Experimental Study of Ion Heating and Acceleration During Magnetic Reconnection (open access)

Experimental Study of Ion Heating and Acceleration During Magnetic Reconnection

Ion heating and acceleration has been studied in the well-characterized reconnection layer of the Magnetic Reconnection Experiment [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)]. Ion temperature in the layer rises substantially during null-helicity reconnection in which reconnecting field lines are anti-parallel. The plasma out flow is sub-Alfvonic due to a downstream back pressure. An ion energy balance calculation based on the data and including classical viscous heating indicates that the ions are heated largely due to non-classical mechanisms. The Ti rise is much smaller during co-helicity reconnection in which field lines reconnect obliquely. This is consistent with a slower reconnection rate and a smaller resistivity enhancement over the Spitzer value. These observations indicate strongly that non-classical dissipation mechanisms can play an important role both in heating the ions and in facilitating the reconnection process.
Date: October 24, 2000
Creator: Hsu, S.C.; Carter, T.A.; Fiksel, G.; Ji, H.; Kulsrud, R.M. & Yamada, M.
Object Type: Report
System: The UNT Digital Library
UTILIZATION OF LIGHTWEIGHT MATERIALS MADE FROM COAL GASIFICATION SLAGS (open access)

UTILIZATION OF LIGHTWEIGHT MATERIALS MADE FROM COAL GASIFICATION SLAGS

The integrated-gasification combined-cycle (IGCC) process is an emerging technology that utilizes coal for power generation and production of chemical feedstocks. However, the process generates large amounts of solid waste, consisting of vitrified ash (slag) and some unconverted carbon. In previous projects, Praxis investigated the utilization of ''as-generated'' slags for a wide variety of applications in road construction, cement and concrete production, agricultural applications, and as a landfill material. From these studies, we found that it would be extremely difficult for ''as-generated'' slag to find large-scale acceptance in the marketplace even at no cost because the materials it could replace were abundantly available at very low cost. It was further determined that the unconverted carbon, or char, in the slag is detrimental to its utilization as sand or fine aggregate. It became apparent that a more promising approach would be to develop a variety of value-added products from slag that meet specific industry requirements. This approach was made feasible by the discovery that slag undergoes expansion and forms a lightweight material when subjected to controlled heating in a kiln at temperatures between 1400 and 1700 F. These results confirmed the potential for using expanded slag as a substitute for conventional lightweight …
Date: April 24, 2000
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Photoisomerization and photodissociation dynamics of reactive free radicals (open access)

Photoisomerization and photodissociation dynamics of reactive free radicals

The photofragmentation pathways of chemically reactive free radicals have been examined using the technique of fast beam photofragment translational spectroscopy. Measurements of the photodissociation cross-sections, product branching ratios, product state energy distributions, and angular distributions provide insight into the excited state potential energy surfaces and nonadiabatic processes involved in the dissociation mechanisms. Photodissociation spectroscopy and dynamics of the predissociative {tilde A}{sup 2}A{sub 1} and {tilde B}{sup 2}A{sub 2} states of CH{sub 3}S have been investigated. At all photon energies, CH{sub 3} + S({sup 3}P{sub j}), was the main reaction channel. The translational energy distributions reveal resolved structure corresponding to vibrational excitation of the CH{sub 3} umbrella mode and the S({sup 3}P{sub j}) fine-structure distribution from which the nature of the coupled repulsive surfaces is inferred. Dissociation rates are deduced from the photofragment angular distributions, which depend intimately on the degree of vibrational excitation in the C-S stretch. Nitrogen combustion radicals, NCN, CNN and HNCN have also been studied. For all three radicals, the elimination of molecular nitrogen is the primary reaction channel. Excitation to linear excited triplet and singlet electronic states of the NCN radical generates resolved vibrational structure of the N{sub 2} photofragment. The relatively low fragment rotational excitation …
Date: August 24, 2000
Creator: Bise, Ryan T.
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Final Report: Update of the Glossary of Meteorology, September 1, 1994 - August 3, 1999 (open access)

Final Report: Update of the Glossary of Meteorology, September 1, 1994 - August 3, 1999

The American Meteorological Society has updated the Glossary of Meteorology from the first addition which was published in 1959. The second edition contains over 12,000 entries in meteorology and related fields. The glossary will be made available in both book and CD-ROM formats. DOE was one of six federal agencies that provided support for this project.
Date: January 24, 2000
Creator: Society, American Meteorological
Object Type: Report
System: The UNT Digital Library
Improvement in moist processes in atmospheric general circulation models: Validation and development through the CHAMMP Program. Final report (open access)

Improvement in moist processes in atmospheric general circulation models: Validation and development through the CHAMMP Program. Final report

None
Date: February 24, 2000
Creator: unknown
Object Type: Report
System: The UNT Digital Library
A coupled Newton-Krylov solver for improved CHAD cache utilization and performance. (open access)

A coupled Newton-Krylov solver for improved CHAD cache utilization and performance.

CHAD (Computational Hydrodynamics for Advanced Design) is a computer program that has been developed to analyze flows in automotive and defense applications. Extensive performance analysis of the CHAD computer program indicated a need to address cache memory use to increase computational performance. Several strategies have been adopted to achieve this goal: simultaneous solution of the coupled Navier-Stokes equations, data clustering, and data ordering. A coupled Newton-Krylov solver has been incorporated into a version of the CHAD program, resulting in consistent improvement in run times that varies from 50% to 200%. Further work will be required to tune the solver for optimal performance. In addition, experiments with data cluster and reordering indicate a potential for performance improvement.
Date: March 24, 2000
Creator: Canfield, T.R.; Chien, T. H.; Domanus, H. M.; Tentner, A. M.; Tzanos, C. P.; Valentin, R. A. et al.
Object Type: Article
System: The UNT Digital Library
What, Why, and Who, is ICFA? (open access)

What, Why, and Who, is ICFA?

ICFA plays an important role as a forum for discussions transcending national or regional boundaries on the future of high-energy accelerators and their associated particle physics, detectors and technology. It is probably true that, to paraphrase an old expression, if ICFA didn't exist, something very similar would have to be invented. As appeared to be true in the 1970s, projects in our field are becoming so large and costly that no single country or group of countries can carry them out alone; more and more international discussion and cooperation is needed. This will be especially relevant if the next major accelerator is a linear e + e - collider in the hundreds of GeV energy range.
Date: October 24, 2000
Creator: Rubinstein, Roy
Object Type: Report
System: The UNT Digital Library
Magnetic imaging of a buried SmCo layer in a spring magnet. (open access)

Magnetic imaging of a buried SmCo layer in a spring magnet.

None
Date: October 24, 2000
Creator: Pollmann, J. P.; Srajer, G. S.; Haskel, D. .H; Lang, J. C. L; Maser, J. M.; Jiang, J. S. J. et al.
Object Type: Article
System: The UNT Digital Library
Preliminary Microstructural Characterization of Gadolinium-Enriched Stainless Steels for Spent Nuclear Fuel Baskets (title change from A) (open access)

Preliminary Microstructural Characterization of Gadolinium-Enriched Stainless Steels for Spent Nuclear Fuel Baskets (title change from A)

Gadolinium (Gd) is a very potent neutron absorber that can potentially provide the nuclear criticality safety required for interim storage, transport, and final disposal of spent nuclear fuel. Gd could be incorporated into an alloy that can be fabricated into baskets to provide structural support, corrosion resistance, and nuclear criticality control. In particular, Gd alloyed with stainless steel has been identified as a material that may fulfill these functional requirements. However, no information is available in the open literature that describes the influence of Gd on the microstructure and resultant mechanical properties of stainless steels alloyed with Gd. Such information is vital for determination of the suitability of these types of alloys for the intended application. Characterization of Gd-stainless steel (Gd-SS) alloys is also necessary for an American Society for Testing and Materials (ASTM) material specification, subsequent code approval by the American Society of Mechanical Engineers (ASME), and regulatory approval by the Nuclear Regulatory Commission for subsequent use by the nuclear industry. The Department of Energy National Spent Nuclear Fuel Program at Idaho National Engineering and Environmental Laboratory has commissioned Lehigh University and Sandia National Laboratories to characterize the properties of a series of Gd-SS alloys to assess their suitability …
Date: July 24, 2000
Creator: Dupont, J. N.; Robino, Charles V.; Stephens, John J., Jr.; Mcconnell, Paul E.; Mizia, R. & Branagan, D.
Object Type: Article
System: The UNT Digital Library
A Defense in Depth Approach to Radiation Protection for Iodine-125 Production Activities (open access)

A Defense in Depth Approach to Radiation Protection for Iodine-125 Production Activities

None
Date: August 24, 2000
Creator: Culp, Todd A.
Object Type: Article
System: The UNT Digital Library
ActiveSpaces on the Grid: The Construction of Advanced Visualization and Interaction Environments (open access)

ActiveSpaces on the Grid: The Construction of Advanced Visualization and Interaction Environments

The Futures Lab group at Argonne National Laboratory and the University of Chicago are designing, building, and evaluating a new type of interactive computing environment that couples in a deep way the concepts of direct manipulation found in virtual reality with the richness and variety of interactive devices found in ubiquitous computing. This environment provides the interactivity and collaboration support of teleimmersive environments with the exibility and availability of desktop collaboration tools. The authors call these environments ActiveSpaces. An ActiveSpace is a physical domain that has been augmented with multiscale multiscreen displays, environment-specific and device-specific sensors, body and object trackers, human-input and instrument-input interfaces, streaming audio and video capture devices, and force feedback devices--and has then been connected to other such spaces via the Grid.
Date: July 24, 2000
Creator: Childers, Lisa; Disz, Terry; Hereld, Mark; Hudson, Randy; Judson, Ivan; Olson, Robert et al.
Object Type: Article
System: The UNT Digital Library
Recent Advances in High-Pressure Equation-of-State Capabilities (open access)

Recent Advances in High-Pressure Equation-of-State Capabilities

For many scientific and programmatic applications, it is necessary to determine the shock compression response of materials to several tens of Mbar. In addition, a complete EOS is often needed in these applications, which requires that shock data be supplemented with other information, such as temperature measurements or by EOS data off the principal Hugoniot. Recent developments in the use of fast pulsed power techniques for EOS studies have been useful in achieving these goals. In particular, the Z accelerator at Sandia National Laboratories, which develops over 20 million amperes of current in 100-200 ns, can be used to produce muM-Mbar shock pressures and to obtain continuous compression data to pressures exceeding 1 Mbar. With this technique, isentropic compression data have been obtained on several materials to pressures of several hundred kbar. The technique has also been used to launch ultra-high velocity flyer plates to a maximum velocity of 14 km/s, which can be used to produce impact pressures of several Mbar in low impedance materials and over 10 Mbar in high impedance materials. The paper will review developments in both of these areas.
Date: July 24, 2000
Creator: Asay, James R.; Hall, Clint A. & Knudson, Marcus D.
Object Type: Article
System: The UNT Digital Library
Phenomenological description of grain growth stagnation for nanocrystalline films and powders (open access)

Phenomenological description of grain growth stagnation for nanocrystalline films and powders

At fixed hold temperatures, grain growth usually stagnates indefinitely after sufficiently long hold times. The change in the growth behavior can be very abrupt, resulting in a sudden plateau in plots of grain size versus time at fixed temperature. Standard grain growth laws do not formally predict the rapid onset of growth stagnation, merely a slow down of grain growth to imperceptible rates. Therefore, the grain size in the plateau regions for long hold times is typically not in agreement with that predicted with kinetic variables derived from the size versus time curves for short hold times where there is pronounced curvature. Standard laws lead to endpoint grain sizes with strong dependences on the hold times. The experimental observation in many cases is a nearly linear temperature dependence that is independent of the hold times after a sufficient duration. Additionally, the growth process may restart from a stagnated state with sufficient temperature increases, where again, the stagnated grain size temperature dependence is linear. For growth laws including size dependent opposing forces, endpoint grain sizes are predicted to be either independent of temperature, or exponentially temperature dependent with thermodynamic reversibility, the latter an impossibility. We derive, heuristically, a stagnation force, phenomenologically …
Date: August 24, 2000
Creator: Dannenberg, R.; Stach, E.A. & Groza, J.R.
Object Type: Article
System: The UNT Digital Library
Energy Efficient Upgrades for Fermilab Infrastructure: Federal Energy Management Program (FEMP) Utility Services Case Study (open access)

Energy Efficient Upgrades for Fermilab Infrastructure: Federal Energy Management Program (FEMP) Utility Services Case Study

At the Fermi National Accelerator Laboratory (Fermilab), originally built in the 1960s, old process and comfort chillers, pumps, and other related central cooling-system equipment were replaced, and pumping configuration changes were made to accelerator heat rejection systems, the employee office space and a ``process system'' for the equipment and accelerators. The new 4500-ton cooling system is expected to use 40% less energy and is free of ozone-depleting chlorofluorocarbons. Energy savings of 20 million kWh and a demand reduction of about 2.5 megawatts are expected, resulting in estimated cost savings of $900,000 per year.
Date: August 24, 2000
Creator: Shah, C.
Object Type: Book
System: The UNT Digital Library
STAR: The Secure Tranportable Autonomous Reactor system, Encapsulated Fission Heat Source. Progress report for period terminating March 31, 2000 (open access)

STAR: The Secure Tranportable Autonomous Reactor system, Encapsulated Fission Heat Source. Progress report for period terminating March 31, 2000

Significant progress has been made since the beginning of this project, in September 1999. Part of the project findings are described in References 1 and 2. So far we have found no ''show-stopper''. In fact, based on the findings accumulated so far it appears to us that the Encapsulated Nuclear Heat Source (ENHS) is technologically feasible and looks even more attractive than initially conceived.
Date: April 24, 2000
Creator: Greenspan, Ehud
Object Type: Report
System: The UNT Digital Library
Radiation Enhanced Porosity and Roughness of Biomaterials (open access)

Radiation Enhanced Porosity and Roughness of Biomaterials

None
Date: April 24, 2000
Creator: Evelyn, A. L.; Rodrigues, M. G.; Ila, D.; Zimmerman, R. L.; Poker, D. B. & Hensley, D. K.
Object Type: Article
System: The UNT Digital Library
Science and technology of ultrananocrystalline diamond (UNCD) thin films for multifunctional devices (open access)

Science and technology of ultrananocrystalline diamond (UNCD) thin films for multifunctional devices

MEMS devices are currently fabricated primarily in silicon because of the available surface machining technology. However, Si has poor mechanical and tribological properties, and practical MEMS devices are currently limited primarily to applications involving only bending and flexural motion, such as cantilever accelerometers and vibration sensors. However, because of the poor flexural strength and fracture toughness of Si, and the tendency of Si to adhere to hydrophyllic surfaces, even these simple devices have limited dynamic range. Future MEMS applications that involve significant rolling or sliding contact will require the use of new materials with significantly improved mechanical and tribological properties, and the ability to perform well in harsh environments. Diamond is a superhard material of high mechanical strength, exceptional chemical inertness, and outstanding thermal stability. The brittle fracture strength is 23 times that of Si, and the projected wear life of diamond MEMS moving mechanical assemblies (MEMS-MMAs) is 10,000 times greater than that of Si MMAs. However, as the hardest known material, diamond is notoriously difficult to fabricate. Conventional CVD thin film deposition methods offer an approach to the fabrication of ultra-small diamond structures, but the films have large grain size, high internal stress, poor intergranular adhesion, and very rough …
Date: August 24, 2000
Creator: Auciello, O.; Krauss, A. R.; Gruen, D. M.; Jayatissa, A.; Sumant, A.; Tucek, J. et al.
Object Type: Article
System: The UNT Digital Library
Ion Sources and Injectors for HIF Induction Linacs (open access)

Ion Sources and Injectors for HIF Induction Linacs

Ion source and injector development is one of the major parts of the HIF program in the USA. Our challenge is to design a cost effective driver-scale injector and to build a multiple beam module within the next couple of years. In this paper, several current-voltage scaling laws are summarized for guiding the injector design. Following the traditional way of building injectors for HIF induction linac, we have produced a preliminary design for a multiple beam driver-scale injector. We also developed an alternate option for a high current density injector that is much smaller in size. One of the changes following this new option is the possibility of using other kinds of ion sources than the surface ionization sources. So far, we are still looking for an ideal ion source candidate that can readily meet all the essential requirements.
Date: July 24, 2000
Creator: Kwan, J. W.; Ahle, L.; Beck, D. N.; Bieniosek, F. M.; Faltens, A.; Grote, D. P. et al.
Object Type: Article
System: The UNT Digital Library
Advanced Transient Simulator for Studying Shallow Gas Blowouts (open access)

Advanced Transient Simulator for Studying Shallow Gas Blowouts

None
Date: October 24, 2000
Creator: RATH,JONATHAN S. & PODIO,AUGUSTO L.
Object Type: Article
System: The UNT Digital Library
Thin film synthesis by energetic condensation (open access)

Thin film synthesis by energetic condensation

None
Date: November 24, 2000
Creator: Monteiro, O.R.
Object Type: Article
System: The UNT Digital Library
A Post Processing Algorithm to Add Damping to Undamped Model Responses (open access)

A Post Processing Algorithm to Add Damping to Undamped Model Responses

None
Date: October 24, 2000
Creator: MAYES,RANDALL L.
Object Type: Article
System: The UNT Digital Library
Final report on the National Conference of State Legislatures project 'Assistance to State Legislatures on Alternative Fuel Vehicle Issues' (open access)

Final report on the National Conference of State Legislatures project 'Assistance to State Legislatures on Alternative Fuel Vehicle Issues'

This report assesses the effectiveness of state alternative fuel vehicle incentives and suggests incentives that might encourage new vehicle technologies. It does not assess whether a state should promote alternative fuel vehicles or whether such vehicles are the most effective means to reduce air pollution.
Date: July 24, 2000
Creator: Brown, Matthew & Sundeen, Matt
Object Type: Report
System: The UNT Digital Library
Enhancement of Dilute-Acid Total-Hydrolysis Process for High-Yield Saccharification of Cellulosic Biomass (open access)

Enhancement of Dilute-Acid Total-Hydrolysis Process for High-Yield Saccharification of Cellulosic Biomass

None
Date: July 24, 2000
Creator: Lee, Y. Y.; Xiang, Qian; Kim, Tae-Hyun & Kim, Junseok
Object Type: Report
System: The UNT Digital Library
Cantilever Epitaxy: A simple Lateral Growth Technique for Reducing Dislocation Densitites in GaN and Other Nitrides (open access)

Cantilever Epitaxy: A simple Lateral Growth Technique for Reducing Dislocation Densitites in GaN and Other Nitrides

None
Date: October 24, 2000
Creator: Ashby, Carol I.; Willan, Christine C.; Han, Jung; Missert, Nancy A.; Provencio, Paula P.; Follstaedt, David M. et al.
Object Type: Article
System: The UNT Digital Library