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Sample records for backscattered diffraction ebsd

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

    SciTech Connect

    McCabe, Rodney J.; Kelly, Ann Marie; Clarke, Amy J.; Field, Robert D.; Wenk, H. R.

    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

  2. Electron backscatter diffraction (EBSD) as a tool for detection of coral diagenesis

    NASA Astrophysics Data System (ADS)

    Cusack, M.; England, J.; Dalbeck, P.; Tudhope, A. W.; Fallick, A. E.; Allison, N.

    2008-12-01

    Fine-scale structures of intact modern and fossil coralline skeletons were analysed to determine alteration to secondary cements and phases using electron backscatter diffraction (EBSD). EBSD analysis revealed secondary aragonite cements in endolithic borings in the modern skeleton and whole dissepiments of the fossil skeleton replaced by calcite, despite X-ray diffraction (XRD) bulk analysis of the general area suggesting only aragonite was present. Non-destructive, in situ screening of coral samples by EBSD analysis provides a valuable tool for assessing the extent of alteration and can determine which areas may produce more reliable climate proxy data.

  3. 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.

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

    PubMed

    van Bremen, R; Ribas Gomes, D; de Jeer, L T H; Ocelík, V; De Hosson, J Th M

    2016-01-01

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

  5. Advanced microstructural analysis of ferrite materials by means of electron backscatter diffraction (EBSD)

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Mücklich, F.

    2010-05-01

    The analysis of the achieved texture is of great importance for the performance of ferrite materials, either bulk or thin films. The recently developed electron backscatter diffraction (EBSD) technique enables a spatially resolved study of the crystallographic orientations by means of recording of Kikuchi patterns. To our knowledge, such a thorough EBSD analysis was not yet performed in any oxidic magnetic material, and only very recently on magnetite thin films by us. A good surface polishing/cleaning is essential for this analysis, as the method requires an undisturbed surface area for a high image quality (IQ). This information is recorded to each measured Kikuchi pattern, together with a parameter describing the quality of indexation. Here, the spatially highly resolved EBSD mappings provide additional information as compared to the standard analysis techniques, which can contribute to an optimization of the growth process. Furthermore, an analysis of the grain aspect ratio is possible which provides further insight to the microstructural dependence of the magnetic properties of ferrites.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  7. Phase Identification of Individual Crystalline Particles by Electron Backscatter Diffraction (EBSD)

    SciTech Connect

    SMALL,J.A.; MICHAEL,JOSEPH R.

    2000-06-12

    Recently, an EBSD system was developed that uses a 1024 x 1024 CCD camera coupled to a thin phosphor. This camera has been shown to produce excellent EBSD patterns. In this system, crystallographic information is determined from the EBSD pattern and coupled with the elemental information from energy or wavelength dispersive x-ray spectrometry. Identification of the crystalline phase of a sample is then made through a link to a commercial diffraction database. To date, this system has been applied almost exclusively to conventional, bulk samples that have been polished to a flat surface. In this investigation, the authors report on the application of the EBSD system to the phase identification analysis (PIA) of individual micrometer and submicrometer particles rather than flat surfaces.

  8. Texture analysis of melt-spun Ni-Mn-Ga tapes by means of electron backscatter diffraction (EBSD)

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Mitra, A.; Panda, A. K.

    2010-01-01

    A texture analysis is performed by means of the electron-backscatter diffraction technique (EBSD) on melt-spun ribbon-like samples of the composition Ni52.5Mn24.5Ga23 (at.-%) were prepared. A dedicated surface treatment is required in order to achieve high quality Kikuchi patterns. For this purpose, mechanical polishing plus ion polishing was employed. EBSD analysis and transmission electron microscopy revealed that the samples have a polycrystalline, granular morphology, with grain sizes around 1 - 2 μm. Several larger grains being present in the region selected for EBSD analysis, and many small grains are found, even embedded in the larger ones. The larger grains exhibit a common direction of elongation, yielding to a specific texture.

  9. Study of ferrous corrosion products on iron archaeological objects by electron backscattered diffraction (EBSD)

    NASA Astrophysics Data System (ADS)

    Azoulay, Ilanith; Conforto, Egle; Refait, Philippe; Rémazeilles, Céline

    2013-02-01

    The corrosion of iron-based archaeomaterials in anoxic environments leads mainly to Fe(II) compounds, like the hydroxychloride β-Fe2(OH)3Cl, chukanovite Fe2(OH)2CO3 or siderite FeCO3. The understanding of the mechanisms then necessarily implies a thorough investigation of the chemical, mechanical and morphological characteristics of the Fe(II)-based layer that develops between the metal surface and the environment. In the peculiar case of Fe(II) compounds, generally very reactive towards O2, the main concern is to prevent any transformation by air during the analysis. The EBSD technique is adapted on a scanning electron microscope (SEM) where the samples are analysed under vacuum and consequently sheltered from air. Different options offered by EBSD for phase characterisation and microstructural study were tested for the first time on the rust layers of two archaeological iron nails. Results were confronted to those obtained by micro-Raman spectroscopy, which was used as reference method. Magnetite, Fe(II) hydroxychloride β-Fe2(OH)3Cl and siderite were analysed successfully but improvements have to be brought for the study of other compounds such as iron oxyhydroxides and chukanovite. The choice of experimental parameters in our approach as well as the potentialities and limits of the technique for this kind of application are discussed.

  10. EBSD characterization and modeling of columnar dendritic grains growing in the presence of fluid flow[Electron Backscattered Diffraction

    SciTech Connect

    Takatani, H.; Gandin, C.A.; Rappaz, M.

    2000-02-09

    Columnar dendritic grains of steel growth in the presence of fluid flow (e.g., solidified on turning rolls) have been characterized by Electron Backscattered Diffraction (EBSD) technique. It is shown that grains have a random crystallographic orientation at the surfaces of the sheet in contact with the mould. In the middle of the sheet, the grains which have survived the growth selection mechanisms exhibit a (100) texture in which the average dendrite trunk direction is not exactly aligned with the thermal gradient (i.e., the normal to the surfaces of the sheet). It is tilted by about 15{degree} toward the upstream direction. This deviation is examined by simulations of grain structure formation based on a three-dimensional Cellular Automation (CA)-Finite Element (FE) (3D CAFE) model, which has been modified in order to account for fluid flow effects. The modified Ca algorithm includes a growth kinetics of the dendrites which is a function of both the undercooling and fluid flow direction. It is validated by comparing the predicted shape of an individual grain growing under given thermal and fluid flow conditions with an analytical solution. The 3D CAFE predictions of the columnar grains grown in the presence of fluid flow are in good agreement with the experimental EBSB results.

  11. Texture analysis of monofilamentary, Ag-sheathed (Pb,Bi) 2Sr 2Ca 2Cu 3O x tapes by electron backscatter diffraction (EBSD)

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Qu, T.; Han, Z.; Mücklich, F.

    2008-02-01

    Using automated orientation imaging, the grain orientations and texture of monofilamentary, Ag-sheathed (Pb,Bi) 2Sr 2Ca 2Cu 3O x (Bi-2223) tape is analysed in detail by means of electron backscatter diffraction (EBSD). The achieved high image quality of the Kikuchi patterns enables multi-phase scans including Bi-2223, Bi 2Sr 2CaCu 2O x, Bi 2Sr 2CuO x, (Sr,Ca) 14Cu 24O 41 and Ag to be performed. Two areas are selected for the EBSD analysis, one close to the silver sheath, the other located in the center of the sample. The grain orientation maps are presented for each phase separately allowing a new insight into the microtexture of Ag-sheathed Bi-2223 tapes. Furthermore, the EBSD analysis provides the possibility for a misorientation angle analysis within each individual phase.

  12. 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, α and β. 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 α-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 α-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 α-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 α-Zr grains (deformed original (prior)

  13. Statistical Reliability of Phase Fraction Determination Based on Electron Backscatter Diffraction (EBSD) Investigations on the Example of an Al-TRIP Steel

    NASA Astrophysics Data System (ADS)

    Davut, Kemal; Zaefferer, Stefan

    2010-09-01

    The aim of this article is to discuss the representativeness of electron backscatter diffraction (EBSD) mapping data for phase fraction determination in multiphase materials. Particular attention is paid to the effect of step size and scanned area. The experimental investigations were carried out on a low-alloyed steel with transformation induced plasticity (TRIP) that shows a relatively heterogeneous distribution of residual austenite in a ferrite matrix. EBSD scans of various area sizes and step sizes were carried out and analyzed with respect to the determined austenite phase fraction. The step size has only an indirect influence on the results, as it determines the size of the investigated area if the number of measurement points is kept constant. Based on the experimental results, the optimum sampling conditions in terms of analyzed area size and the number of measurement points were determined. These values were compared with values obtained from Cochran’s formula, which allows calculation of sampling sizes for predefined levels of precision and confidence. A significant deviation of experimental from theoretical optimum sample sizes was found. This deviation is, for the most part, a result of the heterogeneous distribution of the austenite phase. Depending on grain size and volume fraction of the second phase, the false assignment of phases at grain boundaries also may introduce a significant error. A general formula is introduced that allows estimation of the error caused by these parameters. Finally, a new measurement scheme is proposed that allows improvement of reliability and representativeness of EBSD-based phase determination without large sacrifices in measurement time or data set sizes.

  14. Strain localization in granodiorite mylonites: a microstructural and electron backscatter diffraction (EBSD) study of the South Mountains core complex, Arizona

    NASA Astrophysics Data System (ADS)

    Greenberg, R. M.; Miranda, E.

    2009-12-01

    The quantification of strain localization in detachment fault shear zones is essential to the study of continental core complex development and permits insight into continental crust rheology during extension. We present a microstructural and EBSD study of naturally deformed shear zone rocks from the footwall of the South Mountains, Arizona, core complex to interpret the deformation mechanisms that lead to strain localization along the detachment fault. The footwall of the South Mountains core complex is dominated by a Miocene composite pluton that exhibits Miocene extensional mylonitic fabrics associated with the structural development of the core complex. The composite pluton is composed of granodiorite, granite, and quartzolite, but the granodiorite is the most voluminous of the intrusive units. The detachment fault shear zone is developed within the granodiorite and quartzolite intrusive units. We conducted a microstructural and EBSD study of the Tertiary South Mountains granodiorite and quartzolite mylonites to determine the deformation mechanisms that promote strain localization. We hypothesize that the strength of quartz strongly influences strain localization in the naturally deformed granodiorite mylonites and quartzolite mylonites. The five samples were collected on an up-structure traverse through the ~60 meter thick mylonitic shear zone towards the interpreted detachment fault surface. Microstructural observation of quartz grains reveals the presence of elongate ‘ribbon grains’ with subgrain development along the rims of these grains, and irregular and sinuous sutured grain boundaries. We interpret these microstructures as evidence of Regimes 2 and 3 dynamic recrystallization. In contrast, the plagioclase feldspar and potassium feldspar crystals are microfractured with limited development of bulging grain boundaries on the rims of the feldspar grains, which we interpret as evidence of Regime 1 dynamic recrystallization. Up the traverse in the

  15. 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

  16. Grain-scale processes in actively deforming magma mushes: New insights from electron backscatter diffraction (EBSD) analysis of biotite schlieren in the Jizera granite, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Žák, Jiří; Verner, Kryštof; Týcová, Patricie

    2008-12-01

    In the porphyritic Jizera granite, Bohemian Massif, three distinct types of lattice-preferred orientations of biotite grains were revealed in schlieren-delineated magmatic structures using the electron backscatter diffraction (EBSD) method. (1) Biotite basal planes (001) reorient from schlieren-subparallel near the schlieren base to schlieren-perpendicular in the upper part of the schlieren. Both orientations share subhorizontal ˜N-S to ˜NNE-SSW-trending a axes. (2) In some domains, the a axes are steep and at a high angle to the schlieren plane while the c axes plunge shallowly and rotate around an ill-defined a axis. (3) In other domains, the EBSD coincides with background magnetic fabric of the host granite revealed using the anisotropy of magnetic susceptibility (AMS) method: that is, the a axes plunge shallowly to the SE or NW while the c axes are subhorizontal and cluster around the ˜NE-SW trend. These multiple biotite orientations in the schlieren are interpreted to reflect (1) velocity-gradient in laminar magma flow along channel-like conduits, localized within the high-strength host phenocryst framework, (2) grain-scale gravity-driven constrictional deformation of the magma mush, and (3) overprinting background (tectonic?) deformation transmitted across large parts of the magma chamber prior to its final crystallization. The grain-scale mechanisms of biotite fabric acquisition in the schlieren presumably involved rotation of biotite crystals during flow, with the biotite alignment reflecting the flow geometry and kinematics, replaced after flow cessation by melt-aided grain-boundary sliding of those biotite crystals still enclosed in melt pockets within otherwise static, highly crystallized magma mush. The latter process was sufficient to reorient biotite grains but not to cause destruction of the schlieren. Using the Jizera granite as a case example, we argue that the lattice-preferred orientation of mineral grains in mafic schlieren is highly

  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.

  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. Chirality determination of quartz crystals using electron backscatter diffraction.

    PubMed

    Winkelmann, Aimo; Nolze, Gert

    2015-02-01

    We demonstrate the determination of crystal chirality using electron backscatter diffraction (EBSD) in the scanning electron microscope. The chirality of α-quartz as a space-group-dependent property is verified via direct comparison of experimental diffraction features to simulations using the dynamical theory of electron diffraction.

  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. 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).

  2. Electron backscatter diffraction of a plutonium-gallium alloy

    NASA Astrophysics Data System (ADS)

    Boehlert, C. J.; Zocco, T. G.; Schulze, R. K.; Mitchell, J. N.; Pereyra, R. A.

    2003-01-01

    An experimental technique has recently been developed to characterize reactive metals, including plutonium (Pu) and cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of Pu and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with Pu metal. The experimental technique, 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 and orientation maps for a Pu-gallium alloy is described and the initial microstructural observations based on the analysis are discussed. The phase transformation behavior between the δ (face-centered cubic) and ɛ (body-centered-cubic) structures is explained by combining the SEM and EBSD observations.

  3. Pattern matching approach to pseudosymmetry problems in electron backscatter diffraction.

    PubMed

    Nolze, Gert; Winkelmann, Aimo; Boyle, Alan P

    2016-01-01

    We demonstrate an approach to overcome Kikuchi pattern misindexing problems caused by crystallographic pseudosymmetry in electron backscatter diffraction (EBSD) measurements. Based on the quantitative comparison of experimentally measured Kikuchi patterns with dynamical electron diffraction simulations, the algorithm identifies the best-fit orientation from a set of pseudosymmetric candidates. Using measurements on framboidal pyrite (FeS2) as an example, we also show the improvement of the orientation precision using this approach.

  4. Applications of the electron backscatter diffraction technique to ceramic materials

    NASA Astrophysics Data System (ADS)

    Koblischka, M. R.; Koblischka-Veneva, A.

    2013-07-01

    A technique with a relatively high spatial resolution is required for an effective analysis of the microstructure of ceramic materials. The recently developed electron backscatter diffraction (EBSD) technique, which works within a scanning electron microscope, enables a spatially highly resolved study of crystallographic orientations while recording Kikuchi patterns on a user-defined grid. However, such an EBSD texture analysis was until now not often performed on ceramic materials - in contrary, the technique is widely employed in the analysis of metallic materials, including the investigation of various types of steels. The use of ceramics possesses a variety of problems for EBSD investigations like: (i) complicated crystal structure, (ii) difficult surface preparation, and (iii) problems arising from a low conductivity of the ceramic materials. Here, we discuss these problems and present solutions in order to obtain high-quality Kikuchi patterns from such ceramics.

  5. 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.

  6. Optimizing electron backscatter diffraction of carbonate biominerals-resin type and carbon coating.

    PubMed

    Pérez-Huerta, Alberto; Cusack, Maggie

    2009-06-01

    Electron backscatter diffraction (EBSD) is becoming a widely used technique to determine crystallographic orientation in biogenic carbonates. Despite this use, there is little information available on preparation for the analysis of biogenic carbonates. EBSD data are compared for biogenic aragonite and calcite in the common blue mussel, Mytilus edulis, using different types of resin and thicknesses of carbon coating. Results indicate that carbonate biomineral samples provide better EBSD results if they are embedded in resin, particularly epoxy resin. A uniform layer of carbon of 2.5 nm thickness provides sufficient conductivity for EBSD analyses of such insulators to avoid charging without masking the diffracted signal. Diffraction intensity decreases with carbon coating thickness of 5 nm or more. This study demonstrates the importance of optimizing sample preparation for EBSD analyses of insulators such as carbonate biominerals.

  7. The backscatter electron signal as an additional tool for phase segmentation in electron backscatter diffraction.

    PubMed

    Payton, E J; Nolze, G

    2013-08-01

    The advent of simultaneous energy dispersive X-ray spectroscopy (EDS) data collection has vastly improved the phase separation capabilities for electron backscatter diffraction (EBSD) mapping. A major problem remains, however, in distinguishing between multiple cubic phases in a specimen, especially when the compositions of the phases are similar or their particle sizes are small, because the EDS interaction volume is much larger than that of EBSD and the EDS spectra collected during spatial mapping are generally noisy due to time limitations and the need to minimize sample drift. The backscatter electron (BSE) signal is very sensitive to the local composition due to its atomic number (Z) dependence. BSE imaging is investigated as a complimentary tool to EDS to assist phase segmentation and identification in EBSD through examination of specimens of meteorite, Cu dross, and steel oxidation layers. The results demonstrate that the simultaneous acquisition of EBSD patterns, EDS spectra, and the BSE signal can provide new potential for advancing multiphase material characterization in the scanning electron microscope. PMID:23575349

  8. 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.

  9. Investigation of microstructure of bulk Ni 2MnGa alloy by means of electron backscatter diffraction analysis

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Gachot, C.; Leibenguth, P.; Mücklich, F.

    2007-09-01

    The microstructure of bulk samples of the shape memory alloy Ni 2MnGa is evaluated by means of electron backscatter diffraction (EBSD). The crystallographic orientation of individual grains can be determined with a high spatial resolution using an automated recording of Kikuchi patterns. The obtained data are presented in form of image quality (IQ) and orientation maps, pole figures and orientation distribution functions. Local EBSD maps and pole figures reveal details about the orientation of the twin structure. The twin structure is clearly resolved within the EBSD mappings; the matrix is oriented in [1 0 0] direction and there is a 90° misorientation to the neighboring twin. Furthermore, pole figures obtained by EBSD are compared to those determined by means of X-ray texture analysis. Therefore, the EBSD measurements give information not accessible to the X-ray pole figure analysis.

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

    PubMed

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

    2016-04-01

    The accuracy of electron backscatter diffraction (EBSD) and confocal Raman microscopy (CRM) for small-scale strain mapping are assessed using the multi-axial strain field surrounding a wedge indentation in Si as a test vehicle. The strain field is modeled using finite element analysis (FEA) that is adapted to the near-indentation surface profile measured by atomic force microscopy (AFM). The assessment consists of (1) direct experimental comparisons of strain and deformation and (2) comparisons in which the modeled strain field is used as an intermediate step. Direct experimental methods (1) consist of comparisons of surface elevation and gradient measured by AFM and EBSD and of Raman shifts measured and predicted by CRM and EBSD, respectively. Comparisons that utilize the combined FEA-AFM model (2) consist of predictions of distortion, strain, and rotation for comparison with EBSD measurements and predictions of Raman shift for comparison with CRM measurements. For both EBSD and CRM, convolution of measurements in depth-varying strain fields is considered. The interconnected comparisons suggest that EBSD was able to provide an accurate assessment of the wedge indentation deformation field to within the precision of the measurements, approximately 2×10(-4) in strain. CRM was similarly precise, but was limited in accuracy to several times this value. PMID:26939030

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

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

    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 20nm on such ceramic samples. A high image quality of the recorded Kikuchi patterns was achieved enabling multiphase scans and high spatial resolution measurements. Upon annealing in air, the magnetic properties of the magnetite thin films were found to change considerably. Using the EBSD analysis, we find that misoriented grains remaining after the annealing step form small islands with a size of about 100nm. The size and distribution of these islands correspond well to the observations of antiferromagnetic pinning centers within the magnetic domain structures carried out by magnetic force microscopy on the same samples.

  12. Electron backscatter diffraction study of polycrystalline YBa 2Cu 3O 7- δ ceramics

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, Anjela; Koblischka, Michael R.; Simon, Petra; Mücklich, Frank; Murakami, Masato

    2002-11-01

    The electron backscatter diffraction (EBSD) technique was applied to polycrystalline YBa 2Cu 3O 7- δ ceramics. To obtain good quality EBSD Kikuchi patterns on the ceramic superconductors, a new sample polishing route was established. Samples with and without KClO 3-doping were investigated; and the crystallographic orientations of the grains were analyzed using pole figures and EBSD orientation mapping. On the polycrystalline KClO 3-doped YBa 2Cu 3O 7- δ samples we found two major orientations (0 0 1) and (1 0 0) normal to the sample surface, while the undoped sample did not exhibit any orientation maxima. We ascribe this observation to the effect of a liquid phase due to the KClO 3-additive during the preparation process.

  13. 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

  14. Measurement and Mapping of Small Changes of Crystal Orientation by Electron Backscattering Diffraction

    NASA Astrophysics Data System (ADS)

    Tao, Xiaodong; Eades, Alwyn

    2005-08-01

    We have explored the possibility of measuring small changes of orientation within grains by electron backscattering diffraction (EBSD), in the scanning electron microscope. Conventional orientation maps (using EBSD) index the orientation of each position on the sample separately. This does not give accurate results for small differences of orientation. We have studied methods of measuring small changes in orientation by measuring the change from one EBSD pattern to the next directly, without indexing either. Previous workers have measured the change of position of a zone axis in the EBSD pattern. We have compared this with an alternative method, which we show to be superior, of measuring the shift of the peaks in the Hough transform from one diffraction pattern to the next. This means that we are measuring the change of orientation of sets of crystal planes within the grain, rather than measuring the change of orientation of zone axes. We show that it is possible, with a standard EBSD configuration, to measure the shift of the Kikuchi bands to a precision of about a 10th of a pixel, which corresponds to a change of orientation in the sample of about 0.1 mrad (0.006°).

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

    SciTech Connect

    Wynick, G.L.; Boehlert, C.J. . 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.

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

    PubMed

    Wallis, David; Hansen, Lars N; Ben Britton, T; Wilkinson, Angus J

    2016-09-01

    Dislocations in geological minerals are fundamental to the creep processes that control large-scale geodynamic phenomena. However, techniques to quantify their densities, distributions, and types over critical subgrain to polycrystal length scales are limited. The recent advent of high-angular resolution electron backscatter diffraction (HR-EBSD), based on diffraction pattern cross-correlation, offers a powerful new approach that has been utilised to analyse dislocation densities in the materials sciences. In particular, HR-EBSD yields significantly better angular resolution (<0.01°) than conventional EBSD (~0.5°), allowing very low dislocation densities to be analysed. We develop the application of HR-EBSD to olivine, the dominant mineral in Earth's upper mantle by testing (1) different inversion methods for estimating geometrically necessary dislocation (GND) densities, (2) the sensitivity of the method under a range of data acquisition settings, and (3) the ability of the technique to resolve a variety of olivine dislocation structures. The relatively low crystal symmetry (orthorhombic) and few slip systems in olivine result in well constrained GND density estimates. The GND density noise floor is inversely proportional to map step size, such that datasets can be optimised for analysing either short wavelength, high density structures (e.g. subgrain boundaries) or long wavelength, low amplitude orientation gradients. Comparison to conventional images of decorated dislocations demonstrates that HR-EBSD can characterise the dislocation distribution and reveal additional structure not captured by the decoration technique. HR-EBSD therefore provides a highly effective method for analysing dislocations in olivine and determining their role in accommodating macroscopic deformation. PMID:27337604

  17. Analysis of Kikuchi band contrast reversal in electron backscatter diffraction patterns of silicon.

    PubMed

    Winkelmann, Aimo; Nolze, Gert

    2010-02-01

    We analyze the contrast reversal of Kikuchi bands that can be seen in electron backscatter diffraction (EBSD) patterns under specific experimental conditions. The observed effect can be reproduced using dynamical electron diffraction calculations. Two crucial contributions are identified to be at work: First, the incident beam creates a depth distribution of incoherently backscattered electrons which depends on the incidence angle of the beam. Second, the localized inelastic scattering in the outgoing path leads to pronounced anomalous absorption effects for electrons at grazing emission angles, as these electrons have to go through the largest amount of material. We use simple model depth distributions to account for the incident beam effect, and we assume an exit angle dependent effective crystal thickness in the dynamical electron diffraction calculations. Very good agreement is obtained with experimental observations for silicon at 20keV primary beam energy.

  18. Advanced characterization of twins using automated electron backscatter diffraction

    SciTech Connect

    Wright, S. I.; Bingert, J. F.; Mason, T. A.; Larson, R. J.

    2002-01-01

    This paper describes results obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated collection of spatially specific orientation measurements by electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM). The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equivalent candidates, and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystallization twins in nickel. In addition to the results on characterizing the twin character, results on extending the twin analysis to automated identification of parent and daughter material for structures exhibiting twin deformation are reported as well.

  19. Observation of ferroelectricity in a confined crystallite using electron-backscattered diffraction and piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Gupta, P.; Jain, H.; Williams, D. B.; Kalinin, Sergei V.; Shin, J.; Jesse, S.; Baddorf, A. P.

    2005-10-01

    LaBGeO5 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.

  20. Crystallographic mapping of ferroelectric thin films using piezoresponse force microscopy and electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Lowe, M.; Hegarty, T.; Mingard, K.; Li, J.; Cain, M.

    2008-08-01

    Ferroelectric lead zirconate titanate (PZT) thin films have been analysed using electron backscatter diffraction (EBSD). Grain orientation mapping has been demonstrated, showing that features smaller than 100 nm may be successfully indexed. In conjunction with piezoresponse force microscopy (PFM), which was used to map and quantify the piezoelectric response from the same region of the films with a resolution of 10 nm, an analysis of the effects of grain orientation on the measured response at the nanoscale was possible. The microtexture of the film showed the presence of both mono- and multi-domains within grains exhibiting sizes of hundreds of nanometres.

  1. Validation of neutron texture data on GEM at ISIS using electron backscattered diffraction

    NASA Astrophysics Data System (ADS)

    Davies, Peter; Kockelmann, Winfried; Wynne, Brad; Eccleston, Roger; Hutchinson, Bevis; Rainforth, W. Mark

    2008-03-01

    The high solid angular coverage of the general materials (GEM) diffractometer at the ISIS pulsed neutron source located at the UK Rutherford Appleton Laboratory offers the capability of obtaining quantitative bulk crystallographic texture data in a 'single shot' within a matter of minutes. This enables the possibility of in situ texture measurements to be made as a function of temperature to monitor and quantify texture changes during phase transformation or microstructure restoration processes like recrystallization. The purpose of this paper is to determine the quality of the texture data produced from GEM in order to define a level of confidence for subsequent texture model validation. This has been achieved by comparing textures of sections of a 200 mm diameter titanium alloy billet using data obtained from GEM with data obtained using electron backscattered diffraction (EBSD). In both cases, the data were obtained at room temperature. EBSD, unlike time-of-flight neutron diffraction analysis, obtains texture data directly from orientation measurements via backscattered Kikuchi patterns in the scanning electron microscope. In all analysed locations, both methods show near-identical textures, with regard to both the general orientation distributions and the levels of intensity of the distributions. This shows that the GEM diffractometer is capable of accurately determining bulk textures in a single shot, thus confirming its suitability for in situ high temperature experiments.

  2. 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

  3. 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.

  4. STRAIN CORRELATIONS IN ALLOY 690 MATERIALS USING ELECTRON BACKSCATTER DIFFRACTION AND VICKERS HARDNESS

    SciTech Connect

    Overman, Nicole R.; Toloczko, Mychailo B.; Olszta, Matthew J.; Bruemmer, Stephen M.

    2014-03-09

    High chromium, nickel-base Alloy 690 exhibits an increased resistance to stress corrosion cracking (SCC) in pressurized water reactor (PWR) primary water environments over lower chromium alloy 600. As a result, Alloy 690 has been used to replace Alloy 600 for steam generator tubing, reactor pressure vessel nozzles and other pressure boundary components. However, recent laboratory crack-growth testing has revealed that heavily cold-worked Alloy 690 materials can become susceptible to SCC. To evaluate reasons for this increased SCC susceptibility, detailed characterizations have been performed on as-received and cold-worked Alloy 690 materials using electron backscatter diffraction (EBSD) and Vickers hardness measurements. Examinations were performed on cross sections of compact tension specimens that were used for SCC crack growth rate testing in simulated PWR primary water. Hardness and the EBSD integrated misorientation density could both be related to the degree of cold work for materials of similar grain size. However, a microstructural dependence was observed for strain correlations using EBSD and hardness which should be considered if this technique is to be used for gaining insight on SCC growth rates

  5. Microstructural and microtextural characterization of oxide scale on steel using electron backscatter diffraction.

    PubMed

    Birosca, S; Dingley, D; Higginson, R L

    2004-03-01

    High-temperature oxidation of steel has been extensively studied. The microstructure of iron oxides is, however, not well understood because of the difficulty in imaging it using conventional methods, such as optical or electron microscopy. A knowledge of the oxide microstructure and texture is critical in understanding how the oxide film behaves during high-temperature deformation of steels and more importantly how it can be removed following processing. Recently, electron back-scatter diffraction (EBSD) has proved to be a powerful technique for distinguishing the different phases in scales. This technique gives valuable information both on the microstructure and on the orientation relationships between the steel and the scale layers. In the current study EBSD has been used to investigate the microstructure and microtexture of iron oxide layers grown on interstitial free steel at different times and temperatures. Heat treatments have been carried out under normal oxidation conditions in order to relate the results to real steel manufacturing in industry. The composition, morphologies, microstructure and microtexture of selected conditions have been studied using EBSD. PMID:15009690

  6. Microstructural and microtextural characterization of oxide scale on steel using electron backscatter diffraction.

    PubMed

    Birosca, S; Dingley, D; Higginson, R L

    2004-03-01

    High-temperature oxidation of steel has been extensively studied. The microstructure of iron oxides is, however, not well understood because of the difficulty in imaging it using conventional methods, such as optical or electron microscopy. A knowledge of the oxide microstructure and texture is critical in understanding how the oxide film behaves during high-temperature deformation of steels and more importantly how it can be removed following processing. Recently, electron back-scatter diffraction (EBSD) has proved to be a powerful technique for distinguishing the different phases in scales. This technique gives valuable information both on the microstructure and on the orientation relationships between the steel and the scale layers. In the current study EBSD has been used to investigate the microstructure and microtexture of iron oxide layers grown on interstitial free steel at different times and temperatures. Heat treatments have been carried out under normal oxidation conditions in order to relate the results to real steel manufacturing in industry. The composition, morphologies, microstructure and microtexture of selected conditions have been studied using EBSD.

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    Electron backscatter diffraction (EBSD) analysis is applied to [0 0 1] 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 in [0 0 1]-direction is not yet achieved for the as-grown sample, but develops upon oxygen treatment. Furthermore, the distribution of misorientation angles within the investigated area (=1 grain) is found to change during the annealing steps. After 3 min of annealing, most of the misorientations around 30°-40° have vanished, and some islands with high misorientation angles remain, which may play a role as antiferromagnetic pinning centers.

  8. Application of electron backscatter diffraction to bulk high-Tc superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Simon, P.; Mücklich, F.; Murakami, M.

    2002-05-01

    We have successfully obtained electron backscatter diffraction (EBSD) Kikuchi patterns on various bulk high-Tc superconductors (polycrystalline KClO3-doped and undoped YBa2Cu3O7-δ (YBCO), single crystalline YBCO and NdBa2Cu3O7-y) and on YBCO and NdBCO thin films. We have established a sample polishing procedure to obtain intense Kikuchi patterns without an additional carbon coating of the ceramic superconductors. We present Kikuchi patterns, pole figures and orientation maps of the samples. On the polycrystalline KClO3-doped YBCO samples we find two major orientations (001) and (100) normal to the sample surface, while the undoped sample does not exhibit any orientation maxima, which is ascribed to the effect of a liquid phase due to the KClO3-additive during the preparation process. Furthermore, we discuss the future possibilities for the application of the EBSD technique for growing larger, bulk melt-textured samples for applications.

  9. Position-dependent texture analysis of melt-textured YBCO by means of electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Ogasawara, K.; Murakami, M.

    2003-10-01

    The texture and phase distribution of melt-textured YBa 2Cu 3O x (YBCO) was studied by means of automated electron backscatter diffraction (EBSD) analysis as a function of the position in the bulk pellet of 4 cm diameter. A total of five samples was cut from the pellet; four samples from the surface of the bulk with different distances to the seed crystal, and one cut in vertical direction in the middle of the pellet. The melt-textured YBCO samples require a two-phase analysis to be performed, so a high surface quality is necessary to enable an automated EBSD scan. Good quality Kikuchi patterns are obtained from both the 1 2 3 and 2 1 1 phases. We found an inhomogeneous distribution of the 2 1 1 particles. Whereas the samples cut from the surface contain a large amount of 2 1 1 particles, in the samples of the vertical direction only traces of 2 1 1 particles are found. Furthermore, we measured the misorientation angle distribution of all samples. The data are presented in form of phase mappings, misorientation distribution functions and pole figures.

  10. 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

  11. Electron energy loss and diffraction of backscattered electrons from silicon

    NASA Astrophysics Data System (ADS)

    Winkelmann, Aimo; Aizel, Koceila; Vos, Maarten

    2010-05-01

    Electrons backscattered from crystals can show Kikuchi patterns: variations in intensity for different outgoing directions due to diffraction by the lattice. Here, we measure these effects as a function of their energy loss for 30 keV electrons backscattered from silicon. The change in diffraction contrast with energy loss depends strongly on the scattering geometry. At steep incidence on the sample, diffraction contrast in the observed Kikuchi bands decreases rapidly with energy loss. For an energy loss larger than about 150 eV the contrast is more than 5 times less than the contrast due to electrons near zero energy loss. However, for grazing incidence angles, maximum Kikuchi band contrast is observed for electrons with an energy loss near 60 eV, where the contrast is more than 2.5× larger than near zero energy loss. In addition, in this grazing incidence geometry, the Kikuchi diffraction effects stay significant even for electrons that have lost hundreds of electron volts. For the maximum measured energy loss of 440 eV, the electrons still show a contrast that is 1.5 × larger than that of the electrons near zero energy loss. These geometry-dependent observations of Kikuchi band diffraction contrast are interpreted based on the elastic and inelastic scattering properties of electrons and dynamical diffraction simulations.

  12. EBSD analysis of the microtexture of Ba-hexaferrite samples

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Chen, Y.; Harris, V. G.

    2010-01-01

    The microtexture of differently prepared Ba-hexaferrite samples is investigated by means of electron backscatter diffraction (EBSD). Kikuchi patterns are obtained with a high image quality, enabling a spatial resolution of the EBSD maps of about 20 nm. The spatially highly resolved EBSD mappings provide additional information (individual grain orientation, misorientation angles, grain size distribution) as compared to the standard analysis techniques, which can contribute to an optimization of the growth process. Furthermore, as the crystallographic orientation of each grain is known, an exact analysis of the grain aspect ratio becomes possible which provides further insight to the microstructural dependence of the magnetic properties of ferrites.

  13. Advanced Characterization of Slags and Refractory Bricks Using Electron Backscatter Diffraction

    SciTech Connect

    John Kay; Kurt Eylands

    2007-09-30

    Numerous studies have been conducted to determine changes that occur in slag that cause a rapid change in viscosity, but these studies have been limited by the inability to characterize/identify the phases present in the slag. Rapid freezing of slag in entrained gasifiers and slagging combustion systems can cause a shutdown of the system. The reactions occurring in slag that result in rapid freezing of slags are not well understood. It is believed that electron backscatter diffraction (EBSD) can be used to analyze slags and aid in their characterization although its use has not been found in literature. The EBSD technique allows particle-by-particle mineralogy based on diffraction patterns generated by the electron beam when the sample is tilted to a high angle. The diffraction pattern (Kikuchi bands) can only come from crystalline phases, which makes this technique ideally suited to study crystal formation in slags where oftentimes the crystals are very small and a reasonable chemical analysis cannot be made by conventional energy-dispersive spectrometry (EDS) methods in the scanning electron microscope. The ability to have mineralogical data based on the crystalline structure of a phase rather than a chemical analysis by EDS allows much better interpretation of the temperature regimes in which specific phases tend to form. Knowing the type and relative amounts of a phase crystallizing in a slag is critical in predicting the viscosity of a slag at a given temperature. Six slag samples were selected based on the parent coal. Unfortunately, none of the slags appeared to have any crystalline material associated with them. The funding for this project was not adequate for generating more slags from the various coal types. For this reason, sample archives were searched for those containing slags that were not rapidly quenched. A slag from a bituminous coal was found to contain several dendritic crystals (10 {mu}m to 50 {mu}m in size) that formed near the edges of the

  14. High-quality cubic and hexagonal InN crystals studied by micro-Raman scattering and electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Kamimura, Jumpei; Ramsteiner, Manfred; Jahn, Uwe; Lu, Cheng-Ying James; Kikuchi, Akihiko; Kishino, Katsumi; Riechert, Henning

    2016-04-01

    Large InN microcrystals grown by molecular beam epitaxy are investigated by micro-Raman spectroscopy and electron backscatter diffraction (EBSD). High-quality (phonon linewidths between 1.5 and 2 cm-1) cubic and hexagonal crystals are identified with Raman mapping by the observation of the respective characteristic phonon modes. The unexpected occurrence of metastable cubic InN crystals is confirmed by EBSD measurements. The cubic microcrystals are revealed by EBSD to be single-crystalline and to exhibit  <1 1 1>  orientation. The transverse (TO) and longitudinal-optical (LO) zone-center phonon frequencies of cubic InN are found to be 463 and 584 cm-1, respectively. The bulk carrier density in the microcrystals lies in the range of 2-3  ×  1017 cm-3 as determined by the analysis of LO phonon-plasmon-coupled modes in the Raman spectra.

  15. EBSD analysis of MgB2 bulk superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Inoue, K.; Muralidhar, M.; Berger, K.; Noudem, J.

    2016-04-01

    The grain orientation, the texture and the grain boundary misorientations are important parameters for the understanding of the magnetic properties of the bulk MgB2 samples intended for super-magnet applications. Such data can be provided by electron backscatter diffraction (EBSD) analysis. However, as the grain size (GS) of the MgB2 bulks is preferably in the 100-200 nm range, the common EBSD technique working in reflection operates properly only on highly dense samples. In order to achieve a reasonably good Kikuchi pattern quality on all samples, we apply here the newly developed transmission EBSD (t-EBSD) technique to several bulk MgB2 samples. This method requires the preparation of TEM slices by means of focused ion-beam milling, which are then analyzed within the SEM, operating with a specific sample holder. We present several EBSD mappings of samples prepared with different techniques and at various reaction temperatures.

  16. Study of grain boundary properties in Ag-clad Bi2Sr2Ca2Cu3Ox tapes by multi-phase electron backscatter diffraction analysis

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.

    2008-01-01

    The properties of grain boundaries within Ag-clad (Pb,Bi)2Sr2Ca2Cu3Ox (Bi-2223) tapes are studied by means of electron backscatter diffraction (EBSD). The achieved high image quality of the Kikuchi patterns enables multi-phase EBSD scans including Bi-2223, Bi2Sr2CaCu2Ox (Bi-2212), Bi2Sr2CuOx (Bi-2201), (Sr,Ca)14Cu24O41 and Ag to be performed. For the EBSD scans a maximum spatial resolution of 30 nm was reached enabling a detailed orientation analysis. The nature of the grain boundaries is discussed on the base of the EBSD data. While the main orientation of the tape is in [0 0 1] direction, a large number of misorientations is detected. These misorientations are visualized using crystal direction (CD) maps. Furthermore, EBSD enables the spatially resolved mapping of the misorientation angles within each phase separately. The influence of these grain boundaries on the current transport properties is discussed.

  17. 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.

  18. 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.

  19. EBSD analysis of electroplated magnetite thin films

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Teng, C. L.; Ryan, M. P.; Hartmann, U.; Mücklich, F.

    2010-05-01

    By means of electron backscatter diffraction (EBSD), we analyse the crystallographic orientation of electroplated magnetite thin films on Si/copper substrates. Varying the voltage during the electroplating procedure, the resulting surface properties are differing considerably. While a high voltage produces larger but individual grains on the surface, the surfaces become smoother on decreasing voltage. Good quality Kikuchi patterns could be obtained from all samples; even on individual grains, where the surface and the edges could be measured. The spatial resolution of the EBSD measurement could be increased to about 10 nm; thus enabling a detailed analysis of single magnetite grains. The thin film samples are polycrystalline and do not exhibit a preferred orientation. EBSD reveals that the grain size changes depending on the processing conditions, while the detected misorientation angles stay similar.

  20. 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

  1. A method to correct coordinate distortion in EBSD maps

    SciTech Connect

    Zhang, Y.B. Elbrønd, A.; Lin, F.X.

    2014-10-15

    Drift during electron backscatter diffraction mapping leads to coordinate distortions in resulting orientation maps, which affects, in some cases significantly, the accuracy of analysis. A method, thin plate spline, is introduced and tested to correct such coordinate distortions in the maps after the electron backscatter diffraction measurements. The accuracy of the correction as well as theoretical and practical aspects of using the thin plate spline method is discussed in detail. By comparing with other correction methods, it is shown that the thin plate spline method is most efficient to correct different local distortions in the electron backscatter diffraction maps. - Highlights: • A new method is suggested to correct nonlinear spatial distortion in EBSD maps. • The method corrects EBSD maps more precisely than presently available methods. • Errors less than 1–2 pixels are typically obtained. • Direct quantitative analysis of dynamic data are available after this correction.

  2. Aluminum matrix texture in Al-Al3Ti functionally graded materials analyzed by electron back-scattering diffraction

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshimi; Sequeira, Paulo D.; Sato, Hisashi; Inamura, Tomonari; Hosoda, Hideki

    2016-01-01

    Al matrix functionally graded materials (FGMs) with oriented Al3Ti platelets were fabricated by a centrifugal solid-particle method. The applied centrifugal forces were 30, 60, and 120G (units of gravity). The orientation and volume fraction gradients of the Al3Ti platelets within the samples were measured. Since a good lattice correspondence was reported for the close-packed directions and the close-packed planes between Al and Al3Ti, the Al matrix in the Al-Al3Ti FGMs fabricated by the centrifugal solid-particle method should have some texture. Al matrix texture was, therefore, analyzed by electron back-scattering diffraction (EBSD). Analysis of the resulting pole figures indicates a preferred orientation along the (200) plane for the Al matrix crystals. Furthermore, increasing the applied centrifugal force enhances the orientation effect. A correlation appears to exist between platelet orientation and the preferred texture of the Al matrix.

  3. Interactions of Y2BaCuO5 particles and the YBCO matrix within melt-textured YBCO samples studied by means of electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Mücklich, F.; Ogasawara, K.; Murakami, M.

    2005-02-01

    By means of automated electron backscatter diffraction (EBSD) analysis, we studied the local orientations of embedded Y2BaCuO5(211) particles within melt-textured YBa2Cu3Ox (YBCO) samples. On both components, we obtained high-quality Kikuchi patterns, thus allowing the automated mapping of the crystal orientations and a two-phase analysis of the samples. Investigations were performed on a variety of melt-textured YBCO samples. In melt-textured YBCO with (001) orientation, we find that the embedded 211 particles do not have any preferred orientation. The EBSD maps also reveal that at certain orientations of the 211 particles the YBCO growth is not altered. From the obtained EBSD mappings, we can conclude that the formation of small 211 particles will not disturb the YBCO matrix growth, whereas the presence of large 211 particles causes severe changes in the YBCO growth, leading to the formation of subgrains. The EBSD results are presented in the form of local orientation maps and local pole figures.

  4. Characterization of bulk superconductors through EBSD methods

    NASA Astrophysics Data System (ADS)

    Koblischka, M. R.; Koblischka-Veneva, A.

    2003-10-01

    The application of electron backscatter diffraction (EBSD) technique to bulk high- Tc superconductors is presented and reviewed. Due to the ceramic nature and the complex crystallographic unit cells of the perovskite-type high- Tc superconductors, the EBSD analysis is not yet as common as it deserves. We have successfully performed EBSD analysis on a variety of high- Tc compounds and samples including polycrystalline YBCO (pure and doped by alkali metals), melt-textured YBCO, thin and thick films of YBCO; the “green phase” Y 2BaCuO 5, thin film and melt-textured NdBa 2Cu 3O x and Bi-2212 single crystals and tapes. It is shown that the surface preparation of the samples is crucial due to the small information depth (up to 100 nm) of the EBSD technique. High quality Kikuchi patterns are the requirement in order to enable the automated EBSD mapping, which yields phase distributions, individual grain orientations and the misorientation angle distribution. The results can be presented in form of mappings, as charts, and as pole figures. These informations are required for a better understanding of the growth mechanism(s) of bulk high- Tc superconductors intended for applications.

  5. An electron backscatter diffraction investigation of crystallographic orientations of embedded nanoparticles within melt-textured YBCO high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Shlyk, L.; Krabbes, G.

    2006-07-01

    Microstructures of melt-textured YBCO samples with embedded nanosized particles of Y2BaCuO5 (Y-211) and Y2Ba4CuMOx (M-2411 with M = U,Zr) are analysed by means of electron backscatter diffraction (EBSD). With the recent developments of the EBSD technique, we can directly measure the crystallographic orientation of the embedded nanoparticles, employing a spatial resolution of about 40 nm. The high image quality of the Kikuchi patterns allows true three-phase (YBCO, Y-211 and M-2411) scans to be performed. The Y-211 particles do not exhibit any preferred orientation, even if their size is considerably reduced, to the 100 nm range. The size reduction reduces the negative influence of the Y-211 particles on the YBCO matrix, however. U-2411 particles, which are formed during the processing stage, do not show any orientation, and with increasing concentration, some texture develops. In contrast to this, embedded Zr-2411 particles are fully oriented in the (001) orientation according to the surrounding superconducting matrix.

  6. Skeletal growth phases of the cold-water coral Lophelia pertusa shown by scanning electron microscope and electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Mouchi, Vincent; Vonlanthen, Pierre; Verrecchia, Eric P.; Crowley, Quentin G.

    2016-04-01

    Lophelia pertusa is a cold-water coral, which may form reefs by the association of multiple coralites within which a polyp lives. Each individual polyp builds an aragonite skeleton by an initial phase of early mineralization (traditionally referred to as centres of calcification) from which aragonite fibres grow in thickening deposits. The skeleton wall features successive optically opaque and translucent bands previously attributed to different regimes of growth as either uniform in crystal orientation (translucent bands) or with a chaotic organization (opaque bands). The processes involved in any organizational changes are still unknown. Microlayers in the coral wall, which represent separate periods of skeletal growth, have been recently identified and described. These growth patterns are readily visible under scanning electron microscope (SEM) after etching in dilute formic acid, but they do not necessarily form continuously visible structures. Here we present high quality SEM images and electron backscatter diffraction (EBSD) maps to study aragonite fibre orientation across the wall of L. pertusa. Both microlayers and opaque and translucent bands are compared to the crystallographic orientation of the aragonite fibres. EBSD maps and SEM images indicate that aragonite fibres do not exhibit a chaotic orientation, even in opaque bands. The absence of continuity of microlayers is partially explained by an association of multiple crystallographic preferred orientations of aragonite fibres. In the case of L. pertusa, careful textural characterisation is necessary prior to elemental or isotope analysis in order to select a skeletal transect representing a linear and continuous time period.

  7. Kossel and pseudo Kossel CCD pattern in comparison with electron backscattering diffraction diagrams

    NASA Astrophysics Data System (ADS)

    Däbritz, S.; Langer, E.; Hauffe, W.

    2001-07-01

    Kossel and pseudo Kossel interferences, i.e. lattice source interferences (LSI) and divergent beam X-ray interferences (DBI), as well as electron backscattering diffraction (EBSD) are complementary physical methods of investigation, by means of which material-physical parameters can be obtained from microscopic small specimen areas in a non-destructive way. The interferences are taken with a high-resolution and time-integrating CCD camera [in Proceedings of the 15th International Congress on X-Ray Optics and Microanalysis (ICXOM), August 1998, Antwerp, Belgium; J. Anal. At. Spectrom. (The Royal Society of Chemistry) 14 (1999) 409] and at once transmitted to the computer for evaluation. Thus, these techniques can be used in situ. For the methods LSI and DBI, the reflections are indexed and evaluated with the own developed simulation program KOPSKO [Cryst. Res. Technol. 34 (7) (1999) 801]. In the present case, these three methods, besides other detectors, were additionally installed by us in the CamScan CS44 scanning electron microscope for the analysis of micro regions in solids. Because of the different excitation or diffraction ranges of the techniques, information comes from different specimen depths of some nanometers to about 100 μm. On this way, the range of application for the determination of the parameters was considerably increased. By the examples of a single-crystalline ceramic specimen of BaTiO 3 as well as a Fe monocrystal one the range of application is demonstrated by the determination of the crystallographic direction with respect to the specimen surface all three methods are compared.

  8. The role of dislocations in varied olivine deformation mechanisms investigated using high-angular resolution electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Wallis, David; Hansen, Lars; Britton, Ben; Wilkinson, Angus

    2016-04-01

    Experimentally-derived flow laws can be used to predict the rheology of rocks deformed under natural conditions only if the same microphysical processes can be demonstrated to control the rate-limiting deformation mechanism in both cases. Olivine rheology may exert a principle control on the strength of the lithosphere, and therefore considerable research effort has been applied to assessing its rheology through experimental, geological, and geophysical approaches. Nonetheless, considerable uncertainty remains regarding the dominant deformation mechanisms in the upper mantle. This uncertainty arises in large part due to our limited understanding of the fundamental deformation processes associated with each mechanism. Future improvements to microphysical models of distinct deformation mechanisms require new insight into the contributions those fundamental processes to the macroscopic behaviour. The dynamics of dislocations is central to modelling viscous deformation of olivine, but characterisation techniques capable of constraining dislocation types, densities, and distributions over the critical grain to polycrystal length-scales have been lacking. High angular resolution electron backscatter diffraction (HR-EBSD), developed and increasingly applied in the material sciences, offers an approach capable of such analyses. HR-EBSD utilises diffraction pattern image cross-correlation to achieve dramatically improved angular resolution (~0.01°) of lattice orientation gradients compared to conventional Hough-based EBSD (~0.5°). This angular resolution allows very low densities (≥ 10^11 m^-2) of geometrically necessary dislocations (GND) to be resolved, facilitating analysis of a wide range of dislocation microstructures. We have developed the application of HR-EBSD to olivine and applied it to samples deformed both experimentally and naturally in grain-size sensitive and grain-size insensitive regimes. The results quantitatively highlight variations in the types and

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

    PubMed

    Saowadee, N; Agersted, K; Bowen, J R

    2012-06-01

    This study investigates the effect of focused ion beam (FIB) current and accelerating voltage on electron backscatter diffraction pattern quality of yttria-stabilized zirconia (YSZ) and Nb-doped strontium titanate (STN) to optimize data quality and acquisition time for 3D-EBSD experiments by FIB serial sectioning. Band contrast and band slope were used to describe the pattern quality. The FIB probe currents investigated ranged from 100 to 5000 pA and the accelerating voltage was either 30 or 5 kV. The results show that 30 kV FIB milling induced a significant reduction of the pattern quality of STN samples compared to a mechanically polished surface but yielded a high pattern quality on YSZ. The difference between STN and YSZ pattern quality is thought to be caused by difference in the degree of ion damage as their backscatter coefficients and ion penetration depths are virtually identical. Reducing the FIB probe current from 5000 to 100 pA improved the pattern quality by 20% for STN but only showed a marginal improvement for YSZ. On STN, a conductive coating can help to improve the pattern quality and 5 kV polishing can lead to a 100% improvement of the pattern quality relatively to 30 kV FIB milling. For 3D-EBSD experiments of a material such as STN, it is recommended to combine a high kV FIB milling and low kV polishing for each slice in order to optimize the data quality and acquisition time. PMID:22582798

  10. Principles of depth-resolved Kikuchi pattern simulation for electron backscatter diffraction.

    PubMed

    Winkelmann, A

    2010-07-01

    This paper presents a tutorial discussion of the principles underlying the depth-dependent Kikuchi pattern formation of backscattered electrons in the scanning electron microscope. To illustrate the connections between various electron diffraction methods, the formation of Kikuchi bands in electron backscatter diffraction in the scanning electron microscope and in transmission electron microscopy are compared with the help of simulations employing the dynamical theory of electron diffraction. The close relationship between backscattered electron diffraction and convergent beam electron diffraction is illuminated by showing how both effects can be calculated within the same theoretical framework. The influence of the depth-dependence of diffuse electron scattering on the formation of the experimentally observed electron backscatter diffraction contrast and intensity is visualized by calculations of depth-resolved Kikuchi patterns. Comparison of an experimental electron backscatter diffraction pattern with simulations assuming several different depth distributions shows that the depth-distribution of backscattered electrons needs to be taken into account in quantitative descriptions. This should make it possible to obtain more quantitative depth-dependent information from experimental electron backscatter diffraction patterns via correlation with dynamical diffraction simulations and Monte Carlo models of electron scattering.

  11. 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

  12. 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.

  13. Crystallographic Orientation of Cuttlebone Shield Determined by Electron Backscatter Diffraction

    NASA Astrophysics Data System (ADS)

    Cusack, Maggie; Chung, Peter

    2014-01-01

    In common with many cephalopod mollusks, cuttlefish produce an internal biomineral buoyancy device. This cuttlebone is analogous to a surf board in shape and structure, providing rigidity and a means of controlling buoyancy. The cuttlebone is composed of calcium carbonate in the form of aragonite and comprises an upper dorsal shield and a lower lamellar matrix. The lamellar matrix comprises layers of chambers with highly corrugated walls. The dorsal shield comprises bundles of aragonite needles stacked on top of each other. Electron backscatter diffraction analyses of the dorsal shield reveal that the c-axis of aragonite is parallel with the long axis of the needles in the bundles such that any spread in crystallographic orientation is consistent with the spread in orientation of the fibers as they radiate to form the overall structure of the dorsal shield. This arrangement of c-axis coincident with the long axis of the biomineral structure is similar to the arrangement in corals and in contrast to the situation in the molluskan aragonite nacre of brachiopod calcite where the c-axis is perpendicular to the aragonite tablet or calcite fiber, respectively.

  14. A pseudo-3D approach based on electron backscatter diffraction and backscatter electron imaging to study the character of phase boundaries between Mg and long period stacking ordered phase in a Mg–2Y–Zn alloy

    SciTech Connect

    Afshar, Mehran Zaefferer, Stefan

    2015-03-15

    In Mg–2 at.% Y–1 at.% Zn alloys, the LPSO (Long Period Stacking Ordered) phase is important to improve mechanical properties of the material. The aim of this paper is to present a study on the phase boundary character in these two-phase alloys. Using EBSD pattern analysis it was found that the 24R structure is the dominant LPSO phase structure in the current alloy. The phase boundary character between the Mg matrix and the LPSO phase was investigated using an improved pseudo-3D EBSD (electron backscatter diffraction) technique in combination with BSE or SE (backscatter or secondary electron) imaging. A large amount of very low-angle phase boundaries was detected. The (0 0 0 2) plane in the Mg matrix which is parallel to the (0 0 0 24) plane in the LPSO phase was found to be the most frequent plane for these phase boundaries. This plane is supposed to be the habit plane of the eutectic co-solidification of the Mg matrix and the LPSO phase. - Highlights: • It is shown that for the investigated alloy the LPSO phase has mainly 24R crystal structure. • A new method is presented which allows accurate determination of the 5-parameter grain or phase boundary character. • It is found that the low-angle phase boundaries appearing in the alloy all have basal phase boundary planes.

  15. Comparison of EBSD patterns simulated by two multislice methods.

    PubMed

    Liu, Q B; Cai, C Y; Zhou, G W; Wang, Y G

    2016-10-01

    The extraction of crystallography information from electron backscatter diffraction (EBSD) patterns can be facilitated by diffraction simulations based on the dynamical electron diffraction theory. In this work, the EBSD patterns are successfully simulated by two multislice methods, that is, the real space (RS) method and the revised real space (RRS) method. The calculation results by the two multislice methods are compared and analyzed in detail with respect to different accelerating voltages, Debye-Waller factors and aperture radii. It is found that the RRS method provides a larger view field of the EBSD patterns than that by the RS method under the same calculation conditions. Moreover, the Kikuchi bands of the EBSD patterns obtained by the RRS method have a better match with the experimental patterns than those by the RS method. Especially, the lattice parameters obtained by the RRS method are more accurate than those by the RS method. These results demonstrate that the RRS method is more accurate for simulating the EBSD patterns than the RS method within the accepted computation time.

  16. 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.

  17. Grain Growth Orientation and Anisotropy in Cu6Sn5 Intermetallic: Nanoindentation and Electron Backscatter Diffraction Analysis

    NASA Astrophysics Data System (ADS)

    Choudhury, Soud Farhan; Ladani, Leila

    2014-04-01

    As the size of joints in micro/nano-electronics diminishes, the role of intermetallic (IMC) layers becomes more significant. It was shown that solder joint strength is controlled largely by IMC strength at higher strain rates. Additionally, there is a possibility that very small joints are completely composed of IMCs. Further miniaturization of joints may result in statistical grain size effects. Therefore, it is essential to characterize IMC materials and understand their anisotropic mechanical properties. One of the most common types of IMCs in microelectronic joints is Cu6Sn5, which is formed in a variety of bonding materials with different compositions of Sn, Cu, and Ag. This work studies through nanoindentation elastic-plastic properties of a single grain of Cu6Sn5 IMC in a Sn-3.5Ag/Cu system with reflow soldering. Elastic properties such as elastic modulus and hardness were determined from the nanoindentation load-depth curve. The reverse analysis model described by Dao et al. was used to extract plastic properties such as yield strength and strain hardening exponent from nanoindentation data. Care was taken to achieve indentation of single grains with sufficient accuracy and repeatability. Electron backscatter diffraction (EBSD) mapping was used to determine orientation of Cu6Sn5 grains and to relate the orientation with the load-depth curve results of nanoindentation and the corresponding elastic and plastic properties. The EBSD results indicated that the Cu6Sn5 crystal structure is hexagonal. Columnar growth of the Cu6Sn5 grains was observed as the grains mostly grew along the c-axis of the crystal. Indentation of different grains parallel to the basal plane showed no significant difference in mechanical properties.

  18. The effect of length scale on the determination of geometrically necessary dislocations via EBSD continuum dislocation microscopy.

    PubMed

    Ruggles, T J; Rampton, T M; Khosravani, A; Fullwood, D T

    2016-05-01

    Electron backscatter diffraction (EBSD) dislocation microscopy is an important, emerging field in metals characterization. Currently, calculation of geometrically necessary dislocation (GND) density is problematic because it has been shown to depend on the step size of the EBSD scan used to investigate the sample. This paper models the change in calculated GND density as a function of step size statistically. The model provides selection criteria for EBSD step size as well as an estimate of the total dislocation content. Evaluation of a heterogeneously deformed tantalum specimen is used to asses the method. PMID:26986021

  19. 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 (Fe₃C) 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.

  20. Oriented Nucleation of both Ge-Fresnoite and Benitoite/BaGe4O9 during the Surface Crystallisation of Glass Studied by Electron Backscatter Diffraction

    PubMed Central

    Wisniewski, Wolfgang; Patschger, Marek; Murdzheva, Steliana; Thieme, Christian; Rüssel, Christian

    2016-01-01

    Two glasses of the compositions 2 BaO - TiO2 - 2.75 GeO2 and 2 BaO – TiO2 –3.67 GeO2 (also known as BTG55) are annealed at temperatures from 680 to 970 °C to induce surface crystallization. The resulting samples are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD). Ge-Fresnoite (Ba2TiGe2O8, BTG) is observed at the immediate surface of all samples and oriented nucleation is proven in both compositions. After a very fast kinetic selection, the crystal growth of BTG into the bulk occurs via highly oriented dendrites where the c-axes are oriented perpendicular to the surface. The growth of this oriented layer is finally blocked by dendritc BTG originating from bulk nucleation. The secondary phases BaTiGe3O9 (benitoite) and BaGe4O9 are also identified near the surface by XRD and localized by EBSD which additionally indicates orientation preferences for these phases. This behaviour is in contrast with previous reports from the Ba2TiSi2O8 as well as the Sr2TiSi2O8 systems. PMID:26853738

  1. Oriented Nucleation of both Ge-Fresnoite and Benitoite/BaGe4O9 during the Surface Crystallisation of Glass Studied by Electron Backscatter Diffraction.

    PubMed

    Wisniewski, Wolfgang; Patschger, Marek; Murdzheva, Steliana; Thieme, Christian; Rüssel, Christian

    2016-01-01

    Two glasses of the compositions 2 BaO - TiO2 - 2.75 GeO2 and 2 BaO - TiO2 -3.67 GeO2 (also known as BTG55) are annealed at temperatures from 680 to 970 °C to induce surface crystallization. The resulting samples are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD). Ge-Fresnoite (Ba2TiGe2O8, BTG) is observed at the immediate surface of all samples and oriented nucleation is proven in both compositions. After a very fast kinetic selection, the crystal growth of BTG into the bulk occurs via highly oriented dendrites where the c-axes are oriented perpendicular to the surface. The growth of this oriented layer is finally blocked by dendritc BTG originating from bulk nucleation. The secondary phases BaTiGe3O9 (benitoite) and BaGe4O9 are also identified near the surface by XRD and localized by EBSD which additionally indicates orientation preferences for these phases. This behaviour is in contrast with previous reports from the Ba2TiSi2O8 as well as the Sr2TiSi2O8 systems. PMID:26853738

  2. 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 β, 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.

  3. Quantitative measurements of Kikuchi bands in diffraction patterns of backscattered electrons using an electrostatic analyzer.

    PubMed

    Went, M R; Winkelmann, A; Vos, M

    2009-09-01

    Diffraction patterns of backscattered electrons can provide important crystallographic information with high spatial resolution. Recently, the dynamical theory of electron diffraction was applied to reproduce in great detail backscattering patterns observed in the scanning electron microscope (SEM). However, a fully quantitative comparison of theory and experiment requires angle-resolved measurements of the intensity and the energy of the backscattered electrons, which is difficult to realize in an SEM. This paper determines diffraction patterns of backscattered electrons using an electrostatic analyzer, operating at energies up to 40 keV with sub-eV energy resolution. Measurements are done for different measurement geometries and incoming energies. Generally a good agreement is found between theory and experiment. This spectrometer also allows us to test the influence of the energy loss of the detected electron on the backscattered electron diffraction pattern. It is found that the amplitude of the intensity variation decreases only slowly with increasing energy loss from 0 to 60 eV.

  4. Diffraction-controlled backscattering threshold and application to Raman gap

    SciTech Connect

    Rose, Harvey A.; Mounaix, Philippe

    2011-04-15

    In most classic analytical models of linear stimulated scatter, light diffraction is omitted, a priori. However, modern laser optic typically includes a variant of the random phase plate [Y. Kato et al., Phys. Rev. Lett. 53, 1057 (1984)], resulting in diffraction limited laser intensity fluctuations - or localized speckles - which may result in explosive reflectivity growth as the average laser intensity approaches a critical value [H. A. Rose and D. F. DuBois, Phys. Rev. Lett. 72, 2883 (1994)]. Among the differences between stimulated Raman scatter (SRS) and stimulated Brillouin scatter is that the SRS scattered light diffracts more strongly than the laser light with increase of electron density. This weakens the tendency of the SRS light to closely follow the most amplified paths, diminishing gain. Let G{sub 0} be the one-dimensional power gain exponent of the stimulated scatter. In this paper we show that differential diffraction gives rise to an increase of G{sub 0} at the SRS physical threshold with increase of electron density up to a drastic disruption of SRS as electron density approaches one fourth of its critical value from below. For three wave interaction lengths not small compared to a speckle length, this is a physically robust Raman gap mechanism.

  5. Investigation of plastic deformation heterogeneities in duplex steel by EBSD

    SciTech Connect

    Wronski, S.; Tarasiuk, J.; Bacroix, B.; Baczmanski, A.; Braham, C.

    2012-11-15

    An EBSD analysis of a duplex steel (austeno-ferritic) deformed in tension up to fracture is presented. The main purpose of the paper is to describe, qualitatively and quantitatively, the differences in the behavior of the two phases during plastic deformation. In order to do so, several topological maps are measured on the deformed state using the electron backscatter diffraction technique. Distributions of grain size, misorientation, image quality factor and texture are then analyzed in detail. - Highlights: Black-Right-Pointing-Pointer Heterogeneities in duplex steel is studied. Black-Right-Pointing-Pointer The behavior of the two phases during plastic deformation is studied. Black-Right-Pointing-Pointer IQ factor distribution and misorientation characteristics are examined using EBSD.

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

    SciTech Connect

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

    2012-02-15

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

  7. Electron backscattering diffraction analysis of an ancient wootz steel blade from central India

    SciTech Connect

    Barnett, M.R. Sullivan, A.; Balasubramaniam, R.

    2009-04-15

    The electron backscattering diffraction technique was used to analyse the nature of carbides present in an ancient wootz steel blade. Bulky carbides, pro-eutectoid carbide along the prior austenite grain boundaries and fine spheroidized carbides were detected. Electron backscattering diffraction was employed to understand the texture of these carbides. The orientations of the cementite frequently occur in clusters, which points to a common origin of the members of the cluster. For the bands of coarse cementite, the origin is probably large coarse particles formed during the original cooling of the wootz cake. Pearlite formed earlier in the forging process has led to groups of similarly oriented fine cementite particles. The crystallographic texture of the cementite is sharp whereas that of the ferrite is weak. The sharp cementite textures point to the longevity of the coarse cementite throughout the repeated forging steps and to the influence of existing textured cementite on the nucleation of new cementite during cooling.

  8. EBSD characterization of 8090 Al-Li alloy during dynamic and static recrystallization

    SciTech Connect

    Xun, Y.; Tan, M.J

    2004-06-15

    The microstructures of high-temperature deformed and annealed 8090 Al-Li alloy have been characterized using electron back-scattered diffraction (EBSD). The observed structure refinement, which is attributed to the dynamic and static recrystallization (DRX and SRX, respectively) for the deformation and annealing processes, respectively, was accompanied by a shift in misorientation angle distribution from low- to high-angle side, with more significant effect in the strain-induced case (DRX)

  9. 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

  10. 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.

  11. An electron-backscattered diffraction study of the texture evolution in a coarse-grained AZ31 magnesium alloy deformed in tension at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Wu, Xin

    2006-01-01

    Electron-backscattered diffraction (EBSD) has been used to investigate the texture evolution during tensile deformation at temperatures between 673 and 773 K of a coarse-grained commercial AZ31 magnesium alloy. A weak (0001) fiber texture was initially present in the hot-rolled magnesium alloy plate. The [0001] directions of the grains spread 0 to 45 deg around the normal direction (ND) of the magnesium alloy plate. This pre-existing weak texture evolved during tensile deformation into a strong texture close to the {0001} <1bar 100>. The [0001] directions of the grains rotated toward the orientations perpendicular to the tension axis of the samples, indicating that the <11bar 20> slip system appeared to be the most active slip system, especially in the early stages of deformation. The EBSD Schmid-factor analysis revealed that, however, with an increase in strain and the rotation of the (0001) slip plane, the {11bar 22} <11bar 2bar 3> slip system appeared to be more favorable. The {1bar 200} <11bar 10> and {1bar 201} <11bar 20> slip systems remained favored throughout the strains investigated, indicating that {1bar 100} and {1bar 101} are two important slip planes for cross slip using the <11bar 20> slip vector. It is found that the misorientation across one coarse grain (as high as 38.2 deg) is accommodated by low-angle grain boundaries (LAGBs). The formation of these LAGBs may be an intermediate stage of the coarse grain refinement that occurred during deformation.

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

    NASA Astrophysics Data System (ADS)

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

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

  13. Characterization of nano-composite M-2411/Y-123 thin films by electron backscatter diffraction and in-field critical current measurements

    NASA Astrophysics Data System (ADS)

    Bodea, M. A.; Pedarnig, J. D.; Withnell, T. D.; Weber, H. W.; Cardwell, D. A.; Babu, N. Hari; Koblischka-Veneva, A.

    2010-06-01

    Thin films of nano-composite Y-Ba-Cu-O (YBCO) superconductors containing nano-sized, non-superconducting particles of Y2Ba4CuMOx (M-2411 with M = Ag and Nb) have been prepared by the PLD technique. Electron backscatter diffraction (EBSD) has been used to analyze the crystallographic orientation of nano-particles embedded in the film microstructure. The superconducting YBa2Cu3O7 (Y-123) phase matrix is textured with a dominant (001) orientation for all samples, whereas the M-2411 phase exhibits a random orientation. Angular critical current measurements at various temperature (T) and applied magnetic field (B) have been performed on thin films containing different concentration of the M-2411 second phase. An increase in critical current density Jc at T < 77 K and B < 6 T is observed for samples with low concentration of the second phase (2 mol % M-2411). Films containing 5 mol % Ag-2411 exhibit lower Jc than pure Y-123 thin films at all fields and temperatures. Samples with 5 mol % Nb-2411 show higher Jc(B) than phase pure Y-123 thin films for T < 77 K.

  14. Effect of cold deformation on the recrystallization behavior of FePd alloy at the ordering temperature using electron backscatter diffraction

    SciTech Connect

    Lin, Hung-Pin; Chen, Yen-Chun; Chen, Delphic; Kuo, Jui-Chao

    2014-08-15

    In this study, the evolution of the recrystallization texture and microstructure was investigated after annealing of 50% and 90% cold-rolled FePd alloy at 530 °C. The FePd alloy was produced by vacuum arc melting in an atmosphere of 97% Ar and 3% H{sub 2}. The specimens were cold rolled to achieve 50% and 90% reduction in thickness. Electron backscatter diffraction measurements were performed on the rolling direction–normal direction section. With increased deformation from 50% to 90%, recrystallized texture transition occurs. For the 50% cold-rolled alloy, the preferred orientation is (0 1 0) [11 0 1], which is close to the cubic orientation after 400 h of annealing. For the 90% cold-rolled alloy, the orientation changes to (0 5 4) [22–4 5] after 16 h of annealing. - Highlights: • Texture and microstructure in cold-rolled FePd alloy was investigated during annealing using EBSD. • The recrystallized texture of 50% cold-rolled FePd is (0 1 0) [11 0 1] at 530 °C for 400 hours. • The recrystallized texture of 90% cold-rolled FePd is changed to (0 5 4) [22–4 5] at 530 °C after 16 hours.

  15. Grain orientations and distribution of Y2Ba4CuUOx phase in melt-textured YBCO with addition of depleted uranium oxide studied by EBSD

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Mücklich, F.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Murakami, M.

    2006-07-01

    The local grain orientations and the distribution of Y2Ba4CuUOx (U-2411) phase are measured within melt-textured YBCO samples by means of electron backscatter diffraction (EBSD). In this work, several samples with varying addition (0.1-0.8 wt%) of depleted uranium oxide (DU) were analysed by means of EBSD. The embedded U-2411 particles were found to have sizes around 200 nm, some large particles being present in the samples with a high DU concentration. Combined EBSD and EDX analysis enabled the identification of the Kikuchi patterns of the U-2411 phase, so that a true three-phase EBSD scan (YBCO, Y2BaCuO5 and U-2411) becomes possible.

  16. 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.

  17. Adaptive characterization of recrystallization kinetics in IF steel by electron backscatter diffraction.

    PubMed

    Kim, Dong-Kyu; Park, Won-Woong; Lee, Ho Won; Kang, Seong-Hoon; Im, Yong-Taek

    2013-12-01

    In this study, a rigorous methodology for quantifying recrystallization kinetics by electron backscatter diffraction is proposed in order to reduce errors associated with the operator's skill. An adaptive criterion to determine adjustable grain orientation spread depending on the recrystallization stage is proposed to better identify the recrystallized grains in the partially recrystallized microstructure. The proposed method was applied in characterizing the microstructure evolution during annealing of interstitial-free steel cold rolled to low and high true strain levels of 0.7 and 1.6, respectively. The recrystallization kinetics determined by the proposed method was found to be consistent with the standard method of Vickers microhardness. The application of the proposed method to the overall recrystallization stages showed that it can be used for the rigorous characterization of progressive microstructure evolution, especially for the severely deformed material.

  18. AnyStitch: a tool for combining electron backscatter diffraction data sets.

    PubMed

    Pilchak, A L; Shiveley, A R; Tiley, J S; Ballard, D L

    2011-10-01

    Recent advances in electron backscatter diffraction equipment and software have permitted increased data acquisition rates on the order of hundreds of points per second with additional increases in the foreseeable future likely. This increase in speed allows users to collect data from statistically significant areas of samples by combining beam-control scans and automated stage movements. To facilitate data analysis, however, the individual tiles must be combined, or stitched, into a single data set. In this paper, we describe a matlab(®) (The Mathworks, Inc., Natick, MA, USA) program to facilitate stitching of electron backscatter diffraction data. The method offers users a wide range of controls for tile placement including independent overlaps for horizontal and vertical tiles and also includes a parameter to account for systematic stage positioning errors or improperly calibrated scan rotation. The code can stitch data collected on either square or hexagonal grids and contains a function to reduce the resolution of square grid data if the resulting file is too large (or has too many grains) to be opened by the analysis software. The software was primarily written to work with TSL(®) OIM™ data sets and includes a function to quickly read compressed *.osc files into a variable in the matlab(®) workspace as opposed to using slower, text-reading functions. The output file is in *.ang format and can be opened directly by TSL(®) OIM™ Analysis software. A set of functions to facilitate stitching of text-based *.ctf files produced by Oxford Instruments HKL systems are also included. Finally, the code can also be used to combine *.tif images to produce a montage. The source code, a graphical user interface and a compiled version of the software was made available in the online version of this paper.

  19. Combined electron backscatter diffraction and cathodoluminescence measurements on CuInS{sub 2}/Mo/glass stacks and CuInS{sub 2} thin-film solar cells

    SciTech Connect

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

    2010-01-15

    Electron backscatter diffraction (EBSD) and cathodoluminescence (CL) measurements in a scanning electron microscope were performed on cross sections of CuInS{sub 2} thin films and ZnO/CdS/CuInS{sub 2}/Mo/glass thin-film solar cells. The CuInS{sub 2} layers analyzed for the present study were grown by a rapid thermal process. The regions of the CuInS{sub 2} layers emitting high CL intensity of band-band luminescence are situated near the top surface (or close to the interface with ZnO/CdS). This can be attributed to an enhanced crystal quality of the thin films in this region. The phenomenon may be related to the recrystallization via solid-state reactions with Cu{sub x}S phases, which is assumed to run from the top to the bottom of the growing CuInS{sub 2} layer. The distribution of CL intensities is independent of the sample temperature, the acceleration voltage of the electron beam, and of whether or not the ZnO/CdS window layers are present. When comparing CL images and EBSD maps on identical sample positions, pronounced intragrain CL contrast is found for individual grains. Also, it is shown that at random grain boundaries, the decreases in CL intensities are substantially larger than at {Sigma}3 grain boundaries.

  20. Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

    PubMed Central

    Zhang, Tiantian; Britton, Ben; Shollock, Barbara; Dunne, Fionn

    2016-01-01

    A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270–1480 MPa. PMID:27279765

  1. Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Jiang, Jun; Britton, Ben; Shollock, Barbara; Dunne, Fionn

    2016-05-01

    A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270-1480 MPa.

  2. Evaluation of macrozone dimensions by ultrasound and EBSD techniques

    SciTech Connect

    Moreau, Andre; Toubal, Lotfi; Bocher, Philippe; Humbert, Michel; Uta, Elena; Gey, Nathalie

    2013-01-15

    Titanium alloys are known to have texture heterogeneities, i.e. regions much larger than the grain dimensions, where the local orientation distribution of the grains differs from one region to the next. The electron backscattering diffraction (EBSD) technique is the method of choice to characterize these macro regions, which are called macrozones. Qualitatively, the images obtained by EBSD show that these macrozones may be larger or smaller, elongated or equiaxed. However, often no well-defined boundaries are observed between the macrozones and it is very hard to obtain objective and quantitative estimates of the macrozone dimensions from these data. In the present work, we present a novel, non-destructive ultrasonic technique that provides objective and quantitative characteristic dimensions of the macrozones. The obtained dimensions are based on the spatial autocorrelation function of fluctuations in the sound velocity. Thus, a pragmatic definition of macrozone dimensions naturally arises from the ultrasonic measurement. This paper has three objectives: 1) to disclose the novel, non-destructive ultrasonic technique to measure macrozone dimensions, 2) to propose a quantitative and objective definition of macrozone dimensions adapted to and arising from the ultrasonic measurement, and which is also applicable to the orientation data obtained by EBSD, and 3) to compare the macrozone dimensions obtained using the two techniques on two samples of the near-alpha titanium alloy IMI834. In addition, it was observed that macrozones may present a semi-periodical arrangement. - Highlights: Black-Right-Pointing-Pointer Discloses a novel, ultrasonic NDT technique to measure macrozone dimensions Black-Right-Pointing-Pointer Proposes a quantitative and objective definition of macrozone dimensions Black-Right-Pointing-Pointer Compares macrozone dimensions obtained using EBSD and ultrasonics on 2 Ti samples Black-Right-Pointing-Pointer Observes that macrozones may have a semi

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

    SciTech Connect

    Donius, Amalie E.; Obbard, Rachel W.; Burger, Joan N.; Hunger, Philipp M.; Baker, Ian; Doherty, Roger D.; Wegst, Ulrike G.K.

    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.

  4. Microstrain distribution mapping on CuInSe2 thin films by means of electron backscatter diffraction, X-ray diffraction, and Raman microspectroscopy.

    PubMed

    Schäfer, Norbert; Wilkinson, Angus J; Schmid, Thomas; Winkelmann, Aimo; Chahine, Gilbert A; Schülli, Tobias U; Rissom, Thorsten; Marquardt, Julien; Schorr, Susan; Abou-Ras, Daniel

    2016-10-01

    The investigation of the microstructure in functional, polycrystalline thin films is an important contribution to the enhanced understanding of structure-property relationships in corresponding devices. Linear and planar defects within individual grains may affect substantially the performance of the device. These defects are closely related to strain distributions. The present work compares electron and X-ray diffraction as well as Raman microspectroscopy, which provide access to microstrain distributions within individual grains. CuInSe2 thin films for solar cells are used as a model system. High-resolution electron backscatter diffraction and X-ray microdiffraction as well as Raman microspectroscopy were applied for this comparison. Consistently, microstrain values were determined of the order of 10(-4) by these three techniques. However, only electron backscatter diffraction, X-ray microdiffraction exhibit sensitivities appropriate for mapping local strain changes at the submicrometer level within individual grains in polycrystalline materials. PMID:27459269

  5. 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.; Chiu, C.H.; Hong, I.T.; Tung, H.C.; Chien, F.S.-S.

    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.

  6. Grain boundary studies of high temperature superconducting materials using electron backscatter Kikuchi diffraction

    SciTech Connect

    Goyal, A.; Specht, E.D.; Wang, Z.L.; Kroeger, D.M.

    1996-12-31

    Grain Orientation and gain boundary misorientation distributions in high critical current density, high temperature superconductors were determined using electron backscatter Kikuchi diffraction. It is found that depending on the type of superconductor and the processing method used to fabricate it, there exist different scales of biaxial texture from no biaxial texture, local biaxial texture, to complete biaxial texture. Experimentally obtained grain boundary misorientation distributions (GBMDs) were found to be skewed significantly to low angles in comparison to what is expected on the basis of macroscopic texture alone, suggesting that minimization of energy may be a driving force during the processing of high critical current density materials. In addition, a higher than expected fraction of coincident-site lattice boundaries is observed. Examination of maps of grain boundary misorientations in spatially correlated gains, i.e. the grain boundary mesotexture, suggests the presence percolative paths of high critical current density. A combination of orientation measurements, theoretical modeling of GBMDs and modeling of percolative current flow through an assemblage of gain boundaries is performed to gain an insight into the important microstructural features dictating the transport properties of high temperature superconductors. It is found that maximization of low energy, in particular, low angle boundaries is essential for higher critical currents. The combination of experimental and analytical techniques employed are applicable to other materials where physical properties are dominated by interganular characteristics.

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

    PubMed

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

    2013-08-01

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

  8. Study of grain morphology of various magnetite samples by means of EBSD

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.

    2010-01-01

    (001)- and (111)-oriented magnetite thin films were grown on MgO substrates (film thickness 200 nm) by means of oxygen-plasma-assisted molecular beam epitaxy and by laser-ablation. Further samples are electroplated magnetite thin films on Si/copper substrates and films from biogenic magnetite. The achieved grain orientations are analysed by means of the electron backscatter diffraction (EBSD) technique. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution of up to 40 nm on such ceramic materials. A high image quality of the recorded Kikuchi patterns was achieved enabling multi-phase scans (e.g., Fe3O4, MgO, Fe2O3). The facets of individual grains are analysed in detail.

  9. EBSD and Nanoindentation-Correlated Study of Delamination Fracture in Al-Li Alloy 2090

    NASA Technical Reports Server (NTRS)

    Tayon, Wesley A.; Crooks, Roy E.; Domack, Marcia S.; Wagner, John A.; Elmustafa, A. A.

    2008-01-01

    Al-Li alloys offer attractive combinations of high strength and low density. However, a tendency for delamination fracture has limited their use. A better understanding of the delamination mechanisms may identify methods to control delaminations through processing modifications. A combination of new techniques has been used to evaluate delamination fracture in Al-Li alloys. Both high quality electron backscattered diffraction (EBSD) information and valid nanoindentation measurements were obtained from fractured test specimens. Correlations were drawn between nano-scale hardness variations and local texture along delaminating boundaries. Intriguing findings were observed for delamination fracture through the combined analysis of grain orientation, Taylor factor, and kernel average misorientation.

  10. Electron Backscatter Diffraction and Transmission Kikuchi Diffraction Analysis of an Austenitic Stainless Steel Subjected to Surface Mechanical Attrition Treatment and Plasma Nitriding.

    PubMed

    Proust, Gwénaëlle; Retraint, Delphine; Chemkhi, Mahdi; Roos, Arjen; Demangel, Clemence

    2015-08-01

    Austenitic 316L stainless steel can be used for orthopedic implants due to its biocompatibility and high corrosion resistance. Its range of applications in this field could be broadened by improving its wear and friction properties. Surface properties can be modified through surface hardening treatments. The effects of such treatments on the microstructure of the alloy were investigated here. Surface Mechanical Attrition Treatment (SMAT) is a surface treatment that enhances mechanical properties of the material surface by creating a thin nanocrystalline layer. After SMAT, some specimens underwent a plasma nitriding process to further enhance their surface properties. Using electron backscatter diffraction, transmission Kikuchi diffraction, energy dispersive spectroscopy, and transmission electron microscopy, the microstructural evolution of the stainless steel after these different surface treatments was characterized. Microstructural features investigated include thickness of the nanocrystalline layer, size of the grains within the nanocrystalline layer, and depth of diffusion of nitrogen atoms within the material. PMID:26139391

  11. Electron Backscatter Diffraction and Transmission Kikuchi Diffraction Analysis of an Austenitic Stainless Steel Subjected to Surface Mechanical Attrition Treatment and Plasma Nitriding.

    PubMed

    Proust, Gwénaëlle; Retraint, Delphine; Chemkhi, Mahdi; Roos, Arjen; Demangel, Clemence

    2015-08-01

    Austenitic 316L stainless steel can be used for orthopedic implants due to its biocompatibility and high corrosion resistance. Its range of applications in this field could be broadened by improving its wear and friction properties. Surface properties can be modified through surface hardening treatments. The effects of such treatments on the microstructure of the alloy were investigated here. Surface Mechanical Attrition Treatment (SMAT) is a surface treatment that enhances mechanical properties of the material surface by creating a thin nanocrystalline layer. After SMAT, some specimens underwent a plasma nitriding process to further enhance their surface properties. Using electron backscatter diffraction, transmission Kikuchi diffraction, energy dispersive spectroscopy, and transmission electron microscopy, the microstructural evolution of the stainless steel after these different surface treatments was characterized. Microstructural features investigated include thickness of the nanocrystalline layer, size of the grains within the nanocrystalline layer, and depth of diffusion of nitrogen atoms within the material.

  12. In Situ EBSD Observations of the Evolution in Crystallographic Orientation with Deformation

    NASA Astrophysics Data System (ADS)

    Wright, Stuart I.; Suzuki, Seiichi; Nowell, Matthew M.

    2016-09-01

    Automated electron backscatter diffraction (EBSD) analysis is frequently used to investigate the change in crystallographic orientation that occurs when polycrystalline materials deform. Through crystallographic slip, the crystal lattice within a grain rotates. However, the crystal lattice rotation in each grain is constrained by the lattices of the neighboring grains while rotating. These competing factors lead to the development of orientation gradients and substructure in deformed polycrystals. In situ uniaxial tensile deformation was carried out in the scanning electron microscope while employing simultaneous automated EBSD analysis to characterize grain rotation, both in terms of the overall rotation of the lattice and the development of orientation gradients within the grain. The impact of these factors can be seen at the grain boundaries in the deformed structure where the local orientations diverge from the orientation at the grain interior. Automated in situ EBSD analysis allows the quantitative nature of specific metrics based on local variations in orientation to illuminate the physical mechanisms underlying the stress strain response during a mechanical test.

  13. 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.

  14. Segmentation of 3D EBSD data for subgrain boundary identification and feature characterization.

    PubMed

    Loeb, Andrew; Ferry, Michael; Bassman, Lori

    2016-02-01

    Subgrain structures formed during plastic deformation of metals can be observed by electron backscatter diffraction (EBSD) but are challenging to identify automatically. We have adapted a 2D image segmentation technique, fast multiscale clustering (FMC), to 3D EBSD data using a novel variance function to accommodate quaternion data. This adaptation, which has been incorporated into the free open source texture analysis software package MTEX, is capable of segmenting based on subtle and gradual variation as well as on sharp boundaries within the data. FMC has been further modified to group the resulting closed 3D segment boundaries into distinct coherent surfaces based on local normals of a triangulated surface. We demonstrate the excellent capabilities of this technique with application to 3D EBSD data sets generated from cold rolled aluminum containing well-defined microbands, cold rolled and partly recrystallized extra low carbon steel microstructure containing three magnitudes of boundary misorientations, and channel-die plane strain compressed Goss-oriented nickel crystal containing microbands with very subtle changes in orientation. PMID:26630071

  15. 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

  16. 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.

  17. Deformation Twin Nucleation and Growth Characterization in Magnesium Alloys Using Novel EBSD Pattern Analysis and Machine Learning Tools

    NASA Astrophysics Data System (ADS)

    Rampton, Travis M.

    Deformation twinning in Magnesium alloys both facilitates slip and forms sites for failure. Currently, basic studies of twinning in Mg are facilitated by electron backscatter diffraction (EBSD) which is able to extract a myriad of information relating to crystalline microstructures. Although much information is available via EBSD, various problems relating to deformation twinning have not been solved. This dissertation provides new insights into deformation twinning in Mg alloys, with particular focus on AZ31. These insights were gained through the development of new EBSD and related machine learning tools that extract more information beyond what is currently accessed. The first tool relating to characterization of deformed and twinned materials focuses on surface topography crack detection. The intensity map across EBSD images contains vital information that can be used to detect evolution of surface roughness and crack formation, which typically occurs at twin boundaries. The method of topography recovery resulted in reconstruction errors as low as 2% over a 500 microm length. The method was then applied to a 3 microm x 3 microm area of twinned Tantalum which experienced topographic alterations. The topography of Ta correlated with other measured changes in the microstructure. Additionally, EBSD images were used to identify the presence of cracks in Nickel microstructures. Several cracks were identified on the Ni specimen, demonstrating that cracks as thin as 34 nm could be measured. A further EBSD based tool developed for this study was used to identify thin compression twins in Mg; these are often missed in a traditional EBSD scan due to their size relative to the electron probe. This tool takes advantage of crystallographic relationships that exist between parent and twinned grains; common planes that exist in both grains lead to bands of consistent intensity as a scan crosses a twin. Hence, twin boundaries in a microstructure can be recognized, even when

  18. 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 μm in the x-direction at -150°C and 0.5 μm 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).

  19. 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

  20. Novel Techniques for Examining Detailed Microstructure of Two-phase Lower Mantle Mineral Analogs with SEM and EBSD

    NASA Astrophysics Data System (ADS)

    Kaercher, P. M.; Mariani, E.; Dawson, K.

    2015-12-01

    We examined deformation microstructures of an analog two-phase system of the lower mantle using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Halite (NaCl) and neighborite (NaMgF3) were used as analogs to lower mantle minerals ferropericlase (Mg,Fe)O and bridgmanite MgSiO3, respectively, and deformed to 30% strain at 4 GPa in the D-DIA. We have adapted techniques previously used for EBSD preparation of halite (NaCl) (e.g. Pennock et al. 2002, Journal of Microscopy, v205; Staiger et al. 2010, Materials Characterization, v61) to prepare halite and neighborite for EBSD. Because halite is soft and hydrophilic, it is tricky to prepare for high quality EBSD. On the other hand, neighborite is much harder than halite (with a bulk modulus 5 times that of halite) and requires high quality polishing for longer and through various polishing-medium sizes. EBSD maps were obtained by polishing with very fine colloidal alumina, followed by etching or a final polish in a precision ion polishing system (PIPS). Distribution of phases, grain size and shape, and crystallographic preferred orientation were examined to determine which phase controls the deformation and which deformation mechanisms dominate. Preliminary results show the softer halite is likely interconnected at just 25 volume % or less and controls the deformation through a mechanism that does not promote development of crystallographic preferred orientation. This suggests that periclase may control deformation in the lower mantle resulting in a weaker, more viscous lower mantle and may help to explain why the bulk of the lower mantle is mostly isotropic.

  1. Fluvial suspended sediment characteristics by high-resolution, surrogate metrics of turbidity, laser-diffraction, acoustic backscatter, and acoustic attenuation

    NASA Astrophysics Data System (ADS)

    Landers, Mark Newton

    Sedimentation is a primary and growing environmental, engineering, and agricultural issue around the world. However, collection of the data needed to develop solutions to sedimentation issues has declined by about three-fourths since 1983. Suspended-sediment surrogates have the potential to obtain sediment data using methods that are more accurate, of higher spatial and temporal resolution, and with less manually intensive, costly, and hazardous methods. The improved quality of sediment data from high-resolution surrogates may inform improved understanding and solutions to sedimentation problems. The field experiments for this research include physical samples of suspended sediment collected concurrently with surrogate metrics from instruments including 1.2, 1.5, and 3.0 megahertz frequency acoustic doppler current profilers, a nephelometric turbidity sensor, and a laser-diffraction particle size analyzer. This comprehensive data set was collected over five storms in 2009 and 2010 at Yellow River near Atlanta, Georgia. Fluvial suspended sediment characteristics in this study can be determined by high-resolution surrogate parameters of turbidity, laser-diffraction and acoustics with model errors 33% to 49% lower than traditional methods using streamflow alone. Hysteresis in sediment-turbidity relations for single storm events was observed and quantitatively related to PSD changes of less than 10 microns in the fine silt to clay size range. Suspended sediment particle size detection (PSD) is significantly correlated with ratios of measured acoustic attenuation at different frequencies; however the data do not fit the theoretical relations. Using both relative acoustic backscatter (RB) and acoustic attenuation as explanatory variables results in a significantly improved model of suspended sediment compared with traditional sonar equations using only RB. High resolution PSD data from laser diffraction provide uniquely valuable information; however the size detection

  2. 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

  3. 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.

  4. Measurement of InAsBi mole fraction and InBi lattice constant using Rutherford backscattering spectrometry and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Shalindar, A. J.; Webster, P. T.; Wilkens, B. J.; Alford, T. L.; Johnson, S. R.

    2016-10-01

    Several 1 μm thick, nearly lattice-matched InAsBi layers grown on GaSb are examined using Rutherford backscattering spectrometry and X-ray diffraction. Random Rutherford backscattering measurements indicate that the average Bi mole fraction ranges from 0.0503 to 0.0645 for the sample set, and ion-channeling measurements indicate that the Bi atoms are substitutional. The X-ray diffraction measurements show a diffraction sideband near the main (004) diffraction peak, indicating that the Bi mole fraction is not laterally uniform in the layer. The average out-of-plane tetragonal distortion is determined by modeling the main and sideband diffraction peaks, from which the average unstrained lattice constant of each sample is determined. By comparing the Bi mole fraction measured by random Rutherford backscattering with the InAsBi lattice constant for the sample set, the lattice constant of zinc blende InBi is determined to be 6.6107 Å.

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

    SciTech Connect

    Lin, Hung-Pin; Ng, Tin-San; Kuo, Jui-Chao; Chen, Yen-Chun; Chen, Chun-Liang; Ding, Shi-Xuan

    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.

  6. EBSD study of substrate-mediated growth of hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Dias, J.; Kidambi, P. R.; Hofmann, S.; Ducati, C.

    2014-06-01

    Hexagonal Boron Nitride (h-BN) is a promising insulating material to complement and enable graphene electronics. Given the good lattice match to graphite, graphene/h-BN heterostructures may be grown with negligible amounts of strain and defect states, resulting in high carrier mobilities approaching values for suspended graphene. Chemical vapour deposition (CVD) has emerged as one of the preferred routes for the synthesis of 2D materials for electronic applications. Here we report on the growth of h-BN by low pressure CVD, using borazine as a precursor. Electron backscattered diffraction (EBSD) in conjunction with topographic imaging in the scanning electron microscope are used to investigate the change in crystal structure and orientation of three metallic catalyst substrates: Co, Ni and Cu, by high temperature processing and the growth of nanoscale h-BN domains. The behaviour of the metal foils is interpreted in light of the prevalent growth models. EBSD and imaging conditions are optimized to allow efficient acquisitions for these composite and nanostructured specimens.

  7. Energy-dispersive spectroscopy and electron backscatter diffraction analysis of isothermally aged SAF 2507 type superduplex stainless steel

    NASA Astrophysics Data System (ADS)

    Dobranszky, J.; Szabo, P. J.; Berecz, T.; Hrotko, V.; Portko, M.

    2004-10-01

    Due to thermal effects, several precipitation and segregation processes are known in duplex stainless steels. These microstructural changes influence both of the original phases, but in different ways. Isothermal ageing in a large range of temperature was performed on SAF 2507 type steel. The temperature range was 300-1000 °C, the ageing time was between 100 s and 24 h. This paper discusses the results of ageing at 900 °C. Microstructural changes were investigated by electron microscopy, energy-dispersive spectroscopy and electron backscattered diffraction analysis. This technique allowed the determination of the microstructure of the secondary austenite and sigma phase and their mutual orientation properties. Beside this, thermoelectric power measurements were also performed, which gave information about the kinetics of the precipitation process. Results showed that sigma-phase precipitation started right after 200 s in the case of annealed steel, and faster than 100 s in the cold-rolled state. After 5000 s, the delta-ferrite disappeared. Chemical composition of sigma phase was independent on the ageing time. A small decrease in nickel content was observed with a slight increase of Cr content. Small amount of chi phase had also been observed on the ferrite-ferrite boundaries, but later they changed into sigma phase. Similarly to sigma phase, chi phase showed significant phosphorus enrichment. During ageing, small chrome nitride precipitates developed, which amount increased in time, and some vanadium could be measured in them. The orientation relationship between austenite and sigma phase deviated from Nenno-orientationship with about 24°, and seems to form a [110]‖[310] relationship, which was characteristic right from the beginning of the process, and remains more or less constant.

  8. 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

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

    SciTech Connect

    Zaid, Md; Bhattacharjee, P.P.

    2014-10-15

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

  10. EBSD Characterization of Dendrites in Synthetic and Natural Rocks

    NASA Astrophysics Data System (ADS)

    Hammer, J. E.; Tiley, J.; Shiveley, A.; Knox, S.; Viswanathan, G.

    2011-12-01

    Arborescent crystals in igneous rocks are associated with extreme crystallization environments: the protoplanary disk (chondrules), Earth's ultramafic Archean mantle (komatiite), and terrestrial submarine-erupted lavas (pillow basalts), although the role of morphological instabilities in more mundane settings such as magma reservoirs of modern oceanic islands is increasingly appreciated (see Welsch et al., V16). Fundamentals of dendrite formation are presumably well understood: branching morphologies belie crystal growth conditions in which the driving force for solidification produces a kinetic roughening transition, transforming an atomically smooth crystal-liquid interface into a rough, adhesive interface capable of extremely rapid advancement. However, not since photomicrograhic advances made possible close observations of snow crystals (Nakaya 1936), has there been a more promising set of analytical tools to characterize dendrites in natural and synthetic materials in pursuit of new insights. We are investigating clinopyroxene (cpx) in the quenched top of Fe-rich tholeiitic lava (Munro Township, Northeast Ontario; Fig. 1) and a synthetic basalt of similar character (Hammer 2006) with electron backscatter diffraction (EBSD), 3D reconstruction of optical serial sections, and TEM. Here we report intriguing phenomena observed with EBSD common to both samples. Severe thinning of dendrite trunks and repeated tip splitting destroys the self-similarity associated with classical dendrites and instead presages 'seaweed' morphology. Split tips manifest incremental trajectory deflections, producing gently arched trunks (Fig. 1A) as well as tightly curved (r<10 um) trunks. Crystals progressively rotate clockwise about cpx <010>, producing distinctive misorientation maps and pole figures (Fig. 1C). Parallel branches exhibit similar rotational trajectories, carving parallel arcs in the <010> pole figure. The high incidence of side branching and tip splitting is consistent

  11. Assessment of Creep Strain Distribution Across Base Metal of 316LN Austenitic Stainless Steel Weld Joint by an EBSD-Based Parameter

    NASA Astrophysics Data System (ADS)

    Vijayanand, V. D.; Ganesan, V.; Ganesh Kumar, J.; Parameswaran, P.; Naveena; Laha, K.

    2015-11-01

    Electron backscatter diffraction (EBSD) analysis has been used to estimate the accumulated strain in base metal region of 316LN austenitic stainless steel weld joints, creep tested at 923 K (650 °C), and at stresses of 175 and 225 MPa. The variation in strength of weld metal, heat-affected zone (HAZ), and base metal-induced stress and strain gradients across the weld joint under creep exposure. Finite element analysis (FEA) of von-Mises stress distribution across the joint has been carried out on incorporating strength of different constituents of the joint, derived by miniature specimen testing techniques. The FEA simulations revealed preferential accumulation of von-Mises stress in the base metal region near to HAZ. The variation in accumulated plastic strain across the base metal has been estimated using a `crystal deformation' ( C d) parameter which quantifies the orientation spread within a grain. This parameter was obtained by EBSD analysis carried out using a scanning electron microscope. The trend in variation of accumulated plastic strain across the base metal accounted well with the von-Mises stress variation, which causes plastic deformation. The plastic strain in the base metal in both the stress levels was found to accumulate preferentially near to the HAZ and reduced steadily toward the ridge at the end of specimen. Transmission electron microscopic study has been carried out to substantiate the findings of the EBSD investigation.

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

    PubMed

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

    2014-12-01

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

  13. An ultrahigh-density digital data read-out method based on grazing-angle incidence x-ray backscattering diffraction

    NASA Astrophysics Data System (ADS)

    Bezirganyan, Hakob Akop P.; Bezirganyan, Hayk H., Jr.; Bezirganyan, Siranush E.; Bezirganyan, Petros H., Jr.; Mossikyan, Youri G.

    2005-10-01

    An ultrahigh-density x-ray optical data storage medium useful for terabyte-scale memory applications and named X-ROM is proposed. The X-ROM is a nanocrystalline semiconductor layer, in which non-diffracting nanosized reflectors of x-radiation are embedded. The procedure of digital data read-out from the X-ROM can be performed e.g. by the application of a grazing-angle incidence x-ray backscattering diffraction technique under conditions of specular vacuum wave suppression. The surface storage digital data density of the proposed device, with 20 nm/bit linear size of the single-bit domain, is higher by two orders of magnitude than the volumetric data density actually achieved for a three-dimensional optical data storage medium.

  14. An investigation into the use of electron back scattered diffraction to measure recrystallized fraction

    SciTech Connect

    Black, M.P.; Higginson, R.L. . Dept. of Engineering Materials)

    1999-06-18

    The Electron Back-Scattered Diffraction (EBSD) technique is in its infancy and is a highly promising area of development. Use of EBSD has been predominantly for the determination of crystallographic textures. Other applications have also been considered, which include: crystal structure determination, phase determination, grain boundary studies and both elastic and plastic deformation measurement. Although it has been acknowledged that an important use of the EBSD could be in the measurement of recrystallization and its kinetics there are a number of inherent problems with such measurements using EBSD. These problems include the ability of the system to index deformed microstructures even those on a fine scale, the difficulties of analyzing patterns in the region of grain boundaries and the problems of sample preparation which is critical in the quality of the diffraction patterns obtained. The aim of the present study is to determine whether it is possible to measure the volume fraction recrystallized using EBSP of partially recrystallized stainless steel. This has been done by investigation of the quality of matching between the observed and calculated diffraction patterns, and the quality of the observed patterns measured in terms of their contrast. The material used was stainless steel 316L.

  15. 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.

  16. 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

  17. Modeling of ultrasonic propagation in heavy-walled centrifugally cast austenitic stainless steel based on EBSD analysis.

    PubMed

    Chen, Yao; Luo, Zhongbing; Zhou, Quan; Zou, Longjiang; Lin, Li

    2015-05-01

    The ultrasonic inspection of heavy-walled centrifugally cast austenitic stainless steel (CCASS) is challenging due to the complex metallurgical structure. Numerical modeling could provide quantitative information on ultrasonic propagation and plays an important role in developing advanced and reliable ultrasonic inspection techniques. But the fundamental obstacle is the accurate description of the complex metallurgical structure. To overcome this difficulty, a crystal orientation map of a CCASS specimen in the 96 mm × 12 mm radial-axial cross section was acquired based on the electron backscattered diffraction (EBSD) technique and it was used to describe the coarse-grained structure and grain orientation. A model of ultrasonic propagation for CCASS was built according to the EBSD map. The ultrasonic responses of the CCASS sample were also tested. Some experimental phenomena such as structural noise and signal distortion were reproduced. The simulated results showed a good consistence with the experiments. The modeling method is expected to be effective for the precise interpretation of ultrasonic propagation in the polycrystalline structures of CCASS.

  18. Modeling of ultrasonic propagation in heavy-walled centrifugally cast austenitic stainless steel based on EBSD analysis.

    PubMed

    Chen, Yao; Luo, Zhongbing; Zhou, Quan; Zou, Longjiang; Lin, Li

    2015-05-01

    The ultrasonic inspection of heavy-walled centrifugally cast austenitic stainless steel (CCASS) is challenging due to the complex metallurgical structure. Numerical modeling could provide quantitative information on ultrasonic propagation and plays an important role in developing advanced and reliable ultrasonic inspection techniques. But the fundamental obstacle is the accurate description of the complex metallurgical structure. To overcome this difficulty, a crystal orientation map of a CCASS specimen in the 96 mm × 12 mm radial-axial cross section was acquired based on the electron backscattered diffraction (EBSD) technique and it was used to describe the coarse-grained structure and grain orientation. A model of ultrasonic propagation for CCASS was built according to the EBSD map. The ultrasonic responses of the CCASS sample were also tested. Some experimental phenomena such as structural noise and signal distortion were reproduced. The simulated results showed a good consistence with the experiments. The modeling method is expected to be effective for the precise interpretation of ultrasonic propagation in the polycrystalline structures of CCASS. PMID:25670411

  19. 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 η and pole distance ψ. 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

  20. Identifying Planar Deformation Features Using EBSD and FIB

    NASA Astrophysics Data System (ADS)

    Pickersgill, A. E.; Lee, M. R.

    2015-09-01

    Planar deformation features in quartz grains from the Gow Lake impact structure have been successfully identified and indexed using electron backscatter diffraction in combination with focused ion beam milling.

  1. Electron backscatter diffraction analysis of gold nanoparticles on Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7−δ}

    SciTech Connect

    Bochmann, A.; Teichert, S.; Katzer, C.; Schmidl, F.

    2015-06-07

    It has been shown recently that the incorporation of gold nanoparticles into Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7−δ} enhances the superconducting properties of this material in a significant way. Previous XRD and TEM investigations suggest different crystallographic relations of the gold nanoparticles with respect to the epitaxial Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7−δ}. Here, detailed investigations of the crystal orientations for a large ensemble of gold nanoparticles with electron backscatter diffraction are reported. The average size of the gold nanoparticles is in the range of 60 nm–80 nm. We identified five different types of heteroepitaxial relationships between the gold nanoparticles and the superconductor film, resulting in complex pole figures. The observed different types of crystallographic orientations are discussed based on good lattice matching and the formation of low energy interfaces.

  2. 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.

  3. Calcite sealing in a fractured geothermal reservoir: Insights from combined EBSD and chemistry mapping

    NASA Astrophysics Data System (ADS)

    McNamara, David D.; Lister, Aaron; Prior, Dave J.

    2016-09-01

    Fractures play an important role as fluid flow pathways in geothermal resources hosted in indurated greywacke basement of the Taupo Volcanic Zone, New Zealand, including the Kawerau Geothermal Field. Over time, the permeability of such geothermal reservoirs can be degraded by fracture sealing as minerals deposit out of transported geothermal fluids. Calcite is one such fracture sealing mineral. This study, for the first time, utilises combined data from electron backscatter diffraction and chemical mapping to characterise calcite vein fill morphologies, and gain insight into the mechanisms of calcite fracture sealing in the Kawerau Geothermal Field. Two calcite sealing mechanisms are identified 1) asymmetrical syntaxial growth of calcite, inferred by the presence of single, twinned, calcite crystals spanning the entire fracture width, and 2) 3D, interlocking growth of bladed vein calcite into free space as determined from chemical and crystallographic orientation mapping. This study also identifies other potential uses of combined EBSD and chemical mapping to understand geothermal field evolution including, potentially informing on levels of fluid supersaturation from the study of calcite lattice distortion, and providing information on a reservoir's history of stress, strain, and deformation through investigation of calcite crystal deformation and twinning patterns.

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

    NASA Astrophysics Data System (ADS)

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

    2003-10-01

    By means of automated electron backscatter diffraction (EBSD) analysis, we studied the local orientations of embedded Y 2BaCuO 5 (2 1 1) 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 (0 0 1) orientation, we find that the embedded 211 particles do not have any preferred orientation, but the maps also reveal that at certain orientations of the 211 particles the YBCO growth is not altered. In directional solidified 211 samples, where the 211 is mainly oriented in (0 0 1) direction, the embedded YBCO particles show only some specific orientations.

  5. Matrix grain characterisation by electron backscattering diffraction of powder metallurgy aluminum matrix composites reinforced with MoSi{sub 2} intermetallic particles

    SciTech Connect

    Corrochano, J. Hidalgo, P.; Lieblich, M.; Ibanez, J.

    2010-11-15

    Research highlights: Six extruded PM AA6061/MoSi{sub 2}/15p were processed with and without ball milling {yields} EBSD was used to characterise matrix grain size and grain orientation. {yields} Ball milling decreases matrix grain size to submicrometric level. {yields} Ball milling produces a more equiaxed microstructure and larger misorientation. {yields} Increasing milling time produces matrix texture randomization.

  6. On capturing the grain-scale elastic and plastic anisotropy of alpha-Ti with spherical nanoindentation and electron back-scattered diffraction

    DOE PAGES

    Weaver, Jordan S.; Priddy, Matthew W.; McDowell, David L.; Kalidindi, Surya R.

    2016-07-10

    Here, spherical nanoindentation combined with electron back-scattered diffraction has been employed to characterize the grain-scale elastic and plastic anisotropy of single crystal alpha-Ti of two different compositions (in two different titanium alloys). Data analyses protocols needed to reliably extract the desired properties of interest are extended and demonstrated in this paper. Specifically, the grain-scale mechanical response is extracted in the form of indentation stress-strain curves for commercially pure (CP-Ti) alpha-Ti and alloyed (Ti-64) titanium from measurements on polycrystalline samples. The results are compared with responses of single crystals and nanoindentation tests (hardness and modulus) from the literature, and the measuredmore » indentation moduli are validated using crystal-elastic finite element simulations. The results obtained in this study show that (i) it is possible to characterize reliably the elastic and plastic anisotropy of alpha-Ti (hcp) of varying alloying contents with spherical nanoindentation stress-strain curves, (ii) the indentation modulus of alpha-Ti-64 is 5–10% less than CP-Ti, and (iii) the indentation yield strength of alpha-Ti-64 is 50–80% higher than CP-Ti.« less

  7. High-Resolution EBSD Study of Adiabatic Shear Band and Neighboring Grains After Dynamic Impact Loading of Mn-Steel Used in Vehicle Structure

    NASA Astrophysics Data System (ADS)

    Eskandari, M.; Mohtadi-Bonab, M. A.; Zarei-Hanzaki, A.; Odeshi, A. G.; Szpunar, J. A.

    2016-04-01

    We report the results of the microstructural characterizations and micro-texture analysis of a lightweight austenitic steel deformed at high strain rate (1200 s-1) using a split Hopkinson pressure bar. Formation of adiabatic shear bands (ASB) and plastic deformation mechanisms within neighboring grains are investigated by high-resolution electron backscatter diffraction (HR-EBSD). HR-EBSD reveals formation of athermal ɛ-martensite and ά-martensite within the shear bands, resulting in the formation of a brittle intersection structure. Crack initiation and propagation is seen in intersection structure. The thermally induced ɛ-martensite follows Shoji-Nishiyama crystallographic orientation relationship with parent austenite phase, while ά-martensite shows Burgers relationship with ɛ-martensite. A detailed examination depicts the presence of deformation twins in grains adjacent to the ASB. Furthermore, strain-induced ɛ and ά martensite are formed in the neighboring grains of ASB. The micro-texture of martensite variants is discussed in ASB and in the neighboring grains.

  8. 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.

  9. Strain analysis in quartzites with negative magnetic susceptibility using AMS and EBSD data

    NASA Astrophysics Data System (ADS)

    Rajendraprasad Renjith, A.; Mamtani, Manish A.

    2016-04-01

    This study is being done with the objective of trying to understand whether the anisotropy of magnetic susceptibility (AMS) data can provide information about strain in quartzites with negative magnetic susceptibility. For this, nine quartzite samples have been collected from Rengali Province (located in the eastern part of India) with bulk magnetic susceptibility between -13.6 x 10-6 SI units and -3.06 x 10-6 SI units. Since these rocks did not show any visible foliation or lineation, AMS analysis was performed using KLY-4S Kappabridge and the orientation of three principal axes of the AMS ellipsoid (K1>K2>K3) were determined. Thin sections were prepared parallel to the K1K3 plane of the AMS ellipsoid (plane parallel to lineation and perpendicular to foliation), which is equivalent to the XZ plane of the strain ellipsoid. SEM based electron backscatter diffraction (EBSD) analysis, shape preferred orientation (SPO) analysis and strain analysis were carried out in these sections. Recently, Renjith et al. (2016) used the same samples to establish that the AMS in quartzites gives information about the SPO and not the CPO. To further evaluate the robustness of AMS in strain analysis, the authors have integrated the degree of magnetic anisotropy (Pj - a measure of the eccentricity of AMS ellipsoid; Tarling and Hrouda, 1993) with the intensity of SPO (κ ; Piazolo and Passchier, 2002), and the strain (E - calculated using AMOCADO; Gerik and Kruhl, 2009) from the same samples from Rengali. EBSD data were used as the basis for the above calculations. Whilst the orientation of long axis of quartz grains from EBSD statistical data was used to calculate κ , the grain boundary map generated from EBSD analysis was used as the basis to determine strain (E). It is found that the sample with minimum Pj also has a minimum κ and E, and vice-versa. Hence it is concluded that one-to-one correlation exists between the degree of magnetic anisotropy, strain and intensity of SPO in

  10. EBSD characterization of crystallographic orientations and twin interfaces of modulated martensite in epitaxial NiMnGa thin film

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Zhang, Yudong; Li, Zongbin; Qin, Gaowu; Esling, Claude; Zhao, Xiang; Zuo, Liang

    2015-04-01

    The crystal structure and the global texture of 7M modulated martensite in epitaxial Ni50Mn30Ga20 thin films were investigated by X-ray diffraction (XRD), and the local crystallographic orientations correlated with microstructural features were revealed by electron backscatter diffraction (EBSD). The microstructure of 7M martensite can be classified into two distinct constituents. One refers to long straight strips with relatively homogeneous contrast, running parallel to one edge direction of the substrate. The other refers to shorter and bent plates with relatively high relative contrast, being oriented with the plate length direction roughly in 45° with respect to the substrate edges. Each 7M martensite plate is designated as a single orientation variant, and four orientation variants that are twin-related one another constitute one variant group. With the local crystallographic orientations of martensite plates and the orientations of inter-plate interface traces, the Type I, Type II and compound twin interfaces in the low and high relative contrast zones were determined.

  11. Microstructural of analysis by EBSD during deformation and annealing of ice Ih

    NASA Astrophysics Data System (ADS)

    Mainprice, D.; Hidas, K.; Tommasi, A.; Chauve, T.; Barou, F.; Montagnat, M.

    2015-12-01

    Static recrystallization and grain growth take place during high-temperature annealing following deformation at lower temperature, and they reorganize grain and subgrain boundaries to produce entirely new, strain-free grains. These processes influence the microstructure and mechanical behavior of the material by reducing the level of long-range internal stress field. The non-linear flow law of ice Ih makes it an ideal analogue to model rock deformation, thus analyses of recrystallized ice textures contribute to understanding mechanisms which control the nucleation and grain growth deep in the Earth's interior. Water ice microstructures allow for the study of grain-scale processes including nucleation, grain growth, recovery and recrystallization. On the other hand, these mechanisms directly influence the behavior of terrestrial ice systems (e.g., glaciers and ice sheets) in response to deformation. Therefore, their understanding may help us to improve climatic signal interpretation and predictions, that are mostly based on ice dynamics. However, at present there are no data by which recovery, and strain energy-driven grain boundary migration rates in ice can be estimated. Here we present the results of annealing experiments of pre-deformed polycrystalline water ice together with microstructural analyses by means of Automatic Ice Texture Analyzer (AITA) and high-resolution electron backscatter diffraction (EBSD) crystal orientation maps. We performed constant load uniaxial compression creep experiments at -7°C on columnar samples, composed of mm-sized polycrystals, to attain 4% deformation and we applied post-deformational heat treatment at -5°C. We carried out a series of AITA and EBSD maps in representative time steps up to 25 hours of total annealing in order to study the microstructural evolution. In this contribution, we evaluate the stored energy distribution and the rate of grain boundary migration during post-dynamic and static recrystallization, that

  12. Small area analysis using micro-diffraction techniques

    SciTech Connect

    GOEHNER,RAYMOND P.; TISSOT JR.,RALPH G.; MICHAEL,JOSEPH R.

    2000-02-11

    An overall trend toward smaller electronic packages and devices makes it increasingly important and difficult to obtain meaningful diffraction information from small areas. X-ray micro-diffraction, electron back-scattered diffraction (EBSD) and Kossel are micro-diffraction techniques used for crystallographic analysis including texture, phase identification and strain measurements. X-ray micro-diffraction primarily is used for phase analysis and residual strain measurements. X-ray micro-diffraction primarily is used for phase analysis and residual strain measurements of areas between 10 {micro}m to 100 {micro}m. For areas this small glass capillary optics are used for producing a usable collimated x-ray beam. These optics are designed to reflect x-rays below the critical angle therefore allowing for larger solid acceptance angle at the x-ray source resulting in brighter smaller x-ray beams. The determination of residual strain using micro-diffraction techniques is very important to the semiconductor industry. Residual stresses have caused voiding of the interconnect metal which then destroys electrical continuity. Being able to determine the residual stress helps industry to predict failures from the aging effects of interconnects due to this stress voiding. Stress measurements would be impossible using a conventional x-ray diffractometer; however, utilizing a 30{micro}m glass capillary these small areas are readily assessable for analysis. Kossel produces a wide angle diffraction pattern from fluorescent x-rays generated in the sample by an e-beam in a SEM. This technique can yield very precise lattice parameters for determining strain. Fig. 2 shows a Kossel pattern from a Ni specimen. Phase analysis on small areas is also possible using an energy dispersive spectrometer (EBSD) and x-ray micro-diffraction techniques. EBSD has the advantage of allowing the user to observe the area of interest using the excellent imaging capabilities of the SEM. An EDS detector has

  13. Structural investigations on iron containing natural Zincblende using EBSD

    NASA Astrophysics Data System (ADS)

    Zscheckel, Tilman; Kreher-Hartmann, Birgit; Rüssel, Christian

    2016-05-01

    A sample of natural zinc sulfide containing iron (from Portugal, Albergaria, Velha) was systematically investigated with respect to its microstructure using XRD (X-ray diffraction) and EBSD (electron back scatter diffraction). The habitus of the black sample suggests a hexagonal crystal structure, i.e. the occurrence of the Wurtzite phase. Nevertheless, using XRD and EBSD allowed only detecting and localizing the cubic Zincblende structure within the sample with the fibrous habitus while the expected hexagonal Wurtzite structure and possibly a hexagonal FeS structure were missed. The macroscopic fibrous structures consist of non-uniform and elongated grain structures which possess a preferred orientation with the <224>-direction parallel to the fiber direction. Inside the grains, twinning occurs (Σ3-Twinning) as well as grain fragmentation. Iron is not distributed homogeneously; instead areas with unique iron concentrations occurred. They were arranged like twins with iron concentrations from 4.1 up to 5.1 at% as detected and localized using energy dispersive x-ray spectroscopy (EDS). Fe2+ is incorporated in lattice sites of Zn2+. Although the phase diagram FeS-Zn-S is not yet completely determined in all composition ranges of interest, coexisting phases (zincblende and FeS) should be expected at room temperatures. The results may contribute to further insights into the growth mechanisms of natural zinc sulfide, respectively to the discussion about. Furthermore, it was shown, that the crystal habitus not always allows concluding on the crystals symmetry with certainty.

  14. An EBSD study on mapping of small orientation differences in lattice mismatched heterostructures

    NASA Astrophysics Data System (ADS)

    Tao, Xiaodong

    Electron back scatter diffraction (EBSD) on a Scanning Electron Microscope (SEM) has experienced rapid development in recent years. 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, not because they were optimum. The long term aim of this study is mainly concerned with extending EBSD to characterizing threading dislocations in semiconductor materials. In working toward this objective, a systematic study on the EBSD technique was performed. The possibility of measuring small changes of orientation within grains by EBSD was explored. Conventional orientation maps (using EBSD) index the orientation of each position on the sample separately. This does not give accurate results for small differences of orientation. Therefore, methods of directly measuring small changes in orientation from one EBSD pattern to the others were examined. Previous workers have measured the change of position of zone axes in the EBSD pattern. A comparison between measuring changes of position of zone axes versus measuring the shift of the peaks in the Hough transform from one diffraction pattern to the next suggests that the latter method is superior. More over, it is possible, with a standard EBSD configuration, to measure the shift of the Kikuchi bands to a precision of about 0.1 pixels, which corresponds to a change of orientation of about 0.1 mrad. This method has been successfully applied on a GaN/Sapphire structure. Based on this method, ways to perform high precision orientation mapping are proposed. We have also shown that: (1) More than one method can successfully correct a sampling artifact, which is associated with the Hough transform; (2) There is an optimum binning ratio; (3) Gaussian filtering provides an alternative to "butterfly convolution"; (4) Better alternatives for mapping image quality than those in current use are available; (5) saving all

  15. Thermally-induced amphibole reaction rim development: EBSD insights into microlite orientation

    NASA Astrophysics Data System (ADS)

    De Angelis, Sarah; Lavallée, Yan; Larsen, Jessica; Mariani, Elisabetta

    2014-05-01

    Amphibole is an important mineral present in many calc-alkaline volcanic deposits. A hydrous phase, volcanic amphibole is only stable at pressures greater than 100 MPa (approx. 4 km), temperature less than ~860-870 oC, and in melts containing at least 4 wt % H2O. When removed from their thermal and barometric stability field, amphiboles decompose to form aggregate rims of anhydrous minerals. The thickness, texture, and mineralogy of these rims are thought to be reflective of the process driving amphibole disequilibrium (e.g. heating, decompression, etc). However, significant overlap in rim thicknesses and microlite textures means that distinguishing between processes it not simple. This study employed backscatter diffraction (EBSD) to examine both experimental heating-indced amphibole reaction rims and natural amphibole reaction rim from Augustine Volcano. We collected crystal orientation maps of amphibole reaction rims to investigate if different types of disequilibrium produce different patterns of microlite orientation. We identified two types of reaction rim: Type 1- reaction rim microlites are generally oriented at random and share little or no systematic relationship with the crystallographic orientation of the host amphibole, and; Type 2- reaction rim microlites exhibit a topotactic relationship with the host amphibole (they share the same crystallographic orientation). Experimentally produced heating reaction rims are without exception Type 2. However the natural reaction rims are evenly distributed between Types 1 and 2. Further experimental data on decompression induced reaction rim formation is needed to investigate if Type 1 reaction rims resemble the breakdown of amphibole due to decompression. If so, reaction rim microlite orientation could provide a clear method for distinguishing between heating and decompression processes in amphibole bearing magmas.

  16. A methodology to study crystal plasticity inside a compression test sample based on image correlation and EBSD

    SciTech Connect

    Rehrl, C.; Kleber, S.; Antretter, T.; Pippan, R.

    2011-08-15

    Modified compression tests in a coarse-grained austenitic stainless steel have been carried out in order to examine the crystal plasticity behavior for large plastic deformations. The measurements of local in-plane strains provide deeper insight into the deformation process on the local scale. These measurements are performed by digital image correlation technique (DIC) in combination with local crystal orientation measurements by using the electron backscatter diffraction technique (EBSD). Split test samples are prepared to track the strong microstructural changes during deformation, which is done incrementally in 10% steps up to 60% total macroscopic strain. The clear correlation of local strains with crystal orientation changes - e.g. in the case of mechanical twinning - permits to identify the acting deformation mechanisms. Such, experimentally determined local strain maps can be used for verification of crystal plasticity finite element method simulations (CPFEM). - Research Highlights: {yields} Method to study large strain crystal plasticity inside an austenitic FeCrNi-alloy. {yields} Correlation of local strain analyses with crystal orientation measurements. {yields} Deformation mechanism changes locally from dislocation glide to mechanical twinning. {yields} Suitable to study grain-grain interactions, slip system activation and grain boundary effects. {yields} Provide essential data for crystal plasticity FEM studies.

  17. EBSD analysis of (10–12) twinning activity in Mg–3Al–1Zn alloy during compression

    SciTech Connect

    Wang, Bingshu; Deng, Liping; Guo, Ning; Xu, Zeren; Li, Qiang

    2014-12-15

    The (10–12) twinning activity of Mg–3Al–1Zn magnesium alloy during uniaxial compression at room temperature has been investigated by electron backscatter diffraction. The results indicated that the twinning activity was closely related with two angles: one was the angle between the c-axis and the compression direction and the other was the angle between the a-axis and the titling direction in the basal plane for a given relation between the c-axis and the compression direction. These two parameters can be used to explain which twinning variant will operate under the given strain path. For the grains containing a single (10–12) twinning variant, the (10–12) twinning variant occurred in a wide range of Schmid factor values (0 < Schmid factor < 0.5) and the Schmid factor rank of 1 or 2 was the most commonly observed. By contrast, for the grains containing two (10–12) twinning variants, the (10–12) twinning activity exhibited a stronger orientation dependence and the combinations of Schmid factor ranks 1–3 and 1–2 were the most commonly observed. - Highlights: • Twinning activity of AZ31 magnesium alloy was investigated by EBSD. • (10–12) twinning shows a strong orientation dependence. • Two angles can be used to explain which twin variant will operate.

  18. Textural relationship and compositions of ilmenite-corundum exsolutions in rutile from kimberlitic kyanite eclogite xenoliths: microstructural evidence using EBSD

    NASA Astrophysics Data System (ADS)

    Sobolev, N. V.; Schertl, H.; Neuser, R. D.; Lavrentiev, Y. G.; Logvinova, A. M.; Usova, L. V.

    2007-12-01

    Rutile is one of the most common accessory minerals in high pressure (HP) and ultrahigh-pressure (UHP) rocks of crustal and mantle origin. Among those rocks eclogites are very abundant in metamorphic belts and as xenoliths in kimberlite pipes. Some of these xenoliths contain coesite or diamond. Eclogite xenolith rutiles contain high abundance of minor elements reaching up to 0.8 wt.% Al2O3, 2.5 wt.% Fe2O3, 1.4 wt.% Nb2O5, 0.45 wt.% ZrO2 and are mostly heterogeneous with widely varying Al, Fe and Mg contents. These heterogeneities are caused by the presence of closely associated sigmoidal oriented lamellae of ilmenite and corundum which have been detected for the first time in rutile from Roberts Victor mine eclogite xenolith (Sobolev, Yefimova, 2000, Intern. Geol. Rev., v. 42, p. 758-767). We report here on the wide occurrence of such lamellae in rutiles both from diamondiferous kyanite eclogites of Udachnaya mine, Siberia and more samples from Roberts Victor mine confirmed by EMPA. Electron backscatter diffraction (EBSD) measurements on two rutile grains from Roberts Victor mine kyanite eclogite confirm the presence of ilmenite plus corundum exsolutions. We found evidence for respective different crystallographic orientations related to the surrounded rutile host which will be demonstrated in detail in the present study.

  19. Analysis of dynamic recrystallization of ice from EBSD orientation mapping

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    We present high resolution observations of microstructure and texture evolution during dynamic recrystallization (DRX) of ice polycrystals deformed in the laboratory at high temperature (≈0.98Tm). Ice possesses a significant viscoplastic anisotropy that induces strong strain heterogeneities, which result in an early occurrence of DRX mechanisms. It is therefore a model material to explore these mechanisms. High resolution c-axis measurements at sample scale by optical techniques and full crystallographic orientation measurements by cryo- Electron Back Scattering Diffraction (EBSD) provide a solid database for analyzing the relative impact of the macroscopic imposed stress versus the local and internal stress field on DRX mechanisms. Analysis of misorientation gradients in the EBSD data highlights a heterogeneous dislocation distribution, which is quantified by the Nye tensor estimation. Joint analyses of the dislocation density maps and microstructural observations highlight spatial correlation between high dislocation density sites and the onset of nucleation taking place by grain-boundary bulging, subgrain rotation or by the formation of kink-bands.

  20. 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

    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.

  1. Infrared backscattering

    NASA Technical Reports Server (NTRS)

    Bohren, Craig F.; Nevitt, Timothy J.; Singham, Shermila Brito

    1989-01-01

    All particles in the atmosphere are not spherical. Moreover, the scattering properties of randomly oriented nonspherical particles are not equivalent to those of spherical particles no matter how the term equivalent is defined. This is especially true for scattering in the backward direction and at the infrared wavelengths at which some atmospheric particles have strong absorption bands. Thus calculations based on Mie theory of infrared backscattering by dry or insoluble atmospheric particles are suspect. To support this assertion, it was noted that peaks in laboratory-measured infrared backscattering spectra show appreciable shifts compared with those calculated using Mie theory. One example is ammonium sulfate. Some success was had in modeling backscattering spectra of ammonium sulfate particles using a simple statistical theory called the continuous distribution of ellipsoids (CDE) theory. In this theory, the scattering properties of an ensemble are calculated. Recently a modified version of this theory was applied to measured spectra of scattering by kaolin particles. The particles were platelike, so the probability distribution of ellipsoidal shapes was chosen to reflect this. As with ammonium sulfate, the wavelength of measured peak backscattering is shifted longward of that predicted by Mie theory.

  2. Precession electron diffraction assisted orientation mapping of gradient nanostructure in a Ni-based superalloy

    NASA Astrophysics Data System (ADS)

    Feng, Z. Q.; Chen, Y. X.; Wu, G. L.; Yang, Y. Q.

    2015-08-01

    Surface mechanical grinding of a Ni-based superalloy can introduce a gradient microstructure in the surface layer with a grain size from nanoscale to microscale. In-depth investigation of the crystal orientation distribution of the surface nanostructured layer is more often, however, not an easy work by using the scanning electron microscope (SEM) based electron backscatter diffraction (EBSD) method due to its sensitivity to lattice distortions and spatial resolution limitation. Here we use a newly developed precession electron diffraction (PED) technique coupled with transmission electron microscopy (TEM) to investigate the microstructural and crystallographic characteristics of the surface gradient nanostructure, with particular emphasis on the topmost nanocrystalline layer. A strong shear texture and a minor Copper texture were identified according to orientation analyses of the 1.6 pm thick near-surface nanocrystalline layer. The PED technique is proved to be practical for two dimensional orientation mapping of severely deformed microstructures at the nanoscale.

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

    SciTech Connect

    Cheng, Wei-Jen 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.

  4. Hyperspectral Imaging at the Micro- and Nanoscale using Energy-dispersive Spectroscopy (EDS) with Silicon Drift Detector (SDD) and EBSD Analysis

    NASA Astrophysics Data System (ADS)

    Salge, T.; Goran, D.

    2010-12-01

    SDD systems have become state of the art technology in the field of EDS. The main characteristic of the SDDs is their extremely high pulse load capacity of up to 750,000 counts per second at good energy resolution (<123 eV Mn-Kα, <46 eV C-Kα at 100,000 counts per seconds). These properties in conjunction with electron backscatter diffraction (EBSD) technique and modern data processing allows not only high speed mapping but also hyperspectral analysis. Here, a database is created that contains an EDS spectrum and/or EBSD pattern for each pixel of the SEM image setting the stage for innovative analysis options: The Maximum Pixel Spectrum function [1] synthesizes a spectrum out of the EDS database, consisting of the highest count level found in each spectrum channel. Here, (trace) elements which occur in only one pixel can be detected qualitatively. Areas of similar EDS composition can be made visible with Autophase, a spectroscopic phase detection system. In cases where the crystallographic phase assessment by EBSD is problematic due to pattern similarity, the EDS signal can be used as additional information for phase separation. This paper presents geoscience applications with the QUANTAX system with EDS SDD and EBSD detector using the options described above: (1) Drill core analysis of a Chicxulub impact ejecta sequence from the K/Pg boundary at ODP leg 207 [2] using fast, high resolution element maps. (2) Detection of monazite in granite by the Maximum Pixel Spectrum function. (3) Distribution of elements with overlapping peaks by deconvolution at the example of rare earth elements in zoned monazite. (4) Spectroscopic phase analysis of a sulfate-carbonate-dominated impact matrix at borehole UNAM-7 from the Chicxulub impact crater [3]. (5) EBSD studies with examples of iron meteorites and impact-induced, recrystallized carbonate melts [4]. In addition, continuing technological advances require the elemental analysis of increasingly smaller structures in many

  5. 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.

  6. New Insights on Dynamic Recrystallization Mechanisms in Ice from High Resolution EBSD Observations and Strain Field Measurements.

    NASA Astrophysics Data System (ADS)

    Montagnat, M.; Chauve, T.; Journaux, B.; Barou, F.

    2015-12-01

    Dynamic recrystallization (DRX) strongly affects the evolution of microstructure (grain size and shape) and texture (crystal preferred orientation) 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. Along ice cores extracted from ice sheets, Continuous DRX (CDRX) and Discontinuous DRX (DDRX) mechanisms are observed at various depths, the later being favoured by the high temperature encountered close to the bedrock, and local high level of strain. In laboratory conditions, with higher strain rate and stress levels, DDRX dominates mechanical response during tertiary creep, when deviatoric stress is low enough to avoid micro fracturation (σ < 1MPa). Similarly to the case of metals or rocks, relations between DRX nucleation mechanisms and strain heterogeneities at the grain scale remain poorly known and therefore poorly constrained in DRX modeling. We will present recent observations performed on laboratory made and deformed ice polycrystals (σ ~ 0.5 MPa, T ~ -7°C) that enable to access high resolution observations of intragranular sub-structures (dislocation field, subgrains, nucleus) via Electron BackScattering Diffraction (EBSD), and high resolution strain field measurements around DRX nucleation area. Analyses of these observations highlight the complexity of nucleation mechanisms in ice, with the formation of kink bands, of bulging, and of "spontaneous" nucleation. Strain field measurements evidence the influence of nucleation on the relaxation of strain incompatibilities at grain boundaries and triple junctions. At last, torsion experiments enabled to draw hypotheses about the role of nucleation on DRX textures.

  7. Competitive effects of metal dissolution and passivation modulated by surface structure: An AFM and EBSD study of the corrosion of alloy 22

    NASA Astrophysics Data System (ADS)

    Gray, J. J.; El Dasher, B. S.; Orme, C. A.

    2006-06-01

    Electron backscatter diffraction (EBSD) and atomic force microscopy (AFM) are used to correlate crystallographic grain orientation with corrosion rates of polycrystalline alloy 22 following immersion in 1 and 3 molar (M) hydrochloric acid. For each acid concentration, relative corrosion rates are simultaneously characterized for approximately 50 unique grain orientations. The results demonstrate that the corrosion rate anisotropies are markedly different in the two acid concentrations. In very aggressive acidic environments (3M HCl), where electrochemical impedance spectroscopy and spectroscopic ellipsometry data demonstrate that the passive oxide film of alloy 22 is completely dissolved, alloy dissolution rates scale inversely with the average coordination number of surface atoms for a given grain orientation, where highly correlated surfaces dissolve the slowest. Thus, similar to simple metallic systems, the corrosion rates scale with the surface plane-normal crystallographic orientations as {1 1 1} < {1 0 0} < {1 1 0}. Less intuitively, in milder corrosive environments (1M HCl), where the passive film of the alloy is still intact, the dissolution does not scale inversely with surface atomic density. Rather, corrosion rates scale with crystallographic orientations as {1 1 1} < {1 1 0} < {1 0 0}. This is attributed to the fact that facets most susceptible to corrosion (least coordinated) are also the most able to form protective oxides, so that the dissolution anisotropy is a result of the delicate balance between metal dissolution and oxide growth.

  8. Physics-based simulation models for EBSD: advances and challenges

    NASA Astrophysics Data System (ADS)

    Winkelmann, A.; Nolze, G.; Vos, M.; Salvat-Pujol, F.; Werner, W. S. M.

    2016-02-01

    EBSD has evolved into an effective tool for microstructure investigations in the scanning electron microscope. The purpose of this contribution is to give an overview of various simulation approaches for EBSD Kikuchi patterns and to discuss some of the underlying physical mechanisms.

  9. Advanced characterization of twins using automated EBSD

    SciTech Connect

    Wright, S. I.; Bingert, J. F.; Mason, T. A.; Larsen, Ryan J.

    2002-01-01

    This poster describes resuns obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated EBSD. The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equiwlent candidates. and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystalllzation twins in nickel.

  10. 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 Σ3 or Σ13b 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.

  11. Visco-plasticity of polycrystalline olivine at high pressure and 900°C: fresh outcomes from high resolution EBSD and electron tomography

    NASA Astrophysics Data System (ADS)

    Demouchy, S. A.; Mussi, A.; Barou, F.; Tommasi, A.; Cordier, P.

    2013-12-01

    The rheology of olivine-rich rocks at lithospheric temperatures (<1000°C) remains poorly constrained, in contrast to the extensive experimental dataset on creep of olivine single crystals and aggregates at high temperature (T > 1200°C). Consequently, we have performed tri-axial compression experiments (in a Paterson's press) on two fine-grained polycrystalline olivine (San Carlos olivine) specimens at 900°C, under a confining pressure of 300 MPa. Two dense samples were deformed at constant strain rates of 1.0 × 10-5 s-1 and 3.4 × 10-5 s-1. Mechanical curves show continuous hardening, with a decrease of hardening rate with increasing strain. Both samples failed just before 10% of finite strain and yield final differential stresses of 930 and 1076 MPa. Recovered samples were characterized by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). High resolution EBSD maps (step size 0.15 and 0.2 microns) permit to quantify accurately the microstructure (grain size, shape, aspect ratio, and angle distribution of the grain ellipse relative to the compression axis). Weak crystallographic preferred orientations (CPO) developed in the deformed olivine aggregates, where [010] axes are mostly parallel to the compression axis; [100] and [001] axes are more dispersed, but tend to be oriented at high angle to the compression axis. Misorientations across grain boundaries and sub-grain boundaries were analyzed as well, evidencing common subgrain boundaries parallel to (100) and rotations dominantly around [001], that is an ';ideal' tilt boundary of the [100](010) system. Furthermore, transmission electron microscopy, involving electron tomography of dislocations has identified dislocations with [100] and [001] Burgers vectors gliding on multiple planes, evidence for cross-slip, and dislocation entanglements. These data permit to better constrain the active deformation mechanisms and slip systems involved in the

  12. 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

  13. 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.

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

    SciTech Connect

    Teague, Melissa C.; Gorman, Brian P.; Miller, Brandon D.; 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 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.

  15. Three-dimensional EBSD characterization of thermo-mechanical fatigue crack morphology in compacted graphite iron

    SciTech Connect

    Pirgazi, Hadi; Ghodrat, Sepideh; Kestens, Leo A.I.

    2014-04-01

    In cylinder heads made of compacted graphitic iron (CGI), heating and cooling cycles can lead to localized cracking due to thermo-mechanical fatigue (TMF). To meticulously characterize the complex crack path morphology of CGI under TMF condition, in relation to microstructural features and to find out how and by which mechanisms the cracks predominantly develop, three-dimensional electron back scattering diffraction (EBSD) was employed. Based on the precise quantitative microstructural analysis, it is found that graphite particles not only play a crucial role in the crack initiation, but also are of primary significance for crack propagation, i.e. crack growth is enhanced by the presence of graphite particles. Furthermore, the density of graphite particles on the fracture plane is more than double as high as in any other arbitrary plane of the structure. The obtained results did not indicate a particular crystallographic preference of fracture plane, i.e. the crystal plane parallel to the fracture plane was nearly of random orientation. - Highlights: • Crystallographic features of a thermo-mechanical fatigue (TMF) crack were studied. • Wide-field 3D EBSD is used to characterize the TMF crack morphology. • Data processing was applied on a large length scale of the order of millimeters. • Graphite density in the fracture plane is much higher than any other random plane. • It is revealed that crack growth is enhanced by the presence of graphite particles.

  16. Interference phenomena at backscattering by ice crystals of cirrus clouds.

    PubMed

    Borovoi, Anatoli; Kustova, Natalia; Konoshonkin, Alexander

    2015-09-21

    It is shown that light backscattering by hexagonal ice crystals of cirrus clouds is formed within the physical-optics approximation by both diffraction and interference phenomena. Diffraction determines the angular width of the backscattering peak and interference produces the interference rings inside the peak. By use of a simple model for distortion of the pristine hexagonal shape, we show that the shape distortion leads to both oscillations of the scattering (Mueller) matrix within the backscattering peak and to a strong increase of the depolarization, color, and lidar ratios needed for interpretation of lidar signals.

  17. Dynamic coherent backscattering mirror

    PubMed Central

    Xu, M.

    2016-01-01

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation. PMID:26937296

  18. EBSD characterization of a hot worked 304 austenitic stainless steel under strain reversal.

    PubMed

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

    2009-07-01

    Monotonic and strain reversal hot torsion tests were performed on a 304 austenitic stainless steel, this led to changes in microstructures depending on the strain path. electron backscatter diffraction was used as the tool for characterizing the microstructures. It was possible to find some intragranular microstructural changes due to the reversal of the strain by means of several local and global misorientation-related parameters. Sigma3 boundaries also showed sensitivity to strain reversal. PMID:19566625

  19. A simulation of recrystallization based on EBSD orientation microscopy data

    SciTech Connect

    Engler, O.

    1998-12-01

    The present paper introduces a novel stochastic two-dimensional model to simulate the evolution of microstructure and texture during recrystallization. The model is based on data derived by automated large-scale EBSD local texture analysis, i.e., by orientation microscopy. Each measured point is characterized by its coordinates x and y in the microstructure, its crystallographic orientation g and a parameter q describing the quality of the EBSD-pattern which is affected by lattice strain and hence discloses information on the dislocation density. The concurrent information on the local arrangement of orientations and dislocation densities is utilized to derive conclusions on the nucleation and subsequent growth of the new recrystallized grains. The principles of the model are outlined and three example are shown to illustrate the possibilities of the model to simulate the evolution of microstructure and texture during recrystallization.

  20. 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

  1. Backscattering measurements of micron-sized spherical particles.

    PubMed

    Heffernan, Brendan M; Heinson, Yuli W; Maughan, Justin B; Chakrabarti, Amitabha; Sorensen, Christopher M

    2016-04-20

    An apparatus was designed and assembled to measure scattered light in the range of 180°±6° where enhanced backscattering, the cause of a glory, occurs. The apparatus was calibrated and tested using Fraunhofer circular aperture diffraction, angle of incidence correction, and a diffuse reflector. Theory indicates that backscattering is strongly dependent on particle size, refractive index, and shape. Experimental measurements from polystyrene latex spheres of two sizes and water droplets showed good agreement with Mie theory, but also indicated the extreme sensitivity of the backscattering to particle parameters. The results presented should have use in the fields of particle scattering, particle metrology, and LIDAR. PMID:27140090

  2. Mechanisms of mafic magma emplacement at a mid-crustal level: insights from AMS, AARM and EBSD analyses on the Sondalo gabbroic complex (Alps, N-Italy)

    NASA Astrophysics Data System (ADS)

    Petri, Benoît; Mohn, Geoffroy; Skrzypek, Etienne; Mateeva, Tsvetomila; Robion, Philippe; Schulmann, Karel; Manatschal, Gianreto; Müntener, Othmar

    2016-04-01

    With the aim of assessing the mechanisms of mafic magma ascent and emplacement in the continental crust, we describe the magmatic and magnetic fabrics of the Sondalo gabbroic complex emplaced at a mid-crustal level (~15 km) during the Permian (Campo unit, Eastern Central Alps, N-Italy). Detailed mapping, field observations and petrological investigations enable to study the general structure of the Sondalo gabbroic complex. The pluton is concentrically zoned and composed of Ol-gabbros in the central zone surrounded by gabbros in the intermediate zone and diorites to granodiorites in a border zone of a variable thickness. We characterize the anisotropy of magnetic susceptibility (AMS) fabric of the intrusions. In order to detect potential abnormal (intermediate) magnetic fabrics with respect to the petrofabric, we refine the magnetic fabric characterization with anisotropy of anhysteretic remnant magnetization (AARM) measurements while the identification of magnetic mineralogy is investigated by coercivity-unblocking temperature spectra of ferromagnetic minerals. In addition, the petrofabric is evaluated by measuring the crystallographic preferred orientation (CPO) in test sites with electron backscatter diffraction (EBSD) measurements. Additional petrological and geochemical observations provide insights on the crystallization sequence of the magmatic rocks and facilitate the interpretation of the magnetic record. The bulk susceptibilities of the rocks range from 448 to 3540*10-6 SI with most of values below 10-3 SI, attesting of a mixed contribution to the AMS signal of paramagnetic and ferromagnetic minerals. Variation of the magnetic susceptibilities can be correlated to both the lithology and the magnetic mineralogy. Measured magnetic foliation orientations are remarkably similar to the observed macroscopic magmatic fabrics defined by the preferred orientation of magmatic plagioclase, pyroxene, hornblende and rarely biotite. In the central zone, the magmatic

  3. Extracting electron backscattering coefficients from backscattered electron micrographs

    SciTech Connect

    Zupanic, F.

    2010-12-15

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

  4. 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

  5. Crystal orientation mapping via ion channeling: An alternative to EBSD.

    PubMed

    Langlois, C; Douillard, T; Yuan, H; Blanchard, N P; Descamps-Mandine, A; Van de Moortèle, B; Rigotti, C; Epicier, T

    2015-10-01

    A new method, which we name ion CHanneling ORientation Determination (iCHORD), is proposed to obtain orientation maps on polycrystals via ion channeling. The iChord method exploits the dependence between grain orientation and ion beam induced secondary electron image contrast. At each position of the region of interest, intensity profiles are obtained from a series of images acquired with different orientations with respect to the ion beam. The profiles are then compared to a database of theoretical profiles of known orientation. The Euler triplet associated to the most similar theoretical profile gives the orientation at that position. The proof-of-concept is obtained on a titanium nitride sample. The potentialities of iCHORD as an alternative to EBSD are then discussed. PMID:26094201

  6. 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.

  7. 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.

  8. Radar backscatter modelling

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. Aerosol backscatter studies supporting LAWS

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry

    1989-01-01

    Optimized Royal Signals and Radar Establishment (RSRE), Laser True Airspeed System (LATAS) algorithm for low backscatter conditions was developed. The algorithm converts backscatter intensity measurements from focused continuous-wave (CW) airborne Doppler lidar into backscatter coefficients. The performance of optimized algorithm under marginal backscatter signal conditions was evaluated. The 10.6 micron CO2 aerosol backscatter climatologies were statistically analyzed. Climatologies reveal clean background aerosol mode near 10(exp -10)/kg/sq m/sr (mixing ratio units) through middle and upper troposhere, convective mode associated with planetary boundary layer convective activity, and stratospheric mode associated with volcanically-generated aerosols. Properties of clean background mode are critical to design and simulation studies of Laser Atmospheric Wind Sounder (LAWS), a MSFC facility Instrument on the Earth Observing System (Eos). Previous intercomparisons suggested correlation between aerosol backscatter at CO2 wavelength and water vapor. Field measurements of backscatter profiles with MSFC ground-based Doppler lidar system (GBDLS) were initiated in late FY-88 to coincide with independent program of local rawinsonde releases and overflights by Multi-spectral Atmospheric Mapping Sensor (MAMS), a multi-channel infrared radiometer capable of measuring horizontal and vertical moisture distributions. Design and performance simulation studies for LAWS would benefit from the existence of a relationship between backscatter and water vapor.

  14. An EBSD investigation of cryogenically-rolled Cu–30%Zn brass

    SciTech Connect

    Konkova, T.; Mironov, S.; Korznikov, A.; Korznikova, G.; Myshlyaev, M.M.; Semiatin, S.L.

    2015-03-15

    Electron backscatter diffraction was used to study grain structure development in heavily cryogenically-rolled Cu–30%Zn brass. The produced microstructure was found to be very inhomogeneous. At a relatively coarse scale, it consisted of texture bands having crystallographic orientations close to the α- and γ-fibers. The texture bands contained internal structure comprising shear bands, mechanical twins, and low-angle boundaries. Such features were more pronounced within the γ-fiber, and this resulted in a heterogeneous ultrafine grain structure. The cryogenic rolling was concluded to be not straightforward for production of nanocrystalline grain structure in Cu–30%Zn brass. - Highlights: • Cryogenic rolling produced an inhomogeneous ultrafine-grained microstructure. • Grain refinement was mainly related with twinning and shear banding. • Grain refinement preferentially occurred in (111) fiber texture.

  15. New calculation of surface wave contributions associated with mie backscattering.

    PubMed

    Inada, H

    1973-07-01

    Diffracted field contributions to backscattering of an electromagnetic plane wave by a spherical particle are calculated. The diffracted fields give rise to surface waves in the shadow region and can be evaluated by finding surface wave poles and computing their residues. In order to compute the residues the valid range of the Schobe and Debye asymptotic expansion formulas for the Hankel function is examined. With these asymptotic formulas numerical values of the surface wave complex poles are tabulated. Curves for backscattering cross section due to the first six surface waves are presented as a function of the size parameter kappaa between 5 and 60 for absorbing spheres of refractive index m = 1.61-i0.0025 as well as nonabsorbing spheres with m = 1.60.

  16. Ultrasonic backscatter from cancellous bone: the apparent backscatter transfer function.

    PubMed

    Hoffmeister, Brent K; Mcpherson, Joseph A; Smathers, Morgan R; Spinolo, P Luke; Sellers, Mark E

    2015-12-01

    Ultrasonic backscatter techniques are being developed to detect changes in cancellous bone caused by osteoporosis. Many techniques are based on measurements of the apparent backscatter transfer function (ABTF), which represents the backscattered power from bone corrected for the frequency response of the measurement system. The ABTF is determined from a portion of the backscatter signal selected by an analysis gate of width τw delayed by an amount τd from the start of the signal. The goal of this study was to characterize the ABTF for a wide range of gate delays (1 μs ≤ τd ≤ 6 μs) and gate widths (1 μs ≤ τw ≤ 6 μs). Measurements were performed on 29 specimens of human cancellous bone in the frequency range 1.5 to 6.0 MHz using a broadband 5-MHz transducer. The ABTF was found to be an approximately linear function of frequency for most choices of τd and τw. Changes in τd and τw caused the frequency-averaged ABTF [quantified by apparent integrated backscatter (AIB)] and the frequency dependence of the ABTF [quantified by frequency slope of apparent backscatter (FSAB)] to change by as much as 24.6 dB and 6.7 dB/MHz, respectively. τd strongly influenced the measured values of AIB and FSAB and the correlation of AIB with bone density (-0.95 ≤ R ≤ +0.68). The correlation of FSAB with bone density was influenced less strongly by τd (-0.97 ≤ R ≤ -0.87). τw had a weaker influence than τd on the measured values of AIB and FSAB and the correlation of these parameters with bone density.

  17. 3D Backscatter Imaging System

    NASA Technical Reports Server (NTRS)

    Turner, D. Clark (Inventor); Whitaker, Ross (Inventor)

    2016-01-01

    Systems and methods for imaging an object using backscattered radiation are described. The imaging system comprises both a radiation source for irradiating an object that is rotationally movable about the object, and a detector for detecting backscattered radiation from the object that can be disposed on substantially the same side of the object as the source and which can be rotationally movable about the object. The detector can be separated into multiple detector segments with each segment having a single line of sight projection through the object and so detects radiation along that line of sight. Thus, each detector segment can isolate the desired component of the backscattered radiation. By moving independently of each other about the object, the source and detector can collect multiple images of the object at different angles of rotation and generate a three dimensional reconstruction of the object. Other embodiments are described.

  18. EBSDinterp 1.0: A MATLAB® Program to Perform Microstructurally Constrained Interpolation of EBSD Data.

    PubMed

    Pearce, Mark A

    2015-08-01

    EBSDinterp is a graphic user interface (GUI)-based MATLAB® program to perform microstructurally constrained interpolation of nonindexed electron backscatter diffraction data points. The area available for interpolation is restricted using variations in pattern quality or band contrast (BC). Areas of low BC are not available for interpolation, and therefore cannot be erroneously filled by adjacent grains "growing" into them. Points with the most indexed neighbors are interpolated first and the required number of neighbors is reduced with each successive round until a minimum number of neighbors is reached. Further iterations allow more data points to be filled by reducing the BC threshold. This method ensures that the best quality points (those with high BC and most neighbors) are interpolated first, and that the interpolation is restricted to grain interiors before adjacent grains are grown together to produce a complete microstructure. The algorithm is implemented through a GUI, taking advantage of MATLAB®'s parallel processing toolbox to perform the interpolations rapidly so that a variety of parameters can be tested to ensure that the final microstructures are robust and artifact-free. The software is freely available through the CSIRO Data Access Portal (doi:10.4225/08/5510090C6E620) as both a compiled Windows executable and as source code.

  19. EBSDinterp 1.0: A MATLAB® Program to Perform Microstructurally Constrained Interpolation of EBSD Data.

    PubMed

    Pearce, Mark A

    2015-08-01

    EBSDinterp is a graphic user interface (GUI)-based MATLAB® program to perform microstructurally constrained interpolation of nonindexed electron backscatter diffraction data points. The area available for interpolation is restricted using variations in pattern quality or band contrast (BC). Areas of low BC are not available for interpolation, and therefore cannot be erroneously filled by adjacent grains "growing" into them. Points with the most indexed neighbors are interpolated first and the required number of neighbors is reduced with each successive round until a minimum number of neighbors is reached. Further iterations allow more data points to be filled by reducing the BC threshold. This method ensures that the best quality points (those with high BC and most neighbors) are interpolated first, and that the interpolation is restricted to grain interiors before adjacent grains are grown together to produce a complete microstructure. The algorithm is implemented through a GUI, taking advantage of MATLAB®'s parallel processing toolbox to perform the interpolations rapidly so that a variety of parameters can be tested to ensure that the final microstructures are robust and artifact-free. The software is freely available through the CSIRO Data Access Portal (doi:10.4225/08/5510090C6E620) as both a compiled Windows executable and as source code. PMID:26178688

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

    SciTech Connect

    Li, X.; Duan, Y.L.; Xu, G.F.; Peng, X.Y.; Dai, C.; Zhang, L.G.; Li, Z.

    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.

  1. Backscatter measurements for NIF ignition targets (invited)

    SciTech Connect

    Moody, J. D.; Datte, P.; Krauter, K.; Bond, E.; Michel, P. A.; Glenzer, S. H.; Divol, L.; Suter, L.; Meezan, N.; MacGowan, B. J.; Hibbard, R.; London, R.; Kilkenny, J.; Wallace, R.; Knittel, K.; Frieders, G.; Golick, B.; Ross, G.; Widmann, K.; Jackson, J.; and others

    2010-10-15

    Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of {approx}15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie.

  2. Backscatter measurements for NIF ignition targets (invited).

    PubMed

    Moody, J D; Datte, P; Krauter, K; Bond, E; Michel, P A; Glenzer, S H; Divol, L; Niemann, C; Suter, L; Meezan, N; MacGowan, B J; Hibbard, R; London, R; Kilkenny, J; Wallace, R; Kline, J L; Knittel, K; Frieders, G; Golick, B; Ross, G; Widmann, K; Jackson, J; Vernon, S; Clancy, T

    2010-10-01

    Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of ∼15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie.

  3. Higher order diffractions from a circular disk

    NASA Technical Reports Server (NTRS)

    Marsland, Diane P.; Balanis, Constantine A.; Brumley, Stephen A.

    1987-01-01

    The backscattering from a circular disk is analyzed using the geometrical theory of diffraction. First-, second-, and third-order diffractions are included in the hard polarization analysis, while first-, second-, and third-order slope diffractions are included for soft polarization. Improvements in the prediction of the monostatic radar cross section over previous works are noted. For hard polarization, an excellent agreement is exhibited between experimental and theoretical results, while a very good agreement is noted for soft polarization. To further improve the soft polarization results for wide angles, a model for the creeping wave or circulating current on the edge of the disk is obtained and used to find an additional component of the backscattered field. The addition of this component significantly improves the results for wide angles, leading to excellent agreement for soft polarization also. An axial-caustic correction method using equivalent currents is also included in the analysis.

  4. Backscatter absorption gas imaging system

    DOEpatents

    McRae, T.G. Jr.

    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.

  5. Backscatter absorption gas imaging system

    DOEpatents

    McRae, Jr., Thomas G.

    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.

  6. EBSD analysis of magnesium addition on inclusion formation in SS400 structural steel

    SciTech Connect

    Luo, Sin-Jie; Su, Yen-Hao Frank; Lu, Muh-Jung; Kuo, Jui-Chao

    2013-08-15

    In this study, the effect of magnesium addition on the inclusion formation in SS400 steel was investigated. The experimental specimens with and without Mg addition treatment were compared. The microstructure was observed using optical microscopy after etching with 3% nital. The morphology and chemical composition of the inclusions were analyzed via scanning electron microscopy and energy dispersive spectrometry. The lattice structure and orientation of the inclusions were identified by electron backscattering diffraction. The average size of inclusions in SS400 was between 0.67 and 0.75 μm, and between 0.65 and 0.68 μm in SS400 + Mg. The 2 ppm Mg addition resulted in the oxide formation change from Al{sub 2}O{sub 3} to MgO·Al{sub 2}O{sub 3} and in the inclusion formation change from Al{sub 2}O{sub 3}–MnS to MgO·Al{sub 2}O{sub 3}–MnS. Moreover, a simple-phase MnS with an average grain size of 1 μm to 2 μm was observed in rod-like, globular, and polyhedron forms. - Highlights: • The effect of magnesium addition was investigated for SS400 steel. • 2 ppm Mg addition changes the inclusion formation from Al2O3-MnS to MgO·Al2O3-MnS. • MnS observed in inclusions exhibits rod-like, globular, and polyhedron forms.

  7. EBSD coupled to SEM in situ annealing for assessing recrystallization and grain growth mechanisms in pure tantalum.

    PubMed

    Kerisit, C; Logé, R E; Jacomet, S; Llorca, V; Bozzolo, N

    2013-06-01

    An in situ annealing stage has been developed in-house and integrated in the chamber of a Scanning Electron Microscope equipped with an Electron BackScattered Diffraction system. Based on the Joule effect, this device can reach the temperature of 1200°C at heating rates up to 100°C/s, avoiding microstructural evolutions during heating. A high-purity tantalum deformed sample has been annealed at variable temperature in the range 750°C-1030°C, and classical mechanisms of microstructural evolutions such as recrystallization and grain coarsening phenomena have been observed. Quantitative measurements of grain growth rates provide an estimate of the mean grain boundary mobility, which is consistent with the value estimated from physical parameters reported for that material. In situ annealing therefore appears to be suited for complementing bulk measurements at relatively high temperatures, in the context of recrystallization and grain growth in such a single-phase material. PMID:23521093

  8. EBSD coupled to SEM in situ annealing for assessing recrystallization and grain growth mechanisms in pure tantalum.

    PubMed

    Kerisit, C; Logé, R E; Jacomet, S; Llorca, V; Bozzolo, N

    2013-06-01

    An in situ annealing stage has been developed in-house and integrated in the chamber of a Scanning Electron Microscope equipped with an Electron BackScattered Diffraction system. Based on the Joule effect, this device can reach the temperature of 1200°C at heating rates up to 100°C/s, avoiding microstructural evolutions during heating. A high-purity tantalum deformed sample has been annealed at variable temperature in the range 750°C-1030°C, and classical mechanisms of microstructural evolutions such as recrystallization and grain coarsening phenomena have been observed. Quantitative measurements of grain growth rates provide an estimate of the mean grain boundary mobility, which is consistent with the value estimated from physical parameters reported for that material. In situ annealing therefore appears to be suited for complementing bulk measurements at relatively high temperatures, in the context of recrystallization and grain growth in such a single-phase material.

  9. 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

  10. Dislocation Content Measured Via 3D HR-EBSD Near a Grain Boundary in an AlCu Oligocrystal

    NASA Technical Reports Server (NTRS)

    Ruggles, Timothy; Hochhalter, Jacob; Homer, Eric

    2016-01-01

    Interactions between dislocations and grain boundaries are poorly understood and crucial to mesoscale plasticity modeling. Much of our understanding of dislocation-grain boundary interaction comes from atomistic simulations and TEM studies, both of which are extremely limited in scale. High angular resolution EBSD-based continuum dislocation microscopy provides a way of measuring dislocation activity at length scales and accuracies relevant to crystal plasticity, but it is limited as a two-dimensional technique, meaning the character of the grain boundary and the complete dislocation activity is difficult to recover. However, the commercialization of plasma FIB dual-beam microscopes have made 3D EBSD studies all the more feasible. The objective of this work is to apply high angular resolution cross correlation EBSD to a 3D EBSD data set collected by serial sectioning in a FIB to characterize dislocation interaction with a grain boundary. Three dimensional high angular resolution cross correlation EBSD analysis was applied to an AlCu oligocrystal to measure dislocation densities around a grain boundary. Distortion derivatives associated with the plasma FIB serial sectioning were higher than expected, possibly due to geometric uncertainty between layers. Future work will focus on mitigating the geometric uncertainty and examining more regions of interest along the grain boundary to glean information on dislocation-grain boundary interaction.

  11. On Backscatter in Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Nadiga, Balasubramanya

    2010-05-01

    Downgradient mixing of potential-voriticity and its variants are commonly employed to model the effects of unresolved geostrophic turbulence on resolved scales. This is motivated by the (inviscid and unforced) particle-wise conservation of potential-vorticity and the mean forward or down-scale cascade of potential enstrophy in geostrophic turubulence. By examining the statistical distribution of the transfer of potential enstrophy from mean or filtered motions to eddy or sub-filter motions, we find that the mean forward cascade results from the forward-scatter being only slightly greater than the backscatter. Downgradient mixing ideas, do not recognize such equitable mean-eddy or large scale-small scale interactions and consequently model only the mean effect of forward cascade. Consequently, we consider two alternate approaches to modeling backscatter---one based on the Large Eddy Simulation approach and the other based on regularization approach. We demonstrate the equivalence of the two approaches in a certain limit and present results that use the new parameterizations.

  12. 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

  13. Specimen Preparation for Metal Matrix Composites with a High Volume Fraction of Reinforcing Particles for EBSD Analysis

    NASA Astrophysics Data System (ADS)

    Smirnov, A. S.; Belozerov, G. A.; Smirnova, E. O.; Konovalov, A. V.; Shveikin, V. P.; Muizemnek, O. Yu.

    2016-07-01

    The paper deals with a procedure of preparing a specimen surface for the EBSD analysis of a metal matrix composite (MMC) with a high volume fraction of reinforcing particles. Unlike standard procedures of preparing a specimen surface for the EBSD analysis, the proposed procedure is iterative with consecutive application of mechanical and electrochemical polishing. This procedure significantly improves the results of an indexed MMC matrix in comparison with the standard procedure of specimen preparation. The procedure was verified on a MMC with pure aluminum (99.8% Al) as the matrix, SiC particles being used as reinforcing elements. The average size of the SiC particles is 14 μm, and their volume fraction amounts to 50% of the total volume of the composite. It has been experimentally found that, for making the EBSD analysis of a material matrix near reinforcing particles, the difference in height between the particles and the matrix should not exceed 2 µm.

  14. Beta Backscatter Measures the Hardness of Rubber

    NASA Technical Reports Server (NTRS)

    Morrissey, E. T.; Roje, F. N.

    1986-01-01

    Nondestructive testing method determines hardness, on Shore scale, of room-temperature-vulcanizing silicone rubber. Measures backscattered beta particles; backscattered radiation count directly proportional to Shore hardness. Test set calibrated with specimen, Shore hardness known from mechanical durometer test. Specimen of unknown hardness tested, and radiation count recorded. Count compared with known sample to find Shore hardness of unknown.

  15. Documenting Self Organization in Quartz: A combined EBSD and Laser Mass Spectrometer Investigation of Brazilian Agate

    NASA Astrophysics Data System (ADS)

    Wenk, H.; Grimsich, J. L.

    2012-12-01

    In this project two Brazilian agates were selected for study based upon their complex and variable crystallographic textures. In standard optical microscopy the samples show a variety of repeated oscillatory structures which develop in a regular fashion from rim-to-core as the agate crystallized. The patterns are thought to represent a cyclic form of self organization. The much work has been done, the mechanisms that control this system remain poorly understood. EBSD mapping of these structures offers significant new insight into the growth textures and crystallographic growth orientations. Historically, these structures have been categorized by relative c-axis orientation, representing alternating length fast (LF) and length slow (LS) domains. Detailed rim-to-core EBSD texture analysis shows oscillatory structures develop in pairs of preferred growth orientations. Our samples show a progression from LF (110) dominated growth, developing into LF-LS (110)-(011) oscillation and then to LS-LS (011)-(001) oscillation. The LS-LS oscillations are essentially invisible in polarized light, but dramatic and clear in EBSD scans. Each oscillation period lasts 10-20 cycles and individual cycles are on the order of 70-100 microns. Classic 'chevron' (twisted fiber) extinction bands follow and are uniquely characterized by a mixture of LF-LF (100)-(110) growth orientations. Chemical information linked to these crystallographic structures was obtained using laser ablation mass spectrometry. A continuous laser transect across the agate from rim-to-core provides spatially resolved trace element analysis at ppb sensitivity. 50 elements were analyzed. Preliminary results show well defined and in-phase oscillations of Al, Na and K in the areas that have oscillatory growth (both LF-LS (110)-(011) and LS-LS (011)-(001) oscillations), and not in other areas. Al concentrations are much lower and show no oscillatory behavior in later large macro-Qtz grains near the agate interior. One

  16. Averaging of Backscatter Intensities in Compounds

    PubMed Central

    Donovan, John J.; Pingitore, Nicholas E.; Westphal, Andrew J.

    2002-01-01

    Low uncertainty measurements on pure element stable isotope pairs demonstrate that mass has no influence on the backscattering of electrons at typical electron microprobe energies. The traditional prediction of average backscatter intensities in compounds using elemental mass fractions is improperly grounded in mass and thus has no physical basis. We propose an alternative model to mass fraction averaging, based of the number of electrons or protons, termed “electron fraction,” which predicts backscatter yield better than mass fraction averaging. PMID:27446752

  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. On observing acoustic backscattering from salinity turbulence.

    PubMed

    Goodman, Louis; Sastre-Cordova, Marcos M

    2011-08-01

    It has been hypothesized that at sufficiently high levels of oceanic salinity turbulence it should be possible to observe acoustic backscattering. However, there have been limited in situ measurements to confirm this hypothesis. Using an autonomous underwater vehicle equipped with upward and downward looking 1.2 MHz acoustic Doppler current profilers and with turbulence and fine scale sensors, measurements were performed in a region of intense turbulence and a strong salinity gradient. The approach taken was to correlate variations in the backscattered acoustic intensity, I, with a theoretical acoustic backscattering cross section per volume for salinity turbulence, σ(s), to obtain an estimated scattering cross section per volume, σ(e). Results indicated that of order 50% of the observed region was characterized by salinity turbulence induced backscattering. PMID:21877785

  19. On observing acoustic backscattering from salinity turbulence.

    PubMed

    Goodman, Louis; Sastre-Cordova, Marcos M

    2011-08-01

    It has been hypothesized that at sufficiently high levels of oceanic salinity turbulence it should be possible to observe acoustic backscattering. However, there have been limited in situ measurements to confirm this hypothesis. Using an autonomous underwater vehicle equipped with upward and downward looking 1.2 MHz acoustic Doppler current profilers and with turbulence and fine scale sensors, measurements were performed in a region of intense turbulence and a strong salinity gradient. The approach taken was to correlate variations in the backscattered acoustic intensity, I, with a theoretical acoustic backscattering cross section per volume for salinity turbulence, σ(s), to obtain an estimated scattering cross section per volume, σ(e). Results indicated that of order 50% of the observed region was characterized by salinity turbulence induced backscattering.

  20. Lidar measurements of atmospheric backscattering amplification

    NASA Astrophysics Data System (ADS)

    Banakh, V. A.; Razenkov, I. A.

    2016-02-01

    Results of long-term continuous measurements of the atmospheric backscattering amplification coefficient on a 2-km-long near-ground path with the use of a two-channel micropulse lidar based on a waveguide laser are presented. It is shown that the backscattering amplification coefficient has a pronounced daily variation. In the night and in the afternoon, atmospheric backscattering amplification is maximal and the amplification coefficient can exceed 2. The amplification is low or absent in morning and evening hours at neutral temperature stratification in the near-ground layer of the atmosphere. The backscattering amplification coefficient increases with an increase in the structure constant of the air refracting index and variance of the image jitter of the illumination spot created by the probing laser beam on the wall of a 2-km-distant building.

  1. C-band backscattering from corn canopies

    NASA Technical Reports Server (NTRS)

    Daughtry, C. S. T.; Ranson, K. J.; Biehl, L. L.

    1991-01-01

    A frequency-modulatad continuous-wave C-band (4.8 GHz) scatterometer was mounted on an aerial lift truck, and backscatter coefficients of corn (Zea mays L.) were acquired as functions of polarizations, view angles, and row directions. As phytomass and green-leaf area index increased, the backscatter also increased. Near anthesis, when the canopies were fully developed, the major scattering elements were located in the upper 1 m of the 2.8 m tall canopy and little backscatter was measured below that level for view angles of 30 deg or greater. C-band backscatter data could provide information to monitor tillage operations at small view zenith angles and vegetation at large view zenith angles.

  2. Lidar backscattering measurements of background stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Remsberg, E. E.; Northam, G. B.; Butler, C. F.

    1979-01-01

    A comparative lidar-dustsonde experiment was conducted in San Angelo, Texas, in May 1974 in order to estimate the uncertainties in stratospheric-aerosol backscatter for the NASA Langley 48-inch lidar system. The lidar calibration and data-analysis procedures are discussed. Results from the Texas experiment indicate random and systematic uncertainties of 35 and 63 percent, respectively, in backscatter from a background stratospheric-aerosol layer at 20 km.

  3. Quantitative Ultrasound Imaging Using Acoustic Backscatter Coefficients.

    NASA Astrophysics Data System (ADS)

    Boote, Evan Jeffery

    Current clinical ultrasound scanners render images which have brightness levels related to the degree of backscattered energy from the tissue being imaged. These images offer the interpreter a qualitative impression of the scattering characteristics of the tissue being examined, but due to the complex factors which affect the amplitude and character of the echoed acoustic energy, it is difficult to make quantitative assessments of scattering nature of the tissue, and thus, difficult to make precise diagnosis when subtle disease effects are present. In this dissertation, a method of data reduction for determining acoustic backscatter coefficients is adapted for use in forming quantitative ultrasound images of this parameter. In these images, the brightness level of an individual pixel corresponds to the backscatter coefficient determined for the spatial position represented by that pixel. The data reduction method utilized rigorously accounts for extraneous factors which affect the scattered echo waveform and has been demonstrated to accurately determine backscatter coefficients under a wide range of conditions. The algorithms and procedures used to form backscatter coefficient images are described. These were tested using tissue-mimicking phantoms which have regions of varying scattering levels. Another phantom has a fat-mimicking layer for testing these techniques under more clinically relevant conditions. Backscatter coefficient images were also formed of in vitro human liver tissue. A clinical ultrasound scanner has been adapted for use as a backscatter coefficient imaging platform. The digital interface between the scanner and the computer used for data reduction are described. Initial tests, using phantoms are presented. A study of backscatter coefficient imaging of in vivo liver was performed using several normal, healthy human subjects.

  4. Spectral variability of the particulate backscattering ratio

    NASA Astrophysics Data System (ADS)

    Whitmire, A. L.; Boss, E.; Cowles, T. J.; Pegau, W. S.

    2007-05-01

    The spectral dependency of the particulate backscattering ratio is relevant in the fields of ocean color inversion, light field modeling, and inferring particle properties from optical measurements. Aside from theoretical predictions for spherical, homogeneous particles, we have very limited knowledge of the actual in situ spectral variability of the particulate backscattering ratio. This work presents results from five research cruises that were conducted over a three-year period. Water column profiles of physical and optical properties were conducted across diverse aquatic environments that offered a wide range of particle populations. The main objective of this research was to examine the behavior of the spectral particulate backscattering ratio in situ, both in terms of its absolute magnitude and its variability across visible wavelengths, using over nine thousand 1-meter binned data points for each of five wavelengths of the spectral particulate backscattering ratio. Our analysis reveals no spectral dependence of the particulate backscattering ratio within our measurement certainty, and a geometric mean value of 0.013 for this dataset. This is lower than the commonly used value of 0.0183 from Petzold’s integrated volume scattering data. Within the first optical depth of the water column, the mean particulate backscattering ratio was 0.010.

  5. 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

  6. EBSD and AFM observations of the microstructural changes induced by low temperature plasma carburising on AISI 316

    NASA Astrophysics Data System (ADS)

    Corujeira Gallo, Santiago; Dong, Hanshan

    2011-10-01

    Low temperature plasma carburising (LTPC) has been increasingly accepted as a hardening process for austenitic stainless steels because it produces a good combination of tribological and corrosion properties. The hardening mechanism is based on the supersaturation of the austenitic structure with carbon, which greatly hardens the material, significantly expands the fcc unit cell, produces high levels of compressive residual stresses and, ultimately, leads to the occurrence of deformation bands and rotation of the crystal lattice. The microstructural changes introduced during plasma carburising have a significant impact on the mechanical, tribological and corrosion performance and, for this reason, the microstructure of expanded austenite or S-phase has been extensively studied. However, modern surface characterisation techniques could provide new insights into the formation mechanism of S-phase layers. In this work, backscattered electron diffraction and atomic force microscopy were used to characterise the surface layers of expanded austenite produced by LTPC in an active screen furnace. Based on the experimental results, the plastic deformation, its dependence on crystallographic orientation, the evolution of grain boundaries, and their effects on mechanical, tribological and corrosion properties are discussed.

  7. EBSD analysis of tungsten-filament carburization during the hot-wire CVD of multi-walled carbon nanotubes.

    PubMed

    Oliphant, Clive J; Arendse, Christopher J; Camagu, Sigqibo T; Swart, Hendrik

    2014-02-01

    Filament condition during hot-wire chemical vapor deposition conditions of multi-walled carbon nanotubes is a major concern for a stable deposition process. We report on the novel application of electron backscatter diffraction to characterize the carburization of tungsten filaments. During the synthesis, the W-filaments transform to W2C and WC. W-carbide growth followed a parabolic behavior corresponding to the diffusion of C as the rate-determining step. The grain size of W, W2C, and WC increases with longer exposure time and increasing filament temperature. The grain size of the recrystallizing W-core and W2C phase grows from the perimeter inwardly and this phenomenon is enhanced at filament temperatures in excess of 1,400°C. Cracks appear at filament temperatures >1,600°C, accompanied by a reduction in the filament operational lifetime. The increase of the W2C and recrystallized W-core grain size from the perimeter inwardly is ascribed to a thermal gradient within the filament, which in turn influences the hardness measurements and crack formation. PMID:24423105

  8. High-frequency backscatter from a finned cylinder at grazing incidence - Comparison of two theoretical methods

    NASA Astrophysics Data System (ADS)

    Michaeli, A.

    1986-02-01

    A closed-form, high-frequency approximation is obtained for the diffracted-reflected-diffracted field contribution to the backscattered field resulting from the grazing illumination of a perfectly conducting, infinitely long, finned cylinder by a normally incident cylindrical transverse magnetic (TM) wave. The result, which is valid for any relative magnitudes of the cylinder radius and the fin width provided both of them are electrically large, is derived by two different methods. One of them is the radiation integral method related to the physical theory of diffraction. The other is the complex ray tracing method related to the spectral theory of diffraction (STD). Relative merits and disadvantages of the two methods are pointed out.

  9. Reducing parametric backscattering by polarization rotation

    NASA Astrophysics Data System (ADS)

    Barth, Ido; Fisch, Nathaniel J.

    2016-10-01

    When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in employing lasers in inertial confinement fusion. However, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of 5. A general, fluid-model based analytical estimation for the reflectivity reduction agrees with simulations. However, in identifying the source of the backscatter reduction, it is difficult to disentangle the rotating polarization from the frequency separation based approach used to engineer the beam's polarization. Although the backscatter reduction arises similarly to other approaches that employ frequency separation, in the case here, the intensity remains constant in time.

  10. Near-surface fault detection by migrating back-scattered surface waves with and without velocity profiles

    NASA Astrophysics Data System (ADS)

    Yu, Han; Huang, Yunsong; Guo, Bowen

    2016-07-01

    We demonstrate that diffraction stack migration can be used to discover the distribution of near-surface faults. The methodology is based on the assumption that near-surface faults generate detectable back-scattered surface waves from impinging surface waves. We first isolate the back-scattered surface waves by muting or FK filtering, and then migrate them by diffraction migration using the surface wave velocity as the migration velocity. Instead of summing events along trial quasi-hyperbolas, surface wave migration sums events along trial quasi-linear trajectories that correspond to the moveout of back-scattered surface waves. We have also proposed a natural migration method that utilizes the intrinsic traveltime property of the direct and the back-scattered waves at faults. For the synthetic data sets and the land data collected in Aqaba, where surface wave velocity has unexpected perturbations, we migrate the back-scattered surface waves with both predicted velocity profiles and natural Green's function without velocity information. Because the latter approach avoids the need for an accurate velocity model in event summation, both the prestack and stacked migration images show competitive quality. Results with both synthetic data and field records validate the feasibility of this method. We believe applying this method to global or passive seismic data can open new opportunities in unveiling tectonic features.

  11. A microwave backscattering model for precipitation

    NASA Astrophysics Data System (ADS)

    Ermis, Seda

    A geophysical microwave backscattering model for space borne and ground-based remote sensing of precipitation is developed and used to analyze backscattering measurements from rain and snow type precipitation. Vector Radiative Transfer (VRT) equations for a multilayered inhomogeneous medium are applied to the precipitation region for calculation of backscattered intensity. Numerical solution of the VRT equation for multiple layers is provided by the matrix doubling method to take into account close range interactions between particles. In previous studies, the VRT model was used to calculate backscattering from a rain column on a sea surface. In the model, Mie scattering theory for closely spaced scatterers was used to determine the phase matrix for each sublayer characterized by a set of parameters. The scatterers i.e. rain drops within the sublayers were modelled as spheres with complex permittivities. The rain layer was bounded by rough boundaries; the interface between the cloud and the rain column as well as the interface between the sea surface and the rain were all analyzed by using the integral equation model (IEM). Therefore, the phase matrix for the entire rain column was generated by the combination of surface and volume scattering. Besides Mie scattering, in this study, we use T-matrix approach to examine the effect of the shape to the backscattered intensities since larger raindrops are most likely oblique in shape. Analyses show that the effect of obliquity of raindrops to the backscattered wave is related with size of the scatterers and operated frequency. For the ground-based measurement system, the VRT model is applied to simulate the precipitation column on horizontal direction. Therefore, the backscattered reflectivities for each unit range of volume are calculated from the backscattering radar cross sections by considering radar range and effective illuminated area of the radar beam. The volume scattering phase matrices for each range interval

  12. 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.

  13. Multibeam Sonar Backscatter Data Acquisition and Processing: Guidelines and Recommendations from the GEOHAB Backscatter Working Group

    NASA Astrophysics Data System (ADS)

    Heffron, E.; Lurton, X.; Lamarche, G.; Brown, C.; Lucieer, V.; Rice, G.; Schimel, A.; Weber, T.

    2015-12-01

    Backscatter data acquired with multibeam sonars are now commonly used for the remote geological interpretation of the seabed. The systems hardware, software, and processing methods and tools have grown in numbers and improved over the years, yet many issues linger: there are no standard procedures for acquisition, poor or absent calibration, limited understanding and documentation of processing methods, etc. A workshop organized at the GeoHab (a community of geoscientists and biologists around the topic of marine habitat mapping) annual meeting in 2013 was dedicated to seafloor backscatter data from multibeam sonars and concluded that there was an overwhelming need for better coherence and agreement on the topics of acquisition, processing and interpretation of data. The GeoHab Backscatter Working Group (BSWG) was subsequently created with the purpose of documenting and synthetizing the state-of-the-art in sensors and techniques available today and proposing methods for best practice in the acquisition and processing of backscatter data. Two years later, the resulting document "Backscatter measurements by seafloor-mapping sonars: Guidelines and Recommendations" was completed1. The document provides: An introduction to backscatter measurements by seafloor-mapping sonars; A background on the physical principles of sonar backscatter; A discussion on users' needs from a wide spectrum of community end-users; A review on backscatter measurement; An analysis of best practices in data acquisition; A review of data processing principles with details on present software implementation; and finally A synthesis and key recommendations. This presentation reviews the BSWG mandate, structure, and development of this document. It details the various chapter contents, its recommendations to sonar manufacturers, operators, data processing software developers and end-users and its implication for the marine geology community. 1: Downloadable at https://www.niwa.co.nz/coasts-and-oceans/research-projects/backscatter-measurement-guidelines

  14. On the formation mechanisms, spatial resolution and intensity of backscatter Kikuchi patterns.

    PubMed

    Zaefferer, S

    2007-01-01

    The present paper is divided into two main sections. In the first, the formation mechanisms of backscatter Kikuchi patterns (BKP) are discussed on the basis of measurements on the sharpness of Kikuchi lines and on the spatial, that means the lateral and depth resolution of the technique. We propose that thermal diffuse scattering is the important incoherent scattering mechanism involved in pattern formation. This mechanism is not considered in the classical description of the origin of backscattered electrons in the scanning electron microscope (SEM) which is why there is in some important points no agreement between classical Monte-Carlo-type electron trajectory simulations and experimental results. We assume that the energy spectrum of the backscattered electrons shows, similar to the spectra in transmission electron microscopy, a sharp zero-loss peak. In the second section, we discuss the intensity of Kikuchi bands in BKP. It is shown that the kinematical theory gives-of course-not the correct intensities, but that these intensities are, on the other hand, not too far off the experimental ones. We subsequently introduce a simple intensity correction procedure that is based on the two-beam dynamical theory, originally proposed by Blackman for transmission electron diffraction patterns. It is shown by examples of diffraction patterns of niobium and silicon that this procedure leads to satisfying results, once two unknown variables (a universal constant and the exit depth of the electrons) have been empirically fit. It is assumed that in the future, this correction will improve the possibilities of phase identification by backscatter Kikuchi diffraction patterns.

  15. Backscattering of α-Quartz (0 6 10) for 14.4 keV Mössbauer Photons

    NASA Astrophysics Data System (ADS)

    Imai, Yasuhiko; Yoda, Yoshitaka; Zhang, Xiaowei; Kikuta, Seishi

    2007-01-01

    Backscattering of α-quartz (0 6 10) was investigated using 14.4 keV 57Fe Mössbauer photons from α-57Fe2O3 at nuclear resonant scattering beamline BL09XU, SPring-8. The α-quartz crystal was heated to around 353 K by an oven so that the Bragg angle of α-quartz 0 6 10 diffraction meats 90 degrees. Energy width of the reflection was measured by changing temperature of the oven. The measured bandwidth is 1.14(33) meV. Backscattering by a α-quartz crystal can be applied for high-energy-resolution monochromator or analyzer.

  16. Snowcover influence on backscattering from terrain

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Abdelrazik, M.; Stiles, W. H.

    1984-01-01

    The effects of snowcover on the microwave backscattering from terrain in the 8-35 GHz region are examined through the analysis of experimental data and by application of a semiempirical model. The model accounts for surface backscattering contributions by the snow-air and snow-soil interfaces, and for volume backscattering contributions by the snow layer. Through comparisons of backscattering data for different terrain surfaces measured both with and without snowcover, the masking effects of snow are evaluated as a function of snow water equivalent and liquid water content. The results indicate that with dry snowcover it is not possible to discriminate between different types of ground surface (concrete, asphalt, grass, and bare ground) if the snow water equivalent is greater than about 20 cm (or a depth greater than 60 cm for a snow density of 0.3 g/cu cm). For the same density, however, if the snow is wet, a depth of 10 cm is sufficient to mask the underlying surface.

  17. Incidence angle normalization of radar backscatter data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    NASA’s Soil Moisture Passive Active (SMAP) satellite (~2014) will include a radar system that will provide L-band multi-polarization backscatter at a constant incidence angle of 40º. During the pre-launch phase of the project there is a need for observations that will support the radar-based soil mo...

  18. Visualization of x-ray backscatter data

    SciTech Connect

    Greenawald, E.C.; Ham, Y.S.; Poranski, C.F. Jr.

    1993-12-31

    Of the several processes which occur when x-rays interact with matter, Compton scattering is dominant in the range of energies commonly used in industrial radiography. The Compton interaction between an x-ray photon and a free or outer shell electron causes the electron to recoil and the photon to be propagated in a new direction with a reduced energy. Regardless of the incident beam energy, some photons are always scattered in the backwards direction. The potential for determining material properties by the detection of x-ray backscatter has been recognized for years. Although work in this area has been eclipsed by the rapid development of computerized tomography (CT), a variety of industrial backscatter imaging techniques and applications have been demonstrated. Backscatter inspection is unique among x-ray methods in its applicability with access to only one side of the object. The authors are currently developing the application of x-ray backscatter tomography (XBT) to the inspection of steel-reinforced rubber sonar domes on US Navy vessels. In this paper, the authors discuss the visualization methods they use to interpret the XBT data. They present images which illustrate the capability of XBT as applied to sonar domes and a variety of other materials and objects. They also demonstrate and discuss the use of several data visualization software products.

  19. 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.

  20. Low magnification EBSD mapping of texture distribution in a fine-grained matrix

    NASA Astrophysics Data System (ADS)

    Gardner, Joseph; Mariani, Elisabetta; Wheeler, John

    2016-04-01

    The study of texture (CPO) in rocks is often restricted to individual phases within a given sample or specific area of said sample. Large scale EBSD mapping of the matrix of a greenschist facies albite mylonite has shown that an overall significant CPO within albite grains is strongly domainal, and each domain has a unique CPO that is independent of both common slip systems in plagioclase and the specimen geometry (i.e. foliation and lineation). Observational evidence suggests the metamorphic breakdown of plagioclase to albite (Ab) plus a Ca-bearing phase (clinozoisite, Cz) has produced a two phase mixture in which each phase has a contrasting solubility. New grains of albite are thought to nucleate epitaxially from original plagioclase as a reaction front passes through parent grains. A pseudomorphic region of Ab plus Cz after an original plagioclase crystal, protected from intense deformation by enclosure in a cm-scale augite clast, gives insight into pre-deformation daughter grain distributions. The albite in the region inherits a strong CPO and 180° misorientation peak from a relict twin pattern due to epitaxial growth while clinozoisite is randomly distributed and oriented (despite some grains nucleating from the plagioclase parent twin boundary). In the deformed matrix, daughter Ab is seen to be the more mobile phase, having undergone obvious dissolution, transport and reprecipitation into fractures and pressure shadows, whereas Cz grains are relatively insoluble and rotate into parallelism with the foliation, forming bands that anastamose around Cpx porphyroclasts. Despite this modification, albite in the matrix retains significant CPOs that comprise distinct domains with sharp boundaries. A 180° misorientation peak thought to be a signature of twinning inherited from parent plagioclase is also observed in each domain. Why a CPO should be preserved under these conditions (contrary to our traditional understanding that CPOs are a signature of dislocation

  1. Electromagnetic backscattering from one-dimensional drifting fractal sea surface II: Electromagnetic backscattering model

    NASA Astrophysics Data System (ADS)

    Tao, Xie; William, Perrie; Shang-Zhuo, Zhao; He, Fang; Wen-Jin, Yu; Yi-Jun, He

    2016-07-01

    Sea surface current has a significant influence on electromagnetic (EM) backscattering signals and may constitute a dominant synthetic aperture radar (SAR) imaging mechanism. An effective EM backscattering model for a one-dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant influence on EM backscattering signals from the sea surface. The normalized radar cross section (NRCS) discrepancies between the model for a coupled wave-current fractal sea surface and the model for an uncoupled fractal sea surface increase with the increase of incidence angle, as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the wave can weaken the EM backscattering signal intensity, while the EM backscattering signal is intensified by ocean currents propagating oppositely to the wave direction. The model presented in this paper can be used to study the SAR imaging mechanism for a drifting sea surface. Project supported by the National Natural Science Foundation of China (Grant No. 41276187), the Global Change Research Program of China (Grant No. 2015CB953901), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, the Program for the Innovation Research and Entrepreneurship Team in Jiangsu Province, China, the Canadian Program on Energy Research and Development, and the Canadian World Class Tanker Safety Service Program.

  2. Electromagnetic backscattering from one-dimensional drifting fractal sea surface II: Electromagnetic backscattering model

    NASA Astrophysics Data System (ADS)

    Tao, Xie; William, Perrie; Shang-Zhuo, Zhao; He, Fang; Wen-Jin, Yu; Yi-Jun, He

    2016-07-01

    Sea surface current has a significant influence on electromagnetic (EM) backscattering signals and may constitute a dominant synthetic aperture radar (SAR) imaging mechanism. An effective EM backscattering model for a one-dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant influence on EM backscattering signals from the sea surface. The normalized radar cross section (NRCS) discrepancies between the model for a coupled wave-current fractal sea surface and the model for an uncoupled fractal sea surface increase with the increase of incidence angle, as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the wave can weaken the EM backscattering signal intensity, while the EM backscattering signal is intensified by ocean currents propagating oppositely to the wave direction. The model presented in this paper can be used to study the SAR imaging mechanism for a drifting sea surface. Project supported by the National Natural Science Foundation of China (Grant No. 41276187), the Global Change Research Program of China (Grant No. 2015CB953901), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, the Program for the Innovation Research and Entrepreneurship Team in Jiangsu Province, China, the Canadian Program on Energy Research and Development, and the Canadian World Class Tanker Safety Service Program.

  3. Combined nano-SIMS/AFM/EBSD analysis and atom probe tomography, of carbon distribution in austenite/ε-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 ε-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 ε-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.

  4. Spectra of particulate backscattering in natural waters.

    PubMed

    Gordon, Howard R; Lewis, Marlon R; McLean, Scott D; Twardowski, Michael S; Freeman, Scott A; Voss, Kenneth J; Boynton, G Chris

    2009-08-31

    Hyperspectral profiles of downwelling irradiance and upwelling radiance in natural waters (oligotrophic and mesotrophic) are combined with inverse radiative transfer to obtain high resolution spectra of the absorption coefficient (a) and the backscattering coefficient (b(b)) of the water and its constituents. The absorption coefficient at the mesotrophic station clearly shows spectral absorption features attributable to several phytoplankton pigments (Chlorophyll a, b, c, and Carotenoids). The backscattering shows only weak spectral features and can be well represented by a power-law variation with wavelength (lambda): b(b) approximately lambda(-n), where n is a constant between 0.4 and 1.0. However, the weak spectral features in b(b)b suggest that it is depressed in spectral regions of strong particle absorption. The applicability of the present inverse radiative transfer algorithm, which omits the influence of Raman scattering, is limited to lambda < 490 nm in oligotrophic waters and lambda < 575 nm in mesotrophic waters. PMID:19724619

  5. Flaw detection by spatially coded backscatter radiography.

    PubMed

    Thangavelu, Sivakumar; Hussein, Esam M A

    2007-02-01

    Backscatter imaging is useful for inspecting structures that are accessible only from one side. However, indications provided by scattered radiation are typically weak, convoluted and difficult to interpret. This paper explores the use of the coded aperture technique to detect flaws using gamma-ray backscatter imaging. The viability of this approach is demonstrated with indications obtained from Monte Carlo simulations of radiation scattering measurements. The results show that, with a 2 mm wide beam of 137Cs photons, flaws as small as 1.5 mm in width can be detected using this technique. Indications of changes in flaw size, location, multiplicity and density were also observable. In addition, it is possible to quantify, from the decoded indications, the flaw location and its size.

  6. Aerosol backscatter lidar calibration and data interpretation

    NASA Technical Reports Server (NTRS)

    Kavaya, M. J.; Menzies, R. T.

    1984-01-01

    A treatment of the various factors involved in lidar data acquisition and analysis is presented. This treatment highlights sources of fundamental, systematic, modeling, and calibration errors that may affect the accurate interpretation and calibration of lidar aerosol backscatter data. The discussion primarily pertains to ground based, pulsed CO2 lidars that probe the troposphere and are calibrated using large, hard calibration targets. However, a large part of the analysis is relevant to other types of lidar systems such as lidars operating at other wavelengths; continuous wave (CW) lidars; lidars operating in other regions of the atmosphere; lidars measuring nonaerosol elastic or inelastic backscatter; airborne or Earth-orbiting lidar platforms; and lidars employing combinations of the above characteristics.

  7. Demonstration of differential backscatter absorption gas imaging.

    PubMed

    Powers, P E; Kulp, T J; Kennedy, R

    2000-03-20

    Backscatter absorption gas imaging (BAGI) is a technique that uses infrared active imaging to generate real-time video imagery of gas plumes. We describe a method that employs imaging at two wavelengths (absorbed and not absorbed by the gas to be detected) to allow wavelength-differential BAGI. From the frames collected at each wavelength, an absorbance image is created that displays the differential absorbance of the atmosphere between the imager and the backscatter surface. This is analogous to a two-dimensional topographic differential absorption lidar or differential optical absorption spectroscopy measurement. Gas plumes are displayed, but the topographic scene image is removed. This allows a more effective display of the plume image, thus ensuring detection under a wide variety of conditions. The instrument used to generate differential BAGI is described. Data generated by the instrument are presented and analyzed to estimate sensitivity. PMID:18338030

  8. Microwave backscattering from an anisotropic soybean canopy

    NASA Technical Reports Server (NTRS)

    Lang, R. H.; Saatchi, S.; Levine, D. M.

    1986-01-01

    Electromagnetic backscattering from a soybean canopy is modeled in the L band region of the spectrum. Mature soybean plants are taken as an ensemble of leaves and stems which are represented by lossy dielectric disks and rods respectively. Field data indicated that leaves and stems are not distributed uniformly in the azimuth coordinate. The plant has a tendency to grow out into the area between the rows. The effects on backscattered radar waves was computed by the distorted Born approximation. Results for look directions along the rows and perpendicular to the rows show that only a modest difference occurs in the L band frequency range. The use of another nonuniform distribution, different from those observed experimentally, results in a significant effect due to vegetation asymmetry.

  9. Spectra of Particulate Backscattering in Natural Waters

    NASA Technical Reports Server (NTRS)

    Gordon, Howard, R.; Lewis, Marlon R.; McLean, Scott D.; Twardowski, Michael S.; Freeman, Scott A.; Voss, Kenneth J.; Boynton, Chris G.

    2009-01-01

    Hyperspectral profiles of downwelling irradiance and upwelling radiance in natural waters (oligotrophic and mesotrophic) are combined with inverse radiative transfer to obtain high resolution spectra of the absorption coefficient (a) and the backscattering coefficient (bb) of the water and its constituents. The absorption coefficient at the mesotrophic station clearly shows spectral absorption features attributable to several phytoplankton pigments (Chlorophyll a, b, c, and Carotenoids). The backscattering shows only weak spectral features and can be well represented by a power-law variation with wavelength (lambda): b(sub b) approx. Lambda(sup -n), where n is a constant between 0.4 and 1.0. However, the weak spectral features in b(sub b), suggest that it is depressed in spectral regions of strong particle absorption. The applicability of the present inverse radiative transfer algorithm, which omits the influence of Raman scattering, is limited to lambda < 490 nm in oligotrophic waters and lambda < 575 nm in mesotrophic waters.

  10. SuperDARN backscatter during intense geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Currie, J. L.; Waters, C. L.; Menk, F. W.; Sciffer, M. D.; Bristow, W. A.

    2016-06-01

    It is often stated that high-frequency radars experience a loss of backscatter during geomagnetic storm events. The occurrence of backscatter during 25 intense geomagnetic storms was examined using data from the Bruny Island and Kodiak radars and a superposed epoch analysis. It was found that while a reduction of backscatter occurred in the middle to far ranges, there was an increase in the amount of backscatter from close range following storm onset. Ray tracing showed that an enhanced charge density in the E region can reduce the chance of F region and increase the chance of E region backscatter. It was also shown that reduction in backscatter cannot be explained by D region absorption. Using a normalized SYM-H value, percentage time through recovery phase can be estimated during storm progression which allows a prediction of backscatter return in real time that accounts for varying storm recovery phase duration.

  11. Bomb detection using backscattered x rays

    NASA Astrophysics Data System (ADS)

    Lockwood, Grant J.; Shope, Steve L.; Wehlburg, Joseph C.; Selph, Michael M.; Jacobs, Jennifer

    1999-01-01

    Currently the most common method to determine the contents of a package suspected of containing an explosive device is to use transmission radiography. This technique requires that an x-ray source and film be placed on opposite sites of the package. This poses a problem if the package is placed so that only one side is accessible, such as against a wall. There is also a threat to personnel and property since explosive devices may be 'booby trapped.' We have developed a method to x-ray a package using backscattered x-rays. This procedure eliminates the use of film behind the target. All of the detection is done from the same side as the source. When an object is subjected to x-rays, some of them are scattered back toward the source. The backscattering of x-rays is proportional to the atomic number (Z) of the material raised to the 4.1 power. This Z4.1 dependence allows us to easily distinguish between explosives, wires, timer, batteries, and other bomb components. Backscatter experiments at Sandia National Laboratories have been conducted on mock bombs in packages. We are able to readily identify the bomb components. The images that are obtained in this procedure are done in real time and the image is displayed on a computer screen.

  12. Backscatter in Large-Scale Flows

    NASA Astrophysics Data System (ADS)

    Nadiga, Balu

    2009-11-01

    Downgradient mixing of potential-voriticity and its variants are commonly employed to model the effects of unresolved geostrophic turbulence on resolved scales. This is motivated by the (inviscid and unforced) particle-wise conservation of potential-vorticity and the mean forward or down-scale cascade of potential enstrophy in geostrophic turubulence. By examining the statistical distribution of the transfer of potential enstrophy from mean or filtered motions to eddy or sub-filter motions, we find that the mean forward cascade results from the forward-scatter being only slightly greater than the backscatter. Downgradient mixing ideas, do not recognize such equitable mean-eddy or large scale-small scale interactions and consequently model only the mean effect of forward cascade; the importance of capturing the effects of backscatter---the forcing of resolved scales by unresolved scales---are only beginning to be recognized. While recent attempts to model the effects of backscatter on resolved scales have taken a stochastic approach, our analysis suggests that these effects are amenable to being modeled deterministically.

  13. Flex - rigid behavior of quartzite and its mineralogical, microstructural and textural properties from EBSD

    NASA Astrophysics Data System (ADS)

    Dorabiato Barbosa, Pamela; Ávila, Carlos Fernando; Evangelista Lagoeiro, Leonardo; Pinheiro Sampaio, Ney; Martins Graça, Leonardo

    2016-04-01

    It was investigated the mechanical properties of the quartzite found in the 'Moeda' Formation from the mineral province of the 'Quadrilátero Ferrífero', Brazil. Rocks with variations from flexible (in some portions) to completely rigid are rare and found only in some specific locations in the whole world. It's flexibility has been usually related to the presence of minerals with tabular habit, that act as structural support to the rock and regulates the flexibility. Besides, the intrinsic behavior of this type of rock is marked by their microstructures and the typical preferred crystallographic orientations. In order to characterize the causes of this unique mechanical property, oriented sections of these rocks with different behaviors, flexible and stiff, were prepared and investigated with EBSD. The results showed differences in grain sizes (with grain area as proxy) and grain boundary lengths for quartz grains, the spatial distribution of muscovite, as well as crystallographic fabrics. The boundaries of the quartz grains observed in the stiff sample are linear, while in the flexible sample they're irregular. Quartz grains with sizes smaller than 30 μm2 are 30% larger in the flexible quartzite than those of the rigid counterparts.. This relation reverses for grains with an area greater than 30,000 μm2. Muscovite occurs as isolated grains in the rigid samples while in the flexible ones grains more continuously distributed and interconnected.. When the directions of the samples are plotted in the crystal reference system a contrasting crystallographic texture arises. The X-directions of the sample concentrate in the axes of the quartz. For the rigid samples it is te Y-directions that show preference to align parallel to the poles of the positive rhomb ({01-12} = this is the acute rhomb; rhomb is {01-11]). The rigid quartzite showed a strong <21 ̅1 ̅0> () crystallographic fabric parallel to the macroscopic lineation, whereas for the flexible ones the

  14. Shallow water acoustic backscatter and reverberation measurements using a 68-kHz cylindrical array

    NASA Astrophysics Data System (ADS)

    Gallaudet, Timothy Cole

    2001-10-01

    The characterization of high frequency, shallow water acoustic backscatter and reverberation is important because acoustic systems are used in many scientific, commercial, and military applications. The approach taken is to use data collected by the Toroidal Volume Search Sonar (TVSS), a 68 kHz multibeam sonar capable of 360° imaging in a vertical plane perpendicular to its direction of travel. With this unique capability, acoustic backscatter imagery of the seafloor, sea surface, and horizontal and vertical planes in the volume are constructed from data obtained in 200m deep waters in the Northeastern Gulf of Mexico when the TVSS was towed 78m below the surface, 735m astern of a towship. The processed imagery provide a quasi-synoptic characterization of the spatial and temporal structure of boundary and volume acoustic backscatter and reverberation. Diffraction, element patterns, and high sidelobe levels are shown to be the most serious problems affecting cylindrical arrays such as the TVSS, and an amplitude shading method is presented for reducing the peak sidelobe levels of irregular-line and non-coplanar arrays. Errors in the towfish's attitude and motion sensor, and irregularities in the TVSS's transmitted beampattern produce artifacts in the TVSS-derived bathymetry and seafloor acoustic backscatter imagery. Correction strategies for these problems are described, which are unique in that they use environmental information extracted from both ocean boundaries. Sea surface and volume acoustic backscatter imagery are used to explore and characterize the structure of near-surface bubble clouds, schooling fish, and zooplankton. The simultaneous horizontal and vertical coverage provided by the TVSS is shown to be a primary advantage, motivating further use of multibeam sonars in these applications. Whereas boundary backscatter fluctuations are well described by Weibull, K, and Rayleigh mixture probability distributions, those corresponding to volume backscatter are

  15. Backscatter and attenuation characterization of ventricular myocardium

    NASA Astrophysics Data System (ADS)

    Gibson, Allyson Ann

    2009-12-01

    This Dissertation presents quantitative ultrasonic measurements of the myocardium in fetal hearts and adult human hearts with the goal of studying the physics of sound waves incident upon anisotropic and inhomogeneous materials. Ultrasound has been used as a clinical tool to assess heart structure and function for several decades. The clinical usefulness of this noninvasive approach has grown with our understanding of the physical mechanisms underlying the interaction of ultrasonic waves with the myocardium. In this Dissertation, integrated backscatter and attenuation analyses were performed on midgestational fetal hearts to assess potential differences in the left and right ventricular myocardium. The hearts were interrogated using a 50 MHz transducer that enabled finer spatial resolution than could be achieved at more typical clinical frequencies. Ultrasonic data analyses demonstrated different patterns and relative levels of backscatter and attenuation from the myocardium of the left ventricle and the right ventricle. Ultrasonic data of adult human hearts were acquired with a clinical imaging system and quantified by their magnitude and time delay of cyclic variation of myocardial backscatter. The results were analyzing using Bayes Classification and ROC analysis to quantify potential advantages of using a combination of two features of cyclic variation of myocardial backscatter over using only one or the other feature to distinguish between groups of subjects. When the subjects were classified based on hemoglobin A1c, the homeostasis model assessment of insulin resistance, and the ratio of triglyceride to high-density lipoprotein-cholesterol, differences in the magnitude and normalized time delay of cyclic variation of myocardial backscatter were observed. The cyclic variation results also suggested a trend toward a larger area under the ROC curve when information from magnitude and time delay of cyclic variation is combined using Bayes classification than when

  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. 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)

  18. 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.

  19. 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.

  20. Proton backscatter as a means of mass normalization in PIXE scanning of human hair

    NASA Astrophysics Data System (ADS)

    Russell, S. B.; Gibson, R. S.; Faiq, S.; Campbell, J. L.

    1981-03-01

    Variations in linear density along a given hair can cause changes in X-ray intensity which do not reflect elemental concentration changes. Hairs from different subjects vary by a factor ˜5 in linear density, so that very different X-ray intensities need not necessarily reflect different concentrations. We investigate the usefulness of the backscattered proton intensity as a means of determining the mass undergoing PIXE analysis. Specimen damage can be avoided in the BS measurement via low currents without loss of statistcs. A correlation is found between BS intensity and mass, but a laser diffraction measurement of the hair diameter provides an equally satisfactory mass determination.

  1. Nanometres-resolution Kikuchi patterns from materials science specimens with transmission electron forward scatter diffraction in the scanning electron microscope.

    PubMed

    Brodusch, N; Demers, H; Gauvin, R

    2013-04-01

    A charge-coupled device camera of an electron backscattered diffraction system in a scanning electron microscope was positioned below a thin specimen and transmission Kikuchi patterns were collected. Contrary to electron backscattered diffraction, transmission electron forward scatter diffraction provides phase identification and orientation mapping at the nanoscale. The minimum Pd particle size for which a Kikuchi diffraction pattern was detected and indexed reliably was 5.6 nm. An orientation mapping resolution of 5 nm was measured at 30 kV. The resolution obtained with transmission electron forward scatter diffraction was of the same order of magnitude than that reported in electron nanodiffraction in the transmission electron microscope. An energy dispersive spectrometer X-ray map and a transmission electron forward scatter diffraction orientation map were acquired simultaneously. The high-resolution chemical, phase and orientation maps provided at once information on the chemical form, orientation and coherency of precipitates in an aluminium-lithium 2099 alloy.

  2. Modeling canopy reflectance and microwave backscattering coefficient

    NASA Technical Reports Server (NTRS)

    Goel, N. S.

    1985-01-01

    Various approaches to model canopy reflectance (CR) in the visible/infrared region and backscattering coefficient (BSC) in the microwave region are compared and contrasted. It is noted that BSC can be related to CR in the source direction (the 'hot spot' direction). By assuming a frequency dependent leaf reflectance and transmittance it is shown that the observed dependence of BSC on leaf area index, leaf angle distribution, angle of incidence, soil moisture content, and frequency can be simulated by a CR model. Thus both BSC and CR can, in principle, be calculated using a single model which has essentially the same parameters as many CR models do.

  3. Polarization properties of lidar backscattering from clouds.

    PubMed

    Pal, S R; Carswell, A I

    1973-07-01

    The polarization properties of the backscattering of a lidar pulse from atmospheric clouds have been measured. A linearly polarized signal from a ruby laser at 694.3 nm is transmitted, and the scattering is simultaneously measured on a three-channel receiver that has polarizers oriented parallel, perpendicular, and at 45 degrees to the transmitted polarization. Substantial depolarizations (up to 0.5) are observed, and from the spatial variation of this depolarization the contribution of multiple scattering can be deduced.A wide variation in polarization properties is observed in different cloud types, and the results indicate that polarization signatures could be useful for cloud characterization and classification.

  4. Elementary polarization properties in the backscattering configuration.

    PubMed

    Arteaga, Oriol; Garcia-Caurel, Enric; Ossikovski, Razvigor

    2014-10-15

    In the normal incidence backscattering configuration, a polarimetric measurement always preserves the reciprocal symmetry. For a reciprocal Jones matrix, the number of elementary polarization properties is reduced from six to four. In this work, the physical interpretation of these properties is examined and they are compared with the equivalent polarization properties in transmission. It is found that, with the exception of natural optical activity, a polarimetric backreflection experiment can essentially provide the same type of information about the anisotropy of a medium as a transmission analysis, although transmission and backreflection information comes in a completely different form. Experimental examples are provided to illustrate the discussion.

  5. Backscattering differential ghost imaging in turbid media.

    PubMed

    Bina, M; Magatti, D; Molteni, M; Gatti, A; Lugiato, L A; Ferri, F

    2013-02-22

    In this Letter we present experimental results concerning the retrieval of images of absorbing objects immersed in turbid media via differential ghost imaging (DGI) in a backscattering configuration. The method has been applied, for the first time to our knowledge, to the imaging of thin black objects located inside a turbid solution in proximity of its surface. We show that it recovers images with a contrast better than standard noncorrelated direct imaging, but equivalent to noncorrelated diffusive imaging. A simple theoretical model capable of describing the basic optics of DGI in turbid media is proposed.

  6. 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.

  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. Analysis of the enhancement of backscattering by nonspherical particles with flat surfaces.

    PubMed

    Iwasaki, S; Okamoto, H

    2001-11-20

    We examine backscattering by analyzing large nonspherical particles with flat surfaces for which where the size is much larger than the wavelength, using ray optics and diffraction theory. We show that the backscattering cross section for rectangles can be 1 order of magnitude larger than that for spheres with same geometrical cross sections, depending on the orientation of the particles. Then we show that there is a difficulty in estimating the backscattering cross section for hexagonal columns with the available solutions but that it is possible to estimate the integration of the differential scattering cross section over small solid angles in backward directions. The integral values for hexagonal columns are found to be more than 1 order of magnitude larger than that for spheres with the same volume. As an application, the use of power from hexagonal columns for lidar observations is analyzed. Unlike for spherical particles with their dependence on Z(-2) (where Z is the distance between the particle and the detector), for nonspherical particles such dependence varies with the particles' nonsphericity, such as shape and orientation: Z(0) for a hexagonal plate randomly oriented in the horizontal plane; Z(-1) for a hexagonal column randomly oriented in the horizontal plane. PMID:18364911

  9. Rotational Raman scattering (Ring effect) in satellite backscatter ultraviolet measurements

    NASA Astrophysics Data System (ADS)

    Cebula, Richard P.; Joiner, Joanna; Bhartia, Pawan K.; Hilsenrath, Ernest; McPeters, Richard D.; Park, Hongwoo

    1995-07-01

    A detailed radiative transfer calculation has been carried out to estimate the effects of rotational Raman scattering (RRS) on satellite measurements of backscattered ultraviolet radiation. Raman-scattered light is shifted in frequency from the incident light, which causes filling in of solar Fraunhofer lines in the observed backscattered spectrum (also known as the Ring effect). The magnitude of the rotational Raman scattering filling in is a function of wavelength, solar zenith angle, surface reflectance, surface pressure, and instrument spectral resolution. The filling in predicted by our model is found to be in agreement with observations from the Shuttle Solar Backscatter Ultraviolet Radiometer and the Nimbus-7 Solar Backscatter Ultraviolet Radiometer.

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

    PubMed

    Ansmann, A; Wandinger, U; Riebesell, M; Weitkamp, C; Michaelis, W

    1992-11-20

    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.

  11. Backscatter coefficient estimation using tapers with gaps.

    PubMed

    Luchies, Adam C; Oelze, Michael L

    2015-04-01

    When using the backscatter coefficient (BSC) to estimate quantitative ultrasound parameters such as the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC), it is necessary to assume that the interrogated medium contains diffuse scatterers. Structures that invalidate this assumption can affect the estimated BSC parameters in terms of increased bias and variance and decrease performance when classifying disease. In this work, a method was developed to mitigate the effects of echoes from structures that invalidate the assumption of diffuse scattering, while preserving as much signal as possible for obtaining diffuse scatterer property estimates. Backscattered signal sections that contained nondiffuse signals were identified and a windowing technique was used to provide BSC estimates for diffuse echoes only. Experiments from physical phantoms were used to evaluate the effectiveness of the proposed BSC estimation methods. Tradeoffs associated with effective mitigation of specular scatterers and bias and variance introduced into the estimates were quantified. Analysis of the results suggested that discrete prolate spheroidal (PR) tapers with gaps provided the best performance for minimizing BSC error. Specifically, the mean square error for BSC between measured and theoretical had an average value of approximately 1.0 and 0.2 when using a Hanning taper and PR taper respectively, with six gaps. The BSC error due to amplitude bias was smallest for PR (Nω = 1) tapers. The BSC error due to shape bias was smallest for PR (Nω = 4) tapers. These results suggest using different taper types for estimating ESD versus EAC.

  12. Lidar for multiple backscattering and depolarization observations.

    PubMed

    Allen, R J; Platt, C M

    1977-12-01

    A lidar system that can measure multiple scattering and depolarization in the atmosphere is being used to study the climatic effects of cirrus clouds and to perform other investigations. The lidar system and its novel aspects are described in this paper. The influence of multiple scattering on noise, signal, and SNR is considered. Special receiver field stops incorporated for multiple scattering measurements, use of low voltage to control the photomultiplier tube gain, and a precision power/energy monitor are described. A technique for aligning transmitter and receiver axes and measuring transmitter beamwidth is presented. The multiple-scattered components of backscattered light are determined by inserting a center-blocked field stop to restrict the receiver field of view to the region outside of the diverging transmitted beam. Typical returns with and without the opaque field stop indicate the amplitude of multiple scattering from cirrus clouds and prove the feasibility of this technique. The depolarization ratio delta and backscatter coefficients from an altostratus cloud illustrate the potential of these quantities for the study of cloud structure and phase.

  13. Compton backscattered collmated X-ray source

    DOEpatents

    Ruth, Ronald D.; Huang, Zhirong

    2000-01-01

    A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

  14. Compton backscattered collimated x-ray source

    DOEpatents

    Ruth, R.D.; Huang, Z.

    1998-10-20

    A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

  15. Compton backscattered collimated x-ray source

    DOEpatents

    Ruth, Ronald D.; Huang, Zhirong

    1998-01-01

    A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

  16. Hard Diffraction at CDF

    SciTech Connect

    Melese, P.; CDF Collaboration

    1997-06-01

    We present results on diffractive production of hard processes in {anti p}p collisions at {radical}s = 1.8 TeV at the Tevatron using the CDF detector. The signatures used to identify diffractive events are the forward rapidity gap and/or the detection of a recoil antiproton with high forward momentum. We have observed diffractive W- boson, dijet, and heavy quark production. We also present results on double-pomeron production of dijets.

  17. X-ray Microdiffraction and EBSD Study of FSP Induced Structural/Phase Transitions in a Ni-based Superalloy

    SciTech Connect

    Barabash, Oleg M; Barabash, Rozaliya; Ice, Gene E; Feng, Zhili; Gandy, Dr. David

    2009-01-01

    Severe plastic deformation during Friction Stir Processing (FSP) of an IN738 Ni-based superalloy was studied by means of X-ray polychromatic microdiffraction, EBSD, scanning electron and optical microscopies. Modeling of the physical properties and phase composition was also performed. Several distinct zones are formed during FSP including a stir zone (SZ), a thermal-mechanical affected zone (TMAZ) and a heat affected zone (HAZ). Each zone has distinct microstructure after FSP. The initial dendrite structure is preserved in the HAZ, while strengthening ??-phase particles partially dissolve and coagulate. Plastic deformation of the base material dendrites takes place in the TMAZ and a large number of geometrically necessary dislocations are formed. The extent of deformation increases toward the SZ and the dendrite structure is completely destroyed in the SZ and replaced by a fine submicrocrystalline microstructure.

  18. EBSD characterisation of Y2Ba4CuUOx phase in melttextured YBCO with addition of depleted uranium oxide

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Mücklich, F.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.

    2006-06-01

    Melt-textured YBCO samples processed with added Y2O3 and depleted uranium oxide (DU) contain nano-particles, which have been identified previously as Y2Ba4CuUOx (U-411). This phase has a cubic unit cell, which is clearly distinct from the orthorhombic Y-123 and Y-211 phases within the YBCO system. In samples with a high amount of DU addition (0.8 wt-% DU), U-2411 particles have sizes between 200 nm and several µm, so identification of the Kikuchi patterns of this phase becomes possible. Together with a parallel EDX analysis, the particles embedded in the Y-123 matrix can be identified unambiguously. In this way, a three-phase EBSD scan becomes possible, allowing also the identification of nanometre-sized particles in the sample microstructure.

  19. 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.

  20. Surface Roughness, Optical Shadowing, and Radar Backscatter

    NASA Astrophysics Data System (ADS)

    Shepard, M. K.; Campbell, B. A.

    1996-03-01

    The topography of natural surfaces at scales of a few meters or less is commonly referred to as roughness. These variations in height and slope, their magnitude, and the changes in structure as a function of scale length are of fundamental importance to interpretation of geologic emplacement regimes and subsequent modification. For most planetary studies and many terrestrial situations, no in situ observations of the ground are available, and remote sensing data are used to infer the nature of the terrain. For optical, infrared, and microwave measurements, surface roughness and its scale-dependence have a large impact on the brightness, polarization, angular scattering properties, and wavelength-dependence of reflected energy. The link between surface roughness and specific remote sensing properties for many types of observations, however, remains elusive. We focus here on the nature of roughness and its scale-dependence for terrestrial rocky surfaces, and the effect of such changes on optical shadowing and radar backscatter.

  1. The Discovery of Partially Coherent Backscatter in Radar Observations of Precipitation and Its Potential Impact on Radar Hydrometeorology

    NASA Astrophysics Data System (ADS)

    Jameson, A. R.; Kostinski, A.

    2009-12-01

    This work presents the discovery of radar coherent scatter in precipitation. The theory shows that the coherent scatter can be generated by spatially correlated precipitation structures acting like diffraction gratings in resonance with the radar wavelength in which the elements of the structures all moving at practically the same velocity. Such diffraction gratings are well known to produce fields of maxima and minima of back-scattered intensities. As they move through the radar beam these fields produce distinctive power oscillations of frequencies f that can not be attributed to incoherent scatter. A different kind of back-scattered power spectrum, Z(f) is then defined. This power spectrum is the distribution of the total backscattered power over the power oscillations characterized by f. This then allows us to calculate the coherent scatter contribution to the total back-scattered power. It also has the advantage that it can be computed even for incoherent radars since Doppler information is not required. Data in snow and rain were analyzed. Coherent scatter was found to be pervasive throughout these two minutes of data with only up to at most 4% of the rain observations being examples of pure incoherent scatter. We also note that when coherent scatter is present, the usual relations between the standard deviation of the observed Doppler velocities and the decorrelation time in common use are no longer valid so that signal statistics are affected. Specifically, it is also shown that these lower frequencies are associated with the increased temporal coherency and are directly linked to the Doppler spectral peaks through integer multiples of λ/2, a characteristic of coherent Bragg scatter. It seems, then, that radar coherent scatter from precipitation exists and is generated by the mechanism introduced here. Moreover, it appears to be pervasive in these data. However, because this only represents a few minutes of observations, one should not over generalize

  2. A method for removing arm backscatter from EPID images

    SciTech Connect

    King, Brian W.; Greer, Peter B.

    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.

  3. Transmitted beam profiles, integrated backscatter, and rangeresolved backscatter in inhomogeneous laboratory water droplet clouds.

    PubMed

    Bissonnette, L R; Smith, R B; Ulitsky, A; Houston, J D; Carswell, A I

    1988-06-15

    Using laser sources at wavelengths of 1.06 and 10.6 microm, transmitted beam profiles, integrated backscatter, and range-resolved backscatter were measured in laboratory-generated water droplet clouds. Clouds with carefully controlled properties were produced in a specially designed cloud chamber. Inhomogeneities were introduced by partitioning the cloud chamber into three adjacent sections separated by air screens. The measurements show the influence of multiple-scattering effects in both the forward and backward measurement geometries, and these are investigated as functions of optical depth, cloud inhomogeneity, and receiver field of view. These data are unique in many ways, and they provide a great deal of insight to the scattering processes which directly affect lidar-type measurements. As well, these measurements provide a welldocumented and detailed database for model validation. Very good agreement is demonstrated with the solutions derived from the multiscattering propagation model described in a companion paper [Appl. Opt. 27, 2478 (1988), same issue].

  4. Phononic crystal diffraction gratings

    NASA Astrophysics Data System (ADS)

    Moiseyenko, Rayisa P.; Herbison, Sarah; Declercq, Nico F.; Laude, Vincent

    2012-02-01

    When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

  5. Radial Reflection diffraction tomorgraphy

    DOEpatents

    Lehman, Sean K

    2013-11-19

    A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.

  6. Radial reflection diffraction tomography

    DOEpatents

    Lehman, Sean K.

    2012-12-18

    A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.

  7. Parametric Powder Diffraction

    NASA Astrophysics Data System (ADS)

    David, William I. F.; Evans, John S. O.

    The rapidity with which powder diffraction data may be collected, not only at neutron and X-ray synchrotron facilities but also in the laboratory, means that the collection of a single diffraction pattern is now the exception rather than the rule. Many experiments involve the collection of hundreds and perhaps many thousands of datasets where a parameter such as temperature or pressure is varied or where time is the variable and life-cycle, synthesis or decomposition processes are monitored or three-dimensional space is scanned and the three-dimensional internal structure of an object is elucidated. In this paper, the origins of parametric diffraction are discussed and the techniques and challenges of parametric powder diffraction analysis are presented. The first parametric measurements were performed around 50 years ago with the development of a modified Guinier camera but it was the automation afforded by neutron diffraction combined with increases in computer speed and memory that established parametric diffraction on a strong footing initially at the ILL, Grenoble in France. The theoretical parameterisation of quantities such as lattice constants and atomic displacement parameters will be discussed and selected examples of parametric diffraction over the past 20 years will be reviewed that highlight the power of the technique.

  8. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

    1999-01-01

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

  9. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, M.D.; Britten, J.A.; Nguyen, H.T.; Boyd, R.; Shore, B.W.

    1999-05-25

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described. 7 figs.

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

    SciTech Connect

    Nghiem, S.V.; Li, F.K.

    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.

  11. Fraunhofer Diffraction and Polarization.

    ERIC Educational Resources Information Center

    Fortin, E.

    1979-01-01

    Describes an experiment for the intermediate undergraduate optics laboratory designed to illustrate simultaneously some aspects of the phenomena of diffraction; interference, coherence, apodization, the Fresnel-Arago law; as well as of the interrelations between these concepts. (HM)

  12. Fresnel Coherent Diffractive Imaging

    NASA Astrophysics Data System (ADS)

    Williams, G. J.; Quiney, H. M.; Dhal, B. B.; Tran, C. Q.; Nugent, K. A.; Peele, A. G.; Paterson, D.; de Jonge, M. D.

    2006-07-01

    We present an x-ray coherent diffractive imaging experiment utilizing a nonplanar incident wave and demonstrate success by reconstructing a nonperiodic gold sample at 24 nm resolution. Favorable effects of the curved beam illumination are identified.

  13. Multigap Diffraction at LHC

    SciTech Connect

    Goulianos, Konstantin

    2005-10-06

    The large rapidity interval available at the Large Hadron Collider (LHC) offers an arena in which the QCD aspects of diffraction may be explored in an environment free of gap survival complications using events with multiple rapidity gaps.

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

    SciTech Connect

    Yonamine, T.; Fukuhara, M.; Archanjo, B. S.; Missell, F. P.

    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.

  15. 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.

  16. Reflective diffraction grating

    DOEpatents

    Lamartine, Bruce C.

    2003-06-24

    Reflective diffraction grating. A focused ion beam (FIB) micromilling apparatus is used to store color images in a durable medium by milling away portions of the surface of the medium to produce a reflective diffraction grating with blazed pits. The images are retrieved by exposing the surface of the grating to polychromatic light from a particular incident bearing and observing the light reflected by the surface from specified reception bearing.

  17. X-Ray Backscatter Machine Support Frame

    NASA Technical Reports Server (NTRS)

    Cannon, Brooke

    2010-01-01

    This summer at Kennedy Space Center, I spent 10 weeks as an intern working at the Prototype Development Lab. During this time I learned about the design and machining done here at NASA. I became familiar with the process from where a design begins in Pro/Engineer and finishes at the hands of the machinists. As an intern I was given various small jobs to do and then one project of my own. My personal project was a job for the Applied Physics Lab; in their work they use an X-Ray Backscatter machine. Previously it was resting atop a temporary frame that limited the use of the machine. My job was to design a frame for the machine to rest upon that would allow a full range of sample sizes. The frame was required to support the machine and provide a strain relief for the cords attached to the machine as it moved in the x and y directions. Calculations also had to be done to be sure the design would be able to withstand any loads or outside sources of stress. After the calculations proved the design to be ready to withstand the requirements, the parts were ordered or fabricated, as required. This helped me understand the full process of jobs sent to the Prototype Development Lab.

  18. 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.

  19. Crystallography of Magnetite Plaquettes and their Significance as Asymmetric Catalysts for the Synthesis of Chiral Organics in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.

    2015-01-01

    We have previously observed the magnetite plaquettes in carbonaceous chondrites using scanning electron microscope (SEM) imaging, examined the crystal orientation of the polished surfaces of magnetite plaquettes in CI Orgueil using electron backscattered diffraction (EBSD) analysis, and concluded that these magnetite plaquettes are likely naturally asymmetric materials. In this study, we expanded our EBSD observation to other magnetite plaquettes in Orgueil, and further examined the internal structure of these remarkable crystals with the use of X-ray computed microtomography.

  20. Deformation twinning in polycrystalline NiMnGa alloys

    NASA Astrophysics Data System (ADS)

    Chulist, R.; Pötschke, M.; Lippmann, T.; Oertel, C.-G.; Skrotzki, W.

    2010-07-01

    The texture and local orientation after compression of a NiMnGa polycrystal and a bicrystal with 5M modulated structure were measured with synchrotron radiation and electron backscatter diffraction (EBSD), respectively. Compression of both samples leads to motion of those twin boundaries changing the volume fraction of particular martensitic variants in such a way that the shortest axis (c-axis) becomes preferentially aligned parallel to the compression axis. EBSD directly confirms the motion of twin boundaries within individual grains.

  1. BASIS: A New Backscattering Spectrometer at the SNS

    SciTech Connect

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

    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.

  2. 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.

  3. Comparison of radar backscatter from Antarctic and Arctic sea ice

    NASA Technical Reports Server (NTRS)

    Hosseinmostafa, R.; Lytle, V.

    1992-01-01

    Two ship-based step-frequency radars, one at C-band (5.3 GHz) and one at Ku-band (13.9 GHz), measured backscatter from ice in the Weddell Sea. Most of the backscatter data were from first-year (FY) and second-year (SY) ice at the ice stations where the ship was stationary and detailed snow and ice characterizations were performed. The presence of a slush layer at the snow-ice interface masks the distinction between FY and SY ice in the Weddell Sea, whereas in the Arctic the separation is quite distinct. The effect of snow-covered ice on backscattering coefficients (sigma0) from the Weddell Sea region indicates that surface scattering is the dominant factor. Measured sigma0 values were compared with Kirchhoff and regression-analysis models. The Weibull power-density function was used to fit the measured backscattering coefficients at 45 deg.

  4. Backscattering by very small particles in coastal waters

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Gray, Deric J.

    2015-10-01

    The volume scattering and backscattering by very small particles (VSPs) of sizes <0.2 µm in four coastal waters in U.S. (Chesapeake Bay, Monterey Bay, Mobile Bay, and the LEO-15 site) were estimated by inverting the measured volume scattering functions (VSFs) at 532 nm. The measured VSFs are consistent with concurrent measurements of total scattering coefficients by the ac-meters and angular scattering at 100, 125, and 150° by the ECO-VSF sensor and at 140° by the HydroScat-6 sensor. The inferred backscattering coefficients by the VSPs correlate strongly with the absorption coefficients measured for the colored dissolved organic matter, indicating that the dissolved portion of particles do scatter light. In the coastal waters that we studied, the backscattering by VSPs dominate over larger particles (of sizes >0.2 µm), accounting for 40-80% of total backscattering at 532 nm, while only account for <5% of total scattering.

  5. Preliminary Lidar Experiment to Study the Backscatter Amplification

    NASA Astrophysics Data System (ADS)

    Razenkov, Igor A.; Banakh, Victor A.

    2016-06-01

    Long-term continuous measurements for detection relative backscatter amplification on a horizontal path of 2 km long are performed by using a specific micro pulse lidar. The laser beam path is limited by a solid obstacle. The lidar is located next to an ultrasonic anemometer that measures 3D wind velocity and temperature; the laser spot on the obstacle is observed by using a telephoto lens. The results showed that the backscatter amplification has a clear diurnal variation. Moreover, the backscatter amplification was completely absent in the morning and evening under neutral stratification in the atmospheric surface layer. At night and in the daytime there was a significant increase of the backscatter amplification coefficient.

  6. Lidar measurements of backscatter amplification in a surface atmosphere

    NASA Astrophysics Data System (ADS)

    Banakh, Victor A.; Razenkov, Igor A.

    2015-11-01

    The results of long-term continuous measurements of the atmospheric backscattering amplification on an atmospheric surface path 2 km long with a two-channel micropulse lidar based on waveguide laser are presented. It is shown that the backscatter amplification coefficient has the pronounced diurnal behavior. In the day and night time, the atmospheric backscattering amplification is maximal and the amplification coefficient can exceed two. The amplification is low or absent in the morning and evening hours at the neutral temperature stratification in the atmospheric surface layer. The backscattering amplification coefficient increases with an increase of the structure constant of the refractive index of air, as well as with an increase of random wander of optical image of the probing laser beam spot at the distance 2 km from the lidar.

  7. Diurnal Thermal Cycling Effects on Backscatter of Thin Sea Ice

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Gow, A. J.; Perovich, D. K.; Hsu, C. C.; Ding, K. H.; Kong, J. A.; Grenfell, T. C.

    1996-01-01

    To invesigate effects on polarimetric backscatter of sea ice grown under diurnal cycling conditions, we carried out an experiment inJanuary 1994 at the outdoor Geophysical Research Facility in the Cold Regions Research and Engineering Laboratory.

  8. Quantifying phase function influence in subdiffusively backscattered light.

    PubMed

    Bodenschatz, Nico; Krauter, Philipp; Liemert, André; Kienle, Alwin

    2016-03-01

    Light backscattering at short source-detector separations is considerably influenced by the scattering phase function of a turbid medium. We seek to more precisely relate a medium's subdiffusive backscattering to the angular scattering characteristics of its microstructure. First, we demonstrate the inability of the scattering asymmetry g1 = < cos θ > to predict phase function influence on backscattering and reveal ambiguities related to the established phase function parameter γ. Through the use of high-order similarity relations, we introduce a new parameter that more accurately relates a scattering phase function to its subdiffusive backscattering intensity. Using extensive analytical forward calculations based on solutions to the radiative transfer equation in the spatial domain and spatial frequency domain, we demonstrate the superiority of our empirically derived quantifier σ over the established parameter γ. PMID:26968384

  9. Simulation of coherent backscattering of light in nematic liquid crystals

    SciTech Connect

    Aksenova, E. V. Kokorin, D. I. Romanov, V. P.

    2012-08-15

    Multiple scattering of light by the fluctuations of the director in a nematic liquid crystal (NLC) aligned by a magnetic field is considered. A peak of coherent backscattering is calculated by numerical simulation. Since the indicatrix of single scattering for a liquid crystal (LC) is known exactly, the calculations are carried out without any simplifying assumptions on the parameters of the liquid crystal. Multiple scattering is simulated as a random walk of photons in the medium. A peak of coherent backscattering in such a medium is very narrow; therefore, the so-called semianalytical method is applied. The parameters of the backscattering peak obtained by numerical simulation are compared with the available experimental data and with the results of analytical approximations. It turns out that the experimental data are in good agreement with the results of simulation. The results of numerical simulation adequately describe the anisotropy and the width of the backscattering peak.

  10. Aerosol Lidar for the Relative Backscatter Amplification Measurements

    NASA Astrophysics Data System (ADS)

    Razenkov, Igor A.; Banakh, Victor A.; Nadeev, Alexander I.

    2016-06-01

    Backscatter amplification presents only in a turbulent atmosphere, when the laser beam is propagates twice through the same inhomogeneities. We proposed technical solution to detect backscatter amplification. An aerosol micro pulse lidar with a beam expansion via receiving telescope was built to study this effect. Our system allows simultaneous detection of two returns from the same scattering volume: exactly on the axis of the laser beam and off the axis.

  11. Ultrasonic Backscattering from Suspended Erythrocytes: Dependence on Frequency and Size.

    NASA Astrophysics Data System (ADS)

    Kuo, Ihyuan

    The ultrasonic scattering properties of blood have been intensively investigated since the echo signal from red blood cells carries abundant diagnostic information for the study of blood flow and blood properties in the vessels. Recently, ultrasound of frequency higher than 20 MHz has been implemented in intravascular imaging to obtain better images of the vessel wall. In this research measurements were extended to 30 MHz to better understand the effect of blood on the operation of these intravascular devices. The experimentally measured backscatter of saline suspended porcine erythrocytes for frequency up to 30 MHz agrees very well with the theoretical analysis which indicate that Rayleigh scattering is still valid below this frequency. The analysis utilize the T-matrix method to calculate the backscattering cross section of an erythrocyte modeled as a fluid sphere, disk, and biconcave disk. Measurements on the backscattering coefficients of porcine, bovine, and lamb erythrocytes reveal that the backscatter has a square dependence on cell volume. The cell size dependent backscatter is also analyzed via a continuum approach. It is found that the echo intensity of high frequency ultrasound suffers greatly from the attenuation. The dilemma may be solved by using a spherically focused transducer. An analysis of the focused beam reflected from a perfect planar reflector leads to the modification of the standard substitution method for the backscatter measurement since the "image source" theory is found to be inappropriate for the focused beam. Reflection of the focused beam near the focal point is described based on Huygens' principle. Experimental and theoretical results indicate that the backscatter is dependent upon the position of the scatterer and the geometry of the transducer if a focused beam is used. Since ultrasound velocity information is needed for scattering measurements, an innovative method for measuring the acoustic speed and the attenuation coefficient

  12. Multipath analysis diffraction calculations

    NASA Technical Reports Server (NTRS)

    Statham, Richard B.

    1996-01-01

    This report describes extensions of the Kirchhoff diffraction equation to higher edge terms and discusses their suitability to model diffraction multipath effects of a small satellite structure. When receiving signals, at a satellite, from the Global Positioning System (GPS), reflected signals from the satellite structure result in multipath errors in the determination of the satellite position. Multipath error can be caused by diffraction of the reflected signals and a method of calculating this diffraction is required when using a facet model of the satellite. Several aspects of the Kirchhoff equation are discussed and numerical examples, in the near and far fields, are shown. The vector form of the extended Kirchhoff equation, by adding the Larmor-Tedone and Kottler edge terms, is given as a mathematical model in an appendix. The Kirchhoff equation was investigated as being easily implemented and of good accuracy in the basic form, especially in phase determination. The basic Kirchhoff can be extended for higher accuracy if desired. A brief discussion of the method of moments and the geometric theory of diffraction is included, but seems to offer no clear advantage in implementation over the Kirchhoff for facet models.

  13. TCR backscattering characterization for microwave remote sensing

    NASA Astrophysics Data System (ADS)

    Riccio, Giovanni; Gennarelli, Claudio

    2014-05-01

    A Trihedral Corner Reflector (TCR) is formed by three mutually orthogonal metal plates of various shapes and is a very important scattering structure since it exhibits a high monostatic Radar Cross Section (RCS) over a wide angular range. Moreover it is a handy passive device with low manufacturing costs and robust geometric construction, the maintenance of its efficiency is not difficult and expensive, and it can be used in all weather conditions (i.e., fog, rain, smoke, and dusty environment). These characteristics make it suitable as reference target and radar enhancement device for satellite- and ground-based microwave remote sensing techniques. For instance, TCRs have been recently employed to improve the signal-to-noise ratio of the backscattered signal in the case of urban ground deformation monitoring [1] and dynamic survey of civil infrastructures without natural corners as the Musmeci bridge in Basilicata, Italy [2]. The region of interest for the calculation of TCR's monostatic RCS is here confined to the first quadrant containing the boresight direction. The backscattering term is presented in closed form by evaluating the far-field scattering integral involving the contributions related to the direct illumination and the internal bouncing mechanisms. The Geometrical Optics (GO) laws allow one to determine the field incident on each TCR plate and the patch (integration domain) illuminated by it, thus enabling the use of a Physical Optics (PO) approximation for the corresponding surface current densities to consider for integration on each patch. Accordingly, five contributions are associated to each TCR plate: one contribution is due to the direct illumination of the whole internal surface; two contributions originate by the impinging rays that are simply reflected by the other two internal surfaces; and two contributions are related to the impinging rays that undergo two internal reflections. It is useful to note that the six contributions due to the

  14. Crystallographic Relationships of Silicate-hosted Magnetite Inclusions Determined with Electron Backscatter Pattern Indexing (EBSP)

    NASA Astrophysics Data System (ADS)

    Feinberg, J. M.; Wenk, H.; Renne, P. R.; Scott, G. R.

    2002-12-01

    Crystallographically controlled laths of magnetite exsolved in silicates such as clinopyroxene and plagioclase are common features in gabbros and mafic granulite facies rocks. As the inclusions cool below the Curie temperature of magnetite (580°C) they record a component of the direction and intensity of the Earth's ambient magnetic field. The extreme anisotropy of the inclusions' aspect ratio allows them to retain an unusually stable magnetization, as exemplified by their single-domain behavior. In order to transform these magnetite inclusions into a useful paleomagnetic tool it is necessary to clearly describe the epitaxial relationship between the magnetite and its host silicate phases. In the past the crystallographic orientation of magnetite inclusions and their host silicates were determined using single-crystal X-ray diffraction or diffraction patterns obtained with a transmission electron microscope. Although both of these techniques are ultimately successful, they are time consuming and cumbersome. The Electron Backscatter Diffraction Pattern (EBSP) technique is an alternative approach that uses diffraction patterns of Kikuchi bands generated in a scanning electron microscope. The geometric relationships between intersecting Kikuchi bands can be used to determine the orientation of a crystal. Generally the EBSP technique is used to determine preferred orientation patterns in aggregates. However, in this application we use it to investigate local crystallographic relationships. First, inclusions in a thin section are visualized on a backscattered electron image and verified chemically with an EDX signal. Then EBSPs are produced for both the host silicate and the magnetite inclusions and the orientation relationship is ascertained. The EBSP technique's straightforward sample preparation and rapid measurement time, combined with the broad accessibility of scanning electron microscopes allow scientists to more efficiently determine crystallographic

  15. Bomb Detection Using Backscattered X-Rays

    SciTech Connect

    Jacobs, J.; Lockwood, G.; Selph, M; Shope, S.; Wehlburg, J.

    1998-10-01

    Bomb Detection Using Backscattered X-rays* Currently the most common method to determine the contents of a package suspected of containing an explosive device is to use transmission radiography. This technique requires that an x-ray source and film be placed on opposite sides of the package. This poses a problem if the pachge is placed so that only one side is accessible, such as against a wall. There is also a threat to persomel and property since exTlosive devices may be "booby trapped." We have developed a method to x-ray a paclage using backscattered x-rays. This procedure eliminates the use of film behind the target. All of the detection is done from the same side as the source. When an object is subjected to x-rays, some of them iare scattered back towards the source. The backscattenng of x-rays is propordoml to the atomic number (Z) of the material raised to the 4.1 power. This 24"' dependence allows us to easily distinguish between explosives, wires, timer, batteries, and other bomb components. Using transmission radiography-to image the contents of an unknown package poses some undesirable risks. The object must have an x-ray film placed on the side opposite the x-ray source; this cannot be done without moving the package if it has been placed firmly against a wall or pillar. Therefore it would be extremely usefid to be able to image the contents of a package from only one side, without ever having to disturb the package itself. where E is the energy of the incoming x-ray. The volume of x-rays absorbed is important because it is, of course, directly correlated to the intensity of x-mys that will be scattered. Most of the x-rays that scatter will do so in a genemlly forward direction; however, a small percentage do scatter in a backward direction. Figure 1 shows a diagram of the various fates of x-rays directed into an object. The package that was examined in this ex~enment was an attache case made of pressed fiberboardwith a vinyl covering. It was

  16. Diffraction by nanocrystals II.

    PubMed

    Chen, Joe P J; Millane, Rick P

    2014-08-01

    Nanocrystals with more than one molecule in the unit cell will generally crystallize with incomplete unit cells on the crystal surface. Previous results show that the ensemble-averaged diffraction by such crystals consists of a usual Bragg component and two other Bragg-like components due to the incomplete unit cells. Using an intrinsic flexibility in the definition of the incomplete-unit-cell part of a crystal, the problem is formulated such that the magnitude of the Bragg-like components is minimized, which leads to a simpler and more useful interpretation of the diffraction. Simulations show the nature of the relative magnitudes of the diffraction components in different regions of reciprocal space and the effect of crystal faceting. PMID:25121528

  17. Robust diffraction correction method for high-frequency ultrasonic tissue characterization

    NASA Astrophysics Data System (ADS)

    Raju, Balasundar

    2001-05-01

    The computation of quantitative ultrasonic parameters such as the attenuation or backscatter coefficient requires compensation for diffraction effects. In this work a simple and accurate diffraction correction method for skin characterization requiring only a single focal zone is developed. The advantage of this method is that the transducer need not be mechanically repositioned to collect data from several focal zones, thereby reducing the time of imaging and preventing motion artifacts. Data were first collected under controlled conditions from skin of volunteers using a high-frequency system (center frequency=33 MHz, BW=28 MHz) at 19 focal zones through axial translation. Using these data, mean backscatter power spectra were computed as a function of the distance between the transducer and the tissue, which then served as empirical diffraction correction curves for subsequent data. The method was demonstrated on patients patch-tested for contact dermatitis. The computed attenuation coefficient slope was significantly (p<0.05) lower at the affected site (0.13+/-0.02 dB/mm/MHz) compared to nearby normal skin (0.2+/-0.05 dB/mm/MHz). The mean backscatter level was also significantly lower at the affected site (6.7+/-2.1 in arbitrary units) compared to normal skin (11.3+/-3.2). These results show diffraction corrected ultrasonic parameters can differentiate normal from affected skin tissues.

  18. Calculating cellulose diffraction patterns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although powder diffraction of cellulose is a common experiment, the patterns are not widely understood. The theory is mathematical, there are numerous different crystal forms, and the conventions are not standardized. Experience with IR spectroscopy is not directly transferable. An awful error, tha...

  19. Diffraction with wavefront curvature

    NASA Astrophysics Data System (ADS)

    Nugent, K. A.; Peele, A. G.; Quiney, H. M.; Chapman, H. N.

    2005-05-01

    Modern X-ray optics can produce a focused synchrotron beam with curvature on a scale comparable to that of an isolated biomolecule or to the lattice spacing of a biomolecular crystal. It is demonstrated that diffraction of phase-curved beams from such systems allows unique and robust phase recovery.

  20. DIFFRACTION FROM MODEL CRYSTALS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although calculating X-ray diffraction patterns from atomic coordinates of a crystal structure is a widely available capability, calculation from non-periodic arrays of atoms has not been widely applied to cellulose. Non-periodic arrays result from modeling studies that, even though started with at...

  1. Diffract, then destroy

    NASA Astrophysics Data System (ADS)

    Ball, Philip

    2016-09-01

    A new implementation of X-ray diffraction using free-electron lasers can take snapshots of biological molecules that are inaccessible via X-ray crystallography. As Philip Ball reports, the technique can even be used to create stop-motion films of dynamic molecular processes

  2. Criteria of backscattering in chiral one-way photonic crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Pi-Ju; Chang, Shu-Wei

    2016-03-01

    Optical isolators are important devices in photonic circuits. To reduce the unwanted reflection in a robust manner, several setups have been realized using nonreciprocal schemes. In this study, we show that the propagating modes in a strongly-guided chiral photonic crystal (no breaking of the reciprocity) are not backscattering-immune even though they are indeed insensitive to many types of scatters. Without the protection from the nonreciprocity, the backscattering occurs under certain circumstances. We present a perturbative method to calculate the backscattering of chiral photonic crystals in the presence of chiral/achiral scatters. The model is, essentially, a simplified analogy to the first-order Born approximation. Under reasonable assumptions based on the behaviors of chiral photonic modes, we obtained the expression of reflection coefficients which provides criteria for the prominent backscattering in such chiral structures. Numerical examinations using the finite-element method were also performed and the results agree well with the theoretical prediction. From both our theory and numerical calculations, we find that the amount of backscattering critically depends on the symmetry of scatter cross sections. Strong reflection takes place when the azimuthal Fourier components of scatter cross sections have an order l of 2. Chiral scatters without these Fourier components would not efficiently reflect the chiral photonic modes. In addition, for these chiral propagating modes, disturbances at the most significant parts of field profiles do not necessarily result in the most effective backscattering. The observation also reveals what types of scatters or defects should be avoided in one-way applications of chiral structures in order to minimize the backscattering.

  3. Radiometric analysis of diffraction

    NASA Astrophysics Data System (ADS)

    Castañeda, R.; Betancur, R.; Herrera, J.; Carrasquilla, J.

    2008-04-01

    A description of Fresnel and Fraunhofer diffraction of quasi-homogenous optical fields in any state of spatial coherence is presented, which clearly differs from the classical formalism. Instead of the propagation of the cross-spectral density from the diffracting aperture to the observation plane, the diffracting aperture is regarded as a planar quasi-homogeneous source, whose generalised radiance is carried by the spatial coherence wavelets, and the power distribution at the observation plane is expressed in terms of the generalised radiant intensity. It allows interpreting the negative values of the generalised radiance as "negative energies" emitted along specific directions and subjected to the achievement of the conservation law of energy. This interpretation is not evident in the classical formalism. Consequently, interference can be thought as resulting of energy transfer over a given wavefront, due to the addition of equal amounts of "positive" and "negative" energies, along specific directions, to the contributions provided by the individual radiators of the radiant source. In this sense, the radiant flux from the source, which is provided only by the individual contributions, is redistributed depending on the spatial coherence properties of the field. This redistribution characterises the diffraction phenomenon. It is also shown that the supports of the complex degree of spatial coherence near the aperture edge are vignetted by the edge. This feature is a cause for the generalised radiance providing "negative energies", and constitutes the actual effect of the edge on diffraction. The approach is validated by the close concordance between the numerical and the experimental results, which should be regarded as a proof of the physical existence of the spatial coherence wavelets.

  4. The diffracted distribution of classical trajectories and interference between electrons

    NASA Astrophysics Data System (ADS)

    Zhao, Guo-Peng; Zhang, Yan-Hui; Cai, Xiang-Ji; Xu, Xiu-Lan; Kang, Li-Sha

    2016-10-01

    We use a semiclassical approximation to study the escape of electrons through a circular mesostructure with the diffractive effect at the entrance lead taken into consideration. We find that the fluctuating shapes of the escape probability manifests a good agreement with the diffracted distributions of the incident angles for different transverse modes, and show that several classical trajectories with certain lengths have prominent contributions on the escape probability. In addition, we define the coherence factor to investigate the interference between electrons for different transverse modes and we find that it is the coherent backscattering that is responsible for the prominent interference. Moreover, we find there is a good correspondence between the distribution of classical trajectories and the time-reversed path.

  5. Modeling multi-frequency diurnal backscatter from a walnut orchard

    NASA Technical Reports Server (NTRS)

    Mcdonald, Kyle C.; Dobson, Myron C.; Ulaby, Fawwaz T.

    1991-01-01

    The Michigan Microwave Canopy Scattering Model (MIMICS) is used to model scatterometer data that were obtained during the August 1987 EOS (Earth Observing System) synergism study. During this experiment, truck-based scatterometers were used to measure radar backscatter from a walnut orchard in Fresno County, California. Multipolarized L- and X-band data were recorded for orchard plots for which dielectric and evapotranspiration characteristics were monitored. MIMICS is used to model a multiangle data set in which a single orchard plot was observed at varying impedance angles and a series of diurnal measurements in which backscatter from this same plot was measured continuously over several 24-h periods. MIMICS accounts for variations in canopy backscatter driven by changes in canopy state that occur diurnally as well as on longer time scales. L-band backscatter is dependent not only on properties of the vegetation but also on properties of the underlying soil surface. The behavior of the X-band backscatter is dominated by properties of the tree crowns.

  6. Probabilities and statistics for backscatter estimates obtained by a scatterometer

    NASA Technical Reports Server (NTRS)

    Pierson, Willard J., Jr.

    1989-01-01

    Methods for the recovery of winds near the surface of the ocean from measurements of the normalized radar backscattering cross section must recognize and make use of the statistics (i.e., the sampling variability) of the backscatter measurements. Radar backscatter values from a scatterometer are random variables with expected values given by a model. A model relates backscatter to properties of the waves on the ocean, which are in turn generated by the winds in the atmospheric marine boundary layer. The effective wind speed and direction at a known height for a neutrally stratified atmosphere are the values to be recovered from the model. The probability density function for the backscatter values is a normal probability distribution with the notable feature that the variance is a known function of the expected value. The sources of signal variability, the effects of this variability on the wind speed estimation, and criteria for the acceptance or rejection of models are discussed. A modified maximum likelihood method for estimating wind vectors is described. Ways to make corrections for the kinds of errors found for the Seasat SASS model function are described, and applications to a new scatterometer are given.

  7. Remarks on the definition of the backscattering factor in AES

    NASA Astrophysics Data System (ADS)

    Jablonski, Aleksander

    2002-03-01

    It has been shown that the backscattering factor in AES can be defined as an integral of the product of the excitation depth distribution function and the emission depth distribution function. First function describes the number of ionizations as a function of depth while the second function describes the escape probability of Auger electrons created at different depths. The backscattering factor calculated from such definition is found to depend on the Auger electron emission angle. For emission angles up to 40° with respect to surface normal, this dependence is not pronounced. However, influence of the emission angle on the backscattering factor may be substantial at glancing emission angles. Values of the backscattering factor calculated from the proposed algorithm assuming the emission angle equal to 40° differ noticeably from values resulting from the Shimizu expression. The deviation may reach 18% at primary electron energy of 2000 eV. Furthermore, the backscattering factor may become smaller than unity at primary energies close to the ionization energy. This effect has been suggested in earlier studies.

  8. Colored Diffraction Catastrophes

    NASA Astrophysics Data System (ADS)

    Berry, M. V.; Klein, S.

    1996-03-01

    On fine scales, caustics produced with white light show vividly colored diffraction fringes. For caustics described by the elementary catastrophes of singularity theory, the colors are characteristic of the type of singularity. We study the diffraction colors of the fold and cusp catastrophes. The colors can be simulated computationally as the superposition of monochromatic patterns for different wavelengths. Far from the caustic, where the luminosity contrast is negligible, the fringe colors persist; an asymptotic theory explains why. Experiments with caustics produced by refraction through irregular bathroom-window glass show good agreement with theory. Colored fringes near the cusp reveal fine lines that are not present in any of the monochromatic components; these lines are explained in terms of partial decoherence between rays with widely differing path differences.

  9. Colored diffraction catastrophes.

    PubMed Central

    Berry, M V; Klein, S

    1996-01-01

    On fine scales, caustics produced with white light show vividly colored diffraction fringes. For caustics described by the elementary catastrophes of singularity theory, the colors are characteristic of the type of singularity. We study the diffraction colors of the fold and cusp catastrophes. The colors can be simulated computationally as the superposition of monochromatic patterns for different wavelengths. Far from the caustic, where the luminosity contrast is negligible, the fringe colors persist; an asymptotic theory explains why. Experiments with caustics produced by refraction through irregular bathroom-window glass show good agreement with theory. Colored fringes near the cusp reveal fine lines that are not present in any of the monochromatic components; these lines are explained in terms of partial decoherence between rays with widely differing path differences. Images Fig. 1 Fig. 2 Fig. 3 Fig. 6 Fig. 8 Fig. 9 Fig. 10 PMID:11607642

  10. Multiple wavelength diffractive imaging

    NASA Astrophysics Data System (ADS)

    Chen, Bo; Dilanian, Ruben A.; Teichmann, Sven; Abbey, Brian; Peele, Andrew G.; Williams, Garth J.; Hannaford, Peter; van Dao, Lap; Quiney, Harry M.; Nugent, Keith A.

    2009-02-01

    We demonstrate coherent diffraction imaging using multiple harmonics from a high-harmonic generation source. An algorithm is presented that builds the known incident spectrum into the reconstruction procedure with the result that the useable flux is increased by more than an order of magnitude. Excellent images are obtained with a resolution of (165±5)nm and compare very well with images from a scanning electron microscope.

  11. 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.

  12. Polychromatic diffraction contrast tomography

    SciTech Connect

    King, A.; Reischig, P.; Adrien, J.; Peetermans, S.; Ludwig, W.

    2014-11-15

    This tutorial review introduces the use of polychromatic radiation for 3D grain mapping using X-ray diffraction contrast tomography. The objective is to produce a 3D map of the grain shapes and orientations within a bulk, millimeter-sized polycrystalline sample. The use of polychromatic radiation enables the standard synchrotron X-ray technique to be applied in a wider range of contexts: 1) Using laboratory X-ray sources allows a much wider application of the diffraction contrast tomography technique. 2) Neutron sources allow large samples, or samples containing high Z elements to be studied. 3) Applied to synchrotron sources, smaller samples may be treated, or faster measurements may be possible. Challenges and particularities in the data acquisition and processing, and the limitations of the different variants, are discussed. - Highlights: • We present a tutorial review of polychromatic diffraction contrast tomography techniques. • The use of polychromatic radiation allows the standard synchrotron DCT technique to be extended to a range of other sources. • The characteristics and limitations of all variants of the techniques are derived, discussed and compared. • Examples using laboratory X-ray and cold neutron radiation are presented. • Suggestions for the future development of these techniques are presented.

  13. Effects of optical backscattering on silicon photonic hybrid laser performance

    NASA Astrophysics Data System (ADS)

    Pacradouni, V.; Klein, J.; Pond, J.

    2016-04-01

    We present numerical results on the effect of backscattering at the junctions of double bus ring resonators in a Vernier ring hybrid laser design. The structure is comprised off a pair of III-V gain media evanescently coupled to a silicon on insulator racetrack comprised of a pair of double bus ring resonators coupled together through straight and flared waveguide sections. We show how the small backscattering at the ring resonator junctions has the effect of splitting and shifting the resonances off the clockwise and counter clockwise propagating modes thereby modifying the feedback spectrum from the ideal case. We then simulate results such as light current (LI) curves, relative intensity noise (RIN) and laser spectrum, and compare the laser performance including backscattering effects with the ideal case.

  14. 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

  15. Backscattering between helical edge states via dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Del Maestro, Adrian; Hyart, Timo; Rosenow, Bernd

    2013-04-01

    We show that the nonequilibrium spin polarization of one-dimensional helical edge states at the boundary of a two-dimensional topological insulator can dynamically induce a polarization of nuclei via the hyperfine interaction. When combined with a spatially inhomogeneous Rashba coupling, the steady-state polarization of the nuclei produces backscattering between the topologically protected edge states leading to a reduction in the conductance which persists to zero temperature. We study these effects in both short and long edges, uncovering deviations from Ohmic transport at finite temperature and a current noise spectrum which may hold the fingerprints for experimental verification of the backscattering mechanism.

  16. Backscattering peak of hexagonal ice columns and plates.

    PubMed

    Borovoi, A; Grishin, I; Naats, E; Oppel, U

    2000-09-15

    The backward cross section of hexagonal ice crystals of arbitrary orientation is calculated for visible light by means of a ray-tracing code. It is shown that backscattering of the tilted crystals is caused by a corner-reflector-like effect. A very large peak of backscattering is found for a tilt of 32.5 degrees between the principal particle axis and the incidence direction. This peak is caused by multiple total internal reflections for part of the rays that are incident upon the skewed rectangular faces. Slant lidar measurements for remote sensing of cirrus clouds are proposed.

  17. Probing Molecular Dynamics by Laser-Induced Backscattering Holography.

    PubMed

    Haertelt, Marko; Bian, Xue-Bin; Spanner, Michael; Staudte, André; Corkum, Paul B

    2016-04-01

    We use differential holography to overcome the forward scattering problem in strong-field photoelectron holography. Our differential holograms of H_{2} and D_{2} molecules exhibit a fishbonelike structure, which arises from the backscattered part of the recolliding photoelectron wave packet. We demonstrate that the backscattering hologram can resolve the different nuclear dynamics between H_{2} and D_{2} with subangstrom spatial and subcycle temporal resolution. In addition, we show that attosecond electron dynamics can be resolved. These results open a new avenue for ultrafast studies of molecular dynamics in small molecules. PMID:27081975

  18. Probing Molecular Dynamics by Laser-Induced Backscattering Holography

    NASA Astrophysics Data System (ADS)

    Haertelt, Marko; Bian, Xue-Bin; Spanner, Michael; Staudte, André; Corkum, Paul B.

    2016-04-01

    We use differential holography to overcome the forward scattering problem in strong-field photoelectron holography. Our differential holograms of H2 and D2 molecules exhibit a fishbonelike structure, which arises from the backscattered part of the recolliding photoelectron wave packet. We demonstrate that the backscattering hologram can resolve the different nuclear dynamics between H2 and D2 with subangstrom spatial and subcycle temporal resolution. In addition, we show that attosecond electron dynamics can be resolved. These results open a new avenue for ultrafast studies of molecular dynamics in small molecules.

  19. 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.

  20. 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.

  1. Target reflectance measurements for calibration of lidar atmospheric backscatter data

    NASA Technical Reports Server (NTRS)

    Kavaya, M. J.; Menzies, R. T.; Haner, D. A.; Oppenheim, U. P.; Flamant, P. H.

    1983-01-01

    Wavelength and angular dependence of reflectances and depolarization in the 9-11 micron region are reported for four standard targets: flowers of sulfur, flame-sprayed aluminum, 20-grit sandblasted aluminum, and 400-grit silicon carbon sandpaper. Measurements are presented and compared using a CW CO2 grating-tunable laser in a laboratory backscatter apparatus, an integrating sphere, and a coherent pulsed TEA-CO2 lidar system operating in the 9-11 micron region. Reflectance theory related to the use of hard targets to calibrate lidar atmospheric backscatter data is discussed.

  2. 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.

  3. Optical backscattering properties of the "clearest" natural waters

    NASA Astrophysics Data System (ADS)

    Twardowski, M. S.; Claustre, H.; Freeman, S. A.; Stramski, D.; Huot, Y.

    2007-11-01

    During the BIOSOPE field campaign October-December 2004, measurements of inherent optical properties from the surface to 500 m depth were made with a ship profiler at stations covering over 8000 km through the Southeast Pacific Ocean. Data from a ~3000 km section containing the very clearest waters in the central gyre are reported here. The total volume scattering function at 117°, βt(117°), was measured with a WET Labs ECO-BB3 sensor at 462, 532, and 650 nm with estimated uncertainties of 2×10-5, 5×10-6, and 2×10-6 m-1 sr-1, respectively. These values were approximately 6%, 3%, and 3% of the volume scattering by pure seawater at their respective wavelengths. From a methodological perspective, there were several results: - distributions were resolvable even though some of the values from the central gyre were an order of magnitude lower than the lowest previous measurements in the literature; - Direct in-situ measurements of instrument dark offsets were necessary to accurately resolve backscattering at these low levels; - accurate pure seawater backscattering values are critical in determining particulate backscattering coefficients in the open ocean (not only in these very clear waters); the pure water scattering values determined by Buiteveld et al. (1994) with a [1+0.3S/37] adjustment for salinity based on Morel (1974) appear to be the most accurate estimates, with aggregate accuracies as low as a few percent; and - closure was demonstrated with subsurface reflectance measurements reported by Morel et al. (2007) within instrument precisions, a useful factor in validating the backscattering measurements. This methodology enabled several observations with respect to the hydrography and the use of backscattering as a biogeochemical proxy: -The clearest waters sampled were found at depths between 300 and 350 m, from 23.5° S, 118° W to 26° S, 114° W, where total backscattering at 650 nm was not distinguishable from pure seawater; -Distributions of

  4. Optical backscattering properties of the "clearest" natural waters

    NASA Astrophysics Data System (ADS)

    Twardowski, M. S.; Claustre, H.; Freeman, S. A.; Stramski, D.; Huot, Y.

    2007-07-01

    During the BIOSOPE field campaign October-December 2004, measurements of inherent optical properties from the surface to 500 m depth were made with a ship profiler at stations covering over ~8000 km through the Southeast Pacific Ocean. Data from a ~3000 km section containing the very clearest waters in the central gyre are reported here. The total volume scattering function at 117°, βt(117°), was measured with a WET Labs ECO-BB3 sensor at 462, 532, and 650 nm with estimated uncertainties of 2×10-5, 5×10-6, and 2×10-6 m-1 sr-1, respectively. These values were approximately 6%, 3%, and 3% of the scattering by pure seawater at their respective wavelengths. From a methodological perspective, there were several results: - bbp distributions were resolvable even though some of the values from the central gyre were an order of magnitude lower than the lowest previous measurements in the literature; - Direct in-situ measurements of instrument dark offsets were necessary to accurately resolve backscattering at these low levels; - accurate pure seawater backscattering values are critical in determining particulate backscattering coefficients in the open ocean (not only in these very clear waters); the pure water scattering values determined by Buiteveld et al. (1994) with a [1 + 0.3S/37] adjustment for salinity based on Morel (1974) appear to be the most accurate estimates, with aggregate accuracies as low as a few percent; and - closure was demonstrated with subsurface reflectance measurements reported by Morel et al. (2007) within instrument precisions, a useful factor in validating the backscattering measurements. This methodology enabled several observations with respect to the hydrography and the use of backscattering as a biogeochemical proxy: - The clearest waters sampled were found at depths between 300 and 350 m, from 23.5° S, 118° W to 26° S, 114° W, where total backscattering at 650 nm was not distinguishable from pure seawater; - Distributions of

  5. Diffraction of a Laser Beam.

    ERIC Educational Resources Information Center

    Jodoin, Ronald E.

    1979-01-01

    Investigates the effect of the nonuniform irradiance across a laser beam on diffraction of the beam, specifically the Fraunhofer diffraction of a laser beam with a Gaussian irradiance profile as it passes through a circular aperture. (GA)

  6. Aberrations of diffracted wave fields. II. Diffraction gratings.

    PubMed

    Mahajan, V N

    2000-12-01

    The Rayleigh-Sommerfeld theory is applied to diffraction of a spherical wave by a grating. The grating equation is obtained from the aberration-free diffraction pattern, and its aberrations are shown to be the same as the conventional aberrations obtained by using Fermat's principle. These aberrations are shown to be not associated with the diffraction process. Moreover, it is shown that the irradiance distribution of a certain diffraction order is the Fraunhofer diffraction pattern of the grating aperture as a whole aberrated by the aberration of that order. PMID:11140481

  7. Recent diffractive results from HERA

    NASA Astrophysics Data System (ADS)

    Valkárová, Alice

    2016-07-01

    The diffractive dijet cross sections for photoproduction and deep inelastic scattering were studied and compared with theoretical NLO QCD predictions. The results of exclusive dijet production were compared to predictions from models which are based on different assumptions about the nature of diffractive exchange. Isolated prompt photons in diffractive photoproduction produced inclusively or together with a jet were studied for the first time.

  8. Rutherford Backscattering Spectrometry analysis of iron-containing Bi2Se3 topological insulator thin films

    NASA Astrophysics Data System (ADS)

    Alarcon-Diez, V.; Eddrief, M.; Vickridge, I.

    2016-03-01

    Fe-containing Bi2Se3 topological insulators (TI) thin films have been grown to investigate the intricate interplay between topological order and the incorporation of ferromagnetic atoms. Here we present the quantitative characterisation of the Bi2Se3 thin films with up to 16 at% Fe incorporated during the growth process on GaAs (1 1 1) substrate by Molecular Beam Epitaxy. We report the elemental composition and depth profiles of the Bi2Se3:Fe films obtained using Rutherford Backscattering Spectrometry (RBS) and their formed crystalline phase obtained by X-ray diffraction (XRD). Resistance of the TI to beam-induced damage was investigated by channelling RBS. Using the elemental composition from RBS and the thickness from XRD measurements the Fe-free film density was deduced. For Fe-containing samples, the diffraction reveals the formation of two distinct crystalline phases, as well as their intergrowth pattern, in which the basal planes of Bi2Se3 coexist with an additional Fe-Se phase. This intergrown composite, with chemical compatibility of the Fe-Se phase with the crystalline Bi2Se3 structure, preserves the intrinsic topological surface states of the TI component despite the inhomogeneous distribution of the constituent phases. RBS analysis gives the stoichiometry of the Bi2Se3, and Bi2Se3:Fe samples (estimated between 0 and 16 at% Fe) and gives insights into the composition of FeSex phases present.

  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. Non Specular Diffractive Optics

    NASA Astrophysics Data System (ADS)

    Wang, Yunjin; Overcash, Dan; Morawice, Pawel; Yin, Ming; Datta, Timir

    2009-11-01

    Geometrically decorated two-dimensional (2D) discrete surfaces can be more effective than conventional smooth reflectors in managing wave radiation. Constructive non-specular wave scattering permits the scattering angle to be other than twice that of incidence and can result in gross violations of the law of reflection. A wide range of novel reflective behaviors ensues; including the phenomenon of negative reflection were energy transport remains on the same side of the normal. Also, at a critical incidence coherent superposition can force both the transmitted and reflected waves to graze the scattering surface thus synergistically reinforcing the diffractive process in a behavior reminiscent of critical internal reflection of ray optics. We experimentally demonstrate the concept with measurements on a one-dimensionally periodic system (grating) where the scattering angle is shown to be an inverse circular function of a function that depends on the diffractive index and the two angles. Excellent agreement is found between experimental data and theory. A preliminary report on our observations will be discussed.

  11. Keyhole coherent diffractive imaging

    NASA Astrophysics Data System (ADS)

    Abbey, Brian; Nugent, Keith A.; Williams, Garth J.; Clark, Jesse N.; Peele, Andrew G.; Pfeifer, Mark A.; de Jonge, Martin; McNulty, Ian

    2008-05-01

    The availability of third-generation synchrotrons and ultimately X-ray free-electron lasers is driving the development of many new methods of microscopy. Among these techniques, coherent diffractive imaging (CDI) is one of the most promising, offering nanometre-scale imaging of non-crystallographic samples. Image reconstruction from a single diffraction pattern has hitherto been possible only for small, isolated samples, presenting a fundamental limitation on the CDI method. Here we report on a form of imaging we term `keyhole' CDI, which can reconstruct objects of arbitrary size. We demonstrate the technique using visible light and X-rays, with the latter producing images of part of an extended object with a detector-limited resolution of better than 20nm. Combining the improved resolution of modern X-ray optics with the wavelength-limited resolution of CDI, the method paves the way for detailed imaging of a single quantum dot or of a small virus within a complex host environment.

  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. 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.

  14. Simulation of multistatic and backscattering cross sections for airborne radar

    NASA Astrophysics Data System (ADS)

    Biggs, Albert W.

    1986-07-01

    In order to determine susceptibilities of airborne radar to electronic countermeasures and electronic counter-countermeasures simulations of multistatic and backscattering cross sections were developed as digital modules in the form of algorithms. Cross section algorithms are described for prolate (cigar shape) and oblate (disk shape) spheroids. Backscattering cross section algorithms are also described for different categories of terrain. Backscattering cross section computer programs were written for terrain categorized as vegetation, sea ice, glacial ice, geological (rocks, sand, hills, etc.), oceans, man-made structures, and water bodies. PROGRAM SIGTERRA is a file for backscattering cross section modules of terrain (TERRA) such as vegetation (AGCROP), oceans (OCEAN), Arctic sea ice (SEAICE), glacial snow (GLASNO), geological structures (GEOL), man-made structures (MAMMAD), or water bodies (WATER). AGCROP describes agricultural crops, trees or forests, prairies or grassland, and shrubs or bush cover. OCEAN has the SLAR or SAR looking downwind, upwind, and crosswind at the ocean surface. SEAICE looks at winter ice and old or polar ice. GLASNO is divided into a glacial ice and snow or snowfields. MANMAD includes buildings, houses, roads, railroad tracks, airfields and hangars, telephone and power lines, barges, trucks, trains, and automobiles. WATER has lakes, rivers, canals, and swamps. PROGRAM SIGAIR is a similar file for airborne targets such as prolate and oblate spheroids.

  15. 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.

  16. 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.

  17. 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.

  18. Simulation of Neutron Backscattering applied to organic material detection

    SciTech Connect

    Forero, N. C.; Cruz, A. H.; Cristancho, F.

    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.

  19. Method and Apparatus for Computed Imaging Backscatter Radiography

    NASA Technical Reports Server (NTRS)

    Shedlock, Daniel (Inventor); Meng, Christopher (Inventor); Sabri, Nissia (Inventor); Dugan, Edward T. (Inventor); Jacobs, Alan M. (Inventor)

    2013-01-01

    Systems and methods of x-ray backscatter radiography are provided. A single-sided, non-destructive imaging technique utilizing x-ray radiation to image subsurface features is disclosed, capable of scanning a region using a fan beam aperture and gathering data using rotational motion.

  20. Ku-band ocean radar backscatter observations during SWADE

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Li, F. K.; Lou, S. H.; Neumann, G.

    1993-01-01

    We present results obtained by an airborne Ku-band scatterometer during the Surface Wave Dynamics Experiment (SWADE). The specific objective of this study is to improve our understanding of the relationship between ocean radar backscatter and near surface winds. The airborne scatterometer, NUSCAT, was flown on the NASA Ames C-130 over an instrumented oceanic area near 37 deg N and 74 deg W. A total of 10 flights from 27 Feb. to 9 Mar. 1991 were conducted. Radar backscatter at incidence angles of 0 to 60 deg were obtained. For each incidence angle, the NUSCAT antenna was azimuthally scanned in multiple complete circles to measure the azimuthal backscatter modulations. Both horizontal and vertical polarization backscatter measurements were made. In some of the flights, the cross-polarization backscatter was measured as well. Internal calibrations were carried out throughout each of the flights. Preliminary results indicate that the radar was stable to +/-0.3 dB for each flight. In this paper, we present studies of the backscatter measurements over several crossings of the Gulf Stream. In these crossings, large air-sea temperature differences were encountered and substantial changes in the radar cross section were observed. We summarize the observations and compare them to the changes of several wind variables across the Gulf Stream boundary. In one of the flights, the apparent wind near the cold side of the Gulf Stream was very low (less than 3 m/s). The behavior of the radar cross sections at such low wind speeds and a comparison with models are presented. A case study of the effects of swell on the absolute cross section and the azimuthal modulation pattern is presented. Significant wave heights larger than m were observed during SWADE. The experimentally observed effects of the swell on the radar backscatter are discussed. The effects are used to assess the uncertainties in wind retrieval due to underlying waves. A summary of azimuthal modulation from our ten

  1. Hard diffraction in Pythia 8

    NASA Astrophysics Data System (ADS)

    Overgaard Rasmussen, Christine

    2016-07-01

    We present an overview of the options for diffraction implemented in the general-purpose event generator Pythia 8 [1]. We review the existing model for soft diffraction and present a new model for hard diffraction. Both models use the Pomeron approach pioneered by Ingelman and Schlein, factorising the diffractive cross section into a Pomeron flux and a Pomeron PDF, with several choices for both implemented in Pythia 8. The model of hard diffraction is implemented as a part of the multiparton interactions (MPI) framework, thus introducing a dynamical gap survival probability that explicitly breaks factorisation.

  2. A comparative study of RADAR Ka-band backscatter

    NASA Astrophysics Data System (ADS)

    Mapelli, D.; Pierdicca, N.; Guerriero, L.; Ferrazzoli, Paolo; Calleja, Eduardo; Rommen, B.; Giudici, D.; Monti Guarnieri, A.

    2014-10-01

    Ka-band RADAR frequency range has not yet been used for Synthetic Aperture Radar (SAR) from space so far, although this technology may lead to important applications for the next generation of SAR space sensors. Therefore, feasibility studies regarding a Ka-band SAR instrument have been started [1][2], for the next generation of SAR space sensors. In spite of this, the lack of trusted references on backscatter at Ka-band revealed to be the main limitation for the investigation of the potentialities of this technology. In the framework of the ESA project "Ka-band SAR backscatter analysis in support of future applications", this paper is aimed at the study of wave interaction at Ka-band for a wide range of targets in order to define a set of well calibrated and reliable Ka-band backscatter coefficients for different kinds of targets. We propose several examples of backscatter data resulting from a critical survey of available datasets at Ka-band, focusing on the most interesting cases and addressing both correspondences and differences. The reliability of the results will be assessed via a preliminary comparison with ElectroMagnetic (EM) theoretical models. Furthermore, in support of future technological applications, we have designed a prototypal software acting as a "library" of earth surface radar response. In our intention, the output of the study shall contribute to answer to the need of a trustworthy Ka-Band backscatter reference. It will be of great value for future technological applications, such as support to instrument analysis, design and requirements' definition (e.g.: Signal to Noise Ratio, Noise Equivalent Sigma Zero).

  3. The {sigma} phase formation in annealed UNS S31803 duplex stainless steel: Texture aspects

    SciTech Connect

    Souza, C.M. Abreu, H.F.G.; Tavares, S.S.M.; Rebello, J.M.A.

    2008-09-15

    The influence of sigma phase precipitation on the texture of austenite in a duplex stainless steel UNS S31803 was investigated. Sigma phase quantification was precisely performed by electron backscattered scanning diffraction (EBSD) for some conditions. It was found that the increase of the sigma phase precipitation enhances the amount of Brass texture in the austenite phase.

  4. Dephasing effect on backscattering of helical surface states in 3D topological insulators.

    PubMed

    Liu, Haiwen; Jiang, Hua; Sun, Qing-Feng; Xie, X C

    2014-07-25

    We analyze the dephasing effect on the backscattering behavior of the helical surface states in 3D topological insulators. We show that the combination of dephasing and impurity scattering can cause backscattering in the helical states. Especially for the charge impurity case, the backscattering cross section becomes extremely large around the Dirac point. This large backscattering behavior can lead to the anomalous "gaplike" features found in recent experiments [T. Sato et al., Nat. Phys. 7, 840 (2011)].

  5. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, G.E.

    1996-08-29

    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. 8 figs.

  6. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, Gary E.

    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.

  7. Multilayer diffraction grating

    DOEpatents

    Barbee, T.W. Jr.

    1990-04-10

    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. 2 figs.

  8. Multilayer diffraction grating

    DOEpatents

    Barbee, Jr., Troy W.

    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.

  9. 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.

  10. 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.

  11. Interference of Backscatter from Two Droplets in a Focused Continuous Wave CO2 Doppler Lidar Beam

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Srivastava, Vandana

    1999-01-01

    Superposition of backscatter from two silicone oil droplets in a lidar beam was observed as an interference pattern on a single backscatter pulse with a distinct periodicity of 2 & #61552; also agreeing extremely well with theory. Slightly differing droplet speeds caused phase differences in backscatter, resulting in the interference pattern.

  12. Results on hard diffractive production

    SciTech Connect

    Goulianos, K.

    1995-07-01

    The results of experiments at hadron colliders probing the structure of the pomeron through hard diffraction are reviewed. Some results on deep inelastic diffractive scattering obtained a HERA are also discussed and placed in perspective. By using a properly normalized pomeron flux factor in single diffraction dissociation, as dictated by unitarity, the pomeron emerges as a combination of valence quark and gluon color singlets in a ratio suggested by asymptopia.

  13. 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

  14. 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.

  15. Porosity estimation of alumina samples based on resonant backscattering spectrometry

    NASA Astrophysics Data System (ADS)

    Mokhles Gerami, F.; Kakuee, O.; Mohammadi, S.

    2016-04-01

    In this work, columnar porous alumina samples were investigated using the 16O(α,α)16O resonance scattering at 3.045 MeV. If the incident energy is slightly above the resonance energy, a resonance peak appears in the energy spectra of the backscattered ions. The position and width of this peak for non-porous samples are mainly determined by the experimental setup, whilst for porous materials, the peak position shifts towards higher energies under certain conditions. This effect can be explained by the lower amount of material which the ions encounter along the backscattered trajectories. The energy shift of the resonance peak towards higher energies was revealed experimentally and discussed theoretically. The estimated porosities of the samples based on this energy shift were compared with those evaluated from the graphical analysis of the images obtained by field emission scanning electron microscopy.

  16. The depolarization - attenuated backscatter relation: CALIPSO lidar measurements vs. theory.

    PubMed

    Hu, Yongxiang; Vaughan, Mark; Liu, Zhaoyan; Lin, Bing; Yang, Ping; Flittner, David; Hunt, Bill; Kuehn, Ralph; Huang, Jiangping; Wu, Dong; Rodier, Sharon; Powell, Kathy; Trepte, Charles; Winker, David

    2007-04-30

    Using measurements obtained by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite, relationships between layer-integrated depolarization ratio (delta) and layer-integrated attenuated backscatter (gamma) are established for moderately thick clouds of both ice and water. A new and simple form of the delta-gamma relation for spherical particles, developed from Monte Carlo simulations and suitable for both water clouds and spherical aerosol particles, is found to agree well with the observations. A high-backscatter, low-depolarization delta-gamma relationship observed for some ice clouds is shown to result primarily from horizontally oriented plates and implies a preferential lidar ratio - depolarization ratio relation in nature for ice cloud particles containing plates.

  17. Lidar extinction-to-backscatter ratio of the ocean.

    PubMed

    Churnside, James H; Sullivan, James M; Twardowski, Michael S

    2014-07-28

    Bio-optical models are used to develop a model of the lidar extinction-to-backscatter ratio applicable to oceanographic lidar. The model is based on chlorophyll concentration, and is expected to be valid for Case 1 waters. The limiting cases of narrow- and wide-beam lidars are presented and compared with estimates based on in situ optical measurements. Lidar measurements are also compared with the model using in situ or satellite estimates of chlorophyll concentration. A modified lidar ratio is defined, in which the properties of pure sea water are removed. This modified ratio is shown to be nearly constant for wide-beam lidar operating in low-chlorophyll waters, so accurate inversion to derive extinction and backscattering is possible under these conditions. This ratio can also be used for lidar calibration.

  18. Electron Kinetic Effects on Raman Backscatter in Plasmas

    SciTech Connect

    Hur, M.S.; Suk, H.; Lindberg, R.R.; Charman, A.E.; Wurtele, J.S.

    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.

  19. Stimulated brillouin backscatter of a short-pulse laser

    SciTech Connect

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-11-03

    Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x{prime} = x {minus} V{sub g}t, t{prime} = t, where V{sub g} is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency).

  20. Study on lidar received backscattering signals using Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Yang, Kecheng; Ma, Yong; Lin, Jinzhang

    2003-05-01

    In this paper, an improved semi-analytic Monte Carlo method is used to simulate the lidar received backscattering signals. The H-G function is used to approximate the scattering phase function of seawater, from which we can derive the scattering angle directly, and a modified H-G function is used to calculate the probability of the photons received by the receiver at each scattering point, which greatly improves the accuracy of the simulation. The simulation result shows that the different parameters of air-sea system of lidar, such as lidar"s field of view, attenuation coefficient and single scattering albedo of seawater, greatly influence the lidar received backscattering signal waveform. Multiple scattering is studied to explain these phenomena.

  1. 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.

  2. 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.

  3. 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.

  4. Effects of vegetation canopy on the radar backscattering coefficient

    NASA Technical Reports Server (NTRS)

    Mo, T.; Blanchard, B. J.; Schmugge, T. J.

    1983-01-01

    Airborne L- and C-band scatterometer data, taken over both vegetation-covered and bare fields, were systematically analyzed and theoretically reproduced, using a recently developed model for calculating radar backscattering coefficients of rough soil surfaces. The results show that the model can reproduce the observed angular variations of radar backscattering coefficient quite well via a least-squares fit method. Best fits to the data provide estimates of the statistical properties of the surface roughness, which is characterized by two parameters: the standard deviation of surface height, and the surface correlation length. In addition, the processes of vegetation attenuation and volume scattering require two canopy parameters, the canopy optical thickness and a volume scattering factor. Canopy parameter values for individual vegetation types, including alfalfa, milo and corn, were also determined from the best-fit results. The uncertainties in the scatterometer data were also explored.

  5. Study of optical Laue diffraction

    SciTech Connect

    Chakravarthy, Giridhar E-mail: aloksharan@email.com; Allam, Srinivasa Rao E-mail: aloksharan@email.com; Satyanarayana, S. V. M. E-mail: aloksharan@email.com; Sharan, Alok E-mail: aloksharan@email.com

    2014-10-15

    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. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, Antonio J.; Butler, Michael A.; Sinclair, Michael B.; Senturia, Stephen D.

    1998-01-01

    An electrically-programmable diffraction grating. 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).

  7. CDF experimental results on diffraction

    SciTech Connect

    Gallinaro, Michele; /Rockefeller U.

    2009-04-01

    Experimental results on diffraction from the Fermilab Tevatron collider obtained by the CDF experiment are reviewed and compared. We report on the diffractive structure function obtained from dijet production in the range 0 < Q{sup 2} < 10,000 GeV{sup 2}, and on the |t| distribution in the region 0 < |t| < 1 GeV{sup 2} for both soft and hard diffractive events up to Q{sup 2} {approx} 4,500 GeV{sup 2}. Results on single diffractive W/Z production, forward jets, and central exclusive production of both dijets and diphotons are also presented.

  8. The effects of changes in loblolly pine biomass and soil moisture on ERS-1 SAR backscatter

    SciTech Connect

    Wang, Y.; Melack, J.M.; Davis, F.W. . Center for Remote Sensing and Environmental Optics); Kasischke, E.S.; Christensen, N.L. Jr. . School of the Environment)

    1994-07-01

    For young loblolly pine stands at Duke Forest (North Carolina, USA), when the ground was wet, the observed ERS-1 SAR backscatter from short-grass fields of 0.05 kg/m[sup 2] biomass was [ge] the backscatter from the stands, and there was no significant correlation between the backscatter and biomass. Under dry soil conditions, the backscatter increased about 2--3 dB as the biomass increased from 0.05 kg/m[sup 2] to about 0.5--1.5 kg/m[sup 2], and the backscatter may be saturated near a 0.5--1.5 kg/m[sup 2] biomass level. The correlation coefficient between the backscatter and biomass was r[sup 2] = 0.46. When the Santa Barbara microwave canopy backscatter model was applied to simulate the ERS-1 SAR backscatter from the stands over dry ground, modeled and observed backscatter had similar trends with increasing biomass. For these stands, sensitivity analyses using the model showed that as the surface-soil moisture increased, the major contributor to the total backscatter was changed from canopy volume scattering to surface backscatter between 0.4 kg/m[sup 2] and about 1 kg/m[sup 2]. Signal saturating at low standing biomass and high sensitivity to soil moisture conditions limit the value of a short-wave (C-band) and steep local incidence angle (23[degree]) microwave sensor such as the ERS-1 SAR for forest monitoring.

  9. 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.

  10. Analysis of lidar backscatter profiles in optically thin clouds.

    PubMed

    Young, S A

    1995-10-20

    The solution of the lidar equation for profiles of backscatter and extinction in optically thin clouds is constrained by values of the cloud transmittance determined from the elastically scattered lidar signals below and above the cloud. The method is extended to those cases in which an aerosol layer lies below or above the cloud layer. Examples are given in both cases. An analytical expression for the average lidar ratio in the cloud is derived for those cases in which molecular scattering is significant.

  11. Measurement of magnetic field using Rayleigh backscattering in optical fibres

    SciTech Connect

    Wuilpart, M.; Caucheteur, C.; Goussarov, A.; Aerssens, M.; Massaut, V.; Megret, P.

    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)

  12. Method and apparatus for measuring lung density by Compton backscattering

    DOEpatents

    Loo, B.W.; Goulding, F.S.

    1988-03-11

    The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons compton back-scattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to minimize systematic errors due to the presence of the chestwall and multiple scattering. 11 figs., 1 tab.

  13. Method and apparatus for measuring lung density by Compton backscattering

    DOEpatents

    Loo, Billy W.; Goulding, Frederick S.

    1991-01-01

    The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons Compton backscattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to monimize systematic errors due to the presence of the chestwall and multiple scattering.

  14. Laser transmission-backscattering through inhomogeneous cirrus clouds.

    PubMed

    Ou, Szu-Cheng; Takano, Yoshihide; Liou, Kuo-Nan; Lefevre, Randy J; Johnson, Michael W

    2002-09-20

    We have developed a two-dimensional (2D) model for inhomogeneous cirrus clouds in plane-parallel and spherical geometries for the analysis of the transmission and backscattering of high-energy laser beams. The 2D extinction-coefficient and mean effective ice-crystal size fields for cirrus clouds can be determined from a combination of the remote sensing of cirrus clouds by use of the Advanced Very High Resolution Radiometer on board National Oceanic and Atmospheric Administration satellites and the vertical profiling of ice-crystal size distributions available from limited measurements. We demonstrate that satellite remote sensing of the position and the composition of high cirrus can be incorporated directly in the computer model developed for the transmission and backscattering of high-energy laser beams in realistic atmospheres. The results of laser direct transmission, forward scattering, and backscattering are analyzed carefully with respect to aircraft height, cirrus cloud optical depth, and ice-crystal size and orientation. Uncertainty in laser transmission that is due to errors in the retrieved ice-crystal size is negligible. But uncertainty of the order of 2% can be produced if the retrieved optical depth has errors of +/-0.05. With both the aircraft and the target near the cloud top, the direct transmission decreases, owing to the propagation of the laser beam through the curved portion of the cloud top. This effect becomes more pronounced as the horizontal distance between the aircraft and the target increases.

  15. Visibility related to backscatter at 1.54 micron

    NASA Technical Reports Server (NTRS)

    Barber, T. L.; Larson, D. R.

    1986-01-01

    The lidar process was shown to have the necessary potential to fulfill the need for a remote measurement of visibility. Visibility can be inferred from a lidar return optical extinction. The wavelength 1.54 micron was chosen, being near the visible wavelength region and having a high eye safety threshol, 200,000 times higher than 1.06 micron; 1.54 is the erbium laser wavelength. This research utilized 105 measured height profiles of natural droplet size distributions data, taken in clouds, fog, and haze. These profiles were examined to determine the completeness of the droplet counting data. It was found that the particle spectrometer data were incomplete in the very light ford and haze so this portion of the data was eliminated. Utilizing the Mie theory, these droplet size distribution profiles were converted to backscatter at 1.54 micron and extinction in the visible region, 0.55 micron. Using Koschmeider's relationship, the extinction profiles were converted to visibility. The visibility and backscatter profiles were compared to develop a relationship between visibility and backscatter at 1.54 micron.

  16. Spectral absorption and backscatter measurements of suspended particles

    SciTech Connect

    Wouts, R.; Warnock, R.; Baker, S.; 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.

  17. 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.

  18. Experimental findings in 180{degree} backscattering enhancement from solids

    SciTech Connect

    Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D.

    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}

  19. Inspection of reinforced concrete samples by Compton backscattering technique

    NASA Astrophysics Data System (ADS)

    Boldo, E. M.; Appoloni, C. R.

    2014-02-01

    Reinforced concrete structures require frequent monitoring to ensure the concrete quality during its service life and for evaluation of in situ existing conditions. Compton backscattering of gamma rays is a nondestructive technique used for material characterization and detection of defects and inclusions in materials and can be employed on reinforced concrete. The methodology allows one-sided inspection of large structures, is relatively inexpensive and can be portable. The concept is based on detection of backscattered radiation produced from a collimated beam aimed at the sample. By measuring the spectrum of these scattered gamma rays it is possible to determine local density perturbations. In this work we used the Compton backscattering technique to locate and measure steel, defects and crushed stone inside concrete. The samples were irradiated with gamma rays from a Ø2 mm diameter collimated 241Am (100 mCi) source and the inelastically scattered photons were recorded at an angle of 135° by a high resolution CdTe semiconductor detector. Scanning was achieved by lateral movement of the sample blocks across the source and detector field of view in steps of 1 mm. A previous optimization of the experimental setup was performed with Monte Carlo simulation. The results showed that it was possible to locate inclusions and defects with Ø8 mm positioned at a depth of 20 mm below the surface of the sample. It was observed that aggregates such as crushed stone could mask defects at specific points due to high attenuation of the incident and scattered beam.

  20. Relationships between multipolarized radar backscatter and slash pine stand parameters

    NASA Technical Reports Server (NTRS)

    Hussin, Yousif Ali; Hoffer, Roger M.

    1989-01-01

    Multipolarized L-band (24.5 cm) aircraft radar data was obtained for a primarily forested area in northern Florida. Based on the results of previous studies by Hoffer and Hussin (1989), a swath of medium incidence angle (35-25 deg) data was defined. Three groups of slash pine stands were located in the data: 4- to 17-year-old plantations, 18- to 48-year-old plantations, and 16- to 53-year-old natural stands. Stand data obtained from the forest-products companies operating in the area include age, tree height, diameter-at-breast height, basal area, volume (cords/acre), and density (trees/acre). Each of these stand parameters were compared to each of the four polarizations (HH, VV, VH, and HV) of the radar data for each group of stands. Statistically significant relationships were found between the radar backscatter and the forest stand parameters only for the 4- to 17-year-old slash pine plantation stands. In general, the cross-polarized radar backscatter was more highly correlated with the various stand parameters than the like-polarized backscatter, and the VV-polarized data were more highly correlated than the HH-polarized data.

  1. Dependence of radar backscatter on coniferous forest biomass

    SciTech Connect

    Dobson, M.C.; Ulaby, F.T. ); LeToan, T.; Beaudoin, A. ); Kasischke, E.S. ); Christensen, N. )

    1992-03-01

    This paper discusses two independent experimental efforts which have examined the dependence of radar backscatter on aboveground biomass of mono specie conifer forests using polarimetric airborne SAR data at P-, L- and C-bands. Plantations of maritime pines near Landes, France range in age from 8 to 46 years with aboveground biomass between 5 and 105 tons/ha. Loblolly pine stands established on abandoned agricultural fields near Duke, NC range in age from 4 to 90 years and extend the range of aboveground biomass to 560 tons/ha for the older stands. These two experimental forests are largely complementary with respect to biomass. Radar backscatter is found to increase approximately linearly with increasing biomass until it saturates at a biomass level that depends on the radar frequency. The biomass saturation level is about 200 tons/ha at P-band and 100 tons/ha at L-band, and the C-band backscattering coefficient shows much less sensitivity to total aboveground biomass.

  2. Three-dimensional microstructural characterization of porous cubic zirconia.

    PubMed

    Bobrowski, Piotr; Pędzich, Zbigniew; Faryna, Marek

    2015-11-01

    A set of cubic zirconia samples were investigated using 3-dimensional electron backscatter diffraction (3D EBSD) to analyze the grain structure, grain boundary networks and pore morphology. 3D EBSD is a variation of conventional EBSD, whereby a focused ion beam (FIB) is used in a dual beam scanning electron microscope (SEM) i.e. FIB-SEM to mill away material and to create 'serial sections' through the material being analyzed. Each new surface revealed is subject to an EBSD scan, which continues sequentially until a desired volume of material has been removed. In this manner, many consecutive 2D EBSD scans can be rendered in 3D to gain a greater insight of microstructural features and parameters. The three samples were examined in order to determine the effect of differences in the manufacturing process used for each. For each sample, a volume of ca. 15,000 μm(3) was studied. The analysis of several microstructure parameters revealed a strong dependence on manufacturing conditions. Subsequently, the results of 3D EBSD analysis were compared to conventional 2D EBSD. Significant differences between the values of microstructure parameters determined by 2D and 3D EBSD were observed.

  3. Computer Simulation of Diffraction Patterns.

    ERIC Educational Resources Information Center

    Dodd, N. A.

    1983-01-01

    Describes an Apple computer program (listing available from author) which simulates Fraunhofer and Fresnel diffraction using vector addition techniques (vector chaining) and allows user to experiment with different shaped multiple apertures. Graphics output include vector resultants, phase difference, diffraction patterns, and the Cornu spiral…

  4. Ptychographic Fresnel coherent diffractive imaging

    NASA Astrophysics Data System (ADS)

    Vine, D. J.; Williams, G. J.; Abbey, B.; Pfeifer, M. A.; Clark, J. N.; de Jonge, M. D.; McNulty, I.; Peele, A. G.; Nugent, K. A.

    2009-12-01

    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.

  5. Color Perception with Diffraction Gratings.

    ERIC Educational Resources Information Center

    Kruglak, Haym; Campbell, Don

    1983-01-01

    Describes an experiment enabling students to apply concept of diffraction, determine limits of their color perception, learn how to measure wavelength with a simple apparatus, observe continuous and line spectra, and associate colors with corresponding wavelengths. The homemade diffraction-grating spectrometer used is easily constructed. (JN)

  6. Electron Backscatter Diffraction Analysis of Joints Between AISI 316L Austenitic/UNS S32750 Dual-Phase Stainless Steel

    NASA Astrophysics Data System (ADS)

    Shamanian, Morteza; Mohammadnezhad, Mahyar; Amini, Mahdi; Zabolian, Azam; Szpunar, Jerzy A.

    2015-08-01

    Stainless steels are among the most economical and highly practicable materials widely used in industrial areas due to their mechanical and corrosion resistances. In this study, a dissimilar weld joint consisting of an AISI 316L austenitic stainless steel (ASS) and a UNS S32750 dual-phase stainless steel was obtained under optimized welding conditions by gas tungsten arc welding technique using AWS A5.4:ER2594 filler metal. The effect of welding on the evolution of the microstructure, crystallographic texture, and micro-hardness distribution was also studied. The weld metal (WM) was found to be dual-phased; the microstructure is obtained by a fully ferritic solidification mode followed by austenite precipitation at both ferrite boundaries and ferrite grains through solid-state transformation. It is found that welding process can affect the ferrite content and grain growth phenomenon. The strong textures were found in the base metals for both steels. The AISI 316L ASS texture is composed of strong cube component. In the UNS S32750 dual-phase stainless steel, an important difference between the two phases can be seen in the texture evolution. Austenite phase is composed of a major cube component, whereas the ferrite texture mainly contains a major rotated cube component. The texture of the ferrite is stronger than that of austenite. In the WM, Kurdjumov-Sachs crystallographic orientation relationship is found in the solidification microstructure. The analysis of the Kernel average misorientation distribution shows that the residual strain is more concentrated in the austenite phase than in the other phase. The welding resulted in a significant hardness increase in the WM compared to initial ASS.

  7. Point-group sensitive orientation mapping of non-centrosymmetric crystals

    SciTech Connect

    Winkelmann, Aimo; Nolze, Gert

    2015-02-16

    We demonstrate polarity-sensitive orientation mapping of non-centrosymmetric phases by Electron Backscatter Diffraction (EBSD). The method overcomes the restrictions of kinematic orientation determination by EBSD, which is limited to the centro-symmetric Laue-groups according to Friedel's rule. Using polycrystalline GaP as an example, we apply a quantitative pattern matching approach based on simulations using the dynamical theory of electron diffraction. This procedure results in a distinct assignment of the local orientation according to the non-centrosymmetric point group of the crystal structure under investigation.

  8. Photoinduced diffraction in polymer waveguides.

    PubMed

    Andrews, J H; Singer, K D

    1993-11-20

    We report on techniques for measuring photoinduced diffraction in prism-coupled slab polymer waveguides. Diffraction effects resulting from photochromic gratings in slab waveguides of Disperse Red 1 dye in polymethylmethacrylate were studied. Optical damage in the form of diffractive mode conversion was observed when we coupled in light with a wavelength slightly longer than the absorption edge of Disperse Red 1 dye. Slowly growing satellite beams in the outcoupled light were attributed to anisotropic scattering between the lowest-order TE mode and the lowest-order TM mode caused by self-diffraction from a grating produced through the photochromic effect. We have also investigated the effect of mode-coupling changes on the determination of diffraction efficiency and sensitivity in waveguide experiments. Diffraction efficiencies predicted by measurements of the modulation depth in the guide are found to overstate the actual diffraction efficiencies that could be observed in this geometry. Techniques for overc ming this limitation and for improving estimates of the energy density and interaction length in the guide are noted.

  9. 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.

  10. Backscattering channel-cut high-resolution monochromator for inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Kushnir, Vladimir I.; Abbamonte, Peter M.; Macrander, Albert T.; Schwoerer-Boehning, Markus

    1997-12-01

    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 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 than ideal by a factor of 1.9. Dynamical diffraction theory was used to calculate the throughput of an ideally perfect crystal.

  11. Diffraction techniques in engineering applications

    SciTech Connect

    Kozarczek, K.J.; Hubbard, C.R.; Watkins, T.R.; Wang, X.L.; Spooner, S.

    1995-12-31

    Diffraction techniques applied to crystalline materials provide quantitative information about the crystallographic structure and mechanical condition of the material. Those two characteristics influence the chemical, physical, and mechanical properties of a Component. A concerted application of x-ray and neutron diffraction allows one to comprehensively study the bulk and subsurface variations of such material characteristics as crystallographic texture, residual stress, and cold work. The Residual Stress User Center at the Oak Ridge National Laboratory offers academic and industrial researchers both neutron and x-ray diffraction capabilities. Recent examples of the application of work related to thin film, metal, ceramic and composite material technologies are presented.

  12. Diffraction effects in freeform optics

    NASA Astrophysics Data System (ADS)

    Ricketts, Melissa N.; Winston, Roland; Oliker, Vladimir

    2015-08-01

    Freeform optics is a relatively new field; it uses the methods necessary to describe surfaces lacking symmetry, and/or surfaces that create non-symmetrical irradiance distributions. The Supporting Quadrics Method (SQM) developed by Oliker is a superb for generating any desired irradiance distribution. The SQM uses an envelope of quadrics to create prescribed irradiance distributions. These optical systems are tested in ray trace software, where diffraction effects are not taken into account. It is important to understand the diffraction effects present in an optic, when moving from the ray trace stage to the prototype stage. Here we study the diffraction effects of Supporting Quadrics Method.

  13. Diffractive optics in adverse environments

    NASA Technical Reports Server (NTRS)

    Behrmann, Gregory P.

    1993-01-01

    An investigation at the Army Research Laboratory is in progress to characterize DOE performance in mil-spec environments. One of the most significant environmental influences is temperature. An analysis of a diffractive lens is presented in which optical performance is described as a function of temperature. In particular, we review the thermal dependence of focal length and diffraction efficiency. It is shown that the change in these parameters is independent of lens shape and relates only to material properties. Thermalized hybrid refractive/diffractive designs are discussed.

  14. Concentration measurement of yeast suspensions using high frequency ultrasound backscattering.

    PubMed

    Elvira, Luis; Vera, Pedro; Cañadas, Francisco Jesús; Shukla, Shiva Kant; Montero, Francisco

    2016-01-01

    This work proposes the use of an ultrasound based technique to measure the concentration of yeasts in liquid suspension. This measurement was achieved by the detection and quantification of ultrasonic echoes backscattered by the cells. More specifically, the technique was applied to the detection and quantification of Saccharomyces cerevisiae. A theoretical approach was proposed to get the average density and sound speed of the yeasts, which were found to be 1116 kg/m(3) and 1679 m/s, respectively. These parameters were needed to model the waves backscattered by each single cell. A pulse-echo arrangement working around 50 MHz, being able to detect echoes from single yeasts was used to characterize experimentally yeast solutions from 10(2) to 10(7)cells/ml. The Non-negative Matrix Factorization denoising technique was applied for data analysis. This technique required a previous learning of the spectral patterns of the echoes reflected from yeasts in solution and the base noise from the liquid medium. Comparison between pulse correlation (without denoising) and theoretical and experimental pattern learning was made to select the best signal processing. A linear relation between ultrasound output and concentration was obtained with correlation coefficient R(2)=0.996 for the experimental learning. Concentrations from 10(4) to 10(7)cells/ml were detected above the base noise. These results show the viability of using the ultrasound backscattering technique to detect yeasts and measure their concentration in liquid cultures, improving the sensitivity obtained using spectrophotometric methods by one order of magnitude.

  15. Study on backscattering spectral polarization characteristics of turbid medium

    NASA Astrophysics Data System (ADS)

    Wang, Xuezhen; Wang, Qinghua; Lai, Jiancheng; Li, Zhenhua

    2015-10-01

    Noninvasive monitoring of blood glucose is the current international academic research focus. Near-infrared (NIR) spectroscopy is the most prospective method of the present study, however, with the flaw of insufficient specificity to glucose. Tissue polarimetry has recently received considerable attention due to its specificity to glucose. Thus the glucose predicting accuracy would be improved by combining spectral intensity and polarization characteristics. However the backscattering spectral polarization characteristics of turbid media have not been reported within the wavelength range from visible to near-infrared light. In this paper, we simulated the backscattering spectral Mueller matrix of turbid medium by vector Monte Carlo. And the polarization characteristics, which are linear/circular degree of polarization (DOP) and linear/circular diattenuation, can be extracted from the simulated Mueller matrix by polar decomposition. Circular diattenuation is not discussed because it remains almost zero on the backscattering plane. While reduced scattering coefficient increases linearly with increasing wavelength, the spectral curves show distinct wavelength dependencies. Interestingly, the wavelength dependencies at center position are different from those at off-center position for linear/circular DOP and linear diattenuation. As expected, it is shown that both linear DOP and linear diattenuation increase with the increasing wavelength. However it is not the case for linear DOP in the central area around the incident point. In this area linear DOP decays approximately exponentially with increasing wavelength. As for circular DOP, it varies with wavelength non-monotonically. These results should be meaningful when spectral polarization characteristics are used to combine with spectral intensity to extract glucose concentration by chemometrics.

  16. Laboratory investigations of mineral dust near-backscattering depolarization ratios

    NASA Astrophysics Data System (ADS)

    Järvinen, E.; Kemppinen, O.; Nousiainen, T.; Kociok, T.; Möhler, O.; Leisner, T.; Schnaiter, M.

    2016-07-01

    Recently, there has been increasing interest to derive the fractions of fine- and coarse-mode dust particles from polarization lidar measurements. For this, assumptions of the backscattering properties of the complex dust particles have to be made either by using empirical data or particle models. Laboratory measurements of dust backscattering properties are important to validate the assumptions made in the lidar retrievals and to estimate their uncertainties. Here, we present laboratory measurements of linear and circular near-backscattering (178°) depolarization ratios of over 200 dust samples measured at 488 and 552 nm wavelengths. The measured linear depolarization ratios ranged from 0.03 to 0.36 and were strongly dependent on the particle size. The strongest size-dependence was observed for fine-mode particles as their depolarization ratios increased almost linearly with particle median diameter from 0.03 to 0.3, whereas the coarse-mode particle depolarization values stayed rather constant with a mean linear depolarization ratio of 0.27. The depolarization ratios were found to be insensitive to the dust source region or thin coating of the particles or to changes in relative humidity. We compared the measurements with results of three different scattering models. With certain assumptions for model particle shape, all the models were capable of correctly describing the size-dependence of the measured dust particle, albeit the model particles significantly differed in composition, shape and degree of complexity. Our results show potential for distinguishing the dust fine- and coarse-mode distributions based on their depolarization properties and, thus, can serve the lidar community as an empirical reference.

  17. Coherent Backscatter Opposition Effect from Scratches on Solid Surfaces

    NASA Astrophysics Data System (ADS)

    Hapke, B. W.; Piatek, J. L.; Nelson, R. M.; Smythe, W. D.; Hale, A. S.

    2003-05-01

    Shepard and Arvidson [1] discovered that the solid surfaces of rocks exhibit an opposition effect. We have measured the phase curve of a natural surface of a piece of solid basalt between 0.05 and 5 degrees in circularly polarized light using the JPL long arm goniometer and confirmed that it has an opposition effect. The circular polarization ratio (CPR) increased with decreasing phase angle, consistent with a coherent backscatter opposition effect (CBOE) Recent laboratory investigations of the CBOE in planetary regolith analogs [2,3,4] have revealed that the width of the peak is remarkably insensitive to particle size, in strong contrast to theoretical expectations. We have hypothesized that one of the reasons for this might be that multiple scattering between irregularities, such as scratches, on the surfaces of a particle could cause coherent backscatter, in addition to scattering between particles. To test this hypothesis we ground the surface of a piece of plate glass with 5 micrometer abrasive and measured its phase curve. As the phase angle decreases, the intensity increases and the CPR decreases, consistent with specular reflection. However, near zero phase there is a nonlinear rise about 2 degrees wide superimposed on the linear specular peak accompanied by an increase in CPR, showing that coherent backscatter is occuring. A piece of commercial diffusing glass exhibited the same phenomena. These results support our hypothesis and also provide a possible explanation for the observations of opposition effects from the solid surfaces of rocks. This research was supported by a grant from NASA's PGG Program References cited: [1] Shepard and Arvidson, Icarus, 141, 172-178 (1999). [2] Nelson et al, Icarus, 147, 545-558 (2000). [3] Nelson et al, Planet. Space Sci., 50, 849-856 (2002). [4] Piatek et al, Abstract, DPS Conference (2003).

  18. Estimation of Mars radar backscatter from measured surface rock populations

    USGS Publications Warehouse

    Baron, J.E.; Simpson, R.A.; Tyler, G.L.; Moore, H.J.; Harmon, J.K.

    1998-01-01

    Reanalysis of rock population data at the Mars Viking Lander sites has yielded updated values of rock fractional surface coverage (about 0.16 at both sites, including outcrops) and new estimates of rock burial depths and axial ratios. These data are combined with a finite difference time domain (FDTD) numerical scattering model to estimate diffuse backscatter due to rocks at both the Lander l (VL1) and Lander 2 (VL2) sites. We consider single scattering from both surface and subsurface objects of various shapes, ranging from an ideal sphere to an accurate digitized model of a terrestrial rock. The FDTD cross-section calculations explicitly account for the size, shape, composition, orientation, and burial state of the scattering object, the incident wave angle and polarization, and the composition of the surface. We calculate depolarized specific cross sections at 12.6 cm wavelength due to lossless rock-like scatterers of about 0.014 at VL1 and 0.023 at VL2, which are comparable to the measured ranges of 0.019-0.032 and 0.012-0.018, respectively. We also discuss the variation of the diffuse cross section as the local angle of incidence, ??i, changes. Numerical calculations for a limited set of rock shapes indicate a marked difference between the angular backscattering behavior of wavelength-scale surface and subsurface rocks: while subsurface rocks scatter approximately as a cosine power law, surface rocks display a complex variation, often with peak backscattering at high incidence angles (??i = 70??-75??). Copyright 1998 by the American Geophysical Union.

  19. Concentration measurement of yeast suspensions using high frequency ultrasound backscattering.

    PubMed

    Elvira, Luis; Vera, Pedro; Cañadas, Francisco Jesús; Shukla, Shiva Kant; Montero, Francisco

    2016-01-01

    This work proposes the use of an ultrasound based technique to measure the concentration of yeasts in liquid suspension. This measurement was achieved by the detection and quantification of ultrasonic echoes backscattered by the cells. More specifically, the technique was applied to the detection and quantification of Saccharomyces cerevisiae. A theoretical approach was proposed to get the average density and sound speed of the yeasts, which were found to be 1116 kg/m(3) and 1679 m/s, respectively. These parameters were needed to model the waves backscattered by each single cell. A pulse-echo arrangement working around 50 MHz, being able to detect echoes from single yeasts was used to characterize experimentally yeast solutions from 10(2) to 10(7)cells/ml. The Non-negative Matrix Factorization denoising technique was applied for data analysis. This technique required a previous learning of the spectral patterns of the echoes reflected from yeasts in solution and the base noise from the liquid medium. Comparison between pulse correlation (without denoising) and theoretical and experimental pattern learning was made to select the best signal processing. A linear relation between ultrasound output and concentration was obtained with correlation coefficient R(2)=0.996 for the experimental learning. Concentrations from 10(4) to 10(7)cells/ml were detected above the base noise. These results show the viability of using the ultrasound backscattering technique to detect yeasts and measure their concentration in liquid cultures, improving the sensitivity obtained using spectrophotometric methods by one order of magnitude. PMID:26361271

  20. Lidar inversion with variable backscatter/extinction ratios.

    PubMed

    Klett, J D

    1985-06-01

    The conventional approach to solving the single-scattering lidar equation makes use of the assumption of a power law relation between backscatter and extinction with a fixed exponent and constant of proportionality. An alternative formulation is given herein which assumes the proportionality factor in the power law relationship is itself a function of range or extinction. The resulting lidar equation is solvable as before, and examples are given to show how even an approximate description of deviations from the power law form can yield an improved inversion solution for the extinction. A further generalization is given which includes the effects of a background of Rayleigh scatterers.

  1. Backscatter by azimuthally oriented ice crystals of cirrus clouds.

    PubMed

    Konoshonkin, Alexander; Wang, Zhenzhu; Borovoi, Anatoli; Kustova, Natalia; Liu, Dong; Xie, Chenbo

    2016-09-01

    The backscattering Mueller matrix has been calculated for the first time for the hexagonal ice columns and plates with both zenith and azimuth preferential orientations. The possibility of a vertically pointing polarization lidar measuring the full Mueller matrix for retrieving the orientation distributions of the crystals is considered. It is shown that the element m44 or, equivalently, the circular depolarization ratio distinguishes between the low and high zenith tilts of the crystals. Then, at their low or high zenith tilts, either the element m22 or m34, respectively, should be measured to retrieve the azimuth tilts.

  2. Backscattering by hexagonal ice crystals of cirrus clouds.

    PubMed

    Borovoi, Anatoli; Konoshonkin, Alexander; Kustova, Natalia

    2013-08-01

    Light backscattering by randomly oriented hexagonal ice crystals of cirrus clouds is considered within the framework of the physical-optics approximation. The fine angular structure of all elements of the Mueller matrix in the vicinity of the exact backward direction is first calculated and discussed. In particular, an approximate equation for the differential scattering cross section is obtained. Its simple spectral dependence is discussed. Also, a hollow of the linear depolarization ratio around the exact backward direction inherent to the long hexagonal columns is revealed.

  3. 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.

  4. Coherent Backscattering in the Cross-Polarized Channel

    NASA Technical Reports Server (NTRS)

    Mischenko, Michael I.; Mackowski, Daniel W.

    2011-01-01

    We analyze the asymptotic behavior of the cross-polarized enhancement factor in the framework of the standard low-packing-density theory of coherent backscattering by discrete random media composed of spherically symmetric particles. It is shown that if the particles are strongly absorbing or if the smallest optical dimension of the particulate medium (i.e., the optical thickness of a plane-parallel slab or the optical diameter of a spherically symmetric volume) approaches zero, then the cross-polarized enhancement factor tends to its upper-limit value 2. This theoretical prediction is illustrated using direct computer solutions of the Maxwell equations for spherical volumes of discrete random medium.

  5. HAB detection based on absorption and backscattering properties of phytoplankton

    NASA Astrophysics Data System (ADS)

    Lei, Hui; Pan, Delu; Bai, Yan; Chen, Xiaoyan; Zhou, Yan; Zhu, Qiankun

    2011-11-01

    The coastal area of East China Sea (ECS) suffers from the harmful algal blooms (HAB) frequently every year in the warm season. The most common causative phytoplankton algal species of HAB in the ECS in recent years are Prorocentrum donghaiense (dinoflagellates), Karenia mikimotoi (dinoflagellates which could produce hemolytic and ichthyotoxins) and Skeletonema costatum (diatom). The discrimination between the dinoflagellates and diatom HAB through ocean color remote sensing approach can add the knowledge of HAB events in ECS and help to the precaution. A series of in-situ measurement consisted of absorption coefficient, total scattering and particulate backscattering coefficient was conducted in the southern coast of Zhejiang Province in May 2009, and the estuary of Changjiang River in August 2009 and December 2010, which encountered two HAB events and a moderate bloom. The Inherent Optical Properties (IOPs) of the bloom waters have significant difference between phytoplankton species in absorption and backscattering properties. The chlorophyll a specific absorption coefficient (a*phy(λ)) for the bloom patches (chlorophyll a concentration >6mg m-3) differ greatly from the adjacent normal seawater, with the a*phy(λ) of bloom water lower than 0.03 m2 mg-1 while the a*phy(λ) of the adjacent normal seawater is much higher (even up to 0.06 m2 mg-1). Meanwhile, the backscattering coefficients at 6 wavebands (420, 442, 470, 510, 590 and 700nm) are also remarkably lower for bloom waters (<0.01 m-1) than the normal seawater (> 0.02 m-1). The backscattering coefficient ratio (Rbp(λ)) is much lower for diatom bloom waters than for dinoflagellates types (0.01079 vs. 0.01227). A discrimination model based on IOPs is established, and several typical dinoflagellates and diatom bloom events including Prorocentrum donghaiense, Karenia mikimotoi and Skeletonema costatum in the ECS are picked out for testing with the MODIS-L2 and L3 ocean color remote sensing products from NASA

  6. 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.

  7. Relating the microwave backscattering coefficient to leaf area index

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Allen, C. T.; Eger, G., III; Kanemasu, E.

    1984-01-01

    This paper examines the relationship between the microwave backscattering coefficient of a vegetation canopy, sigma (can, 0) and the canopy's leaf area index (LAI). The relationship is established through the development of one 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 (can, 0) can be accounted for through variations in green LAI alone, if the latter is greater than 0.5.

  8. Spatially resolved concentration measurements based on backscatter absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Ze; Sanders, Scott T.; Robinson, Michael A.

    2016-06-01

    We demonstrate the feasibility of spatially resolved measurements of gas properties using direct absorption spectroscopy in conjunction with backscattered signals. We report a 1-D distribution of H2O mole fraction with a spatial resolution of 5 mm. The peak and average discrepancy between the measured and expected mole fraction are 21.1 and 8.0 %, respectively. The demonstration experiment is related to a diesel aftertreatment system; a selective catalytic reduction brick made of cordierite is used. The brick causes volume scattering interference; advanced baseline fitting based on a genetic algorithm is used to reduce the effects of this interference by a factor of 2.3.

  9. Backscatter by azimuthally oriented ice crystals of cirrus clouds.

    PubMed

    Konoshonkin, Alexander; Wang, Zhenzhu; Borovoi, Anatoli; Kustova, Natalia; Liu, Dong; Xie, Chenbo

    2016-09-01

    The backscattering Mueller matrix has been calculated for the first time for the hexagonal ice columns and plates with both zenith and azimuth preferential orientations. The possibility of a vertically pointing polarization lidar measuring the full Mueller matrix for retrieving the orientation distributions of the crystals is considered. It is shown that the element m44 or, equivalently, the circular depolarization ratio distinguishes between the low and high zenith tilts of the crystals. Then, at their low or high zenith tilts, either the element m22 or m34, respectively, should be measured to retrieve the azimuth tilts. PMID:27607728

  10. Coherent backscatter and the radar characteristics of outer planet satellites

    SciTech Connect

    Hapke, B. )

    1990-12-01

    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. 35 refs.

  11. Quantifying Fish Backscattering using SONAR Instrument and Kirchhoff Ray Mode (KRM) Model

    NASA Astrophysics Data System (ADS)

    Manik, Henry M.

    2016-08-01

    Sonar instrument was used to study backscattering from tuna fish. Extraction of target strength, incidence angle, and frequency dependence of the backscattered signal for individual scatterer was important for biological information. For this purpose, acoustic measurement of fish backscatter was conducted in the laboratory. Characteristics and general trends of the target strength of fish with special reference to tuna fish were investigated by using a Kirchhoff Ray Mode (KRM) model. Backscattering strength were calculated for the KRM having typical morphological and physical parameters of actual fish. Those backscattering amplitudes were shown as frequency, body length, backscattering patterns, the density and sound speed dependences, and orientation dependence. These results were compared with experimentally measured target strength data and good agreement was found. Measurement and model showed the target strength from the fish are depend on the presence of swimbladder. Target Strength increase with increasing the frequency and fish length.

  12. Enhancement of backscattering by a conducting cylinder coated with gradient metasurface

    NASA Astrophysics Data System (ADS)

    Shang, Yuping; Shen, Zhongxiang; Feng, Keming

    2016-07-01

    This paper proposes a highly effective method for enhancing the backscattering by a conducting cylinder that is coated with a gradient metasurface. The employed metasurface exhibits a phase gradient continuously varying along the circumferential direction of the cylinder so that in-phase retroreflection can be produced to enhance the backscattering. It is demonstrated that the cylinder coated with the proposed gradient metasurface can generate backscattering very close to that from a conducting plate with the same dimensions as the cylinder's cross-section perpendicular to the incident plane wave. Compared with a bare conducting cylinder, the backscattering is significantly enhanced by the gradient metasurface made of conducting strips printed on a grounded dielectric substrate. Effects of cell numbers along the cylinder axis, incident angle, and polarization of the incoming electromagnetic wave on the backscattering enhancement are examined and discussed. A good agreement between simulated and measured backscattering results validates the observations.

  13. 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.

  14. Femtosecond single-electron diffraction

    PubMed Central

    Lahme, S.; Kealhofer, C.; Krausz, F.; Baum, P.

    2014-01-01

    Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration. PMID:26798778

  15. Diffraction by random Ronchi gratings.

    PubMed

    Torcal-Milla, Francisco Jose; Sanchez-Brea, Luis Miguel

    2016-08-01

    In this work, we obtain analytical expressions for the near-and far-field diffraction of random Ronchi diffraction gratings where the slits of the grating are randomly displaced around their periodical positions. We theoretically show that the effect of randomness in the position of the slits of the grating produces a decrease of the contrast and even disappearance of the self-images for high randomness level at the near field. On the other hand, it cancels high-order harmonics in far field, resulting in only a few central diffraction orders. Numerical simulations by means of the Rayleigh-Sommerfeld diffraction formula are performed in order to corroborate the analytical results. These results are of interest for industrial and technological applications where manufacture errors need to be considered.

  16. Diffraction by random Ronchi gratings.

    PubMed

    Torcal-Milla, Francisco Jose; Sanchez-Brea, Luis Miguel

    2016-08-01

    In this work, we obtain analytical expressions for the near-and far-field diffraction of random Ronchi diffraction gratings where the slits of the grating are randomly displaced around their periodical positions. We theoretically show that the effect of randomness in the position of the slits of the grating produces a decrease of the contrast and even disappearance of the self-images for high randomness level at the near field. On the other hand, it cancels high-order harmonics in far field, resulting in only a few central diffraction orders. Numerical simulations by means of the Rayleigh-Sommerfeld diffraction formula are performed in order to corroborate the analytical results. These results are of interest for industrial and technological applications where manufacture errors need to be considered. PMID:27505363

  17. Standoff detection of hidden objects using backscattered ultra-intense laser-produced x-rays

    SciTech Connect

    Kuwabara, H.; Mori, Y.; Kitagawa, Y.

    2013-08-28

    Ultra-intense laser-produced sub-ps X-ray pulses can detect backscattered signals from objects hidden in aluminium containers. Coincident measurements using primary X-rays enable differentiation among acrylic, copper, and lead blocks inside the container. Backscattering reveals the shapes of the objects, while their material composition can be identified from the modification methods of the energy spectra of backscattered X-ray beams. This achievement is an important step toward more effective homeland security.

  18. Dependence of the backscattering factor in aes on the primary electron incidence angle

    NASA Astrophysics Data System (ADS)

    Jabłoński, Aleksander

    1983-01-01

    The formulas defining the backscattering factor met with in the literature are derived from the general definition. These formulas are shown to depend on the simplifying assumptions made in the derivation. The Monte Carlo algorithm is used to calculate the dependence of the backscattering factor on the primary electron incidence angle for different defining formulas. Considerable differences were found between values of the backscattering factor resulting from these definitions at grazing incidence of primary electrons.

  19. New CDF results on diffraction

    SciTech Connect

    Mesropian, Christina; /Rockefeller U.

    2006-12-01

    We report new diffraction results obtained by the CDF collaboration in proton-antiproton collisions at the Fermilab Tevatron collider at {radical}s=1.96 TeV. The first experimental evidence of exclusive dijet and diphoton production is presented. The exclusive results are discussed in context of the exclusive Higgs production at LHC. We also present the measurement of the Q{sup 2} and t dependence of the diffractive structure function.

  20. Texture analysis of melt-textured YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Simon, P.; Ogasawara, K.; Murakami, M.

    2003-10-01

    We compare the results of an X-ray based pole figure texture analysis with the local texture analysis by means of electron-backscatter diffraction (EBSD) analysis. As samples, we employ two different melt-textured YBCO samples; one fully processed and one without oxygen treatment. To enable the direct comparison of the two techniques, we employ the [1 0 3] pole figures. We find a clear coincidence between the results obtained by the two measurement techniques on our samples, however, the EBSD results are much more detailed, yielding the local grain orientation distribution and quantitative results of the grain or subgrain misorientation angles. Therefore, the EBSD measurements give information not accessible to the X-ray pole figure analysis. The surface preparation procedure is essential to enable the automated EBSD mapping as high image quality Kikuchi patterns are required. The polishing procedures are discussed in detail.

  1. Effects of soil and canopy characteristics on microwave backscattering of vegetation

    NASA Technical Reports Server (NTRS)

    Daughtry, C. S. T.; Ranson, K. J.

    1991-01-01

    A frequency modulated continuous wave C-band (4.8 GHz) scatterometer was mounted on an aerial lift truck and backscatter coefficients of corn were acquired as functions of polarizations, view angles, and row directions. As phytomass and green leaf area index increased, the backscatter also increased. Near anthesis when the canopies were fully developed, the major scattering elements were located in the upper 1 m of the 2.8 m tall canopy and little backscatter was measured below that level. C-band backscatter data could provide information to monitor vegetation at large view zenith angles.

  2. Rutherford backscattering analysis of the failure of chlorine anodes

    SciTech Connect

    Tilak, B.V.; Vallet, C.E.

    1996-06-01

    Rutherford Backscattering Spectrometry, carried out at the ORNL Surface Modification And Characterization Collaborative Research Center (SMAC) facility, has been applied to the nondestructive analysis of Ru02-Ti02 electrodes of 5000A, which mimic the DSA anodes in composition and the method of preparation. Occidental Chemical Corporation provided electrodes, which had been subjected to lifetime testing in H2S04 solution, for analysis by ORNL. The results were used to test the hypothesis of degradation of these, and similar electrodes, from a process involving a decrease in the Ru02:Ti02 ratio at and near the electrode surface and the related decrease in the electrode electrical conductivity. The drop in electrode activity is closely linked to a decrease in Ru content, and the measured profiles show that the loss takes place across the thin Ru02-Ti02 coating. No buildup of a pure Ti02 layer is apparent. The data agree quantitatively with the critical concentration previously reported by ORNL for materials produced by ion implantation and characterized by Rutherford Backscattering Spectrometry and Photoacoustic Spectrometry. The study has brought a better understanding of the degradation process in electrodes of great technological importance, and has given a more solid background in designing new fabrication procedures for improved electrodes.

  3. Discriminant classification of different fish-species backscattering

    NASA Astrophysics Data System (ADS)

    Zhang, Qiao; Xu, Feng; Liu, Yin; Zhang, Chun

    2012-11-01

    The complex structure of fish and multispecies composition complicate the analysis of acoustic data. Consequently, it is difficult to obtain a highly accurate rate of classification by using current approaches. This paper introduces two discriminating methods: the adaptive segmentation temporal centroid method and the wavelet packet multi-scale information entropy method. To verify and compare these two methods, an ex situ experiment has been performed with three kinds of fish: Crucian carp (Carassius auratus), Yellow-headed catfish (Pelteobagrus fulvidraco) and Bluntnose black bream (Megalobrama amblycephale). The backscattering signals of these fishes are obtained. Then the temporal centroid in the divided sub-segmentation of the backscattering envelope is calculated, and the multi-scale information entropy of the wavelet packet decomposition in different frequency bands is extracted. Finally, three kinds of fish are successfully classified by using a BP neural network. The result shows that the adaptive segmentation temporal centroid method is 4% more accurate than the wavelet packet multi-scale information entropy method.

  4. 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.

  5. Ultrastructural alterations in field carcinogenesis measured by enhanced backscattering spectroscopy

    PubMed Central

    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

  6. Coherent Effects in Microwave Backscattering Models for Forrest Canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; McDonald, Kyle C.

    1997-01-01

    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. To demonstrate this point, the models are first compared based on their underlying theoretical assumptions and then according to simulation results over coniferous and deciduous forests. It is shown that by using the same scattering functions for various components of trees (i.e., leaf, branch, stem), the radiative transfer and distorted Born models are equivalent, except in low frequencies, where surface-volume interaction terms may become important, and the coherent contribution may be significant. In this case, the difference between the two models can reach up to 3 dB in both co-polarized and cross-polarized channels, which can influence the performance of retrieval algorithms.

  7. 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.

  8. 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.

  9. 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.

  10. Observations of HF backscatter decay rates from HAARP generated FAI

    NASA Astrophysics Data System (ADS)

    Bristow, William; Hysell, David

    2016-07-01

    Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

  11. Assembly for Rutherford backscattering at exactly 180{degree}

    SciTech Connect

    Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D.

    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. Terrain-analysis procedures for modeling radar backscatter

    USGS Publications Warehouse

    Schaber, Gerald G.; Pike, Richard J.; Berlin, Graydon Lennis

    1978-01-01

    The collection and analysis of detailed information on the surface of natural terrain are important aspects of radar-backscattering modeling. Radar is especially sensitive to surface-relief changes in the millimeter- to-decimeter scale four conventional K-band (~1-cm wavelength) to L-band (~25-cm wavelength) radar systems. Surface roughness statistics that characterize these changes in detail have been generated by a comprehensive set of seven programmed calculations for radar-backscatter modeling from sets of field measurements. The seven programs are 1) formatting of data in readable form for subsequent topographic analysis program; 2) relief analysis; 3) power spectral analysis; 4) power spectrum plots; 5) slope angle between slope reversals; 6) slope angle against slope interval plots; and 7) base length slope angle and curvature. This complete Fortran IV software package, 'Terrain Analysis', is here presented for the first time. It was originally developed a decade ago for investigations of lunar morphology and surface trafficability for the Apollo Lunar Roving Vehicle.

  13. 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.

  14. Control of collective FSBS and backscatter SRS through plasma composition

    NASA Astrophysics Data System (ADS)

    Rose, Harvey; Lushnikov, Pavel

    2005-10-01

    Nominal NIF parameters are near the collective forward SBS (FSBS) threshold (P. M. Lushnikov and H. A. Rose, Phys. Rev. Lett. 92, 255003 (2004), ``L&R''). It will be shown that being on this instability edge can be used as a control lever: a small amount of high Z dopant may lead to qualitative change in FSBS regime at fixed laser intensity, possibly reducing backscatter instability losses (Such results have already been observed, but absent SSD, a key aspect of our theory: R. M. Stevenson et al., Phys. Plasmas 11, 2709 (2004); L. J. Suter et al., 2738, ib.). Ponderomotive FSBS regimes are determined by the parameter I=F^2( vosc / vosc ve . - ve )^2( ne / ne nc . - nc ) / ( ne / ne nc . - nc ) ν . - ν, with ν the dimensionless ion acoustic damping coefficient and F the optic f/#. Analytical results will be presented which show a decrease of I1pt's threshold value through the addition of high Z dopant to low Z plasma, owing to increased thermal contribution to FSBS. Alternatively, one may raise the threshold by managing the value of νby, e.g., adding He to SiO2. For nominal NIF parameters, a range of He fraction in SiO2 plasma is predicted to suppress backscatter SRS while maintaining control of forward SBS.

  15. Diffraction described by virtual particle momentum exchange: the "diffraction force"

    NASA Astrophysics Data System (ADS)

    Mobley, Michael J.

    2011-09-01

    Particle diffraction can be described by an ensemble of particle paths determined through a Fourier analysis of a scattering lattice where the momentum exchange probabilities are defined at the location of scattering, not the point of detection. This description is compatible with optical wave theories and quantum particle models and provides deeper insights to the nature of quantum uncertainty. In this paper the Rayleigh-Sommerfeld and Fresnel-Kirchoff theories are analyzed for diffraction by a narrow slit and a straight edge to demonstrate the dependence of particle scattering on the distance of virtual particle exchange. The quantized momentum exchange is defined by the Heisenberg uncertainty principle and is consistent with the formalism of QED. This exchange of momentum manifests the "diffraction force" that appears to be a universal construct as it applies to neutral and charged particles. This analysis indicates virtual particles might form an exchange channel that bridges the space of momentum exchange.

  16. Use of electron diffraction for determination of strain distribution in synthetic diamonds

    NASA Astrophysics Data System (ADS)

    Balovsyak, S.; Borcha, M.; Garabazhiv, Ya.; Fodchuk, I.; Tkach, V.

    2012-01-01

    In this paper we demonstrate possibilities of electron backscattering diffraction technique (Kikuchi method) for determination of strain distribution in local areas of synthetic diamond samples. To increase the precision of lattice parameter determination a correlation method and corresponding software were used for accurate identification of coordinates of Kikuchi lines intersections on the Kikuchi patterns. Consequently, subjective factors influencing on accuracy at determination of displacements of image details were minimized. Samples have been investigated by scanning electron microscope "Zeiss" EVO-50 using CCD detector. The complex analysis of location changes of Kikuchi lines intersections and Kikuchi line intensity profiles permits to specify peculiarities of strain distribution for diamonds grown by various methods.

  17. Use of electron diffraction for determination of strain distribution in synthetic diamonds

    NASA Astrophysics Data System (ADS)

    Balovsyak, S.; Borcha, M.; Garabazhiv, Ya.; Fodchuk, I.; Tkach, V.

    2011-09-01

    In this paper we demonstrate possibilities of electron backscattering diffraction technique (Kikuchi method) for determination of strain distribution in local areas of synthetic diamond samples. To increase the precision of lattice parameter determination a correlation method and corresponding software were used for accurate identification of coordinates of Kikuchi lines intersections on the Kikuchi patterns. Consequently, subjective factors influencing on accuracy at determination of displacements of image details were minimized. Samples have been investigated by scanning electron microscope "Zeiss" EVO-50 using CCD detector. The complex analysis of location changes of Kikuchi lines intersections and Kikuchi line intensity profiles permits to specify peculiarities of strain distribution for diamonds grown by various methods.

  18. 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.

  19. Evaluation of the interface of thin GaN layers on c- and m-plane ZnO substrates by Rutherford backscattering

    SciTech Connect

    Izawa, Y.; Oga, T.; Ida, T.; Kuriyama, K.; Hashimoto, A.; Kotake, H.; Kamijoh, T.

    2011-07-11

    Lattice distortion at the interfaces between thin GaN layers with {approx}400 nm in thickness and ZnO substrates with non-polar m-plane (10-10) and polar c-plane (0001) is studied using Rutherford backscattering/ion channeling techniques. The interface between GaN/m-plane ZnO is aligned clearly to m-axis, indicating no lattice distortion, while between GaN/c-plane ZnO causes the lattice distortion in the GaN layer due to the piezoelectric field. The range of distortion exceeds {approx}90 nm from the interface of GaN/c-plane ZnO. These results are confirmed by x-ray diffraction and reflection high energy electron diffraction studies.

  20. EBSD Study on Grain Boundary and Microtexture Evolutions During Friction Stir Processing of A413 Cast Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Shamanian, Morteza; Mostaan, Hossein; Safari, Mehdi; Szpunar, Jerzy A.

    2016-07-01

    The as-cast Al alloys contain heterogeneous distributions of non-deforming particles due to non-equilibrium solidification effects. Therefore, these alloys have poor tribological and mechanical behaviors. It is well known that using friction stir processing (FSP), very fine microstructure is created in the as-cast Al alloys, while their wear resistance can be improved. In this research work, FSP is used to locally refine a surface layer of the coarse as-cast microstructure of cast A413 Al alloy. The main objective of this study is to investigate the effect of FSP on microstructure and microtexture evolutions in A413 cast Al alloy. The grain boundary character distribution, grain structure, and microtexture evolutions in as-cast and friction stir processed A413 Al alloy are analyzed by electron back scatter diffraction technique. It is found that with the FSP, the fraction of low ∑boundary such as ∑3, 7, and 9 are increased. The obtained results show that there are no deformation texture components in the structure of friction stir processed samples. However, some of the main recrystallization texture components such as BR and cubeND are formed during FSP which indicate the occurrence of dynamic recrystallization phenomenon due to the severe plastic deformation induced by the rotation of tool.

  1. Kinematics of Compton backscattering x-ray source for angiography

    SciTech Connect

    Blumberg, L.N.

    1992-05-01

    Calculations of X-Ray production rates, energy spread, and spectrum of Compton-backscattered photons from a Free Electron Laser on an electron beam in a low energy (136-MeV) compact (8.5-m circumference) storage ring indicate that an X-Ray intensity of 34.6 10{sup 7} X-Ray photons per 0.5-mm {times} 0.5-mm pixel for Coronary Angiography near the 33.169-keV iodine K-absorption edge can be achieved in a 4-msec pulse within a scattering cone of 1-mrad half angle. This intensity, at 10-m from the photon-electron interaction point to the patient is about a factor of 10 larger than presently achieved from a 4.5-T superconducting wiggler source in the NSLS 2.5-GeV storage ring and over an area about 5 times larger. The 2.2-keV energy spread of the Compton-backscattered beam is, however, much larger than the 70-eV spread presently attained form the wiggler source and use of a monochromator. The beam spot at the 10-m interaction point-to-patient distance is 20-mm diameter; larger spots are attainable at larger distances but with a corresponding reduction in X-Ray flux. Such a facility could be an inexpensive clinical alternative to present methods of non-invasive Digital Subtraction Angiography (DSA), small enough to be deployed in an urban medical center, and could have other medical, industrial and aerospace applications. Problems with the Compton backscattering source include laser beam heating of the mirror in the FEL oscillator optical cavity, achieving a large enough X-Ray beam spot at the patient, and obtaining radiation damping of the transverse oscillations and longitudinal emittance dilution of the storage ring electron beam resulting from photon-electron collisions without going to higher electron energy where the X-Ray energy spread becomes excessive for DSA. 38 refs.

  2. Single Photon diffraction and interference

    NASA Astrophysics Data System (ADS)

    Hodge, John

    2015-04-01

    A previous paper based on the Scalar Theory of Everything studied photon diffraction and interference (IntellectualArchive, Vol.1, No. 3, P. 20, Toronto, Canada July 2012. http://intellectualarchive.com/?link=item&id=597). Several photons were required in the experiment at the same time. Interference experiments with one photon in the experiment at a time also showed interference patterns. The previous paper with the Bohm Interpretation, models of the screen and mask, and the Transaction Interpretation of Quantum Mechanics were combined. The reverse wave required by the Transaction Interpretation was provided by a reflected plenum wave rather than a reverse time wave. The speed of the plenum wave was assumed to be much faster than the speed of photons/light. Using the assumptions of Fraunhofer diffraction resulted in the same equation for the photon distribution on a screen as the intensity pattern of the Fraunhofer diffraction. (http://myplace.frontier.com/ ~ jchodge/)

  3. Electron diffraction by plasmon waves

    NASA Astrophysics Data System (ADS)

    García de Abajo, F. J.; Barwick, B.; Carbone, F.

    2016-07-01

    An electron beam traversing a structured plasmonic field is shown to undergo diffraction with characteristic angular patterns of both elastic and inelastic outgoing electron components. In particular, a plasmonic grating (e.g., a standing wave formed by two counterpropagating plasmons in a thin film) produces diffraction orders of the same parity as the net number of exchanged plasmons. Large diffracted beam fractions are predicted to occur for realistic plasmon intensities in attainable geometries due to a combination of phase and amplitude changes locally imprinted on the passing electron wave. Our study opens vistas in the study of multiphoton exchanges between electron beams and evanescent optical fields with unexplored effects related to the transversal component of the electron wave function.

  4. Lensless reflective point diffraction interferometer.

    PubMed

    Zhu, Wenhua; Chen, Lei; Zheng, Donghui; Yang, Ying; Han, Zhigang; Li, Jinpeng

    2016-07-01

    A lensless reflective point diffraction interferometer (LRPDI) is proposed for dynamic wavefront measurement. The point diffraction interferometer is integrated on a small substrate with properly designed thin film, which is used for generating the interferogram with high carrier frequency at a CCD target. By lensless imaging, the complex amplitude at the CCD target can be propagated to the conjugated plane of the exit pupil of an incident wavefront, which not only avoids the edge diffraction in the interferogram, but also eliminates systematic error. The accuracy of LRPDI is demonstrated by simulation and experiment, and a precision better than 1/150 wavelength is achieved. The new design with lensless imaging processing is suitable for dynamic wavefront measurement. PMID:27409204

  5. Boundary diffraction wave integrals for diffraction modeling of external occulters.

    PubMed

    Cady, Eric

    2012-07-01

    An occulter is a large diffracting screen which may be flown in conjunction with a telescope to image extrasolar planets. The edge is shaped to minimize the diffracted light in a region beyond the occulter, and a telescope may be placed in this dark shadow to view an extrasolar system with the starlight removed. Errors in position, orientation, and shape of the occulter will diffract additional light into this region, and a challenge of modeling an occulter system is to accurately and quickly model these effects. We present a fast method for the calculation of electric fields following an occulter, based on the concept of the boundary diffraction wave: the 2D structure of the occulter is reduced to a 1D edge integral which directly incorporates the occulter shape, and which can be easily adjusted to include changes in occulter position and shape, as well as the effects of sources-such as exoplanets-which arrive off-axis to the occulter. The structure of a typical implementation of the algorithm is included. PMID:22772218

  6. Detonation diffraction through different geometries

    NASA Astrophysics Data System (ADS)

    Sorin, Rémy; Zitoun, Ratiba; Khasainov, Boris; Desbordes, Daniel

    2009-04-01

    We performed the study of the diffraction of a self-sustained detonation from a cylindrical tube (of inner diameter d) through different geometric configurations in order to characterise the transmission processes and to quantify the transmission criteria to the reception chamber. For the diffraction from a tube to the open space the transmission criteria is expressed by d c = k c · λ (with λ the detonation cell size and k c depending on the mixture and on the operture configuration, classically 13 for alkane mixtures with oxygen). The studied geometries are: (a) a sharp increase of diameter ( D/ d > 1) with and without a central obstacle in the diffracting section, (b) a conical divergent with a central obstacle in the diffracting section and (c) an inversed intermediate one end closed tube insuring a double reflection before a final diffraction between the initiator tube and the reception chamber. The results for case A show that the reinitiation process depends on the ratio d/ λ. For ratios below k c the re-ignition takes place at the receptor tube wall and at a fixed distance from the step, i.e. closely after the diffracted shock reflection shows a Mach stem configuration. For ratios below a limit ratio k lim (which depends on D/ d) the re-ignition distance increases with the decrease of d/λ. For both case A and B the introduction of a central obstacle (of blockage ratio BR = 0.5) at the exit of the initiator tube decreases the critical transmission ratio k c by 50%. The results in configuration C show that the re-ignition process depends both on d/ λ and the geometric conditions. Optimal configuration is found that provides the transmission through the two successive reflections (from d = 26 mm to D ch = 200 mm) at as small d/ λ as 2.2 whatever the intermediate diameter D is. This configuration provides a significant improvement in the detonation transmission conditions.

  7. Diffraction model for thermoreflectance data.

    PubMed

    Kureshi, S; Fabris, D; Tokairin, S; Cardenas, C V; Yang, C Y

    2015-06-10

    Thermoreflectance imaging provides the capability to map temperature spatially on the submicrometer scale by using a light source and CCD camera for data acquisition. The ability to achieve such spatial resolution and observe detailed features is influenced by optical diffraction. By combining diffraction from both the sample and substrate, a model is developed to determine the intensity of the thermoreflectance signal. This model takes into account the effective optical distance, sample width, wavelength, signal phase shift, and reflectance intensity, while showing qualitative and quantitative agreement with experimental thermoreflectance images from 1 and 10 μm wide gold lines at two wavelengths.

  8. High-pressure neutron diffraction

    SciTech Connect

    Xu, Hongwu

    2011-01-10

    This lecture will cover progress and prospect of applications of high-pressure neutron diffraction techniques to Earth and materials sciences. I will first introduce general high-pressure research topics and available in-situ high-pressure techniques. Then I'll talk about high-pressure neutron diffraction techniques using two types of pressure cells: fluid-driven and anvil-type cells. Lastly, I will give several case studies using these techniques, particularly, those on hydrogen-bearing materials and magnetic transitions.

  9. Diffraction encoded position measuring apparatus

    DOEpatents

    Tansey, R.J.

    1991-09-24

    When a lightwave passes through a transmission grating, diffracted beams appear at the output or opposite side of the grating that are effectively Doppler shifted in frequency (phase) whereby a detector system can compare the phase of the zero order and higher order beams to obtain an indication of position. Multiple passes through the grating increase resolution for a given wavelength of a laser signal. The resolution can be improved further by using a smaller wavelength laser to generate the grating itself. Since the grating must only have a pitch sufficient to produce diffracted orders, inexpensive, ultraviolet wavelength lasers can be utilized and still obtain high resolution detection. 3 figures.

  10. Diffraction encoded position measuring apparatus

    DOEpatents

    Tansey, Richard J.

    1991-01-01

    When a lightwave passes through a transmission grating, diffracted beams appear at the output or opposite side of the grating that are effectively Doppler shifted in frequency (phase) whereby a detector system can compare the phase of the zero order and higher order beams to obtain an indication of position. Multiple passes through the grating increase resolution for a given wavelength of a laser signal. The resolution can be improved further by using a smaller wavelength laser to generate the grating itself. Since the grating must only have a pitch sufficient to produce diffracted orders, inexpensive, ultraviolet wavelength lasers can be utilized and still obtain high resolution detection.

  11. Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES.

    PubMed

    Wuttke, Joachim; Zamponi, Michaela

    2013-11-01

    The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.

  12. Combining angular response classification and backscatter imagery segmentation for benthic biological habitat mapping

    NASA Astrophysics Data System (ADS)

    Che Hasan, Rozaimi; Ierodiaconou, Daniel; Laurenson, Laurie

    2012-01-01

    Backscatter information from multibeam echosounders (MBES) have been shown to contain useful information for the characterisation of benthic habitats. Compared to backscatter imagery, angular response of backscatter has shown advantages for feature discrimination. However its low spatial resolution inhibits the generation of fine scale habitat maps. In this study, angular backscatter response was combined with image segmentation of backscatter imagery to characterise benthic biological habitats in Discovery Bay Marine National Park, Victoria, Australia. Angular response of backscatter data from a Reson Seabat 8101 MBES (240 kHz) was integrated with georeferenced underwater video observations for constructing training data. To produce benthic habitat maps, decision tree supervised classification results were combined with mean shift image segmentation for class assignment. The results from mean angular response characteristics show effects of incidence angle at the outer angle for invertebrates (INV) and mixed red and invertebrates (MRI) classes, whilst mixed brown algae (MB) and mixed brown algae and invertebrates (MBI) showed similar responses independent from incidence angle. Automatic segmentation processing produce over segmented results but showed good discrimination between heterogeneous regions. Accuracy assessment from habitat maps produced overall accuracies of 79.6% (Kappa coefficient = 0.66) and 80.2% (Kappa coefficient = 0.67) for biota and substratum classifications respectively. MRI and MBI produced the lowest average accuracy while INV the highest. The ability to combine angular response and backscatter imagery provides an alternative approach for investigating biological information from acoustic backscatter data.

  13. 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.

  14. Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES

    SciTech Connect

    Wuttke, Joachim; Zamponi, Michaela

    2013-11-15

    The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.

  15. Compton backscattering of intracavity storage ring free-electron laser radiation

    SciTech Connect

    Dattoli, G.; Giannessi, L.; Torre, A.

    1995-12-31

    We discuss the{gamma}-ray production by Compton backscattering of intracavity storage ring Free-Electron Laser radiation. We use a semi-analytical model which provides the build up of the signal combined with the storage ring damping mechanism and derive simple relations yielding the connection between backscattered. Photons brightness and the intercavity laser equilibrium intensity.

  16. Observation of semiconductor superstructures with backscattered electrons in a scanning electron microscope

    SciTech Connect

    Bosacchi, A.; Franchi, S.; Govoni, D.; Mattei, G.; Merli, P.G.; Migliori, A.; Nacucchi, M.

    1995-12-31

    Observations of semiconductor superstructures with backscattered electrons in a scanning electron microscope have been used to revisit the concept of resolution of the backscattering imaging mode. It will be shown that the generation volume doesn`t represent in itself a limit to the resolution, which depends only on the beam size and the signal to noise ratio.

  17. 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.

  18. Backscatter absorption gas imaging systems and light sources therefore

    DOEpatents

    Kulp, Thomas Jan; Kliner, Dahv A. V.; Sommers, Ricky; Goers, Uta-Barbara; Armstrong, Karla M.

    2006-12-19

    The location of gases that are not visible to the unaided human eye can be determined using tuned light sources that spectroscopically probe the gases and cameras that can provide images corresponding to the absorption of the gases. The present invention is a light source for a backscatter absorption gas imaging (BAGI) system, and a light source incorporating the light source, that can be used to remotely detect and produce images of "invisible" gases. The inventive light source has a light producing element, an optical amplifier, and an optical parametric oscillator to generate wavelength tunable light in the IR. By using a multi-mode light source and an amplifier that operates using 915 nm pump sources, the power consumption of the light source is reduced to a level that can be operated by batteries for long periods of time. In addition, the light source is tunable over the absorption bands of many hydrocarbons, making it useful for detecting hazardous gases.

  19. 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.

  20. Updated Model of Radar Backscatter for Rough Lunar Craters

    NASA Technical Reports Server (NTRS)

    Thompson, Thomas W.; Ustinov, Eugene A.

    2013-01-01

    We reexamined our radar scattering model for young, rough craters [1] based on unpublished data from the 1980's [2]. Our model for scattering from the lunar surface is a mixing model consisting of varying amounts of diffuse and specular components as shown in Figure 1. The specular component, which consists of only opposite-sense circular (OC) echoes, results from the mirror-like surface and sub-surface layers that are smooth to a tenth of a radar wavelength for large (>10 wavelengths) areas oriented perpendicular to the radar's line-ofsight. The diffuse component, which has both OC and same sense (SC) circular echoes, is associated with either surface roughness (wavelength-sized rocks) or ice, and is assumed to be uniformly bright, with backscatter being proportional to the cosine of the incidence angle. Only diffuse scattering contributes to the SC echoes.

  1. 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.

  2. 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 α-shape method, constructing an output compatible with Geographic Information Systems (GIS).

  3. An Optical Backscatter Sensor for Particulate Matter Measurement

    SciTech Connect

    Parks, II, James E; Prikhodko, Vitaly Y; Partridge Jr, William P

    2009-01-01

    Diesel engines are prone to emit particulate matter (PM) emissions under certain operation conditions. In-cylinder production of PM from diesel combustion control can occur under a wide variety of operating conditions, and in some cases, operation of a multi-cylinder engine can further complicate PM emissions due to variations in air or fuel charge due to manifold mixing effects. In this study, a probe for detecting PM in diesel exhaust was evaluated on a light-duty diesel engine. The probe is based on an optical backscattering effect. Due to the optical nature of the probe, PM sensing can occur at high rates. The feasibility of the probe for examining PM emissions in the exhaust manifold will be discussed.

  4. Pulsed laser linescanner for a backscatter absorption gas imaging system

    DOEpatents

    Kulp, Thomas J.; Reichardt, Thomas A.; Schmitt, Randal L.; Bambha, Ray P.

    2004-02-10

    An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they attenuate the illumination creating a shadow in the image. This disclosure describes a BAGI imager that operates in a linescanned manner using a high repetition rate pulsed laser as its illumination source. The format of this system allows differential imaging, in which the scene is illuminated with light at least 2 wavelengths--one or more absorbed by the gas and one or more not absorbed. The system is designed to accomplish imaging in a manner that is insensitive to motion of the camera, so that it can be held in the hand of an operator or operated from a moving vehicle.

  5. Microwave backscattering and emission model for grass canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; Lang, Roger H.; Levine, David M.

    1991-01-01

    A two-layer model is developed that treats the grass canopy as a collection of randomly oriented elliptical dielectric discs over a layer of thatch with underlying soil surface. The distorted Born approximation in conjunction with the Peake formulation is used to calculate the backscattering coefficient and the emissivity from the canopy. Two particular features of this model which are unique for grass canopies are the variation of the canopy structure and the presence of the thatch layer. The basic parameters in the model such as the size and orientation of grass blades, dielectric constant of soil and vegetation, and thickness and water content of the thatch layer have been obtained from ground truth data. To interpret the available experimental observations of grasslands, numerical results from both passive and active models at L-band (1.4 GHz) are generated and various scattering and emission properties of the grass canopies are discussed.

  6. 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.

  7. Direct wavefront sensing in adaptive optical microscopy using backscattered light.

    PubMed

    Rahman, Saad A; Booth, Martin J

    2013-08-01

    Adaptive optics has been used to compensate the detrimental effects of aberrations in a range of high-resolution microscopes. We investigate how backscattered laser illumination can be used as the source for direct wavefront sensing using a pinhole-filtered Shack-Hartmann wavefront sensor. It is found that the sensor produces linear response to input aberrations for a given specimen. The gradient of this response is dependent upon experimental configuration and specimen structure. Cross sensitivity between modes is also observed. The double pass nature of the microscope system leads in general to lower sensitivity to odd-symmetry aberration modes. The results show that there is potential for use of this type of wavefront sensing in microscopes.

  8. Control of light backscattering in blood during intravenous laser irradiation

    NASA Astrophysics Data System (ADS)

    Melnik, Ivan S.; Popov, V. D.; Rusina, Tatyana V.; Dets, Sergiy M.

    1997-02-01

    One of the most important problems in modern laser medicine is the determination of system response on laser treatment. Reaction of living system is significant during many kinds of laser procedures like surgery, therapy and biostimulation. Our study was aimed to optimize laser exposure using feed-back fiber system for intravenous laser irradiation of blood (ILIB). This system consisted of helium-neon laser (633 nm, 5 mW) with coupled fiber unit, photodetector and PC interface. Photodetector signals produced due to light backscattering were storaged and processed during all blood irradiation procedure. Significant time-dependent variations were observed within 9-15 min after beginning of treatment procedure and were correlated with number of trials, stage and character of disease. The designed feed-back system allows us to register a human blood response on laser irradiation to achieve better cure effect.

  9. Kinetic Enhancement of Raman Backscatter, and Electron Acoustic Thomson Scatter

    SciTech Connect

    Strozzi, D J; Williams, E A; Langdon, A B; Bers, A

    2006-09-01

    1-D Eulerian Vlasov-Maxwell simulations are presented which show kinetic enhancement of stimulated Raman backscatter (SRBS) due to electron trapping in regimes of heavy linear Landau damping. The conventional Raman Langmuir wave is transformed into a set of beam acoustic modes [L. Yin et al., Phys. Rev. E 73, 025401 (2006)]. For the first time, a low phase velocity electron acoustic wave (EAW) is seen developing from the self-consistent Raman physics. Backscatter of the pump laser off the EAW fluctuations is reported and referred to as electron acoustic Thomson scatter. This light is similar in wavelength to, although much lower in amplitude than, the reflected light between the pump and SRBS wavelengths observed in single hot spot experiments, and previously interpreted as stimulated electron acoustic scatter [D. S. Montgomery et al., Phys. Rev. Lett. 87, 155001 (2001)]. The EAW observed in our simulations is strongest well below the phase-matched frequency for electron acoustic scatter, and therefore the EAW is not produced by it. The beating of different beam acoustic modes is proposed as the EAW excitation mechanism, and is called beam acoustic decay. Supporting evidence for this process, including bispectral analysis, is presented. The linear electrostatic modes, found by projecting the numerical distribution function onto a Gauss-Hermite basis, include beam acoustic modes (some of which are unstable even without parametric coupling to light waves) and a strongly-damped EAW similar to the observed one. This linear EAW results from non-Maxwellian features in the electron distribution, rather than nonlinearity due to electron trapping.

  10. 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.

  11. EBSD Study of the Influence of a High Magnetic Field on the Microstructure and Orientation of the Al-Si Eutectic During Directional Solidification

    NASA Astrophysics Data System (ADS)

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Ren, Zhongming; Moreau, Rene

    2016-06-01

    The effect of a high magnetic field on the morphology of the Al-Si eutectic was investigated using EBSD technology. The results revealed that the application of the magnetic field modified the morphology of the Al-Si eutectic significantly. Indeed, the magnetic field destroyed the coupled growth of the Al-Si eutectic and caused the formation of the divorced α-Al and Si dendrites at low growth speeds (≤1 μm/s). The magnetic field was also found to refine the eutectic grains and reduce the eutectic spacing at the initial growth stage. Moreover, the magnetic field caused the occurrence of the columnar-to-equiaxed transition of the α-Al phase in the Al-Si eutectic. The abovementioned effects were enhanced as the magnetic field increased. This result should be attributed to the magnetic field restraining the interdiffusion of Si and Al atoms in liquid ahead of the liquid/solid interface and the thermoelectric magnetic force acting on the eutectic lamellae under the magnetic field.

  12. Atmospheric aerosol and molecular backscatter imaging effects on direct detection LADAR

    NASA Astrophysics Data System (ADS)

    Youmans, Douglas G.

    2015-05-01

    Backscatter from atmospheric aerosols and molecular nitrogen and oxygen causes "clutter" noise in direct detection ladar applications operating within the atmosphere. The backscatter clutter is more pronounced in multiple pulse, high PRF ladars where pulse-averaging is used to increase operating range. As more and more pulses are added to the wavetrain the backscatter increases. We analyze the imaging of a transmitted Gaussian laser-mode multi-pulse wave-train scatteried off of aerosols and molecules at the focal plane including angular-slew rate resulting from optical tracking, angular lead-angle, and bistatic-optics spatial separation. The defocused backscatter images, from those pulses closest to the receiver, are analyzed using a simple geometrical optics approximation. Methods for estimating the aerosol number density versus altitude and the volume backscatter coefficient of the aerosols are also discussed.

  13. 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.

  14. [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

  15. Relating multifrequency radar backscattering to forest biomass: Modeling and AIRSAR measurement

    NASA Technical Reports Server (NTRS)

    Sun, Guo-Qing; Ranson, K. Jon

    1992-01-01

    During the last several years, significant efforts in microwave remote sensing were devoted to relating forest parameters to radar backscattering coefficients. These and other studies showed that in most cases, the longer wavelength (i.e. P band) and cross-polarization (HV) backscattering had higher sensitivity and better correlation to forest biomass. This research examines this relationship in a northern forest area through both backscatter modeling and synthetic aperture radar (SAR) data analysis. The field measurements were used to estimate stand biomass from forest weight tables. The backscatter model described by Sun et al. was modified to simulate the backscattering coefficients with respect to stand biomass. The average number of trees per square meter or radar resolution cell, and the average tree height or diameter breast height (dbh) in the forest stand are the driving parameters of the model. The rest of the soil surface, orientation, and size distributions of leaves and branches, remain unchanged in the simulations.

  16. Fresnel Diffraction for CTR Microbunching

    SciTech Connect

    Tikhoplav, R.; Knyazik, A.; Rosenzweig, J. B.; Andonian, G.

    2009-01-22

    Laser beams of high intensities are routinely used for IFEL experiments. Such beams can potentially destroy microbunching diagnostic tools such as coherent transition radiation foils due to their low damage thresholds. Near-field Fresnel diffraction scheme for termination of CO{sub 2} laser beam has been experimentally studied and is presented in this paper. Novel THz camera was utilized for such study.

  17. Diffraction Plates for Classroom Demonstrations

    ERIC Educational Resources Information Center

    Hoover, Richard B.

    1969-01-01

    Describes the computer generation of random and regular arrays of apertures on photographic film and their applications for classroom demonstrations of the Fraunhofer patterns produced by simple and complex apertures, Babinet's principle, resolution according to the Rayleigh criterion, and many other aspects of diffraction. (LC)

  18. Phonons from neutron powder diffraction

    SciTech Connect

    Dimitrov, D.A.; Louca, D.; Roeder, H. )

    1999-09-01

    The spherically averaged structure function S([vert bar][bold q][vert bar]) obtained from pulsed neutron powder diffraction contains both elastic and inelastic scattering via an integral over energy. The Fourier transformation of S([vert bar][bold q][vert bar]) to real space, as is done in the pair density function (PDF) analysis, regularizes the data, i.e., it accentuates the diffuse scattering. We present a technique which enables the extraction of off-center ([vert bar][bold q][vert bar][ne]0) phonon information from powder diffraction experiments by comparing the experimental PDF with theoretical calculations based on standard interatomic potentials and the crystal symmetry. This procedure [dynamics from powder diffraction] has been [ital successfully] implemented as demonstrated here for two systems, a simple metal fcc Ni and an ionic crystal CaF[sub 2]. Although computationally intensive, this data analysis allows for a phonon based modeling of the PDF, and additionally provides off-center phonon information from neutron powder diffraction. [copyright] [ital 1999] [ital The American Physical Society

  19. Hard diffraction and rapidity gaps

    SciTech Connect

    Albrow, M.G.

    1994-08-01

    I describe the evolution of experiments at hadron colliders on (a) high mass diffraction (b) double pomeron exchange, from the ISR through the Sp{bar p}S to the Tevatron. I emphasize an experimental approach to the question: ``What is the pomeron?``

  20. 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.