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Subharmonic buncher for the Los Alamos free-electron laser oscillator experiment

Description: A high efficiency free-electron laser oscillator experiment is being constructed at Los Alamos National Laboratory. A buncher system has been designed to deliver 30-ps, 5-nC electron bunches to a 20-MeV standing-wave linac at the 60th subharmonic of the 1300-MHz accelerator frequency. The first 108.3-MHz buncher cavity accepts a 5-ns, 5-A peak current pulse from a triode gun. Following a 120-cm drift space, a second 108.3-MHz cavity is used, primarily to enhance the bunching of the trailing half of the bunch. A 1300-MHz cavity with 20-cm drift spaces at the each end completes the beamline components. The bunching process continues into the linac's first three accelerating cells. Two thin iron-shielded lenses and several large-diameter solenoids provide axial magnetic fields for radial focusing.
Date: January 1, 1983
Creator: Fraser, J.S.
Partner: UNT Libraries Government Documents Department

Discussion session: nucleon- and antinucleon-nucleus inelastic scattering and charge exchange

Description: This short article summarizes one part of the discussion session concerning nucleon- and antinucleon-nucleus inelastic scattering and charge exchange. Assigned an unconstrained role somewhere between that of rapporteur and ''rioteur'' I've decided to use a few highlights of the conference to stage a number of personal opinions regarding our current status in this game and where we might be going. 20 refs.
Date: January 1, 1985
Creator: Carey, T.A.
Partner: UNT Libraries Government Documents Department

Radiation damage in optical fibers

Description: While plastic-clad-silica (PCS) fiber shows the greatest radiation resistance, PCS fiber has been difficult to reliably connectorize for routine field operations. For this reason, all-glass fibers have been studied as an alternative to PCS. Based on available literature and some preliminary tests at Los Alamos, we have concentrated on fluorosilicate clad, step index, pure silica core fibers. This paper reviews recent laboratory data for these fibers relative to the PCS fibers. This paper also discusses use of a fiber (or any optical medium) on a Cerenkov radiation-to-light transducer. Since the radiation induces attenuation in the medium, the light output is not proportional to the radiation input. The nonlinearity introduced by this attenuation is calculated.
Date: January 1, 1983
Creator: Lyons, P. B.; Looney, L. D. & Ogle, J. W.
Partner: UNT Libraries Government Documents Department

Testing for nonlinearity in time series: The method of surrogate data

Description: We describe a statistical approach for identifying nonlinearity in time series; in particular, we want to avoid claims of chaos when simpler models (such as linearly correlated noise) can explain the data. The method requires a careful statement of the null hypothesis which characterizes a candidate linear process, the generation of an ensemble of surrogate'' data sets which are similar to the original time series but consistent with the null hypothesis, and the computation of a discriminating statistic for the original and for each of the surrogate data sets. The idea is to test the original time series against the null hypothesis by checking whether the discriminating statistic computed for the original time series differs significantly from the statistics computed for each of the surrogate sets. We present algorithms for generating surrogate data under various null hypotheses, and we show the results of numerical experiments on artificial data using correlation dimension, Lyapunov exponent, and forecasting error as discriminating statistics. Finally, we consider a number of experimental time series -- including sunspots, electroencephalogram (EEG) signals, and fluid convection -- and evaluate the statistical significance of the evidence for nonlinear structure in each case. 56 refs., 8 figs.
Date: January 1, 1991
Creator: Theiler, J.; Galdrikian, B.; Longtin, A. (Los Alamos National Lab., NM (United States)); Eubank, S. & Farmer, J.D. (Los Alamos National Lab., NM (United States) Santa Fe Inst., NM (United States))
Partner: UNT Libraries Government Documents Department

Evidence for stacking faults in multiaxial strained alpha-brass

Description: Two different techniques of x-ray diffraction have been applied to the examination of multiaxial strained alpha-brass. From an examination of the unfolded Fourier coefficients describing the shape of the diffraction profile it has been determined that the true crystallite size probably exceeds 2000 A, a practical upper limit for determining crystallite size by x-ray methods. The localized strain is approximately 0.225% and a combined stacking fault probability (1.5 ..cap alpha..' + ..beta..) = 0.0185 +- 1. From lattice constant variations the single stacking fault probability, ..cap alpha..', has been determined to be 0.0054 +- 22. The twinning stacking fault, ..beta.., is thus 0.0104 +- 22. The reciprocal of the probability is the number of planes of atoms between the indicated stacking fault. The magnitude of the numbers indicates that twinning is twice as common as single stacking faults.
Date: January 1, 1983
Creator: Roof, R.B.
Partner: UNT Libraries Government Documents Department

An explosively driven, fast shock tube

Description: A simple, cylindrically configured fast shock tube (FST) has been employed as a tool to investigate the hydrodynamics of plate drive under a very high impulse-loading condition. The shock tube has a high-explosive outer shell and a low-density foam core. The implosion produces a well-defined Mach disk that is then subsequently used to drive a metallic plate. A thin stainless steel (SS) plate has been successfully launched to 9 km/s with this device. The experimental results from the study of material flow will be presented and compared with numerical calculation. Various interesting measurement techniques will also be discussed.
Date: January 1, 1992
Creator: Tan, T.H. & Marsh, S.
Partner: UNT Libraries Government Documents Department

Creating unstable velocity-space distributions with barium injections

Description: Large Debye lengths relative to detector dimensions and the absence of confining walls makes space an attractive laboratory for studying fundamental theories of plasma instabilities. However, natural space plasmas are rarely found displaced from equilibrium enough to permit isolation and diagnosis of the controlling parameters and driving conditions. Furthermore, any plasma or field response to the departure from equilibrium can be masked by noise in the natural system. Active experiments provide a technique for addressing the chicken or egg dilemma. Early thermite barium releases were generally conducted at low altitudes from sounding rockets to trace electric fields passively or to study configuration-space instabilities. One can also study velocity-space instabilities with barium releases. Neutral barium vapor releases wherein a typical speed greatly exceeds the thermal speed can be used to produce barium ion velocity-space distributions that should be subject to a number of microinstabilities. We examine the ion velocity-space distributions resulting from barium injections from orbiting spacecraft and shaped-charges.
Date: January 1, 1983
Creator: Pongratz, M.B.
Partner: UNT Libraries Government Documents Department

Nuclear models relevant to evaluation

Description: The widespread use of nuclear models continues in the creation of data evaluations. The reasons include extension of data evaluations to higher energies, creation of data libraries for isotopic components of natural materials, and production of evaluations for radiative target species. In these cases, experimental data are often sparse or nonexistent. As this trend continues, the nuclear models employed in evaluation work move towards more microscopically-based theoretical methods, prompted in part by the availability of increasingly powerful computational resources. Advances in nuclear models applicable to evaluation will be reviewed. These include advances in optical model theory, microscopic and phenomenological state and level density theory, unified models that consistently describe both equilibrium and nonequilibrium reaction mechanism, and improved methodologies for calculation of prompt radiation from fission. 84 refs., 8 figs.
Date: January 1, 1991
Creator: Arthur, E. D.; Chadwick, M. B.; Hale, G. M. & Young, P. G.
Partner: UNT Libraries Government Documents Department

Natural air motion in passive buildings

Description: The nature of natural convection is described, and a design chart is presented appropriate to a simple, single-doorway situation. Natural convective loops that can occur in buildings are described and a few experimental results are presented. Observations of stratification are discussed, similitude experiments are described, and the beginnings of a complete-system mathematical model are presented.
Date: January 1, 1985
Creator: Balcomb, J.D. & Jones, G.F.
Partner: UNT Libraries Government Documents Department

Polarized nuclear targets

Description: The static and dynamic methods for producing polarized targets are briefly discussed and compared. Nuclei that have been polarized by these methods are summarized. The equipment necessary for producing a working target is described, as are the capabilities presently available at LAMPF. A short description is presented of a polarized /sup 13/C target proposed for use at the LAMPF HRS spectrometer, as an example of a polarized target for use in nuclear physics research.
Date: January 1, 1986
Creator: Jarmer, J. J.
Partner: UNT Libraries Government Documents Department

Thermophysical properties of liquid niobium

Description: Thermophysical properties of most liquid metals are difficult to measure because of the very high temperatures and pressures required, but they are important for several reasons. These include understanding the fundamental physics of liquid metals and experimental modeling and design of exploding wires, foils and fuses. The melting points of all but a few metals are at high temperatures, with many exceeding 2000 K. The critical points of most metals exceed temperatures and pressures that may be easily achieved in static high-pressure systems. Because of the limitations on temperatures that may be reached in static high-pressure experiments, various dynamic techniques have been developed to study liquid metals. We use a resistive pule heating method in which a cylindrical wire-shaped sample is made to expand along a isobaric path. During an experiment the sample is heated, made to melt, and enthalpy, temperature, and specific volume are measured. After the liquid end state is reached, a single sound speed measurement per experiment is made. From these fundamental properties, other properties such as thermal expansion coefficient bulk modulii, and compressibilities may be calculated. Here we report measurements that we have recently made on liquid niobium. 7 refs., 5 figs., 1 tab.
Date: January 1, 1989
Creator: Hixson, R.S. & Winkler, M.A.
Partner: UNT Libraries Government Documents Department

Analysis results from the Los Alamos 2D/3D program

Description: Los Alamos National Laboratory is a participant in the 2D/3D program. Activities conducted at Los Alamos National Laboratory in support of 2D/3D program goals include analysis support of facility design, construction, and operation; provision of boundary and initial conditions for test-facility operations based on analysis of pressurized water reactors; performance of pretest and posttest predictions and analyses; and use of experimental results to validate and assess the single- and multi-dimensional, nonequilibrium features in the Transient Reactor Analysis Code (TRAC). During fiscal year 1987, Los Alamos conducted analytical assessment activities using data from the Slab Core Test Facility, The Cylindrical Core Test Facility, and the Upper Plenum Test Facility. Finally, Los Alamos continued work to provide TRAC improvements. In this paper, Los Alamos activities during fiscal year 1987 will be summarized; several significant accomplishments will be described in more detail to illustrate the work activities at Los Alamos.
Date: January 1, 1987
Creator: Boyack, B. E.; Cappiello, M. W.; Harmony, S. C.; Shire, P. R. & Siebe, D. A.
Partner: UNT Libraries Government Documents Department

Preliminary evaluation of the electrapette for possible use in the glovebox for pipetting plutonium solutions

Description: At the Los Alamos Laboratory Plutonium Facility, Solution Assay Instruments (SAIs) are used to provide real-time information on the plutonium (Pu) content of the process stream at various stages in the process. Much of the solution analysis must be carried and as a glovebox to protect the operator from radiation. In order to overcome some of the difficulties usually encountered when working in a glovebox, an electronic solution-volume measuring device called an Electrapette was ordered from Matrix Technologies Corporation. It is said to be highly accurate, simple to use, and can handle the 25 ml of solution required for SAI analyses. It is microprocessor-controlled and comes in two components connected by a detachable cable so that the electronic part can be installed outside the box, while the nosepiece is inside. The two pieces are connected through a plug-in on the glovebox wall. The Electrapette was tested in three sets of experiments: a cold'' lab set, a set run is a hood in a production building, and a third set run in a glovebox using a process solution whose density had been predetermined. The accuracy of the determination could not be determined because the samples had been mixed with other feed before being sent for analysis by the Electrapette. 2 refs., 5 tabs.
Date: December 1, 1990
Creator: Hansbury, E.; Ortiz, B. & Roybal, C.
Partner: UNT Libraries Government Documents Department

Hands-on program of IBM-PC training at Los Alamos National Laboratory

Description: Since December 1983, the Laboratory has offered introductory courses of IBM-PC training. A comprehensive needs assessment was conducted and a nine-course module of classes was designed and implemented. Forty classes were completed in the one-year period. The target group includes the novice computer user in the scientific, management, administrative, and secretarial personnel groups. The development, needs assessment, course implementation and design, course evaluations, and future direction of computer training will be discussed. Lab-automation, robotics, design of the lab and office and the impact of computer on society will be discussed briefly.
Date: January 1, 1985
Creator: Lier, R.H.
Partner: UNT Libraries Government Documents Department

Mechanical features of the ATS ramped-gradient DTL

Description: At Los Alamos, a short, lightweight drift-tube linac (DTL) has been designed. This accomplishment is possible by varying the accelerating gradient from 2 MV/m at the RFQ end to 4.4 MV/m at the output end, with the gradient rising as a cubic polynomial. The object of raising the gradient to such a high level is to reduce the length of the proposed 50-MeV machine that ultimately will attach to the ramped-gradient drift-tube linac (RGDTL) tank. This is the first proton linac structure to propose such a ramping scheme and the first to attempt reliable long-term operation at such elevated accelerating gradients. It is also the first to attempt to accomplish this with a lightweight aluminum structure designed to operate at 5% duty factor.
Date: January 1, 1986
Creator: Liska, D.J.; McCauley, G. & Carlisle, L.O.
Partner: UNT Libraries Government Documents Department

Using temperature-programmed reaction for kinetic analysis of reactions in dilute aqueous solutions at high pressure

Description: The technique of temperature-programmed reaction (TPR) is shown to be a practical experimental method for determining reaction-rate expressions and kinetics parameters for reactions in dilute aqueous solutions under high ambient pressure. By sampling and measuring the extent of reaction during a rise in temperature, information normally obtained from a series of isothermal batch kinetics experiments can be found in a single TPR test. The use of nonlinear least-squares regression eliminates the need to achieve a constant rate of temperature rise, simplifies the experimental requirements for TPR results, and gives more accurate answers than does a linear analysis of TPR results. Numerical simulations of TPR tests in the presence of random concentration-measurement error is used to assess the accuracy of the technique and to identify the best values of crucial operating parameters. The results of two TPR experiments measuring the alkaline hydrolysis of ethyl acetate demonstrate the applicability of the technique to reactions in dilute aqueous solutions at high pressure. These preliminary experimental results, along with numerical simulations, allow us to chart a course for future TPR kinetics experiments on a large number of similar reactions. 16 refs., 6 figs., 8 tabs.
Date: January 1, 1986
Creator: Brown, L.F. & Robinson, B.A.
Partner: UNT Libraries Government Documents Department

The heterogeneous explosive reaction zone

Description: The calculated reaction zone of PBX-9404 using solid HMX Arrhenius kinetics is stable to perturbations. The calculated reaction zone Von Neumann spike pressure agrees with the experimental observations within experimental uncertainty associated with different experimental techniques. The calculated homogengeous explosive reaction zone thickness is larger than observed for the heterogeneous explosive. The effect of two volume percent air holes on the reaction zone was modeled using the three-dimensional Eulerian reactive hydrodynamic code, 3DE. The air holes perturb the reaction zone. A complicated, time-dependent, multidimensional reaction region proceeds through the heterogeneous explosive. The experimentally observed reaction zone characteristic of heterogeneous explosives are mean values of an irregular, three-dimensional reaction region. 20 refs., 6 figs.
Date: January 1, 1989
Creator: Mader, C.L. & Kershner, J.D.
Partner: UNT Libraries Government Documents Department

New theories for smectic and nematic liquid-crystal polymers: Backbone LCPs (liquid crystalline polymers) and their mixtures and side-chain LCPs

Description: A summary of predictions and explanations from statistical-physics theories for both backbone and side-chain liquid crystalline polymers (LCPs) and for mixtures with backbone LCPs are presented. Trends in the thermodynamic and molecular ordering properties have been calculated as a function of pressure, density, temperature, and molecule chemical structures (including degree of polymerization and the following properties of the chemical structures of the repeat units: lengths and shapes, intra-chain rotation energies, dipole moments, site-site polarizabilities and Lennard-Jones potentials, etc.) in nematic and multiple smectic-A LC phases and in the isotropic liquid phase. The theoretical results are found to be in good agreement with existing experimental data. These theories can also be applied to combined LCPs. Since these theories have no ad hoc or arbitrarily adjustable parameters, these theories can be used to design new LCPs and new solvents as well as to predict and explain properties. 27 refs., 4 tabs.
Date: January 1, 1987
Creator: Dowell, F.
Partner: UNT Libraries Government Documents Department

Physical characteristics of diblock polyacetylene copolymers: processability-conductivity correlation

Description: The physical properties of polyacetylene diblock copolymers containing polystyrene (PS) or polyisoprene (PI) blocks of various compositions are studied using electron spin resonance, resonance Raman scattering, and room temperature conductivity measurements. This study is performed to investigate the processability-conductivity correlation in these materials and their viability as conducting systems.
Date: January 1, 1986
Creator: Aldissi, M.; Hou, M. & Farrell, J.
Partner: UNT Libraries Government Documents Department

Off-diagonal Coulomb interactions in the extended Peierls-Hubbard model: Exact diagonalization results

Description: For conjugated polymers, the extended Peierls-Hubbard model has been widely accepted as correctly incorporating the effects of both e-p and e-e interactions. In the absence of e-e interactions, the ground state of (CH)/sub x/ is the 2k/sub F/ bond-order wave (BOW) -- dimerization/bond alternation -- predicted by Peierls theorem. It is now well established that for the weak e-p coupling appropriate to (CH)/sub x/, the on-site Coulomb repulsion actually enhances dimerization up to fairly large values (U > 6t/sub 0/). These results are still widely regarded as counter to the conventional wisdom that Coulomb interactions should suppress the build-up of charge anywhere, on the sites or on the bonds. Since the extended Peierls-Hubbard model incorporates only (lattice) site-diagonal parts of the electron-electron interactions (U, V), and omits the off-diagonal bond-charge repulsions (W,X), it is natural to ask whether this model adequately describes the full consequences of e-e interactions. In the specific context of (CH)/sub x/, the potential importance of this omission is readily recognized. Intuitively, the bond-charge repulsion should suppress dimerization, since it opposes the build-up of charge on the bonds. Thus, the absence of W and X terms in the standard extended Peierls-Hubbard models suggests a priori that these models may artificially favor the continuation of dimerization in the half-filled band into the region of intermediate to strong Coulomb interaction. More generally, the omission of terms such as W and X raises significant questions about the appropriateness of Hubbard models for describing e-e interactions in the whole class of novel solid state materials. Thus this issue is extremely important and is, discussed further in this paper. 14 refs., 6 figs.
Date: January 1, 1989
Creator: Campbell, D.K.; Gammel, J.T. & Loh, E.Y. Jr.
Partner: UNT Libraries Government Documents Department

Pulsed laser stereophotography of plasmas and dynamically moving surfaces

Description: A pulsed laser is used as a light source for illuminating the surface of a dynamic event of less than or equal to1 mm/sup 2/ moving at >3 mm/..mu..s. At a predetermined time during the dynamic action, a stereo camera is used to record a pair of images of the dynamically moving surface. The stereoimage pair can be quantified for surface contour. 3 refs., 8 figs.
Date: January 1, 1987
Creator: Paisley, D.L.
Partner: UNT Libraries Government Documents Department

Electron trajectories in a combined wiggler and alternating gradient quadrupole field

Description: This paper reports on studies of electron trajectories in a combined wiggler and alternating gradient quadrupole field. The quadrupole field is assumed to vary continuously along the symmetry axis. The linearized equations of electron motion are solved analytically for a plane-polarized wiggler by using the two-scale perturbation method. A comparison with the numerical solution is presented, and the conditions for unstable trajectories are discussed. 4 refs., 4 figs.
Date: January 1, 1985
Creator: Wang, T. F. & Cooper, R. K.
Partner: UNT Libraries Government Documents Department
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