High field superconducting magnets (12 T and greater) for fusion applications (open access)

High field superconducting magnets (12 T and greater) for fusion applications

The technology for producing high fields in large superconducting magnets has increased greatly in recent years, but must increase still more in the future. In this paper, we examine the present state of the art vis-a-vis the needs of a next-generation fusion machine and outline a program to provide for those needs. We also highlight recent developments that suggest the program goals are within reach.
Date: July 9, 1986
Creator: Miller, J. R.; Summers, L. T. & Kerns, J. A.
Object Type: Article
System: The UNT Digital Library
IDENTIFYING ISOTROPIC EVENTS USING AN IMPROVED REGIONAL MOMENT TENSOR INVERSION TECHNIQUE (open access)

IDENTIFYING ISOTROPIC EVENTS USING AN IMPROVED REGIONAL MOMENT TENSOR INVERSION TECHNIQUE

None
Date: July 9, 2007
Creator: Ford, S R; Dreger, D S & Walter, W R
Object Type: Article
System: The UNT Digital Library
Behavior of Repeating Earthquake Sequences in Central California and the Implications for Subsurface Fault Creep (open access)

Behavior of Repeating Earthquake Sequences in Central California and the Implications for Subsurface Fault Creep

Repeating earthquakes (REs) are sequences of events that have nearly identical waveforms and are interpreted to represent fault asperities driven to failure by loading from aseismic creep on the surrounding fault surface at depth. We investigate the occurrence of these REs along faults in central California to determine which faults exhibit creep and the spatio-temporal distribution of this creep. At the juncture of the San Andreas and southern Calaveras-Paicines faults, both faults as well as a smaller secondary fault, the Quien Sabe fault, are observed to produce REs over the observation period of March 1984-May 2005. REs in this area reflect a heterogeneous creep distribution along the fault plane with significant variations in time. Cumulative slip over the observation period at individual sequence locations is determined to range from 5.5-58.2 cm on the San Andreas fault, 4.8-14.1 cm on the southern Calaveras-Paicines fault, and 4.9-24.8 cm on the Quien Sabe fault. Creep at depth appears to mimic the behaviors seen of creep on the surface in that evidence of steady slip, triggered slip, and episodic slip phenomena are also observed in the RE sequences. For comparison, we investigate the occurrence of REs west of the San Andreas fault within the …
Date: July 9, 2007
Creator: Templeton, D C; Nadeau, R & Burgmann, R
Object Type: Article
System: The UNT Digital Library
Microhole Drilling Tractor Technology Development (open access)

Microhole Drilling Tractor Technology Development

In an effort to increase the U.S. energy reserves and lower costs for finding and retrieving oil, the USDOE created a solicitation to encourage industry to focus on means to operate in small diameter well-Microhole. Partially in response to this solicitation and because Western Well Tool's (WWT) corporate objective to develop small diameter coiled tubing drilling tractor, WWT responded to and was awarded a contract to design, prototype, shop test, and field demonstrate a Microhole Drilling Tractor (MDT). The benefit to the oil industry and the US consumer from the project is that with the MDT's ability to facilitate Coiled Tubing drilled wells to be 1000-3000 feet longer horizontally, US brown fields can be more efficiently exploited resulting in fewer wells, less environmental impact, greater and faster oil recovery, and lower drilling costs. Shortly after award of the contract, WWT was approached by a major oil company that strongly indicated that the specified size of a tractor of 3.0 inches diameter was inappropriate and that immediate applications for a 3.38-inch diameter tractor would substantially increase the usefulness of the tool to the oil industry. Based on this along with an understanding with the oil company to use the tractor in …
Date: July 9, 2007
Creator: Tool, Western Well
Object Type: Report
System: The UNT Digital Library
Azimuthal HBT and Transverse Momentum Fluctuations from CERES. (open access)

Azimuthal HBT and Transverse Momentum Fluctuations from CERES.

CERES is a dilepton experiment at the CERN SPS, known for its observation of enhanced production of low mass efe- pairs in collisions between heavy nuclei [1]. The upgrade of CERES in 1997-1998 by a radial Time Projection Chamber (TPC) [2] allowed to improve the momentum resolution and the particle identification capability while retaining the cylindrical symmetry. The upgraded experiment is shown in Fig. 1. The upgrade also extended the sensitivity of CERES to hadrons and made possible results like those described below. The measurement of central Pb+Au collisions at the maximum SPS energy of 158 GeV per nucleon in the fall of 2000 was the first run of the fully upgraded CERES and at the same time the last run of this experiment. About 30 million Pb+Au collision events at 158 GeV per nucleon were collected, most of them with centrality within the top 7% of the geometrical cross section {sigma}{sub G} = 6.94 b. Small samples of the 20% and the minimum bias collisions, as well as a short run at 80 AGeV, were recorded in addition. The dilepton mass spectra from this experiment were published in [3]. In this talk I present two particular results of hadron …
Date: July 9, 2007
Creator: Miskowiec,D.; Rehak, P. & al., et
Object Type: Article
System: The UNT Digital Library
Recent Lattice Results on Finite Temperature and Density QCD, Part II (open access)

Recent Lattice Results on Finite Temperature and Density QCD, Part II

We discuss recent progress in studies of QCD thermodynamics with almost physical light quark masses and a physical value of the strange quark mass. We summarize results on the transition temperature in QCD and analyze the relation between deconfinement and chiral symmetry restoration.
Date: July 9, 2007
Creator: Karsch, F.
Object Type: Article
System: The UNT Digital Library
Personal Radiation Detector Field Test and Evaluation Campaign (open access)

Personal Radiation Detector Field Test and Evaluation Campaign

Following the success of the Anole test of portable detection system, the U.S. Department of Homeland Security (DHS) Domestic Nuclear Detection Office organized a test and evaluation campaign for personal radiation detectors (PRDs), also known as 'Pagers'. This test, 'Bobcat', was conducted from July 17 to August 8, 2006, at the Nevada Test Site. The Bobcat test was designed to evaluate the performance of PRDs under various operational scenarios, such as pedestrian surveying, mobile surveying, cargo container screening, and pedestrian chokepoint monitoring. Under these testing scenarios, many operational characteristics of the PRDs, such as gamma and neutron sensitivities, positive detection and false alarm rates, response delay times, minimum detectable activities, and source localization errors, were analyzed. This paper will present the design, execution, and methodologies used to test this equipment for the DHS.
Date: July 9, 2007
Creator: Chris A. Hodge, Ding Yuan, Raymond P. Keegan, Michael A. Krstich
Object Type: Article
System: The UNT Digital Library
TOF Electron Energy Analyzer for Spin and Angular Resolved Photoemission Spectroscopy (open access)

TOF Electron Energy Analyzer for Spin and Angular Resolved Photoemission Spectroscopy

Current pulsed laser and synchrotron x-ray sources provide new opportunities for Time-Of- Flight (TOF) based photoemission spectroscopy to increase photoelectron energy resolution and efficiency compared to current standard techniques. The principals of photoelectron timing front formation, temporal aberration minimization, and optimization of electron beam transmission are presented. We have developed these concepts into a high resolution Electron Optical Scheme (EOS) of a TOF Electron Energy Analyzer (TOF-EEA) for photoemission spectroscopy. The EOS of the analyzer includes an electrostatic objective lens, three columns of transport lenses and a 90 degree energy band pass filter (BPF). The analyzer has two modes of operation: Spectrometer Mode (SM) with straight passage of electrons through the EOS undeflected by the BPF, allowing the entire spectrum to be measured, and Monochromator Mode (MM) in which the BPF defines a certain energy window inside the scope of the electron energy spectrum.
Date: July 9, 2008
Creator: Lebedev, Gennadi; Jozwiak, Chris; Andresen, Nord; Lanzara, Alessandra & Hussain, Zahid
Object Type: Article
System: The UNT Digital Library
6th International Special Session on Current Trends in Numerical Simulation for Parallel Engineering Environments (open access)

6th International Special Session on Current Trends in Numerical Simulation for Parallel Engineering Environments

In today's world, the use of parallel programming and architectures is essential for simulating practical problems in engineering and related disciplines. Remarkable progress in CPU architecture (multi- and many-core, SMT, transactional memory, virtualization support, etc.), system scalability, and interconnect technology continues to provide new opportunities, as well as new challenges for both system architects and software developers. These trends are paralleled by progress in parallel algorithms, simulation techniques, and software integration from multiple disciplines. In its 6th year ParSim continues to build a bridge between computer science and the application disciplines and to help with fostering cooperations between the different fields. In contrast to traditional conferences, emphasis is put on the presentation of up-to-date results with a shorter turn-around time. This offers the unique opportunity to present new aspects in this dynamic field and discuss them with a wide, interdisciplinary audience. The EuroPVM/MPI conference series, as one of the prime events in parallel computation, serves as an ideal surrounding for ParSim. This combination enables the participants to present and discuss their work within the scope of both the session and the host conference. This year, ten papers with authors in ten countries were submitted to ParSim, and after a quick …
Date: July 9, 2007
Creator: Schulz, M & Trinitis, C
Object Type: Article
System: The UNT Digital Library
CHARACTERIZATION OF DETECTOR GRADE CDZNTE MATERIAL FROM REDLEN TECHNOLOGIES (open access)

CHARACTERIZATION OF DETECTOR GRADE CDZNTE MATERIAL FROM REDLEN TECHNOLOGIES

CdZnTe (or CZT) crystals can be used in a variety of detector-type applications. This large band gap material shows great promise for use as a gamma radiation spectrometer. Historically, the performance of CZT has typically been adversely affected by point defects, structural and compositional heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity) and secondary phases (SP). The synthesis of CZT material has improved greatly with the primary performance limitation being attributed to mainly SP. In this presentation, we describe the extensive characterization of detector grade material that has been treated with post growth annealing to remove the SPs. Some of the analytical methods used in this study included polarized, cross polarized and transmission IR imaging, I-V curves measurements, synchrotron X-ray topography and electron microscopy.
Date: July 9, 2008
Creator: Duff, M
Object Type: Article
System: The UNT Digital Library
Considerations on the Use of 3-D Geophysical Models to Predict Test Ban Monitoring Observables (open access)

Considerations on the Use of 3-D Geophysical Models to Predict Test Ban Monitoring Observables

The use of 3-D geophysical models to predict nuclear test ban monitoring observables (phase travel times, amplitudes, dispersion, etc.) is widely anticipated to provide improvements in the basic seismic monitoring functions of detection, association, location, discrimination and yield estimation. A number of questions arise when contemplating a transition from 1-D, 2-D and 2.5-D models to constructing and using 3-D models, among them: (1) Can a 3-D geophysical model or a collection of 3-D models provide measurably improved predictions of seismic monitoring observables over existing 1-D models, or 2-D and 2 1/2-D models currently under development? (2) Is a single model that can predict all observables achievable, or must separate models be devised for each observable? How should joint inversion of disparate observable data be performed, if required? (3) What are the options for model representation? Are multi-resolution models essential? How does representation affect the accuracy and speed of observable predictions? (4) How should model uncertainty be estimated, represented and how should it be used? Are stochastic models desirable? (5) What data types should be used to construct the models? What quality control regime should be established? (6) How will 3-D models be used in operations? Will significant improvements in the …
Date: July 9, 2007
Creator: Harris, D. B.; Zucca, J. J.; McCallen, D. B.; Pasyanos, M. E.; Flanagan, M. P.; Myers, S. C. et al.
Object Type: Article
System: The UNT Digital Library
REGIONAL ANALYSIS OF LG ATTENUATION: COMPARISON OF 1D METHODS IN NORTHERN CALIFORNIA AND APPLICATION TO THE YELLOW SEA / KOREAN PENINSULA (open access)

REGIONAL ANALYSIS OF LG ATTENUATION: COMPARISON OF 1D METHODS IN NORTHERN CALIFORNIA AND APPLICATION TO THE YELLOW SEA / KOREAN PENINSULA

None
Date: July 9, 2007
Creator: Ford, S. R.; Dreger, D. S.; Mayeda, K.; Walter, W. R.; Malagnini, L. & Phillips, W. S.
Object Type: Article
System: The UNT Digital Library
Scratch Forensics (open access)

Scratch Forensics

Scratches on optical components which are formed during fabrication, cleaning, handling and end-use, are widespread and almost always detrimental. The impact of scratches on the end-use of the optic includes increased optical scatter, reduced system performance, and reduced strength. In the case of optics used in high intensity laser applications, prevention of scratches is paramount because they are closely associated with laser damage. Evaluation of the characteristics (dimensions, location on optic, shape, and orientation) of a scratch can serve a powerful tool to identify the cause of the scratch and lead to mitigations to prevent their reoccurrence. It is likely that opticians have used such techniques for hundreds of years. In recent years, by applying techniques of fracture mechanics and tribology, several new semi-quantitative rules-of-thumb have been developed allowing one to estimate the size and shape of the scratch inducing asperity or rogue particle, the load on the particle, the depth of the fractures in the scratch, and properties of material housing the rogue particle. The following discussion reviews some these techniques, which as a whole, we refer to as 'Scratch Forsenics'.
Date: July 9, 2008
Creator: Suratwala, T I; Miller, P E; Feit, M D & Menapace, J A
Object Type: Article
System: The UNT Digital Library
Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings (open access)

Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings

Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Iron-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. Ceramic coatings may provide even greater corrosion resistance for container applications, though the boron-containing amorphous metals are still favored for criticality control applications. These amorphous metal and ceramic materials have been produced as gas atomized powders and applied as near full density, non-porous coatings with the high-velocity oxy-fuel process. This paper summarizes the performance of these coatings as corrosion-resistant barriers, and as neutron absorbers. Relevant corrosion models are also discussed, as well as a cost model to quantify the economic benefits possible with these new materials.
Date: July 9, 2007
Creator: Blink, J; Choi, J & Farmer, J
Object Type: Article
System: The UNT Digital Library
Iron-Based Amorphous Metals:The High Performance Corrosion Resistant Materials(HPCRM) Program (open access)

Iron-Based Amorphous Metals:The High Performance Corrosion Resistant Materials(HPCRM) Program

An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature …
Date: July 9, 2007
Creator: Farmer, J
Object Type: Article
System: The UNT Digital Library
Dilepton Measurements with CERES (open access)

Dilepton Measurements with CERES

We report on dilepton measurements for central Pb on Au collisions at the top CERN SPS energy with the upgraded CERES experiment. The dilepton mass spectrum of 2000 data with improved mass resolution shows an enhancement over the expectation from hadron decays that is well described by a model including a strong broadening of the {rho} spectral function. The measured excess yield excludes the dropping mass scenario. We also report on the {phi} meson measured simultaneously both in the K{sup +}K{sup -} and in the dilepton decay channel for the first time in high energy heavy-ion collisions. An excellent agreement is found between the rapidity densities and the shape of the measured transverse momentum spectrum. The data rule out a possible enhancement of the {phi} yield in the leptonic over hadronic channel by a factor larger than 1.6 at 95% CL. CERES results are in agreement with NA49 results.
Date: July 9, 2007
Creator: Marin,A. & Rehak, P. et al.
Object Type: Article
System: The UNT Digital Library
Long-Term Corrosion Testing of Thermal Spray Coatings of Amorphous Metals: Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 and Fe48Mo14Cr15Y2C15B6 (open access)

Long-Term Corrosion Testing of Thermal Spray Coatings of Amorphous Metals: Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 and Fe48Mo14Cr15Y2C15B6

Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of SAM2X5 also made it an effective neutron absorber, and suitable for criticality control applications.
Date: July 9, 2007
Creator: Farmer, J.; Day, D.; Lian, T.; Saw, C.; Hailey, P.; Payer, J. et al.
Object Type: Article
System: The UNT Digital Library
Function-based Biosensor for Hazardous Waste Toxin Detection (open access)

Function-based Biosensor for Hazardous Waste Toxin Detection

There is a need for new types of toxicity sensors in the DOE and other agencies that are based on biological function as the toxins encountered during decontamination or waste remediation may be previously unknown or their effects subtle. Many times the contents of the environmental waste, especially the minor components, have not been fully identified and characterized. New sensors of this type could target unknown toxins that cause death as well as intermediate levels of toxicity that impair function or cause long term impairment that may eventually lead to death. The primary question posed in this grant was to create an electronically coupled neuronal cellular circuit to be used as sensor elements for a hybrid non-biological/biological toxin sensor system. A sensor based on the electrical signals transmitted between two mammalian neurons would allow the marriage of advances in solid state electronics with a functioning biological system to develop a new type of biosensor. Sensors of this type would be a unique addition to the field of sensor technology but would also be complementary to existing sensor technology that depends on knowledge of what is to be detected beforehand. We integrated physics, electronics, surface chemistry, biotechnology, and fundamental neuroscience in …
Date: July 9, 2008
Creator: Hickman, James J
Object Type: Report
System: The UNT Digital Library
Last-In First-Elected Last-Out (LIFELO) Scheme for Real-Time Sequential Analysis of Continuous Spatial Survey (open access)

Last-In First-Elected Last-Out (LIFELO) Scheme for Real-Time Sequential Analysis of Continuous Spatial Survey

Conventionally, sequential analysis of time-dependent observation data follows a simple First-in/ First-out (FIFO) scheme. Under a FIFO scheme, the oldest data point in the system is first chosen for subsequent analysis, such as for computing population mean and sequential probability ratio test (SPRT). Once the analysis is completed or the decision is made, the oldest data point is dropped out of the system and a new sample is drawn. The intrinsic disadvantage of a FIFO scheme is its delayed response. At the time a new sample is drawn, the analysis either cannot tell immediately about the sample, or makes an incorrect statement about the sample. In our research, we adopted a Last-In/ First-Elected/ Last-Out (LIFELO) scheme for realtime sequential analysis of continuous spatial survey data. In this scheme, the most recent data point from a given spatial location in the sequence is first selected for starting the subsequent analysis. If needed, the next youngest data point is chosen to join the analysis. This process is continued until a conclusion is made about the most recent location or data point. LIFELO scheme offers a reduced response time and spatial errors for decision-making for time-and-spatial critical environmental contamination surveys. In terms of …
Date: July 9, 2007
Creator: Kernan, Ding Yuan and Warnick
Object Type: Article
System: The UNT Digital Library
Work Plan: Targeted Investigation to Assess Current Conditions Associated With the Carbon Tetrachloride Plume Downgradient From the Former CCC/Usda Facility at Milford, Nebraska. (open access)

Work Plan: Targeted Investigation to Assess Current Conditions Associated With the Carbon Tetrachloride Plume Downgradient From the Former CCC/Usda Facility at Milford, Nebraska.

The Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA) formerly operated a grain storage facility at Milford, Nebraska. In May 2008, the CCC/USDA directed the Environmental Science Division of Argonne National Laboratory, as its technical consultant, to develop a work plan for a targeted investigation at the Milford site. The purpose of the targeted investigation is to assess the current extent and configuration of the carbon tetrachloride plume downgradient from the former CCC/USDA facility and proximal to the banks of the Big Blue River, which borders the area of concern to the east, southeast, and northeast. In 1995, carbon tetrachloride contamination was detected by the Nebraska Department of Health and Human Services in a private drinking water well and a livestock well 1.25 mi south of Milford (Figure 1.1). The Trojan drinking water well is located directly downgradient (approximately 300 ft east) of the former CCC/USDA facility. Low levels of carbon tetrachloride contamination were also found in the Troyer livestock well, approximately 1,200 ft north of the former CCC/USDA facility.
Date: July 9, 2008
Creator: LaFreniere, L. M.
Object Type: Report
System: The UNT Digital Library
Recent Lattice Results on Finite Temperature and Density QCD, Part 1 (open access)

Recent Lattice Results on Finite Temperature and Density QCD, Part 1

We discuss recent progress made studies of bulk thermodynamics of strongly interacting matter through lattice simulations of QCD with an almost physical light and strange quark mass spectrum. We present results on the QCD equation of state at vanishing and non-vanishing quark chemical potential and show first results on baryon number and strangeness fluctuations, which might be measured in event-by-event fluctuations in low energy runs at RHIC as well as at FAIR.
Date: July 9, 2007
Creator: Karsch, F.
Object Type: Article
System: The UNT Digital Library
Modular Sampling and Analysis Techniques for the Real-Time Analysis of Human Breath (open access)

Modular Sampling and Analysis Techniques for the Real-Time Analysis of Human Breath

At LLNL and UC Davis, we are developing several techniques for the real-time sampling and analysis of trace gases, aerosols and exhaled breath that could be useful for a modular, integrated system for breath analysis. Those techniques include single-particle bioaerosol mass spectrometry (BAMS) for the analysis of exhaled aerosol particles or droplets as well as breath samplers integrated with gas chromatography mass spectrometry (GC-MS) or MEMS-based differential mobility spectrometry (DMS). We describe these techniques and present recent data obtained from human breath or breath condensate, in particular, addressing the question of how environmental exposure influences the composition of breath.
Date: July 9, 2007
Creator: Frank, M.; Farquar, G.; Adams, K.; Bogan, M.; Martin, A.; Benner, H. et al.
Object Type: Article
System: The UNT Digital Library
Benefits of microscopy with super resolution (open access)

Benefits of microscopy with super resolution

Transmission Electron Microscopy developed from an imagingtool into a quantitative electron beam characterization tool that locallyaccesses structure, chemistry, and bonding in materials with sub Angstromresolution. Experiments utilize coherently and incoherently scatteredelectrons. In this contribution, the interface between gallium nitrideand sapphire as well as thin silicon gate oxides are studied tounderstand underlying physical processes and the strength of thedifferent microscopy techniques. An investigation of the GaN/sapphireinterface benefits largely from the application of phase contrastmicroscopy that makes it possible to visualize dislocation corestructures and single columns of oxygen and nitrogen at a closest spacingof 85 pm. In contrast, it is adequate to investigate Si/SiOxNy/poly-Siinterfaces with incoherently scattered electrons and electronspectroscopy because amorphous and poly crystalline materials areinvolved. Here, it is demonstrated that the SiOxNy/poly-Si interface isrougher than the Si/SiOx interface, that desirable nitrogen diffusiongradients can be introduced into the gate oxide, and that a nitridationcoupled with annealing increases its physical width while reducing theequivalent electrical oxide thickness to values approaching 1.2 nm.Therefore, an amorphous SiNxOy gate dielectric seems to be a suitablesubstitute for traditional gate oxides to further increase device speedby reducing dimensions in Si technology.
Date: July 9, 2001
Creator: Kisielowski, C.; Principe, E.; Freitag, B. & Hubert, D.
Object Type: Article
System: The UNT Digital Library
Evaluation of selected chemical processes for production of low-cost silocon. (Phases I and II. ) Final report, October 9, 1975--July 9, 1978. Silicon Material Task, Low-Cost Solar Array Project (open access)

Evaluation of selected chemical processes for production of low-cost silocon. (Phases I and II. ) Final report, October 9, 1975--July 9, 1978. Silicon Material Task, Low-Cost Solar Array Project

The zinc reduction of silicon tetrachloride in a fluidized bed of seed particles to yield a granular product was studied along with several modifications of the thermal decomposition or hydrogen reduction of silicon tetraiodide. Although all contenders were believed to be capable of meeting the quality requirements of the LSA Project, it was concluded that only the zinc reduction of the chloride could be made economically feasible at a cost below $10/kg silicon (1975 dollars). Accordingly, subsequent effort was limited to evaluating that process. A miniplant, consisting of a 5-cm-diameter fluidized-bed reactor and associated equipment was used to study the deposition parameters, temperature, reactant composition, seed particle size, bed depth, reactant throughput, and methods of reactant introduction. It was confirmed that the permissible range of fluidized-bed temperature was limited at the lower end by zinc condensation (918 C) and at higher temperatures by rapidly decreasing conversion efficiency (by 0.1 percent per degree C from 72 percent (thermodynamic) at 927 for a stoichiometric mixture). Use of a graded bed temperature was shown to increase the conversion efficiency over that obtained in an isothermal bed. Other aspects of the process such as the condensation and fused-salt electrolysis of the ZnCl/sub 2/ by-product …
Date: July 9, 1978
Creator: Blocher, J.M. Jr. & Browning, M.F.
Object Type: Report
System: The UNT Digital Library