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Blocking Of Logarithmic Temporal Relaxation Of Magnetic Remanence By Piezomagnetically Induced Domains In Fe1-XZnXF2, J. Kushauer, Christian Binek, Wolfgang Kleemann

Christian Binek Publications

Faraday rotation and superconducting quantum interference device magnetometry were used to investigate the relaxation of the weak-field induced remanence, µ, of the random-field Ising model system Fe_1-xZn_xF₂. The stretched logarithmic decay law, as predicted by Nattermann and Vilfan for the case of compact domains with fractal surfaces, was confirmed for freezing fields of 3≤B≤5 T. Virtually constant remanence, µ, was found at low fields, 0.0002≤B≤1.5 T. This ferrimagnetic moment is due to the piezomagnetic effect acting on random-stress induced immobile domains. Chemical etching, which removes surface stress originating from the sample preparation, proves to …

Relaxation Technique For The Fitting Of Numerical Data, Michael J. Lehmann

Opportunities for Undergraduate Research Experience Program (OURE)

Data, in particular that generated through successive computer approximations, may not always follow the smooth curve it is suppose to. Approximations in input data, round off error, and estimations made in the mathematical formulas, are just some of the things that could cause this problem. In any respect, this data must somehow be smoothed or fitted for publication. One way of fitting such data sets is the relaxation method. This method does not rely on the data conforming to a specific mathematical shape, as opposed to other programs that require the data to be fitable by some mathematically generated curve. …

Renormalization Group Study Of The Standard Model And Its Extensions: The Minimal Supersymmetric Standard Model, Diego Castano, E. J. Piard, P. Ramond

Chemistry and Physics Faculty Articles

In this paper we summarize the minimal supersymmetric standard model as well as the renormalization group equations of its parameters. We proceed to examine the feasibility of the model when the breaking of supersymmetry is parametrized by the soft terms suggested by supergravity theories. In such models, the electroweak symmetry is exact at the tree level and is broken spontaneously at one-loop order. We make the additional assumption that the GUT-inspired relation m_b=m_τ be valid at the scale where the gauge coupling constants unify, which constrains the value of the top quark mass. For all types of …

Tabletop X-Ray Lasers, D. C. Eder, P. Amendt, L. B. Dasilva, R. A. London, B. J. Macgowan, D. L. Matthews, B. M. Penetrante, M. D. Rosen, S. C. Silks, Thomas D. Donnelly, R. W. Falcone, G. L. Strobel

All HMC Faculty Publications and Research

Details of schemes for two tabletop size x‐ray lasers that require a high‐intensity short‐pulse driving laser are discussed. The first is based on rapid recombination following optical‐field ionization. Analytical and numerical calculations of the output properties are presented. Propagation in the confocal geometry is discussed and a solution for x‐ray lasing in Li‐like N at 247 Å is described. Since the calculated gain coefficient depends strongly on the electron temperature, the methods of calculating electron heating following field ionization are discussed. Recent experiments aimed at demonstrating lasing in H‐like Li at 135 Å are discussed along with modeling results. The …

Electrochemical Capacitance-Voltage Analysis Of Delta-Doped Pseudomorphic High-Electron-Mobility Transistor Material, C. E. Stutz, B. Jogai, David C. Look, J. M. Ballingall, T. J. Rogers

Physics Faculty Publications

This work shows how electrochemical capacitance‐voltage (EC‐V) measurements can be used to evaluate delta‐doped pseudomorphic high electron mobility transistor material. These EC‐V measurements are compared with magnetic‐field‐dependent Hall effect (M‐Hall) measurements and a self‐consistent Poisson/k⋅p calculation of the band structure and electron concentration. The EC‐V technique can clearly delineate the cap layer, the delta‐doped layer, and the In_xGa_1−xAs channel layer, whereas the M‐Hall method characterizes only the cap and In_xGa_1−xAs channel layers. The amount of electron charge seen by …

A Monte Carlo Simulation Of Coulomb Collisions And Wave-Particle Interactions In Space Plasma At High Latitudes, Imad Ahmad Barghouthi

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Four studies were considered to simulate the ion behavior in the auroral region and the polar wind.

In study I, a Monte Carlo simulation was used to investigate the behavior of O⁺ ions that are E x B-drifting through a background of neutral O, with the effect of O⁺(Coulomb) self-collisions included. Wide ranges of the ion-to-neutral density ratio n_i / n_n and electrostatic field E were considered in order to investigate the change of ion behavior with respect to the solar cycle and altitude. For low altitudes and/or solar minimum (n_i / …

Ccd Photometry At The Umr Observatory, Christopher P. Smith

Opportunities for Undergraduate Research Experience Program (OURE)

During the summer of 1993 a number of advances at the University of Missouri-Rolla’s observatory have taken place. These advances range from cleaning the mirrors and polar aligning the 16-inch Cassegrain telescope to the acquisition of needed supporting material. A program for observing variable stars, implementing the newly acquired CCD1R image reduction program, searching galaxies for supernova, and the possibility of adding low resolution stellar spectroscopy to our research capabilities will be discussed. This manual will discuss how to implement the new CCDIR program.

Possible Extension Of The Chiral Perturbation Theory Program, Joseph Schechter

Physics - All Scholarship

After a brief discussion of how chiral dynamics has evolved from the ``universal V-A theory of weak interactions'', we present some evidence that symmetry breaking for the vector meson multiplet is not simpler than but rather analogous to that for the pseudoscalar multiplet. This provides a motivation for speculating on how to extend in a systematic way the chiral perturbation theory program to include vectors.

Phase Diagram Of The Ising Model On Percolation Clusters, Miron Kaufman, T. Berger, P. D. Gujrati, D. Bowman

Physics Faculty Publications

The annealed Ising magnet on percolation clusters is studied by means of a mapping into a Potts-Ising model and with the Migdal-Kadanoff renormalization-group method. The phase diagram is determined in the three-dimensional parameter space of the Ising coupling K, the bond-occupation probability p, and the fugacity q, which controls the number of clusters. Three phases are identified: percolating ferromagnetic, percolating paramagnetic, and nonpercolating paramagnetic. For large q the phase diagram includes a multicritical point at the intersection of the Ising critical line and the percolation critical line. In the case of random bond percolation (q = 1) the Ising critical …

High Energy Coupled Nucleon Tranpsort In One Dimension, Stanley L. Lamkin

Physics Theses & Dissertations

The problem of energetic nucleon transport through extended bulk matter is considered in the context of the 'straight ahead' approximation. The applicable form of the Boltzmann transport equation is derived and solved in one dimension. The production term for secondary generation nucleons due to nuclear fragmentation includes 'coupling' of the flux to other types of nucleon projectiles. A physically motivated perturbation series approach is developed to enhance solution convergence. The Boltzmann operator is inverted and the flux is computed using a numerical marching scheme. The secondary production integrals are optimized for second order accuracy using a set of analytical benchmarks. …

Flow Simulations About Steady-Complex And Unsteady Moving Configurations Using Structured-Overlapped And Unstructured Grids, James Charles Newman Iii

Mechanical & Aerospace Engineering Theses & Dissertations

The limiting factor in simulating flows past realistic configurations of interest has been the discretization of the physical domain on which the governing equations of fluid flow may be solved. In an attempt to circumvent this problem, many Computational Fluid Dynamic (CFD) methodologies that are based on different grid generation and domain decomposition techniques have been developed. However, due to the costs involved and expertise required, very few comparative studies between these methods have been performed. In the present work, the two CFD methodologies which show the most promise for treating complex three-dimensional configurations as well as unsteady moving boundary …

Slowing Of 85Rb Atoms With Isotropic Light, Herman Batelaan, S. Padua, D. H. Yang, C. Xie, R. Gupta, Harold Metcalf

Department of Physics and Astronomy: Faculty Publications

We have demonstrated the slowing of a rubidium atomic beam by isotropic monochromatic light. The results agree with a model calculation, thus allowing its use for designing a practical isotropic light slower. The large hyperfine splittings of rubidium lead to natural multifrequency slowing, which is also included in our model.

Absence Of Size Dependence Of The Kondo Resistivity, V. Chandrasekhar, P. Santhanam, N. A. Penebre, Richard A. Webb, H. Vloeberghs, C. Van Haesendonck, Y. Bruynseraede

Faculty Publications

We have measured the low temperature resistivity of AuFe wires in the dilute magnetic impurity limit as a function of wire width, temperature, and magnetic field. When the width dependence of the electron-electron interaction contribution to the resistivity is taken into account, the temperature dependence of the remaining Kondo contribution to the resistivity of all samples with the same impurity concentration is identical. Similar behavior is observed for the magnetic field dependent resistivity. Thus, the Kondo contribution to the resistivity is independent of width down to 38 nm, much smaller than the Kondo length ξ_K=ħv_F/k_{B …}

Feasibility Of Using Ultrasonic Cavitation To Produce Silica Sol, Gary L. Vines

Honors Capstone Projects and Theses

No abstract provided.

On The Absence Of An Exponential Bound In Four Dimensional Simplicial Gravity, Simon Catterall, John B. Kogut, R. Renken

Physics - All Scholarship

We have studied a model which has been proposed as a regularisation for four dimensional quantum gravity. The partition function is constructed by performing a weighted sum over all triangulations of the four sphere. Using numerical simulation we find that the number of such triangulations containing V simplices grows faster than exponentially with V. This property ensures that the model has no thermodynamic limit.

Surface Core-Level Shifts Of Ta(110) And W(110) Vs. Alkali-Atom Coverage: Implications For Thealkali-Substrate Interaction, A. B. Andrews, D. Mark Riffe, G. K. Wertheim

All Physics Faculty Publications

The change in the average surface-atom core-level shift (SCS) produced by submonolayer coverages of alkali adsorbates is quite small for both Ta(110) and W(110), less than 45 meV in magnitude. The small change of the measured SCS’s as a function of coverage decisively supports the covalent-bonding picture of alkali adsorption proposed by Ishida and Terakura.

Coherence Parameters For Electron Capture In H⁺ + He Collisions, C. J. Lundy, Ronald E. Olson, D. R. Schultzi, J. P. Pascale

Physics Faculty Research & Creative Works

The classical trajectory Monte Carlo method is used to calculate coherence parameters for electron capture to H(n = 2, 3 and 4) in 30 to 250 keV H+ + He collisions. The parameters evaluated are the x- and z-components of the dipole moment (D) and the z-component of the perihelion velocity of the captured electron (L x A). The calculated integral values are found to be in reasonable agreement with available experimental results. Components of the dipole moment and (L x A) were also evaluated as a function of projectile scattering angle. Here, rapid variations of the parameters are observed …

Correlated Two-Electron Wave Functions Of Any Symmetry, Christopher Bottcher, David R. Schultz, Don H. Madison

Physics Faculty Research & Creative Works

Using a procedure originally due to Hylleraas, a convenient expansion in coupled spherical harmonics which terminates in a very small number of terms is applied to the treatment of fully correlated two-electron wave functions of any symmetry (total angular momentum, parity, and spin). Coupled equations satisfied by these wave functions are derived which are well adapted to computation and which we discretize on a numerical lattice utilizing the basis-spline collocation method. Use of this method which relies on very flexible basis functions is intended to facilitate subsequently the consideration of time-dependent rearrangments such as autoionization, photoionization, and electron-impact excitation and …

Feasibility Analysis For Predicting A Kinetic Kill Zone For Aircraft Homing Missile Defense, Mark E. Ennis

Theses and Dissertations

An extended Kalman filter is used to predict a kinetic kill zone for use in aircraft self defense versus homing missiles. The analysis is limited to an in-the-plane analysis and focuses on finding the model parameters which have the largest impact on the predicted kill zone. No attempt is made to optimize the design of the filter model itself. The analysis computes the kill zone relative to an assumed aircraft trajectory using strictly filter computed statistics. No Monte-Carlo simulations are used throughout the thesis. The filter assumed to be on the evading aircraft, uses an onboard laser radar (ladar) to …

Generalized Coulomb Gap In The Spherical Version Of A Lattice Model Of Disordered And Correlated Localized Particles, Thomas Vojta, Michael Schreiber

Physics Faculty Research & Creative Works

We study the spherical version of a model of localized particles in a random potential which are subject to a power-law interaction U_ij ~ r_ij^-σ. In the case of a repulsive interaction with σ = 1 the model is identical to the spherical version of the Coulomb-glass model of disordered localized electrons. The use of continuous variables instead of discrete occupation numbers of the sites renders the model exactly solvable. Analytic results are obtained for the free energy and for the single-particle density of states (DOS) as an example for single-particle properties. The zero-temperature DOS shows …

A Measurement Of B(D+S → Φl+Ν) B(D+S → Φπ+), Cleo Collaboration, F. Butler, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

Using the CLEO II detector at CESR, we have measured the ratio of branching fractions B(D → φlν) B(D → φπ) = 0.54 ± 0.05 ± 0.04. We use this measurement to obtain a model dependent estimate of B(D → φπ). © 1994.

On The Theory Of Astronomical Masers In Three Dimensions, Moshe Elitzur

Physics and Astronomy Faculty Publications

In the standard theory of three-dimensional astronomical masers, the radiation field is described as if the source were comprised of a collection of linear masers. To leading order, the standard theory is shown to provide the correct description of three-dimensional masers and its results remain intact, but only within a frequency core whose half-width is χ_sΔν_D, where Δν_D is the Doppler width and χ_s is a dimensionless parameter. For any given geometry, χ_s is ~1θ_sat, where θ_sat is the beaming angle of a maser with that geometry that has …

Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek

Christian Binek Publications

Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.

Tunneling Into Granular Pb Films In The Superconducting And Insulating Regimes, Richard P. Barber Jr., L. Merchant, Porta Arthur La, Robert C. Dynes

Physics

Tunneling measurements have been performed on both sides of the insulator-superconductor transition in quench-condensed granular Pb films. The results indicate that the Pb film consists of fully superconducting grains with essentially bulk values for the superconducting energy gap and transition temperature, even when the film exhibits insulating behavior in transport measurements. The density of states inferred from measurements in perpendicular magnetic field are consistent with magnetic spin-flip broadening.

A Theoretical Study Of The Semiconductor Laser Structures With Lateral Discontinuity In The Optical Cavity, Yi Cai

Theses

A theoretical study of the semiconductor laser structures with lateral discontinuity in the optical resonant cavity is presented in this thesis. Specifically, the lateral discontinuity is referred to the lateral expansion structure newly invented for increasing the power output of semiconductor lasers while keeping single mode operation.

In the first part of the thesis (Chapter 2 and Chapter 3), an explicit expression for calculating the lateral discontinuity problems is formulated by the incorporation of mode-matching method. Our approach is based on the mode expansion theory developed for lossless micro-wave and optical fiber waveguides, but the effect of gain in active …

External Cavity Laser Power Stabilizer, Jie Ding

Theses

In this thesis, we want to design a stabilizer which does not depend on laser source--with external cavity.

In the first part of the thesis ( Chapter 2 and 3 ), we discuss the wave propagation in crystals and the modulation of optical radiation. From the main two types electro-optic modulations, Phase Modulation and Transverse Modulation, we know that the transverse modulation shows an increase in the frequency limit or useful crystal length of (1-c0/ncm)^-1, and we will use this type modulation in this thesis.

The second part of the thesis is the procedure of design and experiment. …

Calibration Of Photoluminescence Experiment, Chihchuan Daniel Lee

Theses

Photoluminescence in a semiconductor at room temperature is quite difficult to distinguish from the many nonlasing optical lines from the laser, therefore, a blank test is very important. In so doing, the noises of the detector has to be taken into account. The calibration, however, mainly depends on the detector and is less dependent on other components. Instead of using black-body radiation light source and pyroelectric detector, we use globar lamp and PbS detector; because of the difficulty in the former case in doing alignment of optical path (invisible) and operating at a lower signal level from the detector. The …

Differential Cross Sections For The Production Of Highly Charged Recoil Ions In 10 Mev F⁸⁺ → Ne Collisions, S. Lencinas, J. Ullrich, R. Domer, Ronald E. Olson, W. Wolff, H. Wolf, L. Spielberger, S. Hagmann, M. Horbatsch, C. L. Cocke, H. Schmidt-Bocking

Physics Faculty Research & Creative Works

Using recoil-ion momentum spectroscopy (rims), we have measured differential cross sections for the production of highly charged Ne ions in collisions with 10 MeV Fs+ as a function of the recoil-ion transverse momentum and charge state. In addition, the outgoing projectiles were charge-state analyzed and detected in coincidence with the Ne recoil-ions. Thus, different reaction channels like direct ionization, single- and double-electron capture by the projectile could be separated. The recoil-ion transverse momentum p£ was determined with an accuracy comparable to a projectile scattering angle resolution of 2.5 x 10"5 rad. The experimental data are compared to results of classical …

Phase Structure Of Four Dimensional Simplicial Quantum Gravity, Simon Catterall, John B. Kogut, R. Renken

Physics - All Scholarship

We present the results of a high statistics Monte Carlo study of a model for four dimensional euclidean quantum gravity based on summing over triangulations. We show evidence for two phases; in one there is a logarithmic scaling on the mean linear extent with volume, whilst the other exhibits power law behaviour with exponent 1/2. We are able to extract a finite size scaling exponent governing the growth of the susceptibility peak

Additive Pulse Mode-Locking Using A Birefringent Optical Fiber, Sandra F. Feldman, B. A. Moore, Doreen A. Weinberger, Herbert G. Winful

Physics: Faculty Publications

A powerful and increasingly common method to mode-lock a variety of lasers is additive pulse mode-locking (APM). In this technique, a nonlinear medium is placed in an external cavity which is coupled to the main laser cavity. As a result of interference at the common mirror between the pulses returning from each cavity, significant pulse shortening may be obtained. Optical fiber is often used as the nonlinear medium, and polarization effects and fiber birefringence are generally neglected. A computer model has been developed in order to simulate the effect of using a birefringent fiber. The simulations indicate that although the …