Sample records for backscattered diffraction ebsd

  1. Electron Backscatter Diffraction (EBSD) Characterization of Uranium and Uranium Alloys

    SciTech Connect

    McCabe, Rodney J. [Los Alamos National Laboratory; Kelly, Ann Marie [Los Alamos National Laboratory; Clarke, Amy J. [Los Alamos National Laboratory; Field, Robert D. [Los Alamos National Laboratory; Wenk, H. R. [University of California, Berkeley

    2012-07-25

    Electron backscatter diffraction (EBSD) was used to examine the microstructures of unalloyed uranium, U-6Nb, U-10Mo, and U-0.75Ti. For unalloyed uranium, we used EBSD to examine the effects of various processes on microstructures including casting, rolling and forming, recrystallization, welding, and quasi-static and shock deformation. For U-6Nb we used EBSD to examine the microstructural evolution during shape memory loading. EBSD was used to study chemical homogenization in U-10Mo, and for U-0.75Ti, we used EBSD to study the microstructure and texture evolution during thermal cycling and deformation. The studied uranium alloys have significant microstructural and chemical differences and each of these alloys presents unique preparation challenges. Each of the alloys is prepared by a sequence of mechanical grinding and polishing followed by electropolishing with subtle differences between the alloys. U-6Nb and U-0.75Ti both have martensitic microstructures and both require special care in order to avoid mechanical polishing artifacts. Unalloyed uranium has a tendency to rapidly oxidize when exposed to air and a two-step electropolish is employed, the first step to remove the damaged surface layer resulting from the mechanical preparation and the second step to passivate the surface. All of the alloying additions provide a level of surface passivation and different one and two step electropolishes are employed to create good EBSD surfaces. Because of its low symmetry crystal structure, uranium exhibits complex deformation behavior including operation of multiple deformation twinning modes. EBSD was used to observe and quantify twinning contributions to deformation and to examine the fracture behavior. Figure 1 shows a cross section of two mating fracture surfaces in cast uranium showing the propensity of deformation twinning and intergranular fracture largely between dissimilarly oriented grains. Deformation of U-6Nb in the shape memory regime occurs by the motion of twin boundaries formed during the martensitic transformation. Deformation actually results in a coarsening of the microstructure making EBSD more practical following a limited amount of strain. Figure 2 shows the microstructure resulting from 6% compression. Casting of U-10Mo results in considerable chemical segregation as is apparent in Figure 2a. The segregation subsists through rolling and heat treatment processes as shown in Figure 2b. EBSD was used to study the effects of homogenization time and temperature on chemical heterogeneity. It was found that times and temperatures that result in a chemically homogeneous microstructure also result in a significant increase in grain size. U-0.75Ti forms an acicular martinsite as shown in Figure 4. This microstructure prevails through cycling into the higher temperature solid uranium phases.

  2. Improving the quality of electron backscatter diffraction (EBSD) patterns from nanoparticles.

    PubMed

    Small, J A; Michael, J R; Bright, D S

    2002-05-01

    In this study, we investigated the relative contributions of atomic number (Z) and density (rho) to the degradation of the electron backscatter diffraction (EBSD) pattern quality for nanoparticles < 500 nm in diameter. This was accomplished by minimizing the diffuse scattering from the conventional thick mounting substrate through the design of a sample holder that can accommodate particles mounted on thin-film TEM substrates. With this design, the contributions of incoherently scattered electrons that result in the diffuse background are minimized. Qualitative and quantitative comparisons were made of the EBSD pattern quality obtained from Al(2)O(3) particles approximately 200 nm in diameter mounted on both thick- and thin-film C substrates. For the quantitative comparison we developed a 'quality' factor for EBSD patterns that is based on the ratio of two Hough transforms derived from a given EBSD pattern image. The calculated quality factor is directly proportional to the signal-to-noise ratio for the EBSD pattern. In addition to the comparison of the thick and thin mounting substrates, we also estimated the effects of Z and rho by comparing the EBSD pattern quality from the Al(2)O(3) particles mounted on thin-film substrates with the quality of patterns obtained from Fe-Co nanoparticles approximately 120 nm in diameter. The results indicate that the increased background generated in EBSD patterns by the electrons escaping through the bottom of the small particles is the dominant reason for the poor EBSD pattern quality from nanoparticles < 500 nm in size. This was supported by the fact that we were able to obtain usable EBSD patterns from Al(2)O(3) particles as small as 130 nm using the thin-film mounting method. PMID:12000557

  3. Crystallographic Orientation Analyses of Magnetite Thin Films Using Electron Backscatter Diffraction (EBSD)

    Microsoft Academic Search

    A. Koblischka-Veneva; M. R. Koblischka; F. Mucklich; S. Murphy; Y. Zhou; I. V. Shvets

    2006-01-01

    The crystallographic orientation of magnetite (Fe3O4) thin films was measured using electron backscatter diffraction (EBSD). Misorientation boundaries appear in maps of angular misorientation data. The distribution of misorientation angles changes after annealing the samples in air at 250degC. Most small-angle misorientations (<5deg) are removed after one minute of annealing, whereas larger misorientations (as high as 60deg) continue to persist

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

    PubMed

    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. PMID:21130663

  5. Metallographic preparation of Zn-21Al-2Cu alloy for analysis by electron backscatter diffraction (EBSD).

    PubMed

    Rodríguez-Hernández, M G; Martínez-Flores, E E; Torres-Villaseñor, G; Escalera, M Dolores

    2014-08-01

    Samples of Zn-21Al-2Cu alloy (Zinalco) that will be heavily deformed were prepared using five different manual mechanical metallographic methods. Samples were analyzed before tensile testing using the orientation imaging microscopy-electron backscatter diffraction (OIM-EBSD) technique. The effect of type and particle size during the final polishing stages for this material were studied in order to identify a method that produces a flat, damage free surface with a roughness of about 50 nm and clean from oxide layers, thereby producing diffraction patterns with high image quality (IQ) and adequate confidence indexes (CI). Our results show that final polishing with alumina and silica, as was previously suggested by other research groups for alloys that are difficult to prepare or alloys with low melting point, are not suitable for manual metallographic preparation of this alloy. Indexes of IQ and CI can be used to evaluate methods of metallographic preparation of samples studied using the OIM-EBSD technique. PMID:24685337

  6. An automated method of quantifying ferrite microstructures using electron backscatter diffraction (EBSD) data.

    PubMed

    Shrestha, Sachin L; Breen, Andrew J; Trimby, Patrick; Proust, Gwénaëlle; Ringer, Simon P; Cairney, Julie M

    2014-02-01

    The identification and quantification of the different ferrite microconstituents in steels has long been a major challenge for metallurgists. Manual point counting from images obtained by optical and scanning electron microscopy (SEM) is commonly used for this purpose. While classification systems exist, the complexity of steel microstructures means that identifying and quantifying these phases is still a great challenge. Moreover, point counting is extremely tedious, time consuming, and subject to operator bias. This paper presents a new automated identification and quantification technique for the characterisation of complex ferrite microstructures by electron backscatter diffraction (EBSD). This technique takes advantage of the fact that different classes of ferrite exhibit preferential grain boundary misorientations, aspect ratios and mean misorientation, all of which can be detected using current EBSD software. These characteristics are set as criteria for identification and linked to grain size to determine the area fractions. The results of this method were evaluated by comparing the new automated technique with point counting results. The technique could easily be applied to a range of other steel microstructures. PMID:24291695

  7. Application of electron backscatter diffraction (EBSD) to fracture studies of ferritic steels.

    PubMed

    Davies, P A; Novovic, M; Randle, V; Bowen, P

    2002-03-01

    The application of electron backscatter diffraction (EBSD) to fracture studies has provided a new method for investigating the crystallography of fracture surfaces. The crystallographic indices of cleavage planes can be measured both directly from the fracture surface and indirectly from metallographic sections perpendicular to the plane of the adjoining fracture surfaces. The results of direct individual cleavage facet plane orientation measurements are presented for carbon-manganese (C-Mn) and low-alloy Mn-Mo-Ni (similar to ASTM A553 type-B). Pressure vessel steel weld metals, obtained from fracture surfaces of Charpy impact test specimens fractured at various test temperatures and for an ultra-low carbon steel (Fe-0.002C- 0.058P) fractured at -196 degrees C by impact. In addition to the direct measurement from the fracture surface, cleavage facet orientation measurements for the ultra-low carbon steel were complemented by the results obtained from the metallographic sections. Fractographic observations revealed that cleavage fracture is accommodated by a microvoid coalescence fracture micromechanism, which was induced by decohesion of second phase particles (inclusions). The correlation between the direct and indirect methodologies shows that the cleavage facet planes are dominated by the [001] plane orientations, and indicated that even when information concerning the full five degrees of freedom is inaccessible, the cleavage facet plane could still be determined. Finally, the advantages and disadvantages of direct orientation measurements from the fracture surface and indirectly by a destructive sectioning technique are discussed. PMID:11996192

  8. Crystallographic preferred orientation (CPO) of gypsum measured by electron backscatter diffraction (EBSD).

    PubMed

    Hildyard, R C; Prior, D J; Mariani, E; Faulkner, D R

    2009-12-01

    An investigation by electron backscatter diffraction on gypsum shows that this technique can be used to study the microstructures and crystallographic preferred orientation of gypsum. Presented here are the methods, verification tests and data obtained from a naturally deformed sample of gypsum-rich rock. The electron backscatter diffraction data show the sample has a strong crystallographic preferred orientation. PMID:19941555

  9. Electron back-scattering diffraction (EBSD) measurements of antigorite lattice-preferred orientations (LPO).

    PubMed

    van de Moortèle, B; Bezacier, L; Trullenque, G; Reynard, B

    2010-09-01

    Lattice preferred orientations of serpentines induce a strong anisotropy of various properties in serpentine bearing-rocks. Lattice preferred orientations had so far been obtained only by X-ray diffraction techniques. We have applied electron back-scattering diffraction to the measurement of the lattice preferred orientations of antigorite in a naturally deformed high-pressure serpentinite. This technique is very sensitive to sample preparation that can lead to surface amorphization in the case of serpentine. A polishing procedure is described that avoids amorphization and allows accurate electron back-scattering diffraction measurements with optimized experimental conditions in a variable pressure scanning electron microscope. Results indicate that deformation leads to lattice preferred orientations characterized by extremely strong c-axis clustering perpendicular to the foliation, as expected for a layered silicate. In the foliation plane, a significant clustering of the a-axis is observed and tentatively attributed to intracrystalline deformation mechanisms. These data suggest that antigorite deforms mostly by gliding along the basal plane of the layered phyllosilicate structure, but that gliding may occur along directions favouring a-axis alignment. Electron back-scattering diffraction appears to be a reliable method for determining phyllosilicate lattice preferred orientations in deformed rocks, with potential applications for determining anisotropy of properties like seismic velocities or thermal and electrical conductivities. PMID:20701663

  10. Characterization of pyramidal inversion boundaries in Sb2O3-doped ZnO by using electron back-scattered diffraction (EBSD).

    PubMed

    Jo, Wook; Park, Chan; Kim, Doh-Yeon

    2007-05-01

    The composition planes of the inversion boundary induced by the addition of Sb2O3 to ZnO ceramics were analyzed crystallographically by the application of electron back-scattered diffraction (EBSD) analysis and stereographic projection techniques. The inversion boundary was determined to consist of three discrete composition planes, {0001}, {1011}, {1010}. PMID:17435286

  11. Crystallographic orientation analysis of magnetite thin films by means of electron backscatter diffraction (EBSD)

    Microsoft Academic Search

    A. D. Koblischka-Veneva; M. R. Koblischka; F. Muecklich; S. Murphy; Y. Zhou; I. V. Shvets

    2006-01-01

    Fe3O4[001] thin films is grown on MgO[001] substrates using oxygen-plasma-assisted molecular beam epitaxy and annealed in air at 250 degC. Automated EBSD scans is performed twice to study the crystallographic orientation by means of recording of Kikuchi patterns.

  12. Characterisation of texture in Ti-6246 alloy fibre laser welds using Electron Backscattered Diffraction (EBSD)

    NASA Astrophysics Data System (ADS)

    Merson, Eleanor; Hammond, Chris; Brydson, Rik

    2006-02-01

    In this study, fibre laser welds of alloy Ti-6%Al-2%Sn-4%Zr-6%Mo have been characterised. It has been found that although the microstructure of the welds is important in predicting properties, it is not enough to simply characterise the welds based on the microstructure, as crystallographic texturing is also important in determining mechanical properties. The texturing of the fibre laser welds is being characterized using EBSD mapping, with light microscopy to characterize the microstructure. This has been carried out for a weld that has been heat treated for 3 hours at 550 °C. At this temperature, relaxation of residual stress will occur, but changes to the microstructure will be minimal. It is planned that EBSD will now be carried out on the as received sample, and the results will be presented, along with a comparison with the heat treated weld.

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

    SciTech Connect

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

    1999-05-19

    Crystallographic orientations in alumina (Al203) and magnesium aluminate spinel (MgAl204) were obtained using electron backscattered diffraction (EBSD) patterns. The texture and mesotexture (grain boundary misorientations) 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 misorientations.

  14. Prediction and identification of calcium-rich phases in Al-Si alloys by electron backscatter diffraction EBSD/SEM

    SciTech Connect

    Zaldivar-Cadena, A.A. [Department of Metallurgical Engineering, Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Saltillo, Carr. Saltillo-Monterrey Km.13, Ramos Arizpe, Coahuila, 25900 (Mexico)]. E-mail: antonio.zaldivar@cinvestav.edu.mx; Flores-Valdes, A. [Department of Metallurgical Engineering, Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Saltillo, Carr. Saltillo-Monterrey Km.13, Ramos Arizpe, Coahuila, 25900 (Mexico)]. E-mail: alfredo.flores@cinvestav.edu.mx

    2007-08-15

    Al-7Si-3Cu-Fe, Al-7Si-3Cu-Fe-0.5Mn, Al-12Si-Mg-Ni-Cu, A319 and A380 alloys containing 0.0020, 0.0040, 0.0080, 0.1 and 0.2 wt.% Ca were used in this research to study the effects of Ca additions on their microstructures and hardness. Samples from the molten alloys were taken and characterized by SEM, EDS and EBSD analysis. Electron backscatter diffraction patterns (EBSDPs) were used to assess the crystallographic characteristics of calcium compounds, thus identifying their stoichiometry. On the other hand, microstructural formation was predicted using an adapted version of Thermo-Calc{sup TM} software. Compounds which contain calcium-rich particles with 'needle-like' or 'plate-like' morphologies were consistent with that of the hexagonal CaAl{sub 2}Si{sub 2} intermetallic phase in all of the alloys used. Moreover, it was found that Ca additions of 40 ppm and higher, refined the eutectic Si particles and coarsened the iron-rich intermetallics as well. Brinell hardness was evaluated to determine the effect of calcium concentration on the hardness of the Al-Si alloys used in this study.

  15. Towards a more comprehensive microstructural analysis of Zr-2.5Nb pressure tubing using image analysis and electron backscattered diffraction (EBSD)

    NASA Astrophysics Data System (ADS)

    Hovington, P.; Pinard, P. T.; Lagacé, M.; Rodrigue, L.; Gauvin, R.; Trudeau, M. L.

    2009-08-01

    Zr-2.5Nb pressure tubes used in CANDU (CANada Deuterium Uranium) reactors have a very complex microstructure, with two major crystallographic phases, ? and ?. These phases include a fair amount of deformation from the extrusion process and the cold working (˜25%) performed at the end of the manufacturing process. This microstructure (texture, grain aspect ratio, etc.) changes along the tube's length and differs from tube to tube. In order to better understand the deformation mechanisms, these microstructural differences must be statistically characterized. Scanning electron microscopy combined with direct image analysis or with electron backscattered diffraction (EBSD) are good techniques for carrying out such a measurement. However it is not possible, using specimen preparation methods specific for each of these techniques, to reveal all of the grain and phase boundaries. We have thus developed post-treatment algorithms to be able to partially analyze the revealed Zr-2.5Nb microstructure. The first algorithm was used for image analysis treatments of micrographs taken at 5 kV on the radial-tangential plane of etched samples using a reactive ion etch (RIE, CF 4 + O 2). The second was developed for EBSD grain mapping and can be used to characterize ?-Zr grain shape and orientation. The two techniques are complementary: EBSD gives information about the micro-texture and the relationship between the microstructure and micro-texture while image analyses of SEM micrographs reveal the direction and distribution of the ?-Zr lamellae more easily and over a greater sample area than EBSD. However, the SEM micrographs that were used did not reveal any grain boundary (only phase boundary). An analysis of EBSD grain maps reveals that the average ?-Zr grain size, mainly in the elongated direction (tangential), is smaller than what is normally obtained from an image analysis of SEM micrographs. The grain size distribution of type I ?-Zr grains (deformed original (prior) ?-Zr) and type II (stress-induced ?-Zr ? ?-Zr phase transformation) is also shown to be different for sizes greater than 0.4 ?m 2.

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

    NASA Technical Reports Server (NTRS)

    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 <100>{010} slip. The deformation bands are unlike curved morphology of crystal-plastic microstructures in tectonically deformed terrestrial zircon, and geometrically similar to dislocation microstructures reported in experimentally shocked zircon. We interpret these crystal-plastic deformation microstructures to have resulted from a significant impact, either directly from impact shock, or during ductile flow directly following the impact. The deformation bands appear to continue undeflected through the non-indexed, radiation-damaged areas of the grain, which suggests that the orientation variation predates any significant mechanical weakening from radiation damage in the grain, and therefore occurred early in its history.

  17. An open-source engine for the processing of electron backscatter patterns: EBSD-image.

    PubMed

    Pinard, Philippe T; Lagacé, Marin; Hovington, Pierre; Thibault, Denis; Gauvin, Raynald

    2011-06-01

    An open source software package dedicated to processing stored electron backscatter patterns is presented. The package gives users full control over the type and order of operations that are performed on electron backscatter diffraction (EBSD) patterns as well as the results obtained. The current version of EBSD-Image (www.ebsd-image.org) offers a flexible and structured interface to calculate various quality metrics over large datasets. It includes unique features such as practical file formats for storing diffraction patterns and analysis results, stitching of mappings with automatic reorganization of their diffraction patterns, and routines for processing data on a distributed computer grid. Implementations of the algorithms used in the software are described and benchmarked using simulated diffraction patterns. Using those simulated EBSD patterns, the detection of Kikuchi bands in EBSD-Image was found to be comparable to commercially available EBSD systems. In addition, 24 quality metrics were evaluated based on the ability to assess the level of deformation in two samples (copper and iron) deformed using 220 grit SiC grinding paper. Fourteen metrics were able to properly measure the deformation gradient of the samples. PMID:21554830

  18. An analysis of microband orientation in a commercial purity aluminium alloy subjected to forward and reverse torsion using Electron Backscatter Diffraction (EBSD).

    PubMed

    Lopez-Pedrosa, M; Wynne, B P; Rainforth, W M

    2006-05-01

    High-resolution electron backscatter diffraction has been used to study the effects of strain reversal on the evolution of microbands in commercial purity aluminium alloy AA1200. Deformation was carried out using two equal steps of forward/forward or forward/reverse torsion at a temperature of 300 degrees C and strain rate of 1 s(-1) to a total equivalent tensile strain of 0.5. In both cases, microbands were found in the majority of grains examined with many having microband walls with more than one orientation. For the forward/forward condition, the microband clusters were centred around -20 degrees and +45 degrees to the equivalent tensile stress axis, whereas for material subjected to a strain reversal, the clusters were at -65 degrees and -45 degrees . There was no evidence of microbands that were formed in the forward deformation step in the reversed material, which would suggest that a strain of 0.25 is sufficient to dissolve any microstructure history generated by the first step. Furthermore, the microbands within the strain-reversed material had a reduction in misorientation compared with the lineally strained material, suggesting that these microbands only formed at the onset of the second deformation step. This confirms that microband formation is complex and sensitive to strain path; however, it is still unclear to what extent microband formation is dependent on strain path history compared with the instantaneous deformation mode. PMID:16774518

  19. Validation of three-dimensional diffraction contrast tomography reconstructions by means of electron backscatter diffraction characterization

    PubMed Central

    Syha, Melanie; Trenkle, Andreas; Lödermann, Barbara; Graff, Andreas; Ludwig, Wolfgang; Weygand, Daniel; Gumbsch, Peter

    2013-01-01

    Microstructure reconstructions resulting from diffraction contrast tomography data of polycrystalline bulk strontium titanate were reinvestigated by means of electron backscatter diffraction (EBSD) characterization. Corresponding two-dimensional grain maps from the two characterization methods were aligned and compared, focusing on the spatial resolution at the internal interfaces. The compared grain boundary networks show a remarkably good agreement both morphologically and in crystallographic orientation. Deviations are critically assessed and discussed in the context of diffraction data reconstruction and EBSD data collection techniques. PMID:24046507

  20. Crystallographic orientation assessment by electron backscattered diffraction.

    PubMed

    Cléton, F; Jouneau, P H; Henry, S; Gäumann, M; Buffat, P A

    1999-01-01

    With an angular orientation accuracy of at least 1 , the ability of electron backscattered diffraction (EBSD) to determine and emphasise crystallographic orientation is illustrated. Using the abilities of specially developed software for computing Euler angles derived from the scanned specimen, misorientations are pointed out with acceptable flexibility and graphic output through crystallographic orientation maps or pole figures. This ability is displayed in the particular case of laser cladding of nickel-based superalloy, a process that combines the advantages of a near net-shape manufacturing and a close control of the solidification microstructure (E-LMF: epitaxial laser metal forming). PMID:10483877

  1. Misorientations in [001] magnetite thin films studied by electron backscatter diffraction and magnetic force microscopy

    Microsoft Academic Search

    A. Koblischka-Veneva; M. R. Koblischka; J. D. Wei; Y. Zhou; S. Murphy; F. Mücklich; U. Hartmann; I. V. Shvets

    2007-01-01

    Magnetite thin films grown on [001] oriented MgO substrates are analyzed by means of electron backscatter diffraction (EBSD) analysis and magnetic force microscopy in applied fields. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution up to 20 nm on such ceramic samples. A high image quality of the recorded Kikuchi

  2. Electron backscatter diffraction on femtosecond laser sulfur hyperdoped silicon

    NASA Astrophysics Data System (ADS)

    Gimpel, Thomas; Höger, Ingmar; Falk, Fritz; Schade, Wolfgang; Kontermann, Stefan

    2012-09-01

    This paper analyzes the impact of femtosecond laser pulse irradiation on the crystallinity of silicon wafers by means of electron backscatter diffraction (EBSD) measurements. EBSD based image quality maps and orientation imaging microscopy maps are correlated to the grade of the silicon crystallinity. We analyze the impact of accumulated net laser irradiation originating from a laser spot overlap that is necessary to process macroscopic areas, e.g., for sulfur doping of semiconductor devices. Furthermore, we demonstrate that post processing annealing recovers crystallinity and therefore allows fs-laser processed silicon to be used in semiconductor device manufacturing.

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

    PubMed

    Saowadee, N; Agersted, K; Ubhi, H S; Bowen, J R

    2013-01-01

    Serial sectioning by focused ion beam milling for three-dimensional electron backscatter diffraction (3D-EBSD) can create surface damage and amorphization in certain materials and consequently reduce the EBSD signal quality. Poor EBSD signal causes longer data acquisition time due to signal 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 ?m. The key to achieving this technique is the combination of a defocused low kV high current ion beam and line scan milling. The line scan was used to restrict polishing to the sample surface and the ion beam was defocused to ensure the beam contacted the complete sample surface. In this study 1 min polishing time per slice increases total acquisition time by approximately 3.3% of normal 3D-EBSD mapping compared to a significant increase of indexing percentage and pattern quality. The polishing performance in this investigation is discussed, and two potential methods for further improvement are presented. PMID:23126405

  4. Present State of Electron Backscatter Diffraction and Prospective Developments

    SciTech Connect

    Schwarzer, R A; Field, D P; Adams, B L; Kumar, M; Schwartz, A J

    2008-10-24

    Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al. 2000) due to the wide availability of SEMs, the ease of sample preparation from the bulk, the high speed of data acquisition, and the access to complementary information about the microstructure on a submicron scale. From the same specimen area, surface structure and morphology of the microstructure are characterized in great detail by the relief and orientation contrast in secondary and backscatter electron images, element distributions are accessed by energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), or cathodoluminescence analysis, and the orientations of single grains and phases can now be determined, as a complement, by EBSD.

  5. Multivariate statistical approaches for electron backscattered diffraction.

    SciTech Connect

    Michael, Joseph Richard; Brewer, Luke N.; Kotula, Paul Gabriel

    2005-07-01

    Electron backscattered diffraction (EBSD) is a widely used technique for both identifying the crystallographic phase and for mapping the orientation of crystalline materials on the micron length scale. Often the operating conditions necessary for phase identification are not suitable for orientation mapping and vice versa. In an effort to optimize the speed involved in the mapping technique, pattern quality is sacrificed and the wealth of information present in an EBSD pattern is compressed to basically 4 values: a matched phase and three Euler angles. However, ab initio identification of phases from EBSD patterns requires high quality patterns and fairly intense computation. Spectrum imaging is an analytical approach that may offer some solutions to the aforementioned problems. Spectrum imaging consists of collecting a whole spectrum at each pixel in a mapping style measurement. This large set of data is then analyzed using multivariate statistical analysis (MSA) techniques such as principle components analysis, multivariate curve resolution, or other least squares based techniques. The result of these calculations is a set of component spectral shapes with corresponding abundances that allow the analyst to extract the greatest amount of physically relevant information from an otherwise enormous data set. Spectrum imaging has been used successfully in EDX microanalysis (both in the SEM and TEM), TOF-SIMS, WDS, and EELS. To examine the potential benefits of the spectrum imaging approach for EBSD data, a series of basic experiments and calculations were run. Test data sets (20 x 20 patterns in .jpeg format) on polycrystalline Al and on the directionally solidified eutectic oxide, CoO/ZrO{sub 2}(CaO), were collected using the HKL Channel 5 system with a Nordlys detector under normal mapping conditions. The data was collected on a FEI dual beam FIB (model DB235) and a Zeiss (Supra 55 VP) SEM at 20keV for Al and CoO/ZrO{sub 2}(CaO), respectively. The data sets were analyzed according to the schematic shown in Figure 1. Each EBSD pattern was hough transformed, unzipped into a 1-D vector of channels with intensities ranging from 0-255, and then added to an overall data matrix. A range of treatments (edge/no edge detection, spatial simplicity/spectral simplicity, etc.) were examined to determine the optimal way of treating the data. The multivariate analyses were performed using the AXSIA code developed at Sandia National Laboratories. The MSA techniques were able to correctly identify individual grains in the Al sample and individual phases in the CoO/ZrO{sub 2}(CaO) sample. For each component EBSD pattern identified from the Al data, a corresponding color map of abundance can be seen which clearly corresponds to a single grain (Figure 2). The success in the CoO/ZrO{sub 2}(CaO) sample is particularly notable due to both phases sharing the Fm-3m space group which would confuse most autoindexing routines. The range of analytical treatments identified two extremes in results: a minimal number of components (patterns) with only kikuchi line positions present or a larger number of components with full intensity information present. The further application of these results to phase mapping will be discussed.

  6. Electron backscatter diffraction of plutonium-gallium alloys

    SciTech Connect

    Boehlert, C. J. (Carl J.); Zocco, T. G. (Thomas G.); Schulze, R. K. (Roland K.); Mitchell, J. N. (Jeremy N.); Pereyra, R. A. (Ramiro A.)

    2002-01-01

    At Los Alamos National Laboratory a recent experimental technique has been developed to characterize reactive metals, including plutonium arid cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of plutonium and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with plutonium metal. The experimental techniques, which included ion-sputtering the metal surface using a scanning auger microprobe (SAM) followed by vacuum transfer of the sample from the SAM to the scanning electron microscope (SEM), used to obtain electron backscatter diffraction Kikuchi patterns (EBSPs) and orientation maps for plutonium-gallium alloys are described and the initial microstructural observations based on the analysis are discussed. Combining the SEM and EBSD observations, the phase transformation behavior between the {delta} and {var_epsilon} structures was explained. This demonstrated sample preparation and characterization technique is expected to be a powerful means to further understand phase transformation behavior, orientation relationships, and texlure in the complicated plutonium alloy systems.

  7. Electron backscatter diffraction of MgB2

    NASA Astrophysics Data System (ADS)

    Mikheenko, P.

    2012-07-01

    MgB2 is one of important new functional materials, which can play significant role in emerging Hydrogen Economy. If adopted, Hydrogen Economy would be a low-CO2 fossil-fuels-free answer to the current and future energy demands. To contribute to this economy, advanced methods of MgB2 preparation and an insight into its properties are required. This paper reports electron backscatter diffraction (EBSD) of dense polycrystalline MgB2 prepared by Hot Isostatic Pressing and Resistive Sintering. The EBSD study was performed in combination with polarised optical microscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and scanning conductivity probe microscopy. The superconducting properties were measured in order to select specimens with highest critical current density to associate this density with structural features of the samples. The investigation shows importance of twist grain boundaries in increasing critical current density in MgB2.

  8. Quantification of plastic strain of stainless steel and nickel alloy by electron backscatter diffraction

    Microsoft Academic Search

    Masayuki Kamaya; Angus J. Wilkinson; John M. Titchmarsh

    2006-01-01

    Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy is applied to assess the plastic strain present in stainless steel and nickel alloys following tensile loading. A parameter, which quantifies the spread of the crystal orientation within individual grains arising due to dislocation accumulation during plastic deformation, is correlated with imposed plastic strain. The parameter is called the ‘modified

  9. Ultrasonic Characterization of Texture in Rolled Aluminium Correlated with Electron Backscatter Diffraction Measurements

    NASA Astrophysics Data System (ADS)

    Essex, S. D.; Potter, M. D. G.; Dixon, S.

    2007-03-01

    Electron Backscatter Diffraction (EBSD) is a microscopic technique that provides detailed crystallographic orientation and microstructural information, allowing for accurate measurement of such properties like average grain size. In order to validate and better understand what information an ultrasonic technique can give us we are correlating the ultrasonic measurements with those from EBSD. It generates an appreciation of the limitations of both techniques, and what each can reasonably deliver. We describe a technique to extrapolate the three independent orientation distribution coefficients (ODCs) for cubic structures W400, W420 and W440 from the Bunge-Euler angle data from EBSD scans. Preliminary EBSD results for thin rolled aluminium sheet are discussed and compared to the ODCs determined on the same sample using an ultrasonic EMAT-EMAT S0 Lamb wave measurement system.

  10. Electron backscatter diffraction analysis applied to [0 0 1] magnetite thin films grown on MgO substrates

    Microsoft Academic Search

    A. Koblischka-Veneva; M. R. Koblischka; Y. Zhou; S. Murphy; F. Mücklich; U. Hartmann; I. V. Shvets

    2007-01-01

    Electron backscatter diffraction (EBSD) analysis is applied to [001] oriented magnetite thin films grown on MgO substrates. A high image quality of the Kikuchi patterns was achieved enabling multi-phase scans. Several types of magnetite thin films were analyzed; one as-grown and the others after different annealing steps in oxygen atmosphere. From the EBSD mappings, we learn that the optimum orientation

  11. Phase analysis on dual-phase steel using band slope of electron backscatter diffraction pattern.

    PubMed

    Kang, Jun-Yun; Park, Seong-Jun; Moon, Man-Been

    2013-08-01

    A quantitative and automated phase analysis of dual-phase (DP) steel using electron backscatter diffraction (EBSD) was attempted. A ferrite-martensite DP microstructure was produced by intercritical annealing and quenching. An EBSD map of the microstructure was obtained and post-processed for phase discrimination. Band slope (BS), which was a measure of pattern quality, exhibited much stronger phase contrast than another conventional one, band contrast. Owing to high sensitivity to lattice defect and little orientation dependence, BS provided handiness in finding a threshold for phase discrimination. Its grain average gave a superior result on the discrimination and volume fraction measurement of the constituent phases in the DP steel. PMID:23920165

  12. Automated twin identification technique for use with electron backscatter diffraction.

    SciTech Connect

    Henrie, B. L. (Benjamin Lyman); Mason, T. A. (Thomas A.); Bingert, J. F. (John F.)

    2004-01-01

    Historically, twinning information has been obtained by optical microscopy, TEM, and neutron diffraction. Recent research has shown that automated electron backscatter diffraction (EBSD) can be used to extract reliable twinning statistics. An automated twin identification technique for use with EBSD has facilitated a greater understanding of deformation twinning in materials. The key features of this automated framework are the use of the crystallographic definition of twin relationships, the inclination of the common K, plane at a twin boundary, and the correct identification of the parent orientation in a parent/twin pair. The complex nature of the parent/twin interactions required the use of a voting scheme to correctly identify parent orientations. In those few cases were the voting scheme was unable to determine parent orientation (< 2 pct) the algorithm allows for manual selection. Twin area fractions are categorized by operative twin systems along with secondary and tertiary twinning. These statistics are reported for {alpha}-zirconium and 316L stainless steel. These improved twin statistics can help quantify deformation processes as well as provide validation of plasticity models for materials that exhibit deformation twinning.

  13. Grain boundary as relevant microstructure feature for electromigration in advanced technology studied by Electron BackScattered Diffraction

    Microsoft Academic Search

    R. Galand; L. Arnaud; E. Petitprez; G. Brunetti; L. Clement; P. Waltz; Y. Wouters

    2011-01-01

    The work presented in this paper shows the links between electromigration (EM) in copper interconnects and microstructure of copper. Metal lines of 70 nm width corresponding to minimum width of 45-40 nm technology node are aged by electromigration (EM) test. Electron Backscattered Diffraction (EBSD) technique is then used to characterize microstructure and orientation of copper grains around void(s) resulting from

  14. Misorientation mapping for visualization of plastic deformation via electron back-scattered diffraction.

    PubMed

    Brewer, L N; Othon, M A; Young, L M; Angeliu, T M

    2006-02-01

    The ability to map plastic deformation around high strain gradient microstructural features is central in studying phenomena such as fatigue and stress corrosion cracking. A method for the visualization of plastic deformation in electron back-scattered diffraction (EBSD) data has been developed and is described in this article. This technique is based on mapping the intragrain misorientation in polycrystalline metals. The algorithm maps the scalar misorientation between a local minimum misorientation reference pixel and every other pixel within an individual grain. A map around the corner of a Vickers indentation in 304 stainless steel was used as a test case. Several algorithms for EBSD mapping were then applied to the deformation distributions around air fatigue and stress corrosion cracks in 304 stainless steel. Using this technique, clear visualization of a deformation zone around high strain gradient microstructural features (crack tips, indentations, etc.) is possible with standard EBSD data. PMID:17481344

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

    PubMed

    Tong, Vivian; Jiang, Jun; Wilkinson, Angus J; Britton, T Ben

    2015-08-01

    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 18nm 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. PMID:25957534

  16. Large Area Stress Distribution in Crystalline Materials Calculated from Lattice Deformation Identified by Electron Backscatter Diffraction

    NASA Astrophysics Data System (ADS)

    Shao, Yongliang; Zhang, Lei; Hao, Xiaopeng; Wu, Yongzhong; Dai, Yuanbin; Tian, Yuan; Huo, Qin

    2014-08-01

    We report a method to obtain the stress of crystalline materials directly from lattice deformation by Hooke's law. The lattice deformation was calculated using the crystallographic orientations obtained from electron backscatter diffraction (EBSD) technology. The stress distribution over a large area was obtained efficiently and accurately using this method. Wurtzite structure gallium nitride (GaN) crystal was used as the example of a hexagonal crystal system. With this method, the stress distribution of a GaN crystal was obtained. Raman spectroscopy was used to verify the stress distribution. The cause of the stress distribution found in the GaN crystal was discussed from theoretical analysis and EBSD data. Other properties related to lattice deformation, such as piezoelectricity, can also be analyzed by this novel approach based on EBSD data.

  17. Large Area Stress Distribution in Crystalline Materials Calculated from Lattice Deformation Identified by Electron Backscatter Diffraction

    PubMed Central

    Shao, Yongliang; Zhang, Lei; Hao, Xiaopeng; Wu, Yongzhong; Dai, Yuanbin; Tian, Yuan; Huo, Qin

    2014-01-01

    We report a method to obtain the stress of crystalline materials directly from lattice deformation by Hooke's law. The lattice deformation was calculated using the crystallographic orientations obtained from electron backscatter diffraction (EBSD) technology. The stress distribution over a large area was obtained efficiently and accurately using this method. Wurtzite structure gallium nitride (GaN) crystal was used as the example of a hexagonal crystal system. With this method, the stress distribution of a GaN crystal was obtained. Raman spectroscopy was used to verify the stress distribution. The cause of the stress distribution found in the GaN crystal was discussed from theoretical analysis and EBSD data. Other properties related to lattice deformation, such as piezoelectricity, can also be analyzed by this novel approach based on EBSD data. PMID:25091314

  18. Use of electropolishing for enhanced metallic specimen preparation for electron backscatter diffraction analysis

    SciTech Connect

    Wynick, G.L. [Alfred University, School of Engineering, Alfred, NY 14802 (United States); Boehlert, C.J. [Michigan State University, Department of Chemical Engineering and Materials Science, East Lansing, MI 48824-1226 (United States)]. E-mail: boehlert@egr.msu.edu

    2005-09-15

    The effects of mechanical polishing with Al{sub 2}O{sub 3} and colloidal SiO{sub 2} followed by electropolishing were studied for preparation of metal alloy specimens for Electron Backscatter Diffraction (EBSD). The alloys studied were Inconel 718, a commonly used nickel-based superalloy, and a Ti-Al-Nb alloy (nominally Ti-22Al-28Nb(at.%)). Atomic Force Microscopy was used to measure the surface topography to attempt to correlate nano-scale surface roughness with EBSD pattern quality. The results suggest that mechanically polishing with Al{sub 2}O{sub 3} followed by electropolishing for a short time can produce EBSD pattern confidence indices and image quality values that are equal to or better than those produced by mechanically polishing with colloidal SiO{sub 2} alone. The data suggests that surface roughness on the scale considered here has much less effect on EBSD pattern quality than had been previously believed. The data suggests that removing the surface damage is more critical than reduction of topography for EBSD.

  19. Use of Reciprocal Lattice Layer Spacing in Electron Backscatter Diffraction Pattern Analysis

    SciTech Connect

    Eades, J.A.; Michael, J.R.

    1999-05-10

    In the scanning electron microscope (SEM), using electron backscattered diffraction (EBSD), it is possible to measure the spacing of the layers in the reciprocal lattice. These values are of great use in confirming the identification of phases. The technique derives the layer spacing from the HOLZ rings which appear in patterns from many materials. The method adapts results from convergent-beam electron diffraction (CBED) in the transmission electron microscope (TEM). For many materials the measured layer spacing compares well with the calculated layer spacing. A noted exception is for higher atomic number materials. In these cases an extrapolation procedure is described that requires layer spacing measurements at a range of accelerating voltages. This procedure is shown to improves the accuracy of the technique significantly. The application of layer spacing measurements in EBSD is shown to be of use for the analysis of two polytypes of SiC.

  20. Observation of Ferroelectricity in a Confined Crystallite Using Electron Backscattered Diffraction and Piezoresponse Force Microscopy

    SciTech Connect

    Gupta, P. [Lehigh University, Bethlehem, PA; Jain, H. [Lehigh University, Bethlehem, PA; Williams, D. B. [Lehigh University, Bethlehem, PA; Kalinin, Sergei V [ORNL; Shin, Junsoo [ORNL; Jesse, Stephen [ORNL; Baddorf, Arthur P [ORNL

    2005-01-01

    LaBGeO{sub 5} is a model transparent ferroelectric glass-ceramic (TFGC) material, developed as an inexpensive alternative to single-crystal nonlinear optical materials. The optical activity of the TFGC originates from the ferroelectric phase which remains under a hydrostatic pressure exerted by the surrounding glass matrix. A combination of two techniques, electron-backscattered diffraction (EBSD) and piezoresponse force microscopy (PFM), is employed to monitor the development of the ferroelectric phase. A method is proposed to theoretically construct PFM amplitude maps from EBSD orientation maps. The theoretical vertical piezoresponse map is compared with the experimental piezoresponse map from PFM. A good correlation between the theoretical and experimental maps is observed.

  1. Combined EBSD/EDS tomography in a dual-beam FIB/FEG-SEM.

    PubMed

    West, G D; Thomson, R C

    2009-03-01

    An automated method for collecting combined three-dimensional (3D) electron backscatter diffraction (EBSD)/energy dispersive spectroscopy (EDS) data sets on a dual-beam focused ion beam (FIB)/field emission gun scanning electron microscope (FEG-SEM) microscope is described. The method uses simple scripting files on the dual beam to move between the EBSD collection and the FIB slicing positions, which are linked to a commercial EBSD data collection programme. The EDS data are collected simultaneously with the EBSD patterns analogous to combined two-dimensional (2D) EBSD/EDS. The technique has been successfully applied to study both the interdiffusion zone between a coating and a substrate and a complex multi-phase coating on a nickel-based superalloy sample. This analysis is shown to enable the complex grain shapes, location of precipitates and phase interconnectivity within these samples to be determined without the ambiguities associated with 2D stereographic analysis. PMID:19250465

  2. Ultrafine 316 L stainless steel particles with frozen-in magnetic structures characterized by means of electron backscattered diffraction

    Microsoft Academic Search

    Yolanda Hedberg; Oskar Karlsson; Peter Szakalos; Inger Odnevall Wallinder

    2011-01-01

    Electron Backscatter Diffraction (EBSD) studies clearly revealed a different crystallographic structure of the smallest particle size fraction of gas-atomized AISI 316L stainless steel powder (<4?m) compared with larger sized fractions of the same powder (<45?m). Despite similar chemical compositions, the predominating structure of the smallest particle size fraction was ferritic (i.e., has ferromagnetic properties) whereas the larger sized particle fractions

  3. Identification of magnetic Fe-Ti oxides in marine sediments by electron backscatter diffraction in scanning electron microscopy

    NASA Astrophysics Data System (ADS)

    Franke, C.; Pennock, G. M.; Drury, M. R.; Engelmann, R.; Lattard, D.; Garming, J. F. L.; von Dobeneck, T.; Dekkers, M. J.

    2007-08-01

    In paleomagnetic and environmental magnetic studies the magnetomineralogical identification is usually based on a set of rock magnetic parameters, complemented by crystallographic and chemical information retrieved from X-ray diffraction (XRD), (electron) microscopy or energy dispersive spectroscopy (EDS) of selected samples. While very useful, each of these supplementary techniques has its limitations when applied to natural sample material which are related to low particle concentrations (down to the ppm range in marine sediments) and very fine grain sizes (down to the nm scale). Therefore, meaningful application of such techniques depends on sample quality. Electron backscatter diffraction (EBSD) of individual grains in scanning electron microscopy (SEM) enables mineralogical identification of grains down to ~0.2 micrometer and is particularly powerful when combined with EDS. In this study, we show the merits of EBSD for rock magnetic investigations by analyzing titanomagnetites and hemoilmenites of various compositions and submicron lamella of titanomagnetite-hemoilmenite intergrowths. Such particles often occur in natural marine sediments where EDS often has a semi-quantitative character and compositionally similar intergrowths may be difficult to distinguish. With the mineralogical information provided by EBSD unambiguous identification of spinel-type and trigonal oxides is obtained. Optimal EBSD patterns are gathered from smooth, polished surfaces, but here we show that interpretable EBSD patterns can be obtained directly from the surface of unconsolidated, so called `non-embedded' particles from marine sediments. This information enhances the interpretative value of rock magnetic parameters.

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

    PubMed

    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. PMID:25461589

  5. Electron backscatter diffraction analysis of microstructural evolution in hot-deformed 6xxx series aluminum alloys

    NASA Astrophysics Data System (ADS)

    van Geertruyden, William H.; Claves, Steven R.; Misiolek, Wojciech Z.

    2002-03-01

    The electron backscatter diffraction (EBSD) technique is used to analyze the crystallographic grain orientation of deformed microstructures for 6xxx series aluminum alloy extrusions. In a partially extruded billet of aluminum, deformation zones with different crystallographic characteristics can be seen. Using compression testing performed on a Gleeble thermal-mechanical simulator under various conditions, the formation of different deformation zones is simulated. The EBSD technique is used to characterize samples deformed in compression testing to analyze the different deformation zones present in the extrusion process. Metal-flow analysis using EBSD is also applied to study the influence of different die designs on the surface texture of an extrudate. Microstructures from a profile that was formed with different die designs are examined. Analysis of a longitudinal weld present in typical hollow profiles is performed to determine the effect of metal-flow conditions on the resultant texture in the extrudate. The texture (or microtexture) measured from individual grains can be correlated to the orientation changes that occur during deformation.

  6. Prediction of Elastic Modulus + Anisotropy Using X-Ray and Electron Backscattered Diffraction Texture Quantification and Ultrasonic (Electromagnetic Acoustic Transducer) Measurements in Aluminum Sheets

    NASA Astrophysics Data System (ADS)

    Davis, C. L.; Strangwood, M.; Potter, M.; Dixon, S.; Morris, P. F.

    2008-03-01

    Crystallographic texture is generally measured using X-ray diffraction, performed off-line using small samples determining near-surface texture only; electron backscattered diffraction (EBSD) can also be used, but only samples relatively small areas. Ultrasonic methods determine elastic property anisotropy and texture, via orientation distribution coefficients (ODCs), and while there is substantial literature comparing ultrasonically determined properties with X-ray or neutron diffraction texture, there is little discussion about texture inhomogeneity (place to place in a sheet or through thickness) and sampling volume effects (X-ray compared to EBSD) on the accuracy of the correlations. In this article, the crystallographic texture of nominally pure aluminum and commercial aluminum alloy sheets has been determined by X-ray diffraction and EBSD and used to calculate the elastic anisotropy, which is then compared to ultrasonic electromagnetic acoustic transducer (EMAT) velocity anisotropy taking into account through-thickness texture variations. Significant and consistent spatial variability in texture occurs in the aluminum sheet samples (sheet edge to center and through thickness). Predictions of elastic anisotropy based on surface texture determination, as characterized by X-ray diffraction or surface EBSD, gave poor correlations with EMAT velocity anisotropy when the sample contained significant through thickness texture variations; however, accounting for this using multiple EBSD scans through thickness gave good correlations.

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

    PubMed

    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 <50 nm. Despite the fact that the IM process generates an increase of temperature at the specimen surface, it was assumed that the milling parameters were sufficient to minimize the heating 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. PMID:25280344

  8. Advances in EBSD and EBSD/EDS integration for the characterization of mineralogical samples

    NASA Astrophysics Data System (ADS)

    Palasse, L.; Goran, D.; Schwager, T.

    2013-12-01

    Electron BackScatter Diffraction (EBSD) is a well-known powerful technique for petrofabric studies using Scanning Electron Microscope. By assessing the quantitative microstructural information, i.e. crystallographic orientation data, it allows a large variety of applications: understanding the deformation mechanisms, seismic properties, metamorphic processes; and more recently, performing phase identification and discrimination when combined with Energy Dispersive X-Ray Spectroscopy (EDS). However, it is known that for multiphase mineralogical samples, the information delivered either by EBSD or by EDS alone is not enough to successfully distinguish the present phases. Typical examples for EBSD related indexing issues are phases creating similar patterns; and for EDS technique alone, phases with similar chemical composition like calcite and aragonite, quartz and cristobalite. Recent software and hardware developments have significantly improved the data quality as well as the efficiency/productivity. This presentation aims to reveal the latest development in data processing that has transformed the combination of the two complementary techniques into a powerful tool for characterizing multiphase materials. Through geosciences application examples, we will present the advantages brought by this new approach which uses the quantified EDS results and EBSP to identify the correct phase, reducing the need of data cleaning, and without spending extra time at the SEM. We will also demonstrate how powerful EBSD indexing algorithm can overcome the limitation from sample preparation, with some examples of high hit rate achieved on polyphase mineralogical specimen and even on shock-metamorphosed minerals. Last but not least, recent developments also enable the investigation of nanostructured materials in the scanning electron microscope (SEM) by Transmission Kikuchi Diffraction (TKD). Through some mineralogical applications, we will demonstrate the high spatial resolution (<10 nm) of this technique compared to conventional EBSD. EBSD phase map of an oxide gabbro collected by the Integrated Ocean Drilling Program Expedition 304/305, U1309D. phases: clinopyroxene, clinohypersthene, magnetite, ilmenite, tremolite, plagioclase, quartz, pyrrhotite, apatite, clinochlore. Sample courtesy: Dr. Angela Halfpenny, CSIRO Perth, Australia.

  9. Electron imaging with an EBSD detector.

    PubMed

    Wright, Stuart I; Nowell, Matthew M; de Kloe, René; Camus, Patrick; Rampton, Travis

    2015-01-01

    Electron Backscatter Diffraction (EBSD) has proven to be a useful tool for characterizing the crystallographic orientation aspects of microstructures at length scales ranging from tens of nanometers to millimeters in the scanning electron microscope (SEM). With the advent of high-speed digital cameras for EBSD use, it has become practical to use the EBSD detector as an imaging device similar to a backscatter (or forward-scatter) detector. Using the EBSD detector in this manner enables images exhibiting topographic, atomic density and orientation contrast to be obtained at rates similar to slow scanning in the conventional SEM manner. The high-speed acquisition is achieved through extreme binning of the camera-enough to result in a 5 × 5 pixel pattern. At such high binning, the captured patterns are not suitable for indexing. However, no indexing is required for using the detector as an imaging device. Rather, a 5 × 5 array of images is formed by essentially using each pixel in the 5 × 5 pixel pattern as an individual scattered electron detector. The images can also be formed at traditional EBSD scanning rates by recording the image data during a scan or can also be formed through post-processing of patterns recorded at each point in the scan. Such images lend themselves to correlative analysis of image data with the usual orientation data provided by and with chemical data obtained simultaneously via X-Ray Energy Dispersive Spectroscopy (XEDS). PMID:25461590

  10. Features of Transmission EBSD and its Application

    NASA Astrophysics Data System (ADS)

    Suzuki, Seiichi

    2013-09-01

    Features of transmission electron backscatter diffraction (EBSD) observation with a standard EBSD ( s-EBSD) detector are surveyed in this study. Heavily deformed Al and 8Cr tempered martensite transmission electron microscope (TEM) specimens were used for this study. It is shown that a specimen tilt angle of ~30°-40° in the opposite direction of the usual 70° and a smaller working distance in the range 4 mm-5 mm are recommended when using a s-EBSD detector. Specimen thickness and accelerating voltage (Acc.V) have a strong affect on the quality of transmission EBSD patterns and orientation maps. Higher Acc.Vs are generally recommended to get good quality orientation maps. In case of very thin specimens, lowering the Acc.Vs will give better results. In the observation of a thin film of an 8Cr tempered martensite steel specimen, it is confirmed that t-EBSD can provide images and detailed quantitative orientation data comparable with that obtained by TEM. It is also shown that small precipitates of Cr23C6 with sizes around 30 nm could be detected and their orientations measured.

  11. Limits of simulation based high resolution EBSD.

    PubMed

    Alkorta, Jon

    2013-08-01

    High resolution electron backscattered diffraction (HREBSD) is a novel technique for a relative determination of both orientation and stress state in crystals through digital image correlation techniques. Recent works have tried to use simulated EBSD patterns as reference patterns to achieve the absolute orientation and stress state of crystals. However, a precise calibration of the pattern centre location is needed to avoid the occurrence of phantom stresses. A careful analysis of the projective transformation involved in the formation of EBSD patterns has permitted to understand these phantom stresses. This geometrical analysis has been confirmed by numerical simulations. The results indicate that certain combinations of crystal strain states and sample locations (pattern centre locations) lead to virtually identical EBSD patterns. This ambiguity makes the problem of solving the absolute stress state of a crystal unfeasible in a single-detector configuration. PMID:23676453

  12. Scanning electron microscopy and transmitted electron backscatter diffraction examination of asbestos standard reference materials, amphibole particles of differing morphology, and particle phase discrimination from talc ores.

    PubMed

    Bandli, Bryan R; Gunter, Mickey E

    2014-12-01

    Since 1972, when the US Occupational Health and Safety Administration established the first limits on occupational exposure to asbestos fibers, numerous analytical methods employing several microscopy techniques have been developed to identify a group of minerals defined by legislation as asbestos. While transmission electron microscopy (TEM) is implemented in standardized analytical methods, these methods specify the use of selected area electron diffraction. Because of this constraint, the diffraction data a TEM can provide are often underutilized due to challenges associated with collecting and interpreting individual diffraction patterns. It has been shown that transmission electron backscatter diffraction (tEBSD) produces diffraction patterns nearly identical to electron backscatter diffraction, but from smaller crystal domains. This paper explores the utility of tEBSD for characterization of asbestiform particles from reference asbestos materials, a suite of amphibole minerals of varying morphologies to determine if there is a correlation between mineral habit (i.e., crystal form), microscopic particle shape preferred orientation, and mineral specimens from an industrial talc deposit to provide a case study of the utility and limitations of the technique. PMID:25339300

  13. A novel approach for site-specific atom probe specimen preparation by focused ion beam and transmission electron backscatter diffraction.

    PubMed

    Babinsky, K; De Kloe, R; Clemens, H; Primig, S

    2014-09-01

    Atom probe tomography (APT) is a suitable technique for chemical analyses with almost atomic resolution. However, the time-consuming site-specific specimen preparation can be improved. Recently, transmission electron backscatter diffraction (t-EBSD) has been established for high resolution crystallographic analyses of thin foils. In this paper we present the first successful application of a combined focused ion beam (FIB)/t-EBSD preparation of site-specific APT specimens using the example of grain boundary segregation in technically pure molybdenum. It will be shown that the preparation of a grain boundary can be substantially accelerated by t-EBSD analyses in-between the annular milling FIB procedure in the same microscope. With this combined method, a grain boundary can easily be recognized and positioned in the first 220nm of an APT sample much faster than e.g. with complementary investigations in a transmission electron microscope. Even more, the high resolution technique of t-EBSD gives the opportunity to get crystallographic information of the mapped area and, therefore, an analysis of the grain boundary character to support the interpretation of the APT data files. To optimize this newly developed technique for the application on needle-shaped APT specimens, a parameter study on enhanced background correction, acceleration voltage, and tilt angle was carried out. An acceleration voltage of 30kV at specimen surface tilt angles between -45° and -35° from horizontal plane leads to the best results. Even for molybdenum the observation of crystal orientation data up to about 200nm specimen thickness is possible. PMID:24815026

  14. The characterization of low-angle boundaries by EBSD.

    PubMed

    Bate, P S; Knutsen, R D; Brough, I; Humphreys, F J

    2005-10-01

    A method of accurately measuring misorientations by electron backscatter diffraction (EBSD), which is an extension of that proposed by Wilkinson and based on the comparison of diffraction patterns, is described. The method has been applied to linescans, and found to improve the angular resolution by a factor of more than 30. The consequent improvement in determining misorientation axes is also analysed. Small changes of orientation very close to some low-angle boundaries were investigated and found to be artefacts of the analysis. Measurements of the area from which diffraction patterns are generated show this to be much larger than the effective spatial resolution of EBSD, and it is concluded that this may be a limiting factor in the use of EBSD for microstructural characterization. PMID:16269062

  15. Application of Electron Backscatter Diffraction to Phase Identification

    SciTech Connect

    El-Dasher, B S; Deal, A

    2008-07-16

    The identification of crystalline phases in solids requires knowledge of two microstructural properties: crystallographic structure and chemical composition. Traditionally, this has been accomplished using X-ray diffraction techniques where the measured crystallographic information, in combination with separate chemical composition measurements for specimens of unknown pedigrees, is used to deduce the unknown phases. With the latest microstructural analysis tools for scanning electron microscopes, both the crystallography and composition can be determined in a single analysis utilizing electron backscatter diffraction and energy dispersive spectroscopy, respectively. In this chapter, we discuss the approach required to perform these experiments, elucidate the benefits and limitations of this technique, and detail via case studies how composition, crystallography, and diffraction contrast can be used as phase discriminators.

  16. Combined electron backscatter diffraction and cathodoluminescence measurements on CuInS2\\/Mo\\/glass stacks and CuInS2 thin-film solar cells

    Microsoft Academic Search

    D. Abou-Ras; U. Jahn; M. Nichterwitz; T. Unold; J. Klaer; H.-W. Schock

    2010-01-01

    Electron backscatter diffraction (EBSD) and cathodoluminescence (CL) measurements in a scanning electron microscope were performed on cross sections of CuInS2 thin films and ZnO\\/CdS\\/CuInS2\\/Mo\\/glass thin-film solar cells. The CuInS2 layers analyzed for the present study were grown by a rapid thermal process. The regions of the CuInS2 layers emitting high CL intensity of band-band luminescence are situated near the top

  17. Estimations of bulk geometrically necessary dislocation density using high resolution EBSD.

    PubMed

    Ruggles, T J; Fullwood, D T

    2013-10-01

    Characterizing the content of geometrically necessary dislocations (GNDs) in crystalline materials is crucial to understanding plasticity. Electron backscatter diffraction (EBSD) effectively recovers local crystal orientation, which is used to estimate the lattice distortion, components of the Nye dislocation density tensor (?), and subsequently the local bulk GND density of a material. This paper presents a complementary estimate of bulk GND density using measurements of local lattice curvature and strain gradients from more recent high resolution EBSD (HR-EBSD) methods. A continuum adaptation of classical equations for the distortion around a dislocation are developed and used to simulate random GND fields to validate the various available approximations of GND content. PMID:23751207

  18. Five-Parameter Grain Boundary Inclination Recovery with EBSD and Interaction Volume Models

    NASA Astrophysics Data System (ADS)

    Sorensen, Caroline; Basinger, John A.; Nowell, Matthew M.; Fullwood, David T.

    2014-08-01

    While electron backscatter diffraction (EBSD) patterns are often used to present two-dimensional information about a material microstructure, they are in fact a product of the three-dimensional electron interaction volume. Consequently, 3D spatial information exists in EBSD images, which is generally not accessed. Specifically, the inclination of the grain boundary plane may be observed in EBSD patterns taken near grain boundaries. If, at the same time, the shape of an electron interaction volume in the material is known, a grain boundary plane normal direction can be obtained from a sequence of EBSD images taken stepwise in a line crossing the grain boundary. Here, these two principles are used for demonstrating the determination of grain boundary normal vectors from EBSD images. Coherent twin boundaries and focused ion beam serial scan data are used for validation. Results indicate a mean error for this approach of 3 deg with a standard deviation of 3.8 deg.

  19. Electron Backscatter Diffraction (EBSD) Study of the Structure and Crystallography of the Barnacle Balanus amphitrite

    NASA Astrophysics Data System (ADS)

    Lewis, Alexis C.; Burden, Daniel K.; Wahl, Kathryn J.; Everett, Richard K.

    2014-01-01

    This work presents novel mapping of the structure and crystallography of the shell of the barnacle Balanus amphitrite. Calcium carbonate in the form of hexagonal calcite was observed, with fine crystallites on the order of 1 ?m in diameter forming clusters of similar orientation. While no apparent preferred orientation was measured in the parietal shell cross section, the base plate shell cross section revealed a preference for the alignment of the <0001> direction at the exterior of the shell, rotating by 90° toward the center of the base plate cross-section. These maps will be used to construct image-based models of the barnacle shell for further study of mechanical response.

  20. EBSD analysis of the growth of (0 0 1) magnetite thin films on MgO substrates

    Microsoft Academic Search

    A. Koblischka-Veneva; M. R. Koblischka; S. Murphy; S. K. Arora; U. Hartmann; F. Mücklich; I. V. Shvets

    2007-01-01

    Magnetite (Fe3O4) thin films grown on (001) MgO substrates are analyzed by means of electron backscatter diffraction (EBSD) analysis. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high-spatial resolution up to 20nm even on ceramic samples. The magnetite films are fully strained due to the lattice mismatch of MgO and Fe3O4. Upon annealing

  1. The application of EBSD to the study of substructural development in a cold rolled single-phase aluminium alloy

    Microsoft Academic Search

    P. J. Hurley; F. J. Humphreys

    2003-01-01

    Scanning electron microscopy and high resolution electron backscatter diffraction (EBSD) have been used to study substructural development during cold rolling of a single-phase Al–0.1 Mg alloy, the use of EBSD enabling more detailed quantitative measurements to be made than are possible with the transmission electron microscope (TEM). At low strains, bands of elongated cells, aligned at approximately 35° to rolling

  2. EBSD study of hydrogen-induced cracking in API5 LX46 pipeline steel

    Microsoft Academic Search

    V. Venegas; F. Caleyo; J. L. González; T. Baudin; J. M. Hallen; R. Penelle

    2005-01-01

    The spatial distribution of plastic deformation and grain orientation surrounding hydrogen-induced cracks (HIC) is investigated in samples of API-5L-X46 pipeline steel using scanning electron microscopy and electron backscattering diffraction (EBSD). This work shows direct experimental evidence of the influence of microstructure, microtexture and mesotexture on HIC crack path.

  3. EBSD Analysis of Friction Stir Weld Textures

    NASA Astrophysics Data System (ADS)

    Fonda, R. W.; Knipling, K. E.; Rowenhorst, D. J.

    2014-01-01

    Electron backscatter diffraction (EBSD) has become established as a convenient and accurate method for obtaining texture information. In friction stir welding, however, the complex, three-dimensional curvature of the deposited shear layers causes the textures to vary in orientation across the weld nugget. Only rarely are the EBSD data acquired in the shear deformation frame of reference. Thus, an analysis of those shear textures needs to take into consideration the local orientation of the shear deformation reference frame at the location of the analysis to appropriately identify the resultant texture. This article presents a systematic methodology for the analysis of friction stir weld textures that uses geometry-based rotations to align the analysis orientation to the local shear deformation frame of reference and thereby enable an accurate identification of the textures produced during the friction stir welding process.

  4. Influence of Surface Preparation on Scanning Kelvin Probe Microscopy and Electron Backscatter Diffraction Analysis of Cross Sections of CdTe/CdS Solar Cells

    SciTech Connect

    Moutinho, H. R.; Dhere, R. G.; Jiang, C. S.; Al-Jassim, M. M.

    2011-01-01

    Electron backscatter diffraction (EBSD) provides information on the crystallographic structure of a sample, while scanning Kelvin probe microscopy (SKPM) provides information on its electrical properties. The advantage of these techniques is their high spatial resolution, which cannot be attained with any other techniques. However, because these techniques analyze the top layers of the sample, surface or cross section features directly influence the results of the measurements, and sample preparation is a main step in the analysis. In this work we investigated different methods to prepare cross sections of CdTe/CdS solar cells for EBSD and SKPM analyses. We observed that procedures used to prepare surfaces for EBSD are not suitable to prepare cross sections, and we were able to develop a process using polishing and ion-beam milling. This process resulted in very good results and allowed us to reveal important aspects of the cross section of the CdTe films. For SKPM, polishing and a light ion-beam milling resulted in cross sections that provided good data. We were able to observe the depletion region on the CdTe film and the p-n junction as well as the interdiffusion layer between CdTe and CdS. However, preparing good-quality cross sections for SKPM is not a reproducible process, and artifacts are often observed.

  5. Spherical EBSD.

    PubMed

    Day, A P

    2008-06-01

    Spheres, or more usually spherical surfaces, are important in electron backscatter diffraction. Both electron backscatter patterns (EBSPs) and pole figure texture data are more accurately represented on the spherical surface, S(2); and unit quaternions, which are the optimal method for orientation calculations, exist on the surface of the hypersphere, S(3). This paper is split into two distinct parts. The first shows a little of the history of the EBSP technique, including the use of spheres to assemble a spherical Kikuchi map (SKM) and as calibration artefacts. The second part relates new developments in the analysis of EBSPs on the surface of a sphere, a new spherical Hough transform and ideas for fully automatic, ab initio analysis of unknown phases using collections of EBSPs assembled as spherical Kikuchi maps. PMID:18503674

  6. A Dictionary Approach to Electron Backscatter Diffraction Indexing.

    PubMed

    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. PMID:26055190

  7. Surface Morphology and Microstructural Characterization of KCl Crystals Grown in Halite-Sylvite Brine Solutions by Electron Backscattered Diffraction Techniques

    NASA Astrophysics Data System (ADS)

    Podder, Jiban; Basu, Ritwik; Evitts, Richard William; Besant, Robert William

    2015-11-01

    In this paper, a study on the ternary NaCl-KCl-H2O system was carried out by an extractive metallurgy technique from mixed brine solutions of different compositions at room temperature (23°C). The surface morphology and microstructure were examined using a scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and an energy dispersive X-ray (EDX) spectroscopy. The presence of Na{ }+ was found to reduce the stability of the solutions and increase the crystallization induction period, interfacial energy, energy of formation of the nucleus and greatly reduce the nucleation rate of KCl crystal. The surface morphology of KCl crystals is significantly changed due to presence of 5 to 10% (w/w) of NaCl as impurities in the binary solutions and shows the formation of co-crystals of different crystallographic orientation of NaCl on the KCl surface. In addition X-ray diffraction studies performed on KCl crystals grown in halite-sylvite binary solutions reveals that these crystals are cubic in nature and its lattice constant is 6.2952 Å when the NaCl concentration is small.

  8. Growth Directions of Precipitates in the Al-Si-Mg-Hf Alloy Using Combined EBSD and FIB 3D-Reconstruction Techniques.

    PubMed

    Wang, Xueli; Xing, Yuan; Huang, Huilan; Li, Yanjun; Jia, Zhihong; Liu, Qing

    2015-06-01

    Nanobelt-like precipitates in an Al-Si-Mg-Hf alloy were studied using electron backscattered diffraction (EBSD) and focused ion beam (FIB) scanning electron microscopy techniques. One grain of the Al matrix with a near [111] normal direction was identified by EBSD and the three-dimensional (3D) microstructure of nanobelt-like precipitates in this grain was studied using 3D-FIB. Ten growth directions of the nanobelt-like precipitates in the grain were identified. PMID:25951774

  9. Coupling of Electron Channeling with EBSD: Toward the Quantitative Characterization of Deformation Structures in the SEM

    NASA Astrophysics Data System (ADS)

    Gutierrez-Urrutia, I.; Zaefferer, S.; Raabe, D.

    2013-09-01

    The coupling of electron channeling contrast imaging (ECCI) with electron backscatter diffraction (EBSD) provides an efficient and fast approach to perform ECCI of crystal defects, such as dislocations, cells, and stacking faults, under controlled diffraction conditions with enhanced contrast. From a technical point of view, the ECCI technique complements two of the main electron microscopy techniques, namely, EBSD and conventional diffraction-based transmission electron microscopy. In this review, we provide several application examples of the EBSD-based ECCI approach on microstructure characterization, namely, characterization of single dislocations, measurement of dislocation densities, and characterization of dislocation substructures in deformed bulk materials. We make use of a two-beam Bloch wave approach to interpret the channeling contrast associated with crystal defects. The approach captures the main features observed in the experimental contrast associated with stacking faults and dislocations.

  10. Determination of the easy axes of small ferromagnetic precipitates in a bulk material by combined magnetic force microscopy and electron backscatter diffraction techniques.

    PubMed

    Batista, L; Rabe, U; Hirsekorn, S

    2014-11-01

    A method to determine the magnetic easy axes of micro- and nanoscopic ferromagnetic precipitates embedded in a bulk material is proposed and applied to globular cementite (Fe?C) embedded in a ferrite matrix. The method combines magnetic force microscopy (MFM) with electron backscattered diffraction (EBSD) measurements. Magnetic domain structures in globular and in lamellar cementite precipitates in unalloyed pearlitic steels were imaged using MFM. The domain structure of the precipitates was analyzed in dependency of their size, shape and crystallographic orientation. It was found that the magnetic moments of the cementite precipitates are highly geared to their crystalline axes. The combined MFM and EBSD studies allow the conclusion that the cementite easy direction of magnetization is the long [010] axis. For fine lamellae cementite the determination of their crystallographic orientations using electron diffraction techniques is very difficult. With the previous knowledge of the behavior of the domain structure in globular cementite, the crystalline orientations of the fine lamellae cementite can be estimated by simply observing the magnetic microstructures and the topographic profiles. PMID:24887154

  11. Magnetic domain structure and crystallographic orientation of electrical steels revealed by a forescatter detector and electron backscatter diffraction.

    PubMed

    Gallaugher, Matthew; Brodusch, Nicolas; Gauvin, Raynald; Chromik, Richard R

    2014-07-01

    The magnetic properties of non-oriented electrical steels (NOES) are an important factor in determining the efficiency of electric vehicle drivetrains. Due to the highly variable texture of NOES, the relationships between crystal orientation, the magnetic domain structure, and the final magnetic properties are complicated and not fully understood. In this study, a NOES sample was characterized with a method capable of imaging surface magnetic domains using scanning electron microscopy (SEM) with an electron backscatter diffraction (EBSD) system equipped with a forescatter detector. This method used type II magnetic contrast without a specialized SEM setup, and imaged with a resolution limit of approximately 250-300nm. The domain structure of the NOES sample was successfully related to ?, which was defined as the angle between the closest magnetic easy axis and the surface of the sample (the RD-TD plane). However, it was shown that if the easy axes were aligned between neighbouring grains with respect to the grain boundary normal, the domain structure could align with an easy axis that was not the closest to the surface, and complex domain structures could be become wider. This structure and width change of complex domain structures has not been previously observed from single crystal or large-grained material studies. The successful application of this method to reveal the influence of surrounding grains can be used to better understand the magnetic properties of NOES. PMID:24769020

  12. High resolution surface morphology measurements using EBSD cross-correlation techniques and AFM.

    PubMed

    Vaudin, M D; Stan, G; Gerbig, Y B; Cook, R F

    2011-07-01

    The surface morphology surrounding wedge indentations in (001) Si has been measured using electron backscattered diffraction (EBSD) and atomic force microscopy (AFM). EBSD measurement of the lattice displacement field relative to a strain-free reference location allowed the surface uplift to be measured by summation of lattice rotations about the indentation axis. AFM was used in intermittent contact mode to determine surface morphology. The height profiles across the indentations for the two techniques agreed within 1 nm. Elastic uplift theory is used to model the data. PMID:21763237

  13. Determination of pattern centre in EBSD using the moving-screen technique.

    PubMed

    Carpenter, D A; Pugh, J L; Richardson, G D; Mooney, L R

    2007-09-01

    The 'moving-screen' or 'pattern magnification' method of calibration for electron backscatter diffraction (EBSD) was reformulated to develop a high-precision technique requiring no crystallographic knowledge of the specimen and no initial estimates of the calibration parameters. The technique depends upon the accurate displacement of the screen and camera assembly. Corresponding points are selected, interactively, from EBSD patterns. It is suggested that, as an alternative, the selection of points from the Hough transform could lead to a completely automated routine. PMID:17760619

  14. A coupled EBSD\\/EDS method to determine the primary- and secondary-alpha textures in titanium alloys with duplex microstructures

    Microsoft Academic Search

    A. A. Salem; M. G. Glavicic; S. L. Semiatin

    2008-01-01

    A method for separating the textures of primary alpha (?p) and secondary alpha (?s) in alpha\\/beta titanium alloys with a duplex microstructure was developed. Utilizing electron backscatter diffraction (EBSD) and energy-dispersive spectroscopy (EDS), the approach relies on the non-uniform partitioning of alloying elements between primary alpha and regions containing secondary-alpha lamellae and residual beta matrix phase. The method was evaluated

  15. Phase differentiation via combined EBSD and XEDS.

    PubMed

    Nowell, M M; Wright, S I

    2004-03-01

    Electron backscatter diffraction (EBSD) and orientation imaging microscopy have become established techniques for analysing the crystallographic microstructure of single and multiphase materials. In certain instances, however, it can be difficult and/or time intensive to differentiate phases within a material by crystallography alone. Traditionally a list of candidate phases is specified prior to data collection. The crystallographic information extracted from the diffraction patterns is then compared with the crystallographic information from these candidate phases, and a best-fit match is determined. Problems may arise when two phases have similar crystal structures. The phase differentiation process can be improved by collecting chemical information through X-ray energy-dispersive spectroscopy (XEDS) simultaneously with the crystallographic information through EBSD and then using the chemical information to pre-filter the crystallographic phase candidates. This technique improves both the overall speed of the data collection and the accuracy of the final characterization. Examples of this process and the limitations involved will be presented and discussed. PMID:15009697

  16. Accuracy assessment of elastic strain measurement by EBSD.

    PubMed

    Villert, S; Maurice, C; Wyon, C; Fortunier, R

    2009-02-01

    A detailed accuracy analysis of electron backscatter diffraction (EBSD) elastic strain measurement has been carried out using both simulated and experimental patterns. Strains are determined by measuring shifts between two EBSD patterns (one being the reference) over regions of interest (ROI) using an iterative cross-correlation algorithm. An original minimization procedure over 20 regions of interests gives a unique solution for the eight independent components of the deviatoric displacement gradient tensor. It is shown that this method leads to strain measurements on simulated patterns with an accuracy better than 10(-4). The influence of the projection parameters is also investigated. The accuracy assessment is illustrated by two worked examples: (i) four-point bending of a silicon single crystal and (ii) Si(1-x)Ge(x) layers on a Si substrate. Experimental results are compared with finite-element simulations. PMID:19220695

  17. Reversed scan direction reduces electron beam damage in EBSD maps.

    PubMed

    Kidder, S; Prior, D

    2014-08-01

    The deleterious effects of electron beam damage on high-resolution electron backscatter diffraction (EBSD) maps of undeformed quartz are significantly reduced by scanning in the direction opposite to that dictated by widely used EBSD acquisition software. Higher quality electron backscatter patterns are produced when the electron beam moves progressively down the sample (the apparent 'up' direction in the resulting maps) for all step sizes where beam damage affects EBSD map quality (? ?0.4 ?m in this study). The relative improvement associated with downward scanning increases as step size is reduced. A comparison of high-resolution maps made in experimentally deformed quartz demonstrates that downward scanning reduces by a factor of ?2 the lower limit in step size relative to maps scanned in the conventional direction. The electron beam damages quartz at its point of entry, forming ?0.1-?m diameter bumps visible in Scanning electron microscope (SEM) images. Downward scanning produces better results because it minimizes the flux of electrons through these loci of damaged crystal. PMID:24943109

  18. Dependence of the electron beam energy and types of surface to determine EBSD indexing reliability in yttria-stabilized zirconia.

    PubMed

    Saraf, Laxmikant V

    2012-04-01

    Electron backscatter diffraction (EBSD) is a powerful technique for surface microstructure analysis. EBSD analysis of cubic yttria-stabilized zirconia (YSZ) is demonstrated. The statistics related to EBSD indexing reliability shows that the probability of accurate grain orientation detection increased significantly when the electron beam energy was increased from 10 to 30 kV. As a result of better sampling with increased interaction volume, a disparity between local and average grain misorientation angle also exhibited the dependence of the electron beam energy to determine the accuracy of grain orientation. To study EBSD indexing reliability as a function of surface roughness and overlayer formation, rapid EBSD measurement tests were performed on (a) YSZ surfaces ion-polished at ion beam energies of 65 nA at 30 kV and 1 nA at 30 kV and (b) carbon-coated versus uncoated YSZ surfaces. The EBSD results at both 10 and 30 kV electron beam energies indicate that EBSD indexing reliability is negatively affected by higher ion beam milling current and amorphous overlayer formation. PMID:22336075

  19. EBSD characterization of carbide-carbide boundaries in WC-Co composites.

    PubMed

    Farooq, M U; Klement, U

    2004-03-01

    A sample of WC-6wt%Co was investigated for grain boundary character distribution and occurrence of coincidence site lattice (CSL) boundaries on a statistical basis. For this purpose orientation measurements of the grains were carried out using electron back-scattered diffraction (EBSD). The dominant misorientation relationships were determined by complementary EBSD data representation tools such as orientation maps, misorientation angle distribution histograms and the sectioned three-dimensional misorientation space. It was found that the grain boundary character distribution of the material is nearly random and the CSL boundaries are not present in statistically significant amounts. It was also found that the amount of binder phase does not play a role in the formation of special boundaries. The paper focuses on the methodology of characterizing grain boundaries in a hexagonal material using EBSD. PMID:15009698

  20. Identification of epsilon martensite in a Fe-based shape memory alloy by means of EBSD.

    PubMed

    Verbeken, K; Van Caenegem, N; Raabe, D

    2009-01-01

    Ferrous shape memory alloys (SMAs) are often thought to become a new, important group of SMAs. The shape memory effect in these alloys is based on the reversible, stress-induced martensitic transformation of austenite to epsilon martensite. The identification and quantification of epsilon martensite is crucial when evaluating the shape memory behaviour of this material. Previous work displayed that promising results were obtained when studying the evolution of the amount of epsilon martensite after different processing steps with Electron BackScatter Diffraction (EBSD). The present work will discuss in detail, on the one hand, the challenges and opportunities arising during the identification of epsilon martensite by means of EBSD and, on the other hand, the possible interpretations that might be given to these findings. It will be illustrated that although the specific nature of the austenite to epsilon martensite transformation can still cause some points of discussion, EBSD has a high potential for identifying epsilon martensite. PMID:18280172

  1. Zirconium deformation behavior: insights from EBSD measurements.

    SciTech Connect

    Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Kaschner, G. C. (George C.); Maudlin, P. J. (Paul J.); Gray, G. T. (George T.), III

    2001-01-01

    The deformation of crystal-bar zirconium was investigated as a function of strain and strain rate through electron back-scattered diffraction (EBSD) characterization. The resultant data provided spatially resolved information on microstructure and texture evolution, individual twin system activity, and subsequent strain partitioning between twinned volume and parent grains. A range of deformation conditions was represented through quasi-static compression, 4-point beam bend tests at room and cryogenic temperature, and Taylor cylinder impact experiments. Effects from the interplay between slip and twinning deformation modes on anisotropic plasticity are considered in order to address the apparent trend toward isotropy at high rates. The role of various length scales on deformation behavior will be considered, along with the implications of these length scales on the assumptions typically invoked for plasticity modeling.

  2. A Dictionary Approach to EBSD Indexing

    E-print Network

    Chen, Yu-Hui; Wei, Dennis; Newstadt, Gregory; Jackson, Michael; Simmons, Jeff P; De Graef, Marc; Hero, Alfred O

    2015-01-01

    We propose a framework for indexing of grain and sub-grain structures in electron backscatter diffraction (EBSD) images of polycrystalline materials. The framework is based on a previously introduced physics-based forward model by Callahan and De Graef (2013) relating measured patterns to grain orientations (Euler angle). The forward model is tuned to the microscope and the sample symmetry group. We discretize the domain of the forward model onto a dense grid of Euler angles and for each measured pattern we identify the most similar patterns in the dictionary. These patterns are used to 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 ...

  3. Thermal-wave infrared radiometric slice diffraction tomography with back-scattering and transmission reconstructions: experimental

    Microsoft Academic Search

    Lena Nicolaides; Mahendra Munidasa; Andreas Mandelis

    1997-01-01

    Laser infrared photothermal radiometry is developed into a thermal-wave slice diffraction tomography (TSDT) instrumentation and measurement methodology for cross sectional imaging of subsurface defects. A mild-steel sample with artificial subsurface defects is used to test the TSDT potential. Experimental reconstructions using the Born approximation both in back-scattering and transmission modes are presented. The numerically reconstructed experimental data constitute the first

  4. Ultrasonic Characterization of Effective Elastic Constants and Texture in Aluminium Correlated with Ebsd

    NASA Astrophysics Data System (ADS)

    Essex, S. D.; Potter, M. D. G.; Dobedoe, R. S.; Dixon, S.

    2008-02-01

    Electron Backscatter Diffraction (EBSD) is a microscopic technique that provides detailed crystallographic orientation information for given samples. It enables the quantitative calculation and visualization of important microstructural properties such as grain size, aspect ratio and the average grain orientation of the aggregate, commonly known as the Orientation Distribution Function (ODF). In order to validate an ultrasonic technique to quantitatively describe texture we are correlating ultrasonic velocity measurements with results from EBSD. The velocity variations as a function of angle from the Rolling Direction in sheet samples are dependent on such quantities measurable by the EBSD technique. We describe here a modified technique to extrapolate the three independent Orientation Distribution Coefficients (ODCs) W400, W420 and W440 for cubic structures from the Bunge-Euler angle data determined through EBSD scans as a description of texture within the sample. EBSD results, taken from through-thickness scans to eliminate the errors that arise with surface-to-bulk inhomogeneity, for rolled aluminium sheets are discussed compared to the ODCs obtained using an ultrasonic EMAT-EMAT S0 Lamb wave velocity measurement system.

  5. Utilizing Ebsd to Validate and Understand Nde Techniques

    NASA Astrophysics Data System (ADS)

    Essex, S. D.; Potter, M. D. G.; Vann, R.; Dixon, S.

    2009-03-01

    Electron Backscatter Diffraction (EBSD) is a destructive, surface-specific technique that measures accurately crystallographic orientations within a scanning electron microscope (SEM). From this data we can infer elastic properties, calculate levels of stress and measure microstructural properties such as the size and aspect ratios of grains. The Electromagnetic Acoustic Transducer (EMAT) is a non-contact, ultrasonic transducer that is suitable for operation on electrically conducting materials such as Aluminium and Steel. This paper highlights some of the work carried out using EBSD as a technique to validate EMAT measurements on rolled sheet to determine microstructural properties such as grain size and aspect ratios via shear wave through-thickness attenuation, and other macroscopic properties like average crystallographic texture. Work is also presented on another application for EBSD, in that it can be used to confirm whether an NDE technique is in fact nondestructive. Here we look at the case of a Nd:Yag pulsed laser irradiating a sample, in the ablative/thermoelastic regime boundary.

  6. The degradation of EBSD-patterns as a tool to investigate surface crystallized glasses and to identify glassy surface layers.

    PubMed

    Wisniewski, Wolfgang; Völksch, Günter; Rüssel, Christian

    2011-12-01

    Surface crystallized samples of glass-ceramics containing cordierite, rhombohedral BaAl?B?O? and fresnoite were analyzed using electron backscatter diffraction (EBSD). The first two materials were chosen because surface crystallized samples of these materials have previously been shown to contain crystals covered by a very thin layer of glass. In all materials, EBSD pattern degradation occurs if the step size of a scan is chosen to be small. It is shown that the minimum step size enabling an evaluable EBSD-scan increases notably, if the crystals are covered by a thin layer of glass. It is also shown that pattern degradation may be utilized to prove the existence of such a thin glass or otherwise thermally sensitive layer. This provides significant information concerning the nucleation process of glasses also with respect to nucleation theory of glass-ceramics. It is also possible to describe the quantity of crystalline surface covered by the thermally sensitive layer. PMID:22088446

  7. Study of microstructure and phase evolution of hot-dipped aluminide mild steel during high-temperature diffusion using electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Cheng, Wei-Jen; Wang, Chaur-Jeng

    2011-03-01

    Mild steel was coated by hot-dipping into a molten aluminum bath. The microstructure and phase evolution in the aluminide layer during diffusion at 750 °C in static air were analyzed by electron backscatter diffraction (EBSD). The results showed that the aluminide layer of the as-coated specimen consisted of an outer aluminum topcoat, minor FeAl3 and major Fe2Al5, respectively. Also, Fe2Al5 possessed a tongue-like morphology, which caused corresponding serration-like morphology in the steel substrate. A portion of the peaks of serration-like substrate were isolated, after short exposure at 750 °C, and accompanied by the formation of voids, which continued to appear with further exposure at 750 °C. As the aluminum topcoat was consumed, FeAl3 phase disappeared and left an aluminide layer of Fe2Al5 phase. After 60 min of exposure, FeAl2 and FeAl phases formed at the interface between Fe2Al5 and the steel substrate. With increasing exposure time, the voids condensed and the serration-like morphology disappeared, while FeAl2 and FeAl phases kept growing. After prolonged exposure, the aluminide layer was composed of FeAl2 and FeAl and possessed a flat interface between FeAl and steel substrate.

  8. In-Situ Scanning Electron Microscopy/Electron Backscattered Diffraction Observation of Microstructural Evolution during ? ? ? Phase Transformation in Deformed Fe-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Fukino, Tatsuya; Tsurekawa, Sadahiro; Morizono, Yasuhiro

    2011-03-01

    This article presents in-situ observation of ferrite ( ?)/austenite ( ?) phase transformation in an Fe-8.5 at. pct Ni alloy deformed by rolling using an automated scanning electron microscopy/energy backscattered diffraction (SEM/EBSD) system. During heating, recrystallization in ? phase and ? ? ? phase transformation independently occurred. The ? grains nucleated in unrecrystallized ? grains were most probably incorporated into the grain interior of recrystallized ? grains. They did not have any specific orientation relation (OR) with recrystallized ? grains and grew in an isotropic manner. On the other hand, the intragranular ? grains nucleated in recrystallized ? grains had a Kurdjumov-Sachs (K-S) OR with the ? grains and grew in a considerably anisotropic manner. They preferentially grew along the common direction of surface traces of {110} ? /{111} ? . Approximately half of grain boundary (GB) allotriomorphs had either the K-S OR or the Nishiyama-Wasserman (N-W) OR with the parent ? grains. The ? allotriomorphs predominantly grew into the ? grain having the special OR with themselves. The GB character distribution of ? phase at high temperatures was measured. The fraction of CSL boundaries was as high as 63 pct, particularly that of ?3 grain boundaries (GBs) was 54 pct.

  9. EBSD characterization of twinned copper using pulsed electrodeposition

    NASA Astrophysics Data System (ADS)

    Lui, Guan-Tai; Chen, Delphic; Kuo, Jui-Chao

    2009-11-01

    We investigated the influence of pulse current density on a crystallographic microstructure of twin Cu films through x-ray diffraction and electron backscatter diffraction (EBSD). With an increase in the pulse current density, the intensity of the preferred orientation (texture), grain size and the fraction of the twins decreased. The high-density twin copper films, including the nanotwins observed from the orientation image maps, were achieved using a pulsed electrodeposition technique at the current density of 0.5 A cm-2, with an average grain size of 818 nm. The crystallographic microstructure of the high-density twin copper films shows a lang0 1 1rang preferred orientation associated with the 60°lang1 1 1rang twin having a {1 1 1} twin plane.

  10. Cryogenic EBSD reveals structure of directionally solidified ice–polymer composite

    SciTech Connect

    Donius, Amalie E., E-mail: amalie.donius@gmail.com [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Obbard, Rachel W., E-mail: Rachel.W.Obbard@dartmouth.edu [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Burger, Joan N., E-mail: ridge.of.the.ancients@gmail.com [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Hunger, Philipp M., E-mail: philipp.m.hunger@gmail.com [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Baker, Ian, E-mail: Ian.Baker@dartmouth.edu [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Doherty, Roger D., E-mail: dohertrd@drexel.edu [Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Wegst, Ulrike G.K., E-mail: ulrike.wegst@dartmouth.edu [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States)

    2014-07-01

    Despite considerable research efforts on directionally solidified or freeze-cast materials in recent years, little fundamental knowledge has been gained that links model with experiment. In this contribution, the cryogenic characterization of directionally solidified polymer solutions illustrates, how powerful cryo-scanning electron microscopy combined with electron backscatter diffraction is for the structural characterization of ice–polymer composite materials. Under controlled sublimation, the freeze-cast polymer scaffold structure is revealed and imaged with secondary electrons. Electron backscatter diffraction fabric analysis shows that the ice crystals, which template the polymer scaffold and create the lamellar structure, have a-axes oriented parallel to the direction of solidification and the c-axes perpendicular to it. These results indicate the great potential of both cryo-scanning electron microscopy and cryo-electron backscatter diffraction in gaining fundamental knowledge of structure–property–processing correlations. - Highlights: • Cryo-SEM of freeze-cast polymer solution reveals an ice-templated structure. • Cryo-EBSD reveals the ice crystal a-axis to parallel the solidification direction. • The honeycomb-like polymer phase favors columnar ridges only on one side. • Combining cryo-SEM with EBSD links solidification theory with experiment.

  11. USING A MULTI-DISCIPLINARY APPROACH, THE FIRST ELECTRON BACKSCATTERED KIKUCHI PATTERNS WERE CAPTURES FOR A PU ALLOY

    SciTech Connect

    C. J. BOEHLERT

    2001-06-01

    Microstructural characterization of plutonium by electron backscattered diffraction (EBSD) has been previously elusive primarily because of the extreme toxicity and surface oxidation rates associated with plutonium metal. In this work, initial electron backscattered diffraction pattern (EBSP) observations of a plutonium-gallium (Pu-Ga) alloy were made. Samples were prepared using standard metallographic and electropolishing techniques that were performed inside gloveboxes and/or an open front hood to prevent spread of radioactive contamination. A scanning Auger microprobe (SAM), equipped with an ion-gun, was used to characterize and remove surface chemical impurities (in particular carbon (C) and oxygen (O)) and a specially designed vacuum transfer device was used to minimize oxidation during the sample transfer from the SAM to the scanning electron microscope (SEM). EBSD patterns of the {delta}-phase (face-centered-cubic) were captured and the experimental techniques and parameters used to perform EBSD characterization are described in detail.

  12. Orientations of Y 2BaCuO 5 and YBCO within melt-textured and directional solidified samples studied by EBSD

    Microsoft Academic Search

    M. R. Koblischka; A. Koblischka-Veneva; E. S. Reddy; G. J. Schmitz; K. Ogasawara; M. Murakami

    2003-01-01

    By means of automated electron backscatter diffraction (EBSD) analysis, we studied the local orientations of embedded Y2BaCuO5 (211) particles within melt-textured YBCO samples, and also the orientations of embedded YBCO particles in directional solidified 211 samples. On both systems, we obtained high-quality Kikuchi patterns, allowing the automated mapping of the crystal orientations and a multi-phase analysis. In melt-textured YBCO with

  13. EBSD image quality mapping.

    PubMed

    Wright, Stuart I; Nowell, Matthew M

    2006-02-01

    Image quality (IQ) maps constructed from electron backscatter diffraction data provide useful visualizations of microstructure. The contrast in these maps arises from a variety of sources, including phase, strain, topography, and grain boundaries. IQ maps constructed using various IQ metrics are compared to identify the most prominent contrast mechanism for each metric. The conventional IQ metric was found to provide the superior grain boundary and strain contrast, whereas an IQ metric based on the average overall intensity of the diffraction patterns was found to provide better topological and phase contrast. PMID:17481343

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

    SciTech Connect

    Toth, Laszlo S., E-mail: laszlo.metz@univ-lorraine.fr [Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), UMR 7239, CNRS/Université de Lorraine, F-57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine (France); Biswas, Somjeet, E-mail: somjeetbiswas@gmail.com [Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine (France); Gu, Chengfan, E-mail: chengfan.gu@unsw.edu.au [School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Beausir, Benoit, E-mail: benoit.beausir@univ-lorraine.fr [Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux (LEM3), UMR 7239, CNRS/Université de Lorraine, F-57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine (France)

    2013-10-15

    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.

  15. A novel EBSD-based finite-element wave propagation model for investigating seismic anisotropy: Application to Finero Peridotite, Ivrea-Verbano Zone, Northern Italy

    NASA Astrophysics Data System (ADS)

    Zhong, Xin; Frehner, Marcel; Kunze, Karsten; Zappone, Alba

    2014-10-01

    A novel electron backscatter diffraction (EBSD) -based finite-element (FE) wave propagation simulation is presented and applied to investigate seismic anisotropy of peridotite samples. The FE model simulates the dynamic propagation of seismic waves along any chosen direction through representative 2D EBSD sections. The numerical model allows separation of the effects of crystallographic preferred orientation (CPO) and shape preferred orientation (SPO). The obtained seismic velocities with respect to specimen orientation are compared with Voigt-Reuss-Hill estimates and with laboratory measurements. The results of these three independent methods testify that CPO is the dominant factor controlling seismic anisotropy. Fracture fillings and minor minerals like hornblende only influence the seismic anisotropy if their volume proportion is sufficiently large (up to 23%). The SPO influence is minor compared to the other factors. The presented FE model is discussed with regard to its potential in simulating seismic wave propagation using EBSD data representing natural rock petrofabrics.

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

    SciTech Connect

    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. EBSD Images Theoretical Background

    E-print Network

    Candea, George

    . Michel Rappaz EBSD images of the welding microstructure in the transverse direction were acquired of the grains is due to the preferential growth in the direction of the thermal gradient. Figure 4 Complete EBSD procedure takes place in the solid state since the melted metal is already solidified when the quenching

  18. Seismic anisotropy of the crust: electron-backscatter diffraction measurements from the Basin and Range

    NASA Astrophysics Data System (ADS)

    Erdman, Monica E.; Hacker, Bradley R.; Zandt, George; Seward, Gareth

    2013-11-01

    Crystal preferred orientations were measured in a suite of rocks from three locations in the Basin and Range using electron-backscatter diffraction. Anisotropic velocities were calculated for all rocks using single-crystal stiffnesses, the Christoffel equation and Voigt-Reuss-Hill averaging. Anisotropic velocities were calculated for all three crustal sections using these values combined with rock proportions as exposed in the field. One suite of rocks previously measured in the laboratory was used as a benchmark to evaluate the accuracy of the calculated velocities. Differences in the seismic anisotropy of the Funeral Mountains, Ruby Mountains and East Humboldt Range sections arise because of differences in mineralogy and strain, with the calc-silicate dominated Ruby Mountains section having higher P-wave speeds and VP/VS ratios because of the reduced quartz content. In all cases, the velocities show either transverse isotropy or nearly so, with a unique slow axis normal to the foliation. Velocity anisotropy can thus be used to infer the flow plane, but not the flow direction in typical crustal rocks. Areas with a subhorizontal foliation have minimal shear wave splitting for vertically propagating waves and are thus good places to measure mantle anisotropy using SKS-splitting.

  19. Three-dimensional EBSD study on the relationship between triple junctions and columnar grains in electrodeposited Co-Ni films.

    PubMed

    Bastos, A; Zaefferer, S; Raabe, D

    2008-06-01

    Electrodeposited nanocrystalline materials are expected to have a homogeneous grain size and a narrow grain size distribution. In Co-Ni electrodeposited films, however, under certain conditions an undesired columnar grain structure is formed. Fully automated three-dimensional (3D) orientation microscopy, consisting of a combination of precise material removal by focussed ion beam and subsequent electron backscatter diffraction (EBSD) analysis, was applied to fully characterize the grain boundaries of these columnar grains in order to gain further understanding on their formation mechanisms. Two-dimensional orientation microscopy on these films indicated that the development of columnar grains could be related to the formation of low-energy triple junctions. 3D EBSD allowed us to verify this suggestion and to determine the boundary planes of these triples. The triplets are formed by grain boundaries of different quality, a coherent twin on the {1011} plane, an incoherent twin and a large-angle grain boundary. These three boundaries are related to each other by a rotation about the <1120> direction. A second particularity of the columnar grains is the occurrence of characteristic orientation gradients created by regular defects in the grain. Transmission electron microscopy was applied to investigate the character of the defects. For this purpose, a sample was prepared with the focussed ion beam from the last slice of the 3D EBSD investigation. From the TEM and 3D EBSD observations, a growth mechanism of the columnar grains is proposed. PMID:18503675

  20. Tiny twists in time; exploring angular resolution of in situ EBSD orientation microstructures in solar system zircon

    NASA Astrophysics Data System (ADS)

    Moser, D. E.

    2012-12-01

    Kikuchi discovered electron diffraction in samples of calcite in the 1920's, and orientation of lattice planes by Electron Backscatter Diffraction (EBSD) is now routinely measured by automated camera systems at a spatial resolution of tens of nanometers using Field Emission Gun SEM. The current methodology is proving particularly powerful when measuring lattice orientation microstructure in U-Pb geochronology minerals such as zircon and baddeleyite that have experienced high temperature deformation or shock metamorphism. These are among the oldest preserved mineral phases in inner solar system materials, and we have been applying EBSD to rare samples of the Early Earth and grains from extraterrestrial environments such as the Moon and Mars. In these cases the EBSD orientation data are useful for identifying high diffusivity pathways that may have afforded isotopic and trace element disturbance, microstructural proxies for shock metamorphic pressures, as well as resolving glide plane systems in ductile zircon and shear twin mechanisms. Blanket estimates of angular resolution for automated EBSD misorientation measurements are often in the range of 0.5 degrees. In some cases strain giving rise to only a few degrees of lattice misorientation has facilitated 100% Pb-loss. In some cases, however, there is a spatial correlation between trace element or cathodoluminescence zoning in zircon and what appears to be low magnitudes misorientation close to the limits of resolution. Given the proven value of performing EBSD analysis on geochronology minerals, a more thorough exploration of the precision and accuracy of EBSD lattice misorientation measurements is warranted. In this talk the relative weighting of the factors that limit EBSD angular resolution will be investigated, focusing on U-Pb dating minerals such as zircon. These factors include; sample surface preparation, phase symmetry, pseudo-symmetry effects, degree of crystallinity, Kikuchi band contrast and indexing, solid solution effects on unit cell, dimension camera calibration and camera-sample distance, beam conditions and focussing, and general microscope operating conditions (e.g. high vacuum vs. variable pressure). An assessment of potential zircon EBSD reference materials and sample preparation protocols will be presented, along with case studies of zircon orientation microstructures from meteorites and terrestrial craters representative of different strain and thermal environments in the inner solar system.BSD lattice misorientation maps of a) crystal-plastically deformed and partly recrystallized zircon, after Rayner et al. (in prep.), and b) shock-metamorphosed lunar zircon (Darling et al., in prep.).

  1. EBSD study of angular deviations from the Goss component in grain-oriented electrical steels.

    PubMed

    Bernier, Nicolas; Leunis, Elke; Furtado, Carlos; Van De Putte, Tom; Ban, Gabor

    2013-01-01

    The magnetic properties of grain-oriented (GO) electrical steels strongly depend on the distribution of the ? and ? angles, i.e., the deviations of the easy magnetisation <100> from the rolling direction (RD) in the rolling plane and out of the rolling plane, respectively. However, most Electron Backscatter Diffraction (EBSD) studies consider the standard Goss deviation angle, which includes the rotation of the (110) plane about the RD. Therefore, in the present work, a new procedure is demonstrated for deriving the ? and ? angles from EBSD mappings to obtain a quantitative texture characterisation in line with the magnetic properties. This procedure is later applied to 37 GO steels after secondary recrystallisation that exhibit a wide range of permeability levels. The relation between the texture and the polarisation at 800A/m (J800) that is measured in the present study by EBSD is compared to the one that has been determined in previous papers with optical goniometers and X-ray diffraction techniques, and this relation is subsequently used to define a relevant parameter to describe the orientation quality of the grains. The results indicate that the average angle of the ? and ? deviations is a relevant deviation parameter for the characterisation of grain orientations. Finally, it is demonstrated that the combination of the quantitative correlation between polarisation and texture with the orientation imaging of EBSD offers the possibilities of both studying the crystallographic environment of highly oriented grains in the primary recrystallised matrix for the production of high-permeability steels and evaluating the spatial distribution of the angular deviations in GO steels after secondary recrystallisation. PMID:24090630

  2. EBSD: a powerful microstructure analysis technique in the field of solidification.

    PubMed

    Boehm-Courjault, E; Gonzales, F; Jacot, A; Kohler, F; Mariaux, A; Niederberger, C; Salgado-Ordorica, M A; Rappaz, M

    2009-01-01

    This paper presents a few examples of the application of electron back-scatter diffraction (EBSD) to solidification problems. For directionally solidified Al-Zn samples, this technique could reveal the change in dendrite growth directions from <100> to <110> as the composition of zinc increases from 5 to 90 wt%. The corresponding texture evolution and grain selection mechanisms were also examined. Twinned dendrites that form under certain solidification conditions in Al-X specimens (with X = Zn, Mg, Ni, Cu) were clearly identified as <110> dendrite trunks split in their centre by a (111) twin plane. In Zn-0.2 wt% Al hot-dip galvanized coatings on steel sheets, EBSD clearly revealed the preferential basal orientation distribution of the nuclei as well as the reinforcement of this distribution by the faster growth of <1010> dendrites. Moreover, in Al-Zn-Si coatings, misorientations as large as 10 degrees mm(-1) have been measured within individual grains. Finally, the complex band and lamellae microstructures that form in the Cu-Sn peritectic system at low growth rate could be shown to constitute a continuous network initiated from a single nucleus. EBSD also showed that the alpha and beta phases had a Kurdjumov-Sachs crystallographic relationship. PMID:19196422

  3. Calculation of Elastic Anisotropy Using Emats Validated by Ebsd in Rolled Aluminium Sheet

    NASA Astrophysics Data System (ADS)

    Essex, S. D.; Potter, M. D. G.; Dixon, S.

    2009-03-01

    Determining the Orientation Distribution Function (ODF) accurately and quickly in a non-destructive manner has many benefits and applications within industry. The ODF is essentially a quantitative description of the existence of anisotropy, or texture, within a metal sheet. The anisotropy can be seen experimentally by the variation in Lamb wave velocities in the plane of the sheet as a function of angle to the Rolling Direction. The anisotropy can be quantitatively described by the Orientation Distribution Coefficients (ODCs) W400, W420 and W440. Electron Backscatter Diffraction (EBSD) is a technique performed in a SEM. It infers the crystallographic directions of crystals near-surface, and can be applied to a number of samples. It enables the accurate quantitative and qualitative description of microstructural properties such as grain size. By manipulating the Bunge-Euler angle data given by the EBSD technique, here we describe a method to extrapolate the effective elastic constants for Aluminium sheet, and go on to generate a method to predict a Lamb wave velocity profile as a function of angle in a directly comparable format to that measured using a commercially available EMAT-EMAT S0 Lamb wave velocity measurement system. Results show a very good correlation between the predicted velocity trace from EBSD compared to that measured ultrasonically, and hence the respective ODCs, except in the cases where surface to bulk texture inhomogeneity exist.

  4. Boundary identification in EBSD data with a generalization of fast multiscale clustering.

    PubMed

    McMahon, Cullen; Soe, Brian; Loeb, Andrew; Vemulkar, Ayyappa; Ferry, Michael; Bassman, Lori

    2013-10-01

    Electron backscatter diffraction (EBSD) studies of cellular or subgrain microstructures present problems beyond those in the study of coarse-grained polycrystalline aggregates. In particular, identification of boundaries delineating some subgrain structures, such as microbands, cannot be accomplished simply with pixel-to-pixel misorientation thresholding because many of the boundaries are gradual transitions in crystallographic orientation. Fast multiscale clustering (FMC) is an established data segmentation technique that is combined here with quaternion representation of orientation to segment EBSD data with gradual transitions. This implementation of FMC addresses a common problem with segmentation algorithms, handling data sets with both high and low magnitude boundaries, by using a novel distance function that is a modification of Mahalanobis distance. It accommodates data representations, such as quaternions, whose features are not necessarily linearly correlated but have known distance functions. To maintain the linear run time of FMC with such data, the method requires a novel variance update rule. Although FMC was originally an algorithm for two-dimensional data segmentation, it can be generalized to analyze three-dimensional data sets. As examples, several segmentations of quaternion EBSD data sets are presented. PMID:23751208

  5. Characterization of dual-phase steel microstructure by combined submicrometer EBSD and EPMA carbon measurements.

    PubMed

    Pinard, Philippe T; Schwedt, Alexander; Ramazani, Ali; Prahl, Ulrich; Richter, Silvia

    2013-08-01

    Electron backscatter diffraction (EBSD) and electron probe microanalysis (EPMA) measurements are combined to characterize an industrial produced dual-phase steel containing some bainite fraction. High-resolution carbon mappings acquired on a field emission electron microprobe are utilized to validate and improve the identification of the constituents (ferrite, martensite, and bainite) performed by EBSD using the image quality and kernel average misorientation. The combination eliminates the ambiguity between the identification of bainite and transformation-induced dislocation zones, encountered if only the kernel average misorientation is considered. The detection of carbon in high misorientation regions confirms the presence of bainite. These results are corroborated by secondary electron images after nital etching. Limitations of this combined method due to differences between the spatial resolution of EBSD and EPMA are assessed. Moreover, a quantification procedure adapted to carbon analysis is presented and used to measure the carbon concentration in martensite and bainite on a submicrometer scale. From measurements on reference materials, this method gives an accuracy of 0.02 wt% C and a precision better than 0.05 wt% C despite unavoidable effects of hydrocarbon contamination. PMID:23742898

  6. HOLZ rings in EBSD patterns of the UFeB? compound: association with a random distribution of planar defects.

    PubMed

    Dias, Marta; Carvalho, Patrícia Almeida; Dos Santos, Isabel Cordeiro; Tougait, Olivier; Havela, Ladislav; Gonçalves, António Pereira

    2013-10-01

    The UFeB? phase present in different alloys of the B-Fe-U system was studied by powder X-ray diffraction (PXRD) and scanning electron microscopy complemented with energy-dispersive spectroscopy and electron backscattered diffraction (EBSD). The PXRD data showed that the ternary compound crystallized adopting essentially the YCrB?-type structure. However, microstructural observations revealed that under high undercooling conditions the UFeB? phase exhibits a random distribution of defects parallel to, which are consistently associated with intense higher-order Laue zone rings in EBSD patterns. Indexation of the EBSD patterns showed that the defective structure is compatible with an intergrowth of YCrB?- and ThMoB?-type layers according to the (010)(YCrB?)//(110)(ThMoB?) and [001]YCrB?//[001](ThMoB?) orientation relation previously reported for an analogous compound. Magnetic studies indicated that the annealed UFeB? compound has a paramagnetic behavior in the 2-300 K temperature range. PMID:24040993

  7. Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM.

    PubMed

    Weikusat, I; DE Winter, D A M; Pennock, G M; Hayles, M; Schneijdenberg, C T W M; Drury, M R

    2011-06-01

    Naturally deformed ice contains subgrains with characteristic geometries that have recently been identified in etched surfaces using high-resolution light microscopy (LM). The probable slip systems responsible for these subgrain boundary types can be determined using electron backscattered diffraction (EBSD), providing the etch features imaged with reflected LM can be retained during EBSD data acquisition in a scanning electron microscope (SEM). Retention of the etch features requires that the ice surface is stable. Depending on the pressure and temperature, sublimation of ice can occur. The equilibrium temperature for a low pressure SEM operating at 1 × 10(-6) hPa is about -112°C and operating at higher temperatures causes sublimation. Although charging of uncoated ice samples is reduced by sublimation, important information contained in the etch features are removed as the surface sublimes. We developed a method for collecting EBSD data on stable ice surfaces in a low pressure SEM. We found that operating at temperatures of <-112°C reduced sublimation so that the original etch surface features were retained. Charging, which occurred at low pressures (<1.5 × 10(-6) to 2.8 × 10(-5) hPa) was reduced by defocusing the beam. At very low pressures (<1.5 × 10(-6) hPa) the spatial resolution with a defocused beam at 10 kV was about 3 ?m in the x-direction at -150°C and 0.5 ?m at -120°C, because at higher temperature charging was less and only a small defocus was needed to compensate it. Angular resolution was better than 0.7° after orientation averaging. Excellent agreement was obtained between LM etch features and EBSD mapped microstructures. First results are shown, which indicate subgrain boundary types comprised of basal (tilt and twist) and nonbasal dislocations (tilt boundaries). PMID:21155992

  8. Inversion of calcite twin data for stress (2) : EBSD as a tool for data measurements

    NASA Astrophysics Data System (ADS)

    Parlangeau, Camille; Lacombe, Olivier; Brisset, Francois; Kohler, Eric; Daniel, Jean-Marc; Schueller, Sylvie

    2015-04-01

    Inversion of calcite twin data are known to be a powerful tool to reconstruct the past state(s) of stress in carbonate rocks of the crust, especially in fold-and-thrust belts and sedimentary basins. Twin data measurements have been for long carried out optically using a Universal-Stage. This data collection is time-consuming and suffers from limitations and bias related to measurements of twin planes oblique at low angle or parallel to the thin section, or the unambiguous evaluation of the twinned/untwinned character of collected twin data. EBSD (electron backscatter diffraction) is a well-known technique applied to characterize textures and microstructures of metals or deformed fine-grained rocks. The challenge is to define a strategy for measuring calcite-twin orientations that should be fast, without any loss of information, and which must reconcile (1) the need for a large amount of calcite twin data (3 mutually perpendicular thin sections and at least 30 crystals per thin section), (2) the spacing between EBSD spots, that should take into account (3) the small width of twin lamellae within grains deformed at low pressure and temperature and (4) the large size (usually several hundreds of microns) of twinned calcite grains used for stress analysis. To date, these multiple requirements preclude any (classical) automatic twin data acquisition but instead imply a preliminary definition of the areas of the thin section to be scanned by the EBSD spots, including grain boundaries, because the stress inversion technique requires to know for each grain the orientations of the C axis and of the 3 potential e twin planes. In order to reconcile a perfectly polished surface as required by EBSD and the recognition of grain boundaries, we adopted the double etching technique (Herwegh, 2000) to first reveal grain and twin boundaries. Then, with a SEM and a very fine coating sample, the section is scanned using secondary electrons bin; each spot of interest is visually defined and its coordinates entered in a file later used to pilot automatically the EBSD spot. This new procedure is applied on sections from natural samples; the EBSD data are converted and restored into the geographical framework and analyzed using the improved Etchecopar stress inversion technique. The results are compared to the results obtained from classical, optically-based measurements of the same sections using the Universal-stage. The advantages and limitations of this approach are discussed.

  9. An analysis of the microstructures developed in experimentally deformed polycrystalline pyrite and minor sulphide phases using electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Barrie, Craig D.; Boyle, Alan P.; Prior, David J.

    2007-09-01

    Samples of polycrystalline pyrite previously deformed in tri-axial compression tests at a confining pressure of 300 MPa and a strain rate of 2 × 10 -4 s -1 but varying temperature were analysed in this study. Five samples including the original starting material have undergone analysis using forescatter orientation contrast (OC) imaging coupled with electron back scatter diffraction (EBSD) to determine how the micro-structures in pyrite and to an extent the surrounding minor phases have changed with increasing temperature. Between 550 °C and 650 °C the dominant deformation mechanism in pyrite is that of dislocation creep. Above 650 °C this mechanism becomes less apparent and few if any dislocation walls are present within pyrite grains by 700 °C. This is a result of either increased dynamic recrystallisation with temperature or a change in the dominant deformation mechanism. Dislocation creep occurs via lattice rotation, principally about a single <100> axis, but also about two separate <100> axes and more rarely about a single <110> axis. Deformation has not resulted in a crystallographic preferred orientation (CPO) within any of the samples. Shape change of pyrite grains has occurred and this can account for most if not all of the shortening applied, but dynamic recrystallisation of pyrite and grain boundary sliding accommodated along the minor phases are also likely to be important mechanisms in all of the samples.

  10. Morphological analyses of minute crystals by using stereo-photogrammetric scanning electron microscopy and electron back-scattered diffraction.

    PubMed

    Kameda, Jun; Inoguchi, Ryoichi; Prior, David J; Kogure, Toshihiro

    2007-12-01

    We present a new method for the morphological analyses of minute faceted crystals by combining stereo-photogrammetric analysis of scanning electron microscope images and electron back-scattered diffraction. Two scanning electron microscope images of the same crystal, recorded at different tilt angles of the specimen stage, are used to determine the orientations of crystal edges in a specimen-fixed coordinate system. The edge orientations are converted to the indices [uvw] in the crystal system using the crystal orientation determined by electron back-scattered diffraction analysis. The Miller indices of crystal facets are derived from the indices of the edges surrounding the facets. The method is applicable to very small crystal facets. The angular error, as derived from tests using a calcite crystal of known morphology, is a few degrees. To demonstrate the applicability of the method, the morphology of boehmite (gamma-AlOOH) precipitated from solution during the dissolution of anorthite was analyzed. The micrometre-sized boehmite crystals are surrounded by two {010} basal facets and eight equivalent side facets that can be indexed equally well as {323}, {434} or {545}. We suggest that these side facets are in fact {111}, the morphology having been modified slightly (by a few degrees) by a small extension associated with opening along (010) microcleavage planes. Tiny {140} facets are also commonly observed. PMID:18045330

  11. Texture and nano-scale internal microstructure of otoliths in the Atlantic molly, Poecilia mexicana: a high-resolution EBSD study.

    PubMed

    Schulz-Mirbach, T; Götz, A; Griesshaber, E; Plath, M; Schmahl, W W

    2013-08-01

    Otoliths of modern bony fishes are massive polycrystalline structures consisting mainly of calcium carbonate (primarily aragonite), and 1-10% organic residuals. Unlike other biomineralisates like shells, teeth and bones, they are not optimized for mechanical loads but serve the senses of hearing and balance in the inner ear. We examined internal structural variation of otoliths through microstructural and texture analyses. Our study applied the electron backscattered diffraction technique (EBSD) to whole sections of saccular otoliths on cave- and surface-dwelling fish. Application of high spatial resolution EBSD on otoliths of the livebearing fish Poecilia mexicana allowed for an investigation of crystal orientation despite the small size (<150 nm) of aragonite crystallites. Crystallites at the rims of otoliths had a higher structural organization than those situated near the center, where no dominant orientation pattern was discernible. Moreover, the medial (sulcal) face of otoliths, which makes contact with the sensory epithelium, was more structured than the lateral (antisulcal) face. PMID:23891259

  12. Estimation of dislocation densities in cold rolled Al-Mg-Cu-Mn alloys by combination of yield strength data, EBSD and strength models.

    PubMed

    Wang, S C; Zhu, Z; Starink, M J

    2005-02-01

    Al-Mg-Cu-Mn alloys have been developed for the packaging industry, in which large cold-working deformations are normally applied that can produce high dislocation densities. In this study, we present a simplified model for the yield strength contributions and apply that to obtain the dislocation densities by determining the orientation factors, which can be obtained via the crystal information of electron backscatter diffraction (EBSD). One alloy subjected to three cold-rolling reductions (10%, 40% and 90%) has been analysed by EBSD, and the density of dislocations are estimated using the strengthening model. This assessment suggests that dislocation densities by the Taylor model are roughly consistent but slightly lower than those determined by transmission electron microscopy. PMID:15683415

  13. EBSD Investigation of Cu-Sn IMC Microstructural Evolution in Cu/Sn-Ag/Cu Microbumps During Isothermal Annealing

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Hsu, L. H.; Wang, N. K.; Ho, C. E.

    2014-01-01

    The microstructural evolution of Cu/Sn-Ag (~5 ?m)/Cu Cu-bump-on-line (CuBOL) joints during isothermal annealing at 180°C was examined using a field-emission scanning electron microscope equipped with an electron backscatter diffraction (EBSD) system. Cu6Sn5 and Cu3Sn were the two key intermetallic compound (IMC) species that appeared in the CuBOL joints. After annealing for 24 h (= t), the solder had completely converted to Cu-Sn IMCs, forming an "IMC" joint with Cu/Cu3Sn/Cu6Sn5/Cu3Sn/Cu structure. EBSD analyses indicated that the preferred orientation of the hexagonal Cu6Sn5 (?) was , while the preferred orientation was (100) for the monoclinic Cu6Sn5 structure (?'). Upon increasing t to 72 h, Cu6Sn5 entirely transformed into Cu3Sn, and the IMC joint became Cu/Cu3Sn/Cu accordingly. Interestingly, the grain size and crystallographic orientation of Cu3Sn displayed location dependence. Detailed EBSD analyses in combination with transmission electron microscopy on Cu3Sn were performed in the present study. This research offers better understanding of crystallographic details, including crystal structure, grain size, and orientation, for Cu6Sn5 and Cu3Sn in CuBOL joints after various annealing times.

  14. EBSD study on crystallographic texture and microstructure development of cold-rolled FePd alloy

    SciTech Connect

    Lin, Hung-Pin; Ng, Tin-San [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China); Kuo, Jui-Chao, E-mail: jckuo@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China); Chen, Yen-Chun [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China); Chen, Chun-Liang [Department of Materials Science and Engineering, I-Shou University, No. 1 Sec. 1 Syuecheng Road, Kaohsiung 840, Taiwan (China); Ding, Shi-Xuan [Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, No. 70, Lienhai Road, Kaohsiung 804, Taiwan (China); Research Center for Physical Properties and Microstructure of Metals, National Sun Yat-Sen University, No. 70, Lienhai Road, Kaohsiung 804, Taiwan (China)

    2014-07-01

    The crystallographic texture and microstructure of FePd alloy after cold-rolling deformation were investigated using electron backscatter diffraction. The major orientations of twin copper and copper after 50% thickness reduction were observed in face-centered cubic-disordered FePd alloy, whereas the main orientation was obtained from brass type after 90% cold rolling. Increase in cold rolling resulted in the change of preferred orientation from copper to brass. Decrease in orientation intensity of copper also increased that of Goss and brass. - Highlights: • The evolution of texture and microstructure in FePd alloy was investigated after cold rolling using EBSD. • Increasing in reduction leads to the change of texture from Copper-type to Brass-type. • The reduction of Copper orientation results in increasing in Goss and Brass orientations.

  15. Distinguishing eclogite from peridotite: EBSD-based calculations of seismic velocities

    NASA Astrophysics Data System (ADS)

    Worthington, James R.; Hacker, Bradley R.; Zandt, George

    2013-04-01

    Seismic velocities were calculated for 11 eclogites from the Western Gneiss Region, Norway, based on electron-backscatter diffraction (EBSD). The P-wave velocities are 8.0-8.5 km s-1 and the S-wave velocities are 4.5-4.8 km s-1; VP/VS1 (the ratio of P-wave to fast S-wave velocities) is 1.74-1.81. All the eclogites are relatively isotropic, with the higher anisotropies (3-4 per cent) in micaceous samples. Peridotite is comparatively more anisotropic (4-14 per cent more for P waves and up to 10 per cent more for S waves), and can have anomalously low VP/VS1, which may be useful means of distinguishing it from eclogite. Micaceous eclogite may be modelled using hexagonal anisotropy with a slow unique axis, whereas peridotite is most robustly modelled using orthorhombic anisotropy.

  16. Experimental study of corrosion behavior for burnished aluminum alloy by EWF, EBSD, EIS and Raman spectra

    NASA Astrophysics Data System (ADS)

    Jinlong, Lv; Hongyun, Luo; Jinpeng, Xie

    2013-05-01

    The effect of burnish process on 2024 aluminum alloy was studied by electron work function and electron backscattered diffraction (EBSD). Moreover, the corrosion resistance of thin passive films formed on 2024 aluminum alloy in borate buffer solutions was studied by the electrochemical impedance spectroscopy (EIS), the Mott-Schottky plots and the galvanostatic techniques. The composition of passive films was analyzed by Raman spectra. The results obtained indicated that the impedance increased due to burnish and this was attributed to decreased electron work function and higher current efficiency in the burnished aluminum alloy which led to thicker passive films. It was further supported by Raman spectra experiment. Moreover, the donor and acceptor concentration of passive films and their the semiconductor type have changed due to burnish.

  17. Distinguishing eclogite from peridotite: EBSD-based calculations of seismic velocities

    NASA Astrophysics Data System (ADS)

    Worthington, J.; Hacker, B. R.; Zandt, G.

    2012-12-01

    Seismic velocities were calculated for eleven eclogites from the Western Gneiss Region, Norway, based on electron-backscatter diffraction (EBSD). The P-wave velocities are 8.0-8.5 km/s and the S-wave velocities are 4.5-4.8 km/s; VP/VS1 (the ratio of P-wave to fast S-wave velocities) is 1.72-1.81. All the eclogites are relatively isotropic, with the higher anisotropies (3-4%) in micaceous samples. Peridotite is comparatively more anisotropic (4-14% more for P-waves and up to 10% more for S-waves), and can have anomalously low VP/VS1, which may be useful means of distinguishing it from eclogite. Micaceous eclogite may be modeled using hexagonal anisotropy with a slow unique axis, whereas peridotite is mostly robustly modeled using orthorhombic anisotropy.

  18. Image distortions in SEM and their influences on EBSD measurements.

    PubMed

    Nolze, Gert

    2007-01-01

    The high sample tilt angle commonly necessary for an orientation determination by EBSD (electron back-scatter diffraction) is responsible for some simple geometrically caused, but nevertheless essential, image distortions. First of all, the influence of the tilt correction and also the trapezium distortion which appears at low magnifications will be discussed. In the second part, an additional rhomboidal distortion will be introduced which is independent of the magnification used. This distortion appears if the scanned sample surface is out of plane to the tilted stage. Even a small deviation from the parallelity produces an approximately three times bigger error of the Euler angle phi(1) when the sample alignment is based on the image captured from the highly tilted sample. This effect especially concerns small samples (e.g. FIB-lamellae) since they cannot be exactly aligned, but the measurements of bigger samples can also be influenced. As an example a correction procedure is described in detail, based on a repetition of the measurement after a 180 degrees sample rotation. PMID:17014961

  19. The Use of Electron Backscatter Diffraction for the Investigation of Nano Crystalline Materials and the Move Towards Orientation Imaging in the TEM

    Microsoft Academic Search

    David J. Dingley; Matthew M. Nowell

    2004-01-01

    Electron backscatter diffraction is shown to have a spatial resolution between 5?nm and 10?nm and is well suited for the investigation of nano crystalline materials. A study of texture and mesotexture in copper Damascene interconnect lines is used as an illustration. Samples were prepared by electro deposition from baths of different compositions and under various power cycles. The resulting grain

  20. Assessment of local deformation using EBSD: quantification of accuracy of measurement and definition of local gradient.

    PubMed

    Kamaya, Masayuki

    2011-07-01

    Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess the magnitude of microstructural scale deformation (local deformation) for deformed Type 316 stainless steel. Local misorientation, which is an averaged misorientation between neighboring measurement points, is often used for assessment of local deformation. However, the local misorientation is unsuitable for a quantitative evaluation because it depends not only on the local deformation but also on various factors such as measurement accuracy and the distance between points used in the misorientation calculation (step size). In this study, first, the measurement accuracy was quantified by a parameter called background noise. The factors which affect the measurement accuracy were then discussed from measurements under various conditions. Secondly, in order to reduce the influence of measurement conditions and exclude the dependency of step size in the local deformation assessment, a parameter called the local gradient G(L) was proposed. The local gradient clearly showed the spatial distribution of local deformation regardless of the measurement accuracy, and it had hardly any effect from grid pattern and step size. Finally, the local gradient was correlated with the plastic strain from which it was revealed that the strain gradient near a notch root could be estimated by the EBSD measurement. PMID:21763236

  1. EBSD and TEM investigation of the hot deformation substructure characteristics of a type 316L austenitic stainless steel.

    PubMed

    Cizek, P; Whiteman, J A; Rainforth, W M; Beynon, J H

    2004-03-01

    The evolution of crystallographic texture and deformation substructure was studied in a type 316L austenitic stainless steel, deformed in rolling at 900 degrees C to true strain levels of about 0.3 and 0.7. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used in the investigation and a comparison of the substructural characteristics obtained by these techniques was made. At the lower strain level, the deformation substructure observed by EBSD appeared to be rather poorly developed. There was considerable evidence of a rotation of the pre-existing twin boundaries from their original orientation relationship, as well as the formation of highly distorted grain boundary regions. In TEM, at this strain level, the substructure was more clearly revealed, although it appeared rather inhomogeneously developed from grain to grain. The subgrains were frequently elongated and their boundaries often approximated to traces of [111] slip planes. The corresponding misorientations were small and largely displayed a non-cumulative character. At the larger strain, the substructure within most grains became well developed and the corresponding misorientations increased. This resulted in better detection of sub-boundaries by EBSD, although the percentage of indexing slightly decreased. TEM revealed splitting of some sub-boundaries to form fine microbands, as well as the localized formation of microshear bands. The substructural characteristics observed by EBSD, in particular at the larger strain, generally appeared to compare well with those obtained using TEM. With increased strain level, the mean subgrain size became finer, the corresponding mean misorientation angle increased and both these characteristics became less dependent on a particular grain orientation. The statistically representative data obtained will assist in the development of physically based models of microstructural evolution during thermomechanical processing of austenitic stainless steels. PMID:15009696

  2. Study of { 11bar{2} 1} Twinning in ?-Ti by EBSD and Laue Microdiffraction

    NASA Astrophysics Data System (ADS)

    Wang, Leyun; Barabash, Rozaliya; Bieler, Thomas; Liu, Wenjun; Eisenlohr, Philip

    2013-08-01

    Activity of the { 11bar{2} 1} < bar{1} bar{1} 26 rangle extension twinning (T2) mode was analyzed in a commercial purity Ti sample after 2 pct tensile strain imposed by four-point bending. The sample had a moderate c-axis fiber texture parallel to the tensile axis. Compared with the many { 10bar{1} 2} < bar{1} 011 rangle extension (T1) twins that formed in 6 pct of the grains, T2 twins were identified in 0.25 pct of the grains by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) maps. Most of the T2 twins exhibited irregular twin boundaries (TBs) on one side of the twin. High-resolution EBSD revealed both intermediate orientations at some matrix/twin interfaces and substantial lattice rotation within some T2 twins. Interactions between matrix < c + a> dislocations 1/3 < 1bar{2} 13 rangle and a { 11bar{2} 1} T2 twin were investigated by combining SEM/EBSD slip trace characterization and Laue microdiffraction peak streak analysis. < c + a> dislocations that originally glided on a pyramidal plane in the matrix were found on other planes in both the matrix and the twin, which was attributed to extensive cross-slip of the screw component, whose Burgers vector was parallel to the twinning plane. On the other hand, thickening of the twin could engulf some pile-up edge components in front of the TB. During this process, these < c + a> dislocations transmuted from a pyramidal plane (0bar{1} 11) in the matrix to a prismatic plane (bar{1} 010)_{{T}} in the twin lattice. Finally, possible mechanisms for the nucleation and growth of T2 twins will be discussed.

  3. Identifying deformation mechanisms in the NEEM ice core using EBSD measurements

    NASA Astrophysics Data System (ADS)

    Kuiper, Ernst-Jan; Weikusat, Ilka; Drury, Martyn R.; Pennock, Gill M.; de Winter, Matthijs D. A.

    2015-04-01

    Deformation of ice in continental sized ice sheets determines the flow behavior of ice towards the sea. Basal dislocation glide is assumed to be the dominant deformation mechanism in the creep deformation of natural ice, but non-basal glide is active as well. Knowledge of what types of deformation mechanisms are active in polar ice is critical in predicting the response of ice sheets in future warmer climates and its contribution to sea level rise, because the activity of deformation mechanisms depends critically on deformation conditions (such as temperature) as well as on the material properties (such as grain size). One of the methods to study the deformation mechanisms in natural materials is Electron Backscattered Diffraction (EBSD). We obtained ca. 50 EBSD maps of five different depths from a Greenlandic ice core (NEEM). The step size varied between 8 and 25 micron depending on the size of the deformation features. The size of the maps varied from 2000 to 10000 grid point. Indexing rates were up to 95%, partially by saving and reanalyzing the EBSP patterns. With this method we can characterize subgrain boundaries and determine the lattice rotation configurations of each individual subgrain. Combining these observations with arrangement/geometry of subgrain boundaries the dislocation types can be determined, which form these boundaries. Three main types of subgrain boundaries have been recognized in Antarctic (EDML) ice core¹². Here, we present the first results obtained from EBSD measurements performed on the NEEM ice core samples from the last glacial period, focusing on the relevance of dislocation activity of the possible slip systems. Preliminary results show that all three subgrain types, recognized in the EDML core, occur in the NEEM samples. In addition to the classical boundaries made up of basal dislocations, subgrain boundaries made of non-basal dislocations are also common. ¹Weikusat, I.; de Winter, D. A. M.; Pennock, G. M.; Hayles, M.; Schneijdenberg, C. T. W. M. Drury, M. R. Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM. J. Microsc., 2010, doi: 10.1111/j.1365-2818.2010.03471.x ²Weikusat, I.; Miyamoto, A.; Faria, S. H.; Kipfstuhl, S.; Azuma, N.; Hondoh. T. Subgrain boundaries in Antarctic ice quantified by X-ray Laue diffraction. J. of Glaciol., 2011, 57, 85-94

  4. Metallographic Preparation of Space Shuttle Reaction Control System Thruster Electron Beam Welds for Electron Backscatter Diffraction

    NASA Technical Reports Server (NTRS)

    Martinez, James

    2011-01-01

    A Space Shuttle Reaction Control System (RCS) thruster failed during a firing test at the NASA White Sands Test Facility (WSTF), Las Cruces, New Mexico. The firing test was being conducted to investigate a previous electrical malfunction. A number of cracks were found associated with the fuel closure plate/injector assembly (Fig 1). The firing test failure generated a flight constraint to the launch of STS-133. A team comprised of several NASA centers and other research institutes was assembled to investigate and determine the root cause of the failure. The JSC Materials Evaluation Laboratory was asked to compare and characterize the outboard circumferential electron beam (EB) weld between the fuel closure plate (Titanium 6Al-4V) and the injector (Niobium C-103 alloy) of four different RCS thrusters, including the failed RCS thruster. Several metallographic challenges in grinding/polishing, and particularly in etching were encountered because of the differences in hardness, ductility, and chemical resistance between the two alloys and the bimetallic weld. Segments from each thruster were sectioned from the outboard weld. The segments were hot-compression mounted using a conductive, carbon-filled epoxy. A grinding/polishing procedure for titanium alloys was used [1]. This procedure worked well on the titanium; but a thin, disturbed layer was visible on the niobium surface by means of polarized light. Once polished, each sample was micrographed using bright field, differential interference contrast optical microscopy, and scanning electron microscopy (SEM) using a backscatter electron (BSE) detector. No typical weld anomalies were observed in any of the cross sections. However, areas of large atomic contrast were clearly visible in the weld nugget, particularly along fusion line interfaces between the titanium and the niobium. This prompted the need to better understand the chemistry and microstructure of the weld (Fig 2). Energy Dispersive X-Ray Spectroscopy (EDS) was used to confirm the chemical composition of the variations in contrast in these areas. Niobium alloys generally require exposure to more aggressive chemical reagents than titanium alloys for etching because of niobium s chemical resistance; therefore, the titanium portion of the sample was etched first. A five second immersion in Kroll s reagent revealed a general microstructure on the titanium portion of the sample; however, the titanium heat affected zone closest to the weld, was over-etched due to higher concentrations of refined grains and an increase in eta-phase. The Kroll s etchant also revealed some microstructure in the weld nugget itself; the niobium portion of the sample remained unetched.

  5. EBSD study of (1 1 0) orientation of iridium (Ir) coating on niobium (Nb) substrate by double glow plasma

    NASA Astrophysics Data System (ADS)

    Wu, Wangping; Chen, Zhaofeng; Cheng, Xingwang; Wang, Yangwei

    2013-07-01

    (1 1 0)-Oriented Ir coating was prepared by double glow plasma technique on (2 0 0)-oriented Nb substrate. The microstructure of the coating was observed by scanning electron microscopy (SEM). The crystal orientation of the coating was determined by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The coating was composed of columnar grains with submicrometer size of 0.2-0.3 ?m. The thickness of the coating was approximately 6-7 ?m. The mean misorientation angles of the surface of the coating were about 38.6°. The columnar Ir coating had a preferential growth orientation of (1 1 0) crystal plane by XRD and EBSD due to the initial nuclei with preferred growth on the surface of the substrate. The vigorous bombardment from the high energy ions prevented the lower energy (1 0 0) crystal face and the lowest energy (1 1 1) crystal face from generating the orientation. Only the highest energy (1 1 0) crystal face could be formed and grew up, which resulted in the preferred (1 1 0) orientation.

  6. Lattice strain across Na-K interdiffusion fronts in alkali feldspar: an electron back-scatter diffraction study

    NASA Astrophysics Data System (ADS)

    Schäffer, Anne-Kathrin; Jäpel, Tom; Zaefferer, Stefan; Abart, Rainer; Rhede, Dieter

    2014-11-01

    Cation exchange experiments between gem quality sanidine and KCl melt produced chemical alteration of alkali feldspar starting at the grain surface and propagating inwards by highly anisotropic Na-K interdiffusion on the alkali sublattice. Diffusion fronts developing in b-direction are very sharp, while diffusion fronts within the a- c-plane are comparatively broad. Due to the composition dependence of the lattice parameters of alkali feldspar, the diffusion induced compositional heterogeneity induces coherency stress and elastic strain. Electron back-scatter diffraction combined with the cross-correlation technique was employed to determine the lattice strain distribution across the Na-K interdiffusion fronts in partially exchanged single crystals of alkali feldspar. The strain changes gradually across the broad fronts within the a- c-plane, with a successive extension primarily in a-direction conferring to the composition strain in unstressed alkali feldspar. In contrast, lattice strain characterised by pronounced extension in b-direction is localised at the sharp diffusion fronts parallel to b, followed by a slight expansion in a-direction in the orthoclase-rich rim. This strain pattern does not confer with the composition induced lattice strain in a stress-free alkali feldspar. It may rather be explained by the mechanical coupling of the exchanged surface layer and the mechanically strong substratum. The lattice distortion localised at the sharp diffusion front may have an influence on the diffusion process and appears to produce a self-sharpening feedback, leading to a local reduction of component mobilities.

  7. A simple algorithm to eliminate ambiguities in EBSD orientation map visualization and analyses: application to fatigue crack-tips/wakes in aluminum alloys.

    PubMed

    Gupta, Vipul K; Agnew, Sean R

    2010-12-01

    A simple algorithm is developed and implemented to eliminate ambiguities, in both statistical analyses of orientation data (e.g., orientation averaging) and electron backscattered diffraction (EBSD) orientation map visualization, caused by symmetrically equivalent orientations and the wrap-around or umklapp effect. Using crystal symmetry operators and the lowest Euclidian-distance criterion, the orientation of each pixel within a grain is redefined. An advantage of this approach is demonstrated for direct determination of the representative orientation of a grain within an EBSD map by mean, median, or quaternion-based averaging methods that can be further used within analyses or visualization of misorientation or geometrically necessary dislocation (GND) density. If one also considers the lattice curvature tensor, five components of the dislocation density tensor-corresponding to a part of the GND content-may be inferred. The methodology developed is illustrated using EBSD orientation data obtained from the fatigue crack-tips/wakes in aerospace aluminum alloys 2024-T351 and 7050-T7451. PMID:20969812

  8. Lattice-Preferred Orientation in Deformed Novaculite - Comparison of in-situ Results Using BEARTEX and Post-Mortem EBSD Analyses

    NASA Astrophysics Data System (ADS)

    Willenweber, A.; Thomas, S.; Burnley, P. C.

    2012-12-01

    The Berkeley Texture Package BEARTEX is a Windows-based computer software that combines various algorithms to analyze lattice-preferred orientation in polycrystalline materials. BEARTEX was initially designed to interpret diffraction intensity data from pole figure goniometers. Recently it has been successfully used to process synthetic forsterite powder diffraction data from in-situ synchrotron X-ray diffraction taken during deformation (Bollinger et al. 2012). Our study aims to test the practicability of using BEARTEX to analyze the evolution of lattice-preferred orientation in natural polycrystalline quartz (novaculite) during deformation. In-situ X-ray diffraction data was collected during the deformation of novaculite at 2.5 GPa and up to 1000 °C in a D-DIA apparatus using the ten-element energy-dispersive detector at the NSLS beamline X17B2. Diffraction intensities are a function of crystal orientation, expressed in azimuth angle ? and pole distance ?. The latter is the angle between the normal of a given diffraction plane and the vertical direction of the D-DIA apparatus - our principal stress direction during compression. Orientation-dependent diffraction intensities were corrected for different responses of the single detectors and x-ray absorption effects of the anvils. Orientation distributions (ODs) and inverse pole figures were calculated using BEARTEX. In addition, electron backscatter diffraction (EBSD) analyses were carried out on the deformed novaculite samples. Generated pole figures were compared with those derived from BEARTEX. Textural properties of our novaculite starting material complicated the BEARTEX analyses. The relatively strong variation of grain sizes in our natural specimens caused non-random diffraction intensity distributions. Those lead to non-random distributions of crystal orientations when analyzed with BEARTEX, although pole figures from EBSD data clearly show random crystal orientations. In an attempt to solve this problem, we employed a scanning routine when recording in-situ synchrotron X-ray diffraction and so collected diffraction from multiple sample volumes rather than from one single spot. Here, we will present a comparison of pole figures derived from independent BEARTEX and EBSD analyses for a series of novaculite experiments and discuss the practicability of BEARTEX to analyze the evolution of lattice-preferred orientation in natural polycrystalline quartz. REFERENCES C. BOLLINGER, S. MERKEL AND P. RATERRON (2012): In situ quantitative analysis of stress and texture development in forsterite aggregates deformed at 6 GPa and 1373 K. J. Appl. Cryst., 45, 263-271.

  9. The use of combined cathodoluminescence and EBSD analysis: a case study investigating grain boundary migration mechanisms in quartz.

    PubMed

    Piazolo, S; Prior, D J; Holness, M D

    2005-02-01

    Grain boundary migration is an important mechanism of microstructural modification both in rocks and in metals. Combining detailed cathodoluminescence (CL) and electron backscatter diffraction (EBSD) analysis offers the opportunity to relate directly changes in crystallographic orientation to migrating boundaries. We observe the following features in naturally heated quartz grains from the thermal aureole of the Ballachulish Igneous Complex (Scotland, U.K.): (a) propagation of substructures and twin boundaries in swept areas both parallel and at an angle to the growth direction, (b) development of slightly different crystallographic orientations and new twin boundaries at both the growth interfaces and within the swept area and (c) a gradual change in crystallographic orientation in the direction of growth. All these features are compatible with a growth mechanism in which single atoms are attached and detached both at random and at preferential sites, i.e. crystallographically controlled sites or kinks in boundary ledges. Additionally, strain fields caused by defects and/or trace element incorporation may facilitate nucleation sites for new crystallographic orientations at distinct growth interfaces but also at continuously migrating boundaries. This study illustrates the usefulness of combined CL and EBSD in microprocess analysis. Further work in this direction may provide detailed insight into both the mechanism of static grain growth and the energies and mobilities of boundaries in terms of misorientation and grain boundary plane orientation. PMID:15683412

  10. Examining Crystal Fabric Develoment in Ice: Cryo EBSD, Deformation Experiments and the Link to En-glacial Reflectivity

    NASA Astrophysics Data System (ADS)

    Vaughan, Matthew; Prior, David; Seidemann, Meike; Gorman, Andrew; Lilly, Kat; Langhorne, Pat; Easingwood, Richard; Golding, Narayana; Durham, Bill

    2014-05-01

    Over the past few years, cryogenic electron back-scatter diffraction (Cryo-EBSD) has been increasingly used to examine micro-structures in both natural and experimentally deformed ice samples on a micron-scale. Experiments that investigate grain size-sensitive behavior require working on fine-grained ice. These samples present a number of experimental challenges. Issues that present particular difficulties include stable mounting of ice samples, transport of mounted samples and producing a planar, frost-free and damage-free surface. Recent work at the new Otago Ice Deformation Lab has led to the development of a number of experimental methods that help overcome these challenges and enable routine EBSD analysis of fine-grained ice. A brief outline of these experimental methods and some EBSD results from variably deformed ice samples will be presented. Shear deformation experiments on polycrystalline ice are being conducted in order to further explore the relationships between deformation, processes of recrystallization, and the development of anisotropic fabrics that lead to en-glacial seismic reflections. Self-contained, refrigerated deformation units fitted with digital controllers and hardware have been designed for unconfined deformation experiments on polycrystalline synthetic ice. Methods of analysis, from time-lapse photography to random-point tracking, are being employed for monitoring strain in real time. Various methods have been explored for monitoring the development of anisotropic fabrics in ice during progressive deformation. Ultra-sonic transducers can be used to monitor wave velocity changes in various orientations in materials under strain. These experiments have been designed with the objective of quantifying the relationship between deformation fabrics and en-glacial seismic reflectivity observed in thick grounded ice sheets.

  11. Microstructural characterization of autogenous laser welds on 316L stainless steel using EBSD and EDS.

    PubMed

    Kell, J; Tyrer, J R; Higginson, R L; Thomson, R C

    2005-02-01

    This research is concerned with autogenous welding of 316L stainless steel and the microstructure generated by such a process. Autogenous welding does not require a filler material and in this case relies on an initial shallow melt phase to maintain a conduction limited weld. Essentially, a high power laser beam traverses the substrate, with the beam shaped by conventional optics, which produces a Gaussian irradiance distribution; or with a diffractive optical element, used to produce a uniform irradiance distribution. Initial results have shown that due to the nature of the heating cycle, complex microstructures are developed. These fine, complicated microstructures cannot be satisfactorily resolved and quantified using standard optical microscopy techniques. Electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) have been carried out on a number of different microstructures prepared using a range of welding parameters. It is demonstrated that the simultaneous determination of the chemistry and crystallography is a very useful tool for rapid identification of the different phases formed on solidification as a consequence of varying welding procedures. PMID:15683414

  12. An EBSD Study of the Deformation of Service-Aged 316 Austenitic Steel

    NASA Astrophysics Data System (ADS)

    Githinji, David N.; Northover, Shirley M.; Bouchard, P. John; Rist, Martin A.

    2013-09-01

    Electron backscatter diffraction (EBSD) has been used to examine the plastic deformation of an ex-service 316 austenitic stainless steel at 297 K and 823 K (24 °C and 550 °C) at strain rates from 3.5 × 10-3 to 4 × 10-7 s-1. The distribution of local misorientations was found to depend on the imposed plastic strain following a lognormal distribution at true strains <0.1 and a gamma distribution at strains >0.1. At 823 K (550 °C), the distribution of misorientations depended on the applied strain rate. The evolution of lattice misorientations with increasing plastic strain of up to 0.23 was quantified using the metrics kernel average misorientation, average intragrain misorientation, and low angle misorientation fraction. For strain rate down to 10-5 s-1, all metrics were insensitive to deformation temperature, mode (tension vs compression), and orientation of the measurement plane. The strain sensitivity of the different metrics was found to depend on the misorientation ranges considered in their calculation. A simple new metric, proportion of undeformed grains, is proposed for assessing strain in both the aged and unaged materials. Lattice misorientations develop with strain faster in aged steel than in unaged material, and most of the metrics were sensitive to the effects of thermal aging. Ignoring aging effects leads to significant overestimation of the strains around welds. The EBSD results were compared with nanohardness measurements, and good agreement was established between the two techniques of assessing plastic strain in aged 316 steel.

  13. Study of multi-carbide B4C-SiC/(Al, Si) reaction infiltrated composites by SEM with EBSD

    NASA Astrophysics Data System (ADS)

    Almeida, B. A.; Ferro, M. C.; Ravanan, A.; Grave, P. M. F.; Wu, H.-Y.; Gao, M.-X.; Pan, Y.; Oliveira, F. J.; Lopes, A. B.; Vieira, J. M.

    2014-03-01

    In the definition of conceptual developments and design of new materials with singular or unique properties, characterisation takes a key role in clarifying the relationships of composition, properties and processing that define the new material. B4C has a rare combination of properties that makes it suitable for a wide range of applications in engineering: high refractoriness, thermal stability, high hardness and abrasion resistance coupled to low density. However, the low self-diffusion coefficient of B4C limits full densification by sintering. A way to overturn this constraint is by using an alloy, for example Al-Si, forming composites with B4C. Multi-carbide B4C-SiC/(Al, Si) composites were produced by the reactive melt infiltration technique at 1200 - 1350 °C with up to 1 hour of isothermal temperature holds. Pressed preforms made from C-containing B4C were spontaneously infiltrated with Al-Si alloys of composition varying from 25 to 50 wt% Si. The present study involves the characterisation of the microstructure and crystalline phases in the alloys and in the composites by X-ray diffraction and SEM/EDS with EBSD. Electron backscatter diffraction is used in detail to look for segregation and spatial distribution of Si and Al containing phases during solidification of the metallic infiltrate inside the channels of the ceramic matrix when the composite cools down to the eutectic temperature (577 °C). It complements elemental maps of the SEM/EDS. The production of a flat surface by polishing is intrinsically difficult and the problems inherent to the preparation of EBSD qualified finishing in polished samples of such type of composites are further discussed.

  14. Assessment of local deformation using EBSD: Quantification of local damage at grain boundaries

    SciTech Connect

    Kamaya, Masayuki, E-mail: kamaya@inss.co.jp

    2012-04-15

    Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess localization of the local misorientation to grain boundary. In order to quantify the degree of localization, a parameter, which was referred to as the grain boundary local misorientation, was proposed. Through crystal orientation measurements using deformed Type 316 stainless steel, it was shown that the grain boundary local misorientation increased with the applied plastic strain. Particularly, at several grain boundaries, the grain boundary local misorientation was more than 3 times the local misorientation averaged for the whole area. Surface observations revealed that the large local misorientation near the grain boundaries was attributed to the impeded slip steps rather than the number of slip steps observed on the surface. The magnitude of the grain boundary local misorientation had a week correlation with grain boundary length or grain boundary misorientation, and no correlation was found for twin boundaries. Finally, it was shown that the maximum grain boundary local misorientation could be estimated statistically, and the estimated maximum value for the specimen surface with an area of 80 mm{sup 2} was 10.6 times the averaged value. - Highlights: Black-Right-Pointing-Pointer The grain boundary local misorientation was proposed. Black-Right-Pointing-Pointer The maximum grain boundary local misorientation could be estimated statistically. Black-Right-Pointing-Pointer The large local misorientation was attributed to the impeded slip steps.

  15. Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification

    NASA Astrophysics Data System (ADS)

    Isasti, Nerea; Jorge-Badiola, Denis; Taheri, Mitra L.; Uranga, Pello

    2013-08-01

    A complete microstructural characterization and phase transformation analysis has been performed for several Nb and Nb-Mo microalloyed low-carbon steels using electron backscattered diffraction (EBSD) and dilatometry tests. Compression thermomechanical schedules were designed resulting in the undeformed and deformed austenite structures before final transformation. The effects of microalloying additions and accumulated deformation were analyzed after CCT diagram development and microstructural quantification. The resulting microstructures ranged from polygonal ferrite and pearlite at slow cooling ranges, to a combination of quasipolygonal ferrite and granular ferrite for intermediate cooling rates, and finally, to bainitic ferrite with martensite for fast cooling rates. The addition of Mo promotes a shift in the CCT diagrams to lower transformation start temperatures. When the amount of Nb is increased, CCT diagrams show little variations for transformations from the undeformed austenite and higher initial transformation temperatures in the transformations from the deformed austenite. This different behavior is due to the effect of niobium on strain accumulation in austenite and its subsequent acceleration of transformation kinetics. This article shows the complex interactions between chemical composition, deformation, and the phases formed, as well as their effect on microstructural unit sizes and homogeneity.

  16. An Assessment and Estimation of the Damage Progression Behavior of IN738LC under Various Applied Stress Conditions Based on EBSD Analysis

    NASA Astrophysics Data System (ADS)

    Kobayashi, Daisuke; Miyabe, Masamichi; Kagiya, Yukio; Sugiura, Ryuji; Yokobori, A. Toshimitsu

    2013-07-01

    In order to characterize the damage progression behavior of IN738LC and the influence of applied stress, the average misorientation within grains was evaluated using the electron backscattered diffraction (EBSD) method, by measuring over a million data points located across almost the whole zone of the tested specimens. It has been shown under various test conditions such as differing temperatures and strain rates that the average misorientation increases linearly with the increase of creep strains. As a result, it is confirmed that it is possible to assess the remaining creep fracture life from its average misorientation value regardless of the testing temperature and strain rate. In addition, the deformation and fracture mechanisms of various types of mechanical damage, such as tensile, impact, and creep conditions, were discussed by evaluating the characteristics of misorientation distribution. As a result, it has been revealed that creep damage affects a large area of the material, but it is localized near grain boundaries, which is completely different from that of tensile or impact damage. In conclusion, detailed investigation into the cross section of fracture samples using the EBSD misorientation analysis allows for the qualitative estimation of the fracture mode under various applied stress conditions, the cause of the fracture.

  17. Subgrain boundary analyses in deformed orthopyroxene by TEM/STEM with EBSD-FIB sample preparation technique

    NASA Astrophysics Data System (ADS)

    Kogure, Toshihiro; Raimbourg, Hugues; Kumamoto, Akihito; Fujii, Eiko; Ikuhara, Yuichi

    2014-12-01

    High-resolution structure analyses using electron beam techniques have been performed for the investigation of subgrain boundaries (SGBs) in deformed orthopyroxene (Opx) in mylonite from Hidaka Metamorphic Belt, Hokkaido, Japan, to understand ductile deformation mechanism of silicate minerals in shear zones. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analysis of Opx porphyroclasts in the mylonitic rock indicated that the crystal orientation inside the Opx crystals gradually changes by rotation about the b-axis by SGBs and crystal folding. In order to observe the SGBs along the b-axis by transmission electron microscopy (TEM) or scanning TEM (STEM), the following sample preparation protocol was adopted. First, petrographic thin sections were slightly etched with hydrofluoric acid to identify SGBs in SEM. The Opx crystals whose b-axes were oriented close to the normal of the surface were identified by EBSD, and the areas containing SGBs were picked and thinned for (S) TEM analysis with a focused ion beam instrument with micro-sampling system. High-resolution TEM imaging of the SGBs in Opx revealed various boundary structures from a periodic array of dissociated (100) [001] edge dislocations to partially or completely incoherent crystals, depending on the misorientation angle. Atomic-resolution STEM imaging clearly confirmed the formation of clinopyroxene (Cpx) structure between the dissociated partial dislocations. Moreover, X-ray microanalysis in STEM revealed that the Cpx contains a considerable amount of calcium replacing iron. Such chemical inhomogeneity may limit glide motion of the dislocation and eventually the plastic deformation of the Opx porphyroclasts at a low temperature. Chemical profiles across the high-angle incoherent SGB also showed an enrichment of the latter in calcium at the boundary, suggesting that SGBs are an efficient diffusion pathway of calcium out of host Opx grain during cooling.

  18. Microstructural evolution during initial stages of static recovery and recrystallization: new insights from in-situ heating experiments combined with electron backscatter diffraction analysis

    NASA Astrophysics Data System (ADS)

    Bestmann, Michel; Piazolo, Sandra; Spiers, Chris J.; Prior, David J.

    2005-03-01

    We present in-situ observations, performed using electron backscatter diffraction, of static recovery and recrystallization processes occurring in a plastically deformed geological material, namely rocksalt. Static heating experiments, carried out in a scanning electron microscope at temperatures of up to 450 °C, allowed direct detailed observations of grain boundary migration between substructured grains in deformed polycrystalline samples. Contrary to expectations, crystallographic orientation maps reveal that behind slowly migrating grain boundaries new subgrain boundaries form while pre-existing subgrain boundaries are sometimes inherited. Moreover, the crystallographic character, especially the preferred orientation of misorientation axes of the new substructures reflects the character of the previous deformation history. These results imply that substructural features, such as subgrain misorientation distributions, may be relatively robust indicators of deformation mechanisms and conditions, even in tectonites that have undergone late, static recrystallization. In addition, our observations suggest that the process of static grain boundary migration does not necessarily reset earlier deformation microstructures as commonly assumed. The kinematic observations of boundary migrations are inconsistent with simple models in which migration is achieved by single atoms jumping across the boundary.

  19. Influence of Surface Preparation on Scanning Kelvin Probe Microscopy and Electron Backscatter Diffraction Analysis of Cross Sections of CdTe/CdS Solar Cells: Preprint

    SciTech Connect

    Moutinho, H. R.; Dhere, R. G.; Jiang, C. S.; Al-Jassim, M. M.

    2011-06-01

    In this work we investigated different methods to prepare cross sections of CdTe/CdS solar cells for EBSD and SKPM analyses. We observed that procedures used to prepare surfaces for EBSD are not suitable to prepare cross sections, and we were able to develop a process using polishing and ion-beam milling. This process resulted in very good results and allowed us to reveal important aspects of the cross section of the CdTe film. For SKPM, polishing and a light ion-beam milling resulted in cross sections that provided good data. We were able to observe the depletion region on the CdTe film and the p-n junction as well as the interdiffusion layer between CdTe and CdS. However, preparing good-quality cross sections for SKPM is not a reproducible process, and artifacts are often observed.

  20. Characterization by EBSD of dislocations and disclinations in olivine: implications for the rheology of olivine-rich aggregates

    NASA Astrophysics Data System (ADS)

    Cordier, P.; Demouchy, S. A.; Beausir, B.; Taupin, V.; Fressengeas, C.

    2013-12-01

    The rheology of olivine-rich rocks remains poorly understood. Only intracrystalline deformation mechanisms involving dislocations are quite well known. In orthorhombic olivine only two slip directions, [100] and [001] can be activated. Most characterizations performed so far involve transmission electron microscopy studies at high magnifications or, at a larger scale, optical or scanning electron microscopy on decorated samples. In the latter case, no detailed characterization of the defects could be done. Orientation maps obtained from high-resolution electron backscattered diffraction allow recovering components of the lattice curvature tensor which in turn allow determination of components of the dislocation density tensor. The geometrically necessary dislocation content can thus be imaged. Recently Beausir & Fressengeas (2013) have shown that with this technique, components of the disclination density tensor could also be determined. Several examples have been provided in metallic alloys. In this study we show that olivine aggregates (both experimentally and naturally deformed) contain pervasive evidence of disclinations dipoles at grain boundaries. The implications on the plastic behavior of olivine rocks are discussed based on a numerical model of the response to an applied shear stress of a grain boundary made of disclinations. Beausir, B. & Fressengeas, C., Disclination densities from EBSD orientation mapping. International Journal of Solids and Structures 50 (1), 137-146 (2013).

  1. Seismic properties and mineral crystallographic preferred orientations from EBSD data: Results from a crustal-scale detachment system, Aegean region

    NASA Astrophysics Data System (ADS)

    Cossette, Élise; Schneider, David; Audet, Pascal; Grasemann, Bernhard; Habler, Gerlinde

    2015-05-01

    The crystallographic preferred orientations (CPOs) were measured on a suite of samples representative of different structural depths along the West Cycladic Detachment System, Greece. Electron backscatter diffraction (EBSD) analyses were conducted on calcitic and mica schists, impure quartzites, and a blueschist, and the average seismic properties of the rocks were calculated with the Voigt-Reuss-Hill average of the single minerals' elastic stiffness tensor. The calcitic and quartzitic rocks have P- and S-wave velocity anisotropies (AVp, AVs) averaging 8.1% and 7.1%, respectively. The anisotropy increases with depth represented by the blueschist, with AVp averaging 20.3% and AVs averaging 14.5%, due to the content of aligned glaucophane and mica, which strongly control the seismic properties of the rocks. Localised anisotropies of very high magnitudes are caused by the presence of mica schists as they possess the strongest anisotropies, with values of ~ 25% for AVp and AVs. The direction of the fast and slow P-wave velocities occurs parallel and perpendicular to the foliation, respectively, for most samples. The fast propagation has the same NE-SW orientation as the lithospheric stretching direction experienced in the Cyclades since the Late Oligocene. The maximum shear wave anisotropy is subhorizontal, similarly concordant with mineral alignment that developed during extension in the Aegean. Radial anisotropy in the Aegean mid-crust is strongly favoured to azimuthal anisotropy by our results.

  2. Optimization of EBSD parameters for ultra-fast characterization.

    PubMed

    Chen, Y; Hjelen, J; Gireesh, S S; Roven, H J

    2012-02-01

    Ultra-fast pattern acquisition of electron backscatter diffraction and offline indexing could become a dominant technique over online electron backscatter diffraction to investigate the microstructures of a wide range of materials, especially for in situ experiments or very large scans. However, less attention has been paid to optimize the parameters related to ultra-fast electron backscatter diffraction. The present results show that contamination on a clean and unmounted specimen is not a problem even at step sizes as small as 1 nm at a vacuum degree of 6.1 × 10(-5) Pa. There exists an optimum step size at about 50 data acquisition board units. A new and easy method to calculate the effective spatial resolution is proposed. Effective spatial resolution tends to increase slightly as the probe current increases from 10 to 100 nA. The fraction of indexed points decreases slightly as the frame rate increases from 128 patterns per second (pps) to 835 pps by compensating the probe current at the same ratio. The value 96 × 96 is found to be the optimum pattern resolution to obtain optimum speed and image quality. For a fixed position of electron backscatter diffraction detector, the fraction of indexed points as a function of working distance has a maximum value and drops sharply by shortening the working distance and it decreases slowly with increasing the working distance. PMID:22251089

  3. A method for accurate localisation of EBSD pattern centres.

    PubMed

    Maurice, Claire; Dzieciol, Krzysztof; Fortunier, Roland

    2011-01-01

    The moving screen technique for pattern centre localisation is revisited. A cross-correlation based iterative procedure is developed to find both the zoom factor and the zoom centre (which is also the pattern centre) between two EBSD diffraction patterns acquired at two camera positions. The procedure involves two steps: first, a rough estimate of the pattern centre position and zoom factor (the ratio of the two detector distances) is obtained by cross-correlating the entire images. Then, based on this first estimate, cross-correlation of smaller regions of interest (ROIs) gives the displacement field which is interpreted as a zoom factor misfit coupled with a zoom centre position misfit. These misfits are iteratively decreased until the displacement field is reduced to the noise level. The procedure is first applied to simulated patterns and it is shown that the iterative procedure converges very rapidly to the exact solution with an accuracy better than 1/100th of pixel. The potential of this technique for experimental patterns is discussed and recommendations for new EBSD detectors are proposed. PMID:21185458

  4. Use of EBSD to study electropulsing induced reverse phase transformations in a Zn-Al alloy (ZA22).

    PubMed

    Zhu, Y H; To, S; Liu, X M

    2011-04-01

    Multi-phase identification and phase transformations in electropulsing treated Zn-Al based alloy wire specimens were studied using electron back-scattered diffraction, back-scattered scanning electron microscopy and X-ray diffraction techniques. By using electron back-scattered diffraction, two phases: ?'(S) and ?'(T) with a small difference of about 1% in lattice parameters (c(0)/a(0) ) were identified, based on the determined lattice parameters of the phases, and the reverse eutectoid phase transformations: ?'(T) +?'(T) +?'(T) ??'(S) and ?+??T'+? were successfully detected. Electron back-scattered diffraction appeared to be an effective technique for studying complex electropulsing induced phase transformations. PMID:21118233

  5. Errors, artifacts, and improvements in EBSD processing and mapping.

    PubMed

    Tao, Xiaodong; Eades, Alwyn

    2005-02-01

    Electron back scatter diffraction (EBSD) mapping and indexing has rapidly come into widespread use. However, inadequate attention has been paid to the details of the method. Many of the algorithms in current use were chosen because they were the first ones that were found to work, rather than because they were optimum. Results of systematic study are presented. It is shown that more than one method can successfully correct a sampling artifact, that there is an optimum binning ratio, that Gaussian filtering provides an alternative to "butterfly convolution," that better alternatives for mapping image quality than those in current use are available, and that saving all the original patterns is practical and advantageous. PMID:15683574

  6. Characterization of Recrystallization and Microstructure Evolution in Lead-Free Solder Joints Using EBSD and 3D-XRD

    NASA Astrophysics Data System (ADS)

    Zhou, Bite; Bieler, Thomas R.; Lee, Tae-Kyu; Liu, Wenjun

    2013-02-01

    Development of vulnerable high-angle grain boundaries (and cracks) from low-angle boundaries during thermal cycling by means of continuous recrystallization was examined in fine-pitch ball grid array (BGA) packages with Sn-3.0Ag-0.5Cu (wt.%) (SAC305) lead-free solder joints. Electron backscatter diffraction (EBSD) and differential-aperture x-ray microscopy (DAXM or 3D-XRD) were used for surface and subsurface characterization. A large number of subgrain boundaries were observed in the parent orientation using both techniques. However, unlike studies of anisotropic deformation in noncubic metals at much lower homologous temperatures, no streaked diffraction peaks were observed in DAXM Laue patterns within each 1 ?m3 voxel after thermal cycling, suggesting that geometrically necessary dislocations (GNDs) are effectively absorbed by the preexisting subgrain boundaries. Storage at room temperature (0.6 T m) prior to DAXM measurement may also facilitate recovery processes to reduce local GND contents. Heterogeneous residual elastic strains were found near the interface between a precipitated Cu6Sn5 particle and the Sn grain, as well as near particular subgrain boundaries in the parent orientation. Grain boundary migration associated with recrystallization resulted in regions without internal strains, subgrain boundaries, or orientation gradients. Development of new grain orientations by continuous recrystallization and subsequent primary recrystallization and grain growth occurred in the regions where the cracks developed. Orientation gradients and subgrain structure were observed within newly formed recrystallized grains that could be correlated with slip systems having high Schmid factors.

  7. From tabular to rhombohedral dolomite crystals in Zechstein 2 dolostones from Scharzfeld (SW Harz/Germany): A case study with combined CL and EBSD investigations

    NASA Astrophysics Data System (ADS)

    Gillhaus, Axel; Richter, Detlev K.; Götte, Thomas; Neuser, Rolf D.

    2010-07-01

    Tabular dolomite crystals found within dolomite rhombs have been investigated by cathodoluminescence (CL) microscopy and spectroscopy combined with electron backscatter diffraction (EBSD) for the first time. The dolomites formed in the Upper Permian Stassfurt Carbonate Ca2 at the southern margin of the German/Polish Zechstein Basin. Cathodoluminescence petrography of the dolostone succession revealed that the dolomites developed in four phases. Electron backscatter diffraction analysis reveals tabular crystal growth during the two first generations, while the last two generations are characterized by rhombohedral crystal shapes. The tabular dolomite cement crystals and their microcrystalline equivalents in matrix and components have a stoichiometric composition with good to very good lattice ordering. Manganese and iron contents of the tabular crystals are low and their carbon and oxygen isotope composition confirms an early diagenetic dolomite formation under marine-evaporitic conditions from precursor carbonates of Upper Permian age. CL spectroscopy reveals that the tabular dolomite generation 1 has a very high percentage of Mn 2+ on the Ca lattice position which results in a visually yellowish-green CL emission. Although relatively increased Mn 2+ contents at the Ca lattice position appear to be rather common in evaporitic dolomites the combination of a tabular crystal shape and a preferred input of Mn 2+ at the Ca lattice position is a remarkable phenomenon. As tabular dolomite crystals so far are exclusively reported from evaporitic diagenetic settings they could be the result of a high Mg/Ca ratio which blocks c-axis orientated growth of dolomite crystal. The occurrence of well ordered dolomite of which the geochemical zoning can be studied in such detail is rare for the earliest, synsedimentary stages of dolomite formation in marine environments, because these early stages commonly consist of not or badly ordered Ca-dolomites. A primary geochemical zoning of such dolomite usually gets lost during stabilisation and transformation to better ordering and stoichiometry.

  8. Advances in EBSD Technology: A Powerful Method for the Analysis of Impactites and Meteorites

    NASA Astrophysics Data System (ADS)

    Palasse, L.; Goran, D.; Schwager, T.; Berlin, J.; Salge, T.

    2012-09-01

    Electron backscatter diffraction is an analytical technique for assessing the petrographic texture of a rock and the crystallographic orientation of minerals. Recent advances in software and hardware can help to understand impact and shock processes.

  9. EBSD characterization of high-temperature phase transformations in an Al-Si coating on Cr-Mo steel

    SciTech Connect

    Cheng, Wei-Jen, E-mail: d9603505@mail.ntust.edu.tw; Wang, Chaur-Jeng

    2012-02-15

    5Cr-0.5Mo steel was coated by hot-dipping in a molten bath containing Al-10 wt.% Si. The phase transformation in the aluminide layer during diffusion at 750 Degree-Sign C in static air was analyzed by electron backscatter diffraction. The results show the aluminide layer of the as-coated specimen consisted of an outer Al-Si topcoat, a middle layer formed of scattered {tau}{sub 5(C)}-Al{sub 7}(Fe,Cr){sub 2}Si particles and minor plate-shaped {tau}{sub 4}-Al{sub 4}FeSi{sub 2} and {tau}{sub 6}-Al{sub 4}FeSi phases in the Al-Si matrix and an inner continuous {tau}{sub 5(H)}-Al{sub 7}Fe{sub 2}Si layer, respectively from the coating surface to the steel substrate. The formation of FeAl{sub 3} and Fe{sub 2}Al{sub 5} with {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates can be observed with increasing exposure time at 750 Degree-Sign C. After 5 h of exposure, the Al-Si topcoat has been consumed, and the aluminide layer consisted of Fe{sub 2}Al{sub 5} and a few {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates. The FeAl phase not only formed at the interface between Fe{sub 2}Al{sub 5} and the steel substrate, but also transformed from {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} after diffusion for 10 h. With prolonged exposure, the aluminide layer comprised only FeAl{sub 2} and FeAl. - Highlights: Black-Right-Pointing-Pointer EBSD can differentiate phases in aluminide layer with similar chemical compositions. Black-Right-Pointing-Pointer Mapping and EBSPs functions in EBSD provide a reliable phase identification. Black-Right-Pointing-Pointer A phase transformation in the aluminide layer has been described in detail. Black-Right-Pointing-Pointer 5 Fe-Al-Si and 4 Fe-Al intermetallic phases are performed during the diffusion. Black-Right-Pointing-Pointer Cubic {tau}{sub 5(C)}-Al{sub 7} (Fe,Cr){sub 2}Si and hexagonal {tau}{sub 5(H)}-Al{sub 7}(Fe,Cr){sub 2}Si are identified.

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

    NASA Astrophysics Data System (ADS)

    Lizano, Laura; Haun, Stefan

    2015-04-01

    The construction of dams and reservoirs disturb the natural morphological behavior of rivers. A natural settling effect occurs due to the reduced turbulences and flow velocities. As a consequence, reservoirs fill up with sediments which results in a reduction of storage volume, influences the operation of hydropower plants and leads in several cases to flood protection problems. The sediment depositions in reservoirs are standardly evaluated by using bathymetric data, obtained by a single beam sonar from pre-defined cross sections or by an extensive evaluation of the reservoir bed by a side scan sonar. However, a disadvantage of this method is that it is not possible to evaluate the pore water content of the depositions, which may lead as consequence to an uncertainty in the measured amount of deposited sediments. Given that a major part of sediments entering reservoirs are transported in suspension, sediment flux measurements along defined transects could give more reliable information on the settled amount of sediments and additional information on the sediment transport mechanism within the reservoir. An evaluation of the sediment fluxes is in practice often conducted by a single suspended sediment concentration (SSC) measurement in combination with a cross sectional calibration factor to take changes in the SSC along the transect into account. However, these calibration factors are often developed only for one specific in-situ condition and may give unreliable results in case that the boundaries change e.g. the hydraulic conditions. Hence an evaluation of the sediment fluxes along the whole transect would give a more reliable number for the amount of transported sediments through the reservoir. This information can afterwards be used to calculate the amount of settled sediments in different sections of the reservoir and the amount of sediments which will enter the intake. For this study the suspended sediment transport within the Peñas Blancas reservoir in 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.

  11. Using transmission Kikuchi diffraction to study intergranular stress corrosion cracking in type 316 stainless steels.

    PubMed

    Meisnar, Martina; Vilalta-Clemente, Arantxa; Gholinia, Ali; Moody, Michael; Wilkinson, Angus J; Huin, Nicolas; Lozano-Perez, Sergio

    2015-08-01

    Transmission Kikuchi diffraction (TKD), also known as transmission-electron backscatter diffraction (t-EBSD) is a novel method for orientation mapping of electron transparent transmission electron microscopy specimen in the scanning electron microscope and has been utilized for stress corrosion cracking characterization of type 316 stainless steels. The main advantage of TKD is a significantly higher spatial resolution compared to the conventional EBSD due to the smaller interaction volume of the incident beam with the specimen. Two 316 stainless steel specimen, tested for stress corrosion cracking in hydrogenated and oxygenated pressurized water reactor chemistry, were characterized via TKD. The results include inverse pole figure (IPFZ) maps, image quality maps and misorientation maps, all acquired in very short time (<60min) and with remarkable spatial resolution (up to 5nm step size possible). They have been used in order to determine the location of the open crack with respect to the grain boundary, deformation bands, twinning and slip. Furthermore, TKD has been used to measure the grain boundary misorientation and establish a gauge for quantifying plastic deformation at the crack tip and other regions in the surrounding matrix. Both grain boundary migration and slip transfer have been detected as well. PMID:25974882

  12. Electromagnetic backscattering by corner reflectors

    NASA Technical Reports Server (NTRS)

    Balanis, C. A.; Griesser, T.

    1986-01-01

    The Geometrical Theory of Diffraction (GTD), which supplements Geometric Optics (GO), and the Physical Theory of Diffraction (PTD), which supplements Physical Optics (PO), are used to predict the backscatter cross sections of dihedral corner reflectors which have right, obtuse, or acute included angles. These theories allow individual backscattering mechanisms of the dihedral corner reflectors to be identified and provide good agreement with experimental results in the azimuthal plane. The advantages and disadvantages of the geometrical and physical theories are discussed in terms of their accuracy, usefulness, and complexity. Numerous comparisons of analytical results with experimental data are presented. While physical optics alone is more accurate and more useful than geometrical optics alone, the combination of geometrical optics and geometrical diffraction seems to out perform physical optics and physical diffraction when compared with experimental data, especially for acute angle dihedral corner reflectors.

  13. A time domain rough surface scattering model based on wedge diffraction: application to low-frequency backscattering from two-dimensional sea surfaces

    PubMed

    Keiffer; Novarini

    2000-01-01

    A time domain method for calculating the acoustic impulse response of impenetrable, rough, two-dimensional (2D) surfaces is presented. The method is based on an extension of the wedge assemblage (WA) method to 2D surfaces and objects. Like the WA method for one-dimensional (1D) surfaces, the approach for 2D surfaces uses Biot's and Tolstoy's exact solution for the impulse response of an infinite impenetrable wedge [J. Acoust. Soc. Am. 29, 381-391 (1957)] as its fundamental building block. The validity of the WA method for backscattering from 2D sea surfaces is assessed through comparisons with calculations based on Milder's operator expansion (OE) method [J. Acoust. Soc. Am. 89, 529-541 (1991)]. Average intensities for backscattering from 2D fully developed seas (20 m/s wind speed) were computed by the WA and OE methods using 50 surface realizations and compared at 11 frequencies between 100 and 200 Hz. A single, moderately low grazing angle of incidence (20 degrees) and several scattered grazing angles (90 degrees, 45 degrees, 20 degrees , and 10 ) were considered. Excellent overall agreement between the two models was obtained. The utility of the WA method as a tool to describe the physics of the scattering process is also discussed. PMID:10641617

  14. Evaluation of misindexing of EBSD patterns in a ferritic steel.

    PubMed

    Karthikeyan, T; Dash, M K; Saroja, S; Vijayalakshmi, M

    2013-01-01

    The systematic misindexing caused by pseudo-symmetry Kikuchi diffraction patterns in automated Electron Backscatter Diffraction analysis has been studied in a 9Cr-1Mo ferritic steel. Grains with its [1 1 1] directed towards detector centre were found to be prone to misindexing, and the solutions exhibit a relative orientation of ±30° and 60° about the common [1 1 1] axis (as compared to the true orientation). Fictitious boundaries were detected within such grains, which satisfy the ?3 or ?13b type coincidence site lattice boundary criteria. Misindexing rate was reduced with more than six detected bands, but 30° rotated solution was comparatively more persistent, as the additional bands of (3 1 0)-type exhibited a nearly good pattern match. Increase in detector collection angle to 0.96 sr or number of detected bands to nine were found to be beneficial in preventing the misindexing problem. PMID:23126369

  15. Microstructural evolution of uranium dioxide following compression creep tests: An EBSD and image analysis study

    NASA Astrophysics Data System (ADS)

    Iltis, X.; Gey, N.; Cagna, C.; Hazotte, A.; Sornay, Ph.

    2015-01-01

    Sintered UO2 pellets with relatively large grains (?25 ?m) are tested at 1500 °C under a compressive stress of 50 MPa, at different deformation levels up to 12%. Electron Back Scattered Diffraction (EBSD) is used to follow the evolution, with deformation, of grains (size, shape, orientation) and sub-grains. Image analyses of SEM images are performed to characterize emergence of a population of micron size voids. For the considered microstructure and test conditions, the results show that the deformation process of UO2 globally corresponds to grain boundary sliding, partly accommodated by a dislocational creep within the grains, leading to a highly sub-structured state.

  16. Interface and growth-mode characterization of Ce/Fe and CeH?2/Fe multilayers by x-ray diffraction and Rutherford backscattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Klose, F.; Steins, M.; Kacsich, T.; Felsch, W.

    1993-07-01

    The detailed structural characterization of ion beam sputtered Ce/Fe and CeH?2/Fe multilayers offers the possibility for a better understanding of their magnetic properties. In the case of the Ce/Fe multilayers the extension of the interface, as one of the most important features, is determined to 5-7 Å by means of Monte Carlo simulations of the small-angle x-ray scattering diagrams. Below a critical thickness of ?24 Å Fe grows in an amorphous structure. Here the interface extension is enhanced. In contrast all CeH?2/Fe multilayers show nearly abrupt interfaces. X-ray scattering experiments at higher angles in reflection and transmission mode provide information about the crystal structure, the texture, and the lateral dimensions of the grains in the samples. Depths profiles of the multilayers are generated by Rutherford backscattering spectroscopy, which confirm the well-ordered periodic structures. Surprisingly indications of an island-like growth mode of the Fe layers onto the Ce and CeH?2 layers could be resolved by using this procedure.

  17. Application of EBSD to the analysis of interface planes: evolution over the last two decades.

    PubMed

    Randle, V

    2008-06-01

    Over the last two decades, several methods, of increasing sophistication, have evolved to measure boundary plane orientation by electron backscatter diffraction. Originally, metallographic sectioning was used to obtain the location of the boundary plane. The most recently designed approach allows the relative frequency distribution of boundary misorientation and boundary plane types to be obtained, for very large sample populations, by a stereological method. In this review, the progress in measuring boundary planes by electron backscatter diffraction is charted. Each technique is described in chronological order, illustrated by a series of examples, all relating to boundary plane reorientation. PMID:18503667

  18. Identifying suboxide grains at the metal-oxide interface of a corroded Zr-1.0%Nb alloy using (S)TEM, transmission-EBSD and EELS.

    PubMed

    Hu, Jing; Garner, Alistair; Ni, Na; Gholinia, Ali; Nicholls, Rebecca J; Lozano-Perez, Sergio; Frankel, Philipp; Preuss, Michael; Grovenor, Chris R M

    2015-02-01

    Here we report a methodology combining TEM, STEM, Transmission-EBSD and EELS to analyse the structural and chemical properties of the metal-oxide interface of corroded Zr alloys in unprecedented detail. TEM, STEM and diffraction results revealed the complexity of the distribution of suboxide grains at the metal-oxide interface. EELS provided accurate quantitative analysis of the oxygen concentration across the interface, identifying the existence of local regions of stoichiometric ZrO and Zr3O2 with varying thickness. Transmission-EBSD confirmed that the suboxide grains can be indexed with the hexagonal ZrO structure predicted with ab initio by Nicholls et al. (2014). The t-EBSD analysis has also allowed for the mapping of a relatively large region of the metal-oxide interface, revealing the location and size distribution of the suboxide grains. PMID:25474748

  19. Relationships Between the Phase Transformation Kinetics, Texture Evolution, and Microstructure Development in a 304L Stainless Steel Under Biaxial Loading Conditions: Synchrotron X-ray and Electron Backscatter Diffraction Studies

    NASA Astrophysics Data System (ADS)

    Cakmak, Ercan; Choo, Hahn; Kang, Jun-Yun; Ren, Yang

    2015-05-01

    The relationships between the martensitic phase transformation kinetics, texture evolution, and the microstructure development in the parent austenite phase were studied for a 304L stainless steel that exhibits the transformation-induced plasticity effect under biaxial loading conditions at ambient temperature. The applied loading paths included: pure torsion, simultaneous biaxial torsion/tension, simultaneous biaxial torsion/compression, and stepwise loading of tension followed by torsion ( i.e., first loading by uniaxial tension and then by pure torsion in sequence). Synchrotron X-ray and electron backscatter diffraction techniques were used to measure the evolution of the phase fractions, textures, and microstructures as a function of the applied strains. The influence of loading character and path on the changes in martensitic phase transformation kinetics is discussed in the context of (1) texture-transformation relationship and the preferred transformation of grains belonging to certain texture components over the others, (2) effects of axial strains on shear band evolutions, and (3) volume changes associated with martensitic transformation.

  20. Texture heterogeneities in alpha/alpha titanium forging analysed by EBSD-relation to fatigue crack propagation.

    PubMed

    Uta, E; Gey, N; Bocher, P; Humbert, M; Gilgert, J

    2009-03-01

    The microstructure and the local texture of a large IMI 834 forging were characterized using the Electron Back Scattered Diffraction (EBSD) technique. Crystallographic domains called macrozones and formed by a majority of primary alpha(p) grains with their axes in nearly the same direction were found. They had a band-like structure, parallel to the axial direction of the forging. The influence of these macrozones on the cold dwell-fatigue properties was studied. Several samples were tested under cold dwell-fatigue conditions. The crack initiation and the short-distance propagation region optically matched a bright region that contained numerous quasi-cleavage facets. The analysis of the EBSD measurements showed that this bright region was enclosed within a sharp textured region with axes at less than 30 degrees from the loading axis. The crystallographic features of the crack nucleation site and the crack propagation path were also analysed. PMID:19250466

  1. Characterization of the multilayered shell of a limpet, Lottia kogamogai (Mollusca: Patellogastropoda), using SEM-EBSD and FIB-TEM techniques.

    PubMed

    Suzuki, Michio; Kameda, Jun; Sasaki, Takenori; Saruwatari, Kazuko; Nagasawa, Hiromichi; Kogure, Toshihiro

    2010-08-01

    The microstructure and its crystallographic aspect of the shell of a limpet, Lottiakogamogai, have been investigated, as the first step to clarify the mechanism of shell formation in limpet. The shell consists of five distinct layers stacked along the shell thickness direction. Transmission electron microscopy (TEM) with the focused ion beam (FIB) sample preparation technique was primarily adopted, as well as scanning electron microscopy (SEM) with electron back-scattered diffraction (EBSD). The five layers were termed as M+3, M+2, M+1, M, M-1 from the outside to the inside in previous works, where M means myostracum. The outmost M+3 layer consists of calcite with a "mosaic" structure; granular submicron sub-grains with small-angle grain boundaries often accompanying dislocation arrays. M+2 layer consists of flat prismatic aragonite crystals with a leaf-like cross section, stacked obliquely to the shell surface. It looks that the prismatic crystals are surrounded by organic sheets, forming a compartment structure. M+1 and M-1 layers adopt a crossed lamellar structure consisting of aragonite flat prisms with rectangular cross section. M layer has a prismatic structure of aragonite perpendicular to the shell surface and with irregular shaped cross sections. Distinct organic sheets were not observed between the crystals in M+1, M and M-1 layers. The {110} twins are common in all aragonite M+2, M+1, M and M-1 layers, with the twin boundaries parallel to the prisms. These results for the microstructure of each layer should be considered in the discussion of the formation mechanism of the limpet shell structure. PMID:20430100

  2. EBSD Imaging of Monazite: a Petrochronological Tool?

    NASA Astrophysics Data System (ADS)

    Mottram, C. M.; Cottle, J. M.

    2014-12-01

    Recent advances in in-situ U-Th/Pb monazite petrochronology allow ages obtained from micron-scale portions of texturally-constrained, individual crystals to be placed directly into a quantitative Pressure-Temperature framework. However, there remain major unresolved challenges in linking monazite ages to specific deformation events and discerning the effects of deformation on the isotopic and elemental tracers in these phases. Few studies have quantitatively investigated monazite microstructure, and these studies have largely focused only on crystals produced experimentally (e.g. Reddy et al., 2010). The dispersion in age data commonly yielded from monazite U-Th/Pb datasets suggest that monazite dynamically recrystallises during deformation. It remains unclear how this continual recrystallisation is reflected in the monazite crystal structure, and how this subsequently impacts the ages (or age ranges) yielded from single crystals. Here, combined laser ablation split-stream analysis of deformed monazite, EBSD imaging and Pressure-Temperature (P-T) phase equilibria modelling is used to quantify the influence of deformation on monazite (re)crystallisation mechanisms and its subsequent effect on the crystallographic structure, ages and trace-element distribution in individual grains. These data provide links between ages and specific deformation events, thus helping further our understanding of the role of dynamic recrystallisation in producing age variation within and between crystals in a deformed rock. These data provide a new dimension to the field of petrochronology, demonstrating the importance of fully integrating the Pressure-Temperature-time-deformation history of accessory phases to better interpret the meaningfulness of ages yielded from deformed rocks. Reddy, S. et al., 2010. Mineralogical Magazine 74: 493-506

  3. In-situ EBSD Phase Transformation and Recrystallisation

    NASA Astrophysics Data System (ADS)

    Ubhi, H. S.; Parsons, J.; Othen, N.; Campbell, S.; Poole, R.; Gholinia, A.

    2014-06-01

    With the advent of in-situ heating stages that can fit into SEM's and the combination with EBSD, it is now possible to directly observe phenomenon such as phase transformations and recrystallisation at high spatial resolution and to link these processes to microstructural parameters. This presentation will report some results from preliminary in-situ EBSD heating experiments conducted in an SEM on the transformation of ausenite to ferrite in a plain carbon steel and recrystallisation in bronze alloy strip cast on a steel substrate. The microstructural changes observed during these experiments will be reported in terms of EBSD maps, grains size and crystallographic texture that evolves during a) a heating cycle from ferrite to austenite and cooling to ferrite and b) the recrystallisation microstructure for bronze and steel during isochronal heating.

  4. Use of EBSD to identify phases in interdendrite region of a cast Zn-Al-based alloy (ZA27).

    PubMed

    To, S; Zhu, Y H; Lee, W B

    2007-02-01

    Electron backscattered Kikuchi diffraction methodology was used to identify phases in the interdendrite region of an alloy ZA27. Two Zn-rich hexagonal close-packed structure phases eta and epsilon phases were distinguished using predetermined lattice parameters of the phases. In relation to studies of scanning electron microscopy and X-ray diffraction, electron backscattered diffraction results revealed that the Al-rich precipitates of the alpha phase were from decomposition of the eta'(T), and the four-phase transformation: alpha+epsilon--> T'+eta, had occurred in the epsilon phase after ageing at 150 degrees C for 8 h. PMID:17359251

  5. EBSD and TEM Characterization of High Burn-up Mixed Oxide Fuel

    SciTech Connect

    Teague, Melissa C. [Idaho National Laboratory (INL), Idaho Falls, ID (United States); Gorman, Brian P. [Colorado School of Mines, Golden, CO (United States); Miller, Brandon D. [Idaho National Laboratory (INL), Idaho Falls, ID (United States); King, Jeffrey [Colorado School of Mines, Golden, CO (United States)

    2014-01-01

    Understanding and studying the irradiation behavior of high burn-up oxide fuel is critical to licensing of future fast breeder reactors. Advancements in experimental techniques and equipment are allowing for new insights into previously irradiated samples. In this work dual column focused ion beam (FIB)/scanning electron microscope (SEM) was utilized to prepared transmission electron microscope samples from mixed oxide fuel with a burn-up of 6.7% FIMA. Utilizing the FIB/SEM for preparation resulted in samples with a dose rate of <0.5 mRem/h compared to approximately 1.1 R/h for a traditionally prepared TEM sample. The TEM analysis showed that the sample taken from the cooler rim region of the fuel pellet had approximately 2.5x higher dislocation density than that of the sample taken from the mid-radius due to the lower irradiation temperature of the rim. The dual column FIB/SEM was additionally used to prepared and serially slice approximately 25 um cubes. High quality electron back scatter diffraction (EBSD) were collected from the face at each step, showing, for the first time, the ability to obtain EBSD data from high activity irradiated fuel.

  6. Grain detection from 2d and 3d EBSD data--specification of the MTEX algorithm.

    PubMed

    Bachmann, Florian; Hielscher, Ralf; Schaeben, Helmut

    2011-12-01

    We present a fast and versatile algorithm for the reconstruction of the grain structure from 2d and 3d Electron Back Scatter Diffraction (EBSD) data. The algorithm is rigorously derived from the modeling assumption that grain boundaries are located at the bisectors of adjacent measurement locations. This modeling assumption immediately implies that grains are composed of Voronoi cells corresponding to the measurement locations. Thus our algorithm is based on the Voronoi decomposition of the 2d or 3d measurement domain. It applies to any geometrical configuration of measurement locations and allows for missing data due to measurement errors. The definition of grains as compositions of Voronoi cells implies another fundamental feature of the proposed algorithm--its invariance with respect to spatial displacements, i.e., rotations or shifts of the specimen. This paper also serves as a reference paper for the texture analysis software MTEX, which is a comprehensive and versatile, freely available MATLAB toolbox that covers a wide range of problems in quantitative texture analysis, including the analysis of EBSD data. PMID:22094374

  7. EBSD and TEM characterization of high burn-up mixed oxide fuel

    NASA Astrophysics Data System (ADS)

    Teague, Melissa; Gorman, Brian; Miller, Brandon; King, Jeffrey

    2014-01-01

    Understanding and studying the irradiation behavior of high burn-up oxide fuel is critical to licensing of future fast breeder reactors. Advancements in experimental techniques and equipment are allowing for new insights into previously irradiated samples. In this work dual column focused ion beam (FIB)/scanning electron microscope (SEM) was utilized to prepared transmission electron microscope samples from mixed oxide fuel with a burn-up of 6.7% FIMA. Utilizing the FIB/SEM for preparation resulted in samples with a dose rate of <0.5 mRem/h compared to ?1.1 R/h for a traditionally prepared TEM sample. The TEM analysis showed that the sample taken from the cooler rim region of the fuel pellet had ?2.5× higher dislocation density than that of the sample taken from the mid-radius due to the lower irradiation temperature of the rim. The dual column FIB/SEM was additionally used to prepared and serially slice ?25 ?m cubes. High quality electron back scatter diffraction (EBSD) were collected from the face at each step, showing, for the first time, the ability to obtain EBSD data from high activity irradiated fuel.

  8. Effect of microscopic parameters on EBSD spatial resolution.

    PubMed

    Chen, Delphic; Kuo, Jui-Chao; Wu, Wen-Tuan

    2011-01-01

    In this study, a quantitative approach is proposed to understand the effect of the accelerating voltage and the probe current on the physical resolution of EBSD. The accelerating voltage was varied from 5 to 30kV and probe currents of 1, 10, and 40nA were selected. The lateral, longitudinal, and depth resolutions at 10kV and 1nA were 34.5, 44.7, and 46nm for copper, respectively. When the accelerating voltage was in the range of 5-20kV, the ratio of the longitudinal to the lateral resolution was below the theoretical ratio of 2.9. Considering the channeling effect, the best physical depth resolution of 38nm was achieved at 5kV and 10nA. The physical depth resolution in an EBSD measurement is much larger due to the channel effect than that obtained without considering this effect. PMID:21930021

  9. EBSD observations of dynamic recrystallization mechanisms in ice.

    NASA Astrophysics Data System (ADS)

    Montagnat, Maurine; Chauve, Thomas; Barou, Fabrice; Beausir, Benoît; Fressengeas, Claude; Tommasi, Andrea

    2014-05-01

    Dynamic recrystallization (DRX) strongly affects the evolution of microstructure (grain size and shape) and texture (crystal preferred orientation) in materials during deformation at high temperature. Since texturing leads to anisotropic physical properties, predicting the effect of DRX in metals is essential for industrial applications, in rocks for interpreting geophysical data and modeling geodynamic flows, or in ice for predicting ice sheet flow and climate evolution. Owing to its high viscoplastic anisotropy, ice has long been considered as a "model material". This happens to be particularly true in the case of the understanding of the fundamental of DRX mechanisms as they occur under a relatively easily controlled environment. Creep compression experiments were performed on polycrystalline ice samples in the laboratory in order to observe the evolution of the fabrics and microstructures during DRX. During the tests, performed at temperatures of -5°C and -7°C, under 0.8 MPa compressive stress, dynamic recrystallization was initiated after 1% macroscopic strain and could be followed up to 18% strain on separated samples. Fabrics and microstructures were analysed post-mortem using an Automatic Ice Texture Analyser (AITA, Russell-Head and Wilson 2001) and EBSD measurements with the Crystal Probe of Géosciences Montpellier. Both techniques enable high resolution observations, both in space and orientation (5 to 50 microns, EBSD: 0.7° - AITA: 3°), which is new for DRX observations in ice. While AITA provides only the c-axis orientations, EBSD provides full orientations (c- and a-axes). In particular, we could access to an estimate of a relative dislocation density (from the Nye tensor obtained with EBSD) and its evolution with strain. Fabric evolution with strain is very similar to what was measured by Jacka and Maccagnan (1984) with a strong strengthening toward a few maxima for c- and a-axes. The c-axes maxima are oriented about 30° from the compression direction. Within our condition range, the grain boundary migration highly dominates the DRX mechanisms and induces strongly serrated grain boundaries. This is to be associated with a highly heterogeneous state of stress and strain that is not "homogenised" by DRX mechanisms. Indeed, higher resolution observations (5 microns) reveal highly distorted areas close to grain boundaries and triple junctions. T. H. Jacka and M. Maccagnan (1984). Ice crystallographic and strain rate changes with strain in compression and extension. Cold Reg. Sci. Technol. Vol. 8 pp 269-286 D. S. Russell-Head and C. J. L. Wilson (2001). Automated fabric analyser system for quartz and ice. J. Glaciol. Vol. 24 Num 90 pp 117-130

  10. EBSD and EDX analyses of a multiphase glass-ceramic obtained by crystallizing an yttrium aluminosilicate glass.

    PubMed

    Keshavarzi, Ashkan; Wisniewski, Wolfgang; Rüssel, Christian

    2013-09-11

    A glass with the mol % composition 23.82 Y2O3·39.82 Al2O3·28.50 SiO2·2.91AlF3·4.95 ZrO2 doped with 2 mol % CeF3 is crystallized at 1250 °C for 20 h. The crystallized samples are studied using X-ray diffraction (XRD), the SEM-based methods EBSD and EDX, as well as fluorescence microscopy. Six crystalline phases are detected in the residual glass including alumina, YAG, Y-stabilized zirconia (YSZ), and three different yttrium silicates of the composition Y2Si2O7. Chemistry-assisted indexing (ChI) is successfully applied to separate YAG and YSZ in EBSD-scans. YAG displays polygon as well as dendritic growth. Some crystals show both mechanisms at opposite ends, indicating that the growth mechanism is influenced by the chemistry of the surrounding glass matrix. PMID:23848162

  11. Evaluation of intragranular misorientation parameters measured by EBSD in a hot worked austenitic stainless steel.

    PubMed

    Jorge-Badiola, D; Iza-Mendia, A; Gutiérrez, I

    2007-12-01

    An extensive characterization of hot deformed austenitic stainless steel was carried out using the electron backscatter diffraction technique. Special emphasis was given to the misorientation parameters related to different length scales. These parameters show a behaviour that is sensitive to the amount of applied strain and also lead to increasing values for both the strain and the scale length. At the same time, the use of different thresholds and scan steps in the evaluation of the parameters were analyzed in order to assess the validity of the results. PMID:18045332

  12. SEM-EBSD based Realistic Modeling and Crystallographic Homogenization FE Analyses of LDH Formability Tests

    NASA Astrophysics Data System (ADS)

    Kuramae, Hiroyuki; Ngoc Tam, Nguyen; Nakamura, Yasunori; Sakamoto, Hidetoshi; Morimoto, Hideo; Nakamachi, Eiji

    2007-05-01

    Homogenization algorithm is introduced to the elastic/crystalline viscoplastic finite element (FE) procedure to develop multi-scale analysis code to predict the formability of sheet metal in macro scale, and simultaneously the crystal texture and hardening evolutions in micro scale. The isotropic and kinematical hardening lows are employed in the crystalline plasticity constitutive equation. For the multi-scale structure, two scales are considered. One is a microscopic polycrystal structure and the other a macroscopic elastic plastic continuum. We measure crystal morphologies by using the scanning electron microscope (SEM) with electron back scattered diffraction (EBSD), and define a three dimensional representative volume element (RVE) of micro ploycrystal structure, which satisfy the periodicity condition of crystal orientation distribution. Since nonlinear multi-scale FE analysis requires large computation time, development of parallel computing technique is needed. To realize the parallel analysis on PC cluster system, the dynamic explicit FE formulations are employed. Applying the domain partitioning technique to FE mesh of macro continuum, homogenized stresses based on micro crystal structures are computed in parallel without solving simultaneous linear equation. The parallel FEM code is applied to simulate the limit dome height (LDH) test problem and hemispherical cup deep drawing problem of aluminum alloy AL6022, mild steel DQSK, high strength steel HSLA, and dual phase steel DP600 sheet metals. The localized distribution of thickness strain and the texture evolution are obtained.

  13. Using EBSD and TEM-Kikuchi patterns to study local crystallography at the domain boundaries of lead zirconate titanate.

    PubMed

    Farooq, M U; Villaurrutia, R; MacLaren, I; Kungl, H; Hoffmann, M J; Fundenberger, J-J; Bouzy, E

    2008-06-01

    Reliable EBSD mapping of 90 degree domains in a tetragonal ferroelectric perovskite has been achieved for the first time, together with reliable automated orientation determination from TEM-Kikuchi patterns. This has been used to determine misorientation angles at 90 degree domain boundaries and thus local c/a ratios. The sources of orientation noise/error and their effects on the misorientation angle data have been thoroughly analyzed and it is found that this gives a cosine distribution of misorientation angles about the mean with a characteristic width related to the width of the orientation noise distribution. In most cases, a good agreement is found between local c/a ratios and global measurements by X-ray diffraction, but some clear discrepancies have also been found suggesting that real local variations are present, perhaps as a consequence of compositional inhomogeneities. PMID:18503671

  14. A review of advances and challenges in EBSD strain mapping

    NASA Astrophysics Data System (ADS)

    Wilkinson, A. J.; Britton, T. B.; Jiang, J.; Karamched, P. S.

    2014-03-01

    High sensitivity cross-correlation based analysis of EBSD patterns was introduced by Wilkinson, Meaden and Dingley in 2006 [1, 2]. This paper will describe the basis of the method and the various modifications and improvements that have been made to it over the past few years. Strain sensitivity of ~ 10-4 is readily obtained and sensitivity to lower strains is achievable if signal to noise ratio in the patterns is improved by simple integration. The method allows maps of local stress and dislocation density distributions to be generated in parallel with information concerning grain orientation, grain boundary misorientation and the presence of other microstructural features. The method is illustrated by example maps from a Ni-based superalloy and deformed Cu.

  15. Recrystallization phenomena in an IF steel observed by in situ EBSD experiments.

    PubMed

    Nakamichi, H; Humphreys, F J; Brough, I

    2008-06-01

    In situ electron backscatter diffraction microstructural analysis of recrystallizing interstitial free steels deformed to strains of 0.75 and 1.6 has been carried out in a FEG-SEM. The experimental procedures are discussed, and it is shown that there is no degradation of the electron backscatter diffraction patterns at temperatures up to 800 degrees C. Analysis of the surface and interior microstructures of annealed samples shows only minor difference, which suggests that in situ annealing experiments are of value. In addition, it is shown that in situ measurements allow a detailed comparison between the same areas before and after annealing, thereby providing information about the recrystallization mechanisms. Sequential recrystallization phenomena, such as initiation and growth of new grains, are observed at temperatures over 740 degrees C, and depending on the deformation histories, different recrystallization behaviour is observed. It is found that {111} <123> recrystallized grains are preferentially formed in the highly deformed material, whereas no strong recrystallization texture is formed in the lower strained material. PMID:18503673

  16. Application of combined EBSD and 3D-SEM technique on crystallographic facet analysis of steel at low temperature.

    PubMed

    Mohseni, P; Solberg, J K; Karlsen, M; Akselsen, O M; Ostby, E

    2013-07-01

    Electron backscatter diffraction has been increasingly used to identify the crystallographic planes and orientation of cleavage facets with respect to the rolling direction in fracture surfaces. The crystallographic indices of cleavage planes can be determined either directly from the fracture surface or indirectly from metallographic sections perpendicular to the plane of the fracture surface. A combination of electron backscatter diffraction and 3D scanning electron microscopy imaging technique has been modified to determine crystallographic facet orientations. The main purpose of this work has been to identify the macroscopic crystallographic orientations of cleavage facets in the fracture surfaces of weld heat affected zones in a well-known steel fractured at low temperatures. The material used for the work was an American Petroleum Institute (API) X80 grade steel developed for applications at low temperatures, and typical heat affected zone microstructures were obtained by carrying out weld thermal simulation. The fracture toughness was measured at different temperatures (0°C, -30°C, -60°C and -90°C) by using Crack Tip Opening Displacement testing. Fracture surfaces and changes in microstructure were analyzed by scanning electron microscopy and light microscopy. Crystallographic orientations were identified by electron backscatter diffraction, indirectly from a polished section perpendicular to the major fracture surface of the samples. Computer assisted 3D imaging was used to measure the angles between the cleavage facets and the adjacent polished surface, and then these angles were combined with electron backscatter diffraction measurements to determine the macroscopic crystallographic planes of the facets. The crystallographic indices of the macroscopic cleavage facet planes were identified to be {100}, {110}, {211} and {310} at all temperatures. PMID:23692572

  17. Radar backscatter modelling

    NASA Astrophysics Data System (ADS)

    Schaber, G. G.; Kozak, R. C.; Gurule, R. L.

    1984-04-01

    The terrain analysis software package was restructured and documentation was added. A program was written to test Johnson Space Center's four band scatterometer data for spurious signals data. A catalog of terrain roughness statistics and calibrated four frequency multipolarization scatterometer data is being published to support the maintenance of Death Valley as a radar backscatter calibration test site for all future airborne and spacecraft missions. Test pits were dug through sand covered terrains in the Eastern Sahara to define the depth and character of subsurface interfaces responsible for either backscatter or specular response in SIR-A imagery. Blocky sandstone bedrock surfaces at about 1 m depth were responsible for the brightest SIR-A returns. Irregular very dense CaCO3 cemented sand interfaces were responsible for intermediate grey tones. Ancient river valleys had the weakest response. Reexamination of SEASAT l-band imagery of U.S. deserts continues.

  18. THERMAL NEUTRON BACKSCATTER IMAGING.

    SciTech Connect

    VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

    2004-10-16

    Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

  19. Microstructure characterization of ZK60 magnesium alloys using TEM and HR-EBSD.

    PubMed

    Cho, Jae-Hyung; Kim, Soo-Hyun; Han, Sang-Ho; Kang, Suk-Bong

    2013-08-01

    ZK60 (Mg-Zn-Zr) alloys exhibited a variation in precipitates with aging, and their mechanical properties also changed. Microindentation tests were carried out on two types of ZK60 alloys of solid solution (T4) and peak aging (T6). Microstructure and texture evolution during indentation was investigated using electron backscatter diffraction. Twinning occurred near the indentation marks in most grains. It was found that tensile twinning was dominant, and two twin variants were usually observed. Texture and microstructure evolution by twinning and slip activation was further examined by uniaxial compression test with strain. The initial random orientation gradually changed into basal fibers with strain. Some grains with nonbasal orientations aligned with the loading direction easily underwent twinning followed by slip deformation. Other grains near basal orientations revealed only slip deformation. PMID:23920164

  20. Grain size measurement by EBSD in complex hot deformed metal alloy microstructures.

    PubMed

    Mingard, K P; Roebuck, B; Bennett, E G; Thomas, M; Wynne, B P; Palmiere, E J

    2007-09-01

    The measurement of grain size by EBSD has been studied to enable representative quantification of the microstructure of hot deformed metal alloys with a wide grain size distributions. Variation in measured grain size as a function of EBSD step size and noise reduction techniques has been assessed. Increasing the EBSD step size from 5% to 20% of the approximate mean grain size results in a change in calculated arithmetic mean grain size of approximately 15% and standard noise reduction techniques can produce a further change in reported size of up to 20%. The distribution of measured grain size is found not to be log-normal, with a long tail of very small sizes in agreement with a computer simulation of linear intercept and areal grain size measurements through randomly oriented grains. Comparison of EBSD with optical measurements of grain size on the same samples shows that, because of the ability of EBSD to distinguish twins and resolve much smaller grains a difference of up to 50% in measured grain size results. PMID:17760627

  1. Ultrasound Microscope: Quantative Backscatter Imaging

    E-print Network

    Greenaway, Alan

    Ultrasound Microscope: Quantative Backscatter Imaging Srikanta Sharma Academic supervisor: Sandy Cochran Industrial supervisor: Jim McAneny #12;Hypothesis of Intra-membrane Cavitation: Ultrasound Induced and cellular membranes that could explain cavitational and non- cavitational ultrasound induced bio

  2. Link Envelope Correlation in the Backscatter Channel

    Microsoft Academic Search

    Joshua D. Griffin; Gregory D. Durgin

    2007-01-01

    High-frequency backscatter radio systems operate in the dyadic backscatter channel, a pinhole channel whose envelope probability density function and bit-error-rate performance are strongly affected by link envelope correlation - the envelope correlation between the forward and backscatter links of the dyadic backscatter channel. This paper shows that link envelope correlation is most detrimental for backscatter radio systems using co-located reader

  3. Effect of the cortex on ultrasonic backscatter measurements of cancellous bone

    NASA Astrophysics Data System (ADS)

    Hoffmeister, Brent K.; Holt, Andrew P.; Kaste, Sue C.

    2011-10-01

    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.

  4. EBSD characterization of twinning in cold-rolled CP-Ti

    SciTech Connect

    Li, X., E-mail: csulixu@hotmail.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Duan, Y.L., E-mail: 876270744@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Xu, G.F., E-mail: csuxgf66@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Changsha 410083 (China); Peng, X.Y., E-mail: pxy0807@126.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Dai, C., E-mail: li-xu@nim.ac.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Zhang, L.G., E-mail: 290571871@qq.com [Zunyi Titanium Industry Co. Ltd., Zunyi 563004 (China); Li, Z., E-mail: lizhou6931@mail.csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

    2013-10-15

    This work presents the use of a mechanical testing system and the electron backscatter diffraction technique to study the mechanical properties and twinning systems of cold-rolled commercial purity titanium, respectively. The dependence of twinning on the matrix orientation is analyzed by the distribution map of Schmid factor. The results showed that the commercial purity titanium experienced strong strain hardening and had excellent formability during rolling. Both the (112{sup ¯}2)<112{sup ¯}3{sup ¯}> compressive twins and (101{sup ¯}2)<101{sup ¯}1{sup ¯}> tensile twins were dependent on the matrix orientation. The Schmid factor of a grain influenced the activation of a particular twinning system. The specific rolling deformation of commercial purity titanium controlled the number and species of twinning systems and further changed the mechanical properties. - Highlights: • CP-Ti experienced strain hardening and had excellent formability. • Twins were dependent on the matrix orientation. • Schmid factor of a grain influenced the activation of a twinning system. • Rolling deformation controlled twinning systems and mechanical properties.

  5. The effect of atomic mass on the physical spatial resolution in EBSD.

    PubMed

    Chen, Delphic; Kuo, Jui-Chao

    2013-08-01

    In this study, bicrystals of silver (Ag) and aluminum (Al) were used to investigate the physical spatial resolution of the electron backscatter diffraction system combining a digital image correlation method. Furthermore, the effect of the accelerating voltage and probe current was investigated on the physical spatial resolution of the lateral and longitudinal resolutions for Ag and Al, respectively. The lateral and longitudinal resolutions show high dependency on the accelerating voltage for a low atomic mass material of Al, In addition, these are almost independent of the accelerating voltage for a high atomic mass material of Ag. Moreover, the probe current does not play any role on both the lateral and longitudinal resolutions. The best lateral resolutions for Al and Ag are 40.5 and 12.1 nm at 10 kV and 1 nA, respectively. The best longitudinal resolutions of 23.2 and 80 nm were obtained at 10 kV and 1 nA for Al and Ag, respectively. PMID:23920163

  6. Petrofabrics in Fine-Grained Rims of Vigarano CV3 Chondrite: Insights from EBSD and AFM Studies

    NASA Astrophysics Data System (ADS)

    Soulié, C.; Ildefonse, B.; Libourel, G.

    2013-09-01

    EBSD and AFM analyses were used to characterize the petrofabric of fayalitic olivines in the matrix and chondrule fine-grained rims of Vigarano CV3 chondrite and to compare them with other CV chondrites.

  7. EBSD investigation of SiC for HTR fuel particles D. Helarya, b,

    E-print Network

    Paris-Sud XI, Université de

    be successfully performed on SiC coatings for HTR fuel particles. EBSD grain maps obtained from thick and thin will fulfil the HTR requirements [2]. The basic fuel unit of HTR is a PyC/SiC multilayer coating about 1 mm in diameter, composed of a porous buffer layer and a SiC coating between two very dense layers of PyC (design

  8. Twinning, grain orientation and texture variation of AZ31 Mg alloy during compression by EBSD tracing

    Microsoft Academic Search

    Guang-Sheng Song; Shi-Hong Zhang; Li Zheng; Liqun Ruan

    2011-01-01

    In order to investigate the micro-mechanism of warm forming of Mg alloys, three specimens cut from a rolled AZ31 sheet were chosen to be compressed along the Rolling Direction (RD) at 100°C, 170°C and 230°C, separately. During compression, an in situ measurement of grain orientation in the plane of RD×TD (Transverse Direction) was carried out with EBSD method. Experimental and

  9. X-ray backscatter imaging

    NASA Astrophysics Data System (ADS)

    Dinca, Dan-Cristian; Schubert, Jeffrey R.; Callerame, J.

    2008-04-01

    In contrast to transmission X-ray imaging systems where inspected objects must pass between source and detector, Compton backscatter imaging allows both the illuminating source as well as the X-ray detector to be on the same side of the target object, enabling the inspection to occur rapidly and in a wide variety of space-constrained situations. A Compton backscatter image is similar to a photograph of the contents of a closed container, taken through the container walls, and highlights low atomic number materials such as explosives, drugs, and alcohol, which appear as especially bright objects by virtue of their scattering characteristics. Techniques for producing X-ray images based on Compton scattering will be discussed, along with examples of how these systems are used for both novel security applications and for the detection of contraband materials at ports and borders. Differences between transmission and backscatter images will also be highlighted. In addition, tradeoffs between Compton backscatter image quality and scan speed, effective penetration, and X-ray source specifications will be discussed.

  10. EBSD for analysing the twinning microstructure in fine-grained TWIP steels and its influence on work hardening.

    PubMed

    Barbier, D; Gey, N; Bozzolo, N; Allain, S; Humbert, M

    2009-07-01

    A 22 Mn-0.6 C twinning induced plasticity steel with an average grain size of 2.6 mum was deformed in tension at room temperature. The electron backscattered diffraction technique was used to characterize the twinning structure in relation with the local texture evolution. For nanoscale analysis, additional transmission electron microscopy analysis was performed. Nanotwins were activated in the largest grains from the beginning of the deformation. They interacted with a well-developed dislocation structure that induced detectable intragranular orientation variations. With increasing deformation, dense bundles of nanotwins preferentially developed in grains oriented close to the <111>//tensile direction fibre (promoted by the deformation) as well as medium to high angle sub-boundaries. These key features of the twinned microstructure were finally related to the remarkably high strain hardening, which evolved according to different stages. PMID:19566628

  11. Fracture sealing in geothermal systems: A combined EBSD and chemical approach

    NASA Astrophysics Data System (ADS)

    Mcnamara, D. D.; Lister, A.; Prior, D. J.; Brenna, M.

    2014-12-01

    Development of natural and enhanced geothermal resources hosted in crystalline, volcanic and plutonic reservoir rocks, or in indurated, metamorphic basement reservoirs has increased over recent years. In these reservoir rocks, permeability is dominated by faults and fractures, with small contributions made by primary permeability. As such the study of how these structures are generated, their properties (e.g. orientation, spatial distribution, aperture, orientation with respect to the stress field), and how they become filled with precipitated minerals is vital to understanding the evolution of these geothermal systems, and is key to their successful development. In particular, fracture sealing is known to decrease the overall permeability of, or create permeability barriers in a geothermal reservoir, limiting its effectiveness as a resource. As such study of this sealing process is vital to discerning the evolution of fractured geothermal systems. We use electron backscatter diffraction combined with cathodoluminescence and energy dispersive X-ray data from calcite and quartz filled veins from high temperature geothermal fields in New Zealand to investigate chemical patterns and microstructures in sealed reservoir fractures. Results indicate that while chemical zonation patterns may appear diverse or complicated, accompanying physical mineral growth and microstructure can either be simple or tell a more convoluted story. Calcite veins explored show little to no deformation and chemical suggesting postkinematic vein growth into free space with no subsequent deformation, while chemical zonation suggests fluid chemistry variation as sealing progressed. Quartz filled veins show crystal orientation of depositing vein crystals is controlled by that of the fracture wall minerals, and that varying chemistry has little to no impact on quartz microstructure.

  12. Backscatter absorption gas imaging system

    DOEpatents

    McRae, Jr., Thomas G. (Livermore, CA)

    1985-01-01

    A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

  13. Diffraction shaders

    Microsoft Academic Search

    Jos Stam

    1999-01-01

    The reflection of light from surfaces is a fundamental problem in computer graphics. Although many reflection models have been proposed, few take into account the wave nature of light. In this paper, we derive a new class of reflection models for metallic sur- faces that handle the effects of diffraction. Diffraction is a purely wave-like phenomenon and cannot be properly

  14. EBSD investigation of the microstructure and texture characteristics of hot deformed duplex stainless steel.

    PubMed

    Cizek, P; Wynne, B P; Rainforth, W M

    2006-05-01

    The microstructure and crystallographic texture characteristics were studied in a 22Cr-6Ni-3Mo duplex stainless steel subjected to plastic deformation in torsion at a temperature of 1000 degrees C using a strain rate of 1 s(-1). High-resolution EBSD was successfully used for precise phase and substructural characterization of this steel. The austenite/ferrite ratio and phase morphology as well as the crystallographic texture, subgrain size, misorientation angles and misorientation gradients corresponding to each phase were determined over large sample areas. The deformation mechanisms in each phase and the interrelationship between the two are discussed. PMID:16774517

  15. Sub-structure characterization of experimentally and naturally deformed ice using cryo-EBSD.

    PubMed

    Piazolo, S; Montagnat, M; Blackford, J R

    2008-06-01

    In this work, we present first results of high-resolution EBSD for ice with a spatial resolution down to 0.25 microm. The study highlights the potential of EBSD to significantly increase our understanding of deformation and annealing processes associated with the build-up of internal stresses due to strain incompatibility between grains. Two polycrystalline samples were analyzed: a natural sample of polar ice from the Vostok ice core (Antarctica) and an experimentally deformed sample of laboratory grown columnar ice. In summary, we observe the following: (1) inhomogeneous deformation through the grains is translated into lattice distortions that are concentrated mainly at grain boundaries and triple junctions (natural and experimental sample), (2) these distortions may be continuous (natural and experimental sample) or may form distinct tilt boundaries and sub-grains of 10-50 microm size (experimental sample). These form mainly by rearrangement of basal edge dislocations into low-energy configurations (i.e. tilt boundaries) in various prism planes. Continuous lattice distortions originate from screw or mixed edge and screw dislocations lying in the basal plane. PMID:18503677

  16. An EBSD study of the textural development of feldspars in a shear zone

    NASA Astrophysics Data System (ADS)

    Mukai, Hiroki; Austrheim, Håkon; Putnis, Andrew

    2013-04-01

    The numerous eclogite and amphibolite facies shear zones of Caledonian age (~420My) that transect the older granulite facies gabbroic anorthosites (~930My) of the Bergen Arc in western Norway provide an opportunity to study in detail the textural and chemical changes from the relatively unaltered granulites which retain the high grade mineralogy and texture, through to highly strained and hydrated minerals within the shear zones. The involvement of fluids has been well documented by the mineral reactions and reaction textures in the vicinity of these shear zones. We have studied the textural evolution of large plagioclase (~An50) grains (several mms in size) within the gabbroic anorthosites by SEM and EBSD. The first stage of microstructural evolution within these plagioclases is a phase separation forming a network of Na-rich (~An25) domains separated by thinner zones of Ca-rich (~An65) domains. This results in a large number of new domain walls which contribute to the weakening of the rock. The Ca-rich domains contain a much higher density of sub-grain boundaries than the Na-rich domains which are relatively homogeneous on an SEM scale. EBSD of this intergrowth shows that both the Na and Ca-rich regions retain the crystallographic orientation of the parent An50 plagioclase crystals. Despite the large number of new domain walls the spread of orientations is very small. In the next stage of shear-zone formation, recrystallisation of the two-phase intergrowth results in a crystal mosaic of grains up to 100µm in size. EBSD shows that the recrystallisation primarily involves the annihilation of the domain structure within the Ca-rich regions which surround the Na-rich cores. Thus each grain in the polygonal texture retains aspects of the chemical zoning from the intergrowth i.e. the crystals have a Na-rich core with a more Ca-rich rim. The resulting texture in the shear zone has a strong shape-preferred orientation made up from polygonal grains with abundant 120° triple junctions. EBSD of 1136 grains from the polygonal texture within one rock thin section taken from the shear zone shows a random distribution of orientations i.e. no crystallographically preferred orientation (CPO). However a more detailed EBSD study of local areas where it is possible to locate the boundary between the two-phase feldspar of stage 1 and the feldspar in the shear zone shows a strong correlation between the crystallographic orientation of groupings of adjacent grains within the shear zone and the Na-rich, Ca-rich intergrowth from which it is derived. In other words, it is possible to trace the crystallographic orientation of a single large crystal of plagioclase from the gabbroic anorthosite, through its phase separation to the Na- and Ca-rich intergrowth and finally to those parts of the polygonal texture which were derived from the original plagioclase crystal. The fact that feldspar in the original gabbroic anorthosite has no CPO means that taken over the whole shear zone the feldspars have no CPO, while small areas appear to have a CPO because it is inherited from the original parent crystal. The development of the textures in the feldspars is consistent with deformation by fluid-induced dissolution-precipitation creep.

  17. Discovering New Minerals at Micron to Nanoscales: A SEM-EBSD-EPMA Approach

    NASA Astrophysics Data System (ADS)

    Ma, C.

    2014-12-01

    With high-resolution analytical field emission scanning electron microscope and electron probe microanalyzer, we are now capable to characterize Earth and planetary materials easier and faster down to nanoscales. Nanofeatures (such as inclusions, exsolution, zonation, coatings, pores) in minerals and rocks are being discovered. Nanominerals and nanoparticles are being revealed. New minerals and new materials are being identified. During our ongoing nanomineralogy investigation since 2006, more than twenty five new minerals have been discovered at micron to nanoscales. Fifteen of them are from the Allende meteorite, including new refractory minerals like allendeite, hexamolybdenum, tistarite, panguite and kangite, which are among the first solids formed in our solar system. Each of the new extraterrestrial minerals reveals distinctive forming environments, providing insights into nebula or parent-body processes. Presented here are a few nanomineralogy projects demonstrating how to find and characterize new minerals with an integrated SEM-EBSD-EPMA approach.

  18. Backscatter Profiles Measured In The Alps

    NASA Astrophysics Data System (ADS)

    Koepp, F.; Herrmann, H.; Werner, Ch.

    1989-12-01

    For global measurements of the wind field in the troposphere and lower stratosphere satellite-borne Doppler lidar sensors have been proposed (ALAI)IN: Atmospheric LAser Doppler INstrument, LAWS: Laser Atmospheric Wind Sounder). The design of the system components requires information about the coherent backscatter values at the wavelength of CO2 lasers. Experimental results of coherent backscatter measured by existing ground-based and airborne Doppler lidars are collected in the Backscatter Experiment (GLOBE). It is desirable to cover large altitude ranges in different geographical regions and during different meteorological conditions. For contribution to GLOBE, aerosol backscatter profiles have been measured From a mountain position using the CO, Laser Doppler Anemometer and the Nd:YAG Microlidar.

  19. Cyclone diagnostics. [rainfall estimation, backscatter, and lidar

    NASA Technical Reports Server (NTRS)

    1984-01-01

    A GOES IR rainfall estimation algorithm was completed and verified. The technique was applied to the South Pacific convergent zone. The NASA earth observation mission series is discussed briefly. Backscatter was investigated using 10.6 micron coherent lidar.

  20. CONVEX BACKSCATTERING SUPPORT IN ELECTRIC IMPEDANCE TOMOGRAPHY

    E-print Network

    Hanke-Bourgeois, Martin

    CONVEX BACKSCATTERING SUPPORT IN ELECTRIC IMPEDANCE TOMOGRAPHY MARTIN HANKE, NUUTTI HYV ¨ONEN for the inverse obstacle problem in impedance tomography. Under mild restrictions on the topological prop- erties can be computed numerically; numerical reconstructions are included to illustrate the viability

  1. A Backscatter-Lidar Forward-Operator

    NASA Astrophysics Data System (ADS)

    Geisinger, Armin; Behrendt, Andreas; Wulfmeyer, Volker; Vogel, Bernhard; Mattis, Ina; Flentje, Harald; Förstner, Jochen; Potthast, Roland

    2015-04-01

    We have developed a forward-operator which is capable of calculating virtual lidar profiles from atmospheric state simulations. The operator allows us to compare lidar measurements and model simulations based on the same measurement parameter: the lidar backscatter profile. This method simplifies qualitative comparisons and also makes quantitative comparisons possible, including statistical error quantification. Implemented into an aerosol-capable model system, the operator will act as a component to assimilate backscatter-lidar measurements. As many weather services maintain already networks of backscatter-lidars, such data are acquired already in an operational manner. To estimate and quantify errors due to missing or uncertain aerosol information, we started sensitivity studies about several scattering parameters such as the aerosol size and both the real and imaginary part of the complex index of refraction. Furthermore, quantitative and statistical comparisons between measurements and virtual measurements are shown in this study, i.e. applying the backscatter-lidar forward-operator on model output.

  2. Time domain attenuation estimation method from ultrasonic backscattered signals

    PubMed Central

    Ghoshal, Goutam; Oelze, Michael L.

    2012-01-01

    Ultrasonic attenuation is important not only as a parameter for characterizing tissue but also for compensating other parameters that are used to classify tissues. Several techniques have been explored for estimating ultrasonic attenuation from backscattered signals. In the present study, a technique is developed to estimate the local ultrasonic attenuation coefficient by analyzing the time domain backscattered signal. The proposed method incorporates an objective function that combines the diffraction pattern of the source/receiver with the attenuation slope in an integral equation. The technique was assessed through simulations and validated through experiments with a tissue mimicking phantom and fresh rabbit liver samples. The attenuation values estimated using the proposed technique were compared with the attenuation estimated using insertion loss measurements. For a data block size of 15 pulse lengths axially and 15 beamwidths laterally, the mean attenuation estimates from the tissue mimicking phantoms were within 10% of the estimates using insertion loss measurements. With a data block size of 20 pulse lengths axially and 20 beamwidths laterally, the error in the attenuation values estimated from the liver samples were within 10% of the attenuation values estimated from the insertion loss measurements. PMID:22779499

  3. Estimating backscatter spectra after deconvolution with Kalman smoothing

    NASA Astrophysics Data System (ADS)

    Guenter, Armin I.

    2001-05-01

    In quantitative tissue characterization. Obtaining processed ultrasonic echoes with a direct relationship to local tissue response (backscatter spectrum) and that are free from systemic depth-dependent effects, such as diffraction, is essential. In general practice today, these unwanted distortions are eliminated by dividing short time power spectra. However, this method has its drawbacks; noise is not taken into account, and shorter time gates lead to an increasing bias within the relative spectra. To overcome these methodological issues, I propose a different approach as follows. Entire deconvolved A-scans are estimated by a Kalman smoothing deconvolution algorithm. These then serve as a basis for estimating the relative backscatter spectra. In addition, due to the principle of the deconvolution algorithm, it is possible to suppress additive noise to some degree. To examine the properties of the method proposed, this paper presents an analytical expression for the power spectrum of the deconvolved signals obtained by Kalman Smoothing. This result is then compared to the expectations of relative short time power spectra. Simulations demonstrate the behavior of the deconvolution method in a non-stationary environment.

  4. EBSD and DTA Characterization of A356 Alloy Deformed by ECAP During Reheating and Partial Re-melting

    NASA Astrophysics Data System (ADS)

    Moradi, Marzyeh; Nili-Ahmadabadi, Mahmoud; Poorganji, Behrang; Heidarian, Bashir; Furuhara, Tadashi

    2013-11-01

    Recrystallization and partial re-melting processes have been developed for producing semi-solid feedstock in a solid state in which a globular microstructure is obtained by plastic deformation followed by reheating. In this research, to induce strain, a cast- and solution-treated Aluminum A356 (7 wt pct Si) alloy was subjected to a repetitive equal channel angular pressing process using a 90 deg die, up to a total accumulated strain of approximately 8 in route A (increasing strain through a sequence of passes with no rotation of the sample after each pass) at ambient temperature. The microstructural evolutions of deformed and reheated materials were studied by optical microscopy, scanning electron microscopy, and electron back-scattered diffraction analysis. In addition, the influences of pre-deformation on the recrystallization mechanism and liquid formation of A356 alloy were presented and discussed. The results are also supported by differential thermal analysis experiments. Evaluation of the observations indicated that the average cell boundary misorientation increased with increasing strain, so this increased misorientation accelerated the mobility of boundaries and recrystallization kinetics. Therefore, the recrystallization mechanism and kinetics affected by deformation, reheating condition, and intrinsic material properties determined the particle size in the semi-solid state.

  5. Analysis of the Deformation and Damage Mechanisms of Pearlitic Steel by EBSD and "in-situ" SEM Tensile Tests

    NASA Astrophysics Data System (ADS)

    Sidhom, Habib; Yahyaoui, H.; Braham, C.; Gonzalez, G.

    2015-05-01

    The processes governing the deformation and damage of C70 pearlitic steel were investigated in nanometer and micrometer scales using electron backscatter diffraction technique and "in-situ" scanning electron microscope tensile testing. The ferrite behavior was identified by "in-situ" x-ray tensile tests. Investigations were carried out on annealed microstructure with two interlamellar spacings of Sp = 170 and Sp = 230 nm. It is shown that pearlite yielding is controlled by the deformation mechanisms occurring in ferrite. Deformation and damage mechanisms were proposed. At low strain, pearlite deforms homogeneously with low misorientation (<5°) inside the pearlite colonies and elongates the cementite plates. At high strain, pearlite deforms heterogeneously in intense localized shear bands inside the more favorably oriented pearlite colonies. Misorientation reaches values up to 15°. Cementite deforms by an offset of lamella along the shear bands. The nucleation of these shear bands occurs at strain level of E 11 = 7% for coarse pearlite and at a higher value for fine pearlite. Damage occurs by brittle fracture of the elongated cementite lamellae parallel to the tensile axis and which are developed by shear micro-cracks along the slip bands. The plastic-induced damage is thus delayed by the fine pearlite structure.

  6. Materials Science: Diffraction

    NSDL National Science Digital Library

    Peter Goodhew

    This suite of websites from the University of Liverpool comprises a learning module that focuses on diffraction. The website features sections on diffraction, the geometry of diffraction, the intensity of diffraction, electron diffraction and X-ray diffraction. Each section features text, images and animations as well as learning exercises. These sites aid in the exploration of the various aspects of diffraction.

  7. An energy-dependent electron backscattering coefficient

    NASA Astrophysics Data System (ADS)

    Williamson, W., Jr.; Antolak, A. J.; Meredith, R. J.

    1987-05-01

    An energy-dependent electron backscattering coefficient is derived based on the continuous slowing down approximation and the Bethe stopping power. Backscattering coefficients are given for 10-50-keV electrons incident on bulk and thin-film aluminum, silver, and gold targets. The results are compared with the Everhart theory and empirical fits to experimental data. The energy-dependent theory agrees better with experimental work.

  8. GLObal Backscatter Experiment (GLOBE) Pacific survey mission

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.; Rothermel, Jeffry; Arnold, James E.; Williams, Steven F.

    1991-01-01

    NASA conducted the GLObal Backscatter Experiment (GLOBE) Survey Mission over the near coastal and remote Pacific Ocean during 6 to 30 Nov. 1989 (GLOBE 1) and 13 May to 5 Jun. 1990 (GLOBE 2). These missions studied the optical, physical, and chemical properties of atmospheric aerosols. Particular emphasis was given to the magnitude and spatial variability of aerosol backscatter coefficients at mid-infrared wavelengths, and to the remote middle and upper troposphere, where these aerosol properties are poorly understood. Survey instruments were selected to provide either direct beta measurements at the key wavelengths, empirical links with long term or global scale aerosol climatologies, or aerosol microphysics data required to model any of these quantities. The survey deployment included both long distance 6 to 8 hour transit flights and detailed 4 to 6 hour local flights. Several general features were observed from preliminary Survey data analyses. Validation and intercomparison results have shown good agreement, usually better than a factor of two. Atmospheric aerosols frequently exhibited a three layer vertical structure, with (1) high and fairly uniform backscatter in the shallow cloud capped marine boundary layer; (2) moderate and highly variable backscatter in a deeper overlaying cloud pumped layer; and (3) low, regionally uniform, but seasonally and latitudinally variable backscatter in the middle and upper troposphere. The survey missions represent two isolated snapshots of a small portion of the global aerosol system. Consequently, Survey results can best be understood by synthesizing them with the more comprehensive GLOBE data base, which is being compiled at NASA-Marshall.

  9. Unit Cell Definition of Polycrystal Sheet Material Based on SEM-EBSD Analyses

    SciTech Connect

    Morimoto, Hideo [Furukawa Electric Co. Ltd., 2-4-3 Okano, Nishiku, Yokohama, 220-0073 (Japan); Nakamachi, Eiji; Kuramae, Hiroyuki; Hagisato, Takehiro [Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka, 535-8585 (Japan)

    2005-08-05

    Recently, the multi scale analysis technology, by using the crystallographic homogenization based dynamic explicit finite element code, has been developed to assess macro continuum sheet material properties and further study the deformation and straining in the actual sheet forming. This homogenization finite element code employs the two scale hierarchical structure, which consists of a polycrystal microstructure and a macro continuum. In this study, for the reality, we focus to discuss 'How to define a proper microstructure for the two scale finite element analysis, by employing the real measurement base polycrystal aggregation, which has been obtained by SEM-EBSD' observations. For scaling up from the micro polycrystal structure to the macro continuum, we define a unit cell by looking at the periodicity of crystal orientation, which is one of morphological factors to feature the polycrystal structure, which is named as 'texture'. Through a statistical study of these measured polycrystal morphologies, finally we found a realistic polycrystal unit cell of the microstructure, which can be adopted for our multi scale finite element analyses.

  10. IOP PUBLISHING NANOTECHNOLOGY Nanotechnology 23 (2012) 135702 (7pp) doi:10.1088/0957-4484/23/13/135702

    E-print Network

    Rohrer, Gregory S.

    2012-01-01

    diffraction technique called diffraction scanning transmission electron microscopy (D-STEM) is coupled with precession electron microscopy to obtain quantitative local texture information in damascene copper using electron backscatter diffraction (EBSD) have been used for this purpose. Kim et al [17] and Lee et

  11. The five-parameter grain boundary character distribution of nanocrystalline tungsten

    E-print Network

    Rohrer, Gregory S.

    boundaries; Nanocrystalline; Tungsten; Precession electron diffraction The properties of materials, including measurements of the GBCD have been carried out exclusively using electron backscatter diffraction (EBSD a transmission electron micro- scope (TEM) [10­12]. In this technique, diffraction pat- terns are acquired while

  12. Measurements of the backscattering of ultrasmooth mirrors

    NASA Astrophysics Data System (ADS)

    Wang, Jingxian; Wang, Ke

    2012-09-01

    In this paper we propose two schemes for measuring the backscattering of ultra-smooth mirrors, the principle of which is discussed detailed. The difference between the two schemes is also disclosed. According to the more sophisticated scheme we have built a practical apparatus, which has the precision and high efficiency advantage. The details of the design are presented. According to the backscattering amplitudes obtained using the apparatus, ultra-smooth mirrors have been divided into four groups. The statistical data has shown that the lock-in thresholds of ring laser gyros are correlative with the backscattering amplitudes of mirrors. Therefore the validity of the measurement is demonstrated. The method and the apparatus presented here can help the ring laser gyro (RLG) manufacturers in reducing the lock-in thresholds of RLGs.

  13. Polarization Measurements of Backscatter on NIF

    NASA Astrophysics Data System (ADS)

    Turnbull, David; Moody, John; di Nicola, Jean-Michel; Divol, Laurent; Hinkel, Denise; Kirkwood, Robert; Kruer, William; MacGowan, Brian; Manes, Ken; Michel, Pierre; Ralph, Joseph; Williams, Ed

    2013-10-01

    Time integrated, spatially localized measurements of the polarization of backward Stimulated Brillouin Scattering (SBS) collected by a Full Aperture Backscatter (FABS) diagnostic have been made on the National Ignition Facility (NIF). Early data from a variety of hohlraum experiments reveal that the backscatter polarization can differ significantly from that of the incident beam. Explanations for this include: more divergent backscatter from neighboring beams that have an orthogonal polarization; Crossed Beam Energy Transfer (CBET) from beams in the outer cones on NIF with polarizations that are tilted with respect to the measured beam, or even beams with nearly orthogonal polarizations (normally assumed to be non-interacting) that scatter from the beat waves driven between other pairs of beams (so-called Brillouin enhanced four-wave mixing); and Faraday rotation caused by laser generated magnetic fields within the target plasma. Preliminary analysis indicates that the dominant effect is the wider divergence of neighboring beams' backscatter. We will discuss the measurements and modeling, and also compare with previous results. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Time integrated, spatially localized measurements of the polarization of backward Stimulated Brillouin Scattering (SBS) collected by a Full Aperture Backscatter (FABS) diagnostic have been made on the National Ignition Facility (NIF). Early data from a variety of hohlraum experiments reveal that the backscatter polarization can differ significantly from that of the incident beam. Explanations for this include: more divergent backscatter from neighboring beams that have an orthogonal polarization; Crossed Beam Energy Transfer (CBET) from beams in the outer cones on NIF with polarizations that are tilted with respect to the measured beam, or even beams with nearly orthogonal polarizations (normally assumed to be non-interacting) that scatter from the beat waves driven between other pairs of beams (so-called Brillouin enhanced four-wave mixing); and Faraday rotation caused by laser generated magnetic fields within the target plasma. Preliminary analysis indicates that the dominant effect is the wider divergence of neighboring beams' backscatter. We will discuss the measurements and modeling, and also compare with previous results. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Membership pending.

  14. Bathymetry and acoustic backscatter: Estero Bay, California

    USGS Publications Warehouse

    Hartwell, Stephen R.; Finlayson, David P.; Dartnell, Peter; Johnson, Samuel Y.

    2013-01-01

    Between July 30 and August 9, 2012, scientists from the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), acquired bathymetry and acoustic-backscatter data from Estero Bay, San Luis Obispo, California, under PCMSC Field Activity ID S-05-12-SC. The survey was done using the R/V Parke Snavely outfitted with a multibeam sonar for swath mapping and highly accurate position and orientation equipment for georeferencing. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

  15. Evaluating roughness models of radar backscatter

    NASA Technical Reports Server (NTRS)

    Engmann, E. T.; Wang, J. R.

    1986-01-01

    Three radar backscatter roughness models were assessed using soil moisture data collected by the Space Shuttle flight 41G SIR-B SAR in an intensively farmed area. The SIR-B data swath included a large number of bare, dry fields with a large variety of surface roughnesses. The small perturbation model gives the best results, particularly when fields with a definite periodic row structure were omitted. The standard deviation of surface heights appears to be a good measure of relative roughness conditions, but the correlation length is not a good descriptor of the surface, and does not seem to be related in any way to the measured backscatter.

  16. Evaluating roughness models of radar backscatter

    NASA Technical Reports Server (NTRS)

    Engman, Edwin T.; Wang, James R.

    1987-01-01

    Three radar backscatter roughness models were assessed using soil moisture data collected by the Space Shuttle flight 41G SIR-B SAR in an intensively farmed area. The SIR-B data swath included a large number of bare, dry fields with a large variety of surface roughnesses. The small perturbation model gives the best results, particularly when fields with a definite periodic row structure were omitted. The standard deviation of surface heights appears to be a good measure of relative roughness conditions, but the correlation length is not a good descriptor of the surface, and does not seem to be related in any way to the measured backscatter.

  17. Application of the EBSD technique to describe the initiation and growth behaviour of microstructurally short fatigue cracks in a duplex steel.

    PubMed

    Krupp, U; Düber, O; Christ, H-J; Künkler, B; Schick, A; Fritzen, C-P

    2004-03-01

    Up to 90% of the fatigue life of engineering alloys results from the initiation and propagation of microstructurally short cracks. Owing to their strong interactions with microstructural features, e.g. grain and phase boundaries, they exhibit substantially non-uniform propagation kinetics as compared with the growth rate of long cracks, which can be well described using a power-law function of the range of the stress-intensity factor DeltaK. In the present paper interactions between the crystallographic misorientation of grain and phase boundaries and microcracks in an austenitic/ferritic stainless steel are discussed and quantified by means of fatigue experiments in combination with the electron backscattered diffraction technique. In the second part a numerical model for the simulation of microcracks is introduced, which is capable of taking real microstructural arrangements into consideration. PMID:15009699

  18. Combined nano-SIMS/AFM/EBSD analysis and atom probe tomography, of carbon distribution in austenite/?-martensite high-Mn steels.

    PubMed

    Seol, Jae-Bok; Lee, B-H; Choi, P; Lee, S-G; Park, C-G

    2013-09-01

    We introduce a new experimental approach for the identification of the atomistic position of interstitial carbon in a high-Mn binary alloy consisting of austenite and ?-martensite. Using combined nano-beam secondary ion mass spectroscopy, atomic force microscopy and electron backscatter diffraction analyses, we clearly observe carbon partitioning to austenite. Nano-beam secondary ion mass spectroscopy and atom probe tomography studies also reveal carbon trapping at crystal imperfections as identified by transmission electron microscopy. Three main trapping sites can be distinguished: phase boundaries between austenite and ?-martensite, stacking faults in austenite, and prior austenite grain boundaries. Our findings suggest that segregation and/or partitioning of carbon can contribute to the austenite-to-martensite transformation of the investigated alloy. PMID:23537886

  19. Optical backscatter measurements to study laser plasma interactions on NIF

    NASA Astrophysics Data System (ADS)

    Moody, J.; Datte, P.; Krauter, K.; Bond, E.; Hibbard, R.; Michel, P.; MacGowan, B. J.; Glenzer, S. H.; Sutter, L.; Meezan, N.; London, R.; Kline, J. L.; Widmann, K.; Divol, L.; Jackson, J.; Niemann, C.; Vernon, S.

    2009-11-01

    We describe measurements of backscattered light from NIF targets under a variety of laser conditions. These measurements will initially be used to validate the point design hohlraum and select phase plates for the ignition experiments. Backscatter measurements are made on two separate groups of 4 beams (a quad). One quad is 30 ,o from the hohlraum axis and the other at 50 ,o. The backscatter measurement utilizes a full aperture backscatter system (FABS) to measure light backscattered into the final focus lens of each beam in the quad and a near backscatter imager (NBI) to measure light backscattered outside of the beam quad. Both instruments must work in conjunction to provide spectrally and temporally resolved backscattered power. We describe the measurements, analysis, and comparison with simulations. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  20. Efficient and reliable low-power backscatter networks

    E-print Network

    Wang, Jue

    There is a long-standing vision of embedding backscatter nodes like RFIDs into everyday objects to build ultra-low power ubiquitous networks. A major problem that has challenged this vision is that backscatter communication ...

  1. Introduction to Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Morniroli, Jean-Paul

    The main types of electron diffraction techniques are described: Selected-Area Electron Diffraction (SAED), Microdiffraction, Convergent-Beam Electron Diffraction (CBED), Large-Angle Convergent-Beam Electron Diffraction (LACBED) and electron precession. They produce spot, ring, disk or line patterns at microscopic or nanoscopic scales in correlation with the image of the diffracted area. An overview of the main applications is given.

  2. Skywave over-the-horizon backscatter radar

    Microsoft Academic Search

    Tang Xiaodong; Han Yunjie; Zhou Wenyu

    2001-01-01

    Skywave over-the-horizon backscatter radar (OTHR) has great potential for detecting such targets as cruise missiles, stealth aircraft, the powered trajectory of ballistic missiles and aircraft carriers over long distances and at the same time. This paper evaluates the detectability of OTHR for small targets through experimental research and emulation, and then brings forth directions for improvement to some shortcomings of

  3. Window flaw detection by backscatter lighting

    NASA Technical Reports Server (NTRS)

    Crockett, L. K.; Minton, F. R.

    1978-01-01

    Portable fiber-optic probe detects tiny flaws in transparent materials. Probe transmits light through surface to illuminate interior of material by backscattering off its edges. Light-sensitive contact paper records scratch pattern. Technique can be used for rapid visual checks. Flexible fiber optics are safely used in explosive or flammable areas; they present no hazard of breakage or contamination in controlled environments.

  4. Backscattering of electrons from solid targets

    NASA Astrophysics Data System (ADS)

    Dapor, Maurizio

    1990-11-01

    A simple equation is derived which describes the electron backscattering coefficient as a function of the target atomic number in the primary energy range 2-45 KeV. Such an equation, very useful for practical purposes, is in better agreement with the experimental data of Palluel and of Cosslett and Thomas than both the treatments of Everhart and of Archard.

  5. Landmine detection with the neutron backscattering method

    Microsoft Academic Search

    Cor P. Datema; Victor R. Bom; Carel W. E. van Eijk

    2001-01-01

    Neutron backscattering was selected as a promising new method for the detection of landmines. With this technique, 252Cf source and a thermal neutron detector are used. Fast neutrons from the Californium source are better moderated by the landmine, especially plastic mines, than in the surrounding soil. This leads to an increase in the number of reflected thermal neutrons above the

  6. Measurement of electron backscattering from plastic scintillator for neutron decay

    E-print Network

    Martin, Jeff

    Measurement of electron backscattering from plastic scintillator for neutron decay Michael J in the decay to obtain a measure of the asymmetry. These electrons, however, may backscatter off of the backscattered electrons with careful attention to s systematic uncertainties. The accurate measurement

  7. The spatial response function of SeaWinds backscatter measurements

    E-print Network

    Long, David G.

    of the normalized radar backscatter of the Earth's surface. SeaWinds backscatter measurements are being used tracking, vegetation, soil moisture, and snow accumulation. Two SeaWinds instruments are currently flying enhanced resolution images are included. Keywords: scatterometer, SeaWinds, radar backscatter, ocean winds

  8. Radar backscatter sensitivity of soil moisture in vegetation covered areas

    Microsoft Academic Search

    Faisal Karim; Susan Steele-Dunne; Nick van de Giesen

    2010-01-01

    Radar backscatter is sensitive to the water content of bare soil surface. Vegetation cover masks the soil surface, reducing the sensitivity of the radar backscatter to soil moisture. The water-cloud model is used to account for vegetation effects on the copolarized backscatter coefficient in C and L band. In this sensitivity study, two different models for opacity are compared to

  9. Comparison between backscattered TerraSAR signals and simulations from the radar backscattering models IEM, Oh, and Dubois

    E-print Network

    Paris-Sud XI, Université de

    link the radar backscattering coefficient to soil parameters (dielectric constant, roughness1 1 Comparison between backscattered TerraSAR signals and simulations from the radar backscattering.baghdadi@teledetection.fr Tel.: 33 4 67 54 87 24; Fax: 33 4 67 54 87 00 The objective of this paper is to evaluate on bare soils

  10. Photoelectron diffraction and holography: Some new directions

    SciTech Connect

    Fadley, C.S. [Lawrence Berkeley Lab., CA (United States)]|[California Univ., Davis, CA (United States). Dept. of Physics

    1993-08-01

    Photoelectron diffraction has by now become a versatile and powerful technique for studying surface structures, with special capabilities for resolving chemical and magnetic states of atoms and deriving direct structural information from both forward scattering along bond directions and back-scattering path length differences. Further fitting experiment to theory can lead to structural accuracies in the {plus_minus}0.03 ){Angstrom} range. Holographic inversions of such diffraction data also show considerable promise for deriving local three-dimensional structures around a given emitter with accuracies of {plus_minus}0.2--0.3 {Angstrom}. Resolving the photoelectron spin in some way and using circularly polarized radiation for excitation provide added dimensions for the study of magnetic systems and chiral experimental geometries. Synchrotron radiation with the highest brightness and energy resolution, as well as variable polarization, is crucial to the full exploitation of these techniques.

  11. Acoustic diffraction by a finite barrier; theories and experiment

    Microsoft Academic Search

    G. M. Jebsen

    1981-01-01

    The Biot-Tolstoy (B-T) exact impulse solution of diffraction by an infinite half-plane is compared to the usual Helmholtz-Kirchhoff (H-K) integral formulation and to the exact continuous wave (CW) solution of Macdonald. For backscatter the B-T and H-K solutions are found to differ significantly, especially near the surface of the half-plane, where the B-T solution gives close agreement with experiment. For

  12. Fast in-situ annealing stage coupled with EBSD: A suitable tool to observe quick recrystallization mechanisms

    SciTech Connect

    Bozzolo, N., E-mail: nathalie.bozzolo@mines-paristech.fr; Jacomet, S.; Loge, R.E.

    2012-08-15

    A heating stage has been developed to perform in-situ annealing in a SEM equipped with an EBSD system in order to study recrystallization mechanisms. High temperature treatments could then be performed inside the SEM, up to 1180 Degree-Sign C and with high heating and cooling rates ({approx} 100 Degree-Sign C s{sup -1}). Samples were cooled down to room temperature to perform EBSD orientation mapping in between successive short-duration heat treatments. Microstructure evolution snapshots obtained this way allow gaining an insight into recrystallization mechanisms. The interest of such experiments is shown for two examples: static recrystallization of cold deformed pure tantalum and post-dynamic evolution of hot-deformed Zircaloy4. - Highlights: Black-Right-Pointing-Pointer Heating stage for in-SEM annealing at high temperature (up to 1200 Degree-Sign C). Black-Right-Pointing-Pointer High heating and cooling rates (100 Degree-Sign C s{sup -1}), no temperature overshoot. Black-Right-Pointing-Pointer Sequential observation of very fast recrystallization mechanisms.

  13. GaAs as a backscattering crystal

    NASA Astrophysics Data System (ADS)

    Alefeld, B.; Dohmen, L.; Heidemann, A.

    2000-06-01

    The first neutron backscattering instrument was developed about 30 years ago, and since this time, mainly silicon wafers were used as monochromator- and analyser-crystals. GaAs is another candidate for backscattering. The internal strains of GaAs wafers with a diameter of 10 cm were studied at five points of the diameter and reached a value ? a/ a?2.5×10 -5. These strains could be removed by cutting the wafer in pieces of 8 mm×8 mm, giving a homogenous lattice constant within an experimental accuracy of ? a/ a=±10 -6. The experimental value of the integrated reflectivity of the (200)-reflex was determined to be R=0.2 cm/s, which is in excellent agreement with the width of the plateau of the Ewald reflection curve. The energy resolution of GaAs is expected to be ten times better than that of silicon.

  14. Auroral backscatter observed at HF from Ottawa

    SciTech Connect

    Montbriand, L.E.

    1988-10-01

    Bistatic HF radar recordings of auroral scattering sources north of Ottawa are reported. Doppler frequency spreads over + or - 100 Hz were obtained at least 35 percent of the time. The peak of the Doppler frequency distribution was sometimes shifted from zero by as much as 50 Hz, and significant contributions often occurred at Doppler frequencies greater than 150 Hz. Signals received simultaneously on both arms of a two-arm direction-finding array were used to identify the specific elevations and bearings of the backscatter signals. A detailed study of a particular hour-long period is reported, and a large number of 'apparent' auroral backscatter sources are identified. The source regions, probably located in the F layer, were elongated mainly in the north-south direction and extended over at least 3 deg of latitude. North-south corridors were found between such sources in which echo returns were either absent or very weak. 14 references.

  15. EBSD studies of microstructure and texture in Ni-Ti-Co shape memory strip and ribbon.

    PubMed

    Goryczka, T

    2010-03-01

    The electron back scattered diffraction method was applied for carrying out detailed surface studies of the ternary Ni-Ti-Co alloy produced using melt-spinning and twin roll casting techniques. The samples were studied in the as-cast state without grinding or polishing. It was found that in the melt-spun ribbon apart from fine narrow columnar grains, that extended along the ribbon thickness, wider columnar grains parallel to the ribbon surface were also observed. These grains were textured along the {100}011 orientation. The twin roll cast strip revealed more complex and inhomogeneous morphology of its surface. Mainly, the axes of the grains were oriented along two textural components: 100 for the fine grains and {100}011 for the columnar grains parallel to the surface. In addition to the results obtained from the X-ray diffraction, the electron back scattered diffraction technique revealed the 111 fibre texture in the sample. PMID:20500377

  16. On the acoustic diffraction by the edges of benthic shells.

    PubMed

    Stanton, Timothy K; Chu, Dezhang

    2004-07-01

    Recent laboratory measurements of acoustic backscattering by individual benthic shells have isolated the edge-diffracted echo from echoes due to the surface of the main body of the shell. The data indicate that the echo near broadside incidence is generally the strongest for all orientations and is due principally to the surface of the main body. At angles well away from broadside, the echo levels are lower and are due primarily to the diffraction from the edge of the shell. The decrease in echo levels from broadside incidence to well off broadside is shown to be reasonably consistent with the decrease in acoustic backscattering from normal incidence to well off normal incidence by a shell-covered seafloor. The results suggest the importance of the edge of the shell in off-normal-incidence backscattering by a shell-covered seafloor. Furthermore, when considering bistatic diffraction by edges, there are implications that the edge of the shell (lying on the seafloor) can cause significant scattering in many directions, including at subcritical angles. PMID:15295983

  17. On the acoustic diffraction by the edges of benthic shells

    NASA Astrophysics Data System (ADS)

    Stanton, Timothy K.; Chu, Dezhang

    2004-07-01

    Recent laboratory measurements of acoustic backscattering by individual benthic shells have isolated the edge-diffracted echo from echoes due to the surface of the main body of the shell. The data indicate that the echo near broadside incidence is generally the strongest for all orientations and is due principally to the surface of the main body. At angles well away from broadside, the echo levels are lower and are due primarily to the diffraction from the edge of the shell. The decrease in echo levels from broadside incidence to well off broadside is shown to be reasonably consistent with the decrease in acoustic backscattering from normal incidence to well off normal incidence by a shell-covered seafloor. The results suggest the importance of the edge of the shell in off-normal-incidence backscattering by a shell-covered seafloor. Furthermore, when considering bistatic diffraction by edges, there are implications that the edge of the shell (lying on the seafloor) can cause significant scattering in many directions, including at subcritical angles.

  18. Dielectric spheres with maximum forward scattering and zero backscattering: A search for their material composition

    E-print Network

    Zhang, Yan; Sáenz, Juan José

    2015-01-01

    Nanoparticles exhibiting zero backscattering but a large scattering cross section in the forward direction should play a key role as light diffracting elements in photonic devices like solar cells. Using Mie theory we address lossless dielectric spheres that were recently reported to possess a magnetodielectric response to the illuminating wave, and analyze their scattering cross section together with their zero-backwards scattering conditions. We show that there is an optimum particle refractive index (m = 2.47), which yields maximum forward scattering without backwards scattering of light.

  19. Connecting forest ecosystem and microwave backscatter models

    NASA Technical Reports Server (NTRS)

    Kasischke, Eric S.; Christensen, Norman L., Jr.

    1990-01-01

    A procedure is outlined to connect data obtained from active microwave remote sensing systems with forest ecosystem models. The hierarchy of forest ecosystem models is discussed, and the levels at which microwave remote sensing data can be used as inputs are identified. In addition, techniques to utilize forest ecosystem models to assist in the validation of theoretical microwave backscatter models are identified. Several examples to illustrate these connecting processes are presented.

  20. Relationship of microstructure to backscattered ultrasonic noise

    NASA Astrophysics Data System (ADS)

    Thompson, R. B.; Margetan, F. J.; Han, Y. H. K.; Paxson, Alen J.; Shamblen, C. E.

    The phenomenological independent scattering model of Margetan et al. (1991) predicts that a simple figure-of-merit (FOM) (together with the ultrasonic attenuation) defines microstructural influences on backscattering. More rigorous calculations, by Rose (1991), have allowed the FOM to be related to the anisotropic elastic constants of the crystallites for measurements on single-phase alloys, and this theory is found to be in good agreement with experiment. For two-phased microstructures, some unexplained anistropies are observed which require further study.

  1. Forensic Value of Backscatter from Email Spam

    Microsoft Academic Search

    Christopher P. Fuhrman

    2008-01-01

    Email backscatter is a side effect of email spam, viruses or worms. When a spam or malware-laden email is sent, it nearly always has a forged sender address. If this email fails to reach its recipient, e.g., because the recipientpsilas mailbox is full or the recipient has set up an out-of-the-office auto-responder, the recipientpsilas mail system may attempt to generate

  2. Assessment of misorientation in metallic and semiconducting nanowires using precession electron diffraction.

    PubMed

    Estradé, Sonia; Portillo, Joaquim; Mendoza, Joan; Kosta, Ivette; Serret, Maria; Müller, Carlos; Peiró, Francesca

    2012-08-01

    Precession electron diffraction (PED) allows for diffraction pattern collection under quasi-kinematical conditions. The combination of PED with fast electron diffraction acquisition and pattern matching software techniques is used for the high magnification ultra-fast mapping of variable crystal orientations and phases, similarly to what is achieved with the Electron Backscattered Diffraction technique in Scanning Electron Microscopes at lower magnifications and longer acquisition times. Here we report, for the first time, the application of this PED-based orientation mapping technique to both metallic and semiconducting nanowires. PMID:22455799

  3. Introduction to Electron Diffraction

    Microsoft Academic Search

    Jean-Paul Morniroli

    The main types of electron diffraction techniques are described: Selected-Area Electron Diffraction (SAED), Microdiffraction,\\u000a Convergent-Beam Electron Diffraction (CBED), Large-Angle Convergent-Beam Electron Diffraction (LACBED) and electron precession.\\u000a They produce spot, ring, disk or line patterns at microscopic or nanoscopic scales in correlation with the image of the diffracted\\u000a area. An overview of the main applications is given.

  4. Backscattering from a Gaussian distributed, perfectly conducting, rough surface

    NASA Technical Reports Server (NTRS)

    Brown, G. S.

    1977-01-01

    The problem of scattering by random surfaces possessing many scales of roughness is analyzed. The approach is applicable to bistatic scattering from dielectric surfaces, however, this specific analysis is restricted to backscattering from a perfectly conducting surface in order to more clearly illustrate the method. The surface is assumed to be Gaussian distributed so that the surface height can be split into large and small scale components, relative to the electromagnetic wavelength. A first order perturbation approach is employed wherein the scattering solution for the large scale structure is perturbed by the small scale diffraction effects. The scattering from the large scale structure is treated via geometrical optics techniques. The effect of the large scale surface structure is shown to be equivalent to a convolution in k-space of the height spectrum with the following: the shadowing function, a polarization and surface slope dependent function, and a Gaussian factor resulting from the unperturbed geometrical optics solution. This solution provides a continuous transition between the near normal incidence geometrical optics and wide angle Bragg scattering results.

  5. Diffractive Charm and Dijet Production

    E-print Network

    Diffractive Charm and Dijet Production at H1 Matthias Mozer Physikalisches Institut Universität Heidelberg #12;Matthias Mozer, Diffraction 2006 2 Introduction universal diffractive parton densities Mozer, Diffraction 2006 3 Factorization diffractive= pdf parton expected to hold (proof by collins

  6. Five-parameter grain boundary analysis by 3D EBSD of an ultra fine grained CuZr alloy processed by equal channel angular pressing

    E-print Network

    Rohrer, Gregory S.

    Five-parameter grain boundary analysis by 3D EBSD of an ultra fine grained CuZr alloy processed boundaries vary in a five-dimensional parameter space as a function of misorientation (3 variables) and grain materials. The five-parameter GBCD specifies the fractions of interface area sections, classified according

  7. Spatial patterns in backscatter strength across the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Jezek, K. C.

    1993-01-01

    The relationship between the physical properties of the Greenland ice sheet and Synthetic Aperture Radar (SAR) data collected from aircraft and from ERS-1 is addressed. Limited aircraft data are combined with a description of the glacier surface to predict qualitatively the spatial and seasonal variation in backscatter strength across the ice sheet. In particular the model predicts relatively low backscatter near the ice edge where scattering is dominated by rough surface effects. Backscatter increases through the lake zone as volume scattering becomes important. Strongest backscatter is found in the percolation facies where volume scatter from snow grains and volume scatter from large, buried ice bodies becomes important. Backscatter weakens in the interior ice sheet where fine grained snow is the only mechanism producing backscatter.

  8. Atmospheric Backscatter Model Development for CO Sub 2 Wavelengths

    NASA Technical Reports Server (NTRS)

    Deepak, A.; Kent, G.; Yue, G. K.

    1982-01-01

    The results of investigations into the problems of modeling atmospheric backscatter from aerosols, in the lowest 20 km of the atmosphere, at CO2 wavelengths are presented, along with a summary of the relevant aerosol characteristics and their variability, and a discussion of the measurement techniques and errors involved. The different methods of calculating the aerosol backscattering function, both from measured aerosol characteristics and from optical measurements made at other wavelengths, are discussed in detail, and limits are placed on the accuracy of these methods. The effects of changing atmospheric humidity and temperature on the backscatter are analyzed and related to the actual atmosphere. Finally, the results of modeling CO2 backscatter in the atmosphere are presented and the variation with height and geographic location discussed, and limits placed on the magnitude of the backscattering function. Conclusions regarding modeling techniques and modeled atmospheric backscatter values are presented in tabular form.

  9. Tensile failure of thin aluminium sheet observed by in-situ EBSD

    NASA Astrophysics Data System (ADS)

    Kahl, S.; Peng, R. L.; Johansson, S.

    2015-04-01

    Tensile tests on two similar 75-?m-thick aluminium sheet materials were carried out inside a scanning electron microscope equipped with an electron backscatter detector. The materials were subjected to simulated brazing prior to the test because this type of material is used for fins in automotive heat exchangers. Grain sizes were large relative to sheet thickness and ND-rotated cube and P texture components dominated the recrystallization textures; their volume fractions differed strongly in the two different materials, though. Strains over the microscope image fields were determined from positions of constituent particles or from grain sizes; the two methods gave consistent results. Grains with high Schmid factors accumulated significantly more deformation than grains with low Schmid factors. Cracks nucleated in high-Schmid factor grains, or in groups of such grains, at the specimen edges. When only low-Schmid factor grains were present at the specimen edges, the crack nucleated inside the specimen. The subsequent crack growth was intragranular and occurred at approximately 90° relative to the load direction.

  10. Demonstration of zero optical backscattering from single nanoparticles.

    PubMed

    Person, Steven; Jain, Manish; Lapin, Zachary; Sáenz, Juan Jose; Wicks, Gary; Novotny, Lukas

    2013-04-10

    We present the first experimental demonstration of zero backscattering from nanoparticles at optical frequencies as originally discussed by Kerker et al. [ Kerker , M. ; Wang , D. ; Giles , C. J. Opt. Soc. A 1983 , 73 , 765 ]. GaAs pillars were fabricated on a fused silica substrate and the spectrum of the backscattered radiation was measured in the wavelength range 600-1000 nm. Suppression of backscattering occurred at ~725 nm, agreeing with calculations based on the discrete dipole approximation. Particles with zero backscattering provide new functionality for metamaterials and optical antennas. PMID:23461654

  11. High Resolution Sapphire Bragg Backscattering Monochromator

    SciTech Connect

    Linden, P. van der; Wille, H.-C. [European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble (France); Shvyd'ko, Yu. V. [Argonne National Laboratory, Advanced Photon Source, Argonne, Il-60439 (United States)

    2007-01-19

    We present a temperature stabilised high resolution sapphire backscattering monochromator. The device consists of a sapphire crystal inside a cold nitrogen gas cooled, temperature stabilised chamber with a passively temperature stabilised screen. The achieved temperature stability of {+-}2mK allows for an energy resolution of {delta}E/E {<=} 10-7 at energies in the range of 30-70 keV. The device was developed for nuclear resonant scattering above 30 keV, where appropriate solutions did not exist until now.

  12. Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar

    NASA Astrophysics Data System (ADS)

    Ansmann, Albert; Wandinger, Ulla; Riebesell, Maren; Weitkamp, Claus; Michaelis, Walfried

    1992-11-01

    Height profiles of the extinction and the backscatter coefficients in cirrus clouds are determined independently from elastic- and inelastic- (Raman) backscatter signals. An extended error analysis is given. Examples covering the measured range of extinction-to-backscatter ratios (lidar ratios) in ice clouds are presented. Lidar ratios between 5 and 15 sr are usually found. A strong variation between 2 and 20 sr can be observed within one cloud profile. Particle extinction coefficients determined from inelastic-backscatter signals and from elastic-backscatter signals by using the Klett method are compared. The Klett solution of the extinction profile can be highly erroneous if the lidar ratio varies along the measuring range. On the other hand, simple backscatter lidars can provide reliable information about the cloud optical depth and the mean cloud lidar ratio.

  13. X-Ray Diffraction.

    ERIC Educational Resources Information Center

    Smith, D. K.; Smith, K. L.

    1980-01-01

    Reviews applications in research and analytical characterization of compounds and materials in the field of X-ray diffraction, emphasizing new developments in applications and instrumentation in both single crystal and powder diffraction. Cites 414 references. (CS)

  14. American Mineralogist, Volume 97, pages 12261233, 2012 0003-004X/12/00071226$05.00/DOI: http://dx.doi.org/10.2138/am.2012.4110 1226

    E-print Network

    Ma, Chi

    ." Field-emission scanning electron microscope, electron-backscatter diffraction (EBSD), electron, as determined by electron micro- probe analysis of the type material, is (wt%) S 35.84, Fe 28.68, Zn 23.54, Mn.46Zn0.32Mn0.16Mg0.04 )0.99S1.01. Electron backscatter diffraction patterns of buseckite are a good

  15. Precession electron diffraction 1

    NASA Astrophysics Data System (ADS)

    Own, C. S.; Marks, L. D.; Sinkler, W.

    2006-11-01

    A multislice method for simulating precession electron diffraction data is presented, and simulated data are compared to experimental data for two materials systems. Dynamical diffraction effects are present in precession data but are somewhat smaller and intensity ordering is better preserved than in conventional transmission electron diffraction. Some of the implications of precession for conventional direct methods are discussed.

  16. Diffractive production of mesons

    NASA Astrophysics Data System (ADS)

    Schicker, Rainer

    2014-11-01

    The interest in the study of diffractive meson production is discussed. The description of diffraction within Regge phenomenology is presented, and the QCD-based understanding of diffractive processes is given. Central production is reviewed, and the corresponding main results from the COMPASS experiment and from the experiments at the ISR, RHIC, TEVATRON and LHC collider are summarised.

  17. Simulation of ultrasound backscatter images from fish

    NASA Astrophysics Data System (ADS)

    Pham, An Hoai; Stage, Bjarne; Hemmsen, Martin Christian; Lundgren, Bo; Pedersen, Mads Møller; Pedersen, Tina Bock; Jensen, Jørgen Arendt

    2011-03-01

    The objective of this work is to investigate ultrasound (US) backscatter in the MHz range from fish to develop a realistic and reliable simulation model. The long term objective of the work is to develop the needed signal processing for fish species differentiation using US. In in-vitro experiments, a cod (Gadus morhua) was scanned with both a BK Medical ProFocus 2202 ultrasound scanner and a Toshiba Aquilion ONE computed tomography (CT) scanner. The US images of the fish were compared with US images created using the ultrasound simulation program Field II. The center frequency of the transducer is 10 MHz and the Full Width at Half Maximum (FWHM) at the focus point is 0.54 mm in the lateral direction. The transducer model in Field II was calibrated using a wire phantom to validate the simulated point spread function. The inputs to the simulation were the CT image data of the fish converted to simulated scatter maps. The positions of the point scatterers were assumed to be uniformly distributed. The scatter amplitudes were generated with a new method based on the segmented CT data in Hounsfield Units and backscatter data for the different types of tissues from the literature. The simulated US images reproduce most of the important characteristics of the measured US image.

  18. Radar backscatter properties of milo and soybeans

    NASA Technical Reports Server (NTRS)

    Bush, T. F.; Ulaby, F. T.; Metzler, T.

    1975-01-01

    The radar backscatter from fields of milo and soybeans was measured with a ground based radar as a function of frequency (8-18 GHz), polarization (HH and VV) and angle of incidence (0 deg-70 deg) during the summer of 1974. Supporting ground truth was gathered contemporaneously with the backscatter data. At nadir sigma deg of milo correlated highly, r = 0.96, with soil moisture in the milo field at 8.6 GHz but decreased to a value of r = 0.78 at a frequency of 17.0 GHz. Correlation studies of the variations of sigma deg with soil moisture in the soybean fields were not possible due to a lack of a meaningful soil moisture dynamic range. At the larger angles of incidence, however, sigma deg of soybeans did appear to be dependent on precipitation. It is suggested this phenomenon was caused by the rain altering plant geometry. In general sigma deg of both milo and soybeans had a relatively small dynamic range at the higher angles of incidence and showed no significant dependence on the measured crop parameters.

  19. Electromagnetic diffraction by plane reflection diffraction gratings

    NASA Technical Reports Server (NTRS)

    Bocker, R. P.; Marathay, A. S.

    1972-01-01

    A plane wave theory was developed to study electromagnetic diffraction by plane reflection diffraction gratings of infinite extent. A computer program was written to calculate the energy distribution in the various orders of diffraction for the cases when the electric or magnetic field vectors are parallel to the grating grooves. Within the region of validity of this theory, results were in excellent agreement with those in the literature. Energy conservation checks were also made to determine the region of validity of the plane wave theory. The computer program was flexible enough to analyze any grating profile that could be described by a single value function f(x). Within the region of validity the program could be used with confidence. The computer program was used to investigate the polarization and blaze properties of the diffraction grating.

  20. Analysis of the backscattering method for testing optical fiber cables

    Microsoft Academic Search

    E.-G. Neumann

    1980-01-01

    The backscattering method for measuring the attenuation of optical glass fiber waveguides and the insertion loss of fiber connections is analysed for a fiber of arbitrary refractive index profile taking into account the different attenuation for the transmitted and the backscattered light as well as the anisotropy of the Rayleigh scattering. The results of the analysis are applied to discuss

  1. Azimuth Variation in Microwave Backscatter over the Greenland Ice Sheet

    E-print Network

    Long, David G.

    ice sheet (see Fig. 2). For each sen- sor, different day ranges were used. SeaWinds uses 2 daysAzimuth Variation in Microwave Backscatter over the Greenland Ice Sheet Ivan S. Ashcraft and David ice sheet. However, most Greenland studies assume constant backscatter for varying azimuth angles

  2. Carbon dioxide laser backscatter signatures from laboratory-generated dust

    Microsoft Academic Search

    D. P. Walter; D. E. Cooper; J. E. van der Laan; E. R. Murray

    1986-01-01

    A dual CO2 laser system was used to measure aerosol backscatter spectral signatures from dust minerals (kaolin, illite, montmorillonite, colemanite, and limestone) as well as from a soil sample from Dugway Proving Ground, UT. Complex refractive indices measured from bulk samples of the materials, and particle size distributions measured with a cascade impactor, were used to compute theoretical backscatter spectra

  3. Backscatter measurements over vegetation by ground-based microwave radars

    Microsoft Academic Search

    Mehmet Kurum; Peggy O'Neill

    2011-01-01

    In the study of radar backscattering from vegetated terrain, it is important to understand how the electromagnetic wave interacts with vegetation and the underlying ground. In this paper, an expression of backscattering from a vegetation canopy in the case of spherical wave illumination is derived. Such an expression might apply to the practical case of a ground-based scatterometer overlooking vegetation.

  4. Relating P-band AIRSAR backscatter to forest stand parameters

    NASA Technical Reports Server (NTRS)

    Wang, Yong; Melack, John M.; Davis, Frank W.; Kasischke, Eric S.; Christensen, Norman L., Jr.

    1993-01-01

    As part of research on forest ecosystems, the Jet Propulsion Laboratory (JPL) and collaborating research teams have conducted multi-season airborne synthetic aperture radar (AIRSAR) experiments in three forest ecosystems including temperate pine forest (Duke, Forest, North Carolina), boreal forest (Bonanza Creek Experimental Forest, Alaska), and northern mixed hardwood-conifer forest (Michigan Biological Station, Michigan). The major research goals were to improve understanding of the relationships between radar backscatter and phenological variables (e.g. stand density, tree size, etc.), to improve radar backscatter models of tree canopy properties, and to develop a radar-based scheme for monitoring forest phenological changes. In September 1989, AIRSAR backscatter data were acquired over the Duke Forest. As the aboveground biomass of the loblolly pine forest stands at Duke Forest increased, the SAR backscatter at C-, L-, and P-bands increased and saturated at different biomass levels for the C-band, L-band, and P-band data. We only use the P-band backscatter data and ground measurements here to study the relationships between the backscatter and stand density, the backscatter and mean trunk dbh (diameter at breast height) of trees in the stands, and the backscatter and stand basal area.

  5. Rayleigh backscattering in a fiber gyroscope with limited coherence sources

    Microsoft Academic Search

    W. Burns; R. Moeller

    1983-01-01

    Noise due to temporal fluctuations of Rayleigh baekscattered light in fiber-optical gyroscopes is studied experimentally with various sources whose coherence length is less than the fiber length. The reduction of the coherent fraction of backscattered light and its fluctuation frequencies with reduced source coherence is demonstrated and fit to an analytical model. Measured backscatter parameters for the fiber and sources

  6. Orientation imaging microscopy of polycrystalline sodium chloride

    SciTech Connect

    Staiger, M.P., E-mail: mark.staiger@canterbury.ac.nz [Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8020 (New Zealand); Kolbeinsson, I. [Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8020 (New Zealand); Newman, J. [Newman Energy Research, 2 Rose Street, Christchurch (New Zealand); Woodfield, T.; Sato, T. [Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, 8020 (New Zealand)

    2010-04-15

    A novel preparation technique is described that makes possible grain size analysis of polycrystalline NaCl using orientation imaging microscopy via electron backscatter diffraction (EBSD). The preparation methodology is specifically developed to overcome difficulties in preparing microporous NaCl for microscopy. The grain size and crystallographic texture of polycrystalline NaCl samples, prepared via solution pressure and sintered in the range of 650-780 deg. C, were able to be measured successfully with EBSD. The limitations of the preparation technique for EBSD analysis of NaCl are also discussed.

  7. A method for removing arm backscatter from EPID images

    SciTech Connect

    King, Brian W. [School of Mathematical and Physics Sciences, University of Newcastle, Newcastle, New South Wales 2308 (Australia); Greer, Peter B. [Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Newcastle, New South Wales 2310 (Australia); School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales 2308 (Australia)

    2013-07-15

    Purpose: To develop a method for removing the support arm backscatter from images acquired using current Varian electronic portal imaging devices (EPIDs).Methods: The effect of arm backscatter on EPID images was modeled using a kernel convolution method. The parameters of the model were optimized by comparing on-arm images to off-arm images. The model was used to develop a method to remove the effect of backscatter from measured EPID images. The performance of the backscatter removal method was tested by comparing backscatter corrected on-arm images to measured off-arm images for 17 rectangular fields of different sizes and locations on the imager. The method was also tested using on- and off-arm images from 42 intensity modulated radiotherapy (IMRT) fields.Results: Images generated by the backscatter removal method gave consistently better agreement with off-arm images than images without backscatter correction. For the 17 rectangular fields studied, the root mean square difference of in-plane profiles compared to off-arm profiles was reduced from 1.19% (standard deviation 0.59%) on average without backscatter removal to 0.38% (standard deviation 0.18%) when using the backscatter removal method. When comparing to the off-arm images from the 42 IMRT fields, the mean {gamma} and percentage of pixels with {gamma} < 1 were improved by the backscatter removal method in all but one of the images studied. The mean {gamma} value (1%, 1 mm) for the IMRT fields studied was reduced from 0.80 to 0.57 by using the backscatter removal method, while the mean {gamma} pass rate was increased from 72.2% to 84.6%.Conclusions: A backscatter removal method has been developed to estimate the image acquired by the EPID without any arm backscatter from an image acquired in the presence of arm backscatter. The method has been shown to produce consistently reliable results for a wide range of field sizes and jaw configurations.

  8. Backscattering at a pulsed neutron source, the MUSICAL instrument

    NASA Astrophysics Data System (ADS)

    Alefeld, B.

    1995-02-01

    In the first part the principles of the neutron backscattering method are described and some simple considerations about the energy resolution and the intensity are presented. A prototype of a backscattering instrument, the first Jülich instrument, is explained in some detail and a representative measurement is shown which was performed on the backscattering instrument IN10 at the ILL in Grenoble. In the second part a backscattering instrument designed for a pulsed neutron source is proposed. It is shown that a rather simple modification, which consists in the replacement of the Doppler drive of the conventional backscattering instrument by a multi silicon monochromator cryst al (MUSICAL) leads to a very effective instrument, benefitting from the peak flux of the pulsed source.

  9. EBSD study of the orientation dependence of substructure characteristics in a model Fe-30wt%Ni alloy subjected to hot deformation.

    PubMed

    Cizek, P; Bai, F; Palmiere, E J; Rainforth, W M

    2005-02-01

    The aim of the present investigation was to determine the orientation dependence of substructure characteristics in an austenitic Fe-30wt%Ni model alloy subjected to hot plane strain compression. Deformation was carried out at a temperature of 950 degrees C using a strain rate of 10 s(-1) to equivalent strain levels of approximately 0.2, 0.4, 0.6 and 0.8. The specimens obtained were analysed using a fully automatic electron backscatter diffraction technique. The crystallographic texture was characterized for all the strain levels studied and the subgrain structure was quantified in detail at a strain of 0.4. The substructure characteristics displayed pronounced orientation dependence. The major texture components, namely the copper, S, brass, Goss and rotated Goss, generally contained one or two prominent families of parallel larger-angle extended subboundaries, the traces of which on the longitudinal viewing plane appeared systematically aligned along the {111} slip plane traces, bounding long microbands subdivided into slightly elongated subgrains by short lower-angle transverse subboundaries. Relatively rare cube-orientated grains displayed pronounced subdivision into coarse deformation bands containing large, low-misorientated subgrains. The misorientation vectors across subboundaries largely showed a tendency to cluster around the sample transverse direction. Apart from the rotated Goss texture component, the stored energy levels for the remaining components were principally consistent with the corresponding Taylor factor values. PMID:15683411

  10. Electron back scattered diffraction characterization of Sm(CoFeCuZr){sub z} magnets

    SciTech Connect

    Yonamine, T.; Fukuhara, M.; Archanjo, B. S. [National Institute of Metrology, Standardization and Industrial Quality, Duque de Caxias, Rio de Janeiro 25250-020 (Brazil); Missell, F. P. [Centro de Ciencias Exatas e Tecnologia, Universidade de Caxias do Sul, Caxias do Sul, Rio Grande do Sul 95070-560 (Brazil)

    2011-04-01

    In permanent magnets based on the Sm{sub 2}Co{sub 17} phase, the high coercivity depends on the presence of a complex microstructure, consisting of a Sm{sub 2}(Co,Fe){sub 17} cell phase, a cell boundary phase Sm(Co,Cu){sub 5}, and a Zr-rich platelet or lamellae phase. The aim of this work is to use electron back scatter diffraction (EBSD) in order to identify the different phases present in the isotropic magnets produced from cast alloys with the composition of Sm(Co{sub bal}Fe{sub 0.2}Cu{sub 0.1}Zr{sub x}){sub 8}, where x = 0, 0.02, or 0.06, and correlate them with the different phases observed in scanning electron microscopy (SEM) images. Due to the combination of careful surface preparation and high resolution microscopy, it was possible to observe the cellular structure characteristic of the 2:17 magnets in the SEM images. Until now, only transmission electron microscopy (TEM) had been used. Composition maps, energy dispersive spectroscopy (EDS), and EBSD measurements were used for doing the phase identification.

  11. Ultrasonic backscatter coefficient quantitative estimates from Chinese hamster ovary cell pellet biophantoms

    E-print Network

    Illinois at Urbana-Champaign, University of

    Ultrasonic backscatter coefficient quantitative estimates from Chinese hamster ovary cell pellet to the ultrasonic backscatter coefficient BSC estimate using Chinese hamster ovary CHO cells. Also introduced

  12. Relationship between wind, waves and radar backscatter

    NASA Technical Reports Server (NTRS)

    Katsaros, Kristina B.; Ataktuerk, Serhad S.

    1991-01-01

    The aim of the research was to investigate the relationship between wind, waves, and radar backscatter from water surface. To this end, three field experiments with periods of 2 to 4 weeks were carried out during summer months in 1988, 1989 and 1990. For these periods, the University of Washington group provided (1) environmental parameters such as wind speed, wind stress, and atmospheric stratification through measurements of surface fluxes (of momentum, sensible heat and latent heat) and of air and water temperatures; and (2) wave height spectra including both the dominant waves and the short gravity-capillary waves. Surface flux measurements were performed by using our well tested instruments: a K-Gill twin propeller-vane anemometer and a fast response thermocouple psychrometer. Wave heights were measured by a resistance wire wave gauge. The University of Kansas group was responsible for the operation of the microwave radars.

  13. Complete k-space visualization of x-ray photoelectron diffraction

    SciTech Connect

    Denlinger, J.D. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Physics; [Lawrence Berkeley Lab., CA (United States). Advanced Light Source; Rotenberg, E. [Univ. of Oregon, Eugene, OR (United States). Dept. of Physics; [Lawrence Berkeley Lab., CA (United States). Advanced Light Source; Kevan, S.D. [Univ. of Oregon, Eugene, OR (United States). Dept. of Physics; Tonner, B.P. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Physics

    1996-12-31

    A highly detailed x-ray photoelectron diffraction data set has been acquired for crystalline Cu(001). The data set for bulk Cu 3p emission encompasses a large k-space volume (k = 3--10 {angstrom}{sup {minus}1}) with sufficient energy and angular sampling to monitor the continuous variation of diffraction intensities. The evolution of back-scattered intensity oscillations is visualized by energy and angular slices of this volume data set. Large diffraction data sets such as this will provide rigorous experimental tests of real-space reconstruction algorithms and multiple-scattering simulations.

  14. Rutherford Backscattering in an industrial environment

    NASA Astrophysics Data System (ADS)

    Strathman, M. D.

    1985-05-01

    Rutherford Backscattering Spectrometry (RBS) is a well established analytical technique, particularly in the university and major research oriented industrial laboratories. Historically, the accelerators used for RBS analysis have been renovated low energy nuclear physics machines rather than a dedicated optimally designed analytical instrument. It is this "requirement" that each machine be individually rebuilt prior to use as a materials analysis tool that has contributed to the limited industrial use of RBS when compared with other analytical techniques such as Auger spectroscopy or Secondary Ion Mass Spectrometry (SIMS). This paper will discuss the design criteria and applications of an RBS system for use in an industrial analytical environment. The design issues which are discussed include the backscattered particle detection, sample positioning, charge integration, vacuum, and automation systems. An RBS system for which the design of these systems has been optimized in light of many current industrial applications will be evaluated. The prototype of this system has been tested for the previous two years with a utilization factor of 4000-5000 individual analyses per year. The applications which have been investigated extend from the familiar electronics related topics to many other diverse fields such as polymeric chemistry, catalysis, and surface modification of synthetic fibers. Some of the electronics applications include high throughput "production line" analysis of silicides, copper doped aluminum, and similar interconnect materials as well as the more sophisticated trace impurity mapping techniques which involve channeled line scans. Catalysis applications include the study of cage compound zeolite particles and the depth distribution of the active catalyst in these particles. Applications in the field of synthetic fibers include the study of the depth distribution of coloring agents and dyes in the near surface region of the fibers.

  15. Dynamic recrystallization in the shear bands of FeCrNi monocrystal: Electron backscatter diffraction characterization

    E-print Network

    Meyers, Marc A.

    of boundary orientation than conventional imaging methods. These measurements can be made more easily than the shear direction. It can be seen that the shear band has a well-defined boundary on one side, and is divergent on the other side of the band. This kind of phenomenon is also observed in steels [3] and Ti [19

  16. Ocean backscatter across the Gulf Stream sea surface temperature front

    SciTech Connect

    Nghiem, S.V.; Li, F.K. [California Institute of Technology, Pasadena, CA (United States)

    1997-06-01

    Ocean backscatter was measured by the Jet Propulsion Laboratory, with the airborne NUSCAT K{sub u}-band scatterometer, across the Gulf Stream sea surface temperature front during the Surface Wave Dynamics Experiment off the coast of Virginia and Maryland in the winter of 1991. Backscatter across the front between the National Oceanic and Atmospheric Administration experimental coastal buoy A (44024) on the cold side and Discus C buoy (44023) on the warm side shows a difference of more than 5 dB for vertical polarization in many cases. This large frontal backscatter change is observed in all upwind, downwind, and crosswind directions. The sea surface temperature difference measured by the buoys was about 9{degrees}C. The corresponding difference in wind speed cannot account for the large backscatter change in view of geophysical model functions depending only on neutral wind velocity such as SASS. The measured backscatter also has larger upwind-downwind and upwind-crosswind ratios compared to the model results. Furthermore, NUSCAT data reveal that upwind backscatter on the cold side was smaller than or close to crosswind backscatter on the warm side for incidence angles between 30{degrees} to 50{degrees}. This suggests that the temperature front can be detected by the scatterometer at these incidence angles for different wind directions in the cold and warm sides.

  17. Quantitative characterization of abyssal seafloor with transit multibeam backscatter data

    NASA Astrophysics Data System (ADS)

    Pockalny, R. A.; Ferrini, V. L.

    2014-12-01

    The expanding volume of deep-water multibeam echosounder data provides emerging opportunities for the improved characterization of the abyssal seafloor. Nearly 500 cruises criss-cross the oceans with modern wide-swath multibeam systems, and these cruise tracks have imaged a variety of morphologic, tectonic and magmatic environments. The qualitative analysis of the seafloor backscatter data strongly suggests a local and regional variability that correlates with sediment thickness, sediment type and/or depositional environment. We present our initial attempts to develop a method that quantifies this observed seafloor backscatter variability and to explore the causes and potential implications of this variability. Our approach is rooted in the Angular Range Analysis methodology, which utilizes changes in backscatter amplitude observed as a function of grazing angle, to characterize the seafloor. The primary difference in our approach is that we do not invert for geo-acoustical parameters, but rather explores empirical relationships between geological observations and stacked slope and y-intercept values. In addition, we also include the mean and the variance of detrended backscatter measurements. Our initial results indicate intriguing relationships between backscatter parameters and the CaCO3 content of surface sediments. Seafloor regions reported to have high manganese nodule concentrations also tend to have characteristic trends in backscatter parameters. We will present these regional correlations as well as some preliminary statistical analyses of the backscatter parameters and key environmental factors.

  18. Direction angle sensitivity of agricultural field backscatter with Airsar data

    NASA Technical Reports Server (NTRS)

    Dubois, Pascale C.; Rignot, Eric; Van Zyl, Jakob J.

    1992-01-01

    The direction angle sensitivity of agricultural field backscatter is studied. The direction angle is defined as the angle between the incident plane and the perpendicular to the row direction. Maximum backscatter power from an angricultural field is expected to occur when the furrow induced slopes are oriented towards the radar, i.e., for a 0 deg direction angle. This effect is known as the cardinal effect. Because of the way the looks are formed in the NASA/JPL airborne synthetic aperture radar (AIRSAR) processor, each look corresponds to a slightly different squint angle. This provides a unique data set to analyze the cardinal effect, as it allows simultaneous observations of the backscatter of a field for sixteen different direction angles. The backscatter variations of the agricultural fields with direction angle at P-, L-, and C-bands is described. The observed variations in backscatter are compared with model predictions. The model predicts that the maximum backscatter occurs for a 0 deg direction angle, but underestimates the backscatter variations with direction angle by more than 10 dB.

  19. Direction angle sensitivity of agricultural field backscatter with AIRSAR data

    NASA Technical Reports Server (NTRS)

    Dubois, Pascale C.; Rignot, Eric; Vanzyl, Jakob J.

    1993-01-01

    This paper presents a study of the direction angle sensitivity of radar backscatter from agricultural fields. The direction angle is defined as the angle between the incident plane and the perpendicular to the field row direction. Previous studies have concentrated on comparing the backscatter of agricultural fields imaged with 0, 45, and 90 degree direction angles. In contrast, this study concentrates on the backscatter changes occurring when the direction angle is modified by a few degrees or even by fractions of a degree. This is possible by using the output of the NASA/JPL AIRSAR processor, in which sixteen independent frames are formed, each one corresponding to the same radar scene imaged with a slightly different squint angle. The studied data set is an agricultural area in La Mancha, Spain acquired in June and July 1991 during the EFEDA experiment. This paper describes the observed backscatter variations of the agricultural fields with direction angle measured at P, L, and C bands. As expected, the backscatter is maximum for a 0 degree direction angle. For several fields, the backscatter at P and L bands drops by more than 10 dB for a 5 degree change in direction angle. Furthermore, the sensitivity to the direction angle decreases with increasing vegetation. The variations in backscatter are compared with model predictions. One model, which agrees with scatterometer data, underestimates the observed backscatter variations with direction angle by more than 10 dB. It does not take into account the possible coherent component of the radar signal. We believe the strong direction sensitivity of agricultural field backscatter obtained with SAR data is due to a Bragg resonant effect, resulting in a strong coherent return when the direction angle is zero. The observations are then projected to the case of spaceborne SAR data.

  20. Ehrenfest Time and the Coherent Backscattering Off Ballistic Cavities

    NASA Astrophysics Data System (ADS)

    Rahav, Saar; Brouwer, Piet W.

    2006-05-01

    If the Ehrenfest time ?E of a ballistic cavity is not negligible in comparison to its dwell time ?D, the weak localization correction to the cavity’s transmission is suppressed proportional to exp?(-?E/?D). At the same time, quantum interference enhances the probability of reflection into the mode of incidence by a factor two. This “enhanced backscattering” does not depend on the Ehrenfest time. We show that, in addition to the diagonal enhanced backscattering, there are off-diagonal contributions to coherent backscattering that become relevant if ?E??D.

  1. Anomalous spectral signatures of high-intensity stimulated Raman backscattering

    SciTech Connect

    Skoric, M.M. [Vinca Institute of Nuclear Sciences, P.O.B. 522, 11001 Belgrade (Yugoslavia); Jovanovic, M.S. [Vinca Institute of Nuclear Sciences, P.O.B. 522, 11001 Belgrade (Yugoslavia)]|[Department of Physics, University of Nis, P.O.B. 91, 18001 Nis (Yugoslavia); Rajkovic, M.R. [Vinca Institute of Nuclear Sciences, P.O.B. 522, 11001 Belgrade (Yugoslavia)

    1996-05-01

    The nonlinear three-wave interaction model of stimulated Raman backscattering in an underdense plasma layer, with a relativistic detuning taken into account, is simulated in space-time. A mechanism is discovered based on a systematic transition to a chaotic state via quasiperiodic and intermittent regimes, that predicts a progressive growth in the backscatter complexity with an increase in laser intensity. Anomalous signatures of the backscatter, such as bursting and incoherence, together with broad, modulated and blue-shifted spectra are readily observed. Consistency with recent data on high-intensity sub-picosecond laser plasma experiments is established. {copyright} {ital 1996 American Institute of Physics.}

  2. CO2 lidar backscatter profiles over Hawaii during fall 1988

    NASA Technical Reports Server (NTRS)

    Post, Madison J.; Cupp, Richard E.

    1992-01-01

    Aerosol and cloud backscatter data, obtained over a 24-day period in fall 1988 with the National Oceanic and Atmospheric Administration's Doppler lidar at 10.59-micron wavelength, are analyzed by using a new technique to lessen biases that are due to dropouts. Typical backscatter cross sections were significantly lower than those routinely observed over the continental United States, although episodic backscatter enhancements caused by cirrus and mineral dust also occurred. Implications of these data on the proposed Laser Atmospheric Wind Sounder wind profiling satellite sensor are discussed.

  3. Effects of Rayleigh backscattering on distributed feedback fiber laser sensors

    NASA Astrophysics Data System (ADS)

    Xu, Tuanwei; Ren, Meizhen; He, Jun; Fang, Gaosheng; Li, Fang; Liu, Yuliang

    2014-12-01

    Rayleigh backscattering induces mode hopping of DFB fiber lasers in the sensor array, and the critical length related to Rayleigh backscattering limits the size of DFB fiber laser sensor networking. Based on three-mirror cavity model, the critical length for DFB fiber lasers are derived. It increases nearly exponentially with the coupling coefficient for the ideal ?-shifted DFB fiber lasers. While the reflectivity of the sub-FBG at lasing wavelength is the main factor to resist Rayleigh backscattering for a non-ideal DFB fiber laser. The corresponding experiments have been carried out, and the results agree with the predictions.

  4. X-ray backscatter imaging of nuclear materials

    DOEpatents

    Chapman, Jeffrey Allen; Gunning, John E; Hollenbach, Daniel F; Ott, Larry J; Shedlock, Daniel

    2014-09-30

    The energy of an X-ray beam and critical depth are selected to detect structural discontinuities in a material having an atomic number Z of 57 or greater. The critical depth is selected by adjusting the geometry of a collimator that blocks backscattered radiation so that backscattered X-ray originating from a depth less than the critical depth is not detected. Structures of Lanthanides and Actinides, including nuclear fuel rod materials, can be inspected for structural discontinuities such as gaps, cracks, and chipping employing the backscattered X-ray.

  5. Microcontamination detection using Heavy Ion Backscattering Spectrometry

    SciTech Connect

    Knapp, J.A.; Banks, J.C. [Sandia National Labs., Albuquerque, NM (United States); Diebold, A.C. [SEMATECH, Austin, TX (United States)

    1994-07-01

    Heavy Ion Backscattering Spectrometry (HIBS) is a new ion beam analysis tool using heavy, low-energy ions in backscattering mode which can detect very low levels of surface contamination. By taking advantage of the greatly increased scattering cross-section for such ion beams and eliminating unwanted substrate scattering with a thin carbon foil, our research system has achieved a sensitivity ranging from {approximately}5{times}10{sup 10} atoms/cm{sup 2} for Fe to {approximately}1{times}10{sup 9} atoms/cm{sup 2} for Au on Si, without preconcentration. A stand-alone HIBS prototype now under construction in collaboration with SEMATECH is expected to achieve detection limits of {approximately}5{times}10{sup 9} atoms/cm{sup 2} for Fe and {approximately}1{times}10{sup 8} atoms/cm{sup 2} for Au on Si, again without preconcentration. Since HIBS is standardless and has no matrix effects, it will be useful not only as a standalone tool, but also for benchmarking standards for other tools. This conference is testimony to the importance of controlling contamination in microelectronics manufacturing. By the turn of the century, very large scale integrated circuit processing is expected to require contamination levels well below 1{times}10{sup 9} atoms/cm{sup 2} in both starting materials and introduced by processing. One of the most sensitive of existing general-purpose tools is Total reflection X-Ray Fluorescence (TXRF), which can detect {approximately}1{times}10{sup 10} atoms/cm{sup 2} levels of some elements such as Fe and Cu, but for many elements it is limited to 1{times}10{sup 12} atoms/cm{sup 2} or worse. TXRF can achieve a sensitivity of 10{sup 8} atoms/cm{sup 2} through the use of synchrotron radiation or via pre-concentration using Vapor Phase Decomposition. HIBS provides an ion beam analysis capability with the potential for providing similar sensitivity at medium Z and higher sensitivity at larger Z, all without pre-concentration or matrix effects.

  6. Software Precession Electron Diffraction

    Microsoft Academic Search

    C. T. Koch; P. Bellina; P. A. Aken

    Precession electron diffraction (PED) [1] has recently become a very useful technique for the determination of crystal symmetry\\u000a and structure. The advantage of this technique is commonly seen in the fact that electron diffraction patterns recorded with\\u000a a precessing illumination can more frequently be interpreted using kinematic scattering theory.

  7. The integration of experimental in-situ EBSD observations and numerical simulations: a novel technique of microstructural process analysis.

    PubMed

    Piazolo, S; Jessell, M W; Prior, D J; Bons, P D

    2004-03-01

    The combination of subgrain- and grain-scale microstructural data collected during in-situ heating experiments and numerical simulations of equivalent microstructural development offers an innovative and powerful tool in the advancement of the understanding of microstructural processes. We present a system that fully integrates subgrain- to grain-scale crystallographic data obtained during in-situ observations during heating experiments in a scanning electron microscope and the two-dimensional hybrid numerical modelling system Elle. Such a system offers the unique opportunity to test and verify theories for microstructural development, as predictions made by numerical simulations can be directly coupled to appropriate physical experiments and, conversely, theoretical explanations of experimental observations should be testable with numerical simulations. Discrepancies between data obtained with both techniques suggest the need for an in-depth investigation and thus open up new avenues of theory development, modification and verification. In addition, because in numerical models it is possible to select the processes modelled, the effect of individual processes on the microstructural development of a specific material can be quantified. To illustrate the potential and methodology of the so-called EBSD2Elle system, two in-situ experiments and their equivalent numerical experiments are presented. These are static heating experiments of (a) an annealed Ni-foil coupled with a front tracking model for grain growth and (b) a cold deformed rock salt with kinetic Monte Carlo simulations for subgrain growth. PMID:15009695

  8. A new EBSD based methodology for the quantitative characterisation of microstructures formed by displacive fcc-bcc transformations.

    PubMed

    Zachrisson, J; Börjesson, J; Karlsson, L

    2013-02-01

    This work is concerned with a new methodology that can be used to quantify the degree to which grains in the microstructure are aligned in the form of packets. The methodology is based on a crystallographic definition of the term packet which is used to deduce the theoretically ideal misorientations of intra-packet grain boundaries. A misorientation distribution obtained from extensive EBSD mapping can thus be split into intra- and inter-packet misorientations and the corresponding fractions can be determined by integration. The theoretical framework of the methodology is explained and a step-by-step description of the procedure is given. Results from a trace analysis are provided to justify the assumptions made regarding habit plane and examples are included showing how the grain boundary network can be split into two separate parts, one for lath boundaries and the other for packet boundaries. Moreover, example weld metal microstructures along with the corresponding misorientation distributions as well as quantitative values of the microstructures are presented. PMID:23238107

  9. Acoustic seabed segmentation from direct statistical clustering of entire multibeam sonar backscatter curves

    Microsoft Academic Search

    L. J. Hamilton; I. Parnum

    2011-01-01

    A fast, simple method is presented to obtain acoustic seabed segmentation from multibeam sonar backscatter data, for situations where processed backscatter curves are already available. Unsupervised statistical clustering is used to classify multibeam sonar backscatter curves in their entirety, with the curves essentially treated as geometrical entities. High variability in the backscatter curves is removed by along-track averaging prior to

  10. Aerosol measurement program strategy for global aerosol backscatter model development

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.

    1985-01-01

    The purpose was to propose a balanced program of aerosol backscatter research leading to the development of a global model of aerosol backscatter. Such a model is needed for feasibility studies and systems simulation studies for NASA's prospective satellite-based Doppler lidar wind measurement system. Systems of this kind measure the Doppler shift in the backscatter return from small atmospheric aerosol wind tracers (of order 1 micrometer diameter). The accuracy of the derived local wind estimates and the degree of global wind coverage for such a system are limited by the local availability and by the global scale distribution of natural aerosol particles. The discussions here refer primarily to backscatter model requirements at CO2 wavelengths, which have been selected for most of the Doppler lidar systems studies to date. Model requirements for other potential wavelengths would be similar.

  11. BASIS: A New Backscattering Spectrometer at the SNS

    SciTech Connect

    Mamontov, Eugene [ORNL; Zamponi, Michaela M [ORNL; Hammons, Stephanie E [ORNL; Keener, Wylie S [ORNL; Hagen, Mark E [ORNL; Herwig, Kenneth W [ORNL

    2008-01-01

    A new spectrometer named BASIS has recently entered the general user program at the Spallation Neutron Source. BASIS is an acronym for Backscattering Silicon Spectrometer. While there are several operational reactor-based spectrometers that utilize backscattering reflection from silicon single crystals, such as IN10 and IN16 [1] at the ILL, France; HFBS [2] at the NCNR, USA; and SPHERES [3] at the FRM-II, JCNS, Germany, BASIS is the first silicon backscattering spectrometer built on a spallation neutron source. Conceptually, it is similar to previously built time-of-flight backscattering spectrometers that utilize reflections from pyrolytic graphite or mica, such as IRIS [4] and OSIRIS [5] at the ISIS, UK; LAM-80 [6] at the KENS, Japan; or MARS [7] at the SINQ, Switzerland.

  12. Interaction-induced backscattering in short quantum wires

    NASA Astrophysics Data System (ADS)

    Rieder, M.-T.; Micklitz, T.; Levchenko, A.; Matveev, K. A.

    2014-10-01

    We study interaction-induced backscattering in clean quantum wires with adiabatic contacts exposed to a voltage bias. Particle backscattering relaxes such systems to a fully equilibrated steady state only on length scales exponentially large in the ratio of bandwidth of excitations and temperature. Here we focus on shorter wires in which full equilibration is not accomplished. Signatures of relaxation then are due to backscattering of hole excitations close to the band bottom which perform a diffusive motion in momentum space while scattering from excitations at the Fermi level. This is reminiscent to the first passage problem of a Brownian particle and, regardless of the interaction strength, can be described by an inhomogeneous Fokker-Planck equation. From general solutions of the latter we calculate the hole backscattering rate for different wire lengths and discuss the resulting length dependence of interaction-induced correction to the conductance of a clean single channel quantum wire.

  13. Automatic scaling of HF swept-frequency backscatter ionograms

    NASA Astrophysics Data System (ADS)

    Song, Huan; Hu, Yaogai; Jiang, Chunhua; Zhou, Chen; Zhao, Zhengyu

    2015-05-01

    This paper describes a method for automatically scaling HF swept-frequency backscatter ionograms, which can be applied to a low-power oblique backscatter sounding system. Based on the information of vertical echo in the ionogram, propagation mode is recognized from the amplitude differences between E layer and F layer echoes. Points on the leading edge are extracted by using minimum group path delay theory. The spurious points are removed by using residual analysis. A multiple linear polynomial was adopted to fit the extracted leading edge points. Smooth fitting curves can then be obtained. Automatic scaling results from 362 ionograms show that the proposed method can efficiently recognize propagation modes and extract leading edge curves by taking full advantages of echo characteristics and echo amplitudes in the ionograms. This novel method can be applied into real-time backscatter ionogram scaling, which facilitates the extensive usage of oblique backscatter soundings.

  14. Imaging of near-surface atomic structure by forward-focused backscattered electrons

    NASA Astrophysics Data System (ADS)

    Pronin, Igor I.; Gomoyunova, Marina V.

    1998-12-01

    Recent original studies related to the mechanism underlying the formation of backscattered electron diffraction patterns in the medium-energy region are reviewed. A set of nearly full-hemispheric spatial distributions of electrons quasi-elastically backscattered from Mo(100) and Si(100) is presented and compared with calculations performed in the frame of single-scattering theory. A new model of Kikuchi bands is proposed. It is demonstrated that the previously mentioned patterns being measured at 2 keV energy are capable of real-space imaging the atomic structure within a few top monolayers of the sample. Results for {sol Ag}/{Si(111) } and {sol Ag}/{Si(100) } systems, including direct observation of recrystallization process that occurs in ultrathin silver films when heating, illustrate this conclusion. It is shown that quantitative analysis of different crystal phases on the surface can be carried out via R-factor fits of experiment and computer simulations. Finally, the technique for real-time structural studies is considered.

  15. Estimating slash pine biomass using radar backscatter

    NASA Technical Reports Server (NTRS)

    Hussin, Yousif Ali; Reich, Robin M.; Hoffer, Roger M.

    1991-01-01

    L-band HV multiple-incidence-angle aircraft synthetic aperture radar (SAR) data were analyzed in relation to average stand biomass, basal area, and tree height for 55 slash pine plantations located in northern Florida. This information was used to develop a system of equations to predict average stand biomass as a function of L-band (24.5-cm) radar backscatter. The system of equations developed in this study using three-stage least-squares and combinatorial screening accounted for 97 percent of the variability observed in average stand biomass per hectare. When applied to an independent data set, the biomass equations had an average bias of less than 1 percent with a standard error of approximately 3 percent. These results indicate that future Shuttle Imaging Radar Systems (e.g., SIR-C, which will have cross-polarized radar sensors) should be able to obtain better estimates of forest biomass than were obtained with previous satellite radar missions, which utilized only HH-polarized SAR data.

  16. Ocean Wave Slope Observations Using Radar Backscatter and Laser Altimeters

    Microsoft Academic Search

    D. Vandemark; B. Chapron; J. Sun; G. H. Crescenti; H. C. Graber

    2004-01-01

    Combination of laser and radar aboard an aircraft is used to directly measure long gravity wave surface tilting simultaneously with nadir-viewing microwave backscatter from the sea surface. The presented dataset is exten- sive, encompassing varied wind conditions over coastal and open-ocean wave regimes. Laser-derived slope statistics and Ka-band (36 GHz) radar backscatter are detailed separately to document their respective variations

  17. A Backscattering Enhanced Microwave Canopy Scattering Model Based On MIMICS

    NASA Astrophysics Data System (ADS)

    Shen, X.; Hong, Y.; Qin, Q.; Chen, S.; Grout, T.

    2010-12-01

    For modeling microwave scattering of vegetated areas, several microwave canopy scattering models, based on the vectorized radiative transfer equation (VRT) that use different solving techniques, have been proposed in the past three decades. As an iterative solution of VRT at low orders, the Michigan Microwave Canopy Scattering Model (MIMICS) gives an analytical expression for calculating scattering as long as the volume scattering is not too strong. The most important usage of such models is to predict scattering in the backscattering direction. Unfortunately, the simplified assumption of MIMICS is that the scattering between the ground and trunk layers only includes the specular reflection. As a result, MIMICS includes a dominant coherent term which vanishes in the backscattering direction because this term contains a delta function factor of zero in this direction. This assumption needs reconsideration for accurately calculating the backscattering. In the framework of MIMICS, any incoherent terms that involve surface scattering factors must at least undergo surface scattering twice and volume scattering once. Therefore, these incoherent terms are usually very weak. On the other hand, due to the phenomenon of backscattering enhancement, the surface scattering in the backscattering direction is very strong compared to most other directions. Considering the facts discussed above, it is reasonable to add a surface backscattering term to the last equation of the boundary conditions of MIMICS. More terms appear in the final result including a backscattering coherent term which enhances the backscattering. The modified model is compared with the original MIMICS (version 1.0) using JPL/AIRSAR data from NASA Campaign Soil Moisture Experimental 2003 (SMEX03) and Washita92. Significant improvement is observed.

  18. Accurate Phase-Based Ranging Measurements for Backscatter RFID Tags

    Microsoft Academic Search

    Chenming Zhou; Joshua D. Griffin

    2012-01-01

    Short-distance, millimeter-level ranging based on backscatter RF tags remains a challenge today. We propose a composite dual-frequency continuous-wave and continuous-wave (DFCW\\/CW) radar system for localization of backscatter RF tags. The coarse DFCW range result is used to correct the cycle ambiguity of the more accurate CW range result. A minimum mean square error (MMSE)-based method is employed to combine the

  19. Coherent backscattering from high-gain scattering media

    NASA Astrophysics Data System (ADS)

    de Oliveira, Paulo C.; Perkins, A. E.; Lawandy, N. M.

    1996-10-01

    We report on experimental observations of coherent backscattering signals from high-gain scattering media in the regime where significant amplification takes place over one transport length. Our samples consist of polymer sheets containing optically pumped dyes as the amplifying medium, with TiO2 nanoparticles providing the scattering. The width of the backscattering cones narrows with increasing amplification, while the enhancement factor remains unchanged.

  20. Radar backscatter across the Gulf Stream sea surface temperature front

    Microsoft Academic Search

    Son V. Nghiem; Fuk K. Li; Edward J. Walsh; Shu-Hsiang Lou

    2000-01-01

    Ku-band backscatter responses to frontal sea surface temperature (SST) changes are studied and applications of a high-resolution scatterometer to remote sensing of an SST front are suggested. Ocean backscatter signatures were measured with an airborne Ku-band scatterometer across the Gulf Stream SST front during the Surface Wave Dynamics Experiment. Oceanic and atmospheric parameters were measured by buoys, by the Scanning

  1. Grain boundary energy and grain growth in Al films: Comparison of experiments and simulations

    E-print Network

    Rohrer, Gregory S.

    backscatter diffraction (EBSD) mapping system (TexSEM Laboratories, Inc.) integrated with a scanning electron dioxide thickness was 100 nm. The Al sputtering target was 99.99% pure. The total metallic impurity content of the target was 5.6 ppm by atom, with Fe accounting for 3.0 ppm of this total. The Si content

  2. Deriving grain boundary character distributions and relative grain boundary

    E-print Network

    Rohrer, Gregory S.

    -dimensional electron backscatter diffraction data, obtained by serial sectioning a nickel­ base superalloy, has been of the procedures. The procedures are applied to data from a Ni base superalloy with a high degree of twining and GBED are inversely correlated. Keywords: Grain boundaries, Grain boundary energy, Superalloy, EBSD

  3. Nano-grained copper strip produced by accumulative roll bonding process

    Microsoft Academic Search

    Mahnoosh Shaarbaf; Mohammad Reza Toroghinejad

    2008-01-01

    Accumulative roll bonding (ARB) process is a severe plastic deformation (SPD) process that has been used for pure copper (99.9%). The ARB process up to 8 cycles was performed at ambient temperature under unlubricated conditions. Microstructural characterizations were done by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). It was found that continuous recrystallization resulted in microstructure covered with

  4. An alternative way to orient the parent phase in the cubic/orthorhombic martensitic transformation of titanium shape memory alloys

    E-print Network

    Paris-Sud XI, Université de

    transformation of titanium shape memory alloys Emmanuel Bertrand1, *, Philippe Castany2 , Thierry Gloriant2 1 is however specific to the cubic/orthorhombic martensitic transformation in titanium shape memory alloys. Keywords: EBSD; Phase reconstruction; Titanium; Shape memory alloys Electron BackScattered Diffraction

  5. Microstructural imaging techniques: a comparison between light and scanning electron microscopy

    Microsoft Academic Search

    Patrick W Trimby; David J Prior

    1999-01-01

    Both light microscopy and scanning electron microscopy are commonly used in microstructural studies of geological specimens. This contribution uses polished thin sections to analyse the same areas in two specimens using both microscopy techniques. The images from a quartz mylonite and a granodiorite are compared to quantitative crystallographic data obtained using electron backscatter diffraction (EBSD). The results indicate that light

  6. Lead foil in dental X-ray film: Backscattering rejection or image intensifier?

    NASA Astrophysics Data System (ADS)

    Hönnicke, M. G.; Delben, G. J.; Godoi, W. C.; Swinka-Filho, V.

    2014-11-01

    Dental X-ray films are still largely used due to sterilization issues, simplicity and, mainly, economic reasons. These films almost always are double coated (double emulsion) and have a lead foil in contact with the film for X-ray backscattering rejection. Herein we explore the use of the lead foil as an image intensifier. In these studies, spatial resolution was investigated when images were acquired on the dental X-ray films with and without the lead foil. Also, the lead foil was subjected to atomic analysis (fluorescent measurements) and structure analysis (X-ray diffraction). We determined that the use of the lead foil reduces the exposure time, however, does not affect the spatial resolution on the acquired images. This suggests that the fluorescent radiation spread is smaller than the grain sizes of the dental X-ray films.

  7. ADCP backscatter measurements in the northeastern Gulf of Mexico: comparison of near-surface with near-bottom biological backscatter

    E-print Network

    Sindlinger, Laurie R

    2003-01-01

    In the Gulf of Mexico, acoustic backscatter intensity (ABI) from an acoustic Doppler current profiler (ADCP) can be a proxy for zooplankton and micronekton biomass, and sperm whale abundance is correlated with regions of locally high ABI...

  8. Evaluation of the impact of backscatter intensity variations on ultrasound attenuation estimation

    PubMed Central

    Omari, Eenas A; Varghese, Tomy; Madsen, Ernest L.; Frank, Gary

    2013-01-01

    Purpose: Quantitative ultrasound based approaches such as attenuation slope estimation can be used to determine underlying tissue properties and eventually used as a supplemental diagnostic technique to B-mode imaging. The authors investigate the impact of backscatter intensity and frequency dependence variations on the attenuation slope estimation accuracy. Methods: The authors compare three frequency domain based attenuation slope estimation algorithms, namely, a spectral difference method, the reference phantom method, and two spectral shift methods: a hybrid method and centroid downshift method. Both the reference phantom and hybrid method use a tissue-mimicking phantom with well-defined acoustic properties to reduce system dependencies and diffraction effects. The normalized power spectral ratio obtained is then filtered by a Gaussian filter centered at the transmit center frequency in the hybrid method. A spectral shift method is then used to estimate the attenuation coefficient from the normalized and filtered spectrum. The centroid downshift method utilizes the shift in power spectrum toward lower frequencies with depth. Numerical phantoms that incorporate variations in the backscatter intensity from ?3 to 3 dB, by varying the scatterer number density and variations in the scatterer diameters ranging from 10 to 100 ?m are simulated. Experimental tissue mimicking phantoms with three different scatterer diameter ranges (5–40, 75–90, and 125–150 ?m) are also used to evaluate the accuracy of the estimation methods. Results: The reference phantom method provided accurate results when the acoustical properties of the reference and the sample are well matched. Underestimation occurs when the reference phantom possessed a higher sound speed than the sample, and overestimation occurs when the reference phantom had a lower sound speed than the sample. The centroid downshift method depends significantly on the bandwidth of the power spectrum, which in turn depends on the frequency dependence of the backscattering. The hybrid method was the least susceptible to changes in the sample's acoustic properties and provided the lowest standard deviation in the numerical simulations and experimental evaluations. Conclusions: No significant variations in the estimation accuracy of the attenuation coefficient were observed with an increase in the scatterer number density in the simulated numerical phantoms for the three methods. Changes in the scatterer diameters, which result in different frequency dependence of backscatter, do not significantly affect attenuation slope estimation with the reference phantom and hybrid approaches. The centroid method is sensitive to variations in the scatterer diameter due to the frequency shift introduced in the power spectrum. PMID:23927359

  9. Microwave backscattering from surf zone waves

    NASA Astrophysics Data System (ADS)

    Catalán, Patricio A.; Haller, Merrick C.; Plant, William J.

    2014-05-01

    The microwave backscatter properties of surf zone waves are analyzed using field observations. By utilizing a preexisting, independent, water surface discrimination technique, the microwave returns were extracted along individual waveforms and the data from shoaling (steepening) waves, surf zone breaking waves, and remnant foam were separated and quantified. In addition, a wave tracking analysis technique allows the returns to be examined on a wave-by-wave basis as individual waves progress through the shoaling zone and break on a nearshore sand bar. Normalized radar cross sections (NRCS), polarization ratios, Doppler spectra, and scatterer velocities were collected using a dual-polarized, X-band radar operating at lower grazing angles than previously reported (1°-3.5°). The results indicate that the maximum NRCS levels are from the active breaking portions of the wave and were consistently about -20 dB, regardless of radar polarization, azimuth angle, wave height, or wind speed. In addition, breaking waves induce broadening of the Doppler spectra and mean scatterer velocities that correlate well with the carrier wave celerity. Analysis of the polarization ratios suggest that the active breaking portions of the wave are depolarized but that higher polarization ratios (>0 dB) are found on the leading edges shoreward of the active breaking portions of the waves, which indicates a clear distinction between two scattering regimes. These results are consistent with scattering from a very rough surface that is being mechanically generated by the breaking process, showing a good agreement with the expected grazing angle dependency of a Lambertian scatterer.

  10. X-Ray Diffraction

    NSDL National Science Digital Library

    Matter.org

    This site from the University of London presents a tutorial on several methods of X-ray diffraction, including the powder, rotating crystal, and Laue methods Each section includes interactive Java applets, exercises, and links to a glossary of terms.

  11. Biopolymer holographic diffraction gratings

    Microsoft Academic Search

    Svetlana Savi? Ševi?; Dejan Pantelic

    2008-01-01

    Surface-relief diffraction gratings are holographically recorded in dextran sensitized with ammonium dichromate (DCD). DCD was exposed with single-frequency 200mW diode pumped ND-YAG laser, at 532nm. The diffraction grating profiles were analyzed by atomic force microscopy (AFM). It was found that different surface profiles could be obtained. Gratings with 330lines\\/mm spatial frequencies were made. Existence of higher harmonics in Fourier Transform

  12. Diffraction and holography of photoelectrons and fluorescent x-rays

    SciTech Connect

    Fadley, C.S. [Lawrence Berkeley Lab., CA (United States)]|[California Univ., Davis, CA (United States). Dept. of Physics

    1993-04-01

    Photoelectron diffraction is by now a powerful technique for studying surface structures, with special capabilities for resolving chemical and magnetic states of atoms and deriving direct structural information from both forward scattering and backscattering. Fitting experiment to theory can lead to structural accuracies in the 0.03 {Angstrom} range. Holographic inversions of such diffraction data also show considerable promise for deriving local three-dimensional structures around a given emitter with accuracies of 0.2--0.3 {Angstrom}. Resolving the photoelectron spin in some way and using circularly polarized radiation for excitation provide added dimensions for the study of magnetic systems and chiral experimental geometries. Synchrotron radiation with the highest brightness and energy resolution, as well as variable polarization, is crucial to the full exploitation of these techniques. X-ray fluorescence holography also has promise for structural studies, but will require intense excitation sources and multichannel detection to be feasible.

  13. SEM/EDS/EBSD study of the behaviour of Ge, Mo and Al impurities in complex-doped crystals of higher manganese silicide

    NASA Astrophysics Data System (ADS)

    Orekhov, A. S.; Solomkin, F. Y.

    2013-11-01

    The structure of Al, Ge, Mo doped higher manganese silicides (HMS) grown by the Bridgman technique has been studied by SEM/EDS/EBSD methods. It is shown that dopants are partially integrated into the HMS crystal lattice. Some inclusions with sizes of 0.1-100 ?m and different shapes (round, irregular, elongated) are formed. The precipitation of tetragonal MoSi2 and Si-Ge solid-solution has been observed. MoSi2 inclusions hundreds of microns in size form a multicomponent texture. The inclusions of Si-Ge solid solution have an irregular shape. The orientation relationship between these inclusions and matrix crystal is determined.

  14. Angularly sensitive detector for transmission Kikuchi diffraction in a scanning electron microscope

    NASA Astrophysics Data System (ADS)

    Jacobson, Bryce T.; Gavryushkin, Dmitriy; Harrison, Mark; Woods, Kaley

    2015-03-01

    We present the design and demonstration of a unique and novel detector for electron microscopy based on microelectromechanical systems (MEMS) technology. The detector is optimized for transmission electron backscatter diffraction, or more specifically for transmission Kikuchi diffraction, and will allow this new analytic tool to realize its full potential. In addition, this single detector is capable of simultaneous acquisition of bright field and dark field images in scanning electron microscopy and transmission electron microscopy and may replace a number of the single-purpose detectors presently used in these devices.

  15. Diffractive control of femtosecond pulses

    Microsoft Academic Search

    O. Mendoza-Yero; G. Minguez-Vega; E. Tajahuerce; J. Lancis; C. Romero; B. Alonso; R. Borrego-Varillas; O. Varela; V. Loriot; R. de Nalda; L. Ban?ares; L. Roso

    2010-01-01

    We make a review of our main results in the field of femtosecond pulses diffracted by diffractive optical elements (DOEs). These results show how amplitude and\\/or phase DOEs can be used to change the spectral and temporal characteristics of the diffracted pulses. We experimentally demonstrate that shaped pulses diffracted by DOEs are useful in nonlinear optics or chemical applications.

  16. Calculations of radar backscattering coefficient of vegetation-covered soils

    NASA Technical Reports Server (NTRS)

    Mo, T.; Schmugge, T. J.; Jackson, T. J. (principal investigators)

    1983-01-01

    A model for simulating the measured backscattering coefficient of vegetation-covered soil surfaces includes both coherent and incoherent components of the backscattered radar pulses from a rough sil surface. The effect of vegetation canopy scattering is also incorporated into the model by making the radar pulse subject to two-way attenuation and volume scattering when it passes through the vegetation layer. Model results agree well with the measured angular distributions of the radar backscattering coefficient for HH polarization at the 1.6 GHz and 4.75 GHz frequencies over grass-covered fields. It was found that the coherent scattering component is very important at angles near nadir, while the vegetation volume scattering is dominant at incident angles 30 degrees.

  17. Mean atomic number quantitative assessment in backscattered electron imaging.

    PubMed

    Sánchez, E; Torres Deluigi, M; Castellano, G

    2012-12-01

    A method for obtaining quantitative mean atomic number images in a scanning electron microscope for different kinds of samples has been developed. The backscattered electron signal is monotonically increasing with the mean atomic number Z, and accordingly Z can be given as a function of the image gray levels. From results obtained from Monte Carlo simulations, an exponential function is fitted to convert the backscattered registered gray levels into a Z image map. Once this fitting was performed, the reproducibility of the Z determination was checked through the acquisition of backscattered electron images from metal and mineral standards. The developed method can be applied to any unknown sample, always controlling the experimental conditions, as shown here for a thin section of a rock in which several unknown mineral phases are present; the results obtained herein are compared to quantitative assessments performed with X-ray spectra from each mineral phase. PMID:23164359

  18. Effect of Backscattered Electrons on Electron Beam Focus

    SciTech Connect

    Falabella, S; Chen, Y-J; Houck, T; McCarrick, J; Sampayan, S; Weir, J

    2000-08-10

    Using an induction linac, ETA-II, we are studying the interaction of a 2 kA, 6 MeV electron beam focused to a <2 mm diameter spot on high-Z foils. A focus shift was noticed when changing from 5 mil to 40 mil tantalum foil targets. This shift was subsequently attributed to the effect of a substantial fraction of the incident electron beam backscattering from the target, reducing the net beam current. This fraction varies with the thickness and density of the target. The presence and magnitude of the backscattered component was confirmed using Faraday cup collectors and beam current monitors. Calculations confirm the magnitude of the focus shift is consistent with the observed backscattered fraction.

  19. Adaptive focus for deep tissue using diffuse backscatter

    NASA Astrophysics Data System (ADS)

    Kress, Jeremy; Pourrezaei, Kambiz

    2014-02-01

    A system integrating high density diffuse optical imaging with adaptive optics using MEMS for deep tissue interaction is presented. In this system, a laser source is scanned over a high density fiber bundle using Digital Micromirror Device (DMD) and channeled to a tissue phantom. Backscatter is then collected from the tissue phantom by a high density fiber array of different fiber type and channeled to CMOS sensor for image acquisition. Intensity focus is directly verified using a second CMOS sensor which measures intensity transmitted though the tissue phantom. A set of training patterns are displayed on the DMD and backscatter is numerically fit to the transmission intensity. After the training patterns are displayed, adaptive focus is performed using only the backscatter and fitting functions. Additionally, tissue reconstruction and prediction of interference focusing by photoacoustic and optical tomographic methods is discussed. Finally, potential NIR applications such as in-vivo adaptive neural photostimulation and cancer targeting are discussed.

  20. Bruce Thompson: Adventures and advances in ultrasonic backscatter

    NASA Astrophysics Data System (ADS)

    Margetan, Frank J.

    2012-05-01

    Over the course of his professional career Dr. R. Bruce Thompson published several hundred articles on non-destructive evaluation, the majority dealing with topics in ultrasonics. One longtime research interest of Dr. Thompson, with applications both to microstructure characterization and defect detection, was backscattered grain noise in metals. Over a 20 year period he led a revolving team of staff members and graduate students investigating various aspects of ultrasonic backscatter. As a member of that team I had the privilege of working along side Dr. Thompson for many years, serving as a sort of Dr. Watson to Bruce's Sherlock Holmes. This article discusses Dr. Thompson's general approaches to modeling backscatter, the research topics he chose to explore to systematically elucidate a better understanding of the phenomena, and the many contributions to the field achieved under his leadership. The backscatter work began in earnest around 1990, motivated by a need to improve inspections of aircraft engine components. At that time Dr. Thompson launched two research efforts. The first led to the heuristic Independent Scatterer Model which could be used to estimate the average grain noise level that would be seen in any given ultrasonic inspection. There the contribution from the microstructure was contained in a measureable parameter known as the Figure-of-Merit or FOM. The second research effort, spearheaded by Dr. Jim Rose, led to a formal relationship between FOM and details of the metal microstructure. The combination of the Independent Scattering Model and Rose's formalism provided a powerful tool for investigating backscatter in metals. In this article model developments are briefly reviewed and several illustrative applications are discussed. These include: the determination of grain size and shape from ultrasonic backscatter; grain noise variability in engine-titanium billets and forgings; and the design of ultrasonic inspection systems to improve defect-signal-to-grain-noise ratios.

  1. Biopolymer holographic diffraction gratings

    NASA Astrophysics Data System (ADS)

    Savi? Ševi?, Svetlana; Panteli?, Dejan

    2008-03-01

    Surface-relief diffraction gratings are holographically recorded in dextran sensitized with ammonium dichromate (DCD). DCD was exposed with single-frequency 200 mW diode pumped ND-YAG laser, at 532 nm. The diffraction grating profiles were analyzed by atomic force microscopy (AFM). It was found that different surface profiles could be obtained. Gratings with 330 lines/mm spatial frequencies were made. Existence of higher harmonics in Fourier Transform of non-sinusoidal profiles shows that DCD is capable of recording spatial frequencies up to 1320 lines/mm (four times fundamental frequency). The measured maximum relief depth of the DCD grating is 402 nm.

  2. Diffractive Interaction of Neutrinos

    NASA Astrophysics Data System (ADS)

    Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Iván; Siddikov, M.

    2013-06-01

    Interactions of high-energy neutrinos expose hadronic properties, in particular, contain a strong diffractive channel. The Adler relation (AR) between soft interactions of neutrinos and pions, might look as a manifestation of pion dominance. However, neutrinos cannot fluctuate to pions because of conservation of the lepton current, and interact via much heavier hadronic components. This fact leads to nontrivial relations between interactions of different hadronic species, in particular, it links diagonal and off-diagonal diffractive interactions of pions. Absorptive corrections break these relations making the AR impossible to hold universally, for any target and at any energy.

  3. Floc Growth and Changes in ADV Acoustic Backscatter Signal

    NASA Astrophysics Data System (ADS)

    Rouhnia, M.; Keyvani, A.; Strom, K.

    2013-12-01

    A series of experiments were conducted to examine the effect of mud floc growth on the acoustic back-scatter signal recorded by a Nortek Vector acoustic Doppler velocimeter (ADV). Several studies have shown that calibration equations can be developed to link the backscatter strength with average suspended sediment concentration (SSC) when the sediment particle size distribution remains constant. However, when mud is present, the process of flocculation can alter the suspended particle size distribution. Past studies have shown that it is still unclear as to the degree of dependence of the calibration equation on changes in floc size. Part of the ambiguity lies in the fact that flocs can be porous and rather loosely packed and therefore might not scatter to the same extent as a grain of sand. In addition, direct, detailed measurements of floc size have not accompanied experiments examining the dependence of ADV backscatter and suspended sediment concentration. In this research, a set of laboratory experiments is used to test how floc growth affects the backscatter strength. The laboratory data is examined in light of an analytic model that was developed based on scatter theory to account for changes in both SSC and the floc properties of size and density. For the experiments, a turbulent suspension was created in a tank with a rotating paddle. Fixed concentrations of a mixture of kaolinite and montmorillonite were added to the tank in a step-wise manner. For each step, the flocs were allowed to grow to their equilibrium size before breaking the flocs with high turbulent mixing, adding more sediment, and then returning the mixing rate to a range suitable for the re-growth of flocs. During each floc growth phase, data was simultaneously collected at the same elevation in the tank using a floc camera to capture the changes in floc size, a Nortek Vector ADV for the acoustic backscatter, and a Campbell Scientific OBS 3+ for optical backscatter. Physical samples of the suspension were also drawn at the same elevation at discrete time intervals throughout the experiments to allow for SSC measurements by filtering and weighing. The floc camera is capable of measuring flocs in the 10 to 2000 ?m range and can report floc size distributions at 1 min intervals. Results showed that floc growth does alter the ADV backscatter signal, even for the rather 'fluffy' flocs formed in the experiment. The strength of the impact though is less than that predicted for solid particles of densities similar to those of the flocs. The overall behavior of the acoustic backscatter time series in each step of the floc growth experiment could be reasonably predicted with the developed model.

  4. A Parametric Study of Tillage Effects on Radar Backscatter

    NASA Technical Reports Server (NTRS)

    Fenner, R. G.; Pels, G. F.; Reid, S. C. (principal investigators)

    1980-01-01

    Radar backscatter data for different field configurations and modulation function curves for angular and frequency variations are presented. A simplistic approach to modeling this effect is presented. It is concluded that: (1) row direction is a significant contributor to radar backscatter from cropland and must be considered when making radar measurements over bare or sparsely vegetated fields; (2) while the effect decrease with increasing frequency, it is still large (5 dB) at 13.3 GHz; (3) row effects are independent of linear polarization; (4) there is a strong aspect angle sensitivity which is a function of the scene and radar system parameters.

  5. Carbon dioxide laser backscatter signatures from laboratory-generated dust

    NASA Astrophysics Data System (ADS)

    Walter, D. P.; Cooper, D. E.; van der Laan, J. E.; Murray, E. R.

    1986-08-01

    A dual CO2 laser system was used to measure aerosol backscatter spectral signatures from dust minerals (kaolin, illite, montmorillonite, colemanite, and limestone) as well as from a soil sample from Dugway Proving Ground, UT. Complex refractive indices measured from bulk samples of the materials, and particle size distributions measured with a cascade impactor, were used to compute theoretical backscatter spectra using Mie theory. The measured signatures agreed well with calculated signatures for most minerals and the soil sample. The experiment demonstrated the feasibility of detecting the compositional elements of dust using a CO2 laser-based system.

  6. X-ray backscatter imaging for aerospace applications

    SciTech Connect

    Shedlock, Daniel [Nucsafe, Inc., 601 Oak Ridge Turnpike, Oak Ridge, TN 37830 (United States); Edwards, Talion [Boeing Research and Technology, 5775 Campus Parkway, Hazelwood, MO 63042 (United States); Toh, Chin [Boeing Research and Technology, 2201 Seal Beach Blvd, Seal Beach, CA 90740 (United States)

    2011-06-23

    Scatter x-ray imaging (SXI) is a real time, digital, x-ray backscatter imaging technique that allows radiographs to be taken from one side of an object. This x-ray backscatter imaging technique offers many advantages over conventional transmission radiography that include single-sided access and extremely low radiation fields compared to conventional open source industrial radiography. Examples of some applications include the detection of corrosion, foreign object debris, water intrusion, cracking, impact damage and leak detection in a variety of material such as aluminum, composites, honeycomb structures, and titanium.

  7. Coherent Effects in Microwave Backscattering Models for Forest Canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan; McDonald, Kyle

    1995-01-01

    In modeling forest canopies, several scattering mechanisms are taken into account: 1) volume scattering, 2) surface-volume interaction, and 3) surface scattering from forest floor. Depending on the structural and dielectric characteristics of forest canopies, the relative contribution of each mechanism in the total backscatter signal of an imaging radar can vary. In this paper, two commonly used first order discrete scattering models, Distorted Born Approximation (DBA) and Radiative Transfer (RT) are used to simulate the backscattered power received by polarimetric radars at P-, L-, and C-bands over coniferous and deciduous forests. The difference between the two models resides on the coherent effect in the surface-volume interaction terms.

  8. Tropospheric aerosol backscatter background mode at CO2 wavelengths

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Bowdle, David A.; Menzies, Robert T.; Post, Madison J.; Vaughan, J. Michael

    1989-01-01

    A comparison is made between three climatologies of backscatter measurements in the troposphere and lower stratosphere at CO2 wavelengths. These were obtained from several locations using ground-based and airborne lidar systems. All three measurement sets show similar features, specifically, a high frequency of occurrence of low backscatter over a limited range of values in the middle and upper atmosphere (the 'background mode'). This background mode is important for the design and performance simulation of the prospective satellite sensors that rely on atmospheric aerosols as scattering targets.

  9. Effect of curvature on the backscattering from leaves

    NASA Technical Reports Server (NTRS)

    Sarabandi, K.; Senior, T. B. A.; Ulaby, F. T.

    1988-01-01

    Using a model previously developed for the backscattering cross section of a planar leaf at X-band frequencies and above, the effect of leaf curvature is examined. For normal incidence on a rectangular section of a leaf curved in one and two dimensions, an integral expression for the backscattered field is evaluated numerically and by a stationary phase approximation, leading to a simple analytical expression for the cross section reduction produced by the curvature. Numerical results based on the two methods are virtually identical, and in excellent agreement with measured data for rectangular sections of coleus leaves applied to the surfaces of styrofoam cylinders and spheres of different radii.

  10. Effect of curvature on the backscattering from a leaf

    NASA Technical Reports Server (NTRS)

    Sarabandi, K.; Senior, T. B. A.; Ulaby, F. T.

    1988-01-01

    Using a model previously developed for the backscattering cross section of a planar leaf at X-band frequencies and above, the effect of leaf curvature is examined. For normal incidence on a rectangular section of a leaf curved in one and two dimensions, an integral expression for the backscattered field is evaluated numerically and by a stationary phase approximation, leading to a simple analytical expression for the cross-section reduction produced by the curvature. Numerical results based on the two methods are virtually identical, and in excellent agreement with measured data for rectangular sections of coleus leaves applied to the surfaces of styrofoam cylinders and spheres of different radii.

  11. Depth from diffracted rotation

    Microsoft Academic Search

    Adam Greengard; Yoav Y. Schechner; Rafael Piestun

    2006-01-01

    The accuracy of depth estimation based on defocus effects has been essentially limited by the depth of field of the imaging system. We show that depth estimation can be improved significantly relative to classical methods by exploiting three-dimensional diffraction effects. We formulate the problem by using information theory analysis and present, to the best of our knowledge, a new paradigm

  12. Calculation of the effects of ice on the backscatter of a ground plane

    NASA Technical Reports Server (NTRS)

    Lambert, K. M.; Peters, L., Jr.

    1988-01-01

    Described is a technique for examining the effect of a rough ice layer on the backscatter of a ground plane. The technique is applied to the special case of a rough ice layer that is periodic in space. By assuming that the roughness is periodic, the backscatter of the ground plane can be found from the backscatter of a single period. Backscatter calculations are presented for a single period in which the thickness of the ice layer has a Gaussian shape.

  13. A method for determining cirrus cloud particle sizes using lidar and radar backscatter technique

    Microsoft Academic Search

    Janet M. Intrieri; Graeme L. Stephens; Wynn L. Eberhard; Taneil Uttal

    1993-01-01

    A method to determine cirrus cloud effective radii remotely using lidar and radar backscatter data is presented. The difference in backscattered returns from instruments widely separated in wavelength holds information on the characteristic sizes of the scatters. The method compares theoretically expected backscatter coefficients to observed backscatter returns from NOAA's 3.2-cm and 8.6-mm radars and the 10.6-[mu]m lidar. Measurements were

  14. N-point processing of optical fibre backscatter signals

    Microsoft Academic Search

    R. D. Jeffery; J. L. Hullett

    1980-01-01

    N-point processing, where many samples are taken from a single optical fibre backscatter return, is shown to be an efficient means of implementing a two-point processor. This method is unaffected by source noise peculiar to single heterostructure lasers, which is shown to limit severely the performance of boxcar integrators.

  15. Helicopter-borne measurements of radar backscatter from forests

    Microsoft Academic Search

    Martti T. Hallikainen; Teemu Tares; Juha Hyyppä; Erkki Somersalo; Pekka Ahola; Martti Toikka; Jouni Pulliainen

    1990-01-01

    Helicopter-borne scatterometer measurements of various forest and surface types were conducted in spring 1988 in Espoo, near Helsinki. The scatterometer operates at 5-4 and 98 GHz and employs four linear polarizations (VV, HH, VH and HV). At each of the eight channels the radar can measure the backscattering properties of a target with a range resolution of 1 metre. The

  16. Thomson backscattered X-rays from an intense laser beam

    Microsoft Academic Search

    Cha-Mei Tang; B. Hafizi; Sally K. Ride

    1993-01-01

    We have formulated and obtained analytical expressions for Thomson backscattered X-ray radiation for an electron beam incident on a linearly polarized electromagnetic undulator at a small angle. The analytical expressions are valid for fundamental and harmonics with arbitrarily large laser intensities. The intensity distribution pattern is evaluated numerically.

  17. A simple backscattering microscope for fast tracking of biological molecules

    Microsoft Academic Search

    Yoshiyuki Sowa; Bradley C. Steel; Richard M. Berry

    2010-01-01

    Recent developments in techniques for observing single molecules under light microscopes have helped reveal the mechanisms by which molecular machines work. A wide range of markers can be used to detect molecules, from single fluorophores to micron sized markers, depending on the research interest. Here, we present a new and simple objective-type backscattering microscope to track gold nanoparticles with nanometer

  18. Inversion of radar backscatter from millimeter wave smoke

    Microsoft Academic Search

    Benjamin Perry; D. J. Hale

    1994-01-01

    This paper describes the results of an analysis of radar backscatter and attenuation data collected during field trials of the MMW Module of the XM56 Large Area Screening Generator. The trials were conducted by Edgewood Research Development and Engineering Center personnel at Dugway Proving Ground in 1989 and 1990, and at Eglin AFB in 1992. The purpose of this analysis

  19. Azimuthal Anisotropy In Radar Backscatter From The Ocean

    NASA Technical Reports Server (NTRS)

    Li, F. K.; Neumann, G.; Shaffer, S. J.; Durden, S. L.

    1991-01-01

    Minima offset from nominal crosswind directions. Report describes experimental and theoretical study of azimuthal anisotropy in radar backscatter from surface of ocean. Important objective of this and related studies to enhance ability to sense speed and direction of surface wind remotely by use of airborne or spaceborne radar.

  20. Ultrasound backscatter microscopy of the eye in vivo

    Microsoft Academic Search

    F. S. Foster; C. J. Pavlin; B. Starkoski; K. Harasiewicz

    1990-01-01

    The construction and early clinical evaluation of the first 50-100-MHz ultrasound backscatter microscope (UBM) are described. This system has a frame rate of five frames per second and examined a field of view of 4 by 4 mm with axial and lateral resolution ranging from 20 to 50 ?m. The critical components of the scanner are described, including the transducer,

  1. Lidar inversion with variable backscatter/extinction ratios Comment

    NASA Astrophysics Data System (ADS)

    Kaestner, M.

    1986-03-01

    An error in Klett's (1985) lidar equation solution is reported and corrected, and the application of a solution of the lidar equation to a satellite lidar system is considered. A discussion is presented on why the extinction coefficient and not the backscatter coefficient should be extracted from the lidar return signals. Finally, a solution for the extinction coefficient due to aerosols is proposed.

  2. Helicity flip of the backscattered circular polarized light

    Microsoft Academic Search

    Vladimir Kuzmin; Igor Meglinski

    2010-01-01

    We study coherent and non-coherent backscattering of circularly polarized light from turbid media. We find that the sign of helicity of circular polarized light does not change for a medium of point-like scatterers and can change significantly for the medium with high anisotropy of scatterers. The helicity flip is observed when the light scattering is described in terms of the

  3. Investigation of sheared liquids by neutron backscattering and reflectivity

    Microsoft Academic Search

    M. Wolff; A. Magerl; R. Hock; B. Frick; H. Zabel

    2002-01-01

    We have investigated by neutron scattering structural and dynamical properties of water solutions of the triblock copolymer P85 under shear. To this end a shear cell that suits the requirements for neutron backscattering and another for reflectivity experiments have been built. In reflectivity measurements we find the polymer concentration (nominal concentration of 33% by weight) to vary right at the

  4. Effect of the stimulated Brillouin backscattering on selffocusing threshold

    SciTech Connect

    Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Shapiro, E.G.; Turitsyn, S.K. [AN SSSR, Novosibirsk (Russian Federation). Inst. Avtomatiki i Ehlektrometrii

    1994-03-01

    In many physical problems stimulated Brillouin scattering (SBS) and selffocusing are manifested simultaneously. We consider effect of the stimulated Brillouin backscattering (SBS) on self-focusing of laser radiation in plasmas. It was found that the self-focusing may be supressed substantionally by the SBS effect.

  5. Full investigation of the backscattering in resonator fiber optic gyro

    NASA Astrophysics Data System (ADS)

    Ma, Huilian; Chang, Xu; Yang, Zhihuai; Jin, Zhonghe

    2011-09-01

    Resonator Fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on the Sagnac effect. The optical fiber ring resonator (OFRR) is the key rotation sensing element. The backscattering characteristics of the OFRR are fully investigated. The Rayleigh backscattering dominates the backscattering spectrum with the input power below the threshold. High carrier suppression is crucial to reduce this Rayleigh backscattering error. Being different from the intrinsic Rayleigh scattering of the fiber, the stimulated Brillouin scattering (SBS) in the OFRR should be avoided. This is because the finesse and the resonance notch depth of the OFRR decrease for the pump depletion through the SBS process. The shot noise limited sensitivity (SLS) of the RFOG is improved by increasing the input power. Through analysis, it is found that the threshold input power is improved after phase modulation. The SLS of the RFOG is analyzed at different modulation parameters and its relevant SBS threshold. Accordingly, the optimized modulation frequency and the corresponding maximum input power are all obtained. A simple method of testing the frequency shift in the SBS is also proposed. In this method, the central frequency of the laser source is locked to the resonance frequency of the OFRR in one direction. A steady SBS light is observed and its frequency shift is measured together.

  6. Backscattered electron imaging of cementitious microstructures: understanding and quantification

    Microsoft Academic Search

    Karen L. Scrivener

    2004-01-01

    During the last 20 years, backscattered electron imaging of polished surfaces has become well established as a method for the study of cement and concrete microstructures. The technique has many advantages, including the visualisation of representative cross-sections over a wide range of magnifications and reproducible contrast dependent on atomic number. Nevertheless the limitations of observing a two-dimensional section of a

  7. Bathymetry and acoustic backscatter: Elwha River Delta, Washington

    USGS Publications Warehouse

    Finlayson, David P.; Miller, Ian M.; Warrick, Jonathan A.

    2011-01-01

    The surveys were conducted using the R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping and real-time kinematic navigation equipment for accurate shallow water operations. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

  8. BLINK: A High Throughput Link Layer for Backscatter Communication

    E-print Network

    Ganesan, Deepak

    BLINK: A High Throughput Link Layer for Backscatter Communication Pengyu Zhang, Jeremy Gummeson for continuous and high-volume sensor data transfer. To address this need, we describe a novel link layer prior specific permission and/or a fee. MobiSys'12, June 25­29, 2012, Low Wood Bay, Lake District, UK

  9. Backscatter gauge description for inspection of neutron absorber content

    NASA Astrophysics Data System (ADS)

    Dewberry, R. A.; Gibbs, K. M.; Couture, A. H.

    2013-05-01

    This paper describes design, calibration, and testing of a dual He-3 detector neutron backscatter gauge for use in the Savannah River Site Mixed Oxide Fuel project. The gauge is demonstrated to measure boron content and uniformity in concrete slabs used in the facility construction.

  10. BACKSCATTER GUAGE DESCRIPTION FOR INSPECTION OF NEUTRON ABSORBER AND UNIFORMITY

    SciTech Connect

    Dewberry, R.; Gibbs, K.; Couture, A.

    2012-05-23

    This paper describes design, calibration, and testing of a dual He-3 detector neutron backscatter gauge for use in the Savannah River Site Mixed Oxide Fuel project. The gauge is demonstrated to measure boron content and uniformity in concrete slabs used in the facility construction.

  11. Rutherford backscattering analysis of gallium implanted 316 stainless steel

    E-print Network

    Ortensi, Javier

    2000-01-01

    Ion implantation of Ga ions into 316 stainless steel was performed at fluences ranging from 8x10¹? to 10¹? ions/cm². The depth profile of Ga in the steel was analyzed via Rutherford Backscattering and ToFSIMS. The surface effects were...

  12. Alpha particle backscattering measurements used for chemical analysis of surfaces

    NASA Technical Reports Server (NTRS)

    Patterson, J. H.

    1967-01-01

    Alpha particle backscattering performs a chemical analysis of surfaces. The apparatus uses a curium source and a semiconductor detector to determine the energy spectrum of the particles. This in turn determines the chemical composition of the surface after calibration to known samples.

  13. Radar Backscatter Across the Gulf Stream Sea Surface Temperature Front

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Li, F. K.; Walsh, E. J.; Lou, S. H.

    1998-01-01

    Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.

  14. Improvement of sensitivity in high-resolution Rutherford backscattering spectroscopy

    Microsoft Academic Search

    H. Hashimoto; K. Nakajima; M. Suzuki; K. Sasakawa; K. Kimura

    2011-01-01

    The sensitivity (limit of detection) of high-resolution Rutherford backscattering spectroscopy (HRBS) is mainly determined by the background noise of the spectrometer. There are two major origins of the background noise in HRBS, one is the stray ions scattered from the inner wall of the vacuum chamber of the spectrometer and the other is the dark noise of the microchannel plate

  15. Experimental confirmation at visible light wavelengths of the backscattering enhancement

    E-print Network

    Ottino, Julio M.

    radiative emission," ACS Nano 4(6), 3390­3396 (2010). 7. Z. Wang, W. Guo, L. Li, B. Luk'yanchuk, A. Khan, Z, "Direct observation of photonic jets and corresponding backscattering enhancement at microwave frequencies EXPRESS 7084 #12;12. S.-C. Kong, A. V. Sahakian, A. Heifetz, A. Taflove, and V. Backman, "Robust detection

  16. Relationship Between Wind Stress, Backscatter, Directional Wave Spectrum (NORCSEX-88)

    Microsoft Academic Search

    K. L. Davidson; C. E. Skupniewicz; R. G. Onstott

    1991-01-01

    Results are presented from a data set consisting of shipboard obtained descriptions and of the surface wind stress, U* , normalized radar backscatter, U', and moored buoy obtained descriptions of surface wave at low and high wave numbers. These were acquired off the west coast of Norway during the NORCSEX ERS-1 pre-launch experiment in March 1988. Comparisons of variations in

  17. Simulation of Neutron Backscattering applied to organic material detection

    SciTech Connect

    Forero, N. C.; Cruz, A. H.; Cristancho, F. [Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); Centro Internacional de Fisica, Apartado Aereo 4948, Bogota (Colombia)

    2007-10-26

    The Neutron Backscattering technique is tested when performing the task of localizing hydrogenated explosives hidden in soil. Detector system, landmine, soil and neutron source are simulated with Geant4 in order to obtain the number of neutrons detected when several parameters like mine composition, relative position mine-source and soil moisture are varied.0.

  18. Rutherford backscattering oscillation in scanning helium-ion microscopy

    SciTech Connect

    Kostinski, Sarah; Yao, Nan [Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544 (United States)

    2011-03-15

    Scanning helium-ion microscopy (SHIM) yields high-resolution imaging and is capable of surface elemental analysis at the nanometer scale. Here we examine recently discovered SHIM backscattered intensity oscillations versus the target atomic number. These oscillations are contrary to the expected monotonic increase of the backscattered helium-ion (He{sup +}) rate with the atomic number of elemental samples. We explore the ion-sample interaction via numerical simulations for a variety of scattering geometries and confirm the presence of oscillations. The oscillations are attributed to the atomic rather than the nuclear structure of the target. To that end, we study the link (near anticorrelation) between backscatter rate and He{sup +} beam stopping power, both versus the target atomic number. This leads us to ascribe the origin of the backscatter oscillation to the ''Z{sub 2}-oscillations'' of the stopping power in ion-beam physics, with the latter being rooted in the valence electron configuration of elemental targets.

  19. Monte Carlo simulation of backscatter from lead for clinical electron beams using EGSnrc

    Microsoft Academic Search

    Grigor N. Grigorov; James C. L. Chow

    2008-01-01

    In electron radiotherapy of superficial lesions in the eyelid, lip, buccal mucosa, ear, and nose, backscattered electrons are produced from the lead shield used to protect the critical tissue underneath the tumor. In this study, the backscattered electrons, produced by clinical electron beams using a Varian 21 EX linear accelerator, were studied using Monte Carlo simulations. The electron backscatter factor

  20. Multiwavelength Comparison of Modeled and Measured Remote Tropospheric Aerosol Backscatter Over Pacific Ocean

    NASA Technical Reports Server (NTRS)

    Cutten, D. R.; Pueschel, R. F.; Srivastava, V.; Clarke, A. D.; Rothermel, J.; Spinhirne, J. D.; Menzies, R. T.

    1996-01-01

    Aerosol concentrations and size distributions in the middle and upper troposphere over the remote Pacific Ocean were measured with a forward scattering spectrometer probe (FSSP) on the NASA DC-8 aircraft during NASA's Global Backscatter Experiment (GLOBE) in May-June 1990. The FSSP size channels were recalibrated based on refractive index estimates from flight-level aerosol volatility measurements with a collocated laser optical particle counter (LOPC). The recalibrated FSSP size distributions were averaged over 100-s intervals, fitted with lo-normal distributions and used to calculate aerosol backscatter coefficients at selected wavelengths. The FSSP-derived backscatter estimates were averaged over 300-s intervals to reduce large random fluctuations. The smoothed FSSP aerosol backscatter coefficients were then compared with LOPC-derived backscatter values and with backscatter measured at or near flight level from four lidar systems operating at 0.53, 1.06, 9.11, 9.25, and 10.59 micrometers. Agreement between FSSP-derived and lidar-measured backscatter was generally best at flight level in homogeneous aerosol fields and at high backscatter values. FSSP data often underestimated low backscatter values especially at the longer wavelengths due to poor counting statistics for larger particles (greater than 0.8 micrometers diameter) that usually dominate aerosol backscatter at these wavelengths. FSSP data also underestimated backscatter at shorter wavelengths when particles smaller than the FSSP lower cutoff diameter (0.35 micrometers) made significant contributions to the total backscatter.

  1. Estimating Surface Oil Extent from the Deepwater Horizon Oil Spill using ASCAT Backscatter

    E-print Network

    Long, David G.

    Estimating Surface Oil Extent from the Deepwater Horizon Oil Spill using ASCAT Backscatter Richard backscatter and observed backscatter indicate areas of the ocean surface affected by oil. The recent oil spill to estimate the spatial extent of surface oil. I. INTRODUCTION The oil spill from the Deepwater Horizon oil

  2. Geological interpretation of a low-backscatter anomaly found on the New Jersey continental margin

    E-print Network

    New Hampshire, University of

    Geological interpretation of a low-backscatter anomaly found on the New Jersey continental margin.J.W. Piper Keywords: U.S. mid-Atlantic continental margin continental slope multibeam backscatter submarine canyons Western Boundary Undercurrent Chesapeake Drift An enigmatic low-backscatter, acoustic anomaly

  3. A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora

    E-print Network

    Paris-Sud XI, Université de

    appreciable HF coherent backscatter, and are only identi®able in the backscatter data as a modi., 1995) are designed to employ backscatter from high- latitude ®eld-aligned ionospheric plasma density observations is of interest, not only as a multi-instrument investigation of large-scale geophysical processes

  4. Automated Textural Image Analysis of Seabed Backscatter Mosaics: A Comparison of Four Methods

    E-print Network

    Müller, Dietmar

    43 Automated Textural Image Analysis of Seabed Backscatter Mosaics: A Comparison of Four Methods *R., and Hughes, M., 2007, Automated textural image analysis of seabed backscatter mosaics: A comparison of four: Geological Association of Canada, Special Paper 47, p. ??-??. Abstract Four seabed backscatter image

  5. Diffraction Studies of Multiferroics

    NASA Astrophysics Data System (ADS)

    Johnson, Roger D.; Radaelli, Paolo G.

    2014-07-01

    In multiferroics, magnetism is coupled to ferroelectricity so that the configuration of magnetic moments may be modified by an external electric field and, conversely, the electrically polar state may be magnetically switched. Such functionality has the potential for new technology such as energy-efficient, electrically written magnetic memories. Furthermore, multiferroics are of interest in fundamental research into quantum matter. Understanding the interplay between magnetism and ferroelectricity has posed a significant challenge to the scientific community. State-of-the-art diffraction experiments have played a unique role, as they are sensitive to both magnetic ordering and the atomic displacements associated with ferroelectricity. Exceptional insights have been gained from neutron polarimetry techniques complemented by X-ray magnetic scattering experiments, which, for the first time, have been applied to a large selection of related materials and problems. In this review, we discuss a broad selection of multiferroics and the diffraction experiments used to explain their phenomenology.

  6. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  7. Diffraction before destruction.

    PubMed

    Chapman, Henry N; Caleman, Carl; Timneanu, Nicusor

    2014-07-17

    X-ray free-electron lasers have opened up the possibility of structure determination of protein crystals at room temperature, free of radiation damage. The femtosecond-duration pulses of these sources enable diffraction signals to be collected from samples at doses of 1000 MGy or higher. The sample is vaporized by the intense pulse, but not before the scattering that gives rise to the diffraction pattern takes place. Consequently, only a single flash diffraction pattern can be recorded from a crystal, giving rise to the method of serial crystallography where tens of thousands of patterns are collected from individual crystals that flow across the beam and the patterns are indexed and aggregated into a set of structure factors. The high-dose tolerance and the many-crystal averaging approach allow data to be collected from much smaller crystals than have been examined at synchrotron radiation facilities, even from radiation-sensitive samples. Here, we review the interaction of intense femtosecond X-ray pulses with materials and discuss the implications for structure determination. We identify various dose regimes and conclude that the strongest achievable signals for a given sample are attained at the highest possible dose rates, from highest possible pulse intensities. PMID:24914146

  8. Diffraction-Based Optical Switch

    NASA Technical Reports Server (NTRS)

    Sperno, Stevan M. (Inventor); Fuhr, Peter L. (Inventor); Schipper, John F. (Inventor)

    2005-01-01

    Method and system for controllably redirecting a light beam, having a central wavelength lambda, from a first light-receiving site to a second light-receiving site. A diffraction grating is attached to or part of a piezoelectric substrate, which is connected to one or two controllable voltage difference sources. When a substrate voltage difference is changed and the diffraction grating length in each of one or two directions is thereby changed, at least one of the diffraction angle, the diffraction order and the central wavelength is controllably changed. A diffracted light beam component, having a given wavelength, diffraction angle and diffraction order, that is initially received at a first light receiving site (e.g., a detector or optical fiber) is thereby controllably shifted or altered and can be received at a second light receiving site. A polynomially stepped, chirped grating is used in one embodiment. In another embodiment, an incident light beam, having at least one of first and second wavelengths, lambda1 and lambda2, is received and diffracted at a first diffraction grating to provide a first diffracted beam. The first diffracted beam is received and diffracted at a second diffraction grating to produce a second diffracted beam. The second diffracted beam is received at a light-sensitive transducer, having at least first and second spaced apart light detector elements that are positioned so that, when the incident light beam has wavelength lambda1 or lambda2 (lambda1 not equal to lambda2), the second diffracted beam is received at the first element or at the second element, respectively; change in a selected physical parameter at the second grating can also be sensed or measured. A sequence of spaced apart light detector elements can be positioned along a linear or curvilinear segment with equal or unequal spacing.

  9. Spectral diffraction efficiency characterization of broadband diffractive optical elements.

    SciTech Connect

    Choi, Junoh; Cruz-Cabrera, Alvaro Augusto; Tanbakuchi, Anthony

    2013-03-01

    Diffractive optical elements, with their thin profile and unique dispersion properties, have been studied and utilized in a number of optical systems, often yielding smaller and lighter systems. Despite the interest in and study of diffractive elements, the application has been limited to narrow spectral bands. This is due to the etch depths, which are optimized for optical path differences of only a single wavelength, consequently leading to rapid decline in efficiency as the working wavelength shifts away from the design wavelength. Various broadband diffractive design methodologies have recently been developed that improve spectral diffraction efficiency and expand the working bandwidth of diffractive elements. We have developed diffraction efficiency models and utilized the models to design, fabricate, and test two such extended bandwidth diffractive designs.

  10. Comparison of Modeled Backscatter using Measured Aerosol Microphysics with Focused CW Lidar Data over Pacific

    NASA Technical Reports Server (NTRS)

    Srivastava, Vandana; Clarke, Antony D.; Jarzembski, Maurice A.; Rothermel, Jeffry

    1997-01-01

    During NASA's GLObal Backscatter Experiment (GLOBE) II flight mission over the Pacific Ocean in May-June 1990, extensive aerosol backscatter data sets from two continuous wave, focused CO2 Doppler lidars and an aerosol microphysics data set from a laser optical particle counter (LOPC) were obtained. Changes in aerosol loading in various air masses with associated changes in chemical composition, from sulfuric acid and sulfates to dustlike crustal material, significantly affected aerosol backscatter, causing variation of about 3 to 4 orders of magnitude. Some of the significant backscatter features encountered in different air masses were the low backscatter in subtropical air with even lower values in the tropics near the Intertropical Convergence Zone (ITCZ), highly variable backscatter in the ITCZ, mid-tropospheric aerosol backscatter background mode, and high backscatter in an Asian dust plume off the Japanese coast. Differences in aerosol composition and backscatter for northern and southern hemisphere also were observed. Using the LOPC measurements of physical and chemical aerosol properties, we determined the complex refractive index from three different aerosol mixture models to calculate backscatter. These values provided a well-defined envelope of modeled backscatter for various atmospheric conditions, giving good agreement with the lidar data over a horizontal sampling of approximately 18000 km in the mid-troposphere.

  11. Ultrasound Backscattering Is Anisotropic in Bovine Articular Cartilage.

    PubMed

    Inkinen, Satu I; Liukkonen, Jukka; Tiitu, Virpi; Virén, Tuomas; Jurvelin, Jukka S; Töyräs, Juha

    2015-07-01

    Collagen, proteoglycans and chondrocytes can contribute to ultrasound scattering in articular cartilage. However, anisotropy of ultrasound scattering in cartilage is not fully characterized. We investigate this using a clinical intravascular ultrasound device with ultrasound frequencies of 9 and 40 MHz. Osteochondral samples were obtained from intact bovine patellas, and cartilage was imaged in two perpendicular directions: through articular and lateral surfaces. At both frequencies, ultrasound backscattering was higher (p < 0.05) when measured through the lateral surface of cartilage. In addition, the composition and structure of articular cartilage were investigated with multiple reference methods involving light microscopy, digital densitometry, polarized light microscopy and Fourier infrared imaging. Reference methods indicated that acoustic anisotropy of ultrasound scattering arises mainly from non-uniform distribution of chondrocytes and anisotropic orientation of collagen fibers. To conclude, ultrasound backscattering in articular cartilage was found to be anisotropic and dependent on the frequency in use. PMID:25933711

  12. Inelastic electron backscattering in a generic helical edge channel

    NASA Astrophysics Data System (ADS)

    Schmidt, Thomas L.; Rachel, Stephan; von Oppen, Felix; Glazman, Leonid I.

    2012-02-01

    We calculate the low-temperature conductance of a generic one-dimensional helical liquid which exists at the edge of a two-dimensional topological insulator (quantum spin Hall insulator). In a generic case, the Sz spin-symmetry is absent, which opens a possibility of single-particle inelastic electron backscattering. We show that although time-reversal invariance is preserved, inelastic backscattering gives rise to a temperature-dependent deviation from the quantized conductance, ?G T^4. In addition, ?G is sensitive to the position of the Fermi level in the gap of the insulator. We present an effective model for this type of helical liquid and determine its parameters explicitly from numerical solutions of microscopic models for two-dimensional topological insulators in the presence of Rashba spin-orbit coupling.

  13. Transition to turbulence via spatiotemporal intermittency in stimulated Raman backscattering

    SciTech Connect

    Skoric, M.M.; Jovanovic, M.S.; Rajkovic, M.R. [Vinca Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade (Yugoslavia)]|[Department of Physics, University of Nis, P.O. Box 91, 18001 Nis (Yugoslavia)

    1996-04-01

    The spatiotemporal evolution of stimulated Raman backscattering in a bounded, uniform, weakly dissipative plasma is studied. The nonlinear model of a three-wave interaction involves a quadratic coupling of slowly varying complex amplitudes of the laser pump, the backscattered and the electron plasma wave. The corresponding set of coupled partial differential equations with nonlinear phase detuning that is taken into account is solved numerically in space time with fixed nonzero source boundary conditions. The study of the above open, convective, weakly confined system reveals a quasiperiodic transition to spatiotemporal chaos via spatiotemporal intermittency. In the analysis of transitions a dual scheme borrowed from fields of nonlinear dynamics and statistical physics is applied. An introduction of a nonlinear three-wave interaction to a growing family of paradigmatic equations which exhibit a route to turbulence via spatiotemporal intermittency is outlined in this work. {copyright} {ital 1996 The American Physical Society.}

  14. Electron Kinetic Effects on Raman Backscatter in Plasmas

    SciTech Connect

    Hur, M.S.; Suk, H. [Center for Advanced Accelerators, KERI, Changwon, Kyongnam 641-120 (Korea, Republic of); Lindberg, R.R.; Charman, A.E. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Wurtele, J.S. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Center for Beam Physics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2005-09-09

    We augment the usual three-wave cold-fluid equations governing Raman backscatter (RBS) with a new kinetic thermal correction, proportional to an average of particle kinetic energy weighted by the ponderomotive phase. From closed-form analysis within a homogeneous kinetic three-wave model and ponderomotively averaged kinetic simulations in a more realistic pulsed case, the magnitude of these new contributions is shown to be a measure of the dynamical detuning between the pump laser, seed laser, and Langmuir wave. Saturation of RBS is analyzed, and the role of trapped particles illuminated. Simple estimates show that a small fraction of trapped particles ({approx}6%) can significantly suppress backscatter. We discuss the best operating regime of the Raman plasma amplifier to reduce these deleterious kinetic effects.

  15. Beta Ray Backscattering Studies from Multi-Component Systems

    NASA Astrophysics Data System (ADS)

    Singh, M.; Sharama, K. K.

    1984-03-01

    Backscattering of beta rays has been studied from two alloy systems, nine compounds, and four systems of aqueous solutions by using three beta emitters, 147Pm, 204Tl, and 90Sr-90Y in an efficient reflection geometry. It is found that the intensity of backscattered radiation can be expressed in terms of the proportions of the constituents of the multi-component system in each case by using the concepts of effective atomic numbers and atomic weights thus allowing the extension of the ‘Z’ dependence results for thick elemental targets to the case of multi-component systems. The importance of these studies in the analysis of multi-component systems is discussed.

  16. Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California

    USGS Publications Warehouse

    Dartnell, Pete; Finlayson, David; Conrad, Jamie; Cochrane, Guy; Johnson, Samuel

    2010-01-01

    In the summer of 2008, as part of the California Seafloor Mapping Program (CSMP) the U.S. Geological Survey, Coastal and Marine Geology mapped a nearshore region of the northern Santa Barbara Channel in Southern California (fig 1). The CSMP is a cooperative partnership between Federal and State agencies, Universities, and Industry to create a comprehensive coastal/marine geologic and habitat basemap series to support the Marine Life Protection Act (MLPA) inititive. The program is supported by the California Ocean Protection Council and the California Coastal Conservancy. The 2008 mapping collected high resolution bathymetry and acoustic backscatter data using a bathymetric side scan system within State waters from about the 10-m isobath out over 3-nautical miles. This Open-File Report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and FGDC metadata.

  17. Side-looking sonar backscatter response at dual frequencies

    NASA Astrophysics Data System (ADS)

    Ryan, William B. F.; Flood, Roger D.

    1996-12-01

    Dual-frequency side-looking sonars have the potential to be used as remote sensing tools to characterize subaqueous terrains. In one case study of the carbonate-ooze-coated Blake Plateau off-shore of Georgia, U.S.A., the difference in acoustic attenuation for 50 and 20 mm wavelengths (30 and 72 kHz frequency) permits the discrimination of sub-bottom scatterers from seabed surface textural features to reveal patchy regions where a buried hard ground had been pock-marked by karst-like depressions. In a second study of the Upper Hudson River in New York, U.S.A., related to environmental contaminates, the backscatter response at 15 and 3 mm acoustic wavelengths (100 and 500 kHz frequency) serves as a useful proxy for sediment grain size with coarser detritus distinguished from finer sediments. Sand and gravel regions inferred from the backscatter were confirmed by ground truth sampling.

  18. How to suppress the backscattering of conduction electrons?

    NASA Astrophysics Data System (ADS)

    Kibis, O. V.

    2014-09-01

    It is shown theoretically that the strong coupling of electrons to a high-frequency electromagnetic field results in the nulling of electron backscattering within the Born approximation. The conditions of the effect depend only on field parameters and do not depend on the concrete form of the scattering potential. As a consequence, this phenomenon is of universal physical nature and can take place in various conducting systems. Since the suppression of electron backscattering results in decreasing electrical resistance, the solved quantum-mechanical problem opens a new way to control electronic transport properties of conductors by a laser-generated field. Particularly, the elaborated theory is applicable to nanostructures exposed to a strong monochromatic electromagnetic wave.

  19. Airborne backscatter lidar measurements at three wavelengths during ELITE

    NASA Astrophysics Data System (ADS)

    Schreiber, H. G.; Wirth, Martin; Moerl, P.; Renger, Wolfgang

    1995-09-01

    The German Aerospace Establishment (DLR) operates an airborne backscatter lidar based on a Nh:YAG laser which is flashlamp-pumped at 10 Hz. It works on the wavelengths 1064, 532, and 354 nm. It is mounted downward-looking on the research aircraft Falcon 20, flying at about 12 km altitude at speeds of 200 m/s. We present airborne measurements correlated with the orbit tracks of the shuttle-borne LITE-instrument (lidar in-space technology experiment). The emphasis in data evalution is on the comparison between the airborne and the shuttle- borne lidars. First results show excellent agreement between the two instruments even on details of cirrus clouds. The results comprise cloud geometrical and optical depths, as well as profiles of aerosol backscattering coefficients at three wavelengths.

  20. RFID tag modification for full depth backscatter modulation

    DOEpatents

    Scott, Jeffrey Wayne [Pasco, WA; Pratt, Richard M [Richland, WA

    2010-07-20

    A modulated backscatter radio frequency identification device includes a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave; communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal; and circuitry configured to increase impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the reverse bias effects on impedance changes. Methods of improving depth of modulation in a modulated backscatter radio frequency identification device are also provided.

  1. Calculations of radar backscattering coefficient of vegetation-covered soils

    NASA Technical Reports Server (NTRS)

    Mo, T.; Schmugge, T. J.; Jackson, T. J.

    1984-01-01

    The present investigation has the objective to develop a simple 'user's' model for simulating the measured radar backscattering coefficients from vegetation-covered fields in conjunction with the data obtained by Jackson et al. (1980, 1982). The theoretical work reported by Fung and Eom (1981) provides the basis for the model. Certain modifications are related to a consideration of the effect of a vegetation canopy. The first part of the model is concerned with a description of scatter from rough bare soil, while the second part takes into account the effect of a vegetation cover. It is shown that the measured angular distribution of the backscattering coefficient of vegetation-covered fields can be satisfactory reproduced by using the developed model.

  2. Improved inline model for Raman backscatter in HYDRA

    NASA Astrophysics Data System (ADS)

    Marinak, M. M.; Kerbel, G. D.; Michel, P.; Strozzi, D. J.; Sepke, S. M.

    2013-10-01

    Backscatter of laser light due to laser plasma instabilities has a pronounced impact on the flow of energy in a National Ignition Facility (NIF) hohlraum. We have implemented a new inline model for stimulated Raman scattering (SRS) in HYDRA. The model integrates the coupled-mode equations for SRS gain and inverse bremsstrahlung absorption along the rays, including pump depletion and energetic electron production by Langmuir waves. This enables more precise resolution of the spatial variation of the backscattered intensity along the beam path. The SRS escaping power and wavelength are constrained to match the experimentally measured history for each beam cone. Run in conjunction with the inline model for energy transfer between crossed laser beams, the new model enables more accurate treatment of energy and momentum deposition in hohlraum simulations. We examine the impact of the model on an integrated HYDRA simulation of a NIF hohlraum. Backscatter of laser light due to laser plasma instabilities has a pronounced impact on the flow of energy in a National Ignition Facility (NIF) hohlraum. We have implemented a new inline model for stimulated Raman scattering (SRS) in HYDRA. The model integrates the coupled-mode equations for SRS gain and inverse bremsstrahlung absorption along the rays, including pump depletion and energetic electron production by Langmuir waves. This enables more precise resolution of the spatial variation of the backscattered intensity along the beam path. The SRS escaping power and wavelength are constrained to match the experimentally measured history for each beam cone. Run in conjunction with the inline model for energy transfer between crossed laser beams, the new model enables more accurate treatment of energy and momentum deposition in hohlraum simulations. We examine the impact of the model on an integrated HYDRA simulation of a NIF hohlraum. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

  3. Measurement of magnetic field using Rayleigh backscattering in optical fibres

    SciTech Connect

    Wuilpart, M.; Caucheteur, C. [Univ. of Mons, Faculty of Engineeering, Electromagnetism and Telecommunications Dept., 31, Boulevard Dolez, 7000 Mons (Belgium); Goussarov, A. [SCK.CEN, 200 Boerentang, 2400 Mol (Belgium); Aerssens, M. [Univ. of Mons, Faculty of Engineeering, Electromagnetism and Telecommunications Dept., 31, Boulevard Dolez, 7000 Mons (Belgium); Massaut, V. [SCK.CEN, 200 Boerentang, 2400 Mol (Belgium); Megret, P. [Univ. of Mons, Faculty of Engineeering, Electromagnetism and Telecommunications Dept., 31, Boulevard Dolez, 7000 Mons (Belgium)

    2011-07-01

    In this paper, we investigate the use of optical reflectometry in optical fibres for the measurement of magnetic field. The dedicated application concerns the measurement of plasma current in the fusion reactor. The measurement is based on the rotation of the polarization state of the Rayleigh backscattered signal when an optical pulse is launched in the fibre. Particular care has been undertaken to evaluate the impact of linear birefringence on the measurement performance. (authors)

  4. Influence of physical surface characteristics on SAR backscatter

    NASA Astrophysics Data System (ADS)

    Frei, Michaela; Henkel, Jochen

    2002-01-01

    An area in the Negev desert in Israel was chosen to demonstrate the capability of the SIR-C sensor system to differentiate lithological units. In addition DAIS hyperspectral data were investigated. The area around Timna mountain is characterized by Cambrian sandstones, carbonates and alluvial fans of Pleistocene and Holocene age. The mountain itself consists of diverse magmatic rock assemblage. The whole area is mapped using conventional methods. The remote sensing data are sensitive for the mapping parameters and allow the extraction of their spectral and radar signatures. Specific areas have been classified on their lithology, mineralogy, stratigraphy, grain size distribution, surface roughness and weathering state. In addition, field measurements of the roughness of the alluvial fan's terraces and of the Cambrian rocks surrounding Mount Timna were investigated. The stereoscopic images taken were used as a basis for the height models of the different targets and the standard deviation (RMS) of the height was calculated. This was used as the parameter for the surface roughness and can be correlated with the radar backscatter. The SIR-C system offers the unique possibility of multi-frequency and multi-polarized data. The sensitivity for the surface roughness for the different wavelengths of X-, C- and L-band in accordance to their incidence angle ranges between 0,13 and 27 cm absolute RMS. The RMS measured for example in the alluvial fan ranges between 0,25 and 7, this corresponds to a smooth surface with pebble size of a few mm and a coarse terrace up to 50 cm block diameter. It can be shown that the age of the terraces corresponds to the backscatter. The more ancient the terrace the lower is the backscatter, the smoother the surface, the younger and rougher the terrace, the higher is the backscatter.

  5. Backscattering suppression in supersonic 1D polariton condensates.

    PubMed

    Tanese, D; Solnyshkov, D D; Amo, A; Ferrier, L; Bernet-Rollande, E; Wertz, E; Sagnes, I; Lemaître, A; Senellart, P; Malpuech, G; Bloch, J

    2012-01-20

    We investigate the effect of disorder on the propagation of one-dimensional polariton condensates in semiconductor microcavities. We observe a strong suppression of the backscattering produced by the imperfections of the structure when increasing the condensate density. This suppression occurs in the supersonic regime and is simultaneous to the onset of parametric instabilities which enable the "hopping" of the condensate through the disorder. Our results evidence a new mechanism for the strong scattering reduction of polaritons at high speeds. PMID:22400767

  6. Determination of backscatter sources in surface type targets

    Microsoft Academic Search

    R. ZOUGHI; R. K. MOORE; F. T. ULABY; L. K. WU; A. AFIFI

    1985-01-01

    A high-resolution X-band FM-CW radar system has been used to investigate the sources of backscatter in various types of crops, trees and surfaces. This system provided a range resolution in air of 6·67 cm and gave a 16 cm diameter illumination area at the target. The surface targets included concrete walkways, grass, soil and asphalt pavements. Although the surfaces of

  7. Neon time-of-flight backscattering spectrometry for surface analysis 

    E-print Network

    Garcia, Richard Michael

    2001-01-01

    OF SCIENCE August 2001 Major Subject: Nuclear Engineering NEON TIME-OF-FLIGHT BACKSCATTERING SPECTROMETRY FOR SURFACE ANALYSIS A Thesis by RICHARD MICHAEL GARCIA Submitted to Texas AkM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE Approved as to style and content by: Ron R. Hart (Chair of Committee) Frederick R. Best (Member) Richard B. Gri fin (Member) Alan E. Waltar (Head of Department) August 2001 Major Subject: Nuclear Engineering...

  8. Laser light backscattering off an electron beam-plasma system

    Microsoft Academic Search

    H. H. Szu

    1983-01-01

    An analysis of the stimulated Raman backscattering instability combined with a Buneman instability was performed for a head-on collision of a 10.6 micron CO2 laser beam with a nonrelativistic electron beam. The electron beam was directed through a laser-induced plasma with a density of up to 10 to the 16th\\/cu cm, which was originally produced by the CO2 laser beam.

  9. Enhanced backscatter of optical beams reflected in turbulent air

    NASA Astrophysics Data System (ADS)

    Nelson, W.; Palastro, J. P.; Wu, C.; Davis, C. C.

    2015-07-01

    Optical beams propagating through air acquire phase distortions from turbulent fluctuations in the refractive index. While these distortions are usually deleterious to propagation, beams reflected in a turbulent medium can undergo a local recovery of spatial coherence and intensity enhancement referred to as enhanced backscatter (EBS). Using a combination of lab-scale experiments and simulations, we investigate the EBS of optical beams reflected from corner cubes and rough surfaces, and identify the regimes in which EBS is most distinctly observed.

  10. Measuring Ultrasonic Backscatter in the Presence of Nonlinear Propagation

    NASA Astrophysics Data System (ADS)

    Stiles, Timothy; Guerrero, Quinton

    2011-11-01

    A goal of medical ultrasound is the formation of quantitative ultrasound images in which contrast is determined by acoustic or physical properties of tissue rather than relative echo amplitude. Such images could greatly enhance early detection of many diseases, including breast cancer and liver cirrhosis. Accurate determination of the ultrasonic backscatter coefficient from patients remains a difficult task. One reason for this difficulty is the inherent nonlinear propagation of ultrasound at high intensities used for medical imaging. The backscatter coefficient from several tissue-mimicking samples were measured using the planar reflector method. In this method, the power spectrum from a sample is compared to the power spectrum of an optically flat sample of quartz. The results should be independent of incident pressure amplitude. Results demonstrate that backscatter coefficients can vary by more than an order of magnitude when ultrasound pressure varies from 0.1 MPa to 1.5 MPa at 5.0 MHz. A new method that incorporates nonlinear propagation is proposed to explain these discrepancies.

  11. Spectral absorption and backscatter measurements of suspended particles

    SciTech Connect

    Wouts, R. [NIOO-CEMO, Yerseke (Netherlands); Warnock, R.; Baker, S. [Univ. Groningen (Netherlands); Kromkamp, J.

    1997-06-01

    Three different methods for determining light attenuation by suspended particles under laboratory conditions are compared. One method, a direct application of Gershun`s equation, by measuring scalar irradiance and the gradient of the net-vector irradiance, allows one to determine the spectral absorption by the particles. Another method, measuring radiance attenuation in an isotropic light field, measures the sum of absorption and backscatter by the particles. The difference gives an estimate for the backscatter. The results were compared with an estimate based on an adaptation of the filterpad method that measures absorption by particles. We found that the filterpad measurements depend heavily on the filter load and the scattering characteristics of the particles involved. Increasing backscatter makes the measurements less reliable. It is argued that the filterpad method should not be used to obtain sea truth data for remote sensing measurements in coastal areas. These measurements were performed in a laboratory scale enclosure (volume 250 liters) on samples of natural silt and/or algal cultures grown in the tank. In our laboratory setup we have put special emphasis on measuring inherent optical properties of natural ({open_quotes}Wester Scheldt{close_quotes} estuary, The Netherlands) silt. Together with available (non-spectral) measurements of the volume scattering function of silt, this information can be used to test models for radiative transfer.

  12. Experimental findings in 180{degree} backscattering enhancement from solids

    SciTech Connect

    Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D. [Institut fuer Experimentalphysik, Johannes-Kepler-Universitaet, A-4040 Linz (Austria)] [Institut fuer Experimentalphysik, Johannes-Kepler-Universitaet, A-4040 Linz (Austria)

    1997-02-01

    We use a backscattering assembly developed recently to investigate the enhanced backscattering from polycrystalline materials near 180{degree}. The nominal scattering angle can be continuously varied between exactly 180.0{degree} and 178.5{degree}. It is shown that the stochastic model of flux peaking, though its predictions are surprisingly consistent with experimental results, either does not apply to real measurements or does only take account of a negligible fraction of the effect, which cannot be documented by experiment. The energy loss of He projectiles along correlated inward and outward trajectories turns out to be the same as in any random direction. To get the enhancement factor unaffected from detector resolution we measured the integrated backscattering yield from a number of targets with different thickness and deduced the yield by two different methods. For 400 keV He projectiles scattered from partly oxidized Ta a maximum enhancement factor of 2.8 is found. {copyright} {ital 1997} {ital The American Physical Society}

  13. Tracers in vascular casting resins enhance backscattering brightness.

    PubMed

    Schraufnagel, Dean E; Ganesan, Dhanalakshmi P

    2002-01-01

    Studying cast microvasculature with scanning electron microscopy has expanded our knowledge of many circulations, but need arises to determine the blood source of vascular beds that are supplied by two circulations. One way to do this is to mark the casting resin by adding a tracer compound that can be detected in the scanning electron microscope. A potential method of distinguishing different substances is to detect the backscattered electrons that are emitted from the tracer if the tracer is a heavier element, because heavier elements backscatter more electrons. To explore different tracers, we tested lead, titanium, iron, osmium, and uranium as solutions of different polarity and powders. The tracers were added to 1 ml of methyl methacrylate in log concentrations. Shrinkage, hardness, cast quality, and change in brightness from the tracer were compared with multivariate analysis at scanning electron microscopic working distances of 15 and 39 mm on carbon-coated and uncoated specimens. Several concentrations caused sedimentation of the tracer and prevented the resin from solidifying. Tetraethyl lead shortened the hardening time: uranyl acetate and osmium tetroxide prolonged it. Most tracers decreased shrinkage. When lead citrate and Reynolds solutions were removed, the brightness correlated with increasing atomic number, concentration of the tracer, and mean atomic number of the specimen (p <0.0001). The substances that increased contrast most were tetraethyl lead and uranium. Backscattering electron detection can distinguish methacrylate casts that have small amounts of heavier elements added to them, but an optimal tracer has not yet been established. PMID:12074492

  14. Simulation Studies of the Backscattering Signal in HSRL Technique

    E-print Network

    Georgakopoulou, Angelika

    2012-01-01

    The technique of High Spectral Resolution Lidar (HSRL) for atmospheric monitoring allows the determination of the aerosol to molecular ratio and can be used in UHECR Observatories using air fluorescence telescopes. By this technique a more accurate estimate of the Cherenkov radiation superimposed to the fluorescence signal can be achieved. A laboratory setup was developed to determine the backscattering coefficients using microparticles diluted in water and diffusion interfaces. In this setup we used a CW SLM laser at 532 nm and a 250 mm Newtonian telescope. Simulations of the above experimental configuration have been made using Scatlab\\c{opyright}, FINESSE\\c{opyright} 0.99.8 and MATLAB\\c{opyright} and are presented in this work. We compare the simulated 2-dimensional Fabry-Perot fringe images of the backscattering signal recorded in the CCD sensor with that of experimental ones. Additionally, we simulated the backscattering of the laser beam by the atmosphere at a height of 2000 m and we have studied the in...

  15. Parametric (integrated backscatter and attenuation) images constructed using backscattered radio frequency signals (25–56 MHz) from human aortae in vitro

    Microsoft Academic Search

    S. Lori Bridal; Paul Fornès; Patrick Bruneval; Geneviève Berger

    1997-01-01

    Quantitative ultrasonic tissue characterization using backscattered high-frequency intravascular ultrasound could provide a basis for the objective identification of lesions in vivo. Representation of local measurements of quantitative ultrasonic parameters in a conventional image format should facilitate their interpretation and thus increase their clinical utility. Toward this goal, the apparent integrated backscatter, the slope of attenuation (25–56 MHz) and the value

  16. Towards understanding the nature of high frequency backscatter from cells and tissues: an investigation of backscatter power spectra from different concentrations of cells of different sizes

    Microsoft Academic Search

    Michael C Kolios; G. J. Czarnota; A. Worthington; A. Giles; A. S. Tunis; M. D. Sherar

    2004-01-01

    During cell death, a series of structural changes occur within the cell. We have shown that cell ensembles and tissues undergoing structural changes associated with various cell death pathways can be detected using high-frequency ultrasound. In our effort to understand better the nature of backscatter from collections of cells (which emulate tissues), we have collected raw RF backscatter data from

  17. Diffraction-based optical correlator

    NASA Technical Reports Server (NTRS)

    Spremo, Stevan M. (Inventor); Fuhr, Peter L. (Inventor); Schipper, John F. (Inventor)

    2005-01-01

    Method and system for wavelength-based processing of a light beam. A light beam, produced at a chemical or physical reaction site and having at least first and second wavelengths, ?1 and ?2, is received and diffracted at a first diffraction grating to provide first and second diffracted beams, which are received and analyzed in terms of wavelength and/or time at two spaced apart light detectors. In a second embodiment, light from first and second sources is diffracted and compared in terms of wavelength and/or time to determine if the two beams arise from the same source. In a third embodiment, a light beam is split and diffracted and passed through first and second environments to study differential effects. In a fourth embodiment, diffracted light beam components, having first and second wavelengths, are received sequentially at a reaction site to determine whether a specified reaction is promoted, based on order of receipt of the beams. In a fifth embodiment, a cylindrically shaped diffraction grating (uniform or chirped) is rotated and translated to provide a sequence of diffracted beams with different wavelengths. In a sixth embodiment, incident light, representing one or more symbols, is successively diffracted from first and second diffraction gratings and is received at different light detectors, depending upon the wavelengths present in the incident light.

  18. Back-scattering channel-cut high-resolution monochromator for inelastic x-ray scattering

    SciTech Connect

    Kushnir, V.I.; Abbamonte, P.M.; Macrander, A.T.; Schwoerer-Boehning, M.

    1997-08-01

    We report on a design and on some experimental results for the performance of a new high energy resolution monochromator. It is a large channel-cut Si crystal with a 197 mm separation between the two faces designed to operate in a near-backscattering regime. The device was tested as a second monochromator on Sector 3 of the Synchrotron Radiation Instrumentation Collaborative Access Team (SRI-CAT) at the Advanced Photon Source using the Si(777) reflection at a photon energy of 13.84 keV. The same monochromator can be used for other energies with reflections of the type (hhh). Special care has been taken to equalize the temperature of the two faces by employing a Peltier heat pump. A Si(111) double-crystal pre-monochromator designed to withstand the high heat load of the undulator radiation was used upstream on the beamline. The measured throughput efficiency of the Si(777) channel-cut monochromator was less ideal by a factor of 1.9. Dynamical diffraction theory was used to calculate the throughput of an ideally perfect crystal.

  19. Optical properties of the scales of Morpho rhetenor butterflies: theoretical and experimental investigation of the back-scattering of light in the visible spectrum.

    PubMed Central

    Plattner, L.

    2004-01-01

    A study of the optical properties of the largely periodic microstructure occurring on the wings of the iridescent tropical butterfly Morpho rhetenor and responsible for its structural colouration is reported. An extensive measurement of the back-scattering of visible light from butterfly scales was performed for various angles of incidence. Efficient low-pass filter behaviour was observed for all angles of incidence and polarizations, with near-complete transmission at wavelengths above the threshold of 550 nm. The angular spread of the back-scattered light was found to be organized in lobes with total extinction of the specular reflection for all conditions of incidence. Retro-reflector behaviour was also observed for angles of incidence of 30 degrees and above. Additionally, the role of periodic geometrical features found in the microstructure for the generation of its spectral response was analysed theoretically. Using finite-difference time-domain and near-field to far-field transformation techniques, the back-scattering of visible light by models was computed numerically and the relevance of geometrical features for the production of structural colour and diffraction was demonstrated. PMID:16849152

  20. Multilayer diffraction grating

    DOEpatents

    Barbee, Jr., Troy W. (Palo Alto, CA)

    1990-01-01

    This invention is for a reflection diffraction grating that functions at X-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3,000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages.

  1. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, Gary E. (Santa Cruz, CA)

    1996-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  2. Dichroic coherent diffractive imaging

    PubMed Central

    Tripathi, Ashish; Mohanty, Jyoti; Dietze, Sebastian H.; Shpyrko, Oleg G.; Shipton, Erik; Fullerton, Eric E.; Kim, Sang Soo; McNulty, Ian

    2011-01-01

    Understanding electronic structure at the nanoscale is crucial to untangling fundamental physics puzzles such as phase separation and emergent behavior in complex magnetic oxides. Probes with the ability to see beyond surfaces on nanometer length and subpicosecond time scales can greatly enhance our understanding of these systems and will undoubtedly impact development of future information technologies. Polarized X-rays are an appealing choice of probe due to their penetrating power, elemental and magnetic specificity, and high spatial resolution. The resolution of traditional X-ray microscopes is limited by the nanometer precision required to fabricate X-ray optics. Here we present a novel approach to lensless imaging of an extended magnetic nanostructure, in which a scanned series of dichroic coherent diffraction patterns is recorded and numerically inverted to map its magnetic domain configuration. Unlike holographic methods, it does not require a reference wave or precision optics. In addition, it enables the imaging of samples with arbitrarily large spatial dimensions, at a spatial resolution limited solely by the coherent X-ray flux, wavelength, and stability of the sample with respect to the beam. It can readily be extended to nonmagnetic systems that exhibit circular or linear dichroism. We demonstrate this approach by imaging ferrimagnetic labyrinthine domains in a Gd/Fe multilayer with perpendicular anisotropy and follow the evolution of the domain structure through part of its magnetization hysteresis loop. This approach is scalable to imaging with diffraction-limited resolution, a prospect rapidly becoming a reality in view of the new generation of phenomenally brilliant X-ray sources. PMID:21825152

  3. Dichroic Coherent Diffractive Imaging

    NASA Astrophysics Data System (ADS)

    Tripathi, Ashish

    Understanding electronic structure at nanometer resolution is crucial to understanding physics such as phase separation and emergent behavior in correlated electron materials. Nondestructive probes which have the ability to see beyond surfaces on nanometer length and sub-picosecond time scales can greatly enhance our understanding of these systems and will impact development of future technologies, such as magnetic storage. Polarized x-rays are an appealing choice of probe due to their penetrating power, elemental and magnetic specificity, and high spatial resolution. The resolution of traditional x-ray microscopy is limited by the nanometer precision required to fabricate x-ray optics. In this thesis, a novel approach to lensless imaging of an extended magnetic nanostructure is presented. We demonstrate this approach by imaging ferrimagnetic "maze" domains in a Gd/Fe multilayer with perpendicular anisotropy. A series of dichroic coherent diffraction patterns, ptychographically recorded, are numerically inverted using non-convex and non-linear optimization theory, and we follow the magnetic domain configuration evolution through part of its magnetization hysteresis loop by applying an external magnetic field. Unlike holographic methods, it does not require a reference wave or precision optics, and so is a far simpler experiment. In addition, it enables the imaging of samples with arbitrarily large spatial dimensions, at a spatial resolution limited solely by the coherent x-ray flux and wavelength. It can readily be extended to other non-magnetic systems that exhibit circular or linear dichroism. This approach is scalable to imaging with diffraction-limited resolution, a prospect rapidly becoming a reality in view of the new generation of phenomenally brilliant x-ray sources.

  4. Optical Diffraction from Colloidal Crystals

    Microsoft Academic Search

    Paul Andrew Rundquist

    1991-01-01

    I examine the diffraction of light from colloidal crystals prepared from deionized aqueous suspensions of charged monodisperse polystyrene spheres. These colloidal crystals self-assemble into three-dimensional crystalline lattices and efficiently diffract visible light in manner analogous to diffraction of x-rays by atomic crystals. Also analogous to atomic crystals, colloidal crystals exhibit collective lattice vibrations, or phonons. The crystalline order and the

  5. Study of optical Laue diffraction

    NASA Astrophysics Data System (ADS)

    Chakravarthy, Giridhar; Allam, Srinivasa Rao; Satyanarayana, S. V. M.; Sharan, Alok

    2014-10-01

    We present the study of the optical diffraction pattern of one and two-dimensional gratings with defects, designed using desktop pc and printed on OHP sheet using laser printer. Gratings so prepared, using novel low cost technique provides good visual aid in teaching. Diffraction pattern of the monochromatic light (632.8nm) from the grating so designed is similar to that of x-ray diffraction pattern of crystal lattice with point defects in one and two-dimensions. Here both optical and x-ray diffractions are Fraunhofer. The information about the crystalline lattice structure and the defect size can be known.

  6. Mode-dependent characteristics of Rayleigh backscattering in weakly-coupled few-mode fiber

    NASA Astrophysics Data System (ADS)

    Yu, Dawei; Fu, Songnian; Tang, Ming; Liu, Deming

    2015-07-01

    We theoretically investigate the mode-dependent characteristics of Rayleigh backscattering arising in weakly-coupled few-mode fibers (FMFs). Based on the theory of Lorentz reciprocity and surface wave excitation, we derive a general analytical equation of excitation efficiency and power distribution of Rayleigh backscattering light among backward propagation modes under the condition of impulse response. Thus, we are able to characterize the Rayleigh backscattering of weakly-coupled FMF with arbitrary refractive index profile. As for the weakly-coupled FMF with a step-index profile, the power distribution ratio of individual modes in the Rayleigh backscattering light is mainly determined by the forward propagation mode. In particular, the backscattering mode with the same profile as the forward propagation one has the highest excitation efficiency. The FMF parameters have influence on the total backscattering power, but little effect on the mode power distribution ratio.

  7. Assessment of material degradation due to corrosion-fatigue using a backscattered Rayleigh surface wave

    Microsoft Academic Search

    Young H Kim; Sung-Jin Song; D. H Bae; Sung-Duk Kwon

    2004-01-01

    Material degradation due to corrosion-fatigue was evaluated nondestructively using backscattered Rayleigh surface wave. A corrosion-fatigue test was carried out for the specimens made of thermo-mechanically controlled process steel in 3.5 wt.% NaCl solution at 25 °C. The Backscattering profile, which is the amplitude variation of backscattered ultrasound according to the incident angle, of the specimens were measured in water at

  8. Algorithm for retrieving lidar ratios at 1064 nm from space-based lidar backscatter data

    Microsoft Academic Search

    Mark Vaughan

    2004-01-01

    Accurate estimation of cloud and aerosol optical depths using backscatter lidar data requires knowledge of the particulate lidar ratio (i.e., the extinction-to-backscatter ratio). In those cases for which a measurement of molecular backscatter can be made on the far side of a layer, knowledge of the lidar ratio can be derived directly from the data. However, obtaining a reliable clear

  9. Aerosol backscatter variability at 10.6 microns over Colorado high plains during JAWS experiment

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Bowdle, David A.; Vaughan, J. Michael

    1988-01-01

    This paper describes the aerosol backscatter profile measurements obtained by an airborne CW focused CO2 Doppler lidar (the Laser True Airspeed System) during the 1982 Joint Airport Weather Studies (JAWS) field experiment. The backscatter sounding flights were made in the lee of the front range of the Colorado Rocky Mountains, at about 1650 m above mean sea level. The qualitative relationships between the backscatter and the vertical distribution of temperature and water vapor are described.

  10. Detonation diffraction in gases

    SciTech Connect

    Pintgen, F.; Shepherd, J.E. [California Institute of Technology, Mail stop 105-50, 1200 E California Blvd, Pasadena, CA 91125 (United States)

    2009-03-15

    We have experimentally investigated detonation diffraction out of a round tube into an unconfined half-space. The focus of our study is examining how the extent of detonation cellular instability influences the quantitative and qualitative features of diffraction. Detailed quantitative and qualitative measurements were obtained through simultaneous schlieren imaging, multiple-exposure chemiluminescence imaging, and planar laser-induced fluorescence imaging of OH molecules. Two types of stoichiometric mixtures, highly diluted H{sub 2}-O{sub 2}-Ar and H{sub 2}-N{sub 2}O, were studied in the sub-critical, critical and super-critical regime. These mixture types represent extreme cases in the classification of cellular instability with highly diluted H{sub 2}-O{sub 2}-Ar mixtures having very regular instability structures and H{sub 2}-N{sub 2}O having very irregular instability structures. The most striking differences between the mixtures occur in the sub-critical and critical regimes, for which the detonation fails to transition into the unconfined half-space. For the H{sub 2}-O{sub 2}-Ar mixture, the velocity on the center line was found to decay significantly slower than for the H{sub 2}-N{sub 2}O mixture. In case of the H{sub 2}-O{sub 2}-Ar mixture, it was evident from simultaneous schlieren-fluorescence images that the reaction front was coupled to the lead shock front up to 2.3 tube diameters from the exit plane. For the H{sub 2}-N{sub 2}O mixture, the reaction front velocity decreased to 60% of the corresponding Chapman-Jouguet value at 1.1 tube diameters from the tube exit plane. A geometric acoustic model showed that the observed differences in failure patterns are not caused by the differences in thermodynamic properties of the two mixtures but is linked to the larger effective activation energy and critical decay time in the H{sub 2}-N{sub 2}O mixture as compared to the H{sub 2}-O{sub 2}-Ar mixture. The re-initiation events appear similar for the two mixtures and are a consequence of local fluctuations at random locations within the region between the lead shock and decoupled reaction zone, resulting in strong transverse detonations sweeping through shocked but largely unreacted gas. (author)

  11. Inelastic Electron Backscattering in a Generic Helical Edge Channel

    NASA Astrophysics Data System (ADS)

    Schmidt, Thomas L.; Rachel, Stephan; von Oppen, Felix; Glazman, Leonid I.

    2012-04-01

    We evaluate the low-temperature conductance of a weakly interacting one-dimensional helical liquid without axial spin symmetry. The lack of that symmetry allows for inelastic backscattering of a single electron, accompanied by forward scattering of another. This joint effect of weak interactions and potential scattering off impurities results in a temperature-dependent deviation from the quantized conductance, ?G?T4. In addition, ?G is sensitive to the position of the Fermi level. We determine numerically the parameters entering our generic model for the Bernevig-Hughes-Zhang Hamiltonian of a HgTe/CdTe quantum well in the presence of Rashba spin-orbit coupling.

  12. A Backscatter-Suppressed Beta Spectrometer for Neutron Decay Studies

    E-print Network

    Wietfeldt, F E; Anderman, R; Bateman, F B; Dewey, M S; Komives, A; Thompson, A K; Balashov, S; Mostovoy, Y; Mostovoy, Yu.

    2004-01-01

    We describe a beta electron spectrometer for use in an upcoming experiment that will measure the beta-antineutrino correlation coefficient (a-coefficient) in neutron beta decay. Electron energy is measured by a thick plastic scintillator detector. A conical array of plastic scintillator veto detectors is used to suppress events where the electron backscattered. A Monte Carlo simulation of this device in the configuration of the a-coefficient experiment is presented. The design, construction, and testing of a full-scale prototype device is described. We discuss the performance of this spectrometer with respect to its suitability for the experiment.

  13. A Backscatter-Suppressed Beta Spectrometer for Neutron Decay Studies

    E-print Network

    F. E. Wietfeldt; C. Trull; R. Anderman; F. B. Bateman; M. S. Dewey; A. Komives; A. K. Thompson; S. Balashov; Yu. Mostovoy

    2004-01-21

    We describe a beta electron spectrometer for use in an upcoming experiment that will measure the beta-antineutrino correlation coefficient (a-coefficient) in neutron beta decay. Electron energy is measured by a thick plastic scintillator detector. A conical array of plastic scintillator veto detectors is used to suppress events where the electron backscattered. A Monte Carlo simulation of this device in the configuration of the a-coefficient experiment is presented. The design, construction, and testing of a full-scale prototype device is described. We discuss the performance of this spectrometer with respect to its suitability for the experiment.

  14. Raman backscatter measurement research on water vapor systems

    NASA Technical Reports Server (NTRS)

    Workman, G. L.

    1975-01-01

    Raman backscatter techniques proved to be a useful remote sensing tool, whose full potential has not been realized. The types of information available from laser probes in atmospheric studies are reviewed. Detection levels for known Raman cross sections are calculated using the laser radar equation. Laboratory experiments performed for H2O, N2, SO2, O2 and HCL indicate that accurate wavelength cross sections need to be obtained, as well as more emphasis on obtaining accurate Raman cross sections of molecular species at wavelengths in the ultraviolet spectra.

  15. Low-Frequency Electromagnetic Backscatter from Buried Tunnels

    SciTech Connect

    Casey, K; Pao, H

    2006-06-21

    This progress report is submitted under a contract between the Special Project Office of DARPA and Lawrence Livermore National Laboratory. The Project Manager at DARPA is Dr. Michael Zatman. Our purpose under this contract is to investigate interactions between electromagnetic waves and a class of buried targets located in multilayered media with rough interfaces. In this report, we investigate three preliminary problems. In each case our specific goal is to understand various aspects of the electromagnetic wave interaction mechanisms with targets in layered media. The first problem, discussed in Section 2, is that of low-frequency electromagnetic backscattering from a tunnel that is cut into a lossy dielectric half-space. In this problem, the interface between the upper (free space) region and the lower (ground) region is smooth. The tunnel is assumed to be a cylindrical free-space region of infinite extent in its axial direction and with a diameter that is small in comparison to the free-space wavelength. Because its diameter is small, the tunnel can be modeled as a buried ''wire'' described by an equivalent impedance per unit length. In Section 3 we extend the analysis to include a statistically rough interface between the air and ground regions. The interface is modeled as a random-phase screen. Such a screen reduces the coherent power in a plane wave that is transmitted through it, scattering some of the total power into an incoherent field. Our analysis of this second problem quantifies the reduction in the coherent power backscattered from the buried tunnel that is caused by the roughness of the air-ground interface. The problem of low-frequency electromagnetic backscattering from two buried tunnels, parallel to each other but at different locations in the ground, is considered in Section 4. In this analysis, we wish to determine the conditions under which the presence of more than one tunnel can be detected via backscattering. Section 5 concludes the report with a summary of the investigations discussed herein and recommendations for future work on problems of this class.

  16. Integrated fiber optic backscatter system for photon correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Dhadwal, Harbans S.; Khan, Romel R.; Suh, Kwang

    1995-04-01

    Design and fabrication of an integrated backscatter fiber optic probe is described in this paper. A short section of a gradient index optical fiber is fusion spliced to two separate monomode optical fibers; the two fibers are mounted into a stainless steel face plate. One fiber is used to transmit either a focussed or collimated laser beam to the scattering region. The second fiber collects and guides the laser light scattered at a predefined scattering angle to a photomultiplier. Subsequent photon correlation and analysis yields size information of the scattering species.

  17. Coherent backscatter and the radar characteristics of outer planet satellites

    NASA Technical Reports Server (NTRS)

    Hapke, Bruce

    1990-01-01

    It is presently suggested that the diffuse component-dominated high radar reflectivities and large polarization of Europa, Ganymede, and Callisto could be due to the illumination by a collimated source of a weakly absorbing particulate medium in which wavelength-scaled scatterers are separated by distances somewhat larger than the wavelength. A plausible medium could be a regolith composed of voids and/or silicate rocks imbedded in an icy matrix; multiply-scattered parts of the wavefront traversing the same path in opposite directions combine coherently in the backscatter direction to generate increased intensity, and the enhancement is different for the two components of polarized reflected radiation.

  18. Stimulated Raman Backscattering Amplification Using Multiple Pump Pulses

    NASA Astrophysics Data System (ADS)

    Ge, Zhe-Yi; Yin, Yan; Chen, De-Peng; Zhuo, Hong-Bin; Ma, Yan-Yun; Shao, Fu-Qiu

    2012-01-01

    A multiple-pump-pulses-stimulated Raman backscattering amplification (m-SRA) scheme is proposed and examined using 1D PIC simulations. Compared with the SRA using a single long pump pulse, higher energy conversion efficiency can be obtained with the same output laser intensity by employing the m-SRA scheme. Unwanted Raman forward scattering can be suppressed in the m-SRA case. Favorable pulse envelope and frequency characteristics of the seed pulse after amplification are obtained by using the m-SRA scheme.

  19. Relating the radar backscattering coefficient to leaf-area index

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T. (principal investigator); Allen, C.; Eger, G.; Kanemasu, E.

    1983-01-01

    The relationship between the radar backscattering coefficient of a vegetation canopy, sigma(0) sub can, and the canopy's leaf area index (LAI) is examined. The relationship is established through the development of a model for corn and sorghum and another for wheat. Both models are extensions of the cloud model of Attema and Ulaby (1978). Analysis of experimental data measured at 8.6, 13.0, 17.0, and 35.6 GHz indicates that most of the temporal variations of sigma(0) sub can can be accounted for through variations in green LAI alone, if the latter is greater than 0.5.

  20. Ptychographic Fresnel coherent diffractive imaging

    SciTech Connect

    Vine, D. J.; Williams, G. J.; Nugent, K. A. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Abbey, B. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Department of Engineering and Science, University of Oxford, Oxford OX1 2JD (United Kingdom); Pfeifer, M. A.; Clark, J. N.; Peele, A. G. [Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); Jonge, M. D. de [Australian Synchrotron, Clayton, Victoria 3168 (Australia); McNulty, I. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 6043 (United States)

    2009-12-15

    This paper reports improved reconstruction of complex wave fields from extended objects. The combination of ptychography with Fresnel diffractive imaging results in better reconstructions with fewer iterations required to convergence than either method considered separately. The method is applied to retrieve the projected thickness of a gold microstructure and comparative results using ptychography and Fresnel diffractive imaging are presented.

  1. Factorisation in Diffraction Matthias Mozer

    E-print Network

    Factorisation in Diffraction Matthias Mozer IIHE Vrije Universiteit Brussel #12;Matthias Mozer precision by combining data sets #12;Matthias Mozer, EPS 2007 Factorization diffractive = pdf parton interactions (similar to pp) DISDIS p direct resolved spectator Interactions #12;Matthias Mozer, EPS 2007

  2. Indexing problems in quasicrystal diffraction

    Microsoft Academic Search

    Veit Elser

    1985-01-01

    Various features of quasicrystal diffraction patterns are discussed. The projection scheme is used throughout and applied in some detail to the pattern formed by icosahedral Al-Mn. Comparison with the diffraction pattern formed by the vertices of a three-dimensional Penrose tiling leads to the value 4.60 Å for the rhombohedron edge length.

  3. Stochastic Theory of Edge Diffraction

    Microsoft Academic Search

    Giorgio Franceschetti; Antonio Iodice; Antonio Natale; Daniele Riccio

    2008-01-01

    We introduce an original formulation for the electromagnetic field diffraction by a knife edge with random roughness: the formulation, based on the asymptotic physical optics approach, leads to closed form evaluations of the statistics of the diffracted field. The edge roughness is described by a stationary zero-mean Gaussian stochastic process with standard deviation sigma and correlation length L. The physical

  4. STRUCTURE ANALYSIS BY ELECTRON DIFFRACTION

    Microsoft Academic Search

    Z. G. Pinsker; B. K. Vaynshteyn

    1957-01-01

    The progress of studies in the field of electron diffraction during the ; iast thirty years is reviewed. The development of structure analysis by eiectron ; diffraction has been the most important trend of investigation, promoting the ; advance of the theory of electron scattering and of the experimental technique. ; In establishing the limit of applicability of the kinematic

  5. Characterization of sputtered and annealed niobium oxide films using spectroscopic ellipsometry, Rutherford backscattering spectrometry and X-ray diffraction

    Microsoft Academic Search

    M. Serenyi; T. Lohner; P. Petrik; Z. Zolnai; Z. E. Horváth; N. Q. Khánh

    2008-01-01

    Niobium oxide films were prepared by radio frequency sputtering using Nb2O5 crystalline powder. The thickness and the complex dielectric functions of the as-prepared films were determined by spectroscopic ellipsometry using the Tauc–Lorentz oscillator model. The as-deposited films were amorphous, their refractive index varies between 2.26 and 2.30 at wavelength of 550 nm and the optical band gap varies between 3.29 and

  6. Mueller matrix of backscattered light of a chicken embryo

    NASA Astrophysics Data System (ADS)

    Sardar, Dhiraj K.; Yow, Raylon M.

    2004-07-01

    An in vivo investigation to determine instrinsic differences in optical activity of tissues of a three-day-old chicken embryo was performed. A homogenous flux of light at 514.4 nm from an argon ion laser was used to develop 13 of the 16 Mueller matrix components of backscattered light. The results show that all tissues backscatter light predominately in the same polarization state as that of the incident light. This effect manifests itself as large non-zero intensities in the diagonal terms of the Mueller matrix. Any change in polarization is distributed unbiased to the other polarization states as the off diagonal Mueller matrix elements each consists of a low intensity image. Depolarization by birefringent tissue structures such as collagen or actin-myosin fibers which would lead to non-zero intensities in the off diagonal Mueller matrix elements, is not observed. This may be due to the lack of such structures given the early age of the embryo.

  7. Feasibility of using Backscattered Mueller Matrix Images for Bioaerosol Detection

    NASA Astrophysics Data System (ADS)

    Li, Changhui; Kattawar, George W.

    2006-03-01

    It has been shown that by looking at the backscattered radiance from an object illuminated by a laser beam one could effectively distinguish different morphologies from one another. However, if one wants to obtain all the information possible from elastic scattering either from a single particle or an ensemble of particles then one must use the Mueller matrix which contains all the polarization and radiance information available. In this talk, we will show that if we take advantage of the polarization information of the object, many more images related to the overall morphology as well as the internal structure of the object can be obtained. We will present images of the complete Mueller matrix to show the sensitivity of its sixteen components to both external and internal particle properties. We will also show that by using only one or two elements of this matrix one might be able to distinguish bioaerosols such as anthrax from more benign aerosols. We also show that the backscattering Mueller images contain more information than the forward scattering ones.

  8. Inversion of radar backscatter from millimeter wave smoke

    NASA Astrophysics Data System (ADS)

    Perry, Benjamin; Hale, D. J.

    1994-08-01

    This paper describes the results of an analysis of radar backscatter and attenuation data collected during field trials of the MMW Module of the XM56 Large Area Screening Generator. The trials were conducted by Edgewood Research Development and Engineering Center personnel at Dugway Proving Ground in 1989 and 1990, and at Eglin AFB in 1992. The purpose of this analysis was to use inversion techniques, similar to those developed for lidar systems, to translate the radar backscatter data from the XM56 smoke clouds into estimates of cloud concentration, and to compare the resulting concentration estimates with those produces by independent, point sampling nephelometers. Three dimensional cloud concentration profiles have been produced and were found to be consistent with the Pasquill stability category. In addition, the overall correlation between the radar-generated concentration data and those collected using the nephelometers was quite good. Examples of these results are presented for the 1989, long range trials, which allowed characterization of a large volume cloud, and the 1990 and 1992 trials, which were performed over a much shorter range, but provided more useful nephelometer data.

  9. Nimbus 7 solar backscatter ultraviolet (SBUV) ozone products user's guide

    NASA Technical Reports Server (NTRS)

    Fleig, Albert J.; Mcpeters, R. D.; Bhartia, P. K.; Schlesinger, Barry M.; Cebula, Richard P.; Klenk, K. F.; Taylor, Steven L.; Heath, Donald F.

    1990-01-01

    Three ozone tape products from the Solar Backscatter Ultraviolet (SBUV) experiment aboard Nimbus 7 were archived at the National Space Science Data Center. The experiment measures the fraction of incoming radiation backscattered by the Earth's atmosphere at 12 wavelengths. In-flight measurements were used to monitor changes in the instrument sensitivity. Total column ozone is derived by comparing the measurements with calculations of what would be measured for different total ozone amounts. The altitude distribution is retrieved using an optimum statistical technique for the inversion. The estimated initial error in the absolute scale for total ozone is 2 percent, with a 3 percent drift over 8 years. The profile error depends on latitude and height, smallest at 3 to 10 mbar; the drift increases with increasing altitude. Three tape products are described. The High Density SBUV (HDSBUV) tape contains the final derived products - the total ozone and the vertical ozone profile - as well as much detailed diagnostic information generated during the retrieval process. The Compressed Ozone (CPOZ) tape contains only that subset of HDSBUV information, including total ozone and ozone profiles, considered most useful for scientific studies. The Zonal Means Tape (ZMT) contains daily, weekly, monthly and quarterly averages of the derived quantities over 10 deg latitude zones.

  10. Ultrastructural alterations in field carcinogenesis measured by enhanced backscattering spectroscopy

    PubMed Central

    Radosevich, Andrew J.; Mutyal, Nikhil N.; Yi, Ji; Stypula-Cyrus, Yolanda; Rogers, Jeremy D.; Goldberg, Michael J.; Bianchi, Laura K.; Bajaj, Shailesh; Roy, Hemant K.; Backman, Vadim

    2013-01-01

    Abstract. Optical characterization of biological tissue in field carcinogenesis offers a method with which to study the mechanisms behind early cancer development and the potential to perform clinical diagnosis. Previously, low-coherence enhanced backscattering spectroscopy (LEBS) has demonstrated the ability to discriminate between normal and diseased organs based on measurements of histologically normal-appearing tissue in the field of colorectal (CRC) and pancreatic (PC) cancers. Here, we implement the more comprehensive enhanced backscattering (EBS) spectroscopy to better understand the structural and optical changes which lead to the previous findings. EBS provides high-resolution measurement of the spatial reflectance profile P(rs) between 30 microns and 2.7 mm, where information about nanoscale mass density fluctuations in the mucosa can be quantified. A demonstration of the length-scales at which P(rs) is optimally altered in CRC and PC field carcinogenesis is given and subsequently these changes are related to the tissue’s structural composition. Three main conclusions are made. First, the most significant changes in P(rs) occur at short length-scales corresponding to the superficial mucosal layer. Second, these changes are predominantly attributable to a reduction in the presence of subdiffractional structures. Third, similar trends are seen for both cancer types, suggesting a common progression of structural alterations in each. PMID:24008865

  11. Assembly for Rutherford backscattering at exactly 180{degree}

    SciTech Connect

    Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D. [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet, A-4040 Linz-Auhof (Austria)] [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet, A-4040 Linz-Auhof (Austria)

    1996-05-01

    We describe a facility which allows us to measure projectiles scattered at an angle arbitrarily near 180{degree}. The backscattered projectiles are deflected in the horizontal plane out of the incoming beam by a combination of electric and magnetic fields. The charged particles, which are spatially dispersed according to their energy, are detected by a cooled 300 mm{sup 2} ion implanted silicon detector. By a judicious choice of the relative strength of both fields we ensure that the essential parts of the spectrum will not be distorted due to an energy dependent percentage of projectiles missing the detector. As the projectiles are also dispersed according to their charge state we are able to distinguish between, e.g., singly and doubly charged He projectiles as they hit the detector at different positions. The detector can be moved in the vertical direction to continuously vary the backscattering angle between 180{degree} and 178.5{degree}. This experimental result shows for the first time the angular range to which the 180{degree} enhancement is confined. Such a device is ideally suited for investigating single crystals by uniaxial channeling blocking. {copyright} {ital 1996 American Institute of Physics.}

  12. Middle East versus Saharan dust extinction-to-backscatter ratios

    NASA Astrophysics Data System (ADS)

    Nisantzi, A.; Mamouri, R. E.; Ansmann, A.; Schuster, G. L.; Hadjimitsis, D. G.

    2015-06-01

    Four years (2010-2013) of observations with polarization lidar and sun/sky photometer at the combined European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) site of Limassol (34.7° N, 33° E), Cyprus, were used to compare extinction-to-backscatter ratios (lidar ratios) for desert dust from Middle East deserts and the Sahara. In an earlier article, we analyzed one case only and found comparably low lidar ratios < 40 sr for Middle East dust. The complex data analysis scheme is presented. The quality of the retrieval is checked within a case study by comparing the results with respective Raman lidar solutions for particle backscatter, extinction, and lidar ratio. The applied combined lidar/photometer retrievals corroborate recent findings regarding the difference between Middle East and Saharan dust lidar ratios. We found values from 43-65 sr with a mean (±standard deviation) of 53 ± 6 sr for Saharan dust and from 33-48 sr with a mean of 41 ± 4 sr for Middle East dust for the wavelength of 532 nm. The presented data analysis, however, also demonstrates the difficulties in identifying the optical properties of dust even during outbreak situations in the presence of complex aerosol mixtures of desert dust, marine particles, fire smoke, and anthropogenic haze.

  13. Lidar backscatter signal recovery from phototransistor systematic effect by deconvolution.

    PubMed

    Refaat, Tamer F; Ismail, Syed; Abedin, M Nurul; Spuler, Scott M; Mayor, Shane D; Singh, Upendra N

    2008-10-10

    Backscatter lidar detection systems have been designed and integrated at NASA Langley Research Center using IR heterojunction phototransistors. The design focused on maximizing the system signal-to-noise ratio rather than noise minimization. The detection systems have been validated using the Raman-shifted eye-safe aerosol lidar (REAL) at the National Center for Atmospheric Research. Incorporating such devices introduces some systematic effects in the form of blurring to the backscattered signals. Characterization of the detection system transfer function aided in recovering such effects by deconvolution. The transfer function was obtained by measuring and fitting the system impulse response using single-pole approximation. An iterative deconvolution algorithm was implemented in order to recover the system resolution, while maintaining high signal-to-noise ratio. Results indicated a full recovery of the lidar signal, with resolution matching avalanche photodiodes. Application of such a technique to atmospheric boundary and cloud layers data restores the range resolution, up to 60 m, and overcomes the blurring effects. PMID:18846166

  14. Detection of Explosive Devices using X-ray Backscatter Radiation

    NASA Astrophysics Data System (ADS)

    Faust, Anthony A.

    2002-09-01

    It is our goal to develop a coded aperture based X-ray backscatter imaging detector that will provide sufficient speed, contrast and spatial resolution to detect Antipersonnel Landmines and Improvised Explosive Devices (IED). While our final objective is to field a hand-held detector, we have currently constrained ourselves to a design that can be fielded on a small robotic platform. Coded aperture imaging has been used by the observational gamma astronomy community for a number of years. However, it has been the recent advances in the field of medical nuclear imaging which has allowed for the application of the technique to a backscatter scenario. In addition, driven by requirements in medical applications, advances in X-ray detection are continually being made, and detectors are now being produced that are faster, cheaper and lighter than those only a decade ago. With these advances, a coded aperture hand-held imaging system has only recently become a possibility. This paper will begin with an introduction to the technique, identify recent advances which have made this approach possible, present a simulated example case, and conclude with a discussion on future work.

  15. Classification of kidney and liver tissue using ultrasound backscatter data

    NASA Astrophysics Data System (ADS)

    Aalamifar, Fereshteh; Rivaz, Hassan; Cerrolaza, Juan J.; Jago, James; Safdar, Nabile; Boctor, Emad M.; Linguraru, Marius G.

    2015-03-01

    Ultrasound (US) tissue characterization provides valuable information for the initialization of automatic segmentation algorithms, and can further provide complementary information for diagnosis of pathologies. US tissue characterization is challenging due to the presence of various types of image artifacts and dependence on the sonographer's skills. One way of overcoming this challenge is by characterizing images based on the distribution of the backscatter data derived from the interaction between US waves and tissue. The goal of this work is to classify liver versus kidney tissue in 3D volumetric US data using the distribution of backscatter US data recovered from end-user displayed Bmode image available in clinical systems. To this end, we first propose the computation of a large set of features based on the homodyned-K distribution of the speckle as well as the correlation coefficients between small patches in 3D images. We then utilize the random forests framework to select the most important features for classification. Experiments on in-vivo 3D US data from nine pediatric patients with hydronephrosis showed an average accuracy of 94% for the classification of liver and kidney tissues showing a good potential of this work to assist in the classification and segmentation of abdominal soft tissue.

  16. Backscattering measuring system for optimization of intravenous laser irradiation dose

    NASA Astrophysics Data System (ADS)

    Rusina, Tatyana V.; Popov, V. D.; Melnik, Ivan S.; Dets, Sergiy M.

    1996-11-01

    Intravenous laser blood irradiation as an effective method of biostimulation and physiotherapy becomes a more popular procedure. Optimal irradiation conditions for each patient are needed to be established individually. A fiber optics feedback system combined with conventional intravenous laser irradiation system was developed to control of irradiation process. The system consists of He-Ne laser, fiber optics probe and signal analyzer. Intravenous blood irradiation was performed in 7 healthy volunteers and 19 patients with different diseases. Measurements in vivo were related to in vitro blood irradiation which was performed in the same conditions with force-circulated venous blood. Comparison of temporal variations of backscattered light during all irradiation procedures has shown a strong discrepancy on optical properties of blood in patients with various health disorders since second procedure. The best cure effect was achieved when intensity of backscattered light was constant during at least five minutes. As a result, the optical irradiation does was considered to be equal 20 minutes' exposure of 3 mW He-Ne laser light at the end of fourth procedure.

  17. Investigation of microwave backscatter from the air-sea interface

    NASA Technical Reports Server (NTRS)

    Mcintosh, Robert E.; Carswell, James R.

    1995-01-01

    Monitoring the ocean surface winds and mean ocean surface level is essential for improving our knowledge of the climate. Two instruments that may provide us with this information are satellite-based scatterometers and altimeters. However, these instruments measure the backscatter characteristics of the ocean surface from which other physical parameters, such as the wind speed or ocean surface height, are derived. To improve the algorithms or models that relate the electromagnetic backscatter to the desired physical parameters, the University of Massachusetts (UMass) Microwave Remote Sensing Laboratory (MIRSL) designed and fabricated three airborne scatterometers: a C-band scatterometer (CSCAT), Ku-band scatterometer (KUSCAT) and C/Ku-band scatterometer (EMBR). One or more of these instruments participated in the Electromagnetic Bias experiment (EM Bias), Shelf Edge Exchange Processes experiment (SEEP), Surface Wave Dynamics Experiment (SWADE), Southern Ocean Wave Experiment (SOWEX), Hurricane Tina research flights, Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE), and Ladir In-space Technology Experiment (LITE). This document describes the three scatterometers, summarizes our measurement campaigns and major contributions to the scientific and engineering communities, lists the publications that resulted, and presents the degrees earned under the support of this NASA grant.

  18. Backscatter Mossbauer Spectrometer (BaMS) for extraterrestrial applications

    NASA Technical Reports Server (NTRS)

    Agresti, D. G.; Shelfer, T. D.; Pimperl, M. M.; Wills, E. L.; Shen, M. H.; Morris, R. V.

    1993-01-01

    Mossbauer spectroscopy is a nuclear gamma resonance technique particularly well suited to the study of materials that contain iron (Fe-57). It can provide information on the oxidation state of iron as well as the type and proportion of iron-containing mineral species in a sample of interest. Iron Mossbauer spectroscopy (FeMS) has been applied to samples believed to have come from Mars (SNC meteorites) and has been helpful in refining the choice among putative Martian surface materials by suggesting a likely nanophase component of the Martian regolity. FeMS spectrum of a Martial analogue material (Hawaiian palagonite) is shown; it is dominated by ferric-bearing phases and shows evidence of a nanophase component. FeMS has also been applied to lunar materials. It can be used to measure the maturity of lunar surface material and has been proposed as a prospector for lunar ilmenite, an oxygen resource mineral. Several years ago we suggested a backscatter Mossbauer spectrometer (BaMS) for a Mars rover mission. Backscatter design was selected as most appropriate for in-situ application because no sample preparation is required. Since that time, we have continued to develop the BaMS instrument in anticipation that it would eventually find a home on a NASA planetary mission. Gooding proposed BaMS as a geochemistry instrument on MESUR. More recently, an LPI workshop has recommended that BaMS be included in a three-instrument payload on the next (1996?) lunar lander.

  19. Electromagnetic diffraction efficiencies for plane reflection diffraction gratings

    NASA Technical Reports Server (NTRS)

    Marathay, A. S.; Shrode, T. E.

    1973-01-01

    Results are presented of research activities on holographic grating research. A large portion of this work was performed using rigorous vector diffraction theory, therefore, the necessary theory has been included in this report. The diffraction efficiency studies were continued using programs based on a rigorous theory. The simultaneous occurrence of high diffraction efficiencies and the phenomenon of double Wood's anomalies is demonstrated along with a graphic method for determining the necessary grating parameters. Also, an analytical solution for a grating profile that is perfectly blazed is obtained. The performance of the perfectly blazed grating profile is shown to be significantly better than grating profiles previously studied. Finally, a proposed method is described for the analysis of coarse echelle gratings using rigorous vector diffraction that is currently being developed.

  20. Diffraction dissociation at the LHC

    SciTech Connect

    Jenkovszky, Laszlo [Bogolyubov Institute for Theoretical Physics (BITP), Ukrainian National Academy of Sciences 14-b, Metrolohichna str., Kiev, 03680, Ukraine and Wigner Research Centre for Physics, Hungarian Academy of Sciences 1525 Budapest, POB 49 (Hungary); Orava, Risto [Institute of Physics, Division of Elementary Particle Physics, P.O. Box 64 (Gustaf Haellstroeminkatu 2a), FI-00014 University of Helsinki, Finland and CERN, CH-1211 Geneva 23 (Switzerland); Salii, Andrii [Bogolyubov Institute for Theoretical Physics (BITP), Ukrainian National Academy of Sciences 14-b, Metrolohichna str., Kiev, 03680 (Ukraine)

    2013-04-15

    We report on recent calculations of low missing mass single (SD) and double (DD) diffractive dissociation at LHC energies. The calculations are based on a dual-Regge model, dominated by a single Pomeron exchange. The diffractively excited states lie on the nucleon trajectory N*, appended by the isolated Roper resonance. Detailed predictions for the squared momentum transfer and missing mass dependence of the differential and integrated single-and double diffraction dissociation in the kinematical range of present and future LHC measurements are given.

  1. Diffraction phases in atom interferometers

    E-print Network

    Caroline Champenois; Matthias Buchner; Remi Delhuille; Cecile Robilliard; Jacques Vigue; Alain Miffre

    2003-03-12

    Diffraction of atoms by laser is a very important tool for matter wave optics. Although this process is well understood, the phase shifts induced by this diffraction process are not well known. In this paper, we make analytic calculations of these phase shifts in some simple cases and we use these results to model the contrast interferometer recently built by the group of D. Pritchard at MIT. We thus show that the values of the diffraction phases are large and that they probably contribute to the phase noise observed in this experiment.

  2. X-Ray Diffraction Microscopy

    NASA Astrophysics Data System (ADS)

    Thibault, Pierre; Elser, Veit

    2010-04-01

    X-ray diffraction phenomena have been used for decades to study matter at the nanometer and subnanometer scales. X-ray diffraction microscopy uses the far-field scattering of coherent X-rays to form the 2D or 3D image of a scattering object in a way that resembles crystallography. In this review, we describe the main principles, benefits, and limitations of diffraction microscopy. After sampling some of the milestones of this young technique and its close variants, we conclude with a short assessment of the current state of the field.

  3. Anisotropic and Heterogeneous Development of Microstructures. Combining Laboratory/Synchrotron X-rays and EBSD on a few SPD Metallic Systems

    NASA Astrophysics Data System (ADS)

    Bolmaro, Raúl E.; De Vincentis, Natalia S.; Benatti, Emanuel; Kliauga, Andrea M.; Avalos, Martina C.; Schell, Norbert; Brokmeier, Heinz-Günter

    2014-08-01

    The onset of Severe Plastic Deformation (SPD) regime is quite instructive on the possible origins of the nano-microstructures developed in metals and alloys. It is known that grain fragmentation and dislocation accumulation, among other defects, proceed at different paces depending fundamentally on grain orientations and active deformation mechanisms. There have been many attempts to characterize nano-microstructure anisotropy, leading all of them to sometimes contradictory conclusions. Moreover, the characterizations rely on different measurements techniques and pos-processing approaches, which can be observing different manifestations of the same phenomena. On the current presentation we show a few experimental and computer pos-processing and simulation approaches, applied to some SPD/alloy systems. Williamson-Hall and Convolutional Multiple Whole Profile (CMWP) techniques will be applied to peak broadening analysis on experimental results stemming from laboratory Cu Ka X-rays, and synchrotron radiation from LNLS (Laboratório Nacional de Luz Síncrotron, Campinas, Brazil) and Petra III line (HEMS station, at DESY, Hamburg, Germany). Taking advantage of the EBSD capability of giving information on orientational and topological characteristics of grain boundaries, microstructures, grain sizes, etc., we also performed investigations on dislocation density and Geometrically Necessary Dislocation Boundaries (GNDB) and their correlation with texture components. Orientation dependent nano-microstructures and domain sizes are shown on the scheme of generalized pole figures and discussions provide some hints on nano-microstructure anisotropy.

  4. Diffraction of short pulses with boundary diffraction wave theory.

    PubMed

    Horváth, Z L; Bor, Z

    2001-02-01

    The diffraction of short pulses is studied on the basis of the Miyamoto-Wolf theory of the boundary diffraction wave, which is a mathematical formulation of Young's idea about the nature of diffraction. It is pointed out that the diffracted field is given by the superposition of the boundary wave pulse (formed by interference of the elementary boundary diffraction waves) and the geometric (direct) pulse (governed by the laws of geometrical optics). The case of a circular aperture is treated in details. The diffracted field on the optical axis is calculated analytically (without any approximation) for an arbitrary temporal pulse shape. Because of the short pulse duration and the path difference the geometric and the boundary wave pulses appear separately, i.e., the boundary waves are manifested in themselves in the illuminated region (in the sense of geometrical optics). The properties of the boundary wave pulse is discussed. Its radial intensity distribution can be approximated by the Bessel function of zero order if the observation points are in the illuminated region and far from the plane of the aperture and close to the optical axis. Although the boundary wave pulse propagates on the optical axis at a speed exceeding c, it does not contradict the theory of relativity. PMID:11308595

  5. Rayleigh backscatter mitigation by RF modulation in a 100-km remote fiber sensing system

    Microsoft Academic Search

    Jong H. Chow; David E. McClelland; Malcolm B. Gray

    2007-01-01

    One of the main factors limiting high performance remote fiber sensing systems is the Rayleigh backscatter associated with a long length of optical delivery fiber. Rayleigh backscatter introduces amplitude and phase noise during interferometric signal extraction, resulting in degradation of system sensitivity. This noise source increases with the length of optical fiber used in the architecture, and thus traditionally sets

  6. Identification of Southern Ocean acoustic targets using aggregation backscatter and shape characteristics

    Microsoft Academic Search

    Rachel S. Woodd-Walker; Jonathan L. Watkins; Andrew S. Brierley

    2003-01-01

    Acoustic surveys for biomass estimation require accurate identification of echoes from the target species. In one objective technique for identifying Antarctic krill, the difference between mean volume-backscattering strength at two frequencies is used, but can misclassify small krill and other plankton. Here, we investigate ways to improve target identification by including characteristics of backscattering energy and morphology of aggregations. To

  7. LINEARIZING NON-LINEAR INVERSE PROBLEMS AND AN APPLICATION TO INVERSE BACKSCATTERING

    E-print Network

    Uhlmann, Gunther

    this scheme to show uniqueness and H¨older stability for the inverse backscattering problem for the acoustic¨older stability for the non-linear map. We recently used this approach for studying boundary rigidity/lens to the inverse backscattering problem for the acoustic equation. In this problem, we are trying to determine

  8. Relationship of light scattering at an angle in the backward direction to the backscattering coefficient

    E-print Network

    Boss, Emmanuel S.

    Relationship of light scattering at an angle in the backward direction to the backscattering theory and new observations of the volume scattering function VSF to evaluate the choice of angle used correlation between observed scattering near 120° and the backscattering coefficient reported by Oishi Appl

  9. Relationship of Light Scattering at an Angle in the Backward Direction to the Backscattering Coefficient

    Microsoft Academic Search

    Emmanuel Boss; W. Scott Pegau

    2001-01-01

    We revisit the problem of computing the backscattering coefficient based on the measurement of scattering at one angle in the back direction. Our approach uses theory and new observations of the volume scattering function (VSF) to evaluate the choice of angle used to estimate bb . We add to previous studies by explicitly treating the molecular backscattering of water (bbw

  10. Design of the optical backscatter diagnostic for laser plasma interaction measurements on NIF

    NASA Astrophysics Data System (ADS)

    Moody, J. D.; Datte, P.; Ng, E.; Maitland, K.; Hsing, W.; MacGowan, B. J.; Froula, D. H.; Neumayer, P.; Sutter, L.; Meezan, N.; Glenzer, S. H.; Kirkwood, R. K.; Divol, L.; Andrews, S.; Jackson, J.; MacKinnon, A.; Jovanovic, I.; Beeler, R.; Bertolini, L.; Landon, M.; Alvarez, S.; Lee, T.; Watts, P.

    2007-11-01

    We describe the design of the backscatter diagnostic for NIF laser-plasma interaction (LPI) studies. It will initially be used to validate the 280 eV point design hohlraum and select phase plates for the ignition experiments. Backscatter measurements are planned for two separate groups of 4 beams (a quad). One quad is 30^o from the hohlraum axis and the other at 50^o. The backscatter measurement utilizes 2 instruments for each beam quad. The full aperture backscatter system (FABS) measures light backscattered into the final focus lens of each beam in the quad. The near backscatter imager (NBI) measures light backscattered outside of the beam quad. Both instruments must work in conjunction to provide spectrally and temporally resolved backscatter power. We describe the design of the diagnostic and its capabilities as well as plans for calibrating it and analyzing the resulting data. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  11. Acoustic backscatter of the 1995 flood deposit on the Eel shelf

    Microsoft Academic Search

    Jeffry C Borgeld; John E Hughes Clarke; John A Goff; Larry A Mayer; Jennifer A Curtis

    1999-01-01

    Acoustic swath mapping and sediment box coring conducted on the continental shelf near the mouth of the Eel River revealed regional variations in acoustic backscatter that can be related to the shelf sedimentology. The acoustic-backscatter variations observed on the shelf were unusually narrow compared to the response of similar sediment types documented in other areas. However, the acoustic data revealed

  12. HELIUM BACKSCATTERING FROM A RANDOMLY STEPPED SURFACE J. LAPUJOULADE and Y. LEJAY

    E-print Network

    Paris-Sud XI, Université de

    L-303 HELIUM BACKSCATTERING FROM A RANDOMLY STEPPED SURFACE J. LAPUJOULADE and Y. LEJAY Service de profil d'intensité sont en bon accord avec la macrorugosité. Abstract. 2014 The backscattering of helium to Bragg interference between helium atoms scattered by terraces separated by steps of one atom. From

  13. Measurement of intrinsic optical backscattering characteristics of cells using fiber-guided near infrared light

    Microsoft Academic Search

    Ching-Huang Hsu; Gwo-Ching Chang; En-Ting Li; Yu-Jing Lin; Jia-Jin Jason Chen

    2010-01-01

    BACKGROUND: Intrinsic optical signals (IOS), which reflect changes in transmittance and scattering light, have been applied to characterize the physiological conditions of target biological tissues. Backscattering approaches allow mounting of the source and detector on the same side of a sample which creates a more compact physical layout of device. This study presents a compact backscattering design using fiber-optic guided

  14. A New Inversion Model to Retrieve the Particulate Backscattering in Coastal\\/Ocean Waters

    Microsoft Academic Search

    Palanisamy Shanmugam; Balasubramanian Sundarabalan; Yu-Hwan Ahn; Joo-Hyung Ryu

    2011-01-01

    Scientific implications and practical applications of spectral particulate backscattering (bbp(?)) in oceanography are wide ranging, particularly in optical remote sensing as the light backscattered from various seawater constituents provides possi- bility to derive information about the particle properties of the water under investigation. Several inversion models have been pre- viously developed for use with remote sensing reflectance (Rrs) data over

  15. Radar BackscatterMeasurementsFrom RADARSAT S A R Imagery of South Pole Station, Antarctica

    E-print Network

    Howat, Ian M.

    Radar BackscatterMeasurementsFrom RADARSAT S A R Imagery of South Pole Station, Antarctica Hong backscatter around South Pole Station was measured from several different azimuthal angles using RADARSAT-1 topography* INTRODUCTION Radarsat-1 acquisitions in support of the 1997 Radarsat Antarctic Mapping Project

  16. Identification of major backscattering sources in trees and shrubs at 10 GHz

    NASA Technical Reports Server (NTRS)

    Zoughi, R.; Wu, L. K.; Moore, R. K.

    1986-01-01

    A short-range very-fine-resolution FM-CW radar scatterometer has been used to identify the primary contributors to 10-GHz radar backscatter from pine, pin oak, American sycamore and sugar maple trees, and from creeping juniper shrubs. This system provided a range resolution of 11 cm and gave a 16-cm diameter illumination area at the target range of about 4 m. For a pine tree, the needles caused the strongest backscatter as well as the strongest attenuation in the radar signal. Cones, although insignificant contributors to the total backscatter, were more important for backscattering than for attenuation. For the rest of the trees, leaves were the strongest cause of backscattering and attenuation. However, in the absence of leaves, the petioles, small twigs, and branches gave relatively strong backscatter. For American sycamore and sugar maple trees, the fruits did not affect the total backscatter unless they were packed in clusters. For creeping juniper the backscattered energy and attenuation in the radar signal were mainly due to the top two layers of the evergreen scales. The contribution of the tree trunks was not determined.

  17. Implementation of a near backscattering imaging system on the National Ignition Facility

    Microsoft Academic Search

    A. J. MacKinnon; T. McCarville; K. Piston; C. Niemann; G. Jones; I. Reinbachs; R. Costa; J. Celeste; G. Holtmeier; R. Griffith; R. Kirkwood; B. MacGowan; S. H. Glenzer; M. R. Latta

    2004-01-01

    A near backscattering imaging diagnostic system is being implemented on the first quad of beams on the National Ignition Facility. This diagnostic images diffusing scatter plates, placed around the final focus lenses on the National Ignition Facility target chamber, to quantitatively measure the fraction of light backscattered outside of the focusing cone angle of incident laser beam. A wide-angle imaging

  18. Underwater x-ray tomography of composite sonar domes via collimated backscatter imaging

    Microsoft Academic Search

    Edward C. Greenawald; Chester F. Poranski; Leroy J. Levenberry; Edgar T. Bellinger

    1998-01-01

    The Naval Research Laboratory has developed a novel one-sided NDE system for inspecting steel reinforced rubber sonar domes without drydocking. The submersible x-ray system scans the dome through an aluminum window in contact with its surface and uses collimated backscatter imaging to create tomographs of the dome structure. In this paper we discuss backscatter imaging, describe the system, and present

  19. Estimation of Specific Differential Phase and Differential Backscatter Phase From Polarimetric Weather Radar Measurements of Rain

    Microsoft Academic Search

    Tobias Otto; Herman W. J. Russchenberg

    2011-01-01

    The estimation of the specific differential phase par- ticularly in the presence of the differential backscatter phase and nonuniform propagation paths is a long-standing goal in weather radar polarimetry. Furthermore, a reliable estimator of the differential backscatter phase for precipitation measure- ments has not been proposed yet, although it contains valuable information about the presence of non-Rayleigh scattering and the

  20. Ultrasonic backscatter coefficients for weakly scattering, agar spheres in agar phantoms

    E-print Network

    Illinois at Urbana-Champaign, University of

    Ultrasonic backscatter coefficients for weakly scattering, agar spheres in agar phantoms Michael R and experimental backscatter coefficient BSC results. The phantoms consisted of agar spheres of various diameters nominally between 90 and 212 m , containing ultrafiltered milk, suspended in an agar background. BSC

  1. Unusual Radar Backscatter Properties Along the Northern Rim of Imbrium Basin

    NASA Technical Reports Server (NTRS)

    Thompson, Thomas W.; Campbell, Bruce A.

    2005-01-01

    Earth-based radar backscatter from the lunar terrae is 2-4 times that of the maria. The largest (most conspicuous) exception is the terra along the northern rim of Imbrium Basin, where highlands that surround Sinus Iridium and crater Pluto have long wavelength (70-cm) radar backscatter that is comparable to (and sometimes weaker) the mare.

  2. Correlation of sidescan backscatter with grain size distribution of surficial seabed sediments

    Microsoft Academic Search

    J. S. Collier; C. J. Brown

    2005-01-01

    The dependence of acoustic backscatter on sediment grain size distribution is examined using dual frequency (100 and 410 kHz) sidescan sonar and 22 sediment grab samples from the Loch Linnhe artificial reef site on the west coast of Scotland. The sidescan data were processed to remove an empirically estimated average grazing angle dependence on backscatter. The processed data were analysed

  3. Predicting seabed properties from acoustic backscatter on the UK continental shelf (Invited)

    Microsoft Academic Search

    C. McGonigle; J. Collier

    2010-01-01

    The relationship between backscatter imagery, sediment grain size and measures of biological community diversity are investigated using a quantitative approach at an aggregate extraction site in the Southern North Sea, UK. Previous work conducted at Oban in Scotland (Collier and Brown, 2005) showed the potential for estimating sediment grain size from first order backscatter statistics. In particular this study reported

  4. Polarimetric backscattering from thin saline ice related to ice physical and morphological characteristics

    Microsoft Academic Search

    S. V. Nghiemt; R. Kwokt; S. H. Yueht; J. A. Kongll; M. A. Tassoudjill; C. C. Hsull; A. J. Gows; D. K. Perovichs

    1994-01-01

    A model for polarimetric backscattering from thin saline ice, including volume and surface scattering mechanisms, is used to relate ice physical and morphological characteristics to the backscattering signatures obtained under controlled laboratory conditions. The model is based on the analytic wave theory and accounts for ellipsoidal brine inclusions, c-axis orientations, rough interfaces, vertical anisotropy, and permittivity tensor determined with brine

  5. The simulation of radar and coherent backscattering with the Monte Carlo model MYSTIC

    NASA Astrophysics Data System (ADS)

    Pause, Christian; Buras, Robert; Emde, Claudia; Mayer, Bernhard

    2013-05-01

    A new method to simulate radar and coherent backscattering within the framework of the 3D Monte Carlo radiative transfer model MYSTIC has been developed. Simulating radar is solved with the help of the already existing lidar simulator. Therefore the larger part of this paper presents a solution to simulate coherent backscattering and shows a comparison to a real case.

  6. Enhanced lidar backscattering by quasi-horizontally oriented ice crystal plates in cirrus clouds

    Microsoft Academic Search

    Ping Yang; Yong X. Hu; David M. Winker; Jun Zhao; Chris A. Hostetler; Lamont Poole; Bryan A. Baum; Michael I. Mishchenko; Jens Reichardt

    2003-01-01

    The backscattering of light by quasi-horizontally oriented hexagonal ice plates is investigated because of its pertinence to lidar measurements of cirrus clouds. For oriented ice crystals, the commonly used geometric optics ray-tracing method is not applicable to the computation of the scattered field in certain scattering directions, in particular, the backscattering direction, because of the singularity problem inherent to the

  7. Sensitivity of radar backscattering to soil surface parameters: a comparison between theoretical analysis and experimental evidence

    Microsoft Academic Search

    Rudi Hoeben; Peter A. Troch; Zhongbo Su; Marco Mancini; Kun-Shan Chen

    1997-01-01

    The understanding of the sensitivity of radar backscattering to surface parameters is essential in applying microwave remote sensing to the retrieval of geo- and bio-physical parameters. A theoretical model, the integral equation model, is used to investigate the sensitivity of radar backscattering to soil surface parameters. This model is first tested against a dataset retrieved under well controlled conditions at

  8. X-Ray Diffraction Apparatus

    NASA Technical Reports Server (NTRS)

    Blake, David F. (Inventor); Bryson, Charles (Inventor); Freund, Friedmann (Inventor)

    1996-01-01

    An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample is introduced. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.

  9. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, A.J.; Butler, M.A.; Sinclair, M.B.; Senturia, S.D.

    1998-05-26

    An electrically-programmable diffraction grating is disclosed. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers). 14 figs.

  10. Quasi-diffraction-free beams.

    PubMed

    Tanaka, K; Taguchi, M; Tanaka, T

    2001-07-01

    A diffraction-free beam is obtained by the superposing of plane waves whose wave vectors make an angle with the propagation axis. These plane waves are realized with point sources that are distributed uniformly around a circle and an infinitely large aperture lens. After the field passes through the lens it has nondiffracting properties and is described by the zero-order Bessel function. Relaxing these conditions makes the beam diffraction free within only a limited region. The beam generated from such a geometry is referred to as a quasi-diffraction-free beam. The effects of the width of the annular source on the beam spread are discussed and compared with those for a Gaussian beam. Approximate expressions for quasi-diffraction-free beams are also obtained. PMID:11444556

  11. A C-band backscatter model for lake ice in Alaska

    NASA Technical Reports Server (NTRS)

    Wakabayashi, H.; Weeks, W. F.; Jeffries, M. O.

    1993-01-01

    ERS-1 SAR imagery of lake ice growing on shallow tundra lakes in northern Alaska shows interesting radar backscatter variations. Based on the analysis of ice cores from these lakes, a multi-layer backscatter model comprised of the following elements has been developed: (1) specular air-ice; ice-water and ice-frozen soil boundaries; (2) an ice layer of variable thickness; (3) ice sub-layers with air inclusions of variable density, size and shape including spheres, prolate spheroids, and cylinders of finite length. Preliminary model results confirm that backscatter is a sensitive function of greater reflectivity than from an ice-frozen soil interface. The model has also been tested using bubble data derived from ice cores in April 1992. The modelled backscatter is compared with backscatter derived from ERS-1 SAR images obtained at the same time as the fieldwork.

  12. [Obtaining aerosol backscattering coefficient using pure rotational Raman-Mie scattering spectrum].

    PubMed

    Rong, Wei; Chen, Si-Ying; Zhang, Yin-Chao; Chen, He; Guo, Pan

    2012-11-01

    Both the traditional Klett and Fernald methods used to obtain atmospheric aerosol backscattering coefficient require the hypothesis of relationship between the extinction coefficient and backscattering coefficient, and this will bring error. According to the theory that the pure rotational Raman backscattering coefficient is only related to atmospheric temperature and pressure, a new method is presented for inverting aerosol backscattering coefficient, which needed the intensity of elastic scattering and rotational Raman combined with atmospheric temperature and pressure obtained with the sounding balloons in this article. This method can not only eliminate the errors of the traditional Klett and Fernald methods caused by the hypothesis, but also avoid the error caused by the correction of the overlap. Finally, the aerosol backscattering coefficient was acquired by using this method and the data obtained via the Raman-Mie scattering Lidar of our lab. And the result was compared with that of Klett and Fernald. PMID:23387171

  13. Characterization of microstructure with low frequency electromagnetic techniques

    SciTech Connect

    Cherry, Matthew R.; Sathish, Shamachary [University of Dayton Research Institute, Structural Integrity Division, 300 College Park, Dayton, OH 45469-0020 (United States); Pilchak, Adam L.; Blodgett, Mark P. [Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXCM), 2230 10th St., WPAFB, OH 45433 (United States); Cherry, Aaron J. [Southwest Ohio Council for Higher Education, 3155 Research Blvd., Suite 204, Dayton, OH 45420-4015 (United States)

    2014-02-18

    A new computational method for characterizing the relationship between surface crystallography and electrical conductivity in anisotropic materials with low frequency electromagnetic techniques is presented. The method is discussed from the standpoint of characterizing the orientation of a single grain, as well as characterizing statistical information about grain ensembles in the microstructure. Large-area electron backscatter diffraction (EBSD) data was obtained and used in conjunction with a synthetic aperture approach to simulate the eddy current response of beta annealed Ti-6Al-4V. Experimental eddy current results are compared to the computed eddy current approximations based on electron backscatter diffraction (EBSD) data, demonstrating good agreement. The detectability of notches in the presence of noise from microstructure is analyzed with the described simulation method and advantages and limitations of this method are discussed relative to other NDE techniques for such analysis.

  14. Models for Precession Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Marks, Laurence D.

    Precession Electron Diffraction has become an increasingly popular method of obtaining crystallographic data, and may well replace older methods such as selected area diffraction or microdiffraction. While a full model has to involve a dynamical calculation, some approximations give some indication how the results vary as a function of thickness and precession angle. This note reviews some of the basic models, their advantages and failures as well as some of the open issues.

  15. Synchrotron X-ray diffraction study of texture evolution in 904L stainless steel under dynamic shock compression

    SciTech Connect

    Li, Nanan; Wang, Y. D.; Peng, R. Lin; Sun, Xin; Ren, Yang; Wang, L.; Cai, H. N.

    2011-01-01

    The influence of strain rate on development of deformation texture under a dynamic shock compression of a 904L stainless steel was quantitatively investigated using synchrotron X-ray diffraction and crystallographic orientation distribution function (ODF) analysis. Split-Hopkinson Pressure Bar technique was used to generate a high strain rate of > 103 s-1 for preparing the deformed samples. Starting with an almost random texture in a solution treatment condition, the deformed material developed several typical texture components, such as ‘Goss’ texture and ‘Brass’ texture. Compared to the texture components displayed in the state of quasi-static compression deformation, it was found that the high-speed deformation generated much weaker texture components. In combination with the change in microstructures observed by EBSD and TEM technique, the high-energy X-ray diffraction provides a powerful tool for characterizing the strain-rate dependence of grain rotation at each stage of deformation. The deformation heterogeneity evident in our experiment can be explained by a transition of deformation mechanism from the dislocation/twin-dominated mode to shear-band-dominated one with increasing strain rate.

  16. Solving difficult structures with electron diffraction.

    PubMed

    Zuo, J M; Rouviére, J L

    2015-01-01

    Precession electron diffraction has solved a long-standing challenge in electron diffraction. Further progress promises a general technique for structure determination of difficult crystals. PMID:25610622

  17. The construction of a high resolution crystal backscattering spectrometer HERMES I

    SciTech Connect

    Larese, J.Z.

    1998-11-01

    There is a need in the United States for a state-of-the-art, cold-neutron, crystal backscattering spectrometer (CBS) designed to investigate the structure and dynamics of condensed matter systems by the simultaneous utilization of long wavelength elastic diffraction and high-energy-resolution inelastic scattering. Cold neutron spectroscopy with CBS-type instruments has already made many important contributions to the study of atomic and molecular diffusion in biomaterials, polymers, semiconductors, liquid crystals, superionic conductors and the like. Such instruments have also been invaluable for ultra high resolution investigations of the low-lying quantum tunneling processes that provide direct insight into the dynamical response of solids at the lowest energies. Until relatively recently, however, all such instruments were located at steady-state reactors. This proposal describes HERMES I (High Energy Resolution Machines I) a CBS intended for installation at the LANSCE pulsed neutron facility of Los Alamos National Laboratory. As explained in detail in the main text, the authors propose to construct an updated, high-performance CBS which incorporates neutron techniques developed during the decade since IRIS was built, i.e., improved supermirror technology, a larger area crystal analyzer and high efficiency wire gas detectors. The instrument is designed in such a way as to be readily adaptable to future upgrades. HERMES I, they believe, will substantially expand the range and flexibility of neutron investigations in the United States and open new and potentially fruitful directions for condensed matter exploration. This document describes a implementation plan with a direct cost range between $4.5 to 5.6 M and scheduled duration of 39--45 months for identified alternatives.

  18. Back-scatter based whispering gallery mode sensing

    PubMed Central

    Knittel, Joachim; Swaim, Jon D.; McAuslan, David L.; Brawley, George A.; Bowen, Warwick P.

    2013-01-01

    Whispering gallery mode biosensors allow selective unlabelled detection of single proteins and, combined with quantum limited sensitivity, the possibility for noninvasive real-time observation of motor molecule motion. However, to date technical noise sources, most particularly low frequency laser noise, have constrained such applications. Here we introduce a new technique for whispering gallery mode sensing based on direct detection of back-scattered light. This experimentally straightforward technique is immune to frequency noise in principle, and further, acts to suppress thermorefractive noise. We demonstrate 27?dB of frequency noise suppression, eliminating frequency noise as a source of sensitivity degradation and allowing an absolute frequency shift sensitivity of 76?kHz. Our results open a new pathway towards single molecule biophysics experiments and ultrasensitive biosensors. PMID:24131939

  19. Towards a Metric to Estimate Atomic Number from Backscattered Photons

    SciTech Connect

    Walston, S; Dietrich, D; Wurtz, R

    2009-08-17

    An ability to determine the atomic number of a material in a cargo container would be helpful in interdicting smuggled nuclear materials. This paper examines two processes by which high energy photons interact with matter; Compton scattering and pair production. The ratio of the number of photons which originate from the annihilation of positrons resulting from pair production and the number of photons coming from Compton scattering gives a good indication of atomic number. At large angles relative to an incident beam - i.e. backscattered, there is good separation in energy between Compton scattered photons and photons from positron annihilations. This ratio can then be cleanly determined in order to estimate atomic number.

  20. Ocean Raman Scattering in Satellite Backscatter UV Measurements

    NASA Technical Reports Server (NTRS)

    Vasilkov, Alexander P.; Joiner, Joanna; Gleason, James; Bhartia, Pawan; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    Ocean Raman scattering significantly contributes to the filling-in of solar Fraunhofer lines measured by satellite backscatter ultraviolet (buy) instruments in the cloudless atmosphere over clear ocean waters. A model accounting for this effect in buy measurements is developed and compared with observations from the Global Ozone Monitoring Experiment (GONE). The model extends existing models for ocean Raman scattering to the UV spectral range. Ocean Raman scattering radiance is propagated through the atmosphere using a concept of the Lambert equivalent reflectively and an accurate radiative transfer model for Rayleigh scattering. The model and observations can be used to evaluate laboratory measurements of pure water absorption in the UV. The good agreement between model and observations suggests that buy instruments may be useful for estimating chlorophyll content.

  1. Polarized Rayleigh back-scattering from individual semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Duming; Wu, Jian; Lu, Qiujie; Gutierrez, Humberto R.; Eklund, Peter C.

    2010-08-01

    A complete understanding of the interaction between electromagnetic radiation and semiconductor nanowires (NWs) is required in order to further develop a new generation of opto-electronic and photonic devices based on these nanosystems. The reduced dimensionality and high aspect ratio of nanofilaments can induce strong polarization dependence of the light absorption, emission and scattering, leading in some cases to the observation of optical antenna effects. In this work we present the first systematic study of polarized Rayleigh back-scattering from individual crystalline semiconductor NWs with known crystalline structure, orientation and diameters. To explain our experimental Rayleigh polar patterns, we propose a simple theory that relies on a secondary calculation of the volume-averaged internal electromagnetic fields inside the NW. These results revealed that the internal and emitted field can be enhanced depending on the polarization with respect to the NW axis; we also show that this effect strongly depends on the NW diameter.

  2. Snow backscatter in the 1-8 GHz region

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.

    1976-01-01

    The 1-8 GHz microwave active spectrometer system was used to measure the backscatter response of snow covered ground. The scattering coefficient was measured for all linear polarization combinations at angles of incidence between nadir and 70 deg. Ground truth data consisted of soil moisture, soil temperature profile, snow depth, snow temperature profile, and snow water equivalent. The radar sensitivity to snow water equivalent increased in magnitude with increasing frequency and was almost angle independent for angles of incidence higher than 30 deg, particularly at the higher frequencies. In the 50 deg to 70 deg angular range and in the 6 to 8 GHz frequency range, the sensitivity was typically between -0.4 dB/.1 g/sq cm and -0.5 dB/,1 g/sq cm, and the associated linear correlation coefficient had a magnitude of about 0.8.

  3. Time-of-flight detector for heavy ion backscattering spectrometry

    SciTech Connect

    Knapp, J.A.; Banks, J.C.; Doyle, B.L. [Sandia National Labs., Albuquerque, NM (United States). Ion Solid Interactions and Defect Physics Dept.

    1994-04-01

    This report describes the results of a two-year laboratory directed research and development project to explore advanced concepts in Heavy Ion Backscattering Spectrometry (HIBS), undertaken with the goal of extending the sensitivity of this relatively new technique to levels unattainable by any other existing trace element surface analysis. Improvements in sensitivity are required for the application of HIBS to contamination control in the microelectronics industry. Tools with sensitivity approaching 10{sup 8} atoms/cm{sup 2} are expected to be essential for enabling advanced IC production by the year 2000. During the project the authors developed a new analysis chamber with channeling goniometer and a prototype time-of-flight detector with a demonstrated sensitivity of {approximately} 5 {times} 10{sup 8} atoms/cm{sup 2} for Au on Si and {approximately} 5 {times} 10{sup 10} for Fe, and sufficient mass resolution to separate contributions from Fe and Cu.

  4. Remote identification of a shipwreck site from MBES backscatter.

    PubMed

    Masetti, Giuseppe; Calder, Brian

    2012-11-30

    The method described attempts to remotely identify the shape of an anthropogenic object, such as a wreck of a modern vessel, using reflectivity data from Multi-Beam Echosounder (MBES) systems. In the beam domain, the backscatter strength values - geometrically and radiometrically corrected - are used to extract a large number of Gray Level Co-occurrence Matrix (GLCM) features with different input parameters. Principal Component Analysis (PCA) is applied in order to achieve dimensionality reduction whilst a K-means algorithm clusters as "shipwreck site" a large number of beams for each line. After the geo-referencing process, a K-nearest-neighbors (K-NN) technique is applied as a filter for possible misclassifications. Finally, the shape of the shipwreck site is defined from the georeferenced beams using the ?-shape method, constructing an output compatible with Geographic Information Systems (GIS). PMID:22820745

  5. Unusual Radar Backscatter along the Northern Rim of Imbrium Basin

    NASA Technical Reports Server (NTRS)

    Thompson, Thomas W.; Campbell, Bruce A.; Ghent, Rebecca R.; Hawke, B. Ray; Leverington, David W.

    2006-01-01

    A viewgraph presentation of the unusual radar backscatter properties along the Northern Rim of Imbrium Basin is shown. The contents include: 1) Visual and Infrared Observations of Moon; 2) Radar Observations of Moon; 3) Lunar Orbiter Photographs Geologic Setting; 4) 70-cm Radar Data; 5) .70-cm Radar Dark Halo Craters; 6) 3.8-cm Radar Data; 7) 7.5-m Radar Data; 8) 70cm, 3.8 cm and 7.5-m Radar Data; 9) Optical and Infrared Data; 10) Plato Rilles; 11) Isopachs of Crater Ejecta; 12) Plato-like Craters; 13) Observation Summary; 14) Interpretation Matrix; 15) Dark Halo Diameters vs. Crater Size; and 16) Radar Geologic Column.

  6. Backscattering and Nonparaxiality Arrest Collapse of Damped Nonlinear Waves

    NASA Technical Reports Server (NTRS)

    Fibich, G.; Ilan, B.; Tsynkov, S.

    2002-01-01

    The critical nonlinear Schrodinger equation (NLS) models the propagation of intense laser light in Kerr media. This equation is derived from the more comprehensive nonlinear Helmholtz equation (NLH) by employing the paraxial approximation and neglecting the backscattered waves. It is known that if the input power of the laser beam (i.e., L(sub 2) norm of the initial solution) is sufficiently high, then the NLS model predicts that the beam will self-focus to a point (i.e.. collapse) at a finite propagation distance. Mathematically, this behavior corresponds to the formation of a singularity in the solution of the NLS. A key question which has been open for many years is whether the solution to the NLH, i.e., the 'parent' equation, may nonetheless exist and remain regular everywhere, in particular for those initial conditions (input powers) that lead to blowup in the NLS. In the current study, we address this question by introducing linear damping into both models and subsequently comparing the numerical solutions of the damped NLH (boundary-value problem) with the corresponding solutions of the damped NLS (initial-value problem). Linear damping is introduced in much the same way as done when analyzing the classical constant-coefficient Helmholtz equation using the limiting absorption principle. Numerically, we have found that it provides a very efficient tool for controlling the solutions of both the NLH and NHS. In particular, we have been able to identify initial conditions for which the NLS solution does become singular. whereas the NLH solution still remains regular everywhere. We believe that our finding of a larger domain of existence for the NLH than that for the NLS is accounted for by precisely those mechanisms, that have been neglected when deriving the NLS from the NLH, i.e., nonparaxiality and backscattering.

  7. Feasibility of using backscattered muons for archeological imaging

    NASA Astrophysics Data System (ADS)

    Bonal, N.; Preston, L. A.

    2013-12-01

    Use of nondestructive methods to accurately locate and characterize underground objects such as rooms and tools found at archeological sites is ideal to preserve these historic sites. High-energy cosmic ray muons are very sensitive to density variation and have been used to image volcanoes and archeological sites such as the Egyptian and Mayan pyramids. Muons are subatomic particles produced in the upper atmosphere that penetrate the earth's crust up to few kilometers. Their absorption rate depends on the density of the materials through which they pass. Measurements of muon flux rate at differing directions provide density variations of the materials between the muon source (cosmic rays and neutrino interactions) and the detector, much like a CAT scan. Currently, muon tomography can resolve features to the sub-meter scale making it useful for this type of work. However, the muon detector must be placed below the target of interest. For imaging volcanoes, the upper portion is imaged when the detector is placed on the earth's surface at the volcano's base. For sites of interest beneath the ground surface, the muon detector would need to be placed below the site in a tunnel or borehole. Placing the detector underground can be costly and may disturb the historical site. We will assess the feasibility of imaging the subsurface using upward traveling muons, to eliminate the current constraint of positioning the detector below the target. This work consists of three parts 1) determine the backscattered flux rate from theory, 2) distinguish backscattered from forward scattered muons at the detector, and 3) validate the theoretical results with field experimentation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  8. Monte Carlo simulation of Tabata’s electron backscattering experiments

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    Electron backscattering coefficients, ?, 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 [15]. 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 ? 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 ? 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 ? 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.

  9. Three-dimensional Quantum Slit Diffraction and Diffraction in Time

    NASA Astrophysics Data System (ADS)

    Beau, M.; Dorlas, T. C.

    2015-06-01

    We derive a self-consistent formula for the quantum propagator of the quantum diffraction by a reflecting (or non-absorbing) screen with an arbitrary aperture, in the transmission region. To achieve this, we use the Green function approach (Brukner and Zeilinger, Phys. Rev. A. 56(5), 3804-3824 1997) that we extend to mixed boundary conditions (including Dirichlet and Neumann) on the shutter's screen and to any initial wave functions, such as Gaussian wave packets. To illustrate our results, we apply this method to the famous rectangular slit diffraction problem. It allows us to take into account the effect of the quantum nature of the motion perpendicular to the screen where the diffraction-in-time phenomenon appears in this direction. Then we derive corrections to the standard semi-classical formula and the diffraction pattern. We also point out situations in which this might be observable. In particular, we discuss the diffraction in space and time in the presence of gravity.

  10. Sensitivity of X-, C-, and L-Band SAR Backscatter to Burn Severity in Mediterranean Pine Forests

    Microsoft Academic Search

    Mihai A. Tanase; Maurizio Santoro; Juan de la Riva; Fernando Pérez-Cabello; Thuy Le Toan

    2010-01-01

    Synthetic aperture radar (SAR) data at X-, C-, and L-bands have been investigated to determine the relationship between backscatter and forest burn severity over three sites in Spain. The dependence of SAR backscatter on local incidence angle and environmental conditions has been analyzed. At HH and VV polarizations, the backscatter increased with burn severity for X- and C-bands, whereas it

  11. The origins of microtexture in duplex Ti alloys

    Microsoft Academic Search

    M. G. Glavicic; B. B. Bartha; S. K. Jha; C. J. Szczepanski

    2009-01-01

    A previously developed methodology was used to transform electron backscatter diffraction (EBSD) data for the primary and secondary alpha phases of Ti–6Al–2Sn–4Zr–6Mo (Ti-6246) to the prior beta phase. The results established that the observed microtexture in duplex alloys is a direct result of the prior beta grain orientations, and variant selection. In addition, for a homogeneous duplex microstructure, all of

  12. Sigma-Boundary Statistics by Length and Number

    Microsoft Academic Search

    Valerie Randle

    2002-01-01

    This paper presents a rationale for comparative use of length fraction and number fraction statistics in grain boundary analysis from orientation maps generated by electron back-scatter diffraction (EBSD). The length and number fraction statistics for S3n coincidence site lattice (CSL) boundaries were measured and compared. The length fraction of S3 boundaries was 0.48 whereas the number fraction was significantly less,

  13. Defect and damage evolution quantification in dynamically-deformed metals using orientation-imaging microscopy

    SciTech Connect

    Gray, George T., III [Los Alamos National Laboratory; Livescu, Veronica [Los Alamos National Laboratory; Cerreta, Ellen K [Los Alamos National Laboratory

    2010-03-18

    Orientation-imaging microscopy offers unique capabilities to quantify the defects and damage evolution occurring in metals following dynamic and shock loading. Examples of the quantification of the types of deformation twins activated, volume fraction of twinning, and damage evolution as a function of shock loading in Ta are presented. Electron back-scatter diffraction (EBSD) examination of the damage evolution in sweeping-detonation-wave shock loading to study spallation in Cu is also presented.

  14. Stir zone microstructure and strain rate during Al 7075-T6 friction stir spot welding

    Microsoft Academic Search

    A. Gerlich; G. Avramovic-Cingara; T. H. North

    2006-01-01

    The factors determining the temperature, heating rate, microstructure, and strain rate in Al 7075-T6 friction stir spot welds\\u000a are investigated. Stir zone microstructure was examined using a combination of transmission electron microscopy (TEM) and\\u000a electron backscattered diffraction (EBSD) microscopy, while the strain rate during spot welding was calculated by incorporating\\u000a measured temperatures and the average subgrain dimensions in the Zener-Hollomon

  15. Microstructural Evolution in Adiabatic Shear Localization in Stainless Steel

    Microsoft Academic Search

    M. A. Meyers; M. T. Perez-Prado; Q. Xue; Y. Xu; T. R. McNelley

    2002-01-01

    Shear bands were generated under prescribed and controlled conditions in stainless steel (Fe-18%Cr-8%Ni). Hat-shaped specimens, deformed in a Hopkinson bar were used, yielding strain rates of approximately 104s-1 and shear strains that could be varied between 1 and 100. Specimens recovered from the collapse of thick-walled cylinders were also investigated. Microstructural characterization was performed by electron backscattered diffraction (EBSD) with

  16. Microstructural Evolution in Adiabatic Shear Localization in Stainless Steel

    Microsoft Academic Search

    M. A. Meyers; M. T. Perez-Prado; Q. Xue; Y. Xu; T. R. McNelley

    2002-01-01

    Shear bands were generated under prescribed and controlled conditions in stainless steel (Fe-18%Cr-8%Ni). Hat-shaped specimens, deformed in a Hopkinson bar were used, yielding strain rates of approximately 104s?1 and shear strains that could be varied between 1 and 100. Specimens recovered from the collapse of thick-walled cylinders were also investigated. Microstructural characterization was performed by electron backscattered diffraction (EBSD) with

  17. Microstructural Evolution in Adiabatic Shear Localization

    Microsoft Academic Search

    M. A. Meyers; M. T. Perez-Prado; T. R. McNelley; Q. Xue; Y. Xu

    2001-01-01

    Shear bands were generated under prescribed and controlled conditions in stainless steel( Fe-18Hat-shaped specimens, deformed in a Hopkinson bar were used, yielding strain rates of approximately 104s-1 and shear strains that could be varied between 1 and 100.Specimens recovered from the collapse of thick-walled cylinders were also investigated. Microstructural characterization was performed by electron backscattered diffraction (EBSD) with orientation imaging

  18. Microstructural evolution in adiabatic shear localization in stainless steel

    Microsoft Academic Search

    M. A. Meyers; Y. B. Xu; Q. Xue; M. T. Pérez-Prado; T. R. McNelley

    2003-01-01

    Shear bands were generated under prescribed and controlled conditions in an AISI 304L stainless steel (Fe–18%Cr–8%Ni). Hat-shaped specimens were deformed in a Hopkinson bar at strain rates of ca 104 s?1 and shear strains that could be varied between 1 and 100. Microstructural characterization was performed by electron backscattered diffraction (EBSD) with orientation imaging microscopy (OIM), and transmission electron microscopy

  19. The effect of deformation temperature on the microstructure evolution of Inconel 625 superalloy

    Microsoft Academic Search

    Qingmiao Guo; Defu Li; Shengli Guo; Haijian Peng; Jie Hu

    2011-01-01

    Hot compression tests of Inconel 625 superalloy were conducted using a Gleeble-1500 simulator between 900°C and 1200°C with different true strains and a strain rate of 0.1s?1. Scanning electron microscope (SEM) and electron backscatter diffraction technique (EBSD) were employed to investigate the effect of deformation temperature on the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). It is found

  20. Electromagnetic diffraction efficiencies for plane reflection diffraction gratings

    NASA Technical Reports Server (NTRS)

    Marathay, A. S.; Shrode, T. E.

    1974-01-01

    The theory and computer programs, based on electromagnetic theory, for the analysis and design of echelle gratings were developed. The gratings are designed for instruments that operate in the ultraviolet portion of the spectrum. The theory was developed so that the resulting computer programs will be able to analyze deep (up to 30 wavelengths) gratings by including as many as 100 real or homogeneous diffraction orders. The program calculates the complex amplitude coefficient for each of the diffracted orders. A check on the numerical method used to solve the integral equations is provided by a conservation of energy calculation.