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The upgrade of the Advanced Photon Source (APS) to a Multi-Bend Achromat (MBA) will increase the brightness of the APS by between two and three orders of magnitude. The APS upgrade (APS-U) project includes a list of feature beamlines that will take full advantage of the new machine. Many of the existing beamlines will be also upgraded to profit from this significant machine enhancement. Optics simulations are essential in the design and optimization of these new and existing beamlines. In this contribution, the simulation tools used and developed at APS, ranging from analytical to numerical methods, are summarized. Three general optical layouts are compared in terms of their coherence control and focusing capabilities. The concept of zoom optics, where two sets of focusing elements (e.g., CRLs and KB mirrors) are used to provide variable beam sizes at a fixed focal plane, is optimized analytically. The effects of figure errors on the vertical spot size and on the local coherence along the vertical direction of the optimized design are investigated.

Stabilization of biological materials by freezing is widespread in the fields of medicine and biomaterials research and yet, in the case of hard biomaterials such as dentin, there is not a good understanding of how such treatments might affect the mechanical properties. The freezing and thawing may have a number of different effects on dentin including formation of cracks in the microstructure and denaturation of the collagen. Using high-energy synchrotron X-ray diffraction, the apparent moduli of bovine dentin samples were measured before and after various numbers of freeze–thaw cycles. It was determined that repeated freezing and thawing has no measurable effect on the hydroxyapatite or fibrillar apparent moduli up to 10 cycles. This confirms that the use of low temperature storage for stabilization of dentin is reasonable in cases where stiffness is a property of importance.

In situ X-ray diffraction and small angle scattering measurements during tensile tests were performed on 9-12% Cr ferritic/martensitic steels. The lattice strains in both particle and matrix phases, along two principal directions, were directly measured. The load transfer between particle and matrix was calculated based on matrix/particle elastic mismatch, matrix plasticity and interface decohesion. In addition, the void or damage evolution during the test was measured using small angle X-ray scattering. By combining stress and void evolution during deformation, the critical interfacial strength for void nucleation was determined, and compared with pre-existing void nucleation criteria. These comparisons show that models overestimate the measured critical strength, and require a larger particle size than measured to match the X-ray observations.

Bone, because of its hierarchical composite structure, exhibits an excellent combination of stiffness and toughness, which is due substantially to the structural order and deformation at the smaller length scales. Here, we focus on the mineralized collagen fibril, consisting of hydroxyapatite plates with nanometric dimensions aligned within a protein matrix, and emphasize the relationship between the structure and elastic properties of a mineralized collagen fibril. We create two- and three-dimensional representative volume elements to represent the structure of the fibril and evaluate the importance of the parameters defining its structure and properties of the constituent mineral and collagen phase. Elastic stiffnesses are calculated by the finite element method and compared with experimental data obtained by synchrotron X-ray diffraction. The computational results match the experimental data well, and provide insight into the role of the phases and morphology on the elastic deformation characteristics. Also, the effects of water, imperfections in the mineral phase and mineral content outside the mineralized collagen fibril upon its elastic properties are discussed.

Three bronze vessels from the ancient Chinese art collection at the Art Institute of Chicago (AIC) were examined—with the advanced non-invasive characterization capabilities of high-energy synchrotron X-ray diffraction performed at the Advanced Photon Source (APS) of Argonne National Laboratory (ANL)—to create a comprehensive overview of each object’s manufacture as well as subsequent corrosion processes. Findings were also complemented with traditional non-invasive characterization techniques, including optical imaging, X-ray radiographic imaging, and X-ray fluorescence (XRF) spectrometry. The results—obtained without sampling—allow a clear distinction between genuinely ancient Chinese bronzes from those with modern restorations and from “archaistic” objects made many centuries later, in emulation of ancient styles.

Radiation-induced defect structures are known to elevate material yield strength and reduce material ductility so that small strains induce plastic instability. This process is commonly known as flow localization . Recent research indicates that the flow localization in face-centered cubic (FCC) materials is controlled by critical stress , the true stress at the onset of necking. Critical stress is found to be independent of irradiation dose, but have strong temperature dependence. Here simplified 9–12% ferritic/martinsetic steels are examined using X-ray diffraction and small angle scattering under in situ tensile deformation, in order to elucidate the controlling mechanisms and temperature dependence of critical stress. It is found that the critical stress for the onset of necking is linearly correlated with critical interfacial strength, which in turn determines the void nucleation. The effects of temperature and particle size on critical stress are correspondingly determined by how temperature and particle size influence the critical interfacial strength.

Interpenetrating Al 2 O 3 /Al composites were created by liquid-metal infiltration of 3D periodic ceramic preforms with face-centered-tetragonal symmetry produced by direct-write assembly. Volume-averaged lattice strains in the ceramic phase of the composite were measured by synchrotron X-ray diffraction for various levels of uniaxial compression stresses. Load transfer is found to occur from the metal phase to the ceramic phase, and the magnitude of the effect is in general agreement with simple rule-of-mixtures models. Spatially resolved diffraction measurements show variations in load transfer at two different positions within the composite for the elastic- and damage-deformation regimes, the latter being observed using phase-enhanced synchrotron imaging. The mechanical behavior of these interpenetrating Al 2 O 3 /Al composites with face-centered-tetragonal symmetry are compared with previous interpenetrating Al 2 O 3 /Al composites with simple-tetragonal symmetry.

Interpenetrating composites are created by infiltration of liquid aluminum into three-dimensional (3-D) periodic Al2O3 preforms with simple tetragonal symmetry produced by direct-write assembly. Volume-averaged lattice strains in the Al2O3 phase of the composite are measured by synchrotron X-ray diffraction for various uniaxial compression stresses up to � 350 MPa. Load transfer, found by diffraction to occur from the metal phase to the ceramic phase, is in general agreement with simple rule-of-mixture models and in better agreement with more complex, 3-D finite-element models that account for metal plasticity and details of the geometry of both phases. Spatially resolved diffraction measurements show variations in load transfer at two different positions within the composite.

A GE Revolution 41RT flat-panel detector (GE 41RT) from GE Healthcare (GE) has been in operation at the Advanced Photon Source for over two years. The detector has an active area of 41 cm x 41 cm with 200 microm x 200 microm pixel size. The nominal working photon energy is around 80 keV. The physical set-up and utility software of the detector system are discussed in this article. The linearity of the detector response was measured at 80.7 keV. The memory effect of the detector element, called lag, was also measured at different exposure times and gain settings. The modulation transfer function was measured in terms of the line-spread function using a 25 microm x 1 cm tungsten slit. The background (dark) signal, the signal that the detector will carry without exposure to X-rays, was measured at three different gain settings and with exposure times of 1 ms to 15 s. The radial geometric flatness of the sensor panel was measured using the diffraction pattern from a CeO(2) powder standard. The large active area and fast data-capturing rate, i.e. 8 frames s(-1) in radiography mode, 30 frames s(-1) in fluoroscopy mode, make the GE 41RT one of a kind and very versatile in synchrotron diffraction. The loading behavior of a Cu/Nb multilayer material is used to demonstrate the use of the detector in a strain-stress experiment. Data from the measurement of various samples, amorphous SiO(2) in particular, are presented to show the detector effectiveness in pair distribution function measurements.

An ultrahigh-carbon steel was heat-treated to form an in situ composite consisting of a fine-grained ferritic matrix with 34 vol.% submicron spheroidized cementite particles. Volume-averaged lattice elastic strains for various crystallographic planes of the α-Fe and Fe3C phases were measured by synchrotron X-ray diffraction for a range of uniaxial tensile stresses up to 1 GPa. In the elastic range of steel deformation, no load transfer occurs between matrix and particles because both phases have nearly equivalent elastic properties. In the steel plastic range after Luders band propagation, marked load transfer takes place from the ductile α-Fe matrix to the elastic Fe3C particles. Reasonable agreement is achieved between phase lattice strains as experimentally measured and as computed using finite-element modeling.

High-energy synchrotron X-ray diffraction and imaging experiments were performed at the Advanced Photon Source on two ancient Chinese bronzes from the Art Institute of Chicago with the goal to nondestructively study their microstructure. The first object, a bronze fragment from an early Western Zhou dynasty vessel (Hu, 11th/10th century B.C.), was investigated with spatially-resolved diffraction to reveal the depth and composition of the surface corrosion layer as well as the composition and grain size of the underlying bronze core. The second object, a bronze dagger-axe (Ge, 3rd/2nd century B.C.) with a silver-inlaid sheath, was studied under both diffraction and imaging conditions. It was found to have been cast as a single object, answering longstanding scholars’ questions on whether the ceremonial object concealed an interior blade.

High-energy X-rays from third-generation synchrotron sources are opening new opportunities for the studies of stresses in materials. At the Advanced Photon Source (APS) 1-ID beamline, the combination of an undulator and specialized high-energy X-ray optics produces a very brilliant photon beam in the 50–100 keV energy range. In this paper, three experiments using this capability are described. In the first the combined effects of residual and applied strain on the austenite and ferrite phases are measured in a duplex steel during deformation. The austenite is seen to yield prior to the ferrite. In the second experiment, high-energy, small-angle scattering (HE-SAXS) and wide-angle scattering (WAXS) were used to study a thermal barrier coating. This allowed information to be obtained on the directionality of the pores in this material, as well as on gradients in the crystallographic texture and phase composition. In the final experiment, the behavior of an individual grain of an aluminum alloy was tracked during deformation using a 3-D X-ray microscope. This is the first phase of a project in which we intend to measure many more individual grains to deduce statistically significant effects of grain size, grain orientation, and effect of neighboring grains during deformation processes. The paper also briefly comments on possible future developments for high-energy X-ray sources.

Synchrotron X rays were used to perform nondestructive transmission diffraction and fluorescence experiments on a group of 24 European and Islamic astrolabes dated between 1350–1720 A.D. in order to determine their compositions. A group of six astrolabes produced in Lahore between 1601–1662 A.D. were found to contain a mixed α+β brass microstructure, proving that the brass was produced by a comelting technique rather than the traditional cementation process. The results also show evidence of dezincification, attributed to heavy annealing of the brass during astrolabe manufacture. This effect was so severe that an accurate analysis of the bulk Zn composition could not be determined from the fluorescence results alone; transmission X-ray diffraction gives a more accurate measurement of the bulk Zn composition.

Demands for designing prime reliant, energy-efficient, and high-performance thermal barrier coatings (TBCs) in gas turbines have led to a growing interest toward comprehensive microstructural characterization. Here we investigate the novel use of high-energy X-rays for small-angle X-ray scattering (SAXS), together with wide-angle scattering and radiography, for the depth-resolved characterization of TBCs grown by electron beam physical vapor deposition (EB-PVD). The coating microstructure is found to consist of columns perpendicular to the substrate, extending through the thickness, with a [001] growth texture and significant intercolumnar porosity. In addition, overshadowing effects during deposition together with gas entrapment give rise to nanoscale intracolumnar porosity consisting of featherlike and globular pores. Radiography showed an increase in the total porosity, from 15% near the substrate to 25% near the coating surface, which is ascribed to an increase in the intercolumnar spacing at the top of the coating. By contrast, the small-angle scattering studies, which are sensitive to fine features, showed the pore internal surface area to be greatest near the substrate.

Local damage evolution in a composite is the primary micromechanical process determining its fracture toughness, strength, and lifetime. In this study, high energy X-ray microdiffraction was used to measure the lattice strains of both phases in a Ti–SiC fiber composite laminate. The data provided in situ load transfer information under applied tensile stress at the scale of the microstructure. To better understand damage evolution, predictions of a modified shear lag model were compared to the strain data. This comparison (1) demonstrated the importance of accounting for the matrix axial and shear stiffness, (2) optimized the stiffness ratio for load transfer, and (3) improved the interpretation of the ideal planar geometry commonly used in micromechanical composite models. In addition, the results proved the matrix within and around the damage zone sustained substantial axial load and locally yielded. It was also shown that an area detector is essential in such a diffraction study as it provides multi-axial strain data and helps eliminate the “graininess” problem.

Fiber fractures are crucial in initiating damage zones that ultimately determine the strength and lifetime of fiber-reinforced metal matrix composites. The evolution of damage in a metal matrix composite (MMC) comprised of a row of unidirectional SiC fibers (32 vol pct) surrounded by a Ti matrix was examined, for the first time, using X-ray microdiffraction. Multiple strain maps including both phases were collected in situ under applied tensile stress. The elastic axial strains were then compared to predictions from a modified shear-lag model, which, unlike other shear-lag models, considers the elastic response of both constituents. The strains showed good correlation with the model. The results confirmed, for the first time, both the need and validity of this new model specifically developed for large scale multifracture simulations of MMCs. The results also provided unprecedented insight for the model, revealing the necessity of incorporating such factors as plasticity of the matrix, residual stress in the composite, and selection of the load sharing parameter.

High-energy synchrotron diffraction offers great potential for experimental study of recrystallization kinetics. Measurements on partially recrystallized samples using a monochromatic high-energy synchrotron beam show that recrystallized grains generate sharp diffraction spots, whereas the intensity from the deformed matrix varies smoothly along the Debye–Scherrer rings. Based on these observations, a method has been developed to separate the recrystallization texture components from those originating from the deformation matrix. The validity of this method is demonstrated with partially recrystallized interstitial-free steel.

To explore quantum effects on the structure of liquid water, we have carried out high-energy x-ray diffraction measurements of quantum differences both under isothermal conditions at 24.5 °C and under isochoral conditions at 0.0997 atom/A3. The measured isothermal difference correlation function is approximately equivalent to an isochoric temperature differential (ITD) of 5.5 °C, reflecting the tendency of quantum effects to introduce more disorder into the liquid. The measured isochoral correlation function is about three times higher in amplitude and is approximately equivalent to an ITD of 19 °C. Since the isochoral measurements for H2O and D2O were made at temperatures 13.5 °C apart, the isothermal and isochoral functions are roughly consistent. The discrepancies are discussed with reference to data on the pressure dependence in the literature. They are comparable with differences in results obtained with different potential functions in path-integral molecular dynamics simulations. The present result...

The planispheric astrolabe occupies a special place among early scientific instruments because of its mathematical sophistication, its elegant appearance, and its usefulness to astronomers in pre-telescopic times. The operation of the astrolabe is based on the mathematical properties of stereographic projection, concepts that were understood by the time of Ptolemy in the second century a.d., although surviving instruments are from much later periods.

Models are presented of sodium tellurite glasses in the composition range (Na{sub 2}0){sub x}-(TeO{sub 2}){sub 1{minus}x}. 0.1 < x < 0.3. The models combine self-consistently data from three different and complementary sources: sodium-23 nuclear magnetic resonance (NMR), neutron diffraction, and x-ray diffraction. The models were generated using the Reverse Monte Carlo algorithm, modified to include NMR data in addition to diffraction data. The presence in the models of all five tellurite polyhedra consistent with the Te{sup +4} oxidation state were found to be necessary to achieve agreement with the data. The distribution of polyhedra among these types varied from a predominance of highly bridged species at low sodium content, to polyhedra with one or zero bridging oxygen at high sodium content. The models indicate that the sodium cations themselves form sodium oxide clusters particularly at the x = 0.2 composition.

Using high- and low-energy x-ray scattering techniques, we have studied the effect of defects on the β1-β2 phase transition in V2H. Since we earlier observed two length scales in this crystal, we focus here exclusively on either the pure bulk or the defective skin layer, which is several micrometres thick. While we found a strong and narrow discontinuous transition in the bulk, there is a continuous transition in this defective skin layer in which the mosaic spread decreases with depth. We suggest that the strain field associated with the change of the mosaic spread most likely prompts the conversion of the order of the phase transition.

The structure of vitreous iron phosphates containing up to 35 wt% of one or more common nuclear waste components such as Na2O, Cs2O, SrO, UO2 or Bi2O3 have been investigated using Fe-57 Mossbauer, X-ray absorption, X-ray photoelectron and Raman spectroscopies and high energy X-ray and neutron diffraction techniques. The glass samples investigated were prepared by melting appropriate chemicals in air at approximately 1200°C for 2 h in alumina crucibles. The chemical durability of the glasses was investigated by measuring their dissolution rates in distilled water at 90°C using the product consistency test (PCT) methodology. The chemical durability of these glasses is characterized by dissolution rates of 10−10–10−11 g/cm2/min. The Mossbauer spectra indicate the presence of both Fe(II) and Fe(III). However, the maximum Fe(II) fraction, Fe(II)/[Fe(II) + Fe(III)], was 0.34. X-ray absorption data show that, on average, both species of iron ions are coordinated with approximately 5 near neighbor oxygens and that the iron–oxygen coordination is only slightly (

A low thermal gradient furnace design is described which utilizes Debye–Scherrer geometry for performing high temperature x-ray powder diffraction with synchrotron radiation at medium and high energies (35–100 keV). The furnace has a maximum operating temperature of 1800 K with a variety of atmospheres including oxidizing, inert, and reducing. The capability for sample rotation, to ensure powder averaging, has been built into the design without compromising thermal stability or atmosphere control. The ability to perform high-resolution Rietveld refinement on data obtained at high temperatures has been demonstrated, and data collected on standard Al2O3 powder is presented. Time-resolved data on the orthorhombic to rhombohedral solid state phase transformation of SrCO3 is demonstrated using image plates. Rietveld refinable spectra, collected in as little as 8 s, opens the possibility of performing time-resolved structural refinements of phase transformations.

Characterization, in the language of synchrotron radiation, was performed on a GE Revolution 41RT flat panel detector using the X-ray light source at the Advanced Photon Source (APS). The detector has an active area of 41 x 41 cm{sup 2} with 200 x 200 {micro}m{sup 2} pixel size. The nominal working photon energy is around 80 keV. Modulation transfer function (MTF) was measured in terms of line spread function (LSF) using a 25 {micro}m x 1 cm tungsten slit. Memory effects of the detector elements, called lag, were also measured. The large area and fast data capturing rate - 8 fps in unbinned mode, 30 fps in binned or region of interest (ROI) mode - make the GE flat panel detector a unique and very versatile detector for synchrotron experiments. In particular, we present data from pair distribution function (PDF) measurements to demonstrate the special features of this detector.

The Fourth Diffraction Limited Storage Ring (DLSR) Workshop was held at Argonne National Laboratory's Advanced Photon Source from November 19 to 21, 2014. The three-day meeting was attended by 120 participants from 22 different institutions. Local organizers of the workshop were Lahsen Assoufid, Herman Cease, Glenn Decker, Kathy Harkay, Dean Haeffner, Dennis Mills, Connie Vanni, and Diane Wilkinson (all Advanced Photon Source). The workshop website is http://dlsr-workshop-2014.aps.anl.gov/.

We have fabricated and characterized the performance of a monolithic Ge Bragg–Laue phase retarder capable of simultaneously producing both right- and left-handed circularly polarized x rays. The energy range of operation of the phase retarder is between 50 and 100 keV making it well suited to the measurement of spin-dependent Compton profiles within the impulse approximation, primarily because of the increased momentum resolution and larger Compton scattering cross section available at these higher incident energies. Although the phase retarder was optimized for operation at 86 keV, it can produce highly circularly polarized x rays over a substantial energy range. The performance of the phase retarder was tested via magnetic Compton scattering measurements on an Fe sample at the undulator A of the Advanced Photon Source. It was found to perform well in terms of flux and degree of circular polarization thereby greatly reducing the data collection times required for this inherently weak scattering process.

This letter describes the combined use of high-energy X-ray diffraction and neutron diffraction to investigate the problem of the structure of liquid FeCl3. The results confirm the picture of liquid iron chloride consisting of closely packed Fe2Cl6 bitetrahedral molecules which have an atomic structure consistent with the electron diffraction results in the vapor. Comparison of the X-ray and neutron results at low Q suggests a paramagnetic moment about half that expected for a free Fe3+ ion, and confirms the picture suggested previously for topological and chemical short-range and intermediate-range order in the melt. Comparison of the X-ray diffraction data with molecular-dynamics results suggests a charge transfer intermediate between an atomic and fully ionic charge distribution, consistent with recent ab initio molecular orbital calculations.

Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near-edge spectra of an elemental species at each location on an arbitrary virtual section through a sample. These spectra reveal the local concentrations of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state, the local atomic structure, and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses.

We have constructed an X-ray phase plate to produce linearly and circularly polarized X-rays at discrete energies between 20 keV and 88 keV. The plate is a monolithic two-crystal design, constructed from germanium. We have measured the degree of circular polarization at 65 keV to be 90%±4%, which is significantly better than that produced by silicon phase plates. This radiation was used to measure the magnetic Compton profile for Fe, which was found to be in good agreement with theory and previous work. The underlying X-ray optics and the characterization of the device between 62 keV and 93 keV at the Cornell High Energy Synchrotron Source are presented.

Over the last five years, based on the operating experiences, many upgrades have been made to the beamline standard components to continue improving beamline performance and reliability at the Advanced Photon Source (APS). In this article, the particular design upgrades, as well as the new component design specifications of APS beamline standard components, are summarized.

Hard mineralized tissues such as bone are the primary load bearing structures in the body. Its basic building block is an organic matrix – mainly type I collagen, a mineral phase – calcium hydroxyapatite and water. These three components interact to form a very complex structure hierarchically organized from the nano– to the macro–scale [1], which is capable of supporting bodily loads and resisting fracture due to its high strength and toughness. However, despite its high resistance, bone fractures occur due to both impact loads and repetitive or sustained loads exerted over larger periods of time. Cyclic loads are the most direct analog to periodic stresses and strains varying in both intensity and type seen in physiological activities like walking and running [2]. It is thus clinically important to gain a deeper understanding of the mechanisms occurring within this complicated structural hierarchy of bone to ultimately predict and prevent such failures thus leading to improved medical treatments. Fatigue damage has been shown to be characterized by cyclic property degradation [3, 4], caused by accumulation and propagation of microcracks [5, 6]. The formation of microcracks is loading mode dependent [7, 8], which in turn affects the degradation of properties during cyclic loading. The macroscopic behavior has been fairly well understood from the vast number of studies done previously. Still lacking is an understanding of the interaction between the different components of the building block and the subsequent hierarchical levels of bone during such loading, which results in the observed macroscopic behavior. The high–energy X–ray diffraction technique used in this work makes it possible to obtain through–thickness (` 5 mm in this case) crystal lattice information from the bulk of the sample, compared to other high resolution techniques like nanoindentation which sample only surface volumes up to depths of about 1000 nm [9], or other imaging techniques like scanning and transmission electron microscopy and atomic force microscopy [10], which are good for obtaining surface structural information. With its in situ testing capability [11], this high–energy X–ray diffraction technique has recently found applications in probing individual components of bone [12] and dentin [13] materials. The aforementioned diffraction technique is used in the current work to determine the strains in the HAP and collagen phases of bone during cyclic loading in compression at body temperature, and study their evolution with cycles.

Real-time evolution of nanoparticles grown at the semiconductor/electrolyte interface formed between a single crystalline n-type GaAs wafer and an aqueous solution of AgNO(3) has been studied by using high-energy synchrotron X-ray diffraction. The results reveal the distinct nucleation and growth steps involved in the growth of anisotropic Ag nanoplates on the surface of the GaAs wafer. For the first time, a quick transit stage is observed to be responsible for the structural transformation of the nuclei to form structurally stable seeds that are critical for guiding their anisotropic growth into nanoplates. Reaction between a GaAs wafer and AgNO(3) solution at room temperature primarily produces Ag nanoplates on the surface of the GaAs wafer in the dark and at room temperature. In contrast, X-ray irradiation can induce charge separation in the GaAs wafer to drive the growth of nanoparticles made of silver oxy salt (Ag(7)NO(11)) and silver arsenate (Ag(3)AsO(4)) at the semiconductor/electrolyte interface if the GaAs wafer is illuminated by the X-ray and reaction time is long enough.

The x-ray structure factor of water measured under ambient conditions with synchrotron radiation is compared with those predicted on the basis of partial structure factors describing the nuclear positions obtained by neutron diffraction and of different assumptions for the electron distribution. The comparison indicates that a charge of approximately 0.5 e is transferred from each hydrogen atom to the oxygen on the same molecule, implying an effective dipole moment of 2.9 D, in good agreement with theoretical estimates.

The elastic properties of dentin, a biological composite consisting of stiff hydroxyapatite (HAP) nano-platelets within a compliant collagen matrix, are determined by the volume fraction of these two phases and the load transfer between them. We have measured the elastic strains in situ within the HAP phase of bovine dentine by high energy X-ray diffraction for a series of static compressive stresses at ambient temperature. The apparent HAP elastic modulus (ratio of applied stress to elastic HAP strain) was found to be 18 ± 2 GPa. This value is significantly lower than the value of 44 GPa predicted by the lower bound load transfer Voigt model, using HAP and collagen volume fractions determined by thermo-gravimetric analysis. This discrepancy is explained by (i) a reduction in the intrinsic Young’s modulus of the nano-size HAP platelets due to the high fraction of interfacial volume and (ii) an increase in local stresses due to stress concentration around the dentin tubules.

Using X-ray diffuse scattering, we investigate the critical behavior of an order-disorder phase transition in a defective "skin-layer" of V2H. In the skin-layer, there exist walls of dislocation lines oriented normal to the surface. The density of dislocation lines within a wall decreases continuously with depth. We find that, because of this inhomogeneous distribution of defects, the transition effectively occurs at a depth-dependent local critical temperature. A depth-dependent scaling law is proposed to describe the corresponding critical ordering behavior., Comment: 5 pages, 4 figures

Dentin is a load bearing multiphase composite composed of a ceramic phase, hydroxyapatite (HAP), a polymeric phase, collagen, and fluid filled porosity. In order to create better dentin replacements it is important to understand how applied load is naturally transferred between the phases during chewing and other stresses. To determine the apparent elastic modulus of HAP in dentin, applied stress over lattice strain in HAP, high energy wide angle x-ray diffraction measurements were performed on in situ loaded bovine dentin samples. It was determined that the average longitudinal apparent elastic modulus of HAP in dentin was 18.3±2.19GPa. This value is much lower than values predicted by the Voigt model when combined with volume fractions determined for the sample by thermo-gravimetric and chemical analysis. It has been determined that the decrease in apparent elastic modulus is most likely due to a decrease in the “bulk” elastic modulus of HAP due to nanometric effects.

CCDs have been the primary sensor in imaging systems for x-ray diffraction and imaging applications in recent years. CCDs have met the fundamental requirements of low noise, high-sensitivity, high dynamic range and spatial resolution necessary for these scientific applications. State-of-the-art CMOS image sensor (CIS) technology has experienced dramatic improvements recently and their performance is rivaling or surpassing that of most CCDs. The advancement of CIS technology is at an ever-accelerating pace and is driven by the multi-billion dollar consumer market. There are several advantages of CIS over traditional CCDs and other solid-state imaging devices; they include low power, high-speed operation, system-on-chip integration and lower manufacturing costs. The combination of superior imaging performance and system advantages makes CIS a good candidate for high-sensitivity imaging system development. This paper will describe a 1344 x 1212 CIS imaging system with a 19.5μm pitch optimized for x-ray scattering studies at high-energies. Fundamental metrics of linearity, dynamic range, spatial resolution, conversion gain, sensitivity are estimated. The Detective Quantum Efficiency (DQE) is also estimated. Representative x-ray diffraction images are presented. Diffraction images are compared against a CCD-based imaging system.

The considerable intensity of Advanced Photon Source (APS) undulator A as a source of high-energy X-rays permits the performance of numerous types of experiments that require such photon energies. Measured and calculated properties, in the 50-200 keV range, of the X-ray beam from undulator A, installed in sector 1 of the APS, are presented. The flux spectra observed at various gaps agree well with calculations that incorporate the actual magnetic field within the device and the emittance and energy spread of the stored positrons. The field errors and energy spread cause the X-ray beam to lose undulator radiation properties at high energies, as seen in the smeared-out spectral harmonics and increased beam divergence, giving resemblance to a low-K wiggler source. Owing to the wiggler-like behavior in this photon-energy range, the optimal operating condition for undulator A is in the vicinity of the closed-gap setting, corresponding to a maximum critical energy.

Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near edge spectra of an elemental species at each location on an arbitrary virtual section through a sample. These spectra reveal the local concentrations of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state, the local atomic structure, and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses. The full XANES spectra reconstructed at each point of the tomographic slice allow to detect slight variations in concentrations of chemical compounds, such as metallic and monovalent copper. The method is applied to the analysis of a heterogeneous catalyst.

Interpenetrating Al2O3/Al composites were created by liquid-metal infiltration of alumina preforms with three-dimensional periodicity produced by a robotic deposition method. Volume-averaged lattice strains in the alumina phase were measured by synchrotron x-ray diffraction at various uniaxial compression stresses up to 350 MPa. Load transfer, which is experimentally found to occur between the aluminum and the alumina phase, is in agreement with simple rule of mixtures models. Spatially resolved measurements showed variations in load transfer at different positions within the composite for the elastic-, plastic-, and damage-deformation regimes. Using phase-enhanced imaging, the extent of damage within the composites was observed.

The radial (i.e., depth below the surface) dependence of the residual strain tensor within shot‐peened samples of cylindrical geometry is measured nondestructively using high‐energy synchrotron radiation (80 keV). Transmission geometry is employed in combination with a triangulation slit and area detector. Thus, a radial gauge length is defined directly by the beam size rather than cumulatively as in conventional reflection geometry. A narrow incident beam of 30 micrometer diameter is used, and we demonstrate that macroscopic grain averaging is achieved even in the bulk, where the grain size is large, by oscillating the samples in two dimensions. Therefore, the samples are rotated with high frequency around the cylinder axis and translated with low frequency parallel to the axis. We argue that the combination of a narrow incident beam, a two‐dimensional sample oscillation, and area detector provides a versatile technique to overcome insufficient grain averaging as the gauge volumes can be flexibly chosen ...

A set of precision horizontal and vertical white‐beam slits has been designed for the Advanced Photon Source x‐ray undulator beamlines at Argonne National Laboratory. There are several new design concepts applied in this slit set, including a grazing‐incidence knife‐edge configuration to minimize the scattering of x rays downstream, enhanced heat transfer tubing to provide water cooling, and a secondary slit to eliminate the thermal distortion on the slit knife edge. The novel aspect of this design is the use of two L‐shaped knife‐edge assemblies, which are manipulated by two precision X‐Z stepping linear actuators. The principal and structural details of the design for this slit set are presented in this paper.

We have used a new approach involving simultaneous diffraction and small angle scattering to study the amorphous-to-crystalline phase transformation in Zr-based bulk metallic glass. In situ, time-resolved data provided the first direct demonstration of a phase separation prior to crystallization. There is evidence that nucleation and growth of the crystalline phase occur in separate stages, with different kinetics. Our data support the view that crystalline nucleation is achieved via short-range diffusion of small atoms (e.g., Ni), whereas the growth is dictated by long-range diffusion.

This paper reports on experiments in which high-energy (65.35 keV) X-rays were used to record the detailed diffuse diffraction patterns of a number of ceramic materials. The methodology has enabled a greater q-range to be explored (up to sintheta/lambda approximately 0.97) than is possible with laboratory-based experiments, with better q-space resolution and increased sensitivity, thus allowing previously unseen detail in diffraction patterns to be recorded. In all, 11 sections of data have been collected for Ca-CSZ, eight for Y-CSZ and six for wuestite.

Because of their high chemical durability and waste loading capacity, iron phosphate glasses are a natural candidate for a nuclear waste disposal medium. We have studied the effects of uranium on the structure of iron phosphate glasses with both neutron and high-energy x-raydiffraction. The results of neutron scattering, which is mostly sensitive to pair correlations involving light atoms i.e. O-O, Fe-O and P-O, indicate the main structural features of the base glass are largely unaffected by the addition of UO2. The nearest-neighborbour P-O, Fe-O and O- O peaks remain at the same position in real space and their intensities scale approximately with concentration. These findings are consistent with earlier results using Raman scattering and EXAFS on the Fe-K edge, where in both cases the spectra remain similar to the base glass. The results of high-energy x-ray scattering, which is sensitive to correlations involving the heavier atoms and thus complements the neutron measurements, are also consistent with the overall picture of uranium occupying interstitial sites in the relatively undisturbed base glass structure. Combining the neutron and x-ray data for a 10 mol% UO2 glass suggests the intriguing possibility of a U6+ uranyl ion configuration although further work is needed to establish the precise local structure and valence state of uranium in these glasses.

A compact tube furnace has been developed for high temperature X-ray diffraction studies using high energy synchrotron radiation. The furnace design has a low absorption path in transmission yet allows for a high degree of control of the sample atmosphere and a minimal temperature gradient across the sample. The design allows for a maximum temperature of 1500°C with a variety of atmospheres including inert, reducing, and oxidizing. Preliminary results obtained at the SRI-CAT I-ID undulator line (60keV) at the APS facility and the A2 24 pole wiggler line (45keV) at CHESS on the Ti5Si3Z5 (Z = C, N, O) system will be presented to demonstrate the feasibility of this approach.

At the Advanced Photon Source (APS), each insertion-device (ID) beamline front end has two X-ray beam position monitors (XBPMs) to monitor the X-ray beam position for both vertical and horizontal directions. Performance challenges for a conventional photoemission-type XBPM during operations are contamination of the signal from the neighbouring bending-magnet sources and the sensitivity of the XBPM to the insertion-device gap variations. Problems are exacerbated because users change the ID gap during their operations, and hence the percentage level of the contamination in the front-end XBPM signals varies. A smart XBPM system with a high-speed digital signal processor has been built at the Advanced Photon Source for the ID beamline front ends. The new version of the software, which uses an artificial-intelligence method, provides a self-learning and self-calibration capability to the smart XBPM system. The structure of and recent test results with the system are presented in this paper.

(2003). National school on Neutron and X‐ray scattering alumni presentations. Synchrotron Radiation News: Vol. 16, No. 5, pp. 24-25.