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Brightness, coherence, and propagation characteristics of synchrotron radiation (open access)

Brightness, coherence, and propagation characteristics of synchrotron radiation

A formalism is presented by means of which the propagation and imaging characteristics of synchrotron radiation can be studied, taking into account the effects of diffraction, electron beam emittance, and the transverse and longitudinal extent of the source. An important quantity in this approach is the Wigner distribution of the electric fields, which can be interpreted as a phase-space distribution of photon flux, and thus can be identified with the brightness. When integrated over the angular variables, the brightness becomes the intensity distribution in the spatial variables and when integrated over the spatial variables, it becomes the intensity distribution in angular variables. The brightness so defined transforms through a general optical medium in exactly the same way as in the case of a collection of geometric rays. Finally, the brightness of different electrons adds in a simple way. Optical characteristics of various synchrotron radiation sources - bending magnets, wigglers and undulators, are analyzed using this formalism.
Date: July 1, 1985
Creator: Kim, K. J.
System: The UNT Digital Library
Laser-driven instabilities in long scalelength plasmas (open access)

Laser-driven instabilities in long scalelength plasmas

In this update lecture we focus on laser-driven instabilities in long scalelength underdense plasmas. Particular attention is given to some recent experiments on Raman scattering of intense laser light. Many important features are in accord with theoretical expectations. These features include a correlation of hot electron generation with Raman scattering, an increase in this scattering as the density scale length increases, and collisional suppression of the instability. Some challenging aspects of the growing data base as well as various deficiencies in the understanding are discussed. The role of the plasmon decay instability 2..omega../sub pe/, Brillouin, and filamentation instabilities is also briefly considered.
Date: July 31, 1985
Creator: Kruer, W.L.
System: The UNT Digital Library
Workshop on the source term for radionuclide migration from high-level waste or spent nuclear fuel under realistic repository conditions: proceedings (open access)

Workshop on the source term for radionuclide migration from high-level waste or spent nuclear fuel under realistic repository conditions: proceedings

Sixteen papers were presented at the workshop. The fourteen full-length papers included in the proceedings were processed separately. Only abstracts were included for the following two papers: Data Requirements Based on Performance Assessment Analyses of Conceptual Waste Packages in Salt Repositories, and The Potential Effects of Radiation on the Source Term in a Salt Repository. (LM)
Date: July 1, 1985
Creator: Hunter, T. O. & Muller, A. B. (eds.)
System: The UNT Digital Library
Chemical kinetics modeling of the influence of molecular structure on shock tube ignition delay (open access)

Chemical kinetics modeling of the influence of molecular structure on shock tube ignition delay

The current capabilities of kinetic modeling of hydrocarbon oxidation in shock waves are discussed. The influence of molecular size and structure on ignition delay times are stressed. The n-paraffin fuels from CH/sub 4/ to n-C/sub 5/H/sub 12/ are examined under shock tube conditions, as well as the branched chain fuel isobutane, and the computed results are compared with available experimental data. The modeling results show that it is important in the reaction mechanism to distinguish between abstraction of primary, secondary and tertiary H atom sites from the fuel molecule. This is due to the fact that both the rates and the product distributions of the subsequent alkyl radical decomposition reactions depend on which H atoms were abstracted. Applications of the reaction mechanisms to shock tube problems and to other practical problems such as engine knock are discussed.
Date: July 1, 1985
Creator: Westbrook, C.K. & Pitz, W.J.
System: The UNT Digital Library
Ambient Pressure Effects on the Sputter Particle Distribution of Insulating Materials (open access)

Ambient Pressure Effects on the Sputter Particle Distribution of Insulating Materials

The effect of ion bombardment on several grades of alumina was investigated. Changes in the electrical resistance of the substrate as a function of incoming ion energy were of particular interest. Attention was also paid to the sputter particle distribution as a function of ambient pressure. This distribution was found to be dependent on the ion to substrate mass ratio. In general, the distribution follows a curve of growth; approximating a cosine distribution at the lower pressures and mass ratio, becoming isotropic at higher pressures. Pressures in the range of 10/sup -2/ to 10/sup -4/ Pascals have been used along with mass ratios in the range of 0.40 to 1.3. Samples of up to 80 cm/sup 2/ were subjected to a 10 cm diameter ion beam at energies of up to 6.25 keV. Average ion current densities of 1ma/cm/sup 2/ were used. Substrate temperatures while subjected to the ion beam were also monitored.
Date: July 1, 1985
Creator: Glaser, J. W.
System: The UNT Digital Library
Weight change measurements of erosion/deposition at beryllium limiter tiles in ISX-B (open access)

Weight change measurements of erosion/deposition at beryllium limiter tiles in ISX-B

The weight changes of Be tiles which functioned as a rail limiter in ISX-B for more than 3500 beam-heated discharges have been determined. The net weight loss for the limiter was 2.0 g, with the central tiles losing a total of 3.2 g and inboard tiles gaining 1.2 g. The weight loss is attributed primarily to the release of Be droplets as a result of limiter surface melting. The weight gains resulted from an inward flow of molten material along the limiter surface. The results indicate high erosion (melt loss) with incomplete and nonuniform redeposition (melt flow) of limiter material during periods of limiter melting.
Date: July 1, 1985
Creator: Roberto, J.B.; Edmonds, P.H.; England, A.C.; Gabbard, A. & Zuhr, R.A.
System: The UNT Digital Library
Twist-four effects in deep inelastic neutrino scattering and sinStheta/sub w/ (open access)

Twist-four effects in deep inelastic neutrino scattering and sinStheta/sub w/

In addition to the standard perturbative QCD corrections to deep inelastic scattering, there are nonperturbative twist-four corrections which behave like 1/QS relative to the lnQS leading log corrections. We have calculated the twist-four, spin-one and spin-two corrections to sigma/sub NC/, sigma/sub CC/, R/sub nu/ and R/sub anti nu/ using the following procedure: The bilocal product of the weak currents is expanded into local operators using the Wilson operator product expansion. The coefficient functions obey the renormalization group equations and, neglecting the anomalous dimensions of the operators, were calculated using perturbative techniques. The nucleon matrix elements of the local operators can then be evaluated assuming some quark confinement model. We found that twist-four, spin-two corrections to the neutral current neutrino scattering decreases sinStheta/sub w/ by about 1%. Taking into account the twist-four, spin-two corrections for the charged current cross section, we found that they give a dominant contribution to the ratio R/sub nu/ and increased sinStheta/sub w/ by about 0.5%. We also have studied the model dependence of our results, and we have found that the twist-four, spin-two corrections to sinStheta/sub w/ are quite model dependent. The twist-four, spin-one corrections to the neutrino scattering were also calculated. These corrections come from …
Date: July 1, 1985
Creator: Fajfer, S. & Oakes, R.J.
System: The UNT Digital Library
Research program with no ''measurement problem'' (open access)

Research program with no ''measurement problem''

The ''measurement problem'' of contemporary physics is met by recognizing that the physicist participates when constructing and when applying the theory consisting of the formulated formal and measurement criteria (the expressions and rules) providing the necessary conditions which allow him to compute and measure facts, yet retains objectivity by requiring that these criteria, rules and facts be in corroborative equilibrium. We construct the particulate states of quantum physics by a recursive program which incorporates the non-determinism born of communication between asynchronous processes over a shared memory. Their quantum numbers and coupling constants arise from the construction via the unique 4-level combinatorial hierarchy. The construction defines indivisible quantum events with the requisite supraluminal correlations, yet does not allow supraluminal communication. Measurement criteria incorporate c, h-bar, and m/sub p/ or (not ''and'') G. The resulting theory is discrete throughout, contains no infinities, and, as far as we have developed it, is in agreement with quantum mechanical and cosmological fact.
Date: July 1, 1985
Creator: Noyes, H. P.; Gefwert, C. & Manthey, M. J.
System: The UNT Digital Library
MINIMARS center cell magnet design options. Viewgraphs (open access)

MINIMARS center cell magnet design options. Viewgraphs

Viewgraphs presented at the meeting are included. (MOW)
Date: July 1, 1985
Creator: Kalsi, Swarn S.
System: The UNT Digital Library
Supersymmetry: proceedings (open access)

Supersymmetry: proceedings

Some lectures in these proceedings examine the theoretical basis for supersymmetry, recent developments in theories with compact dimensions, and experimental searches for supersymmetric signatures. Technologies are explored for obtaining very high energy electron-positron colliding beams. Separate abstracts were prepared for 35 papers in these conference proceedings. (LEW)
Date: July 1, 1985
Creator: Brennan, E.C. (ed.)
System: The UNT Digital Library
Development of mercuric iodide detectors for XAS and XRD measurements (open access)

Development of mercuric iodide detectors for XAS and XRD measurements

A prototype element for an energy dispersive detector (EDD) array was constructed using a Mercuric Iodide detector. Both detector and front end FET could be thermoelectrically cooled. Tested at SSRL, the detector had 250 eV electronic noise and 315 eV resolution at 5.9 keV. K line fluorescence spectra were collected for selected elements between Cl (2622 eV) and Zn (8638 eV). Count rate capability to 60,000 cps was demonstrated. Several detector parameters were measured, including energy linearity, resolution vs. shaping time, and detector dead time. An EXAFS (extended x-ray absorption fine structure) spectrum was recorded and compared to simultaneously collected transmission data.
Date: July 1, 1985
Creator: Warburton, William K.; Iwanczyk, Jan S.; Dabrowski, Andrzej J.; Hedman, Britt; Penner-Hakn, James E.; Roe, A. Lawrence et al.
System: The UNT Digital Library
Computer simulation of nonequilibrium processes (open access)

Computer simulation of nonequilibrium processes

The underlying concepts of nonequilibrium statistical mechanics, and of irreversible thermodynamics, will be described. The question at hand is then, how are these concepts to be realize in computer simulations of many-particle systems. The answer will be given for dissipative deformation processes in solids, on three hierarchical levels: heterogeneous plastic flow, dislocation dynamics, an molecular dynamics. Aplication to the shock process will be discussed.
Date: July 1, 1985
Creator: Wallace, D.C.
System: The UNT Digital Library
Inelastic and Reactive Collisions With Polarized Excited Na Atoms (open access)

Inelastic and Reactive Collisions With Polarized Excited Na Atoms

Polarization effects in inelastic collisions of laser state-prepared Na(3/sup 2/P, M/sub J/) with Na/sup +/ leading to Na(3/sup 2/D) or Na(3/sup 2/S) are discussed for the energy range E/sub cm/ = 5-47.5eV. Studies with linearly polarized light can be explained with a simple ''locking'' model of the Na(P)-orbital. The investigations employing circularly polarized light are a very sensitive test of the models describing the nonadiabatic angular momentum coupling between electronic and nuclear motion. The dynamical effects of the electronic spin on the angular momentum transfer are discussed. Recent crossed-beam experiments on the Na + O/sub 2/ -> NaO = O reaction in the energy range E/sub cm/ = 0/3-0.8eV show a pronounced dependence on the electric electronic symmetry of Na. 17 refs., 11 figs.
Date: July 1, 1985
Creator: Schmidt, H.; Hertel, I. V. & Lee, Y. T.
System: The UNT Digital Library
Materials accounting at Los Alamos National Laboratory (open access)

Materials accounting at Los Alamos National Laboratory

The materials accounting system at Los Alamos has evolved from an ''80-column'' card system to a very sophisticated near-real-time computerized nuclear material accountability and safeguards system (MASS). The present hardware was designed and acquired in the late 70's and is scheduled for a major upgrade in fiscal year 1986. The history of the system from 1950 through the DYMAC of the late 70's up to the present will be discussed. The philosophy of the system along with the details of the system will be covered. This system has addressed the integrated problems of management, control, and accounting of nuclear material successfully. 8 refs., 3 figs., 1 tab.
Date: July 20, 1985
Creator: Roberts, N. J.; Erkkila, B. H. & Kelso, H. F.
System: The UNT Digital Library
Equation of state of dense argon; a comparison of shock and static studies. [R] (open access)

Equation of state of dense argon; a comparison of shock and static studies. [R]

In the present paper we report new diamond anvil cell (DAC) measurements for room temperature solid argon to 800 kbars. This isotherm is in excellent agreement with one predicted from a theoretical analysis of shockwave data. These results are important for several reasons. First they demonstrate agreement between shock and static techniques even in cases where shock temperatures are extremely high and a large thermal correction is required to reduce the Hugoniot to an isotherm. Secondly the results suggest that solid argon may provide a useful pressure standard up to 3 Mbar. 12 refs., 3 figs.
Date: July 1, 1985
Creator: Ross, M.; Mao, H.K.; Bell, P.M. & Xu, J.A.
System: The UNT Digital Library
Iron dominated magnets (open access)

Iron dominated magnets

These two lectures on iron dominated magnets are meant for the student of accelerator science and contain general treatments of the subjects design and construction. The material is arranged in the categories: General Concepts and Cost Considerations, Profile Configuration and Harmonics, Magnetic Measurements, a few examples of ''special magnets'' and Materials and Practices. Extensive literature is provided.
Date: July 1, 1985
Creator: Fischer, G.E.
System: The UNT Digital Library
Improved Approach to Characterizing and Presenting Streak Camera Performance (open access)

Improved Approach to Characterizing and Presenting Streak Camera Performance

The performance of a streak camera recording system is strongly linked to the technique used to amplify, detect and quantify the streaked image. At the Lawrence Livermore National Laboratory (LLNL) streak camera images have been recorded both on film and by fiber-optically coupling to charge-coupled devices (CCD's). During the development of a new process for recording these images (lens coupling the image onto a cooled CCD) the definitions of important performance characteristics such as resolution and dynamic range were re-examined. As a result of this development, these performance characteristics are now presented to the streak camera user in a more useful format than in the past. This paper describes how these techniques are used within the Laser Fusion Program at LLNL. The system resolution is presented as a modulation transfer function, including the seldom reported effects that flare and light scattering have at low spatial frequencies. Data are presented such that a user can adjust image intensifier gain and pixel averaging to optimize the useful dynamic range in any particular application.
Date: July 15, 1985
Creator: Wiedwald, J. D. & Jones, B. A.
System: The UNT Digital Library
Dense Z-pinch plasmas (open access)

Dense Z-pinch plasmas

Early researchers recogniZed the desirable features of the linear Z-pinch configuration as a magnetic fusion scheme. In particular, a Z-pinch reactor might not require auxiliary heating or external field coils, and could constitute an uncomplicated, high plasma ..beta.. geometry. The simple Z pinch, however, exhibited gross MHD instabilities that disrupted the plasma, and the linear Z pinch was abandoned in favor of more stable configurations. Recent advances in pulsed-power technology and an appreciation of the dynamic behavior of an ohmically heated Z pinch have led to a reexamination of the Z pinch as a workable fusion concept.
Date: July 12, 1985
Creator: Shlachter, J. S.; Hammel, J. E. & Scudder, D. W.
System: The UNT Digital Library
Simulation of liquid helium (open access)

Simulation of liquid helium

The author discusses simulation methods for quantum mechanical systems at finite temperatures. Recently it has been shown that static properties of some quantum systems can be obtained by simulation in a straightforward manner using path integrals, albeit with an order of magnitude more computing effort needed than for the corresponding classical systems. Some dynamical information can be gleaned from these simulations as will be discussed below. But this is very limited - there is no quantum version of the molecular dynamics method. The path integral method is illustrated by discussing the application to liquid helium. 12 refs., 8 figs.
Date: July 1, 1985
Creator: Ceperley, D.M.
System: The UNT Digital Library
Quantum density matrix and entropic uncertainty (open access)

Quantum density matrix and entropic uncertainty

A discussion of the determination of the quantum density matrix from realistic measurements using the maximum entropy principle is presented. 3 refs.
Date: July 1, 1985
Creator: Blankenbecler, R. & Partovi, M. H.
System: The UNT Digital Library
Simulations of vibrational relaxation in dense molecular fluids (open access)

Simulations of vibrational relaxation in dense molecular fluids

In the understanding of high-temperatre and -pressure chemistry in explosives, first step is the study of the transfer of energy from translational degrees of freedom into internal vibrations of the molecules. We present new methods using nonequilibrium molecular dynamics (NEMD) for measuring vibrational relaxation in a diatomic fluid, where we expect a classical treatment of many-body collisions to be relevant because of the high densities (2 to 3 times compressed compared to the normal fluid) and high temperatures (2000 to 4000 K) involved behind detonation waves. NEMD techniques are discussed, including their limitations, and qualitative results presented.
Date: July 1, 1985
Creator: Holian, B. L.
System: The UNT Digital Library
Microscopic simulations of shock propagation in condensed media: comparison between real time and frequency domains (open access)

Microscopic simulations of shock propagation in condensed media: comparison between real time and frequency domains

Computer molecular dynamics (CMD) is now recognized as a very powerful technique for examining the microscopic details of a wide variety of chemical and physical phenomena, including the shock-induced fast decomposition processes that characterize the shock-initiation of energetic materials. The purpose of the present paper is to describe some results obtained by new methods of post processing of CMD data. First we present a pictorial history of a canonical system which is bonded with identical potentials and has identical atomic masses. We then present Fourier transforms of the energy components of different units judiciously chosen to show the ''frequency fingerprint'' of the shock impact and passage through specific units of the system, including, e.g., the behavior of spalled fragments. To complement these studies, we also display the behavior of our canonical system when defect (point or line) are present. In these studies we monitor the motion of diatoms above and below a line defect consisting of heavy masses. The Fourier transform techniques provide optimum compromise histories which present neither too much nor too little detail.
Date: July 1, 1985
Creator: Karo, A.M.; Hardy, J.R. & Mehlman, M.H.
System: The UNT Digital Library
Use of field experimental studies to evaluate emergency response models (open access)

Use of field experimental studies to evaluate emergency response models

The three-dimensional diagnostic wind field model (MATHEW) and the particle-in-cell atmospheric transport and diffusion model (ADPIC) are used by the Atmospheric Release Advisory Capability to estimate the environmental consequences of accidental releases of radioactivity into the atmosphere. These models have undergone extensive evaluations against field experiments conducted in a variety of environmental settings ranging from relatively flat to very complex terrain areas. Simulations of tracer experiments conducted in a complex mountain valley setting revealed that 35 to 50% of the comparisons between calculated and measured tracer concentrations were within a factor of 5. This may be compared with a factor of 2 for 50% of the comparisons for relatively flat terrain. This degradation of results in complex terrain is due to a variety of factors such as the limited representativeness of measurements in complex terrain, the limited spatial resolution afforded by the models, and the turbulence parameterization based on sigma/sub theta/ measurements to evaluate the eddy diffusivities. Measurements of sigma/sub theta/ in complex terrain exceed those measured over flat terrain by a factor of 2 to 3 leading to eddy diffusivities that are unrealistically high. The results of model evaluations are very sensitive to the quality and the representativeness of …
Date: July 16, 1985
Creator: Gudiksen, P. H.; Lange, R.; Rodriguez, D. J. & Nasstrom, J. S.
System: The UNT Digital Library
Shock temperature measurements in ammonia (open access)

Shock temperature measurements in ammonia

Our first shock temperature measurements on a cryogenic target are reported for NH/sub 3/. A new fast optical pyrometer and a cryogenic specimen holder for liquid NH/sub 3/ were developed to measure shock temperatures of 4400 and 3600 K at pressures of 61 and 48 GPa. These conditions correspond to those in the ice layers in Uranus and Neptune. The shock temperature data are in reasonable agreement with an equation of state based on an intermolecular potential derived from NH/sub 3/ Hugoniot data.
Date: July 1, 1985
Creator: Radousky, H. B.; Mitchell, A. C.; Nellis, W. J. & Ross, M.
System: The UNT Digital Library