Reinvestigation of the Direct Two-proton Decay of the Long-lived Isomer 94Agm [0.4 s, 6.7 MeV, (21+)] (open access)

Reinvestigation of the Direct Two-proton Decay of the Long-lived Isomer 94Agm [0.4 s, 6.7 MeV, (21+)]

An attempt to confirm the reported direct one-proton and two-proton decays of the (21+) isomer at 6.7(5) MeV in 94Ag has been made. The 0.39(4) s half-life of the isomer permitted use of a helium-jet system to transport reaction products from the 40Ca + natNi reaction at 197 MeV to a low-background area; 24 gas Delta E-(Si) E detector telescopes were used to identify emitted protons down to 0.4 MeV. No evidence was obtained for two-proton radioactivity with a summed energy of 1.9(1) MeV and a branching ratio of 0.5(3)percent. Two groups of one-proton radioactivity from this isomer had also been reported; our data confirm the lower energy group at 0.79(3) MeV with its branching ratio of 1.9(5)percent.
Date: March 5, 2009
Creator: Cerny, J.; Moltz, D. M.; Lee, D. W.; Perajarvi, K.; Barquest, B. R.; Grossman, L. E. et al.
Object Type: Article
System: The UNT Digital Library
Cloud Scavenging Effects on Aerosol Radiative and Cloud-nucleating Properties - Final Technical Report (open access)

Cloud Scavenging Effects on Aerosol Radiative and Cloud-nucleating Properties - Final Technical Report

The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.
Date: March 5, 2009
Creator: Ogren, John A.; Sheridan, Patrick S. & Andrews, Elisabeth
Object Type: Report
System: The UNT Digital Library
Solid Oxide Fuel Cell Technology Stationary Power Application Project (open access)

Solid Oxide Fuel Cell Technology Stationary Power Application Project

The objectives of this program were to: (1) Develop a reliable, cost-effective, and production-friendly technique to apply the power-enhancing layer at the interface of the air electrode and electrolyte of the Siemens SOFC; (2) Design, build, install, and operate in the field two 5 kWe SOFC systems fabricated with the state-of-the-art cylindrical, tubular cell and bundle technology and incorporating advanced module design features. Siemens successfully demonstrated, first in a number of single cell tests and subsequently in a 48-cell bundle test, a significant power enhancement by employing a power-enhancing composite interlayer at the interface between the air electrode and electrolyte. While successful from a cell power enhancement perspective, the interlayer application process was not suitable for mass manufacturing. The application process was of inconsistent quality, labor intensive, and did not have an acceptable yield. This program evaluated the technical feasibility of four interlayer application techniques. The candidate techniques were selected based on their potential to achieve the technical requirements of the interlayer, to minimize costs (both labor and material), and suitably for large-scale manufacturing. Preliminary screening, utilizing lessons learned in manufacturing tubular cells, narrowed the candidate processes to two, ink-roller coating (IRC) and dip coating (DC). Prototype fixtures were successfully …
Date: March 5, 2009
Creator: Pierre, Joseph
Object Type: Report
System: The UNT Digital Library
APPLICATION OF STIR BAR SORPTIVE EXTRACTION TO ANALYSIS OF VOLATILE AND SEMIVOLATILE ORGANIC CHEMICALS OF POTENTIAL CONCERN IN SOLIDS AND AQUEOUS SAMPLES FROM THE HANFORD SITE (open access)

APPLICATION OF STIR BAR SORPTIVE EXTRACTION TO ANALYSIS OF VOLATILE AND SEMIVOLATILE ORGANIC CHEMICALS OF POTENTIAL CONCERN IN SOLIDS AND AQUEOUS SAMPLES FROM THE HANFORD SITE

Stir bar sorptive extraction was applied to aqueous and solid samples for the extraction and analysis of organic compounds from the Hanford chemicals of potential concern list, as identified in the vapor data quality objectives. The 222-S Laboratory analyzed these compounds from vapor samples on thermal desorption tubes as part of the Hanford Site industrial hygiene vapor sampling effort.
Date: March 5, 2009
Creator: JM, FRYE & JM, KUNKEL
Object Type: Report
System: The UNT Digital Library
Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals (open access)

Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals

Cast nickel-based superalloys are used for blades in land-based, energy conversion and powerplant applications, as well as in aircraft gas turbines operating at temperatures up to 1100 C, where creep is one of the life-limiting factors. Creep of superalloy single crystals has been extensively studied over the last several decades. Surprisingly, only recently has work focused specifically on the dislocation mechanisms that govern high temperature and low stress creep. Nevertheless, the perpetual goal of better engine efficiency demands that the creep mechanisms operative in this regime be fully understood in order to develop alloys and microstructures with improved high temperature capability. At present, the micro-mechanisms controlling creep before and after rafting (the microstructure evolution typical of high temperature creep) has occurred have yet to be identified and modeled, particularly for [001] oriented single crystals. This crystal orientation is most interesting technologically since it exhibits the highest creep strength. The major goal of the program entitled ''Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals'' (DOE Grant DE-FG02-04ER46137) has been to elucidate these creep mechanisms in cast nickel-based superalloys. We have utilized a combination of detailed microstructure and dislocation substructure analysis combined with the development of a novel phase-field …
Date: March 5, 2009
Creator: Mills, Michael J.
Object Type: Report
System: The UNT Digital Library
The KamLAND Full-Volume Calibration System (open access)

The KamLAND Full-Volume Calibration System

We have successfully built and operated a source deployment system for the KamLAND detector. This system was used to position radioactive sources throughout the delicate 1-kton liquid scintillator volume, while meeting stringent material cleanliness, material compatibility, and safety requirements. The calibration data obtained with this device were used to fully characterize detector position and energy reconstruction biases. As a result, the uncertainty in the size of the detector fiducial volume was reduced by a factor of two. Prior to calibration with this system, the fiducial volume was the largest source of systematic uncertainty in measuring the number of antineutrinos detected by KamLAND. This paper describes the design, operation and performance of this unique calibration system.
Date: March 5, 2009
Creator: Collaboration, KamLAND; Berger, B. E.; Busenitz, J.; Classen, T.; Decowski, M. P.; Dwyer, D. A. et al.
Object Type: Article
System: The UNT Digital Library
Microstructural Evolution and interfacial motion in systems with diffusion barriers (open access)

Microstructural Evolution and interfacial motion in systems with diffusion barriers

This research program was designed to model and simulate phase transformations in systems containing diffusion barriers. The modeling work included mass flow, phase formation, and microstructural evolution in interdiffusing systems. Simulation work was done by developing Cahn-Hilliard and phase field equations governing both the temporal and spatial evolution of the composition and deformation fields and other important phase variables.
Date: March 5, 2009
Creator: Leo, Perry H.
Object Type: Report
System: The UNT Digital Library
Novel Low-Cost Process for the Gasification of Biomass and Low-Rank Coals (open access)

Novel Low-Cost Process for the Gasification of Biomass and Low-Rank Coals

Farm Energy envisaged a phased demonstration program, in which a pilot-scale straw gasifier will be installed on a farm. The synthesis gas product will be used to initially (i) generate electricity in a 300 kW diesel generator, and subsequently (ii) used as a feedstock to produce ethanol or mixed alcohols. They were seeking straw gasification and alcohol synthesis technologies that may be implemented on farm-scale. The consortium, along with the USDA ARS station in Corvallis, OR, expressed interest in the dual-bed gasification concept promoted by WRI and Taylor Energy, LLC. This process operated at atmospheric pressure and employed a solids-circulation type oxidation/reduction cycle significantly different from traditional fluidized-bed or up-draft type gasification reactors. The objectives of this project were to perform bench-scale testing to determine technical feasibility of gasifier concept, to characterize the syngas product, and to determine the optimal operating conditions and configuration. We used the bench-scale test data to complete a preliminary design and cost estimate for a 1-2 ton per hour pilot-scale unit that is also appropriate for on-farm scale applications. The gasifier configuration with the 0.375-inch stainless steel balls recirculating media worked consistently and for periods up to six hours of grass feed. The other principle …
Date: March 5, 2009
Creator: Barton, Thomas
Object Type: Report
System: The UNT Digital Library
Planarization of High Aspect Ratio P-I-N Diode Pillar Arrays for Blanket Electrical Contacts (open access)

Planarization of High Aspect Ratio P-I-N Diode Pillar Arrays for Blanket Electrical Contacts

Two planarization techniques for high aspect ratio three dimensional pillar structured P-I-N diodes have been developed in order to enable a continuous coating of metal on the top of the structures. The first technique allows for coating of structures with topography through the use of a planarizing photoresist followed by RIE etch back to expose the tops of the pillar structure. The second technique also utilizes photoresist, but instead allows for planarization of a structure in which the pillars are filled and coated with a conformal coating by matching the etch rate of the photoresist to the underlying layers. These techniques enable deposition using either sputtering or electron beam evaporation of metal films to allow for electrical contact to the tops of the underlying pillar structure. These processes have potential applications for many devices comprised of 3-D high aspect ratio structures. Two separate processes have been developed in order to ensure a uniform surface for deposition of an electrode on the {sup 10}Boron filled P-I-N pillar structured diodes. Each uses S1518 photoresist in order to achieve a relatively uniform surface despite the non-uniformity of the underlying detector. Both processes allow for metallization of the final structure and provide good electrical …
Date: March 5, 2009
Creator: Voss, L F; Shao, Q; Reinhardt, C E; Graff, R T; Conway, A M; Nikolic, R J et al.
Object Type: Article
System: The UNT Digital Library