24 Matching Results

Search Results

Advanced search parameters have been applied.

Consistency between Angular Distributions and Integral Quantities Calculated with the Nuclear Ramsauer Model

Description: This report reviews the connection between the exact expression for the scattering amplitude and its approximation by the nuclear Ramsauer model. This approximation is well defined only for integral values of kR, the product of the neutron wave number and a nuclear radius parameter. Using the model between these integral values requires the introduction of an interpolation scheme. We show the effects on physical observables of adding an extra term to the scattering amplitude. By choosing the functional form of this term it is possible to obtain smooth behavior with energy of some of the physical observables, but not all.
Date: December 20, 2004
Creator: Dietrich, F S
Partner: UNT Libraries Government Documents Department

A Revised Magnitude and Distance Amplitude Correction (MDAC2) Procedure for Regional Seismic Discriminants: Theory and Testing at NTS

Description: The Magnitude and Distance Amplitude Correction (MDAC; Taylor and Hartse, 1998; Taylor et al., 2002) procedure for correcting regional seismic amplitudes for seismic event identification has been modified to include more realistic earthquake source models and source scaling. In the MDAC2 formulation we generalize the Brune (1970) earthquake source spectrum to use a more physical apparent stress model that can represent non-constant stress-drop scaling. We also event include a parameter that allows for variable P-wave and S-wave comer frequency scaling, imposing some of the constraints of ratio correction techniques (Rodger and Walter, 2002). Very Stable moment magnitude measures (Mayeda et al., 2002) from regional coda wave envelopes that have been tied to independently derived regional seismic moments are incorporated. This eliminates two fitting parameters that were necessary in relating seismic moment to magnitude. The incorporation of Bayesian tomography to replace the assumption of a constant Q0 model is also described. These modifications allow for more flexibility in the MDAC grid-search procedure. The direct tie to regional seismic moment rather than body wave magnitude reduces effects of upper mantle bias on the corrected amplitudes. In this paper, we develop the theory and test the formulation on Nevada Test Site (NTS) data.
Date: December 21, 2001
Creator: Walter, W R & Taylor, S R
Partner: UNT Libraries Government Documents Department

Inelastic electron scattering from surfaces. Progress report for second grant year

Description: This report contains highlights of accomplishments of the past year, for the University of California, Irvine and the University of Wisconsin, Milwaukee collaboration on surface excitations, and their interactions with low energy electrons. In addition, we present a summary of future research to be carried out in the coming grant year.
Date: December 31, 1991
Creator: Tong, S. Y. & Mills, D. L.
Partner: UNT Libraries Government Documents Department

A tevatron collider beauty factory. [Final report, 1980--1992]

Description: This document which is labeled a final report consists of several different items. The first is a proposal for a detector to be developed for beauty physics. The detector is proposed for the Fermilab Tevatron, and would be designed to measure mixing reactions, rare decay modes, and even CP violation in hadron collider beauty production. The general outline of the work proposed is given, and an estimate of the time to actually design the detector is presented, along with proposed changes to the Tevatron to accommodate the system. A preliminary report on an experiment to verify a reported observation of a 17 keV neutrino in tritium decay is presented. The present results in the decay spectra actually show a depression below expected levels, which is not consistent with a massive neutrino. Additional interest has been shown in finishing an electrostatic beta spectrometer which was started several years previously. The instrument uses hemispherical electrostatic electric fields to retard electrons emitted in tritium decay, allowing measurement of integral spectra. The design goal has a 5 eV energy resolution, which may be achievable. A new PhD student is pursuing this experiment. Also the report contains a proposal for additional work in the field of non-perturbative quantum field theory by the theoretical group at OU. The work which is proposed will be applied to electroweak and strong interactions, as well as to quantum gravitational phenomena.
Date: December 31, 1992
Partner: UNT Libraries Government Documents Department

Theoretical Atomic Physics code development IV: LINES, A code for computing atomic line spectra

Description: A new computer program, LINES, has been developed for simulating atomic line emission and absorption spectra using the accurate fine structure energy levels and transition strengths calculated by the (CATS) Cowan Atomic Structure code. Population distributions for the ion stages are obtained in LINES by using the Local Thermodynamic Equilibrium (LTE) model. LINES is also useful for displaying the pertinent atomic data generated by CATS. This report describes the use of LINES. Both CATS and LINES are part of the Theoretical Atomic PhysicS (TAPS) code development effort at Los Alamos. 11 refs., 9 figs., 1 tab.
Date: December 1, 1988
Creator: Abdallah, J. Jr. & Clark, R.E.H.
Partner: UNT Libraries Government Documents Department

Model tests of OTEC-1: test of HMB with and without cold water pipes

Description: In early 1977, ERDA began an extensive study of various factors which could effect the early design and deployment of OTEC-1, a test platform for evaluation of one megawatt (1 MW) OTEC heat exchangers. The platform was to consist of the Hughes Mining Barge (HMB) and a 3000 foot deep cold water pipe (CWP). One of the factors to be considered was the motions of the HMB and the motions, loads and stresses of the CWP. Several theoretical methods, including one developed at HYDRONAUTICS, Incorporated were to be used to predict motions and CWP loads and stresses. There existed, however, no model tests or other validation of these theoretical methods. The lack of any validation of the theoretical methods was of some concern as early studies indicated that high CWP bending stresses, in particular, could represent a significant design problem. In early May 1977, HYDRONAUTICS proposed to carry out model tests of a one-fiftieth scale model of the HMB with several CWP models representing relatively rigid (steel) and flexible (glass reinforced plastic GRP) CWP's. This proposal was accepted by ERDA, and the model tests were carried out during June 1977. Preliminary results were provided to ERDA during June and July 1977. This report describes the work carried out and presents and discusses the results, including a comparison of measured and predicted results.
Date: December 1, 1977
Creator: Sheldon, L. R.; Barr, R. A. & O'Dea, J. F.
Partner: UNT Libraries Government Documents Department

High energy behavior of fermion--meson and meson--meson scattering in a supersymmetric field theory

Description: A review of the general methods of high energy calculations within the framework of field theory is given. These include Feynman parameter methods, the infinite momentum frame, and Mellin transform methods. A general discussion of supersymmetry is also presented. The basic aspects of the Wess-Zumino model are given. This includes a proof of renormalizability through one-loop, and a derivation of the Feynman rules. The general supersymmetry algebra is presented. The method of generating representations of this algebra through the concept of superfields is discussed. The high energy behavior of fermion-boson and boson-boson scattering amplitudes of a supersymmetric field theory containing a spin-/sup 1///sub 2/ fermion field, a scalar field, and a pseudoscalar field is investigated. The results can be easily modified to apply to the Yukawa model and the neutral version of the linear sigma model. The results are also compared to those of fermion-fermion scattering in the same model. In the leading logarithm approximation, ladders with fermions running along the sides in the t channel and mesons as rungs dominate in each order of two classes of diagrams. The sums of the dominant series give rise to fixed Regge cuts for all amplitudes in each of the three theories. All amplitudes in the supersymmetric theory possess a definite signature factor, while the amplitudes for fermion-fermion and fermion-antifermion scattering in the Y model and the sigma model lack it. The results of the supersymmetric theory are also compared to the results of the spontaneously broken non-Abelian gauge theory.
Date: December 1, 1977
Creator: Opoien, J.W.
Partner: UNT Libraries Government Documents Department

Acoustic emission energy to pulse height converter

Description: An enengy-to-pulse-height converter was developed for use in acoustic emission testing. This instrument accepts an amplified signal from a piezoelectric crystal and generates a pulse whose amplitude is propontional to either the energy or width of the input signal. Either linear or logarithmic responses can be selected. Theory, circuit design, and performance specifications have been determined, based on calculations and measurements. (auth)
Date: December 18, 1973
Creator: Speller, B. W.
Partner: UNT Libraries Government Documents Department

An Analytic Study of the Perpendicularly Propagating Electromagnetic Drift Instabilities in the Magnetic Reconnection Experiment

Description: A local linear theory is proposed for a perpendicularly propagating drift instability driven by relative drifts between electrons and ions. The theory takes into account local cross-field current, pressure gradients and modest collisions as in the Magnetic Reconnection Experiment (MRX) [10]. The unstable waves have very small group velocities in the direction of the pressure gradient, but have a large phase velocity near the relative drift velocity between electrons and ions in the direction of cross-field current. By taking into account the electron-ion collisions and applying the theory in the Harris sheet, we establish that this instability could be excited near the center of the Harris sheet and have enough efoldings to grow to large amplitude before it propagates out of the unstable region. Comparing with the other magnetic reconnection related instabilities (LHDI, MTSI et.) studied previously, we believe the instability we find is a favorable candidate to produce anomalous resistivity because of its unique wave characteristics, such as electromagnetic component, large phase velocity, and small group velocity in the cross current layer direction.
Date: December 3, 2008
Creator: Wang, Y.; Kulsrud, R. & Ji, H.
Partner: UNT Libraries Government Documents Department

Restrictions on TWT Helix Voltage Ripple for Acceptable Notch Filter Performance

Description: An ac ripple on the helix voltage of the 1-2 GHz TWT's creates FM sidebands that cause amplitude and phase modulation of the microwave TWT output signal. A limit of 16 volts peak-to-peak is required for acceptable superconducting notch filter performance.
Date: December 1, 1984
Creator: Hyslop, B.
Partner: UNT Libraries Government Documents Department

3D Sedimentological and geophysical studies of clastic reservoir analogs: Facies architecture, reservoir properties, and flow behavior within delta front facies elements of the Cretaceous Wall Creek Member, Frontier Formation, Wyoming

Description: Significant volumes of oil and gas occur in reservoirs formed by ancient river deltas. This has implications for the spatial distribution of rock types and the variation of transport properties. A between mudstones and sandstones may form baffles that influence productivity and recovery efficiency. Diagenetic processes such as compaction, dissolution, and cementation can also alter flow properties. A better understanding of these properties and improved methods will allow improved reservoir development planning and increased recovery of oil and gas from deltaic reservoirs. Surface exposures of ancient deltaic rocks provide a high-resolution view of variability. Insights gleaned from these exposures can be used to model analogous reservoirs, for which data is sparser. The Frontier Formation in central Wyoming provides an opportunity for high-resolution models. The same rocks exposed in the Tisdale anticline are productive in nearby oil fields. Kilometers of exposure are accessible, and bedding-plane exposures allow use of high-resolution ground-penetrating radar. This study combined geologic interpretations, maps, vertical sections, core data, and ground-penetrating radar to construct geostatistical and flow models. Strata-conforming grids were use to reproduce the observed geometries. A new Bayesian method integrates outcrop, core, and radar amplitude and phase data. The proposed method propagates measurement uncertainty and yields an ensemble of plausible models for calcite concretions. These concretions affect flow significantly. Models which integrate more have different flow responses from simpler models, as demonstrated an exhaustive two-dimensional reference image and in three dimensions. This method is simple to implement within widely available geostatistics packages. Significant volumes of oil and gas occur in reservoirs that are inferred to have been formed by ancient river deltas. This geologic setting has implications for the spatial distribution of rock types (\Eg sandstones and mudstones) and the variation of transport properties (\Eg permeability and porosity) within bodies of a particular rock type. Both ...
Date: December 21, 2009
Creator: White, Christopher D.
Partner: UNT Libraries Government Documents Department

Scaling of radial propagating structures in the scrape-off layer of the National Spherical Torus Experiment (NSTX)

Description: The radial propagation of spatiotemporal turbulent structures in the scrape-off layer of the National Spherical Torus Experiment [M. Ono, M.G. Bell, R.E. Bell, et al. Plasma Phys. Control. Fusion 45, A335 (2003)] is investigated. Two-dimensional spatiotemporal imaging of the Dα emission intensity is used to observe the fluctuation structures in the poloidal plane perpendicular to the ambient magnetic field. Turbulent structures are extracted and the individual properties such as velocity, spatial scale and amplitude are determined. The typical poloidal scale of the structures is kϑ = 0.5 cm−1. The poloidal and radial structure velocities are < 5 km/s and 1 km/s, respectively. The radial velocities do not vary significantly with their spatial size within this set of data.
Date: December 8, 2008
Creator: Windisch, T., Grulke, O., Zweben, S.J., and Maqueda, J.R.
Partner: UNT Libraries Government Documents Department

Maximum Alpha to Minimum Fission Pulse Amplitude for a Parallel-Plate and Hemispherical Cf-252 Ion-Chamber Instrumented Neutron Source

Description: In an instrumented Cf-252 neutron source, it is desirable to distinguish fission events which produce neutrons from alpha decay events. A comparison of the maximum amplitude of a pulse from an alpha decay with the minimum amplitude of a fission pulse shows that the hemispherical configuration of the ion chamber is superior to the parallel-plate ion chamber.
Date: December 7, 2000
Creator: Oberer, R.B.
Partner: UNT Libraries Government Documents Department

Frequency content of current pulses in slapper detonator bridges

Description: DFT amplitudes are obtained for digital current pulse files. The frequency content of slapper detonator bridge current pulses is obtained. The frequencies are confined well within the passband of the CVR used to sample them.
Date: December 18, 2006
Creator: Carpenter, K. H.
Partner: UNT Libraries Government Documents Department

Renormalization Scale-Fixing for Complex Scattering Amplitudes

Description: We show how to fix the renormalization scale for hard-scattering exclusive processes such as deeply virtual meson electroproduction by applying the BLM prescription to the imaginary part of the scattering amplitude and employing a fixed-t dispersion relation to obtain the scale-fixed real part. In this way we resolve the ambiguity in BLM renormalization scale-setting for complex scattering amplitudes. We illustrate this by computing the H generalized parton distribution at leading twist in an analytic quark-diquark model for the parton-proton scattering amplitude which can incorporate Regge exchange contributions characteristic of the deep inelastic structure functions.
Date: December 21, 2005
Creator: Brodsky, Stanley J.; /SLAC; Llanes-Estrada, Felipe J. & U., /Madrid
Partner: UNT Libraries Government Documents Department


Description: The U.S. natural gas pipeline industry is facing the twin challenges of increased flexibility and capacity expansion. To meet these challenges, the industry requires improved choices in gas compression to address new construction and enhancement of the currently installed infrastructure. The current fleet of installed reciprocating compression is primarily slow-speed integral machines. Most new reciprocating compression is and will be large, high-speed separable units. The major challenges with the fleet of slow-speed integral machines are: limited flexibility and a large range in performance. In an attempt to increase flexibility, many operators are choosing to single-act cylinders, which are causing reduced reliability and integrity. While the best performing units in the fleet exhibit thermal efficiencies between 90% and 92%, the low performers are running down to 50% with the mean at about 80%. The major cause for this large disparity is due to installation losses in the pulsation control system. In the better performers, the losses are about evenly split between installation losses and valve losses. The major challenges for high-speed machines are: cylinder nozzle pulsations, mechanical vibrations due to cylinder stretch, short valve life, and low thermal performance. To shift nozzle pulsation to higher orders, nozzles are shortened, and to dampen the amplitudes, orifices are added. The shortened nozzles result in mechanical coupling with the cylinder, thereby, causing increased vibration due to the cylinder stretch mode. Valve life is even shorter than for slow speeds and can be on the order of a few months. The thermal efficiency is 10% to 15% lower than slow-speed equipment with the best performance in the 75% to 80% range. The goal of this advanced reciprocating compression program is to develop the technology for both high speed and low speed compression that will expand unit flexibility, increase thermal efficiency, and increase reliability and integrity. ...
Date: December 1, 2005
Creator: Deffenbaugh, Danny M.; Brun, Klaus; Harris, Ralph E.; Harrell, J. Pete; Mckee, Robert J.; Moore, J. Jeffrey et al.
Partner: UNT Libraries Government Documents Department

Modification of Particle Distributions By MHD Instabilities I

Description: The modification of particle distributions by low amplitude magnetohydrodynamic modes is an important topic for magnetically confined plasmas. Low amplitude modes are known to be capable of producing significant modification of injected neutral beam profiles, and the same can be expected in burning plasmas for the alpha particle distributions. Flattening of a distribution due to phase mixing in an island or due to portions of phase space becoming stochastic is a process extremely rapid on the time scale of an experiment but still very long compared to the time scale of guiding center simulations. Thus it is very valuable to be able to locate significant resonances and to predict the final particle distribution produced by a given spectrum of magnetohydrodynamic modes. In this paper we introduce a new method of determining domains of phase space in which good surfaces do not exist and use this method for quickly determining the final state of the particle distribution without carrying out the full time evolution leading to it.
Date: December 23, 2010
Creator: White, R. B.
Partner: UNT Libraries Government Documents Department

Implications of Pulser Voltage Ripple

Description: In a recent set of measurements obtained by G. Kamin, W. Manning, A. Molvik, and J. Sullivan, the voltage waveform of the diode pulser had a ripple of approximately {+-}1.3% of the 65 kV flattop voltage, and the beam current had a larger corresponding ripple of approximately {+-}8.4% of the 1.5 mA average current at the location of the second Faraday cup, approximately 1.9 m downstream from the ion source. The period of the ripple was about 1 {mu}s. It was initially unclear whether this large current ripple was in fact a true measurement of the current or a spurious measurement of noise produced by the pulser electronics. The purpose of this note is to provide simulations which closely match the experimental results and thereby corroborate the physical nature of those measurements, and to provide predictions of the amplitude of the current ripples as they propagate to the end of linear transport section. Additionally analytic estimates are obtained which lend some insight into the nature of the current fluctuations and to provide an estimate of what the maximum amplitude of the current fluctuations are expected to be, and conversely what initial ripple in the voltage source is allowed, given a smaller acceptable tolerance on the line charge density.
Date: December 21, 2011
Creator: Barnard, J J
Partner: UNT Libraries Government Documents Department

Quantum non-locality in a two-slit interferometer for short-lived particles

Description: We describe a new test of quantum nonlocality, using an interferometer for short-lived particles. The separation is large compared with the particle lifetimes. This interferometer is realized by vector meson production in distant heavy ion collisions. The mesons decay before waves from the two sources (ions) can overlap, so interference is only possible among the decay products. The post-decay wave function must retain amplitudes for all possible decays. The decay products are spatially separated, necessitating a non-local wave function. The interference is measurable by summing the product momenta. Alternately, the products positions could be observed, allowing new tests of the EPR paradox.
Date: December 1, 2001
Creator: Klein, Spencer R. & Nystrand, Joakim
Partner: UNT Libraries Government Documents Department

High Frequency Electromagnetic Impedance Measurements For Characterization, Monitoring And Verification Efforts

Description: Electromagnetic methods in exploration geophysics include many technologies capable of imaging the subsurface. The electromagnetic geophysical spectrum for shallow subsurface imaging is roughly 1 Hz to 500 MHz, with electrical resistivity and other geometric sounding methods located at the low frequency end and the familiar GPR method at the high end of the spectrum. Baseline studies (Pellerin et al., 1997) show that electromagnetic instrumentation in the mid- and low-frequencies (&lt; 300 kHz) and GPR systems (&gt; 30 MHz) are well developed in the commercial sector. In the high-frequency range of 300 kHz to 100 MHz developments have been quite recent and reside within the research community. Accurate theoretical numerical modeling algorithms are available for simulations and interpretation across the entire spectrum (Mackie and Madden, 1993; Pellerin et al., 1995; Pellerin et al., 1997; Alumbaugh and Newman, 1995; Lee et al., 1995, Newmann and Alumbaugh, 1997; Newmann, 1999; Sasaki, 1999, etc.), but instrumentation suitable for collecting calibrated field data in the important high-frequency range is critically lacking. Several attempts to develop reliable, accurate and calibrated instruments (Sternberg and Poulton, 1996; Stewart et al., 1994; Wright et el., 1996) have produced mixed results. We proposed to exploit the concept of electromagnetic impedance, the ratio of orthogonal horizontal electric to horizontal magnetic fields, to provide the necessary technology in the high-frequency band described above. The effective depth of investigation for surface impedance measurements depends on the frequency, and is commonly expressed in terms of the skin depth, the distance into the conductive half space at which the amplitude of the incoming wave has decreased to e-1 of its surface value. In order to achieve skin depths between 0.5 and 10 meters in material of resistivity between 1 and 100 ohm-m and relative permittivity between 1 and 30, frequencies bet ween about 300 kHz ...
Date: December 31, 2000
Creator: Lee, Ki Ha & Becker, Alex
Partner: UNT Libraries Government Documents Department

The Physical Basis of Lg Generation by Explosion Sources

Description: The goal of this project has been to develop a quantitative predictive capability for explosion-generated Lg phases with a sound and unambiguous physical basis. The research program consisted of a theoretical investigation of explosion-generated Lg combined with an observational study. The specific question addressed by this research program is how the Lg phase is generated by underground nuclear explosions. This question is fundamental to how Lg phases are interpreted for use in explosion yield estimation and earthquake/explosion discrimination. To constrain modeling, we have extensively reviewed the existing literature and complemented that work with an examination of several explosion data sets, most notably: (1) Degelen Mountain explosions recorded between 7 and 57 km, with corresponding recordings at Borovoye, at approximately 650 km; (2) recordings from Russian deep seismic sounding experiments; (3) NTS explosion sources including the NPE and nuclear tests covering a range of source depths and media properties. A simple point explosion in an infinite medium generates no shear waves, so the Lg phase is generated entirely by non-spherical components of the source and conversions through reflections and scattering. We find that the most important contributors to the Lg phase are: (1) P to S conversion at the free surface and other near source interfaces, (2) S waves generated directly by a realistically distributed explosion source including nonlinear effects due to the free surface and gravity, and (3) Rg scattering to Lg. Additional effects that contribute significantly to Lg are scattering of converted S phases that traps more of the converted P-to-S in the crust, and randomization of the components of Lg. The pS phase from a spherically symmetric explosion source in media with P-wave velocity less than upper mantle S-wave velocity is trapped in the crust and can explain the observed radial and vertical Lg. The free surface pS ...
Date: December 20, 2004
Creator: Stevens, J. L.; Baker, G. E.; Xu, H.; Bennett, T. J.; Rimer, N. & Day, S. D.
Partner: UNT Libraries Government Documents Department

Fast Particle Destabilization of Toroidicity Induced Alfven Eigenmodes in National Spherical Torus Experiment

Description: Toroidicity induced Alfven Eigenmode (TAE) stability in National Spherical Torus Experiment (NSTX) is analyzed using the improved NOVA-K code, which includes finite orbit width and Larmor radius effects and is able to predicts the saturation amplitude for the mode using the quasilinear theory. Broad spectrum of unstable global TAEs with different toroidal mode numbers is predicted. Due to the strong poloidal field and the presence of the magnetic well in NSTX better particle confinement in the presence of TAEs in comparison with tokamaks is illustrated making use of the ORBIT code.
Date: December 10, 1999
Creator: Cheng, C.Z.; Fu, G.Y.; Gorelenkova, M.V.; Gorelenkov, N.N.; White, R. & Kaye, S.
Partner: UNT Libraries Government Documents Department

Over-the-road tests of nuclear materials package response to normal environments

Description: In support of the development of American National Standards Institute standards for the transport of radioactive materials, Sandia has a program to characterize the normal transport environment. This program includes both analytical modeling of package and trailer responses, and over-the-road tests to measure those responses. This paper presents the results of a series of over-the-road tests performed using Chem-Nuclear equipment in the Barnwell, SC, area. The test events included a variety of road types such as rough concrete, shock events such as railroad grade crossings, and driver responses such as sharp turns. The response of the package and trailer to these events was measured with accelerometers at various locations to determine the inertial loads. Either load cells or strain gages were used to measure tiedown response. These accelerations and loads were measured on systems with flexible and ``rigid`` tiedowns. The results indicated that while significant accelerations occur on the trailer bed, these do not translate into equivalent loads in either the package or the tiedown system. This indicates that trailer-bed response should not be used in determining the load factor for fatigue calculations of the package components or in determining design loads for tiedowns.
Date: December 1, 1991
Creator: Gwinn, K.W.; Glass, R.E. & Edwards, K.R.
Partner: UNT Libraries Government Documents Department