Capstone Depleted Uranium Aerosols: Generation and Characterization (open access)

Capstone Depleted Uranium Aerosols: Generation and Characterization

In a study designed to provide an improved scientific basis for assessing possible health effects from inhaling depleted uranium (DU) aerosols, a series of DU penetrators was fired at an Abrams tank and a Bradley fighting vehicle. A robust sampling system was designed to collect aerosols in this difficult environment and continuously monitor the sampler flow rates. Aerosols collected were analyzed for uranium concentration and particle size distribution as a function of time. They were also analyzed for uranium oxide phases, particle morphology, and dissolution in vitro. The resulting data provide input useful in human health risk assessments.
Date: October 19, 2004
Creator: Parkhurst, MaryAnn; Szrom, Fran; Guilmette, Ray; Holmes, Tom; Cheng, Yung-Sung; Kenoyer, Judson L. et al.
Object Type: Report
System: The UNT Digital Library
Science-driven system architecture: A new process for leadership class computing (open access)

Science-driven system architecture: A new process for leadership class computing

Over the past several years, computational scientists have observed a frustrating trend of stagnating application performance despite dramatic increases in peak performance of high performance computers. In 2002, researchers at Lawrence Berkeley National Laboratory, Argonne National Laboratory, and IBM proposed a new process to reverse this situation [1]. This strategy is based on new types of development partnerships with computer vendors based on the concept of science-driven computer system design. This strategy will engage applications scientists well before an architecture is available for commercialization. The process is already producing results, and has further potential for dramatically improving system efficiency. This paper documents the progress to date and the potential for future benefits. An example of this process is discussed, using IBM Power architecture with a computer architecture design that can lead to a sustained performance of 50 to 100 Tflo p/s on a broad spectrum of applications in 2006 for a reasonable cost. This partnership will establish a collaborative approach to modifying computer architecture to enable heretofore unrealized achievements in computer capability-limited fields such as nanoscience, combustion modeling, fusion, climate modeling, and astrophysics.
Date: October 19, 2004
Creator: Simon, Horst; Kramer, William; Saphir, William; Shalf, John; Bailey, David; Oliker, Leonid et al.
Object Type: Article
System: The UNT Digital Library
Chamber-transport simulation results for heavy-ion fusion drivers (open access)

Chamber-transport simulation results for heavy-ion fusion drivers

The heavy-ion fusion (HIF) community recently developed a power-plant design that meets the various requirements of accelerators, final focus, chamber transport, and targets. The point design is intended to minimize physics risk and is certainly not optimal for the cost of electricity. Recent chamber-transport simulations, however, indicate that changes in the beam ion species, the convergence angle, and the emittance might allow more-economical designs.
Date: October 19, 2004
Creator: Sharp, W. M.; Callahan, D. A.; Tabak, M.; Yu, S. S.; Peterson, P. F.; Rose, D. V. et al.
Object Type: Article
System: The UNT Digital Library
Modulation of calcium oxalate monohydrate crystallization by citrate through selective binding to atomic steps (open access)

Modulation of calcium oxalate monohydrate crystallization by citrate through selective binding to atomic steps

The majority of human kidney stones are composed primarily of calcium oxalate monohydrate (COM) crystals. Thus, determining the molecular mechanisms by which urinary constituents modulate calcium oxalate crystallization is crucial for understanding and controlling urolithiassis in humans. A comprehensive molecular-scale view of COM shape modification by citrate, a common urinary constituent, obtained through a combination of in situ atomic force microscopy (AFM) and molecular modeling is now presented. We show that citrate strongly influences the growth morphology and kinetics on the (-101) face but has much lower effect on the (010) face. Moreover, binding energy calculations show that the strength of the citrate-COM interaction is much greater at steps than on terraces and is highly step-specific. The maximum binding energy, -166.5 kJ {center_dot} mol{sup -1}, occurs for the [101] step on the (-101) face. In contrast, the value is only -56.9 kJ {center_dot} mol-1 for the [012] step on the (010) face. The binding energies on the (-101) and (010) terraces are also much smaller, -65.4 and -48.9 kJ {center_dot} mol{sup -1} respectively. All other binding energies lie between these extremes. This high selectivity leads to preferential binding of citrate to the acute [101] atomic steps on the (-101) face. …
Date: October 19, 2004
Creator: Qiu, S. R.; Wierzbicki, A.; Salter, E. A.; Zepeda, S.; Orme, C. A.; Hoyer, J. R. et al.
Object Type: Article
System: The UNT Digital Library
ADVANCING THE ION BEAM THIN FILM PLANARIZATION PROCESS FOR THE SMOOTHING OF SUBSTRATE PARTICLES (open access)

ADVANCING THE ION BEAM THIN FILM PLANARIZATION PROCESS FOR THE SMOOTHING OF SUBSTRATE PARTICLES

For a number of technologies small substrate contaminants are undesirable, and for one technology in particular, extreme ultraviolet lithography (EUVL), they can be a very serious issue. We have demonstrated that the Ion Beam Thin Film Planarization Process, a coating process designed to planarize substrate asperities, can be extended to smooth {approx}70 nm and {approx}80 nm diameter particles on EUVL reticle substrates to a height of {approx}0.5 nm, which will render them noncritical in an EUVL printing process. We demonstrate this smoothing process using controlled nanoscale substrate particles and lines fabricated with an e-beam lithography process. The above smoothing process was also modified to yield an excellent reflectance/wavelength uniformity and a good EUV reflectivity for the multilayer, which is required for EUVL reticles. Cross-sectional TEM on a smoothed substrate line defect shows excellent agreement with results obtained from our multilayer growth model.
Date: October 19, 2004
Creator: Mirkarimi, P B; Spiller, E; Baker, S L; Robinson, J C; Stearns, D G; Liddle, J A et al.
Object Type: Article
System: The UNT Digital Library
Far SOL Transport and Main Wall Plasma Interaction in DIII-D (open access)

Far SOL Transport and Main Wall Plasma Interaction in DIII-D

Far scrape-off layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge parameters and confinement regime. In L-mode discharges cross-field transport increases with the average discharge density and flattens far SOL profiles, thus increasing plasma-wall contact. In H-mode between edge localized modes (ELMs), plasma-wall contact is generally weaker than in L-mode. During ELMs plasma fluxes to the wall increase to, or above the L-mode levels. Depending on the discharge conditions ELMs are responsible for 30-90% of the ion flux to the outboard chamber wall. Cross-field fluxes in far SOL are dominated by large amplitude intermittent transport events that may propagate all the way to the outer wall and cause sputtering. A Divertor Material Evaluation System (DiMES) probe containing samples of several ITER-relevant materials including carbon, beryllium and tungsten was exposed to a series of upper single null (USN) discharges as a proxy to measure the first wall erosion.
Date: October 19, 2004
Creator: Rudakov, D. L.; Boedo, J. A.; Moyer, R. A.; Stangeby, P. C.; Watkins, J. G.; Whyte, D. G. et al.
Object Type: Article
System: The UNT Digital Library
Babel 1.0 Release Criteria: A Working Document (open access)

Babel 1.0 Release Criteria: A Working Document

In keeping with the Open Source tradition, we want our Babel 1.0 release to indicate a certain level of capability, maturity, and stability. From our first release (version 0.5.0) in July of 2001 to our current (18th) release (version 0.9.6) we have continued to add capabilities in response to customer feedback, our observations in the field, and a consistent vision for interoperability. The key to our maturity is without a doubt the ever-increasing demands of our growing user base... both in terms of sheer size and sophistication with the underlying technology. Stability is a special challenge for any research project. With our 1.0 release, we will branch and maintain a stable Babel 1.0 code line for at least a full year. This means no new features and no backward incompatible changes, only bug fixes. All continuing R&D will be performed on a separate development tree. Currently, Babel has a quarterly release cycle with no guarantee for backward compatibility from one release to the next (though we certainly try to make migration as painless as possible). Now is the time where we can see a good point for a Babel 1.0 release. But, seeing that point is different from being there. …
Date: October 19, 2004
Creator: Kumfert, Gary; Dahlgren, Tamara; Epperly, Thomas & Leek, James
Object Type: Report
System: The UNT Digital Library