Simulation of Plasma Fluxes to Material Surfaces with Self-Consistent Edge Turbulence and Transport for Tokamaks (open access)

Simulation of Plasma Fluxes to Material Surfaces with Self-Consistent Edge Turbulence and Transport for Tokamaks

The edge-plasma profiles and fluxes to the divertor and walls of a divertor tokamak with a magnetic X-point are simulated by coupling a 2D transport code (UEDGE) and a 3D turbulence code (BOUT). An relaxed iterative coupling scheme is used where each code is run on its characteristic time scale, resulting in a statistical steady state. Plasma variables of density, parallel velocity, and separate ion and electron temperatures are included, together with a fluid neutral model for recycling neutrals at material surfaces. Results for the DIII-D tokamak parameters show that the turbulence is preferentially excited in the outer radial region of the edge where magnetic curvature is destabilizing and that substantial plasma particle flux is transported to the main chamber walls. These results are qualitatively consistent with some experimental observations. The coupled transport/turbulence simulation technique provides a strategy to understanding edge-plasma physics in more detailed than previously available and to significantly enhance the realism of predictions of the performance of future devices.
Date: May 24, 2004
Creator: Rognlien, T.; Umansky, M.; Xu, X.; Cohen, R. & LoDestro, L.
Object Type: Article
System: The UNT Digital Library
The Effect of Scale on the Mechanical Properties of Jointed Rock Masses (open access)

The Effect of Scale on the Mechanical Properties of Jointed Rock Masses

These notes were prepared for presentation at the Defense Threat Reduction Agency's (DTRA) Hard Target Research and Analysis Center (HTRAC), at the occasion of a short course held on June 14-15, 2004. The material is intended for analysts who must evaluate the geo-mechanical characteristics of sites of interest, in order to provide appropriate input to calculations of ground shock effects on underground facilities in rock masses. These analysts are associated with the Interagency Geotechnical Assessment Team (IGAT). Because geological discontinuities introduce scale effects on the mechanical properties of rock formations, these large-scale properties cannot be estimated on the basis of tests on small cores.
Date: May 24, 2004
Creator: Heuze, Francois E.
Object Type: Report
System: The UNT Digital Library
Comparison of Plasma Parameters Between QH and ELMing Phases of the Same Discharges (open access)

Comparison of Plasma Parameters Between QH and ELMing Phases of the Same Discharges

H-mode confinement is observed for many energy confinement times without edge localized modes (ELMs) in QH (quiescent high-confinement)-mode discharges in DIII-D. To find critical differences between ELMing and QH modes we compared electron temperature (T{sub e}), density (n{sub e}), and ion temperature (T{sub i}), in the pedestal and scrape-off layer (SOL) for a group of discharges. We also compared the electron pressures P{sub ped}, and maximum pressure gradients P{sub e,ped,max grad} because of their importance in confinement and stability. Experimental results show that the core line averaged density, median T{sub e} (pedestal), SOL T{sub e}, and T{sub e} pedestal width, and SOL T{sub i} are nearly the same in QH mode as that during ELMs. The n{sub e} (average pedestal), n{sub e} pedestal width, P{sub ped}, and P{sub e,ped,max grad} are similar to corresponding values in QH mode and at various times between ELMs. However, the pedestal T{sub i} is 1.6 times higher in QH mode than during ELMing.
Date: May 24, 2004
Creator: Lasnier, C.; West, W.; Burrell, K.; deGrassie, J.; Doyle, E. & Osborne, T.
Object Type: Article
System: The UNT Digital Library
Benchmarking optimization software with COPS 3.0. (open access)

Benchmarking optimization software with COPS 3.0.

The authors describe version 3.0 of the COPS set of nonlinearly constrained optimization problems. They have added new problems, as well as streamlined and improved most of the problems. They also provide a comparison of the FILTER, KNITRO, LOQO, MINOS, and SNOPT solvers on these problems.
Date: May 24, 2004
Creator: Dolan, E. D.; More, J. J. & Munson, T. S.
Object Type: Report
System: The UNT Digital Library
New physics searches with photons in CDF (open access)

New physics searches with photons in CDF

A brief review of searches for physics beyond the Standard Model with photons using the CDF detector at the Tevatron is given here. These include searches for supersymmetry, extra dimensions, excited electrons and W/Z+{gamma} production, as well as anomalous photon production. Recent results from CDF Run II experiment are presented, but some results from Run I are also reviewed.
Date: May 24, 2004
Creator: Lee, Sungwon
Object Type: Article
System: The UNT Digital Library
Fast-neutrons incident on gadolinium. (open access)

Fast-neutrons incident on gadolinium.

Reports in the Argonne National Laboratory Nuclear Data and Measurement Series present results of studies in the field of microscopic nuclear data. The primary objective of the series is the dissemination of information in the comprehensive form required for nuclear technology applications. This Series is devoted to: (a) measured microscopic nuclear parameters, (b) experimental techniques and facilities employed in measurements, (c) the analysis, correlation and interpretation of nuclear data, and (d) the compilation and evaluation of nuclear data. Contributions to this Series are reviewed to assure technical competence and, unless otherwise stated, the contents can be formally referenced. This Series does not supplant formal journal publication, but it does provide the more extensive information required for technological applications (e.g., tabulated numerical data) in a timely manner.
Date: May 24, 2004
Creator: Smith, A. B.
Object Type: Report
System: The UNT Digital Library
Measurement of {gamma}{sub T} with the {gamma}{sub T} quads on and off (open access)

Measurement of {gamma}{sub T} with the {gamma}{sub T} quads on and off

An experimental procedure for measuring {gamma}{sub T} has been developed and tested in two different measurements, with the {gamma}{sub T} quads on and off. The results were compared to MAD calculations. The discrepancy between the measured {gamma}{sub T} and the calculated {gamma}{sub T} is less than 5%.
Date: May 24, 2004
Creator: Xi Yang, James MacLachlan and Charles M. Ankenbrandt
Object Type: Report
System: The UNT Digital Library
Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale (open access)

Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe, which give rise to flow tones, are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, …
Date: May 24, 2004
Creator: Oshkai, P; Geveci, M; Rockwell, D & Pollack, M
Object Type: Report
System: The UNT Digital Library
Elimination of Whole Effluent Toxicity NPDES Permit Limits through the Use of an Alternative Testing Species and Reasonable Potential Analysis (open access)

Elimination of Whole Effluent Toxicity NPDES Permit Limits through the Use of an Alternative Testing Species and Reasonable Potential Analysis

The cladoceran, Ceriodaphnia dubia (C. dubia), is required by the State of South Carolina to be used in whole effluent toxicity (WET) compliance tests in order to meet limits contained within National Pollutant Discharge Elimination System (NPDES) permits. Westinghouse Savannah River Company (WSRC) experienced WET test failures for no clear reason over a long period of time. Toxicity identification examinations on effluents did not indicate the presence of toxicants; therefore, the WET test itself was brought under suspicion. Research was undertaken with an alternate cladoceran, Daphnia ambigua (D. ambigua). It was determined that this species survives better in soft water, so approval was obtained from regulating authorities to use this ''alternate'' species in WET tests. The result was better test results and elimination of non-compliances. The successful use of D. ambigua allowed WSRC to gain approval from the South Carolina Department of Health and Environmental Control (SCDHEC) to remove WET limits from the NPDES permit.
Date: May 24, 2004
Creator: PAYNE, W.L.
Object Type: Article
System: The UNT Digital Library
TOUGHREACT User's Guide: A Simulation Program for Non-isothermal Multiphase Reactive geochemical Transport in Variable Saturated Geologic Media (open access)

TOUGHREACT User's Guide: A Simulation Program for Non-isothermal Multiphase Reactive geochemical Transport in Variable Saturated Geologic Media

Coupled modeling of subsurface multiphase fluid and heat flow, solute transport and chemical reactions can be used for the assessment of mineral alteration in hydrothermal systems, waste disposal sites, acid mine drainage remediation, contaminant transport, and groundwater quality. A comprehensive non-isothermal multi-component reactive fluid flow and geochemical transport simulator, TOUGHREACT, has been developed. A wide range of subsurface thermo-physical-chemical processes is considered under various thermohydrological and geochemical conditions of pressure, temperature, water saturation, and ionic strength. The program can be applied to one-, two- or three-dimensional porous and fractured media with physical and chemical heterogeneity. The model can accommodate any number of chemical species present in liquid, gas and solid phases. A variety of equilibrium chemical reactions are considered, such as aqueous complexation, gas dissolution/exsolution, and cation exchange. Mineral dissolution/precipitation can proceed either subject to local equilibrium or kinetic conditions. Changes in porosity and permeability due to mineral dissolution and precipitation can be considered. Linear adsorption and decay can be included. For the purpose of future extensions, surface complexation by double layer model is coded in the program. Xu and Pruess (1998) developed a first version of a non-isothermal reactive geochemical transport model, TOUGHREACT, by introducing reactive geochemistry into the …
Date: May 24, 2004
Creator: Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas & Pruess, Karsten
Object Type: Report
System: The UNT Digital Library
Investigation on a summer operation effect of a district energy system at Kitakyushu science research city (open access)

Investigation on a summer operation effect of a district energy system at Kitakyushu science research city

In Kitakyushu Science and Research Park, a new district energy system has been introduced. In this study, we chose this system as a case study and have carried out an analysis on the efficiency of the power generation and heat release utilization of the fuel cell and gas engine in summer by using the recorded data. The results can be summarized as follows; (1) Although the power generation efficiencies of the gas engine and fuel cell are a little bit lower than the standard designated value, they are almost running at stable condition. (2) The collected heat energy is lower than the designated value. The heat release utilization, which is used for cooling and hot water, is fairly low. Considering the efficient use of energy, it is a key to have a good use of heat release when we introduce a district energy system. (3) The discarded heat energy of the system is very big in this investigation when evaluating the system as a whole. It is fundamental to the future of energy conservation to use primary energy more efficiently.
Date: May 24, 2004
Creator: Gao, Weijun; Zhou, Nan; Nishida, Masaru; Sagara, Noriyasu; Ryu, Yuji & Ojima, Toshio
Object Type: Article
System: The UNT Digital Library
Estimation of Particle Flux and Remineralization Rate from Radioactive Disequilibrium (open access)

Estimation of Particle Flux and Remineralization Rate from Radioactive Disequilibrium

Reactive radionuclides, such as the thorium isotopes, show measurable deficiencies in the oceanic water column because of their removal by chemical scavenging due to the particle flux. Measurement of the deficiency, coupled with measurement of the radionuclide concentration in particles, allows a determination of the effective particle sinking velocity. Results to date suggest that the effective particle sinking velocity is remarkably invariant with depth. This leads to the tentative suggestion that POC concentration profiles may, to a good approximation, be used directly to determine length scales for the remineralization of sinking organic matter. Further measurements are in progress to test this idea and to evaluate its limitations. Knowledge of the remineralization length scale is essential to an evaluation of the efficiency of the biological pump as a means for deep sequestering of carbon in the ocean.
Date: May 24, 2004
Creator: Bacon, Michael P. & Francois, Roger
Object Type: Report
System: The UNT Digital Library
Simulation of Plasma Fluxes to Material Surfaces with Self-consistent Edge Turbulence and Transport for Tokamaks (open access)

Simulation of Plasma Fluxes to Material Surfaces with Self-consistent Edge Turbulence and Transport for Tokamaks

The edge-plasma profiles and fluxes to the divertor and walls of a divertor tokamak with a magnetic X-point are simulated by coupling a 2D transport code (UEDGE) and a 3D turbulence code (BOUT). An relaxed iterative coupling scheme is used where each code is run on its characteristic time scale, resulting in a statistical steady state. Plasma variables of density, parallel velocity, and separate ion and electron temperatures are included, together with a fluid neutral model for recycling neutrals at material surfaces. Results for the DIII-D tokamak parameters show that the turbulence is preferentially excited in the outer radial region of the edge where magnetic curvature is destabilizing and that substantial plasma particle flux is transported to the main chamber walls. These results are qualitatively consistent with some experimental observations. The coupled transport/turbulence simulation technique provides a strategy to understanding edge-plasma physics in more detailed than previously available and to significantly enhance the realism of predictions of the performance of future devices
Date: May 24, 2004
Creator: Rognlien, T.; Umanksy, M.; Xu, X.; Cohen, R. & LoDestro, L.
Object Type: Article
System: The UNT Digital Library
Design and Characterization of a Neutralized-Transport Experiment for Heavy-Ion Fusion (open access)

Design and Characterization of a Neutralized-Transport Experiment for Heavy-Ion Fusion

In heavy-ion inertial-confinement fusion systems, intense beams of ions must be transported from the exit of the final focus magnet system through the fusion chamber to hit millimeter-sized spots on the target. Effective plasma neutralization of intense ion beams in this final transport is essential for a heavy-ion fusion power plant to be economically competitive. The physics of neutralized drift has been studied extensively with particle-in-cell simulations. To provide quantitative comparisons of theoretical predictions with experiment, the Virtual National Laboratory for Heavy Ion Fusion has completed the construction and has begun experimentation with the Neutralized Transport Experiment (NTX). The experiment consists of three main sections, each with its own physics issues. The injector is designed to generate a very high-brightness, space-charge-dominated potassium beam while still allowing variable perveance by a beam aperturing technique. The magnetic-focusing section, consisting of four pulsed magnetic quadrupoles, permits the study of beam tuning, as well as the effects of phase space dilution due to higher-order nonlinear fields. In the final section, a converging ion beam exiting the magnetic section is transported through a drift region with plasma sources for beam neutralization, and the final spot size is measured under various conditions of neutralization. In this …
Date: May 24, 2004
Creator: Henderson, E.; Eylon, S.; Roy, P.; Yu, S. S.; Anders, A.; Bieniosek, F. M. et al.
Object Type: Article
System: The UNT Digital Library
ANSI/ANS 8.12, Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside Reactors (open access)

ANSI/ANS 8.12, Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside Reactors

None
Date: May 24, 2004
Creator: Huang, S T
Object Type: Article
System: The UNT Digital Library
Deuterium Experiments in the Sustained Spheromak Physics Experiment (open access)

Deuterium Experiments in the Sustained Spheromak Physics Experiment

In this paper we report on the results of isotope exchange experiments in the Sustained Spheromak Physics Experiment (SSPX). We have compared {approx}500 deuterium discharges with similar discharges in hydrogen. Typically, we produce plasmas with peak toroidal currents in the range of 0.6 MA, electron temperatures (T{sub e}) of {approx}200 eV and energy confinement times ({tau}{sub E}) of {approx}200 {micro}s. The D{sub 2} fueled discharges show similar results to those with H{sub 2} fueling with no obvious differences in confinement time. Electron temperatures of {approx}200 eV with similar electron densities were observed. Both the deuterium and hydrogen fueled discharges have a calculated thermal conduction below {chi}{sub e}<10 m{sup 2}/s. However, the D{sub 2} fueled discharges had a modest increase in high-Z (titanium) impurity content suggesting an increase of physical sputtering. We find no significant mass scaling effects.
Date: May 24, 2004
Creator: Wood, R; Hill, D N; Hooper, E; McLean, H; Ryutov, D & Woodruff, S
Object Type: Article
System: The UNT Digital Library
Xradia Performance Summary - Update (open access)

Xradia Performance Summary - Update

High Energy Density Physics (HEDP) Experiments play an important role in corroborating the improved physics codes that underlie LLNL's Stockpile Stewardship mission. Conducting these experiments, whether on the National Ignition Facility (NIF) or another national facility such as Omega, will require not only improvement in the diagnostics for measuring the experiment, but also detailed knowledge of the as-built target components and assemblies themselves. To assist in this effort, a defined set of well-known reference standards designed to represent a range of HEDP targets have been built and are being used to quantify the performance of different characterization techniques. Without the critical step of using reference standards for qualifying characterization tools there can be no verification of either commercial or internallydeveloped characterization techniques and thus an uncertainty in the as-built-model for the initial condition to the physics codes.
Date: May 24, 2004
Creator: Waters, A M; Martz, H E; Chinn, D J; Logan, C M; Gross, J C & Scott, D
Object Type: Report
System: The UNT Digital Library
Degradation of Magnet Epoxy at NSLS X-Ray Ring. (open access)

Degradation of Magnet Epoxy at NSLS X-Ray Ring.

Epoxy resin degradation was analyzed for NSLS X-ring magnets after two decades of 2.58-2.8 GeV continuous electron-beam operation, based on results obtained from thermoluminescent dosimeters irradiated along the NSLS ring and epoxy samples irradiated at the beamline target location. A Monte Carlo-based particle transport code, MCNP, was utilized to verify the dose from synchrotron radiation distributed along the axial- and transverse-direction in a ring model, which simulates the geometry of a ring quadrupole magnet and its central vacuum chamber downstream of the bending-magnet photon ports. The actual life expectancy of thoroughly vacuum baked-and-cured epoxy resin was estimated from radiation tests on similar polymeric materials using a radiation source developed for electrical insulation and mechanical structure studies.
Date: May 24, 2004
Creator: HU,J. P.; Zhong, Z.; Haas, E.; Hulbert, S. & Hubbard, R.
Object Type: Article
System: The UNT Digital Library
Natural Analogue Synthesis Report (open access)

Natural Analogue Synthesis Report

None
Date: May 24, 2004
Creator: Simmons, A. M.
Object Type: Report
System: The UNT Digital Library