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Low-Temperature Growth of DKDP for Improving Laser-Induced Damage resistance at 350nm (open access)

Low-Temperature Growth of DKDP for Improving Laser-Induced Damage resistance at 350nm

A set of twenty-three 20-L crystallizer runs exploring the importance of several engineering variables found that growth temperature is the most important variable controlling damage resistance of DKDP over the conditions investigated. Boules grown between 45 C and room temperature have a 50% probability of 3{omega} bulk damage that is 1.5 to 2 times higher than boules grown between 65 and 45 C. This raises their damage resistance above the NIF tripler specification for 8 J/cm{sup 2} operation by a comfortable margin. Solution impurity levels do not correlate with damage resistance for iron less than 200 ppb and aluminum less than 2000 ppb. The possibility that low growth temperatures could increase damage resistance in NIF-scale boules was tested by growing a large boule in a 1000-L crystallizer with a supplemental growth solution tank. Four samples representing early and late pyramid and prism growth are very close to the specification as best it is understood at the present. Implications of low temperature growth for meeting absorbance, homogeneity, and other material specifications are discussed.
Date: December 6, 2000
Creator: Burnham, A K; Runkel, M; Hawley-Fedder, R A; Carman, M L; Torres, R A & Whitman, P K
System: The UNT Digital Library
Anti-B-B Mixing Constrains Topcolor-Assisted Technicolor (open access)

Anti-B-B Mixing Constrains Topcolor-Assisted Technicolor

We argue that extended technicolor augmented with topcolor requires that all mixing between the third and the first two quark generations resides in the mixing matrix of left-handed down quarks. Then, the anti-B_d--B_d mixing that occurs in topcolor models constrains the coloron and Z' boson masses to be greater than about 5 TeV. This implies fine tuning of the topcolor couplings to better than 1percent.
Date: December 6, 2000
Creator: Burdman, Gustavo; Lane, Kenneth & Rador, Tonguc
System: The UNT Digital Library
Spectral-element agglomerate coarsening in AMGe (open access)

Spectral-element agglomerate coarsening in AMGe

In this talk the authors present a highly accurate coarsening algorithm for constructing coarse finite element spaces to be used in algebraic multigrid methods designed for finite element problems on generally unstructured meshes. The new algorithm relies on removing certain percentage of the high oscillating components from the spectrum of local stiffness matrices corresponding to element agglomerations. By doing so, one is guaranteed that the hierarchical complement finite element subspace gives rise to a well conditioned matrix. The coarsening consists of an agglomeration step and of computing a few minimal eigenvectors of the corresponding assembled agglomerate stiffness matrix. The method requires access to the individual element matrices. Based on the topological agglomeration algorithms they employed one is able to define coarse elements and coarse element matrices thus allowing for recursive use of the same algorithm. Some numerical illustration for elliptic problems is also given.
Date: December 6, 2000
Creator: Vassilevski, P S
System: The UNT Digital Library
Extreme Load Estimation for Wind Turbines: Issues and Opportunities for Improved Practice (open access)

Extreme Load Estimation for Wind Turbines: Issues and Opportunities for Improved Practice

None
Date: December 6, 2000
Creator: Veers, P. S. & Butterfield, S.
System: The UNT Digital Library
Application of natural radionuclides for determination of tropospheric ozone and aerosol transport. (open access)

Application of natural radionuclides for determination of tropospheric ozone and aerosol transport.

Natural radionuclides have been proposed for use in assessing the transport of ozone and aerosols in the troposphere. For example, {sup 7}Be is known to be produced in the upper troposphere and lower stratosphere by interactions with cosmogenic particles. Beryllium-7 has a 53.28-day half-life and is a gamma emitter that attaches itself to fine particles in the atmosphere once it is formed. Indeed, in tropospheric aerosol samples TBe is typically found in association with aerosol particles that are 0.3 {micro}m in diameter. Some investigators have asserted that ozone from aloft can be transported into rural and urban regions during stratospheric/tropospheric folding events, leading to increased background levels of ozone. During the Texas 2000 Air Quality study, aerosol samples with a 2.5-{micro}m cutoff were collected during 12-hour cycles (day/night) for a 30-day period at the Deer Park, Texas, field site in August-September 2000. To monitor {sup 7}Be levels, high-volume samples were collected on glass fiber filters on Julian dates 225-259. Sample collection was at a field site near a city park, away from any nearby traffic. This site is under routine operation by the Texas Natural Resource Conservation Commission. Instruments operated at this same site during the study period included an …
Date: December 6, 2000
Creator: Gaffney, J. S.; Marley, N. A.; Drayton, P. J. & Orlandini, K. A.
System: The UNT Digital Library
Lifetime Predictions for Elastomers from Accelerated Aging Experiments (open access)

Lifetime Predictions for Elastomers from Accelerated Aging Experiments

None
Date: December 6, 2000
Creator: GILLEN,KENNETH T. & CLOUGH,ROGER LEE
System: The UNT Digital Library
Superposition and Wear-Out Approaches Applied to Polymer Lifetime Prediction (open access)

Superposition and Wear-Out Approaches Applied to Polymer Lifetime Prediction

None
Date: December 6, 2000
Creator: CELINA,MATHEW & GILLEN,KENNETH T.
System: The UNT Digital Library
Pointing Control Design for a High Precision Flight Telescope Using Quantitative Feedback Theory (open access)

Pointing Control Design for a High Precision Flight Telescope Using Quantitative Feedback Theory

None
Date: December 6, 2000
Creator: Bentley, Anthony E.
System: The UNT Digital Library
Oxidative Degradation Analysis of HTPB/IPDI Polyurethane Using {sup 17}O and {sup 13}C NMR (open access)

Oxidative Degradation Analysis of HTPB/IPDI Polyurethane Using {sup 17}O and {sup 13}C NMR

None
Date: December 6, 2000
Creator: Harris, D. J. & Assink, R. A.
System: The UNT Digital Library
The Role of Quantum Mechanics in Neutrino Factories. (open access)

The Role of Quantum Mechanics in Neutrino Factories.

A compilation is made of the various ways in which quantum phenomena enter into the design and operation of a neutrino factory. They include production of pions, decay of pions into muons, ionization energy loss of muons in material, scattering and energy straggling of muons in material, polarization of muons, and the decay of muons into neutrinos, and the radiation effect of neutrinos. For each process formulas are presented which cover the basic mechanism. A discussion is presented of the areas of uncertainty and of the experiments, underway and proposed, which will reduce the uncertainty to an acceptable level.
Date: December 6, 2000
Creator: Gallardo, J. C.; Sessler, A. M. & Wurtele, J.
System: The UNT Digital Library
Deactivation of the P, C, and R Reactor Disassembly Basins at the SRS (open access)

Deactivation of the P, C, and R Reactor Disassembly Basins at the SRS

The Facilities Disposition Division (FDD) at the Savannah River Site is engaged in planning the deactivation/closure of three of the site's five reactor disassembly basins. Activities are currently underway at 105-R Disassembly Basin and will continue with the 105-P and 105-C disassembly basins. The basins still contain the cooling and shielding water that was present when operations ceased. Low concentrations of radionuclides are present, with tritium, Cs-137, and Sr-90 being the major contributors. Although there is no evidence that any of the basins have leaked, the 50-year-old facilities will eventually contaminate the surrounding groundwaters. The FDD is pursuing a pro-active solution to close the basins in-place and prevent a release to the groundwater. In-situ ion-exchange is currently underway at the R-Reactor Disassembly Basin to reduce the Cs and Sr concentrations to levels that would allow release of the treated water to previously used on-site cooling ponds. A NEPA Environmental Assessment (EA) is being prepared to propose the preferred closure alternative for each of the three basins. The EA will be the primary mechanism to inform the public and gain stakeholder and regulatory approval.
Date: December 6, 2000
Creator: Pickett, J.B.
System: The UNT Digital Library