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Friday, May 24, 2013

Pat Clancy
University of Toronto

"Resonant X-ray Studies of Sr2Ir1-xRhxO4: Exploring Magnetism in Doped Iridates"

Abstract: The physics of iridium-based transition metal oxides, or iridates, has recently sparked significant interest due to the potential for exotic electronic and magnetic ground states driven by strong spin-orbit coupling effects. One of the most striking examples of this spin-orbit-induced behavior can be found in Sr2IrO4, a layered perovskite compound which is believed to be the first experimental realization of a jeff=1/2 spin-orbital Mott insulator. Intriguing similarities between Sr2IrO4 and La2CuO4, the parent compound of the high-Tc cuprates, have also led to speculation that it may be possible to induce superconductivity in this system through perturbations such as chemical doping. We have used a combination of resonant magnetic x-ray scattering (RMXS), resonant inelastic x-ray scattering (RIXS), and x-ray absorption spectroscopy (XAS) techniques to investigate the magnetic properties of the doped system Sr2Ir1-xRhxO4. These measurements allow us to probe the effect of Rh-doping on the magnetic structure, phase diagram, and characteristic excitations of Sr2IrO4, providing fundamental information about the role of quenched Rh impurities in this material.

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Friday, May 17, 2013

Eric Dooryhee
NSLS II

"Description and Performance calculations of the X-ray powder diffraction wiggler beamline at NSLS-II"

Abstract: The X-ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source II is a multi-purpose high-energy X-ray diffraction beamline, offering rapid acquisition, high angular resolution and in situ capabilities on the same instrument. XPD is designed to combine high Q-space resolution diffraction measurements and high real-space resolution pair distribution function (PDF) measurements. This talk will discuss the optical design and the calculated performance (SHADOW) of the XPD beamline, featuring two operation modes.
The x-ray source is a damping wiggler simulated by the SRW code. A filter system is designed to optimize the photon flux as well as to reduce the heat load on the first optics. The XPD beamline intends to use a cryo-cooled, sagittally bent double-Laue monochromator for providing a focused and adjustable monochromatic beam with optimized flux at the sample over a large energy range (30–70 keV). The optimization and the optical properties of the vertical focusing mirror are also discussed. Finally, the instrumental resolution function of the XPD beamline is described in an analytical method.

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Friday, May 10, 2013

Conal Murray, Research Staff Member
IBM T.J. Watson Research Center

Presentation: (PDF)
Jean Jordan-Sweet Presentation: (PDF)

"Diffraction-based Analysis of The Mechanics of Nanoelectronics"

Abstract: As the demands of high-performance computing technology require increasingly smaller dimensions and greater device density, new types of designs and materials must be incorporated. One such aspect involves the piezoresistive response of strained semiconductor structures, in which mobility can be tailored by imparting the appropriate strain within the regions of current flow. The interaction between devices and their environment necessitates in-situ characterization at a submicron resolution. Synchrotron-based x-ray microbeam diffraction provides us with the ability to directly map deformation within crystalline materials non-destructively. Examples of strain generated within silicon-on-insulator regions will be shown to compare the efficacy of different stressor schemes. Increased device density also poses new challenges to back-end of line metallization, in which stress can exacerbate reliability issues, such as voiding. By combining conventional and glancing-incidence X-ray diffraction, we can investigate the depth-dependent strain generated within metallization structures, where the interplay between plasticity and the constraint imposed on these features will be illustrated.

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Friday, May 3, 2013

Ismail Cevdet Noyan
Columbia University

"Forward Modeling of X-ray Scattering From Crystalline Materials"

Abstract: Accurate, nondestructive, structural characterization of crystalline materials with sizes spanning many length scales is an important and popular research area. X-ray diffraction techniques are well suited for such characterization and are routinely employed. There are, however, quite a few implicit assumptions in these techniques that can cause erroneous results if they are not satisfied. In this seminar we will discuss the basic formalisms that can be used to generate synthetic X-ray diffraction data from crystalline samples with sizes spanning the range from several nm to several cm. The accuracies of these formalisms are then investigated by comparing the refined parameters obtained from traditional analysis codes with the structural parameters used to compute the (inputted) scattering profiles and with experimental results.

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****NOTE: This seminar will be on THURSDAY at 1:00 p.m.****

****This is the 2nd Seminar of the Day.****

Thursday, May 2, 2013

Hermann Schmickler
CERN

"CERN XODR Project"

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****NOTE: This seminar is at 10:00 a.m.****

Thursday, May 2, 2013

Colwyn Gulliford
Cornell University

"CHARACTERIZATION OF THE BEAM DYNAMICS IN THE CORNELL ENERGY RECOVERY LINAC INJECTOR PROTOTYPE"

Abstract: As the electron sources in high energy accelerators are pushed to deliver increasing brightness beams, significant physics and technological challenges must be overcome. To do so requires both a theoretical and computational understanding of the basic physics governing the dynamics in these sources, and experimental demonstration of the feasibility of the conclusions draw from this understanding. In this work we present the a simple theoretical treatment of the linear dynamics in the combined RF and solenoid fields used in the generation of electron bunches at their source. Additionally, a method for computing and characterizing the asymmetric beam focusing caused by the input power couplers of RF cavities is presented. Incorporating these methods, we then present the results of a detailed study of the six dimensional phase space of the electron beam in the Cornell ERL injector prototype, a high-brightness, high repetition rate DC gun based photoinjector. In particular, the emittance results obtained in this work set a new record low for DC based photoinjectors producing comparable bunch charges, and demonstrate that DC gun based photoinjectors are capable of producing high-brightness beams which surpass the quality in storage rings by a factor 20 when the energy spread in each type of machine is considred.

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****NOTE: This seminar is at 12:30 p.m.****

Friday, April 26, 2013

Thorsten Kuerzeder
S-DALINAC, Technische Universitaet Darmstadt

"New Injector Cryostat-Module Based on 3 GHz SRF cavities for the S-DALINAC"

Abstract:  For the S-DALINAC a new cryostat-module has been built to replace the actual injector module. Like before it houses two 20 cell elliptical niobium cavities cooled by a helium bath at 2 K. They are operated at a frequency of 3 GHz and used to accelerate electron beams with gradients up to 7 MV/m. A report on the fabrication of the cavity and the cryostat-module will be given.

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****NOTE: 4:00 PM, Room 120, Physical Sciences Bldg****

****This is a joint seminar with BioPhysics.****

Friday, April 19, 2013

Elspeth Garman
University of Oxford

"New Developments for Structural Biology"

Abstract:  New challenges are arising in structural biology research as attempts are made to investigate larger and more complex biological macromolecular assemblies, and to obtain significant numbers of three-dimensional structures of insoluble membrane proteins. Concomitant with this effort is a necessity to develop new biophysical methodology for the field so that previously intractable problems become possible, and to optimize the quality of the information obtained. This talk will focus on two areas on which we have been working recently: the problem of radiation damage during X-ray crystallographic structure determination, which can result in failed experiments and compromised biological results [1], and the development of a low throughput microPIXE (Proton Induced X-ray Emission) method for uniquely identifying bound metals in macromolecules [2] to a high throughput pipeline which allows this technique to be used as a routine biophysical analysis tool.

[1] Radiation damage in macromolecular crystallography: what is it and why should we care? EF Garman Acta. Cryst. D. 2010, D66, 339–351
[2] Elemental analysis of proteins by microPIXE. EF Garman & GW.Grime. Progress in Biophysics and Molecular Biology 2005, 89/2, 173-205.

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Friday, April 12, 2013

Michael Niemack
Cornell University

"Measuring the Cosmic Microwave Background with Superconducting Sensors"

Presentation: (PDF)

Abstract: Measurements of the cosmic microwave background (CMB) anisotropies are helping to address fundamental questions about dark energy, dark matter, and the GUT-scale physics of inflation. We will review some of the science motivation for recent and future measurements of the CMB, and then will discuss developments in superconducting detector and SQUID measurement technologies that are enabling electromagnetic measurements spanning eight orders of magnitude in wavelength with unprecedented precision.

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****NOTE: Day & Time****

Wednesday, April 3, 2013 11:00 AM Jim Kerby and Genfa Wu APS

Presentation 1: (PDF)
Presentation 2: (PDF)

"The APS Upgrade"

Abstract:  The Advanced Photon Source at Argonne National Laboratory currently provides hard X-rays to approximately 5000 users per year. The Upgrade is a BES Project to open new avenues of research at the APS, including timing studies using short pulse x-rays down to 2 picoseconds in length. This is accomplished using a deflecting cavity system (SPX), a challenging superconducting RF system which will allow users to have these short pulse x-rays in two sectors of the APS. The talk will give an overview of the APS upgrade as well as specifics on the design and status of the SPX system.

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Friday, March 29, 2013

Ashish Chainani
RIKEN Harima Institute at SPring-8

Presentation: (PDF) (PowerPoint)
Additional Info: (PDF) (PowerPoint)

"Hard X-ray Photoelectron Spectroscopy of Correlated Materials"

Abstract:  Synchrotron based hard x-ray photoelectron spectroscopy (HAXPES ; hn = 6-8 keV) has undergone remarkable developments in the last few years. In this talk, we first discuss the salient features of the instrumentation that made it possible to carry out temperature and doping dependent studies of core-levels and valence band spectroscopy using HAXPES. Experimental results on colossal magneto-resistive manganese oxides and high-T_c copper oxides which played a valuable role in distinguishing bulk electronic states compared to conventional soft x-ray PES will be described. Using a variety of examples, we show the importance of using HAXPES to study metal-insulator transitions, mixed-valency, dilute magnetic films, buried interfaces and multilayers, as well as the recoil effect in PES. In combination with model calculations, HAXPES provides a quantification of covalency and metallicity in strongly correlated ‘d’ and ‘f’-electron systems. We conclude with a brief discussion of recent HAXPES studies from the literature, including core-level dichroism and angle-resolved PES, and plans to study low vapor pressure liquids and gels, which suggest that HAXPES is poised for tremendous growth.

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Friday, March 22, 2013

Eric Miller
Tufts University

"Options for Model-Based Information Processing"

Abstract: Characterization of a region of space from indirectly acquired sensor data is a problem encountered in fields including medical and geophysical imaging, security screening, nondestructive evaluation, materials science, and others. Central to extracting from the data the information most relevant to the underlying application is the use of computational models for the physics of the associated sensing technologies. In this talk we discuss a number of options concerning how these models can be used. We focus first on traditional inverse methods in which these models are employed "in the loop." Here we discuss both pixel based methods but also how geometric parameterizations of objects of interest can be better suited as the basis for image formation. In many cases however, an image is not the final processing objective. Rather, one may seek from the data summary statistics, specific features, or other high level information. While these quantities can certainly be obtained by post processing an image, there are various reasons why one may want to bypass image formation or, due to the nature of how the data are acquired, image formation may not even be possible. In these cases, we discuss how a computational physical model can be employed as a central element in a machine learning approach to directly mapping data into the parameters of interest. Concrete examples of both the inverse method as well as the machine learning approach will be provided from the speaker's recent work in the characterization of subsurface zones contaminated by Dense Non-aqueous Phase Liquids (DNAPLs) using combinations of geophysical and hydrological data.

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Friday, March 15, 2013

Robert Suter
Carnegie Mellon University

"Near-field High Energy Diffraction Microscopy: Requirements and Capabilities"

Abstract:  Near-field High Energy Diffraction Microscopy (nf-HEDM) is a synchrotron based x-ray technique that images and spatially resolves diffraction from polycrystalline samples in three dimensions. High performance computing facilities are used to reconstruct the crystallographic orientation field on the ~2 micron length and 0.1 degree orientation scale. Cubic millimeter volumes can be measured in ~12 hours. Being non-destructive in hard materials (ex., metals, ceramics, composites), nf-HEDM provides the ability to track microstructural responses to a wide variety of materials processing conditions. These capabilities have been developed through a collaboration between the staff at Advanced Photon Source beamline 1-ID and my group at Carnegie Mellon. The talk will describe beamline requirements, data collection protocols, and forward modeling reconstructions of microstructural orientation fields. Examples of three dimensional data sets that follow material responses to thermal and mechanical treatments will be given. On-going developments at the APS that point towards increased experimental throughput will be described as will be efforts to allow combined orientation and elastic strain state mapping.

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****NOTE: Day & Time****

Thursday, March 14, 2013
1:00 PM

Tsukasa Miyajima
KEK

"Construction and commissioning plan of compact ERL injector in KEK"

Abstract:  In KEK Photon Factory (PF), a synchrotron light source based on an Energy Recovery Linac with 3 GeV beam energy is planned as a future light source. As a test accelerator toward the ERL light source, compact ERL (cERL) is being constructed to develop key components, such as a DC photo cathode gun and superconducting RF cavity systems, and to demonstrate the generation of high current and high brightness electron beam and the energy recovery. Before the beam commissioning of the whole cERL, the beam commissioning of the cERL injector, which consists of the photo cathode DC gun, the injector super conducting cavities and a beam diagnostic line, is scheduled from April to June 2013 in order to demonstrate the injector performance. Toward the injector commissioning, the construction of the cERL injector is in its final stage. As the DC gun, a photo cathode DC gun system developed by JAEA, which achieved 550 kV operation with segmented ceramic insulator, was employed. In the injector commissioning, the maximum beam current and the beam kinetic energy are about 1 micro ampere and 5 MeV, respectively. The first goal of the commissioning is to verify the hardware performances, and the second goal is to establish beam tuning method to transport the beam without any loss to the dump, which is located on the end of the diagnostic line. After the injector commissioning, the construction of the whole ERL beam line is scheduled on this summer, and its commissioning is scheduled from this autumn.

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Friday, March 8, 2013

Mike Wall
Los Alamos National Lab

"Diffuse X-Ray Scattering to Model Protein Motions"

Abstract:  Crystallographers have produced hundreds of thousands of beautiful protein structure models. Unfortunately these models ignore the rich dynamics of real roteins. Mean electron density maps derived from Bragg peak intensities can provide evidence for the existence of alternative conformations in a crystal, but do not constrain the way that transitions among these conformations are correlated across the whole protein structure. Fortunately we can say something about the correlations using diffuse X-ray scattering, which accounts for about half of the scattered X-rays in a typical protein crystallography experiment. As crystallographers face the limits of the information that can be extracted from Bragg peaks, diffuse scattering holds the potential to further improve protein crystal structures, to yield insight into functionally important motions, and to validate molecular dynamics simulations of proteins.

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Friday, March 1, 2013

Jianqi Zhang
Technische Universität München

"Structural evolution in diblock copolymer thin films during solvent vapor treatment investigated by GISAXS"

Abstract:  Well-ordered structures formed by self-assembling of diblock copolymer have attracted increasing interest due to the potential applications, such as the preparation of nanoporous films, nanostructured templates, ultrahigh-density data storage media, and biosensors. However, the thin film preparation by solvent-casting or spin-coating does not necessarily lead to the equilibrium structure. Often, only short-ranged order is observed in the self-assembled structures, which hampers many applications. Methods to bring the samples into their equilibrium states and to reduce the number of defects are thus highly desirable. Vapor treatment with solvents is a commonly used technique to anneal defects in block copolymer thin films. In the present work, thin films of lamellar poly(styrene-b-butadiene) (P(S-b-B)) diblock copolymers with different internal structure were studied to elucidate the mechanisms of structural changes induced by solvent vapor treatment by means of grazing-incidence small angle X-ray scattering (GISAXS). Herein, films with random oriented lamellae and films with perpendicular lamellae will be focused on.

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****NOTE: Day & Time****

Tuesday, February 26, 2013
4:00 PM

Ronaldo Bellazzini
INFN Pisa - Italy and PIXIRAD Imaging Counters SRL

Presentation:  (PDF)

"A new X-Ray imaging system based on Chromatic Photon Counting technology"

Abstract:  The continuous progress and scale reduction of the CMOS technology has allowed the realization of pixellated VLSI ASICs with direct integration in each pixel of electronics of increased complexity and functionality. By coupling a custom, large area, pixellated ASIC with a thin pixellated CdTe crystal, we have realized an innovative X-ray imaging sensor(PIXIRAD) based on Chromatic Photon Counting technology. The detector is able to count and separate in energy the X-ray photons transmitted or scattered by the sample and converted in each pixel of the CdTe sensor to produce two 'color' images in a single exposure. The individual block of the PIXIRAD imaging system is buttable on two opposite sides and consists of a solid-state sensor (CdTe) connected to the readout ASIC by flip-chip bonding (bump bonding) technique. The system therefore has a hybrid architecture in which the sensor and readout electronics are manufactured and processed separately. The CdTe sensor is a 650 micron thick Schottky type diode with electrons collection on the pixels. It is characterized by a very low leakage current at 400-500 V bias-voltage. The pixels are arranged on a hexagonal matrix at 60 micron pitch and match an analogous pattern on the top metal layer of the VLSI ASIC. In depth testing of several configurations of the PIXIRAD imaging system has been performed. Modules of one, two, four and eight PIXIRAD tile units with almost zero dead space between the blocks have been assembled. They are able to deliver extremely clear and highly detailed X-ray images for medical, biological, industrial and scientific applications in the energy range 1-100 keV. Images are obtained at high count rate. ' Color' X-ray images from 3X2.5 to 25X25cm2 area have been obtained. Photon counting, color mode and a very high spatial resolution (more than 10 l.p./mm at MTF50) allow to have an optimal ratio between image quality and absorbed dose.

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Friday, February 22, 2013

Tsuyoshi Tajima
LANL

"R&D for Superconducting RF Structures at Los Alamos"

Abstract: Current research at Los Alamos will be presented. It includes MgB2 coating toward very high accelerating gradient cavities and hydro-formed seamless copper cavities coated with a Nb film using a technique called coaxial energetic deposition in collaboration with KEK and Alameda Applied Sciences Corporation. If time permits, a development of superconducting photonic band gap structures for high current applications will also be shown.

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****NOTE: Day & Time****

Alvin Acerbo, Photon Sciences Directorate
Brookhaven National Laboratory

"Simultaneous Synchrotron-based SAXS and WAXS Microbeam Mapping of Bone Tissues"

Abstract:  The influence of the macroscale material properties of bone on its mechanical competence have been extensively investigated, but less is known about the contributions of the nanoscale material properties of bone. Although research suggests that these nanoscale properties are affected by aging of the tissue, mechanical strains and stresses, and diseases such as osteoporosis, little is known about how pharmaceutical treatments against osteoporosis might affect these nanoscale properties. To investigate how the nanoscale organization of collagen fibrils and structure of mineral crystals are modulated by osteoporosis and drug treatments, cortical bone samples from healthy, osteoporotic and drug treated rats were investigated using simultaneous synchrotron-based Small and Wide Angle X-ray Scattering (SAXS/WAXS) microbeam mapping. This talk will discuss how this technique is used to yield information about the organizational properties of the collagen network as well as the size and shape of the mineral phase. Further, bone samples from the same animals were analyzed using reflection-based Fourier Transform Infrared Imaging (FTIRI) to map the chemical composition of the bone cortices, thereby providing complementary information about the collagen and mineral components of the tissue. Results from both the X-ray scattering and FTIRI experiments showed that osteoporosis and drug treatments predominantly affected the mineral phase, but more subtle changes to the collagen organization were also noted. These results provide a further understanding of how osteoporosis and drug treatments affect the nanoscale properties of bone that ultimately contribute to bone quality and fracture risk, and may lead to more potent drug treatments to recuperate diseased bone and compromised bone quality.

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CANCELLED

****NOTE: Day & Time****

Tuesday, Jan 22, 2013
9AM

Alvin Acerbo, Photon Sciences Directorate
Brookhaven National Laboratory

"Simultaneous Synchrotron-based SAXS and WAXS Microbeam Mapping of Bone Tissues"

Abstract:  The influence of the macroscale material properties of bone on its mechanical competence have been extensively investigated, but less is known about the contributions of the nanoscale material properties of bone. Although research suggests that these nanoscale properties are affected by aging of the tissue, mechanical strains and stresses, and diseases such as osteoporosis, little is known about how pharmaceutical treatments against osteoporosis might affect these nanoscale properties. To investigate how the nanoscale organization of collagen fibrils and structure of mineral crystals are modulated by osteoporosis and drug treatments, cortical bone samples from healthy, osteoporotic and drug treated rats were investigated using simultaneous synchrotron-based Small and Wide Angle X-ray Scattering (SAXS/WAXS) microbeam mapping. This talk will discuss how this technique is used to yield information about the organizational properties of the collagen network as well as the size and shape of the mineral phase. Further, bone samples from the same animals were analyzed using reflection-based Fourier Transform Infrared Imaging (FTIRI) to map the chemical composition of the bone cortices, thereby providing complementary information about the collagen and mineral components of the tissue. Results from both the X-ray scattering and FTIRI experiments showed that osteoporosis and drug treatments predominantly affected the mineral phase, but more subtle changes to the collagen organization were also noted. These results provide a further understanding of how osteoporosis and drug treatments affect the nanoscale properties of bone that ultimately contribute to bone quality and frac ture risk, and may lead to more potent drug treatments to recuperate diseased bone and compromised bone quality.