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Systematics of Fission-Product Yields
None
Date:
May 5, 2002
Creator:
A.C.Wahl
Object Type:
Report
System:
The UNT Digital Library
Microstructure, Phase Formation, and Stress of Reactively-Deposited Metal Hydride Thin Films
This document summarizes research of reactively deposited metal hydride thin films and their properties. Reactive deposition processes are of interest, because desired stoichiometric phases are created in a one-step process. In general, this allows for better control of film stress compared with two-step processes that react hydrogen with pre-deposited metal films. Films grown by reactive methods potentially have improved mechanical integrity, performance and aging characteristics. The two reactive deposition techniques described in this report are reactive sputter deposition and reactive deposition involving electron-beam evaporation. Erbium hydride thin films are the main focus of this work. ErH{sub x} films are grown by ion beam sputtering erbium in the presence of hydrogen. Substrates include a Al{sub 2}O{sub 3} {l_brace}0001{r_brace}, a Al{sub 2}O{sub 3} {l_brace}1120{r_brace}, Si{l_brace}001{r_brace} having a native oxide, and polycrystalline molybdenum substrates. Scandium dideuteride films are also studied. ScD{sub x} is grown by evaporating scandium in the presence of molecular deuterium. Substrates used for scandium deuteride growth include single crystal sapphire and molybdenum-alumina cermet. Ultra-high vacuum methods are employed in all experiments to ensure the growth of high purity films, because both erbium and scandium have a strong affinity for oxygen. Film microstructure, phase, composition and stress are evaluated using a …
Date:
May 1, 2002
Creator:
ADAMS, DAVID P.; ROMERO, JUAN A.; RODRIGUEZ, MARK A.; FLORO, JERROLD A. & KOTULA, PAUL G.
Object Type:
Report
System:
The UNT Digital Library
ALARA Analysis of Radiological Control Criteria Associated with Alternatives for Disposal of Hazardous Wastes
This ALARA analysis of Radiological Control Criteria (RCC) considers alternatives to continued storage of certain DOE mixed wastes. It also considers the option of treating hazardous wastes generated by DOE facilities, which have a very low concentration of radionuclide contaminants, as purely hazardous waste. Alternative allowable contaminant levels examined correspond to doses to an individual ranging from 0.01 mrem/yr to 10 to 20 mrem/yr. Generic waste inventory data and radionuclide source terms are used in the assessment. Economic issues, potential health and safety issues, and qualitative factors relating to the use of RCCs are considered.
Date:
May 15, 2002
Creator:
Aaberg, Rosanne L.; Bilyard, Gordon R.; Branch, Kristi M.; Lavender, Jay C. & Miller, Peter L.
Object Type:
Report
System:
The UNT Digital Library
Deep Level Transient Spectroscopy and Capacitance-Voltage Measurements of Cu(In,Ga)Se2: Preprint
This conference paper describes the electronic properties of ZnO/CdS/Cu(In,Ga)Se2 (CIGS)/Mo/SLG polycrystalline thin-film solar cells with compositions ranging from Cu-rich to In-rich were investigated by deep level transient spectroscopy and capacitance-voltage (C-V) measurements. This compositional change represents the evolution of the film during growth by the three-stage process. Four thin-film CIGS samples with different Cu content were obtained. The Cu/(In+Ga) ratio ranges from 1.24 (Cu-rich)to 0.88 (In-rich), whereas the Ga/(In+Ga) ratio ranges from 0.19 (Cu-rich)to 0.28 (In-rich).The Cu-rich sample exhibits a shallow majority-carrier trap with an activation energy of 0.12 eV and another deeper trap with an activation energy of 0.28 eV, whereas the In-rich sample has a shallow minority-carrier trap with an activation energy of 0.12 eV. The two samples show evidence of a deeper trap at higher temperature. C-V measurements showed that the average carrier concentration (N values) around the junction of the cell changed as the film transitions from Cu-rich to In-rich. DLTS shows that acceptor-like traps are dominant in samples where CIGS grains did not go through the Cu-rich to In(Ga)-rich transition. While donor-like traps are dominant in the In(Ga)-rich samples.
Date:
May 1, 2002
Creator:
AbuShama, J.; Johnston, S.; Ahrenkiel, R. & Noufi, R.
Object Type:
Article
System:
The UNT Digital Library
Longevity of duct tape in residential air distribution systems: 1-D, 2-D, and 3-D joints
The aging tests conducted so far showed that duct tape tends to degrade in its performance as the joint it is applied to requires a geometrical description of a higher number of space dimensions (1-D, 2-D, 3-D). One-dimensional joints are the easiest to seal with duct tape, and thus the least to experience failure. Two-dimensional joints, such as the flexible duct core-to-collar joints tested in this study, are less likely to fail than three-dimensional collar-to-plenum joints, as the shrinkage could have a positive effect in tightening the joint. Three-dimensional joints are the toughest to seal and the most likely to experience failure. The 2-D flexible duct core-to-collar joints passed the six-month period of the aging test in terms of leakage, but with the exception of the foil-butyl tape, showed degradation in terms hardening, brittleness, partial peeling, shrinkage, wrinkling, delamination of the tape layers, flaking, cracking, bubbling, oozing and discoloration. The baking test results showed that the failure in the duct tape joints could be attributed to the type of combination of the duct tape and the material it is applied to, as the duct tape behaves differently with different substrates. Overall, the foil-butyl tape (Tape 4) had the best results, …
Date:
May 30, 2002
Creator:
Abushakra, Bass
Object Type:
Report
System:
The UNT Digital Library
Certification Testing and Demonstration of Insulated Pressure Vessels for Vehicular Hydrogen Storage
Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen or ambient-temperature compressed hydrogen. This flexibility results in multiple advantages with respect to compressed hydrogen tanks or low-pressure liquid hydrogen tanks. Our work is directed at verifying that commercially available aluminum-lined, fiber-wrapped pressure vessels can be safely used to store liquid hydrogen. A series of tests have been conducted, and the results indicate that no significant vessel damage has resulted from cryogenic operation. Future activities include a demonstration project in which the insulated pressure vessels will be installed and tested on two vehicles. A draft standard will also be generated for certification of insulated pressure vessels.
Date:
May 22, 2002
Creator:
Aceves, S. M.; Martinez-Frias, J. & Espinosa-Loza, F.
Object Type:
Article
System:
The UNT Digital Library
Certification Testing and Demonstration of Insulated Pressure Vessels for Vehicular Hydrogen and Natural Gas Storage
We are working on developing an alternative technology for storage of hydrogen or natural gas on light-duty vehicles. This technology has been titled insulated pressure vessels. Insulated pressure vessels are cryogenic-capable pressure vessels that can accept either liquid fuel or ambient-temperature compressed fuel. Insulated pressure vessels offer the advantages of cryogenic liquid fuel tanks (low weight and volume), with reduced disadvantages (fuel flexibility, lower energy requirement for fuel liquefaction and reduced evaporative losses). The work described in this paper is directed at verifying that commercially available pressure vessels can be safely used to store liquid hydrogen or LNG. The use of commercially available pressure vessels significantly reduces the cost and complexity of the insulated pressure vessel development effort. This paper describes a series of tests that have been done with aluminum-lined, fiber-wrapped vessels to evaluate the damage caused by low temperature operation. All analysis and experiments to date indicate that no significant damage has resulted. Future activities include a demonstration project in which the insulated pressure vessels will be installed and tested on two vehicles. A draft standard will also be generated for obtaining insulated pressure vessel certification.
Date:
May 22, 2002
Creator:
Aceves, S. M.; Martinez-Frias, J.; Espinosa-Loza, F.; Schaffer, R. & Clapper, W.
Object Type:
Article
System:
The UNT Digital Library
Securing collaborative environments
The diverse set of organizations and software components involved in a typical collaboratory make providing a seamless security solution difficult. In addition, the users need support for a broad range of frequency and locations for access to the collaboratory. A collaboratory security solution needs to be robust enough to ensure that valid participants are not denied access because of its failure. There are many tools that can be applied to the task of securing collaborative environments and these include public key infrastructure, secure sockets layer, Kerberos, virtual and real private networks, grid security infrastructure, and username/password. A combination of these mechanisms can provide effective secure collaboration capabilities. In this paper, we discuss the requirements of typical collaboratories and some proposals for applying various security mechanisms to collaborative environments.
Date:
May 16, 2002
Creator:
Agarwal, Deborah; Jackson, Keith & Thompson, Mary
Object Type:
Article
System:
The UNT Digital Library
Supporting collaborative computing and interaction
To enable collaboration on the daily tasks involved in scientific research, collaborative frameworks should provide lightweight and ubiquitous components that support a wide variety of interaction modes. We envision a collaborative environment as one that provides a persistent space within which participants can locate each other, exchange synchronous and asynchronous messages, share documents and applications, share workflow, and hold videoconferences. We are developing the Pervasive Collaborative Computing Environment (PCCE) as such an environment. The PCCE will provide integrated tools to support shared computing and task control and monitoring. This paper describes the PCCE and the rationale for its design.
Date:
May 22, 2002
Creator:
Agarwal, Deborah; McParland, Charles & Perry, Marcia
Object Type:
Article
System:
The UNT Digital Library
Trade and the Americas
None
Date:
May 24, 2002
Creator:
Ahearn, Raymond J.
Object Type:
Report
System:
The UNT Digital Library
U.S.-EU Trade Tensions: Causes, Consequences, and Possible Cures
None
Date:
May 21, 2002
Creator:
Ahearn, Raymond J.
Object Type:
Report
System:
The UNT Digital Library
U.S.-European Union Trade Relations: Issues and Policy Challenges
None
Date:
May 21, 2002
Creator:
Ahearn, Raymond J.
Object Type:
Report
System:
The UNT Digital Library
Developing High Brightness and High Current Beams for HIF Injectors
The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 {pi}-mm-mr). The central issue of focus is whether to carry on the traditional approach of large surface ionization sources or to adopt a multi-aperture approach that transports many smaller ''beamlets'' separately at low energies before allowing them to merge. For the large surface source, the recent commissioning of the 2-MeV injector for the High Current experiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multi-aperture approach we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called the STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress …
Date:
May 10, 2002
Creator:
Ahle, L & Kwan, J W
Object Type:
Article
System:
The UNT Digital Library
Initial experiments of RF gas plasma source for heavy ionfusion
The Source Injector Program for the US Heavy Ion Fusion Virtual National Laboratory is currently exploring the feasibility of using RF gas plasma sources for a HIF driver. This source technology is presently the leading candidate for the multiple aperture concept, in which bright millimeter size beamlets are extracted and accelerated electrostatically up to 1 MeV before the beamlets are allowed to merge and form 1 A beams. Initial experiments have successfully demonstrated simultaneously high current density, {approx} 100 mA/cm{sup 2} and fast turn on, {approx} 1 {micro}s. These experiments were also used to explore operating ranges for pressure and RF power. Results from these experiments are presented as well as progress and plans for the next set of experiments for these sources.
Date:
May 22, 2002
Creator:
Ahle, L.; Hall, R.; Molvik, A. W.; Chacon-Golcher, E.; Kwan, J. W.; Leung, K. N. et al.
Object Type:
Article
System:
The UNT Digital Library
Developing high brightness and high current beams for HIF injectors
The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 {pi}-mm-mr). The central issue of focus is whether to continue pursuing the traditional approach of large surface ionization sources or to adopt a multiaperture approach that transports many smaller ''beamlets'' separately at low energies before allowing them to merge. For the large surface source concept, the recent commissioning of the 2-MeV injector for the High Current eXperiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multiaperture approach, we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress …
Date:
May 24, 2002
Creator:
Ahle, Larry; Grote, Dave & Kwan, Joe
Object Type:
Article
System:
The UNT Digital Library
Search for X-Ray Induced Acceleration of the Decay of the 31-yr Isomer 178Hf Using Synchrotron Radiation
Releasing the energy stored in an isomeric nuclear state in a controlled way with an atomic or electromagnetic trigger is an attractive speculation: the energy gain may be on the order of the ratio of nuclear/atomic energies - MeV/keV. (Nuclear isomers are loosely defined as excited nuclear states with lifetimes longer than 10{sup -9} s.) Nuclear isomers, therefore, represent an opportunity for a stand-alone energy source if suitable schemes for trigger and control of the energy release can be found. Potential applications include space drive, as well as very bright {gamma}-ray sources. The nucleus {sup 178}Hf has a nuclear isomer with excitation energy E{sub x} = 2.447 MeV. The 2.447-MeV isomeric state decays slowly (t{sub 1/2} = 31 y) to the nearby state at 2.433 MeV. The J{sup {pi}} = 13{sup -} state loses energy in a rapid (t {approx} 10{sup -12} s) {gamma}-ray cascade ending at the 8{sup -} rotational band head which in turn decays via the ground-state rotational band cascade. The {gamma}-ray cascade is delayed at the 8{sup -} state at 1.147 MeV, since the 8{sup -} state is also isomeric, with t{sub 1/2} = 4 s. Very scarce quantities of the 16{sup +}, 31-yr isomer are …
Date:
May 9, 2002
Creator:
Ahmad, I.; Banar, J. C.; Becker, J. A.; Gemmell, D. S.; Kraemer, A.; Mashayekhi, A. et al.
Object Type:
Report
System:
The UNT Digital Library
Quantitative determination of {sup 252}Cf.
Sealed {sup 252}Cf sources in the microCurie to milliCurie range are routinely used in industry and research. At present, no reliable analytical method is available for precise determination of the activity. Very strong sources can be analyzed by neutron counting but the error is large. The authors propose to use gamma-ray spectroscopy for such analysis. In particular, high-energy gamma rays (above 1 MeV) of fission fragments in equilibrium with the source are very convenient because they have little absorption in materials surrounding the source. They have measured the gamma/alpha ratio for {sup 252}Cf with an uncertainty of better than 5%. The experiment involved the preparation of several thin {sup 252}Cf sources, alpha pulse height analysis, determination of alpha decay rate, and the measurement of gamma singles spectrum with a well shielded germanium spectrometer. The measured ratio and the gamma ray spectroscopy of unknown samples can provide the activity of {sup 252}Cf in these samples.
Date:
May 1, 2002
Creator:
Ahmad, I.; Moore, E. F.; Greene, J. P.; Porter, C. E. & Felker, L. K.
Object Type:
Article
System:
The UNT Digital Library
Observation of high energy atmospheric neutrinos with antarctic muon and neutrino detector array
The Antarctic Muon and Neutrino Detector Array (AMANDA) began collecting data with ten strings in 1997. Results from the first year of operation are presented. Neutrinos coming through the Earth from the Northern Hemisphere are identified by secondary muons moving upward through the array. Cosmic rays in the atmosphere generate a background of downward moving muons, which are about 10{sup 6} times more abundant than the upward moving muons. Over 130 days of exposure, we observed a total of about 300 neutrino events. In the same period, a background of 1.05 x 10{sup 9} cosmic ray muon events was recorded. The observed neutrino flux is consistent with atmospheric neutrino predictions. Monte Carlo simulations indicate that 90 percent of these events lie in the energy range 66 GeV to 3.4 TeV. The observation of atmospheric neutrinos consistent with expectations establishes AMANDA-B10 as a working neutrino telescope.
Date:
May 7, 2002
Creator:
Ahrens, J.; Andres, E.; Bai, X.; Barouch, G.; Barwick, S. W.; Bay, R. C. et al.
Object Type:
Article
System:
The UNT Digital Library
The Stochastic Engine Initiative: Improving Prediction of Behavior in Geologic Environments We Cannot Directly Observe
The stochastic engine uses modern computational capabilities to combine simulations with observations. We integrate the general knowledge represented by models with specific knowledge represented by data, using Bayesian inferencing and a highly efficient staged Metropolis-type search algorithm. From this, we obtain a probability distribution characterizing the likely configurations of the system consistent with existing data. The primary use will be optimizing knowledge about the configuration of a system for which sufficient direct observations cannot be made. Programmatic applications include underground systems ranging from environmental contamination to military bunkers, optimization of complex nonlinear systems, and timely decision-making for complex, hostile environments such as battlefields or the detection of secret facilities. We create a stochastic ''base representation'' of system configurations (states) from which the values of measurable parameters can be calculated using forward simulators. Comparison of these predictions to actual measurements drives embedded Bayesian inferencing, updating the distributions of states in the base representation using the Metropolis method. Unlike inversion methods that generate a single bestcase deterministic solution, this method produces all the likely solutions, weighted by their likelihoods. This flexible method is best applied to highly non-linear, multi-dimensional problems. Staging of the Metropolis searches permits us to run the simplest model …
Date:
May 9, 2002
Creator:
Aines, R; Nitao, J; Newmark, R; Carle, S; Ramirez, A; Harris, D et al.
Object Type:
Report
System:
The UNT Digital Library
Effect of Mo Back Contact on Na Out-Diffusion and Device Performance of Mo/Cu(In,Ga)Se2/CdS/ZnO Solar Cells: Preprint
This conference paper describes the molybdenum thin films that were deposited on soda lime glass (SLG) substrates using direct-current planar magnetron sputtering, with a sputtering power density of 1.2 W/cm2. The working gas (Ar) pressure was varied from 0.6 to 16 mtorr to induce changes in the Mo films' morphology and microstructure. Thin films of Cu(In,Ga)Se2 (CIGS) were deposited on the Mo-coated glass using the 3-stage co-evaporation process. The morphology of both the Mo-coated SLG and the CIGS thin films grown on it was examined using high-resolution scanning electron microscopy. Na was depth profiled in the Mo and CIGS films by secondary ion mass spectrometry. The device performance was evaluated under standard conditions of 1000 W/m2 and 25 C. Optimum device performance is found for an intermediate Mo sputtering pressure.
Date:
May 1, 2002
Creator:
Al-Thani, H. A.; Hasoon, F. S.; Young, M.; Asher, S.; Alleman, J. L.; Al-Jassim, M. M. et al.
Object Type:
Article
System:
The UNT Digital Library
US DOE and Polish Institute for Ecology of Industrial Areas JCCES FY01 Annual Report
The project Production Scale Implementation of a Petroleum Contaminated Soils Bioreactor was launched in FY00 and showed that bioremediation can be performed under strictly controlled conditions. Initial results showed a 50 percent reduction of total petroleum hydrocarbon concentration in soil from the Czechowice-Dziedzice refinery. It was determined that changes in the design and construction of the bioreactor could improve system performance.
Date:
May 22, 2002
Creator:
Altman, D. J.
Object Type:
Report
System:
The UNT Digital Library
Reservoir Characterization of Upper Devonian Gordon Sandstone, Jacksonburg, Stringtown Oil Field, Northwestern West Virginia
This report gives results on use of a minipermeameter on cores to study very finescale trends in permeability, and use of neural networks to predict permeability in logged, uncored wells.
Date:
May 21, 2002
Creator:
Ameri, S.; Aminian, K.; Avary, K. L.; Bilgesu, H. I.; Hohn, M. E.; McDowell, R. R. et al.
Object Type:
Report
System:
The UNT Digital Library
Reservoir Characterization of Upper Devonian Gordon Sandstone, Jacksonburg, Stringtown Oil Field, Northwestern West Virginia
The purpose of this work was to establish relationships among permeability, geophysical and other data by integrating geologic, geophysical and engineering data into an interdisciplinary quantification of reservoir heterogeneity as it relates to production.
Date:
May 21, 2002
Creator:
Ameri, S.; Aminian, K.; Avary, K. L.; Bilgesu, H. I.; Hohn, M. E.; McDowell, R. R. et al.
Object Type:
Report
System:
The UNT Digital Library
Reservoir Characterization of Upper Devonian Gordon Sandstone, Jacksonburg, Stringtown Oil Field, Northwestern West Virginia
This report gives results of efforts to determine electrofacies from logs; measure permeability in outcrop to study very fine-scale trends; find the correlation between permeability measured by the minipermeameter and in core plugs, define porosity-permeability flow units; and run the BOAST III reservoir simulator using the flow units defined for the Gordon reservoir.
Date:
May 21, 2002
Creator:
Ameri, S.; Aminian, K.; Avary, K. L.; Bilgesu, H. I.; Hohn, M. E.; McDowell, R. R. et al.
Object Type:
Report
System:
The UNT Digital Library