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Diagnostic Spectrometers for High Energy Density X-Ray Sources
2007-01-01
A new generation of advanced laser, accelerator, and plasma confinement devices are emerging that are producing extreme states of light and matter that are unprecedented for laboratory study. Examples of such sources that will produce laboratory x-ray emissions with unprecedented characteristics include megajoule-class and ultrafast, ultraintense petawatt laser-produced plasmas. Tabletop high-harmonic-generation x-ray sources. High-brightness zeta-pinch and magnetically confined plasma sources. And coherent x-ray free electron lasers and compact inverse-Compton x-ray sources. Characterizing the spectra, time structure, and intensity of x rays emitted by these and other novel sources is critical to assessing system performance and progress as well as pursuing the new and unpredictable physical interactions of interest to basic and applied ...
Cryogenic X-Ray Diffraction Microscopy for Biological Samples
2009-01-01
X-ray diffraction microscopy (XDM) is well suited for nondestructive, high-resolution biological imaging, especially for thick samples, with the high penetration power of x rays and without limitations imposed by a lens. We developed nonvacuum, cryogenic (cryo-) XDM with hard x rays at 8 keV and report the first frozen-hydrated imaging by XDM. By preserving samples in amorphous ice, the risk of artifacts associated with dehydration or chemical fixation is avoided, ensuring the imaging condition closest to their natural state. The reconstruction shows internal structures of intact D. radiodurans bacteria in their natural contrast
Recent developments in X-ray and hard X-ray imaging detector, high-intensity sources, hard X-ray imaging optics, calibration, and detection technologies are discussed. Particular attention is given to a high-MTF X-ray image intensifier, application of monolithic CdZnTe linear solid state ionization detectors for X-ray imaging, magnetic response of high-Tc superconductors to X-ray radiation and detection of X-rays, laboratory soft X-ray source with foil target, detection of explosive materials using nuclear radiation, energy response of astronomical CCD X-ray detectors, calibration techniques for high-flux X-ray detectors, fabrication of grazing-incidence optics using flow-polishing techniques, and numerical simulations for capillary-based X-ray optics. (No individual items are abstracted in this volume)
XAFS measurement system at atmospheric pressure in the soft x-ray region
2005-01-01
The investigation about an adsorption behavior of a molecule on solid state surface has been interested in a catalytic and surface reaction fields. Fox X-ray Absorption Fine Structure (XAFS) measurement of liquid or oily samples, there are many difficulties in the soft X-ray energy region. In this report I have constructed the high-throughput system for XAFS measurement with using He-path and Be window at soft X-ray beamline (BL-3) on Hiroshima Synchrotron Radiation Center (HSRC). (author)
X-ray state analysis by means of electron capture decay
1998-01-01
K{alpha} X-ray induced by EC decay of {sup 55}Fe and {sup 71}Ge-labeled compounds were measured by wavelength dispersive X-ray spectrometer equipped position sensitive proportional detector. In both nuclides, peak energies of K{alpha}{sub 2} X-rays are lower (-0.4 - -0.6 eV) than those of Mn and Ga compounds by photoionization. It is thought that the causes of these differences are intensity of high energy satellite peaks by shake up process. (author)
X-ray spectroscopy and dosimetry with a portable CdTe device
2007-01-01
X-ray spectra and dosimetry information are very important for quality assurance (QA) and quality control (QC) in medical diagnostic X-ray systems. An accurate knowledge of the diagnostic X-ray spectra would improve the patient dose optimization, without compromising image information. In this work, we performed direct diagnostic X-ray spectra measurements with a portable device, based on a CdTe solid-state detector. The portable device is able to directly measure X-ray spectra at high photon fluence rates, as typical of clinical radiography. We investigated on the spectral performances of the system in the mammographic energy range (up to approx40 keV). Good system response to monoenergetic photons was measured (energy resolution of 5% FWHM at 22.1 keV). We measured the molybdenum X-ray spectra produced by a mammographic X-ray unit (GE Senographe DMR) at ...
Black hole and neutron star soft X-ray transients: a hard X-ray view of their outbursts
The RXTE public observations of the outbursts of black hole soft X-ray transients XTE J1550-564, XTE J1859+226, 4U 1630-47, XTE J1118+480, XTE J1650-500, and the neutron star soft X-ray transients 4U 1608-52, Aquila X-1, including a variable `persistent' neutron star low mass X-ray binary 4U 1705-44, are summarized in this paper. The hard X-ray view of those outbursts, which is quite different from that of the soft X-ray band, suggests that there are several types of outbursts which result in different hard X-ray outburst profile - the outburst profiles are energy dependent. One type is the low/hard state outbursts, the other type is the outburst showing transitions from the low/hard state to the high/soft state, or to the intermediate or to the very high state. The later has an initial low/hard state, introducing the phenomena that the hard X-ray precedes the soft X-ray in the outburst rise. Such outbursts in XTE J1550-564, Aql X-1 and 4U 1705-44 support a two-accretion-flow model which involves one Keplerian disk flow and one sub-Keplerian flow for the initial outburst rise.
The Discovery of Soft X-ray Loud Broad Absorption Line Quasars
2008-01-09
It is been known for more than a decade that BALQSOs (broad absorption line quasars) are highly attenuated in the X-ray regime compared to other quasars, especially in the soft band ($< $ 1 keV). Using X-ray selection techniques we have found "soft X-ray loud" BALQSOs that, by definition, have soft X-ray (0.3 keV) to UV ($3000 \\AA$) flux density ratios that are higher than typical nonBAL radio quiet quasars. Our sample of 3 sources includes one LoBALQSO (low ionization BALQSO) which are generally considered to be the most highly attenuated in the X-rays. The three QSOs are the only known BALQSOs that have X-ray observations that are consistent with no intrinsic soft X-ray absorption. The existence of a large X-ray luminosity and the hard ionizing continuum that it presents to potential UV absorption gas is in conflict with the ionization states that are conducive to line driving forces within BAL winds (especially for the LoBALs).
High Variability in Vela X-1: Giant Flares and Off States
Aims. We investigate the spectral and temporal behavior of the high mass X-ray binary Vela X-1 during a phase of high activity, with special focus on the observed giant flares and off states. Methods. INTEGRAL observed Vela ...
The high energy emission from black holes
2007-11-07
The origin of the high energy emission (X-rays and gamma-rays) from black holes is still a matter of debate. We present new evidence that hard X-ray emission in the low/hard state may not be dominated by thermal Comptonization. We present an alternative scenario for the origin of the high energy emission that is well suited to explain the high energy emission from GRO J1655-40.
X-ray spectroscopy and dosimetry with a portable CdTe device
2007-01-01
X-ray spectra and dosimetry information are very important for quality assurance (QA) and quality control (QC) in medical diagnostic X-ray systems. An accurate knowledge of the diagnostic X-ray spectra would improve the patient dose optimization, without compromising image information. In this work, we performed direct diagnostic X-ray spectra measurements with a portable device, based on a CdTe solid-state detector. The portable device is able to directly measure X-ray spectra at high photon fluence rates, as typical of clinical radiography. We investigated on the spectral performances of the system in the mammographic energy range (up to 40keV). Good system response to monoenergetic photons was measured (energy resolution of 5% FWHM at 22.1keV). We measured the molybdenum X-ray spectra p...
X-ray holography of biological specimens
The author reviews the reasons for x-ray imaging of biological specimens and the techniques presently being used for x-ray microscopy. The author points out the advantages of x-ray holography and the difficulties of obtaining the requisite coherence with conventional sources. The author discusses the problems of radiation damage and the remarkable fact that short pulse x-ray sources circumvent these problems and obtain high-resolution images of specimens in the living state. Finally, the author reviews some of the efforts underway to develop high-intensity coherent x-ray sources for the laboratory. 14 references, 5 figures, 2 tables.
X-ray holography of biological specimens
1984-01-01
The author reviews the reasons for x-ray imaging of biological specimens and the techniques presently being used for x-ray microscopy. The author points out the advantages of x-ray holography and the difficulties of obtaining the requisite coherence with conventional sources. The author discusses the problems of radiation damage and the remarkable fact that short pulse x-ray sources circumvent these problems and obtain high-resolution images of specimens in the living state. Finally, the author reviews some of the efforts underway to develop high-intensity coherent x-ray sources for the laboratory. 14 references, 5 figures, 2 tables.
X-ray instrumentation for SR beamlines
The main possibilities and parameters of experimental X-ray stations are presented: 'Protein crystallography', 'X-ray structure analysis', 'High-precision X-ray optics', 'X-ray crystallography and material science', 'X-ray topography', 'Photoelectron X-ray standing wave' that are being installed at Kurchatov SR source by A.V. Shubnikov Institute of Crystallography.
A versatile high-resolution x-ray imager (HRXI) for laser-plasma experiments on OMEGA
2008-01-01
A high-resolution x-ray imager (HRXI) devoted to laser-plasma experiments combines two state-of-the-art technologies developed in France: a high-resolution x-ray microscope and a high-speed x-ray streak camera. The resulting streaked imager achieves spatial and temporal resolutions of approx5 mum and approx10 ps, respectively. The HXRI has recorded enhanced spatial and temporal resolution radiographs of indirectly driven targets on OMEGA. This paper describes the main features of the instrument and details the activation process on OMEGA (particularly the alignment). Recent results obtained on joint CEA/LLE radiographic OMEGA experiments will also be presented
2003-01-01
X-rays originating from a series of the cascades after electron capture into highly excited Rydberg states have been observed from low energy, highly charged Krq+ ions (q=27-36) colliding with neutral Ar atoms. The intensity ratio between L (n=3-
Picosecond x-ray absorption spectroscopy of photochemical transient species in solution
2006-08-07
A photoinduced Fe(II) spin crossover reaction in solution is studied with ultrafast x-ray absorption spectroscopy. The iron-nitrogen bond lengthens by 0.21+-0.03 Angstrom in the high-spin transient excited state relative to the ground state.
INTERNATIONAL CONFERENCE ON ULTRASHORT HIGH-ENERGY RADIATION AND MATTER
The workshop is intended as a forum to discuss the latest experimental, theoretical and computational results related to the interaction of high energy radiation with matter. High energy is intended to mean soft x-ray and beyond, but important new results from visible systems will be incorporated. The workshop will be interdisciplinary amongst scientists from many fields, including: plasma physics; x-ray physics and optics; solid state physics and material science; biology ; quantum optics. Topics will include, among other subjects: understanding damage thresholds for x-ray interactions with matter developing {approx} 5 keV x-ray sources to investigate damage; developing {approx} 100 keV Thomsom sources for material studies; developing short pulse (100 fs and less) x-ray diagnostics; developing novel X-ray optics; and developing models for the response of biological samples to ultra intense, sub ps x-rays high-energy radiation.
INTERNATIONAL CONFERENCE ON ULTRASHORT HIGH-ENERGY RADIATION AND MATTER
The workshop is intended as a forum to discuss the latest experimental, theoretical and computational results related to the interaction of high energy radiation with matter. High energy is intended to mean soft x-ray and beyond, but important new results from visible systems will be incorporated. The workshop will be interdisciplinary amongst scientists from many fields, including: plasma physics; x-ray physics and optics; solid state physics and material science; biology ; quantum optics. Topics will include, among other subjects: understanding damage thresholds for x-ray interactions with matter developing {approx} 5 keV x-ray sources to investigate damage; developing {approx} 100 keV Thomsom sources for material studies; developing short pulse (100 fs and less) x-ray diagnostics; developing novel X-ray optics; and developing models for the response of biological samples to ultra intense, sub ps x-rays high-energy radiation.
INTERNATIONAL CONFERENCE ON ULTRASHORT HIGH-ENERGY RADIATION AND MATTER
2004-01-15
The workshop is intended as a forum to discuss the latest experimental, theoretical and computational results related to the interaction of high energy radiation with matter. High energy is intended to mean soft x-ray and beyond, but important new results from visible systems will be incorporated. The workshop will be interdisciplinary amongst scientists from many fields, including: plasma physics; x-ray physics and optics; solid state physics and material science; biology ; quantum optics. Topics will include, among other subjects: understanding damage thresholds for x-ray interactions with matter developing {approx} 5 keV x-ray sources to investigate damage; developing {approx} 100 keV Thomsom sources for material studies; developing short pulse (100 fs and less) x-ray diagnostics; developing novel X-ray optics; and developing models for the response of biological samples to ultra intense, sub ps x-rays high-energy radiation.
Introducing the ARL X'Tra x-ray diffraction system
2002-01-01
Full text: The ARL X'Tra is a state-of-the-art solution for powder X-ray diffraction in a large range of applications such as pharmaceuticals and biosciences, chemicals, earth sciences, semi-conductors, metallurgy and ceramics. The X'Tra offers the latest technology in key diffraction components to produce a high performance instrument at an affordable price. This presentation examines some of the hardware and performance features of this instrument. Copyright (2002) Australian X-ray Analytical Association Inc
We present the results from simultaneous observations of the Narrow-Line Seyfert 1 galaxy NGC 4051 with the Chandra High Energy Transmission Grating Spectrometer and the HST Space Telescope Imaging Spectrograph. The X-ray grating spectrum reveals absorption and emission lines from hydrogen-like and helium-like ions of O, Ne, Mg and Si. We resolve two distinct X-ray absorption systems: a high-velocity blueshifted system at -2340+/-130 km/s and a low-velocity blueshifted system at -600+/-130 km/s. In the UV spectrum we detect strong absorption, mainly from C IV, N V and Si IV, that is resolved into as many as nine different intrinsic absorption systems with velocities between -650 km/s and 30 km/s. Although the low-velocity X-ray absorption is consistent in velocity with many of the UV absorption systems, the high-velocity X-ray absorption seems to have no UV counterpart. In addition to the absorption and emission lines, we also observe rapid X-ray variability and a state of low X-ray flux during the last ~15 ks of the observation. NGC 4051 has a soft X-ray excess which we fit in both the high and low X-ray flux states. The high-resolution X-ray spectrum directly reveals that the soft excess is not composed of narrow emission lines and that it has significant spectral curvature. A power-law model fails to fit it, while a blackbody produces a nearly acceptable fit. We compare the observed spectral variability with the results of previous studies of NGC 4051.
High-Definition X-Ray Fluorescence: Applications
2008-01-01
Energy dispersive X-ray fluorescence (EDXRF) is a well-established and powerful tool for nondestructive elemental analysis of virtually any material. It is widely used for environmental, industrial, pharmaceutical, forensic, and scientific research applications to measure the concentration of elemental constituents or contaminants. The fluorescing atoms can be excited by energetic electrons, ions, or photons. A particular EDXRF method, monochromatic microbeam X-ray fluorescence (MmuEDXRF), has proven to be remarkably powerful in measurement of trace element concentrations and distributions in a large variety of important medical, environmental, and industrial applications. When used with state-of-the-art doubly curved crystal (DCC) X-ray optics, this technique enables high-sensitivity, compact, low-power, safe, reliable, and rugged ...
High Definition X-Ray Fluorescence: Principles and Techniques
2008-01-01
Energy dispersive X-ray fluorescence (EDXRF) is a well-established and powerful tool for nondestructive elemental analysis of virtually any material. It is widely used for environmental, industrial, pharmaceutical, forensic, and scientific research applications to measure the concentration of elemental constituents or contaminants. The fluorescing atoms can be excited by energetic electrons, ions, or photons. A particular EDXRF method, monochromatic microfocus X-ray fluorescence (MmuEDXRF), has proven to be remarkably powerful in measurement of trace element concentrations and distributions in a large variety of important medical, environmental, and industrial applications. When used with state-of-the-art doubly curved crystal (DCC) X-ray optics, this technique enables high-sensitivity, compact, low-power, safe, reliable, and rugged ...
X-ray instrumentation in the LLL Laser-Fusion Program
The LLL Laser-Fusion Program includes an active experimental effort to measure the distributions in energy, space and time of pulses of soft x-rays (.2 to 10 keV) radiated by laser-induced plasmas. Requirements for high resolution in these measurements clearly preclude the use of conventional x-ray diagnostic techniques. The following examples from our program of advanced x-ray instrument development are described. (1) Wavelength-dispersive spectrographs with fractional-electron volt resolution at several keV and imaging systems with 3 micron resolution over a 100 micron source. (2) Advanced solid state x-ray sensors that recover data from these instruments in a more expedient manner than photographic film. (3) Microcomputer-controlled stand-alone spectrograph data systems and minicomputer-based integrated systems that can deal with the large array of data generated by the high resolution instruments. (4) An electrostatically-deflected x-ray streak camera with moderate spectral and spatial resolution and a timing resolution of better than 15 ps.
X-ray instrumentation in the LLL Laser-Fusion Program
The LLL Laser-Fusion Program includes an active experimental effort to measure the distributions in energy, space and time of pulses of soft x-rays (.2 to 10 keV) radiated by laser-induced plasmas. Requirements for high resolution in these measurements clearly preclude the use of conventional x-ray diagnostic techniques. The following examples from our program of advanced x-ray instrument development are described. (1) Wavelength-dispersive spectrographs with fractional-electron volt resolution at several keV and imaging systems with 3 micron resolution over a 100 micron source. (2) Advanced solid state x-ray sensors that recover data from these instruments in a more expedient manner than photographic film. (3) Microcomputer-controlled stand-alone spectrograph data systems and minicomputer-based integrated systems that can deal with the large array of data generated by the high resolution instruments. (4) An electrostatically-deflected x-ray streak camera with moderate spectral and spatial resolution and a timing resolution of better than 15 ps.
X-ray instrumentation in the LLL Laser-Fusion Program
1976-06-23
The LLL Laser-Fusion Program includes an active experimental effort to measure the distributions in energy, space and time of pulses of soft x-rays (.2 to 10 keV) radiated by laser-induced plasmas. Requirements for high resolution in these measurements clearly preclude the use of conventional x-ray diagnostic techniques. The following examples from our program of advanced x-ray instrument development are described. (1) Wavelength-dispersive spectrographs with fractional-electron volt resolution at several keV and imaging systems with 3 micron resolution over a 100 micron source. (2) Advanced solid state x-ray sensors that recover data from these instruments in a more expedient manner than photographic film. (3) Microcomputer-controlled stand-alone spectrograph data systems and minicomputer-based integrated systems that can deal with the large array of data generated by the high resolution instruments. (4) An electrostatically-deflected x-ray streak camera with moderate spectral and spatial resolution and a timing resolution of better than 15 ps.
Ultra-soft x-ray absorption spectroscopy: A bulk and surface probe of materials
Direct comparisons between surface and bulk of diverse materials can be made by simultaneous electron yield (5 nm depth sensitivity) and fluorescence yield (200 nm) ultra soft x-ray absorption spectroscopy measurements utilizing a rapid sample interchange apparatus. For example the orientations of functional groups have been characterized at and near the surface of a series of model polymeric materials highlighting the chemical and molecular sensitivity of ultra soft x-ray absorption spectroscopy. In addition we discuss a bulk sensitive use of fluorescence yield to non destructively study a buried metal polymer interface. A second bulk sensitive example is the use of fluorescence yield oxygen K near edge x-ray spectroscopy as a method to determine the hole state density of high Tc materials.
Ultra-soft x-ray absorption spectroscopy: A bulk and surface probe of materials
Direct comparisons between surface and bulk of diverse materials can be made by simultaneous electron yield (5 nm depth sensitivity) and fluorescence yield (200 nm) ultra soft x-ray absorption spectroscopy measurements utilizing a rapid sample interchange apparatus. For example the orientations of functional groups have been characterized at and near the surface of a series of model polymeric materials highlighting the chemical and molecular sensitivity of ultra soft x-ray absorption spectroscopy. In addition we discuss a bulk sensitive use of fluorescence yield to non destructively study a buried metal polymer interface. A second bulk sensitive example is the use of fluorescence yield oxygen K near edge x-ray spectroscopy as a method to determine the hole state density of high Tc materials.
Ultra-soft x-ray absorption spectroscopy: A bulk and surface probe of materials
1993-06-01
Direct comparisons between surface and bulk of diverse materials can be made by simultaneous electron yield (5 nm depth sensitivity) and fluorescence yield (200 nm) ultra soft x-ray absorption spectroscopy measurements utilizing a rapid sample interchange apparatus. For example the orientations of functional groups have been characterized at and near the surface of a series of model polymeric materials highlighting the chemical and molecular sensitivity of ultra soft x-ray absorption spectroscopy. In addition we discuss a bulk sensitive use of fluorescence yield to non destructively study a buried metal polymer interface. A second bulk sensitive example is the use of fluorescence yield oxygen K near edge x-ray spectroscopy as a method to determine the hole state density of high Tc materials.
Soft X-Ray Diffraction Microscopy of a Frozen Hydrated Yeast Cell
2009-01-01
We report the first image of an intact, frozen hydrated eukaryotic cell using x-ray diffraction microscopy, or coherent x-ray diffraction imaging. By plunge freezing the specimen in liquid ethane and maintaining it below -170 deg. C, artifacts due to dehydration, ice crystallization, and radiation damage are greatly reduced. In this example, coherent diffraction data using 520 eV x rays were recorded and reconstructed to reveal a budding yeast cell at a resolution better than 25 nm. This demonstration represents an important step towards high resolution imaging of cells in their natural, hydrated state, without limitations imposed by x-ray optics
Resonant inelastic soft x-ray scattering of CdS: a two-dimensional electronic structure map approach
2008-09-24
Resonant inelastic x-ray scattering (RIXS) with soft x-rays is uniquely suited to study the elec-tronic structure of a variety of materials, but is currently limited by low (fluorescence yield) count rates. This limitation is overcome with a new high-transmission spectrometer that allows to measure soft x-ray RIXS"maps." The S L2,3 RIXS map of CdS is discussed and compared with density functional calculations. The map allows the extraction of decay channel-specific"absorp-tion spectra," giving detailed insight into the wave functions of occupied and unoccupied elec-tronic states.
Overview and perspective of materials characterization by using synchrotron radiation
2009-01-01
A peculiarity of techniques and the methods of synchrotron radiation are explained. It consists of five sections such as introduction, synchrotron radiation, interaction between X-ray and materials, analytical methods of materials using synchrotron radiation and perspective and problems. The second section described the principles of synchrotron orbit radiation, synchrotron light source, the main formulae and schematic drawing of undulator, and the synchrotron radiation facilities in Japan. The third section explained behavior of X-ray in materials, absorption, reflection, refraction and scattering of X-ray. The fourth section stated many analytical methods of materials. The surface diffractometer, powder diffractometer, high-energy X-ray diffraction, core-electron absorption spectroscopy, micro-beam diffraction, X-ray fluorescence, X-ray ...
Instrumentation for Time-Dependent X-Ray Resonant Raman Scattering
2004-01-01
X-ray absorption/fluorescence spectroscopy probes valence states relative to a core level and thus provides an absolute energy reference. The core hole lifetime broadening can be reduced by restricting the fluorescence signal with a sub-eV crystal energy analyzer. We describe the design and first performance tests of adaptive optics for a bent-crystal analyzer which is characterized by a high counting efficiency and a large solid angle acceptance. The device was designed for the determination of charge carrier dynamics in photoexcited semiconductors in laser pump, x-ray probe experiments. It can also be used in a wide range of near-edge spectroscopic applications and as an ultrafast laser/x-ray cross correlator..
Combined X-ray and neutron fibre diffraction studies of biological and synthetic polymers
2005-01-01
The fibrous state is a natural one for polymer molecules which tend to assume regular helical conformations rather than the globular structures characteristic of many proteins. Fibre diffraction therefore has broad application to the study of a wide range of biological and synthetic polymers. The purpose of this paper is to illustrate the general scope of the method and in particular to demonstrate the impact of a combined approach involving both X-ray and neutron diffraction methods. While the flux of modern X-ray synchrotron radiation sources allows high quality datasets to be recorded with good resolution within a very short space of time, neutron studies can provide unique information through the ability to locate hydrogen or deuterium atoms that are often difficult or impossible to locate using X-ray methods. Furthermore, neutron fibre diffraction methods can, ...
We review the state of the art of the VUV-X ray FEL sources and analyze the limit of the relevant technologies and the future perspectives. Possible strategies aimed at developing the design of a road map toward very short wavelengths, very high brilliance and very short pulses are discussed. Within such a framework we report and comment on the proposed devices.
Simultaneous Chandra X-ray, HST Ultraviolet, and Ulysses Radio Observations of Jupiter's Aurora
Observations of Jupiter carried out by the Chandra ACIS-S instrument over 24-26 February, 2003, show that the auroral X-ray spectrum consists of line emission consistent with high-charge states of precipitating ions, ...
Simultaneous Chandra X-ray, HST Ultraviolet, and Ulysses Radio Observations of Jupiter's Aurora
Observations of Jupiter carried out by the Chandra ACIS-S instrument over 24-26 February, 2003, show that the auroral X-ray spectrum consists of line emission consistent with high-charge states of precipitating ions, ...
Identification of highly active iron sites in N{sub 2}O-activated Fe/MFI.
2002-09-01
Reduction in an H{sub 2} flow at 600 C of Fe/MFI prepared by chemical vapor deposition, followed by its exposure to N{sub 2}O at 250 C, produces a highly active state characterized by an unusual TPR spike at 200 C. In situ X-ray absorption near-edge structure, X-ray absorption fine structure data and literature data on DFT calculations suggest that in this state some Fe will be present in the oxidation state of Fe{sup 4+}.
Soft-x-ray spectroscopy study of nanoscale materials
The ability to control the particle size and morphology of nanoparticles is of crucial importance nowadays both from a fundamental and industrial point of view considering the tremendous amount of high-tech applications. Controlling the crystallographic structure and the arrangement of atoms along the surface of nanostructured material will determine most of its physical properties. In general, electronic structure ultimately determines the properties of matter. Soft X-ray spectroscopy has some basic features that are important to consider. X-ray is originating from an electronic transition between a localized core state and a valence state. As a core state is involved, elemental selectivity is obtained because the core levels of different elements are well separated in energy, meaning that the involvement of the inner level makes this probe localized to one specific atomic site around which the electronic structure is reflected as a partial density-of-states contribution. The participation of valence electrons gives the method chemical state sensitivity and further, the dipole nature of the transitions gives particular symmetry information. The new generation synchrotron radiation sources producing intensive tunable monochromatized soft X-ray beams have opened up new possibilities for soft X-ray spectroscopy. The introduction of selectively excited soft X-ray emission has opened a new field of study by disclosing many new possibilities of soft X-ray resonant inelastic scattering. In this paper, some recent findings regarding soft X-ray absorption and emission studies of various nanostructured systems are presented.
Soft-x-ray spectroscopy study of nanoscale materials
2005-07-30
The ability to control the particle size and morphology of nanoparticles is of crucial importance nowadays both from a fundamental and industrial point of view considering the tremendous amount of high-tech applications. Controlling the crystallographic structure and the arrangement of atoms along the surface of nanostructured material will determine most of its physical properties. In general, electronic structure ultimately determines the properties of matter. Soft X-ray spectroscopy has some basic features that are important to consider. X-ray is originating from an electronic transition between a localized core state and a valence state. As a core state is involved, elemental selectivity is obtained because the core levels of different elements are well separated in energy, meaning that the involvement of the inner level makes this probe localized to one specific atomic site around which the electronic structure is reflected as a partial density-of-states contribution. The participation of valence electrons gives the method chemical state sensitivity and further, the dipole nature of the transitions gives particular symmetry information. The new generation synchrotron radiation sources producing intensive tunable monochromatized soft X-ray beams have opened up new possibilities for soft X-ray spectroscopy. The introduction of selectively excited soft X-ray emission has opened a new field of study by disclosing many new possibilities of soft X-ray resonant inelastic scattering. In this paper, some recent findings regarding soft X-ray absorption and emission studies of various nanostructured systems are presented.
A Transient Black-Hole Low-Mass X-Ray Binary Candidate in Centaurus A
2008-03-06
We report the discovery of a bright transient X-ray source, CXOU J132518.2-430304, towards Centaurus A (Cen A) using six new Chandra X-Ray Observatory observations in 2007 March--May. Between 2003 and 2007, its flux has increased by a factor of >770. The source is likely a low-mass X-ray binary in Cen A with unabsorbed 0.3-10 keV band luminosities of (2-3) x 10^{39} erg s^-1 and a transition from the steep-power law state to the thermal state during our observations. CXOU J132518.2-430304 is the most luminous X-ray source in an early-type galaxy with extensive timing information that reveals transience and a spectral state transition. Combined with its luminosity, these properties make this source one of the strongest candidates to date for containing a stellar-mass black hole in an early-type galaxy. Unless this outburst lasts many years, the rate of luminous transients in Cen A is anomalously high compared to other early-type galaxies.
An additional soft X-ray component in the dim low/hard state of black hole binaries
2009-11-03
We test the truncated disc models using multiwavelength (optical/UV/X-ray) data from the 2005 hard state outburst of the black hole SWIFT J1753.5-0127. This system is both fairly bright and has fairly low interstellar absorption, so gives one of the best datasets to study the weak, cool disc emission in this state. We fit these data using models of an X-ray illuminated disc to constrain the inner disc radius throughout the outburst. Close to the peak, the observed soft X-ray component is consistent with being produced by the inner disc, with its intrinsic emission enhanced in temperature and luminosity by reprocessing of hard X-ray illumination in an overlap region between the disc and corona. This disc emission provides the seed photons for Compton scattering to produce the hard X-ray spectrum, and these hard X-rays also illuminate the outer disc, producing the optical emission by reprocessing. However, the situation is very different as the outburst declines. The optical is probably cyclo-synchrotron radiation, self-generated by the flow, rather than tracing the outer disc. Similarly, limits from reprocessing make it unlikely that the soft X-rays are directly tracing the inner disc radius. This is seen more clearly in a similarly dim low/hard state spectrum from XTE J1118+480. The very small emitting area implied by the relatively high temperature soft X-ray component is completely inconsistent with the much larger, cooler, U V component which is well fit by a truncated disc. We speculate on the origin of this component, but its existence as a clearly separate spectral component from the truncated disc in XTE J1118+480 shows that it does not simply trace the inner disc radius, so cannot constrain the truncated disc models.
Laser Program annual report 1987
This report discusses the following topics: target design and experiments; target materials development; laboratory x-ray lasers; laser science and technology; high-average-power solid state lasers; and ICF applications studies.
Laser Program annual report 1987
This report discusses the following topics: target design and experiments; target materials development; laboratory x-ray lasers; laser science and technology; high-average-power solid state lasers; and ICF applications studies.
Recombination-cascade X-ray spectra of highly charged helium-like ions
It is shown that the relative intensity distribution among the X-ray spectral lines of helium-like ions from the n = 2 states produced through recombination processes such as radiative and charge transfer ...
Laser Program annual report 1987
1989-07-01
This report discusses the following topics: target design and experiments; target materials development; laboratory x-ray lasers; laser science and technology; high-average-power solid state lasers; and ICF applications studies.
X-rays emitted from 2.3 keV/u sup 1 sup 5 N sup 7 sup + ions transmitted through a highly ordered Ni microcapillary were measured with a high-resolution soft X-ray spectrometer. The highly ordered microcapillary has recently become available employing a nano-lithographic technique. A transmission ratio and charge state distribution of ions through the microcapillary target were found to be consistent with theoretical predictions. A preliminary analysis showed that a series of X-rays from np-1s transitions with n as high as 8 were identified, which is consistent with the classical over barrier model.
Fiat Lux - Et Facta Est Lux. The Micro-XAS Beamline Project At The Swiss Light Source (SLS)
2005-03-01
In view of the increasing awareness of the importance of the micrometer domain in many scientific disciplines, considerable effort has been spent in developing high-resolution X-ray microprobes in the hard X-ray regime using state-of-the-art X-ray focusing devices. The MicroXAS beamline at the Swiss Light Source (SLS) is a microprobe facility, optimized for X-ray absorption spectroscopy, X-ray fluorescence and X-ray diffraction experiments requiring high spatial resolution. SL is capable of providing monochromatic and pink X-ray beams (5-22 keV) with high flux and energy resolution, combined with dynamic (sub-)micron focusing capabilities. A brief description of the project status, first commissioning results, and conceptual details concerning the measurements of radioactive samples are presented here. (author)
Since X-ray lithography requires a high photon flux to achieve deep resist exposure, a synchrotron radiation beam, which is not monochromatized, is generally used as a light source. If the synchrotron radiation beam is monochromatized, photon flux will decrease rapidly. Because of this reason, the wavelength dependence of the resist sensitivity has not been investigated for deep X-ray lithography. Measuring the spectrum of a white beam with a Si solid-state detector (SSD) is difficult because a white beam has a high intensity and an SSD has a high sensitivity. We were able to measure the spectrum and the photocurrent of a white beam from a beam line used for deep X-ray lithography by keeping the ring current below 0.05 mA. We evaluated the characteristics of the output beam based on the measured spectrum and photocurrent, and used them to investigate the relationship between the total exposure energy and the dose-processing depth with polymethyl methacrylate (PMMA). We found that it is possible to guess the processing depth of PMMA from the total exposure energy in deep X-ray lithography. (author)
Crystal structure and valence state of Mn in BaLaMnRuO{sub 6}
2008-09-07
High resolution synchrotron x-ray powder diffraction data of BaLaMnRuO{sub 6} double perovskite have been used to examine the crystal structure of this system from room temperature down to 110 K. X-ray absorption spectroscopy has been employed to determine the valence state of Mn at room and liquid nitrogen temperatures. No structural phase transitions were detected and the system was found to possess an orthorhombic structure in the entire measured temperature range. In this system, Mn K-edge x-ray absorption near edge spectroscopy results have shown that both at room and at liquid nitrogen temperatures the oxidation state of Mn is +3.
Soft X-Ray Spectrometer Using 100-Pixel STJ Detectors for Synchrotron Radiation
2009-01-01
Fluorescent X-ray absorption fine structure (XAFS) is an important tool for material analysis, especially for the measurement of chemical states or local structures of elements. Semiconductor detectors are usually used for separating the fluorescent of elements in question from background fluorescence. However, the semiconductor detectors cannot always discriminate K-lines of light elements and L-lines of various elements as different X-ray peaks at an energy range below about 3 keV. Superconducting tunnel junction (STJ) detectors are promising device for the soft X-ray at synchrotron radiation beam lines because of excellent energy resolution, high detection efficiency, and high counting rate. We are constructing a fluorescent X-ray spectrometer having 100-pixel array of STJs with 200 mum square. The array detector is mounted on a liquid ...
X-ray radiography and scattering diagnosis of dense shock-compressed matter
2010-01-01
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 noncollective 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 noncollective regime and the electron density measured in the collective regime mass ...
New quantum detection system for very low dose X-ray radiology
2000-01-01
A new X-ray radiology system has been devised that significantly reduces the dose of radiation administered to patients in spinal X-ray examinations. The apparatus scans the patient, using a high-efficiency linear solid-state detector and highly sensitive electronics, operating in counting mode. Two specific integrated circuits were developed, one of which contains an automatic offset correction. The detection system characterization data will be briefly presented. Data is acquired in real time by a high-speed computer-controlled VME system. The scan parameters and image filtering are also computer-controlled. The first images recorded using this new apparatus are given, along with the preliminary comparative dosimetric analysis
New quantum detection system for very low dose X-ray radiology
A new X-ray radiology system has been devised that significantly reduces the dose of radiation administered to patients in spinal X-ray examinations. The apparatus scans the patient, using a high-efficiency linear solid-state detector and highly sensitive electronics, operating in counting mode. Two specific integrated circuits were developed, one of which contains an automatic offset correction. The detection system characterization data will be briefly presented. Data is acquired in real time by a high-speed computer-controlled VME system. The scan parameters and image filtering are also computer-controlled. The first images recorded using this new apparatus are given, along with the preliminary comparative dosimetric analysis.
X-ray instrumentation for SR beamlines
2000-06-21
The main possibilities and parameters of experimental X-ray stations are presented: 'Protein crystallography', 'X-ray structure analysis', 'High-precision X-ray optics', 'X-ray crystallography and material science', 'X-ray topography', 'Photoelectron X-ray standing wave' that are being installed at Kurchatov SR source by A.V. Shubnikov Institute of Crystallography.
Phenomenological Analogies in TeV Blazars and Black Hole X-ray Binaries in low state
2005-05-09
Blazars are well known for the violent variability from the radio to gamma-ray wavelengths. In this paper, we present a brief summary of the X-ray variability recently obtained for TeV blazars. We also point out the probable similarities of the X-ray variability characteristics between blazars and microblazars. Such phenomenological analogies could be interpreted and unified with the synchrotron X-ray emissions from the jets of the two classes of objects that differ in black hole mass by factors of $\\ga 10^7$. The phenomenological analogies in blazars and microblazars (both are jet-dominated) might be parallel to those in black hole X-ray binaries in high/soft state and Seyfert galaxies (both are disk-dominated).
High resolution ion induced X-ray spectroscopy for chemical state analysis
1993-01-01
Satellite lines of K X-ray lines from K and Cr, and L lines from In are observed for impact by 1.4 MeV/u 1H+, 4He2+, 12C4+, 16O4+ and 35Cl8+. A curved crystal spectrometer was used with a position sensitive proportional counter with improved linearity of the backgammon readout. The distribution of Cr Kalpha satellite lines depends on the chemical state of Cr, being peaked at lower energy for the toxic valency 6 compounds than for valency 3 and metallically bound Cr. Fluorescence excitation of the Cr diagram line is observed for a stainless steel sample from enhancement by Fe X-rays. (orig.)
Optical Spectroscopy of GRO J1655-40
1999-11-17
We have obtained optical spectra of the soft X-ray transient GRO J1655-40 during different X-ray spectral states (quiescence, high-soft and hard outburst) between 1994 Aug and 1997 Jun. Characteristic features observed during the 1996-97 high-soft state were: a) broad absorption lines at Halpha and Hbeta, probably formed in the inner disk; b) double-peaked HeII 4686 emission lines, formed in a temperature-inversion layer on the disk surface, created by the soft X-ray irradiation; c) double-peaked Halpha emission, with a strength associated with the hard X-ray flux, suggesting that it was probably emitted from deeper layers than He II 4686. The observed rotational velocities of all the double-peaked lines suggest that the disk was extended slightly beyond its tidal radius. Three classes of lines were identified in the spectra taken in 1994 Aug-Sep, during a period of low X-ray activity between two strong X-ray flares: broad absorption, broad (flat-topped) emission and narrow emission. We have found that the narrow emission lines (single-peaked or double-peaked) cannot be explained by a thin-disk model. We propose that the system was in a transient state, in which the accretion disk might have had an extended optically thin cocoon and significant matter outflow. After the onset of a hard X-ray flare the disk signatures disappeared, and strong single-peaked Halpha and Paschen emission was detected, suggesting that the cocoon became opaque to optical radiation. High-ionisation lines disappeared or weakened. Two weeks after the end of the flare, the cocoon appeared to be once again optically thin.
X-ray Variability in the Young Massive Triple theta2 Ori A
2006-08-20
Massive stars rarely show intrinsic X-ray variability. The only O-stars credited to be intrinsically variable are theta1 Ori C due to effects from magnetic confinement of its wind, and theta2 Ori A suspected of similar activity. Early Chandra observations have shown that the most massive star system in the Orion Trapezium Cluster, theta2 Ori A, shows rapid variability on time scales of hours. We determine X-ray fluxes and find that the star shows very strong variability over the last 5 years. We observed a second large X-ray outburst in November 2004 with the high resolution transmission grating spectrometer on-board Chandra. In the low state X-ray emissivities indicate temperatures well above 25 MK. In the high state we find an extended emissivity distribution with high emissivities in the range from 3 MK to over 100 MK. The outburst event in stellar terms is one of the most powerful ever observed and the most energetic one in the ONC with a lower total energy limit of 1.5x10^37 ergs. The line diagnostics show that under the assumption that the line emitting regions in the low states are as close as within 1 -- 2 stellar radii from the O-star's photosphere, whereas the hard states suggest a distance of 3 -- 5 stellar radii. The two outbursts are very close to the periastron passage of the stars. We argue that the high X-ray states are possibly the result of reconnection events from magnetic interactions of the primary and secondary stars of the spectroscopic binary. Effects from wind collisions seem unlikely for this system. The low state emissivity and R-ratios strengthen the predicament that the X-ray emission is enhanced by magnetic confinement of the primary wind. We also detect Fe fluorescence indicative of the existence of substantial amounts of neutral Fe in the vicinity of the X-ray emission.
2010-05-01
We present the first femtosecond soft x-ray spectroscopy in liquids, enabling the observation of changes in hydrogen bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water is probed with femtosecond soft x-ray pulses, exploiting the relation between different water structures and distinct x-ray spectral features. After excitation of the intramolecular OH stretching vibration, characteristic x-ray absorption changes monitor the conversion of strongly hydrogen-bonded water structures to more disordered structures with weaker hydrogen-bonding described by a single subpicosecond time constant. The latter describes the thermalization time of vibrational excitations and defines the characteristic maximum rate with which nonequilibrium populations of more strongly hydrogen-bonded water structures convert to less-bonded ones. On short time scales, the relaxation of vibrational excitations leads to a transient high-pressure state and a transient absorption spectrum different from that of statically heated water.
2009-01-01
We report measurements of the photoinduced FeII spin crossover reaction dynamics in solution via time-resolved x-ray absorption spectroscopy. EXAFS measurements reveal that the iron-nitrogen bond lengthens by 0.21+-0.03 A in the high-spin transient excited state relative to the ground state. XANES measurements at the Fe L-edge show directly the influence of the structural change on the ligand-field splitting of the FeII 3d orbitals associated with the spin transition
The quantum X-ray radiology apparatus
2000-01-01
The paper entitled 'New Quantum Detection System for Very Low Dose X-ray Radiology', presented at the talk session, discusses the preliminary data obtained using a new quantum X-ray radiology system with a high-efficiency solid-state detector and highly sensitive electronics, making it possible to reduce significantly the dose administered to a patient in X-ray radiology examinations. The present paper focuses more on the technological aspects of the apparatus, such as the integration of the detector with the two Asics, and the computer system. Namely, it is shown how the computer system calibrates the detection system, acquires the data in real time, and controls the scan parameters and image filtering process
The quantum X-ray radiology apparatus
The paper entitled 'New Quantum Detection System for Very Low Dose X-ray Radiology', presented at the talk session, discusses the preliminary data obtained using a new quantum X-ray radiology system with a high-efficiency solid-state detector and highly sensitive electronics, making it possible to reduce significantly the dose administered to a patient in X-ray radiology examinations. The present paper focuses more on the technological aspects of the apparatus, such as the integration of the detector with the two Asics, and the computer system. Namely, it is shown how the computer system calibrates the detection system, acquires the data in real time, and controls the scan parameters and image filtering process.
The correlation timescale of the X-ray flux during the outbursts of soft X-ray transients
2010-01-01
Recent studies of black hole and neutron star low mass X-ray binaries (LMXBs) show a positive correlation between the X-ray flux at which the low/hard(LH)-to-high/soft(HS) state transition occurs and the peak flux of the following HS state. By analyzing the data from the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE), we show that the HS state flux after the source reaches its HS flux peak still correlates with the transition flux during soft X-ray transient (SXT) outbursts. By studying large outbursts or flares of GX 339-4, Aql X-1 and 4U 1705-44, we have found that the correlation holds up to 250, 40, and 50 d after the LH-to-HS state transition, respectively. These time scales correspond to the viscous time scale in a standard accretion disk around a stellar mass b...
Synchrotron-Radiation Induced X-Ray Emission (SRIXE)
Elemental analysis using emission of characteristic x rays is a well-established scientific method. The success of this analytical method is highly dependent on the properties of the source used to produce the x rays. X-ray tubes have long existed as a principal excitation source, but electron and proton beams have also been employed extensively. The development of the synchrotron radiation x-ray source that has taken place during the past 40 years has had a major impact on the general field of x-ray analysis. Even tier 40 years, science of x-ray analysis with synchrotron x-ray beams is by no means mature. Improvements being made to existing synchrotron facilities and the design and construction of new facilities promise to accelerate the development of the general scientific use of synchrotron x-ray sources for at least the next ten years. The effective use of the synchrotron source technology depends heavily on the use of high-performance computers for analysis and theoretical interpretation of the experimental data. Fortunately, computer technology has advanced at least as rapidly as the x-ray technology during the past 40 years and should continue to do so during the next decade. The combination of these technologies should bring about dramatic advances in many fields where synchrotron x-ray science is applied. It is interesting also to compare the growth and rate of acceptance of this particular research endeavor to the rates for other technological endeavors. Griibler [1997] cataloged the time required for introduction, diffusion,and acceptance of technological, economic, and social change and found mean values of 40 to 50 years. The introduction of the synchrotron source depends on both technical and non-technical factors, and the time scale at which this seems to be occurring is quite compatible with what is seen for other major innovations such as the railroad or the telegraph. It will be interesting to see how long the present rate of technological change and increase in scientific use can be maintained for the synchrotron x-ray source. A short summary of the present state of the synchrotron radiation-induced x-ray emission (SRIXE) method is presented here. Basically, SRIXE experiments can include any that depend on the detection. of characteristic x-rays produced by the incident x-ray beam born the synchrotron source as they interact with a sample. Thus, experiments done to measure elemental composition, chemical state, crystal, structure, and other sample parameters can be considered in a discussion of SRIXE. It is also clear that the experimentalist may well wish to use a variety of complementary techniques for study of a given sample. For this reason, discussion of computed microtomography (CMT) and x-ray diffraction is included here. It is hoped that this present discussion will serve as a succinct introduction to the basic ideas of SRIXE for those not working in the field and possibly help to stimulate new types of work by those starting in the field as well as by experienced practitioners of the art. The topics covered include short descriptions of (1) the properties of synchrotron radiation, (2) a description of facilities used for its production, (3) collimated microprobe, (4) focused microprobes, (5) continuum and monoenergetic excitation, (6) detection limits, (7) quantitation, (8) applications of SRIXE, (9) computed microtomography (CMT), and (10)chemical speciation using x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS). An effort has been made to cite a wide variety of work from different laboratories to show the vital nature of the field.
Synchrotron-Radiation Induced X-Ray Emission (SRIXE)
1999-09-01
Elemental analysis using emission of characteristic x rays is a well-established scientific method. The success of this analytical method is highly dependent on the properties of the source used to produce the x rays. X-ray tubes have long existed as a principal excitation source, but electron and proton beams have also been employed extensively. The development of the synchrotron radiation x-ray source that has taken place during the past 40 years has had a major impact on the general field of x-ray analysis. Even tier 40 years, science of x-ray analysis with synchrotron x-ray beams is by no means mature. Improvements being made to existing synchrotron facilities and the design and construction of new facilities promise to accelerate the development of the general scientific use of synchrotron x-ray sources for at least the next ten years. The effective use of the synchrotron source technology depends heavily on the use of high-performance computers for analysis and theoretical interpretation of the experimental data. Fortunately, computer technology has advanced at least as rapidly as the x-ray technology during the past 40 years and should continue to do so during the next decade. The combination of these technologies should bring about dramatic advances in many fields where synchrotron x-ray science is applied. It is interesting also to compare the growth and rate of acceptance of this particular research endeavor to the rates for other technological endeavors. Griibler [1997] cataloged the time required for introduction, diffusion,and acceptance of technological, economic, and social change and found mean values of 40 to 50 years. The introduction of the synchrotron source depends on both technical and non-technical factors, and the time scale at which this seems to be occurring is quite compatible with what is seen for other major innovations such as the railroad or the telegraph. It will be interesting to see how long the present rate of technological change and increase in scientific use can be maintained for the synchrotron x-ray source. A short summary of the present state of the synchrotron radiation-induced x-ray emission (SRIXE) method is presented here. Basically, SRIXE experiments can include any that depend on the detection. of characteristic x-rays produced by the incident x-ray beam born the synchrotron source as they interact with a sample. Thus, experiments done to measure elemental composition, chemical state, crystal, structure, and other sample parameters can be considered in a discussion of SRIXE. It is also clear that the experimentalist may well wish to use a variety of complementary techniques for study of a given sample. For this reason, discussion of computed microtomography (CMT) and x-ray diffraction is included here. It is hoped that this present discussion will serve as a succinct introduction to the basic ideas of SRIXE for those not working in the field and possibly help to stimulate new types of work by those starting in the field as well as by experienced practitioners of the art. The topics covered include short descriptions of (1) the properties of synchrotron radiation, (2) a description of facilities used for its production, (3) collimated microprobe, (4) focused microprobes, (5) continuum and monoenergetic excitation, (6) detection limits, (7) quantitation, (8) applications of SRIXE, (9) computed microtomography (CMT), and (10)chemical speciation using x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS). An effort has been made to cite a wide variety of work from different laboratories to show the vital nature of the field.
Study of monazite under high pressure
2010-01-01
Monazite was studied under high pressures of up to 20 GPa and 12 GPa by using synchrotron X-ray diffraction and Raman spectroscopy, respectively. X-ray diffraction data suggested that there was a structural distortion at ~11.5 GPa. The pressure-volume data of the monazite was fitted to a third-order Birch-Murnaghan equation of state and yielded a bulk modulus of 109(1) GPa and a pressure derivative of 6.7(1), in agreement with an empirical formula.
High-pressure x-ray diffraction study of LiIO sub 3 to 75 GPa
In situ high-pressure energy-dispersive x-ray diffraction measurements on alpha-LiIO sub 3 have been performed by using a diamond anvil cell device with synchrotron radiation up to 75 GPa at room temperature. No new phase was found. The second Birch-Murnaghan equation of state is fitted with B sub 0 = 55 +- 3 GPa for the zero-pressure bulk modulus, B sub 0 ' = 2.9 +- 0.4 for its pressure derivative.
Development of a Sub-Picosecond Tunable X-Ray Source at the LLNL Electron Linac
2001-08-31
The use of ultrafast laser pulses to generate very high brightness, ultra short (fs to ps) pulses of x-rays is a topic of great interest to the x-ray user community. In principle, femtosecond-scale pump-probe experiments can be used to temporally resolve structural dynamics of materials on the time scale of atomic motion. The development of sub-ps x-ray pulses will make possible a wide range of materials and plasma physics studies with unprecedented time resolution. A current project at LLNL will provide such a novel x-ray source based on Thomson scattering of high power, short laser pulses with a high peak brightness, relativistic electron bunch. The system is based on a 5 mm-mrad normalized emittance photoinjector, a 100 MeV electron RF linac, and a 300 mJ, 35 fs solid-state laser system. The Thomson x-ray source produces ultra fast pulses with x-ray energies capable of probing into high-Z metals, and a high flux per pulse enabling single shot experiments. The system will also operate at a high repetition rate ({approx} 10 Hz).
X-ray Spectral and timing properties of the black hole x-ray transient Swift J1753.5-0127
2007-01-17
We have carried out detailed analysis on the black hole candidate (BHC) X- ray transient Swift J1753.5-0127 observed by the Rossi X-Ray Timing Explorer (RXTE) during its outburst in 2005 {2006. The spectral analysis shows that the emissions are dominated by the hard X-rays, thus revealing the low/hard state of the source during the outburst. The peak luminosity is found lower than the typical value of balancing the mass flow and evaporation of the inner edge of disk (Meyer-Hofmeister 2004). As a result, the disk is prevented from extending inward to produce strong soft X-rays, corresponding to the so-called high/soft state. These are the typical characteristics for a small subset of BHCs, i.e. those soft X-ray transients stay at the low/hard state during the outburst. In most observational time, the QPO frequencies are found to vary roughly linearly with the fluxes and the spectral indices, while the deviation from this relationship at the peak luminosity might provide the first observational evidence of a partially evaporated inner edge of the accretion disk. The anti-correlation between the QPO frequency and spectral color suggests that the global disk oscillation model proposed by Titarchuk & Osherovich (2000) is not likely at work.
A High Efficiency Grazing Incidence Pumped X-ray Laser
2006-08-31
The main objective of the project is to demonstrate a proof-of-principle, new type of high efficiency, short wavelength x-ray laser source that will operate at unprecedented high repetition rates (10Hz) that could be scaled to 1kHz or higher. The development of a high average power, tabletop x-ray laser would serve to complement the wavelength range of 3rd and future 4th generation light sources, e.g. the LCLS, being developed by DOE-Basic Energy Sciences. The latter are large, expensive, central, synchrotron-based facilities while the tabletop x-ray laser is compact, high-power laser-driven, and relatively inexpensive. The demonstration of such a unique, ultra-fast source would allow us to attract funding from DOE-BES, NSF and other agencies to pursue probing of diverse materials undergoing ultrafast changes. Secondly, this capability would have a profound impact on the semiconductor industry since a coherent x-ray laser source would be ideal for ''at wavelength'' {approx}13 nm metrology and microscopy of optics and masks used in EUV lithography. The project has major technical challenges. We will perform grazing-incidence pumped laser-plasma experiments in flat or groove targets which are required to improve the pumping efficiency by ten times. Plasma density characterization using our existing unique picosecond x-ray laser interferometry of laser-irradiated targets is necessary. Simulations of optical laser propagation as well as x-ray laser production and propagation through freely expanding and confined plasma geometries are essential. The research would be conducted using the Physics Directorate Callisto and COMET high power lasers. At the end of the project, we expect to have a high-efficiency x-ray laser scheme operating below 20 nm at 10Hz with a pulse duration of {approx}2 ps. This will represent the state-of-the-art in x-ray lasers and would be a major step forward from our present picosecond laser-driven x-ray lasers. There is an added bonus of creating the shortest wavelength laboratory x-ray laser, below 4.5 nm and operating in the water window, by using the high-energy capability of the Titan laser.
Mechanical design of a high-resolution x-ray powder diffractometer at the Advanced Photon Source.
2007-01-01
A novel high-resolution x-ray powder diffractometer has been designed and commissioned at the bending magnet beamline 11-BM at the Advanced Photon Source (APS), Argonne National Laboratory (ANL). This state-of-the-art instrument is designed to meet challenging mechanical and optical specifications for producing high-quality powder diffraction data with high throughput. The 2600 mm (H) X 2100 mm (L) X 1700 mm (W) diffractometer consists of five subassemblies: a customized two-circle goniometer with a 3-D adjustable supporting base; a twelve-channel high-resolution crystal analyzer system with an array of precision x-ray slits; a manipulator system for a twelve scintillator x-ray detectors; a 4-D sample manipulator with cryo-cooling capability; and a robot-based sample exchange automation system. The mechanical design of the diffractometer as well as the test results of its positioning performance are presented in this paper.
Mechanical design of a high-resolution x-ray powder diffractometer at the Advanced Photon Source
2007-01-01
A novel high-resolution x-ray powder diffractometer has been designed and commissioned at the bending magnet beamline 11-BM at the Advanced Photon Source (APS), Argonne National Laboratory (ANL). This state-of-the-art instrument is designed to meet challenging mechanical and optical specifications for producing high-quality powder diffraction data with high throughput. The 2600 mm (H) X 2100 mm (L) X 1700 mm (W) diffractometer consists of five subassemblies: a customized two-circle goniometer with a 3-D adjustable supporting base. A twelve-channel high-resolution crystal analyzer system with an array of precision x-ray slits. A manipulator system for a twelve scintillator x-ray detectors. A 4-D sample manipulator with cryo-cooling capability. And a robot-based sample exchange automation system. The mechanical design of the diffractometer as well as the test ...
On the complex disc-corona interactions in the soft spectral states of Soft X-ray Transients
2001-06-03
Accreting black holes show a complex and diverse behaviour in their soft spectral states. Although these spectra are dominated by a soft, thermal component which almost certainly arises from an accretion disc, there is also a hard X-ray tail indicating that some fraction of the accretion power is instead dissipated in hot, optically thin coronal material. During such states, best observed in the early outburst of Soft X-ray Transients, the ratio of power dissipated in the hot corona to that in the disc can vary from ~0 (pure disc accretion) to ~1 (equal power in each). Here we present results of spectral analyses of a number of sources, demonstrating the presence of complex features in their energy spectra. Our main findings are: (1) the soft components are not properly described by a thermal emission from accretion discs: they are appreciably broader than can be described by disc blackbody models even including relativistic effects, and (2) the spectral features near 5-9 keV commonly seen in such spectra can be well described by reprocessing of hard X-rays by optically thick, highly ionized, relativistically moving plasma.
Method of an apparatus for x-radiation sorting of raw materials
1993-08-17
An apparatus is described for X-ray sorting of feed stock, consisting essentially of: a feed hopper for containing lumps of feed stock to be sorted; a small gradient conveyor arranged under the feed hopper and provided with a vibrator, means for spreading the lumps in a single layer across a width of the conveyor, and means arranged over the conveyor to adjust the lumps into a stable position; a high gradient conveyor mounted downstream of said small gradient conveyor along the path of movement of the lumps said high gradient conveyor having a vibrator and a horizontal discharge line to provide a single layer of stable unsupported lumps in a free fall state; means to prevent rotation of the lumps, arranged at a joint between the small gradient and high gradient conveyors; a coordinate system to determine the dimensions of the lumps and their position over the width of the single layer of free failing lumps, having electric outputs and provided in the immediate vicinity of said discharge line of said high gradient conveyor; sources of primary X-ray radiation arranged in the immediate vicinity of said coordinate system along the path of movement of said freely falling single layer for directing X-ray radiation toward the lumps in said layer which interacts with the lumps for producing characteristic secondary X-ray radiation of the lumps; a plurality of secondary X-ray radiation detectors, each of which has an electric output and which are positioned in the immediate vicinity of said plurality of primary X-ray radiation sources along the path of movement of said single layer of freely failing lumps for detecting said characteristic secondary X-ray radiation of the lumps; a computing device having a plurality of inputs connected to the respective said outputs of the coordinate system and to the outputs of the secondary X-ray radiation detectors, and having a plurality of outputs.
X-rays spectroscopy with a portable Compton selection chamber: detector design and results
2004-01-01
In this paper a practical solution to perform spectral analysis of diagnostic X-ray beams is described, based on a miniaturized Compton selection chamber (CSC) using a Si-PIN detector. Results are compared with those obtained with a first prototype of CSC based on nitrogen cooled high purity germanium (HPGe) detector. With this method, the direct X-ray spectrum is Compton scattered inside the CSC, collected by a solid-state detector and reconstructed using a simplified scattering matrix experimentally determined. The results obtained will be compared with a reference standard, represented by direct spectra acquired with an HPGe detector in a laboratory facility, not applicable for on-field measurements.
X-rays spectroscopy with a portable Compton selection chamber: detector design and results
2004-01-01
In this paper a practical solution to perform spectral analysis of diagnostic X-ray beams is described, based on a miniaturized Compton selection chamber (CSC) using a Si-PIN detector. Results are compared with those obtained with a first prototype of CSC based on nitrogen cooled high purity germanium (HPGe) detector. With this method, the direct X-ray spectrum is Compton scattered inside the CSC, collected by a solid-state detector and reconstructed using a simplified scattering matrix experimentally determined. The results obtained will be compared with a reference standard, represented by direct spectra acquired with an HPGe detector in a laboratory facility, not applicable for on-field measurements
2007-07-01
In this PhD thesis time-resolved X-ray diffraction in optical pump - X-ray probe scheme was applied for the first time to a High-Temperature Superconductor in the superconducting state. The aim was to study the possible lattice response to optical Cooper pair breaking. As sample a thin YBa{sub 2}Cu{sub 3}O{sub 7} film with a superconducting transition temperature of T{sub c}=90 K, epitaxially grown on a SrTiO{sub 3} single crystal was used. (orig.)
High power, high beam quality solid state lasers for materials processing applications
1994-08-01
The Laser Science and Technology Department at Lawrence Livermore National Laboratory is developing solid state lasers with high average power and high beam quality. Specific systems include a laser to generate 10 to 14 {angstrom} x-rays for proximity print lithography, a 400 mJ, 500 Hz laser for 130 {angstrom} projection lithography and unique systems for speckle imaging, laser radars and medical treatments.
Equation of state of unreacted high explosives at high pressures
1998-08-14
Isotherms of unreacted high explosives (HMX, RDX, and PETN) have been determined to quasi-hydrostatic high pressures below 45 GPa, by using a diamond-anvil cell angle-resolved synchrotron x-ray diffraction method. The equation-of-state parameters (bulk modulus B
X-Ray Diffraction and Imaging Study of Imperfections of Crystallized Lysozyme with Coherent X-Rays
Phase-sensitive x-ray diffraction imaging and high angular-resolution diffraction combined with phase contrast radiographic imaging are employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme ...
X-Ray Diffraction and Imaging Study of Imperfections of Crystallized Lysozyme with Coherent X-Rays
Phase-sensitive x-ray diffraction imaging and high angular-resolution diffraction combined with phase contrast radiographic imaging are employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme ...
Mirror Technology Development for The International X-Ray Observatory Mission
Presentation slides include: International X-ray Observatory (IXO), Lightweight and High Resolution X-ray Optics is Needed; Modular Design of Mirror Assembly, IXO Mirror Technology Development Objectives, Focus of ...
Mirror Technology Development for The International X-Ray Observatory Mission
Presentation slides include: International X-ray Observatory (IXO), Lightweight and High Resolution X-ray Optics is Needed; Modular Design of Mirror Assembly, IXO Mirror Technology Development Objectives, Focus of ...
A Compact X-Ray System for Support of High Throughput Crystallography
Standard x-ray systems for crystallography rely on massive generators coupled with optics that guide X-ray beams onto the crystal sample. Optics for single-crystal diffractometry include total reflection mirrors, ...
A Compact X-Ray System for Support of High Throughput Crystallography
Standard x-ray systems for crystallography rely on massive generators coupled with optics that guide X-ray beams onto the crystal sample. Optics for single-crystal diffractometry include total reflection ...
IR spectra of the microquasar GRS 1915+105 during a low state
2001-01-22
There is controversy regarding the nature of the suspected donor star to the microquasar GRS 1915+105, and hence whether GRS 1915+105 is a high mass X-ray binary (HMXB) or a low-mass X-ray binary (LMXB). In order to clarify this issue, we obtained an infrared (J, H and K) spectrum of GRS 1915+105 in its low state which shows a steeper continuum than the prototype X-ray binary Sco X-1. We did not detect any HeII emission at 2.189 microns from GRS 1915+105 in our quiescent spectrum, indicating that the line is transient and is only observed during episodes of high X-ray activity. For our instrument configuration, there is no detection of the 12CO lines which are characteristic of late-type stars either in GRS1915+105 or Sco X-1.
XMM-Newton observations of EF Eridani: the textbook example of low-accretion rate polars
2007-03-21
Archival X-ray observations of EF Eridani obtained in a low state revealed distinct X-ray detections at a luminosity L_X ~ 2 10^{29} erg/s, three orders of magnitude below its high state value. The plasma temperature was found to be as low as $kT \\loa 2$ keV, a factor 10 below the high state. The X-ray/UV/IR spectral energy distribution suggests faint residual accretion rather than coronal emission as being responsible for the low-state X-ray emission. EF Eri thus showed a clear transition from being shock-dominated in the high state to be cyclotron-dominated in the low state. From the optical/UV spectral energy distribution we re-determine the photospheric temperature of the white dwarf to \\~10000K. Contrary to earlier claims, WD model atmospheres produce sufficient UV flux to reproduce the published GALEX flux and orbital modulation.
Ultrafast Materials Probing with the LLNL Thomson X-Ray Source
2002-09-03
The use of short laser pulses to generate very high brightness, ultra short (fs to ps) x-ray pulses is a topic of great interest. In principle, fantosecond-scale pump-probe experiments can be used to temporally resolve structural dynamics of materials on the time scale of atomic motion. The development of sub-ps x-ray pulses will make possible a wide range of materials and plasma physics studies with unprecedented time resolution. The Thomson scattering project at LLNL will provide such a novel x-ray source of high power using short laser pulses and a high brightness, relativistic electron bunch. The system is based on a 5mm-mrad normalized emittance photoinjector, 100 MeV electron RF linac, and a 300 mJ, 35 fs solid-state laser system. The Thomson source will produce ultra fast pulses with x-ray energies (60 kev) capable of probing into high-Z metals.
High Energy Density Science at the Linac Coherent Light Source
2007-01-01
High energy density science (HEDS), as a discipline that has developed in the United States from National Nuclear Security Agency (NNSA)-sponsored laboratory research programs, is, and will remain, a major component of the NNSA science and technology strategy. Its scientific borders are not restricted to NNSA. 'Frontiers in High Energy Density Physics: The X-Games of Contemporary Science' identified numerous exciting scientific opportunities in this field, while pointing to the need for a overarching interagency plan for its evolution. Meanwhile, construction of the first x-ray free-electron laser, the Office-of-Science-funded Linear Coherent Light Source-LCLS: the world's first free electron x-ray laser, with 100-fsec time resolution, tunable x-ray energies, a high rep rate, and a 10 order-of-magnitude increase in brightness over any other x-ray source--led ...
A high brightness photoinjector has been developed at LLNL. This injector combined with the 100 TW FALCON laser and the LLNL 100 MeV S-Band RF linac will enable development of a high brightness, femtosecond-scale, tunable, hard x-ray probe for time-resolved material measurements, based on Thomson scattering. Short pulse x-rays enable time-resolved characterization of shock dynamics, and examination of materials under extremes of pressure and temperature. Examples include Equation of State characterization on high-density materials, Crystal disorganization and re-growth in shocked and heated materials, and measurement of short time scale phase transition phenomena. Single shot evaluation, requiring high peak flux, is important for complex experiments such as probing of laser shocked actinides. A low emittance electron beam synchronized with femtosecond accuracy to an intense laser will revolutionize x-ray dynamics studies of materials. This project will lead development of ultrafast x-ray dynamics research on problems important in physics, chemistry, biology, and materials.
A high brightness photoinjector has been developed at LLNL. This injector combined with the 100 TW FALCON laser and the LLNL 100 MeV S-Band RF linac will enable development of a high brightness, femtosecond-scale, tunable, hard x-ray probe for time-resolved material measurements, based on Thomson scattering. Short pulse x-rays enable time-resolved characterization of shock dynamics, and examination of materials under extremes of pressure and temperature. Examples include Equation of State characterization on high-density materials, Crystal disorganization and re-growth in shocked and heated materials, and measurement of short time scale phase transition phenomena. Single shot evaluation, requiring high peak flux, is important for complex experiments such as probing of laser shocked actinides. A low emittance electron beam synchronized with femtosecond accuracy to an intense laser will revolutionize x-ray dynamics studies of materials. This project will lead development of ultrafast x-ray dynamics research on problems important in physics, chemistry, biology, and materials.
X-ray spectroscopy of the photosynthetic oxygen-evolving complex
Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn4Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.
Russian X-ray image receivers Otechestvennye rentgenograficheskie priemniki izobrazheniya
2000-01-01
Systematization of the intensifying screen-film sets of general purpose for X-ray radiography, used in present practice of medical establishments, is performed in order to obtain the maximum possible result in every specific type of investigation. Classification of screens regulated by the available state standard is presented. Domestic intensifying screens for general application and their main parameters are enumerated. Technical level of the domestic films and X-ray cassettes are characterized. Sufficiently high technical level of the domestic intensifying screens and plastic X-ray cassettes is marked in contrast to X-ray domestic film
Electronic Structure of AC-Clusters and High-Resolution X-ray Spectra of Actinides in Solids
Ab initio calculations using SCF approach for and analysis of results of investigation of the electronic structure of the clusters RAn+:[L]k with rare earths or actinides were carried out for the clusters in solids and liquids. Theoretical results for the electronic structure, radial integrals and energy of X- ray lines are presented for AC ions with unoccupied 5f-shell in the clusters in oxides, chlorides and fluorides environment. Possibility of collapse of nf-shell for the separate clusters and identification of electronic state of ions with unstable nuclei, are discussed, too. (author)
Electronic Structure of AC-Clusters and High-Resolution X-ray Spectra of Actinides in Solids
2007-01-01
Ab initio calculations using SCF approach for and analysis of results of investigation of the electronic structure of the clusters RAn+:[L]k with rare earths or actinides were carried out for the clusters in solids and liquids. Theoretical results for the electronic structure, radial integrals and energy of X- ray lines are presented for AC ions with unoccupied 5f-shell in the clusters in oxides, chlorides and fluorides environment. Possibility of collapse of nf-shell for the separate clusters and identification of electronic state of ions with unstable nuclei, are discussed, too. (author)
2010-05-14
Bound state, valence electronic excitation spectra of N_2 are probed by nonresonant inelastic x-ray and electron scattering. Within the usual theoretical treatments, dynamical structure factors derived from the two probes should be identical. However, we find strong disagreements outside the dipole scattering limit, even at high probe energies. This suggests an unexpectedly important contribution from intra-molecular multiple scattering of the probe electron from core electrons or the nucleus. These effects should grow progressively stronger as the atomic number of the target species increases.
2004-01-27
The generation of high intensity, ultra-short x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. Thomson backscattering of a high intensity laser pulse with a bright relativistic electron bunch is a promising method for producing such high brightness x-ray pulses in the 10-100 keV range within a compact facility. While a variety of methods for producing sub-picosecond x-ray bursts by Thomson scattering exist, including compression of the electron bunch to sub-picosecond bunch lengths and/or colliding a sub-picosecond laser pulse in a side-on geometry to minimize the interaction time, a promising alternative approach to achieving this goal while maintaining ultra-high brightness is the production of a time correlated (or chirped) x-ray pulse in conjunction with pulse slicing or compression. We present the results of a complete analysis of this process using a recently developed 3-D time and frequency-domain code for analyzing the spatial, temporal, and spectral properties an x-ray beam produced by relativistic Thomson scattering. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, laser focus, and the transverse and longitudinal phase space of the electron beam were examined. Simulations of chirped x-ray pulse production using both a chirped electron beam and a chirped laser pulse are presented. Required electron beam and laser parameters are summarized by investigating the effects of beam emittance, energy spread, and laser bandwidth on the scattered x-ray spectrum. It is shown that sufficient temporal correlation in the scattered x-ray spectrum to produce sub-100 fs temporal slice resolution can be produced from state-of-the-art, high-brightness electron beams without the need to perform longitudinal compression on the electron bunch.
2009-06-16
The hard X-ray source 4U 2206+54 is a peculiar high mass X-ray binary with a main-sequence donor star. Recent X-ray observations suggested that the compact object in 4U 2206+54 may be a neutron star. The X-ray emission comes from the accretion of stellar winds from the massive donor stars, and variability of luminosity may be due to the changes of its orbit phase. To further reveal the nature of compact object, we studied 4U 2206+54 with INTEGRAL/IBIS observations in two years, and found that in most time, 4U 2206+54 undergone a quiescent state and sometime an active state. In the quiescent state the spectrum can be fitted by a power-law model of $\\Gamma\\sim 2.1$ with a hard X-ray luminosity of $\\sim 5\\times 10^{34}$ erg s$^{-1}$ (20-- 100 keV). While in the active state, the 20-- 100 keV hard X-ray luminosity reaches $\\sim 2\\times 10^{35}$ erg s$^{-1}$ and the spectrum is fitted by a thermal bremmstrahlung model of $kT\\sim 43$ keV plus two cyclotron absorption lines at $\\sim$ 30 and 60 keV. Then we derived a magnetic field of 3.3$\\times 10^{12}$ G for the compact object in 4U 2206+54. During the active state, we found a pulsation period of $\\sim$ 5400 s in the light curve of 4U 2206+54. So the compact object in 4U 2206+54 should be a magnetic neutron star with a slow pulsation. Cyclotron absorption lines detected in the active state and non-detection in the quiescent state suggested that two different accretion states have pos sible different hard X-ray emission regions: surface of neutron star in the active state; the magnetic-accretion pressure equivalent point in the quiescent state. The re-analysis of the RXTE/ASM light curve found the modulation periods at $\\sim 9.56$ days and 19.11 days, and the orbit period of 4U 2206+54 should be 19.11 days.
Techniques of absolute low energy x-ray calibration
Recent advances in pulsed plasma research, materials science, and astrophysics have required many new diagnostic instruments for use in the low energy x-ray regime. The characterization of these instruments has provided a challenge to instrument designers and provided the momentum to improve x-ray sources and dosimetry techniques. In this paper, the present state-of-the-art in low energy x-ray characterization techniques is reviewed. A summary is given of low energy x-ray generator technology and dosimetry techniques including a discussion of thin window proportional counters and ionization chambers. A review is included of the widely used x-ray data bases and a sample of ultrasoft x-ray measuring procedures, chopped x-ray source generators, phase sensitive detection of ultralow currents, and angular divergence measurements.
Techniques of absolute low energy x-ray calibration
1986-01-01
Recent advances in pulsed plasma research, materials science, and astrophysics have required many new diagnostic instruments for use in the low energy x-ray regime. The characterization of these instruments has provided a challenge to instrument designers and provided the momentum to improve x-ray sources and dosimetry techniques. In this paper, the present state-of-the-art in low energy x-ray characterization techniques is reviewed. A summary is given of low energy x-ray generator technology and dosimetry techniques including a discussion of thin window proportional counters and ionization chambers. A review is included of the widely used x-ray data bases and a sample of ultrasoft x-ray measuring procedures, chopped x-ray source generators, phase sensitive detection of ultralow currents, and angular divergence measurements.
2009-01-01
A new glancing incident X-ray fluorescence (GIXRF) spectrometer using parallel polycapillary X-ray lens has been developed. Integrated with a Zr filter and slits, a highly collimated and monochromatic X-ray beam has been achieved. This method eliminated the monochromator used in the conventional GIXRF method. Moreover the parallel X-ray lens increased the acceptance solid angle and hence increases intensities of the excitation spectrum. In this paper, this method has been applied in analysis of single crystal and film sample.
Spectral states and state preference of galactic X-ray binaries
2010-01-01
Using observations in the past four years with the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE) and the Burst Alert Telescope (BAT) onboard the Swift, we demonstrate that the hard state and the soft state are the primary spectral states in galactic black hole and neutron star X-ray binaries. In addition, we show quantitatively the preference of the two spectral states for each of the 22 bright persistent sources.
Mammography X-ray unit; Chibusa X sen satsuei sochi
1996-04-01
A device which can meet the market demands for X-ray mammography is developed. Mammography uses low-energy X-ray which significantly decays in soft tissues, such as those in a nipple, where detection of fine changes to a morbid state is essential for diagnostication. Such a device is required to have high resolution and contrast. Mammography is being introduced in breast cancer screening in Japan, and guidelines for quality/technique management and standardization are being modified or developed. The new device meets the mammography guidelines issued by the Japan`s radiology society requiring accurate images produced by adequate photographic techniques. It is equipped with an automatic exposure controller that stops X-ray when an adequate quantity of exposure is secured, and automatic positioner for individual persons. The common X-ray high-voltage device of small tube voltage waveform ripple is also developed for general photographing and mammography. 2 refs., 8 figs., 1 tab.
A Bright Spatially-Coherent Compact X-ray Synchrotron Source
2009-12-10
Each successive generation of x-ray machines has opened up new frontiers in science, such as the first radiographs and the determination of the structure of DNA. State-of-the-art x-ray sources can now produce coherent high brightness keV x-rays and promise a new revolution in imaging complex systems on nanometre and femtosecond scales. Despite the demand, only a few dedicated synchrotron facilities exist worldwide, partially due the size and cost of conventional (accelerator) technology. Here we demonstrate the use of a recently developed compact laser-plasma accelerator to produce a well-collimated, spatially-coherent, intrinsically ultrafast source of hard x-rays. This method reduces the size of the synchrotron source from the tens of metres to centimetre scale, accelerating and wiggling a high electron charge simultaneously. This leads to a narrow-energy spread electron beam and x-ray source that is >1000 times brighter than previously reported plasma wiggler and thus has the potential to facilitate a myriad of uses across the whole spectrum of light-source applications.
2005-12-22
Amorphous tin-nitride thin films were prepared by reactive sputter deposition on smooth float glass substrates in a vacuum chamber with an integrated small magnetron source. The films were investigated using in situ reflection mode X-ray absorption spectroscopy and ex situ X-ray photoelectron spectroscopy (XPS). Both the X-ray absorption near edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS) were analysed, yielding bond distances, coordination numbers and Debye-Waller factors. XPS yields the chemical composition and the binding state of the constituents of the films, specular X-ray reflectivity allows the determination of the sample density and of the roughness and its changes with film thickness. The results were compared to those of crystalline Sn{sub 3}N{sub 4}, indicating that the electronic and atomic structure of the amorphous films determined by EXAFS data analysis are very similar to the stoichiometric reference compound. Two different Sn-N interactions with about 2.09 and 2.19 A bond distance and 4 and 6 nearest neighbours, respectively, are present. These bond distances are slightly relaxed compared to the crystalline reference material, which is consistent with the sample density, which is reduced by about 8% in comparison to Sn{sub 3}N{sub 4}. XPS as well as XANES revealed a Sn valence of about 4+ and the presence of nitric bonds, while XPS also suggests that the nitride is slightly decomposed under X-ray irradiation in ultra-high vacuum.
Parabolic refractive X-ray lenses: a breakthrough in X-ray optics
Refractive X-ray lenses, considered for a long time as unfeasible, have been realized with a rotational parabolic profile at our institute: The main features of the new lenses are: they focus in two directions and are free of spherical aberration. By varying the number of individual lenses in the stack the focal length can be chosen in a typical range from 0.5 to 2 m for photon energies between about 6 and 60 keV. The aperture of the lens is about 1 mm matching the angular divergence of undulator beams at 3d generation synchrotron radiation sources. They cope without problems with the heat load from the white beam of an undulator. Finally, they are easy to align and to operate. Refractive X-ray lenses can be used with hard X-rays in the same way as glass lenses can be used for visible light, if it is take into account that the numerical aperture is small (of the order 10 sup - sup 4). Being high-quality optical elements, the refractive X-ray lenses can be used for generating a focal spot in the mu m range with a gain of a factor 1000 and more, or for imaging purposes as in a hard X-ray microscope. Recent examples from microanalysis, microtomography, fluorescence tomography, X-ray microscopy will be shown to demonstrate the state of the art. Possible new developments will be discussed.
Light-driven oxidation of water to dioxygen in plants, algae and cyanobacteria iscatalyzed within photosystem II (PS II) by a Mn4Ca cluster. Although the cluster has been studied by many different methods, the structure and the mechanism have remained elusive. X-ray absorption and emission spectroscopy and EXAFS studies have been particularly useful in probing the electronic and geometric structure, and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes polarized X-ray absorption spectroscopy measurements of PS II single crystals. Analysis of those results has constrained the Mn4Ca cluster geometry to a setof three similar high-resolution structures. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 Angstrom-resolution X-ray structures or other previously proposed models. The differences between the models derived from X-rayspectroscopy and crystallography are predominantly because of damage to the Mn4Ca cluster by X-rays under the conditions used for structure determination by X-ray crystallography. X-ray spectroscopy studies are also used for studying the changes in the structure of the Mn4Ca catalytic center as it cycles through the five intermediate states known as the Si-states (i=0-4). The electronic structure of the Mn4Ca cluster has been studied more recently using resonant inelastic X-ray scattering spectroscopy (RIXS), in addition to the earlier X-ray absorption and emission spectroscopy methods. These studies are revealing that the assignment of formaloxidation states is overly simplistic. A more accurate description should consider the charge density on the Mn atoms that includes the covalency of the bonds and delocalization of the charge over the cluster. The geometric and electronic structure of the Mn4Ca cluster in the S-states derived from X-ray spectroscopy are leading to a detailed understanding of the mechanism of the O-O bond formation during the photosynthetic water splitting process.
2007-10-24
Light-driven oxidation of water to dioxygen in plants, algae and cyanobacteria iscatalyzed within photosystem II (PS II) by a Mn4Ca cluster. Although the cluster has been studied by many different methods, the structure and the mechanism have remained elusive. X-ray absorption and emission spectroscopy and EXAFS studies have been particularly useful in probing the electronic and geometric structure, and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes polarized X-ray absorption spectroscopy measurements of PS II single crystals. Analysis of those results has constrained the Mn4Ca cluster geometry to a setof three similar high-resolution structures. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 Angstrom-resolution X-ray structures or other previously proposed models. The differences between the models derived from X-rayspectroscopy and crystallography are predominantly because of damage to the Mn4Ca cluster by X-rays under the conditions used for structure determination by X-ray crystallography. X-ray spectroscopy studies are also used for studying the changes in the structure of the Mn4Ca catalytic center as it cycles through the five intermediate states known as the Si-states (i=0-4). The electronic structure of the Mn4Ca cluster has been studied more recently using resonant inelastic X-ray scattering spectroscopy (RIXS), in addition to the earlier X-ray absorption and emission spectroscopy methods. These studies are revealing that the assignment of formaloxidation states is overly simplistic. A more accurate description should consider the charge density on the Mn atoms that includes the covalency of the bonds and delocalization of the charge over the cluster. The geometric and electronic structure of the Mn4Ca cluster in the S-states derived from X-ray spectroscopy are leading to a detailed understanding of the mechanism of the O-O bond formation during the photosynthetic water splitting process.
Synchrotron X-Ray Absorption Study of LiFePO{sub 4} Electrodes
2004-03-01
LiFePO{sub 4} was investigated in practical Li-ion intercalation electrodes used for Li-ion batteries applying X-ray absorption spectroscopy (XAS). The LiFePO{sub 4} electrode was analysed at the initial state (LiFePO{sub 4}, Fe(II)) corresponding to the uncharged state of the battery, and at the Lithium free state (FePO{sub 4}, Fe(III)), which corresponds to the battery's charged state. The XANES region of the X-ray absorption spectra revealed a large Fe K-edge shift and pre-edge features corresponding to a high spin configuration for Fe(II) in LiFePO{sub 4}. (author)
2005-04-07
We present the results of spectral fits made to 57 pointed observations of the Galactic black hole candidate and X-ray transient XTE J1650-500, made with the Rossi X-ray Timing Explorer in 2001 when the source was in a transition from the hard state to the soft state. A strong and variable Fe K-alpha emission line is detected in these spectra. The line flux varies in a non-linear way with the hard X-ray flux, in apparent contradiction to the predictions of simple disc reflection models. We observe a change in the overall trend that coincides with changes in t he continuum X-ray spectrum and the fast X-ray variability. The Fe-line flux versus hard X-ray flux variations are consistent with the predictions of reflection models which consider high disc-ionization states and with a model which considers gravitational light-bending effects. Indications for an anti-correlation between the Fe-line flux and the hard X-ray flux in the spectrally hardest observations and weak variations in the Fe-line energy (as observed with XMM-Newton and BeppoSAX) slightly favour the light-bending interpretation.
Superconducting High-Resolution X-Ray Spectrometers for Chemical State Analysis of Dilute Samples
Cryogenic X-ray spectrometers operating at temperatures below 1 K combine high energy resolution with broadband efficiency for X-ray energies up to 10 keV. They offer advantages for chemical state analysis of dilute samples by fluorescence-detected X-ray absorption spectroscopy (XAS) in cases where conventional Ge or Si(Li) detectors lack energy resolution and grating spectrometers lack detection efficiency. We are developing soft X-ray spectrometers based on superconducting Nb-Al-AlOx-Al-Nb tunnel junction (STJ) technology. X-rays absorbed in one of the superconducting electrodes generate excess charge carriers in proportion to their energy, thereby producing a measurable temporary increase in tunneling current. For STJ operation at the synchrotron, we have designed a two-stage adiabatic demagnetization refrigerator (ADR) with a cold finger that holds a 3 x 3 array of STJs inside the UHV sample chamber at a temperature of {approx}0.1 K within {approx}15 mm of a room temperature sample. Our STJ spectrometer can have an energy resolution below 10 eV FWHM for X-ray energies up to 1 keV, and has total count rate capabilities above 100,000 counts/s. We will describe detector performance in synchrotron-based X-ray fluorescence experiments and demonstrate its use for XAS on a dilute metal site in a metalloprotein.
Superconducting High-Resolution X-Ray Spectrometers for Chemical State Analysis of Dilute Samples
2003-09-02
Cryogenic X-ray spectrometers operating at temperatures below 1 K combine high energy resolution with broadband efficiency for X-ray energies up to 10 keV. They offer advantages for chemical state analysis of dilute samples by fluorescence-detected X-ray absorption spectroscopy (XAS) in cases where conventional Ge or Si(Li) detectors lack energy resolution and grating spectrometers lack detection efficiency. We are developing soft X-ray spectrometers based on superconducting Nb-Al-AlOx-Al-Nb tunnel junction (STJ) technology. X-rays absorbed in one of the superconducting electrodes generate excess charge carriers in proportion to their energy, thereby producing a measurable temporary increase in tunneling current. For STJ operation at the synchrotron, we have designed a two-stage adiabatic demagnetization refrigerator (ADR) with a cold finger that holds a 3 x 3 array of STJs inside the UHV sample chamber at a temperature of {approx}0.1 K within {approx}15 mm of a room temperature sample. Our STJ spectrometer can have an energy resolution below 10 eV FWHM for X-ray energies up to 1 keV, and has total count rate capabilities above 100,000 counts/s. We will describe detector performance in synchrotron-based X-ray fluorescence experiments and demonstrate its use for XAS on a dilute metal site in a metalloprotein.
Hard X-ray Emission From Low Mass X-ray Binaries
We report on Rossi X-ray Timing Explorer observations of four type I X-ray bursters; namely 1E1724-3045, GS1826-238, SLX1735-269 and KS1731-260. The first three were in a low state (LS) whereas KS1731-260 was in a high state. The LS sources have very similar power spectra, displaying high frequency noise up to frequencies below 20 Hz. In addition a quasi-periodic oscillation at 1200 Hz is detected. The 1-200 keV LS spectra are all consistent with resulting from thermal Comptonization with an electron temperature (kTe) around 25-30 keV. For KS1731-260, the spectrum is also dominated by Comptonization, but with kTe around 3 keV and no significant hard X-ray emission. With the exception of GS1826-238, there is an underlying soft component. For all sources, we have detected an iron line at 6.4 keV. A reflection component is present in the spectra of GS1826-238 and SLX1735-269. We suggest a model in which the region of main energy release, where hard X-rays are produced would be an optically thin boundary layer merged with an Advection Dominated Accretion Flow (ADAF). The soft component observed probably represents the unscattered emission from the accretion disk of variable inner radius. When the accretion rate increases, the inner disk radius shrinks, the strength of the reflected component and associated iron line increase, and the Comptonization region cools off in response to an increased cooling flux from the accretion disk and from the reprocessed/reflected component. Finally, in the light of these observations, we discuss extensively the various criteria recently proposed to distinguish between non-quiescent accreting black holes and neutron stars.
The X-ray mirror telescope and the pn-CCD detector of CAST
The Cern Axion Solar Telescope - CAST - uses a prototype 9 Tesla LHC superconducting dipole magnet to search for a hypothetical pseudoscalar particle, the axion, which was proposed by theory in the 1980s to solve the strong CP problem and which could be a dark matter candidate. In CAST a strong magnetic field is used to convert the solar axions to detectable photons via inverse Primakoff effect. The resulting X-rays are thermally distributed in the energy range of 1-7 keV and can be observed with conventional X-ray detectors. The most sensitive detector system of CAST is a pn-CCD detector originally developed for XMM-Newton combined with a Wolter I type X-ray mirror system. The combination of a focusing X-ray optics and a state of the art pn-CCD detector which combines high quantum efficiency, good spacial and energy resolution, and low background improves the sensitivity of the CAST experiment such that for the first time the axion photon coupling constant can be probed beyond the best astrophysical constraints. In this paper we report on the performance and status of the X-ray telescope and pn-CCD detector of CAST.
Diffuse Hard X-ray Emission in Starburst Galaxies as Synchrotron from Very High Energy Electrons
2010-10-18
The origin of the diffuse hard X-ray emission of starburst galaxies is a long-standing problem. We suggest that synchrotron emission of 10 - 100 TeV electrons and positrons can contribute significantly to this emission, because starbursts have strong magnetic fields. We argue that starburst galaxies are typically opaque to 10 - 100 TeV gamma-rays by pair production of their intense FIR radiation, contributing significantly to the electron/positron population at these energies. By creating one-zone steady-state models of the CR population in the Galactic Center, M82, and Arp 220, we calculate the diffuse synchrotron and Inverse Compton (IC) contributions to their X-ray emission. The TeV gamma-ray spectrum of M82 constrains its CR electron population at X-ray emitting energies, implying that 1 - 10% of its diffuse hard X-ray emission is synchrotron. The synchrotron fraction of Arp 220's X-ray emission ranges from ~1 - 100%, although the most realistic injection and escape parameters (based on M82's TeV spectrum) imply that synchrotron is ~5 - 20% of its hard X-ray emission. Synchrotron emission in the Galactic Center contributes negligibly (<~ 1%) to the Galactic Ridge X-ray emission. We also model generic starbursts, including submillimeter galaxies, in the context of the infared-X-ray relation. We find that synchrotron is comparable to or exceeds IC emission at hard X-ray energies for most parameters. Neutrino observations by I ceCube and TeV gamma-ray data from HESS, VERITAS, and CTA will further constrain the synchrotron X-ray emission of starbursts. If synchrotron dominates the observed X-ray emission, an additional hard component of e+/- peaked at multi-TeV energies is necessary, as might be provided by pulsars.
The use of CdTe detectors for dental X-ray spectrometry
2007-07-01
he cadmium telluride (CdTe) semiconductor detector provides high detection efficiency for use in the diagnostic x-rays energy range, because of the high atomic number and high density of the crystal. Moreover, it has the great advantage of working at room temperature, in contrast to the germanium detector, which operates in liquid nitrogen temperature. The CdTe detector has been utilized in diagnostic x-ray spectroscopy, but only scarce information about its use in dental X-ray beams has been published. In this way, a portable 3x3x1 mm{sup 3} CdTe solid state detector (XR-100T CdTe by Amptek, Inc.) with tungsten pinhole collimators, alignment device and associated software was utilized in this work for measuring the photon spectra in the dental x-ray kVp range. A single-phase dental unit with adjustable kVp and mA was employed and the x-ray spectra were experimentally determined at 50, 60 and 70 kVp with 0.5 mA tube current. The pulse height distribution obtained with this detector, however, does not represent the 'true' photon spectra. For this reason, a stripping procedure was implemented to correct the distribution in order to determine the real photon spectra. The x-ray spectra obtained with the CdTe detector were compared with the ones measured with a high-purity germanium detector (EGP200-13-TR by Eurisys Mesures). The reasonable agreement between the results obtained with both detectors for the 50 to 70 keV range show that CdTe detectors can be utilized for dental x-ray spectrometry. (author)
Orbital radiation imaging with various physical principles
2001-01-01
This paper describes the characteristics of orbital radiation and authors' investigations on the high spatial resolution X ray-CT, fluorescence X ray-CT and phase-type X ray imaging. Orbital radiation is an X ray generated by relativistic electron bended by magnet in the synchrotron and possesses the high photon density/unit area (
2010-09-01
The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for resonant inelastic X-ray scattering...Full Text Available
Localized high spin states in transition-metal dimers: X-ray absorption spectroscopy study
2009-01-01
X-ray absorption spectroscopy provides direct evidence for localized valence electrons in Cr2+, Mn2+, and CrMn+ dimer cations. Bonding in these transition-metal molecules is predominantly mediated by 4s electrons. This behavior is markedly different from other 3d transition-metal dimers with open 3d subshells and can be ascribed to the highly stable 3d5(6S) configuration of the 3d subshell in chromium and manganese atoms and ions. In Cr2+, Mn2+, and CrMn+, 3d electron localization indicates local high spin states
600 eV falcon-linac thomson x-ray source
2000-12-15
The advent of 3rd generation light sources such as the Advanced Light Source (ALS) at LBL, and the Advanced Photon Source at Argonne, have produced a revolution in x-ray probing of dense matter during the past decade. These machines use electron-synchrotrons in conjunction with undulator stages to produce 100 psec x-ray pulses with photon energies of several kiloelectronvolts (keV). The applications for x-ray probing of matter are numerous and diverse with experiments in medicine and biology, semiconductors and materials science, and plasma and solid state physics. In spite of the success of the 3rd generation light sources there is strong motivation to push the capabilities of x-ray probing into new realms, requiring shorter pulses, higher brightness and harder x-rays. A 4th generation light source, the Linac Coherent Light Source (LCLS), is being considered at the Stanford Linear Accelerator [1]. The LCLS will produce multi-kilovolt x-rays of subpicosecond duration that are 10 orders of magnitude brighter than today's 3rd generation light sources.[1] Although the LCLS will provide unprecedented capability for performing time-resolved x-ray probing of ultrafast phenomena at solid densities, this machine will not be completed for many years. In the meantime there is a serious need for an ultrashort-pulse, high-brightness, hard x-ray source that is capable of probing deep into high-Z solid materials to measure dynamic effects that occur on picosecond time scales. Such an instrument would be ideal for probing the effects of shock propagation in solids using Bragg and Laue diffraction. These techniques can be used to look at phase transitions, melting and recrystallization, and the propagation of defects and dislocations well below the surface in solid materials. [2] These types of dynamic phenomena undermine the mechanical properties of metals and are of general interest in solid state physics, materials science, metallurgy, and have specific relevance to stockpile stewardship. Another x-ray diagnostic technique, extended x-ray absorption fine structure (EXAFS) spectroscopy, can be used to measure small-scale structural changes to understand the underlying atomic physics associated with the formation of defects. [2]
Multitechnique Analysis of the Lattice Structures of Highly Siliceous Zeolites
The combined use of high-resolution solid state NMR techniques (both 1D and 2D) with synchrotron-based powder x-ray diffraction studies yields detailed information on the lattice structures of highly siliceous zeolites. The two methods are complementary, the former probing short range ordering and structures while the latter is sensitive to long range orderings and periodicities.
Multitechnique Analysis of the Lattice Structures of Highly Siliceous Zeolites
1999-08-26
The combined use of high-resolution solid state NMR techniques (both 1D and 2D) with synchrotron-based powder x-ray diffraction studies yields detailed information on the lattice structures of highly siliceous zeolites. The two methods are complementary, the former probing short range ordering and structures while the latter is sensitive to long range orderings and periodicities.
1996-12-31
This work concerns a parasitic N{sup +}PNN{sup +} transistor appearing in a power MOSFET. 2D Medici simulations point out a close correlation between the static characteristic and the transient values of both the current and the reverse bias of the transistor irradiated by a flash-X ray. The static characteristic points out a steady-state where the transistor behaves as a resistor. If the dose rate is sufficient, it can bring the transistor to the same steady-state. In both cases, this steady-state is reached after the same physical process: conduction of the emitter-base junction, shift of the electric field towards the NN{sup +} junction and highly avalanching conditions in the device. (author).
2009-01-01
Accurate charge density studies by using synchrotron radiation x-rays (SRX) are reviewed with some recent topics in solid state physics. Also are described the analytical details of charge density mapping from the SRX data. They show the high qualities requisite for the accurate analysis. As an example we present the charge density distribution of CoSb3, a promising material for thermoelectric application, determined by the Maximum Entropy Method (MEM), and discuss the bonding nature of inter-atomic charge in terms of the Bader topological analysis. Another topic is the single crystal MEM analysis of H2(a)open-cage-C60 molecule. An H2 molecule is evidently sitting inside the fullerene cage. These experimental results demonstrate the current state of the art of the SRX crystallography is structural materials science. ...
X-ray spectroscopic investigation of optical-field ionized plasmas
1995-01-01
Soft X-ray spectra of N, C, O, S, He, and Ar ions were generated by optical field ionization with fs laser pulses. The experiments were carried out by focusing pulses of a high-power Ti:sapphire laser below a pulsed nozzle, using He, N2, CO2, O2, SF6, and Ar as parent gases. Gain measurements were made by comparing axial and transverse spectra. Gain on lines connecting to the ground state or to a quasi-ground state was not observed. However, strong indications of gain on lines between excited states are reported
Static characteristic and transient behavior of a N+PNN+ transistor irradiated with flash-X ray
1996-01-01
This work concerns a parasitic N+PNN+ transistor appearing in a power MOSFET. 2D Medici simulations point out a close correlation between the static characteristic and the transient values of both the current and the reverse bias of the transistor irradiated by a flash-X ray. The static characteristic points out a steady-state where the transistor behaves as a resistor. If the dose rate is sufficient, it can bring the transistor to the same steady-state. In both cases, this steady-state is reached after the same physical process: conduction of the emitter-base junction, shift of the electric field towards the NN+ junction and highly avalanching conditions in the device. (author)
MAGNETIC INVERSION AS A MECHANISM FOR THE SPECTRAL TRANSITION OF BLACK HOLE BINARIES
2009-01-01
A mechanism for the transition between low/hard, high/soft, and steep power law (SPL) spectral states in black hole X-ray binaries is proposed. The low/hard state is explained by the development of a magnetically arrested accretion disk attributable to the accumulation of a vertical magnetic field in a central bundle. This disk forms powerful jets and consists of thin spiral accretion streams of a dense optically thick plasma surrounded by a hot, magnetized, optically thin corona, which emits most of the energy in hard X-rays. State transition occurs because of the quasi-periodic or random inversion of poloidal magnetic fields in the accretion flow supplied by the secondary star. The inward advection of the inverted field results in a temporal disappearance of the central bundle caused by the annihilation of the opposed fields and restoration of the optically thick disk in the ...
Equation of state of solid neon from x-ray diffraction measurements to 110 GPa
This paper briefly discusses the pressure-volume properties of condensed neon. X-ray diffraction techniques are used to determine solid neon equation of state and crystal structure. 16 refs., 2 figs. (LSP)
Equation of state of solid neon from x-ray diffraction measurements to 110 GPa
1987-01-01
This paper briefly discusses the pressure-volume properties of condensed neon. X-ray diffraction techniques are used to determine solid neon equation of state and crystal structure. 16 refs., 2 figs. (LSP)
A study of core and valence levels in beta-PbO2 by hard X-ray photoemission
2009-01-01
The core and valence levels of beta-PbO2 have been studied using hard X-ray photoemission spectroscopy (hnu = 6000 eV and 7700 eV). The Pb 4f core levels display an asymmetric lineshape which may be fitted with components associated with screened and unscreened final states. It is found that intrinsic final state screening is suppressed in the near-surface region. A shift in the O 1s binding energy due to recoil effects is observed under excitation at 7700 eV. It is shown that conduction band states have substantial 6s character and are selectively enhanced in hard X-ray photoemission spectra. However, the maximum amplitude in the Pb 6s partial density of states is found at the bottom of the valence band and the associated photoemission peak shows the most pronounced enhancement in intensity at high photon energy
2010-01-01
The chemical speciation of phosphorus and sulfur in lake sediment was performed by analyzing Kalpha X-ray spectra recorded with a high-resolution wavelength-dispersive particle-induced X-ray emission (WD-PIXE) system. The concentrations of phosphorus and sulfur in the sediment were 2500 and 7000 ppm, respectively. To measure both minor elements in a reasonable measurement time, a 2-MeV proton beam with a high current density (6 nA/mm2) was used for the chemical speciation. The possible chemical state change caused by the proton irradiation was studied in order to determine the maximal irradiation time without significant change. We found that the chemical states of phosphorus and sulfur were stable under a beam current density of 6 nA/mm2 and a measurement time of 60 min (phosphorus) and 90 min (sulfur). The chemical states of ...
X-Ray Insights Into the Physics of Mini-BAL Quasar Outflows
2009-02-06
We examine the UV and X-ray properties of 256 radio-quiet SDSS quasars (QSOs) observed in X-rays with Chandra and/or XMM-Newton in order to study the relationship between QSOs with broad CIV absorption lines (BALs; width >2000 km/s) and those with CIV mini-BALs (here defined to have widths of 1000--2000 km/s). Our sample includes 42 BAL and 48 mini-BAL QSOs. The relative X-ray brightness and hard spectral slopes of the mini-BAL population are, on average, intermediate between those of BAL and non-BAL QSOs, as might be expected if narrower and broader absorption line outflows are physically related. However, a significant population of mini-BALs has outflow velocities higher than would be expected for BAL QSOs of the same relative X-ray brightness. Consistenly strong X-ray absorption is apparently not required to accelerate at least some mini-BALs to high outflow velocities. Assuming the mini-BAL features are correctly attributed to intrinsic CIV absorption, we suggest that their observed properties may be explained if mini-BALs are "seeds" which can be accelerated to form BALs when sufficient X-ray shielding is present. We also examine several QSOs with broad CIV absorption that have been recently reported to be unusually X-ray bright. Such cases are frequently mini-BAL QSOs, which as a population are generally brighter in X-rays than BAL QSOs. Pointed XMM-Newton observations also suggest that these sources (or unresolved neigh bors) may have been previously observed in a high flux state.
1997-04-01
High-resolution x-ray microscopy is a relatively new technique and is performed mostly at a few large synchrotron x-ray sources that use exposure times of seconds. We utilized a bench-top source of...Full Text Available
The Dynamic X-ray Sky of the Local Universe
of the underlying neutron star, and constrains the enormous magnetic ... What powers the fast flares seen for a small fraction of high-mass X-ray .... The Energetic X-ray Imaging Survey Telescope (EXIST)1 is an AMCS X-ray imaging all- ...
Applications of soft x-ray lasers
The high brightness and short pulse duration of soft x-ray lasers provide unique advantages for novel applications. Imaging of biological specimens using x-ray lasers has been demonstrated by several groups. Other applications to fields such as chemistry, material science, plasma diagnostics, and lithography are beginning to emerge. We review the current status of soft x-ray lasers from the perspective of applications, and present an overview of the applications currently being developed.
Applications of soft x-ray lasers
1993-08-01
The high brightness and short pulse duration of soft x-ray lasers provide unique advantages for novel applications. Imaging of biological specimens using x-ray lasers has been demonstrated by several groups. Other applications to fields such as chemistry, material science, plasma diagnostics, and lithography are beginning to emerge. We review the current status of soft x-ray lasers from the perspective of applications, and present an overview of the applications currently being developed.
High-pressure X-ray diffraction and Raman scattering of LiTaO sub 3
The authors study the energy-dispersive x-ray diffraction and Raman scattering of LiTaO sub 3 at high pressure. The result remains stable up to 36 GPa. The average isothermal bulk modulus and its pressure derivative are obtained to be k sub 0 =(225 +- 6) GPa and k sub 0 '=1.3 +- 0.5 at zero pressure by the Birch-Murnaghan equation of state and the 'universal' equation of state. The linear incompressibility of LiTaO sub 3 between the a- and c-directions differs by a factor of four, which shows that the compression is anisotropic
2009-01-01
Highly crystallized alpha'-NaV2O5 needles were prepared by a simple hydrothermal process. X-ray diffraction showed that the material had an orthorhombic structure. Scanning electron microscopy and high-resolution transmission electron microscopy confirmed that the alpha'-NaV2O5 needles were fabricated along the axis. The local structure of the material was studied by Raman scattering. X-ray photoelectron spectroscopy confirmed that the oxidation state of vanadium of the material was +4.5. The formation mechanism of alpha'-NaV2O5 crystals depended on the hydrothermal conditions. Highly crystallized alpha'-NaV2O5 needles could be obtained with the presence of F-, while ...
Synchrotron radiation techniques for the characterization of $Nb_{3}Sn$ superconductors
The high flux of high energy x-rays that can be provided through state-of-the-art high energy synchrotron beam lines has enabled a variety of new experiments with the highly absorbing Nb3Sn superconductors. We report different experiments with Nb3Sn strands that have been conducted at the ID15 High Energy Scattering beam line of the European Synchrotron Radiation Facility (ESRF). Synchrotron x-ray diffraction has been used in order to monitor phase transformations during in-situ reaction heat treatments prior to Nb3Sn formation, and to monitor Nb3Sn growth. Fast synchrotron micro-tomography was applied to study void growth during the reaction heat treatment of Internal Tin strands. The elastic strain in the different phases of fully reacted Nb3Sn composite conductors can be measured by high resolution x-ray diffraction during in-situ tensile tests.
Synchrotron radiation techniques for the characterization of $Nb_{3}Sn$ superconductors
The high flux of high energy x-rays that can be provided through state-of-the-art high energy synchrotron beam lines has enabled a variety of new experiments with the highly absorbing Nb3Sn superconductors. We report different experiments with Nb3Sn strands that have been conducted at the ID15 High Energy Scattering beam line of the European Synchrotron Radiation Facility (ESRF). Synchrotron x-ray diffraction has been used in order to monitor phase transformations during in-situ reaction heat treatments prior to Nb3Sn formation, and to monitor Nb3Sn growth. Fast synchrotron micro-tomography was applied to study void growth during the reaction heat treatment of Internal Tin strands. The elastic strain in the different phases of fully reacted Nb3Sn composite conductors can be measured by high resolution x-ray diffraction during in-situ tensile tests.
Iron line and diffuse hard X-ray emission from the starburst galaxy M82
2006-11-28
We examine the properties of the diffuse hard X-ray emission in the classic starburst galaxy M82. We use new Chandra ACIS-S observations in combination with reprocessed archival Chandra ACIS-I and XMM-Newton observations. We find E~6.7 keV Fe He-alpha emission is present in the central |r| < 200 pc, |z| < 100 pc of M82 in all datasets at high statistical significance, in addition to a possibly non-thermal X-ray continuum and marginally significant E=6.4 keV Fe K-alpha line emission. No statistically significant Fe emission is found in the summed X-ray spectra of the point-like X-ray sources or the ULX in the two epochs of Chandra observation. The total nuclear region iron line fluxes in the 2004 April 21 XMM-Newton observation are consistent with those of the Chandra-derived diffuse component, but in the 2001 May 6 XMM-Newton observation they are significantly higher and also both E=6.4 and E=6.9 keV iron lines are detected. We attribute the excess iron line emission to the Ultra-Luminous X-ray source in its high state. In general the iron K-shell luminosity of M82 is dominated by the diffuse component. The total X-ray luminosity of the diffuse hard X-ray emission (corrected for emission by unresolved low luminosity compact objects) is L_X ~ 4.4 x 10^39 erg/s in the E=2-8 keV energy band, and the 6.7 keV iron line luminosity is L_X ~ (1.1 -- 1.7) x 10^38 erg/s. The 6.7 keV iron line luminosity is consistent with that expected from the previously unobserved metal-enriched merged supernova ejecta that is thought to drive the larger-scale galactic superwind. The iron line luminosity implies a thermal pressure within the starburst region of P/k ~ 2 x 10^7 K/cm^3, which is consistent with independent observational estimates of the starburst region pressure [Abstract abridged].
High-Resolution Structure of the Photosynthetic Mn4Ca Catalyst from X-ray Spectroscopy
2007-08-01
The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn4Ca cluster, are described. Issues of X-ray damage especially at the metal sites in the Mn4Ca cluster are discussed. The structure of the Mn4Ca catalyst at high-resolution which has so far eluded attempts of determination by X-ray diffraction, EXAFS and other spectroscopic techniques has been addressed using polarized EXAFS techniques applied to oriented PS II membrane preparations and PS II single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and K? emission) have been used earlier to determine the oxidation states of the Mn4Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn4Ca cluster as it cycles through the intermediate S-states.
High-Resolution Structure of the Photosynthetic Mn4Ca Catalyst from X-ray Spectroscopy
The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn4Ca cluster, are described. Issues of X-ray damage especially at the metal sites in the Mn4Ca cluster are discussed. The structure of the Mn4Ca catalyst at high-resolution which has so far eluded attempts of determination by X-ray diffraction, EXAFS and other spectroscopic techniques has been addressed using polarized EXAFS techniques applied to oriented PS II membrane preparations and PS II single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and K? emission) have been used earlier to determine the oxidation states of the Mn4Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn4Ca cluster as it cycles through the intermediate S-states.
Outburst Morphology in the Soft X-ray Transient Aquila X-1
2008-07-23
We present optical and near-IR (OIR) observations of the major outbursts of the neutron star soft X-ray transient binary system Aquila X-1, from summer 1998 -- fall 2007. The major outbursts of the source over the observed timespan seem to exhibit two main types of light curve morphologies, (a) the classical Fast-Rise and Exponential-Decay (FRED) type outburst seen in many soft X-ray transients and (b) the Low-Intensity State (LIS) where the optical-to-soft-X-ray flux ratio is much higher than that seen during a FRED. Thus there is no single correlation between the optical (R-band) and soft X-ray (1.5-12 keV, as seen by the ASM onboard RXTE) fluxes even within the hard state for Aquila X-1, suggesting that LISs and FREDs have fundamentally different accretion flow properties. Time evolution of the OIR fluxes during the major LIS and FRED outbursts is compatible with thermal heating of the irradiated outer accretion disk. No signature of X-ray spectral state changes or any compact jet are seen in the OIR, showing that the OIR color-magnitude diagram (CMD) can be used as a diagnostic tool to separate thermal and non-thermal radiation from X-ray binaries where orbital and physical parameters of the system are reasonably well known. We suggest that the LIS may be caused by truncation of the inner disk in a relatively high mass accretion state, possibly due to matter being diverted into a weak outflow.
Transient molecular structures along chemical reaction pathways are important for predicting molecular reactivity, understanding reaction mechanisms, as well as controlling reaction pathways. During the past decade, X-ray transient absorption spectroscopy (XTA, or LITR-XAS, laser-initiated X-ray absorption spectroscopy), analogous to the commonly used optical transient absorption spectroscopy, has been developed. XTA uses a laser pulse to trigger a fundamental chemical process, and an X-ray pulse(s) to probe transient structures as a function of the time delay between the pump and probe pulses. Using X-ray pulses with high photon flux from synchrotron sources, transient electronic and molecular structures of metal complexes have been studied in disordered media from homogeneous solutions to heterogeneous solution-solid interfaces. Several examples from the studies at the Advanced Photon Source in Argonne National Laboratory are summarized, including excited-state metalloporphyrins, metal-to-ligand charge transfer (MLCT) states of transition metal complexes, and charge transfer states of metal complexes at the interface with semiconductor nanoparticles. Recent developments of the method are briefly described followed by a future prospective of XTA. It is envisioned that concurrent developments in X-ray free-electron lasers and synchrotron X-ray facilities as well as other table-top laser-driven femtosecond X-ray sources will make many breakthroughs and realise dreams of visualizing molecular movies and snapshots, which ultimately enable chemical reaction pathways to be controlled.
Accretion Disk Spectra of the Brightest Ultra-luminous X-ray Source in M82
2006-11-30
Emission spectra of hot accretion disks characteristic of advection dominated accretion flow (ADAF) models are investigated for comparison with the brightest ultra-luminous source, X-1, in the galaxy M82. If the spectral state of the source is similar to the low luminosity hard state of stellar mass black holes in our Galaxy, a fit to the {\\it Chandra} X-ray spectrum and constraints from the radio and infrared upper limits, require a black hole mass in the range of $9 \\times 10^4 - 5 \\times 10^5 \\msun$. Lower black hole masses ($\\la 10^4 \\msun$) are possible if M82 X-1 corresponds to the high luminosity hard state of Galactic black hole X-ray binary sources. Both of these spectrally degenerate hot accretion disk solutions lead to an intermediate mass black hole interpretation for M82 X-1. Since these solutions have different spectral variability with X-ray luminosity and predict different infrared emission, they can be distinguished by future off axis {\\it Chandra} observations or simultaneous sensitive infrared detections.
X-ray study on stellar/intermediate mass black holes
2007-01-01
Based on early Suzaku observations, properties of stellar-mass black-hole binaries (BHBs) and ultra-luminous compact X-ray sources (ULXs) are discussed. A comparison between GRO 1655-40 and Cygnus X-1, both observed in the Low/Hard state, gives new constraints on the characteristics of hot Compton cloud that are considered to be responsible for the formation of the Low/Hard state continua. Hard X-rays, with energies above 10 keV, were detected for the first time from a ULX, namely M82 X-1. Including this case, ULXs showing power-law like spectra are considered to host Comptonized accretion disks, in analogy to BHBs in the Very High state. In contrast, ULXs exhibiting multicolor-disk type spectra are interpreted to harbor 'slim' disks. This sort of analogy between ULXs and BHBs suggests that black holes in ULXs are significantly more massive than those in BHBs. (author)
IDENTIFICATION OF THE X-RAY THERMAL DOMINANT STATE IN AN ULTRALUMINOUS X-RAY SOURCE IN M82
2010-01-01
The thermal dominant state in black hole binaries (BHBs) is well understood but rarely seen in ultraluminous X-ray sources (ULXs). Using simultaneous observations of M82 with Chandra and XMM-Newton, we report the first likely identification of the thermal dominant state in a ULX based on the disappearance of X-ray oscillations, low timing noise, and a spectrum dominated by multicolor disk emission with luminosity varying to the fourth power of the disk temperature. This indicates that ULXs are similar to Galactic BHBs. The brightest X-ray spectrum can be fitted with a relativistic disk model with either a highly super-Eddington (L disk/L Edd = 160) non-rotating black hole (BH) or a close to Eddington (L disk/L Edd approx 2) rapidly rotating BH. The latter interpretation is preferred, due to the absence of such ...
Generation of high brightness x-ray and its medical applications (5th report)
2005-01-01
The double-stream gas-puff target driven by a nano-second laser pulse provides a good X-ray source in the water window spectral range. We measured the X-ray spectra in order to evaluate the performance as a laser produced plasma X-ray source for an X-ray microscope. The intensity of X-ray generation by using the double nozzle gas-puff target was as strong as that by using solid target. A laser produced plasma X-ray source using double-stream gas-puff target and a commercial Nd:YAG laser may be a efficient debris free X-ray source to be applied in a compact X-ray source to be applied in a compact X-ray microscopy. (author)
Radiative Spectra from Disk Corona and Inner Hot Flow in Black Hole X-ray Binaries
2010-03-09
To understand the origin of hard X-ray emissions from black hole X-ray binaries during their low/hard states, we calculate the X-ray spectra of black-hole accretion flow for the following three configurations of hot and cool media: (a) an inner hot flow and a cool outer disk (inner hot flow model), (b) a cool disk sandwiched by disk coronae (disk corona model), and (c) the combination of those two (hybrid model). The basic features we require for successful models are (i) significant hard X-ray emission whose luminosity exceeds that of soft X-rays, (ii) high hard X-ray luminosities in the range of (0.4 - 30) times 10^{37} erg s^{-1}, and (iii) the existence of two power-law components in the hard X-ray band with the photon indices of Gamma_s ~ 2 > Gamma_h, where Gamma_s and Gamma_h are the photon indices of the softer (10 keV) power-law components, respectively. Contribution by non-thermal electrons nor time-dependent evolution are not considered. We find that Models (a) and (b) can be ruled out, since the spectra are always dominated by the soft component, and since only one power-law component, at most, can be reproduced. Only Model (c) can account for sufficiently strong hard X-ray emissions, as well as the existence of the two power-law components, for a large ratio of the accretion rate in the corona to that in the thin disk. The outer disk corona (where the Compton y-parameter is smaller, y < 1) produces the softer power-law component with photon index of Gamma_s ~ 2, whereas the inner hot flow (where y gtrsim 1) generates the harder component with Gamma_h < 2. This model can also account for the observed relationship between the photon index and the reflection fraction.
The High-Energy Spectra of Accreting Black Holes$$bObservational Evidence for Bulk-Motion Infall
1998-03-30
We discuss the emergent spectra from accreting black holes, considering in particular the case where the accretion is characterized by relativistic bulk motion. We suggest that such accretion is likely to occur in a wide variety of black hole enviroments, where the strong gravitational field is expected to dominate the pressure forces, and this likely to lead to a characteristic high-energy spectriscopic signature; an extended power tail. It is in the high (soft) state that matter impinging upon the event horizon can be viewed directly, and intrinsic power-law seen. A test of the model is presented using observational data from the Compton Gamma Ray Observatory and the Rossi X-ray Timing Explorer, covering 2- 200 keV for recent galactic black hole X-ray nova outbursts.
Robust, high-throughput solution structural analyses by small angle X-ray scattering (SAXS)
2009-07-20
We present an efficient pipeline enabling high-throughput analysis of protein structure in solution with small angle X-ray scattering (SAXS). Our SAXS pipeline combines automated sample handling of microliter volumes, temperature and anaerobic control, rapid data collection and data analysis, and couples structural analysis with automated archiving. We subjected 50 representative proteins, mostly from Pyrococcus furiosus, to this pipeline and found that 30 were multimeric structures in solution. SAXS analysis allowed us to distinguish aggregated and unfolded proteins, define global structural parameters and oligomeric states for most samples, identify shapes and similar structures for 25 unknown structures, and determine envelopes for 41 proteins. We believe that high-throughput SAXS is an enabling technology that may change the way that structural genomics research is done.
High resolution x-ray crystal spectrographs
1977-10-21
Observation of x-ray line emissions are valuable for determining the thermodynamic state of the emitting plasma. For laser produced plasmas, diffraction crystals can be used to isolate x-ray monochromes to obtain high resolution spectral measurements. We will describe a versatile multi-crystal high resolution spectrograph used for photon energies from 0.5 to 6 keV. We will discuss a calculational package that tunes the response and sensitivity of the instrument and estimates the effect of source extent on spectral resolution. A scheme using fine slits to obtain spatial resolution with the basic instrument will also be described. An instrument is being built for Shiva diagnostics that incorporates a diffraction crystal and an x-ray streak camera. The design rationale for the crystal stage will be discussed.
L-edge X-ray absorption spectroscopy of pyrococcus furiosus rubredoxin
1992-05-20
In this communication the authors present new experiments and theoretical simulations, using iron L-edge X-ray absorption spectroscopy, to study the metalloprotein Pyrococcus furiosus rubredoxin. the 3d transition metal L-edges are found between 400 and 1100 eV, in the soft X-ray region. Synchrotron radiation beam lines producing the high photon flux and high-energy resolution necessary to observe and resolve 3d transition metal L-edge spectra have only become available in the last few years. L-edge spectra are interesting not only because of the 3-4-fold-higher energy resolution (vs K-edges) but also for the sensitivity to spin state, oxidation state, and ligand field offered by p{r_arrow}d transitions. In addition, the X-ray magnetic circular dichroism (XMCD) of transition metal L-edges is predicted to be strong, and experiments have confirmed these predictions. 21 refs., 1 fig.
Time-resolved spectroscopy of solid-state materials using an x-ray laser (Thesis)
2008-01-01
X-ray laser is a characteristic extreme ultraviolet (EUV) source with short pulse duration of several pico-seconds, narrow spectral width, and high coherence. In particular, x-ray laser with the wavelength of around 13 nm is expected as a powerful tool of various research fields such as EUV lithography because the multilayer mirror with high reflectance is commercially prepared. However, spectroscopic studies of materials optically excited with x-ray laser are few while imaging and interference measurements are intensively studied. In this study, the beam divergence and spatial coherence of x-ray laser was improved and applied to the measurement of time resolved emission spectroscopy of a solid-state material. The beam divergence of the x-ray laser was improved by double target configuration using two gain media. The nickel-like silver x-ray laser at the wavelength of ...
A compact Compton backscatter X-ray source for mammography and coronary angiography
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project objective is to generate a large flux of tunable, monochromatic x-rays for use in mammography and coronary angiography. The approach is based on Compton backscattering of an ultraviolet solid-state laser beam against the high-brightness 20-MeV electron beams from a compact linear accelerator. The direct Compton backscatter approach failed to produce a large flux of x-rays due to the low photon flux of the scattering solid-state laser. The authors have modified the design of a compact x-ray source to the new Compton backscattering geometry with use of a regenerative amplifier free-electron laser. They have successfully demonstrated the production of a large flux of infrared photons and a high-brightness electron beam focused in both dimensions for performing Compton backscattering in a regenerative amplifier geometry.
A summary of research work performed from 11/1/86 to 4/10/93 is presented. Synchrotron x rays were used to probe the short-range-order (SRO) structures in these materials, especially layered semiconductors and high-{Tc} oxide superconductors. X-ray absorption fine structure spectroscopy, grazing incidence x-ray scattering and fluorescence, and total electron yield as probe for surfaces and interfaces were used. A new soft x-ray detector was developed.
1993-09-01
A summary of research work performed from 11/1/86 to 4/10/93 is presented. Synchrotron x rays were used to probe the short-range-order (SRO) structures in these materials, especially layered semiconductors and high-{Tc} oxide superconductors. X-ray absorption fine structure spectroscopy, grazing incidence x-ray scattering and fluorescence, and total electron yield as probe for surfaces and interfaces were used. A new soft x-ray detector was developed.
Development of quantitative x-ray microtomography
1990-01-01
The authors have developed several x-ray microtomography systems which function as quantitative three dimensional x-ray microscopes. In this paper the authors describe the evolutionary path followed from making the first high resolution experimental microscopes to later generations which can be routinely used for investigating materials. Developing the instrumentation for reliable quantitative x-ray microscopy using synchrotron and laboratory based x-ray sources has led to other imaging modalities for obtaining temporal and spatial two dimensional information
Anisotropic inverse Compton emission
1991-01-01
Inverse Compton scattering of soft X-ray photons by electrons is the most likely mechanism for the generation of the hard X-ray spectrum in compact objects. Recent observations of the X-ray spectra of active galactic nuclei and galactic black-hole candidates suggest that the hard X-ray emission originates above and below a soft X-ray emitting disc. The radiation field within the hard X-ray emitting region will therefore be highly anisotropic. Here we consider the angular distribution of the power and spectrum of Compton-scattered radiation in the case of an anisotropic distribution of soft photons. (author).
XAFS at the Canadian Light Source
2007-01-01
Canadian Light Source Hard X-ray Micro-Analysis Beamline (HXMA, 06ID-1) is a hard X-ray spectroscopy beamline currently under commissioning. The source of the beamline is a superconducting wiggler covering 5 to 40 keV. The primary optics include a cryogenically cooled double crystal monochromator (Si 111 and 220), white beam vertical collimating and toroidal focusing mirrors. End station experimental capabilities include XAFS (Ge solid state detectors), microprobe (Kirkpatrick-Baez murors, Ge solid state detector and image plate area detector), and diffraction (Huber psi-8 and powder diffraction setups, with diamond anvil cell high pressure sample environment). Commissioning status for the XAFS capabilities is described
X-ray structural study of poly(ethylene terephthalate) after solid-state postpolycondensation
2007-01-01
The structure of PET samples exposed to multistep annealing below the melting temperature T m in high vacuum (the so-called solid-state postpolycondensation) has been studied by wide-angle X-ray diffraction. The sizes of crystallites have been calculated through the analysis of half-widths of corresponding reflections via the Rietveld, Scherrer, and Hosemann methods. As the molecular mass (M ) of PET is increased from 4.5 104 to 3 105, the sizes of crystallites increase in three crystallographic directions (100, 010, and 001). An increase in the thickness of the crystal core of a lamella (the fold length in direction Formula Not Shown 05) Formula Not Shown from 40 to 58 (the Rietveld method) in the molecular mass range under study is accompanied by a rise in T m by 19C. The ro...
Study of X-ray photoionized Fe plasma and comparisons with astrophysical modeling codes
2005-04-29
The charge state distributions of Fe, Na and F are determined in a photoionized laboratory plasma using high resolution x-ray spectroscopy. Independent measurements of the density and radiation flux indicate the ionization parameter {zeta} in the plasma reaches values {zeta} = 20-25 erg cm s{sup -1} under near steady-state conditions. A curve-of-growth analysis, which includes the effects of velocity gradients in a one-dimensional expanding plasma, fits the observed line opacities. Absorption lines are tabulated in the wavelength region 8-17 {angstrom}. Initial comparisons with a number of astrophysical x-ray photoionization models show reasonable agreement.
Structure and properties of biaxial-oriented crystalline polymers by solid-state crossrolling
2010-01-01
The effect of biaxial orientation by solid-state crossrolling on the morphology of crystalline polymers including polypropylene (PP), high density polyethylene (HDPE) and Nylon 6/6 was investigated with polarized optical microscopy, atomic force microscopy, wide-angle X-ray scattering, and small-angle X-ray scattering techniques. It was found that crossrolling gradually changed the initial spherulitic structure into a biaxially oriented crystal texture with chain axis of crystals becoming parallel to the rolling direction for all three polymers. The effect of microstructure change on the macromechanical properties was studied in tension at both ambient temperature and -40degreeC. In tension at room temperature, the localized necking deformation of HDPE and PP control changed upon orientati...
2009-05-24
We report measurements of the photo-induced Fe(II) spin crossover reaction dynamics in solution via time-resolved x-ray absorption spectroscopy. EXAFS measurements reveal that the iron?nitrogen bond lengthens by 0.21+-0.03 Angstrom in the high-spin transient excited state relative to the ground state. XANES measurements at the Fe L-edge show directly the influence of the structural change on the ligand-field splitting of the Fe(II) 3d orbitals associated with the spin transition.
2010-01-01
Background: CUR is a promising drug candidate based on its good bioactivity, but use of CUR is potentially restricted because of its poor solubility and bioavailability. Aim: The aim of this study was to prepare an aqueous formulation of curcumin nanosuspension (CUR-NS) to improve its solubility and change its in vivo behavior. Methods: CUR-NS was prepared by high-pressure homogenization method. Drug state in CUR-NS was evaluated by powder X-ray diffraction. Pharmacokinetics and biodistribution of CUR-NS after intravenous administration in rabbits and mice were studied. Results: The solubility and dissolution of CUR in the form of CUR-NS were significantly higher than those of crude CUR. X-ray crystallography diffraction indicated that the crystalline state of CUR in nanosuspension was pre...
On the chemical state and distribution of Zr- and V-based additives in reactive hydride composites
2009-01-01
Reactive hydride composites (RHCs) are very promising hydrogen storage materials for future applications due to their reduced reaction enthalpies and high gravimetric capacities. At present, the materials' functionality is limited by the reaction kinetics. A significant positive influence can be observed with addition of transition-metal-based additives. To understand the effect of these additives, the chemical state and changes during the reaction as well as the microstructural distribution were investigated using x-ray absorption near-edge structure (XANES) spectroscopy and anomalous small-angle x-ray scattering (ASAXS). In this work, zirconium- and vanadium-based additives were added to 2LiBH4-MgH2 composites and 2LiH-MgB2 composites and measured in the vicinity of the corresponding absorption edge. The ...
In-line characterization of polypropylene nanocomposites using FT-NIR
2010-01-01
The morphology of polymer nanocomposites is usually characterized by various methods like X-ray diffraction (XRD) or transmission electron microscopy (TEM). In this work, a new approach for characterizing nanocomposites is developed: the results of small angle x-ray scattering, on-line extensional rheometry (level of melt strength) and Youngs modulus out of tensile test are correlated with those of near infrared (NIR) spectroscopy. The disadvantages of the common characterization methods are high costs and very time consuming sample preparation and testing. In contrast, NIR spectroscopy has the advantage to be measured in-line and in real time directly in the melt. The results were obtained for different aggregate states (NIR spectroscopy and on-line rheotens test in melt state, tensile te...
2005-06-15
This paper uses X-ray absorption spectroscopy and vacuum ultra-violet spectroscopic ellipsometry to study the electronic structure of high-k transition metal (TM) oxide gate dielectrics. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d{sup *} states, which define the optical band gap, including their relationship to the band gap, E {sub g}, of the oxide.
X-ray spectral variability in PG1535+547: the changing-look of a 'soft X-ray weak' AGN
2008-02-21
PG1535+547 is a bright NLS1 galaxy, whose high energy emission shows strong variability in shape and flux. ROSAT data classified it as soft X-ray weak QSO (objects whose X-ray-to-optical flux ratio is smaller than in typical QSO): their X-ray spectra are often characterized by highly ionized, complex absorbers and/or reflection from the disk, whose relative importance is currently debated. In both cases, the presence of such features implies that we are looking at matter located in the innermost regions of the AGN. In this paper we want to clarify the nature of the X-ray emission of PG1535+547, and constrain the physical properties of regions where the emission originates. We present new XMM observations, from which we obtained 2 spectra separated by about 1 week, that we compare with a previous XMM observation. The data support the complex and variable nature of the X-ray emission. The broad band flux increases by a factor ~2.3 in 3 years, and then decreases by a factor ~1.3 in about 1 week. In the new EPIC spectra strong absorption features at E<3keV and a complex spectral shape in the Fe line energy range are evident, coupled with a drop in the emission at higher energies. We describe all the states assuming either a warm absorber plus a relativistically blurred ionized reflection, or a two-phase warm absorber partially covering the source plus a scattered component. The variability is ascribed to the warm absorbers, that va ry their physical properties on timescales of years and days. In the reflection scenario all the states require a high fraction of reflection. The strong variability in the X-ray band opposed to a more constant optical emission implies that PG1535+547 can not actually be classified as a soft X-ray weak AGN.
A characterization of the NGC 4051 soft X-ray spectrum as observed by XMM-Newton
2010-03-08
Soft X-rays high resolution spectroscopy of obscured AGNs shows the existence of a complex soft $X$-ray spectrum dominated by emission lines of He and H-like transitions of elements from Carbon to Neon, as well as L-shell transitions due to iron ions. In this paper we characterize the XMM-Newton RGS spectrum of the Seyfert 1 galaxy NGC 4051 observed during a low flux state and infer the physical properties of the emitting and absorbing gas in the soft X-ray regime. X-ray high-resolution spectroscopy offers a powerful diagnostic tool since the observed spectral features strongly depend on the physical properties of matter (ionization parameter U, electron density n_e, hydrogen column density N_H), which in turn are tightly related to the location and size of the X-ray emitting clouds. We carried out a phenomenological study to identify the atomic transitions detected in the spectra. This study suggests that the spectrum is dominated by emission from a photoionised plasma. Then, we used the photoionization code Cloudy to produce synthetic models for the emission line component and the warm absorber observed during phases of high intrinsic luminosity. The low state spectrum cannot be described by a single photoionization component. A multi-ionization phase gas with ionization parameter in the range log U = 0.63-1.90 and column density log N_H = 22.10-22.72 cm^-2 is required, while the electron density n_e remains unconstrained. A warm absorber medium is required by the fit with parameters log U = 0.85, log N_H = 23.40 and log n_e \\ut 5 x 10^-2 pc from the central engine.
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