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Defense Acquisitions: Restructured JTRS Program Reduces Risk, but Significant Challenges Remain (open access)

Defense Acquisitions: Restructured JTRS Program Reduces Risk, but Significant Challenges Remain

A letter report issued by the Government Accountability Office with an abstract that begins "In 1997, the Department of Defense (DOD) initiated the Joint Tactical Radio System (JTRS) program, a key element of its effort to transform military operations to be network centric. Using emerging software-defined radio technology, the JTRS program plans to develop and procure hundreds of thousands of radios that give warfighters the capability to access maps and other visual data, communicate via voice and video, and obtain information directly from battlefield sensors. The JTRS program has encountered a number of problems, resulting in significant delays and cost increases. The program is currently estimated to total about $37 billion. Given the criticality of JTRS to DOD's force transformation, Congress directed GAO to continue its ongoing review of the JTRS program. This report (1) assesses whether a recent restructuring puts the program in a better position to succeed and (2) identifies any risks that challenge the successful fielding of JTRS."
Date: September 11, 2006
Creator: United States. Government Accountability Office.
Object Type: Report
System: The UNT Digital Library
Homeless Veterans Programs: Improved Communications and Follow-up Could Further Enhance the Grant and Per Diem Program (open access)

Homeless Veterans Programs: Improved Communications and Follow-up Could Further Enhance the Grant and Per Diem Program

A letter report issued by the Government Accountability Office with an abstract that begins "About one-third of the nation's adult homeless population are veterans, according to the Department of Veterans Affairs (VA). Many of these veterans have experienced substance abuse, mental illness, or both. The VA's Homeless Providers Grant and Per Diem (GPD) program, which is up for reauthorization, provides transitional housing to help veterans prepare for permanent housing. As requested, GAO reviewed (1) VA homeless veterans estimates and the number of transitional housing beds, (2) the extent of collaboration involved in the provision of GPD and related services, and (3) VA's assessment of GPD program performance. GAO analyzed VA data and methods used for the homeless estimates and performance assessment, and visited selected GPD providers in four states to observe the extent of collaboration."
Date: September 11, 2006
Creator: United States. Government Accountability Office.
Object Type: Report
System: The UNT Digital Library
Stabilizing Iraq: An Assessment of the Security Situation (open access)

Stabilizing Iraq: An Assessment of the Security Situation

Testimony issued by the Government Accountability Office with an abstract that begins "From fiscal years 2003 through 2006, U.S. government agencies have reported significant costs for U.S. stabilization and reconstruction efforts in Iraq. In addition, the United States currently has committed about 138,000 military personnel to the U.S.-led Multinational Force in Iraq (MNF-I). Over the past 3 years, worsening security conditions have made it difficult for the United States to achieve its goals in Iraq. In this statement, we discuss (1) the trends in the security environment in Iraq, and (2) progress in developing Iraqi security forces, as reported by the Departments of Defense (DOD) and State. We also present key questions for congressional oversight, including what political, economic, and security conditions must be achieved before the United States can draw down and withdraw? Why have security conditions continued to deteriorate even as Iraq has met political milestones, increased the number of trained and equipped forces, and increasingly assumed the lead for security? If existing U.S. political, economic, and security measures are not reducing violence in Iraq, what additional measures, if any, will the administration propose for stemming the violence?"
Date: September 11, 2006
Creator: United States. Government Accountability Office.
Object Type: Text
System: The UNT Digital Library
Rhamm-/- mice are defective in skin wound repair due to aberrantERK1,2 signaling in fibroblast migration (open access)

Rhamm-/- mice are defective in skin wound repair due to aberrantERK1,2 signaling in fibroblast migration

None
Date: September 11, 2006
Creator: Tolg, Cornelia; Hamilton, Sara R.; Nakrieko, Kari-Anne; Walton, Paul; McCarthy, James B.; Bissell, Mina J. et al.
Object Type: Article
System: The UNT Digital Library
2005 Quantum Control of Light and Matter - Conference July 31 - August 5, 2005 (open access)

2005 Quantum Control of Light and Matter - Conference July 31 - August 5, 2005

This report is about Quantum Control of Light and Matter Gordon Research Conference
Date: September 11, 2006
Creator: Corkum, Paul B.
Object Type: Article
System: The UNT Digital Library
Project Progress (open access)

Project Progress

The proposed study investigates the effect of low dose and low dose rate radiation exposure (X-rays) on induced genomic instability and the adaptive response, including the molecular mechanisms for these phenomena. The proposed studies will utilize human cell lines containing a stably integrated plasmid that can be caused by certain kinds of mutational insults to recombine to express the green fluorescent proteins, GFP. The study will use this cell line with the fluorescent plasmid recombination reporter system in a direct study of the effects of 1, 2.5, 5, 7.5, 10, 100 and 500 rads acute X-irradiation and the same doses delivered by protraction at 1 rad or 0.01 rad per minute. This system will be used to provide a quantitative measure of the kinetics of genomic instability in colonies of cells exposed to low dose/dose rate, as well as to examine the adaptive response. The study will also apply micro array technology to investigate the molecular mechanisms underlying induced instability and adaptive effects.
Date: September 11, 2006
Creator: Morgan, William F.
Object Type: Report
System: The UNT Digital Library
Low cost digital electronics for isotope analysis with microcalorimeters - final report (open access)

Low cost digital electronics for isotope analysis with microcalorimeters - final report

The overall goal of the Phase I research was to demonstrate that the digital readout electronics and filter algorithms developed by XIA for use with HPGe detectors can be adapted to high precision, cryogenic gamma detectors (microcalorimeters) and not only match the current state of the art in terms of energy resolution, but do so at a significantly reduced cost. This would make it economically feasible to instrument large arrays of microcalorimeters and would also allow automation of the setup, calibration and operation of large numbers of channels through software. We expected, and have demonstrated, that this approach would further allow much higher count rates than the optimum filter algorithms currently used. In particular, in measurements with a microcalorimeter at LLNL, the adapted Pixie-16 spectrometer achieved an energy resolution of 0.062%, significantly better than the targeted resolution of 0.1% in the Phase I proposal and easily matching resolutions obtained with LLNL readout electronics and optimum filtering (0.066%). The theoretical maximum output count rate for the filter settings used to achieve this resolution is about 120cps. If the filter is adjusted for maximum throughput with an energy resolution of 0.1% or better, rates of 260cps are possible. This is 20-50 times …
Date: September 11, 2006
Creator: Hennig, W.
Object Type: Report
System: The UNT Digital Library
An Ab Initio Approach Towards Engineering Fischer-Tropsch Surface Chemistry (open access)

An Ab Initio Approach Towards Engineering Fischer-Tropsch Surface Chemistry

One of the greatest societal challenges over the next decade is the production of cheap, renewable energy for the 10 billion people that inhabit the earth. This will require the development of various energy sources which will likely include fuels derived from methane, coal, and biomass and alternatives sources such as solar, wind and nuclear energy. One approach will be to synthesize gasoline and other fuels from simpler hydrocarbons such as CO derived from methane or other U.S. based sources such as coal. Syngas (CO and H{sub 2}) can be readily converted into higher molecular weight hydrocarbons through Fischer-Tropsch synthesis. Fischer-Tropsch (FT) synthesis involves the adsorption and the activation of CO and H{sub 2}, the subsequent propagation steps including hydrogenation and carbon-carbon coupling, followed by chain termination reactions. The current commercial catalysts are supported Co and Co-alloys particles. This project set out with the following objectives in mind: (1) understand the reaction mechanisms that control FT kinetics, (2) predict how the intrinsic metal-adsorbate bond affects the sequence of elementary steps in FT, (3) establish the effects of the reaction environment on catalytic activity and selectivity, (4) construct a first-principles based algorithm that can incorporate the detailed atomic surface structure and …
Date: September 11, 2006
Creator: Neurock, Matthew
Object Type: Report
System: The UNT Digital Library
Dark Matter Burners: Preliminary Estimate (open access)

Dark Matter Burners: Preliminary Estimate

We show that a star orbiting close enough to an adiabatically grown supermassive black hole can capture a large number of weakly interacting massive particles (WIMPs) during its lifetime. WIMP annihilation energy release in low- to medium-mass stars is comparable with or even exceeds the luminosity of such stars due to thermonuclear burning. The excessive energy release in the stellar core may result in an evolution scenario different from what is expected for a regular star. The model thus predicts the existence of unusual stars within the central parsec of galactic nuclei. If found, such stars would provide evidence for the existence of particle dark matter. The excess luminosity of such stars attributed to WIMP ''burning'' can be used to infer the local WIMP matter density. A white dwarf with a highly eccentric orbit around the central black hole may exhibit variations in brightness correlated with the orbital phase. On the other hand, white dwarfs shown to lack such orbital brightness variations can be used to provide constraints on WIMP matter density, WIMP-nucleus scattering and pair annihilation cross sections.
Date: September 11, 2006
Creator: Moskalenko, Igor V.; /Stanford U., HEPL & Wai, L.
Object Type: Report
System: The UNT Digital Library
Kinetics of PBX9404 Aging (open access)

Kinetics of PBX9404 Aging

PBX 9404 is an early formulation of HMX from which we can learn about the effects of aging in the weapons stockpile. Of particular interest is the presence of 3% nitrocellulose in PBX 9404 as an energetic binder. Nitrocellulose is used pervasively in smokeless gunpowders and was formerly used extensively in the film and art preservation industries. It is well known that nitrocellulose decomposes autocatalytically, and stabilizers, such as the diphenylamine used in PBX 9404, are used to retard its decomposition. Even so, its lifetime is still limited, and the reactions eventually leading to catastrophic autocatalysis are still not understood well despite years of work. In addition to reducing the available energy in the explosive, degradation of nitrocellulose affects the mechanical properties of the pressed PBX 9404 parts by the associated reduction in molecular weight, which reduces the strength of the binder. A structural formula for a monomer of the nitrocellulose used in PBX 9404 is shown. The initial nitration level is 2.3 of 3.0 possible sites, and they have different reactivities. Degradation of nitrocellulose affects many properties. As an aid in examining historical chemical analysis data, several measures of degradation are given for the simple replacement of a nitro …
Date: September 11, 2006
Creator: Burnham, A K & Fried, L E
Object Type: Article
System: The UNT Digital Library
Progress towards a PETN Lifetime Prediction Model (open access)

Progress towards a PETN Lifetime Prediction Model

Dinegar (1) showed that decreases in PETN surface area causes EBW detonator function times to increase. Thermal aging causes PETN to agglomerate, shrink, and densify indicating a ''sintering'' process. It has long been a concern that the formation of a gap between the PETN and the bridgewire may lead to EBW detonator failure. These concerns have led us to develop a model to predict the rate of coarsening that occurs with age for thermally driven PETN powder (50% TMD). To understand PETN contributions to detonator aging we need three things: (1) Curves describing function time dependence on specific surface area, density, and gap. (2) A measurement of the critical gap distance for no fire as a function of density and surface area for various wire configurations. (3) A model describing how specific surface area, density and gap change with time and temperature. We've had good success modeling high temperature surface area reduction and function time increase using a phenomenological deceleratory kinetic model based on a distribution of parallel nth-order reactions having evenly spaced activation energies where weighing factors of the reactions follows a Gaussian distribution about the reaction with the mean activation energy (Figure 1). Unfortunately, the mean activation energy …
Date: September 11, 2006
Creator: Burnham, A. K.; Overturf III, G. E.; Gee, R.; Lewis, P.; Qiu, R.; Phillips, D. et al.
Object Type: Article
System: The UNT Digital Library
Theory and proposal for a quantum-degenerate electron source (open access)

Theory and proposal for a quantum-degenerate electron source

We propose a pulsed electron source capable of a 6Dbrightness orders-of-magnitude greater than that of existing sources. Itcould deliver average current up to 0.5 pA and achieve an emittanceapproaching the quantum limit of one Compton wavelength in each spatialdimension. It could be employed to advantage in electron microscopy,inverse photo-emission, precision low-energy scattering experiments, andelectron holography. This source could make possible pump-probeexperiments with Angstrom spatial and sub-picosecond time resolution.Here we describe basic concepts of the source, including analysis of mainissues that must be addressed for its successful construction andoperation. We have begun an experiment to demonstrate its essentialfeatures.
Date: September 11, 2006
Creator: Zolotorev, Max; Commins, Eugene D. & Fernando, Sannibale
Object Type: Report
System: The UNT Digital Library
Validity of Various Approaches to Global Kinetic Modeling of Material Lifetimes (open access)

Validity of Various Approaches to Global Kinetic Modeling of Material Lifetimes

Chemical kinetic modeling has been used for many years in process optimization, estimating real-time material performance, and lifetime prediction. Chemists have tended towards developing detailed mechanistic models, while engineers have tended towards global or lumped models. Many, if not most, applications use global models by necessity, since it is impractical or impossible to develop a rigorous mechanistic model. Model fitting acquired a bad connotation in the thermal analysis community after that community realized a decade after other disciplines that deriving kinetic parameters for an assumed model from a single heating rate produced unreliable and sometimes nonsensical results. In its place, advanced isoconversional methods, which have their roots in the Friedman and Ozawa-Flynn-Wall methods of the 1960s, have become increasingly popular. In fact, as pointed out by the ICTAC kinetics project in 2000, valid kinetic parameters can be derived by both isoconversional and model fitting methods as long as a diverse set of thermal histories are used to derive the kinetic parameters. The current paper extends the understanding from that project to give a better appreciation of the strengths and weaknesses of isoconversional and model-fitting approaches. Examples are given from a variety of data sets.
Date: September 11, 2006
Creator: Burnham, A K & Dinh, L N
Object Type: Article
System: The UNT Digital Library
Characterization of an Electromagnetic Calorimeter for the Proposed International Linear Collider (open access)

Characterization of an Electromagnetic Calorimeter for the Proposed International Linear Collider

The International Linear Collider (ILC) is part of a new generation of accelerators enabling physicists to gain a deeper understanding of the fundamental components of the universe. The proposed ILC will accelerate positrons and electrons towards each other with two facing linear colliders, each twenty kilometers long. Designing and planning for the future accelerator has been undertaken as a global collaboration, with groups working on several possible detectors to be used at the ILC. The following research at the Stanford Linear Accelerator Center (SLAC) pertained to the design of an electromagnetic calorimeter. The energy and spatial resolution of the calorimeter was tested by using computer simulations for proposed detectors. In order to optimize this accuracy, different designs of the electromagnetic calorimeter were investigated along with various methods to analyze the data from the simulated detector. A low-cost calorimeter design was found to provide energy resolution comparable to more expensive designs, and new clustering algorithms offered better spatial resolution. Energy distribution and shape characteristics of electromagnetic showers were also identified to differentiate various showers in the calorimeter. With further research, a well-designed detector will enable the ILC to observe new realms of physics.
Date: September 11, 2006
Creator: Frey, Merideth & /SLAC, /Wellesley Coll.
Object Type: Report
System: The UNT Digital Library
Analysis of Off-Nuclear X-Ray Sources in Galaxy NGC 4945 (open access)

Analysis of Off-Nuclear X-Ray Sources in Galaxy NGC 4945

Recently, X-ray astronomy has been used to investigate objects such as galaxies, clusters of galaxies, Active Galactic Nuclei (AGN), quasars, starburst superbubbles of hot gas, X-ray binary systems, stars, supernova remnants, and interstellar and intergalactic material. By studying the x-ray emission patterns of these objects, we can gain a greater understanding of their structure and evolution. We analyze X-ray emission from the galaxy NGC 4945 using data taken by the Chandra X-ray Observatory. The Chandra Interactive Analysis of Observations (CIAO) software package was used to extract and fit energy spectra and to extract light curves for the brightest off-nuclear sources in two different observations of NGC 4945 (January, 2000 and May, 2004). A majority of sources were closely fit by both absorbed power law and absorbed bremsstrahlung models, with a significantly poorer {chi}{sup 2}/dof for the absorbed blackbody model, and most sources had little variability. This indicates that the sources are accreting binary systems with either a neutron star or black hole as the compact object. The calculated luminosities were about 10{sup 38} erg/s, which implies that the mass of the accreting object is close to 10 solar masses and must be a black hole.
Date: September 11, 2006
Creator: Harrison, Sarah M. & /SLAC, /MIT
Object Type: Report
System: The UNT Digital Library
OREGON STATE UNIVERSITY (OSU) TRAINING RESEARCH ISOTOPE GENERAL ATOMICS (TRIGA) OVERPACK CLOSURE WELDING PROCESS PARAMETER DEVELOPMENT & QUALIFICATION (open access)

OREGON STATE UNIVERSITY (OSU) TRAINING RESEARCH ISOTOPE GENERAL ATOMICS (TRIGA) OVERPACK CLOSURE WELDING PROCESS PARAMETER DEVELOPMENT & QUALIFICATION

Spent Nuclear Fuel (SNF) from the Oregon State University (OSU) TRIGA{reg_sign} Reactor is currently being stored in thirteen 55-gallon drums at the Hanford Site's low-level burial grounds. This fuel is soon to be retrieved from buried storage and packaged into new containers (overpacks) for interim storage at the Hanford Interim Storage Area (ISA). One of the key activities associated with this effort is final closure of the overpack by welding. The OSU fuel is placed into an overpack, a head inserted into the overpack top, and welded closed. Weld quality, for typical welded fabrication, is established through post-weld testing and nondestructive examination (NDE); however, in this case, once the SNF is placed into the overpack, routine testing and NDE are not feasible. An alternate approach is to develop and qualify the welding process/parameters, demonstrate beforehand that they produce the desired weld quality, and then verify parameter compliance during production welding. Fluor engineers have developed a Gas Tungsten Arc Welding (GTAW) technique and parameters, demonstrating that weld quality requirements for closure of packaged SNF overpacks are met, using this alternate approach. The following reviews the activities performed for this development and qualification effort.
Date: September 11, 2006
Creator: CANNELL, G.R.
Object Type: Article
System: The UNT Digital Library
Highlights of the Comptroller General's Panel on Federal Oversight and the Inspectors General (open access)

Highlights of the Comptroller General's Panel on Federal Oversight and the Inspectors General

Other written product issued by the Government Accountability Office with an abstract that begins "The Inspector General Act of 1978, as amended, (IG Act) created independent offices headed by inspectors general (IG) responsible for conducting and supervising audits and investigations; promoting economy, efficiency, and effectiveness; and preventing and detecting fraud and abuse in their agencies' programs and operations. To carry out the purposes of the act, the IGs have been granted authorities and responsibilities to provide for their independence and effectiveness. These include the authority to have direct access to all records and information of the agency, to hire staff and manage their own resources, to receive and respond to complaints from agency employees, to request assistance from other government agencies, to issue subpoenas to obtain information and documents, and to administer oaths when taking testimony. The Senate Committee on Homeland Security and Governmental Affairs asked us to review whether additional IG authorities and responsibilities such as those provided in H.R. 2489, as well as other changes, could further enhance the independence and effectiveness of the IGs. Introduced in 2005, H.R. 2489 includes provisions for (1) a defined term of office for the IGs and conditions for removal, (2) IGs …
Date: September 11, 2006
Creator: United States. Government Accountability Office.
Object Type: Text
System: The UNT Digital Library
The Baytown Sun (Baytown, Tex.), Vol. 85, No. 292, Ed. 1 Monday, September 11, 2006 (open access)

The Baytown Sun (Baytown, Tex.), Vol. 85, No. 292, Ed. 1 Monday, September 11, 2006

Daily newspaper from Baytown, Texas that includes local, state, and national news along with advertising.
Date: September 11, 2006
Creator: Clements, Clifford E.
Object Type: Newspaper
System: The Portal to Texas History
Provisions in the Pension Protection Act Affecting Tax-Exempt Organizations (open access)

Provisions in the Pension Protection Act Affecting Tax-Exempt Organizations

None
Date: September 11, 2006
Creator: unknown
Object Type: Report
System: The UNT Digital Library
Climatic Forecasting of Net Infiltration at Yucca Montain Using Analogue Meteororological Data (open access)

Climatic Forecasting of Net Infiltration at Yucca Montain Using Analogue Meteororological Data

At Yucca Mountain, Nevada, future changes in climatic conditions will most likely alter net infiltration, or the drainage below the bottom of the evapotranspiration zone within the soil profile or flow across the interface between soil and the densely welded part of the Tiva Canyon Tuff. The objectives of this paper are to: (a) develop a semi-empirical model and forecast average net infiltration rates, using the limited meteorological data from analogue meteorological stations, for interglacial (present day), and future monsoon, glacial transition, and glacial climates over the Yucca Mountain region, and (b) corroborate the computed net-infiltration rates by comparing them with the empirically and numerically determined groundwater recharge and percolation rates through the unsaturated zone from published data. In this paper, the author presents an approach for calculations of net infiltration, aridity, and precipitation-effectiveness indices, using a modified Budyko's water-balance model, with reference-surface potential evapotranspiration determined from the radiation-based Penman (1948) formula. Results of calculations show that net infiltration rates are expected to generally increase from the present-day climate to monsoon climate, to glacial transition climate, and then to the glacial climate. The forecasting results indicate the overlap between the ranges of net infiltration for different climates. For example, the …
Date: September 11, 2006
Creator: Faybishenko, B.
Object Type: Article
System: The UNT Digital Library
Evaluation of 2005 Honda Accord Hybrid Electric Drive System (open access)

Evaluation of 2005 Honda Accord Hybrid Electric Drive System

The Hybrid Electric Vehicle (HEV) program officially began in 1993 as a five-year, cost-shared partnership between the U.S. Department of Energy (DOE) and American auto manufacturers: General Motors, Ford, and Daimler Chrysler. Currently, HEV research and development is conducted by DOE through its FreedomCAR and Vehicle Technologies (FCVT) program. The mission of the FCVT program is to develop more energy efficient and environmentally friendly highway transportation technologies. Program activities include research, development, demonstration, testing, technology validation, and technology transfer. These activities are aimed at developing technologies that can be domestically produced in a clean and cost-competitive manner. The vehicle systems technologies subprogram, which is one of four subprograms under the FCVT program, supports the efforts of the FreedomCAR through a three-phase approach [1] intended to: (1) Identify overall propulsion and vehicle-related needs by analyzing programmatic goals and reviewing industry's recommendations and requirements, then develop the appropriate technical targets for systems, subsystems, and component research and development activities; (2) Develop and validate individual subsystems and components, including electric motors, emission control devices, battery systems, power electronics, accessories, and devices to reduce parasitic losses; and (3) Determine how well the components and subassemblies work together in a vehicle environment or as a …
Date: September 11, 2006
Creator: Staunton, R.H.; Burress, T.A. & Marlino, L.D.
Object Type: Report
System: The UNT Digital Library
Kinetics of HMX and CP Decomposition and Their Extrapolation for Lifetime Assessment (open access)

Kinetics of HMX and CP Decomposition and Their Extrapolation for Lifetime Assessment

Accelerated aging tests play an important role in assessing the lifetime of manufactured products. There are two basic approaches to lifetime qualification. One tests a product to failure over range of accelerated conditions to calibrate a model, which is then used to calculate the failure time for conditions of use. A second approach is to test a component to a lifetime-equivalent dose (thermal or radiation) to see if it still functions to specification. Both methods have their advantages and limitations. A disadvantage of the 2nd method is that one does not know how close one is to incipient failure. This limitation can be mitigated by testing to some higher level of dose as a safety margin, but having a predictive model of failure via the 1st approach provides an additional measure of confidence. Even so, proper calibration of a failure model is non-trivial, and the extrapolated failure predictions are only as good as the model and the quality of the calibration. This paper outlines results for predicting the potential failure point of a system involving a mixture of two energetic materials, HMX (nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and CP (2-(5-cyanotetrazalato) pentaammine cobalt (III) perchlorate). Global chemical kinetic models for the two materials individually …
Date: September 11, 2006
Creator: Burnham, A K; Weese, R K & Adrzejewski, W J
Object Type: Article
System: The UNT Digital Library
What Have We Learned From Decades of CRT, And Where Do We Go From Here? (open access)

What Have We Learned From Decades of CRT, And Where Do We Go From Here?

The Chemical Reactivity Test, or CRT, has been the workhorse for determining short-to-medium term compatibility and thermal stability for energetic materials since the mid 1960s. The concept behind the CRT is quite simple. 0.25 g of material is heated in a 17 cm{sup 3} vessel for 22 hours at 80, 100, or 120 C, and the yield of gaseous products are analyzed by gas chromatography to determine its thermal stability. The instrumentation is shown in Figure 1, and the vessel configuration is shown in Figure 2. For compatibility purposes, two materials, normally 0.25 g of each, are analyzed as a mixture. Recently, data from the past 4 decades have been compiled in an Excel spreadsheet and inspected for reliability and internal consistency. The resulting processed data will be added this year to the LLNL HE Reference Guide. Also recently, we have begun to assess the suitability of the CRT to answer new compatibility issues, especially in view of more modern instrumentation now available commercially. One issue that needs to be addressed is the definition of thermal stability and compatibility from the CRT. Prokosch and Garcia (and the associated MIL-STD-1751A) state that the criterion for thermal stability is a gas yield …
Date: September 11, 2006
Creator: Burnham, A K; Souers, P C; Gagliardi, F J; Weese, R K; DePiero, S C; Tran, T et al.
Object Type: Article
System: The UNT Digital Library
Comparison of Non-Redundant Array and Double Pinhole Coherence Measurements with Soft X-rays (open access)

Comparison of Non-Redundant Array and Double Pinhole Coherence Measurements with Soft X-rays

Experiments on the future Linac Coherent Light Source (LCLS) and other Free Electron Lasers will need to be performed on a single-shot basis. The double pinhole method of measuring spatial coherence requires a separate measurement, with a different pinhole separation distance, for each length scale sampled. This limits its utility for LCLS. A potential alternative uses a Non-Redundant Array (NRA) of apertures designed to probe the coherence over the range of length scales defined by their physical extent, in a single measurement. This approach was tested by comparing diffraction patterns from soft x-rays incident on double pinhole and NRA absorption mask structures. The double pinhole fringe visibility data serve as discrete reference points that verify the continuous spectrum of the NRA coherence data. The results present a quantitative analysis of the double pinhole coherence measurements and a qualitative comparison to the NRA images.
Date: September 11, 2006
Creator: Weil, Gabriel & /SLAC, /Northwestern U.
Object Type: Report
System: The UNT Digital Library