Advanced fusion diagnostics. Final technical report, July 15, 1991--July 14, 1993 (open access)

Advanced fusion diagnostics. Final technical report, July 15, 1991--July 14, 1993

Key among various issues of ignited plasmas is understanding the physics of energy transfer between thermal plasma particles and magnetically confined, highly energetic charged ions in a tokamak device. The superthermal particles are products of fusion reactions. The efficiency of energy transfer by collisions, from charged fusion products (e.g., {alpha}-particles) to plasma ions, grossly determines whether or not plasma conditions are self-sustaining without recourse to auxiliary heating. Furthermore, should energy transfer (efficiency be poor, and substantial auxiliary heating power is required to maintain reacting conditions within the plasma, economics may preclude commercial viability of fusion reactors. The required charged fusion product information is contained in the energy distribution function of these particles. Knowledge of temporal variations of the superthermal particle energy distribution function could be used by a fusion reactor control system to balance plasma conditions between thermal runaway and a modicum of fusion product energy transfer. Therefore, diagnostics providing data on the dynamical transfer of alpha-particle and other charged fusion product energy to the plasma ions are essential elements for a fusion reactor control system to insure that proper plasma conditions are maintained. The objective of this work is to assess if spectral analysis of rf radiation emitted by …
Date: July 14, 1993
Creator: Moses, K. G.
Object Type: Report
System: The UNT Digital Library
Characterization of short pulse laser-produced plasmas at the Lawrence Livermore National Laboratory ultra short-pulse laser (open access)

Characterization of short pulse laser-produced plasmas at the Lawrence Livermore National Laboratory ultra short-pulse laser

The K-shell emission from porous aluminum targets is used to infer the density and temperature of plasmas created with 800 nm and 400 nm, 140 fs laser light. The laser beam is focused to a minimum spot size of 5 {mu}m with 800 nm light and 3 {mu}m with 400 nm light, producing a normal incidence peak intensity of 10{sup 18} Watts/cm{sup 2}. A new 800 fs x-ray streak camera is used to study the broadband x-ray emission. The time resolved and time integrated x-ray emission implies substantial differences between the porous target and the flat target temperature.
Date: July 14, 1993
Creator: Shepherd, R.; Price, D.; White, W.; Osterheld, A.; Walling, R.; Goldstein, W. et al.
Object Type: Article
System: The UNT Digital Library
Ecosystems, Biomes, and Watersheds: Definitions and Use (open access)

Ecosystems, Biomes, and Watersheds: Definitions and Use

This paper describes the meaning and applications of ecosystem and of the related terms watershed and biome. It discusses the pros and cons of all three as organizing principles for land management, and the major issues that are likely to arise in the debate over ecosystem management.
Date: July 14, 1993
Creator: Corn, M. Lynne
Object Type: Report
System: The UNT Digital Library
Fundamental studies of coal liquefaction. Quarterly report No. 7, April 1--July 1, 1993 (open access)

Fundamental studies of coal liquefaction. Quarterly report No. 7, April 1--July 1, 1993

In our last report we discussed observations in our cell concerning the behavior or Illinois No. 6 coal in tetralin to 460{degrees}C. We noted that there were possibly two distinct types of particles comprising the organic phase, reacting respectively at 420{degrees}--430{degrees}C, and at 450{degrees}--460{degrees}C. Alternatively we could interpret the data as describing a range of reactivity bounded by those temperatures. As evidenced by the contraction of the particles, the reactions were rapid. The particles lost half of their substance within 1 min, and we suggested that the rates were too fast to be accommodated by the commonly held scheme for coal liquefaction involving thermolytic scission of weak, bibenzyl-like bonds. Our analyses were aided by our use of Adobe Photoshop, which allows us to store, digitized versions of our recorded images. The images can then be manipulated at will to provide quantitative data on morphological changes. We noted in our last report that printer limitations prevented us from presenting images with the desirable quality, and we are at present attempting to find access to equipment which will provide satisfactory figures. Accordingly our progress will be described here without any photographs, and we expect to present a more complete account of our …
Date: July 14, 1993
Creator: Ross, D. S.
Object Type: Report
System: The UNT Digital Library
Optimum extracted H{sup {minus}} and D{sup {minus}} current densities from gas-pressure-limited high-power hydrogen/deuterium tandem ion sources (open access)

Optimum extracted H{sup {minus}} and D{sup {minus}} current densities from gas-pressure-limited high-power hydrogen/deuterium tandem ion sources

The tandem hydrogen/deuterium ion source is modelled for the purpose of identifying the maximum current densities that can be extracted subject to the gas-pressure constraints proposed for contemporary beam-line systems. Optimum useful extracted current densities are found to be in the range of approximately 7 to 10 mA cm{sup {minus}2}. The sensitivity of these current densities is examined subject to uncertainties in the underlying atomic/molecular rate processes; A principal uncertainty remains the quantification of the molecular vibrational distribution following H{sub 3{sup +}} wall collisions.
Date: July 14, 1993
Creator: Hiskes, J. R.
Object Type: Article
System: The UNT Digital Library
Resonance ionization spectroscopy of molecules, clusters, and ions. Annual technical progress report (open access)

Resonance ionization spectroscopy of molecules, clusters, and ions. Annual technical progress report

High resolution photoionization and fluorescence excitation spectra of dimers of the aromatic molecule fluorene (C{sub 13}H{sub 12}){sub 2} reveal complex excitonic interactions. Comparison of results for isotopically pure and isotopically mixed dimers provide the information necessary to analyze the spectra in terms of intermolecular motion on two perturbed adiabatic potential surfaces. The intermolecular force field on the lower surface is characterized by a perturbed quartic potential, whereas the upper surface is characterized by a displaced quadratic potential. The results provide the first detailed experimental description of strong coupling between an intermolecular coordinate and the excitonic state of a molecular dimer.
Date: July 14, 1993
Creator: Wessel, J.
Object Type: Report
System: The UNT Digital Library
Validation of criticality safety calculational methods for U-AVLIS plant project (open access)

Validation of criticality safety calculational methods for U-AVLIS plant project

The objectives of the Uranium Atomic Vapor Laser isotope Separation (U-AVLIS) are to develop, demonstrate, and deploy a laser-based process to enrich natural uranium in the U-235 isotope to levels useful as fuel in commercial light-water power reactors. Current U-AVLIS production plant criteria call for uranium product enriched in {sup 235}U up to 5 wt%. Development of the U-AVLIS technology is in an advanced stage, and demonstration of the integrated enrichment process is currently in progress using plant-scale equipment in the Uranium Demonstration System (UDS) at Lawrence Livermore National Laboratory. In this paper several existing experimental data which are applicable to the critical systems of importance to the safe design of the U-AVLIS plant are identified. These were used to benchmark a configuration-controlled, work station based version of one state-of-the-art computer code employed by the U-AVLIS program in UDS equipment design, and in U-AVLIS plant conceptual design NCS analyses.
Date: July 14, 1993
Creator: Lewis, K. D.
Object Type: Article
System: The UNT Digital Library