XSD Seminars 2009

X-ray diffraction microscopy, or coherent x-ray diffraction imaging, is ideal for high resolution imaging of thick biological samples, because of its short wavelength, high penetration ability and elimination of limits imposed by x-ray optics. We demonstrated that XDM has the potential to deliver equivalent resolution images using fewer photons, compared with conventional x-ray microscopy. We performed XDM on specifically labeled and freeze dried yeast with a resolution fo about 14 nm. We also obtained the first image of an intact, frozen hydrated eukaryotic cell using x-ray diffraction microscopy. By plunge-freezing the specimen in liquid ethane and maintaining it below -170 degree Celsius, 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.
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Growth of epitaxial thin film on structured substrate has wide applications in microelectronics, and X-ray microprobe has been a powerful tool to characterize film structure at various points on the pre-patterned substrate. X-ray micro-diffraction measurements from selective area grown In_1-xGa_xAs_yP_1-y quaternary film and hematite (alpha-Fe₂O₃) film grown over patterned alpha-Cr₂O₃ buffer layer will be presented as examples. The measured lattice constants of coherent In_1-xGa_xAs_yP_1-y film around a patterned SiO₂ mask indicate that a large unit-cell film was grown in confined space between amorphous SiO₂ masks and connected smoothly to smaller unit-cell film grown in an open area. When an epitaxial buffer layer is used as a mask, epitaxial alpha-Fe₂O₃ film grown on the buffer layer was connected to adjacent film formed on bare substrate with a large lattice mismatch. The laterally connected film on bare substrate sustained epitaxy through mechanism similar to side-wall epitaxy. If a buffer is used as a patterning mask in selective area growth, epitaxial film could be grown directly on a large lattice mismatch substrate adjacent to the buffer. Subsequent fabrication could yield buffer-free epitaxial film directly bonded on the large lattice mismatch substrate. Preliminary microbeam X-ray standing wave measurements from the thin films on the buffer layer and on the adjacent region will be also discussed.
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Ever-increasing clock and data rates are squeezing even the most basic designs to properly characterize jitter and timing margins. This seminar will provide you with an understanding of how jitter affects circuit performance and concepts that are needed to effectively perform jitter analysis. Concepts covered include: jitter definition, jitter statistics, golden PLL jitter analysis, cycle-cycle jitter, TIE, SSC, Rj/Dj separation and BER Estimation.
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Future use of X-ray photons will be based on several exceptional properties, among which are the ability to focus partially coherent X-ray beams to the spot size below 10 nm, and to utilize X-rays with the resolution near 1 meV. Such properties will provide a whole new platform for understanding of the nanoscale physical and chemical properties of materials, functionality of proteins and other crucial issues of modern combinatorial materials and life sciences.

Numerical design and large aspect ratio nanofabrication techniques were utilized to generate X-ray bi-prism arrays and kinoform refractive X-ray lenses for the purpose of focusing, deflecting and characterizing hard X-ray synchrotron radiation, and for sub-micron resolution in X-ray diffraction and X-ray fluorescence characterization efforts. A comparison of different low-Z materials (Si, diamond) will be presented, offering a hope that the focal spot size in 10 nm range in the hard X-ray spectrum can be obtained in the near future.

In addition to nanofocusing studies, I will present results on X-ray interference in Fresnel regime based on a virtual Young’s double slit experiment, leading to measurements of the spatially varying degree of a partial coherence of X-rays. Potential applications of such novel X-ray optic elements in microdiffraction, microfluorescence and in other X-ray characterization techniques will be discussed, including example of their use in understanding collective transport in strongly correlated materials.
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Graphene – a newly discovered two-dimensional form of carbon is at the center stage of intense research on nanodevices [1]. This talk will cover our recent work on top-gated field effect transistors made of single and bilayer graphenes [2,3] wherein transport measurements are combined with in-situ Raman scattering to quantitatively evaluate electron-phonons interaction strength. We show that electrochemical top gate using solid electrolyte with a very high gate capacitance of ~1.5 μF/cm² can achieve much higher doping that the conventional SiO₂ back gate. The effect of electron and hole doping on the graphene phonons is quantitatively understood using ab-initio calculations that take into account effects beyond adiabatic approximation. We will present recent studies on bilayer graphene showing that simultaneous p and n type carrier injection can be achieved by varying the longitudinal bias across the channel and the top-gate voltage [4]. These results will be compared with our studies on metallic and semi-conducting carbon nanotubes [5,6].
[1] For a recent review, See Rao, Sood, et al. Angew.Chem.Int. Ed. 48, 7752 (2009).
[2] Das, Sood, et al. Nature Nanotechnology 3, 210 - 215 (2008).
[3] Das, Sood et al; Phys. Rev. B 79, 155417 (2009).
[4] Chakraborty, Das, Sood, Nanotechnology 20, 365203 (2009).
[5].Das, Sood, et al, Phys.Rev.Lett. 99, 136803(2007).
[6] Das, Sood, Phys. Rev. B, 79, 155417 (2009).
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Raspberry-like biocomposites can be fabricated via a facile approach using bionanoparticles hybridized with poly (4-vinylpyridine) (P4VP). The size of the core-shell biocomposites, analyzed by dynamic light scattering (DLS), can be controlled by varying the ratio of bionanoparticles and P4VP. The structures have hexagonal packing of the bionanoparticles on the surface of polymeric spheres, as characterized by transmission electron microscope (TEM), field emission scanning electron microscope (FESEM) and small angle x-ray scattering (SAXS). In addition, this method can be applied to assemble proteins with P4VP and PCL-/b/-P2VP. The formed protein-polymer composites can be used for application of targeted drug delivery.
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X-ray powder diffraction is a powerful method for analysis of polymorphs and solid forms of pharmaceuticals. Of special interest is the application of X-ray diffraction and Pair Distribution Functions (PDF) to liquid crystals and amorphous dispersions. PDF analysis of liquid crystals has the potential to provide information on the backbone structure of liquid crystals. PDF also provides an approach to assessment of the risk of crystallization of drug-polymer amorphous dispersions by providing information on whether these dispersions are molecular mixtures, nanoamorphous mixtures or amorphous mixtures. X-ray diffraction and PDF may also provide a method to understand the nature of the disorder in milled materials.
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Determining structural change coupled with electron/energy redistribution in solar energy conversion processes is essential in understanding the fundamental reaction mechanism, therefore, realizing the rational designs of solar energy utilization device. Laser-initiated time-resolved X-ray absorption spectroscopy (LITR-XAS) has been used to probe the electron/charge transfers and structural changes of metal complexes during photoreactions. This approach combines with laser transient absorption spectroscopy gives a complete story of energy flows during solar photo conversion processes. The ultrafast structural dynamics study of a homogeneous system: nickel porphyrin in solution and a heterogeneous system: ruthenium dye adsorbed to anatase TiO2 nanoparticle surface will be presented. The electronic configuration as well as the internuclear distance changes in the photoexcited state have been observed in both systems. These measurements demonstrate the significant potential of using LITR-XAS to study the metal complexes in solar energy application.
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Aluminum-lithium (Al-Li) alloys offer advantages of lower density, increased elastic stiffness, and high strength when compared to other aluminum alloys. However, delamination cracking -- mescoscopic failure at elongated grain boundaries oriented perpendicular to a primary crack -- plays a dominant role in the fracture process. With the introduction of these materials into components of aerospace structures, a quantitative understanding of the interplay between delamination cracking and macroscopic fracture must be established as a precursor to reliable design and defect assessment.

In the present work, fracture toughness and fatigue studies are carried out. Digital Image Correlation is employed in mechanical testing to identify the onset of plastic localization, prior to the development of delamination. EBSD mapping methods are used in the characterization of sectioned samples. Collectively, this data is then applied to pose detailed models of a delamination in the presence of a primary crack. Both "crack divider" and "crack arrestor" delaminations are studied in the present work. The measurement of crystallographic orientation in the vicinity of the delamination is utilized in the crystal plasticity formulation. Results indicate the key role of slip incompatibility: a grain oriented favorably for slip sharing a boundary with another with "less favorable" crystallographic orientation promotes the development of a shear stress that sustains delamination.

This work is supported by the NASA Marshall Flight Center through grant NNX09AN21G .
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Purpose: The purpose of this study is to characterize certain aspects of the microscopic structures of cortical and trabecular bone using the Fourier x-ray scattering imaging method. Materials and Methods: The hind limb of a rat and the toe of a pig were imaged ex-vivo under NIH Animal Care and Use Committee approved protocols. A Fourier x-ray scattering imaging device uses a grid mask to modulate the cone-beam and Fourier spectral filters to isolate the harmonic images. It acquires attenuation, scattering and phase-contrast (PC) images in a single exposure. In rat tibia cortical bone, scattering image intensities from orthogonal grid orientations were compared using Wilcoxon signed rank tests. In the pig’s toe, the heterogeneity of scattering and PC signals were compared between trabecular and compact bone regions of uniform attenuation using F-tests. Results: In cortical bone, the scattering image intensity is significantly higher (P<10^-15) when the grid is parallel to the periosteal surface. Trabecular bone appears highly heterogeneous in the scattering and PC images when compared to cortical bone (P<10^-27). Conclusion: The ordered alignment of the mineralized collagen fibrils in compact bone is reflected in its anisotropic scattering image intensity. In trabecular bone, the porosity of the mineralized matrix can explain the granular pattern in the scattering and PC images.
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Random disorder is ubiquitous in virtually all materials and, often, leads to important and dramatic physical consequences. Understanding the role of disorder on materials properties and phase transitions has been the focus of many condensed matter physics efforts. While phase transitions in liquid crystals have been long studied, only within the last decade have techniques been developed to add random disorder to liquid crystals in a controlled way. This has opened a new strand of liquid crystal research. By growing mixtures of random nano-network aerosil gels and thermotropic liquid crystals, experimental systems can be realized that exhibit a random field influence upon the molecular phase orderings of liquid crystals. This talk will discuss the nature of quenched random disorder and how it can be produced in liquid crystalline materials such as the polar butyloxybenzilidene-heptylaniline (4O.7) and the non-polar 4-n-pentylphenylthiol-4′-noctyloxybenzoate (8S5). Particular emphasis will be given to recent experiments that use high resolution x-ray scattering to obtain unique information on phase ordering, transition points, and the universality of liquid crystal phase transitions. This work will be placed within the context of other liquid crystals phase transition experiments. Finally, ideas for complementary measurements of liquid crystalline order using small angle x-ray scattering will be discussed.
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The field of ultrafast science where dynamic structures are studied on the femto-second and smaller time-scales are being enhanced with the development of x-ray laser synchrotrons dedicated for such studies. In order to exploit the capabilities of these new machines, new hybrid x-ray detectors are under development. The typical hybrid device uses high-resistivity Si photo-converters coupled to CMOS electronics. In a typical pump-probe type experiment, the time between the pump (which could be a laser) and probe (synchrotron x-ray laser) is on the femto-second with the probe duty-cycle ranging from 120 Hz to MHz.

This presentation will describe the development of a 2160 x 2560 CMOS Image Sensor (CIS) imaging system with a 6.5 μm pitch for time-resolved x-ray scattering studies. The system is single photon quantum limited from 8 keV to 20 keV with a phosphor-photoconverter. It has a wide dynamic range and can operate at 100 Hz full-frame and at higher frequencies using a ROI readout. Fundamental metrics of linearity, dynamic range, spatial resolution, conversion gain, sensitivity and DQE are estimated. Experimental time-resolved data are also presented.
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At low temperatures, the pyrochlore magnet Tb₂Ti₂O₇ exhibits a dynamically short range ordered magnetic state. No credible evidence for long-range order has been reported in the literature down to temperatures as low as 20 mK, despite the fact that the material displays a Curie-Weiss temperature roughly a thousand times larger than this. Concomitant with the development of these liquid-like magnetic correlations, intriguing critical structural fluctuations have been shown to develop in the crystal lattice. In addition, under the application of magnetic fields at these low temperatures the system displays giant magnetostriction (as large as that of the best commercial materials), and a non-trivial long-range ordered magnetic state. Both effects appear to be strongly sensitive to the direction of the applied magnetic field. We will review new and existing neutron and x-ray scattering measurements of Tb₂Ti₂O₇, with the intention of elucidating the physics of the spin-lattice coupling in this puzzling magnet. Specific attention will be paid to recent high-resolution pulsed-field x-ray scattering measurements, which constitute the first successful experiment using the 30 Tesla, mini-coil magnet at the Advanced Photon Source.
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The macroscopic mechanical properties of composites and two-phase alloys are controlled by the interaction of components and phases on a microscopic length scale. In this seminar in situ studies are presented which were carried out at synchrotron and neutron radiation sources which gave quantitative insight into this interaction. Emphasis is placed on the internal load transfer in particle or fiber reinforced metal matrix composites. Both methodology and materials science are discussed.
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This talk will cover two topics on addressing key issues at the frontier of explorations of surface/interface phenomena in advanced materials by using synchrotron x-ray diffraction/scattering techniques. One is to perform atomic structural imaging of complex epitaxial systems that exhibit novel physical properties by combining high precision synchrotron surface x-ray diffraction technique and phase retrieval direct methods. Another is to investigate surface morphology evolution involving energetic processes by synchrotron x-ray surface scattering technique in-situ and in real-time.
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The characterization of ordering and kinetics at nanostructured surfaces and interfaces has become increasingly critical to understand and optimize the synthesis of ordered nanomaterials on nanometer length scales. This requires innovative in situ and time-resolved surface probes that can also be applied to various experimental environments. Grazing-incidence x-ray scattering is an ideal tool for the studies. At the Advanced Photon Source, using high-resolution small-angle x-ray scattering in grazing-incidence geometry (GISAXS), we successfully captured the growth kinetics of two-dimensional nanocrystal superlattices at the liquid/air interface and identified their ordering, phases and phase transitions in a quantitative manner. As one of the greatest challenges associated with the grazing-incidence technique, a precise reconstruction of the real-space nanostructures from their scattering data requires a comprehensive model in the presence of electric-field intensity enhancement at the grazing-incidence angles. To this end, a rigorous grazing-incidence scattering theory has been developed to analyze the buried nanostructures involving multiple interfaces, which thus far has been difficult, if not impossible. Finally, I will discuss a promising direction for creating an innovative class of materials and structures capable of new functionalities with improved self-assembly efficiencies. This involves supramolecular self-assembly at multiple-level of energy landscapes and length scales, whose structure, kinetics and dynamics can be elucidated by the grazing-incidence x-ray scattering measurements with either incoherent or coherent x-rays.
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Non-periodic multilayer coatings offer engineers great flexibility to achieve tailored spectral performance in EUV, soft X-ray and X-ray region. We have developed a variety of non-periodic multilayer mirrors for the use as optical key components for polarization-sensitive studies, Kirkpatrick-Baez microscopes, Earth’s magnetosphere observations, and reflection of sub-femtosecond pulses. To find an optimal distribution of layer thicknesses for a given spectral response, several numerical algorithms, such as simplex, simulated annealing, and genetic, have been explored to solve the reverse optimization problem. The designed non-periodic multilayers were prepared by using dc magnetron sputtering and characterized by grazing incidence x-ray reflectometry analyses. The synchrotron measurements of these samples were performed at the National Synchrotron Radiation Laboratory, China and at BESSY II Berlin, Germany. This talk will cover our recent results of design and fabrication of non-periodic multilayer coatings.

Zhanshan Wang received his PhD degree in optics in 1996 from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, with a thesis on "Soft X-ray multilayer microscope". He is a full professor of physics at Tongji University in Shanghai and director of Institute of Precision Optical Engineering of Tongji University. His research activities include the study of multilayer components for x-ray optics and X-ray imaging systems. He has authored more than 80 publications and co-hosted the Sino-German High Level Expert Symposium on Optical coatings in 2005 and the Sino-German High Level Expert Symposium on X-ray Optics in 2007.
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Microstructure changes and their characterization during plastic deformation or heat treatment of preprocessed polycrystalline metallic alloys is the key for understanding the complex behavior of these industrially important materials. In engineering applications the optimum properties are achieved by a combination of thermo-mechanical processes and worked out mostly empirically. The advanced synchrotron techniques like Three-dimensional X-Ray Diffraction Microscopy (3DXRD) could provide an efficient way to investigate in-situ a large enough material volume and provide a real 3D quantitative description about its structure. An improvement was introduced combining it with Diffraction Contrast Tomography (DCT) method. In this talk I will present the principles and achievement of these techniques, which were used for investigating the grain structure of an Al-0.5%Mg alloy. The statistical analysis of the reconstructed grain maps will be presented and correlated with Electron Backscattered Diffraction (EBSD) results, furthermore the experienced advantages, disadvantages and difficulties of these techniques will also be discussed.
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The special properties of synchrotron light sources, such as intense flux, high brilliance and partial coherence allow for pushing the limits of hard X-ray imaging methods: full-field micro-tomography can be extended by more sophisticated contrast mechanisms to image weakly attenuating objects or elements with identical absorption contrast. Digital radiography can be used for in situ investigations of fast processes on the millisecond scale, sampled with a spatio-temporal micro-resolution. A focused synchrotron beam in combination with scanning tomographic techniques probes a sample with respect to e.g. its local diffraction behaviour.

This talk focuses on instrumentation and applications of synchrotron micro-imaging exploiting different contrast modalities. Experiments and developments were performed at the BAMline (BESSY-II), TopoTomo (ANKA) as well as ID15a, ID19 and ID22 (ESRF). By developing further indirect 2D X-ray detectors, radiography in vivo of living species as well as in situ of liquid metal foams has been performed. The latter allowed for the first time to image a coalescence event by using an image acquistion speed of 40 000 frames/s. Optimising besides the detector as well the beamline instrumentation makes micro-tomography feasible even at moderate flux light source, i.e. dedicated multilayer monochromators can be used. Examples to apply micro-tomography are bioceramics in regenerating bone and early pore formation in foams.

Subsequent 3D image analysis by means of algorithms based on transformations known from stochastic geometry derives quantitative results like spatial correlations between different constituents within the volume image.
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Magnetic field is, after temperature, the most often and easily changed themodynamic variable when performing experiments in solid state physics. Neutron and X-ray diffraction and spectroscopie are very powerful experimental tools. Unfortunately it is not so easy to combine high magnetic fields with strong sources. We will review the current state of the art including continuous fields, discuss the main limitations for the use of pulsed magnetic fields related to their low duty cycle and show some recent results obtained with the combination of pulsed fields and X-rays or neutrons in Grenoble. We will show what is the maximum field that reasonably could be obtained with current techniques and knowledge. For actual use one needs to compromise on the maximum field value in order to have sufficient duty-cycle (i.e. time at a given field per hour) and access (several type of experiments require fields perpendicular to the optical access and thus a split-coil magnet). Pulsed magnets have a limited lifetime, and we will show that for an optimum use one needs long-pulse rapid cooldown magnets. The practical limits of this type of magnets will be presented. The magnet is only a part of the sample environment, temperature control (cryostat or furnace) are normally required as well. Some solutions compatible with the pulsed magnetic field and with X-rays or neutrons will be presented.
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Coherent diffractive imaging (CDI) represents a different way of thinking about image formation in microscopy. In the place of an image-forming lens or lens-analogue--e.g., a Fresnel zone plate--this "lens-less" method relies on some easily obtained a priori sample information and a scattering measurement, which are used in an iterative algorithm. The algorithm recovers the complex wave in the sample plane that can be used to form a traditional absorption image or manipulated to reveal addition information. Since its initial demonstration in 1999, the method has provided images of a wide variety of samples at resolutions of order 20 nm.

In this seminar, I will briefly describe the method and recall a few representative results, including images of condensed matter, electronics, and biological samples. From this basis, recent modifications to the method will be discussed. In particular, the so-called Fresnel CDI method utilizes a well-characterized diverging beam to illuminate the sample, which provides practical benefit in stabilizing the iterative algorithm as well widening the applicability of the method to extended samples by overcoming the necessity to create an isolated one.

Finally, I will present some recent advances to CDI and summarize the current research effort surrounding the new Partner-User microscope at Sector 2-ID-B.
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The twinning-detwinning behavior and the associated internal strain/stress evolution in a strongly textured magnesium alloy, ZK60A, were investigated under cyclic loading using neutron and synchrotron diffraction/./ The initial preferred orientation in most grains with their c-axes perpendicular to the loading axis favors extension twinning under compression but not under tension, when the alloy is loaded along the extrusion direction. The unique orientation relationship between the parent grains and the twin grains facilitates detwinning during the subsequent strain reversal. The results indicate that such twinning and detwinning alternates with cyclic loading, i.e., most twins formed during compression are removed when the load is reversed. The study of internal strain/stress evolution shows that once the matrix grains twin, the (00.2) matrix and twin grains are relaxed relative to the neighbors. This stress redistribution between the soft- and hard-grain orientations is a result of plastic anisotropy. The twins formed during the initial compression sustain a tensile stress along their c-axes, when the applied compressive stress is unloaded to less than ~ 80 MPa. This local (intergranular) tensile stress is a result of the stress redistribution between different grain orientations, and hypothesized to be effective for driving the detwinning event under a macroscopic compressive stress field.
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The recent discovery of superconductivity in CaC6 (Tc=11.5 K) and YbC6 (Tc=6.5 K) has given rise to a resurgence of interest in Graphite Intercalation Compounds (GICs). Despite early studies suggesting exotic mechanisms for the electron coupling in the superconducting phase, subsequent DFT studies suggest that in GICs the electrons couple via the electron-phonon interaction. This observation naturally motivates the study of the vibrational excitations (phonons) in these materials. Due to the small size of available samples of these materials, inelastic X-ray scattering (IXS) - as opposed to inelastic neutron scattering - is the technique of choice to study the dispersion of the phonons throughout the Brillouin Zone (BZ). IXS measurements of the (00L) phonons in superconducting CaC6 and non-superconducting BaC6 (Tc < 80 mK) will be presented, discussed in relation to DFT calculations. A brief overview of other related IXS experiments will be provided, with a discussion of our plans for the future.
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Multiple-wave x-ray diffraction takes place when more than one set of atomic planes is simultaneously brought into position to diffract an incident beam. As a result of the scattering of x-rays from periodic two- or three-dimensional structures, the multiple-wave diffraction reflects structural crystal information that cannot be obtained from single two-wave diffraction.

However, due to the comparably large number of waves involved in the multiple-wave diffraction process, generally, the correspondent wavefields and diffracted intensities cannot be resolved analytically. For this reason, we have developed several approaches for numerical solution of the multiple-wave dynamical x-ray diffraction equations for bulk crystals and crystalline multilayers in a plane-wave approximation of the incident beam. We also proposed several approximations, including the iterative Born and resonance perturbation Bethe approximations, for the explanation of the fundamental behavior of three-wave x-ray diffraction. Among such behavior we have theoretically predicted and experimentally studied some new phenomena of a multiple-wave interaction of x-rays with matter: the indirect excitation of polarization-forbidden x-ray reflections, the polarization suppression of the detour-exited waves, the anomalous behavior of multiple-wave x-ray interaction at atomic resonance, the coherent multiple-wave x-ray interaction in charge-density wave materials.

Due to the sensitivity to the phases of the structural factors, the multiple-wave diffraction has found its unique application for the solution of the phase problem of x-ray optics, diffraction physics and crystallography. We have proposed some theoretical approaches to explain the phase sensitivity of multiple-wave diffraction, as well as developed the experimental techniques for quantitative determination of reflection phases for bulk crystals, surface layers, macromolecular crystals, charge-density waves, and phase shifts at atomic resonance. Some contributions to an application of the multiple-wave diffraction techniques have also been made for the precise determination of lattice parameters for bulk crystals and thin surface layers, the x-ray topography of thin crystal surface layers, creation of the elements of x-ray optics: the multiple-wave monochromators, high-energy-resolution monochromators and backscattering resonators. The creation of the later ones is still in its beginning stage and could find their development in the near future.
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Transition-edge-sensor (TES) microcalorimeters have the potential to become powerful new detectors at synchrotron light sources. A TES microcalorimeter is a thin superconducting film, electrically biased in its resistive transition. Heat deposited by an incident photon increases the temperature and resistance of the TES. The resulting pulsed decrease in the device current, amplified by a Superconducting Quantum Interference Device (SQUID) amplifier, is used to measure the energy of the photon. TESs have both the high energy resolution associated with wavelength dispersive instruments and the broadband response of energy-dispersive detectors. TESs have achieved about 2 eV (FWHM) energy resolution at 6 keV, and about 25 eV resolution at 100 keV. In addition, although most development has focused on photon detection, TESs are excellent energy-dispersive detectors of any other particle type, including electrons, atoms, and alpha particles.

Single TES pixels have inherent drawbacks, including small collecting area (from ~100 um – 1 mm on a side), and slow response (the maximum count rate per pixel is ~100 Hz for designs with the highest energy resolution). However, the recent development of two-dimensional arrays has allowed systems with much higher overall count rates and collecting areas. Arrays of TESs are now being developed for a variety of applications, including synchrotron applications, x-ray fluorescence for SEM materials-analysis, gamma-ray spectroscopy of U- and Pu-containing materials for nuclear nonproliferation, and millimeter and submillimeter-wave power detection for astronomy.

In this talk, I will review the state of the field, and then discuss the tradeoffs important for a synchrotron TES spectrometer among count rate, energy resolution, and collecting area.
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Low dimensional quantum systems which display collective singlet or spin gap behaviour are of great topical interest due to novelty of the ground states they display. However, while there are many instances of quasi one dimensional spin ladder or chain compounds, there are relatively few good quasi two dimensional experimental examples. SrCu2(BO3)2 is an unusual quantum spin system with a 2D arrangement of spin-1/2 Cu dimers, known to possess a collective singlet ground state. This compound is thought to be the first experimental realisation of the Shastry-Sutherland model. One aspect of the study of SrCu2(BO3)2 for which there is a little information is the influence of impurities on the nature of the singlet ground state. This is due to the relative difficulty of growing high quality single crystals of doped SrCu2(BO3)2. There is much interest in such studies due to the remarkable phenomena associated with doping other quasi-two dimensional copper-oxide quantum magnets, with high-temperature superconductivity being the best appreciated example. In this talk I will discuss the neutron scattering studies of single crystals of doped SrCu2-xMgx(BO3)2 and Sr1-xLaxCu2(BO3)2 and compare these results to our neutron scattering measurements on pure SrCu2(BO3)2. Particular emphasis is placed on the lifetimes of the one-triplet excitations as well as the existence of the in-gap spin excitations in the presence of Mg and La impurities.
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The RIXS cross section is complicated because the resonant contribution generally involves correlation between more than two particles. To date, theoretical studies of the RIXS cross section have mostly been limited to model dependent calculations. Working in the limits of a local, strong (or weak), and short-lived core-hole potential, Ament and co-workers [1] were able to show that, in these limits, the RIXS cross section can be factored into a resonant prefactor that depends on the incident and scattered-photon energies and the dynamic structure factor. It is therefore important to test whether this theory can be applied to real systems or not, and delineate any necessary conditions for the applicability of this theory. We present a systematic comparison of the RIXS spectra and the dielectric loss functions in various copper oxides: Bi₂CuO₄, CuGeO₃, Sr₂Cu₃O₄Cl₂, La₂CuO₄, and Sr₂CuO₂Cl₂. We measured the RIXS spectrum of each sample and extracted a response function that does not depend on the incident energy. This response function is compared with the optical dielectric loss function, measured using spectroscopic ellipsometry on the same sample. Dielectric loss-function data from published EELS studies are also used to augment the optical data. We show that overall energy loss dependence of the RIXS response function is in good agreement with the optical dielectric loss function over a wide energy range for all samples. In particular, the agreement is excellent for the local systems Bi2CuO4 and CuGeO3, suggesting that the RIXS response is intimately related to the dynamic structure factor and thus to the charge density-density correlation function in these materials. On the other hand, additional low-energy spectral features are observed for the corner-sharing two-dimensional copper oxides such as La₂CuO₄ and Sr₂CuO₂Cl₂, indicating that nonlocal nature of intermediate states may play an important role in such compounds.

[1] L. J. P. Ament, F. Forte, and J. van den Brink, Phys. Rev. B 75, 115118 (2007).
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Extremely short pulses of light provide a new paradigm in low-adverse-impact micromachining of materials. Because the process employs new physics in the interaction of light with matter, features can be written in materials with little or no Heat-Affected-Zone (HAZ), splatter, microcracks, recast layer or delamination. Most important is the technology’s ability to nanostructure materials in a highly repeatable and deterministic manner in a direct-write format. Examples will be shown, and present and future applications will be discussed.
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Biological macro/supramolecules ranging from DNA, proteins and viruses have gained substantial attention as inorganic materials synthesis templates over the past two decades. A large array of nanometer scale materials from particles to wires have been synthesized for a variety of applications in nanoelectronics, biomedical imaging, catalysis and energy. Of particular interest are viruses, which offer attractive templating platforms due to their precise dimensions and robust structures conferred by nature.

Our research is mainly focused on exploiting several unique structural, chemical and biological properties of genetically modified Tobacco Mosaic Virus (TMV) as nanotemplates for biosensor and nanocatalyst fabrication. Specifically, TMV is a biologically derived nanotube with 18nm diameter, 300nm length and 4nm inner channel, and consists of 2130 identical coat proteins helically wrapped around a 6.4 kb single strand genomic mRNA. Due to its safety, precise dimensions and extraordinary stability, TMV has been employed for nanowire and inorganic nanoparticle synthesis in a number of studies. Particularly, we harness TMV’s intriguing self-assembly mechanism and small genetic modification for nucleic acid hybridization based assembly, covalent conjugation of small molecules and readily controllable palladium nanoparticle synthesis. Through fluorescence and confocal microscopy and in-depth characterization studies via Atomic Force Microscopy (AFM) and Grazing Incidence Small Angle X-ray Scattering (GISAXS), we envision to address critical challenges in high throughput biosensing and to gain fundamental understanding of nanoparticle growth kinetics. In this presentation, our recent progress in the fabrication of hierarchically assembled viral-synthetic hybrid microparticles and catalytic reaction studies with palladium nanoparticle-assembled TMV chips will also be highlighted.
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New results for fs-laser excited semiconductor crystals probed by ultrashort x-ray pulses excited by a laser produced x-ray plasma-source will be presented. Contribution of fast electronic response, such as electronic pressure and electron diffusion as well as relaxation of the excited semiconductor, such as Ge and InSb will be discuss and compared to simulations. Further the temporal evolution of the laser induced metal-semiconductor phase transition, probed by optical reflectometry and x-ray diffraction of the rare earth compound samarium sulphide will be presented and discussed.
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In strongly correlated electron systems with degenerate orbitals, orbitons are predicted to exist. This collective degree of freedom has so far not been observed uncontroversially. The hallmark of collective excitations is dispersion. To observe the orbiton dispersion, the rapidly developing technique of Resonant Inelastic X-ray Scattering (RIXS) is especially well suited. We analyze RIXS spectra with two theoretical models: one where lattice distortions dominate the orbital dynamics and the other where orbital fluctuations dominate. A comparison of the theories with recent experimental data on YTiO₃ suggests the presence of orbitons.
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A substantial effort in detector development has taken place in the last decade at the Paul Scherrer Institute, Switzerland’s largest national research center. The development yielded the widely known Pilatus and Mythen detectors, based on solid state sensors coupled to CMOS read-out chips, which are operated in single photon counting mode. Pilatus and Mythen detectors are commercially available by the spin-off company DECTRIS Ltd and more than 40 systems are successfully operating at various synchrotron radiation facilities around the world, including the APS. A short profile of the company and its products will be given.

The talk focuses on new opportunities and research results obtained with Pilatus Detectors at the Swiss Light Source, where several systems are in use.

The Pilatus 6M with an active area of 43 × 45 cm² detector is in stable, routine operation at the high resolution diffractometer of the PX beamline X06SA since June 18, 2007. Diffraction data are stored in CBF format and processed with XDS, mosflm or d*trek.

For the users new opportunities open up:

• The 4ms readout time enables continuous shutter-free data acquisition, which doesn’t require any synchronization and is thus the fastest possible data collection mode
• The noise free counting improves the signal-to-noise ratio and allows to record low exposure data sets
• The dynamic range of 20bits enables simultaneous collection of low and high resolution data
• The 12.5 Hz frame rate allows to measure high redundancy data-sets, to conduct time resolved experiments and to minimize radiation damage at room temperature
• With the adjustable energy threshold parasitic fluorescent scattering is suppressed which allows to collect very weak diffraction data, e.g. diffuse scattering

Based on fine-phi slicing experiments with cubic insulin and lysozyme optimal data collection modes are discussed. Counting detectors require careful optimization of data collection and beamline parameters, their influence on the R-Factors are analyzed.

Two examples of systematic research studies are presented:

1. Can radiation damage at room temperature be reduced by faster data acquisition?
2. What is the optimal dose fractionation for a given total dose?

An example for a novel structure solution based on high redundancy measurements is shown. At the cSAXS beamline X12SA, a Pilatus 2M (25 × 29 cm²) detector is used for scanning SAXS experiments. The method is explained as well as some scientific results.
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Split-pair pulse magnets for x-ray diffraction studies in high magnetic fields have been developed in conjunction with synchrotron x-ray beams at the beamline BL19LXU of SPring-8. The magnet consists of coaxial two coils which are made by winding CuAg wire up to 16 layers. The magnet has four windows with a slit width of 3 mm for passage of the x-ray beam. Recently, we performed x-ray diffraction experiments on 2 dimensional orthogonal dimer compound SrCu2(BO3)2 up to 40 T at 1.5 K. We find a negative lattice deformation in the lattice constant, a, with increasing magnetic field. The change in the lattice constant scales with the magnetization curve. We propose the Cu2+-O2--Cu2+ angular dependence of the nearest neighbor interaction in the dimer as a driving force of the lattice contraction. The details of the instrumentation and some experimental results will be presented.
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Structural changes of molecular systems triggered by electronic excitations play an important role for the functionality of biological systems, light-harvesting chemical systems and, last but not least, in the rational design of synthetic structures mimicking biological systems which convert chemical energy to motion. Pulsed X-ray sources such as storage rings provide a new stroboscopic tool, often complementary to laser-based techniques, to probe not only the electronic excitations but also the structural response of molecules. Some examples of laser-initiated X-ray spectroscopy and wide angle x-ray scattering will demonstrate the strength of these techniques which presently find its limitations due to limited photon flux and time-resolution. Alternative detection mechanisms, including optoelectronic techniques, and improved beamline concepts will be presented which have the potential to overcome these obstacles resulting in time resolution of about 1ps. The talk will show how the objectives of the user community and the mandate of the funding agencies are correlated with these technical and programmatic developments.
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The European XFEL will provide short coherent X-ray pulses with an extreme peak power of about 20 GW. Up to 3000 of such pulses can be delivered in a pulse train of 0.6 ms. The challenge for the X-ray optics is to survive these extreme power loads and also conserve the almost perfect wavefront coming from the X-ray laser. After a short update on the actual status of the European XFEL Project, an overview on R&D issues in the area of X-ray optics is presented.
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The water-gas shift (WGS) reaction (CO+H₂O→CO₂+H₂) plays an important role in fuel processing for polymer electrolyte membrane (PEM) fuel-cell applications. The hydrogen in the reformate gas is upgraded by removal of the carbon monoxide, which is a major poison of the anode catalysts in current PEM fuel cells. Active shift catalysts that are also stable under the operating conditions of practical fuel-cell systems are under intense study.¹ Nanostructured Au-CeO₂ holds a prominent position,² and this catalyst exploits the strong interaction of ceria with finely dispersed and stabilized gold atoms and clusters on the surface of ceria.³ Furthermore, gold-doped iron oxide catalysts have been found equally active to gold-doped ceria and more stable for the WGS reaction at temperatures higher than 250°C.⁴ The catalytic performance of the above WGS catalysts is significantly dependent upon their specific surface structures, especially around the active metal sites. In both Au-CeO₂ and Au-FeO_x systems, atomically dispersed gold strongly bound on the support oxide catalyze the WGS reaction.⁴ Based on the H₂-TPR and EXAFS (Au L-III edge) results, the gold species in the used catalysts after the WGS reaction can be fully redispersed.⁵ Particularly, a strong correlation between the WGS activity and the shape (rod, cube or polyhedron) of the supported ceria has been revealed for the Au-CeO₂ catalysts. Gold deposited on CeO₂ {110} surface shows the best catalytic performance.⁶ The conclusion can be extended to other metal-oxide catalysts, such as Cu-CeO₂, or reactions (methanol steam reforming) in fuel cells.

References
[1] W. Deng, M. Flytzani-Stephanopoulos, Angew. Chem. Int. Ed. 45 (2006) 2285.
[2] Q. Fu, A. Weber, M. Flytzani-Stephanopoulos, Catal. Lett. 77 (2001) 87.
[3] Q. Fu, H. Saltsburg, M. Flytzani-Stephanopoulos, Science 301 (2003) 935.
[4] W. Deng, C. Carpenter, N. Yi, M. Flytzani-Stephanopoulos, Top. Catal. 44 (2007) 199.
[5] W. Deng, A. I. Frenkel, R. Si, M. Flytzani-Stephanopoulos, J. Phys. Chem. C 112 (2008) 12834.
[6] R. Si, M. Flytzani-Stephanopoulos, Angew. Chem. Int. Ed. 47 (2008) 2884.
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I will discuss recent results on conversion of Ti:S laser pulses into ultrafast mid-ir (~0.1eV) to X-ray (keV) photon bunches, or into electron bunches (1 MeV-100 MeV). Our work with fs RGAs/MPAs/OPAs was concentrated on mid-infrared efficiency/pulse profile enhancement, on pulse shaping and amplification [1]. I will discuss in detail the laser system for AWA accelerator photoinjector , similar to system at UCI for X-ray pump-probe, and on laser-plasma wakefield accelerator (TUHFF), [2-4]. 10 Hz amplified laser system at AWA enables pulse stretching to 18 ps and generation of e-pulse replicas on 0.1-1 ns time scale. Home-built table-top TUHFF accelerator work included [1-4] (i) electron pulse stability enhancement; (ii) pulse shaping and optimization; (iii) EO sampling; (iv) pulse radiolysis experiments with ~1 ps resolution [6].

[1]. O. J. Korovyanko, R. Rey-de-Castro, C. G. Elles, R. A. Crowell, and Y. Li Proc. SPIE 6100, 61000Q (2006).
[2] D. A. Oulianov, O. J. Korovyanko, R. A. Crowell, D. J. Gosztola, I. A. Shkrob, R. C. Rey-de-Castro, and C. G. Elles, ibid. 6101, 610126 (2006).
[3] D. A. Oulianov, Y. Li, Robert A. Crowell, I. A. Shkrob, D. J. Gozstola, O. J. Korovyanko, and R. C. Rey-de-Castro ibid. 5920, 592002 (2005).
[4]. D.A. Oulianov, R.A. Crowell, I.A. Shkrob, D.J. Gosztola, I.A.Shkrob, O. J. Korovyanko, and R.C. Rey-de-Castro, J. Appl. Physics 101, 053102 (2007).

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Phonon anomalies can be defined as deviations of phonon dispersions from predictions of balls-and-springs models of lattice dynamics. Most these anomalies result from electron-phonon coupling and can be understood using band theory. Phonon anomalies in cuprates, and iron pnictides recently observed in these systems by inelastic X-ray scattering (IXS) are very different in that they are unexpected from band theory. In the cuprates, phonon anomalies at some wavevectors that do not appear in band-theory-based calculations have been reported for some time. I will review these results and also will present some new IXS results for the Hg-based system. Iron pnictides show a completely different behavior: Dispersions of some branches agree well with band-theory calculations whereas other complete branches are softened by about 20%. One theme that ties together these diverse effects is strong coupling between magnetic and charge degrees of freedom.
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Adaptive optics (AO) is widely spread in the visible light applications. Using its proprietary technology, ALPAO has developed new type of deformable mirrors for variety of applications, including astronomy, vision science, etc. After an overview of the use of AO in the above applications, we will focus on our ongoing efforts to extend the technology to x-ray applications. We will review the principle of the deformable mirror and we will show, with a basic demo setup, how our innovative technology might be used to precisely control the shape of deformable mirrors. Perspectives in the field of adaptive optics will be presented.
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Structural changes during deformation in solution- and gel-spun polyacrylonitrile (PAN) fibers prepared with multi- and single-wall carbon nanotubes (CNTs), and vapor-grown carbon nano-fibers were investigated using SAXS/WAXS during in-situ deformation, both below and above the glass transition temperature (Tg) of PAN, at the Argonne Photon Source. Ordered crystalline structure of PAN and the effects of nanoparticles on the morphology/structure of PAN were studied with WAXS. The modulus of the fibers is enhanced not just because the CNTs are significantly stiffer than PAN, but also because CNTs facilitate the orientation of the PAN crystals during deformation and increasing the load transferred to the PAN crystals at temperatures < Tg. Reversible helix to zigzag conformational change along with the reduction of inter-chain spacing and increase of axial repeat were observed. These conformational changes were much larger in gel-spun fibers than in solution-spun fibers, indicating more effective load transfer in gel-spun fibers.

Fibers in general have a hierarchical structure and the structure units at length scales larger than those at the molecular level also affect the mechanical properties. SAXS can be used to understand the morphological changes on the scale of 10-100 nm, and these scattering can be analyzed in elliptical coordinates. The equatorial scattering from gel-spun fiber was characterized with power-law and can be defined as porous system. The gel-spun PAN was surface fractal while gel-spun PAN with single-wall nanotubes is mass-fractal. The scattering from solution-spun fibers mostly arises from the voids and fibrils and is characterized with diamond-shaped pattern. The narrow, intense, equatorial high-q streak is attributed to the highly oriented scattering entities that increase in orientation during deformation, whereas the near-circular low-q scattering could be due to large, isotropic structures that do not respond to deformation. The data suggest that large scale (10-100 nm) deformation does occur, and as such influence the properties of the fiber.
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We developed the femtosecond transient absorption spectrometer at NIH and the picosecond time-resolved X-ray diffraction at BioCARS to watch a protein as it functions. The spectrometer makes it possible to identify the optimal photoexcitation protocol for protein samples and reveal their complicated kinetics occurring over a broad range of times spanning from femtosecond to seconds. The micro-focusing capability allows single crystals as small as ~30 microns in size to be studied. Time-resolved absorbance spectra were analyzed by a global fitting method. Recently we developed the infrastructure for the time-resolved X-ray diffraction methods with 100-ps time resolution on the BioCARS (ID14B) at the Advanced Photon Source. X-ray source was improved to have higher flux and single pulse isolation became capable in the standard operating mode of the APS (24 bunch). The 5-mJ picosecond laser system (Spectra Physics) and beam transport optics have been installed and can deliver ~35ps broadly tunable laser pulses to the sample.
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High temperature superconducting cuprites are intrinsically inhomogeneous due to the dopant atoms. In addition to contributing carriers to the CuO2 planes, the dopants inherently introduce local disorder into the systems. With X-ray diffuse scattering technique, we studied the dopant-induced local structural distortions in two cuprate compounds: La_1.92Sr_0.08CuO₄ and YBa₂Cu₃O_6.92. On both compounds, strong anisotropic diffuse scattering from the strain fields induced by the dopants were observed. In La_1.92Sr_0.08CuO₄, quantitative analysis shows that the local structural distortion near the randomly distributed Sr dopants is strong and of the order of 0.01 angstroms. In YBa₂Cu₃O_6.92, the oxygen vacancies behave in a complex way. They cluster to form kinetically limited 4-unit-cell superlattice with q₀ = (0.25, 0, 0), along the shorter Cu-Cu bonds. This corresponds to the presence of O-ordered "ORTHO-IV" phase patches in the YBa₂Cu₃O₇ matrix. The "ORTHO-IV" phase patches consist of large anisotropic displacements of Cu, Ba, and O atoms, respectively. Furthermore, modeling of the total diffuse scattering reveals a secondary lattice modulation along the 1-D Cu-O chains to reside only within the O-ordered "ORTHO-IV" phase patches with a wavevector q₁=(0, 0.21, 0), which is consistent with the Fermi-Surface nesting vector, (0, 2kF~0.22, 0), for the chains, according to positron annihilation spectroscopy measurements, photoemission results and band structure calculations.
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The dynamics of polymers and confined fluids have been studied by using the single-molecule sensitive technique of fluorescence correlation spectroscopy (FCS). Experiments were conducted by attaching fluorescent dyes directly to polymer coils or by introducing free dyes directly into the solution/film. Research topics that will be covered include: polymer conformation change near the critical point of a binary solvent, comparing the activation energy of an ultrathin fluid film to the bulk, and measuring the diffusion of gold colloids in entangled and unentangled polymer melts. In all cases, information at the molecular level has been obtained through optical measurements of fluorescent dye/gold colloid diffusion. Recent experiments involving the time-resolved ellipsometric study of polymer films near the glass transition will also be discussed.
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The evolving demands of our modern society fuel a drive to develop innovative materials for advanced technological and industrial applications. Pivotal to the rational design of next generation materials optimized for real world applications, is the comprehensive and fundamental understanding of the key structural features underlying the functional behavior. Here we present the application of in-situ structural characterization methods, based on pair distribution functional analysis and powder diffraction, to probe the complex and often disordered structural features underlying the properties of a several functional material systems including negative thermal expansion, guest-binding in porous hosts and high pressure phase transitions.
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The target compounds for this study include AA′BB′O_6-xF_x. Materials with over 20 different combinations of cations were synthesized, but the only stable phases found were (A=K, A′=Sr, Ba, Pb, B=Sc and B′= Nb, Ta). XRD results show these materials are cubic with the space group Pm-3m, however electron diffraction shows some degree of Sc/Ta ordering. In PbKScTaO₅F, electron diffraction shows diffuse scattering indicating correlated movement of the cations in the <111> plane in real space. These materials are insulators with dielectric constants from 70 to 150. The properties of the oxyfluorides differ from those of their oxide counterpart in both their structure and dielectric constant.
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Los Alamos National Laboratory operates an international pulsed field science facility for the National Science Foundation through a National High Magnetic Field Laboratory subcontract. The mission of this endeavor is to provide the highest pulsed magnetic fields for scientific research.

Pulsed magnetic field technology offers a venue whereby solenoid magnets can now generate millisecond-scale nondestructive pulses at field intensities up to:

1. 50 T with a modest 0.25 MJ to 1 MJ capacitor bank infrastructure
2. 65 T to 75 T with a 1.5 MJ to 4 MJ capacitor bank infrastructure
3. 85 T to 90 T with a hybrid generator and capacitor bank infrastructure.

The pulsed field facility staff has extensive experience operating and developing magnet systems in all of the above regimes. Pulsed magnet technology has evolved significantly over the last decade due to advances in materials, engineering understanding, and experience. The results of this work are improvements in maximum magnetic field, magnet recovery time, reliability or magnet lifetime, and an understanding of the nature of fault behavior in pulsed magnets.

A review of the key aspects of pulsed magnet operations and developments will be presented. The latter half the talk will focus on the conceptual development of pulsed split coil technology for optical beam lines to better refine and develop our understanding of the functional requirements for such systems at the APS facility.
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In high-pressure science, accurate measurements of materials’ pressure-volume relations are crucial to obtain the EoS of materials. For amorphous and liquid-state materials, there was not a satisfactory method providing accurate volume/mass density measurements under high pressure. In this work, we proposed to employ tomography to measure the mass density of the materials under high-pressure studies. We have developed a specific algorithm to process tomography data from which accurate mass density can be obtained. The proposed method has been applied to amorphous Se system (a-Se). The measured pressure-volume relation of a-Se helps to solve a long standing enigma of anomalous phase behavior of Se at about 10 GPa.
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The dependence of electron-phonon coupling (EPC) on Fermi momentum is clearly observed by angle-resolved photoemission spectroscopy (ARPES) as an anisotropic mass enhancement factor, 1, for the isotropic (circular) Be(0001) G surface state. The value of 1 for bulk beryllium (Be) is 0.24; while the average value of 1 for the Be(0001) surface state on the circular Fermi surface is 0.9 (~3.75 times the value of the bulk Be). The values of 1 are found to have local maximum around G - M (~1.1) and G - K (~0.9) directions with a minimum (~0.6) located about 10 degrees away from the G - K direction. Given the isotropic nature of the electronic surface state, the anistropic EPC has to originate from the non-anisotropic matrix element coupling the isotropic electrons to the anisotropic surface phonon dispersion.
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