245 Matching Results

Search Results

Advanced search parameters have been applied.

EUV and x-ray emission of nonmagnetic catacysmic variables

Description: Recent results are presented and discussed regarding the EUV and X-ray emission of nonmagnetic cataclysmic variables. Emphasis is given to high accretion rate systems (novalike variables and dwarf novae in outburst), and to a number of apparent discrepancies between observations and the theory of the boundary layer between the accretion disk and the surface of the white dwarf. Discussed are EUV and X-ray light curves, dwarf nova oscillations, and spectra, with new and previously unpublished results on SS Cyg and OY Car.
Date: September 1, 1997
Creator: Mauche, C.W.
Partner: UNT Libraries Government Documents Department

Soft x-ray emission studies of the electronic structure in silicon nanoclusters

Description: Density of states changes in the valence and conduction band of silicon nanoclusters were monitored using soft x-ray emission and absorption spectroscopy as a function of cluster size. a progressive increase in the valence band edge toward lower energy is found fro clusters with decreasing diameters. A similar but smaller shift is observed in the near-edge x-ray absorption data of the silicon nanoclusters.
Date: February 1, 1997
Creator: Van Buuren, T.; Dinh, L.N.; Chase, L.L.; Siekhaus, W.J.; Jumenez, I.; Terminello, L.J. et al.
Partner: UNT Libraries Government Documents Department

Feasibility and applications of cone beam x-ray imaging for containerized wastes

Description: Large area scintillation screens coupled to video and scientific-grade CCD cameras allow high speed digital data acquisition for both single 2-D x-ray projections and tomographic data sets comprised of multiple 2-D projections. While the data cquisition may proceed more rapidly than data acquisition using a linear detector array, there are geometric distortions associated with the projection cone angle long processing times for 3-D tomographic data. This paper reviews issues associated with processing and interpretation of the data and approaches to resolving some of the problems for containerized waste inspection. Results obtained with the Idaho National Engineering Laboratory`s Digital Radiography and Computed Tomography scanner are presented.
Date: December 1, 1995
Creator: Roney, T.; Galbraith, S.; White, T.; Clack, R.; O`Reilly, M.; Defrise, M. et al.
Partner: UNT Libraries Government Documents Department

Study of supra-thermal electrons and K-{alpha} x-rays from high intensity 500 fs laser-produced plasmas

Description: We describe recent laser-solid interaction experiments using the 500 fs Janus Nd:glass (1053 nm) laser presently at 1.5 TW power level. The laser beam path is enclosed in vacuum from the compressor to the target and is focused using an off-axis paraboloid. Optical diagnostics monitor the near field pattern, focal spot, spectrum, temporal shape and pre-pulse level. A 12 {mu}m diameter (FWHM) focal spot is achieved (2.5 {times} diffraction limit) corresponding to a peak irradiance of 8 {times} 1017 W cm{sup {minus}2} on target. A suite of x-ray diagnostics characterize the x-ray emission from the plasma. We present results for normal incidence irradiation of high-Z (Zn, Ge, Mo, Sn) solid targets. The supra-thermal electrons produced in the short scale length plasma have temperature T{sub H} > 100 keV and can efficiently fluoresce the cold K-{alpha} lines in the 8--30 keV energy range.
Date: July 1, 1995
Creator: Dunn, J.; Young, B.K.F.; Hankla, A.K.; Conder, A.D.; White, W.E. & Stewart, R.E.
Partner: UNT Libraries Government Documents Department

Back-side emissions from filtered gold targets

Description: An investigation of the rapid rise time of incoherent x-ray emission from targets heated by an ultra-short pulse (USP) high-intensity optical laser was conducted for use as the x-ray source for inner- shell photo-ionized (ISPI) x ray lasing. Previous studies considered front-side x-ray emission; however, ISPI x-ray lasing requires a filtered x-ray source. Modeling using the hydrodynamics/atomic kinetics code LASNEX of a 40 fs USP driving laser with an intensity of 10 exp(17W/CM2) incident on a flat target of thin Au layered on a Be filter is presented. The filter has a modest influence on the x- ray emission of the Au via conduction cooling but has a large effect on the backside spectrum by removing low energy x rays as the Au emission passes through the filter. The use of such a filtered source is shown to provide the needed x rays to achieve high gain in C at 45A.
Date: August 14, 1997
Creator: Moon, S. J. & Eder, D.C.
Partner: UNT Libraries Government Documents Department

Field experience with a mobile tomographic nondestructive assay system

Description: A mobile tomographic gamma-ray scanner (TGS) developed by Los Alamos National Laboratory was recently demonstrated at the Rocky Flats Environmental Technology Site and is currently in use at Los Alamos waste storage areas. The scanner was developed to assay radionuclides in low-level, transuranic, and mixed waste in containers ranging in size from 2 ft{sup 3} boxes to 83-gallon overpacks. The tomographic imaging capability provides a complete correction for source distribution and matrix attenuation effects, enabling accurate assays of Pu-239 and other gamma-ray emitting isotopes. In addition, the system can reliably detect self-absorbing material such as plutonium metal shot, and can correct for bias caused by self-absorption. The system can be quickly configured to execute far-field scans, segmented gamma-ray scans, and a host of intermediate scanning protocols, enabling higher throughput (up to 20 drums per 8-hour shift). In this paper, we will report on the results of field trials of the mobile system at Rocky Flats and Los Alamos. Assay accuracy is confirmed for cases in which TGS assays can be compared with assays (e.g. with calorimetry) of individual packages within the drums. The mobile tomographic technology is expected to considerably reduce characterization costs at DOE production and environmental technology sites.
Date: December 1, 1995
Creator: Prettyman, T.H.; Betts, S.E.; Taggart, D.P.; Estep, R.J.; Nicholas, N.J.; Lucas, M.C. et al.
Partner: UNT Libraries Government Documents Department

Physics progress report

Description: This document is the November 1948 Physics Division Progress Report from the Mound Laboratory. Items covered include: (1) measurement of the vapor pressure of Postum by effusion and the quartz-sickle gauge, (2) preparation of a Postum sample for x-ray emission spectroscopy studies, (3) possible errors in the vacuum balance, (4) construction of a gamma counter, and (5) preparation of a postum bromide sample.
Date: November 1, 1948
Creator: Haring, M.M.
Partner: UNT Libraries Government Documents Department

Elemental compositions of Spanish and Spanish-colonial majolica ceramics and their use in the identification of provenience

Description: Neutron activation analysis, x-ray diffraction, and petrographic analysis were used to obtain evidence of the origin of pottery and ceramic sherds found in the New World and related to the Spanish empire. (GHT)
Date: January 1, 1977
Creator: Olin, J.S.; Harbottle, G. & Sayre, E.V.
Partner: UNT Libraries Government Documents Department

X-ray microprobe characterization of materials: the case for undulators on advanced storage rings

Description: The unique properties of X rays offer many advantages over electrons and other charged particles for the microcharacterization of materials. X rays are more efficient in exciting characteristic X-ray fluorescence and produce higher fluorescent signals to backgrounds than obtained with electrons. Detectable limits for X rays are a few parts per billion and are 10/sup -3/ to 10/sup -5/ less than for electrons. Energy deposition in the sample by X rays is 10/sup -3/ to 10/sup -4/ less than for electrons for the same detectable concentration. High-brightness storage rings, especially in the 6 GeV class with undulators, will be approximately 10/sup 3/ brighter in the X-ray energy range from 5 keV to 35 keV than existing storage rings and provide for X-ray microprobes that are as bright as the most advanced electron probes. Such X-ray microprobes will produce unprecedented low levels of detection in diffraction, EXAFS, Auger, and photoelectron spectroscopies for both chemical characterization and elemental identification. These major improvements in microcharacterization capabilities will have wide-ranging ramifications not only in materials science but also in physics, chemistry, geochemistry, biology, and medicine.
Date: March 17, 1984
Creator: Sparks, C.J. Jr.
Partner: UNT Libraries Government Documents Department

X-ray fluorescence cross sections for K and L x rays of the elements

Description: X-ray fluorescence cross sections are calculated for the major x rays of the K series 5 less than or equal to Z less than or equal to 101, and the three L series 12 less than or equal to Z less than or equal to 101 in the energy range 1 to 200 keV. This calculation uses Scofield's theoretical partical photoionization cross sections, Krause's evaluation of fluorescence and Coster-Kronig yields, and Scofield's theoretical radiative rates. Values are presented in table and graph format, and an estimate of their accuracy is made. The following x rays are considered: K..cap alpha../sub 1/, K..cap alpha../sub 1/,/sub 2/, K..beta../sub 1/, K..beta../sub 1/,/sub 3/, L..cap alpha../sub 1/, L..cap alpha../sub 1/,/sub 2/, L..beta../sub 1/, L..beta../sub 2/,/sub 15/, L..beta../sub 3/, Ll, L..gamma../sub 1/, L..gamma../sub 4/, and L/sub 1/ ..-->.. L/sub 2/,/sub 3/. For use in x-ray fluorescence analysis, K..cap alpha.. and L..cap alpha.. fluorescence cross sections are presented at specific energies: TiK identical with 4.55 keV, CrK identical with 5.46 keV, CoK identical with 7.00 keV, CuK identical with 8.13 keV, MoK..cap alpha.. identical with 17.44 keV, AgK identical with 22.5 keV, DyK identical with 47.0 keV, and /sup 241/Am identical with 59.54 keV. Supplementary material includes fluorescence and Coster--Kronig yields, fractional radiative rates, fractional fluorescence yields, total L-shell fluorescence cross sections, fluorescence and Coster-Kronig yields in condensed matter, effective fluorescence yields, average L-shell fluorescence yield, L-subshell photoionization cross section ratios, and conversion factors from barns per atom to square centimeters per gram.
Date: June 1, 1978
Creator: Krause, M.O.; Nestor, C.W. Jr.; Sparks, C.J. Jr. & Ricci, E.
Partner: UNT Libraries Government Documents Department

X-Ray Emission Cross Sections following Charge Exchange by Multiply-Charged Ions of Astrophysical Interest

Description: The CTMC method is used to calculate emission cross sections following charge exchange processes involving highly charged ions of astrophysical interest and typical cometary targets. Comparison is made to experimental data obtained on the EBIT-I machine at Lawrence Livermore National Laboratory LLNL for O{sup 8+} projectiles impinging on different targets at a collision energy of 10 eV/amu. The theoretical cross sections are used together with ion abundances measured by the Advanced Composition Explorer to reproduce cometary spectra. Discrepancies due to different estimated delays of solar wind events between the comet and the Earth-orbiting satellite are discussed.
Date: March 12, 2007
Creator: Otranto, S; Olson, R E & Beiersdorfer, P
Partner: UNT Libraries Government Documents Department

Electronic structure of uranyl compounds: an XPS study

Description: X-ray photoemission spectroscopy (XPS) measurements are reported for a series of uranyl compounds in which the primary uranium--oxygen (U--O/sub I/) separation varies substantially. Crystal field splittings of the U 6p$sub 3$/ $sub 2$ core electron energy levels were observed. These splittings are explained with the point charge crystal field model when both first and second near uranium neighbors are considered. The systematics of charge migration (observed by monitoring electron core level shifts) associated with bonding in the uranyl series were also investigated. Core level shifts for compounds with different U--O/sub I/ separations are large, but essentially no relative shifts of uranium and oxygen core levels were observed within the uranyl group. Thus charge appears to flow between the uranyl group (as a unit), and the secondary uranium ligands as U--O/sub I/ is varied. The U 5f electron participation in covalent bonding was also studied by systematically measuring XPS line intensities; U 5f electron occupation appears to be minimal. (auth)
Date: January 1, 1975
Creator: Veal, B.W.; Lam, D.J.; Hoekstra, H.R. & Carnall, W.T.
Partner: UNT Libraries Government Documents Department

Application of synchrotron radiation to elemental analysis

Description: The use of a synchrotron storage ring as a high brightness source for production of monoergic, variable energy, and highly polarized x-ray beams promises to revolutionize the field of elemental analysis. The results of exploratory work using the Cornell synchrotron facility, CHESS, will be described. Design considerations and features of the new X-Ray Microprobe Facility now under construction at the Brookhaven National Synchrotron Light Source will be presented. This facility will be used for bulk analysis and for microanalysis with an initial spatial resolution of the order of 30 ..mu..m.
Date: January 1, 1983
Creator: Jones, K.W.; Gordon, B.M.; Hanson, A.L.; Hastings, J.B.; Howells, M.R.; Kraner, H.W. et al.
Partner: UNT Libraries Government Documents Department

X-ray, neutron, and electron scattering. Report of a materials sciences workshop

Description: The ERDA Workshop on X-ray, Neutron, and Electron Scattering to assess needs and establish priorities for energy-related basic research on materials. The general goals of the Workshop were: (1) to review various energy technologies where x-ray, neutron, and electron scattering techniques might make significant contributions, (2) to identify present and future materials problems in the energy technologies and translate these problems into requirements for basic research by x-ray, neutron, and electron scattering techniques, (3) to recommend research areas utilizing these three scattering techniques that should be supported by the DPR Materials Sciences Program, and (4) to assign priorities to these research areas.
Date: August 1, 1977
Partner: UNT Libraries Government Documents Department

Application of synchrotron radiation to x-ray fluorescence analysis of trace elements

Description: The development of synchrotron radiation x-ray sources has provided the means to greatly extend the capabilities of x-ray fluorescence analysis for determinations of trace element concentrations. A brief description of synchrotron radiation properties provides a background for a discussion of the improved detection limits compared to existing x-ray fluorescence techniques. Calculated detection limits for x-ray microprobes with micrometer spatial resolutions are described and compared with experimental results beginning to appear from a number of laboratories. The current activities and future plans for a dedicated x-ray microprobe beam line at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory are presented.
Date: August 1, 1986
Creator: Gordon, B.M.; Jones, K.W. & Hanson, A.L.
Partner: UNT Libraries Government Documents Department

Some uncertainties associated with preparation of standards in organic matrix

Description: Until recently no techniques which have multielement detection capability, high sensitivity and good spatial resolution in relatively thick tissue sections have existed. The use of proton induced x-ray emission /PIXE/ and synchrotron radiation induced x-ray emission /SRIXE/ using proton and x-ray microbeams changed this situation. However there are some difficulties with the existing standards for quantitatively calibrating the trace elements concentration in biological materials. For the purpose of our experiments a special technique of standard production was applied. 7 refs., 1 tab., 1 fig.
Date: January 1, 1986
Creator: Cholewa, M.; Hanson, A.L.; Jones, K.W.; McNally, W.P. & Fand, I.
Partner: UNT Libraries Government Documents Department

Waste characterization activities at the Lawrence Livermore National Laboratory

Description: Radioactive and hazardous wastes are generated at many national laboratories, military sites, fuel fabrication and enrichment plants, reactors, and many other facilities. At all of these sites, wastes must be separated, categorized, possibly treated, and packed into containers for shipment to waste-storage or disposal sites. Prior to treatment, storage or, shipment, the containers must be characterized to determine the ultimate disposition of the contained waste. Comprehensive and accurate nondestructive evaluation (NDE) and nondestructive assay (NDA) methods can be used to characterize most waste containers in a safe and cost-effective manner without opening them. The Lawrence Livermore National Laboratory (LLNL) is investigating and developing the application of x-ray and {gamma}-ray methods to nonintrusively characterize waste containers and/or items. X-ray NDE methods are being investigated to determine whether they can be used to identify hazardous and nonconforming materials. A {gamma}-ray NDA method is used to identify the radioactive sources within a container and to accurately quantify their strength. In this paper we describe five waste characterization projects being conducted at LLNL that apply both the NDE and NDA methods and present results.
Date: June 28, 1995
Creator: Roberson, G.P.; Martz, H.E. & Haskins, J.J.
Partner: UNT Libraries Government Documents Department

Comparison of synchrotron x-ray microanalysis with electron and proton microscopy for individual particle analysis

Description: This paper is concerned with the evaluation of the use of synchrotron/radiation induced x-ray fluorescences ({mu}-SRXRF) as implemented at two existing X-ray microprobes for the analysis of individual particles. As representative environmental particulates, National Institutes of Science and Technology (NIST) K227, K309, K441 and K961 glass microspheres were analyzed using two types of X-ray micro probes: the white light microprobe at beamline X26A of the monochromatic (15 keV) X-ray microprobe at station 7.6 of the SRS. For reference, the particles were also analyzed with microanalytical techniques more commonly employed for individual particles analysis such as EPMA and micro-PIXE.
Date: January 1, 1991
Creator: Janssens, K.H.; van Langevelde, F.; Adams, F.C. (Universitaire Instelling Antwerpen, Antwerp (Belgium)); Vis, R.D. (Vrije Univ., Amsterdam (Netherlands)); Sutton, S.R.; Rivers, M.L. (Chicago Univ., IL (United States)) et al.
Partner: UNT Libraries Government Documents Department

Survey of chemical speciation of trace elements using synchrotron radiation

Description: Information concerning the chemical state of trace elements in biological systems generally has not been available. Such information for toxic elements and metals in metalloproteins could prove extremely valuable in the elucidation of their metabolism and other biological processes. The shielding of core electrons by binding electrons affect the energy required for creating inner-shell holes. Furthermore, the molecular binding and the symmetry of the local environment of an atom affect the absorption spectrum in the neighborhood of the absorption edge. X-ray absorption near-edge structure (XANES) using synchrotron radiation excitation can be used to provide chemical speciation information for trace elements at concentrations as low as 10 ppM. The structure and position of the absorption curve in the region of an edge can yield vital data about the local structure and oxidation state of the trace element in question. Data are most easily interpreted by comparing the observed edge structure and position with those of model compounds of the element covering the entire range of possible oxidation states. Examples of such analyses are reviewed. 14 refs., 1 fig.
Date: January 1, 1985
Creator: Gordon, B.M.
Partner: UNT Libraries Government Documents Department

Determining cerium in plutonium by anion exchange and x-ray fluorescence

Description: This report describes a procedure for determining cerium in plutonium using an anion-exchange separation and x-ray fluorescence. We add lanthanum to the plutonium solution as an internal standard, oxidize the plutonium to Pu/sup /plus/4/, and pass the solution through an anion-exchange column with 8M HCl. The Pu/sup /plus/4/ sorbs to the resin, and the cerium and lanthanum pass through the column completely. We evaporate the solution containing the cerium and the lanthanum to 0.5 mL for pipetting onto a resin paper disc. The Pu/sup /plus/4/ is eluted off the column using 0.1M HCl. We then measure the K/sub ..cap alpha../ x-ray line for both cerium and lanthanum. The ratio of cerium to lanthanum for the sample is then compared with those from the standards. This method has a precision of 2.8% relative standard deviation for cerium over a concentration range of 0.1 to 5% cerium. 2 refs., 2 figs., 3 tabs.
Date: May 1, 1988
Creator: Martell, C.J. & Hansel, J.M.
Partner: UNT Libraries Government Documents Department

Nuclear methods in environmental and energy research

Description: The topics considered in the seven sessions were nuclear methods in atmospheric research; nuclear and atomic methodology; nuclear methods in tracer applications; energy exploration, production, and utilization; nuclear methods in environmental monitoring; nuclear methods in water research; and nuclear methods in biological research. Individual abstracts were prepared for each paper. (JSR)
Date: January 1, 1977
Creator: Vogt, J.R. (ed.)
Partner: UNT Libraries Government Documents Department

Development and application of the Los Alamos nuclear microprobe: hardware, software, and calibration

Description: There is a great demand for spatially resolved quantitative trace element analyses of geologic samples. This class of samples is characteristically heterogeneous, fine grained, and compositionally complex. The Los Alamos nuclear microprobe has been developed for, and applied to, non-destructive in-situ geochemical analysis, primarily using the proton induced x-ray emission technique (PIXE). Characteristic x-ray spectra are acquired by bombardment with 1 to 200 nA beams of protons from the Los Alamos vertical Van de Graaff accelerator. Beam spot diameters of 10 ..mu..m are routine. After spectrum deconvolution, detection limits of approximately 5 ppM are obtained for an integrated charge on the order of 10 ..mu..C. Applications, concomitant with development have included analyses of meteorites, including one potential sample of Mars, terrestrial oil shales, archaeological artifacts, and ore mineral samples.
Date: January 1, 1985
Creator: Benjamin, T.M.; Rogers, P.S.Z.; Duffy, C.J.; Conner, J.F.; Maggiore, C.J. & Tesmer, J.R.
Partner: UNT Libraries Government Documents Department