Automatic Model Order Reduction (open access)

Automatic Model Order Reduction

None
Date: December 13, 2010
Creator: White, D. A.
Object Type: Article
System: The UNT Digital Library
Innovations in Nuclear Infrastructure and Education (open access)

Innovations in Nuclear Infrastructure and Education

The decision to implement the Innovation in Nuclear Infrastructure and Engineering Program (INIE) was an important first step towards ensuring that the United States preserves its worldwide leadership role in the field of nuclear science and engineering. Prior to INIE, university nuclear science and engineering programs were waning, undergraduate student enrollment was down, university research reactors were being shut down, while others faced the real possibility of closure. For too long, cutting edge research in the areas of nuclear medicine, neutron scattering, radiochemistry, and advanced materials was undervalued and therefore underfunded. The INIE program corrected this lapse in focus and direction and started the process of drawing a new blueprint with positive goals and objectives that supports existing as well the next generation of educators, students and researchers.
Date: December 13, 2010
Creator: Bernard, John
Object Type: Report
System: The UNT Digital Library
National Ignition Facility (NIF) Neutron time-of-flight (nTOF) Measurements (open access)

National Ignition Facility (NIF) Neutron time-of-flight (nTOF) Measurements

The first three of eighteen neutron time-of-flight (nTOF) channels have been installed at the National Ignition Facility (NIF). The role of these detectors includes yield, temperature, and bang time measurements. This article focuses on nTOF data analysis and quality of results obtained for the first set of experiments to use all 192 NIF beams. Targets produced up to 2 x 10{sup 10} 2.45-MeV neutrons for initial testing of the nTOF detectors. Differences in neutron scattering at the OMEGA laser facility where the detectors were calibrated and at NIF result in different response functions at the two facilities. Monte Carlo modeling shows this difference. The nTOF performance on these early experiments indicates the nTOF system with its full complement of detectors should perform well in future measurements of yield, temperature, and bang time.
Date: May 13, 2010
Creator: Lerche, R. A.; Glebov, V. Y.; Moran, M. J.; McNaney, J. M.; Kilkenny, J. D.; Eckart, M. et al.
Object Type: Article
System: The UNT Digital Library
Simulation of e-cloud driven instability and its attenuation using a simulated feedback system in the CERN SPS (open access)

Simulation of e-cloud driven instability and its attenuation using a simulated feedback system in the CERN SPS

Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS, and a feedback system to control the single-bunch instabilities is under active development. We present the latest improvements to the WARP-POSINST simulation framework and feedback model, and its application to the self-consistent simulations of two consecutive bunches interacting with an electron cloud in the SPS. Simulations using an idealized feedback system exhibit adequate mitigation of the instability providing that the cutoff of the feedback bandwidth is at or above 450 MHz. Artifacts from numerical noise of the injected distribution of electrons in the modeling of portions of bunch trains are discussed, and benchmarking of WARP against POSINST and HEADTAIL are presented.
Date: December 13, 2010
Creator: Vay, J. L. & Furman, M. A.
Object Type: Article
System: The UNT Digital Library
First Measurements and Results With a Stretched Wire Test Setup (open access)

First Measurements and Results With a Stretched Wire Test Setup

The LINAC Coherent Light Source [LCLS] is a free electron laser, designed to produce high brilliant X-ray beams using Self Amplified Spontaneous Emission [SASE]. Due to the physics of SASE, the electron beam has to be held very precisely on the same trajectory as the X-ray light beam generated by the undulator magnets. To optimize the SASE output, trajectory deviations between both beams have to be minimized to a few micrometers along the entire undulator section and held stable over the time period between beam-based-alignment processes. Consequently, extremely high position stability of all magnets in the undulator section is required to operate the LCLS successfully. The knowledge of any magnet movement exceeding few micrometers during periods of several weeks is essential for efficient X-ray generation. A well known principle of monitoring transverse component positions along beam lines is the application of stretched wires, associated with suitable wire position sensors and electronics. The particular challenge at LCLS is the required wire system performance in conjunction with the length of the undulator section and the large number of monitors. Verification of system stability and resolution under real conditions is the primary goal of this test setup. A stretched wire test setup has …
Date: December 13, 2010
Creator: Peters, Franz
Object Type: Report
System: The UNT Digital Library
High Efficiency Engine Technologies Program (open access)

High Efficiency Engine Technologies Program

Caterpillar's Product Development and Global Technology Division carried out a research program on waste heat recovery with support from DOE (Department of Energy) and the DOE National Energy Technology Laboratory. The objective of the program was to develop a new air management and exhaust energy recovery system that would demonstrate a minimum 10% improvement in thermal efficiency over a base heavy-duty on-highway diesel truck engine. The base engine for this program was a 2007 C15 15.2L series-turbocharged on-highway truck engine with a LPL (low-pressure loop) exhaust recirculation system. The focus of the program was on the development of high efficiency turbomachinery and a high efficiency turbocompound waste heat recovery system. The focus of each area of development was as follows: (1) For turbine stages, the focus was on investigation and development of technologies that would improve on-engine exhaust energy utilization compared to the conventional radial turbines in widespread use today. (2) For compressor stages, the focus was on investigating compressor wheel design parameters beyond the range typically utilized in production, to determine the potential efficiency benefits thereof. (3) For turbocompound, the focus was on the development of a robust bearing system that would provide higher bearing efficiencies compared to systems …
Date: July 13, 2010
Creator: Kruiswyk, Rich
Object Type: Report
System: The UNT Digital Library
Quark mass variation constraints from Big Bang nucleosynthesis (open access)

Quark mass variation constraints from Big Bang nucleosynthesis

We study the impact on the primordial abundances of light elements created of a variation of the quark masses at the time of Big Bang nucleosynthesis (BBN). In order to navigate through the particle and nuclear physics required to connect quark masses to binding energies and reaction rates in a model-independent way we use lattice QCD data and an hierarchy of effective field theories. We find that the measured {sup 4}He abundances put a bound of {delta}-1% {approx}< m{sub q}/m{sub 1} {approx}< 0.7%. The effect of quark mass variations on the deuterium abundances can be largely compensated by changes of the baryon-to-photon ratio {eta}. Including the bounds on the variation of {eta} coming from WMAP results and some additional assumptions narrows the range of allowed values of {delta}m{sub q}/m{sub q} somewhat.
Date: December 13, 2010
Creator: Bedaque, P.; Luu, T. & Platter, L.
Object Type: Article
System: The UNT Digital Library
Wakefield Calculations for Radiation Stopper 1 (RST1) (open access)

Wakefield Calculations for Radiation Stopper 1 (RST1)

The main result of this note is that no wakefield mitigation is required for the Radiation Stopper (RST1) in the LCLS injector. The RST1 geometry is not symmetric in the vertical direction, and we derive a slight modification to the diffraction model wake for a cylindrically symmetric (2D) cavity that can be used for this problem. Performing a full 3D MAFIA calculation for the nominal 1 mm (rms) long bunch, we show that the modified diffraction model well describes the wakefields generated in RST1. The results imply an on-axis emittance growth of 0.0075%, well below the 0.5% tolerance threshold. To reach the 0.5% threshold the beam would need to be mis-steered by a large amount - 7 mm - from the axis. One reason that the effect is small is that the beta functions at the RST1 are small.
Date: December 13, 2010
Creator: Limborg-Deprey, C.
Object Type: Report
System: The UNT Digital Library
Tests of Coordinate Transfer from Magnetic to Mechanical Reference for LCLS Undulator Fiducialization (open access)

Tests of Coordinate Transfer from Magnetic to Mechanical Reference for LCLS Undulator Fiducialization

Fiducialization of the LCLS undulators will be based on magnetic measurements by Hall probe. Pointed magnets, proposed by I.Vasserman for quadrupole lens fiducialization will be used as an intermediate reference. A prototype of the pointed magnet fixture has been made and tested. In this note we will describe a procedure for measuring the position of the center of the Hall probe sensitive area with respect to the undulator fiducial marks. The pointed magnet calibration procedure, a two-point algorithm for locating the magnetic center of the fixture, and test results are presented.
Date: December 13, 2010
Creator: Levashov, Yu.
Object Type: Report
System: The UNT Digital Library
Temperature Measurements in the Magnetic Measurement Facility (open access)

Temperature Measurements in the Magnetic Measurement Facility

Several key LCLS undulator parameter values depend strongly on temperature primarily because of the permanent magnet material the undulators are constructed with. The undulators will be tuned to have specific parameter values in the Magnetic Measurement Facility (MMF). Consequently, it is necessary for the temperature of the MMF to remain fairly constant. Requirements on undulator temperature have been established. When in use, the undulator temperature will be in the range 20.0 {+-} 0.2 C. In the MMF, the undulator tuning will be done at 20.0 {+-} 0.1 C. For special studies, the MMF temperature set point can be changed to a value between 18 C and 23 C with stability of {+-}0.1 C. In order to ensure that the MMF temperature requirements are met, the MMF must have a system to measure temperatures. The accuracy of the MMF temperature measurement system must be better than the {+-}0.1 C undulator tuning temperature tolerance, and is taken to be {+-}0.01 C. The temperature measurement system for the MMF is under construction. It is similar to a prototype system we built two years ago in the Sector 10 alignment lab at SLAC. At that time, our goal was to measure the lab temperature …
Date: December 13, 2010
Creator: Wolf, Zachary
Object Type: Report
System: The UNT Digital Library
RF Design of the LCLS Gun (open access)

RF Design of the LCLS Gun

Final dimensions for the LCLS RF gun are described. This gun, referred to as the LCLS gun, is a modified version of the UCLA/BNL/SLAC 1.6 cell S-Band RF gun [1], referred to as the prototype gun. The changes include a larger mode separation (15 MHz for the LCLS gun vs. 3.5 MHz for the prototype gun), a larger radius at the iris between the 2 cells, a reduced surface field on the curvature of the iris between the two cells, Z power coupling, increased cooling channels for operation at 120 Hz, dual rf feed, deformation tuning of the full cell, and field probes in both cells. Temporal shaping of the klystron pulse, to reduce the average power dissipated in the gun, has also been adopted. By increasing the mode separation, the amplitude of the 0-mode electric field on the cathode decreases from 10% of the peak on axis field for the prototype gun to less than 3% for the LCLS gun for the steady state fields. Beam performance is improved as shown by the PARMELA simulations. The gun should be designed to accept a future load lock system. Modifications follow the recommendations of our RF review committee [2]. Files and …
Date: December 13, 2010
Creator: Limborg-Deprey, C
Object Type: Report
System: The UNT Digital Library
Application of a Multiscale Model of Tantalum Deformation at Megabar Pressures (open access)

Application of a Multiscale Model of Tantalum Deformation at Megabar Pressures

A new multiscale simulation tool has been developed to model the strength of tantalum under high-pressure dynamic compression. This new model combines simulations at multiple length scales to explain macroscopic properties of materials. Previously known continuum models of material response under load have built upon a mixture of theoretical physics and experimental phenomenology. Experimental data, typically measured at static pressures, are used as a means of calibration to construct models that parameterize the material properties; e.g., yield stress, work hardening, strain-rate dependence, etc. The pressure dependence for most models enters through the shear modulus, which is used to scale the flow stress. When these models are applied to data taken far outside the calibrated regions of phase space (e.g., strain rate or pressure) they often diverge in their predicted behavior of material deformation. The new multiscale model, developed at Lawrence Livermore National Laboratory, starts with interatomic quantum mechanical potential and is based on the motion and multiplication of dislocations. The basis for the macroscale model is plastic deformation by phonon drag and thermally activated dislocation motion and strain hardening resulting from elastic interactions among dislocations. The dislocation density, {rho}, and dislocation velocity, {nu}, are connected to the plastic strain rate …
Date: May 13, 2010
Creator: Cavallo, R. M.; Park, H.; Barton, N. R.; Remignton, B. A.; Pollaine, S. M.; Prisbrey, S. T. et al.
Object Type: Article
System: The UNT Digital Library
Bragg Diffraction Using a 100ps 17.5 Kev X-Ray Backlighter and the Bragg Diffraction Imager (open access)

Bragg Diffraction Using a 100ps 17.5 Kev X-Ray Backlighter and the Bragg Diffraction Imager

A new diagnostic for measuring Bragg diffraction from a laser-driven crystal using a 100ps 17.5 kV x-ray backlighter source is designed and tested successfully at the Omega EP laser facility on static Mo and Ta single crystal samples using a Mo Ka backlighter. The Bragg Diffraction Imager (BDI) consists of a heavily shielded enclosure and a precisely positioned beam block, attached to the main enclosure by an Aluminum arm. Image plate is used as the x-ray detector. The diffraction lines from Mo and Ta <222> planes are clearly detected with a high signal-to-noise using the 17.5 keV and 19.6 keV characteristic lines generated by a petawatt-driven Mo foil. This technique will be applied to shock and ramp-loaded single crystals on the Omega EP laser. Pulsed x-ray diffraction of shock- and ramp-compressed materials is an exciting new technique that can give insight into the dynamic behavior of materials at ultra-high pressure not achievable by any other means to date. X-ray diffraction can be used to determine not only the phase and compression of the lattice at high pressure, but by probing the lattice compression on a timescale equal to the 3D relaxation time of the material, information about dislocation mechanics, including …
Date: May 13, 2010
Creator: Maddox, B. R.; Park, H.; Hawreliak, J.; Comley, A.; Elsholz, A.; Van Maren, R. et al.
Object Type: Article
System: The UNT Digital Library
Development of a Polar Drive Shock Ignition Platform on the National Ignition Facility (open access)

Development of a Polar Drive Shock Ignition Platform on the National Ignition Facility

None
Date: May 13, 2010
Creator: Perkins, L. J.; Schurtz, G. P.; Betti, R.; Craxton, R. S.; LaFortune, K. N.; Casner, A. et al.
Object Type: Report
System: The UNT Digital Library
The Status of De-Inventory of Security Category I/II Nuclear Materials at Lawrence Livermore National Laboratory (LLNL) (open access)

The Status of De-Inventory of Security Category I/II Nuclear Materials at Lawrence Livermore National Laboratory (LLNL)

None
Date: May 13, 2010
Creator: Riley, D C & Dodson, K
Object Type: Article
System: The UNT Digital Library
Polarization-selective vortex-core switching by tailored orthogonal Gaussian-pulse currents (open access)

Polarization-selective vortex-core switching by tailored orthogonal Gaussian-pulse currents

We experimentally demonstrate low-power-consumption vortex-core switching in magnetic nanodisks using tailored rotating magnetic fields produced with orthogonal and unipolar Gaussian-pulse currents. The optimal width of the orthogonal pulses and their time delay are found, from analytical and micromagnetic numerical calculations, to be determined only by the angular eigenfrequency {omega}{sub D} for a given vortex-state disk of polarization p, such that {sigma}=1/{omega}{sub D} and {Delta}t={pi}/2 p/{omega}{sub D} . The estimated optimal pulse parameters are in good agreement with the experimental results. This work lays a foundation for energy-efficient information recording in vortex-core cross-point architecture.
Date: October 13, 2010
Creator: Jung, H.; Choi, Y. S.; Yoo, M. W.; Im, M. Y. & Kim, S. K.
Object Type: Article
System: The UNT Digital Library
Catalog of DC Appliances and Power Systems (open access)

Catalog of DC Appliances and Power Systems

This document catalogs the characteristics of current and potential future DC products and power systems.
Date: October 13, 2010
Creator: Garbesi, Karina; Vossos, Vagelis & Shen, Hongxia
Object Type: Report
System: The UNT Digital Library
CRS Issue Statement on Military Strategies and Force Structure (open access)

CRS Issue Statement on Military Strategies and Force Structure

This report discusses about Military Strategies and force structure. It further discusses about military force structure that includes what types of ground forces and special operation units are required for current and future operations.
Date: January 13, 2010
Creator: Daggett, Stephen
Object Type: Report
System: The UNT Digital Library
Actual Farm Bill Spending and Cost Estimates (open access)

Actual Farm Bill Spending and Cost Estimates

This report discusses the budget for the 2008 Farm Bill, and its reauthorization. Moreover, the report discusses the increasing level of demand for fiscal constraint and the current large budget deficits.
Date: December 13, 2010
Creator: Monke, Jim & Johnson, Renée
Object Type: Report
System: The UNT Digital Library
Renewable Energy Programs in the 2008 Farm Bill (open access)

Renewable Energy Programs in the 2008 Farm Bill

This report discuses the Food, Conservation, and Energy Act of 2008 (P.L. 110-246, the 2008 farm bill) that extends and expands many of the renewable energy programs originally authorized in the Farm Security and Rural Investment Act of 2002.
Date: August 13, 2010
Creator: Stubbs, Megan
Object Type: Report
System: The UNT Digital Library
Emergency Communications: Broadband and the Future of 911 (open access)

Emergency Communications: Broadband and the Future of 911

This report discusses the Summary of 911 Legislation and Policy, Funding and Grants and National Broadband Plan.
Date: December 13, 2010
Creator: Moore, Linda K.
Object Type: Report
System: The UNT Digital Library
China and Proliferation of Weapons of Mass Destruction and Missiles: Policy Issues (open access)

China and Proliferation of Weapons of Mass Destruction and Missiles: Policy Issues

This report discusses the security problem of China’s role in weapons proliferation and issues related to the U.S. policy response since the mid-1990s. China has taken some steps to mollify U.S. and other foreign concerns about its role in weapons proliferation.
Date: September 13, 2010
Creator: Kan, Shirley A.
Object Type: Report
System: The UNT Digital Library
Federal Lands Managed by the Bureau of Land Management (BLM) and the Forest Service (FS): Issues for the 111th Congress (open access)

Federal Lands Managed by the Bureau of Land Management (BLM) and the Forest Service (FS): Issues for the 111th Congress

None
Date: May 13, 2010
Creator: Gorte, Ross W.; Vincent, Carol Hardy; Alexander, Kristina & Humphries, Marc
Object Type: Report
System: The UNT Digital Library
Regulations Pursuant to the Patient Protection and Affordable Care Act (P.L. 111-148) (open access)

Regulations Pursuant to the Patient Protection and Affordable Care Act (P.L. 111-148)

None
Date: April 13, 2010
Creator: unknown
Object Type: Report
System: The UNT Digital Library