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High precision beam alignment of electromagnetic wigglers (open access)

High precision beam alignment of electromagnetic wigglers

The performance of Free-Electron Lasers depends critically on the quality of the alignment of the electron beam to the wiggler's magnetic axis and the deviation of this axis from a straight fine. The measurement of the electron beam position requires numerous beam position monitors in the wiggler, where space is at premium. The beam position measurement is used to set beam steerers for an orbit correction in the wiggler. The authors propose an alternative high precision alignment method in which one or two external Beam Position Monitors (BPM) are used. In this technique, the field in the electro-wiggler is modulated section by section and the beam position movement at the external BPM is detected in synchronism with the modulation. A beam offset at the modulated beam section will produce a modulation of the beam position at the detector that is a function of the of the beam offset and the absolute value of the modulation current. The wiggler errors produce a modulation that is a function of the modulation current. It will be shown that this method allows the detection and correction of the beam position at each section in the presence of wiggler errors with a good resolution. Furthermore, …
Date: January 1, 1993
Creator: Ben-Zvi, Ilan & Qiu, X. Z.
Object Type: Article
System: The UNT Digital Library
The development of in vitro mutagenicity testing systems using T-lymphocytes (open access)

The development of in vitro mutagenicity testing systems using T-lymphocytes

This annual report describes progress in studies on hprt mutations induced by radon or Indium 111 along with the corresponding mutation frequency, cloning and molecular spectra in human T-lymphocytes. Parallel studies on the mutation susceptibility between individuals is being investigated by hprt mutation studies on ataxia telangiectasia and xeroderma pigmentosum.
Date: May 1, 1993
Creator: Albertini, R.J.
Object Type: Report
System: The UNT Digital Library
Diffuse scattering and image contrast of tweed in superconducting oxides: A simulation and interpretation (open access)

Diffuse scattering and image contrast of tweed in superconducting oxides: A simulation and interpretation

Monte Carlo simulations were performed with a lattice gas model which represents the interactions between oxygen atoms in YBa[sub 2](Cu[sub 1-x]M[sub x])[sub 3]O[sub 7+[delta]] (M=Fe, Co, or Al, 0.03< [times] <0.l) system. The amplitudes of concentration waves/displacement waves obtained from these simulations then were used to calculate the intensity of the diffuse scattering of tweed seen in the electron diffraction pattern. The characteristic features of the tweed image were produced by calculation, using a model based on the contrast originating from structures with displacive modulation, stacking on the top of each other. Both calculations agree well with the TEM observations and provide an useful basis for a better insight into the origin of the tweed structure.
Date: January 1, 1993
Creator: Zhu, Yimei & Cai, Zhi-Xiong.
Object Type: Article
System: The UNT Digital Library
Determination of the energy of suprathermal electrons during lower hybrid current drive on PBX-M (open access)

Determination of the energy of suprathermal electrons during lower hybrid current drive on PBX-M

Suprathermal electrons are diagnosed by a hard x-ray pinhole camera during lower hybrid current drive on PBX-M. The experimental hard x-ray images are compared with simulated images, which result from an integration of the relativistic bremsstrahlung along lines-of-sight through the bean-shaped plasma. Images with centrally peaked and radially hollow radiation profiles are easily distinguished. The energy distribution of the suprathermal electrons is analyzed by comparing images taken with different absorber foils. An effective photon temperature is derived from the experimental images, and a comparison with simulated photon temperatures yields the energy of the suprathermal electrons. The analysis indicates that the energy of the suprathermal electrons in the hollow discharges is in the 50 to 100 key range in the center of the discharge. There seems to exist a very small higher energy component close to the plasma edge.
Date: June 1, 1993
Creator: Von Goeler, S.; Bernabei, S.; Davis, W.; Ignat, D.; Kaita, R.; Roney, P. et al.
Object Type: Article
System: The UNT Digital Library
Reorientation of misfit dislocations during annealing in InGaAs/GaAs(001) interfaces (open access)

Reorientation of misfit dislocations during annealing in InGaAs/GaAs(001) interfaces

Transmission electron microscopy is applied to investigate the effect of postannealing on misfit dislocations in an In[sup 0.2]Ga[sup 0.8]As/GaAs(001) heterostructure. An orthogonal array of 60[degree] dislocations along [110] and [110] directions was observed in the interfaces of the samples grown by MBE at 520C. When the as-grown samples were annealed at temperatures ranging from 600 to 800C, the 60[degree] dislocations were gradually reoriented by dislocation reactions occurring at the 90[degree] intersections followed by nonconservative motion driven by dislocation line tension and the residual elastic misfit strain. The final result of this process was a dislocation array lying along [100] and [center dot] [010] directions. The reoriented u =<100> dislocation has a Burgers vector b = a/2 <101>, which is the same as that of 60[degree] dislocation, but the edge component of its Burgers vector in the (001) interfacial plane is larger than that of 60[degree] dislocation by a factor of [radical]2, resulting in a greater contribution to elastic strain relaxation. This nonconservative reorientation of 60[degree] dislocations to form the u=<100> dislocations represents a new strain relaxation mechanism in diamond or zinc blende semiconductor heterostructures.
Date: April 1, 1993
Creator: Chen, Y.; Liliental-Weber, Z.; Washburn, J. (Lawrence Berkeley Lab., CA (United States)); Klem, J.F. & Tsao, J.Y. (Sandia National Labs., Albuquerque, NM (United States))
Object Type: Article
System: The UNT Digital Library
Recovery and purification of nickel-63 from HFIR-irradiated targets (open access)

Recovery and purification of nickel-63 from HFIR-irradiated targets

The production of large quantities of high-specific-activity [sup 63]Ni (>10 Ci/g) requires both a highly enriched [sup 62]Ni target and a long irradiation period at high neutron flux. Trace impurities in the nickel and associated target materials are also activated and account for a significant fraction of the discharged activity and essentially all of the gamma activity. While most of these undesirable activation products can be removed as chloride complexes during anion exchange, chromium, present at [sup 51]Cr, and scandium, present as [sup 46]Sc, are exceptions and require additional processing to achieve the desired purity. Optimized flowsheets are discussed based upon the current development and production experience.
Date: June 1, 1993
Creator: Williams, D. F.; O'Kelley, G. D.; Knauer, J. B.; Porter, C. E. & Wiggins, J. T.
Object Type: Report
System: The UNT Digital Library
Operator overloading as an enabling technology for automatic differentiation (open access)

Operator overloading as an enabling technology for automatic differentiation

We present an example of the science that is enabled by object-oriented programming techniques. Scientific computation often needs derivatives for solving nonlinear systems such as those arising in many PDE algorithms, optimization, parameter identification, stiff ordinary differential equations, or sensitivity analysis. Automatic differentiation computes derivatives accurately and efficiently by applying the chain rule to each arithmetic operation or elementary function. Operator overloading enables the techniques of either the forward or the reverse mode of automatic differentiation to be applied to real-world scientific problems. We illustrate automatic differentiation with an example drawn from a model of unsaturated flow in a porous medium. The problem arises from planning for the long-term storage of radioactive waste.
Date: January 1, 1993
Creator: Corliss, G.F. (Marquette Univ., Milwaukee, WI (United States) Argonne National Lab., IL (United States)) & Griewank, A. (Argonne National Lab., IL (United States))
Object Type: Article
System: The UNT Digital Library
Monthly research and development topical report, March--April 1993 (open access)

Monthly research and development topical report, March--April 1993

This report covers progress made by Gilbert/Commonwealth at the Pittsburgh Energy Technology Center of the U. S. Department of Energy in the provision of research and development support services under Task Orders 30.00 and 32.00 to contract No. DE-AC22-89PC88400 as well as Subtask 3.04, safety activities provided under that contract, and Subtask 7.01, Coal Conversion/Bench Scale Design. The report period runs from March 1 to April 30, 1993.The objective of the R D Support Services and Ancillary Services Tasks is to provide technical support for the in-house R D effort at PETC. This comprises the necessary management, supervision, qualified personnel, facilities, training, technical expertise and services to support the operation of the individual test units, of the analytical chemistry laboratories and of ancillary equipment and utilities assigned to G/C responsibilities. This work is organized into twelve subtasks, seven concerned with operation of test units, and five concerned with general support services.
Date: January 1, 1993
Creator: unknown
Object Type: Report
System: The UNT Digital Library
The role of electric field shear stabilization of turbulence in the H-mode to VH-mode transition in DIII-D (open access)

The role of electric field shear stabilization of turbulence in the H-mode to VH-mode transition in DIII-D

None
Date: May 1, 1993
Creator: Burrell, K.H.; Osborne, T.H.; Groebner, R.J. (General Atomics, San Diego, CA (United States)) & Rettig, C.L. (California Univ., Los Angeles, CA (United States))
Object Type: Article
System: The UNT Digital Library
40Ar/39Ar Age Spectra and Total-Fusion Ages of Tektites from Cretaceous-Tertiary Boundary Sedimentary Rocks in the Beloc Formation, Haiti (open access)

40Ar/39Ar Age Spectra and Total-Fusion Ages of Tektites from Cretaceous-Tertiary Boundary Sedimentary Rocks in the Beloc Formation, Haiti

A report about Haitian tektites at the paleontological K-T boundary along with an Ir abundance anomaly and shocked quartz.
Date: 1993
Creator: Dalrymple, G. Brent; Izett, Glen A.; Snee, Lawrence W. & Obradovich, John D.
Object Type: Report
System: The UNT Digital Library
The Seaman Volcanic Center—A Rare Middle Tertiary Stratovolcano in Southern Nevada (open access)

The Seaman Volcanic Center—A Rare Middle Tertiary Stratovolcano in Southern Nevada

A report about the Seaman volcanic center which is a composite, middle Tertiary stratovolcano in southern Nevada.
Date: 1993
Creator: Du Bray, Edward A.
Object Type: Report
System: The UNT Digital Library
An improved, explosively actuated closing switch for pulsed power applications (open access)

An improved, explosively actuated closing switch for pulsed power applications

An improved, explosively actuated closing switch has been developed for the Pegasus II capacitor bank. The new switch design uses an annular metal jet as the switch contact. It has lower resistance and inductance at early time than the original design. A parallel array of 24 switches on Pegasus II has a resistance of less than 10 [mu][Omega] after 300 ns. Measured time behaviors include an intrinsic jitter of 50 ns and a switching delay that depends inversely on the applied voltage.
Date: January 1, 1993
Creator: Parker, J. V.; Bartsch, R. R.; Cochrane, J. C. & Marsh, S. P.
Object Type: Article
System: The UNT Digital Library
ISO standards on the evaluation of contamination (open access)

ISO standards on the evaluation of contamination

The International Organization for Standardization (ISO) develops radiation calibration standards through Subcommittee 2 (titled Radiation Protection'') of Technical Committee 85 (ISO/TC85/SC2). The subcommittee has also developed standards providing guidance on the performance of measurements. ISO/TC85/SC2 consists of international technical experts who represent their countries through the international consensus process in providing guidance in several radiation protection areas. The purpose of this paper is to summarize ISO's is guidance provided in the area of contamination measurements.
Date: January 1, 1993
Creator: Swinth, K.L. (Pacific Northwest Lab., Richland, WA (United States)) & Tamberg, T.A. (Bundesanstalt fuer Materialforschung und -pruefung, Berlin (Germany))
Object Type: Article
System: The UNT Digital Library
Failure and factors of safety in piping system design (open access)

Failure and factors of safety in piping system design

An important body of test and performance data on the behavior of piping systems has led to an ongoing reassessment of the code stress allowables and their safety margin. The codes stress allowables, and their factors of safety, are developed from limits on the incipient yield (for ductile materials), or incipient rupture (for brittle materials), of a test specimen loaded in simple tension. In this paper, we examine the failure theories introduced in the B31 and ASME III codes for piping and their inherent approximations compared to textbook failure theories. We summarize the evolution of factors of safety in ASME and B31 and point out that, for piping systems, it is appropriate to reconsider the concept and definition of factors of safety.
Date: January 1, 1993
Creator: Antaki, G. A.
Object Type: Article
System: The UNT Digital Library
Energy efficiency and the environment: Innovative ways to improve air quality in the Los Angeles Basin (open access)

Energy efficiency and the environment: Innovative ways to improve air quality in the Los Angeles Basin

This paper focuses on novel, innovative approaches for reducing or delaying the production of photochemical smog in the Los Angeles Basin. These approaches include modifying the surface characteristics of the basin by increasing surface albedo and an extensive tree-planting program. The changes in surface conditions are designed to reduce the basin air temperatures, especially during the summer months, which will result in two possible effects. First, a decrease in temperature would lead to a reduction in energy use with an associated decline in emissions of nitrogen oxides (NO[sub x]) and a lowering of evaporative emission of reactive organic gases. Reductions in these smog precursors could improve the air quality of the basin without imposing additional emissions regulations. The second effect is associated with the possible causal relationship between air temperature and smog formation (i.e., lower temperatures and lower incidence of smog). Since this approach to mitigating air emissions is broad, the studies to date have concentrated on how changes in surface characteristics affect the meteorological conditions of the basin and on how these meteorological changes subsequently affect smog production. A geographic information system database of key surface characteristics (i.e., vegetative cover, albedo, moisture availability, and roughness) was compiled, and these …
Date: February 1, 1993
Creator: Ritschard, R.
Object Type: Article
System: The UNT Digital Library
Theoretical Crystallography With the Advanced Visualization System (open access)

Theoretical Crystallography With the Advanced Visualization System

Space is an Application Visualization System (AVS) graphics module designed for crystallographic and molecular research. The program can handle molecules, two-dimensional periodic systems, and three-dimensional periodic systems, all referred to in the paper as models. Using several methods, the user can select atoms, groups of atoms, or entire molecules. Selections can be moved, copied, deleted, and merged. An important feature of Space is the crystallography component. The program allows the user to generate the unit cell from the asymmetric unit, manipulate the unit cell, and replicate it in three dimensions. Space includes the Buerger reduction algorithm which determines the asymmetric unit and the space group of highest symmetry of an input unit cell. Space also allows the user to display planes in the lattice based on Miller indices, and to cleave the crystal to expose the surface. The user can display important precalculated volumetric data in Space, such as electron densities and electrostatic surfaces. With a variety of methods, Space can compute the electrostatic potential of any chemical system based on input point charges.
Date: May 1, 1993
Creator: Younkin, C. R.; Thornton, E. N.; Nicholas, J. B.; Jones, D. R. & Hess, A. C.
Object Type: Article
System: The UNT Digital Library
A risk-based approach to cost-benefit analysis of software safety activities (open access)

A risk-based approach to cost-benefit analysis of software safety activities

Assumptions about the economics of making a system safe are usually not explicitly stated in industrial and software models of safety-critical systems. These assumptions span a wide spectrum of economic tradeoffs with respect to resources expended to make a system safe. The missing component in these models that is necessary for capturing the effect of economic tradeoffs is risk. A qualitative risk-based software safety model is proposed that combines features of industrial and software systems safety models. The risk-based model provides decision makers with a basis for performing cost-benefit analyses of software safety-related activities.
Date: January 1, 1993
Creator: Fortier, S.C. (Intermetrics, Inc., McLean, VA (United States)) & Michael, J.B. (Argonne National Lab., IL (United States))
Object Type: Article
System: The UNT Digital Library
Fin-efficiency calculation for condensation in the presence of noncondensable gases (open access)

Fin-efficiency calculation for condensation in the presence of noncondensable gases

Plate-fin heat exchangers are being considered for many condenser applications. They are commonly used for the gas-separation process because they can provide a high thermal performance to obtain a low mean-temperature difference, essential for the gas-separation process. Plate-fin heat exchangers are also considered for the heat-pump system using nonazeotropic refrigerant mixtures. The brazed plate-fin condenser was considered to be a leading candidate for the Ocean Thermal Energy Conversion (OTEC) system, where high-performance heat exchangers are essential for maintaining a low mean-temperature difference. Calculation of the fin efficiency is difficult for condensation in the presence of noncondensable gases due to the spatial variation of the interfacial temperature. An analysis was carried out to develop a simplified method to calculate the fin efficiency for condensation of a vapor in the presence of noncondensable gases. The analysis includes the variation in the interfacial temperature along the fin surface. Appropriate assumptions are made to simplify the coupled heat-conduction equation in the fin and the heat/mass fluxes at the interface. The resulting expression for the fin efficiency includes mass-flux parameters, and it is similar to the common expression used for single-phase flow.
Date: January 1, 1993
Creator: Panchal, C.B.
Object Type: Article
System: The UNT Digital Library
Design of large aperture, low mass vacuum windows (open access)

Design of large aperture, low mass vacuum windows

Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions.
Date: January 1, 1993
Creator: Leonhardt, W.J. & Mapes, M.
Object Type: Article
System: The UNT Digital Library
Market and Energy Demand Analysis of a US Maglev System (open access)

Market and Energy Demand Analysis of a US Maglev System

High-speed magnetically levitated (maglev) vehicles can provide an alternative mode of transportation for intercity travel, particularly for short- and medium-distance trips between 100 to 600 mi (160 and 960 km). The patterns of growth and the underlying factors affecting that growth In the year 2010 are evaluated to determine the magnitude of US Intercity travel that would become the basis for maglev demand. A methodology that is sensitive to the travelers' socioeconomic attributes was developed to Forecast intercity travel. Travel between 78 major metropolitan areas by air and highway modes is projected, and 12 high-density travel corridors are Identified and selected. The potential for a maglev system to substitute for part or that travel is calculated by using a model that estimates the extent of diversion from highway and air to maglev. Energy demand is estimated on the basis of energy usage during acceleration and cruise phases for each corridor and corridor connections.
Date: January 1, 1993
Creator: Vyas, A. D. & Rote, D. M.
Object Type: Article
System: The UNT Digital Library
Control and Performance of the AGS and AGS Booster Main Magnet Power Supplies (open access)

Control and Performance of the AGS and AGS Booster Main Magnet Power Supplies

Techniques for precision control of the main magnet power supplies for the AGS and AGS Booster synchrotron will be discussed. Both synchrotrons are designed to operate in a Pulse-to-Pulse Modulation (PPM) environment with a Supercycle Generator defining and distributing global timing events for the AGS Facility. Details of modelling, real-time feedback and feedforward systems, generation and distribution of real time field data, operational parameters and an overview of performance for both machines are included.
Date: January 1, 1993
Creator: Reece, R. K.; Casella, R.; Culwick, B.; Geller, J.; Marneris, I.; Sandberg, J. et al.
Object Type: Article
System: The UNT Digital Library
Structure and damping of toroidal drift waves (and their implications for anomalous transport) (open access)

Structure and damping of toroidal drift waves (and their implications for anomalous transport)

The conventional theory of high-n toroidal drift waves, based on the ballooning representation, indicates that shear-damping is generally reduced in a torus compared to its plane-slab value. It therefore describes the most unstable class of toroidal drift waves. However, modes of this type occur only i f the diamagnetic frequency [omega]*(r) has a maximum in r, and they affect only a small fraction, [Omicron](1/n[sup l/2]), of the plasma radius around this maximum. Consequently they may produce little anomalous transport. In the present work we show that, within the ballooning description, there is another class of toroidal drift waves with very different properties to the conventional ones. The new modes have greater shear-damping (closer to that in a plane-slab) than the conventional ones and so have a higher instability threshold. However, they occur for any plasma profile and at all radii, and they have larger radial extent. Consequently they may produce much greater anomalous transport than the possibly benign conventional modes. This suggests a picture of anomalous transport in which the plasma profile is determined by marginal stability, but marginal to the new class of modes not to the conventional ones. This might explain why marginally stable profiles calculated for drift …
Date: May 1, 1993
Creator: Taylor, J.B. (Texas Univ., Austin, TX (United States). Inst. for Fusion Studies); Connor, J. & Wilson, H.R. (Euratom/UKAEA Fusion Association, Abingdon (United Kingdom). Culham Lab.)
Object Type: Report
System: The UNT Digital Library
TACB Bulletin, Number 2, 1993 (open access)

TACB Bulletin, Number 2, 1993

Newsletter of the Texas Air Control Board including information about the Board as well as news, events, and other relevant information related to air quality in Texas.
Date: 1993
Creator: Texas Air Control Board
Object Type: Journal/Magazine/Newsletter
System: The Portal to Texas History
Lectures of Fermi liquid theory (open access)

Lectures of Fermi liquid theory

The Fermi liquid theory was first introduced by Landau in 1956 to provide a theoretical basis for the properties of strongly correlated Fermi systems. This theory has proven to be crucial for our understanding of a broad range of materials. These include liquid [sup 3]He, [sup 3]He-[sup 4]He mixtures, simple metals, heavy-fermions, and nuclear matter to name a few. In the high temperature superconductors questions have been raised regarding the applicability of Fermi liquid theory to the normal state behavior of these materials. I will not address this issue in these lectures. My focus will be to summarize the foundations of this theory and to explore the consequences. These lectures are in part a summary of the excellent review article by Baym and Pethick and the books by Pines and Nozieres and Baym and Pethick. They include as well a summary of some articles that I have authored and co-authored. In the main body of the lectures I will not make any additional references to the books or articles. In the absence of reading the original materials, my lectures should provide the essentials of a mini-course in Fermi liquid theory.
Date: January 1, 1993
Creator: Bedell, K.S.
Object Type: Article
System: The UNT Digital Library