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Planning for an integrated research experiment (open access)

Planning for an integrated research experiment

We describe the goals and research program leading to the Heavy Ion Integrated Research Experiment (IRE). We review the basic constraints which lead to a design and give examples of parameters and capabilities of an IRE. We also show design tradeoffs generated by the systems code IBEAM.
Date: March 25, 2001
Creator: Barnard, J. J.; Ahle, L. E.; Bangerter, R. O.; Bieniosek, F. M.; Celata, C. M.; Faltens, A. et al.
System: The UNT Digital Library
Beam Simulations for IRE and Driver - Status and Strategy (open access)

Beam Simulations for IRE and Driver - Status and Strategy

The methods and codes employed in the U.S. Heavy Ion Fusion program to simulate the beams in an Integrated Research Experiments (IRE) facility and a fusion driver are presented in overview. A new family of models incorporating accelerating module impedance, multi-beam, and self-magnetic effects is described, and initial WARP3d particle simulations of beams using these models are presented. Finally, plans for streamlining the machine-design simulation sequence, and for simulating beam dynamics from the source to the target in a consistent and comprehensive manner, are described.
Date: March 13, 2001
Creator: Friedman, A; Grote, D P & Lee, E P
System: The UNT Digital Library
Heats of Formation of Energetic Oxetane Monomers and Polymers (open access)

Heats of Formation of Energetic Oxetane Monomers and Polymers

Energetic oxetane polymers have shown promise as performance-enhancing ingredients in gun and missile propellants. In order to correctly predict the performance of energetic materials containing these polymers, it is important to have accurate, experimentally determined values for the polymer heats of formation ({Delta}H{sub f}). In support of a theoretical study on gun propellant performance, heats of combustion were experimentally determined for a series of oxetane polymers and monomers (see below) using combustion calorimetry, and from these, {Delta}H{sub f} values were calculated. Polymers included BAMO/AMMO, BAMO/NMMO (polyol and TPE), and BNMO/NMMO mixtures. In order to calculate the {Delta}H{sub f} of the polymers from heat of combustion data, a number of assumptions were made regarding the polymer structure and molecular weight. A comparison of the {Delta}H{sub f} values for the monomers and polymers were made, and these values were compared to heats of formation measured elsewhere.
Date: March 21, 2001
Creator: Schmidt, R D & Manser, G E
System: The UNT Digital Library
Status of Optical Coatings for the National Ignition Facility (open access)

Status of Optical Coatings for the National Ignition Facility

Optical coatings are a crucial part of the pulse trapping and extraction in the NIF multipass amplifiers. Coatings also steer the 192 beams from four linear arrays to four converging cones entering the target chamber. There are a total of 1600 physical vapor deposited coatings on NIF consisting of 576 mirrors within the multipass cavity, 192 polarizers that work in tandem with a Pockels cell to create an optical switch, and 832 transport mirrors. These optics are of sufficient size so that they are not aperture-limiting for the 40-cm x 40 cm beams over an incident range of 0 to 56.4 degrees. These coatings must withstand laser fluences up to 25 J/cm{sup 2} at 1053 nm (1 {omega}) and 3-ns pulse length and are the 1{omega} fluence-limiting component on NIF. The coatings must have a minimal impact on the beam wavefront and phase to maintain beam focusability, minimize scattered loss, and minimize nonlinear damage mechanisms. This is achieved by specifications ranging from <50 MPa coating stress, <1% coating nonuniformity, <4{angstrom} RMS surface roughness, and a PSD specification to control the amplitude of periodic spatial frequencies. Finally, the primary mission of optical coatings is efficient beam steering so reflection and transmission …
Date: March 5, 2001
Creator: Stolz, C. J.; Weinzapfel, C.; Rogowski, G. T.; Smith, D.; Rigatti, A.; Oliver, J. et al.
System: The UNT Digital Library
Thermal Decomposition of Trinitrotoluene (TNT) with a New One-Dimensional Time to Explosion (ODTX) Apparatus (open access)

Thermal Decomposition of Trinitrotoluene (TNT) with a New One-Dimensional Time to Explosion (ODTX) Apparatus

The thermal explosion of trinitrotoluene (TNT) is used as a basis for evaluating the performance of a new One-Dimensional-Time-to-Explosion (ODTX) apparatus. The ODTX experiment involves holding a 12.7 mm-diameter spherical explosive sample under confinement (150 MPa) at a constant elevated temperature until the confining pressure is exceeded by the evolution of gases during chemical decomposition. The resulting time to explosion as a function of temperature provides valuable decomposition kinetic information. A comparative analysis of the measurements obtained from the new unit and an older system is presented. Discussion on selected performance aspects of the new unit will also be presented. The thermal explosion of TNT is highly dependent on the material. Analysis of the time to explosion is complicated by historical and experimental factors such as material variability, sample preparation, temperature measurement and system errors. Many of these factors will be addressed. Finally, a kinetic model using a coupled thermal and heat transport code (chemical TOPAZ) was used to match the experimental data.
Date: March 23, 2001
Creator: Tran, T. D.; Simpson, R. L.; Maienschein, J. & Tarver, Craig M.
System: The UNT Digital Library
Relative Advantages of Direct and Indirect Drive for an Inertial Fusion Energy Power Plant Driven by a Diode-Pumped Solid-State Laser (open access)

Relative Advantages of Direct and Indirect Drive for an Inertial Fusion Energy Power Plant Driven by a Diode-Pumped Solid-State Laser

This paper reviews our current understanding of the relative advantages of direct drive (DD) and indirect drive (ID) for a 1 GWe inertial fusion energy (IFE) power plant driven by a diode-pumped solid-state laser (DPSSL). This comparison is motivated by a recent study (1) that shows that the projected cost of electricity (COE) for DD is actually about the same as that for ID even though the target gain for DD can be much larger. We can therefore no longer assume that DD is the ultimate targeting scenario for IFE, and must begin a more rigorous comparison of these two drive options. The comparison begun here shows that ID may actually end up being preferred, but the uncertainties are still rather large.
Date: March 6, 2001
Creator: Orth, C D
System: The UNT Digital Library
Operation of a Four-Cylinder 1.9L Propane Fueled Homogeneous Charge Compression Ignition Engine: Basic Operating Characteristics and Cylinder-to-Cylinder Effects (open access)

Operation of a Four-Cylinder 1.9L Propane Fueled Homogeneous Charge Compression Ignition Engine: Basic Operating Characteristics and Cylinder-to-Cylinder Effects

A four-cylinder 1.9 Volkswagen TDI Engine has been converted to run in Homogeneous Charge Compression Ignition (HCCI) mode. The stock configuration is a turbocharged direct injection Diesel engine. The combustion chamber has been modified by discarding the in-cylinder Diesel fuel injectors and replacing them with blank inserts (which contain pressure transducers). The stock pistons contain a reentrant bowl and have been retained for the tests reported here. The intake and exhaust manifolds have also been retained, but the turbocharger has been removed. A heater has been installed upstream of the intake manifold and fuel is added just downstream of this heater. The performance of this engine in naturally aspirated HCCI operation, subject to variable intake temperature and fuel flow rate, has been studied. The engine has been run with propane fuel at a constant speed of 1800 rpm. This work is intended to characterize the HCCI operation of the engine in this configuration that has been minimally modified from the base Diesel engine. The performance (BMEP, IMEP, efficiency, etc) and emissions (THC, CO, NOx) of the engine are presented, as are combustion process results based on heat release analysis of the pressure traces from each cylinder.
Date: March 12, 2001
Creator: Flowers, D.; Aceves, S. M.; Martinez-Frias, J.; Smith, J. R.; Au, M.; Girard, J. et al.
System: The UNT Digital Library
Measurement of synchrotron pulse durations using surfacephotovoltage transients (open access)

Measurement of synchrotron pulse durations using surfacephotovoltage transients

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Date: March 20, 2001
Creator: Glover, T. E.; Ackermann, G. D.; Belkacem, A.; Feinberg, B.; Heimann, P. A.; Hussain, Z. et al.
System: The UNT Digital Library
Automated Sorting of Transuranic Waste (open access)

Automated Sorting of Transuranic Waste

The HANDSS-55 Transuranic Waste Sorting Module is designed to sort out items found in 55-gallon drums of waste as determined by an operator. Innovative imaging techniques coupled with fast linear motor-based motion systems and a flexible end-effector system allow the operator to remove items from the waste stream by a touch of the finger. When all desired items are removed from the waste stream, the remaining objects are automatically moved to a repackaging port for removal from the glovebox/cell. The Transuranic Waste Sorting Module consists of 1) a high accuracy XYZ Stereo Measurement and Imaging system, 2) a vibrating/tilting sorting table, 3) an XY Deployment System, 4) a ZR Deployment System, 5) several user-selectable end-effectors, 6) a waste bag opening system, 7) control and instrumentation, 8) a noncompliant waste load-out area, and 9) a Human/Machine Interface (HMI). The system is modular in design to accommodate database management tools, additional load-out ports, and other enhancements. Manually sorting the contents of a 55-gallon drum takes about one day per drum. The HANDSS-55 Waste Sorting Module is designed to significantly increase the throughput of this sorting process by automating those functions that are strenuous and tiresome for an operator to perform. The Waste …
Date: March 1, 2001
Creator: Shurtliff, Rodney Marvin
System: The UNT Digital Library
Remote Laser Diffraction Particle Size Distribution Analyzer (open access)

Remote Laser Diffraction Particle Size Distribution Analyzer

In support of a radioactive slurry sampling and physical characterization task, an “off-the-shelf” laser diffraction (classical light scattering) particle size analyzer was utilized for remote particle size distribution (PSD) analysis. Spent nuclear fuel was previously reprocessed at the Idaho Nuclear Technology and Engineering Center (INTEC—formerly recognized as the Idaho Chemical Processing Plant) which is on DOE’s INEEL site. The acidic, radioactive aqueous raffinate streams from these processes were transferred to 300,000 gallon stainless steel storage vessels located in the INTEC Tank Farm area. Due to the transfer piping configuration in these vessels, complete removal of the liquid can not be achieved. Consequently, a “heel” slurry remains at the bottom of an “emptied” vessel. Particle size distribution characterization of the settled solids in this remaining heel slurry, as well as suspended solids in the tank liquid, is the goal of this remote PSD analyzer task. A Horiba Instruments Inc. Model LA-300 PSD analyzer, which has a 0.1 to 600 micron measurement range, was modified for remote application in a “hot cell” (gamma radiation) environment. This technology provides rapid and simple PSD analysis, especially down in the fine and microscopic particle size regime. Particle size analysis of these radioactive slurries down in …
Date: March 1, 2001
Creator: Batcheller, Thomas Aquinas; Huestis, Gary Michael & Bolton, Steven Michael
System: The UNT Digital Library
Building Safer Communities: The Integrated Community Safety Approach (open access)

Building Safer Communities: The Integrated Community Safety Approach

This paper discusses an integrated community safety approach to creating safer communities. It defines community broadly to include two categories of community members: “industry” and “neighbors.” Potential community members within the “industry” category include facilities, government/regulators, customers, stockholders, and suppliers. Within the “neighbors” category are towns, cities, counties, states; people/commodity flow systems; news media and special interest groups; environment; and families of employees. Each of these potential community members and its characteristics are discussed. The integrated community safety approach consists of three major activities: (1) define the boundaries of the community; (2) facilitate the sense of community; and (3) address the needs of the community. Defining the boundaries of the community includes determining the geographical and social boundaries; this is accomplished through conducting a hazard analysis and community involvement to identify all of the community members. Facilitating the sense of community includes conducting a capability/needs assessment and continuing community involvement to identify the issues and concerns of community members. Addressing the needs of the community involves master planning to consider safety issues in all community development actions and continuing community education and involvement. The integrated community safety approach is a workable approach for existing industries and their neighbors as well …
Date: March 1, 2001
Creator: Fawcett, Ricky Lee; Kerr, Thomas A & Jordan, Steven Albert
System: The UNT Digital Library
Roadmapping the Resolution of Gas Generation Issues in Packages Containing Radioactive Waste/Materials (open access)

Roadmapping the Resolution of Gas Generation Issues in Packages Containing Radioactive Waste/Materials

Gas generation issues, particularly hydrogen, have been an area of concern for the transport and storage of radioactive materials and waste in the Department of Energy (DOE) complex. Potentially combustible gases can be generated through a variety of reactions, including chemical reactions and radiolytic decomposition of hydrogen-containing materials. Transportation regulations prohibit shipment of explosives and radioactive materials together. This paper discusses the major gas generation issues within the DOE Complex and the research that has been and is being conducted by the transuranic (TRU) waste, nuclear materials (NM), and spent nuclear fuels (SNF) programs within DOE’s Environmental Management (EM) organization to address gas generation concerns. This paper presents a "program level" roadmap that links technology development to program needs and identifies the probability of success in an effort to understand the programmatic risk associated with the issue of gas generation. This "program level" roadmapping involves linking technology development (and deployment) efforts to the programs’ needs and requirements for dispositioning the material/waste that generates combustible gas through radiolysis and chemical decomposition. The roadmapping effort focused on needed technical & programmatic support to the baselines (and to alternatives to the baselines) where the probability of success is low (i.e., high uncertainty) and …
Date: March 1, 2001
Creator: Luke, Dale Elden; Rogers, Adam Zachary & Hamp, S.
System: The UNT Digital Library
Effects of buoyancy on the flowfields of lean premixed turbulentv-flames (open access)

Effects of buoyancy on the flowfields of lean premixed turbulentv-flames

Open laboratory turbulent flames used for investigating fundament flame turbulence interactions are greatly affected by buoyancy. Though much of our current knowledge is based on observations made in these open flames, the effects of buoyancy are usually not included in data interpretation, numerical analysis or theories. This inconsistency remains an obstacle to merging experimental observations and theoretical predictions. To better understanding the effects of buoyancy, our research focuses on steady lean premixed flames propagating in fully developed turbulence. We hypothesize that the most significant role of buoyancy forces on these flames is to influence their flowfields through a coupling with mean and fluctuating pressure fields. Changes in flow pattern alter the mean aerodynamic stretch and in turn affect turbulence fluctuation intensities both upstream and downstream of the flame zone. Consequently, flame stabilization, reaction rates, and turbulent flame processes are all affected. This coupling relates to the elliptical problem that emphasizes the importance of the upstream, wall and downstream boundary conditions in determining all aspects of flame propagation. Therefore, buoyancy has the same significance as other parameters such as flow configuration, flame geometry, means of flame stabilization, flame shape, enclosure size, mixture conditions, and flow conditions.
Date: March 1, 2001
Creator: Cheng, R. K.; Bedat, B.; Yegian, D. T. & Greenberg, P.
System: The UNT Digital Library
Progress in heavy ion drivers inertial fusion energy: From scaled experiments to the integrated research experiment (open access)

Progress in heavy ion drivers inertial fusion energy: From scaled experiments to the integrated research experiment

The promise of inertial fusion energy driven by heavy ion beams requires the development of accelerators that produce ion currents ({approx}100's Amperes/beam) and ion energies ({approx}1-10 GeV) that have not been achieved simultaneously in any existing accelerator. The high currents imply high generalized perveances, large tune depressions, and high space charge potentials of the beam center relative to the beam pipe. Many of the scientific issues associated with ion beams of high perveance and large tune depression have been addressed over the last two decades on scaled experiments at Lawrence Berkeley and Lawrence Livermore National Laboratories, the University of Maryland, and elsewhere. The additional requirement of high space charge potential (or equivalently high line charge density) gives rise to effects (particularly the role of electrons in beam transport) which must be understood before proceeding to a large scale accelerator. The first phase of a new series of experiments in Heavy Ion Fusion Virtual National Laboratory (HIF VNL), the High Current Experiments (HCX), is now being constructed at LBNL. The mission of the HCX will be to transport beams with driver line charge density so as to investigate the physics of this regime, including constraints on the maximum radial filling factor …
Date: March 1, 2001
Creator: Barnard, J. J.; Ahle, L. E.; Baca, D.; Bangerter, R. O.; Bieniosek, F. M.; Celata, C. M. et al.
System: The UNT Digital Library
High-Resolution Energy-Selected Study of the Reaction NH3+ -> NH2 ++H: Accurate Thermo Chemistry for the NH2/NH2+ and NH3/NH3 + Systems (open access)

High-Resolution Energy-Selected Study of the Reaction NH3+ -> NH2 ++H: Accurate Thermo Chemistry for the NH2/NH2+ and NH3/NH3 + Systems

Employing the newly developed high-resolution pulsed field ionization-photoelectron (PFI-PE)-photoion coincidence (PFI-PEPICO) technique, we have examined the dissociation of energy-selected NH{sub 3}{sup +} to form NH{sub 2}{sup +} + H near its threshold. The breakdown curves for NH{sub 2}{sup +} and NH{sub 3}{sup +} thus obtained yield a value of 15.765 {+-} 0.001 eV for the 0 K dissociation threshold or appearance energy (AE) for NH{sub 2}{sup +} from NH{sub 3}. This value, together with the known ionization energy (IE=10.1864 {+-} 0.0001 eV) and 0 K bond dissociation energy (D{sub 0} = 4.6017 {+-} 0.0025 eV) for NH{sub 3}, allows the determination of the D{sub 0}(NH{sub 2}{sup +}-H) and IE(NH{sub 2}), which are 5.5786 {+-} 0.0010 and 11.1633 {+-} 0.0025 eV, respectively. Using the known 0 K heats of formation ({Delta}H{sup 0}{sub f0}) for NH{sub 3} and H and the AE(NH{sub 2}{sup +}), we obtain the {Delta}H{sup o}{sub f0}(NH{sub 2}{sup +}) = 302.60 {+-} 0.08 kcal/mol. The PFI-PE spectrum for NH{sub 3} exhibits a step-like feature at the 0 K AE(NH{sub 2}{sup +}), indicating that the dissociation of excited NH{sub 3} in high-n (n {ge} 100) Rydberg states at energies slightly above the dissociation threshold occurs on a time scale {le}10{sup …
Date: March 1, 2001
Creator: Song, Y.; Qian, X. M.; Lau, K. C.; Ng, C. Y.; Liu, J. B. & Chen, W. W.
System: The UNT Digital Library
Fluid-inclusion gas composition from an active magmatic-hydrothermal system: a case study of The Geysers, California geothermal field (open access)

Fluid-inclusion gas composition from an active magmatic-hydrothermal system: a case study of The Geysers, California geothermal field

Hydrothermal alteration and the active vapor-dominated geothermal system at The Geysers, CA are related to a composite hypabyssal granitic pluton emplaced beneath the field 1.1 to 1.2 million years ago. Deep drill holes provide a complete transect across the thermal system and samples of the modem-day steam. The hydrothermal system was liquid-dominated prior to formation of the modem vapor-dominated regime at 0.25 to 0.28 Ma. Maximum temperatures and salinities ranged from 440 C and 44 wt. percent NaCl equivalent in the biotite hornfels adjacent to the pluton to 305 C and 5 wt. percent NaCl equivalent at distances of 1730 m from the intrusive contact. The major, minor, and noble gas compositions of fluid inclusions in the hydrothermally altered rocks were integrated with microthermometric and mineralogic data to determine their sources and the effects of mixing and boiling. Major and minor gaseous species were released from the inclusions by crushing or thermal decrepitation; noble gases were released by crushing. The samples were analyzed by mass spectrometry. The analyses document the presence of magmatic, crustal, and meteoric components in the trapped fluids. Hydrothermal fluids present during the liquid-dominated phase of the system contained gaseous species derived mainly from crustal and magmatic …
Date: March 1, 2001
Creator: Moore, Joseph N.; Norman, David I. & Kennedy, B. Mack.
System: The UNT Digital Library
Anomalies on orbifolds (open access)

Anomalies on orbifolds

We discuss the form of the chiral anomaly on an S1/Z2 orbifold with chiral boundary conditions. We find that the 4-divergence of the higher-dimensional current evaluated at a given point in the extra dimension is proportional to the probability of finding the chiral zero mode there. Nevertheless the anomaly, appropriately defined as the five dimensional divergence of the current, lives entirely on the orbifold fixed planes and is independent of the shape of the zero mode. Therefore long distance four dimensional anomaly cancellation ensures the consistency of the higher dimensional orbifold theory.
Date: March 16, 2001
Creator: Arkani-Hamed, Nima; Cohen, Andrew G. & Georgi, Howard
System: The UNT Digital Library
Centrality dependence of multiplicity, transverse energy, and elliptic flow from hydrodynamics (open access)

Centrality dependence of multiplicity, transverse energy, and elliptic flow from hydrodynamics

The centrality dependence of the charged multiplicity, transverse energy, and elliptic flow coefficient is studied in a hydrodynamic model, using a variety of different initializations which model the initial energy or entropy production process as a hard or soft process, respectively. While the charged multiplicity depends strongly on the chosen initialization, the p{sub T}-integrated elliptic flow for charged particles as a function of charged particle multiplicity and the p{sub T}-differential elliptic flow for charged particles in minimum bias events turn out to be almost independent of the initialization.
Date: March 21, 2001
Creator: Kolb, Peter F.; Heinz, Ulrich; Huovinen, Pasi; Eskola, Kari J. & Tuominen, Kimmo
System: The UNT Digital Library
Solar Heat Gain Through Fenestration Systems Containing Shading: Summary of Procedures for Estimating Performance From Minimal Data (open access)

Solar Heat Gain Through Fenestration Systems Containing Shading: Summary of Procedures for Estimating Performance From Minimal Data

The computational methods for calculating the properties of glazing systems containing shading from the properties of their components have been developed, but the measurement standards and property data bases necessary to apply them have not. It is shown that with a drastic simplifying assumption these methods can be used to calculate system solar-optical properties and solar heat gain coefficients for arbitrary glazing systems, while requiring limited data about the shading. Detailed formulas are presented, and performance multipliers are defined for the approximate treatment of simple glazings with shading. As higher accuracy is demanded, the formulas become very complicated.
Date: March 1, 2001
Creator: Klems, Joseph H.
System: The UNT Digital Library
A Cartesian grid embedded boundary method for the heat equation on irregular domains (open access)

A Cartesian grid embedded boundary method for the heat equation on irregular domains

We present an algorithm for solving the heat equation on irregular time-dependent domains. It is based on the Cartesian grid embedded boundary algorithm of Johansen and Colella (J. Comput. Phys. 147(2):60--85) for discretizing Poisson's equation, combined with a second-order accurate discretization of the time derivative. This leads to a method that is second-order accurate in space and time. For the case where the boundary is moving, we convert the moving-boundary problem to a sequence of fixed-boundary problems, combined with an extrapolation procedure to initialize values that are uncovered as the boundary moves. We find that, in the moving boundary case, the use of Crank--Nicolson time discretization is unstable, requiring us to use the L{sub 0}-stable implicit Runge--Kutta method of Twizell, Gumel, and Arigu.
Date: March 14, 2001
Creator: McCorquodale, Peter; Colella, Phillip & Johansen, Hans
System: The UNT Digital Library
Popular Berkeley Lab X-Ray Data Booklet Reissued (open access)

Popular Berkeley Lab X-Ray Data Booklet Reissued

X-ray scientists and synchrotron-radiation users who have been patiently waiting for an updated version of the popular X-Ray Data Booklet last published in 1986 by the Center for X-Ray Optics at the Lawrence Berkeley National Laboratory can breathe a sigh of relief. The venerable ''little orange book'' has now been reissued under the auspices of CXRO and the Advanced Light Source (ALS) with an April printing of 10,000 paper copies and the posting of a Web edition at http://xdb.lbl.gov.
Date: March 2, 2001
Creator: Robinson, Art
System: The UNT Digital Library
Potential oscillations and S-shaped polarization curve in the continuous electro-oxidation of CO on platinum single-crystal electrodes (open access)

Potential oscillations and S-shaped polarization curve in the continuous electro-oxidation of CO on platinum single-crystal electrodes

The occurrence of an S-shaped polarization curve in a simple model for the continuous electrochemical oxidation of CO on a platinum electrode is discussed. In the model, the S-shaped polarization curve is caused by the competitive Langmuir-Hinshelwood mechanism between surface-bonded CO and OH. The reaction is studied experimentally on single-crystal platinum rotating disk electrodes in perchloric and sulfuric acid solution, and it is shown that the voltammetry is in good agreement with the model predictions. When studied under current-controlled conditions, a fast galvanodynamic scan indeed suggests the existence of the S-shaped polarization curve. At lower scan rates, however, irregularities and small-amplitude irregular fluctuations or oscillations in potential are observed. Very regular potential oscillations under current-controlled conditions are observed only on Pt(111) in sulfuric acid. The possible origin of these irregularities and oscillations is discussed in relation to the existing theories of electrochemical instabilities.
Date: March 1, 2001
Creator: Koper, Marc T.M.; Schmidt, Thomas J.; Markovic, Nenad M. & Ross, Philip N.
System: The UNT Digital Library
Emittance growth for the thermalization of space-charged nonuniformities (open access)

Emittance growth for the thermalization of space-charged nonuniformities

Beams injected into a linear focusing channel typically have some degree of space-charge nonuniformity. In general, injected particle distributions with systematic charge nonuniformities are not equilibria of the focusing channel and launch a broad spectrum of collective modes. These modes can phase-mix and have nonlinear wave-wave interactions which, at high space-charge intensities, results in a relaxation to a more thermal-like distribution characterized by a uniform density profile. This thermalization can transfer self-field energy from the initial space-charge nonuniformity to the local particle temperature, thereby increasing beam phase space area (emittance growth). In this paper, we employ a simple kinetic model of a continuous focusing channel and build on previous work that applied system energy and charge conservation to quantify emittance growth associated with the collective thermalization of an initial azimuthally symmetric, rms matched beam with a radial density profile that is hollowed or peaked. This emittance growth is shown to be surprisingly modest even for high beam intensities with significant radial structure in the initial density profile.
Date: March 1, 2001
Creator: Lund, Steven M.; Barnard, John J. & Lee, Edward P.
System: The UNT Digital Library
Analysis of Geomechanical Behavior for the Drift Scale Test (open access)

Analysis of Geomechanical Behavior for the Drift Scale Test

The Drift Scale Test (DST) now underway at Yucca Mountain has been simulated using a Drift Scale Distinct Element (DSDE) model. Simulated deformations show good agreement with field deformation measurements. Results indicate most fracture deformation is located above the crown of the Heated Drift. This work is part of the model validation effort for the DSDE model, which is used to assess thermal-mechanical effects on the hydrology of the rock mass surrounding a potential repository.
Date: March 5, 2001
Creator: Blair, S.C.; Carlson, S.R. & Wagoner, J.L.
System: The UNT Digital Library