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1

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

SciTech Connect

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

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

2012-07-25

2

Restoration of firearm serial numbers with electron backscatter diffraction (EBSD).  

PubMed

Firearm serial numbers are a critical identifying mark, and restoration of destroyed serial numbers is often crucial for prosecution of a criminal case. A method is presented utilizing electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM) which allows for clear visualization of die-stamped imprints which have been completely polished away. Evidence of the stamp can be observed to a depth of approximately 760?m below the surface. With further development, the described method is capable of reconstructing an 8 character serial number in approximately 1h. PMID:25747326

White, Ryan M; Keller, Robert R

2015-04-01

3

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

Microsoft Academic Search

For the first time, in situ electron backscatter diffraction (EBSD) measurements during compression experiments by a modified nanoindenter on micron-sized single crystal pillars are demonstrated here. The experimental setup and the requirements concerning the compression sample are described in detail. EBSD mappings have been acquired before loading, under load and after unloading for consecutive compression cycles on a focused ion

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

2010-01-01

4

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

Microsoft Academic Search

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

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

2006-01-01

5

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

PubMed

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

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

2014-08-01

6

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

PubMed

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

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

2014-02-01

7

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

Microsoft Academic Search

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

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

2006-01-01

8

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

SciTech Connect

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

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

2007-08-15

9

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)

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

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

2009-08-01

10

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)

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

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

2009-01-01

11

Electron backscatter diffraction: Strategies for reliable data acquisition and processing  

SciTech Connect

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

Randle, Valerie, E-mail: v.randle@swansea.ac.uk [Materials Research Centre, School of Engineering, Swansea University, Swansea SA2 8PP (United Kingdom)

2009-09-15

12

Chirality determination of quartz crystals using electron backscatter diffraction.  

PubMed

We demonstrate the determination of crystal chirality using electron backscatter diffraction (EBSD) in the scanning electron microscope. The chirality of ?-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. PMID:25436930

Winkelmann, Aimo; Nolze, Gert

2015-02-01

13

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

PubMed

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

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

2013-08-01

14

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

PubMed Central

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

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

2013-01-01

15

Crystallographic orientation assessment by electron backscattered diffraction.  

PubMed

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

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

1999-01-01

16

Comparison of deformation texture in FePd alloy via X-ray diffraction and electron backscatter diffraction techniques.  

PubMed

In this work, textures measured by electron backscatter diffraction (EBSD) and X-ray diffraction in rolled FePd alloys were compared. The effect of scanning size used for EBSD measurements was investigated. The correlation coefficient was first proposed to quantify the similarity of the orientation density profile along the ?- and ?-fibers after cold rolling. The correlation coefficient is approximately 1 for a scanning step range of 1-20 ?m after 50% and 88% reduction. A large scanning step can capture the main components of the macrotexture in EBSD measurements. Thus, the macrotexture measured by EBSD provides another method for the quality control of texture. PMID:23098641

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

2013-01-01

17

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

Microsoft Academic Search

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

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

2007-01-01

18

Dynamical electron backscatter diffraction patterns. Part I: pattern simulations.  

PubMed

A new approach for the simulation of dynamic electron backscatter diffraction (EBSD) patterns is introduced. The computational approach merges deterministic dynamic electron-scattering computations based on Bloch waves with a stochastic Monte Carlo (MC) simulation of the energy, depth, and directional distributions of the backscattered electrons (BSEs). An efficient numerical scheme is introduced, based on a modified Lambert projection, for the computation of the scintillator electron count as a function of the position and orientation of the EBSD detector; the approach allows for the rapid computation of an individual EBSD pattern by bi-linear interpolation of a master EBSD pattern. The master pattern stores the BSE yield as a function of the electron exit direction and exit energy and is used along with weight factors extracted from the MC simulation to obtain energy-weighted simulated EBSD patterns. Example simulations for nickel yield realistic patterns and energy-dependent trends in pattern blurring versus filter window energies are in agreement with experimental energy-filtered EBSD observations reported in the literature. PMID:23800378

Callahan, Patrick G; De Graef, Marc

2013-10-01

19

Ion beam polishing for three-dimensional electron backscattered diffraction.  

PubMed

Serial sectioning by focused ion beam milling for three-dimensional electron backscatter diffraction (3D-EBSD) can create surface damage and amorphization in certain materials and consequently reduce the EBSD signal quality. Poor EBSD signal causes longer data acquisition time due to signal averaging and/or poor 3D-EBSD data quality. In this work a low kV focused ion beam was successfully implemented to automatically polish surfaces during 3D-EBSD of La- and Nb-doped strontium titanate of volume 12.6 × 12.6 × 3.0 ?m. The key to achieving this technique is the combination of a defocused low kV high current ion beam and line scan milling. The line scan was used to restrict polishing to the sample surface and the ion beam was defocused to ensure the beam contacted the complete sample surface. In this study 1 min polishing time per slice increases total acquisition time by approximately 3.3% of normal 3D-EBSD mapping compared to a significant increase of indexing percentage and pattern quality. The polishing performance in this investigation is discussed, and two potential methods for further improvement are presented. PMID:23126405

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

2013-01-01

20

Orientation precision of electron backscatter diffraction measurements near grain boundaries.  

PubMed

Electron backscatter diffraction (EBSD) has become a common technique for measuring crystallographic orientations at spatial resolutions on the order of tens of nanometers and at angular resolutions <0.1°. In a recent search of EBSD papers using Google Scholar™, 60% were found to address some aspect of deformation. Generally, deformation manifests itself in EBSD measurements by small local misorientations. An increase in the local misorientation is often observed near grain boundaries in deformed microstructures. This may be indicative of dislocation pile-up at the boundaries but could also be due to a loss of orientation precision in the EBSD measurements. When the electron beam is positioned at or near a grain boundary, the diffraction volume contains the crystal lattices from the two grains separated by the boundary. Thus, the resulting pattern will contain contributions from both lattices. Such mixed patterns can pose some challenge to the EBSD pattern band detection and indexing algorithms. Through analysis of experimental local misorientation data and simulated pattern mixing, this work shows that some of the rise in local misorientation is an artifact due to the mixed patterns at the boundary but that the rise due to physical phenomena is also observed. PMID:24576405

Wright, Stuart I; Nowell, Matthew M; de Kloe, René; Chan, Lisa

2014-06-01

21

Present State of Electron Backscatter Diffraction and Prospective Developments  

SciTech Connect

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.

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

2008-10-24

22

Analysis of refractory inclusions in the Allende and Axtell CV3 chondrites via electron-backscatter diffraction.  

E-print Network

hypothesized to have formed by several mechanisms including condensation, metasomatic exchange, and flash heating [3, 4]. In this study we used electron backscatter diffraction (EBSD) to determine the detailed the horizontal. Automated EBSD analysis was performed with the HKL Channel 5 software package. Maps were

Grossman, Lawrence

23

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

PubMed

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

Payton, E J; Nolze, G

2013-08-01

24

The complementary use of electron backscatter diffraction and ion channelling imaging for the characterization of nanotwins.  

PubMed

On the example of electrodeposited nickel films, it is shown that unique information on twins with dimensions on the nanoscale can be obtained by suitable combination of ion channelling imaging and electron backscatter diffraction analysis, whereas both (routine) single techniques cannot meet the requirements for analysis of these films. High-resolution electron backscatter diffraction is inadequate for full characterization of nanotwins, but image quality maps obtained from electron backscatter diffraction at least yield a qualitative estimation of the location and number of nanotwins. Complementing this information with ion channelling imaging provides more representative insights into the microstructure, because it supplements the quantitative investigation of the number and width of twin lamellae with additional crystallographic orientation analysis provided by EBSD. To this end, two methods for adjusting EBSD data based on ion channelling images are proposed. Thorough selection of the complementary techniques opens future perspectives for the investigation of other challenging samples with nanoscale features in the microstructure. PMID:23253115

Alimadadi, H; Fanta, A B; Pantleon, K

2013-02-01

25

Electron backscatter diffraction in conservation science: phase identification of pigments in paint layers.  

PubMed

Electron backscatter diffraction (EBSD) was used in Conservation Science for characterization of ancient materials collected from works of art. The results demonstrate the feasibility of EBSD analysis on heterogeneous matrices as very small samples of paint layers collected from paintings. Two reference pigments were selected from those used by artists to investigate the relationship existing between EBSD pattern quality and properties of the investigated material (i.e., average atomic number, density, and Mohs hardness). The technique was also tested to investigate the pigment phases on two real samples collected from Romanino's Santa Giustina altarpiece, an oil on wood painting dated 1514 (Civic Museum, Padova, Italy). Results show for the first time the acquisition of EBSD patterns from painting samples mounted in resin, i.e., painting cross sections, opening a new powerful tool to elucidate the pigment phases avoiding large sampling on works of arts and to further study the complex mechanisms of pigment deterioration. PMID:23663448

Gambirasi, A; Peruzzo, L; Bianchin, S; Favaro, M

2013-08-01

26

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

Microsoft Academic Search

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

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

2007-01-01

27

Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions  

Microsoft Academic Search

As a step towards resolving the genesis of inclusions in diamonds, a new technique is presented. This technique combines cathodoluminescence (CL) and electron backscatter diffraction (EBSD) using a focused ion beam-scanning electron microscope (FIB-SEM) instrument with the aim of determining, in detail, the three-dimensional diamond zonation adjacent to a diamond inclusion. EBSD reveals that mineral inclusions in a single diamond

D. F. Wiggers de Vries; M. R. Drury; D. A. M. de Winter; G. P. Bulanova; D. G. Pearson; G. R. Davies

2011-01-01

28

Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions  

Microsoft Academic Search

As a step towards resolving the genesis of inclusions in diamonds, a new technique is presented. This technique combines cathodoluminescence (CL) and electron backscatter diffraction (EBSD) using a focused ion beam-scanning electron microscope (FIB-SEM) instrument with the aim of determining, in detail, the three-dimensional diamond zonation adjacent to a diamond inclusion. EBSD reveals that mineral inclusions in a single diamond

D. F. Wiggers de Vries; M. R. Drury; D. A. M. de Winter; G. P. Bulanova; D. G. Pearson; G. R. Davies

2010-01-01

29

Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions  

Microsoft Academic Search

As a step towards resolving the genesis of inclusions in diamonds, a new technique is presented. This technique combines cathodoluminescence\\u000a (CL) and electron backscatter diffraction (EBSD) using a focused ion beam–scanning electron microscope (FIB–SEM) instrument\\u000a with the aim of determining, in detail, the three-dimensional diamond zonation adjacent to a diamond inclusion. EBSD reveals\\u000a that mineral inclusions in a single diamond

D. F. Wiggers de Vries; M. R. Drury; D. A. M. de Winter; G. P. Bulanova; D. G. Pearson; G. R. Davies

2011-01-01

30

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

PubMed

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

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

2013-08-01

31

Microstructural characterization by electron backscatter diffraction of a hot worked Al–Cu–Mg alloy  

Microsoft Academic Search

Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al–Cu–Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted in the range 278–467°C, and at two strain rates, 2.1 and 4.5s?1. Electron backscatter diffraction (EBSD) was employed to characterize the microtexture and microstructure before and after testing. The microstructural evolution during torsion deformation

C. M. Cepeda-Jiménez; P. Hidalgo; M. Carsí; O. A. Ruano; F. Carreño

2011-01-01

32

Direct Detection of Electron Backscatter Diffraction Patterns  

NASA Astrophysics Data System (ADS)

We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data.

Wilkinson, Angus J.; Moldovan, Grigore; Britton, T. Benjamin; Bewick, Angus; Clough, Robert; Kirkland, Angus I.

2013-08-01

33

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

PubMed Central

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

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

2014-01-01

34

Large area stress distribution in crystalline materials calculated from lattice deformation identified by electron backscatter diffraction.  

PubMed

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

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

2014-01-01

35

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

36

Application of electron backscatter diffraction for crystallographic characterization of tin whiskers.  

PubMed

Understanding the growth of whiskers or high aspect ratio features on substrates can be aided when the crystallography of the feature is known. This study has evaluated three methods that utilize electron backscatter diffraction (EBSD) for the determination of the crystallographic growth direction of an individual whisker. EBSD has traditionally been a technique applied to planar, polished samples, and thus the use of EBSD for out-of-surface features is somewhat more difficult and requires additional steps. One of the methods requires the whiskers to be removed from the substrate resulting in the loss of valuable physical growth relationships between the whisker and the substrate. The other two techniques do not suffer this disadvantage and provide the physical growth information as well as the crystallographic growth directions. The final choice of method depends on the information required. The accuracy and the advantages and disadvantages of each method are discussed. PMID:22832083

Michael, Joseph R; McKenzie, Bonnie B; Susan, Donald F

2012-08-01

37

Electron backscatter diffraction and electron channeling contrast imaging of tilt and dislocations in nitride thin films  

SciTech Connect

In this paper we describe the use of electron backscatter diffraction (EBSD) mapping and electron channeling contrast imaging--in the scanning electron microscope--to study tilt, atomic steps and dislocations in epitaxial GaN thin films. We show results from a series of GaN thin films of increasing thickness and from a just coalesced epitaxial laterally overgrown GaN thin film. From our results we deduce that EBSD may be used to measure orientation changes of the order of 0.02 deg. , in GaN thin films. As EBSD has a spatial resolution of {approx_equal}20 nm, this means we have a powerful technique with which to quantitatively map surface tilt. We also demonstrate that electron channeling contrast images may be used to image tilt, atomic steps, and threading dislocations in GaN thin films.

Trager-Cowan, C.; Sweeney, F.; Trimby, P. W.; Day, A. P.; Gholinia, A.; Schmidt, N.-H.; Parbrook, P. J.; Wilkinson, A. J.; Watson, I. M. [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 ONG, Scotland (United Kingdom); HKL TECHNOLOGY A/S, Majsmarken 1, Hobro, DK 9500 (Denmark); EPSRC National Centre for III-V Technologies, University of Sheffield (United Kingdom); Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); SUPA, Institute of Photonics, University of Strathclyde, Glasgow G4 ONW, Scotland (United Kingdom)

2007-02-15

38

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

SciTech Connect

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

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

1999-05-10

39

Electron Backscatter Diffraction: An Important Tool for Analyses of Structure-Property Relationships in Thin-Film Solar Cells  

NASA Astrophysics Data System (ADS)

The present work gives an overview of the application of electron backscatter diffraction (EBSD) in the field of thin-film solar cells, which consist of stacks of polycrystalline layers on various rigid or flexible substrates. EBSD provides access to grain-size and local-orientation distributions, film textures, and grain-boundary types. By evaluation of the EBSD patterns within individual grains of the polycrystalline solar cell layers, microstrain distributions also can be obtained. These microstructural properties are of considerable interest for research and development of thin-film solar cells. Moreover, EBSD may be performed three-dimensionally, by alternating slicing of cross sections in a focused ion-beam machine and EBSD acquisition. To relate the microstructural properties to the electrical properties of individual layers as well as to the device performances of corresponding solar cells, EBSD can be combined with electron-beam-induced current and cathodoluminescence measurements and with various scanning-probe microscopy methods such as Kelvin-probe force, scanning spreading resistance, or scanning capacitance microscopy on identical specimen positions. Together with standard device characterization of thin-film solar cells, these scanning microscopy measurements provide the means for extensive analysis of structure-property relationships in solar-cell stacks with polycrystalline layers.

Abou-Ras, D.; Kavalakkatt, J.; Nichterwitz, M.; Schäfer, N.; Harndt, S.; Wilkinson, A. J.; Tsyrulin, K.; Schulz, H.; Bauer, F.

2013-09-01

40

Scaling effects on grain size and texture of lead free interconnects — investigations by electron backscatter diffraction and nanoindentation  

Microsoft Academic Search

In this paper, the application of electron backscatter diffraction (EBSD) methods to solder interconnects is demonstrated, with particular emphasis on the effect of solder material volume on grain orientation, grain size and grain distribution in SnAg3.0Cu0.5 material, as well as with respect to the analysis of intermetallic compounds (IMC) formed in solder to board metallization interfaces. Investigations were carried out

M. Krause; M. Muller; M. Petzold; S. Wiese; K.-J. Wolter

2008-01-01

41

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

PubMed

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

West, G D; Thomson, R C

2009-03-01

42

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

SciTech Connect

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

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

2014-03-09

43

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

PubMed

Dark-field (DF) images were acquired in the scanning electron microscope with an offline procedure based on electron backscatter diffraction (EBSD) patterns (EBSPs). These EBSD-DF images were generated by selecting a particular reflection on the electron backscatter diffraction pattern and by reporting the intensity of one or several pixels around this point at each pixel of the EBSD-DF image. Unlike previous studies, the diffraction information of the sample is the basis of the final image contrast with a pixel scale resolution at the EBSP providing DF imaging in the scanning electron microscope. The offline facility of this technique permits the selection of any diffraction condition available in the diffraction pattern and displaying the corresponding image. The high number of diffraction-based images available allows a better monitoring of deformation structures compared to electron channeling contrast imaging (ECCI) which is generally limited to a few images of the same area. This technique was applied to steel and iron specimens and showed its high capability in describing more rigorously the deformation structures around micro-hardness indents. Due to the offline relation between the reference EBSP and the EBSD-DF images, this new technique will undoubtedly greatly improve our knowledge of deformation mechanism and help to improve our understanding of the ECCI contrast mechanisms. PMID:25461589

Brodusch, Nicolas; Demers, Hendrix; Gauvin, Raynald

2015-01-01

44

Assessing the precision of strain measurements using electron backscatter diffraction--part 1: detector assessment.  

PubMed

We analyse the link between precision of pattern shift measurements and the resolution of the measurement of elastic strain and lattice rotation using high resolution electron backscatter diffraction (HR-EBSD). This study combines analysis of high quality experimentally obtained diffraction patterns from single crystal silicon; high quality dynamical simulations using Bloch wave theory; quantitative measurements of the detector Modulation Transfer Function (MTF) and a numerical model. We have found that increases in exposure time, when 1×1 binning is selected, are the primary reason for the observed increase in sensitivity at greater than 2×2 binning and therefore use of software integration and high bit depth images enables a significant increase in strain resolution. This has been confirmed using simulated diffraction patterns which provide evidence that the ultimate theoretical resolution of the cross correlation based EBSD strain measurement technique with a 1000×1000 pixel image could be as low as 4.2×10(-7) in strain based on a shift precision of 0.001 pixels. PMID:24018163

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

2013-12-01

45

Using cross-correlation for automated stitching of two-dimensional multi-tile electron backscatter diffraction data.  

PubMed

A method for automatically aligning consecutive data sets of large, two-dimensional multi-tile electron backscatter diffraction (EBSD) scans with high accuracy was developed. The method involved first locating grain and phase boundaries within search regions containing overlapping data in adjacent scan tiles, and subsequently using cross-correlation algorithms to determine the relative position of the individual scan tiles which maximizes the fraction of overlapping boundaries. Savitzky-Golay filtering in two dimensions was used to estimate the background, which was then subtracted from the cross-correlation to enhance the peak signal in samples with a high density of interfaces. The technique was demonstrated on data sets with a range of interface densities. The equations were implemented as enhancements to a recently published open source code for stitching of multi-tile EBSD data sets. PMID:23078117

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

2012-11-01

46

Characterization of ultrafine grained Cu-Ni-Si alloys by electron backscatter diffraction  

NASA Astrophysics Data System (ADS)

A combination of rotary swaging and optimized precipitation hardening was applied to generate ultra fine grained (UFG) microstructures in low alloyed high performance Cu-based alloy CuNi3Si1Mg. As a result, ultrafine grained (UFG) microstructures with nanoscopically small Ni2Si-precipitates exhibiting high strength, ductility and electrical conductivity can be obtained. Grain boundary pinning by nano-precipitates enhances the thermal stability. Electron channeling contrast imaging (ECCI) and especially electron backscattering diffraction (EBSD) are predestined to characterize the evolving microstructures due to excellent resolution and vast crystallographic information. The following study summarizes the microstructure after different processing steps and points out the consequences for the most important mechanical and physical properties such as strength, ductility and conductivity.

Altenberger, I.; Kuhn, H. A.; Gholami, M.; Mhaede, M.; Wagner, L.

2014-08-01

47

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

PubMed

Due to its very low hardness and atomic number, pure lithium cannot be prepared by conventional methods prior to scanning electron microscopy analysis. Here, we report on the characterization of pure lithium metallic sheets used as base electrodes in the lithium-ion battery technology using electron backscatter diffraction (EBSD) and X-ray microanalysis using energy dispersive spectroscopy (EDS) after the sheet surface was polished by broad argon ion milling (IM). No grinding and polishing were necessary to achieve the sufficiently damage free necessary for surface analysis. Based on EDS results the impurities could be characterized and EBSD revealed the microsctructure and microtexture of this material with accuracy. The beam damage and oxidation/hydration resulting from the intensive use of IM and the transfer of the sample into the microscope chamber was estimated to be <50 nm. Despite the fact that the IM process generates an increase of temperature at the specimen surface, it was assumed that the milling parameters were sufficient to minimize the heating effect on the surface temperature. However, a cryo-stage should be used if available during milling to guaranty a heating artefact free surface after the milling process. PMID:25280344

Brodusch, Nicolas; Zaghib, Karim; Gauvin, Raynald

2015-01-01

48

A quantitative evaluation of microstructure by electron back-scattered diffraction pattern quality variations.  

PubMed

Band contrast (BC) is a qualitative measure of electron back-scattered diffraction (EBSD), which is derived from the intensity of the Kikuchi bands. The BC is dependent upon several factors including scanning electron microscope measurement parameters, EBSD camera setup, and the specimen itself (lattice defect and grain orientation). In this study, the effective factors for BC variations and the feasibility of using BC variations for the quantification of microstructure evolutions have been investigated. In addition, the effects of the lattice defect and the grain orientation on the BC variations are studied. Next, a shear-deformed microstructure of 316L stainless steel, which contains nanosized grains and a large portion of twin boundaries, is revealed by BC map and histogram. Recovery and recrystallization of shear-deformed 316L stainless steel are displayed by BC variations during isothermal annealing at 700 and 800°C, respectively. It is observed that the BC turns bright as the shear-deformed crystal structure is recovered or recrystallized. PMID:23920181

Kang, Suk Hoon; Jin, Hyung-Ha; Jang, Jinsung; Choi, Yong Seok; Oh, Kyu Hwan; Foley, David C; Zhang, Xinghang

2013-08-01

49

In situ Observation of Grain Growth on Electroplated Cu Film by Electron Backscatter Diffraction  

NASA Astrophysics Data System (ADS)

In situ observations using an automated electron backscatter diffraction (EBSD) system with a heating stage were carried out to clarify the mechanism of grain growth on electroplated Cu and Cu deposited by physical vapor deposition (PVD). Hardness measurements and EBSD observations revealed that the strain in electroplated Cu and Cu deposited by PVD was released by annealing. Little preferential orientation of the texture was observed in electroplated Cu, while Cu deposited by PVD showed strong (111) texture. A greater number of twin boundaries were observed in electroplated Cu than in Cu deposited by PVD. Grains surrounded by random grain boundaries were more enlarged by annealing in electroplated Cu than those in Cu deposited by PVD. Since segregation of impurities with a low melting point, such as sulfur, to grain boundaries could promote grain growth, which is often accompanied by twin boundary formation, the reason that many twin boundaries are found in electroplated Cu is considered to be the existence of impurities such as sulfur at grain boundaries. The effect of a twin grain boundary on resistivity was calculated and the contribution of a twin grain boundary to resistivity was found to be much less than that of a random grain boundary.

Nemoto, Takenao; Fukino, Tatsuya; Tsurekawa, Sadahiro; Gu, Xun; Teramoto, Akinobu; Ohmi, Tadahiro

2009-06-01

50

Elastic strain tensor measurement using electron backscatter diffraction in the SEM.  

PubMed

The established electron backscatter diffraction (EBSD) technique for obtaining crystallographic information in the SEM has been adapted to permit elastic strain measurement. Basically, the displacement of crystallographic features in an EBSD pattern, such as zone axes, which result from strain in a crystal, is determined by comparing those same features as they appear in a pattern from an unstrained region of the crystal. The comparison is made by cross-correlation of selected regions in the two patterns. Tests show that the sensitivity to displacement measurement is 1 part in 10 000, which translates to a strain sensitivity of 2 parts in 10 000. Eight components of the strain tensor are determined directly and the ninth is calculated using the fact that the free surface of the sample is traction-free. Examples discussed are taken from studies of a lenticular fracture in germanium, the strain distribution surrounding a carbide precipitate in a nickel base alloy and grain boundary studies in another nickel base alloy. PMID:20634548

Dingley, David J; Wilkinson, Angus J; Meaden, Graham; Karamched, Phani S

2010-08-01

51

Quantitative Comparison of Microtexture in Near-Alpha Titanium Measured by Ultrasonic Scattering and Electron Backscatter Diffraction  

NASA Astrophysics Data System (ADS)

Ultrasonic backscattering and attenuation data were collected and processed using recently developed theoretical models to estimate the directionally dependent, volume-averaged size, and morphology of microtextured regions (MTRs) in a near-? Ti-8Al-1Mo-1V bar. The sample was also interrogated with electron backscatter diffraction from which MTR sizes were obtained by either manual segmentation and linear intercept analysis or fitting the spatial autocorrelation of similarly oriented c-axes to the geometrical autocorrelation function used in the scattering model. The results of the ultrasonic inversion were in good agreement with the EBSD measurements for the radial direction but were off by a factor of ~2.45 for the longitudinal direction. Reasons for the discrepancy were discussed and strategies to improve the agreement were made.

Pilchak, Adam L.; Li, Jia; Rokhlin, Stanislav I.

2014-09-01

52

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

53

Advanced Characterization of Slags and Refractory Bricks Using Electron Backscatter Diffraction  

SciTech Connect

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 slag. Analysis of these crystals identified the crystalline phase epidote - Ca{sub 2}Al{sub 2}O(Al, Fe{sup 3+})OH(Si{sub 2}O{sub 7})(SiO{sub 4}). The identification could not have been performed from EDS alone because of Ca deficiency. However, looking at the crystal structure combined with EDS shows that the phase present is a Ca-deficient epidote. From this information, a temperature range of formation was determined. This gives a good example of the additional clarity that can be derived from utilizing EBSD. Evaluation of corrosion products by EBSD at the refractory brick and slag interface did reveal penetration and corrosion of slag into the brick through examination of crystalline phases alone. The degree of corrosion was dependent on the type of refractory and chemical makeup of the slag. This technique has not been used before to analyze slags and slag/refractory interactions. More work needs to be performed to better utilize EBSD for this type of analysis. This project demonstrates that the method is a valid technique that can be used to characterize slags and their interactions with refractory materials.

John Kay; Kurt Eylands

2007-09-30

54

Electron imaging with an EBSD detector.  

PubMed

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

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

2015-01-01

55

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

PubMed

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

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

2014-09-01

56

Limits of simulation based high resolution EBSD.  

PubMed

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

Alkorta, Jon

2013-08-01

57

Application of Electron Backscatter Diffraction to Phase Identification  

SciTech Connect

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.

El-Dasher, B S; Deal, A

2008-07-16

58

Electron Backscattered Diffraction Analysis Of Narrow Copper Interconnects In Cross-View To Investigate Scale Effect On Microstructure  

SciTech Connect

In this article, we propose to use Electron Backscattered Diffraction (EBSD) to characterize microstructure of copper interconnects of thin metal level in top view and cross view. These two views give very complementary information about microstructure of copper and thus about recrystallization of copper during annealing. Moreover, for minimum width, as interconnect is two times thicker than wide; It will be easier to analyze smaller interconnect of 45 nm node technology in cross-section. We look for evolution of texture and microstructure of copper with line width in top view and in cross view. We highlight the presence of two recrystallization mechanisms and also the fact that transition from one to the other is progressive with competition of both mechanisms.

Galand, Romain [STMicroelectronics, 850 rue Jean Monnet 38926 Crolles Cedex (France); SIMaP, 1130 rue de la Piscine BP 75 38402 St Martin D'Heres Cedex (France); Clement, Laurent; Waltz, Patrice [STMicroelectronics, 850 rue Jean Monnet 38926 Crolles Cedex (France); Wouters, Yves [SIMaP, 1130 rue de la Piscine BP 75 38402 St Martin D'Heres Cedex (France)

2010-11-24

59

Electron Backscattered Diffraction Analysis Of Narrow Copper Interconnects In Cross-View To Investigate Scale Effect On Microstructure.  

NASA Astrophysics Data System (ADS)

In this article, we propose to use Electron Backscattered Diffraction (EBSD) to characterize microstructure of copper interconnects of thin metal level in top view and cross view. These two views give very complementary information about microstructure of copper and thus about recrystallization of copper during annealing. Moreover, for minimum width, as interconnect is two times thicker than wide; It will be easier to analyze smaller interconnect of 45 nm node technology in cross-section. We look for evolution of texture and microstructure of copper with line width in top view and in cross view. We highlight the presence of two recrystallization mechanisms and also the fact that transition from one to the other is progressive with competition of both mechanisms.

Galand, Romain; Clément, Laurent; Waltz, Patrice; Wouters, Yves

2010-11-01

60

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

PubMed

Multiple three-dimensional reconstructions of a ?/?' phase structure in Alloy 720Li have been carried out by employing a serial milling technique with simultaneous electron backscatter diffraction (EBSD) and energy dispersive x-ray (EDX) analysis data collection. Combining EBSD data with EDX is critical in obtaining maps to distinguish between the chemically differing, but crystallographically similar ? and ?' phases present in the alloy studied. EDX is shown to allow the differentiation of ? and ?' phases, with EBSD providing increased grain shape accuracy. The combination of data sources also allowed identification of coherent ?/?' phase interfaces that would not be identified using solely EBSD or EDX. The study identifies a region of grain banding within the alloy, which provides the basis for a three-dimensional comparison and discussion of ?' phase size between coarse and fine grain regions, whilst also identifying coherent ?' phase interfaces, possible only using both EDX and EBSD systems simultaneously. The majority of the ?' phase lies in the range of 1-10 ?m in non-banded regions, with a detectable particle size limit of 500 nm being established. The validity of the reconstruction has been demonstrated using an electron interaction volumes model, and an assessment of the validity of EBSD and EDX data sources is discussed showing ?' phase connectivity in all dimensions. PMID:22343666

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

2012-03-01

61

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

PubMed

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

Ruggles, T J; Fullwood, D T

2013-10-01

62

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

PubMed

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

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

2012-06-01

63

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

64

Electron Backscatter Diffraction Study on Microstructure, Texture, and Strain Evolution in Armco Iron Severely Deformed by the Differential Speed Rolling Method  

NASA Astrophysics Data System (ADS)

Results of the electron backscatter diffraction (EBSD) study on structural changes in Armco iron subjected to severe plastic deformation by differential speed rolling (DSR) with different values of roll speed mismatch (R = 1, 2, 3, and 4) are shown in the present article. Results of the EBSD microstructure evaluation reveal that a differentiation of roll speeds results in an effect of structure refinement—iron samples processed with high roll speed mismatch are characterized by a high fraction of grains with submicron size. A microtexture examination shows that the DSR process leads to an overall texture weakening effect and a displacement (a shifting to different "stable" positions) of the basic rolling texture components, due to an additional presence of a simple shear component in the deformation gradient imposed to the material. Despite the higher hardness of the DSR-processed samples, results of the EBSD strain analysis indicate that some part of the stored deformation energy is released during rolling with an additional presence of shear strain. This finding points toward the possibility of activating a dynamic transformation of the material structure into some more stable state. However, since the observed structural changes take place inside deformation bands and do not lead directly to the formation of a fully equiaxed grain structure, it seems to be more reasonable to call the observed structure transformation a subgrain structure evolution through accumulated shear deformation, which may be related to the dynamic recovery process.

Polkowski, Wojciech; Jó?wik, Pawe?; Bojar, Zbigniew

2015-02-01

65

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

Microsoft Academic Search

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

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

2007-01-01

66

Crystallographic Orientation of Cuttlebone Shield Determined by Electron Backscatter Diffraction  

NASA Astrophysics Data System (ADS)

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.

Cusack, Maggie; Chung, Peter

2014-01-01

67

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

Microsoft Academic Search

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

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

2005-01-01

68

CCMR: Study of Tailored Oriented Microstructures in Thin Metal Films using SEM and EBSD  

NSDL National Science Digital Library

Thin silver films have many important potential applications but are not presently well understood. Using scanning electron microscopy and electron backscatter diffraction (EBSD) mapping, the microstructure silver films created with a range of different thicknesses, titanium adhesion layers, and annealing temperatures, have been analyzed.

Little, Bethany

2007-08-29

69

EBSD Analysis of Friction Stir Weld Textures  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

70

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

NASA Astrophysics Data System (ADS)

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.

Choudhury, Soud Farhan; Ladani, Leila

2014-04-01

71

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

PubMed

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

Batista, L; Rabe, U; Hirsekorn, S

2014-11-01

72

An electron back-scattered diffraction study on the microstructure evolution of severely deformed aluminum AI6061 alloy  

NASA Astrophysics Data System (ADS)

In this paper dynamic strain ageing behavior in an Al-Mg-Si alloy related to equal channel angular pressing (ECAP) was investigated. In order to examine the combined plastic deformation and ageing effects on microstructure evolutions and strengthening characteristics, the Al6061 alloy were subjected to phi=90° ECAP die for up to 4 passes via route Bc at high temperatures. For investigating the effects of ageing temperature and strain rate in ECAP, Vickers hardness tests were performed. The combination of the ECAP process with dynamic ageing at higher temperatures resulted in a significant increase in hardness. The microstructural evolution of the samples was studied using electron back-scattering diffraction (EBSD). The grains of Al6061 aluminum alloy were refined significantly at 100 and 150 °C with greater pass numbers and the distributions of grain size tended to be more uniform with pass number increasing. Frequency of sub-boundaries and low angle grain boundaries (LAGBs) increased at initial stage of deformation, and sub-boundaries and LAGBs evolved into highangle grain boundaries (HAGBs) with further deformation, which resulted in the high frequency of HAGBs in the alloy after ECAP 4 passes.

Vaseghi, M.; Karimi Taheri, A.; Kim, H. S.

2014-08-01

73

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

PubMed

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

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

2014-07-01

74

Measurement of geometrically necessary dislocation density with high resolution electron backscatter diffraction: effects of detector binning and step size.  

PubMed

Recent advances using cross-correlation analysis of full resolution high quality electron backscatter diffraction (EBSD) patterns have provided a method for quantitatively mapping the stored dislocation density at high spatial resolution. Larger areas could be mapped with image binning or coarser step sizes. We have studied the effects of image binning and step size on the recovery of GND density. Our results suggest that: (i) the measured lower bound GND density noise floor broadly agrees with Wilkinson and Randman's 2009 prediction, where a decrease in step size or an increase in misorientation uncertainty increases the noise floor; (ii) increasing the step size results in a lower GND density being recovered as some dislocations are now considered as statistically stored dislocations (SSDs); (iii) in deformed samples the average GND density stays relatively constant as the degree of pattern binning is increased up to 8×8. Pattern binning thus provides a means of increasing the data acquisition and analysis rate without unduly degrading the data quality. PMID:23262146

Jiang, J; Britton, T B; Wilkinson, A J

2013-02-01

75

Grain structural characterization of 9Cr-ODS steel aged at 973 K up to 10,000 h by electron backscatter diffraction  

NASA Astrophysics Data System (ADS)

In this work, thermal aging experiments on 9Cr-ODS steel were carried out at 973 K from 100 h up to 10,000 h, and grain structural evolution was investigated mainly focusing on analyses by electron backscatter diffraction (EBSD). The EBSD maps revealed no significant morphological changes in the matrix grain structure under the long-term aging. Grain size increased slightly with increasing periods of aging time from 100 h to 10,000 h. Distribution of misorientation angles was not affected by the thermal aging. The fraction of low misorientation angles comprised of subgrains was about 40% before aging, and decreased slightly by aging time up to 10,000 h. Total grain boundary length and density per unit area did not change significantly by aging up to 5000 h. They decreased slightly after aging for 10,000 h, which may be caused by slight recovery of microstructure. However, the effects of slight changes in the grain structure on mechanical properties are expected to be negligible.

Li, Yanfen; Abe, Hiroaki; Li, Feng; Satoh, Yuhki; Matsukawa, Yoshi; Matsunaga, Tetsuya; Muroga, Takeo

2014-12-01

76

Diffraction-controlled backscattering threshold and application to Raman gap  

SciTech Connect

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.

Rose, Harvey A. [New Mexico Consortium, Los Alamos, New Mexico 87544 (United States); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States); Mounaix, Philippe [Centre de Physique Theorique, UMR 7644 du CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France)

2011-04-15

77

Backscatter analysis of dihedral corner reflectors using physical optics and the physical theory of diffraction  

Microsoft Academic Search

The backscatter cross-sections of dihedral corner reflectors in the azimuthal plane are presently determined by both physical optics (PO) and the physical theory of diffraction (PTD), yielding results for the vertical and horizontal polarizations. In the first analysis method used, geometrical optics is used in place of PO at initial reflections in order to maintain the planar character of the

Timothy Griesser; Constantine A. Balanis

1987-01-01

78

Influence of reflector edges diffraction on manifestation of backscatter amplification effect  

Microsoft Academic Search

It is shown that in a regime of weak turbulence the edge diffraction on a reflector has a profound effect on intensity distribution of the reflected wave and on the manifestation of backscatter amplification. Therewith the dependence of the amplification factor on the Fresnel number of the reflector radius has an oscillating nature both for the corner reflector and for

Victor A. Banakh

1993-01-01

79

Investigation of plastic deformation heterogeneities in duplex steel by EBSD  

SciTech Connect

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.

Wronski, S., E-mail: wronski@ftj.agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow (Poland); Tarasiuk, J., E-mail: tarasiuk@ftj.agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow (Poland); Bacroix, B., E-mail: brigitte.bacroix@univ-paris13.fr [LSPM-CNRS, Universite Paris 13, 99, Av. J.-B. Clement, 93430 Villetaneuse (France); Baczmanski, A., E-mail: baczman@ftj.agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow (Poland); Braham, C., E-mail: chedly.braham@paris.ensam.fr [PIMM, Arts et Metiers ParisTech (ENSAM), 151 Bd de l'Hopital 75013 Paris (France)

2012-11-15

80

Reversed scan direction reduces electron beam damage in EBSD maps.  

PubMed

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

Kidder, S; Prior, D

2014-08-01

81

Phase analysis in duplex stainless steel: comparison of EBSD and quantitative metallography methods  

NASA Astrophysics Data System (ADS)

The purpose of the research was to work out the qualitative and quantitative analysis of phases in DSS in as-received state and after thermal aging. For quantitative purposes, SEM observations, EDS analyses and electron backscattered diffraction (EBSD) methods were employed. Qualitative analysis of phases was performed by two methods: EBSD and classical quantitative metallography. A juxtaposition of different etchants for the revealing of microstructure and brief review of sample preparation methods for EBSD studies were presented. Different ways of sample preparation were tested and based on these results a detailed methodology of DSS phase analysis was developed including: surface finishing, selective etching methods and image acquisition. The advantages and disadvantages of applied methods were pointed out and compared the accuracy of the analysis phase performed by both methods.

Michalska, J.; Chmiela, B.

2014-03-01

82

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

SciTech Connect

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.

Barnett, M.R. [Centre for Material and Fibre Innovation, Deakin University, Geelong (Australia)], E-mail: barnettm@deakin.edu.au; Sullivan, A. [Centre for Material and Fibre Innovation, Deakin University, Geelong (Australia); Balasubramaniam, R. [Depertment of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur, Kanpur 208 016 (India)

2009-04-15

83

Development of an economical electron backscattering diffraction system for an environmental scanning electron microscope  

NASA Astrophysics Data System (ADS)

A low cost, highly versatile electron backscattering diffraction system has been developed for an ElectroScan E3 Environmental Scanning Electron Microscope (ESEM). A P20 phosphor coated screen is placed in the microscope environment to image electron backscattering diffraction patterns (EBSP's). A CCD TV camera is used to view the patterns through a leaded glass port in the microscope specimen chamber. This system has a spatial resolution approaching 5 micron and yields analyzable patterns at pressures of up to 6 Torr. With minor modifications this system may be adapted to fit any scanning electron microscope. Comparison of analyses of the grain boundary misorientation of a Ni-16Cr-9Fe alloy with this system and by selected area channeling patterns (SACP's), performed in a standard SEM, yielded excellent agreement between the two techniques.

Thaveeprungsriporn, V.; Mansfield, J. F.; Was, G. S.

1994-07-01

84

A Dictionary Approach to EBSD Indexing  

E-print Network

We propose a framework for indexing of grain and sub-grain structures in electron backscatter diffraction (EBSD) images of polycrystalline materials. The framework is based on a previously introduced physics-based forward model by Callahan and De Graef (2013) relating measured patterns to grain orientations (Euler angle). The forward model is tuned to the microscope and the sample symmetry group. We discretize the domain of the forward model onto a dense grid of Euler angles and for each measured pattern we identify the most similar patterns in the dictionary. These patterns are used to identify boundaries, detect anomalies, and index crystal orientations. The statistical distribution of these closest matches is used in an unsupervised binary decision tree (DT) classifier to identify grain boundaries and anomalous regions. The DT classifies a pattern as an anomaly if it has an abnormally low similarity to any pattern in the dictionary. It classifies a pixel as being near a grain boundary if the highly ranked ...

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

2015-01-01

85

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

NASA Astrophysics Data System (ADS)

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 M?KAMnet and M??KAMave were introduced as the sum of product of the noise subtracted KAMnet and the absolute change from initial value ?KAMave with dislocation movement distance divided by pixel size. M??KAMave 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.

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

86

Characterization of NanoCrystalline Materials Using Electron Backscatter Diffraction in the Scanning Electron Microscope  

Microsoft Academic Search

EBSD should now be considered a standard analytical accessory for the SEM. The spatial resolution of EBSD is quite high (as\\u000a high as a few nm, depending upon material) and is suitable for the study of many nano-crystalline materials. For applications\\u000a of EBSD where the highest spatial resolution is required, an SEM with a field emission electron source is mandatory

J. R. Michael

87

Crystal preferred orientations of garnet: comparison between numerical simulations and electron back-scattered diffraction (EBSD) measurements  

E-print Network

Crystal preferred orientations of garnet: comparison between numerical simulations and electron support plastic deformation of garnet in laboratory experiments and naturally deformed eclogites. To evaluate the crystal preferred orientations (CPO) of garnet formed in axial shortening, pure shear

Bascou, Jérôme

88

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

NASA Astrophysics Data System (ADS)

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.

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

2008-02-01

89

ARPGE: a computer program to automatically reconstruct the parent grains from electron backscatter diffraction data  

PubMed Central

A computer program called ARPGE written in Python uses the theoretical results generated by the computer program GenOVa to automatically reconstruct the parent grains from electron backscatter diffraction data obtained on phase transition materials with or without residual parent phase. The misorientations between daughter grains are identified with operators, the daughter grains are identified with indexed variants, the orientations of the parent grains are determined, and some statistics on the variants and operators are established. Some examples with martensitic transformations in iron and titanium alloys were treated. Variant selection phenomena were revealed. PMID:19461849

Cayron, Cyril

2007-01-01

90

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

NASA Astrophysics Data System (ADS)

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

Fukino, Tatsuya; Tsurekawa, Sadahiro; Morizono, Yasuhiro

2011-03-01

91

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

SciTech Connect

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

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

2013-05-15

92

Effect of the surface preparation techniques on the EBSD analysis of a friction stir welded AA1100-B{sub 4}C metal matrix composite  

SciTech Connect

Aluminum based metal matrix composites (MMCs) have been used in various automobile, aerospace and military industries. Yet characterization of the microstructure in these materials remains a challenge. In the present work, the grain structure in the matrix of B{sub 4}C particulate reinforced MMCs and their friction stir welds is characterized by using optical metallography and the electron backscatter diffraction (EBSD) technique. Optical metallography can partially reveal the grain structure in the matrix of AA1100-16 vol.% B{sub 4}C composite. The EBSD technique has been successfully applied to characterize the grain structure in the AA1100-16 vol.% B{sub 4}C friction stir welds, which provides a powerful tool to follow the microstructural evolution of MMC materials during friction stir welding (FSW). Both mechanical polishing and ion beam polishing are used for the EBSD sample preparation. The effect of the sample preparation on the EBSD data acquisition quality is studied. Some typical examples, such as the identification of grains and subgrains, grain size distribution, deformation fields and the texture components are given. - Highlights: {yields} EBSD has been used to characterize the grain structure of Al-B{sub 4}C MMCs. {yields} Mechanical and ion beam polishing are compared for EBSD sample preparation of MMCs. {yields} EBSD shows great advantages over optical microscopy for microtexture analysis of MMCs.

Guo, J., E-mail: junfeng.guo@cnrc-nrc.gc.ca [University of Quebec at Chicoutimi, Chicoutimi (QC), G7H 2B1 (Canada); Aluminium Technology Centre, National Research Council Canada, Chicoutimi (QC), G7H 8C3 (Canada); Amira, S.; Gougeon, P. [Aluminium Technology Centre, National Research Council Canada, Chicoutimi (QC), G7H 8C3 (Canada); Chen, X.-G. [University of Quebec at Chicoutimi, Chicoutimi (QC), G7H 2B1 (Canada)

2011-09-15

93

Utilizing Ebsd to Validate and Understand Nde Techniques  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

94

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

SciTech Connect

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.

Abou-Ras, D.; Nichterwitz, M.; Unold, T.; Klaer, J.; Schock, H.-W. [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Glienicker Strasse 100, 14109 Berlin (Germany); Jahn, U. [Paul-Drude Institute for Solid-State Electronics, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2010-01-15

95

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

PubMed

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. PMID:24032661

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

2013-12-01

96

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

SciTech Connect

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.

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

2013-09-15

97

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

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

99

Measurement of local plastic strain distribution of stainless steel by electron backscatter diffraction  

SciTech Connect

Electron backscatter diffraction in conjunction with scanning electron microscopy was used to assess the plastic strain on a microstructural scale (local plastic strain) induced in stainless steel deformed up to a nominal strain of 19.7%. Accuracy of the measurement of misorientations was improved by a technique called the Domain Averaging Method (DAM), in which an average of crystal orientation was calculated for several data measured from the same domain. It was shown that the misorientation evaluated using the crystal orientation of which accuracy was improved by DAM showed localized plastic strain in the vicinity of grain boundaries (GB). The distribution of misorientations followed a log-normal distribution and the mean value correlated well with the macroscopic plastic strain induced. By using the correlation between the misorientation and the plastic strain, the distribution of local plastic strain could be quantified. It was shown that the plastic strain becomes more than 15% locally under a macroscopic strain of 4.9%. A procedure for confirming the accuracy of the measurement is also suggested.

Kamaya, Masayuki [Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan)], E-mail: kamaya@inss.co.jp

2009-02-15

100

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

SciTech Connect

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.

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

1996-12-31

101

EBSD Study of Damage Mechanisms in a High-Strength Ferrite-Martensite Dual-Phase Steel  

NASA Astrophysics Data System (ADS)

Electron backscattered diffraction (EBSD) analyses were performed on a fine-grained dual-phase (DP) sheet steel subjected to uniform tensile deformation and the preferred void nucleation sites as well as the micro-mechanisms of void formation were examined. EBSD study of grain average misorientation, grain orientation spread and kernel average misorientation of the deformed microstructure revealed that voids nucleation initially happened at ferrite-martensite interfaces neighboring rather large ferrite grains. This is believed to be mainly due to the higher shear deformation ability of the larger ferrite grains, the higher number of dislocation pile-ups at the martensite particles and the less uniform strain distribution within the larger ferrite grains compared to the smaller ones. The results demonstrated the impact of increasing uniform strain distribution within the DP microstructure on lowering the void nucleation probability.

Saeidi, N.; Ashrafizadeh, F.; Niroumand, B.; Barlat, F.

2015-01-01

102

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

NASA Astrophysics Data System (ADS)

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

Moser, D. E.

2012-12-01

103

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

PubMed

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

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

2013-01-01

104

Designing a standard for strain mapping: HR-EBSD analysis of SiGe thin film structures on Si.  

PubMed

Patterned SiGe thin film structures, heteroepitaxially deposited on Si substrates, are investigated as potential reference standards to establish the accuracy of high resolution electron backscattered diffraction (HR-EBSD) strain measurement methods. The proposed standards incorporate thin films of tetragonally distorted epitaxial Si?-xGex adjacent to strain-free Si. Six films of three different nominal compositions (x=0.2, 0.3, and 0.4) and various thicknesses were studied. Film composition and out-of-plane lattice spacing measurements, by x-ray photoelectron spectroscopy and x-ray diffraction, respectively, provided independent determinations of film epitaxy and predictions of tetragonal strain for direct comparison with HR-EBSD strain measurements. Films assessed to be coherent with the substrate exhibited tetragonal strain values measured by HR-EBSD identical to those predicted from the composition and x-ray diffraction measurements, within experimental relative uncertainties of order 2%. Such films thus provide suitable prototypes for designing a strain reference standard. PMID:25461586

Vaudin, M D; Osborn, W A; Friedman, L H; Gorham, J M; Vartanian, V; Cook, R F

2015-01-01

105

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

PubMed

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

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

2013-10-01

106

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

PubMed

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

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

2013-08-01

107

Alternate formulation of enhanced backscattering as phase conjugation and diffraction: derivation and experimental observation  

PubMed Central

Enhanced backscattering (EBS), also known as weak localization of light, is derived using the Huygens–Fresnel principle and backscattering is generally shown to be the sum of an incoherent baseline and a phase conjugated portion of the incident wave that forms EBS. The phase conjugated portion is truncated by an effective aperture described by the probability function P(s) of coherent path-pair separations. P(s) is determined by the scattering properties of the medium and so characterization of EBS can be used for metrology of scattering materials. A three dimensional intensity peak is predicted in free space at a point conjugate to the source and is experimentally observed. PMID:21716426

Rogers, Jeremy D.; Stoyneva, Valentina; Turzhitsky, Vladimir; Mutyal, Nikhil N.; Pradhan, Prabhakar; Çapo?lu, ?lker R.; Backman, Vadim

2011-01-01

108

Edge diffracted caustic fields. [using equivalent current method for backscattering from cone  

NASA Technical Reports Server (NTRS)

Review of some new results obtained using the equivalent current technique to calculate caustic fields in a study of backscattering from a cone. The caustic region on the back of a conducting cone for an axially incident electromagnetic wave is shown to extend to a distance of the order of a half-wavelength from the center of the caustic, thus fixing the minimum size conducting body such as a cone that can be treated using the ray optical format.

Burnside, W. D.; Peters, L., Jr.

1974-01-01

109

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

PubMed

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

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

2013-10-01

110

Assessing the precision of strain measurements using electron backscatter diffraction--part 2: experimental demonstration.  

PubMed

The residual impression after performing a microhardness indent in silicon has been mapped with high resolution EBSD to reveal residual elastic strain and lattice rotation fields. Mapping of the same area has been performed with variable pattern binning and exposure times to reveal the qualitative and quantitative differences resulting from reducing the pattern size and exposure time. Two dimension 'image' plots of these fields indicate that qualitative assessment of the shape and size of the fields can be performed with as much as 4×4 binning. However, quantitative assessment using line scans reveals that the smoothest profile can be obtained using minimal pattern binning and long exposure times. To compare and contrast with these experimental maps, finite element analysis has been performed using a continuum damage-plasticity material law which has been independently calibrated to Si [9]. The constitutive law incorporates isotropic hardening in compression, and isotropic hardening and damage in tension. To accurately capture the localised damage which develops during indentation via the nucleation and propagation of cracks around the indentation site cohesive elements were assigned along the interfaces between the planes which experience the maximum traction. The residual strain state around the indenter and the size of the cracks agree very well with the experimentally measured value. PMID:24034981

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

2013-12-01

111

EBSD Images Theoretical Background  

E-print Network

function during a welding procedure. Consistent grain growth curves were obtained with this techniqueMotivation EBSD Images Theoretical Background Defects in the Weld Grain Growth Low Speed Welding High Speed Welding Conclusion Heat-Affected Zone Observations Welding Experiments The low density

Candea, George

112

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

PubMed

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

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

2013-08-01

113

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

NASA Technical Reports Server (NTRS)

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

Martinez, James

2011-01-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

115

Preparation of samples with both hard and soft phases for electron backscatter diffraction: examples from gold mineralization.  

PubMed

Preparation of high-quality polished sample surfaces is an essential step in the collection of microanalytical data on the microstructures of minerals and alloys. Poorly prepared samples can yield insufficient or inconsistent results and, in the case of gold, potentially no data due to the "beilby" layer. Currently, preparation of ore samples is difficult as they commonly contain both hard and soft mineral phases. The aim of our research is to produce suitably polished sample surfaces, on all phases, for electron backscatter diffraction analysis. A combination of chemical-mechanical polishing (CMP) and broad ion-beam polishing (BIBP) was used to tackle the problem. Our results show that it is critical to perform CMP first, as it produces a suitable polish on the hard mineral phases but tends to introduce more damage to the soft mineral surfaces. BIBP is essential to produce a high-quality polish to the soft phases (gold). This is a highly efficient method of sample preparation and is important as it allows the complete quantification of ore textures and all constituent mineral phases, including soft alloys. PMID:23721665

Halfpenny, Angela; Hough, Robert M; Verrall, Michael

2013-08-01

116

EBSD study of substrate-mediated growth of hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

117

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

PubMed

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

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

2004-03-01

118

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

119

Insights to Meteorites and Impact Processes provided by Advanced EBSD Analysis  

NASA Astrophysics Data System (ADS)

Electron backscatter diffraction (EBSD) is a powerful analytical technique for assessing the petrographic texture of rocks and the crystallographic orientation of minerals therein using a scanning electron microscope (SEM). Innovations in EBSD technology include colour-coded forescattered electron (FSE) images, high resolution and highly sensitive EBSD detectors, together with advanced EDS integration. It allows to accurately identify and discriminate different phases, and to investigate microstructures related to shock metamorphism. As an example, shocked carbonates and shocked quartz reveal a complex thermal history during post-shock cooling. (A) EBSD studies of calcite ejecta particles from the Chicxulub impact event, at the K-Pg boundary of El Guayal, Mexico (~520 km SW of the Chicxulub crater centre) display various microstructures [1] and spherulitic calcite ejecta particles reveal a fibre texture of elongated crystals with a preferred orientation. This indicates the presence of carbonate melts which were ejected at T>1240°C and P>40 bar from upper target lithologies and crystallized at cooling rates of ~100´s °C/s [2]. The calcite particles of El Guayal and the K/Pg boundary of La Lajilla (~1000 km W of the crater centre) show distinct microstructures represented by unoriented, equiaxed crystals with random orientation distribution. It documents recrystallization upon impact induced thermal stress at T>550°C during prolonged atmospheric transport. (B) Combined EBSD, FSE and cathodoluminescence (CL) studies of semi-amorphous shocked quartz of Chicxulub, Ries and Popigai impactites, reveal various microstructures. Colour-coded FSE imaging reveal recrystallized/deformed bands in Ries and Popigai samples indicative of planar deformation features. EBSD studies of Popigai allow to distinguish twinned Qz, ?-Qz and ?-cristobalite along the transition zone between shocked gneiss clast and impact melt. Recrystallized Qz grains are associated with amorphous SiO2. For Chicxulub, the brecciated impact melt rock from borehole Yaxcopoil-1 (Unit 5, 861.72 m) [3] reveals that the ballen microstructure is only semi-amorphous and cross cuts a fine grained recrystallised microstructure. (C) CB chondrite Gujba: EDS and EBSD data were acquired simultaneously to study chemical and physical interactions between preexisting metal particles and the invading silicate-rich impact melt matrix. Metal particles appear to have different thermal histories. Some of them consist of many small grains (average diameter ~10 µm), which have a similar orientation when they are surrounded by arcuate Fe,Cr-sulfides. [4]. Acknowledgements: P. Claeys, R.H. Jones, ICDP and the Museum of Natural History Berlin for providing samples. References: [1] T. Salge (2007) PhD thesis, Humboldt Universität zu Berlin, 130p. [2] A. P. Jones et al. (2000) Lect. Notes in Earth Sciences 91: 343-361. [3] M. J. Nelson et al. (2012) GCA 86: 1-20. [4]. J. Berlin et al. (2013) 44th LPSC # 2439

Palasse, Laurie; Berlin, Jana; Goran, Daniel; Tagle, Roald; Hamers, Maartje; Assis Fernandes, Vera; Deutsch, Alexander; Schulte, Peter; Salge, Tobias

2013-04-01

120

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

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. PMID:25126753

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

2014-12-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

122

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

PubMed

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 96mm×12mm 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

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

2015-05-01

123

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

PubMed

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

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

2005-02-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

125

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

PubMed

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

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

2005-02-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

127

EBSD study of crystallographic identification of Fe-Al-Si intermetallic phases in Al-Si coating on Cr-Mo steel  

NASA Astrophysics Data System (ADS)

5Cr-0.5Mo steel was coated by hot-dipping in a molten Al-10 wt.% Si bath at 700 °C for 10, 60, 120 or 180 s. The identification of the phases in the Fe-Al-Si intermetallic phases formed in the aluminide layers during hot-dipping was carried out by using a combination of scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The EDS results show a ?5(H)-Al7Fe2Si phase, which exhibited 2 distinct morphologies, small particles widely dispersed and a continuous layer. Also revealed by EDS were ?6-Al4FeSi and ?4-Al3FeSi2 phases, which showed plate-shaped morphology, in an Al-Si topcoat. However, the XRD results show the intermetallic phases in the aluminide layer were composed of outer cubic ?5(C)-Al7(Fe,Cr)2Si and inner hexagonal ?5(H)-Al7Fe2Si. EBSPs and mapping functions in EBSD helped to clarify the confused phase identifications yielded by EDS and XRD. In this way, the small intermetallic particles and the continuous intermetallic layer were identified as cubic ?5(C)-Al7(Fe,Cr)2Si and hexagonal ?5(H)-Al7Fe2Si, respectively, and the plate-shaped intermetallic phase was identified as monoclinic ?6-Al4FeSi and tetragonal ?4-Al3FeSi2 with the same metallographic morphology. EBSD proved to be a very effective technique for local phase identification of aluminide layers with complicated multiphase morphologies.

Cheng, Wei-Jen; Wang, Chaur-Jeng

2011-03-01

128

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

NASA Astrophysics Data System (ADS)

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.

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

129

Diffraction  

NSDL National Science Digital Library

In this optics activity, demonstrate diffraction using a candle or a small bright flashlight bulb and a slide made with two pencils. Learners will observe the diffraction pattern and learn that light has wavelike properties.

The Exploratorium

2011-10-31

130

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

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.

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

2011-06-01

131

Diffraction  

E-print Network

This report summarizes recent results on diffraction obtained at HERA, at the Tevatron and by the fixed target experiment E665. The measurements include vector meson production, inclusive diffraction at HERA and the pomeron structure function as inferred from the HERA and the Tevatron data.

E. Gallo

1997-10-16

132

Characterizing the microstructure of Arctica islandica shells using NanoSIMS and EBSD  

NASA Astrophysics Data System (ADS)

The bivalve mollusc Arctica islandica has received considerable attention in recent years because of its potential as an archive of marine palaeoclimate, based on its annually resolved incremental shell growth, longevity, and synchronous growth within populations. The robust interpretation of the archive depends on a detailed understanding of the shell formation process, and this in turn requires a reliable understanding of the shell microstructure. Research into this aspect, however, has so far been relatively limited. This study uses secondary ion mass spectrometry (NanoSIMS) to examine the compositions of the two annually formed growth increments, i.e., a narrow band of relatively slow growth referred to as growth increment I (GI I) and a usually wider accretion called growth increment II (GI II). High resolution composition maps are presented which clearly show lower concentrations of the organic ions 12C14N- and 32S- in GI I relative to GI II. This is consistent with the growth of larger crystallites in GI I, which is clearly demonstrated using a novel analysis method involving focused ion beam (FIB) milling. Electron backscatter diffraction (EBSD) analysis is also presented, and demonstrates that the orientation of the aragonite c-axis is the same in both GI I and GI II, and that the a- and b-axes assume preferred orientations consistent with the known angle of twinning in aragonite. By analyzing individual crystallites it is deduced that the (001) plane is likely to be the mineralizing face in GI I, and that the (011) and (102) planes are low energy interfaces in GI II.

Karney, Graeme B.; Butler, Paul G.; Speller, Susannah; Scourse, James D.; Richardson, Christopher A.; Schröder, Markus; Hughes, Gareth M.; Czernuszka, Jan T.; Grovenor, Chris R. M.

2012-04-01

133

Synthetic imaging from coherent backscattering  

NASA Astrophysics Data System (ADS)

Scattered fields from radar targets can be processed to construct target images. An analytical simulation of coherent backscattering and synthetic imaging is reviewed. Conducting objects with an axial symmetry are used as examples to demonstrate the results of analytical backscattering and synthesis procedure. An interrogating radar waveform is simulated using the Hamming weighting function. The pulse repetition frequency is selected so as to avoid slant-range image ambiguity. Backscatterings from axially symmetric targets are formulated by using the diffraction coefficients in the plane containing symmetry axis. Target-backscattered pulses are coherently processed along the aspect angles of interrogation. Coherent data are then synthesized using the Woodward method to construct target images. Four examples of synthesized images demonstrate that adequate shape and size estimates can be made even with partial backscatterings. The totally analytical simulations on scattering and imaging constitute an economical tool to visualize scattering mechanisms of complex targets and to more effectively utilize synthetic-imaging capability.

Yu, J. S.; Williams, J. W.

1981-03-01

134

Diffraction  

NSDL National Science Digital Library

This activity from the Exploratorium provides an introduction to the diffraction of light which indicates its wavelike properties. Two pencils are used to create a slit through which a flashlight bulb or candleâ??s light is examined. The site contains an explanation of the observed interference patterns, additional materials that can be experimented with, and an extension activity. This activity is part of Exploratorium's Science Snacks series.

135

The Weighted Burgers Vector: a new quantity for constraining dislocation densities and types using electron backscatter diffraction on 2D sections through crystalline materials.  

PubMed

The Weighted Burgers Vector (WBV) is defined here as the sum, over all types of dislocations, of [(density of intersections of dislocation lines with a map) x (Burgers vector)]. Here we show that it can be calculated, for any crystal system, solely from orientation gradients in a map view, unlike the full dislocation density tensor, which requires gradients in the third dimension. No assumption is made about gradients in the third dimension and they may be non-zero. The only assumption involved is that elastic strains are small so the lattice distortion is entirely due to dislocations. Orientation gradients can be estimated from gridded orientation measurements obtained by EBSD mapping, so the WBV can be calculated as a vector field on an EBSD map. The magnitude of the WBV gives a lower bound on the magnitude of the dislocation density tensor when that magnitude is defined in a coordinate invariant way. The direction of the WBV can constrain the types of Burgers vectors of geometrically necessary dislocations present in the microstructure, most clearly when it is broken down in terms of lattice vectors. The WBV has three advantages over other measures of local lattice distortion: it is a vector and hence carries more information than a scalar quantity, it has an explicit mathematical link to the individual Burgers vectors of dislocations and, since it is derived via tensor calculus, it is not dependent on the map coordinate system. If a sub-grain wall is included in the WBV calculation, the magnitude of the WBV becomes dependent on the step size but its direction still carries information on the Burgers vectors in the wall. The net Burgers vector content of dislocations intersecting an area of a map can be simply calculated by an integration round the edge of that area, a method which is fast and complements point-by-point WBV calculations. PMID:19250469

Wheeler, J; Mariani, E; Piazolo, S; Prior, D J; Trimby, P; Drury, M R

2009-03-01

136

Infrared backscattering  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

137

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

PubMed

Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. PMID:23440636

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

2013-01-01

138

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

SciTech Connect

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.

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

2012-02-15

139

EBSD analysis of eclogitized rocks form the Marun-Keu complex, Polar Urals, Russia  

NASA Astrophysics Data System (ADS)

The transitions from amphibolite, gabbro, and quartzofeldspathic gneiss to eclogite in the high-pressure Marun-Keu complex in the Polar Urals, Russia, make this complex a good candidate for using mineral chemistries and electron backscatter diffraction (EBSD) to study the interplay between metamorphism and deformation and more broadly understand the orogenic evolution of eclogites in high-pressure subduction zone complexes. The Marun-Keu complex results from the deep crustal processes during the Uralian Orogeny formed by collision of the east European platform with Siberian-Kazakhian terranes in the Devonian to Triassic. Eclogite-facies rocks containing garnet, omphacite, and rutile occur in the central and southern part of the complex and the blueschist-facies and low-T eclogitization are found in the north part of the complex. Based on Glodny et al. (2004), Rb/Sr protolith ages for the gabbros are about 500 Ma which is near the crystallization age from U-Pb zircon data and the eclogite-facies metamorphism was occurred about 355 Ma. Field and microscopic observation of the rocks from the Marun-Keu complex show a sharp contact between the host rocks (gabbro and amphibolite) and the eclogite-facies rocks. This study will mainly focus on the chemistry and different microstructures of the minerals in the samples PU-62, J12, J26 and PU-34 which are showing the transition of the host rocks to the eclogite. Samples PU-62 and J-26 including garnets, omphacite and quartz, show the complete transformation from the gabbro to eclogite and the corona textures and replaced minerals in these two samples indicate incomplete reactions (Molina et al., 2002). Samples J12 and PU-34 - boudins in a quartz/white mica vein- are showing the transitions between the amphibolites and eclogites. There is a sharp contact between the amphibolite core and the eclogite rim in these samples. The major minerals in the eclogite rim are omphacite, garnet, phengite and quartz and the transitional part (amphibolites/eclogite) contains of garnet, omphacite and hornblende and the amphibolite core have the amphibole garnet and quartz. The lattice-preferred orientation (LPO) of all phases, especially garnets in the selected thin sections are being measured by the EBSD method at san Francisco State University and the deformation patterns of the minerals from the host rocks (gabbro/amphibolite) to eclogites will be studied. Understanding the deformation mechanisms related to eclogite-facies metamorphism will provide some information about the deep crust and its activities during the tectonic collision. References: Glodny, J., Pease, V., Montero, P., Austrheim, H., and Rusin, A.I., 2004, Protolith ages of eclogites, Marun-Keu Complex, Polar Urals, Russia: implications for the pre- and early Uralian evolution of the northeastern European continental margin: Geological Society, London, Memoirs, v. 30, p. 87-105. Molina, J.F., Austrheim, H., Glodny, J., and Rusin, A., 2002, The eclogites of the Marun-Keu complex, Polar Urals (Russia): fluid control on reaction kinetics and metasomatism during high P metamorphism: Lithos, v. 61, p. 55-78.

Hosseini, P.; Leech, M. L.

2010-12-01

140

Evaluation of misindexing of EBSD patterns in a ferritic steel.  

PubMed

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

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

2013-01-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

142

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

143

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)

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 deformation of olivine at low temperature. The mechanical results are consistent with the recent low temperature flow law for olivine obtained from single crystal data, which suggested a lower strength for the mantle lithosphere than previous proposed by experimental studies.

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

2013-12-01

144

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

PubMed

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

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

2015-02-01

145

In-situ EBSD Phase Transformation and Recrystallisation  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

146

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

SciTech Connect

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.

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

2014-01-01

147

Global backscatter assessment  

NASA Technical Reports Server (NTRS)

The focus of this effort is the development of a global-scale model of aerosol backscatter for laser atmospheric wind sounder (LAWS) design and performance studies. Background parameters are derived from aerosol data sets with global-scale spatial and/or temporal coverage, using objective statistical decomposition and/or a priori stratification based on supplementary data. Backscatter coefficients at the LAWS design wavelength are derived from background aerosol physical, chemical, and optical data, or from direct backscatter measurements at other wavelengths, using background conversion factors. Direct measurements of aerosol backscatter at 10.6 microns from the Royal Signals and Radar Establishment (RSRE) and the Wave Propagation Laboratory (WPL) were selected. The RSRE backscatter data processing code were optimized under low backscatter conditions, performed detailed analyses of collocated intercomparisons between the two lidars, and assisted in the analysis of the long-term backscatter climatologies from the two lidars. Timely presentation of global backscattering experiment (GLOBE) research results to the global geophysical community is required.

Bowdle, David A.

1989-01-01

148

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

PubMed

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

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

2009-07-01

149

Backscatter Data Map  

USGS Multimedia Gallery

Laura Brothers, USGS, pointing to the map of the backscatter data that's collected. The USGS returned from a seafloor data mapping mission offshore of the Delmarva Peninsula (Ocean City, MD) on July 25th, 2014. The data collected is foundational to our continued understanding of coastal change, vul...

150

Radial Reflection Diffraction Tomography Notes  

SciTech Connect

We are developing the theory behind a new imaging modality which uses a single transducer rotating about its center to launch a field radially outward and collect the backscattered (reflected) field. We use diffraction tomography techniques, based upon a linearized version of the field scattering equation, to form images of the medium surrounding the transducer. As there is one transducer which both transmits the incident field and measures the backscattered field, the operation mode is multimonostatic.

Lehman, S K; Norton, S J

2002-06-27

151

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

PubMed

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

Keshavarzi, Ashkan; Wisniewski, Wolfgang; Rüssel, Christian

2013-09-11

152

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

PubMed

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

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

2007-12-01

153

Development from Rutherford backscattering to high energy backscattering spectrometry  

NASA Astrophysics Data System (ADS)

Summarized are the experimental and theoretical studies at Fudan University in high energy backscattering spectrometry (HEBS), including the measurement of non-Rutherford backscattering cross sections and their successful applications, comments on the phenomenon of deviation from Rutherford Backscattering (RBS), and the R-matrix analysis of the elastic scattering cross sections. Advantages of the development from RBS to HEBS are emphasized and references therein are listed.

Tang, J. Y.; Cheng, H. S.; Zhou, Z. Y.; Yang, F. J.

1997-02-01

154

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

NASA Astrophysics Data System (ADS)

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.

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

2007-05-01

155

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

PubMed

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

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

2013-07-01

156

Ultrasound Microscope: Quantative Backscatter Imaging  

E-print Network

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

Greenaway, Alan

157

CO2 lidar backscatter experiment  

NASA Technical Reports Server (NTRS)

The Aerosol/Lidar Science Group of the Remote Sensing Branch engages in experimental and theoretical studies of atmospheric aerosol scattering and atmospheric dynamics, emphasizing Doppler lidar as a primary tool. Activities include field and laboratory measurement and analysis efforts by in-house personnel, coordinated with similar efforts by university and government institutional researchers. The primary focus of activities related to understanding aerosol scattering is the GLObal Backscatter Experiment (GLOBE) program. GLOBE was initiated by NASA in 1986 to support the engineering design, performance simulation, and science planning for the prospective NASA Laser Atmospheric Wind Sounder (LAWS). The most important GLOBE scientific result has been identified of a background aerosol mode with a surprisingly uniform backscatter mixing ratio (backscatter normalized by air density) throughout a deep tropospheric layer. The backscatter magnitude of the background mode evident from the MSFC CW lidar measurements is remarkably similar to that evident from ground-based backscatter profile climatologies obtained by JPL in Pasadena CA, NOAA/WPL in Boulder CO, and by the Royal Signals and Radar Establishment in the United Kingdom. Similar values for the background mode have been inferred from the conversion of in situ aerosol microphysical measurements to backscatter using Mie theory. Little seasonal or hemispheric variation is evident in the survey mission data, as opposed to large variation for clouds, aerosol plums, and the marine boundary layer. Additional features include: localized aerosol residues from dissipated clouds, occasional regions having mass concentrations of nanograms per cubic meter and very low backscatter, and aerosol plumes extending thousands of kilometers and several kilometers deep. Preliminary comparison with meteorological observations thus far indicate correlation between backscatter and water vapor under high humidity conditions. Limited intercomparisons with the Stratospheric Aerosol and Gas Experiment (SAGE) limb extinction sounder shows differences in the troposphere, however, it should be noted that in general SAGE measurements have not yet been validated in the troposphere.

Jarzembski, Maurice A.; Rothermel, Jeffry; Bowdle, David A.; Srivastava, Vandana; Cutten, Dean; Mccaul, Eugene W., Jr.

1993-01-01

158

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

PubMed

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

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

2013-08-01

159

Effect of the cortex on ultrasonic backscatter measurements of cancellous bone  

NASA Astrophysics Data System (ADS)

Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term 'apparent' means that the parameters are sensitive to the frequency-dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

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

2011-10-01

160

Effect of the cortex on ultrasonic backscatter measurements of cancellous bone  

PubMed Central

Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term “apparent” means that the parameters are sensitive to the frequency dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions. PMID:21896966

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

2012-01-01

161

Photoelectron backscattering in vacuum phototubes  

NASA Astrophysics Data System (ADS)

In this article we describe results of studies of a photoelectron backscattering effect in vacuum phototubes: classical photomultipliers (PMT) and hybrid phototubes (PH). Late pulses occurring in PMTs are attributed to the photoelectron backscattering and distinguished from pulses due to an anode glow effect. The late pulses are measured in a number of PMTs and HPs with various photocathode sizes covering 1 50 cm range and different types of the first dynode materials and construction designs. It is shown that the late pulses are a generic feature of all vacuum photodetectors—PMTs and PHs—and they do not deteriorate dramatically amplitude and timing responses of vacuum phototubes.

Lubsandorzhiev, B. K.; Vasiliev, R. V.; Vyatchin, Y. E.; Shaibonov, B. A. J.

2006-11-01

162

A high-frequency ray analysis of the electromagnetic backscattering by a two-dimensional ogive  

NASA Technical Reports Server (NTRS)

The electromagnetic backscattering from a two-dimensional ogive is examined, including a mechanism-by-mechanism account for the scattered field. The uniform theory of diffraction is used in conjunction with a simple creeping wave representation to yield a solution which provides an accurate and continuous backscattering result for a wide range of ogive geometry parameters. Although not a rigorous derivation of higher-order diffraction ceofficients, this solution provides insight into the relative contributions of the various creeping waves which are generated and propagate around the two-dimensional ogive. Comparisons with moment method calculations are used to demonstrate the range of applicability of this high-frequency asymptotic solution.

Shamansky, H.; Dominek, A.; Wang, N.

1992-01-01

163

Diffraction Theory  

Microsoft Academic Search

A critical review is presented of recent progress in classical diffraction theory. Both scalar and electromagnetic problems are discussed. The report may serve as an introduction to general diffraction theory although the main emphasis is on diffraction by plane obstacles. Various modifications of the Kirchhoff and Kottler theories are presented. Diffraction by obstacles small compared with the wavelength is discussed

C J Bouwkamp

1954-01-01

164

In vivo ultrasound backscattering estimation for tumour diagnosis: an animal study.  

PubMed

In this study the efficacy of a quantitative analysis of backscattered ultrasound for the differential diagnosis of intraocular tumours is tested. The data acquisition was performed with an on-line acquisition and processing system for in vivo work. The backscattering spectra were corrected for the beam effects (diffraction and focussing). The measurements were taken from an animal model (rabbit) in which a Greene's amelanotic melanoma was implanted in the anterior chamber of the eye. The special histologic arrangement of this tumour makes it optimally suited to an assessment of the correlation between histology and backscattering cross section. Various backscattering models were considered theoretically and the choice for a practical testing was motivated on the properties of the observed backscattering spectra. We conclude that the backscattering model based on an "inhomogeneous continuum" with a cylindrical Gaussian autocorrelation function fits the data optimally. The relatively low correlation of the backscattering cross-sections to histology cannot yet be fully explained. The range of acoustic scatterer sizes, however, corresponds quite well to the dimension of observed and quantified histologic structures. PMID:2675447

Romijn, R L; Thijssen, J M; van Delft, J L; de Wolff-Rouendaal, D; van Best, J; Oosterhuis, J A

1989-01-01

165

Backscatter absorption gas imaging system  

DOEpatents

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.

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

1985-01-01

166

Edge wave diffraction for flat plates  

Microsoft Academic Search

The tip excited edge wave and the associated interactions between the two adjacent corners of a flat plate are outlined using a more complete depiction of the corner effect. Radar cross section (RCS) calculations and time domain mechanism extraction are used to illustrate the edge wave contributions to the backscatter by knife-edged perfectly conducting plates. The corner diffraction is represented

L. P. Ivrissirntzis; R. J. Marhefka

1990-01-01

167

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

PubMed

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

Chen, Delphic; Kuo, Jui-Chao

2013-08-01

168

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

SciTech Connect

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 ?m, and between 0.65 and 0.68 ?m 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 ?m to 2 ?m 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.

Luo, Sin-Jie [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China); Su, Yen-Hao Frank; Lu, Muh-Jung [China Steel Corporation, Kaohsiung 81233, Taiwan (China); Kuo, Jui-Chao, E-mail: jckuo@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng-Kung University, No. 1, University Road, Tainan 701, Taiwan (China)

2013-08-15

169

EBSD characterization of twinning in cold-rolled CP-Ti  

SciTech Connect

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.

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

2013-10-15

170

Squiral diffraction  

E-print Network

The Thue-Morse system is a paradigm of singular continuous diffraction in one dimension. Here, we consider a planar system, constructed by a bijective block substitution rule, which is locally equivalent to the squiral inflation rule. For balanced weights, its diffraction is purely singular continuous. The diffraction measure is a two-dimensional Riesz product that can be calculated explicitly.

Uwe Grimm; Michael Baake

2012-11-23

171

Backscattering spectroscopy at the NIST Center for Neutron Research  

NASA Astrophysics Data System (ADS)

We discuss the design of a new backscattering spectrometer that is soon to become operational at the NIST Center for Neutron Research. Both monochromator and analyzer are composed of spherically bent Si (1 1 1) crystals that focus the incident and scattered neutron beams. The bending increases the intrinsic lattice gradient of Si beyond its Darwin limit, resulting in an energy resolution of about 0.75 ?eV FWHM. The Doppler-driven monochromator should provide a wide dynamic range of +/-50 ?eV. The elastic Q-range will cover 0.15-1.8 Å-1. The most novel component of this spectrometer is the phase-space-transform chopper. This device rotates at 4730 rpm while neutrons are Bragg-diffracted from sets of HOPG crystals affixed to its periphery. The process enhances the neutron flux at the backscattered energy of 2.08 meV, but at the expense of a larger horizontal divergence. This effectively reduces the divergence mismatch between primary and secondary spectrometers, a long standing problem with backscattering instruments. Simulations suggest a resultant flux increase of order 3 should be obtained.

Gehring, P. M.; Neumann, D. A.

1998-04-01

172

Shock Recrystallisation and Decomposition of Zircon  

NASA Astrophysics Data System (ADS)

In this study, we present the first electron backscatter diffraction (EBSD) characterization of granular and decomposed zircon in order to investigate the mechanism(s) by which these microstructures are produced.

Timms, N. E.; Erickson, T. E.; Schmieder, M.; Tohver, E.

2014-09-01

173

Transactions of NAMRI/SME 351 Volume 32, 2004 FOURIER ANALYSIS OF X-RAY MICRODIFFRACTION PROFILES TO  

E-print Network

compared with the simulation result obtained from FEM analysis and electron backscatter diffraction (EBSD and the sample was cut to size using a wire EDM. FIGURE 1. SAMPLE GEOMETRY AND LASER SHOCK PEENING CONDITION

Yao, Y. Lawrence

174

Novel micro-and nanospectroscopies: study of catalysis in zeolite nanopores  

E-print Network

Novel micro- and nanospectroscopies: study of catalysis in zeolite nanopores Wednesday January 26 was studied with fluorescence microscopy, electron backscattering diffraction (EBSD), and synchrotron micro. Spectroscopic characterization of nano-scale systems with particular emphasis on multi-technique studies

Fisher, Frank

175

Higher order diffractions from a circular disk  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

176

Microemboli detection using ultrasound backscatter.  

PubMed

Microemboli detection and characterisation have recently received great attention due to its clinical importance in the management of cerebrovascular disease. The new method presented in this paper is directly based on the idea that the ultrasound (US) backscattered signal from flowing blood is chaotic (El-Brawany and Nassiri 2002). The detection technique involves building a nonlinear model of the deterministic characteristics of the chaotic backscatter signal from blood, and the use of this model to look at the prediction error as a primary decision-making criterion for the microemboli detector. A complementary feature to the prediction error, namely, the degree of coherence between the US excitation pulse and the prediction error signal is used to enhance the detection process. The detector has been built using a feed-forward neural network with error back-propagation. The detection technique is tested successfully using a vascular flow phantom with solid spheres and bubbles of known sizes introduced in the flow circuit to mimic solid and gaseous emboli. Receiver operating characteristic (ROC) curve is used to assess the performance of the detection process. The total classification rate ranges from 88% to 96%. PMID:12498939

El-Brawany, Mohamed A; Nassiri, Dariush K

2002-01-01

177

Beta Backscatter Measures the Hardness of Rubber  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

178

Depolarization of backscattered linearly polarized light  

E-print Network

Depolarization of backscattered linearly polarized light Luis Fernando Rojas-Ochoa Department of backscattered linearly polarized light with an extended photon dif- fusion formalism taking explicitly, the characteristic depolarization length for linearly polarized light, lp , is deduced. We investigate the dependence

Lacoste, David

179

[Backscattering characteristics of Amphidinium carterae Hulburt].  

PubMed

Variability of the backscattering characteristics of the alga amphidinium carterae hulburt and its interpretation were examined using the measured data performed during July 2012 in the laboratory. The results indicated that the backscattering coefficient has the characteristic of spectral variability, and was highly power correlated with the chlorophyll concentration, the minimum of the correlation coefficient reached up to 0.96; otherwise, the shape of the particulate backscattering coefficient spectra was also changed from the low chlorophyll concentration to the higher concentration because of the influence of chlorophyll absorption. At the same time, the authors got another value of the particulate backscattering ratio ranging between 0.006 4 and 0.011 6 at 620 nm, although a global increase in particulate backscattering ratio with growing chlorophyll concentration was also visible, but the regularity is not obviously especially at the higher chlorophyll concentration and unlike backscattering coefficient, the spectral shapes of the backscattering ratio remained constant. The authors also found that particle density was one of the main factors controlling the variability of particles backscattering ratio for the pure algal water, and the authors fit a power law function to them and the correlation coefficient at 620 nm was as high as 0.98. PMID:24059196

Jiang, Ling-Ling; Wang, Lin; Zhao, Dong-Zhi; Wang, Xiang

2013-07-01

180

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

PubMed

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

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

2013-06-01

181

Mobile spectrometer measures radar backscatter  

NASA Technical Reports Server (NTRS)

The present article is concerned with a helicopter-borne spectrometer (Heloscat), which has been developed to permit high-quality scattering measurements from a mobile platform at remote sites. The term 'spectrometer' referes to a class of scatterometers. The term 'scatterometer' is employed to denote a specialized radar for measuring scattering coefficients as a function of angle. A spectrometer, on the other hand, is a scatterometer which can measure backscatter at several frequencies. The Heloscat system is discussed, taking into account two antennas, RF hardware, and an externally mounted pendulum for angle encoding. A dual-antenna configuration is used for cross-polarized measurements, while a single-antenna system is used for like-polarized measurements. Attention is also given to oscillator characteristics, efficient data handling, and aspects of calibration.

Gogineni, S.; Moore, R. K.; Onstott, R. G.; Kim, Y. S.; Bushnell, D.

1984-01-01

182

Inclusive diffraction  

E-print Network

Results are given on the measurements of the hard diffractive interactions at HERA $ep$ collider. The structure of the diffractive exchange in terms of partons and the factorisation properties are discussed, in particular by comparing the QCD predictions for dijets and $D^*$ with measurements both in the photo and electroproduction regimes.

L. Favart

2006-02-01

183

Radial reflection diffraction tomography  

NASA Astrophysics Data System (ADS)

A wave-based tomographic imaging algorithm based upon a single rotating radially outward oriented transducer is developed. At successive angular locations at a fixed radius, the transducer launches a primary field and collects the backscattered field in a ``pitch/catch'' operation. The hardware configuration, operating mode, and data collection method are identical to that of most medical intravascular ultrasound (IVUS) systems. IVUS systems form images of the medium surrounding the probe based upon ultrasonic B scans, using a straight-ray model of sound propagation. The goal of this research is to develop a wave-based imaging algorithm using diffraction tomography techniques. Given the hardware configuration and the imaging method, this system is referred to as ``radial reflection diffraction tomography.'' Two hardware configurations are considered: a multimonostatic mode using a single transducer as described above, and a multistatic mode consisting of a single transmitter and an aperture formed by multiple receivers. In this latter case, the entire source/receiver aperture rotates about the fixed radius. Practically, such a probe is mounted at the end of a catheter or snaking tube that can be inserted into a part or medium with the goal of forming images of the plane perpendicular to the axis of rotation. An analytic expression for the multimonostatic inverse is derived, but ultimately the new Hilbert space inverse wave (HSIW) algorithm is used to construct images using both operating modes. Applications include improved IVUS imaging, bore hole tomography, and nondestructive evaluation (NDE) of parts with existing access holes. .

Lehman, Sean K.; Norton, Stephen J.

2004-10-01

184

Irradiation study of Ti6Al4V and Ti6Al4V1B for FRIB beam dump: Aida Amroussia, PhD Student  

E-print Network

: · Scanning electron microscopy (SEM) as well as electron backscatter diffraction (EBSD) were usedIrradiation study of Ti6Al4V and Ti6Al4V1B for FRIB beam dump: Aida Amroussia, PhD Student Chemical-EBSD · Nano-indentation tests · Vickers Hardness tests · Insitu-tensile tests 2 #12;Irradiation experiments

McDonald, Kirk

185

[Backscattering spectrum analysis of nonspheroid soot particle].  

PubMed

In the process of measuring soot concentration and grain diameter, the backscattering spectrum of soot particle model was calculated to ascertain and analyze main effective factor of backscattering intensity. In the present paper, ellipsoid, column and generalized Chebyshev, three nonspheroid models, were selected according to micrograph of practical soot particle, which aims to simulate practical soot particle with equivalent diameter of about 1 microm. T-matrix method was used to calculate backscattering spectrum of the three nonspheriod models, and the main effective factor curves of intensity were obtained, too. Both numerical computer simulations and experimental results illustrate that nonspheroid particle backscattering intensity is stronger than that of spheroid particle in the visible/infrared spectrum band, especially for generalized Chebyshev model, whose backscattering intensity can be even 3.5 times higher than that of forward scattering. Meanwhile, the absorbency non-spheroid particle (complex refractive index m = 1.57 - 0.56i) backscattering intensity is stronger than that of non-absorbency nonspheriod particle (complex refractive index m = 1.57 - 0.001i). Furthermore, with the increase in particle equivalent radius, the light source wavelength also needs to be increase to obtain more light intensity information. The backscattering light spectrum information provides a reasonable basis for selecting light source and measure angle. PMID:20939348

Xing, Jian; Sun, Xiao-gang; Yuan, Gui-bin; Qi, Xu; Tang, Hong

2010-08-01

186

Diffraction to De-Diffraction  

E-print Network

De-diffraction (DD), a new procedure to totally cancel diffraction effects from wave-fields is presented, whereby the full field from an aperture is utilized and a truncated geometrical field is obtained, allowing infinitely sharp focusing and non-diverging beams. This is done by reversing a diffracted wave-fields' direction. The method is derived from the wave equation and demonstrated in the case of Kirchhoff's integral. An elementary bow-wavelet is described and the DD process is related to quantum and relativity theories.

V. F. Tamari

2003-03-19

187

C-band backscattering from corn canopies  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

188

Spectral backscattering properties of marine phytoplankton cultures  

E-print Network

of Oceanic & Atmospheric Sciences, 104 COAS Admin. Bldg., Corvallis, OR 97331, USA 2 Oil Spill Recovery that the spectral backscattering properties of phytoplankton deviate from theory at wavelengths where pigment

Boss, Emmanuel S.

189

X band microwave backscattering from ocean waves  

Microsoft Academic Search

Backscattering experiments at microwave frequencies were conducted off the west coast of Scotland in the summer of 1991. Using a dual-polarization, eight-frequency, X band, coherent scatterometer mounted on the bow of a boat, the authors measured time-resolved backscattering from ocean waves at a range of grazing angles from 10° to 70°. From the grazing-angle-dependent signals and their Doppler spectra, the

P. H. Y. Lee; J. D. Barter; K. L. Beach; C. L. Hindman; B. M. Lake; H. Rungaldier; J. C. Shelton; A. B. Williams; R. Yee; H. C. Yuen

1995-01-01

190

Optical backscatter measurements from laser plasma interactions in NIF targets  

Microsoft Academic Search

Backscattered light from NIF targets is detected using a full aperture backscatter system (FABS) and a near backscatter imager (NBI). These measurements allow quantification of the coupling efficiency of the NIF laser to the target. Backscatter measurements in ignition scale hohlraum targets are made on two separate groups of 4 beams (a quad) at 30,o and 50,o from the hohlraum

J. D. Moody; P. Datte; R. Hibbard; E. Bond; P. Michel; B. J. MacGowan; S. H. Glenzer; L. Suter; N. Meezan; R. L. Berger; E. A. Williams; D. Hinkel; K. Widmann; L. Divol; J. Jackson; J. Nelson; S. Vernon; J. L. Kline; C. Niemann

2010-01-01

191

Backscattered fraction of precipitating ionospheric photoelectrons  

NASA Astrophysics Data System (ADS)

The FAST electron spectrometer offers a serendipitous opportunity to determine for the first time the fraction of precipitating photoelectrons that are backscattered. Ionospheric photoelectrons produced by solar EUV radiation can escape into the plasmasphere and travel along magnetic field lines to the opposite hemisphere. In 2002 the FAST satellite orbit sliced through the plasmasphere above 3000 km altitude where it detected photoelectrons coming from both hemispheres with energies in the range 10 to 800 eV. When one hemisphere is sunlit and the other is in darkness, the photoelectrons arriving at the satellite from the dark hemisphere are photoelectrons that are backscattered from the dark thermosphere after traveling from the sunlit hemisphere. This paper compares the measured and modeled backscattered fraction of photoelectrons. The backscatter ratio of precipitating electrons is important in relation to auroral energy deposition rate, which depends on the amount of backscattered energy flux. Direct experimental determination of auroral electron backscatter is not possible because the precipitating auroral flux is too variable in space and time.

Richards, P. G.; Peterson, B. K.

2007-12-01

192

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

NASA Astrophysics Data System (ADS)

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

Mukai, Hiroki; Austrheim, Håkon; Putnis, Andrew

2013-04-01

193

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

NASA Astrophysics Data System (ADS)

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 speculates that the relative Al incorporation into quartz may reflect temperature dependence; hence some source of local heat may play a role in the crystallization dynamics.

Wenk, H.; Grimsich, J. L.

2012-12-01

194

Improved Physical Theory of Diffraction: Removal of the Grazing Singularity  

Microsoft Academic Search

Physical theory of diffraction based on the concept of elementary edge waves [P. Ya. Ufimtsev, Electromagnetics, vol. 11, no. 2, pp. 125-160, 1991] is well suited for analysis of backscattering from perfectly conducting objects with edges. However, it needs to be improved for the investigation of forward scattering, especially in the directions grazing to the edge faces, where it predicts

Pyotr Ya. Ufimtsev

2006-01-01

195

Evaluation of edge-diffracted fields including equivalent currents for the caustic regions  

Microsoft Academic Search

The fields diffracted by a body made up of finite axially symmetric cone frustums are obtained using the concepts of the geometrical theory of diffraction. The backscattered field for plane-wave incidence on such a target is obtained with particular emphasis on those regions that are usually avoided, namely, the caustic region and its immediate vicinity. The method makes use of

CHARLES E. RYAN

1969-01-01

196

Evaluating roughness models of radar backscatter  

NASA Technical Reports Server (NTRS)

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

Engman, Edwin T.; Wang, James R.

1987-01-01

197

Evaluating roughness models of radar backscatter  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

198

Bathymetry and acoustic backscatter: Estero Bay, California  

USGS Publications Warehouse

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.

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

2013-01-01

199

Materials Science: Diffraction  

NSDL National Science Digital Library

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

Peter Goodhew

200

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

PubMed

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

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

2014-02-01

201

Direct estimation of austenitic grain dimensions in heat affected zones of a martensitic steel from EBSD images.  

PubMed

In the context of automated analyses of electron-backscattered-diffraction images, we present in this paper a novel method to automatically extract morphological properties of prior austenitic grains in martensitic steels based on raw crystallographic orientation maps. This quantification includes the estimation of the mean chord length in specific directions, with in addition the reconstruction of the mean shape of austenitic grains inducing anisotropic shape properties. The approach is based on the morphological measure of covariance on a decision curve of grain fidelity per disorientation angle. These efforts have been motivated by the need of realistic microstructures to perform micromechanical studies of grain boundary localized damage phenomenons in steels, one example being the type IV fracture phenomenon occurring in welded joints of grade P91/P92 steel. This failure is attributed to a change of the microstructure due to thermal gradients arising during the welding process. To precisely capture the relationships between microstructural changes and mechanical fields localization in a polycrystalline aggregate, we first need to achieve a reasonable stochastic model of its microstructure, which relies on a detailed knowledge of the microstructural morphology. As martensitic steels possess multiscale microstructures composed of prior austenitic grains, packets and laths, a relevant modelling strategy has to be proposed to account for the observed hierarchies. With this objective, this paper focuses on the larger scale entities present in the microstructure, namely, the austenitic grains. PMID:25689129

Altendorf, H; Faessel, M; Jeulin, D; Latourte, F

2015-05-01

202

The shape of auroral backscatter spectra  

Microsoft Academic Search

Recent observations of auroral backscatter at frequencies from 10 to 933 MHz have found spectral shapes which are intermediate between Lorentzian and Gaussian. To account for these observations a model has been developed consisting of a random distribution of scatterers in the radar field of view. Spectral shape is discussed in terms of the shape of the magnitude of the

D. R. Moorcroft

2004-01-01

203

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...

204

Monte Carlo simulation of polarization backscattering spectroscopy  

NASA Astrophysics Data System (ADS)

In this paper, we have developed a Monte Carlo algorithm that simulates the wavelength dependent, elastic scattering spectroscopy of the polarization light in preinvasive cancer tissue. Using stokes vector formalism and scattering amplitudes calculated with Mie theory. The simulation results show the backscattering spectroscopy is sensitive to cellular and nuclear size.

Deng, Yong; Lu, Qiang; Luo, Qingming; Hu, Rui; Zhu, Dan

2004-08-01

205

Visualization of x-ray backscatter data  

SciTech Connect

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.

Greenawald, E.C.; Ham, Y.S. [Geo-Centers, Inc., Fort Washington, MD (United States); Poranski, C.F. Jr. [Naval Research Lab., Washington, DC (United States). Materials Chemistry Branch

1993-12-31

206

Discrimination of UXO in Soil Using Broadband Polarimetric GPR Backscatter  

E-print Network

- 1 - Discrimination of UXO in Soil Using Broadband Polarimetric GPR Backscatter Kevin O'Neill Cold@crrel.usace.army.mil ABSTRACT Polarimetric analysis of ground penetrating radar (GPR) backscatter offers a new means

Shubitidze, Fridon

207

C-band polarimetric backscatter observations of Great Lakes ice  

Microsoft Academic Search

Two experiments were carried out during the 1997 winter season across the Straits of Mackinac and Lake Superior. C-band radar backscatter signatures of various ice types and open water were measured from U.S. Coast Guard Ice Breaker vessels together with ground truth data. Polarimetric backscatter data were obtained at incident angles up to 60° for all polarizations. Backscatter signatures of

S. V. Nghiem; G. A. Leshkevich; R. Kwokl

1998-01-01

208

Diffraction and diffractive finalDiffraction and diffractive final states at HERAstates at HERA  

E-print Network

Diffraction and diffractive finalDiffraction and diffractive final states at HERAstates at HERA Leszek Adamczyk UST Cracow On behalf of the H1 & ZEUS Collaborations Introduction Diffractive parton densities Tests of QCD factorization at HERA #12;Diffractive DIS at HERADiffractive DIS at HERA Inclusive

209

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

Microsoft Academic Search

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

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

1992-01-01

210

Modelling of backscatter from vegetation layers  

NASA Technical Reports Server (NTRS)

A simple way to build up a library of models which may be used to distinguish between the different types of vegetation and ground surfaces by means of their backscatter properties is presented. The curve of constant power received by the antenna (Gamma sphere) is calculated for the given Stokes Scattering Operator, and model parameters are adopted of the most similar library model Gamma sphere. Results calculated for a single scattering model resembling coniferous trees are compared with the Gamma spheres of a model resembling tropical region trees. The polarization which would minimize the effect of either the ground surface or the vegetation layer can be calculated and used to analyze the backscatter from the ground surface/vegetation layer combination, and enhance the power received from the desired part of the combination.

Van Zyl, J. J.; Engheta, N.; Papas, C. H.; Elachi, C.; Zebker, H.

1985-01-01

211

Spectra of Particulate Backscattering in Natural Waters  

NASA Technical Reports Server (NTRS)

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.

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

2009-01-01

212

Microwave backscattering from an anisotropic soybean canopy  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

213

Backscattering measurement from a single microdroplet.  

PubMed

Backscattering measurements for acoustically trapped lipid droplets were undertaken by employing a P[VDF-TrFE] broadband transducer of f-number = 1, with a bandwidth of 112%. The wide bandwidth allowed the transmission of the 45 MHz trapping signal and the 15 MHz sensing signal using the same transducer. Tone bursts at 45 MHz were first transmitted by the transducer to hold a single droplet at the focus (or the center of the trap) and separate it from its neighboring droplets by translating the transducer perpendicularly to the beam axis. Subsequently, 15 MHz probing pulses were sent to the trapped droplet and the backscattered RF echo signal received by the same transducer. The measured beam width at 15 MHz was measured to be 120 ? m. The integrated backscatter (IB) coefficient of an individual droplet was determined within the 6-dB bandwidth of the transmit pulse by normalizing the power spectrum of the RF signal to the reference spectrum obtained from a flat reflector. The mean IB coefficient for droplets with a 64 ? m average diameter (denoted as cluster A) was -107 dB, whereas it was -93 dB for 90-?m droplets (cluster B). The standard deviation was 0.9 dB for each cluster. The experimental values were then compared with those computed with the T-matrix method and a good agreement was found: the difference was as small as 1 dB for both clusters. These results suggest that this approach might be useful as a means for measuring ultrasonic backscattering from a single microparticle, and illustrate the potential of acoustic sensing for cell sorting. PMID:21507767

Lee, Jungwoo; Chang, Jin Ho; Jeong, Jong Seob; Lee, Changyang; Teh, Shia-Yen; Lee, Abraham; Shung, K Kirk

2011-04-01

214

Backscattering Measurement From a Single Microdroplet  

PubMed Central

Backscattering measurements for acoustically trapped lipid droplets were undertaken by employing a P[VDF-TrFE] broadband transducer of f-number = 1, with a bandwidth of 112%. The wide bandwidth allowed the transmission of the 45 MHz trapping signal and the 15 MHz sensing signal using the same transducer. Tone bursts at 45 MHz were first transmitted by the transducer to hold a single droplet at the focus (or the center of the trap) and separate it from its neighboring droplets by translating the transducer perpendicularly to the beam axis. Subsequently, 15 MHz probing pulses were sent to the trapped droplet and the backscattered RF echo signal received by the same transducer. The measured beam width at 15 MHz was measured to be 120 ?m. The integrated backscatter (IB) coefficient of an individual droplet was determined within the 6-dB bandwidth of the transmit pulse by normalizing the power spectrum of the RF signal to the reference spectrum obtained from a flat reflector. The mean IB coefficient for droplets with a 64 ?m average diameter (denoted as cluster A) was ?107 dB, whereas it was ?93 dB for 90-?m droplets (cluster B). The standard deviation was 0.9 dB for each cluster. The experimental values were then compared with those computed with the T-matrix method and a good agreement was found: the difference was as small as 1 dB for both clusters. These results suggest that this approach might be useful as a means for measuring ultrasonic backscattering from a single microparticle, and illustrate the potential of acoustic sensing for cell sorting. PMID:21507767

Lee, Jungwoo; Chang, Jin Ho; Jeong, Jong Seob; Lee, Changyang; Teh, Shia-Yen; Lee, Abraham; Shung, K. Kirk

2011-01-01

215

Multi Scale Finite Element Analyses By Using SEM-EBSD Crystallographic Modeling and Parallel Computing  

SciTech Connect

A crystallographic homogenization procedure is introduced to the conventional static-explicit and dynamic-explicit finite element formulation to develop a multi scale - double scale - analysis code to predict the plastic strain induced texture evolution, yield loci and formability of sheet metal. The double-scale structure consists of a crystal aggregation - micro-structure - and a macroscopic elastic plastic continuum. At first, we measure crystal morphologies by using SEM-EBSD apparatus, and define a unit cell of micro structure, which satisfy the periodicity condition in the real scale of polycrystal. Next, this crystallographic homogenization FE code is applied to 3N pure-iron and 'Benchmark' aluminum A6022 polycrystal sheets. It reveals that the initial crystal orientation distribution - the texture - affects very much to a plastic strain induced texture and anisotropic hardening evolutions and sheet deformation. Since, the multi-scale finite element analysis requires a large computation time, a parallel computing technique by using PC cluster is developed for a quick calculation. In this parallelization scheme, a dynamic workload balancing technique is introduced for quick and efficient calculations.

Nakamachi, Eiji [Department of Mechanical Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka, Osaka 535-8585 (Japan)

2005-08-05

216

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

PubMed

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

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

2013-09-01

217

On the possibility of using aerosol backscattering in the adaptive loop of atmospheric optical systems  

SciTech Connect

The mean received power of partially coherent cw laser radiation scattered in the atmosphere is calculated depending on the spatial coherence of the initial field and the angular divergence of a laser beam formed by a circular output aperture. It is shown that due to diffraction on the circular aperture, the dependence of the mean radiation power on the divergence angle is nonmonotonic and has a maximum. The divergence angle corresponding to this maximum is determined by the spatial coherence of the initial field. The possibility of controlling the adaptive loop of the laser system by means of signals backscattered in the atmosphere is discussed. (lidars)

Banakh, V A; Rychkov, D S [Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation); Zhmylevskii, V V; Ignat'ev, A B; Morozov, V V [Almaz -Antei Open Joint-Stock Company, Moscow (Russian Federation)

2008-08-31

218

Structural characterization of a Mo/Si multilayer reflector by means of x-ray diffraction measurements  

E-print Network

of these various structural parameters on the small-angle x-ray diffraction XRD pattern are investigated of the Bragg peaks. Based on the above results, we present an analysis of the experimental XRD data in order microscopy TEM , x-ray diffraction XRD , large- angle XRD, Rutherford backscattering spectroscopy RBS

Kim, Jae-Hoon

219

Atmospheric Backscatter Model Development for CO Sub 2 Wavelengths  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

220

Photoelectron diffraction and holography: Some new directions  

SciTech Connect

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

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

1993-08-01

221

Backscattering Differential Ghost Imaging in Turbid Media  

E-print Network

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 small thin black objects located at different depths inside a turbid solution of polystyrene nanospheres and its performances assessed via comparison with standard imaging techniques. A simple theoretical model capable of describing the basic optics of DGI in turbid media is proposed.

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

2012-08-22

222

Backscattering Differential Ghost Imaging in Turbid Media  

E-print Network

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 small thin black objects located at different depths inside a turbid solution of polystyrene nanospheres and its performances assessed via comparison with standard imaging techniques. A simple theoretical model capable of describing the basic optics of DGI in turbid media is proposed.

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

2012-01-01

223

Statistical properties of radar backscatter data for imaging applications  

Microsoft Academic Search

Traditionally radar imaging algorithms implement second-order statistics. In this article, the statistical properties, (Gaussianity, linearity, and frequency-reversibility) of measured backscattered radar data are evaluated in order to determine the statistical dependence of radar data. Non-Gaussianity, nonlinearity, or frequency-irreversibility favors the use of higher order statistics, rather than second-order statistics in modeling radar backscatter data for imaging applications. The backscatter radar

J. W. Odendaal; P. Niemand

2003-01-01

224

A predictive model of backscattering at subdiffusion length scales  

PubMed Central

We provide a methodology for accurately predicting elastic backscattering radial distributions from random media with two simple empirical models. We apply these models to predict the backscattering based on two classes of scattering phase functions: the Henyey-Greenstein phase function and a generalized two parameter phase function that is derived from the Whittle-Matérn correlation function. We demonstrate that the model has excellent agreement over all length scales and has less than 1% error for backscattering at subdiffusion length scales for tissue-relevant optical properties. The presented model is the first available approach for accurately predicting backscattering at length scales significantly smaller than the transport mean free path. PMID:21258528

Turzhitsky, Vladimir; Radosevich, Andrew; Rogers, Jeremy D.; Taflove, Allen; Backman, Vadim

2010-01-01

225

Radar backscatter properties of milo and soybeans  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

226

Compton backscattered collmated X-ray source  

DOEpatents

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.

Ruth, Ronald D. (Woodside, CA); Huang, Zhirong (Stanford, CA)

2000-01-01

227

Compton backscattered collimated x-ray source  

DOEpatents

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.

Ruth, Ronald D. (Woodside, CA); Huang, Zhirong (Stanford, CA)

1998-01-01

228

Compton backscattered collimated x-ray source  

DOEpatents

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.

Ruth, R.D.; Huang, Z.

1998-10-20

229

Diffraction at HERA  

E-print Network

Precision measurements of diffraction have been performed by the H1 and ZEUS experiments at the HERA collider with high statistics for a wide kinematic range of photon virtuality $Q^2$. The diffractive parton densities are extracted by performing the NLO DGLAP QCD fits to diffractive data and can be used to test QCD factorisation with diffractive final states.

Heuijin Lim

2008-05-30

230

Diffraction Shaders Alias wavefront  

E-print Network

Diffraction Shaders Jos Stam Alias wavefront Abstract The reflection of light from surfaces sur- faces that handle the effects of diffraction. Diffraction is a purely wave-like phenomenon- hibits diffraction is the compact disk. A characteristic of such sur- faces is that they reflect light

Toronto, University of

231

Diffraction in QCD  

E-print Network

This lecture presents a short review of the main features of diffractive processes and QCD inspired models. It includes the following topics: (1) Quantum mechanics of diffraction: general properties; (2) Color dipole description of diffraction; (3) Color transparency; (4) Soft diffraction in hard reactions: DIS, Drell-Yan, Higgs production; (5) Why Pomerons interact weakly; (6) Small gluonic spots in the proton; (7) Diffraction near the unitarity bound: the Goulianos-Schlein "puzzle"; (8) Diffraction on nuclei: diffractive Color Glass; (9) CGC and gluon shadowing.

B. Z. Kopeliovich; I. K. Potashnikova; Ivan Schmidt

2006-04-11

232

Diffraction at the Tevatron  

E-print Network

This article contains a summary of the recent results in diffractive physics at the Tevatron. Results from the CDF diffraction program include the single diffractive to non-diffractive ratio in dijet events, observation of exclusive $e^+e^-$ production via two-photon exchange, hints of exclusive $\\gamma\\gamma$ production via Double Pomeron Exchange (DPE), and the observation of exclusive dijet production via DPE. A summary of the current plans for the D\\O\\ diffractive physics program is also presented.

Andrew Hamilton

2007-10-09

233

Spectrum of coherent backscattering of light by two atoms  

E-print Network

We study theoretically inelastic spectrum of coherent backscattering of laser light by two atoms. For an intense laser field, there are frequency domains of not only constructive but also destructive (self-)interference of the inelastic photons. We interpret the emergent spectral features using the dressed states and considering coherent backscattering as a kind of the pump-probe experiment.

Vyacheslav Shatokhin

2006-08-10

234

Klein backscattering and Fabry-Perot resonances in graphene  

E-print Network

Klein backscattering and Fabry- Perot resonances in graphene p-n-p junctions Leonid Levitov of the Klein physics? Shytov, Rudner & LL, arXiv:0808.0488 Fabry-Perot resonances mixed with UCF? Exeter group (Cheianov & Falko) #12;Klein backscattering and Fabry-Perot resonances Phase of backreflection: (i) phase

Gabrieli, John

235

Optical backscatter characteristics of Arctic polar stratospheric clouds  

NASA Technical Reports Server (NTRS)

Airborne lidar measurements have been made of polar stratospheric clouds (PSCs) during the Airborne Arctic Stratospheric Expedition in January-February 1989. These show the existence of a systematic relationship between the backscatter depolarization ratio and the (aerosol + molecular)/molecular backscatter ratio. The data are consistent with a two population PSC particle model.

Kent, G. S.; Schaffner, S. K.; Poole, L. R.; Mccormick, M. P.; Hunt, W. H.

1990-01-01

236

Theory and Measurement of Backscattering from RFID Tags  

E-print Network

Theory and Measurement of Backscattering from RFID Tags Pavel V. Nikitin and K. V. S. Rao Intermec backscattering from RFID tags and for calculating a tag radar cross-section (RCS). We derive a theoretical formula for RCS of an RFID tag with a minimum scattering antenna and describe an experimental measurement

Hochberg, Michael

237

Tracking California seafloor seeps with bathymetry, backscatter and ROVs  

Microsoft Academic Search

The California (USA) margin includes two different tectonic regimes: subduction north of the Mendocino Triple Junction and translation south. Both margins include seeps, and their distribution can be inferred using seafloor bathymetry and backscatter as well as subsurface seismic data. Anomalous bathymetric and backscatter features related to fluid expulsion include headless submarine canyons, fault zones, anticlines, pockmarks, and mud volcanoes.

Daniel L. Orange; Janet Yun; Norman Maher; James Barry; Gary Greene

2002-01-01

238

Backscatter body scanners – A strip search by other means  

Microsoft Academic Search

Backscatter body scanners have only recently been deployed at airports across the US and used as an optional alternative to patdowns – the open hand form of body search. This paper will essentially outline the statutory law and case-law of special relevance in the US to backscatter body scanners and determine the deficiencies and dilemmas of the legal framework with

Demetrius Klitou

2008-01-01

239

An Improved Monte Carlo Algorithm for Elastic Electron Backscattering  

E-print Network

of the backscattering of electrons from metal targets is subject of extensive theoreticel and experimental work in surAn Improved Monte Carlo Algorithm for Elastic Electron Backscattering from Surfaces Ivan T. Dimov- face analysis. We are interested in the angular distribution of the back- scattered electrons. The flow

Dimov, Ivan

240

Relating P-band AIRSAR backscatter to forest stand parameters  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

241

Geometrical form factor determination with Raman backscattering signals  

Microsoft Academic Search

A new method is presented to determine the geometrical form factor in Raman lidar. Mie and Raman backscattering signals are acquired by L625 Raman lidar; then the aerosol backscattering ratio and atmospheric molecular density are derived. By normalizing the molecular density of Raman lidar with radiosonde measurements, the geometrical form factors of lidar are obtained. Experimental results indicate this method

Shunxing Hu; Xiaobin Wang; Yonghua Wu; Chen Li; Huanling Hu

2005-01-01

242

Rayleigh backscattering in a fiber gyroscope with limited coherence sources  

Microsoft Academic Search

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

W. Burns; R. Moeller

1983-01-01

243

Enhanced radar backscatter from space shuttle exhaust in the ionosphere  

Microsoft Academic Search

Enhancements in the backscatter from the 430-MHz radar at Arecibo were recorded during the Spacelab 2 mission when the space shuttle orbital maneuver system (OMS) engines were fired in the ionosphere. The modifications in the backscatter could have been the result of (1) compression of the electrons to produce higher densities, (2) generation of ion acoustic waves, (3) variations in

P. A. Bernhardt; G. Ganguli; M. C. Kelley; W. E. Swartz

1995-01-01

244

A method for removing arm backscatter from EPID images  

SciTech Connect

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.

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

2013-07-15

245

Study of corrosion layers using backscattering ions  

NASA Astrophysics Data System (ADS)

The backscattering technique was applied to materials of steam generator pipes of fossil fired plants in order to study the corrosion layers with respect to elemental amounts and depth structure. The samples were taken from plants and also from treatment in a laboratory device for the simulation of material stress. Using 7.6 MeV He-ions the oxide layer of a sample of a long time operated steam generator pipe was analyzed. Further three samples heated in a laboratory device in air show the initial state of corrosion. A damaged pipe of a coal fired plant was also investigated using 2 MeV He-ions in order to determine the elemental amounts in the oxide layer and in the ash layer at the fire side. The results allowed to draw conclusions for further plant operations.

Zschau, H.-E.; Baumann, H.; Bethge, K.; Link, F.; Wachsmuth, G.

1998-04-01

246

Relationship between wind, waves and radar backscatter  

NASA Technical Reports Server (NTRS)

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

Katsaros, Kristina B.; Ataktuerk, Serhad S.

1991-01-01

247

Rutherford backscattering analysis of contaminants in PET  

NASA Astrophysics Data System (ADS)

Rutherford Backscattering Spectrometry (RBS) was used to understand the sorption and desorption of organic contaminants in the polymer Poly(ethylene terephthalate), or PET. Samples were exposed to a range of organics to simulate contamination of PET that can take place in the post-consumer waste stream. From RBS analysis, concentration depth profiles were shown to vary from a monolayer regime surface layer to a saturation level, depending on the contaminant. Heat treatments were also applied to contaminated polymer to simulate thermal processing steps in the recycling of PET. Heating caused a dramatic decrease in contaminants and in some cases a complete removal of contamination was achieved to the limit of RBS detectability.

Pierce, D. E.; Pfeffer, R. L.; Sadler, G. D.

1997-05-01

248

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

PubMed

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]. PMID:20531781

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

1988-06-15

249

A dynamic localization model with stochastic backscatter  

NASA Technical Reports Server (NTRS)

The modeling of subgrid scales in large-eddy simulation (LES) has been rationalized by the introduction of the dynamic localization procedure. This method allows one to compute rather than prescribe the unknown coefficients in the subgrid-scale model. Formally, the LES equations are supposed to be obtained by applying to the Navier-Stokes equations a 'grid filter' operation. Though the subgrid stress itself is unknown, an identity between subgrid stresses generated by different filters has been derived. Although preliminary tests of the Dynamic Localization Model (DLM) with k-equation have been satisfactory, the use of a negative eddy viscosity to describe backscatter is probably a crude representation of the physics of reverse transfer of energy. Indeed, the model is fully deterministic. Knowing the filtered velocity field and the subgrid-scale energy, the subgrid stress is automatically determined. We know that the LES equations cannot be fully deterministic since the small scales are not resolved. This stems from an important distinction between equilibrium hydrodynamics and turbulence. In equilibrium hydrodynamics, the molecular motions are also not resolved. However, there is a clear separation of scale between these unresolved motions and the relevant hydrodynamic scales. The result of molecular motions can then be separated into an average effect (the molecular viscosity) and some fluctuations. Due to the large number of molecules present in a box with size of the order of the hydrodynamic scale, the ratio between fluctuations and the average effect should be very small (as a result of the 'law of large numbers'). For that reason, the hydrodynamic balance equations are usually purely deterministic. In turbulence, however, there is no clear separation of scale between small and large eddies. In that case, the fluctuations around a deterministic eddy viscosity term could be significant. An eddy noise would then appear through a stochastic term in the subgrid-scale model and could be the source of backscatter.

Carati, Daniele; Ghosal, Sandip

1994-01-01

250

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

E-print Network

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

Illinois at Urbana-Champaign, University of

251

Light backscattering in turbid freshwater: a laboratory investigation  

NASA Astrophysics Data System (ADS)

The relationship between backscattering and inorganic sediment concentration was examined in a controlled laboratory setting. Different concentrations of two sediment sizes (clay/silt and medium sand) of marine clay deposition were added separately in an opaque black tank containing 500 l of distilled water. The experiment used two optical Environmental Characterization Optics-Backscattering sensors to quantify backscattering in m-1 and NTU. Increasing backscatter coefficients (maximum 5.3 m-1) were observed with increasing suspended particulate concentrations up to 272 and 412 mg l-1 for clay/silt and medium sand, respectively. This demonstrates that a greater range of backscattering values can be measured for highly turbid waters than previously measured in situ. Mass-specific backscattering values for clay/silt (0.02 m2 g-1) are on average higher than for medium sand (0.014 m2 g-1). Although the backscattering ratio [b(?)] and refractive index calculated are in accordance with the literature, it is worth noting that the difference in particle size does not exclude differences in matter composition, shape, and other physical factors that contribute to b variation. The results suggest that further investigation of inorganic optical properties affecting particle size as well as matter composition is required in a controlled environment.

Lobo, Felipe L.; Costa, Maycira; Phillips, Stephen; Young, Erika; McGregor, Cory

2014-01-01

252

X-Ray Diffraction.  

ERIC Educational Resources Information Center

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)

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

1980-01-01

253

Crystal rotation in Cu single crystal micropillars: In situ Laue and electron backscatter diffraction  

Microsoft Academic Search

In situ microdiffraction experiments were conducted on focused ion beam machined single crystal Cu pillars oriented for double slip. During deformation, the crystal undergoes lattice rotation on both the primary and critical slip system. In spite of the initial homogeneous microstructure of the Cu pillar, rotation sets in already at yield and is more important at the top of the

R. Maaß; S. van Petegem; D. Grolimund; H. van Swygenhoven; D. Kiener; G. Dehm

2008-01-01

254

Geometrical theory of diffraction  

Microsoft Academic Search

Geometrical theory of diffraction (GTD) is an alternative model of diffraction propounded first by Thomas Young in 1802. GTD\\u000a has a long history of nearly 150 years over which many eminent people enriched this model which has now become an accepted\\u000a tool in the calculation of diffraction patterns. In the conventional Helmholtz-Kirchhoff theory the diffracted field is obtained\\u000a by computing

P B Sunil Kumar; G S Ranganath

1991-01-01

255

X-ray backscatter imaging of nuclear materials  

DOEpatents

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.

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

2014-09-30

256

Physical modeling and measurement of fish acoustic backscatter  

NASA Astrophysics Data System (ADS)

Physical acoustic model of fish is used to explain the variability in backscatter and target size. The research has the aim to apply the theoretical physics-based acoustic scattering models of single animal and laboratory measurements of backscattering by individual fish. The scattering process was modeled using the distorted-wave Born approximation. Results showed that the acoustic backscatter strongly depended on the fish orientation. Predicted scattering over the measured distribution of orientations resulted in predictions of target strength consistent with measurements of target strength of fish.

Manik, Henry M.

2012-06-01

257

Experimental Results on Diffraction  

E-print Network

Experimental Results on Diffraction Hadron Collider Physics Symposium May 28, 2008 Pierre Van Mechelen Pierre.VanMechelen@ua.ac.be #12;Pierre Van Mechelen - Experimental Results on Diffraction - Hadron Collider Physics Symposium -- May 28, 2008 2 Outline b, W, b, W, H Diffractive processes and kinematics

258

Experimental Results on Diffraction  

E-print Network

Results on diffractive scattering observed at HERA and at the TEVATRON are reviewed. This includes the extraction of diffractive parton density functions and determination of the rapidity gap survival probability at HERA and the observation of central exclusive production of final states at the TEVATRON. Finally, preparations to observe diffractive signals at the LHC are discussed.

Pierre Van Mechelen

2008-08-05

259

Factorisation issues in Diffraction  

E-print Network

Factorisation issues in Diffraction Armen Bunyatyan for the H1 and ZEUS Collaborations New Trends factorisation in diffraction with jets and D* · ET dependence of rapidity gap survival probability are diffractive distinguish two classes of events depending on photon virtuality: Q2~0 photoproduction Q2»0 deep

260

Hard diffraction at CDF  

SciTech Connect

Recently published and new preliminary results from the analyses of diffractive events selected with a central or a forward rapidity gap are summarized. New measurements of the ratio of dijet production in single diffractive and non-diffractive events obtained from the Roman Pot data are discussed.

K. Borras

1999-06-18

261

Diffractive production of mesons  

E-print Network

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

R. Schicker

2014-10-17

262

Diffraction at HERA  

E-print Network

Recent results on diffraction at HERA, as measured by the H1 and ZEUS collaborations, are reviewed. Results on the photon-proton total hadronic cross section, on vector meson production both at small and large photon virtuality and on photon diffraction are presented. The experimental signature of diffraction at HERA, as well as the selection methods used by the two collaborations are explained.

Nicolò Cartiglia

1997-03-05

263

Hard diffraction in CDF  

SciTech Connect

We present Run I results on hard diffraction obtained by the CDF Collaboration in proton-antiproton collisions at the Fermilab Tevatron. They are compared with results from the DESY ep collider HERA and/or theoretical predictions to test factorization in hard diffraction. In addition, the CDF program for diffractive studies in Run II is presented briefly.

K. Terashi

2002-07-12

264

Electromagnetic diffraction by plane reflection diffraction gratings  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

265

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

SciTech Connect

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.

Barabash, Oleg M [ORNL; Barabash, Rozaliya [ORNL; Ice, Gene E [ORNL; Feng, Zhili [ORNL; Gandy, Dr. David [Electric Power Research Institute (EPRI)

2009-01-01

266

Statistical simulation of multiple Compton backscattering process  

NASA Astrophysics Data System (ADS)

A number of laboratories are currently developing monochromatic sources of X-rays and gamma quanta based on the Compton backscattering (CBS) of laser photons by relativistic electrons. Modern technologies are capable of providing a concentration of electrons and photons in the interaction point such that each primary electron can emit several hard photons. In contrast to the well-known nonlinear CBS process, in which an initial electron "absorbs" a few laser photons and emits a single hard one, the above-mentioned process can be called a multiple CBS process and is characterized by a mean number of emitted photons. The present paper is devoted to simulating the parameters of a beam of back scattered quanta based on the Monte Carlo technique. It is shown that, even in the case of strong collimation of a resulting photon beam, the radiation monochromaticity may deteriorate because of the contribution coming from the multiple photon emission, which is something that must be considered while designing new CBS sources.

Potylitsyn, A. P.; Kolchuzhkin, A. M.

2014-09-01

267

X-Ray Backscatter Machine Support Frame  

NASA Technical Reports Server (NTRS)

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.

Cannon, Brooke

2010-01-01

268

Inclusive Diffraction at HERA  

E-print Network

The H1 and Zeus collaborations have measured the inclusive diffractive DIS cross section ep -> eXp and these measurements are in good agreement within a normalisation uncertainty. Diffractive parton density functions (DPDFs) have been extracted from NLO QCD fits to inclusive measurements of diffractive DIS and the predictions of these DPDFs are compared with measurements of diffractive dijets in DIS, testing the validity of the factorisation approximations used in their extraction. H1 then use these diffractive dijets in DIS data to provide further constraints in a combined QCD fit, resulting in the next generation of DPDFs which have constrained the diffractive gluon at large momentum fractions. Finally, the predictions of DPDFs are compared to diffractive dijets in photoproduction where the issue of survival probability in a hadron-hadron environment can be studied.

Paul Laycock

2008-10-16

269

Diurnal Thermal Cycling Effects on Backscatter of Thin Sea Ice  

NASA Technical Reports Server (NTRS)

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.

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

270

Radar backscatter modelling of forests using a macroecological approach   

E-print Network

This thesis provides a new explanation for the behaviour of radar backscatter of forests using vegetation structure models from the field of macroecology. The forests modelled in this work are produced using allometry-based ...

Brolly, Matthew

2012-06-25

271

Neon time-of-flight backscattering spectrometry for surface analysis  

E-print Network

Several time-of-flight backscattering spectrometry experiments using singly ionized neon for purposes of analyzing a bismuth coated silicon target were conducted. This work builds upon prior work, done with lighter ions, with the goal of comparing...

Garcia, Richard Michael

2001-01-01

272

L-Band Radar Backscatter Modeling of Forest Stands  

Microsoft Academic Search

An L-band HH radar backscatter model of a coniferous forest stand is described and compared with SIR-B L-band image data of the Mount Shasta region of northern California. Being based upon an identification and implementation of the expected major components of forest backscattering, the model is simple in form and thus fast computationally, making possible extensive simulations of forest stands.

JOHN A. RICHARDS; Guo-Qing Sun; David Simonett

1987-01-01

273

Spatial coherence of backscatter for the nonlinearly produced second harmonic for specific transmit apodizations  

Microsoft Academic Search

To be successful, correlation-based, phase-aberration correction requires a high correlation among backscattered signals. For harmonic imaging, the spatial coherence of backscatter for the second harmonic component is different than the spatial coherence of backscatter for the fundamental component. The purpose of this work was to determine the effect of changing the transmit apodization on the spatial coherence of backscatter for

Russell J. Fedewa; Kirk D. Wallace; M. R. Holland; James R. Jago; Gary C. Ng; Matthew R. Rielly; Brent S. Robinson; James G. Miller

2004-01-01

274

Orientation imaging microscopy of polycrystalline sodium chloride  

SciTech Connect

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

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

2010-04-15

275

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

E-print Network

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

Sindlinger, Laurie R

2003-01-01

276

TCR backscattering characterization for microwave remote sensing  

NASA Astrophysics Data System (ADS)

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 doubly reflected rays define the leading term in the angular region around the boresight direction. The validity of the approach is well assessed by comparisons with experimental results, and its formulation is computer time inexpensive since in closed form. Moreover it is preferable to the model using near-field PO integrations for describing the interactions between the internal TCR's faces since this last requires the evaluation of multi-dimensional integrals, i.e., the expression of the final incident field contains a two-dimensional integral for each previous interaction. [1] Y. Qin, D. Perissin, and L. Lei, "The Design and Experiments on Corner Reflectors for Urban Ground Deformation Monitoring in Hong Kong," Int. J. Antennas Propagat., vol. 2013, pp. 1-8. [2] T. A. Stabile, A. Perrone, M. R. Gallipoli, R. Ditommaso, and F. C. Ponzo, "Dynamic Survey of the Musmeci Bridge by Joint Application of Ground-Based Microwave Radar Interferometry and Ambient Noise Standard Spectral Ratio Techniques," IEEE Geosci. Remote Sens. Lett., vol. 10, no. 4, pp. 870-874, 2013.

Riccio, Giovanni; Gennarelli, Claudio

2014-05-01

277

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

SciTech Connect

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.

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

2011-04-01

278

Combined raman elastic-backscatter LIDAR for vertical profiling of moisture, aerosol extinction, backscatter, and LIDAR ratio  

Microsoft Academic Search

A combined Raman elastic-backscatter lidar has been developed. A XeCl excimer laser is used as the radiation source. Inelastic Raman backscatter signals are spectrally separated from the elastic signal with a filter or grating polychromator. Raman channels can be chosen to register signals from CO2, O2, N2, and H2O. Algorithms for the calculation of the water-vapor mixing ratio from the

A. Ansmann; M. Riebesell; U. Wandinger; C. Weitkamp; E. Voss; W. Lahmann; W. Michaelis

1992-01-01

279

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

280

Diffraction at RHIC  

E-print Network

The relativistic heavy ion collider (RHIC) offers many opportunities to study diffraction in pp, pA and AA collisions. Because both proton beams can be polarized, RHIC offers the unique possibility of studying polarization effects in diffraction. We will introduce diffraction at RHIC and present three compelling physics topics: hard diffraction with polarized beams, identification of exotic mesons (non-q q-bar states) in double-Pomeron collisions, and using diffraction to measure the low-x gluon density in $pA$ collisions, testing models of gluon saturation and the colored glass condensate. This note developed from discussion at a workshop on ``Diffraction and Glueball Production at RHIC'' at Brookhaven National Laboratory, May 17-18, 2002.

A. Bravar; W. Guryn; S. R. Klein; D. Milstead; B. Surrow

2002-08-29

281

Geophysical Diffraction Tomography  

Microsoft Academic Search

Diffraction tomography is the generalization of X-ray tomography to applications such as seismic exploration where diffraction effects must be taken into account. In this paper, the foundations of diffraction tomography for offset vertical seismic profiling and well-to-well tomography are presented for weakly inhomogeneous formations for which the Born or Rytov approximations can be employed. Reconstruction algorithms are derived for approximately

A. J. Devaney

1984-01-01

282

Gyroid Single Crystal Diffraction  

NASA Astrophysics Data System (ADS)

A “single crystal” of a block copolymer / homopolymer blend with the Gyroid morphology was obtained by slow solvent casting. The block copolymer was an I2S2 star shaped block copolymer, which has two polystyrene arms and two polyisoprene arms connected at a single junction point. The homopolymer was low MW polyisoprene. The sample was studied by SAXS and TEM. SAXS of this sample produced single crystal diffraction patterns of several different zones with as many as 128 diffraction peaks in a single diffraction pattern, and 148 total unique diffraction peaks. Analysis of this data provides the most unambiguous proof to date of the Ia3d symmetry and Gyroid structure.

Yang, L.; Hong, S.; Gido, S. P.; Uhrig, D.; Mays, J. W.

2001-03-01

283

A.Bonato Diffraction at HERA, LL07 Diffraction and Diffractive Final States  

E-print Network

A.Bonato ­ Diffraction at HERA, LL07 Diffraction and Diffractive Final States at HERA A Institute, 24/02/2007 #12;A.Bonato ­ Diffraction at HERA, LL07 Outline Introduction: motivations, features and kinematics Inclusive diffraction measurements Diffractive final states: jets and open charm Conclusion 2

284

Experimental results on the enhanced backscatter phenomenon and its dynamics  

NASA Astrophysics Data System (ADS)

Enhanced backscatter effects have long been predicted theoretically and experimentally demonstrated. The reciprocity of a turbulent channel generates a group of paired rays with identical trajectory and phase information that leads to a region in phase space with double intensity and scintillation index. Though simulation work based on phase screen models has demonstrated the existence of the phenomenon, few experimental results have been published describing its characteristics, and possible applications of the enhanced backscatter phenomenon are still unclear. With the development of commercially available high powered lasers and advanced cameras with high frame rates, we have successfully captured the enhanced backscatter effects from different reflection surfaces. In addition to static observations, we have also tilted and pre-distorted the transmitted beam at various frequencies to track the dynamic properties of the enhanced backscatter phenomenon to verify its possible application in guidance and beam and image correction through atmospheric turbulence. In this paper, experimental results will be described, and discussions on the principle and applications of the phenomenon will be included. Enhanced backscatter effects are best observed in certain levels of turbulence (Cn 2?10-13 m-2/3), and show significant potential for providing self-guidance in beam correction that doesn't introduce additional costs (unlike providing a beacon laser). Possible applications of this phenomenon include tracking fast moving object with lasers, long distance (>1km) alignment, and focusing a high-power corrected laser beam over long distances.

Wu, Chensheng; Nelson, William; Ko, Jonathan; Davis, Christopher C.

2014-10-01

285

Multi-beam backscatter measurements used to infer seabed habitats  

NASA Astrophysics Data System (ADS)

Backscatter from multi-beam sonar (MBS) was used to discriminate ecologically relevant seabed characteristics based on 62 reference sites sampled with georeferenced video, sediment grab and rock dredge between 50 and 500 m water depth. A simple biotope characteristic of soft (unconsolidated) and hard (consolidated) was used to compare the acoustic backscatter data with the data on mega-epifauna and substrate type obtained from video and physical sampling. Substrate type of homogeneous reference sites was predicted by matching the backscatter incidence angle profile (0-70°) to that of a seabed scattering model. Referencing the seabed backscatter to a consistent incidence angle (40°) gave a metric with high spatial resolution (2.4-20 m), which minimised errors of range, incident angle and beam compensation. This simple metric provided a consistent approach to analyse and interpret the data and was strongly correlated with substrate type and faunal functional groups. The high resolution backscatter metric was a closer match to the small spatial scale of seabed patch lengths observed by video (50% <50 m).

Kloser, R. J.; Penrose, J. D.; Butler, A. J.

2010-09-01

286

Probabilities and statistics for backscatter estimates obtained by a scatterometer  

NASA Technical Reports Server (NTRS)

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.

Pierson, Willard J., Jr.

1989-01-01

287

Diffraction Results from CDF  

SciTech Connect

We present final results by the CDF II collaboration on diffractive W and Z production, report on the status of ongoing analyses on diffractive dijet production and on rapidity gaps between jets, and briefly summarize results obtained on exclusive production pointing to their relevance to calibrating theoretical models used to predict exclusive Higgs-boson production at the LHC.

Goulianos, Konstantin

2012-04-01

288

Diffraction Results from CDF  

E-print Network

We present final results by the CDF II collaboration on diffractive W and Z production, report on the status of ongoing analyses on diffractive dijet production and on rapidity gaps between jets, and briefly summarize results obtained on exclusive production pointing to their relevance to calibrating theoretical models used to predict exclusive Higgs-boson production at the LHC.

Konstantin Goulianos

2012-04-24

289

Surprises in aperiodic diffraction  

E-print Network

Mathematical diffraction theory is concerned with the diffraction image of a given structure and the corresponding inverse problem of structure determination. In recent years, the understanding of systems with continuous and mixed spectra has improved considerably. Moreover, the phenomenon of homometry shows various unexpected new facets. Here, we report on some of the recent results in an exemplary and informal fashion.

Michael Baake; Uwe Grimm

2009-09-30

290

Pinhole diffraction filter  

NASA Technical Reports Server (NTRS)

Multistage diffraction filter consisting of coalined series of pinholes on parallel sheets can be used as nondegradable UV filter. Beam is attenuated as each pinhole diffracts radiation in controlled manner into divergent beam, and following pinhole accepts only small part of that beam.

Woodgate, B. E.

1977-01-01

291

Edge diffraction in sunlight  

Microsoft Academic Search

Observations of wave-optics effects in sunlight are reported. In particular, conditions are described that allow for visual detection of diffraction phenomena from line edges. Typical fringe patterns are demonstrated, also showing color features that account for the wavelength dependence of the diffraction process. Hints to optimize the observation are given, outlining the aspects of simplicity and naturalness of the occurrence.

Vincenzo Greco; Giuseppe Molesini; R. Tronconi

1997-01-01

292

Calculations of radar backscattering coefficient of vegetation-covered soils  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

293

Adaptive focus for deep tissue using diffuse backscatter  

NASA Astrophysics Data System (ADS)

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

Kress, Jeremy; Pourrezaei, Kambiz

2014-02-01

294

Backscatter and attenuation properties of mammalian brain tissues  

NASA Astrophysics Data System (ADS)

Traumatic Brain Injury (TBI) is a common category of brain injuries, which contributes to a substantial number of deaths and permanent disability all over the world. Ultrasound technology plays a major role in tissue characterization due to its low cost and portability that could be used to bridge a wide gap in the TBI diagnostic process. This research addresses the ultrasonic properties of mammalian brain tissues focusing on backscatter and attenuation. Orientation dependence and spatial averaging of data were analyzed using the same method resulting from insertion of tissue sample between a transducer and a reference reflector. Apparent backscatter transfer function (ABTF) at 1 to 10 MHz, attenuation coefficient and backscatter coefficient (BSC) at 1 to 5 MHz frequency ranges were measured on ovine brain tissue samples. The resulting ABTF was a monotonically decreasing function of frequency and the attenuation coefficient and BSC generally were increasing functions of frequency, results consistent with other soft tissues such as liver, blood and heart.

Wijekularatne, Pushpani Vihara

295

Bruce Thompson: Adventures and advances in ultrasonic backscatter  

NASA Astrophysics Data System (ADS)

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

Margetan, Frank J.

2012-05-01

296

Orientation mapping of nanostructured materials using transmission Kikuchi diffraction in the scanning electron microscope.  

PubMed

In this study, the new technique of transmission Kikuchi diffraction (TKD) in the scanning electron microscope (SEM) has been applied for the first time to enable orientation mapping of bulk, nanostructured metals. The results show how the improved spatial resolution of SEM-TKD, compared to conventional EBSD, enables reliable mapping of truly nanostructured metals and alloys, with mean grain sizes in the 40-200 nm range. The spatial resolution of the technique is significantly below 10nm, and contrasting examples are shown from both dense (Ni) and lighter (Al-alloy) materials. Despite the burden of preparing thin, electron-transparent samples, orientation mapping using SEM-TKD is likely to become invaluable for routine characterisation of nanocrystalline and, potentially, highly deformed microstructures. PMID:22796555

Trimby, Patrick W

2012-09-01

297

Calculating incoherent diffraction MTF  

NASA Astrophysics Data System (ADS)

The incoherent diffraction MTF plays an increasingly important role in the range performance of imaging systems as the wavelength increases and the optical aperture decreases. Accordingly, all NVESD imager models have equations that describe the incoherent diffraction MTF of a circular entrance pupil. NVThermIP, a program which models thermal imager range performance, has built in equations which analytically model the incoherent diffraction MTF of a circular entrance pupil and has a capability to input a table that describes the MTF of other apertures. These can be calculated using CODE V, which can numerically calculate the incoherent diffraction MTF in the vertical or horizontal direction for an arbitrary aperture. However, we are not aware of any program that takes as input a description of the entrance pupil and analytically outputs equations that describe the incoherent diffraction MTF. This work explores the effectiveness of Mathematica to analytically and numerically calculate the incoherent diffraction MTF for an arbitrary aperture. In this work, Mathematica is used to analytically and numerically calculate the incoherent diffraction MTF for a variety of apertures and the results are compared with CODE V calculations.

Friedman, Melvin; Vizgaitis, Jay

2008-04-01

298

Floc Growth and Changes in ADV Acoustic Backscatter Signal  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

299

Measurement of the anisotropy factor with azimuthal light backscattering  

NASA Astrophysics Data System (ADS)

The potential capability of low coherence backscattering (LBS) is explored to determine the anisotropy factor based on azimuthal light backscattering map. The scattering intensity signal measured at azimuthal angle ?=0° is extracted for analysis. By performing nonlinear regression fitting on the experimental signal to the Henyey-Greenstein phase function, the anisotropy factor is determined. The experiments with tissue phantom consisting of the aqueous suspension of polystyrene microspheres are carried out. The results show that the measured anisotropy factor is well described by Mie theory.

Wang, Pin; Li, Yong-ming; Chen, Bo-han

2014-11-01

300

Coherent Effects in Microwave Backscattering Models for Forest Canopies  

NASA Technical Reports Server (NTRS)

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.

Saatchi, Sasan; McDonald, Kyle

1995-01-01

301

The Compton backscattering polarimeter of the A4 experiment  

NASA Astrophysics Data System (ADS)

The A4 collaboration at the Institut für Kernphysik, University of Mainz, is conducting experiments on single-spin asymmetries in the elastic electron-nucleon-scattering which require polarized beams. In order to measure the absolute beam polarization, we have installed a Compton backscattering polarimeter in front of the target, using for the first time the internal cavity concept. A maximum intra-cavity intensity of 90 W has been measured, and in August 2003, first backscattered photons have been detected. Recently, first Compton asymmetries have been measured.

Imai, Y.; the A4 Collaboration

2005-07-01

302

Backscattering peak of hexagonal ice columns and plates.  

PubMed

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. PMID:18066226

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

2000-09-15

303

Effect of curvature on the backscattering from leaves  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

304

A Parametric Study of Tillage Effects on Radar Backscatter  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

305

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

PubMed

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

Zachrisson, J; Börjesson, J; Karlsson, L

2013-02-01

306

Nanowire-Induced Wurtzite InAs Thin Film on Zinc-Blende InAs Substrate  

E-print Network

As substrate. Electron-backscatter diffraction (EBSD) and transmission elec- tron microscopy (TEM) confirm the surface from the base of wurtzite InAs nanowires synthesized by chemical beam epitaxy on a zinc-blende In a fascinating subject because materials with different crystal structures can exhibit very distinct electronic

Bao, Jiming

307

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

SciTech Connect

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.

Souza, C.M. [Universidade Federal do Rio de Janeiro, Departamento de Engenharia Metalurgica e de Materiais (Brazil)], E-mail: eng_marley@yahoo.com.br; Abreu, H.F.G. [Universidade Federal do Ceara, Departamento de Engenharia Metalurgica e de Materiais, Campus do Pici Bl. 702, Fortaleza, CE, CEP 60.455-760 (Brazil); Tavares, S.S.M. [Universidade Federal Fluminense, Departamento de Engenharia Mecanica (Brazil); Rebello, J.M.A. [Universidade Federal do Rio de Janeiro, Departamento de Engenharia Metalurgica e de Materiais (Brazil)

2008-09-15

308

Deriving grain boundary character distributions and relative grain boundary  

E-print Network

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

Rohrer, Gregory S.

309

Multilayer dielectric diffraction gratings  

DOEpatents

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.

Perry, Michael D. (Livermore, CA); Britten, Jerald A. (Oakley, CA); Nguyen, Hoang T. (Livermore, CA); Boyd, Robert (Livermore, CA); Shore, Bruce W. (Livermore, CA)

1999-01-01

310

Multilayer dielectric diffraction gratings  

DOEpatents

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.

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

1999-05-25

311

Hard diffraction in CDF  

SciTech Connect

The aim of these studies is to use hard (large Q{sup 2}) processes to investigate the partonic nature of the pomeron. We have measured events with large rapidity gaps between balancing high E{sub T} jets, events with two forward (same-side) jets and a large gap (diffractive di-jet production), diffractive W{sup {+-}} production and diffractive heavy flavor (J/{psi} and b-quark) production. Candidate events of the type double-pomeron {yields} di-jet are observed. I close with a look at the future (Run II).

Albrow, M.G.; CDF Collaboration

1997-10-01

312

Factorization breaking in diffraction  

NASA Astrophysics Data System (ADS)

The measurements of diffractive dijet and open charm electron-proton cross-sections in deep-inelastic scattering (DIS) and photoproduction at HERA are discussed with an emphasis on possible quantum chromodynamics (QCD) factorization breaking.

Valkárová, Alice

2015-02-01

313

Hard diffraction at CDF  

SciTech Connect

We present new evidence for events with a rapidity gap between jets in {bar p}-p collisions at {radical}s = 1.8 TeV based on data collected by triggering the Collider Detector at Fermilab on two high transverse momentum forward jets and results of a search for diffractive W{+-} and dijet production where diffraction is tagged by the rapidity gap technique. We also present the results of a search for diffractive dijets using data collected by triggering on a very forward particle in the recently installed roman-pot detectors. The dijet events exhibit additional diffractive characteristics such as rapidity gaps and boosted center of mass system, however the recoil antiproton measured in the roman-pots is in a regime in which the non- pomeron contribution is significant.

Melese, P.L. [Rockefeller Univ., New York, NY (United States); CDF Collaboration

1996-07-01

314

Gravitational diffraction radiation  

E-print Network

We show that if the visible universe is a membrane embedded in a higher-dimensional space, particles in uniform motion radiate gravitational waves because of spacetime lumpiness. This phenomenon is analogous to the electromagnetic diffraction radiation of a charge moving near to a metallic grating. In the gravitational case, the role of the metallic grating is played by the inhomogeneities of the extra-dimensional space, such as a hidden brane. We derive a general formula for gravitational diffraction radiation and apply it to a higher-dimensional scenario with flat compact extra dimensions. Gravitational diffraction radiation may carry away a significant portion of the particle's initial energy. This allows to set stringent limits on the scale of brane perturbations. Physical effects of gravitational diffraction radiation are briefly discussed.

Vitor Cardoso; Marco Cavaglia; Mario Pimenta

2006-10-04

315

X-Ray Diffraction  

NSDL National Science Digital Library

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

Matter.org

316

Multigap Diffraction at LHC  

SciTech Connect

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.

Goulianos, Konstantin [Rockefeller University, New York, NY 10021 (United States)

2005-10-06

317

Diffraction at TOTEM  

E-print Network

The TOTEM experiment at the LHC measures the total proton-proton cross section with the luminosity-independent method and the elastic proton-proton cross-section over a wide |t|-range. It also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage of the large common rapidity coverage for charged and neutral particle detection and the large variety of trigger possibilities even at large luminosities. TOTEM will take data under all LHC beam conditions including standard high luminosity runs to maximize its physics reach. This contribution describes the main features of the TOTEM physics programme including measurements to be made in the early LHC runs. In addition, a novel scheme to extend the diffractive proton acceptance for high luminosity runs by installing proton detectors at IP3 is described.

G. Antchev; P. Aspell; V. Avati; M. G. Bagliesi; V. Berardi; M. Berretti; U. Bottigli; M. Bozzo; E. Brucken; A. Buzzo; F. Cafagna; M. Calicchio; M. G. Catanesi; P. L. Catastini; R. Cecchi; M. A. Ciocci; M. Deile; E. Dimovasili; K. Eggert; V. Eremin; F. Ferro; F. Garcia; S. Giani; V. Greco; J. Heino; T. Hilden; J. Kaspar; J. Kopal; V. Kundrat; K. Kurvinen; S. Lami; G. Latino; R. Lauhakangas; E. Lippmaa; M. Lokajicek; M. Lo Vetere; F. Lucas Rodriguez; M. Macri; G. Magazzu; M. Meucci; S. Minutoli; H. Niewiadomski; E. Noschis; G. Notarnicola; E. Oliveri; F. Oljemark; R. Orava; M. Oriunno; K. Osterberg; P. Palazzi; E. Pedreschi; J. Petajajarvi; M. Quinto; E. Radermacher; E. Radicioni; F. Ravotti; G. Rella; E. Robutti; L. Ropelewski; G. Ruggiero; A. Rummel; H. Saarikko; G. Sanguinetti; A. Santroni; A. Scribano; G. Sette; W. Snoeys; F. Spinella; P. Squillacioti; A. Ster; C. Taylor; A. Trummal; N. Turini; J. Whitmore; J. Wu

2008-12-17

318

Acoustic diffraction by a finite barrier; theories and experiment  

NASA Astrophysics Data System (ADS)

The Biot-Tolstoy (B-T) exact impulse solution of diffraction by an infinite half-plane is compared to the usual Helmholtz-Kirchhoff (H-K) integral formulation and to the exact continuous wave (CW) solution of Macdonald. For backscatter the B-T and H-K solutions are found to differ significantly, especially near the surface of the half-plane, where the B-T solution gives close agreement with experiment. For forward scatter the two exact solutions and experimental data are in agreement. B-T is found to agree well with measurements of diffraction by a barrier perpendicular to a rigid base. By considering source and source image in the base separately the concept of 'image of the source in the barrier' is found to be unnecessary. Use of the time domain form of B-T solution in calculating the forward diffraction near a corner and behind a thin strip is shown to give results which agree well with measured data. Secondary diffraction effects are observed in the measurements of diffraction by a thin strip, a non-vertical barrier and a thick edge.

Jebsen, G. M.

1981-03-01

319

Reflective diffraction grating  

DOEpatents

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.

Lamartine, Bruce C. (Los Alamos, NM)

2003-06-24

320

Wire Diffraction Gratings  

NASA Astrophysics Data System (ADS)

In the summer of 1972, I attended the workshop on recreating classic experiments in physics at Barnard College. This was developed by Samuel Devons, and it was a defining experience that set me toward a research career involving early physics teaching apparatus. During the course of the workshop, I became curious about the original diffraction gratings developed by Fraunhofer and built a wire diffraction. A short note about the gratings was published in the American Journal of Physics the next year.2

Greenslade, Thomas B.

2004-02-01

321

Diffraction and holography of photoelectrons and fluorescent x-rays  

SciTech Connect

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

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

1993-04-01

322

Rutherford backscattering analysis of gallium implanted 316 stainless steel  

E-print Network

Ion implantation of Ga ions into 316 stainless steel was performed at fluences ranging from 8x10¹? to 10¹? ions/cm². The depth profile of Ga in the steel was analyzed via Rutherford Backscattering and ToFSIMS. The surface effects were...

Ortensi, Javier

2000-01-01

323

Radar backscatter and biomass saturation: ramifications for global biomass inventory  

Microsoft Academic Search

Two SAR and biomass data sets of forests with different canopy architectures were examined for commonalties regarding backscatter\\/biomass saturation. The SAR data were collected using the NASA\\/JPL AIRSAR at incidence angles between 40° and 50° for tropical broadleaf evergreen forests in Hawaii and coniferous forests in North America and Europe. Radar signal saturation limits with respect to biomass for both

Marc L. Imhoff

1995-01-01

324

Tracking California seafloor seeps with bathymetry, backscatter and ROVs  

NASA Astrophysics Data System (ADS)

The California (USA) margin includes two different tectonic regimes: subduction north of the Mendocino Triple Junction and translation south. Both margins include seeps, and their distribution can be inferred using seafloor bathymetry and backscatter as well as subsurface seismic data. Anomalous bathymetric and backscatter features related to fluid expulsion include headless submarine canyons, fault zones, anticlines, pockmarks, and mud volcanoes. Anomalous backscatter may be caused by authigenic carbonate (related to the bacterial oxidation of methane) or cold seep clams—both have an impedance and roughness that may be higher than the surrounding seafloor. Remote-operated vehicle (ROV) dives to such suspect seep sites document the presence of extensive authigenic carbonate, areally restricted cold seep communities, carpets of chemoautotrophic bacteria, and bubbling gas. Our operations in the Monterey Bay, on the translational California margin, and the Eel River basin, on the convergent margin, indicate that bathymetric and backscatter maps of the seafloor, if sufficiently high resolution, can be used to map seep sites, and that the distribution of such seeps can be used to constrain subsurface conduits of fluid flow. ROVs, due to their combination of visualization, propulsion, manipulation, sonar, and navigation, provide an excellent platform for ground-truthing, mapping, and sampling seafloor seeps.

Orange, Daniel L.; Yun, Janet; Maher, Norman; Barry, James; Greene, Gary

2002-11-01

325

Spectrum of coherently backscattered light from two atoms  

E-print Network

We present a detailed analytical and numerical analysis of the inelastic coherent backscattering spectrum of laser light incident on cold atoms. We identify frequency domains where the interference contribution can be positive \\emph{as well as} negative -- or exhibits dispersive character. These distinctive features are explained by reciprocity arguments and dressed state two-photon scattering amplitudes.

Vyacheslav Shatokhin; Thomas Wellens; Benoît Grémaud; Andreas Buchleitner

2007-12-30

326

Bathymetry and acoustic backscatter: Elwha River Delta, Washington  

USGS Publications Warehouse

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.

Finlayson, David P.; Miller, Ian M.; Warrick, Jonathan A.

2011-01-01

327

Method and Apparatus for Computed Imaging Backscatter Radiography  

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

328

An overview of backscattered radio frequency identification system (RFID)  

Microsoft Academic Search

A radio frequency identification (RFID) system is a wireless communication system in which the radio link between the base station and the transponders are furnished by the modulated backscattered waves. The present paper is intended to provide a brief description of various subsystems of the RFID. The various applications of RFID are discussed. Sample results on read\\/write range for a

K. V. S. Rao

1999-01-01

329

Theory and measurement of backscattering from RFID tags  

Microsoft Academic Search

This paper presents a method for measuring signal backscattering from RFID tags, and for calculating a tag's radar cross section (RCS). We derive a theoretical formula for the RCS of an RFID tag with a minimum-scattering antenna. We describe an experimental measurement technique, which involves using a network analyzer connected to an anechoic chamber with and without the tag. The

Pavel V. Nikitin; K. V. S. Rao

2006-01-01

330

Radar Backscatter Across the Gulf Stream Sea Surface Temperature Front  

NASA Technical Reports Server (NTRS)

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.

Nghiem, S. V.; Li, F. K.; Walsh, E. J.; Lou, S. H.

1998-01-01

331

Measurement of high voltage using Rutherford backscattering spectrometry  

E-print Network

A novel variation of Rutherford Backscattering Spectrometry (RBS) has been utilized to measure a high voltage collected on an aluminum target by Direct Energy Conversion. The maximum high voltage on the target was measured to be 97.5 kV +/- 2 k...

Abrego, Celestino Pete

2007-04-25

332

Backscattering measurements from double-scale randomly rough surfaces  

E-print Network

to obtain information about material properties by analyzing the reflected and refracted light. However,3], microscopy [4,5], and surface char- acterization [6,7] are some of these applications. The problem of light of light backscattered from double-scale randomly rough surfaces (ocean- like surfaces) with different

Dainty, Chris

333

Orientation dependence of broadband acoustic backscattering from live squid  

E-print Network

Orientation dependence of broadband acoustic backscattering from live squid Wu-Jung Lee, Andone C squid (Loligo pealeii) was conducted using linear chirp signals (60­103 kHz) with data collected over with an analytical prolate spheroid model and a three-dimensional numerical model with randomized squid shape, both

Stanton, Tim

334

BACKSCATTER GUAGE DESCRIPTION FOR INSPECTION OF NEUTRON ABSORBER AND UNIFORMITY  

SciTech Connect

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.

Dewberry, R.; Gibbs, K.; Couture, A.

2012-05-23

335

Ultrasonic characterization of cancellous bone using apparent integrated backscatter  

NASA Astrophysics Data System (ADS)

Apparent integrated backscatter (AIB) is a measure of the frequency-averaged (integrated) backscattered power contained in some portion of a backscattered ultrasonic signal. AIB has been used extensively to study soft tissues, but its usefulness as a tissue characterization technique for cancellous bone has not been demonstrated. To address this, we performed measurements on 17 specimens of cancellous bone over two different frequency ranges using a 1 MHz and 5 MHz broadband ultrasonic transducer. Specimens were obtained from bovine tibiae and prepared in the shape of cubes (15 mm side length) with faces oriented along transverse (anterior, posterior, medial and lateral) and longitudinal (superior and inferior) principal anatomic directions. A mechanical scanning system was used to acquire multiple backscatter signals from each direction for each cube. AIB demonstrated highly significant linear correlations with bone mineral density (BMD) for both the transverse (R2 = 0.817) and longitudinal (R2 = 0.488) directions using the 5 MHz transducer. In contrast, the correlations with density were much weaker for the 1 MHz transducer (R2 = 0.007 transverse, R2 = 0.228 longitudinal). In all cases where a significant correlation was observed, AIB was found to decrease with increasing BMD.

Hoffmeister, B. K.; Jones, C. I., III; Caldwell, G. J.; Kaste, S. C.

2006-06-01

336

Helicopter-borne measurements of radar backscatter from forests  

Microsoft Academic Search

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

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

1990-01-01

337

Backscattering grain noise modelling in ultrasonic non-destructive testing  

Microsoft Academic Search

Many materials present an internal grain microstructure. When these materials are subjected to ultrasonic non-destructive testing, the grains behave like scattering centres producing unwanted backscattered noise that can make the detection of true defects difficult. This paper is devoted to the modelling of the probability density and the spacetime correlation functions of the grain noise complex envelope. Assuming statistical independence

Luis Vergara-Dominguez; J. Manuel Paez-Borrallo

1991-01-01

338

A Large-Scale Ku-Band Backscatter Model of the East-Antarctic Megadune Fields  

E-print Network

A Large-Scale Ku-Band Backscatter Model of the East-Antarctic Megadune Fields Ben Lambert and David- ture of the East Antarctic megadune fields observed with QuickSCAT. Backscatter signature has been used

Long, David G.

339

Ku-band ocean radar backscatter observations during SWADE  

NASA Technical Reports Server (NTRS)

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-flight of NUSCAT data is given. Wind velocities, air and sea surface temperature, ocean spectrum, and other variables measured from aircraft and buoys are also shown.

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

1993-01-01

340

Error caused by using a constant extinction/backscattering ratio in the lidar solution  

NASA Technical Reports Server (NTRS)

The Bernoulli solution of the lidar equation with the assumption of a constant extinction/backscattering ratio can lead to errors in the derived aerosol extinction and backscattering profiles. This paper presents a general theoretical analysis of the errors that result from differences between the assumed and actual extinction/backscattering ratio profiles. Examples of the influence of the constant extinction/backscattering ratio assumption on the lidar derived aerosol extinction profile are presented for various laser wavelengths.

Sasano, Y.; Browell, E. V.; Ismail, S.

1985-01-01

341

Error caused by using a constant extinction\\/backscattering ratio in the lidar solution  

Microsoft Academic Search

The Bernoulli solution of the lidar equation with the assumption of a constant extinction\\/backscattering ratio can lead to errors in the derived aerosol extinction and backscattering profiles. This paper presents a general theoretical analysis of the errors that result from differences between the assumed and actual extinction\\/backscattering ratio profiles. Examples of the influence of the constant extinction\\/backscattering ratio assumption on

Yasuhiro Sasano; Edward V. Browell; Syed Ismail

1985-01-01

342

A comparative study of RADAR Ka-band backscatter  

NASA Astrophysics Data System (ADS)

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).

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

2014-10-01

343

Geological interpretation of a low-backscatter anomaly found on the New Jersey continental margin  

E-print Network

Geological interpretation of a low-backscatter anomaly found on the New Jersey continental margin.J.W. Piper Keywords: U.S. mid-Atlantic continental margin continental slope multibeam backscatter submarine canyons Western Boundary Undercurrent Chesapeake Drift An enigmatic low-backscatter, acoustic anomaly

New Hampshire, University of

344

Acoustic Backscattering From the Basin and Margins of the Arctic Ocean  

Microsoft Academic Search

Sound waves created by high-energy explosives were used to measure reverberation and backscattering in the Arctic Ocean. From an ice camp in the Beaufort Sea, signals were backscattered from the continental margin and other major features of the basin. An acoustic array was used to analyze the signals in azimuth. Based on these data we constructed charts of normalized backscatter

I. Dyer; A. B. Baggeroer; J. D. Zittel; R. J. Williams

1982-01-01

345

WET SNOW BACKSCATTERING SENSITIVITY ON DENSITY CHANGE FOR SWE N. Besic1,2  

E-print Network

WET SNOW BACKSCATTERING SENSITIVITY ON DENSITY CHANGE FOR SWE ESTIMATION N. Besic1,2 , G. Vasile1 with the sensitivity of the wet snow backscattering coefficient on density change. The pre- sented backscattering model is based on the approach used in the dry snow analysis [1], appropriately modified to ac- count

Paris-Sud XI, Université de

346

WIND/RAIN BACKSCATTER MODELING AND WIND/RAIN RETRIEVAL FOR SCATTEROMETER AND  

E-print Network

WIND/RAIN BACKSCATTER MODELING AND WIND/RAIN RETRIEVAL FOR SCATTEROMETER AND SYNTHETIC APERTURE. Fulton College of Engineering and Technology #12;#12;ABSTRACT WIND/RAIN BACKSCATTER MODELING AND WIND/RAIN to rain is evaluated. It is demonstrated that C-band radar backscatter can be significantly altered

Long, David G.

347

A New Weighted Monte Carlo Algorithm for Elastic Electron Backscattering from  

E-print Network

A New Weighted Monte Carlo Algorithm for Elastic Electron Backscattering from Surfaces ? Emanouil I a monoenergetic electron beam is bombarding a solid target, some electrons are elastically backscattered. This elastic electron backscattering e#11;ect plays an important role in many experimental techniques, like low

Dimov, Ivan

348

Estimating Surface Oil Extent from the Deepwater Horizon Oil Spill using ASCAT Backscatter  

E-print Network

Estimating Surface Oil Extent from the Deepwater Horizon Oil Spill using ASCAT Backscatter Richard backscatter and observed backscatter indicate areas of the ocean surface affected by oil. The recent oil spill to estimate the spatial extent of surface oil. I. INTRODUCTION The oil spill from the Deepwater Horizon oil

Long, David G.

349

Multiwavelength Comparison of Modeled and Measured Remote Tropospheric Aerosol Backscatter Over Pacific Ocean  

NASA Technical Reports Server (NTRS)

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.

Cutten, D. R.; Pueschel, R. F.; Srivastava, V.; Clarke, A. D.; Rothermel, J.; Spinhirne, J. D.; Menzies, R. T.

1996-01-01

350

Improved scatterer property estimates from ultrasound backscatter for small gate lengths using a gate-edge  

E-print Network

of the scatterers is regular or periodic, a coher- ent component is introduced into the backscattered signal rf signals used to construct conventional ultrasound B-mode images contain frequency-dependent information that can be examined through the backscattered power spectrum. The backscattered power spectrum

Illinois at Urbana-Champaign, University of

351

Three-dimensional Quantum Slit Diffraction and Diffraction in Time.  

E-print Network

Three-dimensional Quantum Slit Diffraction and Diffraction in Time. M. Beau & T. C. Dorlas Dublin 14, 2014 Abstract We study the quantum slit diffraction problem in three dimen- sions. In the treatment of diffraction of particles by a slit, it is usually assumed that the motion perpendicular

Paris-Sud XI, Université de

352

Diffraction tomography of strain  

NASA Astrophysics Data System (ADS)

We consider whether it is possible to recover the three dimensional strain field tomographically from neutron and x-ray diffraction data for polycrystalline materials. We show that the distribution of strain transverse to a ray cannot be deduced from one diffraction pattern accumulated along that path, but that a certain moment of that data corresponds to the transverse ray transform of the strain tensor and so may be recovered by inverting that transform given sufficient data. We show that the whole strain tensor can be reconstructed from diffraction data measured using rotations about six directions that do not lie on a projective conic. In addition we give an inversion formula for complete data for the transverse ray transform. We also show that Bragg edge transmission data, which has been suggested for strain tomography with polychromatic data, cannot provide the strain distribution within the material but only the average along the ray path.

Lionheart, W. R. B.; Withers, P. J.

2015-04-01

353

Diffraction Shaders Jos Stam \\Lambda  

E-print Network

Diffraction Shaders Jos Stam \\Lambda Alias wavefront Abstract The reflection of light from surfaces sur­ faces that handle the effects of diffraction. Diffraction is a purely wave­like phenomenon­ hibits diffraction is the compact disk. A characteristic of such sur­ faces is that they reflect light

Toronto, University of

354

A discussion on electron–photon backscattering lasers and the electron–photon backscattering laser in a laser standing wave cavity  

NASA Astrophysics Data System (ADS)

Electron–photon backscattering lasers are discussed. For producing a laser by means of the backscattering of an incident laser and a monochromatic electron beam, the intensity of the incident laser must be large. The incident laser can form a laser standing wave in a laser standing wave cavity. When the coherence conditions are satisfied, the laser standing wave can cause temporal coherence and spatial coherence of the backscattering light, so the backscattering light can form a quasi-laser or laser. A way of obtaining a better monochromatic electron beam is proposed. An example is given.

Chen, Ziwei; Chen, Shi-Hao

2015-04-01

355

Interference and Diffraction  

NSDL National Science Digital Library

In this video from the ICT Center, learn about interference and diffraction. See how the wave properties of light are used to explain interference patterns on a screen, and learn about related technologies such as the Fabry-Perot cavity, Bragg gratings, interference filters, and antireflection coatings. In addition, learn how diffraction patterns are produced, and study the grating equation.The video runs 4:12 and is accompanied by a background essay, standards alignment, and discussion questions. Users who sign up for a free account can save the resource and download the video as well.

356

Comparison of reflectance with backscatter and absorption parameters for turbid waters  

NASA Technical Reports Server (NTRS)

The relation of reflectance to backscatter and absorption parameters is investigated for waters more turbid than those of previous investigations. Experimental data are examined for river waters in which beam attenuation values range from 8.9 to 18.9 per m at 550 nm. Attenuation, absorption, backscatter, and irradiance reflectance spectral properties are presented for wavelengths between 450 and 800 nm. Comparisons of reflectance with backscatter to absorption ratio and backscatter with absorption plus backscatter ratio indicate that data for turbid waters do not fit linear or polynomial models which are presently available in the literature.

Whitlock, C. H.; Poole, L. R.; Usry, J. W.; Houghton, W. M.; Witte, W. G.; Morris, W. D.; Gurganus, E. A.

1981-01-01

357

Comparison of Modeled Backscatter using Measured Aerosol Microphysics with Focused CW Lidar Data over Pacific  

NASA Technical Reports Server (NTRS)

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.

Srivastava, Vandana; Clarke, Antony D.; Jarzembski, Maurice A.; Rothermel, Jeffry

1997-01-01

358

Point-group sensitive orientation mapping of non-centrosymmetric crystals  

NASA Astrophysics Data System (ADS)

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.

Winkelmann, Aimo; Nolze, Gert

2015-02-01

359

RFID tag modification for full depth backscatter modulation  

DOEpatents

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.

Scott, Jeffrey Wayne [Pasco, WA; Pratt, Richard M [Richland, WA

2010-07-20

360

Optical backscatter characteristics of Arctic polar stratospheric clouds  

SciTech Connect

Airborne lidar measurements have been made of polar stratospheric clouds (PSCs) during the Airborne Arctic Stratospheric Expedition in January-February 1989. These show the existence of a systematic relationship between the backscatter depolarization ratio, {delta}, and the (aerosol + molecular)/molecular backscatter ratio, R. The data are consistent with a two population PSC particle model. The first population consists of particles with low values for {delta} ({le} 0.02) and low to intermediate values for R ({le} 6). The second population is characterized by higher values for {delta} (up to 0.60) and R (up to 40 or greater). The relationship between {delta} and R, observed within a limited range of altitudes and latitudes, corresponds to a mixture of the two populations with variable concentrations but constant optical properties.

Kent, G.S.; Schaffner, S.K. (Science and Technology Corporation, Hampton, VA (USA)); Poole, L.R.; McCormick, M.P. (NASA Langley Research Center, Hampton, VA (USA)); Hunt, W.H. (Wyle Laboratories, Hampton, VA (USA)); Osborn, M.T. (ST Systems Corporation, Hampton, VA (USA))

1990-03-01

361

Joint Radar Backscatter Observations from Pohnpei and Christmas Island  

NASA Astrophysics Data System (ADS)

The space-time characteristics of radar backscatter associated with the development of plasma bubbles in the nighttime equatorial ionosphere were investigated using two approaches. One was to operate two radars, separated by 45 degrees in longitude and 3 hours in local time, simultaneously and continuously, in order to assess whether the spatial correlation of conditions favorable for bubble development remains high over such a distance, and whether such conditions can persist for that length of time. The other approach was to operate the radars using multiple beams, in order to separate spatial from temporal effects, such as produced by large-scale wave structure during the post-sunset rise of the F layer. Multiple beams were also used to determine the temporal evolution of backscatter plumes (bubbles) as they drifted eastward, successively through the radar beams. These results are interpreted in terms of possible processes that lead to bubble development, and its day-to-day variability.

Tsunoda, R. T.; Ecklund, W. L.

2007-05-01

362

Short-Lag Spatial Coherence of Backscattered Echoes: Imaging Characteristics  

PubMed Central

Conventional ultrasound images are formed by delay-and-sum beamforming of the backscattered echoes received by individual elements of the transducer aperture. Although the delay-and-sum beamformer is well suited for ultrasound image formation, it is corrupted by speckle noise and challenged by acoustic clutter and phase aberration. We propose an alternative method of imaging utilizing the short-lag spatial coherence of the backscattered echoes. Compared to matched B-mode images, short-lag spatial coherence (SLSC) images demonstrate superior SNR and CNR in simulated and experimental speckle-generating phantom targets, but are shown to be challenged by limited point target conspicuity. Matched B-mode and SLSC images of a human thyroid are presented. The challenges and opportunities of real-time implementation of SLSC imaging are discussed. PMID:21768022

Lediju, Muyinatu A.; Trahey, Gregg E.; Byram, Brett C.; Dahl, Jeremy J.

2011-01-01

363

Stimulated brillouin backscatter of a short-pulse laser  

SciTech Connect

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).

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

1994-11-03

364

Lidar extinction-to-backscatter ratio of the ocean.  

PubMed

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. PMID:25089487

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

2014-07-28

365

How to suppress the backscattering of conduction electrons?  

NASA Astrophysics Data System (ADS)

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.

Kibis, O. V.

2014-09-01

366

Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California  

USGS Publications Warehouse

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.

Dartnell, Pete; Finlayson, David; Conrad, Jamie; Cochrane, Guy; Johnson, Samuel

2010-01-01

367

Inclusive diffraction at HERA  

SciTech Connect

Results are reported on recent measurements, performed by the H1 and ZEUS Collaborations, of the cross section of the diffractive deep-inelastic process ep{yields}eXp using different experimental methods. In particular, first results using the Very Forward Proton Spectrometer of H1 are discussed.

Favart, Laurent [Universite Libre de Bruxelles, CP 230, Bd. du Triomphe, B-1040 Brussels (Belgium)

2011-07-15

368

Motives from Diffraction  

E-print Network

We look at geometrical and arithmetical patterns created from a finite subset of Z^n by diffracting waves and bipartite graphs. We hope that this can make a link between Motives and the Melting Crystals/Dimer models in String Theory.

Jan Stienstra

2005-11-19

369

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...

370

think forward Diffraction Solutions  

E-print Network

through to structure investigation ­ all of it fast, simple, efficient and with high quality PHASER ­ X-ray diffraction in a new dimension! D2 PHASER ­ the desktop giant! D2 PHASER ­ slide-up front of crystallinity determination Phase properties (cell parameters, crystallite size, and lattice strain) Crystal

Heller, Eric

371

Designing limited diffraction beams  

Microsoft Academic Search

Theoretically, limited diffraction beams can only be produced with an infinite aperture. In practice, they can be closely approximated with a finite aperture over a large depth of field. Because of this property, these beams could have applications in medical imaging, tissue characterization, Doppler velocity estimation, and nondestructive evaluation (NDE) of materials, as well as other physics-related areas such as

Jian-Yu Lu

1997-01-01

372

Diffuse ultrasonic backscatter in a two-dimensional domain  

Microsoft Academic Search

The scattering of elastic waves in polycrystalline materials is relevant for ultrasonic materials characterization and nondestructive\\u000a evaluation (NDE). Diffuse ultrasonic backscatter measurements are used widely to extract the microstructural parameters such\\u000a as grain size and also to detect flaws in materials. Accurate interpretation of experimental data requires robust scattering\\u000a models. Line transducers are often used for ultrasonic experiments such that

Goutam Ghoshal; Joseph A. Turner

2009-01-01

373

Measurement of magnetic field using Rayleigh backscattering in optical fibres  

SciTech Connect

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)

Wuilpart, M.; Caucheteur, C. [Univ. of Mons, Faculty of Engineeering, Electromagnetism and Telecommunications Dept., 31, Boulevard Dolez, 7000 Mons (Belgium); Goussarov, A. [SCK.CEN, 200 Boerentang, 2400 Mol (Belgium); Aerssens, M. [Univ. of Mons, Faculty of Engineeering, Electromagnetism and Telecommunications Dept., 31, Boulevard Dolez, 7000 Mons (Belgium); Massaut, V. [SCK.CEN, 200 Boerentang, 2400 Mol (Belgium); Megret, P. [Univ. of Mons, Faculty of Engineeering, Electromagnetism and Telecommunications Dept., 31, Boulevard Dolez, 7000 Mons (Belgium)

2011-07-01

374

Fractional energies of backscattered electrons and photon yields by electrons  

Microsoft Academic Search

Fractional energies fBE of backscattered electrons and the photon yields Y from semi-infinite absorbers bombarded by electrons have been calculated with the ITS Monte Carlo system, and analytic expressions have been formulated for these parameters. Besides the Monte Carlo results, experimental data collected from the literature have been used to determine the expression for fBE. The two expressions are applicable

Tatsuo Tabata; Pedro Andreo; Kunihiko Shinoda

1999-01-01

375

Dependence of radar backscatter on coniferous forest biomass  

Microsoft Academic Search

Two independent experimental efforts have examined the dependence of radar backscatter on above-ground biomass of monospecie 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 above-ground biomass between 5 and 105 tons\\/ha. Loblolly pine stands established on abandoned agricultural fields near

M. Craig Dobson; Fawwaz T. Ulaby; T. Letoan; A. Beaudoin; E. S. Kasischke; N. Christensen

1992-01-01

376

Ray-based calculations of backscatter in laser fusion targets  

Microsoft Academic Search

A one-dimensional, steady-state model for Brillouin and Raman backscatter from an inhomogeneous plasma is presented. The daughter plasma waves are treated in the strong damping limit, and have amplitudes given by the (linear) kinetic response to the ponderomotive drive. Pump depletion, inverse-bremsstrahlung damping, bremsstrahlung emission, Thomson scattering off density fluctuations, and whole-beam focusing are included. The numerical code DEPLETE, which

D. J. Strozzi; E. A. Williams; D. E. Hinkel; D. H. Froula; R. A. London; D. A. Callahan

2008-01-01

377

Backscattering from capillary waves with application to sea clutter  

Microsoft Academic Search

The results of measurements atX-band of backscattering from water waves of amplitude less than about 0.01 wavelength and with wavelengths of the order of the microwave length are presented and compared with theory. The measurements have been made for both vertical and horizontal polarizations for grazing angles between4degand80deg. The results both as to angular dependence and absolute magnitude are in

J. Wright

1966-01-01

378

Method and apparatus for measuring lung density by Compton backscattering  

DOEpatents

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.

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

1988-03-11

379

Method and apparatus for measuring lung density by Compton backscattering  

DOEpatents

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.

Loo, Billy W. (Oakland, CA); Goulding, Frederick S. (Lafayette, CA)

1991-01-01

380

Radiometric analysis of diffraction  

NASA Astrophysics Data System (ADS)

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.

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

2008-04-01

381

Inspection of reinforced concrete samples by Compton backscattering technique  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

382

Analysis of meteors precipitation using ionospheric back-scatter radar  

NASA Astrophysics Data System (ADS)

A 50 MHz coherent back-scatter radar also known by the anachronism RESCO has been operated since 1998 at S a o Lu i s Space Observatory 2 33 r S 44 2 r W DIP -0 5 near the dip equator The main purpose of RESCO is to study the equatorial electrojet dynamics through spectral analyses of the received echoes that allow us to identify the dominant type of plasma instabilities and its drift speed in the electrojet Using the RESCO radar we are also able to collect data from reflection of the transmitted signal caused by meteor trail generally observed at about 100 km of altitude The energy received in the reflection process is higher than that expected by the back-scatter in the equatorial electrojet irregularities So even during the presence of plasma irregularities it is possible to observe echoes from meteor trail To characterize the presence of meteor reflection over the equatorial electrojet plasma irregularities data it was developed a methodology of detection of meteor echoes due to reflection in meteor trail In this paper we analyze the presence of meteors deduced from the presence of their echoes in the equatorial electrojet heights and discuss the methodology of meteors detection in the 50 MHz coherent back-scatter radar data

Aveiro, H. C.; Moor, L. P.; Denardini, C. M.; Abdu, M. A.; Schuch, N. J.

383

Chip-scale universal detection based on backscatter interferometry  

PubMed

An on-chip detector based on backscatter interferometry has been developed to perform subnanoliter-volume refractive index measurements. The detection system consists of a simple, folded optical train based on the interaction of a laser beam and an etched channel, consisting of two radii joined by a flat portion, thus defining a curved surface in the shape of a hemisphere in a silica (glass) plate. The backscattered light from the channel takes on the form of a high-contrast interference pattern that contains information related to the bulk properties of the fluid contained within the probe volume. Positional changes of the interference pattern (fringes) allow for the determination of deltan at the 10(-6) level, corresponding to 743 microM or 139 x 10(-15) mol or 12.8 x 10(-12) g of sucrose, in a probe volume of only 188 x 10(-12) L. A theoretical model of the on-chip backscatter interferometric detector has also been developed, evaluated, and found to be in agreement with experimental data. It is shown that the model can be used to predict general system performance for changes in the optical train such as the chip's wall thickness and channel diameter. PMID:10905294

Swinney; Markov; Bornhop

2000-07-01

384

Laser transmission-backscattering through inhomogeneous cirrus clouds.  

PubMed

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. PMID:12269574

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

2002-09-20

385

Measuring Ultrasonic Backscatter in the Presence of Nonlinear Propagation  

NASA Astrophysics Data System (ADS)

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.

Stiles, Timothy; Guerrero, Quinton

2011-11-01

386

Recovering a polyhedral obstacle by a few backscattering measurements  

E-print Network

We propose an inverse scattering scheme of recovering a polyhedral obstacle in $\\mathbb{R}^n$, $n=2,3$, by only a few high-frequency acoustic backscattering measurements. The obstacle could be sound-soft or sound-hard. It is shown that the modulus of the far-field pattern in the backscattering aperture possesses a certain local maximum behavior, from which one can determine the exterior normal directions of the front sides/faces. Then by using the phaseless backscattering data corresponding to a few incident plane waves with suitably chosen incident directions, one can determine the exterior unit normal vector of each side/face of the obstacle. After the determination of the exterior unit normals, the recovery is reduced to a finite-dimensional problem of determining a location point of the obstacle and the distance of each side/face away from the location point. For the latter reconstruction, we need make use of the far-field data with phases. Numerical experiments are also presented to illustrate the effectiveness of the proposed scheme.

Jingzhi Li; Hongyu Liu

2015-02-04

387

Visibility related to backscatter at 1.54 micron  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

388

Experimental findings in 180{degree} backscattering enhancement from solids  

SciTech Connect

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}

Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D. [Institut fuer Experimentalphysik, Johannes-Kepler-Universitaet, A-4040 Linz (Austria)] [Institut fuer Experimentalphysik, Johannes-Kepler-Universitaet, A-4040 Linz (Austria)

1997-02-01

389

Enhanced radar backscatter from space shuttle exhaust in the ionosphere  

NASA Astrophysics Data System (ADS)

Enhancements in the backscatter from the 430-MHz radar at Arecibo were recorded during the Spacelab 2 mission when the space shuttle orbital maneuver system (OMS) engines were fired in the ionosphere. The modifications in the backscatter could have been the result of (1) compression of the electrons to produce higher densities, (2) generation of ion acoustic waves, (3) variations in the electron to ion temperature ratio, (4) enhanced scatter cross section by charging of ice particles in the exhaust, or (5) excitation of dust acoustic waves. Rapid cooling and condensation of the exhaust are important in determining the scattering properties of the modified ionosphere. A dusty plasma is formed when electrons are attached to ice particles in the exhaust plume. The calculated neutral temperature inside the exhaust plume is 120 K. Charge exchange between ambient O+ and the cold exhaust molecules yields low-temperature ion beams that excite weakly damped, ion acoustic waves. The enhanced radar echoes are probably the result of scatter from these waves, but the effects of the dusty plasma may be important. During future experiments, the space shuttle will fire the OMS engines over radars located at Arecibo, Puerto Rico; Jicarmarca, Peru; or Kwajalein, Marshall Islands. Measurements of the spectra from these radars will provide the means to distinguish between the various backscatter processes.

Bernhardt, P. A.; Ganguli, G.; Kelley, M. C.; Swartz, W. E.

1995-12-01

390

Diffraction in ep collisions Pierre Van Mechelen  

E-print Network

Diffraction in ep collisions Pierre Van Mechelen University of Antwerpen Pierre Outline: # Introduction Inclusive diffractive DIS cross section # Diffractive photoproduction of jets # Open charm production in diffractive DIS #12; Diffraction in ep collisions Pierre Van

391

Measurement of the spatial backscattering impulse-response at short length-scales with polarized enhanced backscattering (EBS)  

PubMed Central

In this Letter, we describe an easy to implement technique to measure the spatial backscattering impulse-response at length-scales shorter than a transport mean free path with resolution of better than 10 ?m using the enhanced backscattering (EBS) phenomenon. This technique enables spectroscopic measurements throughout the visible range and sensitivity to all polarization channels. Through a combination of Monte Carlo simulations and experimental measurements of latex microspheres, we explore the various sensitivities of our technique to both intrinsic sample properties and extrinsic instrumental properties. We conclude by demonstrating the extraordinary sensitivity of our technique to the shape of the scattering phase function, including higher order shape parameters than the anisotropy factor (or first moment). PMID:22179867

Radosevich, Andrew J.; Mutyal, Nikhil N.; Turzhitsky, Vladimir; Rogers, Jeremy D.; Yi, Ji; Taflove, Allen; Backman, Vadim

2012-01-01

392

Simulation of Secondary Electron and Backscattered Electron Emission in A6 Relativistic Magnetron Driven by Different Cathode  

NASA Astrophysics Data System (ADS)

Prticle-in-cell (PIC) simulations demonstrated that, when the relativistic magnetron with diffraction output (MDO) is applied with a 410 kV voltage pulse, or when the relativistic magnetron with radial output is applied with a 350 kV voltage pulse, electrons emitted from the cathode with high energy will strike the anode block wall. The emitted secondary electrons and backscattered electrons affect the interaction between electrons and RF fields induced by the operating modes, which decreases the output power in the radial output relativistic magnetron by about 15% (10% for the axial output relativistic magnetron), decreases the anode current by about 5% (5% for the axial output relativistic magnetron), and leads to a decrease of electronic efficiency by 8% (6% for the axial output relativistic magnetron). The peak value of the current formed by secondary and backscattered current equals nearly half of the amplitude of the anode current, which may help the growth of parasitic modes when the applied magnetic field is near the critical magnetic field separating neighboring modes. Thus, mode competition becomes more serious.

Liu, Meiqin; Li, Bolun; Liu, Chunliang; Fuks, Mikhail; Edl, Schamiloglu

2015-01-01

393

Diffraction Studies of Multiferroics  

NASA Astrophysics Data System (ADS)

In multiferroics, magnetism is coupled to ferroelectricity so that the configuration of magnetic moments may be modified by an external electric field and, conversely, the electrically polar state may be magnetically switched. Such functionality has the potential for new technology such as energy-efficient, electrically written magnetic memories. Furthermore, multiferroics are of interest in fundamental research into quantum matter. Understanding the interplay between magnetism and ferroelectricity has posed a significant challenge to the scientific community. State-of-the-art diffraction experiments have played a unique role, as they are sensitive to both magnetic ordering and the atomic displacements associated with ferroelectricity. Exceptional insights have been gained from neutron polarimetry techniques complemented by X-ray magnetic scattering experiments, which, for the first time, have been applied to a large selection of related materials and problems. In this review, we discuss a broad selection of multiferroics and the diffraction experiments used to explain their phenomenology.

Johnson, Roger D.; Radaelli, Paolo G.

2014-07-01

394

Inclusive diffraction at HERA  

E-print Network

A new experimental analysis of the diffractive process $ep \\rightarrow eXY$, where $Y$ denotes a proton or its low mass excitation with $M_Y<1.6$ GeV, has been performed with the H1 experiment at HERA \\cite{Aaron:2012ad}. The main results of this study are summarised in this document, together with the comparisons to other measurements and theoretical predictions.

Laurent Schoeffel

2013-06-12

395

SINGLE CRYSTAL NEUTRON DIFFRACTION.  

SciTech Connect

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.

KOETZLE,T.F.

2001-03-13

396

Interactive Tutorial About Diffraction  

NSDL National Science Digital Library

The Interactive Tutorial About Diffraction is a joint effort by professors from Michigan State University, the University of Wuerzburg, and Ludwig-Maximilians University at Munich. A multitude of examples are used to present atom scattering, crystal structure, convolution theorem, Fourier transformations of crystal phase, and other topics. The interactive examples are simulations, using software developed by the authors, where students can input the number of atoms or atom type, etc. and view results as .gif images.

397

Central Diffraction in ALICE  

SciTech Connect

The ALICE experiment consists of a central barrel in the pseudorapidity range -0.9<{eta}<0.9 and of additional detectors covering about 3 units of pseudorapidity on either side of the central barrel. Such a geometry allows the tagging of single and double gap events. The status of the analysis of such diffractive events in proton-proton collisions at {radical}(s) = 7 TeV is presented.

Schicker, R. [Phys. Inst., Philosophenweg 12, 69120 Heidelberg (Germany)

2011-07-15

398

Diffraction before destruction.  

PubMed

X-ray free-electron lasers have opened up the possibility of structure determination of protein crystals at room temperature, free of radiation damage. The femtosecond-duration pulses of these sources enable diffraction signals to be collected from samples at doses of 1000 MGy or higher. The sample is vaporized by the intense pulse, but not before the scattering that gives rise to the diffraction pattern takes place. Consequently, only a single flash diffraction pattern can be recorded from a crystal, giving rise to the method of serial crystallography where tens of thousands of patterns are collected from individual crystals that flow across the beam and the patterns are indexed and aggregated into a set of structure factors. The high-dose tolerance and the many-crystal averaging approach allow data to be collected from much smaller crystals than have been examined at synchrotron radiation facilities, even from radiation-sensitive samples. Here, we review the interaction of intense femtosecond X-ray pulses with materials and discuss the implications for structure determination. We identify various dose regimes and conclude that the strongest achievable signals for a given sample are attained at the highest possible dose rates, from highest possible pulse intensities. PMID:24914146

Chapman, Henry N; Caleman, Carl; Timneanu, Nicusor

2014-07-17

399

Diffraction before destruction  

PubMed Central

X-ray free-electron lasers have opened up the possibility of structure determination of protein crystals at room temperature, free of radiation damage. The femtosecond-duration pulses of these sources enable diffraction signals to be collected from samples at doses of 1000 MGy or higher. The sample is vaporized by the intense pulse, but not before the scattering that gives rise to the diffraction pattern takes place. Consequently, only a single flash diffraction pattern can be recorded from a crystal, giving rise to the method of serial crystallography where tens of thousands of patterns are collected from individual crystals that flow across the beam and the patterns are indexed and aggregated into a set of structure factors. The high-dose tolerance and the many-crystal averaging approach allow data to be collected from much smaller crystals than have been examined at synchrotron radiation facilities, even from radiation-sensitive samples. Here, we review the interaction of intense femtosecond X-ray pulses with materials and discuss the implications for structure determination. We identify various dose regimes and conclude that the strongest achievable signals for a given sample are attained at the highest possible dose rates, from highest possible pulse intensities. PMID:24914146

Chapman, Henry N.; Caleman, Carl; Timneanu, Nicusor

2014-01-01

400

Back-scattering channel-cut high-resolution monochromator for inelastic x-ray scattering  

SciTech Connect

We report on a design and on some experimental results for the performance of a new high energy resolution monochromator. It is a large channel-cut Si crystal with a 197 mm separation between the two faces designed to operate in a near-backscattering regime. The device was tested as a second monochromator on Sector 3 of the Synchrotron Radiation Instrumentation Collaborative Access Team (SRI-CAT) at the Advanced Photon Source using the Si(777) reflection at a photon energy of 13.84 keV. The same monochromator can be used for other energies with reflections of the type (hhh). Special care has been taken to equalize the temperature of the two faces by employing a Peltier heat pump. A Si(111) double-crystal pre-monochromator designed to withstand the high heat load of the undulator radiation was used upstream on the beamline. The measured throughput efficiency of the Si(777) channel-cut monochromator was less ideal by a factor of 1.9. Dynamical diffraction theory was used to calculate the throughput of an ideally perfect crystal.

Kushnir, V.I.; Abbamonte, P.M.; Macrander, A.T.; Schwoerer-Boehning, M.

1997-08-01

401

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

NASA Astrophysics Data System (ADS)

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.

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

1997-12-01

402

Diffraction and its QCD interpretation  

E-print Network

The most important results on hadronic diffractive phenomena obtained at HERA and Tevtaron are reviewed and new issues in nucleon tomography are discussed. Some challenges for understanding diffraction at the LHC, including the discovering of the Higgs boson, are outlined.

Laurent Schoeffel

2009-10-08

403

Diffraction of a Laser Beam.  

ERIC Educational Resources Information Center

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)

Jodoin, Ronald E.

1979-01-01

404

CDF experimental results on diffraction  

E-print Network

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 $0diffractive events up to $Q^2\\approx 4,500$ GeV$^2$. Results on single diffractive W/Z production, forward jets, and central exclusive production of both dijets and diphotons are also presented.

Michele Gallinaro

2009-04-14

405

Diffraction-Based Optical Switch  

NASA Technical Reports Server (NTRS)

Method and system for controllably redirecting a light beam, having a central wavelength lambda, from a first light-receiving site to a second light-receiving site. A diffraction grating is attached to or part of a piezoelectric substrate, which is connected to one or two controllable voltage difference sources. When a substrate voltage difference is changed and the diffraction grating length in each of one or two directions is thereby changed, at least one of the diffraction angle, the diffraction order and the central wavelength is controllably changed. A diffracted light beam component, having a given wavelength, diffraction angle and diffraction order, that is initially received at a first light receiving site (e.g., a detector or optical fiber) is thereby controllably shifted or altered and can be received at a second light receiving site. A polynomially stepped, chirped grating is used in one embodiment. In another embodiment, an incident light beam, having at least one of first and second wavelengths, lambda1 and lambda2, is received and diffracted at a first diffraction grating to provide a first diffracted beam. The first diffracted beam is received and diffracted at a second diffraction grating to produce a second diffracted beam. The second diffracted beam is received at a light-sensitive transducer, having at least first and second spaced apart light detector elements that are positioned so that, when the incident light beam has wavelength lambda1 or lambda2 (lambda1 not equal to lambda2), the second diffracted beam is received at the first element or at the second element, respectively; change in a selected physical parameter at the second grating can also be sensed or measured. A sequence of spaced apart light detector elements can be positioned along a linear or curvilinear segment with equal or unequal spacing.

Sperno, Stevan M. (Inventor); Fuhr, Peter L. (Inventor); Schipper, John F. (Inventor)

2005-01-01

406

Design the diffractive optical element with large diffraction angle  

NASA Astrophysics Data System (ADS)

In this paper, a quite effective method is proposed for designing the diffractive optical element (DOE) to generate a pattern with large diffraction angle. Through analyze the difference between the non-paraxial Rayleigh Sommerfeld integral and the paraxial Fraunhofer diffraction integral, we modify the desired output intensity distribution with coordinate transformation and intensity adjustment. Then the paraxial Fraunhofer diffraction integral can be used to design the DOE, which adopts the fast-Fourier-transform (FFT) algorithm to accelerate the computation. To verify our method, the simulation and the experiments are taken. And the result shows that our method can effectively rectify the pillow distortion and can achieve the exact diffraction angle.

Pang, Hui; Yin, Shaoyun; Zheng, Guoxing; Deng, Qiling; Shi, Lifang; Du, Chunlei

2014-11-01

407

Accuracy in Powder Diffraction IV  

E-print Network

Accuracy in Powder Diffraction IV Program April 22-25, 2013 Photo credit ©2000 Robert Rathe #12;2 3 Accuracy in Powder Diffraction IV Program April 22-25, 2013 Day 1 | 22nd April Time Activity Chair 08 Introduction to program (Madsen, Cline) James Cline Ian Madsen 09:45 - 10:30 Accuracy in Powder Diffraction

Magee, Joseph W.

408

Diffraction at HERA Vitaliy Dodonov  

E-print Network

Diffraction at HERA Vitaliy Dodonov MPI-K, Heidelberg and JINR, Dubna On behalf of the H1 and ZEUS collaborations St. Petersburg, Russia, 20-24 September 2005 #12;Outline Vitaliy Dodonov, Diffraction at HERA by Niklaus Berger #12;HERA Vitaliy Dodonov, Diffraction at HERA, HSQCD Workshop, 20-24 September 2005, St

409

DIFFRACTION BY EDGES ANDRAS VASY  

E-print Network

DIFFRACTION BY EDGES ANDR´AS VASY Abstract. In these expository notes we explain the role of singularities, which describes where solutions of the wave equation may be singular, and the diffractive improvement under non-focusing hypotheses, which states that in certain places the diffracted wave is more

Vasy, András

410

Diffraction measurements at the LHC  

E-print Network

Proton-proton collisions at the LHC can be classified as elastic, non-diffractive, and diffractive. In this paper we discuss various measurements of these above processes at various LHC experiments. We report about the total proton-proton cross-section measurements, about the analysis of diffractive events and also about the pseudorapidity distribution in inelastic events.

M. Csanad

2014-01-28

411

Spectral diffraction efficiency characterization of broadband diffractive optical elements.  

SciTech Connect

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.

Choi, Junoh; Cruz-Cabrera, Alvaro Augusto; Tanbakuchi, Anthony

2013-03-01

412

Estimation of Mars radar backscatter from measured surface rock populations  

USGS Publications Warehouse

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.

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

1998-01-01

413

Low-Frequency Electromagnetic Backscatter from Buried Tunnels  

SciTech Connect

This progress report is submitted under a contract between the Special Project Office of DARPA and Lawrence Livermore National Laboratory. The Project Manager at DARPA is Dr. Michael Zatman. Our purpose under this contract is to investigate interactions between electromagnetic waves and a class of buried targets located in multilayered media with rough interfaces. In this report, we investigate three preliminary problems. In each case our specific goal is to understand various aspects of the electromagnetic wave interaction mechanisms with targets in layered media. The first problem, discussed in Section 2, is that of low-frequency electromagnetic backscattering from a tunnel that is cut into a lossy dielectric half-space. In this problem, the interface between the upper (free space) region and the lower (ground) region is smooth. The tunnel is assumed to be a cylindrical free-space region of infinite extent in its axial direction and with a diameter that is small in comparison to the free-space wavelength. Because its diameter is small, the tunnel can be modeled as a buried ''wire'' described by an equivalent impedance per unit length. In Section 3 we extend the analysis to include a statistically rough interface between the air and ground regions. The interface is modeled as a random-phase screen. Such a screen reduces the coherent power in a plane wave that is transmitted through it, scattering some of the total power into an incoherent field. Our analysis of this second problem quantifies the reduction in the coherent power backscattered from the buried tunnel that is caused by the roughness of the air-ground interface. The problem of low-frequency electromagnetic backscattering from two buried tunnels, parallel to each other but at different locations in the ground, is considered in Section 4. In this analysis, we wish to determine the conditions under which the presence of more than one tunnel can be detected via backscattering. Section 5 concludes the report with a summary of the investigations discussed herein and recommendations for future work on problems of this class.

Casey, K; Pao, H

2006-06-21

414

Improvement and extension of a radar forest backscattering model  

NASA Technical Reports Server (NTRS)

Research to-date has focused on modeling development and programming based on model components proposed during the past several months and research progress made by the Simonett team. The model components and programs (in C language under UNIX) finished to date are summarized. These model components may help explain the contributions of various vegetation structural components to the attenuation and backscattering of vegetated surfaces to extract useful data concerning forest stands and their underlying surfaces for both the seawater-on and seawater-off.

Simonett, David S.; Wang, Yong

1988-01-01

415

Raman backscatter measurement research on water vapor systems  

NASA Technical Reports Server (NTRS)

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.

Workman, G. L.

1975-01-01

416

Backscattering by hexagonal ice crystals of cirrus clouds.  

PubMed

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. PMID:23903169

Borovoi, Anatoli; Konoshonkin, Alexander; Kustova, Natalia

2013-08-01

417

Relating the microwave backscattering coefficient to leaf area index  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

418

Influence of annealing on the microstructure of commercial Mg alloy AZ31 after mechanical forming  

Microsoft Academic Search

The microstructure of commercial rolled magnesium alloy AZ31B (nominal composition Mg–3Al–0.9Zn–0.15Mn in wt.%) was investigated with the help of light microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction technique after annealing in the temperature range from room temperature (RT) to 400°C. Tensile tests at RT were performed to show the influence of the microstructure on mechanical properties. Static recrystallization (SRX)

A. Jäger; P. Luká?; V. Gärtnerová; J. Haloda; M. Dopita

2006-01-01

419

Effect of strain-induced precipitation on the low angle grain boundary in AA7050 aluminum alloy  

Microsoft Academic Search

Effects of the particles induced by strain on dynamic recrystallization and microstructure of the AA7050 aluminum alloy were investigated during hot deformation using X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD). Experimental results showed that partial recrystallized grains containing little sub-structure were produced during the solution treatment. Numerous particles were successfully obtained by the strain-induced precipitation

Yujing Lang; Yuanhua Cai; Hua Cui; Jishan Zhang

2011-01-01

420

A Bayesian approach to seafloor classification using multi-beam echo-sounder backscatter data  

Microsoft Academic Search

Seafloor classification using acoustic remote sensing techniques is an attractive approach due to its high-coverage capabilities and limited costs. The multi-beam echo-sounder (MBES) system provides high-resolution bathymetry and backscatter information with 100% coverage. In this paper, we present a seafloor classification method that employs the MBES backscatter data. The method uses the averaged backscatter data per beam. It, therefore, is

Dick G. Simons; Mirjam Snellen

2009-01-01

421

Simulated and observed L-HH radar backscatter from tropical mangrove forests  

Microsoft Academic Search

We applied the Santa Barbara canopy backscatter model to model radar backscatter from mangrove forest stands in the Ganges delta of southern Bangladesh, and assessed the feasibility of delineating flooding boundaries within the stands. Modelled L-band (0-235 m wavelength) HH backscatter showed that canopy volume scattering dominated for stands under nonflooded ground surface. Double bounce trunk-ground term were enhanced by

Y. Wang; M. L. Imhoff

1993-01-01

422

Lidar-inversion technique based on total integrated backscatter calibrated curves.  

PubMed

The integrated backscatter signal from a smoke cloud contained in a chamber is studied as function of the measured concentration. An analysis based on the total backscattered signal leads to the determination of calibration curves specific to the material and to the lidar system. This procedure leads to a lidar inversion technique based on a calibrated total integrated backscatter curve. The limitation of the technique is discussed in terms of the maximum optical depth permitted for acceptable results. PMID:20856528

Roy, G; Vallée, G; Jean, M

1993-11-20

423

Aerosol backscatter variability at 10.6 microns over Colorado high plains during JAWS experiment  

NASA Technical Reports Server (NTRS)

This paper describes the aerosol backscatter profile measurements obtained by an airborne CW focused CO2 Doppler lidar (the Laser True Airspeed System) during the 1982 Joint Airport Weather Studies (JAWS) field experiment. The backscatter sounding flights were made in the lee of the front range of the Colorado Rocky Mountains, at about 1650 m above mean sea level. The qualitative relationships between the backscatter and the vertical distribution of temperature and water vapor are described.

Rothermel, Jeffry; Bowdle, David A.; Vaughan, J. Michael

1988-01-01

424

Ground-based measurements of atmospheric backscatter and absorption using coherent CO2 lidar  

NASA Technical Reports Server (NTRS)

In the present derivation of vertical profiles of atmospheric absorption and backscatter coefficients from coherent pulsed Doppler lidar by means of a slant path method, a strong seasonal variation of absorption and backscatter is evident throughout the lower troposphere. Measurements beyond the lower troposphere are hampered by modest pulse energy and lidar beam absorption, although small backscatter values are occasionally observed at midtropospheric levels during the winter months, when absorption is minimal. While a monomodal lognormal backscatter distribution is found within the lower boundary layer, evidence of a bimodal lognormal distribution is found at higher levels.

Rothermel, J.; Jones, W. D.

1985-01-01

425

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

NASA Astrophysics Data System (ADS)

Lattice distortion at the interfaces between thin GaN layers with ˜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 ˜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.

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

2011-07-01

426

Rutherford backscattering analysis of the failure of chlorine anodes  

SciTech Connect

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 RuO[sub 2]-TiO[sub 2] electrodes of 5000 Angstroms, which mimic the DSA anodes in composition and the method of preparation. Occidental Chemical Corporation provided electrodes, which had been subjected to life time testing in H[sub 2]S04 solution, for analysis by ORNL. The results were used to test the hypothesis of degradation of theses, and similar electrodes, from a process involving a decrease in the RuO[sub 2]:TiO[sub 2] 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 RuO[sub 2]-TiO[sub 2] coating. No build up of a pure TiO[sub 2] 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.

Vallet, C.E. [Oak Ridge National Lab., TN (United States); Tilak, B.V. [Occidental Chemical Corp., Niagara Falls, NY (United States)

1996-06-01

427

Rutherford backscattering analysis of the failure of chlorine anodes  

SciTech Connect

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.

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

1996-06-01

428

X-band microwave backscattering from ocean waves  

SciTech Connect

Backscattering experiments at microwave frequencies were conducted off the west coast of Scotland in the summer of 1991. Using a dual-polarization, 8-frequency X-band coherent scatterometer mounted on the bow of a boat, we measured time-resolved backscattering from ocean waves at a range of grazing angles from 10{degrees} to 70{degrees}. From the grazing-angle-dependent signals and their Doppler spectra, we differentiate Bragg scattering from non-Bragg scattering and resolve ``peak separation`` between the vertical and horizontal polarizations. We observe instances of ``super`` events, i.e., instances when the horizontal polarization return power equals or exceeds the vertical polarization power. We find that ``super`` events occur not only at low grazing angles but at any grazing angle for against-wind viewing directions. Statistics for such occurrences as a function of grazing angle are obtained. We study the coherence properties of scatterers and find strong evidence that at low grazing angles, lifetime-dominated, non-Bragg scattering contributes noticeably to returns of both polarizations, but is dominant in providing returns for the horizontal polarization. We examine ``spiking`` events and find that they can be related to, but need not be limited to, breaking wave events. By comparing the data of against-wind runs with cross-wind and circle runs, we obtain wind-direction dependence of Doppler spectra which further assists in the identification of scattering mechanisms.

Lee, P.H.Y.; Barter, J.D.; Beach, K.L. [TRW Space and Electronics Group, Redondo Beach, CA (United States)] [and others

1994-01-04

429

Lidar backscatter signal recovery from phototransistor systematic effect by deconvolution.  

PubMed

Backscatter lidar detection systems have been designed and integrated at NASA Langley Research Center using IR heterojunction phototransistors. The design focused on maximizing the system signal-to-noise ratio rather than noise minimization. The detection systems have been validated using the Raman-shifted eye-safe aerosol lidar (REAL) at the National Center for Atmospheric Research. Incorporating such devices introduces some systematic effects in the form of blurring to the backscattered signals. Characterization of the detection system transfer function aided in recovering such effects by deconvolution. The transfer function was obtained by measuring and fitting the system impulse response using single-pole approximation. An iterative deconvolution algorithm was implemented in order to recover the system resolution, while maintaining high signal-to-noise ratio. Results indicated a full recovery of the lidar signal, with resolution matching avalanche photodiodes. Application of such a technique to atmospheric boundary and cloud layers data restores the range resolution, up to 60 m, and overcomes the blurring effects. PMID:18846166

Refaat, Tamer F; Ismail, Syed; Abedin, M Nurul; Spuler, Scott M; Mayor, Shane D; Singh, Upendra N

2008-10-10

430

Feasibility of using Backscattered Mueller Matrix Images for Bioaerosol Detection  

NASA Astrophysics Data System (ADS)

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.

Li, Changhui; Kattawar, George W.

2006-03-01

431

Discriminant classification of different fish-species backscattering  

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

432

Ultrastructural alterations in field carcinogenesis measured by enhanced backscattering spectroscopy  

PubMed Central

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

Radosevich, Andrew J.; Mutyal, Nikhil N.; Yi, Ji; Stypula-Cyrus, Yolanda; Rogers, Jeremy D.; Goldberg, Michael J.; Bianchi, Laura K.; Bajaj, Shailesh; Roy, Hemant K.; Backman, Vadim

2013-01-01

433

Contribution of double scattering in diffuse ultrasonic backscatter measurements.  

PubMed

Diffuse ultrasonic backscatter measurements are used to describe the effective grain scattering present during high frequency ultrasonic inspections. Accurate modeling of the backscatter is important for both flaw detection and microstructural characterization. Previous models have been derived under the assumption of single scattering for which the ultrasound is assumed to scatter only once in the time between excitation and detection. This assumption has been shown to be valid in many experiments for which the time scales are short or the frequency is sufficiently low. However, there are also many instances (e.g., for strongly scattering materials, unfocused beams, or long propagation paths) for which the single scattering assumption appears to break down. In this article, a model for the double scatter is developed within the previous formalism based on Wigner distribution functions. The final expression allows the effect of double scattering to be estimated for any combination of experimental parameters. The improved proposed model is anticipated to increase the capabilities of ultrasonic microstructural evaluation, especially in terms of probability of detection estimates. PMID:25618063

Hu, Ping; Turner, Joseph A

2015-01-01

434

Backscattering measuring system for optimization of intravenous laser irradiation dose  

NASA Astrophysics Data System (ADS)

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.

Rusina, Tatyana V.; Popov, V. D.; Melnik, Ivan S.; Dets, Sergiy M.

1996-11-01

435

Backscatter Mossbauer Spectrometer (BaMS) for extraterrestrial applications  

NASA Technical Reports Server (NTRS)

Mossbauer spectroscopy is a nuclear gamma resonance technique particularly well suited to the study of materials that contain iron (Fe-57). It can provide information on the oxidation state of iron as well as the type and proportion of iron-containing mineral species in a sample of interest. Iron Mossbauer spectroscopy (FeMS) has been applied to samples believed to have come from Mars (SNC meteorites) and has been helpful in refining the choice among putative Martian surface materials by suggesting a likely nanophase component of the Martian regolity. FeMS spectrum of a Martial analogue material (Hawaiian palagonite) is shown; it is dominated by ferric-bearing phases and shows evidence of a nanophase component. FeMS has also been applied to lunar materials. It can be used to measure the maturity of lunar surface material and has been proposed as a prospector for lunar ilmenite, an oxygen resource mineral. Several years ago we suggested a backscatter Mossbauer spectrometer (BaMS) for a Mars rover mission. Backscatter design was selected as most appropriate for in-situ application because no sample preparation is required. Since that time, we have continued to develop the BaMS instrument in anticipation that it would eventually find a home on a NASA planetary mission. Gooding proposed BaMS as a geochemistry instrument on MESUR. More recently, an LPI workshop has recommended that BaMS be included in a three-instrument payload on the next (1996?) lunar lander.

Agresti, D. G.; Shelfer, T. D.; Pimperl, M. M.; Wills, E. L.; Shen, M. H.; Morris, R. V.

1993-01-01

436

Middle East versus Saharan dust extinction-to-backscatter ratios  

NASA Astrophysics Data System (ADS)

Four years (2010-2013) of observations with polarization lidar and sun/sky photometer at the combined European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) site of Limassol (34.7° N, 33° E), Cyprus, were used to compare extinction-to-backscatter ratios (lidar ratios) for desert dust from Middle East deserts and the Sahara. The complex data analysis scheme is presented. The quality of the retrieval is checked within a case study by comparing the results with respective Raman lidar solutions for particle backscatter, extinction, and lidar ratio. The applied combined lidar/photometer retrievals corroborate recent findings regarding the difference between Middle East and Saharan desert dust lidar ratios. We found values from 44-65 sr with a mean value of 52.7 sr for Saharan dust and from 35-46 sr with a mean value of 41.1 sr for Middle East dust. The presented data analysis, however, also demonstrates the difficulties in identifying the optical properties of dust even during outbreak situations in the presence of complex aerosol mixtures of desert dust, marine particles, fire smoke, and anthropogenic haze.

Nisantzi, A.; Mamouri, R. E.; Ansmann, A.; Schuster, G. L.; Hadjimitsis, D. G.

2015-02-01

437

Particle characterisation in highly concentrated dispersions using ultrasonic backscattering method.  

PubMed

Determining particle size and concentration in highly concentrated suspensions and emulsions is challenging, especially under process conditions. In general, ultrasound therefore can be used for particle characterisation due to the ability of sound waves to pass opaque dispersions, whereas optical detection principles mostly are limited to low particulate contents. An established acoustic method, the ultrasonic attenuation spectroscopy, uses a transmission setup for measuring the attenuation of a dispersion. A major drawback of this measurement method is caused by the fact, that the measuring gap tends to plug, which again limits the inline capability. To overcome this limitation, an ultrasonic reflection setup is used for gathering the sound waves, which are reflected, respectively backscattered by the dispersion. Statistically analysing the corresponding backscattering signal yields the sound attenuation as well as a scattering intensity equivalent. Both measurement parameters can be shown to be sensitive against particle size and concentration. Based on a single scattering theory, a semi-empirical approach is presented for interpretation of measurement results with respect to particle size and concentration. Measurements, performed on a glass beads in water dispersion, show good agreement with theory for dimensionless wave number 0.1

Weser, Robert; Wöckel, Sebastian; Wessely, Benno; Hempel, Ulrike

2013-03-01

438

Nimbus 7 solar backscatter ultraviolet (SBUV) ozone products user's guide  

NASA Technical Reports Server (NTRS)

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.

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

439

Assembly for Rutherford backscattering at exactly 180{degree}  

SciTech Connect

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.}

Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D. [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet, A-4040 Linz-Auhof (Austria)] [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet, A-4040 Linz-Auhof (Austria)

1996-05-01

440

Measurement of intraocular distances by backscattering spectral interferometry  

Microsoft Academic Search

The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.

A. F. Fercher; C. K. Hitzenberger; G. Kamp; S. Y. El-Zaiat

1995-01-01

441

Diffraction-based optical correlator  

NASA Technical Reports Server (NTRS)

Method and system for wavelength-based processing of a light beam. A light beam, produced at a chemical or physical reaction site and having at least first and second wavelengths, ?1 and ?2, is received and diffracted at a first diffraction grating to provide first and second diffracted beams, which are received and analyzed in terms of wavelength and/or time at two spaced apart light detectors. In a second embodiment, light from first and second sources is diffracted and compared in terms of wavelength and/or time to determine if the two beams arise from the same source. In a third embodiment, a light beam is split and diffracted and passed through first and second environments to study differential effects. In a fourth embodiment, diffracted light beam components, having first and second wavelengths, are received sequentially at a reaction site to determine whether a specified reaction is promoted, based on order of receipt of the beams. In a fifth embodiment, a cylindrically shaped diffraction grating (uniform or chirped) is rotated and translated to provide a sequence of diffracted beams with different wavelengths. In a sixth embodiment, incident light, representing one or more symbols, is successively diffracted from first and second diffraction gratings and is received at different light detectors, depending upon the wavelengths present in the incident light.

Spremo, Stevan M. (Inventor); Fuhr, Peter L. (Inventor); Schipper, John F. (Inventor)

2005-01-01

442

Diffraction at HERA  

E-print Network

Between 1992 and 2007, the HERA accelerator provided $ep$ collisions at center of mass energies beyond $300 \\ {\\rm GeV}$ at the interaction points of the H1 and ZEUS experiments. Interesting results to emerge relate to the newly accessed field of perturbative strong interaction physics at low Bjorken-$x$, where parton densities become extremely large. Questions arise as to how and where non-linear dynamics tame the parton density growth and challenging features such as geometric scaling are observed. Central to this low $x$ physics landscape is a high rate of diffractive processes, in which a colorless exchange takes place and the proton remains intact. A review is given for main results obtained by H1 and ZEUS experiments in this field.

Laurent Schoeffel

2011-07-18

443

Multilayer diffraction grating  

DOEpatents

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.

Barbee, T.W. Jr.

1990-04-10

444

Inverse problems in diffraction  

NASA Technical Reports Server (NTRS)

A two-dimensional problem of diffraction of a plane electromagnetic wave on a smooth 2 pi-periodic surface is considered. A numerical algorithm solving this problem is developed. An inverse problem of determination of the shape of 2 pi-periodic surface using the performance data of reverse scattering is considered. The inverse problem was solved by means of minimization of the residual functional with the help of the gradient descent method. The initial data were calculated with the help of the numerical method. On each step of the iterative method of minimization, the residual functional was calculated approximately with the help of the small slope method. The examples of the shape determination are considered.

Mikheev, Andrew G.; Shamaev, Aleksey S.

1991-01-01

445

Phase shifting diffraction interferometer  

DOEpatents

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.

Sommargren, Gary E. (Santa Cruz, CA)

1996-01-01

446

Multilayer diffraction grating  

DOEpatents

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.

Barbee, Jr., Troy W. (Palo Alto, CA)

1990-01-01

447

Diffractive phenomena at Tevatron  

SciTech Connect

Preliminary results from the D0 experiment on jet production with rapidity gaps in p{anti p} collisions are presented. A class of dijet events with a forward rapidity gap is observed at center-of-mass energies {radical}s = 1800 GeV and 630 GeV. The number of events with rapidity gaps at both center-of-mass energies is significantly greater than the expectation from multiplicity fluctuations and is consistent with a hard single diffractive process. A class of events with two forward gaps and central dijets are also observed at 1800 GeV. This topology is consistent with hard double pomeron exchange. We also present proposed plans for extending these analysis into Run II through the use of a forward proton detector.

Santoro, A.; DO Collaboration

1997-07-01

448

Phase shifting diffraction interferometer  

DOEpatents

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.

Sommargren, G.E.

1996-08-29

449

Dichroic coherent diffractive imaging  

PubMed Central

Understanding electronic structure at the nanoscale is crucial to untangling fundamental physics puzzles such as phase separation and emergent behavior in complex magnetic oxides. Probes with the ability to see beyond surfaces on nanometer length and subpicosecond time scales can greatly enhance our understanding of these systems and will undoubtedly impact development of future information technologies. Polarized X-rays are an appealing choice of probe due to their penetrating power, elemental and magnetic specificity, and high spatial resolution. The resolution of traditional X-ray microscopes is limited by the nanometer precision required to fabricate X-ray optics. Here we present a novel approach to lensless imaging of an extended magnetic nanostructure, in which a scanned series of dichroic coherent diffraction patterns is recorded and numerically inverted to map its magnetic domain configuration. Unlike holographic methods, it does not require a reference wave or precision optics. In addition, it enables the imaging of samples with arbitrarily large spatial dimensions, at a spatial resolution limited solely by the coherent X-ray flux, wavelength, and stability of the sample with respect to the beam. It can readily be extended to nonmagnetic systems that exhibit circular or linear dichroism. We demonstrate this approach by imaging ferrimagnetic labyrinthine domains in a Gd/Fe multilayer with perpendicular anisotropy and follow the evolution of the domain structure through part of its magnetization hysteresis loop. This approach is scalable to imaging with diffraction-limited resolution, a prospect rapidly becoming a reality in view of the new generation of phenomenally brilliant X-ray sources. PMID:21825152

Tripathi, Ashish; Mohanty, Jyoti; Dietze, Sebastian H.; Shpyrko, Oleg G.; Shipton, Erik; Fullerton, Eric E.; Kim, Sang Soo; McNulty, Ian

2011-01-01

450

Quantum theory of light diffraction  

E-print Network

At present, the theory of light diffraction only has the simple wave-optical approach. In this paper, we study light diffraction with the approach of relativistic quantum theory. We find that the slit length, slit width, slit thickness and wave-length of light have affected to the diffraction intensity and form of diffraction pattern. However, the effect of slit thickness on the diffraction pattern can not be explained by wave-optical approach, and it can be explained in quantum theory. We compare the theoretical results with single and multiple slits experiment data, and find the theoretical results are accordance with the experiment data. Otherwise, we give some theory prediction. We think all the new prediction will be tested by the light diffraction experiment.

Xiang-Yao Wu; Bai-Jun Zhang; Jing-Hai Yang; Li-Xin Chi; Xiao-Jing Liu; Yi-Heng Wu; Qing-Cai Wang; Yan Wang; Jing-Wu Li; Yi-Qing Guo

2011-04-01

451

Diffraction and Vector Meson Production at HERA  

E-print Network

Diffraction and Vector Meson Production at HERA 1 M.Kapishin, JINR On behalf of the H1 and ZEUS Collaborations Inclusive diffractive DIS Diffractive PDFs from combined QCD Fit to inclusive diffractive DIS meson production and DVCS Diffraction and Vector Meson Production at HERA #12;Diffractive DIS at HERA 2

452

New Diffraction Results from CDF  

E-print Network

We report measurements of hard diffractive processes performed by the CDF collaboration in proton-antiproton collisions at the Fermilab Tevatron collider at $\\sqrt{s}$=1960 GeV. The characteristics of the diffractive structure function from diffractive dijet production studies are presented. The results of exclusive dijet production in double pomeron exchange are discussed in the context of exclusive Higgs production at the LHC.

Christina Mesropian

2005-10-14

453

CMS Results on Hard Diffraction  

E-print Network

In these proceedings we present CMS results on hard diffraction. Diffractive dijet production in pp collisions at $\\sqrt{s}$=7 TeV is discussed. The cross section for dijet production is presented as a function of $\\tilde{\\xi}$, representing the fractional momentum loss of the scattered proton in single-diffractive events. The observation of W and Z boson production in events with a large pseudo-rapidity gap is also presented.

Christina Mesropian on behalf of the CMS collaboration

2013-10-20

454

Kinematics of Compton backscattering x-ray source for angiography  

SciTech Connect

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.

Blumberg, L.N.

1992-05-01

455

Simulation of backscattering of high frequency sound from complex objects and sand sea-bottom  

Microsoft Academic Search

This paper describes the simulation of backscattering of high frequency sound from complex objects and sand sea-bottom. Backscattering data from complex objects and seabottom were generated using a Universal High Resolution Imaging Sonar Simulation Toolkit (UHRISST) developed by the authors. Our approach here involves the approximation of objects and the sea-bottom through a series of facets that are small compared

Oommen George; Rajendar Bahl

1995-01-01

456

Comparison of TRMM and NSCAT Observationsof Surface Backscatter Over the Amazon Rain Forest  

E-print Network

Comparison of TRMM and NSCAT Observationsof Surface Backscatter Over the Amazon Rain Forest David G@ee.byu.edu Abstruct-The Tropical Rain Measuring Mission (TRMM) pre- cipitation radar (PR) is designed to measure backscatter from rain in order to map the ;mountand extent of rain in the tropical regions. The TRMM F'R also

Long, David G.

457

Estimating random errors due to shot noise in backscatter lidar observations  

Microsoft Academic Search

We discuss the estimation of random errors due to shot noise in backscatter lidar observations that use either photomultiplier tube (PMT) or avalanche photodiode (APD) detectors. The statistical characteristics of photodetection are reviewed, and photon count distributions of solar background signals and laser backscatter signals are examined using airborne lidar observations at 532 nm using a photon-counting mode APD. Both

Zhaoyan Liu; William Hunt; Mark Vaughan; Chris Hostetler; Matthew McGill; Kathleen Powell; David Winker; Yongxiang Hu

2006-01-01

458

The modulation of radar backscatter by long ocean waves: A quadratically nonlinear process?  

Microsoft Academic Search

Radar imaging of ocean scenes requires knowledge of the modulation of the radar backscatter by long ocean waves. By using the conventional composite surface theory, the modulation of the radar backscatter can be related to a single parameter of the ocean wave field, such as slope or orbital velocity of the long waves. Usually, this relationship is assumed to be

Anke Schmidt; Mingquan Bao

1998-01-01

459

The relationship between strength of turbulence and backscattering radar power at HF and VHF  

NASA Technical Reports Server (NTRS)

The formulae relating turbulence and other atmospheric parameters to backscattered power for radar observations are reviewed. Emphasis is on the case of scatter from turbulent irregularities which have scales corresponding to the range of isotropic, inertial range turbulence. The applicability of this assumption is discussed. A formula is introduced for the mesosphere which relates ionospheric electron densities to backscattered power.

Hocking, W. K.

1983-01-01

460

ICES Journal of Marine Science, 53: 359361. 1996 Temporal sampling of backscattered sonar signals  

E-print Network

ICES Journal of Marine Science, 53: 359­361. 1996 Temporal sampling of backscattered sonar signals Jules S. Jaffe Jaffe, J. S. 1996. Temporal sampling of backscattered sonar signals. ­ ICES Journal sound from an active sonar system. Here, it is demonstrated how the beam patterns of the sonar, when

Jaffe, Jules