. Brown, Phys. Plasmas 6, 1717 (1999)] are reported. In its new configuration, SSX is optimized to study field reversed configuration (FRC) formation and stability by counter-helicity spheromak merging. A pair of midplane coils magnetically restricts the merging process to determine how the stability of the resulting magnetic configuration depends upon the quantity of toroidal flux remaining from the initial spheromaks. The diagnostic set at SSX, featuring the capability of measuring up to 600 magnetic field components at 800 ns time resolution, …

Secondary Electron Emission Study Of Annealed Graphitic Amorphous Carbon, Jodie Corbridge

Senior Theses and Projects

In the 1880s a curious phenomena was observed: when a ray of light, no matter how weak, hit certain metals; electrons were emitted from the surface. Called the “photoelectric effect”, this puzzle was never explained until much later. In 1905, Albert Einstein put forth one possible explanation, which is currently accepted as correct. Einstein proposed that light propagated in discrete energy packets rather than as a continuous wave. While most scientists disbelieved Einstein theory, it was later proved in detail by Robert Milikan.1 Rays of light traveling in discrete packets hit metal surfaces, depositing energy. If the energy is high …

Ga Vacancies As Dominant Intrinsic Acceptors In Gan Grown By Hydride Vapor Phase Epitaxy, J. Oila, J. Kivioja, V. Ranki, K. Saarinen, David C. Look, Richard J. Molnar, S. S. Park, S. K. Lee, J. Y. Han

Physics Faculty Publications

Positron annihilation measurements show that negative Ga vacancies are the dominant acceptors in n-type gallium nitride grown by hydride vapor phase epitaxy. The concentration of Ga vacancies decreases, from more than 10¹⁹ to below 10¹⁶ cm⁻³, as the distance from the interface region increases from 1 to 300 μm. These concentrations are the same as the total acceptor densities determined in Hall experiments. The depth profile of O is similar to that of V_Ga, suggesting that the Ga vacancies are complexed with the oxygen impurities.

Review Of Tritium On Ice: The Dangerous New Alliance Of Nuclear Weapons And Nuclear Power By Kenneth D. Bergeron, David W. Hafemeister

Physics

No abstract provided.

Hyperspherical Close-Coupling Calculations For Charge-Transfer Cross Sections In He²⁺ +H(1s) Collisions At Low Energies, Chen-Nan Liu, Anh-Thu Le, Toru Morishita, B. D. Esry, C. D. Lin

Physics Faculty Research & Creative Works

A theory for ion-atom collisions at low energies based on the hyperspherical close-coupling (HSCC) method is presented. In hyperspherical coordinates the wave function is expanded in analogy to the Born-Oppenheimer approximation where the adiabatic channel functions are calculated with B-spline basis functions while the coupled hyperradial equations are solved by a combination of R-matrix propagation and the slow/smooth variable discretization method. The HSCC method is applied to calculate charge-transfer cross sections for He²⁺ +H(1s)-->He⁺ (n=2) + H⁺ reactions at center-of-mass energies from 10 eV to 4 keV. The results are shown to be in general good agreement with calculations …

Evolution Of The Band Structure Of Β-In2 S3−3x O3x Buffer Layer With Its Oxygen Content, N. Barreau, S. Marsillac, J. C. Bernède, L. Assmann

Electrical & Computer Engineering Faculty Publications

The evolution of the band structure of β-In2 S3−3x O3x (BISO) thin films grown by physical vapor deposition, with composition x, is investigated using x-ray photoelectron spectroscopy. It is shown that the energy difference between the valence-band level and the Fermi level remains nearly constant as the optical band gap of the films increases. As a consequence, the difference between the conduction band level and the Fermi level increases as much as the optical band gap of the films. The calculation of the electronic affinity [ ] of the BISO thin films shows that it decreases linearly from 4.65 …

Measurement Of High-Q2 E- P Neutral Current Cross Sections At Hera And The Extraction Of Xf3: The Zeus Collaboration, S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch, I. Brock

Faculty Publications

Cross sections for e- p neutral current deep inelastic scattering have been measured at a centre-of-mass energy of 318 GeV using an integrated luminosity of 15.9 pb-1 collected with the ZEUS detector at HERA. Results on the double-differential cross-section d2σ/dx dQ2 in the range 185 < Q2 < 50 000 GeV2 and 0.0037 < x < 0.75, as well as the single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy for Q2 > 200GeV2, are presented. To study the effect of Z-boson exchange, dσ/dx has also been measured for Q2 > 10 000 GeV2. The structure function xF3 has been extracted by combining the e-p results presented here with the recent ZEUS measurements of e+ p neutral current deep inelastic scattering. All results agree well with the predictions of …

The Scalar Sector And The Eta -> 3 Pi Problem, Joseph Schechter, Abdou Abdel-Rehim, Deirdre Black, Amir H. Fariborz

Physics - All Scholarship

First, recent work on light scalar mesons, which is of possible interest in connection with the strong coupling region of QCD is briefly discussed. Then a very short highlighting of a paper concerned with an application to the eta -> 3 pi problem is presented.

Wide Angle Achromatic Prism Beam Steering For Infrared Countermeasures Applications, Bradley D. Duncan, Philip J. Bos, Vassili Sergan

Electro-Optics and Photonics Faculty Publications

The design and analysis of achromatic doublet prisms for use in laser beam steering is presented. The geometric relationships describing the maximum steering angle are given, as are discussions of first- and second-order dispersion reduction. Infrared (IR) material alternatives and optimum IR material characteristics for wide-angle achromatic prism beam steering are also investigated. Sixteen materials in 120 different combinations have been examined to date. For midwave IR applications it is shown that the minimum dispersion currently achievable across the full 2 to 5 μm spectrum is 1.7816 mrad at an average maximum steering angle of 45 deg. This is accomplished …

Rapid Multiplexed Data Acquisition: Application To Three-Dimensional Magnetic Field Measurements In A Turbulent Laboratory Plasma, Matthew Joseph Landreman , '03, C. D. Cothran, Michael R. Brown, M. Kostora, J. T. Slough

Physics & Astronomy Faculty Works

Multiplexing electronics have been constructed to reduce the cost of high-speed data acquisition at the Swarthmore Spheromak Experiment (SSX) and Redmond Plasma Physics Laboratory. An application of the system is described for a three-dimensional magnetic probe array designed to resolve magnetohydrodynamic time scale and ion inertial spatial scale structure of magnetic reconnection in a laboratory plasma at SSX. Multiplexing at 10 MHz compresses 600 pick-up coil signals in the magnetic probe array into 75 digitizer channels. An external master timing system maintains synchronization of the multiplexers and digitizers. The complete system, calibrated and tested with Helmholtz, line current, and magnetofluid …

Searching For Planetary Transits In The Field Of Open Cluster Ngc 6819 – I, R. A. Street, Keith Horne, T. A. Lister, A. Penny, Y. Tsapras, A. Quirrenbach, N. Safizadeh, David Mitchell, J. Cooke, A. Collier Cameron

Physics

We present results from our survey for planetary transits in the field of the intermediate-age (∼2.5 Gyr), metal-rich ([Fe/H] ∼+0.07) open cluster NGC 6819. We have obtained high-precision time-series photometry for over 38 000 stars in this field and have developed an effective matched-filter algorithm to search for photometric transits. This algorithm identified 8 candidate stars showing multiple transit-like events, plus 3 stars with single eclipses. On closer inspection, while most are shown to be low-mass stellar binaries, some of these events could be the result of brown dwarf companions. The data for one of the single-transit candidates indicate a …

Rapid Multiplexed Data Acquisition: Application To Three-Dimensional Magnetic Field Measurements In A Turbulent Laboratory Plasma, Michael R. Brown

Physics & Astronomy Faculty Works

Multiplexingelectronics have been constructed to reduce the cost of high-speed data acquisition at the Swarthmore SpheromakExperiment (SSX) and Redmond Plasma Physics Laboratory. An application of the system is described for a three-dimensional magnetic probe array designed to resolve magnetohydrodynamic time scale and ion inertial spatial scale structure of magnetic reconnection in a laboratory plasma at SSX. Multiplexing at 10 MHz compresses 600 pick-up coil signals in the magnetic probe array into 75 digitizer channels. An external master timing system maintains synchronization of the multiplexers and digitizers. The complete system, calibrated and tested with Helmholtz, line current, and magnetofluid fields, reads …

Has Feminism Changed Physics?, Amy Lisa Graves

Physics & Astronomy Faculty Works

No abstract provided.

Study Of Energy Sampling Weights In The Dø Detector Using Multiparameter Fitting Method, Qun Yu

Doctoral Dissertations

The DØ calorimeter at Fermilab is a sampling calorimeter measuring the energy of particles produced in high energy proton-antiproton collisions. A set of accurate sampling weights is of significant importance to DØ research activity. The objective of this work was to obtain a set of optimized sampling weights for the DØ central calorimeter, the Inter-Cryostat Detector (ICD), the Central Calorimeter Massless Gap (CCMG), and the End Calorimeter Massless Gap (ECMG).

The foundation of the optimization method is that, in high energy physics, the ratio of energy E and the corresponding momentum P of a particle is approximately 1, in units …