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X-ray microimaging by diffractive techniques
The report summarizes the development of soft x-ray microscopes at the National Synchrotron Light Source X-1A beamline. We have developed a soft x-ray microscopy beamline (X-1A) at the National Synchrotron Light Source at Brookhaven National Laboratory. This beamline has been upgraded recently to provide two endstations dedicated to microscopy experiments. One endstation hosts a brand new copy of the redesigned room temperature scanning x-ray microscope (STXM), and the other end station hosts a cryo STXM and the original redesigned room temperature microscope, which has been commissioned and has started operation. Cryo STXM and the new microscope use the same new software package, running under the LINUX operating system. The new microscope is showing improved image resolution and extends spectromicroscopy to the nitrogen, oxygen and iron edges. These microscopes are used by us, and by users of the facility, to image hydrated specimens at 50 nm or better spatial resolution and with 0.1-0.5 eV energy resolution. This allows us to carry out chemical state mapping in biological, materials science, and environmental and colloidal science specimens. In the cryo microscope, we are able to do chemical state mapping and tomography of frozen hydrated specimens, and this is of special importance for radiation-sensitive …
Date:
July 31, 2001
Creator:
Kirz, Janos & Jacobsen, Chris
Object Type:
Report
System:
The UNT Digital Library
X-Ray Observations of Unidentified H.E.S.S. Gamma-Ray Sources
In a survey of the inner part of the Galaxy, performed with the H.E.S.S. Instrument (High energy stereoscopic system) in 2004 and 2005, a large number of new unidentified very high energy (VHE) {gamma}-ray sources above an energy of 100 GeV was discovered. Often the {gamma}-ray spectra in these sources reach energies of up to {approx} 10 TeV. These are the highest energy particles ever attributed to single astrophysical objects. While a few of these sources can be identified at other wavebands, most of these sources remain unidentified so far. A positive identification of these new g-ray sources with a counterpart object at other wavebands requires (a) a positional coincidence between the two sources,( b) a viable {gamma}-ray emission mechanism and (c) a consistent multiwavelength behavior of the two sources. X-ray observations with satellites such as XMM-Newton, Chandra or Suzaku provide one of the best channels to studying these enigmatic {gamma}-ray sources at other wavebands, since they combine high angular resolution and sensitivity with the ability to access non-thermal electrons through their synchrotron emission. We therefore have started a dedicated program to investigate VHE {gamma}-ray sources with high-sensitivity X-ray instruments.
Date:
October 10, 2007
Creator:
Funk, S.
Object Type:
Article
System:
The UNT Digital Library
X-ray Optics and Diagnostics for the First Experiments on the Linac Coherent Light Source
The Linac Coherent Light Source (LCLS) is a 1.5 to 15 {angstrom}-wavelength free-electron laser (FEL), currently proposed for the Stanford Linear Accelerator Center (SLAC). The photon output consists of high brightness, transversely coherent pulses with duration < 300 fs, together with a broad spontaneous spectrum with total power comparable to the coherent output. The output fluence, and pulse duration, pose special challenges for optical component and diagnostic designs. We discuss some of the proposed solutions, and give specific examples related to the planned initial experiments.
Date:
June 13, 2001
Creator:
Wootton, A.; Arthur, J.; Barbee, T.; Bionta, R.; London, R.; Park, H. S. et al.
Object Type:
Article
System:
The UNT Digital Library
X-Ray Optics Research for Linac Coherent Light Source: Interaction of Ultra-Short X-Ray Pulses with Matter
Free electron lasers operating in the 0.1 to 1.5 nm wavelength range have been proposed for the Stanford Linear Accelerator Center (USA) and DESY (Germany). The unprecedented brightness and associated fluence predicted for pulses <300 fs pose new challenges for optical components. A criterion for optical component design is required, implying an understanding of x-ray - matter interactions at these extreme conditions. In our experimental effort, the extreme conditions are simulated by currently available sources ranging from optical lasers, through x-ray lasers (at 14.7 nm) down to K-alpha sources (-0.15 nm). In this paper we present an overview of our research program, including (a) Results from the experimental campaign at a short pulse (100 fs - 5 ps) power laser at 800 nm, (b) K-{alpha} experiments, and (c) Computer modeling and experimental project using a tabletop high brightness ps x-ray laser at the Lawrence Livermore National Laboratory.
Date:
April 16, 2003
Creator:
Kuba, J; Wootton, A; Bionta, R M; Shepherd, R; Fill, E E; Dunn, J et al.
Object Type:
Article
System:
The UNT Digital Library
X-Ray Optics Research for the Linac Coherent Light Source: Interaction of Ultra-Short X-Ray Laser Pulses with Optical Materials
Free electron lasers operating in the 0.1 to 1.5 nm wavelength have been proposed for the Stanford Linear Accelerator Center and DESY (Germany). The unprecedented brightness and associated fluence predicted for pulses <300 fs pose new challenges for optical components. A criterion for optical component design is required, implying an understanding of x-ray-matter interactions at these extreme conditions. In our experimental effort, the extreme conditions are simulated by currently available sources ranging from optical lasers, through x-ray lasers (at 14.7 nm) down to K-alpha sources ({approx}0.15 nm). In this paper we present an overview of our research program, including (a) Results from the experimental campaign at a short pulse (100 fs-5 ps) power laser at 800 nm, (b) K-a experiments, and (c) Computer modeling and experimental project using a tabletop high brightness ps x-ray laser at the Lawrence Livermore National Laboratory.
Date:
July 24, 2002
Creator:
Kuba, J; Wootton, A; Bionta, R M; Shepherd, R; Dunn, J; Smith, R F et al.
Object Type:
Article
System:
The UNT Digital Library
X-ray photoelectron spectroscopy of negative electrodes from high-power lithium-ion cells showing various levels of power fade
High-power lithium-ion cells for transportation applications are being developed and studied at Argonne National Laboratory. The current generation of cells containing LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2}-based cathodes, graphite-based anodes, and LiPF6-based electrolytes show loss of capacity and power during accelerated testing at elevated temperatures. Negative electrode samples harvested from some cells that showed varying degrees of power and capacity fade were examined by X-ray photoelectron spectroscopy (XPS). The samples exhibited a surface film on the graphite, which was thicker on samples from cells that showed higher fade. Furthermore, solvent-based compounds were dominant on samples from low power fade cells, whereas LiPF{sub 6}-based products were dominant on samples from high power fade cells. The effect of sample rinsing and air exposure is discussed. Mechanisms are proposed to explain the formation of compounds suggested by the XPS data.
Date:
February 28, 2004
Creator:
Herstedt, Marie; Abraham, Daniel P. & Kerr, John B.
Object Type:
Article
System:
The UNT Digital Library
X-ray Photoelectron Spectroscopy ofGaP_{1-x}N_x Photocorroded as a Result of Hydrogen Productionthrough Water Electrolysis
Photoelectrochemical (PEC) cells produce hydrogen gas through the sunlight driven electrolysis of water. By extracting hydrogen and oxygen from water and storing solar energy in the H-H bond, they offer a promising renewable energy technology. Addition of dilute amounts of nitrogen to III-V semiconductors has been shown to dramatically increase the stability of these materials for hydrogen production. In an effort to learn more about the origin of semiconductor photocorrosion in PEC cells, three samples of p-type GaP with varying levels of nitrogen content (0%, 0.2%, 2%) were photocorroded and examined by X-ray Photoelectron Spectroscopy (XPS). GaPN samples were observed to be more efficient during the hydrogen production process than the pure GaP samples. Sample surfaces contained gallium oxides in the form of Ga{sub 2}O{sub 3} and Ga(OH){sub 3} and phosphorus oxide (P{sub 2}O{sub 5}), as well as surface oxides from exposure to air. A significant shift in intensity from bulk to surface peaks dramatic nitrogen segregation to the surface during photoelectrochemical hydrogen production. Further investigations, including using a scanning electron microscope to investigate sample topography and inductively coupled plasma mass spectroscopy (ICP-MS) analysis for solution analyses, are under way to determine the mechanism for these changes.
Date:
September 27, 2006
Creator:
Mayer, Marie A. & /Illinois U., Urbana /SLAC
Object Type:
Report
System:
The UNT Digital Library
X-ray photoemission electron microscopy, a tool for the investigation of complex magnetic structures.
X-ray Photoemission Electron Microscopy unites the chemical specificity and magnetic sensitivity of soft x-ray absorption techniques with the high spatial resolution of electron microscopy. The discussed instrument possesses a spatial resolution of better than 50 nm and is located at a bending magnet beamline at the Advanced Light Source, providing linearly and circularly polarized radiation between 250 and 1300 eV. We will present examples which demonstrate the power of this technique applied to problems in the field of thin film magnetism. The chemical and elemental specificity is of particular importance for the study of magnetic exchange coupling because it allows separating the signal of the different layers and interfaces in complex multi-layered structures.
Date:
August 30, 2001
Creator:
Scholl, Andreas; Ohldag, Hendrik; Nolting, Frithjof; Stohr, Joachim & Padmore, Howard A.
Object Type:
Article
System:
The UNT Digital Library
X-Ray Photoionized Plasmas in the Laboratory
The advanced spectroscopic capabilities of the new X-ray telescopes Chandra and XMM lead to a need for improved benchmarking of models for the photoionized accretion-disk plasmas which represent over half of known astrophysical X-ray sources. They report the first laboratory experimental results using 120 TW, 180 eV Z-pinch plasmas to drive iron samples into the photoionized equilibrium. The pinch spectrum, temperature, power and uniformity have been characterized in order to qualify it as a photoionization driver. Preliminary time-integrated (8 {angstrom} to 18 {angstrom}) and time-resolved (12.5 {angstrom} to 16 {angstrom}) absorption and emission spectra of photoionized L-shell Fe and K-shell Na and F were observed using X-ray crystal spectrometers. Plans for upcoming experiments are also discussed.
Date:
April 22, 2000
Creator:
Heeter, R. F.; Foord, M. E.; Thoe, R. S.; Emig, J. A.; Springer, P. T.; Bailey, J. et al.
Object Type:
Article
System:
The UNT Digital Library
X-ray Polarization Measurements at Relativistic Laser Intensities
An effort has been started to measure the short pulse laser absorption and energy partition at relativistic laser intensities up to 10{sup 21} W/cm{sup 2}. Plasma polarization spectroscopy is expected to play an important role in determining fast electron generation and measuring the electron distribution function.
Date:
March 20, 2004
Creator:
Beiersdorfer, P; Shepherd, R; Mancini, R C; Chen, H; Dunn, J; Keenan, R et al.
Object Type:
Article
System:
The UNT Digital Library
X-Ray Powder Diffraction Study of Synthetic Palmierite, K{sub 2}Pb(SO{sub 4}){sub 2}
Palmierite (K{sub 2}Pb(SO{sub 4}){sub 2}) has been prepared via a chemical synthesis method. Intensity differences were observed when X-ray powder data from the newly synthesized compound were compared to the published powder diffraction card (PDF) 29-1015 for Palmierite. Investigation of these differences indicated the possibility of preferred orientation and/or chemical inhomogeneity affecting intensities, particularly those of the basal (00{ell}) reflections. Annealing of the Palmierite was found to reduce the effects of preferred orientation. Electron microprobe analysis confirmed K:Pb:S as 2:1:2 for the annealed Palmierite powder. Subsequent least-squares refinement and Rietveld analysis of the annealed powder showed peak intensities very close to that of a calculated Palmierite pattern (based on single crystal data), yet substantially higher than many of the PDF 29-1015 published intensities. Further investigation of peak intensity variation via calculated patterns suggested that the intensity discrepancies between the annealed sample and those found in PDF 29-1015 were potentially due to chemical variation in the K{sub 2}Pb(SO{sub 4}){sub 2} composition. X-ray powder diffraction and crystal data for Palmierite are reported for the annealed sample. Palmierite is Trigonal/Hexagonal with unit cell parameters a = 5.497(1){angstrom}, c = 20.864(2) {angstrom}, space group R-3m (166), and Z = 3.
Date:
December 19, 2000
Creator:
Tissot, Ralph G., Jr.; Rodriguez, Mark A.; Sipola, Diana L. & Voigt, James A.
Object Type:
Article
System:
The UNT Digital Library
The X-Ray Properties of the Most Luminous Quasars From the Sloan Digital Sky Survey
This article studies the X-ray properties of a representative sample of 59 of the most optically luminous quasars in the universe spanning a redshift range of z ≈ 1.5-4.5.
Date:
May 18, 2007
Creator:
Just, Dennis W.; Brandt, William Nielsen; Shemmer, Ohad; Steffen, Aaron; Schneider, Donald P.; Chartas, George et al.
Object Type:
Article
System:
The UNT Digital Library
X-ray Pulse Length Characterization using the Surface Magneto Optic Kerr Effect
It will be challenging to measure the temporal profile of the hard X-ray SASE beam independently from the electron beam in the LCLS and other 4th generation light sources. A fast interaction mechanism is needed that can be probed by an ultrafast laser pulse in a pump-probe experiment. It is proposed to exploit the rotation in polarization of light reflected from a thin magnetized film, known as the surface magneto optic Kerr effect (SMOKE), to witness the absorption of the x-ray pulse in the thin film. The change in spin orbit coupling induced by the x-ray pulse occurs on the subfemtosecond time scale and changes the polarization of the probe beam. The limitation to the technique lies with the bandwidth of the probe laser pulse and how short the optical pulse can be made. The SMOKE mechanism will be described and the choices of materials for use with 1.5 {angstrom} x-rays. A schematic description of the pump-probe geometry for x-ray diagnosis is also described.
Date:
October 4, 2006
Creator:
Krejcik, P.
Object Type:
Article
System:
The UNT Digital Library
X-ray Radiography and Scattering Diagnosis of Dense Shock-Compressed Matter
Highly coupled Boron plasma has been probed by spectrally resolving an x-ray source scattered by the plasma. Electron density was inferred from the inelastic feature in the collective scattering regime. In addition, the mass density inferred from the non-collective X-ray Thomson scattering has been tested with independent characterization using X-ray radiography in the same drive condition. High-intensity laser produced K-alpha radiation was used as a backlighter for these dynamically compressed plasma experiments providing a high temporal resolution of the measurements. Mass density measurements from both methods are in good agreement. The measurements yield a compression of 1.3 in agreement with detailed radiation-hydrodynamic modeling. From the charge state measured in the non-collective regime and the electron density measured in the collective regime the mass density can then be constrained to 3.15 {+-} 0.16.
Date:
November 23, 2009
Creator:
Pape, S L; Neumayer, P; Fortmann, C; Doeppner, T; Davis, P; Krichter, A et al.
Object Type:
Article
System:
The UNT Digital Library
X-Ray Raman Spectroscopy of High-Pressure Phases and Novel Materials derived from Low-Z Compounds
None
Date:
December 19, 2004
Creator:
Evans, W. J.; Eng, P. J.; Maddox, B.; Newville, M.; Baer, B.; Cynn, H. et al.
Object Type:
Report
System:
The UNT Digital Library
X-ray resonant magnetic scattering investigations of hexagonal multiferroics RMnO3 (R = Dy, Ho, Er)
Electricity and magnetism were unified into a common subject by James Clerk Maxwell in the nineteenth century yielding the electromagnetic theory. Four equations govern the dynamics of electric charges and magnetic fields, commonly known as Maxwell's equations. Maxwell's equations demonstrate that an accelerated charged particle can produce magnetic fields and a time varying magnetic field can induce a voltage - thereby linking the two phenomena. However, in solids, electric and magnetic ordering are most often considered separately and usually with good reason: the electric charges of electrons and ions are responsible for the charge effects, whereas the electron spin governs magnetic properties.
Date:
December 19, 2009
Creator:
Nandi, Shibabrata
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
X-ray resonant scattering studies of charge and orbital ordering in Pr{sub 1{minus}z}, Ca{sub x}, MnO{sub 3}
We present the results of x-ray scattering studies of the charge and orbital ordering in the manganite series Pr{sub 1{minus}z}, Ca{sub x}, MnO{sub 3} with x = 0.25, 0.4 and 0.5. The polarization and azimuthal dependence of the charge and orbital ordering in these compounds is characterized both in the resonant and nonresonant limits, and compared with the predictions of current theories. The results are qualitatively consistent with both cluster and LDA+U calculations of the electronic structure.
Date:
August 14, 2000
Creator:
V. Zimmermann, M.; Nelson, C. S.; Hill, J. P.; Gibbs, D.; Blume, M.; Casa, D. et al.
Object Type:
Article
System:
The UNT Digital Library
X-ray Scanner for ODP Leg 204: Drilling Gas Hydrates on Hydrate Ridge, Cascadia Continental Margin
An x-ray scanner was designed and fabricated at Lawrence Berkeley National Laboratory to provide high speed acquisition of x-ray images of sediment cores collected on the Ocean Drilling Program (ODP) Leg 204: Drilling Gas Hydrates On Hydrate Ridge, Cascadia Continental Margin. This report discusses the design and fabrication of the instrument, detailing novel features that help reduce the weight and increase the portability of the instrument. Sample x-ray images are included. The x-ray scanner was transferred to scientific drilling vessel, the JOIDES Resolution, by the resupply ship Mauna Loa, out of Coos Bay, Oregon on July 25. ODP technicians were trained in the instruments operation. The availability of the x-ray scanner at the drilling site allows real-time imaging of cores containing methane hydrate immediately after retrieval. Thus, imaging experiments on cores can yield information on the distribution and quantity of methane hydrates. Performing these measurements at the location of core collection eliminates the need for high pressures or low temperature core handling while the cores are stored and transported to a remote imaging laboratory.
Date:
August 8, 2002
Creator:
Freifeld, Barry; Kneafsey, Tim; Pruess, Jacob; Reiter, Paul & Tomutsa, Liviu
Object Type:
Report
System:
The UNT Digital Library
X-ray scattering intensities of water at extreme pressure and temperature
We have calculated the coherent x-ray scattering intensity of several phases of water at 1500 and 2000 K under high pressure, using ab initio Density Functional Theory (DFT). Our calculations span the molecular liquid, ice VII, and superionic solid phases, including the recently predicted symmetrically hydrogen bonded region of the superionic phase. We show that wide angle x-ray scattering intensity could be used to determine phase boundaries between these high pressure phases, and we compare the results for ice VII and superionic water. We compute simulated spectra and provide new atomic scattering form factors for water at extreme conditions, which take into account frequently neglected changes in ionic charge and electron delocalization. We show that our modifed atomic form factors allow for a nearly exact comaprison to the total x-ray scattering intensities calculated from DFT. Finally, we analyze the effect our new form factors have on determination of the oxygen-oxygen radial distribution function.
Date:
January 3, 2007
Creator:
Goldman, N & Fried, L E
Object Type:
Article
System:
The UNT Digital Library
X-ray scattering studies of correlated polarons in La(0.7)Ca(0.3)MnO(3)
None
Date:
August 16, 2000
Creator:
Nelson, C. S.; Zimmermann, M.; Hill, J. P.; Gibbs, D.; Kiryukhin, V.; Koo, T. Y. et al.
Object Type:
Article
System:
The UNT Digital Library
X-ray Scattering Techniques for Characterization of Nanosystems in Lifescience
The intent of this chapter is to provide the basics of using x-ray diffraction techniques in order to obtain information on the structure and morphology of the nanosystems, and also to point out some of its strengths and weaknesses when compare to other characterization techniques. X-ray scattering examines over a wide range of density domains from a tenth to a thousandth angstrom. Essentially, this covers a whole range of condensed matter, including the structure and morphology of nanosystems, particularly useful for examining nanostructures in lifescience. This range of domain size requires both the wide-angle x-ray scattering (WAXS) and small-angle (SAXS) x-ray scattering techniques. Roughly WAXS covers from 2 nm down, and SAXS covers from .5 nm to 100 nm and possibly 1,000 nm for a finely tuned instrument. Brief theoretical description of both WAXS and SAXS will be given in this chapter. WAXS, by itself is a powerful technique in providing information on the crystallographic structure or lack of structure, atomic positions and sizes in a unit cell, to some extend, chemical compositions and as well as chemical stoichiometry. Examples of such experiments will also be given. In order to be able to describe the technique of x-ray scattering, some …
Date:
April 11, 2005
Creator:
Saw, C K
Object Type:
Article
System:
The UNT Digital Library
X-ray Sources Generated from Gas-Filled Laser-Heated Targets
The X-ray sources in the 4-7 keV energy regime can be produced by laser-irradiating high-Z gas-filled targets with high-powered lasers. A series of experiments have been performed using underdense targets that are supersonically heated with {approx} 35 W of 0.35 {micro}m laser light. These targets were cylindrical Be enclosures that were filled with 1-2 atms of Xe gas. L-shell x-ray emission is emitted from the plasma and detected by Bragg crystal spectrometers and x-ray diodes. Absolute flux measurements show conversion efficiencies of {approx} 10% in the multi-kilovolt x-ray emission. These sources can be used as bright x-ray backlighters or for material testing.
Date:
June 6, 2000
Creator:
Back, C. A.; Grun, J.; Decker, C. D.; Davis, J.; Laming, J. M.; Feldman, U. et al.
Object Type:
Article
System:
The UNT Digital Library
X-ray speckle contrast variation at a sample-specific absorption edges
The authors measured static x-ray speckle contrast variation with the incident photon energy across sample-specific absorption edges. They propose that the variation depends strongly on the spectral response function of the monochromator. Speckle techniques have been introduced to the x-ray regime during recent years. Most of these experiments, however, were done at photon energies above 5 keV. They are working on this technique in the 1 to 4 keV range, an energy range that includes many important x-ray absorption edges, e.g., in Al, Si, P, S, the rare-earths, and others. To their knowledge, the effect of absorption edges on speckle contrast has not yet been studied. In this paper, they present their initial measurements and understanding of the observed phenomena.
Date:
May 3, 2000
Creator:
Retsch, C. C.; Wang, Y.; Frigo, S. P.; Stephenson, G. B. & McNulty, I.
Object Type:
Article
System:
The UNT Digital Library
X-ray Spectral Measurements and Collisional Radiative Modeling of Hot, High-Z Plasmas at the Omega Laser
M-Band and L-Band Gold spectra between 3 to 5 keV and 8 to 13 keV, respectively, have been recorded by a photometrically calibrated crystal spectrometer. The spectra were emitted from the plasma in the laser deposition region of a 'hot hohlraum'. This is a reduced-scale hohlraum heated with {approx} 9 kJ of 351 nm light in a 1 ns square pulse at the Omega laser. The space- and time-integrated spectra included L-Band line emission from Co-like to Ne-like gold. The three L-Band line features were identified to be the 3s {yields} 2p, 3d{sub 5/2} {yields} 2p{sub 3/2} and 3d{sub 3/2} {yields} 2p{sub 1/2} transitions at {approx}9 keV, {approx}10 keV and {approx}13 keV, respectively. M-Band 5f {yields} 3d, 4d {yields} 3p, and 4p {yields} 3s transition features from Fe-like to P-like gold were also recorded between 3 to 5 keV. Modeling from the radiation-hydrodynamics code LASNEX, the collisional-radiative codes FLYCHK and SCRAM, and the atomic structure code FAC were used to model the plasma and generate simulated spectra for comparison with the recorded spectra. Through these comparisons, we have determined the average electron temperature of the emitting plasma to be {approx} 6.5 keV. The electron temperatures predicted by LASNEX appear to …
Date:
February 20, 2008
Creator:
May, M. J.; Schneider, M. B.; Hansen, S. B.; Chung, H.; Hinkel, D. E.; Baldis, H. A. et al.
Object Type:
Article
System:
The UNT Digital Library