Physical Sciences and Mathematics Commons^™

Electrostatic Micro Actuators For Mirror And Other Applications, Xingtao Wu

Dissertations

Micro-electro-mechanical systems (MEMS) based electrostatic micro actuators are becoming important building blocks for innovations in optical signal processing and computing systems due to their inherently small size, high density, high speed and low power consumption. Generally, the principle of operation in these systems can be described as: an electrostatic attractive force causes a mechanical rotation, translation or deformation of a mirror plate, controlling the power, phase or direction of a light beam while it propagates through some medium or through free space. The fast paced, competitive research and development efforts widely being undertaken, both in academia and industry, are demanding …

Electroproduction Of The Λ(1520) Hyperon, S P. Barrow, L Dennis, S B. Mcaleer, B Asavapibhop, R S. Hicks, D Lawrence, R Miskimen, Gerald Alvin Peterson, J Shaw

Gerald Alvin Peterson

The reaction ep⃗e′K+Λ(1520) with Λ(1520)→p′K- was studied at electron beam energies of 4.05, 4.25, and 4.46 GeV, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cosθK+, φK+, Q2, and W dependencies of Λ(1520) electroproduction are presented for the kinematic region 0.9

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides: Quarterly Report 5/15/01-8/15/01, Yitung Chen, Darrell Pepper, Randy Clarksean

Fuels Campaign (TRP)

No abstract provided.

Stimulated Emission Of Polarization-Entangled Photons, Antia Lamas-Linares, John C. Howell, Dik Bouwmeester

Mathematics, Physics, and Computer Science Faculty Articles and Research

Entangled photon pairs—discrete light quanta that exhibit non-classical correlations—play a crucial role in quantum information science (for example, in demonstrations of quantum non-locality^{1,2,3,4,5,6,7}, quantum teleportation^8,9 and quantum cryptography^10,11,12,31). At the macroscopic optical-field level non-classical correlations can also be important, as in the case of squeezed light¹³, entangled light beams^14,15 and teleportation of continuous quantum variables¹⁶. Here we use stimulated parametric down-conversion to study entangled states of light that bridge the gap between discrete and macroscopic optical quantum correlations. We demonstrate experimentally the onset of laser-like action for entangled photons, through …

Simultaneous Projectile And Target Ionization In He⁺ + Ne Collisions, J. Fiol, Ronald E. Olson, A. C.F. Santos, G. M. Sigaud, E. C. Montenegro

Physics Faculty Research & Creative Works

Cross sections for single and multiple ionization of the target atom with simultaneous ionization of the projectile have been measured for 1-4 MeV collisions of He⁺ with Ne. The observations are interpreted using the n-body classical trajectory Monte Carlo method. The 11-body calculations include the L-shell electrons of the Ne and the K-shell electron on the He⁺. In this model, each electron interacts with both nuclei and with all the electrons belonging to the other centre. For single ionization from both centres, it is found that the dynamical electron-electron (e-e) interaction produces a clear signature in the …

Renormalization Of The Inverse Square Potential, Horacio E. Camblong

Physics and Astronomy

The quantum-mechanical D-dimensional inverse square potential is analyzed using field-theoretic renormalization techniques. A solution is presented for both the bound-state and scattering sectors of the theory using cutoff and dimensional regularization. In the renormalized version of the theory, there is a strong-coupling regime where quantum-mechanical breaking of scale symmetry takes place through dimensional transmutation, with the creation of a single bound state and of an energy-dependent s-wave scattering matrix element.

Static-Electric-Field Behavior In Negative Ion Detachment By An Intense, High-Frequency Laser Field, M. V. Frolov, N. L. Manakov, B. Borca, Anthony F. Starace

Anthony F. Starace Publications

Based upon the exact numerical solution of the complex quasienergy problem for a 3-dimensional short-range potential as well as upon analytical evaluations, we demonstrate for any finite frequency ω that the action of an ultra-intense laser field (with electric vector F(ωt)) on a weakly bound atomic system may be described by the cycle-averaging of results for an instantaneous static electric field of strength |F(ωt)|.

Electric Field Autocorrelation Functions For Beginning Multiple Rayleigh Scattering, James A. Lock

Physics Faculty Publications

The polarization-resolved electric field autocorrelation function for p-order scattering was derived from the order-of-scattering solution of the exact equations for electromagnetic multiple Rayleigh scattering and was calculated for 2 less than or equal to p less than or equal to 6 for particles undergoing diffusive motion in an idealized sample cell. It was found that the polarization-channel and the scattering-angle dependence of the p-order autocorrelation function approximately decoupled from the delay-time dependence for p greater than or similar to 3. The polarization-channel and the scattering-angle dependence were analytically calculated, and the delay-time dependence was analytically approximated. The resulting analytical model …

Exchange Bias In A Generalized Meiklejohn-Bean Approach, Christian Binek

Christian Binek Publications

A generalized Meiklejohn–Bean model is considered in order to derive an analytic expression for the dependence of the previous exchange bias term field on the layer thickness involved in ferromagnetic/antiferromagnetic heterosystems, on the orientation of the applied magnetic field with respect to the magnetic easy axes and on the quenched magnetization MAF of the antiferromagnetic pinning layer. While MAF is a well-known feature of field-cooled dilute antiferromagnets, it seems to occur quite generally also in pure AF pinning substrates. The new analytic expressions are successfully compared with recent experimental results and Monte Carlo investigations.

Analysis Of Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Dale L. Perry

Transmutation Sciences Materials (TRP)

The goal is to achieve a basic understanding of the corrosion of stainless steel by Lead Bismuth Eutectic (LBE), which has been proposed for use in the transmuter as both a coolant and as a sputtering target.

Anomalous Barium Filling Fraction And N-Type Thermoelectric Performance Of Ba[Sub Y]Co[Sub 4]Sb[Sub 12]., L. Chen, T. Kawahara, X. Tang, T. Goto, T. Hirai, Jeffrey Dyck, W. Chen, C. Uher

Jeffrey Dyck

Barium-filled skutterudites BaCoSb with an anomalously large filling fraction of up to y=0.44 have been synthesized. The lattice parameters increase linearly with Ba content. Magnetic susceptibility data show that BaCoSb is paramagnetic, which implies that some of the Co atoms in BaCoSb have acquired a magnetic moment. The presence of the two different valence states of Co (Co3+ and Co2+) leads to the anomalously large barium filling fraction even without extra charge compensation. All samples show n-type conduction. The electrical conductivity increases with increasing the Ba filling fraction. The lattice thermal conductivity of BaCoSb is significantly depressed as compared to …

Charge Transfer And X-Ray Emission Reactions Involving Highly Charged Ions And Neutral Hydrogen, J. A. Perez, Ronald E. Olson, P. Beiersdorfer

Physics Faculty Research & Creative Works

The electron capture from hydrogen by highly charged-bare ions was studied using a three-body classical trajectory Monte Carlo (CTMC) method. The state-selective capture cross sections, calculated for a wide range of collision energies, were used to estimate x-ray emission cross sections. The capture process produced excited hydrogen-like ions and captured majority of electrons into one or two dopant states at low collision energies. The calculations predicted a large increase in the fraction of prompt x-rays produced with the lowering of the collision energy. The analysis suggested that ionization potential change for each collision and multiple capture played significant role in …

Radiation Transport Modeling Of Beam-Target Experiments For The Aaa Project, William Culbreth

Reactor Campaign (TRP)

The AAA program will rely on the use of an accelerator-based transmuter to expose spent nuclear fuel to high-energy neutrons. The neutron flux will be sufficient to activate or fission the long-lived isotopes of Tc, I, Pu, Am, Cm, and Np that present a significant safety hazard in commercial spent fuel. Transmuter fuel will be subcritical and a high-energy proton accelerator is needed to maintain the necessary neutron flux through the use of a neutron spallation target. The maximum neutron energy produced by spallation (~ 600 MeV) is significantly higher than that produced by a commercial light water reactor (~ …

Nuclear Criticality Analyses Of Separations Processes For The Transmutation Fuel Cycle, William Culbreth, Pang Tao

Separations Campaign (TRP)

To mitigate the waste created by conventional fission reactors, spent nuclear fuel must be mechanically separated from its cladding. For the development of fuel processing technology to support the Advanced Accelerator Applications (AAA) Program, aqueous and pyrochemical processes will be used to further separate technetium and iodine, uranium and the higher actinides (see Figure 1 for an example of the process layout)1. The higher actinides, including plutonium, americium, curium, and neptunium will be separated from the waste to facilitate their fabrication into new fuel for placement in a transmuter. High-energy neutrons generated by spallation in the transmuter break down these …

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. A detailed design description for the manufacturing of each candidate fuel type would support the informed selection of fuel for a transmutation system. We will collect pertinent manufacturing and process-related information and create an information database that will document the design, operations, and cost implications of various fuel choices. Fabrication processes for different fuel types will likely differ in terms of equipment types, throughput, and cost.

Year 1 of the project will be devoted to the analysis and assessment of the multiple steps …

Measurement Of The Inclusive Jet Cross Section In Pp̅ Collisions At √S =1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present results from the measurement of the inclusive jet cross section for jet transverse energies from 40 to 465 GeV in the pseudorapidity range 0.1<|η|-1 of data collected by the CDF Collaboration at the Fermilab Tevatron collider. The data are consistent with previously published results. The data are also consistent with QCD predictions given the flexibility allowed from current knowledge of the proton parton distributions. We develop a new procedure for ranking the agreement of the parton distributions with data and find that the data are best described by QCD predictions using the parton distribution functions which have a large gluon contribution at high E_T (CTEQ4HJ).

Statistics And Supermetallicity: The Metallicity Of Ngc 6791, B. J. Taylor

Faculty Publications

For the old galactic cluster NGC 6791, Peterson & Green (1998a) and Chaboyer et al. (1999) have found that [Fe/H] approximately + 0.4 dex. A second look at that conclusion is taken in this paper. Zero-point problems are reviewed for a high-dispersion analysis done by Peterson & Green, and it is found that accidental errors have not been determined rigorously for the results of that analysis. It is also noted that in a color-magnitude analysis performed by Chaboyer et al., the important metallicity range between 0.0 and + 0.3 dex is not explored and hence is not ruled out. Moreover, …

Search For Heavy Particles Decaying Into Electron-Positron Pairs In Pp̅ Collisions, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We present results of searches for technirho (ρ_T), techniomega (ω_T), and Z ′ particles, using the decay channels ρ_T, ω_T, Z ′ → ℯ⁺ℯ^-. The search is based on 124.8 pb^-1 of data collected by the D0 detector at the Fermilab Tevatron during 1992–1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp̅ → ρ_T, ω_T, Z ′ → ℯ⁺ℯ^- as a function of the mass of the decaying …

Yang-Lee Edge Singularities From Experimental High Field Magnetization Data, Christian Binek

Christian Binek Publications

The isothermal magnetization m(H) of the metamagnet FeCl2 is measured in axial magnetic fields 0≤µ0Ha≤12 T at temperatures 34≤T≤53 K above the Néel temperature, where the system is essentially a two-dimensional Ising ferromagnet. The analysis of the data indicates experimental accessibility of the critical exponent µ of the Yang-Lee edge singularities. They manifest themselves in divergences of the density functions g(θ), which quantify the distribution of the zeros of the partition function on the Lee-Yang unit circle in the complex plane. In accordance with the hypothesis of universality, a critical exponent close to the theoretical prediction for the two-dimensional Ising …

Yang-Lee Edge Singularities Determined From Experimental High-Field Magnetization Data, Christian Binek, Wolfgang Kleemann, H. Aruga Katori

Christian Binek Publications

The isothermal magnetization m (H) of the metamagnet FeCl₂ is measured in axial magnetic fields 0 ≤ μ₀H_a ≤ 12 T at temperatures 34 ≤ T ≤ 53 K above the Néel temperature, where the system is essentially a two-dimensional Ising ferromagnet. The analysis of the data indicates experimental accessibility of the critical exponent μ of the Yang-Lee edge singularities. They manifest themselves in divergences of the density functions g(θ), which quantify the distribution of the zeros of the partition function on the Lee-Yang unit circle in the complex plane. In accordance with …

Predicted Maximum Mobility In Bulk Gan, David C. Look, J. R. Sizelove

Physics Faculty Publications

A 300 K bulk (three-dimensional) mobility of 1245 cm²/V s has been measured in free-standing GaN. Temperature-dependent Hall-effect data on this particular sample are fitted to obtain unknown lattice-scattering parameters, as well as shallow donor (N_D) and acceptor (N_A) concentrations, which are N_D = 6.7×10¹⁵ and N_A = 1.7×10¹⁵ cm⁻³. Realistic values of the maximum mobility attainable in bulk GaN are then obtained by assuming two-orders-of-magnitude lower values of N_D and N_A, leading to a maximum 300 K mobility of 1350 cm^{2 …}

Coherent Control Of Stimulated Raman Scattering Using Chirped Laser Pulses, Evan S. Dodd, Donald P. Umstadter

Donald Umstadter Publications

A novel method for the control of stimulated Raman scattering and hot electron production in short-pulse laser-plasma interactions is proposed. It relies on the use of a linear frequency chirp in nonbandwidth limited pulses. Theoretical calculations show that a 12% bandwidth will eliminate Raman forward scattering for a plasma density that is 1% of the critical density. The predicted changes to the growth rate are confirmed in two-dimensional particle-in-cell simulations. Relevance to areas of current research is also discussed.

Vortex-Defect Interactions In High-Temperature Superconductors, Valentina Tobos

Dissertations

The topics covered in this thesis are related to two objectives: one refers to the search for methods of improving die critical current density of high-temperature superconductors, a subject which remains of continuing interest for its importance in technological applications. The other direction is aimed at clarifying the phase diagram of high-Tc materials.

The interaction between the structural defects and the vortex system plays a significant role in the capability of these materials to carry large electrical transport currents. Through proton irradiation induced defects we follow the evolution of the critical current density, and its enhancement with increasing point-like defects …

Critique Of The Wigner Tunneling Speed And A Proposed Alternative, P Krekora, Q Su, Rainer Grobe

Faculty publications – Physics

In the context of superluminal propagation of wave packets through potential barriers, the tunneling speed is usually characterized by the Wigner velocity. We propose an alternative speed that takes into account the interference between the incoming and the reflected waves and leads to a better estimation of arrival time for a wave packet entering the tunneling region. This arrival time is derived by an extrapolation from inside the barrier. The analytical theory is based on the stationary phase approximation whose validity is justified by a comparison with the numerical solution of the time-dependent Dirac equation.

Measurement Of The Tt̅ Production Cross Section In Pp̅ Collisions At √S =1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We update the measurement of the tt̅ production cross section using the CDF detector at the Fermilab Tevatron. This measurement uses tt̅ decays to the final states e+ν+jets and μ+ν+jets. We search for b quarks from t decays via secondary-vertex identification or the identification of semileptonic decays of the b and cascade c quarks. The background to the tt̅ production is determined primarily through a Monte Carlo simulation. However, we calibrate the simulation and evaluate its uncertainty using several independent data samples. For a top quark mass of 175 GeV/c², we measure σ _{t t}^{¯ …}

Magnetic Microstructure Of Bacterial Magnetite By Electron Holography, Martha R. Mccartney, Ulysses Lins, Marcos Farina, Peter R. Buseck, Richard B. Frankel

Physics

A brackish lagoon at Itaipu, Brazil, contains magnetotactic bacteria with unusually large magnetite magnetosomes (lengths 100–200 nm). The micromagnetic structures of the magnetosomes from two different coccoid organisms from the lagoon have been determined by electron holography. The results are consistent with single-magnetic-domain structure in the elongated magnetosomes from one organism and metastable, single-magnetic-domain structure in the larger, more equi-axed, magnetosomes from the other organism. The results are consistent with theoretical predictions of the transition dimension between stable and metastable single-domain structure in magnetite.

Quantum Phase Transition Of Itinerant Helimagnets, Thomas Vojta, Rastko Sknepnek

Physics Faculty Research & Creative Works

We investigate the quantum phase transition of itinerant electrons from a paramagnet to a state which displays long-period helical structures due to a Dzyaloshinskii instability of the ferromagnetic state. In particular, we study how the self-generated effective long-range interaction recently identified in itinerant quantum ferromagnets is cut off by the helical ordering. We find that for a sufficiently strong Dzyaloshinskii instability the helimagnetic quantum phase transition is of second order with mean-field exponents. In contrast, for a weak Dzyaloshinskii instability the transition is analogous to that in itinerant quantum ferromagnets, i.e., it is of first order, as has been observed …

X-Ray Photoelectron Spectroscopy (Xps) And Magnetization Studies Of Iron–Vanadium Phosphate Glasses, M. A. Salim, G. D. Khattak, Petru S. Fodor, Lowell E. Wenger

Physics Faculty Publications

Vanadium phosphate glasses containing Fe2O3 with the chemical composition [(Fe2O3)x(V2O5)0.6−x(P2O5)0.4], where x=0.00, 0.10, 0.20, 0.25 and 0.30, have been prepared and investigated by X-ray photoelectron spectroscopy (XPS) and magnetic susceptibility measurements. The core level binding energies of V 2p, Fe 2p, P 2p and P 2s in the Fe2O3–vanadium phosphate glasses have been measured and shifts from the corresponding binding energies measured for V2O5, Fe2O3 and P2O5 powders are accounted for by changes in the next-nearest neighbor environment of these atoms in the P4O10 local structure. The O 1s spectra for the glasses are single, symmetric peaks arising from nearly …

Dynamic Hyperpolarizability And Two-Photon Detachment In The Presence Of A Strong Static Electric Field: Application To H-, M.V. Frolov, N.L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

Our recent analysis [J. Phys. B 33, R141 (2000)] of the problem of H^- in both laser and strong static electric fields, which treated effects that are linear in the laser intensity l (e.g., the dynamic polarizability and the single-photon detachment cross section), is extended here to treat effects of higher order (∼l²) in the laser intensity (e.g., the dynamic hyperpolarizability, the two-photon detachment cross section, the linear in l corrections to the single-photon detachment rate, etc). We introduce the concept of the dynamic hyperpolarizability of an atom in the presence of a strong electric field …

University Of Nevada, Las Vegas Advanced Accelerator Applications University Participation Program: Quarterly Report First Quarter (March-May 2001), Anthony Hechanova

Transmutation Research Program Reports (TRP)

This Quarterly Report is a primary deliverable from the University of Nevada, Las Vegas (UNLV) Advanced Accelerator Applications (AAA) University Participation Program (UPP) director to the U.S. Department of Energy Office of Nuclear Energy, Science and Technology (DOE-NE) as defined in the UNLV AAA Proposal.

The foundation of the UNLV AAA University Participation Program started as a grassroots effort in the late 1990s among community members and local, state, and federal representatives to encourage research and development of technical alternatives to direct disposal of used nuclear fuel which had been targeted since the early 1980s for Yucca Mountain, Nevada. A …