Resource Type

The energy dependence of the total charm cross section (open access)

The energy dependence of the total charm cross section

We discuss the energy dependence of the total charm cross section and some of its theoretical uncertainties including the quark mass, scale choice and the parton densities. We compare the next-to-leading order calculation of the total cross section with results obtained using PYTHIA.
Date: October 18, 2007
Creator: Vogt, R
System: The UNT Digital Library
Pump and probe damage testing for investigation of transient material modifications associated with laser damage in optical materials (open access)

Pump and probe damage testing for investigation of transient material modifications associated with laser damage in optical materials

Laser-induced breakdown in the bulk of transparent dielectric materials is associated with the generation of extreme localized conditions of temperatures and pressures. In this work, we perform pump and probe damage testing experiments to investigate the evolution of transient absorption by the host material arising from modifications following confined laser energy deposition in fused silica and DKDP materials. Specifically, we measure the size of the damage sites observed in the region of spatial overlap between the pump and probe pulses versus probe time delay and energy. Results of this proof-of-principle experimental work confirm that material modifications under extreme conditions created during a damage event include transient optical absorption. In addition, we found that the relaxation times of the induced absorption are very distinct for DKDP and SiO{sub 2} even under identical excitation conditions, on the order of 100 ns and 100 {micro}s, respectively.
Date: October 18, 2007
Creator: Negres, R A; Feit, M D; DeMange, P; Bude, J D & Demos, S G
System: The UNT Digital Library
Dielectric Wall Accelerator Technology (open access)

Dielectric Wall Accelerator Technology

The dielectric wall accelerator (DWA) is a compact pulsed power device where the pulse forming lines, switching, and vacuum wall are integrated into a single compact geometry. For this effort, we initiated a extensive compact pulsed power development program and have pursued the study of switching (gas, oil, laser induced surface flashover and photoconductive), dielectrics (ceramics and nanoparticle composites), pulse forming line topologies (asymmetric and symmetric Blumleins and zero integral pulse forming lines), and multilayered vacuum insulator (HGI) technology. Finally, we fabricated an accelerator cell for test on ETAII (a 5.5 MeV, 2 kA, 70 ns pulsewidth electron beam accelerator). We review our past results and report on the progress of accelerator cell testing.
Date: October 18, 2007
Creator: Sampayan, S.; Caporaso, G.; Chen, Y.; Harris, J.; Hawkins, S.; Holmes, C. et al.
System: The UNT Digital Library
Derivative-free optimization methods for surface structuredetermination of nanosystems (open access)

Derivative-free optimization methods for surface structuredetermination of nanosystems

Many properties of nanostructures depend on the atomicconfiguration at the surface. One common technique used for determiningthis surface structure is based on the low energy electron diffraction(LEED) method, which uses a high-fidelity physics model to compareexperimental results with spectra computed via a computer simulation.While this approach is highly effective, the computational cost of thesimulations can be prohibitive for large systems. In this work, wepropose the use of a direct search method in conjunction with an additivesurrogate. This surrogate is constructed from a combination of asimplified physics model and an interpolation that is based on thedifferences between the simplified physics model and the full fidelitymodel.
Date: October 18, 2007
Creator: Meza, Juan C.; Garcia-Lekue, Arantzazu; Abramson, Mark A. & Dennis, John E.
System: The UNT Digital Library
DEVELOPMENT AND TESTING OF THE BLANTON CLAMSHELL CLOSUREFOR USE ON RADIOACTIVE MATERIAL PACKAGING DRUMS (open access)

DEVELOPMENT AND TESTING OF THE BLANTON CLAMSHELL CLOSUREFOR USE ON RADIOACTIVE MATERIAL PACKAGING DRUMS

This paper provides a brief history of the U.S. Type B 6M specification container, its introduction into U.S. Code of federal regulations and its scheduled elimination three decades later. The paper also presents development, testing and deployment by the Department of Energy (DOE) of an enhanced drum closure called the 'Blanton Clamshell' (patent pending) that was designed to replace the standard open-head C-ring closure for the 55- and 85-gallon drums described in the 6M specification to extend their safe use. Nuclear Filter Technology has the Exclusive License for Clamshell production. Drum packages utilizing the standard C-ring closure have been a main-stay for over a half of a century in the national and international nuclear industry for shipping radioactive materials and will remain so in the foreseeable future. Drum package use in the U.S. increased heavily in the 1950's with development of the Weapons Complex and subsequently the commercial nuclear reactor industry.
Date: October 18, 2007
Creator: Blanton, P
System: The UNT Digital Library