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  Partner: UNT Libraries Government Documents Department
 Decade: 1990-1999
0.5 {mu}m E/D AlGaAs/GaAs heterostructure field effect transistor technology with DFET threshold adjust implant
A doped-channel heterostructure field effect transistor (H-FET) technology has been developed with self-aligned refractory gate processing and using both enhancement- and depletion-mode transistors. D-HFET devices are obtained with a threshold voltage adjust implant into material designed for E-HFET operation. Both E- and D-HFETs utilize W/WSi bilayer gates, sidewall spacers, and rapid thermal annealing for controlling short channel effects. The 0.5 {mu}m E- HFETs (D-HFETs) have been demonstrated with transconductance of 425 mS/mm (265-310 mS/mm) and f{sub t} of 45-50 GHz. Ring oscillator gate delays of 19 ps with a power of 0.6 mW have been demonstrated using direct coupled FET logic. These results are comparable to previous doped-channel HFET devices and circuits fabricated by selective reactive ion etching rather than ion implantation for threshold voltage adjustment. digital.library.unt.edu/ark:/67531/metadc686113/
D-0 End Calorimeter Warm Tube/TeV Dry Air Purge
This Engineering Note studies the design of the Dry Air Purge that is going to flow through the Warm Tube of the End Calorimeter of the D-O Calorimeter. The Tev tubes through the E.C. can be thought of as a cluster of concentric tubes: The Tev tube, the warm (vacuum vessel) tube, 15 layers of superinsulation, the cold (argon vessel) tube, and the Inner Hadronic center support tube. The Dry Air Purge will involve flowing Dry Air through the annular region between the Warm Tube and the Tev Beam Pipe. This air flow is intended to prevent condensation from forming in this region which could turn to ice under cryogenic temperatures. Any ice formed in this gap, could cause serious problems when these tubes are moved. The Air will flow through a Nylon Tube Fitting -1/4-inch I.D. to 1/8-inch male pipe thread (Cole Palmer YB-06465-15) see Drawing MC-295221 (Appendix A). This fitting will be attached to the Nylon 2-inch Tube-Wiper and Seal Assembly which is clamped to the ends of the Warm Tube (Appendix A). This note includes drawings and calculations that explain the setup of the Dry Air Purge and give the required information on the pressure drops through the setup. The Equations and properties used in the calculations were obtained from the Applied Fluid Dynamics Handbook by Robert D. Blevins and Fluid Dynamics Second Edition by Frank M. White. digital.library.unt.edu/ark:/67531/metadc840985/
D-0 North End Cap Calorimeter Cold Test Results
The North endcap calorimeter vessel was recieved on July 1, 1990. A cooldown of the pressure vessel with liquid nitrogen was performed on July 10-11 to check the vessel's integrity. With the pressure vessel cold, the insulating vacuum was monitored for leaks. Through out the testing, the insulating vacuum remained good and the vessel passed the test. The cold test was carried out per the procedures of D-Zero engineering note 3740.220-EN-250. The test was very similar to the cold test performed on the Central Calorimeter in October of 1987. Reference D-Zero engineering notes 3740.210-EN-122, 3740.000-EN107, and 3740.210-EN-110 for information about the CC cold test. The insulating vacuum space was pumped on while equipment was being connected to the pressure vessel. Two hours after starting to pump with the blower the vacuum space pressure was at about 210 microns. Pumping on the vacuum space for the next 15 hours showed no progress and a leak detector was connected to the pumping line. A leak check showed a leak in a thermocouple feedthru on the vacuum space relief plate. After fixing the leak, the pressure dropped to 16 microns in less than one hour. A rate of rise test was performed starting at a pressure of 13 microns. The pressure rose to 39 microns within 8 minutes and then only rose to 43 microns in 2.5 hours (1.6 microns/hour). After all connections were made to the pressure vessel, a vacuum pump with an estimated effective pumping speed of about 70 scfm was valved on. The lowest pressure achieved after 2 days of pumping was 80 microns. Valving out the pump for 30 minutes resulted in a 5 micron per minute rate of rise. The rate of rise was considered acceptable since there were known leak paths through the bolts of the signal ports. The EC North vessel was rolled outside of Lab A in preparation for a 5000 gallon liquid nitrogen trailer which arrived July, 10 at 8:00am. Before filling the vessel, the vacuum space pump was valved off. The pressure in the vacuum space was 12 microns at that point. During the next 24 hours of the test, the vacuum space pressure decreased to 5 microns. A plot of the vacuum space pressure with time is included at the end of this note. The liquid nitrogen was pressure transferred from the trailer at 29 psig to the pressure vessel at 1 psig for ten hours. At that time there was sufficient (16-inch) of liquid nitrogen in the vessel to turn the LN2 trailer delivery pump on. Thirteen and one half hours after starting the fill, the vessel had 50-inch of LN2 collected. During the latter part of the filling, about twelve loud metallic bangs were heard. The noises came at random intervals with sometimes five minutes between and other times an hour between. The best way to describe the sound is to imagine the sound made if someone was trapped inside the vessel with a baseball bat and took a good swing. The trailer was disconnected and the the vessel was left overnight for ten hours. Due to the slow LN2 fill rate, the temperature gradient in the pressure vessel shell was not very large, only about 25 kelvin difference was found from a RTD in the warm-up nozzle of the vessel and the resistors of the liquid level probe. A temperature versus time graph is included at the end of this note. digital.library.unt.edu/ark:/67531/metadc831688/
D-0 South End Cap Calorimeter Cold Test Results
The South endcap calorimeter vessel was moved into Lab A on Sept. 18, 1990. A cooldown of the pressure vessel with liquid nitrogen was performed on Sept. 26 to check the vessel's integrity. With the pressure vessel cold, the insulating vacuum was monitored for leaks. Through out the testing, the insulating vacuum remained good and the vessel passed the test. The cold test was carried out per the procedures of D-Zero engineering note 3740.220-EN-250. The test was very similar to the cold test performed on the Central Calorimeter in October of 1987. The test of the ECS was performed in the same manner using the same equipment as the ECN cold test. Reference D-Zero engineering notes 3740.210-EN-122, 3740.000-EN-I07, and 3740.210-EN-II0 for information about the CC cold test. Reference EN-260 for the results of the ECN cold test. The insulating vacuum space was pumped on while equipment was being connected to the pressure vessel. Two hours after starting to pump with the blower the vacuum space pressure was at about 40 microns. The pumping continued overnight (another 16 hours). In the morning the pressure was 11.5 microns. A rate of rise test was performed. With the pump valved off, the pressure rose to 14 microns within 5 minutes and then rose to 16 microns in 6 hours (0.33 microns/hour). After all connections were made to the pressure vessel, a vacuum pump with an estimated effective pumping speed of about 70 scfm was valved on. After 18 hours, the pressure vessel was down to 270 microns. An additional day of pumping took the pressure down to only 250 microns. A leak was then found and fixed around the seal of the rupture disc. The pump was put on line again. The pressure vessel with pump on line was 27 microns after 16.5 hours. A rate of rise was then conducted. The pressure was 90 microns after valving out the pump. After 30 minutes the pressure increased to 107 microns. (34 microns/hr). digital.library.unt.edu/ark:/67531/metadc838127/
1.2 MW klystron for Asymmetric Storage Ring B Factory
A cw klystron operating at 476 MHz has been developed jointly by SLAC and Varian Associates. The unique set of characteristics of this tube were strongly guided by requirements of the fast feedback necessary to prevent oscillations of the storage ring beams caused by the detuned accelerating cavity. This requires a combination of bandwidth and short group delay within the klystron. The RF feedback stabilization scheme also requires amplitude modulation making it necessary to operate the klystron about 10% below saturation. Performance specifications and initial operating results are presented. digital.library.unt.edu/ark:/67531/metadc666784/
A 1.5 GeV compact light source with superconducting bending magnets
This paper describes the design of a compact electron synchrotron light source for producing X-rays for medical imaging, protein crystallography, nano-machining and other uses up to 35 keV. The source will provide synchrotron light from six 6.9 tesla superconducting 60{degree} bending magnet stations. In addition the ring, contains conventional quadrupoles and sextupoles. The light source has a circumference of 26 meters, which permits it to be located in a variety of industrial and medical facilities. digital.library.unt.edu/ark:/67531/metadc793152/
1.8.2.1.2 Site system engineering implementation Fiscal Year 1998 multi-year work plan
Manage the Site Systems Engineering process to provide a traceable, integrated, requirements-driven, and technically defensible baseline., Through the Site Integration Group, Systems Engineering ensures integration of technical activities across all site projects. Systems Engineering`s primary interfaces are with the Project Direction Office and with the projects, as well as with the Planning organization. digital.library.unt.edu/ark:/67531/metadc688671/
1.8.3 Site system engineering FY 1997 program plan
The FY 1997 Multi-Year Work Plan (MYWP) technical baseline describes the functions to be accomplished and the technical standards that govern the work. The following information is provided in this FY 1997 MYWP: technical baseline, work breakdown structure, schedule baseline, cost baseline, and execution year. digital.library.unt.edu/ark:/67531/metadc683550/
1-GeV Linac Upgrade Study at Fermilab
A linac injector for a new proton source complex at Fermilab is assumed to have a kinetic energy of 1 GeV. This linac would be sized to accelerate 100 mA of H{sup -} beam in a 200 microsecond pulse at a 15 Hz repetition rate. This would be adequate to produce {approximately}10{sup 14} protons per pulse allowing for future improvements of the new proton source complex. An alternate proposal is to add 600 MeV of side coupled cavity linac at 805 MHz to the existing 400 MeV Linac. This addition may either be in a new location or use the present Booster tunnel. A discussion of these possibilities will be given. digital.library.unt.edu/ark:/67531/metadc669837/
A 1-kW power demonstration from the advanced free electron laser
This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The main objective of this project was to engineer and procure an electron beamline compatible with the operation of a 1-kW free-electron laser (FEL). Another major task is the physics design of the electron beam line from the end of the wiggler to the electron beam dump. This task is especially difficult because electron beam is expected to have 20 kW of average power and to simultaneously have a 25% energy spread. The project goals were accomplished. The high-power electron design was completed. All of the hardware necessary for high-power operation was designed and procured. digital.library.unt.edu/ark:/67531/metadc690546/
O(1/M{sup 3}) effects for heavy-light mesons in lattice NRQCD
The masses of spin-singlet and spin-triplet S-wave mesons containing a single heavy quark are computed in the quenched approximation. The light quark action and gauge field action are both classically-improved and tadpole-improved, and the couplings to the heavy quark are organized by the 1/M expansion of tadpole-improved NRQCD. At each of two lattice spacings, near 0.22fm and 0.26fm, meson masses are obtained for heavy quarks spanning the region between charmed and bottom mesons. Results up to O(1/M), O(1/M{sup 2})and O(1/M{sup 3}) are displayed separately, so that the convergence of the heavy quark expansion can be discussed. Also, the effect of each term in the O(1/M{sup 3}) contribution is computed individually. For bottom mesons the 1/M-expansion appears to be satisfactory, but the situation for charmed mesons is less clear. digital.library.unt.edu/ark:/67531/metadc711949/
1: Mass asymmetric fission barriers for {sup 98}Mo; 2: Synthesis and characterization of actinide-specific chelating agents
Excitation functions have been measured for complex fragment emission from the compound nucleus {sup 98}Mo, produced by the reaction of {sup 86}Kr with {sup 12}C. Mass asymmetric fission barriers have been obtained by fitting the excitation functions with a transition state formalism. The extracted barriers are {approximately} 5.7 MeV higher, on average, than the calculations of the Rotating Finite Range Model (RFRM). These data clearly show an isospin dependence of the conditional barriers when compared with the extracted barriers from {sup 90}Mo and {sup 94}Mo. Eleven different liquid/liquid extractants were synthesized based upon the chelating moieties 3,2-HOPO and 3,4-HOPO; additionally, two liquid/liquid extractants based upon the 1,2-HOPO chelating moiety were obtained for extraction studies. The Pu(IV) extractions, quite surprisingly, yielded results that were very different from the Fe(III) extractions. The first trend remained the same: the 1,2-HOPOs were the best extractants, followed closely by the 3,2-HOPOs, followed by the 3,4-HOPOs; but in these Pu(IV) extractions the 3,4-HOPOs performed much better than in the Fe(III) extractions. 129 refs. digital.library.unt.edu/ark:/67531/metadc685938/
A-01 metals in stormwater runoff evaluation
As a part of the A-01 investigation required by the NPDES permit, an investigation was performed to ascertain the concentrations of metals specifically copper (Cu), lead (Pb), and zinc (Zn) in stormwater being discharged through the outfall. This information would indicate whether all water being discharged would have to be treated or if only a portion of the discharged stormwater would have to be treated. A study was designed to accomplish this. The first goal was to determine if the metal concentrations increased, decreased, or remained the same as flow increased during a rain event. The second goal was to determine if the concentrations in the storm water were due to dissolved. The third goal was to obtain background data to ascertain if effluent credits could be gained due to naturally occurring metals.Samples from this study were analyzed and indicate that the copper and lead values increase as the flow increases while the zinc values remain essentially the same regardless of the flow rate. Analyses of samples for total metals, dissolved metals, TSS, and metals in solids was complicated because in all cases metals contamination was found in the filters themselves. Some conclusions can be derived if this problem is taken into account when analyzing the data. Copper concentrations in the total and dissolved fractions as well as the TSS concentrations followed the hydrograph at this outfall but the copper in solids concentration appeared to peak in the first flush and decline to nondetectable rapidly over the course of the storm event. Lead was present in the total analysis but not present in the dissolved fraction or the solids fraction of the samples. The data for zinc was interesting in that the dissolved fractions were higher than the total fraction in three out of four samples. This is probably due to the high zinc concentrations on the filters being transferred to the dissolved faction of the sample. (Abstract Truncated) digital.library.unt.edu/ark:/67531/metadc695366/
1 MeV electron irradiation of solid Xe nanoclusters in Al : an in-situ HRTEM study.
Thin film samples of a simple embedded nanocluster system consisting of solid Xe precipitates in Al have been subjected to 1 MeV electron irradiation in a high-voltage electron microscope. High-resolution images have been recorded on videotape in order to monitor the changes to the system resulting from the passage of electrons through the film. Inspection of the video recordings (in some cases frame-by-frame) reveals that complex, rapid processes occur under the electron beam. These include, movement of small clusters, coalescence of neighboring clusters, shape changes, the apparent melting and resolidification of the Xe, and the creation and annealing of extended defects within the Xe lattice. A tentative interpretation of some of the observations is presented in terms of the electron-induced displacement processes at the surface of the clusters. digital.library.unt.edu/ark:/67531/metadc738815/
1 nA beam position monitoring system
A system has been developed at Jefferson Lab for measuring transverse position of very low current beams delivered to the Experimental Hall B of the Continuous Electron Beam Accelerator Facility (CEBAF). At the heart of the system is a position sensitive cavity operating at 1497 MHz. The cavity utilizes a unique design which achieves a high sensitivity to beam position at a relatively low cavity Q. The cavity output RF signal is processed using a down-converter and a commercial lock-in amplifier operating at 100 kHz. The system interfaces with a VME based EPICS control system using the IEEE, 488 bus. The main features of the system are simple and robust design, and wide dynamic range capable of handling beam currents from 1 nA to 1000 nA with an expected resolution better than 100 {mu}m. This paper outlines the design of the system. digital.library.unt.edu/ark:/67531/metadc675723/
A 1- to 5-MW, RCS-based, short-pulse spallation neutron source
Two accelerator configurations, the linac/compressor ring scheme and the linac/RCS scheme, are commonly used to provide the proton beam power for a short-pulse spallation neutron source. In one configuration, a full-power linac provides the beam power and a compressor ring shortens the pulse length from 1-ms down to 1 {micro}s. In the other, rapid cycling synchrotrons (RCSs) provide the beam power and also shorten the pulse length. A feasibility study of a staged approach to a 5-MW proton source utilizing RCS technology, allowing intermediate operation at 1 MW, was performed at ANL and is presented in this paper. This study is complementary to a study in progress at ORNL based on a linac and an accumulator ring. The 1-MW facility consists of a 400-MeV injector linac that delivers 0.5-mA time-averaged current, a synchrotron that accelerates the beam to 2 GeV at a 30-Hz rate, and two neutron-generating target stations. In the second phase, the 2-GeV beam is accelerated to 10 GeV by a larger RCS, increasing the facility beam power to 5 MW. digital.library.unt.edu/ark:/67531/metadc680327/
1-watt composite-slab Er:YAG laser. Revision 1
A diode-side-pumped discrete-optic Er{sup 3+} :YAG laser employs pump-light coupling through a sapphire plate diffusion-bonded to the laser slab, removing heat directly at the pump face of the slab instead of requiring conduction through to its far side. This lowers the temperature in the gain region and gives reduced thermal lensing, which produces exceptional beam quality (M{sup 2} {approx} 1.3) at output powers {approx} 0.3 Watt. Powers above 1 Watt have been demonstrated with peak slope efficiencies {approx}20%. The novel architecture is also applicable to other side-pumped lasers. digital.library.unt.edu/ark:/67531/metadc696997/
2-1/2-D electromagnetic modeling of nodular defects in high-power multilayer optical coatings
Advances in the design and production of high damage threshold optical coatings for use in mirrors and polarizers have been driven by the design requirements of high-power laser systems such as the proposed 1.8-MJ National Ignition Facility (NIF) and the prototype 12- kJ Beamlet laser system. The present design of the NIF will include 192 polarizers and more than 1100 mirrors. Currently, the material system of choice for high-power multilayer optical coatings with high damage threshold applications near 1.06 {mu}m are e-beam deposited HfO{sub 2}/Si0{sub 2} coatings. However, the optical performance and laser damage thresholds of these coatings are limited by micron-scale defects and insufficient control over layer thickness. In this report, we will discuss the results of our 2-1/2-D finite-element time- domain (FDTD) EM modeling effort for rotationally-symmetric nodular defects in multilayer dielectric HR coatings. We have added a new diagnostic to the 2-1/2-D FDTD EM code, AMOS, that enables us to calculate the peak steady-state electric fields throughout a 2-D planar region containing a 2-D r-z cross-section of the axisymmetric nodular defect and surrounding multilayer dielectric stack. We have also generated a series of design curves to identify the range of loss tangents for Si0{sub 2} and HfO{sub 2} consistent with the experimentally determined power loss of the HR coatings. In addition, we have developed several methods to provide coupling between the EM results and the thermal-mechanical simulation effort. digital.library.unt.edu/ark:/67531/metadc684881/
(02.2) Scoping experiments; (02.3) long-term corrosion testing and properties evaluation of candidate waste package basket material
The work described in this activity plan addresses Information Need 2.7.3 of the Yucca Mountain Site Characterization Plan (l), which reads Determination that the design criteria in lOCFR60.130 through 60.133 and any appropriate additional design objectives pertaining to criticality control have been met. This work falls under section WBS 1.2.2.5 2 (Basket Materials) of WBS 1.2.2.5 (Waste Package Materials) in the Work Breakdown Structure of the Yucca Mountain Site Characterization Project. digital.library.unt.edu/ark:/67531/metadc666681/
The 2.3 {angstrom} crystal structure of cholera toxin B subunit pentamer: Choleragenoid
Cholera toxin, a heterohexameric AB{sub 5} enterotoxin released by Vibrio cholera, induces a profuse secretory diarrhea in susceptible hosts. Choleragenoid, the B subunit pentamer of cholera toxin, directs the enzymatic A subunit to its target by binding to GM{sub 1} gangliosides exposed on the luminal surface of intestinal epithelial cells. We have solved the crystal structure of choleragenoid at 2.3 {Angstrom} resolution by combining single isomorphous replacement with non-crystallographic symmetry averaging. The structure of the B subunits, and their pentameric arrangement, closely resembles that reported for the intact holotoxin (choleragen), the heat-labile enterotoxin from E. coli, and for a choleragenoid-GM{sub 1} pentasaccharide complex. In the absence of the A subunit the central cavity of the B pentamer is a highly solvated channel. The binding of the A subunit or the receptor pentasaccharide to choleragenoid has only a modest effect on the local stereochemistry and does not perceptibly alter the subunit interface. digital.library.unt.edu/ark:/67531/metadc671655/
A 2.14 ms candidate optical pulsar in SN1987A: Ten years after
We have monitored Supernova 1987A in optical/near-infrared bands from a few weeks following its birth until the present time in order to search for a pulsar remnant. We have found an apparent pattern of emission near the frequency of 467.5 Hz - a 2.14 ms pulsar candidate, first detected in data taken on the remnant at the Las Campanas Observatory (LCO) 2.5-m Dupont telescope during 14-16 Feb. 1992 UT. We detected further signals near the 2.14 ms period on numerous occasions over the next four years in data taken with a variety of telescopes, data systems and detectors, at a number of ground- and space-based observatories. The sequence of detections of this signal from Feb. `92 through August `93, prior to its apparent subsequent fading, is highly improbable (< 10{sup -10} for any noise source). We also find evidence for modulation of the 2.14 ms period with a {approx}1,000 s period which, when taken with the high spindown of the source (2-3 x 10{sup -10} Hz/s), is consistent with precession and spindown via gravitational radiation of a neutron star with a non- axisymmetric oblateness of {approx}10{sup -6}, and an implied gravitational luminosity exceeding that of the Crab Nebula pulsar by an order of magnitude. digital.library.unt.edu/ark:/67531/metadc690450/
2-D electric fields and drifts near the magnetic separatrix in divertor tokamaks
A 2-D calculation is presented for the transport of plasma in the edge region of a divertor tokamak solving continuity, momentum, and energy balance fluid equations. The model uses anomalous radial diffusion, including perpendicular ion momentum, and classical cross-field drifts transport. Parallel and perpendicular currents yield a self-consistent electrostatic potential on both sides of the magnetic separatrix. Outside the separatrix, the simulation extends to material divertor plates where the incident plasma is recycled as neutral gas and where the plate sheath and parallel currents dominate the potential structure. Inside the separatrix, various radial current terms - from viscosity, charge-exchange and poloidal damping, inertia, and {triangledown}B - contribute to the determining the potential. The model rigorously enforces cancellation of gyro-viscous and magnetization terms from the transport equations. The results emphasize the importance of E x B particle flow under the X-point which depends on the sign of the toroidal magnetic field. Radial electric field (E{sub y}) profiles at the outer midplane are small with weak shear when high L-mode diffusion coefficients are used and are large with strong shear when smaller H-mode diffusion coefficients are used. The magnitude and shear of the electric field (E{sub y}) is larger both when the core toroidal rotation is co-moving with the inductive plasma current and when the ion {triangledown}B-drift is towards the single-null X-point. digital.library.unt.edu/ark:/67531/metadc667325/
2-D Finite Element Cable and Box IEMP Analysis
A 2-D finite element code has been developed for the solution of arbitrary geometry cable SGEMP and box IEMP problems. The quasi- static electric field equations with radiation- induced charge deposition and radiation-induced conductivity y are numerically solved on a triangular mesh. Multiple regions of different dielectric materials and multiple conductors are permitted. digital.library.unt.edu/ark:/67531/metadc669433/
2-D image segmentation using minimum spanning trees
This paper presents a new algorithm for partitioning a gray-level image into connected homogeneous regions. The novelty of this algorithm lies in the fact that by constructing a minimum spanning tree representation of a gray-level image, it reduces a region partitioning problem to a minimum spanning tree partitioning problem, and hence reduces the computational complexity of the region partitioning problem. The tree-partitioning algorithm, in essence, partitions a minimum spanning tree into subtrees, representing different homogeneous regions, by minimizing the sum of variations of gray levels over all subtrees under the constraints that each subtree should have at least a specified number of nodes, and two adjacent subtrees should have significantly different average gray-levels. Two (faster) heuristic implementations are also given for large-scale region partitioning problems. Test results have shown that the segmentation results are satisfactory and insensitive to noise. digital.library.unt.edu/ark:/67531/metadc628011/
2-D linear motion system. Innovative technology summary report
The US Department of Energy's (DOE's) nuclear facility decontamination and decommissioning (D and D) program requires buildings to be decontaminated, decommissioned, and surveyed for radiological contamination in an expeditious and cost-effective manner. Simultaneously, the health and safety of personnel involved in the D and D activities is of primary concern. D and D workers must perform duties high off the ground, requiring the use of manlifts or scaffolding, often, in radiologically or chemically contaminated areas or in areas with limited access. Survey and decontamination instruments that are used are sometimes heavy or awkward to use, particularly when the worker is operating from a manlift or scaffolding. Finding alternative methods of performing such work on manlifts or scaffolding is important. The 2-D Linear Motion System (2-D LMS), also known as the Wall Walker{trademark}, is designed to remotely position tools and instruments on walls for use in such activities as radiation surveys, decontamination, and painting. Traditional (baseline) methods for operating equipment for these tasks require workers to perform duties on elevated platforms, sometimes several meters above the ground surface and near potential sources of contamination. The Wall Walker 2-D LMS significantly improves health and safety conditions by facilitating remote operation of equipment. The Wall Walker 2-D LMS performed well in a demonstration of its precision, accuracy, maneuverability, payload capacity, and ease of use. Thus, this innovative technology is demonstrated to be a viable alternative to standard methods of performing work on large, high walls, especially those that have potential contamination concerns. The Wall Walker was used to perform a final release radiological survey on over 167 m{sup 2} of walls. In this application, surveying using a traditional (baseline) method that employs an aerial lift for manual access was 64% of the total cost of the improved technology. However, for areas over approximately 600 m{sup 2}, the Wall Walker would cost less than the baseline. Using the Wall Walker 2-D LMS, ALARA exposure and worker safety is improved, and there is potential for increased productivity. This innovative technology performed better than the baseline by providing real-time monitoring of the tool or instrument position. Also, the Wall Walker 2-D LMS can traverse any two-dimensional path at constant speeds of up to 18.3 linear meters per minute (60 linear feet per minute). The survey production rate for the innovative technology was about 0.6 m{sup 2}/min (6 ft{sup 2}/min); the baseline production rate was approximately 0.3 m{sup 2}/min (3 ft{sup 2}/min), using the same surveying instrument and maximum scanning rate. digital.library.unt.edu/ark:/67531/metadc682357/
A 2-D Self-Consistent DSMC Model for Chemically Reacting Low Pressure Plasma Reactors
This paper will focus on the methodology of using a 2D plasma Direct Simulation Monte Carlo technique to simulate the species transport in an inductively coupled, low pressure, chemically reacting plasma system. The pressure in these systems is typically less than 20 mtorr with plasma densities of approximately 10{sup 17} {number_sign}/m{sup 3} and an ionization level of only 0.1%. This low ionization level tightly couples the neutral, ion, and electron chemistries and interactions in a system where the flow is subsonic. We present our strategy and compare simulation results to experimental data for Cl{sub 2} in a Gaseous Electronics Conference (GEC) reference cell modified with an inductive coil. digital.library.unt.edu/ark:/67531/metadc717421/
2 HZ, 30 T SPLIT PULSE WATER COOLED MAGNET FOR NEUTRON SCATTERING EXPERIMENTS (MATERIALS CHARACTERIZATION AND DESIGN OPTIONS)
No abstract prepared. digital.library.unt.edu/ark:/67531/metadc723997/
N = 2 string amplitudes
In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically. digital.library.unt.edu/ark:/67531/metadc622294/
2 {times} 2 TeV {mu}{sup +}{mu}{sup {minus}} collider: Lattice and accelerator-detector interface study
The design for a high-luminosity {mu}{sup +}{mu}{sup {minus}} superconducting storage ring is presented based on first-pass calculations. Special attention is paid to two Iowa interaction regions (IR) whose optics are literally interlaced with the collider detectors. Various sources of backgrounds in IR are explored via realistic Monte Carlo simulations. An improved design of the collider lattice in the neighborhood of the interaction points (EP) is determined by the need to reduce significantly background levels in the detectors. digital.library.unt.edu/ark:/67531/metadc710146/
A 2 to 4 nm high power FEL on the SLAC linac
We report the results of preliminary studies of a 2 to 4 nm SASE FEL, using a photoinjector to produce the electron beam, and the SLAC linac to accelerate it to an energy up to 10 GeV. Longitudinal bunch compression is used to increases ten fold the peak current to 2.5 kA, while reducing the bunch length to the subpicosecond range. The saturated output power is in the multi-gigawatt range, producing about 10{sup 14} coherent photons within a bandwidth of about 0.2% rms, in a pulse of several millijoules. At 120Hz repetition rate the average power is about 1 W. The system is optimized for x-ray microscopy in the water window around 2 to 4 nm, and will permit imaging a biological sample in a single subpicosecond pulse. digital.library.unt.edu/ark:/67531/metadc621303/
2 x 2 TeV mu(superscript +) mu (superscript) collider
The scenarios for high-luminosity 2 x 2 TeV and 250 x 250 GeV {mu}{sup +}{mu}{sup -} colliders are presented. Having a high physics potential, such a machine has specific physics and technical advantages and disadvantages when compared with an e{sup +}e{sup -} collider. Parameters for the candidate designs and the basic components - proton source, pion production and decay channel, cooling, acceleration and collider storage ring - are considered. Attention is paid to the areas mostly affecting the collider performance: targetry, energy spread, superconducting magnet survival, detector backgrounds, polarization, environmental issues. 13 refs., 9 figs., 4 tabs. digital.library.unt.edu/ark:/67531/metadc687319/
A 3-axis force balanced accelerometer using a single proof-mass
This paper presents a new method for wideband force balancing a proof-mass in multiple axes simultaneously. Capacitive position sense and force feedback are accomplished using the same air-gap capacitors through time multiplexing. Proof of concept is experimentally demonstrated with a single-mass monolithic surface micromachined 3-axis accelerometer. digital.library.unt.edu/ark:/67531/metadc687321/
3-D computer simulations of EM fields in the APS vacuum chamber: Part 1, Frequency-domain analysis
The vacuum chamber proposed for the storage ring of the 7-GeV Advanced Photon Source (APS) basically consists of two parts: the beam chamber and the antechamber, connected to each other by a narrow gap. A sector of 1-meter-long chamber with dosed end plates, to which are attached the 1-inch-diameter beampipes centered at the beam chamber, has been built for experimental purposes. The 3-D code MAFIA has been used to simulate the frequency-domain behaviors of EM fields in this setup. The results are summarized in this note and are compared with that previously obtained from 2-D simulations and that from network analyzer measurements. They are in general agreement. A parallel analysis in the time-domain is reported in a separate note. The method of our simulations can be briefly described as follows. The 1-inch diameter beampipes are terminated by conducting walls at a length of 2 cm. The whole geometry can thus be considered as a cavity. The lowest RF modes of this geometry are computed using MAFIA. The eigenfrequencies of these modes are a direct output of the eigenvalue solver E3, whereas the type of each mode is determined by employing the postprocessor P3. The mesh sizes are chosen such that they are small enough for computations in the frequency region in which we are interested (the sampling theorem), while the total number of mesh points is still well within the range that our computer system can cope with. digital.library.unt.edu/ark:/67531/metadc625418/
3-D electromagnetic modeling of wakefields in accelerator components
We discuss the use of 3-D finite-difference time-domain (FDTD) electromagnetic codes for modeling accelerator components. Computational modeling of cylindrically symmetric structures such as induction accelerator cells has been very successful in predicting the wake potential and wake impedances of these structures, but full 3-D modeling of complex structures has been limited due to substantial computer resources required for a full 3-D model. New massively parallel 3-D time domain electromagnetic codes now under development using conforming unstructured meshes allow a substantial increase in the geometric fidelity of the structures being modeled. Development of these new codes are discussed in context of applicability to accelerator problems. Various 3-D structures are tested with an existing cubical cell FDTD code and wake impedances compared with simple analytic models for the structures; results will be used as benchmarks for testing the new time time domain codes. Structures under consideration include a stripline beam position monitor as well as circular and elliptical apertures in circular waveguides. Excellent agreement for monopole and dipole impedances with models were found for these structures below the cutoff frequency of the beam line. digital.library.unt.edu/ark:/67531/metadc685010/
3-D field computation: The near-triumph of commerical codes
In recent years, more and more of those who design and analyze magnets and other devices are using commercial codes rather than developing their own. This paper considers the commercial codes and the features available with them. Other recent trends with 3-D field computation include parallel computation and visualization methods such as virtual reality systems. digital.library.unt.edu/ark:/67531/metadc794259/
3-D Finite Element Analyses of the Egan Cavern Field
Three-dimensional finite element analyses were performed for the two gas-filled storage caverns at the Egan field, Jennings dome, Louisiana. The effects of cavern enlargement on surface subsidence, storage loss, and cavern stability were investigated. The finite element model simulated the leaching of caverns to 6 and 8 billion cubic feet (BCF) and examined their performance at various operating conditions. Operating pressures varied from 0.15 psi/ft to 0.9 psi/ft at the bottom of the lowest cemented casing. The analysis also examined the stability of the web or pillar of salt between the caverns under differential pressure loadings. The 50-year simulations were performed using JAC3D, a three dimensional finite element analysis code for nonlinear quasistatic solids. A damage criterion based on onset of dilatancy was used to evaluate cavern instability. Dilation results from the development of microfractures in salt and, hence, potential increases in permeability onset occurs well before large scale failure. The analyses predicted stable caverns throughout the 50-year period for the range of pressures investigated. Some localized salt damage was predicted near the bottom walls of the caverns if the caverns are operated at minimum pressure for long periods of time. Volumetric cavern closures over time due to creep were moderate to excessive depending on the salt creep properties and operating pressures. However, subsidence above the cavern field was small and should pose no problem, to surface facilities. digital.library.unt.edu/ark:/67531/metadc686870/
3-d finite element model development for biomechanics: a software demonstration
Finite element analysis is becoming an increasingly important part of biomechanics and orthopedic research, as computational resources become more powerful, and data handling algorithms become more sophisticated. Until recently, tools with sufficient power did not exist or were not accessible to adequately model complicated, three-dimensional, nonlinear biomechanical systems. In the past, finite element analyses in biomechanics have often been limited to two-dimensional approaches, linear analyses, or simulations of single tissue types. Today, we have the resources to model fully three-dimensional, nonlinear, multi-tissue, and even multi-joint systems. The authors will present the process of developing these kinds of finite element models, using human hand and knee examples, and will demonstrate their software tools. digital.library.unt.edu/ark:/67531/metadc697585/
A 3-D hydrodynamic dispersion model for modeling tracer transport in Geothermal Reservoirs
A 3-D hydrodynamic dispersion model for tracer transport is developed and implemented into the TOUGH2 EOS3 (T2R3D) module. The model formulation incorporates a full dispersion tensor, based on a 3-D velocity field with a 3-D, irregular grid in a heterogeneous geological system. Two different weighting schemes are proposed for spatial average of 3-D velocity fields and concentration gradients to evaluate the mass flux by dispersion and diffusion of a tracer or a radionuclide. This new module of the TOUGH2 code is designed to simulate processes of tracer/radionuclide transport using an irregular, 3-D integral finite difference grid in non-isothermal, three-dimensional, multiphase, porous/fractured subsurface systems. The numerical method for this transport module is based on the integral finite difference scheme, as in the TOUGH2 code. The major assumptions of the tracer transport module are: (a) a tracer or a radionuclide is present and transported only within the liquid phase, (b) transport mechanisms include molecular diffusion and hydrodynamic dispersion in the liquid phase in addition to advection, and (c) first order decay and linear adsorption on rock grains are taken into account. The tracer or radionuclide is introduced as an additional mass component into the standard TOUGH2 formulation, time is discretized fully implicitly, and non-linearities of the conservation equations are handled using the Newton/Raphson iteration. We have verified this transport module by comparison with results of a 2-D transport problem for which an analytical solution is available. In addition, a field application is described to demonstrate the use of the proposed model. digital.library.unt.edu/ark:/67531/metadc719687/
3-D Measurement of Deformation Microstructure of Al(0.2%)Mg Using Submicron Resolution White X-Ray Microbeams
We have used submicron-resolution white x-ray microbeams on the MHATT-CAT beamline 7-ID at the Advanced Photon Source to develop techniques for three-dimensional investigation of the deformation microstructure in a 20% plane strain compressed Al(0.2%)Mg tri-crystal. Kirkpatrick-Baez mirrors were used to focus white radiation from an undulator to a 0.7 x 0.7 {micro}m{sup 2} beam that was scanned over bi- and tri-crystal regions near the triple-junction of the tri-crystal. Depth resolution along the x-ray microbeam of less than 5 microns was achieved by triangulation to the diffractibn source point using images taken at a series of CCD distances from the microbeam. Computer indexing of the deformation cell structure in the bi-crystal region provided orientations of individual subgrains to {approximately}0.01 degrees, making possible detailed measurements of the rotation axes between individual cells. digital.library.unt.edu/ark:/67531/metadc707283/
A 3-d modular gripper design tool
Modular fixturing kits are precisely machined sets of components used for flexible, short-turnaround construction of fixtures for a variety of manufacturing purposes. A modular vise is a parallel-jaw vise, where each jaw is a modular fixture plate with a regular grid of precisely positioned holes. A modular vise can be used to locate and hold parts for machining, assembly, and inspection tasks. To fixture a part, one places pins in some of the holes so that when the vise is closed, the part is reliably located and completely constrained. The modular vise concept can be adapted easily to the design of modular parallel-jaw grippers for robots. By attaching a grid plate to each jaw of a parallel-jaw gripper, the authors gain the ability to easily construct high-quality grasps for a wide variety of parts from a standard set of hardware. Wallack and Canny developed a previous algorithm for planning planar grasp configurations for the modular vise. In this paper, the authors expand this work to produce a 3-d fixture/gripper design tool. They describe several analyses added to the planar algorithm to improve its utility, including a three-dimensional grasp quality metric based on geometric and force information, three-dimensional geometric loading analysis, and inter-gripper interference analysis to determine the compatibility of multiple grasps for handing the part from one gripper to another. Finally, the authors describe two applications which combine the utility of modular vise-style grasping with inter-gripper interference: The first is the design of a flexible part-handling subsystem for a part cleaning workcell under development at Sandia National Laboratories; the second is the automatic design of grippers that support the assembly of multiple products on a single assembly line. digital.library.unt.edu/ark:/67531/metadc675560/
A 3-d modular gripper design tool
Modular fixturing kits are sets of components used for flexible, rapid construction of fixtures. A modular vise is a parallel-jaw vise, each jaw of which is a modular fixture plate with a regular grid of precisely positioned holes. To fixture a part, one places pins in some of the holes so that when the vise is closed, the part is reliably located and completely constrained. The modular vise concept can be adapted easily to the design of modular parallel-jaw grippers for robots. By attaching a grid-plate to each jaw of a parallel-jaw gripper, one gains the ability to easily construct high-quality grasps for a wide variety of parts from a standard set of hardware. Wallack and Canny developed an algorithm for planning planar grasp configurations for the modular vise. In this paper, the authors expand this work to produce a 3-d fixture/gripper design tool. They describe several analyses they have added to the planar algorithm, including a 3-d grasp quality metric based on force information, 3-d geometric loading analysis, and inter-gripper interference analysis. Finally, the authors describe two applications of their code. One of these is an internal application at Sandia, while the other shows a potential use of the code for designing part of an agile assembly line. digital.library.unt.edu/ark:/67531/metadc674520/
A 3-D numerical study of pinhole diffraction to predict the accuracy of EUV point diffraction interferometry
A 3-D electromagnetic field simulation is used to model the propagation of extreme ultraviolet (EUV), 13-nm, light through sub-1500 {Angstrom} dia pinholes in a highly absorptive medium. Deviations of the diffracted wavefront phase from an ideal sphere are studied within 0.1 numerical aperture, to predict the accuracy of EUV point diffraction interferometersused in at-wavelength testing of nearly diffraction-limited EUV optical systems. Aberration magnitudes are studied for various 3-D pinhole models, including cylindrical and conical pinhole bores. digital.library.unt.edu/ark:/67531/metadc687713/
3-D Ray-tracing and 2-D Fokker-Planck Simulations of Radiofrequency Application to Tokamak Plasmas
A state of the art numerical tool has been developed to simulate the propagation and the absorption of coexisting different types of waves in a tokamak geometry. The code includes a numerical solution of the three-dimensional (R, Z, {Phi}) toroidal wave equation for the electric field of the different waves in the WKBJ approximation. At each step of integration, the two-dimensional (v{sub {parallel}}, v{sub {perpendicular}}) Fokker-Planck equation is solved in the presence of quasilinear diffusion coefficients. The electron Landau damping of the waves is modeled taking into account the interaction of the wave electric fields with the quasilinearly modified distribution function. Consistently, the code calculates the radial profiles of non-inductively generated current densities, the transmitted power traces and the total power damping curves. Synergistic effects among the different type of waves (e.g., lower hybrid and ion Bernstein waves) are studied through the separation of the contributions of the single wave from the effects due to their coexistence. digital.library.unt.edu/ark:/67531/metadc703436/
3-D Silicon Photonic Lattices- Cornerstone of an Emerging Photonics Revolution
Three-dimensional photonic lattices are engineered materials which are the photonic analogues of semiconductors. These structures were first proposed and demonstrated in the mid-to-late 1980's. However, due to fabrication difficulties, lattices active in the infrared are only just emerging. Wide ranges of structures and fabrication approaches have been investigated. The most promising approach for many potential applications is a diamond-like structure fabricated using silicon microprocessing techniques. This approach has enabled the fabrication of 3-D silicon photonic lattices active in the infrared. The structures display band gaps centered from 12{micro} down to 1.55{micro}. digital.library.unt.edu/ark:/67531/metadc793231/
3-D Spectral Induced Polarization (IP) Imaging: Non-Invasive Characterization Of Contaminant Plumes
The overall objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earth's subsurface using field measurements of induced polarization (IP) effects. Three specific objectives towards this end are 1. 2. 3. Understanding IP at the laboratory level through measurements of complex resistivity as a function of frequency in rock and soil samples with varying pore geometries, pore fluid conductivities and saturations, and contaminant chemistries and concentrations. Developing effective data acquisition techniques for measuring the critical IP responses (time domain or frequency domain) in the field. Developing modeling and inversion algorithms that permit the interpretation of field IP data in terms of subsurface geology and contaminant plume properties. digital.library.unt.edu/ark:/67531/metadc785886/
3-D Spectral IP Imaging: Non-Invasive Characterization of Contaminant Plumes
The overall objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earth's subsurface using field measurements of induced polarization (IP) effects. Three specific objectives towards this end are: (1) Understanding IP at the laboratory level through measurements of complex resistivity as a function of frequency in rock and soil samples with varying pore geometries, pore fluid conductivities and saturations, and contaminant chemistries and concentrations. (2) Developing effective data acquisition techniques for measuring the critical IP responses (time domain or frequency domain) in the field. (3) Developing modeling and inversion algorithms that permit the interpretation of field IP data in terms of subsurface geology and contaminant plume properties. digital.library.unt.edu/ark:/67531/metadc782451/
3-D spectral IP imaging: Non-invasive characterization of contaminant plumes. 1998 annual progress report
'The overall objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earth''s subsurface using field measurements of induced polarization (IP) effects. Three specific objectives towards this end are: (1) understanding IP at the laboratory level through measurements of complex resistivity as a function of frequency in rock and soil samples with varying pore geometries, pore fluid conductivities and saturations, and contaminant chemistries and concentrations; (2) developing effective data acquisition techniques for measuring the critical IP responses (time domain or frequency domain) in the field; (3) developing modeling and inversion algorithms that permit the interpretation of field IP data in terms of subsurface geology and contaminant plume properties. The authors laboratory experiments to date are described in Appendices A and B, which consist of two papers submitted to the annual SAGEEP conference (Frye et al., 1998; Sturrock et al., 1998). The experiments involved measurements of complex resistivity vs. frequency on a suite of brine saturated sandstone samples. In one set of experiments, the fluid chemistry (pH, ionic strength, and cation type) was varied. In a second set of experiments, the microgeometry of the rock matrix was varied. The experiments showed that spectral IP responses are sensitive to subtle variations in both the solution chemistry and rock microgeometry. The results demonstrate that spectral IP responses have the potential of being sensitive indicators of in-situ chemistry and microgeometry, the latter of which may be related to the hydraulic properties. Data Acquisition The authors have been looking in some detail at the effects of electromagnetic coupling and how to practically deal with it. In this area, the results to date are summarized in Vandiver (1998). The progress in the development of modeling and inversion algorithms for IP is described in Appendix C, a paper submitted to the annual SAGEEP conference (Shi et al., 1998). The authors have developed algorithms for forward modeling and inversion of spectral IP data in 3-D media. The algorithms accommodate a general earth model with a complex electrical conductivity as a function of frequency and 3-D spatial position. Using regularization and optimization techniques, the inversion algorithm obtains a 3-D image of resistivity amplitude and phase for each frequency contained in the data set. They have begun testing their algorithms on synthetic data generated from a simple model of a contaminant plume. The complex resistivity parameters of the background medium and plume are based on the laboratory results described above.' digital.library.unt.edu/ark:/67531/metadc625746/
3-D spectral IP imaging: Non-invasive characterization of contaminant plumes. Annual progress report, September 15, 1996--September 14, 1997
'The objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earth''s subsurface using field measurements of induced polarization (IP) effects. The first-year accomplishments are (1) laboratory experiments on fluid-saturated sandstones quantifying the dependence of spectral IP responses on solution chemistry and rock micro-geometry; (2) library research on the current understanding of electromagnetic coupling effects on IP data acquired in the field: and (3) development of prototype forward modeling and inversion algorithms for interpreting IP data in terms of 3-D models of complex resistivity.' digital.library.unt.edu/ark:/67531/metadc620009/
3-D Target Location from Stereoscopic SAR Images
SAR range-Doppler images are inherently 2-dimensional. Targets with a height offset lay over onto offset range and azimuth locations. Just which image locations are laid upon depends on the imaging geometry, including depression angle, squint angle, and target bearing. This is the well known layover phenomenon. Images formed with different aperture geometries will exhibit different layover characteristics. These differences can be exploited to ascertain target height information, in a stereoscopic manner. Depending on the imaging geometries, height accuracy can be on the order of horizontal position accuracies, thereby rivaling the best IFSAR capabilities in fine resolution SAR images. All that is required for this to work are two distinct passes with suitably different geometries from any plain old SAR. digital.library.unt.edu/ark:/67531/metadc619742/
3-D vertical seismic profiling at LLNL Site 300
The initial goal of the 3-D Vertical Seismic Profiling (VSP) work at LLNL was to characterize seismic wave velocities and frequencies below the vadose zone to design the acquisition geometry for a 3-D shallow surface seismic reflection survey. VSPs are also used routinely to provide a link between surface seismic data and well logs. However, a test 2-D seismic line recorded at LLNL in the Spring of 1994 indicated that obtaining high quality reflection images below the vadose zone, yet shallower that 50 m, would require an expensive, very finely sampled survey ({lt} 1 m receiver spacing). Extensive image processing of the LLNL 2-D test line indicated that the only reliable reflection was from the top of the water table. Surprisingly, these results were very different than recent 3-D seismic work recorded at other sites, where high quality, high frequency surface (up to 300 Hz) reflection images were obtained as shallow as 20m. We believe that the differences are primarily due to the comparatively deep vadose zone at LLNL (15 to 30m) as compared to 0-5m at other sites. The thick vadose zone attenuates the reflection signals, particularly at the high frequencies (above 100 @). In addition, the vadose zone at LLNL creates a seismogram in which surface-propagating noise overlaps with the reflection signals for reflections above 50 m. By contrast, when the vadose zone is not thick, high frequencies can propagate and noise will not overlap with reflections as severely. Based on the results from the 2-D seismic line and the encouraging results from a VSP run concurrent with the 2-D seismic experiment, we modified the objectives of the research and expanded the scope of the VSP imaging at LLNL. We conducted two 3-D multi-offset VSP experiments at LLNL in the Summer and Fall of 1994. These VSP experiments were designed to characterize the seismic propagation characteristics at two different locations on the LLNL site: the first was a well with a relatively shallow water table (10m), while the second was a well with a relatively deep water table (about 25m). Other goals of the VSP experiments were to characterize the velocity structure in the vicinity of boreholes, and to attempt to image reflections away from the boreholes. We found that the usable frequency content appeared to vary with water table level. digital.library.unt.edu/ark:/67531/metadc693116/
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