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Lie-Poisson bifurcations for the Maxwell-Bloch equations

Description: We present a study of the set of Maxwell-Bloch equations on R{sup 3} from the point of view of Hamiltonian dynamics. These equations are shown to be bi-Hamiltonian, on the one hand, and to possess several inequivalent Lie-Poisson structures, on the other hand, parametrized by the group SL(2,R). Each structure is characterized by a particular distinguished function. The level sets of this function provide two-dimensional surfaces onto which the motion takes various symplectic forms. 4 refs.
Date: January 1, 1990
Creator: David, D.
Partner: UNT Libraries Government Documents Department

A fluor and wire-shadow diagnostic for low-energy ion beams

Description: A video diagnostic technique utilizing a fluorescent screen and a video camera has been developed to monitor the two-dimensional beam-intensity profile and angular divergence of low-energy (25--35 keV) ion beams. Detailed off-line analysis is used to compare and augment standard beam emittance data. Experimental results on 2-D beam profiles will be presented.
Date: January 1, 1990
Creator: Saadatmand, K. (Grumman Corp., Bethpage, NY (USA). Corporate Research Center); Schneider, J.D.; Geisik, C. & Stevens, R.R. Jr. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Internal dynamics of electrical discharges

Description: The existence of thresholds for electrical discharge onset suggests a functional relation between macroscopic resistivity and current. At low current, the resistivity should be inversely proportional to the magnitude of the current. Macroscopic models which employ this scaling predict many empirically observed properties of transient electrical discharges, such as (1) thresholds for onset of current, (2) abrupt termination of current in active regions of a current channel, (3) current restart in passive regions of current channels, (4) leaders, and (5) residual charge, both in channels and at sources when current terminates. We present an overview of research with these models and use examples to illustrate the results that have been obtained. We also show how these models predict current channel formation and describe results of efforts to benchmark theory with experimental data. 12 refs., 9 figs.
Date: January 1, 1990
Creator: Kadish, A.; Maier, W.B. II (Los Alamos National Lab., NM (USA)) & Robiscoe, R.T. (Montana State Univ., Bozeman, MT (USA))
Partner: UNT Libraries Government Documents Department

Universal Fast Breeder Reactor Subassembly Counter manual

Description: A neutron coincidence counter has been designed for the measurement of fast breeder reactor fuel assemblies. This assay system can accommodate the full range of geometries and masses found in fast breeder subassemblies under IAEA safeguards. The system's high-performance capability accommodates high plutonium loadings of up to 16 kg. This manual describes the system and its operation and gives performance and calibration parameters for typical applications.
Date: August 1, 1984
Creator: Menlove, H.O.; Eccleston, G.W.; Swansen, J.E.; Goris, P.; Abedin-Zadeh, R. & Ramalho, A.
Partner: UNT Libraries Government Documents Department

Automated homogeneous oxalate precipitation of Pu(III)

Description: Homogeneous oxalate precipitation using diethyl oxalate was compared to precipitating Pu(III) oxalate with solid oxalic acid. The diethyl oxalate technique at 75{degree}C is better because it gives 50% less plutonium in the filtrate with a reasonable filtering time. Also, the procedure for the homogeneous precipitation is easier to automate because the liquid diethyl oxalate is simpler to introduce into the precipitator than solid oxalic acid. It also provides flexibility because the hydrolysis rate and therefore the precipitation rate can be controlled by varying the temperature. 5 refs., 3 figs., 3 tabs.
Date: January 1, 1990
Creator: Yarbro, S.L.; Schreiber, S.B.; Dunn, S.L. & Mills, C.W.
Partner: UNT Libraries Government Documents Department

Antimatter gravity experiment

Description: An experiment is being developed to measure the acceleration of the antiproton in the gravitational field of the earth. Antiprotons of a few MeV from the LEAR facility at CERN will be slowed, captured, cooled to a temperature of about 10 K, and subsequently launched a few at a time into a drift tube where the effect of gravity on their motion will be determined by a time-of-flight method. Development of the experiment is proceeding at Los Alamos using normal matter. The fabrication of a drift tube that will produce a region of space in which gravity is the dominant force on moving ions is of major difficulty. This involves a study of methods of minimizing the electric fields produced by spatially varying work functions on conducting surfaces. Progress in a number of areas is described, with stress on the drift-tube development.
Date: January 1, 1990
Creator: Brown, R.E.; Camp, J.B. & Darling, T.W.
Partner: UNT Libraries Government Documents Department

AFDM: An Advanced Fluid-Dynamics Model

Description: This volume describes the Advanced Fluid-Dynamics Model (AFDM) for topologies, flow regimes, and interfacial areas. The objective of these models is to provide values for the interfacial areas between all components existing in a computational cell. The interfacial areas are then used to evaluate the mass, energy, and momentum transfer between the components. A new approach has been undertaken in the development of a model to convect the interfacial areas of the discontinuous velocity fields in the three-velocity-field environment of AFDM. These interfacial areas are called convectible surface areas. The continuous and discontinuous components are chosen using volume fraction and levitation criteria. This establishes so-called topologies for which the convectible surface areas can be determined. These areas are functions of space and time. Solid particulates that are limited to being discontinuous within the bulk fluid are assumed to have a constant size. The convectible surface areas are subdivided to model contacts between two discontinuous components or discontinuous components and the structure. The models have been written for the flow inside of large pools. Therefore, the structure is tracked only as a boundary to the fluid volume without having a direct influence on velocity or volume fraction distribution by means of flow regimes or boundary layer models. 17 refs., 7 tabs., 18 figs.
Date: September 1, 1990
Creator: Wilhelm, D.
Partner: UNT Libraries Government Documents Department

LAVA/CIS Version 2. 0: A software system for vulnerability and risk assessment

Description: LAVA (the Los Alamos Vulnerability/Risk Assessment system) is an original systematic approach to risk assessment developed at the Los Alamos National Laboratory. It is an alternative to existing quantitative methods, providing an approach that is both objective and subjective, and producing results that are both quantitative and qualitative. LAVA was developed as a tool to help satisfy federal requirements for periodic vulnerability and risk assessments of a variety of systems and to satisfy the resulting need for an inexpensive, reusable, automated risk assessment tool firmly rooted in science. LAVA is a three-part systematic approach to risk assessment that can be used to model a variety of application systems such as computer security systems, communications security systems, information security systems, and others. The first part of LAVA is the mathematical model based on classical risk assessment, hierarchical multilevel system theory, decision theory, fuzzy possibility theory, expert system theory, utility theory, and cognitive science. The second part is the implementation of the mathematical risk model as a general software engine executed on a large class of personal computers. The third part is the application data sets written for a specific application system. The user of a LAVA application is not required to have knowledge of formal risk assessment techniques. All the technical expertise and specialized knowledge are built into the software engine and the application system itself. 36 refs., 5 figs.
Date: January 1, 1990
Creator: Smith, S.T.
Partner: UNT Libraries Government Documents Department

Simulant-material experimental investigation of flow dynamics in the CRBR Upper-Core Structure

Description: The results of a simulant-material experimental investigation of flow dynamics in the Clinch River Breeder Reactor (CRBR) Upper Core Structure are described. The methodology used to design the experimental apparatus and select test conditions is detailed. Numerous comparisons between experimental data and SIMMER-II Code calculations are presented with both advantages and limitations of the SIMMER modeling features identified.
Date: September 1, 1982
Creator: Wilhelm, D.; Starkovich, V.S. & Chapyak, E.J.
Partner: UNT Libraries Government Documents Department

An interpersonal multimedia visualization system

Description: Media View is a computer program that provides a generic infrastructure for authoring and interacting with multimedia documents. Among its many applications is the ability to furnish a user with a comprehensive environment for analysis and visualization. With MediaView the user produces a document'' that contains mathematics, datasets and associated visualizations. From the dataset or embedded mathematics animated sequences can be produced in situ. The mathematical content of the document'' can be explored through manipulation with Mathematica {trademark}. Since the document'' is all digital, it can be shared with a co-worker on a local network or mailed electronically to a colleague at a distant site. Animations and any other substructure of the document'' persist through the mailing process and can be awakened at the destination by the recipient. 5 refs., 4 figs.
Date: January 1, 1990
Creator: Phillips, R.L.
Partner: UNT Libraries Government Documents Department

Laser-induced breakdown spectroscopy: A new technique for nondestructive analysis of solutions

Description: Laser-induced breakdown spectroscopy has been applied to the continuous determination of uranium in solutions. The technique is rapid, non-invasive, and unaffected by radioactivity. Powerful laser pulses are focused through an optical access onto the solution surface to produce a hot spark plasma. In experiments on static solutions, uranium concentrations between 0.1 and 300 g/L were determined, using a pulsed Md:YAG laser and a time-gated photodiode array. A concentration of 4.2 g/L was measured with 1.0% precision in 3 minutes. Substances that absorb at the laser wavelength, suspended materials, and variations in the acidity of the solution have little or no effect on the results. Experiments are in progress on flowing streams contained in a test loop that simulates plant operating conditions. 1 ref., 3 figs., 3 tabs.
Date: January 1, 1987
Creator: Gutmacher, R.G.; Cremers, D.A. & Wachter, J.R.
Partner: UNT Libraries Government Documents Department

Test ventilation with smoke, bubbles, and balloons

Description: The behavior of smoke, bubbles, and helium-filled balloons was videotaped to demonstrate the mixing of air in the plutonium chemistry laboratories, a plutonium facility. The air-distribution patterns, as indicated by each method, were compared. Helium-filled balloons proved more useful than bubbles or smoke in the visualization of airflow patterns. The replay of various segments of the videotape proved useful in evaluating the different techniques and in identifying airflow trends responsible for air mixing. 6 refs.
Date: January 1, 1987
Creator: Pickering, P.L.; Cucchiara, A.L.; McAtee, J.L. & Gonzales, M.
Partner: UNT Libraries Government Documents Department

Phenomenology of some rare and forbidden. eta. -decays

Description: We discuss the contribution from possible new physics to the decays {eta} {yields} {mu}{sup +}{mu}{sup {minus}}, {eta} {yields} e{sup +}e{sup {minus}}, {eta} {yields} {mu}e and {eta} {pi}{mu}e, and assess the sensitivities required for experimental studies of these decays to extend our knowledge about the new interactions. 61 refs.
Date: January 1, 1990
Creator: Herczeg, P.
Partner: UNT Libraries Government Documents Department

Confinement of nonneutral plasma in unconventional geometries

Description: Our interest in efficient storage of cold, nonneutral plasma has been motivated by the elegant studies on cryogenic nonneutral electron plasmas at UCSD and by the remarkable results obtained from the laser-cooled ion plasmas at the NIST, Boulder, Colorado. Also motivating our study is the perceived need to develop the most expedient means of storing antimatter, whether it be antiprotons for gravitational studies or positrons for a variety of physics experiments and diagnostic purposes. One of the most explored technologies of confining nonneutral plasmas is the Penning trap. The maximum number density of cold nonneutral plasma that can be stored in such a trap is B{sup 2}/2{mu}{sub 0}mc{sup 2}, in which B{sup 2}/2{mu}{sub 0} is the (homogeneous) magnetic energy density and mc{sup 2} is the rest energy of the stored charges. In this paper, we shall present a synopsis of the results of our theoretical exploration of the effect on this hydrostatic limit, the so-called Brillouin'' limit, of altering the geometry of the confining vacuum magnetic field while maintaining the field's azimuthal symmetry. In particular, we shall analyze equilibrium confinement by, first, a poloidal magnetic field, B{sub 4}(r,z){cflx r} + B{sub z}(r,z){cflx z}, and second, a toroidal magnetic field, along with the concomitant electrostatic fields.
Date: January 1, 1990
Creator: Turner, L.
Partner: UNT Libraries Government Documents Department

Radiation-induced transient absorption in single mode optical fibers

Description: This paper reviews the measurements conducted by the Los Alamos National Laboratory in support of these NATO efforts wherein radiation-induced transient absorption was measured over time ranges from a few ns to several ..mu..s for two single mode fibers. Experimental conditions were varied to provide data for future development of standarized test conditions for single mode fibers. 8 refs., 11 figs.
Date: January 1, 1988
Creator: Looney, L.D. & Lyons, P.B.
Partner: UNT Libraries Government Documents Department

Spent-fuel composition: a comparison of predicted and measured data

Description: The uncertainty in predictions of the nuclear materials content of spent light-water reactor fuel was investigated to obtain guidelines for nondestructive spent-fuel verification and assay. Values predicted by the reactor operator were compared with measured values from fuel reprocessors for six reactors (three PWR and three BWR). The study indicates that total uranium, total plutonium, fissile uranium, fissile plutonium, and total fissile content can be predicted with biases ranging from 1 to 6% and variabilities (1-sigma) ranging from 2 to 7%. The higher values generally are associated with BWRs. Based on the results of this study, nondestructive assay measurements that are accurate and precise to 5 to 10% (1sigma) or better should be useful for quantitative analyses of typical spent fuel.
Date: March 1, 1981
Creator: Thomas, C.C. Jr.; Cobb, D.D. & Ostenak, C.A.
Partner: UNT Libraries Government Documents Department

Pellet injection in the RFP (Reversed Field Pinch)

Description: Observation of pellets injected into the ZT-40M Reversed Field Pinch has allowed a new twist on the usual tokamak ablation physics modeling. The RFP provides a strong ohmic heating regime with relatively high electron drift parameter (xi/sub drift/ /approximately/ 0.2), in the presence of a highly sheared magnetic field geometry. In situ photos of the pellet ablation cloud using a grated-intensified CCD camera, as well as two-view integrated photos of the pellet trajectory show substantial modification of the original pellet trajectory, in both direction and speed. Depending on the launch geometry, increases in the initial 500 m/s pellet speed by 50% have been observed, and a ski jump deflector plate in the launch port has been used to counteract strong poloidal curvature. In contrast to the tokamak, the D/sub ..cap alpha../ light signature is strongest near the edge, and weaker in the plasma center. Additional information on ion temperature response to pellet injection with 20 ..mu..sec time resolution has been obtained using a 5-channel neutral particle analyzer (NPA). The energy confinement is transiently degraded while the beta is largely unchanged. This may be indicative of pellet injection into a high-beta plasma operating at fixed beta. 10 refs., 6 figs.
Date: January 1, 1988
Creator: Wurden, G.A.; Weber, P.G.; Munson, C.P.; Cayton, T.E.; Bunting, C.A. & Carolan, P.G.
Partner: UNT Libraries Government Documents Department

Performance evaluation of the IBM RISC (reduced instruction set computer) System/6000: Comparison of an optimized scalar processor with two vector processors

Description: RISC System/6000 computers are workstations with a reduced instruction set processor recently developed by IBM. This report details the performance of the 6000-series computers as measured using a set of portable, standard-Fortran, computationally-intensive benchmark codes that represent the scientific workload at the Los Alamos National Laboratory. On all but three of our benchmark codes, the 40-ns RISC System was able to perform as well as a single Convex C-240 processor, a vector processor that also has a 40-ns clock cycle, and on these same codes, it performed as well as the FPS-500, a vector processor with a 30-ns clock cycle. 17 refs., 2 figs., 6 tabs.
Date: January 1, 1990
Creator: Simmons, M.L. & Wasserman, H.J.
Partner: UNT Libraries Government Documents Department

Moment methods for simulation and design

Description: It is often advantageous to describe a particle beam by the moments of its phase-space distribution. This paper relates original work by Sacherer to presently-used linear design codes like TRACE3D and to some recent results. 15 refs., 1 fig.
Date: January 1, 1990
Creator: Lysenko, W.P.
Partner: UNT Libraries Government Documents Department

Thermal-hydraulic analyses of pressurized-thermal-shock-induced vessel ruptures. [PWR]

Description: A severe overcooling transient was postulated to produce vessel wall temperatures below the nil-ductility transition temperature which in conjunction with system repressurization, led to vessel rupture at the core midplane. Such transients are referred to as pressurized-thermal-shock transients. A wide range of vessel rupture sizes were investigated to assess the emergency system's ability to cool the fuel rods. Ruptures greater than approximately 0.015 m/sup 2/ produced flows greater than those of the emergency system and resulted in core uncovery and subsequent core damage.
Date: May 1, 1982
Creator: Dobranich, D.
Partner: UNT Libraries Government Documents Department

The use of molecular dynamics for the thermodynamic properties of simple and transition metals

Description: The technique of computer simulation of the molecular dynamics in metallic systems to calculate thermodynamic properties is discussed. The nature of a metal as determined by its electronic structure is used to determine the total adiabatic potential. The effective screened ion-ion interaction can then be used in a molecular dynamics simulation. The method for the construction of a molecular dynamics ensemble, its relation to the canonical ensemble, and the definition of thermodynamic functions from the Helmholtz free energy is given. The method for the analysis of the molecular dynamics results from quasiharmonic lattice dynamics and the decomposition in terms of harmonic and anharmonic contributions is given for solids. For fluid phase metals, procedures for calculating the thermodynamics and determining the constant of entropy are presented. The solid-fluid phase boundary as a function of pressure and temperature is determined using the results of molecular dynamics. Throughout, examples and results for metallic sodium are used. The treatment of the transition metal electronic d-states in terms of an effective pair-wise interaction is also discussed and the phonon dispersion curves of Al, Ni, and Cu are calculated.
Date: April 1, 1987
Creator: Straub, G.K.
Partner: UNT Libraries Government Documents Department

Stability of some stationary solutions for the forced KdV equation

Description: The forced KdV (fKdV) equation has been established by recent studies as a simple mathematical model capable of describing the physics of a shallow layer of fluid subject to external forcing. For a particular one-parameter family of forcings which is characterized by a wave amplitude parameter for supercritical forcing distributions, exact stationary solutions are known. We study the stability of these solutions as the parameter varies. The linear stability analysis is first carried out, and we discuss the structure of the spectrum of the associated eigenvalue problem using a perturbation approach, about isolated parameter values where eigenfunctions can be expressed in closed form and are the fixed-point solutions of the fKdV equation corresponding to zero eigenvalues. The results identify a set of intervals in the parameter space corresponding to different types of manifestation of instability. In the region of the parameter space where the linear stability analysis fails to provide an answer, we have developed a nonlinear analysis to provide a sufficient condition for stability. 13 refs.
Date: January 1, 1990
Creator: Camassa, R. (Los Alamos National Lab., NM (USA)) & Yao-tsu Wu, T. (California Inst. of Tech., Pasadena, CA (USA). Div. of Engineering and Applied Science)
Partner: UNT Libraries Government Documents Department