Physical Sciences and Mathematics Commons^™

Refractive-Index Measurements Of Zinc Germanium Diphosphide At 300 And 77 K By Use Of A Modified Michelson Interferometer, Glen D. Gillen, Shekhar Guha

Physics

A method to determine the absolute refractive index of materials available in the shape of flat wafers with parallel sides by using interferometric techniques is presented. With this method, nondestructive, sample-specific measurements can be made. The method is tested by using silicon, germanium and zinc selenide, and measurements for both the ordinary and extraordinary axes of ZnGeP₂ for temperatures of 300 and 77 K are reported.

Amps-1d Modeling Of A-Si:H N^{+}-I-N^{+} Structure: The Validity Of Space Charge Limited Current Analysis, Aynur Eray, G. Nobile

Turkish Journal of Physics

In this paper, the AMPS-1D (Analysis of Microelectronic and photonic structure) simulation program is used to understand the origin of the differences observed in Space Charge Limited Current (SCLC) analysis in thin and thick a-Si:H n^{ +} -i- n^{+} structure. For that purpose, the problem of applicability of SCLC measurements to n^{+}-i-n^{+} a-Si:H samples are investigated by using both the thin (0.3 \mu m) and thick (3 \mu m) samples. The simulation results show that activation energy in thick samples is larger than in thinner samples, which are an agreement with the experimental results. It is emphasized that this method …

Chemistry-Induced Intrinsic Stress Variations During The Chemical Vapor Deposition Of Polycrystalline Diamond, Ashok Rajamani, Brian W. Sheldon, Sumit Nijhawan, Alan Schwartzman, Janet Rankin, Barbara L. Walden, Laura Riester

Faculty Scholarship

Intrinsic tensile stresses in polycrystalline films are often attributed to the coalescence of neighboring grains during the early stages of film growth, where the energy decrease associated with converting two free surfaces into a grain boundary provides the driving force for creating tensile stress. Several recent models have analyzed this energy trade off to establish relationships between the stress and the surface∕interfacial energy driving force, the elastic properties of the film, and the grain size. To investigate these predictions, experiments were conducted with diamond films produced by chemical vapor deposition. A multistep processing procedure was used to produce films with …

High-Speed Electronic Speckle Pattern Interferometry, Carol Armstrong

Masters

Electronic Speckle Pattern Interferometry (ESPI) is used to measure surface displacements. Phase shifting can be used to obtain a fringe pattern which depicts the phase at every point in an image. Previous studies have used algorithms such as the 4-bucket algorithm to obtain phase maps of objects. After the object is displaced a second phase map is obtained in the same way and by correlation the phase difference due to the displacement can be determined. When the object is in rapid continuous motion these algorithms cannot be used. Towards this end a 5-frame algorithm was written, in which the calibrated …

Radiation Transport Modeling Using Parallel Computational Techniques, William Culbreth, Denis Beller

Reactor Campaign (TRP)

The second year of this project involved modeling several aspects of the LANCSE beam experiments:

• Modeling targets of varying diameter in air, in a vacuum, and in the presence of humid air;
• Modeling various proton beam profiles;
• Modeling the effects of off-axis proton beam impingement on the target;
• Modeling the asymmetry introduced by the steel table below the target;
• Modeling the effect of varying ratios of Pb to Bi and the effect of impurities; and
• Modeling the system, including other structures within the test room.

With the experience gained through modeling these systems, the UNLV researchers plan, with the assistance …

University Of Nevada, Las Vegas Transmutation Research Program Annual Report Academic Year 2003-2004, Anthony Hechanova, Elizabeth Johnson, Gary Cerefice

Transmutation Research Program Reports (TRP)

It is my pleasure to present the UNLV Transmutation Research Program’s third annual report that highlights the academic year 2003 – 2004. Supporting this document are the many technical reports and scientific papers that have been generated over the past three years.

In the third year of our program, we experienced infrastructure growth despite a decreasing budget. This past year we continued into the final phases of the initial 16 independent student research tasks started in 2001 and 2002, supporting 45 graduate students and 11 undergraduates in 6 academic departments across the UNLV scientific and engineering communities during the academic …

Investigation Of Optical Spectroscopy Techniques For On-Line Materials Accountability In The Solvent Extraction Process, Gary Cerefice, Kenneth Czerwinski

Safeguards Campaign (TRP)

The goal of this project is to examine the potential for using optical spectroscopy techniques, such as UV-Visible Spectroscopy and Laser Fluorescence Spectroscopy, for special nuclear materials accountability applications for the UREX+ and other solvent extraction processes. To increase the inherent proliferation resistance of the solvent extraction process, it is necessary to develop on-line techniques to directly measure the concentrations of special nuclear materials in-process. By providing on-line materials accountability for the processes, the potential for covert diversion of the materials streams becomes much more difficult to implement. On-line monitoring of material streams will also allow for improved plant operation, …

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

Transmutation Sciences Materials (TRP)

There is an active international interest in lead-bismuth eutectic and similar liquid lead systems because of the relevance to the transmutation of nuclear waste, fast reactors, and spallation neutron sources. A successful program in nuclear waste processing that includes transmutation in accelerator-driven systems and fast reactors, would significantly decrease the space requirements for geological repositories.

Materials in these systems must be able to tolerate high neutron fluxes, high temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge because the corrosive behaviors of materials in LBE are not well understood. Most of the available information …

Stress Corrosion Cracking Of Target Material, Mohammad K. Hossain

Transmutation Sciences Materials (TRP)

The primary objective of this paper is to evaluate the effect of hydrogen on environment assisted cracking of candidate target materials for transmutation applications. Transmutation refers to transformation of long-lived actinides and fission products from spent nuclear fuels (SNF), and occurs when the nucleus of an atom changes because of natural radioactive decay, nuclear fission, nuclear fusion, neutron capture, or other related processes. Martensitic Alloy EP 823 was selected to be the candidate alloy for this investigation. During the initial phase, the stress corrosion cracking (SCC) behavior of this alloy was evaluated in neutral (pH: 6-7) and acidic (pH: 2-3) …

Neutron Multiplicity Measurements Of Target/Blanket Materials, Denis Beller

Transmutation Sciences Physics (TRP)

To optimize the performance of accelerator-driven transmutation subcritical systems (ADS), engineers will need to design the system to operate with a neutron multiplication factor just below that of a critical, or self-sustaining, system. This design criterion requires particle transport codes that instill the highest level of confidence with minimal uncertainty, because larger uncertainties in the codes require larger safety margins in the design and result in a lower efficiency of the ADS transmuter. For current design efforts in the U.S., a Monte Carlo particle transport code MCNPX is used to model neutron production and transport for spallation neutron systems.

While …

Development Of Dose Coefficients For Radionuclides Produced In Spallation Targets, Phillip W. Patton, Mark Rudin

Transmutation Sciences Physics (TRP)

Dose coefficients permit simple determination of radiation dose associated with various exposure scenarios, and ultimately permit radiation safety personnel to assess the health risks to workers in a nuclear facility. Specifically, radiation safety personnel use dose coefficients to determine the radiation dose incurred to a tissue or organ system from a given exposure. These parameters are often expressed in terms of Annual Limits on Intake (ALIs) and Derived Air Concentrations (DACs).

Results from this study will be used to produce ALIs and DACs for these rare radionuclides created by spallation target systems that are not included in Federal Guidance Report …

Nuclear Criticality, Shielding, And Thermal Analyses Of Separations Processes For The Transmutation Fuel Cycle, William Culbreth

Separations Campaign (TRP)

The first step in any transmutation strategy is the separation of radionuclides in used nuclear fuel. The current separation strategy supporting the Advanced Fuel Cycle Initiative (AFCI) program is based on the use of a solvent extraction separation process to separate the actinides, fission products, and uranium from used commercial nuclear fuel, and on the use of pyrochemical separation technologies to process used transmuter fuels. To separate the fission products and transuranic elements from the uranium in used fuel, the national program is developing a new solvent extraction process, the Uranium Extraction Plus, or UREX+, process based on the traditional …

Performance Characteristics Of Beamline 6.3.1 From 200 Ev To 2000 Ev At The Advanced Light Source, Ponnusamy Nachimuthu, J. H. Underwood, C. D. Kemp, Eric M. Gullikson, Dennis W. Lindle, David K. Shuh, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

Bend magnet beamline 6.3.1 at the Advanced Light Source operates from 200 eV to 2000 eV, primarily used for x-ray absorption fine structure investigations. The beamline optics consist of a compact, entrance-slitless, Hettrick-Underwood type variable-line-spacing plane-grating monochromator and refocusing mirrors to provide a 25 μm × 500 μm spot at the focal point in the reflectometer end station. Wavelength is scanned by the simple rotation of the grating and illuminates a fixed exit slit. The LabView based beamline control and data acquisition computer code has been implemented to provide a convenient interface to the user. The dedicated end station is …

Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Darrell Pepper, Randy Clarksean

Fuels Campaign (TRP)

The goal of this project is to investigate the casting processes for metallic fuels to help design a process that minimizes the loss of the volatile actinide elements from the fuel. The research effort centers on the development of advanced numerical models to assess conditions that significantly impact the transport of volatile actinides during the melt casting process and represents a joint effort between researchers at UNLV and Argonne National Laboratory (ANL). Assessing critical equipment and process variables is required to build a successful system that will operate efficiently.

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski

Fuels Campaign (TRP)

This project will examine inert fuels containing ZrO₂ and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO₂. Reactor physics calculations will be used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10 % of ²³⁹Pu. Ceramics will be synthesized and characterized based on the reactor physics results. The solubility the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, will be investigated in a manner to provide …

Global Assimilation Of Ionospheric Measurements (Gaim), Robert W. Schunk, Ludger Scherliess, Jan Josef Sojka, Donald C. Thompson, David N. Anderson, Mihail Codrescu, Cliff Minter, Timothy J. Fuller-Rowell, Roderick A. Heelis, Marc Hairston, Bruce M. Howe

All Physics Faculty Publications

The ionosphere is a highly dynamic medium that exhibits weather disturbances at all latitudes, longitudes, and altitudes, and these disturbances can have detrimental effects on both military and civilian systems. In an effort to mitigate the adverse effects, we are developing a physics-based data assimilation model of the ionosphere and neutral atmosphere called the Global Assimilation of Ionospheric Measurements (GAIM). GAIM will use a physics-based ionosphere-plasmasphere model and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. Some of the data to be assimilated include in situ density measurements from satellites, ionosonde …

Development Of A Physics-Based Reduced State Kalman Filter For The Ionosphere, Ludger Scherliess, Robert W. Schunk, Jan Josef Sojka, Donald C. Thompson

All Physics Faculty Publications

A physics-based data assimilation model of the ionosphere is under development as the central part of a Department of Defense/Multidisciplinary University Research Initiative (MURI)-funded program called Global Assimilation of Ionospheric Measurements (GAIM). With the significant increase in the number of ionospheric observations that will become available over the next decade, this model will provide a powerful tool toward an improved specification and forecasting of the global ionosphere, with an unprecedented accuracy and reliability. The goal of this effort will be specifications and forecasts on spatial grids that can be global, regional, or local (25 km × 25 km). The specification/forecast …

Understanding Mid-Latitude Space Weather: Storm Impacts Observed At Blo On 31 March 2001, Jan Josef Sojka, D. Rice, J. V. Eccles, F. T. Berkey, P. Kintner, W. Denig

All Physics Faculty Publications

On 30 March 2001 in the late evening an auroral display was observed over the United States of America. The Bear Lake Observatory (BLO) magnetometer in Utah measured changes of 550 nT in less than 30 min. During the same period, BLO ionosonde measurements showed deep high-frequency radio wave absorption up to 7 MHz. BLO's GPS single-frequency receiver experienced geolocation errors of 20 m for over 3 hours. These storm signatures were also accompanied by L-band scintillation effects which approached an S4 value of 0.2, which is large for midlatitudes. Although such measurements have been have been made at …

Ionospheric Assimilation Techniques For Argos Low-Resolution Airglow And Aurora Spectrograph (Loraas) Tomographically Reconstructed Equatorial Electron Density Profiles, Jan Josef Sojka, J. V. Eccles, Robert W. Schunk, S. Mcdonald, S. Thonnard, K. Dymond, R. P. Mccoy

All Physics Faculty Publications

The LORAAS instrument aboard the ARGOS satellite observes line-of-sight ultraviolet limb intensities from ionosphere and thermosphere airglow. This study uses tomographically reconstructed electron density profiles (EDPs) from the nightside emissions. The ionospheric reconstruction is performed using a two-dimensional O+ 1356Å radiative recombination forward model and discrete inverse theory. The forward model assumes a Chapman layer for the vertical electron density distribution from which h m F 2, N m F 2, and topside scale height are derived for every 90 s limb scan, which is equivalent to 5° resolution in latitude. Since ARGOS is in a near Sun-synchronous orbit, these …

Space Weather Effects On Mid-Latitude Hf Propagation Paths: Observations And A Data-Driven D-Region Model, J. V. Eccles, R. D. Hunsucker, D. Rice, Jan Josef Sojka

All Physics Faculty Publications

A two-pronged study is under way to improve understanding of the D region response to space weather and its effects on HF propagation. One part, the HF Investigation of D region Ionospheric Variation Experiment (HIDIVE), is designed to obtain simultaneous, quantitative propagation and absorption data from an HF signal monitoring network along with solar X-ray flux from the NOAA GOES satellites. Observations have been made continuously since late December 2002 and include the severe disturbances of October–November 2003. GOES satellite X-ray observations and geophysical indices are assimilated into the Data-Driven D Region (DDDR) electron density model developed as the second …

Observations Of Atmosphericgravity Waves Using Airglow All-Sky Ccd Imager At Cachoeira Paulista (23° S, 45° W), A. F. Medeiros, H. Takahashi, P. P. Batista, D. Gobbi, Michael J. Taylor

All Physics Faculty Publications

An all-sky CCD imager for OH, O2 and OI (557.7 nm) airglow was operated at Cachoeira Paulista (CP), Brazil, (23° S, 45° W), from October 1998 to September 1999, with Utah State University. Dominant gravity wave components are extracted and seasonal variations are investigated. These waves have typically short horizontal wavelengths (5 - 60 km), short periods (5 - 35 minutes), and horizontal phase speeds of 1 - 80 m/s. Band-type waves of horizontal wavelength between 10 and 60 km showed clear seasonal dependence in the horizontal propagation direction to southeast in summer and to northwest in winter. The direction …

Lisa Time-Delay Interferometry Zero-Signal Solution: Geometrical Properties, Massimo Tinto, Shane L. Larson

All Physics Faculty Publications

Time-delay interferometry (TDI) is the data processing technique needed for generating interferometric combinations of data measured by the multiple Doppler readouts available onboard the three Laser Interferometer Space Antenna (LISA) spacecraft. Within the space of all possible interferometric combinations TDI can generate, we have derived a specific combination that has zero response to the gravitational wave signal, and called it the zero-signal solution (ZSS). This is a two-parameter family of linear combinations of the generators of the TDI space, and its response to a gravitational wave becomes null when these two parameters coincide with the values of the angles of …

Cosmology, Cohomology, And Compactification, Charles G. Torre

All Physics Faculty Publications

Ashtekar and Samuel have shown that Bianchi cosmological models with compact spatial sections must be of Bianchi class A. Motivated by general results on the symmetry reduction of variational principles, we show how to extend the Ashtekar-Samuel results to the setting of weakly locally homogeneous spaces as defined, e.g., by Singer and Thurston. In particular, it is shown that any m-dimensional homogeneous space G/K admitting a G-invariant volume form will allow a compact discrete quotient only if the Lie algebra cohomology of G relative to K is non-vanishing at degree m.

Thermochemical And Green Luminescence Analysis Of Zinc Oxide Thin Films Grown On Sapphire By Chemical Vapor Deposition, Abdelkader Djelloul, R. A. Rabadanov

Turkish Journal of Physics

This study has been carried out to detail an integral thermochemical analysis of the principal reaction in the production of zinc oxide (ZnO) thin films, including developing an analytical form of the equilibrium constant. Zinc oxide thin films prepared by chemical vapor deposition have been studied in terms of deposition time and substrate temperature. The growth of the single-crystal films present two regimes depending on the substrate temperature, with increasing constant growth rates at lower, and higher, temperature ranges, respectively. Growth rates above 6 \mu m \cdot min^{-1} can be achieved at T_s = 880 K. The variation of the …

Single Mode Optical Radiation Distribution And Reflectivity Calculations In Novel-Hot Electron Light Emission And Lasing In Semiconductor Heterostructures Vcsels, Ebru Şenadim Tüzemen, Yüksel Ergun

Turkish Journal of Physics

In this work, we calculate the power reflectivity in vertical cavity surface emitting lasers (VCSELs) using a new method. In VCSELs, the stop band of the reflectivity spectrum should exhibit a dip at the lasing wavelength, which is a condition for lasing. This current approximation method gives a simple analytical expression to find the power reflectivity as a function of wavelength in the vicinity of lasing wavelength, \lambda_°. The proposed method can generally be applied to semiconductor VCSEL systems for a given lasing wavelength.

Polar Optical Phonon Modes And Fröhlich Electron-Phonon Interaction Hamiltonians In Coaxial Cylindrical Quantum Cables, Li Zhang, Hong-Jing Xie

Turkish Journal of Physics

By using the dielectric continuum approximation, the polar optical phonon modes of coaxial cylindrical quantum cables with arbitrary layer-number were studied. In order to describe the vibrating of the longitudinal-optical (LO) phonons, a set of legitimate eigenfunctions for LO phonon modes are constructed and adopted. In order to deal with the interface optical (IO) phonon modes, the transfer matrix method is employed. The quantized LO and IO phonons fields, as well as their corresponding Fröhlich electron-phonon interaction Hamiltonians, are also derived. Numerical calculations on a four-layer GaAs/Al_xGa_{1-x}As QC have been performed. Results reveal that there are six branches of IO …

Logical Pre- And Post-Selection Paradoxes, Measurement-Disturbance And Contextuality, Matthew S. Leifer, R. W. Spekkens

Mathematics, Physics, and Computer Science Faculty Articles and Research

Many seemingly paradoxical effects are known in the predictions for outcomes of measurements made on pre- and post-selected quantum systems. A class of such effects, which we call “logical pre- and post-selection paradoxes”, bear a striking resemblance to proofs of the Bell-Kochen-Specker theorem, which suggests that they demonstrate the contextuality of quantum mechanics. Despite the apparent similarity, we show that such effects can occur in noncontextual hidden variable theories, provided measurements are allowed to disturb the values of the hidden variables.

Low Temperature Silicon Epitaxy On Hydrogen Terminated Si(100) Surfaces, J. -Y. Ji, T. -C. Shen

T. -C. Shen

Si deposition on H terminated Si(001)-2×1 surfaces at temperatures 300–530K is studied by scanning tunneling microscopy. Hydrogen apparently hinders Si adatom diffusion and enhances surface roughening. The post-growth annealing effect is analyzed. Hydrogen is shown to remain on the growth front up to at least 10ML. Si deposition onto the H/Si(001)-3×1 surface at 530K suggests that dihydride units further suppress Si adatom diffusion and increase surface roughness.

Global Dayside Ionospheric Uplift And Enhancements Due To Interplanetary Shock Electric Fields, B. R. Tsurutani, A. Mannucci, B. Ijima, A. Saito, K. Yumoto, M. A. Abdu, J. H.A. Sobral, W. D. Gonzalez, F. L. Guarnieri, T. Tsuda, Bela G. Fejer, T. J. Fuller-Rowell, J. U.O. Kozyra, J. C. Foster, A. Coster, V. M. Vasyliumas

Bela G. Fejer

[1] The interplanetary shock/electric field event of 5–6 November 2001 is analyzed using ACE interplanetary data. The consequential ionospheric effects are studied using GPS receiver data from the CHAMP and SAC-C satellites and altimeter data from the TOPEX/Poseidon satellite. Data from ∼100 ground-based GPS receivers as well as Brazilian Digisonde and Pacific sector magnetometer data are also used. The dawn-to-dusk interplanetary electric field was initially ∼33 mV/m just after the forward shock (IMF BZ = −48 nT) and later reached a peak value of ∼54 mV/m 1 hour and 40 min later (BZ = −78 nT). The electric field was …

Magnetospheric Electric Fields And Plasma Sheet Injections To Low-Lshells During The June 4-5, 1991 Magnetic Storm: Comparison Between The Rice Convectionmodel And Observations, T. W. Garner, R. A. Wolf, R. W. Spiro, W. J. Burke, Bela G. Fejer, S. Sazykin, J. L. Roeder, M. R. Hairston

Bela G. Fejer

[1] The major magnetic storm of 4–5 June 1991 was well observed with the Combined Release and Radiation Experiment (CRRES) satellite in the duskside inner magnetosphere and with three Defense Meteorological Satellite Program (DMSP) spacecraft in the polar ionosphere. These observations are compared to results from the Rice Convection Model (RCM), which calculates the inner magnetospheric electric field and particle distribution self-consistently. This case study, which uses the most complete RCM runs to date, demonstrates two significant features of magnetospheric storms, the development of subauroral polarization streams (SAPS) and plasma-sheet particle injection deep into the inner magnetosphere. In particular, the …