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Sample records for electron backscattering diffraction

  1. Bragg's Law diffraction simulations for electron backscatter diffraction analysis

    International Nuclear Information System (INIS)

    Kacher, Josh; Landon, Colin; Adams, Brent L.; Fullwood, David

    2009-01-01

    In 2006, Angus Wilkinson introduced a cross-correlation-based electron backscatter diffraction (EBSD) texture analysis system capable of measuring lattice rotations and elastic strains to high resolution. A variation of the cross-correlation method is introduced using Bragg's Law-based simulated EBSD patterns as strain free reference patterns that facilitates the use of the cross-correlation method with polycrystalline materials. The lattice state is found by comparing simulated patterns to collected patterns at a number of regions on the pattern using the cross-correlation function and calculating the deformation from the measured shifts of each region. A new pattern can be simulated at the deformed state, and the process can be iterated a number of times to converge on the absolute lattice state. By analyzing an iteratively rotated single crystal silicon sample and recovering the rotation, this method is shown to have an angular resolution of ∼0.04 o and an elastic strain resolution of ∼7e-4. As an example of applications, elastic strain and curvature measurements are used to estimate the dislocation density in a single grain of a compressed polycrystalline Mg-based AZ91 alloy.

  2. Application of electron back-scatter diffraction to texture research

    International Nuclear Information System (INIS)

    Randle, V.

    1996-01-01

    The application of electron back-scatter diffraction (EBSD) to materials research is reviewed. A brief history of the technique is given, followed by a description of present-day operation. The methodology of 'microtexture', i.e. spatially specific orientations, is described and recent examples of its application using EBSD are given, in particular to interstitial-free steel processing, growth of phases in a white iron and grain boundary phenomena in a superplastic alloy. The advantages and disadvantages of EBSD compared to use of X-rays for texture determination are discussed in detail

  3. Lattice constant measurement from electron backscatter diffraction patterns

    DEFF Research Database (Denmark)

    Saowadee, Nath; Agersted, Karsten; Bowen, Jacob R.

    2017-01-01

    Kikuchi bands in election backscattered diffraction patterns (EBSP) contain information about lattice constants of crystallographic samples that can be extracted via the Bragg equation. An advantage of lattice constant measurement from EBSPs over diffraction (XRD) is the ability to perform local ...

  4. Electron backscatter diffraction: Strategies for reliable data acquisition and processing

    International Nuclear Information System (INIS)

    Randle, Valerie

    2009-01-01

    In electron backscatter diffraction (EBSD) software packages there are many user choices both in data acquisition and in data processing and display. In order to extract maximum scientific value from an inquiry, it is helpful to have some guidelines for best practice in conducting an EBSD investigation. The purpose of this article therefore is to address selected topics of EBSD practice, in a tutorial manner. The topics covered are a brief summary on the principles of EBSD, specimen preparation, calibration of an EBSD system, experiment design, speed of data acquisition, data clean-up, microstructure characterisation (including grain size) and grain boundary characterisation. This list is not meant to cover exhaustively all areas where EBSD is used, but rather to provide a resource consisting of some useful strategies for novice EBSD users.

  5. A Dictionary Approach to Electron Backscatter Diffraction Indexing.

    Science.gov (United States)

    Chen, Yu H; Park, Se Un; Wei, Dennis; Newstadt, Greg; Jackson, Michael A; Simmons, Jeff P; De Graef, Marc; Hero, Alfred O

    2015-06-01

    We propose a framework for indexing of grain and subgrain structures in electron backscatter diffraction patterns of polycrystalline materials. We discretize the domain of a dynamical forward model onto a dense grid of orientations, producing a dictionary of patterns. For each measured pattern, we identify the most similar patterns in the dictionary, and identify boundaries, detect anomalies, and index crystal orientations. The statistical distribution of these closest matches is used in an unsupervised binary decision tree (DT) classifier to identify grain boundaries and anomalous regions. The DT classifies a pattern as an anomaly if it has an abnormally low similarity to any pattern in the dictionary. It classifies a pixel as being near a grain boundary if the highly ranked patterns in the dictionary differ significantly over the pixel's neighborhood. Indexing is accomplished by computing the mean orientation of the closest matches to each pattern. The mean orientation is estimated using a maximum likelihood approach that models the orientation distribution as a mixture of Von Mises-Fisher distributions over the quaternionic three sphere. The proposed dictionary matching approach permits segmentation, anomaly detection, and indexing to be performed in a unified manner with the additional benefit of uncertainty quantification.

  6. Orientation effects on indexing of electron backscatter diffraction patterns

    International Nuclear Information System (INIS)

    Nowell, Matthew M.; Wright, Stuart I.

    2005-01-01

    Automated Electron Backscatter Diffraction (EBSD) has become a well-accepted technique for characterizing the crystallographic orientation aspects of polycrystalline microstructures. At the advent of this technique, it was observed that patterns obtained from grains in certain crystallographic orientations were more difficult for the automated indexing algorithms to accurately identify than patterns from other orientations. The origin of this problem is often similarities between the EBSD pattern of the correct orientation and patterns from other orientations or phases. While practical solutions have been found and implemented, the identification of these problem orientations generally occurs only after running an automated scan, as problem orientations are often readily apparent in the resulting orientation maps. However, such an approach only finds those problem orientations that are present in the scan area. It would be advantageous to identify all regions of orientation space that may present problems for automated indexing prior to initiating an automated scan, and to minimize this space through the optimization of acquisition and indexing parameters. This work presents new methods for identifying regions in orientation space where the reliability of the automated indexing is suspect prior to performing a scan. This methodology is used to characterize the impact of various parameters on the indexing algorithm

  7. Comparative study of macrotexture analysis using X-ray diffraction and electron backscattered diffraction techniques

    International Nuclear Information System (INIS)

    Serna, Marilene Morelli

    2002-01-01

    The macrotexture is one of the main characteristics in metallic materials, which the physical properties depend on the crystallographic direction. The analysis of the macrotexture to middles of the decade of 80 was just accomplished by the techniques of Xray diffraction and neutrons diffraction. The possibility of the analysis of the macrotexture using, the technique of electron backscattering diffraction in the scanning electronic microscope, that allowed to correlate the measure of the orientation with its location in the micro structure, was a very welcome tool in the area of engineering of materials. In this work it was studied the theoretical aspects of the two techniques and it was used of both techniques for the analysis of the macrotexture of aluminum sheets 1050 and 3003 with intensity, measured through the texture index 'J', from 2.00 to 5.00. The results obtained by the two techniques were shown reasonably similar, being considered that the statistics of the data obtained by the technique of electron backscatter diffraction is much inferior to the obtained by the X-ray diffraction. (author)

  8. Bragg's Law diffraction simulations for electron backscatter diffraction analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kacher, Josh, E-mail: jkacherbyu@gmail.com [Department of Mechanical Engineering, Brigham Young University, 455B Crabtree Technology Building, Provo, UT 84602 (United States); Landon, Colin; Adams, Brent L.; Fullwood, David [Department of Mechanical Engineering, Brigham Young University, 455B Crabtree Technology Building, Provo, UT 84602 (United States)

    2009-08-15

    In 2006, Angus Wilkinson introduced a cross-correlation-based electron backscatter diffraction (EBSD) texture analysis system capable of measuring lattice rotations and elastic strains to high resolution. A variation of the cross-correlation method is introduced using Bragg's Law-based simulated EBSD patterns as strain free reference patterns that facilitates the use of the cross-correlation method with polycrystalline materials. The lattice state is found by comparing simulated patterns to collected patterns at a number of regions on the pattern using the cross-correlation function and calculating the deformation from the measured shifts of each region. A new pattern can be simulated at the deformed state, and the process can be iterated a number of times to converge on the absolute lattice state. By analyzing an iteratively rotated single crystal silicon sample and recovering the rotation, this method is shown to have an angular resolution of {approx}0.04{sup o} and an elastic strain resolution of {approx}7e-4. As an example of applications, elastic strain and curvature measurements are used to estimate the dislocation density in a single grain of a compressed polycrystalline Mg-based AZ91 alloy.

  9. Time-lapse misorientation maps for the analysis of electron backscatter diffraction data from evolving microstructures

    NARCIS (Netherlands)

    Wheeler, J.; Cross, A.; Drury, M.; Hough, R.M.; Mariani, E.; Piazolo, S.; Prior, D.J.

    2011-01-01

    A “time-lapse misorientation map” is defined here as a map which shows the orientation change at each point in an evolving crystalline microstructure between two different times. Electron backscatter diffraction data from in situ heating experiments can be used to produce such maps, which then

  10. Electron backscatter diffraction characterization of laser-induced periodic surface structures on nickel surface

    Energy Technology Data Exchange (ETDEWEB)

    Sedao, Xxx, E-mail: sedao.xxx@gmail.com [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France); Maurice, Claire [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 St-Etienne (France); Garrelie, Florence; Colombier, Jean-Philippe; Reynaud, Stéphanie [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France); Quey, Romain; Blanc, Gilles [Laboratoire Georges Friedel, Ecole Nationale Supérieure des Mines, 42023 St-Etienne (France); Pigeon, Florent [Laboratoire Hubert Curien, Université Jean Monnet, 42000 St-Etienne (France)

    2014-05-01

    Graphical abstract: -- Highlight: •Lattice rotation and its distribution in laser-induced periodic surface structures (LIPSS) and the subsurface region on a nickel substrate are revealed using electron backscatter diffraction (EBSD). -- Abstract: We report on the structural investigation of laser-induced periodic surface structures (LIPSS) generated in polycrystalline nickel target after multi-shot irradiation by femtosecond laser pulses. Electron backscatter diffraction (EBSD) is used to reveal lattice rotation caused by dislocation storage during LIPSS formation. Localized crystallographic damages in the LIPSS are detected from both surface and cross-sectional EBSD studies. A surface region (up to 200 nm) with 1–3° grain disorientation is observed in localized areas from the cross-section of the LIPSS. The distribution of the local disorientation is inhomogeneous across the LIPSS and the subsurface region.

  11. Microstructural evolution in adiabatic shear bands of copper at high strain rates: Electron backscatter diffraction characterization

    International Nuclear Information System (INIS)

    Tang Lin; Chen Zhiyong; Zhan Congkun; Yang Xuyue; Liu Chuming; Cai Hongnian

    2012-01-01

    The microstructural evolution of adiabatic shear bands in annealed copper with different large strains at high strain rates has been investigated by electron backscatter diffraction. The results show that mechanical twinning can occur with minimal contribution to shear localization under dynamic loading. Elongated ultrafine grains with widths of 100–300 nm are observed during the evolution of the adiabatic shear bands. A rotational dynamic recrystallization mechanism is proposed to explain the formation of the elongated ultrafine grains. - Highlights: ► The microstructural evolution of ASB is studied by electron backscatter diffraction. ► Twinning can occur in ASB while the contribution to shear localization is slight. ► Elongated ultrafine grains are observed during the evolution process of ASB. ► A possible mechanism is proposed to explain the microstructure evolution of ASB.

  12. Time-lapse misorientation maps for the analysis of electron backscatter diffraction data from evolving microstructures

    International Nuclear Information System (INIS)

    Wheeler, J.; Cross, A.; Drury, M.; Hough, R.M.; Mariani, E.; Piazolo, S.; Prior, D.J.

    2011-01-01

    A 'time-lapse misorientation map' is defined here as a map which shows the orientation change at each point in an evolving crystalline microstructure between two different times. Electron backscatter diffraction data from in situ heating experiments can be used to produce such maps, which then highlight areas of microstructural change and also yield statistics indicative of how far different types of boundary (with different misorientations) have moved.

  13. Quantitative microstructure characterization of self-annealed copper films with electron backscatter diffraction

    DEFF Research Database (Denmark)

    Pantleon, Karen; Gholinia, A.; Somers, Marcel A. J.

    2008-01-01

    Electron backscatter diffraction (EBSD) was applied to analyze cross sections of self-annealed copper electrodeposits, for which earlier the kinetics of self-annealing had been investigated by in-situ X-ray diffraction (XRD). The EBSD investigations on the grain size, grain boundary character...... and crystallographic texture of copper films with different thicknesses essentially supplement results from in-situ XRD. Twin relations between neighboring grains were identified from the orientation maps and the observed twin chains confirm multiple twinning in copper electrodeposits as the mechanism...

  14. In situ electron backscattered diffraction of individual GaAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Prikhodko, S.V. [Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095 (United States)], E-mail: sergey@seas.ucla.edu; Sitzman, S. [Oxford Instruments America, Concord, MA 01742 (United States); Gambin, V. [Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States); Kodambaka, S. [Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095 (United States)

    2008-12-15

    We suggest and demonstrate that electron backscattered diffraction, a scanning electron microscope-based technique, can be used for non-destructive structural and morphological characterization of statistically significant number of nanowires in situ on their growth substrate. We obtain morphological, crystal phase, and crystal orientation information of individual GaAs nanowires in situ on the growth substrate GaAs(1 1 1) B. Our results, verified using transmission electron microscopy and selected area electron diffraction analyses of the same set of wires, indicate that most wires possess a wurtzite structure with a high density of thin structural defects aligned normal to the wire growth axis, while others grow defect-free with a zincblende structure. The demonstrated approach is general, applicable to other material systems, and is expected to provide important insights into the role of substrate structure on nanowire structure on nanowire crystallinity and growth orientation.

  15. Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

    Energy Technology Data Exchange (ETDEWEB)

    Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburg, PA (United States); Dickey, Elizabeth C. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC (United States)

    2017-02-15

    A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO{sub 3} single crystals. Further, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system. - Highlights: • A novel technique to directly polar domains utilizing EBSD is demonstrated. • The technique relies on dynamical diffraction simulations of EBSD patterns. • The technique is demonstrated by mapping 180° domains in LiNbO{sub 3} single crystals. • Further application of this technique to other materials classes is discussed.

  16. Accurate measurement of the orientation relationship of lath martensite and bainite by electron backscatter diffraction analysis

    International Nuclear Information System (INIS)

    Miyamoto, G.; Takayama, N.; Furuhara, T.

    2009-01-01

    A new method to determine the orientation relationship between martensite and bainite with the parent austenite is developed based on electron backscatter diffraction analysis. This method can determine the orientation relationship accurately without the presence of retained austenite, and is applicable to lath martensite and bainite in low-alloyed carbon steels. The angles between close-packed directions are about 3 o for lath martensite regardless of the carbon content, while the angles between close-packed planes become smaller with increasing carbon content.

  17. High resolution electron backscatter diffraction (EBSD) data from calcite biominerals in recent gastropod shells.

    Science.gov (United States)

    Pérez-Huerta, Alberto; Dauphin, Yannicke; Cuif, Jean Pierre; Cusack, Maggie

    2011-04-01

    Electron backscatter diffraction (EBSD) is a microscopy technique that reveals in situ crystallographic information. Currently, it is widely used for the characterization of geological materials and in studies of biomineralization. Here, we analyze high resolution EBSD data from biogenic calcite in two mollusk taxa, Concholepas and Haliotis, previously used in the understanding of complex biomineralization and paleoenvironmental studies. Results indicate that Concholepas has less ordered prisms than in Haliotis, and that in Concholepas the level of order is not homogenous in different areas of the shell. Overall, the usefulness of data integration obtained from diffraction intensity and crystallographic orientation maps, and corresponding pole figures, is discussed as well as its application to similar studies. © 2010 Elsevier Ltd. All rights reserved.

  18. Assessing strain mapping by electron backscatter diffraction and confocal Raman microscopy using wedge-indented Si

    International Nuclear Information System (INIS)

    Friedman, Lawrence H.; Vaudin, Mark D.; Stranick, Stephan J.; Stan, Gheorghe; Gerbig, Yvonne B.; Osborn, William; Cook, Robert F.

    2016-01-01

    The accuracy of electron backscatter diffraction (EBSD) and confocal Raman microscopy (CRM) for small-scale strain mapping are assessed using the multi-axial strain field surrounding a wedge indentation in Si as a test vehicle. The strain field is modeled using finite element analysis (FEA) that is adapted to the near-indentation surface profile measured by atomic force microscopy (AFM). The assessment consists of (1) direct experimental comparisons of strain and deformation and (2) comparisons in which the modeled strain field is used as an intermediate step. Direct experimental methods (1) consist of comparisons of surface elevation and gradient measured by AFM and EBSD and of Raman shifts measured and predicted by CRM and EBSD, respectively. Comparisons that utilize the combined FEA–AFM model (2) consist of predictions of distortion, strain, and rotation for comparison with EBSD measurements and predictions of Raman shift for comparison with CRM measurements. For both EBSD and CRM, convolution of measurements in depth-varying strain fields is considered. The interconnected comparisons suggest that EBSD was able to provide an accurate assessment of the wedge indentation deformation field to within the precision of the measurements, approximately 2×10"−"4 in strain. CRM was similarly precise, but was limited in accuracy to several times this value. - Highlights: • We map strain by electron backscatter diffraction and confocal Raman microscopy. • The test vehicle is the multi-axial strain field of wedge-indented silicon. • Strain accuracy is assessed by direct experimental intercomparison. • Accuracy is also assessed by atomic force microscopy and finite element analyses. • Electron diffraction measurements are accurate; Raman measurements need refinement.

  19. Assessing strain mapping by electron backscatter diffraction and confocal Raman microscopy using wedge-indented Si

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Lawrence H.; Vaudin, Mark D.; Stranick, Stephan J.; Stan, Gheorghe; Gerbig, Yvonne B.; Osborn, William; Cook, Robert F., E-mail: robert.cook@nist.gov

    2016-04-15

    The accuracy of electron backscatter diffraction (EBSD) and confocal Raman microscopy (CRM) for small-scale strain mapping are assessed using the multi-axial strain field surrounding a wedge indentation in Si as a test vehicle. The strain field is modeled using finite element analysis (FEA) that is adapted to the near-indentation surface profile measured by atomic force microscopy (AFM). The assessment consists of (1) direct experimental comparisons of strain and deformation and (2) comparisons in which the modeled strain field is used as an intermediate step. Direct experimental methods (1) consist of comparisons of surface elevation and gradient measured by AFM and EBSD and of Raman shifts measured and predicted by CRM and EBSD, respectively. Comparisons that utilize the combined FEA–AFM model (2) consist of predictions of distortion, strain, and rotation for comparison with EBSD measurements and predictions of Raman shift for comparison with CRM measurements. For both EBSD and CRM, convolution of measurements in depth-varying strain fields is considered. The interconnected comparisons suggest that EBSD was able to provide an accurate assessment of the wedge indentation deformation field to within the precision of the measurements, approximately 2×10{sup −4} in strain. CRM was similarly precise, but was limited in accuracy to several times this value. - Highlights: • We map strain by electron backscatter diffraction and confocal Raman microscopy. • The test vehicle is the multi-axial strain field of wedge-indented silicon. • Strain accuracy is assessed by direct experimental intercomparison. • Accuracy is also assessed by atomic force microscopy and finite element analyses. • Electron diffraction measurements are accurate; Raman measurements need refinement.

  20. Electron backscatter diffraction as a useful method for alloys microstructure characterization

    Energy Technology Data Exchange (ETDEWEB)

    Klimek, Leszek; Pietrzyk, Bozena

    2004-11-17

    Microstructure examination of cast Co-Cr-Mo alloy is presented in this paper. The surface morphology and chemical composition of the alloy were investigated by means of scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX). An identification of alloy phases was carried out using electron backscatter diffraction (EBSD). Two different kinds of precipitates in metallic matrix were found. They were identified as MC and M{sub 23}C{sub 6} type of carbides in Co-lattice solid solution. The advantages and limits of the EBSD method are described. It is presented that EBSD, as excellent tool for phase identification, is a valuable supplementary method for materials research.

  1. Notes on representing grain size distributions obtained by electron backscatter diffraction

    International Nuclear Information System (INIS)

    Toth, Laszlo S.; Biswas, Somjeet; Gu, Chengfan; Beausir, Benoit

    2013-01-01

    Grain size distributions measured by electron backscatter diffraction are commonly represented by histograms using either number or area fraction definitions. It is shown here that they should be presented in forms of density distribution functions for direct quantitative comparisons between different measurements. Here we make an interpretation of the frequently seen parabolic tales of the area distributions of bimodal grain structures and a transformation formula between the two distributions are given in this paper. - Highlights: • Grain size distributions are represented by density functions. • The parabolic tales corresponds to equal number of grains in a bin of the histogram. • A simple transformation formula is given to number and area weighed distributions. • The particularities of uniform and lognormal distributions are examined

  2. Practical considerations in the calculation of orientation distribution functions from electron back-scattered diffraction patterns

    International Nuclear Information System (INIS)

    Bowen, A.W.

    1994-01-01

    Using model data sets for the Brass orientation, the importance of scatter width, angular accuracy and grain size and volume fraction on the sensitivity of the calculated Orientation Distribution Functions have been determined in order to highlight some of the practical considerations needed in the processing of experimental data from individual grain orientation measurements determined by the Electron Back-Scattered Diffraction technique. It is suggested that the most appropriate scatter width can be calculated from the maximum function height versus scatter width curve in order to accommodate variations in texture sharpness. The sensitivity of the ODF to careful sample preparation, mounting and pattern analysis, in order to keep errors in angular accuracy to 1 or less is demonstrated, as is the imperative need to correct for the size of grains, and their volume fractions. (orig.)

  3. Understanding deformation with high angular resolution electron backscatter diffraction (HR-EBSD)

    Science.gov (United States)

    Britton, T. B.; Hickey, J. L. R.

    2018-01-01

    High angular resolution electron backscatter diffraction (HR-EBSD) affords an increase in angular resolution, as compared to ‘conventional’ Hough transform based EBSD, of two orders of magnitude, enabling measurements of relative misorientations of 1 x 10-4 rads (~ 0.006°) and changes in (deviatoric) lattice strain with a precision of 1 x 10-4. This is achieved through direct comparison of two or more diffraction patterns using sophisticated cross-correlation based image analysis routines. Image shifts between zone axes in the two-correlated diffraction pattern are measured with sub-pixel precision and this realises the ability to measure changes in interplanar angles and lattice orientation with a high degree of sensitivity. These shifts are linked to strains and lattice rotations through simple geometry. In this manuscript, we outline the basis of the technique and two case studies that highlight its potential to tackle real materials science challenges, such as deformation patterning in polycrystalline alloys.

  4. Spatially resolved determination of lattice distortions in silicon nanostructures by means of electron-backscattering diffraction

    International Nuclear Information System (INIS)

    Krause, Michael

    2013-01-01

    In the submitted thesis, a novel combined approach of both focused ion beam (FIB) based target preparation and strain determination using electron backscatter diffraction (EBSD) in semiconductor nanostructures is presented. In the first part, a powerful cross-correlation algorithm for detecting small feature shifts within EBSD patterns and, consequently, determining the strain, is presented. The corresponding strain sensitivity is demonstrated using dynamically simulated diffraction patterns. Furthermore, novel procedures for automated pattern analysis are introduced. Results of systematic studies concerning the influence of ion species, ion energy and dose density on the surface quality of silicon surfaces are presented in the second part. For that matter, the assessment of surface amorphization and rippling is based on high resolution microstructural diagnostics (TEM, AFM, Raman) and molecular dynamics simulation. The high application potential of combined FIB preparation and strain analysis using EBSD is exemplarily demonstrated for a 60 nm thick sSOI-sample. The good agreement with established techniques like Raman spectroscopy and X-ray diffraction is also shown.

  5. On the optimum resolution of transmission-electron backscattered diffraction (t-EBSD)

    Energy Technology Data Exchange (ETDEWEB)

    Bremen, R. van; Ribas Gomes, D.; Jeer, L.T.H. de; Ocelík, V., E-mail: v.ocelik@rug.nl; De Hosson, J.Th.M.

    2016-01-15

    The work presented aims at determining the optimum physical resolution of the transmission-electron backscattered diffraction (t-EBSD) technique. The resolution depends critically on intrinsic factors such as the density, atomic number and thickness of the specimen but also on the extrinsic experimental set-up of the electron beam voltage, specimen tilt and detector position. In the present study, the so-called physical resolution of a typical t-EBSD set-up was determined with the use of Monte Carlo simulations and confronted to experimental findings. In the case of a thin Au film of 20 nm, the best resolution obtained was 9 nm whereas for a 100 nm Au film the best resolution was 66 nm. The precise dependence of resolution on thickness was found to vary differently depending on the specific elements involved. This means that the resolution of each specimen should be determined individually. Experimentally the median probe size of the t-EBSD for a 140 nm thick AuAg specimen was measured to be 87 nm. The first and third quartiles of the probe size measurements were found to be 60 nm and 118 nm. Simulation of this specimen resulted in a resolution of 94 nm which fits between these quartiles. - Highlights: • Intrinsic and extrinsic factors affecting resolution of t-EBSD are determined and characterized. • Distinction between resolutions of transmitted and detected electrons is determined. • The simulated results are confirmed experimentally on 140 nm thick AuAg foil.

  6. Effects of focused ion beam milling on electron backscatter diffraction patterns in strontium titanate and stabilized zirconia

    DEFF Research Database (Denmark)

    Saowadee, Nath; Agersted, Karsten; Bowen, Jacob R.

    2012-01-01

    This study investigates the effect of focused ion beam (FIB) current and accelerating voltage on electron backscatter diffraction pattern quality of yttria‐stabilized zirconia (YSZ) and Nb‐doped strontium titanate (STN) to optimize data quality and acquisition time for 3D‐EBSD experiments by FIB...

  7. Identification of phases in zinc alloy powders using electron backscatter diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Perez, Martin G. [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States); Kenik, Edward A. [Oak Ridge National Laboratory, 100 Bethel Valley Rd., Bldg. 4515, MS-6064, P.O. Box 2008, Oak Ridge, TN 37831 (United States); O' Keefe, Matthew J. [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States)]. E-mail: mjokeefe@umr.edu; Miller, F. Scott [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States); Johnson, Benedict [Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO 65409 (United States)

    2006-05-25

    Scanning electron microscopy and electron backscatter diffraction (EBSD) were used for the structural characterization of phases in Zn alloy powders. Commercial Zn alloy powders contained additions of <1000 ppm of Bi, In, Al or Mg. Bismuth and In have extremely low solubility in Zn and form intermetallic Bi-In compounds which segregate to the Zn grain boundaries. The Bi-In phases were <0.3 {mu}m in size, had low melting points, and were not abundant enough for EBSD analysis. Increasing the alloying additions 20-40-fold resulted in Bi-In phases >1 {mu}m that could be used for EBSD analysis for phase characterization. Deformation-free microstructures were obtained by mechanical polishing and ion milling. The Zn matrix was characterized as Zn via EBSD. A BiIn{sub 2} phase was identified in the powder microstructures via EBSD. An In phase with 8-9 wt.% Bi was identified using low voltage energy dispersive spectroscopy and closely matched the composition predicted by the Bi-In phase diagram.

  8. A preliminary electron backscattered diffraction study of sintered NdFeB-type magnets.

    Science.gov (United States)

    Lillywhite, S J; Williams, A J; Davies, B E; Harris, I R

    2002-03-01

    This paper reports, for the first time, the use of electron backscattered diffraction (EBSD) to study orientation in sintered NdFeB type magnets. The magnetic properties of NdFeB magnets are greatly improved if a strong crystallographic texture is firstly achieved, namely, the direction of the c-axis is along the direction of magnetization. A systematic survey of sample preparation techniques showed that samples that were mechanically polished and then etched gave the most reliable EBSD data. Analyses were made using both fully automated EBSD scans and by EBSD measurements taken after manual movement of the beam. The EBSD results are presented as secondary electron SEM micrographs, orientation images and 001 pole figures. For the selection of grains investigated, the deviation of the c-axis was shown to be between 10 degrees and 30 degrees from the ideal [001]//magnetization direction. It is demonstrated that EBSD is a valuable tool for characterizing the microstructure and texture relationships and for assessing the performance of the processing routes of NdFeB magnets.

  9. Electron backscatter diffraction applied to lithium sheets prepared by broad ion beam milling.

    Science.gov (United States)

    Brodusch, Nicolas; Zaghib, Karim; Gauvin, Raynald

    2015-01-01

    Due to its very low hardness and atomic number, pure lithium cannot be prepared by conventional methods prior to scanning electron microscopy analysis. Here, we report on the characterization of pure lithium metallic sheets used as base electrodes in the lithium-ion battery technology using electron backscatter diffraction (EBSD) and X-ray microanalysis using energy dispersive spectroscopy (EDS) after the sheet surface was polished by broad argon ion milling (IM). No grinding and polishing were necessary to achieve the sufficiently damage free necessary for surface analysis. Based on EDS results the impurities could be characterized and EBSD revealed the microsctructure and microtexture of this material with accuracy. The beam damage and oxidation/hydration resulting from the intensive use of IM and the transfer of the sample into the microscope chamber was estimated to be effect on the surface temperature. However, a cryo-stage should be used if available during milling to guaranty a heating artefact free surface after the milling process. © 2014 Wiley Periodicals, Inc.

  10. Plastic strain characterization in austenitic stainless steels and nickel alloys by electron backscatter diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Saez-Maderuelo, A., E-mail: alberto.saez@ciemat.es [CIEMAT, Av. Complutense, 22-28040 Madrid (Spain); Castro, L.; Diego, G. de [CIEMAT, Av. Complutense, 22-28040 Madrid (Spain)

    2011-09-01

    Stress corrosion cracking (SCC) is enhanced by cold work and causes many problems in components of the nuclear power plants. Besides, during manufacturing, installation, welding and service of the material, residual strains can be produced increasing the susceptibility to SCC. For this reason, it is important to characterize the degree of plastic strain due to dislocation accumulation in each crystal. Electron backscatter diffraction (EBSD), in conjunction with scanning electron microscope (SEM), has been a great advance in this field because it enables to estimate the plastic strain in a quick and easy way. Nevertheless, over the last few years, a lot of different mathematical expressions to estimate the plastic strain have appeared in the literature. This situation hinders the election of one of them by a novel scientist in this field. Therefore, in this paper some of the more common expressions used in the calculation of the angular misorientation have been presented and discussed in order to clarify their more important aspects. Then, using one of these expressions (average local misorientation), curves relating misorientation density with known levels of strain will be obtained for an austenitic stainless steel 304L and nickel base alloy 690, which have shown a linear behaviour that is in good agreement with results found in the literature. Finally, using curves obtained in previous steps, levels of plastic strain in a plate of nickel base alloy 600 welded with weld metal 182 were estimated between 8 and 10% for a high temperature mill annealing sample.

  11. Plastic strain characterization in austenitic stainless steels and nickel alloys by electron backscatter diffraction

    International Nuclear Information System (INIS)

    Saez-Maderuelo, A.; Castro, L.; Diego, G. de

    2011-01-01

    Stress corrosion cracking (SCC) is enhanced by cold work and causes many problems in components of the nuclear power plants. Besides, during manufacturing, installation, welding and service of the material, residual strains can be produced increasing the susceptibility to SCC. For this reason, it is important to characterize the degree of plastic strain due to dislocation accumulation in each crystal. Electron backscatter diffraction (EBSD), in conjunction with scanning electron microscope (SEM), has been a great advance in this field because it enables to estimate the plastic strain in a quick and easy way. Nevertheless, over the last few years, a lot of different mathematical expressions to estimate the plastic strain have appeared in the literature. This situation hinders the election of one of them by a novel scientist in this field. Therefore, in this paper some of the more common expressions used in the calculation of the angular misorientation have been presented and discussed in order to clarify their more important aspects. Then, using one of these expressions (average local misorientation), curves relating misorientation density with known levels of strain will be obtained for an austenitic stainless steel 304L and nickel base alloy 690, which have shown a linear behaviour that is in good agreement with results found in the literature. Finally, using curves obtained in previous steps, levels of plastic strain in a plate of nickel base alloy 600 welded with weld metal 182 were estimated between 8 and 10% for a high temperature mill annealing sample.

  12. Tackling pseudosymmetry problems in electron backscatter diffraction (EBSD) analyses of perovskite structures

    Science.gov (United States)

    Mariani, Elisabetta; Kaercher, Pamela; Mecklenburgh, Julian; Wheeler, John

    2016-04-01

    Perovskite minerals form an important mineral group that has applications in Earth science and emerging alternative energy technologies, however crystallographic quantification of these minerals with electron backscatter diffraction (EBSD) is not accurate due to pseudosymmetry problems. The silicate perovskite Bridgmanite, (Mg,Fe)SiO3, is understood to be the dominant phase in the Earth's lower mantle. Gaining insight into its physical and rheological properties is therefore vital to understand the dynamics of the Earth's deep interior. Rock deformation experiments on analogue perovskite phases, for example (Ca,Sr)TiO3, combined with quantitative microstructural analyses of the recovered samples by EBSD, yield datasets that can reveal what deformation mechanisms may dominate the flow of perovskite in the lower mantle. Additionally, perovskite structures have important technological applications as new, suitable cathodes for the operation of more efficient and environmentally-friendly solid oxide fuel cells (SOFC). In recent years they have also been recognised as a potential substitute for silicon in the next generation of photovoltaic cells for the construction of economic and energy efficient solar panels. EBSD has the potential to be a valuable tool for the study of crystal orientations achieved in perovskite substrates as crystal alignment has a direct control on the properties of these materials. However, perovskite structures currently present us with challenges during the automated indexing of Kikuchi bands in electron backscatter diffraction patterns (EBSPs). Such challenges are represented by the pseudosymmetric character of perovskites, where atoms are subtly displaced (0.005 nm to 0.05 nm) from their higher symmetry positions. In orthorhombic Pbnm perovskites, for example, pseudosymmetry may be evaluated from the c/a unit cell parameter ratio, which is very close to 1. Two main types of distortions from the higher symmetry structure are recognised: a

  13. Initial microstructural study of a Ce-La alloy using electron backscattered diffraction

    International Nuclear Information System (INIS)

    Scott, Thomas B.; Younes, Charles M.; Ling, Michael; Jones, Christopher P.; Nicholson, John A.; Heard, Peter J.; Jenkins, Roderick

    2011-01-01

    Research highlights: → First ever successful EBSD microstructural analysis of Ce-La alloy. → Successful preparation using electro-polishing in the open laboratory. → Equiaxed grains 20-40 μm in size dominate the microstructure, with random orientations, relatively straight grain boundary contacts and no evidence for crystal twinning. → All grains matched to a fcc γ-phase. → Problematic presence of entrapped oxide particles. - Abstract: To better understand and exploit the unique electronic and structural properties of f-block metals and their alloys it is perceived that an improved knowledge of the microstructural characteristics and phase changes as a function of temperature and pressure, is necessary. For other different types of metallic systems, the use of electron back-scattered diffraction (EBSD) is becoming a common practice in order to obtain detailed microstructural information, but this has, as yet, been very limited in case of f-block metals. Because of their extreme affinity to oxygen and rapid surface reaction, EBSD studies of this metal-category are very sparse with only one work published on cerium metal providing an example of technical hurdles for a prerequisite oxide-free metal surface. Specifically the need to remove the oxide by ion etching was considered essential to enable a successful EBSD analysis. The current work presents the results of a first attempt to characterise the microstructure of a Ce-La alloy using EBSD. It demonstrates that high quality diffraction patterns and crystal orientation maps can be successfully obtained following a carefully controlled preparation of the alloy surface in the open laboratory by applying a simple and reproducible electro-polishing procedure without a further need for ion etching in vaccuo.

  14. In situ electron backscatter diffraction investigation of recrystallization in a copper wire.

    Science.gov (United States)

    Brisset, François; Helbert, Anne-Laure; Baudin, Thierry

    2013-08-01

    The microstructural evolution of a cold drawn copper wire (reduction area of 38%) during primary recrystallization and grain growth was observed in situ by electron backscatter diffraction. Two thermal treatments were performed, and successive scans were acquired on samples undergoing heating from ambient temperature to a steady state of 200°C or 215°C. During a third in situ annealing, the temperature was continuously increased up to 600°C. Nuclei were observed to grow at the expense of the deformed microstructure. This growth was enhanced by the high stored energy difference between the nuclei and their neighbors (driving energy in recrystallization) and by the presence of high-angle grain boundaries of high mobility. In the early stages of growth, the nuclei twin and the newly created orientations continue to grow to the detriment of the strained copper. At high temperatures, the disappearance of some twins was evidenced by the migration of the incoherent twin boundaries. Thermal grooving of grain boundaries is observed at these high temperatures and affects the high mobile boundaries but tends to preserve the twin boundaries of lower energy. Thus, grooving may contribute to the twin vanishing.

  15. The effect of pattern overlap on the accuracy of high resolution electron backscatter diffraction measurements

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Vivian, E-mail: v.tong13@imperial.ac.uk [Department of Materials, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Jiang, Jun [Department of Materials, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Wilkinson, Angus J. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Britton, T. Ben [Department of Materials, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)

    2015-08-15

    High resolution, cross-correlation-based, electron backscatter diffraction (EBSD) measures the variation of elastic strains and lattice rotations from a reference state. Regions near grain boundaries are often of interest but overlap of patterns from the two grains could reduce accuracy of the cross-correlation analysis. To explore this concern, patterns from the interior of two grains have been mixed to simulate the interaction volume crossing a grain boundary so that the effect on the accuracy of the cross correlation results can be tested. It was found that the accuracy of HR-EBSD strain measurements performed in a FEG-SEM on zirconium remains good until the incident beam is less than 18 nm from a grain boundary. A simulated microstructure was used to measure how often pattern overlap occurs at any given EBSD step size, and a simple relation was found linking the probability of overlap with step size. - Highlights: • Pattern overlap occurs at grain boundaries and reduces HR-EBSD accuracy. • A test is devised to measure the accuracy of HR-EBSD in the presence of overlap. • High pass filters can sometimes, but not generally, improve HR-EBSD measurements. • Accuracy of HR-EBSD remains high until the reference pattern intensity is <72%. • 9% of points near a grain boundary will have significant error for 200nm step size in Zircaloy-4.

  16. Reconstruction of Laser-Induced Surface Topography from Electron Backscatter Diffraction Patterns.

    Science.gov (United States)

    Callahan, Patrick G; Echlin, McLean P; Pollock, Tresa M; De Graef, Marc

    2017-08-01

    We demonstrate that the surface topography of a sample can be reconstructed from electron backscatter diffraction (EBSD) patterns collected with a commercial EBSD system. This technique combines the location of the maximum background intensity with a correction from Monte Carlo simulations to determine the local surface normals at each point in an EBSD scan. A surface height map is then reconstructed from the local surface normals. In this study, a Ni sample was machined with a femtosecond laser, which causes the formation of a laser-induced periodic surface structure (LIPSS). The topography of the LIPSS was analyzed using atomic force microscopy (AFM) and reconstructions from EBSD patterns collected at 5 and 20 kV. The LIPSS consisted of a combination of low frequency waviness due to curtaining and high frequency ridges. The morphology of the reconstructed low frequency waviness and high frequency ridges matched the AFM data. The reconstruction technique does not require any modification to existing EBSD systems and so can be particularly useful for measuring topography and its evolution during in situ experiments.

  17. In situ electron backscatter diffraction (EBSD) during the compression of micropillars

    International Nuclear Information System (INIS)

    Niederberger, C.; Mook, W.M.; Maeder, X.; Michler, J.

    2010-01-01

    For the first time, in situ electron backscatter diffraction (EBSD) measurements during compression experiments by a modified nanoindenter on micron-sized single crystal pillars are demonstrated here. The experimental setup and the requirements concerning the compression sample are described in detail. EBSD mappings have been acquired before loading, under load and after unloading for consecutive compression cycles on a focused ion beam (FIB) milled GaAs micropillar. In situ EBSD allows for the determination of crystallographic orientation with sub-100 nm spatial resolution. Thereby, it provides highly localized information pertaining to the deformation phenomena such as elastic bending of the micropillar or the formation of deformation twins and plastic orientation gradients due to geometrically necessary dislocations. The most striking features revealed by in situ EBSD are the non-negligible amount of reversible (elastic) bending of the micropillar and the fact that deformation twinning and dislocation glide initiate where the bending is strongest. Due to this high spatial and orientation resolution, in situ EBSD measurements during micromechanical testing are demonstrated to be a promising technique for the investigation of deformation phenomena at the nano- to micro-scale.

  18. Electron backscatter diffraction studies of focused ion beam induced phase transformation in cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Jones, H.G., E-mail: helen.jones@npl.co.uk [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Day, A.P. [Aunt Daisy Scientific Ltd, Claremont House, High St, Lydney GL15 5DX (United Kingdom); Cox, D.C. [National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom); Advanced Technology Institute, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2016-10-15

    A focused ion beam microscope was used to induce cubic to hexagonal phase transformation in a cobalt alloy, of similar composition to that of the binder phase in a hardmetal, in a controlled manner at 0°, 45° and 80° ion incident angles. The cobalt had an average grain size of ~ 20 μm, allowing multiple orientations to be studied, exposed to a range of doses between 6 × 10{sup 7} and 2 × 10{sup 10} ions/μm{sup 2}. Electron backscatter diffraction (EBSD) was used to determine the original and induced phase orientations, and area fractions, before and after the ion beam exposure. On average, less phase transformation was observed at higher incident angles and after lower ion doses. However there was an orientation effect where grains with an orientation close to (111) planes were most susceptible to phase transformation, and (101) the least, where grains partially and fully transformed at varying ion doses. - Highlights: •Ion-induced phase change in FCC cobalt was observed at multiple incidence angles. •EBSD was used to study the relationship between grain orientation and transformation. •Custom software analysed ion dose and phase change with respect to grain orientation. •A predictive capability of ion-induced phase change in cobalt was enabled.

  19. Analysis of soft magnetic materials by electron backscatter diffraction as a powerful tool

    Directory of Open Access Journals (Sweden)

    David Schuller

    2018-04-01

    Full Text Available The current work demonstrates that electron backscatter diffraction (EBSD is a powerful and versatile characterization technique for investigating soft magnetic materials. The properties of soft magnets, e.g., magnetic losses strongly depend on the materials chemical composition and microstructure, including grain size and shape, texture, degree of plastic deformation and elastic strain. In electrical sheet stacks for e-motor applications, the quality of the machined edges/surfaces of each individual sheet is of special interest. Using EBSD, the influence of the punching process on the microstructure at the cutting edge is quantitatively assessed by evaluating the crystallographic misorientation distribution of the deformed grains. Using an industrial punching process, the maximum affected deformation depth is determined to be 200 - 300 μm. In the case of laser cutting, the affected deformation depth is determined to be approximately zero. Reliability and detection limits of the developed EBSD approach are evaluated on non-affected sample regions and model samples containing different indentation test bodies. A second application case is the investigation of the recrystallization process during the annealing step of soft magnetic composites (SMC toroids produced by powder metallurgy as a function of compaction pressure, annealing parameters and powder particle size. With increasing pressure and temperature, the recrystallized area fraction (e.g., grains with crystallographic misorientations 3°.

  20. Electron Backscatter Diffraction Studies on the Formation of Superlattice Metal Hydride Alloys

    Directory of Open Access Journals (Sweden)

    Shuli Yan

    2017-12-01

    Full Text Available Microstructures of a series of La-Mg-Ni-based superlattice metal hydride alloys produced by a novel method of interaction of a LaNi5 alloy and Mg vapor were studied using a combination of X-ray energy dispersive spectroscopy and electron backscatter diffraction. The conversion rate of LaNi5 increased from 86.8% into 98.2%, and the A2B7 phase abundance increased from 42.5 to 45.8 wt % and reduced to 39.2 wt % with the increase in process time from four to 32 h. During the first stage of reaction, Mg formed discrete grains with the same orientation, which was closely related to the orientation of the host LaNi5 alloy. Mg then diffused through the ab-phase of LaNi5 and formed the AB2, AB3, and A2B7 phases. Diffusion of Mg stalled at the grain boundary of the host LaNi5 alloy. Good alignments in the c-axis between the newly formed superlattice phases and LaNi5 were observed. The density of high-angle grain boundary decreased with the increase in process time and was an indication of lattice cracking.

  1. Experimental evidence concerning the significant information depth of electron backscatter diffraction (EBSD)

    Energy Technology Data Exchange (ETDEWEB)

    Wisniewski, Wolfgang, E-mail: wolfgang.w@uni-jena.de [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany); Saager, Stefan [Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, Winterbergstraße 28, 01277 Dresden (Germany); Böbenroth, Andrea [Fraunhofer Institute for the Microstructure of Materials and Systems IMWS, Walter-Huelse-Straße 1, 06120 Halle (Saale) (Germany); Rüssel, Christian [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)

    2017-02-15

    Experiments concerning the information depth of electron backscatter diffraction (EBSD) are performed on samples featuring an amorphous wedge on a crystalline substrate and a crystalline wedge on an amorphous substrate. The effects of the acceleration voltage and exemplary software settings on the ability to measure through an amorphous layer are presented. Changes in the EBSD-signal could be detected through a ≈142 nm thick layer of amorphous Si while orientation measurements could be performed through a ≈116 nm thick layer when using a voltage of 30 kV. The complexity of the information depth significant to a given EBSD-pattern and the multiple parameters influencing it are discussed. It is suggested that a “core information depth” is significant to high quality patterns while a larger “maximum information depth” becomes relevant when the pattern quality decreases or the sample is inhomogeneous within the information volume, i.e. in the form of partially crystalline materials or crystal layers in the nm scale. - Highlights: • Experimental evidence of the significant information depth of EBSD is presented. • Effects of the voltage and exemplary software settings are discussed. • Dependence of the significant information depth on the pattern quality is proposed. • The information depth may reach up to 142 nm in Si when using a voltage of 30 kV. • The information depth depends on the available technology.

  2. Microstructural characterization by electron backscatter diffraction of a hot worked Al-Cu-Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Cepeda-Jimenez, C.M., E-mail: cm.cepeda@cenim.csic.es [Department of Physical Metallurgy, CENIM, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain); Hidalgo, P.; Carsi, M.; Ruano, O.A.; Carreno, F. [Department of Physical Metallurgy, CENIM, CSIC, Av. Gregorio del Amo 8, 28040 Madrid (Spain)

    2011-03-25

    Research highlights: {yields} The most favourable conditions for hot workability have been determined. {yields} EBSD was employed to characterize the obtained microtexture and microstructure. {yields} The Al 2024 alloy torsion tested at 408 deg. C and 2.1 s{sup -1} showed maximum ductility. {yields} Solid solution and fine precipitates favour a fine microstructure at 408 deg. C. {yields} The increase in test temperature to 467 deg. C produces a sharp decrease in ductility. - Abstract: Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al-Cu-Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted in the range 278-467 deg. C, and at two strain rates, 2.1 and 4.5 s{sup -1}. Electron backscatter diffraction (EBSD) was employed to characterize the microtexture and microstructure before and after testing. The microstructural evolution during torsion deformation at different temperatures and strain rate conditions determines the mechanical properties at room temperature of the Al 2024 alloy since grain refining, dynamic precipitation and precipitate coalescence occur during the torsion test. These mechanical properties were measured by Vickers microhardness tests. At 408 deg. C and 2.1 s{sup -1} the optimum combination of solid solution and incipient precipitation gives rise to maximum ductility and large fraction of fine and misoriented grains (f{sub HAB} = 54%). In contrast, the increase in test temperature to 467 deg. C produces a sharp decrease in ductility, attributed to the high proportion of alloying elements in solid solution. Both the stress-strain flow curves obtained by torsion tests and the final microstructures are a consequence of recovery phenomena and the dynamic nature of the precipitation process taking place during deformation.

  3. Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements

    International Nuclear Information System (INIS)

    Basu, I.; Chen, M.; Loeck, M.; Al-Samman, T.; Molodov, D.A.

    2016-01-01

    One of the key aspects influencing microstructural design pathways in metallic systems is grain boundary motion. The present work introduces a method by means of which direct measurement of grain boundary mobility vs. misorientation dependence is made possible. The technique utilizes datasets acquired by means of serial electron backscatter diffraction (EBSD) measurements. The experimental EBSD measurements are collectively analyzed, whereby datasets were used to obtain grain boundary mobility and grain aspect ratio with respect to grain boundary misorientation. The proposed method is further validated using cellular automata (CA) simulations. Single crystal aluminium was cold rolled and scratched in order to nucleate random orientations. Subsequent annealing at 300 °C resulted in grains growing, in the direction normal to the scratch, into a single deformed orientation. Growth selection was observed, wherein the boundaries with misorientations close to Σ7 CSL orientation relationship (38° 〈111〉) migrated considerably faster. The obtained boundary mobility distribution exhibited a non-monotonic behavior with a maximum corresponding to misorientation of 38° ± 2° about 〈111〉 axes ± 4°, which was 10–100 times higher than the mobility values of random high angle boundaries. Correlation with the grain aspect ratio values indicated a strong growth anisotropy displayed by the fast growing grains. The observations have been discussed in terms of the influence of grain boundary character on grain boundary motion during recrystallization. - Highlights: • Statistical microstructure method to measure grain boundary mobility during recrystallization • Method implementation independent of material or crystal structure • Mobility of the Σ7 boundaries in 5N Al was calculated as 4.7 × 10"–"8 m"4/J ⋅ s. • Pronounced growth selection in the recrystallizing nuclei in Al • Boundary mobility values during recrystallization 2–3 orders of magnitude

  4. Analysis of soft magnetic materials by electron backscatter diffraction as a powerful tool

    Science.gov (United States)

    Schuller, David; Hohs, Dominic; Loeffler, Ralf; Bernthaler, Timo; Goll, Dagmar; Schneider, Gerhard

    2018-04-01

    The current work demonstrates that electron backscatter diffraction (EBSD) is a powerful and versatile characterization technique for investigating soft magnetic materials. The properties of soft magnets, e.g., magnetic losses strongly depend on the materials chemical composition and microstructure, including grain size and shape, texture, degree of plastic deformation and elastic strain. In electrical sheet stacks for e-motor applications, the quality of the machined edges/surfaces of each individual sheet is of special interest. Using EBSD, the influence of the punching process on the microstructure at the cutting edge is quantitatively assessed by evaluating the crystallographic misorientation distribution of the deformed grains. Using an industrial punching process, the maximum affected deformation depth is determined to be 200 - 300 μm. In the case of laser cutting, the affected deformation depth is determined to be approximately zero. Reliability and detection limits of the developed EBSD approach are evaluated on non-affected sample regions and model samples containing different indentation test bodies. A second application case is the investigation of the recrystallization process during the annealing step of soft magnetic composites (SMC) toroids produced by powder metallurgy as a function of compaction pressure, annealing parameters and powder particle size. With increasing pressure and temperature, the recrystallized area fraction (e.g., grains with crystallographic misorientations particle boundaries or areas with existing plastic deformation. The progress of recrystallization is visualized as a function of time and of different particle to grain size distributions. Here, large particles with coarse internal grain structures show a favorable recrystallization behavior which results in large bulk permeability of up to 600 - 700 and lower amount of residual misorientations (>3°).

  5. Microstructural characterization by electron backscatter diffraction of a hot worked Al-Cu-Mg alloy

    International Nuclear Information System (INIS)

    Cepeda-Jimenez, C.M.; Hidalgo, P.; Carsi, M.; Ruano, O.A.; Carreno, F.

    2011-01-01

    Research highlights: → The most favourable conditions for hot workability have been determined. → EBSD was employed to characterize the obtained microtexture and microstructure. → The Al 2024 alloy torsion tested at 408 deg. C and 2.1 s -1 showed maximum ductility. → Solid solution and fine precipitates favour a fine microstructure at 408 deg. C. → The increase in test temperature to 467 deg. C produces a sharp decrease in ductility. - Abstract: Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al-Cu-Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted in the range 278-467 deg. C, and at two strain rates, 2.1 and 4.5 s -1 . Electron backscatter diffraction (EBSD) was employed to characterize the microtexture and microstructure before and after testing. The microstructural evolution during torsion deformation at different temperatures and strain rate conditions determines the mechanical properties at room temperature of the Al 2024 alloy since grain refining, dynamic precipitation and precipitate coalescence occur during the torsion test. These mechanical properties were measured by Vickers microhardness tests. At 408 deg. C and 2.1 s -1 the optimum combination of solid solution and incipient precipitation gives rise to maximum ductility and large fraction of fine and misoriented grains (f HAB = 54%). In contrast, the increase in test temperature to 467 deg. C produces a sharp decrease in ductility, attributed to the high proportion of alloying elements in solid solution. Both the stress-strain flow curves obtained by torsion tests and the final microstructures are a consequence of recovery phenomena and the dynamic nature of the precipitation process taking place during deformation.

  6. Geometrically necessary dislocation densities in olivine obtained using high-angular resolution electron backscatter diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Wallis, David, E-mail: davidwa@earth.ox.ac.uk [Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3AN (United Kingdom); Hansen, Lars N. [Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3AN (United Kingdom); Ben Britton, T. [Department of Materials, Imperial College London, Royal School of Mines, Exhibition Road, London SW7 2AZ (United Kingdom); Wilkinson, Angus J. [Department of Materials, University of Oxford, Parks Road, Oxford, Oxfordshire, OX1 3PH (United Kingdom)

    2016-09-15

    Dislocations in geological minerals are fundamental to the creep processes that control large-scale geodynamic phenomena. However, techniques to quantify their densities, distributions, and types over critical subgrain to polycrystal length scales are limited. The recent advent of high-angular resolution electron backscatter diffraction (HR-EBSD), based on diffraction pattern cross-correlation, offers a powerful new approach that has been utilised to analyse dislocation densities in the materials sciences. In particular, HR-EBSD yields significantly better angular resolution (<0.01°) than conventional EBSD (~0.5°), allowing very low dislocation densities to be analysed. We develop the application of HR-EBSD to olivine, the dominant mineral in Earth's upper mantle by testing (1) different inversion methods for estimating geometrically necessary dislocation (GND) densities, (2) the sensitivity of the method under a range of data acquisition settings, and (3) the ability of the technique to resolve a variety of olivine dislocation structures. The relatively low crystal symmetry (orthorhombic) and few slip systems in olivine result in well constrained GND density estimates. The GND density noise floor is inversely proportional to map step size, such that datasets can be optimised for analysing either short wavelength, high density structures (e.g. subgrain boundaries) or long wavelength, low amplitude orientation gradients. Comparison to conventional images of decorated dislocations demonstrates that HR-EBSD can characterise the dislocation distribution and reveal additional structure not captured by the decoration technique. HR-EBSD therefore provides a highly effective method for analysing dislocations in olivine and determining their role in accommodating macroscopic deformation. - Highlights: • Lattice orientation gradients in olivine were measured using HR-EBSD. • The limited number of olivine slip systems enable simple least squares inversion for GND

  7. Distinguishing Biologically Controlled Calcareous Biomineralization in Fossil Organisms Using Electron Backscatter Diffraction (EBSD)

    Science.gov (United States)

    Päßler, Jan-Filip; Jarochowska, Emilia; Bestmann, Michel; Munnecke, Axel

    2018-02-01

    Although carbonate-precipitating cyanobacteria are ubiquitous in aquatic ecosystems today, the criteria used to identify them in the geological record are subjective and rarely testable. Differences in the mode of biomineralization between cyanobacteria and eukaryotes, i.e. biologically induced calcification (BIM) vs. biologically controlled calcification (BCM), result in different crystallographic structures which might be used as a criterion to test cyanobacterial affinities. Cyanobacteria are often used as a ‘wastebasket taxon’, to which various microfossils are assigned. The lack of a testable criterion for the identification of cyanobacteria may bias their fossil record severely. We employed electron backscatter diffraction (EBSD) to investigate the structure of calcareous skeletons in two microproblematica widespread in Palaeozoic marine ecosystems: Rothpletzella, hypothesized to be a cyanobacterium, and an incertae sedis microorganism Allonema. We used a calcareous trilobite shell as a BCM reference. The mineralized structure of Allonema has a simple single-layered structure of acicular crystals perpendicular to the surface of the organism. The c-axes of these crystals are parallel to the elongation and thereby normal to the surface of the organism. EBSD pole figures and misorientation axes distribution reveal a fibre texture around the c-axis with a small degree of variation (up to 30°), indicating a highly ordered structure. A comparable pattern was found in the trilobite shell. This structure allows excluding biologically induced mineralization as the mechanism of shell formation in Allonema. In Rothpletzella, the c-axes of the microcrystalline sheath show a broader clustering compared to Allonema, but still reveal crystals tending to be perpendicular to the surface of the organism. The misorientation axes of adjacent crystals show an approximately random distribution. Rothpletzella also shares morphological similarities with extant cyanobacteria. We

  8. Measuring the Shock Stage of Asteroid Regolith Grains by Electron Back-Scattered Diffraction

    Science.gov (United States)

    Zolensky, Michael; Martinez, James; Sitzman, Scott; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Terada, Yasuko; Yagi, Naoto; Komatsu, Mutsumi; Ozawa, Hikaru; hide

    2018-01-01

    We have been analyzing Itokawa samples in order to definitively establish the degree of shock experienced by the regolith of asteroid Itokawa, and to devise a bridge between shock determinations by standard light optical petrography, crystal structures as determined by electron and X-ray diffraction. These techniques would then be available for samples returned from other asteroid regoliths.

  9. Electron backscatter diffraction study of dislocation content of a macrozone in hot-rolled Ti-6Al-4V alloy

    International Nuclear Information System (INIS)

    Britton, T. Ben; Birosca, Soran; Preuss, Michael; Wilkinson, Angus J.

    2010-01-01

    We compare the dislocation substructure within macrozone and non-macrozone regions of hot-rolled Ti-6Al-4 V. Hough-based and cross-correlation-based analysis of electron backscatter diffraction (EBSD) patterns are used to establish the grain orientations and intra-granular misorientations, respectively. The set of geometrically necessary dislocations (GNDs) that support measured lattice curvatures and minimize the total GND line energy are calculated. The GND content in the macrozone is approximately twice that in the non-macrozone region, and GNDs are present at densities ∼10 times higher than GNDs.

  10. Quantitative analysis of localized stresses in irradiated stainless steels using high resolution electron backscatter diffraction and molecular dynamics modeling

    International Nuclear Information System (INIS)

    Johnson, D.C.; Kuhr, B.; Farkas, D.; Was, G.S.

    2016-01-01

    Quantitative measurements of stress near dislocation channel–grain boundary (DC–GB) interaction sites were made using high resolution electron backscatter diffraction (HREBSD) and have been compared with molecular dynamics (MD) simulations. Tensile stress normal to the grain boundary was significantly elevated at discontinuous DC–GB intersections with peak magnitudes roughly an order of magnitude greater than at sites where slip transfer occurred. These results constitute the first measurement of stress amplification at DC–GB intersections and provide support to the theory that high normal stress at the grain boundary may be a key driver for the initiation of irradiation assisted stress corrosion cracks.

  11. Determination of dislocation density by electron backscatter diffraction and X-ray line profile analysis in ferrous lath martensite

    International Nuclear Information System (INIS)

    Berecz, Tibor; Jenei, Péter; Csóré, András; Lábár, János; Gubicza, Jenő

    2016-01-01

    The microstructure and the dislocation density in as-quenched ferrous lath martensite were studied by different methods. The blocks, packets and variants formed due to martensitic transformation were identified and their sizes were determined by electron backscatter diffraction (EBSD). Concomitant transmission electron microscopy (TEM) investigation revealed that the laths contain subgrains with the size between 50 and 100 nm. A novel evaluation procedure of EBSD images was elaborated for the determination of the density and the space distribution of geometrically necessary dislocations from the misorientation distribution. The total dislocation density obtained by X-ray diffraction line profile analysis was in good agreement with the value determined by EBSD, indicating that the majority of dislocations formed due to martensitic transformation during quenching are geometrically necessary dislocations.

  12. Dark-field imaging based on post-processed electron backscatter diffraction patterns of bulk crystalline materials in a scanning electron microscope.

    Science.gov (United States)

    Brodusch, Nicolas; Demers, Hendrix; Gauvin, Raynald

    2015-01-01

    Dark-field (DF) images were acquired in the scanning electron microscope with an offline procedure based on electron backscatter diffraction (EBSD) patterns (EBSPs). These EBSD-DF images were generated by selecting a particular reflection on the electron backscatter diffraction pattern and by reporting the intensity of one or several pixels around this point at each pixel of the EBSD-DF image. Unlike previous studies, the diffraction information of the sample is the basis of the final image contrast with a pixel scale resolution at the EBSP providing DF imaging in the scanning electron microscope. The offline facility of this technique permits the selection of any diffraction condition available in the diffraction pattern and displaying the corresponding image. The high number of diffraction-based images available allows a better monitoring of deformation structures compared to electron channeling contrast imaging (ECCI) which is generally limited to a few images of the same area. This technique was applied to steel and iron specimens and showed its high capability in describing more rigorously the deformation structures around micro-hardness indents. Due to the offline relation between the reference EBSP and the EBSD-DF images, this new technique will undoubtedly greatly improve our knowledge of deformation mechanism and help to improve our understanding of the ECCI contrast mechanisms. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Analysis of recrystallization behavior of hot-deformed austenite reconstructed from electron backscattering diffraction orientation maps of lath martensite

    International Nuclear Information System (INIS)

    Kubota, Manabu; Ushioda, Kohsaku; Miyamoto, Goro; Furuhara, Tadashi

    2016-01-01

    The recrystallization behavior of hot-deformed austenite of a 0.55% C steel at 800 °C was investigated by a method of reconstructing the parent austenite orientation map from an electron backscattering diffraction orientation map of lath martensite. Recrystallized austenite grains were clearly distinguished from un-recrystallized austenite grains. Very good correlation was confirmed between the static recrystallization behavior investigated mechanically by double-hit compression tests and the change in austenite microstructure evaluated by the reconstruction method. The recrystallization behavior of hot-deformed 0.55% C steel at 800 °C is directly revealed and it was observed that by addition of 0.1% V the recrystallization was significantly retarded.

  14. Deformation micro-mechanism for compression of magnesium alloys at room temperature analyzed by electron backscatter diffraction

    International Nuclear Information System (INIS)

    Song, G.S.; Chen, Q.Q.; Zhang, S.H.; Xu, Y.

    2015-01-01

    Highlights: • In-situ tracking on the evolution of grains orientation of magnesium alloy was carried out by EBSD. • Distributions of twin bands were closely related to the activation of extension twin variants. • Activation of extension twin significantly changes the order of Schmid factor of slips. • Pyramidal slips become the dominant deformation mode at the late stage of compression. - Abstract: In-situ tracking on the evolution of grains orientation of rolled magnesium alloy sheets compressed uniaxially at room temperature was carried out by the method of electron backscatter diffraction (EBSD), and meanwhile, distributions of twin bands, activations of twin and slips were also analyzed. The results show that the distributions of twin bands were closely related to the activation of extension twin variants. The activation of extension twin significantly changes the order of Schmid factor of different slips, and accordingly affects the activation of slips during the subsequent deformation

  15. Assessment of surface hardening effects from shot peening on a Ni-based alloy using electron backscatter diffraction techniques

    International Nuclear Information System (INIS)

    Child, D.J.; West, G.D.; Thomson, R.C.

    2011-01-01

    An electron backscatter diffraction (EBSD)-based tool is described to assess the depth of strain-hardening effects of shot-peening treatments applied to the Ni-based superalloy, Udimet (copy right) alloy 720Li. The method consists of a statistical analysis of a number of data points from each grain scanned based on the grain orientation spread and their relative position from the shot-peened edge. The output is a quantitative measure of the depth of strain-hardening effects. The tool is used at various shot-peening intensities to demonstrate the ability to distinguish between these changes, using a range of intensities from 4 to 10 Almen. An increase in shot-peening intensity is observed to increase the depth of strain-hardening effects in the alloy. A comparison with residual stress measurements using X-ray diffraction for the same material shows that the strain-hardened depth determined by EBSD extends to approximately half the distance of the residual stress present due to shot peening. A comparison is also made with predicted profiles from the Peenstress SM model and subsequent microhardness testing. A positive correlation is observed between strained hardened depth and surface roughness of the peened samples. In each case, the increases in surface roughness and strain-hardened depth diminish toward the upper end of the shot-peening intensity range studied for this alloy.

  16. High resolution electron back-scatter diffraction analysis of thermally and mechanically induced strains near carbide inclusions in a superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Karamched, Phani S., E-mail: phani.karamched@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Wilkinson, Angus J. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2011-01-15

    Cross-correlation-based analysis of electron back-scatter diffraction (EBSD) patterns has been used to obtain high angular resolution maps of lattice rotations and elastic strains near carbides in a directionally solidified superalloy MAR-M-002. Lattice curvatures were determined from the EBSD measurements and used to estimate the distribution of geometrically necessary dislocations (GNDs) induced by the deformation. Significant strains were induced by thermal treatment due to the lower thermal expansion coefficient of the carbide inclusions compared to that of the matrix. In addition to elastic strains the mismatch was sufficient to have induced localized plastic deformation in the matrix leading to a GND density of 3 x 10{sup 13} m{sup -2} in regions around the carbide. Three-point bending was then used to impose strain levels within the range {+-}12% across the height of the bend bar. EBSD lattice curvature measurements were then made at both carbide-containing and carbide-free regions at different heights across the bar. The average GND density increases with the magnitude of the imposed strain (both in tension and compression), and is markedly higher near the carbides particles. The higher GND densities near the carbides (order of 10{sup 14} m{sup -2}) are generated by the large strain gradients produced around the plastically rigid inclusion during mechanical deformation with some minor contribution from the pre-existing residual deformation caused by the thermal mismatch between carbide and nickel matrix.

  17. Comparison between magnetic force microscopy and electron back-scatter diffraction for ferrite quantification in type 321 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Warren, A.D., E-mail: Xander.Warren@bristol.ac.uk [Interface Analysis Centre, HH Wills Laboratory, University of Bristol, Bristol BS8 1FD (United Kingdom); Harniman, R.L. [School of Chemistry, University of Bristol, Bristol BS8 1 TS (United Kingdom); Collins, A.M. [School of Chemistry, University of Bristol, Bristol BS8 1 TS (United Kingdom); Bristol Centre for Functional Nanomaterials, Nanoscience and Quantum Information Centre, University of Bristol, Bristol BS8 1FD (United Kingdom); Davis, S.A. [School of Chemistry, University of Bristol, Bristol BS8 1 TS (United Kingdom); Younes, C.M. [Interface Analysis Centre, HH Wills Laboratory, University of Bristol, Bristol BS8 1FD (United Kingdom); Flewitt, P.E.J. [Interface Analysis Centre, HH Wills Laboratory, University of Bristol, Bristol BS8 1FD (United Kingdom); School of Physics, HH Wills Laboratory, University of Bristol, Bristol BS8 1FD (United Kingdom); Scott, T.B. [Interface Analysis Centre, HH Wills Laboratory, University of Bristol, Bristol BS8 1FD (United Kingdom)

    2015-01-15

    Several analytical techniques that are currently available can be used to determine the spatial distribution and amount of austenite, ferrite and precipitate phases in steels. The application of magnetic force microscopy, in particular, to study the local microstructure of stainless steels is beneficial due to the selectivity of this technique for detection of ferromagnetic phases. In the comparison of Magnetic Force Microscopy and Electron Back-Scatter Diffraction for the morphological mapping and quantification of ferrite, the degree of sub-surface measurement has been found to be critical. Through the use of surface shielding, it has been possible to show that Magnetic Force Microscopy has a measurement depth of 105–140 nm. A comparison of the two techniques together with the depth of measurement capabilities are discussed. - Highlights: • MFM used to map distribution and quantify ferrite in type 321 stainless steels. • MFM results compared with EBSD for same region, showing good spatial correlation. • MFM gives higher area fraction of ferrite than EBSD due to sub-surface measurement. • From controlled experiments MFM depth sensitivity measured from 105 to 140 nm. • A correction factor to calculate area fraction from MFM data is estimated.

  18. Texture development study during the primary recrystallization of ferritic steels by using X ray and electron backscattering diffraction

    International Nuclear Information System (INIS)

    Loew, Marjorie

    2006-01-01

    X ray and electron backscattering diffraction, in distinct levels, were applied to evaluate microstructural changes in two low carbon ferritic steels (2 per cent Si and ABNT 1006), observing the texture development in cold lamination step (skin-pass) and in the subsequent annealing at 760 deg C. In these two steels, results showed that after the skin-pass and annealing in the conditions of the present work, the observed phenomenon is the primary recrystallization. By applying skin-pass dislocations were introduced mostly in low Taylor factor grains as they are prone to be more deformed. Nucleation and grain growth were observed in high density dislocation cell regions. Silicon presence delayed the recovery favoring the sub-boundaries increase. It was not observed the abnormal grain growth, even in the presence of Gross grains. CSL boundaries did not guarantee the grains growth. Growing nuclei gave rise to grains with distinct orientations, showing that the grain growth was not dependent on the previous presence of grains with the developed orientation. This fact demonstrates that the abnormal grain growth is not necessarily related to the Gross grains. (author)

  19. Anelasticity of olivine single crystals investigated by stress-reduction tests and high-angular resolution electron backscatter diffraction

    Science.gov (United States)

    Wallis, D.; Hansen, L. N.; Kempton, I.; Wilkinson, A. J.

    2017-12-01

    Geodynamic phenomena, including glacial isostatic adjustment and postseismic deformation, can involve transient deformation in response to changes in differential stress acting on mantle rocks. As such, rheological models of transient deformation are incorporated in predictions of associated processes, including sea-level rise and stress redistribution after earthquakes. However, experimental constraints on rheological models for transient deformation of mantle materials are sparse. In particular, experiments involving stress reductions have been lacking. Moreover, a material's response to a reduction in stress can provide clues to the microphysical processes controlling deformation. To constrain models of transient deformation of mantle rocks we performed stress-reduction tests on single crystals of olivine at 1250-1300°C. Mechanical and piezoelectric actuators controlled constant initial stress during creep. At various strain intervals stress was reduced near-instantaneously using the piezoelectric actuator, inducing both elastic and anelastic (time-dependent) lengthening of the samples. A range of magnitudes of stress reduction were applied, typically unloading 10-90% of the initial stress. High-angular resolution electron backscatter diffraction (HR-EBSD), based on cross-correlation of diffraction patterns, was used to map dislocation density and elastic strain distributions in the recovered samples. Magnitudes of anelastic back-strain increase with increasing magnitudes of stress reduction and show a marked increase when stress reductions exceed 50% of the initial stress, consistent with previous observations in metals and alloys. This observation is inconsistent with the Burgers rheological model commonly used to describe transient behaviour and suggests that the style of rheological behaviour depends on the magnitude of stress change. HR-EBSD maps reveal that the crystal lattices are smoothly curved and generally lack subgrain boundaries and elastic strain

  20. A study of the breakdown of Friedel's law in electron backscatter Kikuchi diffraction patterns: Application to zincblende-type structures

    International Nuclear Information System (INIS)

    Baba-Kishi, K.Z.

    1991-01-01

    The breakdown of Friedel's law has been observed in backscatter Kikuchi diffraction patterns (BKDP) obtained in the scanning electron microscope (SEM) from a series of zincblende structures including GaAs, InP, GaSb, CdHgTe and the minerals sphalerite (ZnS), chalcopyrite (CuFeS 2 ) and tetrahedrite (Cu 12 Sb 4 S 13 ). Differences in intensities were observed between the reflections 11anti 1 and 5anti 1anti 1 in InP, GaSb, CdHgTe and sphalerite, thus allowing the non-centrosymmetric point group anti 43 m to be determined. In GaAs, differences in intensities were noted between anti 511 and anti 5anti 11. In chalcopyrite and tetrahedrite, non-equivalent intensities were observed between anti 215 and 2anti 1anti 5 and between 3anti 1anti 2 and 31anti 2, respectively. In addition, BKDPs obtained from chalcopyrite revealed a small displacement at the point where the pair of equivalent reflections anti 406 and 460 intersect within the Kikuchi band 02anti 2. The presence of this displacement together with observation of the breakdown of Friedel's law confirmed the tetragonal point group anti 42m for chalcopyrite. Although the point groups of GaAs, chalcopyrite and tetrahedrite were derived successfully using BKDPs, determination of their space groups proved unsuccessful. The superstructure reflections were invisible because the structure factors are very small. The behaviour of the invisible 200 reflection in GaAs is investigated using many-beam dynamical intensity profiles calculated across the h00 systematic row of reflections. Dynamical intensity profiles calculated across the h00 systematic rows of reflections for Ge, InP and sphalerite are also discussed. (orig.)

  1. Damage measurement of structural material by electron backscatter diffraction. Quantification of measurement quality toward standardization of measurement procedure

    International Nuclear Information System (INIS)

    Kamaya, Masayuki

    2011-01-01

    Several attempts have been made to assess the damage induced in materials by crystal orientation distributions identified using electron backscatter diffraction (EBSD). In particular, the local misorientation, which is the misorientation between neighboring measurement points, was shown to correlate well with the degree of material damage such as plastic strain, fatigue and creep. However, the damage assessments conducted using the local misorientations were qualitative rather than quantitative. The local misorientation can be correlated theoretically with physical parameters such as dislocation density. However, the error in crystal orientation measurements makes quantitative evaluation of the local misorientation difficult. Furthermore, the local misorientation depends on distance between the measurement points (step size). For a quantitative assessment of the local misorientation, the error in the crystal orientation measurements must be reduced or the degree of error must be shown quantitatively. In this study, first, the influence of the quality of measurements (accuracy of measurements) and step size on the local misorientation was investigated using stainless steel specimens damaged by tensile deformation or fatigue. By performing the crystal orientation measurements with different conditions, it was shown that the quality of measurement could be represented by the error index, which was previously proposed by the author. Secondly, a filtering process was applied in order to improve the accuracy of crystal orientation measurements and its effect was investigated using the error index. It was revealed that the local misorientations obtained under different measurement conditions could be compared quantitatively only when the error index and the step size were almost or exactly the same. It was also shown that the filtering process could successfully reduce the measurement error and step size dependency of the local misorientations. By applying the filtering

  2. Application of Electron Backscattered Diffraction (EBSD) and Atomic Force Microscopy (AFM) to Determine Texture, Mesotexture, and Grain Boundary Energies in Ceramics

    International Nuclear Information System (INIS)

    Glass, S.J.; Rohrer, G.S.; Saylor, D.M.; Vedula, V.R.

    1999-01-01

    Crystallographic orientations in alumina (Al 2 0 3 ) and magnesium aluminate spinel (MgAl 2 0 4 ) were obtained using electron backscattered diffraction (EBSD) patterns. The texture and mesotexture (grain boundary mis-orientations) were random and no special boundaries were observed. The relative grain boundary energies were determined by thermal groove geometries using atomic force microscopy (AFM) to identify relationships between the grain boundary energies and mis-orientations

  3. Extracting electron backscattering coefficients from backscattered electron micrographs

    International Nuclear Information System (INIS)

    Zupanic, F.

    2010-01-01

    Electron backscattering micrographs possess the so-called Z-contrast, carrying information about the chemical compositions of phases present in microstructures. The intensity at a particular point in the backscattered electron micrograph is proportional to the signal detected at a corresponding point in the scan raster, which is, in turn, proportional to the electron backscattering coefficient of a phase at that point. This article introduces a simple method for extracting the electron backscattering coefficients of phases present in the microstructure, from the backscattered electron micrographs. This method is able to convert the micrograph's greyscale to the backscattering-coefficient-scale. The prerequisite involves the known backscattering coefficients for two phases in the micrograph. In this way, backscattering coefficients of other phases can be determined. The method is unable to determine the chemical compositions of phases or the presence of an element only from analysing the backscattered electron micrograph. Nevertheless, this method was found to be very powerful when combined with energy dispersive spectroscopy, and the calculations of backscattering coefficients. - Research Highlights: →A simple method for extracting the electron backscattering coefficients →The prerequisite is known backscattering coefficients for two phases →The information is complementary to the EDS-results. →This method is especially useful when a phase contains a light element (H, Li, Be, and B)

  4. Electron backscatter diffraction study of deformation and recrystallization textures of individual phases in a cross-rolled duplex steel

    Energy Technology Data Exchange (ETDEWEB)

    Zaid, Md; Bhattacharjee, P.P., E-mail: pinakib@iith.ac.in

    2014-10-15

    The evolution of microstructure and texture during cross-rolling and annealing was investigated by electron backscatter diffraction in a ferritic–austenitic duplex stainless steel. For this purpose an alloy with nearly equal volume fraction of the two phases was deformed by multi-pass cross-rolling process up to 90% reduction in thickness. The rolling and transverse directions were mutually interchanged in each pass by rotating the sample by 90° around the normal direction. In order to avoid deformation induced phase transformation and dynamic strain aging, the rolling was carried out at an optimized temperature of 898 K (625 °C) at the warm-deformation range. The microstructure after cross warm-rolling revealed a lamellar structure with alternate arrangement of the bands of two phases. Strong brass and rotated brass components were observed in austenite in the steel after processing by cross warm-rolling. The ferrite in the cross warm-rolling processed steel showed remarkably strong RD-fiber (RD//< 011 >) component (001)< 011 >. The development of texture in the two phases after processing by cross warm-rolling could be explained by the stability of the texture components. During isothermal annealing of the 90% cross warm-rolling processed material the lamellar morphology was retained before collapse of the lamellar structure to the mutual interpenetration of the phase bands. Ferrite showed recovery resulting in annealing texture similar to the deformation texture. In contrast, the austenite showed primary recrystallization without preferential orientation selection leading to the retention of deformation texture. The evolution of deformation and annealing texture in the two phases of the steel was independent of one another. - Highlights: • Effect of cross warm-rolling on texture formation is studied in duplex steel. • Brass texture in austenite and (001)<110 > in ferrite are developed. • Ferrite shows recovery during annealing retaining the (001

  5. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

    Science.gov (United States)

    Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

    2014-12-01

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. A study of intergranular corrosion of austenitic stainless steel by electrochemical potentiodynamic reactivation, electron back-scattering diffraction and cellular automaton

    Energy Technology Data Exchange (ETDEWEB)

    Yu Xiaofei [Department of Chemistry, Shandong University, Jinan 250100 (China); Chen Shenhao [Department of Chemistry, Shandong University, Jinan 250100 (China); State Key Laboratory for Corrosion and Protection, Shenyang 110016 (China)], E-mail: shchen@sdu.edu.cn; Liu Ying; Ren Fengfeng [Department of Chemistry, Shandong University, Jinan 250100 (China)

    2010-06-15

    The impact of solution and sensitization treatments on the intergranular corrosion (IGC) of austenitic stainless steel (316) was studied by electrochemical potentiodynamic reactivation (EPR) test, and the results showed the degree of sensitization (DOS) decreased as solution treatment temperature and time went up, but it increased as sensitization temperature prolonged. Factors that affected IGC were investigated by field emission scanning electron microscope (FE-SEM) and electron back-scattering diffraction (EBSD). Furthermore, the precipitation evolution of Cr-rich carbides and the distribution of chromium concentration were simulated by cellular automaton (CA), clearly showing the effects of solution and sensitization treatments on IGC.

  7. An electron back-scattered diffraction study on the microstructure evolution of AZ31 Mg alloy during equal channel angular extrusion

    International Nuclear Information System (INIS)

    Jin Li; Lin Dongliang; Mao Dali; Zeng Xiaoqin; Ding Wenjiang

    2006-01-01

    Microstructure evolution of AZ31 Mg alloy during equal channel angular extrusion (ECAE) was investigated by electron back-scattered diffraction (EBSD). The grains of AZ31 Mg alloy were refined significantly after ECAE 1-8 passes at 498 K and the distributions of grain size tended to be more uniform with pass number increasing. Frequency of sub-boundaries and low angle grain boundaries (LAGBs) increased at initial stage of deformation, and sub-boundaries and LAGBs evolved into high angle grain boundaries (HAGBs) with further deformation, which resulted in the high frequency of HAGBs in the alloy after ECAE 8 passes. Preferred misorientation angle with frequency peak near 30 deg. and 90 deg. were observed. The frequency peaks were weak after ECAE 1 pass but became stronger with the increase of pass numbers. Micro-textures were formed in AZ31 microstructure during ECAE and were stronger with the pass number increasing

  8. Correlation of electron backscatter diffraction and piezoresponse force microscopy for the nanoscale characterization of ferroelectric domains in polycrystalline lead zirconate titanate

    Science.gov (United States)

    Burnett, T. L.; Weaver, P. M.; Blackburn, J. F.; Stewart, M.; Cain, M. G.

    2010-08-01

    The functional properties of ferroelectric ceramic bulk or thin film materials are strongly influenced by their nanostructure, crystallographic orientation, and structural geometry. In this paper, we show how, by combining textural analysis, through electron backscattered diffraction, with piezoresponse force microscopy, quantitative measurements of the piezoelectric properties can be made at a scale of 25 nm, smaller than the domain size. The combined technique is used to obtain data on the domain-resolved effective single crystal piezoelectric response of individual crystallites in Pb(Zr0.4Ti0.6)O3 ceramics. The results offer insight into the science of domain engineering and provide a tool for the future development of new nanostructured ferroelectric materials for memory, nanoactuators, and sensors based on magnetoelectric multiferroics.

  9. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gazder, Azdiar A., E-mail: azdiar@uow.edu.au [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Al-Harbi, Fayez; Spanke, Hendrik Th. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia); Mitchell, David R.G. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Pereloma, Elena V. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia)

    2014-12-15

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. - Highlights: • Multi-condition segmentation of austenite, martensite, polygonal ferrite and ferrite in bainite. • Ferrites in granular bainite and bainitic ferrite segmented by variation in relative carbon counts. • Carbon partitioning during growth explains variation in carbon content of ferrites in bainites. • Developed EBSD image processing tools can be applied to the microstructures of a variety of alloys. • EBSD-based segmentation procedure verified by correlative TEM results.

  10. Effect of Welding Heat Input on Microstructure and Texture of Inconel 625 Weld Overlay Studied Using the Electron Backscatter Diffraction Method

    Science.gov (United States)

    Kim, Joon-Suk; Lee, Hae-Woo

    2016-12-01

    The grain size and the texture of three specimens prepared at different heat inputs were determined using optical microscopy and the electron backscatter diffraction method of scanning electron microscopy. Each specimen was equally divided into fusion line zone (FLZ), columnar dendrite zone (CDZ), and surface zone (SZ), according to the location of the weld. Fine dendrites were observed in the FLZ, coarse dendrites in the CDZ, and dendrites grew perpendicular to the FLZ and CDZ. As the heat input increased, the melted zone in the vicinity of the FLZ widened due to the higher Fe content. A lower image quality value was observed for the FLZ compared to the other zones. The results of grain size measurement in each zone showed that the grain size of the SZ became larger as the heat input increased. From the inverse pole figure (IPF) map in the normal direction (ND) and the rolling direction (RD), as the heat input increased, a specific orientation was formed. However, a dominant [001] direction was observed in the RD IPF map.

  11. Analytical purpose electron backscattering system

    International Nuclear Information System (INIS)

    Desdin, L.; Padron, I.; Laria, J.

    1996-01-01

    In this work an analytical purposes electron backscattering system improved at the Center of Applied Studies for Nuclear Development is described. This system can be applied for fast, exact and nondestructive testing of binary and AL/Cu, AL/Ni in alloys and for other applications

  12. Electron Backscatter Diffraction (EBSD) Analysis and U-Pb Geochronology of the Oldest Lunar Zircon: Constraining Early Lunar Differentiation and Dating Impact-Related Deformation

    Science.gov (United States)

    Timms, Nick; Nemchin, Alexander; Grange, Marion; Reddy, Steve; Pidgeon, Bob; Geisler, Thorsten; Meyer, Chuck

    2009-01-01

    The evolution of the early moon was dominated by two processes (i) crystallization of the Lunar Magma Ocean (LMO) and differentiation of potassium-rare earth element-phosphorous-rich residual magma reservoir referred to as KREEP, and (ii) an intense meteorite bombardment referred to as lunar cataclysm . The exact timing of these processes is disputed, and resolution relies on collection and interpretation of precise age data. This study examines the microstructure and geochronology of zircon from lunar impact breccias collected during the Apollo 17 mission. A large zircon clast within lunar breccia 72215,195 shows sector zoning in optical microscopy, cathodoluminescence (CL) imaging and Raman mapping, and indicates that it was a relict fragment of a much larger magmatic grain. Sensitive high resolution ion microprobe (SHRIMP) U-Pb analysis of the zircon shows that U and Th concentration correlate with sector zoning, with darkest CL domains corresponding with high-U and Th (approx.150 and approx.100 ppm respectively), and the brightest-CL sectors containing approx.30-50 ppm U and approx.10-20 ppm Th. This indicates that variations in optical CL and Raman properties correspond to differential accumulation of alpha-radiation damage in each sector. Electron backscatter diffraction (EBSD) mapping shows that the quality of electron backscatter patterns (band contrast) varies with sector zoning, with the poorest quality patterns obtained from high-U and Th, dark-CL zones. EBSD mapping also reveals a deformation microstructure that is cryptic in optical, CL and Raman imaging. Two orthogonal sets of straight discrete and gradational low-angle boundaries accommodate approx.12 misorientation across the grain. The deformation bands are parallel to the crystallographic {a}-planes of the zircon, have misorientation axes parallel to the c-axis, and are geometrically consistent with formation by dislocation creep associated with {010} slip. The deformation bands are unlike curved

  13. Three-dimensional characterization of bainitic microstructures in low-carbon high-strength low-alloy steel studied by electron backscatter diffraction

    International Nuclear Information System (INIS)

    Kang, J.S.; Seol, Jae-Bok; Park, C.G.

    2013-01-01

    We investigated the microstructural evolution of high strength low alloy steel, Fe–2.0Mn–0.15Si–0.05C (wt.%), by varying the continuous cooling rates from 1 K/s to 50 K/s using three-dimensional electron backscatter diffraction and transmission electron microscopy. Granular bainitic microstructure was prevalent under a slow cooling rate of 1–10 K/s, while lath-type bainite was dominant at a high cooling rate of 50 K/s. The acicular ferrite that was the major microstructure under the intermediate ranges of cooling rates between 10 K/s and 30 K/s was tangled with each other, leading to a three-dimensional interwoven structure with highly misoriented grains. Because of the formation of three-dimensional structures, we propose that the terms “acicular ferrite” and “bainitic ferrite,” which are currently used in steel, be replaced by the terms “interwoven acicular bainite” and “lath bainite,” respectively. Moreover, we also confirmed that the cooling rate is an important factor in determining whether bainitic microstructures occur in the form of granular bainite, interwoven bainite, or lath bainite. - Highlights: • The morphology of bainitic grains was characterized by 3D-EBSD. • The ‘interwoven bainite’ and ‘lath bainite’ were suggested. • Interwoven bainite consisted of lenticular plates that were interlinked in 3D regime. • The packets of lath bainite were aligned in a specific direction

  14. Three-dimensional characterization of bainitic microstructures in low-carbon high-strength low-alloy steel studied by electron backscatter diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Kang, J.S. [Department of Materials Science and Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Technical Research Laboratories, POSCO, Pohang 790-300 (Korea, Republic of); Seol, Jae-Bok, E-mail: j.seol@mpie.de [Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Park, C.G. [Department of Materials Science and Engineering, POSTECH, Pohang 790-784 (Korea, Republic of)

    2013-05-15

    We investigated the microstructural evolution of high strength low alloy steel, Fe–2.0Mn–0.15Si–0.05C (wt.%), by varying the continuous cooling rates from 1 K/s to 50 K/s using three-dimensional electron backscatter diffraction and transmission electron microscopy. Granular bainitic microstructure was prevalent under a slow cooling rate of 1–10 K/s, while lath-type bainite was dominant at a high cooling rate of 50 K/s. The acicular ferrite that was the major microstructure under the intermediate ranges of cooling rates between 10 K/s and 30 K/s was tangled with each other, leading to a three-dimensional interwoven structure with highly misoriented grains. Because of the formation of three-dimensional structures, we propose that the terms “acicular ferrite” and “bainitic ferrite,” which are currently used in steel, be replaced by the terms “interwoven acicular bainite” and “lath bainite,” respectively. Moreover, we also confirmed that the cooling rate is an important factor in determining whether bainitic microstructures occur in the form of granular bainite, interwoven bainite, or lath bainite. - Highlights: • The morphology of bainitic grains was characterized by 3D-EBSD. • The ‘interwoven bainite’ and ‘lath bainite’ were suggested. • Interwoven bainite consisted of lenticular plates that were interlinked in 3D regime. • The packets of lath bainite were aligned in a specific direction.

  15. Principles of electron backscattering by solids and thin films

    International Nuclear Information System (INIS)

    Niedrig, H.

    1977-01-01

    The parameters concerning the electron backscattering from thin films and solids (atomic scattering cross-section, atomic number, single/multiple scattering, film thickness of self-supporting films and of surface films on bulk substrates, scattering angular distribution, angle of incidence, diffraction effects) are described. Their influence on some important contrast mechanisms in scanning electron microscopy (thickness contrast, Z/material contrast, tilting/topography contrast, orientation contrast) is discussed. The main backscattering electron detection systems are briefly described. (orig.) [de

  16. Determining the sputter yields of molybdenum in low-index crystal planes via electron backscattered diffraction, focused ion beam and atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.S., E-mail: 160184@mail.csc.com.tw [New Materials Research and Development Department, China Steel Corporation, 1 Chung Kang Road, Hsiao Kang, Kaohsiung 812, Taiwan, ROC (China); Chiu, C.H.; Hong, I.T.; Tung, H.C. [New Materials Research and Development Department, China Steel Corporation, 1 Chung Kang Road, Hsiao Kang, Kaohsiung 812, Taiwan, ROC (China); Chien, F.S.-S. [Department of Physics, Tunghai University, 1727, Sec. 4, Xitun Dist., Taiwan Boulevard, Taichung 407, Taiwan, ROC (China)

    2013-09-15

    Previous literature has used several monocrystalline sputtering targets with various crystalline planes, respectively, to investigate the variations of the sputter yield of materials in different crystalline orientations. This study presents a method to measure the sputtered yields of Mo for the three low-index planes (100), (110), and (111), through using an easily made polycrystalline target. The procedure was firstly to use electron backscattered diffraction to identify the grain positions of the three crystalline planes, and then use a focused ion beam to perform the micro-milling of each identified grain, and finally the sputter yields were calculated from the removed volumes, which were measured by atomic force microscope. Experimental results showed that the sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}, coincidental with the ranking of their planar atomic packing densities. The concept of transparency of ion in the crystalline substance was applied to elucidate these results. In addition, the result of (110) orientation exhibiting higher sputter yield is helpful for us to develop a Mo target with a higher deposition rate for use in industry. By changing the deformation process from straight rolling to cross rolling, the (110) texture intensity of the Mo target was significantly improved, and thus enhanced the deposition rate. - Highlights: • We used EBSD, FIB and AFM to measure the sputter yields of Mo in low-index planes. • The sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}. • The transparency of ion was used to elucidate the differences in the sputter yield. • We improved the sputter rate of polycrystalline Mo target by adjusting its texture.

  17. Damage Assessment of Heat Resistant Steels through Electron BackScatter Diffraction Strain Analysis under Creep and Creep-Fatigue Conditions

    Science.gov (United States)

    Fujiyama, Kazunari; Kimachi, Hirohisa; Tsuboi, Toshiki; Hagiwara, Hiroyuki; Ogino, Shotaro; Mizutani, Yoshiki

    EBSD(Electron BackScatter Diffraction) analyses were conducted for studying the quantitative microstructural metrics of creep and creep-fatigue damage for austenitic SUS304HTB boiler tube steel and ferritic Mod.9Cr piping steel. KAM(Kernel Average Misorientation) maps and GOS(Grain Orientation Spread) maps were obtained for these samples and the area averaged values KAMave and GOSave were obtained. While the increasing trends of these misorientation metrics were observed for SUS304HTB steel, the decreasing trends were observed for damaged Mod.9Cr steel with extensive recovery of subgrain structure. To establish more universal parameter representing the accumulation of damage to compensate these opposite trends, the EBSD strain parameters were introduced for converting the misorientation changes into the quantities representing accumulated permanent strains during creep and creep-fatigue damage process. As KAM values were dependent on the pixel size (inversely proportional to the observation magnification) and the permanent strain could be expressed as the shear strain which was the product of dislocation density, Burgers vector and dislocation movement distance, two KAM strain parameters MεKAMnet and MεδKAMave were introduced as the sum of product of the noise subtracted KAMnet and the absolute change from initial value δKAMave with dislocation movement distance divided by pixel size. MεδKAMave parameter showed better relationship both with creep strain in creep tests and accumulated creep strain range in creep-fatigue tests. This parameter can be used as the strain-based damage evaluation and detector of final failure.

  18. Analytical expressions for the electron backscattering coefficient

    International Nuclear Information System (INIS)

    August, H.J.; Wernisch, J.

    1989-01-01

    Several analytical expressions for the electron backscattering coefficient for massive homogeneous samples are compared with experimental data, directing special attention to the dependence of this quantity on the electron acceleration energy. It is shown that this dependence generally cannot be neglected. The expression proposed by Hunger and Kuechler turns out to be better than that of Love and Scott, although even the better formula can be slightly improved by a small modification. (author)

  19. Electron backscattering for process control in electron beam welding

    International Nuclear Information System (INIS)

    Ardenne, T. von; Panzer, S.

    1983-01-01

    A number of solutions to the automation of electron beam welding is presented. On the basis of electron backscattering a complex system of process control has been developed. It allows an enlarged imaging of the material's surface, improved adjustment of the beam focusing and definite focus positioning. Furthermore, both manual and automated positioning of the electron beam before and during the welding process has become possible. Monitoring of the welding process for meeting standard welding requirements can be achieved with the aid of a control quantity derived from the results of electronic evaluation of the high-frequency electron backscattering

  20. The use of combined three-dimensional electron backscatter diffraction and energy dispersive X-ray analysis to assess the characteristics of the gamma/gamma-prime microstructure in alloy 720Li™

    International Nuclear Information System (INIS)

    Child, D.J.; West, G.D.; Thomson, R.C.

    2012-01-01

    Multiple three-dimensional reconstructions of a γ/γ′ phase structure in Alloy 720Li have been carried out by employing a serial milling technique with simultaneous electron backscatter diffraction (EBSD) and energy dispersive x-ray (EDX) analysis data collection. Combining EBSD data with EDX is critical in obtaining maps to distinguish between the chemically differing, but crystallographically similar γ and γ′ phases present in the alloy studied. EDX is shown to allow the differentiation of γ and γ′ phases, with EBSD providing increased grain shape accuracy. The combination of data sources also allowed identification of coherent γ/γ′ phase interfaces that would not be identified using solely EBSD or EDX. The study identifies a region of grain banding within the alloy, which provides the basis for a three-dimensional comparison and discussion of γ′ phase size between coarse and fine grain regions, whilst also identifying coherent γ′ phase interfaces, possible only using both EDX and EBSD systems simultaneously. The majority of the γ′ phase lies in the range of 1–10 μm in non-banded regions, with a detectable particle size limit of 500 nm being established. The validity of the reconstruction has been demonstrated using an electron interaction volumes model, and an assessment of the validity of EBSD and EDX data sources is discussed showing γ′ phase connectivity in all dimensions. -- Highlights: ► Use of combined EBSD/EDX for the 3D analysis of gamma prime in a Ni-based alloy. ► Assessment of 3D reconstruction accuracy using CASINO. ► Observation and validation of gamma prime phase connectivity throughout the alloy. ► Identification and characterisation of grain banding in gamma prime. ► Distinction of phase coherency between gamma and gamma prime.

  1. The use of combined three-dimensional electron backscatter diffraction and energy dispersive X-ray analysis to assess the characteristics of the gamma/gamma-prime microstructure in alloy 720Li Trade-Mark-Sign

    Energy Technology Data Exchange (ETDEWEB)

    Child, D.J., E-mail: d.child@lboro.ac.uk [Department of Materials, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom); West, G.D., E-mail: g.west@lboro.ac.uk [Department of Materials, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom); Thomson, R.C., E-mail: r.c.thomson@lboro.ac.uk [Department of Materials, Loughborough University, Loughborough, Leicestershire, LE11 3TU (United Kingdom)

    2012-03-15

    Multiple three-dimensional reconstructions of a {gamma}/{gamma} Prime phase structure in Alloy 720Li have been carried out by employing a serial milling technique with simultaneous electron backscatter diffraction (EBSD) and energy dispersive x-ray (EDX) analysis data collection. Combining EBSD data with EDX is critical in obtaining maps to distinguish between the chemically differing, but crystallographically similar {gamma} and {gamma} Prime phases present in the alloy studied. EDX is shown to allow the differentiation of {gamma} and {gamma} Prime phases, with EBSD providing increased grain shape accuracy. The combination of data sources also allowed identification of coherent {gamma}/{gamma} Prime phase interfaces that would not be identified using solely EBSD or EDX. The study identifies a region of grain banding within the alloy, which provides the basis for a three-dimensional comparison and discussion of {gamma} Prime phase size between coarse and fine grain regions, whilst also identifying coherent {gamma} Prime phase interfaces, possible only using both EDX and EBSD systems simultaneously. The majority of the {gamma} Prime phase lies in the range of 1-10 {mu}m in non-banded regions, with a detectable particle size limit of 500 nm being established. The validity of the reconstruction has been demonstrated using an electron interaction volumes model, and an assessment of the validity of EBSD and EDX data sources is discussed showing {gamma} Prime phase connectivity in all dimensions. -- Highlights: Black-Right-Pointing-Pointer Use of combined EBSD/EDX for the 3D analysis of gamma prime in a Ni-based alloy. Black-Right-Pointing-Pointer Assessment of 3D reconstruction accuracy using CASINO. Black-Right-Pointing-Pointer Observation and validation of gamma prime phase connectivity throughout the alloy. Black-Right-Pointing-Pointer Identification and characterisation of grain banding in gamma prime. Black-Right-Pointing-Pointer Distinction of phase coherency

  2. Electron diffraction from carbon nanotubes

    International Nuclear Information System (INIS)

    Qin, L-C

    2006-01-01

    The properties of a carbon nanotube are dependent on its atomic structure. The atomic structure of a carbon nanotube can be defined by specifying its chiral indices (u, v), that specify its perimeter vector (chiral vector), with which the diameter and helicity are also determined. The fine electron beam available in a modern transmission electron microscope (TEM) offers a unique probe to reveal the atomic structure of individual nanotubes. This review covers two aspects related to the use of the electron probe in the TEM for the study of carbon nanotubes: (a) to understand the electron diffraction phenomena for inter-pretation of the electron diffraction patterns of carbon nanotubes and (b) to obtain the chiral indices (u, v), of the carbon nanotubes from the electron diffraction patterns. For a nanotube of a given structure, the electron scattering amplitude from the carbon nanotube is first described analytically in closed form using the helical diffraction theory. From a known structure as given by the chiral indices (u, v), its electron diffraction pattern can be calculated and understood. The reverse problem, i.e. assignment of the chiral indices from an electron diffraction pattern of a carbon nanotube, is approached from the relationship between the electron scattering intensity distribution and the chiral indices (u, v). We show that electron diffraction patterns can provide an accurate and unambiguous assignment of the chiral indices of carbon nanotubes. The chiral indices (u, v) can be read indiscriminately with a high accuracy from the intensity distribution on the principal layer lines in an electron diffraction pattern. The symmetry properties of electron diffraction from carbon nanotubes and the electron diffraction from deformed carbon nanotubes are also discussed in detail. It is shown that 2mm symmetry is always preserved for single-walled carbon nanotubes, but it can break down for multiwalled carbon nanotubes under some special circumstances

  3. Electron microscopy and diffraction

    International Nuclear Information System (INIS)

    Gjoennes, J.; Olsen, A.

    1986-01-01

    This report is a description of research activities and plans at the electron microscopy laboratorium, Physics Department, University of Oslo. Since the first electron microscope was installed in 1968, the research has covered inorganic structures, physical metallurgy, as well as theory of electron scattering and the development of methods in this field. The current plans involve efforts in the development of crystallographic and spectroscopic methods

  4. Diffraction of high energy electrons

    International Nuclear Information System (INIS)

    Bourret, A.

    1981-10-01

    The diffraction of electrons by a crystal is examined to study its structure. As the electron-substance interaction is strong, it must be treated in a dynamic manner. Using the N waves theory and physical optics the base equations giving the wave at the outlet are deduced for a perfect crystal and their equivalence is shown. The more complex case of an imperfect crystal is then envisaged in these two approaches. In both cases, only the diffraction of high energy electrons ( > 50 KeV) are considered since in the diffraction of slow electrons back scattering cannot be ignored. Taking into account an increasingly greater number of beams, through fast calculations computer techniques, enables images to be simulated in very varied conditions. The general use of the Fast Fourier Transform has given a clear cut practical advantage to the multi-layer method [fr

  5. About the information depth of backscattered electron imaging

    Czech Academy of Sciences Publication Activity Database

    Piňos, Jakub; Mikmeková, Šárka; Frank, Luděk

    2017-01-01

    Roč. 266, č. 3 (2017), s. 335-342 ISSN 0022-2720 Institutional support: RVO:68081731 Keywords : backscattered electrons * information depth * penetration of electrons Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Materials engineering Impact factor: 1.692, year: 2016

  6. Axial channeling in electron diffraction

    International Nuclear Information System (INIS)

    Ichimiya, A.; Lehmpfuhl, G.

    1978-01-01

    Kossel patterns from Silicon and Niobium were obtained with a convergent electron beam. An intensity maximum in the direction of the zone axes [001] and [111] of Nb was interpreted as axial channeling. The intensity distribution in Kossel patterns was calculated by means of the Bloch wave picture of the dynamical theory of electron diffraction. Particularly zone axis patterns were calculated for different substance-energy combinations and they were compared with experimental observations. The intensity distribution in the calculated Kossel patterns was very sensitive to the model of absorption and it was found that a treatment of the absorption close to the model of Humphreys and Hirsch [Phil. Mag. 18, 115 (1968)] gave the best agreement with the experimental observations. Furthermore it is shown which Bloch waves are important for the intensity distribution in the Kossel patterns, how they are absorbed and how they change with energy. (orig.) [de

  7. Validation Test of Geant4 Simulation of Electron Backscattering

    CERN Document Server

    Kim, Sung Hun; Basaglia, Tullio; Han, Min Cheol; Hoff, Gabriela; Kim, Chan Hyeong; Saracco, Paolo

    2015-01-01

    Backscattering is a sensitive probe of the accuracy of electron scattering algorithms implemented in Monte Carlo codes. The capability of the Geant4 toolkit to describe realistically the fraction of electrons backscattered from a target volume is extensively and quantitatively evaluated in comparison with experimental data retrieved from the literature. The validation test covers the energy range between approximately 100 eV and 20 MeV, and concerns a wide set of target elements. Multiple and single electron scattering models implemented in Geant4, as well as preassembled selections of physics models distributed within Geant4, are analyzed with statistical methods. The evaluations concern Geant4 versions from 9.1 to 10.1. Significant evolutions are observed over the range of Geant4 versions, not always in the direction of better compatibility with experiment. Goodness-of-fit tests complemented by categorical analysis tests identify a configuration based on Geant4 Urban multiple scattering model in Geant4 vers...

  8. Distribution of uranium in kolm. Evidence from backscattered electron imagery

    Energy Technology Data Exchange (ETDEWEB)

    Parnell, J [Dep. of Geology, Belfast (Northern Ireland)

    1985-02-06

    The distribution of uranium in kolm from Upper Cambriam alum shales has been studied using backscattered electron imagery, and found to be concentrated in discrete mineral phases. Authigenic minerals in kolm include pyrite, galena, and a cerium-bearing mineral referable to monazite. Uranium occurs within the monazite and generally shows a close relationship with phosphorus. Uranium bearing monazite has also been identified within the host alum shale.

  9. High-energy electron diffraction and microscopy

    CERN Document Server

    Peng, L M; Whelan, M J

    2011-01-01

    This book provides a comprehensive introduction to high energy electron diffraction and elastic and inelastic scattering of high energy electrons, with particular emphasis on applications to modern electron microscopy. Starting from a survey of fundamental phenomena, the authors introduce the most important concepts underlying modern understanding of high energy electron diffraction. Dynamical diffraction in transmission (THEED) and reflection (RHEED) geometries is treated using ageneral matrix theory, where computer programs and worked examples are provided to illustrate the concepts and to f

  10. Composition quantification of electron-transparent samples by backscattered electron imaging in scanning electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Müller, E., E-mail: erich.mueller@kit.edu; Gerthsen, D.

    2017-02-15

    The contrast of backscattered electron (BSE) images in scanning electron microscopy (SEM) depends on material parameters which can be exploited for composition quantification if some information on the material system is available. As an example, the In-concentration in thin In{sub x}Ga{sub 1−x}As layers embedded in a GaAs matrix is analyzed in this work. The spatial resolution of the technique is improved by using thin electron-transparent specimens instead of bulk samples. Although the BSEs are detected in a comparably small angular range by an annular semiconductor detector, the image intensity can be evaluated to determine the composition and local thickness of the specimen. The measured intensities are calibrated within one single image to eliminate the influence of the detection and amplification system. Quantification is performed by comparison of experimental and calculated data. Instead of using time-consuming Monte-Carlo simulations, an analytical model is applied for BSE-intensity calculations which considers single electron scattering and electron diffusion. - Highlights: • Sample thickness and composition are quantified by backscattered electron imaging. • A thin sample is used to achieve spatial resolution of few nanometers. • Calculations are carried out with a time-saving electron diffusion model. • Small differences in atomic number and density detected at low electron energies.

  11. LEED (Low Energy Electron Diffraction)

    International Nuclear Information System (INIS)

    Aberdam, M.

    1973-01-01

    The various types of systems studied by LEED, and for which the geometry of diffraction patterns is exploited, are reviewed, intensity profiles being another source of information. Two representative approaches of the scattering phenomenon are examined; the band structure theory and the T matrix approach [fr

  12. Monte Carlo simulation of Tabata's electron backscattering experiments

    International Nuclear Information System (INIS)

    Kirihara, Y.; Namito, Y.; Iwase, H.; Hirayama, H.

    2010-01-01

    Electron backscattering coefficients, η, obtained from several targets in the MeV range were calculated by using electron-photon Monte Carlo transport calculation codes, i.e., EGS5 and ITS 3.0. These calculated values were compared with those obtained from the electron backscattering experiment performed by Tabata using an ionization chamber . We found that Tabata's estimation of the multiplication factor of the ionization chamber, f, had a non-negligible error. Then, we calculated the ionization chamber output, I, which is a product of η and f. The ratios of I between the experimental and the calculated values were within 1.5 and 1.3 for the EGS5 code and the ITS 3.0 code, respectively. The ratios of η between the experimental and the calculated values were within 2.4 and 1.5 for the EGS5 code and the ITS 3.0 code, respectively. The differences between the experimental and the calculated values of I and η are large for low-Z targets (Be and C). Here, the ratios obtained by using the ITS 3.0 code are closer to unity than those obtained by using the EGS5 code. The reason of this is the fact that the calculated value obtained by using the ITS 3.0 code is underestimated for low-Z targets; this underestimation can, in turn, be attributed to the use of the default value of the number of steps in the electron transport algorithm in the ITS 3.0 code.

  13. Transport equation theory of electron backscattering and x-ray production

    International Nuclear Information System (INIS)

    Fathers, D.J.; Rez, P.

    1978-02-01

    A transport equation theory of electron backscattering and x ray production is derived and applied to energy dissipation of 30-KeV electrons for copper as a function of depth and to the energy distribution of backscattered electrons for copper, aluminum, and gold. These results are plotted and compared with experiment. Plots for variations of backscattering with atomic number and with angle of incidence, and polar plots of backscattering for 30-keV electrons at normal incidence are also presented. 10 references, seven figures

  14. Uniting Electron Crystallography and Powder Diffraction

    CERN Document Server

    Shankland, Kenneth; Meshi, Louisa; Avilov, Anatoly; David, William

    2012-01-01

    The polycrystalline and nanocrystalline states play an increasingly important role in exploiting the properties of materials, encompassing applications as diverse as pharmaceuticals, catalysts, solar cells and energy storage. A knowledge of the three-dimensional atomic and molecular structure of materials is essential for understanding and controlling their properties, yet traditional single-crystal X-ray diffraction methods lose their power when only polycrystalline and nanocrystalline samples are available. It is here that powder diffraction and single-crystal electron diffraction techniques take over, substantially extending the range of applicability of the crystallographic principles of structure determination.  This volume, a collection of teaching contributions presented at the Crystallographic Course in Erice in 2011, clearly describes the fundamentals and the state-of-the-art of powder diffraction and electron diffraction methods in materials characterisation, encompassing a diverse range of discipl...

  15. Energy-weighted dynamical scattering simulations of electron diffraction modalities in the scanning electron microscope.

    Science.gov (United States)

    Pascal, Elena; Singh, Saransh; Callahan, Patrick G; Hourahine, Ben; Trager-Cowan, Carol; Graef, Marc De

    2018-04-01

    Transmission Kikuchi diffraction (TKD) has been gaining momentum as a high resolution alternative to electron back-scattered diffraction (EBSD), adding to the existing electron diffraction modalities in the scanning electron microscope (SEM). The image simulation of any of these measurement techniques requires an energy dependent diffraction model for which, in turn, knowledge of electron energies and diffraction distances distributions is required. We identify the sample-detector geometry and the effect of inelastic events on the diffracting electron beam as the important factors to be considered when predicting these distributions. However, tractable models taking into account inelastic scattering explicitly are lacking. In this study, we expand the Monte Carlo (MC) energy-weighting dynamical simulations models used for EBSD [1] and ECP [2] to the TKD case. We show that the foil thickness in TKD can be used as a means of energy filtering and compare band sharpness in the different modalities. The current model is shown to correctly predict TKD patterns and, through the dictionary indexing approach, to produce higher quality indexed TKD maps than conventional Hough transform approach, especially close to grain boundaries. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  16. Ultrafast electron diffraction using an ultracold source

    Directory of Open Access Journals (Sweden)

    M. W. van Mourik

    2014-05-01

    Full Text Available The study of structural dynamics of complex macromolecular crystals using electrons requires bunches of sufficient coherence and charge. We present diffraction patterns from graphite, obtained with bunches from an ultracold electron source, based on femtosecond near-threshold photoionization of a laser-cooled atomic gas. By varying the photoionization wavelength, we change the effective source temperature from 300 K to 10 K, resulting in a concomitant change in the width of the diffraction peaks, which is consistent with independently measured source parameters. This constitutes a direct measurement of the beam coherence of this ultracold source and confirms its suitability for protein crystal diffraction.

  17. Ion beam polishing for three-dimensional electron backscattered diffraction

    DEFF Research Database (Denmark)

    Saowadee, Nath; Agersted, Karsten; Ubhi, H.S.

    2013-01-01

    averaging and/or poor 3D-EBSD data quality. In this work a low kV focused ion beam was successfully implemented to automatically polish surfaces during 3D-EBSD of La- and Nb-doped strontium titanate of volume 12.6 × 12.6 × 3.0 μm. The key to achieving this technique is the combination of a defocused low k...

  18. Modification of diode characteristics by electron back-scatter from high-atomic-number anodes

    International Nuclear Information System (INIS)

    Mosher, D.; Cooperstein, G.; Rose, D.V.; Swanekamp, S.B.

    1996-01-01

    In high-power vacuum diodes with high-atomic-number anodes, back-scattered electrons alter the vacuum space charge and resulting electron and ion currents. Electron multiple back-scattering was studied through equilibrium solutions of the Poisson equation for 1-dimensional, bipolar diodes in order to predict their early-time behavior. Before ion turn-on, back-scattered electrons from high-Z anodes suppress the diode current by about 10%. After ion turn-on in the same diodes, electron back-scatter leads to substantial enhancements of both the electron and ion currents above the Child-Langmuir values. Current enhancements with ion flow from low-Z anodes are small. (author). 5 figs., 7 refs

  19. Modification of diode characteristics by electron back-scatter from high-atomic-number anodes

    Energy Technology Data Exchange (ETDEWEB)

    Mosher, D; Cooperstein, G [Naval Research Laboratory, Washington, DC (United States); Rose, D V; Swanekamp, S B [JAYCOR, Vienna, VA (United States)

    1997-12-31

    In high-power vacuum diodes with high-atomic-number anodes, back-scattered electrons alter the vacuum space charge and resulting electron and ion currents. Electron multiple back-scattering was studied through equilibrium solutions of the Poisson equation for 1-dimensional, bipolar diodes in order to predict their early-time behavior. Before ion turn-on, back-scattered electrons from high-Z anodes suppress the diode current by about 10%. After ion turn-on in the same diodes, electron back-scatter leads to substantial enhancements of both the electron and ion currents above the Child-Langmuir values. Current enhancements with ion flow from low-Z anodes are small. (author). 5 figs., 7 refs.

  20. Deep-inelastic electron-proton diffraction

    International Nuclear Information System (INIS)

    Dainton, J.B.

    1995-11-01

    Recent measurements by the H1 collaboration at HERA of the cross section for deep-inelastic electron-proton scattering in which the proton interacts with minimal energy transfer and limited 4-momentum transfer squared are presented in the form of the contribution F 2 D(3) to the proton structure function F 2 . By parametrising the cross section phenomenologically in terms of a leading effective Regge pole exchange and comparing the result with a similar parametrisation of hadronic pp physics, the proton interaction is demonstrated to be dominantly of a diffractive nature. The quantitative interpretation of the parametrisation in terms of the properties of an effective leading Regge pole exchange, the pomeron (IP), shows that there is no evidence for a 'harder' BFKL-motivated IP in such deep-inelastic proton diffraction. The total contribution of proton diffraction to deep-inelastic electron-proton scattering is measured to be ∝10% and to be rather insensitive to Bjorken-x and Q 2 . A first measurement of the partonic structure of diffractive exchange is presented. It is shown to be readily interpreted in terms of the exchange of gluons, and to suggest that the bulk of diffractive momentum transfer is carried by a leading gluon. (orig.)

  1. Evaluation of the photon monitor backscatter in medical electron accelerators

    International Nuclear Information System (INIS)

    Zrenner, M.; Krieger, H.

    1999-01-01

    Background: Modern linear accelerators permit the use of irregular fields due to their flexible collimator systems with separately movable jaws or multileaf collimators. When using such irregular fields in the clinical practice output factors have to be corrected for enhanced backscatter to the dose monitor as compared with the conventional block shieldings. Methods: A method is presented to detect the monitor backscatter contributions to the output factor for irregular field settings. Results: The monitor backscatter factors have been measured using a telescopic device for 2 different treatment head geometries (Varian Clinac 2100C/D, General Electric Saturne 15) and for 3 photon radiation qualities (nominal energies X6, X18, X12). A method is introduced to calculate the monitor backscatter for arbitrary irregular treatment fields from the experimental data for square or rectangular fields. Conclusions: Besides the corrections for changes in phantom scatter and changes in the aperture, corrections for monitor backscatter have to be taken into account in many clinical cases. They can contribute up to more than 10% compared with the monitor values for free regular fields. (orig.) [de

  2. A multislice theory of electron scattering in crystals including backscattering and inelastic effects.

    Science.gov (United States)

    Spiegelberg, Jakob; Rusz, Ján

    2015-12-01

    In the framework of the slice transition operator technique, a general multislice theory for electron scattering in crystals is developed. To achieve this generalization, we combine the approaches for inelastic scattering derived by Yoshioka [J. Phys. Soc. Jpn. 12, 6 (1957)] and backscattering based on the formalism of Chen and Van Dyck [Ultramicroscopy 70, 29-44 (1997)]. A computational realization of the obtained equations is suggested. The proposed computational scheme is tested on elastic backscattering of electrons, where we consider single backscattering in analogy to the computational scheme proposed by Chen and Van Dyck. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Precession electron diffraction – a topical review

    Directory of Open Access Journals (Sweden)

    Paul A. Midgley

    2015-01-01

    Full Text Available In the 20 years since precession electron diffraction (PED was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis.

  4. Influence of Plastic Deformation of Steel Samples on the Fast electron Backscattering

    International Nuclear Information System (INIS)

    Sierra Trujillo, J. X.; Herrera Palma, V.; Desdin Garcia, L. F.; Codorniu Pujals, D.

    2013-01-01

    A considerable fraction of a fast electron beam incident on a target is scattered in backward direction. It is a very complex process involving electron - nucleus and electron - electron collisions. The fraction of backscattered electrons is described by a parameterization as a function of the atomic number and energy of the incident electrons. In such approaches the possible influence of the material structure is not taken into account. In this paper, the behavior of the 90 Sr/ 90 Y backscattered electrons from 08JuA and 15GJuT steel strained samples is investigated. A clear dependence between the degree of plastic deformation and the fraction of backscattered electrons was observed. This relationship is explained by the interaction of electrons with the dislocations in the material, whose density depends on the magnitude of the strain in the plastic region. On the basis of a simple model for describing this interaction, a mathematical expression is obtained for the relationship between the fraction of backscattered electrons and the degree of deformation. (Author)

  5. Future of Electron Scattering and Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Ernest [GE Global Research, Niskayuna, New York (United States); Stemmer, Susanne [Univ. of California, Santa Barbara, CA (United States); Zheng, Haimei [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Zhu, Yimei [Brookhaven National Lab. (BNL), Upton, NY (United States); Maracas, George [Dept. of Energy (DOE), Washington DC (United States). Office of Science

    2014-02-25

    The ability to correlate the atomic- and nanoscale-structure of condensed matter with physical properties (e.g., mechanical, electrical, catalytic, and optical) and functionality forms the core of many disciplines. Directing and controlling materials at the quantum-, atomic-, and molecular-levels creates enormous challenges and opportunities across a wide spectrum of critical technologies, including those involving the generation and use of energy. The workshop identified next generation electron scattering and diffraction instruments that are uniquely positioned to address these grand challenges. The workshop participants identified four key areas where the next generation of such instrumentation would have major impact: A – Multidimensional Visualization of Real Materials B – Atomic-scale Molecular Processes C – Photonic Control of Emergence in Quantum Materials D – Evolving Interfaces, Nucleation, and Mass Transport Real materials are comprised of complex three-dimensional arrangements of atoms and defects that directly determine their potential for energy applications. Understanding real materials requires new capabilities for three-dimensional atomic scale tomography and spectroscopy of atomic and electronic structures with unprecedented sensitivity, and with simultaneous spatial and energy resolution. Many molecules are able to selectively and efficiently convert sunlight into other forms of energy, like heat and electric current, or store it in altered chemical bonds. Understanding and controlling such process at the atomic scale require unprecedented time resolution. One of the grand challenges in condensed matter physics is to understand, and ultimately control, emergent phenomena in novel quantum materials that necessitate developing a new generation of instruments that probe the interplay among spin, charge, orbital, and lattice degrees of freedom with intrinsic time- and length-scale resolutions. Molecules and soft matter require imaging and

  6. A simple way to obtain backscattered electron images in a scanning transmission electron microscope.

    Science.gov (United States)

    Tsuruta, Hiroki; Tanaka, Shigeyasu; Tanji, Takayoshi; Morita, Chiaki

    2014-08-01

    We have fabricated a simple detector for backscattered electrons (BSEs) and incorporated the detector into a scanning transmission electron microscope (STEM) sample holder. Our detector was made from a 4-mm(2) Si chip. The fabrication procedure was easy, and similar to a standard transmission electron microscopy (TEM) sample thinning process based on ion milling. A TEM grid containing particle objects was fixed to the detector with a silver paste. Observations were carried out using samples of Au and latex particles at 75 and 200 kV. Such a detector provides an easy way to obtain BSE images in an STEM. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. Monte Carlo simulation of MOSFET dosimeter for electron backscatter using the GEANT4 code.

    Science.gov (United States)

    Chow, James C L; Leung, Michael K K

    2008-06-01

    The aim of this study is to investigate the influence of the body of the metal-oxide-semiconductor field effect transistor (MOSFET) dosimeter in measuring the electron backscatter from lead. The electron backscatter factor (EBF), which is defined as the ratio of dose at the tissue-lead interface to the dose at the same point without the presence of backscatter, was calculated by the Monte Carlo simulation using the GEANT4 code. Electron beams with energies of 4, 6, 9, and 12 MeV were used in the simulation. It was found that in the presence of the MOSFET body, the EBFs were underestimated by about 2%-0.9% for electron beam energies of 4-12 MeV, respectively. The trend of the decrease of EBF with an increase of electron energy can be explained by the small MOSFET dosimeter, mainly made of epoxy and silicon, not only attenuated the electron fluence of the electron beam from upstream, but also the electron backscatter generated by the lead underneath the dosimeter. However, this variation of the EBF underestimation is within the same order of the statistical uncertainties as the Monte Carlo simulations, which ranged from 1.3% to 0.8% for the electron energies of 4-12 MeV, due to the small dosimetric volume. Such small EBF deviation is therefore insignificant when the uncertainty of the Monte Carlo simulation is taken into account. Corresponding measurements were carried out and uncertainties compared to Monte Carlo results were within +/- 2%. Spectra of energy deposited by the backscattered electrons in dosimetric volumes with and without the lead and MOSFET were determined by Monte Carlo simulations. It was found that in both cases, when the MOSFET body is either present or absent in the simulation, deviations of electron energy spectra with and without the lead decrease with an increase of the electron beam energy. Moreover, the softer spectrum of the backscattered electron when lead is present can result in a reduction of the MOSFET response due to stronger

  8. Structure determination of modulated structures by powder X-ray diffraction and electron diffraction

    Czech Academy of Sciences Publication Activity Database

    Zhou, Z.Y.; Palatinus, Lukáš; Sun, J.L.

    2016-01-01

    Roč. 3, č. 11 (2016), s. 1351-1362 ISSN 2052-1553 Institutional support: RVO:68378271 Keywords : electron diffraction * incommensurate structure * powder diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.036, year: 2016

  9. Mineralogical applications of electron diffraction. 1. Theory and techniques

    Science.gov (United States)

    Ross, Malcolm; Christ, C.L.

    1958-01-01

    The small wavelengths used in electron-diffraction experiments and the thinness of the crystals necessary for the transmission of the electron beam combine to require a somewhat different diffraction geometry for the interpretation of electron-diffraction patterns than is used in the interpretation of X-ray diffraction patterns. This geometry, based on the reciprocal lattice concept and geometrical construction of Ewald, needed for the interpretation.

  10. Backscattering of projectile-bound electrons from solid surfaces

    International Nuclear Information System (INIS)

    Tobisch, M.; Schosnig, M.; Kroneberger, K.; Kuzel, M.; Maier, R.; Jung, M.; Fiedler, C.; Rothard, H.; Clouvas, A.; Suarez, S.; Groeneveld, K.O.

    1994-01-01

    The contribution of projectile ionization (PI) to secondary electron emission is studied by collision of H 2 + and H 3 + ions (400 keV/u and 700 keV/u) with carbon, copper and gold targets (600 A). The measured doubly differential intensity distribution shows a peak of lost projectile electrons near - v p . We describe the subtraction of the contribution of target ionization (TI), and compare the remaining electron intensities with a BEA calculation. For solids we observe a strong energy shift of the electron loss peak, which is compared with the influence of electron transport and binding energy. Furthermore, the low energy tail of the electron loss peak indicates the simultaneous occurrence of PI and TI. Finally we discuss the influence of surface conditions and the dependence of the observation angles on the measured electron intensities. (orig.)

  11. The ELSA laser beamline for electron polarization measurements via Compton backscattering

    Energy Technology Data Exchange (ETDEWEB)

    Switka, Michael; Hinterkeuser, Florian; Koop, Rebecca; Hillert, Wolfgang [Electron Stretcher Facility ELSA, Physics Institute of Bonn University (Germany)

    2016-07-01

    The Electron Stretcher Facility ELSA provides a spin polarized electron beam with energies of 0.5 - 3.2 GeV for double polarization hadron physics experiments. As of 2015, the laser beamline of the polarimeter based on Compton backscattering restarted operation. It consists of a cw disk laser with design total beam power of 40 W and features two polarized 515 nm photon beams colliding head-on with the stored electron beam in ELSA. The polarization measurement is based on the vertical profile asymmetry of the back-scattered photons, which is dependent on the polarization degree of the stored electron beam. After recent laser repairs, beamline and detector modifications, the properties of the beamline have been determined and first measurements of the electron polarization degree were conducted. The beamline performance and first measurements are presented.

  12. Absorption and backscatter of internal conversion electrons in the measurements of surface contamination of 137Cs

    International Nuclear Information System (INIS)

    Yunoki, A.; Kawada, Y.; Yamada, T.; Unno, Y.; Sato, Y.; Hino, Y.

    2013-01-01

    We measured 4π and 2π counting efficiencies for internal conversion electrons (ICEs), gross β-particles and also β-rays alone with various source conditions regarding absorber and backing foil thickness using e-X coincidence technique. Dominant differences regarding the penetration, attenuation and backscattering properties among ICEs and β-rays were revealed. Although the abundance of internal conversion electrons of 137 Cs- 137 Ba is only 9.35%, 60% of gross counts may be attributed to ICEs in worse source conditions. This information will be useful for radionuclide metrology and for surface contamination monitoring. - Highlights: • Counting efficiencies for internal conversion electrons from 137 Cs were measured, and compared with those for β-rays. • Electron-X coincidence technique was employed. • A thin NaI(Tl) scintillation detector was used for X-ray detection. • Backscattering fractions of electrons and beta particles were studied by similar experiments

  13. Carbon/Hydrogen ratio determination in hydrocarbons and its mixtures by electron backscattering technique

    International Nuclear Information System (INIS)

    Padron, I.; Desdin, L.F.; Navarro, A.; Fuentes, M.

    1996-01-01

    A method carbon/hydrogen ratio (C/H) determination in hydrocarbons and its mixtures was improved using the electron backscattering technique. Besides the hetero atoms (S,O and N) influence in petroleum is studied for being able to determinate the C/H ratio in cuban petroleum with high sulphur contents

  14. Contribution of back-scattered electromagnetic rays to the Moessbauer conversion electron spectrum

    International Nuclear Information System (INIS)

    Ruskov, T.; Ruskov, R.; Paneva, D.; Lefterov, D.

    1999-01-01

    The contribution of back-scattered electromagnetic rays in a 57 Fe conversion electron Moessbauer spectrum is considered using proportional counter as a detector. A simplified method for measuring this contribution is described. The experimental results show that this contribution strongly depends on the construction of the counter and the selected fraction in the pulse-height spectrum

  15. Evaluation of backscatter dose from internal lead shielding in clinical electron beams using EGSnrc Monte Carlo simulations.

    Science.gov (United States)

    De Vries, Rowen J; Marsh, Steven

    2015-11-08

    Internal lead shielding is utilized during superficial electron beam treatments of the head and neck, such as lip carcinoma. Methods for predicting backscattered dose include the use of empirical equations or performing physical measurements. The accuracy of these empirical equations required verification for the local electron beams. In this study, a Monte Carlo model of a Siemens Artiste linac was developed for 6, 9, 12, and 15 MeV electron beams using the EGSnrc MC package. The model was verified against physical measurements to an accuracy of better than 2% and 2mm. Multiple MC simulations of lead interfaces at different depths, corresponding to mean electron energies in the range of 0.2-14 MeV at the interfaces, were performed to calculate electron backscatter values. The simulated electron backscatter was compared with current empirical equations to ascertain their accuracy. The major finding was that the current set of backscatter equations does not accurately predict electron backscatter, particularly in the lower energies region. A new equation was derived which enables estimation of electron backscatter factor at any depth upstream from the interface for the local treatment machines. The derived equation agreed to within 1.5% of the MC simulated electron backscatter at the lead interface and upstream positions. Verification of the equation was performed by comparing to measurements of the electron backscatter factor using Gafchromic EBT2 film. These results show a mean value of 0.997 ± 0.022 to 1σ of the predicted values of electron backscatter. The new empirical equation presented can accurately estimate electron backscatter factor from lead shielding in the range of 0.2 to 14 MeV for the local linacs.

  16. Quantitative Test of the Evolution of Geant4 Electron Backscattering Simulation

    CERN Document Server

    Basaglia, Tullio; Hoff, Gabriela; Kim, Chan Hyeong; Kim, Sung Hun; Pia, Maria Grazia; Saracco, Paolo

    2016-01-01

    Evolutions of Geant4 code have affected the simulation of electron backscattering with respect to previously published results. Their effects are quantified by analyzing the compatibility of the simulated electron backscattering fraction with a large collection of experimental data for a wide set of physics configuration options available in Geant4. Special emphasis is placed on two electron scattering implementations first released in Geant4 version 10.2: the Goudsmit-Saunderson multiple scattering model and a single Coulomb scattering model based on Mott cross section calculation. The new Goudsmit-Saunderson multiple scattering model appears to perform equally or less accurately than the model implemented in previous Geant4 versions, depending on the electron energy. The new Coulomb scattering model was flawed from a physics point of view, but computationally fast in Geant4 version 10.2; the physics correction released in Geant4 version 10.2p01 severely degrades its computational performance. Evolutions in ...

  17. 3D invariant embedding model for backscattering electrons applied to materials characterization

    International Nuclear Information System (INIS)

    Figueroa, C.; Nieva, N.; Heluani, S.P.

    2007-01-01

    In this work, the results of a 3D model used to describe the fraction of backscattered electrons, together with its energy and angular distributions, are reported. This 3D model is the result of improvements in the Invariant Embedding Approach to Microanalysis (IEAM). Comparisons with experiment show that the theoretical results follow the general trend of experimental data, when parameters (such as atomic number, energy of the impinging electrons and tilted angle) are changed

  18. NIST/Sandia/ICDD Electron Diffraction Database: A Database for Phase Identification by Electron Diffraction.

    Science.gov (United States)

    Carr, M J; Chambers, W F; Melgaard, D; Himes, V L; Stalick, J K; Mighell, A D

    1989-01-01

    A new database containing crystallographic and chemical information designed especially for application to electron diffraction search/match and related problems has been developed. The new database was derived from two well-established x-ray diffraction databases, the JCPDS Powder Diffraction File and NBS CRYSTAL DATA, and incorporates 2 years of experience with an earlier version. It contains 71,142 entries, with space group and unit cell data for 59,612 of those. Unit cell and space group information were used, where available, to calculate patterns consisting of all allowed reflections with d -spacings greater than 0.8 A for ~ 59,000 of the entries. Calculated patterns are used in the database in preference to experimental x-ray data when both are available, since experimental x-ray data sometimes omits high d -spacing data which falls at low diffraction angles. Intensity data are not given when calculated spacings are used. A search scheme using chemistry and r -spacing (reciprocal d -spacing) has been developed. Other potentially searchable data in this new database include space group, Pearson symbol, unit cell edge lengths, reduced cell edge length, and reduced cell volume. Compound and/or mineral names, formulas, and journal references are included in the output, as well as pointers to corresponding entries in NBS CRYSTAL DATA and the Powder Diffraction File where more complete information may be obtained. Atom positions are not given. Rudimentary search software has been written to implement a chemistry and r -spacing bit map search. With typical data, a full search through ~ 71,000 compounds takes 10~20 seconds on a PDP 11/23-RL02 system.

  19. The Heisenberg Uncertainty Principle Demonstrated with An Electron Diffraction Experiment

    Science.gov (United States)

    Matteucci, Giorgio; Ferrari, Loris; Migliori, Andrea

    2010-01-01

    An experiment analogous to the classical diffraction of light from a circular aperture has been realized with electrons. The results are used to introduce undergraduate students to the wave behaviour of electrons. The diffraction fringes produced by the circular aperture are compared to those predicted by quantum mechanics and are exploited to…

  20. Energy analyzer for Auger electron spectroscopy and low-energy backscattering ion spectroscopy

    International Nuclear Information System (INIS)

    Volkov, S.S.; Gorelik, V.A.; Gutenko, V.T.; Protopopov, O.D.; Trubitsin, A.A.; Shuvalova, Z.A.; Yakushev, G.A.

    1988-01-01

    Energy analyzer for electron Auger spectroscopy and low-energy backscattering ion spectroscopy is described. Analyzer presents one-cascade variant of cylindrical mirror with second-order focusing. Energy relative resolution is continuously adjusted within 0.2-1.2% limits. Signal/noise relation by Cu Auger-line at 1 muA current of exciting beam changes upper limit of range 150-450

  1. Atomic resolution three-dimensional electron diffraction microscopy

    International Nuclear Information System (INIS)

    Miao Jianwei; Ohsuna, Tetsu; Terasaki, Osamu; Hodgson, Keith O.; O'Keefe, Michael A.

    2002-01-01

    We report the development of a novel form of diffraction-based 3D microscopy to overcome resolution barriers inherent in high-resolution electron microscopy and tomography. By combining coherent electron diffraction with the oversampling phasing method, we show that the 3D structure of a nanocrystal can be determined ab initio at a resolution of 1 Angstrom from 29 simulated noisy diffraction patterns. This new form of microscopy can be used to image the 3D structures of nanocrystals and noncrystalline samples, with resolution limited only by the quality of sample diffraction

  2. Direct observation of the hydrogen peak in the energy distribution of electrons backscattered elastically from polyethylene

    International Nuclear Information System (INIS)

    Varga, D.; Toekesi, K.; Berenyi, Z.; Toth, J.; Koever, L.

    2004-01-01

    Complete text of publication follows. Observation of the hydrogen peak is either challenging or impossible task for the conventional electron spectroscopy. Hydrogen was observed earlier in electron scattering experiments using transmission geometry and formvar film. In this work we show an alternative way for the detection of hydrogen peak analyzing the spectra of elastically backscattered electrons from polyethylene ((CH 2 ) n ). We take advantage of the fact that the elastic peak from polyethylene split into carbon and hydrogen components. The energy of the elastically scattered electrons is shifted from the nominal values due to the energy transfer between the primary electron and the target atoms (recoil effect). Due to the motion of the scattering atoms, a broadering of the energy width of the spectra takes place. We performed Monte Carlo simulation for 2 keV electrons penetrated and elastically backscattered from polyethylene sample. In our calculations both the elastic and inelastic scattering events were taken into account. We further assume that the thermal motion of the target atoms follows the Maxwell-Boltzmann energy distribution. After each elastic scattering the recoil energy was calculated according to ref Fig. 1 shows the geometric configuration used in the calculation. The initial angle of incident beam (θ) was 50 deg. Fig. 2 shows the gray scale plot of the intensity of electrons backscattered elastically from polyethylene. The separation between the carbon and hydrogen peaks is clearly seen. Our results show that the multiple electron scattering causes only minor changes in the energy shifts and broadenings of elastic peaks. Moreover, our simulations are in good agreement with our experimental observations. (author)

  3. Calculation and construction of electron-diffraction photographs using computer

    International Nuclear Information System (INIS)

    Khayurov, S.S.; Notkin, A.B.

    1981-01-01

    A method of computer construction and indexing of theoretical electronograms for monophase structures with arbitrary type of crystal lattice and for polyphase ones with known orientational coorrelations between phases is presented. Electron-diffraction photograph is presented, obtained from the foil area of two-phase VT22 alloy at β phase orientation in comparison with theoretical electron-diffraction photographs, built ap by computer, with the [100] β phase zone axis and with three variants of α phase orientation relatively to β phase. It is shown that on the experimental electron-diffraction photograph simultaneously presents α-phase three orientations, which reflexes can be indexing correctly [ru

  4. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Musumeci, P. [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA 90095-1547 (United States)], E-mail: musumeci@physics.ucla.edu; Moody, J.T.; Scoby, C.M. [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA 90095-1547 (United States)

    2008-10-15

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10{sup 7}-10{sup 8} electrons packed in bunches of {approx}100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics.

  5. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory

    International Nuclear Information System (INIS)

    Musumeci, P.; Moody, J.T.; Scoby, C.M.

    2008-01-01

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10 7 -10 8 electrons packed in bunches of ∼100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics

  6. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory.

    Science.gov (United States)

    Musumeci, P; Moody, J T; Scoby, C M

    2008-10-01

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10(7)-10(8) electrons packed in bunches of approximately 100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics.

  7. rf streak camera based ultrafast relativistic electron diffraction.

    Science.gov (United States)

    Musumeci, P; Moody, J T; Scoby, C M; Gutierrez, M S; Tran, T

    2009-01-01

    We theoretically and experimentally investigate the possibility of using a rf streak camera to time resolve in a single shot structural changes at the sub-100 fs time scale via relativistic electron diffraction. We experimentally tested this novel concept at the UCLA Pegasus rf photoinjector. Time-resolved diffraction patterns from thin Al foil are recorded. Averaging over 50 shots is required in order to get statistics sufficient to uncover a variation in time of the diffraction patterns. In the absence of an external pump laser, this is explained as due to the energy chirp on the beam out of the electron gun. With further improvements to the electron source, rf streak camera based ultrafast electron diffraction has the potential to yield truly single shot measurements of ultrafast processes.

  8. High energy electron multibeam diffraction and imaging

    International Nuclear Information System (INIS)

    Bourret, Alain.

    1980-04-01

    The different theories of dynamical scattering of electrons are firstly reviewed with special reference to their basis and the validity of the different approximations. Then after a short description of the different experimental set ups, structural analysis and the investigation of the optical potential by means of high energy electrons will be surveyed

  9. Backscattered electron imaging at low emerging angles: A physical approach to contrast in LVSEM

    Energy Technology Data Exchange (ETDEWEB)

    Cazaux, J., E-mail: jacques.cazaux@univ-reims.fr [LISM, EA 4695 Faculty of Sciences, BP 1039, 51687 Reims Cedex 2 (France); Kuwano, N. [Malaysia–Japan International Institute of Technology, Universiti Teknologi Malaysia, Jalan Semarak, 54100 Kuala Lumpur (Malaysia); Sato, K. [Steel Research Laboratory, JFE Steel Corporation, 1 Kawasaki-cho, Chuo-ku, Chiba 260-0835 (Japan)

    2013-12-15

    Due to the influence of refraction effects on the escape probability of the Back-Scattered Electrons (BSE), an expression of the fraction of these BSE is given as a function of the beam energy, E°, and emission angle (with respect to the normal) α. It has been shown that these effects are very sensitive to a local change of the work function in particular for low emerging angles. This sensitivity suggests a new type of contrast in Low Voltage Scanning Electron Microscopy (LVSEM for E°<2 keV): the work function contrast. Involving the change of ϕ with crystalline orientation, this possibility is supported by a new interpretation of a few published images. Some other correlated contrasts are also suggested. These are topographical contrasts or contrasts due to subsurface particles and cracks. Practical considerations of the detection system and its optimization are indicated. - Highlights: • Refraction effects experienced by Back-Scattered Electrons at sample/vacuum interfaces are evaluated as a function of energy and angles. • Sensitive to local work function changes with crystalline orientation these effects concern mainly keV-electrons at low emerging angles. • A new type of contrast in SEM is thus deduced and illustrated. • Some other correlated contrasts, topographical contrasts or contrasts due to subsurface particles and cracks are also suggested.

  10. Backscattered electron emission after proton impact on carbon and gold films: Experiments and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Hespeels, F.; Heuskin, A.C. [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium); Scifoni, E. [TIFPA-INFN, Trento Institute for Fundamental Physics and Applications, Via Sommarive 14, I-38123 Trento (Italy); GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Kraemer, M. [GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Lucas, S., E-mail: stephane.lucas@unamur.be [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium)

    2017-06-15

    This work aims at measuring the proton induced secondary electron energy spectra from nanometer thin films. Backscattered electron energy spectra were measured within an energy range from 0 to 600 eV using a Retarding Field Analyser (RFA). This paper presents energy spectra obtained for proton (0.5 MeV; 1 MeV; 1.5 MeV; 2 MeV) irradiation of thin carbon films (50 and 100 nm thick) and thin gold film (200 nm). These experimental spectra were compared with Monte Carlo simulations based on TRAX code and Geant4 simulation toolkit. Good agreement between experimental, TRAX and Geant4 results were observed for the carbon target. For the gold target, we report major differences between both Monte Carlo environments. Limitation of Geant4 models for low energy electron emission was highlighted. On the contrary, TRAX simulations present encouraging results for the modeling of low-energy electron emission from gold target.

  11. Quantitative analysis of the energy distributions of electrons backscattered elastically from polyethylene

    International Nuclear Information System (INIS)

    Tőkési, K.; Varga, D.; Berényi, Z.

    2015-01-01

    We present results of theoretical and experimental studies of the spectra of electrons backscattered elastically from polyethylene in the primary energy range between 1 and 5 keV. The experiments were performed using a high energy resolution electron spectroscopy. The theoretical interpretation is based on a Monte Carlo simulation of the recoil and Doppler effects. The separation between the carbon and hydrogen peak in the energy distributions is shown as a function of the primary electron energy. The simulations give many partial distributions separately, depending on the number of elastic scatterings (single, and multiple scatterings of different types). We show our results for intensity ratios, peak shifts and broadenings. We also present detailed analytical calculations for the main parameters of a single scattering. Finally, we present a qualitative comparison with the experimental data. We find our resulting energy distribution of elastically scattered electrons to be in good agreement with our measurements

  12. Time evolution analysis of the electron distribution in Thomson/Compton back-scattering

    International Nuclear Information System (INIS)

    Petrillo, V.; Bacci, A.; Curatolo, C.; Maroli, C.; Serafini, L.; Rossi, A. R.

    2013-01-01

    We present the time evolution of the energy distribution of a relativistic electron beam after the Compton back-scattering with a counter-propagating laser field, performed in the framework of the Quantum Electrodynamics, by means of the code CAIN. As the correct angular distribution of the spontaneous emission is accounted, the main effect is the formation of few stripes, followed by the diffusion of the more energetic particles toward lower values in the longitudinal phase space. The Chapman-Kolmogorov master equation gives results in striking agreement with the numerical ones. An experiment on the Thomson source at SPARC-LAB is proposed

  13. Ultrafast electron diffraction studies of optically excited thin bismuth films

    International Nuclear Information System (INIS)

    Rajkovic, Ivan

    2008-01-01

    This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)

  14. Ultrafast electron diffraction studies of optically excited thin bismuth films

    Energy Technology Data Exchange (ETDEWEB)

    Rajkovic, Ivan

    2008-10-21

    This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)

  15. Electron and ion currents relevant to accurate current integration in MeV ion backscattering spectrometry

    International Nuclear Information System (INIS)

    Matteson, S.; Nicolet, M.A.

    1979-01-01

    The magnitude and characteristics of the currents which flow in the target and the chamber of an MeV ion backscattering spectrometer are examined. Measured energy distributions and the magnitude of high-energy secondary electron currents are reported. An empirical universal curve is shown to fit the energy distribution of secondary electrons for several combinations of ion energy, targets and ion species. The magnitude of tertiary electron currents which arise at the vacuum vessel walls is determined for various experimental situations and is shown to be non-negligible in many cases. An experimental arrangement is described which permits charge integrations to 1% arruracy without restricting access to the target as a Faraday cage does. (Auth.)

  16. Contrast of Backscattered Electron SEM Images of Nanoparticles on Substrates with Complex Structure

    Directory of Open Access Journals (Sweden)

    Thomas Kowoll

    2017-01-01

    Full Text Available This study is concerned with backscattered electron scanning electron microscopy (BSE SEM contrast of complex nanoscaled samples which consist of SiO2 nanoparticles (NPs deposited on indium-tin-oxide covered bulk SiO2 and glassy carbon substrates. BSE SEM contrast of NPs is studied as function of the primary electron energy and working distance. Contrast inversions are observed which prevent intuitive interpretation of NP contrast in terms of material contrast. Experimental data is quantitatively compared with Monte-Carlo- (MC- simulations. Quantitative agreement between experimental data and MC-simulations is obtained if the transmission characteristics of the annular semiconductor detector are taken into account. MC-simulations facilitate the understanding of NP contrast inversions and are helpful to derive conditions for optimum material and topography contrast.

  17. Contrast of Backscattered Electron SEM Images of Nanoparticles on Substrates with Complex Structure.

    Science.gov (United States)

    Kowoll, Thomas; Müller, Erich; Fritsch-Decker, Susanne; Hettler, Simon; Störmer, Heike; Weiss, Carsten; Gerthsen, Dagmar

    2017-01-01

    This study is concerned with backscattered electron scanning electron microscopy (BSE SEM) contrast of complex nanoscaled samples which consist of SiO 2 nanoparticles (NPs) deposited on indium-tin-oxide covered bulk SiO 2 and glassy carbon substrates. BSE SEM contrast of NPs is studied as function of the primary electron energy and working distance. Contrast inversions are observed which prevent intuitive interpretation of NP contrast in terms of material contrast. Experimental data is quantitatively compared with Monte-Carlo- (MC-) simulations. Quantitative agreement between experimental data and MC-simulations is obtained if the transmission characteristics of the annular semiconductor detector are taken into account. MC-simulations facilitate the understanding of NP contrast inversions and are helpful to derive conditions for optimum material and topography contrast.

  18. A method of combining STEM image with parallel beam diffraction and electron-optical conditions for diffractive imaging

    International Nuclear Information System (INIS)

    He Haifeng; Nelson, Chris

    2007-01-01

    We describe a method of combining STEM imaging functionalities with nanoarea parallel beam electron diffraction on a modern TEM. This facilitates the search for individual particles whose diffraction patterns are needed for diffractive imaging or structural studies of nanoparticles. This also lays out a base for 3D diffraction data collection

  19. False colour backscatter electron images and their application during electron microprobe analysis of ores and host rocks

    International Nuclear Information System (INIS)

    Cousens, D.R.; French, D.H.; Ramsden, A.R.

    1989-01-01

    The limited contrast range of conventional black and white imaging does not enable full use to be made of the dynamic range of the video signal obtained from a scanning electron microscope or microprobe. The use of false colour substantially increases the information that can be derived from such images enabling relationships to be displayed that cannot be observed in black and white. This capability is now used extensively in combination with quantitative electron microprobe analysis as a research tool for ore characterization and host rocks studies related to minerals exploration in the CSIRO Div.sion of Exploration Geoscience. Thus the CAMEBAX scanning electron microprobe has been modified to allow digital images acquisition and software (IMAGE) developed which allows false colour backscatter electron (BSE) images to be obtained during the course of routine electron microprobe analysis. 1 fig

  20. Evaluation of computational models and cross sections used by MCNP6 for simulation of electron backscattering

    Energy Technology Data Exchange (ETDEWEB)

    Poškus, Andrius, E-mail: andrius.poskus@ff.vu.lt

    2016-02-01

    This work evaluates the accuracy of the single-event (SE) and condensed-history (CH) models of electron transport in Monte Carlo simulations of electron backscattering from thick layers of Be, C, Al, Cu, Ag, Au and U at incident electron energies from 200 eV to 15 MeV. The CH method is used in simulations performed with MCNP6.1, and the SE method is used in simulations performed with an open-source single-event code MCNelectron written by the author of this paper. Both MCNP6.1 and MCNelectron use mainly ENDF/B-VI.8 library data, but MCNelectron allows replacing cross sections of certain types of interactions by alternative datasets from other sources. The SE method is evaluated both using only ENDF/B-VI.8 cross sections (the “SE-ENDF/B method”, which is equivalent to using MCNP6.1 in SE mode) and with an alternative set of elastic scattering cross sections obtained from relativistic (Dirac) partial-wave (DPW) calculations (the “SE-DPW method”). It is shown that at energies from 200 eV to 300 keV the estimates of the backscattering coefficients obtained using the SE-DPW method are typically within 10% of the experimental data, which is approximately the same accuracy that is achieved using MCNP6.1 in CH mode. At energies below 1 keV and above 300 keV, the SE-DPW method is much more accurate than the SE-ENDF/B method due to lack of angular distribution data in the ENDF/B library in those energy ranges. At energies from 500 keV to 15 MeV, the CH approximation is roughly twice more accurate than the SE-DPW method, with the average relative errors equal 7% and 14%, respectively. The energy probability density functions (PDFs) of backscattered electrons for Al and Cu, calculated using the SE method with DPW cross sections when energy of incident electrons is 20 keV, have an average absolute error as low as 4% of the average PDF. This error is approximately twice less than the error of the corresponding PDF calculated using the CH approximation. It is concluded

  1. Characterizing deformed ultrafine-grained and nanocrystalline materials using transmission Kikuchi diffraction in a scanning electron microscope

    International Nuclear Information System (INIS)

    Trimby, Patrick W.; Cao, Yang; Chen, Zibin; Han, Shuang; Hemker, Kevin J.; Lian, Jianshe; Liao, Xiaozhou; Rottmann, Paul; Samudrala, Saritha; Sun, Jingli; Wang, Jing Tao; Wheeler, John; Cairney, Julie M.

    2014-01-01

    Graphical abstract: -- Abstract: The recent development of transmission Kikuchi diffraction (TKD) in a scanning electron microscope enables fast, automated orientation mapping of electron transparent samples using standard electron backscatter diffraction (EBSD) hardware. TKD in a scanning electron microscope has significantly better spatial resolution than conventional EBSD, enabling routine characterization of nanocrystalline materials and allowing effective measurement of samples that have undergone severe plastic deformation. Combining TKD with energy dispersive X-ray spectroscopy (EDS) provides complementary chemical information, while a standard forescatter detector system below the EBSD detector can be used to generate dark field and oriented dark field images. Here we illustrate the application of this exciting new approach to a range of deformed, ultrafine grained and nanocrystalline samples, including duplex stainless steel, nanocrystalline copper and highly deformed titanium and nickel–cobalt. The results show that TKD combined with EDS is a highly effective and widely accessible tool for measuring key microstructural parameters at resolutions that are inaccessible using conventional EBSD

  2. Angle selective backscattered electron contrast in the low-voltage scanning electron microscope: Simulation and experiment for polymers

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Q., E-mail: qwan2@sheffield.ac.uk [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Masters, R.C. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Lidzey, D. [Department of Physics and Astronomy, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Abrams, K.J. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Dapor, M. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT-FBK) and Trento Institute for Fundamental Physics and Applications (TIFPA-INFN), via Sommarive 18, I-38123 Trento (Italy); Plenderleith, R.A. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Rimmer, S. [Department of Chemistry, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Claeyssens, F.; Rodenburg, C. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom)

    2016-12-15

    Recently developed detectors can deliver high resolution and high contrast images of nanostructured carbon based materials in low voltage scanning electron microscopes (LVSEM) with beam deceleration. Monte Carlo Simulations are also used to predict under which exact imaging conditions purely compositional contrast can be obtained and optimised. This allows the prediction of the electron signal intensity in angle selective conditions for back-scattered electron (BSE) imaging in LVSEM and compares it to experimental signals. Angle selective detection with a concentric back scattered (CBS) detector is considered in the model in the absence and presence of a deceleration field, respectively. The validity of the model prediction for both cases was tested experimentally for amorphous C and Cu and applied to complex nanostructured carbon based materials, namely a Poly(N-isopropylacrylamide)/Poly(ethylene glycol) Diacrylate (PNIPAM/PEGDA) semi-interpenetration network (IPN) and a Poly(3-hexylthiophene-2,5-diyl) (P3HT) film, to map nano-scale composition and crystallinity distribution by avoiding experimental imaging conditions that lead to a mixed topographical and compositional contrast - Highlights: • An optimised model for nano-scale analysis of beam sensitive materials by LVSEM. • Simulation and separation of composition and topography in a CBS detector. • Selective angle backscattered electron collection for mapping of polymers.

  3. Angle selective backscattered electron contrast in the low-voltage scanning electron microscope: Simulation and experiment for polymers

    International Nuclear Information System (INIS)

    Wan, Q.; Masters, R.C.; Lidzey, D.; Abrams, K.J.; Dapor, M.; Plenderleith, R.A.; Rimmer, S.; Claeyssens, F.; Rodenburg, C.

    2016-01-01

    Recently developed detectors can deliver high resolution and high contrast images of nanostructured carbon based materials in low voltage scanning electron microscopes (LVSEM) with beam deceleration. Monte Carlo Simulations are also used to predict under which exact imaging conditions purely compositional contrast can be obtained and optimised. This allows the prediction of the electron signal intensity in angle selective conditions for back-scattered electron (BSE) imaging in LVSEM and compares it to experimental signals. Angle selective detection with a concentric back scattered (CBS) detector is considered in the model in the absence and presence of a deceleration field, respectively. The validity of the model prediction for both cases was tested experimentally for amorphous C and Cu and applied to complex nanostructured carbon based materials, namely a Poly(N-isopropylacrylamide)/Poly(ethylene glycol) Diacrylate (PNIPAM/PEGDA) semi-interpenetration network (IPN) and a Poly(3-hexylthiophene-2,5-diyl) (P3HT) film, to map nano-scale composition and crystallinity distribution by avoiding experimental imaging conditions that lead to a mixed topographical and compositional contrast - Highlights: • An optimised model for nano-scale analysis of beam sensitive materials by LVSEM. • Simulation and separation of composition and topography in a CBS detector. • Selective angle backscattered electron collection for mapping of polymers.

  4. Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

    Energy Technology Data Exchange (ETDEWEB)

    Pekin, Thomas C. [Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, USA 94720 (United States); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States); Gammer, Christoph [Erich Schmid Institute of Materials Science, Jahnstrasse 12, Leoben, Austria 8700 (Austria); Ciston, Jim [National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States); Minor, Andrew M. [Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, USA 94720 (United States); National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States); Ophus, Colin, E-mail: cophus@gmail.com [National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, USA 94720 (United States)

    2017-05-15

    Scanning nanobeam electron diffraction strain mapping is a technique by which the positions of diffracted disks sampled at the nanoscale over a crystalline sample can be used to reconstruct a strain map over a large area. However, it is important that the disk positions are measured accurately, as their positions relative to a reference are directly used to calculate strain. In this study, we compare several correlation methods using both simulated and experimental data in order to directly probe susceptibility to measurement error due to non-uniform diffracted disk illumination structure. We found that prefiltering the diffraction patterns with a Sobel filter before performing cross correlation or performing a square-root magnitude weighted phase correlation returned the best results when inner disk structure was present. We have tested these methods both on simulated datasets, and experimental data from unstrained silicon as well as a twin grain boundary in 304 stainless steel.

  5. Electronic diffraction tomography by Green's functions and singular values decompositions

    International Nuclear Information System (INIS)

    Mayer, A.

    2001-01-01

    An inverse scattering technique is developed to enable a three-dimensional sample reconstruction from the diffraction figures obtained for different sample orientations by electronic projection microscopy, thus performing a diffraction tomography. In its Green's-functions formulation, this technique takes account of all orders of diffraction by performing an iterative reconstruction of the wave function on the observation screen and in the sample. In a final step, these quantities enable a reconstruction of the potential-energy distribution, which is assumed real valued. The method relies on the use of singular values decomposition techniques, thus providing the best least-squares solutions and enabling a reduction of noise. The technique is applied to the analysis of a three-dimensional nanometric sample that is observed in Fresnel conditions with an electron energy of 40 eV. The algorithm turns out to provide results with a mean relative error around 3% and to be stable against random noise

  6. Highlighting material structure with transmission electron diffraction correlation coefficient maps.

    Science.gov (United States)

    Kiss, Ákos K; Rauch, Edgar F; Lábár, János L

    2016-04-01

    Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Serial single molecule electron diffraction imaging: diffraction background of superfluid helium droplets

    Science.gov (United States)

    Zhang, Jie; He, Yunteng; Lei, Lei; Alghamdi, Maha; Oswalt, Andrew; Kong, Wei

    2017-08-01

    In an effort to solve the crystallization problem in crystallography, we have been engaged in developing a method termed "serial single molecule electron diffraction imaging" (SS-EDI). The unique features of SS-EDI are superfluid helium droplet cooling and field-induced orientation: together the two features constitute a molecular goniometer. Unfortunately, the helium atoms surrounding the sample molecule also contribute to a diffraction background. In this report, we analyze the properties of a superfluid helium droplet beam and its doping statistics, and demonstrate the feasibility of overcoming the background issue by using the velocity slip phenomenon of a pulsed droplet beam. Electron diffraction profiles and pair correlation functions of ferrocene-monomer-doped droplets and iodine-nanocluster-doped droplets are presented. The timing of the pulsed electron gun and the effective doping efficiency under different dopant pressures can both be controlled for size selection. This work clears any doubt of the effectiveness of superfluid helium droplets in SS-EDI, thereby advancing the effort in demonstrating the "proof-of-concept" one step further.

  8. Ultrafast molecular imaging by laser-induced electron diffraction

    International Nuclear Information System (INIS)

    Peters, M.; Nguyen-Dang, T. T.; Cornaggia, C.; Saugout, S.; Charron, E.; Keller, A.; Atabek, O.

    2011-01-01

    We address the feasibility of imaging geometric and orbital structures of a polyatomic molecule on an attosecond time scale using the laser-induced electron diffraction (LIED) technique. We present numerical results for the highest molecular orbitals of the CO 2 molecule excited by a near-infrared few-cycle laser pulse. The molecular geometry (bond lengths) is determined within 3% of accuracy from a diffraction pattern which also reflects the nodal properties of the initial molecular orbital. Robustness of the structure determination is discussed with respect to vibrational and rotational motions with a complete interpretation of the laser-induced mechanisms.

  9. Electron back scattered diffraction study of SmCo magnets

    International Nuclear Information System (INIS)

    Yonamine, T.; Fukuhara, M.; Machado, R.; Missell, F.P.

    2008-01-01

    The remanence and energy product of permanent magnets is a strong function of their crystallographic texture. Electron back scattered diffraction (EBSD) is a tool for texture analysis providing information about the atomic layers up to 50 nm below the surface of the material. This paper discusses experimental requirements for performing EBSD measurements on rare-earth permanent magnets and presents results on commercial SmCo magnet material. EBSD measurements proved to be very sensitive to misaligned grains and were sensitive to texture in good agreement with information provided by X-ray diffraction scans. Results for nanostructured Sm(CoFeCuZr) z magnets are also discussed

  10. Highlighting material structure with transmission electron diffraction correlation coefficient maps

    International Nuclear Information System (INIS)

    Kiss, Ákos K.; Rauch, Edgar F.; Lábár, János L.

    2016-01-01

    Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. - Highlights: • We propose a novel technique to image the structure of polycrystalline TEM-samples. • Correlation coefficients maps highlights the evolution of the diffracting signal. • 3D views of grain boundaries are provided for nano-particles or polycrystals.

  11. Low-temperature system for simultaneous counting of conversion electrons and backscattered [gamma]-rays in Moessbauer effect experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ruskov, Todor (Institute for Nuclear Research and Nuclear Energy, Tsarigradsko shosse 72, Sofia 1784 (Bulgaria)); Passage, Guener (Institute for Nuclear Research and Nuclear Energy, Tsarigradsko shosse 72, Sofia 1784 (Bulgaria)); Rastanawi, Abdallah (Institute for Nuclear Research and Nuclear Energy, Tsarigradsko shosse 72, Sofia 1784 (Bulgaria)); Radev, Rumen (Institute for Nuclear Research and Nuclear Energy, Tsarigradsko shosse 72, Sofia 1784 (Bulgaria))

    1994-12-01

    A system for simultaneous detection of conversion electrons, emitted after resonant exciting of [sup 57]Fe, and resonant backscattered [gamma]-rays and X-rays, accompanying the conversion electrons, is described. The system includes a helium proportional counter, for detection of conversion electrons, and a toroidal ''Keisch-type'' proportional counter, connected to the vacuum part of a helium cryostat. ((orig.))

  12. Application of backscatter electrons for large area imaging of cavities produced by neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Pastukhov, V.I. [Joint Stock Company “Institute of Nuclear Materials” (JSC “INM”), Zarechny, Sverdlovsk Region (Russian Federation); Ural Federal University Named After the First President of Russia, B. N. Yeltsyn, Ekaterinburg (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Averin, S.A.; Panchenko, V.L. [Joint Stock Company “Institute of Nuclear Materials” (JSC “INM”), Zarechny, Sverdlovsk Region (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Portnykh, I.A. [Joint Stock Company “Institute of Nuclear Materials” (JSC “INM”), Zarechny, Sverdlovsk Region (Russian Federation); Freyer, P.D. [Westinghouse Electric Company, Pittsburgh, PA (United States); Giannuzzi, L.A. [L.A. Giannuzzi & Associates LLC, Fort Myers, FL (United States); Garner, F.A., E-mail: frank.garner@dslextreme.com [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Radiation Effects Consulting LLC, Richland, WA (United States); Texas A& M University, College Station, TX (United States)

    2016-11-15

    It is shown that with proper optimization, backscattered electrons in a scanning electron microscope can produce images of cavity distribution in austenitic steels over a large specimen surface for a depth of ∼500–700 nm, eliminating the need for electropolishing or multiple specimen production. This technique is especially useful for quantifying cavity structures when the specimen is known or suspected to contain very heterogeneous distributions of cavities. Examples are shown for cold-worked EK-164, a very heterogeneously-swelling Russian fast reactor fuel cladding steel and also for AISI 304, a homogeneously-swelling Western steel used for major structural components of light water cooled reactors. This non-destructive overview method of quantifying cavity distribution can be used to direct the location and number of required focused ion beam prepared transmission electron microscopy specimens for examination of either neutron or ion-irradiated specimens. This technique can also be applied in stereo mode to quantify the depth dependence of cavity distributions.

  13. Response function and optimum configuration of semiconductor backscattered-electron detectors for scanning electron microscopes

    International Nuclear Information System (INIS)

    Rau, E. I.; Orlikovskiy, N. A.; Ivanova, E. S.

    2012-01-01

    A new highly efficient design for semiconductor detectors of intermediate-energy electrons (1–50 keV) for application in scanning electron microscopes is proposed. Calculations of the response function of advanced detectors and control experiments show that the efficiency of the developed devices increases on average twofold, which is a significant positive factor in the operation of modern electron microscopes in the mode of low currents and at low primary electron energies.

  14. Development of splitting convergent beam electron diffraction (SCBED)

    Energy Technology Data Exchange (ETDEWEB)

    Houdellier, Florent, E-mail: Florent.Houdellier@cemes.fr [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse (France); Röder, Falk [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse (France); Triebenberg Lab, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Snoeck, Etienne [CEMES-CNRS, 29 Rue Jeanne Marvig, 31055 Toulouse (France)

    2015-12-15

    Using a combination of condenser electrostatic biprism with dedicated electron optic conditions for sample illumination, we were able to split a convergent beam electron probe focused on the sample in two half focused probes without introducing any tilt between them. As a consequence, a combined convergent beam electron diffraction pattern is obtained in the back focal plane of the objective lens arising from two different sample areas, which could be analyzed in a single pattern. This splitting convergent beam electron diffraction (SCBED) pattern has been tested first on a well-characterized test sample of Si/SiGe multilayers epitaxially grown on a Si substrate. The SCBED pattern contains information from the strained area, which exhibits HOLZ lines broadening induced by surface relaxation, with fine HOLZ lines observed in the unstrained reference part of the sample. These patterns have been analyzed quantitatively using both parts of the SCBED transmitted disk. The fine HOLZ line positions are used to determine the precise acceleration voltage of the microscope while the perturbed HOLZ rocking curves in the stained area are compared to dynamical simulated ones. The combination of these two information leads to a precise evaluation of the sample strain state. Finally, several SCBED setups are proposed to tackle fundamental physics questions as well as applied materials science ones and demonstrate how SCBED has the potential to greatly expand the range of applications of electron diffraction and electron holography. - Highlights: • Using a condenser biprism, we split the CBED pattern in two half-CBED disks. • We have determined the electron optical conditions used to perform various SCBED. • We propose new applications possible for this new SCBED configuration.

  15. Relativistic electron planar channeling and diffraction in thin monocrystals

    International Nuclear Information System (INIS)

    Vorob'ev, S.A.; Nurmagambetov, S.B.; Kaplin, V.V.; Rozum, E.I.

    1985-01-01

    The interaction of relativistic electrons with thin monocrystals was investigated in approximation of continuous potential of crystal plane system. Numerical technique for solution of one-dimensional Schroedinger equation with a periodic potential was developed. Numerical solutions conducted according to the technique were used to determine the forms of ngular distributions of electrons located in various zones of lteral motion. Calculation results were applied for analyzing experimentally obtained data on agular distribution of 5.1 MeV electrons projected at small angles onto the (110) planar system of a Si monocrystal. The conducted complex experimental and theoretical: investigations demonstrated the possibility of prevalen occupation of certain states of lateral motion and enabled to determine angular reg in directions of the electron beam projection on a crystal where either channeling effects or those of electron diffraction are important

  16. Diffraction and microscopy with attosecond electron pulse trains

    Science.gov (United States)

    Morimoto, Yuya; Baum, Peter

    2018-03-01

    Attosecond spectroscopy1-7 can resolve electronic processes directly in time, but a movie-like space-time recording is impeded by the too long wavelength ( 100 times larger than atomic distances) or the source-sample entanglement in re-collision techniques8-11. Here we advance attosecond metrology to picometre wavelength and sub-atomic resolution by using free-space electrons instead of higher-harmonic photons1-7 or re-colliding wavepackets8-11. A beam of 70-keV electrons at 4.5-pm de Broglie wavelength is modulated by the electric field of laser cycles into a sequence of electron pulses with sub-optical-cycle duration. Time-resolved diffraction from crystalline silicon reveals a propagates in space and time. This unification of attosecond science with electron microscopy and diffraction enables space-time imaging of light-driven processes in the entire range of sample morphologies that electron microscopy can access.

  17. Electron diffraction, elemental and image analysis of nanocrystals

    Czech Academy of Sciences Publication Activity Database

    Šlouf, Miroslav; Pavlova, Ewa; Hromádková, Jiřina; Králová, Daniela; Tyrpekl, Václav

    2009-01-01

    Roč. 16, 2a (2009), s. 33-34 ISSN 1211-5894. [Struktura - Colloquium of Czech and Slovak Crystallographic Association. Hluboká nad Vltavou, 22.06.2009-25.06.2009] R&D Projects: GA AV ČR KAN200520704; GA ČR GA203/07/0717 Institutional research plan: CEZ:AV0Z40500505 Keywords : TEM * electron diffraction * nanocrystals Subject RIV: CD - Macromolecular Chemistry

  18. Introduction to the theory of low-energy electron diffraction

    International Nuclear Information System (INIS)

    Fingerland, A.; Tomasek, M.

    1975-01-01

    An elementary introduction to the basic principles of the theory of low-energy electron diffraction is presented. General scattering theory is used to classify the hitherto known approaches to the problem (optical potential and one-electron approximation; formal scattering theory: Born expansion and multiple scattering; translational symmetry: Ewald construction; classification of LEED theories by means of the T matrix; pseudokinematical theory for crystal with clean surface and with an adsorbed monomolecular layer; dynamical theory; inclusion of inelastic collisions; discussion of a simple example by means of the band-structure approach)

  19. Solving complex and disordered surface structures with electron diffraction

    International Nuclear Information System (INIS)

    Van Hove, M.A.

    1987-10-01

    The past of surface structure determination with low-energy electron diffraction (LEED) will be briefly reviewed, setting the stage for a discussion of recent and future developments. The aim of these developments is to solve complex and disordered surface structures. Some efficient solutions to the theoretical and experimental problems will be presented. Since the theoretical problems dominate, the emphasis will be on theoretical approaches to the calculation of the multiple scattering of electrons through complex and disordered surfaces. 49 refs., 13 figs., 1 tab

  20. Development and characterization of electron sources for diffraction applications

    Energy Technology Data Exchange (ETDEWEB)

    Casandruc, Albert

    2015-12-15

    The dream to control chemical reactions that are essential to life is now closer than ever to gratify. Recent scientific progress has made it possible to investigate phenomena and processes which deploy at the angstroms scale and at rates on the order femtoseconds. Techniques such as Ultrafast Electron Diffraction (UED) are currently able to reveal the spatial atomic configuration of systems with unit cell sizes on the order of a few nanometers with about 100 femtosecond temporal resolution. Still, major advances are needed for structural interrogation of biological systems like protein crystals, which have unit cell sizes of 10 nanometers or larger, and sample sizes of less than one micrometer. For such samples, the performance of these electron-based techniques is now limited by the quality, in particular the brightness, of the electron source. The current Ph.D. work represents a contribution towards the development and the characterization of electron sources which are essential to static and time-resolved electron diffraction techniques. The focus was on electron source fabrication and electron beam characterization measurements, using the solenoid and the aperture scan techniques, but also on the development and maintenance of the relevant experimental setups. As a result, new experimental facilities are now available in the group and, at the same time, novel concepts for generating electron beams for electron diffraction applications have been developed. In terms of existing electron sources, the capability to trigger and detect field emission from single double-gated field emitter Mo tips was successfully proven. These sharp emitter tips promise high brightness electron beams, but for investigating individual such structures, new engineering was needed. Secondly, the influence of the surface electric field on electron beam properties has been systematically performed for flat Mo photocathodes. This study is very valuable especially for state

  1. Development and characterization of electron sources for diffraction applications

    International Nuclear Information System (INIS)

    Casandruc, Albert

    2015-12-01

    The dream to control chemical reactions that are essential to life is now closer than ever to gratify. Recent scientific progress has made it possible to investigate phenomena and processes which deploy at the angstroms scale and at rates on the order femtoseconds. Techniques such as Ultrafast Electron Diffraction (UED) are currently able to reveal the spatial atomic configuration of systems with unit cell sizes on the order of a few nanometers with about 100 femtosecond temporal resolution. Still, major advances are needed for structural interrogation of biological systems like protein crystals, which have unit cell sizes of 10 nanometers or larger, and sample sizes of less than one micrometer. For such samples, the performance of these electron-based techniques is now limited by the quality, in particular the brightness, of the electron source. The current Ph.D. work represents a contribution towards the development and the characterization of electron sources which are essential to static and time-resolved electron diffraction techniques. The focus was on electron source fabrication and electron beam characterization measurements, using the solenoid and the aperture scan techniques, but also on the development and maintenance of the relevant experimental setups. As a result, new experimental facilities are now available in the group and, at the same time, novel concepts for generating electron beams for electron diffraction applications have been developed. In terms of existing electron sources, the capability to trigger and detect field emission from single double-gated field emitter Mo tips was successfully proven. These sharp emitter tips promise high brightness electron beams, but for investigating individual such structures, new engineering was needed. Secondly, the influence of the surface electric field on electron beam properties has been systematically performed for flat Mo photocathodes. This study is very valuable especially for state

  2. Structure refinement using precession electron diffraction tomography and dynamical diffraction: tests on experimental data

    Czech Academy of Sciences Publication Activity Database

    Palatinus, Lukáš; Correa, Cinthia Antunes; Steciuk, G.; Jacob, D.; Roussel, P.; Boullay, P.; Klementová, Mariana; Gemmi, M.; Kopeček, Jaromír; Domeneghetti, C.; Cámara, F.; Petříček, Václav

    2015-01-01

    Roč. 71, č. 6 (2015), 740-751 ISSN 2052-5206 R&D Projects: GA MŠk(CZ) LM2011029; GA ČR GA13-25747S; GA MŠk LO1409 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132; FUNBIO(XE) CZ.2.16/3.1.00/21568 Keywords : XRD * structure refinement * precession electron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.892, year: 2015

  3. Quantitative convergent beam electron diffraction measurements of bonding in alumina

    International Nuclear Information System (INIS)

    Johnson, A.W.S.

    2002-01-01

    Full text: The QCBED technique of measuring accurate structure factors has been made practical by advances in energy filtering, computing and in the accurate measurement of intensity. Originally attempted in 1965 by the late Peter Goodman (CSIRO, Melbourne) while working with Gunter Lehmpfuhl (Fritz Haber Institut, Berlin), QCBED has been successfully developed and tested in the last decade on simple structures such as Si and MgO. Our work on Alumina is a step up in complexity and has shown that extinction in X-ray diffraction is not correctable to the precision required. In combination with accurate X-ray diffraction, QCBED promises to revolutionize the accuracy of bonding charge density measurements, experimental results which are of significance in the development of Density Functional Theory used in predictive chemistry. Copyright (2002) Australian Society for Electron Microscopy Inc

  4. Precession electron diffraction for SiC grain boundary characterization in unirradiated TRISO fuel

    International Nuclear Information System (INIS)

    Lillo, T.M.; Rooyen, I.J. van; Wu, Y.Q.

    2016-01-01

    Highlights: • SiC grain orientation determined by TEM-based precession electron diffraction. • Orientation data improved with increasing TEM sample thickness. • Fraction of low angle grain boundaries lower from PED data than EBSD data. • Fractions of high angle and CSL-related boundaries similar to EBSD data. - Abstract: Precession electron diffraction (PED), a transmission electron microscopy-based technique, has been evaluated for the suitability for evaluating grain boundary character in the SiC layer of tristructural isotropic (TRISO) fuel. This work reports the effect of transmission electron microscope (TEM) lamella thickness on the quality of data and establishes a baseline comparison to SiC grain boundary characteristics, in an unirradiated TRISO particle, determined previously using a conventional electron backscatter diffraction (EBSD) scanning electron microscope (SEM)-based technique. In general, it was determined that the lamella thickness produced using the standard focused ion beam (FIB) fabrication process (∼80 nm), is sufficient to provide reliable PED measurements, although thicker lamellae (∼120 nm) were found to produce higher quality orientation data. Also, analysis of SiC grain boundary character from the TEM-based PED data showed a much lower fraction of low-angle grain boundaries compared to SEM-based EBSD data from the SiC layer of a TRISO-coated particle made using the same fabrication parameters and a SiC layer deposited at a slightly lower temperature from a surrogate TRISO particle. However, the fractions of high-angle and coincident site lattice (CSL)-related grain boundaries determined by PED are similar to those found using SEM-based EBSD. Since the grain size of the SiC layer of TRSIO fuel can be as small as 250 nm (Kirchhofer et al., 2013), depending on the fabrication parameters, and since grain boundary fission product precipitates in irradiated TRISO fuel can be nano-sized, the TEM-based PED orientation data

  5. Interpretation of diffuse low-energy electron diffraction intensities

    International Nuclear Information System (INIS)

    Saldin, D.K.; Pendry, J.B.; Van Hove, M.A.; Somorjai, G.A.

    1985-01-01

    It is shown that the diffuse low-energy electron diffraction (LEED) that occurs between sharp LEED beams can be used to determine the local bonding configuration near disordered surface atoms. Two approaches to the calculation of diffuse LEED intensities are presented for the case of lattice-gas disorder of an adsorbate on a crystalline substrate. The capabilities of this technique are most similar to those of near-edge extended x-ray absorption fine structure, but avoid the restrictions due to the use of photons

  6. Hydrogen positions in single nanocrystals revealed by electron diffraction

    Czech Academy of Sciences Publication Activity Database

    Palatinus, Lukáš; Brázda, Petr; Boullay, P.; Pérez, O.; Klementová, Mariana; Petit, S.; Eigner, Václav; Zaarour, M.; Mintova, S.

    2017-01-01

    Roč. 355, č. 6321 (2017), s. 166-169 ISSN 0036-8075 R&D Projects: GA ČR GA16-10035S; GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : hydrogen atoms * crystal structure * electron diffraction tomography * nanocrystalline materials Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 37.205, year: 2016

  7. Inferential statistics of electron backscatter diffraction data from within individual crystalline grains

    DEFF Research Database (Denmark)

    Bachmann, Florian; Hielscher, Ralf; Jupp, Peter E.

    2010-01-01

    -spatial statistical analysis adapts ideas borrowed from the Bingham quaternion distribution on . Special emphasis is put on the mathematical definition and the numerical determination of a `mean orientation' characterizing the crystallographic grain as well as on distinguishing several types of symmetry......Highly concentrated distributed crystallographic orientation measurements within individual crystalline grains are analysed by means of ordinary statistics neglecting their spatial reference. Since crystallographic orientations are modelled as left cosets of a given subgroup of SO(3), the non...... of the orientation distribution with respect to the mean orientation, like spherical, prolate or oblate symmetry. Applications to simulated as well as to experimental data are presented. All computations have been done with the free and open-source texture toolbox MTEX....

  8. Assessing the precision of strain measurements using electron backscatter diffraction – Part 2: Experimental demonstration

    International Nuclear Information System (INIS)

    Britton, T.B.; Jiang, J.; Clough, R.; Tarleton, E.; Kirkland, A.I.; Wilkinson, A.J.

    2013-01-01

    The residual impression after performing a microhardness indent in silicon has been mapped with high resolution EBSD to reveal residual elastic strain and lattice rotation fields. Mapping of the same area has been performed with variable pattern binning and exposure times to reveal the qualitative and quantitative differences resulting from reducing the pattern size and exposure time. Two dimension ‘image’ plots of these fields indicate that qualitative assessment of the shape and size of the fields can be performed with as much as 4×4 binning. However, quantitative assessment using line scans reveals that the smoothest profile can be obtained using minimal pattern binning and long exposure times. To compare and contrast with these experimental maps, finite element analysis has been performed using a continuum damage-plasticity material law which has been independently calibrated to Si [9]. The constitutive law incorporates isotropic hardening in compression, and isotropic hardening and damage in tension. To accurately capture the localised damage which develops during indentation via the nucleation and propagation of cracks around the indentation site cohesive elements were assigned along the interfaces between the planes which experience the maximum traction. The residual strain state around the indenter and the size of the cracks agree very well with the experimentally measured value. - Highlights: • Similar deformation fields around a microhardness indent have been characterised with HR-EBSD and simulated with a finite element model. • Qualitative assessment of the stress field can be performed with significant EBSD pattern binning (i.e. faster capture of maps). • Quantitative assessment of the stress fields benefits significantly from increased exposure times and minimal binning

  9. Microstructural characterization and electron backscatter diffraction analysis across the welded interface of duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhiqiang; Jing, Hongyang [School of Materials Science and Engineering, Tianjin University, Tianjin 300350 (China); Tianjin Key Laboratory of Advanced Joining Technology, Tianjin 300350 (China); Xu, Lianyong, E-mail: xulianyong@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300350 (China); Tianjin Key Laboratory of Advanced Joining Technology, Tianjin 300350 (China); Han, Yongdian; Gao, Zhanqi; Zhao, Lei [School of Materials Science and Engineering, Tianjin University, Tianjin 300350 (China); Tianjin Key Laboratory of Advanced Joining Technology, Tianjin 300350 (China); Zhang, Jianli [Welding laboratory, Offshore Oil Engineering (Qing Dao) Company, Qing Dao 266520 (China)

    2017-08-15

    Highlights: • Apparent change in LTHAZ was the intergranular secondary austenite precipitation. • Ferrite in HAZ maintained same distribution as ferrite texture in base metal. • Different austenite in different zones showed different orientation with ferrite. • Ferrite and austenite grains exhibited different boundary characteristics. • Local deformations were generated in grain boundary and within deformed grain. - Abstract: The microstructural evolution, orientation relationships, boundary characteristics, grain type, local deformation, and microhardness across the welded interface of duplex stainless steel (DSS) were investigated. The DSS welded joint consisted of four typical zones: base metal (BM), low-temperature heat-affected zone (LTHAZ), high-temperature heat-affected zone (HTHAZ), and weld metal (WM). The apparent microstructural changes in the HTHAZ and LTHAZ were secondary austenite and Cr{sub 2}N precipitation. A modified cooperative precipitation mechanism of secondary austenite and Cr{sub 2}N at the interface was proposed. Furthermore, the ferrite in both the HTHAZ and LTHAZ maintained the same distribution as the ferrite texture in the BM, while this ferrite texture disappeared completely in the WM. Different austenite grains in the different zones exhibited different orientation relationships with the ferrite matrix. Special grain boundaries were mainly distributed between the austenite grains, while the ferrite grains primarily contained random grain boundaries. Austenite twins constituted the largest proportion of the special boundaries. The special austenite grain boundaries in the BM and LTHAZ were higher in relative frequency than those in the HTHAZ and WM. The ferrite grains in the HTHAZ and WM mainly consisted of substructured grains. In the BM, the recrystallization degree of ferrite was significantly lower than that of austenite grains. The local deformations were mainly generated in the grain boundaries and within the deformed grains. The HTHAZ exhibited the highest hardness, while the BM had the lowest hardness. The LTHAZ had a lower hardness than the HTHAZ and higher hardness than the BM.

  10. Microstructural characterization and electron backscatter diffraction analysis across the welded interface of duplex stainless steel

    Science.gov (United States)

    Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Gao, Zhanqi; Zhao, Lei; Zhang, Jianli

    2017-08-01

    The microstructural evolution, orientation relationships, boundary characteristics, grain type, local deformation, and microhardness across the welded interface of duplex stainless steel (DSS) were investigated. The DSS welded joint consisted of four typical zones: base metal (BM), low-temperature heat-affected zone (LTHAZ), high-temperature heat-affected zone (HTHAZ), and weld metal (WM). The apparent microstructural changes in the HTHAZ and LTHAZ were secondary austenite and Cr2N precipitation. A modified cooperative precipitation mechanism of secondary austenite and Cr2N at the interface was proposed. Furthermore, the ferrite in both the HTHAZ and LTHAZ maintained the same distribution as the ferrite texture in the BM, while this ferrite texture disappeared completely in the WM. Different austenite grains in the different zones exhibited different orientation relationships with the ferrite matrix. Special grain boundaries were mainly distributed between the austenite grains, while the ferrite grains primarily contained random grain boundaries. Austenite twins constituted the largest proportion of the special boundaries. The special austenite grain boundaries in the BM and LTHAZ were higher in relative frequency than those in the HTHAZ and WM. The ferrite grains in the HTHAZ and WM mainly consisted of substructured grains. In the BM, the recrystallization degree of ferrite was significantly lower than that of austenite grains. The local deformations were mainly generated in the grain boundaries and within the deformed grains. The HTHAZ exhibited the highest hardness, while the BM had the lowest hardness. The LTHAZ had a lower hardness than the HTHAZ and higher hardness than the BM.

  11. Two and three dimensional electron backscattered diffraction analysis of solid oxide cells materials

    DEFF Research Database (Denmark)

    Saowadee, Nath

    in solid oxide fuel cell and electrolysis cell. Conductivity of STN is one of the important properties that researchers desire to improve. Grin boundary conductivity contributes to the overall conductivity of the STN. Grain boundary density controlled by mainly grain growth in material processing. Grain......There are two main technique were developed in this work: a technique to calculate grain boundary energy and pressure and a technique to measure lattice constant from EBSD. The techniques were applied to Nb-doped Strontium titanate (STN) and yttria stabilized zirconia (YSZ) which are commonly used...... boundary migration in grain growth involves grain boundary mobility and net pressure on it. Thus grain boundary energy and pressure of STN were calculated in this work. Secondary phase is undesired in STN and YSZ synthesis. The secondary phase in ceramics with the same compounds can have different lattice...

  12. High-efficiency detector of secondary and backscattered electrons for low-dose imaging in the ESEM.

    Science.gov (United States)

    Neděla, Vilém; Tihlaříková, Eva; Runštuk, Jiří; Hudec, Jiří

    2018-01-01

    A new Combined System for high-efficiency detection of Secondary and Backscattered Electrons (CSSBE) in the ESEM consists of three detectors: an ionisation SE detector, an improved scintillation BSE detector, and a new Ionisation Secondary Electron Detector with an electrostatic Separator (ISEDS). The ISEDS optimizes conditions for electron-gas ionisation phenomena in the ESEM to achieve a strongly amplified signal from the secondary electrons with a minimal contribution from backscattered and beam electrons. For this purpose, it is originally equipped with an electrostatic separator, which focuses signal electrons towards a detection electrode and controls the concentration of positive ions above the sample. The working principle of the ISEDS is explained by simulations of signal electron trajectories in gas using the EOD program with our Monte Carlo module. The ability to detect the signal electrons in a selected range of energies is described with Geant4 Monte Carlo simulations of electron-solid interactions and proven by experimental results. High-efficiency detection of the ISEDS is demonstrated by imaging a low atomic number sample under a reduced beam energy of 5 keV, very low beam currents of up to 0.2 pA, and gas pressure of hundreds of Pa. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Ultrashort electron bunch length measurement with diffraction radiation deflector

    Science.gov (United States)

    Xiang, Dao; Huang, Wen-Hui

    2007-01-01

    In this paper, we propose a novel method to measure electron bunch length with a diffraction radiation (DR) deflector which is composed of a DR radiator and three beam position monitors (BPMs). When an electron beam passes through a metallic aperture which is tilted by 45 degrees with respect to its trajectory, backward DR that propagates perpendicular to the beam’s trajectory is generated which adds a transverse deflection to the beam as a result of momentum conservation. The deflection is found to be largely dependent on the bunch length and could be easily observed with a downstream BPM. Detailed investigations show that this method has wide applicability, high temporal resolution, and great simplicity.

  14. Ultrashort electron bunch length measurement with diffraction radiation deflector

    Directory of Open Access Journals (Sweden)

    Dao Xiang

    2007-01-01

    Full Text Available In this paper, we propose a novel method to measure electron bunch length with a diffraction radiation (DR deflector which is composed of a DR radiator and three beam position monitors (BPMs. When an electron beam passes through a metallic aperture which is tilted by 45 degrees with respect to its trajectory, backward DR that propagates perpendicular to the beam’s trajectory is generated which adds a transverse deflection to the beam as a result of momentum conservation. The deflection is found to be largely dependent on the bunch length and could be easily observed with a downstream BPM. Detailed investigations show that this method has wide applicability, high temporal resolution, and great simplicity.

  15. Acceleration of Electrons in a Diffraction Dominated IFEL

    CERN Document Server

    Musumeci, Pietro; Pellegrini, Claudio; Ralph, J; Rosenzweig, J B; Sung, C; Tochitsky, Sergei Ya; Travish, Gil

    2004-01-01

    We report on the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected ina 50 cm long undulator strongly tapered both in period and field amplitude. A CO2 10 μ m laser with power >300 GW is used as the IFEL driver. The Rayleigh range of the laser (1.8cm) is shorter than the undulator length so that the interaction is diffraction dominated. Few per cent of the injected particles are trapped in stable accelerating buckets and electrons with energies up to 35 MeV are detected on the magnetic spectrometers. Experimental results on the scaling of the accelerator characteristics versus input parameters like injection energy, laser focus position and laser power are discussed. Three dimensional simulations are in good agreement with the electron energy spectrums observed in the experiment and indicate that substantial energy exchange between laser and electron beam only occurs in the firs...

  16. Effect of different electron elastic-scattering cross sections on inelastic mean free paths obtained from elastic-backscattering experiments

    International Nuclear Information System (INIS)

    Jablonskiz, A.; Salvatz, F.; Powellz, C.J.

    2004-01-01

    Inelastic mean free paths (IMFPs) of electrons with energies between 100 eV and 5,000 eV have been frequently obtained from measurements of elastic-backscattering probabilities for different specimen materials. A calculation of these probabilities is also required to determine IMFPs. We report calculations of elastic-backscattering probabilities for gold at energies of 100 eV and 500 eV with differential elastic-scattering cross sections obtained from the Thomas-Fermi-Dirac potential and the more reliable Dirac-Hartree-Fock potential. For two representative experimental configurations, the average deviation between IMFPs obtained with cross sections from the two potentials was 11.4 %. (author)

  17. Absorptive form factors for high-energy electron diffraction

    International Nuclear Information System (INIS)

    Bird, D.M.; King, Q.A.

    1990-01-01

    The thermal diffuse scattering contribution to the absorptive potential in high-energy electron diffraction is calculated in the form of an absorptive contribution to the atomic form factor. To do this, the Einstein model of lattice vibrations is used, with isotropic Debye-Waller factors. The absorptive form factors are calculated as a function of scattering vector s and temperature factor M on a grid which enables polynomial interpolation of the results to be accurate to better than 2% for much of the ranges 0≤Ms 2 ≤6 and 0≤M≤2 A 2 . The computed values, together with an interpolation routine, have been incorporated into a Fortran subroutine which calculates both the real and absorptive form factors for 54 atomic species. (orig.)

  18. Acquisition parameters optimization of a transmission electron forward scatter diffraction system in a cold-field emission scanning electron microscope for nanomaterials characterization.

    Science.gov (United States)

    Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald

    2013-01-01

    Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. © Wiley Periodicals, Inc.

  19. Can X-ray spectrum imaging replace backscattered electrons for compositional contrast in the scanning electron microscope?

    Science.gov (United States)

    Newbury, Dale E; Ritchie, Nicholas W M

    2011-01-01

    The high throughput of the silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS) enables X-ray spectrum imaging (XSI) in the scanning electron microscope to be performed in frame times of 10-100 s, the typical time needed to record a high-quality backscattered electron (BSE) image. These short-duration XSIs can reveal all elements, except H, He, and Li, present as major constituents, defined as 0.1 mass fraction (10 wt%) or higher, as well as minor constituents in the range 0.01-0.1 mass fraction, depending on the particular composition and possible interferences. Although BSEs have a greater abundance by a factor of 100 compared with characteristic X-rays, the strong compositional contrast in element-specific X-ray maps enables XSI mapping to compete with BSE imaging to reveal compositional features. Differences in the fraction of the interaction volume sampled by the BSE and X-ray signals lead to more delocalization of the X-ray signal at abrupt compositional boundaries, resulting in poorer spatial resolution. Improved resolution in X-ray elemental maps occurs for the case of a small feature composed of intermediate to high atomic number elements embedded in a matrix of lower atomic number elements. XSI imaging strongly complements BSE imaging, and the SDD-EDS technology enables an efficient combined BSE-XSI measurement strategy that maximizes the compositional information. If 10 s or more are available for the measurement of an area of interest, the analyst should always record the combined BSE-XSI information to gain the advantages of both measures of compositional contrast. Copyright © 2011 Wiley Periodicals, Inc.

  20. Low temperature electron microscopy and electron diffraction of the purple membrane of Halobacterium halobium

    International Nuclear Information System (INIS)

    Hayward, S.B.

    1978-09-01

    The structure of the purple membrane of Halobacterium halobium was studied by high resolution electron microscopy and electron diffraction, primarily at low temperature. The handedness of the purple membrane diffraction pattern with respect to the cell membrane was determined by electron diffraction of purple membranes adsorbed to polylysine. A new method of preparing frozen specimens was used to preserve the high resolution order of the membranes in the electron microscope. High resolution imaging of glucose-embedded purple membranes at room temperature was used to relate the orientation of the diffraction pattern to the absolute orientation of the structure of the bacteriorhodopsin molecule. The purple membrane's critical dose for electron beam-induced damage was measured at room temperature and at -120 0 C, and was found to be approximately five times greater at -120 0 C. Because of this decrease in radiation sensitivity, imaging of the membrane at low temperature should result in an increased signal-to-noise ratio, and thus better statistical definition of the phases of weak reflections. Higher resolution phases may thus be extracted from images than can be determined by imaging at room temperature. To achieve this end, a high resolution, liquid nitrogen-cooled stage was built for the JEOL-100B. Once the appropriate technology for taking low dose images at very high resolution has been developed, this stage will hopefully be used to determine the high resolution structure of the purple membrane

  1. Ultrafast electron diffraction with megahertz MeV electron pulses from a superconducting radio-frequency photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Feng, L. W.; Lin, L.; Huang, S. L.; Quan, S. W.; Hao, J. K.; Zhu, F.; Wang, F.; Liu, K. X., E-mail: kxliu@pku.edu.cn [Institute of Heavy Ion Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Jiang, T.; Zhu, P. F.; Fu, F.; Wang, R.; Zhao, L.; Xiang, D., E-mail: dxiang@sjtu.edu.cn [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-11-30

    We report ultrafast relativistic electron diffraction operating at the megahertz repetition rate where the electron beam is produced in a superconducting radio-frequency (rf) photoinjector. We show that the beam quality is sufficiently high to provide clear diffraction patterns from gold and aluminium samples. With the number of electrons, several orders of magnitude higher than that from a normal conducting photocathode rf gun, such high repetition rate ultrafast MeV electron diffraction may open up many new opportunities in ultrafast science.

  2. Analytic model of electron pulse propagation in ultrafast electron diffraction experiments

    International Nuclear Information System (INIS)

    Michalik, A.M.; Sipe, J.E.

    2006-01-01

    We present a mean-field analytic model to study the propagation of electron pulses used in ultrafast electron diffraction experiments (UED). We assume a Gaussian form to characterize the electron pulse, and derive a system of ordinary differential equations that are solved quickly and easily to give the pulse dynamics. We compare our model to an N-body numerical simulation and are able to show excellent agreement between the two result sets. This model is a convenient alternative to time consuming and computationally intense N-body simulations in exploring the dynamics of UED electron pulses, and as a tool for refining UED experimental designs

  3. High resolution electron microscopy and electron diffraction of YBa2Cu3O(7-x)

    International Nuclear Information System (INIS)

    Krakow, W.; Shaw, T.M.

    1988-01-01

    Experimental high resolution electron micrographs and computer simulation experiments have been used to evaluate the visibility of the atomic constituents of YBa 2 Cu 3 O(7-x). In practice, the detection of oxygen has not been possible in contradiction to that predicted by modelling of perfect crystalline material. Preliminary computer experiments of the electron diffraction patterns when oxygen vacancies are introduced on the Cu-O sheets separating Ba layers show the diffuse streaks characteristic of short range ordering. 7 references

  4. Backscattered electron SEM imaging of resin sections from plant specimens: observation of histological to subcellular structure and CLEM.

    Science.gov (United States)

    Rizzo, N W; Duncan, K E; Bourett, T M; Howard, R J

    2016-08-01

    We have refined methods for biological specimen preparation and low-voltage backscattered electron imaging in the scanning electron microscope that allow for observation at continuous magnifications of ca. 130-70 000 X, and documentation of tissue and subcellular ultrastructure detail. The technique, based upon early work by Ogura & Hasegawa (1980), affords use of significantly larger sections from fixed and resin-embedded specimens than is possible with transmission electron microscopy while providing similar data. After microtomy, the sections, typically ca. 750 nm thick, were dried onto the surface of glass or silicon wafer and stained with heavy metals-the use of grids avoided. The glass/wafer support was then mounted onto standard scanning electron microscopy sample stubs, carbon-coated and imaged directly at an accelerating voltage of 5 kV, using either a yttrium aluminum garnet or ExB backscattered electron detector. Alternatively, the sections could be viewed first by light microscopy, for example to document signal from a fluorescent protein, and then by scanning electron microscopy to provide correlative light/electron microscope (CLEM) data. These methods provide unobstructed access to ultrastructure in the spatial context of a section ca. 7 × 10 mm in size, significantly larger than the typical 0.2 × 0.3 mm section used for conventional transmission electron microscopy imaging. Application of this approach was especially useful when the biology of interest was rare or difficult to find, e.g. a particular cell type, developmental stage, large organ, the interface between cells of interacting organisms, when contextual information within a large tissue was obligatory, or combinations of these factors. In addition, the methods were easily adapted for immunolocalizations. © 2015 The Author. Journal of Microscopy published by John Wiley & Sons, Ltd on behalf of the Royal Microscopical Society.

  5. Characterization of gold nanoparticle films: Rutherford backscattering spectroscopy, scanning electron microscopy with image analysis, and atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Pia C. Lansåker

    2014-10-01

    Full Text Available Gold nanoparticle films are of interest in several branches of science and technology, and accurate sample characterization is needed but technically demanding. We prepared such films by DC magnetron sputtering and recorded their mass thickness by Rutherford backscattering spectroscopy. The geometric thickness dg—from the substrate to the tops of the nanoparticles—was obtained by scanning electron microscopy (SEM combined with image analysis as well as by atomic force microscopy (AFM. The various techniques yielded an internally consistent characterization of the films. In particular, very similar results for dg were obtained by SEM with image analysis and by AFM.

  6. Giant Andreev Backscattering through a Quantum Point Contact Coupled via a Disordered Two-Dimensional Electron Gas to Superconductors

    International Nuclear Information System (INIS)

    den Hartog, S.G.; van Wees, B.J.; Klapwijk, T.M.; Nazarov, Y.V.; Borghs, G.

    1997-01-01

    We have investigated the superconducting-phase-modulated reduction in the resistance of a ballistic quantum point contact (QPC) connected via a disordered two-dimensional electron gas (2DEG) to superconductors. We show that this reduction is caused by coherent Andreev backscattering of holes through the QPC, which increases monotonically by reducing the bias voltage to zero. In contrast, the magnitude of the phase-dependent resistance of the disordered 2DEG displays a nonmonotonic reentrant behavior versus bias voltage. copyright 1997 The American Physical Society

  7. Auger electron spectroscopy and Rutherford backscattering studies of copper in 2024-T3 aluminum following electrochemical anodization in phosphoric acid

    Science.gov (United States)

    Solomon, J. S.

    1981-05-01

    The effects of the electrochemical anodization of dioxidized 2024-T3 aluminum on copper were characterized by Auger electron spectroscopy and Rutherford backscattering. Anodization was performed in phosphoric acid at constant potential. Data is presented which shows that constant potential anodization of 2024-T3 is more efficient than aluminum in terms of oxide growth rates for short anodization times. However the maximum anodic oxide thickness achievable on the alloy is less than the pure metal. Copper is shown to be enriched at the oxide metal interface because of its diffusion from the bulk during anodization. The presence of copper at the oxide-metal interface is shown to affect oxide morphology.

  8. Monte-Carlo study of the influence of backscattered electrons on the transmission of a mini-orange β spectrometer

    Science.gov (United States)

    Detistov, Pavel; Balabanski, Dimiter L.

    2015-04-01

    This work work is a part of the performance investigation of the recently constructed Mini-Orange beta spectrometer. The spectrometer has eight different configurations using three different magnet shapes and combination of three, four, and six magnet pieces allowing detection of electrons in wide kinetic energy range. The performance of the device is studied using the GEANT4 simulation tool. Evaluation of the device's basic parameters has been made, paying special attention to the backscattering, for which a study of the dependence of this process on the energy and the angle is made.

  9. Monte-Carlo study of the influence of backscattered electrons on the transmission of a mini-orange β spectrometer

    International Nuclear Information System (INIS)

    Detistov, Pavel; Balabanski, Dimiter L

    2015-01-01

    This work work is a part of the performance investigation of the recently constructed Mini-Orange beta spectrometer. The spectrometer has eight different configurations using three different magnet shapes and combination of three, four, and six magnet pieces allowing detection of electrons in wide kinetic energy range. The performance of the device is studied using the GEANT4 simulation tool. Evaluation of the device's basic parameters has been made, paying special attention to the backscattering, for which a study of the dependence of this process on the energy and the angle is made. (paper)

  10. Hard x-ray monochromator with milli-electron volt bandwidth for high-resolution diffraction studies of diamond crystals

    Energy Technology Data Exchange (ETDEWEB)

    Stoupin, Stanislav; Shvyd' ko, Yuri; Shu Deming; Khachatryan, Ruben; Xiao, Xianghui; DeCarlo, Francesco; Goetze, Kurt; Roberts, Timothy; Roehrig, Christian; Deriy, Alexey [Advanced Photon Source, Argonne National Laboratory, Illinois 60439 (United States)

    2012-02-15

    We report on design and performance of a high-resolution x-ray monochromator with a spectral bandwidth of {Delta}E{sub X}{approx_equal} 1.5 meV, which operates at x-ray energies in the vicinity of the backscattering (Bragg) energy E{sub H} = 13.903 keV of the (008) reflection in diamond. The monochromator is utilized for high-energy-resolution diffraction characterization of diamond crystals as elements of advanced x-ray crystal optics for synchrotrons and x-ray free-electron lasers. The monochromator and the related controls are made portable such that they can be installed and operated at any appropriate synchrotron beamline equipped with a pre-monochromator.

  11. Low-kilovolt coherent electron diffractive imaging instrument based on a single-atom electron source

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chun-Yueh [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Chang, Wei-Tse; Chen, Yi-Sheng; Hwu, En-Te; Chang, Chia-Seng; Hwang, Ing-Shouh, E-mail: ishwang@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China); Hsu, Wei-Hao [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2016-03-15

    In this work, a transmission-type, low-kilovolt coherent electron diffractive imaging instrument was constructed. It comprised a single-atom field emitter, a triple-element electrostatic lens, a sample holder, and a retractable delay line detector to record the diffraction patterns at different positions behind the sample. It was designed to image materials thinner than 3 nm. The authors analyzed the asymmetric triple-element electrostatic lens for focusing the electron beams and achieved a focused beam spot of 87 nm on the sample plane at the electron energy of 2 kV. High-angle coherent diffraction patterns of a suspended graphene sample corresponding to (0.62 Å){sup −1} were recorded. This work demonstrated the potential of coherent diffractive imaging of thin two-dimensional materials, biological molecules, and nano-objects at a voltage between 1 and 10 kV. The ultimate goal of this instrument is to achieve atomic resolution of these materials with high contrast and little radiation damage.

  12. Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Weathersby, S. P.; Brown, G.; Chase, T. F.; Coffee, R.; Corbett, J.; Eichner, J. P.; Frisch, J. C.; Fry, A. R.; Gühr, M.; Hartmann, N.; Hast, C.; Hettel, R.; Jobe, R. K.; Jongewaard, E. N.; Lewandowski, J. R.; Li, R. K., E-mail: lrk@slac.stanford.edu; Lindenberg, A. M.; Makasyuk, I.; May, J. E.; McCormick, D. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); and others

    2015-07-15

    Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.

  13. Molecular structure of tetramethylgermane from gas electron diffraction

    Science.gov (United States)

    Csákvári, Éva; Rozsondai, Béla; Hargittai, István

    1991-05-01

    The molecular structure of Ge(CH 3) 4 has been determined from gas-phase electron diffraction augmented by a normal coordinate analysis. Assuming tetrahedral symmetry for the germanium bond configuration, the following structural parameters are found: rg(GeC) = 1.958 ± 0.004 Å, rg(CH) = 1.111 ± 0.003 Å and ∠(GeCH) = 110.7 ± 0.2° ( R=4.0%). The methyl torsional barrier V 0 is estimated to be 1.3 kJ mol -1 on the basis of an effective angle of torsion 23.0 ± 1.5°, from the staggered form, yielded directly by the analysis. The GeC bond length of Ge(CH 3) 4 is the same, within experimental error, as that of Ge(C 6H 5) 4 and is in agreement with the prediction of a modified Schomaker-Stevenson relationship.

  14. 'Ab initio' structure solution from electron diffraction data obtained by a combination of automated diffraction tomography and precession technique

    International Nuclear Information System (INIS)

    Mugnaioli, E.; Gorelik, T.; Kolb, U.

    2009-01-01

    Using a combination of our recently developed automated diffraction tomography (ADT) module with precession electron technique (PED), quasi-kinematical 3D diffraction data sets of an inorganic salt (BaSO 4 ) were collected. The lattice cell parameters and their orientation within the data sets were found automatically. The extracted intensities were used for 'ab initio' structure analysis by direct methods. The data set covered almost the complete set of possible symmetrically equivalent reflections for an orthorhombic structure. The structure solution in one step delivered all heavy (Ba, S) as well as light atoms (O). Results of the structure solution using direct methods, charge flipping and maximum entropy algorithms as well as structure refinement for three different 3D electron diffraction data sets were presented.

  15. Structural studies of glasses by transmission electron microscopy and electron diffraction

    International Nuclear Information System (INIS)

    Kashchieva, E.P.

    1997-01-01

    The purpose of this work is to present information about the applications of transmission electron microscopy (TEM) and electron diffraction (ED) for structural investigations of glasses. TEM investigations have been carried out on some binary and on a large number of ternary borate-telluride systems where glass-forming oxides, oxides of transitional elements and modified oxides of elements from I, II and III groups in the periodic table, are used as third component. The large experimental data given by TEM method allows the fine classification of the micro-heterogeneities. A special case of micro-heterogeneous structure with technological origin occurs near the boundary between the 2 immiscible liquids obtained at macro-phase separation. TEM was also used for the direct observation of the glass structure and we have studied the nano-scale structure of borate glasses obtained at slow and fast cooling of the melts. The ED possesses advantages for analysis of amorphous thin films or micro-pastilles and it is a very useful technique for study in materials containing simultaneously light and heavy elements. A comparison between the possibilities of the 3 diffraction techniques (X-ray diffraction, neutron diffraction and ED) is presented

  16. Femtosecond electron diffraction. Next generation electron sources for atomically resolved dynamics

    International Nuclear Information System (INIS)

    Hirscht, Julian

    2015-08-01

    Three instruments for femtosecond electron diffraction (FED) experiments were erected, partially commissioned and used for first diffraction experiments. The Relativistic Electron Gun for Atomic Exploration (REGAE) was completed by beamline elements including supports, a specimen chamber and dark current or electron beam collimating elements such that the commissioning process, including first diffraction experiments in this context, could be started. The temporal resolution of this machine is simulated to be 25 fs (fwhm) short, while a transverse coherence length of 30 nm (fwhm) is feasible to resolve proteins on this scale. Whether this machine is capable of meeting these predictions or whether the dynamics of the electron beam will stay limited by accelerator components, is not finally determined by the end of this work, because commissioning and improvement of accelerator components is ongoing. Simultaneously, a compact DC electron diffraction apparatus, the E-Gun 300, designed for solid and liquid specimens and a target electron energy of 300 keV, was built. Fundamental design issues of the high potential carrying and beam generating components occurred and are limiting the maximum potential and electron energy to 120 keV. Furthermore, this is limiting the range of possible applications and consequently the design and construction of a brand new instrument began. The Femtosecond Electron Diffraction CAmera for Molecular Movies (FED-CAMM) bridges the performance problems of very high electric potentials and provides optimal operational conditions for all applied electron energies up to 300 keV. The variability of gap spacings and optimized manufacturing of the high voltage electrodes lead to the best possible electron pulse durations obtainable with a compact DC setup, that does not comprise of rf-structures. This third apparatus possesses pulse durations just a few tenth femtoseconds apart from the design limit of the highly relativistic REGAE and combines the

  17. Femtosecond electron diffraction. Next generation electron sources for atomically resolved dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Hirscht, Julian

    2015-08-15

    Three instruments for femtosecond electron diffraction (FED) experiments were erected, partially commissioned and used for first diffraction experiments. The Relativistic Electron Gun for Atomic Exploration (REGAE) was completed by beamline elements including supports, a specimen chamber and dark current or electron beam collimating elements such that the commissioning process, including first diffraction experiments in this context, could be started. The temporal resolution of this machine is simulated to be 25 fs (fwhm) short, while a transverse coherence length of 30 nm (fwhm) is feasible to resolve proteins on this scale. Whether this machine is capable of meeting these predictions or whether the dynamics of the electron beam will stay limited by accelerator components, is not finally determined by the end of this work, because commissioning and improvement of accelerator components is ongoing. Simultaneously, a compact DC electron diffraction apparatus, the E-Gun 300, designed for solid and liquid specimens and a target electron energy of 300 keV, was built. Fundamental design issues of the high potential carrying and beam generating components occurred and are limiting the maximum potential and electron energy to 120 keV. Furthermore, this is limiting the range of possible applications and consequently the design and construction of a brand new instrument began. The Femtosecond Electron Diffraction CAmera for Molecular Movies (FED-CAMM) bridges the performance problems of very high electric potentials and provides optimal operational conditions for all applied electron energies up to 300 keV. The variability of gap spacings and optimized manufacturing of the high voltage electrodes lead to the best possible electron pulse durations obtainable with a compact DC setup, that does not comprise of rf-structures. This third apparatus possesses pulse durations just a few tenth femtoseconds apart from the design limit of the highly relativistic REGAE and combines the

  18. Electron diffraction patterns with thermal diffuse scattering maxima around Kikuchi lines

    International Nuclear Information System (INIS)

    Karakhanyan, R. K.; Karakhanyan, K. R.

    2011-01-01

    Transmission electron diffraction patterns of silicon with thermal diffuse maxima around Kikuchi lines, which are analogs of the maxima of thermal diffuse electron scattering around point reflections, have been recorded. Diffuse maxima are observed only around Kikuchi lines with indices that are forbidden for the silicon structure. The diffraction conditions for forming these maxima are discussed.

  19. Experimental observations of electron-backscatter effects from high-atomic-number anodes in large-aspect-ratio, electron-beam diodes

    Energy Technology Data Exchange (ETDEWEB)

    Cooperstein, G; Mosher, D; Stephanakis, S J; Weber, B V; Young, F C [Naval Research Laboratory, Washington, DC (United States); Swanekamp, S B [JAYCOR, Vienna, VA (United States)

    1997-12-31

    Backscattered electrons from anodes with high-atomic-number substrates cause early-time anode-plasma formation from the surface layer leading to faster, more intense electron beam pinching, and lower diode impedance. A simple derivation of Child-Langmuir current from a thin hollow cathode shows the same dependence on the diode aspect ratio as critical current. Using this fact, it is shown that the diode voltage and current follow relativistic Child-Langmuir theory until the anode plasma is formed, and then follows critical current after the beam pinches. With thin hollow cathodes, electron beam pinching can be suppressed at low voltages (< 800 kV) even for high currents and high-atomic-number anodes. Electron beam pinching can also be suppressed at high voltages for low-atomic-number anodes as long as the electron current densities remain below the plasma turn-on threshold. (author). 8 figs., 2 refs.

  20. Secondary mineralization in carious lesions of human dentin. Electron-probe, electron microscope, and electron diffraction studies

    Energy Technology Data Exchange (ETDEWEB)

    Ogiwara, H [Tokyo Dental Coll. (Japan)

    1975-02-01

    Dentinal carious lesions having a remineralized surface layer were studied by means electron-probe microanalysis, electron microscopy, electron diffraction. As the results of electron-probe study, F, Mg, and Na were found to be distributed mainly in the remineralized surface layer and S in the decalcified region where decreases in Ca, P, and Mg concentration were usually observed. The decrease in Mg concentration always started earlier than that of Ca and P concentration. Electron microscope and electron diffraction studies revealed that apatic crystals in the remineralized surface layer were much larger than those in the intact dentin. Although they were less conspicuous, crystals in the decalcified region also were larger than those in the intact region. Dentinal tubules, occluded by many crystals, were frequently seen during the observations. Crystals in the tubules varied in morphology, showing granular, needle, rhomboid, and tabular shapes. By means of electron diffraction, the granular- or needle-shaped crystals were identified as apatite and the rhomboid-shaped crystals as whitlockite. Some of the tabular-shaped crystals appeared to be cotacalcium phosphate.

  1. A measurement of electron-wall interactions using transmission diffraction from nanofabricated gratings

    International Nuclear Information System (INIS)

    Barwick, Brett; Gronniger, Glen; Yuan, Lu; Liou, Sy-Hwang; Batelaan, Herman

    2006-01-01

    Electron diffraction from metal coated freestanding nanofabricated gratings is presented, with a quantitative path integral analysis of the electron-grating interactions. Electron diffraction out to the 20th order was observed indicating the high quality of our nanofabricated gratings. The electron beam is collimated to its diffraction limit with ion-milled material slits. Our path integral analysis is first tested against single slit electron diffraction, and then further expanded with the same theoretical approach to describe grating diffraction. Rotation of the grating with respect to the incident electron beam varies the effective distance between the electron and grating bars. This allows the measurement of the image charge potential between the electron and the grating bars. Image charge potentials that were about 15% of the value for that of a pure electron-metal wall interaction were found. We varied the electron energy from 50 to 900 eV. The interaction time is of the order of typical metal image charge response times and in principle allows the investigation of image charge formation. In addition to the image charge interaction there is a dephasing process reducing the transverse coherence length of the electron wave. The dephasing process causes broadening of the diffraction peaks and is consistent with a model that ascribes the dephasing process to microscopic contact potentials. Surface structures with length scales of about 200 nm observed with a scanning tunneling microscope, and dephasing interaction strength typical of contact potentials of 0.35 eV support this claim. Such a dephasing model motivated the investigation of different metallic coatings, in particular Ni, Ti, Al, and different thickness Au-Pd coatings. Improved quality of diffraction patterns was found for Ni. This coating made electron diffraction possible at energies as low as 50 eV. This energy was limited by our electron gun design. These results are particularly relevant for the

  2. Automated grain mapping using wide angle convergent beam electron diffraction in transmission electron microscope for nanomaterials.

    Science.gov (United States)

    Kumar, Vineet

    2011-12-01

    The grain size statistics, commonly derived from the grain map of a material sample, are important microstructure characteristics that greatly influence its properties. The grain map for nanomaterials is usually obtained manually by visual inspection of the transmission electron microscope (TEM) micrographs because automated methods do not perform satisfactorily. While the visual inspection method provides reliable results, it is a labor intensive process and is often prone to human errors. In this article, an automated grain mapping method is developed using TEM diffraction patterns. The presented method uses wide angle convergent beam diffraction in the TEM. The automated technique was applied on a platinum thin film sample to obtain the grain map and subsequently derive grain size statistics from it. The grain size statistics obtained with the automated method were found in good agreement with the visual inspection method.

  3. Electron diffraction of CBr{sub 4} in superfluid helium droplets: A step towards single molecule diffraction

    Energy Technology Data Exchange (ETDEWEB)

    He, Yunteng; Zhang, Jie; Kong, Wei, E-mail: wei.kong@oregonstate.edu [Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003 (United States)

    2016-07-21

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr{sub 4} as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr{sub 4} similar to those of gas phase molecules can be observed. The experimental data from CBr{sub 4} doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.

  4. Physical methods for studying minerals and solid materials: X-ray, electron and neutron diffraction; scanning and transmission electron microscopy; X-ray, electron and ion spectrometry

    International Nuclear Information System (INIS)

    Eberhart, J.-P.

    1976-01-01

    The following topics are discussed: theoretical aspects of radiation-matter interactions; production and measurement of radiations (X rays, electrons, neutrons); applications of radiation interactions to the study of crystalline materials. The following techniques are presented: X-ray and neutron diffraction, electron microscopy, electron diffraction, X-ray fluorescence analysis, electron probe microanalysis, surface analysis by electron emission spectrometry (ESCA and Auger electrons), scanning electron microscopy, secondary ion emission analysis [fr

  5. Evaluation of suspended sediment concentrations, sediment fluxes and sediment depositions along a reservoir by using laser diffraction and acoustic backscatter data

    Science.gov (United States)

    Lizano, Laura; Haun, Stefan

    2015-04-01

    Costa Rica was investigated where huge depositions have been recorded since the reservoir was built. The SSC's were measured with a LISST-SL (Laser In-Situ Scattering and Transmissometry instrument) which is based on the laser diffraction method and measures simultaneously the SSC as well as the particle size distribution. The measured SSC's were subsequently used to calculate the sediment fluxes within the transects, based on the intensity of backscattered sound from an acoustic measurement device. The total amount of deposited sediments could be calculated from the sediment fluxes, obtained by moving ADCP measurements (Acoustic Doppler Current Profiler) along chosen transects and so an image of the amount of settled sediments could be drawn. The results of this study show the advantage of using two highly sophisticated measurement devices in parallel to receive accurate numbers for sediment fluxes within reservoirs, which can in addition be used in further studies to develop management strategies to reduce sediment depositions.

  6. Retabulation of space group extinctions for electron diffraction

    International Nuclear Information System (INIS)

    Goodman, P.; Tanaka, M.

    1989-01-01

    The space group tables previously published by one of the authors and others are here presented in a revised and compacted form designed to make for compatability with existing tables for X-ray diffraction. 136 of the 230 space groups are subject to dynamic extinctions due to glide planes and screw axes, and the observables from these space groups in specific settings are tabulated. Tabs

  7. Staining plastic blocks with triiodide to image cells and soft tissues in backscattered electron SEM of skeletal and dental tissues

    Directory of Open Access Journals (Sweden)

    A Boyde

    2012-07-01

    Full Text Available Backscattered electron scanning electron microscopy (BSE SEM is an invaluable method for studying the histology of the hard, mineralised components of poly-methyl methacrylate (PMMA or other resin embedded skeletal and dental tissues. Intact tissues are studied in micro-milled or polished block faces with an electron-optical section thickness of the order of a half to one micron and with the area of the section as big as a whole – large or small – bone organ. However, BSE SEM does not give information concerning the distribution of uncalcified, ‘soft’, cellular and extracellular matrix components. This can be obtained by confocal microscopy of the same block and the two sorts of images merged but the blocks have to be studied in two microscope systems. The present work shows a new, simple and economic approach to visualising both components by using the triiodide ion in Lugol's iodine solution to stain the block surface prior to the application of any conductive coating – and the latter can be omitted if charging is suppressed by use of poor vacuum conditions in the SEM sample chamber. The method permits the use of archival tissue, and it will be valuable in studies of both normal growth and development and pathological changes in bones and joints, including osteoporosis and osteoarthritis, and tissue adaptation to implants.

  8. Monte Carlo simulation of electron depth distribution and backscattering for carbon films deposited on aluminium as a function of incidence angle and primary energy

    Science.gov (United States)

    Dapor, Maurizio

    2005-01-01

    Carbon films are deposited on various substrates (polymers, polyester fabrics, polyester yarns, metal alloys) both for experimental and technological motivations (medical devices, biocompatible coatings, food package and so on). Computational studies of the penetration of electron beams in supported thin film of carbon are very useful in order to compare the simulated results with analytical techniques data (obtained by scanning electron microscopy and/or Auger electron spectroscopy) and investigate the film characteristics. In the present paper, the few keV electron depth distribution and backscattering coefficient for the special case of film of carbon deposited on aluminium are investigated, by a Monte Carlo simulation, as a function of the incidence angle and primary electron energy. The simulated results can be used as a way to evaluate the carbon film thickness by a set of measurements of the backscattering coefficient.

  9. Development of a model using narrow slit beam profiles to account for the backscatter response of an amorphous silicon electronic portal imaging device

    International Nuclear Information System (INIS)

    Maria Das, K.J.; Ostapiak, Orest

    2008-01-01

    An electronic portal imaging device (EPID), currently used for determining proper patient placement during irradiation in a radiotherapy treatment, can also be used for the purpose of pre- treatment IMRT QA. However, the Varian aS500 portal imager exhibits dosimetric artifacts caused by non-uniform backscatter from mechanical support structures located behind the imager

  10. Time-resolved measurements with streaked diffraction patterns from electrons generated in laser plasma wakefield

    Science.gov (United States)

    He, Zhaohan; Nees, John; Hou, Bixue; Krushelnick, Karl; Thomas, Alec; Beaurepaire, Benoît; Malka, Victor; Faure, Jérôme

    2013-10-01

    Femtosecond bunches of electrons with relativistic to ultra-relativistic energies can be robustly produced in laser plasma wakefield accelerators (LWFA). Scaling the electron energy down to sub-relativistic and MeV level using a millijoule laser system will make such electron source a promising candidate for ultrafast electron diffraction (UED) applications due to the intrinsic short bunch duration and perfect synchronization with the optical pump. Recent results of electron diffraction from a single crystal gold foil, using LWFA electrons driven by 8-mJ, 35-fs laser pulses at 500 Hz, will be presented. The accelerated electrons were collimated with a solenoid magnetic lens. By applying a small-angle tilt to the magnetic lens, the diffraction pattern can be streaked such that the temporal evolution is separated spatially on the detector screen after propagation. The observable time window and achievable temporal resolution are studied in pump-probe measurements of photo-induced heating on the gold foil.

  11. X-ray diffraction analysis device with electronic photon counter

    International Nuclear Information System (INIS)

    Fillit, R.Y.; Bruyas, H.; Patay, F.

    1985-01-01

    The means provided to control the movements around the three axes are composed of step-by-step motors related to exits control logic which is connected to the calculation and monitored by a clock. The clock monitors also the calculator so as that the calculator controls, together with the programmable clock and control logic, the coordination of the whole rotation movements, along the three rotation axes, their velocity, their duration and the acquisition of the measured intensities of the diffracted X-ray beam [fr

  12. Instrumental development of a quasi-relativistic ultrashort electron beam source for electron diffractions and spectroscopies.

    Science.gov (United States)

    Shin, Young-Min; Figora, Michael

    2017-10-01

    A stable femtosecond electron beam system has been configured for time-resolved pump-probe experiments. The ultrafast electron diffraction (UED) system is designed with a sub-MeV photoelectron beam source pulsed by a femtosecond UV laser and nondispersive beamline components, including a bunch compressor-a pulsed S-band klystron is installed and fully commissioned with 5.5 MW peak power in a 2.5 μs pulse length. A single-cell RF photo-gun is designed to produce 1.6-16 pC electron bunches in a photoemission mode with 150 fs pulse duration at 0.5-1 MeV. The measured RF system jitters are within 1% in magnitude and 0.2° in phase, which would induce 3.4 keV and 0.25 keV of ΔE, corresponding to 80 fs and 5 fs of Δt, respectively. Our particle-in-cell simulations indicate that the designed bunch compressor reduces the time-of-arrival jitter by about an order of magnitude. The transport and focusing optics of the designed beamline with the bunch compressor enables an energy spread within 10 -4 and a bunch length (electron probe) within quasi-relativistic UED system.

  13. Size effect in X-ray and electron diffraction patterns from hydroxyapatite particles

    International Nuclear Information System (INIS)

    Suvorova, E.I.; Buffat, P.-A.

    2001-01-01

    High-resolution transmission electron microscopy (HRTEM), electron microdiffraction, and X-ray diffraction were used to study hydroxyapatite specimens with particle sizes from a few nanometers to several hundreds of nanometers. Diffuse scattering (without clear reflections in transmission diffraction patterns) or strongly broadened peaks in X-ray diffraction patterns are characteristic for agglomerated hydroxyapatite nanocrystals. However, HRTEM and microdiffraction showed that this cannot be considered as an indication of the amorphous state of the matter but rather as the demonstration of size effect and the morphological and structural features of hydroxyapatite nanocrystals

  14. A note on extracting electronic stopping from energy spectra of backscattered slow ions applying Bragg's rule

    Science.gov (United States)

    Bruckner, B.; Roth, D.; Goebl, D.; Bauer, P.; Primetzhofer, D.

    2018-05-01

    Electronic stopping measurements in chemically reactive targets, e.g., transition and rare earth metals are challenging. These metals often contain low Z impurities, which contribute to electronic stopping. In this article, we present two ways how one can correct for the presence of impurities in the evaluation of proton and He stopping in Ni for primary energies between 1 and 100 keV, either considering or ignoring the contribution of the low Z impurities to multiple scattering. We find, that for protons either method leads to concordant results, but for heavier projectiles, e.g. He ions, the influence on multiple scattering must not be neglected.

  15. High peak power THz source for ultrafast electron diffraction

    Directory of Open Access Journals (Sweden)

    Shengguang Liu

    2018-01-01

    Full Text Available Terahertz (THz science and technology have already become the research highlight at present. In this paper, we put forward a device setup to carry out ultrafast fundamental research. A photocathode RF gun generates electron bunches with ∼MeV energy, ∼ps bunch width and about 25pC charge. The electron bunches inject the designed wiggler, the coherent radiation at THz spectrum emits from these bunches and increases rapidly until the saturation at ∼MW within a short wiggler. THz pulses can be used as pump to stimulate an ultra-short excitation in some kind of sample. Those electron bunches out of wiggler can be handled into bunches with ∼1pC change, small beam spot and energy spread to be probe. Because the pump and probe comes from the same electron source, synchronization between pump and probe is inherent. The whole facility can be compacted on a tabletop.

  16. Electron diffraction using ultrafast electron bunches from a laser-wakefield accelerator at kHz repetition rate

    Science.gov (United States)

    He, Z.-H.; Thomas, A. G. R.; Beaurepaire, B.; Nees, J. A.; Hou, B.; Malka, V.; Krushelnick, K.; Faure, J.

    2013-02-01

    We show that electron bunches in the 50-100 keV range can be produced from a laser wakefield accelerator using 10 mJ, 35 fs laser pulses operating at 0.5 kHz. It is shown that using a solenoid magnetic lens, the electron bunch distribution can be shaped. The resulting transverse and longitudinal coherence is suitable for producing diffraction images from a polycrystalline 10 nm aluminum foil. The high repetition rate, the stability of the electron source, and the fact that its uncorrelated bunch duration is below 100 fs make this approach promising for the development of sub-100 fs ultrafast electron diffraction experiments.

  17. Electron diffraction using ultrafast electron bunches from a laser-wakefield accelerator at kHz repetition rate

    Energy Technology Data Exchange (ETDEWEB)

    He, Z.-H.; Thomas, A. G. R.; Nees, J. A.; Hou, B.; Krushelnick, K. [Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48106-2099 (United States); Beaurepaire, B.; Malka, V.; Faure, J. [Laboratoire d' Optique Appliquee, ENSTA-CNRS-Ecole Polytechnique, UMR 7639, 91761 Palaiseau (France)

    2013-02-11

    We show that electron bunches in the 50-100 keV range can be produced from a laser wakefield accelerator using 10 mJ, 35 fs laser pulses operating at 0.5 kHz. It is shown that using a solenoid magnetic lens, the electron bunch distribution can be shaped. The resulting transverse and longitudinal coherence is suitable for producing diffraction images from a polycrystalline 10 nm aluminum foil. The high repetition rate, the stability of the electron source, and the fact that its uncorrelated bunch duration is below 100 fs make this approach promising for the development of sub-100 fs ultrafast electron diffraction experiments.

  18. Giant Andreev backscattering and reentrant resistance in a 2- dimensional electron gas coupled to superconductors

    NARCIS (Netherlands)

    den Hartog, Sander; Wees, B.J. van; Nazarov, Yu.V.; Klapwijk, T.M.; Borghs, G.

    1998-01-01

    We have investigated the superconducting-phase modulated reduction in the resistance of a ballistic quantum point contact (QPC) connected via a disordered 2-dimensional electron gas (2DEG) to superconductors. We show that this reduction is caused by coherent Andreev back scattering of holes through

  19. Inversion of convergent-beam electron diffraction patterns

    International Nuclear Information System (INIS)

    Bird, D.M.; Saunders, M.

    1992-01-01

    The problem of recovering the structure factors that contribute to a zone-axis convergent-beam diffraction pattern is discussed. It is shown that an automated matching procedure that minimizes the sum-of-squares difference between experimental and simulated patterns is effective whether one is refining accurate structure factors in a known crystal or attempting ab initio structure determination. The details of the minimization method are analysed and it is shown that a quasi-Newton method that uses analytically derived gradients is particulary effective when several structure factors are varied. The inversion method for ab initio structure determination is tested on the [110] axis of GaP, using simulated patterns as ideal 'experimental' data. (orig.)

  20. Aspects of electron acoustic wave physics in laser backscatter from plasmas

    International Nuclear Information System (INIS)

    Sircombe, N J; Arber, T D; Dendy, R O

    2006-01-01

    Recent experimental results from the Trident laser confirm the importance of kinetic effects in determining laser reflectivities at high intensities. Examples observed include scattering from low frequency electron acoustic waves (EAWs) and the first few stages of a cascade towards turbulence through the Langmuir decay instability. Interpretive and predictive computational capability in this area is assisted by the development of Vlasov codes, which offer high velocity space resolution in high energy regions of particle phase space and do not require analytical pre-processing of the fundamental equations. A direct Vlasov solver, capable of resolving these kinetic processes, is used here to address fundamental aspects of the existence and stability of the electron acoustic wave, together with its collective scattering properties. These simulations are extended to realistic laser and plasma parameters characteristic of single hot-spot experiments. Results are in qualitative agreement with experiments displaying both stimulated Raman and stimulated electron acoustic scattering. The amplitude of simulated EAWs is greater than that observed experimentally and is accompanied by a higher phase velocity. These minor differences can be attributed to the limitations of a one-dimensional collisionless model

  1. Absorption distances in the dynamical theory of electron diffraction

    International Nuclear Information System (INIS)

    Kamiya, Yoshihiko; Goto, Toshiaki.

    1982-01-01

    The contrast effect of the electron microscopic image at crystal defects is characterized by two parameters; extincion distance and absorption distance. Both quantities are orginally defined for the elastic scattering. Since the inelastic scattering contributes to the electron microscopic image, parameters used for the interpretation of the images are not the same as those for the elastic scattering. It is shown that the difference of absorption distance beteen the theoretical estimation and that used for interpretation is due to the contrst effect of the small angle inelastic scattering. (author)

  2. Phase analysis of nano-phase materials using selected area electron diffraction in the TEM

    International Nuclear Information System (INIS)

    Labar, J. L.

    2002-01-01

    In analogy to X-ray power diffraction (XRD), we are developing a method to help phase identification when examining a large number of grains simultaneously by electron diffraction. Although XRD is well established, it can not be used for small quantities of materials (volumes below 1 mm 3 ). Examining a usual TEM sample with thickness of 100 nm and using a selected area of 1 mm in diameter, the selected area electron diffraction pattern (SAED) carries information about several thousands of grains from a material with an average grain size of about 10 nm. The accuracy of XRD can not be attained by electron diffraction (ED). However, simultaneous visual observation of the nanostructure is an additional benefit of TEM (beside the small amount of needed material). The first step of the development project was the development of a computer program ('ProcessDiffraction') that processes digital versions of SAED patterns and presents them in an XRD-like form (intensity vs. scattering vector). In the present version (V2.0.3) phase identification is carried out by comparing the measured distribution to 'Markers', i.e. data of known phases. XRD data cards are used if the detailed structure of a phase is not known. Kinematic electron diffraction intensities are calculated for phases with known atomic positions (Author)

  3. A FORTRAN program for an IBM PC compatible computer for calculating kinematical electron diffraction patterns

    International Nuclear Information System (INIS)

    Skjerpe, P.

    1989-01-01

    This report describes a computer program which is useful in transmission electron microscopy. The program is written in FORTRAN and calculates kinematical electron diffraction patterns in any zone axis from a given crystal structure. Quite large unit cells, containing up to 2250 atoms, can be handled by the program. The program runs on both the Helcules graphic card and the standard IBM CGA card

  4. Ultrafast electron diffraction and electron microscopy: present status and future prospects

    International Nuclear Information System (INIS)

    Ishchenko, A A; Aseyev, S A; Ryabov, E A; Bagratashvili, V N; Panchenko, V Ya

    2014-01-01

    Acting as complementary research tools, high time-resolved spectroscopy and diffractometry techniques proceeding from various physical principles open up new possibilities for studying matter with necessary integration of the 'structure–dynamics–function' triad in physics, chemistry, biology and materials science. Since the 1980s, a new field of research has started at the leading research laboratories, aimed at developing means of filming the coherent dynamics of nuclei in molecules and fast processes in biological objects ('atomic and molecular movies'). The utilization of ultrashort laser pulse sources has significantly modified traditional electron beam approaches to and provided high space–time resolution for the study of materials. Diffraction methods using frame-by-frame filming and the development of the main principles of the study of coherent dynamics of atoms have paved the way to observing wave packet dynamics, the intermediate states of reaction centers, and the dynamics of electrons in molecules, thus allowing a transition from the kinetics to the dynamics of the phase trajectories of molecules in the investigation of chemical reactions. (reviews of topical problems)

  5. Electronic diffraction study of the chlorination of nickel; Etude par diffraction electronique de la chloruration du nickel

    Energy Technology Data Exchange (ETDEWEB)

    Vigner, D [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    A study has been made of the chlorination of the (100), (110) and (111) crystal faces of nickel using high energy electron diffraction and electron microscopy. Two methods have been used: bombardment with chlorine ions having an energy of between 10 and 30 keV, and direct chlorination in a diffractor at pressures of about 10{sup -4} torr. It has thus been possible to show the very special properties of nickel chloride (CdBr{sub 2} type, space group R 3-bar m) which is always formed along the (0001) plane, whatever the orientation of the substrate. It has also been possible to attain the metal-halide interface and to show the existence of two-dimensional chemisorbed films which are ordered or disordered according to the crystal orientation. (author) [French] La chloruration des faces (100) (110) et (111) du nickel a ete etudiee par diffraction des electrons de haute energie et par microscopie electronique. Deux methodes ont ete utilisees: le bombardement avec des ions chlore ayant une energie comprise entre 10 et 30 keV, et la chloruration directe dans un diffracteur pour des pressions de l'ordre de 10{sup -4} torr. Ainsi ont ete mises en evidence les proprietes tres particulieres du chlorure de nickel (type CdBr{sub 2}, groupe spatial R 3-bar m) qui s'accole toujours suivant le plan (0001), quelle que soit l'orientation du substrat. Il a ete egalement possible d'atteindre l'interface metal-halogenure et de montrer l'existence de couches chimisorbees bidimensionnelles, ordonnees ou desordonnees suivant l'orientation cristalline etudiee. (auteur)

  6. High resolution electron exit wave reconstruction from a diffraction pattern using Gaussian basis decomposition

    International Nuclear Information System (INIS)

    Borisenko, Konstantin B; Kirkland, Angus I

    2014-01-01

    We describe an algorithm to reconstruct the electron exit wave of a weak-phase object from single diffraction pattern. The algorithm uses analytic formulations describing the diffraction intensities through a representation of the object exit wave in a Gaussian basis. The reconstruction is achieved by solving an overdetermined system of non-linear equations using an easily parallelisable global multi-start search with Levenberg-Marquard optimisation and analytic derivatives

  7. Study of the local structure of binary surfaces by electron diffraction (XPS, LEED)

    OpenAIRE

    Gereová, Katarína

    2006-01-01

    Study of local structure of binary surface with usage of ultra-thin film of cerium deposited on a Pd (111) single-crystal surface is presented. X-ray photoelectron spectroscopy and diffraction (XPS, XPD), angle resolved UV photoemission spectroscopy (ARUPS) and low energy electron diffraction (LEED) was used for our investigations. LEED and X-ray excited photoemission intensities results represent a surface-geometrical structure. As well, mapping of ultra-violet photoelectron intensities as a...

  8. Electron diffraction study of {alpha}-AlMnSi crystals including non-crystallographic axes

    Energy Technology Data Exchange (ETDEWEB)

    Song, G.L.; Bursill, L.A.

    1997-06-01

    The structure of crystalline {alpha}-AlMnSi is examined by electron diffraction. Six distinct zone axes are examined, including both normal crystallographic and non-crystallographic zones axes, allowing the space group symmetry to be studied. Electron diffraction patterns characteristic of Pm3-bar were obtained for thicker specimens. However, for very thin specimens, as used for HRTEM imaging, the electron diffraction patterns were characteristic of Im3-bar space group symmetry. The structural basis of the Pm3-bar to Im3-bar transformation may be understood in terms of an analysis of the icosahedral structural elements located at the corners and body-centers of the cubic unit cell. A method for indexing the non-crystallographic zone axis diffraction patterns is described. An electron diffraction pattern of the 5-fold axis of the quasicrystalline phase i-AlMnSi is also included; this is compared with the experimental results and calculations for the [0{tau}1] axis of Pm3-bar and Im3-bar crystalline phases. 26 refs., 4 tabs., 7 figs.

  9. Ultrashort and coherent single-electron pulses for diffraction at ultimate resolutions

    International Nuclear Information System (INIS)

    Kirchner, Friedrich Oscar

    2013-01-01

    Ultrafast electron diffraction is a powerful tool for studying structural dynamics with femtosecond temporal and sub-aangstroem spatial resolutions. It benefits from the high scattering cross-sections of electrons compared X-rays and allows the examination of thin samples, surfaces and gases. One of the main challenges in ultrafast electron diffraction is the generation of electron pulses with a short duration and a large transverse coherence. The former limits the temporal resolution of the experiment while the latter determines the maximum size of the scattering structures that can be studied. In this work, we strive to push the limits of electron diffraction towards higher temporal and spatial resolutions. The decisive step in our approach is to eliminate all detrimental effects caused by Coulomb repulsion between the electrons by reducing the number of electrons per pulse to one. In this situation, the electrons' longitudinal and transverse velocity distributions are determined solely by the photoemission process. By reducing the electron source size on the photocathode, we make use of the small transverse velocity spread to produce electron pulses with a transverse coherence length of 20 nm, which is about an order of magnitude larger than the reported values for comparable experiments. The energy distribution of an ensemble of single-electron pulses from a photoemission source is directly linked to the mismatch between the photon energy and the cathode's work function. This excess energy can be reduced by using a photon energy close to the material's work function. Using a tunable source of ultraviolet pulses, we demonstrate the reduction of the velocity spread of the electrons, resulting in a shorter duration of the electron pulses. The reduced electron pulse durations achieved by a tunable excitation or by other approaches require new characterization techniques for electron pulses. We developed a novel method for the characterization of electron pulses at

  10. Determination of the analyzing power of the A4 Compton-backscattering polarimeter for the measurement of the longitudinal spin polarization of the MAMI electron beam

    International Nuclear Information System (INIS)

    Diefenbacher, Juergen

    2010-01-01

    The A4 experiment determines the strange quark contribution to the electromagnetic from factors of the nucleon by measuring the parity violation in elastic electron nucleon scattering. These measurements are carried out using the spin polarized electron beam of the Mainzer Mikrotron (MAMI) with beam energies in the range from 315 to 1508 MeV. For the data analysis it is essential to determine the degree of polarization of the electron beam in order to extract the physics asymmetry from the measured parity violating asymmetry. For this reason the A4 collaboration has developed a novel type of Compton laser backscattering polarimeter that allows for a non-destructive measurement of the beam polarization in parallel to the running parity experiment. In the scope of this work the polarimeter was refined in order to enable reliable continuous operation of the polarimeter. The data acquisition system for the photon and electron detector was re-designed and optimized to cope with high count rates. A novel detector (LYSO) for the backscattered photons was commissioned. Furthermore, GEANT4 simulations of the detectors have been performed and an analysis environment for the extraction of Compton asymmetries from the backscattered photon data has been developed. The analysis makes use of the possibility to detect backscattered photons in coincidence with the scattered electrons, thus tagging the photons. The tagging introduces a differential energy scale which enables the precise determination of the analyzing power. In this work the analyzing power of the polarimeter has been determined. Therefore, at a beam current of 20 μA the product of electron and laser polarization can be determined, while the parity experiment is running, with a statistical accuracy of 1 % in 24 hours at 855 MeV or 2 =0.6 (GeV/c) 2 the analysis yields a raw asymmetry of A Roh PV =(-20.0±0.9 stat ) x 10 -6 at the moment. For a beam polarization of 80 % the total error would be 1,68 x 10 -6 with ΔP e

  11. Use of backscattered electron imaging, X-ray microanalysis and X-ray microscopy in demonstrating physiological cell death

    International Nuclear Information System (INIS)

    Bowen, I.D.; Worrill, N.A.; Winters, C.A.; Mullarkey, K.

    1988-01-01

    The cytochemical localization of enzymatic activity by means of backscattered electron imaging (BEI) is reviewed and the application of BEI to changes in acid phosphatase and ATPase distribution during physiological (programmed) cell death in Heliothis midgut is explored. Programmed cell death entails the release of nascent free acid phosphatase as extracisternal hydrolase. This shift can readily be detected by means of the atomic number contrast imparted by BEI of the lead phosphatase reaction product, thus enabling the distribution of dying cells to be mapped. BEI is particularly useful in this context as it allows the examination of bulk specimens at low magnification. Death of cells is also accompanied by a collapse in ATPase activity which shows up as cytochemically negative areas in the X-ray microscope and by means of BEI. Acid phosphatase in normal cells is localized in the apical microvilli and lysosomes. Senescent or dying cells, however, clearly show a basally situated free hydrolase which migrates throughout the cell. Parallel TEM results confirm that this enzyme is ribosomal and extracisternal rather than lysosomal in origin. ATPase activity is largely limited to the apical microvilli, although there is some activity associated with the basal plasma membranes. The apical ATPase, however is partially resistant to ouabain. Young and mature cells are positive although in the latter case some microvilli may be lost as the cells acquire a negative cap or dome. Inhibition by bromotetramizole indicates that apical activity is not to any significant extent contributed to by alkaline phosphatase. Degenerate or dead cells are negative and can be seen as a mozaic of black patches among normal cells when imaged by means of BEI or X-ray microscopy

  12. Thermal expansion coefficient measurement from electron diffraction of amorphous films in a TEM.

    Science.gov (United States)

    Hayashida, Misa; Cui, Kai; Malac, Marek; Egerton, Ray

    2018-05-01

    We measured the linear thermal expansion coefficients of amorphous 5-30 nm thick SiN and 17 nm thick Formvar/Carbon (F/C) films using electron diffraction in a transmission electron microscope. Positive thermal expansion coefficient (TEC) was observed in SiN but negative coefficients in the F/C films. In case of amorphous carbon (aC) films, we could not measure TEC because the diffraction radii required several hours to stabilize at a fixed temperature. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.

  13. Role of diffraction and electron analysis in the fast reactor programme

    Energy Technology Data Exchange (ETDEWEB)

    Ferguson, I. F. [ed.

    1975-09-15

    After first discussing irradiation damage, the whole range of new methods of probe analysis were reviewed with a special reference to the study of surfaces. Further papers discussed scanning auger microscopy and the nuclear microprobe. Current diffraction studies were then described on uranium dioxide and the neutron poisons: boron carbide and europia. Finally, new techniques were covered with special reference to the scanning electron microscope and the application of the Harwell 6000 series electronics to x-ray diffraction. Separate records were prepared for each paper covered.

  14. Identification of intermetallic phases in a eutectic Al-Si casting alloy using electron backscatter diffraction pattern analysis

    International Nuclear Information System (INIS)

    Kral, M.V.; McIntyre, H.R.; Smillie, M.J.

    2004-01-01

    Intermetallic phases in sand cast eutectic Al-Si alloys were characterized using a combination of SEM, EDS and EBSD pattern analysis. Chinese script α-phase particles were consistent with cubic Al 19 (Fe,Mn) 5 Si 2 . Plate-shaped β-phase particles were consistent with tetragonal Al 3 (Fe,Mn)Si 2

  15. Growth mechanism of extension twin variants during annealing of pure magnesium: An ‘ex situ’ electron backscattered diffraction investigation

    Energy Technology Data Exchange (ETDEWEB)

    Sabat, R.K. [Department of Materials Engineering, IISc, Bangalore 560012 (India); Panda, D. [Department of Metallurgical & Materials Engineering, NIT, Rourkela 769008 (India); Sahoo, S.K., E-mail: sursahoo@gmail.com [Department of Metallurgical & Materials Engineering, NIT, Rourkela 769008 (India)

    2017-04-15

    Pure magnesium was subjected to plastic deformation through CSM (continuous stiffness measurement) indentation followed by annealing at 200 °C for 30 min. Nucleation of no new grains was observed neither at the twin–twin intersections nor at the multiple twin variants of a grain after annealing. Significant growth of off-basal twin orientation compared to basal twin orientation was observed in the sample after annealing and is attributed to the partial coherent nature of twin boundary in the later case. Further, growth of twins was independent of the strain distribution between parent and twinned grains. - Highlights: • An ‘ex situ’ EBSD of pure Mg during annealing was investigated. • Nucleation of no new grains was observed. • Significant growth of off-basal twin orientation was observed. • Growth of twins may be attributed to the partial coherent nature of twin boundary.

  16. Electron backscatter and X-ray diffraction studies on the deformation and annealing textures of austenitic stainless steel 310S

    Energy Technology Data Exchange (ETDEWEB)

    Nezakat, Majid, E-mail: majid.nezakat@usask.ca [Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3 (Canada); Akhiani, Hamed [Westpower Equipment Ltd., 4451 54 Avenue South East, Calgary, AB T2C 2A2 (Canada); Sabet, Seyed Morteza [Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL 33431 (United States); Szpunar, Jerzy [Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 (Canada)

    2017-01-15

    We studied the texture evolution of thermo-mechanically processed austenitic stainless steel 310S. This alloy was cold rolled up to 90% reduction in thickness and subsequently annealed at 1050 °C. At the early stages of deformation, strain-induced martensite was formed from deformed austenite. By increasing the deformation level, slip mechanism was found to be insufficient to accommodate higher deformation strains. Our results demonstrated that twinning is the dominant deformation mechanism at higher deformation levels. Results also showed that cold rolling in unidirectional and cross rolling modes results in Goss/Brass and Brass dominant textures in deformed samples, respectively. Similar texture components are observed after annealing. Thus, the annealing texture was greatly affected by texture of the deformed parent phase and martensite did not contribute as it showed an athermal reversion during annealing. Results also showed that when the fraction of martensite exceeds a critical point, its grain boundaries impeded the movement of austenite grain boundaries during annealing. As a result, recrystallization incubation time would increase. This caused an incomplete recrystallization of highly deformed samples, which led to a rational drop in the intensity of the texture components. - Highlights: •Thermo-mechanical processing through different cold rolling modes can induce different textures. •Martensite reversion is athermal during annealing. •Higher fraction of deformation-induced martensite can increase the annealing time required for complete recrystallization. •Annealing texture is mainly influenced by the deformation texture of austenite.

  17. Detection of electron magnetic circular dichroism signals under zone axial diffraction geometry

    Energy Technology Data Exchange (ETDEWEB)

    Song, Dongsheng [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE) and The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Rusz, Jan [Department of Physics and Astronomy, Uppsala University, Box 516, S-751 20 Uppsala (Sweden); Cai, Jianwang [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn [National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE) and The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2016-10-15

    EMCD (electron magnetic circular dichroism) technique provides us a new opportunity to explore magnetic properties in the transmission electron microscope. However, specific diffraction geometry is the major limitation. Only the two-beam and three-beam case are demonstrated in the experiments until now. Here, we present the more general case of zone axial (ZA) diffraction geometry through which the EMCD signals can be detected even with the very strong sensitivity to dynamical diffraction conditions. Our detailed calculations and well-controlled diffraction conditions lead to experiments in agreement with theory. The effect of dynamical diffraction conditions on EMCD signals are discussed both in theory and experiments. Moreover, with the detailed analysis of dynamical diffraction effects, we experimentally obtain the separate EMCD signals for each crystallographic site in Y{sub 3}Fe{sub 5}O{sub 12}, which is also applicable for other materials and cannot be achieved by site-specific EMCD and XMCD technique directly. Our work extends application of more general diffraction geometries and will further promote the development of EMCD technique. - Highlights: • The zone axial (ZA) diffraction geometry is presented for EMCD technique. • The detailed calculations for EMCD signals under ZA case are conducted. • The EMCD signals are obtained under the ZA case in the experiments. • The effect of dynamical effect on EMCD signals under ZA case is discussed. • Site-specific EMCD signals of Fe in Y{sub 3}Fe{sub 5}O{sub 12} are obtained by specific ZA conditions.

  18. The Use of Backscattered Electron Imaging and Transmission Electron Microscopy to Assess Bone Architecture and Mineral Loci: Effect of Intermittent Slow-Release Sodium Fluoride Therapy

    Science.gov (United States)

    Zerwekh, Joseph E.; Bellotto, Dennis; Prostak, Kenneth S.; Hagler, Herbert K.; Pak, Charles Y. C.

    1996-04-01

    Backscattered electron imaging (BEI) and transmission electron microscopy (TEM) were used to examine the effects of treatment with intermittent slow-release sodium fluoride (SRNaF) and continuous calcium citrate on bone architecture and crystallinity. Examination was performed in nondecalcified biopsies obtained from patients following up to four years of therapy (placebo or SRNaF) and compared to pretreatment biopsies from each patient, as well as to bone from young, normal subjects. BEI images disclosed increased areas of recent bone formation following fluoride administration. There was no evidence of a mineralization defect in any biopsy and both cortical and trabecular architecture remained normal. TEM analysis demonstrated intrafibrillar platelike crystals and extrafibrillar needlelike crystals for both the pre- and post-treatment biopsies as well as for the bone from young normal subjects. There was no evidence of increased crystal size or of an increase in extrafibrillar mineral deposition. These observations suggest that intermittent SRNaF and continuous calcium therapy exerts an anabolic action on the skeleton not accompanied by a mineralization defect or an alteration of bone mineral deposition. The use of BEI and TEM holds promise for the study of the pathophysiology and treatment of metabolic bone diseases.

  19. Low-energy electron diffraction and induced damage in hydrated DNA

    International Nuclear Information System (INIS)

    Orlando, Thomas M.; Oh, Doogie; Chen Yanfeng; Aleksandrov, Alexandr B.

    2008-01-01

    Elastic scattering of 5-30 eV electrons within the B-DNA 5 ' -CCGGCGCCGG-3 ' and A-DNA 5 ' -CGCGAATTCGCG-3 ' DNA sequences is calculated using the separable representation of a free-space electron propagator and a curved wave multiple scattering formalism. The disorder brought about by the surrounding water and helical base stacking leads to a featureless amplitude buildup of elastically scattered electrons on the sugar and phosphate groups for all energies between 5 and 30 eV. However, some constructive interference features arising from diffraction are revealed when examining the structural waters within the major groove. These appear at 5-10, 12-18, and 22-28 eV for the B-DNA target and at 7-11, 12-18, and 18-25 eV for the A-DNA target. Although the diffraction depends on the base-pair sequence, the energy dependent elastic scattering features are primarily associated with the structural water molecules localized within 8-10 A spheres surrounding the bases and/or the sugar-phosphate backbone. The electron density buildup occurs in energy regimes associated with dissociative electron attachment resonances, direct electronic excitation, and dissociative ionization. Since diffraction intensity can be localized on structural water, compound H 2 O:DNA states may contribute to energy dependent low-energy electron induced single and double strand breaks

  20. Micro-channel plate detector for ultra-fast relativistic electron diffraction

    International Nuclear Information System (INIS)

    Musumeci, P.; Moody, J.T.; Scoby, C.M.; Gutierrez, M.S.; Bender, H.A.; Hilko, B.; Kruschwitz, C.A.; Wilcox, N.S.

    2011-01-01

    Using relativistic ultra-short electron beams to obtain single-shot diffraction patterns holds the promise to yield real-time resolution of atomic motion in an easily accessible environment, such as a university laboratory, at a fraction of the cost of fourth-generation X-ray sources. One of the main issues in bringing this technique to full maturity is the development of efficient detector systems to record the diffraction pattern using a few MeV electron beams. Low noise, high spatial resolution, and single-electron detection capability are all characteristics of an ideal detector. In this paper, we compare the performances of a traditional fluorescent phosphor screen with a detection system based on the micro-channel plate (MCP). Since MCPs are typically used with lower energy electron beams, these tests constitute one of the few experimental data points available on the use of these devices with MeV energy beams.

  1. Micro-channel plate detector for ultra-fast relativistic electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Musumeci, P., E-mail: musumeci@physics.ucla.edu [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA, 90095-1547 (United States); Moody, J.T.; Scoby, C.M.; Gutierrez, M.S. [UCLA Department of Physics and Astronomy, 475 Portola Plaza, Los Angeles, CA, 90095-1547 (United States); Bender, H.A.; Hilko, B.; Kruschwitz, C.A.; Wilcox, N.S. [National Security Technologies, LLC, Los Alamos Operations, Los Alamos, NM (United States)

    2011-05-01

    Using relativistic ultra-short electron beams to obtain single-shot diffraction patterns holds the promise to yield real-time resolution of atomic motion in an easily accessible environment, such as a university laboratory, at a fraction of the cost of fourth-generation X-ray sources. One of the main issues in bringing this technique to full maturity is the development of efficient detector systems to record the diffraction pattern using a few MeV electron beams. Low noise, high spatial resolution, and single-electron detection capability are all characteristics of an ideal detector. In this paper, we compare the performances of a traditional fluorescent phosphor screen with a detection system based on the micro-channel plate (MCP). Since MCPs are typically used with lower energy electron beams, these tests constitute one of the few experimental data points available on the use of these devices with MeV energy beams.

  2. On a semiclassical analysis of high energy electron diffraction by imperfect crystals: the stacking fault

    International Nuclear Information System (INIS)

    Smith, A.E.; Chadderton, L.T.; Johnson, E.

    1978-01-01

    Electron diffraction amplitudes at the lower surface of a displaced sandwich crystal are obtained for the high energy limit in the real space formulation. Using semiclassical methods analytical approximations to a resulting overlap integral - central to the problem - are derived. (Auth.)

  3. A pipeline for comprehensive and automated processing of electron diffraction data in IPLT.

    Science.gov (United States)

    Schenk, Andreas D; Philippsen, Ansgar; Engel, Andreas; Walz, Thomas

    2013-05-01

    Electron crystallography of two-dimensional crystals allows the structural study of membrane proteins in their native environment, the lipid bilayer. Determining the structure of a membrane protein at near-atomic resolution by electron crystallography remains, however, a very labor-intense and time-consuming task. To simplify and accelerate the data processing aspect of electron crystallography, we implemented a pipeline for the processing of electron diffraction data using the Image Processing Library and Toolbox (IPLT), which provides a modular, flexible, integrated, and extendable cross-platform, open-source framework for image processing. The diffraction data processing pipeline is organized as several independent modules implemented in Python. The modules can be accessed either from a graphical user interface or through a command line interface, thus meeting the needs of both novice and expert users. The low-level image processing algorithms are implemented in C++ to achieve optimal processing performance, and their interface is exported to Python using a wrapper. For enhanced performance, the Python processing modules are complemented with a central data managing facility that provides a caching infrastructure. The validity of our data processing algorithms was verified by processing a set of aquaporin-0 diffraction patterns with the IPLT pipeline and comparing the resulting merged data set with that obtained by processing the same diffraction patterns with the classical set of MRC programs. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Characterization of calcium crystals in Abelia using x-ray diffraction and electron microscopes

    Science.gov (United States)

    Localization, chemical composition, and morphology of calcium crystals in leaves and stems of Abelia mosanensis and A. ×grandiflora were analyzed with a variable pressure scanning electron microscope (VP-SEM) equipped with an X-ray diffraction system, low temperature SEM (LT-SEM) and a transmission ...

  5. Study of thermal stability of ultrafine-grained copper by means of electron back scattering diffraction

    Czech Academy of Sciences Publication Activity Database

    Man, O.; Pantělejev, L.; Kunz, Ludvík

    2010-01-01

    Roč. 51, č. 2 (2010), s. 209-213 ISSN 1345-9678 R&D Projects: GA AV ČR 1QS200410502 Institutional research plan: CEZ:AV0Z20410507 Keywords : ultra-fine grained copper * thermal stability of microstructure * electron back scattering diffraction * grain size * texture Subject RIV: JG - Metallurgy Impact factor: 0.779, year: 2010

  6. Electro-optic sampling for time resolving relativistic ultrafast electron diffraction

    International Nuclear Information System (INIS)

    Scoby, C. M.; Musumeci, P.; Moody, J.; Gutierrez, M.; Tran, T.

    2009-01-01

    The Pegasus laboratory at UCLA features a state-of-the-art electron photoinjector capable of producing ultrashort (<100 fs) high-brightness electron bunches at energies of 3.75 MeV. These beams recently have been used to produce static diffraction patterns from scattering off thin metal foils, and it is foreseen to take advantage of the ultrashort nature of these bunches in future pump-probe time-resolved diffraction studies. In this paper, single shot 2-d electro-optic sampling is presented as a potential technique for time of arrival stamping of electron bunches used for diffraction. Effects of relatively low bunch charge (a few 10's of pC) and modestly relativistic beams are discussed and background compensation techniques to obtain high signal-to-noise ratio are explored. From these preliminary tests, electro-optic sampling is suitable to be a reliable nondestructive time stamping method for relativistic ultrafast electron diffraction at the Pegasus lab.

  7. Electron Paramagnetic Resonance and X-ray Diffraction of Boron- and Phosphorus-Doped Nanodiamonds

    Science.gov (United States)

    Binh, Nguyen Thi Thanh; Dolmatov, V. Yu.; Lapchuk, N. M.; Shymanski, V. I.

    2017-11-01

    Powders of boron- and phosphorus-doped detonation nanodiamonds and sintered pellets of non-doped nanodiamond powders were studied using electron paramagnetic resonance and x-ray diffraction. Doping of detonation nanodiamond crystals with boron and phosphorus was demonstrated to be possible. These methods could be used to diagnose diamond nanocrystals doped during shock-wave synthesis.

  8. Structural study of disordered SiC nanowires by three-dimensional rotation electron diffraction

    International Nuclear Information System (INIS)

    Li, Duan; Guo, Peng; Wan, Wei; Zou, Ji; Shen, Zhijian; Guzi de Moraes, Elisângela; Colombo, Paolo

    2014-01-01

    The structure of disordered SiC nanowires was studied by using the three-dimensional rotation electron diffraction (RED) technique. The streaks shown in the RED images indicated the stacking faults of the nanowire. High-resolution transmission electron microscopy imaging was employed to support the results from the RED data. It suggested that a 2H polytype is most possible for the nanowires. (paper)

  9. Ultrafast coherent diffractive imaging of nanoparticles using X-ray free-electron laser radiation

    International Nuclear Information System (INIS)

    Kassemeyer, Stephan

    2014-01-01

    Coherent diffractive imaging with X-ray free-electron lasers (X-FEL) promises high-resolution structure determination of single microscopic particles without the need for crystallization. The diffraction signal of small samples can be very weak, a difficulty that can not be countered by merely increasing the number of photons because the sample would be damaged by a high absorbed radiation dose. Traditional X-ray crystallography avoids this problem by bringing many sample particles into a periodic arrangement, which amplifies the individual signals while distributing the absorbed dose. Depending on the sample, however, crystallization can be very difficult or even impossible. This thesis presents algorithms for a new imaging approach using X-FEL radiation that works with single, non-crystalline sample particles. X-FELs can deliver X-rays with a peak brilliance many orders of magnitude higher than conventional X-ray sources, compensating for their weak interaction cross sections. At the same time, FELs can produce ultra-short pulses down to a few femtoseconds. In this way it is possible to perform ultra-fast imaging, essentially ''freezing'' the atomic positions in time and terminating the imaging process before the sample is destroyed by the absorbed radiation. This thesis primarily focuses on the three-dimensional reconstruction of single (and not necessarily crystalline) particles using coherent diffractive imaging at X-FELs: in order to extract three-dimensional information from scattering data, two-dimensional diffraction patterns from many different viewing angles must be combined. Therefore, the diffraction signal of many identical sample copies in random orientations is measured. The main result of this work is a globally optimal algorithm that can recover the sample orientations solely based on the diffraction signal, enabling three-dimensional imaging for arbitrary samples. The problem of finding three-dimensional orientations is

  10. Measurements of transient electron density distributions by femtosecond X-ray diffraction

    International Nuclear Information System (INIS)

    Freyer, Benjamin

    2013-01-01

    This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

  11. A study on displacement of crystalline diffraction peaks in electron-beam irradiated filter paper cellulose

    International Nuclear Information System (INIS)

    Zhou Ruimin; Xiang Qun; Song Jing

    1997-01-01

    It is found that the crystalline diffraction angles of the electron-beam irradiated filter paper cellulose shift regularly when the irradiation dose is increased. The experiments indicate that the molecules between crystalline area and amorphous area in the filter paper cellulose will be degraded by the irradiation and the cellulose molecules in the surface of crystal will come off, thus the microcrystalline dimension will be reduced and the diffraction angle will become smaller. The fact that intensity of the 002 peak for filter paper samples decreases gradually with the increasing storage time can be attributed to the post-irradiation effect

  12. Crystallographic orientation study of silicon steels using X-ray diffraction, electrons diffraction and the Etch Pit method

    International Nuclear Information System (INIS)

    Santos, Hamilta de Oliveira

    1999-01-01

    The aim of the present study is the microstructural and crystallographic orientation of Fe-3%Si steel. The silicon steel shows good electrical properties and it is used in the nuclear and electrical power fields. The studied steel was supplied by Cia. Acos Especiais Itabira S/A - ACESITA. The material was received in the hot compressed condition, in one or two passes. The hot compressing temperatures used were 900, 1000 and 1100 deg C with soaking times ranging from 32 to 470 s. The material preferential crystallographic orientation was evaluated in every grain of the samples. The characterization techniques used were: scanning electron microscopy (SEM) using the etch pit method; X ray diffraction using the Laue back-reflection method; orientation imaging microscopy (OIM). Microstructural characterization in terms of grain size measurement and mean number of grains in the sample were also undertaken. The Laue method was found an easy technique to access crystallographic orientation of this work polycrystalline samples 2.5 mm average grain size. This was due to the inability to focus the X-rays on a single grain of the material. The scanning electron microscopy showed microcavities left by the etch pit method, which allowed the observation of the crystallographic orientation of each grain from the samples. No conclusive grain crystallographic orientation was possible to obtain by the OIM technique due to the non-existing rolling direction. A more extensive work with the OIM technique must be undertaken on the Fe-3%Si with oriented grains and non oriented grains. (author)

  13. Femtosecond Electron Wave Packet Propagation and Diffraction: Towards Making the ``Molecular Movie"

    Science.gov (United States)

    Miller, R. J. Dwayne

    2003-03-01

    Time-resolved electron diffraction harbors great promise for achieving atomic resolution of the fastest chemical processes. The generation of sufficiently short electron pulses to achieve this real time view of a chemical reaction has been limited by problems in maintaining short electron pulses with realistic electron densities to the sample. The propagation dynamics of femtosecond electron packets in the drift region of a photoelectron gun are investigated with an N-body numerical simulation and mean-field model. This analyis shows that the redistribution of electrons inside the packet, arising from space-charge and dispersion contributions, changes the pulse envelope and leads to the development of a spatially linear axial velocity distribution. These results have been used in the design of femtosecond photoelectron guns with higher time resolution and novel electron-optical methods of pulse characterization that are approaching 100 fs timescales. Time-resolved diffraction studies with electron pulses of approximately 500 femtoseconds have focused on solid-liquid phase transitions under far from equilibrium conditions. This work gives a microscopic description of the melting process and illustrates the promise of atomically resolving transition state processes.

  14. 2D Spin-Dependent Diffraction of Electrons From Periodical Chains of Nanomagnets

    Directory of Open Access Journals (Sweden)

    Teshome Senbeta

    2012-03-01

    Full Text Available The scattering of the unpolarized beams of electrons by nanomagnets in the vicinity of some scattering angles leads to complete spin polarized electrons. This result is obtained with the help of the perturbation theory. The dipole-dipole interaction between the magnetic moment of the nanomagnet and the magnetic moment of electron is treated as perturbation. This interaction is not spherically symmetric. Rather it depends on the electron spin variables. It in turn results in spinor character of the scattering amplitudes. Due to the smallness of the magnetic interactions, the scattering length of this process is very small to be proved experimentally. To enhance the relevant scattering lengths, we considered the diffraction of unpolarized beams of electrons by linear chains of nanomagnets. By tuning the distance between the scatterers it is possible to obtain the diffraction maximum of the scattered electrons at scattering angles which corresponds to complete spin polarization of electrons. It is shown that the total differential scattering length is proportional to N2 (N is a number of scatterers. Even small number of nanomagnets in the chain helps to obtain experimentally visible enhancement of spin polarization of the scattered electrons.

  15. Dynamical electron diffraction simulation for non-orthogonal crystal system by a revised real space method.

    Science.gov (United States)

    Lv, C L; Liu, Q B; Cai, C Y; Huang, J; Zhou, G W; Wang, Y G

    2015-01-01

    In the transmission electron microscopy, a revised real space (RRS) method has been confirmed to be a more accurate dynamical electron diffraction simulation method for low-energy electron diffraction than the conventional multislice method (CMS). However, the RRS method can be only used to calculate the dynamical electron diffraction of orthogonal crystal system. In this work, the expression of the RRS method for non-orthogonal crystal system is derived. By taking Na2 Ti3 O7 and Si as examples, the correctness of the derived RRS formula for non-orthogonal crystal system is confirmed by testing the coincidence of numerical results of both sides of Schrödinger equation; moreover, the difference between the RRS method and the CMS for non-orthogonal crystal system is compared at the accelerating voltage range from 40 to 10 kV. Our results show that the CMS method is almost the same as the RRS method for the accelerating voltage above 40 kV. However, when the accelerating voltage is further lowered to 20 kV or below, the CMS method introduces significant errors, not only for the higher-order Laue zone diffractions, but also for zero-order Laue zone. These indicate that the RRS method for non-orthogonal crystal system is necessary to be used for more accurate dynamical simulation when the accelerating voltage is low. Furthermore, the reason for the increase of differences between those diffraction patterns calculated by the RRS method and the CMS method with the decrease of the accelerating voltage is discussed. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  16. Diffraction and absorption of inelastically scattered electrons for K-shell ionization

    International Nuclear Information System (INIS)

    Josefsson, T.W.; Allen, L.J.

    1995-01-01

    An expression for the nonlocal inelastic scattering cross section for fast electrons in a crystalline environment, which explicitly includes diffraction as well as absorption for the inelastically scattered electrons, is used to carry out realistic calculations of K-shell electron energy loss spectroscopy (EELS) and energy dispersive x-ray (EDX) analysis cross sections. The calculations demonstrate quantitatively why, in EDX spectroscopy, integration over the dynamical states of the inelastically scattered electron averages in such a way that an effective plane wave representation of the scattered electrons is a good approximation. This is only the case for large enough acceptance angles of the detector in an EELS experiment. For EELS with smaller detector apertures, explicit integration over the dynamical final states is necessary and inclusion of absorption for the scattered electrons is important, particularly for thicker crystals. 50 refs., 7 figs

  17. Advances in imaging and electron physics time resolved electron diffraction for chemistry, biology and material science

    CERN Document Server

    Hawkes, Peter W

    2014-01-01

    Advances in Imaging & Electron Physics merges two long-running serials-Advances in Electronics & Electron Physics and Advances in Optical & Electron Microscopy. The series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. Contributions from leading authorities Informs and updates on all the latest developments in the field.

  18. Development of an ellipse fitting method with which to analyse selected area electron diffraction patterns

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, D.R.G., E-mail: dmitchel@uow.edu.au [Electron Microscopy Centre, Australian Institute for Innovative Materials, Innovation Campus, University of Wollongong, North Wollongong, NSW 2500 (Australia); Van den Berg, J.A. [Electron Microscopy Centre, Australian Institute for Innovative Materials, Innovation Campus, University of Wollongong, North Wollongong, NSW 2500 (Australia); Catalyst Fundamentals, Fischer-Tropsch and Syngas Conversion Research, Sasol Technology R & D, Sasolburg 1947 (South Africa)

    2016-01-15

    A software method has been developed which uses ellipse fitting to analyse electron diffraction patterns from polycrystalline materials. The method, which requires minimal user input, can determine the pattern centre and the diameter of diffraction rings with sub-pixel precision. This enables accurate crystallographic information to be obtained in a rapid and consistent manner. Since the method fits ellipses, it can detect, quantify and correct any elliptical distortion introduced by the imaging system. Distortion information derived from polycrystalline patterns as a function of camera length can be subsequently recalled and applied to single crystal patterns, resulting in improved precision and accuracy. The method has been implemented as a plugin for the DigitalMicrograph software by Gatan, and is a freely available via the internet. - Highlights: • A robust ellipse fitting method is developed. • Freely available software for automated diffraction pattern analysis is demonstrated. • Measurement and correction of elliptical distortion is routinely achieved.

  19. Three-dimensional nanostructure determination from a large diffraction data set recorded using scanning electron nanodiffraction

    Directory of Open Access Journals (Sweden)

    Yifei Meng

    2016-09-01

    Full Text Available A diffraction-based technique is developed for the determination of three-dimensional nanostructures. The technique employs high-resolution and low-dose scanning electron nanodiffraction (SEND to acquire three-dimensional diffraction patterns, with the help of a special sample holder for large-angle rotation. Grains are identified in three-dimensional space based on crystal orientation and on reconstructed dark-field images from the recorded diffraction patterns. Application to a nanocrystalline TiN thin film shows that the three-dimensional morphology of columnar TiN grains of tens of nanometres in diameter can be reconstructed using an algebraic iterative algorithm under specified prior conditions, together with their crystallographic orientations. The principles can be extended to multiphase nanocrystalline materials as well. Thus, the tomographic SEND technique provides an effective and adaptive way of determining three-dimensional nanostructures.

  20. Ab-initio crystal structure analysis and refinement approaches of oligo p-benzamides based on electron diffraction data

    DEFF Research Database (Denmark)

    Gorelik, Tatiana E; van de Streek, Jacco; Kilbinger, Andreas F M

    2012-01-01

    Ab-initio crystal structure analysis of organic materials from electron diffraction data is presented. The data were collected using the automated electron diffraction tomography (ADT) technique. The structure solution and refinement route is first validated on the basis of the known crystal stru...

  1. Three-dimensional rotation electron diffraction: software RED for automated data collection and data processing.

    Science.gov (United States)

    Wan, Wei; Sun, Junliang; Su, Jie; Hovmöller, Sven; Zou, Xiaodong

    2013-12-01

    Implementation of a computer program package for automated collection and processing of rotation electron diffraction (RED) data is described. The software package contains two computer programs: RED data collection and RED data processing. The RED data collection program controls the transmission electron microscope and the camera. Electron beam tilts at a fine step (0.05-0.20°) are combined with goniometer tilts at a coarse step (2.0-3.0°) around a common tilt axis, which allows a fine relative tilt to be achieved between the electron beam and the crystal in a large tilt range. An electron diffraction (ED) frame is collected at each combination of beam tilt and goniometer tilt. The RED data processing program processes three-dimensional ED data generated by the RED data collection program or by other approaches. It includes shift correction of the ED frames, peak hunting for diffraction spots in individual ED frames and identification of these diffraction spots as reflections in three dimensions. Unit-cell parameters are determined from the positions of reflections in three-dimensional reciprocal space. All reflections are indexed, and finally a list with hkl indices and intensities is output. The data processing program also includes a visualizer to view and analyse three-dimensional reciprocal lattices reconstructed from the ED frames. Details of the implementation are described. Data collection and data processing with the software RED are demonstrated using a calcined zeolite sample, silicalite-1. The structure of the calcined silicalite-1, with 72 unique atoms, could be solved from the RED data by routine direct methods.

  2. Diffraction efficiency of plasmonic gratings fabricated by electron beam lithography using a silver halide film

    Energy Technology Data Exchange (ETDEWEB)

    Sudheer,, E-mail: sudheer@rrcat.gov.in, E-mail: sudheer.rrcat@gmail.com; Tiwari, P.; Srivastava, Himanshu; Rai, V. N.; Srivastava, A. K.; Naik, P. A. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Porwal, S. [Solid State Lasers Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Bhartiya, S. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Laser Materials Development and Device Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Rao, B. T. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Sharma, T. K. [Homi Bhabha National Institute, Mumbai, Maharashtra 400094 (India); Solid State Lasers Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India)

    2016-07-28

    The silver nanoparticle surface relief gratings of ∼10 μm period are fabricated using electron beam lithography on the silver halide film substrate. Morphological characterization of the gratings shows that the period, the shape, and the relief depth in the gratings are mainly dependent on the number of lines per frame, the spot size, and the accelerating voltage of electron beam raster in the SEM. Optical absorption of the silver nanoparticle gratings provides a broad localized surface plasmon resonance peak in the visible region, whereas the intensity of the peaks depends on the number density of silver nanoparticles in the gratings. The maximum efficiency of ∼7.2% for first order diffraction is observed for the grating fabricated at 15 keV. The efficiency is peaking at 560 nm with ∼380 nm bandwidth. The measured profiles of the diffraction efficiency for the gratings are found in close agreement with the Raman-Nath diffraction theory. This technique provides a simple and efficient method for the fabrication of plasmonic nanoparticle grating structures with high diffraction efficiency having broad wavelength tuning.

  3. High current table-top setup for femtosecond gas electron diffraction

    Directory of Open Access Journals (Sweden)

    Omid Zandi

    2017-07-01

    Full Text Available We have constructed an experimental setup for gas phase electron diffraction with femtosecond resolution and a high average beam current. While gas electron diffraction has been successful at determining molecular structures, it has been a challenge to reach femtosecond resolution while maintaining sufficient beam current to retrieve structures with high spatial resolution. The main challenges are the Coulomb force that leads to broadening of the electron pulses and the temporal blurring that results from the velocity mismatch between the laser and electron pulses as they traverse the sample. We present here a device that uses pulse compression to overcome the Coulomb broadening and deliver femtosecond electron pulses on a gas target. The velocity mismatch can be compensated using laser pulses with a tilted intensity front to excite the sample. The temporal resolution of the setup was determined with a streak camera to be better than 400 fs for pulses with up to half a million electrons and a kinetic energy of 90 keV. The high charge per pulse, combined with a repetition rate of 5 kHz, results in an average beam current that is between one and two orders of magnitude higher than previously demonstrated.

  4. Reciprocal space mapping by spot profile analyzing low energy electron diffraction

    International Nuclear Information System (INIS)

    Meyer zu Heringdorf, Frank-J.; Horn-von Hoegen, Michael

    2005-01-01

    We present an experimental approach for the recording of two-dimensional reciprocal space maps using spot profile analyzing low energy electron diffraction (SPA-LEED). A specialized alignment procedure eliminates the shifting of LEED patterns on the screen which is commonly observed upon variation of the electron energy. After the alignment, a set of one-dimensional sections through the diffraction pattern is recorded at different energies. A freely available software tool is used to assemble the sections into a reciprocal space map. The necessary modifications of the Burr-Brown computer interface of the two Leybold and Omicron type SPA-LEED instruments are discussed and step-by-step instructions are given to adapt the SPA 4.1d software to the changed hardware. Au induced faceting of 4 deg. vicinal Si(001) is used as an example to demonstrate the technique

  5. Molecular structure determination of cyclooctane by Ab Initio and electron diffraction methods in the gas phase

    International Nuclear Information System (INIS)

    Almeida, Wagner B. de

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can make a significant contribution for an unambiguous determination of the geometrical parameters. In this article the determination for an unambiguous determination of the geometrical parameters. In this article the determination of the molecular structure of the cyclooctane molecule by electron diffraction in the gas phase an initio calculations will be addressed, providing an example of a comparative analysis of theoretical and experimental predictions. (author)

  6. Correlated microradiography, X-ray microbeam diffraction and electron probe microanalysis of calcifications in an odontoma

    International Nuclear Information System (INIS)

    Aoba, T.; Yoshioka, C.; Yagi, T.

    1980-01-01

    Using microradiography, X-ray microbeam diffraction and electron probe microanalysis, a correlated morphologic and crystallographic study was performed on dysplastic enamel in a compound odontoma. The tumor was found in the lateral incisor-canine region of the left mandible of a 36-year-old woman. A conspicuous feature was the presence of hypomineralized areas, which were situated in the proximity of enamel surface and distinctly demarcated from the adjacent enamel. X-ray microbeam diffraction and electron microanalysis showed that these lesions have a lower crystallinity and a higher concentration of magnesium as compared with the adjacent enamel. In addition, the present study revealed the presence of two other types of calcifications: 1) calcified structures within the fissure or on the enamel surface, which include lacunae of varying size and which resemble a form of coronal cementum, and 2) spherical calcifications which may be an epithelial product. (author)

  7. Molecular structure determination of cyclootane by ab initio and electron diffraction methods in the gas phase

    OpenAIRE

    De Almeida, Wagner B.

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can ma...

  8. Calculation of diffraction patterns associated with electron irradiation induced amorphization of CuTi

    International Nuclear Information System (INIS)

    Devanathan, R.; Meshii, M.; Sabochik, M.J.

    1990-11-01

    A new approach that uses the multislice method in conjunction with molecular dynamics simulations to study electron irradiation induced amorphisation is presented. Diffraction patterns were calculated for CuTi and found to be more sensitive than the pair correlation function to the structural changes preceding amorphisation. The results from this approach and from a study of long range order are presented. 16 refs., 8 figs

  9. Diffraction structures in delta electron spectra emitted in heavy-ion atom collisions

    International Nuclear Information System (INIS)

    Liao, C.; Bhalla, C.; Shingal, R.; Schmidt-Boecking, H.; Shinpaugh, J.; Wolf, W.; Wolf, H.

    1992-01-01

    We have measured doubly differential cross sections DDCS for projectiles between F and Au and find evidence for strong diffraction structure in the Binary Encounter region of the emitted electron spectra for Au(Z=79), I(Z=53) and Cu(Z=29) projectiles, however not for F projectiles in the collision energy range between 0.2 and 0.5 MeV/u. (orig.)

  10. Scanning Precession Electron Diffraction Study of 2xxx Series Aluminium Alloys Exhibiting Several Coexisting Strengthening Phases

    OpenAIRE

    Sunde, Jonas Kristoffer

    2016-01-01

    Throughout this thesis, scanning precession electron diffraction is applied to heat-treated Al-Cu-Li and Al-Mg-Cu-Ag alloys, shedding light on the distribution of phases present and the complex interplay between these microstructural features. The employed technique yielded high quality data sets, which through subsequent data processing enabled a detailed phase mapping of these multi-component Al alloys. Among the main results presented, are virtual dark field images highlighting all separat...

  11. Abiotic versus biotic iron mineral transformation studied by a miniaturized backscattering Mössbauer spectrometer (MIMOS II), X-ray diffraction and Raman spectroscopy

    Science.gov (United States)

    Markovski, C.; Byrne, J. M.; Lalla, E.; Lozano-Gorrín, A. D.; Klingelhöfer, G.; Rull, F.; Kappler, A.; Hoffmann, T.; Schröder, C.

    2017-11-01

    Searching for biomarkers or signatures of microbial transformations of minerals is a critical aspect for determining how life evolved on Earth, and whether or not life may have existed in other planets, including Mars. In order to solve such questions, several missions to Mars have sought to determine the geochemistry and mineralogy on the Martian surface. This research includes the two miniaturized Mössbauer spectrometers (MIMOS II) on board the Mars Exploration Rovers Spirit and Opportunity, which have detected a variety of iron minerals on Mars, including magnetite (Fe2+Fe3+2O4) and goethite (α-FeO(OH)). On Earth, both minerals can derive from microbiological activity (e.g. through dissimilatory iron reduction of ferrihydrite by Fe(III)-reducing bacteria). Here we used a lab based MIMOS II to characterize the mineral products of biogenic transformations of ferrihydrite to magnetite by the Fe(III)-reducing bacteria Geobacter sulfurreducens. In combination with Raman spectroscopy and X-ray diffraction (XRD), we observed the formation of magnetite, goethite and siderite. We compared the material produced by biogenic transformations to abiotic samples in order to distinguish abiotic and biotic iron minerals by techniques that are or will be available onboard Martian based laboratories. The results showed the possibility to distinguish the abiotic and biotic origin of the minerals. Mossbauer was able to distinguish the biotic/abiotic magnetite with the interpretation of the geological context (Fe content mineral assemblages and accompanying minerals) and the estimation of the particle size in a non-destructive way. The Raman was able to confirm the biotic/abiotic principal peaks of the magnetite, as well as the organic principal vibration bands attributed to the bacteria. Finally, the XRD confirmed the particle size and mineralogy.

  12. Ab initio structure determination and quantitative disorder analysis on nanoparticles by electron diffraction tomography.

    Science.gov (United States)

    Krysiak, Yaşar; Barton, Bastian; Marler, Bernd; Neder, Reinhard B; Kolb, Ute

    2018-03-01

    Nanoscaled porous materials such as zeolites have attracted substantial attention in industry due to their catalytic activity, and their performance in sorption and separation processes. In order to understand the properties of such materials, current research focuses increasingly on the determination of structural features beyond the averaged crystal structure. Small particle sizes, various types of disorder and intergrown structures render the description of structures at atomic level by standard crystallographic methods difficult. This paper reports the characterization of a strongly disordered zeolite structure, using a combination of electron exit-wave reconstruction, automated diffraction tomography (ADT), crystal disorder modelling and electron diffraction simulations. Zeolite beta was chosen for a proof-of-principle study of the techniques, because it consists of two different intergrown polymorphs that are built from identical layer types but with different stacking sequences. Imaging of the projected inner Coulomb potential of zeolite beta crystals shows the intergrowth of the polymorphs BEA and BEB. The structures of BEA as well as BEB could be extracted from one single ADT data set using direct methods. A ratio for BEA/BEB = 48:52 was determined by comparison of the reconstructed reciprocal space based on ADT data with simulated electron diffraction data for virtual nanocrystals, built with different ratios of BEA/BEB. In this way, it is demonstrated that this smart interplay of the above-mentioned techniques allows the elaboration of the real structures of functional materials in detail - even if they possess a severely disordered structure.

  13. Ultrafast electron diffraction from non-equilibrium phonons in femtosecond laser heated Au films

    Energy Technology Data Exchange (ETDEWEB)

    Chase, T. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Trigo, M.; Reid, A. H.; Dürr, H. A. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Li, R.; Vecchione, T.; Shen, X.; Weathersby, S.; Coffee, R.; Hartmann, N.; Wang, X. J. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Reis, D. A. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)

    2016-01-25

    We use ultrafast electron diffraction to detect the temporal evolution of non-equilibrium phonons in femtosecond laser-excited ultrathin single-crystalline gold films. From the time-dependence of the Debye-Waller factor, we extract a 4.7 ps time-constant for the increase in mean-square atomic displacements. The observed increase in the diffuse scattering intensity demonstrates that the energy transfer from laser-heated electrons to phonon modes near the X and K points in the Au fcc Brillouin zone proceeds with timescales of 2.3 and 2.9 ps, respectively, faster than the Debye-Waller average mean-square displacement.

  14. CL 19: Anisotropy of the electron diffraction from femtosecond Laser excited Bismuth

    International Nuclear Information System (INIS)

    Zhou, P.; Ligges, M.; Streubuehr, C.; Brazda, Th.; Payer, Th.; Meyer zu Heringdorf, F.; Horn-von Hoegen, M.; Von der Linde, D.

    2010-01-01

    We report an electron diffraction experiment in Bi in which a linearly polarized E g optical phonon mode is detected after excitation of the material by a femtosecond laser pulse. Bismuth is a semimetal with rhombohedral crystal structure with two atoms in the unit cell. There are two types of optical phonon modes: (i) The totally symmetric A 1g mode which corresponds to a displacement of the atoms along the trigonal (111) direction, and (ii) the doubly degenerate E g mode which represents a motion in the plane perpendicular to (111). The A 1g mode can be coherently excited both by displacive excitation (DE) and by impulsive stimulated Raman scattering (ISRS). Symmetry properties prevent DE of E g modes leaving ISRS as a likely excitation mechanism. We performed time resolved electron diffraction experiments on femtosecond laser excited Bi membranes of 15 nm thickness which were grown on a NaCl crystal and detached by floating in water. The experimental setup is described elsewhere. The fundamental laser beam (800 nm) was used for the excitation of the Bi films. The films had a crystalline structure with the (111) axis perpendicular to the surface. The electron beam passed perpendicular to the surface through the film. In this geometry the diffraction pattern is insensitive to atomic displacements along the (111) direction, i.e. insensitive to A 1g phonon modes. On the other hand, the excitation of E g modes corresponding to atomic displacements in the plane normal to (111) decreases the intensity of particular diffraction orders. The individual cycles of the E g vibrations (duration 475 fs) could not be resolved because our time resolution about 700 fs was not sufficient. In our experiment excitation beam with a fluence of 1 mJ/cm 2 and variable linear polarization was incident from the backside at an angle of 40 degrees (counter propagating electron and laser beam). The diffraction patterns were recorded as a function of the delay time between laser pump and

  15. Desorption of hydrogen from magnesium hydride: in-situ electron diffraction study

    International Nuclear Information System (INIS)

    Paik, B.; Jones, I.P.; Walton, A.; Mann, V.; Book, D.; Harris, I.R.

    2009-01-01

    The dynamics of a phase change has been studied where electron beam in Transmission Electron Microscope (TEM) has been used to transform MgH 2 into magnesium. A combination of in-situ Electron Diffraction (ED) and an in-situ Electron Energy Loss Spectroscopy (EELS) study under ED mode describes the phase transformation in terms of, respectively, change in the crystal structure and Plasmon energy shift. The orientation relation [001] MgH2 //[-2110] Mg and (-110) MgH2 //(0001) Mg , obtained from the ED study, has been used to propose a model for the movements of magnesium atoms in the structural change to describe the dynamics of the process. The in-situ EELS study has been compared with the existing H-desorption model. The study aims to describe the sorption dynamics of hydrogen in MgH 2 which is a base material for a number of promising hydrogen storage systems. (author)

  16. Controlled molecules for X-ray diffraction experiments at free-electron lasers

    International Nuclear Information System (INIS)

    Stern, Stephan

    2013-12-01

    X-ray diffractive imaging is at the very heart of materials science and has been utilized for decades to solve unknown molecular structures. Nowadays, it serves as the key method of structural biology to solve molecular structures of large biological molecules comprising several thousand or even millions of atoms. However, X-ray diffraction from isolated molecules is very weak. Therefore, the regular and periodic arrangement of a huge number of identical copies of a certain molecule of interest within a crystal lattice has been a necessary condition in order to exploit Bragg diffraction of X-rays. This results in a huge increase in scattered signal and a strongly improved signal-to-noise ratio compared to diffraction from non-crystalline samples. The major bottleneck of structural biology is that many of biologically interesting molecules refuse to form crystals of sufficient size to be used at synchrotron X-ray lightsources. However, novel X-ray free-electron lasers (XFELs), which became operational very recently, promise to address this issue. X-ray pulses provided by XFELs are many orders of magnitude more intense than X-ray pulses from a synchrotron source and at the same time as short as only several tens of femtoseconds. Combined with wavelengths in the nm-pm range, XFELs are well-suited to study ultrafast atomic and molecular dynamics. Additionally, the ultrashort pulses can be utilized to circumvent the damage threshold which set a limit to the incident intensity in X-ray diffraction experiments before. At XFELs, though eventually destroying the investigated sample, no significant sample deterioration happens on the ultrashort timescale of the XFEL pulse and the measured diffraction pattern is due to an (almost) unharmed sample. In the framework of this thesis, the approach of utilizing the highly intense XFEL pulses for X-ray diffraction of weakly-scattering non-crystalline samples was taken to the limit of small isolated molecules. X-ray diffraction was

  17. Controlled molecules for X-ray diffraction experiments at free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Stern, Stephan

    2013-12-15

    X-ray diffractive imaging is at the very heart of materials science and has been utilized for decades to solve unknown molecular structures. Nowadays, it serves as the key method of structural biology to solve molecular structures of large biological molecules comprising several thousand or even millions of atoms. However, X-ray diffraction from isolated molecules is very weak. Therefore, the regular and periodic arrangement of a huge number of identical copies of a certain molecule of interest within a crystal lattice has been a necessary condition in order to exploit Bragg diffraction of X-rays. This results in a huge increase in scattered signal and a strongly improved signal-to-noise ratio compared to diffraction from non-crystalline samples. The major bottleneck of structural biology is that many of biologically interesting molecules refuse to form crystals of sufficient size to be used at synchrotron X-ray lightsources. However, novel X-ray free-electron lasers (XFELs), which became operational very recently, promise to address this issue. X-ray pulses provided by XFELs are many orders of magnitude more intense than X-ray pulses from a synchrotron source and at the same time as short as only several tens of femtoseconds. Combined with wavelengths in the nm-pm range, XFELs are well-suited to study ultrafast atomic and molecular dynamics. Additionally, the ultrashort pulses can be utilized to circumvent the damage threshold which set a limit to the incident intensity in X-ray diffraction experiments before. At XFELs, though eventually destroying the investigated sample, no significant sample deterioration happens on the ultrashort timescale of the XFEL pulse and the measured diffraction pattern is due to an (almost) unharmed sample. In the framework of this thesis, the approach of utilizing the highly intense XFEL pulses for X-ray diffraction of weakly-scattering non-crystalline samples was taken to the limit of small isolated molecules. X-ray diffraction was

  18. Computer programs for unit-cell determination in electron diffraction experiments

    International Nuclear Information System (INIS)

    Li, X.Z.

    2005-01-01

    A set of computer programs for unit-cell determination from an electron diffraction tilt series and pattern indexing has been developed on the basis of several well-established algorithms. In this approach, a reduced direct primitive cell is first determined from experimental data, in the means time, the measurement errors of the tilt angles are checked and minimized. The derived primitive cell is then checked for possible higher lattice symmetry and transformed into a proper conventional cell. Finally a least-squares refinement procedure is adopted to generate optimum lattice parameters on the basis of the lengths of basic reflections in each diffraction pattern and the indices of these reflections. Examples are given to show the usage of the programs

  19. A three-dimensional polarization domain retrieval method from electron diffraction data

    International Nuclear Information System (INIS)

    Pennington, Robert S.; Koch, Christoph T.

    2015-01-01

    We present an algorithm for retrieving three-dimensional domains of picometer-scale shifts in atomic positions from electron diffraction data, and apply it to simulations of ferroelectric polarization in BaTiO 3 . Our algorithm successfully and correctly retrieves polarization domains in which the Ti atom positions differ by less than 3 pm (0.4% of the unit cell diagonal distance) with 5 and 10 nm depth resolution along the beam direction, and we also retrieve unit cell strain, corresponding to tetragonal-to-cubic unit cell distortions, for 10 nm domains. Experimental applicability is also discussed. - Highlights: • We show a retrieval method for ferroelectric polarization from TEM diffraction data. • Simulated strain and polarization variations along the beam direction are retrieved. • This method can be used for 3D strain and polarization mapping without specimen tilt

  20. Low-energy electron diffraction experiment, theory and surface structure determination

    CERN Document Server

    Hove, Michel A; Chan, Chi-Ming

    1986-01-01

    Surface crystallography plays the same fundamental role in surface science which bulk crystallography has played so successfully in solid-state physics and chemistry. The atomic-scale structure is one of the most important aspects in the understanding of the behavior of surfaces in such widely diverse fields as heterogeneous catalysis, microelectronics, adhesion, lubrication, cor­ rosion, coatings, and solid-solid and solid-liquid interfaces. Low-Energy Electron Diffraction or LEED has become the prime tech­ nique used to determine atomic locations at surfaces. On one hand, LEED has yielded the most numerous and complete structural results to date (almost 200 structures), while on the other, LEED has been regarded as the "technique to beat" by a variety of other surface crystallographic methods, such as photoemission, SEXAFS, ion scattering and atomic diffraction. Although these other approaches have had impressive successes, LEED has remained the most productive technique and has shown the most versatility...

  1. In-situ Indentation and Correlated Precession Electron Diffraction Analysis of a Polycrystalline Cu Thin Film

    Science.gov (United States)

    Guo, Qianying; Thompson, Gregory B.

    2018-04-01

    In-situ TEM nanoindentation of a polycrystalline Cu film was cross-correlated with precession electron diffraction (PED) to quantify the microstructural evolution. The use of PED is shown to clearly reveal features, such as grain size, that are easily masked by diffraction contrast created by the deformation. Using PED, the accompanying grain refinement and change in texture as well as the preservation of specific grain boundary structures, including a ∑3 boundary, under the indent impression were quantified. The nucleation of dislocations, evident in low-angle grain boundary formations, was also observed under the indent. PED quantification of texture gradients created by the indentation process linked well to bend contours observed in the bright-field images. Finally, PED enabled generating a local orientation spread map that gave an approximate estimation of the spatial distribution of strain created by the indentation impression.

  2. Bunch evolution study in optimization of MeV ultrafast electron diffraction

    Science.gov (United States)

    Lu, Xian-Hai; Du, Ying-Chao; Huang, Wen-Hui; Tang, Chuan-Xiang

    2014-12-01

    Megaelectronvolt ultrafast electron diffraction (UED) is a promising detection tool for ultrafast processes. The quality of diffraction image is determined by the transverse evolution of the probe bunch. In this paper, we study the contributing terms of the emittance and space charge effects to the bunch evolution in the MeV UED scheme, employing a mean-field model with an ellipsoidal distribution as well as particle tracking simulation. The small transverse dimension of the drive laser is found to be critical to improve the reciprocal resolution, exploiting both smaller emittance and larger transverse bunch size before the solenoid. The degradation of the reciprocal spatial resolution caused by the space charge effects should be carefully controlled.

  3. Bunch evolution study in optimization of MeV ultrafast electron diffraction

    International Nuclear Information System (INIS)

    Lu Xianhai; Du Yingchao; Huang Wenhui; Tang Chuanxiang

    2014-01-01

    transverse ultrafast electron diffraction (UED) is a promising detection tool for ultrafast processes. The quality of diffraction image is determined by the transverse evolution of the probe bunch. In this paper, we study the contributing terms of the emittance and space charge effects to the bunch evolution in the MeV UED scheme, employing a mean-field model with an ellipsoidal distribution as well as particle tracking simulation. The small transverse dimension of the drive laser is found to be critical to improve the reciprocal resolution, exploiting both smaller emittance and larger transverse bunch size before the solenoid. The degradation of the reciprocal spatial resolution caused by the space charge effects should be carefully controlled. (authors)

  4. Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders.

    Science.gov (United States)

    Yun, Yifeng; Zou, Xiaodong; Hovmöller, Sven; Wan, Wei

    2015-03-01

    Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni-Se-O-Cl crystals, zeolites, germanates, metal-organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED methods

  5. Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders

    Directory of Open Access Journals (Sweden)

    Yifeng Yun

    2015-03-01

    Full Text Available Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED data collection, namely automated diffraction tomography (ADT and rotation electron diffraction (RED, have been developed. Compared with X-ray diffraction (XRD and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni–Se–O–Cl crystals, zeolites, germanates, metal–organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three

  6. A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals

    Energy Technology Data Exchange (ETDEWEB)

    Nederlof, Igor; Genderen, Eric van; Li, Yao-Wang; Abrahams, Jan Pieter, E-mail: abrahams@chem.leidenuniv.nl [Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands)

    2013-07-01

    An ultrasensitive Medipix2 detector allowed the collection of rotation electron-diffraction data from single three-dimensional protein nanocrystals for the first time. The data could be analysed using the standard X-ray crystallography programs MOSFLM and SCALA. When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e{sup −} Å{sup −2}), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLM and SCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins.

  7. A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals

    International Nuclear Information System (INIS)

    Nederlof, Igor; Genderen, Eric van; Li, Yao-Wang; Abrahams, Jan Pieter

    2013-01-01

    An ultrasensitive Medipix2 detector allowed the collection of rotation electron-diffraction data from single three-dimensional protein nanocrystals for the first time. The data could be analysed using the standard X-ray crystallography programs MOSFLM and SCALA. When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e − Å −2 ), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLM and SCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins

  8. Strain fields in crystalline solids: prediction and measurement of X- ray diffraction patterns and electron diffraction contrast images

    NARCIS (Netherlands)

    Bor, Teunis Cornelis

    2000-01-01

    Lattice imperfections, such as dislocations and misfitting particles, shift and/or broaden X-ray diffraction (XRD) line profiles. Most of the present analysis methods of the shift and broadening of XRD line profiles do not provide the characteristics of lattice imperfections. The main part of this

  9. Analysis of dislocation loops by means of large-angle convergent beam electron diffraction

    CERN Document Server

    Jäger, C; Morniroli, J P; Jäger, W

    2002-01-01

    Diffusion-induced dislocation loops in GaP and GaAs were analysed by means of large-angle convergent beam electron diffraction (LACBED) and conventional contrast methods of transmission electron microscopy. It is demonstrated that LACBED is perfectly suited for use in analysing dislocation loops. The method combines analyses of the dislocation-induced splitting of Bragg lines in a LACBED pattern for the determination of the Burgers vector with analyses of the loop contrast behaviour in transmission electron microscopy bright-field images during tilt experiments, from which the habit plane of the dislocation loop is determined. Perfect dislocation loops formed by condensation of interstitial atoms or vacancies were found, depending on the diffusion conditions. The loops possess left brace 110 right brace-habit planes and Burgers vectors parallel to (110). The LACBED method findings are compared with results of contrast analyses based on the so-called 'inside-outside' contrast of dislocation loops. Advantages o...

  10. Extra spots in the electron diffraction patterns of neutron irradiated zirconium and its alloys

    International Nuclear Information System (INIS)

    Madden, P.K.

    1977-01-01

    Specimens of neutron irradiated zirconium and its alloys were examined in the transmission electron microscope. Groups of extra spots, often exhibiting four-fold symmetry, were observed in thin foil electron diffraction patterns of these specimens. The 'extra-spot' structure, like the expected black-dot/small scale dislocation loop neutron irradiated damage, is approximately 100 A in size. Its nature is uncertain. It may be related to irradiation damage or to some artefact introduced during specimen preparation. If it is the latter, then published irradiation damage defect size distributions and determined irradiation growth strains of other investigators, may require modification. The present inconclusive results indicate that extra-spot structure is likely to consist of oxide particles, but may correspond to hydride precipitation or decoration effects, or even, to electron beam effects. (author)

  11. Reassessment of the electron density in Cu2O using γ-ray diffraction.

    Science.gov (United States)

    Jauch, Wolfgang; Reehuis, Manfred

    2014-12-01

    The electron-density distribution in Cu2O has been critically reexamined to test controversial conclusions from earlier experimental and theoretical studies. The electron density is derived via multipole refinement of high-quality single-crystal diffraction data, collected at room temperature with 316.5 keV gamma radiation. Four γ-lines in the energy range 200-600 keV have been used to extrapolate extinction-free low-order structure factors. The remaining extinction corrections refine to a crystal mosaicity identical to the observed one. There is no support for anharmonic contributions to the thermal parameters. Important features of the derived electron density are (i) a partially filled d_{z^2} orbital, (ii) an incomplete ionization of Cu and O, and (iii) no interstitial Cu-Cu charge pileup, thereby refuting the covalent bonding hypothesis.

  12. Pulse shape and spectrum of coherent diffraction-limited transition radiation from electron beams

    Energy Technology Data Exchange (ETDEWEB)

    van Tilborg, J.; Schroeder, C.B.; Esarey, E.; Leemans, W.P.

    2003-12-20

    The electric field in the temporal and spectral domain of coherent diffraction-limited transition radiation is studied. An electron bunch, with arbitrary longitudinal momentum distribution, propagating at normal incidence to a sharp metal-vacuum boundary with finite transverse dimension is considered. A general expression for the spatiotemporal electric field of the transition radiation is derived, and closed-form solutions for several special cases are given. The influence of parameters such as radial boundary size, electron momentum distribution, and angle of observation on the waveform (e.g., radiation pulse length and amplitude) are discussed. For a Gaussian electron bunch, the coherent radiation waveform is shown to have a single-cycle profile. Application to a novel THz source based on a laser-driven accelerator is discussed.

  13. Strain mapping for the semiconductor industry by dark-field electron holography and nanobeam electron diffraction with nm resolution

    International Nuclear Information System (INIS)

    Cooper, David; Hartmann, Jean Michel; Carron, Veronique; Béché, Armand; Rouvière, Jean-Luc

    2010-01-01

    There is a requirement of the semiconductor industry to measure strain in semiconductor devices with nm-scale resolution. Here we show that dark-field electron holography and nanobeam electron diffraction (NBED) are both complementary techniques that can be used to determine the strain in these devices. We show two-dimensional strain maps acquired by dark holography and line profiles that have been acquired by NBED of recessed SiGe sources and drains with a variety of different gate lengths and Ge concentrations. We have also used dark-field electron holography to measure the evolution in strain during the silicidation process, showing that this can reduce the applied uniaxial compressive strain in the conduction channel by up to a factor of 3

  14. The Harwell back-scattering spectrometer

    International Nuclear Information System (INIS)

    Windsor, C.G.; Bunce, L.J.; Borcherds, P.H.; Cole, I.; Fitzmaurice, M.; Johnson, D.A.G.; Sinclair, R.N.

    1976-01-01

    Neutron diffraction spectra in which both high resolution (Δ Q/Q approximately equal to 0.003) and high intensity are maintained up to scattering vectors as high as 30A -1 (sin theta/lambda = 2.5) have been obtained with the back-scattering spectrometer (BSS) recently installed on the Harwell electron linac. The theory behind the spectrometer design is described, and it is shown how the above resolution requirement leads to its basic features of a 12m incident flight path, a 2m scattering flight path and a scattering angle (2theta) acceptance from 165 0 to 175 0 . Examples of the resolution, intensity and background are given. It is shown that the problem of frame overlap may be overcome by using an absorbing filter. (author)

  15. Multiobjective optimizations of a novel cryocooled dc gun based ultrafast electron diffraction beam line

    Directory of Open Access Journals (Sweden)

    Colwyn Gulliford

    2016-09-01

    Full Text Available We present the results of multiobjective genetic algorithm optimizations of a single-shot ultrafast electron diffraction beam line utilizing a 225 kV dc gun with a novel cryocooled photocathode system and buncher cavity. Optimizations of the transverse projected emittance as a function of bunch charge are presented and discussed in terms of the scaling laws derived in the charge saturation limit. Additionally, optimization of the transverse coherence length as a function of final rms bunch length at the sample location have been performed for three different sample radii: 50, 100, and 200  μm, for two final bunch charges: 10^{5} electrons (16 fC and 10^{6} electrons (160 fC. Example optimal solutions are analyzed, and the effects of disordered induced heating estimated. In particular, a relative coherence length of L_{c,x}/σ_{x}=0.27  nm/μm was obtained for a final bunch charge of 10^{5} electrons and final bunch length of σ_{t}≈100  fs. For a final charge of 10^{6} electrons the cryogun produces L_{c,x}/σ_{x}≈0.1  nm/μm for σ_{t}≈100–200  fs and σ_{x}≥50  μm. These results demonstrate the viability of using genetic algorithms in the design and operation of ultrafast electron diffraction beam lines.

  16. Surface structure of Bi2Se3(111) determined by low-energy electron diffraction and surface x-ray diffraction

    DEFF Research Database (Denmark)

    dos Reis, Diogo Duarte; Barreto, Lucas; Bianchi, Marco

    2013-01-01

    The surface structure of the prototypical topological insulator Bi2Se3 is determined by low-energy electron diffraction and surface x-ray diffraction at room temperature. Both approaches show that the crystal is terminated by an intact quintuple layer. Specifically, an alternative termination by ...... by a bismuth bilayer is ruled out. Surface relaxations obtained by both techniques are in good agreement with each other and found to be small. This includes the relaxation of the van der Waals gap between the first two quintuple layers....

  17. A comparison of texture results obtained using precession electron diffraction and neutron diffraction methods at diminishing length scales in ordered bimetallic nanolamellar composites

    International Nuclear Information System (INIS)

    Carpenter, J.S.; Liu, X.; Darbal, A.; Nuhfer, N.T.; McCabe, R.J.; Vogel, S.C.; LeDonne, J.E.; Rollett, A.D.; Barmak, K.; Beyerlein, I.J.; Mara, N.A.

    2012-01-01

    Precession electron diffraction (PED) is used to acquire orientation information in Cu–Nb nanolamellar composites fabricated by accumulative roll bonding (ARB). The resulting maps quantify the grain size, shape, orientation distributions and interface planes in the vicinity of nanometer-thick deformation twins. The PED-based texture results compare favorably with bulk textures provided by neutron diffraction measurements, indicating uniformity in the ARB Cu–Nb texture. Additionally, {1 1 2} Cu ||{1 1 2} Nb interfaces are present, suggesting that ARB techniques can lead to stable interfaces with a special crystallography.

  18. Semiconductor Quantum Electron Wave Transport, Diffraction, and Interference: Analysis, Device, and Measurement.

    Science.gov (United States)

    Henderson, Gregory Newell

    Semiconductor device dimensions are rapidly approaching a fundamental limit where drift-diffusion equations and the depletion approximation are no longer valid. In this regime, quantum effects can dominate device response. To increase further device density and speed, new devices must be designed that use these phenomena to positive advantage. In addition, quantum effects provide opportunities for a new class of devices which can perform functions previously unattainable with "conventional" semiconductor devices. This thesis has described research in the analysis of electron wave effects in semiconductors and the development of methods for the design, fabrication, and characterization of quantum devices based on these effects. First, an exact set of quantitative analogies are presented which allow the use of well understood optical design and analysis tools for the development of electron wave semiconductor devices. Motivated by these analogies, methods are presented for modeling electron wave grating diffraction using both an exact rigorous coupled-wave analysis and approximate analyses which are useful for grating design. Example electron wave grating switch and multiplexer designs are presented. In analogy to thin-film optics, the design and analysis of electron wave Fabry-Perot interference filters are also discussed. An innovative technique has been developed for testing these (and other) electron wave structures using Ballistic Electron Emission Microscopy (BEEM). This technique uses a liquid-helium temperature scanning tunneling microscope (STM) to perform spectroscopy of the electron transmittance as a function of electron energy. Experimental results show that BEEM can resolve even weak quantum effects, such as the reflectivity of a single interface between materials. Finally, methods are discussed for incorporating asymmetric electron wave Fabry-Perot filters into optoelectronic devices. Theoretical and experimental results show that such structures could

  19. Foucault imaging and small-angle electron diffraction in controlled external magnetic fields.

    Science.gov (United States)

    Nakajima, Hiroshi; Kotani, Atsuhiro; Harada, Ken; Ishii, Yui; Mori, Shigeo

    2016-12-01

    We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La 0.7 Sr 0.3 MnO 3 (LSMO) and Nd 0.5 Sr 0.5 MnO 3 , in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured LSMO, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. Lines of Evidence–Incremental Markings in Molar Enamel of Soay Sheep as Revealed by a Fluorochrome Labeling and Backscattered Electron Imaging Study

    Science.gov (United States)

    Kierdorf, Horst; Kierdorf, Uwe; Frölich, Kai; Witzel, Carsten

    2013-01-01

    We studied the structural characteristics and periodicities of regular incremental markings in sheep enamel using fluorochrome injections for vital labeling of forming enamel and backscattered electron imaging in the scanning electron microscope. Microscopic analysis of mandibular first molars revealed the presence of incremental markings with a daily periodicity (laminations) that indicated successive positions of the forming front of interprismatic enamel. In addition to the laminations, incremental markings with a sub-daily periodicity were discernible both in interprismatic enamel and in enamel prisms. Five sub-daily increments were present between two consecutive laminations. Backscattered electron imaging revealed that each sub-daily growth increment consisted of a broader and more highly mineralized band and a narrower and less mineralized band (line). The sub-daily markings in the prisms of sheep enamel morphologically resembled the (daily) prisms cross striations seen in primate enamel. Incremental markings with a supra-daily periodicity were not observed in sheep enamel. Based on the periodicity of the incremental markings, maximum mean daily apposition rates of 17.0 µm in buccal enamel and of 13.4 µm in lingual enamel were recorded. Enamel extension rates were also high, with maximum means of 180 µm/day and 217 µm/day in upper crown areas of buccal and lingual enamel, respectively. Values in more cervical crown portions were markedly lower. Our results are in accordance with previous findings in other ungulate species. Using the incremental markings present in primate enamel as a reference could result in a misinterpretation of the incremental markings in ungulate enamel. Thus, the sub-daily growth increments in the prisms of ungulate enamel might be mistaken as prism cross striations with a daily periodicity, and the laminations misidentified as striae of Retzius with a supra-daily periodicity. This would lead to a considerable overestimation of

  1. Low-energy positron and electron diffraction and positron-stimulated secondary electron emission from Cu(100)

    International Nuclear Information System (INIS)

    Weiss, A.H.

    1983-01-01

    The results of two series of experiments are reported. In the first, an electrostatically guided beam of low-energy (40-400 eV) positrons, delta/sub p/ was used to study low-energy positron diffraction (LEPD) from a Cu(100) surface under ultrahigh-vacuum conditions. Low-energy electron diffraction (LEED) data were obtained from the same sample in the same apparatus. Comparison of LEPD and LEED intensity versus energy data with model calculations made using computer programs developed by C.B. Duke and collaborators indicated that: LEPD data is adequately modeled using potentials with no exchange-correlation term. The inelastic mean free path, lambda/sub ee/, is shorter for positrons than for electrons at low (< approx.80 eV). LEED is better than LEPD at making a determination of the first-layer spacing of Cu(100) for the particular data set reported. In the second set of experiments, the same apparatus and sample were used to compare positron- and electron-stimulated secondary-electron emission (PSSEE and ESSEE). The results were found to be consistent with existing models of secondary-electron production for metals. The energy distributions of secondary-electrons had broad low-energy (<10 eV) peaks for both positron and electron stimulation. But the PSEE distribution showed no elastic peak. Measurements of secondary-electron angular distributions, found to be cosine-like in both the PSSEE and ESSEE case, were used to obtain total secondary yield ratios, delta, at four beam energies ranging from 40-400 eV. The secondary yield ratio for primary positrons and the yield for primary electrons, delta/sub e/, were similar at these energies. For 400-eV primary particles the secondary yields were found to be delta/sub p/ = 0.94 +/- 0.12 and delta/sub e/ = 0.94 +/- 0./12, giving a ratio of unity for positron-stimulated secondary yield to electron-stimulated secondary yield

  2. Electron diffraction determination of 11.5 Å and HySo structures: candidate water carriers to the Upper Mantle

    Czech Academy of Sciences Publication Activity Database

    Gemmi, M.; Merlini, M.; Palatinus, Lukáš; Fumagalli, P.; Hanfland, M.

    2016-01-01

    Roč. 101, č. 12 (2016), s. 2645-2654 ISSN 0003-004X Institutional support: RVO:68378271 Keywords : subduction * MASH system * electron diffraction tomography Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.021, year: 2016

  3. Complex (Nonstandard) Six-Layer Polytypes of Lizardite Revealed from Oblique-Texture Electron Diffraction Patterns

    International Nuclear Information System (INIS)

    Zhukhlistov, A.P.; Zinchuk, N.N.; Kotel'nikov, D.D.

    2004-01-01

    Association of simple (1T and 3R) and two complex (nonstandard) orthogonal polytypes of the serpentine mineral lizardite from the Catoca kimberlite pipe (West Africa) association is revealed from oblique-texture electron diffraction patterns. A six-layer polytype with an ordered superposition of equally oriented layers (notation 3 2 3 2 3 4 3 4 3 6 3 6 or ++ - -00) belonging to the structural group A and a three-layer (336 or I,I,II) or a six-layer (336366 or I,I,II,I,II,II) polytype with alternating oppositely oriented layers and semi-disordered structure are identified using polytype analysis

  4. Novel radio-frequency gun structures for ultrafast relativistic electron diffraction.

    Science.gov (United States)

    Musumeci, P; Faillace, L; Fukasawa, A; Moody, J T; O'Shea, B; Rosenzweig, J B; Scoby, C M

    2009-08-01

    Radio-frequency (RF) photoinjector-based relativistic ultrafast electron diffraction (UED) is a promising new technique that has the potential to probe structural changes at the atomic scale with sub-100 fs temporal resolution in a single shot. We analyze the limitations on the temporal and spatial resolution of this technique considering the operating parameters of a standard 1.6 cell RF gun (which is the RF photoinjector used for the first experimental tests of relativistic UED at Stanford Linear Accelerator Center; University of California, Los Angeles; Brookhaven National Laboratory), and study the possibility of employing novel RF structures to circumvent some of these limits.

  5. Towards a full retrieval of the deformation tensor F using convergent beam electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Y. [CEA, INAC-SP2M, LEMMA, F-38000 Grenoble (France); Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble (France); Rouviere, J.L., E-mail: jean-luc.rouviere@cea.fr [CEA, INAC-SP2M, LEMMA, F-38000 Grenoble (France); Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble (France); Zuo, J.M. [Department of Material Science and Engineering and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Favre-Nicolin, V. [Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble (France); CEA, INAC-SP2M, LEMMA, F-38000 Grenoble (France)

    2016-01-15

    A new method to retrieve the local lattice parameters and rotations in a crystal from off-axis convergent beam electron diffraction (CBED) patterns is presented and validated using Bloch wave dynamical simulations. The originality of the method is to use both the diffracted and transmitted beams and to use kinematical approximations in the fitting algorithm. The study is based on the deformation gradient tensor F which includes rotation and strain. Working on simulated images it is shown that (i) from a single direction of observation, seven parameters out of the nine parameters of F can be determined with an accuracy of 3×10{sup −4} for the normal strain parameters ε{sub xx}, ε{sub yy}, and ε{sub zz}, (ii) the unit cell volume can only be retrieved if the diffracted and transmitted beams are both included in the fitting and (iii) all the nine parameters of F can be determined by combining two directions of observation separated by about 20°. - Highlights: • New CBED strain retrieval method using both deficient and excess HOLZ lines. • From a single CBED pattern, the unit cell volume can be measured without ambiguity. • From a single pattern, seven parameters of the deformation tensor F can be determined. • From two patterns from two directions separated by 20°, the nine parameters are retrieved. • Algorithm validated using dynamical simulations.

  6. Synchrotron Bragg diffraction imaging characterization of synthetic diamond crystals for optical and electronic power device applications.

    Science.gov (United States)

    Tran Thi, Thu Nhi; Morse, J; Caliste, D; Fernandez, B; Eon, D; Härtwig, J; Barbay, C; Mer-Calfati, C; Tranchant, N; Arnault, J C; Lafford, T A; Baruchel, J

    2017-04-01

    Bragg diffraction imaging enables the quality of synthetic single-crystal diamond substrates and their overgrown, mostly doped, diamond layers to be characterized. This is very important for improving diamond-based devices produced for X-ray optics and power electronics applications. The usual first step for this characterization is white-beam X-ray diffraction topography, which is a simple and fast method to identify the extended defects (dislocations, growth sectors, boundaries, stacking faults, overall curvature etc. ) within the crystal. This allows easy and quick comparison of the crystal quality of diamond plates available from various commercial suppliers. When needed, rocking curve imaging (RCI) is also employed, which is the quantitative counterpart of monochromatic Bragg diffraction imaging. RCI enables the local determination of both the effective misorientation, which results from lattice parameter variation and the local lattice tilt, and the local Bragg position. Maps derived from these parameters are used to measure the magnitude of the distortions associated with polishing damage and the depth of this damage within the volume of the crystal. For overgrown layers, these maps also reveal the distortion induced by the incorporation of impurities such as boron, or the lattice parameter variations associated with the presence of growth-incorporated nitrogen. These techniques are described, and their capabilities for studying the quality of diamond substrates and overgrown layers, and the surface damage caused by mechanical polishing, are illustrated by examples.

  7. First measurements of subpicosecond electron beam structure by autocorrelation of coherent diffraction radiation

    CERN Document Server

    Lumpkin, Alex H; Rule, D W

    2001-01-01

    We report the initial measurements of subpicosecond electron beam structure using a nonintercepting technique based on the autocorrelation of coherent diffraction radiation (CDR). A far infrared (FIR) Michelson interferometer with a Golay detector was used to obtain the autocorrelation. The radiation was generated by a thermionic rf gun beam at 40 MeV as it passed through a 5-mm-tall slit/aperture in a metal screen whose surface was at 45 deg. to the beam direction. For the observed bunch lengths of about 450 fs (FWHM) with a shorter time spike on the leading edge, peak currents of about 100 A are indicated. Also a model was developed and used to calculate the CDR from the back of two metal strips separated by a 5-mm vertical gap. The demonstrated nonintercepting aspect of this method could allow on-line bunch length characterizations to be done during free-electron laser experiments.

  8. Multiscale phase mapping of LiFePO4-based electrodes by transmission electron microscopy and electron forward scattering diffraction.

    Science.gov (United States)

    Robert, Donatien; Douillard, Thierry; Boulineau, Adrien; Brunetti, Guillaume; Nowakowski, Pawel; Venet, Denis; Bayle-Guillemaud, Pascale; Cayron, Cyril

    2013-12-23

    LiFePO4 and FePO4 phase distributions of entire cross-sectioned electrodes with various Li content are investigated from nanoscale to mesoscale, by transmission electron microscopy and by the new electron forward scattering diffraction technique. The distributions of the fully delithiated (FePO4) or lithiated particles (LiFePO4) are mapped on large fields of view (>100 × 100 μm(2)). Heterogeneities in thin and thick electrodes are highlighted at different scales. At the nanoscale, the statistical analysis of 64 000 particles unambiguously shows that the small particles delithiate first. At the mesoscale, the phase maps reveal a core-shell mechanism at the scale of the agglomerates with a preferential pathway along the electrode porosities. At larger scale, lithiation occurs in thick electrodes "stratum by stratum" from the surface in contact with electrolyte toward the current collector.

  9. Surface structure of VN0.89(100) determined by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Gauthier, Y.; Joly, Y.; Rundgren, J.; Johansson, L.I.; Wincott, P.

    1990-01-01

    The structure of the (100) surface of substoichiometric vanadium nitride was studied by low-energy electron diffraction on a VN 0.89 (100) sample. A simple 1x1 (100) diffractogram was observed. To describe the electron scattering in substoichiometric VN we apply the averaged t-matrix approximation to the nitrogen atoms. We find that the best structural model is one having no nitrogen vacancies in the surface region. It turns out that the first layer is rippled with the N atoms displaced 0.17 A above the subplane of V atoms, that the spacing between this subplane and the second layer is 1.92 A, and that the spacing between the second and the third layer is 2.08 A. In relation to the (100) spacing of the bulk, 2.06 A, these spacings are 6.8% contracted and 1% expanded, respectively. The Debye temperature of VN is found to be 660 K in good agreement with a prediction from entropy data and from neutron diffraction and helium-ion channeling experiments

  10. ESCA and electron diffraction studies of InP surface heated under As molecular beam exposure

    International Nuclear Information System (INIS)

    Sugiura, Hideo; Yamaguchi, Masafumi; Shibukawa, Atsushi

    1983-01-01

    Chemical composition of InP substrate surface heattreated under As molecular beam exposure in an ultrahigh vacuum chamber was studied with ESCA, and surface reconstruction of the substrate was examined by in-situ electron diffraction. The InP substrate heated under the exposure of As molecular beam has mirror surface up to 590 0 C while the surface of InP heated above 400 0 C in vacuum is roughened. The ESCA study shows that thin InAs layer (thickness 0 C under the exposure of As. The electron diffraction study indicates that the InP is cleaned at about 500 0 C in As pressures of 10 -7 - 10 -5 Torr. The InP surface is prevented from thermally decomposing by the coverage of the InAs layer, which may be formed through the following process: 2InPO 4 + As 4 → 2InAs + P 2 O 5 + As 2 O 3 . (author)

  11. First indication of the coherent unipolar diffraction radiation generated by relativistic electrons

    Science.gov (United States)

    Naumenko, G.; Shevelev, M.

    2018-05-01

    As is generally known, the integral of the electric field strength over all time for usual (bipolar) radiation is zero. The first demonstration of the possibility of unipolar radiation generation has been considered theoretically by Bessonov in 1981 [E.G. Bessonov, Zh. Eksp. Teor. Fiz. 80 (1981) 852]. According to this work, the unipolar radiation (or strange electromagnetic waves) is radiation for which the integral of the electric field strength over the entire duration of a pulse differs significantly from zero. Later, several theoretical papers devoted to this phenomenon have appeared in the literature, where authors investigated mainly synchrotron radiation. However, despite the critical interest, the experimental investigations ignored this effect. In this paper we present results of the first experimental investigation of the unipolar radiation generated by a relativistic electron beam. To detect the unipolar radiation the detector that is sensitive to the selected direction of the electric field strength has been elaborated and tested. We used a designed detector to observe the coherent backward diffraction radiation appearing when a bunched electron beam travels in the vicinity of a flat conductive target. The asymmetry of the electric field strength of the coherent backward diffraction radiation has been demonstrated.

  12. 'Diffraction-free' optical beams in inverse free electron laser accelerators

    International Nuclear Information System (INIS)

    Cai, S.Y.; Bhattacharjee, A.; Marshall, T.C.

    1988-01-01

    'Diffraction-free' optical beams correspond to exact solutions of the wave equation in free space with the remarkable property that they propagate with negligible transverse spreading for distances much larger than the Rayleigh range. The requirement for this to occur is a large aperture. Using a 2D computer code, we find that these optical beams will also propagate with negligible diffraction even when perturbed by the electron beam in an IFEL; indeed they match well the FEL requirement for the accelerator. The numerical simulations are performed for the proposed facility at Brookhaven in which λ s =10 μm, B=1.5 T (linearly tapered l w =1.31-6.28 cm) and the optical beam power is either 8x10 11 W or 2.3x10 10 W. Approximately 70% of the electrons constituting a beam of current 5 mA or 15 A, radius 0.14 mm and initial energy of 50 MeV is accelerated at 50 MeV/m. (orig.)

  13. Direct observation of the formation of silver precipitations by means of electron diffraction

    International Nuclear Information System (INIS)

    Benz, V.; Ostwald, R.; Weil, K.G.

    1976-01-01

    Thin films (20-1,000 A) of copper (I)-, silver, and lead(II)-halides were prepared by evaporation onto silver (III), gold (III), and PbTe (III)-surfaces. These films were irradiated in vacuo with 40 kV-electrons, in some cases also with the light of a Xenon-lamp. At the same time the diffraction pattern, produced by the electron beam at glancing incidence, was observed and registered photographically. Silver precipitates could be detected by their diffraction pattern, when the crystallites had grown to a size of about 50 A. From all materials investigated silveriodide showed maximum sensitivity. The precipitates formed show no orientation with respect to the host crystal. From the temperature dependence of the sensitivity an activation energy of 0.12 eV can be deduced leading to interstitial ion migration as rate determining step. Pure silverchloride can not been radiolyzed by 40 kV-electrons. After doping it with 0.3 mol% CaCl 2 or MgCl 2 it becomes very sensitive. The precipitate showes orientation with respect to the host lattice. Also pure CuJ is resistant against the electron beam. Mixed crystals (Ag, Cu)J with xsub(AgJ) > 0.5 behave similar as pure AgJ. Pb(II)-halides show no sensitivity, but the compounds AgBr x 2 PbBr 2 and 5 AgJ x PbJ 2 are readily radiolyzed, forming polycrystalline silver precipitates. The mechanism of radiolysis, its dependency on temperature and film thickness is discussed. (orig.) [de

  14. Analytical Electron Diffraction from Iii-V and II-Vi Semiconductors

    Science.gov (United States)

    Spellward, Paul

    Available from UMI in association with The British Library. This thesis describes the development and evaluation of a number of new TEM-based techniques for the measurement of composition in ternary III-V and II-VI semiconductors. New methods of polarity determination in binary and ternary compounds are also presented. The theory of high energy electron diffraction is outlined, with particular emphasis on zone axis diffraction from well-defined strings. An account of TEM microstructural studies of Cd_{rm x}Hg _{rm 1-x}Te and CdTe epitaxial layers, which provided the impetus for developing the diffraction-based analytical techniques, is given. The wide range of TEM-based compositional determination techniques is described. The use of HOLZ deficiency lines to infer composition from a lattice parameter measurement is evaluated. In the case of Cd_{ rm x}Hg_{rm 1-x}Te, it is found to be inferior to other techniques developed. Studies of dynamical aspects of HOLZ diffraction can yield information about the dispersion surface from which a measure of composition may be obtained. This technique is evaluated for Al_{rm x}Ga_{rm 1-x} As, in which it is found to be of some use, and for Cd_{rm x}Hg _{rm 1-x}Te, in which the large Debye-Waller factor associated with mercury in discovered to render the method of little value. A number of critical voltages may be measured in medium voltage TEMs. The (111) zone axis critical voltage of Cd_{rm x}Hg _{rm 1-x}Te is found to vary significantly with x and forms the basis of an accurate technique for composition measurement in that ternary compound. Other critical voltage phenomena are investigated. In Al _{rm x}Ga_ {rm 1-x}As and other light ternaries, a non-systematic critical voltage is found to vary with x, providing a good indicator of composition. Critical voltage measurements may be made by conventional CBED or by various other techniques, which may also simultaneously yield information on the spatial variation of composition. The

  15. An analytical model for light backscattering by coccoliths and coccospheres of Emiliania huxleyi.

    Science.gov (United States)

    Fournier, Georges; Neukermans, Griet

    2017-06-26

    We present an analytical model for light backscattering by coccoliths and coccolithophores of the marine calcifying phytoplankter Emiliania huxleyi. The model is based on the separation of the effects of diffraction, refraction, and reflection on scattering, a valid assumption for particle sizes typical of coccoliths and coccolithophores. Our model results match closely with results from an exact scattering code that uses complex particle geometry and our model also mimics well abrupt transitions in scattering magnitude. Finally, we apply our model to predict changes in the spectral backscattering coefficient during an Emiliania huxleyi bloom with results that closely match in situ measurements. Because our model captures the key features that control the light backscattering process, it can be generalized to coccoliths and coccolithophores of different morphologies which can be obtained from size-calibrated electron microphotographs. Matlab codes of this model are provided as supplementary material.

  16. On the annealing behaviour of dysprosium ion implanted nickel: a combined study using Rutherford backscattering, transmission electron microscopy, and total current spectroscopy

    International Nuclear Information System (INIS)

    Chadderton, L.T.; Johnson, E.

    1977-01-01

    Despite continuing improvements in applications of the analytical method of Rutherford backscattering (RBS) to solid state physics it is recognized that more complete information can be obtained if other techniques - for example transmission electron microscopy (TEM) - are employed simultaneously. Experiments are described in which a combined RBS and TEM study of the annealing of nickel, rendered amorphous by implantation of 20 keV dysprosium ions is supplemented with a completely new technique - total current spectroscopy (TCS). In TCS low energy electrons (0-15 eV) are used to probe the damaged nickel. Observations have been made during annealing of both the reappearance of the bulk band structure of the metal and of a 'surface peak' which is highly sensitive to the recovery process. Changes in the height of the surface peak reveal three sharp annealing stages, the first two being preceded by reverse annealing which correlates well with RBS and TEM results. The first annealing stage - following the amorphous to crystalline transition - may be associated with electronic effects in the vicinity of the Curie point. Changes in the position of the surface peak allow one to trace the diffusion of dysprosium to the surface. Quantum mechanical resonances at the damage/crystal interface have also been followed throughout annealing. The initially amorphous layer (approximately 2.2nm) increases in thickness slightly during recovery. (Auth.)

  17. Circular Hough transform diffraction analysis: A software tool for automated measurement of selected area electron diffraction patterns within Digital MicrographTM

    International Nuclear Information System (INIS)

    Mitchell, D.R.G.

    2008-01-01

    A software tool (script and plugin) for computing circular Hough transforms (CHT) in Digital Micrograph TM has been developed, for the purpose of automated analysis of selected area electron diffraction patterns (SADPs) of polycrystalline materials. The CHT enables the diffraction pattern centre to be determined with sub-pixel accuracy, regardless of the exposure condition of the transmitted beam or if a beam stop is present. Radii of the diffraction rings can also be accurately measured with sub-pixel precision. If the pattern is calibrated against a known camera length, then d-spacings with an accuracy of better than 1% can be obtained. These measurements require no a priori knowledge of the pattern and very limited user interaction. The accuracy of the CHT is degraded by distortion introduced by the projector lens, and this should be minimised prior to pattern acquisition. A number of optimisations in the CHT software enable rapid processing of patterns; a typical analysis of a 1kx1k image taking just a few minutes. The CHT tool appears robust and is even able to accurately measure SADPs with very incomplete diffraction rings due to texture effects. This software tool is freely downloadable via the Internet

  18. Circular Hough transform diffraction analysis: A software tool for automated measurement of selected area electron diffraction patterns within Digital Micrograph{sup TM}

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, D.R.G. [Institute of Materials and Engineering Science, ANSTO, PMB 1, Menai, NSW 2234 (Australia)], E-mail: drm@ansto.gov.au

    2008-03-15

    A software tool (script and plugin) for computing circular Hough transforms (CHT) in Digital Micrograph{sup TM} has been developed, for the purpose of automated analysis of selected area electron diffraction patterns (SADPs) of polycrystalline materials. The CHT enables the diffraction pattern centre to be determined with sub-pixel accuracy, regardless of the exposure condition of the transmitted beam or if a beam stop is present. Radii of the diffraction rings can also be accurately measured with sub-pixel precision. If the pattern is calibrated against a known camera length, then d-spacings with an accuracy of better than 1% can be obtained. These measurements require no a priori knowledge of the pattern and very limited user interaction. The accuracy of the CHT is degraded by distortion introduced by the projector lens, and this should be minimised prior to pattern acquisition. A number of optimisations in the CHT software enable rapid processing of patterns; a typical analysis of a 1kx1k image taking just a few minutes. The CHT tool appears robust and is even able to accurately measure SADPs with very incomplete diffraction rings due to texture effects. This software tool is freely downloadable via the Internet.

  19. Electron microscopy and diffraction of ordering in Ni-W alloys

    International Nuclear Information System (INIS)

    Mishra, N.S.

    1995-01-01

    Electron microscopy and diffraction studies of ordering in stoichiometric Ni-20%W and off-stoichiometric Ni-15%W alloys have been carried out. The specimens of Ni-20%W were first 1,398 K for 4 h and then quenched rapidly into water. Short range order (SRO) spots were observed at {1 1/2 0}* positions. Two hitherto unknown metastable phases: D 2h 25 -Ni 2 W and D0 22 -Ni 3 W were observed in the diffraction patterns. Long range order (LRO) transformations were studied at 1,103 and 1,213 K. Kinetics and mechanism of transformations have been identified. Ni-15%W specimens were solution treated at 1,523 K for 1 h followed by quenching in water. SRO spots similar to those found in Ni-20%W were observed in this alloy as well. The transition to LRO was studied at 1,093 K. Distinct Ni 4 W precipitates could be observed after 5 h of annealing at this temperature. After 100 h of annealing precipitates were found to grow into faceted shape coherent with the disordered matrix. After prolonged annealing for over 150 h the Ni 4 W precipitates began to lose coherency by the generation of misfit dislocations. The microstructural observations have been compared for the stoichiometric and off-stoichiometric alloys

  20. Investigation of electronic order using resonant soft X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Schlappa, J.

    2006-12-01

    The aim of this PhD work was the application of resonant soft X-ray diffraction technique for the investigation of electronic order in transition metal oxides at the TM L{sub 2,3}-edge, trying to obtain a quantitative understanding of the data. The method was first systematically explored through application to a model system in order to test the feasibility of the technique and to understand of how X-ray optical effects have to be taken into account. Two more complex systems were investigated; stripe order in La{sub 1.8}Sr{sub 0.2}NiO{sub 4} and charge and orbital order in Fe{sub 3}O{sub 4}. The main focus of the work was on the spectroscopic potential of the technique, trying to obtain a level of quantitative description of the data. For X-ray absorption spectroscopy (XAS) from transition metal oxides, cluster configuration interaction calculation provides a powerful and realistic microscopic theory. In the frame work of this thesis cluster theory, considering explicit hybridization effects between the TM-ion and the surrounding oxygen ligands, has been applied for the first time to describe resonant diffraction data. (orig.)

  1. A deep convolutional neural network to analyze position averaged convergent beam electron diffraction patterns.

    Science.gov (United States)

    Xu, W; LeBeau, J M

    2018-05-01

    We establish a series of deep convolutional neural networks to automatically analyze position averaged convergent beam electron diffraction patterns. The networks first calibrate the zero-order disk size, center position, and rotation without the need for pretreating the data. With the aligned data, additional networks then measure the sample thickness and tilt. The performance of the network is explored as a function of a variety of variables including thickness, tilt, and dose. A methodology to explore the response of the neural network to various pattern features is also presented. Processing patterns at a rate of  ∼ 0.1 s/pattern, the network is shown to be orders of magnitude faster than a brute force method while maintaining accuracy. The approach is thus suitable for automatically processing big, 4D STEM data. We also discuss the generality of the method to other materials/orientations as well as a hybrid approach that combines the features of the neural network with least squares fitting for even more robust analysis. The source code is available at https://github.com/subangstrom/DeepDiffraction. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Investigation of electronic order using resonant soft X-ray diffraction

    International Nuclear Information System (INIS)

    Schlappa, J.

    2006-01-01

    The aim of this PhD work was the application of resonant soft X-ray diffraction technique for the investigation of electronic order in transition metal oxides at the TM L 2,3 -edge, trying to obtain a quantitative understanding of the data. The method was first systematically explored through application to a model system in order to test the feasibility of the technique and to understand of how X-ray optical effects have to be taken into account. Two more complex systems were investigated; stripe order in La 1.8 Sr 0.2 NiO 4 and charge and orbital order in Fe 3 O 4 . The main focus of the work was on the spectroscopic potential of the technique, trying to obtain a level of quantitative description of the data. For X-ray absorption spectroscopy (XAS) from transition metal oxides, cluster configuration interaction calculation provides a powerful and realistic microscopic theory. In the frame work of this thesis cluster theory, considering explicit hybridization effects between the TM-ion and the surrounding oxygen ligands, has been applied for the first time to describe resonant diffraction data. (orig.)

  3. Strain at a semiconductor nanowire-substrate interface studied using geometric phase analysis, convergent beam electron diffraction and nanobeam diffraction

    DEFF Research Database (Denmark)

    Persson, Johan Mikael; Wagner, Jakob Birkedal; Dunin-Borkowski, Rafal E.

    2011-01-01

    Semiconductor nanowires have been studied using electron microscopy since the early days of nanowire growth, e.g. [1]. A common approach for analysing nanowires using transmission electron microscopy (TEM) involves removing them from their substrate and subsequently transferring them onto carbon...... with CBED and NBED [4,5] have shown a high degree of consistency. Strain has previously only been measured in nanowires removed from their substrate [6], or only using GPA [7]. The sample used for the present investigation was an InP nanowire grown on a Si substrate using metal organic vapor phase...

  4. Some possibilities of the slow electron diffraction method when studying film systems

    International Nuclear Information System (INIS)

    Kirsanova, T.S.; Tumareva, T.A.; Kiseleva, L.A.

    1982-01-01

    A film structure of an initial thickness was studied with film probing in depth by an electron beam; for this purpose energy of incident electrons changed in sufficient wide ranges. Barium oxide films of 6-10 monolayer thickness deposited on a monocrystal (110) W have been chosen for the investigation. The structure was detected in a certain temperature range (850-1250 K) and the maximum development, the largest energy range fit approximatly 1000-1100 K temperature. Optimal temperature increases slightly with increasing an initial film thickness. The investigations carried on have shown that the structure of barium oxide films is heterogeneous in the layer thickness. This is concerned espicially the films of 6-10 monolayers. Notwithstanding the thickness trifle, the ''surface'' which structure was different from a region immediately adjacent to a substrate may be separated in films of this area. The method of the investigation in layers, i. e. the method for observing the film structure when varying incident electron energy permitted to establish that an absolute by certain structure of the layer adjacent to a substrate corresponds to each structure of the surface layer. In turn the structures of the layer adjacent to a substrate for the total film thickness of 6-10 monolayers turn out to be similar to the structures of 2-5 monolayer film, anyhow these structures are described with similar diffraction pictures

  5. Analysis of dislocation loops by means of large-angle convergent beam electron diffraction

    International Nuclear Information System (INIS)

    Jaeger, Ch; Spiecker, E; Morniroli, J P; Jaeger, W

    2002-01-01

    Diffusion-induced dislocation loops in GaP and GaAs were analysed by means of large-angle convergent beam electron diffraction (LACBED) and conventional contrast methods of transmission electron microscopy. It is demonstrated that LACBED is perfectly suited for use in analysing dislocation loops. The method combines analyses of the dislocation-induced splitting of Bragg lines in a LACBED pattern for the determination of the Burgers vector with analyses of the loop contrast behaviour in transmission electron microscopy bright-field images during tilt experiments, from which the habit plane of the dislocation loop is determined. Perfect dislocation loops formed by condensation of interstitial atoms or vacancies were found, depending on the diffusion conditions. The loops possess {110}-habit planes and Burgers vectors parallel to (110). The LACBED method findings are compared with results of contrast analyses based on the so-called 'inside-outside' contrast of dislocation loops. Advantages of the LACBED method consist in the possibility of determining the complete Burgers vector of the dislocation loops and of an unambiguous and fast loop type analysis

  6. Development of lamellar structures in natural waxes - an electron diffraction investigation

    Energy Technology Data Exchange (ETDEWEB)

    Dorset, Douglas L. [Electron Diffraction Department, Hauptman-Woodward Medical Research Institute, Inc., Buffalo, NY (United States)

    1999-06-07

    When they are recrystallized from the melt, natural plant or insect waxes tend to form solid phases with a nematic-like structure (i.e. a parallel array of polymethylene chains with little or no aggregation of the molecules into distinct layers). An electron diffraction study of carnauba wax and two types of beeswax has shown that the degree of molecular organization into lamellar structures can be enhanced by annealing in the presence of benzoic acid, which also acts as an epitaxial substrate. Nevertheless, the resultant layer structure in the annealed solid is not the same as that found for paraffin wax fractions refined from petroleum. Probably because of a small but significant fraction of a very long chain ingredient, the lamellar separation is incomplete, incorporating a number of 'bridging molecules' that span the nascent lamellar interface.The same phenomenon has been described recently for a low molecular weight polyethylene. (author)

  7. Development of lamellar structures in natural waxes - an electron diffraction investigation

    Science.gov (United States)

    Dorset, Douglas L.

    1999-06-01

    When they are recrystallized from the melt, natural plant or insect waxes tend to form solid phases with a nematic-like structure (i.e. a parallel array of polymethylene chains with little or no aggregation of the molecules into distinct layers). An electron diffraction study of carnauba wax and two types of beeswax has shown that the degree of molecular organization into lamellar structures can be enhanced by annealing in the presence of benzoic acid, which also acts as an epitaxial substrate. Nevertheless, the resultant layer structure in the annealed solid is not the same as that found for paraffin wax fractions refined from petroleum. Probably because of a small but significant fraction of a very long chain ingredient, the lamellar separation is incomplete, incorporating a number of `bridging molecules' that span the nascent lamellar interface.The same phenomenon has been described recently for a low molecular weight polyethylene.

  8. Phase mapping of iron-based rapidly quenched alloys using precession electron diffraction

    International Nuclear Information System (INIS)

    Svec, P.; Janotova, I.; Hosko, J.; Matko, I.; Janickovic, D.; Svec, P. Sr.; Kepaptsoglou, D. M.

    2013-01-01

    The present contribution is focused on application of PED and phase/orientation mapping of nanocrystals of bcc-Fe formed during the first crystallization stage of amorphous Fe-Co-Si-B ribbon. Using precession electron diffraction and phase/orientation mapping the formation of primary crystalline phase, bcc-Fe, from amorphous Fe-Co-Si-B has been analyzed. Important information about mutual orientation of the phase in individual submicron grains as well as against the sample surface has been obtained. This information contributes to the understanding of micromechanisms controlling crystallization from amorphous rapidly quenched structure and of the structure of the original amorphous state. The presented technique due to its high spatial resolution, speed and information content provided complements well classical techniques, especially in nanocrystalline materials. (authors)

  9. Precipitate statistics in an Al-Mg-Si-Cu alloy from scanning precession electron diffraction data

    Science.gov (United States)

    Sunde, J. K.; Paulsen, Ø.; Wenner, S.; Holmestad, R.

    2017-09-01

    The key microstructural feature providing strength to age-hardenable Al alloys is nanoscale precipitates. Alloy development requires a reliable statistical assessment of these precipitates, in order to link the microstructure with material properties. Here, it is demonstrated that scanning precession electron diffraction combined with computational analysis enable the semi-automated extraction of precipitate statistics in an Al-Mg-Si-Cu alloy. Among the main findings is the precipitate number density, which agrees well with a conventional method based on manual counting and measurements. By virtue of its data analysis objectivity, our methodology is therefore seen as an advantageous alternative to existing routines, offering reproducibility and efficiency in alloy statistics. Additional results include improved qualitative information on phase distributions. The developed procedure is generic and applicable to any material containing nanoscale precipitates.

  10. Study of electron-beam-evaporated MgO films using electron diffraction, optical absorption and cathodoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Aboelfotoh, M.O.; Ramsey, J.N.

    1982-05-21

    Reflection high energy electron diffraction, optical absorption and cathodoluminescence were used to study MgO films deposited onto fused silica, single-crystal silicon and LiF substrates at various temperatures. Results showed that some of the same optical absorption and emission bands observed in X- or UV-irradiated, additively colored or mechanically deformed MgO crystals were observed in evaporated MgO films. The peak positions and the relative peak intensities of the optical absorption and emission bands depended on the substrate temperature during film deposition as well as on the structure of the film. The effect of heating the films in air and vacuum on the optical absorption and emission bands is also discussed.

  11. Contrast of HOLZ lines in energy-filtered convergent-beam electron diffraction patterns from silicon

    International Nuclear Information System (INIS)

    Lehmpfuhl, G.; Krahl, D.; Uchida, Y.

    1995-01-01

    Higher-order Laue-zone (HOLZ) lines were investigated in convergent-beam electron diffraction patterns from silicon near the low-indexed zone axes [100], [110] and [111]. The visibility of these lines depends on the effective structure potentials of the reflections from the first Laue zone depending on their Debye-Waller factor. The contrast of the HOLZ lines is strongly reduced by inelastically scattered electrons. They can be excluded by an imaging Ω filter for energy losses above 2 eV. The diffraction patterns were compared with many-beam calculations. Without absorption, an excellent agreement could be achieved for the [111] and [100] zone axes, while the simulation of the [110] zone-axis pattern needed a calculation with absorption. The reason for this observation is explained in the Bloch-wave picture. Calculations with absorption, however, lead to artefacts in the intensity distribution of the [100] HOLZ pattern. In order to obtain agreement with the experiment, the Debye-Waller factor had to be modified in different ways for the different zone axes. This corresponds to a strong anisotropy of the Debye-Waller factor. To confirm this observation, the temperature dependence of the itensity distributions of the HOLZ patterns was investigated between 50 and 680 K. At room temperature, the parameter D in the Debye-Waller factor exp(-Ds 2 ) was determined as 0.13, 0.26 and 0.55 A 2 for the zone axes [100], [111] and [110], respectively. The reliability of the conclusions is discussed. (orig.)

  12. High-efficiency detector of secondary and backscattered electrons for low-dose imaging in the ESEM

    Czech Academy of Sciences Publication Activity Database

    Neděla, Vilém; Tihlaříková, Eva; Runštuk, Jiří; Hudec, Jiří

    2018-01-01

    Roč. 184 (2018), s. 1-11 ISSN 0304-3991 R&D Projects: GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : detectors * scintillators * low-dose imaging * energy filtration * MC simulations Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Electrical and electronic engineering Impact factor: 2.843, year: 2016

  13. Application of particle-induced X-ray emission, backscattering spectrometry and scanning electron microscopy in the evaluation of orthodontic materials

    International Nuclear Information System (INIS)

    Gihwala, D.; Mars, J.A.; Pineda-Vargas, C.

    2013-01-01

    The focus of this investigation was on orthodontic materials used in the manufacture of dental brackets. The properties of these dental materials are subjected to various physical parameters such as elongation, yield strength and elasticity that justify their application. In turn, these parameters depend on the quantitative elemental concentration distribution (QECD) in the materials used in the manufacture. For compositional analysis, proton-induced X-ray emission (PIXE), backscatter spectrometry (BS) and scanning electron microscopy (SEM) were applied. QECD analysis was performed to correlate the physical parameters with the composition and to quantify imperfections in the materials. PIXE and BS analyses were performed simultaneously with a 3 MeV proton beam while electrons accelerated at 25 keV were used for the SEM analysis. From the QECDs it was observed that: (1) the major elements Cr, Fe and Ni were homogeneously distributed in the orthodontic plate; (2) the distribution of Mo and O correlated with one another; (3) there was a spread of Cr around regions of high C concentration; and, (4) areas of high concentrations of Mo and O corresponded to a decrease in C concentrations. Elemental concentration correlations are shown to indicate the similarities and differences in the ease of formation of phases, based on the tangent of linearity. (author)

  14. Experimental Observation of Generation of Superradiance Pulses in the Process of Backscattering of Pump Wave on the Intense Electron Bunch

    CERN Document Server

    Ginzburg, N S; Denisov, G G; Rozental, R M; Sergeev, A; Zotova, I V

    2005-01-01

    Recently significant progress was archived in the generation of multimegawatt subnanosecond pulses in millimeter wave band utilizing the cyclotron and Cherenkov mechanisms of superradiance (SR) [1,2]. We study the novel mechanism of SR when the powerful pumping wave undergoes the stimulated back scattering on the intense electron bunch. Due to the Doppler up shift the radiation frequency can significantly exceed the frequency of the pumping wave. With the relativistic microwave generator as a pumping wave source such a mechanism can be used for generation of the powerful pulse radiation in the short millimeter and submillimeter wave bands. Experiments on the observation of the stimulated scattering in the superradiance regime were carried out at Institute of Electrophysics RAS with two synchronized accelerators. The 4 ns electron beam from the first accelerator is used for generation of the 38 GHz 100 MW pumping wave which subsequently scattered on the subnanosecond 250 keV 1 kA electron bunch produced by the...

  15. Multiobjective optimization design of an rf gun based electron diffraction beam line

    Directory of Open Access Journals (Sweden)

    Colwyn Gulliford

    2017-03-01

    Full Text Available Multiobjective genetic algorithm optimizations of a single-shot ultrafast electron diffraction beam line comprised of a 100  MV/m 1.6-cell normal conducting rf (NCRF gun, as well as a nine-cell 2π/3 bunching cavity placed between two solenoids, have been performed. These include optimization of the normalized transverse emittance as a function of bunch charge, as well as optimization of the transverse coherence length as a function of the rms bunch length of the beam at the sample location for a fixed charge of 10^{6} electrons. Analysis of the resulting solutions is discussed in terms of the relevant scaling laws, and a detailed description of one of the resulting solutions from the coherence length optimizations is given. For a charge of 10^{6} electrons and final beam sizes of σ_{x}≥25  μm and σ_{t}≈5  fs, we found a relative coherence length of L_{c,x}/σ_{x}≈0.07 using direct optimization of the coherence length. Additionally, based on optimizations of the emittance as a function of final bunch length, we estimate the relative coherence length for bunch lengths of 30 and 100 fs to be roughly 0.1 and 0.2  nm/μm, respectively. Finally, using the scaling of the optimal emittance with bunch charge, for a charge of 10^{5} electrons, we estimate relative coherence lengths of 0.3, 0.5, and 0.92  nm/μm for final bunch lengths of 5, 30 and 100 fs, respectively.

  16. High quality single shot diffraction patterns using ultrashort megaelectron volt electron beams from a radio frequency photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Musumeci, P.; Moody, J. T.; Scoby, C. M.; Gutierrez, M. S. [Department of Physics and Astronomy, UCLA, Los Angeles, California 90095 (United States); Bender, H. A.; Wilcox, N. S. [National Security Technologies, LLC, Los Alamos Operations, Los Alamos, New Mexico 87544 (United States)

    2010-01-15

    Single shot diffraction patterns using a 250-fs-long electron beam have been obtained at the UCLA Pegasus laboratory. High quality images with spatial resolution sufficient to distinguish closely spaced peaks in the Debye-Scherrer ring pattern have been recorded by scattering the 1.6 pC 3.5 MeV electron beam generated in the rf photoinjector off a 100-nm-thick Au foil. Dark current and high emittance particles are removed from the beam before sending it onto the diffraction target using a 1 mm diameter collimating hole. These results open the door to the study of irreversible phase transformations by single shot MeV electron diffraction.

  17. High quality single shot diffraction patterns using ultrashort megaelectron volt electron beams from a radio frequency photoinjector.

    Science.gov (United States)

    Musumeci, P; Moody, J T; Scoby, C M; Gutierrez, M S; Bender, H A; Wilcox, N S

    2010-01-01

    Single shot diffraction patterns using a 250-fs-long electron beam have been obtained at the UCLA Pegasus laboratory. High quality images with spatial resolution sufficient to distinguish closely spaced peaks in the Debye-Scherrer ring pattern have been recorded by scattering the 1.6 pC 3.5 MeV electron beam generated in the rf photoinjector off a 100-nm-thick Au foil. Dark current and high emittance particles are removed from the beam before sending it onto the diffraction target using a 1 mm diameter collimating hole. These results open the door to the study of irreversible phase transformations by single shot MeV electron diffraction.

  18. High quality single shot diffraction patterns using ultrashort megaelectron volt electron beams from a radio frequency photoinjector

    International Nuclear Information System (INIS)

    Musumeci, P.; Moody, J. T.; Scoby, C. M.; Gutierrez, M. S.; Bender, H. A.; Wilcox, N. S.

    2010-01-01

    Single shot diffraction patterns using a 250-fs-long electron beam have been obtained at the UCLA Pegasus laboratory. High quality images with spatial resolution sufficient to distinguish closely spaced peaks in the Debye-Scherrer ring pattern have been recorded by scattering the 1.6 pC 3.5 MeV electron beam generated in the rf photoinjector off a 100-nm-thick Au foil. Dark current and high emittance particles are removed from the beam before sending it onto the diffraction target using a 1 mm diameter collimating hole. These results open the door to the study of irreversible phase transformations by single shot MeV electron diffraction.

  19. Reduction of dose enhancement from backscattered radiation at tissue-metal interfaces irradiated with 6MeV electrons

    International Nuclear Information System (INIS)

    Steel, B.

    1996-01-01

    Due to Electron Back Scatter (EBS), electron irradiation of tissue having under lying lead shielding results in an increase in dose to the tissue on the entrance side of the lead. In these situations dose increases as high as 80% have been reported in the literature. Saunders (British Journal of Radiology, 47, 467-470) noted that dose enhancement is dependent on atomic number of the under lying material approximately as Z 0.5 , and it increases at lower incident electron energies. In our clinic we use 2mm of lead shielding to protect under lying normal tissue when 6MeV electrons are used to treat lips and ears. The object of this study was to find the thinnest combination of materials to reduce the total dose to an acceptable level, with the provisos that; the patient does not come into contact with the lead or other metals, the finished shield could comfortabley be placed between the patient's lip and teeth, and that the materials are sufficietly malleable to work into custom shields. Various combinations of dental wax and aluminium were trialed. That which proved to give the best compromise between reduction of EBS and total shielding thickness was, 1mm of aluminim on the beam side of the lead with 1mm of dental wax to completely enclose the shield. In practice the manufactured shields are approximately 6 mm thick, and are usually not uncomfortable for the patient. (author)

  20. Electron diffraction analysis of an AB{sub 2}-type Laves phase for hydrogen battery applications

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Z.; Chumbley, S.; Laabs, F.C. [Iowa State Univ., Ames, IA (United States). Ames Lab.

    2000-11-16

    A multicomponent AB{sub 2} type nickel-metal hydride (Ni-MH) battery alloy prepared by high-pressure gas atomization (HPGA) was investigated by transmission electron microscopy (TEM) in both the as-atomized and heat treated condition. TEM examination showed a heavily faulted dendritic growth structure in as-atomized powder. Selected area diffraction (SAD) showed that this region consisted of both a cubic C15 structure with lattice constant a=7.03 A and an hexagonal C14 structure with lattice parameter a=4.97 A, c=8.11 A. The orientation relationship (OR) between the C14 and C15 structures was determined to be (111)[1 anti 10]{sub C15}//(0001)[11 anti 20]C{sub 14}. An interdendritic phase possessing the C14 structure was also seen. There was also a very fine grain region consisting of the C14 structure. Upon heat treatment, the faulted structure became more defined and appeared as intercalation layers within the grains. Spherical particles rich in Zr and Ni appeared scattered at the grain boundries instead of the C14 interdendritic phase. The polycrystalline region also changed to a mixture of C14 and C15 structures. The phase stability of the C15 and C14 structures based on a consideration of atomic size factor and the average electron concentration is discussed. (orig.)

  1. Local, atomic-level elastic strain measurements of metallic glass thin films by electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ebner, C. [Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Sarkar, R. [Department of Materials Science and Engineering, School for Engineering of Matter Transport and Energy, Arizona State University, Tempe 85287 (United States); Rajagopalan, J. [Department of Materials Science and Engineering, School for Engineering of Matter Transport and Energy, Arizona State University, Tempe 85287 (United States); Department of Mechanical and Aerospace Engineering, School for Engineering of Matter Transport and Energy, Arizona State University, Tempe 85287 (United States); Rentenberger, C., E-mail: christian.rentenberger@univie.ac.at [Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria)

    2016-06-15

    A novel technique is used to measure the atomic-level elastic strain tensor of amorphous materials by tracking geometric changes of the first diffuse ring of selected area electron diffraction patterns (SAD). An automatic procedure, which includes locating the centre and fitting an ellipse to the diffuse ring with sub-pixel precision is developed for extracting the 2-dimensional strain tensor from the SAD patterns. Using this technique, atomic-level principal strains from micrometre-sized regions of freestanding amorphous Ti{sub 0.45}Al{sub 0.55} thin films were measured during in-situ TEM tensile deformation. The thin films were deformed using MEMS based testing stages that allow simultaneous measurement of the macroscopic stress and strain. The calculated atomic-level principal strains show a linear dependence on the applied stress, and good correspondence with the measured macroscopic strains. The calculated Poisson’s ratio of 0.23 is reasonable for brittle metallic glasses. The technique yields a strain accuracy of about 1×10{sup −4} and shows the potential to obtain localized strain profiles/maps of amorphous thin film samples. - Highlights: • A TEM method to measure elastic strain in metallic glass films is proposed. • Method is based on tracking geometric changes in TEM diffraction patterns. • An automatic procedure is developed for extracting the local strain tensor. • Atomic-level strain in amorphous TiAl film was analysed during in-situ deformation. • Capability of the method to obtain micrometer scale strain profiles/maps is shown.

  2. Double and triple crystal diffraction investigation on ion implanted and electron beam annealed silicon

    International Nuclear Information System (INIS)

    Servidori, M.; Cembali, F.; Winter, U.; Zaumseil, P.; Richter, H.

    1985-01-01

    Double (DCD) and triple crystal (TCD) diffractometry was used to investigate radiation damage produced in silicon by silicon bombardment and its evolution after electron beam annealing. The implantation processes were carried out at 60 keV energy and at doses of 0.5, 1, 5, 10, 50, 100, and 200 x 10 13 ions/cm 2 . As to the annealing treatments, an electron gun was used, operating in the ranges 7.5 to 24 W/cm 2 and 2 to 20 seconds. DCD rocking curves were analyzed by means of the dynamical theory of X-ray diffraction. The formalism introduced by Taupin was used to simulate the experimental intensity profiles. From the resulting best fits, the lattice strain vs. depth profiles were obtained, indicating an increase of the damage with dose for the as-implanted samples up to 1 x 10 14 cm -2 dose, whereas amorphous layers are produced for the higher doses. After annealing, lowering of the residual strain was observed to be directly proportional to the implanted dose. In particular, a complete recovery of the damage occurred for the 0.5 and 1 x 10 13 cm -2 samples. The results obtained by the fitting procedure were substantially independent from the power densities and times used during electron beam irradiation. TCD as a very sensitive method to investigate lattice defects after implantation was used to obtain information about the crystallographic perfection of the surface layer. The absence of diffuse scattering indicates that the annealed layers do not contain microdefects within the detection limits. (author)

  3. Advanced technique for ultra-thin residue inspection with sub-10nm thickness using high-energy back-scattered electrons

    Science.gov (United States)

    Han, Jin-Hee

    2018-03-01

    Recently the aspect ratio of capacitor and via hole of memory semiconductor device has been dramatically increasing in order to store more information in a limited area. A small amount of remained residues after etch process on the bottom of the high aspect ratio structure can make a critical failure in device operation. Back-scattered electrons (BSE) are mainly used for inspecting the defect located at the bottom of the high aspect ratio structure or analyzing the overlay of the multi-layer structure because these electrons have a high linearity with the direction of emission and a high kinetic energy above 50eV. However, there is a limitation on that it cannot detect ultra-thin residue material having a thickness of several nanometers because the surface sensitivity is extremely low. We studied the characteristics of BSE spectra using Monte Carlo simulations for several cases which the high aspect ratio structures have extreme microscopic residues. Based on the assumption that most of the electrons emitted without energy loss are localized on the surface, we selected the detection energy window which has a range of 20eV below the maximum energy of the BSE. This window section is named as the high-energy BSE region. As a result of comparing the detection sensitivity of the conventional and the high-energy BSE detection mode, we found that the detection sensitivity for the residuals which have 2nm thickness is improved by more than 10 times in the high-energy BSE mode. This BSE technology is a new inspection method that can greatly be improved the inspection sensitivity for the ultra-thin residual material presented in the high aspect ratio structure, and its application will be expanded.

  4. The potential of materials analysis by electron rutherford backscattering as illustrated by a case study of mouse bones and related compounds.

    Science.gov (United States)

    Vos, Maarten; Tökési, Károly; Benkö, Ilona

    2013-06-01

    Electron Rutherford backscattering (ERBS) is a new technique that could be developed into a tool for materials analysis. Here we try to establish a methodology for the use of ERBS for materials analysis of more complex samples using bone minerals as a test case. For this purpose, we also studied several reference samples containing Ca: calcium carbonate (CaCO(3)) and hydroxyapatite and mouse bone powder. A very good understanding of the spectra of CaCO(3) and hydroxyapatite was obtained. Quantitative interpretation of the bone spectrum is more challenging. A good fit of these spectra is only obtained with the same peak widths as used for the hydroxyapatite sample, if one allows for the presence of impurity atoms with a mass close to that of Na and Mg. Our conclusion is that a meaningful interpretation of spectra of more complex samples in terms of composition is indeed possible, but only if widths of the peaks contributing to the spectra are known. Knowledge of the peak widths can either be developed by the study of reference samples (as was done here) or potentially be derived from theory.

  5. Observation of coherent optical phonons excited by femtosecond laser radiation in Sb films by ultrafast electron diffraction method

    Energy Technology Data Exchange (ETDEWEB)

    Mironov, B. N.; Kompanets, V. O.; Aseev, S. A., E-mail: isanfemto@yandex.ru [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation); Ischenko, A. A. [Moscow Technological University, Institute of High Chemical Technologies (Russian Federation); Kochikov, I. V. [Moscow State University (Russian Federation); Misochko, O. V. [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation); Chekalin, S. V.; Ryabov, E. A. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)

    2017-03-15

    The generation of coherent optical phonons in a polycrystalline antimony film sample has been investigated using femtosecond electron diffraction method. Phonon vibrations have been induced in the Sb sample by the main harmonic of a femtosecond Ti:Sa laser (λ = 800 nm) and probed by a pulsed ultrashort photoelectron beam synchronized with the pump laser. The diffraction patterns recorded at different times relative to the pump laser pulse display oscillations of electron diffraction intensity corresponding to the frequencies of vibrations of optical phonons: totally symmetric (A{sub 1g}) and twofold degenerate (E{sub g}) phonon modes. The frequencies that correspond to combinations of these phonon modes in the Sb sample have also been experimentally observed.

  6. Strong-Field Modulated Diffraction Effects in the Correlated Electron-Nuclear Motion in Dissociating H2+

    International Nuclear Information System (INIS)

    He Feng; Becker, Andreas; Thumm, Uwe

    2008-01-01

    We show that the electronic dynamics in a molecule driven by a strong field is complex and potentially even counterintuitive. As a prototype example, we simulate the interaction of a dissociating H 2 + molecule with an intense infrared laser pulse. Depending on the laser intensity, the direction of the electron's motion between the two nuclei is found to follow or oppose the classical laser-electric force. We explain the sensitive dependence of the correlated electronic-nuclear motion in terms of the diffracting electronic momentum distribution of the dissociating two-center system. The distribution is dynamically modulated by the nuclear motion and periodically shifted in the oscillating infrared electric field

  7. Quantum-chemical calculations and electron diffraction study of the equilibrium molecular structure of vitamin K3

    Science.gov (United States)

    Khaikin, L. S.; Tikhonov, D. S.; Grikina, O. E.; Rykov, A. N.; Stepanov, N. F.

    2014-05-01

    The equilibrium molecular structure of 2-methyl-1,4-naphthoquinone (vitamin K3) having C s symmetry is experimentally characterized for the first time by means of gas-phase electron diffraction using quantum-chemical calculations and data on the vibrational spectra of related compounds.

  8. Structure of ultrathin Pd films determined by low-energy electron microscopy and diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Santos, B; De la Figuera, J [Centro de Microanalisis de Materiales, Universidad Autonoma de Madrid, Madrid 28049 (Spain); Puerta, J M; Cerda, J I [Instituto de Ciencia de Materiales, CSIC, Madrid 28049 (Spain); Herranz, T [Instituto de Quimica-Fisica ' Rocasolano' , CSIC, Madrid 28006 (Spain); McCarty, K F [Sandia National Laboratories, Livermore, CA 94550 (United States)], E-mail: benitosantos001@gmail.com

    2010-02-15

    Palladium (Pd) films have been grown and characterized in situ by low-energy electron diffraction (LEED) and microscopy in two different regimes: ultrathin films 2-6 monolayers (ML) thick on Ru(0001), and {approx}20 ML thick films on both Ru(0001) and W(110). The thinner films are grown at elevated temperature (750 K) and are lattice matched to the Ru(0001) substrate. The thicker films, deposited at room temperature and annealed to 880 K, have a relaxed in-plane lattice spacing. All the films present an fcc stacking sequence as determined by LEED intensity versus energy analysis. In all the films, there is hardly any expansion in the surface-layer interlayer spacing. Two types of twin-related stacking sequences of the Pd layers are found on each substrate. On W(110) the two fcc twin types can occur on a single substrate terrace. On Ru(0001) each substrate terrace has a single twin type and the twin boundaries replicate the substrate steps.

  9. Sample preparation and study by electronic diffraction of oxidations and fluorinations of some metals and alloys

    International Nuclear Information System (INIS)

    Auguin, B.

    1963-06-01

    After having recalled that electron diffraction is particularly adapted to the study of thin films and surface layers, notably those forming during corrosions, and recalled some characteristics of this technique (wavelength, interactions with substances, parasite reactions, observation by transmission or reflection, obtained diagrams for polycrystalline and mono-crystalline substances), the author describes how samples are prepared in the case of examinations performed by transmission and by reflection. As fluorination agents are used for the separation of uranium 235 and 238, the second part discusses some works related to the fluorination of metals and alloys, some of them being used in these separation installations. Chlorine trifluoride is generally used and materials are generally oxidised. Thus, the author reports the study of the action of ClF 3 on different oxides. Oxidations of iron, nickel and Monel are addressed, as well as the behaviour of stainless steel. The study of fluorinations of metals (nickel, chromium, copper), alloys (stainless steel, Monel) and oxides is reported. The author finally addresses treatments performed after fluorinations: vacuum heating, action of humid air

  10. Thiobenzamide: Structure of a free molecule as studied by gas electron diffraction and quantum chemical calculations

    Science.gov (United States)

    Kolesnikova, Inna N.; Putkov, Andrei E.; Rykov, Anatolii N.; Shishkov, Igor F.

    2018-06-01

    The equilibrium (re) molecular structure of thiobenzamide along with rh1 structure has been determined in gas phase using gas electron-diffraction (GED) at about 127 °C and quantum-chemical calculations (QC). Rovibrational distance corrections to the thermal averaged GED structure have been computed with anharmonic force constants obtained at the MP2/cc-pVTZ level of theory. According to the results of GED and QC thiobenzamide exists as mixture of two non-planar enantiomers of C1 symmetry. The selected equilibrium geometrical parameters of thiobenzamide (re, Å and ∠e, deg) are the following: (Cdbnd S) = 1.641(4), (Csbnd N) = 1.352(2), (Csbnd C) = 1.478(9), (Cdbnd C)av = 1.395(2), CCN = 114.7(5), CCS = 123.4(5), C2C1C7S = 31(4), C6C1C7N = 29(4). The structure of thiobenzamide in the gas phase is markedly different to that in the literature for the single crystal. The differences between the gas and the solid structures are ascribed to the presence of intermolecular hydrogen bonding in the solid phase.

  11. Crystallography of waxes - an electron diffraction study of refined and natural products

    Science.gov (United States)

    Dorset, Douglas L.

    1997-02-01

    The crystal structure of four waxes has been investigated by electron crystallography. Two of these waxes, including a refined petroleum product (Gulfwax) and a material from lignite (montan wax), form well ordered crystals and their structure could be solved quantitatively from the observed 0022-3727/30/3/018/img1 diffraction patterns. As also found previously for simpler binary n-paraffin solid solutions, the average structure resembles that of a pure paraffin (e.g. n-0022-3727/30/3/018/img2) but with a Gaussian distribution of atomic occupancies near the chain ends to account for the statistical distribution of chain lengths within a lamella. Two other waxes from living organisms, South African bee honeycomb and the leaves of the Brazilian carnauba palm, are much less ordered, even though they share the same methylene subcell packing of the most crystalline parts of the previous materials. It appears that these waxes cannot fully separate into distinct lamellae, perhaps due to the presence of very long `tie' molecules, and are therefore `frustrated' crystal structures.

  12. Big-data reflection high energy electron diffraction analysis for understanding epitaxial film growth processes.

    Science.gov (United States)

    Vasudevan, Rama K; Tselev, Alexander; Baddorf, Arthur P; Kalinin, Sergei V

    2014-10-28

    Reflection high energy electron diffraction (RHEED) has by now become a standard tool for in situ monitoring of film growth by pulsed laser deposition and molecular beam epitaxy. Yet despite the widespread adoption and wealth of information in RHEED images, most applications are limited to observing intensity oscillations of the specular spot, and much additional information on growth is discarded. With ease of data acquisition and increased computation speeds, statistical methods to rapidly mine the data set are now feasible. Here, we develop such an approach to the analysis of the fundamental growth processes through multivariate statistical analysis of a RHEED image sequence. This approach is illustrated for growth of La(x)Ca(1-x)MnO(3) films grown on etched (001) SrTiO(3) substrates, but is universal. The multivariate methods including principal component analysis and k-means clustering provide insight into the relevant behaviors, the timing and nature of a disordered to ordered growth change, and highlight statistically significant patterns. Fourier analysis yields the harmonic components of the signal and allows separation of the relevant components and baselines, isolating the asymmetric nature of the step density function and the transmission spots from the imperfect layer-by-layer (LBL) growth. These studies show the promise of big data approaches to obtaining more insight into film properties during and after epitaxial film growth. Furthermore, these studies open the pathway to use forward prediction methods to potentially allow significantly more control over growth process and hence final film quality.

  13. Production of muscovite-feldspathic glass composite: scanning electron microscopy and X-ray diffraction analysis

    International Nuclear Information System (INIS)

    Costa, F.P.F.; Ogasawara, T.; Santos, S.F.

    2009-01-01

    The objective of this work was to find the sintering conditions for the feldspathic glass + muscovite mixture to produce a dense composite block for manufacturing dental prosthesis by using CAD-CAM. Each 20g of the glass-frit had : 15.55g of Armil-feldspar; 0.53g of Al 2 O 3 ; 1.56g of Na 2 CO 3 ; 0.5g of borax; 1.74g of K 2 CO 3 ; 0.13g of CeO 2 . Frit's powder finer than 350 Tyler mesh was mixed with 0 wt%, 10 wt%, 20 wt% and 100 wt% of muscovite pressed cylinders (5600 pounds force) 16mm in diameter and sintered under vacuum Vacumat (VITA) furnace at 850 deg C, 900 deg C, 950 deg C, 1000 deg C, 1050 deg C, 1100 deg C and 1150 deg C. X-ray diffraction analysis and scanning electron microscopy were carried out. The necessary temperature for high densification depended on the composition of the mixture: 850 deg C (for pure frit); 1050 deg C (for 10 wt% mica) and 1150 deg C (for 20 wt% mica); pure mica degraded during sintering. (author)

  14. Interference phenomena at backscattering by ice crystals of cirrus clouds.

    Science.gov (United States)

    Borovoi, Anatoli; Kustova, Natalia; Konoshonkin, Alexander

    2015-09-21

    It is shown that light backscattering by hexagonal ice crystals of cirrus clouds is formed within the physical-optics approximation by both diffraction and interference phenomena. Diffraction determines the angular width of the backscattering peak and interference produces the interference rings inside the peak. By use of a simple model for distortion of the pristine hexagonal shape, we show that the shape distortion leads to both oscillations of the scattering (Mueller) matrix within the backscattering peak and to a strong increase of the depolarization, color, and lidar ratios needed for interpretation of lidar signals.

  15. Oxygen adsorption on Cu-9 at. %Al(111) studied by low energy electron diffraction and Auger electron spectroscopy

    Science.gov (United States)

    Yoshitake, Michiko; Bera, Santanu; Yamauchi, Yasuhiro; Song, Weijie

    2003-07-01

    Cu-based alloys have been used for electric cables for long time. In the field of microelectronics, Al had been used for electrical wiring. However, it became clear that electromigration occurs in Al that causes breaking of wires in minute wirings. Due to this problem, Cu wiring is used in most advanced microprocessors. Cu metal is more corrosive than Al and Cu-based alloys with a small amount of Al is expected to solve problems both on electromigration and corrosion. The initial stage of corrosion is oxygen adsorption. We studied surface segregation of Al on Cu-9% Al(111) and oxygen adsorption on the surface with/without Al segregation in ultrahigh vacuum by low energy electron diffraction (LEED) and Auger electron spectroscopy. It was found that Al segregates on the surface to form (√3×√3)R30° structure and the structure vanishes above 595 K to give (1×1) structure while Al still segregates. The specimen was exposed to oxygen at different temperatures. The amount of oxygen uptake was not structure dependent but temperature dependent. Below 595 K, only a small amount of oxygen adsorbed. Between 595 and 870 K, oxygen adsorbed surface showed amorphous LEED pattern. The specimen was annealed at 1070 K after oxygen exposure. When the specimen was exposed oxygen below 870 K, the oxygen Auger intensity decreased significantly by annealing and the annealed surface showed (√3×√3)R30° structure at room temperature. When the specimen was exposed to oxygen at 870 K, diffused spots developed newly in LEED pattern but the pattern disappeared after 1070 K annealing while oxygen Auger intensity remained almost constant. Exposing the specimen to oxygen at 995 K resulted in clear spots in the LEED pattern, which were attributed to the (7/√3×7√3)R30° structure.

  16. Development of a high repetition rate laser-plasma accelerator for ultra-fast electron diffraction experiments

    International Nuclear Information System (INIS)

    Beaurepaire, B.

    2009-01-01

    Electronic microscopy and electron diffraction allowed the understanding of the organization of atoms in matter. Using a temporally short source, one can measure atomic displacements or modifications of the electronic distribution in matter. To date, the best temporal resolution for time resolved diffraction experiments is of the order of a hundred femto-seconds (fs). Laser accelerators are good candidates to reach the femtosecond temporal resolution in electron diffraction experiments. Such accelerators used to work at a low repetition rate, so that it was necessary to develop a new one operating at a high repetition rate in order to accumulate a large amount of data. In this thesis, a laser-plasma accelerator operating at the kHz repetition rate was developed and built. This source generates electron bunches at 100 keV from 3 mJ and 25 fs laser pulses. The physics of the acceleration has been studied, and the effect of the laser wavefront on the electron transverse distribution has been demonstrated. (author)

  17. A Low-Temperature Electron Microscopy and Electron Diffraction Study of La1.84Sr0.16CuO4

    Science.gov (United States)

    Onozuka, Takashi; Omori, Mamoru; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-10-01

    A high-Tc superconducting compound, La1.84Sr0.16CuO4, has been investigated by electron microscopy and electron diffraction in the range from 10 K to ambient temperature. The tetragonal K2NiF4-type structure undergoes an orthorhombic distortion below about 130 K. In the low-temperature phase, extra diffraction spots and twin lamellae are observed reversibly on cooling and heating in situ. Based on the observed results, a plausible structure model with orthorhombic distortion is proposed.

  18. A low-temperature electron microscopy and electron diffraction study of La1.84Sr0.16CuO4

    International Nuclear Information System (INIS)

    Onozuka, Takashi; Omori, Mamoru; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-01-01

    A high-T c superconducting compound, La 1.84 Sr 0.16 CuO 4 , has been investigated by electron microscopy and electron diffraction in the range from 10 K to ambient temperature. The tetragonal K 2 NiF 4 -type structure undergoes an orthorhombic distortion below about 130 K. In the low-temperature phase, extra diffraction spots and twin lamellae are observed reversibly on cooling and heating in situ. Based on the observed results, a plausible structure model with orthorhombic distortion is proposed. (author)

  19. Low-temperature electron microscopy and electron diffraction study of La/sub 1. 84/Sr/sub 0. 16/CuO/sub 4/

    Energy Technology Data Exchange (ETDEWEB)

    Onozuka, Takashi; Omori, Mamoru; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-10-01

    A high-T/sub c/ superconducting compound, La/sub 1.84/Sr/sub 0.16/CuO/sub 4/, has been investigated by electron microscopy and electron diffraction in the range from 10 K to ambient temperature. The tetragonal K/sub 2/NiF/sub 4/-type structure undergoes an orthorhombic distortion below about 130 K. In the low-temperature phase, extra diffraction spots and twin lamellae are observed reversibly on cooling and heating in situ. Based on the observed results, a plausible structure model with orthorhombic distortion is proposed

  20. Dynamic coherent backscattering mirror

    Energy Technology Data Exchange (ETDEWEB)

    Zeylikovich, I.; Xu, M., E-mail: mxu@fairfield.edu [Physics Department, Fairfield University, Fairfield, CT 06824 (United States)

    2016-02-15

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.

  1. Measurements of transient electron density distributions by femtosecond X-ray diffraction; Messungen transienter Elektronendichteverteilungen durch Femtosekunden-Roentgenbeugung

    Energy Technology Data Exchange (ETDEWEB)

    Freyer, Benjamin

    2013-05-02

    This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

  2. Elucidating structural order and disorder phenomena in mullite-type Al4B2O9 by automated electron diffraction tomography

    International Nuclear Information System (INIS)

    Zhao, Haishuang; Krysiak, Yaşar; Hoffmann, Kristin; Barton, Bastian; Molina-Luna, Leopoldo; Neder, Reinhard B.; Kleebe, Hans-Joachim; Gesing, Thorsten M.; Schneider, Hartmut; Fischer, Reinhard X.

    2017-01-01

    The crystal structure and disorder phenomena of Al 4 B 2 O 9 , an aluminum borate from the mullite-type family, were studied using automated diffraction tomography (ADT), a recently established method for collection and analysis of electron diffraction data. Al 4 B 2 O 9 , prepared by sol-gel approach, crystallizes in the monoclinic space group C2/m. The ab initio structure determination based on three-dimensional electron diffraction data from single ordered crystals reveals that edge-connected AlO 6 octahedra expanding along the b axis constitute the backbone. The ordered structure (A) was confirmed by TEM and HAADF-STEM images. Furthermore, disordered crystals with diffuse scattering along the b axis are observed. Analysis of the modulation pattern implies a mean superstructure (AAB) with a threefold b axis, where B corresponds to an A layer shifted by ½a and ½c. Diffraction patterns simulated for the AAB sequence including additional stacking disorder are in good agreement with experimental electron diffraction patterns. - Graphical abstract: Crystal structure and disorder phenomena of B-rich Al 4 B 2 O 9 studied by automated electron diffraction tomography (ADT) and described by diffraction simulation using DISCUS. - Highlights: • Ab-initio structure solution by electron diffraction from single nanocrystals. • Detected modulation corresponding mainly to three-fold superstructure. • Diffuse diffraction streaks caused by stacking faults in disordered crystals. • Observed streaks explained by simulated electron diffraction patterns.

  3. Data processing software suite SITENNO for coherent X-ray diffraction imaging using the X-ray free-electron laser SACLA

    International Nuclear Information System (INIS)

    Sekiguchi, Yuki; Oroguchi, Tomotaka; Takayama, Yuki; Nakasako, Masayoshi

    2014-01-01

    The software suite SITENNO is developed for processing diffraction data collected in coherent X-ray diffraction imaging experiments of non-crystalline particles using an X-ray free-electron laser. Coherent X-ray diffraction imaging is a promising technique for visualizing the structures of non-crystalline particles with dimensions of micrometers to sub-micrometers. Recently, X-ray free-electron laser sources have enabled efficient experiments in the ‘diffraction before destruction’ scheme. Diffraction experiments have been conducted at SPring-8 Angstrom Compact free-electron LAser (SACLA) using the custom-made diffraction apparatus KOTOBUKI-1 and two multiport CCD detectors. In the experiments, ten thousands of single-shot diffraction patterns can be collected within several hours. Then, diffraction patterns with significant levels of intensity suitable for structural analysis must be found, direct-beam positions in diffraction patterns determined, diffraction patterns from the two CCD detectors merged, and phase-retrieval calculations for structural analyses performed. A software suite named SITENNO has been developed to semi-automatically apply the four-step processing to a huge number of diffraction data. Here, details of the algorithm used in the suite are described and the performance for approximately 9000 diffraction patterns collected from cuboid-shaped copper oxide particles reported. Using the SITENNO suite, it is possible to conduct experiments with data processing immediately after the data collection, and to characterize the size distribution and internal structures of the non-crystalline particles

  4. The potential of materials analysis by electron Rutherford backscattering as illustrated by a case study of mouse bones and related compounds

    International Nuclear Information System (INIS)

    Vos, M.; Toekesi, K.; Benkoe, I.

    2012-01-01

    Complete text of publication follows. Electron Rutherford backscattering (ERBS) has a number of distinct advantages for semi-quantitative analysis of samples. These are for example: a) Its high energy makes it rather insensitive to surface effects. b) The peaks appear well approximated by Gaussian with no obvious problems due to background subtraction. c) All the electrons involved have very similar kinetic energy, and hence one does not need to consider changes of the mean-free path or the analyzer transmission function. d) There are no intrinsic satellites to complicate the quantitative interpretation. On the other hand ERBS has a weak point, peaks tend to overlap. Peak separation is proportional to the incoming energy E0, but the intrinsic peak width increases proportional to the square root of E 0 . In practice one has to live with overlapping peaks. In the present work we mainly focus on the measurement and analysis procedure, and compare our best estimate of the concentration of the various elements in mouse bone with that obtained in a recent paper. The promise of ERBS as an analytical technique is clear from the successful analysis of the simple case of calcium carbonate and the somewhat more complicated case of hydroxyapatite. Here agreement between the measured and actual composition are on a very respectable 10% level. The actual bone sample showed more variation in outcome and a somewhat less satisfactory agreement between experiment and theory (see Fig. 1). The variation in outcome between the different measurements can be due to the fact that we average over very few grains, and that the grain composition will vary somewhat with its original position in the bone. In summary, ERBS can become a useful tool to study bone mineralization. As our knowledge of bone mineralization is incomplete this is currently an active topic of multidisciplinary research involving people working in physics, chemistry and biological/medical sciences. One of the important

  5. LACDIF, a new electron diffraction technique obtained with the LACBED configuration and a C{sub s} corrector: Comparison with electron precession

    Energy Technology Data Exchange (ETDEWEB)

    Morniroli, J.P. [Laboratoire de Metallurgie Physique et Genie des Materiaux, UMR CNRS 8517, USTL and ENSCL, Cite Scientifique, 59655 Villeneuve d' Ascq (France)], E-mail: jean-paul.morniroli@univ-lille1.fr; Houdellier, F.; Roucau, C. [CEMES-CNRS, 29 Rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4 (France); Puiggali, J.; Gesti, S. [Departament d' Enginyeria Quimica, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Redjaimia, A. [Laboratoire de Science et Genie des Surfaces, UMR CNRS 7570, Ecole des Mines de Nancy, Parc de Saurupt 54042 Nancy (France)

    2008-01-15

    By combining the large-angle convergent-beam electron diffraction (LACBED) configuration together with a microscope equipped with a C{sub s} corrector it is possible to obtain good quality spot patterns in image mode and not in diffraction mode as it is usually the case. These patterns have two main advantages with respect to the conventional selected-area electron diffraction (SAED) or microdiffraction patterns. They display a much larger number of reflections and the diffracted intensity is the integrated intensity. These patterns have strong similarities with the electron precession patterns and they can be used for various applications like the identification of the possible space groups of a crystal from observations of the Laue zones or the ab-initio structure identifications. Since this is a defocused method, another important application concerns the analysis of electron beam-sensitive materials. Successful applications to polymers are given in the present paper to prove the validity of this method with regards to these materials.

  6. Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector

    Energy Technology Data Exchange (ETDEWEB)

    Genderen, E. van; Clabbers, M. T. B. [Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands); Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, CH-4058 Basel (Switzerland); Das, P. P. [Nanomegas SPRL, Boulevard Edmond Machtens 79, B 1080, Brussels (Belgium); Stewart, A. [Department of Physics and Energy, Materials and Surface Science Institute (MSSI), University of Limerick, Limerick (Ireland); Nederlof, I. [Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands); Amsterdam Scientific Instruments, Postbus 41882, 1009 DB Amsterdam (Netherlands); Barentsen, K. C. [Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands); Portillo, Q. [Nanomegas SPRL, Boulevard Edmond Machtens 79, B 1080, Brussels (Belgium); Centres Científics i Tecnològics de la Universitat de Barcelona, University of Barcelona, Carrer de Lluís Solé i Sabaris, 1-3, Barcelona (Spain); Pannu, N. S. [Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands); Nicolopoulos, S. [Nanomegas SPRL, Boulevard Edmond Machtens 79, B 1080, Brussels (Belgium); Gruene, T., E-mail: tim.gruene@psi.ch [Biology and Chemistry, Laboratory of Biomolecular Research, Paul Scherrer Institute (PSI), 5232 Villigen (Switzerland); Abrahams, J. P., E-mail: tim.gruene@psi.ch [Biophysical Structural Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands); Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, CH-4058 Basel (Switzerland); Biology and Chemistry, Laboratory of Biomolecular Research, Paul Scherrer Institute (PSI), 5232 Villigen (Switzerland)

    2016-02-05

    A specialized quantum area detector for electron diffraction studies makes it possible to solve the structure of small organic compound nanocrystals in non-cryo conditions by direct methods. Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e{sup −} Å{sup −2} s{sup −1}) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014)

  7. Structure and microstructure of hexagonal Ba3Ti2RuO9 by electron diffraction and microscopy

    International Nuclear Information System (INIS)

    Maunders, C.; Etheridge, J.; Whitfield, H.J.

    2005-01-01

    We have used electron microscopy and diffraction to refine the structure and investigate the microstructure of Ba 3 Ti 2 RuO 9 . The parent compound is hexagonal BaTiO 3 with the space group P6 3 /mmc. Using convergent-beam electron diffraction (CBED) combined with electron-sensitive image plates we have found that the space group of Ba 3 Ti 2 RuO 9 is the non-centrosymmetric group P6 3 mc. at room temperature and at ∝ 110 K. This is consistent with the Ru and Ti atoms occupying alternate face-sharing octahedral sites in the h0001i direction. This maintains the c-glide, but breaks the mirror normal to the c axis and consequently removes the centre of symmetry. Using powder X-ray diffraction, we have measured the lattice parameters from polycrystalline samples to be a = 5.7056 ± 0.0005, c = 14.0093 ± 0.0015 Aa at room temperature. Using high-resolution electron microscopy (HREM) we observed highly coherent, low-strain {10 anti 10} grain boundaries intersecting at 60 and 120 . From CBED we deduce that adjacent grains are identical but for the relative phase of the Ti and Ru atom ordering along the c axis. HREM also revealed occasional stacking faults, normal to the c-axis

  8. Multipole electron-density modelling of synchrotron powder diffraction data: the case of diamond

    DEFF Research Database (Denmark)

    Svendsen, H.; Overgaard, J.; Busselez, R.

    2010-01-01

    between experiment and theory, and the study therefore demonstrates that synchrotron powder diffraction can indeed provide accurate structure-factor values based on data measured in minutes with limited sample preparation. Thus, potential systematic errors such as extinction and twinning commonly......Accurate structure factors are extracted from synchrotron powder diffraction data measured on crystalline diamond based on a novel multipole model division of overlapping reflection intensities. The approach limits the spherical-atom bias in structure factors extracted from overlapping powder data...

  9. Diffraction contrast as a sensitive indicator of femtosecond sub-nanoscale motion in ultrafast transmission electron microscopy

    Science.gov (United States)

    Cremons, Daniel R.; Schliep, Karl B.; Flannigan, David J.

    2013-09-01

    With ultrafast transmission electron microscopy (UTEM), access can be gained to the spatiotemporal scales required to directly visualize rapid, non-equilibrium structural dynamics of materials. This is achieved by operating a transmission electron microscope (TEM) in a stroboscopic pump-probe fashion by photoelectrically generating coherent, well-timed electron packets in the gun region of the TEM. These probe photoelectrons are accelerated down the TEM column where they travel through the specimen before reaching a standard, commercially-available CCD detector. A second laser pulse is used to excite (pump) the specimen in situ. Structural changes are visualized by varying the arrival time of the pump laser pulse relative to the probe electron packet at the specimen. Here, we discuss how ultrafast nanoscale motions of crystalline materials can be visualized and precisely quantified using diffraction contrast in UTEM. Because diffraction contrast sensitively depends upon both crystal lattice orientation as well as incoming electron wavevector, minor spatial/directional variations in either will produce dynamic and often complex patterns in real-space images. This is because sections of the crystalline material that satisfy the Laue conditions may be heterogeneously distributed such that electron scattering vectors vary over nanoscale regions. Thus, minor changes in either crystal grain orientation, as occurs during specimen tilting, warping, or anisotropic expansion, or in the electron wavevector result in dramatic changes in the observed diffraction contrast. In this way, dynamic contrast patterns observed in UTEM images can be used as sensitive indicators of ultrafast specimen motion. Further, these motions can be spatiotemporally mapped such that direction and amplitude can be determined.

  10. Backscattering of gyrotron radiation and short-wavelength turbulence during electron cyclotron resonance plasma heating in the L-2M stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Batanov, G. M.; Borzosekov, V. D., E-mail: tinborz@gmail.com; Kovrizhnykh, L. M.; Kolik, L. V.; Konchekov, E. M.; Malakhov, D. V.; Petrov, A. E.; Sarksyan, K. A.; Skvortsova, N. N.; Stepakhin, V. D.; Kharchev, N. K. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

    2013-06-15

    Backscattering of gyrotron radiation ({theta} = {pi}) by short-wavelength density fluctuations (k{sub Up-Tack} = 30 cm{sup -1}) in the plasma of the L-2M stellarator was studied under conditions of electron cyclotron resonance (ECR) plasma heating at the second harmonic of the electron gyrofrequency (75 GHz). The scattering of the O-wave emerging due to the splitting of the linearly polarized gyrotron radiation into the X- and O-waves was analyzed. The signal obtained after homodyne detection of scattered radiation is a result of interference of the reference signal, the quasi-steady component, and the fast oscillating component. The coefficients of reflection of the quasi-steady component, R{sub =}{sup 2}(Y), and fast oscillating component, R{sub {approx}}{sup 2}(Y), of scattered radiation are estimated. The growth of the R{sub {approx}}{sup 2}(Y) coefficient from 3.7 Multiplication-Sign 10{sup -4} to 5.2 Multiplication-Sign 10{sup -4} with increasing ECR heating power from 190 to 430 kW is found to correlate with the decrease in the energy lifetime from 1.9 to 1.46 ms. The relative density of short-wavelength fluctuations is estimated to be Left-Pointing-Angle-Bracket n{sub {approx}}{sup 2} Right-Pointing-Angle-Bracket / Left-Pointing-Angle-Bracket n{sub e}{sup 2} Right-Pointing-Angle-Bracket = 3 Multiplication-Sign 10{sup -7}. It is shown that the frequencies of short-wavelength fluctuations are in the range 10-150 kHz. The recorded short-wavelength fluctuations can be interpreted as structural turbulence, the energy of which comprises {approx}10% of the total fluctuations energy. Simulations of transport processes show that neoclassical heat fluxes are much smaller than anomalous ones. It is suggested that short-wavelength turbulence plays a decisive role in the anomalous heat transport.

  11. Quantitative investigation of precipitate growth during ageing of Al-(Mg,Si) alloys by energy-filtered electron diffraction

    DEFF Research Database (Denmark)

    Wollgarten, M.; Chang, C. S. T.; Duchstein, Linus Daniel Leonhard

    2011-01-01

    Besides other application fields, light-weight Al-(Mg, Si) (6XXX series) alloys are of substantial importance in automotive industries where they are used for the production of car body panels. The material gains its strength by precipitation of metastable Mg-Si-based phases. Though the general...... accepted that the early stages of precipitate growth are important for the understanding of this peculiar behaviour. During these stages, electron diffraction patterns of Al-(Mg, Si) alloys show diffuse features (Figure 1 (a) and (b)) which can be traced back to originate from β'' Mg5Si6 precipitates [5......-7]. In this paper, we use energy-filtered electron diffraction to determine dimensions of the β'' Mg5Si6 precipitates along their a, b and c-axes as a function of ageing time and alloy composition. In our contribution, we first derive that there is an optimal zone axis - - from the view point of practicability. We...

  12. Experimental determination of spin-dependent electron density by joint refinement of X-ray and polarized neutron diffraction data.

    Science.gov (United States)

    Deutsch, Maxime; Claiser, Nicolas; Pillet, Sébastien; Chumakov, Yurii; Becker, Pierre; Gillet, Jean Michel; Gillon, Béatrice; Lecomte, Claude; Souhassou, Mohamed

    2012-11-01

    New crystallographic tools were developed to access a more precise description of the spin-dependent electron density of magnetic crystals. The method combines experimental information coming from high-resolution X-ray diffraction (XRD) and polarized neutron diffraction (PND) in a unified model. A new algorithm that allows for a simultaneous refinement of the charge- and spin-density parameters against XRD and PND data is described. The resulting software MOLLYNX is based on the well known Hansen-Coppens multipolar model, and makes it possible to differentiate the electron spins. This algorithm is validated and demonstrated with a molecular crystal formed by a bimetallic chain, MnCu(pba)(H(2)O)(3)·2H(2)O, for which XRD and PND data are available. The joint refinement provides a more detailed description of the spin density than the refinement from PND data alone.

  13. Strain characterization of fin-shaped field effect transistors with SiGe stressors using nanobeam electron diffraction

    International Nuclear Information System (INIS)

    Kim, Sun-Wook; Byeon, Dae-Seop; Jang, Hyunchul; Koo, Sang-Mo; Ko, Dae-Hong; Lee, Hoo-Jeong

    2014-01-01

    This study undertook strain analysis on fin-shaped field effect transistor structures with epitaxial Si 1−x Ge x stressors, using nano-beam electron diffraction and finite elements method. Combining the two methods disclosed dynamic strain distribution in the source/drain and channel region of the fin structure, and the effects of dimensional factors such as the stressor thickness and fin width, offering valuable information for device design.

  14. Growth Mechanism of Single-Walled Carbon Nanotubes on Iron–Copper Catalyst and Chirality Studies by Electron Diffraction

    DEFF Research Database (Denmark)

    He, Maoshuai; Liu, Bilu; Chernov, Alexander I.

    2012-01-01

    Chiralities of single-walled carbon nanotubes grown on an atomic layer deposition prepared bimetallic FeCu/MgO catalyst were evaluated quantitatively using nanobeam electron diffraction. The results reveal that the growth yields nearly 90% semiconducting tubes, 45% of which are of the (6,5) type...... by impregnation, showing similar catalytic performance as the atomic layer deposition-prepared catalyst, yielding single-walled carbon nanotubes with a similar narrow chirality distribution....

  15. Investigations in space-related molecular biology. [cryo-electron microscopic and diffraction studies on terrestrial and extraterrestrial specimens

    Science.gov (United States)

    Fernandez-Moran, H.; Pritzker, A. N.

    1974-01-01

    Improved instrumentation and preparation techniques for high resolution, high voltage cryo-electron microscopic and diffraction studies on terrestrial and extraterrestrial specimens are reported. Computer correlated ultrastructural and biochemical work on hydrated and dried cell membranes and related biological systems provided information on membrane organization, ice crystal formation and ordered water, RNA virus linked to cancer, lunar rock samples, and organometallic superconducting compounds. Apollo 11, 12, 14, and 15 specimens were analyzed

  16. Interpretation of the shape of electron diffraction spots from small polyhedral crystals by means of the crystal shape amplitude

    International Nuclear Information System (INIS)

    Neumann, W.; Hofmeister, H.; Heydenreich, J.; Komrska, J.

    1988-01-01

    The influence of the crystal shape on the fine structure of transmission electron diffraction (TED) patterns described by the crystal shape amplitude is discussed. A general algebraic expression for the crystal shape amplitude of any crystal polyhedron is used for computing the intensity distribution of TED reflections. The computer simulation method is applied to the analysis of the fine structure of TED patterns of small gold and palladium crystals having octahedral and tetrahedral habits. (orig.)

  17. Quantitative low-energy electron diffraction analysis of the GaN(000-1) (1×1) reconstruction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Jiříček, Petr; Paskova, T.

    2012-01-01

    Roč. 606, 7-8 (2012), s. 740-743 ISSN 0039-6028 R&D Projects: GA ČR GPP204/10/P028 Institutional research plan: CEZ:AV0Z10100521 Keywords : gallium nitride * semiconductor surfaces * quantitative low-energy electron diffraction * LEED Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.838, year: 2012

  18. Strain characterization of fin-shaped field effect transistors with SiGe stressors using nanobeam electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sun-Wook; Byeon, Dae-Seop; Jang, Hyunchul; Koo, Sang-Mo; Ko, Dae-Hong, E-mail: dhko@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Hoo-Jeong, E-mail: hlee@skku.edu [Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-08-25

    This study undertook strain analysis on fin-shaped field effect transistor structures with epitaxial Si{sub 1−x}Ge{sub x} stressors, using nano-beam electron diffraction and finite elements method. Combining the two methods disclosed dynamic strain distribution in the source/drain and channel region of the fin structure, and the effects of dimensional factors such as the stressor thickness and fin width, offering valuable information for device design.

  19. Crystallization and preliminary electron diffraction study to 3. 7 A of DNA helix-destabilizing protein gp32*I

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, W; Hosoda, J

    1978-01-01

    A two-dimensionally large and thin crystal has been obtained from gp32*I, a proteolytically digested product of a DNA helix-destabilizing protein coded by gene 32 in bacteriophage T4. High-resolution electron diffraction patterns (approx. 3.7 A) are recorded from both unstained and stained protein crystals embedded in glucose. The crystal is of orthorhombic space group with a = 62.9 A and b = 47.3 A.

  20. Structure determination of a new phase Ni.sub.8./sub.Ti.sub.5./sub. by electron diffraction tomography

    Czech Academy of Sciences Publication Activity Database

    Klementová, Mariana; Karlík, M.; Novák, P.; Palatinus, Lukáš

    2017-01-01

    Roč. 85, Jun (2017), s. 110-116 ISSN 0966-9795 R&D Projects: GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : shape- memory alloys * crystal chemistry * nanocrystalline structure * powder metallurgy * electron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.140, year: 2016

  1. Monitoring non-pseudomorphic epitaxial growth of spinel/perovskite oxide heterostructures by reflection high-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Schütz, P.; Pfaff, F.; Scheiderer, P.; Sing, M.; Claessen, R. [Physikalisches Institut and Röntgen Center for Complex Material Systems (RCCM), Universität Würzburg, Am Hubland, D-97074 Würzburg (Germany)

    2015-02-09

    Pulsed laser deposition of spinel γ-Al{sub 2}O{sub 3} thin films on bulk perovskite SrTiO{sub 3} is monitored by high-pressure reflection high-energy electron diffraction (RHEED). The heteroepitaxial combination of two materials with different crystal structures is found to be inherently accompanied by a strong intensity modulation of bulk diffraction patterns from inelastically scattered electrons, which impedes the observation of RHEED intensity oscillations. Avoiding such electron surface-wave resonance enhancement by de-tuning the RHEED geometry allows for the separate observation of the surface-diffracted specular RHEED signal and thus the real-time monitoring of sub-unit cell two-dimensional layer-by-layer growth. Since these challenges are essentially rooted in the difference between film and substrate crystal structure, our findings are of relevance for the growth of any heterostructure combining oxides with different crystal symmetry and may thus facilitate the search for novel oxide heterointerfaces.

  2. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  3. Single-particle coherent diffractive imaging with a soft x-ray free electron laser: towards soot aerosol morphology

    Science.gov (United States)

    Bogan, Michael J.; Starodub, Dmitri; Hampton, Christina Y.; Sierra, Raymond G.

    2010-10-01

    The first of its kind, the Free electron LASer facility in Hamburg, FLASH, produces soft x-ray pulses with unprecedented properties (10 fs, 6.8-47 nm, 1012 photons per pulse, 20 µm diameter). One of the seminal FLASH experiments is single-pulse coherent x-ray diffractive imaging (CXDI). CXDI utilizes the ultrafast and ultrabright pulses to overcome resolution limitations in x-ray microscopy imposed by x-ray-induced damage to the sample by 'diffracting before destroying' the sample on sub-picosecond timescales. For many lensless imaging algorithms used for CXDI it is convenient when the data satisfy an oversampling constraint that requires the sample to be an isolated object, i.e. an individual 'free-standing' portion of disordered matter delivered to the centre of the x-ray focus. By definition, this type of matter is an aerosol. This paper will describe the role of aerosol science methodologies used for the validation of the 'diffract before destroy' hypothesis and the execution of the first single-particle CXDI experiments being developed for biological imaging. FLASH CXDI now enables the highest resolution imaging of single micron-sized or smaller airborne particulate matter to date while preserving the native substrate-free state of the aerosol. Electron microscopy offers higher resolution for single-particle analysis but the aerosol must be captured on a substrate, potentially modifying the particle morphology. Thus, FLASH is poised to contribute significant advancements in our knowledge of aerosol morphology and dynamics. As an example, we simulate CXDI of combustion particle (soot) morphology and introduce the concept of extracting radius of gyration of fractal aggregates from single-pulse x-ray diffraction data. Future upgrades to FLASH will enable higher spatially and temporally resolved single-particle aerosol dynamics studies, filling a critical technological need in aerosol science and nanotechnology. Many of the methodologies described for FLASH will

  4. Toward atomic resolution diffractive imaging of isolated molecules with x-ray free-electron lasers

    DEFF Research Database (Denmark)

    Stern, Stephan; Holmegaard, Lotte; Filsinger, Frank

    2014-01-01

    We give a detailed account of the theoretical analysis and the experimental results of an x-ray-diffraction experiment on quantum-state selected and strongly laser-aligned gas-phase ensembles of the prototypical large asymmetric rotor molecule 2,5-diiodobenzonitrile, performed at the Linac Cohere...

  5. Texture investigation in the trench depth direction of very fine copper wires less than 100 nm wide using electron backscatter diffraction

    International Nuclear Information System (INIS)

    Khoo, Khyoupin; Onuki, Jin

    2010-01-01

    We clarified the correlations between resistivity and microstructures in the depth direction of copper (Cu) wires. The resistivity of Cu wires increased with the polishing depth ΔH, and the influence of ΔH on resistivity increment was significant for 60 nm wide Cu wires. We attributed this to the fact that the deeper the depth and the finer the line width, the smaller are the grain sizes and the lower are the fractions of {111} textures and Σ3 coincident site lattice boundaries. Among the above factors, the grain size was the dominant factor determining the resistivity of less than 100 nm wide Cu wire.

  6. The Weighted Burgers Vector: a new quantity for constraining dislocation densities and types using electron backscatter diffraction on 2D sections through crystalline materials.

    Science.gov (United States)

    Wheeler, J; Mariani, E; Piazolo, S; Prior, D J; Trimby, P; Drury, M R

    2009-03-01

    The Weighted Burgers Vector (WBV) is defined here as the sum, over all types of dislocations, of [(density of intersections of dislocation lines with a map) x (Burgers vector)]. Here we show that it can be calculated, for any crystal system, solely from orientation gradients in a map view, unlike the full dislocation density tensor, which requires gradients in the third dimension. No assumption is made about gradients in the third dimension and they may be non-zero. The only assumption involved is that elastic strains are small so the lattice distortion is entirely due to dislocations. Orientation gradients can be estimated from gridded orientation measurements obtained by EBSD mapping, so the WBV can be calculated as a vector field on an EBSD map. The magnitude of the WBV gives a lower bound on the magnitude of the dislocation density tensor when that magnitude is defined in a coordinate invariant way. The direction of the WBV can constrain the types of Burgers vectors of geometrically necessary dislocations present in the microstructure, most clearly when it is broken down in terms of lattice vectors. The WBV has three advantages over other measures of local lattice distortion: it is a vector and hence carries more information than a scalar quantity, it has an explicit mathematical link to the individual Burgers vectors of dislocations and, since it is derived via tensor calculus, it is not dependent on the map coordinate system. If a sub-grain wall is included in the WBV calculation, the magnitude of the WBV becomes dependent on the step size but its direction still carries information on the Burgers vectors in the wall. The net Burgers vector content of dislocations intersecting an area of a map can be simply calculated by an integration round the edge of that area, a method which is fast and complements point-by-point WBV calculations.

  7. Structural evolution of a Ta-filament during hot-wire chemical vapour deposition of Silicon investigated by electron backscatter diffraction

    CSIR Research Space (South Africa)

    Oliphant, CJ

    2012-03-01

    Full Text Available , encapsulating a Ta inner core. The tantalum rich Ta5Si3, Si3Ta5 and Ta2Si phases however formed in addition to TaSi2 at the centre regions. Cracks and porosity were found throughout the length of the filament. The microstructure evolution of the aged tantalum...

  8. Genesis of diamond inclusions: An integrated cathodoluminescence (CL) and Electron backscatter diffraction (EBSD) study on eclogitic and peridotitic inclusions and their diamond host.

    Science.gov (United States)

    van den Heuvel, Quint; Matveev, Sergei; Drury, Martyn; Gress, Michael; Chinn, Ingrid; Davies, Gareth

    2017-04-01

    Diamond inclusions are potentially fundamental to understanding the formation conditions of diamond and the volatile cycles in the deep mantle. In order to fully understand the implications of the compositional information recorded by inclusions it is vital to know whether the inclusions are proto-, syn-, or epigenetic and the extent to which they have equilibrated with diamond forming fluids. In previous studies, the widespread assumption was made that the majority of diamond inclusions are syngenetic, based upon observation of cubo-octahedral morphology imposed on the inclusions. Recent work has reported the crystallographic relationship between inclusions and the host diamond to be highly complex and the lack of crystallographic relationships between inclusions and diamonds has led some to question the significance of imposed cubo-octahedral morphology. This study presents an integrated EBSD and CL study of 9 diamonds containing 20 pyropes, 2 diopsides, 1 forsterite and 1 rutile from the Jwaneng and Letlhakane kimberlite clusters, Botswana. A new method was developed to analyze the crystallographic orientation of the host diamond and the inclusions with EBSD. Diamonds plates were sequentially polished to expose inclusions at different levels in the diamond. CL imaging at different depths was performed in order to produce a 3D view of diamond growth zones around the inclusions. Standard diamond polishing techniques proved too aggressive for silicate inclusions as they were damaged to such a degree that EBSD measurements on the inclusions were impossible. The inclusions were milled with a Ga+ focused ion beam (FIB) at a 12° angle to clean the surface for EBSD measurements. Of the 24 inclusions, 9 have an imposed cubo-octahedral morphology. Of these inclusions, 6 have faces orientated parallel to diamond growth zones and/or appear to have nucleated on a diamond growth surface, implying syngenesis. In contrast, other diamonds record resorption events such that inclusions now cut diamond growth zones. In most cases, the growth zonation around inclusions is not well defined due to CL haloes but some inclusions clearly disrupt diamond growth. Crystallographic orientations of diamond and the inclusions, determined using EBSD, revealed that each inclusion has a homogeneous orientation and record no compositional zonation. The diamonds also showed no angular deviations despite many having multiple growth and resorption zones; implying epitaxial growth of diamond. Crystallographic alignment between diamond and inclusions was not recorded for the principle planes and limited to 3 possible coincidences on minor planes from the 24 inclusions studied. The CL data show no evidence of syngenesis for these 3 inclusions. Analyses of two diamonds with inclusion clusters in different growth zones, 400 µm apart, revealed the same chemical composition and orientation, potentially implying they originated from an original larger inclusion. Combined EBSD and CL data suggest that there is no direct orientational correlation (epitaxial growth) between silicate inclusions and the host diamond, even when the mineral phases are of the same symmetry group. The presentation will provide a detailed evaluation of the genesis of individual inclusions.

  9. Integral staggered point-matching method for millimeter-wave reflective diffraction gratings on electron cyclotron heating systems

    International Nuclear Information System (INIS)

    Xia, Donghui; Huang, Mei; Wang, Zhijiang; Zhang, Feng; Zhuang, Ge

    2016-01-01

    Highlights: • The integral staggered point-matching method for design of polarizers on the ECH systems is presented. • The availability of the integral staggered point-matching method is checked by numerical calculations. • Two polarizers are designed with the integral staggered point-matching method and the experimental results are given. - Abstract: The reflective diffraction gratings are widely used in the high power electron cyclotron heating systems for polarization strategy. This paper presents a method which we call “the integral staggered point-matching method” for design of reflective diffraction gratings. This method is based on the integral point-matching method. However, it effectively removes the convergence problems and tedious calculations of the integral point-matching method, making it easier to be used for a beginner. A code is developed based on this method. The calculation results of the integral staggered point-matching method are compared with the integral point-matching method, the coordinate transformation method and the low power measurement results. It indicates that the integral staggered point-matching method can be used as an optional method for the design of reflective diffraction gratings in electron cyclotron heating systems.

  10. Integral staggered point-matching method for millimeter-wave reflective diffraction gratings on electron cyclotron heating systems

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Donghui [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); Huang, Mei [Southwestern Institute of Physics, 610041 Chengdu (China); Wang, Zhijiang, E-mail: wangzj@hust.edu.cn [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); Zhang, Feng [Southwestern Institute of Physics, 610041 Chengdu (China); Zhuang, Ge [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China)

    2016-10-15

    Highlights: • The integral staggered point-matching method for design of polarizers on the ECH systems is presented. • The availability of the integral staggered point-matching method is checked by numerical calculations. • Two polarizers are designed with the integral staggered point-matching method and the experimental results are given. - Abstract: The reflective diffraction gratings are widely used in the high power electron cyclotron heating systems for polarization strategy. This paper presents a method which we call “the integral staggered point-matching method” for design of reflective diffraction gratings. This method is based on the integral point-matching method. However, it effectively removes the convergence problems and tedious calculations of the integral point-matching method, making it easier to be used for a beginner. A code is developed based on this method. The calculation results of the integral staggered point-matching method are compared with the integral point-matching method, the coordinate transformation method and the low power measurement results. It indicates that the integral staggered point-matching method can be used as an optional method for the design of reflective diffraction gratings in electron cyclotron heating systems.

  11. Spatially coded backscatter radiography

    International Nuclear Information System (INIS)

    Thangavelu, S.; Hussein, E.M.A.

    2007-01-01

    Conventional radiography requires access to two opposite sides of an object, which makes it unsuitable for the inspection of extended and/or thick structures (airframes, bridges, floors etc.). Backscatter imaging can overcome this problem, but the indications obtained are difficult to interpret. This paper applies the coded aperture technique to gamma-ray backscatter-radiography in order to enhance the detectability of flaws. This spatial coding method involves the positioning of a mask with closed and open holes to selectively permit or block the passage of radiation. The obtained coded-aperture indications are then mathematically decoded to detect the presence of anomalies. Indications obtained from Monte Carlo calculations were utilized in this work to simulate radiation scattering measurements. These simulated measurements were used to investigate the applicability of this technique to the detection of flaws by backscatter radiography

  12. Structure studies by electron microscopy and electron diffraction at Physics Department, University of Oslo, 1976-1985

    International Nuclear Information System (INIS)

    Gjoennes, J.K.; Olsen, A.

    1985-08-01

    The paper describes the reasearch activities and plans at the electron microscopy laboratorium, Physics Departmen, University of Oslo. Since the first electron microscope was installed in 1968, the research has covered inorganic structures, physical metallurgy, as well as theory of electron scattering and the development of methods in this field. The current plans involve efforts in the development of crystallographic and spectroscopic methods

  13. Temperature-dependent surface structure, composition, and electronic properties of the clean SrTiO3(111) crystal face: Low-energy-electron diffraction, Auger-electron spectroscopy, electron energy loss, and ultraviolet-photoelectron spectroscopy studies

    International Nuclear Information System (INIS)

    Lo, W.J.; Somorjai, G.A.

    1978-01-01

    Low-energy-electron diffraction, Auger-electron spectroscopy, electron-energy-loss, and ultraviolet-photoelectron spectroscopies were used to study the structure, composition, and electron energy distribution of a clean single-crystal (111) face of strontium titanate (perovskite). The dependence of the surface chemical composition on the temperature has been observed along with corresponding changes in the surface electronic properties. High-temperature Ar-ion bombardment causes an irreversible change in the surface structure, stoichiometry, and electron energy distribution. In contrast to the TiO 2 surface, there are always significant concentrations of Ti 3+ in an annealed ordered SrTiO 3 (111) surface. This stable active Ti 3+ monolayer on top of a substrate with large surface dipole potential makes SrTiO 3 superior to TiO 2 when used as a photoanode in the photoelectrochemical cell

  14. Structure of solid surfaces and of adsorbates by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Somorjai, G.A.

    1977-01-01

    LEED theory has developed to the point where the diffraction beam intensities can be computed using the locations of the surface atoms as the only adjustable parameters. The position of atoms in many clean monatomic solid surfaces and the surface structures of ordered monolayers of adsorbed atoms have been determined this way. Surface crystallography studies are now extended to small hydrocarbon molecules that are adsorbed on metal surfaces. These studies are reviewed

  15. Diffraction and depths-of-field effects in electron beam imaging at SURF III

    International Nuclear Information System (INIS)

    Arp, U.

    2001-01-01

    Imaging an electron beam with visible light is a common method of diagnostics applied to electron accelerators. It is a straightforward way to deduce the transverse electron distribution as well as its changes over time. The electrons stored in the Synchrotron Ultraviolet Radiation Facility (SURF) III at the National Institute of Standards and Technology (NIST) were studied over an extended period of time to characterize the upgraded accelerator. There is good agreement between experimental and theoretical horizontal beam sizes at three different electron energies

  16. Electronic structure of nanoscale Cu/Pt alloys: A combined X-ray diffraction and X-ray absorption investigations

    International Nuclear Information System (INIS)

    Chen Xing; Chu Wangsheng; Cai Quan; Xia Dingguo; Wu Zhonghua; Wu Ziyu

    2006-01-01

    PVP-protected Cu/Pt clusters were prepared by glycol/water reduction method and characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD) and absorption spectra. TEM and XRD analysis show that the Cu/Pt clusters with different molar ratio have fcc structure with particle size of about 4 nm, while the lattice parameters in these clusters reduce with increasing Cu concentration. From the X-ray absorption near edge structure (XANES) at Cu-K edge and Pt-L 2,3 edge, we demonstrate that the d-electronic states of Cu and Pt are affected by the local environment as a function of Cu/Pt molar ratio. With increasing Cu concentration, Pt loses a fraction of 5d electrons and the hybridization between p- and d-states at Cu sites is enhanced

  17. Electronic structure of nanoscale Cu/Pt alloys: A combined X-ray diffraction and X-ray absorption investigations

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xing [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); Graduate School of the Chinese Academy of Sciences, 100864 Beijing (China); Chu Wangsheng [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); University of Science and Technology of China, Hefei, 230036 (China); Cai Quan [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); Graduate School of the Chinese Academy of Sciences, 100864 Beijing (China); Xia Dingguo [College of Environmental and Energy Engineering, Beijing University of Technology, 100022 Beijing (China); Wu Zhonghua [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China); Wu Ziyu [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, CAS, Beijing (China) and National Center for Nanoscience and Technology (China)]. E-mail: wuzy@ihep.ac.cn

    2006-11-15

    PVP-protected Cu/Pt clusters were prepared by glycol/water reduction method and characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD) and absorption spectra. TEM and XRD analysis show that the Cu/Pt clusters with different molar ratio have fcc structure with particle size of about 4 nm, while the lattice parameters in these clusters reduce with increasing Cu concentration. From the X-ray absorption near edge structure (XANES) at Cu-K edge and Pt-L{sub 2,3} edge, we demonstrate that the d-electronic states of Cu and Pt are affected by the local environment as a function of Cu/Pt molar ratio. With increasing Cu concentration, Pt loses a fraction of 5d electrons and the hybridization between p- and d-states at Cu sites is enhanced.

  18. The vacancy order-disorder transition in Ba2YCu3Osub(7-delta) observed by means of electron diffraction and electron microscopy

    International Nuclear Information System (INIS)

    Tendeloo, G. Van; Amelinckx, S.; Zandbergen, H.W.

    1987-01-01

    It is shown by means of electron microscopy and electron diffraction that the ''structural'' vacancies in Ba 2 YCu 3 Osub(7-delta) undergo an order-disorder transformation accompanied by a change in symmetry from orthorhombic to tetragonal. A superstructure due to the ordering of vacancies was found in certain crystal parts; it leads to doubling of the asub(0) parameter. It is shown that the ordering of the vacancies is important for the superconducting behaviour. In order to obtain a high Tsub(c) superconductor the final heat treatment is crucial. (author)

  19. High resolution electron microscopy and electron diffraction of YBa/sub 2/Cu/sub 3/O/sub 7-x/

    International Nuclear Information System (INIS)

    Krakow, W.; Shaw, T.M.

    1988-01-01

    Experimental high resolution electron micrographs and computer simulation experiments have been used to evaluate the visibility of the atomic constituents of YBa/sub 2/Cu/sub 3/O/sub 7-x/. In practice, the detection of oxygen has not been possible in contradiction to that predicted by modelling of perfect crystalline material. Preliminary computer experiments of the electron diffraction patterns when oxygen vacancies are introduced on the Cu-O sheets separating Ba layers show the diffuse streaks characteristic of short range ordering

  20. Heavy atom disorder in the high Tsub(c) superconductor Ba2YCu3Osub(7-delta) studied by means of electron microscopy and electron diffraction

    International Nuclear Information System (INIS)

    Tendeloo, G. van; Okabe, T.; Zandbergen, H.W.; Amelinckx, S.

    1987-01-01

    It is shown that on rapid cooling of the compound Ba 2 YCu 3 Osub(7-δ) one obtains a highly disordered material in which the perovskite framework is conserved but in which barium and yttrium atoms exhibit a high degree of disorder. This leads to lattice deformations, which can be visualized in the electron microscope. The electron diffraction patterns also reveal the disorder. As-quenched specimens are no longer high Tsub(c) superconductors, but the superconducting properties can be recovered by an adequate heat treatment whereby the vacancies become ordered. (author)

  1. Elucidating structural order and disorder phenomena in mullite-type Al{sub 4}B{sub 2}O{sub 9} by automated electron diffraction tomography

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Haishuang; Krysiak, Yaşar [Institute of Inorganic Chemistry and Analytical Chemistry, Jakob-Welder-Weg 11, Johannes Gutenberg-University Mainz, 55128 Mainz (Germany); Hoffmann, Kristin [Crystallography, Department of Geosciences, Klagenfurter Str. 2, GEO, University of Bremen, 28359 Bremen (Germany); Institute of Inorganic Chemistry and Crystallography, Leobener Str. NW2, University of Bremen, 28359 Bremen (Germany); Barton, Bastian [Institute of Inorganic Chemistry and Analytical Chemistry, Jakob-Welder-Weg 11, Johannes Gutenberg-University Mainz, 55128 Mainz (Germany); Molina-Luna, Leopoldo [Department of Materials and Geoscience, Technische Universität Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany); Neder, Reinhard B. [Department of Physics, Lehrstuhl für Kristallographie und Strukturphysik, Friedrich-Alexander University Erlangen-Nürnberg, Staudtstr.3, 91058 Erlangen (Germany); Kleebe, Hans-Joachim [Department of Materials and Geoscience, Technische Universität Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany); Gesing, Thorsten M. [Institute of Inorganic Chemistry and Crystallography, Leobener Str. NW2, University of Bremen, 28359 Bremen (Germany); MAPEX Center for Materials and Processes, Bibliothekstr.1, University of Bremen, 28359 Bremen (Germany); Schneider, Hartmut [Crystallography, Department of Geosciences, Klagenfurter Str. 2, GEO, University of Bremen, 28359 Bremen (Germany); Fischer, Reinhard X. [Crystallography, Department of Geosciences, Klagenfurter Str. 2, GEO, University of Bremen, 28359 Bremen (Germany); MAPEX Center for Materials and Processes, Bibliothekstr.1, University of Bremen, 28359 Bremen (Germany); and others

    2017-05-15

    The crystal structure and disorder phenomena of Al{sub 4}B{sub 2}O{sub 9}, an aluminum borate from the mullite-type family, were studied using automated diffraction tomography (ADT), a recently established method for collection and analysis of electron diffraction data. Al{sub 4}B{sub 2}O{sub 9}, prepared by sol-gel approach, crystallizes in the monoclinic space group C2/m. The ab initio structure determination based on three-dimensional electron diffraction data from single ordered crystals reveals that edge-connected AlO{sub 6} octahedra expanding along the b axis constitute the backbone. The ordered structure (A) was confirmed by TEM and HAADF-STEM images. Furthermore, disordered crystals with diffuse scattering along the b axis are observed. Analysis of the modulation pattern implies a mean superstructure (AAB) with a threefold b axis, where B corresponds to an A layer shifted by ½a and ½c. Diffraction patterns simulated for the AAB sequence including additional stacking disorder are in good agreement with experimental electron diffraction patterns. - Graphical abstract: Crystal structure and disorder phenomena of B-rich Al{sub 4}B{sub 2}O{sub 9} studied by automated electron diffraction tomography (ADT) and described by diffraction simulation using DISCUS. - Highlights: • Ab-initio structure solution by electron diffraction from single nanocrystals. • Detected modulation corresponding mainly to three-fold superstructure. • Diffuse diffraction streaks caused by stacking faults in disordered crystals. • Observed streaks explained by simulated electron diffraction patterns.

  2. Electron-density distribution in cubic SrTiO3: a comparative γ-ray diffraction study

    International Nuclear Information System (INIS)

    Jauch, W.; Reehuis, M.

    2005-01-01

    The electron density and atomic displacements in the perovskite SrTiO 3 have been studied using extensive and accurate γ-ray diffraction data (λ=0.0392 Aa) at room temperature. The six strongest low-order structure factors have been determined under extinction-free conditions. Gram-Charlier series expansion of the thermal parameters have revealed no evidence for anharmonicity. The population of the 3d subshell on Ti is found to be close to zero, in agreement with the observed magnetic behaviour. The electronic properties at the bond critical points indicate ionic Ti-O and Sr-O interactions of different strengths, which is corroborated by the net charges of the atomic basins [q(Sr)=1.18 vertical stroke e vertical stroke, q(Ti)=3.10 vertical stroke e vertical stroke, q(O)=1.42 vertical stroke e vertical stroke ]. A critical comparison is made with earlier experimental results from laboratory X-ray, synchrotron X-ray, electron and neutron diffraction studies. Agreement and discrepancies are identified and resolved. (orig.)

  3. Electron-density distribution in cubic SrTiO{sub 3}: a comparative {gamma}-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Jauch, W. [Hahn-Meitner-Inst., Berlin (Germany); Reehuis, M. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2005-07-01

    The electron density and atomic displacements in the perovskite SrTiO{sub 3} have been studied using extensive and accurate {gamma}-ray diffraction data ({lambda}=0.0392 Aa) at room temperature. The six strongest low-order structure factors have been determined under extinction-free conditions. Gram-Charlier series expansion of the thermal parameters have revealed no evidence for anharmonicity. The population of the 3d subshell on Ti is found to be close to zero, in agreement with the observed magnetic behaviour. The electronic properties at the bond critical points indicate ionic Ti-O and Sr-O interactions of different strengths, which is corroborated by the net charges of the atomic basins [q(Sr)=1.18 vertical stroke e vertical stroke, q(Ti)=3.10 vertical stroke e vertical stroke, q(O)=1.42 vertical stroke e vertical stroke ]. A critical comparison is made with earlier experimental results from laboratory X-ray, synchrotron X-ray, electron and neutron diffraction studies. Agreement and discrepancies are identified and resolved. (orig.)

  4. Atomic scattering in the diffraction limit: electron transfer in keV Li+-Na(3s, 3p) collisions

    International Nuclear Information System (INIS)

    Poel, M van der; Nielsen, C V; Rybaltover, M; Nielsen, S E; Machholm, M; Andersen, N

    2002-01-01

    We measure angle differential cross sections (DCS) in Li + + Na → Li + Na + electron transfer collisions in the 2.7-24 keV energy range. We do this with a newly constructed apparatus which combines the experimental technique of cold target recoil ion momentum spectroscopy with a laser-cooled target. This setup yields a momentum resolution of 0.12 au, an order of magnitude better angular resolution than previous measurements on this system. This enables us to clearly resolve Fraunhofer-type diffraction patterns in the angle DCS. In particular, the angular width of the ring structure is given by the ratio of the de Broglie wavelength λ dB = 150 fm at a velocity v = 0.20 au and the effective atomic diameter for electron capture 2R = 20 au. Parallel AO and MO semiclassical coupled-channel calculations of the Na(3s, 3p) → Li(2s, 2p) state-to-state collision amplitudes have been performed, and quantum scattering amplitudes are derived by the eikonal method. The resulting angle-differential electron transfer cross sections and their diffraction patterns agree with the experimental level-to-level results over most scattering angles in the energy range

  5. Three-dimensional structure determination protocol for noncrystalline biomolecules using x-ray free-electron laser diffraction imaging.

    Science.gov (United States)

    Oroguchi, Tomotaka; Nakasako, Masayoshi

    2013-02-01

    Coherent and intense x-ray pulses generated by x-ray free-electron laser (XFEL) sources are paving the way for structural determination of noncrystalline biomolecules. However, due to the small scattering cross section of electrons for x rays, the available incident x-ray intensity of XFEL sources, which is currently in the range of 10(12)-10(13) photons/μm(2)/pulse, is lower than that necessary to perform single-molecule diffraction experiments for noncrystalline biomolecules even with the molecular masses of megadalton and submicrometer dimensions. Here, we propose an experimental protocol and analysis method for visualizing the structure of those biomolecules by the combined application of coherent x-ray diffraction imaging and three-dimensional reconstruction methods. To compensate the small scattering cross section of biomolecules, in our protocol, a thin vitreous ice plate containing several hundred biomolecules/μm(2) is used as sample, a setup similar to that utilized by single-molecule cryoelectron microscopy. The scattering cross section of such an ice plate is far larger than that of a single particle. The images of biomolecules contained within irradiated areas are then retrieved from each diffraction pattern, and finally provide the three-dimensional electron density model. A realistic atomic simulation using large-scale computations proposed that the three-dimensional structure determination of the 50S ribosomal subunit embedded in a vitreous ice plate is possible at a resolution of 0.8 nm when an x-ray beam of 10(16) photons/500×500 nm(2)/pulse is available.

  6. Colloid morphological and crystalline studies in Bikini dust from the No. 5 Fukuryu Maru by electron microscopy and diffraction methods

    Energy Technology Data Exchange (ETDEWEB)

    Suito, E; Takiyama, K; Uyeda, N

    1954-01-01

    Dust was collected from the deck, fishes, and other parts of the ship. The dust was white granules, approximately 0.3 mm. in size and sp. gr. 2.42. These granules were composed of unit particles which were cubic or spindle of 0.1 to 3. ..mu.. in size. The Bikini dust was calcite as determined by electron microdiffraction and x-ray diffraction studies. The coral reef is aragonite. It is suggested that coral reef was evapd. by the H-bomb explosion.

  7. The effect of a non-hermitian crystal potential on the scattering matrix in reflection electron diffraction

    International Nuclear Information System (INIS)

    Smith, A.E.; Josefsson, T.W.

    1994-01-01

    An extension to include general inelastic scattering effects is developed for the case of reflection electron diffraction scattering from surfaces. In this extension of work by Lynch and Moodie, it is shown how the resultant non-Hermitian matrix problem can be recast in a form that is suitable for computation. In particular, a computational method is outlined based on techniques developed by Eberlein for matrix diagonalisation using complex rotations and shears. The resultant methods are applied to the problem of Convergent Beam RHEED. 23 refs., 3 figs

  8. A semiclassical analysis of high energy electron diffraction by stacking faults: arrival at the classical limit

    International Nuclear Information System (INIS)

    Smith, A.E.; Chadderton, L.T.

    1978-01-01

    In a recent note the authors summarised results for an extension of Berry's theory to cover the one-dimensional problem of systematic reflections (planes) for a thin crystal sandwich consisting of two identical slabs of lattice parameter 'a' with a relative horizontal displacement 'f'. The diffraction amplitudes at the lower surface of the crystal were shown to depend on a double summation over the various transverse energy states in the upper and lower slab respectively, and on the transitions between them. In this report the authors demonstrate the arrival at the classical limit for the problem and, in particular, indicate briefly the nature of the topologically different classical paths. (Auth.)

  9. Disorder and transport properties of In3SbTe2 - an X-ray, neutron and electron diffraction study

    International Nuclear Information System (INIS)

    Schroeder, Thorsten; Rosenthal, Tobias; Grott, Sebastian; Stiewe, Christian; Boor, Johannes de; Oeckler, Oliver

    2013-01-01

    Quenched metastable In 3 SbTe 2 was investigated by X-ray and neutron powder diffraction as well as by single-crystal X-ray diffraction. The average structure corresponds to the rocksalt type, the anion position being occupied by antimony and tellurium. Neutron data indicate no antisite disorder of indium and antimony. The compound is a high-temperature phase that can be quenched to yield a metastable compound at ambient temperature which, upon heating, decomposes at ca. 320 C into InSb and InTe. Diffuse scattering in reconstructed X-ray and selected area electron diffraction patterns indicates local distortions of the crystal structure due to static atom displacement along <100> from the average positions, caused by the different size of the anions, but no superstructure. The electrical conductivity of In 3 SbTe 2 is 3.2 x 10 4 S.cm -1 at 25 C, the temperature characteristics correspond to metallic behavior. Consequently, the thermal conductivity is also rather high. The decomposition into InSb and InTe reduces the electrical conductivity by a factor of 3 in heterogeneous microstructures. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Synchrotron Bragg diffraction imaging characterization of synthetic diamond crystals for optical and electronic power device applications1 1

    Science.gov (United States)

    Tran Thi, Thu Nhi; Morse, J.; Caliste, D.; Fernandez, B.; Eon, D.; Härtwig, J.; Mer-Calfati, C.; Tranchant, N.; Arnault, J. C.; Lafford, T. A.; Baruchel, J.

    2017-01-01

    Bragg diffraction imaging enables the quality of synthetic single-crystal diamond substrates and their overgrown, mostly doped, diamond layers to be characterized. This is very important for improving diamond-based devices produced for X-ray optics and power electronics applications. The usual first step for this characterization is white-beam X-ray diffraction topography, which is a simple and fast method to identify the extended defects (dislocations, growth sectors, boundaries, stacking faults, overall curvature etc.) within the crystal. This allows easy and quick comparison of the crystal quality of diamond plates available from various commercial suppliers. When needed, rocking curve imaging (RCI) is also employed, which is the quantitative counterpart of monochromatic Bragg diffraction imaging. RCI enables the local determination of both the effective misorientation, which results from lattice parameter variation and the local lattice tilt, and the local Bragg position. Maps derived from these parameters are used to measure the magnitude of the distortions associated with polishing damage and the depth of this damage within the volume of the crystal. For overgrown layers, these maps also reveal the distortion induced by the incorporation of impurities such as boron, or the lattice parameter variations associated with the presence of growth-incorporated nitrogen. These techniques are described, and their capabilities for studying the quality of diamond substrates and overgrown layers, and the surface damage caused by mechanical polishing, are illustrated by examples. PMID:28381981

  11. Card controlled beta backscatter thickness measuring instrument

    International Nuclear Information System (INIS)

    Schlesinger, J.

    1978-01-01

    An improved beta backscatter instrument for the nondestructive measurement of the thickness of thin coatings on a substrate is described. Included therein is the utilization of a bank of memory stored data representative of isotope, substrate, coating material and thickness range characteristics in association with a control card having predetermined indicia thereon selectively representative of a particular isotope, substrate material, coating material and thickness range for conditioning electronic circuit means by memory stored data selected in accord with the predetermined indicia on a control card for converting backscattered beta particle counts into indicia of coating thickness

  12. Single-particle coherent diffractive imaging with a soft x-ray free electron laser: towards soot aerosol morphology

    International Nuclear Information System (INIS)

    Bogan, Michael J; Starodub, Dmitri; Hampton, Christina Y; Sierra, Raymond G

    2010-01-01

    The first of its kind, the Free electron LASer facility in Hamburg, FLASH, produces soft x-ray pulses with unprecedented properties (10 fs, 6.8-47 nm, 10 12 photons per pulse, 20 μm diameter). One of the seminal FLASH experiments is single-pulse coherent x-ray diffractive imaging (CXDI). CXDI utilizes the ultrafast and ultrabright pulses to overcome resolution limitations in x-ray microscopy imposed by x-ray-induced damage to the sample by 'diffracting before destroying' the sample on sub-picosecond timescales. For many lensless imaging algorithms used for CXDI it is convenient when the data satisfy an oversampling constraint that requires the sample to be an isolated object, i.e. an individual 'free-standing' portion of disordered matter delivered to the centre of the x-ray focus. By definition, this type of matter is an aerosol. This paper will describe the role of aerosol science methodologies used for the validation of the 'diffract before destroy' hypothesis and the execution of the first single-particle CXDI experiments being developed for biological imaging. FLASH CXDI now enables the highest resolution imaging of single micron-sized or smaller airborne particulate matter to date while preserving the native substrate-free state of the aerosol. Electron microscopy offers higher resolution for single-particle analysis but the aerosol must be captured on a substrate, potentially modifying the particle morphology. Thus, FLASH is poised to contribute significant advancements in our knowledge of aerosol morphology and dynamics. As an example, we simulate CXDI of combustion particle (soot) morphology and introduce the concept of extracting radius of gyration of fractal aggregates from single-pulse x-ray diffraction data. Future upgrades to FLASH will enable higher spatially and temporally resolved single-particle aerosol dynamics studies, filling a critical technological need in aerosol science and nanotechnology. Many of the methodologies described for FLASH will

  13. Single-shot mega-electronvolt ultrafast electron diffraction for structure dynamic studies of warm dense matter

    Energy Technology Data Exchange (ETDEWEB)

    Mo, M. Z., E-mail: mmo09@slac.stanford.edu; Shen, X.; Chen, Z.; Li, R. K.; Dunning, M.; Zheng, Q.; Weathersby, S. P.; Reid, A. H.; Coffee, R.; Makasyuk, I.; Edstrom, S.; McCormick, D.; Jobe, K.; Hast, C.; Glenzer, S. H.; Wang, X. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Sokolowski-Tinten, K. [Faculty of Physics and Centre for Nanointegration Duisburg-Essen, University of Duisburg-Essen, Lotharstrasse 1, D-47048 Duisburg (Germany)

    2016-11-15

    We have developed a single-shot mega-electronvolt ultrafast-electron-diffraction system to measure the structural dynamics of warm dense matter. The electron probe in this system is featured by a kinetic energy of 3.2 MeV and a total charge of 20 fC, with the FWHM pulse duration and spot size at sample of 350 fs and 120 μm respectively. We demonstrate its unique capability by visualizing the atomic structural changes of warm dense gold formed from a laser-excited 35-nm freestanding single-crystal gold foil. The temporal evolution of the Bragg peak intensity and of the liquid signal during solid-liquid phase transition are quantitatively determined. This experimental capability opens up an exciting opportunity to unravel the atomic dynamics of structural phase transitions in warm dense matter regime.

  14. Coherent phonon excitation and linear thermal expansion in structural dynamics and ultrafast electron diffraction of laser-heated metals.

    Science.gov (United States)

    Tang, Jau

    2008-04-28

    In this study, we examine the ultrafast structural dynamics of metals induced by a femtosecond laser-heating pulse as probed by time-resolved electron diffraction. Using the two-temperature model and the Grüneisen relationship we calculate the electron temperature, phonon temperature, and impulsive force at each atomic site in the slab. Together with the Fermi-Pasta-Ulam anharmonic chain model we calculate changes of bond distance and the peak shift of Bragg spots or Laue rings. A laser-heated thin slab is shown to exhibit "breathing" standing-wave behavior, with a period equal to the round-trip time for sound wave and a wavelength twice the slab thickness. The peak delay time first increases linearly with the thickness (linear thermal expansion due to lattice temperature jump are shown to contribute to the overall structural changes. Differences between these two mechanisms and their dependence on film thickness and other factors are discussed.

  15. Diffraction-unlimited optical imaging of unstained living cells in liquid by electron beam scanning of luminescent environmental cells.

    Science.gov (United States)

    Miyazaki, Hideki T; Kasaya, Takeshi; Takemura, Taro; Hanagata, Nobutaka; Yasuda, Takeshi; Miyazaki, Hiroshi

    2013-11-18

    An environmental cell with a 50-nm-thick cathodoluminescent window was attached to a scanning electron microscope, and diffraction-unlimited near-field optical imaging of unstained living human lung epithelial cells in liquid was demonstrated. Electrons with energies as low as 0.8 - 1.2 kV are sufficiently blocked by the window without damaging the specimens, and form a sub-wavelength-sized illumination light source. A super-resolved optical image of the specimen adhered to the opposite window surface was acquired by a photomultiplier tube placed below. The cells after the observation were proved to stay alive. The image was formed by enhanced dipole radiation or energy transfer, and features as small as 62 nm were resolved.

  16. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments

    Directory of Open Access Journals (Sweden)

    Maxime Deutsch

    2014-05-01

    Full Text Available Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  17. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments.

    Science.gov (United States)

    Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

    2014-05-01

    Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  18. Effect of processing on the microstructure of finger millet by X-ray diffraction and scanning electron microscopy.

    Science.gov (United States)

    Dharmaraj, Usha; Parameswara, P; Somashekar, R; Malleshi, Nagappa G

    2014-03-01

    Finger millet is one of the important minor cereals, and carbohydrates form its major chemical constituent. Recently, the millet is processed to prepare hydrothermally treated (HM), decorticated (DM), expanded (EM) and popped (PM) products. The present research aims to study the changes in the microstructure of carbohydrates using X-ray diffraction and scanning electron microscopy. Processing the millet brought in significant changes in the carbohydrates. The native millet exhibited A-type pattern of X-ray diffraction with major peaks at 2θ values of 15.3, 17.86 and 23.15°, whereas, all other products showed V-type pattern with single major peak at 2θ values ranging from 19.39 to 19.81°. The corresponding lattice spacing and the number of unit cells in a particular direction of reflection also reduced revealing that crystallinity of starch has been decreased depending upon the processing conditions. Scanning electron microscopic studies also revealed that the orderly pattern of starch granules changed into a coherent mass due to hydrothermal treatment, while high temperature short time treatment rendered a honey-comb like structure to the product. However, the total carbohydrates and non-starch polysaccharide contents almost remained the same in all the products except for DM and EM, but the individual carbohydrate components changed significantly depending on the type of processing.

  19. Electron diffraction and resistivity measurements on the one-dimensional orthorhombic and monoclinic structures of TaS3

    International Nuclear Information System (INIS)

    Roucau, C.; Ayroles, R.; Monceau, P.

    1980-01-01

    Electron diffraction patterns are obtained of the orthorhombic and monoclinic structures of TaS 3 . For the orthorhombic structure one set of superlattice spots is observed at (l+-0.5)a*, (m+-0.125)b*, (n+-0.25)c* below 210 K. For the monoclinic structure two sets of superlattice spots are observed, the first one at la*, (m+-0.253)b*, nc* below 240 K, the second one at (l+-0.5)a*, (m+-0.245)b*, (n+-0.5)c* below 160 K. Diffuse scattering lines are present for the two structures. Resistivity measurements are performed on crystals with the two structures which show strong increase of the resistivity indicating metal-semiconducting transitions at the same temperatures where the superlattice spots appear. These transitions are interpreted as successive Peierls transitions on the different types of chains of TaS 3 . Also electron diffraction patterns are shown of NbSe 3 at very low temperatures where the two charge density waves that occur at 145 and 59 K are formed. A comparison is given between TaS 3 and NbSe 3 . (author)

  20. Camera for coherent diffractive imaging and holography with a soft-x-ray free-electron laser

    International Nuclear Information System (INIS)

    Bajt, Sasa; Chapman, Henry N.; Spiller, Eberhard A.; Alameda, Jennifer B.; Woods, Bruce W.; Frank, Matthias; Bogan, Michael J.; Barty, Anton; Boutet, Sebastien; Marchesini, Stefano; Hau-Riege, Stefan P.; Hajdu, Janos; Shapiro, David

    2008-01-01

    We describe a camera to record coherent scattering patterns with a soft-x-ray free-electron laser (FEL). The camera consists of a laterally graded multilayer mirror, which reflects the diffraction pattern onto a CCD detector. The mirror acts as a bandpass filter for both the wavelength and the angle, which isolates the desired scattering pattern from nonsample scattering or incoherent emission from the sample. The mirror also solves the particular problem of the extreme intensity of the FEL pulses, which are focused to greater than 10 14 W/cm 2 . The strong undiffracted pulse passes through a hole in the mirror and propagates onto a beam dump at a distance behind the instrument rather than interacting with a beam stop placed near the CCD. The camera concept is extendable for the full range of the fundamental wavelength of the free electron laser in Hamburg (FLASH) FEL (i.e., between 6 and 60 nm) and into the water window. We have fabricated and tested various multilayer mirrors for wavelengths of 32, 16, 13.5, and 4.5 nm. At the shorter wavelengths mirror roughness must be minimized to reduce scattering from the mirror. We have recorded over 30,000 diffraction patterns at the FLASH FEL with no observable mirror damage or degradation of performance

  1. Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction.

    Science.gov (United States)

    Sokolowski-Tinten, K; Shen, X; Zheng, Q; Chase, T; Coffee, R; Jerman, M; Li, R K; Ligges, M; Makasyuk, I; Mo, M; Reid, A H; Rethfeld, B; Vecchione, T; Weathersby, S P; Dürr, H A; Wang, X J

    2017-09-01

    We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.

  2. Temperature-induced itinerant-electron metamagnetism in ErCo3 studied by neutron diffraction

    International Nuclear Information System (INIS)

    Gratz, E.; Markosyan, A.S.; Gaidukova, I.Yu.; Rodimin, V.E.; Paul-Boncour, V.; Hoser, A.; Stuesser, N.

    2002-01-01

    Powder neutron diffraction studies in the temperature range from 2 K to 450 K of the ferrimagnetic ErCo 3 compound (T C =401 K) revealed an increase of the unit-cell volume at 100 K (T m ) when cooling down (ΔV/V∼4 x 10 -3 ). This is referred to as a temperature-induced change in the Co sublattice magnetization from a low-magnetic state (T>T m ) to a high-magnetic state (T m ). From the temperature variation of the sublattice magnetization (ErI (3a sites), ErII (6c), CoI (3b), CoII (6c) and CoIII (18h)) it was found that the Co moments at the 6c and 18h sites change near 100 K, giving rise to the volume anomaly at T m . A qualitative discussion of the mechanism behind this phenomenon is given. (orig.)

  3. Critical voltage effects in electron channeling patterns

    International Nuclear Information System (INIS)

    Farrow, R.C.

    1984-01-01

    Electron channeling patterns were used to study critical voltage effects in the metals molybdenum and tungsten. The purpose was to characterize both theoretically and experimentally how a critical voltage will affect the channeling pattern line shapes. The study focused on the second order critical voltage that results from the degeneracy between the Bloch wave states of the (110) and (220) reflections. Theoretical (110) series electron channeling pattern line profiles were calculated using the dynamical theory of Hirsch and Humphreys (1970). A 10 beam dynamical electron diffraction calculation was performed (using complex Fourier lattice potentials) to generate Bloch wave coefficients, excitation amplitudes, and absorption coefficients needed for determining backscattering coefficients and subsequent backscattered electron intensities. The theoretical model is applicable to electron diffraction at all energies since no high energy approximation or perturbation method was used

  4. Electron density distribution in ferromagnetic nickel: A γ -ray diffraction study

    Science.gov (United States)

    Jauch, W.; Reehuis, M.

    2008-12-01

    High-accuracy single-crystal structure factors, complete up to sinθ/λ=1.9Å-1 , have been measured from ferromagnetic nickel at 295 K using 316.5-keV gamma radiation. The experimental uncertainty of the structure factors is of the order of 10 millielectrons per atom for all data. A detailed description of the electron density distribution is presented in terms of a multipolar atomic deformation model. Achievement of a reliable Debye-Waller factor is of vital importance in this context. The charge asphericity is due to an excess eg orbital occupancy of 43.4(2)%. The 3d shell in the metal is contracted by 2.07(5)% relative to the free atom. The results are discussed and compared with earlier experimental and theoretical works. In contrast to bcc Cr and Fe, solid-state effects are less pronounced in fcc Ni. Clear disentanglement between the 3d and 4s valence electrons could be accomplished for the first time. The general expectation that the number of 3d electrons in the metal should be increased as compared to the atom was confirmed in the case of iron by combining spin and charge-density data. In the case of nickel, it is rejected as revealed by the γ -ray data alone. Only with the d8 configuration, consistency is achieved between observed and refined mosaic widths of the sample crystal. A 3d8 configuration implies that the majority-spin d band cannot be full. Strong support is lent to a localized atomic character of the valence electrons.

  5. Non-destructive assessment of the polarity of GaN nanowire ensembles using low-energy electron diffraction and x-ray photoelectron diffraction

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Fernández-Garrido, S.; Jiříček, Petr; Bartoš, Igor; Geelhaar, L.; Brandt, O.; Paskova, T.

    2015-01-01

    Roč. 106, č. 2 (2015), "021602-1"-"021602-4" ISSN 0003-6951 Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaN nanowires * X-ray photoelectron diffraction * LEED I-V * GaN polarity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.142, year: 2015

  6. Simplified models for the Monte Carlo simulation of energy distributions of keV electrons transmitted or back-scattered in various solids

    International Nuclear Information System (INIS)

    Liljequist, D.

    1978-01-01

    Simplified models, based on stopping power, transport mean free path and classical straggling, are shown to give results in rather good agreement with experiment and comparable with the results of more detailed, direct Monte Carlo procedure hitherto constructed. The small effects of features such as large-angle scattering and the interaction between straggling and scattering are studied. A description based on the near linearity of the transport mean free path is used to obtain empirical corrections in some cases of the total transmission and back-scattering simulation and empirical estimates of the (Bethe) range and the transport mean free path. The estimates of the range are consistent with a rough calculation of the effect of large binding energies. (author)

  7. Single-pass high-gain tapered free-electron laser with transverse diffraction in the postsaturation regime

    Directory of Open Access Journals (Sweden)

    Cheng-Ying Tsai

    2018-06-01

    Full Text Available It has been well known that the resonant interaction of an ultrarelativistic electron beam and the radiation field in the single-pass high-gain free electron laser (FEL amplifier leads to the optical gain guiding. The transverse Laplacian term of the slowly varying wave equation in the linear regime can be approximated as a constant detuning parameter, i.e., |∇_{⊥}^{2}|∼k_{R}/z_{R} where k_{R} is the resonant wave number and z_{R} is the Rayleigh range of the laser. In the post-saturation regime, the radiation power begins to oscillate about an equilibrium for the untapered case while continues to grow by undulator tapering. Moreover, in this regime the gain guiding decreases and the simple constant detune is no longer valid. In this paper we study the single-pass high-gain FEL performance in the post-saturation regime with inclusion of diffraction effect and undulator tapering. Our analysis relies upon two constants of motion, one from the energy conservation and the other from the adiabatic invariant of the action variable. By constructing a two-dimensional axisymmetric wave equation and the coupled one-dimensional electron dynamical equations, the performance of a tapered FEL in the postsaturation regime can be analyzed, including the fundamental mode profile, the power efficiency and the scaled energy spread. We begin the analytical investigation with two different axisymmetric electron beam profiles, the uniform and bounded parabolic ones. It is found that the tapered FEL power efficiency can be smaller but close to the taper ratio provided the resonant phase remains constant and the beam-wave is properly matched. Such a tapered efficiency is nearly independent of transverse electron beam size before significant electron detrapping occurs. This is essentially different from the untapered case, where the power extraction efficiency is around the essential FEL gain bandwidth (or ρ, the Pierce or FEL parameter and depends on the beam

  8. Ultrafast Coherent Diffraction Imaging with X-ray Free-Electron Lasers

    International Nuclear Information System (INIS)

    Chapman, H N; Bajt, S; Barty, A; Benner, W; Bogan, M; Frank, M; Hau-Riege, S; London, R; Marchesini, S; Spiller, E; Szoke, A; Woods, B; Boutet, S; Hodgson, K; Hajdu, J; Bergh, M; Burmeister, F; Caleman, C; Huldt, G; Maia, F; Seibert, M M; der Spoel, D v

    2006-01-01

    The ultrafast pulses from X-ray free-electron lasers will enable imaging of non-periodic objects at near-atomic resolution [1, Neutze]. These objects could include single molecules, protein complexes, or virus particles. The specimen would be completely destroyed by the pulse in a Coulomb explosion, but that destruction will only happen after the pulse. The scattering from the sample will give structural information about the undamaged object. There are many technical challenges that must be addressed before carrying out such experiments at an XFEL, which we are doing so with experiments at FLASH, the soft-X-ray FEL at DESY

  9. Holography and coherent diffraction with low-energy electrons: A route towards structural biology at the single molecule level.

    Science.gov (United States)

    Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2015-12-01

    The current state of the art in structural biology is led by NMR, X-ray crystallography and TEM investigations. These powerful tools however all rely on averaging over a large ensemble of molecules. Here, we present an alternative concept aiming at structural analysis at the single molecule level. We show that by combining electron holography and coherent diffraction imaging estimations concerning the phase of the scattered wave become needless as the phase information is extracted from the data directly and unambiguously. Performed with low-energy electrons the resolution of this lens-less microscope is just limited by the De Broglie wavelength of the electron wave and the numerical aperture, given by detector geometry. In imaging freestanding graphene, a resolution of 2Å has been achieved revealing the 660.000 unit cells of the graphene sheet from a single data set. Once applied to individual biomolecules the method shall ultimately allow for non-destructive imaging and imports the potential to distinguish between different conformations of proteins with atomic resolution. Copyright © 2015. Published by Elsevier B.V.

  10. The molecular structure of 4-methylpyridine-N-oxide: Gas-phase electron diffraction and quantum chemical calculations

    Science.gov (United States)

    Belova, Natalya V.; Girichev, Georgiy V.; Kotova, Vitaliya E.; Korolkova, Kseniya A.; Trang, Nguyen Hoang

    2018-03-01

    The molecular structure of 4-methylpiridine-N-oxide, 4-MePyO, has been studied by gas-phase electron diffraction monitored by mass spectrometry (GED/MS) and quantum chemical (DFT) calculations. Both, quantum chemistry and GED analyses resulted in CS molecular symmetry with the planar pyridine ring. Obtained molecular parameters confirm the hyperconjugation in the pyridine ring and the sp2 hybridization concept of the nitrogen and carbon atoms in the ring. The experimental geometric parameters are in a good agreement with the parameters for non-substituted N-oxide and reproduced very closely by DFT calculations. The presence of the electron-donating CH3 substituent in 4-MePyO leads to a decrease of the ipso-angle and to an increase of r(N→O) in comparison with the non-substituted PyO. Electron density distribution analysis has been performed in terms of natural bond orbitals (NBO) scheme. The nature of the semipolar N→O bond is discussed.

  11. Atmospheric deterioration of clean surface of epitaxial (001)-YBaCuO films studied by low-energy electron diffraction

    International Nuclear Information System (INIS)

    Ohara, Tomoyuki; Sakuta, Ken; Kamishiro, Makio; Kobayashi, Takeshi

    1991-01-01

    The effects of gas exposure on the clean surface of the epitaxial YBaCuO thin films were closely investigated using the low-energy electron diffraction (LEED) method. The clean surface was obtained by in-vacuum annealing at 500degC. Once the clean surface was exposed to air, even at room temperature, the LEED spots disappeared or sometimes became faint. To ensure the degradation mechanism of the YBaCuO clean surface, the specimens were exposed to pure O 2 and N 2 gases separately and measured by LEED. As a result, it was found that O 2 is very safe but N 2 serves as a poisonous gas for the YBaCuO clean surface. (author)

  12. X-ray diffraction and electron microscopy data for amyloid formation of Aβ40 and Aβ42

    Directory of Open Access Journals (Sweden)

    Olga M. Selivanova

    2016-09-01

    Full Text Available The data presented in this article are related to the research article entitled “One of the possible mechanisms of amyloid fibrils formation based on the sizes of primary and secondary folding nuclei of Aβ40 and Aβ42” (Dovidchenko et al., 2016 [1]. Aβ peptide is one of the most intensively studied amyloidogenic peptides. Despite the huge number of articles devoted to studying different fragments of Aβ peptide there are only several papers with correct kinetics data, also there are a few papers with X-ray data, especially for Aβ42. Our data present X-ray diffraction patterns both for Aβ40 and Aβ42 as well for Tris–HCl and wax. Moreover, our data provide kinetics of amyloid formation by recombinant Аβ40 and synthetic Аβ42 peptides by using electron microscopy.

  13. Photoelectron diffraction from single oriented molecules: Towards ultrafast structure determination of molecules using x-ray free-electron lasers

    Science.gov (United States)

    Kazama, Misato; Fujikawa, Takashi; Kishimoto, Naoki; Mizuno, Tomoya; Adachi, Jun-ichi; Yagishita, Akira

    2013-06-01

    We provide a molecular structure determination method, based on multiple-scattering x-ray photoelectron diffraction (XPD) calculations. This method is applied to our XPD data on several molecules having different equilibrium geometries. Then it is confirmed that, by our method, bond lengths and bond angles can be determined with a resolution of less than 0.1 Å and 10∘, respectively. Differently from any other scenario of ultrafast structure determination, we measure the two- or three-dimensional XPD of aligned or oriented molecules in the energy range from 100 to 200 eV with a 4π detection velocity map imaging spectrometer. Thanks to the intense and ultrashort pulse properties of x-ray free-electron lasers, our approach exhibits the most probable method for obtaining ultrafast real-time structural information on small to medium-sized molecules consisting of light elements, i.e., a “molecular movie.”

  14. Simple convergent-nozzle aerosol injector for single-particle diffractive imaging with X-ray free-electron lasers

    Directory of Open Access Journals (Sweden)

    R. A. Kirian

    2015-07-01

    Full Text Available A major challenge in high-resolution x-ray free-electron laser-based coherent diffractive imaging is the development of aerosol injectors that can efficiently deliver particles to the peak intensity of the focused X-ray beam. Here, we consider the use of a simple convergent-orifice nozzle for producing tightly focused beams of particles. Through optical imaging we show that 0.5 μm particles can be focused to a full-width at half maximum diameter of 4.2 μm, and we demonstrate the use of such a nozzle for injecting viruses into a micro-focused soft-X-ray FEL beam.

  15. Convergent-beam electron diffraction study of incommensurately modulated crystals. Pt. 2. (3 + 1)-dimensional space groups

    International Nuclear Information System (INIS)

    Terauchi, Masami; Takahashi, Mariko; Tanaka, Michiyoshi

    1994-01-01

    The convergent-beam electron diffraction (CBED) method for determining three-dimensional space groups is extended to the determination of the (3 + 1)-dimensional space groups for one-dimensional incommensurately modulated crystals. It is clarified than an approximate dynamical extinction line appears in the CBED discs of the reflections caused by an incommensurate modulation. The extinction enables the space-group determination of the (3 + 1)-dimensional crystals or the one-dimensional incommensurately modulated crystals. An example of the dynamical extinction line is shown using an incommensurately modulated crystal of Sr 2 Nb 2 O 7 . Tables of the dynamical extinction lines appearing in CBED patterns are given for all the (3 + 1)-dimensional space groups of the incommensurately modulated crystal. (orig.)

  16. Characterization of x-ray diffraction and electron spin resonance: Effects of sintering time and temperature on bovine hydroxyapatite

    International Nuclear Information System (INIS)

    Kusrini, Eny; Sontang, Muhammad

    2012-01-01

    The physical and chemical properties of a hydroxyapatite produced by the sintering of bovine bone were investigated by powder x-ray diffraction (PXRD), electron spin resonance (ESR), energy dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and differential thermal analysis (DTA). A bovine bone powder was sintered at different temperatures ranging from 500 to 1400 °C. The influences of post-irradiation storage on the radiation ESR response of the bovine bone powder before and after sintering were also studied. The results indicate that the sintered bovine bone powder contained hydroxyapatite. Diffraction patterns were sharp and clear based on the (211), (300), and (202) reflections corresponding to bovine hydroxyapatite (BHA), which confirmed the phase purity and high crystalline grade of the BHA produced. The PXRD profile of BHA was dependent on sintering temperatures and times. The molecular formula of BHA was determined by Rietveld analysis showed a similar structure and composition to calcium hydroxyapatite in hexagonal P6 3 /m space group a=b=9.435 Å and c=6.895 Å. ESR data showed that the sintering process can decrease the number of free radicals in BHA; it also revealed that the number of free radicals is constant during long storage periods (75 days). The sintering technique described in this study may be used to extract hydroxyapatite from biowaste bovine bone, leading to its application as a bone filler. - Highlights: ► Natural hydroxyapatite was produced from the bio-wasting bovine bones by sintering method. ► PXRD profile of BHA is dependent on the different temperatures and times in sintering process. ► ESR data is useful to study the typical of free radicals formed in the samples after irradiation. ► Stability and physicochemical properties of BHA is dependent on the different storage times. ► Technique is able to be used to find the natural hydroxyapatite applicable for bone filler.

  17. Spot profile analysis and lifetime mapping in ultrafast electron diffraction: Lattice excitation of self-organized Ge nanostructures on Si(001

    Directory of Open Access Journals (Sweden)

    T. Frigge

    2015-05-01

    Full Text Available Ultrafast high energy electron diffraction in reflection geometry is employed to study the structural dynamics of self-organized Germanium hut-, dome-, and relaxed clusters on Si(001 upon femtosecond laser excitation. Utilizing the difference in size and strain state the response of hut- and dome clusters can be distinguished by a transient spot profile analysis. Surface diffraction from {105}-type facets provide exclusive information on hut clusters. A pixel-by-pixel analysis of the dynamics of the entire diffraction pattern gives time constants of 40, 160, and 390 ps, which are assigned to the cooling time constants for hut-, dome-, and relaxed clusters.

  18. Structure determination of disordered organic molecules on surfaces from the Bragg spots of low-energy electron diffraction and total energy calculations

    International Nuclear Information System (INIS)

    Poon, H.C.; Weinert, M.; Saldin, D.K.; Stacchiola, D.; Zheng, T.; Tysoe, W.T.

    2004-01-01

    We show that an analysis of the intensity versus energy variation of Bragg spots due to low-energy electron diffraction from a disordered overlayer of molecules on a crystal surface allows a much more convenient method of determining the local adsorption geometries of such molecules than previously analyzed weak diffuse diffraction patterns. For the case of methanol on Pd(111), we show that the geometry determined by this means from experimental diffraction data is in excellent agreement with the predictions of density functional total energy calculations

  19. Phasing of the Triatoma virus diffraction data using a cryo-electron microscopy reconstruction

    International Nuclear Information System (INIS)

    Estrozi, L.F.; Neumann, E.; Squires, G.; Rozas-Dennis, G.; Costabel, M.; Rey, F.A.; Guerin, D.M.A.; Navaza, J.

    2008-01-01

    The blood-sucking reduviid bug Triatoma infestans, one of the most important vector of American human trypanosomiasis (Chagas disease) is infected by the Triatoma virus (TrV). TrV has been classified as a member of the Cripavirus genus (type cricket paralysis virus) in the Dicistroviridae family. This work presents the three-dimensional cryo-electron microscopy (cryo-EM) reconstruction of the TrV capsid at about 25 A resolution and its use as a template for phasing the available crystallographic data by the molecular replacement method. The main structural differences between the cryo-EM reconstruction of TrV and other two viruses, one from the same family, the cricket paralysis virus (CrPV) and the human rhinovirus 16 from the Picornaviridae family are presented and discussed

  20. Direct detection of near-surface faults by migration of back-scattered surface waves

    KAUST Repository

    Yu, Han; Guo, Bowen; Hanafy, Sherif; Lin, Fan-Chi; Schuster, Gerard T.

    2014-01-01

    We show that diffraction stack migration can be used to estimate the distribution of near-surface faults. The assumption is that near-surface faults generate detectable back-scattered surface waves from impinging surface waves. The processing steps

  1. Angular correlations of photons from solution diffraction at a free-electron laser encode molecular structure

    International Nuclear Information System (INIS)

    Mendez, Derek; Watkins, Herschel; Qiao, Shenglan; Raines, Kevin S.; Lane, Thomas J.

    2016-01-01

    During X-ray exposure of a molecular solution, photons scattered from the same molecule are correlated. If molecular motion is insignificant during exposure, then differences in momentum transfer between correlated photons are direct measurements of the molecular structure. In conventional small- and wide-angle solution scattering, photon correlations are ignored. This report presents advances in a new biomolecular structural analysis technique, correlated X-ray scattering (CXS), which uses angular intensity correlations to recover hidden structural details from molecules in solution. Due to its intense rapid pulses, an X-ray free electron laser (XFEL) is an excellent tool for CXS experiments. A protocol is outlined for analysis of a CXS data set comprising a total of half a million X-ray exposures of solutions of small gold nanoparticles recorded at the Spring-8 Ångström Compact XFEL facility (SACLA). From the scattered intensities and their correlations, two populations of nanoparticle domains within the solution are distinguished: small twinned, and large probably non-twinned domains. Finally, it is shown analytically how, in a solution measurement, twinning information is only accessible via intensity correlations, demonstrating how CXS reveals atomic-level information from a disordered solution of like molecules.

  2. Determination of the Projected Atomic Potential by Deconvolution of the Auto-Correlation Function of TEM Electron Nano-Diffraction Patterns

    Directory of Open Access Journals (Sweden)

    Liberato De Caro

    2016-11-01

    Full Text Available We present a novel method to determine the projected atomic potential of a specimen directly from transmission electron microscopy coherent electron nano-diffraction patterns, overcoming common limitations encountered so far due to the dynamical nature of electron-matter interaction. The projected potential is obtained by deconvolution of the inverse Fourier transform of experimental diffraction patterns rescaled in intensity by using theoretical values of the kinematical atomic scattering factors. This novelty enables the compensation of dynamical effects typical of transmission electron microscopy (TEM experiments on standard specimens with thicknesses up to a few tens of nm. The projected atomic potentials so obtained are averaged on sample regions illuminated by nano-sized electron probes and are in good quantitative agreement with theoretical expectations. Contrary to lens-based microscopy, here the spatial resolution in the retrieved projected atomic potential profiles is related to the finer lattice spacing measured in the electron diffraction pattern. The method has been successfully applied to experimental nano-diffraction data of crystalline centrosymmetric and non-centrosymmetric specimens achieving a resolution of 65 pm.

  3. Standards for backscattering analysis

    International Nuclear Information System (INIS)

    Mitchell, I.V.; Eschbach, H.L.

    1978-01-01

    The need for backscattering standards appears to be twofold and depends on the uses and requirements of the users. The first is as a calibrated reference by which samples of a similar nature to the standard may be absolutely compared. The second is as a means of intercomparing the relative results obtained by different laboratories using, as near as possible, identical samples. This type of comparison is of a relative nature and the absolute values are not necessarily required. In the present work the authors try to satisfy both needs by providing identical samples which have been absolutely calibrated to a high accuracy. Very thin copper and vanadium layers were evaporated onto bismuth implanted silicon crystals and on glass plates under carefully controlled conditions. The mass of the deposits was determined in situ using a sensitive UHV microbalance. In addition, two quartz oscillator monitors were used. The samples have been analysed by Rutherford backscattering and the absolute quantity of bismuth determined by a comparison with the known amounts of deposited material. (Auth.)

  4. Burgers Vector Analysis of Vertical Dislocations in Ge Crystals by Large-Angle Convergent Beam Electron Diffraction.

    Science.gov (United States)

    Groiss, Heiko; Glaser, Martin; Marzegalli, Anna; Isa, Fabio; Isella, Giovanni; Miglio, Leo; Schäffler, Friedrich

    2015-06-01

    By transmission electron microscopy with extended Burgers vector analyses, we demonstrate the edge and screw character of vertical dislocations (VDs) in novel SiGe heterostructures. The investigated pillar-shaped Ge epilayers on prepatterned Si(001) substrates are an attempt to avoid the high defect densities of lattice mismatched heteroepitaxy. The Ge pillars are almost completely strain-relaxed and essentially defect-free, except for the rather unexpected VDs. We investigated both pillar-shaped and unstructured Ge epilayers grown either by molecular beam epitaxy or by chemical vapor deposition to derive a general picture of the underlying dislocation mechanisms. For the Burgers vector analysis we used a combination of dark field imaging and large-angle convergent beam electron diffraction (LACBED). With LACBED simulations we identify ideally suited zeroth and second order Laue zone Bragg lines for an unambiguous determination of the three-dimensional Burgers vectors. By analyzing dislocation reactions we confirm the origin of the observed types of VDs, which can be efficiently distinguished by LACBED. The screw type VDs are formed by a reaction of perfect 60° dislocations, whereas the edge types are sessile dislocations that can be formed by cross-slips and climbing processes. The understanding of these origins allows us to suggest strategies to avoid VDs.

  5. Puzzling Intergrowth in Cerium Nitridophosphate Unraveled by Joint Venture of Aberration-Corrected Scanning Transmission Electron Microscopy and Synchrotron Diffraction.

    Science.gov (United States)

    Kloß, Simon D; Neudert, Lukas; Döblinger, Markus; Nentwig, Markus; Oeckler, Oliver; Schnick, Wolfgang

    2017-09-13

    Thorough investigation of nitridophosphates has rapidly accelerated through development of new synthesis strategies. Here we used the recently developed high-pressure metathesis to prepare the first rare-earth metal nitridophosphate, Ce 4 Li 3 P 18 N 35 , with a high degree of condensation >1/2. Ce 4 Li 3 P 18 N 35 consists of an unprecedented hexagonal framework of PN 4 tetrahedra and exhibits blue luminescence peaking at 455 nm. Transmission electron microscopy (TEM) revealed two intergrown domains with slight structural and compositional variations. One domain type shows extremely weak superstructure phenomena revealed by atomic-resolution scanning TEM (STEM) and single-crystal diffraction using synchrotron radiation. The corresponding superstructure involves a modulated displacement of Ce atoms in channels of tetrahedra 6-rings. The displacement model was refined in a supercell as well as in an equivalent commensurate (3 + 2)-dimensional description in superspace group P6 3 (α, β, 0)0(-α - β, α, 0)0. In the second domain type, STEM revealed disordered vacancies of the same Ce atoms that were modulated in the first domain type, leading to sum formula Ce 4-0.5x Li 3 P 18 N 35-1.5x O 1.5x (x ≈ 0.72) of the average structure. The examination of these structural intricacies may indicate the detection limit of synchrotron diffraction and TEM. We discuss the occurrence of either Ce displacements or Ce vacancies that induce the incorporation of O as necessary stabilization of the crystal structure.

  6. On the Use of Dynamical Diffraction Theory To Refine Crystal Structure from Electron Diffraction Data: Application to KLa5O5(VO4)2, a Material with Promising Luminescent Properties.

    Science.gov (United States)

    Colmont, Marie; Palatinus, Lukas; Huvé, Marielle; Kabbour, Houria; Saitzek, Sébastien; Djelal, Nora; Roussel, Pascal

    2016-03-07

    A new lanthanum oxide, KLa5O5(VO4)2, was synthesized using a flux growth technique that involved solid-state reaction under an air atmosphere at 900 °C. The crystal structure was solved and refined using an innovative approach recently established and based on three-dimensional (3D) electron diffraction data, using precession of the electron beam and then validated against Rietveld refinement and denisty functional theory (DFT) calculations. It crystallizes in a monoclinic unit cell with space group C2/m and has unit cell parameters of a = 20.2282(14) Å, b = 5.8639(4) Å, c = 12.6060(9) Å, and β = 117.64(1)°. Its structure is built on Cresnel-like two-dimensional (2D) units (La5O5) of 4*3 (OLa4) tetrahedra, which run parallel to (001) plane, being surrounded by isolated VO4 tetrahedra. Four isolated vanadate groups create channels that host K(+) ions. Substitution of K(+) cations by another alkali metal is possible, going from lithium to rubidium. Li substitution led to a similar phase with a primitive monoclinic unit cell. A complementary selected area electron diffraction (SAED) study highlighted diffuse streaks associated with stacking faults observed on high-resolution electron microscopy (HREM) images of the lithium compound. Finally, preliminary catalytic tests for ethanol oxidation are reported, as well as luminescence evidence. This paper also describes how solid-state chemists can take advantages of recent progresses in electron crystallography, assisted by DFT calculations and powder X-ray diffraction (PXRD) refinements, to propose new structural types with potential applications to the physicist community.

  7. X-ray diffraction, XAFS and scanning electron microscopy study of otolith of a crevalle jack fish (caranx hippos)

    Energy Technology Data Exchange (ETDEWEB)

    Pattanaik, Sidhartha [Bailey Hall 703, Illinois Institute of Technology, 3101 S. Wabash Avenue, Chicago, IL 60616 (United States)]. E-mail: sidpattanaik@yahoo.com

    2005-04-01

    The otolith of a crevalle jack fish (caranx hippos) has been investigated by means of X-ray diffraction, X-ray absorption fine structure spectroscopy and scanning electron microscopy techniques. The results suggest that the biomineralization of otolith occurs predominantly in the aragonite phase. A detailed X-ray Rietveld analysis showed that the first shell Ca-O distances in otolith lay in the range 2.371-2.652 A, with each calcium atom coordinated to 9 oxygen atoms. While the average Ca-O distance remains same in both otolith and aragonite, certain Ca-O distances in otolith differ markedly from those in aragonite. Such difference reflects the remarkable degree of control that the protein matrix exercised over packing of calcium and carbonate ions to promote growth of rarer aragonite otolith. In view of the complex coordination chemistry of calcium in otoliths, the EXAFS analysis was limited to obtaining local atomic environment about calcium up to the first Ca-O shell. EXAFS data showed an asymmetric distribution of Ca-O bond distances with the centroid of distribution at 2.48 A, which is closer to the average Ca-O distance in aragonite than in calcite. The asymmetry in the Ca-O peak is consistent with an apparent departure of Ca-O distances from a near regular distribution, as expected of an aragonite otolith.

  8. X-ray diffraction, XAFS and scanning electron microscopy study of otolith of a crevalle jack fish (caranx hippos)

    International Nuclear Information System (INIS)

    Pattanaik, Sidhartha

    2005-01-01

    The otolith of a crevalle jack fish (caranx hippos) has been investigated by means of X-ray diffraction, X-ray absorption fine structure spectroscopy and scanning electron microscopy techniques. The results suggest that the biomineralization of otolith occurs predominantly in the aragonite phase. A detailed X-ray Rietveld analysis showed that the first shell Ca-O distances in otolith lay in the range 2.371-2.652 A, with each calcium atom coordinated to 9 oxygen atoms. While the average Ca-O distance remains same in both otolith and aragonite, certain Ca-O distances in otolith differ markedly from those in aragonite. Such difference reflects the remarkable degree of control that the protein matrix exercised over packing of calcium and carbonate ions to promote growth of rarer aragonite otolith. In view of the complex coordination chemistry of calcium in otoliths, the EXAFS analysis was limited to obtaining local atomic environment about calcium up to the first Ca-O shell. EXAFS data showed an asymmetric distribution of Ca-O bond distances with the centroid of distribution at 2.48 A, which is closer to the average Ca-O distance in aragonite than in calcite. The asymmetry in the Ca-O peak is consistent with an apparent departure of Ca-O distances from a near regular distribution, as expected of an aragonite otolith

  9. The architecture of amyloid-like peptide fibrils revealed by X-ray scattering, diffraction and electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Langkilde, Annette E., E-mail: annette.langkilde@sund.ku.dk [University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen (Denmark); Morris, Kyle L.; Serpell, Louise C. [University of Sussex, Falmer, Brighton (United Kingdom); Svergun, Dmitri I. [European Molecular Biology Laboratory, Hamburg Outstation, 22607 Hamburg (Germany); Vestergaard, Bente [University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen (Denmark)

    2015-04-01

    The aggregation process and the fibril state of an amyloidogenic peptide suggest monomer addition to be the prevailing mechanism of elongation and a model of the peptide packing in the fibrils has been obtained. Structural analysis of protein fibrillation is inherently challenging. Given the crucial role of fibrils in amyloid diseases, method advancement is urgently needed. A hybrid modelling approach is presented enabling detailed analysis of a highly ordered and hierarchically organized fibril of the GNNQQNY peptide fragment of a yeast prion protein. Data from small-angle X-ray solution scattering, fibre diffraction and electron microscopy are combined with existing high-resolution X-ray crystallographic structures to investigate the fibrillation process and the hierarchical fibril structure of the peptide fragment. The elongation of these fibrils proceeds without the accumulation of any detectable amount of intermediate oligomeric species, as is otherwise reported for, for example, glucagon, insulin and α-synuclein. Ribbons constituted of linearly arranged protofilaments are formed. An additional hierarchical layer is generated via the pairing of ribbons during fibril maturation. Based on the complementary data, a quasi-atomic resolution model of the protofilament peptide arrangement is suggested. The peptide structure appears in a β-sheet arrangement reminiscent of the β-zipper structures evident from high-resolution crystal structures, with specific differences in the relative peptide orientation. The complexity of protein fibrillation and structure emphasizes the need to use multiple complementary methods.

  10. Atomic structure of Mg-based metallic glass investigated with neutron diffraction, reverse Monte Carlo modeling and electron microscopy

    Directory of Open Access Journals (Sweden)

    Rafał Babilas

    2017-05-01

    Full Text Available The structure of a multicomponent metallic glass, Mg65Cu20Y10Ni5, was investigated by the combined methods of neutron diffraction (ND, reverse Monte Carlo modeling (RMC and high-resolution transmission electron microscopy (HRTEM. The RMC method, based on the results of ND measurements, was used to develop a realistic structure model of a quaternary alloy in a glassy state. The calculated model consists of a random packing structure of atoms in which some ordered regions can be indicated. The amorphous structure was also described by peak values of partial pair correlation functions and coordination numbers, which illustrated some types of cluster packing. The N = 9 clusters correspond to the tri-capped trigonal prisms, which are one of Bernal’s canonical clusters, and atomic clusters with N = 6 and N = 12 are suitable for octahedral and icosahedral atomic configurations. The nanocrystalline character of the alloy after annealing was also studied by HRTEM. The selected HRTEM images of the nanocrystalline regions were also processed by inverse Fourier transform analysis. The high-angle annular dark-field (HAADF technique was used to determine phase separation in the studied glass after heat treatment. The HAADF mode allows for the observation of randomly distributed, dark contrast regions of about 4–6 nm. The interplanar spacing identified for the orthorhombic Mg2Cu crystalline phase is similar to the value of the first coordination shell radius from the short-range order.

  11. 1D chain formation by coadsorption of Pb and Bi on Cu(001): Determination using low energy electron diffraction

    Science.gov (United States)

    Kabiruzzaman, Md; Ahmed, Rezwan; Nakagawa, Takeshi; Mizuno, Seigi

    2017-10-01

    Coadsorption of two heavy metals, Pb and Bi, on Cu(001) at room temperature has been studied using low energy electron diffraction (LEED). c(4 × 4), c(2 × 2), and c(9√{ 2}×√{ 2}) phases are obtained at different coverages; here, we have determined the best-fit structure of c(4 × 4) phase. This structure can be described as a 1D substitutional chain arrangement of Pb and Bi atoms between the Cu rows along the [110] direction. The unit cell in the two-dimensional (2D) surface consists of one Bi atom, two Pb atoms, and four Cu atoms with one vacancy at the center. The optimal structure parameters demonstrate that Bi atoms are located at fourfold-hollow sites and that Pb atoms are laterally displaced by 0.78 Å from the fourfold-hollow site toward the vacancy. The reasons for the formation of the c(4 × 4) structure upon deposition of Pb and Bi on Cu(001) are discussed in comparison with a similar structure formed by the individual adsorption of Pb on the same substrate.

  12. Surface segregation of InGaAs films by the evolution of reflection high-energy electron diffraction patterns

    International Nuclear Information System (INIS)

    Zhou Xun; Luo Zi-Jiang; Guo Xiang; Zhang Bi-Chan; Shang Lin-Tao; Zhou Qing; Deng Chao-Yong; Ding Zhao

    2012-01-01

    Surface segregation is studied via the evolution of reflection high-energy electron diffraction (RHEED) patterns under different values of As 4 BEP for InGaAs films. When the As 4 BEP is set to be zero, the RHEED pattern keeps a 4×3/(n × 3) structure with increasing temperature, and surface segregation takes place until 470 °C. The RHEED pattern develops into a metal-rich (4 × 2) structure as temperature increases to 495 °C. The reason for this is that surface segregation makes the In inside the InGaAs film climb to its surface. With the temperature increasing up to 515 °C, the RHEED pattern turns into a GaAs(2 × 4) structure due to In desorption. While the As 4 BEP comes up to a specific value (1.33 × 10 -4 Pa−1.33 × 10 -3 Pa), the surface temperature can delay the segregation and desorption. We find that As 4 BEP has a big influence on surface desorption, while surface segregation is more strongly dependent on temperature than surface desorption. (condensed matter: structural, mechanical, and thermal properties)

  13. Reciprocity in electron diffraction

    International Nuclear Information System (INIS)

    Gunning, J.; Goodman, P.

    1991-01-01

    The symmetry of reciprocity is reviewed in the context of relativistic quantum mechanics with the specific aim of relating to P-C-T invariances. From this investigation global time reversal is found to be sufficient condition for reciprocity to hold in scattering from a vector potential. Elastic scattering is assumed. The paper also deals exclusively with the scattering of a charged particle by an electromagnetic field. The present proof is free from assumptions of small angle scattering and from restrictions on z-dependent terms in the scattering equation, and by avoiding S-matrix theory is thought to be accessible to undergraduate teaching. 9 refs., 1 tab., 1 fig

  14. Reciprocity in electron diffraction

    International Nuclear Information System (INIS)

    Gunning, J.; Goodman, P.

    1992-01-01

    The symmetry of reciprocity is reviewed in the context of relativistic quantum mechanics with the specific aim of relating to C, P and T invariances. From this investigation global time reversal is found to be a sufficient condition for reciprocity to hold in scattering from a vector potential. The present proof is free from assumptions of small-angle scattering and from restrictions on z-dependent terms in the scattering equation, and by avoiding S-matrix theory is thought to be accessible to undergraduate teaching. (orig.)

  15. In situ observation of low temperature growth of Ge on Si(1 1 1) by reflection high energy electron diffraction

    International Nuclear Information System (INIS)

    Grimm, Andreas; Fissel, Andreas; Bugiel, Eberhard; Wietler, Tobias F.

    2016-01-01

    Highlights: • Investigation of the initial stages of epitaxial growth of Ge on Si(1 1 1) in situ by RHEED. • Impact of growth temperature on strain evolution for temperatures between 200 °C and 400 °C. • Epitaxy with a high degree of structural perfection already at growth temperature of 200 °C. • Ordered interfacial dislocation networks already at 200 °C. • Tensile strain contribution of Si(1 1 1) 7 × 7-surface reconstruction to strain relaxation process for epitaxial growth of Ge. - Abstract: In this paper we investigate the initial stages of epitaxial growth of Ge on Si(1 1 1) and the impact of growth temperature on strain evolution in situ by reflection high energy electron diffraction (RHEED) for temperatures between 200 °C and 400 °C. The change in surface morphology from a flat wetting layer to subsequent islanding that is characteristic for Stranski–Krastanov growth is monitored by spot intensity analysis. The corresponding critical layer thickness is determined to 3.1 < d c < 3.4 ML. In situ monitoring of the strain relaxation process reveals a contribution of the Si(1 1 1) 7 × 7-surface reconstruction to the strain relaxation process. High resolution transmission electron microscopy confirms that the Ge islands exhibit a high degree of structural perfection and an ordered interfacial misfit dislocation network already at a growth temperature of 200 °C is established. The temperature dependency of island shape, density and height is characterized by atomic force microscopy and compared to the RHEED investigations.

  16. Electron diffraction and high-resolution transmission electron microscopy of the high temperature crystal structures of GexSb2Te3+x (x=1,2,3) phase change material

    NARCIS (Netherlands)

    Kooi, B.J.; de Hosson, J.T.M.

    2002-01-01

    The crystal structures of GeSb2Te4, Ge2Sb2Te5, and Ge3Sb2Te6 were determined using electron diffraction and high-resolution transmission electron microscopy. The structure determined for the former two crystals deviates from the ones proposed in the literature. These crystal structures were

  17. Geometrical and electronic structure of LaI3 molecule as determined by gas electron diffraction and quantum-chemical calculations

    International Nuclear Information System (INIS)

    Giricheva, N.I.; Shlykov, S.A.; Girichev, G.V.; Galanin, I.E.

    2006-01-01

    The saturated vapor over LaI 3 has been studied using the electron diffraction method with mass-spectral monitoring. It was determined that at a temperature 1142(10) K, along with monomer molecules, dimers are present in the vapor in the quantity of 0.7 mol.%. Effective configuration parameters of LaI 3 molecule were obtained: r g (La-I)=2.961(6) A, g (I-La-I)=116.5(9) deg, l(La-I)=0.106(1) A and l(I...I)=0.412(7) A. A small deviation of the valence angle g (I-La-I) from 120 deg can be totally caused by a contraction effect of the distance r g (I...I) of LaI 3 molecule with planar equilibrium configuration. The electronic structure of LaI 3 molecule was examined by the B3LYP/SDD method. In terms of the NBO-analysis, the participation of lanthanum 4f-AO in bonding orbitals La-I is noted. It is shown that the NBO-analysis describes the bond La-I in LaI 3 molecule as predominantly ionic one with a noticeable covalence component. The energy of the heterolytic bond breakage E(La-I) het =1216 kJ/mole was calculated [ru

  18. Applications of anomalous diffraction systems, generation of attosecond electron and photon pulses and Raman amplification by stimulated emission of radiation

    Science.gov (United States)

    Vartak, Sameer Dinkar

    1998-10-01

    Anomalous diffraction is scattering process due to phase distortion introduced on incident phase front by scattering object. Phase mask or hologram, Christiansen filter, PDLC are examples of an anomalously diffracting systems. Phase hologram modulates an input wavefront to produce a wavefront which when Fourier transformed using a converging lens gives desired image on to a screen. We made a nonlinear optical element using phase mask made up of nonlinear material. It forms a lens because of nonlinear index of refraction when a high intensity beam is incident. This lens Fourier transforms the phase mask and images the phase mask. This nonlinear optical element can be used for various applications like image gating and 3-D memory writing and read out. Christiansen filter (CF) is a two component scattering system whose dispersion curves intersect at certain wavelength. Thus light corresponding to this wavelength traverses the filter without any scattering and light at other wavelengths gets scattered. This results in narrow wavelength dependent transmission curve centered at the index matching wavelength. When materials with an intensity dependent refractive index are used to make a CF, the index matching condition of CF becomes function of the input intensity resulting in intensity dependent beam size and transmittance through the filter. This property of nonlinear CF can be used to switch beam optically in both self and cross-modulation modes. Polymer Dispersed Liquid Crystal (PDLC) is dispersion of liquid crystal droplets in polymer whose index of refraction is same as ordinary refractive index of liquid crystal. PDLC shows voltage dependent scattering and are used in flat panel displays. We used this element as voltage controlled intracavity loss element in a laser cavity to make a lasing pixel projection display. Output of this pixel shows all desired properties for a projection display like narrow linewidth, high brightness, TTL switching compatibility and

  19. Splitting diffraction peak in different thickness LL-interferometer and determination of thickness of damaged layer induced by electron irradiation of plates

    International Nuclear Information System (INIS)

    Truni, K.G.; Sedrakyan, A.G.; Papoyan, A.A.; Bezirganyan, P.A.

    1988-01-01

    Amplitude of twice reflected beam is calculated analytically, oscillatory dependence of peak intensity in the centre of diffraction image on the small variations in thickness is shown. The expression, clearly binding the splitting value of diffraction peak with variation in thickness of the interferometer plates, is received. The effect of variation in thickness on the splitting value of focal line is studied experimentally in case of irradiation of the equal-arm Π-shaped interferometer blocks by fast electron flow, thickness of the originated damaged layers are determined

  20. Crystal structure of the martensite phase in the ferromagnetic shape memory compound Ni2MnGa studied by electron diffraction

    International Nuclear Information System (INIS)

    Fukuda, Takashi; Kushida, Hiroaki; Todai, Mitsuharu; Kakeshita, Tomoyuki; Mori, Hirotaro

    2009-01-01

    The electron diffraction patterns of Ni 2 MnGa show six satellites at ±q M , ±2q M and ±3q M , with q M = 0.427(5) g 22 -bar 0 between fundamental reflections in the martensite phase, and two satellites at ±q I , with q I = 0.340(5) g 22 -bar 0 in the intermediate phase, meaning that these phases have incommensurate structures. In addition, the diffraction pattern of the intermediate phase continuously changes to that of the parent phase via the X-phase, suggesting the existence of a multicritical phenomenon.

  1. Compton backscattered collmated X-ray source

    Science.gov (United States)

    Ruth, Ronald D.; Huang, Zhirong

    2000-01-01

    A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

  2. Compton backscattered collimated x-ray source

    Science.gov (United States)

    Ruth, R.D.; Huang, Z.

    1998-10-20

    A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

  3. Design and implementation of an optimal laser pulse front tilting scheme for ultrafast electron diffraction in reflection geometry with high temporal resolution

    Directory of Open Access Journals (Sweden)

    Francesco Pennacchio

    2017-07-01

    Full Text Available Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity between the overlapping pump light and the electron probe pulses, which affects the overall temporal resolution of the experiment. A solution already available in the literature involved pulse front tilt of the pump beam at the sample, providing a sub-picosecond time resolution. However, in the reported optical scheme, the tilted pulse is characterized by a temporal chirp of about 1 ps at 1 mm away from the centre of the beam, which limits the investigation of surface dynamics in large crystals. In this paper, we propose an optimal tilting scheme designed for a radio-frequency-compressed ultrafast electron diffraction setup working in reflection geometry with 30 keV electron pulses containing up to 105 electrons/pulse. To characterize our scheme, we performed optical cross-correlation measurements, obtaining an average temporal width of the tilted pulse lower than 250 fs. The calibration of the electron-laser temporal overlap was obtained by monitoring the spatial profile of the electron beam when interacting with the plasma optically induced at the apex of a copper needle (plasma lensing effect. Finally, we report the first time-resolved results obtained on graphite, where the electron-phonon coupling dynamics is observed, showing an overall temporal resolution in the sub-500 fs regime. The successful implementation of this configuration opens the way to directly probe structural dynamics of low-dimensional systems in the sub-picosecond regime, with pulsed electrons.

  4. Molecular structure of tris(cyclopropylsilyl)amine as determined by gas electron diffraction and quantum-chemical calculations

    Science.gov (United States)

    Vishnevskiy, Yuri V.; Abaev, Maxim A.; Ivanov, Arkadii A.; Vilkov, Lev V.; Dakkouri, Marwan

    2008-10-01

    The molecular structure and conformation of tris(cyclopropylsilyl)amine (TCPSA) has been studied by means of gas-phase electron diffraction at 338 K and quantum-chemical calculations. A total of 12 relatively stable conformations of TCPSA molecule were considered. According to the experimental results and the DFT calculations the most stable conformer corresponds to a configuration (according to the Prelog-Klyne notation) of the type (-ac)(-ac)(+ac)-(-ac)(-ac)(+ac), where the first three parentheses describe the three different Si-N-Si-C torsional angles and the latter ones depict the rotation of the three cyclopropyl groups about the C ring-Si axes, respectively. The quantum-mechanical calculations were performed using various density functional (B3LYP, X3LYP and O3LYP) and perturbation MP2 methods in combination with double- and triple- ζ basis sets plus polarization and diffuse functions. The most important experimental geometrical parameters of TCPSA ( ra Å, ∠ h1 degrees) are: (Si-N) av = 1.741(3), (Si-C) av = 1.866(4), (C-C) av = 1.510(3), (C-C(Si)) av = 1.535(3), (N-Si-C) av = 115.1(18)°. For the purpose of comparison and searching for reasons leading to the planarity of the Si 3N moiety in trisilylated amines we carried out NBO analysis and optimized the geometries of numerous silylamines. Among these compounds was tris(allylsilyl)amine (TASA), which is isovalent and isoelectronic to TCPSA. Utilizing the structural results we obtained we could show that Si +⋯Si + electrostatic repulsive interaction is predominantly responsible for the planarity of the Si 3N skeleton in TCPSA and in all other trisilylamines we considered. We also found that regardless the size and partial charges of the substituents the Si-N-Si bond angle in various disilylamines amounts to 130 ± 2°.

  5. Proton diffraction

    International Nuclear Information System (INIS)

    Den Besten, J.L.; Jamieson, D.N.; Allen, L.J.

    1998-01-01

    The Lindhard theory on ion channeling in crystals has been widely accepted throughout ion beam analysis for use in simulating such experiments. The simulations use a Monte Carlo method developed by Barret, which utilises the classical 'billiard ball' theory of ions 'bouncing' between planes or tubes of atoms in the crystal. This theory is not valid for 'thin' crystals where the planes or strings of atoms can no longer be assumed to be of infinite proportions. We propose that a theory similar to that used for high energy electron diffraction can be applied to MeV ions, especially protons, in thin crystals to simulate the intensities of transmission channeling and of RBS spectra. The diffraction theory is based on a Bloch wave solution of the Schroedinger equation for an ion passing through the periodic crystal potential. The widely used universal potential for proton-nucleus scattering is used to construct the crystal potential. Absorption due to thermal diffuse scattering is included. Experimental parameters such as convergence angle, beam tilt and scanning directions are considered in our calculations. Comparison between theory and experiment is encouraging and suggests that further work is justified. (authors)

  6. Surface structure of Bi2Sr2CaCu2O(8+delta) high-temperature superconductors studied using low-energy electron diffraction

    Science.gov (United States)

    Lindberg, P. A. P.; Shen, Z.-X.; Wells, B. O.; Mitzi, D. B.; Lindau, I.

    1988-12-01

    The surface structure of Bi2Sr2CaCu2O(8+delta) has been studied using low-energy electron diffraction (LEED). Sharp diffraction spots indicative of a well-ordered surface are observed. The LEED patterns unequivocally show that this type of material preferentially cleaves along the a-b planes of the nearly tetragonal unit cell. A superstructure extending along one of the axes in the a-b plane (b) is found to have a periodicity of 27 + or - 0.5 A, in good agreement with earlier studies of the three-dimensional crystal structure. The superstructure at the surface is nonlocal in character and reflects the long-range superlattice of the bulk along the b axis. Intensity modulations of the diffraction spots oriented along the b axis are also reported and discussed in terms of the cell dimension of the unit cell along the b axis.

  7. Surface structure of Bi2Sr2CaCu2O/sub 8+//sub δ high-temperature superconductors studied using low-energy electron diffraction

    International Nuclear Information System (INIS)

    Lindberg, P.A.P.; Shen, Z.; Wells, B.O.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

    1988-01-01

    The surface structure of Bi 2 Sr 2 CaCu 2 O/sub 8+//sub δ has been studied using low-energy electron diffraction (LEED). Sharp diffraction spots indicative of a well-ordered surface are observed. The LEED patterns unequivocally show that this type of material preferentially cleaves along the a-b planes of the nearly tetragonal unit cell. A superstructure extending along one of the axes in the a-b plane (b) is found to have a periodicity of 27 +- 0.5 A, in good agreement with earlier studies of the three-dimensional crystal structure. We conclude that the superstructure at the surface is nonlocal in character and reflects the long-range superlattice of the bulk along the b axis. Intensity modulations of the diffraction spots oriented along the b axis are also reported and discussed in terms of the cell dimension of the unit cell along the b axis

  8. Thermal analysis, X-ray powder diffraction and electron microscopy data related with the production of 1:1 Caffeine:Glutaric Acid cocrystals

    Directory of Open Access Journals (Sweden)

    Íris Duarte

    2016-09-01

    Full Text Available The data presented in this article are related to the production of 1:1 Caffeine:Glutaric Acid cocrystals as part of the research article entitled “Green production of cocrystals using a new solvent-free approach by spray congealing” (Duarte et al., 2016 [1]. More specifically, here we present the thermal analysis and the X-ray powder diffraction data for pure Glutaric Acid, used as a raw material in [1]. We also include the X-ray powder diffraction and electron microscopy data obtained for the 1:1 Caffeine:Glutaric Acid cocrystal (form II produced using the cooling crystallization method reported in “Operating Regions in Cooling Cocrystallization of Caffeine and Glutaric Acid in Acetonitrile” (Yu et al., 2010 [2]. Lastly, we show the X-ray powder diffraction data obtained for assessing the purity of the 1:1 Caffeine:Glutaric cocrystals produced in [1].

  9. Orientation and phase mapping in the transmission electron microscope using precession-assisted diffraction spot recognition: state-of-the-art results.

    Science.gov (United States)

    Viladot, D; Véron, M; Gemmi, M; Peiró, F; Portillo, J; Estradé, S; Mendoza, J; Llorca-Isern, N; Nicolopoulos, S

    2013-10-01

    A recently developed technique based on the transmission electron microscope, which makes use of electron beam precession together with spot diffraction pattern recognition now offers the possibility to acquire reliable orientation/phase maps with a spatial resolution down to 2 nm on a field emission gun transmission electron microscope. The technique may be described as precession-assisted crystal orientation mapping in the transmission electron microscope, precession-assisted crystal orientation mapping technique-transmission electron microscope, also known by its product name, ASTAR, and consists in scanning the precessed electron beam in nanoprobe mode over the specimen area, thus producing a collection of precession electron diffraction spot patterns, to be thereafter indexed automatically through template matching. We present a review on several application examples relative to the characterization of microstructure/microtexture of nanocrystalline metals, ceramics, nanoparticles, minerals and organics. The strengths and limitations of the technique are also discussed using several application examples. ©2013 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

  10. X-ray Diffraction from Isolated and Strongly Aligned Gas-Phase Molecules with a Free-Electron Laser

    DEFF Research Database (Denmark)

    Küpper, Jochen; Stern, Stephan; Holmegaard, Lotte

    2014-01-01

    We report experimental results on x-ray diffraction of quantum-state-selected and strongly aligned ensembles of the prototypical asymmetric rotor molecule 2,5-diiodobenzonitrile using the Linac Coherent Light Source. The experiments demonstrate first steps toward a new approach to diffractive...... imaging of distinct structures of individual, isolated gas-phase molecules. We confirm several key ingredients of single molecule diffraction experiments: the abilities to detect and count individual scattered x-ray photons in single shot diffraction data, to deliver state-selected, e. g., structural......-isomer-selected, ensembles of molecules to the x-ray interaction volume, and to strongly align the scattering molecules. Our approach, using ultrashort x-ray pulses, is suitable to study ultrafast dynamics of isolated molecules....

  11. A three-dimensional, two-way, parabolic equation model for acoustic backscattering in a cylindrical coordinate system

    DEFF Research Database (Denmark)

    Zhu, Dong; Jensen, Leif Bjørnø

    2000-01-01

    . The major drawback of using the cylindrical coordinate system, when the backscattering solution is valid within a limited area, is analyzed using a geometrical-optical interpretation. The model may be useful for studying three-dimensional backscattering phenomena comprising azimuthal diffraction effects...

  12. Relationship between the v2PO4/amide III ratio assessed by Raman spectroscopy and the calcium content measured by quantitative backscattered electron microscopy in healthy human osteonal bone

    Science.gov (United States)

    Roschger, Andreas; Gamsjaeger, Sonja; Hofstetter, Birgit; Masic, Admir; Blouin, Stéphane; Messmer, Phaedra; Berzlanovich, Andrea; Paschalis, Eleftherios P.; Roschger, Paul; Klaushofer, Klaus; Fratzl, Peter

    2014-06-01

    Raman microspectroscopy and quantitative backscattered electron imaging (qBEI) of bone are powerful tools to investigate bone material properties. Both methods provide information on the degree of bone matrix mineralization. However, a head-to-head comparison of these outcomes from identical bone areas has not been performed to date. In femoral midshaft cross sections of three women, 99 regions (20×20 μ) were selected inside osteons and interstitial bone covering a wide range of matrix mineralization. As the focus of this study was only on regions undergoing secondary mineralization, zones exhibiting a distinct gradient in mineral content close to the mineralization front were excluded. The same regions were measured by both methods. We found a linear correlation (R2=0.75) between mineral/matrix as measured by Raman spectroscopy and the wt. %Mineral/(100-wt. %Mineral) as obtained by qBEI, in good agreement with theoretical estimations. The observed deviations of single values from the linear regression line were determined to reflect biological heterogeneities. The data of this study demonstrate the good correspondence between Raman and qBEI outcomes in describing tissue mineralization. The obtained correlation is likely sensitive to changes in bone tissue composition, providing an approach to detect potential deviations from normal bone.

  13. Molecular beam epitaxial growth mechanism of ZnSe epilayers on (100) GaAs as determined by reflection high-energy electron diffraction, transmission electron microscopy and X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ruppert, P.; Hommel, D.; Behr, T.; Heinke, H.; Waag, A.; Landwehr, G. (Physikalisches Inst., Univ. Wuerzburg (Germany))

    1994-04-14

    The properties of molecular beam epitaxial growth of ZnSe epilayers deposited directly on a GaAs substrate are compared to those grown on a GaAs buffer layer. The superior quality of the latter is confirmed by RHEED, TEM and X-ray diffraction. Based on RHEED oscillation studies, a model explaining the dependence of the ZnSe growth rate on Zn and Se fluxes and the substrate temperature is developed taking into account physisorbed and chemisorbed states. For partially relaxed epilayers, the correlation between the relaxation state and the crystalline mosaicity, as found by high resolution X-ray diffraction, is discussed

  14. An incommensurately modulated structure of eta '-phase of Cu.sub.3+x./sub.Si determined by quantitative electron diffraction tomography

    Czech Academy of Sciences Publication Activity Database

    Palatinus, Lukáš; Klementová, Mariana; Dřínek, Vladislav; Jarošová, Markéta; Petříček, Václav

    2011-01-01

    Roč. 50, č. 8 (2011), s. 3743-3751 ISSN 0020-1669 R&D Projects: GA ČR GA203/09/1088 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z40720504 Keywords : copper silicide * incommensurate structure * electron diffraction tomography * ab inition structure solution * superspace Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.601, year: 2011

  15. Crystal structure redetermination of ε-Ni.sub.3./sub.Si.sub.2./sub. from a single nanowire by dynamical refinement of precession electron diffraction data

    Czech Academy of Sciences Publication Activity Database

    Correa, Cinthia Antunes; Klementová, Mariana; Dřínek, Vladislav; Kopeček, Jaromír; Palatinus, Lukáš

    2016-01-01

    Roč. 672, Jul (2016), s. 505-509 ISSN 0925-8388 R&D Projects: GA ČR GA13-25747S Institutional support: RVO:68378271 ; RVO:67985858 Keywords : precession electron diffraction tomography * structure determination * nanowire * dynamical refinement Subject RIV: BM - Solid Matter Physics ; Magnetism; CA - Inorganic Chemistry (UCHP-M) OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.); Inorganic and nuclear chemistry (UCHP-M) Impact factor: 3.133, year: 2016

  16. The structure and conformations of piracetam (2-oxo-1-pyrrolidineacetamide): Gas-phase electron diffraction and quantum chemical calculations

    Science.gov (United States)

    Ksenafontov, Denis N.; Moiseeva, Natalia F.; Khristenko, Lyudmila V.; Karasev, Nikolai M.; Shishkov, Igor F.; Vilkov, Lev V.

    2010-12-01

    The geometric structure of piracetam was studied by quantum chemical calculations (DFT and ab initio), gas electron diffraction (GED), and FTIR spectroscopy. Two stable mirror symmetric isomers of piracetam were found. The conformation of pyrrolidine ring is an envelope in which the C4 atom deviates from the ring plane, the angle between the planes (C3 sbnd C4 sbnd C5) and (C2 sbnd C3 sbnd C5) is 154.1°. The direction of the deviation is the same as that of the side acetamide group. The piracetam molecule is stabilized in the gas phase by an intramolecular hydrogen bond between the N9H 2 group and the oxygen O6, bonded to C2. The principal structural parameters ( re, Å and ∠e, degrees; uncertainties are 3 σLS values) were found to be: r(С3 sbnd С4) = 1.533(1), r(C4 sbnd C5) = 1.540(1), r(N1 sbnd C5) = 1.456(1), r(C2 sbnd C3) = 1.520(1), r(N1 sbnd C7) = 1.452(1), r(C7 sbnd C8) = 1.537(1), r(N1 sbnd C2) = 1.365(2), r(C8 sbnd N9) = 1.360(2), r(C2 dbnd O6) = 1.229(1), r(C8 dbnd O10) = 1.221(1), ∠C2 sbnd N1 sbnd C5 = 113.4(6), ∠N1 sbnd C2 sbnd C3 = 106.9(6), ∠N1 sbnd C7 sbnd C8 = 111.9(6), ∠C7 sbnd C8 sbnd N9 = 112.5(6), ∠N1 sbnd C2 sbnd O6 = 123.0(4), ∠C3 sbnd N1 sbnd C7 = 120.4(4), ∠C7 sbnd C8 sbnd O10 = 120.2(4), ∠C5 sbnd N1 sbnd C2 sbnd O6 = 170(6), ∠C3 sbnd C2 sbnd N1 sbnd C7 = 178(6), ∠C2 sbnd N1 sbnd C7 sbnd C8 = 84.2, ∠N1 sbnd C7 sbnd C8 sbnd O10 = 111.9.

  17. Diffractive interactions

    International Nuclear Information System (INIS)

    Del Duca, V.; Marage, P.

    1996-08-01

    The general framework of diffractive deep inelastic scattering is introduced and reports given in the session on diffractive interactions at the international workshop on deep-inelastic scattering and related phenomena, Rome, April 1996, are presented. (orig.)

  18. Diffraction theory

    NARCIS (Netherlands)

    Bouwkamp, C.J.

    1954-01-01

    A critical review is presented of recent progress in classical diffraction theory. Both scalar and electromagnetic problems are discussed. The report may serve as an introduction to general diffraction theory although the main emphasis is on diffraction by plane obstacles. Various modifications of

  19. Multibeam sonar backscatter data processing

    Science.gov (United States)

    Schimel, Alexandre C. G.; Beaudoin, Jonathan; Parnum, Iain M.; Le Bas, Tim; Schmidt, Val; Keith, Gordon; Ierodiaconou, Daniel

    2018-06-01

    Multibeam sonar systems now routinely record seafloor backscatter data, which are processed into backscatter mosaics and angular responses, both of which can assist in identifying seafloor types and morphology. Those data products are obtained from the multibeam sonar raw data files through a sequence of data processing stages that follows a basic plan, but the implementation of which varies greatly between sonar systems and software. In this article, we provide a comprehensive review of this backscatter data processing chain, with a focus on the variability in the possible implementation of each processing stage. Our objective for undertaking this task is twofold: (1) to provide an overview of backscatter data processing for the consideration of the general user and (2) to provide suggestions to multibeam sonar manufacturers, software providers and the operators of these systems and software for eventually reducing the lack of control, uncertainty and variability associated with current data processing implementations and the resulting backscatter data products. One such suggestion is the adoption of a nomenclature for increasingly refined levels of processing, akin to the nomenclature adopted for satellite remote-sensing data deliverables.

  20. Order-disorder phase transformations in quaternary pyrochlore oxide system: Investigated by X-ray diffraction, transmission electron microscopy and Raman spectroscopic techniques

    International Nuclear Information System (INIS)

    Radhakrishnan, A.N.; Prabhakar Rao, P.; Sibi, K.S.; Deepa, M.; Koshy, Peter

    2009-01-01

    Order-disorder transformations in a quaternary pyrochlore oxide system, Ca-Y-Zr-Ta-O, were studied by powder X-ray diffraction (XRD) method, transmission electron microscope (TEM) and FT-NIR Raman spectroscopic techniques. The solid solutions in different ratios, 4:1, 2:1, 1:1, 1:2, 1:4, 1:6, of CaTaO 3.5 and YZrO 3.5 were prepared by the conventional high temperature ceramic route. The XRD results and Rietveld analysis revealed that the crystal structure changed from an ordered pyrochlore structure to a disordered defect fluorite structure as the ratios of the solid solutions of CaTaO 3.5 and YZrO 3.5 were changed from 4:1 to 1:4. This structural transformation in the present system is attributed to the lowering of the average cation radius ratio, r A /r B as a result of progressive and simultaneous substitution of larger cation Ca 2+ for Y 3+ at A sites and smaller cation Ta 5+ for Zr 4+ at B sites. Raman spectroscopy and TEM analysis corroborated the XRD results. - Graphical abstract: Selected area electron diffraction (SAED) patterns showed highly ordered diffraction maxima with characteristic superlattice weak diffraction spots of the pyrochlore structure for (a) Ca 0.6 7Y 1.33 Zr 1.33 Ta 0.33 O 7 (C2YZT2) and bright diffraction maxima arranged in a ring pattern of the fluorite structure for (b) Ca 0.29 7Y 1.71 Zr 1.71 Ta 0.29 O 7 (CY6Z6T).

  1. 3D Backscatter Imaging System

    Science.gov (United States)

    Whitaker, Ross (Inventor); Turner, D. Clark (Inventor)

    2016-01-01

    Systems and methods for imaging an object using backscattered radiation are described. The imaging system comprises both a radiation source for irradiating an object that is rotationally movable about the object, and a detector for detecting backscattered radiation from the object that can be disposed on substantially the same side of the object as the source and which can be rotationally movable about the object. The detector can be separated into multiple detector segments with each segment having a single line of sight projection through the object and so detects radiation along that line of sight. Thus, each detector segment can isolate the desired component of the backscattered radiation. By moving independently of each other about the object, the source and detector can collect multiple images of the object at different angles of rotation and generate a three dimensional reconstruction of the object. Other embodiments are described.

  2. FELIX: an algorithm for indexing multiple crystallites in X-ray free-electron laser snapshot diffraction images

    DEFF Research Database (Denmark)

    Beyerlein, Kenneth R.; White, Thomas A.; Yefanov, Oleksandr

    2017-01-01

    A novel algorithm for indexing multiple crystals in snapshot X-ray diffraction images, especially suited for serial crystallography data, is presented. The algorithm, FELIX, utilizes a generalized parametrization of the Rodrigues-Frank space, in which all crystal systems can be represented without...

  3. On line ultrasonic integrated backscatter

    International Nuclear Information System (INIS)

    Landini, L.; Picano, E.; Mazzarisi, A.; Santarelli, F.; Benassi, A.; De Pieri, G.

    1988-01-01

    A new equipment for on-line evaluation of index based on two-dimensional integrated backscatter from ultrasonic images is described. The new equipment is fully integrated into a B-mode ultrasonic apparatus which provides a simultaneous display of conventional information together with parameters of tissue characterization. The system has been tested with a backscattering model of microbubbles in polysaccharide solution, characterized by a physiological exponential time decay. An exponential fitting to the experimental data was performed which yielded r=0.95

  4. Characterization of calcium and zinc spatial distributions at the fibrocartilage zone of bone-tendon junction by synchrotron radiation-based micro X-ray fluorescence analysis combined with backscattered electron imaging

    Science.gov (United States)

    Lu, Hongbin; Chen, Can; Wang, Zhanwen; Qu, Jin; Xu, Daqi; Wu, Tianding; Cao, Yong; Zhou, Jingyong; Zheng, Cheng; Hu, Jianzhong

    2015-09-01

    Tendon attaches to bone through a functionally graded fibrocartilage zone, including uncalcified fibrocartilage (UF), tidemark (TM) and calcified fibrocartilage (CF). This transition zone plays a pivotal role in relaxing load transfer between tendon and bone, and serves as a boundary between otherwise structurally and functionally distinct tissue types. Calcium and zinc are believed to play important roles in the normal growth, mineralization, and repair of the fibrocartilage zone of bone-tendon junction (BTJ). However, spatial distributions of calcium and zinc at the fibrocartilage zone of BTJ and their distribution-function relationship are not totally understood. Thus, synchrotron radiation-based micro X-ray fluorescence analysis (SR-μXRF) in combination with backscattered electron imaging (BEI) was employed to characterize the distributions of calcium and zinc at the fibrocartilage zone of rabbit patella-patellar tendon complex (PPTC). For the first time, the unique distributions of calcium and zinc at the fibrocartilage zone of the PPTC were clearly mapped by this method. The distributions of calcium and zinc at the fibrocartilage zone of the PPTC were inhomogeneous. A significant accumulation of zinc was exhibited in the transition region between UF and CF. The highest zinc content (3.17 times of that of patellar tendon) was found in the TM of fibrocartilage zone. The calcium content began to increase near the TM and increased exponentially across the calcified fibrocartilage region towards the patella. The highest calcium content (43.14 times of that of patellar tendon) was in the transitional zone of calcified fibrocartilage region and the patella, approximately 69 μm from the location with the highest zinc content. This study indicated, for the first time, that there is a differential distribution of calcium and zinc at the fibrocartilage zone of PPTC. These observations reveal new insights into region-dependent changes across the fibrocartilage zone of

  5. Deciphering igneous and metamorphic events in high-grade rocks of the Wilmington complex, Delaware: Morphology, cathodoluminescence and backscattered electron zoning, and SHRIMP U-Pb geochronology of zircon and monazite

    Science.gov (United States)

    Aleinikoff, J.N.; Schenck, W.S.; Plank, M.O.; Srogi, L.A.; Fanning, C.M.; Kamo, S.L.; Bosbyshell, H.

    2006-01-01

    High-grade rocks of the Wilmington Complex, northern Delaware and adjacent Maryland and Pennsylvania, contain morphologically complex zircons that formed through both igneous and metamorphic processes during the development of an island-arc complex and suturing of the arc to Laurentia. The arc complex has been divided into several members, the protoliths of which include both intrusive and extrusive rocks. Metasedimentary rocks are interlayered with the complex and are believed to be the infrastructure upon which the arc was built. In the Wilmingto n Complex rocks, both igneous and metamorphic zircons occur as elongate and equant forms. Chemical zoning, shown by cathodoluminescence (CL), includes both concentric, oscillatory patterns, indicative of igneous origin, and patchwork and sector patterns, suggestive of metamorphic growth. Metamorphic monazites are chemically homogeneous, or show oscillatory or spotted chemical zoning in backscattered electron images. U-Pb geochronology by sensitive high resolution ion microprobe (SHRIMP) was used to date complexly zoned zircon and monazite. All but one member of the Wilmington Complex crystallized in the Ordovician between ca. 475 and 485 Ma; these rocks were intruded by a suite of gabbro-to-granite plutonic rocks at 434 ?? Ma. Detrital zircons in metavolcanic and metasedimentary units were derived predominantly from 0.9 to 1.4 Ga (Grenvillian) basement, presumably of Laurentian origin. Amphibolite to granulite facies metamorphism of the Wilmington Complex, recorded by ages of metamorphic zircon (428 ?? 4 and 432 ?? 6 Ma) and monazite (429 ?? 2 and 426 ?? 3 Ma), occurred contemporaneously with emplacement of the younger plutonic rocks. On the basis of varying CL zoning patterns and external morphologies, metamorphic zircons formed by different processes (presumably controlled by rock chemistry) at slightly different times and temperatures during prograde metamorphism. In addition, at least three other thermal episodes are

  6. Effect of the cortex on ultrasonic backscatter measurements of cancellous bone

    International Nuclear Information System (INIS)

    Hoffmeister, Brent K; Holt, Andrew P; Kaste, Sue C

    2011-01-01

    Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term 'apparent' means that the parameters are sensitive to the frequency-dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

  7. Effect of the cortex on ultrasonic backscatter measurements of cancellous bone

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmeister, Brent K; Holt, Andrew P [Department of Physics, Rhodes College, Memphis, TN (United States); Kaste, Sue C, E-mail: hoffmeister@rhodes.edu [Department of Diagnostic Imaging, St Jude Children' s Research Hospital, Memphis, TN (United States)

    2011-10-07

    Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term 'apparent' means that the parameters are sensitive to the frequency-dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

  8. Small area analysis using micro-diffraction techniques

    International Nuclear Information System (INIS)

    Goehner, Raymond P.; Tissot, Ralph G. Jr.; Michael, Joseph R.

    2000-01-01

    An overall trend toward smaller electronic packages and devices makes it increasingly important and difficult to obtain meaningful diffraction information from small areas. X-ray micro-diffraction, electron back-scattered diffraction (EBSD) and Kossel are micro-diffraction techniques used for crystallographic analysis including texture, phase identification and strain measurements. X-ray micro-diffraction primarily is used for phase analysis and residual strain measurements. X-ray micro-diffraction primarily is used for phase analysis and residual strain measurements of areas between 10 microm to 100 microm. For areas this small glass capillary optics are used for producing a usable collimated x-ray beam. These optics are designed to reflect x-rays below the critical angle therefore allowing for larger solid acceptance angle at the x-ray source resulting in brighter smaller x-ray beams. The determination of residual strain using micro-diffraction techniques is very important to the semiconductor industry. Residual stresses have caused voiding of the interconnect metal which then destroys electrical continuity. Being able to determine the residual stress helps industry to predict failures from the aging effects of interconnects due to this stress voiding. Stress measurements would be impossible using a conventional x-ray diffractometer; however, utilizing a 30 microm glass capillary these small areas are readily assessable for analysis. Kossel produces a wide angle diffraction pattern from fluorescent x-rays generated in the sample by an e-beam in a SEM. This technique can yield very precise lattice parameters for determining strain. Fig. 2 shows a Kossel pattern from a Ni specimen. Phase analysis on small areas is also possible using an energy dispersive spectrometer (EBSD) and x-ray micro-diffraction techniques. EBSD has the advantage of allowing the user to observe the area of interest using the excellent imaging capabilities of the SEM. An EDS detector has been

  9. Superlattice structure of Ce{sup 3+}-doped BaMgF{sub 4} fluoride crystals - x-ray diffraction, electron spin-resonance, and optical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Yamaga, M.; Hattori, K. [Department of Electrical and Electronic Engineering, Faculty of Engineering, Gifu University, Gifu (Japan); Kodama, N. [Department of Materials Science and Engineering, Faculty of Engineering and Resource Science, Akita University, Akita (Japan); Ishizawa, N. [Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama (Japan); Honda, M. [Faculty of Science, Naruto University of Education, Naruto (Japan); Shimamura, K.; Fukuda, T. [Institute for Materials Research, Tohoku University, Sendai (Japan)

    2001-09-14

    The x-ray diffraction patterns for Ce{sup 3+}-doped BaMgF{sub 4} (BMF) crystals suggest the existence of superlattice structure. The superlattice model is consistent with the characterization of the 4f{sup 1} ground state of Ce{sup 3+} as a probe ion using the electron spin-resonance (ESR) technique. The distinct Ce{sup 3+} luminescence spectra with different peak energies and lifetimes also support the superlattice model. Although the detailed superlattice structure could not be analysed using the diffraction spots, a model has been proposed, taking into account the eight Ce{sup 3+} polyhedra with different anion coordinations in the unit cell of the BMF crystal obtained from the ESR experiments. (author)

  10. A general method for baseline-removal in ultrafast electron powder diffraction data using the dual-tree complex wavelet transform

    Directory of Open Access Journals (Sweden)

    Laurent P. René de Cotret

    2017-07-01

    Full Text Available The general problem of background subtraction in ultrafast electron powder diffraction (UEPD is presented with a focus on the diffraction patterns obtained from materials of moderately complex structure which contain many overlapping peaks and effectively no scattering vector regions that can be considered exclusively background. We compare the performance of background subtraction algorithms based on discrete and dual-tree complex (DTCWT wavelet transforms when applied to simulated UEPD data on the M1–R phase transition in VO2 with a time-varying background. We find that the DTCWT approach is capable of extracting intensities that are accurate to better than 2% across the whole range of scattering vector simulated, effectively independent of delay time. A Python package is available.

  11. Studies of deformation-induced texture development in sheet materials using diffraction techniques

    International Nuclear Information System (INIS)

    Banovic, S.W.; Vaudin, M.D.; Gnaeupel-Herold, T.H.; Saylor, D.M.; Rodbell, K.P

    2004-01-01

    Crystallographic texture measurements were made on a series of rolled aluminum sheet specimens deformed in equi-biaxial tension up to a strain level of 0.11. The measurement techniques used were neutron diffraction with a 4-circle goniometer, electron backscatter diffraction, conventional powder X-ray diffraction (XRD), and XRD using an area detector. Results indicated a complex texture orientation distribution function which altered in response to the applied plastic deformation. Increased deformation caused the {1 1 0} planes, to align parallel to the plane of the sheet. The different techniques produced results that were very consistent with each other. The advantages and disadvantages of the various methods are discussed, with particular consideration of the time taken for each method, the range of orientation space accessible, the density of data that can be obtained, and the statistical significance of each data set with respect to rolled sheet product

  12. Nodule bottom backscattering study using multibeam echosounder

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Raju, Y.S.N.; Nair, R.R.

    A study is carried out to observe the angular dependence of backscattering strength at nodule area where grab sample and photographic data is available. Theoretical study along with the experimentally observed data shows that the backscattering...

  13. Classification of projection images of proteins with structural polymorphism by manifold: A simulation study for x-ray free-electron laser diffraction imaging

    Science.gov (United States)

    Yoshidome, Takashi; Oroguchi, Tomotaka; Nakasako, Masayoshi; Ikeguchi, Mitsunori

    2015-09-01

    Coherent x-ray diffraction imaging (CXDI) enables us to visualize noncrystalline sample particles with micrometer to submicrometer dimensions. Using x-ray free-electron laser (XFEL) sources, two-dimensional diffraction patterns are collected from fresh samples supplied to the irradiation area in the "diffraction-before-destruction" scheme. A recent significant increase in the intensity of the XFEL pulse is promising and will allow us to visualize the three-dimensional structures of proteins using XFEL-CXDI in the future. For the protocol proposed for molecular structure determination using future XFEL-CXDI [T. Oroguchi and M. Nakasako, Phys. Rev. E 87, 022712 (2013), 10.1103/PhysRevE.87.022712], we require an algorithm that can classify the data in accordance with the structural polymorphism of proteins arising from their conformational dynamics. However, most of the algorithms proposed primarily require the numbers of conformational classes, and then the results are biased by the numbers. To improve this point, here we examine whether a method based on the manifold concept can classify simulated XFEL-CXDI data with respect to the structural polymorphism of a protein that predominantly adopts two states. After random sampling of the conformations of the two states and in-between states from the trajectories of molecular dynamics simulations, a diffraction pattern is calculated from each conformation. Classification was performed by using our custom-made program suite named enma, in which the diffusion map (DM) method developed based on the manifold concept was implemented. We successfully classify most of the projection electron density maps phase retrieved from diffraction patterns into each of the two states and in-between conformations without the knowledge of the number of conformational classes. We also examined the classification of the projection electron density maps of each of the three states with respect to the Euler angle. The present results suggest

  14. Electron diffraction and microscopy study of the structure and microstructure of the hexagonal perovskite Ba3Ti2MnO9

    International Nuclear Information System (INIS)

    Maunders, C.

    2007-01-01

    This paper reports a structural and microstructural investigation of the hexagonal perovskite Ba 3 Ti 2 MnO 9 using electron microscopy and diffraction. Convergent-beam electron diffraction (CBED) revealed the structure has the noncentrosymmetric space group P6 3 mc (186) at room temperature and at ∝ 110 K. Compared with the centrosymmetric parent structure BaTiO 3 , with space group P6 3 /mmc, this represents a break in mirror symmetry normal to the c axis. This implies the Ti and Mn atoms are ordered on alternate octahedral sites along the left angle 0001 right angle direction in Ba 3 Ti 2 MnO 9 . Using high-resolution electron microscopy (HREM), we observed occasional 6H/12R interfaces on (0001) planes, however, no antiphase boundaries were observed, as were seen in Ba 3 Ti 2 RuO 9 . Using powder X-ray Rietveld refinement we have measured the lattice parameters from polycrystalline samples to be a=5.6880±0.0005, c=13.9223±0.0015 Aa at room temperature. (orig.)

  15. Study of deformation and fracture micro mechanisms of titanium alloy Ti-6Al-4V using electron microscopy and and X-ray diffraction techniques

    International Nuclear Information System (INIS)

    Morcelli, Aparecido Edilson

    2009-01-01

    This present work allowed the study of deformation and fracture micro mechanisms of titanium alloy Ti-6Al-4V, used commercially for the manufacture of metallic biomaterials. The techniques employed for the analysis of the material under study were: scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The study of the influence and behavior of the phases present in titanium alloys is important to evaluate the behavior of cracks in titanium alloys with high mechanical strength, which have fine alpha (α), beta (β) and (α±β) microstructure, linking the presence of the phases with the strength of the material. The evaluation in situ of deformation and fracture micro mechanisms were performed by TEM and was also a study of phase transformations during cooling in titanium alloys, using the techniques of bright field, dark field and diffraction of electrons in the selected area. After heat treatment differences were observed between the amount of in relation to the original microstructure of the β and α phases material for different conditions used in heat treatment applied to the alloy. The presence of lamellar microstructure formed during cooling in the β field was observed, promoting the conversion of part of the secondary alpha structure in β phase, which was trapped between the lamellar of alpha. (author)

  16. Characterization by Raman scattering, x-ray diffraction, and transmission electron microscopy of (AlAs)m(InAs)m short period superlattices grown by migration enhanced epitaxy

    DEFF Research Database (Denmark)

    Bradshaw, J.; Song, X.J.; Shealy, J.R.

    1992-01-01

    We report growth of (InAs)1(AlAs)1 and (InAs)2(AlAs)2 strained layer superlattices by migration enhanced epitaxy. The samples were grown on InP (001) substrates and characterized by Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Satellite peaks in the x-ray data...... confirm the intended periodicity and indicate the presence of some disorder in the monolayer sample. The energies of the zone folded and quantum confined optic phonons are in reasonable agreement with calculations based on one-dimensional elastic continuum and linear chain models. Journal of Applied...

  17. Localized electron nature of the antiferromagnetism of (CePd sub 3) sub 8 Ge Response to hydrostatic pressure and neutron diffraction

    CERN Document Server

    Tabata, Y; Ohoyama, K

    2003-01-01

    The magnetic properties of the compound (CePd sub 3) sub 8 Ge have been studied by means of neutron diffraction and specific heat measurement at ambient pressure and also of measurements of susceptibility and electrical resistivity under hydrostatic pressure. The magnetic modulation vector, q, of the antiferromagnetic phase is left brace 001 right brace and the spin polarization is parallel to q. With increasing the applied pressure up to 6 GPa, the Neel temperature keeps increasing, which indicates a strongly localized nature of the 4f-electrons of the compound.

  18. Induced alignment of a solution-cast discotic hexabenzocoronene derivative for electronic devices investigated by surface X-ray diffraction

    DEFF Research Database (Denmark)

    Bunk, Oliver; Nielsen, Martin Meedom; Sølling, Theis Ivan

    2003-01-01

    A surface X-ray diffraction study is presented showing that highly ordered and uniaxially aligned hexa(3,7-dimethyl-octanyl)hexa-peri-hexabenzocoronene (HBC-C8,2) films can be fabricated by crystallization from solution onto friction-transferred poly(tetrafluoroethylene) (PTFE) layers. Three...... crystalline HBC-C8,2 majority phases result. In all three phases, the HBC-C8,2 molecules self-organize into columns which are uniaxially aligned along the direction defined by the PTFE macromolecules of the substrate. The three phases are quite similar, the major difference being their orientation...

  19. The use of extraction and electronic diffraction replicas for precipitates characterization in welded Cr-Mo Steels

    International Nuclear Information System (INIS)

    Gutierrez de Saiz-Solabarria, S.; San Juan Nunez, J.M.

    1997-01-01

    The precipitates and phases found in the structure of welded joints of Heat Interchanges Tubes were studied and identified. The base material satisfied the requirements of ASME Sec II, SA 213 Gr T22 (2 1/4 Cr 1 Mo). Compositions of Filler Metals were: 2 1/4 Cr 1 Mo and 2 1/4 Cr 1 Mo 1/4 Nb. The chemical composition of base and weld materials were analyzed by atomic emission spectroscopy in high vacuum electric discharge and by inductive plasma coupled. For the constituents characterization extraction and diffraction microscopy replicas were used. (Author) 65 refs

  20. Characterization of Burnt Clays by X-ray Diffraction Analysis, Chemical Analysis and Environmental Scanning Electron Microscopy

    Czech Academy of Sciences Publication Activity Database

    Navrátilová, Eva; Neděla, Vilém

    2016-01-01

    Roč. 22, S3 (2016), s. 1862-1863 ISSN 1431-9276 Institutional support: RVO:68081731 Keywords : burnt clays * pozzolanic activity * amorphous phase * environmental scanning electron microscope Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.891, year: 2016